Effectiveness of Orofacial Myofunctional Therapy for Speech Sound Disorders in Children: A Systematic Review

Abstract

Orofacial myofunctional therapy (OMT) is an intervention approach used to remediate orofacial myofunctional disorders (OMDs). OMDs are abnormal patterns involving the oral and orofacial musculature that can subsequently interfere with the normal growth, development, or function of orofacial structures, including speech production. Historically, articulation therapy is used to remediate speech sound disorders (SSDs). Currently, there is a dearth of literature on the use of OMT to treat non-developmental (organic) SSDs in children. The aim of this systematic review is to examine the effectiveness of OMT in treating organic SSDs in children and adolescents between 4 and 18 years of age. A search of five electronic databases (ProQuest, Scopus, Ovid, CINAHL, and Embase) was conducted, including backward (identifying and reviewing references from earlier studies from sources) and forward searching (reviewing newer studies that have cited a source). Only primary research including OMT with post-treatment outcome measures for speech production were included. Thirteen studies were reviewed, including a total of 397 participants between 4 and 17 years of age. A range of study designs, diagnoses, and intervention approaches were discussed. Studies yielded mixed results on the effectiveness of OMT to treat organic SSDs. OMT alone, and in combination with articulation therapy, was not found to be more effective than articulation therapy alone. The methodological quality of the studies ranged from limited to strong. Findings from high quality studies showed no improvement to speech that could be directly attributed to OMT, and lower quality studies yielded mixed results. This review found no conclusive evidence supporting the use of OMT as a standalone treatment for the effective remediation of SSDs. This is attributed to significant variability in speech outcomes, small sample sizes, limited comparison groups, diverse participant diagnoses, and inconsistent methodologies and treatment protocols, yielding mixed results. In addition, while the term OMT was used in the papers to designate treatment methodology, an analysis of the exercise descriptions revealed that some reported OMT exercises were non-speech oral motor exercises (NSOMEs) and oral motor therapies. Overall, many of the techniques utilized across studies did not provide speech-like movements in their therapeutic interventions based on their description. Finally, traditional articulation therapy, including speech drills to work on articulation disorders, was not included in many of the included studies. SLPs using OMT as a modality would typically combine this with articulation practice to treat the SSD. This study highlights the need for robust future studies including prospective cohort studies to compare OMT, combined OMT and articulation therapy, and articulation therapy alone to provide clearer guidance for future clinical practice.

1. Introduction

Orofacial myofunctional disorders (OMDs) are abnormal muscle movement patterns arising from structural differences, involving complex interactions between the orofacial structures and their daily functions. These can impact airway, swallowing, structural development, and speech production [1,2,3]. Primary examples of OMDs include abnormal labial–lingual rest posture, bruxism (teeth grinding), poor nasal breathing, tongue thrust during swallowing, impaired mastication and bolus management, atypical oral placements during speech, lip incompetence, digit sucking, and general sucking habits [4]. There have been some patterns of co-occurrence observed between the presence of OMD and speech sound disorders (SSDs) [4,5], though the cause of OMDs varies widely and involves the interplay of multiple factors, including learned behaviors, genetic factors, structural/physical variables, and environmental factors.

Specific characteristics of OMDs and their association with SSDs have been documented in the literature. The American Speech-Hearing Association (ASHA) [4,6] discussed that an articulation deficit may be secondary to an OMD if it includes distorted productions of /s, z/; distortion of velar sounds /k/, /g/ and /ŋ/; interdental, atypical lingual dental articulatory placement of /t, d, l, n, ʧ, ʤ, ʃ, ʒ/; weak bilabial productions, including vowels and diphthongs; /ɹ/ distortions; and nasal emission. The inability to conduct differentiated movements of the tongue and jaw, and the incorrect resting posture of the tongue and mandible may impact the location from which speech production begins and ends. Therefore, when an SSD co-occurs with an OMD, speech-language pathologists (SLPs) may expedite the resolution of articulation errors more efficiently if they first address the OMD [5].

When evaluating organic speech sound disorders (SSDs) secondary to orofacial myofunctional disorders (OMDs), it is crucial to understand the interaction of phonetic placements, structural conditions, and other OMDs on the client’s ability to achieve appropriate placement [7]. Organic SSDs arise from identifiable causes such as motor/neurological disorders (e.g., childhood apraxia of speech, dysarthria), structural abnormalities (e.g., cleft lip/palate), and sensory/perceptual deficits (e.g., hearing loss) [5]. In contrast, functional SSDs involve difficulties in speech sound production without an underlying structural or neurological cause, traditionally categorized as articulation and phonological disorders. For instance, Preston et al. [8] described four key placements of articulators for accurate /ɹ/ production: oral constriction, tongue root retraction, posterior tongue body lowering, and lateral bracing against the molars. Structural variations, such as a narrow palate or crossbite, may hinder lateral bracing, making /ɹ/ production more difficult [9]. Likewise, ankyloglossia can restrict lingual mobility, preventing proper tongue placement and limiting progress with traditional articulation therapy [10]. Marchesan [11] further found that 48.81% of individuals with an altered frenulum struggled with /ɹ/, /s/, and /z/ production.

Studies have shown that 31% of children diagnosed with chronic mouth breathing exhibit an articulation disorder [12]; 62.0% to 73.3% have SSDs concurrent with malocclusion or receive orthodontic intervention [13,14]; and 97.9% of patients with SSDs present with TMD [15]. Other researchers have noted a correlation between SSDs and malocclusions. Alhazami [16] found that anterior open bite and posterior crossbite were related to speech distortion, and Amr-Rey et al. [17] found a positive correlation between SSDs and malocclusion. Additionally, Maspero and colleagues [18] suggested that addressing abnormal lingual, labial, or open-mouth postures in therapy prior to targeting speech sounds can enhance the effectiveness of articulation intervention. Clinicians have also reported that individuals with OMDs often do not respond optimally to traditional articulation therapy unless underlying structural or muscular deficits are addressed. When left unaddressed, these deficits may lead to prolonged therapy durations and limited progress [10].

Ankyloglossia and its impact on speech have been widely explored in the literature. Carnino et al. [19] concluded that frenectomy is an effective treatment for addressing speech issues in select tongue-tied patients when identified in early childhood. Similarly, Baxter et al. [20] reported that 89% of subjects experienced speech improvement following frenectomy. Cordray et al. [21] highlighted that speech and articulation difficulties can be partially influenced by ankyloglossia, while Dydyk et al. [22] emphasized that a short tongue frenulum adversely affects both speech and dental occlusion.

SSDs can be treated via multiple modalities, including traditional articulation therapy in isolation or in combination with other modalities. Traditional articulation therapy is supported by the literature as an effective option for children with SSD [23,24,25,26,27]. ‘Oral motor’ is an umbrella term used to describe a range of therapeutic approaches, including oral motor exercises (OMEs), oral myofunctional therapy (OMT), and oral placement therapy (OPT) [1,4,27]. Some studies have identified a high prevalence of SSDs in their participants with OMDs [5], indicating a potential correlation between the two conditions. Table 1 provides a glossary of definitions for the types of therapy approaches for children with OMD.

Recently, there has been an increase in the use of OMT, which has, in turn, initiated an increase in related research [28]. This includes the use of treatment for organic SSDs, which involve difficulties in articulation, and motor planning and execution. Despite the lack of high-quality evidence for this treatment, Rumbach et al. [29] found that 38% of Australian Speech Pathologists reported using OMEs with pediatric clients diagnosed with speech sound difficulties. The OMEs used by clinicians varied in their inclusion of OMT, and the most prevalent population receiving OMT was children with dysarthria [28].

OMT may be effective in remediating deficits contributing to OMD; for example, tongue strength and stabilization are common OMT targets [1,28]. Green [30] found that 41% of parents reported speech concerns in children with ongoing digit sucking, a form of OMD. The high percentage of parents who identified concerns contrasts with the prevalence of speech sound disorders in the United States, which is estimated between 2.3 and 24.6% [6]. The widespread use of OMEs by practicing clinicians, the presence of apparent deficits related to speech production, such as tongue strength and mobility, and the higher prevalence of speech difficulties in children presenting with OMDs provide a basis to justify an investigation into the efficacy of OMT.

One recent literature review exploring the effectiveness of OMT on a range of speech production measures found no significant change in speech sound production secondary to OMT [28]. That review included studies investigating participants under 4 years, which does not align with this paper’s qualifications for the treatment; manual searching was relied on more heavily, and search terms differed.

Table 1. Glossary of definitions of therapy approaches for children and adults with orofacial myofunctional disorders.

Term	Therapy Approach	Definition
Articulation therapy	Traditional articulation therapy [31]	It is defined as a therapeutic approach designed to address speech or articulation disorders at the phonetic level [6]. It is used for patients with functional speech sound disorders (SSDs) with speech errors at the phonetic level, e.g., /s/ or /r/, or non-phonologically based delays and disorders. Goals are to progress from simple to complex speech contexts, ensuring that clients achieve generalization of correct sound production across various settings. Methodology remains rooted in the auditory, visual, and kinaesthetic feedback methods [31]. Modern methodology may include perceptual training, articulatory cues that guide patient articulation, visual, auditory, and tactile feedback to help clients understand the correct tongue, jaw, and lip positions for accurate sound production; typically follows a structured progression of identifying the target sound, discriminating between correct and incorrect sound, and practiced production in isolation.
Oral motor therapy *	Oral placement therapy (OPT) [32]	It is defined as a therapeutic approach to address speech production in individuals who do not respond well to traditional articulation therapy. It is used for patients with muscle-based SSDs in addition to other conditions (i.e., OMD, hypotonia, dysarthria) who do not respond to traditional audio and visual cues and require tactile-proprioceptive input. Goals are to develop motor skills for speech and replicating speechlike movements. Methodology is derived from occupational therapy and physical therapy and emphasizes use of guided articulatory placements with the additional component of tactile/proprioceptive feedback techniques to facilitate muscle control to achieve proper speech articulation.
	Oral motor exercises (OMEs) [3]	It is defined as a therapeutic approach to address poor coordination and strength of oral musculature to facilitate normal function. It is used for patients of any age with orofacial hypotonia, dysphagia, dysarthria. Goals are facilitating range of motion of articulators and addressing remediation of atypical swallowing patterns, abnormal orofacial musculature associated with disease, injury, or congenital anomaly. Methodology targets grading of the jaw, lips and tongue with passive or active specialized exercises aimed at improving coordination; The primary difference between OME and OMT is OME may be passive where the patient is not actively engaged in therapy (i.e., infants), whereas OMT exercises must be considered active which generally applies for children ages 4 and above.
	Orofacial myofunctional therapy (OMT) [3,4,33]	It is defined as a therapeutic approach to address poor coordination and strength of oral musculature in patients that play an active role (not passive) in therapy. It is used for patients with poor coordination and strength of oral musculature that are old enough to actively engage in therapy and have self-awareness and self-monitoring to facilitate progress towards goals generally thought to occur after 3;0 to 4;0 years of age. Goals are to increase muscle strength, dexterity and endurance, develop patient’s ability to control musculature, and improve oral resting posture; generally, goals are to create and maintain an environment in which age-appropriate orofacial function (speech, breathing, swallowing) can develop and be sustained. Methodology Exercises with patients old enough to engage in bidirectional feedback, this approach utilizes repetitive patient-controlled movement of oral structures, often with oral appliances, to aid in developing posture and muscle engagement. Different components and techniques may be provided by multiple healthcare providers in different fields depending on scope of practice and patient factors.
	Non-speech oral motor exercises (NSOMEs) [29,32]	It is defined as movements that focus on strengthening and coordinating the agility and range of motion of the articulators without practicing articulation itself [29]. It is used for patients with speech sound disorders who have underlying muscle of motor weakness. Goals are to address underlying oral dysfunction related to oral motor control, by strengthening and enhancing agility, resistance, and range of oral structures, such as the mouth, lips, tongue and jaw. Methodology is derived from part to whole theory and includes movements such as puckering the lips or wagging the tongue. While these exercises are intended to improve oral motor skills, they do not specifically focus on producing speech, and are distinctly different from using speech-like movements implemented in OPT.

* Oral motor therapy is an umbrella term with various associated treatment methodologies including oral sensory–motor exercises or oral motor exercises (OME), orofacial myofunctional therapy (OMT), pre-feeding exercises, and oral placement therapy (OPT) [3].

Table 1. Glossary of definitions of therapy approaches for children and adults with orofacial myofunctional disorders.

Term	Therapy Approach	Definition
Articulation therapy	Traditional articulation therapy [31]	It is defined as a therapeutic approach designed to address speech or articulation disorders at the phonetic level [6]. It is used for patients with functional speech sound disorders (SSDs) with speech errors at the phonetic level, e.g., /s/ or /r/, or non-phonologically based delays and disorders. Goals are to progress from simple to complex speech contexts, ensuring that clients achieve generalization of correct sound production across various settings. Methodology remains rooted in the auditory, visual, and kinaesthetic feedback methods [31]. Modern methodology may include perceptual training, articulatory cues that guide patient articulation, visual, auditory, and tactile feedback to help clients understand the correct tongue, jaw, and lip positions for accurate sound production; typically follows a structured progression of identifying the target sound, discriminating between correct and incorrect sound, and practiced production in isolation.
Oral motor therapy *	Oral placement therapy (OPT) [32]	It is defined as a therapeutic approach to address speech production in individuals who do not respond well to traditional articulation therapy. It is used for patients with muscle-based SSDs in addition to other conditions (i.e., OMD, hypotonia, dysarthria) who do not respond to traditional audio and visual cues and require tactile-proprioceptive input. Goals are to develop motor skills for speech and replicating speechlike movements. Methodology is derived from occupational therapy and physical therapy and emphasizes use of guided articulatory placements with the additional component of tactile/proprioceptive feedback techniques to facilitate muscle control to achieve proper speech articulation.
	Oral motor exercises (OMEs) [3]	It is defined as a therapeutic approach to address poor coordination and strength of oral musculature to facilitate normal function. It is used for patients of any age with orofacial hypotonia, dysphagia, dysarthria. Goals are facilitating range of motion of articulators and addressing remediation of atypical swallowing patterns, abnormal orofacial musculature associated with disease, injury, or congenital anomaly. Methodology targets grading of the jaw, lips and tongue with passive or active specialized exercises aimed at improving coordination; The primary difference between OME and OMT is OME may be passive where the patient is not actively engaged in therapy (i.e., infants), whereas OMT exercises must be considered active which generally applies for children ages 4 and above.
	Orofacial myofunctional therapy (OMT) [3,4,33]	It is defined as a therapeutic approach to address poor coordination and strength of oral musculature in patients that play an active role (not passive) in therapy. It is used for patients with poor coordination and strength of oral musculature that are old enough to actively engage in therapy and have self-awareness and self-monitoring to facilitate progress towards goals generally thought to occur after 3;0 to 4;0 years of age. Goals are to increase muscle strength, dexterity and endurance, develop patient’s ability to control musculature, and improve oral resting posture; generally, goals are to create and maintain an environment in which age-appropriate orofacial function (speech, breathing, swallowing) can develop and be sustained. Methodology Exercises with patients old enough to engage in bidirectional feedback, this approach utilizes repetitive patient-controlled movement of oral structures, often with oral appliances, to aid in developing posture and muscle engagement. Different components and techniques may be provided by multiple healthcare providers in different fields depending on scope of practice and patient factors.
	Non-speech oral motor exercises (NSOMEs) [29,32]	It is defined as movements that focus on strengthening and coordinating the agility and range of motion of the articulators without practicing articulation itself [29]. It is used for patients with speech sound disorders who have underlying muscle of motor weakness. Goals are to address underlying oral dysfunction related to oral motor control, by strengthening and enhancing agility, resistance, and range of oral structures, such as the mouth, lips, tongue and jaw. Methodology is derived from part to whole theory and includes movements such as puckering the lips or wagging the tongue. While these exercises are intended to improve oral motor skills, they do not specifically focus on producing speech, and are distinctly different from using speech-like movements implemented in OPT.

* Oral motor therapy is an umbrella term with various associated treatment methodologies including oral sensory–motor exercises or oral motor exercises (OME), orofacial myofunctional therapy (OMT), pre-feeding exercises, and oral placement therapy (OPT) [3].

Another systematic review by McCauley et al. [34] on NSOMEs, which included OMT studies, found inconclusive evidence for their effectiveness on speech. This review, though comprehensive at the time, was limited by the small number of available studies and the broad range of treatment approaches, presentations, and age groups it encompassed. As the findings of this research were not conclusive, it was suggested that there was inadequate evidence to justify the use of NSOMEs in clinics and exercises were labeled as ‘experimental’ [34]. The review included 15 articles due to the limited research at the time of publication, despite McCauley et al. [34] reporting that over 70% of US speech pathologists used OMEs during clinical practice. The limited number of articles and the wide range of treatment approaches, presentations, and age ranges explored in the review indicate that the results may not represent the true effectiveness of OMT in the pediatric population. One research article included infants as young as 3 months, while OMT requires understanding and the ability to follow directions [3]. Additionally, the review excluded studies noted to employ mixed methods [34]. Speech-language pathologists commonly include phoneme production tasks within OMT, indicating that some OMT studies may have been erroneously excluded, even while following standard OMT protocols [3]. In addition, the McCauley et al. systematic review was conducted 15 years ago, and the specificity and quantity of research in the area has increased since that time [34].

While existing reviews indicate that OMT is not effective for treating non-developmental SSDs, the limitations in these reviews highlight the need for a more focused investigation. This paper aims to address these limitations with the inclusion of more contemporary research, more comprehensive search terms, and stricter parameters for treatment classification, which may help to more specifically determine which populations experience significant benefit from OMT. The purpose of this systematic review is to examine the effectiveness of OMT in treating non-developmental (organic) SSDs in children and adolescents between 4 and 18 years of age. This is to provide improved specificity regarding the effectiveness of OMT in a pediatric population and to inform evidence-based clinical practice.

2. Methods

A systematic review was conducted in accordance with the Pickering and Byrne [35] framework, informed by Lasserson et al. [36]. A systematic review was selected as the most appropriate method to investigate the effectiveness of OMT in a pediatric population due to the specific nature of the research topic. A meta-analysis was not conducted due to variability in study designs, participant characteristics, and measures of outcomes, which precluded meaningful statistical synthesis. The structure of a systematic review allowed for a specific analysis of all relevant primary research relevant to the selected topic [37]. The review was registered and embargoed with Open Science Framework (OSF) (https://osf.io/37deh/) online on 5 September 2024.

2.1. Search Methods

The structure of the search methods followed the steps laid out in the PRISMA [38] guidelines for systematic reviews. The search terms were based around therapeutic techniques, population, intervention, and target conditions. These search terms were edited to allow for all possible terms of each key area to be included and to adhere to the specific Boolean operators of each database such as truncations and wildcards (

Table 2. Search terms included.

Therapy	Intervention	Population	Target
OMT Orofacial myofunctional therap * Oral myology Myofacial Oromyofunction * Orofacial myofunction * Oral Moto * Exercise *	Interven * Therapy *	P * ediatric Adolescen * Teen * Kid * Student * School age	SSD Speech sound disorder Articulat * Phonolog * CAS Childhood apraxia of speech Motor speech Dysarthri * Speech * Intelligib * Speech sound * Lisp * Apraxi */Dyspraxi *

Note: ‘*’ delineates differences in truncation and search spelling differences across different operators and search bases.

). Following identification of full-text papers, backward (identifying and reviewing references from earlier studies from sources) and forward searching (reviewing newer studies that have cited a source) were conducted to locate any articles that were missed during systematic searches.

Five databases were searched: Medline, Embase, Scopus, Proquest, and CINAHL. The search was conducted by three reviewers in August 2024, and studies were uploaded to Covidence [39]. Covidence [39] is an online platform designed to streamline the systematic review process by facilitating article screening, data extraction, and quality assessment. It enables researchers to efficiently manage large volumes of literature, collaborate with multiple reviewers, and track decisions on study inclusion. Covidence supports blinded screening, automatic duplication detection, and consensus resolution, enhancing the transparency and rigor of evidence synthesis. Articles were screened first by their titles and abstracts, then their full text, before determining whether they were eligible for inclusion. All articles required agreement between at least two reviewers to include or exclude them. Discrepancies were discussed between at least two reviewers or sent to authors not participating in this stage, for consideration.

2.2. Inclusion and Exclusion Criteria

The age range investigated was 4;0 to 18;0 years. Children below 4;0 years were excluded based on existing literature that OMT is suitable only with older children who can self-monitor their motor performance and comply with treatment [3]. Adults were excluded as the focus of this review is on children with organic SSDs. Developmental or phonologically based SSDs were excluded as OMT is typically implemented for organic SSDs [3].

Systematic and scoping reviews were excluded as they did not represent any addition to research, nor were they beneficial for determining the current research base within this field of study. This review included both observational and experimental studies, as including only randomized control trials would yield too few results. Non-English articles were also excluded due to a lack of translations available. All publication dates were included to facilitate a thorough review of the research and due to the low availability of contemporary studies.

NSOMEs were excluded due to the existing presence of systematic reviews on this topic [34] and their established lack of efficacy [40].

2.3. Quality Analysis

Following full-text review, included articles were screened for quality using the Kmet [41] quality grading tool. The Kmet [41] quality grading tool provides a structured framework for assessing the methodological rigor of research articles. It evaluates studies based on predefined criteria and categorizes articles into four levels of evidence quality: limited, adequate, good, and strong. These ratings were based on an overall score between zero (0) and one (1). This systematic approach ensures consistency in evaluating research validity. Any discrepancies in scoring or article inclusion were resolved through discussion among reviewers.

2.4. Data Extraction and Synthesis

Data extraction was conducted by recording relevant information from each included article into a shared Microsoft Excel spreadsheet. Each article was extracted by two reviewers, and results were agreed upon by a minimum of two reviewers. Data extraction included focusing on location and type of studies, hypothesis, aims, population characteristics, OMT exercises used, speech outcomes measured, and main findings of the article. Data were synthesized by two reviewers, with a third reviewer present for conflict resolution.

3. Results

3.1. Search Results

A total of 3494 studies were identified for screening from the initial search. A total of 1025 duplicates were removed, leaving 2469 studies for screening. In total, four reviewers screened the titles and abstracts, with agreement between two reviewers required for each article to be considered for full-text review. Following title and abstract screening, 218 studies were deemed eligible for full-text review, including seven located using backward and forward searching. Discrepancies regarding final study inclusions were discussed with authors not involved in this stage to determine eligibility. A total of 13 articles were included for final data extraction, quality analysis, and synthesis. Figure 1 (PRISMA flow diagram) summarizes this information.

3.2. Study Designs and Locations

Of the 13 studies included in this systematic review, three were single subject studies: one single experimental design [42], one with a comparison treatment [43], and one with multiple baselines [44]. Three were single-group studies: one using pre-test and post-test measures [45], one controlled study [46], and one using single-treatment counterbalanced design [47]. One article was a collection of six case studies [48], and one was a retrospective analysis [49]. Two papers were randomized control trials [50,51], and three were uncontrolled randomized trials [33,52,53]. Table 3 provides a summary of the data extracted.

A total of 12 published journal articles and one thesis were included. Papers were published in the United States (n = 4), Spain (n = 2), Brazil (n = 2), and one each in Germany, Canada, Sweden, and Belgium, respectively. Seven out of thirteen (53.8%) of paper reviews were published more than 15 years ago, and three (23.1%) of papers were published within the last five years.

Several papers included professors across multiple professions (n = 6), including speech pathology (n = 5), dentistry (n = 3), orthodontics (n = 4), pediatrics (n = 1), speech science directorship (n = 1), otolaryngology (n = 1), medical doctor (n = 1), neuro-pediatrics (n = 1), behavioral science (n = 1), biotechnics (n = 1), psychology (n = 1), and unknown (n = 1). Table 3 shows a breakdown of author professions by paper.

Table 3. Summary of included papers including country of origin, study design, participant details, overview of treatment, practitioner, and quality ratings (n = 13).

	First Author (Year), Country (Citation)	Study Design	Total Participants	Participants Receiving OMT	Participant Background	Overview of Treatment	Who Did the Treatment	Quality
1	Carminatti et al. (2022), Brazil [51]	Randomized, single-blinded, parallel-group, controlled study	N = 40. Age: 6–10 years. 39/40 male	N = 20. Age: 6–10 years (M = 8). 11/20 male	Participants post lingual frenectomy	All participants received a frenectomy. One group received isotonic exercises 15 days post-surgery, and one did not (control).	Dentist performed frenectomy, participant and parents provided OMT.	88% (strong)
2	Cervera-Mérida et al. (2020), Spain [42]	Single-subject experimental study	N = 1. Age: 10 years. 0/1 male	N = 1. Age: 10 years. 0/1 male	Nemaline myopathy	Participant underwent a period of treatment integrating tongue strengthening exercises and diadochokinetic exercises.	SLP.	75% (good)
3	Christensen and Hanson, (1981), USA [33]	Randomized trial	N = 10. Age: 5–6 years (M = 6). 6/4 male	N = 5. Age: 5–6 years (M = 6). 3/5 male	Frontal lisp, anterior tongue thrust	G1: Articulation therapy—14 weeks. G2: Tongue thrust treatment- six weeks before switching to articulation therapy.	SLP. Participant and mother delivered home practice.	71% (good)
4	Costa et al. (2013), Brazil [48]	Case studies (N = 6)	N = 6. Age: 6–13 years. 1/6 male	N = 6. Age: 6–13 years. 1/6 male	Phonological disorders, phonetic disorders, phonetic-phonological disorders	All participants received isotonic, lip and tongue exercises.	Not provided.	55% (adequate)
5	Fischer-Brandies et al. (1987), Germany [45]	Single-group case series pre-test post-test design	N = 71. Age: 4–14 years (M = 10). 34/71 male	N = 71. Age: 4–14 years (M = 10). 34/71 male	Cerebral palsy (mixed subtypes)	Participants wore removable stimulatory plates. A modified Castillo-Morales protocol was used with one third of participants in addition to the plates.	Protocols at beginning and end of treatment delivered by neuropediatrician (N = 1), palatal plate treatment provided by orthodontic department.	25% (limited)
6	Gommerman and Hodge (1987), Canada [44]	Single-subject ABC multiple baseline	N = 1. Age: 16 years (M = 16). 0/1 male	N =1. Age: 16 years (M = 16). 0/1 male	Lisp (interdental, lateral), tongue thrust during swallow	Participant underwent a baseline phase and phase of OMT followed by a phase of articulation therapy.	SLP.	55% (adequate)
7	Korbmacher et al. (2004), Germany [50]	Randomized control trial	N = 45. Age: 3–16 years. 32/45 male	N = 26. Age: 3;11–15;10 years (M = 8;4). 17/26 male	Orofacial dysfunctions (open mouth breathing, pathological swallow including tongue thrust)	Participants were split into a control group (OMT only) and an orthodontic appliance group (OMT and appliance).	Face Former therapy delivered by dental assistant under supervision of dentist, OMT provided by SLPs. Participant wore Face Former over night as home practice.	83% (strong)
8	Mucciolo (2013), USA [43]	Case study, single subject with comparison treatment	N = 1. Age: 5 years. 1/1 male	N = 1. Age: 5 years. 1/1 male	Speech sound disorder (with lisp)	Participant underwent a period of combined OMT and articulation therapy followed by pure articulation therapy.	SLP. Participant and parents/homework partner delivered home practice.	67% (adequate)
9	Overstake (1975), USA [52]	Randomized trial	N = 48. Age: 7–12 years (M = 9)	N = 28. Age: 7–12 years (M = 9)	Deviant swallow, open bite and/or overjet orthodontic problems, and /s/ speech sound defects (lisp)	One group received swallow therapy only, and one received a combination of swallow and speech therapy.	SLP. Participant and parents delivered home practice.	46% (limited)
10	Ray (2001), India [46]	Single-group, controlled study	N = 16. Age: 7–10 years (M = 8). 9/7 male	N = 16. Age: 7–10 years (M = 8). 9/7 male	Mild-moderate spastic cerebral palsy	All participants underwent 4 months of OMT.	Tongue and lips resting posture (Phase 1) verified by Orthodontist, physical therapist or occupational therapist sitting posture assistance throughout treatment, SLP provided OMT. Participant and parents delivered home practice.	55% (adequate)
11	Scarano et al. (2023), Italy [49]	Retrospective study	N = 130. Age: 4–11 years. 54/130 male	N = 130. Age: 4–11 years. 54/130 male	Ankyloglossia class III or IV (with symptoms including frenectomy and: mouth breathing, dysfunctional swallow, snoring, clenching, and/or myofascial pain/tension)	All participants underwent a lingual frenectomy and subsequent OMT.	SLP. Participant and parents delivered home practice.	39% (limited)
12	Sjögreen et al. (2010), Sweden [47]	One-group single-treatment counterbalanced design	N = 8. Age: 7–17 years. 4/6 male	N = 8. Age: 7–17 years. 4/6 male	Muscular dystrophy type 1	Participants were split into groups following baseline measures. One group delayed treatment (control). All students received OMT for 8 weeks (either immediately, or after 8 weeks baseline).	Self-administered (parent, teachers, participant).	75% (good)
13	Van Dyck et al. (2016), Belgium [53]	Prospective pilot randomized study	N = 22. Age: 7–10 years	N = 10. Age: 7–9 years (M = 8)	Anterior open bite, tongue dysfunction	Participants were divided into non-OMT and OMT (either in clinic or at home) treatment groups.	Qualification of session provider not provided—possibly orthodontists. Participant and parents delivered home practice.	79% (good)

Table 3. Summary of included papers including country of origin, study design, participant details, overview of treatment, practitioner, and quality ratings (n = 13).

	First Author (Year), Country (Citation)	Study Design	Total Participants	Participants Receiving OMT	Participant Background	Overview of Treatment	Who Did the Treatment	Quality
1	Carminatti et al. (2022), Brazil [51]	Randomized, single-blinded, parallel-group, controlled study	N = 40. Age: 6–10 years. 39/40 male	N = 20. Age: 6–10 years (M = 8). 11/20 male	Participants post lingual frenectomy	All participants received a frenectomy. One group received isotonic exercises 15 days post-surgery, and one did not (control).	Dentist performed frenectomy, participant and parents provided OMT.	88% (strong)
2	Cervera-Mérida et al. (2020), Spain [42]	Single-subject experimental study	N = 1. Age: 10 years. 0/1 male	N = 1. Age: 10 years. 0/1 male	Nemaline myopathy	Participant underwent a period of treatment integrating tongue strengthening exercises and diadochokinetic exercises.	SLP.	75% (good)
3	Christensen and Hanson, (1981), USA [33]	Randomized trial	N = 10. Age: 5–6 years (M = 6). 6/4 male	N = 5. Age: 5–6 years (M = 6). 3/5 male	Frontal lisp, anterior tongue thrust	G1: Articulation therapy—14 weeks. G2: Tongue thrust treatment- six weeks before switching to articulation therapy.	SLP. Participant and mother delivered home practice.	71% (good)
4	Costa et al. (2013), Brazil [48]	Case studies (N = 6)	N = 6. Age: 6–13 years. 1/6 male	N = 6. Age: 6–13 years. 1/6 male	Phonological disorders, phonetic disorders, phonetic-phonological disorders	All participants received isotonic, lip and tongue exercises.	Not provided.	55% (adequate)
5	Fischer-Brandies et al. (1987), Germany [45]	Single-group case series pre-test post-test design	N = 71. Age: 4–14 years (M = 10). 34/71 male	N = 71. Age: 4–14 years (M = 10). 34/71 male	Cerebral palsy (mixed subtypes)	Participants wore removable stimulatory plates. A modified Castillo-Morales protocol was used with one third of participants in addition to the plates.	Protocols at beginning and end of treatment delivered by neuropediatrician (N = 1), palatal plate treatment provided by orthodontic department.	25% (limited)
6	Gommerman and Hodge (1987), Canada [44]	Single-subject ABC multiple baseline	N = 1. Age: 16 years (M = 16). 0/1 male	N =1. Age: 16 years (M = 16). 0/1 male	Lisp (interdental, lateral), tongue thrust during swallow	Participant underwent a baseline phase and phase of OMT followed by a phase of articulation therapy.	SLP.	55% (adequate)
7	Korbmacher et al. (2004), Germany [50]	Randomized control trial	N = 45. Age: 3–16 years. 32/45 male	N = 26. Age: 3;11–15;10 years (M = 8;4). 17/26 male	Orofacial dysfunctions (open mouth breathing, pathological swallow including tongue thrust)	Participants were split into a control group (OMT only) and an orthodontic appliance group (OMT and appliance).	Face Former therapy delivered by dental assistant under supervision of dentist, OMT provided by SLPs. Participant wore Face Former over night as home practice.	83% (strong)
8	Mucciolo (2013), USA [43]	Case study, single subject with comparison treatment	N = 1. Age: 5 years. 1/1 male	N = 1. Age: 5 years. 1/1 male	Speech sound disorder (with lisp)	Participant underwent a period of combined OMT and articulation therapy followed by pure articulation therapy.	SLP. Participant and parents/homework partner delivered home practice.	67% (adequate)
9	Overstake (1975), USA [52]	Randomized trial	N = 48. Age: 7–12 years (M = 9)	N = 28. Age: 7–12 years (M = 9)	Deviant swallow, open bite and/or overjet orthodontic problems, and /s/ speech sound defects (lisp)	One group received swallow therapy only, and one received a combination of swallow and speech therapy.	SLP. Participant and parents delivered home practice.	46% (limited)
10	Ray (2001), India [46]	Single-group, controlled study	N = 16. Age: 7–10 years (M = 8). 9/7 male	N = 16. Age: 7–10 years (M = 8). 9/7 male	Mild-moderate spastic cerebral palsy	All participants underwent 4 months of OMT.	Tongue and lips resting posture (Phase 1) verified by Orthodontist, physical therapist or occupational therapist sitting posture assistance throughout treatment, SLP provided OMT. Participant and parents delivered home practice.	55% (adequate)
11	Scarano et al. (2023), Italy [49]	Retrospective study	N = 130. Age: 4–11 years. 54/130 male	N = 130. Age: 4–11 years. 54/130 male	Ankyloglossia class III or IV (with symptoms including frenectomy and: mouth breathing, dysfunctional swallow, snoring, clenching, and/or myofascial pain/tension)	All participants underwent a lingual frenectomy and subsequent OMT.	SLP. Participant and parents delivered home practice.	39% (limited)
12	Sjögreen et al. (2010), Sweden [47]	One-group single-treatment counterbalanced design	N = 8. Age: 7–17 years. 4/6 male	N = 8. Age: 7–17 years. 4/6 male	Muscular dystrophy type 1	Participants were split into groups following baseline measures. One group delayed treatment (control). All students received OMT for 8 weeks (either immediately, or after 8 weeks baseline).	Self-administered (parent, teachers, participant).	75% (good)
13	Van Dyck et al. (2016), Belgium [53]	Prospective pilot randomized study	N = 22. Age: 7–10 years	N = 10. Age: 7–9 years (M = 8)	Anterior open bite, tongue dysfunction	Participants were divided into non-OMT and OMT (either in clinic or at home) treatment groups.	Qualification of session provider not provided—possibly orthodontists. Participant and parents delivered home practice.	79% (good)

3.3. Participants

This review included a total of 397 children across all 13 included studies, comprising 131 females and 149 males. Participants ranged from 4;0 to 16;11 years of age. The results from two 19-year-old participants were excluded, since they were individually reported and met the exclusion criteria [47]. Only three studies included participants below the age of five, [33,45,50] and four papers included participants 13;0 years or older [44,45,46,47].

All papers included an assessment of speech sound production. Concomitant medical diagnoses varied across studies. Two studies investigated children with cerebral palsy [45,46]; two children with muscular weakness (myotonic dystrophy type 1 and nemaline myopathy) [42,47]; two children with tongue tie [49,51]; three with tongue thrust [33,44,53]; and two with orofacial motricity alterations or dysfunctions [52,53], or no other comorbidities (n = 1) [43,48].

3.4. Treatment

All papers in Table 4 included elements of OMT; however, only four of the thirteen papers measured articulation skills pre- and post- OMT treatment, and only two included specific speech sound goals alongside OMT. None of the studies conducted a three-way comparison between OMT, articulation therapy, and a combined OMT articulation approach. Treatment durations varied significantly, ranging from two weeks to three years. Some studies included the use of appliances within their OMT treatment program. Other participants underwent a frenectomy during treatment (Table 4).

Regarding phoneme targets, two studies included no specific phoneme targets [33,45], while others looked at individualized target sounds per participant. A total of seven studies focused on sibilants, particularly /s/ [33,44,48,50,52,53], while three investigated alveolar phonemes (/t/, /d/, /n/, /l/) [50,51,53]. Table 5 shows a full breakdown of phoneme targets by paper.

Table 4. Types of Treatment within Included Papers, including Author Stated, Articulation Therapy, Orofacial Myofunctional Therapy, and Non-Speech Oral Motor Exercises (n = 13).

	First Author (Year), Country	Author Definition of OMT	Summary of Exercises	Artic Tx	Oral Motor Therapy Techniques
					OME	NSOME	OMT
1	Carminatti et al. (2022), Brazil [51]	No explicit definition given, treatment definition: “isotonic tongue exercises, language and techniques for the production of phonemes”.	Running the tongue around closed lips and teeth. Touching four points outside of the mouth with the tip of the tongue. Pronouncing the sounds /l/ and /n/ alternatively, performed 3 times a day at home.	✓		✓
2	Cervera-Mérida et al. (2020), Spain [42]	Treatment is “based on myofunctional techniques” with no definition given.	Sensory stimulation and message—hot/cold vibrating thermal roller for sensory stimulation; oral motor exercises—only movements of tongue apex (client specific), vertical and lateral tongue movement; tongue strengthening—Ora-Light and IOPI devices; DDK—repetition of syllables.		✓		✓
3	Christensen and Hanson (1981), USA [33]	No explicit definition. Goal relates to correcting tongue resting positions.	Subjects in Group 2 (treatment group) received only tongue-thrust services for the first six weeks, then alternating sessions of tongue thrust and articulation services for the remaining eight weeks. See Appendix A for a full description of each lesson.	✓	✓		✓
4	Costa et al. (2013), Brazil [48]	No definition given. OMT is viewed as it relates to oral myofunctional structures.	A total of 3 sets of 15 reps over 30 min. Tongue exercises: rub tongue on palate, open and close mouth with tongue on anterior of palate, hold tongue in position, suck tongue to palate and open mouth to stretch lingual frenulum; lip exercises: close contracted lips exaggeratedly, stretch superior lip under the verge of the superior incisors, exaggerated smile; cheek exercises: inflate and release cheeks, alternate cheek inflation, exaggerated articulation of “i-u”, blow in balloon or party whistles. Nil home exercises.		✓	✓	✓
5	Fischer-Brandies et al. (1987), Germany [45]	No explicit definition, treatment definition given as “stimulatory plates (i.e., removable devices for the upper jaw) and an exercise program based on physiotherapy and motor speech therapy.”	All based on Castillo-Morales. Changes made to address cerebral palsy subtype needs. The Castillo-Morales method of orofacial/appliance therapy is a method of orofacial regulation therapy consisting of manual stimulation and facilitation in conjunction with an orthodontic plate (Castillo-Morales et al., 1983 in Limbrock et al., 1991). The intervention was developed to target articulation, swallowing, chewing, and swallowing, with a particular focus on modifying tongue and upper-lip movement (Marinone et al., 2017). The orthodontic appliance consists of a device like an orthodontic retainer, with beads and/or buttons along the frame to encourage movement of the tongue and lips (Marinone et al., 2017).	✓			✓
6	Gommerman and Hodge (1987), Canada [44]	No definition given.	Adapted from Bennett, 1985 and Gardiner, 1981. Tongue pushes: tongue holds; 1 and 2 liquorice swallows (3-piece swallow discontinued secondary to posterior piece slipping to central position); slurp-swallows; sip-swallows; open-closes; continuous drinking; biting exercises; tongue clicks; water trap swallows; snack swallows; new swallow; peanut butter licks. Repetitions determined subjectively by investigators and adjusted as necessary during session				✓
7	Korbmacher et al. (2004), Germany [50]	No explicit definition given. Primary therapeutic objectives outline as; strengthening of the orofacial muscles to pave the way for mouth closure, establishment of nasal breathing, and learning a physiological swallowing pattern.	Using a Face Former device: sustained rest position, tongue pressed against the palate; active compression of the lip wedge for 6 s then 6 s rest 3x per day; after 3 weeks of training, Face Former worn over night.			✓	✓
8	Mucciolo (2013), USA [43]	No explicit definition given, does not explicitly refer to orofacial myofunctional therapy. Refers to inconsistent literature differentiating between oral motor treatment and NSOMEs. Discusses the distinction between oral motor exercises and NSOME as “whether or not the oral motor exercises target movements specific to speech sound production” (Lof, 2008). Delineates between exercises that target speech specific movements and those that do not (NSOME).	Tongue lift and press to hard palate; tongue snaps; tongue push against resistance; hold straw horizontally with blade of tongue; hold tongue in position; slide tongue backwards across alveolar ridge; tongue lifts while hold straw in place with teeth. Home practice.	✓	✓	✓	✓
9	Overstake (1975), USA [52]	No explicit definition given. Treatment described as “specific swallow therapy”.	Tongue and mandibular positioning exercises		✓	✓	✓
10	Ray (2001), India [46]	No explicit definition given. Treatment described as focusing on “lip-closed, tongue-in palate resting posture, along with facilitation of appropriate muscle movements of jaw, lips, and tongue to facilitate accurate oral postures for articulation of speech sounds.”	Lip exercises (active lip stretch, lip closure, lip seal, holding button, lip pucker and smile, tongue depressor); jaw exercises (opening and closing, rotary movements); tongue exercises (curl around, rotary movements, touch nose, tongue posture); DDK movements.		✓	✓	✓
11	Scarano et al. (2023), Italy [49]	No explicit definition given. Object of a myofunctional program described as “to establish a new neuromuscular pattern and to correct abnormal functional and resting postures.”	All exercises performed while supine on postural bench: active (tongue tip against hard palate with mouth open and closed, lingual protrusion and lateralisation, palate brush stroke with mouth open and closed, upper and lower wiper, lingual walks, lingual snaps, sucker tongue); passive (lingual stretching, scar massage). Home practice exercises—passive exercises (tongue positioning); active exercises (tongue stretches, push against palate); scar massage with gauze.		✓	✓	✓
12	Sjögreen et al. (2010), Sweden [47]	No explicit definition given.	Lip resistance against pulling oral screen; passive retention of oral screen behind lips		✓	✓	✓
13	Van Dyck et al. (2016), Belgium [53]	No explicit definition given. Aim of a myofunctional program given as “to establish a new neuromuscular pattern and to correct abnormal functional and resting postures.” Other treatment objectives given as “strengthening of the orofacial muscles to pave the way for mouth closure, establish nasal breathing, and learn a physiological swallowing pattern”.	Tongue and lip muscle strengthening, swallowing practice, tongue position training		✓	✓	✓

Table 4. Types of Treatment within Included Papers, including Author Stated, Articulation Therapy, Orofacial Myofunctional Therapy, and Non-Speech Oral Motor Exercises (n = 13).

	First Author (Year), Country	Author Definition of OMT	Summary of Exercises	Artic Tx	Oral Motor Therapy Techniques
					OME	NSOME	OMT
1	Carminatti et al. (2022), Brazil [51]	No explicit definition given, treatment definition: “isotonic tongue exercises, language and techniques for the production of phonemes”.	Running the tongue around closed lips and teeth. Touching four points outside of the mouth with the tip of the tongue. Pronouncing the sounds /l/ and /n/ alternatively, performed 3 times a day at home.	✓		✓
2	Cervera-Mérida et al. (2020), Spain [42]	Treatment is “based on myofunctional techniques” with no definition given.	Sensory stimulation and message—hot/cold vibrating thermal roller for sensory stimulation; oral motor exercises—only movements of tongue apex (client specific), vertical and lateral tongue movement; tongue strengthening—Ora-Light and IOPI devices; DDK—repetition of syllables.		✓		✓
3	Christensen and Hanson (1981), USA [33]	No explicit definition. Goal relates to correcting tongue resting positions.	Subjects in Group 2 (treatment group) received only tongue-thrust services for the first six weeks, then alternating sessions of tongue thrust and articulation services for the remaining eight weeks. See Appendix A for a full description of each lesson.	✓	✓		✓
4	Costa et al. (2013), Brazil [48]	No definition given. OMT is viewed as it relates to oral myofunctional structures.	A total of 3 sets of 15 reps over 30 min. Tongue exercises: rub tongue on palate, open and close mouth with tongue on anterior of palate, hold tongue in position, suck tongue to palate and open mouth to stretch lingual frenulum; lip exercises: close contracted lips exaggeratedly, stretch superior lip under the verge of the superior incisors, exaggerated smile; cheek exercises: inflate and release cheeks, alternate cheek inflation, exaggerated articulation of “i-u”, blow in balloon or party whistles. Nil home exercises.		✓	✓	✓
5	Fischer-Brandies et al. (1987), Germany [45]	No explicit definition, treatment definition given as “stimulatory plates (i.e., removable devices for the upper jaw) and an exercise program based on physiotherapy and motor speech therapy.”	All based on Castillo-Morales. Changes made to address cerebral palsy subtype needs. The Castillo-Morales method of orofacial/appliance therapy is a method of orofacial regulation therapy consisting of manual stimulation and facilitation in conjunction with an orthodontic plate (Castillo-Morales et al., 1983 in Limbrock et al., 1991). The intervention was developed to target articulation, swallowing, chewing, and swallowing, with a particular focus on modifying tongue and upper-lip movement (Marinone et al., 2017). The orthodontic appliance consists of a device like an orthodontic retainer, with beads and/or buttons along the frame to encourage movement of the tongue and lips (Marinone et al., 2017).	✓			✓
6	Gommerman and Hodge (1987), Canada [44]	No definition given.	Adapted from Bennett, 1985 and Gardiner, 1981. Tongue pushes: tongue holds; 1 and 2 liquorice swallows (3-piece swallow discontinued secondary to posterior piece slipping to central position); slurp-swallows; sip-swallows; open-closes; continuous drinking; biting exercises; tongue clicks; water trap swallows; snack swallows; new swallow; peanut butter licks. Repetitions determined subjectively by investigators and adjusted as necessary during session				✓
7	Korbmacher et al. (2004), Germany [50]	No explicit definition given. Primary therapeutic objectives outline as; strengthening of the orofacial muscles to pave the way for mouth closure, establishment of nasal breathing, and learning a physiological swallowing pattern.	Using a Face Former device: sustained rest position, tongue pressed against the palate; active compression of the lip wedge for 6 s then 6 s rest 3x per day; after 3 weeks of training, Face Former worn over night.			✓	✓
8	Mucciolo (2013), USA [43]	No explicit definition given, does not explicitly refer to orofacial myofunctional therapy. Refers to inconsistent literature differentiating between oral motor treatment and NSOMEs. Discusses the distinction between oral motor exercises and NSOME as “whether or not the oral motor exercises target movements specific to speech sound production” (Lof, 2008). Delineates between exercises that target speech specific movements and those that do not (NSOME).	Tongue lift and press to hard palate; tongue snaps; tongue push against resistance; hold straw horizontally with blade of tongue; hold tongue in position; slide tongue backwards across alveolar ridge; tongue lifts while hold straw in place with teeth. Home practice.	✓	✓	✓	✓
9	Overstake (1975), USA [52]	No explicit definition given. Treatment described as “specific swallow therapy”.	Tongue and mandibular positioning exercises		✓	✓	✓
10	Ray (2001), India [46]	No explicit definition given. Treatment described as focusing on “lip-closed, tongue-in palate resting posture, along with facilitation of appropriate muscle movements of jaw, lips, and tongue to facilitate accurate oral postures for articulation of speech sounds.”	Lip exercises (active lip stretch, lip closure, lip seal, holding button, lip pucker and smile, tongue depressor); jaw exercises (opening and closing, rotary movements); tongue exercises (curl around, rotary movements, touch nose, tongue posture); DDK movements.		✓	✓	✓
11	Scarano et al. (2023), Italy [49]	No explicit definition given. Object of a myofunctional program described as “to establish a new neuromuscular pattern and to correct abnormal functional and resting postures.”	All exercises performed while supine on postural bench: active (tongue tip against hard palate with mouth open and closed, lingual protrusion and lateralisation, palate brush stroke with mouth open and closed, upper and lower wiper, lingual walks, lingual snaps, sucker tongue); passive (lingual stretching, scar massage). Home practice exercises—passive exercises (tongue positioning); active exercises (tongue stretches, push against palate); scar massage with gauze.		✓	✓	✓
12	Sjögreen et al. (2010), Sweden [47]	No explicit definition given.	Lip resistance against pulling oral screen; passive retention of oral screen behind lips		✓	✓	✓
13	Van Dyck et al. (2016), Belgium [53]	No explicit definition given. Aim of a myofunctional program given as “to establish a new neuromuscular pattern and to correct abnormal functional and resting postures.” Other treatment objectives given as “strengthening of the orofacial muscles to pave the way for mouth closure, establish nasal breathing, and learn a physiological swallowing pattern”.	Tongue and lip muscle strengthening, swallowing practice, tongue position training		✓	✓	✓

Table 5. Speech sound targets within included studies (n = 13).

	First Author (Year), Country (Citation)	Speech Sound Target and Intelligibility Measures
		Bilabial	Interdental/Dental	Alveolar	Palatal	Nasal	Sibilant	Fricative	Affricate	General Intelligibility
1	Carminatti et al. (2022), Brazil [51]			/l, n/						Yes
2	Cervera-Mérida et al. (2020), Spain [42]									Yes
3	Christensen and Hanson (1981), USA [33]						/s, z/
4	Costa et al. (2013), Brazil [48]			/ɹ/			/s, z/
5	Fischer-Brandies et al. (1987), Germany [45]	Yes *	Yes *		Yes *
6	Gommerman and Hodge (1987), Canada [44]						/s, z/	/ʃ/
7	Korbmacher et al. (2004), Germany [50]		/t, d/	/l/		/n/	/s/
8	Mucciolo (2013), USA [43]						/ʃ/
9	Overstake (1975), USA [52]						/s/
10	Ray (2001), India [46]	Yes *						Yes *	Yes *
11	Scarano et al. (2023), Italy [49]									Yes
12	Sjögreen et al. (2010), Sweden [47]	/p, b/				/m/		/f, v/
13	Van Dyck et al. (2016), Belgium [53]		/t, d/	/l/		/n/	/s/
		3	3	4	1	3	7	3	1	3

* Exact target not specified in paper.

Table 5. Speech sound targets within included studies (n = 13).

	First Author (Year), Country (Citation)	Speech Sound Target and Intelligibility Measures
		Bilabial	Interdental/Dental	Alveolar	Palatal	Nasal	Sibilant	Fricative	Affricate	General Intelligibility
1	Carminatti et al. (2022), Brazil [51]			/l, n/						Yes
2	Cervera-Mérida et al. (2020), Spain [42]									Yes
3	Christensen and Hanson (1981), USA [33]						/s, z/
4	Costa et al. (2013), Brazil [48]			/ɹ/			/s, z/
5	Fischer-Brandies et al. (1987), Germany [45]	Yes *	Yes *		Yes *
6	Gommerman and Hodge (1987), Canada [44]						/s, z/	/ʃ/
7	Korbmacher et al. (2004), Germany [50]		/t, d/	/l/		/n/	/s/
8	Mucciolo (2013), USA [43]						/ʃ/
9	Overstake (1975), USA [52]						/s/
10	Ray (2001), India [46]	Yes *						Yes *	Yes *
11	Scarano et al. (2023), Italy [49]									Yes
12	Sjögreen et al. (2010), Sweden [47]	/p, b/				/m/		/f, v/
13	Van Dyck et al. (2016), Belgium [53]		/t, d/	/l/		/n/	/s/
		3	3	4	1	3	7	3	1	3

* Exact target not specified in paper.

3.5. Quality Appraisal

Quality ratings were determined using the standard quality reporting guidelines analysis [39]. A score of less than 50% was determined to be limited quality; 50 to 70% was adequate quality; 70 to 80% was good quality; and greater than 80% was strong quality. Of the papers, two were found to be of strong quality, four good, four adequate, and three of limited quality. Table 3 shows the details of each paper’s quality appraisal and score.

3.6. Overall Outcomes

During analysis, three of the authors with clinical experience treating OMDs reviewed the included exercises for each of the 13 papers and reached a consensus about the type(s) of treatment provided. Treatments identified were articulation therapy, OME, NSOME, and OMT (Table 4). It is important to note that the Carminatti [51] paper reported using OMT as a modality, but upon review, the movements were categorized as NSOME and articulation therapy (Table 6).

Only one participant received pure OMT intervention [44]. A total of 71 participants received a combination of OMT and articulation therapy [45]; 40 had NSOME in conjunction with articulation therapy [51]; 11 received a combination of OMT and OME only [33,42]; 45 received a combination of OMT and NSOME [50]; 230 received a combination of all three therapy types (OMT, OME, and NSOME) [46,47,48,49,52,53]; and 1 received a combination of all three therapy types along with traditional articulation therapy [43].

Across the papers in this review, four broad outcomes emerged: no significant improvement following OMT; significant improvement following OMT; OMT resulting in similar- or less-effective outcomes than traditional articulation treatment; and mixed or inconclusive results. Of the two papers with strong quality (over 80%), no statistically significant difference was found between OMT and non-OMT groups [50,51]. In the four papers with good quality (70–80%), two papers showed no difference in speech outcomes between treatment and control groups [33,53], one showed improvements in speech but had no control group [42], one showed mixed improvements between groups [47]. Varied results were reported for papers with adequate quality (50–70%) [43,44,46,48]. One study had improvements with speech outcomes with traditional articulation therapy, but no improvement with ‘OMT followed by articulation therapy [43]. One study showed no differences in speech outcomes between OMT and articulation therapy only phases in therapy [44], whereas one showed improvements with speech outcomes with OMT [46]. The fourth paper showed mixed outcomes [48]. Three with limited quality (less than 50%) found mixed improvements in speech outcomes with OMT [45], one study showed significant reported improvements in as reported by parent satisfaction [49], and one found similar outcomes between OMT and articulation therapy only [52].

Table 6. Summary of outcomes for included papers (n = 13).

	First Author (Year), Country (Citation)	Summary of Outcomes
1	Carminatti et al. (2022), Brazil [51]	All participants (n = 40) improved in both speech and speech-related markers * post-frenectomy (speech: p =< 0.001, other aspects of speech *: p = 0.49). No statistically significant difference in outcomes between OMT and non-OMT groups (speech: p = 0.588, other aspects of speech: p = 0.828).
2	Cervera-Mérida et al. (2020), Spain [42]	All participants (n = 1) demonstrated improved speech intelligibility following treatment (40–67%, p = 0.002). Participants received OMT and diadochokinetic treatment simultaneously. No comparison group or period was included in the study.
3	Christensen and Hanson (1981), USA [33]	All participants (n = 10) improved in measure of articulation errors (p =< 0.05, exact value not provided). No statistically significant difference in speech outcomes between treatment and control groups (p =< 0.05, exact value not provided).
4	Costa et al. (2013), Brazil [48]	All participants (n = 6) corrected inaccurate phonemes. Three required eight sessions of OMT over four weeks to achieve speech adequacy (correction of one phoneme), one required sixteen sessions over eight weeks (correction of four phonemes), one required 72 sessions over 36 weeks (correction of five phonemes), and one achieved speech adequacy for all but one phoneme after 56 sessions over 28 weeks but was not able to correct the final phoneme even after 72 sessions (correction of six phonemes).
5	Fischer-Brandies et al. (1987), Germany [45]	Of participants with inaccurate production at the onset of the study, 24/38 (63%) improved production of labial phonemes while 2/38 (5%) worsened; 26/57 (46%) improved production of palatal phonemes while 2/57 (4%) worsened; and 24/53 (45%) improved production of dental phonemes while 4/53 (8%) worsened. All participants received OMT and physiotherapy simultaneously. No comparison group or period was included in the study.
6	Gommerman and Hodge (1987), Canada [44]	For all participants (n = 1) measures of % sibilant distortion were collected at baseline, during OMT-only phase, traditional articulation treatment phase, and at a six-month follow up (baseline 1–9% distortion → OMT only 0–9% distortion → traditional articulation 1–3% distortion → follow up 0% distortion). No statistical analysis was provided bar observation of slight upward trend in distortion through both the baseline and OMT phases.
7	Korbmacher et al. (2004), Germany [50]	No statistically significant improvement was observed in any participants (n = 45), regardless of therapy, at any time point within the 6-month observation period (treatment group: p = 0.368, control: 0.368, total: p = 0.135). Chi-square analysis revealed no differences between treatment groups at any time point (T0: p = 0.578, T1: p = 0.576, T2: p = 0.603).
8	Mucciolo (2013), USA [43]	For all participants (n = 1) traditional articulation treatment alone yielded faster, larger, and generalized improvements. OMT followed by articulation treatment yielded no significant improvements until the sixth session of articulation treatment, and no observed generalization.
9	Overstake (1975), USA [52]	Of participants receiving only OMT (n = 28), 85% (chi-square of 22.04, significantly below the 0.005 level) acquired a generalized /s/ by the conclusion of the ten-month treatment period. Of participants receiving OMT and Speech Therapy (n = 20), 75% (chi-square of 13.06, at the 0.005 level) acquired a generalized /s/ by the conclusion of the ten-month treatment period.
10	Ray (2001), India [46]	Of all participants (n = 16), a statistically significant but unspecified number of participants improved speech intelligibility in English following OMT (p = 0.0023). Generalization of intelligibility to native dialects was not able to be assessed in 40% of participants due to unfamiliarity with their languages. Lingua-alveolar and lingua-dental sounds were also subjectively observed to be more intelligible to the assessor’s following treatment.
11	Scarano et al. (2023), Italy [49]	Overall change in participant’s (n = 130) Parents Speech Satisfaction scores indicated statistically significant improvement in speech (p =< 0.0001) at one week and two months post-frenectomy and OMT. No objective measures were gathered during study. Effect of lingual frenulum release on speech was not controlled for.
12	Sjögreen et al. (2010), Sweden [47]	Participants (n = 8) were assigned to a treatment group A or a delayed treatment group B. Group A demonstrated mixed results (Following treatment: /b, p, m/ articulation: 1 participant improved, 2 participants worsened, and 1 participant remained consistent; /f v/ articulation: 2 participants improved, 1 participant worsened, and 1 participant remained consistent). Group B demonstrated no improvement following treatment (/b, p, m/ articulation: all participants remained consistent /f v/ articulation: all participants remained consistent).
13	Van Dyck et al. (2016), Belgium [53]	All participants (n = 22) demonstrated no statistically significant improvement following treatment (/l, n, d, t/ articulation Time 1: p = 0.40, Time 2: p => 0.99; /s/ articulation Time 1: p = 0.34, Time 2: p = 0.76). Participants were divided into expansion and non-expansion groups and then divided between non-OMT and OMT groups.

* Assessment of speech-related markers entailed assessment of mouth opening, tongue position, jaw movement, speed, accuracy of speech, and voice.

Table 6. Summary of outcomes for included papers (n = 13).

	First Author (Year), Country (Citation)	Summary of Outcomes
1	Carminatti et al. (2022), Brazil [51]	All participants (n = 40) improved in both speech and speech-related markers * post-frenectomy (speech: p =< 0.001, other aspects of speech *: p = 0.49). No statistically significant difference in outcomes between OMT and non-OMT groups (speech: p = 0.588, other aspects of speech: p = 0.828).
2	Cervera-Mérida et al. (2020), Spain [42]	All participants (n = 1) demonstrated improved speech intelligibility following treatment (40–67%, p = 0.002). Participants received OMT and diadochokinetic treatment simultaneously. No comparison group or period was included in the study.
3	Christensen and Hanson (1981), USA [33]	All participants (n = 10) improved in measure of articulation errors (p =< 0.05, exact value not provided). No statistically significant difference in speech outcomes between treatment and control groups (p =< 0.05, exact value not provided).
4	Costa et al. (2013), Brazil [48]	All participants (n = 6) corrected inaccurate phonemes. Three required eight sessions of OMT over four weeks to achieve speech adequacy (correction of one phoneme), one required sixteen sessions over eight weeks (correction of four phonemes), one required 72 sessions over 36 weeks (correction of five phonemes), and one achieved speech adequacy for all but one phoneme after 56 sessions over 28 weeks but was not able to correct the final phoneme even after 72 sessions (correction of six phonemes).
5	Fischer-Brandies et al. (1987), Germany [45]	Of participants with inaccurate production at the onset of the study, 24/38 (63%) improved production of labial phonemes while 2/38 (5%) worsened; 26/57 (46%) improved production of palatal phonemes while 2/57 (4%) worsened; and 24/53 (45%) improved production of dental phonemes while 4/53 (8%) worsened. All participants received OMT and physiotherapy simultaneously. No comparison group or period was included in the study.
6	Gommerman and Hodge (1987), Canada [44]	For all participants (n = 1) measures of % sibilant distortion were collected at baseline, during OMT-only phase, traditional articulation treatment phase, and at a six-month follow up (baseline 1–9% distortion → OMT only 0–9% distortion → traditional articulation 1–3% distortion → follow up 0% distortion). No statistical analysis was provided bar observation of slight upward trend in distortion through both the baseline and OMT phases.
7	Korbmacher et al. (2004), Germany [50]	No statistically significant improvement was observed in any participants (n = 45), regardless of therapy, at any time point within the 6-month observation period (treatment group: p = 0.368, control: 0.368, total: p = 0.135). Chi-square analysis revealed no differences between treatment groups at any time point (T0: p = 0.578, T1: p = 0.576, T2: p = 0.603).
8	Mucciolo (2013), USA [43]	For all participants (n = 1) traditional articulation treatment alone yielded faster, larger, and generalized improvements. OMT followed by articulation treatment yielded no significant improvements until the sixth session of articulation treatment, and no observed generalization.
9	Overstake (1975), USA [52]	Of participants receiving only OMT (n = 28), 85% (chi-square of 22.04, significantly below the 0.005 level) acquired a generalized /s/ by the conclusion of the ten-month treatment period. Of participants receiving OMT and Speech Therapy (n = 20), 75% (chi-square of 13.06, at the 0.005 level) acquired a generalized /s/ by the conclusion of the ten-month treatment period.
10	Ray (2001), India [46]	Of all participants (n = 16), a statistically significant but unspecified number of participants improved speech intelligibility in English following OMT (p = 0.0023). Generalization of intelligibility to native dialects was not able to be assessed in 40% of participants due to unfamiliarity with their languages. Lingua-alveolar and lingua-dental sounds were also subjectively observed to be more intelligible to the assessor’s following treatment.
11	Scarano et al. (2023), Italy [49]	Overall change in participant’s (n = 130) Parents Speech Satisfaction scores indicated statistically significant improvement in speech (p =< 0.0001) at one week and two months post-frenectomy and OMT. No objective measures were gathered during study. Effect of lingual frenulum release on speech was not controlled for.
12	Sjögreen et al. (2010), Sweden [47]	Participants (n = 8) were assigned to a treatment group A or a delayed treatment group B. Group A demonstrated mixed results (Following treatment: /b, p, m/ articulation: 1 participant improved, 2 participants worsened, and 1 participant remained consistent; /f v/ articulation: 2 participants improved, 1 participant worsened, and 1 participant remained consistent). Group B demonstrated no improvement following treatment (/b, p, m/ articulation: all participants remained consistent /f v/ articulation: all participants remained consistent).
13	Van Dyck et al. (2016), Belgium [53]	All participants (n = 22) demonstrated no statistically significant improvement following treatment (/l, n, d, t/ articulation Time 1: p = 0.40, Time 2: p => 0.99; /s/ articulation Time 1: p = 0.34, Time 2: p = 0.76). Participants were divided into expansion and non-expansion groups and then divided between non-OMT and OMT groups.

* Assessment of speech-related markers entailed assessment of mouth opening, tongue position, jaw movement, speed, accuracy of speech, and voice.

4. Discussion

This systematic review aimed to investigate the effectiveness of OMT as a treatment for organic SSDs in children and reported mixed results. The authors found limited literature investigating the use of OMT to treat children with co-occurring OMDs and SSDs. Studies finding improvements in articulation following OMT lacked control or comparison groups. As a result, their findings are not able to separate the effects of OMT and that of concurrent treatment, nor do they account for potential change over time. Papers that found statistically significant improvement with OMT alone relate to musculature modifying diagnoses, which is consistent with previously referenced literature where hypotonia was a treatment target for OMTs [54]; however, there is no research specifically into OMT’s effectiveness due to differing diagnoses.

All papers with strong quality measures showed no statistically significant improvement in speech outcomes with OMT. When compared directly to articulation therapy, OMT was generally as effective as, or less effective than traditional treatments, but has not been shown to have a greater improvement to speech sound production. It is important to note that OMT should only be considered as a potential therapy modality in situations where an organic SSD is present, an OMD has been identified and is impacting the client’s ability to make gains with traditional articulation therapy alone. Clients with functional deficits may benefit from OMT to address dysfunction, combined with articulation therapy to improve speech sound accuracy [46]. Therefore, the effectiveness of OMT as a treatment for SSDs is not yet supported by current evidence. Additional research is needed to establish its efficacy in this context.

An ongoing issue is the debate of terminology defining the variations between NSOMEs, OME, OMT, and OPT. There are overlapping properties to each of these oral motor therapy therapies, as outlined in the glossary of definitions, and many have overlapping treatment techniques with OMT. The key difference lies in whether there is a substantial focus on these exercises in a speech-based context or whether treatment follows a purely OMT program [32,55,56]. Several papers included in this review reported using OMT to address organic speech sound disorders, but upon analysis, the exercises were focusing on strengthening and enhancing the agility, resistance, and range of motion of oral structures used for speech, but without directly practicing speech itself, which is considered an NSOME or OPT [28]. Other reviews highlighted similar challenges in locating strong and comprehensive research on OMT, with issues such as inconsistent treatment methods and the absence of comparison groups [32,56].

The type of therapy and combination of therapy techniques should be considered when interpreting the results from this review. Given that only two of the thirteen studies from this review include speech sound goals together with true OMT, the research around the effectiveness of OMT on SSDs is minimal, compared to evidence-based articulation therapy. The paper by Carminatti et al. and Christensen and Hansen included speech goals within the oral motor therapy goals and tasks; however, the protocols were not consistent [51,52]. Therefore, it is challenging to compare findings, since speech-language pathologists do not use one single method within a treatment session, but most work on a combination of speech sound and oral motor intervention goals, including OMT tasks individualized to the patient’s individual needs. This limits the ability to interpret the results and definitively draw conclusions on the effectiveness of OMT on SSD. Furthermore, none of the intervention protocols used in the papers in this study were classified as pure OMT, being a combination of OMT and at least one other form of intervention (OME, NSOME, or traditional articulation therapy). This is important when considering the results of this review because it highlights the difficulties of finding a significant group of similar studies to draw conclusions from and raises a spotlight on the need for more standardization for future studies.

Another consideration is the evolution of the evidence-based practice (EBP) framework from a triangle to a diamond, reflecting the inclusion of ‘internal evidence’ alongside external evidence, client perspectives and clinical expertise [57]. Whilst the traditional EBP triangle focuses on these three elements, performance data collected by clinicians during therapy are omitted. The expanded diamond addresses the importance of tracking client progress, evaluating the effectiveness of interventions, and determining when therapy goals have been achieved [57]. In the context of the systematic review, this expanded EBP framework influenced the evaluation of studies by emphasizing the importance of tracking client progress, measuring intervention effectiveness, and determining therapy outcomes. The review also considered clinician factors (e.g., training, experience, and expertise) and client factors (e.g., severity of speech sound disorders and comorbid conditions) as critical variables affecting treatment outcomes. By adopting this broader perspective, the review ensured a more comprehensive assessment of the available evidence and its applicability to clinical practice,

Limitations and Future Research

This systematic review has several limitations. The review includes only studies written in English. The papers include a range of study designs, but exclude grey literature, which may limit potential other sources of information. Many studies have small sample sizes, limiting the external validity, ability to generalize, and replicability of results. There was variability in the definition of OMT across research and a range of methodologies utilized in terms of study treatment designs, levels of reporting, outcome measurement, and therapeutic procedures. Collectively, these sources of variability in nearly every parameter of study design highlight the need for a concerted and standardized effort in designing future studies that will allow for comparison between treatment modalities to guide future evidence-based best practices.

Future studies would benefit from standardized methodology. Given that many of these studies occur in specialty clinics or practices, where appropriate controls are not always possible, the effects of variability can be minimized by using standardized and validated assessment tools and reporting standards. Specifically, future studies of OMT and the effects on SSDs will yield high value data if they utilize the following:

• Standardized reporting of objective, replicable, and validated measures of oral function and speech sound production. Outcome measures should be reported both before and after the intervention.
• Clear definitions, characteristics and categorical standards that correctly identify different oral motor therapies and techniques, including OME, OMT, NSOMEs, OPT, and traditional articulation therapy. Generalized agreement with respect to terminology, conditions to be addressed, the type of patients these can be used with, and who can administer the therapy, will allow for greater comparison across studies.

Future studies that utilize these parameters will aid in clarifying and identifying the benefits of OMT or combinations of therapies, reduce variability amongst future studies, and provide evidence for the conditions under which these therapies provide optimal outcomes for patients.

5. Conclusions

This study found no conclusive evidence supporting OMT as a standalone effective treatment for SSDs. This conclusion is attributed to the significant variability in investigated speech outcomes, small sample sizes, limited comparison groups, and diverse participant diagnoses, and inconsistent methodologies and treatment protocols, with mixed results. In addition, while the term OMT was used in the papers to designate treatment methodology, an analysis of the exercise descriptions revealed there were NSOMEs and oral motor therapies being implemented across studies. Many of the techniques utilized across studies did not incorporate speech-like movements in their therapeutic interventions, as described, and, therefore, may be less effective as therapies that include speech production goals. Although some SSDs can have an organic basis due to underlying OMDs, research has identified consistent patterns of phonemic distortions that may stem from structural or muscular abnormalities [4]. Therefore, the remediation of the root cause of the deficits prior to, or in conjunction with, traditional articulation therapy may provide additional positive outcomes for those with SSDs directly attributed to OMD.

When an OMD is present, OMT and articulation therapy work together to address SSDs. It is important to consider not only the observable speech sound difficulties but also the underlying factors that may contribute to these challenges. Future research should focus on identifying the presence of OMDs and understanding their impact on specific speech sounds, including potential influences from palatal shape, tongue mobility, or range of motion. Addressing these underlying factors first—such as through therapy targeting muscle function—may support more effective articulation therapy by refining and integrating these movements into accurate speech production. This approach aims to enhance therapy outcomes by ensuring interventions are comprehensive and tailored to individual needs.

Current external evidence does not support the use of OMT in isolation for improving speech sound production [51]. However, the treatment of SSDs should consider all tiers of the evidence-based practice framework, including clinical expertise, external and internal evidence, and perspectives of clients, patients, and caregivers [50]. While there is support for the use of OMT when an OMD and SSD co-occur, it is important to rely on well-established evidence-based articulation approaches, either alone or in combination with OMT. Further research, including robust cohort studies comparing OMT, combined OMT and articulation therapy, and articulation therapy alone, are important to provide clearer guidance for future clinical practice. These results highlight that SLPs are essential in the remediation of SSDs, including those associated with OMDs, and other underlying causes, by implementing targeted interventions to improve speech sound production.