Geminated Maxillary Incisors: The Success of an Orthodontic Conservative Approach: 15 Years Follow-Up Study

Abstract

Tooth gemination is often presented clinically and radiologically as merged crowns or “megadonts” with or without a longitudinal fissure, single root, and a single pulp chamber. The increased mesiodistal width of these teeth results in poor anterior aesthetics, anterior crowding, and incisor rotation. Our aim is to present a conservative non-extraction orthodontic approach that provides both good aesthetics and long-term stability. It aims to achieve extra space to incorporate the megadonts into the dental arch and to exceed “super” class I dental relationships. Accordingly, this study shows that geminated teeth were successfully retained by means of conservative non-extraction orthodontic mechanotherapy and without premolar extractions or enamel reduction. It demonstrated stability during a long-term 15-year follow-up, in addition to high patient satisfaction, good aesthetics, and periodontal health. The solution protocol is definitive and achieved the aesthetic, psychological, and functional objectives at a feasible cost. Thus, this treatment has proven to be preferable to other alternative surgical prosthodontic and endodontic approaches in terms of its long-term stability, and by providing a solution that does not necessitate further multidisciplinary interventions. Dental practitioners in the fields of pediatric dentistry, endodontics and prosthodontics should be well aware of this option.

1. Introduction

Tooth gemination is defined as an incomplete formation of two teeth from a single tooth bud. Clinically, it is often presented in the incisor area of the maxilla as a merged crown or “megadont” with or without a longitudinal crown fissure and a single undivided root [1,2,3]. Radiographically, the single root, which is enlarged in the mesiodistal dimension, incorporates a single, wide pulp chamber that may include two root canals. It appears that gemination is caused by complex genetic and environmental factors [4]. The incidence of gemination is 0.1–0.47% in the general population and 0.07% in orthodontic patients [5], with no gender predilection [6]. It can be diagnosed in the permanent and primary dentitions [7] and may be associated with dental anomalies, such as dens in dente, macrodontia, hypodontia, and supernumerary teeth [2]. The differential diagnosis of gemination is tooth fusion: a complete or incomplete fusion of two adjacent teeth.

As fusion with a supernumerary tooth or missing teeth have also been reported [8], accurate diagnosis cannot rely on teeth counting, but rather on clinical and radiographic assessment. Patients presenting with anterior teeth gemination often report aesthetic concerns due to the crown’s malformation, longitudinal fissure, and the unique enlarged mesiodistal dimension, which may exceed or double the regular incisors’ crown size [9]. The enlarged crown size may also contribute to malocclusion, functional disorders, and compromised oral hygiene. Anterior crowding and rotations may be aggravated by the increased geminated tooth crown’s width [10], which can lead to increased caries. Other than the approach we suggest in this paper, a few treatment modalities are available for patients with geminated central incisors (

Table 1. The three treatment alternatives for gemination.

	Procedures	Advantages	Disadvantages
Prosthetic+Surgical (non-conservative)	Extraction Anterior alveolar augmentation Implant placement	Superior aesthetics	Age 18 and older Anterior alveolar bone loss Multi-disciplinal All life management Expensive
Prosthetic+Endodontic (fairly conservative)	Reshaping Root canal tx. Restoration Decoronation	Fast Superior aesthetics?	Age 18 and older Possible root canal failure Multi-disciplinal All life management Expensive
Orthodontic (very conservative)	Distalization Maxillary expansion Minor incisor proclination Interproximal reduction (possibly)	Younger age Tooth material conservation No surgical intervention Orthodontic involvement only Stable Reasonable Cost	A minor aesthetic defect Prolonged treatment No class I relationship

). The first option is extraction and later prosthodontic treatment. The second treatment is more complicated and extensive, combining a multidisciplinary approach of endodontic, surgical, and later prosthodontic treatment. The aim of this study was to present an alternative conservative non-surgical orthodontic treatment option, instead of the aforementioned approaches, to provide both good aesthetics and long-term stability.

2. Materials and Methods

(a)

Patients

Five patients with geminated central incisors were studied retrospectively. All of the patients were examined at the mixed dentition stages. Their pretreatment demographic and orthodontic information is presented in

Table 2. Demographic data and clinical information.

	Patient 1	Patient 2	Patient 3	Patient 4	Patient 5
Age at start of treatment	10	10	7	12	11
Sex	M	F	M	F	F
Geminated tooth	11,21	11,21	11,21	22	42
Angle classification	class II div 1	class II div 1	class I	class II div 1	class II div 1
M-D width of geminated incisors	14/14	10.5/12	11.5/12	11.5	9
Transverse relationship	bilateral X-bite	normal	normal	bilateral X-bite	normal

. Four of the patients had maxillary geminated central incisors (3 cases—bilateral, and 1 case—unilateral) and one had a mandibular geminated lateral incisor.

(b)

Gemination Characteristics

Gemination in the first three patients occurred in the mixed dentition stage with bilateral double maxillary central incisors. In addition, two cases of gemination of either the upper or lower lateral incisors were present. All cases presented a class II division 1 (Figure 1A) malocclusion associated with an enlarged overjet and overbite tendency. Transversally, the maxilla ranged between normal and narrow, with a bilateral posterior X-bite. Figure 1 presents a 10-year-old patient with maxillary right and left central incisors that demonstrate malalignment and rotation with an abnormal shape. The mesiodistal width of the two central maxillary abnormal incisors was 14 mm on average. The panoramic, periapical, and Cone Beam Computerized Tomography (CBCT) views of the upper incisors revealed fused crowns on both central incisors; a single wide root with a single root canal is clearly demonstrated in the CBCT view (Figure 1B,C). A pretreatment lateral cephalometric radiograph analysis revealed a skeletal class II relationship with a retrognathic mandible with a convex profile, a high angle pattern, and a mandibular clockwise rotation with an enlarged lower facial height (

Table 3. Cephalometric pre- and post-treatment values in patient No 1.

	Parameters	Pre	Post
1	SNA *	890	930
2	SNB **	810	860
3	ANB ***	80	70
4	Lower facial height	58%	55%
5	Mandibular plane angle	200	250
6	Upper 1 to SN	1100	1100
7	Lower 1 to MP	1000	920

* indicates position of the maxilla. ** indicates position of the mandible. *** indicates whether the skeletal relationship between the maxilla and mandible is a normal skeletal class I (+2 degrees), a skeletal Class II (+4 degrees or more), or skeletal class III (0 or negative) relationship.

). The maxillary and mandibular incisors were proclined.

(1)

SNA (Sella, Nasion, A point) indicates the position of the maxilla mandible (whether or not it is normal, prognathic, or retrognathic);

(2)

SNB (Sella, Nasion, B point) Indicates the position of the mandible (whether or not it is normal, prognathic, or retrognathic);

(3)

ANB (A point, Nasion, B point) indicates whether the skeletal relationship between the maxilla and mandible is a normal skeletal class I (+2 degrees), a skeletal class II (+4 degrees or more), or skeletal class III (0 or negative) relationship;

(4)

Lower facial height to indicate facial proportions;

(5)

Angle between Frankfort horizontal line and the line intersecting Gonion–Menton;

(6)

Upper incisors inclination;

(7)

Lower incisors inclination.

(c)

Treatment Protocol and Technique

An orthodontic treatment approach that consisted of a distalization and expansion, without premolar extractions was planned. The geminated incisors non-extraction orthodontic conservative technique included 3 components: (1) a maxillary molar teeth distalization of 3–4 mm to exceed the “super” class I dental relationship; (2) a maxillary expansion of 3–4 mm per side; and (3) an incisor teeth protrusive inclination of 7–8 degrees. At first, distalization with a pendulum, a noncompliance orthodontic appliance, was started. Its adverse effect of incisor proclination is also favorable in gemination for its contribution to arch length. Thus, cervical head gear aimed to increase distalization, but which limits the incisor proclination was achieved just 3–4 months later. After the class I relationship was accomplished, a bonded pre-adjusted upper fixed orthodontic appliance was used to expand the upper arch. In the other patients an upper arch expansion was started by Hyrax, enabling an upper median diastema opening. A fixed pre-adjusted appliance was immediately bonded to take advantage of the space created in the upper frontal area to alleviate the upper crowding. The Hyrax was removed after 6 months of retention. In the next step, a lower fixed pre-adjusted appliance was performed to achieve arch coordination and additional lower arch expansion. In addition, a slight upper proclination was considered. The main objectives of the treatment modality were: (1) to obtain healthy periodontal tissue while avoiding bone loss in the median region; (2) to meet aesthetic and functional requirements; (3) to reach upper and lower anterior crowding alleviation; and (4) to establish normal overjet and overbite with full alignment of the geminated teeth.

3. Results

(a) The post-treatment results indicate that the treatment objectives were fully achieved. The facial profile (Figure 2) was improved, with good periodontal health. The angle class III molar relationship and class I canine relationship was achieved with a 4–5 mm overjet and normal overbite. Teeth 11 and 21 were aligned in the arch as well as leveling, and alignment of the maxillary and mandibular dental arches was achieved. The lower incisors were retruded and the upper incisors sustained the same inclination. No change in the skeletal Anteroposterior (AP) discrepancy and vertical dimension was measured (Table 3). A conservative acid-etched restoration concealed the aesthetic defect in the central incisors in two of the cases; the third was not found to require any restoration. The treatment of two of the cases with unilateral geminated lateral incisors has not yet finished. The retention protocol included a combined maxillary and mandibular fixed retainer and a vacuum formed removable retainer for nighttime use.

(b) Long-term outcomes: the preservation of anterior alveolar bone at an 11 and 15 year post-treatment follow-up is presented, showing stable occlusion and correct occlusal parameters, superb aesthetics, and good periodontal health (Figure 3). No change in dental or skeletal dimensions were noticed. The patients were pleased with the results.

4. Discussion

Double teeth may involve an unaesthetic appearance and space problems, making normal teeth alignment impossible and creating functional disorders and difficulties with maintaining oral hygiene. Three treatment alternatives for the gemination phenomenon were considered (Table 1). The first two alternatives are multidisciplinary and based on a prosthodontic approach; thus, presenting an extended and expensive treatment option until permanent crown restoration is performed aged 18 or later. The first option, involving surgical extraction of the geminated tooth and later prosthodontic treatment, can be especially tempting in cases where a geminated or fused tooth is present, to avoid asymmetry. The future restoration may include a ceramic crown [6] via implant placement or an acid-etched bridge. An adverse effect of such a treatment plan is early alveolar bone loss at the anterior aesthetic area, due to tooth extraction at a young age before full skeletal maturation is achieved. In cases where there are two geminated anterior incisor extractions, extensive bone loss is anticipated, requiring extensive bone augmentation, which is essential to support future implants. Therefore, extractions of teeth from the anterior area should be avoided. Decoronation—removal of the tooth crown in infra-occlusion—leaving the root in its alveolus to be replaced by bone, is aimed at preserving the alveolar ridge for a future prosthodontic solution [11,12]. It can also serve as another option for the geminated tooth. Although this option can be advantageous compared to surgical extraction, it can compromise an orthodontic treatment, if needed. the increased mesiodistal width of the root can either prevent good root approximation and alignment [13] or hinder tooth movement into the decoronated site until complete root resorption occurs. The second solution is a combined prosthodontic-endodontic treatment. A mesiodistal slicing of the mega-crown is performed, usually followed by a root canal treatment and prosthetic restoration. The endodontic approach may interfere with the conservative treatment principle since the success rate of root canal treatment is 82.8–97.3% [14]. In addition, geminated teeth have a crown-root dilaceration [15], or complicated root canal morphology [16]. Root resection, which was proposed in fused teeth with wide crowns [3,17], can be contradicted in geminated teeth because a single pulp chamber is present. Literature reports of two cases of geminated teeth with root resection followed later by reshaping and restoration exist [18,19]. Orthodontics is the third treatment modality, aimed at obtaining healthy periodontal tissue and avoiding bone loss, which is most likely to happen in the median region following the extraction of adjacent teeth [20]; thus, this option enables both functional and aesthetic results. The success of orthodontic treatment is dependent on a few parameters; one of these is a correct arch relationship [21]. However, the ratio between the available maxillary and mandibular tooth sizes is not precise in gemination. In the first three presented cases, both Bolton’s overall and anterior ratios were reduced by more than two standard deviations from the expected ratio. In such cases, with significant discrepancy from the Bolton’s mean values, incorporation of the findings into an orthodontic treatment plan is essential to meet the patients’ expectations [14,22,23]. In the presented cases, the skeletal cephalometric measurements are described in an increased ANB angle; and this demonstrated maxillo mandibular discrepancy is derived from the relative protrusive maxilla and retrusive mandible. These skeletal relationships enable a dento-alveolar compensation, which could resolve the tooth size discrepancy in tooth width between the two arches. In the presented cases, space is created by the non-extraction means of upper distalization, expansion, and minor teeth proclination. The establishment of buccal occlusion toward an angle class Ill relationship allows for the alignment of the wide geminated teeth accompanied with an overjet reduction. Not all skeletal relationships are capable of sustaining such a dento-alveolar compensation, as a skeletal class II relationship is mandatory. Orthodontic treatment provides a sole immediate solution in preadolescence or adolescence at a feasible cost. It avoids having to wait until full skeletal maturation, prevents impaction of the adjacent tooth, violation of the occlusal ratios, and the exacerbation of the orthodontic deformity can be observed [24]. In addition, psychological and self-esteem problems [25] are an important contributing factor in preferring this treatment modality. Teeth were reported as one of the most common physical features leading to teasing and harassment among children [12]. Loss of anterior teeth, in geminated teeth, can cause not only a deterioration in the child’s facial and smile aesthetics but may also make them the target of teasing and ridicule by other children [11,12,26,27]. This orthodontic approach also saves on intermediate post-operative restoration [12,28], either fixed or removable, along with many years of childhood and adolescent treatments until growth cessation occurs [26].

Literature reports of three cases of mega teeth exist: in one a geminated tooth [18] and in the other two, fusion [3,19] with a dental sectioning root resection. It was followed later by reshaping and orthodontic treatment to align the adjacent teeth and alleviate crowding in the extraction sites. In addition, orthodontics associated with megadont removal, closing extraction sites, successful movement across the midline, and alignment of a supplemental tooth [26,29] are described. Retention of the geminated teeth by achieving sufficient space was described, following full orthodontic treatment using extractions of the first maxillary premolars [30]. However, creating enough space for wide central incisors, using the orthodontic option of a non-extraction approach, poses a real clinical challenge. A non-extraction approach was performed to maintain a slight angle class III buccal occlusion, avoiding problems of aesthetics and overjet. The limitations of the orthodontic solution for geminated teeth are prolonged treatment time and possible side effects associated with orthodontic treatment, such as caries, periodontal complications, and root resorption. In addition, patient compliance is essential. Further, the aesthetic solution provided is not perfect due to possible crown malformations that can cause aesthetic and occlusal disturbances in the anterior segment [24]. In the current data, a conservative acid-etched restoration was performed in two patients, and the third was not found to need any restoration. However, theoretically, even in cases with a larger aesthetic defect, teeth preservation with later conservative restoration is beneficial and clearly preferable as long as the roots and alveolar area are preserved. The achieved results can be stable and long-lasting, as illustrated in the cases above, preventing the lifelong need for endodontic and prosthodontic follow-up and possible retreatment.

5. Conclusions

The choice of orthodontic treatment rather than prosthetic surgical or endodontic approaches to retain geminated incisors should be considered, since it provides a natural, conservative, and an immediate solution at a reasonable cost. The pleasing aesthetic and functional results of this complex management treatment have been proven to be stable for a long time, sparing unnecessary dental intervention. Dental practitioners in the fields of pediatric dentistry, endodontics and prosthodontics should be made aware of this option.