Optimal Insertion Torque for Orthodontic Anchoring Screw Placement: A Comprehensive Review
Department of Orthodontics, and Division of Clinical Research, Dental Research Center, School of Dentistry, Nihon University, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan
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Author to whom correspondence should be addressed.
Appl. Sci. 2023, 13(19), 10681; https://doi.org/10.3390/app131910681
Submission received: 2 September 2023
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Revised: 19 September 2023
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Accepted: 23 September 2023
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Published: 26 September 2023
(This article belongs to the Special Issue Clinical Applications of Orthodontic TSADs and CBCT)
Abstract
:The optimal insertion torque (IT) for orthodontic anchoring screws (OASs) was hypothesized to vary with OAS features and insertion methods. This review examines the indexed English literature, to determine the appropriate IT range for OAS success based on area of insertion and OAS features. Eleven original articles with OAS placement in humans including IT and success rate were selected and were used to evaluate the relationships among IT, success rates, screw design, and placement methods at different sites. The ITs and success rates ranged from 6.0 ± 3.2 to 15.7 ± 2.3 Ncm and from 62.5 to 100.0% in the upper and lower buccal alveolar areas, respectively. For the mid-palatal area, the range was 14.5 ± 1.6 to 25.6 ± 5.5 Ncm and 83.0 to 100.0%, respectively. ITs of 5–12 and 6–14 Ncm were found to be optimal for the commonly used φ1.5–1.7 mm OASs in the upper and lower interproximal areas, respectively. In the mid-palatal suture area, ITs of 11–16 and 20–25 Ncm were considered suitable for tapered φ1.5 mm and φ2.0 mm OASs, respectively. Although identified optimal IT ranges deserve the recommendations, care must be taken to monitor the IT during placement constantly.
1. Introduction
Orthodontic anchoring screws (OASs) used for various movements are simple to use and reliable. OASs are frequently employed as absolute anchorage devices in the buccal interproximal areas of upper and lower jaws, and the mid-palatal area for en masse retraction of the anterior teeth and distalization of the dental arch. Therefore, information about OAS stability is exceedingly important for the success of orthodontic treatment.
Insertion torque (IT) has been considered one of the factors affecting OAS stability [1,2,3]. Screws used in orthodontics generally have a diameter of 1.0–2.3 mm and a length of 3–15 mm [4,5,6]. Motoyoshi et al. [7] investigated φ1.6 × 8 mm OASs and recommended that the optimal IT was 5–10 Ncm and this range has been adopted by many clinicians and researchers. However, there have been variations in the literature. A previous study used tapered, self-tapping, φ2.0 × 6 mm OASs, and reported ITs of 25.6 ± 5.5 Ncm [8], whereas another study used cylindrical, self-drilling, φ1.5 × 7 mm OASs in the maxillary buccal alveolar area and reported ITs of 6.0 ± 3.2 Ncm [9]. Thus, the IT values vary greatly with the placement method and OAS design (screw diameter, length, and tapered or cylindrical form) [1,5,6,7,8,9,10,11,12,13,14,15]. Therefore, clinicians may be hesitant to apply these values in practice.
For instance, the mid-palatal area contains cortical bone that is thicker than the bone in the interproximal area, and thus higher ITs may be more suitable. Moreover, ITs for OASs may be different according to OAS designs or insertion techniques.
The aim of this review was to examine the previous literature and to determine the optimal ITs for successful OASs based on the areas of insertion and OAS design, and to identify the optimal IT ranges that deserve the recommendations in orthodontic practice.
2. Methods
2.1. Search Strategy
The addressed question was “What is the optimal IT range in various areas on the basis of OAS features?”. The initial PubMed/MedLine (National Library of Medicine, Bethesda, MD, USA) search, up to and including November 2021, was performed using the Mesh terms, “Orthodontic anchorage procedures”, “Bone screws”, and “Torque”. A Boolean operator “AND” was used to link different concepts together. This initial search yielded 102 articles. Search filters include the records with unavailable abstract or full-text, articles written in languages other than English, and studies using subjects other than human.
2.2. Eligibility Criteria
The eligibility criteria were as follows.
- Original articles except for review articles, and case reports, unpublished articles.
- Original articles in which OASs were placed in humans for orthodontic treatment.
- Original articles that reported success rates for OAS placement.
- Original articles that reported IT data for OAS placement.
The outcomes from these studies were evaluated to determine the optimal ITs for successful OASs based on the placement methods, OAS design and the areas of insertion (Figure 1).
3. Results
3.1. Selection
Review articles, case reports, unpublished articles, and articles written in languages other than English were excluded. Initially, the abstracts were evaluated by the author (Y.U.) to exclude articles that lacked the required data, such as ITs and success rates. Secondly, studies using animals or artificial bones instead of orthodontic patients for IT measurements were also excluded. This resulted in a total of 20 articles. In the third phase, an in-depth evaluation of these articles, including the main texts, was performed by the authors (Y.U. and Y.N.). The availability of the required data (e.g., IT values) was confirmed and similar articles from the same research institutions were excluded, which narrowed them down to 11 articles [1,6,7,8,9,10,11,12,13,14,15]. These 11 articles, which fulfilled the eligibility criteria, were reextracted.
The outcomes of these studies were examined to consider the relationships among ITs, success rates, OAS designs, and placement techniques in different sites.
3.2. Overview of the Selected Studies (Table 1)
The total number of patients in the selected studies ranged from 26 to 142, while the number of OASs ranged from 59 to 280. Among these studies, 81.8% (9/11) examined the buccal alveolar area, and included nine [1,6,7,9,10,11,13,14,15] and five [7,9,10,13,15] studies for the maxilla and mandible, respectively.
Table 1.
Summary of the adopted studies.
| Authors | Patients (n) | Mean Age (y) | Screws (n) | Placement Location | Methods | Loading | Definition of Success (or Failure) | Notes |
|---|---|---|---|---|---|---|---|---|
| Watanabe et al., 2017 [1] | 60 | 25.4 ± 10.5 | 120 | Maxillary buccal and lingual alveolar area | Self-Drilling | Loaded 3 months after placement | dislodgement of a screw during active treatment (failure) | female subjects only |
| Geshay et al., 2021 [6] | 26 | 27.4 | 82 | Maxillary buccal alveolar area | Self-Drilling | Immediate | if screws exhibited any degree of mobility (failure) | Comparison between anterior and posterior area using OASs of 3 mm in length |
| Motoyoshi et al., 2007 [7] | 30 | 15.9 ± 1.9 | 83 (adolescent) | Maxillary and Mandibular buccal alveolar area | Self-Tapping | Loaded from 2 to 4 weeks after placement (early-load) | if screw endured orthodontic force for 6 months or more without mobility | Comparison between adolescent and adult subjects |
| Loaded from 3 months or more after placement (late-load) | ||||||||
| 27 | 26.2 ± 5.6 | 86(adult) | Loaded from 2 to 4 weeks after placement (early-load) | |||||
| Uchida et al., 2021 [8] | 83 | 26.8 ± 9.8 | 161 | Mid-palatal suture area | Self-Tapping | Immediate | if screw endured the orthodontic force for 6 months or more | Comparison between φ1.2 mm and 1.5 mm in pre-drilling diameter |
| Lee et al., 2021 [9] | 142 | 20.7 ± 7.5 | 280 | Maxillary and Mandibular buccal alveolar area | Self-Drilling | 3 weeks after placement | if screw endured the orthodontic force for 6 months or more | Comparison among Cylindrical screws with and without dual thread |
| Sreenivasagan et.al., 2021 [10] | 31 | 27 ± 9 | 59 | Maxillary and Mandibular buccal alveolar area, Infrazygomatic crest and Buccal shelf | Self-Drilling | Immediate | unknown | - |
| Moghaddam et al., 2021 [11] | 31 | 18.5 | 62 | Maxillary buccal alveolar area | Self-Drilling | 6 weeks after insertion | useful up to the end of the treatment | Comparison according to surface characteristics |
| Di Leonardo et al., 2018 [12] | 40 | 17.3 (female) 15.7 male) | 80 | paramedian suture area | Self-Drilling | within one week after placement | unknown | Comparison according to force system |
| Yoo et al., 2014 [13] | 132 | 25.3 ± 8.0 | 227 | Maxillary and Mandibular buccal alveolar area | Self-Drilling | unknown | if screw endured the orthodontic force for 6 months or more | Comparison according to screw design |
| Son et al., 2014 [14] | 70 | 23.2 ± 7.7 | 70 | Maxillary buccal alveolar area | Self-Tapping | Immediate | when screw endured an orthodontic force applied for 6 months or more without clinical mobility | Comparison according to placement methods |
| 22.3 ± 7.4 | 70 | Self-Drilling | ||||||
| Suzuki and Suzuki 2011 [15] | 95 | 25.6 ± 6.7 | 120 | Maxillary and Mandibular buccal alveolar area, and Mid-palatal suture area | Self-Tapping | Healing period of at least two weeks | unknown | Comparison according to placement methods |
| 160 | Self-Drilling |
One of the nine maxillary studies also examined the lingual alveolar area [1]. In studies that investigated the alveolar area, all OASs were placed in the molar region, except for one study, which included the incisor area [13]. Among the remaining studies, three investigated the mid-palatal area [8,12,15], while one investigated the infrazygomatic crest and the buccal shelf areas [10].
Seven of the studies used a self-drilling method [1,6,9,10,11,12,13], two used a self-tapping method [7,8], and two used both methods [14,15]. Regarding the timing to load the orthodontic force, four studies employed immediate loading [6,8,10,14], while five used delayed loading [1,9,11,12,15]. The duration of the delay ranged from less than 1 week [12] to beyond 3 months [1,7] after placement. One study [7] compared the success rates on the basis of duration of healing after OAS placement in adolescent participants and used both early (2–4 weeks after placement) and late loading (≥3 months after placement).
4. Discussion
The abstracts of searched 102 studies were evaluated to exclude those articles that lacked the required data as ITs and success rates, and studies using animals or artificial bones instead of orthodontic patients were excluded further. This resulted in a total of 20 articles. Then, 11 articles [1,6,7,8,9,10,11,12,13,14,15] that fulfilled the eligibility criteria, were reextracted by an in-depth evaluation.
The outcomes of these studies were examined to consider the relationships among ITs, success rates, OAS designs, and placement techniques in different sites.
4.1. Placement Methods (Self-Drilling or Self-Tapping)
ITs and success rates of OASs placed in the buccal alveolar and mid-palatal areas are listed in Figure 2, Figure 3 and Figure 4. However, data from one study [10] were not included because the data for φ1.3 mm and φ1.5 mm OASs in the buccal alveolar area were unified, and separate values were not available.
In self-drilling OASs, the ITs ranged from 6.0 ± 3.2 Ncm [9] to 21.1 ± 2.2 Ncm [15], while the success rates ranged from 64.3% [6] to 100.0% [10,15]. Thinner, cylindrical, φ1.5 mm OASs had the lowest ITs [9], whereas the highest ITs were in the mid-palatal area [15]. Thus, IT in self-drilling OASs was affected not only by OAS diameter but also by the placement site. Short 3.0 mm OASs had the lowest success rates [6] (Table 2 and Table 3). Therefore, short, self-drilling OASs were found to increase the risk of failure.
Regarding self-tapping OASs, Motoyoshi et al. [7] used tapered φ1.6 × 8.0 mm OASs in the upper and lower buccal alveolar areas. In their study, OASs with a 1.0 mm pilot hole in maxilla (diameter ratio: bone drilling diameter/screw diameter × 100 [%] = 62.5%) and a 1.3 or 1.4 mm pilot hole in the mandible (diameter ratio = 81.3–87.5%) showed ITs and success rates of 7.6–8.9 Ncm and 91.8–95.0% in the maxilla and 8.5–8.8 Ncm and 91.9–100.0% in the mandible, respectively (except for the early-loading adolescent group) [7] (Table 2 and Table 3, Figure 2 and Figure 3). They also stated that the pilot-hole diameter in the mandible was extended from 1.3 mm to 1.4 mm when IT exceeded 10 Ncm depending on bone stiffness or cortical bone thickness. ITs and pilot-hole diameters are likely to affect the success rates in self-tapping OASs [7].
In the mid-palatal area, tapered φ2.0 × 6 mm OASs placed into 1.2 mm (diameter ratio = 60.0%) and 1.5 mm pilot holes (diameter ratio = 75.0%) had success rates of 94.5% (IT = 25.6 ± 5.5 Ncm) and 83.0% (IT not available), respectively, with a significant difference [8] (Table 2). Therefore, it is suggested that the IT should be controlled, using different pilot-hole diameters in different placement sites with varying cortical bone thickness, to prevent bone and OAS fracture.
Son et al. [14] compared the two placement methods in the maxillary buccal alveolar area using tapered OASs (φ1.6 × 8 mm) and found no significant differences in ITs and success rates between self-tapping (1.0 mm pilot hole) and self-drilling OASs (Table 2). In contrast, Suzuki and Suzuki [15] also examined ITs in φ1.5 × 8 mm self-drilling (tapered) and self-tapping OASs (cylindrical; 1.1 mm pilot hole) and reported that self-drilling OASs had higher ITs than self-tapping OASs in the maxillary buccal alveolar area [15] (Table 1 and Table 2).
This contradiction between the results of two studies [14,15] may be explained by the differences in OAS characteristics. One important difference was the diameter ratio for self-tapping OASs (62.5% in the Son et al. [14] study). The tightness for tapered OASs could increase the IT and may be considered equivalent to the ITs observed in self-drilling OASs. Another study by Suzuki and Suzuki [15] used a diameter ratio of 75.0% in self-tapping OASs [15]. Under such conditions, the diameter ratio may cause lower ITs that are not equivalent to the ITs of self-drilling OASs. Another difference was the shape of the OASs. Suzuki and Suzuki [15] used cylindrical self-tapping OASs in contrast to the tapered screws in the Son et al. study [14].
As a result, no significant differences in ITs and success rates were recognized between the self-drilling and self-tapping OASs if the same OAS shape was used. However, an in vitro study using the synthetic bone blocks by Tepedino et al. evaluated the relationship between insertion torque and stability of the self-tapping and the self-drilling OASs and concluded that the self-drilling OASs showed a higher maximum IT than the self-tapping OASs under the same conditions of bone-like support and same inner diameter [2].
Therefore, further investigation of the IT comparing both placement methods on orthodontic patients would be needed, although the placement method seemed to have no impact on the success rate.
4.2. Shapes and Dimensions of OASs
4.2.1. Tapered and Cylindrical OASs
Yoo et al. [13] compared tapered and cylindrical self-drilling φ1.5 × 7 mm OASs and reported significantly higher ITs in tapered OASs (8.3 ± 3.7 Ncm) than in cylindrical OASs (6.3 ± 2.8 Ncm) in the maxillary buccal alveolar area. They reported no significant differences in success rates [13] (Table 2 and Table 3, Figure 2 and Figure 3).
Suzuki and Suzuki [15] used tapered (self-drilling) and cylindrical (self-tapping) OASs of the same dimension (φ1.5 × 8 mm in the buccal alveolar area, and φ1.5 × 6 mm in the mid-palatal suture area), and found that tapered OASs had higher ITs (12.1 ± 3.1 Ncm, 15.7 ± 2.3 Ncm, and 21.1 ± 2.2 Ncm, respectively) than cylindrical OASs (7.2 ± 1.4 Ncm, 12.4 ± 1.2 Ncm, and 14.5 ± 1.6 Ncm) in all sites [15] (Table 2 and Table 3, Figure 2 and Figure 3).
In an in vitro study, Assad-Loss et al. [16] evaluated the fracture torques for several OAS designs (φ1.5–1.6 × 6–7 mm) and reported that the characteristic that most influenced the results was the ratio between the internal and external diameters. Cunha et al. [17] compared ITs in tapered and cylindrical φ1.6 × 8 mm OASs using low- and high-density bovine bone and reported that tapered OASs had higher ITs than cylindrical OASs in the high-density bone, but there were no significant differences in the low-density bone [17].
Ghorbanyjavadpour et al. [18] used finite element analysis to measure the stresses exerted on the bone with a 2 mm thick cortex assuming the maxillary interproximal area by tapered versus cylindrical OASs (φ1.6 × 8 mm) produced during insertion. They concluded that the greatest bone stress during insertion was caused by the self-drilling tapered OAS (10.18 MPa) and the lowest stress was exerted by the self-drilling cylindrical OAS (0.74 MPa) [18]. However, excessive insertion torques may cause bone stress and deformation, leading to congestion and necrosis or even resorption and remodeling around the screw, which leads to OAS failure [19,20]. Therefore, special attention must be paid during the placement of tapered OASs to prevent excessive IT.
Consequently, it was suggested that IT varies with the OAS shape and bone features and that the tapered form of OASs seemed to influence the IT. Therefore, tapered OASs were considered to have higher ITs than cylindrical OASs, although there was no difference in the success rates.
4.2.2. OAS Dimensions
The smallest OAS diameter in the selected studies was 1.3 mm, used in the buccal alveolar area in Sreenivasagan et al. [10]. They reported success rates of 87.5% and 72.7% for maxilla and mandible, respectively (Table 2 and Table 3, Figure 2 and Figure 3).
An in vitro study by Chen et al. [21] examined the mechanical properties of φ1.3 × 7 mm OASs (self-drilling) using artificial bone with densities of 20, 30, and 40 pcf, and reported ITs of 3.9, 5.2, and 10.0 Ncm, respectively.
An in vivo study by Suzuki et al. [22] used φ1.3 mm OASs of different lengths (5.0, 6.0, and 7.0 mm) considering root proximity, and evaluated the ITs and success rates. They divided the OASs into three groups on the basis of ITs (<5 Ncm, 5.1–10 Ncm, and >10.1 Ncm) and reported the success rates of 100.0%, 80.0%, and 50.0% for 5.0 mm OASs; 96.3%, 88.9%, and 66.7% for 6.0 mm OASs and 96.2%, 100.0%, and 83.3% for 7.0 mm OASs, respectively, in the maxillary buccal alveolar area [22]. The values for the mandibular buccal alveolar area were 64.3%, 25.0%, and 50.0% for 5.0 mm OASs, 100.0%, 77.8%, and 40.0% for 6.0 mm OASs, and 100.0%, 75.0%, and 62.5% for 7.0 mm OASs, [22]. The smaller φ1.3 mm OASs tended to have higher success rates, and resultantly lower ITs in the maxilla and mandible.
Large φ2.0 × 6 mm OASs used in one study in the mid-palatal suture area had a success rate of 94.5% and the highest ITs (25.6 ± 5.5 Ncm) [8] (Figure 4). An in vitro study by Nienkemper et al. [23] evaluated φ2.0 × 9 mm OASs using pig pelvic bone and reported that the ITs for insertion depths of 4 mm, 5 mm, and 6 mm were 15.4 ± 7.0 Ncm, 26.2 ± 10.4 Ncm, and 27.2 ± 14.1 Ncm, respectively. Considering these results [23], the high ITs of φ2.0 × 6 mm OASs [8] may be appropriate for regions with high-density bone, such as the mid-palatal suture area.
Another study used large OASs (φ2.0 × 12 mm) at the infrazygomatic crest and the buccal shelf area and reported ITs and success rates of 10.1 Ncm and 91.7% for the infrazygomatic crest, and 10.3 Ncm and 100.0% for the buccal shelf area, respectively [10]. An in vitro study by Wang et al. [24] measured the ITs of OASs (φ2.0 × 12 mm) placed into artificial bone, assuming the placement in the infrazygomatic area, and reported that the IT for cylindrical OASs was 10.9 Ncm. These results were similar to Sreenivasagan et al. [10]. Nevertheless, further in vivo studies are required to determine the optimal IT for longer OASs.
Geshay et al. [6] evaluated the shorter φ1.7 × 3 mm OASs placed in two maxillary buccal alveolar areas (between the canine and the first bicuspid, and between the second premolar and the first molar) and reported ITs of 7.4 ± 1.9 Ncm and 7.8 ± 1.2 Ncm and success rates of 64.3% and 70.0%, respectively (Table 2, Figure 2). In an in vitro study, Shah et al. [25] compared φ1.75 mm OASs of different lengths (3.0 mm and 6.0 mm) in synthetic bone and reported that longer OASs (6.0 mm) had significantly higher ITs than shorter OASs (3.0 mm). They also reported that as the cortical thickness or the bone density increased, this tendency also increased [25]. Thus, shorter OASs of 3.0 mm in length seemed to have lower ITs. Lower success rates (64.3–70.0%) of these OASs (3.0 mm) reported by Geshay et al. [6] (Table 2, Figure 2) might also be explained in this way. The authors would, therefore, like to recommend the use of OASs with a 3.0 mm length as a second option in anatomically difficult areas, such as small inter-root distances.
4.3. Placement Location
4.3.1. Buccal Alveolar Area
The buccal alveolar area is a frequent site for OAS placement in orthodontic practice because of the simplicity of the procedure and advantageous anchorage. Motoyoshi et al. [7] recommended ITs of 5–10 Ncm to improve the success rate of φ1.6 mm OASs. As diameters of 1.3–1.7 mm were used in this area [1,6,7,8,9,10,11,12,13,14,15], a reference IT range for various conditions would be desirable. The present review aimed to determine the optimal IT using the outcomes of previous studies [1,6,7,8,9,10,11,12,13,14,15].
Based on these studies, φ1.5–1.7 mm OASs were commonly used in this area, and ITs of 5–8 Ncm and 6–12 Ncm were optimal for cylindrical OASs in the upper and lower buccal alveolar areas, respectively. For tapered OASs, ITs of 6–12 Ncm and 8–15 Ncm were most suitable (Table 2 and Table 3, Figure 2 and Figure 3).
However, an in vitro study by Wilmes et al. [26] reported fracture torques of 20.1 ± 3.8 Ncm to 28.7 ± 2.4 Ncm for φ1.5–1.7 mm OASs. Dalla Rosa et al. [27] also reported that the yield torque to fracture (i.e., the boundary torque between the elastic region without permanent deformation and the plasticity region with that deformation on tightening the OASs) for φ1.5–1.7 mm OASs ranged from 16.3 ± 1.6 Ncm to 25.2 ± 2.8 Ncm. Therefore, the authors would like to recommend that ITs of 5–14 Ncm may be suitable for φ1.5–1.7 mm OASs in the buccal alveolar area, and the reported fracture and yield torques must be considered during placement.
4.3.2. Mid-Palatal Area
OAS placement in the mid-palatal area is used for various purposes, such as the retraction of anterior teeth and intrusion, distalization, and protraction of molars in the maxillary arch [28]. OAS placement in this area is also considered anatomically more favorable than the interproximal area [29]. However, as reported by Naya-Imai et al. [30], the sutured depth of mid-palatal suture should be considered using adequate imaging, such as cone-beam computed tomography, before OAS placement because there could be incomplete suture closure even in adults. Concerning this matter, they concluded that the OAS placement in mid-palatal sutures should be avoided regardless of age to prevent the insertion into unsutured areas.
The mid-palatal area has a thicker cortex, especially close to the median suture, which often requires pre-drilling before OAS placement for IT control [8,15]. Suzuki and Suzuki [15] used both cylindrical and tapered OASs (φ1.5 mm) in this area and reported lower ITs for the former. Cylindrical OASs had ITs and success rates of 14.5 ± 1.6 Ncm and 100.0%, respectively. For tapered OASs, Suzuki and Suzuki [15] and Uchida et al. [8] reported ITs and success rates of 21.1 ± 2.2 Ncm and 100.0% (φ1.5 mm OASs), and 25.6 ± 5.5 Ncm and 94.5% (φ2.0 mm OAS), respectively. Thus, a greater IT is indicated, even for OASs with smaller diameters, such as 1.5 mm, in this area (Table 2, Figure 4).
In an in vitro study, Wilmes et al. [26] reported that the maximum torques at the time of fracture for φ1.5 mm and φ2.0 mm OASs were 20.1 ± 3.8 Ncm and 49.2 ± 7.5 Ncm, respectively. In an in vitro study by Dalla Rosa et al. [27], the yield torque to fracture for φ1.5 mm OASs was 16.3 ± 1.6 Ncm. Based on these studies, the ITs of 21.1 ± 2.2 Ncm for φ1.5 mm OASs reported by Suzuki and Suzuki [15] exceeded the yield torque. Therefore, the use of φ2.0 mm tapered OASs with ITs of 20–25 Ncm is thought to be suitable in the mid-palatal suture area.
In the paramedian area, Di Leonardo et al. [12] reported ITs and success rates of 16.0 ± 5.2 Ncm to 18.1 ± 5.6 Ncm and 98.8%, respectively, for tapered OASs (φ1.7 × 8 mm) (Table 2, Figure 4). Nienkemper et al. [31] also assessed the stability of OASs (φ2.0 × 9 mm) and reported ITs of 14.1 ± 4.6 Ncm in the paramedian area. IT values in this area were likely to be lower than in the mid-palatal area. Chang et al. [32] also investigated the total and cortical bone thickness in the palate and demonstrated that the thickness tended to decrease laterally from the mid-palatal suture. Due to differences in the cortical thickness, ITs appeared to be lower in the paramedian area compared to the mid-palatal suture area. Further, Dalla Rosa et al. [27] reported that the yield torque to fracture for φ1.7 mm OASs was approximately 20 Ncm. Consequently, ITs of 12–18 Ncm were considered to be appropriate for φ1.7 mm tapered OASs in the paramedian area.
4.3.3. Infrazygomatic Crest and the Buccal Shelf Areas
The infrazygomatic crest and the buccal shelf area have some clinical advantages over alveolar interproximal areas [33,34], but few studies have investigated OASs in these sites. Sreenivasagan et al. [3] investigated the ITs of OASs (φ2.0 × 12 mm) in these areas and found that the ITs and success rates at the infrazygomatic crest (12 screws) and buccal shelf (four screws) areas were 10.1 Ncm and 83.3%, and 10.3 Ncm and 100.0%, respectively. Approximately 10 Ncm IT is considered optimal in these areas, but further studies are required to investigate these placement sites.
4.4. Limitation
This review was carried out carefully, nevertheless, some limitations still remained for further discussion. First, a small number of clinical studies was recruited and further investigation in the form of a systematic review using PRISMA is needed to obtain a more reliable conclusion. Secondly, the inadequate data such as unseparated IT data by drilling diameter and use of female subjects only in some studies caused the unsatisfactory investigation. Third, this review did not establish age and gender criteria.
5. Conclusions
The studies included in this review are indicated as follows. The ITs and success rates ranged from 6.0 ± 3.2 Ncm to 15.7 ± 2.3 Ncm and from 62.5% to 100.0% in the upper and lower buccal alveolar areas, respectively. For the mid-palatal area, the range was 14.5 ± 1.6 Ncm to 25.6 ± 5.5 Ncm and 83.0% to 100.0%, respectively. ITs of 5–12 Ncm and 6–14 Ncm were found to be optimal for the commonly used φ1.5–1.7 mm OASs in the upper and lower interproximal areas, respectively. In the mid-palatal suture area, ITs of 11–16 Ncm and 20–25 Ncm were considered suitable for tapered φ1.5 mm and φ2.0 mm OASs, respectively.
Although the above identified optimal IT ranges deserve recommendations in orthodontic practice, it was considered that care must be taken to monitor the IT during insertion constantly to avoid OAS and bone fractures for safety placement.
Author Contributions
Conceptualization, Y.U.; methodology, Y.U.; validation, Y.U.; formal analysis, Y.U.; investigation, Y.U. and Y.N.; resources, Y.U.; data curation, Y.U. and Y.N.; writing—original draft preparation, Y.U.; writing—review and editing, Y.U.; visualization, Y.U. and Y.N.; supervision, M.M.; project administration, Y.U.; funding acquisition, M.M. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Conflicts of Interest
The authors have no conflict of interest to declare.
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Figure 1.
Flow chart representative of the selecting process carried out for this review.
Figure 2.
Insertion torques (ITs) and success rates according to OAS features in the maxillary buccal alveolar area. Explanations for each bar graph in the figure were listed in the following order: screw dimensions, screw form, authors, and published year [1,6,7,9,11,13,14,15].
Figure 3.
Insertion torques (ITs) and success rates according to OAS features in the mandibular buccal alveolar area. Explanations for each bar graph in the figure were listed in the following order: screw dimensions, screw form, authors, and published year [7,9,13,15].
Figure 4.
Insertion torques (ITs) and success rates according to OAS features in the mid-palatal area. Explanations for each bar graph in the figure were listed in the following order: screw dimensions, screw form, authors, and published year [8,12,15].
Table 2.
Parameters regarding the OAS placement in Maxilla in each clinical study.
| Authors | Screws (n) | Placement Location | Diameter (mm) | Length (mm) | Bland (Country) | Shape | Methods | Insertion Torque: IT (Ncm) | Success Rate (%) | Pre-Drilling Diameter (mm) | Notes | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Watanabe et al., 2017 [1] | 50 | Maxillary buccal alveolar area | between 2nd bicuspid and 1st molar | 1.4 | 6.0 | Jeil Medical (Korea) | unknown | Self-Drilling | 8.7 ± 2.2 | 78.0 | - | female subjects only |
| 70 | Maxillary lingual alveolar area | 8.8 ± 2.3 | 91.4 | - | ||||||||
| Geshay et al., 2021 [6] | 42 | Maxillary buccal alveolar area | between canine and 1st bicuspid | 1.7 | 3.0 | Dentos (Korea) | Cylindrical | Self-Drilling | 7.8 ± 1.2 | 64.3 | - | - |
| 40 | Maxillary buccal alveolar area | between 2nd bicuspid and 1st molar | 7.4 ± 1.9 | 70.0 | - | |||||||
| Motoyoshi et al., 2007 [7] | 31 | Maxillary buccal alveolar area | between 2nd premolar and 2nd molar | 1.6 | 8.0 | Biodent (Janan) | Tapered | Self-Tapping | 8.9 ± 2.6 | 64.5 | 1.0 | early loading in adolescent subjects |
| 20 | Maxillary buccal alveolar area | 7.6 ± 2.7 | 95.0 | 1.0 | late loading in adolescent subjects | |||||||
| 49 | Maxillary buccal alveolar area | 8.8 ± 2.8 | 91.8 | 1.0 | early loading in adult subjects | |||||||
| Uchida et al., 2021 [8] | 73 | Mid-palatal suture area | corresponding area to 2nd premolar and 1st molar | 2.0 | 6.0 | Biodent (Janan) | Tapered | Self-Tapping | 25.6 ± 5.5 | 94.5 | 1.2 | placement torque data of φ1.2 mm pre-drilling screws only |
| 88 | None | 83.0 | 1.5 | |||||||||
| Lee et al., 2021 [9] | 91 | Maxillary buccal alveolar area | No mention in antero-posterior placement location | 1.5 | 7.0 | Biomaterials Korea (Korea) | Cylindrical | Self-Drilling | 6.0 ± 3.2 | 79.1 | - | - |
| 85 | Maxillary buccal alveolar area | 1.5 | 7.0 | Biomaterials Korea (Korea) | Cylindrical (Dual Thread) | Self-Drilling | 6.2 ± 2.6 | 88.2 | - | |||
| Sreenivasagan et.al., 2021 [10] | 12 | Infrazygomatic crest | - | 2.0 | 12.0 | Favanchor TM (India) | unknown | Self-Drilling | 10.1 | 83.3 | - | - |
| 32 | Maxillary buccal alveolar area | No mention in antero-posterior placement location | 1.3 and 1.5 | unknown | SK Surgicals (India) | unknown | Self-Drilling | 6.6 | 87.5 | - | data of φ1.3 and 1.5 mm OASs were unified | |
| Moghaddam et al., 2021 [11] | 31 | Maxillary buccal alveolar area | between 2nd bicuspid and 1st molar | 1.6 | 10.0 | Jeil Medical (Korea) | Cylindrical | Self-Drilling | 12.1 ± 6.3 | 90.3 | - | sandblasted acid-etched |
| 31 | 12.4 ± 5.8 | 83.9 | - | control | ||||||||
| Di Leonardo et al., 2018 [12] | 44 | Paramedian suture area | immediately posterior to the palatal rugae | 1.7 | 8.0 | Forestadent, (Germany) | Tapered | Self-Drilling | 17.1 ± 3.3 | 98.8 | - | use for distalize |
| 20 | 16.0 ± 5.2 | - | use for mesialize | |||||||||
| 16 | 18.1 ± 5.6 | - | use for RPE | |||||||||
| Yoo et al., 2014 [13] | 55 | Maxillary buccal alveolar area | including incisor area | 1.5 | 7.0 | Biomaterials Korea (Korea) | Tapered | Self-Drilling | 8.3 ± 3.7 | 80.0 | - | - |
| 55 | Maxillary buccal alveolar area | 1.5 | 7.0 | Biomaterials Korea (Korea) | Cylindrical | Self-Drilling | 6.3 ± 2.8 | 78.2 | - | - | ||
| Son et al., 2014 [14] | 70 | Maxillary buccal alveolar area | between 2nd bicuspid and 1st molar | 1.6 | 8.0 | Biodent (Janan) | Tapered | Self-Tapping | 7.0 ± 2.1 | 95.7 | 1.0 | - |
| 70 | Self-Drilling | 7.5 ± 3.1 | 95.7 | - | - | |||||||
| Suzuki and Suzuki 2011 [15] | 78 | Maxillary buccal alveolar area | No mention in antero-posterior placement location | 1.5 | 8.0 | Sistema Nacional de Implantes (Brazil) | Cylindrical | Self-Tapping | 7.2 ± 1.4 | 94.9 | 1.1 | - |
| 27 | Mid-palatal suture area | 6.0 | 14.5 ± 1.6 | 100 | - | |||||||
| 98 | Maxillary buccal alveolar area | 8.0 | BioMaterials Korea (Korea) | Tapered | Self-Drilling | 12.1 ± 3.1 | 91.8 | - | - | |||
| 30 | Mid-palatal suture area | 6.0 | 21.1 ± 2.2 | 100 | - | - | ||||||
Table 3.
Parameters regarding the OAS placement in Mandible in each clinical study.
| Authors | Screws (n) | Placement Location | Diameter (mm) | Length (mm) | Bland (Country) | Shape | Methods | Insertion Torque: IT (Ncm) | Success Rate (%) | Pre-Drilling Diameter (mm) | Notes | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Motoyoshi et al., 2007 [7] | 16 | Mandibular buccal alveolar area | between 2nd premolar and 2nd molar | 1.6 | 8.0 | Biodent (Janan) | Tapered | Self-Tapping | 8.5 ± 3.0 | 62.5 | 1.3 or 1.4 | early loading in adolescent subjects |
| 16 | Mandibular buccal alveolar area | 8.8 ± 3.0 | 100.0 | 1.3 or 1.4 | late loading in adolescent subjects | |||||||
| 37 | Mandibular buccal alveolar area | 8.8 ± 2.6 | 91.9 | 1.3 or 1.4 | early loading in adult subjects | |||||||
| Lee et al., 2021 [9] | 54 | Mandibular buccal alveolar area | No mention in antero-posterior placement location | 1.5 | 7.0 | Biomaterials Korea (Korea) | Cylindrical | Self-Drilling | 6.5 ± 2.8 | 87.0 | - | - |
| 50 | Mandibular buccal alveolar area | 1.5 | 7.0 | Biomaterials Korea (Korea) | Cylindrical (Dual Thread) | Self-Drilling | 8.0 ± 3.9 | 78.0 | - | |||
| Sreenivasagan et.al., 2021 [10] | 4 | Buccal shelf | — | 2.0 | 12.0 | Favanchor TM (India) | unknown | Self-Drilling | 10.3 | 100.0 | - | - |
| 11 | Mandibular buccal alveolar area | No mention in antero-posterior placement location | 1.3 and 1.5 | unknown | SK Surgicals (India) | unknown | Self-Drilling | 6.6 | 72.7 | - | data of φ1.3 and 1.5 mm OASs were unified | |
| Yoo et al., 2014 [13] | 50 | Mandibular buccal alveolar area | including incisor area | 1.5 | 7.0 | Biomaterials Korea (Korea) | Tapered | Self-Drilling | 9.2 ± 4.0 | 86.0 | - | - |
| 67 | Mandibular buccal alveolar area | 1.5 | 7.0 | Biomaterials Korea (Korea) | Cylindrical | Self-Drilling | 7.8 ± 3.5 | 82.1 | - | - | ||
| Suzuki and Suzuki 2011 [15] | 15 | Mandibular buccal alveolar area | No mention in antero-posterior placement location | 1.5 | 8.0 | Sistema Nacional de Implantes (Brazil) | Cylindrical | Self-Tapping | 12.4 ± 1.2 | 80.0 | 1.1 | - |
| 32 | Mandibular buccal alveolar area | 8.0 | BioMaterials Korea (Korea) | Tapered | Self-Drilling | 15.7 ± 2.3 | 87.5 | - | - | |||
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Uchida, Y.; Namura, Y.; Motoyoshi, M. Optimal Insertion Torque for Orthodontic Anchoring Screw Placement: A Comprehensive Review. Appl. Sci. 2023, 13, 10681. https://doi.org/10.3390/app131910681
AMA Style
Uchida Y, Namura Y, Motoyoshi M. Optimal Insertion Torque for Orthodontic Anchoring Screw Placement: A Comprehensive Review. Applied Sciences. 2023; 13(19):10681. https://doi.org/10.3390/app131910681
Chicago/Turabian StyleUchida, Yasuki, Yasuhiro Namura, and Mitsuru Motoyoshi. 2023. "Optimal Insertion Torque for Orthodontic Anchoring Screw Placement: A Comprehensive Review" Applied Sciences 13, no. 19: 10681. https://doi.org/10.3390/app131910681
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