Arch Width Changes Research Articles

Model analysis through two-dimensional evaluation of alveolar changes of untreated unilateral cleft lip and palate infants

The primary objective of therapeutic interventions for unilateral cleft lip and palate (UCLP) is to reestablish typical role and anatomy. The efficacy of nasoalveolar molding relies on the age at which it is initiated, thus early initiation is recommended. Evaluating the success of presurgical orthopedics involves assessing the after-treatment maxillary arch form and proportions in UCLP infants and comparing them to age-matched infants without clefts. Untreated UCLP cases exhibit various changes in the transverse and angular dimensions of the alveolar segment. Utilizing digital analysis of UCLP plaster casts through Photoshop software (version 24.0.0) can serve as an alternative method to predict changes in cleft width, arch width, and angular measurements in untreated cases.

Vertical and transverse treatment effects of Invisalign First system compared to Hyrax maxillary expanders with fixed appliances in mixed dentition patients.

To compare vertical and transverse changes in mixed dentition patients treated with the Invisalign First System (IFS) to those treated with a banded hyrax expander with fixed appliances (Hyrax) and control groups, and to assess the efficiency rate of dental arch expansion with IFS. The study included 80 mixed dentition patients, with 40 in each group (IFS and Hyrax) and 40 controls from the American Association of Orthodontists Foundation Craniofacial Growth Legacy Collection. Skeletal and dental vertical dimension changes and arch width changes between pretreatment (T1) and posttreatment (T2) were evaluated. Age at T1, time interval (T1-T2), sex, and Angle class did not significantly differ among the groups. Mandibular plane angle changes showed a similar reduction for the control and IFS groups, with no changes in the Hyrax group. However, the differences among the three groups did not reach statistical significance (P = .06). The Hyrax group showed significantly greater expansion in maxillary intermolar width compared to the IFS group, 4.4 vs 2.5 mm, respectively. The efficiency of maxillary expansion using IFS ranged from 52.3% to 76.87%. During the mixed dentition stage, no significant changes occurred in vertical dimensions among the control, Hyrax, and IFS groups. Although there was a trend suggesting a greater reduction in mandibular plane angle in the IFS group compared to the Hyrax group, this may not be clinically significant given the less than 1° difference. IFS can be a viable option for addressing mild arch width deficiencies, with a predictable increase in intermolar width of approximately 2.5 mm.

A Comparative Analysis of Arch Widths in Class I and Class II Malocclusion: Extraction vs. Non-extraction Treatment.

This study aimed to assess and compare dental arch widths in the anterior and posterior regions among patients undergoing extraction and non-extraction treatments for Class I and Class II malocclusions. A total of 40 patients were selected, with 10 in each of the categorized groups based on malocclusion type and treatment status. Dental arch widths were meticulously measured using a digital Vernier caliper at the canine and molar regions to ensure precise data collection. Statistically significant differences were noted when comparing mean inter-canine and molar widths between pre- and post-treatment periods among extraction cases in Class I malocclusion (p < 0.001). Conversely, there were no significant changes observed in arch widths among non-extraction cases in Class I malocclusion. Similarly, significant changes were observed in both extraction and non-extraction cases of Class II malocclusion when comparing mean inter-canine and molar widths between pre- and post-treatment periods (p < 0.05). After treatment, both Class I and Class II extraction cases showed an increase in inter-canine arch width, while intermolar arch width remained unchanged, suggesting that the treatment did not significantly alter the buccal corridor. Additionally, there were no notable changes in inter-canine arch widths between pre- and post-treatment in Class I non-extraction cases. However, the Class II non-extraction group exhibited increased upper and lower inter-canine arch widths after treatment.

Association of Mandibular Incisor Proclination and Mandibular Arch Widths with The Levelling of Curve of Spee

Background: In this study, we aimed to determine the changes in mandibular incisor proclination and mandibular arch widths after leveling the curve of Spee (COS). Methods: Patients included in this quasi-experimental study were scheduled for fixed orthodontic treatment with a non-extraction therapy in the mandibular arch, no posterior crowding, eruption of all mandibular teeth except third molars, no spacing and Little’s irregularity index greater than 2. The COS depth and mandibular arch widths (inter-canine and inter-molar widths) were measured on plaster casts and recorded in millimeters. Mandibular incisors inclinations were measured on a cephalometric radiograph according to the incisor mandibular plane angel (IMPA) and lower incisor to NB (L1) angle. The pre-treatment and post-treatment values were compared using paired sample T-test. Pearson correlation was used to analyze the association between COS changes and other variables. P-value &lt;0.05 was considered statistically significant. Results: A total of 58 subjects with an average age of 25.10±6.81 years participated in this study. COS depth values significantly reduced after treatment (2.34±0.78mm vs 1.75±0.56mm), (P&lt;0.001). Average IMPA and L1-NB values significantly increased following COS flattening (P&lt;0.001). Mandibular inter-canine and inter-molar widths also showed significant increase after treatment (P&lt;0.001). Pearson’s correlation revealed a significant and inverse correlation between COS changes and mandibular arch width and mandibular incisor proclination values (P&lt;0.001 for both). Patient’s age and gender did not have a significant effect on COS depth. Conclusion: Flattening of COS leads to an increase in lower incisor proclination and mandibular arch width.

Changes in the arch width and buccal corridor after fixed orthodontic treatment with Damon self-ligating system: premolar extraction vs. non-extraction.

Extraction vs. non-extraction is a crucial decision in orthodontic therapy. The aim of the present study was to investigate the changes in the dental arch width and buccal corridor after orthodontic treatment using extraction and non-extraction therapy with Damon self-ligating system. This retrospective study consisted of 35 patients (20 female and 15 male patients with median age of 12.5 years), treated by extracting 4 or 2 premolars, and 37 patients (16 female and 21 male patients with the median age of 12.8 years), treated without premolar extraction. Both groups were treated with Damon self-ligating system. Plaster models before (T0) and after (T1) treatment were measured, and the arch width values were determined at the level of the first molars, second premolars, canines and palatal rugae. Buccal corridor width was measured using the extraoral images at T0 and T1. Paired t-test was used for the analysis of the normally distributed data, and Wilcoxon Mann-Whitney U test was used for the data with non-normal distribution. Values of p<0.05 were set as statistically significant. The upper intercanine width increased significantly in both groups (p<0.01). In the non-extraction group, the arch width increased significantly in the maxillary second premolar and first molar region (p<0.01) as well as in the region of the canines (p=0.04), second premolars (p=0.01) and first molars (p<0.01) of the mandible. The buccal corridor decreased significantly in the non-extraction group (p<0.01). Premolar extraction in combination with Damon self-ligating system did not lead to reduction of the dental arch width in the maxilla, nor did it increase the size of the buccal corridors.

Effect of mandibular third molars on crowding of mandibular teeth in patients with or without previous orthodontic treatment: a systematic review and meta-analysis.

To assess the scientific evidence related to the role of the mandibular third molars on the late crowding of the lower anterior teeth in patients with or without previous orthodontic treatment. The secondary outcomes included changes in mandibular arch width and arch length. The databases PubMed, Scopus, ProQuest, and Google Scholar were searched from inception until April 2022. The included papers were studies evaluating the role of mandibular third molars on crowding of mandibular anterior teeth in patients of any age and gender, with mandibular third molars impacted or semi-impacted or erupted. Predetermined and prepiloted data collection forms were used to record the necessary information. Thirteen observational studies were included in the present systematic review. Most of them were assigned an overall risk of bias of moderate risk while the rest of them were at high risk. Four studies found an association between the presence of mandibular third molar and mandibular incisor crowding. Finally, seven studies were included in the quantitative analysis. Three different meta-analyses were conducted: for patients (a) with or (b) without previous orthodontic treatment and (c) in combination for patients with and without previous orthodontic treatment. According to the pooled results of all three meta-analyses, random effects model yielded a significant benefit for those without third molars compared to those with third molars regarding crowding, mean Little's irregularity index and mean arch length. Lower third molars may contribute to mandibular crowding and lower arch constriction. Further prospective research of high quality is needed to clarify the impact of third molars on anterior mandibular crowding.

A Comparative Evaluation of Mandibular Intercanine Arch Width Changes in Class I and Class II Division 1 Malocclusions Treated with Extraction— An Occlusogram Study

A Comparative Evaluation of Mandibular Intercanine Arch Width Changes in Class I and Class II Division 1 Malocclusions Treated with Extraction— An Occlusogram Study

Treatment effects after maxillary expansion using tooth-borne vs tissue-borne miniscrew-assisted rapid palatal expansion appliance

The study investigated the skeletal effects and root resorption in young adults with maxillary transverse deficiency after tissue-borne or tooth-borne mini-implant anchorage maxillary expansion. Ninety-one young adults with maxillary transverse deficiency, aged 16-25 years, were divided into 3 groups according to the treatment method: group A (n= 29) comprising patients treated with tissue-borne miniscrew-assisted rapid palatal expansion (MARPE), the group B (n= 32) comprising patients treated with tooth-borne MARPE, and the control group (n= 30) comprising patients only treated with fixed orthodontic therapies. Pretreatment and posttreatment cone-beam computed tomography images were used to assess the change of maxillary width, nasal width, first molar torque and root volume by paired t test in the 3 groups, respectively. Analysis of variance and Tukey least significant difference analysis were used to detect the changes of all descriptions among the 3 groups P<0.05. In the 2 experimental groups, we observed significant increases in the width of the maxilla, nasal, and arch width, as well as the molar torque. In addition, the height of the alveolar bone and the root volume decreased significantly. There were no significant differences in the maxilla, nasal, and arch width change between the 2 groups. Group B displayed more increases in buccal tipping, alveolar bone loss, and root volume loss than group A (P<0.05). Compared with groups A and B, the control group showed negligible tooth volume loss, with no expansion effect in both skeletal and dental descriptions. Tissue-borne MARPE produced the same expansion efficiency as tooth-borne MARPE. However, tooth-borne MARPE causes more dentoalveolar side effects in buccal tipping, root resorption and alveolar bone loss.

Evaluation of The Effect of Self- Ligating Bracket and Conventional Bracket Systems on The Arch Width And Buccal Corridor Changes (Clinical Comparative Study)

Evaluation of The Effect of Self- Ligating Bracket and Conventional Bracket Systems on The Arch Width And Buccal Corridor Changes (Clinical Comparative Study)

Association between arch width changes and long-term stability 20 years after orthodontic treatment with and without extractions.

To investigate long-term stability 20 years after orthodontic treatment and the association with arch width changes during treatment. This retrospective study investigated 103 patients with Class I and II malocclusions treated with fixed appliances with and without extractions. The sample was treated by one experienced orthodontist and collected from a private orthodontic office. Dental casts were obtained pretreatment (T1), posttreatment (T2), and long-term postretention (T3); they were scanned and converted to STL files. Measurements were evaluated in for the upper and lower arch: intercanine width (IC), intermolar (IM) width, Little's irregularity index (LII). There were 73 female and 30 male patients. Class I was present in 74 patients and Class II in 29. Average postretention time was 17.2 (±6.5) years after an average active retention time of 3.4 (±1.17) years. Extraction was performed in 55 patients while 48 received nonextraction treatment. Bonferroni Post Hoc test showed that LII in the upper and lower arches at T1 was significantly higher in the extraction group (P < .001). Upper and lower arch LII at T3 was slightly higher in extraction cases but remained under 2.05 mm. LII at T3 in the upper and lower arches showed negative correlation with IM T3 in the upper arch (Pearson, N = 103, P = .047), while IC in the upper and lower arches at T3 correlated with IM T3 in the upper and lower (N = 103, P < .001). Clinically relevant long-term stability in both arches was found in extraction and nonextraction cases. Intermolar width and its change during orthodontic treatment was an influential factor on long-term stability in extraction cases.

Assessment of Dimensional Changes in Arch Width and Palatal Rugae Pattern in Pre and Post Orthodontic Treatment

Introduction The three-dimensional alterations in the dentition and the entire dento-facial complex must be taken into account during orthodontic diagnosis and treatment planning. Palatal rugae gives us the reference plane we need for a longitudinal cast analysis and the structural stability of an orthodontic treatment is correlated with how much the palate surface has been deformed.Objective To evaluate the changes in arch width and quantify the dimensions positional variations and area of the rugae in extraction and non-extraction orthodontic cases.Methodology The study included a sample of 52 sets of pre and post models of orthodontically treated patients. Using digital calipers inter canine and inter premolar distances were measured in pre and post orthodontic treatment models and palatal rugae were carefully highlighted using 0.3 mm lead pencil. The highlighted palatal rugae were traced using matte acetate tracing sheet and graph sheet overlapped and measurements were done.Results A significant difference was found in the inter canine p lt0.026 and inter premolar p lt0.021 measurements in extraction group.Conclusion Inter canine width increased in extraction group. The antero posterior dimension of palatal rugae showed significant increase in dimension and increase in the surface area of palatal rugae pattern in non-extraction group.nbsp

Longitudinal changes in the dental arch width and symmetry in identical and fraternal twins

This study aimed to assess growth-related dental and symmetry changes in the dental arch within and between identical and fraternal twins in mixed and permanent dentition. Three-dimensional scanned dental models of eligible subjects were selected from the Forsyth-Moorrees Twin Study sample. This retrospective cohort study was carried out on 36 identical (18 pairs) and 28 fraternal (14 pairs) twins in mixed dentition and 36 identical (18 pairs) and 38 fraternal (19 pairs) twins in permanent dentition stages on the basis of the availability of the dental casts scanned each year from each group (Table I). Linear measurements from dental casts were performed in patients aged 8-16 years. Student t test and Pearson's correlation were used to compare the symmetry between and within the identical and fraternal twins. The resemblance and heritability patterns were retrospectively obtained from the Pearson correlation coefficient and Falconer's heritability test (H2= 2 × b). Adjusted mixed-effects estimates and 95% confidence intervals were calculated to test the association between age and dental parameters for both mixed and permanent dentition groups. Intercanine and intermolar widths significantly increased (P<0.05) during the mixed dentition but became stable after 13 years old. No statistically significant differences were found in arch symmetry between the 2 groups (ie, identical and fraternal) in any of the included measurements. Evaluation of the resemblance and heritability pattern showed nonsignificant results for all variables measured (H2 range, -0.67 to 0.56). The dental arch becomes wider at a higher rate in the canine region than the molar region in both the mixed and early permanent dentition. The dental arches of twins develop symmetrically, and their growth is not mainly affected by genetics. Asymmetrical teeth will maintain their relative position to reference planes throughout growth.

Transverse digital dental analysis of patients treated with self ligating Damon Q system with different patterns of retention- A longitudinal study with three years follow up

The study aims to evaluate and compare the maxillary and mandibular intercanine, interpremolar, intermolars width of pretreatment, posttreatment and two years after treatment, in patients treated with the Damon Q bracket system. Further, to compare the arch width changes during 3 years of follow up, in patients under complete retention for 3 years and the cases under retention for 2 years. A sample of 60 patients treated with all four first premolar extraction, using Damon Q bracket system were selected from the Department of Orthodontics. The pre-treatment and post-treatment models were collected. Patients were divided into Group I with 2-year retention and Group II with 3 years retention. The patients of these groups were recalled after 3 years. The records were taken and the models were scanned using an intraoral scanner. The transverse widths between the canines, premolar and molars were measured through a third-party software. The parameters were compared, within the group at three-time intervals and between the groups.The intercanine width increased, whereas, the interpremolar and intermolar width decreased in both the groups after treatment. However, the comparison of the parameters from post treatment to follow up showed that in Group I the inter canine width decreased, but the interpremolar, and intermolar width increased, whereas, in group II the values remained almost the same. The parameters tend to revert to their original position once the retention is removed, whereas the cases under retention showed negligible changes in arch width.

Comparative evaluation of transverse dental arch width changes with conventional and self-ligating brackets

Aim: This study aims at comparing the transverse width changes during leveling and aligning phase with conventional and self-ligating brackets. Materials and Methods: The study consisted of twenty samples. The sample was split into two groups. Group 1 consisted of ten samples treated with conventional brackets and ten samples treated with self-ligating brackets. Pretreatment and leveling aligning cast were used for the study. Measurement of transverse dimension was taken at two different regions, premolar and molar. Reference points were chosen according to the Pont's model analysis. In the premolar region, measurements were made from the distal pit of the first premolar on either side, and in the molar region, measurements were made from the mesial pit on either side. The overall values are compiled and compared among both the bracket groups. Results: The results of the study showed that there were changes in the interpremolar and intermolar arch width during leveling and aligning phase in both the bracket types. Conclusion: Since the arch width changes can affect the stability in the posttreatment phase, an orderly use of custom-made archwires from the very beginning is advised. The amount of arch width changes that occur with the treatment is irrespective of the bracket type, provided that other factors are maintained to be constant. Both conventional metal-ligated brackets and dual-activation self-ligating brackets provide an equal amount of changes in the dental arch transverse dimensions.

Occlusal changes in orthodontically treated subjects 40 years after treatment and comparison with untreated control subjects

The objective of this study was to compare the aging changes of the dental arches in orthodontically treated and untreated subjects after a 4-decade follow-up period. This retrospective study analyzed 2 groups. The treated group comprised 29 patients (11 male, 18 female) presenting with Class I or Class II malocclusions orthodontically treated with extractions of 4 first premolars. Dental models taken at pretreatment (12.84years), posttreatment (14.95years), and long-term posttreatment (51.37years) were evaluated. The untreated (control) group consisted of 22 untreated patients with dental models taken at 13.32, 17.82, and 60.95years of age. The dental models were digitized, and the following variables were evaluated: Little irregularity index, intercanine, interpremolar and intermolar widths, arch length, arch perimeter, overjet, and overbite. Interphase comparison of the treated group was performed with repeated measures analysis of variance and Tukey tests. Intergroup comparisons were performed using t tests (P<0.05). Crowding was corrected with treatment but relapsed significantly in the long term. Intercanine width increased with treatment and decreased in the long term. Interpremolar and intermolar widths, arch perimeter, and length decreased with treatment and continued to decrease long-term posttreatment. Overjet and overbite were corrected with treatment and remained stable in the long term. From posttreatment to long-term posttreatment, a greater crowding increase was observed in the treated group than in the untreated group. The treated group demonstrated a greater decrease in mandibular intercanine and maxillary and mandibular interpremolar widths than the untreated sample. Overbite increased in the treated group and decreased in the untreated group. The multiple regression analysis showed that previous 4-premolar extractions orthodontic treatment is significantly associated with anterior crowding in the long term. In the long-term, the treated patients showed relapse of crowding and a decrease in arch form. Long-term changes of treated patients were different from untreated subjects. Relapse might have contributed to greater changes in incisor crowding and arch widths observed in the treated patients.

Assessment of arch width changes in Class I and Class II Division 1 patients treated with fixed orthodontics

Background: The orthodontic treatment should aim to maintain the inter-canine and inter-molar width to that of the pre-treatment values. The study was conducted with objective to evaluate arch width changes in Class I and Class II patients treated with fixed orthodontics.&#x0D; Methods: This was a hospital-based cross-sectional study with two study groups. The first group included patients with Class I malocclusion, treated with four first premolar extractions and the second group included patients with Class II Div 1 malocclusion, treated with upper two first premolar extractions. The inter-canine and inter-molar width of the pre and post-treatment study model were measured. To compare the changes observed amongst two groups, independent samples t-test was performed. A paired sample t-test was used to evaluate the treatment changes within each group.&#x0D; Results: There was significant increase in inter-canine width in both maxillary and mandibular arches in both the groups. In Class I extraction group there was significant decrease in the inter-molar width in both maxillary and mandibular arches. The Class II Div1 maxillary extraction group also showed significant increase in inter-canine width in both maxillary and mandibular arches. In the same group there was decrease in post treatment&#x0D; Methods: This was a hospital-based cross-sectional study with two study groups. The first group included patients with Class I malocclusion, treated with four first premolar extractions and the second group included patients with Class II Div 1 malocclusion, treated with upper two first premolar extractions. The inter-canine and inter-molar width of the pre and post-treatment study model were measured. To compare the changes observed amongst two groups, independent samples t-test was performed. A paired sample t-test was used to evaluate the treatment changes within each group.&#x0D; Results: There was significant increase in inter-canine width in both maxillary and mandibular arches in both the groups. In Class I extraction group there was significant decrease in the inter-molar width in both maxillary and mandibular arches. The Class II Div1 maxillary extraction group also showed significant increase in inter-canine width in both maxillary and mandibular arches. In the same group there was decrease in post-treatment inter-molar width in both arches with significant decrease in the maxillary inter-molar width.&#x0D; Conclusion: There was increase in inter-canine width in both Class I extraction group and Class II Div 1 maxillary extraction group with decrease in inter-molar width in both the groups.&#x0D;

Orthopedic outcomes of hybrid and conventional Hyrax expanders.

To compare the effects of a hybrid miniscrew-supported expander versus a conventional Hyrax (CH) expander in growing patients. Forty patients were randomized into two groups: a hybrid Hyrax (HH) expander group using a Hyrax expander with two miniscrews and a CH expander group. The final sample had 18 subjects (8 female, 10 male; initial age of 10.8 years) in the HH group and 14 subjects (6 female, 8 male; initial age of 11.4 years) in the CH group. Cone-beam computed tomography examinations and digital dental models were obtained before expansion and 11 months postexpansion. The primary outcomes included the orthopedic transverse effects of expansion. Intergroup comparison was performed using analysis of covariance (P < .05). Significantly greater increases in the nasal cavity width, maxillary width, and buccal alveolar crest width were found for the HH group. No intergroup differences were observed for dental arch width or shape changes. The HH group showed greater increases in the nasal cavity width, maxillary width, and buccal alveolar crest width. No differences were observed for intermolar, interpremolar, or intercanine widths; arch length; or arch perimeter. Arch size and shape showed similar changes in both groups.

Dental arch changes comparison between expander with differential opening and fan-type expander: a randomized controlled trial.

To compare posterior crossbite correction frequency and dentoalveolar changes of the expander with differential opening (EDO) and the fan-type expander (FE). Two-arm parallel randomized controlled trial. Forty-eight patients from 7 to 11 years of age were allocated into two groups. Twenty-four patients were treated with the EDO and 24 patients were treated with the FE. Block randomization was performed. The study was single blind. Digital dental models were acquired before treatment and 6 months after rapid maxillary expansion. The primary outcomes were crossbite correction rate and maxillary arch width changes. Secondary outcomes were interincisal diastema, arch perimeter, length, size and shape, and mandibular dental arch changes. The final sample comprised 24 patients (13 female and 11 male; mean initial age of 7.62 years) in the EDO group and 24 patients (14 female and 10 male; mean initial age of 7.83 years) in the FE group. The crossbites were corrected in 100 per cent of subjects from EDO group and in 75 per cent of patients in FE group. EDO showed greater increases in maxillary intermolar region (P < 0.001), while the FE demonstrated greater increases in the intercanine distance (P = 0.008). Increase in mandibular inter-first permanent molar distance was slightly greater in the EDO group (mean difference of 0.8 mm). Changes in arch length and perimeter were similar in both groups. Both expanders changed the maxillary arch shape. The post-treatment arch shape was larger in the anterior region for FE and in the posterior region in the EDO group. Discomfort during activation was reported by 54 per cent of the participants. A temporary change in the nasal bridge was reported by one patient from FE group. Maxillary arch width and shape changes were distinct between the EDO and the FE. Greater transversal increases of the anterior and posterior regions were observed for the FE and the EDO, respectively. A slightly greater mandibular spontaneous expansion was observed for the EDO only at the molar region. NCT03705871.

Evaluation of Mandibular Arch Width Changes following Fixed Retention in Post Orthodontic Patients - a Randomized Clinical Trial

Background: Retention is an integral phase in which teeth are maintained in their newly adapted position for which retainers are inserted. Retainers are generally of two types: removable and fixed. Fixed retainers are indicated in the mandibular arch for an indefinite period specifically in the non-extraction cases. Changes in intercanine and intermolar widths are valuable parameters to evaluate the stability. The objectives of this study were to assess and compare the mandibular intercanine and intermolar width changes following orthodontic treatment after insertion of two types of fixed lingual retainers for one year. Methods: Total 54 subjects were recruited in which two types of fixed lingual retainers were inserted in the mandibular arch randomly. Intercanine and intermolar arch widths were measured by digital caliper of 0.01 mm accuracy. Data was analyzed by using Statistical Package of Social Sciences (SPSS V-21). Chi-square and independent t tests were used to compare baseline characteristics. Intercanine and intermolar widths were assessed and compared using independent t test, p-value ≤ 0.05 is considered as statistically significant. Results: Intercanine width increased from baseline to T4 in both retainers. When mean differences of intercanine width were compared between two retainers significant differences were observed at T1, T2, T3 and T4 with significant p-values (&lt; 0.05) and increased intercanine width with multistranded stainless steel wire (MSW) retainers. Conclusion: Mandibular intercanine width increases significantly in post retention phase with multistranded stainless steel retainers. Thus, fiber reinforced composite retainers are more effective in preserving the arch width changes.

Is There a Need to Increase Palatal Root Torque of Upper Incisors in Lingual Appliance? A Finite Element Analysis.

Objectives:To understand the effect of the biomechanical differences by assessing pre and post retraction torque, amount of retraction and arch width changes in both techniques.Methodology:A three-dimensional geometric model of maxilla with all upper teeth except first premolar was generated based on computed tomography radiograph of a dry skull using the computer program Hypermesh. 13.0. Virtual models of 0.022 ”Roth labial brackets and 0.018 ”ORMCO 7th generation lingual brackets; and for labial brackets 0.019 × 0.025” SS archwire and for lingual brackets 0.016 × 0.024” SS archwire were constructed. Sliding mechanics was used during en-masse retraction by applying a 300 g distal force on both sides of the dentition from canine to the second premolar brackets in the labial and lingual simulation. The finite element program ANSYS 12.1 was used to calculate the torque and displacement.Results:The results stipulated that in transverse direction there was lingual tipping of anteriors, mild buccal flaring in second premolars and first molars and lingual tipping in second molar in lingual appliance. In the sagittal plane, the greater distal movement of posteriors and an up-righting tendency of molars were observed in lingual appliance. Extrusion of anterior teeth were observed in both appliances. Regarding the premolars and first molars, labial movements and relative intrusion were observed in lingual appliance compared to labial appliance.Conclusion:In lingual treatment, it is crucial to increase the lingual root torque. The amount of retraction and arch widening were more in lingual appliance compared to labial technique.