Incisor Retraction Research Articles

Study on the effect of chin morphology on orthodontic treatment.

To investigate the effect of different soft-tissue morphologies on the treatment of skeletal class Ⅰ malocclusion patients by analyzing measurement data before and after treatment. Pre- and post-treatment lateral cephalograms of 55 adult female Angle class Ⅰ patients were collected in the Department of Orthodontics, Hospital of Stomatology, Jilin University from January 2012 to December 2020. Chin soft-tissue morphologies in the lateral cranial radiographs were used to divide the patients into an abnormal chin morphology group (flat and retracted chins, n=27) and a normal chin morphology group (rounded and prominent chins, n=28). Relevant soft- and hard-tissue indexes were selected to study in-group varieties and intergroup differences in the varying chin morphologies before and after treatment. The chin-lip angle, mandibular chin angle, mandibular chin vertex angle, PP-MP, LL-E, UL-E, Po-Pos, and B-B' thickness in the abnormal chin morphology group were significantly higher than those in the normal chin morphology group (P<0.05). Furthermore, m∶BMe and n∶B'Mes in the abnormal chin morphology group were signi-ficantly lower than those in the normal chin morphology group (P<0.05). After treatment, the mandibular chin angle, mandibular chin vertex angle, U1-SN, L1-MP, LL-E, UL-E, SNA, SNB, and B-B' thickness of the abnormal chin morphology group significantly decreased (P<0.05), whereas the nasolabial angle, m∶BMe, n∶B' Mes, and Po-Pos significantly increased (P<0.05). In the normal chin morphology group, the U1-SN, L1-MP, LL-E, UL-E, and B-B' thicknesses decreased significantly (P<0.05), whereas the nasolabial angle significantly increased (P<0.05). Among them, m∶BMe and n∶B' Mes were positively correlated. Chin morphology affects the formulation of treatment plans. Compared with the normal chin morphology group, the abnormal chin morphology group required a larger retraction of incisors. Although the chin of soft-tissue morphology is related to the morphology of bones, the changes in soft tissue chin after treatment cannot be directly predicted according to the bone changes. Soft-tissue chin morphology affects the aesthetic assessment of the soft-tissue lateral profile and the change in soft tissue before and after treatment. The method of predicting the change in soft-tissue chin after treatment should consider the morphology of the soft-tissue chin.

Changes in condylar position during orthodontic treatment depending on the amount of incisor retraction: a cone-beam computed tomography study.

Orthodontic treatment may be associated with temporomandibular disorders through changes in the condylar position. This study aimed to evaluate changes in the condylar position among different amounts of maxillary incisor retraction during orthodontic treatment using cone-beam computed tomography images. Fifty-four participants were enrolled and divided into minimal (n = 14), moderate (n = 20), and maximal (n = 20) retraction groups based on the amount of incisor retraction (< 1, 1-6, and > 6mm, respectively). Changes in condylar position before (T0) and after (T1) orthodontic treatment were assessed for the superior, anterior, posterior, and medial joint spaces (SJS, AJS, PJS, and MJS, respectively). Changes in joint spaces were compared between T0 and T1 in each group using paired t-tests and among the three groups using analysis of variance. Anterior movement of the condyle was observed in the maximal retraction group with a 0.2mm decrease in ΔAJS and a 0.2mm increase in ΔPJS, significantly greater than those in the minimal retraction group. The AJS and PJS showed statistically significant differences between T0 and T1 (P < 0.05) in the maximal retraction group. The condyle may show a statistically significant but clinically insignificant forward movement in the maximal incisor retraction group, whereas it was relatively stable in the minimal and moderate incisor retraction groups. More attention should be paid to the signs and symptoms of the condyle in patients with excessive incisor retraction during orthodontic treatment.

Three-dimensional finite element study on the effects of maxillary anterior two-step retraction and en-masse retraction with clear aligners

Objective: To investigate the effects of two-step retraction and en-masse retraction on tooth movement pattern of anterior teeth and posterior anchorage with clear aligners using three-dimensional finite element analysis. Methods: A finite element model of maxillary first premolar extraction case undergoing clear aligner treatment was established based on maxillofacial cone-beam CT data of a 24-year-old adult male with individual normal occlusion, who visited Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine for impacted mandibular third molar in June, 2022. The initial tooth displacement of five anterior retraction protocols (two-step with canine retraction, two-step with incisor bodily retraction, two-step with incisor retraction-overtreatment, en-masse bodily retraction, and en-masse retraction-overtreatment) were evaluated. Results: Two step with canine retraction caused distal tipping of the canine and labial tipping of the incisors (0.18° for central incisor and 0.13° for lateral incisor). Two step with incisor retraction caused mesial tipping of the canine. In two step with bodily retraction protocol, uncontrolled lingual tipping was found in central incisor (0.29°) and lateral incisor (0.32°). In two-step with incisor retraction-overtreatment protocol, the movement pattern of the incisors didn't change, but the inclinations reduced to 0.21° and 0.18°. En-masse retraction caused distal tipping of the canine. In en-masse bodily retraction protocol, uncontrolled lingual tipping was also found in central incisor (0.19°) and lateral incisor (0.27°). In en-masse retraction-overtreatment protocol, the central incisor showed controlled lingual tipping (0.02°) and the lateral incisor showed palatal root movement (0.03° labial inclination). Posterior teeth exhibited mesial tipping in all five protocols. Conclusion: En-masse retraction with incisor overtreatment was beneficial to incisor torque control in clear aligner treatment.

Labial and Palatal Pressure Changes in Extraction Cases Before and After Maxillary Incisor Retraction: A Quasi-Experimental Study.

To evaluate the changes in lip and tongue pressure before and after incisor retraction in patients undergoing orthodontic treatment with premolar extraction and incisor retraction. A Quasi-experimental study Place and Duration of the Study: Orthodontic Department at Dow University of Health Sciences, Pakistan, from January 2018 to November 2019. The study included 64 patients who were divided into two groups, (32 patients of class I and 32 patients of class II malocclusion). The lip and tongue pressures were recorded before and after incisor retraction with the help of Flexiforce sensor. The collected data were statistically analysed using the SPSS V-24 software. Shapiro-Wilk test was used to test the normality of data. The mean difference between lip and tongue pressure before and after incisor retraction was analyzed by Wilcoxon Signed Ranks Test. The difference in soft tissue pressures between class I and class II treatment groups was carried out using the Mann Whitney test. The mean pressure on the labial surface of incisors was significantly reduced after premolar extraction and incisor retraction (p ≤0.001). On the other hand tongue pressure on the palatal side of incisors was enhanced after incisor retraction (p=0.008) Comparing the differences between Angle's class I and class II malocclusion in mean pressure changes before and after incisor retraction revealed that the difference was not statistically significant on labial (p=0.58) or palatal side (p=0.28) of maxillary incisors. Reduced lip pressure and increased tongue pressure were observed after incisor retraction, whereas no significant change was seen in between the class I and class II cases. This signifies that orthodontic extraction affects the pressure changes on incisors and teeth do not remain in balance equilibrium at rest. Lip pressure, Tongue pressure, Orthodontic treatment, Flexiforce resistive sensor, Extraction, neutral zone.

Labial and Palatal Pressure Changes in Extraction Cases Before and After Maxillary Incisor Retraction: A Quasi-Experimental Study

Labial and Palatal Pressure Changes in Extraction Cases Before and After Maxillary Incisor Retraction: A Quasi-Experimental Study

Three-dimensional (3D) quantitative evaluation of the morphological changes of the upper anterior alveolar bone after retraction of a maxillary incisor

BackgroundThe purpose of this study was to assess morphological changes of the upper anterior alveolus after retraction of a maxillary incisor by applying three-dimensional (3D) superimposition of pretreatment (T1) and posttreatment (T2) cone-beam computed tomography (CBCT) data.MethodsThe study group was comprised of 28 patients with skeletal Class II malocclusion who underwent incisor retraction. CBCT data were acquired before (T1) and after (T2) orthodontic treatment. Labial and palatal alveolar thickness were assessed at the crestal, midroot and apical levels of the retracted incisors. Following three-dimensional (3D) cranial base superimposition, we performed surface modeling and inner remodeling of the labial and palatal alveolar cortex of the maxillary incisors. Paired t-tests were used to compare T0 and T1 bone thickness and volume measurements. Comparisons between labial and palatal surface modeling, inner remodeling and outer surface modeling were performed with paired t-tests in SPSS 20.0 version.ResultsWe observed controlled tipping retraction of the upper incisor. After treatment, the alveolar thickness on the labial sides increased and the palatal alveolar thickness decreased. The labial cortex showed a wider range of modeling area with a larger bending height and a smaller bending angle than the palatal side. The extent of inner remodeling was more prominent than the outer surface on both the labial and palatal sides.ConclusionsAdaptive alveolar surface modeling occurred in response to incisor tipping retraction on both the lingual and labial sides although these changes occurred in an uncoordinated manner. Tipping retraction of the maxillary incisors led to a reduction in alveolar volume.

Closure of first molar extraction spaces and correction of Class II malocclusion using anterior bite turbo and Class II elastics: A case report

At present, orthodontists are treating more adult patients with missing or hopeless first molars as these teeth have the highest incidence of decay in permanent dentition. This case report presented the closure of extraction spaces of four first molars in a patient with Class II malocclusion. High torque self-ligating brackets were used combined with anterior bite turbo and Class II elastics. According to the case report, the combination of anterior bite turbo and Class II elastics may have the possibility to correct bite deepening during space closure and allow further upper incisor retraction and Class II correction.

The Assessment of the Rank of Torque Control during Incisor Retraction and Its Impact on the Resorption of Maxillary Central Incisor Roots According to Incisive Canal Anatomy-Systematic Review.

Root resorption is one of the complications of orthodontic treatment, and has a varied and unclear aetiology. To evaluate the relationship between upper incisor resorption and contact with the incisive canal and the risk of resorption during orthodontic treatment associated with upper incisor retraction and torque control. According to PRISMA guidelines, the main research question was defined in PICO. Scientific databases MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials were searched for linking keywords: Resorption of roots incisive canal, Resorption of roots nasopalatine canal, Incisive canal retraction and Nasopalatine canal retraction. No time filters were applied due to the significantly limited number of studies. Publications in the English language were selected. Based on the information provided in the abstracts, articles were selected according to the following criteria: controlled clinical prospective trials and case reports. No randomised clinical trials (RCTs) or controlled clinical prospective trials (CCTs) were found. Articles unrelated to the topic of the planned study were excluded. The literature was reviewed, and the following journals were searched: American Journal of Orthodontics and Dentofacial Orthopedics, International Orthodontics, Journal of Clinical Orthodontics, Angle Orthodontist, Progress in Orthodontics, Orthodontics and Craniofacial Research, Journal of Orofacial Orthopedics, European Journal of Orthodontics and Korean Journal of Orthodontics. The articles were subjected to risk of bias and quality assessment using the ROBINS-I tool. Four articles with a total of 164 participants were selected. In all studies, differences in root length were observed after contact with the incisive canal, which was statistically significant. The contact of incisor roots with the incisive canal increases the risk of resorption of these roots. IC anatomy should be considered in orthodontic diagnosis using 3D imaging. The risk of resorption complications can be reduced by appropriate planning of the movement and extent of the incisor roots (torque control) and the possible use of incisor brackets with built-in greater angulation. Registration CRD42022354125.

Maxillary cortical bone remodeling characteristics in extraction patients: A cone-beam computed tomography study

This study aimed to evaluate labial and palatal cortical bone remodeling (BR) characteristics and related aspects of maxillary incisors after retraction, as these aspects are still controversial among orthodontists. Cortical BR and incisor movement of 44 patients (aged 26.18 ± 4.71 years) who underwent maxillary first premolar extraction and incisor retraction were analyzed using superimposed cone-beam computed tomography images. Labial BR/tooth movement (BT) ratios at the crestal, midroot (S2), and apical (S3) levels were compared using the Friedman test and pairwise comparisons. Multivariate linear regressions were used to explore the relationships between the labial BT ratio and several factors, including age, ANB angle, mandibular plane angle, and incisor movement patterns. According to the type of palatal cortical BR observed, the patients were divided into 3 groups: type I (no BR without root penetration of the original palatal border [RPB]), type II (BR with RPB), and type III (no BR with RPB). Student's t test was used to compare the type II and III groups. The mean labial BT ratios at all levels were<1.00 (0.68-0.89). This value at the S3 level was significantly smaller than that at the crestal and S2 levels (P<0.01). Multivariate linear regression indicated that the tooth movement pattern negatively correlates with the BT ratio at S2 and S3 levels (P<0.01). Type I was noted in 40.9% of the patients, and similar proportions exhibited type II (29.5%, 25.0%) or type III remodeling (29.5%, 34.1%). The retraction distance of the incisors in type III patients was significantly larger than in type II patients (P<0.05). The amount of cortical BR secondary to maxillary incisor retraction is less than the tooth movement. Bodily retraction may lead to lower labial BT ratios at the S3 and S2 levels. Roots penetrating the original border of the cortical plate are necessary for palatal cortical BR initiation.

Effectiveness of the Attachment Design and Thickness of Clear Aligners during Orthodontic Anterior Retraction: Finite Element Analysis.

Clear aligner treatment (CAT) provides orthodontic patients with a comfortable treatment alternative; however, this device has limited capacity to facilitate tooth movements. Although composite attachment has been proposed to facilitate tooth displacement, some of its aspects, such as aligner thickness, can influence CAT's precision. This work aimed to compare the stress distribution patterns produced by clear aligners with different thicknesses and composite attachment shapes during anterior retraction. Maxillary models consisting of clear aligners, maxillary teeth, and various attachments to the upper central incisor's labial surface were generated. Three models were built to mimic the retraction of the upper central incisors. Each had a distinct attachment design (rectangular attachment, ellipsoid attachment, and pyramidal attachment) and various aligner thicknesses (0.75, 0.85, 0.95, 1.05, and 1.15 mm). Upper central incisor retraction was accomplished using clear aligners. Finite element analysis was used to examine the built models. Stress distribution pattern was examined. The greater the thickness of the aligner, the higher the stress experienced by the teeth. The 0.75 mm-thick aligner induces the lightest stress with a minimum of 0.0037623 MPa and a maximum of 0.32859 MPa. Meanwhile, the 1.5 mm-thick aligner has the highest stress with a minimum of 0.004679 MPa and a maximum of 0.43858 MPa. The force distribution on rectangular attachments appears evenly distributed. The maximum pressure force on rectangular attachments has a minimum of 0.38828 MPa, which is smaller than the maximum on ellipsoid and pyramidal attachments at 0.40933 and 0.45099 MPa, respectively. The best aligner thickness is 0.75 to 0.85 mm for anterior retraction. An aligner with 0.95 mm thickness can still be used when a remarkable amount of tooth movement force is needed; however, this exception is only applicable to a limited number of clear aligner trays. The ellipsoid attachment is the best type of attachment because the resulting force is substantial and evenly distributed.

Maxillary molar distalization with a 2-week clear aligner protocol in patients with Class II malocclusion: A retrospective study

This study aimed to investigate the efficacy of molar distalization with or without anterior teeth retraction. Forty-three patients who received maxillary molar distalization with clear aligners were retrospectively enrolled and further divided into 2 groups: a retraction group (with maxillary incisor retraction ≥2 mm in ClinCheck) and a nonretraction group (without anteroposterior movement or with the labial movement of the maxillary incisor in ClinCheck). Pretreatment and posttreatment models were collected and laser-scanned to obtain the virtual models. Three-dimensional digital assessments of molar movement, anterior retraction and arch width were analyzed in the reverse engineering software Rapidform 2006. To calculate the efficacy of tooth movement, the achieved tooth movement assessed on the virtual model was compared with the predicted tooth movement in ClinCheck. The achieved efficacy rates of molar distalization for the maxillary first and second molars were 36.48% and 41.94%, respectively. There was a significant difference in molar distalization efficacy between the retraction group (31.50% at the first molar and 35.63% at the second molar) and the nonretraction group (48.14% at the first molar and 52.51% at the second molar). In the retraction group, the efficacy of incisor retraction was 56.10%. The efficacy of dental arch expansion was more than 100% at the first molar levels in the retraction group and at the second premolar and first molar levels in the nonretraction group. There is a discrepancy between the outcome and the predicted maxillary molar distalization with clear aligners. The efficacy of molar distalization with clear aligners was significantly affected by anterior teeth retraction, and the arch width significantly increased at the premolar and molar levels.

Does mandibular advancement with clear aligners have the same skeletal and dentoalveolar effects as traditional functional appliances?

BackgroundThe study aimed to compare the dentoskeletal effects of Vanbeek Activator, Herbst, Twin-Block and Mandibular Advancement with clear aligners in children with skeletal Class II malocclusions.MethodsA sample with sixty-three patients (37 males, 26 females) was included and divided into untreated control group (C, n = 12), Vanbeek Activator group (V, n = 14), Herbst group (H, n = 11), Twin-Block group (TB, n = 12) and MA group (MA, n = 14). Cephalometric analysis and Johnston Pitchfork analysis were performed to quantify the skeletal and dentoalveolar components in molar relationship and overjet correction. Compare the differences of cephalometric data and Johnston-analysis data.ResultsThe treatment changes showed significant differences in SNB, FH-NP, NA-PA, Co-Go, Co-Pog, ANB, lower facial height ratio, U1-PP, U6-PP, L1-MP and U1-L1. All the appliances improved overjet relationships significantly (Vanbeek, Herbst, Twin-Block and MA were 2.77 mm, 5.53 mm, 4.73 mm and 3.66 mm respectively) with significant retraction of maxillary incisors. The lower incisor displacement of group V and MA was negative, while that of group H and TB was positive and there were significant differences. Molar relationships were also improved by 3.45 mm, 6.85 mm, 3.48 mm and 0.92 mm for Vanbeek, Herbst, Twin-Block and MA. Mandible displacement showed a trend of group H > TB > V > MA. The displacement of maxillary molars in group H was greater than that in group C, TB and MA, and that of mandibular ones was greater than that in group C, V and MA, significantly. Herbst, Twin-Block and MA have more significant dentoalveolar effect than Vanbeek, while Vanbeek has more skeletal effect than the others especially in restraining maxillary growth.ConclusionsFour appliances are all effective in mandibular advancement, modification of class II molar relationship and deep overjet, with unavoidable increase in lower facial ratio. Vanbeek Activator has the most skeletal effects. Vanbeek and MA have a good control of mandibular incisors while more compensatory lower incisors proclination in Herbst and Twin-Block. Herbst has greater maxillary molar distalization. MA allows aligning and leveling meanwhile leading the mandible forward.

A Fractal Dimension Analysis to Evaluate the Change in the Alveolar Osseous Structure of Mandibular Incisors after Orthodontic Treatment: A Retrospective Study

Introduction: As bone traces tooth movement during orthodontic treatment, leading to biological response of the surrounding tissues of the teeth resulting in remodelling of the socket, favourable bone response is expected after incisor retraction. Orthodontic treatment causing changes in alveolar bone can be evaluated using Fractal dimension (FD) analysis, a mathematical method of information processing, where the input data is in the form of an image and generated information is displayed as numbers. Aim: To evaluate changes in the trabecular structure of alveolar bone after incisor retraction in the mandibular symphysis region in adult patients using fractal analysis. Materials and Methods: This retrospective study was conducted with digital Orthopantomogram (OPG) of 30 patients with class I and class II malocclusion with mandibular incisor protrusion treated with extraction and retraction of anterior teeth were taken with standard protocols at the three different periods, before orthodontic treatment (T0), before retraction (T1) and after retraction of anterior teeth (T2) included in the study. Regions of interest were located between the apices of mandibular incisors. FD was calculated using ImageJ software. Statistical Analysis was carried out by repeated Analysis of Variance (ANOVA) test and post-hoc test. Results: Total of 30 cases were selected, out of which 15 were males and 15 females with the mean age of 21±2 years. FD values of the alveolar bone of mandibular incisors at T0 were 1.470±0.09 which reduced to 1.390±0.09 at T1 and to 1.350±0.08 at T2. This overall changes in FD values were significant (p-value=0.001). Conclusion: Fractal dimension analysis demonstrate significant changes in bone trabeculation of the mandibular symphysis region before and after orthodontic treatment. It has valuable impact in the cases of fenestration, dehiscence’s, and osteoporosis.

Root resorption of maxillary incisors after en masse intrusion and retraction with controlled tipping versus bodily movement in adults.

The purpose of this study was to evaluate and compare the incidence of orthodontically induced inflammatory root resorption (OIIRR) after en masse maxillary incisors intrusion and retraction with controlled tipping versus bodily movement using cone beam computed tomography (CBCT). This study is a retrospective study performed on CBCT scans of 36 adult females who had their maxillary first premolars extracted followed by en masse anterior retraction and intrusion using labial biocreative therapy type II. Subjects were divided into two groups of 18 subjects each based on the type of tooth movement required during en masse retraction: Group I; the controlled tipping group, and Group II; the bodily movement group. The amount of intrusion, crown and root retraction, change in incisor inclination, and difference in tooth length was measured from the CBCT scans. Independent t tests were used to compare the measurements between the two groups. Pearson rank correlation analysis was applied to identify the relationship between the mean dental changes and the mean changes in tooth length for all four upper incisors. OIIRR was found in all four maxillary incisors in both groups. No significant differences were found between the two groups. OIIRR was positively correlated to the amount of root apex retraction and negatively correlated to the change in incisor inclination. Anterior retraction and intrusion lead to obvious root resorption affecting all maxillary incisors. No significant differences were found between the two groups. Careful clinical monitoring is needed for patients requiring anterior retraction with intrusion with maximum anchorage.

Rate of upper incisor retraction in Class II division 1 patients managed with palatal versus buccal miniscrew supported segmental orthodontics: Randomized parallel clinical trial

This study was conducted to compare maxillary incisor retraction rates using buccal orthodontics with segmented arch approach supported by a buccal or palatal mini-screw in non-growing Class II Division 1 patients during a 3-month period. All patients between September 2018 and December 2021 with following criteria were included: non-growing class II division 1 protrusion, indication for premolar extraction, no or little crowding, normal overbite, no previous orthodontic treatment, no systematic disease, good oral hygiene, no periodontal problems or oral habits. Mini-implant was inserted buccally or palatally between upper second premolar and first molar bilaterally. Incisor retraction was manipulated by a 200-gram force through a nickel-titanium closed-coil spring extended from the mini-implant to the segmental design. Study casts were made before retraction and after every 4 weeks (T0: baseline, T1: 4 weeks, T2, 8 weeks, T3: 12 weeks). A repeated measures ANOVA was performed for total comparison of data (mm of retraction) on 3D casts. A pairwise t test with Bonferroni correction was used for comparison between two experimental periods for the same group. An independent samples t-test was also used for comparison between two groups for the same experimental period. Of 30 patients meeting the eligibility criteria, only 28 were included with mean age 16±2.5 years. Repeated measures ANOVA revealed significant differences in incisor retraction between the time intervals for both buccal and palatal groups (P=0.001). In addition, the paired-sample t test indicated a significant difference between each time interval for both the buccal and palatal groups (P=0.001), except between T3 and T2 for the palatal group (P=0.09). The independent sample t-test revealed significant differences between the buccal and palatal groups at T1 (Mean: 0.55 [0.355-0.748],=0.001) and T2 (Mean: 1.4 [0.91-1.88], P=0.001); whereas no significant difference was found at T3 (Mean: 1.15 [0.67-1.63], P=0.945). Anterior retraction using a segmental palatal model with mini-screws was effective regardless of the buccal or palatal situation of the minivis. Retraction of incisors with palatal miniscrews was significantly faster in the first two months.

Relationship between premolar extraction on the dimension of upper airway and tongue posture in skeletal class II malocclusion

Correction of skeletal Class II malocclusion with camouflage orthodontic treatment generally requires the extraction of the maxillary first premolars to provide space for retraction of the maxillary incisors. Retraction of incisors changes the position of the incisors and the dimensions of the dental arch, which can cause changes in tongue posture and affect the upper airway. The purpose of this study was to determine the relationship between premolar extraction on the dimensions of upper airway and tongue posture in skeletal Class II malocclusion. This study was designed as a retrospective cohort using lateral cephalometric radiographs before and after orthodontic treatment. The samples in this study consisted of 44 samples of adult patients (n = 44) aged 18-40 years, who were divided into 2 groups: 22 subjects treated without premolar extraction and 22 subjects treated with premolar extraction. Lateral cephalometric radiographic analysis were used to measure the dimensions of the upper airway by analyzing superior posterior airway space (SPAS), middle airway space (MAS), inferior airway space (IAS), vertical airway length (VAL), and tongue posture (tongue length and height tongue) using imageJ software. No Statistically significant different changes were observed as seen from the following results: SPAS (p = 0.709), MAS (p = 0.365), IAS (p = 0.562), (p = 0.401), tongue length (p = 0.578), tongue height (p = 0.086) in the sample group without extraction premolar. No significant alterations in the upper airway and tongue posture measurement were observed in the sample group with extraction premolar. Premolar extraction with retraction on upper incisors did not affect upper airway dimensions and toung posture in skeletal Class II malocclusion.

The three-dimensional displacement tendency of teeth depending on incisor torque compensation with clear aligners of different thicknesses in cases of extraction: a finite element study

BackgroundDespite the popularity of clear aligner treatment, the effect of the thickness of these aligners has not been fully investigated. The objective of this study was to assess the effects of incisor torque compensation with different thicknesses of clear aligner on the three-dimensional displacement tendency of teeth in cases of extraction.MethodsThree-dimensional finite element models of the maxillary dentition with extracted first premolars, maxilla, periodontal ligaments, attachments, and aligners were constructed and subject to Finite Element Analysis (FEA). Two groups of models were created: (1) with 0.75 mm-thick aligners and (2) with 0.5 mm-thick aligners. A loading method was developed to simulate the action of clear aligners for the en masse retraction of the incisors. Power ridges of different heights were applied to both groups to mimic torque control, and the power ridges favoring the translation of the central incisors were selected. Then, we used ANSYS software to analyze the initial displacement of teeth and the principle stress on the PDL.ResultsDistal tipping, lingual tipping and extrusion of the incisors, distal tipping and extrusion of the canines, and mesial tipping and intrusion of the posterior teeth were all generated by clear aligner therapy. With the 0.5 mm-thick aligner, a power ridge of 0.7 mm could cause bodily retraction of the central incisors. With the 0.75 mm-thick aligner, a power ridge of 0.25 mm could cause translation of the central incisors. Aligner torque compensation created by the power ridges generated palatal root torque and intrusion of the incisors, intrusion of the canines, mesial tipping and the intrusion of the second premolar; these effects were more significant with a 0.75 mm-thick aligner. After torque compensation, the stress placed on the periodontal ligament of the incisors was distributed more evenly with the 0.75 mm-thick aligner.ConclusionsThe torque compensation caused by power ridges can achieve incisor intrusion and palatal root torque. Appropriate torque compensation with thicker aligners should be designed to ensure bodily retraction of anterior teeth and minimize root resorption, although more attention should be paid to the anchorage control of posterior teeth in cases of extraction.

Alveolar Bone After Intrusion and Retraction of Anterior Teeth: Fractional Dimensional Analysis

Objective: To evaluate changes in the trabecular structure of alveolar bone in maxillary incisors segment after maxillary incisor intrusion and retraction with fixed orthodontic treatment in adult patients using fractal dimensional analysis (FD). Methods: This study was conducted using a digital panoramic radiograph of 30 patients (Age Group 18 - 25 years) with class II malocclusion with maxillary incisor protrusion treated with intrusion and retraction of anterior teeth. Panoramic radiographs were taken with standard protocols at the three different periods, before orthodontic treatment (T0), immediately after alignment but before intrusion and retraction (T1), and after intrusion & retraction of anterior teeth (T2). Regions of interest were located between the apices of maxillary incisors. Findings: Fractal dimension (FD) was calculated using ImageJ software. Repeated Measure ANOVA test; indicates significant difference at p0.05. FD values of the alveolar bone of maxillary incisors at T0 were 1.312  0.09, which reduced to 1.273  0.10 at T1 and again increased to 1.325  0.07 at T2. This overall change in FD values was significant (p=0.050. Novelty: The study revealed that, during orthodontic tooth movement, the alveolar bone around the teeth was reduced. However, after a period of bone recovery, the reduced bone density recovered to its previous state from before the orthodontic treatment. Keywords: Alveolar bone; Bone trabeculae; Fractal analysis; Orthodontic tooth movement; Panaromic radiograph

COMPARISON OF MAXILLARY AND MANDIBULAR ARCH FORM IN CLASS I, CLASS II AND CLASS III PATIENTS REPORTING FOR TREATMENT

Background: - Archforms play an important role in orthodontic diagnosis and treatment planning. Limitations for tooth movement, especially for incisor retraction arise from the basal bone where teeth are rooted. If teeth move excessively over the alveolar bone, periodontal complications and unstable treatment effects, even the tooth exfoliation may occur. The aim of this study is to compare the maxillary and mandibular arch forms of class I, class II, class III patients reporting for treatment in Saveetha dental college and hospitals, Chennai, Tamil nadu from June 2019 to January 2021.Materials and method: - It is a single centered retrospective study conducted in a private dental institution, Chennai. The data of patients reporting was collected from the dental hospital management system and the arch form was compared. Ethical clearance for this study was obtained from the Institutional review board. Statistical analysis was obtained using SPSS version 20.Results:-The results showed that there is no significant correlation in maxillary and mandibular arch forms among Angle’s Class I, Class II, and Class III malocclusion. Class I occlusal relationship was the most common class of malocclusion followed by Class II malocclusion. Ovoid arch was more common in class I, Class II, Class III malocclusion. Conclusion: - Within the study limits, it was concluded that Class I occlusal relationship was the most common class of malocclusion followed by Class II. Ovoid arch was more common in class I, Class II, Class III malocclusion followed by v-shaped and square arch forms in class I and class III and V-shaped arch was more prominent in class II patients.

Comparisons of maxillary incisor retraction effects for patients with first premolar extractions between Damon Q and Invisalign®: A retrospective study.

Torque control of maxillary incisors is very important in maxillary protrusion patients with first premolars extraction, but the efficacy of maxillary incisor retraction of clear aligners is still controversial now. This retrospective study was aimed to compare the retraction effects between Damon Q and Invisalign® appliances in patients with first premolar extractions. 59 patients (33 cases with Damon Q and 26 cases with Invisalign®) with first premolar extraction were selected in this study. Subsequently, patients of each group were allocated into three subgroups according to the pretreatment value of U1-NA (°). The retraction effects of maxillary incisors and upper lips were accessed by the variations of cephalometric, overbite and overjet measurements. Treatment duration with Invisalign® (31.4 ± 6.4 months) was longer than Damon Q (27.7 ± 6.3 months) (P = .03). The angular measurements, U1-NA (°) and U1-SN (°) showed more lingual crown inclinations in Invisalign® group than Damon Q group (P ≤ .04). When evaluating linear measurements, the retractions of the maxillary incisors and upper lip positions showed no significant differences (P ≥ .13). Invisalign® group also showed more lingual crown retractions and labial root deviations compared to Damon Q group in subgroup Ⅲ (P ≤ .037). As regards to the molar relationship, Invisalign® displayed less Class Ⅰ molar relationship than Damon Q group. The increased overbite of anterior incisors was also showed in the Invisalign® treatment group (P ≤ .047). Invisalign® was not sufficiently effective in retracting maxillary incisors compared with Damon Q appliances. Invisalign® led to more lingual inclination movement and increased overbite.