Long-term changes of the anterior palatal alveolar bone after treatment with bialveolar protrusion, evaluated with computed tomography

Combined distalization and lingual cortex remodeling during mandibular growth for facial profile improvement: a case report

Borderline crowding poses a challenge in deciding whether or not to prescribe premolar extraction. This case report describes the two-phase nonextraction orthodontic treatment of an 11-year-old girl with a hyperdivergent skeletal Class I pattern exhibiting anterior crowding and moderate lip protrusion. The initial phase of treatment included maxillary and mandibular expansion to correct the transverse discrepancy as an early intervention. Subsequently, comprehensive treatment was initiated at the age of 13 years, with fully erupted permanent second molars and growth potential remaining. Phase II treatment involved a second round of maxillary expansion, followed by simultaneous bimaxillary total arch intrusive distalization, using interradicular, temporary skeletal anchorage devices to correct dental crowding and improve the facial profile. Although the limited retromolar space posed a challenge to mandibular tooth distalization, gradual bone remodeling was observed in the lingual cortex of the mandibular body, enabling sufficient orthodontic tooth movement without noticeable side effects. After 4 years 3 months of treatment, her dental crowding was relieved, with significant improvement in the facial profile and proper occlusion. The treatment outcomes remained stable 2 years 4 months after retention.

A retrospective study of alveolar bone remodelling after anterior retraction in orthodontic tooth extraction cases with clear aligners and fixed appliances

OBJECTIVES

To evaluate alveolar bone dimensions and its relationship with tooth movement (retraction, intrusion and torque) during orthodontic treatment with fixed appliance and clear aligners.

METHODS

Thirty-two patients were included in this retrospective clinical study. Cone beam computed tomography (CBCT) was collected before and after treatment to measure the volume of dehiscence and fenestrations in the maxillary anterior region, anterior alveolar bone thickness and height and degree of tooth movement. Rank-sum tests were used to compare the differences in alveolar bone defect volumes between clear aligners and fixed appliance, multiple linear regression analysis was used for study evaluation, and kappa statistics were used to assess internal consistency and test-retest reliability.

RESULTS

Post-operatively, most alveolar bone defects occurred on the labial side. The incidence of bone fenestration was 23.96% in the clear aligner group and 26.18% in the fixed appliance group, which was higher than the incidence of bone dehiscence (5.21%). The labial bone height decreased by 0.272 mm, and the palatal bone height increased by 0.617 mm for every 1 mm downward intrusion of the anterior tooth apex in the fixed appliance group. In the clear aligner group, there was no significant change in the labial bone height, and the palatal bone height decreased by 0.447 mm for every 1 mm of anterior tooth retraction coronally.

CONCLUSIONS

In the fixed appliance group, anterior tooth intrusion and retraction may have led to alveolar bone resorption by its compression at the cervical level. This study provides a three-dimensional tooth movement evaluation method by using CBCT.

Recovery bone formation on radiographic palatal bone dehiscences after incisor retraction with microimplants

OBJECTIVES

To investigate the difference in labial and palatal alveolar bone thickness and height during the retention period after incisor retraction treatment with microimplant.

MATERIALS AND METHODS

A sample of 21 patients (mean age: 17.80 ± 4.38 years) who underwent incisor retraction treatment using microimplants after premolar extraction was investigated. The cone-beam computed tomography images at pretreatment, posttreatment, and retention were used to measure anterior alveolar bone thickness (labial, palatal, and total; at three vertical levels) and height (labial and palatal) and differences in the incisor position during treatment or retention. Repeated-measures analysis of variance with Bonferroni correction was performed to compare the variables at T0, T1, and T2.

RESULTS

The maxillary central incisor moved posteriorly by approximately 8.0 mm along with intrusive movement of 1.8 mm after treatment. The alveolar bone thickness significantly decreased on the palatal side and increased on the labial side after treatment. Thereafter, the palatal bone thickness significantly increased and labial bone thickness decreased during the retention period. The palatal interdental bone depressed by incisor retraction showed substantial bone deposition after retention.

CONCLUSIONS

Radiographic palatal bone dehiscences on the incisor root and palatal bone depression between the incisor roots were apparent after treatment. This palatal bone loss around the incisor roots noticeably recovered with newly formed bone during retention.

Long-term bone remodeling of maxillary anterior teeth with post-treatment alveolar bone defect in adult patients with maxillary protrusion: a prospective follow-up study

BACKGROUND

Alveolar bone defects, particularly palatal bone dehiscence (PBD) and labial bone fenestration (LBF), occur frequently as a result of retraction of the maxillary anterior teeth. The study aims to explore the long-term bone remodeling of maxillary anterior teeth in adult patients with post-orthodontic treatment PBD and LBF.

MATERIALS AND METHODS

The study includes 24 adult patients with maxillary protrusion (8 males, 16 females) who were treated with extraction of four first premolars and had alveolar bone defects (PBD or LBF) in maxillary anterior teeth following orthodontic treatment. Cone-beam computed tomography imaging measurements were obtained before (T1), after (T2) orthodontic treatment, and after at least 1-year removable thermoplastic retainer retention (T3). The maxillary anterior teeth with PBD or LBF at T2 were divided into the PBD or LBF groups, respectively. The labial and palatal alveolar bone height (ABH), alveolar bone thickness (ABT), and movement of maxillary anterior teeth were measured during retraction (T2-T1) and retention (T3-T2) periods.

RESULTS

The incidence of PBD and LBF in maxillary anterior teeth significantly increased after orthodontic treatment and decreased during the retention period. In the PBD group, the palatal ABH of all maxillary anterior teeth significantly increased from T1 to T2 but decreased from T2 to T3. The ABT of the maxillary central incisor and canine significantly increased on the palatal side and decreased on the labial side during the retention period. In the LBF group, the labial ABT of the maxillary central incisor at the apical level showed a significant decrease from T1 to T2, followed by an increase from T2 to T3. In both groups, the maxillary central incisor showed significant labial movement, with a relative intrusion during the retention period.

CONCLUSION

For adult patients with maxillary protrusion, the alveolar bone defect of maxillary anterior teeth caused by orthodontic retraction significantly improved during the retention period, indicating good long-term bone remodeling. Our findings suggest that a combination of spontaneous reorientation of maxillary anterior teeth and bone remodeling contributed to alveolar bone covering in these patients.

Long-term morphometric changes in the anterior alveolar bone in adolescents and adults after space closure: A retrospective study

OBJECTIVES

To analyse the morphometric changes in the anterior alveolar bone of both the maxilla and mandible after space closure and retention for 18-36 mo in adults and adolescents.

MATERIALS AND METHODS

Forty-two subjects with 4 first premolars extracted followed by retracting anterior teeth were included and divided into two age groups: adult group (4 males, 17 females, mean age: 23.67 ± 5.29 y, treatment duration: 27.95 mo, retention duration: 26.96 mo, ANB: 4.8 ± 2.1, U1-L1: 117.2 ± 9.2, U1-PP: 120.2 ± 7.2, L1-MP: 99.2 ± 5.3) and adolescent group (6 males, 15 females, mean age: 11.52 ± 1.21 y, treatment duration: 26.18 mo, retention duration: 25.79 mo, ANB: 5.2 ± 2.1, U1-L1: 116.0 ± 8.6, U1-PP: 119.8 ± 4.9, L1-MP: 99.7 ± 4.9). Alveolar bone height and thickness of anterior teeth in both groups were measured using cone beam computed tomography (CBCT) imaging performed at the pretreatment (T1), posttreatment (T2) and retention phases (T3). One-way repeated-measure ANOVAs were performed to evaluate the alveolar bone changes. Voxel-based superimpositions were performed to measure the amount of tooth movement.

RESULTS

After orthodontic treatment, the lingual bone height and thickness of both arches and the labial bone height of the mandible decreased significantly in both age groups (P < .05). Most of the labial bone height and thickness of the maxilla in both groups remained unchanged (P > .05). After retention, the lingual bone height and thickness increased significantly in both age groups (P < .05). The amounts of increased height ranged from 1.08 to 1.64 mm in adults and from 0.78 to 1.21 mm in adolescents, and the amounts of increased thickness ranged from 0.23 mm to 0.62 mm in adults and from 0.16 mm to 0.36 mm in adolescents. Obvious movements of the anterior teeth during retention were not found (P > .05).

CONCLUSIONS

Although lingual alveolar bone loss occurred in adolescents and adults during orthodontic treatment, continuous remodelling occurred in the later retention phase, which provides a reference for clinical treatment planning of bimaxillary dentoalveolar protrusion.

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

INTRODUCTION

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Changes of maxillary central incisor and alveolar bone in Class II Division 2 nonextraction treatment with a fixed appliance or clear aligner: A pilot cone-beam computed tomography study

INTRODUCTION

This retrospective clinical study investigated the clinical changes of maxillary central incisor and alveolar bone in Class II Division 2 nonextraction treatment with fixed appliances or clear aligners on the basis of cone-beam computed tomography.

METHODS

Fifty-nine Chinese Han patients with similar demographic characteristics were collected from a conventional bracket group, a self-ligating bracket group, and a clear aligner group. All measurements about root resorption and alveolar bone thickness on the cone-beam computed tomography images were tested. Changes between pretreatment and posttreatment were evaluated by paired-sample t test. The variation among the 3 groups was compared by 1-way analysis of variance.

RESULTS

The resistance center of the maxillary central incisor showed upward or forward movement, and the axial inclination was increased in 3 groups (P <0.0001). Root volume loss in the clear aligner group (23.68 ± 4.82 mm³) was significantly less than that in the fixed appliances group (28.24 ± 6.44 mm³ in the conventional bracket group, 28.17 ± 6.07 mm³ in the self-ligating bracket group) (P <0.05). All 3 groups showed a significant decrease in palatal alveolar bone and total bone thickness at all 3 levels at posttreatment. In contrast, labial bone thickness significantly increased except for crestal level l. Among the 3 groups, the clear aligner group had a prominent increase in labial bone thickness at the apical level (P = 0.0235).

CONCLUSIONS

Clear aligner treatment for Class II Division 2 malocclusions could effectively reduce the incidence of fenestration and root resorption. Our findings will be beneficial to comprehensively understand the effectiveness of different appliances for Class II Division 2 malocclusions treatment.

Effect of lip thickness and competency on soft-tissue changes

INTRODUCTION

Improvement in facial esthetics is a major reason for seeking orthodontic treatment. Soft tissues responsible for esthetics show a variable response to the movement of underlying teeth during orthodontics.

METHODS

The purpose of this cross-sectional study was to analyze the response of soft tissues and compare it among groups presenting with different lip thickness and competence. It was carried out on 37 patients with Class I and Class II Division 1 malocclusion who had undergone extractions of maxillary first premolars and had completed their orthodontic treatment. Data were obtained by corresponding lateral cephalometric radiographs taken before and at the end of orthodontic treatment. Association was analyzed with a Pearson correlation test. Differences among groups exhibiting varying competency and lip thickness were tested with an independent sample t test. A P value of ≤0.05 was considered statistically significant.

RESULTS

Pearson correlation revealed significant associations among incisor tip retraction with lip base retraction (r = 0.68), lip base thinning (r = 0.41) and vermilion retraction (UV) (r = 0.73). Regression analysis showed a moderate increase in lip length (AB) and thickness at vermilion, which were 0.11 mm and 0.15 mm for each mm of incisor retraction at the tip, whereas stronger effects were observed for UV (0.38 mm) and lip base retraction (0.55 mm). There was significantly more lip base thinning (P = 0.03) and UV (P = 0.04) in the incompetent group compared with the competent group. The AB increased significantly in the sample with thicker lips (P = 0.01). Pearson correlation coefficient showed a strong association of lip retraction at the base and vermilion with the incisor movement at the cervical area, for competent and incompetent lips, and thicker and thinner lips.

CONCLUSIONS

Lip retraction at vermilion and lip base thinning was significantly more in patients with incompetent lips, whereas the AB increased significantly more in the group with thicker lips.

An unusual extraction pattern for retreatment in a patient with dental protrusion and a deficient soft-tissue chin

A patient with dental protrusion and deficient soft-tissue chin, previously treated with maxillary first premolar extraction, sought retreatment to improve his facial profile. Orthognathic surgery was proposed as the ideal treatment option, but the patient declined. Therefore, other orthodontic options were considered. The combined intrusion and retraction force systems supported with skeletal anchorage on both arches and a midpalatal miniscrew successfully reduced the protrusion and rotated the mandible counterclockwise to improve the facial profile and chin projection. Sagittal correction enhanced by active vertical control with skeletal anchorage and de-wedging with posterior extraction was illustrated. In addition, advancement genioplasty was performed after orthodontic treatment to improve the chin projection further. The mechanics and results of this retreatment case were discussed.

Difference in the alveolar bone remodeling between the adolescents and adults during upper incisor retraction: a retrospective study

The purpose of this study was to compare the difference of alveolar bone remodeling between the adolescents and adults in the maxillary incisor area during retraction. This retrospective study included 72 female patients who needed moderate anchorage to correct the bimaxillary protrusion. Subjects were further divided into the minor group (n = 36, 11-16 years old) and adult group (n = 36, 18-35 years old). Digital lateral cephalography and cone beam CT scanning were taken in each patient before (T0) and after treatment (T1). Cephalometry was conducted to assess incisor retraction, while alveolar bone thickness (ABT), alveolar bone distance (ABD), and alveolar bone area (ABA) were detected to assess changes in the alveolar bone. No difference in the inclination of upper incisors was observed at both T0 and T1 between two groups. Changes in the alveolar bone showed a similar tendency with bone apposition on the labial side and bone resorption on the palatal side in both groups. Less increase in the labial ABT (T1-T0) and more decrease in the palatal ABT (T1-T0) was found in the adult group, leading to less total ABT in the adult group. Higher reduction in ABD (T1-T0) was found in the adult group. Moreover, more decrease in the ABA (T1-T0) was found in the adult group. Adult patients have less alveolar bone support after treatment when compared with young adolescents. Orthodontists should take the age into consideration to reduce the potential periodontal risks during the treatment planning.

Alveolar bone thickness and height changes following incisor retraction treatment with microimplants

OBJECTIVES

To evaluate alveolar bone remodeling following incisor retraction treatment with microimplants and to examine the relationship between crown/root distal movement and thickness/height changes of the alveolus.

MATERIALS AND METHODS

A total of 24 patients (mean age, 19.29 ± 4.64 years) with bialveolar protrusion treated by incisor retraction with microimplants were included. The distances of the crown and root tip movements as well as the thickness (alveolar bone thickness [ABT]; labial, lingual, and total) and vertical level (vertical bone level [VBL]; labial and lingual) of the alveolar bone were assessed using cone-beam computed tomography images obtained before treatment (T1) and after treatment (T2). All T1 and T2 variables were compared, and further comparisons of alveolar bone changes were conducted between the two groups based on the distance of the crown (low-crown-movement and high-crown-movement groups) and root movements (low-root-movement and high-root-movement groups). To determine the correlation of the crown or root movement with the variables of alveolar bone changes, Pearson correlation coefficients were calculated.

RESULTS

Significant differences were found in all VBL and ABT variables after treatment in both jaws but not in total ABT. Based on the crown and root movements, alveolar bone change significantly differed between the root-movement groups, whereas there was no significant difference between the crown-movement groups. In addition, root movement showed significant correlations with the variables.

CONCLUSIONS

Remarkable changes in the height and thickness of alveolar bone were found after microimplant-aided incisor retraction treatment in all groups except for total ABT. Root movement was significantly correlated with the alveolar bone changes.

Long-term changes in the anterior alveolar bone after orthodontic treatment with premolar extraction: A retrospective study

OBJECTIVES

To evaluate the morphometric changes in maxillary and mandibular anterior alveolar bone after orthodontic treatment and retention for 18-24 months by cone-beam computed tomography (CBCT).

SETTING AND SAMPLE POPULATION

Thirty-four adolescent patients (12 males and 22 females; mean age: 14.29 ± 1.24 years) diagnosed with bimaxillary dentoalveolar protrusion and with extractions of the 4 first premolars were included.

MATERIALS AND METHODS

The labial and lingual (palatal) alveolar bone thickness, height and root length of the maxillary and mandibular anterior teeth were assessed using CBCT imaging at the pre-treatment (T1), post-treatment (T2) and retention phases (T3). Voxel-based superimpositions of the T2 and T3 images were performed, and the distances of incisal and apical movement between T2 and T3 were measured to determine whether relapses occurred.

RESULTS

After orthodontic treatment, the labial and lingual (palatal) bone height decreased significantly (P < .05) and the labial thickness at the crestal (L1), midroot (L2), and apical levels (L3) had no significant change, while the lingual (palatal) bone thickness at all three levels decreased significantly (P < .05). After 18-24 months of retention, the lingual (palatal) height and the lingual (palatal) thickness at the crestal (L1) level increased significantly (P < .05). There were no obvious incisal and apical movements of the anterior teeth between T2 and T3 (P > .05), indicating that no relapses occurred.

CONCLUSIONS

Even though lingual (palatal) alveolar loss occurred due to the orthodontic treatment, the cervical alveolar bone seemed to recover over time. Therefore, appropriate camouflage treatment can be used in patients with bimaxillary dentoalveolar protrusion, and this treatment will not irreversibly deteriorate periodontal health and affect the orthodontic treatment stability.

Displacement in root apex and changes in incisor inclination affect alveolar bone remodeling in adult bimaxillary protrusion patients: a retrospective study

BACKGROUND

Periodontal health is of great concern for periodontists and orthodontists in the inter-disciplinary management of patients with bimaxillary protrusion. The aim of present study is to investigate changes in the alveolar bone in the maxillary incisor region and to explore its relationship with displacement of root apex as well as changes in the inclination of maxillary incisors during incisor retraction.

METHODS

Samples in this retrospective study consisted of 38 patients with bimaxillary protrusion. Cone-beam computed tomography (CBCT) images was taken before(T0) and after (T1) treatment. Alveolar bone thickness (ABT), height (ABH) and area (ABA) were utilized to evaluate changes in the alveolar bone, while incisor inclination and apex displacement were used to assess changes in the position of maxillary central and lateral incisors. Correlations between alveolar bone remodeling and apex displacement as well as changes in the inclination were investigated.

RESULTS

The labial ABT of central and lateral incisors at the mid-root third was increased. In contrast, the palatal ABT at crestal, mid-root and apical third level were consistently decreased. ABH was not altered on the labial side, while significantly decreased on the palatal side. ABA was not significantly increased on the labial side, but significantly decreased on the palatal side, leading to a significantly reduced total ABA. Orthodontic treatment significantly reduced inclination of upper incisors. Changes in the amount (T1-T0) of ABA was remarkably correlated with apex displacement and changes of inclination (T1-T0); in addition, using the multivariate linear regression analysis, changes of ABA on the palatal side (T1-T0) can be described by following equation: Changes of palatal ABA (T1-T0) = - 3.258- 0.139× changes of inclination (T1-T0) + 2.533 × apex displacement (T1-T0).

CONCLUSIONS

Retraction of incisors in bimaxillary protrusion patients may compromise periodontal bone support on the palatal side. An equation that incorporated the displacement of root apex and change in the incisor inclination may enable periodontist-orthodontist interdisciplinary coordination in assessing treatment risks and developing an individualized treatment plan for adult patients with bimaxillary protrusion. Moreover, the equation in predicating area of alveolar bone may reduce the risks of placing the teeth out of the bone boundary during 3D digital setups.

A study on the morphologic change of palatal alveolar bone shape after intrusion and retraction of maxillary incisors

The purpose of this study is to evaluate the changes in the palatal alveolar bone thickness and find the factors related to the resorption of the palatal alveolar bone caused by tooth movement after the maxillary incisors were retracted and intruded during orthodontic treatment. The study group comprised of 33 skeletal Class II malocclusion patients who underwent extraction for orthodontic treatment. Palatal alveolar bone thickness changes and resorption factors were identified and analyzed. The changes of maxillary central incisors and palatal alveolar bone thickness were measured, and the corresponding sample t test was performed using SPSS (IBM SPSS version 22). The amount of palatal alveolar bone resorption was measured and various parameters were analyzed to determine which factors affected it. Correlation analysis adopting the amount of palatal alveolar bone resorption as a dependent variable demonstrated that the SNB, mandibular plane angle, and the inclination of the maxillary central incisor were significantly correlated with before treatment. On the other hand, mandibular plane angle, angle of convexity, the inclination of the upper incisor, and the occlusal plane (UOP, POP) were significantly correlated with post-treatment. In addition, the variables related to palatal contour (PP to PAS, SN to PAS, palatal surface angle) and occlusal planes (UOP/POP) were significantly correlated with the difference in palatal bone resorption. During initial diagnosis, high angle class II with normal upper incisor inclination can be signs of high-risk factors. In addition, maintaining the occlusal plane during treatment helps to prevent palatal bone loss.

Alveolar bone remodeling during maxillary incisor intrusion and retraction

Background

Maxillary incisor protrusion is a prevalent dental deformity and is often treated by upper incisor intrusion and retraction. The mechanical loading triggers the resorption and apposition of the bone. Alveolar bone remodeling is expected to follow orthodontic tooth movement in a one-to-one relationship. However, in many cases, the outcomes are different. Alveolar bone might still remain thick causing lip protrusion and other aesthetic problems after treatment. Additional corrective procedures such as alveoloplasty. On the other hand, if the labial bone becomes too thin, periodontal problems like gingival recession might occur. The unpredictability of the treatment result and the risk of requiring corrective procedures pose significant challenges to both the providers and patients. The aim of this study is to determine factors that can help to predict the alveolar bone reaction before maxillary incisor intrusion and retraction.

Methods

The cohort included 34 female patients (mean age 25.8 years) who were diagnosed with skeletal class II malocclusion with upper incisor protrusion. These patients underwent extraction and orthodontic treatment with upper incisor intrusion and retraction. Lateral cephalograms at pre-treatment and post-treatment were taken. Linear and angular measurements were analyzed to evaluate the alveolar bone changes based on initial conditions.

Results

The study found that the relative change, calculated as change in alveolar bone thickness after treatment divided by the initial alveolar thickness, was inversely correlated with the initial thickness. There was a significant increase of labial alveolar bone thickness at 9-mm apical from cementoenamel junction (B3) (P < 0.05) but no statistically significant change in the thickness at other levels. In addition, the change in angulation between the incisor and alveolar bone was inversely correlated with several initial angulations: between the initial palatal plane and upper incisor angle, between the initial palatal plane and upper incisor labial surface angle, and between the initial palatal plane and bone labial surface angle. On the other hand, the change in labial bone thickness was neither significantly correlated with the initial thickness nor significantly correlated to the amount of retraction.

Conclusion

The unpredictability of alveolar bone remodeling after upper incisor intrusion and retraction poses significant challenges to treatment planning and patient experience. The study showed that the initial angulation between the incisor and alveolar bone is correlated with the change in angulation after treatment, the initial thickness of the alveolar bone was correlated with the relative change of the alveolar bone thickness (defined as change in thickness after treatment divided by its initial thickness), and the amount of intrusion was correlated with the alveolar bone thickness change at 9-mm apical from the cementoenamel junction after treatment. The results of the present study also revealed that the change in labial alveolar bone thickness was neither significantly correlated with the initial thickness nor significantly correlated to the amount of retraction.