Comparison of alveolar bone loss around incisors in normal occlusion samples and surgical skeletal class III patients

Dehiscence and fenestration of skeletal Class III malocclusions with different vertical growth patterns in the anterior region: A cone-beam computed tomography study

INTRODUCTION

This study aimed to evaluate the incidence and distribution of alveolar bone dehiscence and fenestration in skeletal Class III malocclusions with different vertical growth patterns in the anterior region using cone-beam computed tomography (CBCT).

METHODS

In this retrospective study, 84 patients with skeletal Class III malocclusions who underwent CBCT were selected. This study included 28 patients with hypodivergence (mean age, 22.9 ± 3.9 years), 28 with normodivergence (mean age, 21.0 ± 3.0 years), and 28 with hyperdivergence (mean age, 21.0 ± 3.7 years). Teeth in the anterior region were examined using CBCT to detect dehiscence and fenestration. The incidences of dehiscence and fenestration in the anterior teeth region were recorded, and statistical analysis was conducted using SPSS software (version 25.0, IBM, Armonk, NY).

RESULTS

Among the patients with skeletal Class III malocclusions, dehiscence and fenestration were prone to occur in the mandible. Dehiscence and fenestration were more prevalent in patients with hyperdivergence compared with in patients with hypodivergence and normodivergence.

CONCLUSIONS

Dehiscence and fenestration are prevalent among patients with skeletal Class III malocclusion. Furthermore, the occurrence of alveolar bone defects is higher in patients with hyperdivergence.

Bone Remodeling of Maxilla after Retraction of Incisors during Orthodontic Treatment with Extraction of Premolars Based on CBCT Study: A Systematic Review

Background: Incisor retraction is often a crucial phase in ongoing orthodontic treatment, with significant implications for alveolar remodeling mechanisms. There are two prevailing theories which seek to explain this. According to the first, teeth move with the bone, while according to the second, teeth move within the bone. This systematic review seeks to assess morphometric changes in the maxillary alveolar process resulting from incisor retraction following premolar extraction and to evaluate the potential for bone remodeling associated with orthodontic movement. Methods: The study was conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The following electronic databases were searched: PubMed, Google Scholar, Web of Science EMBASE and the Cochrane Central Register of Controlled Trials. The databases were searched using the following keywords: "Bone remodeling and retraction of incisors", "Alveolar bone and incisor retraction", "Bone thickness and incisor retraction", and "Bone changes and orthodontic treatment". Search filters were utilized to identify relevant papers and articles written in English and published during the last 10 years. Based on the information provided in their abstracts, papers and articles were selected according to the following criteria: randomized clinical trials (RCTs), controlled clinical prospective trials (CCTs), and retrospective studies. Articles unrelated to the study's scope or failing to meet inclusion criteria were excluded. These generally comprised individual case reports, case series reports, literature reviews, experimental studies, studies with limited data (including conference abstracts and journal writings), studies involving an unrepresentative group of patients (less than 10 patients), studies concerning patients with syndromes, and animal experiments. The remaining articles which were deemed relevant underwent comprehensive reference review and such journals as the American Journal of Orthodontics, Dentofacial Orthopedics, International Orthodontics, Journal of Clinical Orthodontics, and Angle Orthodontist were manually searched. Results: Seven articles meeting the inclusion criteria articles were selected for final evaluation, with a total of 284 participants, including 233 women and 51 men. During the analysis of the results included in the publications, a lack of homogeneity was observed, rendering a reliable statistical analysis and heterogeneity assessment unobtainable. Noteworthy disparities in methodologies and measurements posed a risk of drawing inappropriate conclusions. Consequently, emphasis was placed on qualitative analysis, emphasizing the need for standardization in future studies of a similar nature, to enable valid and comparable analyses. Conclusions: The research findings incorporated in this review demonstrate that significant bone loss occurs because of incisor retraction, which diminishes distance between the bone surface and the root surface on the palatal aspect. The magnitude of this change may vary, contingent upon both the extent of incisor displacement and alterations in their inclination, thereby affecting the positioning of the root tips. This change is significantly higher in adults than in growing adolescents. The rationale behind this assertion lies in the widely recognized phenomenon of declining cellular activity with advancing age. The decrease in the speed and intensity of cellular changes may explain the diminished capacity for remodeling as patient age increases. There is ongoing discourse regarding alterations in the volume of bone on the labial aspect of the alveolar process. Further research is necessary to measure whether bone remodeling during orthodontic movement is contingent upon other factors, such as the speed and biomechanics of retraction, the level of applied orthodontic force, and the patient age.

Inclination of mandibular incisors and symphysis in severe skeletal class III malocclusion

OBJECTIVE

The aim of this study was to systematically explore the inclination of the lower central incisor and symphysis in alveolar bone in severe skeletal class III patients.

MATERIALS AND METHODS

A total of 198 severe skeletal class III patients (ANB ≤ -4°) who underwent combined orthodontic and orthognathic treatment were divided into three groups based on the mandibular plane angle (MP-SN). Pretreatment lateral cephalograms were analysed and compared among the three groups. We also assessed cone-beam computed tomography (CBCT) images of 11 samples to investigate the reliability of the cephalometric analysis.

RESULTS

ANOVA showed no statistically significant differences in the angle between the long axis of the mandibular symphysis and the long axis of the lower central incisor (MIA) among the low-angle, normal-angle and high-angle groups (P > 0.05), while significant differences were found in the angle between the axis of the lower incisor and the mandibular plane (IMPA) among the three groups (P < 0.001). The mean IMPA decreased with increasing MP-SN in the 198 patients. The mean MIA in the low-angle and normal-angle groups was 3.70° and 3.52°, respectively, while the value (2.33°) was smaller in the high-angle group. Paired-samples t test showed no statistically significant differences between the cephalometric and CBCT measurements of the MP-SN, the angle between the mandibular plane and the Frankfort plane (FH-MP) and the MIA (P > 0.05).

CONCLUSIONS

In severe skeletal class III patients, the long axis of the lower central incisor was highly consistent with the long axis of the mandibular symphysis, which was more obvious in the high-angle subjects. The MIA reflects the physiological inclination of the lower central incisor better than the IMPA.

Evaluation of root resorption in the lower incisors after orthodontic treatment of skeletal Class III malocclusion by three-dimensional volumetric measurement with cone-beam computed tomography

OBJECTIVES

To investigate the volumetric changes of the lower incisor roots in skeletal Class III orthodontic patients with anterior crossbite after premolar extraction therapy.

MATERIALS AND METHODS

Thirty-six adults, aged 18-28 years, had four-premolar extraction treatment. Pre- and posttreatment cone-beam computed tomography (CBCT) images were used to assess the thickness and height of alveolar bone, root volume, and length. A paired t-test was used to detect changes in root volume and length before and after treatment. Pearson's correlation analysis was applied to estimate the correlation between root volume and dentoskeletal morphology.

RESULTS

Both the central and lateral incisors had intrusion and tipping movement after treatment. Compared with pretreatment data, root length decreased significantly. The lingual root volume of root cervical, apical third, and the labial root volume of the root apical third decreased significantly (P < .05), among which the percentage of tooth loss at the tip volume was the highest. The pretreatment height of the alveolar ridge crest, thickness of the alveolar bone, and type of incisor movement were related to the volume and length loss.

CONCLUSIONS

Volume and length loss in the apical third of the lower incisor roots in skeletal Class III patients treated with a Class III bicuspid extraction pattern is common. The pretreatment height of the alveolar ridge crest, thickness of the alveolar bone, and type of tooth movement are related to the loss.

Augmented corticotomy-assisted presurgical orthodontic treatment to prevent alveolar bone loss in patients with skeletal Class III malocclusion

INTRODUCTION

The objective of this study was to explore the effect of augmented corticotomy (AC) on anterior alveolar bone morphology in presurgical orthodontic treatment for skeletal Class III malocclusion.

METHODS

Thirty-six surgical patients with skeletal Class III malocclusion with high-angle were included: 18 (AC group) accepted AC surgery during presurgical orthodontic treatment, and 18 (control group) accepted traditional presurgical orthodontic treatment. Cone-beam computed tomography scans were obtained before treatment (T0) and after presurgical orthodontic treatment (T1). The alveolar bone morphology, root length, dehiscence, and movement of mandibular central incisors were measured by cone-beam computed tomography using Dolphin software. Statistical analyses were performed with independent-sample t tests, paired t tests, and multiple linear regression.

RESULTS

After presurgical orthodontic treatment, the whole alveolar bone thickness at each level, alveolar bone area, and alveolar bone height decreased significantly in the control group but increased or remained unchanged in the AC group. In the AC group, the lower the labial alveolar bone height at T0 was, the greater the increase after T1; the change in alveolar bone thickness was related to ΔL1-MP and sex. At T0, the incidences of dehiscence were similar in the 2 groups, ranging from 11.11% to 16.67%. At T1, the labial and lingual incidences of dehiscence in the AC group were 0% and 27.78%, compared with 55.56% and 66.67% in the control group.

CONCLUSIONS

During presurgical orthodontic treatment, AC is effective in preventing alveolar bone resorption and dehiscence without additional root resorption. AC can be recommended for high-angle skeletal Class III patients with thin alveolar bone around anterior teeth during presurgical orthodontic treatment.

Association between alveolar bone height changes in mandibular incisors and three-dimensional tooth movement in non-extraction orthodontic treatment with Invisalign

OBJECTIVE

The purpose of this study was to investigate associations between alveolar bone height changes on the labial and lingual sides in mandibular incisors and three-dimensional orthodontic tooth movement, involving apex displacement, tooth inclination, and angulation.

MATERIALS AND METHODS

The samples consisted of 43 adult patients treated with Invisalign aligners. All subjects were skeletal Class I patients without extraction in mandible. Pre-treatment and post-treatment cone-beam computed tomographic images were obtained to measure labial and lingual alveolar bone height and bone thickness at apex level in four mandibular incisors. An x, y, z coordinate system, superimposing on mandibular body, was established to analyse three-dimensional apex movement and tooth inclination and angulation changes. Multiple linear regression was applied to identify the determining factors of marginal bone changes during orthodontic treatment.

RESULTS

Three directions of apex movement (anteroposterior, vertical, transverse) significantly associated with alveolar bone height changes. Inclination changes had a strong effect on lingual marginal bone, while tooth angulation had no significant effect on alveolar bone height. Incisors with lingual bodily movement were more susceptible to lingual marginal bone recession compared with lingual tipping movement.

CONCLUSIONS

Alveolar bone height changes on the labial and lingual sides were associated with three-dimensional apex movement, inclination changes, and movement patterns. Appropriate tooth movement should be considered to avoid excessive marginal bone loss around mandibular incisors.

The position and morphology characteristics of multiple impacted anterior teeth in the unilateral maxillary area: A retrospective study based on cone-beam computed tomography

INTRODUCTION

This study investigated the position and morphologic characteristics of multiple impacted anterior teeth in the unilateral maxillary area.

METHODS

Cone-beam computed tomography images of 21 patients (11 males and 10 females; median age 9.42 years [9.08-11.29]) with multiple teeth impacted were collected and imported into Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif). The vertical height, crown orientation, twist direction, and root curvature of each impacted tooth were described. The crown length, root length, and root canal width of impacted and homonym teeth were measured.

RESULTS

The positions of the impacted lateral incisors are lower than that of the other 2 anterior teeth. Most crowns of impacted central incisors are positioned distally, labial surfaces in mesial torsion, with most roots, bent toward the distal and labial. Crowns of impacted lateral incisors are positioned mesiolabially, with labial surfaces mostly in distal torsion, and most roots bent toward the mesial and labial. Crowns of impacted canines are mostly positioned mesiolabially, with labial surfaces in mesial torsion. The crowns and roots of the impacted central and lateral incisors were shorter than those of the homonym (P <0.05); however, the difference in crown length is clinically negligible, and there was no difference in root canal widths. There was no difference in the comparison of parameters for the canine group.

CONCLUSIONS

There are certain rules in the vertical height, crown orientation, twist direction, and root curvature of multiple impacted anterior teeth in the unilateral maxillary area. Root development of impacted central and lateral incisors was restricted.

Three-dimensional measurement of periodontal support during surgical orthodontic treatment of high-angle skeletal Class III malocclusion: A retrospective study

INTRODUCTION

This study aimed to quantify the periodontal health of incisors during surgical orthodontic treatment in patients with high-angle Class III malocclusion using a cone-beam computed tomography (CBCT) 3-dimensional (3D) reconstruction technique.

METHODS

The sample consisted of 30 patients with high-angle Class III malocclusion (mean age, 20.53 ± 2.86 years). CBCT images were taken before treatment (T0), after presurgical orthodontic treatment, and after treatment (T2). In addition, 3D tooth and alveolar bone models were generated. The root surface area, periodontal ligament (PDL)_Area, and vertical bone level (VBL) around the maxillary and mandibular central incisors were measured.

RESULTS

The root surface area and PDL_Area of maxillary and mandibular central incisors decreased continuously between T0 and T2 (P <0.01). At T2, mandibular central incisors showed 38.64 ± 13.39% PDL_Area loss, and maxillary central incisors exhibited 21.13 ± 16.48% PDL_Area loss. For mandibular central incisors, the PDL_Area loss caused by VBL loss was significantly greater than that for maxillary central incisors (P <0.01) and significantly greater than the PDL_Area loss caused by root resorption (P <0.01). From T0 to T2, the lingual surface of maxillary central incisors exhibited greater VBL loss than the other 3 surfaces (P <0.01), and the labial and lingual surfaces of mandibular central incisors demonstrated greater VBL loss than proximal surfaces (P <0.01).

CONCLUSIONS

The 3D CBCT reconstruction method provides useful information regarding the periodontal defects of incisors in patients with high-angle skeletal Class III malocclusion. The PDL_Area of maxillary and mandibular central incisors decreased continuously during the treatment. Vertical alveolar bone levels at proximal surfaces appeared to be relatively stable.

[Evaluation of root resorption after surgical orthodontic treatment of skeletal Class Ⅲ malocclusion by three-dimensional volumetric measurement with cone-beam CT]

OBJECTIVE

To explore the method of measuring root volume with cone-beam computed tomography (CBCT) three-dimensional reconstruction technology, and to study root length and root volume of upper and lower central incisors in patients with skeletal Class Ⅲ malocclusion treated by surgical orthodontic treatment.

METHODS

Twenty patients with skeletal Class Ⅲ malocclusion undergoing surgical orthodontic treatment were selected. CBCT data at three time points, before decompensation treatment (T0), after decompensation treatment (before orthognathic surgery, T1), and the end of post-operative orthodontic treatment (T2) were collected. Three-dimensional reconstruction technology was used to measure the root length and root volume of the upper and lower central incisors (including total root volume, cervical root and apical root), calculate the percentage of reduction volume, and measure the distance of tooth movement after orthodontic treatment. Data were statistically analyzed by SPSS 20.0 software. Least significant difference (LSD) method was used for pair comparison between the groups subject to normal distribution, and non-parametric test was used for comparison between the groups not subject to normal distribution. The differences of root length and root volume of upper and lower incisors were compared, and the characteristics of root absorption were analyzed.

RESULTS

Root length and root volume of the upper and lower central incisors were reduced during the surgical orthodontic treatment (P < 0.05) in cases. Both the root volume of cervical root and apical root were significantly reduced (P < 0.05), the reduction of apical root was more significant. The percentage of root volume reduction of the upper central incisor was (30.51±23.23)%, and lower central incisor (23.24±11.96)%. Compared with the upper central incisor, the root volume reduction amount and percentage of the lower central incisor were smaller, and apical root volume reduction of the upper central incisor was greater than that of the lower central incisor, which was statistically significant (P < 0.05). During pre-surgical orthodontic treatment, maxillary central incisor palatal moving was in a controlled tipping manner, and the mandibular central incisor tipped labially.

CONCLUSION

In patients with skeletal Class Ⅲ malocclusion, root length and total root volume of upper and lower central incisors decreased during surgical orthodontic treatment. Root volume measurement indicated that the cervical root also had root resorption. The difference in root resorption of the upper and lower central incisors might be related to the distance and direction of teeth movement. CBCT three-dimensional reconstruction will compensate for the limitation of root length measurement in evaluating root resorption.

Symphysis morphology and mandibular alveolar bone thickness in patients with β-thalassemia major and different growth patterns

Objective:

The present study aimed to assess the morphology of symphysis and alveolar bone thickness (ABT) surrounding mandibular incisors in thalassemic patients, as compared to unaffected individuals.

Methods:

This case-control study was conducted on lateral cephalograms of 60 thalassemic and 60 unaffected patients with Class II malocclusion seeking orthodontic treatment at Dental School, Shiraz University of Medical Sciences. The sample was divided into three subgroups including hyperdivergent, normodivergent, and hypodivergent, according to the Jarabak index. Symphysis dimensions and alveolar bone thickness surrounding mandibular incisors were measured using AutoCad software. Finally, the correlation between alveolar bone thickness and symphysis morphology was assessed.

Results:

In general, chin dimensions and bone thickness at different levels of mandibular incisor roots (cervical, middle, apical) were smaller in thalassemic adolescents than controls. Concerning the total sample as well as the normodivergent subgroup, significantly lower values were observed in thalassemic patients for symphysis width, total ABT at the cervical, and lingual ABT at the apical root area compared to controls (p < 0.05). The hypodivergent growth pattern was not associated with any statistical differences between the groups (p> 0.05). In both thalassemic and control subjects, symphysis width showed a weak to moderate positive correlation with ABT of lower incisors (p< 0.05), whereas symphysis height showed a moderate positive correlation with cervical ABT in only ß‐thalassemia patients (p< 0.05).

Conclusions:

Compared to controls, ß-thalassemia patients showed thinner alveolar bone at different levels of lower incisor roots and smaller symphysis dimensions. There were significant correlations between symphysis dimensions and alveolar bone thickness of mandibular incisors in the sample.

Impact of piezocision-assisted orthodontics on root resorption and alveolar bone: a prospective observational study

OBJECTIVES

To assess the impact of orthodontic treatment combined with piezocision (OT-PC) on root structure and alveolar bone.

MATERIALS AND METHODS

Twelve adults were treated with OT-PC. Pre- and post-treatment CBCT examinations evaluated apical root resorption (ARR) and alveolar bone height and thickness changes. Pre- and post-treatment differences were compared using one-sample t test and Wilcoxon signed-rank test.

RESULTS

ARRs were generalized and significantly more severe in both anterior sextants compared with posterior sextants. Bone thickness decreased significantly in the maxilla at mid-root and apex areas. The majority of mandibular alveolar bone dehiscences occurred on the buccal aspect at the mid-root level, especially where thickness was less than 0.3 mm. Overall bone height decreased twice as much on the buccal aspect (1.43 mm, P < 0.001) compared with the lingual aspect (0.67 mm, P = 0.001), most significantly in the lower incisors, where the average median loss was 2.10 mm (P = 0.003).

CONCLUSION

OT-PC causes minor negative effects on both alveolar bone and root resorption.

CLINICAL RELEVANCE

Orthodontic treatment combined with piezocision causes minor negative effects on periodontal support. Nevertheless, mild bone height loss on the buccal aspect of the mandibular teeth and root resorption in both anterior sextants have been detected with this new treatment.

Changes in alveolar bone morphology after traction of buccally vs palatally unilateral maxillary impacted canines: A cone-beam computed tomography study

INTRODUCTION

The objective of this study was to evaluate the 3-dimensional changes in alveolar bone morphology after traction of buccally vs palatally unilateral maxillary impacted canines (MIC).

METHODS

Following a split-mouth model, 27 cone-beam computed tomography images of unilaterally MIC (14 palatally and 13 buccally) and 27 contralateral unimpacted controls were obtained before and after traction using nickel-titanium closed-coil springs and a rigid anchorage appliance. Alveolar bone height and width were measured in the axial, coronal, and sagittal slides by 3 calibrated orthodontists, taking into account the impaction characteristics. A t test was used to compare the 2 groups, and a paired t test was applied for intragroup comparisons (both sides). A multiple linear regression model was used to evaluate the influence of the predictor variables on alveolar bone dimensional changes.

RESULTS

The alveolar height showed a significantly greater decrease in palatally MIC (2.09 to 2.79 mm) than buccally MIC (0.28 to 0.57 mm) (P <0.05) for all surfaces. However, the alveolar width increased similarly in both groups up to 1.36 mm. In general, the affected side had a more significant height loss and greater increases in alveolar width than the nonaffected side. Regression analysis indicated that buccally MIC and age decreased alveolar changes, whereas female sex increased alveolar changes (P <0.05).

CONCLUSIONS

MIC traction with nickel-titanium closed-coil springs and heavy anchorage induces significant 3-dimensional changes in alveolar bone characterized by alveolar bone height decreases and cervical alveolar bone width increases. The height decrease is greater in palatally than in buccally MIC.

Architectural changes in alveolar bone for dental decompensation before surgery in Class III patients with differing facial divergence: a CBCT study

This study aimed to investigate alveolar bone change around mandibular anterior teeth during orthodontic decompensation in patients with skeletal Class III malocclusion and different vertical facial patterns. The records of 29 consecutive Class III patients selected from those pending two-jaw orthognathic surgery were divided into low (≤ 28°), average (30°-37°), and high (≥ 39°) mandibular plane angle (MPA) groups. The DICOM files of CBCT scans and STL files of digital dental models, taken before (T1) and after (T2) presurgical orthodontic treatment, were imported into Dolphin imaging software to reconstruct dentoskeletal images. T1 and T2 images were superimposed and analyzed for bone thickness and height at the level of root apex on each mid-sagittal slice of six mandibular anterior teeth. Differences between T1 and T2 were analyzed by non-parametric tests and mixed-effect model analysis. The results showed that the measurements of alveolar bone height generally decreased after treatment, regardless of MPA. The facial divergence, incisor irregularity, tooth site, treatment time, and change in proclination were identified as the significant factors affecting alveolar bone thickness and height during treatment. The presurgical orthodontic treatment to decompensate mandibular anterior teeth should be very careful in all MPA groups.

Assessment of buccal and lingual alveolar bone thickness and buccolingual inclination of maxillary posterior teeth in patients with severe skeletal Class III malocclusion with mandibular asymmetry

INTRODUCTION

The purpose of this study was to evaluate the buccal and lingual alveolar bone thickness and buccolingual inclination of maxillary posterior teeth in patients with severe skeletal Class III malocclusion with and without mandibular asymmetry and compare with those in patients with skeletal Class I malocclusion.

METHODS

Cone-beam computed tomography images of 69 patients with severe skeletal Class III malocclusion and 30 patients with skeletal Class I malocclusion were collected and reconstructed with Dolphin 3D software. Based on the distance from menton to the sagittal plane (d), the patients with skeletal Class III malocclusion were divided into a symmetry group (d ≤ 2 mm) and an asymmetry group (d ≥ 4 mm). Buccal and lingual alveolar bone thickness and buccolingual inclination of maxillary posterior teeth were measured and compared. Correlations among dental measurements, severity of sagittal discrepancy, and mandibular deviation were analyzed.

RESULTS

Maxillary posterior teeth on the deviated side in Class III asymmetry group and symmetry group were buccally inclined compared with the Class I group (P < 0.001). A significant negative correlation was noted between buccolingual inclination of maxillary posterior teeth and ANB value with Spearman correlation coefficient of maxillary first molar, second premolar, and first premolar of -0.687, -0.485 and -0.506, respectively (P < 0.001). Maxillary first molar showed thinner buccal alveolar bone on deviated side in asymmetry group and symmetry group of Class III, compared with the Class I group, with average values of 1.21 mm, 1.19 mm, and 1.83 mm, respectively (P < 0.05). The maxillary first premolar also showed thinner buccal alveolar bone on deviated side in Class III asymmetry group compared with the Class I group, with average values of 0.87 mm and 1.28 mm, respectively (P < 0.05).

CONCLUSIONS

Decompensation of buccally inclined posterior teeth in patients with skeletal Class III malocclusion should be more cautious owing to thinner buccal alveolar bone to avoid a high risk of fenestration and dehiscence.

Periodontal soft- and hard-tissue changes after augmented corticotomy in Chinese adult patients with skeletal Angle Class III malocclusion: A non-randomized controlled trial

BACKGROUND

To investigate soft- and hard-tissue changes after augmented corticotomy in Chinese adult patients with skeletal Angle Class III malocclusion.

METHODS

This non-randomized controlled trial included 357 anterior teeth from 30 Chinese adult patients with skeletal Angle Class III malocclusion for whom the proposed treatment was augmented corticotomy. Jaws receiving surgery were allocated to a test group (S, surgical group, n = 47) and jaws not receiving surgery were allocated to a control group (NS, non-surgical group, n = 13). Changes in the periodontal biotype, width of the keratinized gingiva (WKG), and labial and lingual horizontal bone thicknesses (BTs) were compared 6 months after surgery by univariate and multivariate analyses.

RESULTS

After adjustment for confounding variables, average gains of 0.473 mm in the WKG and 0.649 mm in the labial BT were found in the S group relative to the NS group (P <0.05). The odds of transition from a thin periodontal biotype to a thick biotype in the S group were about 230 times those in the NS group, and the odds of the reverse biotype transition in the NS group were about 83 times those in the S group (P <0.05).

CONCLUSIONS

Within the limitations of the present study, augmented corticotomy is a promising approach to improve insufficient periodontal soft and hard tissues in Chinese adult patients with skeletal Angle Class III malocclusion.

[Alveolar crest and relevant analysis of labial side of anterior teeth on skeletal Angle class III patients]

OBJECTIVE

To measure the distance from cemento-enamel junction (CEJ) to alveolar crest (AC) of labial side of anterior teeth on skeletal Angle class III patients under direct vision during periodontal bone augmentation surgery and to make relevant analysis to find the relevant factors.

METHODS

In the study, 46 skeletal Angle class III patients (10 males and 36 females) received periodontal bone augmentation surgery of anterior teeth were included, with 67 jaws (27 maxillae and 40 mandibles) and 400 anterior teeth (161 maxillary anterior teeth and 239 mandibular anterior teeth). The mean age was 23.65 years. Maxillary anterior teeth consisted of 54 central incisors, 53 lateral incisors and 54 canines. Mandibular anterior teeth consisted of 79 central incisors, 80 lateral incisors and 80 canines. CEJ-AC was measured in three sites (mesial sites, central sites and distal sites) by Williams periodontal probes during periodontal bone augmentation surgery under direct vision by the same researcher.

RESULTS

The average CEJ-AC of 400 anterior teeth was (2.21±1.48) mm. The average CEJ-AC of maxillary anterior teeth was (1.72±1.13) mm, more than (2.54±1.60) mm of mandibular anterior teeth (P<0.05). The average CEJ-AC of canines was (2.42±1.78) mm, more than (2.06±1.27) mm of central incisors or (2.16±1.32) mm of lateral incisors (P<0.05). The average CEJ-AC of central sites was (3.04±2.01) mm, more than (1.79±0.86) mm of mesial sites or (1.81±0.89) mm of distal sites (P<0.05). CEJ-AC of 233 anterior teeth was more than 2 mm, accounting for 58.25%, and 117 anterior teeth with dehiscence were found, accounting for 29.25%. Multilevel and multivariate Logistic regression showed age, jaw, tooth and site were the relevant factors to the position of alveolar crest.

CONCLUSION

The position of alveolar crest of skeletal Angle class III patients who received periodontal bone augmentation surgery was lower than that of the general population, causing periodontal risks during decompensation orthodontics therapy before orthognathic surgery. The position of alveolar crest was lower in older patients than in younger patients, in mandibular teeth than in maxillary teeth, in canines than in central incisors or lateral incisors, and in central sites than in mesial sites or distal sites of labial side, which showed much higher risk.

Comparison of anterior mandibular alveolar thickness and height in young adults with different sagittal and vertical skeletal relationships: A CBCT Study

OBJECTIVE

Alveolar bone surrounding mandibular incisors dictates the range of buccolingual inclination that can be achieved with treatment. The objective of this study was to evaluate the mandibular anterior alveolar thickness and height in individuals with different sagittal and vertical skeletal relationships.

MATERIALS AND METHODS

Cone beam computed tomography scans of 53 individuals (22 males and 31 females; mean age 21.19±3.7 years) were classified into 3 groups according to the sagittal skeletal relationship (class I, class II, and class III) and the vertical growth pattern (hyperdivergent, normodivergent, and hypodivergent). The alveolar thickness and height of both mandibular central incisors were measured. Group comparisons were performed with analysis of variance and post hoc Scheffé tests. Multiple linear regression was applied to evaluate the influence of all variables on the alveolar conditions.

RESULTS

Alveolar thickness and height showed no significant differences among the class I, II and III groups (6 and 7mm regardless of the sagittal group, P>0.05). The middle and lower alveolar thicknesses were significantly smaller in hyperdivergent (5.76mm and 6.34mm) and normodivergent (6.29mm and 7.40mm) than hypodivergent individuals (6.63mm and 8.27mm respectively). The lingual alveolar height was smaller in hyperdivergent (6.04mm) than hypodivergent individuals (7.93mm) (P=0.029, 95%CI: 0.15-3.63) and the lingual bone height was smaller in hypodivergent (3.24mm) than hyperdivergent individuals (5.06mm) (P=0.029, 95%CI: 0.15-3.48). Multiple linear regression indicated a significant influence of the root length on the alveolar thickness and height.

CONCLUSIONS

The sagittal skeletal relationship showed no influence on the alveolar thickness or height, even if dental compensation was present. Hyperdivergent individuals showed smaller alveolar thicknesses and heights than hypodivergent individuals.

Segmental Corticotomy-Assisted Orthodontic Treatment With Platelet-Rich Fibrin Augmentation of Class III Anomaly

This clinical report presents the outcomes of segmental corticotomy-assisted orthodontic treatment in a class III patient. A 13.5-year-old female patient presented with class III anomaly and a thin alveolus in the mandibular anterior region. After the alignment of the mandibular incisors, segmental corticotomy with platelet-rich fibrin (PRF) was performed in the mandibular incisor area to facilitate incisor retraction to ensure periodontal support after the changes in the inclination of the teeth. Lateral cephalograms were taken at the beginning (T0), precorticotomy (T1), at the end of the treatment (T2), and 2 years after the treatment (T3). Cone-beam computed tomography (CBCT) records were collected at the T1, T2, and T3 periods to evaluate the bone structures. The measurements included the inclination and the position of the mandibular incisors, symphysis width, symphysis height, B-B' width, cervical alveolar width, the vertical alveolar bone level on the labial and the lingual sides, and the amount of labial and lingual bone at the apex in the mandibular central incisor and canine areas.The class I molar and canine relationship was achieved in this borderline case. The amount of labial bone at the root apex and the B-B' width increased. A vertical alveolar bone gain was observed. The facial profile was improved significantly. The treatment outcome was stable at the 2-year follow-up. The segmental anterior mandibular corticotomy provided an effective correcting inclination of the mandibular teeth with the use of class III elastics. This technique ensured the maintenance of a sufficient amount of labial bone with no periodontal side effects.

Analysis of Alveolar Bone Morphology of the Maxillary Central and Lateral Incisors with Normal Occlusion

Background and objectives: This study investigated the morphology of the labial and palatal bony wall of the maxillary central and lateral incisors using cone-beam computed tomography (CBCT). The difference between males and females and the measurement between right and left sides were measured. Materials and Methods: Twenty participants, consisting of 11 females and 9 males having normal occlusion, were used for the analysis. The mean age was 21.9 ± 3.0 years. The thickness of the labial bony wall and palatal bony wall, perpendicular to the long axis of the root, were evaluated at 3 and 5 mm apical from the cemento-enamel junction (CEJ) and at the root apex. The available bony wall below the apex of the central and lateral incisors, and the angulation between the long axis of the tested tooth and outer surface of the labial bone were measured. Results: The mean labial bony wall thickness at the 3 and 5 mm apical from the CEJ were 1.1 ± 0.3 mm and 1.0 ± 0.4 mm for central incisors, respectively, as well as 1.2 ± 0.4 mm and 1.0 ± 0.4 mm for lateral incisors, respectively. The mean palatal bony wall thickness at 5 mm from the CEJ was above 2 mm in the central and lateral incisors. The percentage of labial bony wall thickness 2 mm or greater at the root apex in central incisors was higher than in lateral incisors (62.5% vs. 55.0%). The percentage of palatal bony wall thickness ≥2 mm at 3 mm apical from the CEJ in the central incisors was higher than in the lateral incisors (37.5% vs. 15.0%). The results on the left and right sides did not show statistically significant differences, except in the labial and palatal bony wall thickness at 3 mm from the CEJ in the lateral incisor. Generally, no significant differences were seen between males and females, but males had a significantly higher labial bony wall thickness at 3 and 5 mm from the CEJ in the central and lateral incisors when compared with females. Conclusions: This study showed that a majority of the cases of Korean participants had less than 2 mm of labial bony wall thickness at 3 and 5 mm apical from the CEJ at central and lateral incisors, and this should be kept in mind while performing dental practices, including tooth extraction or immediate implantation in anterior regions. Preoperative analysis using CBCT may be beneficial for establishing the treatment plan.

Association between palatally displaced maxillary central incisors and lateral incisors: A retrospective cone-beam computed tomographic study

INTRODUCTION

The objective of this study was to investigate the location, orientation and root development of maxillary lateral incisors in patients with palatally impacted central incisors. Comparison was made between the lateral incisor on the affected side and that on the normally erupted side.

METHODS

Cone-beam computed tomographic images from 20 patients (10 boys, 10 girls, mean age (9.01 ± 1.52 years old) with unilateral palatally impacted maxillary central incisors were imported into Dolphin imaging software 11.8 for 3-dimensional reconstruction and reorientation. Software measurement tools were used to measure the root length, crown distance, angle to palatal plane, distance to midline, and angle to midsagittal plane of the maxillary lateral incisors on both the impacted and unaffected sides.

RESULTS

The Wilcoxon signed rank test indicated that lateral incisors on the impacted side were more proclined, at a mean angle difference of 29.47° in the sagittal plane (P < 0.001). The mean length of the roots of the lateral incisors was 1.21 mm shorter (P < 0.05) on the affected side compared with the normal side, and the lateral incisor crowns on the impacted side were located at an average of 4.57 mm closer to the palatal plane than on the normally erupted side (P < 0.001). The angle of long axis of the lateral incisors on the affected side had a greater angulation to the midsagittal plane compared with the unaffected side, with a mean difference of 30.27° (P < 0.001).

CONCLUSIONS

Maxillary lateral incisors adjacent to palatally impacted maxillary central incisors side had abnormal root development and demonstrated angulation and position change compared with those adjacent to normally erupted central incisors.

Relationship between alveolar bone thickness, tooth root morphology, and sagittal skeletal pattern : A cone beam computed tomography study

PURPOSE

The goal of this work was to examine the relationship between sagittal facial pattern and thickness of alveolar bone in conjunction with root morphology of teeth by using cone beam computed tomography (CBCT).

METHODS

The study was carried out on the CBCT scans from 3 group of patients (n = 20 in each group). The first group involved skeletal class 1, the second group involved skeletal class 2, and the third group involved skeletal class 3 patients. In all, 14 permanent teeth and interdental regions in the maxilla and mandible were evaluated. Root length and root width were measured on each tooth. Buccal cortical bone thickness, cancellous bone thickness, and lingual cortical bone thicknesses were measured in each interdental region. Analysis of variance, Kruskall-Wallis H and Mann-Whitney U tests were used for statistical comparisons.

RESULTS

No significant difference was found between the groups for root length, root width, buccal cortical bone and lingual cortical bone thickness. A significant difference was observed between the groups for cancellous bone thickness as it was thicker in skeletal class 2 group. Cortical bone was thicker in the mandible compared to maxilla on both buccal and lingual sides and it was thicker in the posterior region compared to the anterior region on the buccal side.

CONCLUSIONS

Differences in cancellous bone thickness between different sagittal facial patterns and differences in cortical bone thickness between different alveolar regions should be taken into consideration when planning orthodontic tooth movements and anchorage mechanics.

Morphological analysis of the alveolar bone of the anterior teeth in severe high-angle skeletal Class II and Class III malocclusions assessed with cone-beam computed tomography

Objective

This Cross-sectional study used cone-beam computed tomography (CBCT) to evaluate the difference in the alveolar bone of the anterior teeth between high-angle adults with severe skeletal Class II malocclusions and Class III malocclusions.

Materials and methods

The CBCT archives from 62 high-angle adults were selected from patients of the Stomatology Hospital of Peking University between October 2017 to January 2018. The 62 high-angle adult subjects were divided into the following 2 groups based on their sagittal jaw relationships: severe skeletal Class II and severe skeletal Class III. Vertical bone level (VBL), alveolar bone area (ABA), and thickness of alveolar bone were measured at 2 mm, 4 mm, and 6 mm below and above to the cemento-enamel junction (CEJ) level, as well as at the apical level. Then, independent samples t-test were conducted for statistical comparisons.

Results

In the maxillary incisors, the labial VBL was smaller in the patients in skeletal Class III group than those in skeletal Class II group (P<0.05). On the labial side, the ABA was significantly thinner in patients in skeletal Class II group than those in skeletal Class III group, especially in terms of the maxillary central incisors’ ABA at 4 mm and 6 mm above the CEJ level (P<0.05), in terms of apical ABA and total ABA of the maxillary lateral incisors (P<0.05). The alveolar bone thickness around maxillary lateral incisors was significantly thinner in patients of skeletal Class II than that of patients of skeletal Class III, especially regarding the apical level on the labial side (P<0.05). The ABA of the mandibular alveolar bone in the area of the lower anterior teeth was significantly thinner in patients in skeletal Class III group than those in skeletal Class II group, especially in terms of apical ABA, total ABA on the labial and lingual sides, and ABA at 6 mm below the CEJ level on the lingual side (P<0.05). In the mandibular lateral incisors, the alveolar bone thickness was significantly thinner in patients in skeletal Class III group than it was in patients in skeletal Class II group, especially regarding the apical level on the lingual side (P<0.05).

Conclusions

The ABA and the alveolar bone thickness of the mandibular anterior teeth were significantly thinner in the severe high-angle group of skeletal Class III adult patients than in the sample of severe high-angle skeletal Class II adult cases. Our study firstly revealed that the roots of the maxillary central and lateral incisors were placed more labially in the subjects of severe high-angle skeletal Class II than in those of severe high-angle skeletal Class III, especially in the lateral incisors.

Influence of bone loss and inclination of incisor on periradicular stresses due to simulated bite force

Abstract Introduction Adults with sequelae of periodontal disease tend to have bone loss, with consequent flaring of the maxillary incisors. Objective The influence of bone loss and the inclination of the maxillary incisor in the distribution of stresses due to simulated bite forces was studied. Material and method Models in epoxy resin were made in three conditions (without bone loss and with bone loss of 5mm and 8mm). Increases in the labial inclination of the maxillary incisor of 10° and 20° were obtained with a beveled metallic block. Loads of 100N were applied five times in each condition using a universal test machine. The models were observed and filmed with a circular polariscope. Orders of isochromatic fringes (stresses) on the labial, lingual, and apex surfaces were recorded. The agreement of the data was evaluated using the weighted kappa test, and the results were 0.89 and 0.82 for intra- and inter-examiners, respectively. Result The results of the Kruskal–Wallis and SNK tests indicated higher stresses (2.0) with increased labial inclination in the labial surface; higher stresses (2.67) with increased bone loss; higher greater stresses with the association of bone loss and labial-inclination (3.6); and the highest stresses tended to concentrate on the labial surfaces, except in cases of normal inclination and without bone loss (0.45). Conclusion It was concluded that increases in both the labial inclination of the maxillary incisors and bone loss increase periradicular stresses, and the combination of these factors further increases the stresses due to bite forces, with the highest concentration on the labial side.

Combining virtual model and cone beam computed tomography to assess periodontal changes after anterior tooth movement

Background

Orthodontic force may affect not only periodontal ligaments, but also the alveoloar bone and the gingiva according to the type of tooth movements. The authors assessed changes in gingival thickness (GT) and alveolar bone thickness (ABT) after orthodontic treatment using a new method.

Methods

This study included 408 teeth (208 central incisors, 200 lateral incisors) from the upper and lower 4 anterior teeth of 52 patients who had completed orthodontic treatment. GT and ABT were measured using virtual casts fabricated from impressions and cone beam computed tomography (CBCT). Two sectioned images of every tooth axis were acquired by partitioning each tooth with a line connecting the midpoint of the incisal edge to the midpoint of the cementoenamel junction in the virtual models and the root apex in CBCT images. After superimposing the two sectioned images, GT and ABT were measured before and after orthodontic tooth movement. Correlations between GT and ABT before and after treatment, and changes in GT and ABT associated with sex, tooth arch, tooth position, orthognathic surgery, and tooth inclination and rotation were assessed.

Results

Before orthodontic treatment, GT and ABT were significantly correlated. Patients who underwent orthognathic surgery exhibited an increase in GT thickness compared with those who did not. ABT was significantly decreased in proclined teeth and in rotated teeth.

Conclusions

GT and ABT can be affected by the nature of tooth movement and can be accurately assessed by comparing sectioned CBCT images and virtual models.

Comparison of ultrasound imaging and cone-beam computed tomography for examination of the alveolar bone level: A systematic review

Background and objective

The current methods to image alveolar bone in humans include intraoral 2D radiography and cone-beam computed tomography (CBCT). However, these methods expose the subject to ionizing radiation. Therefore, ultrasound imaging has been investigated as an alternative technique, as it is both non-invasive and free from ionizing radiation. In order to assess the validity and reliability of ultrasonography in visualizing alveolar bone, a systematic review was conducted comparing ultrasound imaging to CBCT for examination of the alveolar bone level.

Study design

Seven databases were searched. Studies addressing examination of alveolar bone level via CBCT and ultrasound were selected. Risk of bias under Cochrane guidelines was used as a methodological quality assessment tool.

Results

All the four included studies were ex vivo studies that used porcine or human cadaver samples. The alveolar bone level was measured by the distance from the alveolar bone crest to certain landmarks such as cemento-enamel junction or gingival margin. The risk of bias was found as low. The mean difference between ultrasound and CBCT measurements ranged from 0.07 mm to 0.68 mm, equivalent to 1.6% - 8.8%.

Conclusions

There is currently preliminary evidence to support the use of ultrasonography as compared to CBCT for the examination of alveolar bone level. Further studies comparing ultrasound to gold standard methods would be necessary to help validate the accuracy of ultrasonography as a diagnostic technique in periodontal imaging.

Assessment of lower incisor alveolar bone width using cone-beam computed tomography images in skeletal Class III adults of different vertical patterns

Objective

This study was performed to investigate the alveolar bone of lower incisors in skeletal Class III adults of different vertical facial patterns and to compare it with that of Class I adults using cone-beam computed tomography (CBCT) images.

Methods

CBCT images of 90 skeletal Class III and 29 Class I patients were evaluated. Class III subjects were divided by mandibular plane angle: high (SN-MP > 38.0°), normal (30.0° < SN-MP < 37.0°), and low (SN-MP < 28.0°) groups. Buccolingual alveolar bone thickness was measured using CBCT images of mandibular incisors at alveolar crest and 3, 6, and 9 mm apical levels. Linear mixed model, Bonferroni post-hoc test, and Pearson correlation analysis were used for statistical significance.

Results

Buccolingual alveolar bone in Class III high, normal and low angle subjects was not significantly different at alveolar crest and 3 mm apical level while lingual bone was thicker at 6 and 9 mm apical levels than on buccal side. Class III high angle group had thinner alveolar bone at all levels except at buccal alveolar crest and 9 mm apical level on lingual side compared to the Class I group. Class III high angle group showed thinner alveolar bone than the Class III normal or low angle groups in most regions. Mandibular plane angle showed negative correlations with mandibular anterior alveolar bone thickness.

Conclusions

Skeletal Class III subjects with high mandibular plane angles showed thinner mandibular alveolar bone in most areas compared to normal or low angle subjects. Mandibular plane angle was negatively correlated with buccolingual alveolar bone thickness.

Control of anterior segment using an antero-posterior lingual sliding retraction system: a preliminary cone-beam CT study

BACKGROUND

This study was performed to evaluate the treatment effects of the antero-posterior lingual retractor (APLR), focusing on the 3-dimensional (3D) tooth movement of the maxillary anterior teeth and their alveolar bone levels.

METHODS

En masse retraction was performed using either the C-lingual retractor (CLR, C-group, n = 9) or the antero-posterior lingual retractor (APLR, AP-group, n = 8). We evaluated 3D movement of the maxillary anterior teeth and alveolar bone levels, root length of the central incisors, long axes of the maxillary canines, and occlusal plane changes from CBCT images.

RESULTS

After retraction, the central incisors were more significantly intruded and their root apex was more retracted in the AP-group. The long axis of the canine was well maintained in the AP-group. There were no differences in the steepness of occlusal plane and the incidence of alveolar bone loss or of root resorption during en masse retraction with the two retractors.

CONCLUSIONS

The clockwise bowing effect of the anterior segment was less with the APLR, which prevented unwanted canine movement.

Correlation between periodontal soft tissue and hard tissue surrounding incisors in skeletal Class III patients

OBJECTIVES

To investigate the association between the periodontal soft tissue, alveolar bone and dental parameters surrounding the incisors at baseline in patients with skeletal Class III malocclusion.

MATERIALS AND METHODS

The study sample comprised 154 teeth from 28 patients with skeletal Class III malocclusion (19 men and 9 women, 21.15 ± 4.02 years). Periodontal soft tissue examination and hard tissue measurements with cone-beam computed tomography (CBCT) were performed. Factor analysis was used to reduce the CBCT variables, and correlation analysis between the hard tissue factors and soft tissue parameters was performed. Differences in hard tissue parameters between thick and thin gingival types were evaluated.

RESULTS

CBCT measurements were reduced to three hard tissue factors: lingual plate, coronal-buccal plate, and apical-buccal plate. Keratinized gingiva width and thickness were positively correlated with the coronal-buccal plate factor and negatively correlated with the apical-buccal plate factor. In the thin gingival biotype, mandibular incisors were more proclined, and the apical part of the buccal alveolar plate and the coronal part of lingual alveolar plate were thicker than in the thick gingival biotype.

CONCLUSIONS

In the anterior teeth in cases of skeletal Class III malocclusion, hard tissue structures on the buccal side can be grouped based on coronal and apical factors that are significantly correlated with keratinized gingival width and thickness. Thick and thin gingival biotypes exhibited differences in tooth inclination and alveolar plate thickness with regard to the mandibular incisors.

Changes in alveolar bone support induced by the Herbst appliance: a tomographic evaluation

Objective:

This study evaluated alveolar bone loss around mandibular incisors, induced by the Herbst appliance.

Methods:

The sample consisted of 23 patients (11 men, 12 women; mean age of 15.76 ± 1.75 years), Class II, Division 1 malocclusion, treated with the Herbst appliance. CBCT scans were obtained before treatment (T₀) and after Herbst treatment (T₁). Vertical alveolar bone level and alveolar bone thickness of mandibular incisors were assessed. Buccal (B), lingual (L) and total (T) bone thicknesses were assessed at crestal (1), midroot (2) and apical (3) levels of mandibular incisors. Student's t-test and Wilcoxon t-test were used to compare dependent samples in parametric and nonparametric cases, respectively. Pearson's and Spearman's rank correlation analyses were performed to determine the relationship of changes in alveolar bone thickness. Results were considered at a significance level of 5%.

Results:

Mandibular incisors showed no statistical significance for vertical alveolar bone level. Alveolar bone thickness of mandibular incisors significantly reduced after treatment at B1, B2, B3, T1 and significantly increased at L2. The magnitude of the statistically significant changes was less than 0.2 mm. The changes in alveolar bone thickness showed no statistical significance with incisor inclination degree.

Conclusions:

CBCT scans showed an association between the Herbst appliance and alveolar bone loss on the buccal surface of mandibular incisors; however, without clinical significance.

Quantitative cone-beam computed tomography evaluation of premaxilla and symphysis in Class I and Class III malocclusions

AIMS

In order to compare the premaxilla and symphysis in Class I and Class III individuals, we measured the following parameters on CBCT scans: incisor inclination, symphyseal morphology, upper alveolar process morphology, symphyseal and maxillary leeway space, as well as anterior and posterior maxillary and mandibular bone thickness at various points below the cementoenamel junction.

MATERIALS AND METHODS

CBCT scans were taken of 62 individuals (41 females and 21 males) of ages ranging between 11 and 53years (mean 23.26). The dentoskeletal relationship and alveolar process morphology (thickness) were evaluated on axial slices of the upper and lower jaws, and Student's parametric t-test for paired data was used to compare Class I and Class III values within different facial types.

RESULTS

Many significant differences in measurements between the two facial types were noted in terms of tooth inclination, alveolar thickness, and leeway space.

CONCLUSIONS

Our findings confirm that Class III patients have little periodontal support at the upper and lower incisors, irrespective of the amount of symphyseal leeway space available, and any tooth movement must therefore be carefully planned and monitored.

Effects of occlusion on mandibular morphology and architecture in rats

BACKGROUND

A rodent occlusal hypofunction model has been widely established in jawbone-related studies. However, the effects of occlusal stimuli, with total elimination of molar contacts, and its rehabilitation on mandibular remodeling remain unclear.

MATERIALS AND METHODS

Forty-eight 5-wk-old Sprague-Dawley male rats were used. Twenty-four experimental rats underwent occlusal hypofunction by insertion of a bite-raising appliance. Twenty-four rats received no treatment (control group). Two weeks later, half the experimental rats (occlusal hypofunction group) were killed; the appliance was removed from the remaining experimental rats (recovery group) for two additional weeks before killing. Control animals were killed biweekly. Body weight and masseter muscle weight were measured, and the mandibles were subjected to micro-computed tomography to evaluate the mandibular morphology and cortical bone characteristics. The expressions of osteoblast- and osteoclast-related genes were evaluated with quantitative polymerase chain reaction.

RESULTS

No significant body weight differences were observed between the experimental and control rats. However, lighter masseter muscle, shorter mandibular incisor crown, mandibular body and ramus, and higher mandibular alveolar process and first molar fossae were observed in the occlusal hypofunction group. Moreover, the cortical bone characteristics associated with the expression of osteoblast- and osteoclast-related genes were remarkably different in the central and posterior mandible in the occlusal hypofunction group. At the 2-wk recovery time point after occlusal stimuli, the altered parameters in the masseter and mandible returned to normal levels.

CONCLUSIONS

Mandibular remodeling via bone turnover is region specific for altered occlusal stimuli. Normal occlusion is an important determinant of the mandibular morphology and architecture.

Accuracy of cone-beam computed tomography in detecting alveolar bone dehiscences and fenestrations

INTRODUCTION

The purposes of this study were to evaluate the accuracy of cone-beam computed tomography (CBCT) for detecting naturally occurring alveolar bone dehiscences and fenestrations and to find a better method to diagnose them.

METHODS

The sample consisted of 122 anterior teeth in 14 patients with Class III malocclusion who accepted accelerated osteogenic orthodontic surgery in the anterior tooth region. Dehiscences and fenestrations were measured both directly, with a gauge during surgery, and indirectly, by CBCT scans collected before treatment. A Bland-Altman plot for calculating agreement between the 2 methods was used. Direct data were regarded as the gold standard, and indirect data were analyzed to evaluate the accuracy of CBCT for detecting dehiscences and fenestrations by sensitivity, specificity, positive predictive value, negative predictive value, Youden index, positive likelihood ratio, and negative likelihood ratio. Receiver operator characteristic curves were also used to determine the area under curve and the best critical points of CBCT for detecting dehiscences and fenestrations.

RESULTS

Both the sensitivity and specificity of CBCT for dehiscences and fenestrations were over 0.7. The negative predictive values were high (dehiscence, 0.82; fenestration, 0.98), whereas the positive predictive values were relatively low (dehiscence, 0.75; fenestration, 0.16). Areas under the curve were 0.873 for dehiscences and 0.766 for fenestrations. The best critical points for detecting both dehiscences and fenestrations were 2.2 mm.

CONCLUSIONS

Our study showed that the CBCT method has some diagnostic value for detecting naturally occurring alveolar bone dehiscences and fenestrations. However, this method might overestimate the actual measurements.

Evaluation of Bone Thickness and Density in the Lower Incisors' Region in Adults with Different Types of Skeletal Malocclusion using Cone-beam Computed Tomography

OBJECTIVES

To evaluate the bone thickness and density in the lower incisors' region in orthodontically untreated adults, and to examine any possible relationship between thickness and density in different skeletal patterns using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

The CBCT records of 48 patients were obtained from the archive of orthodontic department comprising three groups of malocclusion (class I, II and III) with 16 patients in each group. Using OnDemand 3D software, sagittal sections were made for each lower incisor. Thicknesses and densities were measured at three levels of the root (cervical, middle and apical regions) from the labial and lingual sides. Accuracy and reliability tests were undertaken to assess the intraobserver reliability and to detect systematic error. Pearson correlation coefficients were calculated and one-way analysis of variance (ANOVA) was employed to detect significant differences among the three groups of skeletal malocclusion.

RESULTS

Apical buccal thickness (ABT) in the four incisors was higher in class II and I patients than in class III patients (p < 0.05). There were significant differences between buccal and lingual surfaces at the apical and middle regions only in class II and III patients. Statistical differences were found between class I and II patients for the cervical buccal density (CBD) and between class II and III patients for apical buccal density (ABD). Relationship between bone thickness and density values ranged from strong at the cervical regions to weak at the apical regions.

CONCLUSIONS

Sagittal skeletal patterns affect apical bone thickness and density at buccal surfaces of the four lower incisors' roots. Alveolar bone thickness and density increased from the cervical to the apical regions.

Lower incisor dentoalveolar compensation and symphysis dimensions among Class I and III malocclusion patients with different facial vertical skeletal patterns

OBJECTIVE

To compare lower incisor dentoalveolar compensation and mandible symphysis morphology among Class I and Class III malocclusion patients with different facial vertical skeletal patterns.

MATERIALS AND METHODS

Lower incisor extrusion and inclination, as well as buccal (LA) and lingual (LP) cortex depth, and mandibular symphysis height (LH) were measured in 107 lateral cephalometric x-rays of adult patients without prior orthodontic treatment. In addition, malocclusion type (Class I or III) and facial vertical skeletal pattern were considered. Through a principal component analysis (PCA) related variables were reduced. Simple regression equation and multivariate analyses of variance were also used.

RESULTS

Incisor mandibular plane angle (P < .001) and extrusion (P  =  .03) values showed significant differences between the sagittal malocclusion groups. Variations in the mandibular plane have a negative correlation with LA (Class I P  =  .03 and Class III P  =  .01) and a positive correlation with LH (Class I P  =  .01 and Class III P  =  .02) in both groups. Within the Class III group, there was a negative correlation between the mandibular plane and LP (P  =  .02). PCA showed that the tendency toward a long face causes the symphysis to elongate and narrow. In Class III, alveolar narrowing is also found in normal faces.

CONCLUSIONS

Vertical facial pattern is a significant factor in mandibular symphysis alveolar morphology and lower incisor positioning, both for Class I and Class III patients. Short-faced Class III patients have a widened alveolar bone. However, for long-faced and normal-faced Class III, natural compensation elongates the symphysis and influences lower incisor position.

Morphometric evaluation of changes in the alveolar bone and roots of the maxillary anterior teeth before and after en masse retraction using cone-beam computed tomography

OBJECTIVE

To evaluate the morphometric changes in the alveolar bone and roots of the maxillary anterior teeth (MXAT) after en masse retraction with maximum anchorage (EMR-MA).

MATERIALS AND METHODS

The samples consisted of 37 female adult patients who had Class I dentoalveolar protrusion (CI-DAP) and were treated by extraction of the first premolars and EMR-MA. Using three-dimensional cone-beam computed tomography taken before treatment and after space closure, the maxillary central incisors (MXCI, N  =  66), lateral incisors (MXLI, N  =  69), and canines (MXC, N  =  69) were superimposed using individual reference planes. After alveolar bone area (ABA), vertical bone level (VBL), root length (RL), root area (RA), and prevalence of dehiscence (PD) were measured at the cervical, middle, and apical levels, statistical analyses were performed.

RESULTS

On the palatal side, ABA significantly decreased in all levels of MXAT (P < .001; middle of MXC, P < .01). MXCI and MXLI exhibited a greater decrease in the ratio of change in palatal ABA than did MXC (cervical, P < .01; middle and apical, P < .05; total, P < .001). Palatal/labial ABA ratios decreased in MXCI (cervical, middle, total, P < .001; apical, P < .05) and MXLI (cervical, P < .001; apical, P < .05). They showed greater amounts and ratios of change in VBL on the palatal side compared to the labial side (all P < .001). The palatal side showed more PD in the cervical area than did the labial side (MXCI and MXLI, P < .001; MXC, P < .01). Significant root resorption occurred in MXAT (RL and RA, all P < .001).

CONCLUSIONS

During EMR-MA in cases with CI-DAP, ABA and VBL on the palatal side and RL and RA of MXCI and MXLI were significantly decreased.

The thickness of alveolar bone at the maxillary canine and premolar teeth in normal occlusion

Purpose

The main purpose of this study was to investigate bone thickness on the buccal and palatal aspects of the maxillary canine and premolars using cone-beam computed tomography (CBCT). The differences between left- and right-side measurements and between males and females were also analyzed.

Methods

The sample consisted of 20 subjects (9 males and 11 females; mean age, 21.9±3.0) selected from the normal occlusion sample data in the Department of Orthodontics, The Catholic University of Korea. The thickness of the buccal and palatal bone walls, perpendicular to the long axis of the root were evaluated at 3 mm and 5 mm apical to cemento-enamel junction (CEJ) and at root apex.

Results

At the canines and first premolars regions, mean buccal bone thickness of at 3 mm and 5 mm apical to CEJ were less than 2 mm. In contrast, at the second premolar region, mean buccal bone thickness at 3 mm and 5 mm apical from CEJ were greater than 2 mm. Frequency of thick bone wall (≥2 mm) increased from the canine to the second premolar.

Conclusions

This result should be considered before tooth extraction and planning of rehabilitation in the canine and premolar area of maxilla. Careful preoperative analysis with CBCT may be beneficial to assess local risk factors and to achieve high predictability of success in implant therapy.