Three-dimensional evaluation of mandibular lingula: Comparisons of skeletal angle classifications and growth patterns.

OBJECTIVES: This study aimed to evaluate the position of the mandibular lingula (ML) in adult patients (aged between 18 and 35 years old) with different skeletal and growth patterns using cone-beam computed tomography (CBCT). DESIGN: Cross-sectional. SETTING: Dentistry department of University. SUBJECTS: Subjects comprised CBCT images of 150 adult patients, including 300 rami. METHODS AND MATERIALS: In total, 150 CBCT aged between 18 and 35 were selected and divided into three main groups of 50 samples based on their skeletal relationships (classes I, II and III). Patients were subdivided based on their growth pattern (vertical vs. horizontal), resulting in 25 samples per subgroup. Distances between the mandibular lingula and occlusal plane (ML-OP), sigmoid notch (ML-SN), external oblique ridge (ML-EOR), internal oblique ridge (ML-IOR), posterior border of the ramus (ML-PBR), inferior border of the ramus (ML-IBR), and horizontal and vertical distances to the mandibular foramen (ML-hMF and ML-vMF). One-way ANOVA variance analysis was employed to compare different angle classifications, and Bonferroni analysis was used for multiple comparisons. The Student's t-test was also used to compare growth patterns within each main group and genders within the subgroup. RESULTS: The study revealed statistically significant differences in the position of the mandibular lingula between different angle classifications, growth patterns, and genders. Class II samples showed a more anterior position of the ML, whereas Class III samples displayed a more posterior position of the ML. Patients with horizontal growth patterns and Angle Class III had a more posteriorly positioned ML. Gender differences were observed, particularly in Class I and Class III classifications, suggesting that gender may influence the variability of ML position in these specific classifications. CONCLUSION: The position of the mandibular lingula showed high variability among individuals with different angle classifications, growth patterns and genders.

Digital analyses of Bolton tooth size ratios and their association to gender, angle class, and other occlusal traits: a study using a partially automated digital 3D model analysis.

BACKGROUND: This study aims to verify Bolton's values for tooth size ratios and to evaluate possible relationships to different occlusal traits using precise digital measurement methods. MATERIALS AND METHODS: Including 1000 consecutively selected patients from three study centres a digital, partially automated model analysis was performed utilizing the software OnyxCeph. The measurements comprised tooth width for calculation of anterior (AR) and overall ratio (OR) as a percentage, arch width, length, perimeter, overjet, overbite, space analysis in millimetre and the assessment of the angle classification. RESULTS: AR and OR were significantly increased compared to Bolton's ratios of 77.2% (AR) and 91.3% (OR). In the gender comparison, male patients showed larger tooth size ratios, especially in the OR. Patients with Angle Class II/1 and II/2 had smaller tooth size ratios than patients with Angle Class III and I. Thus, patients with Angle Class II/1 had the largest tooth diameters in all maxillary teeth and with Angle Class II/2 the smallest tooth sizes in the mandible. The largest tooth widths in the lower jaw were observed in the Angle Class III patient group. Furthermore, a negative correlation from AR/OR to overjet, overbite, and available space in lower jaw as well as a positive correlation to available space in upper jaw was detected. CONCLUSIONS: There is a clear correlation between the tooth size ratios and the present dysgnathia as well as other orthodontically relevant occlusal traits. This prior knowledge about our patients is extremely important to create an individualized treatment plan and enable sufficient occlusion. To achieve a functionally good occlusion with correct overjet and overbite, it is essential that the maxillary and mandibular teeth are proportional in size. Any deviation from the ideal patient in terms of tooth size, number, shape, or arch must be considered in the pre-therapeutic treatment plan in combination with the existing dysgnathia in order to be able to achieve a stable anterior and posterior occlusion with appropriate adjustments to the therapy post-therapeutically.

Credibility of Pont's index in Egyptian population.

BACKGROUND: Many indices have been suggested to help orthodontists in predicting the ideal dental arch width. One of these was Pont's index which was established by Pont. He suggested equations to predict the ideal maxillary dental arch width (interpremolar and intermolar) from the combined mesiodistal width of the maxillary incisors. This study aimed to test the applicability of Pont's index as an orthodontic diagnostic tool in Egyptian population and to compare the results with those obtained from studies of different ethnic subjects. METHODS: This study was performed using dental casts of 184 Egyptian individuals (82 males and 102 females; age range, 19-24 years). The casts were divided into 46 casts with normal occlusion, 46 casts with class I, 46 casts with class II and 46 casts with class III malocclusion, according to Angle's classification. Alginate impressions were taken for all patients and poured immediately using dental plaster. The real models were transformed into digital models using three-dimensional laser scanner to allow digital model analysis. Predicted arch widths were calculated using Pont's equations. The predicted values were compared to the measured values. RESULTS: Intra class correlation coefficient (ICC) (absolute agreement) between measured and predicted arch widths was determined. Poor absolute agreement was found between measured arch width values and the corresponding values calculated according to Pont's index. CONCLUSION: According to the results of this study, Pont's index is not a reliable method for predicting the ideal dental arch widths in Egyptian populations.

Retrospective analysis of the upper airway anatomy and Sella turcica morphology across different skeletal malocclusions: a computerized technique.

OBJECTIVE: This study aimed to investigate the normal volumetric space and variations in the measurements of different landmarks in adults with different skeletal relations of the maxilla and the mandible based on CBCT data. The study also analyses these landmarks to locate any correlations. BACKGROUND: Numerous studies in orthodontics have found a relationship between orthodontic treatment and changes in the anatomy and function of the airway. Severe changes in airway morphology can cause breathing difficulties, lower quality of life, and even result in life-threatening conditions such as obstructive sleep apnoea. Consequently, orthodontic diagnosis and treatment planning require a thorough understanding of the airway space and its function. METHODS: The present retrospective study was conducted using CBCT records of 120 adult patients, containing 40 samples of each skeletal class (20 males and 20 females). The boundaries were defined for the 3 major regions: the nasopharynx, the oropharynx, and the hypopharynx. Various measurements were recorded across these regions, as well as selective cephalometric landmarks. The obtained data was used to calculate average and standard deviation, while regression analysis was used to evaluate correlations and t-test was used to test statistical significance of gender differences. RESULTS: The results demonstrate that skeletal Class III individuals exhibit a reduced airway volume in the nasopharynx compared to other groups, whereas skeletal Class II individuals displayed a diminished airway volume in the hypopharynx. A strong correlation was observed for Sella turcica parameters. There were no significant differences in skeletal parameters across genders. Nasopharynx cavity volume demonstrated significant differences between skeletal Class I-Class III as well as between skeletal Class II-Class III. Hypopharynx cavity volume also demonstrated significant differences between skeletal Class I-Class II and between skeletal Class II-Class III. CONCLUSION: The major findings are the presence of a reduced nasopharyngeal volume in skeletal Class III malocclusions while skeletal Class II individuals displayed a diminished hypopharyngeal volume, making these critical areas to consider during the diagnostic and orthodontic treatment planning stages. This study also revealed a consistent correlation between Sella turcica parameters across various facial skeletal profiles, with skeletal Class II patients exhibiting a distinct pattern and skeletal Class I and Class III demonstrating an average relationship.

Network analysis of three-dimensional hard-soft tissue relationships in the lower 1/3 of the face: skeletal Class I-normodivergent malocclusion versus Class II-hyperdivergent malocclusion.

BACKGROUND: The determining effect of facial hard tissues on soft tissue morphology in orthodontic patients has yet to be explained. The aim of this study was to clarify the hard-soft tissue relationships of the lower 1/3 of the face in skeletal Class II-hyperdivergent patients compared with those in Class I-normodivergent patients using network analysis. METHODS: Fifty-two adult patients (42 females, 10 males; age, 26.58 ± 5.80 years) were divided into two groups: Group 1, 25 subjects, skeletal Class I normodivergent pattern with straight profile; Group 2, 27 subjects, skeletal Class II hyperdivergent pattern with convex profile. Pretreatment cone-beam computed tomography and three-dimensional facial scans were taken and superimposed, on which landmarks were identified manually, and their coordinate values were used for network analysis. RESULTS: (1) In sagittal direction, Group 2 correlations were generally weaker than Group 1. In both the vertical and sagittal directions of Group 1, the most influential hard tissue landmarks to soft tissues were located between the level of cemento-enamel junction of upper teeth and root apex of lower teeth. In Group 2, the hard tissue landmarks with the greatest influence in vertical direction were distributed more forward and downward than in Group 1. (2) In Group 1, all the correlations for vertical-hard tissue to sagittal-soft tissue position and sagittal-hard tissue to vertical-soft tissue position were positive. However, Group 2 correlations between vertical-hard tissue and sagittal-soft tissue positions were mostly negative. Between sagittal-hard tissue and vertical-soft tissue positions, Group 2 correlations were negative for mandible, and were positive for maxilla and teeth. CONCLUSION: Compared with Class I normodivergent patients with straight profile, Class II hyperdivergent patients with convex profile had more variations in soft tissue morphology in sagittal direction. In vertical direction, the most relevant hard tissue landmarks on which soft tissue predictions should be based were distributed more forward and downward in Class II hyperdivergent patients with convex profile. Class II hyperdivergent pattern with convex profile was an imbalanced phenotype concerning sagittal and vertical positions of maxillofacial hard and soft tissues.

The relationship of anterior occlusion and skeletal variables with the frontal sinus index: An analytical cross-sectional study.

OBJECTIVE: To determine the relationship of anterior occlusion and skeletal variables with the frontal sinus index. METHODS: The retrospective, analytical, cross-sectional, study was conducted from July to November 2020 at Dr Ishratul- Ebad Khan Institute of Oral Health Sciences and Dow Dental College, Dow University of Health Sciences, Karachi, and comprised data from 2015 to 2018 related to pre-treatment lateral cephalograms for determining frontal sinus index and other cephalometric variables. The dental casts were observed for incisor classification. Patients with Class I incisors formed the comparison group, while the rest comprised 5 malocclusion groups. The frontal sinus was traced, and the sinus index was calculated. Data was analysed using STATA 15 and R 3.5.1. RESULTS: Of the 240 subjects, there were 40(16.66%) in each of the 6 groups; 155(64.6%) females and 85(35.4%) males. The mean age of the sample was 21.33±3.52 years (range: 16-29 years). The mean sinus index was higher in all malocclusion groups than the comparison group, but it was significantly higher only in Class II division 2 and anterior open bite groups (p<0.05). The only exception to the trend was Class II division 1 with and without contact in which the value was lower (p>0.05). The anterior cranial base length, sella-nasion mandibular plane angle, and upper incisor palatal plane angle significantly affected the frontal sinus index (p<0.05). CONCLUSIONS: The frontal sinus index could be considered an indicator of harmonious anterior occlusion.

Relationships among tongue volume, hyoid position, airway volume and maxillofacial form in paediatric patients with Class-I, Class-II and Class-III malocclusions.

OBJECTIVES: To clarify the associations among tongue volume, hyoid position, airway volume and maxillofacial form using cone beam computed tomography (CBCT) data for children with Class-I, Class-II and Class-III malocclusion. SETTING AND SAMPLE POPULATION: Sixty children (mean age, 9.2 years) divided into Class-I, Class-II and Class-III malocclusion groups according to the A-nasion-B angle. MATERIAL AND METHODS: Cone beam computed tomography was used for three-dimensional reconstruction of the maxillofacial region and airway. The hyoid position and the tongue, airway and oral cavity volumes were evaluated. Upper airway ventilation status was calculated using computational fluid dynamics. The groups were compared using analysis of variance and Kruskal-Wallis tests; relationships among the parameters were assessed using Pearson's and Spearman's rank correlation tests. RESULTS: The tongue volume was larger in Class-III patients (50.63 cm3 ) than in Class-I patients (44.24 cm3 ; P < 0.05). The hyoid position was lower (49.44 cm), and anatomical balance (AB; tongue volume/oral cavity volume; 85.06%) was greater in Class-II patients than in Class-I patients (46.06 cm, 80.57%, respectively; P < 0.05 for both). The hyoid height showed a positive correlation with AB (r = 0.614; P < 0.001). CONCLUSIONS: Children with Class-III malocclusion have large tongue volumes and small AB; the reverse is true for children with Class-II malocclusion. The hyoid position is closely associated with AB in children with malocclusion.

Craniofacial growth spurt in Class I subjects.

INTRODUCTION: The objective was to study the growth spurt of Class I subjects, focusing on the ability to predict the peak of the growth spurt of the maxillary (Co-A) and mandibular (Co-Pog) lengths from the maturational changes of the cervical vertebrae. METHODS: The longitudinal lateral cephalographs of 14 males (ages, 10-15 years) and 12 females (ages, 9-14 years) were selected from the Craniofacial Growth Studies Legacy Collection of the American Association of Orthodontists Foundation. The cephalographs were taken at regular 1-year intervals. A cervical vertebral maturation (CVM) method that divided skeletal maturation into 6 stages was used for growth prediction. Growth increments calculated for the annual age intervals were used to examine the diagnostic performance of the CVM method. RESULTS: In males, the most peaks for Co-Pog were detected in the CVM3-CVM4 interval in 7 males (50%); for Co-A, the most peaks were found in the CVM2-CVM3 interval in 7 males (50%). In females, the most peaks for both Co-Pog and Co-A were seen in the CVM2-CVM3 interval in 7 females (58%) and in 6 females (50%), respectively. The fewest peaks were detected in CVM4-CVM5 for both males and females. CONCLUSIONS: In Class I subjects with balanced anteroposterior jaw relationships, presence of CVM3 would indicate the peak of the growth spurt, and CVM2 would mean that the peak has not yet arrived. During CVM2, the shapes of cervical vertebrae 3 and 4, whether trapezoid or horizontal rectangular, would indicate whether the subject is in the early CVM2 or is about to be in CVM3.

Dentoskeletal morphology in adults with Class I, Class II Division 1, or Class II Division 2 malocclusion with increased overbite.

INTRODUCTION: The treatment options for adults with increased overbite are limited to dentoalveolar changes that camouflage the condition. Because of high relapse tendency, defining the problem area is important when creating a treatment plan. This study aimed to evaluate dentoskeletal morphology in skeletal Class I and II anomalies associated with Angle Class I, Class II Division 1 (Class II/1), and Class II Division 2 (Class II/2) malocclusions with increased overbite compared with normal occlusion. METHODS: Pretreatment cephalograms of 306 patients (131 men, 175 women; overall ages 18-45 years) were evaluated. Four groups were constructed. Three groups had increased overbite (>4.5 mm): group 1 (n = 96) skeletal Class I (ANB = 0.5°-4°), group 2 (n = 85) skeletal Class II (ANB >4.5°) with Class II/1; and group 3 (n = 79) skeletal Class II with Class II/2 malocclusion. Group 4 as a control (n = 46) skeletal Class I normal overbite. Dental and skeletal characteristics of the groups were compared by sex. For statistical evaluations, analysis of variance followed by Tukey post hoc, Mann-Whitney U, and Kruskall-Wallis tests were used. Additionally correlation coefficients between overbite and skeletal/dental parameters were calculated. RESULTS: Between sexes, with regard to skeletal parameters, the men had greater values in millimetric measurements, and the women had higher SN/GoGn values. Maxillary/mandibular molar heights and the mandibular incisor heights were higher in men. In group 1, decreased lower anterior facial height (LAFH), retrusive mandibular incisors, and increased interincisal degree were determined. The maxillary molars were intrusive, whereas the vertical position of the mandibular molars and incisors in both jaws were normal. In group 2, retrognathic mandible, increased LAFH and mandibular plane angle, extrusive maxillary/mandibular incisors, protrusive mandibular incisors, and decreased interincisal degree were found. In group 3, decreased LAFH, increased interincisal degree, and retrusive incisors in both jaws were determined. There were significant negative correlations between SN/GoGN, palatal plane, and overbite in group 2 and between ANS-SN and overbite in group 3, and positive correlation between interinsical angle and overbite in all increased overbite groups. CONCLUSIONS: Dental morphology seems to be the main factor of increased overbite. Differences between groups were related primarily to inclinations and vertical positions of the incisors, rather than molar positions.

Craniofacial morphology in women with Class I occlusion and severe maxillary anterior crowding.

INTRODUCTION: Our objective was to investigate craniofacial morphology in women with Class I occlusion and maxillary anterior crowding (MxAC) with bilateral palatal displacement of the lateral incisors and facial displacement of the canines. METHODS: Thirty-three women with normal occlusion (mean age, 20.7 ± 2.3 years) were selected as the control group, and 33 women with severe MxAC (mean age, 23.3 ± 3.8 years) with bilateral palatal and facial displacement of the lateral incisors and canines, respectively, were selected as the MxAC group. Mesiodistal tooth crown diameter, arch length discrepancy, facial-palatal displacement of lateral incisors and canines, and dental arch dimensions were measured. Fourteen skeletal and 10 dental cephalometric measurements were made. Medians, interquartile ranges, means, and standard deviations were calculated for each parameter, and the nonparametric Mann-Whitney U test (P <0.05) was used to compare the 2 groups. RESULTS: Compared with the control group, the MxAC group showed a significantly wider angle (P <0.05) and shorter length (P <0.01) in the cranial base, a smaller sagittal maxillary base (P <0.01), and a hyperdivergent skeletal pattern (P <0.01 and P <0.05). CONCLUSIONS: Women with Class I occlusion and severe MxAC exhibited a significantly wider angle and shorter length in the cranial base, a smaller sagittal maxillary base, and a hyperdivergent skeletal pattern. These skeletal and dental characteristics and cranial base dysmorphology may be helpful as potential indicators for orthodontic treatment with extractions.

Long-term (≥15 years) post-treatment changes and outcome quality after Class II:1 treatment in comparison to untreated Class I controls.

Aim: To investigate the long-term (≥15 years) post-treatment (Tx) occlusal changes and outcome quality after Class II:1 Tx. Subjects and Methods: Herbst-MBA Tx had been performed at age 12.8 ± 2.7 years in 119 patients. A recall was conducted and study models from before and after active Tx, after retention as well as after recall were evaluated using standard occlusal variables and the PAR index. These data were compared to 31 untreated Class I controls. Results: 52 out of 119 patients could be located and participated at 33.6 ± 3.1 years. Compared to the 67 patients who did not participate in the recall, the pre- and post-Tx occlusal data of the participants did not differ systematically; however, the PAR scores were higher by 3.0-4.7 points at all times. Pre-Tx, the mean values of the 52 participants were: PAR = 27.2 ± 7.6, Class II molar relationship (MR) = 0.7 cusp widths (cw), overjet = 8.2 mm, overbite = 4.1 mm. After Tx, the PAR score was 3.4 ± 2.2. A Class I MR (0.0 ± 0.1 cw) with normal overjet (2.3 ± 0.7 mm) and overbite (1.3 ± 0.7 mm) existed. At recall, a mild PAR score increase to 8.2 ± 5.5 points had occurred; this was mainly due to increased overjet and overbite values (3.6 ± 1.1 and 2.8 ± 1.6 mm) while the MR was stable (0.0 ± 0.2 cw). For all these variables, similar findings were made in the untreated controls. Conclusion: The occlusal outcome of Class II:1 Tx showed very good long-term stability. While mild changes occur post-Tx, the long-term result is similar to untreated Class I controls.

Comparison of the occlusal contact area of virtual models and actual models: a comparative in vitro study on Class I and Class II malocclusion models.

BACKGROUNDS: The occlusal registration of virtual models taken by intraoral scanners sometimes shows patterns which seem much different from the patients' occlusion. Therefore, this study aims to evaluate the accuracy of virtual occlusion by comparing virtual occlusal contact area with actual occlusal contact area using a plaster model in vitro. METHODS: Plaster dental models, 24 sets of Class I models and 20 sets of Class II models, were divided into a Molar, Premolar, and Anterior group. The occlusal contact areas calculated by the Prescale method and the virtual occlusion by scanning method were compared, and the ratio of the molar and incisor area were compared in order to find any particular tendencies. RESULTS: There was no significant difference between the Prescale results and the scanner results in both the molar and premolar groups (p = 0.083 and 0.053, respectively). On the other hand, there was a significant difference between the Prescale and the scanner results in the anterior group with the scanner results presenting overestimation of the occlusal contact points (p < 0.05). In Molars group, the regression analysis shows that the two variables express linear correlation and has a linear equation with a slope of 0.917. R2 is 0.930. Groups of Premolars and Anteriors had a week linear relationship and greater dispersion. CONCLUSIONS: Difference between the actual and virtual occlusion revealed in the anterior portion, where overestimation was observed in the virtual model obtained from the scanning method. Nevertheless, molar and premolar areas showed relatively accurate occlusal contact area in the virtual model.

The morphology and bridging of the sella turcica in adult orthodontic patients.

BACKGROUND: The purpose of this study was to determine and compare the shapes, sizes, and bridging of the sella turcica in patients with different skeletal patterns and genders. METHODS: It was a cross-sectional comparative study. The samples were divided into three groups according to the skeletal pattern viz. Class I, Class II and Class III, and each group consisted of 40 samples (20 males and 20 females). The lateral cephalograms were traced and the sella turcica was assessed for its size, shape, and bridging. RESULTS: The mean length, anteroposterior diameter and depth of sella turcica were 8.13 ± 2.03 mm, 9.60 ± 1.43 mm and 6.40 ± 1.21 mm respectively. The mean length of sella turcica was 7.91 ± 1.52 mm in Class I, 7.32 ± 1.62 mm in Class II and 9.16 ± .2.42 in Class III skeletal pattern; anteroposterior diameter was 9.30 ± 1.02 mm in Class I, 9.15 ± 1.28 mm in Class II and 10.35 ± 1.64 mm in Class III skeletal pattern; and the depth was 6.40 ± 0.92 mm in Class I, 6.07 ± 1.01 mm in Class II and 6.74 ± .1.54 mm in Class III skeletal pattern. There were significant differences in length and anteroposterior diameter and sella turcica between Class I, Class II and Class III skeletal patterns (p = 0.01), (p = 0.01) respectively. There was no significant difference in size of sella turcica between different genders and age groups. Sixty percent of the patients studied had normal Sella morphology. Partial Sella turcica bridging and Sella turcica bridging was seen in this study in 23.33% and 11.67% of patients respectively. CONCLUSION: Sixty percent of the patients had normal sella turcica. There were significant differences in lengths and anteroposterior diameters among Class I, Class II and Class III patients. The larger size was present in skeletal Class III patients.

Use of Interarch Width Ratio to measure Transverse Relationship: A New Method to measure and assess Interarch Discrepancy.

AIM: The purpose of this study was to assess the arch width, transverse discrepancy, and transverse interarch ratio for class I malocclusion sample, with and without crossbite, in permanent dentition stage. MATERIALS AND METHODS: Records of class I malocclusion patients with minimal crowding and spacing with and without posterior crossbite were selected. Each group consisted of 40 pairs of dental casts (20 males and 20 females). Arch widths were measured for the canine, first, and second premolars, and first permanent molars using the buccal approach. Means and standard deviations (SDs) of dental arch widths were measured for the maxillary and mandibular arches, and the interarch width ratio was calculated. RESULTS: There was a highly significant difference between the noncrossbite and crossbite groups regarding the maxillary width, p < 0.001. However, no differences were found between groups for the mandibular widths, p > 0.01. There were also significant differences between both groups for the intercanine, first and second premolars, and first molar ratios, p < 0.001. CONCLUSION: This new simple method showed that a transverse maxillary-mandibular ratio of 1:1.1 is ideal. A ratio less than 1:0.9 will indicate the presence of crossbite. CLINICAL SIGNIFICANCE: The interarch ratio significantly aids in orthodontic treatment planning in patients requiring maxillary expansion and/or surgical cases.

Comparative Assessment of Facial Asymmetry in Malocclusion using Posteroanterior View.

AIM: The study was conducted to assess facial asymmetry in various dental malocclusions and to determine asymmetry in lower, mid, and upper face and jaws using posteroanterior cephalometric analysis. MATERIALS AND METHODS: Overall, 120 posteroanterior cepha-lograms were taken of individuals between 12 and 25 years of both sexes, and were divided into four groups: Angle's class I excellent occlusion, Angle's class I malocclusion, Angle's class II malocclusion, and Angle's class III malocclusion. These cepha-lograms were traced and Grummon's analysis was performed. RESULTS: In Angle's class I occlusion and Angle's class II malocclusion, the results obtained showed asymmetry present in the upper face. Correlation was found between occlusion, maloc-clusion, and facial asymmetry. CONCLUSION: Facial asymmetry was found in all dental occlusions whether excellent or malocclusion group, with maximum asymmetry having upward trend toward upper face starting from lower. CLINICAL SIGNIFICANCE: For the success of the orthodontic treatments in various types of malocclusion and to determine the facial asymmetry, posteroanterior view can be very helpful, as it gives additional information which can be utilized to augment treatment planning and improve prognosis in terms of relapse prevention.

The relationship between the incisor position and lingual surface morphology in normal occlusion.

This study aimed to investigate the relationship between the morphological characteristics of maxillary incisors and the anterior occlusion. The study materials comprised dental casts and lateral cephalograms of 26 modern Mongolian females with Angle Class I normal occlusion (mean age, 21 years 5 months). Computed tomography (CT) images of the dental casts were taken with an X-ray micro-CT system (SMX-100CT, Shimadzu, Kyoto Japan). The thickness of the marginal ridges and incisal edges, and the overjet and overbite, was measured on the three-dimensional images of the dental casts. On the lateral cephalogram, maxillary incisor to sella-nasion plane angle (U1 to SN angle), maxillary incisor to nasion-point A plane distance (U1 to NA distance), mandibular incisor to nasion-point B plane distance (L1 to NB distance), incisor mandibular plane angle, and interincisal angle were measured by tracing the left incisors of the maxilla and mandible. Spearman's single rank correlation coefficients were used to investigate any correlation between measurement items for each maxillary incisor. The thickness of the marginal ridges and incisal edges was positively correlated with the overbite. The thickness of the incisal edges was positively correlated with the irregularity index of the maxilla. There were significant negative correlations between overbite and U1 to SN angle, U1 to NA distance, and L1 to NB distance. Significant positive correlations were noted between the overbite and the overjet. In conclusion, there was no strong relationship between the morphological characteristics of maxillary incisors and the anterior occlusion.

Buccolingual angulation and intermolar width changes in the maxillary first molars of untreated growing children.

INTRODUCTION: Buccolingual inclinations of the maxillary permanent molars and intermolar widths increase with growth for Class I subjects. Changes for untreated Class II subjects have not yet been assessed. The aim of this study was to test the hypothesis that changes in palatal inclination of the maxillary molars and intermolar width throughout growth vary between Class I and Class II molar occlusions. METHODS: Patients were selected from the Forsyth/Moorrees Twin Study. Dental models taken for 6 consecutive years of 55 untreated subjects (28 with Angle Class I and 27 with Angle Class II occlusion) were scanned. The images were superimposed on the palatal rugae, and the angle between a reference plane and the buccolingual inclination plane was used to calculate the buccolingual molar inclination at each time point. The distance between lingual groove points was used to calculate the intermolar width. RESULTS: All molars showed increasing palatal inclinations over the 6 years. The change for each time interval was statistically significant. Class I subjects demonstrated significantly greater palatal inclination at each time point. The molar inclination changed by means of 4.99° for Class I subjects and 6.25° for Class II subjects. Intermolar width increased continuously (P <0.001) and was significantly greater (P <0.05) for Class I patients. CONCLUSIONS: These results suggest that palatal inclination of the maxillary permanent first molars occurs continuously between ages 9 and 14 years, with Class II subjects showing greater changes. The intermolar width increases steadily during this time, with Class II subjects having a narrower intermolar width and less change over time.

Longitudinal cephalometric growth of untreated subjects with Class II Division 2 malocclusion.

INTRODUCTION: Our objective was to evaluate the craniofacial growth of subjects with untreated Class II Division 2 malocclusion. METHODS: A mixed longitudinal sample of 39 white Class II Division 2 subjects was analyzed at 5 time points: T1 (6 or 7 years), T2 (9 or 10 years), T3 (12 or 13 years), T4 (15 or 16 years), and T5 (18 or 19 years). They were compared with an age- and sex- matched sample of Class I controls. Seventeen measurements (12 angular, 5 proportional) were computed. Multilevel modeling procedures were used to statistically describe the growth changes and to evaluate group differences. RESULTS: There were no group differences in the relative sizes and anteroposterior positions of the jaws during childhood, adolescence, or early adulthood. Subjects with Class II Division 2 malocclusion demonstrated significantly (P <0.05) smaller mandibular plane angles, smaller palatal-to-mandibular plane angles, larger posterior-to-anterior facial height ratios, smaller gonial angles, smaller cranial base angles, larger interincisal angles, and more retroclined maxillary incisors than did the Class I subjects. The hypodivergent patterns were established early and became more pronounced over time. Group differences in the mandibular plane angle, palatal-to-mandibular plane angle, gonial angle, interincisal angle, and maxillary incisor-to-cranial base angle, as well as the posterior-to-anterior facial height ratio all increased over time; the difference in the cranial base angle remained unchanged over time. Retroclination of the maxillary incisors occurred primarily during the early mixed dentition. CONCLUSIONS: Subjects with Class II Division 2 malocclusion are more hypodivergent and have more upright maxillary incisors than do subjects with Class I occlusion. Hypodivergence establishes itself early and increases progressively through early adulthood; maxillary incisor retroclination occurs early.

Transverse dental compensation in relation to sagittal and transverse skeletal discrepancies in skeletal Class III patients.

INTRODUCTION: The purposes of this study were to compare the buccolingual inclinations of the posterior teeth in skeletal Class III patients with and without facial asymmetry with those of skeletal Class I patients and to investigate their relationships with sagittal and transverse skeletal discrepancies. METHODS: Sixty-three skeletal Class III adult patients were divided into 2 groups according to the degree of menton deviation: a symmetry group with deviation less than 2 mm (n = 30), and an asymmetry group with deviation greater than 4 mm (n = 33). The control group comprised 25 skeletal Class I patients. The buccolingual inclinations of the posterior teeth measured on cone-beam computed tomography images were compared among the 3 groups, and regression analysis was performed to investigate the relationships between the inclinations and the sagittal and transverse skeletal discrepancies. RESULTS: The symmetry group showed greater buccal inclinations of the maxillary posterior teeth and lingual inclinations of the mandibular second molars than did the control, and this was correlated with the ANB angles. The deviated sides in the asymmetry group showed the greatest transverse dental compensation, which was correlated with menton deviation, whereas the nondeviated sides showed no significant transverse dental compensation. CONCLUSIONS: Transverse dental compensation is closely related to sagittal and transverse skeletal discrepancy in skeletal Class III patients.

Three-dimensional evaluation of the airway spaces in patients with and without cleft lip and palate: A digital volume tomographic study.

INTRODUCTION: Patients with cleft lip and palate (CLP) suffer from several esthetic and functional challenges. Comprehensive treatment of these patients involves orthognathic surgery that may lead to velopharyngeal insufficiency or reduction in lower airway. Several cases of airway insufficiency, velopharyngeal incompetence, snoring, hypopnea, and obstructive sleep apnea have been reported in subjects with CLP. The aim of this study was to compare the anteroposterior dimensions of the oropharyngeal airway at 5 levels, the height of the oropharyngeal column, and the volume of the oropharyngeal airway in subjects with and without CLP. METHODS: The sample consisted of 62 patients with CLP and 42 subjects with Angle Class I malocclusion. Anteroposterior dimension, height, and volume of the oropharyngeal airway were measured using the midsagittal and axial slices obtained from 3-dimensional digital volume tomographic scans for both groups. RESULTS: The anteroposterior dimensions of the airway were significantly reduced in the study subjects compared with the control group at the level of the postnasal spine, the base of the tongue, and the epiglottis. The airway dimensions measured on the axial sections at the level of the palatal and epiglottic plane were also significantly lower in the study group. The height and volume of the oropharyngeal airway were also significantly smaller in patients with CLP compared with subjects without CLP. CONCLUSIONS: Patients with CLP showed reduced dimensions and volumes of the oropharyngeal airway in all 3 planes compared with the control group.