Is Incisor Compensation Related to Skeletal Discrepancies in Skeletal Class III? A Retrospective Cephalometric Study

This study investigated compensation in skeletal Class III subjects to compare various severities of abnormal jaws. A retrospective analysis of 137 skeletal Class III cephalograms (63 males and 74 females) was conducted, with cephalometric assessments determining skeletal and dental values. The results were compared with Class I cephalograms. Incisor compensation was examined by pairing normal jaws with varied abnormal jaws, classified by severity using one standard deviation (SD). Statistical analyses included Kruskal-Wallis tests, Bonferroni tests, Spearman's correlations, and multiple linear regression. Four skeletal Class III groups were identified: OMx+PMd, RMx+OMd, OMx+OMd, and PMx+PMd (P = prognathic; O = orthognathic; R = retrognathic; Mx = maxilla; Md = mandible.). The upper central incisor (U1) showed proclination, and the lower central incisor (L1) showed retroclination across all groups except for U1 in PMx+PMd and L1 in OMx+OMd, which exhibited normal inclination. U1 exhibited limited compensation even with progressive maxillary retrognathism, while L1 showed limited compensation after one SD of mandibular prognathism. Maxilla (SNA) and jaw discrepancy (ANB) were inversely related to the U1 degree, whereas only jaw discrepancy (ANB) was positively related to the L1 degree. U1 in PMx+PMd and L1 in OMx+OMd showed no incisor compensation. U1 had limited compensation even with progressive maxillary retrognathism while L1 showed limited compensation after one SD mandibular prognathism.

Association between the Obstructive Sleep Apnea and Cephalometric Parameters in Teenagers

BACKGROUND

OSA is a common problem in children and adolescents. Angle class II malocclusion, a tendency toward the vertical type of growth, causes a decrease in the volume of the oral air space, increasing the risk of OSAS. The aim of this study was to evaluate the relationship between cephalometric and OSA parameters, to develop collaborative approaches between orthodontists and somnologists in the treatment of adolescents with OSA.

METHODS

We analyzed data from 41 adolescents with OSA. Their mean age was 15.8 ± 1.08 years. Orthodontic and polysomnographic examinations of patients were conducted. Statistical analysis was performed in SPSS 19.0.0.

RESULTS

Most often in patients with distal occlusion, a violation of the harmony in the development of the dental system was observed. The sagittal incisive fissure, characteristic of a distal occlusion, was absent due to the palatal inclination of the upper incisors in 25 (60.98%) patients. The SNB was 79.4 ± 3.1°, indicating a distal position of the mandible relative to the anterior cranial base. The SNA exceeded the normal value, which is one of the prerequisites for mandibular retrognathia. The ANB angle was 4.3 ± 1.9°. Tonsillar hypertrophy affected 6 patients, 21 had adenoid hypertrophy, and 3 had both of them. Movements of the masticatory muscles during sleep were recorded in 22.0% of patients.

CONCLUSION

To improve the quality of diagnosis and treatment of OSA, a multidisciplinary approach is needed that will correct the processes of child growth and development.

Proposed parameters of optimal central incisor positioning in orthodontic treatment planning: A systematic review

OBJECTIVE

Planning of incisal position is crucial for optimal orthodontic treatment outcomes due to its consequences on facial esthetics and occlusion. A systematic summary of the proposed parameters is presented.

METHODS

Studies on Google Scholar©, PubMed©, and Cochrane Library, providing quantitative information on optimal central incisor position were included.

RESULTS

Upper incisors supero-inferior position (4-5 mm to upper lip, 67-73 mm to axial plane through pupils), antero-posterior position (3-4 mm to Nasion-A, 3-6 mm to A-Pogonion, 9-12 mm to true vertical line, 5 mm to A-projection, 9-10 mm to coronal plane through pupils), bucco-lingual angulation (4-7° to occlusal plane perpendicular on models, 20-22° to Nasion-A, 57-58° to upper occlusal plane, 16-20° to coronal plane through pupils, 108-110° to anterior-posterior nasal spine), mesio-distal angulation (5° to occlusal plane perpendicular on models). Lower incisors supero-inferior position (41-48 mm to soft-tissue mandibular plane), antero-posterior position (3-4 mm to Nasion-B, 1-3 mm to A-Pogonion, 12-15 mm to true vertical line, 6-8 mm to coronal plane through pupils), bucco-lingual angulation (1-4° to occlusal plane perpendicular on models, 87-94° to mandibular plane, 68° to Frankfurt plane, 22-25° to Nasion-B, 105° to occlusal plane, 64° to lower occlusal plane, 21° to A-Pogonion), mesio-distal angulation (2° to occlusal plane perpendicular on models).

CONCLUSIONS

Although these findings can provide clinical guideline, they derive from heterogeneous studies in terms of subject characteristics and reference methods. Therefore, the optimal incisal position remains debatable.

Effects of anterior tooth crown inclination on occlusal relationship-A study in three-dimensional reconstruction

OBJECTIVE

This study aims to analyze the relationship between the central incisor crown inclination and occlusal relationship via three-dimensional study.

METHODS

Ten Chinese volunteers with normal occlusion were selected from physical examination of college students. Lateral cephalograms and CT scans were taken, and the CT data were imported into Simplant pro 11.04 to reconstruct three-dimensional model. In the three-dimensional model, every tooth was separated independently. The upper and lower central incisors were moved labial inclination(up) or lingual inclination(down) and then the upper and lower tooth were aligned based on the central incisor's position according to the principles of Andrew's six keys. Four groups were set up with different changes of central incisors. The upper and the lower arch were aligned again based on the moved central incisors. After every motion, the mesio-distal distances of upper and lower canines and first molars were recorded. All data were analyzed using t-test via SPSS19.0, and the significance level was set at 5%.

RESULTS

The results showed that the mesio-distal distances of occlusal relationship were different from normal occlusal relations, when either upper incisor crown inclination or lower incisor crown inclination was changed, and both upper and lower incisor crown inclination were moved in same or opposite direction. According to the statistical analysis, there was no significant difference when the changes of U1-L1 were no more than 10° (P > 0.05). But there was statistically significant difference (P < 0.05) when changes of U1-L1 were more than 20°.

CONCLUSIONS

The incisor crown inclination has influence on the establishment of occlusal relationships. The bigger difference upper and lower incisor crown inclination has, the more deviations from the normal occlusal relationship exist.

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.

Dentoalveolar compensation according to skeletal discrepancy and overjet in skeletal Class III patients

INTRODUCTION

This study was designed to investigate dentoalveolar compensation in untreated skeletal Class III patients with either positive or negative overjet.

METHODS

The positive overjet groups consisted of 104 adults, divided into group 1 (angle between sella-nasion to mandibular plane (SN-MP) > 38°, n = 30), group 2 (30° < SN-MP < 38°, n = 43), and group 3 (SN-MP <30°, n = 31). The negative overjet groups (groups 4-6) consisted of 90 adults who were closely matched to the positive overjet groups with regard to the ANB and SN-MP angles. Twenty-two cephalometric measurements were compared between the matched groups. In the positive overjet groups, correlation analysis was performed between the skeletal and dental measurements, and regression analysis was performed to determine the incisor-mandibular plane angle.

RESULTS

The maxillary incisors were more proclined and the occlusal plane was more flattened in the positive overjet groups than in the negative overjet groups; however, there was no statistically significant difference between them with regard to mandibular incisor inclination. The inclinations of the maxillary and mandibular incisors were correlated with both the sagittal and vertical skeletal measurements. Eight regression equations for the incisor-mandibular plane angle were calculated with the highest coefficient of determination of 0.547.

CONCLUSIONS

Proclination of the maxillary incisors and flattening of the occlusal plane contributed to a positive overjet. Mandibular incisor inclination was more closely associated with sagittal and vertical skeletal discrepancies and was not affected by the incisal relationship.

Lower incisor position in different malocclusions and facial patterns

Introduction: The position of lower incisor has been of considerable concern when planning an orthodontic treatment, having been recognized as one of diagnostic keys, Very important in the development of malocclusion and facial pattern. Objectives: In this study we claim to determine the importance of the position and inclination of lower incisor in the different malocclusions and facial patterns, and to base which of the cephalometric measurement parameters are the mostreliable. Material and Methods: Ninety lateral radiographies were taken, and they were classified by skeletal malocclusion and facial pattern.These teleradiographies have been performed cephalometric analysis, which includelower incisor position belong the following analysis: Ricketts, Riolo, Tweed, McHorris, Jarabak-MSE and Holdaway. Study Design: Cross-sectional study where we perform statistical analysis Anova test, Pearson correlations and Bonferroni analysis. Results: The analyzed measurements present a statistically significant differentiation in lower incisor inclination respect to the anterior cranial base, McHorris angle, angulation of lower incisor respect to occlusal plane and mandibular plane. Conclusions: There are statistically significant differentiation in lower incisor position and inclination respect the malocclusion and individual facial pattern.

Key words:Lower incisor, cephalometric analysis, facial patterns, facial biotype, skeletal malocclusions.

On the relevance of "ideal" occlusion concepts for incisor inclination target definition

INTRODUCTION

The concept of "ideal" occlusion in harmony with craniofacial structures is often proposed as an ultimate goal of orthodontic treatment. The aim of this study was to assess the impact of slight variations in posterior occlusion and the history of straight-wire orthodontic treatment on the predictability of incisor inclination and third-order angles.

METHODS

Axial incisor inclinations, third-order angles, and craniofacial relationships were assessed on lateral headfilms and corresponding dental casts of 75 healthy white subjects, 16 to 26 years old, selected by the general inclusion criterion of a good interincisal relationship. Four groups were formed: group A (n = 17), Angle Class I occlusion subjects with no orthodontic treatment; group B (n = 20), Angle Class I occlusion subjects treated with standardized straight-wire orthodontics; group C (n = 20), up to a half-cusp distal occlusion after straight-wire treatment; and group D (n = 18), up to a half-cusp distal occlusion and no orthodontic treatment. Regression analysis was used to insert predictor angles into selected regression equations of the subjects with "ideal" occlusion, and the absolute differences between predicted and observed response angles were determined.

RESULTS

Small differences in incisor inclination were found between subjects with "ideal" occlusion and those who slightly deviated from "ideal" with a mild occlusion of the Angle Class II category. Posterior occlusion was not relevant to the validity of the vast majority of predictor-response pairs. Straight-wire treatment produced incisor inclination that was slightly protruded compared with subjects who had good natural occlusion.

CONCLUSIONS

The "ideal" posterior occlusion concepts as a general orthodontic treatment goal should be reconsidered.