A Superimposition-Based Cephalometric Method to Quantitate Craniofacial Changes

Evaluation of an Automatic Cephalometric Superimposition Method Based on Feature Matching

The objective of the study is to establish a novel method for automatic cephalometric superimposition on the basis of feature matching and compare it with the commonly used Sella-Nasion (SN) superimposition method. A total of 178 pairs of pre- (T1) and post-treatment (T2) lateral cephalometric radiographs (LCRs) from adult orthodontic patients were collected. Ninety LCR pairs were used to train the you only look once version 8 (YOLOv8) model to automatically recognize stable cranial reference areas. This approach represents a novel method for automated superimposition on the basis of feature matching. The remaining 88 LCR pairs were used for landmark identification by three orthodontic experts to evaluate the accuracy of the two superimposition methods. The Euclidean distances of 17 hard tissue landmarks were measured and statistically compared after superimposition. Significant differences were observed in the superimposition error of most landmarks between the two methods (p < 0.05). The successful detection rate (SDR) of automatic superimposition of each landmark within the precision ranges of 1 mm, 2 mm, and 3 mm via the new method was higher than that via the SN method. The new automatic superimposition method is more accurate than the SN method and is a reliable method for superimposing adult LCRs, thus providing support for clinical or research work.

Skeletal stability after maxillary distraction osteogenesis or conventional Le Fort I osteotomy in patients with cleft lip and palate: A superimposition-based cephalometric analysis

PURPOSE

The aim was to assess skeletal stability after maxillary advancement using either distraction osteogenesis (DO) or conventional Le Fort I osteotomy (CO) in patients with cleft lip and palate (CLP) or cleft palate (CP) utilising a new superimposition-based cephalometric method.

METHOD

This retrospective study included patients who were treated with DO (N = 12) or CO (N = 9). Sagittal and vertical changes after surgery, and skeletal stability at 18 months post-operatively were assessed with superimposition-based cephalometry, comparing lateral cephalograms performed pre-operatively (T0), post-operatively after CO or immediately after completed distraction in DO (T1), and at 18 months of follow-up (T2).

RESULTS

The mean sagittal movements from T0 to T2 in the DO and CO groups were 5.9 mm and 2.2 mm, respectively, with a skeletal relapse rate of 16% in the DO group and 15% in the CO group between T1 and T2. The vertical mean movement from T0 to T2 in the DO and CO groups was 2.8 mm and 2.0 mm, respectively, and the skeletal relapse rate between T1 and T2 was 36% in the DO group and 32% in the CO group.

CONCLUSION

Sagittal advancement of the maxilla was stable, in contrast to the vertical downward movement, which showed more-extensive relapse in both groups. Despite more-extensive maxillary advancement in the DO group, the rates of skeletal relapse were similar.

Comparison of Diagnostic Validity of Cephalometric Analyses of the ANB Angle and Tau Angle for Assessment of the Sagittal Relationship of Jaw and Mandible

BACKGROUND

Cephalometric analysis is an essential tool used in orthodontic diagnosis and treatment planning. The aim of this study was to evaluate the reliability and repeatability of new cephalometric points introduced in Tau angle analysis, in contrast to the gold standard, which is the analysis of the ANB angle. For this purpose, an attempt was made to assess the repeatability and reliability of the introduction of anthropometric points by evaluating both inter- and intraobserver parameters, as well as the agreement among the orthodontists participating in the study.

METHODS

Repeatability and reliability assessments for all six anthropometric points (N, A, B, T, M, G) used in the analysis of the ANB and Tau angles were conducted individually by 29 orthodontists. This assessment was performed in triplicate on the day of the study, on the day following the first study, and on the seventh day after the second study. Measurement errors for the ANB and Tau angles were evaluated using the Dahlberg formula and intraclass correlation coefficients (ICCs).

RESULTS

The orthodontists in the study measured sagittal discrepancy significantly more accurately using the ANB angle compared to the Tau angle (p < 0.001). The Dahlberg error for measuring the Tau angle was three times greater than that for the ANB angle (p < 0.001). Additionally, the ICC for the Tau angle was more than 3.5 times smaller than that for the ANB angle, while the R&R error for Tau measurement was more than three times greater than that for the ANB angle (p < 0.001).

CONCLUSIONS

The results of ANB angle measurements exhibit fewer errors in comparison to Tau angle measurements.

Dentoskeletal and soft tissue changes after treatment of crowding with premolar extractions: a 50-year follow-up

BACKGROUND

The long-term effects on dentofacial morphology of interceptive treatment with premolar extractions, in the absence of subsequent orthodontic treatment, have not been fully explored.

OBJECTIVE

The aim was to investigate the effects of premolar extractions (without subsequent orthodontic treatment) on the dentoskeletal and soft tissue profile of patients aged between 12 and 62 years with Class I malocclusion with severe crowding, as compared to untreated controls.

MATERIALS AND METHODS

The Extraction group (N = 30 with Class I crowding malocclusion) had their first premolars removed in early adolescence without subsequent orthodontic treatment. The Control group included 30 untreated subjects with Class I normal occlusion. Cephalograms were taken at 12 (T1), 15 (T2), 30 (T3), and 62 (T4) years of age. A superimposition-based cephalometric method was used to assess the dentoskeletal and soft tissue changes.

RESULTS

There were no significant differences between the Extraction and Control groups in terms of skeletal sagittal relation, incisor inclination, and protrusion, or most of the soft tissue parameters throughout the observation period. However, significant differences were observed between the groups with respect to the vertical relations in T2-T3, such that the Extraction group showed more-pronounced decreases in the ML/NSL, ML/NL, and Gonial angles and more-pronounced increases in facial heights.

CONCLUSIONS AND IMPLICATIONS

Treatment for subjects with Class I malocclusion with severe crowding by the extraction of four premolars, without subsequent orthodontic treatment, does not affect the long-term dentoskeletal and soft tissue profile, as compared to an untreated Control group. The degree of crowding, rather than changes in dentofacial morphology, is crucial in deciding on extraction therapy.

Three-Dimensional Analysis of Posterior Mandibular Displacement in Rats

Mandibular protrusion and its treatment is challenging for the orthodontist. The aim of the present research was to identify macroscopic changes in the mandible, based on three-dimensional Cone Beam Computed Tomography analysis. Seventy-two male Wistar rats were divided into two equal groups, experimental (group A) and control (group B). Each consisted of three equal subgroups of 12 rats (A1, A2, A3, B1, B2, B3). Full-cast orthodontic intraoral devices were attached to the maxillary incisors of the experimental animals, and effected functional posterior mandibular displacement. Throughout the experimental period, all animals were fed with mashed food. Animals were sacrificed at 30 days (A1, B1), 60 days (A2, B2) and 90 days (A3, B3). At the 60th day of the experiment, the orthodontic devices were removed from the remaining experimental subgroup A3. Measurements revealed significant differences in the anteroposterior dimensions between experimental and control subgroups. However, the observed changes in the vertical dimensions, Condylion/Go’–Menton and the Intercondylar distance proved insignificant. Posterior mandibular displacement of the mandible in growing rats affects the morphology of the mandible and culminates in the development of a smaller mandible at a grown age.

Early extractions of premolars reduce age-related crowding of lower incisors: 50 years of follow-up

Objectives

To study the effects of extraction of four premolars, without subsequent orthodontic treatment, on the crowding of lower incisors in subjects between early adolescence and late adulthood, as compared to untreated subjects.

Materials and methods

A total of 45 subjects were included in this study. The extraction group comprised 24 subjects who had all the first premolars removed at a mean age of 11.5 years, to relieve crowding in a class I malocclusion without subsequent orthodontic treatment. The control group had 21 untreated subjects, having a normal occlusion at a mean age of 13.0 years. The participants were documented with dental casts and cephalograms at mean ages of 11.4 and 13.0 years, for the two groups respectively (T1), and at mean ages of 30.9 years (T2) and 61.7 years (T3). Changes in lower incisor crowding were described as changes in “irregularity” and “space deficiency.”

Results

The extraction group showed no changes in the irregularity of the lower incisors and significant improvement of the space deficiency of the lower teeth into late adulthood. While in the control group, both irregularity of the lower incisors and space deficiency of the lower teeth increased significantly into late adulthood.

Conclusion

Lower incisor alignment remains mainly unchanged into late adulthood in subjects who have all their first premolars removed in childhood, as the only treatment to relieve teeth crowding.

Clinical relevance

Severe crowding in a class I occlusion can be solved solely with premolar extraction, allowing for spontaneous adjustments with more stable incisor alignment up to late adulthood.