Application of the foramina of the trigeminal nerve as landmarks for analysis of craniofacial morphology

Mandibular asymmetry types and differences in dental compensations of Class III patients analyzed with cone-beam computed tomography

OBJECTIVES

To assess differences in dental compensation of the incisors and first molars in skeletal Class III patients with roll-, yaw-, and translation-dominant mandibular asymmetries.

MATERIALS AND METHODS

A total of 90 skeletal Class III adult patients (mean age, 22.00 ± 3.31 years; range, 18-37.9 years) with facial asymmetry were enrolled and divided into the roll-, yaw-, and translation-dominant type groups (n = 30 per group). The vertical, transverse, and anteroposterior distances and axial angles of the teeth were measured using cone-beam computed tomography images. The measurements were compared between the deviated and nondeviated sides using a paired t-test and among the three groups using one-way analysis of variance with a Tukey post hoc test.

RESULTS

The roll-dominant groups showed the greatest values for the bilateral difference in the vertical position of the maxillary (2.42 ± 1.24 mm) and mandibular molars (2.23 ± 1.28 mm; P < .001). The transverse deviations of the maxillary (2.19 ± 1.51 mm) and mandibular incisors (-2.11 ± 1.39 mm) were greater in the yaw-dominant groups than those of other groups. Regarding tooth axial angle, the yaw-dominant group showed the greatest tipping of the mandibular incisor (-4.13 ± 3.30°; P < .001).

CONCLUSIONS

Dental compensation differed depending on the type of facial asymmetry. The roll-dominant type showed more vertical compensation of the posterior teeth, whereas the yaw-dominant type exhibited more tipping of the molars and incisors. By precisely assessing dental compensation in each asymmetry type, sufficient dental decompensation could be achieved.

Use of a novel body mandibular plane (mental foramen-protuberance menti) in analyzing mandibular asymmetry compared with conventional border mandibular plane

OBJECTIVES

To compare a novel body mandibular horizontal plane (mental foramen-protuberance menti; Body-MHP) with the conventional border mandibular horizontal plane (gonion-menton [Me]; Border-MHP) to assess mandibular body inclination and dental compensation of skeletal Class III patients with and without facial asymmetry.

MATERIALS AND METHODS

Retrospective data obtained from diagnostic cone-beam computed tomography of 90 skeletal Class III patients (mean age, 21.67 ± 2.93 years; range, 15.0-30.6 years) were divided into symmetry (n = 30) and asymmetry groups (n = 60). The asymmetry group was subdivided into roll (n = 30) and non-roll types (n = 30). The differences in body inclination and dental measurements (distance and angle) according to two mandibular planes (Body-MHP and Border-MHP) were assessed in the groups and subgroups.

RESULTS

Mandibular body inclinations relative to the Body-MHP were not different in the roll-type asymmetric mandible between the sides, while those relative to the Border-MHP were different (P < .001). For the mandibular first molar positions relative to the Border-MHP, the differences in vertical distance between the sides were undermeasured and the inclination differences were overmeasured when compared relative to the Body-MHP.

CONCLUSIONS

The Body-MHP demonstrated better bilateral similarity in body inclination compared with the Border-MHP in patients with roll-type facial asymmetry. The novel body mandibular plane ensures an accurate diagnosis for tooth movement and jaw surgery, particularly in the roll-type asymmetric mandible.

Anatomy of the greater palatine foramen and canal and their clinical significance in relation to the greater palatine artery: a systematic review and meta-analysis

PURPOSE

Accurate knowledge of greater palatine foramen (GPF) and greater palatine canal (GPC) anatomy is necessary to avoid injury to the greater palatine artery (GPA) when performing a variety of anesthesiologic, dental or surgical procedures. The aim of this paper was to perform a systematic review and meta-analysis of literature on the anatomy and localization of bony structures associated with the GPA, namely the GPF and GPC.

METHODS

A systematic literature search was performed using PubMed, Embase, ScienceDirect, and Web of Science databases. Seventy-five studies were included in the meta-analysis (n = 22,202 subjects).

RESULTS

The meta-analysis showed that the GPF is positioned 17.21 mm (95% CI = 16.34-18.09 mm) from the posterior nasal spine, 2.56 mm (95% CI = 1.90-3.22 mm) from the posterior border of the hard palate, 46.24 mm (95% CI = 44.30-48.18 mm) from the anterior nasal spine, 15.22 mm (95% CI = 15.00-15.43 mm) from the midline maxillary suture, 37.32 mm (95% CI = 36.19-38.45 mm) from the incisive foramen, and opposite the third maxillary molar (M3) in 64.9% (58.7-70.7%) of the total population.

CONCLUSION

An up-to-date, comprehensive analysis of GPF and GPC clinical anatomy is presented. The results from this evidence-based anatomical study provides a unified set of data to aid clinicians in their practice.

Automatic 3-Dimensional Cephalometric Landmarking via Deep Learning

The increasing use of 3-dimensional (3D) imaging by orthodontists and maxillofacial surgeons to assess complex dentofacial deformities and plan orthognathic surgeries implies a critical need for 3D cephalometric analysis. Although promising methods were suggested to localize 3D landmarks automatically, concerns about robustness and generalizability restrain their clinical use. Consequently, highly trained operators remain needed to perform manual landmarking. In this retrospective diagnostic study, we aimed to train and evaluate a deep learning (DL) pipeline based on SpatialConfiguration-Net for automatic localization of 3D cephalometric landmarks on computed tomography (CT) scans. A retrospective sample of consecutive presurgical CT scans was randomly distributed between a training/validation set (n = 160) and a test set (n = 38). The reference data consisted of 33 landmarks, manually localized once by 1 operator(n = 178) or twice by 3 operators (n = 20, test set only). After inference on the test set, 1 CT scan showed "very low" confidence level predictions; we excluded it from the overall analysis but still assessed and discussed the corresponding results. The model performance was evaluated by comparing the predictions with the reference data; the outcome set included localization accuracy, cephalometric measurements, and comparison to manual landmarking reproducibility. On the hold-out test set, the mean localization error was 1.0 ± 1.3 mm, while success detection rates for 2.0, 2.5, and 3.0 mm were 90.4%, 93.6%, and 95.4%, respectively. Mean errors were -0.3 ± 1.3° and -0.1 ± 0.7 mm for angular and linear measurements, respectively. When compared to manual reproducibility, the measurements were within the Bland-Altman 95% limits of agreement for 91.9% and 71.8% of skeletal and dentoalveolar variables, respectively. To conclude, while our DL method still requires improvement, it provided highly accurate 3D landmark localization on a challenging test set, with a reliability for skeletal evaluation on par with what clinicians obtain.