Comparison of Techniques for Obtaining Centric Relation Based on the Reproducibility of the Condylar Positions in Centric Relation—A Systematic Review

The objective of this systematic review was to compare centric relation (CR) techniques that belong to the same method of obtaining CR (guided, graphical, or physiological method), to verify which CR technique within each method of obtaining CR generates the greatest reproducibility of the condylar positions (or mandibular position) in CR. The PubMed, Cochrane Library, SciELO, Scopus, and Web of Science databases were searched for articles published up to May 5, 2021. The search terms were combinations of “dental centric relation” (MeSH), with each of the following terms (individually): “reproducibility of findings” (MeSH); “jaw relation record” (MeSH); “chin point”; “gothic arch”; “bimanual manipulation”; “swallowing” (MeSH); and “jig.” Inclusion criteria: clinical studies in English; individuals without temporomandibular dysfunction and with complete or almost complete dentition or complete edentulous; and comparison between CR techniques belonging to the same method of obtaining CR based on the reproducibility of condylar positions in CR. For each method of obtaining the CR, the following CR techniques were considered: guided method (chin point guidance and bimanual manipulation); graphic method (intraoral and extraoral gothic arch tracing); and physiologic method (swallowing and tongue retrusion along the palate). A total of 1692 articles were screened. After the inclusion and exclusion criteria were applied, six articles were included in this review. None of the included studies evaluated edentulous individuals. All included articles compared CR techniques of the guided method. Three articles concluded that the bimanual technique showed greater reproducibility of the condylar positions in CR than the chin point guidance technique, two articles showed equivalence between these techniques, and 1 article concluded that the chin point guidance technique showed greater reproducibility of the condylar positions in CR than the bimanual technique. Thus, in this systematic review, the bimanual technique was often superior (generated greater reproducibility of the CR) or at least equivalent to the chin point guidance technique. Therefore, for individuals with complete dentition and without temporomandibular disorders, the bimanual technique is more recommended.

PSI-Guided Mandible-First Orthognathic Surgery: Maxillo-Mandibular Position Accuracy and Vertical Dimension Adjustability

In orthognathic surgery, patient-specific osteosynthesis implants (PSIs) represent a novel approach for the reproduction of the virtual surgical planning on the patient. The aim of this study is to analyse the quality of maxillo-mandibular positioning using a hybrid mandible-first mandibular-PSI-guided procedure on twenty-two patients while the upper maxilla was fixed using manually bent stock titanium miniplates. The virtual surgical plan was used to design PSIs and positioning guides, which were then 3D printed using biocompatible materials. A Cone Beam Computed Tomography (CBCT) scan was performed one month after surgery and postoperative facial skeletal models were segmented for comparison against the surgical plan. A three-dimensional cephalometric analysis was carried out on both planned and obtained anatomies. A Spearman correlation matrix was computed on the calculated discrepancies in order to achieve a more comprehensive description of maxillo-mandibular displacement. Intraoperatively, all PSIs were successfully applied. The procedure was found to be accurate in planned maxillo-mandibular positioning reproduction, while maintaining a degree of flexibility to allow for aesthetics-based verticality correction in a pitch range between −5.31 and +1.79 mm. Such a correction did not significantly affect the achievement of planned frontal symmetry.

Effect of Tooth Agenesis on Mandibular Morphology and Position

Congenital missing teeth (OMIM #106600) is the most common dental abnormality. The aim of the study was to evaluate the effects of tooth agenesis on the total mandibular length, length of the mandibular body and alveolar process, and the mandibular anteroposterior position. The material was obtained from the Department of Orthodontics, Medical University of Warsaw. The study group included 116 patients aged 9–18 years with a congenital absence of at least two permanent tooth buds in the maxilla and/or mandible (mean: 6.2 teeth missing/patient). All patients were Caucasians: 68 (59%) females and 48 (41%) males. The control group included 115 patients without tooth agenesis matched with the age and gender of the study group. A cephalometric analysis was performed, and it was focused on assessing anteroposterior mandibular measurements. This assessment was based on 17 measurements (12 linear and 5 angular). Statistical analysis of the cephalometric measurements between the study group and the control group showed significant changes regarding selected mandibular measurements. Tooth agenesis does not affect the total length of the mandible and the length of the mandibular body, but it might reduce the length of the mandibular arch length and result in a more retrusive mandibular position.

RELATION BETWEEN SAGITTAL POSITION OF THE MANDIBLE AND PHARYNGEAL AIRWAY VOLUME IN ADULTS USING CONE BEAM COMPUTED TOMOGRAPHY

Introduction: Many authors have discussed the relationship between craniofacial morphology and pharyngeal airway spaces in different malocclusions and skeletal patterns. So the aim of this work was to study the relation between sagittal position of the mandible and pharyngeal airway volume in adults using CBCT. Materials And Methods:Twentyone CBCT radiographs were collected from the archive of Radiology Department at Suez Canal University and were divided into 3 groups according to the measured SNB angle. Group 1 normal mandibular position, group 2 retrognathic mandible and group 3 prognathic mandible. Dolphin 3D imaging software was used to measure the airway volume for all the radiographs. Nasopharyngeal, oropharyngeal, hypopharyngeal and total pharyngeal airway volumes were measured for all the radiographs. F-test (ANOVA) was used for comparison between groups and Tukey test for pairwise comparisons. Correlations between variables were tested using PearsonÂ’s correlation coefficient. Results: there was statistically significant difference in the mean total pharyngeal airway volume and oropharyngeal airway volumes between the three groups. Nasopharyngeal airway volume and hypopharyngeal airway volume had non-significant difference between groups. There was a significant positive correlation between total pharyngeal airway volume (mm3) and SNB angle. Conclusion: Pharyngeal airway volume differs with different sagittal positions of the mandible. Pharyngeal airway volume decreases with mandibular retrognathism and increases with mandibular prognathism.

Does Maxillary Retrusion in Skeletal Class III Malocclusion Affect the Perception of Facial Aesthetics? Evaluation of Different Groups

Background: The perception of facial aesthetics is a complex topic due to its subjective nature and it can be influenced by several factors. The purpose of this study was to compare the perception of general dentists, orthodontists, maxillofacial surgeons, and lay people by evaluating facial aesthetics in skeletal class III patients, especially for maxillary sagittal position. Methods: A survey consisting of three sets of pre-treatment photographs of four dysmorphic patients was used. The questionnaire was submitted to a total of 200 participants divided into the following four subgroups: general dentists, orthodontists, maxillofacial surgeons, and lay people. Their opinion on facial disharmony, sagittal position of the jaws, asymmetry of the chin, projection of the cheekbone area, and lip aesthetics was recorded. Results: Significant differences were found between experts and non-experts in the perception of the maxillary position, asymmetry of the chin and zygomatic area (p < 0.01). No statistically significant differences were found among the groups in the perception of mandibular position and lip aesthetics. Conclusion: The respondents with a medical or dental background perceived the presence of maxillary retrusion more than others. Only orthodontists and maxillofacial surgeons have recognized an alteration of the middle facial third as a greater component of skeletal class III malocclusion.

The Airway Volume Related to the Maxillo-Mandibular Position Using 3D Analysis

Objective. The aim of this research was to compare three cephalometric analyses and their correlation with the airway volume in subjects with different skeletal classes using 2D and 3D images. Study Design. Cross-sectional descriptive study. Material and Method. Steiner, McNamara, and Ricketts analyses and the airway volume were compared in 115 subjects who were candidates for orthognathic surgery under diagnosis using cone beam computed tomography (CBCT); 46 males (40%) and 69 females (60%) were included. The sagittal positions of the maxilla and mandible, the angulation of the mandibular plane, the sagittal positions of the upper and lower incisors, measurements of the largest or shortest airway area, and the volume were compared using Spearman’s test considering a p value < 0.05. Results. Differences were observed between the Steiner and McNamara techniques for the sagittal position of the maxilla ( p = 0.01 ). For mandibular angulation, there was a greater difference between values for Steiner and Ricketts techniques ( p = 0.001 ). In the upper incisor, the results for McNamara and Ricketts techniques were significantly different ( p = 0.004 ). Analysing the airway, subjects with a class II skeletal pattern had a smaller volume than those with a class III pattern ( p = 0.034 ). Conclusion. It may be concluded that skeletal class II patients have a significantly smaller airway volume than class III patients. The skeletal parameter does not always relate to the airway volume; however, the high mandibular angle could be related to the airway conditions.

Targeted sequencing of NOTCH signaling pathway genes and association analysis of variants correlated with mandibular prognathism

Introduction The purpose of this study was to systematically identify variants in NOTCH signaling pathway genes that correlate with mandibular prognathism (MP) in the general Chinese population. Methods Targeted sequencing of NOTCH signaling pathway genes was conducted in 199 MP individuals and 197 class I malocclusion control individuals. The associations of common and rare variants with MP, cephalometric parameters, and continuous cephalometric phenotypes were analyzed by principal component (PC) analysis. The associations between rare variants and MP were tested for each gene. Results Six SNPs, including rs415929, rs520688, and rs423023 in an exonic region of NOTCH4; rs1044006 in an exonic region of NOTCH3; rs1051415 in an exonic region of JAG1; and rs75236173 in the 3′-untranslated region (3′-UTR) of NUMB were associated with MP (P < 0.05). One common variant, rs1051415, in an exonic region of JAG1 was significantly related to PC1 (P = 3.608 × 10− 4), which explained 24.3% of the overall phenotypic variation observed and corresponded to the sagittal mandibular position towards the maxilla, ranging from a posterior positioned mandible to an anterior positioned mandible. Additionally, 41 other variants were associated with PC1–5 (P < 0.05). With respect to rare variant analysis, variants within the EP300, NCOR2, and PSEN2 gene showed an association with MP (t < 0 .05). Conclusions An association between NOTCH signaling pathway genes and MP has been identified.

Is Any Feature of the Stabilometric Evaluation Clinically Relevant in Patients with Temporomandibular Disorders? A Cross-Sectional Study

Current neuroanatomical evidence showed the anatomical relationship between the temporomandibular joint innervation with the vestibular system. However, there is no clear evidence regarding if temporomandibular disorders are associated with balance impairments. Therefore, the aims of this study were to assess the clinical relevance of stabilometric features in populations with temporomandibular disorders and to analyze the influence of the mandibular position and visual afference in the balance scores in both healthy and clinical populations. This observational study was conducted in one sample of healthy controls and one sample with temporomandibular disorders. Sociodemographic data (age, gender, height, weight, body mass index, and foot size), clinical data (presence or absence of temporomandibular disorders) and stabilometric data under six different conditions were collected. Sixty-nine subjects (43.5% male; 36.2% patients) were assessed. No differences between Temporomandibular disorders and healthy groups were found in any stabilometric outcomes, unlike oscillation area with closed eyes and medium interscuspidal position (p < 0.01). Although visual feedback showed to be relevant (p < 0.0001), mandibular position produced no differences in any stabilometric measurement (p > 0.05). This study found that healthy subjects and patients with temporomandibular disorders showed no balance differences in the stabilometric outcomes assessed. Although visual input played an important role in the balance, mandibular position seems to be irrelevant.