A novel approach for determining instantaneous centers of rotation of the mandible with an intraoral scanner: A preliminary study.

OBJECTIVES: Recording and reproducing mandibular movements have been of key importance in the practice of dentistry for over a century. Recently, it has become possible to use digital technologies for these tasks. This study presents a preliminary method to try to identify the mandibular instantaneous centres of rotation based solely on intraoral scanners. METHODS: The dentitions of four participants were scanned, multiple inter-occlusal registrations and buccal scans were performed in closed and opened positions. Blender software was used to align the meshes during the post-scan digital workflow. Bite alignment accuracy was assessed and then improved with a strict exclusion protocol. An automated algorithm was used to find rotations between closed stage and open stage meshes. RESULTS: Our exclusion protocol reduced the bite alignment error significantly (p = 0.001) and the root-mean-square error value of the meshes decreased from 0.09 mm (SD = 0.15) to 0.03 mm (SD = 0.017). However, the remaining translational error caused an unexpectedly large shift in the axis of rotation (mean = 1.35 mm, SD = 0.77) with a 41.83: 1 ratio. As found in other studies, our results showed even a small amount of error during registration can shift the axis of rotation a large amount. This phenomenon will compromise the results of common pantographic methods which assume a rotation axis of the condyle. It also adds valuable information to the concept of instantaneous centers of rotation by revealing their true characteristics.

Patterns of Facial Profile Preference in a Large Sample of Dental Students: A Cross-Sectional Study.

The objective of this study was to explore dental students' facial profile preferences in a large sample of students. Nine hundred and nineteen dental students of four dental schools were involved. As part of a larger study on dentofacial esthetics, six photo series consisting of one unaltered and four altered variants of the same female profile were distributed among the students. The altered features were ones that are esthetically significant according to the literature. The students had to indicate the photo in each series that they preferred. The data were analyzed in a regression model in which preference in the given photo series was the dependent variable and gender, grade of studies, and dental school were the factors. Eight hundred and sixty-one students (93.7%) responded. Gender and dental school were not associated with the observed preferences, but the grade of studies was associated for three of the modified parameters: chin prominence, the sagittal position of the maxillary dental arch, and the simultaneous modification of the prominence of the chin and the nose. This study has confirmed several earlier observations, and new observations have also been made. We have demonstrated that the anteroposterior position of the maxillary incisors may be an important determinant of profile esthetics, even if this position does not influence the situation of the soft tissues and if the forehead cannot be used as a reference. We have also shown that the harmony between the nose and the chin overrides the importance of their individual dimensions.

Evaluation of the Soft Tissue Changes after Rapid Maxillary Expansion Using a Handheld Three-Dimensional Scanner: A Prospective Study.

Facial soft tissue esthetics is a priority in orthodontic treatment, and emerging of the digital technologies can offer new methods to help the orthodontist toward an esthetic outcome. This prospective study aimed to assess the soft tissue changes of the face after six months of retention following Rapid Maxillary Expansion (RME). The sample consisted of 25 patients (13 females, 12 males, mean age: 11.6 years) who presented with unilateral or bilateral posterior crossbite requiring RME, which was performed with a Hyrax expander. 3D facial images were obtained before treatment (T0) and at the end of a six-month retention period after the treatment (T1) using a structured-light 3D handheld scanner. Linear and angular measurements were performed and 3D deviation analyses were done for six morphological regions of the face. Significant changes in various areas of the nasal and the upper lip regions were observed. Based on the results of the study and within the limitations of the study, RME with a Hyrax expander results in significant morphological changes of the face after a six-month retention period.

Accuracy of virtual planning in orthognathic surgery: a systematic review.

BACKGROUND: The elaboration of a precise pre-surgical plan is essential during surgical treatment of dentofacial deformities. The aim of this study was to evaluate the accuracy of computer-aided simulation compared with the actual surgical outcome, following orthognathic surgery reported in clinical trials. METHODS: Our search was performed in PubMed, EMBASE, Cochrane Library and SciELO for articles published in the last decade. A total of 392 articles identified were assessed independently and in a blinded manner using eligibility criteria, out of which only twelve articles were selected for inclusion in our research. Data were presented using intra-class correlation coefficient, and linear and angular differences in three planes. RESULTS: The comparison of the accuracy analyses of the examined method has shown an average translation (< 2 mm) in the maxilla and also in the mandible (in three planes). The accuracy values for pitch, yaw, and roll (°) were (< 2.75, < 1.7 and < 1.1) for the maxilla, respectively, and (< 2.75, < 1.8, < 1.1) for the mandible. Cone-beam computed tomography (CBCT) with intra-oral scans of the dental casts is the most used imaging protocols for virtual orthognathic planning. Furthermore, calculation of the linear and angular differences between the virtual plan and postoperative outcomes was the most frequented method used for accuracy assessment (10 out of 12 studies) and a difference less than 2 mm/° was considered acceptable and accurate. When comparing this technique with the classical planning, virtual planning appears to be more accurate, especially in terms of frontal symmetry. CONCLUSION: Virtual planning seems to be an accurate and reproducible method for orthognathic treatment planning. However, more clinical trials are needed to clearly determine the accuracy and validation of the virtual planning in orthognathic surgery.

Dentofacial mini- and microesthetics as perceived by dental students: A cross-sectional multi-site study.

BACKGROUND: How dental education influences students' dental and dentofacial esthetic perception has been studied for some time, given the importance of esthetics in dentistry. However, no study before has studied this question in a large sample of students from all grades of dental school. This study sought to fill that gap. The aim was to assess if students' dentofacial esthetic autoperception and heteroperception are associated with their actual stage of studies (grade) and if autoperception has any effect on heteroperception. METHODS: Between October 2018 and August 2019, a questionnaire was distributed to 919 dental students of all 5 grades of dental school at all four dental schools in Hungary. The questionnaire consisted of the following parts (see also the supplementary material): 1. Demographic data (3 items), Self-Esthetics I (11 multiple- choice items regarding the respondents' perception of their own dentofacial esthetics), Self-Esthetics II (6 Likert-type items regarding the respondents' perception of their own dentofacial esthetics), and Image rating (10 items, 5 images each, of which the respondents have to choose the one they find the most attractive). Both the self-esthetics and the photo rating items were aimed at the assessment of mini- and microesthetic features. RESULTS: The response rate was 93.7% (861 students). The self-perception of the respondents was highly favorable, regardless of grade or gender. Grade and heteroperception were significantly associated regarding maxillary midline shift (p < 0.01) and the relative visibility of the arches behind the lips (p < 0.01). Detailed analysis showed a characteristic pattern of preference changes across grades for both esthetic aspects. The third year of studies appeared to be a dividing line in both cases, after which a real preference order was established. Association between autoperception and heteroperception could not be verified for statistical reasons. CONCLUSION: Our findings corroborate the results of most previous studies regarding the effect of dental education on the dentofacial esthetic perception of students. We have shown that the effect can be demonstrated on the grade level, which we attribute to the specific curricular contents. We found no gender effect, which, in the light of the literature, suggests that the gender effect in dentofacial esthetic perception is highly culture dependent. The results allow no conclusion regarding the relation between autoperception and heteroperception.

Craniofacial and cervical morphology related to sagittal spinal posture in children and adolescents.

Studies on the relationship between body posture and craniofacial parameters often focus on the cervical spine. Thus, less attention has been paid to the morphology of the vertebra C2 that serves as both a structural and functional link between the craniofacial area and the other part of the spine. The objective of this study was to assess the relation of craniofacial features to certain morphological and positional characteristics of the cervical vertebrae and the spine during growth. We determined body posture indices for 69 children and adolescents by means of a radiation-free method (rasterstereography). The morphological and positional analysis of the craniofacial area and the cervical vertebrae was based on standardized lateral X-ray cephalograms. Medium to strong correlations were found between body posture, C2 morphology, and craniofacial parameters. We found significant correlations between the C2 dens axis height and maxillary indices as well as between the C2 dens axis inclination and cephalometrical values of the mandibular area. Similarly the correlation between the C2 dens axis inclination and the postural index flèche cervicale was highly significant (P < 0.05, r = 0.333). These results suggest that morphological features of the odontoid process may serve as valuable predictive markers in interdisciplinary orthopedic-orthodontic diagnostics.

Orofacial characteristics of adolescents with diagnosed spinal disorders.

The objective of the current epidemiological study is to show the correlation of various postural abnormalities and spinal deformities and the clinically identifiable dentofacial anomalies by orthodontic examination. Twenty-three children with Scheuermann's disease [mean age: 14 years 8 months; standard deviation (SD): 1 year 8 months] and 28 with scoliosis (mean age: 14 years 7 months; SD: 2 years 3 months) participated in the study. Standardized orthodontic screening protocols were used to map the occlusal relations in the sagittal, vertical, and horizontal dimensions; the space relations of the maxillary and mandibular frontal segment; the temporomandibular joint (TMJ) status; and the facial asymmetries. Statistically significant differences (p<0.05) were found between the values of the examined groups of patients for the following measurements: incisal overjet and overbite, upper and lower midline deviation, mandibular frontal spacing, TMJ pathological symptoms and functional characteristics, and frequency of facial asymmetries. A large percentage of patients with pre-pubertal developments of spinal deformities have various dentofacial anomalies. The majority of these anomalies are present in patients with Scheuermann's disease. Early treatment of the malocclusions closely correlated to postural disorders should minimize the progression of the dentofacial anomalies, making necessary performing orthodontic screening of these patients as early as possible.

[The objective assessment of the quality of oral health care and development of quality indicators]. / A fogászati ellátás minoségének objektív mérése, minoségi indikátorok fejlesztése.

Public health care administration and decision-makers need appropriate tools and information to assess and monitor oral health needs and improve the performance of the oral health system. The aim of the article is to introduce the available methods of measurement of the quality of service, to give a brief summary considering the role of quality indicators in domestic and international sources and the European indicator project (EGOHID) and to introduce ICDAS (International Caries Detection and Assessment System), the method used for clinical examinations. The clinical indicators - that are produced from data gained from the questionnaires and screenings--provide an opportunity to improve and develop quality. Quality indicators are objective measure of the process or outcome of patient care. The 40 indicators were created by the experts of EGOHID program which are described in four categories. Part A is indicators for monitoring the oral health of children and adolescents, Part B is in general population, Part C is indicators for monitoring the oral health systems, Part D concerns indicators for monitoring the oral health quality of life. The purpose of developing public health care and--within it--dental care is the effective use of resources and besides it, reaching the popular level of health gain for which it is a necessary tool when forming and continuously developing the quality approach of providers.

Sagittal back contour and craniofacial morphology in preadolescents.

The aim of this study was to analyze the correlation ratios between the sagittal back contour (flèche cervicale and lombaire, trunk inclination) and selected parameters of craniofacial morphology in children. The patient sample consisted of 66 healthy children with a mean age of 11.2 years (SD 1.6 years), of which 34 were male (mean age 11.5 years, SD 1.3 years) and 32 were females (mean age 10.9 years, SD 1.9 years). The children were recruited during the preparation of the initial orthodontic treatment records. Craniofacial morphology was analyzed by six angular measurements: facial axis, mandibular plane angle, inner gonial angle, lower facial height, facial depth and maxilla position. Rasterstereography was used for reconstruction of the spinal back sagittal profile. From the profile flèche cervicale, flèche lombaire and trunk inclination were determined and the correlations with the craniofacial morphology were calculated (Pearson and Mann-Whitney U test). Significant correlations were found with respect to the inner gonial angle and the flèche cervicale, the mandibular plane angle and the flèche lombaire, the inner gonial angle and the flèche lombaire, and the angular lower facial height and the flèche lombaire, as well as the inner gonial angle and the trunk inclination. The craniofacial vertical growth pattern, presented by mandibular plane angle, inner gonial angle and the angular lower facial height, and the correlation to flèche cervicale and lombaire as well as trunk inclination reveal correlations between growth pattern and sagittal back contour.

Craniofacial features of children with spinal deformities.

BACKGROUND: The objective of this epidemiological study is to map the dentofacial anomalies that can be correlated to the two most frequent spinal diseases responsible for postural abnormalities and that can be clinically identified by the orthodontic examination. METHODS: Twenty-three children with Scheuermann's disease participated in the study (mean age: 14Y8M; SD: 1Y8M), 28 with Scoliosis (mean age: 14Y7M; SD: 2Y3M) and a control group of 68 orthopedically healthy children (mean age: 14Y8M; SD: 0Y11M). Standardized orthodontic screening protocols were used to map the occlusal relations in the sagittal, vertical, and transversal dimensions, space relations of the maxillary and mandibular frontal segment, and the TMJ status and function. The examinations for the children with orthopedic disorders were supplemented by the evaluation of routine orthodontic radiograms - lateral cephalograms and panoramic X-rays. RESULTS: The majority of the dentofacial features examined revealed more and greater abnormalities among patients in the Scheuermann's disease group than in the scoliosis group. In the latter group the proportion of the TMJ symptoms and the consecutive functional deviations were greater. When comparing the values of the two spinal-disorder groups and the control group, statistically significant differences (p < .05) occurred for the following measurements: frequency of unilateral Cl.II. molar occlusion, overjet and extreme overjet mean value (Scheuermann's disease group), as well as the frequency of TMJ pathological symptoms (scoliosis group). The evaluation of the panoramic X-rays showed significant differences among the mandibular measurements of the two spinal-disorder groups. Within the framework of the evaluation of the cephalograms significant differences (p < .05) were found only in the case of dental relations. However, several values differed significantly from the Ricketts' norms, none of the indices strictly characterized any of the groups with spinal disorders. CONCLUSION: The more extended treatment of the malocclusions closely correlated to postural disorders draws attention to the indicators of a higher frequency and severity occurring in the case of the dentofacial deviations in the patients of the MSCH group who had previously been less examined.