Patterns and sexual dimorphism of non-syndromic hypodontia among a French orthodontic population.

OBJECTIVES: This retrospective study aimed to estimate the prevalence of non-syndromic congenitally missing teeth (CMT) and to explore the frequency of CMT patterns in a French orthodontic population. In addition, the study sought to assess sex-based differences in CMT patterns. DESIGN: Panoramic radiographs of 4569 orthodontic patients between 9 and 21 years-old performed over a 16-year period (2006-2022) were examined to identify non-syndromic tooth agenesis, excluding third molars. A chi-square test or a Fisher exact test were used to determine the difference in the prevalence of tooth agenesis between sex and between arches. RESULTS: Tooth agenesis was observed in 7.3% of the sample (7.9% for females and 6.6% for males). Approximately 86% of the included subjects presented 1 or 2 missing teeth. Single tooth agenesis was significantly more frequent in females than males (p = 0.002, χ2). In total, 23 of the 67 different patterns of CMT observed, were present more than once. 75.5% of male patients and 79.5% of female patients presented one or both missing lateral incisors or second premolars, rarely affected at the same time. This study showed no sex difference in the patterns of tooth agenesis. LIMITATIONS: This study has limitations due to its retrospective nature and our findings apply solely to an orthodontic population from a white ethnic background. CONCLUSIONS: Clinicians should be aware of this particular incisor/premolar phenotype regardless of biological sex. Issues associated with congenitally missing teeth can be managed more effectively with early teenage diagnosis.

Implementation of orthodontic extraction for pre-implant soft tissue management: A systematic review.

OBJECTIVE: This systematic review aims to define the recommendations allowing an optimized clinical implementation for orthodontic extraction as a pre-implant soft tissue management procedure. MATERIALS AND METHODS: A digital search was performed in the Cochrane Library, PubMed, Scopus, and DOSS databases; a pre-screening was conducted according to the title and summary of the articles. After a complete reading, only the articles meeting all of our inclusion criteria were selected, and a second search, this time manual, was performed within their references. The selected articles were then analysed according to twelve parameters. RESULTS: Thirty-nine articles were included. Despite low statistical evidence in the available literature, some principal guidelines, which seem generally accepted by the scientific community, could be highlighted based on this analysis. However, no ideal clinical protocol could be established. CONCLUSIONS: Orthodontic extraction is an efficient procedure for pre-implant soft tissue management, however, further studies are needed to establish full clinical recommendations and optimize its clinical implementation.

Monomer release from orthodontic retentions: An in vitro study.

INTRODUCTION: The adhesives used to bond orthodontic retentions are low-loaded composite resins with a resinous matrix containing bisphenol A diglycidyl ether dimethacrylate synthesized from bisphenol A (BPA), fluidizers such as triethylene glycol dimethacrylate (TEGDMA) and hydrophilic polymers such as hydroxyethylmethacrylate. BPA disrupts the endocrine balance, and TEGDMA has high risks for human health: eg, allergies and cytotoxicity. The aim of this study was to evaluate in vitro the release of monomers from orthodontic bonded retentions. METHODS: A reproducible model of bonded retentions was carried out using calibrated molds. We analyzed the release of monomers by gas phase chromatography coupled with mass spectrometry. RESULTS: This model allowed us to qualitatively and quantitatively evaluate the in-vitro release of monomers from orthodontic adhesives. The quantitative and qualitative analyses showed no BPA release above the 0.02 ppm detection limit. A greater release of TEGDMA was observed with Transbond LR (31.7 µg/mL) than with Transbond XT (13.12 µg/mL) (both, 3M Unitek, Monrovia, Calif). Other toxic components (iodobenzene, iodobiphenyl, triphenyl stibine, and so on) were also identified. CONCLUSIONS: Toxic and carcinogenic molecules not mentioned in the material safety data sheets were identified.

Release of monomers from orthodontic adhesives.

INTRODUCTION: Most composite resins release both bisphenol A (BPA), which disrupts the endocrine balance, and triethylene glycol dimethacrylate (TEGDMA), which has high risks for human health: eg, allergies and cytotoxicity. The aim of this study was to characterize monomers released from orthodontic adhesives. METHODS: We studied samples of orthodontic adhesives by associating 2 techniques: gas phase chromatography and mass spectrometry. RESULTS: The in-vitro analysis detected significant quantities of BPA, TEGDMA, and other monomers in orthodontic adhesives used in daily practice: Transbond XT, Transbond Supreme LV (both, 3M Unitek, Monrovia, Calif), Blugloo (Ormco, Orange, Calif), and MonoLok 2 (Rocky Mountain Orthodontics, Denver, Colo). CONCLUSIONS: Clinicians should consider that orthodontic adhesives contain BPA, an endocrine disruptor; TEGDMA, an allergic and a cytotoxic compound; and carcinogenic genotoxic compounds. These molecules are not mentioned in the material safety data sheets. Manufacturers should declare all components of dental composites to identify these substances that may result in allergic or undesirable side effects for patients and dental staff.

[Orthodontic failures in Class II cases]. / Les échecs orthodontiques dans le traitement des classes II∗.

In Class II treatment, as with all malformations, therapeutic failure can impact some or all of our treatment aims, whether occlusal, functional or esthetic. Using clinical cases, we will first define the concept of failure and the limits of what is acceptable in these different areas. We will then attempt to determine the main causes underlying our failures in order to better avoid them. An analysis of the literature and of the clinical cases demonstrates that our failures are most often caused by a misevaluation of the amount and direction of residual growth, poor control of the vertical dimension, inadequate management of functional problems, an inadequate position of the maxillary and mandibular incisors. In addition to these major treatment errors, one also encounters insufficient patient cooperation, which needs to be assessed and maintained in order to limit the number of failures and treatment drop-outs.

[Orthognathic mandibular osteotomy and condyle positioning: update and innovation]. / Ostéotomie mandibulaire orthognathique et positionnement condylien : point et innovation.

The temporomandibular joints function in synergy with the dental occlusion within the manducatory system. Orthodontists and surgeons must take into account the condylar position since any problem related to positioning of the condyle could result in occlusal disorders including relapse and the risk of occurrence, decompensation or worsening of temporomandibular dysfunction. We wanted to answer three questions: What is the position of the condyle following orthognathic surgery? What benefit is there in repositioning the condyle? What means are available to check condylar position? Finally, in the light of the answers, we describe an innovative occlusal and condylar positioning device for mandibular osteotomies based on computer-assisted surgical planning techniques. It consists of a three-dimensional, printed guide enabling surgeons to position the condyles as desired. It is accurate, simple, reproducible, independent of operator experience as well as rapid and economical.

[Not Available]. / Caractéristiques des muscles masticateurs en tomodensitométrie : variations en fonction de la typologie squelettique.

The aim of the study is to assess the dimensions of the masticatory muscles from CT scans using C2000 software and to analyse their variations depending on sagittal and vertical skeletal pattern. The maximal length, the area and the volume of the right and left masticatory muscles were measured from CT scans of 34 subjects selected upon their skeletal pattern. The analysis of the results shows that masticatory muscles dimensions vary depending on sagittal and vertical skeletal pattern. They are more developed in brachyfacial subjects and to a lesser degree in subjects without antero-posterior skeletal discrepancy. This method is time-consuming but allows a good evaluation of masticatory muscles dimensions.

Amelogenesis imperfecta and nephrocalcinosis: a new case of this rare syndrome.

This article describes a new case of a rare syndrome including enamel agenesis of the primary and permanent dentition, delayed or absent eruption of the permanent dentition, coronal intra-alveolar resorption and gingival enlargement. Renal symptoms include medullary nephrocalcinosis without any apparent cause, and evolution to a renal failure. The early diagnosis provided by the oral symptoms leads to a better renal prognosis. As a consequence, pediatric dentists should be aware of this pathology.

[Etiopathogenic and clinical aspects of asymmetry]. / Approche étiopathogénique et clinique des asymétries.

Complex dysmorphies, asymmetries can affect the various elements of the stomatognathic system: cranial base, maxilla, mandible, musculature and dental arches, in the three dimensions of space. Their etiopathogenesis, as well as their clinical forms, vary considerably. Dysembryopathies, growth disorders, TMJ damages, postural or functional disorders and dental anomalies can create, according to their severity and their moment of appearance, severe or minor facial asymmetries, or asymmetries of the arches. An exo- and endobuccal clinical examination endeavors to specify the localization and the severity of the damage, and to evaluate the importance of the possible alveolar compensations. Consolidated by additional examinations, it enables the clinician to differentiate the various forms of asymmetries.

[Orthodontic approach to asymmetry]. / Approche orthodontique des asymétries.

From an orthodontic point of view, asymmetries can be gathered in three great clinical entities: mandibular lateral deviations, dental asymmetries without skeletal involvement, skeletal asymmetries. Once the therapeutic aims and the principles of the orthodontic approach of these dysmorphoses have been recalled, the authors present the various orthodontic means implemented in this type of treatment. Four cases treated illustrate those types of treatment. Vertical non-surgical asymmetry may have an obvious local origin, for instance, a unilateral damage to a nerve. but usually, there is no evident origin. Frequently the occlusal slippage of a severe sagittal or a vertical malformation, which may evolve as a borderline surgery case, is suspected to be the real cause. In these cases, the diagnosis is always late, with the ending growth. The treatment needs peculiar strong asymmetric mechanics and, sometimes, unilateral mixed extractions. The post-treatment occlusion can be unstable; for this reason, the finishing steps must be carefully conducted. Four clinical case reports develop these points ov view. Multidisciplinary treatments prove very useful to solve three types of clinical situations. In the adult patient, facial esthetics are indicated in severe dentofacial asymmetries. Esthetic improvements of dental nature are still required in deviated smiles, or frontal tippings of the occlusal plane. In addition, asymmetrical intermaxillary relationships will lead to functional anomalies: TMJ disorders, dental wear or lingual dysfunctions. Finally, multidisciplinary treatments in the adult concern the occlusal transverse anomalies, the lateral crossbites, the Class II subdivisions, the deviations of the inter-incisor midlines or unilateral edentulousness. The various plans of treatment, as well as the orthodontic mechanics used, are illustrated in the following development by clinical cases.