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Concept: Orthodontics

176

The aim of this longitudinal study was to compare the prevalence of malocclusion at ages 3 and 7 years in a sample of children, exploring the hypothesis that prevalence of malocclusion is higher at 3 than at 7 years of age and may be influenced by sucking habits. The study sample comprised 386 children (199 girls and 187 boys), aged 3 years at study start, sourced from three Public Dental Service clinics in Sweden. Malocclusion was diagnosed by clinical examination, using a specific protocol. Data on allergy, traumatic injuries, sucking habits, and breathing pattern including nocturnal breathing disturbances were obtained by means of a questionnaire answered by child and parent in conjunction with the initial and final clinical examination. The overall prevalence of malocclusion decreased significantly, from 70 to 58% (P < 0.0001): predominantly anterior open bite, excessive overjet, and Class III malocclusion. Although high rates of spontaneous correction were also noted for deep bite, Class II malocclusion and posterior and anterior crossbites, new cases developed at almost the same rate; thus, the prevalence was unchanged at the end of the observation period. Anterior open bite and posterior crossbite were the only conditions showing significant associations with sucking habits. The results confirm the hypothesis of higher prevalence of malocclusion at 3 years of age and clearly support the strategy of deferring orthodontic correction of malocclusion until the mixed dentition stage.

Concepts: Sociology, Cohort study, Epidemiology, Prognathism, Dental braces, Age, Orthodontics, Malocclusion

152

Maxillary protraction with the novel N2 mini-implant- and micro-implant-assisted rapid palatal expander (MARPE) can potentially provide significant skeletal effects without surgery, even in older patients where conventional facemask therapy has limited skeletal effects. However, the skeletal effects of altering the location and direction of force from mini-implant-assisted maxillary protraction have not been extensively analyzed. In this study, the application of the novel N2 mini-implant as an orthopedic anchorage device is explored in its ability to treat patients with class III malocclusions.

Concepts: Class III railroad, Malocclusion, Novel, Orthodontics, Palatal expander, Dental braces

145

In the present report, we describe the successful use of miniscrews to achieve vertical control in combination with the conventional sliding MBT™ straight-wire technique for the treatment of a 26-year-old Chinese woman with a very high mandibular plane angle, deep overbite, retrognathic mandible with backward rotation, prognathic maxilla, and gummy smile. The patient exhibited skeletal Class II malocclusion. Orthodontic miniscrews were placed in the maxillary anterior and posterior segments to provide rigid anchorage and vertical control through intrusion of the incisors and molars. Intrusion and torque control of the maxillary incisors relieved the deep overbite and corrected the gummy smile, while intrusion of the maxillary molars aided in counterclockwise rotation of the mandibular plane, which consequently resulted in an improved facial profile. After 3.5 years of retention, we observed a stable, well-aligned dentition with ideal intercuspation and more harmonious facial contours. Thus, we were able to achieve a satisfactory occlusion, a significantly improved facial profile, and an attractive smile for this patient. The findings from this case suggest that nonsurgical correction using miniscrew anchorage is an effective approach for camouflage treatment of high-angle cases with skeletal Class II malocclusion.

Concepts: Prognathism, Horse, Torque, Orthodontics, Teeth, Maxilla, Mandible, Malocclusion

31

Celiac disease is a gluten enteropathy that is treated with dietary elimination of gluten. Exposure to nondietary sources of gluten, which are used in the manufacture of products such as plastics, dental equipment, and cosmetics, can also trigger or exacerbate disease. We report the case of a 9-year-old child who presented with nonspecific abdominal discomfort with abnormal serology for celiac disease. She underwent duodenal biopsies that revealed Marsh 3B histopathology. Despite strict dietary elimination of gluten, she continued to be symptomatic and demonstrate positive serum markers for active disease. It was then discovered that the child was exposed to gluten from her orthodontic retainer that contained a plasticized methacrylate polymer. Gluten is a common additive in plastics. She discontinued its use and demonstrated symptom resolution and complete normalization of serology. All possible sources of gluten, including nondietary, must be considered when managing a child with celiac disease.

Concepts: Coeliac disease, Orthodontics, Retainer, Dental equipment

29

Resorbable screw fixation for orthognathic surgery is widely used in oral and maxillofacial surgery and has several advantages. However, surgeons are concerned about using resorbable screws in orthognathic surgery because of possible postoperative complications such as relapse, screw fracture, and infection. The purpose of this study was to evaluate the skeletal stability of bicortical resorbable screw fixation after sagittal split ramus osteotomies for mandibular prognathism.

Concepts: Dentistry, Microsurgery, Reconstructive surgery, Orthodontics, Orthognathic surgery, Surgery, American College of Surgeons, Oral and maxillofacial surgery

28

This study investigated short- and long-term postoperative skeletal changes following intraoral vertical ramus osteotomy (IVRO) for mandibular prognathism, as determined from lateral cephalograms. The subjects were 20 patients with mandibular prognathism who had undergone surgical orthodontic treatment combined with IVRO. Lateral cephalograms were taken at six time points: 1 month before surgery, and 1 day, 3 months, 6 months, 1 year, and approximately 2 years after surgery. Intermaxillary fixation (IMF) with four monocortical screws was maintained for 1 week in all patients. Mean posterior movement of the menton (Me) was 5.9mm at surgery. 3 months after surgery, the FMA and FH-CorMe angles had increased 6.3 and 6.2 degrees, respectively, indicating clockwise rotation of the distal segment of the mandible. This rotation was observed in all 20 patients, suggesting that postoperative rotation of the mandible in the postoperative short term is likely to occur after IVRO and could be considered an adaptation of the mastication system newly established by surgery. In the long term after IVRO, Me had moved anteriorly by only 0.9mm and the relapse ratio was 15.3%. These findings suggest the excellent long-term stability of surgical orthodontic treatment combined with IVRO in patients with mandibular prognathism.

Concepts: Prognathism, Economics, Surgery, Dentistry, Orthodontics, Oral and maxillofacial surgery, Time, Term

28

OBJECTIVE: While all manufacturers of orthodontic brackets label these products for single use, there are commercial providers offering bracket reconditioning (or “recycling”). We conducted this study to investigate the effects of different recycling techniques on material-related parameters in orthodontic brackets, aiming to derive indications for clinical use and conclusions about the biocompatibility, longevity, and application of recycled brackets. MATERIALS AND METHODS: New metal brackets (equilibrium®; Dentaurum, Ispringen, Germany) were compared to brackets recycled by different techniques, including direct flaming with a Bunsen burner, chemical reconditioning in an acid bath, a commercial unit (Big Jane; Esmadent, IL, USA), and outsourcing to a company (Ortho Clean, Dellstedt, Germany). Material-related examinations included the following: (1) corrosion behavior by static immersion testing and use of a mass spectrometer to determine nickel-ion concentrations in the corrosive medium, (2) surface features in scanning electron micrographs before and after corrosion testing, (3) Vickers hardness using a hardness testing machine, (4) shear bond strength as defined in DIN 13990-1, (5) dimensional stability of the bracket slots by light microscopy, and (6) frictional loss as assessed by an orthodontic measurement and simulation system (OMSS). Each examination was performed on ten brackets. Student’s t-test was used for statistical analysis. RESULTS: Compared to the new brackets, those recycled in an acid bath or by a commercial provider revealed significant dimensional changes (p<0.05). Corrosion on the recycled brackets varied according to the recycling techniques employed. The group of brackets recycled by one company revealed hardness values that differed from those of all the other groups. No significant differences were observed in nickel-ion release, frictional loss, and shear bond strength. CONCLUSION: Recycling was found to significantly reduce the corrosion resistance and dimensional stability of orthodontic brackets. As the savings generated by recycling do not justify the risks involved, the practice of labeling orthodontic brackets for single use remains a responsible precaution that safeguards patients and orthodontists against definite risks.

Concepts: Aluminium, Statistics, Materials science, Corrosion, Micrograph, Scanning electron microscope, Orthodontics, Rockwell scale

27

Objectives: The aim of this investigation was to present and evaluate an original method of mini-invasive oral surgery and orthodontics based on 3D images from a computed tomography software (3DNEO(®), 3DNEOVISION). Materials and methods: Three patients with impacted teeth were examined and their data were analyzed with this software based on the “region growing” method. Results: Several clinical interests emerge : locate and visualize precisely the relationships of the impacted tooth with the adjacent anatomical elements under the desired angle, associate/dissociate the different elements of the 3D scene, measure the distances, calculate the axes of traction, materialize the way of traction and the optimal point for bonding, prepare virtually the surgical exposure and orthodontic treatment plan. Conclusion: This 3D method might provide information for improved diagnosis and treatment plans in order to ultimately result in more successful treatment outcomes and better care for patients.

Concepts: Medical imaging, Plan, Surgery, Tooth, Dentistry branches, Dentistry, Physician, Orthodontics

27

ObjectivesLoosening and loss rates of monocortical mini-implants are relatively high, therefore the following null hypothesis was tested: ‘The local bone stress in mono and bicortically-anchored mini-implants is identical’.Material and MethodsAnisotropic Finite Element Method (FEM) models of the mandibular bone, including teeth, periodontal ligaments, orthodontic braces, and mini-implants of varying length, were created. The morphology was based on the Computed Tomography data of an anatomical preparation. All mini-implants with varying insertion depths (monocortical short, monocortical long, bicortical) were typically loaded, and the induced effective stress was calculated in the cervical area of the cortical bone. The obtained values were subsequently analysed descriptively and exploratively using the SPSS 19.0 software.ResultsThe null hypothesis was rejected, since the stress values of each anchorage type differed significantly (Kruskal-Wallis Test, P < 0.001). Therefore, the lowest effective stress values were induced in bicortical anchorage (mean = 0.65MPa, SD = 0.06MPa) and the highest were induced in monocortical (short) anchorage of the mini-implants (mean = 1.79MPa, SD = 0.29MPa). The Spearman rank correlation was 0.821 (P < 0.001).ConclusionsThe deeper the mini-implant was anchored, the lower were the effective stress values in the cervical region of the cortical bone. Bicortical implant anchorage is biomechanically more favourable than monocortical anchorage; therefore, bicortical anchorage should be especially considered in challenging clinical situations requiring heavy anchorage.

Concepts: Finite element method in structural mechanics, Orthodontics, Statistical tests, Null hypothesis, Spearman's rank correlation coefficient, Non-parametric statistics, Finite element method

27

In a retrospective multicentre study, the success rate and efficiency of activator treatment were analysed. All patients from two University clinics (Giessen, Germany and Berne, Switzerland) that fulfilled the selection criteria (Class II division 1 malocclusion, activator treatment, no aplasia, no extraction of permanent teeth, no syndromes, no previous orthodontic treatment except transverse maxillary expansion, full available records) were included in the study. The subject material amounted to 222 patients with a mean age of 10.6 years. Patient records, lateral head films, and dental casts were evaluated. Treatment was classified as successful if the molar relationship improved by at least half to three-fourths cusp width depending on whether or not the leeway space was used during treatment. Group comparisons were carried out using Wilcoxon two-sample and Kruskal-Wallis tests. For discrete data, chi-square analysis was used and Fisher’s exact test when the sample size was small. Stepwise logistic regression was also employed. The success rate was 64 per cent in Giessen and 66 per cent in Berne. The only factor that significantly (P¡0:001) influenced treatment success was the level of co-operation. In approximately 27 per cent of the patients at both centres, the post-treatment occlusion was an ideal Class I. In an additional 38 per cent of the patients, marked improvements in occlusal relationships were found. In subjects with Class II division 1 malocclusions, in which orthodontic treatment is performed by means of activators, a marked improvement of the Class II dental arch relationships can be expected in approximately 65% of subjects. Activator treatment is more efficient in the late than in the early mixed dentition.

Concepts: Class II railroad, Non-parametric statistics, Statistical tests, Teeth, Orthodontics, Chi-square test, Fisher's exact test, Malocclusion