Microdamage in the alveolar process of rat maxillae after orthodontic tooth movement.

OBJECTIVE: Playing a decisive role in bone remodeling, microdamage was recently associated with orthodontic tooth movement in pigs. The present study was conducted to evaluate microdamage and its potential association with orthodontic tooth movement in the alveolar process of rat maxillae. MATERIAL AND METHODS: The upper right molars of 24 male Wistar rats (10 weeks old) were splinted and loaded against the (likewise splinted) upper incisors with 25 cN using a Nitinol coil spring. Four groups of 6 animals were treated in this fashion for 1, 2, 4, or 7 days. The upper left quadrants served as controls. The maxillae were halved, gently prepared, and stained en bloc with basic fuchsin. After embedding in resin, 80-µm-thick parasagittal sections were ground parallel to the mesial root of the first molar. These were used to assess microdamage under transmitted and epifluorescent light, also counting and measuring the length of microcracks. Differences between the loaded and unloaded side and between mesial and distal were checked using a Wilcoxon test and were considered significant at ≤ 0.05. RESULTS: Microdamage (in the form of diffuse damage and microcracks) was observed in both the loaded and control jaw halves, as well as on the mesial and distal sides in all four groups. Microcracks averaged 30-100 µm in length and 0.3-1.7/mm(2) in density. While they were more prevalent in the loaded than the control jaw halves, this difference was not statistically significant. CONCLUSION: The alveolar process of rat maxillae is characterized by microdamage (in the form of microcracks and diffuse damage) regardless of whether and for how long orthodontic loading has taken place. Within the limitations of this experimental study, our results do not confirm previous findings of significantly higher prevalence on the pressure side on the first day after initiating orthodontic tooth movement.

Bone condition of the maxillary zygomatic process prior to orthodontic anchorage plate fixation.

OBJECTIVES: The clinical success of orthodontic miniplates depends on the stability of the miniscrews used for fixation. For good stability, it is essential that the application site provides enough bone of good quality. This study was performed to analyze the amount of bone available for orthodontic miniplates in the zygomatic process of the maxilla. METHODS: We examined 51 dental CT scans (Somatom Plus 4; Siemens, Erlangen, Germany) obtained from 51 fully dentate adult patients (mean age 24.0 ± 8.1 years; 27 male and 24 female) prior to third molar surgery. The amount of bone in the zygomatic process region at the level of the first molar root tips and at several other cranial levels as far as 15 mm from the root tips was measured RESULTS: Bone thickness at the root tip level averaged 4.1 ± 1.0 mm; the lowest value measured at this level in any of the patients was 2.7 mm. Bone thickness averaged 8.3 ± 1.0 mm at 15 mm cranial to the root tips; 6.9 mm was the lowest value. CONCLUSION: The zygomatic process appears to provide sufficient bone to accommodate screws for miniplate fixation. While some patients may possess a borderline amount of bone at more caudal levels, lack of volume is not a problem near the zygomatic bone.

Histomorphometry in antigen-induced arthritis of the rabbit temporomandibular joint.

BACKGROUND: Juvenile idiopathic arthritis (JIA) of the temporomandibular joint (TMJ) can cause severe growth disturbances of the craniomandibular system. Antigen-induced arthritis (AIA) of the rabbit TMJ is simulating the inflammatory process of the TMJ in JIA. The aim of this study was to investigate the effect of a systemic administration of the tumor necrosis factor-alpha (TNF-α) antagonist etanercept on AIA in rabbits by means of three different histological staining methods. METHODS: After sensitization, a bilateral arthritis of the TMJ was induced and maintained by repeated intra-articular administrations of ovalbumin in 12 New Zealand white rabbits aged 10 weeks. From the 13th week of age, 6 of the 12 rabbits received weekly subcutaneous injections of etanercept, and the other 6 animals remained without therapy. Another 6 animals served as controls, receiving no treatment or intra-articular injections at all. After euthanasia at the age of 22 weeks, all TMJs were retrieved en bloc. Sagittal sections were cut and stained with hematoxylin-eosin (H-E), Safranin-O for the evaluation of the Mankin score, and tartrate-resistant acid phosphatase (TRAP). RESULTS: In the arthritis group, a chronic inflammation with degeneration of the articular cartilage was visible. In the etanercept group, the signs of cartilage degeneration were significantly reduced but present. In contrast, the joints in the control group were inconspicuous. A strong correlation between the Mankin score and TRAP-positive cells could be found. CONCLUSIONS: Antigen-induced arthritis causes severe damage in the TMJ of young rabbits. An improvement seems to be achievable by a systemic administration of etanercept.

Demineralization adjacent to orthodontic brackets after application of conventional and self-etching primer systems.

OBJECTIVES: The goal of this work was to compare the demineralization of enamel associated with two different self-etching primers and traditional acid etching. MATERIALS AND METHODS: A total of 15 volunteers (23-32 years, 8 male and 7 female) were provided with a removable archwire/resin appliance to be worn 20 h/day for 28 days. The device was attached to the mandibular posterior teeth and included samples of human enamel (from extracted third molars) located in both posterior vestibules. Both sides featured the same distribution of samples, including one untreated control sample (group A) and three samples with brackets (Victory™ APC II) bonded to their surface after conditioning with a self-etching non-fluoride primer (iBond™ Gluma® Inside; group B), a self-etching fluoride-releasing primer (Transbond™ Plus; group C), or traditional acid-etching with 35% phosphoric acid and Transbond™ XT (group D). Mineral loss was assessed extraorally under standardized conditions using quantitative light-induced fluorescence (QLF) with a specialized camera system (Inspektor Pro). Results were expressed as relative fluorescence loss (ΔF in %). A baseline measurement (T0) was taken before the appliance was first inserted but with the brackets already bonded. Fluorescence loss was analyzed after 3 (T1), 7 (T2), 14 (T3), and 28 days (T4) and compared to the baseline loss (T0) for each of the four study groups (A to D). Kruskal-Wallis and Mann-Whitney U tests were used to compare the results for statistical significance. RESULTS: The lowest percentages of fluorescence loss both at baseline and during the follow-up assessments was found in group C. While all three experimental groups (B, C, D) presented total decreases in fluorescence loss after 28 days, indicating remineralization, the decrease in group C was the largest. The Kruskal-Wallis test yielded no significant differences between the three groups other than a significantly lower percentage of fluorescence loss in group C than in group D during the last assessment (T4). The untreated samples of control enamel (group A) revealed increasing percentages of fluorescence loss over the entire study period. CONCLUSION: Use of the self-etching primers (groups B and C) was not associated with patterns of enamel demineralization different from those noted after traditional etching with phosphoric acid (group D). The only significant difference we observed was between the self-etching fluoride-releasing primer (group C) and traditional etching (group D) at the final assessment (T4). Thus, the fluoride-releasing system Transbond™ Plus was advantageous.

Assessing bone volume for orthodontic miniplate fixation below the maxillary frontal process.

OBJECTIVES: The maxillary bone below the frontal process is used for orthodontic anchorage; indications have included skeletally anchored protraction of the maxilla for treating Class III malocclusions or the intrusion of teeth in patients with a deep bite. This study was conducted to assess the condition of bone before cortically implanting miniplates in that area of the maxilla. PATIENTS AND METHODS: A total of 51 thin-sliced computed tomography scans of 51 fully-dentate adult patients (mean age 24.0 ± 8.1 years; 27 men and 24 women) obtained prior to third-molar osteotomy were evaluated. Study parameters included total bone thickness, thickness of the facial cortical plate, and width of the nasal maxillary buttress. All these parameters were measured at different vertical levels. RESULTS: The bone volume adjacent to the piriform aperture was most pronounced at the basal level and decreased progressively toward more cranial levels. The basal bone structure had a mean total thickness of 7.8 mm, facial cortical plate thickness of 1.9 mm, and nasal maxillary buttress width of 9.2 mm. At 16 mm cranial to the aperture base, these values fell to 5.6 mm, 1.3 mm, and 5.8 mm, respectively. CONCLUSION: These bone measurements suggest that screws 7 mm in length can be inserted at the base level of the piriform aperture and screws 5 mm long at the cranial end of the bone.

SureSmile--CAD/CAM system for orthodontic treatment planning, simulation and fabrication of customized archwires.

SureSmile is an all-digital system which uses new 3-D imaging and computer techniques for diagnostics and treatment planning and uses robotics to customize fixed orthodontic appliances. Treatment can be simulated in advance and different treatment strategies can be visualized; this allows detailed treatment planning. The application of CAD/CAM aims at improving reproducibility, efficiency, and quality of orthodontic treatment.

TMJ morphology and function in a patient with Klippel-Trenaunay syndrome. Case report.

Klippel-Trenaunay syndrome is a rare congenital mesodermal disturbance of uncertain etiology in variable expression. The classic manifestation is the triad of congenital mesodermal abnormalities. Clinically a diversity of phenotypes with subjacent malformations may be encountered. The deviations of the mesioblastic germ layer affecting angioblastic, lymphoblastic and osteoblastic structures, may give rise to malformations either alone or in an unlimited diversity of associations. While this syndrome may be diagnosed by chance in the course of ultrasonic scanning during pregnancy, it is normally diagnosed during infancy or early childhood. Evaluation and carefully coordinated medical treatment are important in minimizing morbidity and relieving multiple complaints. The aim of our investigation was to evaluate and correlate the clinical, functional, radiographic and MRI findings in a patient suffering from this syndrome. We present a 13-year-old male patient suffering from extreme facial asymmetry in association with hypertrophy of the complete right side of the body. In spite of pronounced functional and morphologic asymmetry, no signs of degenerative joint disease were identified by radiography or MRI. Since temporomandibular joint dysfunction and facial asymmetry can result in irreversible degenerative joint disease, close follow-up monitoring is indispensable if joint damage is to be prevented.

Neurinoma of the facial nerve mimicking a parotid tumour. A case report.

A case of a facial neurinoma localized in the right parotid gland is presented. Neurinomas derived from the facial nerve are very rare especially when extracranially located. Despite imaging and other investigations, extirpation of the tumour and histopathological examination are the only way to establish the diagnosis. Neurinomas are encapsulated and can be dissected without interruption of nerve branches.