Histological and molecular temporomandibular joint analyses after mandibular advancement surgery: study in minipigs

Objectives. The objective of this study was to elucidate the changes occurring in the temporomandibular joint (TMJ) after surgical mandibular advancement with different fixation techniques: bicortical screws (rigid fixation) and miniplates (semi-rigid fixation). Study design. Eighteen minipigs were equally and randomly divided into 3 groups: Group I (control), nonoperated animals; Group II, animals submitted to surgical advancement surgery and osteosynthesis by bicortical screws; and Group III, animals submitted to surgical advancement surgery and osteosynthesis by miniplates. Four months after the surgeries, the presence of interleukin (IL)-6 and IL-10 in synovial fluid samples was assessed in ELISA experiments. TMJs were histologically prepared. Results. Higher levels of IL-10 (P = .0436) were found for Group II. Descriptive histological analysis was compatible with the ELISA findings. Conclusions. Rigid fixation evokes more pronounced signs of bone remodeling in the TMJ, whereas malleable fixation promotes a more intense inflammatory activity. Therefore, rigid fixation seems to transmit a higher impact of postoperative masticatory forces to the TMJ.

Influence of root parallelism on the stability of extraction-site closures

Introduction: In premolar extraction cases, root parallelism is recommended to preserve the stability of space closures. The influence of the degree of root parallelism on relapse of tooth extraction spaces has been a controversial topic in the literature. The aim of this study was to compare the angle between the long axes of the canine and the second premolarin patients with and without stability of extraction-space closures. Methods: A sample of 56 patients, treated with 4 premolar extractions, was divided into 2 groups: group 1, consisting of 25 patients with reopening of extraction spaces; and group 2, consisting of 31 patients without reopening of extraction spaces. Panoramic radiographs of each patient were analyzed at the posttreatment and 1-year posttreatment stages. The data were statistically analyzed by using chi-square tests, t tests, analysis of variance (ANOVA), and Pearson correlation coefficients. Results: The results showed that the groups did not differ regarding the angle between the canine and the second premolar, and there was no correlation between angular changes and reopening of extraction spaces, showing that dental angular changes are not determining factors for relapse, and other factors should be investigated. Conclusions: The final angle and the posttreatment changes observed in the angle between the long axes of the canine and the second premolar showed no influence on the relapse of extraction spaces. (Am J Orthod Dentofacial Orthop 2011; 139: e505-e510)

The influence of storage condition and duration on the resistance to fracture of different fiber post systems

Purpose: To evaluate the effects of storage condition and duration on the resistance to fracture of different fiber post systems (and to morphologically assess the post structure before and after storage. Methods: Three types of fiber posts (DT Light Post, GC Post, FRC Postect Plus) were divided in different groups (n=12) according to the storage condition (dry at 37 degrees C; saline water at 37 degrees C; mineral oil at 37 degrees C and storage inside the roots of extracted human teeth immersed in saline water at 37 degrees C and duration (6, 12 months). A universal testing machine loading at a 90 degrees angle was employed for the three-point bending test. The test was carried out until fracture of the post. A 3-way ANOVA and Tukey`s test (alpha= 0.05) were used to compare the effect of the experimental factors on the fracture strength. Two posts of each group were observed before and after the storage using a scanning electron microscope. Results: Storage condition and post type had a significant effect on post fracture strength (P< 0.05). The interaction between these factors was significant (P< 0.05). Water storage significantly decreased the fracture strength, regardless of the post type and the storage duration. Storage inside roots, in oil, and at dry conditions did not significantly affect post fracture strength. SEM micrographs revealed voids between fibers and resin matrix for posts stored in water. Posts stored under the other conditions showed a compact matrix without porosities. (Am J Dent 2009;22:366-370).

Post space debridement in oval-shaped canals: The use of a new ultrasonic tip with oval section

This study evaluates the effect on post space debridement in oval-shaped canals of an experimental ultrasonic tip with oval section (Satelec) compared with a circular ultrasonic tip (KaVo). Thirty teeth with an oval-shaped canal were endodontically treated and obturated and then randomly divided into 3 groups (n = 10) according to the procedure used for post space debridement: Satelec tip, Largo #2 drill + KaVo file, and Largo #2 drill + water. Debris and dentin tubules were evaluated by assigning scores to scanning electron microscope post spaces images; lower scores corresponded to fewer debris and higher number of open tubules. The Satelec group showed significantly lower debris and open tubules scores than KaVo group (p < .05) and control group (p < .05), which differed significantly between each other (p < .05). Also the debris and open tubules scores in different post space regions differed significantly among the experimental groups (p < .001). The oval ultrasonic tip resulted in a better post space debridement than a circular ultrasonic tip in oval-shaped canals.

Post space cleaning using a new nickel titanium endodontic drill combined with different cleaning regimens

This study compared the effect of two drills and five cleaning regimens on post space debridement. One hundred extracted premolars were instrumented and obturated with warm vertical compaction of gutta percha. The teeth were divided into two groups according to the drill used to remove gutta percha/sealer and for post space preparation: a Largo drill (Largo; Dentsply, St Quentin en Yvelines, France) or a MTwo-PF drill (Sweden&Martina, Due Carrare, Padova, Italy). The following cleaning regimens were used: EDTA, ultrasonics, ultrasonics + EDTA, phosphoric acid, and distilled water. Scanning electron microscopic images of the post spaces were taken, and the presence of debris and of open dentin tubules were evaluated. The ultrasonics + EDTA, phosphoric acid, and EDTA groups were comparable in open tubules scores for both drills and in debris scores after the use of MTwo-PF (p > 0.05). The ultrasonics and control groups performed significantly worse (p < 0.05). The MTwo-PF drill resulted as effective as the Largo drill in obtaining a good post space cleaning, especially when followed by ultrasonics + EDTA irrigant regimen.

Bite force, electromyography, and mandible mobility during the 6-month period after surgical treatment for isolated fractures of the zygomatico-orbital complex

Objective. The aim of this study was to identify the behavior of masticatory muscles after fractures of the zygomatico-orbital complex (ZOC) and subsequent surgical treatment, by using analyses of bite force, electromyography (EMG), and mandible mobility during a 6-month period after surgery. Study design. Five patients with fractured ZOCs treated surgically by using an intraoral approach and fixation exclusively in the region of the zygomaticomaxillary buttress were evaluated. The control group included 12 other patients. During postoperative follow-up, bite force, mandible mobility, and EMG analysis of the masticatory muscles were evaluated. Results. There was an increase in bite force with time, but a decline in EMG activity during the same period. In the mandible mobility analysis, only maximum mouth-opening values increased significantly after the surgical treatment. Conclusions. The masticatory musculature, according to bite force and EMG, returned to its normal condition by the second month after surgery, and maximum mouth opening was observed after the first month. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;111:e1-e7)

Morphodigital study of bone quality in the mandibular angle in patients with third molar impacted

The aim of this study was to analyze if the presence of impacted third molars, and their positions in the mandibular angle, can change the bone quality in this area, considering the measure of the cortical thickness in this region as representative or not for mandible fracture risk. Software was used to analyze 50 digital images from panoramic radiographs of patients who had one or two impacted third molars in the mandible, and 30 digital images of patients with agenesis of the mandibular third molar. The thickness of the cortical region of the mandible was measured; it was possible to draw a parallel line to the posterior portion of the mandible and a parallel line to the body of this bone on each side of the image. At the intersection of these lines near the distal portion of the second molar, another line was set up to serve as reference in the cortical thickness measurement. It could be concluded that the cortical thickness of the mandibular angle in male patients without impacted third molars was greater than the thickness in patients with these teeth, and no difference in thickness was found for the female group.