The influence of fixed orthodontic appliances on masticatory and swallowing threshold performances.

To test the hypothesis that treatment with orthodontic appliances disturbs masticatory and swallowing performances. Twenty-seven subjects with malocclusions requiring orthodontic treatment were included in this prospective study. The masticatory and swallowing performances were evaluated at five different times: before bracket placement (T0), immediately after archwire placement (T1), 48 h after archwire placement (T2), 30 days after archwire placement (T3) and 3 months after the initial appointment (T4). Masticatory performance was determined by the median particle sizes for the Optocal test food after 15 chewing strokes, and the swallowing thresholds were registered for both the test food and a natural food (peanuts). Pain during mastication was evaluated using a 100-mm visual analogue scale. Masticatory performance was significantly reduced at T2, at which time patients reported the highest pain values. The time spent to the first swallow was increased at T2 for the natural food but not for the test food. The values for pain, masticatory and swallowing performances at T3 and T4 were similar to those at T0. Orthodontic patient masticatory function is only reduced during the period of higher pain experience, which could also disrupt the deglutition of harder foods. However, neither mastication nor deglutition processes were disturbed by orthodontic appliances in long-term treatment.

Electromyographic activity and thickness of masticatory muscles in children with unilateral posterior crossbite.

The aim of this study was to assess the electromyographic (EMG) activity and thickness of the masseter and anterior temporalis muscles in children with unilateral posterior crossbite (PCB). Thirty-six children (22 boys, 14 girls, and mean age of 8.8 +/- 1.1 years) were divided into the following groups: The case group with 20 PCB patients (10 on the left side, 10 on the right side); the control group with 16 normal occlusion (NOccl) subjects. EMG activity was recorded with bipolar surface electrodes at rest and during maximal clenching. The muscle thickness was measured with real-time ultrasound. Data were compared between groups and between sides. The correlation between EMG activity and muscle thickness was also evaluated. The data were analyzed using the Shapiro-Wilks test, Pearson's correlation and Spearman as appropriate, paired and unpaired t- test, and Mann-Whitney test. The results revealed that the masseter of the crossbite side was more active than that of the non-crossbite side in PCB group during maximal clenching. The comparisons of EMG activity between PCB and NOccl groups revealed some variability in the results, depending on the crossbite side. The ultrasonographic evaluation did not show statistically significant differences between groups, nor between sides in the PCB and NOccl groups. Significant correlation between EMG activity and thickness was observed only in the left masseter in the NOccl group. In conclusion, these findings showed that asymmetric muscle activity of the masticatory muscles was not related to the thickness of these muscles in children with PCB.

Histological analysis of orthodontic root resorption in rats treated with the cyclooxygenase-2 (COX-2) inhibitor celecoxib.

INTRODUCTION: It has been reported that anti-inflammatory drugs used for treatment of pain and discomfort related to orthodontic treatment could slow down tooth movement. However, the effect of these drugs on orthodontic root resorption is not well understood. OBJECTIVES: The aim of this study was to investigate whether the COX-2 inhibitor celecoxib offers some protection against orthodontically induced root resorption. DESIGN: Male Wistar rats were divided into four groups: Groups I and II were treated with saline and celecoxib (10 mg / kg), respectively for 3 days. Groups III and IV were treated with saline and celecoxib for 14 days. The upper left first molars of all rats were moved mesially for 14 days with 50 g of force. An area including the disto-apical aspect of the mesial root of the first molar was processed for histological and histochemical techniques with tartarate-resistant acid phosphatase (TRAP). OUTCOME MEASURE: The degree of root resorption was measured using an image analysis system with a grid-sheet superimposed in the root were resorption lacunae were counted. The number of TRAP-positive cells on the tooth root surface defined as odontoclasts were also evaluated. RESULTS: The results revealed that there were no significant differences in the degree of root resorption and in the number of odontoclasts on the root between the four groups studied. CONCLUSION: The short and long-term celecoxib administration did not suppress the root resorption in case of experimental orthodontic force application.