Evaluation of root resorption associated with orthodontic movement in stressed rats.

AIM: The aim of this study was to investigate the effects of acute and chronic systemic stress response on orthodontically induced root resorption. METHODS: Male Wistar rats were restrained during 1 hour a day by stress models of short (3 days) and long duration (40 days), while control group was not submitted to restraint (N.=10/group). The upper left first molars of all rats were moved mesially by a fixed orthodontic appliance exerting 50 g force upon insertion during the last 14 days of the experiment. Then, animals were killed for blood collection and mensuration of plasmatic corticosterone by radioimmunoassay; the tissues around mesial root of the first molar were processed for histological and histochemical techniques with tartrate-resistant acid phosphatase. The degree of root resorption and the number of odontoclasts were evaluated, being the contralateral side of each animal serving as its control (split-mouth design). RESULTS: The results revealed that the plasmatic levels of corticosterone were significantly higher in both the stressed groups than in the control one. There were no significant differences in the degree of root resorption and in the number of odontoclasts on the root between the 3 groups studied. CONCLUSIONS: These results indicate that systemic stress alone can not be considered a risk factor for root resorption induced by orthodontic tooth movement.

Effect of incisal tooth wear and restoration on interocclusal distance during Brazilian Portuguese language speech.

AIM: The aim of this study was to investigate changes in interocclusal distance (IOD) during pronunciation of /m/ and /s/ sounds in Brazilian Portuguese, in patients presenting dental wear due to bruxism, before and after placement of a stabilization appliance and restorative treatment. METHODS: Subjects were divided into a control group of 19 patients with no dental wear and an experimental group of 18 patients presenting dental wear on anterior teeth due to bruxism. A stabilization appliance was placed in each patient in the experimental group and anterior teeth were restored. A magnetic jaw-tracking device measured the interocclusal distance during pronunciation of /m/ and /s/ phonemes. Interocclusal distance for the experimental group was evaluated one week before and again immediately before the appliance was inserted and 24 hours, 7 days, 1 month and 2 months after appliance insertion. The same evaluation was performed 7 days and 1 month after restorative treatment. In the control group, the measurements were carried out at the same intervals. RESULTS: Comparison between groups revealed a significant difference (P<0.05) in interocclusal distance for the /m/ sound at all evaluation intervals. No differences were found before and after appliance insertion and restorative treatment with either phoneme. CONCLUSION: Stabilization appliance therapy and restorative treatment of subjects with dental wear did not change the interocclusal distance during speech of /m/ and /s/ sounds in the Brazilian Portuguese language, however, when compared with normal subjects, the IOD values were higher for the dental wear group during pronunciation of the /m/ sound.