Identification and adjustment of experimental occlusal interference using functional magnetic resonance imaging.

BACKGROUND: The purpose of this study was to use functional magnetic resonance imaging (fMRI) to quantify changes in brain activity during experimental occlusal interference. METHODS: Fourteen healthy volunteers performed a rhythmical tapping occlusion task with experimental occlusal interference of the right molar tooth at 0 mm (no occlusion), 0.5 mm, and 0.75 mm. The blood-oxygen-level dependent (BOLD) signal was quantified using statistical parametric mapping and compared between rest periods and task periods. RESULTS: In tapping tasks with experimental occlusal interference of 0.75 mm or 0.5 mm, there was clear activation of the contralateral teeth-related primary sensory cortex and Brodmann's area 46. At 0 and 30 minutes after removal of the experimental occlusal interference, the activation clearly appeared in the bilateral teeth-related primary sensory cortices and Brodmann's area 46. At 60 minutes after the removal of the experimental occlusal interference, the activation of Brodmann's area 46 had disappeared, and only the bilateral teeth-related primary sensory cortices were active. CONCLUSIONS: The present results suggest that adjustments for experimental occlusal interference can be objectively evaluated using fMRI. We expect that this method of evaluating adjustments in occlusal interference, combined with fMRI and the tapping task, could be applied clinically in the future.

Biomechanical analysis of combined treatment of high calcium and bisphosphonate in tibia of steroid-treated growing-phase rats.

Childhood systemic diseases are commonly treated with steroids. Consequently, steroid-induced osteoporosis is often observed as a side effect of steroid therapy. However, osteoporosis of tibia resulting from steroid therapy has not been reported yet. Herein we constructed a steroid-induced osteoporosis in tibia of the growing phase rats to examine internal structural changes of the bone and tried to find out the effect of bisphosphonates as a new and early treatment method. Biomechanical analysis was performed using two-dimensional microdensitometry and three-dimensional pQCT method. In addition, the following evaluations were carried out: noninvasive bone strength measurements in steroid-induced osteoporotic rat tibiae; comparing the effectiveness of single high-calcium diet versus combined treatment of high calcium and bisphosphonate for osteoporosis; and quantitative measurement of four elements (Ca, P, Mg, Zn) in bone matrix. Our data suggested that a combined treatment of high calcium and bisphosphonate was an effective new method to improve and treat steroid-induced osteoporosis in childhood.

Determination of salivary peroxidase activity in human mixed whole saliva.

Mixed whole saliva contains salivary peroxidase (SPX) and myeloperoxidase (MPO), thus it is important to discriminate between the two peroxidases in order to understand their functions in the oral cavity. We developed a method to measure SPX activity in mixed whole saliva using an oxygen electrode. According to our results, when 50% of the peroxidase activity in saliva was due to MPO, determined using a typical substrate for peroxidase guaiacol, almost all oxygen evolved was due to SPX. We propose that measurement of H(2)O(2)-dependent oxygen evolution is a useful method for determining SPX activity in whole saliva.

Aluminum concentrations in human deciduous enamel and dentin related to dental caries.

The aluminum (Al) concentrations in the enamel and dentin of 314 human deciduous teeth were determined in order to examine the relationship between Al and dental caries. The sample teeth were divided into three groups: the sound tooth group, carious tooth group and filled tooth group. The teeth of the carious tooth group were further classified into three groups depending on the stage of caries. The Al content was determined using graphite furnace atomic absorption spectrometry. In both the enamel and dentin, the Al concentrations were unaffected by sex, but did depend on tooth type. In enamel, the Al concentration was significantly higher in the sound tooth group (42.8 +/- 37.3 microg/g) than in the three carious groups (20.7 +/- 17.1-24.9 +/- 22.0 microg/g) and the filled tooth group (27.3 +/- 25.5 microg/g). As for dentin, the Al concentration was also significantly higher in the sound tooth group (36.2 +/- 35.1 microg/g) than in the three carious groups (15.1 +/- 13.3-24.5 +/- 23.4 microg/g) and the filled tooth group (17.2 +/- 20.6 microg/g). Even when analyzing incisors alone, the Al concentrations were significantly higher in the sound tooth group than in the other groups, for both enamel and dentin. Furthermore, the Al levels in carious enamel and dentin did not decrease with the advance of caries. These findings indicated that the deciduous teeth containing higher Al concentrations on average had less caries than the teeth with lower Al concentrations, and suggest that Al acts as a possible cariostatic agent by itself.

Mechanical evaluation of effect of grape seed proanthocyanidins extract on debilitated mandibles in rats.

Grape seed proanthocyanidins extract (GSPE), whose principal ingredient is proanthocyanidins, shows many activities such as cholesterol lowering effects, antioxidant effects, anti-tumor effects, cardioprotective effects, and protection against ultraviolet rays. However, reports of the effects of GSPE on bone are rare. We performed a mechanical analysis of the effect of GSPE on the interior structure of rat mandibular bone in the growth period, using three-dimensional peripheral quantitative computed tomography (pQCT). A low-calcium/high-calcium diet with supplementary GSPE was compared to a low-calcium/high-calcium diet in rats with debilitated mandibular bones. The group who received added GSPE showed a significant increase in cortical bone density, cross-sectional area, and trabecular bone mineral content (p<0.05). A significant increase was also seen in the results of a non-invasive stress strain index (SSI) (p<0.01) in the added GSPE. Our findings suggest that GSPE can increase bone quality and bone strength of rat mandibles in the growth period.

Effects of dietary consistency on the mandible of rats at the growth stage: computed X-ray densitometric and cephalometric analysis.

Thirty 3-week-old male Wistar rats were grouped into a hard diet control group, a kneaded-diet group, and a powdered-diet group. After 6 weeks of growth, all rats were killed under deep anesthesia. The effects of dietary physical consistency on the mandible were investigated with respect to morphology and bone mineral content using lateral cephalometric analysis and computed X-ray densitometry. Significant differences between the experimental and control groups were determined by measuring the means and standard deviation of the coordinates and differences between 15 points selected on the mandibles. Gonion (Go), which is a measurement of depth to the X-axis, was significantly less in the powdered-diet group, while the kneaded-diet group showed no significant differences. The most posterior point of the coronoid process (Cr) and the most posterior point of condylar process (Cd), which are measures of height to the Y-axis, were less in the kneaded-diet group than in the control group. In the powdered-diet group, Cr, Cd, Go and Infradentale were significantly less than in the control group. On the other hand, the bone mineral content was significantly lower in the coronoid process and angle of mandible in only the powdered-diet group.

The effect of oral ipriflavone on the rat mandible during growth.

Different types of ipriflavone (IF) have been reported to be effective when used as a remedy for bone loss due to osteoporosis. However, no information is available regarding the relationship between IF and jaw bone structure. The aim of this study was to examine the effect of IF on rat mandibles during the growth stage. Thirty-two 5-week-old Wistar male rats were divided into four groups. The control group was fed a standard diet, group A received a low calcium diet (calcium content 30 per cent of the standard diet) for 6 weeks, and the other two groups were fed a low calcium diet for 3 weeks and then a standard diet without IF (group B) or with IF (group C) for 3 weeks. In addition, distilled water was provided for all groups. The effects of IF on mandibular size and bone mineral content were investigated, using lateral cephalometric analysis and peripheral quantitative computed tomography (pQCT). For mandibular length, the control group showed a significantly higher value than groups A and B (P < 0.01, P < 0.05, respectively), while group C demonstrated a significantly higher value than group A (P < 0.01). In addition, the control group and group C showed significantly higher values for mandibular ramus height than group A (P < 0.01). However, bone mineral density in trabecular bone was significantly higher in the control group than in the other groups (P < 0.01) and bone mineral density in cortical bone was significantly higher in the control group than groups A, B and C (P < 0.01, P < 0.01, P < 0.05, respectively). Bone mineral density in both trabecular and cortical bone was significantly higher in group C than in groups A and B (P < 0.01, P < 0.05, respectively). These results indicate that complete recovery from calcium deficiency to the level of the control group may not be attainable, even though IF enhances calcium absorption to act on bone cells and promote bone construction. The importance of calcium intake in the early stages of development was confirmed. These findings also suggest an effect of IF on jaw bone structure.

Grape seed proanthocyanidins extract promotes bone formation in rat's mandibular condyle.

We studied the effect of dietary supplementation with grape seed proanthocyanidins extract (GSPE) 3 mg added in 100 g high-calcium diet with a calcium content of 1697 mg 100 g(-1) on mandibular condyle bone debility, which was induced by a low-calcium diet. Forty Wistar male rats, 5 week old, were randomly divided into control (Co), low-calcium diet (LC), low-calcium/high-calcium diet (LCH), and low-calcium/high-calcium with supplementary GSPE diet (LCHG) groups for 6 wk. Bone formation of the mandibular condyle was measured using peripheral quantitative computed tomography (pQCT). Significant differences were not seen among the four groups for body weight, measured weekly. The LCHG group scored significantly higher in cortical bone density, total bone cross-sectional area, cortical bone cross-sectional area, cortical bone mineral content, total bone density, total bone mineral content, and in the stress-strain index to the reference axis x when compared with the LCH group. We concluded that a high-calcium diet combined with GSPE supplementation is more effective in reversing mandibular condyle bone debility in rats than is a low-calcium diet, standard diet, or high-calcium diet alone.

Effect of zinc on rat mandibles during growth.

Zinc is a constituent of enzymes such as alkaline phosphatase and is an essential trace element involved in bone formation. The purpose of this study was to examine the effects of low levels of zinc intake on bone density and the area of cortical and trabecular bone in rat mandibles during the growth stage with peripheral quantitative computed tomography. The cartilaginous ossification in the femur was also measured. In the mandible, the low-zinc group showed significantly lower trabecular bone density compared with the control group, whereas the zinc-deficient group showed significantly lower levels of cortical bone density and trabecular bone density in the area. On the other hand, in the femur, both the zinc-deficient group and the low-zinc group showed a significantly lower value in cortical bone density and trabeculae bone density when compared with those of the control group. Moreover, the area of cortical bone and trabecular bone in the zinc-deficient group showed significantly lower values than those of the control group, whereas the low-zinc group only showed a significantly lower area of cortical bone than that of the control group. These results suggested that changes in zinc intake might exert an effect on the osseous tissue of the mandible and femur, and the femur was more sensitive to change of dietary zinc content than mandibles.