Expansion of the mandibular arch in children during the mixed dentition period--a clinical study.

A review of the dental literature revealed relatively few studies on the expansion of the mandibular dental arch. The present study attempted expansion of the mandibular arch using a Bihelix appliance. The subjects were 16 children, exhibiting crowding, age ranges from 7 to 11 years. The mandible was expanded 2.0 mm every 3 months. Significant expansion, not only of the individual tooth inter-arch dimensions but also of the overall arch length, was obtained during the period of incisor tooth replacement. The mode of expansion was classified as follows: Type I, those, which showed no effect on the apical base; Type II, those which showed no consistency of the measurement lines. In this study, 6 of 16 cases were classified as type I and 10 cases as type II. Expansion was continued over a period of 1.5 to 3 years. We concluded that considerable lateral expansion of the mandibular arch is possible using the Bihelix appliance. It is suggested that this might contribute greatly to non-extraction orthodontic treatment. Further studies are recommended.

Management of a root fracture in an immature permanent tooth.

A 9-year-old girl with trauma to the maxillary right permanent central incisor is reported. Clinically the tooth appeared extruded with one third of the root visible. The radiographic examination revealed a root fracture. The extruded tooth was repositioned and splinted with a heavy wire and adhesive resin, after which a resorbable collagen tissue was placed to cover the buccal region. Subsequent to the injury, swelling was observed and the patient complained of pressure pain in the periapical region of the tooth with no response to electric pulp testing. It was treated successfully with periodontal therapy and endodontic therapy with Vitapex.

Human salivary peroxidase-catalyzed oxidation of nitrite and nitration of salivary components 4-hydroxyphenylacetic acid and proteins.

Human saliva contains high activities of peroxidase and high concentrations of nitrite (about 0.2 mM in average). If H2O2 is provided by bacteria and leukocytes in the oral cavity, peroxidase-dependent formation of reactive nitrogen species, which can nitrate phenolics like 4-hydroxyphenylacetic acid (HPA) and tyrosine residues in salivary proteins, is possible. H2O2-dependent oxidation of nitrite and H2O2-dependent nitration of HPA were observed in dialyzed saliva and by partially purified salivary peroxidase (SPX). The nitration was inhibited by a physiological electron donor to salivary peroxidase, SCN-. When concentrations of H2O2 and nitrite were increased, nitration of HPA was also observed in control (non-dialyzed) saliva. In addition, H2O2-dependent nitration of tyrosine residues in salivary proteins was observed in dialyzed saliva as an increase in absorbance around 420 nm at pH 7.2. Kinetic studies of the increase in absorbance indicated that sulfhydryl groups in salivary proteins as well as glutathione, ascorbate, urate and SCN- could inhibit the nitration. Since the nitration of proteins can lead to impairment of their functions, it is discussed how the oral cavity is protected from the damages caused by reactive nitrogen species under normal conditions and also discussed that reactive nitrogen species generated by the H2O2/nitrite/peroxidase system can participate in the host defence mechanism in the oral cavity.

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.

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.

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.