Effect of remineralization and inhibition to demineralization after fluoride gel or hydroxyapatite paste application on stripped enamel / 대한치과교정학회지

OBJECTIVE: The aim of this study was to evaluate the effect of remineralization and inhibition to demineralization after fluoride gel (acidulated phosphate fluoride, APF) or hydroxyapatite (HAp) paste application on interdentally stripped teeth. METHODS: After interdental stripping, 1.23% APF or 5%, 10% HAp paste were applied for 7 days for remineralization. Afterwards, teeth were exposed to lactate carbopol buffer solution for demineralization. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to compare change in surface contents and crystal structures after remineralization, and then after demineralization. RESULTS: EDS analysis indicated that calcium (p < 0.001) and phosphate (p < 0.01) contents were increased after 10% HAp paste application on stripped enamel, calcium (p < 0.05) and phosphate (p < 0.01) contents were increased after 5% HAp paste application, and fluoride (p < 0.01) contents were increased after 1.23% APF application. SEM image showed that enamel surfaces became smoother and crystal structures became small and compact after APF or HAp application. After demineralization, calcium (p < 0.05) and phosphate (p < 0.05) contents remained increased on the enamel remineralized with 10% HAp paste, and phosphate (p < 0.05) contents remained increased on the enamel remineralized with 5% HAp paste. After demineralization, surfaces looked less destroyed in the enamel remineralized beforehand than those of the control, and small pores between crystal structures, formed by remineralization were remained. CONCLUSIONS: Hydroxyapatite paste and fluoride gel were helpful to remineralize and inhibit deminerlization on stripped enamel.

A 3-D finite element analysis on the mandibular movement pattern and stress distribution during symphyseal widening / 대한치과교정학회지

OBJECTIVE: The objective of this study was to evaluate the displacement pattern and the stress distribution of the finite element model 3-D visualization during symphyseal widening according to the osteotomy position, osteotomy type, and distraction device. METHODS: The kinds of distraction devices used were tooth-borne type, hybrid type, bone-borne type and tooth-borne type 30degrees angulated, and the kinds of osteotomy design were vertical osteotomy line between the central incisors and step osteotomy line through the symphysis. RESULTS: All reference points of the mandible including the condyles were displaced laterally irrespective of the osteotomy position, osteotomy method and distraction device. The anteroposterior or vertical displacements showed small differences between the groups. The widening pattern of the osteotomy line in the tooth-borne type of device was v shaped, and that of bone-borne type was a reverse v shape. However, the pattern in the hybrid type was parallel. The lateral displacement of the mandibular angle by the bone-borne device was more remarkable than the other types of devices. The displacement by the 30degrees angulated tooth-borne type was different between the left and right sides in both the transverse and anteroposterior aspects. CONCLUSION: The design of the distraction devices and osteotomy line can influence the displacement pattern and the stress distribution during mandibular symphyseal distraction osteogenesis procedures.

Changes in surface content and crystal structure after fluoride gel or hydroxyapatite paste application on stripped enamel / 대한치과교정학회지

OBJECTIVE: The aim of this study was to evaluate the remineralization of interdentally stripped teeth after fluoride gel or hydroxyapatite paste application. METHODS: After interdental stripping, 1.23% fluoride gel or 10% hydroxyapatite paste was applied three times a day, with a duration of four minutes, for a week. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to compare the change of surface contents and crystal structures before and after the application of fluoride gel or hydroxyapatite paste. RESULTS: EDS analysis indicated that calcium contents were increased after 10% HAp paste application on stripped enamel (p < 0.01). SEM view showed that enamel surfaces in groups of 1.23% APF gel or 10% HAp paste application were smoother than those of control group, which was regarded as filling of the pore structure. And pores between crystal structures in groups treated with 1.23% APF gel or 10% HAp paste were smaller than those of control group. CONCLUSIONS: Application of APF or HAp on stripped enamel could positively influence on the surface contents or crystal structure.

Pulp and periodontal tissue changes following rapid tooth retraction by periodontal distraction in young adult dogs / 대한치과교정학회지

OBJECTIVE: The aim of this study was to evaluate pulp and periodontal changes following rapid tooth retraction by periodontal distraction after bone undermining surgery in young adult dogs. METHODS: After extraction of second premolars, the interseptal bone mesial to the upper 3rd premolar was undermined. After activating the distraction appliance at 0.5 mm/day for six days, the dogs were sacrificed at 0, 1, 3, 5, 7, and 9 weeks during the consolidation period. Tissue changes of periodontium and pulp were evaluated radiologically, histologically, and immunohistochemically. RESULTS: Digital subtraction radiography showed active bone formation in the stretched periodontal ligament from 0 - 4 weeks. Resorption of the alveolar bone, appearance of osteoclasts, and infiltration of inflammatory cells were observed just after the activation period at the pressure side, and distinctive bone formation was seen in the tension side of the periodontal ligament from 1 week. New bone formation was active at 1 - 3 weeks. The expression of calcitonin gene-related peptide in the experimental group was increased at the alveolar bone and pulp, and periodontal ligament at the pressure side from 0 - 1 week, and it decreased after 5 weeks to become similar to that of the control group. CONCLUSIONS: The results showed that rapid tooth movement using periodontal distraction can be new form of orthodontic tooth movement for accelerating normal bone formation.