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Background: With transitions in the disease concept of orthokeratinized odontogenic cyst (OOC), the pathogenesis and etiology have not been sufficiently elucidated. Objectives: OOC cases were reclassified and observed to understand the clinico-histopathological characteristics. In addition, literature review of OOC was performed to better organize the pathology. Materials and methods: Subjects with jawbone cysts lined by keratinized stratified squamous epithelium from 2005 to 2018 were reclassified, and clinico-histopathological findings were analyzed. Previous reports of OOC/orthokeratinized-type odontogenic keratocyst (OKC) from 1980 to 2019 were organized. Results: Five cases of OOC were diagnosed, representing 2.1% of odontogenic developmental cysts (total, 239 cases). Mean age was 37.6 years, with a female predominance. The mandibular molar area was the frequent site, and all cysts were solitary. Sixty percent involved an impacted tooth. Mean maximum diameter of the cyst was 2.2 cm. Histopathologically, 4 cases were unilocular, and partial palisading of the basal layer and scattered epithelial islands were observed in 2 cases each and formation of daughter cysts was noted in 3 cases. Previous papers described that most were unilocular and related to impacted teeth. Mean age ranged between 20 and 40 years, and the mandibular molar region was dominant. Recurrence rates were low. Conclusion: OOC shows a different biological attitude to OKC and is closer to dentigerous cyst. Meanwhile, OOC shows a similar histology of epidermoid cysts accompanying the granular layer. We thus surmised that OCC represents an independent concept as an odontogenic developmental cyst.

The materials of high molecular compounds have been widely used in the field of dental clinics. Although preparation of the tooth abutment and contamination of the metal fragments are known to cause the discoloration and injury in the periodontal tissues in the field of crown and bridge prosthodontic clinics, the changes by the precipitation of composite resin fragments have not been fully clarified, yet. In addition, diabetes mellitus has recently been increased because of an advanced age, life style and conditions, and also, the patients with diabetes have increased in dental clinics. Therefore, the present study was undertaken the histopathological, histochemical and immunohistochemical analyses, in order to elucidate the changes of the periodontal tissues by injecting the composite resin fragments. The histopathological reactions of the periodontal tissues in both healthy (m+/m+) and diabetic (db/db) mice were also compared. Histopathologically, neutrophil infiltration was remarkably observed around the fragments of the composite resin at 3 days after the injection, and then, the formation of the granulation tissues with appearance of macrophages (foamy cells) at 7 and 14 days in m+/m+. Multinuclear giant cells were also observed at 14 days in m+/m+. In db/db, neutrophil infiltration was not so remarkable at 3 days, and relatively increase of the infiltration was observed at 7 days, and formation of the granulation tissues with appearance of the foamy cells at 14 days. The numbers of the mast cells, indicated metachromasia with toluidine blue pH 2.5 staining, peaked at 3 days and then decreased at 7 and 14 days in m+/m+, whereas the peak of the mast cells was at 7 days in db/db. Immunohistochemically, the peak cell rate of CD68-positive macrophage was found at 3 days after the injection, and the rate decreased at 7 and 14 days in m+/m+, whereas the rate gradually increased and showed the peak at 14 days after the injection in db/db. The peak of the cell rate of matrix metalloproteinase-2-positive macrophage was observed at 3 days, and the rates tended to gradually decrease at 7 and 14 days after the injection in m+/m+, whereas lower cell rate without peak point was recognized at each day in db/db. These results suggested that db/db showed delay of the process of biological reactions for the foreign bodies of the composite resin fragments compared to m+/m+. Furthermore, the delay of the reaction depended on the inhibition for the fibrosis accelerated by macrophages and mast cells.

Purpose The effects of bleaching times, types of etching agent and storage period of bleached bovine tooth on the shear bond strength of resin cement to the enamel were examined. Materials and methods Bovine teeth were repeatedly bleached 0, 1, 3, and 5 times then stored in 37 degrees C water for 1 week. The effect of bleaching number of the bovine tooth on the bond strength of resin cement to the enamel was investigated using 40% phosphoric acid (EG) etching technique. Next, the effects of types of etching agent and of storage period of bleached bovine tooth with three times in 37 degrees C water on the bond strength were studied using 10% citric acid-3% ferric chloride (10-3) or 10% citric acid (10-0) solution. Results The bleaching of bovine tooth allowed for a dramatic decrease in the bond strength from 18.3 MPa to 9.8 MPa (1 time), and 3.9 MPa (3 times), even though the bovine enamel was etched by EG. However, when 10-3 or 10-0 solution was applied to the three times bleached enamel, bond strengths were 13.9 and 10.0 MPa, respectively. Furthermore, prolonging of the storage period of the three times bleached bovine tooth in water to 2 months resulted in a increase in the bond strength from 3.9 to 10.1 MPa, even if bovine enamel was etched by EG, and close to that obtained from the 10-3 etching. Conclusion To obtain the expected bond strength to bleached enamel, it is better to wait for 2 months for a restoration and use the 10-3 etching.

The effects of bleaching times, types of etching agent and storage period of bleached bovine tooth on the shear bond strength of resin cement to the enamel were examined.Bovine teeth were repeatedly bleached 0, 1, 3, and 5 times then stored in 37 degrees C water for 1 week. The effect of bleaching number of the bovine tooth on the bond strength of resin cement to the enamel was investigated using 40% phosphoric acid (EG) etching technique. Next, the effects of types of etching agent and of storage period of bleached bovine tooth with three times in 37 degrees C water on the bond strength were studied using 10% citric acid-3% ferric chloride (10-3) or 10% citric acid (10-0) solution.The bleaching of bovine tooth allowed for a dramatic decrease in the bond strength from 18.3 MPa to 9.8 MPa (1 time), and 3.9 MPa (3 times), even though the bovine enamel was etched by EG. However, when 10-3 or 10-0 solution was applied to the three times bleached enamel, bond strengths were 13.9 and 10.0 MPa, respectively. Furthermore, prolonging of the storage period of the three times bleached bovine tooth in water to 2 months resulted in a increase in the bond strength from 3.9 to 10.1 MPa, even if bovine enamel was etched by EG, and close to that obtained from the 10-3 etching.To obtain the expected bond strength to bleached enamel, it is better to wait for 2 months for a restoration and use the 10-3 etching.