The purpose of this study was to assess the precision and accuracy of an optical densitometric analysis that used an SUS step wedge as a calibrator, and to analyze bone quality and bone mineral quantity from intraoral dental X-ray (IODX) images of the mandible of both males and females in their 60's. A total of 32 subjects (16 males, mean age 63.9+/-3.3 yrs; 16 females, mean age 63.8+/-3.6 yrs) participated in this investigation.The location where the bone quality and bone mineral quantity were studied was the part of the alveolar bone where mandibular first molars (M_1s) had been extracted from the mandible, and an SUS (stainless used steel) wedge with 5 steps was used for image analysis. The measurement precision and accuracy of a pseudocolored densitometric image analysis (PCDIA) system, in which a personal computer was used to analyze bone quality and bone mineral quantity on IODX images, were high.The mean values of the coefficients of variation (CV) of bone mineral content (BMC) calculated within the region of interest (ROI) of a square of 8 by 8 mm (0.64 cm²) in the mandible were less than 0.7%. Regarding image density within the ROI around the M1 in males and females in their 60's, the difference between grades I and V ranged from 1/4 to 2/3, i.e., 37.9% of all in image data, of the 256 gray levels. No statistical difference was recognized in the mean BMC between males and females in their 60's, but the mean value for males (0.23 mm+/-0.04 SUS equivalent values) was larger than that for females (0.20 mm+/-0.05 SUS equivalent values).Both grades of IV and V were significantly larger in males than in females when compared with the mean values (%) of BMC in each grade between the sexes. The distribution of maximum BMC for males and females was 43.8% in grade Ⅲ,and was 81.3% in grades Ⅲ and Ⅳ of males and 93.8% in grades Ⅰ,Ⅱ and Ⅲ of females.Therefore, a tendency of sexual dimorphism was clearly shown. Simple correlation analysis revealed insignificant relationships between BMC and aging for the decade from the age of 60 to 69 years in both sexes.
These results suggest that densitometric analysis is useful for assessing the bone quality and bone mineral quantity in the mandible when considering implants for patients aged 60 and over.

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　Temporary cements are frequently used for implant-supported fixed prostheses to facilitate the retrievability of cement-retained implant superstructures. To date,however, only a few studies have systematically examined the cementation of implant superstructures using temporary cements. Therefore, this study evaluated the effect of the mixing ratio of temporary cements on retention force and seating discrepancy to examine whether the mixing ratio could be used to control the retrievability of cement-retained implant superstructures.
　Six implant abutment analogs (f4.3 mmRN Replace Select Easy Abutment Replica, Nobel Biocare) were fixed to an aluminum table using adhesive resin cement. Six cement-retained implant superstructures made of gold-silver-palladium alloy, which were fabricated from plastic-coping, were cemented to abutment analogs using three temporary cements: eugenol-free, zinc oxide eugenol, or polycarboxylate temporary cements. The retention force and seating discrepancy were measured for different mixing ratios of these temporary cements.
　There were statistically significant correlations between the mixing ratio and retention force for the eugenol-free and zinc oxide eugenol cements, while no significant correlation was found for the polycarboxylate cement. The average seating discrepancy for the eugenol-free temporary cement was significantly lower than that for the other two temporary cements.
　The mixing ratio of the temporary cements could be used to control the retrievability of cement-retained implant superstructures, but not the seating discrepancy. Of the temporary cements tested, the seating discrepancy was lowest for the eugenol-free temporary cement.

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Explantation of failing or unfavorable implants is indicated in some patients. Here, we report the experience of two cases of surgical treatment required after extraction of implants by other dentists.
　In the first case, which was a 56-year-old male, another dentist had accidentally introduced a fixture into the left maxillary sinus during its explantation. Because we estimated the size of the perforation was too small to pull the fixture through, we performed endoscopic surgery to remove it another day after provisional closing of the perforation.
　The second case was a 58-year-old female. She had an oroantral fistula at the maxillary right molar region, resulting from the removal of implants. The fistula had been left untreated for about three months and the patient had chronic sinusitis and pustulosis palmaris et plantaris at the time she visited our hospital. Her uncontrolled diabetes required treatment to bring her diabetic status under control by the internist before surgery. Then, we repaired the oroantral fistula. In addition, ethmoidectomy and enlargement of the semilunar hiatus were simultaneously performed with an endoscope in cooperation with an otolaryngologist. The patient showed satisfactory progress, and recovered from pustulosis palmaxis et plantaris about one month later.
　Besides careful preoperative planning for implant therapy, primary management of surgical complications is also important.

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