Frictional heat produced by cutting tools during dental implantation procedure may destroy the surrounding bone tissue and regenerative capacity and interfere ossointegration by formation of undifferentiated connective tissue. To study the effect of frictional heat according to various rotational speeds on the regenerative capacity of surrounding bone tissue, 13 ITI HS implants (8 mm) were inserted at 4 mongrel dogs. Temperatures were measured using thermocouple located 6 mm below from the marginal crest and 0.5 mm from the periphery of trephine mill during implant bed preparation. After 4 and 9 months, animals were sacrificed and specimens were examined using x-rays and light microscope. Results were as follows: 1. With drill speeds of 300，800，2,000, 3,500 rpm and saline irrigation, temperatures of surrounding bone were decreased from -2.9° to -1.7°C. Temperature rises of 2.0° and 2 .1°C were recorded with a drill speed of 5,000 rpm and irrigation. 2. With drill speeds of 800，3,500, 5,000 rpm and no irrigation, temperatures of surrounding bone rose from +1.5° to +6.8°C, but maximum temperature was 40°C at 5,000 rpm. 3. On radiographic examination, bone resorptions were observed at the upper half of implant of 5.000 rpm without irrigation and one case of 5,000 rpm with irrigation. 4. Osseointegration was unsuccessful in cases of 3,500, 5,000 rpm without irrigation due to fibrous connective tissue formation to the outer surface and hollow, but it was successful in a case of 800 rpm without irrigation. 5. Osseointegration was successful in cases of 300，800，2,000 and 3,500 rpm with irrigation. But fibrous connective tissue formation was observed at the hollow of implant inserted with 5.000 rpm with irrigation.
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