Background: Bone overheating during osteotomy preparation for dental implant has been extensively investigated. However, thermal changes during implant insertion were seldom reported. Several factors might influence heat generation, such as the osteotomy dimension, implant surface and the friction between implant and bone. A common approach to reach high levels of primary stability is to undersize the implant osteotomy and the use of rough implant surfaces, which might increase the risk of bone overheating.

Aim/Hypothesis: The aim was to evaluate the in vivo bone temperature change at implant placement using different osteotomy dimensions, implant surfaces and frictional characteristics. It is hypothesized that the insertion in an undersized osteotomy would generate a greater temperature change.

Materials and Methods: On ten female Finnish Dorset crossbred sheep, four implants were placed in both metatarsal bones. To modify the implant-bone friction, the presence of a lubricant body fluid (sheep saliva) was tested. Eight experimental groups were created based on the following features- undersized and conventional osteotomy, moderately rough and turned surface, presence and absence of a lubricant fluid on the implant surface (Table 1). Intraosseous bone temperature was measured with a type-K thermocouple. The position of the sensor tip was at the distance of 1 mm from implant surface and depth of 2 mm from bone surface. Bone temperature was continuously measured from just before implant placement until 1 minute after the implant placement. Maximum and minimum values were registered. The values of temperature change for each implant were calculated. Three-way ANOVA was used to evaluate the influence of the osteotomy preparation, implant surface and frictional characteristics.

Results: The mean values of temperature change were 6.4 8,2, 4.0, 5.1, 8.1, 9.6, 3.4, and 5.2 degrees Celsius increase respectively from Group 1 to 8 (Figure 1). Regarding the surgical drilling protocol, the overall test showed that undersized groups showed significantly higher temperature than conventional osteotomy groups (P value = 0.000). In the presence or absence of a lubricant body fluid, the overall test showed that absence of a lubricant body fluid, showed significant higher temperature change than when it was present (P value = 0.002). Differences of implant surface topography, the overall test presented no statistical differences between moderately rough surface and turned surface (P value = 0.651).

Conclusion and Clinical Implications: Intraosseous temperature change during implant insertion was mainly affected by osteotomy dimension. Undersized osteotomy induces a greater risk of bone overheating. The presence of a lubricant fluid on implant surface reduced the temperature increase, while surface characteristics did not show any influence on temperature modifications. To reduce the risk of implant failure due to bone overheating, implant installation in undersized sites should be cautiously performed in cortical bone.