Ex vivo porcine study of thermal changes in the bone marrow region during osseodensification and osteotomy

Aim Bone milling performed during osteotomy requires caution in controlling the temperature rise. In addition to the bone being sensitive to heat, there are several factors that influence bone heating, such as cortical thickness, bone density, time used during milling and drill speed. The objective of the present study was to measure and compare the thermal variations during osteotomy with osseodensifying drills at different distances in the peripheral region of the mental foramen artificially made in vitro and ex vivo using porcine ribs, correlating the thermal variation with the bone density determined through the unit of Hounsfield and with the different distances, between the thermal verification point and the osteotomy point.
Materials and methods The specimens were osteotomized using Densah Bur drills at 720 RPM with a torque of 20N.cm3 in a universal testing machine (EMIC DL 200MF, Emic-Instron, São José dos Pinhais, BR) in a load of 2 kg/force interspersed with peaks of return and advance of 1 mm until reaching the depth of 10 mm. The maximum thermal peaks were computed in a thermometer with a 4-channel K-type digital thermocouple sensor (HT-9815, Lefavor, Guangdong, CN) inserted in the pre-established areas, followed by analysis in the SkyScan 1172 microtomograph (Bruker-μCT, Kontich, Belgium) and correlating the density bone verified in the μCT with the thermal variations and the distance of the previously verified osteotomy points.
Results Thermal variations showed increases of up to 1.7 ºC in the medullary bone. The data suggested that there was a direct relationship between medullary bone heating and bone density, with overheating in the D1 density groups and no overheating in the D2 bone density group.
Conclusions Medullary bone heating suggested that it was directly correlated with the bone quality present in the osteotomized bed. This generated heat can propagate in different directions, in the middle and apical third of the milled bed, and even to the buccal cortical wall in atrophic bone crests, reaching the anatomical structures supported in these areas. In addition, the quality of osseodensification presented after the trials suggested a direct dependent relationship with the bone marrow quality to achieve the totality of osseodensification in the osteotomized bed.