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Influence of Different Drilling Protocols for Primary Stability at Low-Density Bone Detected by Bone Density
Yusuke Morimoto1, Reiko Kobatake1, Kazuya Doi1
1Department of Advanced Prosthodontics, Hiroshima University Graduate School of Biomedical and Health Sciences, Hiroshima, Japan.
Objectives:
Intraoperative bone assessment is critical for achieving primary implant stability, particularly at low-density bone sites. Drilling torque value (DTV) has been proposed as an indicator of bone density and may help guide drilling preparation protocols to improve primary stability. However, the relationship between DTV and primary stability, especially histological bone parameters in biological bone, remains unclear. This study aimed to clarify the influence of different drilling protocols for primary stability at low-density bone detected by DTVs in biological cancellous bones.
Materials And Methods:
Cancellous bone blocks obtained from bovine ribs were used. A specially designed torque measurement drill was used to assess bone density intraoperatively. Based on the DTVs, low-density bone sites corresponding to Misch D4 and D5 were selected. The dental Implants were placed using either a normal or undersized drilling protocol. The DTVs, insertion torque values (ITVs), and implant stability quotient (ISQ) were recorded. Histological evaluation was performed to assess the bone area fraction (BAF) around the implant.
Results:
The ITVs were lower than the clinically recommended range for primary stability in both groups; however, they were significantly higher in the undersized group than in the normal-sized group. The DTVs positively correlated with the ITVs in both groups. A positive correlation between DTV and ISQ was observed only in the normal-sized group, whereas ITV was positively correlated with ISQ in both groups. Histological analysis revealed no significant difference in BAF between the two groups. BAF positively correlated with DTV, ITV, and ISQ.
Conclusions:
DTV reflects the existing bone volume of low-density tissue and is correlated with primary stability. Intraoperative assessment of drilling torque would facilitate the selection of appropriate drilling protocols to achieve primary stability. Bone density evaluation by measuring the DTV may provide a clinically useful method for the intraoperative evaluation at low-density implant sites.
