# Heat generation of autologous bone harvesting drills: an in vitro study

## TL;DR

This study measured heat generated by bone harvesting drills in vitro and found that certain drilling parameters keep temperatures below critical thresholds.

## Contribution

The study provides empirical data on temperature changes during autologous bone harvesting using specific drill parameters.

## Key findings

- Donor bone temperatures stayed below 10°C with 20N axial load or 600 rpm drilling.
- Drill wear significantly increased temperatures after 30 uses.
- Bone chip temperatures remained under 5°C for all tested conditions.

## Abstract

Bone collecting drills are utilized in implantology to harvest autologous bone chips. This study aimed to assess intraosseous and bone chip temperature changes during bone collecting procedures. Auto-Max (Megagen, Luton, UK) drills were evaluated at rotational speeds of 300, 600, 1200, and 2000 revolutions per minute (rpm), each combined with axial loads of 15 N, 20 N, and 25 N, using fresh pig ribs. Axial load along the perpendicular axis was maintained via a dedicated drilling tower. Bone chip temperatures were measured using an infrared non-contact thermometer, whereas donor bone temperatures were monitored with thermocouple sensors positioned 0.5 mm from the osteotomy periphery. Drill wear was assessed through scanning electron microscopy. The highest donor bone temperature observed was 10.1 ± 3.04 °C at 1200 rpm and 25 N. With a 20 N load, temperature increases ranged from 3.01 to 4.84 °C. At 25 N, temperatures at 300 rpm (1.84 ± 0.58 °C) and 600 rpm (6.70 ± 2.64 °C) consistently stayed below 10 °C. Bone chip temperature rises were all under 5 °C. The slowest drilling occurred at 15 N/600 rpm (6.49s), and the fastest at 2000 rpm (< 1.65s). Drill wear was moderate up to 10 uses, but significant after 30, with bone temperatures rising by 240% to an average of 10.22 ± 2.45 °C. With respect to chip temperatures, all evaluated drilling parameters produced maximum temperature elevations below 5 °C. Donor bone temperature increases remained consistently under the theoretical threshold of 10 °C when an axial load of 20 N was applied—regardless of rotational speed—or when drilling at 600 rpm, independent of axial load. It is recommended that drills be replaced prior to 30 uses.