Temperature Changes During Intraosseous Anaesthesia in Vitro

Objective: To evaluate the temperature changes with a newly developed drill system to penetrate the cortical substance of bone and apply anaesthetic into the cancellous bone.

Methods: Isolated mandibularies of the pig were used to measure the: (1) temperature rise during drilling in the bone and the deformation of the rotating needle (n=14), (2) temperature rise of the oral mucosa during direct rotational contact of the needle socket with the mucosa to simulate contact with the lower lip (n=10), (3) temperature rise of anaesthetic during the rotation of the carpule in the handpiece (n=5). Measurements were taken with a temperature probe (Testoterm 901, Testoterm GmbH & Co., Lenzkirch, Germany), which was either located in a hole close (2±1mm) to the penetration spot (1), in the mucosa (2) or in the carpule (3). Additionally, the tips of the needles were morphologically analysed by a light microscope (SZ60, Olympus, Hamburg, Germany, magnification: 60x).

Results: During drilling, mean temperature increased for 6 to 14s with an average increase of 9.44±3.38°C (p>0.001). In a linear model, this is related to an average temperature increase of 0.63°C per second (curve fit: linear, p<0.001). In the rotating carpule the temperature change of the anaesthetic was 4.0±0.91°C (p<0.001). The temperature of the oral mucosa increased by 2.22±1.27°C (p<0.001). Needle deformation was found in 95%, no needle breakage or partial loss of the needle tip were observed.

Conclusions: If the recommended application rules were complied the tested prototype of intraosseous anaesthesia is not to be expected to cause irreversible damage due to temperature changes in vitro. Further tests are necessary to clarify the association between needle deformation and increase of temperature.

This study was supported by a grant from W&H.