Methods: Thirty intact third molars were prepared by 30 round-end taper single or multi-use medium grit diamond burs (SSWhite, Brasseler). Rectangular tunnels were prepared to expose the axial wall of the pulp chamber (APC) from the lingual view. Dentinal thickness between buccal wall and APC was measured from 10 points and averaged. Buccal surface preparations were performed in occluso-gingival direction for 2 minutes with 150g pressure, 350,000rpm speed and 50ml/min water coolant rates.Thermal-imaging (Thermovision-A20M FLIR Systems) assessed heat generation on buccal and APC facilitated by high-reflectance first-surface mirror (Edmund Industrial Optics). Reflectance of APC with minimal energy-loss provided simultaneous thermal recordings of both surfaces. Dentinal thickness was re-measured following preparation to determine the amount of removed tooth structure as well as remaining thickness (DT). Temperature data was analyzed using ThermaCAMTM software (Flir Systems) and applied to a 1-D thermal diffusion equation to determine dentin thermal diffusivity in joules/sec with respect to DT and bur type. Bur type, DT and thermal diffusivity (Joules/sec) were applied to least-squares estimation.
Results: Statistical analysis showed that bur type added predictive power to thermal diffusivity (p<0.003). DT was shown to significantly predict diffusivity on a curvilinear relation (p<0.03). Thermal diffusivity caused by burs is shown in table. Levels not connected with the same letter are significantly different (P<0.05)
| Bur Type |
| Mean(joules/sec)±SD | |
| SS White-Piranha | A |
| 0.69±0.12 |
| SS White-Medium | A | B | 0.41±0.10 |
| Brasseler-Medium |
| B | 0.18±0.10 |
Conclusions: Bur type and dentin thickness significantly affects heat generation on the APC. Caution should be taken during preparations of teeth with small dimensions, especially with single-use burs.
Brasseler-USA supported this study.