THE BALL MILL AS A MEANS OF INVESTIGATING THE MECHANICAL FAILURE OF DENTAL MATERIALS

Objective: The main purpose of this paper is to present a new method o f predicting clinical performance using mechanical loading in a ball m ill. Methods: A series of four experiments (two involving a hybrid com posite and one each on orthodontic brackets and bands) is described in which the ball mill was used to subject specimens to mechanical fatig ue. Results: A reproducibility study using composite beam specimens sh owed no significant difference between the Mean Survival Time (MST) in all the three experimental runs (P = 0.42). When subjected to thermal cycling, the MST of the cycled group was 155.0 min compared to 247.0 min fur the control group (P < 0.01). The MST of untreated and sandbla sted brackets was 7.9 h and 14 h respectively (P < 0.01). There is als o a significant difference (P < 0.001) in the MST of sandblasted bands when compared to the untreated bands. Conclusions: The ball mill prov ed to be a convenient and reproducible means of producing mechanical f atigue and may be useful in predicting the clinical performance of den tal materials.