Factors Affecting the Results of a Leakage Test Using Centrifugation

OBJECTIVES: Evaluation of the extent of apical microleakage under various conditions.

METHODS: 90 root canals of bovine single-rooted teeth were prepared to apical size 140 with MicroMega rotary reamers (MircoMega, Besancon, France). Root canal were filled with AH Plus (DeTrey/Dentsply, Konstanz, Germany) and a single gutta-percha cone. Teeth were coated with two layers of nail varnish and randomly assigned to 9 groups (n = 10 each). Concerning the method of leakage evaluation used, possible parameters of influence were varied in different groups, each representing one of the following parameters: “rotational speed”, “centrifugation time”, “methylene blue dye level”, “coronal instead of apical dye penetration” and “apex position upwards instead of downwards”. Groups were compiled as follows (rotational speed / time / dye level): group1: 400rpm/ 3min/ 30mm; group2: 400rpm/ 15min/ 30mm, group3: 400rpm/ 60min/ 30mm; group4: 1000rpm/ 3min/ 30mm; group5: 400rpm/ 3min/ 80mm, group6: 400rpm/ 3min/ 21mm; group 7: coronal access downside and open, 400rpm/ 3min/ 30mm; group 8: apex upside and open 400rpm/ 3min/ 30mm; group 9: no centrifugation; storage within dye for 7d. Teeth were cut horizontally and examined for dye penetration under a stereomicroscope. Statistics were computed with SPSS 14.0 software (SPSS Corporation, Chicago/IL/USA).

RESULTS: Leakage to methylene blue was fairly deep compared to studies with human teeth. Multifactorial ANOVA showed significantly different results (p<0.05) for all parameters except centrifugation time (p=0.643).

CONCLUSION: Centrifugation speed, apex position, coronal or apical ingress and dye level influence the results of the dye penetration test used. To achieve comparability, experimental parameters should be standardized and kept constant. Bovine teeth could be used instead of human teeth, but the size of instruments and points for root canal filling should get better adapted to the size of the teeth.