Predicting Transmitted Light Radiant Exposure of Fiber Dowel Cross Sections from Dowel Diameter and Length

Purpose: To determine whether dowel diameter and length predict a significant amount of variance in transmitted light radiant exposure (TLRE) while controlling for possible dowel system effects. Materials and methods: Fiber dowels (Fiber Kleer sizes 1.25, 1.375, and 1.5; Postec Plus sizes 0, 1, and 3) were used. Ten fiber dowels from each system and size were embedded in C&B temporary resin cylinders. The detector of a radiometer was placed on the apical end of each embedded dowel, and the probe tip of an LED curing light was placed on the coronal end. The light cure machine was activated for 40s. The cylinders were shortened in 1-mm increments and TLRE (in mill joules/centimeter squared) was measured at each increment. TLRE values were analyzed using hierarchical multiple linear regression (α = 0.001) with SPSS software. Results: Dowel system effects explained 0.3% of the variance in TLRE. The total variance explained by the model as a whole was 44% (p < 0.001). Dowel diameter and length explained an additional 43.6% of the variance in TLRE after controlling for dowel system effects [R2 change = 0.436, p < 0.001]. The beta value for dowel length (beta = -0.517, p < 0.001) was larger than that for dowel diameter (beta = 0.208, p < 0.001). Conclusion: Dowel diameter and length and length can predict TLRE at the apical end of a dowel cross section after controlling for dowel system effects. Dowel system effects did not contribute significantly.