Vertical root fracture and dentin deformation in curved roots: the influence of spreader design

The effect of lateral condensation using different tapered spreaders was evaluated. Curved mesiobuccal roots of maxillary molars were step-back prepared. Strain gauges applied to the root surfaces measured dentin deformation (distortion) during controlled lateral condensation with either fine finger or D11 spreaders. After obturation, roots were cross sectioned and analyzed under the stereomicroscope to detect the presence and pattern of fractures. The results showed no statistical difference between spreader designs as to mean distortion and the incidence of fractures; however several specimens in the D11 group showed high root distortion measurements. When fractures occurred, there were no consistent patterns of fracture in either spreader group. In conclusion, although there were no significant differences in mean deformation or fracture incidence in curved roots between the spreaders, the roots showing high deformation readings in the D11 group may be more susceptible to future vertical root fractures.