Influence of dental crown topography on fracture resistance of premolars with MOD preparation and subjected to different restorative protocols.

To evaluate whether dental crown topography influences the fracture resistance of premolars treated endodontically and with MOD preparation subjected to different restorative protocols. Sixty-four human premolars with one or two roots in equal numerical proportions (n) were selected and randomly divided into four groups (n = 8): (S = single-rooted; D = double-rooted) SS: sound single-rooted; SNR: endodontics (E) + MOD cavity preparation; SR: E + MOD + resin restoration (RS); SP: E + MOD + RS + horizontal zirconia post (ZP); DS: sound double-rooted; DNR: E + MOD; DR: E + MOD + RS; and DP: E + MOD + RS + ZP. After allocation to the groups, the samples were thermocycled and then subjected to the fracture resistance test. Failures after the fracture test were classified as irreparable (with pulp floor fracture) or reparable (without pulp floor fracture). Data were analysed using one-way anova and the Tukey test (alpha = 0.05). Single-rooted premolars were more resistant to fracture than double-rooted premolars. The restorative treatment using a horizontally transfixed zirconia post improved fracture resistance, resembling that of a healthy tooth.