Comparative evaluation of fracture resistance of endodontically treated maxillary premolars restored with post-and-core vs. post-and-core with full-coverage crown: an in-vitro study

INTRODUCTION. The extensive loss of coronal and radicular tooth structure, changes to dentin characteristics, and biomechanical constraints make endodontically treated teeth (ETT) more prone to fractures. Prosthodontic rehabilitation, including post-and-core systems and full-coverage crowns, is a standard approach to restore their function and structural integrity. However, a clear, stepwise comparison of the fracture resistance imparted by endodontic treatment alone versus subsequent stages of prosthodontic restoration is needed to guide clinical decision-making.

MATERIALS AND METHODS. Forty extracted human maxillary premolars of similar dimensions were selected and randomly allocated into four groups (n = 10): Group I (Control) – intact sound teeth; Group II (ETT) – endodontically treated teeth with access cavities left unrestored; Group III (ETT + PC) – endodontically treated, restored with a fiber post and composite core; and Group IV (ETT + PC + C) – endodontically treated, restored with a fiber post, composite core, and a full-coverage cast metal crown. After the specimens underwent thermocycling, they were placed in acrylic resin blocks that included a periodontal ligament simulation. Until fracture occurred, a universal testing machine was used to apply a compressive force at a speed of 1 mm/min to the central fossa of each tooth, which was angled at 90 degrees to the occlusal plane. It was noted the maximum load at crack (in Newtons, N). The data was examined with the use of Tukey’s post hoc test (α = 0.05) and one-way ANOVA.

RESULTS. The average fracture resistance values (± standard deviation) for the four groups were as follows: 1650.5 ± 180.2 N for Group I, 615.8 ± 95.4 N for Group II, 950.3 ± 110.7 N for Group III, and 1425.6 ± 155.1 N for Group IV. Statistical analysis using one-way ANOVA showed that there was a notable difference between the several groups (p < 0.001). Every group except Group I (intact) was much weaker. Group IV (ETT + PC + C) showed a noticeably greater resistance to fracture compared to Group II (ETT) and Group III (ETT + PC) (p < 0.05). In comparison to Group II, Group III was likewise much stronger (p < 0.05). The fracture resistance of Group IV was still noticeably lower than the intact control group (p < 0.05), nevertheless.

CONCLUSIONS. For premolars, the fracture resistance is significantly reduced only by preparing the endodontic access. Placing a full-coverage crown is necessary to provide a major strengthening of the tooth structure, while adding a post-and-core gives a small improvement in strength. But, the strength of an unbroken tooth when it was first cracked is not entirely restored by modern restorative procedures.

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