J Prosthet Dent. 2026 Mar 23:S0022-3913(26)00162-9. doi: 10.1016/j.prosdent.2026.03.005. Online ahead of print.
ABSTRACT
STATEMENT OF PROBLEM: Although cracked teeth have been a prevalent clinical concern, a consensus on appropriate treatment strategies-particularly for early-stage cracks without clinical symptoms-remains lacking. Current guidelines do not specify the critical crack dimensions, in terms of depth and width, at which tooth structural integrity becomes significantly compromised, leading to uncertainty in clinical decision-making between monitoring and restorative intervention.
PURPOSE: The purpose of this study was to investigate the effects of crack depth and width on the ultimate strength and stress distribution of human first premolars to guide clinical treatment decisions.
MATERIAL AND METHODS: Forty extracted, sound human first premolars were divided into 5 groups: a control group (no crack) and 4 groups with experimental mesio-occluso-distal cracks of varying depth (D:2 to 4 mm) and width (W:0.5 to 1 mm). Compression tests were conducted to assess ultimate strength, fracture origin, and propagation direction. Statistical analyses were performed using 1-way ANOVA and multiple linear regression (α=.05). Finite element analysis (FEA) was used to simulate stress distribution based on both principal stress and energy-based failure theories. The computational results were validated with experimental findings. Smaller cracks (D:1 to 3 mm; W:0.1 to 0.5 mm) were modeled via FEA to identify subclinical critical thresholds.
RESULTS: Crack depth dominated tooth ultimate strength reduction (β=-.803, P<.001), while width became insignificant at a depth of 4 mm (β=-.059, P=.480). Fractures in cracked teeth originated at crack tips (91% of cases), whereas fractures in sound teeth occurred at the palatal cusp. The von Mises stress criterion accurately predicted the behavior of cracked teeth, unlike the principal stress theory. Critical crack size thresholds were identified: a 15% strength reduction in the D1W0.5 and D2W0.1 cases and a 67% strength reduction (relative to sound teeth) when cracks extended to the pulp chamber in the D3W1 case.
CONCLUSIONS: Increasing crack size significantly weakens tooth strength, with depth being the dominant factor. The von Mises stress theory is recommended for analyzing cracked teeth. The identified critical crack sizes provide actionable thresholds for restorative intervention.
PMID:41876301 | DOI:10.1016/j.prosdent.2026.03.005
