Cuspal Coverage Direct Resin Composite Restorations for Cracked Teeth: A Five-Year Clinical Study

ABSTRACT Introduction: The restorative strategies for cracked teeth vary considerably, and both direct and indirect restorations, with and without cuspal coverage have been proposed. However, the literature has shown no consensus among authors, and long-term clinical studies focusing on the direct restorative treatment of cracked teeth remain limited. This five-year retrospective clinical study aimed to evaluate the survival rate of teeth affected by coronal cracks, treated with cuspal coverage direct resin composite restorations, and to evaluate the risk factors associated with tooth loss. Methods and Materials: The study was conducted following the principle of the Declaration of Helsinki and good clinical practice after the approval by the Ethics Committee of the University. Clinical charts, photographs, and videos of 321 patients were retrospectively evaluated. The inclusion criteria were as follows: only posterior cracked teeth with at least five-year follow-up and no pre-existing endodontic treatment. The patients were treated in a private practice between January 1991 and December 2018. Two types of direct resin composite restorative techniques were performed based on the fracture and tooth type. One approach involved a cavity design with full cusp coverage; the other utilized partial cusp coverage, in which only the cracked cusp was covered, and box-shaped restorations were performed to reinforce the opposing walls. No indirect restorations were performed in any of the groups. All treatments were provided by a single operator. The primary outcome was to assess tooth survival at five years. Stepwise logistic regression analysis was performed to identify variables as potential predictors of tooth loss. Results: A total of 321 teeth and 321 patients were included (mean follow-up: 63 months, mean age: 53.9 years). The sample consisted of 79 maxillary and 21 mandibular premolars and 78 maxillary and 143 mandibular molars. At the five-year follow-up, the survival rate was 94.1% (302/321 teeth), with only 19 teeth extracted; 126 root canal treatments were performed (39.2%), and 41 teeth (12.8%) developed periodontal lesions during the follow-up, due to the deepening of the crack. Endodontic treatment (OR: 2.67, 95% CI 1.04-6.89, p = 0.04) and development of a periodontal lesion (OR: 10.52, 95% CI 4.1-27.1, p < 0.0001) were independent risk factors for tooth loss. The type of fracture and other tooth-related factors (ie, pulp calcification, tooth vitality, apical periodontitis) were not statistically significant ( p > 0.05). Conclusions: The different restorations exhibited similar clinical performance. Our results suggest that the treatment of coronal cracks with direct resin composite restorations may achieve the remission of symptoms and stop the progression of the crack pattern, improving long-term durability. However, when endodontic treatment is required for a cracked tooth, its long-term prognosis may be reduced.