Endocrown restorations milled in lithium disilicate and hybrid ceramic: influence of different ferrule heights on fracture load after thermocycling and fatigue test

• Grant number: 25/12528-7
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2026
• End date: February 28, 2027
• Field of knowledge: Health Sciences - Dentistry - Dental Clinics
• Principal Investigator: Flávio Henrique Baggio Aguiar
• Grantee: Eduarda Oliveira de Souza
• Host Institution: Faculdade de Odontologia de Piracicaba (FOP). Universidade Estadual de Campinas (UNICAMP). Piracicaba , SP, Brazil

Abstract

Due to the loss of coronal structure, endodontically treated teeth are more susceptible to fractures. There is still no consensus regarding the best approach for the rehabilitation of such cases. Traditionally, rehabilitation is performed through the placement of prefabricated fiberglass posts, chosen for their elastic modulus similar to that of dentin, followed by prosthetic rehabilitation with full crowns. However, the placement of these posts involves certain risks, such as root weakening due to the additional removal of dentinal tissue to adapt the canal to the diameter of the post, and the risk of root perforation. Endocrown restorations have emerged as a conservative and safe alternative for the rehabilitation of molars, as their retention does not depend on intraradicular posts. The importance of the ferrule is well established in treatments involving full crowns; however, the literature presents conflicting views regarding its relevance in endocrown restorations. Previous studies that sought to investigate the importance of the ferrule showed methodological shortcomings, as they failed to consider important factors in evaluating the fracture resistance of materials. The aim of this study is to investigate the influence of different ferrule heights on the fracture resistance of endocrowns, addressing the limitations of previous research. Samples will be randomly divided into eight groups (n=15) based on four types of restorations: (A) full crown with fiberglass post and 2 mm ferrule (control group), (B) endocrown without ferrule, (C) endocrown with 1 mm ferrule, and (D) endocrown with 2 mm ferrule; and two CAD/CAM milled materials: lithium disilicate and nanohybrid resin. The specimens will undergo aging through thermocycling (10,000 cycles, 5°C to 55°C) and chewing simulation (300,000 cycles, 50 N, 1.2 Hz). Subsequently, the samples will be subjected to static compressive loading until fracture (500 kgf, 0.5 mm/min), followed by classification of the failure mode (I - cohesive failure; II - adhesive failure; III - mixed adhesive-cohesive failure; IV - fracture of the restoration/tooth complex above the cementoenamel junction (CEJ); V - fracture of the restoration/tooth complex below the CEJ). Furthermore, finite element analysis (FEA) will be employed to determine the location of stress concentration and assist in the interpretation of the results. Data will be subjected to the most appropriate statistical analysis, with the level of significance set at 5% (= 0.05), using the R software. (AU)