TY - JOUR T1 - Preparation Ferrule Design Effect on Endocrown Failure Resistance. AU - Einhorn,Michael, AU - DuVall,Nicholas, AU - Wajdowicz,Michael, AU - Brewster,John, AU - Roberts,Howard, Y1 - 2017/10/06/ PY - 2017/05/18/accepted PY - 2017/10/7/pubmed PY - 2019/6/4/medline PY - 2017/10/7/entrez KW - CAD/CAM KW - endodontically treated teeth KW - failure load KW - failure stress KW - lithium disilicate KW - preparation features SP - e237 EP - e242 JF - Journal of prosthodontics : official journal of the American College of Prosthodontists JO - J Prosthodont VL - 28 IS - 1 N2 - PURPOSE: To evaluate the effect of preparation ferrule inclusion with fracture resistance of mandibular molar endocrowns. MATERIALS AND METHODS: Recently extracted mandibular third molars were randomly divided into 3 groups (n = 12) with the coronal tooth structure removed perpendicular to the root long axis approximately 2 mm above the cemento-enamel junction with a slow-speed diamond saw. The pulp chamber was exposed using a diamond bur in a high-speed handpiece with pulpal remnants removed and canals instrumented using endodontic hand instruments. The chamber floor was restored using a resin core material with a two-step, self-etch adhesive and photopolymerized with a visible light-curing unit to create a 2 mm endocrown preparation pulp chamber extension. One and two millimeter ferrule height groups were prepared using a diamond bur in a high-speed handpiece following CAD/CAM guidelines. Completed preparation surface area was determined using a digital measuring microscope. Scanned preparations were restored with lithium disilicate restorations with a self-adhesive resin luting agent. All manufacturer recommendations were followed. Specimens were stored at 37°C/98% humidity and tested to failure after 24 hours at a 45° angle to the tooth long axis using a universal testing machine. Failure load was converted to MPa using the available bonding surface area with mean data analyzed using Kruskal-Wallis/Dunn (p = 0.05). RESULTS: Calculated failure stress found no difference in failure resistance among the three groups; however, failure load results identified that the endocrown preparations without ferrule had significantly lower fracture load resistance. Failure mode analysis identified that all preparations demonstrated a high number of catastrophic failures. CONCLUSIONS: Under the conditions of this study, ferrule-containing endocrown preparations demonstrated significantly greater failure loads than standard endocrown restorations; however, calculated failure stress based on available surface area for adhesive bonding found no difference between the groups. Lower instances of catastrophic failure were observed with the endocrown preparations containing 1 mm of preparation ferrule design; however, regardless of the presence of ferrule, this study found that all endocrown restorations suffered a high proportion of catastrophic failures but at loads greater than reported under normal masticatory function. SN - 1532-849X UR - https://www.unboundmedicine.com/medline/citation/28985446/Preparation_Ferrule_Design_Effect_on_Endocrown_Failure_Resistance_ DB - PRIME DP - Unbound Medicine ER -