Importance of Crown Height Ratios in Dental Implants on the Fracture Strength of Different Connection Designs: An In Vitro Study

Abstract

The aim of the present in vitro study was to assess the resistance to static fatigue of implants with different connections at various crown heights. Sixty conical implants and 60 abutments were used with the smallest diameters available for each model. Three groups (n = 20) were established based on the implant connections: Morse taper Ø3.50 mm (group 1), external hexagon Ø3.50 mm (group 2), and internal hexagon Ø3.50 mm (group 3). Four crown heights were tested: h1 = 8 mm, h2 = 10 mm, h3 = 12 mm, and h4 = 14 mm. All groups were subjected to quasi-static loading at a 30° angle to the implant axis in a universal testing machine. The mean fracture strengths for group 1 were 1524 N (h1 ), 1469 N (h2 ), 750 N (h3 ), and 729 N (h4 ). Those for group 2 were 1504 N (h1 ), 814 N (h2 ), 491 N (h3 ), and 325 N (h4 ). Those for group 3 were 1543 N (h1 ), 672 N (h2 ), 403 N (h3 ), and 390 N (h4 ). Resistance to loading decreases significantly with increasing crown height, and the connection design can affect the performance.