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

Abstract

Purpose: 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.

Materials and methods: 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.

Results: 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 ).

Conclusions: Resistance to loading decreases significantly with increasing crown height, and the connection design can affect the performance.

Keywords: abutment; crown height; dental implant; fracture mode; fracture strength; implant connection.