•  
  •  
 

Document Type

Original Study

Abstract

Purpose: the aim of this study was to evaluate the effect of collar diameter and cement space thickness on fracture resistance of two types of implant retained CAD/CAM zirconia crowns. Materials and methods: implant analogs with different collar diameters (2.5mm and 4.5m) were embedded in epoxy resin blocks simulating bone. Zirconia crowns were designed and constructed by CAD/CAM and then divided into two groups; group (1) crowns were made from bilayer zirconia while group (2) crowns were made from monolithic zirconia. The two groups were divided into 2 subgroups according to collar diameter of implant; subgroup (A) with collar diameter 2.5mm, subgroup (B) with collar diameter 4.5 mm. Furthermore all subgroups were divided into three divisions according to cement space thickness; division 1 with cement space thickness 50µm, division 2 with cement space thickness 100µm and division 3 with cement space thickness 200µm. All crowns were adhesively bonded to their corresponding implant abutments by using dual cure self-adhesive resin cement and subjected to thermo-mechanical fatigue simulating 3 months of clinical situations then fracture resistance was measured until fracture of crowns and then the fractured parts were evaluated under electron microscope. Results: Statistical analysis showed that the mean fracture resistance of zirconia crowns in Group A and Group B with sub group 4.5 mm collar diameter were (1688.75N), (2936.25 N) respectively. A statistically significant difference (p ≤ 0.05) of the fracture resistance values among tested groups was found. The tests showed significant impact of cement space thickness on the fracture strength of zirconia crowns (p ≤ 0.05). Conclusions: increasing cement space parameter setting significantly improved the fracture strength of zirconia retained implant restorations. There was no statistically significant difference between narrow collar diameter of implant and normal diameter. Fracture resistance of monolithic zirconia crowns was significantly higher than bilayered zirconia crowns

Keywords

Monolithic zirconia, cement space, implant diameter, fracture resistance

Subject Area

Restorative Dentistry Issue (Removable Prosthodontics, Fixed Prosthodontics, Endodontics, Dental Biomaterials, Operative Dentistry)

Download

Included in

Dentistry Commons

Share

COinS