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Influence of thermomechanical fatigue on the fracture strength of CAD-CAM-fabricated occlusal veneers
Authors:Majed Al-Akhali  Matthias Kern  Adham Elsayed  Abdulaziz Samran  Mohamed Sad Chaar
Affiliation:1. Visiting Researcher, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Kiel, Germany;1. Assistant Professor, Department of Prosthodontics, School of Dentistry, Ibb University, Ibb, Yemen;2. Professor and Chairman, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Kiel, Germany;3. Assistant Professor, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Kiel, Germany;4. Visiting Researcher, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Kiel, Germany;2. Assistant Professor, Department of Prosthodontics, School of Dentistry, Ibb University, Ibb, Yemen;3. Assistant Professor, Department of Restorative and Prosthetic Dental Sciences, School of Dentistry, Dar AlUloom University, Riyadh, Saudi Arabia;5. Senior Lecturer, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Kiel, Germany
Abstract:

Statement of problem

With the development of new computer-aided design and computer-aided manufacturing (CAD-CAM) restorative dental materials, limited data regarding their survival rate and fracture strength are available when they are used as occlusal veneers. Therefore, these materials should be evaluated under conditions similar to those of the oral environment before being recommended for clinical use.

Purpose

To evaluate the influence of thermomechanical fatigue loading on the fracture strength of minimally invasive occlusal veneer restorations fabricated from different CAD-CAM materials and bonded to human maxillary premolars using self-etchnig bonding technique.

Material and methods

Sixty-four CAD-CAM occlusal veneer restorations were fabricated from group LD (lithium disilicate [e.max CAD]), LS (zirconia-reinforced lithium silicate [Vita Suprinity]), PI (polymer-infiltrated ceramic [Vita Enamic]), and PM (polymethylmethacrylate [Telio CAD]). The occlusal veneers were luted to enamel (n=16) using a self-etching primer (Multilink Primer A/B) and a luting composite resin (Multilink Automix). Half of the specimens of each group (n=8) were randomly selected and subjected to thermomechanical fatigue loading in a masticatory simulator (1.2 million cycles at 98 N with 5°C-55°C thermocycling). All specimens were quasistatically loaded until fracture. The statistical analysis was made using the Kruskal-Wallis and Mann-Whitney U tests (α=.05).

Results

According to the Kaplan-Meier analysis after the thermomechanical fatigue of the 4 groups, the cumulative survival rate was as follows: group LD, 50% group LS, 62.5% group PI, 37.5%; and group PM, 50%. Although some of the surviving specimens exhibited microcracking, their integrity or bonding to teeth was not affected. Thermomechanical fatigue significantly reduced the fracture strength of group PI (P=.047) and group PM (P=.025). Without thermomechanical fatigue, group PM showed significantly higher fracture strength than group LS (P=.015).

Conclusions

In general, thermomechanical fatigue decreased the survival rate and fracture strength in all test groups.
Keywords:Corresponding author: Dr Majed Al-Akhali   Department of Prosthodontics   Propaedeutics   and Dental Materials   School of Dentistry   Christian-Albrechts University   Arnold-Heller-Str. 16   24105 Kiel   GERMANY
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