Chewing simulation of zirconia implant supported restorations

Abstract

PURPOSE To test three potential prosthetic material options for zirconia implants in regard to their mechanical properties, loading and retention capacity as well as to record abrasion after chewing simulation followed by thermocyclic aging. METHODS Molar crowns (n = 96) of three different computeraided design/computer-aided manufacturing (CAD/CAM) materials were produced and cemented on zirconia implants (ceramic.implant, Vita) with a diameter of 4.5 mm. Monolithic zirconia (Vita YZ [YZ] with RelyX Unicem 2 Automix [RUN], polymer-infiltrated ceramic (Vita Enamic [VE]) with Vita Adiva F-Cem [VAF] and acrylate polymer (CAD Temp [CT]) with RelyX Ultimate [RUL]. Fracture load and retentive force of the crowns were measured after 24 h water storage at 37°C and after a chewing simulation followed by thermocyclic aging. Abrasion was recorded by matching stereolithography-data of the crowns obtained before and after chewing simulation. Additionally, the mechanical properties and bonding capabilities of the crown and cement materials were assessed. RESULTS Fracture load values were significantly highest for YZ > VE = CT. Retention force values did not differ significantly between the materials. The aging procedure did not affect the fracture load values nor the retention force significantly. Abrasion depth of the crowns was lowest for YZ followed by VE and CT. On unpolished crowns, abrasion of YZ and VE tended to be higher than on polished specimens. CONCLUSIONS Based on the obtained in-vitro results, all tested materials can be recommended for the use on zirconia implants, although CT is only approved for temporary crowns. The loading and retention capacity of the materials were not significantly affected by aging.

Retention of different temporary cements tested on zirconia crowns and titanium abutments in vitro

“…Therefore, the first null hypothesis must be rejected since the objective of this study was to demonstrate homogeneous retention values of the three cements tested. Other studies also showed heterogeneous results regarding the retentive strength of different cements [5,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Therefore, some studies published guidelines for clinicians since no cement served for all demands [40,41].…”

“…However, thermocycling can be used to mimic the clinical situation, but it has no relevance for direct comparisons to in vivo conditions [19]. Some studies have performed thermocycling in order to evaluate retention forces of the cements tested [5,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. For temporary cements, a considerable decrease in regards to the pull-off forces has been proven to be caused by the artificial ageing process [22].…”

“…The water storage was used to simulate oral cavity moisture. During water storage, moisture absorption occurs in the cement gap, which causes an increase in volume of the cement [ 37 , 38 ]. In addition, water storage leads to a wash-out effect within the cement structure and thus simulates the ageing process of the cements in the oral cavity [ 5 , 10 , 37 ].…”

“…During water storage, moisture absorption occurs in the cement gap, which causes an increase in volume of the cement [ 37 , 38 ]. In addition, water storage leads to a wash-out effect within the cement structure and thus simulates the ageing process of the cements in the oral cavity [ 5 , 10 , 37 ]. This artificial ageing can be enhanced by TC and influences the retention forces of the different cements very differently depending on the number of cycles [ 5 , 37 , 38 ].…”

“…In addition, water storage leads to a wash-out effect within the cement structure and thus simulates the ageing process of the cements in the oral cavity [ 5 , 10 , 37 ]. This artificial ageing can be enhanced by TC and influences the retention forces of the different cements very differently depending on the number of cycles [ 5 , 37 , 38 ]. Thermocycling is an artificial ageing in vitro and imitate temperature changes as they occur naturally intraorally.…”