Retention Of Cast Copings Cemented To ITI Abutements Using4Luting Cements

Objectives:The aim of this study was to evaluate the retention force of cast copings cemented to ITI regular neck cementable abutments using four glass ionomer cements.Methods:Ten regular neck ITI analogs and one metal hook were invested with acrylic resin into the respective steel tubes. Ten ITI regular neck cementable abutments were screwed onto the respective analogs with35Ncm torque. After ten loop of wax had been prepared onto the respective ITI burn-out cap, they were invested and casted with Co-Cr alloy. Each cast coping was tried in the respective abutment until passive fitting was obtained,marked from0#to9#. Four luting cements were used as following:two glass ionomer cements (Fuji I, GC,Japan;Ketac Cem Easymix,3M ESPE, Germany);one glass ionomer provisional luting cement (Fuji Temp, GC,Japan), and one a resin modified glass ionomer cement (RelyX Luting,3M ESPE,USA). All luting cements were applied according to the manufacturer’s instructions. After the0#-4#copings and the5#-9#copings were cemented respectively with Fuji I (GC) and RelyX Luting (3M ESPE), respectively, and stored in tap water in room temperature for24h, and they were subjected to a debonding test with a universal testing machine (Zwick/Roell72.5, Germanny) at a testing speed of0.5mm/min until dislodgement. The first peak at which the dislogement take place was recorded as the retention force. After the debonding tests, the cast copings were heated to600℃for1.5h and cooled on the bench at room temperature. After cooling, the residual cements within the copings were removed with dental air prophy unit (EWIS, Switzerland) using hydrocarbonate powder (Powder Max, France). Subsequently, the copings and abutments were cleansed with ultrasonic cleaner in distilled water for10min and steam for lmin, and dried in air. After cleansing, the0#-4#copings and the5#-9#copings were cemented using cross design with RelyX Luting (3M ESPE) and Fuji I (GC), respectively. The debonding tests were performed the same as above-mentioned. The coping cementations with Fuji Temp (GC) or Ketac Cem Easymix (3M ESPE) and debonding tests were exact the same as above-mentioned. All the casting copings and abutments were repeatedly used for4times. Retention force for each cement was calculated in N. The data was analyzed with One-Way ANOVA and a post hoc least square difference (LSD) test for pairwise comparison using SPSS16.0(α=0.05)Results:Fuji Temp gained the highest retention force (183.6±29.4N),and was significantly higher than Relyx Luting (144.4±34.3N) and Fuji I (109.9±26.9N)(p<0.05). Fuji I exhibited the lowest retention force, and was significantly lower than Fuji Temp, Relyx Luting and Ketac Cem Easymix.(153.4±26.2N)(P<0.05)Conclusions:According to the limited study, glass ionomer cements (Fuji I, Ketac Cem Easymix) and resin-modified glass ionomer cements (Relyx Luting) possessed the clinically acceptable retention forces for the cementation of ITI cementable abutments. Fuji Temp was not suitable for the provisional cementation of ITI cementable abutments due to the too high retention force.