Fracture resistance of pressable ceramic fused to metal custom implant abutment
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Statement of problem . The restoration of single implant-supported crowns presents an aesthetically prosthetic challenge. The commercially available choices for abutment selection are limited and present either questionable aesthetics or questionable strength. There is need for development of an alternative technique for an aesthetic custom implant abutment that would be able to withstand high occlusal and functional forces. The predictable nature of the hot pressing technique has several applications but no study has evaluated its application for the fabrication of custom implant abutments. Purpose of this study . To evaluate the fracture resistance of an experimentally designed pressable ceramic fused to metal custom abutment for Nobel Biocare internal connection narrow platform (NP) implants and compare it with the fracture resistance of duplicated Procera zirconia abutments. Materials and methods . Two groups of 10 samples each were tested. The experimental group consisted of all-ceramic crowns cemented on pressable ceramic fused to metal custom narrowplatform implant abutments. The control group consisted of all-ceramic crowns cemented on duplicate Procera zirconia abutments. The experimental abutments were fabricated on fixture level narrow-platform abutments (GoldAdapt, Nobel Biocare), cast with ceramic alloy (Lodestar, Ivoclar Vivadent) according to sample design dimensions. InLine PoM (Press Over Metal ceramic, Ivoclar Vivadent) ceramic was pressed over the metal according to design dimensions. Each pressable ceramic fused to metal abutment was individually scanned with Procera Picolo scanner and 10 duplicate zirconia abutments were fabricated by Nobel Biocare for the control group. The crowns had standard predetermined dimensions of an average lateral incisor (B-L width = 7mm, M-D width = 7mm, I-C length = 10mm) according to Diamond’s anatomy, and were pressed with IPS e.max Press. A total of 20 all-ceramic crowns were prepared individually for each abutment. A dual-polymerizing resin luting agent (Multilink Automix, Ivoclar Vivadent) was used to bond the all-ceramic crowns to the abutments. The samples were mounted on a device, thermocycled and then subjected to cyclic loading using the Universal Testing Machine (UTM, MTS). All specimens were loaded off axis 30° to the lingual surface. The samples that did not fail were statically loaded to failure. An independent t-test (one-sided) was used to determine if the mean values of the fracture load differed significantly between the 2 groups. A significance level of 0.05 was used. Results . No sample failed during cyclic loading. During static loading, the mean load to failure for the experimental group was 525.89 N (SD = 143.547 N) and for the control group it was 413.70 N (SD = 35.515 N). The results indicate that the fracture resistance of the experimental pressable ceramic fused to metal custom abutment is significantly higher than that of the zirconia abutment for Nobel Biocare internal connection narrow platform (NP) implant (t 8 =2.283, p=0.0245). Failure was initiated at the screw and internal connection level of the complex analog-screw-internal connection-abutment-crown for both the experimental and control groups for Nobel Biocare internal connection narrow platform (NP) implants. Conclusions . Within the limitations of this study, it can be concluded that the experimental pressable ceramic fused to metal abutment presents a statistically significantly higher fracture resistance than the zirconia abutment for Nobel Biocare internal connection narrow platform (NP) implants. Clinical application . The development of a pressable ceramic fused to metal custom implant abutment will provide an alternative aesthetic solution in patients with heavy occlusal and functional load conditions.