Crimping Effects on Fracture Resistance of Esthetic Veneered Pediatric Crowns

Objectives: To investigated the effects of crimping on anterior preveneered primary stainless steel crowns. Methods: Forty-two crowns of 2 resin-type veneered crowns, (NuSmile, Orthodontic Technologies, Inc., USA; KinderKrowns, Mayclin Dental Studios, USA) were evenly divided into four groups, and 1 thermoplastic-type veneered crown (Flex Crown, Space Maintainers Laboratory, USA), were evenly divided into 3 groups. Each type of crown was randomly assigned to both a non-crimped group and a lingual crimped group. An additional group was included for the thermoplastic group in which the crowns were crimped along the entire gingival surface. After cementation onto a duplicate incisor, each specimen was subjected to thermocycling and then loaded on a universal test machine (Instron, Norwood, MA. USA). The force required to fracture or dislodge the veneer and the amount of veneer loss upon fracture was statistically analyzed by ANOVA and Tukey post hoc test at the 0.05 significance level. Results: Lingual crimping significantly reduced the amount of fracture resistance for all types (p< 0.001). The mean fracture resistance was significantly weaker (p<0.001) for both resin types at 922.2 N and 1017.2 N (KinderKrown and NuSmile respectively), compared to the thermoplastic type at 1153.5 N. There was no significant difference in the amount of veneer fracture when crimped on the lingual compared to crimping along the entire gingival margin for the thermoplastic type (p=0.94). When compared to resin types, the thermoplastic type had the least amount of veneer fracture. Conclusions: Crimping on the lingual, and type of veneer material, had a significantly effect on the amount of fracture resistance for all types of crowns. No significant difference in veneer fracture was demonstrated for the thermoplastic type when crimped on the lingual compared to the entire gingival margin. Support in part by Mayclin Dental Studios, Orthodontic Technologies, Inc. and to Space Maintainers Laboratory.