Early Flexural Strength of Temporary Crown and Bridge Materials

Objectives: This study aimed to determine the early flexural strength [FS] (i.e. <10 minutes) of different crown and bridge materials in early stages of the prosthesis fabrication process.
Methods: Materials tested were Integrity™ [IN] (Dentsply), Luxatemp Star [LS], Luxatemp Automix Plus [LA] (both by DMG), Protemp™ 4 [P4], and an experimental material [EXP] (both 3M Oral Care). FS was determined using a three point flexural test according to ISO 4049 (specimen size 4mm x 6mm x 25mm) with a universal testing machine (Zwick Z010, crosshead speed 2mm/min). Specimens (n=10) were prepared and allowed to cure for the time according to manufacturers’ instructions (MI). All specimens were also tested after 3.5 minutes and 7 minutes self-curing time. Mean maximum FS at sample breakage was analyzed using Pairwise Comparisons (Tukey’s HSD p<0.05).
Results: EXP demonstrated higher FS at its MI curing time when compared to other products after MI curing time (P<0.001). EXP also demonstrated higher FS than other products when all products were self-cured for 7 minutes. There was no statistically significant difference between other materials after MI time and 3.5 minutes. Table-1 summarizes the results.
Conclusions: At its MI curing time of 3.5 minutes, EXP showed a higher early FS than other tested materials regardless of their curing time. This faster development of mechanical strength may prevent micro-cracks and reduce risk of damage with early manipulation of the temporary prosthesis during the fabrication process. These comparisons are important in assessing clinical performance, strength, and durability of temporary prostheses. Early stage FS is only one determining factor of overall mechanical strength. Future studies in mid-stage and late-stage FS can help to reinforce this data.