Category: Laboratory Research
Award Category: Student Scientist
Influence of Deep Margin Elevation on Fracture Strength of Indirect Composite Onlays
Emine Kitina* (eminekitin@istanbul.edu.tr) | Oktay Yazıcıoğlua
aIstanbul University, Istanbul, Türkiye
Objective: To investigate if Deep Margin Elevation (DME) procedure effects the fracture strength (FS) and fracture type of onlay restorations made of three different indirect resin composites (IRCs).
Methods: Ninety-six freshly extracted,similar sized upper premolar teeth randomly divided into eight groups (n=12) and standardized MOD onlay cavities were prepared on both proximal boxes located 2.00 mm below the Cemento-Enamel Junction (CEJ). Three different IRCs (Gradia Plus,GC (GRA); Signum,Kulzer (SIG); TesceraATL,Bisco (TES)) used for onlay restorations with and without DME for six groups and two control groups were created. Groups are respectively; 1)DME+GRA, 2)DME+SIG, 3)DME+TES, 4)GRA, 5)SIG, 6)TES, 7)PCG (Positive Control Group), 8)NCG (Negative Control Group). DME was performed with Single Bond Universal (3M ESPE) adhesive, Filtek Supreme Flowable (3M ESPE) and Z250 Universal Composite (3M ESPE) for 2mm thickness. IRCs were manufactured according to manufacturer’s instructions and cemented with RelyX Ultimate (3M ESPE) dual-cure cement by using Single Bond Universal (3M ESPE) adhesive. All specimens were exposed to Thermo-mechanical cycling (5,000 cycle). Compressive loading test (1mm/1sn) was performed with Universal Testing Machine (Shimadzu Corporation, Japan). Failure values (Newton) and fracture types (Restorable, Nonrestorable) were recorded and samples were examined by Scanning Electron Microscope. Shapiro-Wilk Test was used for the normality of data distribution. Statistical analyses were performed by using Mann-Whitney U Test and Independent Sample T-Test (α=0.05).
Results: Statistically; PCG has significantly highest FS (2136,6±350,6N) and NCG has the lowest FS (273,9±88,1) in all groups. Comparing the FS of IRCs numerically; it is found that GRA>TES>SIG for both DME applied and DME unapplied groups. DME did not affect the FS of onlay restorations to a statistically significant level (p=0.149) but conspicuously affected the fracture type (p<0.001). While the restorable fracture rate was 61% in DME performed groups, it was 39% in the groups DME not performed.
Conclusion: Within the limitations of this study, DME application had no effect on fracture strength value of onlay restorations. However, DME application improved the fracture type and more restorable fractures occurred on DME applied groups among DME unapplied groups.
Funding/Conflict of Interest: The present work was supported by Scientific Research Projects Coordination Unit of Istanbul University. Project Number:38173
Keywords: fracture strength, indirect resin composite, Indirect restoration, onlay, deep margin elevation
