Fracture resistance of root canal-treated molars restored with ceramic overlays with/without different resin composite base materials: an in vitro study

Shehabeldin Mohamed Saber Prof.Dr., The British University in Egypt

The objective of the study was to evaluate the effect of different restorative protocols on fracture resistance of root canal-treated molars. 48 mandibular first molars were used and divided into six groups (n = 8); G1 (negative control): teeth kept intact. G2 (positive control): teeth had root canal treatment and standard MOD cavity preparations but kept unrestored. G3: prepared as G2 and directly restored with VitaEnamic ceramic overlays (CO). G4: as G3, but the pulp chamber was restored first with smart dental restorative (SureFil SDR flow = SDR) bulk-fill flowable composite base. G5: as G3, but the pulp chamber was restored first with SonicFill (SF) bulk-fill composite base. G6: as G3, but the pulp chamber was restored first with a fiber-reinforced composite (FRC) base. All samples were subjected to thermocycling between 5 °C and 55 °C in a water bath for a total of 2000 cycles with 10 s dwell time. Then specimens were individually mounted on a computer-controlled testing machine with a load cell of 5 kN, and the maximum load to produce fracture (N) was recorded. Data were analyzed using one-way ANOVA followed by Tukey’s post hoc test (P = 0.05). There was a significant difference between the groups (P < 0.001). Teeth restored with FRC and ceramic overlays had the highest load-bearing capacity. Pulp chamber restoration with either FRC or SDR before ceramic overlay fabrication provided significantly better tooth reinforcement than ceramic overlay alone (P < 0.001). Fracture modes were analyzed to determine the type of fracture as repairable or catastrophic, where FRC + CO and SDR + CO groups had favorable fracture modes that were mostly repairable. When restoring root canal-treated molars with overlays, the pulp chamber should be sealed with either FRC or SDR to ensure the best possible fracture resistance. The clinical relevance of the study is that a new simple restorative protocol is presented to enhance the survival of root canal-treated molars using ceramic overlays

Abstract