Effect of different indirect composite onlay and core materials on fracture resistance of endodontically treated maxillary premolars

Abstract

To compare and evaluate the effects of different indirect composite onlay and/or core buildup materials on the fracture resistance and fracture mode of restored endodontically treated premolars. Methods: Two conventional handmade indirect composite resins (SR Nexco (NC) and Ceramage (CM)) and two core buildup materials, dual-cure composite resin (MultiCore Flow (MC)), and short fiber-reinforced composite resin (EverX Posterior (EXP)), were selected. Sixty maxillary premolars were randomly divided into six groups (n=10). Group 1 included intact teeth (INT; negative control). Mesio-occluso-distal cavity preparation and endodontic treatment was performed on the remaining premolars. Group 2 was restored with polymer-reinforced zinc oxide eugenol intermediate restorative material (IRM; positive control), whereas the experimental groups (groups 3-6) were restored with core buildup material and indirect composite onlay (MC_NC, MC_CM, EXP_NC, and EXP_CM). The specimens received compressive loading using a universal testing machine, at 45° to the long axis with a crosshead speed of 0.5 mm/min until fracture. Fracture modes were visually analyzed. Fracture resistance was measured and statistically analyzed using two-way and one-way ANOVA (α=0.05). Results: Only the type of indirect composite onlay affected the fracture resistance of the experimental groups (P=0.009). The MC_CM group showed the highest fracture resistance, which was significantly higher than that of the MC_NC group (P=0.031). No statistically significant differences were found between the INT group and other experimental groups(P>0.05). All groups had a greater incidence of restorable than unrestorable failures. Conclusion:The type of indirect composite onlay affected the fracture resistance of restored endodontically treated maxillary premolars.

Fracture resistance and fracture modes in endodontically treated maxillary premolars restored using different CAD-CAM onlays

“…The root surface was cleaned, painted using a die spacer (Distanzlack, Bredent, Germany) of 0.2 mm thickness to imitate the periodontal ligament space [39,40], and left to dry. All teeth were embedded in autopolymerized acrylic resin (Ortho-Jet; Lang Dental Manufacturing, Illinois, USA) in polyvinyl chloride blocks at 2 mm apical to the cementoenamel junction (CEJ) and perpendicular to the horizontal plane using a surveyor.…”

“…The tooth abutment was cleaned using pumice slurry and dried. Finally, the onlays were cemented on the prepared teeth using a self-adhesive dual-polymerizing resin cement (Rely X U200; 3M ESPE Dental Products) using rounded-end steel under a 50-N constant load [40], and pre-cured for 2 s using the LED curing device. Thereafter, excess cement was removed, glycerin was applied, and the teeth were cured for 20 s per side using the LED curing device as recommended by the manufacturers.…”

“…After 24 h, the teeth were removed from the acrylic blocks. The die spacer at the root surface was removed and replaced with an elastomeric impression material (Silagum, light-body silicone; 3M ESPE Dental Products) to simulate the periodontal ligament space [39,40]. The teeth were then placed back into the acrylic blocks using a surveyor.…”

“…The teeth were then placed back into the acrylic blocks using a surveyor. Each specimen was fixed at a 45° angle to the long axis of the tooth [40,45]. Fracture resistance was measured using a universal testing machine (LR30KPlus; Lloyd Instruments/AMETEK, Inc., Bognor Regis, United Kingdom) at a speed of 0.5 mm/min using a metal sphere of diameter 3 mm [31,40] positioned at the palatal incline of the buccal cusp [40].…”

“…Each specimen was fixed at a 45° angle to the long axis of the tooth [40,45]. Fracture resistance was measured using a universal testing machine (LR30KPlus; Lloyd Instruments/AMETEK, Inc., Bognor Regis, United Kingdom) at a speed of 0.5 mm/min using a metal sphere of diameter 3 mm [31,40] positioned at the palatal incline of the buccal cusp [40]. The compressive axial load was applied until the specimen fractured and was recorded as the maximum force value.…”