Methods: Thirty extracted human permanent maxillary molars were endodontically treated. Standardized preparations were done to provide for 2mm intra-coronal extensions of the endocrowns into the pulp chamber. Teeth were divided into three groups (n=10); each group was restored with standardized CAD/CAM fabricated endocrowns using one of the three tested materials . All endocrowns were cemented with resin cement, stored in distilled water for 24 hours, subjected to thermocycling, and then immersed in a 5% methylene blue dye solution for 24 hours. Roots were embedded in fast-curing resin and a compressive load was applied at 135 degrees to the long axis of the teeth using a universal testing machine until failure. Failure load was recorded and specimens were examined with stereo-microscopy for modes of failure and microleakage. Results were analyzed using one-way analysis of variance and Post Hoc multiple comparison tests (α=0.05).
Results:
The following table shows fracture load and die penetration of the investigated materials. Standard deviations are given in parentheses.
Material |
Fracture load (N) |
Die penetration (mm) |
CB |
1255.46 (226.24)A |
1.11 (0.20)A |
EX |
1342.03 (343.07)A |
1.91 (0.15)B |
LU |
1422.32 (362.12)A |
2.80 (0.19)C |
*Different superscript capital letters indicate significant differences by Post Hoc multiple comparison test.
LU showed more favorable fracture mode than CB and EX (i.e fracture of the endocrown without fracture of tooth).
Conclusions:
Although using resin composite blocks for fabrication of endocrowns resulted in good resistance to fracture and more favorable failure modes than ceramic blocks, more microleakage may be expected with this material.