Marginal gap distance and cyclic fatigue loading for different all-ceramic endocrowns

- OBJECTIVE: The aim of the study was to evaluate the effect of the fabrication tech-niques of two types of glass ceramics on the mar-ginal gap distance and the fracture resistance of endocrown restorations after cyclic loading.MATERIALS AND METHODS: Forty extract-ed mandibular first molars were root canal treat-ed. Decoronation was done for all the endodon-tically treated teeth 2 mm above the cemen-to-enamel junction. The teeth were individual-ly fixed vertically into epoxy resin mounting cyl-inders. All teeth were prepared to receive en-docrown restorations. The prepared teeth were randomly divided into four equal groups (n=10) according to the all-ceramic materials and tech-nique used for endocrown construction as fol-lows: Group I (n=10): Pressable lithium disili-cate glass ceramics (IPS e-max Press), Group II (n=10): Pressable zirconia-reinforced lithium di -silicate glass ceramics (Celtra Press), Group III (n=10): Machinable lithium disilicate glass ce-ramics (IPS e-max CAD), Group IV (n=10): Ma-chinable zirconia-reinforced lithium disilicate glass ceramics (Celtra Duo). The endocrowns were cemented using dual-cure resin cement. All endocrowns were subjected to fatigue load-ing. The cycles were repeated 120,000 times to clinically simulate one year chewing condition. Marginal gap distance of all endocrowns was measured directly using a digital microscope with x100 magnification. The load required to failure was recorded in Newton. Data were col-lected, tabulated, and statistically analyzed.RESULTS: Fracture resistance testing of all -ce-ramic crowns revealed a statistically significant difference between all different ceramic materials used in this study (p-value <0.001). On the other hand, there was a statistically significant differ-ence between all the four ceramic crowns for the marginal gap distance either before or after fa-tigue cyclic loading.CONCLUSIONS: After considering the limita-tion of the current study, the following conclu-sions were given: endocrowns are considered one of the promising minimally invasive resto-rations for root canal treated molars. CAD/CAM technology revealed better results than heat press technology regarding the fracture resis-tance of glass ceramics. Heat Press technology revealed better results than CAD/CAM technolo-gy regarding the marginal accuracy of glass ce-ramics