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

Abstract

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.