Retention of different all ceramic endocrown materials cemented with two different adhesive techniques.

OBJECTIVE: The purpose of this in vitro study was to evaluate the influence of two adhesive techniques on the retentive force of four all ceramic endocrowns. MATERIALS AND METHODS: Forty maxillary first molars of approximately similar size and shape were collected. The teeth were all decoronated 2 mm above the level of proximal cement-enamel junction (CEJ) and were all endodontically treated. The teeth were then randomly divided equally into four groups (10 each) according to all ceramic material used, as follows: Group I (VE) - Ten prepared molars were restored with hybrid ceramic (Vita Enamic); Group II (LU) - Ten prepared molars were restored with resin Nano-ceramic (Lava Ultimate). Group III (CD) - Ten prepared molars were restored with zirconia-reinforced lithium di-silicate ceramic material (Celtra Duo); Group IV (LZ) - Ten prepared molars were restored with zirconia ceramic (Lava Zirconia). Each group was then subdivided into two equal subgroups (n=5) according to the type of cement (adhesive technique) used for cementation. Subgroup A (RX ARC): the endocrowns were cemented with a total-etch adhesive resin cement (RelyX ARC). Subgroup B (RXU): the endocrowns were cemented with self-adhesive resin luting cement (RelyX UniCem). The restorations were designed with an outer cylindrical handle located on buccal and palatal surfaces to provide a mean for the removal of the endocrowns during the pull-out testing. The cemented endocrowns were thermocycled and then removed along the path of insertion using a universal testing machine at 0.5 mm/min. The retentive force was recorded, and the stress of dislodgement was calculated using the surface area of each preparation. RESULTS: The highest mean dislodgement stresses were 64.3 MPa for Group I (VE), whereas there was no statistically significant difference between Group I, II and III and LZ showed the lowest values with significant difference between the other three groups. Regarding the type of cement, there was a statistically significant difference between RelyX ARC (mean=60.09 MPa) and RelyX Unicem (mean=49.73 MPa). CONCLUSIONS: Retention of Vita Enamic, Lava Ultimate, and Celtra Duo are significantly higher than Lava Zirconia.

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 techniques of two types of glass ceramics on the marginal gap distance and the fracture resistance of endocrown restorations after cyclic loading. MATERIALS AND METHODS: Forty extracted mandibular first molars were root canal treated. Decoronation was done for all the endodontically treated teeth 2 mm above the cemento-enamel junction. The teeth were individually fixed vertically into epoxy resin mounting cylinders. All teeth were prepared to receive endocrown restorations. The prepared teeth were randomly divided into four equal groups (n=10) according to the all-ceramic materials and technique used for endocrown construction as follows: Group I (n=10): Pressable lithium disilicate glass ceramics (IPS e-max Press), Group II (n=10): Pressable zirconia-reinforced lithium disilicate glass ceramics (Celtra Press), Group III (n=10): Machinable lithium disilicate glass ceramics (IPS e-max CAD), Group IV (n=10): Machinable zirconia-reinforced lithium disilicate glass ceramics (Celtra Duo). The endocrowns were cemented using dual-cure resin cement. All endocrowns were subjected to fatigue loading. 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 collected, tabulated, and statistically analyzed. RESULTS: Fracture resistance testing of all-ceramic 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 difference between all the four ceramic crowns for the marginal gap distance either before or after fatigue cyclic loading. CONCLUSIONS: After considering the limitation of the current study, the following conclusions were given: endocrowns are considered one of the promising minimally invasive restorations for root canal treated molars. CAD/CAM technology revealed better results than heat press technology regarding the fracture resistance of glass ceramics. Heat Press technology revealed better results than CAD/CAM technology regarding the marginal accuracy of glass ceramics.