The effect of restorative material selection and cementation procedures on the durability of endocrowns in the anterior teeth: an in-vitro study.

OBJECTIVE: To investigate the fracture resistance and failure modalities of anterior endocrown restorations fabricated employing diverse ceramic materials, and bonded using various cementation methodologies. MATERIALS AND METHODS: Forty maxillary central incisors were divided into two main groups based on the ceramic materials used; GroupI (Zir): zirconia endocrwons (Zolid HT+, Ceramill, Amanngirrbach) and GroupII (E-Max): e-max endocrowns (IPS e.max CAD, Ivoclar Vivadent). Both groups were further split into two subgroups depending on the cementation protocols; subgroup IA "ZirMDP": endocowns cemented with MDP primer + MDP resin cement, subgroup IB (ZirNon-MDP): cemented with MDP primer + non-MDP resin cement, subgroup IIA (E-maxMDP): cemented with MDP primer + MDP resin cement, subgroup IIB (E-maxNon-MDP): cemented with MDP primer + non-MDP resin cement. (n = 10/subgroup). Endocrowns were manufactured using CAD/ CAM. Teeth were subjected to 10,000 thermal cycles. The fracture test was performed at 45o with a palatal force direction until the fracture occurred. Test results were recorded in Newton. The failure mode was examined using a stereomicroscope. A One-way ANOVA test was utilized to compare different groups regarding fracture strength values. Tukey`s Post Hoc was utilized for multiple comparisons. RESULTS: The comparative analysis of fracture strength across the diverse groups yielded non-significant differences, as indicated by a p-value exceeding 0.05. Nonetheless, an observable trend emerged regarding the mode of failure. Specifically, a statistically significant prevalence was noted in fractures localized within the endocrown/tooth complex below the cementoenamel junction (CEJ) across all groups, except for Group IIB, "E-max Non-MDP," where fractures within the endocrown/tooth complex occurred above the CEJ. CONCLUSIONS: Combining an MDP-based primer with an MDP-based resin cement did not result in a significant effect on the anterior endocrown fracture strength. CLINICAL RELEVANCE: Regardless of the presence of the MDP monomer in its composition, adhesive resin cement achieved highly successful fracture strength when used with MDP-based ceramic primers. Additionally, ceramic materials exhibiting elastic moduli surpassing those of dentin are discouraged due to their propensity to induce catastrophic fractures within the tooth structure.

Influence of resin cements and aging on the fracture resistance of IPS e.max press posterior crowns.

The purpose of this study was to evaluate the effect of different adhesive cements and thermocycling on the fracture resistance of IPS e.max Press posterior single crowns. Thirty-two sound maxillary molars were subjected to standardized preparation and received IPS e.max Press crowns. Another 16 molars were left unprepared to serve as controls (group 1). Panavia F 2.0 and Rely X Unicem luting cements were used to bond the fabricated crowns (n = 16 each) to their respective prepared teeth. Eight specimens from each of the three groups were selected randomly for further thermocycling (5,000 cycles). All specimens were then subjected to fracture resistance testing using anatomical metal attachments fixed to the upper portion of the universal testing machine (1 mm/min). Data were analyzed statistically using two-way analysis of variance and the Student t test (α = .05). Natural teeth presented significantly higher (1,043 and 1,279 N) fracture resistance than that of adhesively cemented ceramic crowns (907 to 986 N) before and after thermocyling, respectively (P < .05). Cement type did not significantly affect fracture resistance results (986 N and 974 N for Panavia F 2.0 and Rely X Unicem, respectively; P > .05). Thermocycled specimens showed lower fracture resistance than that of nonthermocycled ones (P < .05). Neither conventional adhesive cement nor self-etching adhesive cement affected the fracture resistance of IPS e.max crowns. Thermocycling decreased the fracture strength of the crowns in both cement groups. Natural teeth fractured at significantly higher loads than the ceramic crowns.

Influence of fabrication techniques and artificial aging on the fracture resistance of different cantilever zirconia fixed dental prostheses.

PURPOSE: To evaluate the influence of dynamic fatigue on fracture load and failure mode of different types of adhesive zirconia restorations. MATERIALS AND METHODS: Eighty adhesive cantilever fixed dental prostheses (CFDP) were fabricated and assigned to four equal groups (n = 20) using the following materials and techniques. Group 1: machine copy-milling zirconia (Cercon), group 2: manual copy-milling technique (ZirkonZahn), group 3: slip casting technique (Vita In-ceram Zirconia), group 4: metal-ceramic CFDP. Specimens in groups 1and 2 received selective infiltration-etching surface treatment, specimens in group 3 were acid etched with hydrofluoric acid and silanated, while those of group 4 were airborne particle abraded. All specimens were bonded with resin cement (Panavia F2.0) and thermocycled (5000 cycles/ 5 to 55°C). Then, half the number of the specimens of each group (n = 10) underwent dynamic loading (one million cycles at alternating loads between 10 and 40 N in a water bath at 37°C). All specimens were subjected to one-cycle loading to failure to evaluate fracture resistance. One-way and two-way ANOVA and Bonferroni post-hoc tests were used to analyze the data (α = 0.05). The intaglio surfaces of fractured specimens were examined using stereomicroscopy and scanning electron microscope (SEM). RESULTS: Statistical analysis revealed that the failure load of metal (413 ± 26 N) and machine copy-milled zirconia (368 ± 24 N) restorations was significantly higher (F = 129, p < 0.001) than manually copy-milled (316 ± 18) and In-ceram zirconia (210 ± 17) restorations. Dynamic fatigue significantly (p < 0.03) reduced failure load of the manually copy-milled and In-ceram zirconia restorations, while metal and machine copy-milling zirconia restorations were not influenced by fatigue. CONCLUSIONS: The fatigue strength of adhesive zirconia restorations is influenced by cyclic loading and the technique used to manufacture these restorations.

Effect of surface conditioning and taper angle on the retention of IPS e.max Press crowns.

PURPOSE: The objective of this study was to evaluate the retentive strength of single-unit crowns with 10 degrees and 26 degrees taper angles cemented using two surface conditioning methods. MATERIALS AND METHODS: Thirty-two freshly extracted sound human molars were divided into two groups (n = 16) and prepared in a standardized manner with 10 degrees and 26 degrees taper angles. All-ceramic (IPS e.max Press) single crowns were fabricated for the prepared teeth. The crowns were then subdivided into two groups (n = 8), according to type of surface conditioning for the intaglio surfaces. Half the groups were HF acid etched and silanized, and the other half were conditioned with tribochemical silica coating and silanization. The crowns were cemented using adhesive cement (Panavia F 2.0). Retentive strength was measured in a universal testing machine. RESULTS: No significant difference was found between the mean retention forces for both 10 degrees and 26 degrees taper angles when the crowns were conditioned either with silica coating (613 +/- 190 N and 525 +/- 90 N, respectively), or with hydrofluoric (HF) acid etching and silanization (550 +/- 110 N and 490 +/- 130 N for 10 degrees and 26 degrees, respectively) (p= 0.32). CONCLUSION: Neither the surface conditioning type, nor the taper angle affected the retentive strength of IPS e.max Press single-unit crowns when cemented adhesively. Since silica coating and silanization did not show significant differences from HF acid gel and silanization, the former can be preferred for conditioning intaglio surfaces of glass ceramic crowns to avoid the use of the hazardous compound HF acid gel chairside.

Fracture resistance of metal- and galvano-ceramic crowns cemented with different luting cements: in vitro comparative study.

This study aimed to compare the fracture resistance of galvano-ceramic crowns with metal-ceramic crowns cemented to natural premolar teeth with different luting cements. Sixty intact maxillary premolars were prepared to receive full-coverage crown restorations and were divided into 2 equal groups (n = 30): galvano-ceramic crowns and metal-ceramic crowns. Each group was further subdivided into 3 equal subgroups (n = 10) according to the luting cement used: zinc-phosphate, glass-ionomer, or adhesive-resin cement. The specimens were then compressively loaded until failure in a universal testing machine. The metal-ceramic crowns exhibited higher resistance to fracture compared to galvano-ceramic crowns, but both exceeded the normal documented values of occlusal masticatory forces.