Immediate loading seems to be a relatively safe procedure. From the prosthodontic point of view, there are specific guidelines to follow. They are: implants should be splinted with a metallic bar and acrylic interim prostheses until full osseointegration occurs. To have a successful outcome, screw-retained interim prostheses are recommended. CAD/CAM systems can improve the placement of implants with minimum risk. Regarding occlusion, there is a disagreement on when and how to provide occlusal contacts, but all authors agree on keeping centric contacts only. Finally, concerning the number of implants required for an immediate overdenture, no conclusive evidence could be found.

Objectives The purpose of this in vitro study was to evaluate the fracture resistance and failure modes of endocrowns made of three computer‐aided design/computer‐aided manufacturing (CAD/CAM) materials subjected to thermo‐mechanical cycling loading. Materials and Methods Eighty mandibular molars were divided into four groups (n = 20): one (C E) was restored with lithium disilicate glass‐ceramic conventional crowns, three were restored with endocrowns made of three different CAD/CAM materials; (E E) lithium disilicate glass‐ceramic, (E V) zirconia‐reinforced lithium silicate glass‐ceramic, and (E C) resin nano‐ceramic. After cycling loading, half of the samples from each group were loaded axially and the other half was loaded laterally. Fracture resistance was recorded in Newton (N) and failure modes were classified. Two‐way ANOVA, Bonferroni post hoc (α = .05), Chi‐square, and multiple logistic regression tests were used to analyze data. Results Statistically significant interaction were recorded between fracture resistance (N) and loading (P < .001), and groups (conventuional crown and endocrowns; P < .001). Endocrowns presented higher fracture strength than conventional crowns. Fracture resistance was significantly larger under axial loading. The numbers of irreparable failures were extremely important in the endocrowns groups (Groups E E, E V, E C), and only conventional crowns (Group C E) showed almost no irreparable failures under axial loading. Conclusion Lithium disilicate glass‐ceramic recorded the highest fracture resistance under axial and lateral loading. Clinical Significance The number of irreparable failures with all endocrown materials tested do not suggest yet the use of this type of restorations in posterior teeth.

Purpose: The purpose of this study was to assess fracture resistance, failure mode and stress concentration of a modified endocrown preparation design, under axial and lateral forces. Materials and Methods: Forty lower molars were divided into two groups (n ¼ 20) and were restored with lithium disilicate glass-ceramic endocrowns following 2 preparation designs: Conventional, with circumferential butt margin 2 mm above the cemento-enamel junction; and Modified, by adding 2 grooves on the mesial side of the vestibular dentinal wall and on the distal side of the lingual dentinal wall. After cementation and thermomechanical cycling loading, half of the samples (n ¼ 10) from each group were loaded axially and the other half (n ¼ 10) was loaded laterally. Fracture resistance and failure modes were observed and the finite element analysis (FEA) was used to identify the stress concentration. Two-way ANOVA and Chi-square tests (a ¼ 0.05) were used for in vitro data analyzes. Results: Fracture resistance showed a statistically significant difference between conventional and modified preparations (p < .001), and between axial and lateral loadings (p < .001). Conventional preparation recorded 2914 N under axial loading and 1516 N under lateral loading, while modified preparation recorded 3329 N under axial loading and 1871 N under lateral loading. FEA showed that retention grooves have reduced the stress concentration under both loads for the tooth and the restoration. Conclusion: Modified endocrown design showed higher fracture resistance than conventional endocrown. Lateral loading displayed a high percentage of severe fracture but under higher load to failure than the values reported for normal masticatory forces.

Purpose To evaluate and to compare the marginal and the internal fit of milled (MLE) and heat‐pressed lithium disilicate endocrowns (PLE). Materials and Methods Thirty mandibular molars were prepared following the circumferential butt margin endocrown preparations; the cervical margin is parallel to the occlusal surface without ferrule design. A digital scan of molars was made using an intraoral digital scanner. The samples were separated into two groups (n = 15 per group); MLE: endocrowns were milled using LDS blocks and a 5‐axis milling machine, PLE: endocrowns were heat‐pressed using lost wax technique and LDS ingots. Marginal and internal adaptation were assessed using a replica technique and a stereomicroscope, selecting 32 measurements on each endocrown. Data were analyzed with one‐way repeated measures ANOVA, two‐way repeated measures ANOVA, student's t‐test and paired student t‐test (α = 0.05). Results Statistically significant interactions were recorded between fabrication technique and region (p < 0.05), F (1.97, 27.69) = 5.462. Group MLE displayed significantly smaller gaps than PLE in all regions (p < 0.001). The largest gap was observed at the pulpal floor in both groups. The internal gap was significantly larger than the marginal gap in MLE group (p < 0.001), while no statistically significant difference was observed in PLE group (p = 0.082). Conclusion Heat‐pressed and milled lithium disilicate endocrowns are clinically suitable, but the milled technique displayed a better fit than heat‐pressed technique when marginal and internal adaptation were examined.

Within the limitations of this study there was no difference for the same inlay/onlay cavity design between vital and nonvital teeth. In nonvital teeth, it seems that filling the pulp chamber with a ceramic core material is not important. Long-term observation periods are needed to reinforce the clinical behavior outcome.

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