Aim: This study was designed to compare the retention strength of monolithic CAD/CAM PEEK crowns to that of CAD/CAM monolithic YTZP-zirconia crowns, both resin-cemented to epoxy resin dies resembling lower molar teeth; after thermomechanical aging simulating 3 months of in-vivo service. Materials and methods: 22 identical epoxy dies, resembling the preparation of a lower second molar (4mm height, 6° axial convergence and 1 mm-thick deep chamfer finish line), were produced by replicating one master stainless steel die via 22 polyvinyl siloxane impressions. The epoxy dies were randomly equally distributed into 2 groups (Zr and P groups); 11 dies each. The first (control) group (Zr) received CAD/CAM milled monolithic Y-TZP zirconia crowns (Katana™ ML), while the other group (intervention) received CAD/CAM milled monolithic PEEK crowns (breCAM.BioHPP™). Two opposing, laterally projecting (mesial and distal) arms were included in the design of all crowns for the retention test. The fitting surfaces of crowns of both groups were sandblasted with 110-µm alumina particles. All crowns were cemented over their corresponding epoxy dies using the (hand-mixed) dual-cured, self-adhesive resin cement (RelyX™ U200) (3-kg seating force). Samples were stored in water incubator for 24 hours (37 °C); then, subjected to mechanical aging (37,500 cycles, 49 N load) with simultaneous thermocycling (300 cycles, 5-55 °C, 12 s dwell time). Retention strength was evaluated by vertically pulling-up the crowns from their corresponding dies, through the pull-out test performed via a universal testing machine (UTM). Failure modes were then observed under digital microscope. The mean dislodgment force (retention strength) for each group was calculated, and statistically compared using Student t-test. Statistical analysis was performed with three-way ANOVA. Pair-wise comparison of groups was made with the Tukey test. Pearson’s Chi-Square test was used to analyze the failure modes. Results: PEEK crowns group (P) demonstrated statistically insignificant higher retention strength (171.28 N ± 26.30) than zirconia (Zr) crowns group (150.40 N ± 24.40). “Mixed” failure mode was predominant in both groups, followed by the adhesive “cement on crown” failure-mode.

Background. Diabetes mellitus (DM) is a chronic serious health problem which characterized by elevated blood glucose levels. Exogenous insulin administration is needed for type I DM management. Bone marrow-mesenchymal stem cells (BM-MSCs) provide cell based approach for DM treatment. Objectives. to explore the effectiveness of BM-MSCs versus insulin on circumvallate and foliate papillae of diabetic rats. Materials and methods. The study was carried out on 56 male albino rats that were divided into 4 groups: Control group (Gp 1): rats received no drug. Diabetic group (Gp 2): rats received a single intra-peritoneal injection of Streptozotocin (STZ) (40mg/kg). BM-MSCs treated diabetic group (Gp 3): After diabetes confirmation; rats were given a single intravenous injection of PKH26 labeled BM-MSCs (million units) through tail vein. Insulin treated diabetic group (Gp 4): After diabetes confirmation; rats received subcutaneous injection of insulin (5IU/kg/day). After 4 weeks, half of the tongue specimens were processed and stained by Hematoxyline & Eosin, then examined by light microscope. While the other half were examined by scanning electron microscope. Results. Circumvallate and foliate papillae of Gp 2 showed significant histological and morphological alterations. While in Gp 3 and 4, the papillae showed noticeable improvements, being more obvious in insulin treated one. Moreover, in Gp 3 and 4, there was a significant increase in body weight in comparison to Gp 2. Conclusions. BM-MSCs administration could help in reducing the damaging effects of DM on circumvallate and foliate papillae. Insulin therapy caused more efficient improvements in diabetic rats than BM-MSCs.

OBJECTIVES: The objective of the study was to evaluate the marginal and internal fit of anterior nano-ceramic composite endocrowns with different preparation designs. METHODS: 28 extracted upper anterior teeth were selected and divided into 2 groups (n=14), group A: prepared with short extension (2 mm) and group B with long extension (5 mm). The two groups were further divided into another 2 subgroups; subgroup 1: with 2 mm ferrule while subgroup 2: without ferrule. Endocrowns were fabricated using Cerec CAD/CAM system (Dentsply Sirona, Germany) and the material for endocrowns fabrication was Lava ultimate blocks (3M ESPE, Germany). The internal and marginal fit were then measured using replica technique. General Linear Model (GLM) procedure was used for testing the significance of the main effects; (ferrule effect, endocrown extension) and their interaction, on the internal and marginal fit. (ANOVA with two fixed effects). RESULTS: 1- Marginal fit: the mean marginal replica thickness ranged from (22.05 µm) for group A1 to (36.42 µm) for group A2 with no significant effect of both ferrule and extension on marginal adaptation. P>0.05. 2-internal fit: The mean replica thickness ranged from (41.52 µm) for group A1 to (75.68 µm) for group A2. With high significant effect of ferrule P0.05. CONCLUSION: the ferrule significantly improved the internal fit of CAD/CAM nano-ceramic composite anterior endocrown, but it had no significant effect on the marginal fit. The extension of endocrown did not affect neither internal nor marginal fit.