PURPOSEThis study aimed to evaluate the fit of zirconia ceramics before and after veneering, using 3 different veneering processes (layering, press-over, and CAD-on techniques).MATERIALS AND METHODSThirty standardized zirconia CAD/CAM frameworks were constructed and divided into three groups of 10 each. The first group was veneered using the traditional layering technique. Press-over and CAD-on techniques were used to veneer second and third groups. The marginal gap of specimens was measured before and after veneering process at 18 sites on the master die using a digital microscope. Paired t-test was used to evaluate mean marginal gap changes. One-way ANOVA and post hoc tests were also employed for comparison among 3 groups (α=.05).RESULTSMarginal gap of 3 groups was increased after porcelain veneering. The mean marginal gap values after veneering in the layering group (63.06 µm) was higher than press-over (50.64 µm) and CAD-on (51.50 µm) veneered groups (P<.001).CONCLUSIONThree veneering methods altered the marginal fit of zirconia copings. Conventional layering technique increased the marginal gap of zirconia framework more than pressing and CAD-on techniques. All ceramic crowns made through three different veneering methods revealed clinically acceptable marginal fit.

Significantly, cast posts and cores had a higher failure threshold including teeth fracture; whereas, fiber posts failure was due to core fracture, with or without fractures in coronal portion of posts. Difference in FRC posts did not provide any significant difference in the load failure and the mode of fracture.

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BackgroundDental pulp stem cells (DPSCs) play an important role in tissue regeneration. This study compares the growth kinetics and characterization of third molar and first premolar human DPSCs.Material and MethodsDental pulp tissues were isolated from human first premolar and third molar teeth and were digested by treating them with collagenase type I. Single-cell suspensions from each dental pulp were seeded in T25 culture flasks and the media were replaced every 3 days until 70% confluence. The cells were enumerated to determine the population doubling time (PDT). Cells were characterized using flow cytometry, RT-PCR and osteogenic medium for differentiation of DPSCs. Karyotyping assay was also performed till passage 7th.ResultsThe DPSCs had spindle-shaped morphology. There was an increase in PDT in third molar DPSCs when compared to first premolar teeth. Positive expression of CD44, CD73, and CD90 and negative expression of CD34 and CD45 were illustrated. A normal karyotype was visible for all seven passages. The Alizarin red staining was positive for osteogenic induction of DPSCs.ConclusionsWhen DPSCs are needed, third molar teeth can be a good and convenient candidate for cell transplantation, yielding high number of cells with mesenchymal characteristics. They can be a source for further investigations in vitro and work on tissue engineering protocols. Key words:Stem cells, dental pulp, growth kinetics, characterization.

Background and aims. Because of compromised angulations of implants, the abutments are sometimes prepared. The purpose of this study was to investigate the effect of removing one wall of the implant abutment on the retention of cement-retained crowns.Materials and methods. Four prefabricated abutments were attached to analogues and embedded in acrylic resin blocks. The first abutment was left intact. Axial walls were partially removed from the remaining abutments to produce abutments with three walls. The screw access channel for the first and second abutments were completely filled with composite resin. For the third and fourth abutments, only partial filling was done. Wax-up models were made by CAD/CAM. Ten cast copings were fabricated for each abutment. The copings of fourth abutment had an extension into the screw access channel. Copings were cemented with Temp Bond. The castings were removed from the abutment using an Instron machine, and the peak removal force was recorded. A one-way ANOVA was used to test for a significant difference followed by the pairwise comparisons.Results. The abutments with opened screw access channel had a significantly higher retention than the two other abutments. The abutment with removed wall and no engagement into the hole by the castings exhibited the highest retention.Conclusion. Preserving the opening of screw access channel significantly increases the retention where one of the axial walls of implant abutments for cement-retained restorations is removed during preparation.