Abstract Back ground: Full coverage porcelain fused to metal crowns (PFM) is commonly recommended for restoration of extensively damaged teeth. Ability of the dentist to adequately prepare teeth is necessary to achieve a proper success and longevity of these restoration. Aims: This study aimed to determine the degree of axial taper and total occlusal convergence angles (TOC) for Porcelain Fused To Metal crowns (PFM) prepared with clinically practiced values, that carried out by dental practitioners in Tripoli center, Libya. Materials and Methods: It was a descriptive, cross-sectional study design and held at Alzendah private dental laboratory, Tripoli Libya. A convenience sample (40) models of Porcelain Fused To Metal Crowns (PFM) preparations carried out by private dental practitioners were scanned by employing a 3D model scanner (Ceramill Map300, Amanngirrbach, Austria). Evaluation of the total occlusal convergence (TOC), bucco-lingual and mesio-distal convergence angles of each abutment tooth was proceeded using B&B dental software (Guide system, B&B, Italy). The degree of taper was measured on the axial walls of each crown preparation and the bucco-lingual and mesio-distal convergence angles subsequently calculated. Results: A total of 40 casts having crown preparations (15 anterior, 25 posterior). The mean convergence angles mesio-distally for all preparations was 40.29° (sd 21.8°), and for the bucco-lingual was 29.92° (sd 9.3°), with mean of TOC was 35.10°. In anterior preparations, the mean bucco-lingual convergence angle was 42.32° (sd 12.2°) compared to 24.52° (sd 15.5°) for posterior preparations (p
Dr. Khaled Omar & Abdussalam Eljabali(1-2022)

INTRODUCTION: CAD/CAM denture base materials are milled from pre-polymerized pucks of resin that are highly condensed. So, they provide no polymerization shrinkage eliminating its subsequent disadvantages. This technology offered improved fit, strength properties and more bio-hygienic denture bases compared with conventional processing of the denture base material. OBJECTIVES: The aim of the study was to evaluate the physico-mechanical properties of CAD/CAM denture base material and the effect of thermo-cycling on it compared with the conventional one. MATERIALS AND METHODS: The study was conducted on two parallel groups, divided according to the denture material used. Group (1) conventional PMMA (control group), group (II) CAD/CAM PMMA (study group) of 40 specimens each (16 for impact strength, 16 for flexural strength, 8 for surface roughness and grinded powder form both materials for residual monomer test). Each group was divided into 2 sub-groups: (A) No thermo-cycling and (B) Thermo-cycling, then subjected to 4 different tests, impact strength, flexural strength, surface roughness and residual monomer tests. Data were collected, tabulated and statistically analyzed. Significance level was set at 5%. Bar charts were used for graphical presentations. RESULTS: Our study revealed a highly statistically significant decrease in residual monomer of CAD/CAM PMMA material in both conditions before and after thermo-cycling when compared to conventional PMMA material, which therefore leads to enhanced impact strength and significantly reduced surface roughness after heat treatment. On the other hand, also a highly significant reduction of its flexural strength after thermocycling has been observed. CONCLUSIONS: CAD/CAM dentures with lower amount of methacrylate monomer exhibit more favourable physico-mechanical properties and they have a long-term biocompatibility even with thermal changes making them a more satisfactory as a denture base material for edentulous patients.
Yusra Muftah Saad Elfaidy, Ahmed M. Abdelhamid, Sonia M. Elshabrawy(12-2018)

Abstract Introduction: Provisional restoration is an important part of fixed prosthodontics. It must provide pulp protection, positional stability, occlusion maintenance , and space preservation. There are two methods for provisional restoration fabrication; direct and indirect techniques. Aim: the study aims to identify the most preferred technique of fabricating provisional fixed restorations according to different parameters and situations and to highlight the advantages and disadvantages of each technique, by specialist dentists practicing in different dental clinics in Tripoli. Methodology: In this study, 120 closed ended questionnaires were distributed to specialist dentists in dental fixed restoration among different private dental clinics in Tripoli/Libya to find out which technique they prefer to apply in their clinics. Results: This study has revealed that dentists prefer the direct technique for the anterior area and single unit and up to 3-4 units fixed partial denture. While indirect technique was more commonly used by dentists in cases of multi-units and posterior teeth. In addition, it has a higher success rate and does not cause pulpal and gingival irritation.
NARJES ELGHEZAWI HANAN IRHOMA , ABDUSSALAM ELJABALI (7-2021)