one of the main factors that affect the success of the cast crown is the accuracy of the internal and marginal fit, a well-fitting crown reduces the chance for recurrent caries and periodontal disease, whereas the space between a poorly-fitting crown and tooth preparation enables accumulation of bacterial plaque, the use of paint- on die spacing technique to produce the cement gap and subsequently to improve the seating of the cast crowns has become quite popular in the recent years. The purpose of the study is to compare the marginal gap and the internal fit produced by two paint-on die spacing materials (Manicure and paint on die spacer ). Twenty four identical stone dies were made, 12 were coated with paint- on die spacer material, and 12 were coated with nail varnish material, the dies coated with die spacer were divided into three groups (DA,DB,DC), and the dies coated with nail varnish were also divided into three groups (VA,VB,VC), groups DA and VA were coated with one layer, DB and VB were coated with two layers, DC and VC were coated with three layers, for both groups wax patterns were made and casted using the lost waxing technique and all steps were standardized, impression replicas of the casted crowns were made and sectioned by means of the impression replica technique, measurements were taken using Scanning Electron Microscope, from 4 points (marginal gap, mid-axial, axio-occlusal and mid-occlusal). There was no statistical significant difference in accuracy between crowns fabricated on die spacer coated dies and crowns fabricated on nail varnish coated dies. with the crowns fabricated on die spacer coated dies being slightly more accurate.
ABDUSSALAM ELJABALI(12-2019)

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)

Background: Management of partially edentulous patients with hard and soft tissue undercuts is complicated, and the use of flexible dentures for these cases offers dual advantages of aesthetics and flexibility. However, research shows a varying preference for flexible dentures among general dental practitioners, prosthodontists, and other dental specialties. Objectives: The aim of this study was to survey the attitude and awareness of a sample of Libyan dental clinicians towards advantages, disadvantages, indications, and contraindications of flexible dentures. Material and methods: A descriptive cross-sectional study was conducted among 250 dentists currently practicing in different cities of Libya. Only 218 dentists responded. Using Google form software, a self-administrable e-questionnaire consisting of thirty-one multiple choice questions with "yes," "no" or "not sure" answers encompassing major aspects of flexible dentures was conducted through an online survey. Results: Out of 250 Libyan dentists to whom the questionnaire was sent, only 218 dentists responded and our results revealed that the respondents were females more than males with a ratio (2:1) and more than half of them were of age group (35-60 years) work in governmental dental practice with more than ten years of experience and 34.9% of them prefer and often offer flexible dentures to their patients. The majority of respondents with a long-term success of the flexible denture were prosthodontists who had more than ten years of experience with a correct response rate of more than 50% of questions that reflected their attitude and knowledge. Conclusions: Despite the fact that flexible dentures are not taught in Libyan universities of dentistry, about more than one-third of respondents prefer and recommend this treatment to their patients, and the long-term success of these prostheses was dependent on clinicians' education and their clinical experience.
Yusra Muftah Saad Elfaidy, Warida Abdalla Elnaihoum, Aseidah Abdullah Elgotrany(4-2022)