RESUMEN
BACKGROUND: The marginal fit of crowns is of clinical importance. It is found that marginal and occlusal discrepancies are commonly increased following cementation. The resistance of cementing materials is a factor that prevents cast restorations from being correctly seated. Different finish lines behave differently in facilitating the escape of the cement. When the escape path of the cement decreases, the crown fails to seat further. MATERIALS AND METHODS: This study was planned with an aim to evaluate the effect of various finish lines on the marginal seal and occlusal seat of full crown preparations. Six stainless steel metal dies were machined to simulate molar crown preparations. The diameter was 10 mm and height was 6mm. The occlusal surface was kept flat and a small circular dimple was machined for reorientation of the wax pattern and metal copings, margins of various designs were machined accurately. The margins prepared were Group A- 90(0)C shoulder, Group B- Rounded shoulder, Group C- 45 degree sloped shoulder, Group D- Chamfer, Group E- Long chamfer, Group F- Feather edge. Full cast metal crowns of base metal alloy were fabricated over the metal dies. Zinc phosphate luting cement was used for the cementation. After twenty four hours, the cemented crown and die assembly were embedded in clear acrylic resin so as to hold the assembly together while sectioning. Twenty four hours later, all the samples were sectioned sagitally. The sectioned halves were focused under a stereomicroscope and the cement spaces were measured to the nearest micron. The cement thickness was measured at two points on the occlusal surface and one at each margin. RESULTS: Significant differences were observed in the occlusal seat and marginal seal of all the finish line configurations. The rounded shoulder had the best occlusal seat, followed by 90(0)C shoulder. The occlusal seat and marginal seal afforded by the shoulder finish lines were similar whereas there was a vast difference in the seating and sealing of long chamfer and feather edged preparations. They showed the worst occlusal seat. CONCLUSION: It was found that the finish lines like shoulder preparations which exhibit poor sealing prior to complete cementation allow good seating whereas margins which seal earlier do not allow escape of cement and hence do not seat completely.
RESUMEN
BACKGROUND: Denture fracture is an unresolved problem in complete denture prosthodontics. However, the repaired denture often experiences a refracture at the repaired site due to poor transverse strength. Hence, this study was conducted to evaluate the effect of joint surface contours and glass fiber reinforcement on the transverse strength of repaired acrylic resins. MATERIALS AND METHODS: A total of 135 specimens of heat polymerized polymethyl methacrylate resin of dimensions 64 × 10 × 2.5 mm were fabricated. Fifteen intact specimens served as the control and 120 test specimens were divided into four groups (30 specimens each), depending upon the joint surface contour (butt, bevel, rabbet and round), with two subgroups based on type of the repair. Half of the specimens were repaired with plain repair resin and the other half with glass fibers reinforced repair resin. Transverse strength of the specimens was determined using three-point bending test. The results were analyzed using one-way ANOVA and Tukey post-hoc test (α= 0.05). RESULTS: Transverse strength values for all repaired groups were significantly lower than those for the control group (P < 0.001) (88.77 MPa), with exception of round surface design repaired with glass fiber reinforced repair resin (89.92 MPa) which was significantly superior to the other joint surface contours (P < 0.001). Glass fiber reinforced resin significantly improved the repaired denture base resins as compared to the plain repair resin (P < 0.001). CONCLUSION: Specimens repaired with glass fiber reinforced resin and round surface design exhibited highest transverse strength; hence, it can be advocated for repair of denture base resins.
RESUMEN
Phonetics is an important function of oral cavity. It has been overlooked quite frequently while fabricating the complete dentures. In this study modification of anterior palatal surface of denture is done and assessed for its impact on phonetics. Purpose is to assess acoustic and speech intelligibility analysis in edentulous patients and also to evaluate the influence of conventional dentures, arbitrary rugae and customized rugae dentures on speech in complete denture wearers. Ten healthy edentulous patients 55-70 years of age were selected for the study. Dentures were fabricated in conventional way for these patients. Recordings were done for intelligibility and acoustic analysis of the speech. Recordings were done without denture, with conventional denture, with arbitrary rugae denture, with customized rugae denture. Each recording was done at an interval of 10 days period. All four recordings were analyzed and comparison was done using paired 't' test. There was significant improvement in frequency peak noise energy for 's', antiformant frequency for 'n' in rugae incorporated dentures. There was relative improvement in frequency peak noise energy for 'sh', frequency proximity burst, voice onset time for 'd', with rugae incorporated dentures. Findings of intelligibility analysis have shown substitution errors with conventional dentures. There was relative improvement of speech with rugae incorporated dentures. Among these, customized rugae dentures showed better results than arbitrary rugae dentures.
RESUMEN
Identification of individuals in crime or mass disaster is a daunting task for the forensic experts. The purpose of this study is to evaluate the feasibility of using a memory card for the forensic identification of dentures. The memory card was programmed with all the relevant information regarding the patient identification and the photograph of the patient. A recess was made in the maxillary denture's polished surface on the palatal aspect. The card was wrapped in cellophane, placed in the recess and then covered with pink auto polymerizing acrylic resin. On retrieval of the card from the denture, the entire data could be read as before without any distortion. The identification cards did not pose any problems in function and speech and were esthetically acceptable by the patients.