Comparison the Marginal and Internal Fit of Metal Copings Cast from Wax Patterns Fabricated by CAD/CAM and Conventional Wax up Techniques.

STATEMENT OF PROBLEM: Metal-ceramic crowns are most commonly used as the complete coverage restorations in clinical daily use. Disadvantages of conventional hand-made wax-patterns introduce some alternative ways by means of CAD/CAM technologies. PURPOSE: This study compares the marginal and internal fit of copings cast from CAD/CAM and conventional fabricated wax-patterns. MATERIALS AND METHOD: Twenty-four standardized brass dies were prepared and randomly divided into 2 groups according to the wax-patterns fabrication method (CAD/CAM technique and conventional method) (n=12). All the wax-patterns were fabricated in a standard fashion by means of contour, thickness and internal relief (M1-M12: representative of CAD/CAM group, C1-C12: representative of conventional group). CAD/CAM milling machine (Cori TEC 340i; imes-icore GmbH, Eiterfeld, Germany) was used to fabricate the CAD/CAM group wax-patterns. The copings cast from 24 wax-patterns were cemented to the corresponding dies. For all the coping-die assemblies cross-sectional technique was used to evaluate the marginal and internal fit at 15 points. The Student's t- test was used for statistical analysis (α=0.05). RESULTS: The overall mean (SD) for absolute marginal discrepancy (AMD) was 254.46 (25.10) um for CAD/CAM group and 88.08(10.67) um for conventional group (control). The overall mean of internal gap total (IGT) was 110.77(5.92) um for CAD/CAM group and 76.90 (10.17) um for conventional group. The Student's t-test revealed significant differences between 2 groups. Marginal and internal gaps were found to be significantly higher at all measured areas in CAD/CAM group than conventional group (p< 0.001). CONCLUSION: Within limitations of this study, conventional method of wax-pattern fabrication produced copings with significantly better marginal and internal fit than CAD/CAM (machine-milled) technique. All the factors for 2 groups were standardized except wax pattern fabrication technique, therefore, only the conventional group results in copings with clinically acceptable margins of less than 120um.

Effect of beverages on the hardness and tensile bond strength of temporary acrylic soft liners to acrylic resin denture base.

STATEMENT OF PROBLEM: Two potential problems commonly identified with a denture base incorporating a resilient liner are failure of the bond between acrylic resin and soft liner material, and loss of resiliency of the soft liner over time. Since patients may drink different beverages, it is important to evaluate their effects on physical properties of soft lining materials. PURPOSE: The objective of this in vitro study was to evaluate the effect of different beverages on the hardness of two temporary acrylic-based soft lining materials and their bond strength to the denture base resin. MATERIALS AND METHOD: For the hardness test; a total of 80 rectangular specimens (40mm×10mm×3mm) were fabricated from a heat-polymerized polymethylmethacrylate. Two commercially auto-polymerized acrylic resin-based resilient liners; Coe-Soft and Visco-gel were prepared according to the manufacturers' instructions and applied on the specimens. For the tensile test, 160 cylindrical specimens (30mm×10mm) were prepared. The liners were added between specimens with a thickness of 3 mm. The specimens of both soft liners were divided into 4 groups (n=10) and immersed in distilled water as the control group, Coca-Cola, 8% and 50% ethanol. All groups were stored in separate containers at 37(o)C for 12 days. All beverages were changed daily. The hardness was determined using a Shore A durometer and tensile bond strength was determined in a ZwickRoell testing machine at a cross-head speed of 5mm/min. The results were analyzed using two-way ANOVA. RESULTS: There was no significant interaction between the soft liners and the drinks for both hardness (p= 0.748) and bond strength (p= 0.902). There were statistically significant differences between all drinks for both hardness (p< 0.001) and bond strength (p< 0.05). CONCLUSION: Within the limitations of this study, it seems that drinking Coca-Cola and alcoholic beverages would not be potentially causing any problems for the temporary acrylic soft liners.

The effect of thermal and mechanical cycling on bond strength of a ceramic to nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloys.

PURPOSE: This study evaluates the effect of thermo-mechanical cycling (TMC) on the bond strength of a ceramic to three cobalt-chromium (Co-Cr) and two nickel-chromium (Ni-Cr) alloys. MATERIALS AND METHODS: One hundred metal-ceramic specimens were prepared. While half of the specimens from each metal-ceramic combination (n = 10) were tested after storage in water at 37°C for 24 hours, the other half were subjected to TMC before testing. The bond strength was evaluated by the flexural strength test according to ISO 9693:1999 (E) recommendations. RESULTS: TMC decreased the bond strength of the tested metal-ceramic systems as compared to the water storage (control groups) (P=0.04). Although metal alloys were significantly different from each other in their bond strength with porcelain (P<0.001), the effect of TMC on the various metal-ceramic systems was not significantly different (P=0.99). CONCLUSION: It may be concluded that base metal-ceramic bond strength is affected by aging and the effect is relatively the same for all the tested porcelain-metal systems.

Oral rehabilitation of a patient with amelogenesis imperfecta using removable overlay denture: a clinical report.

AIM: The aim of this study was oral rehabilitation of 17-year old patient with amelogenesis imperfecta using removable overlay denture in order to satisfy her esthetic and functional expectations and enhance her self-image. BACKGROUND: Amelogenesis imperfecta (AI) is a group of genetic disorders that primarily affect the quality and quantity of amelogenesis in both primary and permanent dentitions. The main clinical characteristics are severe attrition, tooth sensitivity and unesthetic appearance. CASE REPORT: This clinical report illustrates the oral rehabilitation of a 17-year-old girl with hypoplastic-hypomature type of AI with cobalt-chromium (Co-Cr) overlay removable partial denture (ORPD) that is one of the most economical and biocompatible replacements for noble metal and nickel-chromium (Ni-Cr) alloy. CONCLUSION: The presented case report suggests that Co-Cr ORPD can be a good temporary or even permanent treatment option for AI patients with limited budget, low esthetic concerns or medical limitations. CLINICAL SIGNIFICANCE: There are major advantages in cast metal ORPDs; they are simpler, less traumatic and less expensive than fixed prosthetic options. This case report supports their use in patients with amelogenesis imperfecta.

Evaluation of cellular toxicity of three denture base acrylic resins.

OBJECTIVE: This study aimed to evaluate the cellular toxicity of two newly-released acrylic resins (Futura Gen and GC Reline Hard) in comparison with the conventional heat-cure resin (Meliodent). MATERIALS AND METHODS: Sample discs from each acrylic resin were placed in 24-well culture plates along with L929 mouse fibroblast cell line. A mixture of the RPMI 1640 medium, antibiotics and 10% FBS was added to the plates and the specimens were incubated in a CO(2) incubator. The amount of light absorption by each plate was determined after 1 hour, 24 hours and 1 week by the MTT assay and ELISA. The cytotoxic effect of the resins was compared among groups using the two-way ANOVA and further paired comparison was performed using the post-hoc Tukey's test. RESULTS: After 1 hour, Futura Gen displayed a significantly lower level of light absorption in comparison with Meliodent (P=0.03). After 24 hours, GC Reline Hard rendered a significantly lower level of light absorption compared to Meliodent (P=0.02). After one-week of incubation, the mean absorption rates for GC Reline Hard, Meliodent and Futura Gen were relatively similar (P>0.05). The lowest and highest level of cytotoxicity among all resins were observed after one week and 1 hour of immersion in water, respectively. CONCLUSION: All the tested resins induced some degree of cytotoxicity. Cytotoxicity of Futura Gen, GC Reline Hard and Meliodent resins failed to show any significant reduction from 24 hours to one week. Thus, it is recommended to immerse the dentures in water for 24 hours prior to delivery to the patient.

Congenital Insensitivity to Pain with Anhidrosis (CIPA): A Case Report.

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare disorder characterized by episodes of fever and the inability to sense of pain despite the fact that all other sensory modalities remain intact or minimally impaired. The patient also may exhibit the signs of self-mutilation, mental retardation and little or no perspiration. We present a 10 years old Iranian patient diagnosed with CIPA with the above-mentioned clinical characteristics. The prosthetic treatment and the subsequent six month follow-up are discussed. Follow-up of the patient revealed that, with the use of this prosthesis, the patient's oral function and esthetics were established and the mouth lesions improved. Therefore especial dental management of CIPA patients according to their mental status, age, oral and dental condition is essential for solving the specific problems each case may present and the full mouth teeth extraction should be considered as the last treatment.

Experimental kerosene poisoning in goats.

Eighteen young native male and female goats were divided into 3 equal groups. Kerosene was given to Groups 1, 2 and 3 as single doses of 10, 20 or 40 ml/kg bw respectively. Clinical signs In-Group 1 were mild behavioral changes and in Group 2 were mild to moderate bloat, coughing and behavioral changes. None of the goats of Groups 1 and 2 died. Goats of Group 3 had severe signs of poisoning and died within 4 h to 11 d after dosing with clinical signs of severe bloat, frequent coughing, vomiting, and expelling of kerosene from the mouth and nose. Star-gazing, depression, recumbency and dyspnea also occurred. Postmortem changes in Group 3 were gangrenous pneumonia, pleuropneumonia, congestion in brain and kidney, perivascular and perineuronal edema in brain tissue, and renal nephrosis.