Purpose: To evaluate tooth preparation for full veneer cast restorations performed by final year dental students in Sudan. Materials and Methods: 117 stone dies from two different dental institutions were collected an...Purpose: To evaluate tooth preparation for full veneer cast restorations performed by final year dental students in Sudan. Materials and Methods: 117 stone dies from two different dental institutions were collected and evaluated. Polyvinylsilioxane impression material was used to produce two impressive replicas of which one was sectioned in faciolingual plane and the other in mesiodistal plane. Occlusal clearance was measured using a digital caliper. Amount of axial preparation was also measured. Impression silhouettes that were produced using an overhead projector were used to measure convergence angle. Working casts were examined for smoothness and evenness of the preparations, existence or absence of additional features of retention and the finishing line were evaluated for its position and continuity. All obtained data were statistically analyzed by using T-test, ANO-VA, and Pearson Chi square tests. P-values ≤ 0.05 were considered as statistically significant. Results: Average taper of the examined preparations was 39.98?, with 44.1? in the faciolingual, and 35.8? in the mesiodistal dimensions. Preparations for full coverage restorations were over prepared. 38.5% of the total number of preparations were found to have finishing lines in the sub and supra gingival positions. 19.66% were unable to maintain continuity of the finishing line all around the preparation. All preparations were generally smooth with no sharp angles, and 1.7% of the preparations had additional retentive features. Conclusion: Within the limitations of this study, it could be concluded that the convergence angle and finishing line preparations were less than adequate in a sizeable proportion of the preparations examined.展开更多
Purpose: To evaluate the quality of the composite restorations. Material and Methods: A total of 246 composite restorations in 125 patients attending the Conservative Dentistry Clinics at the Faculty of Dentistry, Uni...Purpose: To evaluate the quality of the composite restorations. Material and Methods: A total of 246 composite restorations in 125 patients attending the Conservative Dentistry Clinics at the Faculty of Dentistry, University of Khartoum were examined. Both anterior and posterior composite restorations were included. California Dental Association Quality Evaluation System was used for the evaluation. Results: Fifty two percent of all restorations were found to be satisfactory, while the remaining 48% were not satisfactory. With regard to surface and colour criteria, colour mismatch within the range (34.8%) and slight surface roughness (26.6%) were the most common defects. The most frequent defects of the anatomical form were restoration overhang (26.8%). The majority of the restorations above 4 years old were of unacceptable anatomical form (66.7%), and their marginal integrity was less acceptable than more recent restorations (46.7%). Conclusions: Forty eight percent of the examined composite restorations needed to be replaced, and the unacceptable anatomic form was the main cause of failure of composite restorations.展开更多
Aim: To investigate the bond strengths achieved by using a Bleaching Curing Light (BCL) to polymerize orthodontic bonding cement. Material and Methods: 160 anterior bovine teeth were used to form 20 average sized huma...Aim: To investigate the bond strengths achieved by using a Bleaching Curing Light (BCL) to polymerize orthodontic bonding cement. Material and Methods: 160 anterior bovine teeth were used to form 20 average sized human dental arches, and distributed into 2 groups according to which light curing method used: Group 1: BCL for 40 seconds, or Group 2: LED for 10 seconds. After storage in a controlled environment, Shear Bond Strength (SBS) and Adhesive Remnant Index (ARI) were determined. Results: Group 1 showed significantly lower SBS in the most posterior (first molar) position of the dental arch, (Group 1: 0.7 ± 1.0 MPa, Group 2: 2.9 ± 1.7 MPa, p Conclusion: Simultaneous full-arch curing of orthodontic bracket cement using a BCL is clinically acceptable in all but the most posterior locations along the dental arch.展开更多
Background: Effective polymerization of the composite resin is essential to obtain long term clinical success and has a great importance obtaining improved mechanical properties. The purpose of this study was to measu...Background: Effective polymerization of the composite resin is essential to obtain long term clinical success and has a great importance obtaining improved mechanical properties. The purpose of this study was to measure the effect of the light intensity of LED and QTH curing devices in relation to the light distances, on the hardness (KHN) of two light cure nano-resin composite. Material and Methods: The top and bottom surfaces of the two nanofill composite specimens were evaluated. Two LED and two QTH light curing devices were used at nine different distances. Light intensity was measured with two radiometers placed at these same distances from the curing tip. 360 pvc dies were prepared with circular cavity 3 mm in diameter and 2 mm thick. The tested materials were placed in each cavity. The different light curing distances were standardized by adding pvc spacers dies at different height matching the different distances. Top and bottom surface microhardness were evaluated with a Micro Hardness Tester in knoop hardness numbers (Kg/mm2). Data were statistically analyzed using: Three-way ANOVA, Tukey and Pearsons test. Results: It was revealed that there was a statistically significant difference in microhardness between the composites (p < 0.001), between the nine distances (p < 0.001) and between the four light curing devices (p < 0.001). Increasing the distance of the light source from composite resin, the light intensity and the microhardness values at the top and bottom surface decrease. LED light curing devices produced a greater microhardness results at the bottom surface of the specimens. The Filtek Ultimate nanocomposite (3 m) showed highest microhardness values on the top and bottom surfaces, polymerized with all four curing devices and all nine distances compared to Empress Direct nano composite (Ivoclar vivadent). Clinical significant: Even with high power LED curing light, the distance between the tip of the light source and the restoration surface should be as close as possible. In this study, Filtek Ultimate showed better results (highest microhardness values) than Empress Direct.展开更多
文摘Purpose: To evaluate tooth preparation for full veneer cast restorations performed by final year dental students in Sudan. Materials and Methods: 117 stone dies from two different dental institutions were collected and evaluated. Polyvinylsilioxane impression material was used to produce two impressive replicas of which one was sectioned in faciolingual plane and the other in mesiodistal plane. Occlusal clearance was measured using a digital caliper. Amount of axial preparation was also measured. Impression silhouettes that were produced using an overhead projector were used to measure convergence angle. Working casts were examined for smoothness and evenness of the preparations, existence or absence of additional features of retention and the finishing line were evaluated for its position and continuity. All obtained data were statistically analyzed by using T-test, ANO-VA, and Pearson Chi square tests. P-values ≤ 0.05 were considered as statistically significant. Results: Average taper of the examined preparations was 39.98?, with 44.1? in the faciolingual, and 35.8? in the mesiodistal dimensions. Preparations for full coverage restorations were over prepared. 38.5% of the total number of preparations were found to have finishing lines in the sub and supra gingival positions. 19.66% were unable to maintain continuity of the finishing line all around the preparation. All preparations were generally smooth with no sharp angles, and 1.7% of the preparations had additional retentive features. Conclusion: Within the limitations of this study, it could be concluded that the convergence angle and finishing line preparations were less than adequate in a sizeable proportion of the preparations examined.
文摘Purpose: To evaluate the quality of the composite restorations. Material and Methods: A total of 246 composite restorations in 125 patients attending the Conservative Dentistry Clinics at the Faculty of Dentistry, University of Khartoum were examined. Both anterior and posterior composite restorations were included. California Dental Association Quality Evaluation System was used for the evaluation. Results: Fifty two percent of all restorations were found to be satisfactory, while the remaining 48% were not satisfactory. With regard to surface and colour criteria, colour mismatch within the range (34.8%) and slight surface roughness (26.6%) were the most common defects. The most frequent defects of the anatomical form were restoration overhang (26.8%). The majority of the restorations above 4 years old were of unacceptable anatomical form (66.7%), and their marginal integrity was less acceptable than more recent restorations (46.7%). Conclusions: Forty eight percent of the examined composite restorations needed to be replaced, and the unacceptable anatomic form was the main cause of failure of composite restorations.
文摘Aim: To investigate the bond strengths achieved by using a Bleaching Curing Light (BCL) to polymerize orthodontic bonding cement. Material and Methods: 160 anterior bovine teeth were used to form 20 average sized human dental arches, and distributed into 2 groups according to which light curing method used: Group 1: BCL for 40 seconds, or Group 2: LED for 10 seconds. After storage in a controlled environment, Shear Bond Strength (SBS) and Adhesive Remnant Index (ARI) were determined. Results: Group 1 showed significantly lower SBS in the most posterior (first molar) position of the dental arch, (Group 1: 0.7 ± 1.0 MPa, Group 2: 2.9 ± 1.7 MPa, p Conclusion: Simultaneous full-arch curing of orthodontic bracket cement using a BCL is clinically acceptable in all but the most posterior locations along the dental arch.
文摘Background: Effective polymerization of the composite resin is essential to obtain long term clinical success and has a great importance obtaining improved mechanical properties. The purpose of this study was to measure the effect of the light intensity of LED and QTH curing devices in relation to the light distances, on the hardness (KHN) of two light cure nano-resin composite. Material and Methods: The top and bottom surfaces of the two nanofill composite specimens were evaluated. Two LED and two QTH light curing devices were used at nine different distances. Light intensity was measured with two radiometers placed at these same distances from the curing tip. 360 pvc dies were prepared with circular cavity 3 mm in diameter and 2 mm thick. The tested materials were placed in each cavity. The different light curing distances were standardized by adding pvc spacers dies at different height matching the different distances. Top and bottom surface microhardness were evaluated with a Micro Hardness Tester in knoop hardness numbers (Kg/mm2). Data were statistically analyzed using: Three-way ANOVA, Tukey and Pearsons test. Results: It was revealed that there was a statistically significant difference in microhardness between the composites (p < 0.001), between the nine distances (p < 0.001) and between the four light curing devices (p < 0.001). Increasing the distance of the light source from composite resin, the light intensity and the microhardness values at the top and bottom surface decrease. LED light curing devices produced a greater microhardness results at the bottom surface of the specimens. The Filtek Ultimate nanocomposite (3 m) showed highest microhardness values on the top and bottom surfaces, polymerized with all four curing devices and all nine distances compared to Empress Direct nano composite (Ivoclar vivadent). Clinical significant: Even with high power LED curing light, the distance between the tip of the light source and the restoration surface should be as close as possible. In this study, Filtek Ultimate showed better results (highest microhardness values) than Empress Direct.