PURPOSE: The aim of this study was to evaluate the effects of abutment diameter, cement type, and re-cementation on the retention of implant-supported CAD/CAM metal copings over short abutments. MATERIALS AND METHODS: Sixty abutments with two different diameters, the height of which was reduced to 3 mm, were vertically mounted in acrylic resin blocks with matching implant analogues. The specimens were divided into 2 diameter groups: 4.5 mm and 5.5 mm (n=30). For each abutment a CAD/CAM metal coping was manufactured, with an occlusal loop. Each group was sub-divided into 3 sub-groups (n=10). In each subgroup, a different cement type was used: resin-modified glass-ionomer, resin cement and zinc-oxide-eugenol. After incubation and thermocycling, the removal force was measured using a universal testing machine at a cross-head speed of 0.5 mm/min. In zinc-oxide-eugenol group, after removal of the coping, the cement remnants were completely cleaned and the copings were re-cemented with resin cement and re-tested. Two-way ANOVA, post hoc Tukey tests, and paired t-test were used to analyze data (α=.05). RESULTS: The highest pulling force was registered in the resin cement group (414.8 N), followed by the re-cementation group (380.5 N). Increasing the diameter improved the retention significantly (P=.006). The difference in retention between the cemented and recemented copings was not statistically significant (P=.40). CONCLUSION: Resin cement provided retention almost twice as strong as that of the RMGI. Increasing the abutment diameter improved retention significantly. Re-cementation with resin cement did not exhibit any difference from the initial cementation with resin cement.
Cementation ; Dental Cements ; Resin Cements

Glassionomer cement used for atraumatic resto rative treatement (ART) is a simple and affordable technique for protection filling cavity in children’s teeth
Dental Restoration, Permanent ; Dental Cements

The purpose of this study was to evaluate and compare the shear bond strengths and failure sites of metal brackets bonded with chemically cured adhesive and light-cured adhesive. 10 brackets were bonded on prepared enamel surfaces with Transbond(R) (Unitek/3M; U.S.A.) light-cured orthodontic adhesive and another 10 brackets were bonded with Ortho-one(R) (Bisco: U.S.A.) chemically cured orthodontic adhesive. 24 hours after bonding, the Instron universal testing machine was used to measure the shear bond strengths. The failure sites were examined under streoscopic microscope. The results were as follows: 1. The mean shear bond strength of metal brackets bonded with light-cured adhesive was lower than that of metal brackets bonded with chemically cured adhesive, but the difference was not statistically significant (p<0.05). 2. Regardless of the type of adhesives, the brackets were failed primarily at the bracket baseadhesive interface. 3. Bonding of metal brackets with light-cured adhesive is considered to be clinically acceptable.
Adhesives* ; Dental Cements ; Dental Enamel

No abstract available.
Crowns* ; Dental Cements*

STATEMENT OF PROBLEMS: Long-term success of esthetic restorations, depends on various factors, especially on color stability of the restorations. The color stability is affected by resin cements beneath the porcelain laminate veneers. PURPOSE: The purpose of this study was to comprehend the color stability of resin cements by comparing with 4 different kinds of resin cements (Choice, Variolink II, Nexus 2, Rely-X). MATERIAL AND METHODS: Porcelain laminate disk samples were luted with resin cements. After thermocycling of each 1000, 2000 and 3000 cycle, specimens were measured by spectrophotometers and the color differences were. RESULTS: 1. After thermocycling of 1000, 2000 and 3000cycle, color difference, (deltaE*) of all specimens were incresed, but were not statiscally significant differences. 2. In the Choice of A1 shade and the Nexus 2 of A3 shade, color difference(deltaE*) after thermocycling of 3000cycle was incre*ased significantly than after thermocycling of 1000cycle. However, other groups did not show any statistically significant differences (P<0.05). 3. After thermocycling of 3000cycle, color difference(deltaE*) between A1 shade and A3 shade of Nexus 2 showed statistically significant difference. However no statistically significant differences were observed in other groups (P<0.05). 4. The mean of color difference(deltaE*) is 1.0-2.06 after 3000 thermocycling and the data were ranked in the ascending order of Variolink II, Nexus 2, Choice and Rely-X in A1 shade group and Choice, Rely-X, Variolink II and Nexus 2 in A3 shade group. CONCLUSION: Above results revealed that, after 3000thermocycing, the color difference (deltaE*) of experimental resin cements was within clinically acceptable ranges. Color stability of 4 different resin cements was comparatively excellent.
Dental Porcelain* ; Resin Cements*

Dental Cements ; Humans

No abstract available.
Dental Porcelain* ; Resin Cements*

OBJECTIVETo compare the adaptation of porcelain fused-to-metal (PFM) restorations made from Ni-Cr alloy, precious alloy and galvanized forming copings after cementation and to provide a theory guidance for their application.

METHODSThree kinds of crowns (Ni-Cr alloy, precious alloy and galvanized forming) were manufactured and cleaned by ultrasonic vibrate with alcoholic solution for 5 minutes, and cemented on their dies as their order. All the crowns were cemented by polycarboxylate zinc-cement and maintained 10 minutes. After coated in the center of methyl acrylic resins, all the samples were cut vertically along buccolingual direction. The cement thickness of PFM was measured by scanning electron microscope and the data were analyzed by multivariate ANOVA.

RESULTSNo significant difference was found between the cement thickness of precious alloy crown and galvanized forming crown (P>0.05), while both of these two kinds of crown had significant differences in cement thickness with Ni-Cr crown (P<0.05).

CONCLUSIONThe adaptation of precious alloy crown and galvanized forming crown are superior to Ni-Cr crown.

No abstract available.
Dental Porcelain* ; Hardness* ; Resin Cements*

The porpuse of this in vito study was to evaluate the effects of different acid etching times on the enamel srface morphology, shear bond strength and debinding failure mode of orthodontic attachment. Ninety six extracted human mandibular premolars were divided into eight groups of twelve teeth. The buccal surfaces were etched with 37% phosphoric acid 5, 10, 15, 30, 45, 60, 90 and 120 seconds, respectively. Two teeth from each group were used for scanning electron mocroscope examination. On the etched buccal aurfaces of remaining teeth, orthodontic attachments(lingual buttons) were bonded with light cured orthodontic adhesive. Twenty four hours after bonding, a Instron universal testing machine was used to determine shear bond strength of orhtodontic attachment to enamel. After debonding, bases of orthodontic attachments and enamel surfaces were examined under stereoscopic microscope to determine failure mode. Statistical analysis of the data was carried out with one way ANOVA and Duncan';s multiple range test. The results were as follows : 1. There was no statistically significant difference in shear bond strengths between the various etching times(p<0.05). 2. The failure modes of orthodontic attachments had some differences. In 5, 10 and 15 seconds etching groups, the percentage of adhesive/ enamel interface failure was higher than that of adhesive/attachment interface failure. On the contrary, 30, 45, 60, 90 and 120 seconds etching groups, the recults were reersed. 3. The etching parerns of enmel surfaces had a great variation. So, we could not find any correlation between etching pattern and bond strength. 4. The findings in this study indicate that in vito reduction of the etching time to 5 seconds maintains clinically acceptable bond strength. However, further study is required to determine the cause of failure mode in 5, 10 and 15 seconds groups.
Bicuspid ; Dental Cements ; Dental Enamel* ; Humans ; Tooth