[ clinical evaluation on CL II amalgam restorations failure at dental school in Yazd]

Clinical longevity is a primary concern when selecting a restorative dental material. Clinical failure is the point at which the restoration is no longer useful and may pose sever risks if not replaced. The aim of this clinical study was to evaluate the failure in CL II amalgam restorations in operative department of dental school affiliated to Shahid Sadoughi University of Medical Sciences. This was an analytic-descriptive study performed on 69 patients who were previously treated at Yazd dental school and invited to be reexamined for treated teeth. All Patients [220 teeth] with problems in their amalgam restoration were thoroughly examined under appropriate light. Evaluation criteria were direct observation, probing by explorer, dental floss, and radiography. Patients were requested to fill a questionnaire regarding a number of subjective questions and oral hygiene. Objective observations were overhang 25.5%, secondary caries 15%, improper contact 7.3%, fracture 1.4%, improper anatomic form 3.6%, ditch 3.6%, gap 0.4%, and restoration avulsion 0.5%. Regarding the subjective criteria, problems such as food impaction 13.2%, sensitivity to cold 8.2%, sensitivity to heat 5.9%, sensitivity to pressure 3.2%, gingival discomfort 3.2%, spontaneous pain 2.3%, and poor oral hygiene 15.8% were revealed. Although he difference in failure of amalgam restoration among all study groups was shown to be insignificant however, more strict supervision by dental attending concerning the proper implementation of procedures for an ideal restoration is recommended

[Effect of different methods of enamel conditioning on bond strength of orthodontic brackets]

With the introduction of different bondable restorative materials in dentistry, various methods have been suggested to enhance the polymerization and shear bond strength of these materials. The aim of this study was to determine the effects of different methods of enamel conditioning on bond strength of orthodontic brackets and on the bracket/ adhesive failure mode. In this experimental in vitro study, brackets were bonded to thirty-six bovine incisor teeth with different protocols according to the manufacturer's instructions as follows: Group 1: conventional multistep adhesive [n=12]; Group 2: self-etching primer system [n=12]; Group 3: acid+self-etching primer system [n=12]. Specimens were loaded in a universal testing machine [Instron, Canton and Mass] and the mode of failure was recorded. Data were analyzed by ANOVA and Kruskall-Wallis tests with p<0.05 as the limit of significance. The mean shear bond strength was 11.7 +/- 4.2, 10.5 +/- 4.4, and 10.9 +/- 4.8 MPa for group 1, 2, and 3 respectively. There was no significant difference in bond strength among the three groups [P=0.800]. No significant difference was observed among the three groups with respect to residual adhesive on the enamel surfaces [P=0.554]. Based on the results of the present study, the use of self-etching primers may be an alternative to conventional phosphoric acid pre-treatment in orthodontic bonding

invitro evaluation of the effect of 10% carbamide peroxide on microleakage of two types of microfilled and hybrid resin composites

Composite resin restorations are widely used in dentistry. Therefore, it is important to identify possible causes of failures in this regard. The purpose of this study was to investigate the microleakage of two microfiled and hybrid resin composites following the use of 10% carbamide peroxide. In this experimental study, Class V cavities were prepared on the buccal surfaces of 150 human anterior teeth. These teeth were randomly divided into six groups and filled with two microfilled [D-E] and hybrid resin composites [B-C]. The groups B and D were kept in contact with 10% carbamide peroxide for three weeks. Likewise, groups C and E were kept in contact with the same solution for four weeks. The specimens were rinsed and sectioned after being emmersed in 0.5% buffered fushin, and the microleakage was evaluated under stereomicroscope. Kruskal-Wallis and Mann-Whitney tests as well as Hotteling trace were used to determine the significant differences between the groups. In comparison with the control group, composite microleakage was observed in all groups after emerging the samples in 10% carbamide peroxide. Microleakage was lower in the three-week group, when compared with the four-week one. However, the difference was statistically significant in the microfilled group. The microfilled composite restorations should be changed after using carbamide peroxide

[ comparison of the shear bond strength of self-etch systems in superficial and deep dentin]

The appearance of superficial and deep dentin differs and this may affect the bond strength of adhesive system. The aim of this study was to evaluate the shear bond strength of superficial and deep dentin using self-etch system. This in vitro and experimental study was done on 48 human extracted premolar teeth. After mechanical cleaning, they were disinfected with hypochlorite 5.25% and the roots mounted in acrylic resin. Teeth were divided into 4 groups: A, B, C, D. In A and B groups, buccal surface was reduced until dentino-enamel junction [DEJ]. In C and D groups, buccal surface was reduced 3 mm deeper than DEJ. We used 2 groups of setf-etch systems: Prompt-Lpop and Prime and Bond NT. Prompt-Lpop was used in A and C groups, and Prime and Bond NT was used in B and D, according to their manufacturers' instructions. Pieces of composite with 1.5 mm diameter and 2 mm height were bonded on treated buccal surface of teeth. Finally specimens were loaded to failure in a universal testing machine at a crosshead speed of 1mm/min. The two-way analysis of variance was used for comparing the shear bond strength among the various groups. The mean value of shear bond strength of Prompt-Lpop in superficial dentin was 26.42 +/- 3.40 MPa and in deep dentin was 11.83 +/- 2.62, and of Prime and Bond NT in superfacial dentin was 24.33 +/- 4.70 MPa and in deep dentin was 12.91 +/- 2.21. The mean value of shear bond strength of superficial dentin was 25.37 +/- 4.10 MPa and deep dentin was 12.35 +/- 2.42 Mpa. Statistical analysis of the data showed that there was not a significant difference in shear bond strength between Prompt-Lpop and Prime and Bond NT [P=0.613]. There was a statistically significant difference in shear bond strength between superficial and deep dentin in each self etch system separately. According to data analysis conservative cavity preparation with less depth is recommended for efficient restoration when using self etchant dentin adhesive systems

[ effect of light-curing time to adhesive layer on shear bond strength of composite to dentin]

For reducing light exposure time of tooth-colored restorations, and chair time reduction, different experiments have been conducted. The purpose of this study was to determine the effect of different light exposure times to adhesive layers [Excite and Prompt L-pop] on the shear bond strength of dentincomposite interface. In this in-vitro study, 72 human intact premolar teeth were mounted in acrylic casts and enamel buccal surfaces were removed. The bonding surfaces were equalized using a surface index. Teeth were divided into six equal groups each of 12 [A, B, C, D, E, and F]. According to the manufacturer instructions, Excite adhesive in groups A, B and C, and prompt L-pop in groups D, E and F was used. A and D groups were not exposed to light, but the exposure time in groups B, E and C, F was 20s, and 40s respectively. After one week of storage in 37 degree C water, synergy composite resin was applied and then was exposed to light. The specimens were loaded by shear force with 1 mm/min cross head speed. Data were analyzed by two-way analysis of variance [ANOVA]. The means shear bond strength of groups A,B,C,D,E, and F were 3.9, 13.45, 18.1, 8.3, 24.81, 24.99 Mpa, respectively. The differences between shear bond strength of groups A, B and C and between groups B, D were statistically significant [p=0.0001]. However, the differences between groups E, F were not statistically significant. In all exposure times, the bond strength of Prompt L-pop was significantly higher than that of Excite. According to the results of this study, increase in the light exposure led to the higher bond strengths in Excite groups. In Prompt L-pop groups, 20s exposure time was adequate and by increasing the light exposure time, shear bond strength was not affected. Without light exposure in both materials, the least bond strength for the composite resins was not attainable

Microleakage comparison of polyacid composite resin restorations and resin modified glass ionomer before and after ultrasonic scaling

In different investigations, the destructive effect of ultrasonic sealers on the margins of composites has been studied, but there are very few studies on the effects of ultrasonic sealers on the microleakage of poly-acid modified composite resin and resin modified glass ionomers. The main purpose of this study was to evaluate the marginal microleakage of class V preparations restored with resin modified glass ionomer and poly-acid modified composite resin before and after scaling with an ultrasonic sealer. This in vitro study was performed on 160 premolar teeth. Standard class V cavities were prepared on the buccal surfaces of the selected teeth. Occlusal and cervical margins were placed entirely in enamel and cementum, respectively. Teeth were randomly divided to two groups of eighty, each. For one half of each group, [40 teeth] resin modified glass ionomer and for the other half, polyacid modified composite resin was used. Each one of the binary groups was subdivided to two groups. First subgroup was restored with Fuji II Lc [Fuji Japan] and Vitremer [3M USA] and the second subgroup was restored with F[2000] compomer [3M USA] and Compoglass[Vivadent Germany]. For bonding to enamel, dentinte,cementum Singlebond [3M USA] and Adhese 2 [Vivadent Germany] were used and all of the restorations were done according to instructions of the manufacturers. In ten teeth of each group, ultrasonic scaling was done and in the other ten teeth, scaling was not done. After that, all of the teeth were thermocycled and immersed in fuschin. After cutting the microleakage was evaluated. The data was analyzed by Mann - Whitney, Kruskal - Wallis and Wilcoxon tests and significant border was 0.05. The results showed that the degree of microleakage in enamel margins of poly -acid modified resin composites was lower than resin modified glass ionomers and in all groups and subgroups, the microleakage in enamel and cementum after scaling was significantly more than the groups without scaling. Use of resin modified glass ionomers in class V restorations has no advantages over polyacid modified composite resins