Wear effect of different abrasive materials on tooth enamel: a comparative study

Objectives: The purpose of the study was to measure and compare mean enamel loss caused by microabrasion treatment of different abrasive materials under a fixed variable

Materials and Methods: In this laboratory study, three commonly used abrasive materials were compared: Dental Pumice, Zircate® Prophy Paste, Opalustre® and a controlled group [distilled water]. Hundred extracted human premolars were randomly allocated into four groups; each group was subjected to fixed pressure, time and rotational speed mimicking dental office setting

Results: Data was collected and statistically analyzed. The results of the study [p < 0.01] was statistically significant and showed that Opalustre® caused the highest mean difference in enamel loss. Followed by dental Pumice and Prophy paste in order with minimal difference between them. And the controlled group [distilled water] had the least mean enamel loss

Conclusion: microabrasion offers a great approach in treating enamel defect/staining in a minimally invasive procedure in order to achieve acceptable aesthetic results while preserving the tooth's microstructure as much as possible. As shown in the result; Combined chemical acid with mechanical abrasive particles produce most effective results

Molecular characterization of methicillin-resistant Staphylococcus aureus recovered from outpatient clinics in Riyadh, Saudi Arabia

To examine the recovered strains phenotypically, by conventional methods and genotypically by polymerase chain reaction [PCR], for direct detection of Staphylococcus aureus [S. aureus] 16S ribosomal Ribonucleic Acid [rRNA] gene [which serves as an internal control] and mecA gene. Secondly, introduce multiplex PCR targeting at the same time S. aureus 16S rRNA, Panton-Valentine Leucocidin [PVL], and staphylococcal cassette chromosome mec [SCCmec] type IV. Thirty-seven strains of S. aureus collected in 2007 from outpatient clinics in King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia, were tested in the College of Pharmacy phenotypically by conventional methods and genotypically by PCR for direct detection of S. aureus 16S rRNA and mecA genes. All the 37 strains, were tested also by multiplex PCR targeting at the same time S. aureus 16S rRNA, PVL, and [SCCmec] type IV. Polymerase chain reaction detected all the 37 bacteriologically positive S. aureus [100%] and the mecA gene in all strains phenotypically resistant to methicillin [100%], at the same time it detected the mecA gene in 2 strains phenotypically sensitive to methicillin. Only 3 strains [8.1%] recovered from skin and soft tissue infections were positive for PVL and SCCmec type IV. The PCR assay can be used for rapid detection of S. aureus and mecA gene. At the same time the multiplex PCR assay explained in this study is a rapid, sensitive, and reliable test for direct detection of community-acquired methicillin-resistant S. aureus

influence of dentin bonding agent on the fluoride uptake by the tooth structure from restorative materials

Objectives: To show the depth of fluoride uptake by the tooth structure from a restorative and dentine bonding agent material using a wavelength dispersive X ray analysis [WDX] at Oum, lOOum and 200um from the surface of a restoration, as well as the degree to which the dentine bonding agent prevented the passage of this fluoride released

Material and methods: Six human premolars teeth scadueled to be extracted for orthodontic treatment were used in this study. Two it was filled with the Rite-Dent composite, while the distal cavity was filled with the Dyract AP composite. Half of the teeth was filled with both composites directly without the use of bonding agent. The other half was subjected to the routine bonding technique. All teeth were stored in distilled water at 37°C for one month before they were tested. The fluoride concentration was measured using wavelength dispersive x-ray analysis [WDX] at Oum, l00microm and 200um from the surface of a restoration

Results: At Oum the cavities restored with Dyract AP with and without the application of adhesive Prim and Bond NT gave the highest fluoride uptake values and are insignificantly different from each other while that restored with Rite-Dent composite with and without application of adhesive were insignificantly different from each other and gave a lower values. At 100 um and 200microm the cavities restored with Dyract AP without the application of adhesive was significantly different from all cavities and gave the highest fluoride uptake values. Conclusion: 1- The amount of fluoride uptaked by the tooth structure depend upon the fluoride present in the restoration as well as the ability of the dentine to uptake this fluoride. 2- The concentration of fluoride uptaked by the tooth structure dropped as the sites were moved further away from the cavity wall. 3- The dentin bonding agent systems do not prevent the passage of fluoride to the tooth structure

Retentive capability of luting materials to fiber reinforced posts at cjement/radicular dentin interface

This study was concerned with the evaluation of retentive capability of the luting materials namely; adhesive composite resin and glass ionomer cements along the bonded length of fiber reinforced posts with radicular dentin. As well as, characterization of the type of the bond at cement/ dentininterface. Ten single rooted maxillary anterior teeth free of defects were decapitated. An endodontic mechanical preparation was performed followed by post space preparation of 9 mm length. Five root canals were acid etched, adhesive resin was applied to dentin substrate and then the posts were luted with light cured composite resin. The other five root canals were irrigated by 2.5% NaOCl and then posts were luted by glass ionomer cements. Each root was cut transversely to obtain three specimens: cervical, middle and apical sections of 3 mm thickness each. For SEM study: two roots were decapitated, endodontically prepared and then post holes were drilled. One of the root canal of these roots was acid etched and the other one was irrigated with 2.5% NaOCl. Both roots were sectioned longitudinally and photomicrographed at X 1500. Also, two specimens luted with the two investigated cements were photomicrographed after dislodgement of the posts by mechanical testing. enerally, both luting materials showed significant difference of the retention bonding strength among their three sections of the roots. The cervical section recorded the highest significant value while the apical section recorded the least significant value. Luting with glass ionomer cement showed higher significant retention strength values in middle and apical sections when compared with the corresponding ones luted with adhesive resin composite cement but comparison of the cervical sections of both groups showed higher insignificant difference. SEM study of acid etched den-tin surface showed widened dentinal tubules and severe rugosity and an adhesive failure was evident after mechanical testing of posts luted with adhesive composite resin cement suggesting mechanical interlocking attachment of this cement to radicular dentin. Meanwhile, more solid dentin and narrow orifices of the dentinal tubules was observed after irrigation with 2.5% NaOCl and a cohesive failure of the glass ionomer cement after mechanical testing suggesting stronger chemical bonding to the dentin substrate

Surface roughness assessment of selected direct cosmetic restorative materials at different ph challenges

The ideal dental restorative material and associated techniques continue to be the goal of materi- scientists and clinicians alike. The [gold standard] for restoration quality is considered to be its long term performance in clinical service. However, laboratory tools are useful as indicators of the clinical performance of restorations. An increase in surface roughness has been used as a criterion to assess and predict the clinical deterioration of restorations of different types of material. This study was conducted to assess surface roughness of four direct cosmetic restorative materials; a resin modified glass ionomer [Photac-Fil], a compomer [Dyract], a flowable resin composite [Tetric Flow] and a packable composite [Tetric Ceram HB] at different storage media. A total of 60 disc-shaped specimens [2x2 mm] were prepared, 15 for each material. Baseline surface roughness measurement [Ra value] was performed using image analysis method. Then, each group was divided into three sub groups [n = 5] according to the pH of the storage media used pH 2.5, pH 4 and pH 6.8. Surface roughness assessment was performed using the same method after a storage period of three months. Data were submitted to Duncan's Multiple Range Test to identify significant difference in Ra values among the variables analyzed [restorative materials and storage media]. The results showed no significant difference between restorative materials tested at baseline measurements. However, after the storage period all restorative materials showed a significant increase in surface roughness [Ra value] in all pH storage media compared to baseline Ra measurements. Regarding the pH storage media, a statistically significant difference was found in Ra value of all restorative materials. Increase in acidity of the storage media, increases the surface roughness of the restorative materials. While regarding the restorative material interaction, at pH 4 and at pH 6.8 no significant difference in Ra values was revealed between any of the restorative materials. However, at acidic pH 2.5 packable composite showed a significantly higher mean Ra value than that of compomer and flowable composite. It was therefore concluded that, pH challenge of direct cosmetic restorative materials* remarkably increased the surface roughness of all restorative materials tested, especially at acidic pH. Moreover, the effect of pH on the surface roughness of the materials was not material-dependent except at highly acidic challenge. Clinical Relevance An acidic oral environment may adversely affect long-term clinical performance of direct esthetic restoratives. Careful selection of restorative materials is crucial in patients with history of gastric flux, eating disorders or increased consumption of dietary acids. All current cosmetic restoratives require ongoing maintenance, including periodic repolishing

effect of different immersion media on the color stability of ceramic optimized polymer with different thickness

Aim: The purpose of this in vitro study was to evaluate the color change [AE] of 3 shades of a ceramic optimized polymer veneering composite resin material [Targis] at different thickness [1 and 2 mm] after immersion in distilled water, pH4 and tea solutions for 30 days

Materials and Methods: A total of 54 Targis dentin discs were divided into three equal groups; 18 discs each to be covered with one of the used enamel shades. According to the thickness of Targis enamel layer applied to the surface, each group was further subdivided into two equal subgroups of 9 each. The first subgroup had 1mm thickness of enamel shade while the second had 2 mm thickness. For each subgroup its samples were assigned, coded and stored for 30 days in three different storage media: three samples stored in distilled water at 37°C to be used as control group, another three samples were stored in pH4 that represents the pH of the plaque accumulation and the last three samples were immersed in tea at 55-60°C for 4-6 hours daily. At the end of storage time, the calorimetric measurements L, a and b were determined using scanning spectrophotometer and the color change [AE] was calculated

Results: L values of the samples stored in pH4 were comparable to those of control group. Meanwhile, L values of samples stored in tea showed marked decrease i.e darker appearance, a values of samples stored either in distilled water or pH4 showed a change in the range of +/- 1 while those samples stored in tea had high +ve a value indicating increased chromaticity of red color, b values of samples stored in tea showed the highest yellowish discoloration +ve b except for shade 2 in thickness 2mm. Color change [AE] of transparent enamel layer immersed in pH4 showed clinical acceptability in both thickness as well as those of shade 2 in 1 mm thickness, where AE < 3.3. Shade 2 in 2mm thickness and shade 3 in both thickness revealed clinical unacceptability of AE. Immersion of Targis in tea resulted in very high AE i.e. obvious color change of all shades and in both thickness. Conclusion: Targis with different tested shades and using 1 and 2 mm thickness revealed the greatest shift to yellow +ve b and redness +ve a as well darker appearance [less L value] when immersed in tea. The decreased lightness was also obtained when the thickness of Targis enamel layer was increased. The resultant color crmnge [AE] due to immersion in tea was always prominent and clinically unacceptable. Meanwhile, immersion in pH 4 gave clinically acceptable color change AE < 3.3 with transparent shade and some thin translucent shades