The effect of gingival wall location on the marginal seal of class ii restorations prepared with a flowable bulk-fill resin-based composite.

SureFil SDR is a flowable resin-based composite that allows a single incremental bulk placement. The marginal seal of SureFil SDR at the gingival margins of class II restorations located apical to the cemento-enamel-junction (CEJ) has not been adequately evaluated compared to those located occlusal to the CEJ. Forty class II cavities were prepared in human molars. The gingival margins of 20 preparations were located 0.5 mm occlusal to the CEJ, and the other 20 preparations were located 0.5 mm apical to the CEJ. The cavities surfaces were bonded with XenoV dental adhesive and filled with SDR in one bulk increment up to 4 mm, after which they were covered with CeramX. The teeth were subjected to thermo-and load-cycling, and their gingival margins were exposed to 0.5% basic-fuchsin solution. The specimens were sectioned mesio-distally and scored for microleakage. A Wilcoxon test for pairwise comparison was performed to determine significance. Dye penetration was observed in 30% of the 20 restorations with cavo-surface margins located occlusal to the CEJ and in 55% of the 20 restorations with cavo-surface margins located apical to the CEJ. The bulk-fill flowable resin base SureFil SDR with XenoV dental adhesive provided a better marginal seal in class II restorations with gingival margins above the CEJ compared to restorations with gingival margins below the CEJ. SDR should not be recommended for class II cavity preparations with gingival margins located below the CEJ.

Efficient procedure for grapevine embryogenic suspension establishment and plant regeneration: role of conditioned medium for cell proliferation.

An efficient system for the establishment and multiplication of highly prolific embryogenic cell cultures of grapevine (Vitis sp.) was developed. Using anther-derived pro-embryogenic masses as starting material, cell suspensions of different grapevine cultivars (Tempranillo, Cabernet-Sauvignon) and rootstocks (Kober 125 AA, Kober 5 BB, 110 Richter) were initiated in liquid medium containing NOA (1.0 mg l(-1)) and BAP (0.25 mg l(-1)) as growth regulators. Conditioned medium was recovered and utilised for establishing new, highly totipotent cell cultures. The suspensions obtained, showed embryogenic competence resulting in somatic embryo induction and subsequent plant regeneration. In this study, a simplified establishment procedure for grapevine embryogenic cell suspension allowing the fast multiplication of embryogenic material is described. Evidence for the promoting effect of the protein fraction derived from conditioned medium, on cell proliferation was found. In bioassays, addition of ss-D: -GlcY affect cell proliferation suggesting that arabinogalactan proteins are required for growth processes in grapevine cell cultures.

Effect of preliminary treatment of the dentin surface on the shear bond strength of resin composite to dentin.

This study evaluated the effect of two dentin disinfectants (Consepsis, Tubulicid), one aqueous HEMA solution (Aqua Prep), a combination of Aqua Prep and Tubulicid and an air abrasion treatment (50 microns aluminum oxide) on the shear bond strength (SBS) of two acetone-based single bottle adhesives (One Step and Prime & Bond 2.1). The occlusal surfaces of 167 freshly extracted human third molars were ground flat to expose the dentin, then polished with a 600 grit-polishing disc. The teeth were randomly assigned to 12 test groups (two bonding agents, six pretreatment protocols). The exposed dentin was etched with 35% phosphoric acid for 20 seconds, rinsed and briefly (1-2 seconds) air dried. Six pretreatment protocols were then applied. The air abrasion groups were exceptional, as etching was carried out only after pretreatment. One Step, or Prime & Bond 2.1 was applied according to the manufacturer's instructions. Cylinders of Z-100 composite were bonded to the flat dentin surfaces by transparent gelatin capsules. Specimens were thermocycled in water baths between 5 degrees and 55 degrees C, then sheared in an Instron Testing Machine. One-way and two-way ANOVA and Tukey HSD post-hoc tests were used for statistical analysis. In the One Step group, Consepsis yielded a significantly higher SBS (17.8 MPa) than air abrasion (9.5 MPa), Control (11.8 MPa) and Aqua Prep + Tubilicid (11.9 MPa), and a comparable SBS with Tubilicid (12.5 MPa) and Aqua Prep (14.8 MPa). In the Prime & Bond 2.1 group, Aqua Prep (24.9 MPa) showed a significantly higher SBS than all other groups: air abrasion (9.3 MPa), Control (9.97 MPa), Tubilicid (12.2 MPa), Consepsis (13.0 MPa) and Tubilicid + Aqua Prep (13.3 MPa).

Improving the seal of amalgam cores with cemented dowels: a comparative in vitro radioactive tracer study.

Amalgam cores with cemented dowels are commonly used to restore endodontically treated teeth. These restorations were widely studied for their mechanical properties; however, less is known about their sealing ability. The effect of the cement type used for the dowel and that of a bonding agent application were studied in a radioactive tracer coronal leakage study. The sealing ability of posts and cores was also compared with that of 5 mm remaining root canal fillings. Composite luting cement provided a better seal than zinc phosphate cement. The seal provided by 5 mm root canal fillings was poorer than that provided by posts and cores. High variability in seal quality was found among all types of posts and cores studied. This may indicate that the seal provided by cemented dowels with amalgam cores is unpredictable. Because neither the remaining root canal filling nor the post and core may be trusted alone for a seal, each should be performed with the greatest care and both covered with a crown as soon as possible.

Effect of repeated vertical loads on microleakage of IRM and calcium sulfate-based temporary fillings.

Temporary fillings are commonly used to seal endodontic access cavities between visits. IRM and Cavidentin were selected to represent two widely used groups of temporary filling materials. The first is a reinforced zinc oxide-eugenol preparation that is mixed at chairside, whereas the second is a ready-to-use calcium sulfate-based material that gained popularity due to its convenience of application. The seal provided by the aforementioned materials was studied using a radioactive tracer quantitative assay. When compared as passive temporary filling, the two provided a similar quality of seal. However, when subjected to repetitive "occlusal" cyclic loading of 4 kg, IRM was clearly superior to the calcium sulfate-based material. Whereas IRM maintained a reasonable seal, the calcium sulfate-based fillings deteriorated and lost the ability to seal. These results suggest that even though calcium sulfate-based materials may be useful when not subjected to any occlusal forces, IRM should be preferred whenever occlusal loads may be applied. Furthermore it is demonstrated that testing such materials for microleakage with no reference to mastication forces may be of limited value.

pH changes of glass-ionomer lining materials at various time intervals.

The purpose of this in vitro study was to evaluate pH changes of resin modified glass-ionomer (RMGI) and conventional glass-ionomer liners at short-term intervals after mixing to relate the timing of light activation on the acidity of RMGI lining materials. The RMGI liners tested were Vitrebond (3M), Variglass VLC (Dentsply), Fuji Lining LC (GC Dental Industrial Corp.) compared to a traditional glass-ionomer liner: Lining Cement (GC, control). Light activation of liners was carried out at different time intervals after mixing. The pH changes of each liner were evaluated immediately after mixing and thereafter every minute for 8 min using a surface pH meter. All liners tested exhibited a gradual increase in surface pH over time. The delay of light activation of RMGI lining materials after mixing did not significantly decrease the acidity of the liner during the first 9 min post-mixing.

Comparison of microleakage for three one-bottle and three multiple-step dentin bonding agents.

PURPOSE: This in vitro study compared the ability of several recently introduced 1-bottle adhesives to their preceding multiple-step dentin bonding agents in reducing microleakage around Class V composite restorations. MATERIAL AND METHODS: Facial and lingual Class V cavities were prepared in 48 molar teeth, which were randomly divided into 6 equal groups. Three groups used the fourth-generation multiple-step systems, and 3 used the fifth-generation single-bottle adhesives. All cavities were restored by composite and subjected to thermocycling and intermittent occlusal loading. After immersion in 0.5% basic fuchsin, the teeth were cut faciolingually in 5 consecutive sections and evaluated for dye penetration using a binocular stereomicroscope. RESULTS: There was no statistically significant difference in the degree of microleakage comparing the adhesive's generation and manufacturer and the location of the cavity margins. A significant interaction was found between margin location and manufacturer, which implied that the sealing capacity at the enamel and cementum margins was material-specific. CONCLUSION: Scotchbond Multi-Purpose and Single Bond adhesives provided the best seal for enamel margins, and One-Step and Optibond FL adhesives were best for cementum margins.

Marginal seal of composite inlays using different polymerization techniques.

The effect of indirect and semi-direct curing systems of Cl II composite inlays on microleakage was investigated in vitro and compared to conventional direct posterior composite restorations. Nearly identical Cl II cavities were restored with the same composite resin using different polymerization systems. Microleakage assessment was carried out after cyclic loading and thermal stressing by assessing the dye penetration. The data showed that all inlay techniques resulted in improved marginal sealing compared with conventional restorations. However, the indirect procedure resulted in significantly reduced microleakage compared to the semi-direct inlay techniques.

Reduction of microleakage in class II composite resin restorations using retentive pins.

The effect on microleakage of Bondent parapulpal pins used in class II composite resin restorations was evaluated in vitro. Bulk and incremental packing and polymerization techniques were compared, using pins anchored at the gingival cavity walls. Evaluation of microleakage was carried out following cyclic load application and an extended thermocycling procedure by the assessment of dye penetration. The results showed that the use of pins at the gingival wall of class II composite resin restorations provided significantly improved marginal sealing. The procedure should, therefore, be regarded as an effective clinical practice.

The rate of OH- ion release from lining materials containing calcium hydroxide.

Four light-cured calcium hydroxide and three chemically cured resin-based lining materials were compared for hydoxil ion (OH-) release. Results indicated that the chemically cured calcium hydroxide cements were capable of OH- release for a longer period than the light-cured resin bases. Alkaliner (a chemically cured liner) produced and maintained the highest alkaline environment in the long-term, whereas calcium fluoride liner and Basic-L (both resin-based) showed the lowest values of OH- ion release.

Antibacterial activity of three dental liners.

PURPOSE: The purpose of the present study was to assess the antibacterial activity of the following three dental liners: Vitrebond (3M, St Paul, MN), Dycal (LD Caulk, Dentsply International, Milford, DE), and Life (Kerr, Romulus, MI). MATERIALS AND METHODS: The test was based on a modification of the agar diffusion test in which samples were placed on agar plates previously inoculated with Streptococcus mutans and were removed after predetermined time periods. The material's effect on bacterial growth was evaluated. RESULTS: Results show that Vitrebond has a strong antibacterial effect that was evident after 1 minute of direct contact with the inoculated bacteria. It was significantly more effective (P<.0001) than Dycal or Life. CONCLUSIONS: This method allows for the evaluation of the antibacterial effect of dental materials.

Removal of overextended gutta-percha root canal fillings in endodontic failure cases.

A procedure is proposed for the complete removal of an overextended root canal filling when associated with a root canal treatment failure. First, the gutta-percha is softened with xylene and removed to a distance of 2 to 3 mm short of the apex. Second, the remaining gutta-percha, which is preserved as solid as possible, is removed by a Hedstrom file. The file is extended 0.5 to 1.0 mm beyond the apex, firmly engages the gutta-percha and is slowly removed. In 17 of the 18 cases, this procedure successfully removed the overextended gutta-percha.

Effect of mouthguard bleaching on enamel surface.

PURPOSE: To evaluate in vitro the effect of 10% carbamide peroxide in a mouthguard on the shear bond strength of resin composite to bleached enamel surfaces and morphological changes in these surfaces. MATERIALS AND METHODS: Thirty anterior extracted were divided into a control and a test group. Plastic trays were made for each tooth and the test group treated with Opalescence bleaching gel and incubated at 37 degrees C humid environment for 8 hours. The bleaching agent was washed and the trays replaced with water-soaked cotton wool for another 16 hours in the incubator. This procedure was repeated every day for 21 days. The control group was just treated with the water-soaked cotton wool. Selected teeth from both groups were evaluated with the SEM and 72 hours after the bleaching treatment, Scotchbond 2/Silux Plus rings were bonded to the enamel surfaces in both groups and sher bond strength testing performed. RESULTS: Bleaching created some enamel porosity and significant reduction in the resin composite shear bond strength.

The sealing of the tooth/amalgam interface by corrosion products.

A marginal gap exists between the amalgam restoration and the cavity walls. At this interface, there is a constant percolation of fluid containing ions, molecules and bacteria. With time, corrosion products of the amalgam components seal the gap at the amalgam/tooth interface. The corrosion processes for conventional and high copper amalgam and factors affecting the corrosion deposits are reviewed. Better amalgam adaptation to the cavity walls improves the chances of sealing the restoration by corrosion products. The effectiveness of cavity varnish in preventing microleakage until corrosive deposits are formed is discussed.

Long term sealing properties of Amalgambond under amalgam restorations.

The degree of microleakage at 14 days, 6 months and 1 year between Class V amalgam restorations lined with Copalite varnish or with Amalgambond was compared in this in vitro study. The restored teeth were subjected to cyclic occlusal loading, thermocycling procedures and then stored in a dye solution at the appropriate intervals. Dye penetration was assessed at the gingival and occlusal margins of the restorations. The results showed that with Amalgambond, there was significantly better sealing of the dentin tubules than with Copalite or unlined restorations (P < 0.001) at all times tested. Amalgambond showed significantly less microleakage as compared to unlined restorations (P < 0.01) at all time periods, and significantly less short-term (14 days) microleakage compared with the Copalite-lined group (P < 0.01).

The effect of porcelain color on the hardness of luting composite resin cement.

Visible light- and dual-curing composite resin luting cements were cured under porcelain disks of different colors to examine the effect of porcelain color on surface hardness. Knoop microhardness measurements were made at exposure times of 48, 72, and 120 seconds. Higher levels of hardness were obtained with dual-cured resin. Visible light-cured resin irradiated through colored porcelain required more prolonged exposure times to reach a degree of hardness approaching that of dual-cure resin. From the standpoint of microhardness, dual-cured composite resin is preferred for luting porcelain restorations of > or = 2 mm thickness.

Varnish application technique and microleakage of amalgam restorations.

Various techniques for applying two types of varnish to control microleakage of Class V amalgam restorations were compared in vitro. The drying time for each layer of varnish with a gentle air spray was varied, including delays in applying the second coat and the placement of the amalgam restoration. Microleakage was recorded by dye penetration. Both varnishes were inefficient at reducing dye penetration at the gingival wall. There were no statistical differences in dye penetration at the gingival wall between the two varnishes, regardless of the method of application, or the presence of varnish. Both varnishes exhibited good sealing properties at the occlusal wall when used according to the manufacturer's instructions, but varnish application was technique-sensitive. Short-cuts in the procedure may increase leakage; too short a drying time of either varnish can cause microleakage similar to the control group without a varnish.

The fluid-filled gap under amalgam and resin composite restorations.

This article discusses the factors involved in the formation of marginal gaps between amalgam or resin composite restorative materials and cavity walls. The fluid that penetrates the microspace from the oral cavity and from the dentinal tubules is followed by bacterial invasion. This process can lead to secondary caries and irritation of the dentin/pulp complex. The bacterial growth is controlled by effective sealing at the tooth/restoration interface, partial obliteration of the gap, accumulation of solids at the cavosurface margins of the restorations, and by antibacterial linings.

Effect of water spray on lining materials and their adhesion to composite and dentin cavity walls.

The effect of an air-water spray on the adhesion of lining materials to both overlying composite restorations and cavity walls was evaluated. An in vitro study was performed on extracted molar teeth: Two resinous light-cured liners and one calcium hydroxide, chemically activated liner were compared. Teeth were restored with composite materials and subjected to cyclic thermal changes so that microleakage could be evaluated. Results indicated that adaptation between the restorative material and the liner was effective, regardless of whether the oxygen-inhibited layer was removed by being rinsed. A definite gap was detected between the liners tested and the dentin cavity walls.