Compomers, reattachment method expand restoration capabilities.

The purpose of this article is to review one new material and one new technique being used in restorative dentistry today. Compomers, new fluoride-releasing resin restorative materials, are compared to conventional glass ionomers in terms of classification, physical properties, and clinical usage. Compomers are not true glass ionomer materials since the acid/base setting reaction, charactheristic of conventional glass ionomers, does not occur. As a consequence, their physical properties of translucency, coefficient of thermal expansion, and strength more closely resemble composite resins than conventional glass ionomers. These differences in physical properties have clinical implications in their usage. In terms of new techniques, clinical and laboratory data now exist to support the method of reattachment of fractured tooth fragments using only dentin bonding agents, in cases where the tooth fragment is available. This method can restore up to 50 percent of the original strength of intact teeth. The technique advocates the use of acid etching and enamel and dentin bonding, without any tooth preparation. In vitro studies have achieved total (100 percent) restoration of intact teeth by bonding a porcelain veneer to the tooth after the reattachment.

In vitro corrosion behavior and microstructure examination of a gallium-based restorative.

Concerns of mercury toxicity have led to the development of gallium-based restorative materials to replace dental amalgam. A new gallium-based dental restorative, Galloy, was compared with a high-copper amalgam, Permite, for anodic polarization behavior in deoxygenated Ringer's solution and by immersion testing in normal Ringer's solution at 37 degrees C. Corrosion products were analyzed using energy dispersive X-ray spectrometry and transmission electron diffraction. The data from both sources were consistent with the presence of alpha-Ga2O3 and SnO2 as the primary corrosion products of Galloy. Anodic polarization behavior of Galloy- and Permite-coupled specimens suggests that coupling Galloy with the more noble Permite amalgam may cause accelerated electrochemical corrosion and that Galloy is more corrosion prone than Permite.

Using a resin-modified glass ionomer as an occlusal sealant: a one-year clinical study.

The authors compared the retention and clinical performance of a resin-modified glass ionomer, or RMGI, restorative and a light-cured resin sealant. The first permanent molars on one side of the dental arch in 50 children were sealed with an RMGI, and the same teeth on the other side were sealed with a resin sealant. At baseline, six months after placement and one year after placement, examiners documented sealant retention, secondary caries, marginal discrepancy and marginal staining. In general, the RMGI appeared to wear markedly. At one year, the retention of the RMGI was significantly less than the resin, but the RMGI had significantly fewer marginal discrepancies. There were no significant differences in caries development or marginal discoloration.

Competency-based education at the Indiana University School of Dentistry.

This article discusses competency-based education at Indiana University School of Dentistry (IUSD). Competency-based education is not a new concept in health education, but is relatively new to dental education. The authors hope that this article will help Indiana dentists understand a process that will radically alter the way we teach dentistry at IUSD.

Bond strength of resin cements to microfilled composites.

The in vitro bond strengths of three resin cements and a light-cured and a laboratory-processed micro-filled composite were measured. Effects of two surface treatments, and three bond enhancers were analyzed. Resin cements were bonded to sandblasted composite substrates, stored at 37 degrees C in 100% humidity overnight, and debonded in tension. An analysis of variance revealed significant differences among bond strengths. Overall, the composite substrate had the largest effect on bond strength, followed by bond enhancer, cement and, finally, surface treatment. Mean bond strengths ranged from 0.9 to 13.6 MPa. A combination of Concept, Dual Cement, phosphoric acid and Silane produced the lowest mean bond strength (0.9 MPa), while EOS, Dual Cement, hydrofluoric acid, and Heliobond produced the highest recorded mean bond strength (13.6 MPa). In general, the highest bonds were produced using the light-cured composite (EOS), the acrylic monomer (Special Bond II) or the dimethacrylate monomer (Heliobond), the adhesive cement (CR Inlay Cement), and surface treatment with hydrofluoric acid (Comp-Etch). Most of the bond failures (86%) with the laboratory-cured microfilled composite were adhesive. With the light-cured composite, 69% of the failures were mixed adhesive-cohesive types.

Bond strength of resin cements to a hybrid composite.

Tensile bond strengths among three resin inlay cements and a light-cured and a post-cured hybrid composite prepared with two different surface treatments and three different bond-enhancing liquids were measured in vitro. The resin cements were bonded to sandblasted hybrid composite, stored at 37 degrees C in 100% humidity overnight, and debonded in tension. Interfacial bond strengths were affected most by the type of pre-bond surface treatment. Hydrofluoric acid produced weaker bond strengths than surface treatment with phosphoric acid. Post-cured Herculite XRV produced weaker bond strengths than the light-cured Herculite XRV. Porcelite cement produced the highest bond strengths. Of the surface enhancers, the acrylic monomer (Special Bond II) produced the highest bond strengths, regardless of which cement or surface preparation was used. Fracture analysis revealed mostly adhesive failures with hydrofluoric acid treatment in both light-cured and post-cured Herculite.

Postoperative pain incidence related to the type of emergency treatment of symptomatic pulpitis.

Some endodontic emergencies occur as a result of attempts to relieve symptoms of pulpitis. The aim of this study was to identify any predictor of postoperative pain in a patient population treated by dental students. Patients who reported for treatment of symptomatic pulpitis were subjected to three different emergency treatment regimens. Clinical data was collected on those patients who reported in the emergency service with severe postoperative pain within 24 hours of emergency endodontic treatment. Statistical analysis of these data suggested that the type of endodontic emergency procedure carried out was a significant predictor of severe postoperative pain.

Quantitative analysis of six composite polishing techniques on a hybrid composite material.

Determining the best technique for finishing and polishing composite resins is important to ensure longevity of the restoration and prevention of recurrent decay and periodontal disease. This study quantitatively compared the surface roughness of a small particle hybrid composite material finished and polished using six different techniques. Five composite samples were randomly assigned to one of six polishing techniques. Uniform composite surfaces were prepared by finishing samples with a 600-grit carborundum disk prior to polishing. The unpolished surfaces were analyzed with the Taylor-Hobson Talysurf 10 surface texture measuring instrument. The surfaces were then polished and analyzed again. There were no statistical differences among treatment groups prior to polishing. There was a statistical difference between treatment groups after polishing. The smoothest surfaces were obtained using Centrix System rubber points alone, Centrix System rubber points plus Caulk's Prisma Gloss fine and super-fine pastes, and Caulk's Enhance disks plus Caulk's Prisma Gloss fine and super-fine pastes. There was no statistical difference between these methods and 3M Sof-flex disks alone. The roughest surface was produced by the Enhance disks only without using the Prisma Gloss pastes. There was no statistical difference between this method, however, and the use of Sof-flex disks plus Kerr's Lustre Paste. Lustre Paste, included with Herculite kits, did not improve a surface polished with Sof-flex disks.

In vitro tensile bond strengths of amalgam to treated dentin.

Since amalgam traditionally relies on undercuts in the tooth preparation for retention, extensive tooth structure must be removed for amalgam core build-ups. In contrast, the ideal build-up material would achieve its retention by directly bonding to tooth structure. This study compared tensile bond strengths of amalgam to dentin using All-Bond Liner-FX with three different dentin pretreatment conditions and Amalgambond according to the manufacturer's directions. One hundred and twenty dentin samples were tested. Groups 1-3 used All-Bond Liner-FX as a bonding agent. Group 1 received a 15-second application of 10 percent phosphoric acid on the dentin; Group 2 received the recommended dentin conditioner; and Group 3 received no dentin pretreatment. Group 4 used Amalgambond as the bonding agent after a 10-second application of 10 percent citric acid/3 percent ferric chloride. Analysis of the data was conducted using both ANOVA and the Weibull statistic. Results of the analysis of variance indicate that there were no statistical differences among mean tensile bond strengths for the three dentin pretreatment conditions using All-Bond. All (30) of the Amalgambond specimens debonded prior to testing. The All-Bond fracture data was well described by the Weibull function as evidenced by the high coefficient of determination (R2 = 0.98-0.99). Fracture analysis indicated that all of the Amalgambond failures were adhesive at the Amalgambond-amalgam interface. All-Bond fractures were mixed cohesive/adhesive failures indicating similar bonding to amalgam and dentin.

In vitro bond strength of repaired amalgam with adhesive bonding systems.

The in vitro tensile bond strengths of Amalgambond and All-Bond were evaluated as adhesive systems for the repair of amalgam (Valiant Ph.D.) by two repair amalgams (Valiant or Valiant Ph.D.). Other variables evaluated were two surface finishes (SiC finish and sandblasted) and two storage conditions (37 degrees C, 24 h, and thermocycled). The Amalgambond bond was not reliable. All-Bond bonded amalgam to amalgam with Liner-FX. Bond strengths ranged from 3.4 to 8.8 MPa. The highest bond strengths were achieved with a sandblasted surface repaired with Valiant. Thermocycling did not affect bond strength.

A comparative study of fluoride release from glass-ionomer cements.

This study compared the amounts and patterns of fluoride release from 11 commercially available glass-ionomer cements into artificial saliva over an 84-day period. The results indicated that the materials differed in the amount of fluoride released, and that Miracle Mix released the highest cumulative total of fluoride over the test period. Along with old Fuji II, Miracle Mix also released the most fluoride during the last time interval (56 to 84 days). All of the materials released the greatest proportion of their cumulative total fluoride in the first 24 hours after mixing.

Fracture strength of Class I versus Class II restored premolars tested at the marginal ridge. I. Standard preparations.

Two groups of maxillary premolars with Class I cavities were prepared with one marginal ridge thickness to a width of 1.0 mm. One group was restored with amalgam and the other group with composite resin. Two groups of Class II cavities also were prepared and restored with amalgam and composite resin. The teeth in the four treatment groups were subjected to a centric load at the marginal ridge until fracture occurred. A two-factor analysis of variance revealed a statistically significant difference between the class of preparation (Class I preparations were weaker than were Class II preparations) but differences in strength between restorative materials (composite resin versus amalgam) and the interaction effect (class of preparation x restorative materials) were not found to be statistically significant (alpha = .05). A Newman-Keuls sequential range test found no statistically significant differences in strength between groups (alpha = .05). Fracture patterns were observed under scanning electron microscope. Fractures extended into the enamel and into the material in the Class I composite resin, Class I amalgam, and Class II composite resin restorations. Fractures extended only into the material in Class II amalgam restorations.

Fluoride release from light-cured liners.

This study compared the relative amounts and patterns of fluoride release from six commercially available light-cured liners in artificial saliva over a 28-day period. Cavalite and two Zionomer products released relatively small amounts of fluoride. Timeline and XR Ionomer released the highest cumulative total of fluoride over time. During the last time interval (14-28 days), Timeline released the greatest amount of fluoride. Patterns of fluoride release for all materials were similar with the largest proportion of the total fluoride release being in the first 24-48 hours, followed by a dramatic reduction in release rate.

Antibacterial effects of light-cured liners.

Light-cured liners and glass ionomers have recently been introduced and it has not been established if they are antimicrobial. This study determined the effectiveness of several light-cured liners against Streptococcus mutans #6715. Fluoride release and pH determination tests were performed to define their antibacterial activity. After evaluation with agar diffusion methodology, two of the light-cured glass ionomers were considered inhibitory. These two liners released fluoride into the agar in excess of the minimum inhibitory value of 20 ppm. The other four materials released fluoride below reported inhibitory values, failed to lower the pH below 4.0 and were ineffective against Streptococcus mutans. The findings suggested that light-cured glass ionomers react similarly to conventionally-cured glass ionomers regarding antibacterial activity against Streptococcus mutans. It also indicated that antibacterial activity was dependent upon a lower pH. Fluoride release may not be as important to the mechanism of action; however, it cannot be ruled out.

Antibacterial effects of glass ionomers.

Glass ionomer cements have been shown to possess antimicrobial activity. Proposed mechanisms of action include acidity and fluoride. It was the purpose of this study to determine the antimicrobial effect of 11 glass ionomer cements, their individual powder and liquid components and one resin-bonded liner containing high fluoride ionomer glass against Streptococcus mutans #6715. The role of fluoride and pH in the antibacterial activity was also studied. Using agar diffusion assay methodology, the following results were obtained. All of the glass ionomer cements were inhibitory against S. mutans. The antibacterial cements and slurries that were tested for fluoride, released the ion in excess of reported minimum inhibitory values. The antimicrobial activity of the liquid components, that were tested for the effects of pH changes, was totally lost when the pH was adjusted to 5. The resin bonded liner was inactive against S. mutans and did not release inhibitory concentrations of fluoride. These results indicate that freshly-mixed glass ionomer cements are antimicrobial against S. mutans and that the mechanism of action is probably a function of both fluoride and pH although additional factors may be involved.