The use of liners under amalgam restorations: an in vitro study on marginal leakage

OBJECTIVE: Marginal leakage of amalgam restorations may lead to secondary caries and pulpal damage. The purpose of this study was to determine the effect various cavity liners might have on microleakage. METHOD AND MATERIALS: Mesio-occlusodistal amalgam restorations with margins on enamel and dentin were treated with different liner materials (an adhesive system, a topical fluoride gel, a cavity varnish, and a glass-ionomer cement) in vitro. Following restoration, the teeth were submitted to thermocycling in a stained solution and sectioned to allow assessment of microleakage. RESULTS: On enamel, the control group (no liner) and the glass-ionomer-lined group had equivalent leakage scores and were superior to every other group. On dentin, only the glass-ionomer specimens had superior performance. The cavity varnish and fluoride-lined specimens exhibited the highest leakage scores. CONCLUSION: The use of liners does not reduce microleakage on amalgam restorations when the cavity margins remain on enamel. On dentin margins, a glass-ionomer liner can reduce microleakage.     

Marginal integrity and postoperative sensitivity in Class 2 resin composite restorations in vivo

INTRODUCTION: Problems that may arise in resin composite Class 2 restorations include microleakage and postoperative sensitivity. However, limited in-vivo research is conducted to evaluate these processes. AIM: The aim of this study was to assess postoperative sensitivity, microleakage and the pooling of adhesives in relation to Class 2 box-type composite restorations placed in vivo using various adhesive systems and application techniques. MATERIALS AND METHODS: One hundred and forty-four Class 2 box restorations were placed in the mesial and distal surfaces of 72 premolar teeth in-vivo using one of three combinations of adhesive systems and three filling techniques. After 6 weeks of clinical service postoperative sensitivity was recorded. The teeth were then extracted, immersed in a dye solution and sectioned. Microleakage and pooling of the adhesive was recorded. Statistical analysis involved logistic regression and chi2 tests to identify differences between groups at p < 0.05. RESULTS: Of the 144 restorations, 65 showed minimal cervical leakage in enamel, 5 suffered leakage into dentin and 74 were free of microleakage. No statistically significant differences were found in cervical microleakage between the adhesive systems or between filling procedures. Occlusal microleakage in the enamel was present in 16 of the 160 restorations. Liner Bond 2 restorations leaked significantly more at the occlusal surface (p < 0.05). Pooling of the adhesive was significantly less when PhotoBond was used. No spontaneous postoperative sensitivity was reported. Twenty-eight restorations were sensitive to loading. Postoperative sensitivity was significantly less in patients with Liner Bond 2 restorations. CONCLUSIONS: The adhesive systems used in this study showed minimal leakage into dentin in vivo. Using Liner Bond 2, restorations exhibited more occlusal leakage but were significantly less sensitive to loading.     

Three-year clinical evaluation of the Clearfil Liner Bond system

Modern dental adhesive systems have improved the bond of restorative materials to mineralized tooth structures. The purpose of this study was to evaluate the clinical performance of composite restorations placed in abrasion and erosion lesions using the Clearfil Liner Bond dental adhesive system. Following ADA clinical guidelines for dentin and enamel adhesive materials, 62 facial class 5 smooth surface erosion or abrasion lesions with no undercuts and involving primarily root surfaces were restored in 25 adult male and female patients. The teeth were restored without preparations using Clearfil Liner Bond and Clearfil Photo Anterior composite resin. The clinical performance of the restorations was assessed by two examiners at baseline, 6 months, 1, 2, and 3 years using the following evaluative parameters: color match, marginal discoloration, and marginal integrity according to modified Ryge criteria; the presence or absence of recurrent decay; pre- and postoperative sensitivity; and restoration failure due to loss of retention or other causes. At the end of 3 years, four of the 55 restorations remaining in the study failed due to lack of retention (92.7% retention rate). The evaluations of the other clinical parameters demonstrated excellent performance by this system.     

Value of the search for anticardiolipin antibodies during the course of systemic lupus erythematosus

This study investigates the shear bond strengths (SBS) of different products used for bonding amalgam to dentine and the marginal seal provided by these materials. The SBS test was carried out by bonding cylinders of Dispersalloy amalgam to human dentine with an intermediate layer of Amalgambond Plus, All-Bond 2, Imperva Bond/Dual or Scotch Bond Multi-Purpose was first placed. Thereafter the samples were tested to failure in the shear mode. For the microleakage test, standardized class V cavities were prepared in human molars with one cavo margin abutting enamel and another dentine/cementum. Amalgam was condensed into the cavities, pretreated with one of the products mentioned above. In addition two further groups were prepared. One receiving treatment with Polyvar varnish and the other remained untreated as the control. Microleakage was assessed with a reflecting light microscope using I.S.O. criteria and the fracture sites and marginal gaps were examined in a scanning electron microscope. Results indicate that All-Bond 2 and Amalgambond Plus induced similar SBS and Scotchbond Multi-Purpose the weakest. At both enamel and dentine/cementum junctions resin bonding agents reduced microleakage. However, this reduction was greater at the enamel interface than at the other. Varnish allowed the greatest amount of marginal leakage and leakage was similar to the untreated control. Amalgam bonding agents are more effective at preventing marginal leakage at the enamel margin than at the dentine/cementum margin. Cavity varnish is not effective in preventing microleakage around amalgam restorations. There is a correlation between shear bond strength and marginal leakage. Materials giving the highest shear bond strength also exhibited the least marginal leakage. All-Bond 2, Amalgambond Plus and Imperva Bond/Dual are recommended to improve the seal around amalgam restorations.     

Microleakage of multi-step and simplified-step bonding systems

PURPOSE: To measure and compare the microleakage of Class V resin composite restorations using the following three pairs of multi- and simplified-step dentin bonding systems (DBS): OptiBond vs. OptiBond FL, All-Bond 2 vs. One-Step, and Tenure vs. Tenure Quik. MATERIALS AND METHODS: V-shaped cavities were prepared in the mesial and distal surfaces of 30 extracted human mandibular molars with margins in both enamel and cementum, and randomly assigned into three equal groups of 10 each. All DBSs were applied strictly following manufacturers' specifications before three incremental layers of resin composite (Pertac-Hybrid) were applied in all cavities. Specimens were stored for 7 days in 37 degrees C water, thermocycled for 300 cycles between 5 degrees C and 55 degrees C, immersed in 0.5% basic fuchsin solution for 24 hours, and embedded in resin before being sectioned longitudinally in multiple sections. Dye solution penetration at the tooth/composite interface was scored from 0 to 4 under a microscope at x100 at both enamel (E) and cementum (C) margins. Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests with alpha = 0.05. RESULTS: OptiBond FL and One-Step showed less microleakage at the cementum margins compared to their multi-step versions. At the enamel margins Tenure Quik showed less microleakage compared to Tenure, and none of the other DBSs tested showed significant dye penetration at that interface. All DBSs showed significantly less microleakage at the enamel margins compared to the cementum margins except for OptiBond FL and One-Step that did not show any significant dye penetration at the cementum margins as well.     

Effects of etchants, surface moisture, and resin composite on dentin bond strengths

This in vitro study evaluated the effects of etchant type, surface moisture, and resin composite type on the shear bond strength of dentin adhesives. Three adhesives which bond to etched dentin were used in the study: All-Bond 2, Amalgambond, and Clearfil Photo Bond. Occlusal enamel was removed from 200 human molars to expose dentin. The dentin surfaces were etched, treated with a dentin adhesive system, and bonded with resin composite. After thermocycling and storage, the composite columns were fractured from dentin using an Instron machine. Bond strengths were calculated and subjected to a statistical analysis. Etchant type, surface moisture, and resin composite type all had significant effects on dentin bond strengths. Overall, the highest bond strengths were obtained with 10/3 etchant, moist dentin, and hybrid composite. The highest bond strengths for All-Bond 2 and Amalgambond were obtained by using the manufacturer's recommended etchant, moist dentin, and a hybrid composite. The mean bond strengths for All-Bond and Amalgambond under these conditions were 22.5 and 19.0 MPa, respectively. Clearfil Photo Bond had significantly lower bond strengths, but was relatively unaffected by changes in experimental conditions.     

Microleakage of dentin bonding systems used with spherical and admixed amalgams

PURPOSE: To evaluate the effectiveness of the dentin bonding systems (DBS) Tenure, Syntac, Amalgambond and All-Bond 2 using a resin-lined amalgam technique in preventing short-term microleakage in Class V cavity preparations restored with a spherical and an admixed alloy. MATERIALS AND METHODS: Class V cavity preparations were made on the mesial and distal surfaces of non-carious human mandibular molars with the occlusal margins in enamel and gingival margins in cementum. Prepared teeth were randomly assigned to 12 treatment groups (n = 10) consisting of each DBS, no liner and Copalite for both amalgam alloys. Samples were thermocycled, stained and sectioned to evaluate microleakage. RESULTS: The DBS-lined restorations had significantly less microleakage at both occlusal and gingival margins than the Copalite and unlined restorations. Among DBS, Syntac had significantly more microleakage with both alloys than either All-Bond 2 or Amalgambond. These results do not totally correlate to a previous study which used the same experimental design but included viscous liners in addition to the same DBS, indicating a potential difference between resin-lined versus resin-bonded amalgam techniques in preventing microleakage.     

Bond strength, interfacial characterization, and fracture surface analysis for a new stress-breaking bonding agent

Three commercial dentin bonding systems were analyzed by tensile bond testing, area analysis of fractured surfaces, and SEM analysis of the tooth-resin interfaces. Tensile bond strengths in megapascals(SD) were Tenure-Marathon V ([T-M]; 8.86[3.02]), new system with low-viscosity resin ([K-LVR-P]; 6.50[2.01]), and new system without low-viscosity resin ([K-P] = 7.28[1.75]), which were significantly greater than Scotch-bond 2-P50 ([SB-P50]; 3.96[1.02]). Gaps that ranged up to 5.6 microns (mean for the group) were observed around most of the restorations at dentin surfaces and less so at enamel surfaces, where some of the restorations remained free of gaps. The gaps near the dentin margin were significantly smaller for K-LVR-P than for SB-P50. The tensile test revealed mixed failure modes in all systems, and in the cross sections of class V restorations, the gaps were confined to the dentin-resin junction.     

Microleakage of new dentin bonding systems using human and bovine teeth

The objective of this study was twofold: to evaluate the microleakage behavior of three dentin bonding systems and to determine if bovine teeth are comparable substrates to human teeth when studying the microleakage of various materials. The materials evaluated were Scotchbond Multi-Purpose Adhesive, Prisma Universal Bond 3, and All-Bond 2. All three bonding systems were used in combination with Prisma APH hybrid composite for comparison of microleakage behavior. Sixty class 5 preparations were cut at the cementoenamel junction for groups containing 30 human and 30 bovine teeth. A 1 mm 45 degree bevel was placed at the enamel margin. Teeth were grouped according to the dentin bonding system used and then restored according to the manufacturer's directions. After restoration, the teeth from each group were stored in distilled water at 37 degrees C for 3 days. The teeth were then thermocycled between 4 degrees C and 58 degrees C for 100 cycles and returned to distilled water at 37 degrees C for an additional 4 days. The teeth were then sealed with nail polish up to 1 mm from the margins of the restoration and placed in 45Ca isotope for 2 hours. The teeth were then sectioned and placed on x-ray film to produce autoradiographs. Microleakage was evaluated for the enamel and dentin margins separately using the following scale: 0 = no leakage, 1 = penetration of isotope to less than 1/2 the distance to the axial wall, 2 = penetration of isotope greater than 1/2 of the distance to the axial wall but short of the axial wall, and 3 = penetration of isotope to the axial wall or beyond. The materials were compared to each other using the Mann-Whitney U and Kruskal-Wallis tests. The gingival margins were compared to the incisal margins for all materials. No statistically significant differences in microleakage were revealed between the incisal and gingival location for human substrates, but there was statistically significant greater gingival microleakage for bovine substrates. All-Bond 2 leaked significantly more than Scotchbond Multi-Purpose for human substrates at the incisal margin. All-Bond 2 had significantly more microleakage than Prisma Universal Bond 3 at both dentin and enamel margins for the bovine substrate. There were no statistically significant differences in microleakage among the bonding systems for the human substrate. No statistically significant differences between the microleakage behavior of human and bovine substrates were found. These results support the use of bovine teeth for in vitro microleakage studies.     

Adhesion of a compomer to dental structures

The objective of this study was to evaluate the bond strength of a compomer to dental enamel, dentin, and cementum. Flat surfaces of these tissues were obtained from recently extracted human teeth. The different substrates were either treated with PSA (a primer and adhesive) or acid etched (35% phosphoric acid gel) and treated with PSA. Cylindrical specimens of compomer were then bonded to the substrates. Shear bond strength was determined after a 24-hour immersion in 37 degrees C water. Significant differences were found between both treatments on enamel, while none were found on dentin or cementum. The use of acid etchant on enamel as a surface-conditioning step previous to priming with PSA allowed a better bond between Dyract compomer and that substrate; acid etching was not particularly needed on dentin and cementum.     

An in-vitro investigation of microleakage and gap size of glass ionomer/composite resin "sandwich" restorations in primary teeth

Eighty extracted primary molars were divided into four groups of twenty teeth. Class II cavities were prepared in all teeth with equal numbers of proximal boxes having cavosurface margins either in enamel, or dentin/cementum. Each group was allocated to an open or closed sandwich technique using glass ionomer as a lining. Following the placement of the composite resin restorations, the gap size measured at the proximal box was greatest for the closed sandwich group with the cavosurface margin on enamel (0.203 microns) or dentin/cementum (0.174 microns). Microleakage scores were measured at the proximal box and were greatest for the closed sandwich group with the cavosurface margin on dentin/cementum. The best result was obtained for the open sandwich group with the cavosurface margin on enamel.     

Optometric record keeping in a comprehensive health care environment

We determined the relative shear bond strength (SBS) to dentine and cementum and the microleakage of All-Bond 2 universal dental adhesive and OptiBond multi-use filled adhesive. We found that for both systems the SBS increased significantly (p < 0.001) from 15 minutes to 24 hours and 7 days, but there was a slight significant (p < 0.001) weakening towards 30 days. At each time point the shear bond strength of All-Bond 2 and OptiBond were also compared and it was found that OptiBond had significantly higher values (p < 0.05) at all times except at 15 minutes. Optibond also had the lower value for the microleakage (p < 0.001). This study showed that OptiBond had significantly higher shear bond strengths to and lower microleakage in dentine which may increase the longevity of the material in the clinical situation.     

Bond strength to crown and root dentin

PURPOSE: To investigate (1) the tensile bond strengths of four commercial dentin bonding systems to bovine crown and root dentin and (2) the structure of the hybrid layers for each system bonded to the two dentin substrates. MATERIALS AND METHODS: Superficial surfaces were exposed in bovine crown and root dentin. The teeth were embedded in plaster and a 3 mm diameter bonding area was demarcated. The four bonding systems used were All-Bond 2, Super-Bond D-Liner Plus, Clearfil Liner Bond II, and ProBond. Bonding procedures followed the manufacturers' instructions with the exception of Super-Bond D-Liner Plus where the primer was left in situ for 60 seconds. Tensile bond strengths were tested after 24-hour storage in 37 degrees C deionized water. Specimens were also prepared for SEM observation of the hybrid layer, after treatment with 10% phosphoric acid, and 10% phosphoric acid and 5% sodium hypochlorite. RESULTS: Statistically lower bond strengths to crown dentin when compared with root dentin were observed for All-Bond 2, whereas Liner Bond II showed the opposite (P < 0.01). Both ProBond and Super-Bond D-Liner Plus showed no statistical differences between crown and root dentin (P > 0.05). Hybrid layers could be observed for All-Bond 2, Liner Bond II and Super-Bond D-Liner Plus, with no apparent differences between the hybrid layers of crown and root dentin. In the case of ProBond, where the smear layer was not removed during the priming stage, it appeared that the primer had infiltrated and caused hybridization of the smear layer. The differences in bond strength were thought to be related to the different bonding mechanisms of each material, as well as possible variations in the crown and root dentin substrates.     

Cysteine and glutathione deficiency in AIDS patients: a rationale for the treatment with N-acetyl-cysteine

The purpose of this study was to determine the effect of accidental dentin primer contact with etched enamel on shear bond strength of composite resin to enamel. Four dentin bonding systems were included in this study: GLUMA Dentin Bond, Scotchbond, and Prisma Universal Bond 2 and 3. Eighty extracted human permanent anterior teeth were used and divided in eight test groups. The vestibular surfaces were ground and acid etched. For each dentin bonding system 10 samples were treated with dentin primer prior to placement of resin. Shear bond testing showed that enamel contact with dentin primer in the above two systems decreased the shear bond strength between composite and enamel by 31 to 44%.     

Microleakage of cervical restorations etched with a weak organic acid

This in-vitro study evaluated the microleakage of Class V restorations prepared using 10 per cent maleic acid and a composite resin. Thirty human premolar teeth were evenly distributed and randomly assigned to three groups. Conventional retentive preparations, etched with 10 per cent maleic acid for either 15, 30, or 60 seconds, were cut in the enamel on the facial surface of each tooth to a 1.5 mm depth (dentin). All teeth were restored with Z-100, a small particle composite resin. The teeth were then stored in deionized water for seven days, thermocycled, stained with methylene blue dye, invested, and sectioned vertically through the centre of the restoration. Leakage was established along each wall of the sectioned restoration. Analysis of variance (ANOVA) tests indicate that the restored teeth in Group 1 (15-second etch) had significantly greater microleakage (p < 0.05) on the enamel wall than the restored teeth in Group 2 (30-second etch) or Group 3 (60-second etch). In addition, Group 1 restorations had significantly greater overall microleakage (p < 0.05) than Group 2 or Group 3 restorations. Although the results were not statistically significant, it would appear that etching with 10 per cent maleic acid for 30 seconds could be clinically significant. Since a 30-second etch time was found to produce the least amount of microleakage (not statistically significant), it can be assumed that this etch time would also be optimal for etching enamel and dentin. Similarly, since Group 1 revealed the most overall microleakage, it can be assumed that a 15-second etch would be inadequate for etching enamel and dentin. Restorations in Groups 2 and 3 displayed statistically significant lower overall microleakage results.     

Laboratory evaluation of the XR-Bond Dentin/Enamel Bonding System

The shear bond strengths of the XR-Bonding System used in conjunction with Herculite composite, to the dentine of forty extracted human permanent first and second molars were determined after the test specimens were stored in physiological saline at 37 degrees C for 48 hours, one week, two weeks and four weeks, respectively. A shear load was applied to the base of the bonded composite cylinders with a knife-edged rod at a crosshead speed of 0.5 mm/minute. The shear bond strengths were expressed in megapascals (MPa). The quantitative microleakage of Class V preparations in dentine (cementum) in forty-eight extracted human maxillary permanent canines restored with the same dentinal bonding system and after storage in physiological saline at 37 degrees C for the same time intervals as for the shear bond strength tests, was determined. On the final day of each time interval the teeth were thermocycled X 500 in a 2 per cent methylene blue solution between 8 degrees C and 50 degrees C with a dwell time of 15 seconds. Microleakage was determined by a spectrophotometric dye-recovery method and expressed in microgram dye/restoration. There was a significant trend for the shear bond strengths to increase with duration of storage (p = 0.01) but the quantitative microleakage was not significantly different (p = 0.75).     

Resin-modified glass ionomers for luting posterior ceramic restorations

OBJECTIVES: Until recently, esthetic inlay restorations in posterior teeth have been limited to cavities surrounded by enamel. Dentin adhesive systems in combination with luting composites and light-cured resin-modified glass ionomer cements offer a possibility for bonding ceramic inlays to cavities when the cervical margin is in dentin. This study was designed to compare in vitro marginal integrity of ceramic inlays bonded to dentin to restorations placed in cavities with margins located entirely in the enamel. METHODS: In the present in vitro study, the sealing abilities of a dentin bonding agent/luting composite combination (Syntac/Dual Cement, Vivadent) and resin-modified glass ionomers (Photac Fil, Photac Bond, ESPE; Dyract, De Trey Dentsply; Fuji II LC, GC Dental Industrial Corp.; and Vitremer, 3M Dental Products) used as luting agents in cavities extending beyond the cemento-enamel junction, were compared to the sealing abilities of a conventional luting composite (Vita Cerec Duo Cement, Vita) in cavities within sound enamel. SEM analysis and dye penetration were performed to evaluate marginal integrity at the cervical cavity margins. RESULTS: The dentin bonding agent/luting composite combination (Syntac/Dual Cement) rendered a marginal seal within the dentin similar to the quality obtained with the conventional luting procedures within sound enamel. When three out of the five resin-modified glass ionomers were used as luting agents (Dyract, Fuji II LC and Vitremer), the results were comparable to those reported for the dentin bonding agents and the conventional method. SIGNIFICANCE: Light-cured resin-modified glass ionomer cements may be considered as an alternative to dentin bonding agents when the cavity margins of ceramic inlay restorations are within the dentin. However, further studies, e.g., wear resistance, must be performed.     

The effect of eugenol containing and non-eugenol temporary cements on the resin-enamel bond

This study was undertaken to compare the effect of eugenol containing and non-eugenol temporary cements on the bond strength of three brands of luting cements to enamel. Flat enamel surfaces were prepared on 90 surgically removed, unerupted, human third molar teeth. The teeth were randomly divided into three groups of thirty. The flat enamel surfaces in two of the groups were treated with either a eugenol containing or non-eugenol temporary cement and the third group was left untreated. The teeth were stored in water for 7 days and the cements then removed and all surfaces etched. The teeth were divided into 9 sub-groups of 10 each and one of the three resin cements was then bonded to each sub-group. The relevant shear bond strengths were determined after 7 days. The results indicated that prior use of a eugenol containing temporary cement reduced the resin cement-enamel bond strengths. No differences were found between the bonds achieved by the three brands. It was concluded that eugenol containing temporary cements should not be used prior to bonding with resin luting cements.     

Dentastic bond strength to dentin

PURPOSE: To evaluate the shear bond strength to the dentin of permanent teeth and failure site of Dentastic hydrophilic dentin bonding agent. MATERIALS AND METHODS: Forty permanent noncarious molar teeth stored in distilled water were obtained. The teeth were cleaned with pumice and a rubber cup. The mesio-buccal surface of the teeth was ground flat with hand pressure with a series of SiC paper ending with the 600 grit to provide a uniform surface on dentin to which the resin composite could be applied. After preparing the tooth surface, the teeth were stored in distilled water for 48 hours. They were then divided at random into four groups of 10 specimens each: Group 1: Dentastic, five coats of primer; Group 2: Dentastic, three coats of primer; Group 3: Dentastic, five coats of primer, light-cured adhesive before resin bonding; Group 4: Dentastic, three coats of primer, light-cured adhesive before resin bonding. All specimens were thermocycled (500x) and sheared in a testing machine. After shear testing, the debonded sites of all samples were examined with a stereomicroscope and a scanning electron microscope. RESULTS: The results in MPa were: Group 1: 22.63 +/- 6.24; Group 2: 23.35 +/- 5.14; Group 3: 23.58 +/- 5.66; Group 4: 27.26 +/- 8.22. ANOVA and Student-Newman-Keuls showed no statistically significant difference between the groups. In all groups, all specimens failed at the dentin (dentin cohesive failure = dentin fracture) or at the resin (resin cohesive failure = resin fracture). This means that the bond strength of the product is stronger than the cohesive strengths of the dentin and the resin.     

Hospice and managed care

Carbon dioxide (CO2) lasers are capable of producing surface irregularities in human enamel which resemble those resulting from etching of enamel with orthophosphoric acid. This report presents the results of a laboratory study which examined the effect of selected tooth-related variables on shear bond strength between a current generation bonding agent (Scotchbond MultiPurpose) and acid-etched or laser-conditioned human enamel. There were no significant differences in shear bond strength between human maxillary central incisor teeth, first premolars, and third molars in either the acid etch or laser-conditioned groups. Polishing of enamel to give a flat surface increased the shear bond strength obtained with acid etching, but did not alter significantly bond strengths achieved with laser conditioning. There was a tendency for a higher bond strength with acid etching, but not with laser conditioning, in porcine molar enamel compared with human molar and bovine incisor enamel. In terms of the mode of operation of the laser, the repetitively pulsed mode resulted in a two-fold improvement in shear bond strength compared with the single pulse mode. These results indicate that shear bond strengths in the order of 10 MPa can be obtained reliably on human teeth using laser conditioning with pulsed modes in the absence of any other preparation of the natural enamel surface.