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PubMed2002

Microleakage of composite resin restoration in cavities prepared by Er:YAG laser irradiation in primary teeth.

AIM: The purposes of this study were to investigate the surface morphology of cavities prepared by Er:YAG laser irradiation and to compare the microleakage degree after composite resin restoration with etched bur cavities in primary teeth, in vitro. MATERIALS AND METHODS: On the buccal (facial) and lingual (palatal) surfaces of 25 primary teeth, a round cavity was prepared with the Er:YAG laser system and with a high-speed diamond bur, respectively. Five cavities from each group were investigated by scanning electron microscopy (SEM). The remaining cavities were filled with a composite resin and subjected to a microleakage test (0.6% rodamine B solution) under thermocycling. Only bur cavities were acid-etched before filling. Statistical analysis was performed using the Mann-Whitney's U test; a value of p < 0.01 was considered significant. RESULTS: SEM observation of the laser and etched bur cavities revealed an absence of a smear layer; enamel rods and opening of dentinal tubules were recognized. No statistically significant differences were noted between microleakage of composite resin restorations of the laser and the etched bur cavities. Crosscut sections of the cavities with no microleakage showed good adhesion between the restorative material and dental hard tissues; there was also no gap at the interface. DISCUSSION: The highly irregular surface or the removal of the debris-like smear layer after laser irradiation may facilitate good adhesion of composite resin with enamel or dentine, and these surfaces might play a major role in decreasing microleakage of laser cavities. CONCLUSION: It can be concluded that cavities prepared by Er:YAG laser are capable of decreasing microleakage of composite resin restorations in primary teeth, and the efficiency is similar to etched bur cavities.

Journal Article↗

PubMedDate not supplied

The effect of incremental versus bulk fill techniques on the microleakage of composite resin using a glass-ionomer liner.

Incremental placement of composite resin has been suggested to reduce microleakage, particularly at the gingival margin of class 5 cervical restorations. It has become clinically advantageous to place a glass-ionomer liner over dentin to further minimize microleakage resulting from a bond between the dentin and glass ionomer, and glass ionomer and resin. The objective of this study was to compare the microleakage behavior of three hybrid composite/bonding agent systems using bulk and incremental filling techniques utilizing a glass-ionomer liner. This was accomplished in vitro using freshly extracted bovine incisors and a Ca45 radioisotope and autoradiography. Sixty bovine incisors were divided into six experimental groups of 10 specimens per group. Class 5 preparations were cut at the cementoenamel junction and restored with the appropriate combination of Herculite XR/Bondlite, P50/Scotchbond 2, or Pertac Hybrid/Pertac Bond. All teeth were lined with the glass ionomer Ketac Bond before the final restoration was placed. The samples were finished and stored for 24 hours in distilled water before thermocycling. The samples were tested for microleakage using a Ca45 radioisotope technique and autoradiography. Incisal (enamel) and gingival (dentin) margins were scored separately for microleakage but grouped for statistical analysis. Results were analyzed using the Kruskal-Wallis H test. Pertac Hybrid exhibited more leakage than Herculite XR or P50. The difference between microleakage of bulk and incremental filling techniques was only significant for P50.

Analysis of Variance↗

PubMed2004

Effects of dentin collagen removal on microleakage of bonded restorations.

PURPOSE: To evaluate the effects of removing dentin collagen exposed by acid etching on the microleakage of bonded restorations with and without flowable composite application and submitted to thermocycling and long-term water storage. MATERIALS AND METHODS: Standardized Class V cavities were prepared in 180 bovine incisors. They were randomly assigned to three groups according to the adhesive technique used. Conventional group (C): Single Bond was applied according to the manufacturer's instructions and Z250 composite was placed. Hypochlorite group (H): After acid etching a 10% NaOCl aqueous solution was applied for 1 min, then Single Bond and Z250 were applied. Hypochlorite and Flowable group (HF): Similar to group H, but following adhesive application, a thin layer of Natural Flow flowable composite was applied before the Z250. Each group was divided into three subgroups (0, 6, 12), which remained immersed in distilled water for 24 h or 6 or 12 months and underwent 500, 1500 or 2500 thermal cycles, respectively. At the end of each storage time, the specimes were stained with silver nitrate, decalcified, immersed in methyl salicylate for clearing and observed under a stereomicroscope to determine microleakage (scores 0 to 4). The data were analyzed using the Kruskal-Wallis and the Multiple Comparison Tests (alpha = 0.05). RESULTS: After 12 months, every group showed significant increases in microleakage. There was no significant difference between Groups H and HF for the three different periods of time, but they showed statistically less microleakage than Group C. CONCLUSION: The removal of dentinal collagen reduced the marginal microleakage when compared to the conventional technique. The use of the flowable composite did not produce significant effects. No technique was completely effective in preventing microleakage.

Acid Etching, Dental↗

PubMed2004

Effect of two different restorative techniques using resin-based composites on microleakage.

PURPOSE: To evaluate in vitro the extent of microleakage of Class II cavities restored with two different brands of resin-based composite, one hybrid (Tetric Ceram) and the other "packable" (Surefil) taking into account two variables: the localization of the margins and the insertion technique. METHODS: 100 bovine teeth, recently extracted, had standardized Class II slot cavities prepared on the mesial and distal surfaces with the gingival floor located on enamel or dentin, for a total 200 cavities. The teeth were randomly divided into eight groups of 25 teeth each (25 restorations in each group): (1) margin on dentin, restored with Surefil, bulk insertion; (2) margin on dentin, restored with Tetric Ceram, bulk insertion; (3) Margin on enamel, restored with Surefil, incremental technique; (4) margin on enamel, restored with Tetric Ceram, incremental technique; (5) margin on enamel, restored with Surefil, bulk insertion; (6) margin on enamel, restored with Tetric Ceram, bulk insertion; (7) margin on dentin, restored with Surefil, incremental technique; (8) margin on dentin, restored with Tetric Ceram, incremental technique. After this procedure, the teeth were subjected to 1000 thermocycles, stained with 2% methylene blue solution, and then sectioned in the mesiodistal direction. Dye penetration at tooth/restoration interface was scored based upon the extent of the dye using a light stereoscope x 35. RESULTS: All groups showed considerable levels of microleakage at both dentin and enamel margins (P < 0.05). Restorations with margins in enamel using the hybrid resin-based composite with the incremental technique did not show statistically significant differences when compared to bulk placement. However, restorations with hybrid resin-based composite have significantly less microleakage than either bulk or incremental technique for the "packable" resin-based composite Surefil. As for the margins in dentin, Tetric Ceram in bulk placement did not differ from the incremental technique and Tetric in bulk placement had significantly less microleakage than Surefil either bulk or incremental technique. The hybrid resin-based composite with margins in dentin and incremental technique showed less microleakage than the "packable" resin in bulk placement. CLINICAL SIGNIFICANCE: The two types of resin-based composites, hybrid and "packable" were unable to completely prevent microleakage. The study demonstrated the difficulty in sealing a proximal margin.

Animals↗

PubMed2004

Microleakage of cervical cavities restored with flowable composites.

PURPOSE: To investigate the microleakage of cervical cavities restored with flowable composites in conjunction with an all-in-one adhesive system (AQ Bond) and an experimental two-step self-etching primer system (ABF) after thermocycling or flexural load cycling. METHODS: 180 wedge-shaped cervical cavities on the labial surfaces of bovine incisors were treated with AQ Bond or ABF according to the manufacturers' instructions. The treated cavities were filled with one of three flowable composites (AElite Flo, Metafil Flo or Protect Liner F). Ten of 30 specimens for each group were immersed in 0.5% basic fuchsin solution immediately after finishing of the restorations. Specimens to be subjected to thermocycling (5-60 degrees C, 15 seconds dwell time, 5000 cycles) or to flexural load cycling (approximately 0.5 mm labio-lingual displacement at the incisal edge, 10,000 cycles, 1 Hz) prior to immersion in the dye were also prepared. After 24-hour storage in the dye solution, the teeth were sectioned longitudinally through the center of the restorations, and the degrees of dye penetration scored. The microleakage scores of a hybrid composite (Clearfil AP-X) obtained from our previous study were used for comparison. The data were analyzed with the Kruskal-Wallis test and the Mann-Whitney U-test (P < 0.05). RESULTS: No significant differences in the microleakage patterns and scores were found among the flowable composites. On the other hand, significant differences in the microleakage patterns and scores were observed between the flowable and the hybrid composites. Thermocycling caused deterioration of marginal integrity, and the flowable composites showed more microleakage than the hybrid composite. In contrast, flexural load cycling did not cause deterioration of the marginal integrity when the cavities were filled with the flowable composites. Statistical analysis also revealed that the adhesive systems played a large role in the microleakage patterns.

Animals↗

PubMedDate not supplied

Coronal microleakage of temporary restorations in previously restored teeth with amalgam and composite.

AIM: This study evaluated microleakage at the interface between various temporary restorative materials and existing amalgam or composite restorations, and dental tissues in previously restored teeth after partial removal of the restoration. MATERIALS AND METHODS: The distal half of amal gam (Ag) and composite restorations (Co) in 45 teeth were removed, then filled with temporary restorative materials (IRM, Coltosol and CLIP). After thermal cycling, microleakage was measured microscopically as the penetration of basic fuchsine according to a four-unit-scale: The data were evaluated with Friedman and Kruskal-Wallis tests using Bonferroni correction (p < 0.05). RESULTS: In almost all groups except the Co-IRM and Ag-CLIP interface, lower microleakage values were observed in temporary restoration-permanent restoration interfaces compared to temporary restoration-tooth interfaces. For the Ag and Co groups except for the Ag-IRM-b interfaces, the highest microleakage values were observed with IRM for b and c interfaces followed by Coltosol and CLIP. Interestingly, although CLIP was a temporary restoration, CLIP-tooth interface (Ag-CLIP-c) values were lower than amalgam-tooth interface (Ag-CLIP-a) values. CONCLUSIONS: CLIP provided a better seal against microleakage at amalgam and especially composite interfaces. This material also provided a better seal against microleakage at the tooth tissue interface. The use of a resin based temporary restorative material over partially removed resin composite restorations could be beneficial in achieving better resistance to marginal leakage. Within the limitations of this study, maintaining partially removed permanent restorations does not seem to cause a problem with achieving marginal seal.

Acrylic Resins↗

PubMed1990

Microleakage of Gluma Bond, Scotchbond 2 and a glass ionomer/composite sandwich technique.

Bonding to dentin with long-term success has been a quest of dentistry for some time. Microleakage is a major problem that can lead to staining and discolorization of the restoration and postoperative sensitivity. Some of the newer dentin bonding systems include Gluma Bond and Scotchbond 2. A glass ionomer/composite "sandwich" technique has also been advocated for dentin bonding. Here a glass ionomer is first bonded to the dentin, bonding agent is applied to the glass ionomer and a composite restoration is then placed into the cavity preparation. The purpose of this study was to compare the microleakage of Gluma Bond, Scotchbond 2, the glass ionomer/composite sandwich technique along with a positive and negative control. This was accomplished, in vitro, using extracted human teeth and a Ca45 radioisotope technique. The teeth were examined for microleakage at periods of 1 week, 6 months and 12 months. The results of this study indicate that, in vitro, the glass ionomer sandwich technique does not stop microleakage. The results also indicate that, in vitro, Gluma Bond and especially Scotchbond 2 restorations can resist microleakage for short periods of time. However, at the end of the 12 months, all Gluma Bond and Scotchbond 2 specimens exhibited gross microleakage.

Adhesives↗

PubMed1994

Do adhesives prevent microleakage?

All the polymeric composite restorative resins shrink during polymerisation resulting in the development of tensile and/or shear stresses at the tooth/restoration interface. The major part of the contraction stresses develops within 15 minutes after the initiation of polymerisation but with the light activated resins it occurs within seconds after irradiation. The tensile stresses may disrupt the adhesive bonding of the restorative system to the cavity walls resulting in microleakage at the tooth/restoration interface. The properties of the restorative resins which include polymerisation shrinkage during hardening, differences in the coefficients of thermal expansion of the tooth and the restoration, and water sorption of the restoration on exposure to the oral environment, play an important role in determining the marginal gap dimensions and hence microleakage. Microleakage at the enamel/restoration interface has been eliminated by the acid etch technique provided that adequate enamel thickness is present. Microleakage at the dentine/restoration interface, however, is much more difficult to eliminate. None of the dentinal bonding restorative systems eliminates microleakage at the gingival margins of restorations that extend to or beyond the cementum/enamel junction. Microleakage is reduced by using an incremental restorative technique but is increased when the restored teeth are subjected to masticatory stress or occlusal loading. None of the dentinal bonding systems prevents the development of marginal gaps at the dentine/restoration interface when evaluated 10 minutes after placement of the restorations but hygroscopic expansion resulting from water or saline immersion results in a significant reduction in marginal gap dimensions. An increase in the cavosurface margins reduces marginal gap dimensions but it is not dependent on cavity depth.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesives↗

PubMed1997

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.

Acid Etching, Dental↗

PubMed1997

Microleakage evaluation of bonded amalgam restorations: confocal microscopy versus radioisotope.

The purpose of this study was to compare the degree and pathway of microleakage in bonded amalgam restorations utilizing fluorescent dyes with scanning laser confocal microscopy and 45Ca radioisotope with autoradiographs. Mesial slot preparations with enamel cervical margins and distal preparations with dentin margins were prepared in extracted human molars. Four liners, Copalite (control) All-Bond 2/Resinomer, Amalcoden, and Panavia 21, were used. Teeth were restored with Dispersalloy or Tytin. After thermocycling, 7 days' storage, and staining, the degree of microleakage was measured on an ordinal scale. Dental adhesive liners minimized microleakage; the ranking was, from most to least effective, All-Bond 2, Panavia 21, and Amalcoden. The control exhibited the greatest microleakage. Microleakage occurred most frequently at the liner-tooth interface. No significant difference was observed between amalgams. The high correlation between the results of the fluorescent and radioisotope studies indicated that these two microleakage tests can be directly compared.

Autoradiography↗

PubMed1998

Microleakage of tooth-colored restorations with a beveled gingival margin.

OBJECTIVE: Microleakage of tooth-colored restorative systems was tested in preparations with and without beveled gingival margins. METHOD AND MATERIALS: A resin composite, Z-100, and two "compomer" restoratives, Dyract and Geristore, with their accompanying adhesive systems, were placed in nonretentive cervical cavity preparations (at the cementoenamel junction), with and without a beveled gingival margin (dentin or cementum) and beveled occlusal (enamel) margins in extracted bovine teeth. Microleakage was assessed as the ratio of the extent of methylene blue dye penetration at the tooth-restoration interface of the length of the wall. RESULTS: Z-100 restorations, without a gingival bevel, exhibited significantly less microleakage along the gingival wall and less microleakage overall than did the other materials. Dyract restorations without a gingival bevel and placed without a surface conditioner displayed greater microleakage overall than did the other groups. CONCLUSION: With all materials, Class V restorations with gingival bevels displayed greater microleakage than did nonbeveled margins.

Analysis of Variance↗

PubMed2003

A study on surface roughness and microleakage test in cavities prepared by Er:YAG laser irradiation and etched bur cavities.

The purposes of this study were to investigate the surface morphology, suface roughness of cavities prepared by Er:YAG laser irradiation, and compared the microleakage degree after composite resin restoration with etched bur cavities, in vitro. In each of the 30 human extracted teeth, two shallow cavities were prepared; one prepared with the Er:YAG laser system on the buccal surface, and one produced on the lingual (palatal) surface with a high-speed turbine. Five cavities from each group were investigated by scanning electron microscopy (SEM), and five were subjected to surface roughness analysis by a colour laser three-dimensional (3D) microscope. The remaining cavities were filled with a composite resin and subjected to a microleakage test under thermocycling. Only bur cavities were acid-etched before filling. Statistical analysis was performed using the Mann-Whitney U test; a value of p <0.01 was considered significant. Morphologically, the prepared cavities showed an irregular surface with the absence of a debris-like smear layer; enamel prisms and opening of dentinal tubules were recognised. Surface roughness was significantly increased with the laser system. Microleakage test revealed no significant differences between the laser and bur cavities. Crosscut sections of the cavities with no microleakage showed no gap at the interface. Laser cavity may facilitate good adaptation of composite resin with enamel and dentine, because an increase of surface roughness and the openings of dentinal tubules may facilitate the formation of a hybrid zone, since a primer and an adhesive can penetrate the surface better when the smear layer is removed. It can be concluded that shallow cavity prepared by Er:YAG laser is capable of decreasing microleakage of composite resin restorations, and its efficiency is similar to etched bur cavities.

Acrylic Resins↗

PubMed1991

Microleakage of composite resin cores treated with various dentin bonding systems.

Composite resin post and cores have gained widespread acceptance as an alternative for cast-gold post and core systems. A prefabricated metal post is generally used. Substantial microleakage at the interface between the composite resin core and the dentin substrate may occur. A tight and impervious bond between the dentin and the restorative material is critical for the longevity of core restorations. This study compared the microleakage of composite resin cores treated with various dentin bonding agents, including the recently developed Gluma, Tenure, and Scotchbond 2. The results indicated that Tenure and Scotchbond 2 bonding agents were most effective in reducing microleakage, followed by Gluma and conventional Scotchbond (Dual Cure) bonding agents. Although all proprietary dentin bonding systems used in this study significantly reduced microleakage, no system was capable of preventing microleakage completely.

Analysis of Variance↗

PubMed1989

Early marginal microleakage in Class II resin composite restorations.

The aim of this study was to evaluate in vitro the early marginal microleakage around conventional and sandwich Class II (MOD) restorations. Ten different combinations of dentin bonding agents, glass-ionomer cements, and posterior resin composites were used. Class II cavities were prepared in freshly extracted third molars whose root surfaces had previously been coated. All gingival margins were prepared at the cementum-enamel junction. Teeth were filled by use of a multi-incremental technique, finished with discs, and immediately immersed in 2% erythrosin B for 12 h at 37 degrees C. Three transverse sections were made at 0.5 mm, 2 mm, and 3.5 mm over the cementum-enamel margin and evaluated under a stereomicroscope. Microleakage was scored linearly along the dentin/enamel-restoration interface. Sections at the cementum-enamel level showed significantly higher microleakage than the other two. Significant differences were observed between the various combinations of materials. Early marginal microleakage in Class II restorations depends not only on filling technique and on dentin bonding systems but also on the resin composite. Glass-ionomer cements significantly reduce early marginal microleakage in Class II restorations.

Composite Resins↗

PubMed1991

Comparison of two-surface and multiple-surface scoring methodologies for in vitro microleakage studies.

Investigators differ on the use of a two-surface or multiple-surface scoring methodology in sectional microleakage studies. This study compared microleakage scores using both two-surface and multiple-surface scoring methods for two preparation types and two different dentin bonding agents. Twenty freshly extracted molars each received one box-shaped and one V-shaped restoration on the mesial or distal surface. Each restoration was cut occlusogingivally into four sections, yielding eight surfaces for scoring. Surfaces were marked to identify central (I), lateral (II), and end (III) locations, then scored by two calibrated raters. The Wilcoxon Matched-Pairs Signed-Rank Test showed a statistically significant difference (p less than or equal to 0.05) in median microleakage scores obtained by an end two- surface and multiple-surface evaluation for V-shaped preparations restored with Scotchbond 2, P-50. No other statistically significant comparisons were detected. Results suggest that microleakage may be more extreme at end surfaces and that these end surfaces should be scored so that an accurate microleakage value could be assigned to composite restorations.

Analysis of Variance↗

PubMed1994

Permeability and microleakage of Class II resin composite restorations.

The aim of this study was to evaluate the variations in microleakage of large Class II (MOD) restorations over time. Three different combinations of dentine bonding agents and posterior resin composites which had previously shown promise were used: Vitrebond/Scotchbond 2 plus P50, Tripton plus Occlusin and Clearfil Photo Bond plus Clearfil Photo Posterior. Conventional Class II cavities were prepared in freshly extracted third molars. All gingival margins were terminated at the cemento-enamel junction. A fluid-under-pressure apparatus connected with the pulp chamber of each tooth was used to evaluate the permeability and marginal leakage of the restorations at 0.069 MPa. Microleakage was tested after insertion of restorations at 2, 15, 45, 150 min, after 1, 2, 7, 14 days, after 1, 2, 3 months, after thermal cycling and 10 months later, after occlusal loading. Finally, all specimens were exposed to silver nitrate solution to measure microleakage as dye penetration. Immediately after insertion of the restorations, all the materials showed a higher microleakage than after 1-2 days. After 4-8 weeks, all the restorations exhibited an increased permeability suggesting that hygroscopic expansion was not sufficient to keep pace with hydrolytic degradation of the restorations. Neither thermocycling or occlusal stresses increased the microleakage of the restorations.

Composite Resins↗

PubMed2006

Penetration ability and microleakage of a fissure sealant applied on artificial and natural enamel fissure caries.

OBJECTIVES AND METHODS: This study investigated the sealing ability of a current available unfilled fissure sealant applied over sound (n=80), artificially created (n=80) and naturally carious fissures (n=80) under different humidity conditions (90+/-2 and 45+/-2% relative humidity) and etching times (40 and 60s). All samples were submitted to 5000 thermal cycles and examined by light microscopy after sectioning. Microleakage, penetration ability, fissure type, fissure entrance angle, sealant occlusal length, caries location and caries depth were assessed. RESULTS: The significantly longer sealant occlusal length and larger entrance angle exhibited by shallow fissures, contributed to their higher microleakage and smaller amounts of unfilled areas compared to deep fissures. Sealant microleakage was significantly influenced by the condition of the enamel (sound, artificial and natural caries) and the caries location in the fissures, but not by enamel caries depth (D1 and D2), etching time, or humidity condition. Natural caries exhibited significantly higher microleakage than sound or artificially created carious fissures. CONCLUSIONS: Based on the results of this study, it can be concluded that location of caries in the fissure rather than its depth should be taken into account when applying a fissure sealant. When the borders of the fissure sealant are on carious enamel, a significantly higher microleakage must be expected. The artificial caries model was not a suitable method to assess the behavior of natural fissure caries.

Dental Caries↗

PubMed2006

The evaluation of microleakage and bond strength of a silicone-based resilient liner following denture base surface pretreatment.

STATEMENT OF PROBLEM: The failure of adhesion between a silicone-based resilient liner and a denture base is a significant clinical problem. PURPOSE: The purpose of this study was to examine the effects of denture base resin surface pretreatments with different chemical etchants preceding the silicone-based resilient liner application on microleakage and bond strength. The initial effects of chemical etchants on the denture base resin in terms of microstructural changes and flexural strength were also examined. MATERIAL AND METHODS: Forty-two polymethyl methacrylate (PMMA) denture base resin (Meliodent) specimens consisting of 2 plates measuring 30 x 30 x 2 mm were prepared and divided into 7 groups (n = 6). Specimen groups were treated by immersion in acetone for 30 (A30) or 45 (A45) seconds, methyl methacrylate monomer for 180 (M180) seconds, and methylene chloride for 5 (MC5), 15 (MC15) or 30 (MC30) seconds. Group C had no surface treatment and served as the control. Subsequently, an adhesive (Mollosil) and a silicone-based resilient denture liner (Mollosil) were applied to the treated surfaces, and all specimens were immersed in the radiotracer solution (thalium-201 chloride) for 24 hours. Tracer activity (x-ray counts), as a parameter of microleakage, was measured using a gamma camera. For bond-strength measurement, 84 rectangular PMMA specimens (10 x 10 x 40 mm) were surface-smoothed for bonding and treated with the different chemical etchants using the same previously described group configurations. The adhesive and the silicone-based denture liner were applied to the treated surfaces. Tensile bond-strength (MPa) was measured in a universal testing machine. Flexural strength measurement was performed with 49 PMMA specimens (65 x 10 x 3.3 mm according to ISO standard 1567) in 7 groups (n = 7), with 1 flat surface of each treated with 1 of the chemical etchants preceding adhesive application. The flexural strength (MPa) was measured using a 3-point bending test in a universal testing machine. The data were analyzed by 1-way analysis of variance and the Tukey HSD test (alpha = .05). RESULTS: Significant differences were found between the groups in terms of microleakage (P < .0001). The lowest microleakage was observed in group M180 (30,000 x-ray counts) and the highest in the control group (44,000 x-ray counts). The mean bond strength to PMMA resin ranged from 1.44 to 2.22 MPa. All treated specimens showed significantly higher bond strength than controls (P < .01). The flexural strength values all significantly differed (P < .05). All experimental specimens that had chemical surface treatments showed lower flexural strength than controls (P < .05). CONCLUSION: Treating the denture base resin surface with chemical etchants increased the bond strength of silicone-based resilient denture liner to denture base and decreased the microleakage between the 2 materials. Considering the results of both tests together, the use of methyl methacrylate monomer for 180 seconds was found to be the most effective chemical treatment.

Acid Etching, Dental↗