Microleakage evaluation in amalgam restorations used with bases.

Marginal leakage in amalgam restorations often precedes the development of secondary caries. One potential way to improve the marginal seal of such restorations, and thus minimize the risk of caries development, is to apply a glass-ionomer base prior to amalgam placement. This study compared microleakage resistance among amalgam restorations placed with and without light-cured glass-ionomer base materials. Preparations were made in extracted human molar teeth. Four groups were studied, including copal varnish, which was used as a control. All specimens were restored with amalgam. Results indicated significantly greater leakage at the cavity wall/base interface for restorations with a copal varnish cavity liner than for those with a glass-ionomer base. Leakage differences among bases were also found at the amalgam/base interface. Best results were obtained with a dual-cure resin-based system. These samples showed minimal leakage at both the cavity wall/base and the base/amalgam interfaces. These findings suggest that light-cured glass-ionomer bases can be effective in the prevention of microleakage in amalgam restorations.     

Microleakage in conventional and bonded amalgam restorations: influence of cavity volume

This study verified the relationship between the volume and microleakage of conventional and bonded amalgam restorations. Also, the microleakage influence of intermediate materials, substrates and the direction of sectioning was investigated. Fifty-six bovine incisors were selected. Standard Class V cavities were prepared in buccal and lingual surfaces. For each tooth, two cavity sizes were prepared, corresponding to two cavity volumes: one larger (A) and the other smaller (B). The cervical wall was located in cementum/dentin and the incisal wall in enamel. The teeth were distributed in four groups (n=28) according to the intermediate material employed (glass-ionomer cement, resin cement, adhesive system and copal varnish-control). The materials were applied following manufacturers' directions. After restoration, the teeth were submitted to thermal cycling. They were then immersed in a dye solution and sectioned in two directions inciso-cervical (IC) and mesio-distal (MD) sections to evaluate the microleakage. Data were subjected to non-parametric statistical analysis (Wilcoxon's paired test and Kruskal-Wallis test). No significant difference was found between the two cavity sizes. Leakage in enamel was statistically lower than in the cementum/dentin interface (p < 0.05). In some situations, glass-ionomer or resin cement lined amalgam restorations presented less dye leakage than copal varnish lined restorations (p < 0.05). No significant difference was observed in microleakage between IC or MD sectioning. Within the limitations of this study, it was concluded that cavity size and direction of section were not significant factors for microleakage, while substrate and intermediate materials had a significant effect on the sealing ability in amalgam restorations.     

Secondary caries formation in vitro around glass ionomer-lined amalgam and composite restorations

SUMMARY The aim of this in vitro secondary caries study was to examine the glass-ionomer liner's effect on wall-lesion inhibition when a conventional and a light-cured glass ionomer liner was placed under amalgam and composite resin restorations. Class V preparations in extracted upper premolars were used and ten restorations were used for each of the following groups: (i) two layers of copal varnish and amalgam; (ii) conventional glass-ionomer and amalgam; (iii) light-cured glass-ionomer and amalgam; (iv) bonding agent and light-cured composite resin; (v) conventional glass-ionomer, bonding agent and light-cured composite resin; (vi) light-cured glass-ionomer, extended 0.3 mm short of the enamel margin bonding agent and light-cured composite resin; and (vii) light-cured glass-ionomer, extended 1 mm short of the enamel margin, bonding agent and light-cured composite resin. The teeth were thermocycled and artificial caries were created using an acid-gel. The results of this study showed that artificial recurrent caries can be reduced significantly ( P < 0.05) with a glass-ionomer liner under amalgam restorations. The results also showed that when the light-cured glass-ionomer liner was placed 0.3 mm from the cavo-surface margin under composite resin restoration, the artificial recurrent caries reduced significantly ( P < 0.05).     

不同窝洞处理剂对银汞合金充填微渗漏的影响

目的：探讨减少银汞合金充填后边缘微渗漏的有效方法。方法：选择无龋的离体磨牙４８个，随机分为４组，每个牙分别制面洞、颊面颈１／３洞。比较几种窝洞洞壁处理后对微渗漏的影响。结果：银汞合金充填１个月后，１０％ＥＤＴＡ处理窝洞组、１０％ＥＤＴＡ加护洞漆组与空白组之间的边缘微渗漏无明显差异，而含３％ＦｅＣｌ３的１０％枸橼酸（１０－３液）处理加银汞合金粘结剂组则明显减少微渗漏。结论：离体牙实验证明银汞合金粘结修复可明显减少银汞合金充填术后的微渗漏     

Effect of a resin-based desensitizing agent and a self-etching dentin adhesive on marginal leakage of amalgam restorations

AIM: The purpose of this study was to compare the marginal leakage of Class II amalgam restorations whose preparations were lined with a resin-based desensitizing agent, a self-etching adhesive system, and copal varnish. METHODS AND MATERIALS: Fifty-six freshly extracted human premolar teeth were divided into four groups. A Class II preparation was prepared with only a proximal box on the mesial and distal surfaces of each tooth. The cavities in one group were lined with a desensitizing agent (VivaSens) and a second group with an adhesive (Clearfil S3 Bond). A third group was lined with copal varnish (Copalite) and a fourth group was used as the control without any cavity liner. Spherical high copper amalgam was hand-condensed into each preparation, specimens were thermocycled, stained, and sectioned. Microleakage was graded using a stereomicroscope. Microleakage scores were calculated and analyzed using the Kruskal Wallis and the Mann-Whitney tests (alpha=0.05). RESULTS: Less microleakage was indicated with the VivaSens liner when compared with the other groups (P<0.05). Clearfil S3 Bond showed less microleakage than the control group (P<0.05), but the leakage with copal varnish and Clearfil S3 Bond was similar (P>0.05). CONCLUSION: VivaSens reduced the microleakage of Class II high copper amalgam restorations significantly more than the Clearfil S3 Bond and copal varnish.     

Effect of a copal varnish, ZOE or glass ionomer cement bases on microleakage of amalgam restorations

The purpose of this study was to evaluate the sealing ability of four cavity preparation treatment modalities under amalgam restorations. Class V cavity preparations were placed in 20 extracted teeth and randomly divided into four groups of five teeth each (10 restorations for each group): 1) no liner; 2) two applications of Copalite; 3) a base of IRM; and 4) a base of Chelon-Silver. After assigned cavity preparation treatment was accomplished, the teeth were restored with amalgam. The restored teeth were subjected to thermocycling and subsequently stained with basic fuchsin. The teeth were longitudinally sectioned and dye penetration recorded. Amalgam restorations with a Copalite or Chelon-Silver base exhibited significantly less microleakage than those amalgam restorations with an IRM base or no cavity preparation treatment. With the Copalite varnish, microleakage extended beyond the axial wall (toward the pulp chamber through the dentinal tubules) while with the Chelon-Silver base, microleakage was limited to the restoration-tooth interface.     

Addition of fresh amalgam to existing amalgam: microleakage study.

The purpose of this in vitro study was to determine whether adhesive lining materials reduce microleakage in amalgam restorations, and to observe the degree of microleakage at the interface between freshly placed (new) and existing (old) amalgam. Forty-eight specimens were used in the experimental groups. The materials used to study microleakage in this investigation were: copal varnish, a dentin bonding agent (Clearfil New Bond), and a 4-META adhesive (Amalgambond). No significant difference in microleakage was found at the interfaces between freshly placed and existing amalgam. Significantly less microleakage was noted in specimens using the 4-META adhesive and the dentin bonding agent as compared to specimens in which no lining material was placed. Significantly less microleakage was noted in specimens using the 4-META adhesive compared to specimens using cavity varnish.     

Microleakage of bonded amalgam restorations: effect of thermal cycling

This study examined the effect of thermal cycling on the microleakage of bonded amalgam restorations. Three dental amalgam alloys and a gallium alloy were tested with two adhesive resin systems and copal varnish as a control. Class V cavity preparations were prepared on 168 freshly extracted premolars or molars. The preparations were placed parallel to and 1.0 mm occlusal to the cementoenamel junction (CEJ). Four groups of 42 teeth each were treated with one of the following adhesive dentin systems: Bond-It, All-Bond 2/Resinomer or a copal varnish (Copalite). The four groups of 42 teeth each were then restored with one of three dental amalgams: Orosphere Plus, Indiloy, Oralloy or a Gallium alloy (Galloy), resulting in 12 test groups of 14 teeth each. The specimens were stored in double distilled water at 37 degrees C for 24 hours. Final contouring and polishing of the restorations were performed under water spray. Half of the restorations in each group were thermocycled for 3000 cycles (5 degrees C-37 degrees C-55 degrees C-37 degrees C) with a dwell time of 15 sec at each temperature. The other half were stored in double distilled water at 37 degrees C for 24 hours. Then all 168 restorations were stained with dye, sectioned and scored for microleakage. Results showed that the adhesive dentin systems reduced microleakage in amalgam restorations compared to copal varnish only in non-thermocycled specimens. Statistical analysis of the results showed that there was an extremely significant difference (p < 0.001) in microleakage between the non-thermocycled and the thermocycled specimens in all test groups, whereas, there was no significant difference (p > 0.05) among thermocycled specimens. The reduction of microleakage was not significantly different between Bond-It and All-Bond 2/Resinomer in non-thermocycled specimens. Oralloy showed the most microleakage in the non-thermocycled groups when compared to the other alloys using the same adhesive liner.     

Addition of Fresh Amalgam to Existing Amalgam: Microleakage Study

The purpose of this in vitro study was to determine whether adhesive lining materials reduce microleakage in amalgam restorations, and to observe the degree of microleakage at the interface between freshly placed (new) and existing (old) amalgam. Forty-eight specimens were used in the experimental groups. The materials used to study microleakage in this investigation were: copal varnish, a dentin bonding agent (Clearfil New Bond), and a 4-META adhesive (Amalgambond). No significant difference in microleakage was found at the interfaces between freshly placed and existing amalgam. Significantly less microleakage was noted in specimens using the 4-META adhesive and the dentin bonding agent as compared to specimens in which no lining material was placed. Significantly less microleakage was noted in specimens using the 4-META adhesive compared to specimens using cavity varnish.     

In vitro marginal leakage of cervical composite restorations lined with a light-cured glass ionomer.

The purpose of this research effort was to investigate the microleakage of cervical restorations lined with a light-cured glass-ionomer liner. Wedge-shaped cervical cavities were cut on extracted teeth with the gingival cavosurface margin involving dentin. The cavities were randomly assigned to each of each of three groups: (1) restored with a microfilled composite resin, (2) restored with a light-cured glass-ionomer liner and microfilled resin as in the "sandwich" technique, and (3) restored entirely with the light-cured glass-ionomer liner. Half of the specimens in each group were thermocycled. Microleakage of these restorations was assessed by dye penetration. The results showed that differences were more pronounced at the gingival margin. Composite restorations inserted over the glass-ionomer liner demonstrated significantly less leakage than when the liner was not used.     

Base-varnish interactions around amalgam restorations: spectrophotometric and microscopic assessment of leakage

Abstract — The effects of bases and cavity varnishes on microleakage around amalgam restorations were investigated in vitro. Restored teeth were examined after storage for 48 hours, 1 and 3 months, temperature cycling and immersion in methylene blue. Leakage of specimens, assessed quantitatively by microscopy (linear measurement) and spectrophotometry (volumetric measurement), showed the following decreasing order: no varnish, varnish-base, and varnish. Leakage around amalgam restorations can be minimized by the application of two layers of copal resin varnish limited to the walls and cavo-surface margins.     

3种银汞黏接剂抗微渗漏的效果研究

目的检验三种银汞黏接剂应用于粘接银汞修复时,其抗微渗漏的能力,寻找一种简单有效的黏接材料。方法选28颗新鲜前磨牙,在其近中及远中邻面制备边长分别是2 mm和4 mm的长方形,使其龈壁位于牙本质-牙骨质界,牙合壁位于牙釉质。28颗前磨牙按黏接材料的不同分为4组:空白对照组,树脂加强玻璃离子水门汀组,玻璃离子水门汀组,树脂型银汞黏接剂组。充填后,37℃水浴7 d,然后浸入亚甲蓝染色液中,37℃恒温染色48 h,统计其微渗漏结果。结果非参数统计显示实验组微渗漏小(P<0.01),树脂加强型玻璃离子组无微渗漏,与其他组有着显著差异(P<0.05),釉质侧的渗漏低于牙本质-牙骨质侧。结论粘接银汞修复是一项有效的技术,并且用树脂加强型玻璃离子作黏接剂有着更有效的防微渗漏效果,值得在临床推广应用。     

Microleakage in bonded amalgam restorations using different adhesive materials

The aim of this study was to verify the ability of different adhesive materials to prevent microleakage in bonded amalgam restorations. Standard cavities were prepared in both buccal and lingual surfaces of 35 bovine incisors. The gingival wall was located in cementum/dentin and the occlusal wall in enamel. Teeth (n=35) were divided into 5 groups, according to material employed (one glass-ionomer cement, two resin cements, one adhesive system, and Copalex varnish as a control). Following restoration, the teeth were submitted to thermal cycling. The teeth were subsequently immersed in methylene blue dye and sectioned to allow assessment of microleakage. Non-parametric statistical analysis indicated that all materials demonstrated less leakage than the control group (p<0.01). No leakage was found using the resin-modified glass-ionomer cement, which was significantly different from the other adhesive materials (p<0.05). Leakage in enamel was lower than in cementum/dentin margins. It was concluded that bonded amalgam was an effective technique, since all materials prevented microleakage in enamel and cementum/dentin, when compared to the control group, except Panavia in cementum/dentin margins.     

Creep as a mechanism for sealing amalgams

Dental amalgam seals itself over time. The reduction of microleakage in amalgam restorations has been explained by corrosion products filling in the interface gap between amalgam and tooth structure in order to seal the restoration interface. This concept has been widely accepted; yet, curiously, there is little research supporting this theory. The creep mechanism may be a plausible alternative to explaining why microleakage is reduced over time in amalgam restorations. Amalgam restorations are confined to the fixed space of the cavity preparation; expansion of the amalgam through internal phase changes in this confined area must be relieved. The resultant creep-expansion of the amalgam restoration fills in the tooth/amalgam interface gap. Once the interfacial gap is filled and amalgam has made intimate contact with the cavity wall, the dental amalgam slides along the tooth preparation plane as predicted by classic metallurgical studies. The results of the creep of amalgam have been observed clinically as the extrusion of amalgam from the cavity preparation. This explanation for amalgam sealing the tooth/amalgam gap fits many clinical observations and certain research data.     

Microleakage in amalgam restorations: influence of cavity cleanser solutions and anticariogenic agents

This study evaluated in vitro the influence of five solutions used to treat cavity preparations on microleakage of amalgam restorations. Seventy-two standard Class V cavities were prepared in buccal and lingual surfaces of 36 recently extracted human third molars. The cervical wall was located in cementum and the occlusal wall was located in enamel. Specimens were randomly divided into six groups (n=12) according to the solution employed to treat the cavities: Group I-2.5% sodium hypochlorite; Group II-Calcium hydroxide solution; Group III-1.23% Acidulated phosphate fluoride; Group IV-2% digluconate of chlorhexidine; Group V-anionic detergent solution (1.25% sodium lauryl sulfate) and Group VI-control group. The solutions were applied for one minute, followed by washing and drying. Two coats of copal varnish were applied in each cavity. The cavities were filled with capsuled amalgam GS-80 (SDI). After finishing and polishing, the specimens were submitted for thermal cycling followed by immersion in methylene blue. Then, the specimens were sectioned and microleakage was evaluated based on a standard ranking under magnification (40x). Data were subjected to statistical analysis using non-parametric tests. Results of the study concluded that leakage was higher in cementum than enamel (p<0.01). The substances employed have no influence on microleakage except for sodium hypochlorite, which increased leakage values in enamel (p<0.05).     

In vitro evaluation of two microleakage detection tests.

Two microleakage detection tests were evaluated to compare their capabilities for revealing the extent of leakage at the interface between amalgam restorations and tooth structure. Class V cavities were prepared in the buccal surfaces of extracted human canine and premolar teeth and were treated in one of the following ways: no liner or varnish, a copal varnish, or an adhesive resin liner. The cavities were restored with a high-copper single composition spherical amalgam alloy and the specimens thermally cycled. Following storage for 6 months, the teeth were exposed to separate solutions of 45Ca and an ultraviolet fluorescing dye. The teeth were hemisected longitudinally and leakage was evaluated by determining the degree of penetration of the two tracers at the occlusal and gingival margins. Statistical analysis revealed a significant difference between the two leakage techniques (P less than 0.05). The radioisotope test generally indicated a greater degree of leakage than did the ultraviolet dye test.     

Microleakage of a consolidated silver direct filling material.

Microleakage of an experimental direct filling material comprised of a chemically precipitated silver powder that had been surface treated with a dilute acid to promote cold welding upon consolidation was evaluated. Microleakage was compared to both dispersed-phase and spherical amalgam by use of an in vitro gas-diffusion method and in class 5 restorations placed in extracted human teeth. The effect of two cavity varnishes and two dentin adhesives as cavity liners on microleakage was also evaluated using extracted teeth. Microleakage of silver powder consolidated with dental instruments was less than that found with dental amalgam. The use of copal or polyamide cavity varnish resulted in the lowest combination of microleakage on dentin and enamel margins.     

Reducing microleakage with the glass-ionomer/resin sandwich technique

The effect on microleakage of two glass-ionomer/resin "sandwich" restorations and an incrementally placed microfilled resin restoration was tested in class 5 preparations extending apical to the cementoenamel junction. There was significantly less leakage detected in the sandwich restorations with microfilled resin placed in one or two increments. These results indicate that a glass-ionomer/microfilled resin sandwich restoration may significantly reduce microleakage in restorations extending below the cementoenamel junction.     

Experimental microleakage around ageing dental amalgam restorations: a review

In vitro and in vivo experimental microleakage around ageing dental amalgam restorations has been reviewed. The methodologies, materials and results were examined and discussed. The initial experimental microleakage which occurred around unlined/ unvarnished dental amalgam restorations and the development of leakage around lined/varnished dental amalgam restorations underlines the problem of attaining a permanent effective seal around dental amalgam restorations. The limitations of microleakage studies have been outlined and the importance of an understanding of the chemical changes which occur in the microcrevices stressed. This understanding may facilitate the production of a lifelong successful dental amalgam restoration and perhaps the development of an anticariogenic amalgam type fissure sealant.     

Liner and light exposure: effect on in-vitro Class V microleakage

This in vitro study evaluated the influence of different glass ionomer liners and curing methods on microleakage of resin composite restorations. Class V root preparations were made in 120 bovine incisors randomly divided into 12 groups according to liner and curing method. The resin composite system (Single Bond + Z100) was inserted and polymerized in one increment in all groups. Cavity preparations were either not lined (control), lined with a resin modified glass-ionomer cement (Vitrebond) or a conventional glass-ionomer cement (Ketac Bond). The restorations were light-cured using one of four curing methods. The teeth were thermocycled and immersed in 0.5% basic fuchsin, sectioned, and dye penetration was measured (Image Tool). No significant difference in leakage among conventional, ramp or pulse-delay methods was seen. High intensity light groups showed significantly greater penetration compared to other curing methods. No significant difference existed in marginal leakage between liners, but microleakage was significantly higher in groups restored using no liner. No relationship between lining technique and light curing method was observed. The use of glass ionomer liners reduced microleakage, while high intensity light curing produced the greatest dye penetration.