Er:YAG laser cavity preparation and composite resin bonding with a single-component adhesive system: relationship between shear bond strength and microleakage

BACKGROUND AND OBJECTIVES

The purpose of this study was to assess the performances of a single-component adhesive system when an Er:YAG laser was used to prepare cavities.

STUDY DESIGN/MATERIALS AND METHODS

Shear bond strength tests were performed on composite rods bonded with a single-component adhesive system to dentin surfaces prepared using either bur+acid, Er:YAG laser (fluence = 44 J/cm2), or Er:YAG laser+acid. Class V cavities were prepared differently according to the molar surface: buccal surfaces were prepared using a diamond bur, and lingual surfaces using the Er:YAG laser. In group 1, cavity walls were not acid treated after Er:YAG laser preparation. In group 2, only the enamel walls were acid treated. In group 3, all the enamel and dentin walls were acid treated. Microleakage was assessed using a methylene blue dye penetration method.

RESULTS

Bond strength values did not differ significantly between the three groups (P = 0.162). Better marginal adaptation was obtained between the composite resin and cavity walls when Er:YAG laser preparation was followed by a total acid etching (P = 0.008).

CONCLUSIONS

Our results supported the use of single-component adhesive systems in cavities prepared using Er:YAG laser. The step of acid etching must be maintained for the whole cavity walls in regard of the microleakage values.

Effect of surface penetrating sealant on surface texture and microhardness of composite resins

The application of Fortify (Bisco, Lombard, IL), an unfilled resin, to the surface of composite resin restorations is intended to fill in defects in the surface that persist despite polishing, improve marginal integrity, and increase these materials' resistance to abrasion. The aim of this study was to observe the surface texture by scanning electron microscopy and measure the microhardness of the surface. For each sample of composite resin covered with glaze, 40 measurements were made of the thickness of the resin. Measurements of the Vickers microhardness included three samples of composite resin, three samples of glaze, and six samples of composite resin covered with glaze. A relationship was established between microhardness and thickness. Scanning electron microscopy showed a noticeable improvement in the surface texture. Nevertheless, areas were seen in which glaze seemed very thin or even completely absent. Measurements of the thickness ranged from 0-70 microm. The mean microhardness of composite resin was 65.8 +/- 0.7, while the mean hardness of glaze was 7.3 +/- 0.7. The microhardness of the double layer was reduced, depending on the thickness of the glazing resin. The capacity of glaze to mask surface defects of composite resin was shown, but it was difficult to obtain a regular surface with liquid resin. The application of this product caused a decrease of the microhardness of the composite resin's surface.

In vitro action of Bordeaux red wine on the microhardness of human dental enamel

Several studies have demonstrated that the regular and large consumption of wine is associated with increased risk of tooth erosion. Here, the effect of Bordeaux red wine on enamel was estimated by measuring changes in its Vickers microhardness. Thirty premolars were used; microhardness tests were performed on buccal areas before and after 10, 30, 90 and 120 s immersion in the wine (pH=3.9). Enamel surfaces were also observed by scanning electron microscopy. No statistically significant difference was found between the mean Vickers microhardness obtained at t=0 and 90 s, but slight signs of enamel demineralisation were observed with the scanning electron microscope. It appears that wine has no disastrous effect on the microhardness of dental enamel when the two are in contact for less than 90 s. When the exposure is for at least 120 s, it may become harmful, as the decrease in the microhardness of enamel was then significant (P<0.05).

Shear bond strength of self-etching adhesive systems to Er:YAG-laser-prepared dentin

This study was conducted to compare the shear bond strengths of composite resin bonded to Er:YAG laser or bur-prepared dentin surfaces using three self-etching adhesive systems. The occlusal surfaces of 120 human third molars were ground flat to expose dentin. The dentin was prepared using either a carbide bur or an Er:YAG laser at 350 mJ/pulse and 10 Hz (fluence, 44.5 J/cm(2)). Three different self-etching adhesive systems were applied: iBond, Xeno III and Clearfil SE Bond. Rods of composite resin were bonded to dentin surfaces and shear bond tests were carried out. Both dentin surfaces after debonding and resin rods were observed using a scanning electron microscope. When the Xeno III was used, no difference was observed on shear bond strength values when bur and Er:YAG laser were compared. When using iBond and Clearfil SE Bond, bond strength values measured on Er:YAG-laser-prepared surfaces were lower than those observed on bur-prepared surfaces. The absence of smear layer formation during the preparation of the dentin by the Er:YAG laser did not improve the adhesion values of self-etching adhesive systems.

Root canal posts for the restoration of root filled teeth

BACKGROUND

The foundation for the reconstruction of endodontically-treated teeth can be provided by a metal or a non-metal post and core system but no guidelines exist for choosing one or the other in particular clinical cases.

OBJECTIVES

To assess the effectiveness of different post and core systems for the restoration of endodontically-treated teeth. The primary objective of this review was to compare the clinical failure rates of the different types of posts.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2005, Issue 3), MEDLINE (from 1966 to September 2005), Scopus (from January 1985 to December 2004) and EMBASE (until December 2004). We looked through reference lists of articles and dental conference proceedings. We contacted researchers in the field and manufacturers.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials (RCTs) comparing failures on endodontically-treated permanent teeth with different types of post. The outcomes were loss of retention, post fracture and root fracture.

DATA COLLECTION AND ANALYSIS

Two review authors (Michele Muller-Bolla (MMB) and Cybele Borg (CB)) independently assessed the quality of trials and extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Two trials involving 317 participants were included but only one of them, involving 200 participants, compared metal to non-metal posts. The other answered to the secondary objective. The risk of failure was greater with metal-cast posts (9/98) compared to carbon fibre posts (0/97) (risk ratio (RR) = 0.05 (95% confidence interval (CI) 0.00 to 0.90)) but the study was at high risk of bias. Thus fewer failures occurred when using non-metal posts but the evidence is unreliable.

AUTHORS' CONCLUSIONS

Our systematic review could not specify which type of post and core system should be used when two or three dentine walls remain. More RCTs are needed to confirm whether fibre-reinforced post and core systems are superior and to clarify the influence of the remaining tooth structure on the treatment outcome of the different post and core systems available. Well-defined inclusion criteria focusing on the number of dentine walls (two or three) should be used.

Shear bond strength of self-etching adhesive systems to Er:YAG laser-prepared dentine with and without pulpal pressure simulation

OBJECTIVE

This study was conducted to study the role of pulpal pressure on the shear bond strength of composite resin bonded to Er:YAG laser-prepared or bur-prepared dentine surfaces using a self-etching adhesive system.

MATERIALS AND METHODS

The occlusal surfaces of 80 human third molars were ground flat to expose the dentine. The dentine was prepared using either a carbide bur or an Er:YAG laser at 350 mJ/pulse and 10 Hz (fluence 44.5 J/cm(2)). Clearfil SE Bond was then applied with or without pressure. Rods of composite resin were bonded to dentine surfaces and shear bond tests were carried out.

RESULTS

When the Clearfil SE Bond was used without pressure, the difference between the shear bond strength values of bur-prepared and laser-prepared dentine surfaces was significant. When the Clearfil SE Bond was used with pressure, the difference of shear bond strength values was not significant between the two types of surface preparation.

CONCLUSION

The absence of smear layer formation during the preparation of the dentine by the Er:YAG laser did not improve the adhesion values of self-etching adhesive systems.

WITHDRAWN: Root canal posts for the restoration of root filled teeth

BACKGROUND

The foundation for the reconstruction of endodontically-treated teeth can be provided by a metal or a non-metal post and core system but no guidelines exist for choosing one or the other in particular clinical cases.

OBJECTIVES

To assess the effectiveness of different post and core systems for the restoration of endodontically-treated teeth. The primary objective of this review was to compare the clinical failure rates of the different types of posts.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2005, Issue 3), MEDLINE (from 1966 to September 2005), Scopus (from January 1985 to December 2004) and EMBASE (until December 2004). We looked through reference lists of articles and dental conference proceedings. We contacted researchers in the field and manufacturers.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials (RCTs) comparing failures on endodontically-treated permanent teeth with different types of post. The outcomes were loss of retention, post fracture and root fracture.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the quality of trials and extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Two trials involving 317 participants were included but only one of them, involving 200 participants, compared metal to non-metal posts. The other answered to the secondary objective. The risk of failure was greater with metal-cast posts (9/98) compared to carbon fibre posts (0/97) (risk ratio (RR) = 0.05 (95% confidence interval (CI) 0.00 to 0.90)) but the study was at high risk of bias. Thus fewer failures occurred when using non-metal posts but the evidence is unreliable.

AUTHORS' CONCLUSIONS

Our systematic review could not specify which type of post and core system should be used when two or three dentine walls remain. More RCTs are needed to confirm whether fibre-reinforced post and core systems are superior and to clarify the influence of the remaining tooth structure on the treatment outcome of the different post and core systems available. Well-defined inclusion criteria focusing on the number of dentine walls (two or three) should be used.