Effect of chlorhexidine application on the long-term shear bond strength to dentin of a resin-modified glass ionomer

PURPOSE

The aim of this study was to investigate the effect of chlorhexidine digluconate (CHX) application on the shear bond strength (SBS) of a resin-modified glass ionomer cement (RMGIC) to polyalkenoic acid-preconditioned dentin after 24 hours, six months, and 12 months of water storage at 37°C.

MATERIALS AND METHODS

Cylindrical molds, placed on flat, polyalkenoic acid (Cavity Conditioner® [GC]) preconditioned dentin surfaces of 90 human teeth embedded in resin, were filled with Fuji II LC® (GC), a RMGIC, with (n=45) or without (n=45) the prior application of a 0.05% CHX solution. Within each group, SBS was determined after 24 hours (n=15), six months (n=15), and 12 months (n=15) of storage in water at 37°C. The results were analyzed with two-way analysis of variance followed by Tukey multiple means comparisons (p<0.05). The type of bond failure (adhesive/cohesive/mixed) was noted and the results were analyzed with chi-square test (p<0.05).

RESULTS

After 24 hours, the SBS of RMGIC was not significantly different with (9.0 ± 2.8 MPa) or without (8.3±0.6 MPa) the application of CHX. After six months, however, SBS increased significantly in the group without CHX (12.7±3.4 MPa) but remained unchanged in the CHX group (9.4±4.0 MPa). Similar results without CHX (12.6±3.8 MPa) and with CHX (9.5±3.2 MPa) were obtained after 12 months. No significant differences in the type of debonding were found between the various groups tested.

CONCLUSION

The application of 0.05% CHX after dentin preconditioning did not seem to have affected the 24-hour SBS of RMGIC. However, the six- and 12-month SBS was significantly lower for CHX-treated samples, possibly as a result of CHX interference with both the bonding mechanism and the maturation reaction of RMGIC.

Influence of the time-point of salivary contamination on dentin shear bond strength of 3 dentin adhesive systems

PURPOSE

The aim of this study was to evaluate the influence of the duration of salivary contamination at different stages during the bonding procedures on shear bond strengths (SBS) of 3 dentin adhesives.

MATERIALS AND METHODS

Flat human dentin surfaces were produced by wet grinding on SiC paper 800. The adhesives used were Syntac Sprint (SS) (Vivadent), One Step (OS) (Bisco), Clearfil Liner Bond 2 (LB2) (Kuraray). Three durations of contamination (3 s, 10 s, and 20 s) at 3 stages (before adhesive application, after its application, and after its polymerization). In all cases the saliva was not rinsed off. Twenty-seven groups of 10 samples were studied according to 3 adhesives, 3 stages, and 3 durations of contamination. For each adhesive, 1 control group, 3 groups with contamination before adhesive application, 3 groups with salivary contamination on the uncured adhesive, and 3 groups with contamination after polymerization (except for SS) were studied. Composite cylinders (Z100, 3M; 3 mm Ø, 5 mm high) were polymerized on the surfaces and stored in 37 degrees C H2O for 48 hours prior to shear bond testing (v = 5 mm/min).

RESULTS

Anova and Scheffe tests showed that for the one-bottle systems tested, salivary contamination prior to adhesive application had no adverse effect on bonding efficacy, SBS decreased significantly when saliva contamination occurred after adhesive application. The self-etching primer tested was more tolerant to salivary contamination, except when the salivary contamination occurred before the polymerization of the adhesive.

CONCLUSIONS

Salivary contamination does not have the same influence at different stages of the bonding process with modern adhesives. Pending better knowledge of the mechanisms involved in the influence of salivary contamination on bonded assemblies, it seems necessary to continue to recommend using the rubber dam in adhesive dentistry.

Influence of a simulated oral environment on dentin bond strength of two adhesive systems

PURPOSE

To evaluate in vitro the influence of different clinical conditions (temperature, relative humidity) on dentin bond strength.

MATERIALS AND METHODS

Two different bonding systems were studied, ScotchBond Multi-Purpose Plus (SBMP) and Clearfil SE Bond (SE Bond). In the first part of the study, the different environmental conditions were: ambient conditions, i.e. 20 degrees C/30% relative humidity (RH), 30 degrees C/50% RH, 30 degrees C/65% RH, 33 degrees C/80% RH and 35 degrees C/95% RH. In the second part, the different interfaces (dentin/primer, primer/adhesive and adhesive/composite for SBMP and primer/adhesive, adhesive/composite for SE Bond) were also studied in order to explain the results obtained in the first part of the study. After the bonding procedure, a composite cylinder (Z100) was bonded to the surface using a Teflon mold (diameter: 3 mm/height: 5 mm). The different specimens were tested in a shear bond mode after a 24-hour storage in distilled water at 37 degrees C.

RESULTS

For SBMP, the shear bond strengths decreased when temperature/RH increased. The average values were very low when the 35 degrees C/95% RH conditions were simulated. A study of the interfaces showed that the primer/adhesive interface was the most sensitive to the environmental conditions simulated. For SE Bond, a decrease occurred but only at the highest temperature/humidity conditions. The interface study did not provide an explanation of the results obtained in the first part of the study.

An 18-month clinical study of bond failures with resin-modified glass ionomer cement in orthodontic practice

The purpose of this study was to evaluate, over an 18-month period, the clinical performances of a resin-modified glass ionomer cement for bonding orthodontic brackets and to analyze various factors that influenced their survival and failure rates. Two orthodontists using the edgewise technique participated in this study; 6113 brackets, including 20 molar tubes, were bonded with Fuji Ortho LC (GC, Europe, N.V. Leuven, Belgium) in 135 patients. Ceramic, metal, and resin brackets were tested, and both operators used the same bonding method for the brackets. The survival rate and the failure rate of the brackets were evaluated. The rates were determined by operator, bracket type, tooth position in the dental arch, and age and sex of the patients. Bracket survival rates were estimated using the Kaplan-Meier test. The Cox-Mantel statistical test with a level of significance set at 0.05 was used to compare survival curves. The chi-square test was used at a level of P < .05 to compare failure rates. The overall failure rate for the sample was 7%, and the overall survival rate was equal to 0.918. Age had no significant influence on the failure rate (P = .07); however, it had a significant influence on the survival rate (P < .01). The best survival rates were obtained in the groups aged 16 to 20 years (S[t] = 0.943) and older than 20 years (S[t] = 0.929). The difference between males and females was not statistically significant in terms of failure rate (P = .17). However, the Cox-Mantel test showed a higher bracket survival rate for the males (S[t] = 0.924) than for the females (S[t] = 0.839) (P < .00001). The influence of the operator was not statistically significant on the failure rate (P = .08); however, it was significant on the survival rate (P < .0002). Location in the arch had a significant influence on the failure and survival rates. The worst results were obtained in the upper incisors and the canines, and the best results in the lower premolars. Fifteen percent of the molar tubes failed; their survival rate was equal to 0.833. The failure rate was significantly greater for resin brackets than for metal or ceramic brackets (P = .007). The highest survival rate was obtained with ceramic brackets (P = .0001). This in vivo study showed that bonding brackets and molar tubes with Fuji Ortho LC is compatible with clinical orthodontic practice.

Bonding of resin cements to a metal substrate: influence of pretreatment on the adherence energy

The adherence of resin cements to restoration as well as tooth structure is of prime importance for the longevity of cemented restorations. It was the aim of the study to investigate the effect of an acid and a base primer on (i) surface polarity of a nonprecious alloy and on (ii) adherence energy of resin cements bonded to the alloy. The beams were pretreated with a 3% acetone solution of either maleic acid or N,N-diethanol-p-toluidine, and the solvent evaporated. The polarity was determined by means of measurements of contact angles. The adherence energy was measured by means of the wedge test, according to which 2 beams were glued together with the resin cement. A wedge was introduced between the joined beams to create a fissure, and on the basis of the length of the fissure, the adherence energy was calculated. It was found that the polar component of the surface free energy of the alloy increased as a consequence of the pretreatments. The results also showed that the pretreatments gave rise to an increase in adherence energy of 11-15 J/m2, equivalent to relative increases of 22-54%. The observed increases in adherence energy may be due to an increase in polar interactions at the interface between adhesive and substrate.

Factors affecting the adherence energy of experimental resin cements bonded to a nickel-chromium alloy

Reliable adherence of resin-based cements is of prime importance for the longevity of cemented restorations. The present study investigated whether a relationship exists between adherence energy to a metal substrate and the degree of cross-linking and wetting characteristics of resin-based luting agents. The adherence energies between a sand-blasted metal surface and a series of experimental resin cements were measured by means of the wedge test. The degree of cross-linking was calculated from the monomer composition of the resin cements. The measured wetting characteristics were work of adhesion and surface tension, and their dispersive and polar components. Adherence energy varied between 22 and 81 J/m2 and was influenced by the nature of the resin cements: Those with a low degree of cross-linking resulted in high adherence values. Furthermore, resin cements whose monomers were relatively polar gave rise to high adherence values. Although other metals may not behave in exactly the same way, these results may help in the formulation of new, more retentive resin cements.

Effects of surface treatment on the free surface energy of dentin

OBJECTIVES

The purpose of this study was to evaluate the influence of six treatments on the dispersive, acid, and base components of the free surface energy of dentin.

METHODS

Occlusal dentin surfaces were polished with 4000 grit abrasive paper, washed and air dried. Characteristics of the surface energy were calculated by measuring contact angles of the four following liquids:alpha-bromonaphtalene, glycerol, ethylene glycol, and water. The dentin was then treated with aqueous solutions containing: (1) oxalic acid and glycine (OX/GLY),(2) oxalic acid, glycine, and HEMA (OX/GLY/HEMA), (3) phosphoric acid (PA), (4) maleic acid (MA),(5) EDTA, or (6) NaCIO. After treatment, washing and air drying, the energy characteristics of the samples were evaluated again.

RESULTS

Three kinds of wetting behavior were observed: an increase (OX/GLY/HEMA), a stabilization (PA, NaCIO) or a decrease (OX/GLY, MA, EDTA) of the wettability of the dentin surface. The calculations demonstrated that dentin surfaces are basic.

SIGNIFICANCE

This study of the evolution of the surface energy components gave information on adhesion mechanisms involving hydrophilic and hydrophobic interactions. The results may be helpful in the formulation of conditioners and primers.

Bonding of luting materials for resin-bonded bridges: clinical relevance of in vitro tests

A retrospective clinical study on 78 resin-bonded bridges placed between 1981 and 1992 was used to validate the wedge test in the assessment of the bonding of resin-based luting material. According to the correlation obtained between the findings of the in vivo and the in vitro studies, the wedge test may be considered to be predictive of the clinical performance of resin bonds. The life expectancy of resin-bonded bridges bonded with the 4 META containing material tested appears to be longer than that for bridges bonded with conventional resin cements.

Adherence of resin-based luting agents assessed by the energy of fracture

The present study assessed the adherence of nine commercial resin cements by means of the wedge test. The beams of the test were made of a Ni-Cr-Be alloy, and the adhering surfaces were sandblasted with 250 microns Al2O3. The energy of fracture of the investigated cements varied from less than 10 J/m2 to 121 J/m2. The fracture energies were not influenced by 1) the thickness of the joint, 2) the width of the beams, 3) the use of an intermediary noncomposite resin, or 4) storage in water beyond 24 h. In spite of a rather high variability within groups, it is concluded that the wedge test may give relevant data on the performance of adhesive joints.