Adhesion to dentin mediated by Gluma: effect of pretreatment with various amino acids

Dentin surfaces were treated with various amino acids. The treatment caused an alteration of the dentin surface that influenced the tensile bond strength to a restorative resin obtained with the Gluma system. The bond strengths varied between 5.6 and 14.2 MPa. Among the amino acids tested, N-phenylglycine produced the strongest bonds.

Dentine and enamel bonding agents

Previous studies have shown that sequential use of aqueous FO (ferric oxalate containing a small concentration of HNO3), acetone solutions of NPG (N-phenylglycine), and PMDM (the reaction product of pyromellitic dianhydride and 2-hydroxyethylmethacrylate) yields strong adhesive bonding of composite resins to both dentine and enamel. The purpose of this study was to determine if aluminum ions could be substituted for ferric ions and if the procedure could be simplified. Aqueous solutions containing aluminum oxalate and aluminum nitrate, followed in sequence by acetone solutions of NPG and PMDM, gave strong tensile adhesive bond strengths between a composite and extracted human teeth. Comparable values have been obtained with FO, NPG and PMDM. Aluminum oxalate solutions containing no nitrate gave lower bond strengths, as was the case with FO. Aqueous solutions of acidified aluminum oxalate can dissolve NPG, thereby allowing a simplification of the procedure. Tested for comparison, commercially available dentine bonding agents gave lower average bond strengths on dentine than did some of the experimental materials.

Effect of acidic pretreatment on adhesion to dentin mediated by Gluma

Tensile bond strengths between dentin and a typical restorative resin were measured after the dentin was treated with Gluma. Solutions of phosphoric, pyruvic, nitric, or oxalic acid, also containing various amino acids, were used as pretreatments. Without amino acids in the solutions, the pretreatments conferred bonds of low strength. Use of acidic solutions containing glycine or N-phenylglycine was found to give bonds of high strength to both dentin and enamel.

Surface discoloration of restorative resins in relation to surface softening and oral hygiene

Restorative resins are susceptible to softening caused by organic acids produced in plaque. Consequently, plaque-covered resin restorations may be liable to pronounced surface staining. In the clinical part of the study a relationship between surface staining and local oral hygiene was demonstrated. This may be explained by the results from the laboratory part of the study, in which a relationship between surface staining and softening was found.

Dentin-polymer bond promoted by Gluma and various resins

Gluma-treated dentin was covered with various resins before a microfilled composite was applied. The strength of the bond between dentin and composite established by this procedure was measured in shear and tensile tests. The effectiveness of the bonding was further tested by the width of the marginal contraction gap around fillings made in dentin by the above procedure. Resins containing propanal promoted shear bond strength of about 15 MPa. The tensile bond strength exceeded 22 MPa by one of the resins, but could not be measured because of frequent rupture in the composite. Between 30 and 70% of the fillings were without contraction gaps when propanal or p-toluenesulfinate-containing resins were used. It is proposed that oxygen inhibition of the polymerization on the dentin surface suppresses the bonding. Resins containing reducing agents may reduce oxygen inhibition and increase bonding by the adhesive.

Cavity preparation for restorative resins used with dentin adhesives

The marginal adaptation of Silux used with and without previous application of different dentin adhesives was analyzed for correlation between maximum marginal contraction gap (MG) and different combinations of one or more of the following variables: area of cavity walls (A), the total area of cavity bottom and cavity walls (B), cavity depth (h), area of cavity surface (S) and cavity volume (V). The best fit to linear regression was found with MG = a + b . V/A with the mean of the correlation coefficients being 0.907. The statistical analysis showed that in order to maintain the V/A ratio at a minimum, root caries lesions should not be prepared after excavation if the retention of the restorative resin can be ensured with an effective dentin adhesive. The greatest influence on the V/A ratio was found to be exerted by the radius of the cavity bottom; variation of the radius of the surface of the cavity also influenced the V/A ratio, but to a minor degree.

Dentin-polymer bond mediated by glutaraldehyde/HEMA

A restorative resin was bonded to EDTA-treated dentin by means of a mixture of glutaraldehyde and HEMA. The bond exhibited a tensile strength of 17.5 +/- 1.0 MPa (mean +/- SEM) and was unaffected by water storage at 37 degrees C for up to 6 months. The glutaraldehyde/HEMA mixture was found to be most effective when the pH was between 2 and 5; an application time of 10 s was found to be sufficient for the glutaraldehyde/HEMA mixture as well as for the EDTA-solution.

Effect of combining dentin bonding agents

The wall-to-wall polymerization contraction of a light-cured composite was measured in cylindrical dentin cavities treated with the bonding agents: Scotchbond, Clearfil Bond, Gluma/Scotchbond, Gluma/Silux Enamel Bond or Gluma/Clearfil Bond. Marginal gaps were prevented in 29 out of 30 cases when Gluma was used in combination with Clearfil Bond. This combination mediates a mean bond strength between composite and dentin of 20 MPa.

Comparative study of dentin adhesives

The marginal adaptation of Silux after application of different dentin adhesives was investigated in dentin cavities prepared in extracted human teeth. The cavity diameter ranged from 1.8 to 6.4 mm and the cavosurface angle was 90 degrees, 110 degrees, 135 degrees or 160 degrees. The investigation included the following adhesives: Clearfil, Creation 1150, GLUMA, NPG-GMA + PMDM, Palfique, Panavia, Scotchbond and Superbond. Silux Enamel Bond was used as control. The most effective adhesive was GLUMA followed by Superbond and then NPG-GMA + PMDM; Palfique, Panavia and Scotchbond were all less effective than NPG-GMA + PMDM, and both Clearfil and Creation 1150 were inferior to the control, Silux Enamel Bond. None of the adhesives were able to prevent the formation of marginal gaps when measured 10 min after polymerization. After water absorption for 1 day, only GLUMA and Superbond produced gapfree fillings. Increasing the cavosurface angle resulted in a significant improvement of the effect of all adhesives, the main reason for this being the reduced ratio volume of filling to area of cavity wall.

Bonding of restorative resins to dentine promoted by aqueous mixtures of aldehydes and active monomers

Effective bonding between restorative resins and hard dental tissues would eliminate the need for retentive undercuts and prevent the formation of marginal gaps. While bonding to enamel has found a satisfactory solution with the advent of the acid etch technique, bonding to dentine has been more elusive. Restorative resins may bond to dentine through mechanisms involving either the inorganic or the organic constituents of the dentine. In the present work the possibility of bonding to the organic part of dentine was investigated. Since the water present in the surface of moist dentine may impede bonding, the research was focused on adhesives that are operational in aqueous environments. Aqueous mixtures of aldehydes and certain active monomers constitute such adhesives. The strength of the bond between a restorative resin and dentine was measured using the mixtures as intermediaries. To remove the smear layer the dentine was pretreated with 0.5 M EDTA, pH = 7.4. Among the aliphatic aldehydes especially propionic aldehyde and glutaraldehyde were found to be effective. Aromatic aldehydes resulted in bonds of low strength. Among the monomers investigated HEMA (hydroxyethyl-methacrylate) gave rise to the bond of highest strength. Using an adhesive based on HEMA and propionic aldehyde or HEMA and glutaraldehyde bond strengths of 15 and 18 MN/m2, respectively, were obtained. The latter adhesive significantly reduced the width of the polymerization contraction gaps between resin and dentine.

Composite wall-to-wall polymerization contraction in dentin cavities treated with various bonding agents

Extracted human teeth are frequently used in studies on bonding of composites to dentin. However, little is known about the effect of storing conditions on the results recorded. The purpose of the present work was to measure the wall-to-wall polymerization contraction of a light-cured composite material with and without the use of five different dentin bonding agents in cylindrical dentin cavities prepared in extracted human teeth, either fresh or after storing for up to 4 wk in four different media. No effect of the storing conditions on the width of contraction gaps could be demonstrated when the teeth were stored in tap water or in a 1.0% aqueous chloramine solution. Aqueous solutions of either 0.1% benzalkonium chloride or 0.9% sodium chloride did occasionally affect the size of the contraction gap.

Effect of five adhesives on adaptation of resin in dentin cavities

Cylindric dentin cavities ranging from 2 to 6 mm in diameter were treated with different dentin adhesives: Clearfil, Gluma, NPG-GMA + PMDM, Scotchbond or Superbond before filling with Silux. The maximal contraction gap was measured 10 min after curing and compared with results from cavities where an adhesive was omitted. The effectiveness in reducing contraction gaps increased in the following order: Clearfil, Scotchbond, NPG-GMA + PMDM, Superbond and Gluma.

Formaldehyde as bonding agent between dentin and restorative resins

The bonding of restorative resins to dentin by means of formaldehyde used in conjunction with an OH-containing monomer as intermediary was investigated. In this way a bonding to the organic constituent of dentin is conceivable. Mean bond strengths of 0.6 kg/mm2 were obtained. Bond strengths of this order of size may be of clinical interest.

Bond strength between dentin and restorative resins mediated by mixtures of HEMA and glutaraldehyde

We investigated the bond strength between restorative resin and dentin pre-treated with mixtures of HEMA and glutaraldehyde. It is suggested that the mixture acts by forming a chemical bond of HEMA molecules to a collagen-glutaraldehyde reaction complex. Subsequently applied resin will then co-polymerize with the collagen-linked methacrylate groups. Statistical analysis of the results from varying mixtures of HEMA and glutaraldehyde revealed that the bond strength was highly dependent on the HEMA concentration, with a maximum at 35%, and nearly independent of the glutaraldehyde concentration when greater than 3%. The highest mean bond strength was about 1.8 kg/mm2, and bond strength of this order of size may be attractive for clinical use.

Softening of BISGMA-based polymers by ethanol and by organic acids of plaque

The Wallace indentation hardness is a determinant for the abrasion resistance of smooth surface resins. It was the aim of the present study to investigate the softening effect of ethanol and of organic acids of plaque on BISGMA-based polymers. The hardness was measured before and after soaking for 1 day in ethanol, acetic acid, propionic acid, or lactic acid. The last three liquids were found to induce a softening of the polymers. The softening effect was more pronounced when the polymer originated from monomer mixtures with low content of diluting monomer. This finding reflects the extent of polymerization of the polymers.