Glutaraldehyde/2-Hydroxyethylmethacrylate (GLUMA[R]) is a chemical frequently used for desensitization of teeth and has other uses as suggested in the literature. Some newer recommendations have been made relative to its use during tooth preparation, as a disinfectant, rewetting during bonding, prior to cementation of crowns and bridges, and in dealing with pulpal exposures. This article will explore the science behind these and other applications for this chemical and its effect on the tooth structure and its local environment.
Glutaraldehyde/2-Hydroxyethylmethacrylate (GLUMA[R]) has two active chemicals that affect tooth structure. 2-Hydroxyethylmethacrylate (HEMA) has been used as a bonding agent, (1,2) alone and in combination with other materials. (3) Glutaraldehyde has been used as a disinfectant alone and in combination with other chemicals. (4) GLUMA[R] was originally developed in 1984, and its patent has recently expired. Newer clone products are now available that are less expensive than the original GLUMA[R] Desensitizing product (not to be confused with GLUMA[R] Comfort Bond, a dentin bonding system; Heraeus Kulzer, South Bend IN), such as: G5 (Clinician's Choice, Boca Raton FL); Calmit (Caulk, Milford DE); Microprime G (Danville, Danville CA); Hema-Glu Desensitizer G (Health Dent'l, Naperville IL); Glu-Sense (Centrix, Shelton CT); Alpha-Ease (Dental Technologies Inc. Lincolnwood IL); and Hema-Seal G (Germiphene, Bantford, ON, Canada).
Effect on Dentin
As dentin matures, the triple helix structure of the collagen in it transforms reducible cross-links among the collagen fibrils with the nucleophilic addition of lysine and/or hydroxylysine, which results in more cross-linking collagen molecules than found in their reducible precursors. (5) More stable cross-linked bonds tend to give the tooth an ability to bend and recover, preventing fracture and making the tooth able to withstand normal occlusal forces.
When Glutaraldehyde-HEMA is added to the collagen of dentin, it reduces the lysine and hydroxylysine residues and decreases these residues in the reducible cross-links. The amino acids and cross-link composition is altered by this compound, increasing the cross-links and making the dentin stiffer. (6) Plain glutaraldehyde has been shown to improve dentin collagen stability and bond strength in both sound and caries-affected dentin. (7) Higher and increased stability of the tensile properties of glutaraldehyde-treated dentin were found after eight-month exposure to collagenase and water storage, indicating an enhanced preventive and restorative durability. (8) Glutaraldehyde increases cross-linked collagen and decreases the reducible cross-linking (easily broken bonds), increasing the toughness of the dentin and blocking the action of collagenase, preventing biodegradation. (9) Wet bonding to dentin causes a degradation of the collagen, which is prevented by the addition of the cross-linking agent glutaraldehyde. (10,11)
Munksgaard describes the chemical reaction when gluteraldehyde with HEMA is used: "... on application of GLUMA[R], amino-group-containing substances in dentin react with glutaraldehyde and start the formation of a HEMA polymer. This product may be cross-linked by an alpha,beta-unsaturated glutaraldehyde aldol condensation product and may bond to dentin by aldehyde fixation to dentin proteins. Resin composite will bond to this product by copolymerization." (12) The bond is thought to be to lysine and hydroxylysine in the collagen fibrils. (5,6)
Use of increased collagen cross-linking during dentin bonding can increase the mechanical properties of the dentin over time and improve the durability of the collagen bonding over time. (13,14) In addition, the combination of glutaraldehyde and HEMA is antimicrobial and occludes dentinal tubules, limiting the fluid flow and decreasing pulpal sensitivity. (14,15,16)
Use of dentin bonding systems alone in pulp capping has been shown to lead to persistent pulpal inflammatory reactions with a lack of dentin bridging found with calcium hydroxide. (17) Self-etching adhesive systems have a similar result in vivo. In an in vivo study using a rat model, calcium hydroxide produced remarkably better results with less pulpal inflammation. It was noted that more bacteria were seen with the dentin adhesives used than with the calcium hydroxide. (19,20) The use of GLUMA[R] in the event of a pulp exposure or near pulp exposure is thought to aid in improving the durability of any subsequent bond and eliminate bacterial infection in the applied area because of the gluteraldehyde.
In an in vivo study of primary teeth, glutaraldehyde, ferric sulfate, and formocresol were tested with a self-etching adhesive bonded to dentin for shear bond strength. The ferric sulfate and formocresol affected the shear bond strength adversely, whereas the glutaraldehyde-treated dentin had a significantly higher shear bond strength.
Testing of a dentin primer such as GLUMA[R] used prior to bonding as a wetting agent has shown that GLUMA[R] does not affect the erosion or the compressive strengths of Dycal. (22)
The hydrodynamic theory of stimulus transmission in dentin first hypothesized by Brannstrom in 1967 states that "... any stimulus causing an inward or outward movement of dentinal fluid stimulates nerves either in the pulpal one-half of dentin and/ or nerves in the pulp to elicit pain." (23) Capillary movement of dentinal fluid outward will cause activation of the A-delta nerve fibers and elicit a sharp pain response. (24) Application of cold in fluid-filled gaps containing bacteria will elicit this response. The hydrodynamic theory is accepted by experts as the most inclusive theory that explains the phenomenon of sensitivity and pain as well as the effects of microleakage. (25)
Sealing the exposed dentinal tubules, or occluding them, decreases the sensitivity. (26) The amount of dentinal sensitivity is directly related to the size and patency of the dentinal tubules. Occlusion of the tubules either by peri-tubular dentin deposition or the introduction of intra-tubular material reduces the flow of fluid. Irregular reparative dentin does this naturally. Reducing dentin permeability and fluid flow will decrease dentin sensitivity. (27)
GLUMA[R] Desensitizer has been shown to decrease hydraulic conductance of dentinal tubules; (28) decrease demineralization at the site of application; (29) decrease dentin permeability; (30,31,32,33) occlude dentinal tubules to a depth of 200 microm; (34,4) and is effective in humans to stop tooth sensitivity for at least six months, (35,36,37) to a year.38 Changing the viscosity of the GLUMA[R] product into a gel did not alter its effectiveness in decreasing tooth sensitivity. (39)
Effect of GLUMA[R] on Bonding to Dentin
Bonding to dentin is made difficult by the wetness of the vital dentin, the pulpal pressure, the thickness of the remaining dentin, and the position in the dentin relative to the pulp. Caries-affected dentin has mineral deposits in the dentinal tubules. Non-carious cervical lesions have hyper-mineralized dentin and denatured collagen, all of which affect the bond strength of adhesive materials. When self-etching adhesives are tested for bond strength, they lose bond strength after six months due to the effect of the pulpal pressure and the degradation of the bond. (40) Some dentin desensitizers have been recommended to prevent tooth sensitivity but also to block the tubular fluid from affecting the bond strength. (41) GLUMA[R]-treated dentin has higher hardness values, indicating a more thorough polymerization. (42) After etching for a dentin bonding procedure, if GLUMA[R] is used to rewet the dentin prior to bonding, subsequent drying had no effect on the adhesion of the bonding resin. (43) Rewetting the etched dentin with GLUMA[R] can improve mean bond strengths. (44) GLUMA[R] has been shown to either maintain, (45,46) or significantly improve, dentin bond strengths with a variety of dentin bonding agents. (47,48,49) The glutaraldehyde in GLUMA[R] will significantly improve bond strength (49) as well as act as a potent disinfectant even in low concentrations. (50) The gluteraldehyde causes cross-linking between the collagen fibrils found in the intertubular dentin, whereas dentin-bonding systems enmesh the collagen fibrils after etching has opened them. Dentin bonding agents also impregnate the dentinal tubules and form an impermeable layer, isolating the pulp from bacterial infection and preventing dentinal fluid flow. Both actions eliminate postoperative sensitivity.
Effect of GLUMA[R] on Cementation
The use of GLUMA[R] and potassium nitrate was tested in vivo on 75 vital teeth, and both the potassium nitrate and the GLUMA[R] reduced the post-operative sensitivity before cementation. However, the Gluma was more effective post-cementation than the potassium nitrate. (51) GLUMA[R] was tested for retentive strength after cementation using zinc phosphate, glass ionomer, and resin modified glass ionomer cements. GLUMA[R]-treated samples tested highest in retentive strength compared to a control when no desensitizer was used, and highest with resin-modified glass ionomer > glass ionomer > zinc phosphate. (52)
Adhesive luting agents have been tested with the use of GLUMA[R] to desensitize teeth after tooth preparation and before cementation. The results indicate that the GLUMA[R] either did not affect the bond strength (53,54) or actually improved the bond strength after cementation. (55,56,57,58) GLUMA[R] was also able to maintain bond strength after thermocycling and water storage better than the control group where an adhesive cement was used with no GLUMA[R]. (56) The GLUMA[R] samples also maintained their bond strength after chewing simulation better than the control cemented with a resin cement with no GLUMA[R]. (57) Contamination with provisional cement on the dentin did not alter the bond strength of adhesive cements used with GLUMA[R]. (55)
From this literature review, it is apparent that GLUMA[R] is effective at decreasing tooth sensitivity; either not affecting bond strength or actually improving bond strength when used with various dentin bonding systems as a rewetting agent after acid etching; improving bond strengths when used on caries-affected dentin and killing bacteria on affected dentin and in pulp capping situations; and either maintaining or improving bond strength when used either before temporization or before cementation on teeth prepared for crowns. GLUMA[R] also seems to improve the durability of dentin bonding over time, and after exposure to water, temperature changes, and forces of occlusion.
The author has no financial interest in any dental material companies nor in either publicly traded or privately held dental supply companies.
This article is another installment in the series of articles by Dr. Thomas Larson which demonstrate his and Northwest Dentistry's continuing commitment to presenting topics which address clinical situations and choices our dentist/readers deal with on a daily basis. "I chose Northwest Dentistry," Dr. Larson told us, "because if I were to publish in national journals, many of my former students would never see the articles. They are the audience to which my academic career is devoted. They are they audience that I am trying to affect by publishing best practices." The Northwest Dentistry Editorial Advisory Board feels that to have someone of Dr. Larson's academic experience and credentials providing our journal with his extensive yet concise reviews of the literature is of great value, and we have dedicated a portion of our clinical department to these articles.
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Thomas D. Larson, D.D.S., M.S.D.*
* Dr. Larson is Associate Professor, Department of Restorative Sciences, Division of Operative Dentistry, University of Minnesota School of Dentistry, Minneapolis, Minnesota 55455. Email is firstname.lastname@example.org.