Edward J. Swift

Enamel and Dentin Bond Strengths of a New Self‐Etch Adhesive System

UNLABELLED statement of problem:  Self-etch adhesives typically are mildly acidic and therefore less effective than etch-and-rinse adhesives for bonding to enamel. PURPOSE   The purpose of this study was to evaluate the enamel and dentin shear bond strengths of a new two-step self-etch adhesive system, OptiBond XTR (Kerr Corporation, Orange, CA, USA). MATERIALS AND METHODS   The labial surfaces of 80 bovine teeth were ground to create flat, 600-grit enamel or dentin surfaces. Composite was bonded to enamel or dentin using the new two-step self-etch system or a three-step etch-and-rinse (OptiBond FL, Kerr), two-step self-etch (Clearfil SE Bond, Kuraray America, Houston, TX, USA), or one-step self-etch adhesive (Xeno IV, Dentsply Caulk, Milford, DE, USA). Following storage in water for 24 hours, shear bond strengths were determined using a universal testing machine. The enamel and dentin data sets were subjected to separate analysis of variance and Tukeys tests. Scanning electron microscopy was used to evaluate the effects of each system on enamel. RESULTS   Mean shear bond strengths to enamel ranged from 18.1 MPa for Xeno IV to 41.0 MPa for OptiBond FL. On dentin, the means ranged from 33.3 MPa for OptiBond FL to 47.1 MPa for Clearfil SE Bond. OptiBond XTR performed as well as Clearfil SE Bond on dentin and as well as OptiBond FL on enamel. Field emission scanning electron microscope revealed that OptiBond XTR produced an enamel etch pattern that was less defined than that of OptiBond FL (37.5% phosphoric acid) but more defined than that of Clearfil SE Bond or Xeno IV. CONCLUSION   The new two-step self-etch adhesive system formed excellent bonds to enamel and dentin in vitro. CLINICAL SIGNIFICANCE OptiBond XTR, a new two-step self-etch adhesive system, is a promising material for bonding to enamel as well as to dentin.

Computer-aided design/computer-aided manufacturing technology in customized orthodontic appliances

Why would the orthodontist want to customize treatment? Current bracket systems are based on an average tooth shape—but only a small percentage of our patients will have average teeth. When was the last time you had an average patient? The interand intra-individual variation is the reason why orthodontists must adapt their treatment to the patient’s specific tooth shape and morphology in order to achieve ideal alignment, esthetics, and occlusion.

Review of dental materials citations: Part B, July to December 1995

OBJECTIVE A lag of many months occurs between journal issue publication and updates to electronic databases. The objective of this literature analysis was to identify and categorize all of the dental materials citations in biomedical journals that were published from July 1995 through December 1995. METHODS Seventeen primary and 51 secondary journals were searched using their tables of contents to detect and record dental materials publications from July to December of 1995. Those journals that were typically rich in dental materials articles were classified as primary ones. Citations were categorized into 17 topics and divided into subsections. The review excluded case reports, most literature related primarily to dental implants, and most articles on biomedical materials used outside of the field of general dentistry. RESULTS The greatest number of citations was related to topics of dentin bonding and resin-based restorative filling materials (composites and glass ionomers). There was no major change in the number of dental materials publications per year reported from 1993 (n = 786) to 1995 (n = 751). SIGNIFICANCE This citation list provides a comprehensive resource for use by academicians and researchers to bridge the gap between initial publication and access to electronic searching methods for major databases.

Contemporary approaches to orthodontic retention.

Wouldn’t it be nice if teeth stayed aligned for life? In the absence of orthodontic movement, teeth exist in their current positions as a result of a dynamic equilibrium of multiple forces acting upon them (cheeks, tongue, lips, periodontal ligament, etc.).1 Following orthodontic movement, teeth have a tendency to return to their initial positions; hence, a retention phase is an integral part of orthodontic treatment.

Clinically relevant issues related to preheating composites: Commentary

Resin composite is the most commonly used material for direct placement restorations. In particular, composite is now used more frequently than amalgam for direct posterior restorations. However, resin composite still suffers from some disadvantages, including the use of an adhesive interfacial bond that degrades with time, moisture, and function in the mouth, and certain key mechanical properties (e.g., modulus of elasticity) that are inferior to those of amalgam. As such, there is a concern that the resin composite should be inserted into a preparation with as few voids as possible to enhance interfacial adaptation, and maximizing the composite degree of conversion so as to maximize mechanical properties. The use of preheated composite has been suggested to aid in both of these goals. This Critical Appraisal looks at evidence in the peer-reviewed scientific literature that examines the value of inserting warm composite into cavity preparations.

Dentin Bonding: Matrix Metalloproteinases and Chlorhexidine

Contemporary resin-dentin bonding is initiated by systems that use phosphoric acid or acidic resin monomers to remove mineral, exposing the superficial dentin collagen matrix. Collagen-associated proteins, including enzymes known as matrix metalloproteinases (MMPs), also are exposed. The collagen matrix is subsequently infiltrated with resins that are polymerized to establish an adhesive attachment to the dentin. Exposed collagen matrix that is not infiltrated with the adhesive can be degraded by associated MMPs, which might result in deterioration of the adhesive-dentin bond over time. Chlorhexidine (CHX) is able to inhibit MMPs by binding calcium and zinc ions necessary for proteolytic activity. This Critical Appraisal presents salient publications on research that evaluate CHX and its ability to limit MMP degradation of dentin bonds created by etch-and-rinse and self-etch adhesive systems.

Management of High Caries Risk Patients: Part 1—Risk Assessment

The global burden of oral disease and dental caries has been steadily rising even as improved and novel tools for reconstructing the damaged dentition are rapidly evolving. The increased burden of the dental caries worldwide may be attributed to the fact that dentists and dental schools still typically focus on treatment rather than prevention of the disease. The World Health Organization through the 60th World Health Assembly has passed a resolution that advocates integration of prevention and early intervention measures of dental caries for all the member nations. Although the traditional “drill and fill” approach has served well to restore function and esthetics, it has failed to prevent the incidence of new caries lesions. This becomes an even larger challenge in patients who are at a higher risk for developing new lesions.

Partial caries excavation

Regular readers will note that we depart from our normal Critical Appraisal format in this issue of the Journal. This particular Critical Appraisal resembles an expanded Contemporary Issues feature and describes a protocol for partial caries excavation that was recently implemented in the student clinics of the University of North Carolina (UNC) School of Dentistry.

Reversal of Compromised Bonding after Bleaching

Bleaching with peroxide agents compromises the adhesion of resin-based materials to enamel and dentin. The problem is likely caused by delayed release of oxygen from the teeth that inhibits resin polymerization at the interface. The typical method for avoiding problems with bonding to bleached teeth is simply to delay the bonding procedure for a week or two after bleaching. However, there is evidence that bonding can be done immediately if bleaching is followed by the application of an antioxidant. This Critical Appraisal reviews some of the published reports on the reversal of compromised bonding after bleaching via the use of antioxidants such as sodium ascorbate.

Current Usage of Glutaraldehyde/HEMA

The use of glutaraldehyde/2-hydroxyethylmethacrylate (HEMA) combinations has been recommended for routine use in restorative dentistry by many authors and opinion leaders. Clinical restorative sites are colonized by bacteria that can contribute to postoperative sensitivity or recurrent caries. The structure of dentin allows for fluid conductance, which has been identified by Brännström as the cause of dentin sensitivity and as well, its water content challenges short- and long-term adhesion. The glutaraldehyde/HEMA combination is stated to be antimicrobial, a flocculating agent that strengthens collagen, and an agent that can create tubular occlusion, thereby reducing postoperative sensitivity by limiting fluid movement without affecting the strength of bonding or adhesive cements. This Critical Appraisal reviews five publications that deal with the various issues and clinical challenges described above, and provides suggestions for additional reading. A Bottom Line summary is provided.