Shear bond strength of four orthodontic bonding systems.

Recently new orthodontic bonding systems have been developed for attachment of brackets to the etched facial surfaces of teeth. Two of these new systems use bonding agents that contain solvents. It is claimed that this improves the polymerization of the unfilled resin primer and may increase bond strength. A new light-cured restorative enamel/dentin-bonding agent has also recently been introduced. Its value in orthodontic bonding has not been determined. The aim of this investigation was to evaluate the shear bond strengths of the three new bonding systems and to compare these with a conventional orthodontic bonding system. Forty-eight enamel specimens were prepared with 600-grit silicone carbide paper, acid etched with 37% phosphoric acid, and assigned to four enamel-bonding treatment groups: (A) Saga sealant; (B) Maximum Cure; (C) Scotchbond-2; and (D) Concise enamel bond. After enamel priming, the specimens were bonded to Concise orthodontic bonding resin. The bonded specimens were thermocycled (15 degrees C to 45 degrees C) and then stored in distilled water at 37 degrees C for 7 days. Shear bond strength was tested with an Instron testing machine at a strain rate of 0.02 in/min. The mean shear bond strengths and standard deviations reported in MN/m2 were (A) 20.34 (5.37); (B) 25.33 (5.96); (C) 14.59 (5.25); and (D) 20.13 (4.98). The mean shear bond strengths for groups A, B, and D were significantly greater (p less than 0.05) than that for group C. The addition of solvents to the new orthodontic bonding systems does not appear to have a clinically significant effect. The new restorative bonding resin does not provide comparable enamel bond strengths.

Bonding glass-ionomer cements to chemomechanically-prepared dentin.

The aim of this investigation was to compare the shear bond strengths of two commercially available glass-ionomer cement base materials to remaining dentin: (1) after conventional caries removal and polyacrylic acid conditioning; (2) after chemomechanical caries removal (Caridex); and (3) after chemomechanical caries removal and polyacrylic acid conditioning. Ninety freshly extracted carious teeth were randomly assigned for caries removal with either the chemomechanical technique (N = 60), or with conventional mechanical drilling (N = 30). Caries removal was continued until the remaining dentin surfaces were judged sound. The remaining dentin in 30 of the teeth prepared with the chemomechanical technique, and in all of the teeth prepared with mechanical drilling, was treated with 10% aqueous polyacrylic acid for 10 seconds. Groups of 15 teeth were assigned for bonding with either Ketac-Bond or Shofu Glasionomer Base Cement. All bonded specimens were stored in a humidor at 37 degrees C for 24 hr. Shear bond strength was tested by means of a mechanical testing machine at a cross-head speed of 0.05 cm/min. Analysis of variance indicated no significant difference (p greater than 0.05) in the mean bond strength among the groups.

A bond strength study of luted castable ceramic restorations.

Accurate intracoronal castings can be produced using a castable ceramic--DICOR--for which there is a need to identify a suitable luting cement. The aim of this investigation was to evaluate the bond strength of three glass-ionomer luting cements and one resin cement to treated and untreated DICOR, enamel, and dentin surfaces. Forty "cerammed" DICOR specimens were assigned to four groups: (1-3) grit-blasting and bonding to each of the three glass-ionomer cements; and (4) acid-etching, silane coating, and bonding to the resin cement. Seventy enamel specimens were assigned to seven groups: (1-3) no etching and bonding to each of the glass-ionomer cements; (4-7) acid-etching and bonding to the glass-ionomer cements and the resin cement. Seventy dentin specimens were assigned to seven groups: (1-4) bonding to each of the three glass-ionomer cements and the resin cement; (5-7) polyacrylic acid preconditioning and bonding to each of the three glass-ionomer cements. The mean resin cement bond strengths (MN/m2) to DICOR (9.4) and to etched enamel (10.7) were significantly greater (p less than 0.01) than those of the glass-ionomer cements (DICOR, 0.8-1.2; enamel, 0.4-0.9). Preconditioning of enamel and dentin significantly increased (p less than 0.05) the bond strengths to the glass-ionomer cements. The mean bond strength of the resin cement to untreated dentin (4.3) was significantly higher (p less than 0.05) than the glass-ionomer bond strengths to untreated dentin (1.0-1.7) and to preconditioned dentin (2.1-3.3). The high bond strengths achieved with the resin cement are encouraging. Selected surface treatment of DICOR, enamel, and dentin prior to luting should be clinically useful.

Orthodontic bonding to porcelain--bond strength and refinishing.

Glazed porcelain surfaces are not amenable to resin penetration for orthodontic bonding. The aims of this study were to evaluate (1) the bond strengths of two orthodontic composite materials to treated porcelain surfaces, (2) the effect of thermocycling, and (3) the porcelain surfaces after refinishing. Sixty glazed porcelain disks were assigned to three surface treatment groups: Silane (S), roughening and silane (RS), and roughening (R). The acid-etched enamel surfaces of 20 extracted teeth served as a control group. Ten specimens in each group were bonded with either Concise or System 1. They were stored in water at 37 degrees C or thermocycled 8 degrees to 45 degrees C. Shear bond strength was tested with an Instron testing machine (0.05 cm/min). Analysis of variance showed that the four surface treatment groups and the two composite materials produced significantly different bond strengths (P less than 0.01 and P less than 0.05, respectively). The effect of thermocycling was not significant (P greater than 0.05). Acid-etched enamel/Concise produced the highest mean bond strength (17.4 MN/m2). This was significantly greater (P less than 0.05) than the mean bond strengths of S/Concise (11.1), RS/System 1 (8.6), RS/Concise (8.1), and enamel/System 1 (7.8). The latter four mean bond strengths in turn were significantly greater (P less than 0.05) than S/System 1 (2.5), R/Concise (2.1), and R/System 1 (1.8). Of the four refinishing systems evaluated, all produced smooth surfaces but were unable to reproduce a glazed appearance. Roughening of porcelain and the silane treatment achieve bond strengths that should be clinically successful.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemomechanical caries removal--a clinical evaluation.

The aim of this investigation was to evaluate the efficacy and convenience of decayed dentine removal with N-monochloro-DL-2 aminobutyrate (CARIDEX) in all classes of cavities. Fifty-seven patients, each with two teeth having similarly sized carious cavities, participated in this study. One cavity in each patient was treated with the chemomechanical CARIDEX technique and the other cavity was treated with conventional mechanical drilling. The cavities were restored with either amalgam, composite or glass ionomer restorative materials. The time taken for access and caries removal was noted and the efficacy of caries removal with each technique was evaluated. The chemomechanical caries removal technique was effective in removing 90-100% of decayed dentine in 98% of the cavities treated. Multiple regression adjusted access and caries removal time to account for volume of caries removed. This adjusted time was operator dependent, and ranged from 4 to 10 minutes longer for CARIDEX than for the conventional technique. Ninety-three per cent of patients preferred the chemomechanical method of caries removal over the conventional technique (highly significant P less than 0.001). Even though the chemomechanical removal of caries is slower than the conventional technique, the efficacy of CARIDEX and its high patient acceptance provides a viable alternative method for dentinal caries removal in all classes of cavities.

Managing orthodontic data on a small computer.

A literature survey of file management, relational database management, and network/hierarchical database management systems led to selection of dBASE III to manage patient records on an IBM PC in the Department of Orthodontics at the Louisiana State University School of Dentistry. The versatility of this system's internal language enables ad hoc analysis of clinical and personal data to meet both anticipated and unanticipated management and scientific needs.

Daily release of copper from dental alloy restorations in a patient with Wilson's disease.

Wilson's disease is a rare genetic disorder in which copper accumulates in tissues. Its victims must adhere to a strict dietary regimen yielding less than 2 mg of copper per day. Three major variables have been identified as being of critical importance in the treatment of these patients: the amount of copper naturally occurring in foods, the amount of copper introduced during the preparation of foods, and the amount of copper in the environment. An environmental variable that rarely has been addressed is the amount of copper in dental restorations. A case report is presented to discuss the possible consequences of copper-containing dental restorations for the patient with Wilson's disease.

The effectiveness of opaquer and color-modifier materials: a laboratory study.

New, direct bonding composite resin products are available for esthetic and restorative dentistry. As in vitro study was conducted to evaluate the stain-masking effectiveness of 57 opaquers or color modifiers. Results of the testing on 265 specimens are reported, ranging from minimal to excellent masking.

Retention of orthodontic bands with new fluoride-releasing cements.

The prevalence of enamel decalcification beneath orthodontic bands has indicated the need for a fluoride-releasing, enamel-adhesive orthodontic luting cement. The purpose of this study was to compare the retentive bond strengths of orthodontic bands cemented with two new fluoride-releasing cements, a zinc polycarboxylate and a glass ionomer, with the retentive bond strength of bands cemented with the standard orthodontic cement zinc phosphate. The site of cement failure was also evaluated. One hundred eighty extracted human molar teeth were embedded in resin blocks and randomly assigned to three cement groups. Adapted bands were cemented by a clinically acceptable technique. The cemented teeth were then assigned to one of three time intervals--24 hours, 7 days, and 60 days--and thermocycled in synthetic saliva. The force required to initially fracture the cement bond was used as a measure of cement retention. By means of the Instron, a tensile load was applied to each cemented band. The maximum retentive strength (cement failure) was interpreted from the stress-strain curve at the point where linearity deviated. The failure site was judged subjectively: between cement and enamel, within the cement, or between cement and the band. Using stress at failure, an analysis of variance showed no significant differences among the retentive strengths of the three cements. The chi-square test revealed a significant difference (P less than 0.01) between failure sites of the zinc phosphate and glass ionomer cements. Significantly more bands cemented with the glass ionomer failed at the cement/band interface, leaving the cement adhered to the tooth.(ABSTRACT TRUNCATED AT 250 WORDS)

The pulpal response to dilute citric acid smear removers.

The aim of this study was to determine the pulpal response to three dilute citric acid smear removers. Forty-eight vervet monkeys (Cercopithecus aethiops pygerythrus), in three groups of sixteen animals provided 384 tooth specimens for the histological evaluation of the pulpal response at 3, 31, and 59 days post-operatively. Labial Class V cavities were prepared in the maxillary and mandibular incisor teeth. The pulpal responses elicited by 1% aqueous citric acid, 1% citric acid in 30% ethanol and 0.1% citric acid in 30% ethanol solutions, in unlined cavities and in cavities lined with Dycal after acid application, were compared with those elicited by a negative control material--(Nobetec), and a positive control material--(Syntrex). Using Stanley's criteria the most severe pulpal responses were seen in teeth treated with 1% aqueous citric acid and 1% citric acid in 30% ethanol without a subsequent liner, and by Syntrex at all three time intervals. The use of Dycal as a liner after smear removal markedly reduced the pulpal responses.

Force degradation of orthodontic elastomeric chains--a product comparison study.

In the last 20 years, synthetic elastic modules have been introduced to the orthodontist. However, force decay of these materials has been a clinical problem and the purpose of this project was to evaluate the force decay patterns of three commercially available elastomeric products--Ormco Power Chain II, Rocky Mountain Energy Chain, and TP Elast-O Chain--in a simulated oral environment. Thermal-cycled samples experienced less force decay over a 21-day period than samples stored at 37 degrees C. Furthermore, statistical analysis confirmed that there was a highly significant difference (p less than 0.01) between the mean force exerted by short modules and long modules for each material. Overall, modules producing higher initial forces (short modules) underwent less force decay after 21 days than did modules producing lower initial force values (long modules). All materials exerted 216 to 459 grams of force initially. After 21 days of simulated tooth movement, the force exerted by the elastic modules was 70 to 230 grams--a significant reduction (p less than 0.001).

Pulpal responses evaluated by two assessment systems. Use of Nobetec as negative and Super-Syntrex as positive control materials.

In the assessment of pulpal responses to dental materials there is no general agreement regarding which system should be used in the selection of histologic sections for assessment and which negative and positive control materials should be used. The present study is an evaluation, on 227 sections, of two pulpal assessment systems and three section-selection methods using a negative (zinc oxide and eugenol cement) and a positive (silicate) control material. The results indicate that, depending on which system is used, considerable variation in response can be noted. Better standardization of methods is necessary.