Clinical Significance of Bis-GMA and HEMA Orthodontic Resins Bonding to Enamel and Ceramic Materials.

The advancement of new ceramic materials for dental crowns has prompted the need for improved methods of bonding orthodontic brackets to these surfaces. Currently, lithium-disilicate is the primary material being used for anterior crowns, while zirconia is the primary material being used in the posterior. The purpose of this study was to compare the shear bond strength of HEMA (Assure® Universal Bonding Resin) and bis-GMA (Assure® PLUS All Surface Bonding Resin) orthodontic bonding resins on enamel, lithium-disilicate, and zirconia materials. Two groups were formed, with three tested surfaces per group (n = 20). The categories included premolars, zirconia rods, and lithium-disilicate rods. Group 1 was treated with Assure, and group 2 was treated with Assure PLUS. Zirconia rods (1 cm x 1 cm x 4 cm) were used to represent zirconia crowns, and IPS e.max CAD rods (1 cm x 1 cm x 2 cm) were used to represent lithium-disilicate crowns. Assure and Assure PLUS bonding agents were applied according to the manufacturer's specifications, and standard edgewise universal premolar brackets were secured using Light Bond™ paste without fluoride. After 24 hours the brackets were sheared with a universal testing machine (Instron® 5566A) and the results were recorded. Data were analyzed using a combination of ANOVA and Tukey tests. A P value of less than .05 was considered statistically significant. Although group 1 and group 2 gave statistically equivalent results, the authors found that the ease of use when applying the group 2 bonding agent made it a safer, superior product within the confines of this study. It did not require a 4-minute hydrofluoric acid-etch and needed half the curing time of the group 1 agent when bonding to ceramic materials.

Two-year evaluation indicates zirconia bridges acceptable alternative to PFMs.

OBJECTIVE: The aim of this in-vivo study was to evaluate the 2-year clinical performance of zirconia computer-aided design/computer-aided manufacturing (CAD/CAM)-generated bridges. METHODS: A total of 16 three- or four-unit Lava zirconia bridges were done on 15 subjects. The bridges were cemented using RelyX™ Unicem Self-Adhesive Universal Resin Cement. Evaluation was done at 6-month, 1-year, and 2-year recall visits. Evaluation criteria were color stability and matching, marginal integrity, marginal discoloration, incidence of caries, changes in restoration-tooth interface, changes in surface texture, postoperative sensitivity, maintenance of periodontal health, changes in proximal and opposing teeth, and maintenance of anatomic form. In each of these parameters, the bridges were rated in one of three possible categories: "A" (alpha)--ideal; "B" (bravo)--acceptable; and "C" (charlie)--unacceptable. RESULTS: After 2 years, 100% of the bridges were rated "A" for color stability and matching, marginal discoloration, incidence of caries, changes in restoration-tooth interface, changes in surface texture, postoperative sensitivity, and change in proximal or opposing teeth. In the parameter of marginal integrity, 6.25% of the bridges were rated "B;" the remaining 93.75% were rated "A." Maintenance of periodontal health was rated "B" for 6.25% of the bridges and "A" for 93.75%. At 2 years, 12.5% of the bridges rated "C" in maintenance of anatomic form and 87.5% rated "A." CONCLUSION: The overall clinical outcome was that the CAD/CAM-generated zirconia bridges were clinically acceptable.

Provisional materials: key components of interim fixed restorations.

Clinicians have many choices of provisional materials from which to choose when fabricating interim fixed restorations. While traditional materials are still in use today, temporary materials are continuously being updated and improved upon. In addition to the functional necessities required of the provisional material, it must also provide esthetic value for the patient. This article provides an overview of provisional materials, including newer bis-acryls that have helped eliminate some of the challenges associated with traditional acrylic materials. Composite resin preformed crowns for single-unit provisional applications are also discussed, along with CAD/CAM-fabricated materials. Regardless of the material selected, a provisional restoration must maintain and protect the underlying tooth structure from ill effects.

Investigation of a new approach to measuring contact angles for hydrophilic impression materials.

PURPOSE: The purpose of this investigation was to examine the initial water contact angles of seven unset impression materials using commercially available equipment, in an effort to determine whether polyether impression materials (Impregum) have lower contact angles and are, therefore, more hydrophilic than VPS impression materials. MATERIALS AND METHODS: The hydrophilic properties of unset polyether and VPS impression materials were analyzed with respect to their water contact angle measurements using the commercially available Drop Shape Analysis System DSA 10. Twenty-five data points per second were collected via video analysis. There was no delay from start of measurement and data collection. Data was collected for approximately 12 s. Droplet size was determined on the thickness of canula. If the droplets became too small in volume, the water that evaporated during the measurement was large in comparison to the volume of the droplet. Therefore, 5 microl was chosen as the lowest volume. Five trials were conducted per series for each featured material. Contact angles were calculated using the circle fitting method. Three tests using this technique were designed to control the variables of contact angle measurement with regard to time, the varying amount of fluid in contact with impression material during clinical use, and material thickness. Sample thickness of impression material was controlled by stripping the paste flat on a glass plate using a marking template to ensure a constant film thickness. Tests were conducted in a climatized room at 24 degrees C +/- 1 degree C. Deionized water was used as the fluid. The device was calibrated according to manufacturer's instruction for Young-Laplace fitting prior to the measurements. Results were analyzed using One-Way ANOVA, Tukey test, and t-test, as appropriate. RESULTS: Comparing the fast setting impression materials by One-Way ANOVA and Tukey tests (p < .05) revealed the initial contact angles to range from 66.2 +/- 1.5 degrees to 127.5 +/- 4.4 degrees , of which the polyether material was the lowest after 45 s (66.2 +/- 1.5 degrees ), 120 s (70.3 +/- 2.8 degrees ), and 24 h (80.3 +/- 1.0 degrees ) after start of the mix. The selected times represent the different stages of unset material, ranging from 45 s as the earliest practical data collection time to 24 h, at which a stone model would be poured. The polyether materials tested exhibited lower contact angles and, thus, significantly higher initial hydrophilicity than all measured VPS materials. Additionally, Impregum impression materials are more hydrophilic in the unset stage than in the set stage. VPS may show a stepwise development of hydrophilicity in the set stage that was not observed in the unset stage. CONCLUSIONS: The polyether impression materials tested were significantly more hydrophilic before, during, and after setting than that of VPS impression materials. Regardless of the amount of water in contact with the impression material, the polyether impression materials showed a significantly higher hydrophilicity in the unset stage than the VPS materials. The initial contact angle was not dependent on the thickness of the material. All parameters, including variation of time, volume of water droplet, and thickness of material, resulted in different absolute contact angles, but did not lead to a dramatic change in the ranking of the materials with regard to their hydrophilic behavior.

Clinical evaluation of total-etch and self-etch bonding systems for preventing sensitivity in Class 1 and Class 2 restorations.

The author conducted an in vivo investigation to compare the clinical performance of 4 commercial bonding agents on postoperative sensitivity. Restorations in this study were limited to Class I and Class II lesions. The patient pool consisted of 36 patients and 72 teeth (2 teeth per patient) with either a Class I or Class II lesion > 1 mm in depth present in both teeth. The 4 adhesives tested in this study were distributed among patients as follows: on the first tooth, 12 patients received an application of adhesive 1, 12 received adhesive 2, and 12 received adhesive 3. All 36 patients received an application of adhesive 4 on the second tooth. All lesions were restored using a submicron particle hybrid composite. One-day and 1-week recall evaluations to measure sensitivity were taken by administrative staff in-office and by telephone. An independent clinician assessed the 1-month recall of each patient with the patient present in a clinical setting. No statistically significant differences were seen among the groups at any recall interval; however, the fourth adhesive performed consistently better than the other 3 at all intervals. All 4 bonding agents performed with clinically acceptable outcomes after a 30-day period. Certain lesion, tooth, and patient characteristics may predispose restorations to sensitivity.

Applicable research in practice: understanding the hydrophilic and flow property measurements of impression materials.

The flow properties and hydrophilicity of an impression material are key factors that affect its performance. This article details in vitro studies comparing these properties in 1 polyether and several vinyl polysiloxane light-body impression materials. The first series of studies examined the materials' flow properties used in a "shark fin" measurement procedure to determine which exhibited superior flow characteristics. The second series of studies reviewed the hydrophilic properties of the materials. Video analysis was used to record contact angle measurements at the early- and late-stage working times. Results showed 1 polyether material to be more hydrophilic. Applying this knowledge to practice, the authors present a clinical case in which a polyether's superior flow and quality of detail were used to make impressions for a patient receiving 8 single-unit zirconia crowns.

Comparison of temperature changes in the pulp chamber induced by various light curing units, in vitro.

This study compared the temperature increase in a pulp chamber as a result of using various light-curing units during resin composite polymerization, and it determined the effect of remaining dentin thickness on temperature rise. A Class II occlusodistal cavity with a remaining dentin thickness of 2 mm was prepared in an extracted human mandibular molar. A 2-mm layer of fine hybrid resin composite was placed on the floor of the proximal box. A K-type thermocouple was inserted into pulp chambers filled with heat sink compound, and pulp chamber temperature rise (starting temperature: 37.0 +/- 0.1 degrees C) during polymerization of the composite was measured. The light-curing units tested included two halogen lights, Spectrum 800 and Elipar Trilight (Standard and Exponential mode); a light-emitting diode (LED, Elipar Freelight) and a plasma arc (Virtuoso, Xenon Power Arc). Irradiation time was 40 seconds for the halogen and LED lights and 3 seconds for the plasma arc light. Five measurements were carried out for every light-curing unit. The same experimental design was conducted after the cavity preparation was modified, leaving a 1-mm thick dentin layer. The Kruskal-Wallis and multiple comparison tests were used to evaluate the differences among the tested curing units. Mann Whitney-U tests were used to compare the mean temperature rise in each curing unit for different remaining dentin thicknesses. The increase in pulp chamber temperature ranged between 1.40-3.8 degrees C. The highest temperature rise was observed when using Elipar Trilight Standard mode, and the lowest temperature rise was observed with light emitting diode for both remaining dentin thicknesses. The only significant differences in temperature rise were observed between Elipar Trilight Standard mode and LED. No significant difference (p > 0.01) existed for the different modes of Elipar Trilight. A statistically significant higher temperature rise was observed within each curing unit at a depth of 1 mm compared to 2 mm. Although the tested light-curing units caused a temperature rise in the pulp chamber, none exceed the critical value of 5.5 degrees C.

Restoring anterior maxillary dentition using alumina- and zirconia-based CAD/CAM restorations.

Despite proven strength, durability, and improved esthetics, ceramometal restorations have not consistently enabled the most esthetic, lifelike reproduction of natural dentition. Also, inherent weaknesses in many metal-free materials have precluded their use in the high stress-bearing posterior region. Therefore, as a result of the need for esthetic and durable all-ceramic restorations, manufacturers have introduced ceramics with an increased alumina or zirconia content that are recommended for placement anywhere in the mouth for single units and as far back as the first premolar.

Success with inlays/onlays: the seven essentials.

Direct restorative materials have revolutionized the industry over the last several years. They offer the convenience to the patient of a one-visit procedure and they decrease overhead in the dental practice. However, it is essential to remember that direct procedures are not always the treatment of choice. For this reason, we should not discount the need for--or the value of--indirect techniques and laboratory-based procedures, such as inlays and onlays. Fit, form, and function can be more predictable when a procedure involves the ultraprecise workings of the dental laboratory--if the impression-making and other focus areas are given their due significance. This article provides key information about and clinical tips for the seven main facets of inlay/onlay fabrications that will lead to clinical success: diagnosis, tooth preparation, tissue management, impression making, temporization, laboratory communications, and final fit/occlusion.

Clinical evaluation of a 35% hydrogen peroxide in-office whitening system.

This study evaluated the effectiveness of light-curing (heat conversion) vs no light-curing (no heat conversion) of a 35% hydrogen peroxide in-office tooth whitening system. Twenty patients with sound medical history (without tooth sensitivity) participated in this randomized, parallel clinical evaluation. Only six maxillary anterior teeth with discoloration and a tooth shade of A3 or darker were selected. Patients received a complete prophylaxis and were evaluated for initial (baseline) shade by three independent evaluators, precalibrated at 85% rater reliability in determining shades before the experiment began. Participants received a 20-minute chairside whitening treatment with a 35% hydrogen peroxide agent using a reflective resin barrier for gingival isolation. During the whitening treatment, the 35% hydrogen peroxide agent was light-activated with a halogen curing light on teeth Nos. 6 through 8 (Group I), but was not light-activated on teeth Nos. 9 through 11 (Group II). All patients returned 24 hours after the whitening application for shade evaluation. Although there were isolated instances (7 out of 20 patients) of greater degrees of lightening in the light-curing group, there was no statistically significant difference using the Mann-Whitney U test (P > .05). This study indicates that light-curing is optional with this 35% tooth whitening system.