Composite Luting Agents Research Articles

Comparison of titanium dowel retention using four different luting agents

Luting material, surface properties, and loading conditions affect the retention of prefabricated dowels to varying degrees. The purpose of this study was to evaluate the effect of roughening of the dentinal walls and artificial aging on the retention of prefabricated tapered titanium dowels, using 4 different luting materials. One-hundred twenty-eight single-rooted teeth were selected, the coronal aspect of each tooth was removed, and the remaining root received endodontic therapy. All specimens were divided into 4 groups (n=32). Dowel spaces were prepared to a depth of 10 mm using ISO 90 rotary cutting instruments. Tapered titanium dowels were luted with the following luting materials: zinc-phosphate cement (Harvard cement), glass-ionomer cement (Ketac Cem EasyMix), resin composite luting agent (Panavia 21) with autopolymerizing dentin primer (ED-Primer), or a self-adhesive composite luting agent (RelyX Unicem). Both composite luting agents were used without acid etching of the canal dentin. Each luting agent was used under 2 conditions: in 1 subgroup (n=16) the dentinal walls were not roughened, and in the other subgroup (n=16), walls were roughened with a diamond rotary cutting instrument. Eight specimens from each subgroup were stored in water at 37 degrees C for 3 days; the other 8 specimens were stored for 150 days and subjected to simulated aging conditions using 37,500 thermal cycles (5 degrees C/55 degrees C) and 300,000 mechanical loading cycles with 30 N. Dowel retention (N) was measured using a universal testing machine with a crosshead speed of 2 mm/min. Data were analyzed using 2- and 3-way ANOVAs and the Tukey HSD test (alpha=.05). The dislodged dowels were examined microscopically to evaluate mode of failure. The nonroughened dentinal walls showed no significant differences between the different luting agents. Roughening the dentinal walls increased the retention significantly for all groups. This increase was significantly higher for the resin composite groups (P=.0001). Storage for 150 days with thermal cycling and mechanical loading caused a significant decrease in dowel retention (P=.001). The failure mode was purely adhesive at the luting material-dentin interface for all dowels cemented in nonroughened root canals. A mixed failure mode, adhesive at the luting material-dentin interface and cohesive in the luting material, was observed for dowels cemented in roughened root canals. Roughening the dentinal walls and the use of resin luting cements provided statistically significant increases in dowel retention values.

Qualitative assessment of surface topography of XeCl laser etched Ni–Cr alloy

The aims of this study were to compare the mode of debonding (adhesive or cohesive) of laser-etched Ni-Cr alloy (Wiron 99) to a standard sandblasting technique, and to a combination of sandblasting and laser etching. The etched surfaces were examined using optical and electron microscopy techniques. Five groups of randomly allocated Ni-Cr cylinders were prepared: Group I-sandblasted; Groups II-IV-laser etched at three fluences (3.0, 4.0 and 4.9 J/cm2), Group V-combination sandblasting and laser etching (4.0 J/cm2). Within groups specimens were bonded into pairs (N=8) with composite luting cement (Panavia 21) prior to tensile debonding. Optical and scanning electron microscopy were performed both prior to and following debonding. An oxide layer was observed on sample surfaces before surface preparation by lasing or abrasion. Sandblasting removed the oxidation layer, which low and medium laser fluences alone failed to fully ablate. The highest (4.9 J/cm2) laser fluence melted the surface of the Ni-Cr alloy, covering the oxidation layer. A combination of sandblasting and lasing at 4.0 J/cm2 allowed full removal of the surface oxidation layer due to abrasion, followed by roughening of the surface with the laser. This resulted in greater mean tensile debonding strengths [Murray, A, Attrill, D, Dickinson, M. Dent Mater, 2004, In press] and a tendency for cohesive rather than adhesive interface failures. Groups I-IV underwent partial adhesive failure at both surfaces. Group V, in the main, underwent cohesive failure with a layer of adhesive remaining on both surfaces. Laser etching of Ni-Cr alloy in combination with sandblasting optimises bonding to composite luting agents, resulting in a high proportion of cohesive failures when compared to sandblasting or lasing alone.

Computer-Aided Direct All-Ceramic Crowns: Preliminary 1-Year Results of a Prospective Clinical Study

The objective of this study was to investigate the clinical performance of: (1) adhesively placed Cerec crowns with reduced stump preparations, and (2) Cerec endo crowns. The crowns were examined at baseline using modified USPHS criteria in 20 patients with 10 Cerec crowns with reduced stump preparations and 10 Cerec endo crowns. All crowns had been produced chairside with the Cerec 3 CAD/CAM method using the function mode. The crowns were machined from Vita Mk II feldspathic ceramic blocks, polished manually, and placed with dual-curing composite luting agent using a functional adhesive. After 1 year, a follow-up examination of the crowns was conducted; all 20 Cerec crowns were rated with a clinically acceptable A or B rating. Fractures or loss of retention were not observed. The method of producing and placing all-ceramic crowns with reduced stump preparations and endo crowns chairside in one appointment can be implemented successfully in private practice.

Influence of different adhesive resin cements on the fracture strength of aluminum oxide ceramic posterior crowns

The influence of different types of adhesive resin cements on the long-term prognosis of aluminum oxide ceramic posterior crowns is unclear. The purpose of this study was to evaluate the fracture resistance of aluminum oxide ceramic on maxillary posterior crowns cemented with different resin luting agents before and after cyclic thermomechanical loading. Material and methods Forty-eight maxillary first molars were prepared and restored with standardized aluminum oxide ceramic (In-Ceram Alumina) crowns. The test specimens were randomly divided into 3 groups (n=16). The crowns were luted with an acrylic resin cement (Super-Bond C&B, control, Group SB) and 2 composite luting agents (Panavia F, Group PV; and Rely X Unicem, Group RX). Half of the specimens were exposed to thermomechanical fatigue in a masticatory simulator. All specimens were tested for fracture strength (N) using quasistatic loading. The Wilcoxon rank sum test was used to compare the fracture strength (alpha=.05). All specimens survived the exposure to the simulator. The following median fracture strength values were obtained without/with thermomechanical fatigue loading: Group SB, 2726 N/2673 N; Group PV, 2520 N/2083 N; and Group RX, 2036 N/2369 N. The fracture strength in Group PV after thermomechanical fatigue loading was significantly lower compared to the fracture strength in Group PV without artificial aging (P =.016), as well as significantly lower compared to Group SB with artificial aging (P =.003). Within the limitations of this study, all tested cements are capable of successfully luting aluminum oxide ceramic crowns. The fracture strength of Group PV after artificial aging was comparatively low.

The effect of surface coating on the bond strength of machinable ceramics

This study examined the nature of the surface presented by a machinable feldspathic porcelain and by a machinable glass–ceramic for bonding to conventional composite luting agents and measured the bond strengths which may be achieved with various surface treatments. There was no significant difference between the bond strengths achieved to etched porcelain, Silicoated porcelain or etched glass–ceramic. Silicoated glass–ceramic specimens showed a significantly higher adhesive assembly strength ( p=0.02). Examination of the fractured specimens showed that in all cases the failure involved part cohesive failure of the ceramic surface and part failure at the cement–ceramic interface.

Clinical performance of pressed ceramic inlays luted with resin-modified glass ionomer and autopolymerizing resin composite cements

Statement of problem. Several in vitro studies have been published showing the incapability of the chemical cure of dual-cured resin composite luting agents to compensate for absence of visible light activation. Purpose. This study evaluated and compared pairs of Empress ceramic inlays luted with 2 chemical-cured luting agents: a resin-modified glass ionomer cement and a resin composite within individual patients. Material and methods. Seventy-nine ceramic inlays were placed in class II cavities in 29 patients. In each patient half of the inlays were luted with a resin-modified glass ionomer cement and the other half with a chemical-cured resin composite cement. The inlays were evaluated clinically, according to modified USPHS criteria, at baseline, after 6 months, and 1 and 2 years. Results. No failed inlays were observed during the 2-year follow-up. A slight ditching of the cement margins was observed in both luting groups. No significant difference was seen between the 2 luting techniques. Conclusion. IPS Empress inlays luted with both chemical-cured luting agents functioned satisfactorily in the short-term follow-up. Longer observation periods are necessary to evaluate the long-term clinical behavior of both luting techniques. (J Prosthet Dent 1999;82:529-35.)

Seating of composite inlays with ultrasonic vibration.

The use of vibration enables the clinician to use high-viscosity luting agents when seating composite inlays and allows quick and efficient placement of the inlay. The film of composite luting agent is achieved in a much shorter time and with lower loads by ultrasonic vibration than using manual methods. In order to achieve a thin lute, the vibrations of the ultrasonic scaler must be directed perpendicular to the surface of the inlay.

A 5-year clinical evaluation of ceramic inlays (Cerec) cemented with a dual-cured or chemically cured resin composite luting agent

Sixty-six class-II CAD/CAM-manufactured ceramic inlays (Cerec) were placed in 27 patients. Each patient received at least one inlay luted with a dual-cured resin composite and one inlay luted with a chemically cured resin composite. The inlays were examined 5 years after luting using the California Dental Association (CDA) criteria. Eighty-nine percent of the 66 inlays were rated 'satisfactory'. During the follow-up period replacement was required for 3 inlays because of inlay fractures (4.5%) and 1 inlay because of fracture of the tooth substance (1.5%). All those inlays were luted with the dual-cured resin composite luting agent. Of the remaining 62 inlays the CDA rating 'excellent' was given to 84% for color, 97% for surface, and 81% for anatomic form. 'Excellent' margin integrity was seen in 52% of the dual-cured resin composite luted inlays and in 61% of the chemically cured resin composite luted inlays. No statistically significant (P > 0.05) difference was observed between the two luting agents.

Effect of different etching periods on the bond strength of a composite resin to a machinable porcelain

Objectives: The purpose of this study was to evaluate microstructure changes of Cerec 2 Vitablocs Mark II porcelain etched by a 5% hydrofluoric acid and examine the effect of different etching times on the bond strength between the porcelain and a composite resin. Methods: Six different etching times (0, 5, 30, 60, 120 and 180 s) were used to etch the surfaces of the porcelain, respectively. Etched relief patterns were observed by means of a scanning electron microscope and the bond strength was determined between a dual-cured composite luting agent and the porcelain. Results: The results showed that composite resin did not bond to unetched porcelain but bonded to etched porcelain, the 120 s etch giving the highest bond strength. Conclusion: The bond strength values corresponded well to the microstructure changes caused by etching.

Filler content and gap width after luting of ceramic inlays, using the ultrasonic insertion technique and composite resin cements: An in vitro study

The effect of ultrasonic insertion on the filler content and the gap width for two brands of composite resin luting agents, intended for luting with the ultrasonic insertion technique, were studied after MOD ceramic inlays (Cerec) had been placed. In addition, the internal and marginal gap widths were determined after MOD ceramic days (Celay) had been luted on extracted premolars with this technique. No statistically significant differences (P>0.05) were observed for either brand between the filler content obtained from the internal surfaces, from the exes luting agent, or from the luting agent as delivered. There were no statistically significant differences (P > 0.05) between the final internal and marginal gap widths when the two brands of luting agent were compared with each other. Except for the final occlusal and internal gap widths obtained for the inlays luted with the Sono-Cem luting agent, no statistically significant differences (P > 0.05) were observed between the gap widths at the different locations determined. Thus, the ultrasonic insertion technique used did not significantly influence the filler ratio of the hybrid luting agents studied. Judged by the findings in this study, the properties of luting agents seem to greatly influence die final marginal and internal gap widths.

Influence of film thickness on joint bend strength of a ceramic/resin composite joint

Objectives. The purpose of this study was to evaluate the influence of different film thicknesses of resin composite luting agents on the joint bend strength of a ceramic/resin interface.Methods. Mirage FLC (Chamelon Dental Products) and Vita Cerec (Coltène AG) duo cement were used in combination with the ceramic materials, Mirage and Vita Cerec blocks. Cement layers with thicknesses of 20 μm, 50 μm, 100 μm and 200 μm were light-cured with a high-intensity curing light. Ten specimens of each ceramic/cement combination and thickness provided a total of 80 complete test specimens. Each specimen was placed in a four-point bending jig mounted in a universal tensile testing machine and underwent loading. A paired two-tailed Student's t-test was used to evaluate differences between different series of film thicknesses and resin cement combinations.Results. Within each ceramic-cement combination, the bond strength values were significantly lower for the 20 μm film than the thicker films.Significance. Taking into account the physical and clinical properties of resin-based luting agents, available knowledge indicates that a marginal gap on the order of 50–100 μm seems to optimize performance.

Radiographic detection of overhangs formed by resin composite luting agents

Objectives: An in vitro model was used to assess the ability of standard radiographic techniques to detect marginal overhangs of resin composite luting agents beside porcelain and resin composite inlays. Methods: The radiodensity of five commercially available luting resins was determined using ISO 4049 methodology. For four of the luting agents, artificial overhangs (0.5 × 0.5 × 2 mm) were created at the cervical margin of standard resin composite and porcelain inlays. Radiographs were recorded, using wax as a tissue equivalent, and the overhangs reduced incrementally in depth by 0.5 mm with serial images at each depth. The images were assessed in random sequence by three observers. Results: There were significant differences between the radiopacity of the luting resins. These correlated well with the ability of the observers to detect marginal overhangs adjacent to resin composite inlays. Conclusions: Even with the most radiopaque luting material, a substantial marginal ledge could not be detected in association with a radiopaque resin composite inlay. The threshold for detection of the overhang was lower when using a radiolucent porcelain inlay.

Clinical and semiquantitative marginal analysis of four tooth-coloured inlay systems at 3 years

Objectives: The marginal quality of four tooth-coloured inlay systems was clinically investigated and subjected to computer-aided semiquantitative marginal analysis under scanning electron microscopy (SEM) after 3 years of clinical service. Methods: Three of the restoration types were made using the Cerec CAD-CAM apparatus: one was milled from preformed glass ceramic blocks, and the two other inlay types were milled from preformed porcelain blocks. The fourth system was based on an experimental indirect resin composite inlay system. Each inlay type was luted with a different luting resin composite. The clinical evaluation was performed with a mirror and explorer by two clinicians separately, and the marginal analysis was conducted microscopically on replicas (SEM × 200). Results: After 3 years in situ, all the restorations were clinically acceptable. No recurrent caries was observed. Marginal analysis under SEM detected a high percentage of submargination for all four systems, which suggests that their respective resin composite luting agents were all subject to wear. The percentage of marginal fractures on the enamel side as well as on the inlay side did not increase dramatically compared to the 6-month results. Conclusion: The first recall after 6 months of clinical service indicated how tooth-coloured inlays behave at their margins. The 3-year results confirmed the early findings, indicating that wear of resin composite lutes is important and present in all systems. The two ceramic materials showed a similar behaviour at the margins. The resin composite inlay performed better at the inlay site than at the enamel site.

APPLYING COMPOSITE LUTING AGENT ULTRASONICALLY: A SUCCESSFUL ALTERNATIVE

The authors conducted research to determine if sonic vibration affected the viscosity of a composite luting agent. They found that using either an ultrasonic or a sonic scaler can thin composite resin. The thickness of the lute is similar to that resulting from manual loading methods, but it is obtained in much shorter time periods and with lower loads.

Time required to remove totally bonded tooth-colored posterior restorations and related tooth substance loss

Objectives. The study was conducted to measure the time required to remove large totally bonded tooth-colored posterior restorations and related tooth substance loss. This information was collected to determine if there were differences between bonded restorations and conventional restorations. Methods. Molars were restored with the following materials: amalgam, composite, glass ionomer cement or glass ceramic cusp coverages. After submitting them to an in vitro aging process, they were attached to a lower jaw model in phantom head. Six dentists removed the test restorations under standardized, quasi-clinical conditions. Results. While the amalgam was completely removed, some glass ionomer cement vestiges were found. In the glass-ceramic group, the margins were covered with remnants of the composite luting agent in several places. The most restorative material was left in the composite group. The loss of tooth structure after removal of amalgam, glass ionomer cement, composite and glass ceramic was 17.6 mm3, 19.6 mm3, 39.9 mm3 and 41.8 mm3, respectively. When comparing the removal time, the glass ionomer group scored best with an average of 11.9 min followed by the amalgam group with an average of 15.2 min, followed by 24.9 min for the composite group and 30.4 min for the glass ceramic group. Significance. The removal of totally bonded posterior restorations made of composite and ceramic is more technically demanding and more time-consuming than the removal of glass ionomer and amalgam restorations.

Measurement of water sorption by resin composite adhesives with near-infrared spectroscopy.

Spectroscopic methodology was used to follow the water uptake of disks of two resin composite luting agents during long-term storage. Fourier-transform near-infrared (FT-NIR) spectroscopy was used for collection of spectra over the 4200-6500 cm-1 spectral region. The 5200-cm-1 absorption band of water was monitored initially, at 24 h, seven days, two weeks, and then monthly over a period of 12 months. The disks were stored in water, air, and desiccated conditions. Disks were also subjected to two alternate cycles (two weeks each) of hydration and desiccation. A spectral manipulation program was used for quantitation of the area under the water absorbance band. Area ratios demonstrated similar water-uptake patterns for the two adhesives. Rapid water uptake was seen within the first two weeks of storage. Alternate hydration and desiccation of the samples showed that water uptake by the filler/polymer network was partially reversible. The desiccant was unable to remove all the water from the samples, which indicated that some water was tightly held within the sample matrix. FT-NIR spectroscopy is recommended as an effective method for study of the equilibration of resin composites in water.

Retention of serrated endodontic posts with a composite luting agent: Effect of cement thickness

When Prosthodent composite was used as a cementation material for endodontic posts (ParaPost), adaptation of the post to the canal was not crucial. Changes of the composite layer thickness up to 500 microns did not decrease retention. Variation in the diameter of the posts did not effect the retention. The retention obtained for the combinations of posts and cements was high and suitable to resist dislodgment of the posts. Consequently, the thinnest post in the root canal, cemented with a composite is recommended. Thus the removal of tooth structure is unnecessary because the cylindrical preparation is formed in the composite.