Original Article
Effects of conventional and high-intensity light-curing on enamel shear bond strength of composite resin and resin-modified glass-ionomer*,**,*,**,*,**

https://doi.org/10.1067/mod.2001.111399Get rights and content

Abstract

The purpose of this study was to evaluate the shear bond strengths of a composite resin (Transbond XT; 3M/Unitek, Monrovia, Calif) and a resin-modified glass ionomer (Fuji Ortho LC; GC America Inc, Alsip, Ill) cured with 2 different light-curing units: a conventional visible light unit (Ortholux XT; 3M Dental Products, St Paul, Minn) and a xenon arc light unit (Plasma Arc Curing [PAC] System; American Dental Technologies, Corpus Christi, Texas). One hundred twenty freshly extracted bovine permanent mandibular incisors were randomly divided into 1 of 8 groups; each group consisted of 15 specimens. Two groups (1 group for each type of adhesive) were exposed to the visible light for 20 seconds (Transbond XT) and 40 seconds (Fuji Ortho LC), respectively, and used as control groups. The remaining 6 groups (3 for each adhesive) were cured with the xenon arc light for 2, 5, and 10 seconds. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested in a shear mode on an Instron universal testing machine (Instron Corp, Canton, Mass). For the groups bonded with Transbond XT, no statistically significant differences (P =.868) were found between the shear bond strength of the control group cured with Ortholux XT and those of the groups cured with the PAC System for 2, 5, or 10 seconds. When the shear bond strengths of the groups bonded with Fuji Ortho LC were evaluated, no statistically significant differences (P =.087) were found between the control group that was cured with Ortholux XT and those cured with the PAC System. The bond strength of the composite resin was significantly higher than that of the resin-modified glass ionomer in all the groups tested (P <.0001). The present findings indicate that, compared with visible light-curing, the xenon arc light enables the clinician to significantly reduce the curing time of both bonding agents, without affecting their shear bond strengths. Therefore, xenon arc light sources can be recommended as an advantageous alternative for curing both composite resins and resin-modified glass ionomers. (Am J Orthod Dentofacial Orthop 2001;119:30-5)

Section snippets

Material and methods

One hundred twenty freshly extracted bovine permanent mandibular incisors were collected from a local slaughterhouse and stored in a solution of 0.1% (weight/volume) thymol for 1 week. The criteria for tooth selection included intact buccal and lingual enamel with no cracks caused by the pressure of the extraction forceps and no caries. The teeth were randomly assigned to 1 of 8 groups. Each group consisted of 15 specimens. The teeth were cleansed of soft tissue and embedded in cold-curing,

Results

The descriptive statistics of the shear bond strength for each group are shown in Table I and Fig 1.

. Descriptive statistics (in megapascals) of shear bond strengths of 8 groups tested

Empty CellMean ± SD (MPa)Median (MPa)Range (MPa)Sample size (n)
Transbond XT
 Ortholux XT24.1 ± 5.523.313.0-34.615
 Plasma arc
 2 sec25.8 ± 5.927.09.7-32.015
 5 sec24.8 ± 5.325.69.6-32.015
 10 sec25.3 ± 5.226.313.0-34.215
Fuji Ortho LC
 Ortholux XT18.2 ± 3.218.712.6-25.015
 Plasma arc
 2 sec17.9 ± 3.617.311.2-25.215
 5 sec15.9 ± 3.715.111.0-23.0

Discussion

The present study indicated that, regardless of the adhesive used (composite or resin-modified glass ionomer), the shear bond strength of each bonding agent cured with the PAC System for 2, 5, and 10 seconds was not significantly different from that of the same adhesive cured with a conventional VLC unit.

Previous studies have shown that bovine and human enamel are similar in their physical properties, composition, and bond strength.14, 19 Bovine enamel has been reported to be a reliable

Conclusions

After a 24-hour period, both Transbond XT and Fuji Ortho LC provide bond strengths adequate for clinical use when cured with the xenon arc light. The shear bond strengths of both adhesives cured with the xenon arc light are not statistically different from those achieved by curing with the conventional VLC unit. Light-curing for only 2 seconds with the xenon arc light does not preclude clinically acceptable bond strength of composite resin or resin-modified glass ionomer. Composite resin has a

Acknowledgements

We thank Leone, 3M/Unitek, and GC America Inc for providing the materials tested in this study and Mr Gabriele Scommegna and Mr Elia Ladani (Leone) for their technical assistance.

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    *

    aPostgraduate Resident, Department of Orthodontics, University of Pavia.

    **

    bAssistant Clinical Professor, Department of Orthodontics, University of Pavia and University of Aarhus.

    *

    cStatistician, Clinical Epidemiology and Biometry Unit, Scientific Direction.

    **

    dProfessor and Chair, Department of Orthodontics, University of Pavia.

    *

    Reprint requests to: Vittorio Cacciafesta, DDS, MSc, c/o studio Prof Giuseppe Sfondrini, Via Libertà 17, 27100 Pavia, Italy; e-mail, [email protected].

    **

    Am J Orthod Dentofacial Orthop 2001;119:30-5

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