Both studies, performed at the University of Texas (UT) Health Science Center at the Houston School of Dentistry, were presented during a poster session at the recent American Association for Dental Research (AADR) annual meeting in Tampa.
"Usually, enamel will have different results than dentin because of the configuration of the enamel -- it bonds better," said Magda Eldiwany, DDS, an associate professor at UT Health School of Dentistry who led the study testing bond strengths to enamel. "Clearfil in particular has very good bonding agents," she told DrBicuspid.com.
However, Clearfil SE was outperformed by both generations of Optibond adhesives when bond strengths to dentin were tested.
"If you need to work on dentin, go with Optibond," explained Michelle Eldiwany, Dr. Eldiwany's daughter and a dental student at UT, who led the study testing bond strengths to dentin. "If you are working on enamel, go with Clearfil SE."
Enamel bond strengths
The study examining bond strengths to enamel included Moxie TE/5th generation and Moxie SE/6th generation (Discus Dental), OptiBond Solo Plus/5th generation, OptiBond XTR/6th generation, and Clearfil SE Protect Bond/6th generation, all of which were provided by the manufacturers.
The researchers created a flat surface on the enamel of human molars and premolars ground to 60 grit. Next, the surface was polished to 320 grit. SDI Glacier composite resin was then bonded and cured to the enamel following the manufacturer's instructions.
“If you need to work on dentin, go with Optibond. If you are working on enamel, go with Clearfil SE.”
— Michelle Eldiwany, UT School of
After being stored for 24 hours, the specimens (n = 10) were loaded with an Instron to determine shear bond strength in megapascals (MPa). Finally, the researchers performed an analysis of variance and post hoc Tukey test at a 0.05 level of significance.
The researchers found that Clearfil SE Protect Bond and Moxie SE were significantly different: (p = 0.02): The former had a mean bond strength (MPa) and standard deviation of 15 (4.9) and the latter of 9.3 (4.1). Enamel bond strengths were similar among Moxie TE, Moxie SE, OptiBond Solo Plus, and OptiBond XTR (p > 0.05), the researchers noted.
Dentin bond strengths
The same adhesives used in the study testing bond strengths to enamel were used in the study testing bond strengths to dentin.
"The etchant and the composite were the same; the only variable was the bonding agent," Michelle told DrBicuspid.com.
After cleaning, human teeth were assembled on an Isomet and sliced mesiodistally. Next, pulp tissues were cleaned and the teeth were assembled in a plastic mold that was filled with acrylic. When the acrylic had set, the molds were separated from the base and the teeth were ground to expose superficial dentin which was polished to 320 grit.
The adhesives were cured for 20 seconds, and each sample was bonded to SDI Glacier composite in a cylinder mold. As in the other study, the samples were incubated for 24 hours, bond testing was performed with an Instron, and the same analyses were run.
"We found that OptiBond had significantly stronger bonding," explained Michelle.
While the 5th and 6th generations of OptiBond were similar (p = 0.73), both were significantly stronger than Moxie 5th (p < 0.001), Moxie 6th (p < 0.001), and Clearfil SE Protect (p = 0.001). The Moxie adhesives had similar strengths and Clearfil was not significantly different from either of them, the researchers noted.
Dr. Eldiwany said she hopes the dental community will find the data from the studies useful.
"I'm a clinician and a researcher," she said. "I can't do all of the research working in private practice; I rely on research to tell me in very simple terms, 'This is better than the other.'"