ORAL HEALTH EVIDENCE-BASED PRACTICE PROGRAM
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Title MDP or MDP + Silane Primers Result in the Highest Shear Bond Strength Between Metal Orthodontic Brackets and Zirconia Restorations
Clinical Question In patients with full-coverage zirconia restorations, would using a silane primer as compared to a MDP primer provide better orthodontic metal bracket shear bond strength?
Clinical Bottom Line For patients with zirconia restorations who are undergoing orthodontic treatment, a MDP or MDP + silane primer provides the highest metal bracket shear bond strength (SBS). This is supported by laboratory studies in which using a MDP or MDP + silane primer provided the highest metal bracket SBS as long as the surface was mechanically roughened prior to bonding. Using a silane-only primer provides a statistically significant lower bond strength compared to using MDP or MDP + silane primer. Using a MDP or MDP + silane primer is within the capability of the average orthodontic practice and likely to be implemented by a practicing orthodontist.
Best Evidence (you may view more info by clicking on the PubMed ID link)
PubMed ID Author / Year Patient Group Study type
(level of evidence)
#1) 28772508Byeon/2017130 cuboid shaped polished zirconia (Y-TZP) specimens Laboratory study
Key resultsThe bond strength between zirconia restorations and metal orthodontic brackets was highest when an MDP or MDP + silane primer was used following mechanical roughening via alumina sandblasting. The bond strengths that were noted to be the highest were statistically significant (p < 0.05). Micro-mechanical chemical bonding is possible between the MDP primer and ZrO2 in the roughened Y-TZP surface, contributing to the higher bond strength. Silane primers should not be used, as they cannot chemically bond to the zirconia due to the lack of silica. Using a silane primer creates a bond that relies only on mechanical strength from the sandblasted mechanical roughening. The bond strength shown in this study from the silane-only primer was lower than what was is thought to be necessary to support normal orthodontic forces.
#2) 28195275Kim/2017190 polished zirconia (Y-TZP) discsLaboratory study
Key resultsThe highest bond strength was observed in specimens that were treated with an MDP or MDP + silane primer and mechanically roughened with alumina sandblasting. The bond strengths that were noted to be the highest were statistically significant (p < 0.05). It was hypothesized that the MDP + silane combination primer may have a synergistic effect when together. This may be due to the silane being rapidly hydrolyzed by the MDP. The bond strength shown in this study from the silane-only primer was on average lower than what is thought to be necessary to support normal orthodontic forces.
#3) 29109822Kim/2017124 polished zirconia (Y-TZP) discsLaboratory study
Key resultsThe highest bond strength was seen in the groups that were treated with MDP + silane primer and mechanically roughened with CoJet. In the group that was mechanically roughened by alumina, the MDP or MDP + silane primer still showed the highest bond strength. The bond strengths that were noted to be the highest were statistically significant (p < 0.05). The CoJet roughened samples were hypothesized to have a higher bond strength due to the increase in surface area as well as the chemical bonding potential to the MDP and silane. The bond strength shown in this study from the silane-only primer was deemed to be clinically acceptable to support normal orthodontic forces, although it was considered significantly lower than the MDP or MDP + silane bond strengths.
Evidence Search “bracket bonding to zirconia”
Comments on
The Evidence
Validity: All three articles came to similar conclusions that MDP or MDP + silane increases SBS; however, they have the limitation that they are laboratory studies and therefore, they provide weaker evidence than a clinical based study. There were no disclosed conflicts of interest in any of the three articles. Perspective: Based on these research articles, using an MDP + silane or a MDP only primer will provide you a better SBS than using a silane only primer; however, it is important to note that the primer type chosen will only work to its potential if the zirconia surface has been mechanically roughened prior to primer application. Additionally, the studies only looked at polished zirconia crowns and did not account for glazed zirconia crowns. Overall, there is more in-vitro and clinical research that needs to be done on this topic.
Applicability The primer type chosen to bond metal brackets to zirconia crowns plays an important role in preventing bracket failure. Based on these studies, MDP and MDP + silane primers provide the best bond strength; however, that is with the caveat that the surface has been mechanically roughened prior to application. This mechanical roughening should be a key point that is made, as it differs from the traditional orthodontic bonding protocol, and this point may make acceptance by practitioners more difficult. However, if the point of mechanical roughening can be implemented by a clinician, selecting the correct primer type is a simple task and could be expected to be accepted by most clinicians.
Specialty/Discipline (General Dentistry) (Orthodontics) (Prosthodontics)
Keywords Bracket, Bonding to Zirconia, Bond Strength, Primer
ID# 3442
Date of submission: 11/24/2020spacer
E-mail polczynski@livemail.uthscsa.edu
Author Alexis Polczynski
Co-author(s) Belal Heddaya
Co-author(s) e-mail heddaya@livemail.uthscsa.edu
Faculty mentor/Co-author Dr. Ravikumar Anthony BDS, MDS, MS
Faculty mentor/Co-author e-mail anthyonyr@uthscsa.edu
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