Abstract
Abstract Aim The objective of the present study was to determine which of six bonding protocols yielded a clinically acceptable shear bond strength (SBS) of metal orthodontic brackets to CAD/CAM lithium disilicate porcelain restorations. A secondary aim was to determine which bonding protocol produced the least surface damage at debond. Methods Sixty lithium disilicate samples were fabricated to replicate the facial surface of a mandibular first molar using a CEREC CAD/CAM machine. The samples were split into six test groups, each of which received different mechanical/chemical pretreatment protocols to roughen the porcelain surface prior to bonding a molar orthodontic attachment. Shear bond strength testing was conducted using an Instron machine. The mean, maximum, minimal, and standard deviation SBS values for each sample group including an enamel control were calculated. A t-test was used to evaluate the statistical significance between the groups. Results No significant differences were found in SBS values, with the exception of surface roughening with a green stone prior to HFA and silane treatment. This protocol yielded slightly higher bond strength which was statistically significant. Conclusion Chemical treatment alone with HFA/silane yielded SBS values within an acceptable clinical range to withstand forces applied by orthodontic treatment and potentially eliminates the need to mechanically roughen the ceramic surface.
Highlights
Since the number of adult patients seeking treatment has increased, the orthodontist is faced with the challenge of bonding brackets to porcelain restorations
The bond strengths of the attachments to the ceramic surface that were mechanically roughened with a green stone prior to bonding (Group 3) had a significantly higher bond strength (18.3 MPa, p < 0.0158) compared with the ceramic control group that received hydrofluoric acid (HFA) and silane conditioning
All other test groups fell within the same statistical range with bond strengths between 15.8 MPa for the ceramic control and 20.2 MPa for the enamel control
Summary
Since the number of adult patients seeking treatment has increased, the orthodontist is faced with the challenge of bonding brackets to porcelain restorations. It is common to band porcelain-crowned posterior teeth due to the difficulty in otherwise obtaining an efficient attachment that does not cause irreversible damage to the crown upon removal.[1] Banding requires an extra appointment to place separating alastics, which produces additional discomfort and the absence of the patient from work. Two types of restorative porcelain commonly used in the posterior part of the mouth are feldspathic and lithium disilicate.[2] Feldspathic porcelain is used for porcelain fused to metal crowns, while lithium disilicate is used in all ceramic crowns.[1,3]. Australian Orthodontic Journal Volume 32 No 1 May 2016
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