In vitro testing of shear bond strength of orthodontic brackets bonded to different novel CAD/CAM ceramics

Abstract

Background. The present study aimed to evaluate the bond strength of metal bracket (MB) and ceramic bracket (CB) bonded to different CAD/CAM ceramic substrates etched with hydrofluoric acid (HFA) vs. phosphoric acid (PA). Methods. A total of 120 CAD/CAM ceramic blocks in 12 groups were fabricated from three different CAD/CAM ceramic materials: VITABLOCS Mark II, VITAENAMIC, and IPS e.max CAD. Each ceramic material group was divided into two etching groups: one treated with 9.5% HFA and the other treated with 37%. Sixty metal and CBs of the upper right central incisor were bonded to the HFA-treated blocks. Another 60 metal and CBs were bonded to the PA treated blocks. All the bonded specimens were thermocycled before shear bond strength (SBS) testing. Then the bond failure mode was recorded Results. There were no significant differences in SBS values between the three CAD/CAM ceramic materials. The HFA-treated specimens exhibited significantly higher SBS values than the PA-treated specimens. Also, the SBS values of CBs were significantly higher than the metal brackets (MBs). The adhesive remnant index (ARI) score was 4 for most of the groups, indicating that almost no adhesive remained on the porcelain surface. Conclusion. The CAD/CAM ceramic type did not influence SBS; however, HFA exhibited significantly higher SBS compared to PA.

Effects of Novel versus Conventional Porcelain Surface Treatments on Shear Bond Strength of Orthodontic Brackets: A Systematic Review and Meta-Analysis

“…(1) Phosphoric Acid 37%, Silane, and Bonding . The metasample of the included two studies [ 23 , 24 ] was homogenous ( I 2 = 0.0%, P = 0.734). Both studies similarly showed effect sizes close to the gold standard.…”

“…(1) Metal Brackets: Phosphoric Acid 37%, Silane, and Bonding . This meta-analysis included three studies [ 23 , 24 , 28 ]. There heterogeneity was significant ( I 2 = 73.8%, P = 0.018).…”

“…(2) Ceramic Brackets: Phosphoric Acid 37%, Silane, and Bonding . Only two studies existed that had tested this treatment [ 23 , 24 ]. No heterogeneity was observed ( I 2 = 0.0%, P = 0.365).…”

“…HF acid may be utilized to chemically alter the porcelain surface [ 8 , 53 ], and its 9.6% concentration may be advantageous over its 5% concentration [ 52 ]. The use of 9.6% HF acid gel has been the most common, but due to its high strength and tissue damage, its use should be controlled [ 4 , 23 ]. Silanization (after surface preparation and before bonding agent application) as well seems to be one of the factors that can increase the bonding adhesion to the tooth surface or restoration [ 59 ].…”

“…Another method replacing HF etching is Cojet, which was shown to produce overall SBS values close to those of the gold standard despite the controversy observed over the three studies [ 30 , 34 , 36 ]. Some studies have suggested the use of phosphoric acid instead of HF [ 2 , 22 – 28 ]; although the two available studies on ceramic brackets showed an overall SBS similar to that of the gold standard [ 23 , 24 ], most studies on metal brackets showed bond strengths weaker than those of the gold standard [ 2 , 22 – 28 ]. The results of those two studies on ceramic brackets should be approached with caution as well, as both of them were slightly poorer than the gold standard [ 23 , 24 ].…”