The effect of acid concentration and etch time on morphology and tensile bond strength of primary dentin An in vitro study

Background: There are conflicting results concerning the ideal time for etching primary dentin and its effect on the bond strength of adhesive restorative materials. Aim: To assess in vitro, the effect of varied acid concentration and etch time on the morphological features and tensile bond strength of primary dentin. Materials and Methods: Forty healthy primary molars were prepared by exposing the dentin of the occlusal surface, creating a smear layer. A 3 mm × 3 mm test indow was demarcated, and specimens were randomly allocated to four groups (n = 10): Group 1A 10% phosphoric acid, 7 s; Group 1B 10% phosphoric acid, 15 s; Group 2A 37% phosphoric acid, 7 s and Group 2B 37% phosphoric acid, 15 s. Surface analysis was done using atomic force microscope and scanning electron microscope. For tensile bond strength evaluation, 24 specimens prepared as mentioned were mounted in acrylic blocks and allocated to four groups according to the prescribed etching protocol. Resin rods were bonded and tested in tension after 24 h (n = 6). Data were analyzed statistically using unpaired t-test. Results: Etching of primary dentin using 37% phosphoric acid for 7 s produced the highest tensile bond strength of 9.51 ± 2.19 MPa. Conclusion: Etching time of 7 s may improve the adhesion of resin restorative materials with primary dentin.

Effect of hydrofluoric acid-based etchant at an elevated temperature on the bond strength and surface topography of Y-TZP ceramics

OBJECTIVES: This study investigated the effects of a hydrofluoric acid (HA; solution of hydrogen fluoride [HF] in water)-based smart etching (SE) solution at an elevated temperature on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics in terms of bond strength and morphological changes.MATERIALS AND METHODS: Eighty sintered Y-TZP specimens were prepared for shear bond strength (SBS) testing. The bonding surface of the Y-TZP specimens was treated with 37% phosphoric acid etching at 20°C–25°C, 4% HA etching at 20°C–25°C, or HA-based SE at 70°C–80°C. In all groups, zirconia primers were applied to the bonding surface of Y-TZP. For each group, 2 types of resin cement (with or without methacryloyloxydecyl dihydrogen phosphate [MDP]) were used. SBS testing was performed. Topographic changes of the etched Y-TZP surface were analyzed using scanning electron microscopy and atomic force microscopy. The results were analyzed and compared using 2-way analysis of variance.RESULTS: Regardless of the type of resin cement, the highest bond strength was measured in the SE group, with significant differences compared to the other groups (p < 0.05). In all groups, MDP-containing resin cement yielded significantly higher bond strength values than MDP-free resin cement (p < 0.05). It was also shown that the Y-TZP surface was etched by the SE solution, causing a large change in the surface topography.CONCLUSIONS: Bond strength significantly improved when a heated HA-based SE solution was applied to the Y-TZP surface, and the etched Y-TZP surface was more irregular and had higher surface roughness.

Clearfil Protect Bond™ versus Uni‑Etch™ antibacterial self‑etchant: A war of giants against shear bond strength.

Aims and Objectives: To use antibacterial agents with two conventional bonding systems and evaluate the shear bond strength (SBS) of bracket to enamel. Materials and Methods: Overall, 120 human‑extracted first premolars were used. The specimens were equally divided into six sub‑groups of 20 samples. Control groups were bonded with Transbond XT™ light cure (Group I, after etching with 37% phosphoric acid, 3M Unitek™) and Unite™ self‑cure adhesive (Group II, after etching with 37% phosphoric acid, 3M Unitek™). Experimental groups included teeth surface first coated with Clearfil Protect Bond™ (Kuraray, Osaka, Japan) (and then bonded with Transbond XT™ [Group III] or Unite™ [Group IV]) or bonded with Uni‑Etch™ antibacterial self‑etchant (and then bonded with Transbond XT™ [Group V] or Unite™ [Group VI]). The third generation MBT bracket bonding system with 0.022 slots was used for bonding. All specimens were tested on Instron machine 5567 (SIES Institute of packaging, Nerul, Navi Mumbai, India) to evaluate the SBS. The sheared surfaces were also investigated with a stereomicroscope to assess adhesive remnants index (ARI scores) on the specimen surfaces. Results: Mean SBS in Group I–Group VI was 10.53 (2.91), 9.12 (2.56), 9.86 (1.98), 6.96 (2.92), 9.57 (2.02), and 7.65 (2.34) megapascals, respectively. Significant differences were only seen between Group III and IV and between Group II and IV. With respect to ARI scores, significant differences were seen only for comparison between Groups II, IV, and VI. Conclusion: Newly developed antibacterial agent could be used with conventional bonding systems effectively to decrease white spots; when used with Transbond XT™ light cure, the original SBS did not get affected, but when used with Unite™ self‑cure bonding system, it led to reduced SBS significantly.

Iatrogenic chemical burn on facial skin by 37% phosphoric acid etchant / 대한치과보존학회지

When we use the total-etch dentin adhesive system for composite resin restorations, gel or liquid acid etchant such as 37% phosphoric acid is commonly used. Thirty seven percentage phosphoric acid is very powerful erosive agent, and can cause severe harmful effects when it contacts with an oral mucosa and facial skin. This case describes iatrogenic chemical burn on facial skin caused by phosphoric acid which was happened during composite resin restorative procedure. Chemical burn by acid etchant can be evoked by careless handling of remnant and syringe. In order to prevent these iatrogenic injuries, we should check the complete removal of the etching agent both in intra and extra-oral environments after etching and rinsing procedure and it is necessary to use of the rubber dam or isolation instruments. If accidental burn were occurred, immediate wash with copious water. And bring the patient to the dermatologist as soon as possible.

Effects of phosphoric acid concentration on depth of etch and shear bond strength of orthodontic brackets to bovine enamel / 대한치과교정학회지

Previous study had shown the diversities in the propriety for optimal bond strength on the concentration of the etchant. The aim of present study in vitro was to evaluate and compare the shear bond strength of orthodontic brackets to enamel and to measure the depth of etch on the phosphoric acid concentrations. A hundred and seventy six extracted bovine lower centrals were ground to yield flat surfaces and etched by the concentration 0%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% and 85% of phosphoric acid respectively during 60 seconds. The shear bond strength of orthodontic brackets, the depth of etch and surface roughness of the enamel were measured, and scanning electron microscopic observations on the etched enamel surfaces were carried out. The data obtained from the very experiments were processed and statistically analyzed and evaluated. The gradual increase in the depth of etch to enamel as the accretion of the concentration of the phosphoric acid up to 40-50% and decline henceforth were manifested. The surface roughness showed no correlation with the depth of etch, yet moderate correlation with the shear bond strength of brackets. Scanning electron microscopic investigation revealed that morphological patterns of the etched enamel surfaces for 5% to 40% of concentrations were even and homogenous, and those for 50% as well as 60% exhibited the overetched and unhomogenous. The shear bond strengths from 10% to 60% of concentration showed no statistically significant differences. It was suggested that the shear bond strengths at 5% and 70% were sufficient to tolerate the force levels of the ordinary orthodontic treatment notwithstanding to be significantly lower than those from 10% to 60% phosphoric acid solution.