Factors that affect zirconia-resin interface durability and bond strength: an in vitro study

Abstract

[EN] The introduction of ceramic zirconium oxide as a restorative material dealt a major clinical and research interest in the dental community. The zirconia bioceramic presents as a wide range of applications due to its high biocompatibility and good physical and optical properties. This is a relatively new and promising material, but remains controversial from a scientific point of view, the best method to optimize and promote their effective substrates used in dental adhesion. Conventional bonding techniques are ineffective on the surface of zirconia, given their relative chemical resistance (molecular composition unpolarized) and its pure crystalline structure (no glassy phase). For these reasons, adherence (defined as integration ultrastructural substrates through a contact interface) is difficult to achieve and, to date, no clear guidelines for clinicians to ensure sustainable and effective adhesion. The objectives of this thesis were: 1) review the literature on zirconia, with special focus on state of the art of its recent use as implant abutment; 2) evaluate the effect of particle size on the blasting force of adhesion at the interface of zirconia / resin; 3) investigate the effect of surface treatment of zirconia with tribochemical silica coating and / or irradiation of Er: YAG laser on bond strength of zirconia / resin interface; 4) determine whether the composition of resin cement influences its bond strength to zirconia and what is the best combination of cement type and surface conditioning to provide reliable adhesion zirconia / resin; 5) assess the impact of thermocycling on the bond strength of various self-adhesive cements resin pretreated zirconia. Experimental tests of this thesis were designed to determine some guidelines for action to improve the interface of zirconia / resin. The in vitro study was conducted to evaluate the factors that affect the durability and strength of adhesion on zirconia / resin interface. For this study, two hundred and eighty zirconia blocks were used and divided into two experiments: A) Forty-shaped cylinder block (O 19.5 mm x 10.25 mm height) which were selected to evaluate the influence of grain size sandblasting and composition of the resin cement bond strength to zirconia microtensile; and B) 240 square specimens (measuring 3 x 3 x 1 mm) were used to evaluate the effect of thermal cycling on the adhesion strength to micro-shear test of zirconia treated with Er: YAG and tribochemical silica coating and surface conditioning. In the first trial, zirconia blocks were polished and separated randomly as follows: Group 1 (NT): no treatment; Group 2 (PAC-I): sanding (APA) using particles of aluminum oxide (Al2O3) of 25 microns; in Group 3 (APA-II): APA with Al2O3 particles with 50 microns, and Group 4 (EPA-III): APA using Al2O3 particles 110 microns. The ceramic blocks were duplicated in composite. Samples of each pretreatment group were randomly divided into two subgroups according to the resin cement used for joining composite blocks treated surfaces of zirconia: Subgroup 1 (PAN), which employs a system containing cemented 10-MDP (Panavia F 2.0, Kuraray Medical Ltd., Osaka, Japan) and Subgroup 2 (BIF) in which a self-adhesive cement (Bifix SE, VOCO, Cuxhafen, Germany) was used. After 24 h, the samples were cut into bars 1 micro ± 0.1mm2. In the second trial the zirconia samples were polished and randomized into four groups according applied surface treatment as follows: 1) no treatment (NT); 2) silica coating Rocatec (Rocatec Soft, 3M ESPE, Seefeld, Germany) (ROC), 3) irradiation with Er: YAG (LAS: 2.940 nm, 200 mJ, 10 Hz), and 4) laser followed by Rocatec (LAROC). A small cylinder of a resin cement with 1 mm diameter and 2 mm in height each joined ceramic samples. Each group was divided into two subgroups according to the resin used: A) BIF (Bifix SE, VOCO, Cuxhafen, Germany) and B) CLE (Clearfil SA, Kuraray Medical Ltd., Osaka, Japan). After 24 hours, half of the samples of each group were tested. The other half was stored and subjected to thermocycling (5th-55/5000 cycles). The values ??of the resistance tests of adherence to the microtensile (MTBS) and microcizalla strength (MSBS) were obtained using a universal testing machine (crosshead speed = 0.5 mm / min). The failure modes were recorded and the morphology of the interfacial zone was observed severed by scanning electron microscopy (SEM). Data were analyzed with ANOVA, Student tests, chi-square tests and linear regression (p