Quintessenz Journals

CLINICAL RESEARCH

Bond strength of a self-adhesive resin cement to enamel and dentin Virgílio Vilas Boas Fernandes, Jr, Prof, MSc Pindamonhangaba Dental School, Pindamonhangaba College, Brazil

José Roberto Rodrigues, Prof, DDS Department of Restorative Dentistry, São José dos Campos Dental School, São Paulo State University, Brazil

João Maurício Ferraz da Silva, Prof, DDS Department of Restorative Dentistry, São José dos Campos Dental School, São Paulo State University, Brazil

Clovis Pagani, Prof, PhD Department of Restorative Dentistry, São José dos Campos Dental School, São Paulo State University, Brazil

Rodrigo Othávio Assunção Souza, Prof, DDS Department of Restorative Dentistry, Federal University of Paraíba, João Pessoa, PB, Brazil

Correspondence to: Virgílio Vilas Boas Fernandes Jr, Master in Restorative Dentistry Rua Enseada, 46 – Cidade Jardim, São José dos Campos, 12230630 São Paulo, Brazil; Tel: +55 12 988040749; E-mail: [email protected]

146 THE INTERNATIONAL JOURNAL OF ESTHETIC DENTISTRY 70-6.&t/6.#&3t413*/(

FERNANDES JR ET AL

Abstract

The enamel–dentin resin cement blocks were sectioned to produce non-trimmed

The purpose of this study was to evalu-

bar specimens, which were divided

ate the influence of surface treatments

into two storage conditions: dry, μTBS

and thermocycling on the microtensile

immediately after cutting; TC (5,000 x;

bond strength (μTBS) of self-adhesive

5°C/55°C). The samples were submit-

resin cement to human enamel and

ted to μTBS, and data were statistically

dentin. Eighty human third molars were

analyzed by ANOVA and Tukey’s test.

selected. The crowns of 40 teeth were

The results showed statistical differ-

transversally sectioned, exposing the

ences between UnicemC and the oth-

mid-coronal dentin. The buccal surfac-

ers. UnicemPA and VR showed better

es of the other 40 teeth were grinded to

bond strength to dentin during the pe-

mm2

flat enamel area. Eighty

riod before and after thermocycling,

resin blocks were produced and ce-

respectively. For the enamel, UnicemP

mented to the dental surfaces with Re-

showed better bond strength for both

lyX Unicem, then grouped according to

situations. Only for UnicemPA did the

the surface treatment (n = 10): UnicemC

thermocycling

with no conditioning, UnicemP with 37%

the bond strength values. Within the lim-

phosphoric acid/15 s, and UnicemPA

its of this study, it could be concluded

with 37% phosphoric acid/15 s plus ad-

that the bond strength is influenced by

hesive bonding (Single Bond 2). There

the surface treatments, and that ther-

were two control groups, one for enamel

mocycling decreases the bond strength

and the other for dentin: VR with 37%

of all groups, but significantly only for

phosphoric

UnicemPA.

obtain a 5

acid/15 s

plus

adhesive

bonding (Single Bond 2) plus Variolink II.

significantly

decrease

(Int J Esthet Dent 2015;10:146–156)


CLINICAL RESEARCH

Introduction

with good results on ceramic, metal pins, and indirect restorations.11-14

Restorative dentistry has been continu-

Previous investigations have provided

ously modified by the development of

the materials context for the introduction

new products, including modifications

of self-adhesive resin cements, of which

of adhesive procedures, such as resin

RelyX Unicem (3M ESPE) represents the

cements.1,2

first of this new class of materials.15

With the advent of dual-curing resin-

Despite the factors reported previ-

based cements, there has been signifi-

ously, the inorganic composition of these

cant improvement in the cementation

systems comprise weak acids, which

gap,3

can reduce their bonding to enamel

inadequate polymerization,4 secondary

and their conditioning capacity when

procedures relating to marginal infiltration.5

In addi-

compared to conventional phosphoric

tion, these cements have shown impor-

acid-etching procedures.10 On the other

tant features, such as high mechanical

hand, the demineralization process and

resistance and excellent esthetic6 and

the bonding to dentin are improved.16

caries, and marginal

adhesive

properties.7

However, cemen-

To optimize the conditioning capacity

tation procedures require careful clinic-

and reduce possible adhesive failures,

al manipulation due to the high number

manufacturers have developed prod-

of operative steps involved, which make

ucts with low pH, leading to an increase

them a critical and sensitive technique.

in their acidity and the degree of condi-

Moreover, to increase the bonding to

tioning. However, they can be consid-

these cements, the acid etching of the

ered more biologically aggressive.17,18

dental surface is recommended, which can result in dental sensitivity.8

Although self-conditioning cements have certain advantages (mainly their

have

practicality and the reduced clinical

been recently introduced onto the mar-

time), further studies have been required

ket with the objective of combining the

to test their adhesive efficiency. This is

simple manipulation of glass-ionomer

what encouraged the present study to

cements with the mechanical, esthetic

assess one of these cements in terms

and adhesive properties of resin-based

of its bond strength to both enamel and

cements. This process is based on den-

dentin.

Self-adhesive

resin

cements

tal surface etching by a methacrylate

The hypotheses were: (1) that the

monomer, which contains groups of

bond strength is influenced by particular

phosphoric acids that can etch and dif-

surface treatments; and (2) that thermo-

fuse through the dental surface without

cycling decreases the bond strength to

the need of previous treatment,9 simplify-

both enamel and dentin.

ing adhesive procedures. This results in a lower risk of dental sensitivity because of the reduced possibility of non-impreg-

Material and methods

nated and demineralized dentin.10 Some authors have investigated the

The present study was approved by

bond strength of these cement agents,

the Ethical Committee in Research, No.


FERNANDES JR ET AL

Table 1

Description of dental materials selected

Commercial name

Manufacturer

Variolink II

Ivoclar Vivadent

Adper Single Bond 2

3M ESPE

Composition

#JT(."6%."5&(%."%."CBSJVNTVMGBUF Ba-Al-F-Si-glass/silica, Benzoperoxiglycerol

#JT(."a, HEMAb, dimethacrylate, methacrylate functional copolymer of polyacrylic and polytaconic acid, water, alcohol, photoinitiator

Base paste: methacrylate monomers with phosphoric acid, methacrylate monomers, silanized fillers, RelyX Unicem

3M ESPE

initiator, and stabilizers Catalyst paste: methacrylate monomers, alkaline fillers, silanized fillers, initiator components, and stabilizers

067/2008 – PH/CEP of the São Paulo

week later, the resin block surfaces were

State University – UNESP, São José dos

airborne-particle abraded using 30-μm

Campos, Brazil.

Al2O3 for 10 s under a pressure of 1 bar

The trade name and composition of

(MicroEtcher ERC, Danville).

dental materials selected for this research are presented in Table 1.

Dental preparation

Resin blocks manipulation

For the enamel groups, 40 extracted human third molar teeth were cleaned

A silicone mold was used to prepare 80

and submitted to finishing and polish-

blocks (2 mm x 4 mm x 4 mm) of Z1OO

ing with 600-, 800- and 1,200-grit met-

direct composite resin (3M ESPE). The

allographic paper in a polishing ma-

resin was applied into the mold in 2 incre-

chine (DP-10, Panambra) in order to

ments (1 mm). Each increment was light

obtain a 5 mm2 enamel flat area on the

cured through a light-curing unit (Curing

buccal surface.

Light XL 3000, 3M ESPE) for 1 min at a light intensity of 600

mW/cm2.

For the dentin groups, 40 teeth had

Before the

one third of their coronal part removed

polymerization of the last increment, a

with the aid of a diamond disc at low

polyester strip was placed onto the top

speed, and were then submitted to the

of the mold to achieve a flat and uniform

same protocol as described for the

surface. The final light curing was ob-

enamel groups.

tained by placing the resin blocks into

All surfaces were cleaned with 70%

a light oven for a period of 4 mins. One

alcohol solution prior to the cementation.


CLINICAL RESEARCH

Cementation protocol

All specimens were stored in distilled water at 37°C for 24 h before sectioning.

The resin blocks and teeth were ran-

Following the storage period, the speci-

domly divided into 8 groups according

mens were sectioned into 6 mm-long mi-

to the dental surface treatment and the

crobars using the diamond-coated disc

luting material.

of a precision cutting machine (Labcut

UnicemC groups: two pastes of du-

1010, Extec), at 300 rpm in cold water.

(RelyX

The sections were performed from the

Unicem) were mixed using similar pro-

mesial to the distal sides and from the

portions and applied onto the previously

cervical to the occlusal surfaces in order

polished dental surface. A resin block

to obtain a 1 mm2 cross-section adhe-

was placed over the cement area and

sive area for each microbar.

al-cured

resin-based

cement

kept under a pressure of 20 N with the

About 9 specimens were obtained

arm of a prosthetic delineator. Five mins

from each resin–dental surface block.

later, the cement excess was removed

The

and the sample was light activated. The

chined (non-trimmed) bonding areas,

cement was then light cured for 40 s

with a bonded area measuring approxi-

through each side of the resin block.

mately 1.0 ± 0.1 mm2.

UnicemP

groups:

the

dental

beam

specimens

had

non-ma-

sur-

The 9 specimens were then randomly

face was etched with 37% phosphoric

divided into 2 testing conditions. In the

acid (Vococid, Voco) for 30 s (enamel)

dry condition (Dry), the specimens were

and 15 s (dentin), rinsed for 60 s with

immediately submitted to microtensile

water, and dried prior to the cementa-

testing after sectioning. In the aged con-

tion. Thereafter, the luting agent (RelyX

dition (TC), the specimens were sub-

Unicem) was mixed and applied, as pre-

mitted to thermocycling (5,000 cycles;

viously described.

5°C/55°C, dwelling time: 30 s, transfer

UnicemPA groups: the dental surface was etched with 37% phosphoric

time: 2 s) (Nova Etica) and then submitted to testing.

acid (Vococid) for 30 s (enamel) and 15 s (dentin), rinsed for 60 s with water,

Microtensile bond strength test

and gently dried with the aid of a cotton pellet to maintain adequate humidity

The microbar specimens were attached

prior to the cementation. Two thin lay-

with cyanoacrylate gel (Super Bonder

ers of adhesive (Adper Single Bond 2,

(FM -PDUJUF UPUIFNJDSPUFOTJMFEFWJDF

3M ESPE) were actively applied onto the

of a universal testing machine (DL1000,

conditioned surface of the enamel and

EMIC) (Figs 1a and 1b) and submitted

dentin with the aid of a microbrush and

to an axial tensile on the adhesion inter-

light cured for 10 s. Thereafter, the luting

face at a 0.5 mm/min crosshead speed.

agent (RelyX Unicem) was mixed and

The fracture surfaces were analyzed

applied, as previously described.

under light microscopy (x 40) (Olym-

The VR groups received the same

pus, CBB). The type of adhesive failure

cementation protocol as the UnicemPA

was classified into different categories:

groups.

adhesive failure at the enamel–cement


FERNANDES JR ET AL

interface; mixed adhesive and cohesive failure of the cement; adhesive failure at the cement–resin interface, and adhesive failure at the dentin–cement interface.

Statistical analysis Descriptive statistics were used to evaluate the results, including the three-way

Fig 1a

ANOVA (cements, thermal cycling, and

before the experiment.

Testing sample

dental substrate [enamel or dentin]) and Tukey’s post-hoc test. Significance for all statistical tests was set at P ≤ 0.05 (95% significance).

Results The ANOVA results are shown in Table 2. The mean (in MPa) and standard deviation values for all groups are shown in

Fig 1b

Table 3.

after the experiment.

Table 2

Testing sample

Results of three-way ANOVA for μTBS data (P