Page 46 - SPEMD_60-3

134 rev port estomatol med dent cir maxilofac. 2019;60(3):130-136

Figure 3. Influence of mouthwash on shear bond strength Figure 5. Failure mode distribution according to
[DW – distilled water; LT – Listerine Teeth & Gum; EP – experimental group
Eludril Perio; LO – Lacer Oros; No statistically significant [DW – distilled water; LT – Listerine Teeth & Gum; EP –
(p=0.214) differences were found between groups under the Eludril Perio; LO – Lacer Oros; NT – no surface treatment; SB
same horizontal line]. – sandblasted with 50-µm aluminum oxide (Al2O3)
particles; DB – abraded with a coarse diamond bur; No
statistically significant (p>0.05) differences were found].

ness to those immersed in the mouthwash with no alcohol
(Eludril Perio and Lacer Oros).
The pH of the tested solutions provides another potential
preponderant factor for the composite matrix degradation. (30)
According to the manufacturers’ information, each of the
tested mouthwashes has other components (such as benzoic
and citric acid) that may also have a deleterious effect on the
composite resin, and this needs to be taken into consider-
ation. Compared to distilled water (pH=5.5), the higher acidi-
ty of the mouthwashes may have altered the polymeric ma-
trix of the resin composites by catalysis of ester groups from
dimethacrylate monomers present in their compositions. The
hydrolysis of these ester groups may have formed molecules
capable of accelerating the degradation of the composite res-
Figure 4. Influence of surface treatment on shear bond in. On the other hand, the low pH may have also caused the
30
strength erosion in the surface of the filler particles, accelerating their
[NT – no surface treatment; SB – sandblasted with 50-µm debonding. 16
aluminum oxide (Al2O3) particles; DB – abraded with a
coarse diamond bur; No statistically significant (p=0.165) Bonding between an aged composite resin and added fresh
differences were found between groups under the same composite resin can be affected by several factors, such as
horizontal line]. surface roughness, adhesive system, repairing material and
34
aging period. When performing a conventional composite
restoration using the incremental technique, the presence of
an oxygen-inhibited unpolymerized layer ensures the bonding
23
ness than when this restorative material was exposed to water, between two composite increments. However, bonding new
which is in agreement with the results obtained in previous composite material to an aged composite restoration presents
studies. 30-33 Mouthwashes are capable of diffusing through the a different and harder challenge, as there are few or no unre-
35
polymeric matrix, expanding the polymer chains and causing acted methacrylate groups remaining. In order to overcome
chemical softening with loss of constituents, thus leading to this limitation, several techniques have been recommended
the deterioration of the properties of the composite resin. 14,15 to improve the composite-composite bond strength, such as
Alcohol is a good methacrylate solvent, and may swell the chemical and mechanical conditioning of the aged restoration
polymeric matrix of the resin composites, increasing the surface. 36,37 Mechanical surface treatment aims to remove the
amount of unreacted monomers and oligomers that diffuse superficial layer, increase the surface energy and area, rough-
38
18
out of materials. However, specimens exposed to mouth- en it, and promote mechanical interlocking. However, rough-
wash with alcohol (Listerine Teeth & Gum) had similar hard- ening the composite surface may decrease the bond strength