Development of a primer containing a silane coupling agent for zirconia /Kimura H1, Kato T1, 2, Saigo K2,Yamada B1,Yamauchi J1, Anraku T1 (1 Yamamoto Precious Metal Co. Ltd., 2 Kochi University of Technology) : For firm adhesion between a dental
resin and a zirconia frame, sandblasting followed by suitable priming is required. γ-Methacryloyloxypropyltrimethoxysilane was employed
after sandblasting with and without heat treatment (1000 ˚C). The use of silane coupling after sandblasting was found to significantly
enhance the adhesive strength. The sandblasting/heat treatment, which might induce the phase transformation of zirconia, slightly reduced
the adhesive strength in comparison to treatment by sandblasting only.

[Abstract]
In recent years, the clinical application of zirconia has
been increasing due to considerations ofbiocompatibility. In order to achieve firm adhesion
between zirconia and resin when building in resin on a
zirconia frame, sandblasting of the frame, followed bypriming using a primer specifically suitable for use withzirconia, is required. A body of literature states thatadhesion with zirconia can be improved by the use of aprimer which includes phosphoric-acid monomers;
however, the effectiveness of using a silane coupling
agent has yet to be clarified. In this investigation, theinfluence of sandblasting treatment and the use of silane
coupling on adhesive strength between resin andzirconia is investigated.

obtained on fracturing.

Adhesive strength [MPa][Results and Discussion]
Figure 1 gives adhesive strength values for zirconia
under the various surface treatments applied. Whilea l m o s t n o e ff e c t i v e n e s s w a s d i s p l a y e d u n d e r
sandblasting alone, adhesive strength increased
significantly (0.1 MPa → 9.7 MPa) under TR
treatment. However, heat treatment following
sandblasting caused adhesive strength values to decline
by 23% (9.7 MPa → 7.5 MPa).

[Materials and Methods]
A disc of zirconia (Aadva, manufactured by GC) wasused for adhesion testing. The surface was (1) polishedwith #600 water-resistant paper, (2) subjected tosandblasting treatment (alumina sand, particle diameter
50 µm) after polishing and (3) subjected to heat
treatment at 1000˚C for 15 min after sandblasting.
Adhesive strength was evaluated under the conditions
obtaining after the three types of treatment above. γ-Methacryloyloxypropyltrimethoxysilane.
An ethanol solution (TR) of γ-Methacryloyloxypropyltrimethoxysilane (manufactured by Momentive
Performance Materials Japan) was used as a slilane
coupling agent. After the bonding plane was provided
with tape with φ5 mm perforations, an opaque resin(TWiNY IvO, manufactured by Yamamoto PreciousMetal) was lightly applied and curing was conductedusing a photopolymerization device (LED CURE
Master, Yamamoto Precious Metal). Molds of 2 mmin thickness and with φ5 mm perforations werealigned with the bonding plane and fixed withdouble-sided tape. An indirect composite resin(TWiNY DA3, manufactured by Yamamoto PreciousMetals) was supplied and curing was conducted bymeans of photopolymerization. The molds wereremoved from the cured test specimens, and after
immersion for 24 hours in distilled water at 37˚C, thetest specimens were placed in a small-sized universal
tester (Ez-Graph, manufactured by Shimadzu). Loadwas applied to the cured test specimens in a shearing
direction at a rate of 1.0 mm/min.; shear adhesivestrength was ascertained from test strength values

1510Without silane coupling
TR treated

9.7
7.5

500.00.2

#600

0.1

0.0

Sandblasting

Sandblastingand heating

Fig. 1: Shear adhesive strength of each zirconia specimen

Table 1 shows shear adhesive strengths obtained
between the bonding surface and TR after polishingand heat treatment.
Table 1. Surface area and adhesive strength
Treatment

Surface area*( µm2)

Adhesive strength(S.D.) (MPa)#600 sand paper

0.016900.2 (0.2)

Sandblasting

0.02947

9.7 (3.4)

Sandblasting/heating

0.02967

7.5 (2.4)

Surface area*= Relative to field of vision (128µm x 128µm = 0.01638µm2)

While adhesive strength increases in line with theincrease in surface area caused by sandblastingtreatment, adhesive strength values decline under heat
treatment regardless of the fact that the surface area
undergoes no significant change. A surface hydroxyl
group on the target bonding surface is necessary forsilane coupling2) ; it is thought that heat treatment athigh temperatures impacts zirconia in such a way as todecrease the surface hydroxyl volume. There is also thepossibility that for partially stabilized zirconia, which iswidely used as a dental material, the stresses resulting
from sandblasting may induce a phase transformation of
the surface crystals from tetragonal to monoclinic01crystals, with reversion to tetragonal form under heat
treatment at 1,000˚C and over. It is thought that thiskind of phase transformation has an influence on theadhesive strength.
[Conclusion]
This investigation demonstrates that, for zirconia which
has undergone sandblasting treatment, silane coupling
improves adhesion with resin.
[Reference]
1) Kimura H et al.: J J Dent Mater, 30, 344, 20112) J. P. Matinlina et al. : Surf Interface Anal, 36, 246–253, 2004
3) H. Sato et al: Key. Eng. Mat., 330 ~ 332, 1263 –1266, 200702