Asystem of bonding com posite resins to dental porcelain w ith a silane solution produced a reliable bond. Tests were perform ed on buccal surfaces of 84 denture teeth. The specimens treated with silane solution appeared to have significantly higher resistance to shearing forces than the control specimens. This technique may be a clinical solution to intraoral repair of fractured o r chipped porcelain restorations.
Composite resins bonded to porcelain with silane solution
R. Newburg, DMD, MScO C. H. Pameijer, DMD, MScD, DSc, Bostonl^BBBi
The use o f porcelain-fused-to-metal has gained considerable favor during the past years. It is to be expected that with increased application o f this technique the number o f failures also will in crease. The clinician will have a problem with fractured restorations whether the failures occur with precious or nonprecious metals. Fractured or chipped dental porcelain can be repaired only by replacing or stripping and reapplying the porce lain. The complexity depends on whether there is a single restoration or multiple units o f fixed bridgework. In this study, com posite resin mate rial and a chemical bonding agent were used to repair dental porcelain.
study found that failure occurred, not at the tooth-resin interface, but within the body o f the porcelain, indicating a true bonding. Semmelman and Kulp also considered the bond more reliable with cold-cured resins. M yerson6 concluded from his experiments that cold-cured resins produced a stronger bond than mechanically retained porce lain teeth, but that thermal cycling was detrimen tal to the bond. A clinical study o f porcelain teeth in cold-cured dentures indicated that retention by bonding with silane solution was as satisfactory as mechanical retention.7 To our best knowledge, there is no data available on bonding composite resins to porcelain; therefore the following inves tigation was undertaken.
Review of the literature Methods and materials In I960, silane coupling agents were introduced commercially in glass-reinforced plastics.1 Bowen (1962)2 used these materials in the devel opment o f com posite resins that were reported to the dental profession in 1963.3 Paffenbarger and others (1967)4 bonded porce lain teeth to acrylic resin using silane solution as the coupling agent. Semmelman’s and Kulp’s5 2 8 8 ■ JADA, Vol. 96, February 1978
The lingual surfaces o f central incisor denture teeth* were embedded in a block o f cold-curing acrylic resin. The pins provided adequate m e chanical interlocking for the experiment. The fa cial surfaces were ground flat to provide a surface greater than 6 mm in diameter; then they were smoothed on a microtome hone (coarse side) to
remove any penetrating scoring that might pro vide mechanical retention. A 0.5% aqueous silane solution was made from stock y-methacryl-oxyprophyltrimethoxysilane.t Before application, the solution was hydrolyzed for one hour by adding 0.05 ml o f IN acetic acid per 10 ml o f aqueous silane solution. The prepared porcelain surface was cleaned with 33% phos phoric acid for a minute, then washed with tap water and blown dry with residue-free com pressed air. The silane solution was then applied for five minutes within two hours of its hydroly sis and allowed to evaporate completely (about five minutes) under a warm, incandescent heatlamp (about 120 F). An unfilled resin bonding agentt was polymerized on the porcelain surface. A button of composite resin* 4 mm in diameter was then fab ricated. In the group serving as control, the silane solution treatment was omitted, but the speci mens were otherwise prepared similarly. All specimens were kept dry and stored in air for a week, at room temperature, before testing. In addition, wet, thermal cycling of several groups was accomplished immediately before the specimens were subjected to testing forces. The water temperature variance was 150 F and 40 F; the specimens remained at each temperature for 30 seconds with a total cycling time of an hour. The specimens were tested by the application o f a point force load on the composite resin button at its junction with the porcelain. The direction of the force was parallel to the surface of the flat porcelain and was applied at a constant rate until the specimen integrity was destroyed. The type of fracture was noted and the resistance recorded in pounds force. On selected specimens, scanning electron micrographs were made of the samples to examine the characteristics o f the fractured sur faces. A total of 102 specimens was prepared and assigned to the following groups: The specimens in group A served to determine if there would be an effective bonding when silane solution was used as an intermediary coupling agent. In this group, six teeth were treated with silane solution and Nuva-Fil§ (A3), six teeth with silane solution and Adaptici (A2), and six teeth received no silane solution and were treated with Nuva-Fil (A l). The specimens of group B were prepared somewhat differently in that all samples received Nuva-Fil buttons, and in addition, six were ex posed to thermal cycling as described previously. The other 12 specimens received only silane solu tion treatment. The specimens in group C were
prepared like those in group A , except, instead of the use o f freshly prepared silane solution, a two-week-old solution was used. Group D con tained 48 specimens, 12 o f which underwent thermal cycling. All samples were treated with silane solution and received an Adaptic button.
Results The results are compiled in the Table. In group A , the composite resin applied to the porcelain surface that was not treated with silane solution had a mean rupture strength of 39 lb (SD 14). The composite resin left the porcelain surface smooth and intact. The composites bonded with silane solution consistently left an irregular and rough porcelain surface fractured within itself when loaded to breakage. These samples also demonstrated a significantly higher mean strength (841b [ S D 2 l] and 88 lb [S D 17] than when silane solution was not used ( P < .05). N o significant dif ference was noted between the data when the two composite materials were used. To compare the three techniques o f group A , we used the one-way analysis o f variance followed by the Scheffe test. (The F-test was significant). The Scheffe test showed that A2and A3 (84±21 and 88± 17 respec tively) were significantly different from A l (39± 14).
Dr. Newburg is assistant research professor at Boston University S chool of Graduate Den tistry, 100 E New ton St, Boston, 02118. Dr. Pameijer is professor and chairm an o f prostho don tics, division o f biom aterials, and assis tan t dire ctor, C linical Research Center, at that university. Address requests fo r reprints to Dr. Pameijer.
New burg— Pameijer: COMPOSITE RESINS BONDED TO PORCELAIN BY SILANE SOLUTION ■ 289
Table ■ Treatments for each test group and data obtained from statistical
analysis. No. sam ples
M ean rupture strength (lb)
S tandard deviation
c Nuva-Fil§/ no silane
Nuva-Fil/ + silane
G r o u p 't A1 A2
A3Adaptic+/ + silane B1 Nuva-Fil/ + silane B2 N uva-Fil/ + silane + therm al cycling D1 A daptic/ + silane D2 A daptic/ + silane + therm al cycling
Group C was treated with w h at appeared to be an unstable silane solution. Th e results could not be analyzed (see text). + Th e porcelain surfaces in all groups except A1 w ere fractured or chip ped and irregular.
The effect o f thermal cycling tested in group B resulted in a mean of 67 lb of rupture strength (SD 12), whereas the values for the other 12 specimens without thermal cycling averaged 69 lb o f rupture force (SD 13), which was not significantly differ ent. The data from group C were so inconsistent and erratic that no statistical analysis was attempted. The silane solution at the time o f application was cloudy, an indication o f condensation. The samples in group D that did not undergo thermal cycling averaged 69 lb o f rupture force (S D 20). The specimens that did undergo thermal cycling had a mean o f 56 lb (SD 16). A nonpaired t test o f r=2.331 indicated that a significant differ ence existed between them (P