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Effect of Viscosity on the Strength of Luting Agents for Stainless Steel Crowns Effect of Viscosity on the Strength of Luting Agents for Stainless Steel Crowns
MS Fuselier, VA Marker, CFG Wilson
Baylor College of Dentistry - Texas A&M University System Health Science Center
Results
Table 4. Results of DTS measurements as a function of powder liquid ratios. The effect of modifying the powder/liquid ratios was not significant for Temrex (Table 4).
The diametral tensile strength of Vitremer was significantly reduced by increasing the
mixing ratio to a clinical consistency. However, even the lower strength value of the
Vitremer cement was an order of magnitude greater than the values obtained with the
Temrex cement mixed at either consistency. For each cement, the effect of setting time produced a significant difference in the di-
ametral tensile strength (Table 5). The importance of setting times on strength was most
evident for the Temrex cements. Waiting 4 minutes past the recommended setting time
failed to yield an immediate Temrex specimen that could be removed from the mold
without crumbling. Therefore, we were unable to obtain data with this cement at the
immediate test condition. Of the cements we were able to test, the greatest increase in
diametral tensile strength was obtained with the Vitremer cement. These specimens
showed a the two-fold increase after 24 hours. Immediately after mixing, the cements tended to plastically deform under loading (barrel-
ing) while specimens that had cured 24 hours responded in a brittle manner. The speci-
mens in Figure 1 are typical examples of the resin modified glass ionomer cements.
Figure 2 shows the specimens for each cement after testing at 24 hours. At the immediate test time, the ultimate diametral tensile strength of Durelon cement was
difficult to identify because of the pronounced barreling effect in this material. After a
slight decrease, the load continued to increase as the specimen deformed plastically
(Figure 3). We selected the first peak as an arbitrary failure point because the speci-
mens had obviously failed (changed shaped) by this point. An unusual fracture pattern was observed in the Temrex specimens after storage in water
for 24 hrs (Figure 4). The specimens cracked as if the disk was serially sectioned. The effect of the storage conditions on the diametral tensile strength was not significant
for any of the cements (Table 5). DTS values obtained after 24hrs storage in 37
o
C were
comparable to the values obtained after thermocycling. Comparisons among cements were statistically significant for all of the test conditions,
except for Durelon and Vitremer cements at the immediate and 24 hr tests (Table 5).
Figure 2. Comparison of specimens stored for 24 hrs in 100%
humidity: Fuji Plus, Temrex, Vitremer, Durelon (left to right).
Note the fracture in Temrex is atypical.
Attin T, Vataschki M, Hellwig E. Properties of resin-modified glass-ionomer restorative materials
and two polyacid-modified resin composite materials. Quintessence Int. 1996 27:203-9.
Craig RG. Restorative Dental Materials. 10th ed, pp 172-175, St. Louis: C.V. Mosby Co., 1997.
Einwag J, Dunninger P. Stainless steel crown versus multisurface amalgam restorations: an 8
year longitudinal clinical study. Quintessence Int 1996 27(5):321-323.
Galun IA, Saleh N, Lewinstein I. Diametral tensile strength and bonding to dentin of type I glass
ionomer cements. J Pros Dent 1994 72:424-429.
Garcia-Godoy F, Bugg JL. Clinical evaluation of glass cementation on stainless steel crown
retention. J Pedo 1987 11:339-44.
Garica-Godoy J, Landry JK. Evaluation of stainless steel crowns luted with glass ionomer cement.
J Pedo 1989 13:328-30.
Giovannitti JA. Dental Anesthesia and Pediatric Dentistry. Anesthesia Prog. 1995 42(3-4):95-99
McDonald and Avery. Dentistry for the Child and Adolescent, 6th ed. pp.373-378, St. Louis: C.V.
Mosby Co., 1994.
Personal Communication, Fuselier MS. My observation of 4 private practitioners and 14 residents
is that a thinner powder to liquid ratio of cement is often requested by the doctor when
cementing stainless steel crowns.
Powers JM, Farah JW, Craig RC. Modulus of elasticity and strength properties of dental cements.
J Am Dent Assoc 1976 92:568-591.
Prosser HJ, Powis DR, Brant P, Wilson AD. Characterization of glass-ionomer cements: the
physical properties of current materials. J Dent 1983 12:231-240.
Shiflett KS, White SN. Microleakage of cements for stainless steel crowns. Ped Dent 1997
19:262-266.
Smith DC. A new dental cement. Brit Dent J 1967 124:540-41.
Tjan AHL, Miller GD, Whang SB, Sarkissian R. The effect of thermal stress on the marginal seal
of cast gold full crowns. J Am Dent Assoc 1980 100:48-51.
White SN, Sorenson JA, Kang SK, Caputo AA. Microleakage of new crown and fixed partial den-
ture luting agents. J Prosthet Dent 1992 67:156-161.
White SN, Zhaokun Y. Compressive and diametral tensile strengths of current adhesive luting
agents. J Prosthet Dent 1993 69:568-572.
White SN, Yu Z, Tom JFMD, Sangsursak S. In vivo microleakage of luting cements for cast crowns.
J Prosthet Dent 1994 71:333-338.
White SN, Furuichi RS, Kyomen SM. Microleakage through dentin after crown cementation. J
Endod 1995 21:9-12.
Wilder AD, Boghosian AA, Bayne SC, Heymann HO, Sturdevant JR, Poberson TM. Effect of pow-
der / liquid ratio on the clinical and laboratory performance of resin-modified glass-
ionomers. J Dent 1998 26:369-377.
Wilson AD, Kent BE. A new translucent dental filling material: The glass-ionomer. Br Dent J
1972 132:133-350.
References
Discussion Unlike most cements, the DTS of Temrex was not appreciably affected by lowering the P/L ratio. This finding might
suggest that another parameter other than strength plays a key role in the clinical success of Temrex. Even though Vitremer luting cement was more sensitive to P/L ratio fluctuations, the DTS obtained with a low viscos-
ity mix was an order of magnitude greater than the values for Temrex. We have yet to prove that a higher DTS will
results in better retention of SS crowns. Especially for the cements that bond to teeth, the optimum properties are a compromise between factors such as a
high P/L ratio that produces a stronger material and a low P/L ratio that wets the tooth and produces a better bond. In pediatric dentistry, the initial cement strength is critical to the success of the restoration. Fuji Plus has an advantage
because it developed more than 70% of its ultimate strength by the immediate test time as compared to Vitremer
which had an initial strength that was ~40% of its ultimate value. Even the early strength of Vitremer and Durelon were
significantly greater than the ultimate strength of Temrex The findings from the setting time test suggest that the clinical failures of the SS crowns luted with Temrex may be a
consequence of the very weak early strength of this material. The non-brittle response of Durelon specimens tested immediately after mixing may account for its effectiveness in
retaining SS crowns. The retention mechanisms of luted stainless steel crowns are not clearly understood; it is pos-
sible that the plastic deformation behavior, i.e., absorbing the energy of loading, may compensate for the low
strength. All of the cements exhibited some plastic deformation at the immediate test time. The least barreling was observed
with the Fuji Plus cement. This finding is consistent with the fact that this cement also exhibited the highest DTS value. At the 24 hr DTS test, the Temrex specimens (Fig. 4) failed in a brittle manner, exhibiting a linear delamination pattern
that was unlike the other cements (Fig. 2). It is difficult to find an explanation for why these brittle specimens would
appear to separate into thin wafers rather than in the fracture pattern seen in the other cements at this time period. The lack of differentiation between the specimens that were stored for 24 hrs at 100% humidity and those that were
thermocycled for 2000 cycles demonstrated that fluid absorption and thermal stresses had less influence than the
other variables we tested, i.e., setting time and P/L ratios. We did not see differences in the deformation patterns or
the DTS values for any of the cements compared in the specimens. Since the cements tested in this study represent several different categories of materials, we expected to see a
range of DTSs among the products tested. It was interesting that the difference between the resin modified glass
ionomer cements, Vitremer and Fuji Plus, was significant. Obviously, the differences in composition contribute to this
finding. These materials also exhibited different handling characteristics. The clinician who prepared all of the samples noted the handling characteristics of the cements were vastly different.
Temrex was messy, smelly and the hard to clean up. Durelon was the most difficult to mix; it was sticky and hard to
clean up if the initial setting time was exceeded. For mixing and loading the molds, there was little difference between
the resin modified glass ionomer cements. The Fuji Plus set faster and was easier to remove from the molds than
the Vitremer Luting cement. Both of these materials were much faster to clean up than Temrex and Durelon.
Figure 1. Comparison of Fuji Plus specimens loaded imme-
diately after setting (left) and loaded after 24 hr storage in 100%
humidity (right). The early specimen shows a moderate amount
of barreling and the 24 hr specimen shows a typical fracture.
Materials
Temrex