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Abstract
Purpose
The purpose of this study is to see what impact the heat and press-on-metal technique has on the marginal fit of metal ceramic crown.
Materials and methods
Prior to the experiment, 4 metal master models were prepared. Each model has margin of chamfer, margin of heavy chamfer, margin of shoulder with bevel and margin of shoulder (collarless). Additionally, 10 crowns were made for each margin, total of 40 crowns. Marginal discrepancy between the master model and crown was observed at ×100 microscopic magnification in two states; in coping state and upon completion of making metal ceramic crown. Data analysis was performed using paired t-test along with one-way ANOVA and Duncan multiple comparison test.
Results
After analyzing mean and standard deviation of marginal discrepancy, it was confirmed that marginal discrepancies were within the clinical permitted range for all states; in coping state and upon completion of making metal ceramic crown. For the chamfer group, a significant increase in marginal discrepancy upon completion of making metal ceramic crown was observed compared to the heavy chamfer group. Also, a marginal discrepancy of porcelain margin in shoulder group was significantly less than the marginal discrepancy of metal margin in chamfer and shoulder group.
Conclusion
From the test result, one can conclude that marginal fit of metal ceramic crown built with heat and press-on-metal technique is not significantly different from marginal fit of metal ceramic crown built with traditional technique. And along with efficiency of this system, heat and press-on-metal technique is considered in clinic. (J Korean Acad Prosthodont 2014;52:90-6)
REFERENCES
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Fig. 1.
Four master models used in this study (From the left side, chamfer, heavy chamfer, shoulder with bevel, and shoulder).
Fig. 2.
Microscopic measuring of marginal discrepancy at the middle point of labial margin of heavy chamfer. (A) Metal coping, (B) Metal ceramic crown.
Fig. 3.
Comparison of the marginal discrepancy in Group C (㎛). ∗ P-value is determined by t-test procedure.
Fig. 4.
Comparison of the marginal discrepancies after completion of metal ceramic crown (㎛). ∗ P-value is determined one-way ANOVA procedure.
Fig. 5.
Comparison between each group in the marginal adaptation discrepancy at the same point of metal margin after completion of metal ceramic crown (㎛). ∗P-value is determined one-way ANOVA procedure.
Table 1.
Marginal type for each group
| G | N | Type of labial margin |
|---|---|---|
| C | 10 | Chamfer |
| HC | 10 | Heavy chamfer |
| SB | 10 | Shoulder with bevel |
| S | 10 | Shoulder |
Table 2.
Firing parameters of each step
| T | B | S | t ↗ | H | V1 | V2 | |
|---|---|---|---|---|---|---|---|
| ℃/℉ | ℃/℉ | min | ℃/℉/min | min | ℃/℉ | ℃/℉ | |
| 1st + 2nd Opaquer firing | 930/1706 | 403/757 | 6 | 100/180 | 2 | 450/842 | 929/1704 |
| Touch-Up firing | 840/1544 | 403/757 | 4 | 60/108 | 1 | 450/842 | 839/1542 |
| Shade/Stains firing | 800/1472 | 403/757 | 6 | 60/108 | 1 | 450/842 | 799/1470 |
| Glaze firing | 800/1472 | 403/757 | 6 | 60/108 | 2 | 450/842 | 799/1470 |
| Add-On after Glaze firing (690℃/1274℉) | 690/1274 | 403/757 | 4 | 60/108 | 1 | 450/842 | 689/1272 |
Table 3.
Average marginal discrepancy and standard deviation of each group (㎛)
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