Table 3. Descriptive statistics for Ra.
Ra - average roughness
| Scaling type | Metal crowns | Porcelain fused to metal crown | P-value |
| Hand scaling | 0.0686 ± 0.007 | 0.134 ± 0.0283 | 0.009 |
| Ultrasonic scaling | 0.0983 ± 0.018 | 0.304 ± 0.06 | 0.001 |
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