Table 1. Number of patients, early failures, failure rates within groups, and differences among groups (chi-squared test) .
| Patients n° | Early failures | Failure rate (%) | P-value* | |
| Overall | 885 | 35 | 3.9% | – |
| Gender | ||||
| Males | 455 | 18 | 3.9% | 0.998 |
| Females | 430 | 17 | 3.9% | |
| Age at surgery | ||||
| <40 years | 100 | 5 | 5.0% | 0.832 |
| 40‒60 years | 412 | 15 | 3.6% | |
| >60 years | 373 | 15 | 4.0% | |
| Smoking habit | ||||
|
Heavy smokers (>15 cigarettes/day) |
98 | 6 | 6.1% | 0.473 |
|
Light smokers (1‒15 cigarettes/day) |
184 | 8 | 4.3% | |
| Non smokers | 603 | 21 | 3.4% | |
| History of periodontal disease | ||||
| Generalized periodontitis | 97 | 6 | 6.1% | 0.386 |
| Localized periodontitis | 218 | 10 | 4.5% | |
| No periodontitis | 570 | 19 | 3.3% | |
| Vitamin D serum levels | ||||
| <10 ng/mL | 27 | 3 | 11.1% | 0.105 |
| 10‒30 ng/mL | 448 | 20 | 4.4% | |
| >30 ng/mL | 410 | 12 | 2.9% |
*Chi-squared test, with statistically significant difference set at P<0.05.