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1 - y e a r s t u d y o f n o n s u b m e r g e d i m p l a n t s above- mentioned regression models were esti- mated following a generalized estimating equa- tion approach. The implant was used as the unit of analysis. We adjusted the estimates of the coefficients’ standard errors and confidence intervals using a robust variance–covariance estimator.26 The same analysis was performed for gingival biotype. A multiple linear regression model with step- wise selection was fitted to evaluate the rela- tionship between MBL at 12 months and the following variables: sex (male/female), location (mandible/maxilla), tooth type (anterior/posterior), endodontically treated adjacent teeth (yes/no), implant placement (immediate, early, delayed), implant diameter (3.80, 4.25 or 5.00 mm), implant length (10.0/11.5 mm) and gingival bio- type (thin/thick). All statistical analysis was performed using Stata (Version 13.1, StataCorp, College Station, Texas, U.S.). Results Based on the inclusion and exclusion criteria, 54 patients (62 implants) with a mean age of 56.8 ± 12.0 years (26 men and 28 women) were included. Table 1 depicts implant distribution and MBL (mean ± SD) at 12 months according to the pre-, intra- and postoperative parameters evaluated. The survival rate was 100%. The total patient dropout rate was 1.85%. No wound infection, osteitis, bone graft sequestration or implant loosening occurred during the follow-up period. Mean MBL values according to implant placement group and gingival biotype are reported in Tables 2 and 3, respectively. The delayed implant group showed the greatest bone loss from T6 to T12, the difference being statistically significant (P < 0.05) with respect to both the early and immediate groups. The early implant group showed the lowest bone loss at all times. Interestingly, all 3 groups showed a statistically different MBL at T3 with respect to T1. Considering gingival thickness, MBL signifi- cantly (P < 0.01) decreased with time in both groups, but patients with a thin biotype showed a greater bone loss (P < 0.01) than patients with a thick biotype. A statistically significant differ- ence (P < 0.01) in MBL between groups was found at 6 and at 12 months. The results of the multiple linear regression (Table 4a) showed that implant diameter and gingival biotype were the only variables significantly (P < 0.01) related to MBL at T12, the gingival biotype being the most important one (Table 4b). As soft-tissue evaluation parameters, PES and PI assessment are reported in Tables 5 and 6. Adequate/good PES scores were reported for all implants, increasing from T6 to T12. Also, PI increased from T6 to T12. Plaque score and BoP are reported in Table 7. A clinical photograph sequence of an example of implant rehabilitation is shown in Figure 2. A periapical radiograph sequence of a representative case is presented in Figure 3. Discussion The study has demonstrated that the proposed nonsubmerged technique with a hyperbolic neck design allows the achievement of a stable periimplant MBL and an adequate soft-tissue morphology. MBL was evaluated at 1 and 3 months after implant insertion (preloading period) and demonstrated very limited bone loss despite the gingival emergence of a yellow implant neck. Previous studies have evaluated MBL from initial loading (postloading period), not consid- ering that bone loss may occur during the pre- loading time.5 Interestingly, in the present study, a stable MBL was observed after 1 month from insertion. The flapless technique27–29 probably minimized surgical trauma that may be respon- sible for initial marginal bone loss.30 Our investigation is the first prospective clin- ical study to evaluate a high number of clinical (BoP, PI and plaque score), radiographic (MBL) and esthetic (PES) parameters and include a reasonable number of implants and patients. Currently, only a case report8 and a prospective cohort study10 at 18 months with just 14 patients, showing a stable MBL and a soft-tissue improve- ment, have been published on the Prama implant. A study on another implant system demon- strated in both flapless and flapped groups a marginal bone loss of 0.5 mm after the stress- free healing period,31 not far from our results. Similar values were reported in other investiga- tions regarding different implant systems and the flapless technique.28, 29 Long-term results from a randomized clinical trial on a 1-piece implant with a conical neck shape (similar to the hyperbolic profile) have recently been pub- lished,32 reporting high success (96.4%) and survival rates (100%) and acceptable periimplant 36 Volume 3 | Issue 4/2017 Journal of Oral Science & Rehabilitation