## 3 Results  
Ossoeintegration was achieved for all 105 narrow diameter implants. Five patients (three provided with AGC and two provided with all-ceramic crowns) did not reach the 16-year follow-up after the load application, because three patients relocated to another city and two patients chose to rely on other dental clinics. As for the other fixtures, standardized periapical radiographs revealed a marginal bone resorption ranging from 0.46 to 1.32 mm 1 year after prosthetic loading and from 0.62 to 1.81 mm (mean of 1.2 \(\pm\) 0.61 mm) at a 16-year follow-up. Correspondingly, four-point peri-implant examination revealed the following probing measures:  
* a mean mesial probing 3.4 \(\pm\) 0.2 mm;
* a mean buccal probing of 2.6 \(\pm\) 0.1 mm;
* a mean distal probing of 3.2 \(\pm\) 0.1 mm;
* a mean palatal probing of 2.3 \(\pm\) 0.2 mm. The one-way ANOVA and [PERSON]'s post hoc tests did not show any significant difference between both the buccal and palatal aspects (\(p>0.05\)) and between the mesial and distal sides (\(p>0.05\)) of the implants. Conversely, statistically significant differences emerged between buccal vs. mesial (\(p<0.05\)), buccal vs. distal (\(p<0.05\)), palatal vs. mesial (\(p<0.05\)), and palatal vs. distal aspects (\(p<0.05\)) of the implants (Table 1). Ninety-four prostheses revealed a PI = 0, whereas the other 6 restorations showed a PI = 1. BOP was negative for 97 implants. Furthermore, a PIS = 1 score was found in 5 crowns, PIS = 2 score in 6 crowns, and PIS = 3 score in 86 crowns. After 16 years of clinical function, descriptive analysis resulted in 80% and 87.1% cumulative success rates for patients provided with AGC prostheses onto titanium abutments and all-ceramic crowns onto zirconia abutments, respectively, as reported in the Kaplan-Meier graph considering complications as events (Figure 9). No statistically significant difference was found with the log-rank test (\(p>0.05\)). As regards the peri-implant tissue conditions (Table 2), at the 16-year follow-up, 95 restorations showed a GI = 0 (95%). \begin{table}
\begin{tabular}{c c c c} \hline
**Time** & **Aspect** & **Mean Difference (mm)** & _p-Value_ \\ \hline  & B vs. P & 0.31 & \(>\)0.05 \\  & B vs. M & 1.2 & \(<\)0.05 \\  & B vs. D & 1.08 & \(<\)0.05 \\  & P vs. M & 1.07 & \(<\)0.05 \\  & P vs. D & 1.08 & \(<\)0.05 \\
16-year follow up & M vs. D & 0.38 & \(>\)0.05 \\ \hline \end{tabular}
\end{table} 
Table 1: Results of the one-way analysis of variance (ANOVA) and [PERSON]’s post hoc test for the interproximal marginal bone resorption and the four-point peri-implant probing at 16-year follow-up. \begin{table}
\begin{tabular}{c c} \hline
**Periodotal** & **16-Year Follow-Up** \\
**Parameters** & **n = 100** \\ \hline GI 0 & 95 \\ GI 1 & 2 \\ GI 2 & 3 \\ GI 3 & 0 \\ PI 0 & 94 \\ PI 1 & 6 \\ PI 2 & 0 \\ PI 3 & 0 \\ PIS 0 & 3 \\ PIS 1 & 5 \\ PIS 2 & 6 \\ PIS 3 & 86 \\ PIS 4 & 0 \\ \hline \end{tabular}
\end{table} 
Table 2: Gingival Index (GI) score, Plaque Index (PI) score, and Papilla Index Score (PIS) at 16-year follow-up. Figure 9: Kaplan–Meier graph showing cumulative success rates in relation to time. Two different curves were reported for patients wearing AGC and all-ceramic crowns, respectively. The cumulative survival rate calculated for AGC group was 93.3%, whereas the all-ceramic group showed a cumulative survival rate of 95.7% (Figure 10). No statistically significant difference was found with the log-rank test (\(p>0.05\)). The overall success and survival rates calculated for all the restorations were 85% and 95%, respectively. During the entire period of observation, in the AGC group the following complications were reported: 1 aesthetic failure after 8 years of clinical function (3.33%), at the 11-year recall 1 loss of retention (3.33%), 2 mucositis after 12 years and 1 mucositis at the 15-year follow-up (10%). At the 16-year recall, 1 case of severe peri-implantitis was observed in the AGC group, causing loss of the implant (3.33%).