## 4 Discussion  
As dental implants continue to enter the \"main-stream\" of dentistry, demand for predictable dental implant therapy continues to grow. To what extent implant design modifications such as PS and LM can tweak and perfect an already predicable, albeit imperfect, treatment modality is still an unanswered question. Both LM collars and PS collar designs have shown promise in clinical application. However, to the authors' best knowledge, no study has been conducted to test whether the addition of PS to LM collar implants and abutments will show additional benefit over and above LM collar implants and abutments alone. The primary outcome evaluated in the present study was the comparison between test and control implants on the difference in MBL values at 6 months and 12 months follow-ups compared to baseline (\(\Delta\)MBL values in Table 2). No significant differences between test and control implants were found in the temporal variation of MBL values. MBL changes obtained in the present study are smaller than those found via meta-analysis for both LM collar implants: 0.72 mm (95% CI: 0.59 to 0.85 mm) [11] and PS implants, 0.49 mm (95% CI: 0.38 to 0.60 mm) [16]. However, it should be stressed that the present study is shorter in duration than many studies included in the meta-analysis and further bone remodelling may occur over time. The marginal bone loss in both groups is well within the success criteria proposed by [PERSON]: less than 1.5 mm bone loss after the first year in function, and less than 0.2 mm per year [52]. According to the newest classifications of peri-implant health and disease, there is no maximum value of early marginal bone remodelling after placement of an implant; however, all implants were well below the 3-mm threshold to diagnose peri-implantitis without a previous radiograph as proposed by the newest classifications [50]. The average MBL change from baseline, 6-month and 12-month follow-ups in test implants was found to be statistically significant, although there was no statistically significant change noted from 6-month to 12-month. Hence, in the present investigation the bulk of the bone remodelling appeared to have occurred in the first 6 months after placement. No clinically statistically significant bone remodelling was detected in the months following restoration. This is in agreement with a study by [PERSON] et al. where marginal bone remodelling was detectable radiographically as early as one month after placement of transmucosal implants in a dog model [53] and it is also corroborated by a study by [PERSON] et al. [54] where the vast majority of bone remodelling was seen to occur in the first 6 months of placement in immediately loaded implants. From baseline to final review, there was a slight gain in MTH (0.5%) in test implants, but this increase was not significant. MTH variation in soft tissues was not found to be different between test and control implants. Such little soft tissue remodelling could be considered \"successful\" given the apparent tissue stability. These changescompare favourably to the soft tissue changes reported around LM collar implants which range from 0.16 \(\pm\) 0.3 mm to 1.08 \(\pm\) 0.4 mm [40; 41]. PPD values did not change significantly over time in control and test implants. In addition, PPD values were not different between test and control implants at baseline and at final review. Although there is no PPD strictly defining disease [50], the most recent classification indicates that, without previous records, a PPD equal or greater than 6 mm with BOP and signs of inflammation can be considered as peri-implantitis [50]. Furthermore, deep PPD is associated with a higher chance of BOP [55] which in turn is predictive of progressive bone loss [56]. Hence, test and control implants appeared to have clinically acceptable readings at both time points, and no signs of \"disease associated\" pocket depths were recorded. Regarding the BOP, no difference was found in the recordings between tests and controls at the 12-month follow-up.