Letter to the Editor: Authors' Response

Biological mechanisms underlying complications related to implant site preparation

Implant site preparation is a critical stage of implant surgery that may underpin various complications related to implant surgery. This review discusses the latest available scientific information on risk factors related to implant site preparation. The role of the drilling process in relation to the density of the available alveolar bone, the effects of insertion torque on peri-implant osseous healing, and implant-related variables such as macrodesign and implant-abutment connection are all factors that can influence implant success. Novel information that links osteotomy characteristics (including methods to improve implant initial stability, the impact of drilling speed, and increase of the implant insertion torque modifying the bone-implant interface) with the appropriate instrumentation techniques will be discussed, as well as interactions at the bone-biomaterial interface that may lead to biologic complications mediated by implant dissolution products.

Peri-implant conditions and marginal bone loss around cemented and screw-retained single implant crowns in posterior regions: A retrospective cohort study with up to 4 years follow-up

The aim of the present study was to identify the peri-implant conditions (bleeding on probing (BOP), pocket probing depth (PPD), modified plaque index (mPI)) and marginal bone loss (MBL, marginal bone level change between follow-up and occlusal loading) around cemented and screw-retained posterior single crowns on tissue-level implants. The study was a retrospective cohort study with up to 4 years (mean 2.5 years) follow-up. Patients with either cemented or screw-retained crowns in posterior regions were included. Implant survival, technical complications, BOP, PPD, mPI, MBL, biologic complications (peri-implant mocositis and peri-implantitis) were evaluated. Mann-Whitney U test was used to test the difference between the screw-retained group (SG) and cemented group (CG). 176 patients (SG: 94, CG: 82) were included. The implant survival rates were 100% in SG and 98.8% in CG. Prosthetic screw loosening was found in 8 restorations (8.7%) at follow-up visit. Peri-implant mucositis rate was significantly higher in the SG group (42.1%) than that in the CG group (32.2%) (P = 0.04). Six patients (6.38%) in the screw-retained group and 5 patients (6.10%) in the cemented group were diagnosed with peri-implantitis, the difference did not reach statistical significance (P>0.05). No significant difference of PPD, mPI and MBL were found between two groups (P = 0.11, 0.13 and 0.08, respectively). High implant survival rates were achieved in both groups. Cemented single crowns on tissue-level implants showed comparable peri-implant conditions in comparison with two-piece screw-retained crowns. Well-designed prospective cohort or randomized controlled clinical trials with longer follow-up are needed to confirm the result.