Smoking-induced subgingival dysbiosis precedes clinical signs of periodontal disease.

Smoking accelerates periodontal disease and alters the subgingival microbiome. However, the relationship between smoking-associated subgingival dysbiosis and progression of periodontal disease is not well understood. Here, we sampled 233 subgingival sites longitudinally from 8 smokers and 9 non-smokers over 6-12 months, analyzing 804 subgingival plaque samples using 16 rRNA sequencing. At equal probing depths, the microbial richness and diversity of the subgingival microbiome was higher in smokers compared to non-smokers, but these differences decreased as probing depths increased. The overall subgingival microbiome of smokers differed significantly from non-smokers at equal probing depths, which was characterized by colonization of novel minority microbes and a shift in abundant members of the microbiome to resemble periodontally diseased communities enriched with pathogenic bacteria. Temporal analysis showed that microbiome in shallow sites were less stable than deeper sites, but temporal stability of the microbiome was not significantly affected by smoking status or scaling and root planing. We identified 7 taxa-Olsenella sp., Streptococcus cristatus, Streptococcus pneumoniae, Streptococcus parasanguinis, Prevotella sp., Alloprevotella sp., and a Bacteroidales sp. that were significantly associated with progression of periodontal disease. Taken together, these results suggest that subgingival dysbiosis in smokers precedes clinical signs of periodontal disease, and support the hypothesis that smoking accelerates subgingival dysbiosis to facilitate periodontal disease progression.

Stability of healthy subgingival microbiome across space and time.

The subgingival microbiome is one of the most stable microbial ecosystems in the human body. Alterations in the subgingival microbiome have been associated with periodontal disease, but their variations over time and between different subgingival sites in periodontally healthy individuals have not been well described. We performed extensive, longitudinal sampling of the subgingival microbiome from five periodontally healthy individuals to define baseline spatial and temporal variations. A total of 251 subgingival samples from 5 subjects were collected over 6-12 months and deep sequenced. The overall microbial diversity and composition differed significantly between individuals. Within each individual, we observed considerable differences in microbiome composition between different subgingival sites. However, for a given site, the microbiome was remarkably stable over time, and this stability was associated with increased microbial diversity but was inversely correlated with the enrichment of putative periodontal pathogens. In contrast to microbiome composition, the predicted functional metagenome was similar across space and time, suggesting that periodontal health is associated with shared gene functions encoded by different microbiome consortia that are individualized. To our knowledge, this is one of the most detailed longitudinal analysis of the healthy subgingival microbiome to date that examined the longitudinal variability of different subgingival sites within individuals. These results suggest that a single measurement of the healthy subgingival microbiome at a given site can provide long term information of the microbial composition and functional potential, but sampling of each site is necessary to define the composition and community structure at individual subgingival sites.

Bacterial Colonization of the Implant-Abutment Interface (IAI) of Dental Implants with a Sloped Marginal Design: An in-vitro Study.

PURPOSE: The aim of this study is to utilize an in vitro dynamic loading model to assess the potential risk of bacterial invasion into the Implant Abutment Interface (IAI) microgap of dental implants with sloped marginal design. MATERIALS AND METHODS: Forty implants were divided into two groups (n = 20 per group) based on implant marginal design. Group 1 was comprised of implants with Morse-taper connection and conventional marginal design that connected to titanium abutments. Group 2 was comprised of implants with Morse-taper connection and sloped marginal design that connected to titanium abutments. The specimens were immersed in a bacterial solution of E. coli and loaded with 500,000 cycles of 160N using a chewing simulator. Following disconnection of fixtures and abutments, microbial samples were taken from the threaded portion of the abutment, plated and cultured under appropriate conditions. RESULTS: Ten out of twenty implants of Group 1 and eight out of twenty implants of Group 2 had IAI microgaps colonized by E. Coli. There was not a statistically significant difference in the mean number of E. Coli CFU detected between implants of Group 1 (mean 19.2, SD 23.6) and Group 2 (mean 12.5, SD18.9) (p > .05). CONCLUSIONS: The present study demonstrated that implants with a sloped marginal design exhibited similar risk for bacterial invasion into the IAI microgap under in vitro dynamic loading conditions compared to implants with conventional marginal design.

The Role of Chlorhexidine on Endotoxin Penetration to the Implant-Abutment Interface (IAI).

PURPOSE: The aim of this study is to assess the risk of endotoxin penetration to the implant-abutment interface (IAI) of implants with Morse-taper connection and the effect of chlorhexidine in the prevention of such penetration. MATERIALS AND METHODS: Thirty implants with Morse-taper connection were divided into three groups (n = 10/group) based on type of inoculation of the internal aspect of the implant. Implants in Group 1 were inoculated with 1 µl Escherichia coli for 24 hours; supernatant was removed and 0.5 µl of sterile saline was added. Implants in Group 2 were inoculated with 1 µl E. coli for 24 hours; supernatant was removed and 0.5 µl 0.2% chlorhexidine solution was added. Implants in Group 3 were inoculated with 0.5 µl of sterile saline and served as controls. Following inoculation procedures, implants were connected to standard abutments, immersed in sterile culture media, and loaded with 200,000 cycles of 160 N in a wear simulator. Samples were collected from the supernatant solution of each implant for endotoxin identification at the beginning of the loading cycle (T0) and following 9 hours (T9), 18 hours (T18), 27 hours (T27), 36 hours (T36), 45 hours (T45), and 54 hours (T54). RESULTS: For Group 1 and Group 2, there were statistically significant differences between the endotoxin concentration at T0 and the endotoxin concentration at the subsequent sampling points (p < .05 Kruskal-Wallis with Bonferoni corrections for intragroup comparisons). There were no statistically significant differences between Group 1 and Group 2 at all sampling points. CONCLUSIONS: This study indicates that bacterial endotoxin can penetrate the IAI of implants with Morse-taper connection, and 0.2% chlorhexidine solution had no significant effect on that penetration.

The effect of healing abutment reconnection and disconnection on soft and hard peri-implant tissues: a short-term randomized controlled clinical trial.

PURPOSE: It has been reported that multiple abutment disconnections and reconnections following implant placement may compromise the peri-implant mucosal seal and may lead to increased marginal bone loss. Thus, the aim of this study was to evaluate the effect of healing abutment disconnection and reconnection on soft and hard peri-implant tissues. MATERIALS AND METHODS: Sixteen patients were included in this prospective randomized controlled clinical trial. Following one-stage implant placement, test group implants (n = 10) received a permanent abutment and control group implants (n = 11) received a healing abutment. After 2 months of healing, control group implants underwent a prosthetic protocol involving implant-level impressions and a two-time abutment disconnection and reconnection process prior to delivery of the definitive prosthesis. Test group implants underwent a prosthetic protocol involving abutment-level impressions without any abutment disconnection. Clinical parameters were recorded at 2 weeks, 2 months, 3 months, and 6 months, and marginal bone levels were assessed radiographically at implant placement, 3 months, and 6 months. RESULTS: The overall survival rate from implant placement to the last follow-up visit was 100% for both groups. The mean marginal bone loss at the 6-month examination was 0.13 mm for test group implants and 0.28 mm for control group implants. There were no significant differences regarding changes in peri-implant mucosal dimensions between the two groups. CONCLUSION: The present study indicates that implants receiving a final abutment at the time of implant placement exhibited minimal marginal bone loss and were similar to implants subjected to abutment disconnection and reconnection two times. Disconnection and reconnection of the abutment two times did not cause negative dimensional changes in the peri-implant mucosa.