The role of nicotine, cotinine and caffeine on the electrochemical behavior and bacterial colonization to cp-Ti

Insight Into Corrosion of Dental Implants: From Biochemical Mechanisms to Designing Corrosion-Resistant Materials

Purpose of Review

Despite advanced technologies to avoid corrosion of dental implants, the mechanisms toward the release of metals and their role in the onset of peri-implant diseases are still under-investigated. Effective knowledge on the etiopathogenesis of corrosive products and preventive strategies mitigating the risks for surface degradation are thus in dire need. This review aimed to summarize evidence toward biocorrosion in the oral environment and discuss the current strategies targeting the improvement of dental implants and focusing on the methodological and electrochemical aspects of surface treatments and titanium-based alloys.

Recent Findings

Recent studies suggest the existence of wear/corrosion products may correlate with peri-implantitis progress by triggering microbial dysbiosis, the release of pro-inflammatory cytokines, and animal bone resorption. Furthermore, current clinical evidence demonstrating the presence of metal-like particles in diseased tissues supports their possible role as a risk factor for peri-implantitis. For instance, to overcome the drawback of titanium corrosion, researchers are primarily focusing on developing corrosion-resistant alloys and coatings for dental implants by changing their physicochemical features.

Summary

The current state-of-art discussed in this review found corrosion products effective in affecting biofilm virulence and inflammatory factors in vitro. Controversial and unstandardized data are limitations, making the premise of corrosion products being essential for peri-implantitis onset. On the other hand, when it comes to the strategies toward reducing implant corrosion rate, it is evident that the chemical and physical properties are crucial for the in vitro electrochemical behavior of the implant material. For instance, it is foreseeable that the formation of films/coatings and the incorporation of some functional compounds into the substrate may enhance the material’s corrosion resistance and biological response. Nevertheless, the utmost challenge of research in this field is to achieve adequate stimulation of the biological tissues without weakening its protective behavior against corrosion. In addition, the translatability from in vitro findings to clinical studies is still in its infancy. Therefore, further accumulation of high-level evidence on the role of corrosion products on peri-implant tissues is expected to confirm the findings of the present review besides the development of better methods to improve the corrosion resistance of dental implants. Furthermore, such knowledge could further develop safe and long-term implant rehabilitation therapy.

The Synergistic Effect of Nicotine and Staphylococcus aureus on Peri-Implant Infections

Smoking is considered a key risk factor for implant survival; however, how it interacts with the pathogens in peri-implant infections is not clear. Here, we identified that nicotine, the key component of cigarette smoking, can interact with Staphylococcus aureus and synergistically induce peri-implant infections in a rat osteolysis model. The nicotine–S. aureus combination group increased the gross bone pathology, osteolysis, periosteal reactions, and bone resorption compared to the nicotine or S. aureus single treated group (p < 0.05). Nicotine did not promote the proliferation of S. aureus both in vitro and in vivo, but it can significantly upregulate the expression of staphylococcal protein A (SpA), a key virulence factor of S. aureus. The nicotine–S. aureus combination also synergistically activated the expression of RANKL (receptor activator of nuclear factor-kappa B ligand, p < 0.05) to promote the development of peri-implant infections. The synergistic effects between nicotine and S. aureus infection can be a new target to reduce the peri-implant infections.

Clinical, radiographic and restorative parameters for short tuberosity implants placed in smokers: a retrospective study with 5 year follow-up

This study aimed to estimate and compare the clinical, radiographic, and restorative parameters around short tuberosity implants (STIs) placed in cigarette smokers (CS) and never smokers (NS). In this 60-month follow-up retrospective study, a total of 50 (37 males + 13 females) individuals who had received 82 dental implants were included. These participants were categorized into two groups as follows: (i) Group-1: 25 self-reported systemically healthy CS with 43 STIs; and (ii) Group-2: 25 self-reported systemically healthy NS with 39 STIs. In both groups, peri-implant plaque index (PI), probing depth (PD), bleeding on probing (BOP), and crestal bone loss (CBL) and restorative parameters were measured at 12 and 60 months of follow-up. Group comparisons were performed utilizing the Kruskal-Wallis test. The significance level was set at p < 0.05. In CS and NS, the mean age of participants was 58.5 and 60.7 years, respectively. No statistically significant differences were observed in the overall mean levels of PD and CBL around STIs among CS and NS. However, a statistically significant increase was observed in the mean scores of BOP and PI around STIs in the NS and CS at 12 and 60 months follow-up, respectively. In both groups, the loosening of the implant was the most frequently encountered type of STI failure. The outcomes of the present study suggest that STIs placed in maxillary tuberosity can show reliable clinical, radiographic, and restorative stability among cigarettes smokers and non-smokers. However, the role of smoking status and oral hygiene cannot be disregarded in this scenario.

Efficacy of Adjunctive Antimicrobial Photodynamic Therapy to Mechanical Debridement in the Treatment of Peri-implantitis or Peri-implant Mucositis in Smokers: A Systematic Review and Meta-analysis

This systematic review and meta-analysis aimed to determine whether adjunctive use of antimicrobial photodynamic therapy (a-PDT) in peri-implant diseases improves clinical outcomes in smokers. An electronic search was performed in MEDLINE (through PubMed), Scopus, Cochrane Library, Embase, Web of Science and Google Scholar. The primary outcome measures were bleeding on probing (BOP) and pocket depth (PD). Plaque index (PI) was the secondary outcome. Four RCTs, (188 participants) comprised of 118 cigarette smokers, 38 E-cig smokers and 32 water pipe smokers with follow-up periods ranged from 6 weeks to 6 months were recruited. All trials applied diode laser in one session with wavelengths ranged from 660 to 670 nm. There was a significant difference between mechanical debridement (MD)+a-PDT and MD alone groups in PD (WMD = -1.26 mm, 95% CI: -2.19 to -0.32, P = 0.01) and PI (WMD = -10.60%, 95% CI: -14.46 to -6.74, P < 0.001) at 3-month follow-up. However, a great amount of heterogeneity was observed (PD: χ² = 199.19, I² = 98%, P < 0.001 and PI: χ² = 25.63, I² = 84.4%, P < 0.001). Due to methodological heterogeneity and small number of studies, this systematic review was unable to reach conclusive evidence in regards of adjunctive a-PDT efficacy in improving clinical parameters in smokers.

Evidence-based analysis of the effect of smoking on osseointegrated implant outcome

The outcome of the osseointegrated implant is influenced by various conditions, one of which is smoking. Literature shows conflicting results for the association between smoking and implant success. Hence, the study was conducted to assess the effects of smoking on survival and marginal bone loss of osseointegrated implants. Literature search of published articles in Medline, Scopus, Ovid, and Journal of Web till June 2020 were analyzed for the determined outcomes. Revman 5.4 software was used for the analysis of the study. Of the 437 articles screened, nine were chosen for review and analysis. Meta-analytic results showed that implant success rate was better in nonsmokers than smokers (odds ratio = 0.43, 95% confidence interval = 0.26-0.72, P < 0.0001). Smoking habit does seem to affect the implant outcome of survival and marginal bone loss negatively.

Synthesis of multifunctional chlorhexidine-doped thin films for titanium-based implant materials

Our goal was to create bio-functional chlorhexidine (CHX)-doped thin films on commercially pure titanium (cpTi) discs using the glow discharge plasma approach. Different plasma deposition times (50, 35 and 20 min) were used to create bio-functional surfaces based on silicon films with CHX that were compared to the control groups [no CHX and bulk cpTi surface (machined)]. Physico-chemical and biological characterizations included: 1. Morphology, roughness, elemental chemical composition, film thickness, contact angle and surface free energy; 2. CHX-release rate; 3. Antibacterial effect on Streptococcus sanguinis biofilms at 24, 48 and 72 h; 4. Cytotoxicity and metabolic activity using fibroblasts cell culture (NIH-F3T3 cells) at 1, 2, 3 and 4 days; 5. Protein expression by NIH-F3T3 cells at 1, 2, 3 and 4 days; and 6. Co-culture assay of fibroblasts cells and S. sanguinis to assess live and dead cells on the confocal laser scanning microscopy, mitochondrial activity (XTT), membrane leakage (LDH release), and metabolic activity (WST-1 assay) at 1, 2 and 3 days of co-incubation. Data analysis showed that silicon films, with or without CHX coated cpTi discs, increased surface wettability and free energy (p < 0.05) without affecting surface roughness. CHX release was maintained over a 22-day period and resulted in a significant inhibition of biofilm growth (p < 0.05) at 48 and 72 h of biofilm formation for 50 min and 20 min of plasma deposition time groups, respectively. In general, CHX treatment did not significantly affect NIH-F3T3 cell viability (p > 0.05), whereas cell metabolism (MTT assay) was affected by CHX, with the 35 min of plasma deposition time group displaying the lowest values as compared to bulk cpTi (p < 0.05). Moreover, data analysis showed that films, with or without CHX, significantly affected the expression profile of inflammatory cytokines, including IL-4, IL-6, IL-17, IFN-y and TNF-α by NIH-F3T3 cells (p < 0.05). Co-culture demonstrated that CHX-doped film did not affect the metabolic activity, cytotoxicity and viability of fibroblasts cells (p > 0.05). Altogether, the findings of the current study support the conclusion that silicon films added with CHX can be successfully created on titanium discs and have the potential to affect bacterial growth and inflammatory markers without affecting cell viability/proliferation rates.

Synthesis of bioactive glass-based coating by plasma electrolytic oxidation: Untangling a new deposition pathway toward titanium implant surfaces

HYPOTHESIS

Although bioactive glass (BG) particle coatings were previously developed by different methods, poor particle adhesion to surfaces and reduced biological effects because of glass crystallization have limited their biomedical applications. To overcome this problem, we have untangled, for the first time, plasma electrolytic oxidation (PEO) as a new pathway for the synthesis of bioactive glass-based coating (PEO-BG) on titanium (Ti) materials.

EXPERIMENTS

Electrolyte solution with bioactive elements (Na₂SiO₃-5H₂O, C₄H₆O₄Ca, NaNO₃, and C₃H₇Na₂O₆P) was used as a precursor source to obtain a 45S5 bioglass-like composition on a Ti surface by PEO. Subsequently, the PEO-BG coating was investigated with respect to its surface, mechanical, tribological, electrochemical, microbiological, and biological properties, compared with those of machined and sandblasted/acid-etched control surfaces.

FINDINGS

PEO treatment produced a coating with complex surface topography, Ti crystalline phases, superhydrophilic status, chemical composition, and oxide layer similar to that of 45S5-BG (~45.0Si, 24.5 Ca, 24.5Na, 6.0P w/v%). PEO-BG enhanced Ti mechanical and tribological properties with higher corrosion resistance. Furthermore, PEO-BG had a positive influence in polymicrobial biofilms, by reducing pathogenic bacterial associated with biofilm-related infections. PEO-BG also showed higher adsorption of blood plasma proteins without cytotoxic effects on human cells, and thus may be considered a promising biocompatible approach for biomedical implants.

Comparison between Plasma Electrolytic Oxidation Coating and Sandblasted Acid-Etched Surface Treatment: Histometric, Tomographic, and Expression Levels of Osteoclastogenic Factors in Osteoporotic Rats

Plasma electrolytic oxidation (PEO) has been a promising surface coating with better mechanical and antimicrobial parameters comparing to conventional treatment surfaces. This study evaluated the peri-implant bone repair using (PEO) surface coatings compared with sandblasted acid (SLA) treatment. For this purpose, 44 Wistar rats were ovariectomized (OVX-22 animals) or underwent simulated surgery (SS-22 animals) and received implants in the tibia with each of the surface coatings. The peri-implant bone subsequently underwent molecular, microstructural, bone turnover, and histometric analysis. Real-time PCR showed a higher expression of osteoprotegerin (OPG), receptor activator of nuclear kappa-B ligand (RANKL), and osteocalcin (OC) proteins in the SLA/OVX and PEO/SS groups (p < 0.05). Computed microtomography, confocal microscopy, and histometry showed similarity between the PEO and SLA surfaces, with a trend toward the superiority of PEO in OVX animals. Thus, PEO surfaces were shown to be promising for enhancing peri-implant bone repair in ovariectomized rats.

Proteomic profile of the saliva and plasma protein layer adsorbed on Ti-Zr alloy: the effect of sandblasted and acid-etched surface treatment

Titanium-zirconium (Ti-Zr) alloy has been widely used as a biomaterial for implant devices, and it is commonly treated by sandblasting followed by acid etching (SLA) to improve biological responses. Although protein adsorption is the first biological response, the effect of this SLA treatment on the proteomic profile of proteins adsorbed from saliva and blood plasma has not been tested. In this study, the proteomic profile was evaluated by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Streptococcus sanguinis was used to test whether the protein layer affects bacterial adhesion. SLA treatment affected the proteomic profile, showing exclusive proteins adsorbed from saliva (14) and plasma (3). However, both groups exhibited close patterns of intensity for common proteins, molecular functions and biological processes mediated by proteins. Interestingly, Ti-Zr_SLA showed higher bacterial adhesion (∼1.9 fold over) for the surface coated with plasma proteins. Therefore, SLA treatment of Ti-Zr alloy changed the proteomic profile, which may affect bacterial adhesion.

Comparison of peri-implant clinical and radiographic inflammatory parameters among cigarette and waterpipe (narghile) smokers and never-smokers

BACKGROUND

The authors hypothesized that peri-implant clinical and radiographic inflammatory parameters are worse in waterpipe smokers (WS) and cigarette smokers (CS) compared with never-smokers (NS). The aim of the present retrospective study is to compare peri-implant clinical and radiographic inflammatory parameters among WS, CS, and NS.

METHODS

Forty-four CS (group 1), 41 WS (group 2), and 43 NS (group 3) were included. Demographic data were collected using a questionnaire. Peri-implant plaque index (PI), bleeding on probing (BOP), and probing depth (PD) were measured, and crestal bone loss (CBL) was assessed on standardized digital radiographs. Sample size was estimated, and statistical analyses were performed using Kruskal-Wallis and Wilcoxon rank-sum tests. For multiple comparisons, Bonferroni post hoc test was performed. P values < 0.05 were considered statistically significant.

RESULTS

Peri-implant PI and PD were higher in groups 1 (P < 0.05) and 2 (P < 0.05) compared with group 3. Peri-implant BOP was significantly higher in group 3 compared with individuals in groups 1 (P < 0.01) and 2 (P < 0.01). Peri-implant total marginal bone loss was significantly higher in groups 1 (P < 0.05) and 2 (P < 0.05) compared with group 3. There were differences in PI, BOP, PD, and CBL among participants in groups 1 and 2.

CONCLUSIONS

Peri-implant soft tissue inflammatory parameters and CBL are worse in CS and WS compared with NS. There is no difference in these parameters between CS and WS.

Influence of a light-activated glaze on the adhesion of Streptococcus sanguinis to the surface of polymers used in fabrication of interim prostheses

AIM

This study aimed to investigate the adhesion of Streptococcus sanguinis to the surface of interim prostheses that were treated or not treated with a light-activated glaze, and subjected or not subjected to a thermocycling procedure.

METHODS

36 specimens of each resin were divided into 4 groups: heat-activated acrylic resin; chemically-activated acrylic resin; bis-acryl composite resin (Protemp; 3M ESPE); and bis-GMA (Charisma; Heraeus Kulzer). Half of the specimens underwent application of glaze and the other half underwent mechanical polishing. Specimens were randomly distributed into groups (N = 9) with and without thermocycling (2000 cycles). Surface energy, roughness and microbiological analyses were performed.

RESULTS

Groups treated with glaze showed lower roughness when compared with the same groups without glaze treatment, before and after thermocycling, except for the bis-acryl groups after thermocycling. Surface energy values were higher in the groups treated with glaze, except the bis-acryl group before and after thermocycling. After thermocycling, the values of bacterial adhesion decreased numerically, with the exception of the chemically-activated acrylic resin group treated with glaze and the heat-activated acrylic resin group without glaze treatment.

CONCLUSION

The application of glaze and the thermocycling do not influence, in a statistically significant manner, the bacterial adhesion on polymer surfaces.

Nicotine enhances the thickness of biofilm and adherence of Candida albicans ATCC 14053 and Candida parapsilosis ATCC 22019

Candida albicans ATCC 14053 and Candida parapsilosis ATCC 22019 hyphal-wall protein 1 (HWP1) are involved in hyphae formation and pathogenesis. The transcriptional agglutinin-like sequence 3 (ALS3) genes in both species are responsible for the development of biofilm and colonization on tooth surfaces. Therefore, we investigated the expression of HWP1 and ALS3 quantitatively in C. albicans and C. parapsilosis and examined the biofilm structure upon exposure to various nicotine concentrations. In vitro, biofilms of Candida species were developed directly on slides using the Lab-Tek Chamber Slide System and visualized by confocal laser scanning microscopy. Quantitative real-time polymerase chain reaction was used to measure HWP1 and ALS3 expression in C. albicans ATCC 14053 and C. parapsilosis ATCC 22019. The results indicated that nicotine multiplied the number of yeast cells and increased the extracellular polysaccharides of Candida species. We also found that 1-2 mg/mL nicotine could enhance the formation of biofilm. The findings also revealed that the expression of HWP1 and ALS3 in Candida species were increased as the nicotine concentration increased. Therefore, nicotine influences the biofilm development of oral-associated C. albicans ATCC 14053 and C. parapsilosis ATCC 22019.

Effect of Smoking and Locations of Dental Implants on Peri-Implant Parameters: 3-Year Follow-Up

BACKGROUND Smoking may be a risk factor for marginal bone loss (MBL) and oral mucosal inflammation surrounding dental implants. This retrospective study evaluated the effects of smoking on dental implants in patients with fixed implant-supported prostheses over a period of 36 months following loading. MATERIAL AND METHODS We assessed 120 patients (68 women, 52 men, ages 19-74 years (mean age: 55.10 years) with 315 implants. Implants were classified according to location in the upper and lower jaws and anterior (placed between canines) or posterior (placed between pre-molars and molars) as follows: 1=maxilla anterior, 2=maxilla posterior, 3=mandible anterior, 4=mandible posterior. We also measured MBL, plaque index (PI), sulcus bleeding index (SBI), and probing depth (PD). P-values less than 0.05 were considered statistically significant. RESULTS MBL was statistically greater in smokers (P<0.001) as compared to non-smokers in both jaws. MBL did not vary significantly by location in either group (smokers: p=0.415; non-smokers: p=0.175). Mean PI and PD scores were significantly higher in smokers as compared to non-smokers (P<0.001). A positive correlation was found between PI and PD scores in both groups. No statistically significant difference in SBI was observed between the 2 groups (P>0.05). CONCLUSIONS Smoking was associated with increases in marginal bone loss around implants, independent of their location in the jaws. Also, both plaque indices and probing depths were greater in smokers than in non-smokers.

Effect of waterpipe smoking on peri-implant health: A systematic review and meta-analysis

The aim of the present review was to evaluate the effect of waterpipe smoking (WS) on clinical peri-implant inflammatory parameters compared to non-smokers (NS) with dental implants. Literature searches were performed using bibliographic databases up to May 2018. Primary outcomes included peri-implant bone loss (PIBL), while secondary outcomes were probing depth (PD), plaque index, and bleeding on probing. Relative risk (RR) and 95% confidence intervals (CI) for each PIBL and PD were estimated by a random-effect model. Four retrospective case-control studies were included in the qualitative and quantitative syntheses. All of the included studies showed statistically-significantly worse peri-implant outcomes in WS compared to NS. Considering the effects of WS on peri-implant parameters, significant heterogeneity for PIBL (Q-value = 34.21, P < 0.0001, I²  = 94.16%) and PD (Q-value = 51.97, P < 0.0001, I²  = 96.15%) was observed between both groups. The overall RR for PIBL (RR = 3.32, 95% CI = 1.01-3.97, P = 0.001) and PD (RR = 3.40, 95% CI = 1.91-7.17, P = 0.001) were significant between WS and NS groups. WS has detrimental effect on peri-implant health. Clinicians should instruct and advise patients about poor prognosis and peri-implant diseases caused by WS.

[Oral hygiene maintenance of locator attachments implant overdentures in edentulous population: A longitudinal study]

OBJECTIVE

To investigate the oral hygiene status of edentulous patients with locator attachments implant overdentures (IOD) and to analyze the relationship among daily hygiene behavior, oral hygiene status and peri-implant diseases.

METHODS

Edentulous patients who received IOD treatment with locator attachments from January 2012 to May 2016 were recruited. Clinical and radiographic examinations were conducted to assess the peri-implant tissue status. Modified plaque index (mPLI), sulcus bleeding index (SBI), gingival index (GI), and probing depth (PD) were recorded and peri-implant marginal bone loss (MBL) was measured using paralleling projection technique. Patients' peri-implant oral hygiene maintainence habits were investigated. The correlation between peri-implant diseases and oral hygiene status and behaviors was analyzed.

RESULTS

Fifty patients (125 implants) with an average follow-up time of 22 months (6-54 months) were enrolled. The mean values of mPLI, SBI, and GI were 1.4±1.2, 0.8±0.7, and 0.7± 0.6, respectively. Average PD was (2.2±0.7) mm. Mesial and distal maginal bone resorptions were (1.1±1.1) mm and (0.9±0.9) mm, respectively. The prevalance of mucositis and peri-implantitis of the implants were 49.6% and 0. The prevelance of mucositis in the patients with poor oral hygiene (mPLI≥2) was 11.9 times as much as that of those with adequate oral hygiene (mPLI<1). The patients who performed oral hygiene procedure on attachments at least twice a day achieved much lower mPLI scores than those who cleaned less than twice a day.

CONCLUSION

Oral hygiene condition in the group of patients with implant overdentures was poor, and it contributed to increased risk of peri-implant mucositis. The prevelance of musositis of the paitients with poor oral hygiene was 11.9 times as much as that of those with proper oral hygiene. Patients wearing IOD should pay more attention to the hygiene of the attachments.

Proteome analysis of the salivary pellicle formed on titanium alloys containing niobium and zirconium

The chemical composition of biomaterials can drive their biological responses; therefore, this in vitro study aimed to evaluate the proteomic profile of the salivary pellicle formed on titanium (Ti) alloys containing niobium (Nb) and zirconium (Zr). The experimental groups consisted of Ti35NbxZr (x = 5 and 10 wt%) alloys, and commercially pure titanium (cpTi); titanium aluminium vanadium (Ti6Al4V) alloys were used as controls. The physical and chemical characteristics of the Ti materials were analysed. The proteomic profile was evaluated by liquid chromatography coupled with tandem mass spectrometry. Bacterial adhesion (2 h) of mixed species (Streptococcus sanguinis and Actinomyces naeslundii) was investigated as colony-forming units (n = 6). This paper reports the finding that salivary pellicle composition can be modulated by the composition of the Ti material. The Ti35NbxZr group showed a significant ability to adsorb proteins from saliva, which can favour interactions with cells and compatibility with the body.

Peri-implant clinical and radiographic status and whole salivary cotinine levels among cigarette and waterpipe smokers and never-smokers

The aim was to compare the peri-implant clinical and radiographic inflammatory parameters and whole salivary cotinine levels among cigarette smokers (CS), waterpipe smokers (WS) and never-smokers (NS). Thirty-four CS (Group 1), 33 WS (Group 2), and 31 NS (Group 3) were included. Peri-implant plaque index (PI), bleeding-on-probing (BOP), and probing depth (PD) were measured, and crestal bone loss (CBL) was assessed on standardized digital radiographs. Unstimulated whole saliva samples were collected and whole salivary cotinine levels were measured. Peri-implant PI and PD were higher in Groups 1 (P < 0.05) and 2 (P < 0.05) than in Group 3. Peri-implant BOP was significantly higher in Group 3 than in Groups 1 (P < 0.01) and 2 (P < 0.01). Peri-implant MBL was significantly higher in Groups 1 (P < 0.05) and 2 (P < 0.05) than in Group 3. There were significant differences in PI, BOP, PD, and CBL between Groups 1 and 2. There was no significant difference in the whole salivary cotinine levels in Groups 1 and 2. Peri-implant sites with plaque accumulation, PD, CBL, and whole salivary cotinine levels were higher in CS and WS than in NS, but did not differ between CS and WS.

Peri-implant soft-tissue parameters and crestal bone levels among narghile smokers and nonsmokers

This retrospective convenient sample case-control study investigated the peri-implant soft-tissue inflammatory parameters and crestal bone loss (CBL) among narghile smokers (NS) (Group I) and nonsmoking controls (Group II). Demographic data were collected using a questionnaire. Peri-implant plaque index (PI), bleeding-on-probing (BOP) and pocket-depth (PD) were assessed; and peri-implant CBL was measured on standardized digital bite-wing radiographs. Sample-size was estimated and statistical analysis were done using Mann-Whitney U-test. Level of significance was set at p < .05. Seventy-two male individuals (35 in Group I and 37 in Group II) were included. The mean age of individuals in Groups I and II were 45.3 ± 5.2 and 42.6 ± 3.3 years, correspondingly. In Group 1, the duration and daily frequency of narghile smoking was 17.5 ± 1.6 years and 6.3 ± 0.5 times per day, respectively. The mean duration of each narghile smoking session was 28.5 ± 0.6 min. The mean peri-implant PI (p < .05), PD (p < .05) and mesial (p < .05) and distal (p < .05) CBL were statistically significantly higher among individuals in Group I compared with Group II. BOP was significantly higher in Group II than Group I (p < .05). Narghile smoking increases peri-implant soft-tissue inflammation and CBL.

Nicotine is a risk factor for dental caries: An in vivo study

Background/purpose

Streptococcus mutans is an important pathogen in the development of dental caries. Many studies have focused on the relationship between nicotine and S. mutans in vitro. The aim of this study was to investigate the effect of nicotine on the growth of S. mutans and its cariogenic potential in vivo.

Materials and methods

Sixteen male Specific-pathogen-free Wistar rats were divided into 2 groups (nicotine-treated and nicotine-untreated group) and infected with S. mutans. The S. mutans suspension was treated with 1 mg/mL nicotine in the nicotine-treated group. The Keyes method was used to evaluate sulcal caries of rats, and dental plaque on molar teeth was observed by scanning electron microscopy (SEM).

Results

Incidence of sulcal caries was higher in nicotine-treated group compared to nicotine-untreated group (42.7 ± 1.7 vs 37.3 ± 4.9, P = 0.009). Severity of caries increased with nicotine treatment. The slightly dentinal caries scores and moderate dentinal caries scores were higher in the presence of nicotine (P < 0.001). Increased number of S. mutans cells attached to dental surface was observed under SEM in the nicotine-treated group.

Conclusion

Nicotine would promote the attachment of S. mutans to dental surface, and further increase the incidence and severity of dental caries. Therefore, nicotine might be a risk factor for smoking-induced caries.

Initial investigation of the corrosion stability of craniofacial implants

STATEMENT OF PROBLEM

Although craniofacial implants have been used for retention of facial prostheses, failures are common. Titanium undergoes corrosion in the oral cavity, but the corrosion of craniofacial implants requires evaluation.

PURPOSE

The purpose of this in vitro study was to investigate the corrosion stability of commercially pure titanium (CP Ti) exposed to simulated human perspiration at 2 different pH levels (5.5 and 8).

MATERIAL AND METHODS

Fifteen titanium disks were divided into 3 groups (n=5 per group). The control group was subjected to simulated body fluid (SBF) (control). Disks from the 2 experimental groups were immersed in simulated alkaline perspiration (SA_KP) and simulated acidic perspiration (SA_CP). Electrochemical tests, including open circuit potential (3600 seconds), electrochemical impedance spectroscopy, and potentiodynamic tests were performed according to the standardized method of 3-cell electrodes. Data were analyzed by 1-way ANOVA and the Tukey honestly significant difference tests (α=.05).

RESULTS

Simulated human perspiration reduced the corrosion stability of CP Ti (P<.05). The SBF group presented the lowest capacitance values (P<.05). SA_KP and SA_CP groups showed increased values of capacitance and showed no statistically significant differences (P>.05) from each other. The increase in capacitance suggests that the acceleration of the ionic exchanges between the CP Ti and the electrolyte leads to a lower corrosion resistance. SA_KP reduced the oxide layer resistance of CP Ti (P<.05), and an increased corrosion rate was noted in both simulated human perspiration groups.

CONCLUSIONS

Craniofacial implants can corrode when in contact with simulated human perspiration, whereas alkaline perspiration shows a more deleterious effect. Perspiration induces a more corrosive effect than simulated body fluid.

Nicotine Enhances Interspecies Relationship between Streptococcus mutans and Candida albicans

Streptococcus mutans and Candida albicans are common microorganisms in the human oral cavity. The synergistic relationship between these two species has been deeply explored in many studies. In the present study, the effect of alkaloid nicotine on the interspecies between S. mutans and C. albicans is explored. We developed a dual-species biofilm model and studied biofilm biomass, biofilm structure, synthesis of extracellular polysaccharides (EPS), and expression of glucosyltransferases (Gtfs). Biofilm formation and bacterial and fungal cell numbers in dual-species biofilms increased in the presence of nicotine. More C. albicans cells were present in the dual-species biofilms in the nicotine-treated groups as determined by scanning electron microscopy. The synthesis of EPS was increased by 1 mg/ml of nicotine as detected by confocal laser scanning microscopy. The result of qRT-PCR showed gtfs expression was upregulated when 1 mg/ml of nicotine was used. We speculate that nicotine promoted the growth of S. mutans, and more S. mutans cells attracted more C. albicans cells due to the interaction between two species. Since S. mutans and C. albicans are putative pathogens for dental caries, the enhancement of the synergistic relationship by nicotine may contribute to caries development in smokers.

Efficacy of periimplant mechanical debridement with and without adjunct antimicrobial photodynamic therapy in the treatment of periimplant diseases among cigarette smokers and non-smokers

OBJECTIVE

The aim was to assess the efficacy of mechanical debridement (MD) with and without adjunct antimicrobial photodynamic therapy (aPDT) in reducing periimplant inflammation among cigarette-smokers and non-smokers.

METHODS

Cigarette-smokers and non-smokers were randomly divided into 2 groups. In the test-group, participants underwent full mouth scaling and periimplant MD with adjunct aPDT; and in the control-group, the participants underwent full mouth scaling and periimplant MD alone. Periimplant bleeding on probing (BOP), probing depth (PD) and crestal bone loss (CBL) were measured at baseline and at 6- and 12-months follow-up. Statistical analysis was performed using the Kruskal-Wallis test. P-values<0.05 were considered statistically significant.

RESULTS

Eighty-four smokers (41 patients in the test group and 43 in the control group) and 82 non-smokers (40 patients in the test group and 42 in the control group) were included. Among smokers and non-smokers, periimplant PD was significantly higher in the control-group compared with the test-group (P<0.05) at 6-months of follow-up. There was no statistically significant difference in BOP, PD and CBL among smokers and non-smokers in the test- and control-groups at 12-months of follow-up. BOP was comparable among smokers at all time intervals.

CONCLUSION

In the short-term, MD with adjunct aPDT is more effective in reducing periimplant probing depth than MD alone in smokers and non-smokers. However, in the long-term outcomes of MD either with or without aPDT among smokers and non-smokers are comparable.

Nicotine inhibits activation of microglial proton currents via interactions with α7 acetylcholine receptors

Alpha 7 subunits of nicotinic acetylcholine receptors (nAChRs) are expressed in microglia and are involved in the suppression of neuroinflammation. Over the past decade, many reports show beneficial effects of nicotine, though little is known about the mechanism. Here we show that nicotine inhibits lipopolysaccharide (LPS)-induced proton (H⁺) currents and morphological change by using primary cultured microglia. The H⁺ channel currents were measured by whole-cell patch clamp method under voltage-clamp condition. Increased H⁺ current in activated microglia was attenuated by blocking NADPH oxidase. The inhibitory effect of nicotine was due to the activation of α7 nAChR, not a direct action on the H⁺ channels, because the effects of nicotine was cancelled by α7 nAChR antagonists. Neurotoxic effect of LPS-activated microglia due to inflammatory cytokines was also attenuated by pre-treatment of microglia with nicotine. These results suggest that α7 nAChRs in microglia may be a therapeutic target in neuroinflammatory diseases.

Influence of stress corrosion on the mechanical properties of laser-welded titanium

STATEMENT OF PROBLEM

Whether laser-welded (LW) titanium can resist the stress corrosion produced by the combination of fluoride ions and stress in the oral environment is unknown.

PURPOSE

The purpose of this in vitro study was to investigate the influence of stress corrosion on the mechanical properties of LW titanium.

MATERIAL AND METHODS

Twenty-seven titanium bars (25×2 mm) with a circular cross-section were cut in half and laser-welded, while another 27 nonwelded (NW) bars were used as the control. Thirty bars were submitted to a flexural load of 480 N at 1 Hz and immersed in artificial saliva at pH 6 (S1) or in 1000 ppm fluoride-containing saliva at pH 6.0 (S2) or 2.0 (S3) at room temperature for up to 4000 cycles. After the stress corrosion simulation, the tensile strength and Vickers microhardness were determined (n=5). Twelve LW and NW bars were submitted to the corrosion immersion test media for 51 days (n=2) to determine polarization curves (n=2) in an artificial saliva media. The corroded surface was examined with scanning electron microscopy (SEM).

RESULTS

The combination of fluoride and low pH significantly decreased the tensile strength of LW (P<.05). Stress corrosion did not affect the hardness of LW or NW (P>.05). NW bars immersed in S3 exhibited progressive surface dissolution, while LW bars spontaneously fractured at the welded area after 25 days of immersion in the same medium. SEM images demonstrated pitting corrosion without the presence of cracks in both groups immersed in S3.

CONCLUSIONS

Stress corrosion caused by acidic fluoride-containing saliva and flexural load cycling decreased the tensile strength and hardness of LW titanium bars.