A Comparative Study on the Effect of Nicotine Administration and Cigarette Smoke Inhalation on Bone Healing Around Titanium Implants

Bone Resorption in Apical Periodontitis Enhanced by Cigarette Smoke Inhalation: Histometric, Immunohistochemical, and Microtomographic Analysis in Rats

INTRODUCTION

This study evaluated the effects of cigarette smoke inhalation (CSI) on apical periodontitis (AP) induced in rats by histometric, immunohistochemical, and microtomographic analysis.

METHODS

A total of 32 male Wistar rats were divided into 4 experimental groups (n = 8): control, CSI, AP, and CSI + AP. Rats in the CSI and CSI + AP groups inhaled cigarette smoke by remaining inside a smoking chamber for 8 minutes 3 times a day for 50 days. After 20 days of smoke inhalation, rats in the AP and CSI + AP groups had the pulp of their first right lower molar exposed to induce AP. Blood was collected on day 50 to evaluate nicotine and serum cotinine levels. The animals' mandibles were removed for histologic processing to evaluate bone resorption by histometric, immunohistochemical (receptor activator of nuclear factor kappa B ligand/osteoprotegerin), and microtomographic analysis. The Student t test was applied.

RESULTS

Histometric analysis showed a larger area of bone resorption (P < .05) and microtomographic analysis found greater resorption volume (P < .001) for the CSI + AP group compared with the AP group. The CSI + AP group presented a high RANKL immunostaining pattern compared with the AP group (P < .001).

CONCLUSIONS

CSI increased bone resorption caused by AP.

Effects of cigarette smoke inhalation on the immune-inflammatory profile of experimental apical periodontitis in rats

OBJECTIVE

To evaluate the effects of cigarette smoke inhalation on the immune-inflammatory profile of experimental apical periodontitis in rats.

METHODOLOGY

In total, 32 male Wistar rats were divided into four groups (n = 8): AP-induced apical periodontitis; S-cigarette smoke inhalation; APS-induced AP and cigarette smoke inhalation; and C (control)-neither AP nor cigarette smoke inhalation. To induce cigarette smoke inhalation, the animals were kept in a chamber filled with tobacco smoke for 8 min thrice a day for 50 days. AP was induced 20 days after inhalation initiation by exposing their coronary pulp to their oral environment for 30 days. After animals were euthanized, their right hemimaxillae were removed for histopathological, semi-quantitative and immunohistochemical (F4/80, CD206 and iNOS) analyses.

RESULTS

Quantitative data showed a moderate number of inflammatory infiltrates in AP and an intense number in APS (p < .05). Comparing F4/80+ cells showed no statistically significant differences among groups, but we found more CD206+ cells in AP than in C and S (p > .05). INOS+ immunostaining showed a significant increase in AP and APS, when compared with C and S (p < .05). APS had more iNOS+ cells than AP (p < .05).

CONCLUSION

Cigarette smoke inhalation worsened AP, leading to a predominantly pro- inflammatory profile in our experimental model.

Inflammatory profile of apical periodontitis exacerbated by cigarette smoke inhalation: Histological and immunohistochemical analysis in rats

AIM

The aim of this study was to evaluate the effects of cigarette smoke inhalation (CSI) on inflammation, pro-inflammatory mediators and haematological parameters in rats with induced apical periodontitis (AP).

METHODOLOGY

Thirty-two 3-month-old male Wistar rats were divided into four experimental groups (n = 8): C-Control; S-rats with CSI; AP-rats with AP; and SAP-rats with CSI + AP. Animals in groups S and SAP inhaled cigarette smoke by remaining inside a smoking chamber for 8 min, three times daily, for 50 days. After 20 days of smoke inhalation, animals in AP and SAP groups had the pulps of the lower right first molar exposed to oral environment for 30 days to induce AP. In these subsequent 30 days, animals in group S and SAP continued with CSI. On Day 50, animals were euthanized and mandibles were histologically processed to assess inflammatory infiltrate, immunohistochemical interleukins (IL-1β, IL-6 and TNF-α), and blood samples collected for laboratory analysis. The Mann-Whitney test was performed for non-parametric data and the pairwise analyses of Student's t-test for parametric data, with a significance level of p < .050.

RESULTS

Inflammatory infiltrate was moderate in AP group and more severe in the SAP (p = .010). The interleukins IL-6, IL-1β and TNF-α were higher in SAP group (p < .001) when compared to the AP group. A greater number of red blood cells (p = .010), haemoglobin (p = .007) and neutrophils (p = .014) were observed in the SAP group in comparison with the AP group.

CONCLUSION

Cigarette smoke inhalation induced a more severe inflammatory infiltrate, with increased levels of pro-inflammatory cytokines and changes in haematological parameters in rats with induced AP. Thus, CSI aggravated AP, exacerbating the inflammatory response.

The effect of cigarette smoke versus vaporized nicotine on healing of a rat femur

INTRODUCTION

Little data exists regarding the effects of vaporized nicotine on healing. Our goal was to compare vaporized nicotine, combusted nicotine and control with respect to bone healing in a rat femur fracture model.

MATERIALS AND METHODS

Forty-five male Sprague Dawley rats were divided into three equal cohorts. Rats were exposed to two cigarettes daily, an equivalent dose of vaporized nicotine, or control, six days a week. Exposures occurred for 4 weeks prior to iatrogenic femur fracture and intramedullary repair. Four additional weeks of exposure occurred prior to sacrifice. Radiographic, biomechanical and histologic analysis was conducted.

RESULTS

No significant difference between the three groups was identified for total mineralized bone volume (p = 0.14), total volume of mature bone (p = 0.12) or immature bone (p = 0.15). Importantly, less total mineralized bone volume and immature bone volume was seen in the vaporized nicotine group compared to combusted tobacco, but results were not significant. Biomechanical testing revealed no significant difference in group torsional stiffness (p = 0.92) or maximum torque (p = 0.31) between the three groups. On histologic analysis, chi-square testing showed no significant difference in any category.

CONCLUSIONS

This exploratory study compared combusted nicotine, vaporized nicotine and a control on rat femur fractures. While no statistically significant differences were identified, there were trends showing less total mineralized bone volume and immature bone volume in the vaporized nicotine group compared to the other groups. Additional study is warranted based on our findings.

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.

Effect of nicotine on orthodontic tooth movement and bone remodeling in rats

Objective

To quantitatively analyze the effect of nicotine on orthodontic tooth movement (OTM) and bone remodeling in rats using micro-computed tomography and tartrate-resistant acid phosphatase immunostaining.

Methods

Thirty-nine adult male Sprague–Dawley rats were randomized into three groups group A, 0.5 mL normal saline (n = 9, 3 per 3, 7, and 14 days); group B, 0.83 mg/kg nicotine (n = 15, 5 per 3, 7, and 14 days); and group C, 1.67 mg/kg nicotine (n = 15, 5 per 3, 7, and 14 days). Each animal received daily intraperitoneal injections of nicotine/saline from the day of insertion of identical 30-g orthodontic force delivery systems. A 5-mm nickel-titanium closed-coil spring was applied between the left maxillary first molar (M1) and the two splinted incisors. The rate of OTM and volumetric bone changes were measured using micro-computed tomography. Osteoclasts were counted on the mesial alveolar bone surface of the distobuccal root of M1. Six dependent outcome variables, including the intermolar distance, bone volume fraction, bone mineral density, trabecular thickness, trabecular volume, and osteoclast number, were summarized using simple descriptive statistics. Nonparametric Kruskal–Wallis tests were used to evaluate differences among groups at 3, 7, and 14 days of OTM.

Results

All six dependent outcome variables showed no statistically significant among group-differences at 3, 7, and 14 days.

Conclusions

The findings of this study suggest that nicotine does not affect OTM and bone remodeling, although fluctuations during the different stages of OTM in the nicotine groups should be elucidated in further prospective studies.

Influence of Smoking on Dental Implant Osseointegration: A Radiofrequency Analysis of 194 Implants

Although many studies have related smoking to peri-implantitis and marginal bone loss, little is known of its potential impact on dental implant osseointegration. The present clinical study explores the influence of smoking on secondary stabilization based in radiofrequency analysis. A total of 194 implants in 114 patients were included. Implant stability was evaluated on the day of surgery and at a minimum of 90 days after implantation, when osseointegration is considered to have been completed. The evolution of implant stability was compared between 2 groups: smokers and nonsmokers. The following variables were also analyzed: implant brand and model, length, diameter, insertion torque, bone density according to the Misch classification, location of the implant, and patient age and gender. The results showed that smoking did not affect the primary stability of the implant, although it was associated with a marked decrease in secondary stability. The nonsmokers showed a gain of 2.69 points (95% confidence interval [CI]: 1.529-3.865; P < .001) in the osseointegration process. However, in the smokers group, implant stability was seen to decrease 0.91 points (95% CI: -3.424 to 1.600; P < .004), generating a difference of 3.61 points between smokers and nonsmokers. Smoking is thus concluded to be an important factor that must be taken into account when seeking good implant osseointegration outcomes.

Does the systemic administration of L-arginine affect dental implant stability in nicotine consumer dogs?

Background

Nicotine can have detrimental effects on dental implant osseointegration. This study aimed to evaluate the influence of systemic l-arginine supplement on the osseointegration of dental implants in nicotine consumer dogs.

Methods

Twelve 1-year Labrador Retriever dogs had their right and left third and fourth mandibular premolars removed, and the sockets were left to heal for 6 months. Dogs were randomly divided into three groups (n = 16): group 1—0.2 mg/kg nicotine was injected twice daily; group 2—0.2 mg/kg nicotine was injected twice daily in addition to 200 mg/kg l-arginine capsules taken orally; and group 3—placebo. Forty-eight dental implants were inserted into the healed sockets of the dog’s mandible and were assessed by implant stability quotient (ISQ) using resonance frequency analysis (RFA) during 4 weeks and insertion and removal torque value analysis.

Results

No implant failure occurred during the study period. The change in torque value between insertion and removal was similar in the placebo and nicotine+arginine consumer dogs (p = 0.276), which shows a positive effect of arginine supplementation in nicotine consumers. There was a significant difference in torque value change between nicotine+arginine vs. nicotine consumers (p = 0.049) and placebo vs. nicotine (p = 0.003). After 4 weeks, the placebo had the most significant improvement in torque value (47.0 ± 16.9), followed by nicotine+arginine (25.1 ± 37.8), and the worst torque value was for the nicotine group (− 5.7 ± 24.0) pound per inch. The results show that except in the first week, there are significant differences in ISQ between the groups in different periods. ISQ in all of the groups has reduced at first but then increased over time. At the time of implant placement, insertion torque was significantly higher in the nicotine consumer group than the nicotine+arginine consumer group and placebo group (p = 0.020).

Conclusion

Arginine supplementation promotes bone healing and implant primary stability by improving dental implant osseointegration biomechanical characteristics.

Osseointegration Pharmacology: A Systematic Mapping Using Artificial Intelligence

Clinical performance of osseointegrated implants could be compromised by the medications taken by patients. The effect of a specific medication on osseointegration can be easily investigated using traditional systematic reviews. However, assessment of all known medications requires the use of evidence mapping methods. These methods allow assessment of complex questions, but they are very resource intensive when done manually. The objective of this study was to develop a machine learning algorithm to automatically map the literature assessing the effect of medications on osseointegration. Datasets of articles classified manually were used to train a machine-learning algorithm based on Support Vector Machines. The algorithm was then validated and used to screen 599,604 articles identified with an extremely sensitive search strategy. The algorithm included 281 relevant articles that described the effect of 31 different drugs on osseointegration. This approach achieved an accuracy of 95%, and compared to manual screening, it reduced the workload by 93%. The systematic mapping revealed that the treatment outcomes of osseointegrated medical devices could be influenced by drugs affecting homeostasis, inflammation, cell proliferation and bone remodeling. The effect of all known medications on the performance of osseointegrated medical devices can be assessed using evidence mappings executed with highly accurate machine learning algorithms.

Time Course of Immune Response and Immunomodulation During Normal and Delayed Healing of Musculoskeletal Wounds

Single trauma injuries or isolated fractures are often manageable and generally heal without complications. In contrast, high-energy trauma results in multi/poly-trauma injury patterns presenting imbalanced pro- and anti- inflammatory responses often leading to immune dysfunction. These injuries often exhibit delayed healing, leading to fibrosis of injury sites and delayed healing of fractures depending on the intensity of the compounding traumas. Immune dysfunction is accompanied by a temporal shift in the innate and adaptive immune cells distribution, triggered by the overwhelming release of an arsenal of inflammatory mediators such as complements, cytokines and damage associated molecular patterns (DAMPs) from necrotic cells. Recent studies have implicated this dysregulated inflammation in the poor prognosis of polytraumatic injuries, however, interventions focusing on immunomodulating inflammatory cellular composition and activation, if administered incorrectly, can result in immune suppression and unintended outcomes. Immunomodulation therapy is promising but should be conducted with consideration for the spatial and temporal distribution of the immune cells during impaired healing. This review describes the current state of knowledge in the spatiotemporal distribution patterns of immune cells at various stages during musculoskeletal wound healing, with a focus on recent advances in the field of Osteoimmunology, a study of the interface between the immune and skeletal systems, in long bone fractures. The goals of this review are to (1) discuss wound and fracture healing processes of normal and delayed healing in skeletal muscles and long bones; (2) provide a balanced perspective on temporal distributions of immune cells and skeletal cells during healing; and (3) highlight recent therapeutic interventions used to improve fracture healing. This review is intended to promote an understanding of the importance of inflammation during normal and delayed wound and fracture healing. Knowledge gained will be instrumental in developing novel immunomodulatory approaches for impaired healing.

Evaluation of marginal bone loss around dental implants in cigarette smokers and nonsmokers. A comparative study

Background:

The overall success of osteointegrated dental implants depends on various factors. The deleterious effects of smoking on wound healing after the tooth extraction and its association with poor quality of bone are well documented. Similar effects of tobacco use on the success of dental implants are expected. Cigarette smoke mainly contains nicotine that delays the bone healing and increases the rate of infections at the implant insertion site.

Aim:

The purpose of the present study was to evaluate and compare the marginal bone loss around dental implants in smokers and nonsmokers.

Materials and Methods:

The study was conducted on 500 individuals who received dental implants in maxillary or mandibular edentulous regions from 2010 to 2017. The sample was divided into two groups: Group I (smokers, n = 280) and Group II (nonsmokers, n = 220). Marginal bone loss was measured on mesial, distal, buccal, and lingual side of each implant using periapical radiographs 3 months after loading, 6 months after loading, and 12 months after loading.

Results:

The crestal bone loss around dental implants was significantly greater in smokers (Group I) as compared to nonsmokers (Group II) irrespective of the duration of loading (P < 0.001). Marginal bone loss did vary significantly by location in either groups.

Conclusion:

Smoking overall lowers the success rate of dental implants. Increased duration and frequency of smoking leads to a greater degree of marginal bone loss around dental implants.

In Vitro Models, Standards, and Experimental Methods for Tobacco Products

Traditional tobacco products have well-known systemic and local oral effects, including inflammation, vasoconstriction, delayed wound healing, and increased severity of periodontal disease. Specifically in the oral cavity and the lung, cigarette smoking produces cancer, increased infectivity, acute and chronic inflammation, changes in gene expression in epithelial lining cells, and microbiome changes. In recent years, cigarette smoking has greatly decreased in the United States, but the use of new tobacco products has gained tremendous popularity. Without significant knowledge of the oral sequelae of products such as electronic cigarettes, researchers must evaluate current in vitro and in vivo methods to study these agents, as well as develop new tools to adequately study their effects. Some in vitro testing has been performed for electronic cigarettes, including toxicologic models and assays, but these mostly study the effect on the respiratory tract. Recently, direct exposure of the aerosol to in vitro 3-dimensional tissue constructs has been performed, demonstrating changes in cell viability and inflammatory cytokines. For in vivo studies, a universal e-cigarette testing machine or standard vaping regime is needed. A standard research electronic cigarette has recently been developed by the National Institute of Drug Abuse, and other devices delivering aerosols with different nicotine concentrations are becoming available. One of the biggest challenges in this research is keeping up with the new products and the rapidly changing technologies in the industry.

Tobacco-product usage as a risk factor for dental implants

The oral cavities of tobacco smokers and users of smokeless tobacco products are exposed to high concentrations of nicotine. A limited number of animal studies have assessed the effect of nicotine on osseointegration. Results from experimental studies have reported a statistically significant decrease, at 4 weeks of follow-up, in bone-to-implant contact among rats exposed to nicotine compared with unexposed rats. Nicotine increases the production of inflammatory cytokines (such as interleukin-6 and tumor necrosis factor-alpha) by osteoblasts. Waterpipe, pipe, and cigarette smokers are at increased risk of developing oral cancer, periodontal disease, and alveolar bone loss. One explanation for this is that smokers (regardless of the type of tobacco product) are exposed to similar chemicals, such as nicotine, tar, oxidants, polyaromatic hydrocarbons, and carbon monoxide. Moreover, raised levels of proinflammatory cytokines have been identified in the gingival crevicular fluid of cigarette smokers with peri-implant diseases. Therefore, it is hypothesized that nicotine and chemicals in tobacco smoke induce a state of oxidative stress in peri-implant tissues (gingiva and alveolar bone), thereby increasing the likelihood of peri-implant disease development via an inflammatory response, which if left uncontrolled, will result in implant failure/loss. In this regard, tobacco smoking (including cigarettes, waterpipe, and pipe) is a significant risk factor for peri-implant diseases. The impact of vaping electronic cigarettes using nicotine-containing e-juices remains unknown. Habitual use of smokeless tobacco products is associated with oral inflammatory conditions, such as oral precancer, cancer, and periodontal disease. However, the effect of habitual use of smokeless tobacco products on the success and survival of dental implants remains undocumented.

The influence of LLLT applied on applied on calvarial defect in rats under effect of cigarette smoke

Objective

Considering the global public health problem of smoking, which can negatively influence bone tissue repair, the aim of this study is to analyze the influence of photobiomodulation therapy (PBM) on calvaria defects created surgically in specimens under the effect of cigarette smoke and analyzed with use of histomorphometric and immunohistochemistry techniques.

Methodology

Calvaria defects 4.1 mm in diameter were surgically created in the calvaria of 90-day-old rats (n=60) that were randomly divided into 4 experimental groups containing 15 animals each: control group (C), smoking group (S), laser group (L), and smoke associated with laser group (S+L). The animals were subjected to surgery for calvaria defects and underwent PBM, being evaluated at 21, 45, and 60 days post-surgery. The specimens were then processed for histomorphometric and immunohistochemistry analyses. The area of bone neoformation (ABN), percentage of bone neoformation (PBNF), and the remaining distance between the edges of the defects (D) were analyzed histometrically. Quantitative analysis of the TRAP immunolabeled cells was also performed. The data were subjected to analysis of variance (ANOVA) in conjunction with Tukey’s test to verify the statistical differences between groups (p<0.05).

Results

The smoking group showed less ABN compared to the other experimental groups in all periods, and it also showed more D at 21 days compared to the remaining groups and at 45 days compared to the laser group. The smoking group showed a lower PNBF compared to the laser group in all experimental periods and compared to smoking combined with LLLT group at 21 days.

Conclusions

PBM acted on bone biomodulation, thus stimulating new bone formation and compensating for the negative factor of smoking, which can be used as a supportive therapy during bone repair processes.

Minimally invasive lateral transiliac sacroiliac joint fusion using 3D-printed triangular titanium implants

Background: Minimally invasive sacroiliac joint (SIJ) fusion (SIJF) has become an increasingly accepted surgical option for chronic SI joint dysfunction, a prevalent cause of chronic low back/buttock pain.

Objective: To report clinical and functional outcomes of SIJF using 3D-printed triangular titanium implants (TTI) for patients with chronic SI joint dysfunction.

Methods: A total of 28 subjects with SIJ dysfunction at 8 centers underwent SIJF with 3D TTI and had scheduled follow-up to 6 months (NCT03122899).

Results: Mean preoperative SIJ pain score was 79.1 and mean preoperative Oswestry Disability Index (ODI) was 49.9. At 6 months, pain scores decreased by 51 points and ODI decreased by 23.6 points (both p<0.0001). The proportion of subjects able to perform various back/pelvis-related physical functions with minimal difficulty improved significantly for nearly all activities. Opioid use decreased and physical function, as assessed with three objective tests, improved.

Conclusion: Early results from this prospective multicenter trial confirm that clinical responses to a 3D triangular titanium implant for SIJF are similar to those from prior trials, with improved physical function and decreased opioid use.

Level of evidence: Level II.

Cigarette Smoke Extract Exposure: Effects on the Interactions between Titanium Surface and Osteoblasts

The aim of this study was to explore the changes in the characteristics of titanium surface and the osteoblast-titanium interactions under cigarette smoke extract (CSE) exposure. In this study, CSE was used to simulate the oral liquid environment around the implant under cigarette smoke exposure. Titanium samples were immersed in CSE to explore the changes in the characteristics of titanium surface. The physical properties of titanium surface were measured, including surface micromorphology, surface elemental composition, roughness, and surface hydrophilicity. MC3T3-E1 cells were cultured on the titanium surface in vitro under different concentrations of CSE exposure, and cell adhesion, cell proliferation, and osteogenic differentiation were observed. The surface micromorphology and elemental composition of titanium surface changed under CSE exposure. No obvious changes were found in the surface roughness and the hydrophilicity of titanium samples. Moreover, the results of in vitro study showed that CSE exposure downregulated the cell spreading, proliferation, and osteogenic differentiation of MC3T3-E1 cells on the titanium surface. It could be speculated that some carbon-containing compounds from CSE adsorbed on the titanium surface and the osteoblast-titanium interactions were influenced under CSE exposure. It is hoped that these results could provide valuable information for further studies on smoking-mediated inhibition of implants osseointegration.

Influence of Cigarette Smoke Inhalation on an Autogenous Onlay Bone Graft Area in Rats with Estrogen Deficiency: A Histomorphometric and Immunohistochemistry Study

PURPOSE

The present study aimed to evaluate the influence of cigarette smoke inhalation on an autogenous onlay bone graft area, either covered with a collagen membrane or not, in healthy and estrogen-deficient rats through histomorphometry and immunohistochemistry.

MATERIALS AND METHODS

Sixty female rats (Wistar), weighing 250-300 g, were randomly divided and allocated into groups (either exposed to cigarette smoke inhalation or not, ovariectomized and SHAM). After 15 days, the test group underwent cigarette smoke inhalation. Sixty days after exposition, autogenous bone grafting was only performed on all right hemimandibles, and the left ones underwent autogenous onlay bone grafting with the collagen membrane (BioGide^®). The graft was harvested from the parietal bone and attached to the animals' jaws (right and left). They were euthanized at 21, 45, and 60 days after grafting. Histological measurements and immunohistochemical analyses were performed, and results were submitted to a statistical analysis.

RESULTS

The addition of a collagen membrane to the bone graft proved more efficient in preserving graft area if compared to the graft area without a collagen membrane and the one associated with cigarette smoke inhalation at 21 (p = 0.0381) and 60 days (p = 0.0192), respectively. Cigarette smoke inhalation combined with ovariectomy promoted a significant reduction of the autogenous graft area at 21 and 60 days. At 45 days, no statistically significant results were observed. In the immunohistochemical analysis, the ovariectomized and smoking subgroups, combined or not with collagen membrane, received moderate and intense immunolabeling at 21 days for Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL) (p = 0.0017 and p = 0.0381, respectively). For Osteoprotegerin (OPG), intense immunolabeling was observed in most subgroups under analysis at 60 days.

CONCLUSION

Smoking inhalation promoted resorption on the autogenous onlay bone graft, mainly when associated with ovariectomy. Furthermore, when associated with the collagen membrane, a lower resorption rate was observed if compared to the absence of the membrane.

Video-based kinetic analysis of calcification in live osteogenic human embryonic stem cell cultures reveals the developmentally toxic effect of Snus tobacco extract

Epidemiological studies suggest tobacco consumption as a probable environmental factor for a variety of congenital anomalies, including low bone mass and increased fracture risk. Despite intensive public health initiatives to publicize the detrimental effects of tobacco use during pregnancy, approximately 10-20% of women in the United States still consume tobacco during pregnancy, some opting for so-called harm-reduction tobacco. These include Snus, a type of orally-consumed yet spit-free chewing tobacco, which is purported to expose users to fewer harmful chemicals. Concerns remain from a developmental health perspective since Snus has not reduced overall health risk to consumers and virtually nothing is known about whether skeletal problems from intrauterine exposure arise in the embryo. Utilizing a newly developed video-based calcification assay we determined that extracts from Snus tobacco hindered calcification of osteoblasts derived from pluripotent stem cells early on in their differentiation. Nicotine, a major component of tobacco products, had no measurable effect in the tested concentration range. However, through the extraction of video data, we determined that the tobacco-specific nitrosamine N'-nitrosonornicotine caused a reduction in calcification with similar kinetics as the complete Snus extract. From measurements of actual nitrosamine concentrations in Snus tobacco extract we furthermore conclude that N'-nitrosonornicotine has the potential to be a major trigger of developmental osteotoxicity caused by Snus tobacco.

The Effect of Smoking Behavior on Alveolar Bone Marrow Mesenchymal Stem Cells of Clinical Implant Patient

Objective

The hazardous effects of smoking on the alveolar bone healing after implant surgery and nicotine on the biofunction of human alveolar bone marrow mesenchymal stem cells (hABMMSCs) were reported. There was little direct evidence regarding the specific detrimental effects of the smoking on hABMMSCs. The aim of this study was to test the influence of smoking behavior on hABMMSCs and the osseointegration situation after implant surgery.

Methods

hABMMSCs from 6 dental implant patients randomly (3 smokers and 3 nonsmokers) were compared. The cell viability, colony forming unit, and cell cycle were performed to assay proliferation capacity. The Oil Red O staining, Alizarin Red staining, alkaline phosphatase staining and activity, adipogenic and osteogenic gene expressions in vitro, and bone formation ectopically in vivo were performed under proper inductions, respectively, to assay multilineage differentiation. Besides the implant stability quotient and marginal bone loss were checked in both groups.

Results

Smoking hABMMSCs showed lower proliferation in vitro and poorer bone regeneration capacity in vivo. Moreover, smokers performed worse on bone healing after implant surgery.

Conclusions

Our results suggested smoking had the detrimental genetic effect on proliferation and osteogenesis of hABMMSCs and the decreased biofunction of hABMMSCs was positively related with bone healing.

Clinical Significance

The present study provided direct evidence about hazardous effects of smoking behavior on hABMMSCs. Smoking decreased the osteogenesis and proliferation of hABMMSCs in vivo and in vitro, and smoking was positively related with osseointegration reduction. Prevention of smoking behavior may promote biofunction of hABMMSCs and successful rate of dental implant.

Effect of orthodontic force associated with cigarette smoke inhalation in healthy and diseased periodontium. A histometric and immunohistochemistry analysis in rats

BACKGROUND

The aim of the present study is to evaluate the effect of orthodontic forces in healthy or diseased periodontium of rats submitted/not submitted to cigarette smoke inhalation.

MATERIAL AND METHODS

Fifty-six male Wistar rats were allocated into two groups of conditions: smoking and non-smoking. Each group was divided into the following subgroups: control (C), orthodontic tooth movement (OTM), ligature-induced periodontitis (P) and P+OTM (POTM), with n = 14 each. Periodontitis was induced in the lower first molar by cotton ligature, and a 4 mm closed stainless steel spring was used for orthodontic movement. Animals were exposed to the smoke of 10 cigarettes for 8 minutes, 3 times a day for 60 days before P induction and OTM. Evaluation parameters were macroscopic analysis of dental movement, bone loss and bone density. In addition, the receptor activator of nuclear factor-kappaB (RANK) immunostaining and RANK ligand/osteoprotegerin ratio in the furcation region were assessed.

RESULTS

There was no statistically significant difference between groups, ie, smoking and non-smoking conditions (P = .338). Bone loss intragroup analysis between the P and POTM groups was not significant in smoking (P = 1) and non-smoking (P = .5) conditions; both were different from OTM and C in each condition. Regarding bone density, POTM and P were significant to C (P < .05). The POTM group was significant to the P and C (P = .001) regarding dental movement. The RANK ligand/osteoprotegerin ratio in the non-smoking condition was higher in P and POTM compared to C and OTM and to P and POTM in the smoking condition. RANK immunostaining was significant in the smoking condition for the P and POTM groups (P < .05).

CONCLUSION

Within the limitations of the present study, it was concluded that cigarette smoke inhalation had no influence on the evaluated groups, even with the presence of low levels of nicotine, carbon monoxide and tar. The POTM groups did not present greater bone loss compared to P groups, thus periodontal disease is essential for bone loss.

Influence of nicotine on orthodontic tooth movement: A systematic review of experimental studies in rats

OBJECTIVE

The objective of this systematic review was to assess the impact of nicotine administration on orthodontic tooth movement (OTM).

METHODS

A systematic search was conducted in PubMed, Scopus, EMBASE, MEDLINE (OVID) and Web of Knowledge databases and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Studies evaluating the influence of nicotine on OTM, and with the presence of a control group (OTM without nicotine administration), were included. Quality assessment of the selected studies was performed following the Animal Research Reporting in Vivo Experiment (ARRIVE) guidelines.

RESULTS

Six of the initially identified 108 articles fulfilled the inclusion criteria and were selected. All included studies were performed in male rats, which underwent OTM with or without nicotine administration. Since there was a variation among the included studies regarding nicotine dosage and the duration and magnitude of force application during OTM only a qualitative analysis could be performed. The studies reported that nicotine administration accelerated OTM by inducing alveolar bone resorption around the moving teeth. It was also found that nicotine increased root resorption during experimental OTM. More standardized animal research or clinical studies are warranted to further evaluate the impact of nicotine on OTM.

CONCLUSIONS

On an experimental level, nicotine exposure in rats jeopardizes OTM by increasing alveolar bone loss and root resorption. From a clinical perspective, further studies are needed to assess the impact of habitual use of tobacco products on OTM.

Influence of involuntary cigarette smoke inhalation on osseointegration: a systematic review and meta-analysis of preclinical studies

There are no studies that have systematically reviewed the influence of involuntary cigarette smoke inhalation (ICSI) on the stability of implants. The aim of the present study was to perform a systematic review and meta-analysis of preclinical studies that assessed the influence of involuntary cigarette smoke inhalation ICSI on osseointegration. Indexed databases (PubMed, Google-Scholar, Scopus, EMBASE, and Web of Knowledge) were searched till September 2017. Titles and abstracts of studies identified using the above-described protocol were independently screened by 2 authors. Full-texts of studies judged by title and abstract to be relevant were independently evaluated for the stated eligibility criteria. Nine studies were included. Six studies showed that ICSI compromised bone area contact around implants. In 4 studies, peri-implant bone mineral density was significantly higher in the control group than among subjects exposed to ICSI. For the effects of ICSI on the osseointegration of dental implants, significant differences could be observed for bone-to-implant contact for test subjects in cancellous (Z=-4.08, p<0.001) and cortical bone (Z=-4.31, p<0.001) respectively. ICSI may negatively influence osseointegration of dental implants. It is imperative to educate patients about the negative effects of passive smoking on dental and systemic health.

Influence of nicotine on machined- and anodized-surface implants. Histometric analysis

BACKGROUND

The nicotine may generate a influence on bone repair and longevity of dental implants. This fact makes studies to improve the surface of the implants are constantly conducted. This study aimed to evaluate the influence of subcutaneous nicotine injection in the osseointegration process on different implant surfaces, through histomorphometric analysis.

MATERIAL AND METHODS

Therefore, twenty-two male rabbits were randomly distributed into two groups according to the subcutaneous injections: (1) nicotine, 3 mg/day/kg and (2) 0.9% NaCI, 3 mL/day/kg, three times a day. Subgroups were then designated - machined and anodized dental implants were installed in the right and left tibia bones, respectively. The animals were subjected to euthanasia after periods of eight weeks for histomorphometric analysis. The bone samples with implants were removed and the routine histological processing was performed. Next, the images obtained from the blades were evaluated by the Image Tool™ software, assessing the osseointegrated areas of implants (BIC), in pixels. Data obtained were subjected to intergroup statistical analysis through the Kruskal-Wallis non-parametric test (α=5%).

RESULTS

The test result showed no statistically significant difference among the groups studied (p=0.446).

CONCLUSIONS

Based on the methodology studied, it is concluded that the daily application of low doses of nicotine did not interfere with the osseointegration of machined and anodized implants. Key words:Bone-implant interface, implants, osseointegration.

Impact of resveratrol on bone repair in rats exposed to cigarette smoke inhalation: histomorphometric and bone-related gene expression analysis

This study investigated the effect of resveratrol on bone healing and its influence on the gene expression of bone-related markers in rats exposed to cigarette smoke. Two calvarial defects were created in each of 60 rats, which were assigned equally (n=20) to three groups: (1) resveratrol (10mg/kg)+smoke exposure (SMK+RESV); (2) placebo+smoke exposure (SMK+PLA); or (3) placebo+no smoke exposure (NS+PLA). Substances were administered daily for 30days following surgery. Smoke inhalation was started 7days before surgery and continued for 30days after surgery. One defect was processed for histomorphometric analysis and the other was used for mRNA quantification of bone-related gene expression by qPCR. The remaining defect was smaller in the SMK+RESV (2.27±0.61mm, P=0.0003) and NS+PLA (2.17±0.74mm, P=0.0005) groups than in the SMK+PLA group (3.12±0.47mm). Higher levels of Runx2 were observed in the NS+PLA group than in the smoke exposure groups (vs. SMK+PLA, P=0002; vs. SMK+RESV, P=0.052); levels of Lrp-5 were also higher in the no smoke exposure group (vs. SMK+RESV, P=0.009; vs. SMK+PLA, P=0.003). Resveratrol therapy decreased RANKL/OPG expression when compared to placebo (SMK+RESV vs. SMK+PLA, P=0.017). Dkk1 levels were decreased in the SMK+RESV group when compared to the SMK+PLA (P=0.006) and NS+PLA groups (P=0.005). In conclusion, resveratrol optimizes the repair of critical-sized bone defects, up-regulating the gene expression of important bone remodelling markers in rats exposed to cigarette smoke inhalation.

Fortifying the Bone-Implant Interface Part 1: An In Vitro Evaluation of 3D-Printed and TPS Porous Surfaces

BACKGROUND

An aging society and concomitant rise in the incidence of impaired bone health have led to the need for advanced osteoconductive spinal implant surfaces that promote greater biological fixation (e.g. for interbody fusion cages, sacroiliac joint fusion implants, and artificial disc replacements). Additive manufacturing, i.e. 3D-printing, may improve bone integration by generating biomimetic spinal implant surfaces that mimic bone morphology. Such surfaces may foster an enhanced cellular response compared to traditional implant surfacing processes.

METHODS

This study investigated the response of human osteoblasts to additive manufactured (AM) trabecular-like titanium implant surfaces compared to traditionally machined base material with titanium plasma spray (TPS) coated surfaces, with and without a nanocrystalline hydroxyapatite (HA) coating. For TPS-coated discs, wrought Ti6Al4V ELI was machined and TPS-coating was applied. For AM discs, Ti6Al4V ELI powder was 3D-printed to form a solid base and trabecular-like porous surface. The HA-coating was applied via a precipitation dip-spin method. Surface porosity, pore size, thickness, and hydrophilicity were characterized. Initial cell attachment, proliferation, alkaline phosphatase (ALP) activity, and calcium production of hFOB cells (n=5 per group) were measured.

RESULTS

Cells on AM discs exhibited expedited proliferative activity. While there were no differences in mean ALP expression and calcium production between TPS and AM discs, calcium production on the AM discs trended 48% higher than on TPS discs (p=0.07). Overall, HA-coating did not further enhance results compared to uncoated TPS and AM discs.

CONCLUSIONS

Results demonstrate that additive manufacturing allows for controlled trabecular-like surfaces that promote earlier cell proliferation and trends toward higher calcium production than TPS coating. Results further showed that nanocrystalline HA may not provide an advantage on porous titanium surfaces.

CLINICAL RELEVANCE

Additive manufactured porous titanium surfaces may induce a more osteogenic environment compared to traditional TPS, and thus present as an attractive alternative to TPS-coating for orthopedic spinal implants.

Implantology and otorhinolaryngology team-up to solve a complicated case

PURPOSE

The aim of this article was to highlight the importance of the collaboration between implantologists and ear, nose, and throat (ENT) specialists to treat complex cases.

MATERIALS AND METHODS

A 46-year-old patient underwent a maxillary sinus elevation and implant placement 3 years before but because of a severe postop infection, the patient was treated with functional endoscopic sinus surgery (FESS) and lost the graft and the implants. Later, the patient consulted us and was referred to an ENT specialist because of sinus opacity. She underwent a second functional endoscopic sinus surgery (FESS); various ENT consultations and computer tomographies (CTs) were performed to assess sinus health.

RESULTS

After having confirmed with sinus health, sinus elevation, implant placement, and loading were performed with success.

CONCLUSION

Collaboration between the implantologist and ENT specialist is necessary to distinguish between nonpathological membrane thickening because of the healing process after FESS and a pathological thickening due to infection.

Gene Expression Profiles of Early Implant Adherent Cells in Smokers and Nonsmokers

The objective of this study was to evaluate the impact of smoking on the early molecular events involved in peri-implant healing at either a micro-roughened or a micro-roughened with superimposed nanofeatures surface implant in humans. Twenty-one subjects, 10 smokers and 11 nonsmokers received 4 mini-implants (2.2 × 5.0 mm; 2 of each surface). After 3 and 7 days, paired mini-implants were retrieved by reverse threading and RNA isolated from implant adherent cells. Whole genome microarrays were used interrogate the gene expression profiles. The study failed to identify differences in the gene expression profiles of implant adherent cells at this early stage of osseointegration (up to day 7) comparing smoker and nonsmoker individuals.

Current perspective of the impact of smoking on the progression and treatment of periodontitis

This literature review provides an overview of the current scenario regarding the impact of smoking on the progression and treatment of periodontitis; clinical, microbiological and immunological data from studies from our and other groups are presented. In general, preclinical and clinical data are unanimous in demonstrating that smokers present increased susceptibility, greater severity and faster progression of periodontal disease compared with nonsmokers. The evidence further demonstrates that smokers lose more teeth and have a less favorable response to therapy than do nonsmokers. Although it is well established that smoking significantly impacts on the onset, progression and outcome of periodontal disease, the mechanisms involved remain unclear. More importantly, some of the reported deleterious effects of smoking on periodontal tissues have been reported to be reversible upon participation in smoking-cessation programs. Therefore, clinicians should strongly advise smokers to enroll in cessation strategies, even temporarily, in order to improve the overall outcome.

Implications of tobacco smoking on the oral health of older adults

Cigarette smoking is the foremost health risk issue affecting individuals of all age groups globally. It specifically influences the geriatric population as a result of chronic exposure to toxins. Its role in various systemic and oral diseases including cancer, premalignant lesions, periodontitis, tooth loss, dental caries and implant failures is well established. Smoking causes immuno-inflammatory imbalances resulting in increased oxidative stress in the body. The latter hastens the immunosenescence and inflammaging process, which increases the susceptibility to infections. Thus, implementation of smoking cessation programs among older adults is imperative to prevent the development and progression of oral and systemic diseases. The present review focuses on smoking-associated oral health problems in older adults, and the steps required for cessation of the habit.

Cigarette smoke inhalation increases the alveolar bone loss caused by primary occlusal trauma in a rat model

BACKGROUND AND OBJECTIVE

Occlusal trauma (OT) and smoking are both factors that alter alveolar bone metabolism and therefore could synergistically act on alveolar bone loss. The aim of this experimental study was to evaluate the influence of short-term cigarette smoke inhalation (CSI) on inter-radicular alveolar bone loss promoted by primary OT in a rat model.

MATERIAL AND METHODS

Forty-eight animals were randomly assigned to one of three groups based on treatment type: OT + CSI (n = 16), animals were exposed to CSI three times per day, for 8 min per exposure, and they concomitantly received unilateral vertical augmentation creating an occlusal interference inducing experimental OT; OT (n = 16), animals received only unilateral vertical augmentation; negative control (NC; n = 16), animals maintained for equal periods to achieve periodontal baseline values of periodontal ligament dimension. Each group was divided into two subgroups (n = 8) based on treatment length: 7 or 14 d.

RESULTS

After 7 d, the OT + CSI group exhibited significantly higher bone loss compared to the NC group (p = 0.0022). After 14 d, the OT (p < 0.0001) and OT + CSI (p < 0.0001) groups presented significantly higher bone loss compared to the NC group, and OT + CSI resulted in significantly higher bone loss than OT alone (p = 0.0241). The number of tartrate-resistant acid phosphatase-positive cells on the linear surface of the bone crest after 7 d was significantly higher in the OT + CSI group as compared to the NC and OT groups (p < 0.0001 and p = 0.0045, respectively) and remained significantly higher in the OT + CSI group after 14 d, compared to the OT group (p < 0.0001).

CONCLUSION

Short-term CSI increases early bone loss in association with OT after 7 d, and this worsens in severity after 14 d of exposure.

Effects of tobacco smoking on the survival rate of dental implants placed in areas of maxillary sinus floor augmentation: a systematic review

OBJECTIVES

The objective of this systematic review was to evaluate the effects of smoking on the survival rate of dental implants placed in areas of maxillary sinus floor augmentation.

MATERIAL AND METHODS

The Cochrane Oral Health Group's Trials Register (CENTRAL), MEDLINE and EMBASE were searched in duplicate up to, and including, October 2012 without language restrictions. Studies were considered eligible for inclusion if they involved the treatment of smokers and non-smokers with titanium implants and sinus floor elevation procedures. The Newcastle-Ottawa Scale and the Cochrane Collaboration's quality assessment tool were used for the assessment of the risk of bias in included studies. Random effects meta-analyses were used to assess the number of implants lost in smokers vs. number of implants lost in non-smokers.

RESULTS

Of 3360 potentially eligible papers, eight studies were included. More than half (62.5%) of the studies found that smoking adversely affects implant survival in sites of sinus floor augmentation. Similarly, the pooled analysis indicated a statistically significantly increased risk of implant failure in smokers when the outcomes of all studies available to be included into meta-analysis were evaluated [RR: 1.87 (95% CI: 1.35, 2.58), P = 0.0001]. Conversely, a subgroup analysis including only prospective studies (3 studies) did not reveal significant differences in implant failure between smokers and non-smokers [RR: 1.55 (95% CI: 0.91, 2.65), P = 0.11].

CONCLUSIONS

Although smoking was associated with implant failure in most of individual studies and in the overall meta-analysis, the detrimental effect of smoking was not confirmed when only prospective data were assessed.

The in vitro and in vivo effects of nicotine on bone, bone cells and fracture repair

INTRODUCTION

Cigarette smoke has negative effects on bone metabolism and fracture repair. However, no study has reviewed effects of nicotine on bone and fracture repair independent of other constituents of cigarette smoke. The authors review the existing evidence of the effect of nicotine on 'bone' and 'bone cells' and fracture repair, drawing conclusions relevant to clinical practice and future research.

AREAS COVERED

A literature review was conducted using PRISMA guidelines and PubMed, Cochrane, MEDLINE/OVID, EMBASE, NHS Evidence and Google scholar databases. Articles were included if they specifically investigated the effects of nicotine on 'bone' or fracture repair in animal or human models or in vitro effects on 'bone cells'. A total of 64 papers were included in this review, of which 15 were human in vitro studies and 49 animal studies wherein 9 were in vitro and 40 in vivo. In vivo studies of the effects of nicotine in animals demonstrated widespread effects on bone including osteoneogenesis, osseointegration, steady-state skeletal bone and genes and cytokines relevant to bone cell physiology and bone homeostasis. In these studies, nicotine's effects are predominately negative, inhibiting bone cell metabolism and fracture repair, whereas most in vitro studies reported biphasic responses in all bone cells except osteoclastic cells.

EXPERT OPINION

The review suggests that nicotine has effects on osteoneogenesis, osseointegration and steady-state skeletal bone in animal in vivo models, as well as effects on all 'bone cells', via several mechanisms in both animal and human cell in vitro studies. The effect of nicotine is dose-dependent, with higher concentrations having predominantly negative effects, whereas at low concentrations a stimulatory effect is seen. Stimulatory effects on certain cells may indicate a possible, limited therapeutic role; advice regarding smoking cessation perioperatively should remain due to the other harmful components of cigarette smoke, but there may be scope for allowing the use of nicotine patches instead of complete abstention. Further research into clinical outcomes is required before the exact response of bone and fracture repair in humans to nicotine is known.

Cigarette smoke inhalation influences bone healing of post-extraction tooth socket: a histometric study in rats

The aim of this study was to evaluate, histometrically, the bone healing of the molar extraction socket just after cigarette smoke inhalation (CSI). Forty male Wistar rats were randomly assigned to a test group (animals exposed to CSI, starting 3 days before teeth extraction and maintained until sacrifice; n=20) and a control group (animals never exposed to CSI; n=20). Second mandibular molars were bilaterally extracted and the animals (n=5/group/period) were sacrificed at 3, 7, 10 and 14 days after surgery. Digital images were analyzed according to the following histometric parameters: osteoid tissue (OT), remaining area (RA), mineralized tissue (MT) and non-mineralized tissue (NMT) in the molar socket. Intergroup analysis showed no significant differences at day 3 (p>0.05) for all parameters. On the 7(th) day, CSI affected negatively (p<0.05) bone formation with respect to NMT and RA (MT: 36%, NMT: 53%, RA: 12%; and MT: 39%, NMT: 29%, RA: 32%, for the control and test groups, respectively). In contrast, no statistically significant differences (p>0.05) were found at days 10 and 14. It may be concluded that CSI may affect socket healing from the early events involved in the healing process, which may be critical for the amount and quality of new-bone formation in smokers.

The effect of transdermal nicotine on fracture healing in a rabbit model

OBJECTIVE

Cigarette smoking inhibits fracture healing and places the patient at a higher risk of delayed union and nonunion. Nicotine has been implicated as the primary ingredient responsible for these effects. However, an analysis of current published investigations reveals conflicting data, with some evidence that nicotine alone does not significantly affect healing. We undertook an animal study of the effects of transdermal nicotine on fracture healing.

METHODS

Twenty-two adult male New Zealand white rabbits were randomly assigned to the nicotine group or the control group. A midshaft tibial osteotomy was performed on the left tibiae of all 22 rabbits. The nicotine rabbits were exposed using a 10.5-mg transdermal patch applied daily to the ear. Radiographs were obtained, and the area of fracture callus was assessed. Rabbits were euthanized at 21 days. Fractures were stressed to failure, and load/deformation curves were recorded.

RESULTS

The average area of callus formation was greater in the control group (

CONTROL

0.158 cm, Nicotine: 0.124 cm), but the difference was not statistically significant (P = 0.30). There was a significant difference between the 2 groups for mean normalized torque to failure (Nicotine: 36% of nonfractured side,

CONTROL

69% of nonfractured side, P = 0.028). The control group mean normalized stiffness was significantly greater than that for the nicotine rabbits (

CONTROL

87%, Nicotine: 43%, P = 0.036). There were 3 nonunions in the nicotine group (27%) compared with none in the control group (P = 0.062).

CONCLUSIONS

In a rabbit model of fracture healing, transdermal nicotine exposure resulted in decreased mechanical strength of healing fractures at 21 days and a higher rate of nonunion at 21 days compared with that of controls.

Systematic review of pre-clinical models assessing implant integration in locally compromised sites and/or systemically compromised animals

OBJECTIVE

The aim was to systematically search the dental literature for pre-clinical models assessing implant integration in locally compromised sites (part 1) and systemically compromised animals (part 2), and to evaluate the quality of reporting of included publications.

METHODS

A Medline search (1966-2011) was performed, complimented by additional hand searching. The quality of reporting of the included publications was evaluated using the 20 items of the ARRIVE (Animals in Research In Vivo Experiments) guidelines.

RESULTS

One-hundred and seventy-six (part 1; mean ARRIVE score = 15.6 ± 2.4) and 104 (part 2; 16.2 ± 1.9) studies met the inclusion criteria. The overall mean score for all included studies amounted to 15.8 ± 2.2. Housing (38.3%), allocation of animals (37.9%), numbers analysed (50%) and adverse events (51.4%) of the ARRIVE guidelines were the least reported. Statistically significant differences in mean ARRIVE scores were found depending on the publication date (p < 0.05), with the highest score of 16.7 ± 1.6 for studies published within the last 2 years.

CONCLUSIONS

A large number of studies met the inclusion criteria. The ARRIVE scores revealed heterogeneity and missing information for selected items in more than 50% of the publications. The quality of reporting shifted towards better-reported pre-clinical trials within recent years.

Effects of cigarette smoke and nicotine on cell viability, migration and myofibroblastic differentiation

BACKGROUND AND OBJECTIVE

Several studies have analysed the role of nicotine as a prominent agent affecting wound repair in smokers. However, tobacco smoke contains several components that may alter gingival wound healing. The present study aimed to analyse the roles of cigarette smoke condensate (CSC) and nicotine on cell viability, cell migration/invasion and myofibroblastic differentiation using primary cultures of human gingival fibroblasts.

MATERIAL AND METHODS

To compare the effects of CSC and nicotine, gingival fibroblasts were stimulated with CSC (0.4–500 lg/mL) and the corresponding nicotine concentrations (0.025–32 lg/mL) present in research cigarettes (1R3F). Cell viability was evaluated through the MTS assay. Cell migration and invasion were assessed through scratch wound assays, collagen nested matrices and trans well migration. a-Smooth muscle actin production was evaluated by western blotting.

RESULTS

Cigarette smoke condensate at 50 lg/mL induced a moderate increase in cell viability, whereas the corresponding nicotine concentration (3.2 lg/mL) did not produce this response. Cigarette smoke condensate at 250 lg/mL, but not nicotine at 16 lg/mL (the corresponding nicotine concentration), induced cell death. Both nicotine and CSC stimulated cell migration (50 lg/mL CSC; 3.2 lg/mL nicotine). At 150 lg/mL, CSC inhibited cell migration; however, the corresponding concentration of nicotine (9.6 lg/mL), did not have this effect. Although both nicotine and CSC inhibited a-smooth muscle actin production, only the latter induced a statistically significant effect on this response.

CONCLUSION

Cigarette smoke condensate may stimulate cell survival and migration at low concentrations and inhibit these cell responses at higher levels of exposure. Moreover, CSC may interfere in myofibroblastic differentiation.These results show that cigarette smoke, but not nicotine, may significantly alter cell viability, cell migration and myofibroblastic differentiation in gingival mesenchymal cells.

Parathyroid hormone (1-34) compensates the negative effect of smoking around implants

OBJECTIVES

This study aimed to investigate the effect of Recombinant Human Parathyroid Hormone (PTH 1-34) on attenuating the influence of cigarette smoke on bone around titanium implants.

MATERIAL AND METHODS

Forty-eight female Wistar rats were used. At the beginning of the study, 15 animals were randomly assigned to Group 1 (control) and received subcutaneous injections of saline solution, three-times/week, after implant placement. The other animals received intermittent cigarette smoke inhalation (CSI), 60 days prior and 60 days after implant placement ( Al 2 O 3 -blasted titanium implants - 4.0 × 2.2 mm). After surgery, these animals were randomly assigned to: Group 2 - subcutaneous injections of saline solution, three-times/week (n = 16) and Group 3 - intermittent doses of PTH (1-34) (40 μg/Kg), three-times/week (n = 17). Animals were sacrificed 60 days after surgery, and degree of bone-to-implant contact (BIC), bone area (BA) within the limits of the threads and proportion of mineralized tissue (PMT) adjacent to the implants (500 μm wide zone) were separately obtained in cortical and cancellous bone.

RESULTS

Data analysis confirmed that CSI negatively affects bone around implants, as observed for BIC in cortical zone (Cohen's d (d) = -1.26) and for PMT in both zones (d = -6.09 and d = -4.46 for cortical and cancellous zones, respectively). In addition, in the presence of CSI, PTH (1-34) promoted the highest BIC in both regions and BA and PMT in cancellous bone (P < 0.05). The histometric parameter that was not influenced by both PTH and CSI (1-34) was BA in cortical bone (P > 0.05).

CONCLUSION

In the presence of cigarette smoke, a factor related to poor bone healing and low bone density, PTH (1-34) increased bone volume around implants.

Aryl hydrocarbon receptor-mediated impairment of chondrogenesis and fracture healing by cigarette smoke and benzo(a)pyrene

The clinical literature strongly suggests that bone healing in cigarette smokers is impaired. Since cigarette smoke (CS) contains numerous polycyclic aromatic hydrocarbons (PAHs), and since dioxins impair bone formation in vivo via the Aryl Hydrocarbon Receptor (AHR), we investigated the impact of PAH/AHR signaling on chondrogenesis and on healing in a mouse tibial fracture model. We established that CS activates AHR signaling in fractures by up-regulating the AHR target gene cytochrome p4501A1 (Cyp1A1). For in vitro studies, we employed the mouse limb bud micromass chondrogenesis model. After confirming that chondrocytes express AHR during differentiation, we treated cells with a prototypical PAH found in CS, benzo(a)pyrene (BaP), or cigarette smoke extract (CSE). Both BaP and CSE strongly inhibited chondrogenesis in mesenchymal cells generated from E11 limb buds, with BaP also accelerating chondrocyte hypertrophy in cultures generated from E12 limb buds. Detection of DNA adducts in the BaP-treated cultures suggests that the distinct phenotypic effects of BaP may be due to the formation of reactive metabolites. Blockade of AHR signaling with the AHR antagonist MNF reverses the effects of BaP, but not CSE, suggesting that CSE inhibition of chondrogenesis is AHR-independent. Correlating with these results, tibial fracture calluses from BaP-treated mice were smaller and contained less mineralized tissue than vehicle controls. Overall, BaP is identified as a potent inhibitor of chondrogenesis in vitro with correlated effects on fracture healing similar to those of CS itself, suggesting a basis for PAHs as key compounds in the influence of CS on fracture repair.