Wear and corrosion of titanium in oral simulating environments

The oral cavity can be considered as an aggressive environment to restorative materials considering that several acidic substances can be retained in the saliva and biofilms as well as loads from mastication and abrasive particles take place in the wear of oral surfaces. The objective of this work is to investigate the in-vitro corrosion and wear in fluoridated artificial saliva and in presence of biofilms. Electrochemical tests of titanium surfaces were performed in artificial saliva containing different fluoride concentrations at 37 oC. Another group of titanium surfaces were prepared to the growth of oral mixed biofilms for 9 days in a specific culture medium. Then, electrochemical tests were carried out with titanium surfaces covered with biofilms in artificial saliva without fluorides. After that, wear sliding tests were performed in the same mediums using a tribometer equipped with a test viewer software. Also, electrochemical measurements were carried during the wear sliding tests. After corrosion-wear tests, worn and unworn surfaces were analyzed by AFM and SEM. A localized corrosion of titanium was only noticed in high fluoride concentration. Therefore, there was a decrease of the corrosion resistance of titanium when the fluoride concentration was increased. Moreover, the presence of biofilms affected harmfully the corrosion resistance of titanium probably due to acids release from the biofilms. However, the wear was decreased when low loads were applied on the biofilms.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/CTM/67500/2006Programa Alban - Bolsas de Alto Nível da União Europeia para a América Latina - E06D103407BRFlemish Science Foundation. Scientific Research Community on Surface Modification of Material

Effect of oral biofilms on the biotribocorrosion of titanium

The oral cavity is a complex environment where corrosive substances from dietary, human saliva and oral biofilms may accumulate in retentive areas of implant-supported prostheses promoting a corrosion of their surfaces. On the other side, during mastication, micro-movements may occur in artificial joints causing a relative contact motion between surfaces. Both processes result in a tribocorrosion system. The objective of this work is to investigate the in-vitro tribocorrosion behavior of titanium covered by biofilms and immersed in artificial saliva. Reciprocating sliding wear tests coupled with electrochemical techniques were performed at 25 o C on titanium samples covered or not with biofilms. Mixed biofilms of Candida albicans and Streptococcus mutans were grown at 37 oC on titanium surfaces for 9 days in Tryptic Soy Broth medium, containing mucin, yeast extract, peptone and sucrose. The open-circuit potential (OCP) was measured until stabilization in artificial saliva. After that, electrochemical impedance spectroscopy (EIS) measurements were carried out at open circuit potential. Subsequently, sliding tests were performed at normal loads of 0.1, 0.2 and 3 N, at a sliding frequency of 1 Hz, and linear displacement amplitudes of 0.5 and 2 mm using a tribometer equipped with a test viewer software. During the sliding tests, the OCP was constantly monitored. At the end of the sliding test, the OCP was further monitored until stabilization, and another series of EIS measurements was made. Worn and unworn surfaces were inspected by SEM. The detachment of the biofilms was not noticed when low loads were applied, and biofilms appear to have some lubricating effect. However, it was found that acidic substances released from Streptococcus mutans and external substances accumulated into the biofilm might corrode surfaces located below and around the biofilms. At a normal load of 3 N, the biofilms were removed from the contact region by the sliding action, and it was observed that the repassivation rate of titanium covered with biofilms was lower than without biofilms.Fundação para a Ciência e a Tecnologia (FCT)ALBANFlemish Science Foundation. Scientific Research Community on Surface Modification of MaterialsPrograma Alban - Bolsas de Alto Nível da União Europeia para a América Latin

Corrosion behaviour of titanium in the presence of Streptococcus mutans

Objective The main aim of this in vitro study was to evaluate the influence of Streptococcus mutans on the corrosion of titanium. Methods S. mutans biofilms were formed on commercially pure titanium (CP-Ti) square samples (10 mm × 10 mm × 1 mm) using a culture medium enriched with sucrose. Open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements were used to evaluate the corrosion behaviour of CP-Ti in the presence of S. mutans in Fusayama's artificial saliva. The corrosion of biofilm-free CP-Ti samples was also evaluated in artificial saliva. Biofilms biomass was measured by spectrophotometry, using crystal violet staining, after 1, 2 and 7 days. Results The OCP values recorded on CP-Ti in the presence of S. mutans (−0.3 ± 0.02 V vs. SCE) was lower than those on biofilm-free CP-Ti (−0.1 ± 0.01 V vs. SCE) after 2 h of immersion in artificial saliva (p < 0.05). That reveals a high reactivity of titanium in presence of S. mutans. Impedance spectra revealed the formation of a compact passive film on titanium in artificial saliva or in the presence of a 2 days old S. mutans biofilm even though the corrosion resistance of CP-Ti has decreased in presence of a S. mutans biofilm. Conclusion The presence of bacterial colonies, such as S. mutans, negatively affected the corrosion resistance of the titanium.The authors acknowledge the financial support provided by Alban Programme (cod. E06D103407BR), the Erasmus Student Exchange Programme of the CEC, FCT (PTDC/CTM/67500/2006) and the Scientific Research Community on Surface Modification of Materials funded by the Flemish Science Foundation (WOG-FWO-Vlaanderen)

Alternative therapies in controlling oral malodour: a systematic review.

peer reviewedIs there a role for alternative therapies in controlling intra-oral halitosis? Treatments other than tongue cleaning and anti-halitosis products containing zinc, chlorhexidine and cetylpyridinium chloride were considered as alternative therapies. Four databases were searched (PubMed, EMBASE, Web of Science and The Cochrane Library). Inclusion criteria were: examination of alternative halitosis therapies, study population with oral malodour, a (negative or positive) control group and evaluation of breath odour via organoleptic and/or instrumental assessment. Data were extracted for descriptive analysis. The screening of 7656 titles led to the inclusion of 26 articles. Analysis showed heterogeneity concerning the population of interest (from cysteine-induced to genuine halitosis), the examined treatment and the reported outcomes. This made a meta-analysis impossible. Essential oils, fluoride-containing products and herbal substances were the most studied. Results varied enormously and none of the active ingredients had an unambiguously positive effect on the malodour. The risk of bias was assessed as high in all articles. Given the fact that little evidence was found for each of the investigated treatments, it could be concluded that there is currently insufficient evidence that alternative therapies are of added value in the treatment of halitosis.Clinical relevanceScientific rationale:Halitosis is a common problem causing social isolation. Out of embarrassment, patients search the internet, leading to many questions about alternative solutions (e.g. oil pulling, herbs). This is the first systematic review on these alternative therapies.Principal findings: Results varied among studies. Some promising results were found for fluoride-containing toothpastes and probiotics. For other products (such as herbal and antibacterial products and essential oils) results were inconsistent. Long-term follow-up studies on these products are scarce. Moreover, the quality of the studies was poor.Practical implications:No clear evidence was found to support a certain alternative anti-halitosis therapy

Periodontal screening and referral behaviour of general dental practitioners in Flanders.

peer reviewedOBJECTIVES: The objective of this study was to investigate the screening and referral behaviour of Flemish dentists concerning periodontitis and more specific, the use of the Dutch Periodontal Screening Index (DPSI). MATERIALS AND METHODS: An online questionnaire was electronically distributed through the different professional dental societies. It consisted of two parts: the first aimed at describing the profile of the dentist. The second part inquired the screening method, when this was applied, periodontal risk factors and referral behaviour. RESULTS: One thousand fifty dentists attended to the questionnaire. One hundred fifty-nine questionnaires were excluded since they did not match the target audience. Sixty-four percent of Flemish dentists used DPSI as a periodontal screening method, 28% screened based on probing pocket depth, 4% used solely radiographs and 4% had no screening method at all. The usage of DPSI is influenced by the year of graduation: the longer the dentists were graduated, the less they used DPSI. No influence of sex, education centre and location was found. Referral behaviour is influenced by different patient- and dentist-related factors. CONCLUSIONS: Regarding the screening behaviour, there seems a consensus among Flemish dentists that a periodontal probe should be used. For referral, there is no consensus about if and when to refer to a specialist. CLINICAL RELEVANCE: It is encouraging that 92% of the Flemish general dental practitioners use a probe when screening for periodontitis. However, DPSI is mainly used by younger dentists. An effort should be made to encourage all dentists to use this, so that in every patient, periodontitis can be detected timely, securing the best treatment outcome

Clinical effects of probiotics containing Bacillus species on gingivitis: a pilot randomized controlled trial.

peer reviewedBACKGROUND AND OBJECTIVE: Lactobacillus spp. and bifidobacteria are the most frequently used probiotics in oral health research. However, although probiotic effects have been suggested for other genera, such as bacilli, no trials are available to describe the effect of bacilli probiotics on gingivitis in humans. The aim of the present study was to evaluate the clinical effects of a bacilli-containing toothpaste, a mouthrinse and a toothbrush cleaner versus a placebo in patients with generalized gingivitis. MATERIAL AND METHODS: In this double-blind placebo-controlled randomized clinical trial, nonsmoking, systemically healthy patients with generalized gingivitis were included. They used a placebo or an experimental probiotic Bacillus subtilis-, Bacillus megaterium- and Bacillus pumulus-containing toothpaste, mouthrinse and toothbrush cleaner for 8 wk. Primary outcome measures of interest were plaque and gingivitis index, and the secondary outcome measures were pocket probing depth and bleeding on probing. RESULTS: Twenty male and 20 female patients were randomized over the two groups. All participants could be included in the final analysis. Although plaque and gingivitis indices were significantly reduced after 8 wk, no intergroup differences could be found at any time point. Also, for the secondary outcome measure, intragroup but no intergroup differences could be detected. No harm or unintended effects were reported by the patients after using the study products. CONCLUSIONS: This study did not show any statistically significant differences between a placebo and a bacilli-containing toothpaste, mouthrinse and toothbrush cleaner on gingivitis parameters

A global optimization approach applied to structural dynamic updating

In this paper, the application of stochastic global optimization tech- niques, in particular the GlobalSearch and MultiStart solvers from MatLab®, to improve the updating of a structural dynamic model, are presented. For com- parative purposes, the efficiency of these global methods relatively to the local search method previously used in a Finite Element Model Updating program is evaluated. The obtained solutions showed that the GlobalSearch and MultiStart solvers are able to achieve a better solution than the local solver previously used, in the updating of a structural dynamic model. The results show also that the GlobalSearch solver is more efficient than the MultiStart, since requires less computational effort to obtain the global solution.Fundação para a Ciência e a Tecnologia (FCT

A pilot study combining individual-based smoking cessation counseling, pharmacotherapy, and dental hygiene intervention

BACKGROUND: Dentists are in a unique position to advise smokers to quit by providing effective counseling on the various aspects of tobacco-induced diseases. The present study assessed the feasibility and acceptability of integrating dentists in a medical smoking cessation intervention. METHODS: Smokers willing to quit underwent an 8-week smoking cessation intervention combining individual-based counseling and nicotine replacement therapy and/or bupropion, provided by a general internist. In addition, a dentist performed a dental exam, followed by an oral hygiene treatment and gave information about chronic effects of smoking on oral health. Outcomes were acceptability, global satisfaction of the dentist's intervention, and smoking abstinence at 6-month. RESULTS: 39 adult smokers were included, and 27 (69%) completed the study. Global acceptability of the dental intervention was very high (94% yes, 6% mostly yes). Annoyances at the dental exam were described as acceptable by participants (61% yes, 23% mostly yes, 6%, mostly no, 10% no). Participants provided very positive qualitative comments about the dentist counseling, the oral exam, and the resulting motivational effect, emphasizing the feeling of oral cleanliness and health that encouraged smoking abstinence. At the end of the intervention (week 8), 17 (44%) participants reported smoking abstinence. After 6 months, 6 (15%, 95% CI 3.5 to 27.2) reported a confirmed continuous smoking abstinence. DISCUSSION: We explored a new multi-disciplinary approach to smoking cessation, which included medical and dental interventions. Despite the small sample size and non-controlled study design, the observed rate was similar to that found in standard medical care. In terms of acceptability and feasibility, our results support further investigations in this field. TRIAL REGISTRATION NUMBER: ISRCTN67470159