Titanium implant functionalization with phosphate-containing polymers may favour in vivo osseointegration.

AIM: Osseointegration of titanium implants is predictable, but can be improved via surface functionalization. MATERIALS AND METHODS: One hundred and twenty implants were installed in parietal bone of 12 domestic pigs and left to heal for 1 or 3 months. Five groups were defined according surface treatments: immersion in water (H2 O), 10% polyphosphoric acid (PPA10), 1% phosphorylated pullulan (PPL1), 10% phosphorylated pullulan (PPL10) or 10% phosphorylated pullulan + 1 µg bone morphogenetic protein-2 (PPL10 BMP). As primary outcome, implant osseointegration was evaluated by quantitative histology, namely peri-implant bone formation (B/T in %) and bone-to-implant contact (BIC in %) for each healing period. The Wilcoxon signed-rank test and Mann-Whitney U-test with α = 0.05 were performed. RESULTS: PPL10 and PPA10 groups showed significantly higher B/T and BIC results than the control (H2 O) group at 1-month (p < .05). No significant difference was found between PPL1 and H2 O or between PPL10 BMP and H2 O, irrespective of healing time (1 or 3 months) or investigated parameter (B/T and BIC; p > .05). After 3 months, no experimental group showed a significant difference compared to the control group (H2 O) for both investigated parameters (B/T and BIC; p > .05). CONCLUSION: Functionalizing titanium implants with inorganic or organic phosphate-containing polymers at 10 wt% concentration may stimulate peri-implant bone formation and implant osseointegration at early healing times.

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

Although smoking promotes deleterious effect to bone healing, there is a lack of study investigating its role on the implant structure and biofilm growth. We hypothesized that nicotine, cotinine and caffeine would impair the corrosion resistance of commercially-pure titanium (cp-Ti) and would enhance Streptococcus sanguinis biofilm growth. Neither the smoking products nor the caffeine affected the corrosion tendency (P>.05) and the oxide layer resistance (P=.762) of cp-Ti. Lower capacitance values were noted in the presence of nicotine (P=.001) and cotinine (P=.0006). SEM showed no pitting corrosion, and the EDS spectra did not differ among groups. Nicotine (300µg/mL) induced higher surface roughness (P=.03) and greater surface change of cp-Ti. Nicotine at 3µg/mL, and cotinine at 0.3 and 3µg/mL increased the number of viable cells (P<.05). Biofilm exposed to nicotine (0.3, 3 and 30µg/mL) (P=.025, .030, .040, respectively) and cotinine (3 and 30µg/mL) (P=.027, .049, respectively) enhanced carbohydrate content. Biofilm biomass and protein content were similar among groups (P>.05). These findings suggest a greater biofilm accumulation in smokers, a risk factor that may lead to peri-implantitis.

Discrepancies in marginal and internal fits for different metal and alumina infrastructures cemented on implant abutments.

Cemented crowns are increasingly being used on dental implants instead of on screw-retained prostheses because of the reliability of internal Morse taper implant-abutment connections. However, there is a lack of information on the fit of metal ceramic and premachined alumina infrastructures. Therefore, the aim of this study was to evaluate the marginal and internal fits of different metal and alumina infrastructures cemented on universal post abutments. A total of 45 abutments (6 mm in height and 3.3 mm in diameter) were divided into five groups on the basis of their infrastructure material: cobalt-chromium (CoCr), nickel-chromium (NiCr), nickel-chromium-molybdenum-titanium (NiCrMoTi), gold (Au), and premachined alumina. The alumina group showed marginal overextension, and the Au group showed the highest discrepancy in marginal fit among the metal alloys. The CoCr and alumina groups showed the lowest discrepancies in internal fit. In conclusion, the alumina cylinders exhibited the best internal fit, despite their horizontal overextension. Among the metal alloys, CoCr exhibited the best fit at critical regions, such as the cervical and occlusal areas.

Aerosol-phase activity of iodine captured from a triiodide resin filter on fine particles containing an infectious virus.

AIMS: To avoid interference by water-iodine disinfection chemistry and measure directly the effect of iodine, captured from a triiodide complex bound to a filter medium, on viability of penetrating viral particles. METHODS AND RESULTS: Aerosols of MS2 coli phage were passed through control P100 or iodinated High-Efficiency Particulate Air media, collected in plastic bags, incubated for 0-10 min, collected in an impinger containing thiosulphate to consume all unreacted iodine, plated and enumerated. Comparison of viable counts demonstrated antimicrobial activity with an apparent half-life for devitalization in tens of seconds; rate of kill decreased at low humidity and free iodine was captured by the bags. CONCLUSIONS: The results support the mechanism of near-contact capture earlier proposed; however, the disinfection chemistry in the aerosol phase is very slow on the time scale of inhalation. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that disinfection by filter-bound iodine in the aerosol phase is too slow to be clinically significant in individual respiratory protection, but that it might be of benefit to limit airborne transmission of infections in enclosed areas.

Plasma proteins in the acquired denture pellicle enhance substrate surface free energy and Candida albicans phospholipase and proteinase activities.

AIM: The objective of the present study was to determine if blood plasma proteins could change the proteome of the acquired denture pellicle by label-free quantitative proteomics. As pellicle proteome modulates the interaction between substrates and Candida cells, we investigated its effect on the surface free energy (SFE) of the coated resin and on Candida albicans phospholipase and aspartyl proteinase activities. METHODS: Poly(methylmethacrylate) discs were exposed to saliva (control) or saliva enriched with blood plasma (experimental group). The pellicle proteome was analyzed by mass spectrometry coupled with liquid chromatography. SFE was determined by acid-base technique. After biofilm formation, phospholipase and proteinase activities were determined accordingly to classic plate methods. Data were analyzed by two-way anova and Tukey test (P < 0.05). RESULTS: α-Amylase, cystatins, mucins, and host-immune system proteins were the main proteins identified in the control group. Fibrinogen and albumin were observed only in the experimental group. Coated discs of the experimental group presented an increased SFE (P < 0.05). For both enzymes tested, the experimental group showed higher proteolytic activity (P < 0.001). CONCLUSION: Blood plasma changes the proteome of the acquired denture pellicle, increasing surface free energy and the activity of Candida albicans phospholipase and aspartyl proteinase.

Confocal analysis of the exopolysaccharide matrix of Candida albicans biofilms.

AIM: Confocal laser-scanning microscopy (CLSM) was carried out to investigate the exopolysaccharide matrix of Candida albicans (C. albicans) biofilms developed on denture material under dietary carbohydrate exposure. METHODS: Biofilms were developed on poly(methyl methacrylate) discs in culture media without (control) or with supplementation by glucose or sucrose for 72 h. For the CLSM analysis, biofilms were labeled with concanavalin A (ConA) during its development. Afterwards, biofilms were also labeled with SYTO-9. To confirm the results, the matrix was investigated by the phenol-sulfuric method. Data were analyzed by anova, followed by Tukey's test, with the level of significance set at 5%. RESULTS: The use of ConA during biofilm development provided effective labeling of the exopolysaccharide matrix. The exposure to sucrose resulted in biofilms with the highest exopolysaccharide matrix biovolume (P < 0.05). The characterization obtained by CLSM was confirmed by the phenol-sulfuric method. CONCLUSION: Confocal laser-scanning microscopy was found to be an effective tool for investigating the exopolysaccharide matrix of C. albicans biofilms, and exposure to sucrose resulted in increased matrix production.

Influence of surface free energy of denture base and liner materials on Candida albicans biofilms.

AIM: This study aimed to evaluate the influence of surface free energy (SFE) of denture base and liner materials on Candida albicans biofilm development. METHODS: Discs were fabricated using poly(methyl methacrylate) acrylic resin and poly(ethyl methacrylate) denture liner, according to the manufacturers' instructions. For SFE test, discs were pellicle-coated with saliva alone, saliva + blood plasma, or blood plasma alone. Candida albicans biofilms were allowed to form on pellicle-coated discs for 48 h. Biofilms were evaluated for cell counts, metabolic activity, and structural characteristics at adhesion phase (after 1.5 h of development) and at biofilm maturity (after 48 h of development). Data were analyzed by anova and Tukey tests using a significance level of 5%. RESULTS: Saliva + blood plasma pellicles had a higher SFE compared to pellicles of saliva or blood plasma alone (P < 0.001). Differences in SFE by pellicle-coating did not affect the cell counts, metabolic activity, or structure at the adhesion phase (P > 0.05). In contrast, the presence of blood plasma resulted in higher cell counts, biovolume, and thickness of mature biofilms on both materials (P < 0.001). CONCLUSIONS: Increases in SFE from pellicle-coating leads to robust mature C. albicans biofilms on both denture materials.

A combined segmenting and non-segmenting approach to signal quality estimation for ambulatory photoplethysmography.

Continuous cardiac monitoring of healthy and unhealthy patients can help us understand the progression of heart disease and enable early treatment. Optical pulse sensing is an excellent candidate for continuous mobile monitoring of cardiovascular health indicators, but optical pulse signals are susceptible to corruption from a number of noise sources, including motion artifact. Therefore, before higher-level health indicators can be reliably computed, corrupted data must be separated from valid data. This is an especially difficult task in the presence of artifact caused by ambulation (e.g. walking or jogging), which shares significant spectral energy with the true pulsatile signal. In this manuscript, we present a machine-learning-based system for automated estimation of signal quality of optical pulse signals that performs well in the presence of periodic artifact. We hypothesized that signal processing methods that identified individual heart beats (segmenting approaches) would be more error-prone than methods that did not (non-segmenting approaches) when applied to data contaminated by periodic artifact. We further hypothesized that a fusion of segmenting and non-segmenting approaches would outperform either approach alone. Therefore, we developed a novel non-segmenting approach to signal quality estimation that we then utilized in combination with a traditional segmenting approach. Using this system we were able to robustly detect differences in signal quality as labeled by expert human raters (Pearson's r = 0.9263). We then validated our original hypotheses by demonstrating that our non-segmenting approach outperformed the segmenting approach in the presence of contaminated signal, and that the combined system outperformed either individually. Lastly, as an example, we demonstrated the utility of our signal quality estimation system in evaluating the trustworthiness of heart rate measurements derived from optical pulse signals.

Efficacy of calcium hydroxide paste prepared with different vehicles against salivary microbial infiltration of root canals.

This in vitro study evaluated the efficacy of calcium hydroxide Ca(OH)2 pastes prepared with different vehicles in preventing bacterial infiltration in teeth exposed to human saliva. This study used 52 central incisors, of which 4 teeth were used as positive and negative controls (n = 2). The root canals were instrumented and filled with Ca(OH)2 paste prepared with different vehicles: saline solution (Group 1), polyethylene glycol (Group 2), or polyethylene glycol and camphorated paramonochlorophenol (Group 3). Only 6 teeth in Group 1 showed contamination. All teeth in Groups 2 and 3 were contaminated after 32 days of incubation. There were significant differences between Groups 1 and the other groups (P < 0.05) in terms of the mean time to contamination. By contrast, there was no such difference in terms of mean time to contamination between Groups 2 and 3 (P > 0.05). Based on the results, it was possible to conclude that calcium hydroxide paste prepared with saline solution was most effective for retarding microbial contamination.

Standard method for deposition of dry, aerosolized, silica-coated Bacillus spores onto inanimate surfaces.

AIMS: To evaluate a standard aerosolization method for uniformly depositing threat-representative spores onto surfaces. METHODS AND RESULTS: Lyophilized Bacillus anthracis ΔSterne spores, coated in silica, were aerosolized into a containment chamber and deposited onto nine surface types by two independent laboratories. Laboratory A produced a mean loading concentration of 1·78 × 10(5) CFU cm(-2) ; coefficient of variation (CV) was <40% for 96% of samples. Laboratory B produced a mean loading concentration of 7·82 × 10(6) CFU cm(-2) ; 68% of samples demonstrated CV <40%. CONCLUSIONS: This method has been shown to meet the goal of loading threat-representative spores onto surfaces with low variability at concentrations relevant to the Department of Defense. SIGNIFICANCE AND IMPACT OF THE STUDY: As demonstrated in 2001, a biological attack using anthrax disseminated as a dry powder is a credible threat. This method will provide a means to load spores onto surfaces that mimic a 'real-world' scenario of an aerosolized anthrax attack. The method has utility for evaluating sporicidal technologies and for nondecontamination studies, for example fate and transport or reaerosolization.

Direct electrical stimulation of the somatosensory cortex in humans using electrocorticography electrodes: a qualitative and quantitative report.

OBJECTIVE: Recently, electrocorticography-based brain-computer interfaces have been successfully used to translate cortical activity into control signals for external devices. However, the utility of such devices would be greatly enhanced by somatosensory feedback. Direct stimulation of somatosensory cortex evokes sensory perceptions, and is thus a promising option for closing the loop. Before this can be implemented in humans it is necessary to evaluate how changes in stimulus parameters are perceived and the extent to which they can be discriminated. APPROACH: Electrical stimulation was delivered to the somatosensory cortex of human subjects implanted with electrocorticography grids. Subjects were asked to discriminate between stimuli of different frequency and amplitude as well as to report the qualitative sensations elicited by the stimulation. MAIN RESULTS: In this study we show that in humans implanted with electrocorticography grids, variations in the amplitude or frequency of cortical electrical stimulation produce graded variations in percepts. Subjects were able to reliably distinguish between different stimuli. SIGNIFICANCE: These results indicate that direct cortical stimulation is a feasible option for sensory feedback with brain-computer interface devices.

Adding denture cleanser to microwave disinfection regimen to reduce the irradiation time and the exposure of dentures to high temperatures.

BACKGROUND: The microwave energy is an efficient disinfection method; however, it can generate high temperatures that can result in distortion of the dentures. OBJECTIVES: To evaluate whether the addition of an enzymatic cleanser to microwave disinfection regimen would disinfect dentures with shorter irradiation time. MATERIALS AND METHODS: Seven resin discs colonized with Candida albicans biofilm were placed on the palatal surface of sterile dentures to be randomly assigned to the following treatments: immersion in distilled water for 3 min with 0 (DW), 1 (DW + M1), 2 (DW + M2), or 3 min (DW + M3) of microwave irradiation; or immersion in denture cleanser for 3 min with 0 (DC), 1 (DC + M1), 2 (DC + M2) or 3 min (DC + M3) of irradiation. After the treatments, the viable cells were counted by a blinded examiner. The temperature was measured immediately after irradiation. The data were analyzed by ANOVA and Tukey post hoc tests (α = 0.05). RESULTS: No viable cells were found after DC + M2, DC + M3, and DW + M3 treatments, of which DC + M2 achieved the lowest temperature. No significant difference was found between the effectiveness of DW, DW + M1 and DC treatments (p > 0.05). CONCLUSION: Within the limits of this study, the association of a denture cleanser and microwave energy is efficient to disinfect dentures in lower irradiation time and temperature.

Design, construction and validation of a nose-only inhalation exposure system to measure infectivity of filtered bioaerosols in mice.

AIMS: The aim of this project was to validate a method to deliver a reproducible, selected dose of infective bioaerosol through a respiratory protective technology to an animal that exhibits a proportional clinical response. METHODS AND RESULTS: The Controlled Aerosol Test System (CATS) was designed to generate and condition a viable infective aerosol, pass it through a treatment technology and thence to the breathing zone of a mouse constrained in a Nose-Only Inhalation Exposure System (NOIES). A scanning mobility particle sizer and impingers at sampling ports were used to show that viability is preserved and particle size distribution (PSD) is acceptably uniform throughout the open CATS, including the 12 ports of the NOIES, and that a particle filter used caused the expected attenuation of particle counts. CONCLUSIONS: Controlled Aerosol Test System delivers uniformly to mice constrained in the NOIES a selectable dose of viral bioaerosol whose PSD and viable counts remain consistent for an hour. SIGNIFICANCE AND IMPACT OF THE STUDY: This study's characterization of CATS provides a new test system in which a susceptible small-animal model can be used as the detector in a quantitative method to evaluate the ability of respiratory protective technologies to attenuate the infectivity of an inspired pathogenic aerosol. This provides a major improvement over the use of viable bioaerosol collectors (e.g. impactors and impingers), which provide data that are difficult to relate to the attenuation of pathogenicity.

Proportional mouse model for aerosol infection by influenza.

AIMS: The aim of this study was to demonstrate a prototype tool for measuring infectivity of an aerosolized human pathogen - influenza A/PR/8/34 (H1N1) virus - using a small-animal model in the Controlled Aerosol Test System (CATS). METHODS AND RESULTS: Intranasal inoculation of nonadapted H1N1 virus into C57BL, BALB/c and CD-1 mice caused infection in all three species. Respiratory exposure of CD-1 mice to the aerosolized virus at graduated doses was accomplished in a modified rodent exposure apparatus. Weight change was recorded for 7 days postexposure, and viral populations in lung tissue homogenates were measured post mortem by DNA amplification (qRT-PCR), direct fluorescence and microscopic evaluation of cytopathic effect. Plots of weight change and of PCR cycle threshold vs delivered dose were linear to threshold doses of ~40 TCID(50) and ~12 TCID(50) , respectively. CONCLUSIONS: MID(50) for inspired H1N1 aerosols in CD-1 mice is between 12 and 40 TCID(50) ; proportionality to dose of weight loss and viral populations makes the CD-1 mouse a useful model for measuring infectivity by inhalation. SIGNIFICANCE AND IMPACT OF THE STUDY: In the CATS, this mouse-virus model provides the first quantitative method to evaluate the ability of respiratory protective technologies to attenuate the infectivity of an inspired pathogenic aerosol.

Analysis of residual chemicals on filtering facepiece respirators after decontamination.

The N95 filtering facepiece respirator (FFR) is commonly used to protect individuals from infectious aerosols. Health care experts predict a shortage of N95 FFRs if a severe pandemic occurs, and an option that has been suggested for mitigating such an FFR shortage is to decontaminate and reuse the devices. Before the effectiveness of this strategy can be established, many parameters affecting respiratory protection must be measured: biocidal efficacy of the decontamination treatment, filtration performance, pressure drop, fit, and toxicity to the end user post treatment. This research effort measured the amount of residual chemicals created or deposited on six models of FFRs following treatment by each of 7 simple decontamination technologies. Measured amounts of decontaminants retained by the FFRs treated with chemical disinfectants were small enough that exposure to wearers will be below the permissible exposure limit (PEL). Toxic by-products were also evaluated, and two suspected toxins were detected after ethylene oxide treatment of FFR rubber straps. The results provide encouragement to efforts promoting the evolution of effective strategies for decontamination and reuse of FFRs.

Characterization of reaerosolization from impingers in an effort to improve airborne virus sampling.

AIMS: To assess the impact of reaerosolization from liquid impingement methods on airborne virus sampling. METHODS AND RESULTS: An AGI-30 impinger containing particles [MS2 bacteriophage or 30-nm polystyrene latex (PSL)] of known concentration was operated with sterile air. Reaerosolized particles as a function of sampling flow rate and particle concentration in the impinger collection liquid were characterized using a scanning mobility particle sizer. Reaerosolization from the impinger was also compared to that from a BioSampler. Results show that reaerosolization increases as flow rate increases. While the increased particle concentration in the impinger collection liquid leads to an increase in the reaerosolization of PSL particles, it does not necessarily lead to an increase in the reaerosolization of virus particles. Reaerosolization of virus particles begins to decrease as the particle concentration in the impinger collection liquid rises above 10(6) PFU ml(-1). This phenomenon results from aggregation of viral particles at high concentrations. Compared with micron-sized particles, nanosized virus particles are easier to aerosolize because of reduced inertia. Reaerosolization from the BioSampler is demonstrated to be significantly less than that from the impinger. CONCLUSIONS: Reaerosolization from impingement sampling methods is a mode of loss in airborne virus sampling, although it is not as significant a limitation as the primary particle size of the aerosol. Utilizing a BioSampler coupled with short sampling periods to prevent high accumulative concentrations can minimize the impact of reaerosolization. SIGNIFICANCE AND IMPACT OF THE STUDY: This study confirms reaerosolization of virus particles to be a mode of loss in impingement sampling and identifies methods to minimize the loss.

Assessment of iodine-treated filter media for removal and inactivation of MS2 bacteriophage aerosols.

AIMS: To investigate the performance of an iodine-releasing filter medium for use as a protective device against airborne pathogens. METHODS AND RESULTS: The filter's physical and viable removal efficiencies (VRE) were investigated with challenges of MS2 bacteriophage aerosols, and the infectivity of MS2 collected on the filter was analysed. To test a proposed inactivation mechanism, media containing thiosulfate or bovine serum albumin (BSA) were put in impingers to quench and consume I(2) released from the filter. In direct plating experiments, treated filters presented significantly higher VREs than did untreated filters; however, collection in excess BSA decreased VRE by half and in thiosulfate the apparent VRE decreased drastically. No significant difference in infectivity of retained viruses on treated and untreated filters was observed at the same environmental condition. CONCLUSIONS: Evidence presented herein for competition by dissolved I(2) in infectivity assays supports a mechanism of induced displacement and capture of I(2.) It also requires that dissociation of iodine from the filter and capture of iodine by MS2 aerosols as they pass through the filter be factored in the design of the assessment methodology. The filter's strong retention capability minimizes reaerosolization but also makes it difficult to discriminate the antimicrobial effect at the surface. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows the direct plating assay method to be sensitive to interference by iodine-releasing materials. This requires reevaluation of earlier reports of VRE measurements.

The Dry Aerosol Deposition Device (DADD): an instrument for depositing microbial aerosols onto surfaces.

Concerns surrounding the contamination of infrastructure and equipment with biowarfare agents have led to the development of antimicrobial surfaces/coatings that are designed to "self-sterilize." Surfaces will likely be contaminated via an aerosol exposure and thus antimicrobial efficacy measurements should also be performed using biological aerosols. Standard methods that use microbial agents suspended in aqueous buffers may provide misleading results that overestimate the performance of the surface. A settling chamber is the most common instrument for applying biological aerosols to surfaces. However, settling chambers have some drawbacks (e.g., slow loading times, large footprint, variable loading, etc.) that make them undesirable for many applications. We have developed a Dry Aerosol Deposition Device (DADD) that uses impaction rather than settling to load surfaces with biological aerosols. The use of impaction allows for rapid and highly reproducible loading of microorganisms onto surfaces. We have demonstrated that the DADD can deliver both Bacillus atrophaeus spores and Staphylococcus aureus vegetative cells to glass coupons at concentrations exceeding 1x10(4) CFU/cm(2). The average coefficient of variation (CV) for sample-to-sample loading within an experiment was 13.6% for spores and 6.1% for S. aureus cells. The DADD is also a relatively simple and inexpensive device that can easily be contained within a 4-foot biological safety cabinet.

Efficacy of iodine-treated biocidal filter media against bacterial spore aerosols.

AIMS: To assess the effectiveness of iodine-treated biocidal filter media against bacterial spore aerosols. METHODS AND RESULTS: Bacillus subtilis spores were aerosolized and introduced into a filtration system. Both treated and untreated filters exhibited high viable removal efficiency (>99.996%) with negligible variation in pressure drop during the entire experiment. The viability of collected spores on the filter was investigated by enumeration of spores extracted from the filter by vortexing. At room temperature and low relative humidity (RH), the survival fraction of the treated filter was significantly lower than that of the untreated filter (P-value < 0.05). Meanwhile, at room temperature and high RH and at high temperature and high RH, the survival fractions on the treated medium were statistically the same as the untreated control at room temperature and low RH. CONCLUSIONS: Both treated and untreated filters achieved excellent viable removal efficiency for spores. The pressure drop of the treated filter was not affected by the iodine treatment. The viability of collected bacterial spores was decreased because of the exertion of iodine disinfectant. SIGNIFICANCE AND IMPACT OF THE STUDY: The evaluation demonstrates that the iodine-treated filter is a viable medium for respiratory protection against infectious spore aerosols. The results warrant further evaluation of smaller biological agents, which exhibit higher penetration.

Inequalities in public water supply fluoridation in Brazil: An ecological study.

BACKGROUND: The literature is scarce on the social and geographic inequalities in the access to and implementation of the fluoridation of public water supplies. This study adds knowledge to the Brazilian experience of the chronic privation of water and wastewater policies, access to potable water and fluoridation in the country. Thus, the aim of this study was to verify possible inequalities in the population's access to fluoridated drinking water in 246 Brazilian municipalities. METHODS: The information on the process of water fluoridation in the municipalities and in the macro region in which each municipality is located was obtained from the national epidemiological survey which was concluded in 2003. The data relating to the human development index at municipal level (HDI-M) and access to mains water came from the Brazilian Human Development Atlas, whilst the size of the population was obtained from a governmental source. The Fisher exact test (P < 0.05) was employed to identify significant associations between the explanatory variables and their ability to predict the principal outcomes of interest to this study, namely the presence or absence of the water fluoridation process in the municipalities as well as the length of time during which this measure has been implemented. Linear regression was used to observe the associations between the relevant variables in a multivariate environment. RESULTS: The results clearly showed that there is a relationship between municipalities with larger populations, located in more socio-economically advantaged regions and with better HDI-M, and where fluoridation is both present and has been implemented for a longer period of time (started before 1990). CONCLUSION: The findings suggest that the aim of treating water with fluoride may not be being adequately achieved, requiring more effective strategies so that access to this measure can be expanded equitably.