Varnish Formulations Research Articles

Preparation and properties of UV curing varnish suited for various substrates

UV-curing varnish has gained widespread application in the field of surface treatment due to its advantages such as low-temperature curing, easy fading, and environmental friendliness. The aim of this study is to develop a high-performance UV-curing varnish compatible with various substrates. Five prepolymers, Polymethyl Methacrylate (PMMA), Poly (methyl methacrylate-random-acrylic acid) P(MMA-r-AA), Poly (methyl methacrylate-random-glycidyl methacrylate-random-styrene) (P(MMA-r-GMA-r-St)), Poly (methyl methacrylate-random-butyl acrylate-random-glycidyl methacrylate) (P(MMA-r-BA-r-GMA)) and Poly (butyl acrylate-random acrylic acid-random glycidyl methacrylate-random styrene)(P(BA-r-AA-r-GMA-r-St)), were synthesized by free radical polymerization. The film-forming effect of prepolymer on 13 substrates such as glass, coated paper, polyethylene, polyethylene glycol terephthalate and low density polyethylene was investigated. Based on the results, the two prepolymers with the best film-forming properties were selected and combined with five distinct diluents and two types of photoinitiators to produce multiple UV-curing varnish formulations. The effects of the types of prepolymer, the types and contents of photoinitiator, the types of diluent and the ratios of prepolymer to diluent on the photocuring rate of UV curing varnish were investigated. The structures of prepolymer were characterized by Fourier infrared spectrometer. The experimental results show that PMMA and P(MMA-r-GMA-r-St) have better film-forming effects on 13 substrates. When the prepolymer is P(MMA-r-GMA-r-St), the photoinitiator is ITX, the photoinitiator content is 75 mg/mL, diethylenetriamine:GMA = 1:3 (diluent), and the ratio of prepolymer to diluent is 1:4, the photocuring rate of UV curing varnish is the fastest.

A Formulation for a New Environmentally Friendly Varnish for Paintings

Laropal® A81 is a urea-aldehyde resin used as a varnish for paintings requiring 30%–40% of aromatic solvents to be dissolved. Considering the dangers of aromatic solvents for the environment and health, an attempt was made to replace them with less impactful and low-toxic solvents. The present research investigates a new formulation with aliphatic hydrocarbons and esters (isobutyl isobutyrate, IBIB) as an alternative to traditional aromatics mixture. Traditional and alternative varnish formulations of Laropal® A81 were studied on an inert support and paint samples to test the resin by itself and in interaction with paint film, respectively. This study aims to compare the two different formulations of Laropal® A81 by evaluating their optical, colorimetric, and stability proprieties before and after natural and accelerated ageing. Colorimetry and spectroscopic techniques (transmittance and reflectance UV-VIS-NIR, FORS, transmittance and total reflectance FT-IR, and 1H-NMR) were used for the assessment. Very promising results have been obtained with the application of the alternative formulation, with data comparable to those of the traditional formulation, paving the way for the replacement of the aromatic-based solvents traditionally used with IBIB. This allows a safer and more sustainable conservation practice with considerable benefits for the health of the operators and the environment.

Stradivari's Varnish Revisited: Feature Improvements Using Chemical Modification.

The most widespread varnish formulations used by master violin-makers of the "Italian Golden Age", including Antonio Stradivari, were based on mixtures of siccative oils (e.g., linseed oil) and natural resins (e.g., colophony). Similar formulations are still used for the finish of contemporary instruments. Although most precious violins made by Stradivari and other Cremonese Masters are kept in museums, several instruments are still played and their finish may undergo deterioration due to contact with the players. Moreover, the decay of the traditional varnish may occur due to mechanical stress and natural aging caused by environmental agents (e.g., exposure to uncontrolled light, humidity, and temperature changes). The main aim of this research work is to investigate the possible improvement of varnish resistance to the decay induced by different aging processes. For this purpose, the traditional varnish (linseed oil/colophony 3:1 w/w) was recreated in the laboratory following an ancient recipe and then it was functionalized with a cross-linking agent (3-Glycidyloxypropyltrimethoxysilane, GLYMO). Plain and functionalized varnishes underwent artificial aging (UV light, temperature, and humidity variations), and their properties were comparatively studied using different techniques. All the results suggest that the functionalized varnish displays improved resistance to the aging process and particularly enhanced photostability and increased hardness (resistance to scratches).

Evaluation of the Cytocompatibility of Fluoride Varnish and Its Effect on Human Gingival Fibroblasts (hGFs): An In Vitro Study.

Introduction Untreated dental decay poses a significant oral health challenge, leading to pain, tooth loss, and infections. Fluoride varnishes are in prolonged contact with the tooth surface and thisprevents dental decay. However, limited research has been conducted regarding the cytotoxicity and cytocompatibility of varnishes on oral cells. Recent studies have shed light on the cytotoxic effect of these varnishes on human fibroblast cells. Material and Methods The fibroblasts were isolated and cultured in0.00001, 0.0001, 0.001, 0.01, 0.1, and 1 % fluoride concentration The cells were incubated for 72 hours at a temperature of 37°C and cell viability after the application of varnish was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) assay. Results This study observed that fluoride varnish had a concentration dependant cytotoxic effect on human gingival fibroblasts (hGFs). As the concentration of fluoride increased, the cell viability decreased. At 1% concentration, there was maximum cell cytotoxicity.At the lowest concentration (0.00001), more than 78% of the cells were found to be viable. Conclusion Further research is necessary to develop safer and more biocompatible fluoride varnish formulations to ensure their efficacy in preventing dental caries without causing harm to oral tissues.

Flame-retardant performance of phosphorylated furan-containing alkyd resins

Over the past decade, with the emergence of environmental and human health concerns, research has focused on developing new solutions to replace fossil resources with more sustainable biobased resources. Furan derivatives can be obtained from plants, and their structures provide high resistance to high temperatures. Furan derivatives have been functionalized with phosphorus (P) to increase their fire-resistance properties. Thus, a new biobased bisfuran containing nitrogen and phosphorus (diethyl (((3-((((diethoxyphosphoryl)(hydroxy)(4-(hydroxymethyl)cyclopenta-1,3-dien-1-yl)methyl)amino)methyl)benzyl)amino)(hydroxy)(4-(hydroxymethyl)cyclopenta-1,3-dien-1-yl)methyl)phosphonate (HMF-MXDA-DEP)) was synthesized and used for the first time in polymerization to develop alkyd resins. The flame-retardant (FR) properties of these resins were studied. Alkyd resins are generally used as a binder in paint or varnish formulations. The use of a reactive FR during the polycondensation reaction of alkyd resins makes it possible to form covalent bonds and offer better durability over time. The impact of HMF-MXDA-DEP on film properties such as drying time, flexibility, adhesion and color was studied, and the thermal and FR properties were evaluated by differential scanning calorimetry, thermogravimetric analysis and pyrolysis–combustion flow calorimetry. Increased thermal stability and good FR properties of alkyd resins were demonstrated. In the cone calorimeter test, the lowest peak heat release rate (pHRR) was obtained with a coating of 2 wt% phosphorus HMF-MXDA-DEP on wood, and a 49% decrease in pHRR compared with that of FR-free alkyd resins was demonstrated.

Bioactive surfaces with well-defined amphiphilic copolymers containing a natural terpene-based monomer

New amphiphilic cationic copolymers based on poly((methacryloyloxy) ethyl trimethylammonium chloride) (PMETAC) and bio-based poly(thymol methacrylate) (PTMA) were prepared by atom transfer radical polymerization (ATRP) methods, using low concentration of metal catalyst and a bio-based eutectic mixture (EM), composed of L-menthol and thymol. The antimicrobial activity of the polymers was evaluated against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria.The results in solution showed that increasing the terpenic segment (PTMA) in the copolymers resulted in lower antimicrobial activity against S. aureus (as the MIC increases from 3.1 to 100 μM) and higher activity against E. coli (as the MIC decreases from 400 to 200 μM).Scanning electron microscopy (SEM) analysis suggests that polymers affected the bacterial viability by damaging the cell structure. The synthesized biocidal polymers were used as additives in polyurethane-based varnish formulations to produce bioactive coated surfaces that were found to be more active against E. coli. Coatings containing either PTMA or PMETAC homopolymers were more efficient than those containing PMETAC-co-PTMA copolymers. A dramatic improvement in the antimicrobial activity of PMETAC-containing varnish against both S. aureus (3 orders of magnitude) and E. coli (4 orders of magnitude) was observed when an aqueous solution of the homopolymer was applied to the dried varnish instead of being incorporated into the varnish formulation. The strategy presented here is simple and opens the door for the preparation of customized bioactive surfaces to prevent bacterial infections.

In vitro determination of the remineralizing potential and cytotoxicity of non-fluoride dental varnish containing bioactive glass, eggshell, and eggshell membrane.

This study compares in vitro remineralization potential and cytotoxicity of fluoride-free varnish combinations containing bioactive glass, eggshell, and membrane powder and fluoride varnish formulations on artificial caries lesions. Artificial caries lesions were formed in two windows on third molars. One of the windows was coated with one of the following varnish formulations: FV (fluoride varnish), F-BAGV (fluoride and bioactive glass containing varnish), BAGV (bioactive glass containing varnish), EPV (eggshell powder containing varnish), EMP-EPV (eggshell membrane protein and eggshell powder containing varnish), STMP-EMP-EPV (sodium trimetaphosphate-treated eggshell membrane protein and eggshell powder containing varnish). The samples were remineralized, then investigated under scanning electron microscopy, and elemental analyses were performed by X-ray dispersive analysis (EDX). In addition, the traditional colorimetric tetrazolium-based reduction assay (XTT) and the modern impedance-based real-time cell analysis system (RTCA) were used to investigate their cytotoxicity. The varnish applied area's Ca/P ratio was lower than stoichiometric hydroxyapatite except for EPV (1.66) and STMP-EMP-EPV (1.67) groups. Undiluted extracts of all varnishes, 1:2 dilutions of FV and F-BAGV groups were cytotoxic in XTT assay. In RTCA, the normalised cell index of the EMP-EPV and STMP-EMP-EPV groups was higher than the control group. Bioactive glass, eggshell, eggshell membrane proteins and STMP-treated eggshell and eggshell membrane protein containing varnish have similar remineralizing effect to fluoride-containing varnish on demineralized enamel. Integrating biological or bioactive components instead of fluoride into the dental varnishes might reduce cytotoxicity.

Evaluation of Natural Oil Adducts in Alkyd-Based Varnish Emulsion and Effect on Rowan (Sorbus torminalis) Wood

In these days, preparation of eco-friendly wood surface coating agents has become important topic for environmental concerns. In this study, an alternative surface coating formulations was prepared with adducts of oils of apricot kernel (A), sesame (S) and grape seed (G) were mixed with oil modified alkyd-based synthetic varnish system. These emulsions were applied on Rowan (Sorbus torminalis) wood and exposed artificial UV irradiation. However, all emulsion coated samples show lower water sorptions regardless of conditions or level of treatments. Increasing adduct charges from 5.0% to 10% have not considerably effects for water sorptions. The reducing water sorption properties of 35.5%, 35.2% and 39.4% were obtained with 10% sesame oil-varnish coated samples of 10Sı and 10 Sıı in one- and two-time coatings and three-times coated samples of 5Sııı in 5.0% sesame oil-varnish emulsion coatings, respectively. Moreover, selected oil adducts into varnish had one and two point lowering effects on coated surface hardness (in 4H-5H levels). The UV exposure seems to not much influence on surface hardness properties. The similar tendency were also observed for cross-cut resistance that marginally similar adhesion (scratch resistance) for both control and UV exposured samples. Increasing coatings and charge of apricot kernel oil in varnish emulsion looks like more effective than other varnish formulations, in terms of gloss stability. However, increasing adducts charges and UV radiation time, have more less similar effects on all coated and UV irradiated samples.

Light-Activated Antimicrobial Surfaces Using Industrial Varnish Formulations to Mitigate the Incidence of Nosocomial Infections.

Evidence has shown that hospital surfaces are one of the major vehicles of nosocomial infections caused by drug-resistant pathogens. Smart surface coatings presenting multiple antimicrobial activity mechanisms have emerged as an advanced approach to safely prevent this type of infection. In this work, industrial waterborne polyurethane varnish formulations containing for the first time cationic polymeric biocides (SPBs) combined with photosensitizer curcumin were developed to afford contact-active and light-responsive antimicrobial surfaces. SPBs were prepared by atom transfer radical polymerization, which allows control over the polymer features that influence antimicrobial efficiency (e.g., molecular weight), while natural curcumin was employed to impart photodynamic activity to the surface. Antibacterial testing against Gram-negative Escherichia coli revealed that glass surfaces coated with the new formulations displayed photokilling effect under white-light (42 mW/cm2) irradiation within only 15 min of exposure. In addition, it was observed a combined antimicrobial effect between the two biocides (cationic SPB and curcumin), with a higher reduction in the number of viable bacteria observed for the surfaces containing cationic SPB/curcumin mixtures in comparison with the one obtained for surfaces only with polymer or without biocides. The waterborne industrial varnish formulations allowed the formation of homogeneous films without the need for addition of a coalescing agent, which can be potentially applied in diverse surface substrates to reduce bacterial transmission infections in healthcare environments.

Composições de Solventes de Baixa Toxicidade para Formulação de Vernizes de Uso em Restauro

Varnishes consist basically of a resin and solvent. Aromatic solvents are widely used for varnish formulations, but they present considerable toxicity which requires their replacement. Two binary solvent systems with an oxygenated solvent (ethyl acetate or isoamyl acetate) and cyclohexane were studied as possible substitutes for xylene in varnish formulations. The toxicity of solvents was analyzed using data from the Globally Harmonized System of Classification and Labeling of Chemicals and the National Institute for Occupational Safety and Health. The solubility of Damar, Paraloid B72, Regalrez 1094, and Laropal K80 resins in these solvents was evaluated by Hansen and Teas Solubility Parameters, sigma profiles, and experimental method. Vapor pressure measurements were obtained from solvents and viscosity and gloss measurements from varnish formulations. The results indicated the potential of binary solvent systems as substitutes for xylene, but require further studies on their effects on pictorial materials on which they are applied.

Fluoride varnish containing chitosan demonstrated sustained fluoride release.

Fluoride varnish is a professionally applied product that prevents dental caries. However, fluoride varnishes do not provide sustained fluoride release. The objective of this study was to prepare fluoride varnish formulations containing various amounts of chitosan that would generate sustained fluoride release. We evaluated their chemical structure, viscosity, and in vitro fluoride release. Furthermore, the 3-(4, 5-dimethylthiazolyl-2)-2,5diphenyltetrazolium bromide (MTT) assay and direct contact test were used to determine varnish cytotoxicity. We found that all fluoride varnish formulations had the same chemical structure. Their viscosity demonstrated a chitosan concentration-dependent increase. In vitro fluoride release showed a sustained fluoride release. The chitosan fluoride varnishes were cytotoxic to human gingival fibroblasts. We propose the new fluoride varnish formulation as a potential material to be used as a sustained release fluoride varnish.

Synthesis and evaluation of new anti-microbial additive based on pyrimidine derivative incorporated physically into polyurethane varnish for surface coating and into printing ink paste

In this study, heterocyclic compounds containing 3-((4-bromophenyl)diazenyl)-5-(methylthio)-6-(phenylsulfonyl)pyrazolo-[1,5-a]pyrimidine-2,7-diamine (compound II) and 4-(methylthio)-3-phenylsulfonyl)benzo[4,5]imidazo[1,2-a]pyrimidin-2-amine (compound III) were prepared and their chemical structures were confirmed by spectral data. The new compounds were screened for antimicrobial activity against six different microbial strains when physically incorporated into polyurethane varnish formula and printing ink paste. Experimental coatings were manufactured on laboratory scale and applied by brush onto glass and steel panels. Results of the biological activity indicated that polyurethane varnishes and printing ink paste containing compounds II and III exhibit a very good antimicrobial effect. The physical and mechanical resistances of the polyurethane varnish formulations were also studied to evaluate any drawbacks associated with this addition. The studies revealed that the physical incorporation of compounds II and III enhances slightly the physical and mechanical properties.

Clinical Effectiveness of Two Commercial Fluoride Varnish Formulations on the Control of White Spot Lesion in Primary Teeth: A Pilot Study

Objective: To evaluate the in vivo clinical effectiveness of two commercial fluoride varnish formulations. Material and Methods: The sample consisted of seven children aged 2-5 years for a total of 24 active white spot lesions (WSL) in primary teeth. Children were randomly divided into two groups in accordance with the varnish used: G1 - Duraphat® - DR (n = 14 WSL); and G2 - Duofluorid XII® - DF (n = 10 WSL). Children were submitted to treatment with varnishes applied once a week for four consecutive weeks. Maximum mesiodistal and incisogengival dimensions were measured with a periodontal probe at the beginning of treatment and on the fifth week of treatment. The average between the two dimensions represented the value of the WSL dimension. The comparison of the mean final values of WSL dimensions between groups of fluoride varnishes tested was analyzed by the Mann-Whitney U test. The significance level adopted was 5%. Results: After five weeks, most WSL were ranked as inactive (G1 = 71.4% and G2 = 40%). No significant difference between G1 and G2 in relation to lesion activity was observed (p = 0.124). There was a significant decrease of 24% between initial (3.12 mm ± 1.49 mm) and final WSL dimension (2.35 mm ± 1.06 mm) (p = 0.012) in G1. In G2, there was a significant reduction of 40% in lesion dimension with initial value of 5.7 mm (± 3.82 mm) and final value of 3.4 mm (± 3.35 mm) (p = 0.013). Regarding the reduction in the WSL dimension, no significant difference between groups was observed (p = 0.931). Conclusion: Both fluoride varnish formulations tested had similar effect on the control of active white spot lesions in primary teeth.

Synthesis and characterization of coumarin thiazole derivative 2-(2-amino-1,3-thiazol-4-yl)-3H-benzo[f]chromen-3-one with anti-microbial activity and its potential application in antimicrobial polyurethane coating

Coumarin, thiazole and their respective derivative products are some of the oldest and most commonly known class of nitrogen and sulphur containing compounds. In recent years there has been considerable interest in this coumarin–thiazole derivatives, which have been reported to exhibit significant biological activity and are widely used as pharmaceuticals. They are capable of imparting anti-microbial activity properties when incorporated into polymers and polymer composites. In this research, coumarin–thiazole derivative 2-(2-amino-1,3-thiazol-4-yl)-3H benzo[f]chromen-3-one (compound III), was prepared and its structure was confirmed by means of its spectra data. It was also screened for its anti-microbial activity against eight different micro-organisms when physically incorporated into a polyurethane varnish formula. Experimental coatings were manufactured on a laboratory scale and applied by means of a brush on both glass and steel panels. The results of the biological activity indicated that the polyurethane varnishes containing the 2-(2-amino-1,3-thiazol-4-yl)-3H-benzo[f]chromen-3-one (compound III) derivative, exhibit a very good antimicrobial effect. The molecular modeling study revealed that it is biologically safe, it is active and it fulfills Lipinski's rule of five. The physical and mechanical resistances of the polyurethane varnish formulations were also studied to evaluate any drawbacks associated with the addition of the derivative. The studies indicate that the physical incorporation of compound III actually enhances slightly both the physical and mechanical properties.

In-Line Monitoring of the Thickness of Printed Layers by NIR Spectroscopy: Elimination of the Effect of the Varnish Formulation on the Prediction of the Coating Weight

Near-infrared (NIR) reflection spectroscopy was used for in-line monitoring of the coating weight of printed layers of acrylate-based clear varnishes. Quantitative analysis of the spectral data was carried out by means of chemometric techniques based on partial least-squares (PLS) regression. The influence of variations of the chemical composition of the varnish formulations on the multivariate calibration models may lead to mispredictions of the coating weight. Therefore, it was compensated by special calibration procedures. Two different approaches were compared. Single-stage universal calibration included the different varnish formulations into one joint PLS model. Alternatively, the multistage procedure combined a preliminary identification step with subsequent quantitative analysis using specific calibration models for each varnish. The efficiency of both approaches was investigated by the prediction of the coating weights of independent test samples. Moreover, in-line measurements were carried out a...

Aromatic amine‐epoxidized sunflower free‐fatty‐acid adducts as corrosion inhibitors in epoxy‐curable varnishes

AbstractWith strict regulation of environmental pollution, sunflower fatty acids were used to prepare high‐molecular‐weight aromatic amine adducts by reaction of their epoxidized form [epoxidized sunflower free fatty acid (ESFA)] with five aromatic amines [o‐toluidine (o‐T), m‐toluidine (m‐T), p‐toluidine (p‐T), p‐anizidine (p‐A), and p‐chloroaniline (p‐ClA)] under severe conditions of an inert atmosphere and high temperature. The produced adducts were characterized physically, chemically, and by IR spectroscopy. The acid values and oxirane contents of the prepared adducts were determined to confirm the participation of carboxylic groups and epoxy groups, respectively, in the reaction of ESFA with aromatic amines. Also, to avoid volatile organic compounds, the prepared adducts of ESFA (o‐T–ESFA, m‐T–ESFA, p‐T–ESFA, p‐A–ESFA, and p‐ClA–ESFA) were evaluated as corrosion inhibitors of mild steel in electron‐beam‐curable epoxy acrylate oligomer formulations. Physical and mechanical measurements were carried out, in addition to corrosion‐resistance tests and weight loss measurements of the coated steel panels. The optimum concentration of each adduct was determined for the prepared formulations. The corrosion‐inhibition efficiency of the adducts in varnish formulations were determined. It was found that varnish formulations containing the prepared aromatic amine adducts could protect steel from corrosion. The corrosion‐inhibition efficiencies of the prepared aromatic amines in epoxy acrylate oligomer varnishes were arranged as follows: p‐A–ESFA > p‐T–ESFA > m‐T–ESFA > o‐T–ESFA > p‐ClA–ESFA. Superior corrosion‐inhibition efficiency was obtained in the varnish formula containing 0.6% p‐A–ESFA adduct. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis and characterization of a nanocomposite anti-corrosion waterborne epoxy coating

In this study, polyamidoamine hardener (PAH) is modified with 3-glycidoxypropyltrimethoxysilane (GPTMS) through ring opening addition polymerization reaction. The structural elucidation of the siloxane-modified hardener (SMH) was carried out by FT-IR spectroscopic technique. Average particle size of silica particles in the solution of SMH was about 5 nm using light scattering technique. Using PAH as control, PAH and SMH were mixed with diglycidyl ether of bisphenol A (DGEBA) epoxy resin and applied on mild steel strips as varnish formulations. Then, the epoxy-PAH and epoxy-SMH coated panels were cured at room temperature. Evaluated by salt-spray tests, the anti-corrosive performance of the epoxy-SMH varnish was remarkably enhanced in comparison with that of the epoxy-PAH varnish. Moreover, scanning electron microscopy (SEM) was used to monitor the interface of the varnish films with the substrate. Surface topography of the coatings investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM) indicated that the silica particles’ dimensions of the siloxane-modifed coating are at the nanoscale.

Preparation and application of new ecofriendly inhibitor in varnishes for protection of corrosion of steel

5-mercapto-1-methyl tetrazole (5-MMT) has been reacted with epoxidised soybean oil in sealed ampoule at ≥130°C for 5 h. The reaction product was characterised physically and was evaluated with infrared spectroscopy and gel permeation chromatography. Different concentrations of 5-MMT adduct have been incorporated in varnish formulations based on medium soya oil alkyd to detect the optimum concentration of adduct as corrosion inhibitor. Chemical, mechanical, corrosion resistance and water up-take tests of varnish films were measured. Weight loss measurements (mg cm–2), for mild steel panels under varnish films and the mild steel corrosion inhibition efficiency of adduct have been determined. It was found that the reaction between epoxidised soybean oil and thiol compound has taken place successfully. The reaction product was relatively high molecular weight adduct and had suitable characteristics to inhibit corrosion of steel. Also it was found that, the prepared adduct could protect steel from corrosion with 0·02 g adduct per 100 g varnish.

Therapeutic effect of two fluoride varnishes on white spot lesions: a randomized clinical trial

The aim of this randomized clinical trial study was to evaluate the therapeutic effect of two varnish formulations (G1 = 5% NaF, G2 = 6% NaF + 6% CaF(2)) on the remineralization of white spot lesions (WSL). The sample was composed of 15 (7- to 12-year-old) children with 45 active WSL in anterior permanent teeth. The children were randomly divided into two groups providing 22 lesions for G1 and 23 for G2. The children were submitted to weekly varnish applications 4 times. The WSL were evaluated twice: baseline and on week 4. Maximum lesion dimensions (mesiodistal and incisogingival) were measured in millimeters and classified in four grades of size. WSL were also assessed regarding lesion activity by one calibrated examiner. The Pearson chi-square and Fisher's exact tests were used (P < 0.01). WSL reductions were observed in both varnish groups (Chi-square = 0.15, d.f. = 1, P = 0.90), and with similar magnitude (in mm): 1.19 and 1.29 for G1 and G2, respectively. Thirty-six WSL (15 in G1 and 21 in G2) were classified as inactive on week 4, reaching an overall value of 80%. No difference was observed between G1 and G2 regarding activity scores (Fisher's exact test, p > 0.01). It was concluded that after 4 applications the two varnish formulations tested produced similar clinical effects, indicating the reduction and the control of carious activity in most WSL.

The Effect of Chlorhexidine Varnish Treatment on Salivary Mutans Streptococcal Levels in Child Orthodontic Patients

A chlorhexidine dental varnish was applied to the teeth of 26 children, ten to 17 years of age, in an attempt to limit the increase in colonization by mutans streptococci that normally accompanies the placement of fixed orthodontic appliances and to assess the acceptance of the application procedure. Despite the insertion of the appliances in the month following the varnish application, the numbers of detectable salivary mutans streptococci in the children were found to remain significantly lower than baseline values for seven months (p less than 0.01). Among the 26 children, 16 exhibited high counts (greater than 2.5 x 10(5) cfu/mL saliva) at baseline, but none exhibited such counts until three months post-treatment, when one child did. By seven months, eight children had high counts. No significant difference in effectiveness was observed between varnish formulations containing 10% or 20% chlorhexidine acetate, or between children of different ages or past caries experience. The lack of drop-outs and the results of a questionnaire indicated that acceptance of the treatment by the children was excellent. The study indicates that chlorhexidine varnish therapy was acceptable to the children and was effective in suppressing oral mutans streptococcal levels for long periods, even when used prior to the placement of fixed orthodontic appliances.