Can glass polyalkenoate (glass-ionomer) dental cements be considered bioactive? A review.

Objectives: This paper reviews the chemical behaviour of glass polyalkenoate (glass-ionomer) dental cements, both conventional and resin-modified, in contact with natural tissues, with the aim of determining whether these materials can be considered to be bioactive. Data: Relevant papers describing the behaviour of bioactive glasses and ceramics, and glass-ionomer (glass polyalkenoate) cements have been identified using PubMed and Science Direct. This has allowed a comparison to be made between the behaviour of glass-ionomers and the speciality glasses and ceramics that are widely classified as bioactive, a designation considered valid for over fifty years. More recent papers concerning bioactive metals and polymers have also been studied and both in vitro and in vivo studies are included. Sources: Have included general papers on the chemistry and biological behaviour of bioactive glasses and ceramics, as well as papers on glass-ionomers dealing with (i) ion release, (ii) bonding to the surface of teeth, (iii) influence on surrounding pH and (iv) interaction with bone. Conclusion: The literature shows that glass-ionomers (glass polyalkenoates) have three types of behaviour that are similar to those of bioactive glasses as follows: Formation of direct bonds to living tissue (teeth and bones) without fibrous capsule; release of biologically beneficial ions; and change of the local pH. However, in in vitro tests, they do not cause calcium phosphate to precipitate from solutions of simulated body fluid, SBF. Despite this, studies show that, in patients, glass-ionomers interact chemically with hard tissues and this suggests that may indeed be considered bioactive.

Fluoride exchange by glass-ionomer dental cements and its clinical effects: a review.

The topic of fluoride release and uptake by glass-ionomer (glass polyalkenoate) dental cements is reviewed. The study was based on a literature search carried out using PubMed. The main key words used were glass-ionomer and fluoride, and further refinements were made by adding the keywords anti-microbial, anti-caries and remineralization. Papers were selected from the initial search, which concentrated on fundamental aspects of fluoride release, including kinetics and the influence of the cement composition, and resulting clinical performance against caries. Other relevant papers were cited where they added useful and relevant data. From these published papers, it was possible to explain the detailed mechanism of fluoride release by glass-ionomer cements and also its uptake. Fluoride release has been shown to be a two-step process. In neutral solutions, the steps can be divided into early wash-out and long-term diffusion. In acid conditions, the early wash-out remains, though with greater amounts of fluoride released, and the long-term release becomes one of slow dissolution. The effect of fluoride on the viability of oral micro-organisms has been described, and glass-ionomers have been shown to release sufficient fluoride to reduce the size and viability of adjacent populations of oral bacteria. The effect of low levels of fluoride on the remineralization of tooth tissue has been considered. Levels needed to increase remineralization are much lower than those needed to adversely affect oral bacteria, from which we conclude that glass-ionomers release sufficient fluoride to promote remineralization. Despite this, there remains uncertainty about their overall contribution to sound oral health, given the widespread use of other sources of fluoride, such as toothpastes.

Apical Extrusion of Debris during Root Canal Preparation with ProTaper Next, WaveOne Gold and Twisted Files.

(1) Background: Apical extrusion of debris is an example of a complication that may arise during root canal treatment, and it has been proven to be an unavoidable occurrence during endodontic treatment by numerous authors. Even though it may not hinder the long-term outcome of treatment, it may lead directly to increased levels of postoperative pain and, therefore, lower levels of patient acceptance and satisfaction. The aim of the study was to assess the weight of apically extruded debris during root canal preparation with instruments that use different movement kinematics (rotary, reciprocating, and adaptive motion); (2) Methods: The study was performed using the Myers and Montgomery model. Sixty human premolar teeth were inserted into preweighed Eppendorf tubes and randomly classified into three groups. After manual glide-path preparation, teeth in each group were instrumented to working length set 1 mm short of the anatomical apex using the standard sequence provided by the manufacturers (for Group 1: ProTaper Next X1 & X2; for Group 2: WaveOne Gold Primary, for Group 3: Twisted Files SM1-SM3). Root canals were irrigated with 1 mL of 0.9% NaCl solution between each file insertion. The tubes with collected debris were stored in an incubator at 70 °C for 5 days in order to evaporate the liquid component. Measurement of the weight of extruded debris was performed by subtracting the preinstrumentation from the postinstrumentation weight of the tubes. The results were analyzed with Kruskal-Wallis ANOVA, with significance level set at 0.05; (3) Results: The weight of extruded debris was 0.337 mg (SD = 0.148) for Group 1, 0.305 mg (SD = 0.201) for Group 2, and 0.348 mg (SD = 0.135) for Group 3. (4) Conclusions: Engine-driven root canal preparation with the use of instruments ProTaper Next, WaveOne Gold and Twisted Files that use different movement kinematics (rotary, reciprocating, and adaptive motion) was associated with apical extrusion of debris to a similar extent.

Surface Studies on Glass Powders Used in Commercial Glass-Ionomer Dental Cements.

The surface properties of three commercial ionomer glass powders, i.e., Fuji IX, Kavitan Plus and Chemadent G-J-W were studied. Samples were analyzed by X-ray fluorescence spectroscopy (XRF), and the density was determined by gas pycnometry. Morphology was studied using scanning electron microscopy (SEM) and laser diffraction (LD) technique, whereas low-temperature nitrogen sorption measurements determined textural parameters like specific surface area and pore volume. Thermal transformations in the materials studied were evaluated by thermogravimetric analysis (TGA), which was carried out in an inert atmosphere between 30 °C and 900 °C. XRF showed that Fuji IX and Kavitan Plus powders were strontium-based, whereas Chemadent G-J-W powder was calcium-based. Powders all had a wide range of particle sizes under SEM and LD measurements. Specific surface areas and pore volumes were in the range 1.42-2.73 m2/g and 0.0029 to 0.0083 cm3/g, respectively, whereas densities were in the range 2.6428-2.8362 g/cm3. Thermogravimetric analysis showed that the glass powders lost mass in a series of steps, with Fuji IX powder showing the highest number, some of which are attributed to the dehydration and decomposition of the polyacrylic acid present in this powder. Mass losses were more straightforward for the other two glasses. All three powders showed distinct losses at around 780 °C and 835 °C, suggesting that similar dehydration steps occur in all these glasses. Other steps, which differed between glass powders, are attributed to variations in states of water-binding on their surfaces.

Novel nanosystems to enhance biological activity of hydroxyapatite against dental caries.

This work aimed to study for the first time to our knowledge the influence of the structure of the dental flosses (DF) coated by hydroxyapatite nanoparticles (HAP NPs) on the biological performance of saliva probiotic bacteria (S. salivarius), and human dermal and osteoblast-like cells. We used three types of HAP@DF composites (based on two unwaxed dental flosses - "fluffy" and "smooth", and one waxed "smooth") with different morphologies. Obtained composites were characterized from the point of view of their structure, morphological characteristics, elemental and chemical composition. We observed that HAP NPs coated "smooth" dental flosses led to an increase of viability and proliferation of oral cavity probiotic bacteria (Streptococcus salivarius) and human cells (dermal fibroblasts and osteoblast-like). In contrast, the highest viability loss of probiotic bacteria (S. salivarius), fibroblasts, and osteoblast-like cells were observed for "fluffy" unwaxed dental flosses due to high cytotoxicity. Our studies showed that HAP NPs significantly improved the biological properties of "fluffy" dental floss. Pristine "smooth" DFs (waxed and unwaxed), as well as all HAP-coated DFs, induced acceptable biocompatibility toward selected human cells.

Inverse gas chromatography in the examination of adhesion between tooth hard tissues and restorative dental materials.

The adhesion is a crucial issue in the bonding of dental restorative materials to tooth hard tissues. A strong and durable bond between artificial and natural materials is responsible for the success of the restoration in the oral cavity; therefore it has to be thoroughly examined before new restorative material is introduced to the market and used clinically. Among all methods used to examine bonding strength, most of them require a large number of healthy teeth to be conducted. In this paper, the bond strength between tooth hard tissues (dentin and enamel) and an exemplary restorative composite was examined with the non-conventional method, i.e. inverse gas chromatography. Dentin and enamel from bovine teeth were separated and subjected to the standard preparation procedure using the 3-component etch-and-rinse commercial bonding system. Tissues, as well as commercial restorative composite, were examined using inverse gas chromatography. The work of adhesion between dentin/enamel and composite was calculated. Obtained results were compared with the values of shear bond strength of six configurations, i.e. etched dentin/enamel-composite, primed dentin/enamel-composite, and bonded dentin/enamel-composite. All obtained results proved that there is a correlation between the values describing bond strength obtained from inverse gas chromatography and direct mechanical tests (shear bond strength tests). It proves that inverse gas chromatography is a powerful perspective tool for the examination of bond strength between tooth hard tissues and potential dental materials without using a large number of health tooth tissues.

Enhancing the Mechanical Properties of Glass-Ionomer Dental Cements: A Review.

This paper reviews the strategies that have been reported in the literature to attempt to reinforce glass-ionomer dental cements, both conventional and resin-modified. These cements are widely used in current clinical practice, but their use is limited to regions where loading is not high. Reinforcement might extend these applications, particularly to the posterior dentition. A variety of strategies have been identified, including the use of fibres, nanoparticles, and larger particle additives. One problem revealed by the literature survey is the limited extent to which researchers have used International Standard test methods. This makes comparison of results very difficult. However, it does seem possible to draw conclusions from this substantial body of work and these are (1) that powders with conventional particle sizes do not reinforce glass-ionomer cements, (2) certain fibres and certain nanoparticles give distinct improvements in strength, and (3) in the case of the nanoparticles these improvements are associated with differences in the morphology of the cement matrix, in particular, a reduction in the porosity. Despite these improvements, none of the developments has yet been translated into clinical use.

The effect of bonding system application on surface characteristics of bovine dentin and enamel.

The main objective of this study was to examine the surface changes of bovine teeth hard tissues (dentin and enamel) after surface preparation with the use of commercial 3-component etch-and-rinse bonding system. Surface composition changes, morphology, BET specific surface area and surface energy parameters were examined after etching, application of primer and adhesive. Characteristic of tissues composition was carried out with the use of Raman spectroscopy. Morphological changes were followed by scanning electron microscopy, while specific surface area values were measured by the means of gas porosimetry. For the first time surface energy of prepared teeth hard tissues was studied with the use of inverse gas chromatography. A detailed characteristic of surface parameters of bovine teeth hard tissues was made. Obtained results show that each step of dentin and enamel preparation is reflected in all studied parameters. Application of etchant, primer and adhesive causes an increase of surface activity of all examined tissues, measured as surface energy parameters. Surface parameters changes caused by the application of bonding system are crucial from dentin/enamel - restorative material adhesion point of view.

The effect of petroleum jelly, light-cured varnish and different storage media on the flexural strength of glass ionomer dental cements.

This study determined the influence of coating with either petroleum jelly or light-cured varnish and storage medium on the flexural strength of glass-ionomer cements (GIC). The flexural strength of two glass-ionomer cements (Fuji Equia Fil and Ketac Molar Aplicap) was measured. Specimens (2 × 2 × 25 mm) were prepared in three groups: uncoated, coated with petroleum jelly, or coated with light-cured varnish (EquiaCoat) cured for 20 s using a cure lamp (Bluephase G2, Ivoclar Vivadent, Schaan, Liechtenstein). Specimens were stored for 1 week at 37 °C in water, artificial saliva or 20 mmol dm-3 lactic acid, then flexural strength was determined in 3-pont bend. Data were analyzed by ANOVA and Tukey HSD post hoc test (p < 0.05). In addition, the mold was filled with water and the temperature change caused by the cure lamp was measured with a thermocouple. For both materials, storage in water gave the lowest flexural strength. It was slightly higher in either saliva or lactic acid, and was improved by coating in petroleum jelly. Specimens coated with light-cured varnish, that also involved heating with a cure lamp, gave the highest flexural strength. The heating effect of the lamp was demonstrated by the temperature rise in the water in the mold after light exposure from 21.9 (± 1.0) °C to 26.8 (± 1.0) °C. hence, sealing of GIC from aqueous media improves flexural strength. The cure lamp emitted heat, which may enhance the flexural strength of specimens coated with light-cured varnish.

Heat transfer properties and thermal cure of glass-ionomer dental cements.

Under clinical conditions, conventional glass-ionomer dental cements can be cured by application of heat from dental cure lamps, which causes acceleration in the setting. In order for this to be successful, such heat must be able to spread sufficiently through the cement to enhance cure, but not transmit heat so effectively that the underlying dental pulp of the tooth is damaged. The current study was aimed at measuring heat transfer properties of modern restorative glass-ionomers to determine the extent to which they meet these twin requirements. Three commercial glass ionomer cements (Ionofil Molar, Ketac Molar and Equia™ Fill) were used in association with three different light emitting diode cure lamps designed for clinical use. In addition, for each cement, one set of specimens was allowed to cure without application of a lamp. Temperature changes were measured at three different depths (2, 3 and 4 mm) after cure times of 20, 40 and 60 s. The difference among the tested groups was evaluated by ANOVA (P < 0.05) and post hoc Newman-Keuls test. All brands of glass-ionomer showed a small inherent setting exotherm in the absence of heat irradiation, but much greater temperature increases when exposed to the cure lamp. However, temperature rises did not exceed 12.9 °C. Application of the cure lamp led to the establishment of a temperature gradient throughout each specimen. Differences were typically significant (P < 0.05) and did not reflect the nominal power of the lamps, because those lamps have variable cooling systems, and are designed to optimize light output, not heating effect. Because the thermal conductivity of glass-ionomers is low, temperature rises at 4 mm depths were much lower than at 2 mm. At no time did the temperature rise sufficiently to cause concern about potential damage to the pulp.

Surface energy of bovine dentin and enamel by means of inverse gas chromatography.

Adhesion between tooth tissues and dental fillings depends on the surface energy of both connected materials. Bond strength can be determined directly or indirectly as a work of adhesion on the basis of values of surface energy of these materials. Inverse gas chromatography (IGC) is one of the methods of surface energy examination. In this study the values of total surface energy components of wet and dry teeth fragments (enamel, crown dentin and root dentin) were determined with the use of inverse gas chromatography. Inverse gas chromatography has never been used for investigation of surface energy of natural tooth tissues. Different storage conditions were examined - wet and dry. Different values of surface energy are observed according to the type of tooth tissue (dentin or enamel), occurring place (crown or root) and storage conditions (dry or wet). The effect of tissue type and occurring place was the greatest, while storage conditions were of secondary importance. Surface energy depends on composition of tissue, its surface area and the presence of pores.

Adhesion of resin-modified glass-ionomer cements may affect the integrity of tooth structure in the open sandwich technique.

OBJECTIVE: To study the interfaces between model cavities prepared in teeth and four glass ionomer cements (two conventional and two resin-modified). METHODS: Ten non-cavitated molars and premolars were used and, in each, two 3mm deep slot preparations were created on opposing sides of the tooth. The teeth were conditioned as appropriate, then restored using the open sandwich technique, using a conventional glass ionomer (Fuji IX, Ketac Molar) or resin modified glass ionomer (Fuji II LC or N100), followed by completion with composite resin. The teeth were then embedded in a transparent acrylic resin and cut parallel to the long axis through both restorations, using a low speed diamond wheel saw. Samples were evaluated using a metallographic light microscope (100×). Three areas were assessed: the axial wall, the axial gingival line angle and the cavo-surface line angle. Bonding was categorized as inadequate or adequate based on the appearance and inadequate bonding was further studied and classified. Data were analysed statistically using the McNamara analysis. RESULTS: The majority of materials failed to make adequate contact with the axial wall, and there were also flaws at the axial/gingival line angle in several samples. By contrast, the cavo-surface line angle was generally soundly filled and the materials showed intimate contact with the tooth surface in this region. The most serious inadequacy, though, was not lack of intimate contact and/or adhesive bond, but the presence of perpendicular cracks in 30% of the Fuji II LC samples which extended into the underlying dentin. SIGNIFICANCE: The problems of placement and dentin cracking experienced with these materials demonstrate that adhesive bond strength alone cannot be used as the criterion of success for restorative materials. In fact good adhesion can, in certain cases, promote cracking of the dentin due to stresses within the material, an outcome which is undesirable.

Maturation affects fluoride uptake by glass-ionomer dental cements.

OBJECTIVES: Four commercial glass-ionomer cements have been studied for their ability to take up fluoride from aqueous solution following variable maturation times in the dry at 37°C. METHODS: Sets of five specimens of four different materials were cured for times of 10 min, 24 h and 1 month, then transferred to a neutral solution of NaF at approximately 1000 ppm in fluoride. Fluoride concentration was then measured at regular time intervals up to 1 month using a fluoride ion selective electrode. RESULTS: Specimens cured for 1 month showed little or no uptake over 24 h, specimens cured for 24 h showed fluctuating uptake over time, and specimens cured for 10 min showed the greatest fluoride uptake. For the latter specimens, simple kinetic models were found to apply in two cases (pseudo-first order and pseudo-second order for Chemflex and Ketac Molar Quick respectively). SIGNIFICANCE: The ability to take up fluoride has been shown to decline with age of cement which suggests that in clinical use glass-ionomers may become less effective at undergoing fluoride recharge than has been previously assumed.

Effect of denture cleansers on chemical and mechanical behavior of selected soft lining materials.

OBJECTIVES: The aim of this investigation was to determine the effect of storage in disinfectants and artificial saliva on a series of commercial soft lining materials for dentures. Changes in mechanical properties and the nature of chemicals released into these solutions were studied. METHODS: Four soft lining materials were studied (Vertex Soft® and Villacryl Soft®, both of which are plasticized acrylics; Molloplast B® and Mollosil®, both of which are silicone elastomers). All were cured according to manufacturers' instructions, and then cylindrical specimens (6 mm height × 10 mm diameter) prepared. These were stored under various conditions then loaded in uniaxial compression and the stress measured at a strain corresponding to a 10% deformation to determine Young's modulus. Storage involved exposure either to the following disinfectants: 2% aqueous chlorhexidine gluconate, 2% aqueous sodium hypochlorite, Corega Tabs® cleansing tablets or 3% aqueous hydrogen peroxide; or to artificial saliva. For the latter, storage involved either immersion in artificial saliva at 37°C for the whole study, or immersion for 16h a day and dry at room temperature for the next 8h each day. GC/MS was used to determine species leached into these solutions. RESULTS: The acrylic materials Villacryl Soft and Vertex Soft became less elastic on storage for up to 28 days whereas the silicone materials Molloplast B and Mollosil, showed no change in elastic properties. Various compounds were found to be released from these materials, including EGDMA, methyl methacrylate and dibutyl phthalate. Generally, the silicones were more stable than acrylics, releasing smaller amounts of the various eluants. In all cases, amounts eluted were well below permitted exposure limits. SIGNIFICANCE: Practical denture cleansing agents affect the properties of soft lining materials, reducing their elastomeric character, acrylics being more adversely affected than the silicones. These changes are associated with the loss of various chemicals, including plasticizers and monomers, from the soft lining materials.

Review paper: Role of aluminum in glass-ionomer dental cements and its biological effects.

The role of aluminum in glass-ionomers and resin-modified glass-ionomers for dentistry is reviewed. Aluminum is included in the glass component of these materials in the form of Al(2)O(3) to confer basicity on the glass and enable the glass to take part in the acid-base setting reactions. Results of studies of these reactions by FTIR and magic-angle spinning (MAS)-NMR spectroscopy are reported and the role of aluminum is discussed in detail. Aluminum has been shown to be present in the glasses in predominantly 4-coordination, as well as 5- and 6-coordination, and during setting a proportion of this is converted to 6-coordinate species within the matrix of the cement. Despite this, mature cements may contain detectable amounts of both 4- and 5-coordinate aluminum. Aluminum has been found to be leached from glass-ionomer cements, with greater amounts being released under acidic conditions. It may be associated with fluoride, with which it is known to complex strongly. Aluminum that enters the body via the gastro-intestinal tract is mainly excreted, and only about 1% ingested aluminum crosses the gut wall. Calculation shows that, if a glass-ionomer filling dissolved completely over 5 years, it would add only an extra 0.5% of the recommended maximum intake of aluminum to an adult patient. This leads to the conclusion that the release of aluminum from either type of glass-ionomer cement in the mouth poses a negligible health hazard.

Shear bond strength of epoxy resin-based endodontic sealers to bovine dentin after ozone application.

The idea of using ozone to disinfect root canals is of recent origin. The wide acceptance of epoxy resin-based sealers lead us to investigate whether ozone can influence the adhesion to the dentin. In this study, we tested the shear bond strength of AH Plus and EZ Fill. Forty freshly extracted bovine teeth were randomly divided into 5 groups. 16 of these samples were treated with ozone for 60 seconds (HealOzone, Kavo). 8 samples were conditioned with the G Bond bonding system. The groups tested were: (1) AH Plus, (2) AH Plus and ozone, (3) EZ Fill, (4) EZ Fill and ozone, (5) AH Plus and G Bond. 48 hours after being prepared the specimens were tested for shear bond strength. Statistical analysis showed significant differences between materials (AH Plus > EZ Fill) and significant, positive influence of ozone and bonding agent on the shear bond strength.

The biocompatibility of resin-modified glass-ionomer cements for dentistry.

OBJECTIVES: The biological effects of resin-modified glass-ionomer cements as used in clinical dentistry are described, and the literature reviewed on this topic. METHODS: Information on resin-modified glass-ionomers and on 2-hydroxyethyl methacrylate (HEMA), the most damaging substance released by these materials, has been collected from over 50 published papers. These were mainly identified through Scopus. RESULTS: HEMA is known to be released from these materials and has a variety of damaging biological properties, ranging from pulpal inflammation to allergic contact dermatitis. These are therefore potential hazards from resin-modified glass-ionomers. However, clinical results with these materials that have been reported to date are generally positive. CONCLUSIONS/SIGNIFICANCE: Resin-modified glass-ionomers cannot be considered biocompatible to nearly the same extent as conventional glass-ionomers. Care needs to be taken with regard to their use in dentistry and, in particular, dental personnel may be at risk from adverse effects such as contact dermatitis and other immunological responses.

The kinetics of water loss from zinc phosphate and zinc polycarboxylate dental cements.

The water desorption behaviour of three different zinc oxide dental cements (two polycarboxylates, one phosphate) has been studied in detail. Disc-shaped specimens of each material were prepared and allowed to lose water by being subjected to a low humidity desiccating atmosphere over concentrated sulfuric acid. In all three cements, water loss was found to follow Fick's second law for at least 6 h (until M(t)/M(infinity) values were around 0.5), with diffusion coefficients ranging from 6.03 x 10(-8 )cm(2 )s(-1) (for the zinc phosphate) to 2.056 x 10(-7 )cm(2 )s(-1) (for one of the zinc polycarboxylates, Poly F Plus). Equilibration times for desorption were of the order of 8 weeks, and equilibrium water losses ranged from 7.1% for zinc phosphate to 16.9% and 17.4% for the two zinc polycarboxylates.

[Smoking and periodontal disease--results of an epidemiological survey]. / Palenie a choroby przyzebia--wyniki badan epidemiologicznych.

A questionnaire concerning oral health designed for young people aged between 18 and 30 and based on one produced by Tokyo University entitled Medical Outcome Study (MOS) and Oral Health Score) 8020, was submitted to a group of Poznan citizens. One of the 10 questions in the OHS part of the questionnaire concerned smoking habits. A condition for participation in the survey was an absence of professional or educational connections with medicine, dentistry or pharmacy. 506 persons (398 women and 198 men) living in Poznan, with an average of age 20.1 years took part. For a clearer evaluation of the health habits in this group, an additional comparison was made between the youngest (18 y old) and oldest (25-30 y old) groups. The Oral health Score (with a possible maximum 20 points) for the examined group was 14.4 which is one of the lowest among evaluated European countries. Smoking was most frequent among the 18 year olds (20.7%) whereas among the respondents in the older group it was approximately only half of this value (11.29%). Moreover in, both age groups, women were more often smokers than men; 22% of 18 year old women smoked and 7.5% in the older group whereas in younger men 7.5% smoked and 3.8% in the older group. Comparing the answers relating to oral health with the frequency of smoking revealed a connection between this habit and the presence of periodontal disease.

Kinetic studies of water uptake and loss in glass-ionomer cements.

The water sorption and desorption behaviour of three commercial glass-ionomer cements used in clinical dentistry have been studied in detail. Cured specimens of each material were found to show slight but variable water uptake in high humidity conditions, but steady loss in desiccating ones. This water loss was found to follow Fick's law for the first 4-5 h. Diffusion coefficients at 22 degrees C were: Chemflex 1.34 x 10(-6) cm(2) s(-1), Fuji IX 5.87 x 10(-7) cm(2) s(-1), Aquacem 3.08 x 10(-6) cm(2) s(-1). At 7 degrees C they were: Chemflex 8.90 x 10(-7) cm(2) s(-1), Fuji IX 5.04 x 10(-7) cm(2) s(-1), Aquacem 2.88 x 10(-6) cm(2) s(-1). Activation energies for water loss were determined from the Arrhenius equation and were found to be Chemflex 161.8 J mol(-1), Fuji IX 101.3 J mol(-1), Aquacem 47.1 J mol(-1). Such low values show that water transport requires less energy in these cements than in resin-modified glass-ionomers. Fick's law plots were found not to pass through the origin. This implies that, in each case, there is a small water loss that does not involve diffusion. This was concluded to be water at the surface of the specimens, and was termed "superficial water". As such, it represents a fraction of the previously identified unbound (loose) water. Superficial water levels were: Chemflex 0.56%, Fuji IX 0.23%, Aquacem 0.87%. Equilibrium mass loss values were shown to be unaffected by temperature, and allowed ratios of bound:unbound water to be determined for all three cements. These showed wide variation, ranging from 1:5.26 for Chemflex to 1:1.25 for Fuji IX.