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Purpose: To create and investigate artificial mucin-based saliva substitutes with properties similar to natural saliva., Materials and Methods: Natural saliva and six saliva preparations were tested. Saliva substitutes were made using phosphate buffered saline (PBS) prepared in deionised water or plasma-treated water (PBSPT) with addition of porcine gastric mucin and guar gum or poloxamer 407. A wide range of properties were characterised: physicochemical (changes of pH, conductivity and surface tension over time: 1, 24, 96, 168 h after mixing ingredients), rheological (viscosity and viscoelasticity), tribological (coefficient of friction for titanium alloy Ti-6Al-7Nb kinematic couple) and corrosive (open circuit potential, corrosion potential, polarisation resistance)., Results: Saliva preparations based only on mucin had pH, viscosity, coefficient of friction and corrosion parameters similar to those of natural saliva. Guar gum increased the values of viscosity, viscoelasticity and the coefficient of friction. Similar results were obtained for poloxamer 407, whereas it decreased the surface tension of tested preparations. Plasma-treated PBS enhanced the corrosion resistance of saliva substitutes with guar gum and poloxamer 407., Conclusion: Among the tested compositions, saliva substitutes based only on mucin were found to have parameters similar to human whole saliva. Mucin saliva preparations may have wide applicability for patients with e.g. xerostomia or patients using a metal prosthesis.

Purpose: To evaluate the color masking effect of infiltration treatment of artificial white spot lesions (AWSL) using a dedicated resin in comparison to different adhesive systems., Materials and Methods: Enamel/dentin specimens were obtained from bovine incisors and baseline color was assessed using a reflectance spectrophotometer, according to the CIE L*a*b* system. AWSL were produced using a buffered acid solution and a new color evaluation was performed. The specimens were divided into 8 groups: control: artificial saliva changed daily for 7 days; IC: infiltrating resin Icon; EC: EquiaCoat; FU: Futurabond U; SBU: Single Bond U; SBMP: Scotchbond MP; OB: OptibondFL; BF: Bioforty. After the treatments, the color was evaluated again and the values for the parameters ΔL (change in lightness), Δa (change in chroma), Δb (change in hue), and ΔE (general color difference) were calculated in relation to baseline. Data were analyzed by one-way ANOVA and Tukey's tests., Results: After treatment, ANOVA showed significant differences for all parameters (p = 0.001). Tukey's test showed the greatest lightness reduction (ΔL) for the IC group, followed by EC, FU, and SBU. The SBMP, OB, and BF groups were similar to the control. For Δb values, all groups showed differences in relation to the control, with no differences between them. In relation to ΔE, all groups showed differences in relation to the control (ΔE = 5.24), with no significant differences between them. ΔE values after application of all resinous materials were lower than the threshold of 3.7, indicating effective color masking., Conclusions: The Icon infiltrant produced a greater lightness reduction of white lesions (ΔL). For general color difference (ΔE), all the resinous materials tested were able to color mask artificial AWSL.

Purpose: To determine the optimal electric current intensity of fluoride iontophoresis (FI) for remineralisation of early caries lesions in vitro., Materials and Methods: Sixty specimens were made from bovine incisors and immersed in a demineralising gel for 96 h. Specimens were divided into control (conventional fluoride application) and experimental (FI) groups. All of the specimens were covered with fluoride for 4 min every day. Different electric current intensities (100, 200, 300 and 400 μA) were applied in the FI groups using the FI device. The concentration of KOH-soluble fluoride was determined to evaluate the amount of CaF2 formed on the tooth surface. The reduction in lesion depth was measured by polarised light microscopy., Results: The concentration of KOH-soluble fluoride was the highest in the specimens of the 300 μA FI group. However, there was no significant difference in the reduction of lesion depth between the experimental groups and the control group., Conclusion: Variations in the electric current intensity influenced the amount of CaF2 formed on the enamel surface, with the greatest amount found for 300 μA.

Purpose: To determine the influence of aging in artificial saliva compared to distilled water on the dentin microtensile bond strength (μTBS) of different adhesive systems., Materials and Methods: Occlusal enamel and superficial dentin of 42 teeth were removed and roots were sectioned to expose the pulp chamber for connecting the tooth segments to an intrapulpal pressure assembly. According to the tested adhesives, tooth segments were allocated to three groups (n = 14): an etch-and-rinse adhesive (Adper Scotchbond Multi-Purpose, SBMP), a two-step self-etching adhesive (Clearfil SE Bond, CSE), and a singlestep self-etching adhesive (Clearfil S3 Bond, S3). Each adhesive system was applied to the dentin surface according to its manufacturer's instructions, while intrapulpal pressure was simulated. Resin composite (3M ESPE) was built up in two increments of 2 mm each. Each bonded specimen was sectioned to obtain eight sticks (0.8 ± 0.01 mm2). Sticks of each group were divided equally (n = 56) according to the storage solution, either distilled water or artificial saliva. For each storage solution, half of the sticks of each subgroup (n = 28) was stored for 24 h at 37°C and the other half was thermocycled for 10,000 cycles between 5°C and 55°C. Sticks were then subjected to μTBS testing. Data were statistically analyzed using multifactor ANOVA with repeated measures and Bonferroni's post-hoc test (p < 0.05). Student's t-test was used for pairwise comparison. Failure modes were determined for all tested sticks using scanning electron microscopy., Results: The decrease in bond strength of the three adhesives was significantly higher in distilled water than in artificial saliva. The predominant failure modes were adhesive and mixed., Conclusion: The decrease in bond strength was more pronounced for specimens stored in distilled water than in artificial saliva.

Purpose: This study evaluated (1) the dentin bond strength of fluoridated restorative systems following aging and (2) the enamel/dentin microhardness around restorations after a pH-cycling regimen., Materials and Methods: Sixty-four human third molars and four restorative systems were used. A resin-modified glass ionomer (GC Fuji II LC) was used as a fluoride-containing material in the positive control group, while Adper Easy Bond adhesive and Filtek Z350 XT composite resin, which are not fluoridated, were used together in the negative control group. Beautifil II composite resin and FL-Bond II adhesive, both fluoride-containing materials, were compared to Bond Force and Estelite Sigma Quick restorative system, which only contain fluoride in the adhesive. For dentin bond strengths, specimens of each material were fabricated for two test groups (n=8): group 1: tested after 24 h; group 2: tested after 1 year of storage in artificial saliva. Both groups were tested using a microtensile method. For the cross-sectional microhardness test, standardized Class V cavities were prepared and filled with the different restorative systems. After experiencing repeated thermocycling and being subjected to pH-cycling, the teeth were sectioned. The microhardness was measured in enamel and dentin at 50 μm from the cavity wall and at six depths in relation to the surface subjected to pH cycling., Results: None of the restorative systems showed decreased bond strength after storage for one year in artificial saliva. No significant differences in microhardness were observed among the restorative materials on enamel and dentin., Conclusion: All the restorative systems evaluated presented stable bond strength after one year of storage. The pH cycling caused a reduction in the superficial enamel microhardness close to the cavity wall. In dentin, the demineralization affected the superficial and sub-surface areas.

Purpose: This study examined the effects of matrix metalloproteinase-inhibiting solutions and aging methods on the bond strength between resin composite and human dentin., Materials and Methods: Crown segments of 105 human non-carious molars were bonded using simulated pulpal pressure at 20 cm water pressure. The teeth were randomly split into 5 groups according to the solution applied: CG (control, no solution), CHX (0.2% chlorhexidine), EPE (10% ethanolic propolis extract), APE (aqueous propolis extract), and E (70% ethanol). Each solution was left on the acid-etched dentin for 1 min. Adper Single Bond 2 and resin composite (Filtek Z350 XT) were applied to all specimens. The 5 groups were subdivided according to the aging method: SI (sectioned immediately); S (storage in artificial saliva for 6 months); and T (thermomechanical aging with 240,000 mechanical cycles and 1000 thermal cycles). Specimens were sectioned into sticks and subjected to microtensile testing. Bond strength data were analyzed by two-factor ANOVA followed by a post-hoc Tukey's test (α=0.05)., Results: For the factor "solution", there was no significant difference among the groups (p=0.32). For the factor "aging method", significant differences were found (p<0.001), with the following mean bond strengths (MPa): SI: 31.1; S: 24.4; T: 26.8., Conclusions: The use of matrix metalloproteinase-inhibiting solutions on dentin as an adjunct to the application of an etch-and-rinse adhesive does not prevent the loss of bond strength after aging. Nevertheless, these solutions have no adverse effect on adhesion to tooth structure.

Purpose: To investigate the effect of pre-repair aging periods and intermediate adhesive systems based on different monomers on the repair bond strength of silorane-based resin composite., Materials and Methods: A total of 32 Filtek P90 (3M ESPE) substrate specimens (4 mm diameter and 4 mm height) were made. Substrate specimens were grouped according to the pre-repair time periods into four groups (n = 8/group): 15 to 30 min, 24 h, 1 month, and 3 months. All substrate specimens were ground flat using a diamond stone and were etched using Scotchbond phosphoric acid etchant (3M ESPE). The specimens of each pre-repair time period were equally distributed among the two repair groups, using either silorane-based (P90 System Adhesive) or acrylamide-based (AdheSE One F, Ivoclar Vivadent) intermediate adhesive systems. Specimens of P90 System adhesive received Filtek P90 as the repair resin composite, and Tetric N-Ceram (Ivoclar Vivadent) was used with AdheSE One F specimens. Additional specimens were made from the repair resin composite materials to study the cohesive strength. Specimens were sliced into sticks (0.6 ± 0.01 mm2) for microtensile bond strength testing (μTBS). Modes of failure were determined., Results: Two-way ANOVA with repeated measures revealed no significant effect for the pre-repair aging periods, intermediate adhesive systems based on different monomers, or their interaction on repair bond strength of silorane-based resin composite., Conclusion: Up to 3 months of pre-aging the repaired silorane-based resin composite had no negative effect on its repair bond strength, even when an intermediate adhesive system based on a different monomer (acrylamide) was used.

Purpose: To assess the long-term effect of a 2% aqueous chlorhexidine (CHX) solution on bond strength to artificially eroded dentin compared to sound dentin., Materials and Methods: Flat mid-coronal dentin surfaces of extracted third molars (n = 28) were subjected only to grinding with a 600-grit SiC paper for 1 min (sound dentin S, n = 14) or additionally to erosive pH cycling with a cola-based soft-drink (eroded dentin E, n = 14). After acid etching, rinsing, and air drying, S and E were rehydrated with 1.5 μl of 2% CHX (S2%, n = 7; E2%, n = 7) or of distilled water (control SC, n = 7; EC, n = 7). Composite buildups were incrementally constructed with Filtek Z350 following Adper Single Bond 2 application. Specimens were sectioned into beams, which were subjected to microtensile testing immediately or after 6 or 12 months of aging. Fractured surfaces were observed under a digital microscope (50X magnification). Microtensile bond strength (μTBS) (MPa) was analyzed by three-way ANOVA and Tukey's tests (α = 0.05) and failure mode by the Kruskal-Wallis test (α = 0.05)., Results: Compared to sound dentin, eroded dentin was consistently related to lower μTBS. Immediately and after 12-month aging, the effect of CHX was insignificant, but it was significant after 6-month aging, when it conserved the bond strength to both eroded and sound dentin. The percentage of adhesive and mixed failures were equivalent, and significantly more frequent than cohesive failures, whether in dentin or in composite., Conclusion: The 2% CHX effect on bond strength conservation to both eroded and sound dentin was not found to be persistent.

Purpose: To determine the influence of the relative enamel abrasivity (REA) of fluoridated toothpaste on the uptake of KOH-soluble and structurally bound fluoride into enamel., Materials and Methods: Bovine enamel samples were randomly allocated to 6 groups (n=36 per group). Groups A to C were treated with sodium fluoride (NaF) toothpastes and groups D to F with amine fluoride (AmF) toothpastes (1500 ppm F each). The REA in groups A and D was 2, in groups B and E it was 6 and in groups C and F it was 9. Twice a day, 18 samples of each group were immersed for 2 min in a slurry (toothpaste:artificial saliva=1:3), while the remaining samples were brushed with the respective slurry (2.5 N force; 60 strokes/min; 2 min). All samples were stored at 37°C and 100% humidity. After five days, the amount of KOH-soluble and structurally bound fluoride was determined and statistically compared by Scheffe's post-hoc tests., Results: REA value and mode of application (immersion or brushing) had no significant influence on the amount of either kind of fluoride from NaF toothpastes. Only for the NaF toothpaste with REA 6 was the amount of KOH-soluble fluoride significantly higher after brushing. With AmF toothpastes, KOH-soluble and structurally bound fluoride concentrations were significantly higher when the samples were brushed. Furthermore, in the REA-2 group, the amounts of KOH-soluble fluoride (brushed or immersed) and structurally bound fluoride (brushed) were significantly higher than in the other groups., Conclusion: The REA dependency of KOH-soluble and structurally bound fluoride was found only for the AmF toothpastes. Using AmF toothpaste, the mode of application influenced the uptake of KOH-soluble and structurally bound fluoride into enamel.

Purpose: To evaluate the effect of three different liquids used for intrapulpal pressure (IPP) simulation on the microtensile bond strength (µTBS) of three adhesive systems to dentin., Materials and Methods: The occlusal surfaces of sound human molars were ground flat down to mid-dentin depth. The teeth were bonded under 15 mmHg simulated IPP using distilled water, phosphate buffered saline, or human plasma as a simulating liquid. Three adhesive systems were tested: a single-bottle etch-and-rinse adhesive (SingleBond, 3M ESPE), and two single-step self-etching adhesives (G-Bond, GC) and (iBond, Heraeus Kulzer). Resin composite (Tetric EvoCeram, Ivoclar Vivadent) buildups were made in 2 increments, each 2 mm in height. Specimens were stored in artificial saliva under 20 mmHg IPP at 37°C for 24 h prior to testing. µTBS (n = 15) was tested using a universal testing machine, and failure modes were determined. Data were statistically analyzed using ANOVA and Bonferroni post-hoc tests at p <= 0.05., Results: With SingleBond adhesive, distilled water showed significantly higher µTBS compared to plasma and phosphate buffered saline. With G-Bond, no significant difference was found between distilled water and phosphate buffered saline, whereas plasma showed significantly lower µTBS values. In contrast, no significant difference was encountered between the three IPP liquids for iBond adhesive. Predominant modes of failure were adhesive and mixed., Conclusion: A difference in intrapulpal pressure simulating liquids influences the bonding of adhesives to dentin. Etch-and-rinse adhesives are more sensitive to intrapulpal simulating liquids than are self-etching adhesives. Adhesives containing protein-coagulating components perform better with plasma perfusion than those lacking such components.

Purpose: This study evaluated the effect of chlorhexidine (CHX) incorporation into experimental dentin adhesives with different hydrophilicities on the microtensile bond strength (µTBS) to dentin., Materials and Methods: Flat, deep dentin surfaces were prepared from 60 extracted human third molars. Three ethanol-solvated (50 wt% ethanol/50 wt% comonomers) experimental adhesives with varying degrees of hydrophilicity were prepared for the CHX-free groups. For the CHX-containing groups, chlorhexidine diacetate was further added to the ethanol-solvated adhesives to form a concentration of 2.0 wt% CHX. Dentin surfaces were etched with 37% phosphoric acid for 15 s, rinsed and blot dried before bonding. The adhesives were generously applied to dentin with a microbrush for 15 s. A second application of fresh adhesive was made and light cured for 20 s (600 mW/cm2) after solvent evaporation. Composite buildups were made using Filtek Z250 (3M ESPE). The bonded teeth were sectioned into 0.9 mm x 0.9 mm beams and stressed to failure at a crosshead speed of 1 mm/min. Testing was performed 24 h after specimen preparation and 12 months after storage in artificial saliva. The µTBS data were analyzed using three-way ANOVA and Tukey's multiple comparison tests. Fractographic analysis was performed by SEM., Results: Significant differences were observed for the three factors "adhesive hydrophilicity" (p < 0.001), "CHX incorporation" (p = 0.001), and "storage time" (p < 0.001). Interaction among these three factors was also significant (p < 0.001). Incorporation of CHX had no effect on the immediate bond strength of the three experimental adhesives (p > 0.05). After storage in artificial saliva, significant reduction in bond strength was observed in all adhesive groups, except for CHX-containing adhesive I (p < 0.001). The µTBS of the CHX-containing experimental adhesive III was significantly higher than the corresponding CHX-free adhesive (p < 0.001) after aging., Conclusion: When incorporated into hydrophilic dental adhesives, chlorhexidine can partially reduce the degradation of the resin-dentin bonds.

Objectives: To examine the initial shear bond strength of orthodontic brackets bonded to bleached teeth with a self-etching adhesive system, as well as the effect of the length of time after bleaching on the initial bond strength., Method and Materials: Ninety premolars were collected and divided equally among a control group (CG) of unbleached teeth with brackets bonded, an immediate group (IG) with teeth bonded soon after bleaching, and a delayed group (DG) consisting of teeth bleached and then immersed in artificial saliva for 7 days before bracket bonding. Subsequently, the teeth of each group were equally assigned to two different primer adhesive systems: the acid-etch-and-rinse adhesive system (35% phosphoric acid gel and Transbond XT primer) and the self-etching adhesive system (Transbond Plus self-etching primer). Initial bond strength was measured 24 hours after bracket bonding., Results: IG registered the lowest mean initial bond strength when the self-etching adhesive system was in use, followed by DG and CG (in that order). As for the acid-etch-and-rinse adhesive system, the mean initial bond strength was significantly lower in IG than in CG and DG. Significant differences in mean initial bond strength were noted between the two adhesive systems in IG and DG., Conclusion: In trials using a self-etching adhesive system, the mean initial bond strength that declined immediately after bleaching returned to a clinically acceptable level of 6 MPa after the specimens were immersed in artificial saliva for 7 days but fell short of the level of unbleached teeth.

Objective: New fluoride varnishes have been marketed that reportedly release more fluoride (Enamel Pro) or release fluoride more slowly (Vanish XT). The purpose of this study was to compare the amount and rate of fluoride release of new fluoride varnishes with other traditional fluoride varnishes., Method and Materials: Extracted molars were cut into block sections. The enamel surfaces of the sections were painted with Enamel Pro, Duraphat, Vanish, or Vanish XT fluoride varnishes. One group was not treated and served as a negative control. The tooth sections were immersed in artificial saliva. The concentration of fluoride in parts per million was measured after the first 30 minutes, daily for the first week, and weekly until the level was below the limit of detection. Fluoride release was plotted over time. Cumulative fluoride release and rate of release (slope) were analyzed using one-way ANOVA/Tukey (α = .05)., Results: Enamel Pro had the greatest cumulative fluoride release. There was no significant difference between Duraphat and Vanish. Vanish XT had the lowest cumulative fluoride release. The rate of fluoride release from 1 week to limit of detection was Enamel Pro > Vanish > Duraphat > Vanish XT., Conclusion: The two newly marketed fluoride varnishes (Enamel Pro and Vanish XT) had significantly different fluoride release from the two conventional fluoride varnishes (Duraphat and Vanish).

Purpose: This study analyzed the influence of 10% sodium ascorbate (SA) on tag formation in bleached enamel., Materials and Methods: Five groups were tested: G1 - control; G2 - bleaching with 10% carbamide peroxide (CP) + restoration; G3 - CP + SA + restoration; G4 - bleaching with 35% hydrogen peroxide (HP) + restoration; and G5 - HP + SA + restoration. The teeth were sectioned and decalcified, and the resin tags were analyzed at 400X magnification using an optical light microscope and Axiovision software., Results: The resin tag lengths in µm for each group were as follows: G1 - 36.1A; G2 - 5.8C; G3 - 14.4B; G4 - 1.7D; G5 - 6.5C. Different letters indicate statistically significant differences., Conclusion: Tooth bleaching with CP or HP impairs the formation of resin tags, and the utilization of sodium ascorbate increases tags length.

Purpose: This in vitro investigation assessed whether different dentifrices would be capable of controlling the enamel erosion progression caused by HCl., Materials and Methods: Sixty bovine enamel slabs were covered with acid-resistant varnish, except for a 2.5-mm2 circular area on the labial surface. According to a complete block design, the experimental units were immersed in HCl solution (pH 1.2; 0.1M). After storage in artificial saliva for 1 h, specimens (n = 15) were exposed to different dentifrices: Sensodyne Cool Gel (1100 ppm F), Sensodyne ProNamel (1450 ppm F), and PrevDent 5000 (5000 ppm F). The control group was immersed in deionised water. Following five cycles of erosive challenge, the slabs were prepared for porosity evaluation using solutions of copper sulfate and rubeanic acid., Results: ANOVA demonstrated no difference in the enamel porosity as a function of the dentifrice employed (P = 0.5494)., Conclusion: The damage caused by a simulated intrinsic erosive challenge seems unable to be controlled by fluoridated dentifrices, even when this ion is found in elevated concentrations.

Objectives: In this in vitro study, the authors sought to determine the effects of 1.23% acidulated phosphate fluoride gel (APF) or drinkable yogurt on human enamel after exposure to an acidic drink., Method and Materials: Sixteen surgically removed, caries-free, human third molars were cut into four portions: mesial, distal, buccal, and lingual. Each portion was distributed into one of four groups, with each specimen embedded in acrylic resin and its enamel center lightly ground and polished. Three groups of specimens were immersed in orange juice for 2 minutes. One group received no other treatment (OR), one group was subsequently immersed in drinkable yogurt for 5 minutes (OR:YO), while another group had 1.23% APF applied for 4 minutes (OR:APF). The final group was immersed in only drinkable yogurt for 5 minutes (YO). Each exposure was performed twice daily for 60 days; between exposures, the samples were stored in artificial saliva. The enamel surfaces were monitored by three criteria: erosion depth, surface hardness, and SEM., Results: Erosion depth increased progressively in all groups. Surface microhardness progressively decreased in all groups except the OR:APF group, where hardness was significantly higher than other groups at 60 days (P < .05). SEM inspection revealed preferential loss of rod crystallites with retention of interrod crystallites in all specimens exposed to orange juice. The enamel exposed to only drinkable yogurt revealed modest and uniform etching., Conclusion: Drinkable yogurt alone or posttreatment of enamel after exposure to an acidic drink with either 1.23% APF or drinkable yogurt leads to enamel dissolution and does not reduce enamel erosion, in vitro.

Purpose: This laboratory study assessed the influence of surface roughness and contact time on the formation of a multi-species biofilm on dental materials (adhesive patch, composite, amalgam and enamel)., Materials and Methods: Rough and smooth specimens of each material were prepared and the mean surface roughness was assessed profilometrically. The biofilms were then allowed to grow either for 15 min or 15 h respectively on saliva-preconditioned specimens of each material, and colony-forming units on blood agar were counted (N = 9/group) Surface morphology was assessed using a scanning electron microscope., Results: No difference was found in the biofilm formation rate among all the materials that were tested. After a short incubation period, a statistical significant difference between smooth and rough samples could be detected on amalgam and on the resin composite material (P < or = 0.001)., Conclusions: Surface roughness may influence the initial biofilm adherence, but differences vanish following growth and maturation. The multi-species biofilm offers a reliable laboratory model for studying plaque formation.

Objective: To compare in vitro the influence of 3 cementation techniques on leakage and fracture strength of alumina all-ceramic crowns after cyclic loading in an artificial chewing simulator., Method and Materials: Forty-eight extracted molars were mounted in a way that simulates natural tooth mobility. Crowns (Procera Alumina, Nobel Biocare) were fabricated and inserted with either conventional cementation with zinc phosphate cement without pretreatment (group ZOP); cementation with a universal adhesive resin cement without pretreatment (group HYB); or adhesive bonding with composite resin after pretreatment of the tooth (dentin bonding agent) and the crown (airborne-particle abrasion and a special ceramic priming agent containing adhesive monomers that bond to metal-oxide ceramics) (group ADH). All specimens were stored in artificial saliva and subjected to 1.2 million load cycles in a dual-axis chewing simulator (Willytec). Eight specimens per group were subjected to compressive load until failure, while the remaining 8 specimens were stained and sectioned for measuring of dye penetration. One-way ANOVA and Tukey HSD were used for statistical analyses (alpha = .05)., Results: Cementation techniques were significantly different (P = .009) in regard to mean load at failure. Fracture strength was significantly greater for ADH (mean load at fracture, 2,782 +/- 419 N) as compared to HYB (1,980 +/- 270 N) or ZOP (1,788 +/- 242 N). All groups differed significantly for leakage values (P < .001), with ADH showing the lowest mean leakage (0.04 +/- 0.07 mm), followed by HYB (0.96 +/- 0.16 mm) and ZOP (2.44 +/- 0.19 mm)., Conclusion: Cementation technique affects fracture strength and leakage of all-ceramic molar crowns. Fracture strengths were well above natural chewing forces for all cementation methods. However, adhesive bonding significantly increased fracture strength and improved marginal seal of alumina crowns.

Purpose: One of the recommended measures to prevent and control dental erosion is the oral rinse with sodium bicarbonate solution, which would neutralise the dietary acids. However, the prescription of this aqueous suspension has been made on an empirical basis. The aim of this in vitro study was to evaluate whether the demineralisation caused by erosive episodes could be controlled by the potential neutralising effect exerted by a sodium bicarbonate solution., Materials and Methods: Bovine enamel slabs were embedded in epoxy resin, ground/polished and tested for initial surface microhardness. Twice daily for 2 days, specimens were subjected to an erosive challenge with orange juice in an orbital shaker. Following each erosive episode, specimens (n = 15) were immersed for either 30 or 60 seconds in a sodium bicarbonate solution or deionised water. The negative control group was left untreated. For the remaining daily time, specimens were kept in artificial saliva. New microhardness indentations were then made as described for the initial measurements., Results: ANOVA applied to the percentage of surface microhardness change (%deltaSMH) showed no statistically significant difference among treatments (P = 0.5810)., Conclusion: The use of sodium bicarbonate solution, at least under in vitro conditions, may not be a feasible strategy for managing enamel erosion.

Objectives: Remineralization of dentin by mucin-containing saliva substitutes might be inhibited by sialic acids bound to mucin, which are known to complex calcium. Thus, the aim of this investigation was to evaluate the effects of various mucin-containing solutions, differing in calcium phosphate concentrations, to be used as saliva substitutes on demineralized bovine dentin in vitro., Method and Materials: Bovine specimens (153) were embedded in epoxy resin, polished (4,000 grit), and partly covered with nail varnish (control of sound dentin). After demineralization for 14 days (pH 5.5), the specimens (n = 9) were exposed to 14 mucin-based solutions (30 g/L) at 2 different pH values (5.5 or 6.5) and differing in saturation with respect to apatites. Two fluoride-free solutions and the commercially available saliva substitute Saliva Orthana(Orthana, Kastrup) served as controls. Differences in mineral loss (deltadeltaZ) and lesion depth (deltaLD) between the values prior to and after storage in the various solutions were evaluated from microradiographs of thin sections (100 microm)., Results: The general linear model revealed an almost significant dependency on calcium for deltadeltaZ (P = .050) and a significant dependency on calcium for deltaLD (P = .037). pH influenced deltadeltaZ significantly (P < .001), whereas deltaLD was not influenced significantly (P = .169). Neither deltadeltaZ (P = .475) nor deltaLD (P = .703) were influenced significantly by phosphate., Conclusion: Even with low concentrations of calcium and phosphates, mucin-based saliva substitutes are capable of inhibiting demineralization of bovine dentin, whereas with solutions supersaturated with respect to apatites, a remineralizing effect could be observed.

Purpose: The purpose of this work was to determine microtensile dentin bond strengths (microTBS) of dentin-resin composite bonds after three-month storage in artificial saliva containing either collagenase (COL) or cholesterol esterase (EST). The null hypothesis tested is that the resin-dentin bond strength is equivalent for each storage medium at the tested storage times., Materials and Methods: Resin composite was bonded to occlusal dentin, and microTBS specimens were formed and stored in the artificial saliva, COL, EST, or synthetic oil. After 24 h and 12-week storage, microTBS was determined and failure modes were characterized by SEM. The interfacial ultrastructure was evaluated by transmission electron microscopy as unstained and stained sections (phosphotungstic acid/uranyl acetate). Statistical analysis was performed by ANOVA and Weibull survival analyses at the 0.05 level of statistical significance., Results: There were significantly weaker bond strengths after 12 weeks for all experimental storage media (p < 0.001). Artificial saliva containing EST lowered bond strengths to a significantly greater extent than did COL after 12 weeks of storage, while no difference between these groups could be discerned after 24 h. Therefore, the null hypothesis of this experiment is rejected., Conclusion: Exogenous enzymatic challenge to resin-dentin bonds decreased bond durability only with EST. However, when further challenges to ideal infiltration of the comonomers into the hybrid layer were carried out using inadequate removal of solvent, additional alterations in hybrid layer ultrastructure were discerned by TEM that may represent different potential degradative processes. The contribution of endogenous enzymatic challenges to the primary degradative process, ie, hydrolysis, is unknown and deserves continued attention.

Objective: The purpose of this study was to test the hypothesis that remineralized dentin lesions induced by glass ionomer are less vulnerable to subsequent acid challenge., Method and Materials: Baseline demineralized (BDe) lesions were created in 50 bovine dentin slices immersed for 3 weeks in acid solution. A resin-modified glass ionomer (RMGI) was applied to the specimens before immersion in salivalike solution to allow remineralization (Re) for 2 weeks (V2W) or 6 weeks (V6W). Resin-modifed glass ionomer was coated to block further ion release before a 3-week immersion in acid solution as a second demineralization (SDe). Control groups (C2W and C6W) were done simultaneously without RMGI. In another group, RMGI was left undisturbed (V2W+) to allow continuous ion release during SDe. Mineral content was converted from microradiographs, after BDe, Re, and SDe steps. Changes in mineral content were calculated and compared between groups., Results: The remineralized surface zone was maintained after SDe, but the lesion body became deeper. Percentage of mineral loss from SDe was not significantly different between V2W and C2W (t test, P > .05). When remineralization was extended to 6 weeks, V6W showed significantly less mineral loss than C6W. Mineral loss was lowest when RMGI was not blocked (V2W+)., Conclusion: Dentin lesions remineralized in the presence of RMGI maintained the highly mineralized surface zone when subjected to second demineralization. However, the remineralized surface zone could not prevent advance of the lesion body. The subsequent demineralization was markedly reduced by extending the remineralization period or by leaving the RMGI undisturbed to resume ion release.

Purpose: To evaluate bonding penetration into different enamel substrates., Materials and Methods: Ten extracted human molars were mesiodistally sectioned. Buccal and lingual enamel surfaces were divided into four equal areas using sticky wax. The central two areas of each tooth (n = 20) were demineralized for 12 weeks using an acidic gel (pH 4.8). The lateral areas served as controls. After demineralization, ten specimens were remineralized in a saliva substitute for three weeks. An amine fluoride solution (Elmex Fluid) was applied on one half of each specimen before acid etching. After etching for 120 s, an enamel-bonding agent (Heliobond) containing 0.1% rhodamine was applied onto test and control areas, and was light cured for 60 s. Subsequently, the specimens were sectioned and tag length was determined using a confocal laser scanning microscope (CLSM). Results were statistically compared with ANOVA followed by Scheffe's and Bonferroni/Dunn post hoc tests., Results: With a mean penetration depth of 68 +/- 22 microm, tags in demineralized enamel were significantly longer than in other groups (p < or = 0.01). Penetration decreased significantly in remineralized areas or when fluoride was used (p < or = 0.01), but was still significantly deeper than in control sites (p < or = 0.01)., Conclusion: Penetration of an unfilled resin into enamel was considerably influenced by the degree of dental hard tissue mineralization. Penetration was increased in demineralized enamel; however, remineralized enamel also allowed good penetration of the bonding agent.