Impact of transparent tray-based application of bioactive glasses desensitizer on the permeability of enamel and dentin to hydrogen peroxide: an in vitro study.

BACKGROUND: To investigate the effect of transparent tray-based application of bioactive glasses (BGs) desensitizer on the permeability of enamel and dentin to hydrogen peroxide (H2O2). METHODS: Freshly extracted human first premolars were divided into 6 groups (n = 8). Group A and B: without pretreatments; Group C and E: treated with BGs desensitizer only; Group D and F: treated with BGs desensitizer dispensed with a transparent tray. After roots and pulp tissues of the treated tooth specimens were thoroughly removed, acetate buffer was added into pulp chambers and the treated specimens were immersed in distilled water (Groups A, E, and F) or 30% H2O2 (Groups B, C, and D) for 30 min at 37 °C. The amount of H2O2 in the pulp chamber of each group was measured using ultraviolet-visible spectrophotometry. RESULTS: In control groups (Group A, E, and F), H2O2 was not detected. The amount of pulpal H2O2 in Group B, C, and D were 21.149 ± 0.489 µg, 9.813 ± 0.426 µg, and 4.065 ± 0.268 µg respectively. One-way ANOVA analysis indicated that significant differences existed in these groups (F = 459.748, p < 0.05). CONCLUSIONS: The effect of BGs desensitizer in reducing the permeability of enamel and dentin to H2O2 could be enhanced when dispensed with a transparent tray.

In Vitro Assessment of Enamel Permeability in Primary Teeth with and without Early Childhood Caries Using Laser Scanning Confocal Microscope.

OBJECTIVE: To compare the permeability of the enamel of primary teeth from individuals free of Early Childhood Caries (ECC) with that from individuals affected with ECC by assessment of dye penetration using Laser Scanning Confocal Microscope (LSCM). STUDY DESIGN: Experimental in vitro study. Exfoliated primary maxillary anterior teeth (n = 44) were collected and divided into two groups (n=22 per group): samples with ECC (Group 1) and without ECC (Group 2). The samples were immersed in Rhodamine B dye solution for 1 day, cut longitudinally into 3 sections, observed using LSCM. Dye penetration depths in the incisal, middle, cervical thirds and on labial, lingual surfaces were recorded. Data were analyzed by the Mann-Whitney test (α = 5%, p < .005). RESULTS: The overall mean penetration depth for group 1 (100.6 µm ± 58.48 µm) was significantly higher than that of group 2 (31.55 µm ± 23.40 µm, p < .000). Mean penetration depth in the incisal, middle, and cervical thirds and on the labial and lingual surfaces of group 1 also presented significantly higher scores than in group 2 (p < .005). CONCLUSION: There was significantly more dye penetration in the ECC group than in the non-ECC group. This could be related to a higher level of enamel permeability in teeth affected with ECC.

In vivo scanning electron microscope assessment of enamel permeability in primary teeth with and without early childhood caries.

BACKGROUND: Over the years, certain primary teeth have been shown to be highly sensitive to dental caries, while others have remained caries-free. It has been hypothesized that this may be attributed to differences in the permeability of the enamel surface. AIM: The aim of the study was to evaluate the hypothesized differences in the permeability of primary tooth enamel in children with and those without Severe Early Childhood Caries (S-ECC) using scanning electron microscopy. MATERIALS AND METHODS: Sixteen children between 3 and 6 years of age were randomly selected and divided into two groups: Group 1, children without S-ECC (n = 8), and Group 2, children with S-ECC (n = 8). In each child, 4 teeth (the maxillary right and left central and lateral incisors) were subjected to evaluation. An impression was made with polyvinylsiloxane impression material, and scanning electron microscopy was used to inspect the negative replicas for droplets. RESULTS: The results indicated higher significance when individual regions (cervical, middle, and incisal thirds) in the two groups were evaluated and compared. Similarly, the overall results showed high statistical significance between S-ECC and non-S-ECC teeth. CONCLUSION: There could be a positive relationship between the permeability of tooth enamel and the development of caries, which needs further research.

Replacing Amalgam Restorations: A Standardized Protocol Based on Analyzing Tissue Physicochemical Modifications.

Almost 60% of operative dentistry is devoted to replacing restorations. When practitioners have to replace an amalgam restoration, they tend to opt for an adhesive restoration, as it is conservative of tooth tissues and mimics the natural appearance of teeth. Based on a literature review, the aim of this article is to determine the best tissue approach when replacing an old amalgam by a new adhesive restoration. After analyzing and understanding tissue alterations due to the amalgam corrosion process, the authors propose an analytical approach to managing the situation. Both tissue orientated and specific mechanical approaches are developed and should be implemented to carry out the optimal clinical procedure and achieve the most conservative and durable treatment.

Comparison of the enamel solubility reduction from Various prescription and OTC fluoride toothpastes and gels.

OBJECTIVE: The purpose of this in vitro study was to determine if a novel 970 ppm F ion SnF2OTC gel (Enamelon Preventive Treatment Gel) and a 1150 ppm F- ion SnF2OTC Enamelon Toothpaste, each delivering amorphous calcium phosphate (ACP), can significantly reduce the effect of an acid challenge to enamel as compared to two prescription (Rx) strength 5000 ppm F- ion (NaF) dentifrices containing tri-calcium phosphate (TCP), and an Rx 900 ppm F- ion (NaF) paste with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). The effect will be determined by measuring the resistance of enamel specimens to an acid challenge before and after treatment with the test dentifrices. METHODS: The procedure used in this study was the FDA Test Method #33 for the determination of the effect of different test dentifrices on enamel solubility reduction. Twelve sets of three extracted human teeth were unprotected and etched prior to treatment with 0.1 M lactic acid buffer solution. The amount of phosphate dissolved from the teeth was quantified via measuring the phosphate in the retained lactate buffer solution with phosphorous analysis (pre-treatment phosphorous levels). The teeth sets were then exposed to the following treatments (diluted 1:3 parts in preheated [37 degrees C] distilled water): 5000 ppm F- ion, sodium fluoride (NaF) Rx dentifrice containing TCP; 5000 ppm F- ion, NaF Rx dentifrice; 900 ppm F- ion, NaF Rx paste with CPP-ACP; 1150 ppm F- ion, stannous fluoride (SnF2) OTC toothpaste delivering ACP Enamelon Toothpaste; and 970 ppm F- ion, SnF2 OTC gel delivering ACP (Enamelon Preventive Treatment Gel). The teeth sets were rinsed with distilled water and then exposed to 0.1 M buffered lactic acid solution. The amount of phosphate in the lactic acid buffer was determined for a second time (post-treatment phosphorous levels). The percent of enamel solubility reduction was then computed as the difference between the amount of phosphorous in the pre- and post-treatment lactic acid solutions divided by the amount of phosphorous in the pre-treatment solution, and multiplied by 100. RESULTS: The percent reduction in enamel solubility recorded in this study was as follows: 60.14 ± 0.79 for the Enamelon Toothpaste; 56.91 ± 1.05 for the Enamelon Preventive Treatment Gel; 18.78 ± 3.20 for the 5000 ppm F- ion, NaF prescription dentifrice "A' with TCP; 6.84 ± 1.20 for the 900 ppm F- ion, NaF paste with CPP-ACP; 5.82 ± 3.10 for the 5000 ppm F- ion, NaF prescription dentifrice "B" with TCP; and -5.45 ± 1.86 for the negative control. The differences between all the products tested were statistically significant (p < 0.05), except for the Enamelon products that were not statistically different. The 900 ppm F- ion, NaF paste with CPP-ACP and the 5000 ppm F- ion, NaF toothpaste results were also not statistically different. CONCLUSION: The Enamelon products (970 ppm and 1150 ppm F- ion, SnF2 OTC dentifrices) delivering ACP were statistically significantly more effective in reducing enamel solubility than two Rx strength 5000 ppm F- ion NaF toothpastes containing TCP and the Rx 900 ppm F- ion NaF paste containing CPP-ACP.

Infiltration of natural caries lesions in relation to their activity status and acid pretreatment in vitro.

This study aimed at testing how active and inactive enamel caries lesions differ by their degree of resin infiltration, and whether the choice of acid pretreatment plays a crucial role. Four examiners assessed 104 human molars and premolars with noncavitated enamel lesions and classified them as 'active' or 'inactive' using the Nyvad criteria. Forty-five teeth were included in this study after independent unanimous lesion activity assessment. Lesions were cut perpendicularly into 2 halves. Each half lesion was pretreated with either 15% hydrochloric acid or 35% phosphoric acid. The lesions were infiltrated after staining with rhodamine isothiocyanate. Thin sections of 100 µm were prepared and the specimens were bleached with 30% hydrogen peroxide. The specimens were then counterstained with sodium fluorescein, subjected to confocal laser scanning microscopy and analyzed quantitatively. Outcome parameters were maximum and average infiltration depths as well as relative penetration depths and areas. In active lesions no significant difference of percentage maximum penetration depth and percentage average penetration depth between lesions pretreated with hydrochloric or phosphoric acid could be observed. In inactive lesions, however, phosphoric acid pretreatment resulted in significantly lower penetration compared to hydrochloric acid pretreatment. Surface conditioning with hydrochloric acid led to similar infiltration results in active and inactive lesions. Moreover, inactive lesions showed greater variability in all assessed infiltration parameters than did active lesions. In conclusion, caries lesion activity and acid pretreatment both influenced the infiltration. The use of phosphoric acid to increase permeability of the surface layer of active lesions should be further explored.

Natural enamel caries: a comparative histological study on biochemical volumes.

This study aimed to test the hypothesis that organic volume is the main variable for explaining the optical properties and predictive degree of diffusion of enamel histological points at zones of natural enamel caries (NEC; surface layer, SL, n = 30, and body of the lesion, BL, n = 58) and normal enamel (NE, n = 131). Molars with either NEC or NE were quantitatively analyzed regarding the mineral, organic and water volumes (considered as effective pore volume), opacity (predicted in 94% of cases by water volume in NEC), and water volume more easily available for diffusion, αd (squared water volume divided by the nonmineral volume; related to permeability). NEC presented lower mineral volumes and higher organic volumes, effective pore volume and opacity than NE. External origin of organic volume in NEC was evidenced by an organic gradient decreasing from the surface inward (R2 = -0.7), which was not detected in teeth with NE only; αd values of the SL and NE were similar and both were lower (p < 0.0001) than that of the BL. Comparing the SL from both NEC and artificial enamel caries (AEC; published data; n = 71), with similar mineral volumes, against developing enamel (published data), AEC showed more effective pore volume (3 times higher), higher αd and opacity than NEC mainly due to differences in organic volumes. Our results reasonably matched widely known features of NEC histological zones, and confirmed the organic volume as the main variable for explaining optical properties and αd (related to permeability).

Low toxic effects of a whitening strip to cultured pulp cells.

PURPOSE: To assess the trans-enamel and trans-dentin toxicity of a 10% hydrogen peroxide (HP) whitening strip to odontoblast-like cells (MDPC-23). METHODS: Enamel surfaces of enamel/dentin discs adapted to artificial pulp chambers were subjected to two 30-minute whitening strip applications to obtain indirect extracts (DMEM + bleaching components that diffused across enamel and dentin). The extracts were applied for 1 hour to the cells for 1 or 5 days. A bleaching gel with 35% HP was used as the positive control. Cell viability (MTT assay) and morphology (SEM) as well as the quantity of HP in the extracts were assessed. RESULTS: Discrete cell viability reduction (21.9%) associated with slight alterations in cell morphology occurred after application of the extracts for 5 days to the MDPC-23 cells (Tukey's test; P < 0.05). Lower enamel/dentin diffusion of HP was observed after the use of the whitening strip compared with the bleaching gel (Mann-Whitney; P < 0.05).

Hydrogen peroxide penetration into the pulp chamber and dental permeability after bleaching.

This study sought to quantify the concentration of hydrogen peroxide (HP) in the pulp chamber and evaluate changes on dental permeability after bleaching with 3 HP concentrations (10%, 35%, and 50%). This study was divided into 2 experiments and the bleaching treatments consisted of 3 applications of HP for 30 minutes during a single session. The first experiment tested HP penetration into the pulp chamber of 4 experimental groups (n = 10) of bovine crowns, which were divided by HP concentration: an unbleached control group (0% HP), 10% HP, 35% HP, and 50% HP. Acetate buffer solution was placed into the pulp chamber and after each application of HP. This solution was collected to determine spectrophotometrically the concentration of HP that reached the pulp chamber. The second experiment evaluated dental permeability. Bovine crowns were divided into 3 groups (n = 10). The crowns were connected to a permeability device and the initial permeability was measured at 10 psi. Three different concentrations of HP gels (10%, 35% and 50%) were applied to the buccal enamel surfaces and the dental permeability was measured after the first, second, and third applications of HP. The data were analyzed by 2-way ANOVA and Tukey test (P ≤ 0.05). All concentrations of HP reached the pulp chamber, although no significant differences were noted between the 3 concentrations tested (P > 0.05). However, the increase of dental permeability in the group that received 50% HP was significantly higher than the 10% HP group (P < 0.05). The results indicate that the HP bleaching treatments increased dental permeability.

Penetration of experimental infiltrants with different penetration coefficients and ethanol addition into natural caries lesions in primary molars.

This study evaluated the influence of the penetration coefficient (PC) and ethanol addition on the penetration depth (PD) of experimental infiltrants into proximal caries lesions in primary molars. Caries lesions (n = 45) were randomly treated with 1 of 4 experimental infiltrants (PC63; PC185; PC204; PC391) for 5 min. Lesion depths and PDs were analysed using dual fluorescence confocal microscopy. Lesions were almost completely infiltrated in all groups. Median PDs and percentage penetrations were not significantly different between groups (p > 0.05). When applied for 5 min, all tested infiltrants were able to infiltrate proximal caries in primary molars nearly completely.

Effect of caries infiltrant application on shear bond strength of different adhesive systems to sound and demineralized enamel.

PURPOSE: To investigate the influence of caries infiltrant application on the shear bond strength of different adhesives on sound and demineralized enamel. MATERIALS AND METHODS: Sound and artificially demineralized (14 days, acidic buffer, pH 5.0) bovine enamel specimens were treated with a caries infiltrant (Icon, DMG), three different commercial adhesives (unfilled etch and- rinse adhesive: Heliobond, Ivoclar Vivadent; filled etch-and-rinse adhesive: Optibond FL, Kerr; or self-etching adhesive: iBOND Self Etch, Heraeus Kulzer) or a combination of caries infiltrant and adhesive. The shear bond strength of a nanohybrid composite was analyzed after thermocycling (5000x, 5° to 55°C) at a crosshead speed of 1 mm/min. Failure mode was inspected under a stereomicroscope at 25X magnification. RESULTS: In both sound and demineralized enamel, the shear bond strength of the caries infiltrant was not significantly different from the etch-and-rinse adhesives, while the self-etching adhesive showed significantly lower values compared to all other groups. Pretreatment with the caries infiltrant significantly increased the bond strength of the self-etching adhesive in both substrates and of the filled etch-and-rinse adhesive in demineralized enamel. While shear bond strength was not significantly different between the two substrates, cohesive failures were more likely to occur in demineralized than sound specimens. CONCLUSION: The shear bond strength of the caries infiltrant was similar to the etch-and-rinse adhesives. The caries infiltrant did not impair bonding to sound or demineralized enamel, and even increased adhesion of the selfetching agent.

Penetration depths of an infiltrant into proximal caries lesions in primary molars after different application times in vitro.

BACKGROUND: Caries infiltration aims to inhibit lesion progression, by occluding the porosities within the lesion body with low-viscosity resins. The ability in hampering lesion progression is correlated with the penetration depth (PD) of the infiltrant. AIM: This study aimed to compare the infiltration depths into proximal lesions in primary molars after different application times. DESIGN: Noncavitated natural caries lesions (n = 83) were etched with 15% HCl for 2 min and infiltrated for 0.5, 1, 3, or 5 min. Specimens were sectioned and PD at the maximum lesion depth (LD(max)) were analysed using dual fluorescence confocal microscopy. RESULTS: Percentage penetrations (PD/LD(max)) were significantly higher after 3 or 5 min compared with 0.5-min application (P < 0.05; Mann-Whitney test). For LD(max) <400 µm, no significant differences were observed between application times (P > 0.05). For LD(max) ≥400 µm, 3- and 5-min application resulted in significantly deeper infiltration compared with 0.5 min (P < 0.05). After 1-min application, PD was significantly lower than 5 min (P < 0.05), PD/LD(max) did not differ from all other groups (P > 0.05). CONCLUSIONS: Natural noncavitated proximal lesions in primary molars were deeply infiltrated after 1-min application in vitro. For deeper lesions, however, more consistent results were obtained after 3 min.

The use of a 'bleach-etch-seal' deproteinization technique on MIH affected enamel.

AIMS: To ascertain whether deproteinization pretreatment of molar-incisor hypomineralization (MIH) enamel affects resin sealant infiltration. DESIGN: Thirty one extracted MIH teeth were divided into three sections and randomly allocated into the Control (etch and FS), Treatment 1 (5% NaOCl, etched and fissure sealed), and Treatment 2 (5% NaOCl and fissure sealed with no etch) groups. Two hundred seventy nine sealant tag/enamel grade observations were recorded by scanning electron microscopy. RESULTS: Control and Treatment 1 were similar in their outcomes, and Treatment 2 was markedly different. There was no statistical evidence to suggest that there was any difference between Treatment 1 and the Control Treatment (95% CI, 0.52, 1.51; P = 0.6). There was a marked difference between Treatment 2 and the Control Treatment (95% CI, 0.07, 0.25; P < 0.001). All treatments also demonstrated a high-predicted probability of obtaining 'poor' sealant tags (Control = 47%, Treatment 1 = 49%, and Treatment 2 = 40%). CONCLUSIONS: The findings suggest that there was no significant difference in the tag quality between the conventional technique (Control) and the 'bleach-etch-seal' technique (Treatment 1). There was no benefit in pre-treating with NaOCl alone (without etch) before sealing. This research also showed that there was a high-predicted probability of obtaining 'poor' sealant tags in MIH enamel, regardless of which of the three treatments was used.

Primary enamel permeability: a SEM evaluation in vivo.

AIM: The aim of this study was to evaluate in vivo the occurrence of outward fluid flow on primary tooth sound enamel surface. MATERIALS AND METHODS: Sixty primary upper canines from preadolescent patients (mean age 8.0±1.9) and 24 retained primary upper canines from adult subjects (mean age 35.0±1.8) were analysed. The enamel surface was gently polished and air dried for 10 s. An impression was immediately obtained by vinyl polyxiloxane. Replicas were then obtained by polyether impression material, gold coated and inspected under SEM. The hydrophobic vinyl polyxiloxane material enabled to obtain in situ a morphological image of the presence of droplets, most likely resulting from outward fluids flow through outer enamel. For each sample three different representative areas of 5µ² in the cervical, medium and incisal third were examined and droplets presence values was recorded. All data were analysed by by Fisher's exact test. RESULTS: Primary enamel showed a substantial permeability expressed as droplets discharge on its surface. Droplets distribution covered, without any specific localisation, the entire enamel surface in all the samples. No signs of post-eruptive maturation with changes in droplets distribution were observed in samples from adult subjects. No statistically significant differences (P = 0.955) were noted in the percentage distribution of enamel area covered with droplets among the two group studied. CONCLUSION: SEM evaluation of droplets distribution on enamel surface indicated a substantial enamel permeability in primary teeth, accordingly with histological features, without changes during aging. A relationship between enamel permeability, caries susceptibility and bonding procedures effectiveness could be hypothesised.

Resin infiltration of proximal caries lesions differing in ICDAS codes.

Resin infiltration of non-cavitated proximal caries lesions has been shown to inhibit further demineralization. However, the effect of resin infiltration in cavitated lesions is unknown. Therefore, the aim of this in vitro study was to evaluate infiltration patterns of proximal caries lesions differing in International Caries Detection and Assessment System (ICDAS) codes. Extracted human molars and premolars showing proximal caries lesions with and without cavitations (ICDAS codes 2-5) were etched with 15% hydrochloric acid gel and resin infiltrated according to the manufacturer's instructions. Three sections from each lesion were prepared and analyzed using a dual-fluorescence staining technique and confocal microscopy. The dimensions of the demineralized and cavitated lesions areas, as well as the resin-infiltrated parts within these lesions, were measured. The demineralized parts were infiltrated from 73% to 100% (median values) but the cavities were filled only negligibly (0-5%). Teeth that had an ICDAS code of 5 showed a significantly lower percentage infiltration/filling of lesions compared to teeth with ICDAS codes of 2 and 3. It was concluded that under in vitro conditions the tested infiltrant penetrates most parts of the demineralized enamel but is not capable of filling up cavities and therefore the efficacy of caries infiltration, particularly in lesions with larger cavitations, might be impaired.

Transenamel and transdentinal cytotoxicity of carbamide peroxide bleaching gels on odontoblast-like MDPC-23 cells.

AIM: To evaluate the transenamel and transdentinal cytotoxicity of bleaching gels based on carbamide peroxide (CP) on odontoblast-like cells after different contact times of the products with enamel. METHODOLOGY: Enamel/dentine discs were obtained from bovine incisors and placed in artificial pulp chambers. Bleaching gels containing 10% or 16% CP were applied for 8 h day(-1) on the enamel side of the discs during periods of 1, 7 or 14 days. Deionized water and artificial saliva served as controls. The extracts (culture medium plus bleaching gel products that diffused through the discs) were collected and applied on previously cultured MDPC-23 cells for 1 h. Cell metabolism was evaluated by the MTT assay, and the data were analysed statistically by one-way anova and Tukey's test (α=0.05). Cell morphology was analysed by SEM. RESULTS: There was no significant difference (P>0.05) between the controls and the groups bleached with 10% CP gel. In the groups bleached with 16% CP gel, however, cell metabolism decreased significantly (P<0.05) by 40.32%, 30.16% and 26.61% at 1, 7 and 14 days, respectively. There was no significant difference (P>0.05) between 1, 7 or 14 applications of the gels for either of the CP concentrations. CONCLUSION: Regardless of the number of applications on an enamel surface, the 10% CP bleaching gel did not cause transenamel and transdentinal cytotoxicity to the MDPC-23 cell cultures. However, diffusion of products from the 16% CP gel through enamel and dentine and cytopathic effects to the pulp cells occurred even after a single application of this product on enamel.

The impact of fissure depth and enamel conditioning protocols on glass-ionomer and resin-based fissure sealant penetration.

PURPOSE: To evaluate the effect that fissure depth and enamel conditioning protocols have on penetration abilities of resin-based and glass-ionomer fissure sealants. MATERIALS AND METHODS: Fifty extracted human molars were randomized into 10 experimental groups. Conditioning was performed as follows: groups I and VI, no pretreatment; groups II and VII, 10% polyacrylic acid and 37% phosphoric acid, respectively; groups III and VIII, self-etching adhesive; groups IV and IX, Er:YAG laser; groups V and X, Er:YAG laser/10% polyacrylic acid and laser/37% phosphoric acid, respectively. In groups I to V, teeth were sealed with a glass-ionomer material, and in groups VI to X a resin-based sealant was used. The sealed teeth were sectioned and the penetration ability was evaluated using scanning electron microscopy (SEM). RESULTS: Pretreatment with a suitable acid resulted in superior penetration of glass-ionomer and resin-based sealant when compared with other conditioning protocols (p < 0.0001), except for the teeth treated with both Er:YAG laser and acid. Both conditioning protocol and fissure depth significantly affected the sealant penetration (p < 0.0001), but fissure depth had a greater impact on fissure penetration than did conditioning protocol. CONCLUSION: Resin-based and glass-ionomer sealing materials show similar potential for pit-and-fissure penetration. Penetration of a fissure sealant is largely influenced by the fissure depth. Regarding the conditioning protocol, a pretreatment with a suitable acid is essential to obtain an adequate penetration of a sealing material.

In vivo effects of fluoride on enamel permeability.

This in vivo study evaluated the effects of topical fluoride application on enamel by repeated scanning electron microscopy analysis of replicas. Baseline fluid droplets were employed as qualitative indication of enamel permeability. CaF(2)-like globules were detected in vivo after fluoride application and were not found after professional brushing, ultrasound action, or chemical extraction. Absence of water permeability of enamel was demonstrated even after removal of CaF(2)-like globules. Droplets reappeared within 1 h in sodium fluoride-treated teeth, but they did not reappear even after 1 week following topical enamel treatment with acidulated phosphate fluoride. Teeth treated with an acidulate fluoride-free solution showed lack of CaF(2)-like globules and no droplets for at least 1 week as detected in acidulate phosphate fluoride-treated teeth. The caries-preventing action of fluoride may be due to its ability to decrease permeability and diffusion pathways. CaF(2)-like globules seem to be indirectly involved in enamel protection over time maintaining an impermeable barrier, and phosphoric acid seemed to play an unexpected fluoride-independent preventive role.

Effect of dentifrices against hydrochloric acid-induced erosion.

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.

Relevance of in vitro tests of adhesive and composite dental materials. A review in 3 parts. Part 3: in vitro tests of adhesive systems.

In the third part of this review of laboratory testing, methods of testing adhesive systems are evaluated. Test set-ups that are used to analyze the restorative material in combination with the adhesive system are presented. Currently, there is no standardized protocol available for the evaluation of adhesives. This complicates any direct comparisons of values between different testing institutes. Therefore, the statistically evaluated ranking of the different adhesives is more important than mean values. Depending on the testing institute, a correlation between bond strength measurements and clinical outcomes may exist. Qualitative analysis of adhesive/tooth interaction can help explain the functioning of a system, but the depth of penetration of the adhesive cannot predict bond strength. Indirect bond measurements or analyses of the interactions of adhesive and composite materials, such as dye penetration or marginal analysis, do not correlate or correlate only partially with clinical findings. Adhesive systems should be tested in vitro and compared to a well-known standard adhesive before they are used in the clinic. Water storage of specimens for several months before testing increases the predictability of the bonding performance of the tested adhesive.