Interplay Between Minerals in Bottled Water and Fluoride Toothpaste and Caries Lesion Remineralization.

OBJECTIVES: he aim of this in vitro study was to evaluate the effects of some bottled waters on fluoride toothpaste efficacy in enhancing caries lesion remineralization. METHODS: Early caries lesions were created in bovine enamel specimens and stratified into treatment groups based on Vickers surface microhardness (VHN). The present study followed a two (fluoride and fluoride-free toothpaste) by five (four bottled waters and tap water) factorial design. The treatment groups were bottled water with the following attributes: (a) 309.9 ppm Ca/1.20 ppm F; (b) 118.4 ppm Ca/0.16 ppm F; (c) 1.00 ppm Ca/1.01 ppm F; and (d) 0.1 ppm Ca/0.04 ppm F and tap water (48.7 ppm Ca/0.7 ppm F). The five water groups were paired either with 1100 ppm fluoride or fluoride-free toothpaste, yielding 10 groups. Specimens were pH-cycled for 10 days with the daily regimen comprised of twice daily toothpaste slurry, with four exposures to water in between. VHN was measured again and the difference was calculated (ΔVHN). Data were analyzed using two-way ANOVA at a 5% significance level. RESULTS: The two-way interaction between water and toothpaste was significant (p<0.001). All groups except fluoride-free toothpaste/bottled water with 0.1 ppm Ca/0.04 ppm F (p=0.411) had significant increases in VHN after pH cycling (p≤0.023). Fluoridated toothpaste resulted in a higher rate of remineralization compared to fluoride-free toothpaste (all p<0.001). Bottled water with 1.20 ppm F/309.9 ppm Ca exhibited the greatest extent of remineralization within fluoride toothpaste groups (p<0.001) and higher remineralization than lower fluoride water in fluoride-free toothpaste groups (p≤0.006). Within the fluoridated toothpaste group, tap water exhibited significantly less remineralization than all bottled waters (all p<0.001). CONCLUSION: Within the limitation of this study, bottled water with higher fluoride and calcium concentrations might improve fluoridated toothpaste efficacy by enhancing remineralization of early enamel caries-like lesions.

Microbial Indicators of Dental Health, Dysbiosis, and Early Childhood Caries.

Dental caries lesions are a clinical manifestation of disease, preceded by microbial dysbiosis, which is poorly characterized and thought to be associated with saccharolytic taxa. Here, we assessed the associations between the oral microbiome of children and various caries risk factors such as demographics and behavioral and clinical data across early childhood and characterized over time the salivary and dental plaque microbiome of children before clinical diagnosis of caries lesions. Children (N = 266) were examined clinically at ~1, 2.5, 4, and 6.5 y of age. The microbiome samples were collected at 1, 2.5, and 4 y. Caries groups consisted of children who remained caries free (International Caries Detection and Assessment System [ICDAS] = 0) at all time points (CFAT) (n = 50); children diagnosed with caries (ICDAS ≥ 1) at 6.5 y (C6.5), 4 y (C4), or 2.5 y of age (C2.5); and children with early caries or advanced caries lesions at specific time points. Microbial community analyses were performed on zero-radius operational taxonomic units (zOTUs) obtained from V4 of 16S ribosomal RNA gene amplicon sequences. The oral microbiome of the children was affected by various factors, including antibiotic use, demographics, and dietary habits of the children and their caregivers. At all time points, various risk factors explained more of the variation in the dental plaque microbiome than in saliva. At 1 y, composition of saliva of the C4 group differed from that of the CFAT group, while at 2.5 y, this difference was observed only in plaque. At 4 y, multiple salivary and plaque zOTUs of genera Prevotella and Leptotrichia were significantly higher in samples of the C6.5 group than those of the CFAT group. In conclusion, up to 3 y prior to clinical caries detection, the oral microbial communities were already in a state of dysbiosis that was dominated by proteolytic taxa. Plaque discriminated dysbiotic oral ecosystems from healthy ones better than saliva.

Concurrent validity of the short-form Family Impact Scale (FIS-8) in 4-year-old US children.

BACKGROUND: US data on the validity and reliability of the short-form Family Impact Scale (FIS-8; a scale for measuring the impact of a child's oral condition on his/her family) are lacking. METHODS: Cross-sectional analysis of data on four-year-old US children taking part in a multi-center cohort study. For child-caregiver dyads recruited at child age 12 months, the impact of the child's oral condition on the family was assessed at age 48 months using the FIS-8, with a subsample of 422 caregivers (from 686 who were approached). Internal consistency reliability was assessed using Cronbach's α, with concurrent validity assessed against a global family impact item ("How much are your family's daily lives affected by your child's teeth, lips, jaws or mouth?") and a global oral health item ("How would you describe the health of your child's teeth and mouth?"). RESULTS: Cronbach's alpha was 0.83. Although gradients in mean scores across ordinal response categories of the global family impact item were inconsistent, there were marked, consistent gradients across the ordinal categories of the global item on the child's oral health, with scores highest for those rating their child's oral health as 'Poor'. CONCLUSIONS: While the findings provide some evidence for the utility of the FIS in a US child sample, the study's replication in samples of preschoolers with greater disease experience would be useful.

Three-Dimensional Surface Texture Characterization of In Situ Simulated Erosive Tooth Wear.

This in situ erosive tooth wear (ETW) study tested enamel 3-dimensional (3D) surface texture outcomes for the detection and differentiation of ETW lesions simulated in clinically relevant conditions. Twenty participants enrolled in this 3-arm crossover intraoral ETW simulation and wore their own partial denture for 14 d holding 2 human enamel specimens (per arm). In each arm, participants were assigned to 1 of 3 different dental erosion protocols: severe (lemon juice/pH 2.5), moderate (grapefruit juice/pH 3.5), and no erosion (bottled drinking water, control). Enamel specimens were evaluated by white-light scanning confocal profilometry for 3D surface texture and surface loss (ETW model validation). Individual point clouds were analyzed using standard dental microwear texture characterization protocols for surface roughness and anisotropy. Fractal complexity (Asfc), texture aspect ratio (Str), and arithmetical mean height (Sa) values were generated at baseline, 7 d, and 14 d. Data were analyzed by analysis of variance models suitable for the crossover design with repeated measurements, and correlation coefficients were used to examine the relationship between outcomes. Asfc and Sa differentiated ETW severity (no erosion < moderate < severe, P < 0.001) at days 7 and 14. Asfc and Sa were lower at baseline compared to days 7 and 14 (P < 0.001) for moderate and severe challenges. Asfc increased from day 7 to 14 (P = 0.042) for the severe challenge. For Str, ETW severity did not have a significant effect overall (P = 0.15). Asfc and Sa were highly positively correlated (r = 0.89, P < 0.001), while Asfc and Sa were not correlated overall with Str (r < 0.1, P ≥ 0.25). Enamel surface loss increased with ETW severity (no erosion < moderate < severe, P < 0.001) at days 7 and 14, validating the ETW simulation model. Complexity (Asfc) and roughness (Sa) outcomes were able to detect and differentiate ETW levels, with Asfc being able to monitor the progression of severe lesions. No clear characterization of ETW lesions could be provided by the anisotropy (Str) parameter.

Randomised study of the effects of fluoride and time on in situ remineralisation of acid-softened enamel.

OBJECTIVES: This single-centre, randomised, crossover study used a short-term in situ dental erosion remineralisation model to explore the remineralisation of acid-softened enamel in the 4-h period immediately following brushing with an anti-erosion, dentin hypersensitivity test dentifrice containing 1150 ppm fluoride (as sodium fluoride [NaF]) or a placebo dentifrice with no fluoride. MATERIALS AND METHODS: Fifty participants wearing a palatal appliance holding surface-softened bovine enamel specimens brushed their natural teeth with their assigned dentifrice. Specimens were removed at 5-, 10-, 15-, 30-, 60-, 120- and 240-min post brushing. Enamel remineralisation effect was evaluated at each timepoint by percent surface microhardness recovery (%SMHR) and enamel fluoride uptake (EFU). After a second in vitro erosive challenge, the percent relative erosion resistance (%RER) was calculated. RESULTS: Statistically significant differences in %SMHR were observed for the test dentifrice compared with the placebo dentifrice from the 60-min timepoint onwards (all p < 0.02; mean difference of 8.66 [95% CI 3.46, 13.87] at 60 min). At each specimen removal time, %RER and EFU were statistically significantly higher for the test dentifrice compared with the placebo dentifrice (p < 0.0001 for all). No treatment-related or serious adverse events were reported. CONCLUSIONS: The NaF-containing anti-erosion, dentin hypersensitivity dentifrice improved remineralisation of acid-softened enamel starting at 60 min of intra-oral exposure. It also improved enamel erosion resistance and fluoride uptake as early as 5 min after exposure to fluoridated dentifrice slurry. CLINICAL RELEVANCE: Brushing with a NaF-containing dentifrice can rapidly improve remineralisation, enamel erosion resistance and fluoride uptake.

Early diagnosis and daily practice management of erosive tooth wear lesions.

This paper explores some of the most relevant questions faced by dental practitioners when diagnosing early erosive tooth wear (ETW) and implementing non-operative management of this condition over time. It focuses on the identification of clinical signs and common locations of ETW lesions, the assessment of individual risk and the implementation of non-operative management strategies, aiming to arrest and/or reduce the rate of ETW progression and avoid its advance to pathological stages. To this end, we present a novel and comprehensive approach that considers the whole dentition of patients rather than individual groups of teeth or dental surfaces only, illustrating it with a series of clinical photographs. Dental practitioners may find this approach particularly helpful as it closely simulates the clinical examinations of patients of all age groups carried out in daily practice. The clinical signs of early ETW lesions are subtle and often not perceived as relevant by unaware clinicians. However, the early diagnosis and implementation of non-operative management strategies, especially at younger ages, is fundamental for the proper control of ETW over time.

Susceptibility of partially desalivated rats to erosive tooth wear by calcium-supplemented beverages.

OBJECTIVES: To investigate the susceptibility of partially desalivated rats to erosive tooth wear (ETW); the anti-erosive effect of a calcium-supplemented beverage; and the quantification of ETW by microcomputed tomography (micro-CT). METHODS: The study population consisted of thirty-eight rats, divided into partially desalivated (n = 19) and normal salivary flow (n = 19). They were randomly allocated into three subgroups (n = 6-7): A-diet soda, B-diet soda + calcium, C-water (control). Solutions were provided ad libitum for 28 days, and the rats were euthanized afterwards. Each left hemi-mandible was scanned using micro-CT for enamel volume (three molars) calculation. Visual analysis of photographs of the lingual surface of first molars was performed independently by three blinded examiners. Data were statistically analysed (α = .05). RESULTS: Micro-CT revealed no significant differences between partially desalivated or normal groups. Rats consuming A had more enamel loss than those consuming B or C, which did not differ from each other. For visual analysis, desalivation did not affect ETW. Rats consuming C showed the lowest ETW, followed by B and then A, for both partially desalivated and normal rats. Spearman correlation between the two ETW quantification methods was -.65. CONCLUSIONS: Partial desalivation did not increase ETW. Ca-containing beverage prevented ETW. Micro-CT quantified ETW, although it was not as sensitive as visual analysis.

In Situ Study to Confirm the Anticaries Potential of a Sodium Monofluorophosphate Dentifrice Containing Calcium Sodium Phosphosilicate.

OBJECTIVES: A randomized, investigator-blind, five-treatment, crossover, non-inferiority study was conducted to investigate the effect of the addition of calcium sodium phosphosilicate (CSPS), an agent known to relieve dentin hypersensitivity, to a sodium monofluorophosphate (SMFP)-containing dentifrice on the enamel remineralization potential of fluoride (F), as assessed by percentage surface microhardness recovery (%SMHR) and enamel fluoride uptake (EFU) using a standard in situ caries model. METHODS: Seventy-seven subjects wearing bilateral mandibular partial dentures holding partially demineralized bovine enamel specimens 24 hours/day brushed their teeth with their assigned randomized dentifrice containing either 1500 or 0 ppm F with 5% CSPS or 1500, 500, or 0 ppm F with 0% CSPS twice daily for 21 days. The success criterion was to observe a difference in % SMHR between dentifrices containing 1500 ppm F of six units or less in the upper bound of the two-sided 95% confidence interval (CI). RESULTS: Following 21 days of treatment, the upper bound CI of the %SMHR difference between the dentifrices containing 1500 ppm F was 1.66, thus within the non-inferiority limit. No statistically significant differences for %SMHR (p = 0.2601) and EFU (p = 0.2984) were noted between these two dentifrices. CONCLUSIONS: The present in situ caries study provides evidence demonstrating that the addition of the calcium-containing compound CSPS to a 1500 ppm F dentifrice does not interfere with the ability of fluoride to remineralize surface-softened enamel; i.e., CSPS neither impairs nor improves the potential cariostatic value of SMFP dentifrice.

Toothpastes and enamel erosion/abrasion - Impact of active ingredients and the particulate fraction.

OBJECTIVES: To investigate in vitro a range of differently characterised toothpastes with respect to their efficacy in an erosion/abrasion setting with special emphasis on the role of the particulate ingredients. METHODS: Human enamel samples were erosively demineralised with citric acid (2min, 6×/day; 0.5%, pH 2.5; 10 days) and immersed in slurries (2min, 2×/day) either without or with brushing (15s, load 200g). The toothpastes were eight NaF-toothpastes, three hydroxyapatite-toothpastes (one without and two with NaF), one fluoride-free chitosan-toothpaste and three Sn-toothpastes. Negative control was erosion only, positive control was SnF2 gel. Tissue loss was quantified profilometrically. RESULTS: The SnF2 gel was most effective (reduction of tissue loss of 79%). Most of the products reduced tissue loss significantly when applied as slurries (between 28 and 66%). Brushing increased tissue loss in almost all toothpastes, only 5 formulations (all Sn-toothpastes and 2 NaF-toothpastes) reduced tissue loss significantly when compared to negative control (between 33 and 59%). There was a non-linear association between abrasiveness and amount of particles in a formulation, the particle size had no impact. CONCLUSIONS: Toothpastes had a protecting effect when applied as slurries but to a much lesser degree when applied with brushing. The particulate fraction may be a determinant for toothpaste efficacy in erosion/abrasion settings. CLINICAL SIGNIFICANCE: Toothpastes are important carriers of active agents against erosion, but physical impacts through brushing modifies efficacy distinctly. Understanding the role of the particulate fraction in toothpastes may offer perspectives for designing effective formulations for patients with erosive lesions.

Toothbrushing abrasion susceptibility of enamel and dentin bleached with calcium-supplemented hydrogen peroxide gel.

UNLABELLED: The objective of this study was to evaluate enamel and dentin susceptibility to toothbrushing abrasion, after bleaching with 7.5% hydrogen peroxide (HP) gel supplemented or not with 0.5% calcium gluconate (Ca). Toothbrushing was performed immediately and 1h after bleaching, with two suspensions (high and low abrasivity). Bovine enamel and dentin specimens were divided into 12 groups (n=10) according to the bleaching gel (with and without Ca), slurry abrasivity (high or low) and elapsed time after bleaching (immediately and after 1h). As control, a group was not bleached, but abraded. The treatment cycle (7 d) consisted of bleaching (1h) and toothbrushing (135 strokes/day) immediatelly or after 1h of artificial saliva exposure. Surface roughness and surface loss (µm) were measured by profilometry and analysed by three-way ANOVA (5%). Surface roughness means were significantly influenced by slurry abrasivity (p<0.0001). For enamel loss, significant triple interaction was observed (p<0.0001). HP-bleached groups and immediately brushed with high-abrasive slurry exhibited increased loss (1.41±0.14) compared to other groups (µm). Control and HP+Ca-bleached groups brushed after 1h with low abrasive slurry presented the lowest loss (0.21±0.03/0.27±0.02). For dentin loss, significant interaction was observed for bleaching and interval factors (p<0.001). 7.5%HP-bleached groups and immediately brushed showed significantly higher loss (8.71±2.45) than the other groups. It was concluded that surface roughness increased when high abrasive was used, independently of bleaching. 7.5%HP increased enamel and dentin loss, mainly with high abrasive slurries. Calcium supplementation of bleaching gel reduced surface loss. Additionally, in order to minimize tooth wear susceptibility, it is recommended to delay brushing after bleaching. CLINICAL RELEVANCE: After bleaching gel application, postponing toothbrushing is recommended, as well as brushing with low abrasive dentifrices. Additionally, supplementation of hydrogen peroxide gel with calcium-based remineralizing agent potentially reduces tooth loss after abrasion.

Dental Surface Texture Characterization Based on Erosive Tooth Wear Processes.

The differential diagnosis of dental wear lesions affects their clinical management. We hypothesized that surface texture parameters can differentiate simulated erosion, abrasion, and erosion-abrasion lesions on human enamel and dentin. This in vitro study comprised 2 parts (both factorial 4 × 2), with 4 lesion types (erosion, abrasion, erosion-abrasion, and sound [no lesion; control]) and 2 substrates (enamel and dentin). Flattened/polished dental specimens were used in part 1, whereas natural dental surfaces were used in part 2. Testing surfaces were evaluated in blind conditions, using average surface roughness (Sa) and the following scale-sensitive fractal analysis parameters: area-scale fractal complexity (Asfc), exact proportion length-scale anisotropy of relief (eplsar), scale of maximum complexity (Smc), and textural fill volume (Tfv). Two-way analyses of variance, followed by Fisher's protected least significant difference tests (α = 0.05), were used to evaluate the effects of lesion and substrate. Classification trees were constructed to verify the strength of potential associations of the tested parameters. In part 1,Asfc, Sa, and Tfv were able to differentiate erosion and erosion-abrasion lesions from the sound (no lesion) control in both substrates; only Asfc differentiated erosion and erosion-abrasion enamel lesions (allP< 0.05). The best association of parameters correctly classified up to 84% and 94% of the lesions on enamel and dentin, respectively. In part 2, only Asfc differentiated erosion and erosion-abrasion lesions from the sound (no lesion) control in both substrates, whereas eplsar was able to differentiate erosion from erosion-abrasion (allP< 0.05). The association of parameters correctly classified up to 81% and 91% of the lesions in enamel and dentin, respectively.Asfc, Sa, and Tfv were able to differentiate erosion and erosion-abrasion lesions, despite their complicated surface textures. The association of parameters improved the differentiation of lesions for both enamel and dentin in polished or natural surfaces.

The impact of stannous, fluoride ions and its combination on enamel pellicle proteome and dental erosion prevention.

OBJECTIVES: To compare the effects of stannous (Sn) and fluoride (F) ions and their combination on acquired enamel pellicle (AEP) protein composition (proteome experiment), and protection against dental erosion (functional experiment). METHODS: In the proteome experiment, bovine enamel specimens were incubated in whole saliva supernatant for 24h for AEP formation. They were randomly assigned to 4 groups (n=10), according to the rinse treatment: Sn (800ppm/6.7mM, SnCl2), F (225ppm/13mM, NaF), Sn and F combination (Sn+F) and deionized water (DIW, negative control). The specimens were immersed 3× in the test rinses for 2min, 2h apart. Pellicles were collected, digested, and analyzed for protein content using liquid chromatography electrospray ionization tandem mass spectrometry. In the functional experiment, bovine enamel specimens (n=10) were similarly treated for pellicle formation. Then, they were subjected to a five-day erosion cycling model, consisting of 5min erosive challenges (15.6 mM citric acid, pH 2.6, 6×/d) and 2min treatment with the rinses containing Sn, F or Sn+F (3×/d). Between the treatments, all specimens were incubated in whole saliva supernatant. Surface loss was determined by profilometry. RESULTS: Our proteome approach on bovine enamel identified 72 proteins that were common to all groups. AEP of enamel treated with Sn+F demonstrated higher abundance for most of the identified proteins than the other groups. The functional experiment showed reduction of enamel surface loss for Sn+F (89%), Sn (67%) and F (42%) compared to DIW (all significantly different, p<0.05). CONCLUSION: This study highlighted that anti-erosion rinses (e.g. Sn+F) can modify quantitatively and qualitatively the AEP formed on bovine enamel. Moreover, our study demonstrated a combinatory effect that amplified the anti-erosive protection on tooth surface.

Dose-response effect of fluoride dentifrice on remineralisation and further demineralisation of erosive lesions: A randomised in situ clinical study.

OBJECTIVE: The objective was to evaluate the ability of fluoride in a conventional, non-specialised sodium fluoride-silica dentifrice to promote tooth remineralisation and enamel fluoride uptake (EFU), and assess the resistance of the newly formed mineral to attack by dietary acid, across the concentration range used in mass-market dentifrices. METHODS: Subjects wore a palatal appliance containing eight polished bovine enamel specimens, each including an early erosive lesion. In a randomised full-crossover sequence, 62 healthy subjects were treated with dentifrices containing four different fluoride concentrations: no fluoride; 250ppm, 1150ppm and 1426ppm fluoride. At each treatment visit, under supervision, subjects brushed with 1.5g dentifrice and rinsed once while wearing the appliance; the appliance was removed after a 4-h remineralisation period and effects on the enamel specimens determined. The primary efficacy variable was surface microhardness recovery (SMHR); others included EFU, relative erosion resistance (RER) and comparative erosion resistance. RESULTS: Highly significant linear and, with the exception of SMHR, quadratic dose-response relationships were observed between all efficacy variables and fluoride concentration. For SMHR, EFU and RER, values for the different fluoride concentrations were statistically resolved from one another, with the exception of the two highest fluoride concentrations. The degree of remineralisation and the acid resistance of enamel after treatment were closely related to EFU. CONCLUSION: After a single brushing, conventional non-specialised sodium fluoride-silica dentifrices promoted remineralisation of early enamel lesions, and imparted increased acid-resistance to the enamel surface, in a dose-dependent manner at least up to 1500ppm fluoride. CLINICAL SIGNIFICANCE: Enamel erosive tissue loss is an increasing concern, associated with modern diets. This study demonstrated that sodium fluoride, in a conventional non-specialised dentifrice formulation, can promote repair of the earliest stages of enamel erosion after a single application, in a dose-dependent fashion across the fluoride concentration range used in mass-market dentifrices. This study is registered in the GlaxoSmithKline Study Register (ID RH01299), available at: www.gsk-clinicalstudyregister.com/study/RH01299.

Interplay between experimental dental pellicles and stannous-containing toothpaste on dental erosion-abrasion.

The interaction between stannous-containing dentifrice slurry and experimentally formed pellicles was investigated on enamel and root dentin using an erosion-remineralization-abrasion cycling model. The remineralizing solutions contained no proteins (negative control), mucin, casein, mucin + casein or albumin, for experimental pellicle formation. Toothbrushing was performed with fluoride toothpaste, with (TP + Sn) and without (TP) 3,500 ppm Sn. TP + Sn reduced surface loss for both enamel and root dentin (p < 0.05). The association between TP + Sn and albumin resulted in a significantly lower enamel surface loss (p < 0.05), suggesting positive interaction of stannous ion and albumin on dental erosion-abrasion protection. A similar trend was observed for root dentin, although less pronounced.

A defined-multispecies microbial model for studying enamel caries development.

The aims of this study were to describe and validate an in vitro multispecies microbial biofilm model for caries development by evaluating the effects of varying medium concentration of sucrose (0.5 and 1.0%) and fluoride (0.4, 0.8 and 1.0 ppm F) in study 1, and calcium (1.0 and 2.0 mM Ca) in study 2. Defined-multispecies biofilms, formed by Lactobacillus casei, Streptococcus mutans, S. salivarius and S. sanguinis, were grown on the surface of salivary-pellicle-coated enamel slabs, with known baseline surface hardness; growth medium was changed daily. Counts of viable cells on biofilms and the percentage of surface microhardness change (%SMC), lesion depth (LD) and integrated mineral loss (IML) on enamel slabs were assessed after 4 days of biofilm formation under the tested conditions. Counts of viable cells on biofilms were significantly affected by sucrose, fluoride and calcium concentrations (p < 0.05). There was a decrease in %SMC in response to increased fluoride and calcium concentrations (p < 0.001). Lower IML (p < 0.001) and LD (p < 0.05) were found in the presence of 0.8 and 1.0 ppm F. A negative correlation was found between the response variables (%SMC, LD and IML) and fluoride and calcium concentrations. The results suggest that the microbial caries model developed was able to show distinct levels of caries inhibition in response to fluoride and calcium concentrations, corroborating clinical observations. An effect of sucrose concentration on caries development was found only in the presence of the lowest fluoride concentration.

Strontium and caries: a long and complicated relationship.

Investigations into the role of strontium (Sr) in caries prevention have attracted great interest in the research community in the past, with their peak in the 1970-80s. To this date, no clear indication of the relative importance of Sr in caries prevention has been provided. A vast number of animal caries, epidemiological and mechanistic studies have been conducted. Although there is much discrepancy, the majority of studies suggest that Sr exhibits some cariostatic properties, predominantly in the presence of fluoride. An optimum Sr concentration of 5-10 ppm in drinking water has been proposed as a direct result of several epidemiological caries studies. Despite these results, no direct link can be established between Sr and caries prevention as, to date, no relevant, randomized controlled trials have been reported. The extrapolation of potential cariostatic properties of Sr from epidemiological studies is difficult due to the co-presence of several other trace elements in the water of the study areas, with many of these elements being attributed cariostatic properties in their own right. Furthermore, the role of caries risk factors was not taken into consideration. There is a clear need for further research, especially on the mineral phases in the dental hard tissues, plaque and plaque fluid associated with Sr as these may give rise to a better understanding of this subject matter. Based on the current data, the cariostatic properties of Sr, or at least those proposed by some authors, cannot be supported.

Effect of fluoride, lesion baseline severity and mineral distribution on lesion progression.

The present study investigated the effects of fluoride (F) concentration, lesion baseline severity (ΔZ(base)) and mineral distribution on lesion progression. Artificial caries lesions were created using three protocols [methylcellulose acid gel (MeC), hydroxyethylcellulose acid gel (HEC), carboxymethylcellulose acid solution (CMC)] and with low and high ΔZ(base) groups by varying demineralization times within protocols. Subsequently, lesions were immersed in a demineralizing solution for 24 h in the presence of 0, 1, 2 or 5 ppm F. Changes in mineral distribution characteristics of caries lesions were studied using transverse microradiography. At baseline, the protocols yielded lesions with three distinctly different mineral distributions. Secondary demineralization revealed differences in F response between and within lesion types. In general, lowΔZ lesions were more responsive to F than highΔZ lesions. LowΔZ MeC lesions showed the greatest range of response among all lesions, whereas highΔZ HEC lesions were almost unaffected by F. Laminations were observed in the presence of F in all but highΔZ HEC and CMC lesions. Changes in mineral distribution effected by F were most pronounced in MeC lesions, with remineralization/mineral redeposition in the original lesion body at the expense of sound enamel beyond the original lesion in a dose-response manner. Both ΔZ(base) and lesion mineral distribution directly impact the F response and the extent of secondary demineralization of caries lesions. Further studies - in situ and on natural white spot lesions - are required to better mimic in vivo caries under laboratory conditions.

In situ evaluation of the erosive potential of orange juice modified by food additives.

The aim of this study was to evaluate the erosive potential of orange juice modified with food-approved additives: 0.4 g/l of calcium (Ca) from calcium lactate pentahydrate, 0.2 g/l of linear sodium polyphosphate (LPP) or their combination (Ca+LPP) were added to a commercially available orange juice (negative control, C-). A commercially available calcium-modified orange juice (1.6 g/l of calcium) was the positive control (C+). These juices were tested using a short-term erosion in situ model, consisting of a five-phase, single-blind crossover clinical trial involving 10 subjects. In each phase, subjects inserted custom-made palatal appliances containing 8 bovine enamel specimens in the mouth and performed erosive challenges for a total of 0 (control), 10, 20, and 30 min. Two specimens were randomly removed from the appliances after each challenge period. Enamel surface microhardness was measured before and after the clinical phase and the percentage of surface microhardness change (%SMC) was determined. Before the procedures, in each phase, the subjects performed a taste test, where the juice assigned to that phase was blindly compared to C-. Overall, C+ showed the lowest %SMC, being the least erosive solution (p < 0.05), followed by Ca+LPP and Ca, which did not differ from each other (p > 0.05). LPP and C- were the most erosive solutions (p < 0.05). Taste differences were higher for C+ (5/10 subjects) and Ca (4/10 subjects), but detectable in all groups, including C- (2/10 subjects). Calcium reduced the erosive potential of the orange juice, while no protection was observed for LPP.

Biomimetic approach for root caries prevention using a proanthocyanidin-rich agent.

The aim of this study was to evaluate the effects of a proanthocyanidin-rich grape seed extract (GSE) on the in vitro demineralization of root dentine. Root fragments were obtained from sound human teeth. The fragments were randomly assigned to different treatments solutions: GSE, fluoride (F), GSE+F and distilled water (control). Samples were treated daily for 30 min and subjected to a pH cycling artificial caries protocol using demineralization cycles (2.2 mM CaCl(2)×H(2)O, 2.2 mM KH(2)PO(4), 50 mM acetic acid, pH 4.3) for 6 h and remineralization cycles (20 mM HEPES, 2.25 mM CaCl(2)×H(2)O, 1.35 mM KH(2)PO(4), 130 mM KCl, pH 7.0) for 17.5 h. Mineral loss (ΔZ) and lesion depth (LD) were determined after 18 days of treatment/pH cycling, by transverse microradiography. GSE was able to minimize ΔZ and LD compared with the control group (p < 0.0001). The GSE+F and F groups showed the lowest values of ΔZ and LD (p < 0.05), with no statistically significant differences between them (p = 0.554 and p = 0.726, respectively). A biomimetic approach to strengthen root dentine using GSE results in decreased rates of root demineralization and may be used in conjunction with F to prevent root caries.

In situ fluoride response of caries lesions with different mineral distributions at baseline.

The present in situ study investigated the fluoride response of caries lesions with similar mineral loss but two distinct mineral distributions (low- and high-'R', calculated as the ratio of mineral loss to lesion depth). Sixteen subjects wore eight gauze-covered enamel specimens with preformed lesions placed buccally on their mandibular partial dentures for periods up to 4 weeks. The participants brushed twice daily for 1 min with an 1,100 ppm F (as NaF) dentifrice. After 3 and 4 weeks, specimens were retrieved and analyzed microradiographically (TMR) and by quantitative light fluorescence (QLF). TMR results revealed that low- and high-R lesions showed opposite behaviors - low-R lesions further demineralized, whereas high-R lesions exhibited some remineralization. In comparison, lesion depth increased in low-R, but remained unchanged in high-R lesions; R decreased in both, but more in high-R lesions; mineral density at the lesion surface remained unchanged in low-R, but increased in high-R lesions. Differences in mineral loss between lesion types increased further between 3 and 4 weeks. QLF did not mirror TMR results as low-R lesions were found to remineralize, whereas high-R lesions remained unchanged. It is likely that low-R lesions differ from high-R lesions chemically and microstructurally; therefore rendering low-R lesion more susceptible to further dissolution. During lesion formation, low-R in contrast to high-R lesions may not lose all of the solubility-determining impurities such as magnesium and carbonate, which can reprecipitate again in different mineral phases within the lesion. In conclusion, mineral distribution at baseline directly impacts in situ lesion response to fluoride.