Fluoride concentrations in unerupted fluorotic human enamel.

Unerupted fluorotic human enamel was obtained from teeth surgically removed from patients with dental fluorosis. Fluoride was measured in samples produced by serial acid etching from the surface to the interior of blocks of buccal and lingual enamel. The severity of fluorosis, according to the TF index, was determined from the macroscopic and microradiographic appearance of the specimens. The shape of the fluoride profiles was not affected by the degree of severity of fluorosis, but the fluoride concentrations increased with increasing severity of lesions. Fluoride concentrations were similar to those previously recorded in erupted fluorotic enamel and were not related to the length of time the teeth had been present in the jaws. It was concluded that the fluoride content of erupted fluorotic enamel represents fluoride acquired during tooth formation and that further uptake prior to eruption may be negligible.     

Effect of biomimetic mineralization on enamel and dentin: A Raman and EDX analysis

ObjectiveTo investigate the effect of an experimental biomimetic mineralization kit (BIMIN) on the chemical composition and crystallinity of caries-free enamel and dentin samples in vitro.MethodsEnamel and dentin samples from 20 human teeth (10 for enamel; 10 for dentin) were divided into a control group without treatment and test samples with BIMIN treatment. Quantitative analysis of tissue penetration of fluoride, phosphate, and calcium was performed using energy-dispersive X-ray spectroscopy (EDX). Mineralization depth was measured by Raman spectroscopy probing the symmetric valence vibration near 960 cm⁻¹ as a marker for crystallinity. EDX data was statistically analyzed using a paired t-test and Raman data was analyzed using the Student’s t-test.ResultsEDX analysis demonstrated a penetration depth of fluoride of 4.10 ± 3.32 μm in enamel and 4.31 ± 2.67 μm in dentin. Calcium infiltrated into enamel 2.65 ± 0.64 μm and into dentin 5.58 ± 1.63 μm, while the penetration depths for phosphate were 4.83 ± 2.81 μm for enamel and 6.75 ± 3.25 μm for dentin. Further, up to 25 μm of a newly mineralized enamel-like layer was observed on the surface of the samples. Raman concentration curves demonstrated an increased degree of mineralization up to 5–10 μm into the dentin and enamel samples.SignificanceBiomimetic mineralization of enamel and dentin samples resulted in an increase of mineralization and a penetration of fluoride into enamel and dentin.     

Sodium fluoride effect on erosion–abrasion under hyposalivatory simulating conditions

ObjectivesTo investigate the effect of fluoride (0, 275 and 1250 ppm F; NaF) in combination with normal and low salivary flow rates on enamel surface loss and fluoride uptake using an erosion–remineralization–abrasion cycling model.DesignEnamel specimens were randomly assigned to 6 experimental groups (n = 8). Specimens were individually placed in custom made devices, creating a sealed chamber on the enamel surface, connected to a peristaltic pump. Citric acid was injected into the chamber for 2 min followed by artificial saliva at 0.5 (normal flow) or 0.05 (low flow) ml/min, for 60 min. This cycle was repeated 4×/day, for 5 days. Toothbrushing with abrasive suspensions containing fluoride was performed for 2 min (15 s of actual brushing) 2×/day. Surface loss was measured by optical profilometry. KOH-soluble fluoride and enamel fluoride uptake were determined after the cycling phase. Data were analysed by two-way ANOVA.ResultsNo significant interactions between fluoride concentration and salivary flow were observed for any tested variable. Low caused more surface loss than normal flow rate (p < 0.01). At both flow rates, surface loss for 0 was higher than for 275, which did not differ from 1250 ppm F. KOH-soluble and structurally-bound enamel fluoride uptake were significantly different between fluoride concentrations with 1250 > 275 > 0 ppm F (p < 0.01).ConclusionsSodium fluoride reduced enamel erosion/abrasion, although no additional protection was provided by the higher concentration. Higher erosion progression was observed in low salivary flow rates. Fluoride was not able to compensate for the differences in surface loss between flow rates.     

Effect of application sequence of fluoride and CPP-ACP on remineralization of white spot lesions in primary teeth: An in-vitro study

ObjectiveTo explore how application sequence of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride influences remineralization of enamel white spot lesions (WSL) in primary teeth.DesignIn this in-vitro study, artificial WSLs were created in 130 primary teeth. Teeth were divided into 4 groups (n = 27) and a control group (n = 22) and exposed to one of the following remineralization regimens for 10 weeks: Group-1; 500 ppm fluoride dentifrice; Group-2; 10% w/v CPP-ACP; Group-3; fluoride applied first, then CPP-ACP; Group-4; CPP-ACP applied first, then fluoride, and Group-5 was control. All groups were kept in a remineralizing solution. Mineral changes (ΔF) were quantified weekly using quantitative light-induced fluorescence. Statistical analysis was done using Statistical Package for the Social Sciences (SPSS version 20.0).ResultsRemineralization occurred in all groups to different degrees; changes from baseline were significant in groups 1–4 (P ≤ 0.05). Group-4 showed the earliest significant remineralization (after 2 weeks) among groups, (P < 0.001). Group-4 showed maximum changes in ΔF among groups; however, only differences with Groups 1 and 5 were significant (P < 0.05 and P < 0.01, respectively). Group-3 showed better remineralization than Groups 1, 2 and 5; however, the difference was only significant with Group-5 (P < 0.001). There were no significant differences between Group 1and 2, however, only Group 2 showed better remineralization than Group 5, (P < 0.01).ConclusionCombined treatment with CPP-ACP followed by fluoride exhibited the best remineralization of white spot lesions in primary teeth in this study. Combined treatment with fluoride followed by CPP-ACP showed a tendency towards better remineralization than fluoride or CPP-ACP alone.     

Two types of intraoral distribution of fluorotic enamel

Abstract Different distributions of fluorotic dental enamel within the dentition have been described in the literature. This report describes two patterns of intraoral distribution. In nine Tanzanian low fluorosis communities with a prevalence of pitting fluorosis of less than 2% and in live moderate fluorosis communities with a prevalence of pitting fluorosis of 16–59%, incisors and first molars were the least affected teeth. In four high fluorosis communities with a prevalence of pitting fluorosis of 86–97%, maxillary incisors exhibited lower Thylstrup-Fejerskov Index values than the maxillary canines, premolars and molars. The mandibular teeth exhibited increasing Thylstrup-Fejerskov Index values from the anterior to the posterior region. The curves presenting the intraoral distribution of the severity of dental fluorosis corresponded with the curve presenting the completion time of primary enamel formation of the various tooth types, with the exception of the first molars in high fluorosis communities. The similarity of the curves suggests that the later in life enamel is completed, the higher is the severity of dental fluorosis. This relation seems to be explained by the prevailing feeding and dietary habits, which result in minimal intake of fluoride in the first 18 months of life during breastfeeding, followed by increasing fluoride ingestion in the following years through consumption of tea, seafish and F-containing magadi salt.     

Diagnostic guide enabling distinction between taphonomic stains and enamel hypomineralisation in an archaeological context

ObjectiveMolar Incisor Hypomineralisation (MIH) is a structural anomaly that affects the quality of tooth enamel and has important consequences for oral health. The developmentally hypomineralised enamel has normal thickness and can range in colour from white to yellow or brown with or without surface breakdown. The possibility of finding MIH in ‘ancient populations' could downplay several current aetiological hypotheses (e.g., dioxin derivatives, bisphenols, antibiotics) without excluding the possible multifactorial aspect of the anomaly. In an archaeological context, chemical elements contained in the burial ground can stain teeth yellow or brown and therefore might create a taphonomic bias. The purpose of the present study is to test a proposed diagnostic guide enabling determination of the pathological or taphonomic cause of enamel discolouration and defects that resemble MIH present on ‘ancient teeth'.DesignTwo sample groups including MIH discoloration (n = 12 teeth) from living patients, taphonomic discoloration (n = 9 teeth) and unknown discoloration (n = 2 teeth) from medieval specimens were tested. Three non-destructive methods—Raman spectroscopy, X-ray micro-computed tomography and X-ray fluorescence were utilised.ResultsHypomineralised enamel has decreased mineral density (p < 0.0001) and increased phosphate/β-carbonate ratio (p < 0.01) compared to normal enamel whereas relative concentrations of manganese, copper, iron and lead are similar. In taphonomic discoloration, relative concentrations of these elements are significantly different (p < 0.05) to normal enamel whereas mineral density and Raman spectra profile are comparable.ConclusionsEnamel hypomineralisation can be distinguished from taphonomic staining in archaeological teeth.     

Incremental lines in mouse molar enamel

ObjectiveThe purpose of the present study was to investigate the occurrence and periodicity of enamel incremental lines in mouse molars in an attempt to draw attention to some key questions about the rhythm in the activity of the secreting ameloblasts during formation of mouse molar enamel.MethodsThe mouse molars were ground, etched, and studied using scanning electron microscopy.ResultsLines interpreted as incremental lines generally appeared as grooves of variable distinctness, and were only observed cervically, in the region about 50–250 μm from the enamel–cementum junction. The lines were most readily observable in the outer enamel and in the superficial prism-free layer, and were difficult to identify in the deeper parts of enamel, i.e. in the inner enamel with prism decussation. However, in areas where the enamel tended to be hypomineralized the incremental lines were observed as clearly continuous from outer into inner enamel. The incremental lines in mouse molar enamel exhibited an average periodicity of about 4 μm, and the distance between the lines decreased towards the enamel surface.ConclusionsWe conclude that incremental lines are to some extent visible in mouse molar enamel. Together with data from the literature and theoretical considerations, we suggest that they probably represent a daily rhythm in enamel formation. This study witnesses the layered apposition of mouse molar enamel and supports the theory that circadian clock probably regulates enamel development.     

Inhibition of enamel mineral loss by fissure sealant: An in situ study

ObjectivesThis study evaluated the effect of fluoride and non-fluoride sealants on hardness decrease (HD) and marginal adaptation (MA) on enamel substrates after cariogenic challenge.MethodsOcclusal enamel blocks, from human third molars, were randomly divided into six groups (n = 12), according to occlusal fissures condition (S – sound; C – caries-like lesion; CF – caries-like lesion + topical fluoride) and sealants (F – FluroShield; H – Helioseal Clear Chroma). Lesion depths were 79.3 ± 33.9 and 61.3 ± 23.9 for C and CF groups, respectively. Sealants were placed on occlusal surface and stored at 100% humidity (37 °C; 24 h/d). HD was measured by cross-sectional microhardness analysis at the sealant margin distances: ?1 (under sealant), 0 (sealant margin), 1, 2 (outer sealant). Sealant MA was observed by polarized light microscopy and scored according to: 0 – failure (no sealant MA or total sealant loss); 1 – success (sealant MA present). MA and HD were analysed by ANOVA-R and mixed model analysis, respectively.ResultsFor HD (ΔS), F values (6900.5 ± 3686.6) were significantly lower than H values (8534.6 ± 5375.3) regardless of enamel substrates and sealant margin distances. Significant differences were observed among sealant margin distances: ?1 (5934.0 ± 3282.6) < 0 (8701.5 ± 6175.7) = 1 (8473.2 ± 4299.4) = 2 (7761.5 ± 4035.1), regardless of sealant and substrate. MA was similar for all groups (p ≥ 0.05).ConclusionMA was not affected by sealant type or substrate condition, whereas enamel HD was favourably impacted by fluoride in the sealant. In addition, sealants were more effective as a physical barrier than as its chemical potency in reducing enamel HD.Clinical significanceSealing with a fluoride material is a recommended procedure to prevent caries of occlusal permanent molars in high-caries-risk patients, even though those exhibiting white spot lesions, since the enamel hardness decrease when fluoride sealant was used in vitro.     

Acoustic emission analysis of the effect of simulated pulpal pressure and cavity type on the tooth–composite interfacial de-bonding

ObjectiveThe aim of this study was to evaluate the influence of in vitro pulpal pressure and cavity type on the tooth–composite bonding interface by means of acoustic emission (AE) analysis.MethodsClasses I and II cavities on extracted third molars were prepared and assigned to four groups of seven teeth each: (1) direct composite restoration without simulated pulpal pressure (SPP) in class I cavity, (2) direct composite restoration with SPP in class I cavity, (3) direct composite restoration without SPP in class II cavity, (4) direct composite restoration with SPP in class II cavity. The teeth were restored with Filtek Z250 composite and Adper Scotchbond Multi-Purpose adhesive system (3M ESPE, St. Paul, MN, USA). AE events were recorded for 2000 s during light-curing. Groups 2 and 4 were subjected to 20 cm H₂O hydrostatic pressure throughout the procedures. The data were analyzed with two-way ANOVA. After the AE test, teeth were sectioned longitudinally in mesio-distal direction, the tooth–composite interface was examined using SEM.ResultsSPP in Groups 2 (4.57 ± 1.40) and 4 (3.43 ± 1.13) yielded significantly higher AE events number than those of Groups 1 (3.43 ± 1.51) and 3 (1.71 ± 0.95) where the SPP was not applied (p < 0.05). The number of AE events of class I cavity in Groups 1 and 2 were significantly higher than those of class II cavity in Groups 3 and 4 (p < 0.05). SEM examination showed that all groups had intact enamel–composite interface, while micro-gaps were observed at the dentin–composite interface, mainly at the pulpal floor of the cavity. The class I cavities with SPP in Group 2 showed wider gaps more frequently than class II cavities without SPP in Group 3.SignificanceThe SPP and class I cavity with high C-factor triggered more AE events, confirming its negative impact on the bonding interface.     

Promotion of enamel caries remineralization by an amelogenin-derived peptide in a rat model

ObjectiveAn amelogenin-derived peptide has been shown to promote remineralization of demineralized enamel in an in vitro model of initial caries induced by pH cycling. The present study examines whether the peptide exerts similar effects within the complex oral environment in vivo.DesignSpecific pathogen-free Sprague-Dawley rats (n = 36) were infected with Streptococcus mutans, given ad libitum access to Diet 2000 and drinking water supplemented with sucrose (10%, w/v), and then randomly divided into three groups treated with 25 μM peptide solution, 1 g/L NaF or deionized water. Molar teeth were swabbed twice daily with the respective solutions for 24 days. Then animals were killed, their jaws were removed and caries lesions were analyzed using the quantitative light-induced fluorescence-digital (QLF-D) technique to measure changes in mineral content. To verify QLF-D results, caries were scored for lesion depth and size using the Keyes method, and analyzed using polarized light microscopy (PLM).ResultsMineral gain was significantly higher in teeth treated with peptide or NaF than in teeth treated with water (p < 0.05), based on the QLF-D results (ΔF and ΔQ). Incidence of smooth-surface and sulcal caries based on Keyes scores was similar in rats treated with peptide or NaF, and significantly lower in these groups than in rats treated with water (p < 0.05). Lesions on teeth treated with peptide or NaF were shallower, based on PLM. No significant differences were observed between molar enamel caries treated with peptide or NaF.ConclusionsThis amelogenin-derived peptide can promote remineralization in a rat caries model, indicating strong potential for clinical use.     

The proteomic profile of the acquired enamel pellicle according to its location in the dental arches

ObjectiveThis study evaluated the variation in the protein profile of the acquired enamel pellicle (AEP) formed in vivo according to its location in the dental arches.DesignThe AEP was formed for 120 min in 9 volunteers. Pellicle formed at upper + lower anterior facial (ULAFa; teeth 13–23 and 33–43), upper anterior palatal (UAPa; teeth 13–23), lower anterior lingual (LALi; teeth 33–43), upper + lower posterior facial (ULPFa; teeth 14–17 24–27, 34–37 and 44–47), upper posterior palatal (UPPa; teeth 14–17 and 24–27) and lower posterior lingual (LPLi; teeth 34–37 and 44–47) regions were collected separately and processed for analysis by label-free LC-ESI–MS/MS.ResultsThree-hundred sixty three proteins were identified in total, twenty-five being common to all the locations, such as Protein S100-A8, Lysozyme C, Lactoferrin, Statherin, Ig alpha-2, ALB protein, Myeloperoxidase and SMR3B. Many proteins were found exclusively in the AEP collected from one of the regions (46-UAPa, 33-LALi, 59-ULAFa, 31-ULPFa, 44-LPLi and 39-UPPa).ConclusionsThe protein composition of the AEP varied according to its location in the dental arches. These results provide important insights for understanding the differential protective roles of the AEP as a function of its location in the dental arches.     

Effect of full crown preparation on pulpal blood flow in man

ObjectiveTo determine if full crown preparation causes an increase in pulpal blood flow (PBF), indicating inflammation, in human subjects.DesignThe experiments were carried out on 35 intact, mandibular posterior teeth in 13 subjects: 32 were abutments for 16 fixed bridges that replaced first molars; the other 3 were first premolars adjacent to abutment teeth that served as un-operated controls. Crown preparations were made using an air-rotor with water-spray under regional block anaesthesia (4% articaine with epinephrine 1:100,000). PBF was recorded with a laser Doppler flow meter (LDF) before and after administering the anaesthetic, with the LDF probe on the buccal enamel. PBF was then recorded from the abutment teeth with the probe on buccal dentine after preparing the buccal surfaces of both teeth, after completing the crown preparations, and after 1 and 7 days. PBF was also recorded from the buccal enamel of the control teeth on each occasion.ResultsThe mean ± S.D. PBF values before and after anaesthesia were 2.63 ± 2.13 and 2.42 ± 2.38P.U. respectively, which were not significantly different (Paired t-test). The mean values for the abutment teeth after buccal preparation, after complete crown preparation, and after 1 and 7 days were 5.20 ± 2.49, 4.53 ± 2.52, 4.92 ± 2.98 and 5.48 ± 2.65P.U. respectively. The 4 values for each tooth were not significantly different (two-way RM ANOVA). In the control group, the values under all six conditions were not significantly different.ConclusionsRegional block anaesthesia produced no change in PBF, nor did full-crown preparation, neither immediately after the procedure nor 1 and 7 days later.     

Effect of fluoride toothpaste with nano-sized trimetaphosphate on enamel demineralization: An in vitro study

ObjectiveThis study evaluated the effect of toothpastes containing 1100 ppm F associated or not with micrometric or nano-sized sodium trimetaphosphate (TMP) on enamel demineralization in vitro, using a pH cycling model.DesignBovine enamel blocks (4 mm × 4 mm, n = 96) were randomly allocated into eight groups (n = 12), according to the test toothpastes: Placebo (without fluoride or TMP); 1100 ppm F (1100F); 1100F plus micrometric TMP at concentrations of 1%, 3% or 6%; and 1100F plus nanosized TMP at 1%, 3% or 6%. Blocks were treated 2×/day with slurries of toothpastes and submitted to a pH cycling regimen for five days. Next, final surface hardness (SHf), integrated hardness loss (IHL), differential profile of integrated hardness loss (ΔIHL) and enamel fluoride (F) concentrations were determined. Data were analyzed by ANOVA and Student-Newman-Keuls’ test (p < 0.05).ResultsThe use of 1100F/3%TMPnano led to SHf 30% higher (p < 0.001) and IHL ∼ 80% lower (p < 0.001) when compared to 1100F. This toothpaste also resulted in ∼64% reduction of mineral loss (ΔIHL) when compared to 1100F. Moreover, the addition of nano-sized TMP promoted increases in enamel F uptake of 90%, 160% and 100%, respectively for the concentrations of 1%, 3% and 6%, when compared to 1100F (p < 0.001).ConclusionThe addition of nano-sized TMP at 3% to a conventional toothpaste significantly decreased enamel demineralization when compared to its counterparts without TMP or supplemented with micrometric TMP.     

Scanning electron microscopic study of fluorotic permanent teeth enamel

The materia comprised 8 caries-free fluorotic permanent teeth (4 with severe and 4 with very mild fluorosis) and 4 caries-free non-fluorotic permanent teeth. The surface of teeth with severe fluorosis was mainly rought with discrete pitting and small parts of relative sound enamel. The subsurface enamel of teeth with severe fluorosis was with irregular cross-sectional shape of rod and more extensive inter-rod enamel spaces in comparison with other parts of enamel. The surface enamel of teeth with very mild fluorosis was mainly smooth, similar to the sound enamel, with small parts of rough enamel. In subsurface enamel of teeth with very mild fluorosis no difference was found between cross-sectional shape of rod and dimension of inter-rod enamel spaces in comparison with other parts of enamel.     

Multiscale analysis of stress distribution in teeth under applied forces

ObjectivesThe present study aimed to clarify stress distribution in teeth under an external applied load using microindentation and multiscale simulation.MethodsAnisotropic material properties of enamel and dentin were measured using a microindentation method with a dynamic ultra microhardness tester. The numerical model was constructed using the finite element mesh superposition method with a microscale (enamel rods), mesoscale (teeth), and macroscale (bone). Multiscale simulation was used to analyze different scale structures. A concentrated load (10 N) was applied to the labial surface of the central incisor.ResultsThe results revealed stresses of 5 MPa (normal stress) and 6.5 MPa (shear stress) in the enamel sheath at the center of the labial region compared to 1.4 MPa (normal stress) and 21.4 MPa (shear stress) in the cervical region.SignificanceThese results suggest that shear stresses in the enamel sheath may play significant roles in stress transmission.     

Appropriate real-time PCR reference genes for fluoride treatment studies performed in vitro or in vivo

ObjectiveQuantitative real-time PCR (qPCR) is routinely performed for experiments designed to identify the molecular mechanisms involved in the pathogenesis of dental fluorosis. Expression of reference gene(s) is expected to remain unchanged in fluoride-treated cells or in rodents relative to the corresponding untreated controls. The aim of this study was to select optimal reference genes for fluoride experiments performed in vitro and in vivo.DesignFive candidate genes were evaluated: B2m, Eef1a1, Gapdh, Hprt and Tbp. For in vitro experiments, LS8 cells derived from mouse enamel organ were treated with 0, 1, 3 and/or 5 mM sodium fluoride (NaF) for 6 or 18 h followed by RNA isolation. For in vivo experiments, six-week old rats were treated with 0 or 100 ppm fluoride as NaF for six weeks at which time RNA was isolated from enamel organs. RNA from cells and enamel organs were reverse-transcribed and stability of gene expression for the candidate reference genes was evaluated by qPCR in treated versus non-treated samples.ResultsThe most stably expressed genes in vitro according to geNorm were B2m and Tbp, and according to Normfinder were Hprt and Gapdh. The most stable genes in vivo were Eef1a1 and Gapdh. Expression of Ddit3, a gene previously shown to be induced by fluoride, was demonstrated to be accurately calculated only when using an optimal reference gene.ConclusionsThis study identifies suitable reference genes for relative quantification of gene expression by qPCR after fluoride treatment both in cultured cells and in the rodent enamel organ.     

Influence of bonding surface and bonding methods on the fracture resistance and survival rate of full-coverage occlusal veneers made from lithium disilicate ceramic after cyclic loading

ObjectivesThe purpose of this laboratory study was to evaluate the influence of bonding method and type of dental bonding surface on fracture resistance and survival rate of resin bonded occlusal veneers made from lithium disilicate ceramic after cyclic loading.MethodsFourty-eight extracted molars were divided into three groups (N = 16) depending on the preparation: within enamel, within dentin/enamel or within enamel/composite resin filling. Lithium disilicate occlussal veneers were fabricated with a fissure-cusp thickness of 0.3–0.6 mm. Restorations were etched (5% HF), silanated and adhesively luted using a dual-curing luting composite resin. Test groups were divided into two subgroups, one using a only a self-etching primer, the other additionally etching the enamel with phosphoric acid. After water storage (37 °C; 21 d) and thermocycling (7500 cycles; 5–55 °C), specimens were subjected to dynamic loading in a chewing simulator (600,000 cycles; 10 kg/2 Hz). Surviving specimens were loaded until fracture using a universal testing machine.ResultsAll specimens survived artificial aging, several specimens showed some damage. ANOVA revealed that enamel etching provided statistically significantly (p ≤ 0.05) higher fracture resistance than self-etching when bonding to enamel and dentin. Self-etching provided statistically significant (p ≤ 0.05) higher fracture resistance for the enamel-composite group than for the enamel group. Enamel etching provided statistically significant (p ≤ 0.05) higher fracture resistance for the enamel and dentin group than for groups enamel and enamel-composite.SignificanceEtching enamel improved the fracture resistance of occlusal veneers when bonding to dentin and enamel and increased the survival rate when bonding to enamel.     

Frequency of intake and amount of fluoride in milk for remineralisation of artificial caries on enamel and dentine: Ex vivo/in situ study

ObjectivesThis study analysed the effect of frequency of intake and amount of fluoride in milk on the remineralisation of artificial enamel and dentine caries lesions ex vivo/in situ.Materials and methodsPre-demineralised bovine enamel and dentine slabs were randomly allocated into 5 groups and fixed in removable appliances used by subjects for 7 days in each phase. Each treatment comprised milk containing 2.5 ppm fluoride daily (T1), or every other day (T2), 5.0 ppm F daily (T3), or every other day (T4) or no treatment (T5).ResultsEnamel alterations were quantified by surface hardness recovery (%SHR) and transversal microradiography (TMR), and in dentine by TMR only. Data were analysed by ANOVA and Tukey’s test (p < 0.05). For enamel, the highest %SHR was found for T1 and T3 compared to control, without significant differences between them. All groups showed positive values of ΔΔZ − T1 (247.3 ± 198.5); T2 (110.9 ± 303.2); T3 (226.0 ± 299.2); T5 (5.0 ± 288.0), except T4 (−274.5 ± 407.3). For dentine, the only group that presented remineralisation was T2 (350.0 ± 657.5).ConclusionsFluoridated milk daily seems to have higher remineralising effect on enamel than its use every other day. Dentine, does not seem to benefit from daily use of fluoridated milk.     

Wear evaluation of the human enamel opposing different Y-TZP dental ceramics and other porcelains

PurposeThis study examined the wear resistance of human enamel and feldspathic porcelain after simulated mastication against 3 zirconia ceramics, heat-pressed ceramic and conventional feldspathic porcelain.Materials and methodsHuman teeth and feldspathic porcelain cusp were tested against ceramic discs. 5 brands were tested – 3 monolithic zirconia, Prettau, Lava, and Rainbow, one lithium disilicate, IPS e.max Press, and one feldspathic porcelain, Vita-Omega 900. The surface was polished using a 600 grit and 1200 grit SiC paper. Each group was loaded for 300,000 cycles in a chewing simulator. The wear resistance was analyzed by measuring the volume of substance lost. The wear surfaces were observed by scanning electron microscopy to determine the wear characteristics.ResultsVita-Omega 900 led to the greatest amount of enamel wears followed by IPS e.max Press, Prettau, Lava and Rainbow. There was a significant difference between Vita-Omega 900 and IPS e.max Press (p < 0.05). The wear values for human enamel were significantly greater than those for feldspathic porcelain, regardless of the surface roughness of the ceramic specimens (p < 0.05).ConclusionThe wear behaviour of human enamel and feldspathic porcelain varies according to the type of substrate materials. On the other hand, 3 zirconia ceramics caused less wear in the abrader than the conventional ceramic.Clinical significanceDental professionals should be aware of the wear effect of dental restorations on the opposing teeth or restorations. The amount of enamel wear was highest in feldspathic porcelains whereas zirconia ceramics caused less wear on the opposing teeth.