Bonding strategies for MIH-affected enamel and dentin

Objectives

Aim of the present study was to evaluate resin composite adhesion to dental hard tissues affected by molar incisor hypomineralisation (MIH).

Genes expressed in dental enamel development are associated with molar-incisor hypomineralization

Genetic disturbances during dental development influence variation of number and shape of the dentition. In this study, we tested if genetic variation in enamel formation genes is associated with molar-incisor hypomineralization (MIH), also taking into consideration caries experience. DNA samples from 163 cases with MIH and 82 unaffected controls from Turkey, and 71 cases with MIH and 89 unaffected controls from Brazil were studied. Eleven markers in five genes [ameloblastin (AMBN), amelogenin (AMELX), enamelin (ENAM), tuftelin (TUFT1), and tuftelin-interacting protein 11 (TFIP11)] were genotyped by the TaqMan method. Chi-square was used to compare allele and genotype frequencies between cases with MIH and controls. In the Brazilian data, distinct caries experience within the MIH group was also tested for association with genetic variation in enamel formation genes. The ENAM rs3796704 marker was associated with MIH in both populations (Brazil: p = 0.03; OR = 0.28; 95% C.I. = 0.06–1.0; Turkey: p = 1.22e?012; OR = 17.36; 95% C.I. = 5.98–56.78). Associations between TFIP11 (p = 0.02), ENAM (p = 0.00001), and AMELX (p = 0.01) could be seen with caries independent of having MIH or genomic DNA copies of Streptococcus mutans detected by real time PCR in the Brazilian sample. Several genes involved in enamel formation appear to contribute to MIH.     

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.     

Graded changes in enamel component volumes resulted from a short tooth bleaching procedure

AimTo test the hypothesis that changes in enamel component volumes (mineral, organic, and water volumes, and permeability) are graded from outer to inner enamel after a short bleaching procedure.Materials and methodsExtracted unerupted human third molars had half of their crowns bleached (single bleaching session, 3 × 15 min), and tooth shade changes in bleached parts were analyzed with a spectrophotometer. Ground sections were prepared, component volumes and permeability were quantified at histological points located at varying distances from the enamel surface (n = 10 points/location), representing conditions before and after bleaching.ResultsTooth shade changes were significant (p < 0.001; 95% CI = −1/−8; power = 99%), and most of the enamel layer was unaffected after bleaching, except at the outer layers. Multiple analysis of covariances revealed that most of the variance of the change in enamel composition after bleaching was explained by the combination of the set of types of component volume (in decreasing order of relevance: mineral loss, organic gain, water gain, and decrease in permeability) with the set of distances from the enamel surface (graded from the enamel surface inward) (canonical R² = 0.97; p < 0.0001; power > 99%).ConclusionsChanges in enamel composition after a short bleaching procedure followed a gradient within component volumes (mineral loss > organic gain > water gain > decrease in permeability) and decreased from the enamel surface inward.     

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 effect of magnesium hydroxide-containing dentifrice using an extrinsic and intrinsic erosion cycling model

ObjectiveTo evaluate, in vitro, the effect of Mg(OH)₂ dentifrice, and the influence of the number of experimental days, on the extrinsic (citric acid –CA) and intrinsic (hydrochloric acid –HCl) enamel erosion models.DesignHuman enamel slabs were selected according to surface hardness and randomly assigned to 3 groups (n = 9) as follows: non-fluoridated (negative control), NaF (1450 ppm F- positive control) and Mg(OH)₂ (2%) dentifrices. The slabs were daily submitted to a 2-h period of pellicle formation and, over a period of 5 days, submitted to cycles (3×/day) of erosive challenge (CA 0.05 M, pH = 3.75 or HCl 0.01 M, pH = 2 for 30 s), treatment (1 min −1:3 w/w of dentifrice/distilled water) and remineralization (artificial saliva/120 min). Enamel changes were determined by surface hardness loss (SHL) for each day and mechanical profilometry analysis. Data were analyzed by two-way ANOVA followed by Tukey’s test to % SHL and one-way ANOVA to profilometry (p < 0.05).ResultsThe number of experimental days influenced the erosion process for the two types of erosion models (p < 0.001). Mg(OH)₂-containing dentifrices were effective in reducing enamel extrinsic acid erosion as determined by % SHL (p < 0.001) when compared to the control group, being better than positive control (p < 0.001); however, the dentifrices were not effective for the intrinsic model (p = 0.295). With regards to surface wear, no statistically significant differences were found among the groups for CA (p = 0.225) and HCl (p = 0.526).ConclusionThe findings suggest that Mg(OH)₂ dentifrices might protect enamel against slight erosion, but protection was not effective for stronger acid erosion.     

Effects of different radiation doses on the microhardness,superficial morphology,and mineral components of human enamel

ObjectiveTo evaluate the effects of three different radiotherapy doses (20, 40, and 70 Gy) on the microhardness, superficial morphology, and mineral content (based on Ca and P values) of three different depths of human enamel (cervical, middle, and occlusal).DesignThirty-four third molars were cut, separated, and prepared. Microhardness samples (n = 30) were embedded in acrylic resin and then polished, and depths were delimited. Microhardness tests were performed on cervical, middle, and occlusal enamel pre- and post-radiotherapy with a load of 50 g for 30 s. For the scanning electron microscopy (SEM) analysis (n = 4) and energy dispersive X-ray spectroscopy (EDS) (n = 12), samples were fixed in a 3% glutaraldehyde solution, washed in 0.1 M cacodylate solution, and dehydrated in crescent concentrations of ethanol. Microhardness data were tested for significant differences using a two-way analysis of variance (ANOVA) and Tukey’s test (p < 0.05), while SEM and EDS were evaluated qualitatively.ResultsThe results showed a decrease in microhardness values only in the cervical enamel, regardless of the radiation dose used; no morphological or mineral change was observed.ConclusionRadiotherapy can affect the microhardness values of only cervical enamel without compromising the morphological or mineral (Ca and P) content at any depth.     

Vertical and horizontal polymerization shrinkage in composite restorations

ObjectivePolymerization shrinkage developed in vertical and horizontal directions after light activation of light-curing composite restorative materials. The purpose of this study was to examine the effects of vertical and horizontal polymerization shrinkage on: (a) dimensional changes of resin composites in tooth cavities; (b) shear bond strengths to enamel and dentin; and (c) marginal gap width in a non-reacting Teflon mold.MethodsVertical and horizontal polymerization shrinkage in tooth cavities were measured immediately (3 min) after light activation. With the same time lapse, shear bond strengths to enamel and dentin and marginal gap widths in Teflon mold were also measured.ResultsThere was a significant correlation between vertical and horizontal polymerization shrinkage (r = 0.647, p = 0.043) in the tooth cavity. Composite materials which produced small vertical shrinkage also produced smaller horizontal shrinkage. Composite materials which produced small vertical shrinkage in the tooth cavity exhibited greater shear bond strengths to both enamel (r = −0.697, p = 0.025) and dentin (r = −0.752, p = 0.012). Composite materials which produced smaller horizontal shrinkage produced smaller marginal gap widths in the Teflon mold (r = 0.829, p = 0.003). No relationships were observed between horizontal shrinkage in the tooth cavity and shear bond strengths to both enamel and dentin (p > 0.05).SignificanceDuring the early stage of setting (<3 min) in tooth cavities, the vertical shrinkage of light-activated composite restorative materials was correlated with horizontal shrinkage.     

Frequency of periodontal pathogens in equivalent peri-implant and periodontal clinical statuses

ObjectivesThis study tested the hypotheses that there is: (1) higher bacterial frequency in peri-implantitis/periodontitis, followed by mucositis/gingivitis and peri-implant/periodontal health; (2) similar bacterial frequency between comparable peri-implant and periodontal clinical statuses.Design of studyThe presence of Porphyromonas gingivalis, Tannerella forsythia, Campylobacter rectus, Prevotella intermedia, Treponema denticola and Aggregatibacter actinomycetemcomitans was evaluated in peri-implant (n = 53) and periodontal (n = 53) health; mucositis (n = 50), gingivitis (n = 50), peri-implantitis (n = 50) and periodontitis (n = 50).ResultsThe pattern of peri-implant bacterial frequency was not as expected (peri-implantitis > mucositis > health). Except for P. intermedia (p > 0.05), bacterial frequency was higher in peri-implantitis than health (p < 0.05). The frequency of P.gingivalis and red complex species were higher in peri-implantitis than mucositis (p < 0.05). In periodontal samples, T. forsythia and T. denticola showed the expected pattern of frequency (periodontitis > gingivitis > health). The frequencies of C. rectus and T. forsythia were higher in healthy teeth/gingivitis than healthy implants/mucositis, respectively (p < 0.05). The frequency of P. gingivalis and A. actinomycetemcomitans were similar between periodontitis and peri-implantitis (p > 0.05) while all other species occurrences were higher in periodontitis than peri-implantitis (p < 0.05).ConclusionsBacterial frequency increased from peri-implant/periodontal health to peri-implantitis/periodontitis but not from mucositis/gingivitis to peri-implantitis/periodontitis. There was a trend towards higher bacterial frequency in teeth than implants.     

In vitro enamel erosion and abrasion-inhibiting effect of different fluoride varnishes

ObjectiveTo investigate the erosion and abrasion inhibiting effect of CPP-ACP/NaF and xylitol/NaF varnishes.MethodsBovine enamel samples (n = 40) were exposed to the following treatments (n = 10): NaF varnish (Duraphat^®, positive control); CPP-ACP/NaF varnish (MI varnishTM); xylitol/NaF (Profluorid^®) or distilled and deionized water (MilliQ^®, negative control). The samples were submitted for 3 days to 4 cycles/day of erosion (5 min in Sprite Zero) and 2 cycles of abrasion/day after the first and last erosive challenge, with a toothbrush machine and slurries of a placebo toothpaste for 15 s (50 strokes/s). Among the cycles and after the last daily cycle, the specimens remained in artificial saliva. The change in the enamel surface was evaluated by using 3D non-contact optical profilometry with surface roughness (Ra and Sa values) and tooth structure loss (TSL) measurements. Scanning electron microscopy (SEM) assessed the enamel topographic characteristics. Differences in the Ra, Sa and TSL among treatments were tested using one-way ANOVA followed by the Tukey test.ResultsAll varnishes promoted better results for Ra and Sa values than the negative control (p = 0.0001), without difference among them (p > 0.05). However, CPP-ACP/NaF varnish stimulated fewer TSL (7.09 ± 0.70 μm) compared to NaF varnish (10.33 ± 1.36 μm, p = 0.002), xylitol/NaF varnish (9.96 ± 0.41 μm, p = 0.007) and the negative control (18.38 ± 3.32 μm, p = 0.0001).ConclusionA single-application of fluoride topical varnishes was effective in reducing enamel wear. The CPP-ACP/NaF varnish had the best effect against enamel loss from an erosion-abrasion challenge.     

A new optical detection method to assess the erosion inhibition by in vitro salivary pellicle layer

ObjectivesApplication of the recently developed optical method based on the monitoring of the specular reflection intensity to study the protective potential of the salivary pellicle layer against early enamel erosion.MethodsThe erosion progression was compared between two treatment groups: enamel samples coated by the 15 h-in vitro-formed salivary pellicle layer (group P, n = 90) and the non-coated enamel surfaces (control group C, n = 90). Different severity of the erosive impact was modelled by the enamel incubation in 1% citric acid (pH = 3.6) for 2, 4, 8, 10 or 15 min. Erosion quantification was performed by the optical method as well as by the microhardness and calcium release analyses.ResultsOptical assessment of the erosion progression showed erosion inhibition by the in vitro salivary pellicle in short term acidic treatments (≤4 min) which was also confirmed by microhardness measurements proving significantly less (p < 0.05) enamel softening in the group P at 2 and 4 min of erosion compared to the group C. SEM images demonstrated less etched enamel interfaces in the group P at short erosion durations as well.ConclusionsMonitoring of the specular reflection intensity can be successfully applied to quantify early erosion progression in comparative studies. In vitro salivary pellicle (2 h) provides erosion inhibition but only in short term acidic exposures.Clinical significanceThe proposed optical technique is a promising tool for the fast and non-invasive erosion quantification in clinical studies.     

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.     

Optimization of calcium concentration of saliva with phosphoryl oligosaccharides of calcium (POs-Ca) for enamel remineralization in vitro

ObjectivePhosphoryl oligosaccharides of calcium (POs-Ca) are highly soluble calcium source made from potato starch. The aim of this study was to investigate the optimal concentrations of POs-Ca for the remineralization of subsurface enamel lesions in vitro.DesignDemineralized bovine enamel slabs (n = 5) were remineralized in vitro for 24 h at 37 °C with artificial saliva (AS) containing 0–0.74% POs-Ca to adjust the Ca/P ratio to 0.4–3.0, then sectioned and analysed by transversal microradiography (TMR). The data were analysed by Scheffe's post hoc test. The Ca/P ratio with most remineralization was used to investigate the effect of calcium on enamel remineralization (n = 11). The demineralized slabs were treated with AS with calcium-chloride- (CaCl₂-) or POs-Ca with an identical calcium content, and sectioned for TMR and wide-angle X-ray diffraction (WAXRD) analyses to evaluate the local changes in hydroxyapatite (HAp) crystal content. The data were analysed using the Mann–Whitney U-test.ResultsThe highest mineral recovery rate resulted from addition of POs-Ca to adjust the Ca/P to 1.67. At this ratio, the mineral recovery rate for AS containing POs-Ca (24.2 ± 7.4%) was significantly higher than that for AS containing CaCl₂ (12.5 ± 11.3%) (mean ± SD, p < 0.05). The recovery rate of HAp crystallites for AS containing POs-Ca (35.7 ± 10.9%) was also significantly higher than that for AS containing CaCl₂ (23.1 ± 13.5%) (p < 0.05). The restored crystallites were oriented in the same directions as in sound enamel.ConclusionsPOs-Ca effectively enhances enamel remineralization with ordered HAp at a Ca/P ratio of 1.67.     

Nanohybrid vs. fine hybrid composite in Class II cavities: Clinical results and margin analysis after four years

ObjectivesThis controlled prospective split-mouth study evaluated the clinical behavior of two different resin composites in extended Class II cavities over a period of four years.MethodsThirty patients received 68 direct resin composite restorations (Grandio bonded with Solobond M: n = 36, Tetric Ceram bonded with Syntac: n = 32) by one dentist in a private practice. All restorations were replacement fillings, 24 cavities (35%) revealed no enamel at the bottom of the proximal box, in 33 cavities (48%) the proximal enamel width was less than 0.5 mm. The restorations were examined according to modified USPHS criteria at baseline, and after six months, one, two, and four years. At each recall, impressions were taken for replica preparation. Replicas of 44 select subjects were assessed for marginal quality under a stereo light microscope (SLM) at 130× and 22 replicas were assessed under a scanning electron microscope (SEM) at 200×.ResultsBoth recall rate and survival rate were 100% after four years of clinical service. No significant difference was found between the restorative materials (p > 0.05; Mann–Whitney U-test). Hypersensitivities were significantly reduced over time (p < 0.05; Friedman test). A significant deterioration over time was found for the criteria marginal integrity (66% bravo after four years), tooth integrity (15% bravo), filling integrity (73% bravo) and proximal contact (p < 0.05; Friedman test). SLM and SEM analysis of restoration margins revealed differences in the amount of perfect margins, in favor of Tetric Ceram (p < 0.05).SignificancesBoth materials performed satisfactorily over the four-year observation period. Due to the extension of the restorations, wear was clearly visible after four years of clinical service with 50% bravo ratings.     

Impact of high-speed sintering,layer thickness and artificial aging on the fracture load and two-body wear of zirconia crowns

ObjectiveTo investigate the impact of high-speed sintering, layer thickness and artificial aging in a chewing simulator on the fracture load (FL) and two-body wear (2BW) of 4Y-TZP crowns.Methods4Y-TZP crowns (Ceramill Zolid HT+, Amann Girrbach AG) in three different layer thicknesses (0.5, 1.0, 1.5; N = 192, n = 64/group) were manufactured using CAD/CAM technology and sintered at 1580 °C (high-speed sintering) or 1450 °C (control group). Specimens were polished in two-steps and bonded to standardized CoCr abutments with Multilink Automix (Ivoclar Vivadent). 2BW after 6000 thermo- and 1,200,000 chewing-cycles employing enamel antagonists was determined using best fit machining. FL was tested before and after artificial aging. Univariate ANOVAs, post hoc Scheffé, unpaired t-, Kruskal–Wallis- and Mann–Whitney-U-test were computed (p < 0.05).ResultsHigh-speed sintering resulted in less 2BW of the zirconia than the control group (p = 0.013). High-speed sintering (p = 0.001–0.006) and an increase in layer thickness (p < 0.001–0.012) resulted in higher FL values, while artificial aging led to a reduction of FL (p < 0.001).SignificanceAs high-speed sintering resulted in less two-body wear of the zirconia and comparable or even higher fracture load results than the control group, this cost- and time efficient alternative presents promising mechanical results.     

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.     

Operator vs. material influence on clinical outcome of bonded ceramic inlays

ObjectiveThe aim of the present study was to clinically evaluate the suitability of Definite Multibond and Definite ormocer resin composite for luting of Cergogold glass ceramic inlays in a two-center trial involving two dentists.MethodsThirty-nine patients received 98 Cergogold inlays with at least one inlay luted with Definite Multibond/Definite (n = 45) and at least one inlay luted with Syntac/Variolink Ultra (n = 53) in a split mouth design. Treatments were carried out in two private practices by two operators (Operator A: n = 38; Operator B: n = 60). Forty-four cavities required caries profunda treatment, 23 cavities exhibited no enamel at the cervical margin. At baseline (2 months), and after 6, 14, 27, and 51 months of clinical service, the restorations were investigated according to modified USPHS criteria.ResultsThe drop-out rate was 3% after 4 years. After 48 months of clinical service, 21 restorations in 16 patients (9 luted with Definite, 12 with Variolink; 2 placed by operator A and 19 by operator B) had to be replaced due to inlay fracture (n = 11), tooth fracture (n = 4), hypersensitivities (n = 3), or marginal gap formation (n = 3). Seventy-seven inlays were in good condition (survival rate 89.9%, median survival time 4.2 years (95% confidence interval ±0.25; survival analysis by Kaplan–Meier algorithm). Survival rate after 4 years was 97.4% for operator A, and 75.4% for operator B (p = 0.002; Log Rank/Mantel-Cox) resulting in annual failure rates of 0.6% and 6.2%, respectively. The operators did not differently judge the clinical behaviour of the luting procedures (Mann–Whitney U-test, p > 0.05). Independent of the operator and the used luting system, the following criteria significantly changed over time: color match, marginal integrity, tooth integrity, inlay integrity, sensitivity, hypersensitivity, and X-ray control (p < 0.05; Friedman test). Significant differences between operators over the whole period were computed for the criteria marginal integrity, tooth integrity, and inlay integrity (p < 0.05, Mann–Whitney test). Differences between luting materials were only present during single recalls.SignificancesFor luting of ceramic inlays, only slight differences between the two luting systems were detectable. The operator influence on clinical outcome was clearly proven.     

Fabrication and characterization of remineralizing dental composites containing calcium type pre-reacted glass-ionomer (PRG-Ca) fillers

ObjectiveTo fabricate and characterize dental composites with calcium type pre-reacted glass-ionomer (PRG-Ca) fillers.MethodsPRG-Ca fillers were prepared by the reaction of calcium fluoroaluminosilicate glass with polyacrylic acid. Seven dental composites were produced from the same organic matrix (70/30 wt% Bis-GMA/TEGDMA), with partial replacement of barium borosilicate (BaBSi) fillers (60 wt%) by PRG-Ca fillers (wt%): E0 (0) – control, E1 (10), E2 (20), E3 (30), E4 (40), E5 (50) and E6 (60). Enamel remineralization was evaluated in caries-like enamel lesions induced by S. mutans biofilm using micro-CT. The following properties were characterized: degree of conversion (DC%), roughness (Ra), Knoop hardness (KHN), flexural strength (FS), flexural modulus (FM), water sorption (W_sp), water solubility (W_sl), and translucency (TP). Data were analyzed to one-way ANOVA and Tukey’s HSD test (α = 0.05).ResultsAll composites with PRG-Ca induced enamel remineralization. E0 and E1 presented similar and highest DC% than E2 = E3 = E4 = E5 = E6. Ra and KHN were not influenced by PRG-Ca fillers (p < 0.05). The higher the content of PRG-Ca, the lower FS, FM and TP (p < 0.05). W_sp increased linearly with the content of PRG-Ca fillers (p < 0.05). E6 presented the highest W_sl (p < 0.05), while the W_sl of the other composites were not different from each other (p > 0.05).SignificanceIncorporation of 10–40 wt.% of PRG-Ca fillers endowed remineralizing potential to dental composites without jeopardizing the overall behavior of their physicochemical properties. Dental composites with PRG-Ca fillers seems to be a good alternative for reinforcing the enamel against caries development.     

Clinical performance and SEM marginal quality of extended posterior resin composite restorations after 12 years

ObjectiveTo investigate the clinical behavior of two different resin-based restorative systems in extended Class II cavities in a controlled prospective split-mouth study over 12 years and to assess marginal quality under a SEM using epoxy replicas.MethodsThirty patients received 68 resin composite restorations (Solobond M + Grandio: n = 36; Syntac + Tetric Ceram: n = 32) by one dentist in a private practice. 35% of cavities revealed no enamel at the bottom of the proximal box, 48% of cavities provided <0.5 mm remaining proximal enamel. Restorations were examined according to modified USPHS criteria at baseline, and after six months, one, two, four, six, eight, 10, and 12 years. Expoxy replicas of 21 restoration pairs were analysed under a SEM at 200× magnification regarding marginal quality.ResultsAt the 12-years recall, 59 of the original 68 restorations in 27 of 30 patients were available (drop out 13%). Two restorations failed due to cusp fracture (Tetric Ceram) and marginal fracture (Grandio). The overall success rate of all restorations was 97.1% (Kaplan–Meier survival algorithm) with no differences between the two materials (p = 0.923). After 144 months of clinical service, restorations in molars performed worse than in premolars regarding the integrity of restoration and tooth (p < 0.05) being detected as wear, chippings, and cracks. Beyond the 4-year recall, marginal staining significantly increased. SEM evaluation of replicas revealed that perfect margin (49% baseline vs. 10% after 12 years), overhang (13% at baseline vs. 3% after 12 years), negative step formation (34% at baseline vs. 75% after 12 years), and marginal fractures (0% at baseline vs. 6% after 12 years) significantly changed during the evaluation period (p < 0.001).SignificanceExtended direct resin composite restorations performed satisfactorily over 12 years of clinical service. SEM analysis delivered qualitative data regarding marginal deterioration over time.     

Mineralization-defects are comparable in fluorotic impacted human teeth and fluorotic mouse incisors

ObjectiveFluoride excess of 0.05–0.07 mg F/kg bw/day in water or food additives like salt is the principal cause of endemic dental fluorosis. How fluoride causes these defects is not clear yet. Recent studies in rodents suggest that development of enamel fluorosis is associated with insufficient neutralization of protons released during the formation of hypermineralized lines.DesignHere we examined whether hypermineralization could also be assessed by MicroCT in developing molar enamel of humans exposed to fluoride.ResultMicro-CT analysis of hypomineralized enamel from human fluorotic molars graded by the Thylstrup–Fejerskov (TF) Index as III–IV showed weak hypermineralized lines and hypermineralized patches not seen in TF-I/II grade enamel. The mesio-distal sides of these molar teeth were significantly smaller (∼18%, p = 0.02) than in TF-I/II teeth.ConclusionThe patterns of changes observed in human fluorotic teeth were similar to those in fluorotic rodent incisors. The data are consistent with the hypothesis that also in developing human teeth fluoride-stimulated local acidification of enamel could be a mechanism for developing fluorotic enamel.