Influence of different pre-treatments on the resin infiltration depth into enamel of teeth affected by molar-incisor hypomineralization (MIH).

OBJECTIVES: This in vitro pilot study aimed to evaluate whether different pre-treatments (demineralization, deproteinization, (chemo-)mechanical reduction of the surface layer) influence the penetration depth of a resin infiltrant into MIH-affected enamel compared to initial carious lesions. METHODS: Thirty extracted human permanent molars with non-cavitated initial carious lesions (n = 5) or MIH (n = 25) were chosen and randomly assigned to six experimental groups: IC: initial caries; M: MIH; MN: MIH, 5.25% sodium hypochlorite; MM: MIH, microabrasion; MA: MIH, air abrasion; MAN: MIH, air abrasion and 5.25% sodium hypochlorite. A modified indirect dual fluorescence staining method was adopted to assess the penetration depth (PD) of the resin infiltrant and the lesion depth (LD) by confocal laser scanning microscopy (CLSM). Exemplarily, scanning electron microscopic (SEM) images were captured. The relationship between group assignment and penetration/lesion depth was estimated using a linear mixed model incorporating the tooth as random effect (two observations/tooth). The significance level was set at p < 0.05. RESULTS: For MIH-affected molars, the mean PD (in µm; median, [minimum-maximum]) were M (178.2 [32.5-748.9]), MN (275.6 [105.3-1131.0]), MM (48.7 [0.0-334.4]), MA (287.7 [239.4-491.7]), and MAN (245.4 [76.1-313.5]). Despite the observed differences in PD between the groups, these could not be statistically verified (Bonferroni, p = 0.322). The percentage penetration was significantly higher for IC than for MIH groups (Bonferroni, p < 0.05). SIGNIFICANCE: Compared to IC, resin infiltration into MIH-affected enamel ist more variable. Different pre-treatments influence the resin penetration into developmentally hypomineralized enamel to a fluctuating level.

Dentin Bonding Performance of Universal Adhesives in Primary Teeth In Vitro.

(1) Background: The aim of this in vitro study was to evaluate the micro-tensile bond strength (µ-TBS) of universal adhesives to primary tooth dentin after different storage periods. (2) Methods: Dentin of 100 extracted primary molars was exposed. Dentin surfaces were bonded with six universal adhesives (Adhese®Universal [AU], All-Bond Universal® [ABU], G-Premio Bond [GPB], iBond®Universal [IBU], Prime&Bond active™ [PBa], and Prime&Bond®NT as control [PBN]) and restored with a resin composite build-up (Filtek™ Z250). After 24 h, 6 months, and 12 months of water storage, specimens were cut into sticks, and µ-TBS was measured and analyzed using one-way ANOVA (p < 0.05) for normal distributions and the Mann-Whitney U-test (p < 0.05) for non-normal distribution. Pretesting failures were recorded as 0 MPa. Fracture modes were analyzed under a fluorescence microscope; interfaces were visualized with SEM/TEM. (3) Results: Compared with the reference group (PBN: 32.5/31.2 MPa after 6/12 months), two adhesives showed a significantly higher bond strength after 6 months (AU: 44.1 MPa, ABU: 40.9 MPa; p < 0.05) and one adhesive after 12 months (AU: 42.9 MPa, p < 0.05). GPB revealed significantly lower bond strengths in all storage groups (16.9/15.5/10.9 MPa after 24 h/6 months/12 months; p < 0.05). AU and IBU did not suffer pre-test-failures [PTF]. (4) Conclusions: After 12 months, PBN, IBU, AU, and GPB showed significantly lower results compared ithw initial µ-TBS, whereas AU revealed the highest µ-TBS and no PTF.

Marginal Quality and Wear of Bulk-fill Materials for Class-II Restorations in Primary Molars.

PURPOSE: The aim of this in-vitro study was to evaluate the marginal integrity and wear of eight bulk-fill materials in comparison to a compomer in Class-II cavities in primary molars after thermomechanical loading (TML). MATERIALS AND METHODS: Prepared Class-II cavities in 72 extracted primary molars were filled with eight bulk-fill materials. A compomer served as the control group. After water storage (incubator, 28 days, 37°C), samples were subjected to TML (2500 thermal cycles 5°C/55°C; 100,000 load cycles, 50 N, 1.67 Hz). Before and after TML, replicas were made which were used for both SEM analysis of marginal integrity and 3-D wear analysis. Statistical analysis was performed using Kruskal-Wallis and Wilcoxon tests (p < 0.05). RESULTS: A significant reduction in perfect margins was observed for all groups, while marginal gap formation increased (Wilcoxon test, p < 0.02) for all groups but the compomer. Significant interindividual differences were observed between the tested materials regarding marginal integrity (Kruskal-Wallis test, p < 0.05). Wear analysis revealed no significant differences between groups (Kruskal-Wallis test, p > 0.05). CONCLUSION: Some of the bulk-fill materials investigated here achieved better results than the compomer and should be further evaluated clinically.

Effect of Chlorhexidine-containing Etch-and-Rinse Adhesives on Dentin Microtensile Bond Strength after Biological Loading.

PURPOSE: This study compared a 2%-CHX dentin pre-treatment with three CHX adhesives (experimentally admixed 0.1% CHX in primer or bonding agent, or industrially added 0.2% CHX in universal adhesive) by evaluating dentin bond strengths after biological loading in a fully automated artificial mouth model. MATERIALS AND METHODS: The occlusal dentin of 50 freshly extracted human third molars was exposed, and the teeth were randomly assigned to 5 groups according to the adhesive protocol (n = 10): 1. control, Scotchbond Multipurpose (3M Oral Care; CTRL); 2. 2% CHX dentin pre-treatment (DENT); 3. 0.1% CHX experimentally admixed into the primer (PRIM); 4. 0.1% CHX experimentally admixed into the bonding agent (BOND); 5. Peak Universal Bond containing 0.2% CHX (Ultradent; PEAK). The teeth were restored with composite resin. Microtensile bond strength testing (bonding area 0.46 mm2 ± 0.04 mm2, crosshead speed 1 mm/min) was performed after 24-h storage in distilled water (baseline) or after 2-day biological loading with S. mutans (demineralization 1 h / remineralization 5 h). The mode of fracture was recorded and exemplary sticks were evaluated under SEM. RESULTS: CTRL exhibited significantly higher µTBS at baseline in comparison to PRIM (p = 0.000), BOND (p = 0.002), and PEAK (p = 0.000). After undergoing the caries model, CTRL demonstrated significantly lower µTBS compared to DENT (p = 0.000), PRIM (p = 0.008), and PEAK (p = 0.000). The same behavior was observed for BOND vs DENT (p = 0.000), PRIM (p = 0.003), and PEAK (p = 0.001). After biological loading, DENT (p = 0.041), PRIM (p = 0.000), and BOND (p = 0.000) exhibited significantly fewer adhesive fractures than CTRL. CONCLUSIONS: CHX addition to the primer protects dentin bond strength from declining after biological loading. Thus, it may offer some clinical advantage in terms of secondary caries inhibition around composite restorations. However, since loss of adhesion at baseline was less when 2% CHX was used as a dentin pre-treatment, it can be suggested as a safer option. so that bonding is not undermined by potential chemical interactions from CHX with the adhesives.

Long-term microtensile bond strength of self-etch adhesives and influence of 7-s phosphoric acid etching on adhesion of a 3-step etch-and-rinse adhesive to the dentine of primary teeth.

BACKGROUND: The immediate microtensile bond strength (µTBS) of self-etch (SE) adhesives to primary dentine is promising, but evidence about the durability is scarce. AIM: To assess the long-term µTBS of SE adhesives to primary dentine and to examine the effect of 7-s etching on µTBS of a 3-step etch-and-rinse (ER) adhesive. DESIGN: The enamel of 115 caries-free human primary teeth was ground flat, and bonding was performed according to group assignment: G-aenial™ Bond/GC [GB], Clearfil™ SE Bond/Kuraray [CS], OptiBond™ XTR/Kerr [OX], Scotchbond™ Universal/3M™ [SU], Prime&Bond® NT™/Dentsply [PB], and OptiBond™ FL/Kerr [OF]. After storage (24 h, 6 mos., 12 mos.), 1,762 beams were cut for µTBS testing. Fracture analysis was performed using light/fluorescence microscopy. Resin-dentine interfaces were exemplarily analyzed using SEM. RESULTS: After 24 h, OX and SU showed significantly higher estimated mean µTBS than GB, which exhibited the lowest µTBS at all stages (p < .05). µTBS within each adhesive group showed slight variations over time (p > .05). OF_SE produced acceptable µTBS. Etching increased the mean immediate µTBS for OF (p > .05) and the percentage of cohesive fractures. CONCLUSIONS: SE adhesives achieved durable µTBS to primary dentine. 7-s etching may improve the immediate µTBS of a 3-step ER adhesive.

Data for microbe resistant engineered recombinant spider silk protein based 2D and 3D materials.

Data presented in this article describe bacterial and fungal repellent properties of 2D-films and 3D-hydrogels made of different recombinantly produced spider silk proteins based on consensus sequences of Araneus diadematus dragline silk proteins (fibroin 3 and 4). Here, the attachment, growth, and microbial colonization of Streptococcus mutans (S. mutans) as well as Candida albicans (C. albicans) on plane and micro-patterned films were visualized by scanning electron microscopy (SEM). Also, microbial viability data are provided of Escherichia coli (E. coli) and Pichia pastoris (P. pastoris) on hydrogels made of eADF4(C16) and eADF4(C16)-RGD, quantified using the Alamar blue assay. Experimental results, design of a post-operative contamination model of microbes with mammalian cells, and methods in the data article refer to the research paper "Engineered spider silk-based 2D and 3D materials prevent microbial infestation" published recently [1].

Inhibition of secondary caries in vitro by addition of chlorhexidine to adhesive components.

OBJECTIVE: To investigate secondary caries inhibition after dentine pre-treatment with 2% CHX, experimental addition of CHX in primer and adhesive of a 3-step adhesive system, and industrial addition od CHX in a 2-step adhesive system. MATERIALS AND METHOD: Sixty Class-V cavities were restored according to the adhesive protocol (n=12): 1) control group, Scotchbond Multi-Purpose, 3M (CTRL), 2) 2% CHX dentine pre-treatment (DENT), 3) 0.1% CHX in primer (PRIM), 4) 0.1% CHX in bonding agent (BOND), 5) Peak Universal Bond including 0.2% CHX (PEAK). Specimens were thermocycled (10,000 cycles) and inserted into a Streptococcus mutans biofilm artificial mouth (caries model). The 10-day biological loading protocol consisted of consecutive phases of demineralisation (1h) and remineralisation (5h). Evaluation under a fluorescence microscope (demineralisation) and an SEM (marginal gap) followed, at restoration margins, and at 0.3mm and 0.5mm distance from the margins, in enamel and in dentine. Total demineralization was calculated as the sum of demineralisation and substance loss due to demineralisation. RESULTS: PRIM (p=0.007, mod. LSD), BOND (p=0.012, mod. LSD) and PEAK (p=0.008, mod. LSD) exhibited significantly higher total demineralisation values in enamel margins than CTRL. No significant differences were noted for total demineralisation in dentine. Regarding marginal gaps, DENT exhibited significantly lower enamel gap values compared to all other groups (p=0.001). CONCLUSIONS: 2% CHX as dentine pre-treatment, 0.1% or 0.2% CHX added in adhesives did not provide any antibacterial effect regarding secondary caries in dentine. On the other hand, 2% CHX dentine pre-treatment managed to limit marginal gap formation in enamel compared to the other adhesive protocols in the study.

Secondary caries formation with a two-species biofilm artificial mouth.

OBJECTIVES: The present study aimed to establish Lactobacillus casei in a completely automated Streptococcus mutans-based artificial mouth model and to investigate secondary caries inhibiting properties of glass ionomer cements / resin composite groups in vitro. METHODS: Sixty extracted, caries-free human third molars were used for preparation of standardized class-V-cavities. Specimens were restored with a resin-modified (Photac Fil; PF) as well as a conventional glass ionomer cement (Ketac Molar; KM) and one resin composite bonded with and without conduction of etch-and-rinse technique (Prime&Bond NT, Ceram X mono; C+ERT, C). Following an incubation in distilled water for 28d at 37°C, specimens were exposed to 10,000 thermocycles (+5 °C/+55°C). A completely automated S. mutans-based (DSM No.: 20523) artificial mouth model was extended by establishment of L. casei (DSM No.: 20021). During microbiological loading, demineralization (4h/d) was caused by acid production resulting from bacterial glycolysis and artificial saliva was used for remineralization (20h/d). For quantitative margin analysis under am SEM, epoxy replicas were produced from impressions taken after thermocycling and after microbiological loading. Specimens were cut in half perpendicularly to restoration surfaces and demineralization depths at restoration margins and in 500µm distance from margins were evaluated by means of a fluorescence microscope (FITC filter). RESULTS: After microbiological loading, overall demineralization depths in enamel at restoration margin (EM) and in 500µm distance (ED) as well as in cementum/dentin at restoration margin (DM) and in 500µm distance (DD) were measured as follows (µm±SD): PF: EM 42±15, ED 60±17, DM 83±18; DD 127±16; KM: EM 46±22, ED 62±17, DM 104±21, DD 143±28; C+ERT: EM 67±19, ED 61±17, DM 165±31, DD 176±35; C: EM 65±23, ED 64±17, DM 161±27, DD 166±33. For the glass ionomer cements, the overall demineralization depths at restoration margins were significantly lower than in 500µm distance from margins (T-test, p<0.05). Especially at restoration margins in cementum/dentin, the resin composite groups showed significantly larger overall demineralizations than the glass ionomer cements (ANOVA, mod. LSD, p<0.05). Decreases of marginal quality were detected in all groups after microbiological loading (Friedman-test, p<0.05). SIGNIFICANCE: The refined experimental setup was suitable for production of artificial secondary caries-like lesions. Glass ionomer cements as fluoride-releasing materials may show an inhibition of secondary caries formation to a certain extent.

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). METHODS: 94 freshly extracted human molars and incisors (53 suffering MIH) were used. 68 teeth (35 with MIH) were used for µ-TBS tests in enamel and dentin, 26 (18 with MIH) for qualitative evaluation. Specimens were bonded with Clearfil SE Bond, Scotchbond Universal, and OptiBond FL. For MIH affected enamel, additional OptiBond FL groups with NaOCl and NaOCl+Icon were investigated. Beside fractographic analysis, also qualitative evaluations were performed using SEM at different magnifications as well as histological sectioning. RESULTS: Highest µ-TBS values were recorded with dentin specimens (ANOVA, mod. LSD, p<0.05). Results were independent of adhesive and dentin substrate (p>0.05). Pre-test failures did not occur in dentin specimens. Sound enamel specimens exhibited significantly higher µ-TBS values than MIH enamel (p<0.05). The two-step self-etch adhesive (Clearfil SE Bond) and the two-step etch-and-rinse adhesive (Scotchbond Universal) showed the lowest values in affected enamel specimens (p<0.05) with most pre-test failures (p<0.05). OptiBond FL on affected enamel showed better results than Clearfil SE Bond (p<0.05). An additional pre-treatment of affected enamel with NaOCl or NaOCl and Icon did not enhance enamel bonding (p>0.05), however, it caused less pre-test failures (p<0.05). Micromorphological analyses revealed that conventional phosphoric acid etching produces a much less pronounced etching pattern in affected enamel and a porous structure as weak link for the resin-enamel bond was identified. SIGNIFICANCE: Bonding to porous hypomineralized MIH enamel is the limiting factor in adhesion to MIH teeth. MIH-affected dentin may be bonded conventionally.

Glass ionomer cement inhibits secondary caries in an in vitro biofilm model.

OBJECTIVES: The objective of this study was to investigate the effect of different glass ionomer cements on secondary caries inhibition in a fully automated in vitro biofilm model. MATERIALS AND METHODS: One hundred and twenty-four extracted third molars received class V cavities and were filled with one conventional (Ketac Molar/KM), and two resin-modified glass ionomer cements (Photac Fil/PF, Ketac N100/KN, 3M Espe). A bonded resin composite (Single Bond Plus/Filtek Supreme XTE) served as control. After 14 days water storage at 37 °C, specimens were thermocycled (10,000 × 5/55 °C). Over a period of 10 days, specimens were subjected to cariogenic challenge for 3/4/6 h/day. Demineralization was caused by Streptococcus mutans (DSM 20523) alternatingly being rinsed over specimens using artificial saliva. After biological loading, teeth were cut longitudinally and demineralization depths were evaluated at the margins and at a distance of 0.5 mm from the margins using fluorescence microscopy. Marginal quality was investigated under a SEM at ×200 magnification. RESULTS: Four-hour demineralization depths were for enamel margins (EM), enamel (E), dentin margin (DM), and dentin (D) (µm ± SD): KM: EM 12 ± 8, E 33 ± 7, DM 56 ± 11, D 79 ± 6; PF: EM 19 ± 13, E 34 ± 13, DM 53 ± 10, D 77 ± 12; and KN: EM 26 ± 5, E 38 ± 6, DM 57 ± 11, D 71 ± 7. For all glass ionomer cements (GICs), demineralization depth at the margins was less compared to 0.5 mm distance, with demineralization depth having been correlated to duration of cariogenic challenge (ANOVA [mod. LSD, p < 0.05]). Compared to the bonded resin composite, all GICs exhibited caries inhibition at restoration margins in enamel and dentin. CONCLUSIONS: Fluoride-releasing GIC materials exhibit a secondary caries inhibiting effect in vitro. CLINICAL RELEVANCE: Glass ionomer cements have a higher secondary caries inhibiting effect than resin composites.

Effect of microparticulate silver addition in dental adhesives on secondary caries in vitro.

OBJECTIVES: The aim of the present study was evaluate the effect of microparticulate silver additions in adhesives on secondary caries formation using an artificial mouth model. MATERIALS AND METHODS: One hundred eight intact human third molars received standardized Class-V resin composite restorations (Filtek Supreme XTE bonded with Syntac, Scotchbond 1 XT, Futurabond M). Adhesives were charged with different amounts of microparticulate silver (0 %/0.1 %/0.5 %). After storage for 4 weeks at 37 °C, teeth were subjected to 10,000 thermocycles (+5 °C and +55 °C), and impressions were taken. Streptococcus mutans 10449 was used in a nutrition medium for secondary caries simulation in a fully automated artificial mouth. After completion of thermocycling and biological load cycling, impressions were taken and replicas were investigated under a light microscope for gap widths at enamel and dentin margins. Evaluation of fluorescence was carried out using a special FITC filter. The demineralization depths at the cavity margin were evaluated using Xpert for Windows working at a pixel distance of 5 µm. RESULTS: After thermocycling, no difference in gap widths and demineralization depths was found (p > 0.05). After incubation, gap widths and demineralization depths were significantly reduced with higher amounts of silver loading in most of the adhesives (p < 0.05). The 0.5 % silver addition resulted in a slight decrease of secondary caries at resin-dentin margins (p < 0.05). CONCLUSIONS: Addition of microparticulate silver in commercially available dental adhesives has the potential of reducing secondary caries. CLINICAL RELEVANCE: The chosen setup was able to produce secondary caries with a distinct in vivo appearance. Microparticulate silver additions in dental adhesives may have an impact on inhibition of secondary caries.

Status of ten self-etch adhesives for bonding to dentin of primary teeth.

OBJECTIVE: Aim of this in vitro study was to compare self-etch adhesives regarding microtensile bond strength (µ-TBS) to dentin of primary teeth. METHODS: Fifty freshly extracted primary molars were ground to expose caries-free dentin. Specimens were bonded with ten self-etch adhesives (iBond self-etch/Heraeus, Xeno V+/Dentsply, G-Bond, Gaenial Bond/GC, BeautiBond/Shofu, AdheSE One F/Ivoclar Vivadent, Adper Easy Bond/3M ESPE, Clearfil SE Bond/Kuraray, OptiBond XTR/KerrHawe, Prime&Bond NT/Dentsply). After 24-h storage (distilled water, 37°C), resin-dentin beams were cut and 848 resin-dentin sticks were subjected to µ-TBS tests. Fracture analysis was carried out at 40× magnification under a fluorescence microscope and under a SEM. RESULTS: Three adhesives (iBond SE, Clearfil SE Bond, Prime&Bond NT) did not suffer pre-test failures (PTF). AdheSE One F revealed the largest portion of PTF (28%; P < 0.05). Clearfil SE Bond and OptiBond XTR exhibited more cohesive fractures than the other adhesives (77.3% vs 64.8%; P < 0.05). iBond SE, Gaenial Bond, Clearfil SE, and OptiBond XTR achieved µ-TBS of >60 MPa, whereas Xeno V+ and AdheSE One F ranged only at ~20 MPa (P < 0.05). CONCLUSION: Within the limits of this study, the self-etch adhesives under investigation proved different extents of initial µ-TBS to primary dentin with iBond SE, Gaenial Bond, Clearfil SE, and OptiBond XTR having been most successful.