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PURPOSE: To evaluate the effect of different substrate stiffness [sound dentin (SD), resin composite core (RC) or metal core (MC)] on the stress distribution of a zirconia posterior three-unit fixed partial denture (FPD). METHODS: The abutment teeth (first molar and first premolar) were modeled, containing 1.5 mm of axial reduction, and converging axial walls. A static structural analysis was performed using a finite element method and the maximum principal stress criterion to analyze the fixed partial denture (FPD) and the cement layers of both abutment teeth. The materials were considered isotropic, linear, elastic, homogeneous and with bonded contacts. An axial load (300 N) was applied to the occlusal surface of the second premolar. RESULTS: The region of the prosthetic connectors showed the highest tensile stress magnitude in the FPD structure depending on the substrate stiffness with different core materials. The highest stress peak was observed with the use of MC (116.4 MPa) compared to RC and SD. For the cement layer, RC showed the highest values in the molar abutment (14.7 MPa) and the highest values for the premolar abutment (14.4 MPa) compared to SD (14.1 and 13.4 MPa) and MC (13.8 and 13.3 MPa). Both metal core and resin composite core produced adequate stress concentration in the zirconia fixed partial denture during the load incidence. However, more flexible substrates, such as composite cores, can increase the tensile stress magnitude on the cement. CLINICAL SIGNIFICANCE: The present study shows that the choice of the cast core and metallic post by the resin composite core and fiberglass post did not improve the biomechanical behavior of the FPD. This choice must be performed based on clinical criteria (other) than mechanical.

Purpose: To examine the influence of different bulk and block composite and flowable and glass-ionomer material combinations in a multi-layer technique and in a unique technique, in deep Class I dental restorations. Methods: 3D CAD of the sound tooth were built-up from a CT scan dataset using reverse engineering techniques. Four restored tooth models with Class I cavity were virtually created from a CAD model of a sound tooth. 3D-finite element (FE) models were created and analyzed starting from CAD models. Model A with flowable resin composite restoring the lower layer and bulk-fill resin composite restoring the upper layer, model B with glass-ionomer cement (GIC) restoring the lower layer and bulk-fill resin composite restoring the upper layer, model C with block composite as the only restoring material and model D with bulk-fill resin composite as the only restoring material. Polymerization shrinkage was simulated with the thermal expansion approach. Physiologic masticatory loads were applied in combination with shrinkage effect. Nodal displacements on the lower surfaces of FE models were constrained in all directions. Static linear analyses were carried out. The maximum normal stress criterion was used to assess the influence of each factor. Results: Considering direct restoring techniques, models A, B and D exhibited a high stress gradient at the tooth/restorative material interface. Models A and D showed a similar stress trend along the cavity wall where a similar stress trend was recorded in the dentin and enamel. Model B showed a similar stress trend along enamel/restoration interface but a very low stress gradient along the dentin/restoration interface. Model C with a restoring block composite material showed a better response, with the lowest stress gradient at the dentin, filling block composite and enamel sides. Clinical significance: Bulk resin-based composite materials applied in a multilayer technique to deep and large Class I cavities produced adverse stress distributions versus block resin composite. Polymerization shrinkage and loading determined high stress levels in deep Class I cavities with bulk multi-layer restorations, while its impact on adhesion in block composite restorations was insignificant.

Purpose: To compare two different enamel pretreatments and their effect on the efficiency of penetration of a one-component adhesive into natural carious lesions. Methods: Eight extracted human molars and premolars with non-cavitated interproximal lesions were selected. ICDAS code 1-2 was assessed by visual, microscopic, X-ray and Diagnocam record analysis. Samples were cut vertically across the demineralization to obtain two symmetrical lesions, (n=16). After isolating the cut surfaces with nail varnish, paired lesion halves’ surfaces were pretreated with two different techniques: Group 1: surfaces were firstly abraded with fine diamond-coated metallic strips (Steelcarbo) and then etched with 37% H3PO4 acid (Omni-etch, 120 seconds); Group 2: lesion surfaces were etched with 15% HCl acid (Icon-etch, 120 seconds). All teeth were stained with rhodamine isothiocyanate (RITC) solution (12 hours) and subsequently stored in dry chamber (3 hours). All samples were penetrated with a one-component adhesive (Scotchbond Universal) for 180 seconds and coated with a thin layer of flowable composite (Tetric Flow). After light curing, un-encapsulated dye was bleached by immersion in 30% hydogen peroxide for 12 hours at 37°C. Remaining lesion pores were stained with sodium fluorescein solution. Thin cuts of the teeth were observed with confocal microscopy and computer image analysis was performed (ImageJ). The percentage of penetration (area of resin penetration/area of total demineralization ×100) was calculated. Results: Pretreatment with fine aluminum oxide-coated metallic strip followed by 37% H3PO4 acid showed a larger infiltration area (51.7% ± 12.2) in almost all samples compared to pretreatment with 15% HCl acid alone (22.1% ± 13.2). Statistical analysis using t-test showed a significant difference between the two groups (P= 0.011). (Am J Dent 2016;29:3-9).

To investigate the infiltration potential of different self-etch adhesives into natural non-cavitated proximal lesions and the effect of dehydration protocol on the infiltration of a self-etch adhesive.29 extracted molars and premolars with natural proximal lesions (ICDAS 1-2) were sectioned through the lesion providing two samples from each lesion. To compare the different adhesives, three groups of eight lesions were abraded with fine metallic strips and then etched with 37% H3PO4 acid for 120 seconds. All teeth were stained with rhodamine isothiocyanate. After drying with compressed air and ethanol application, lesions were infiltrated with Scotchbond Universal, Clearfil SE Protect or OneCoat 7 Universal for 180 seconds and then coated with a thin layer of flowable composite (Tetric Flow). To compare the effect of dehydration protocol on infiltration, two groups of nine paired lesions were pretreated as described above. One group was dried using compressed air alone and the second group was dried using compressed air and ethanol, both groups were then infiltrated with Scotchbond Universal then coated with a thin film of flowable composite. After light curing, un-encapsulated dye was bleached by immersion in hydrogen peroxide. Remaining lesion pores were stained with sodium fluorescein solution. Thin cuts of the teeth were observed with confocal microscopy and computer image analysis was performed (ImageJ).ANOVA and Duncan post-hoc tests showed no significant differences of the infiltrated area between the three adhesives (P= 0.835), no significant difference was found between the group dried with air compared to the one dried with air and ethanol. It can be concluded that the tested adhesives may be used for infiltration of natural lesions following the described pretreatment.Enamel pretreatment with metallic strip and 37% H3PO4 acid promotes the infiltration of different adhesives into natural non-cavitated caries lesions.

To assess the clinical ability of marginal detection of different intraoral optical scanning (IOS) systems.The Ethics Committee of the University of Siena, Italy approved the research project. Thirty patients in need of an onlay/inlay with supra-gingival margins were included and randomly divided in three groups of 10 (3× n=10) according to the IOS for chairside capturing:(A) GC-Europe (Aadva); (B) True-Definition-TD; (C) Trios. A total of 1 scans from each IOS test group (A-C), were obtained clinically and stored as STL-files. In addition, corresponding conventional impressions were taken for all 30 patients, poured with stone, and then processed by a laboratory scanner (Aadva), serving as controls. All 60 STL-files were imported to the Exocad platform for analysis. The horizontal distance between each preparation margin and the adjacent tooth was measured using the ruler tool in the software. The distance at which the detection of the margin started to become visibly unclear was recorded for the horizontal distances. Data was processed statistically by one-way ANOVA (P0.05).No statistically significant inter-test group differences could be identified (IOS A-C). The minimum distance from which a clear margin was visible, was 4.5 (SD 0.1) mm for all images, regardless of which IOS was used. Under these experimental clinical conditions, all tested IOS performed similarly. In contrast, all margins of the controls were clearly visible.None of the tested intraoral scanning systems in this study were capable of recording a clear impression when the cervical margin for a posterior partial crown was located at a distance of less than 0.5 mm from the interproximal neighbor.

Resin-based dental restorative materials release residual monomers that may affect the vitality of pulp cells. The purpose of this study was to evaluate the cytotoxic effect of two light-cured restorative materials with and without bis-GMA resin, respectively (Clearfil Majesty Posterior and Clearfil Majesty Flow) and a self-curing one (Clearfil DC Core Automix) when applied to the fibroblast cell line NIH-3T3. Samples of the materials were light-cured and placed directly in contact to cells for 24, 48, 72 and 96h. Cytotoxicity was evaluated by measuring cell death by flow cytometry, cell proliferation by proliferation curves analysis and morphological changes by optical microscopy analysis. All the composite materials tested caused a decrease in cell proliferation, albeit at different degrees. However, only Clearfil DC Core Automix induced cell death, very likely by increasing apoptosis. Morphological alteration of treated cells was also evident, particularly in the Clearfil DC Core Automix-treated cells. The different cytotoxic effects of dental composites should be considered when selecting an appropriate resin-based dental restorative material for operative restorations. Copyright © 2011 John Wiley & Sons, Ltd.

Objectives: The objective of this study was to evaluate the effect of a novel dentifrice (Diamynt, with fluoride, xylitol, herbal extracts, hydrated silica and diamond particles) on the surface roughness and gloss of two commercially available dental porcelains following simulated toothbrushing. Methods: Two commercially available porcelains (Vita VM13 and Ceramco 3) were used, as well as commercial finishing and polishing instruments (Dialite wheels). The porcelain samples were fabricated and polished by a professional dental laboratory with the same dimensions and polishing method. Roughness (Ra) was evaluated with a stylus profilometer (Federal PocketSurf). Gloss measurements were obtained by using a 60° small object glossmeter (Rhopoint NovoCurve Glossmeter). Following initial surface analysis of gloss and profilometry, the polished side of every sample was treated with a simulated toothbrushing technique previously published using a toothbrushing device (Sabri Dental V-8 Toothbrush Abrasion Machine). Diamynt and Arm & Hammer Whitening toothpaste were independently used to create a 50:50 w/w slurry with deionized water. Each surface was brushed 10,000 times. (Equivalent to 1 year toothbrushing) Then, the samples were rinsed with tap water and stored in 100% humidity until roughness and gloss values were obtained using the glossmeter and profilometer. Data was analyzed using two-tailed, unequal variance t-tests. Results: Diamynt toothpaste had no significant effect on surface roughness or gloss on either porcelain tested. Arm and Hammer had no effect on the surface roughness of either porcelain, but a significant effect (P

SUMMARY The objective of our study was to evaluate the association of molar-incisor hypomineralizations (MIHs) with prospectively collected potential causative factors from the first 4 years of life, e.g. respiratory diseases, breastfeeding, maternal smoking and parental education. A total of 692 children (10 years old) from the GINI birth cohort study participated. The dental examination included the registration of enamel hypomineralizations (EHs) according to the EAPD criteria. Children with EH were sub-categorized into those with at least one EH (MIH/1), those with a minimum of one EH on at least one first permanent molar (MIH/2) and those with EH on at least one first permanent molar and a permanent incisor (MIH/3). All relationships between causative factors and caries or MIH were evaluated using simple and multiple logistic regression analyses. EHs were observed in 37.9% (MIH/1), 14.7% (MIH/2) and 9.2% (MIH/3) of all subjects. After adjustment for confounding factors, 10-year-old children with at least one episode of respiratory disease had a significantly higher risk (2.48 times, adjusted OR) for the development of MIH/3. In case of breastfeeding, a non-significant association was observed. None of the tested factors was associated with either MIH/1 or MIH/2. Early respiratory diseases seem to be directly or indirectly related to MIH/3 only. The role of (systemic) medications used for treatment of these diseases needs to be investigated in future studies.

Purpose: To compare the fracture resistance and failure patterns of endodontically-treated teeth with a progressively reduced number of residual walls restored using resin composites, with or without translucent glass fiber posts. Methods: Ninety extracted human single-rooted maxillary premolars were used. After endodontic treatment, the following groups were created: Group 1 (control group): endodontically-treated single-rooted maxillary premolars with four residual walls; Group 2: three residual walls; Group 3: two residual walls; Group 4: one residual wall, and Group 5: no residual wall. Groups 2-5 were each divided into two subgroups: subgroups "a" were restored with resin composites, while subgroups "b" were restored with translucent glass fiber posts and resin composites. Static fracture resistance tests and statistical analyses (P= 0.05) were performed. Results: The mean failure loads (N) were 502.4 +/- 152.5 (Group 1), 416.4 +/- 122.2 (Group 2a), 423.0 +/- 103.3 (Group 2b) 422.1 +/- 138.9 (Group 3a) 513.2 +/- 121.7 (Group 3b), 488.7 +/- 153.7 (Group 4a) 573.4 +/- 169.2 (Group 4b), 856.7 +/- 112.2 (Group 5a) and 649.5 +/- 163.5 (Group 5b), respectively. The samples restored with fiber posts exhibited predominantly restorable fractures. The number of residual cavity walls influenced the mechanical resistance of endodontically-treated teeth.