Faculty Bibliography

OBJECTIVE:To evaluate the influence of the degree of dentin moisture on interfacial ultramorphology and bond strength (μTBS) of universal adhesives. MATERIALS AND METHODS/METHODS:Futurabond U (FBU), Scotchbond Universal (SBU), Adhese Universal (ADU), and Prime&Bond active (PBA) were used. After acid-etching, moist or over-dried dentin surfaces were tested. Teeth were restored for scanning and transmission electron microscopy (n = 3) and μTBS evaluation (n = 5). μTBS results were analyzed by two-way ANOVA and Tukey. RESULTS:For moist dentin, a well-formed hybrid layer (HL) was observed. However, when applied to over-dried dentin, remarkable differences were observed. Defects, gaps, and reduced HL thickness were observed mainly for ADU and FBU. When applied to wet dentin, μTBS values were similar for all adhesives, except for FBU, which was significantly lower. When applied to over-dried dentin, PBA presented the highest μTBS values, followed by SBU, ADU, and FBU. ADU presented significantly lower μTBS when applied to over-dried dentin. CONCLUSION/CONCLUSIONS:PBA, SBU, and FBU μTBS values were not sensitive to the degree of moisture. Even though application to over-dried dentin revealed defects, gaps and reduced HL thickness for SBU, ADU, and FBU, μTBS analysis only revealed a significant reduction for ADU. CLINICAL SIGNIFICANCE/CONCLUSIONS:Universal adhesives can be applied in either self-etching or etch-and-rinse mode. However, clinicians are not aware which universal adhesives should be strictly applied on a moist dentin for bonding in the etch-and-rinse mode.

AIM/OBJECTIVE:Die silicone materials are used to build chairside composite restorations. The purpose of this study was to compare the flowability, dimension accuracy, and tear strength of four elastomeric die materials. MATERIAL AND METHODS/METHODS:Materials were divided into four groups: Mach-2 (M2), Scan Die (SD), GrandioSO Inlay System (GIS), and Impregum-F (IM). Flowability analysis was carried out using the shark fin test (SFT). For dimension accuracy, impressions were taken from a premolar Class I preparation and an elastomeric model was cast. Composite resin restorations were built and positioned into the premolar for gap measurement. The mean gap length was divided into three levels: acceptable (A), not acceptable (NA), and misfit (M). For tear strength, strip specimens were made with a V-shaped notch (n = 6). The specimens were tested in a universal machine until tear. All data were analyzed statistically with a confidence interval of 95%. RESULTS:GIS showed the lowest flowability values, with no differences between IM, M2, and SD. For dimension accuracy, IM showed 100% 'A' gap values, followed by M2 (80%), SD (60%), and GIS (60%). For tear strength, IM showed the highest values, followed by M2, GIS, and SD. CONCLUSIONS:M2, SD, and IM had similar flowability, while GIS had the lowest. IM presented higher tear strength than M2, followed by GIS and SD. IM showed the highest degrees of acceptable gap filling, followed by M2.

OBJECTIVE:To quantify the volumetric polymerization shrinkage (VPS) of different conventional and bulk fill resin composites, through micro-computed tomography (μCT), and qualitative comparison of gap formation through optical coherence tomography (OCT). METHODS:Box-shaped class I cavities were prepared in 30 third-molars and divided into 5 groups (n=6): G1- Filtek Z100 (Z100); G2- Tetric Evoceram Bulk Fill (TEC); G3- Tetric EvoFlow Bulk fill (TEF); G4- Filtek Bulk fill (FBU); and G5- Filtek Bulk fill Flowable (FBF). All groups were treated with Adper Single Bond Plus adhesive and light cured (Bluephase 20i). Each tooth was scanned three times using a μCT apparatus: after cavity preparation (empty scan); after cavity filling (uncured scan) and after light curing of the restorations (cured scan). The μCT images were imported into a three-dimensional rendering software, and volumetric polymerization shrinkage percentage was calculated (%) for each sample. In the same images, interfacial gaps in the pulpal floor were qualitatively evaluated. After μCT evaluation, the pulpal floor from each tooth was polished until a thin tooth structure was obtained and OCT images were obtained by scanning the pulpal portion. Gap formation was observed and qualitatively compared to the μCT images. RESULTS:VPS means ranged from 2.31 to 3.96% for the studied resin composites. The bulk fill materials, either high viscosity or flowable, were not statistically different from each other (p>0.05). The conventional resin composite Z100 presented statistically higher VPS than both high viscosity bulk fill materials studied (p<0.05), although it was statistically similar to the flowable bulk fill materials studied (p>0.05). Both μCT and OCT methodologies enabled gap formation visualization, and images from both technologies could be associated. Gap formation was mostly observed for G1-Z100, G4-FBU, and G5-FBF. VPS% and pulpal gap formation could not be completely associated with each other for all groups and samples. Voids were observed in most of the resin composite fillings, and most VPS were observed in the occlusal area of the samples. SIGNIFICANCE/CONCLUSIONS:Volumetric polymerization shrinkage was material-dependent, although bulk fill materials did not differ from each other. Both μCT and OCT enabled interfacial pulpal gap formation visualization. VPS and gap formation cannot be completely associated with one another.

New resin-based restorative materials have been developed, such as computer-aided design/computer-aided manufacturing (CAD/CAM) and bulk-fill composites, as an alternative to traditional layering techniques. This study evaluated the biaxial flexural strength (BFS) before and after thermocycling of five different resin composites: one hybrid resin/ceramic CAD/CAM indirect material, Lava Ultimate CAD-CAM Restorative (LU, 3M Oral Care); a conventional composite, Filtek Z350 XT (Z350, 3M Oral Care); two bulk-fill composites, Tetric N-Ceram Bulk Fill (TBF, Ivoclar Vivadent) and Filtek Bulk Fill (FBF, 3M Oral Care); and one bulk-fill flow resin composite, Filtek Bulk Fill Flow (FBFF, 3M Oral Care). Three hundred disc-shaped specimens (6.5 mm in diameter and 0.5 mm thick) were fabricated and divided into five groups (n=30 for each composite and condition). The BFS test was performed in a universal testing machine at a crosshead speed of 0.5 mm/min immediately (i, 24 hours) and after thermocycling (a, 500 thermal cycles of 5°C to 55°C with a 30-second dwell time). The Weibull modulus (m) and characteristic stress (η) were calculated, and a contour plot was used (m vs η) to detect differences between groups (95% two-sided confidence intervals). Significantly higher characteristic stress was observed for LUi (286.6 MPa) and Z350i (248.8 MPa) compared to the bulk-fill groups (FBFi=187.9 MPa, FBFFi=175.9 MPa, TBFi=149.9 MPa), with no differences between LUi and Z350i. Thermocycling significantly decreased the characteristic stress of all groups with the highest values observed for LUa (186.7 MPa) and Z350a (188.9 MPa) and the lowest for FBFFa (90.3 MPa). Intermediate values were observed for FBFa (151.6 MPa) and TBFa (122.8 MPa). The Weibull modulus decreased only for FBFa compared to FBFi. Composition and thermocycling significantly influenced the biaxial flexural strength of resin composite materials.

OBJECTIVES:/UNASSIGNED:This study evaluated the effect of argon plasma treatment (PLA) and its combination with sandblasting (SAN), silanization (SIL), and hydrophobic bonding resin (HBR) application on the micro-shear bond strength of water-aged restorative resin composite to a newly placed composite, simulating restoration repair. METHODS AND MATERIALS:/UNASSIGNED:Forty-five light-cured composite plates (20-mm long × 20-mm wide × 4-mm thick) were fabricated using a hybrid composite and stored at 37°C in distilled water for six months. The aged composite surfaces were treated according to the following experimental groups, varying both treatment and order of application: 1) SAN + SIL + HBR (control), 2) SAN + PLA for 30 seconds + SIL + HBR, 3) SAN + SIL + PLA + HBR, 4) PLA + SIL + HBR, 5) PLA + SIL, 6) PLA + HBR, 7) SIL + PLA + HBR, 8) SIL + PLA, and 9) PLA. After the surface treatments, four fresh resin composite cylinders (1.5-mm high × 1.5-mm diameter) of the same composite were built on each aged composite surface using a silicone mold. After water storage for 24 hours or one year, the specimens were submitted to shear bond strength testing. Data were statistically analyzed by two-way analysis of variance and Tukey's test (5%). RESULTS:/UNASSIGNED:Groups 1, 2, and 4 presented significantly higher bond strength means at 24 hours, although group 4 did not differ from group 7. Groups 5, 8, and 9 demonstrated significantly lower means than the other groups. Even though groups 1 and 2 had a significant bond strength reduction after 1 year, they still demonstrated higher bond strength at one year of storage. CONCLUSIONS:/UNASSIGNED:While PLA application combined with surface treatment methods demonstrated high bond strength results, this treatment alone was not as beneficial as other methods that included SAN, SIL and HBR.

STATEMENT OF PROBLEM/BACKGROUND:Color matching in restorative and prosthetic dentistry is important for the success of dental treatments, although communication with the dental laboratory remains subjective, and studies of the performance of objective communication methods are lacking. PURPOSE/OBJECTIVE:The purpose of this study was to evaluate color differences (ΔE) and compare color luminosity (L*) values among different types of digital photography equipment used to document tooth color, with and without a gray reference card, and to determine whether the gray card could be used to standardize color assessment in dental photography. MATERIAL AND METHODS/METHODS:Sixty photographs were made (n=10) using different equipment: a D7000 digital camera (Nikon Corp) with an 85-mm lens and wireless close-up flash (DC+WCF); close-up flash surrounded by 80 grams per square meter (gsm; specification of paper thickness) white printing paper (DC+WPP); ring flash (DC+RF); close-up flash attached to a dual-point rigid flash bracket (DC+DPRF); cross-polarizing filter attached to a close-up flash (DC+CPF); and iPhone 7 (I7). For all photographs, a gray reference card with known color values was positioned at the patients' mandibular teeth, acting as a parameter for the analysis of white-balanced digital photographs. Each photograph underwent white balance with the reference card and software. ΔE were obtained from each piece of equipment by comparing images with and without white balance (original photo) with software and the smallest ΔE achieved was used as the gold standard for comparisons of luminosity. Values of luminosity were subsequently obtained for the different equipment with and without white balancing the photographs; these values were compared using a general estimating equation with Huber-White standard error (α=.05). RESULTS:The use of a cross-polarizing filter was used as the gold standard for luminosity evaluation, as the smallest ΔE (3.4) among photographs were observed when those with and without white balance were compared. Luminosity results from the cross-polarizing filter method (DC+CPF) were not significantly different from those of the DC+DPRF (P=.73), DC+WPP (P=.106), and DC+WCF (P=.551) groups but were statistically different from DC+RF (P=.028) and I7 groups (P<.001). Use of a gray card was significant when a ring flash (P=.008) or the iPhone (P=.023) were used but not statistically significant for the other groups (P>.05). CONCLUSIONS:The use of a cross-polarizing filter results in more color-standardized photographs, while the ring flash system and the iPhone 7 result in less standardized photographs. The gray reference card had a significant effect when a ring flash system or iPhone 7 was used.

Proper gingival displacement is an important prerequisite to obtain good quality impressions. Retraction pastes could eliminate the need for retraction cords, as they have advantages such as comfort reported by patients, faster technique, ease of use, no need for anesthesia, and reduced tissue trauma. The objective of this paper was to present a clinical case of ceramic veneers and crowns in which a retraction paste was used for gingival displacement during both the impression and cementation stages, with 3 years of follow-up. Treatment planning consisted of the replacement of preexisting crowns and ceramic veneers on the anterior teeth. After finishing the preparations, gingival displacement with Astringent Retraction Paste was performed without anesthesia or the use of cords and the impression was taken. Before cementation of the crowns and veneers, the Astringent Retraction Paste was applied. Avoiding the use of cords during cementation prevented trauma. The soft tissue margins remained stable and healthy after a period of 3 years. It can be concluded that retraction pastes could be indicated for displacement of soft tissue when preparation margins are at the gingival level or slightly intrasulcular prior to impressions, restoration cementations, direct restorations, and before relining provisional restorations. Clinical significance: The impression appointment can be traumatic to some patients. The use of cords for gingival displacement usually requires local anesthesia and is time consuming. Retraction astringent pastes instead of cords seems to be a good option for some cases in gingival tissue displacement.

The stability and health of the periodontal tissues should be a common goal for all dental care providers with regard to natural or restored teeth as well as implant-supported restorations or any other type of prosthesis. The objective of this study was to address the key aspects to be respected when executing adhesive oral rehabilitations involving ceramic restorations, regardless of their thickness, and to reinforce the importance of each step to ensure the success and longevity of the treatment from a periodontal standpoint. This article reviews the fundamentals of the periodontics that relate directly or indirectly to adhesive ceramic dental restorations, and also addresses their clinical relevance.