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http://dx.doi.org/10.1016/j.dental.2014.08.178

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Usage of nanotechnology for the superlubrication of orthodontic wires

C.C. Lombardi 1,∗, A. Gracco 2, L. Siviero 1,∗, F.Deflorian 3, C. Zanella 3, G. Siciliani 1, G.Bonetti 4

1 University of Ferrara, Italy2 University of Padova, Italy3 University of Trento, Italy4 University of Bologna, Italy

Purpose: The aim of this work was to reduce frictionbetween orthodontic stainless steel wires and brackets bycoating the wires with self-lubricating nickel-phosphorous(NiP) films containing inorganic amorphous nanoparticles (NP)of tungsten disulfide (WS2) and molybdenum disulfide (MoS2),which are well-known lubricants.

Methods and materials: The test setup was built in Instronmachine. It simulated the clinical setting by sliding theorthodontic stainless-steel wires through self-ligating brac-kets (Damon Q and In-Ovation) arranging mutual angles � = 0◦,5◦ and 10◦. Wires were coated with NiP plus NiP + NP (WS2or MoS2) films through electroless co-deposition. SEM (scan-ning electron microscope) and EDS (energy-dispersive X-rayspectrometer) analysis were carried on over wear tracks.

Results: Friction reduction range was 1.2 ÷ 30.1% for WS2and 12.2 ÷ 38.8 for MoS2. Wear and friction benefits alwaysincreased with tribological stress (wider �’s). Damon Q brac-kets performed greater reduction in friction than In-Ovationones. Wear of WS2 coating looked lighter than MoS2’s at SEManalysis. Moreover EDS spectra revealed greater chemical sta-bility for WS2.

Conclusion: Cost/effectiveness of the tested nanomaterialoffers a novel opportunity to reduce friction in orthodontictreatments through composite coatings. WS2 films are pre-ferred to MoS2 films thanks to greater wear resistance.

Keywords: Nanotechnology; Superlubrication; Orthodonticwires

http://dx.doi.org/10.1016/j.dental.2014.08.179

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Mechanical behaviors of class II compositerestorations under cyclic loading

S.F. Chuang ∗, X.F. Hong, T.Y.F. Chen

National Cheng Kung University, Tainan, Taiwan

Purpose: The viscoelasticity of composite materials mayalter the creep behaviors of dental restorations, but this fact israrely revealed by experimental mechanical studies. The pur-pose of this study was to investigate the mechanical responsesand interface sealing of class II restorations with differentcomposite materials under dynamic loading.

Methods and materials: Forty intact extracted molarswere mounted and prepared with a class II MOD cavity(4(W) × 4(H) mm). These teeth were divided into four groups,and then restored with one of four techniques: a microhy-brid composite Filtek Z250 (3M ESPE) filling, Z250; a packablecomposite Filtek P60 filling, P60; Z250 filling with Filtek Z350flowable lining, Z250/F; and P60 filling with Z350-flowable lin-ing, P60/F. After restoration, these teeth were sprayed withblack paint to generate surface patterns. These teeth receiveda dynamic loading test by a cyclic load of 100 N at a frequencyof 1 Hz. After either 1000, 3000, and 5000 cycles, the deforma-tion states of the restorations were photographed through amicroscope at the speed of 10 fps for 5 cycles. A non-contactingoptical measuring technique, digital-image-correlation (DIC),was used to calculate the full-field deformation by comparingthe images obtained at different states. These displacementsand strain on the proximal surfaces were analyzed with aDIC program Vic-2009. The viscoelasticity of all compositematerials were measured by a dynamic material analyzer. Theteeth also received micro-CT examination for their resin-toothinterface bonding after 5000-cycle loading.

Results: The deformation of composite restoration con-tinued to increase with the loading cycles. P60 showed theleast deformation, while Z250/F showed the greatest deforma-tion. The strain was greater at the middle of the restoration,while the displacements were greater at the bottom. The lininggroups showed both greater deformation and strain comparedto unlining groups. The lining groups showed more microleak-age than those of unlining groups especially on the bottom.

Conclusion: The viscoelastic property of resin compos-ites may affect the strain and creep strains of the composite

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restorations. The use of low modulus lining materials signifi-cantly increased the creep strain of the whole restorations andmay disrupt the interfacial sealing at the cavity floor.

Keywords: Composite; Creep; Digital image correlation

http://dx.doi.org/10.1016/j.dental.2014.08.180

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Two-year prospective clinical study ofposterior CAD–CAM cobalt-chromium singlecrowns

R. Leone ∗, F. Zarone, P. Piombino, R.Sorrentino

University “Federico II” of Naples, Naples, Italy

Purpose: Base metal dental alloys are in great demandworldwide because of their lower cost compared to pre-cious alloys but difficulties encountered during castinglimit their use. Application of these alloys might beenhanced if new techniques are used. The aim of thisprospective study was to evaluate the clinical performanceof computer-aided design/computer-assisted manufacturing(CAD–CAM) cobalt-chromium (Co–Cr) based single crownssupported by natural teeth after 24 months of clinicalfunction.

Methods and materials: Twenty-five single crowns werefabricated and used in 25 patients. The restorations replacedeither a premolar or a molar. Specific inclusion criteriawere needed. Tooth preparation was standardized. CAD–CAMframeworks were made. The frameworks were fused with twolayers of opaque, followed by two layers of dentin and one layerof dental porcelain according to the manufacturer’s instruc-tions. The restorations were luted using zinc oxide (eugenolfree) cement. The patients were recalled after 1, 3, 6, 12, and24 months. The survival and success of the ceramics andCo–Cr alloy were evaluated. The technical and aesthetic out-comes were examined using the United States Public HealthService criteria. The biologic outcomes were analyzed at abut-ment and contralateral teeth and descriptive statistics wereperformed.

Results: All of the 25 Co–Cr single crowns were examinedduring 24 months of clinical function. No patient was lostat follow-up or censored. As to the technical problems, nei-ther fractures of the frameworks nor losses of retention wereobserved in all of the samples. The cumulative survival ratewas 100% and the cumulative success rate was 100% after24 months according to Kaplan–Meier. No losses of retentionwere recorded. Twenty-four restorations were rated alpha inall measured parameters. No chipping of the ceramics wasdetected. According to the Wilcoxon test, the periodontalparameters of the test and the control teeth were not sig-nificantly different. Furthermore, the single crowns had noeffect on the periodontal parameters after 24 months of clin-ical function.

Conclusion: Within the limitations of the present study andits observational period, the excellent survival rate of singleposterior Co–Cr frameworks made with CAD–CAM techniqueallows to address this kind of restoration as a valid treatment

option and a viable alternative to noble metal-ceramic singlecrowns.

Keywords: Prosthesis, CAD–CAM; Cobalt–chromium

http://dx.doi.org/10.1016/j.dental.2014.08.181

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Efficacy of clinical trial management

F. Fazzi ∗, R. Lorenzi, G. Dondi Dall’orologio

University of Bologna, Italy

http://dx.doi.org/10.1016/j.dental.2014.08.182

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Connexin 43 is required fortopography-mediated osteoblasticdifferentiation on titanium

E. Manfredi, A. Toffoli ∗, C. Galli, S. Lumetti,G. Ghiacci, G.M. Macaluso, A. Di Blasio, M.Bonanini

Dep. Biomedical, Biotechnological andTranslational Sciences, University of Parma,Parma, Italy

Purpose: The aim of the present study was to investi-gate the role of Connexin 43, one of the main componentof cell-to-cell junctions and membrane hemichannels onsurface-induced osteoblastic differentiation on titanium sur-faces.

Methods and materials: Pickled (P), acid-etched, sand-blasted (SLA) or hyperhydrophilic SLA (modSLA) commerciallypure titanium samples were kindly provided by StraumannInstitut AG (Basel, Switzerland), as sterile discs of 1 mm thick-ness, 16 mm diameter. The murine calvaria MC3T3-E1 cell linewas grown in Dulbecco modified MEM (Life Technologies), 10%fetal bovine serum, 1% penicillin and streptomycin and 1%glutamine (Sigma–Aldrich). Connexons were inhibited with50 mM 18 beta-glycyrrhetinic acid (18BGA, Sigma–Aldrich).For cell viability 10,000 MC3T3 cells were plated on P, SLAor modSLA discs in 24 well plates and assayed 1, 3 or 6days after plating with or without 18BGA using a biolu-minescent assay. For gene expression, 100,000 MC3T3 cellswere plated on P, SLA or modSLA discs in 24 well platesand assayed 6 days after seeding by Real Time PCR. Two-way ANOVA statistical test was performed to analyze thedata.

Results: MC3T3 cells expressed higher levels of transcriptfor Connexin 43 on rough, SLA and modSLA surfaces. Additionof 18BGA did not affect cell viability on titanium surfaces atany time point, however, it did tend to reduce the expressionof osteoblast-specific genes Alkaline Phosphatase, Osteopro-tegerin and Osteocalcin on SLA and modSLA surfaces.

Conclusion: Our results indicate that osteoblastic cells onrough and hyperhydrophilic surfaces express higher levels ofConnexin 43. Moreover, physiological connexion functionality