Mechanical behavior of Class I cavities restored by different material combinations under loading and polymerization shrinkage stress. A 3D-FEA study.

 

Pietro Ausiello, dds, phd, Stefano Ciaramella, eng, phd, Antonio Lanzotti, eng, phd, MAURIZIO VENTRE, eng, phd, Alexandre L.S. Borges, dds, phd, msd, Joao P. Tribst, dds, ms, Amanda Dal Piva, dds, ms &  Franklin Garcia-Godoy, dds, ms, phd, phd

 

Abstract: 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 displace-ments 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. (Am J Dent 2019;32:55-60).

 

 

Mail: Dr. Pietro Ausiello, School of Dentistry, via S. Pansini, 5-80131 Naples, Italy. E-mail: pietro.ausiello@unina.it

 

 

Influence of pulse duration when performing Er:YAG laser irradiation on dental tissues

 

Izabella Nerushay, med dent,  Ivo Krejci, dr med dent, phd,  Anastasia Ryabova, med dent &  Tissiana Bortolotto, dr med dent, msc, phd

 

Abstract: Purpose: To evaluate the marginal adaptation of mixed Class V composite restorations in cavities prepared with the Quantum Square Pulse (QSP) mode Er:YAG laser, compared to Super Short Pulse (SSP) and diamond bur. The impact of Er:YAG laser finishing with low pulse energy and two irradiation distances was also evaluated. Methods: Class V cavities were prepared in enamel and dentin by varying the above parameters, and then restored with Clearfil SE Bond and Clearfil AP-X composite under dentin fluid simulation. The control groups were prepared and finished using conventional diamond burs (80 and 25 µm respectively). Scanning electron microscope (SEM) marginal adaptation analysis at ×200 magnification was performed on replicas before and after thermo-mechanical cyclic loading in order to determine the percentage of continuous margins (i.e. from 0 to 100% of gap free margins). The differences between groups were analyzed with one-way ANOVA and Duncan post hoc test. Results: Dentin treated with SSP showed significantly lower percentages of “continuous margin” than the QSP and control groups. QSP was as effective as bur preparation. (Am J Dent 2019;32:61-68).

 

 

 

 

Mail: Dr. Izabella Nerushay, Division of Cariology and Endodontology, University Clinic of Dental Medicine, Faculty of Medicine, University of Geneva, Rue Barthelemy-Menn, 19, 1205 Geneva, Switzerland.  E-mail: izabella.nerushay@unige.ch

 

 

Laboratory efficacy of an oscillating-rotating toothbrush with a uniquely designed head and extremely tapered bristles

 

Samuel L. Yankell, ms, phd, rdh, Christine M. Spirgel, ms, Xiuren Shi, dds, Supinda Watcharotone, phd &  James Cwik, bsba, mba

 

Abstract: Purpose: This laboratory study compared a newly designed GUM oscillating-rotating power toothbrush with a unique head design that combines both standard nylon filament and extremely tapered filaments to the Oral-B oscillating-rotating-pulsating power toothbrush with the Precision Clean head and to the Oral-B Compact 35 Indicator manual toothbrush for their ability to reach and remove artificial plaque deposits from hard-to-reach interproximal and subgingival sites. Methods: Interproximal access efficacy (IAE) was evaluated using an artificial plaque substrate placed around simulated teeth. Subgingival access efficacy (SAE) was determined by using simulated gingiva prepared with a 0.2 mm space between the gingiva and artificial plaque substrate covering the simulated teeth. Results were recorded on the same artificial plaque substrate placed under the gingiva and around the simulated teeth. Results: The overall IAE value for the new GUM oscillating-rotating power head indicated that it was significantly more effective  compared to the Oral-B power and manual toothbrushes in interproximal access (P< 0.001). The mean value for SAE for the new and commercially available power products also were significantly more effective compared to the manual toothbrush in subgingival access (P< 0.001). (Am J Dent 2019;32:69-73).

 

 

 

Mail: Dr. Samuel L. Yankell, Yankell Research Consultants Inc., 15 East Maple Avenue, Moorestown, NJ 08057 USA, E-mail: YRCInc@aol.com

 

Evaluation of detecting proximal caries in posterior teeth via visual inspection, digital bitewing radiography and near-infrared light transillumination

 

Jan Kühnisch, dds,  Gerrit Schaefer, dds,  Vinay Pitchika, dds, phd,  Franklin Garcia-Godoy, dds, ms, phd, phd &  Reinhard Hickel, dds, phd

 

Abstract: Purpose: This prospectively designed, non-validated in vivo diagnostic study compared the results of visual examination, digital bitewing (BW) radiography and near-infrared light transillumination (NIR-LT, DIAGNOcam) on proximal caries detection in posterior teeth. Methods: A total of 203 subjects (122 men/81 women; mean age, 23.0 years) were included. All subjects were visually examined according to the standards by the World Health Organization and the International Caries Detection and Assessment System. In addition, digital BW radiographs were performed. NIR-LT images were captured from all posterior teeth. All BWs and NIR-LT images were blindly evaluated for the presence of enamel caries lesions (ECLs) and dentin caries lesions (DCLs). No histological validation was performed due to the impossibility to investigate healthy surfaces and non-cavitated caries lesions invasively. The statistical analysis included both descriptive and exploratory data evaluations. Results: The diagnostic outcome differed for each method. Compared with BW radiography (8.0 surfaces) and NIR-LT (10.5 surfaces), visual examination revealed the fewest caries-related findings (4.2 surfaces). BW radiography or NIR-LT detected either 86.2% or 89.6% of all ECLs/DCLs in posterior teeth alone. When combining visual examination with NIR-LT, 70.9% of all ECLs/DCLs were similarly detected; when visual examination and BW radiography were combined, this proportion was lower (52.6%). (Am J Dent 2019;32:74-80).

 

 

 

 

Mail: Dr. Jan Kühnisch, University Hospital, Ludwig-Maximilians University of Munich, Department of Conservative Dentistry and Periodontology, Goethestraße 70, 80336 Munich, Germany. E-mail: jkuehn@dent.med.uni-muenchen.de

 

 

Pre-treatment of dentin with chondroitin sulfate or L-arginine modulates dentin tubule occlusion by toothpaste components

 

Grigoriy Sereda, phd  &  Shahaboddin Saeedi, bs

 

Abstract: Purpose: To evaluate the effect on dentin of chondroitin sulfate and L-arginine on dentin tubule occlusion. Methods: The dentin samples were activated by submersion in an aqueous (aq.) solution of chondroitin sulfate (ChS) or L-arginine prior to application of a commercial or custom-made toothpaste. After rinsing with water and ultrasonication, adhesion to dentin and occlusion of dentin tubules were evaluated by scanning electron microscopy and the elemental composition of the deposits was evaluated by energy-dispersive x-ray spectroscopy. Results: Rinsing a dentin sample with a solution of ChS resulted in an increase in the adherence of dentifrices containing either titanium dioxide (TiO₂) or calcium-based nanoparticles (hydroxyapatite (HA) or calcium carbonate) to the dentin surface. ChS does not appear to enhance the adherence of dentifrices lacking TiO₂. Pretreatment by L-arginine improved adherence of calcium carbonate nanoparticles, but less efficiently than ChS. Addition of nanoparticles of hydroxyapatite or calcium citrate to dentifrices improved their adherence to dentin without any pre-treatment. (Am J Dent 2019;32:81-88).

 

 

Mail: Dr. Grigoriy Sereda, Department of Chemistry, University of South Dakota, 414 East Clark Street, Vermillion, SD 57069, USA. E-mail: Grigoriy.Sereda@usd.edu

 

Influence of silanes on the stability of resin-ceramic bond strength

 

Daniel Baptista da Silva, dds, phd, Greciana Bruzi, dds, phd, Bruna Pauli Schmitt, dds, Alfredo Meyer Filho, dds, phd  &  Mauro Amaral Caldeira de Andrada, dds, phd

 

Abstract: Purpose: To evaluate the in vitro stability of resin-ceramic bond strength provided for silanes with acidic functional monomers. Methods: Five ceramic blocks were fabricated. The blocks were randomly divided into groups (n=30) and assigned to the following surface treatments: (C) HF + RelyX Ceramic Primer, (G1) HF + Porcelain Liner M, (G2) HF + Clearfil Ceramic Primer, (G3) Phosphoric acid (H₃PO₄) + Clearfil Ceramic Primer, (G4) H₃PO₄ + Porcelain Liner M. Two adhesives were used: Single Bond in Group C and Clearfil SE Bond in the other groups, after which, each block received four 1 mm increments of resin composite Filtek Z350. The resin-ceramic blocks were sectioned, obtaining samples of approximately 0.8 mm × 0.8 mm. The groups were subdivided according to aging mode: I - immediate (24 hours storage in artificial saliva) and A - aged (3 months in artificial saliva + 5,000 thermal cycles 5°C/55°C). The microtensile test was performed with a 0.5 mm/minute crosshead speed (n = 15) on a universal testing machine. The fracture patterns were categorized with scanning electron microscopy. The results were analyzed using three-way ANOVA and Tukey’s test (P≤ 0.05). Results: Silanes containing acidic functional monomers did not affect the stability of the resin-ceramic bond strength. The use of HF acid was a necessary condition for stability. The highest values after aging were obtained by silanes with functional molecules without a statistically significant difference. The storage influenced the values of bond strength. The use of acidic functional monomers did not affect the resin-ceramic bond after storage in saliva followed by thermal cycling. (Am J Dent 2019;32:89-93).

 

 

Mail: Dr. Daniel Baptista da Silva, Lauro Linhares 1288, Ap 301, Ed. Stoneville, Bairro Trindade, Florianópolis, Santa Catarina, Brazil 88036-002.  E-mail: djaniels2002@yahoo.com.br

 

 

Evaluation of polymethyl methacrylate containing chlorhexidine: A randomized, controlled, split-mouth in situ study

 

Caroline Vieira Maluf, dds, ms, Tatiana Kelly da Silva Fidalgo, dds, ms, phd, Ana Paula Valente, dds, ms, phd, Marcelino José dos Anjos, dds, ms, phd,  Raphael Hirata Junior, dds, ms, phd &  Daniel de Moraes Telles, dds, ms, phd

 

Abstract: Purpose: To evaluate the antimicrobial action and elemental composition of chlorhexidine (CHX) diacetate in acrylic resins based on PMMA (polymethyl methacrylate) in situ. In addition, ex vivo evaluation of the CHX release mechanism was performed over a 14-day period. Methods: Three discs of PMMA incorporating CHX and three control discs were mounted on individual oral splints and exposed to the oral cavity of 32 participants for 24 hours. The antimicrobial activity was evaluated by the plate count method. In the second test, elemental analysis of the specimens (n = 10) was performed by X-ray fluorescence before and after use of the device. Chlorhexidine release over a 14-day period was evaluated ex vivo in saliva samples collected from five individuals through proton nuclear magnetic resonance spectroscopy (¹H NMR) (500 MHz). Results: Bacterial adhesion, evaluated by the plate count method, did not differ between the experimental material and control. (P> 0.05) The presence of the CHX molecule was detected by X-ray fluorescence before and after insertion of discs containing CHX into the oral cavity of participants. With regard to release, CHX was detected in saliva samples for 14 days and highest during the first 24 hours. When partial least squares discriminant analysis (PLS-DA) was applied in 1H NMR, we observed a greater difference between the test and control groups. (Am J Dent 2019;32:94-98).

 

 

Mail: Dr. Daniel de Moraes Telles, Department of Prosthodontics, School of Dentistry, Rio de Janeiro State University, Boulevard 28 de Setembro, 157 Vila Isabel, Rio de Janeiro, RJ, Brazil 20551-030.  E-mail:  dmtelles@uerj.br

 

 

 

 

Influence of infrastructure design and ceramic coverage material on stress development in posterior crowns

 

Haine Beck, dds, msc  &  Roberta Tarkany Basting, dds, msc, phd

 

Abstract: Purpose: To evaluate the influence of the infrastructure design and type of ceramic coverage on residual stresses after occlusal loading of crowns with yttria-stabilized zirconium oxide (Y-TZP) infrastructure, analyzed by means of the finite element method. Methods: 3D models of a mandibular first molar total crown were constructed with two different types of infrastructures: a coping with a uniform thickness of 0.3 mm, and an anatomic coping with a thickness ranging from 0.3 mm to 1.5 mm, depending on the external anatomy of the crown, and three types of ceramic coverages: feldspathic, leucite- and lithium disilicate-reinforced types. Fusion 360 software (Autodesk) was used to simulate occlusal loading of 300 N in an area of 1 mm² on the internal slopes of the mesial vestibular cusps. Results: Higher tensile stress values (σ1 positive) were observed for the ceramics with anatomic copings (800.3 MPa for feldspathic; 800.1 MPa for leucite, and 799.0 MPa for lithium disilicate), in comparison with the groups of uniform coping (482.0 MPa for feldspathic, 480.0 MPa for leucite, and 479.4 MPa for lithium disilicate). Stress distribution in all the groups followed the same type of pattern, with stresses developing in the load application region and following in the direction of the facial-lingual regions of the coverage crowns. The main maximum peaks of tensile strength were located below the points of load application and on the internal surface of the crown in the distolingual direction. The magnitudes of tensile stress on the anatomic coping ceramics were higher than on the uniform coping ceramics; the different coverage ceramics used did not influence the stress distribution pattern. (Am J Dent 2019;32:99-104).

 

 

 

 

Mail: Prof. Dr. Roberta Tarkany Basting, Department of Restorative Dentistry, Faculty of Dentistry and Institute of Research, Rua José Rocha Junqueira, 13, Bairro Swift, Campinas, SP CEP: 13045-755, Brazil. E-mail: rbasting@yahoo.com