Research Article

Influence of different post-endodontic restorations on the fatigue survival and biomechanical behavior of central incisors

 

Guilherme Schmitt De Andrade, dds, msc,  João Paulo Mendes Tribst, dds, msc, Esteban Isai Flores Orozco, dds, msc, phd,  Marina Gullo Augusto, dds, msc, phd, Marco Antonio Bottino, dds, msc, phd,  Alexandre Luiz Souto Borges, dds, msc, phd, Lilian Costa Anami, dds, msc, phd  &  Guilherme de Siqueira Ferreira Anzaloni Saavedra, dds, msc, phd

 

Abstract: Purpose: To evaluate the influence of different post-endodontic techniques on the fatigue survival and biomechanical behavior of crowned restored central incisors. Methods: The crowns of 69 bovine incisors were cut, and the roots were treated endodontically and assigned randomly into three groups (n=23): resin composite buildup (BUP), glass fiber post-retained resin composite buildup (GFP), and cast post-and-core (CPC). They received full crown preparation with 2 mm ferrule, and a leucite-reinforced ceramic crown was cemented adhesively. Three specimens from each group were tested monotonically. The remaining specimens were subjected to the stepwise stress fatigue test until fracture or suspension after 1.5 × 10⁶ cycles in a chewing simulator. The load and step at which each specimen failed were analyzed by Kaplan-Meier and Mantel-Cox (log-rank test) statistics, followed by multiple pairwise comparisons, at 5% significance level. The three groups tested (BUP, GFP, and CPC) were 3D modeled (Rhinoceros 4.0) and the maximum principal stress (MPa) criteria were used to calculate the results using FEA. Results: There was no statistical difference between the treatments regarding the load or the number of cycles (Mantel-Cox log-rank test for trend, X²= 0.015, df=1, P= 0.901, X² =3.171, df=1, P= 0.995). Crown cracks were the predominant failure mode, and oblique root fractures were only observed in groups GFP and CPC. In endodontically treated incisors with a 2-mm ferrule, the post-endodontic treatment had no significant effect on fatigue survival. Non-restorable fractures only occurred in teeth restored with posts. (Am J Dent 2020;33:227-234).

 

 

Mail: Dr. João Paulo Mendes Tribst, Av. Eng. Francisco José Longo, nº 777, Jardim São Dimas, São José dos Campos, São Paulo 12245-000  Brazil.  E-mail: joao.tribst@gmail.com

 

 

                                                                                                                                               Research Article

Antimicrobial effects of viscous mouthrinses containing cetylpyridinium chloride and isopropyl methylphenol

 

Yasuhiko Abe, dds, phd, Yohei Okazaki, dds, phd,  Kana Dainobu, dh,  Kenya Matsuo,  Hideyuki Ishida, dds, phd &  Kazuhiro Tsuga, dds, phd

 

Abstract: Purpose: To evaluate the in vitro antimicrobial effect of low- and high-viscosity experimental mouthrinses con-taining cetylpyridinium chloride (CPC) and 4-isopropyl-3-methylphenol (IPMP) on Streptococcus pneumoniae, Klebsiella pneumoniae, Porphyromonas gingivalis, Streptococcus mutans, and Candida albicans. Methods: Low- and high-viscosity experimental mouthrinses containing 0.05% CPC and 0.1% IPMP were fabricated. Non-viscous mouthrinses containing either CPC- or IPMP were used as controls. The antimicrobial activity (sterilization or exposure time) of mouthrinses was evaluated based on the bactericidal criterion of <10¹ viable cells in 0.1 mL of culture medium. Results: The sterilization time of the low-viscosity experimental mouthrinse was shorter than that of the high-viscosity mouthrinse. However, whereas a 10-minute exposure to the low-viscosity mouthrinse resulted in no viable cells of C. albicans, neither the CPC- or IPMP mouthrinses had an antimicrobial effect for the same exposure time. These findings show that the low-viscosity experimental mouthrinse containing anodal CPC and neutral IPMP exhibited superior antimicrobial effects against pneumonia- and oral infection-related bacteria compared with the control mouthrinses. (Am J Dent 2020;33:235-238).

 

 

Mail: Dr. Yasuhiko Abe, Department of Advanced Prosthodontics, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3, Kasumi, Minami-ku, Hiroshima 734-8553, Japan. E-mail: abey@hiroshima-u.ac.jp

 

 

                                                                                                                                              Research Article

Proanthocyanidin protects the enamel against initial erosive challenge when applied over acquired pellicle

 

Ana Paula Boteon, dds, Gabriela Guarda Dallavilla, Fabrícia Cardoso, dds, ms, Linda Wang, dds, ms, phd, Daniela Rios, dds, ms, phd  &  Heitor Marques Honório, dds, ms, phd

 

Abstract: Purpose: To evaluate the effect of proanthocyanidin applied over acquired pellicle in the inhibition of enamel demineralization, in a short-term erosive challenge. Methods: The acquired pellicle was formed in situ by the placement of intraoral palatal devices in two healthy volunteers for 2 hours. The enamel blocks of each group (n = 16) were treated in vitro according to the following groups: G1: 6.5% proanthocyanidin gel and acquired pellicle formed in situ; G2: only 6.5% proanthocyanidin gel; G3: only acquired pellicle formed in situ; and G4: no intervention (neither gel nor acquired pellicle). Gels were applied for 1 minute. Then, enamel blocks were immersed in 0.5% citric acid, pH 2.5, for 30 seconds to promote a short erosive challenge. The response variable used was the percentage of surface hardness loss (Knoop Hardness Number). Data were analyzed by Kruskal-Wallis and Dunn’s test (P< 0.001). Results: Statistical analysis showed that the G1 group presented a statistically significant difference compared to the other groups (P< 0.001), since it showed the lowest values of hardness loss (G1: median= 7.7a; 1ºQ= 4.7; 3ºQ= 10.3; G2: median= 17.7b; 1ºQ= 10.8; 3ºQ= 23.4; G3: median= 19.1b; 1ºQ= 11.1; 3ºQ= 21,1; G4: median= 24.9b; 1ºQ= 19.4; 3ºQ= 31.9). (Am J Dent 2020;33:239-242).

 

 

Mail: Dr. Heitor Marques Honório, Bauru School of Dentistry, University of São Paulo (FOB-USP), Department of Pediatric Dentistry, Orthodontics and Public Health, Alameda Octávio Pinheiro Brisola, 9-75, Vila Universitária, 17012-901   Bauru, SP, Brazil.  E-mail:  heitorhonorio@usp.br

 

 

                                                                                                                                               Research Article

Flexural resistance of CAD-CAM blocks. Part 3: Polymer-based restorative materials for permanent restorations

 

Alessandro Vichi, dds, msc, phd,  Cecilia Goracci, dds, msc, phd,  Michele Carrabba, dds, phd, Gianluca Tozzi, msc, phd  &  Chris Louca, bsc, bds, phd

 

Abstract: Purpose: Concurrently with the growing interest in CAD-CAM systems, several new materials of different chemical nature have become available. As an alternative to ceramics, numerous polymer-based materials have recently been proposed for permanent prosthetic restorations. Aim of this study was to test the CAD-CAM polymer-based materials available on the market, comparing mean flexural strength, Weibull characteristic strength and Weibull modulus. Methods: Seven types of polymer-based blocks were tested: Lava Ultimate, 3M; Brilliant Crios, Coltene; Cerasmart, GC; Block HC, Shofu; Katana Avencia, Noritake; Grandio Blocs, Voco; Tetric CAD, and  Ivoclar-Vivadent. Specimens were cut out from blocks, finished, polished, and tested in a three-point bending test apparatus until failure (n=30). Flexural strength, Weibull characteristic strength, and Weibull modulus were calculated. Flexural strength data were statistically analyzed. ANOVA on Ranks was applied, followed by the Dunn’s test for post hoc comparisons (P= 0.05). Results: Flexural strength values (MPa) were measured (mean±standard deviation). Different letters in parentheses label statistically significant differences: Grandio Blocs 266±24(a), Brilliant Crios 259±21(ab); Tetric CAD 254±15(ab); Katana Avencia 241±29(bc); Cerasmart 221±24(cd); Lava Ultimate 196±23(de); Block HC 139±10(e). All the tested materials had flexural strengths greater than 100 MPa, thereby satisfying the requirements of ISO standards for polymer-based materials. For all the tested materials the Weibull characteristic strength was greater than 100 MPa. Weibull modulus ranged between 21.20 (Tetric CAD) and 9.09 (Katana Avencia). (Am J Dent 2020;33:243-247).

 

 

Mail: Dr. Alessandro Vichi, Via Derna 4, 58100 Grosseto, Italy. E-mail: alessandro.vichi@port.ac.uk

 

 

 

 

                                                                                                                                               Research Article

Evaluation of the use of PEEK material in post-core and crown restorations using finite element analysis

 

Samet Tekin, dds, phd,  Ozkan Adiguzel, dds, phd,  Suzan Cangul, dds, phd,  Osman Atas, dds, phd, &  Begum Erpacal, dds

 

Abstract: Purpose: To compare the stresses generated after the use of low elastic modulus polyetheretherketone (PEEK) as dental post and crown material with glass fiber post and metal supported ceramic crowns using finite element analysis. Methods: First an image of a maxillary central incisor taken on micro-computed tomography (micro-CT) was uploaded to a computer program. Modeling was made of all the materials in the computer environment and 3-dimensional (3D) virtual models were obtained. Using two different post materials (glass fiber and PEEK post) and two different crown materials (metal supported ceramic and PEEK crown), the modeling of the maxillary central tooth was completed and a total of four groups were obtained. Finally, 135° and 100 N forces were applied from the midpoint of the palatal surface. Results: The FEA analysis showed the use of PEEK as post material decreased the stress values in the post, post cement and composite core models and did not have any significant change in the dentin and crown cement models. The use of composite veneer with PEEK substructure as crown material reduced stress values in dentin, the post and composite core and increased stress values in both the post cement and the crown cement. (Am J Dent 2020;33:251-257).

 

 

 

 

Mail: Dr. Suzan Cangul, Department of Restorative Dentistry, Faculty of Dentistry, Dicle University, Diyarbakir, Turkey. E-mail: suzanbali@outlook.com

 

 

                                                                                                                                             Research Article

Enhanced plaque removal to improve gingival health: 3-month randomized clinical study of the effects of baking soda toothpaste on plaque and gingivitis

 

Naresh C. Sharma, dds,  C. Ram Goyal, dds,  Jimmy G. Qaqish, bsc,  Linda M. Vorwerk, bs, William J. Hooper, phd  &  Annahita Ghassemi, phd

 

Abstract: Purpose: To compare the effectiveness in reducing plaque and gingivitis of a fluoride toothpaste with 20% baking soda and a fluoride toothpaste control. Methods: 159 subjects, who met the entry criteria, participated in this single-center, double-blind, randomized, parallel-group clinical study. Gingival Index (MGI), Gingival Bleeding Index (GBI), and Plaque Index (PI) were assessed after 4, 8, and 12 weeks use of the assigned test or control toothpaste. After 12 weeks, participants resumed 4 weeks of their customary oral hygiene after which they were re-evaluated using the same measures. Results: Both toothpastes statistically significantly reduced MGI, GBI, and PI versus baseline at all-time points. Brushing with the 20% baking soda toothpaste statistically significantly reduced MGI, PI, and GBI compared to the control toothpaste at all time points. After 12 weeks, the reductions in MGI, PI, and GBI were 12.6%, 9.6%, and 44.2%, respectively. After the 4-week customary oral hygiene period, the benefits of the study period had begun to diminish, but statistically significant reductions in MGI and GBI for the test versus control were still evident. This 3-month clinical study shows that brushing with fluoride toothpaste containing 20% baking soda reduces dental plaque and concurrently reduces gingival inflammation and bleeding compared to toothpaste with fluoride alone. (Am J Dent 2020;33:258-264).

 

 

Mail: Dr. A. Ghassemi, 469 North Harrison Street, Princeton, NJ 08543, USA. E-mail: annahita.ghassemi@churchdwight.com

 

 

                                                                                                                                               Research Article

The effects of two baking-soda toothpastes in enhancing mechanical plaque removal and improving gingival health: A 6-month randomized clinical study

 

Annahita Ghassemi, phd,  William J. Hooper, phd,  Linda M. Vorwerk, bs,  Elena Petrovicova, phd, C. Ram Goyal, bds,  Kathleen Qaqish, rdh,  Jimmy G. Qaqish, bsc   &   Sylvia Santos, rdh, ms

 

Abstract: Purpose: To compare the effectiveness in reducing plaque and gingivitis of two fluoride toothpastes containing baking soda (35% and 20%) with a fluoride toothpaste control. Methods: 319 subjects, who met entry criteria, participated in this single-center, three-cell, double-blind, randomized, parallel-group clinical study. Gingival Index (MGI), Gingival Bleeding Index (GBI), and Plaque Index (PI) were assessed at baseline, and after 6 weeks, 3 and 6 months. Results: All three toothpastes significantly (P< 0.0001) reduced MGI, GBI, and PI versus baseline, and the two baking soda toothpastes significantly (P< 0.0001) reduced MGI, GBI, and PI compared to the fluoride control, at all three time points. After 6 months use, the 35% and 20% baking soda toothpastes had reduced MGI, GBI and PI by 15.0%, 46.9%, and 18.3%, and 9.4%, 25.9%, and 12.4%, respectively, compared to the control. In addition, the 35% baking soda toothpaste had reduced (P≤ 0.0005) MGI, GBI, and PI by 6.2%, 28.4%, and 6.8%, respectively, compared to the 20% baking soda toothpaste. This clinical study showed that brushing with fluoride toothpastes containing baking soda at 35% and 20% reduces plaque, gingival inflammation and bleeding more effectively than regular fluoride toothpaste. Further, it showed that 35% baking soda toothpaste was more effective in reducing these parameters than 20% baking soda toothpaste. (Am J Dent 2020;33:265-272).

 

 

 

 

 

Mail: Dr. A. Ghassemi, 469 North Harrison Street, Princeton, NJ 08543, USA. E-mail: annahita.ghassemi@churchdwight.com

 

 

                                                                                                                                               Research Article

Glass-ionomer cement modifies the gene expression of Streptococcus mutansproviding a lower virulent biofilm

 

Igor Alves da Silva, dds, ms,  Isaac Jordão de Souza Araújo, dds, ms,  Rafael Nóbrega Stipp, dds, ms, phd &  Regina Maria Puppin Rontani, dds, ms,phd

 

Abstract: Purpose: To evaluate the effect of glass-ionomer cement (GIC) on gene expression (gtfC, gtfD, covR, and vicR) of Streptococcus mutans (S. mutans) biofilms at 2, 4 and 24 hours. Methods: Six groups were tested according to the materials and time observation, as follows: ceramic (IPS Empress Esthetic), as the control group, and GIC (Ketac Molar Easymix); and time points of S. mutans biofilm formation (2, 4, and 24 hours). Round-shaped samples (10 × 2 mm) of each material were prepared according to the manufacturers’ specifications. GIC discs were handled in a laminar flow hood under aseptic conditions and stored at 100% relative humidity at 37°C for 24 hours to complete setting reaction. The samples were placed in a 24-well plate and immersed in 1.5 ml BHI + 1% sucrose with an inoculum of S. mutans UA159 to allow biofilm growth during 2, 4, and 24 hours. Next, the samples were removed, vortexed and centrifuged to collect cell pellets (n=5) for each material and time point. Pellets were stored at -80°C. Then, RNA was purified using the RNeasy Mini Kit protocol. The RNA was converted in cDNA using iScript cDNA Synthesis according to the manufacturer's recommendations. Analysis of gtfC, gtfD, vicR, and covR expressions was performed using Step One Real-Time qPCR device with specific primers for each gene and the analysis normalized by 16S reference gene expression. Data from gtfC, gtfD, and vicR were analyzed by t-test to compare between groups while Mann-Whitney was used to analyze covR expression (α= 0.05). Results: No significant differences at 2 and 4 hours between materials for all analyzed genes were noted. However, in the 24-hour period, a significant decrease in gtfC and vicR expressions were observed, while covR expression increased when GIC was compared to ceramic. (Am J Dent 2020;33:273-276).

 

 

 

 

 

Mail: Dr. Regina Maria Puppin-Rontani, Department of Pediatric Dentistry, Piracicaba Dental School. Av. Limeira, 901 – Areião, Piracicaba 13414-903, Brazil.  E-mail:  rmpuppin@unicamp.br

 

 

 

                                                                                                                                             Research Article

Effects of Na-DNA mouthwash solutions on oral soft tissues. A bioreactor-based reconstituted human oral epithelium model

 

Andrei C. Ionescu, dds, phd, Elena Vezzoli, ms, phd, Vincenzo Conte, ms, Patrizia Procacci, ms, Franklin Garcia-Godoy, dds, ms, phd, phd  &  Eugenio Brambilla, dds

 

Abstract: Purpose: To investigate whether the addition of sodium-DNA (Na-DNA) to chlorhexidine (CHX)-containing mouthwash influenced morphology and viability of a reconstituted human oral epithelium (ROE), and protects ROE against oxidative stress. Methods: Multi-layered 0.5 cm² ROE specimens were positioned inside a continuous flow bioreactor and grown air-lifted for 24 hours. They were treated with phosphate-buffered saline (PBS)  (n= 16) or 1 vol% H₂O₂ for 1 minute (n= 16). Then, they were treated for 5 (n= 8) or 30 minutes (n= 8) with the experimental mouthwash solutions containing: 0.2 wt% CHX, 0.2 wt% CHX + 0.2 wt% Na-DNA, 0.2 wt% Na-DNA, PBS. After 60 minutes washout specimens were subjected to tetrazolium-based viability assay (MTT) confocal laser-scanning microscopy (CLSM), and histological evaluation using optical microscopy and transmission electron microscopy (TEM). Results: ROE treated with Na-DNA for 30 minutes revealed significantly higher viability than PBS, and CHX + Na-DNA showed higher viability after 30-minute treatment than after 5 minutes, suggesting a significant protective activity of Na-DNA. Moreover, the protective effect of Na-DNA on cell viability was higher after the induction of oxidative stress. After treatment with CHX, CLSM revealed cell stress, leading to cell death in the outer layer. On the contrary, specimens treated with Na-DNA showed a much lower number of dead cells compared to PBS, both in the absence or presence of oxidative stress. Histological examination showed that the protective action of Na-DNA formulations reached more in-depth into the epithelium exposed to oxidative stress, due to intercellular spaces opening in the outer epithelium layers, giving way to Na-DNA to the inner parts of the epithelium. It can be concluded that Na-DNA had a topical protective activity when applied for 30 minutes unless the epithelium barrier is damaged, allowing it to act more in-depth. (Am J Dent 2020;33:277-284).

 

 

 

 

Mail: Prof. Eugenio Brambilla, Department of Biomedical, Surgical and Dental Sciences, Università degli Studi di Milano, Via Pascal, 36, 20133 Milan, Italy. E-mail: eugenio.brambilla@unimi.it

 

 

                                                                                                                                       Review Article

 

Use of povidone as a mouthrinse to decrease the viral load of Covid-19 before dental care: Review of the literature

 

Julieta Mendez, dds, msc  &  Ulises Villasanti, dds, msc

 

Abstract: Purpose: To review the literature on the use of povidone prior to dental treatment for the reduction of  viruses  in the oral cavity. Methods: PubMed and Cochrane databases published from January 2019 to June 2020 were reviewed. Studies that met the inclusion criteria were reviewed by two authors separately. A qualitative review of the data was performed. Results: There were no randomized controlled trials or clinical observation studies on the curative or preventive effect of povidone against COVID-19, but there are clinical trial protocols  in the recruitment process. The use of a dose between 0.2% to 2.5% is recommended four times a day for 15-30 seconds. (Am J Dent 2020;33:248-250).

 

 

Mail: Dr. Julieta Méndez, Instituto Regional de Investigación en Salud, Universidad Nacional de Caaguazú, Coronel Oviedo, Paraguay. E-mail: julieta_mendez92@hotmail.com