Effects of combined exogenous dextranase and sodium fluoride on Streptococcus mutans 25175 monospecies biofilms

Ying-Ming  Yang, md,  Dan  Jiang, md,  Yuan-Xin  Qiu, md,  Rong  Fan, md,  Ru  Zhang, dds, phd,  Mei-Zhi  Ning, md, Mei-Ying  Shao, md,  Chao-Liang  Zhang, md,  Xiao  Hong, dds, phd   &   Tao  Hu, dds, phd

Abstract: Purpose: To investigate the effects of exogenous dextranase and sodium fluoride on a S. mutans monospecies biofilm. Methods: S. mutans 25175 was grown in tryptone soya broth medium, and biofilm was formed on glass slides with 1.0% sucrose. Exogenous dextranase and sodium fluoride were added alone or together. The biofilm morphology was analyzed by confocal laser scanning microscopy. The effects of the drug on the adhesion and exopolysaccharide production by the biofilms were evaluated by scintillation counting and the anthrone method, respectively. Results: In this study, we found that the structure of initial biofilm and mature biofilm were partly altered by dextranase and high concentrations of sodium fluoride separately. However, dextranase combined with a low concentration of sodium fluoride could clearly destroy the typical tree-like structure of the biofilm, and led to less bacterial adhesion than when the dextranase or fluoride were used alone (P< 0.05). The amounts of soluble and insoluble exopolysaccharide were significantly reduced by combining dextranase with a low concentration of sodium fluoride, much more than when they were used alone (P< 0.05). These data indicate that dextranase and a low concentration of sodium fluoride may have synergistic effects against S. mutans biofilm and suggest the application of a low concentration of sodium fluoride in anticaries treatment. (Am J Dent 2013;26:239-243).

Mail: Dr. Tao Hu, State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, 14 South Renmin Road, Section 3, Chengdu, Sichuan 610041, PR China. E-mail: hutao@scu.edu.cn

Site specific properties of carious dentin matrices biomodified with collagen cross-linkers

Ana K. Bedran-Russo, dds, ms, phd,  Sachin  Karol, ms,  David  H.  Pashley, dds, phd  &  Grace  Viana, ms

Abstract: Purpose: To assess in non-cavitated carious teeth the mechanical properties of dentin matrix by measuring its reduced modulus of elasticity and the effect of dentin biomodification strategies on three dentin matrix zones: caries-affected, apparently normal dentin below caries-affected zone and sound dentin far from carious site. Methods: Nano-indentations were performed on dentin matrices of carious molars before and after surface modification using known cross-linking agents (glutaraldehyde, proanthocyanidins from grape seed extract and carbodiimide). Results: Statistically significant differences were observed between dentin zones of demineralized dentin prior to surface biomodification (P< 0.05). Following surface modification, there were no statistically significant differences between dentin zones (P< 0.05). An average increase of 30-fold, 2-fold and 2.2-fold of the reduced modulus of elasticity was observed following treatments of the three dentin zones with proanthocyanidin, carbodiimide and glutaraldehyde, respectively. (Am J Dent 2013;26:244-248).

                Mail: Dr. Ana K. Bedran-Russo, Department of Restorative Dentistry, College of Dentistry, Room #551, 801 South Paulina Street, Chicago, IL 60612 USA.  E-mail: bedran@uic.edu

Oral biofilms, oral and periodontal infections, and systemic disease

Abhiram Maddi, bds, msc, phd  &  Frank A. Scannapieco, dmd, phd

Abstract: Purpose: Oral biofilms harbor several hundreds of species of bacteria as well as spirochetes, protozoa, fungi and viruses. The composition of the oral biofilm varies from health to disease. It is the source of microorganisms that cause dental and periodontal infections. Oral infections and periodontal disease have been implicated in the etiopathogenesis of several important chronic systemic diseases. (Am J Dent 2013;26:249-254).

Mail: Dr. Frank A Scannapieco, Professor and Chair, Department of Oral Biology, 116 & 109 Foster Hall, Buffalo, NY 14214, USA. E-mail:  fas1@buffalo.edu

Flexural resistance of Cerec CAD/CAM system ceramic blocks. Part 1: Chairside materials

Alessandro Vichi, dds, phd, Maurizio Sedda, dds, Francesco Del Siena, dds, Chris Louca, bsc, bds, phd &  Marco Ferrari, md, dds, phd

Abstract: Purpose: This study tested the materials available on the market for Cerec CAD/CAM, comparing the mean flexural strength in an ISO standardized set-up, since the ISO standard for testing such materials was issued later than the marketing of the materials tested. Methods: Following the recent Standard ISO 6872:2008, eight types of ceramic blocks were tested: Paradigm C, IPS Empress CAD LT, IPS Empress CAD Multi, Cerec Blocs, Cerec Blocs PC, Triluxe, Triluxe Forte, Mark II. Specimens were cut out from ceramic blocks, finished, polished, and tested in a three-point bending test apparatus until failure. Flexural strength, Weibull characteristic strength, and Weibull modulus, were calculated. Results: The results obtained from the materials for flexural strength were IPS Empress CAD (125.10±13.05), Cerec Blocs (112.68±7.97), Paradigm C (109.14±10.10), Cerec Blocs PC (105.40±5.39), Triluxe Forte (105.06±4.93), Mark II (102.77±3.60), Triluxe (101.95±7.28) and IPS Empress CAD Multi (100.86±15.82). All the tested materials had a flexural strength greater than 100 MPa, thereby satisfying the requirements of the ISO standard for the clinical indications of the materials tested. In all tested materials the Weibull characteristic strength was greater than 100 MPa. (Am J Dent 2013;26:255-259).

Mail: Dr. Alessandro Vichi, Via Derna 4, 58100 Grosseto, Italy. E-mail: alessandrovichi1@gmail.com

Influence of curing light power and energy on shrinkage force and acoustic emission characteristics of a dental composite restoration

Sang-Jae Yoon, meng,  Ja-Uk Gu, meng, Nak-Sam Choi, phd  &  Kazuo Arakawa, phd

Abstract: Purpose: To evaluate the density effects of light power and energy on the volumetric polymerization shrinkage and acoustic emission (AE) characteristics of a dental resin composite in the cavities of human teeth. Methods: Two experiments were performed at different power levels (1,000 and 4,000 mW/cm²) using a light curing unit: (1) cylindrical cavities with diameters of 4 mm and depths of 2 mm were constructed using two symmetric steel molds. The cavities were filled with resin, and the shrinkage force during polymerization was measured using a load cell attached to the mold. Polymerization shrinkage forces were measured under four conditions (1,000 mW/cm² × 10 seconds, 1,000 mW/cm² × 20 seconds, 4,000 mW/cm² × 3 seconds, and 4,000 mW/cm² × 5 seconds); (2) tooth specimens with cavity diameters of 6 mm and depths of 2 mm were made from human molars. AE signals during polymerization shrinkage were monitored in real time for 10 minutes after irradiation and two AE factors (amplitude for defect size and hit number for defect number) were assessed in the examination of defects. Two levels of light energy (20 J/cm² = 1,000 mW/cm² × 20 seconds and 12 J/cm² = 4,000 mW/cm² × 3 seconds) were used. Results: Shrinkage occurred more quickly at 4,000 mW/cm² than at 1,000 mW/cm² during the initial phase. The shrinkage force became almost the same for equivalent light energy as time increased. Higher light energy (20 J/cm²) under low-power conditions (1,000 mW/cm²) caused larger cumulative numbers of AE hits than did lower light energy (12 J/cm²) under high-power conditions (4,000 mW/cm²). At 4,000 mW/cm² and 12 J/cm² (i.e., high power, low energy), the average amplitude of the AE signals was larger than at 1,000 mW/cm² and 20 J/cm² (low power, high energy). (Am J Dent 2013;26:260-264).

Mail: Mr. Sang-Jae Yoon, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga-koen 6-1, kasuga, Fukuoka 816-8580, Japan. E-mail: ar-s-yoon@mms.kyushu-u.ac.jp

Mechanical properties and color stability of provisional restoration resins

Hidehiko Watanabe, dds, ms,  Eunghwan Kim, dds, ms, Noah L. Piskorski, dds,  Jennifer Sarsland, dds, David A. Covey, dds, ms, ms  &  William W. Johnson, dds, ms

Abstract: Purpose: To evaluate the mechanical strength and color stability of provisional restoration materials. Methods: For mechanical testing, four groups [Trim (PEMA), Alike (PMMA), Versatemp (bis-acrylic resin composite, BARC) and Perfectemp II (bis-acrylic fluoride enriched resin, BAFC)] of resin disks were prepared for fracture toughness and shear punch strength testing, respectively. Five samples were fabricated for each group; therefore, a total of 20 resin disks for each testing method was prepared. The load at fracture and shear punch values of each specimen were recorded after 24-hour storage in distilled water. The stress intensity factors (K_Ic) were calculated by the formula reported by Atkinson et al. For shear strength, the following formula was used: Shear strength = Force (N)/section thickness (mm) × punch circumference (mm). Values of each group in both tests were analyzed using one-way-ANOVA and Tukey multiple comparison test. For color stability testing, provisional resin disk specimens of the above mentioned materials were fabricated. Five samples were prepared for each subgroup (with and without a surface coating agent - Permaseal) and three different solutions (distilled water, red wine and curry); a total of 120 disk specimens were fabricated. Color values of each group were measured using a spectrophotometer after 24 hours and 2 weeks of aging in the aforementioned solutions. The color differences (∆E*ab) between before and after aging were calculated by CIE Lab color-difference formula. The interaction of ∆E*ab values were analyzed by two-way analysis of variance followed by Newman-Keuls Multiple comparison test. Results: The highest fracture toughness value [(MPa (m)^1/2)] was obtained by PMMA (0.89) followed by BARC (0.67), PEMA (0.54) and BAFC (0.42). Significant differences were observed among all test groups (P< 0.05). The highest shear punch strength (MPa) was obtained by BARC (160), followed by PMMA (141) and PEMA (132). The lowest value was obtained by BAFC (106). BARC showed a significantly higher mean value than the other groups (P< 0.05). PEMA and PMMA demonstrated better color stability than the two bis-acrylic resin composites. Wine and curry showed higher stainability than water, recording higher ∆E*ab values than the clinically perceptible difference level of ∆E*ab 3.3. The surface coating agent groups demonstrated more staining than the non-coated groups. All groups, except for BARC, demonstrated significant differences dependent upon surface coating and solutions (P< 0.05). (Am J Dent 2013;26:265-270).

Mail: Dr. Hidehiko Watanabe, Department of Adult Restorative Dentistry, University of Nebraska Medical Center College of Dentistry, 40th and Holdrege Streets, Lincoln, NE 68583, USA. E-mail: hwatanabe@unmc.edu

Microleakage of Class II restorations and microtensile bond strength to dentin of low-shrinkage composites

Jelena  Juloski, dds,  Michele  Carrabba, dds,  Juan  Manuel  Aragoneses, md, dds, phd,

Leopoldo Forner, md, dds, phd, Alessandro Vichi, dds, msc, phd  &  Marco Ferrari, md, dds, phd

Abstract: Purpose: To evaluate the microleakage of Class II cavities restored with experimental low-shrinking resin composites proposed for bulk filling and to measure their microtensile bond strength (μTBS) to dentin and compare to those of previously marketed low-shrinkage composites. Methods: Class II cavities (7 mm occluso-gingival height, 2 mm mesio-distal depth of the box, 4 mm occlusal depth, 4 mm bucco-lingual width) were prepared in 50 molars and randomly divided into five groups (n=10), according to the material: SureFil SDR flow (SDR), Filtek Silorane (FS) and experimental materials (G-ænial Flo bulk fill, GF; G-ænial Universal Flo bulk fill, GUF; GC Kalore bulk fill, GK). Microleakage was separately assessed at enamel and dentin margins by scoring the depth of silver-nitrate penetration. Twenty teeth divided into five groups (n= 4) were selected for μTBS testing. The same materials as for microleakage assessment were placed in bulk to mid-coronal dentin. Microtensile beams were loaded in tension, and μTBS at failure was calculated in MPa. Microleakage and μTBS data were analyzed by ANOVA on ranks, followed Dunn’s post hoc test (P< 0.05). Results: Microleakage was not observed at the enamel interface in any of the groups. At the dentin interface, SDR recorded significantly higher microleakage than the other materials. μTBS of GF, GUF and GK did not differ among each other (33±12 MPa, 31±11 MPa, 30±9 MPa, respectively), while SDR (63±17 MPa) and FS (55±17MPa) achieved significantly higher μTBS values. No direct association between the sealing properties and the bond strength values was observed. (Am J Dent 2013;26:271-277).

Mail: Dr. Jelena Juloski, Department of Dental Materials and Fixed Prosthodontics of Siena, Policlinico Le Scotte, Viale Bracci, 53100 Siena, Italy. E-mail: jelenajuloski@gmail.com

Erosive potentials of brewed teas

Julie L. Hendricks, dds,  Teresa A. Marshall, rd/ld, phd,  Jeffrey D. Harless, ms,   Mary M. Hogan, ba, Fang Qian, phd   &   James S. Wefel, phd

Abstract: Purpose: To measure the pH, titratable acidity, fluoride concentration and erosive potential of brewed teas. Methods: Bag teas were purchased to represent black, green, citrus, fruity, and floral tea flavors from Tulsi, Bigelow, HyVee, Tazo, and Yogi brands and brewed (1 bag/240 ml) in boiling water for 3 minutes. The pH, titratable acidity, and fluoride concentrations were measured. Following these measurements, a representative tea from each flavor was selected for investigation of erosion potential. Six extracted human molars were randomly assigned to each tea. Teeth were painted with fingernail polish to expose a 1 × 4 mm window and then soaked in tea for a total of 25 hours with teas refreshed every 5 hours. Teeth were then sectioned using a microtome and photographed using a polarized light microscope. Lesion depths (i.e., eroded surfaces) were measured using Image Pro Plus software. Differences in physiochemical properties and lesion depths between beverages were investigated using one-way ANOVA with post-hoc Tukey’s HSD test. Relationships among lesion depths and physiochemical properties were evaluated using the Pearson correlation test. Results: pH, titratable acidity and fluoride concentrations differed between tea flavors (P< 0.05) and between brands (P< 0.05). Lesion depths produced by the citrus tea (83.1 ± 10.3µm) were greater than those produced by the fruity tea (56.5 ± 6.1 µm); both teas produced greater depths than black (30.1 ± 7.4 µm), floral (25.0 ± 3.2 µm) or green (22.3 ± 6.3 µm) teas (P< 0.05). pH (r= -0.96; P= 0.009) was inversely and titratable acidity (r= 0.97; P= 0.006) was positively associated with lesion depths. (Am J Dent 2013;26:278-282).

Mail: Dr. Teresa A. Marshall,  Department of Preventive & Community Dentistry, College of Dentistry, University of Iowa, N335 Dental Science Building,  Iowa City, IA 52340, USA. E-mail: teresa-marshall@uiowa.edu

Low toxic effects of a whitening strip to cultured pulp cells

Diana Gabriela Soares, dds, ms, Elaine Cristina Voltoline Pontes, dds, ms, Ana Paula Dias Ribeiro, dds, ms, phd, Fernanda GonÇalves Basso, dds, ms, Josimeri Hebling, dds, ms, phd  &  Carlos Alberto De Souza Costa, dds, ms, phd

Abstract: Purpose: To assess the trans-enamel and trans-dentin toxicity of a 10% hydrogen peroxide (HP) whitening strip to odontoblast-like cells (MDPC-23). Methods: Enamel surfaces of enamel/dentin discs adapted to artificial pulp chambers were subjected to two 30-minute whitening strip applications to obtain indirect extracts (DMEM + bleaching components that diffused across enamel and dentin). The extracts were applied for 1 hour to the cells for 1 or 5 days. A bleaching gel with 35% HP was used as the positive control. Cell viability (MTT assay) and morphology (SEM) as well as the quantity of HP in the extracts were assessed. Results: Discrete cell viability reduction (21.9%) associated with slight alterations in cell morphology occurred after application of the extracts for 5 days to the MDPC-23 cells (Tukey’s test; P< 0.05). Lower enamel/dentin diffusion of HP was observed after the use of the whitening strip compared with the bleaching gel (Mann-Whitney; P< 0.05). (Am J Dent 2013;26:283-285).

Mail: Prof. Carlos Alberto de Souza Costa, Department of Physiology and Pathology, Univ. Estadual Paulista – UNESP, Araraquara School of Dentistry, Humaitá Street, 1680, Araraquara, CEP 14801-903, Brazil. E-mail: casouzac@foar.unesp.br

Ability of Barrier Coat S-PRG coating to arrest artificial enamel lesions in primary teeth

Yumiko  Hosoya, dds, phd,  Susumu  Ando, dds, phd,  Hideji  Otani, dds,  Tetsuhiro  Yukinari, dds,

Masashi  Miyazaki, dds, Phd  &  Franklin  GarcÍa-Godoy, dds, ms, phd, phd

Abstract: Purpose: To evaluate the effects of a surface pre-reacted glass-ionomer (S-PRG) filled coating material to arrest artificial enamel lesions in primary teeth. Methods: Buccal and lingual enamel was demineralized in 0.1 M lactic acid buffer solution (pH 4.75) for 5 days and then divided in the PRG-applied and non-PRG areas. Proximal surfaces were used as a control area without demineralization and coating application. Teeth were divided into three groups (n= 4) according to the 1-week immersion in different solutions: Group 1 (distilled water), Group 2 (demineralizing solution) and Group 3 (artificial saliva). Hardness and Young’s modulus by nano-indentation test, and elemental contents and ultrastructure by SEM/EDX analysis were obtained. Data were statistically analyzed using ANOVA and Fisher’s PLSD at α= 0.05. Results: Only for the non-PRG area in Group 1, the hardness and Young’s modulus of the demineralized surface enamel were significantly lower than those of the enamel 30-60 µm beneath the surface. Demineralized enamel of non-PRG and PRG-applied areas showed similar SEM views. Only for the non-PRG area in Group 2 and control area in Group 3, the Ca/P of the surface enamel was significantly higher than that of the enamel 5- 10 µm beneath the surface. There was no significant difference of the Ca/P among the measuring points from the surface to 10 µm depth of enamel for the PRG applied area in Group 2. (Am J Dent 2013;26:286-290).

Mail: Dr. Yumiko Hosoya, Department of Pediatric Dentistry, Unit of Translational Medicine, Course of Medical and Dental Science, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1, Sakamoto, Nagasaki 852-8588, Japan. E-mail: hosoya@nagasaki-u.ac.jp

Remineralization efficacy of a toothpaste containing 8% arginine and

calcium carbonate on enamel surface

Yajing  Huang, mds, Yanxia  Duan, mds, Yingzi  Qian, mds, Rui  Huang, mds,

 Zhengyan  Yang, mds, Yueheng  Li, mds  &  Zhi  Zhou, dds

Abstract: Purpose: To investigate the remineralization efficacy of different types of toothpastes on initial enamel lesions in vitro. Methods: Artificial initial lesions were created on 150 enamel discs from freshly extracted bovine incisors. These enamel discs were divided into five groups. The test treatment consisted of undiluted Colgate Sensitive Pro-Relief Toothpaste containing 8.0% arginine, calcium carbonate and 1,450 ppm fluoride that was applied on the enamel surface under a pH-cycling including 4 × 3-minute application daily for 12 days and soaked in remineralizing solution during the untreated periods. The two other test products were commercial products: Crest Cavity Protection Toothpaste, containing 0.11% fluoride and GC Tooth Mousse, a professional remineralizing treatment paste (the active ingredients: casein phosphopeptide – amorphous calcium phosphate, fluoride). NaF solution (0.14% fluoride) was used as the positive control, while double distilled water (ddH₂O) was used as the negative control. The remineralization of enamel discs was evaluated using Knoop hardness test, confocal laser scanning microscopy (CLSM) and polarized light microscopy (PLM), and the caries lesion depth was quantified using an image analyzer. The data were analyzed by ANOVA. Results: All test products showed a recovery of the Knoop Hardness Number (KHN) after remineralization cycling treatment. The recovery of enamel KHN for Colgate Sensitive Pro-Relief, GC Mousse, Crest toothpaste and NaF groups were 44.53±6.72%, 35.00±7.83%, 24.56±5.95% and 42.51±6.74% respectively, while the recovery of negative control group was 18.99±4.98%. PLM results indicated the lesion depth recovery of 49.63±8.06%, 35.08±2.19%, 22.60±7.30% and 53.20±1.48% respectively, which were also significantly greater than that of the negative group (20.51±4.80%). CLSM analysis showed a reduction of average area, and total and average dye fluorescence of the lesions after treatment. The Colgate Sensitive Pro-Relief group presented significantly greater remineralization than the other toothpaste groups, while the Crest toothpaste group showed the lowest remineralization ability. (Am J Dent 2013;26:291-297).

Mail: Dr. Zhi Zhou, The Affiliated Hospital of Stomatology, Chongqing Medical University, No. 426, Songshibei Road, Yubei District, Chongqing, 401147, China. E-mail: Zhouzhi_050918@hotmail.com

Tooth bleaching induces changes in the vascular permeability of rat incisor pulps

Vanessa Guarino Ferreira, dds, Cleber Keiti Nabeshima, dds, mdsc, MÁrcia Martins Marques, dds, mdsc, phd, Adriana Fraga Costa Samos Paris, bsc, mdsc, Marco AntÔnio Gioso, dds, dvm, mdsc, phd, Rodrigo Sant’anna Aguiar dos Reis, dds, mdsc, phd  &  Manoel Eduardo de Lima Machado, dds, mdsc, phd

Abstract: Purpose: To evaluate the inflammatory response in dental pulps of rat incisors subjected to tooth bleaching protocols with different HP concentrations and application times. Methods: 42 incisors from Wistar rats were submitted to tooth bleaching using concentrations of 25% or 35% HP for treatment times of 15, 30 or 45 minutes. Four non-bleached teeth were used as controls. The animals received an intravenous injection of India ink immediately after the bleaching procedure and were sacrificed 1 hour later. Six bleached teeth from each group and three controls were made transparent, and one sample from each group was processed for histological analysis. The data were statistically analyzed using Kruskal Wallis and Dunn’s tests (P≤ 0.05). Results: The amount of dental pulp ink content was significantly higher in the samples that were bleached with 35% HP for 30 minutes and with both HP concentrations (25 and 35%) for 45 minutes than in the controls. For the samples bleached with the same HP concentration, the ink content was higher in samples that were bleached for 45 minutes. These results indicate that HP tooth bleaching can induce an increase in vascular permeability in rat incisors. Importantly, this increase is more dependent on the length of the bleaching procedure than on the concentration of the bleaching agent. (Am J Dent 2013;26:298-300).

Mail: Dr. Cleber K. Nabeshima, Av. Prof. Lineu Prestes, 2227, Cidade Universitária, 05508-000, São Paulo, SP, Brazil. E-mail: cleberkn@hotmail.com