Changing concepts in caries microbiology
Roy R. Russell, ba, phd, fdsrcs
Abstract: Concepts and beliefs about the cause of dental caries have evolved over many centuries, with the involvement of microorganisms being recognized since the late 1800s. A main thrust of enquiry since then has been to tackle the question of the relative importance of different bacteria in the disease and this article will consider how technical advances in our ability to identify, cultivate and count different species has influenced our understanding. Over the last decade, molecular biological approaches have had a major impact on views of the relative contribution of particular species of plaque bacteria to the caries process. At a more detailed level, molecular genetic studies of species such as Streptococcus mutans have given new insights into the way in which particular genes and the functions that they encode may affect virulence. (Am J Dent 2009;22:304-310).
*: Prof. Roy R.B. Russell, Oral Biology, School of Dental Sciences, Newcastle University, Newcastle upon Tyne, NE2 4BW United Kingdom. E-*: email@example.com
Surface roughness of enamel and four resin composites
Ana Carolina Botta, dds, ms, phd, Sillas Duarte Jr, dds, ms, phd, Pedro Iris Paulin Filho, dds, ms, phd, Simoni Maria Gheno, dds, ms, phd & John M. Powers, phd
Abstract: Purpose: To assess surface roughness of resin composites submitted to different polishing techniques compared to intact human enamel. Methods: Nanofilled (Filtek Supreme XT), microhybrid (Point 4), hybrid (Tetric Ceram), and microfilled (Durafill VS) resin composites were selected. Four polishing techniques were tested (T0: Mylar matrix – control; T1: aluminum oxide discs; T2: felt + diamond paste; T3: aluminum oxide discs + felt + diamond paste) with each resin composite. The specimens were assigned to 16 experimental groups and one control group (n=4). Flat buccal surfaces of four human maxillary central incisors were used for the analysis of enamel roughness and served as control. The mean roughness was evaluated under atomic force microscopy in the contact mode. The obtained data were submitted to Student’s t-test, ANOVA, and Tukey’s Test, at 0.05 level of significance. Results: The roughness of enamel was 46.6 ± 10.7 nm. The smoothest surface was obtained for the Mylar matrix with nanofiller (23.6 ± 3.0 nm), microhybrid (12.8 ± 1.4 nm), or hybrid resin (15.2 ± 1.9 nm). Microfilled resin showed the lowest roughness with aluminum oxide discs (43.0 ± 5.2 nm). Diamond paste increased the roughness of composites, whereas aluminum oxide discs yielded the smoothest surfaces. (Am J Dent 2009;22:252-254).
*: Dr. Sillas Duarte, Jr., Department of Comprehensive Care, Case Western Reserve University School of Dental Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-4905. E-*: firstname.lastname@example.org
Optimization of the marginal gap of all-ceramic restorations
and gold crowns by ultrasound activated, suspended Al2O3 powder
Sabine S. Linsen, dr med dent, Daniela Wirtz, dr med dent, Carola Fischer, dr med dent & Bernd Koeck, prof dr med dent
Abstract: Purpose: To evaluate if the use of ultrasound activated Al2O3 powder improved the fit especially of all-ceramic restorations. Methods: 21 extracted teeth were prepared for 14 all-ceramic IPS Empress2 (IPS Empress2) restorations (four crowns, four partial crowns, two inlays, four veneers) and seven gold crowns (Degudent H). Each restoration was adjusted with a suspension of Al2O3 of 25 µm and 50 µm grit, respectively. The effect of the fitting adjustments was recorded with the silicone disclosing medium technique and measured at 11 points under the microscope in an interval of 0.4 mm. Results: A significant (P< 0.001) improvement of the tight fit of all restorations by means of ultrasound activated Al2O3 powder was noticed. The approach of the restoration towards the prepared stump by the sonoerosive fitting correction was in the mean 201 ± 60 µm in Empress2 restorations and 87 ± 24 µm in gold crowns within a period of 10 minutes. SEM observation of the Empress2 specimens showed no microdamage after ultrasound machining. (Am J Dent 2009;22:255-258).
*: Dr. Sabine Linsen, Department of Prosthodontics, University of Bonn, Welschnonnenstr. 17, 53111 Bonn, Germany. E-*: email@example.com
Micro-shear bond strength of current one-step adhesives
to cementum and dentin
Hiroshi Okada, dds, Alireza Sadr, dds, phd, Yasushi Shimada, dds, phd & Junji Tagami, dds, phd
Abstract: Purpose: To investigate the bonding performance of current one-step adhesives to human cementum and compare the results with those of two-step adhesives. Methods: Four commercially available adhesives were investigated: two one-step adhesives (Clearfil Tri-S Bond and G-Bond), and two two-step adhesives: a self-etch adhesive (Clearfil SE Bond) and a total-etch wet bonding adhesive (Adper Single Bond). The cementum and dentin regions were chosen from the mesial surface of extracted human molars and bonded with each adhesive. A micro-shear bond test was employed to evaluate the bond strength in this study. Morphological micrographs of cementum and dentin after etching, as well as bonded interfaces were obtained using scanning electron microscopy. Results: The shear bond test results showed significantly lower bonding of all adhesives when they were applied to cementum (P< 0.05). The mean bond strength values in MPa obtained from dentin and cementum were 33.7 and 26.7 for Clearfil Tri-S Bond, 28.9 and 22.4 for G-Bond, 42.9 and 35.2 for Clearfil SE Bond and 38.6 and 32.5 for Adper Single Bond, respectively. One-step adhesives showed significantly lower bond strengths than two-step adhesives to both cementum and dentin (P< 0.05). (Am J Dent 2009;22:259-263).
*: Dr. Hiroshi Okada, Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan. E-*: firstname.lastname@example.org
Influence of mechanical and chemical degradation on surface gloss
of resin composite materials
Stefano Ardu, dmd, Vedrana Braut, dmd, Ivone Uhac, dmd, phd, Nacer Benbachir, dmd,
Albert J. Feilzer, dmd, phd & Ivo Krejci, dmd, phd
Abstract: Purpose: To determine the changes in surface gloss of different
composite materials after simulation of mechanical and chemical aging
mechanisms. Methods: 36 specimens
were fabricated for each material and polished with 120-, 220-, 500-, 1200-, 2400-
and 4000- grit SiC abrasive paper, respectively. Gloss measurements were made
with a glossmeter (Novo-Curve) prior to testing procedures. Specimens of each
material were randomly divided into three groups. Group 1 was conditioned for 7
days at 37°C in 75% ethanol aqueous solution. Group 2 was immersed in fluoride
gel (Elmex Gelée) at
*: Dr. Stefano Ardu, Division of Cariology & Endodontology, Dental School, University of Geneva, Geneva, Switzerland. E-*: email@example.com
Optimal use of silver nitrate and marginal leakage at the sealant-enamel interface using micro-CT
Xi Chen, dds, Vincent Cuijpers, bsc, MingWen Fan, dds, phd & Jo E. Frencken, dds, msc, phd
Abstract: Purpose: To investigate the optimal silver nitrate concentration and tooth immersion period for assessing marginal leakage at the sealant-enamel interface, using micro-CT. Methods: Two experiments were conducted, using eight teeth sealed with a resin composite without etching, in dried but not desiccated, pits and fissures. Five teeth were immersed in 50% silver nitrate for 0, 1, 2, 3, and 4 hours and scanned, using micro-CT, and two evaluators using a newly developed index assessed marginal leakage at the sealant-enamel interface (Experiment A). Experiment B was carried out in the same way as Experiment A, with the difference that teeth were immersed in 50% and 60% silver nitrate for 2 and 3 hours. Reliability of scores was estimated, using weighted kappa coefficient. ANOVA and t-test were applied to test for period and concentration effects. Results: Reliability of collected data was substantial. A statistically significant difference was observed between 50% silver nitrate penetration scores at 0-1 and 2-4 hours of immersion (P< 0.0001) but not between 50% silver nitrate penetration scores at 2-, 3-, and 4-hours of immersion (P> 0.05) (experiment A). Analysis in experiment B showed a period effect (P= 0.03) but no concentration (P= 0.07) and interaction effect (P= 0.64). Combining all data from 50% silver nitrate immersion, analysis showed no statistically significant difference in penetration scores between 2, 3 and 4 hours of immersion (P= 0.33). The newly developed index showed substantial reliability. (Am J Dent 2009;22:269-272).
*: Prof. M. Fan, Key Laboratory for Oral Biomedical Engineering, School and Hospital of Stomatology, Wuhan University, 237 LuoYu Road, Wuhan 430079, China. E-*: firstname.lastname@example.org; email@example.com
Effect of dual-cured adhesive resin cements on cell proliferation
of pulp and human fibroblasts
Elisabeth A. Koulaouzidou, dds, phd, Maria Helvatjoglou-Antoniades, dds, phd, Georgios Palaghias, dds, phd & Dimitrios Antoniades, dds, phd
Abstract: Purpose: To comparatively evaluate the effects of three dual activated adhesive resin cements on cell proliferation of rat pulp cells (RPC-C2A) and human lung fibroblasts (MRC5). Methods: The cements tested were RelyX ARC, RelyX Unicem and Panavia F. The cements were prepared according to manufacturers’ instructions and placed in contact with the cells. Cell survival was estimated by the sulphorhodamine-B staining assay after 24 and 72 hours and cellular changes in morphology were examined under microscope. Results: All resin cements decreased cell proliferation. The decrease observed was material- and time-dependent. Panavia F was found more potent in decreasing cell proliferation. Differences were found in the effect on cell proliferation among the materials tested, that might be associated to their clinical behavior. (Am J Dent 2009;22:273-277).
*: Dr. Elisabeth A. Koulaouzidou, 1 Xenofontos Street, GR 55132 Kalamaria, Thessaloniki, Greece. E-*: firstname.lastname@example.org
Effect of a calcium glycerophosphate fluoride dentifrice formulation
on enamel demineralization in situ
Livia Maria Andaló Tenuta, dds, phd, Maximiliano Sergio Cenci, dds, phd, Altair A. Del Bel Cury, dds, phd, Tatiana Pereira-Cenci, dds, phd, Cínthia Pereira Machado Tabchoury, pharmd, phd, Gisele Pedroso Moi, dds, msc & Jaime Aparecido Cury, dds, phd
Abstract: Purpose: To evaluate in situ the effect and mechanisms involved in the anticariogenic effect of a calcium glycerophosphate fluoride dentifrice. Methods: In a double-blind, crossover design, a non-F dentifrice (negative control), a F dentifrice and a F dentifrice containing 0.13% CaGP were compared regarding the inhibition of enamel demineralization. Both F dentifrices contained 1500 µg F/g (w/w) as sodium monofluorophosphate (MFP). Bovine enamel blocks were mounted in contact with a S. mutans test plaque, in palatal appliances worn by 10 volunteers. 30 minutes after treatment with the dentifrices, a sucrose rinse was performed and enamel demineralization was assessed after an additional 45 minutes. Results: No significant difference was observed among groups in the calcium and inorganic phosphate concentrations in the fluid phase of the test plaque 30 minutes after the dentifrice use (P> 0.05), but F concentration was significantly higher for both F dentifrices (P< 0.05). Also, the dentifrices did not differ regarding the pH before or 5 minutes after the sugar challenge (P> 0.05). A higher mineral loss was observed for the non-F dentifrice group (P< 0.05), but no significant difference was observed between the F dentifrices containing CaGP or not (P> 0.05). Using this in situ model, the findings suggested that CaGP at the concentration tested did not enhance the inhibition of enamel demineralization promoted by F dentifrice. (Am J Dent 2009;22:278-282).
*: Dr. Livia M.A. Tenuta, Piracicaba Dental School, University of Campinas – UNICAMP, P.O. Box 52, 13414-903 - Piracicaba, SP, Brazil. E-*: email@example.com
Novel method to measure enamel surface porosity
with hydrogen peroxide bleaching
Zhiyu Yang, ms, Mingjian Zou, Xinhui Lin, bs, Xiaoda Yang, phd, Na Li, phd & Kui Wang, bs
Abstract: Purpose: To establish methods to quantitate the physical surface change, not the chemical color bleaching change, of enamel occurring with hydrogen peroxide treatment in solution and commercially available plastic strips. Methods: Bovine enamel was polished to a sound, uniform, optical flat, white subsurface that was used as the initial substrate for all substrate modification, treatment and instrumental measurement using digital photography-image analysis, SEM and profilometry. Sound enamel was treated with 10, 20 and 30% solutions of hydrogen peroxide. Plastic strips were used to treat both sound and acid modified enamel surfaces. Etched enamel, similar to a 10-second exposure to lemon juice, was treated with 0.5, 1, 3, 5, 10, and 15% hydrogen peroxide for 24-hour exposure at 37ºC to obtain a dose response curve to this modified enamel. Results: The digital photography-image analysis system and scanning electron microscopy (SEM) were effective in detecting enamel surface porosity and structure disruptive changes, respectively. Plastic strip treatment of both sound and etched enamel produced little surface change. Measurable surface change of etched enamel was detected with as low as 1% hydrogen peroxide in solution. The surface change with 15% hydrogen peroxide was statistically significant. Dye uptake as measured by image analysis indicated an increase in surface porosity that was more evident with the acid modified surface. SEM studies were consistent with this observation. (Am J Dent 2009;22:283-289).
*: Prof. Xiaoda Yang, School of Pharmaceutical Sciences, Health Science Center of Peking University, Beijing, 100083, China. E-*: firstname.lastname@example.org; email@example.com
Resin cement thickness in oval-shaped canals: Oval vs. circular fiber posts
in combination with different tips/drills for post space preparation
Ivanovic Coniglio, dds, msc, Franklin Garcia-Godoy, dds, ms, Elisa Magni, dds, msc,
Carlos Augusto Carvalho, dds, msc & Marco Ferrari, md, dds, phd
Abstract: Purpose: To evaluate the cement thickness around oval and circular posts luted in oval post spaces prepared with different drills/tips. Methods: Extracted premolars were endodontically treated and obturated, then randomly divided into three groups (n=5) according to the tips/drills used for post-space preparation and to the type of fiber post luted: medium grit oval tip + oval posts, fine grit oval tip + oval posts, Mtwo Post File drill + circular posts. The specimens were sectioned in horizontal slices; one slice per canal third was chosen for each post-space, resulting in three slices for each specimen. The distances between the canal wall and the post perimeter were measured on SEM images of each slice. Results: The fine grit tip + oval post group obtained statistically significant lower cement thicknesses than the other groups (P< 0.05), in particular in the apical third. The MtwoPF + circular post group showed the highest cement thickness, comparable to that of the medium tip + oval post group. A good post fitting in oval-shaped canals can be obtained using a fine grit oval tip combined with oval posts. (Am J Dent 2009;22:290-294).
*: Prof. Marco Ferrari, Department of Fixed Prosthodontics and Dental Materials, School of Dental Medicine, Policlinico “Le Scotte”, University of Siena, Viale Bracci, Siena, 53100, Italy. E-*: firstname.lastname@example.org
Effect of collagenase and esterase on resin-dentin interface: A comparative
study between a total-etch adhesive and a self-etch adhesive
Young-Jung Jung, dds, msd, phd, Hong-Keun Hyun, dds, msd, phd, Young-Jae Kim, dds, msd, phd
& Ki-Taeg Jang, dds, msd, phd
Abstract: Purpose: To examine the effects of collagenase and esterase activity on the microtensile bond strength and nanoleakage at the resin-dentin interfaces of two adhesive systems: a total-etch adhesive (Single Bond 2: SB) and a self-etch adhesive (Clearfil SE Bond: SE). Methods: Resin composites were bonded to the occlusal dentin surfaces of extracted human premolars with either SB or SE. The bonded teeth were sectioned into beams and assigned to one of four storage conditions: phosphate buffer solution (24 hours), phosphate buffer solution (4 weeks), collagenase solution (4 weeks), or esterase solution (4 weeks). Microtensile bond strength was evaluated and analyzed by two-way ANOVA. Failure mode was analyzed under SEM, and nanoleakage was examined with TEM. Results: The bond strength of SE was superior to that of SB after 4-week storage in three aqueous solutions. Collagenase and esterase solutions did not decrease the bond strength of SB any more than the phosphate buffer solution (P> 0.05). In regard to SE, the bond strength after 4-week storage in collagenase solution was lower than in the phosphate buffer solution (P< 0.05). TEM images revealed increasing tendency of nanoleakage in the bonded interfaces after storage in collagenase and esterase solutions. (Am J Dent 2009;22:295-298).
*: Dr. Ki-Taeg Jang, Department of Pediatric Dentistry, School of Dentistry and Dental Research Institute, Seoul National University, 275-1, Yeongun-dong, Chongno-gu, Seoul, 110-768, South Korea. E -*: email@example.com
Hybrid Root SEAL (MetaSEAL) creates hybrid layers in radicular
dentin only when EDTA is used as the final rinse
Luigi Pinna, dds, Robert J. Loushine, dds, Frank D. Bishop Jr., dmd, Elisabetta Cotti, dds, ms,
R. Norman Weller, dmd. ms, David H. Pashley, dmd, phd & Franklin R. Tay, bdsc (hons), phd
Abstract: Purpose: To test if the hybrid layer formation by Hybrid Root SEAL (Sun Medical Co.), a 4-META-containing auto-adhesive self-etching root canal sealer, is affected by the sequence of irrigants employed for removing canal wall smear layers during root canal treatment. Methods: Single-rooted teeth were shaped and irrigated with EDTA as initial rinse/NaOCl as active final rinse (Group 1), or NaOCl as initial rinse/EDTA as active final rinse (Group 2). All canals were obturated with Hybrid Root SEAL using a single-cone technique. Root slices derived from the coronal, middle and apical thirds of the roots were processed for transmission electron microscopy after removing the gutta-percha, leaving the sealer intact. Additional filled canals from the two groups were evaluated for fluid leakage. Results: Hybrid layer was absent in Group 1 and was present only when a collagen matrix was produced by EDTA demineralization (Group 2). Significantly more leakage (4.03 ± 1.94 µLmin-1 vs. 1.50 ± 0.42 µLmin-1; P< 0.05) was observed in the absence of dentin hybridization. (Am J Dent 2009;22:299-303).
*: Dr. Franklin Tay, Department of Endodontics, School of Dentistry, Medical College of Georgia, Augusta, GA, 30912-1129, USA. E-*: firstname.lastname@example.org
Optimum post and tooth root diameters for a cast post-core system
& Kevin H-K. Yip, bds, phd, med, mmedsc
Abstract: Purpose: To investigate the optimum diameter for the tapered post
of a cast alloy post-core system relative to the root diameter, when measured
at the root face, that is required to minimize both post and root failures. Methods: 32 extracted maxillary central
incisor teeth were each decoronated perpendicular to the long axis at a point
*: Professor Ya-Ming Chen, Department of Prosthetic Dentistry, College of Stomatology, Nanjing Medical University, Nanjing 210029, PR China. E-*: email@example.com; firstname.lastname@example.org.
Comparing the effects of brushing with a new gel-to-foam dentifrice
to brushing with regular fluoride control dentifrices on viable bacteria
levels in saliva
David Santos, ba, Lyndsay Schaeffer, bs, phd, Laurence Du-Thumm, bs, ms, phd, Mark Vandeven, b eng, phd & Diane Cummins, bsc, phd
Abstract: Purpose: To compare the effects of a new gel-to-foam dentifrice to two standard fluoride control dentifrices on foam generation, levels of total viable anaerobes and total viable volatile sulfur compound (VSC)-producing bacteria in expectorate after brushing. Methods: 36 subjects participated in this investigator-blind, randomized, crossover study. After a 1-week wash-out period prior to each product use, participants reported to the test site having refrained from oral hygiene, eating and drinking on the morning prior to the visit. Subjects brushed with a full ribbon of assigned dentifrice (Aquafresh Iso-active, Aquafresh Extreme Clean or Aquafresh Fresh & Minty), then expectorated the slurry into a collection vessel after 30 and 60 seconds of supervised brushing. Total foam volume was immediately measured. Subjects then rinsed with sterile water for 10 seconds and expectorated into the same vessel, which was processed for microbiological analysis. Total viable anaerobes and total viable VSC-producing bacteria were enumerated using appropriate selective media. Results: No statistically significant difference was indicated between the gel-to-foam dentifrice and either of the control dentifrices with respect to the level of total viable anaerobes (P> 0.05). The level of total viable VSC-producing bacteria was statistically significantly lower for the gel-to-foam dentifrice (Aquafresh Iso-active) than for one of the control dentifrices (Aquafresh Fresh & Minty) (P< 0.05), and numerically lower for the gel-to-foam dentifrice than for the other control dentifrice (Aquafresh Extreme Clean) (P= 0.0526). Use of the gel-to-foam dentifrice resulted in statistically significantly greater (P< 0.05) foam generation than the two control dentifrices. (Am J Dent 2009;22:315-320).
*: Dr. Diane Cummins, Colgate-Palmolive Technology Center, 909 River Road, PO Box 1343, Piscataway, NJ 08855-1343, USA. E-*: email@example.com
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