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October 2011

Research Article

Dielectrophoresis enhances the whitening effect of carbamide peroxide on enamel


Chris S. Ivanoff, dds, Timothy L. Hottel, dds, ms, mba, Franklin GarcÍa-Godoy, dds, ms  &  Alan T. Riga, phd


Abstract: Purpose: To compare the enamel whitening effect of a 20-minute dielectrophoresis enhanced electrochemical delivery to a 20-minute diffusion treatment. Methods: Forty freshly extracted human teeth without detectable caries or restoration were stored in distilled water at 4°C and used within 1 month of extraction. Two different bleaching gels (Plus White 5 Minute Speed Whitening Gel and 35% Opalescence PF gel) were tested. The study had two parts: Part 1 - Quantitative comparison of hydrogen peroxide (H2O2, HP) absorption - following application of an over-the-counter 35% HP whitening gel (Plus White 5 Minute Speed Whitening Gel) to 30 (n=30) extracted human teeth by conventional diffusion or dielectrophoresis. The amount of H2O2 that diffused from the dentin was measured by a colorimetric oxidation-reduction reaction kit. HP concentration was measured by UV-Vis spectroscopy at 550 nm. Part 2 – HP diffusion in stained teeth - 35% carbamide peroxide whitening gel (35% Opalescence PF gel) was applied to 10 extracted human teeth (n=10) stained by immersion in a black tea solution for 48 hours. The teeth were randomly assigned to the 20-minute dielectrophoresis or diffusion treatment group; whitening was evaluated by a dental spectrophotometer and macro-photography. Results: Part 1: The analysis found significant differences between both groups with relative percent errors of 3% or less (a single outlier had an RPE of 12%). The average absorbance for the dielectrophoresis group in round 1 was 79% greater than the diffusion group. The average absorbance for the dielectrophoresis group in round 2 was 130% greater than the diffusion group. A single-factor ANOVA found a statistically significant difference between the diffusion and dielectrophoresis groups (P= 0.01). Part 2 - The average change in Shade Guide Units (SGU) was 0.6 for the diffusion group, well under the error of measurement of 0.82 SGU. The average change in SGU for the dielectrophoresis group was 9, significantly above the error of measurement and 14 times or 1,400% greater than the diffusion group average. A single-factor ANOVA found a statistically significant difference between the diffusion and dielectrophoresis treatment groups (P< 0.001). (Am J Dent 2011;24:259-263).


Clinical significance: Dielectrophoresis increased whitening effects compared to the conventional diffusion method used by current whitening systems.



Mail: Dr. Chris S. Ivanoff, Department of Bioscience Research, College of Dentistry, University of Tennessee Health Science Center, 875 Union Avenue, Memphis, TN 38163, USA. E-mail:

Research Article

Comparative evaluation of mechanical characteristics of nanofiller containing resin composites


Hidekazu  Takahashi, dds, phd,  Werner  J.  Finger, dr med dent, phd,  Tatsuo  Endo, dds, phd, Masafumi  Kanehira, dmd, phd, Natthavoot  Koottathape, dds, ms, Masashi Komatsu, dds, phd &  Markus Balkenhol, dr med dent


Abstract: Purpose: To determine basic mechanical characteristics of six commercially available nanofiller containing resin composites compared to a microhybrid and a microfilled reference material. The tested hypothesis was that there are no differences in mechanical properties between the materials. Methods: Durafill VS (DUR) and Filtek Z250 (Z250) were used as microfilled and microhybrid references. The nanofiller containing products were: Filtek Supreme XT (FIL), Grandio (GRA), Kalore (KAL), MI Flow (MIF), Tetric EvoCeram (TET), and Venus Diamond (VED). The following material characteristics were determined after 24 hours water storage (n=6): Flexural strength and modulus (FM), yield stress (0.02%), tensile strength and modulus (TM), diametral tensile strength, Knoop hardness (KHN), and fracture toughness (KIC). Results: The microfilled composite DUR consistently showed the lowest values for each property investigated. The group of nanofiller containing products could be subdivided into two groups: the nanohybrid products GRA and VED and the nanofilled FIL with higher values, on the one hand, and the flowable MIF, and the prepolymer containing composites KAL and TET, on the other. The mechanical performance of the microhybrid reference material Z250 was overall slightly better or in line with the nanohybrid and nanofilled materials. Stringent linear relationships were found between KHN and the moduli FM and TM, respectively (r> 0.95). Linear relations between the other material values investigated were moderate to high. (Am J Dent 2011;24:264-270).


Clinical significance: The nanofilled material FIL and the nanohybrids GRA and VED show mechanical properties similar to the microhybrid Z250 and could thus be recommended for the same clinical indications as universal resin composites. MIF and the prepolymer loaded KAL and TET, in contrast, should presumably be used more restrictedly for restoration of posterior teeth. The microfilled DUR should only be used in non stress bearing areas.


Mail: Dr. Werner J. Finger, Division of Operative Dentistry, Department of Restorative Dentistry, Tohoku University Graduate School of Dentistry, 4-1 Seiryo machi, Aoba-ku, Sendai 980-8575, Japan. E- mail:



Research Article

Comparison of experienced and inexperienced operators on bond strengths of total-etch and self-etch bonding systems


Luca  Giachetti, md, dmd, msc, Daniele  Scaminaci  Russo, dds,  Edoardo  Rossi  Campani, dds, Matteo  Baldini, dds,  Michele  Nieri, dds  &  Marco  Ferrari, md, dmd, phd


Abstract: Purpose: To compare a two-step etch-and-rinse adhesive system and a one-step self-etch adhesive system in order to evaluate the influence of clinical experience on dentin bond strength. Methods: 24 human molars were sectioned to obtain two 1 mm-thick slabs of mid-coronal dentin. Both surfaces of one of the two slabs that were obtained from each tooth were treated with a two-step etch-and-rinse adhesive (OptiBond Solo Plus), while both surfaces of the other slab were treated with a one-step self-etch adhesive (OptiBond All-In-One). 24 undergraduate, second-year students applied the adhesive on one of the two surfaces of each slab (Student group), while 12 dentists with experience in adhesive restorative dentistry (Expert group) applied the same adhesive on the other surface of the slab. Nine conical frustum-shaped resin composite (Premise Flowable) build-ups, whose smaller base was bonded to the dentin surface, were constructed on both surfaces of each dentin slab using a custom-made device. After thermocycling, specimens were subjected to microshear bond strength test. Data were analyzed by a multilevel statistical model. Results: The interaction term Experience x Adhesive resulted statistically significant (P< 0.0001). The bond strength (MPa) resulting from the self-etch adhesive was similar in the Student (27.8 ± 9.0) and in the Expert group (26.5 ± 7.0). The etch-and-rinse adhesive bond strength within the Student group (23.6 ± 10.4) was lower than that within the Expert group (28.1 ± 8.9). (Am J Dent 2011;24:271-276).


Clinical significance: While the etch-and-rinse adhesive used in this study showed to be experience-sensitive, the self-etch one proved to be less experience-sensitive in obtaining a reliable bond strength with dentin.


Mail: Dr. Luca Giachetti, Department of Public Health Dentistry, Viale Morgagni 85, 50134 Firenze, Italy. E- mail:


Research Article

The influence of daily application of fluoride products on subsurface bovine enamel lesions stored in saliva substitutes


Daniela  L.  Zandim, dds, ms, phd,  Peter  Tschoppe, dds,  JosÉ  E. C.  Sampaio, dds, ms, phd &  Andrej  M.  Kielbassa, dds, phd


Abstract: Purpose: To evaluate in the laboratory the effects of daily fluoride applications on remineralization of subsurface bovine enamel lesions stored in different saliva substitutes. Methods: Enamel specimens were prepared (n = 144) and demineralized (subsurface lesions; 37°C; pH 4.95; 10 days). Before and after demineralization, specimen surfaces were partly covered with nail varnish (control of sound/demineralized enamel). The specimens were either stored (5 weeks; 37°C) in mineral water (W, control, SOCP 0.7, pH 7.0), Glandosane (G, SOCP 0.3, pH 5.2), or modified Saliva Natura (SN, SOCP 2.0, pH 5.98), and were submitted to the following treatments twice daily: (0) no treatment; (ES) immersion in pure Elmex Sensitive mouthrinse (10 minutes); (D) brushing with Duraphat toothpaste/storage solution slurry (5 seconds + contact time 115 seconds; ratio 1:3); (ES+D) combination of ES and D treatments. Mineral parameters before and after storage/treatment were evaluated from microradiographs. Results: Specimens stored in G showed significantly higher demineralization compared to the other solutions (P< 0.05, ANOVA, Tukey’s post hoc test); the combined treatment with fluoride products significantly reduced the demineralizing effect of G. After 2 and 5 weeks, specimens stored in SN revealed a higher remineralization compared to the control solution (P< 0.05). Daily application of fluoride products did not promote an additional effect on remineralization of specimens stored in SN (P> 0.05). (Am J Dent 2011;24:277-283).


Clinical significance: The results of this laboratory study suggest that Glandosane is a demineralizing saliva substitute that should be used in combination with fluoride products by dentate patients suffering from hyposalivation, whereas Saliva Natura supersaturated with respect to calcium phosphates seems to enable remineralization of enamel subsurface lesions.



Mail: Dr. Peter Tschoppe, Department of Operative Dentistry and Periodontology, University School of Dental Medicine, Campus Benjamin Franklin, Charité - Universitätsmedizin Berlin, Assmannshauser Straße 4-6, 14197 Berlin, Germany.  E- mail:


Research Article

Dentin protection by a primer-less adhesive technique


Morakot  Piemjai, dds, mdsc, phd,  Onusa  Waleepitackdej, dds,  Franklin  GarcÍa-Godoy, dds, ms &  Nobuo  Nakabayashi, phd


Abstract: Purpose: To identify the remaining demineralized dentin (the permeable layer that allows leakage) when using primer-less wet bonding with a total etching period of 10 to 60 seconds compared with contemporary resin adhesives. Methods: Extracted human molars were selected and Class V cavities were prepared on the axial surfaces at the CEJ, providing margins in enamel and dentin for leakage testing using a basic dye (n= 10). Seven groups of conditioned teeth [1-1 etched for 10, 30, and 60 seconds (primer-less wet), All-Bond 2 and Single-Bond 2 (wet), AQ-Bond (self-etched), Super-Bond C&B (dry)] were used as bonding systems for resin composite restoration. All specimens were stored in water at 37°C for 24 hours before soaking in a 0.5% basic fuchsin solution for 24 hours. The distance of dye penetration was measured using stereomicroscopy. Results: No leakage at the enamel- and dentin-resin interfaces was found for all etching periods of 1-1 primer-less, Super-Bond C&B, and AQ-Bond specimens. However, leakage was observed at dentin margins in two wet with primer systems, All-Bond 2 (1.31 ± 1.39 mm) and Single-Bond 2 (0.37 ± 0.28 mm), which required phosphoric etching to remove a weak smear layer on prepared dentin. (Am J Dent 2011;24:284-288).


Clinical significance: Simplified primer-less wet bonding with etching periods of 10 to 60 seconds can provide leakagefree seals at both the enamel and dentin margins of Class V resin-composite restorations. This may suggest that no demineralized layer, the leakage pathway, remained to initiate the detachment of restorations, which may produce secondary caries and pulpal infection. Dentin completely sealed and microleakage free with light-cured resin composite is reported in this study.


Mail: Dr. Morakot Piemjai, Department of Prosthodontics, Faculty of Dentistry, Chulalongkorn University, Henri-Dunant Road, Patumwon, Bangkok 10330, Thailand.  E-mail:


Position Article

Recommendation for a non-animal alternative to rat caries testing


John D.B. Featherstone, msc, phd, George K. Stookey, phd, Michael A. Kaminski, phd  &  Robert V. Faller, bs


Abstract: Purpose: As a requirement of the Food & Drug Administration’s final monograph on “Anticaries drug products for over-the-counter human use”, the toothpaste industry has been conducting animal caries tests on every fluoride-containing toothpaste introduced into the U.S. market since 1996. The practice of testing in animals, although required by law, is in stark conflict with the corporate policy of many U.S. and global toothpaste manufacturers, in which, if possible, alternatives to animal testing are utilized. A provision does exist within the regulation which allows the use of an alternative method to demonstrate efficacy. However, to take advantage of this provision, a petition must be submitted to the FDA and in this petition data demonstrating the alternative provides results of “equivalent accuracy” must be included. After many years of research, model development and model comparisons, we have identified one particular laboratory model that demonstrated excellent correlation with the currently accepted animal caries models. This model, known as the Featherstone pH cycling model, is discussed in this paper. Methods: The Featherstone pH cycling model has been shown to produce results of equivalent accuracy to the animal caries model by: (1) demonstrating a clinically relevant fluoride dose response similar to that shown in the animal caries model (including 1100 ppm F, 250 ppm F and placebo); (2) demonstrating similar results to the animal caries model for clinically proven dentifrice formulations relative to positive and negative controls; (3) demonstrating discriminating ability in strong agreement with the animal caries model for differentiating between a dentifrice formulation with attenuated fluoride activity and a USP standard; and (4) providing a clinically relevant representation of the caries process, as demonstrated by orthodontic banding studies. In addition, the model sufficiently addresses both salivary and abrasive/anticalculus agent interference concerns. Results: For more than 50 years, fluoride has been the first defense in the fight against dental caries. The clinical effectiveness of fluoride is well accepted and documented extensively in the literature. The mechanism through which fluoride provides its benefit is very straightforward and well understood. The proposed laboratory model effectively simulates the effect of the caries process and has been shown to demonstrate equivalent accuracy to animal caries. This indicates that there are strong scientific grounds for the use of this model as an alternative to the animal caries test. Based on the strength of the data and the correlations noted between the two models, we recommend that the scientific community and the toothpaste industry broadly accept the Featherstone laboratory pH cycling model as an appropriate alternative to animal testing, particularly for ionic fluoride based dentifrices. (Am J Dent 2011;24:289-294).


Clinical significance: The proposed Featherstone pH cycling laboratory model effectively simulated the effect of the caries process and has been shown to demonstrate equivalent accuracy to animal caries. This indicated that there are strong scientific grounds for the use of this model as an alternative to the animal caries test.


Mail: Dr. John D. B. Featherstone, School of Dentistry, University of California San Francisco, San Francisco, CA 94143, USA.  E-mail:


Research Article

Profiling of dental plaque microflora on root caries lesions and the protein-denaturing activity of these bacteria


Kazuhiro  Hashimoto, dds, phd,  Takuichi  Sato, dds, phd,  Hidetoshi  Shimauchi, dds, phd & Nobuhiro  Takahashi, dds, phd


Abstract: Purpose: To profile plaque microflora on root-caries lesions, and to examine the protein-denaturing activity as a pilot study. Methods: Six subjects with root-caries were investigated. Plaque samples on root caries lesions (R), as well as from healthy supragingival sites (S) and periodontal pockets (≥5 mm) (P) were collected and cultured anaerobically on blood agar plates. The isolated bacteria were identified by 16S rRNA sequencing analysis, and examined for the protein-denaturing activity using the skim-milk plates and the SDS-PAGE, and for the acidogenicity using the FAB broth containing 1% glucose. Results: Propionibacterium, Actinomyces, Streptococcus, Lactobacillus and Bifidobacterium were predominant in R, while Actinomyces, Streptococcus, Veillonella and Capnocytophaga in S, and Actinomyces, Prevotella, Actinobaculum, Streptococcus, Olsenella and Eubacterium were predominant in P. Proteolytic bacteria comprised 40%, 26% and 57% of microflora in R, S and P, respectively. The skim-milk plates distinguished between protein-degrading and protein-coagulating bacteria, which comprised 7 and 33%, 0 and 26%, and 17 and 40% of microflora, in R, S and P, respectively. The SDS-PAGE analysis revealed that protein-degrading isolates were capable of degrading collagen molecules. Furthermore, the final culture pHs of protein-degrading and -coagulating bacteria were 5.0-5.4 and 3.8-3.9, respectively. The latter pH was low enough to denature proteins in skim milk. The microbial composition of R was distinct from those of S and P. (Am J Dent 2011;24:295-299).


Clinical significance: Cohabitation of coagulating- and degrading-bacteria in R suggested that in the process of root surface caries the former bacteria demineralize hydroxyapatite and denature proteins of root dentin/cementum, and subsequently the latter bacteria degrade denatured proteins.


Mail: Dr. Takuichi Sato, Division of Oral Ecology and Biochemistry, Tohoku University Graduate School of Dentistry, Sendai 980-8575, Japan.  E-mail:


Research Article

Sensitivity of digital dental photo CIE L*a*b* analysis compared to spectrophotometer clinical assessments over 6 months


Ariel  Sluzker, dds, ms, Michael KnÖsel, dds, dr med dent, priv doc  &  Athanasios  E.  Athanasiou, dds, msd, dr dent


Abstract: Purpose: To assess the sensitivity of digital dental photo CIE L*a*b* analysis compared to clinical spectrophotometer assessments over 6 months. Methods: CIE L*a*b* values for the upper right central incisors of 14 predoctoral dental students subjected to certain color-relevant exclusion criteria were recorded at baseline (T0), after 6 months (T1), and 1 week later (T2), using (Method 1) a spectrophotometer and (Method 2) a method of digital photo analysis. Statistical analysis of color and lightness data between both methods and time points were assessed using the Shapiro-Wilk test, Pearson’s correlation coefficient (r), Dahlberg’s formula for method error calculation, and paired samples t-tests, adopting a level of significance α= 0.05. Results: Between T0 - T1, the spectrophotometer recorded significant changes in lightness (75.51 > 77.75) and color values (a*: 3.25 > 2.38; b*: 18.47 > 17.31), whereas significant changes with Method 2 were only seen for b* (21.51 > 20.57). No significant changes for overall color and lightness changes ΔΕ to ΔΕ2 were found for either of the methods. The error of the method (T1-T2) and corresponding correlation coefficients r for values L*a*b* were found to be 1.44 / 0.43 / 0.62 (r: 0.69; P= 0.007/0.64; P= 0.14/0.9; P< 0.001) for Method 1 and 0.97/0.67/1.25 (r : 0.87; P< 0.001/0.63; P= 0.17/0.57, P= 0.04) for Method 2, respectively. (Am J Dent 2011;24:300-304).


Clinical significance: This clinical study evaluated the intra-examiner sensitivity of measurements of natural anterior permanent teeth using either a reflectance spectrophotometer or digital photo analysis while conducting a cross-sectional assessment under standardized lighting conditions, which has so far not been reported in the literature for these two methods. The spectrophotometer was considered more suitable for detecting slight changes in color and lightness appearance than the digital photo method.


Mail: Dr. Athanasios E. Athanasiou, Department of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece. E-mail:


Research Article

Comparison of ropivacaine and lidocaine with epinephrine for infiltration anesthesia in dentistry. A randomized study


Tadeusz  Faustyn  KrzemiŃski, md, phd,  Łukasz  Gilowski, md,  Rafał  Wiench, md,  Iwona  Płocica, md, Piotr  Kondzielnik, md  &  Andrzej  SielaŃczyk, md


Abstract: Purpose: To compare the efficacy of maxillary infiltration anesthesia with 0.5% plain ropivacaine or 2% lidocaine with epinephrine 1:100,000. Methods: 60 volunteers received 1.8 ml of the anesthetic for infiltration anesthesia of maxillary central and lateral incisors and canine teeth. The onset time and duration of pulp anesthesia were assessed with an electric pulp tester. The duration time of numbness of the upper lip was also monitored. Blood pressure and heart rate were measured before and after administration of the solution. Results: The efficacy of anesthesia of the  lateral and central incisors was 100% for both anesthetics. There were small insignificant differences in effectiveness of canine pulp anesthesia. The mean onset time was significantly shorter for ropivacaine – 2.2 minutes vs. 5.1 for lidocaine. Ropivacaine also had a significantly longer duration of action – mean time 79.2 minutes. Ropivacaine caused statistically significant increases in blood pressure and heart rate. (Am J Dent 2011;24;305-309).


Clinical significance: The study shows that 0.5% ropivacaine causes effective and very long duration of pulp and soft tissue anesthesia. Ropivacaine could be useful for long lasting procedures without the need of a vasoconstrictor.


Mail: Dr. Łukasz Gilowski, Chair, Department of Pharmacology, Medical University of Silesia, Jordana 19, 41-808 Zabrze, Poland.  E-mail:


Research Article

Effect of spherical silica additions on marginal gaps and compressive strength of experimental glass-ionomer cements


Masao Irie, dds, phd, Noriyuki Nagaoka, me, phd, Yoshiyuki Tamada, dds, Yukinori Maruo, dds, phd, Goro Nishigawa, dds, phd, Shogo Minagi, dds, phd &  Werner J. Finger, dr med dent, phd


Abstract: Purpose: To clarify the effects of the addition of silanized (S) and unsilanized (U) spherical silica filler to resin-modified glass-ionomer cement and of powder-liquid ratio on (1) the early marginal gap-width of restorations in both tooth cavities and Teflon molds, (2) the gap-formation of restorations in Class V cavities, and (3) the compressive strength of the cement. Methods: Resin-modified glass-ionomer powder (Fuji II LC EM, GC) was modified by adding 5 and 10 wt% of powder respectively, of S and U, and then the powder-liquid ratio was increased up to 4.8. Human premolars, extracted for orthodontic reasons, were used for this study. Cylindrical cavities (1.5 mm deep, 3.5 mm in diameter; one cavity was prepared in each tooth in the coronal region and medial surface) were prepared in extracted human premolar teeth and restored with resin-modified glass-ionomer cements. Each restoration margin was inspected immediately after curing and polishing (as the immediate condition was the most severe), the maximum gap-width and the opposing width (if any) were determined microscopically (n= 10). An additional test was conducted in model Class V cavities. After finishing of restorations in model Class V cavities, each tooth was sectioned in a bucco-lingual direction through the center of the restoration, and the presence or absence of gaps along the cavity interface was evaluated (n=10). Additionally, the maximum marginal gap-width and the opposing-width along margins of restorations in cylindrical Teflon molds were measured (n= 10). The compressive strengths of the restorative materials were determined immediately after light-activation (n=10). Results: Marginal gap (tooth cavity: 0.32 to 0.25-0.20%, P< 0.05; Teflon cavity: 0.94 to 0.6-0.8%, P< 0.05) and cavity adaptation (no gap in the Class V: 22 to 40-50%, P< 0.05) of the restorations improved with increasing powder-liquid ratio (3.0 to 4.4-4.8) and compressive strength increased (111 to 150-170 MPa, P< 0.05). Highly significant correlation coefficients were found for the relationships between powder-liquid ratio and (1) percentage of marginal gap width in the tooth cavity (r= -0.96, P= 0.002, n= 6), (2) gap-free tooth/cement interfaces (r= 0.90, P= 0.015, n= 6), (3) percentage of marginal gap widths in the Teflon mold (r= 0.98, P= 0.0004, n= 6) and (4) compressive strengths of the cements (r= 0.95, P= 0.004, n= 6). (Am J Dent 2011;24:310-314).


Clinical significance: Addition of spherical silica filler to resin-modified glass-ionomer cement increased compressive strength and improved the marginal and cavity adaptation of restorations with increasing powder-liquid ratio.


Mail: Dr. Masao Irie, Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Phamaceutical Sciences, 2-5-1, Shikata-cho, Kita-ku, Okayama 700-8525, Japan. E-mail:


Research Article

Release of monomers from four different composite materials after halogen and LED curing


Olga  Polydorou, dds, dr med dent, pd,  Armin  KÖnig,  Markus JÖrg  Altenburger, dds, dr med dent, pd, Martin  Wolkewitz, dr ch hum,  Elmar  Hellwig, dds, dr med dent, prof  &  Klaus  KÜmmerer, dipl-chem, dr rer nat, prof


Abstract: Purpose: To evaluate the release of monomers from four different composite materials (Ceram X, Filtek Supreme XT, Tetric Flow, Tetric EvoCeram), polymerized using either halogen or LED unit. Methods: Ten specimens were made for each material/unit combination. Each specimen was stored in 1 ml 75% ethanol. The storage medium was renewed after 1, 7 and 28 days. Aliquots of this medium were analyzed by LC-MS/MS. Results: The effect of the curing unit on monomers’ release differed significantly among the materials (P< 0.0001). The amount of BisGMA and TEGDMA released from Ceram X was not influenced by the unit used (P> 0.05). Curing with LED reduced the amount of Bisphenol A released from Ceram X compared to halogen. For Filtek Supreme XT, the type of unit exerted a significant effect on the elution of BisGMA (P≤ 0.05). LED curing resulted in a higher release of TEGDMA and UDMA compared to halogen (P≤ 0.05). For Tetric Flow, LED curing resulted in lower monomer release (P< 0.0001). For Tetric EvoCeram, the amounts of BisGMA, UDMA and Bisphenol A were higher when polymerizing with LED compared to halogen. The release of substances was more material dependent and less influenced by the curing unit used. (Am J Dent 2011;24:315-321).


Clinical significance: The composite materials used in  restorations should be chosen carefully, as the type of the material is more important than the curing unit, concerning the elution of monomers.


Mail: Dr. Olga Polydorou, Department of Operative Dentistry and Periodontology, University Medical Center Freiburg, Dental School and Hospital, Hugstetter Straße 55, 79106 Freiburg, Germany. E-mail:



Research Article

The Featherstone laboratory pH cycling model: A prospective, multi-site validation exercise


George K. Stookey, phd,  John D.B. Featherstone, msc, phd,  Marcia Rapozo-Hilo, bs, ba,  Bruce R. Schemehorn, ms, Ross  A.  Williams, bs,  Robert  A.  Baker, ms,  Matthew  L.  Barker, phd,  Michael  A.  Kaminski, phd, Christine  M.  McQueen, bs, mba,  Jack  S.  Amburgey, phd,  Keith  Casey  &  Robert  V.  Faller, bs


Abstract: Purpose: To demonstrate the robustness of the Featherstone pH cycling model when tested in three independent laboratories and to evaluate the use of “non-inferiority” testing at those laboratories. Methods: The fundamental principles for the Featherstone laboratory pH cycling model to be an appropriate alternative to animal testing is that it must demonstrate equivalent accuracy to the “Gold Standard” (rat caries model) by: (1) providing a meaningful representation of the caries process; (2) demonstrating a proportionate response to fluoride dose (or concentration); (3) being able to show that clinically proven formulations perform similarly relative to the controls; and (4) differentiating products that have attenuated fluoride activity. Results: This cross-validation study confirmed the ability of the three independent laboratories to discriminate between various concentrations of fluoride-containing dentifrice formulations, demonstrated that clinically proven formulas perform as expected and identified an attenuated fluoride formulation (NaF/CaCO3 dentifrice - 1100 ppm NaF) as inferior compared to the 1100 ppm F- (NaF/silica) positive control. (Am J Dent 2011;24:322-328).




Clinical significance: The ability to conduct a study that included the same set of nine test products at each site and produce data that can be directly compared and interpreted in the same fashion at each of these sites provides a significant level of credibility and robustness to the model with regard to its ability to confirm the clinical effectiveness of fluoride-containing formulations.




Mail: Dr. George K. Stookey, Therametric Technologies, Inc., 9880 Douglas Floyd Parkway, Noblesville, IN 46060, USA. E-mail:

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