Kanae  Wada, dds,  Michiyo  Miyashin, dds, phd,  Nobuhito  Nango, phd  &  Yuzo  Takagi, dds, phd

Abstract: Purpose: To determine whether resin composites are appropriate for full crown restoration of primary molars by evaluating their wear characteristics. Specifically, the wear properties of resin composite specimens and the opposing enamel surfaces were characterized by means of impacting-sliding wear testing. Methods: Three types of light-cured resin composites (Estelite Σquick, Litefill IIP, and Metafil C), one type of chemical-cured resin composite (Clearfil FII), and a hybrid composite (Estenia C&B) were tested in this study. The enamel sample was used as the control. The hemispherically prepared specimens were subjected to impacting-sliding wear testing against the flattened enamel of primary molars. The worn surfaces were examined by laser scanning microscopy and scanning electron microscopy. The volumetric loss was estimated by using micro-CT images. The areas of worn enamel surfaces were measured by 3D color laser microscopy. On most of the worn enamel surfaces, cracks appeared. Scatter plot analyses between their width and depth were carried out. Data for each specimen were statistically analyzed by multiple comparisons among the means of treatment by Bonferroni’s method (P< 0.01). Results: Clearfil showed significantly higher surface area wear, volumetric loss, and worn enamel surface area than did the other resin composites and the control enamel (P< 0.01). There was no significant difference among the worn surface areas of Estelite, Litefill, Metafil, and Estenia (P< 0.01). The control enamel showed significantly lower worn surface area than did the resin composites (P< 0.01). There was no significant difference in volumetric loss and worn enamel surface areas among Estelite, Litefill, Metafil, Estenia, and the control enamel (P< 0.01). Cracks larger than that on the control enamel were seen on the worn enamel surface opposing Estenia. (Am J Dent 2011;24:67-73).

Mail:  Dr. Kanae Wada, Division of Development Oral Health Science, Graduate School, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo 113-8549,  Japan.  E-mail: kan978.dohs@tmd.ac.jp

Research Article

Detection of cavitated or non-cavitated approximal enamel caries lesionsusing CMOS and CCD digital X-ray sensors and conventional D and F- speed films at different exposure conditions

Peter Bottenberg, dds, phd, Wolfgang Jacquet, msc, phd, Vitus Stachniss, dds, phd, Johann Wellnitz, dds  &   Andreas G. Schulte, dds, phd

Abstract: Purpose: To determine the ability of digital sensors (CMOS and CCD sensors) and D and F-speed films to detect cavitated and non-cavitated enamel caries lesions at different exposure conditions compared to a gold standard. Methods: 100 extracted human molars and premolars were selected and mounted in a block between two neighboring teeth. Sensors or films were exposed with voltages of 60 or 70 kVp at varying times. Three observers assessed each approximal site independently. Lesion depth was rated according to an anatomical five-point scale (0 = no lesion to 4 = lesion reaching inner half of dentin). Serial sections of resin-embedded teeth were prepared. Gold-standard scores were established by consensus based on histological sectioning. A carious lesion was present at scores of 1 and higher. Statistical evaluation (sensitivity, specificity and receiver-operating curves) was based on caries-free surfaces and those presenting enamel caries (n=116). Results: The ROC curves had “area under the curve” values (Az) from 0.50 (F-speed, 70 kVp, 0.20 seconds) to 0.58 (CCD 60 kVp, 0.08 seconds). The detection percentage of cavitated lesions was generally higher (0-52%, depending on technique and observer) than that of non-cavitated lesions (3-32%). The CMOS sensor showed Az values comparable to the CCD sensors but required higher exposure times. There was no significant difference between 60 and 70 kVp. (Am J Dent 2011;24:74-78).

Mail: Prof. Dr. Peter Bottenberg, Dept. of Operative Dentistry, Free University of Brussels, Laarbeeklaan 103, B-1090 Brussels, Belgium. E-mail: pbottenb@vub.ac.be

Research Article

Evaluation of silica-coating techniques for zirconia bonding

Liang Chen, phd,  Byoung In Suh, phd, Jongryul Kim, phd  &  Franklin R. Tay, dds, phd

Abstract: Purpose: To evaluate silica-coating/silane treatment techniques for zirconia bonding. Methods: 19 groups of zirconia disks were subjected to different surface treatments: polished or sandblasted by CoJet or alumina, and treatment with silane or zirconia primers (containing phosphate- or phosphonate-monomer). After surface treatments, the zirconia disks were cemented with resin cements and stored in deionized water for 2 hours at 37°C prior to shear bond strength testing. Zirconia surface (polished and unpolished), CoJet sand, Cojet-treated zirconia surface (before and after water rinsing) and representative debonded surfaces were examined by scanning electron microscopy (SEM). The zirconia surface after silica-coating was examined by Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy. Results: A non-phosphate-containing resin cement (Choice 2) had almost no bond strength on polished zirconia, while MDP-containing cements (Panavia F2.0) had mild bond strength. After zirconia was sandblasted with CoJet or alumina, bond strengths were slightly increased. Silane treatment did not increase bond strength, while phosphate/carboxylate-based primer (i.e. Exp Z-Prime) doubled the bond strengths. Silica nanoparticles identified by FTIR-ATR spectra, were observed by SEM on the zirconia surface after CoJet treatment. However, these nanoparticles were removed by forceful water stream. (Am J Dent 2011;24:79-84).

Mail: Dr. Liang Chen, BISCO, Inc., 1100 W. Irving Park Road, Schaumburg, IL 60193,  USA.  E-mail: lchen@bisco.com

Research Article

Aikaterini Patsouri, dds, ms, Afroditi Mavrogiannea, dds, ms, Eudoxie Pepelassi, dds, ms, dr dent, Marianna Gaintantzopoulou, dds, mds, dr dent   &   Afrodite Kakaboura, dds, dr dent

Abstract: Purpose: To evaluate the efficacy of the DenShield desensitizing system, based on calcium sodium phosphosilicate, in the hypersensitivity reduction for a 6-month period in periodontitis patients previously subjected to periodontal treatment and to compare the combination of the in-office paste and at-home dentifrice use to the at-home dentifrice use alone. Methods: A total of 248 teeth (eight teeth in each subject) in 31 periodontitis patients (mean age 48 ± 8 years) previously subjected to periodontal treatment were studied. 193 (77.8%) teeth had been treated with phase I periodontal treatment alone (non-surgical treatment) and 55 (22.2%) had been additionally subjected to periodontal surgery. Periodontal clinical parameters were recorded for each subject. Hypersensitivity was assessed by tactile and air-blast stimuli. The hypersensitive teeth of each of two quadrants in each subject were randomly assigned with split-mouth design to in-office application of DenShield Starter paste (four teeth) or placebo (distilled water) (four teeth). After the in-office application each patient used the DenShield dentifrices (Builder and Saver) for 6 months. The final evaluation was at 6 months. Results: The prevalence and the degree of baseline hypersensitivity was significantly higher for the surgically than the non-surgically-treated teeth (83.6% versus 68.4%) and it was greater in teeth with attachment loss. The dentin hypersensitivity observed after periodontal treatment was significantly reduced in periodontitis patients who used the DenShield system for 6 months. There was no difference in hypersensitivity reduction between the additional in-office application of the DenShield and the at-home use of the DenShield dentifrices alone. (Am J Dent 2011;24:85-92).

Mail: Dr. Eudoxie Pepelassi, Department of Periodontology, School of Dentistry, University of Athens, Greece. E-mail: kgkostop@netscape.net

Research Article

Bond strengths of a silorane composite to various substrates

Lee  W.  Boushell, dmd, ms,  George  Getz, dds,  Edward  J.  Swift, Jr., dmd, ms  &  Ricardo  Walter, dds, ms

Abstract: Purpose: To evaluate the shear bond strength (SBS) of a novel low-shrink posterior resin composite (Filtek LS) to various substrates. Methods: The dedicated LS System Adhesive was used to bond Filtek LS to bovine dentin, ground bovine enamel, resin-modified glass-ionomer liner (Vitrebond Plus), conventional glass-ionomer restorative material (Fuji IX GP Extra), and bovine dentin previously exposed to zinc oxide-eugenol (IRM) (n=10 for each group). Vitrebond Plus and Fuji IX GP Extra substrates were fabricated by filling standardized preparations that had been made in epoxy resin. Adper Scotchbond SE/Filtek Z250 was used as a control. Composites were applied using the Ultradent specimen former. The bonded specimens were stored in water at 37°C for 24 hours, and SBS testing was done using an Instron universal testing machine. The data were analyzed using ANOVA and Tukey-Kramer HSD test at a significance level of 0.05. Results: The mean SBS values of the Filtek LS system were generally somewhat lower than the values of Adper Scotchbond SE/Filtek Z250 to the various substrates, but the differences were not statistically significant. Exposure of dentin to IRM resulted in a statistically significant reduction in the mean SBS values of Adper Scotchbond SE/Z250 and a slight but statistically insignificant reduction for the Filtek LS system. (Am J Dent 2011;24:93-96).

Mail: Dr. Ricardo Walter, Department of Operative Dentistry, 433 Brauer Hall, CB# 7450, School of Dentistry, University of North Carolina, Chapel Hill, NC  27599-7450, USA.  E-mail: rick_walter@dentistry.unc.edu

Research Article

Polymerization characteristics, flexural modulus and microleakageevaluation of silorane-based and methacrylate-based composites

Bo-tao Gao, bds, msc,  Hong Lin, bds, phd,  Jian-min Han, bds, msc  &  Gang Zheng, phd

Abstract: Purpose: To compare the behavior of a new low-shrinkage silorane-based composite (P90) with two conventional methacrylate-based composites, in terms of polymerization shrinkage, polymerization stress, gel point, flexural modulus and microleakage. Methods: The materials tested were P90 (3M ESPE), AP-X (Kuraray), Quixfil (Dentsply). Polymerization shrinkage was measured using the Accuvol method. Polymerization stress was assessed using a stress-strain analyzer. Polymerization shrinkage (%) and force (N) were continuously recorded for 300 seconds. Polymerization shrinkage and stress after 300 seconds and gel point were recorded. Flexural modulus was obtained by three-point bending. A laboratory microleakage test was performed. Class V cavities prepared on labial surfaces of 70 freshly extracted human teeth were randomly assigned to the seven groups (N=10): P90/PSA (P90 System Adhesive), AP-X/CBA (Clearfil SE Bond Adhesive), Quixfil/XBA (XP Bond Adhesive), P90/CBA, P90/XBA, AP-X/PSA, Quixfil/PSA. The teeth were immersed in 1% basic fuchsin dye for 24 hours at room temperature. All teeth were cut in a labial-lingual direction and the penetration of dye along the wall of cavities was observed under a stereoscopic light microscope. Statistical analysis was performed with one-way ANOVA, Kruskal-Wallis ANOVA test and post hoc tests (P< 0.05). Results: The low-shrinkage silorane-based composite (P90) exhibited significantly lower polymerization shrinkage, polymerization stress, flexural modulus and a later gel point than the conventional methacrylate-based composites. In the microleakage test, P90/PSA, AP-X/CBA, AP-X/PSA demonstrated the lowest microleakage scores without a significant difference among them (P> 0.05). Quixfil/XPA exhibited the highest microleakage scores. (Am J Dent 2011;24:97-102).

Mail: Dr. Gang Zheng, Department of Dental Materials, Peking University School and Hospital of Stomatology, Beijing, P.R. China.  E-mail: zhengang101@126.com

Research Article

Influence of laboratory degradation methods and bonding application parameters on µTBS of self-etch adhesives to dentin

Maria  Carolina  G.  Erhardt, dds, ms, phd,  Jatyr  Pisani-ProenÇa, dds, ms, phd,  Estrella  Osorio, dds, phd, FÁtima  S.  Aguilera, dds, phd,  Manuel  Toledano, md, bds, phd  &  Raquel  Osorio, dds, phd

Abstract: Purpose: To evaluate the laboratory resistance to degradation and the use of different bonding treatments on resin-dentin bonds formed with three self-etching adhesive systems. Methods: Flat, mid-coronal dentin surfaces from extracted human molars were bonded according to manufacturer’s directions and submitted to two challenging regimens: (A) chemical degradation with 10% NaOCl immersion for 5 hours; and (B) fatigue loading at 90 N using 50,000 cycles at 3.0 Hz. Additional dentin surfaces were bonded following four different bonding application protocols: (1) according to manufacturer’s directions; (2) acid-etched with 36% phosphoric acid (H₃PO₄) for 15 seconds; (3) 10% sodium hypochlorite (NaOClaq) treated for 2 minutes, after H₃PO₄-etching; and (4) doubling the application time of the adhesives. Two one-step self-etch adhesives (an acetone-based: Futurabond/FUT and an ethanol-based: Futurabond NR/FNR) and a two-step self-etch primer system (Clearfil SE Bond/CSE) were examined. Specimens were sectioned into beams and tested for microtensile bond strength (µTBS). Selected debonded specimens were observed under scanning electron microscopy (SEM). Data (MPa) were analyzed by ANOVA and multiple comparisons tests (α= 0.05). Results: µTBS significantly decreased after chemical and mechanical challenges (P< 0.05). CSE showed higher µTBS than the other adhesive systems, regardless the bonding protocol. FUT attained the highest µTBS after doubling the application time. H₃PO₄ and H₃PO₄ + NaOCl pretreatments significantly decreased bonding efficacy of the adhesives. (Am J Dent 2011;24:103-108).

Mail: Prof. Manuel Toledano, Avda. de las Fuerzas Armadas 1, 1B, 18014 Granada, Spain. E-mail: toledano@ugr.es

Research Article

Elaine Pereira da Silva Tagliaferro, phd, Vanessa Pardi, phd, GlÁucia Maria Bovi Ambrosano, phd, Marcelo de Castro Meneghim, phd, Silvio Rocha CorrÊa da Silva, phd  &  Antonio Carlos Pereira, dR phd

Abstract: Purpose: To evaluate the caries-preventive effect of a resin-modified glass-ionomer cement used as occlusal sealant (Vitremer) compared with fluoride varnish (Duraphat) application on occlusal surfaces of permanent first molars (OSPFM) in 6-8 year-old schoolchildren (n=268) at high (HR) and low (LR) caries risk. Methods: The children were followed-up for 24 months after being systematically allocated into six groups as follows: Control Groups HRC and LRC: children receiving oral health education (OHE) every 3 months; Groups HRV and LRV: children receiving OHE plus varnish application biannually; and Groups HRS and LRS: children receiving OHE plus a single sealant application). The baseline and follow-up examinations were performed by the same calibrated dentist under natural light, using CPI probes and mirrors, after toothbrushing and air-drying. The DMFS was used to record dental caries, in addition to the detection of initial lesions (IL). Data analysis was performed with two primary outcome measures: DMF and DMF+ IL on the OSPFM. Results: After 24 months, only the HRS group showed statistically lower DMF and DMF+IL increments on OSPFM compared with HRC group. HRV group did not differ from HRC and HRS groups. For LR groups, no statistical difference (P> 0.05) was observed among the treatments. (Am J Dent 2011;24:109-114).

Mail: Prof. Dr. Antonio Carlos Pereira, Av. Limeira 901 - 13414-903, Piracicaba, SP, Brazil. E-mail: apereira@fop.unicamp.br

Research Article

Ana Raquel Benetti, dds, ms, phd, Anne Peutzfeldt, dds, phd, dr odont,  Erik Asmussen, ms, dr odont, Ulla Pallesen, dds  &  Eduardo Batista Franco, dds, ms, phd

Abstract: Purpose: To investigate the effect of curing rate on softening in ethanol, degree of conversion, and wear of resin composites. Methods: With a given energy density and for each of two different light-curing units (QTH or LED), the curing rate was reduced by modulating the curing mode. Thus, the irradiation of resin composite specimens (Filtek Z250, Tetric Ceram, Esthet-X) was performed in a continuous curing mode and in a pulse-delay curing mode. Wallace hardness was used to determine the softening of resin composite after storage in ethanol. Degree of conversion was determined by infrared spectroscopy (FTIR). Wear was assessed by a three-body test. Data were submitted to Levene’s test, one and three-way ANOVA, and Tukey HSD test (α= 0.05). Results: Immersion in ethanol, curing mode, and material all had significant effects on Wallace hardness. After ethanol storage, resin composites exposed to the pulse-delay curing mode were softer than resin composites exposed to continuous cure (P< 0.0001). Tetric Ceram was the softest material followed by Esthet-X and Filtek Z250 (P< 0.001). Only the restorative material had a significant effect on degree of conversion (P< 0.001): Esthet-X had the lowest degree of conversion followed by Filtek Z250 and Tetric Ceram. Curing mode (P= 0.007) and material (P< 0.001) had significant effect on wear. Higher wear resulted from the pulse-delay curing mode when compared to continuous curing, and Filtek Z250 showed the lowest wear followed by Esthet-X and Tetric Ceram. (Am J Dent 2011;24:115-118).

Mail: Dr. Ana Raquel Benetti, University North of Paraná (UNOPAR) Center of Biological and Health Sciences, Av. Paris 675, Jd. Piza, 86041-140, Caixa Postal 401, Londrina PR, Brazil. E-mail: anabenetti@hotmail.com

Research Article

Arzu Pinar Erdem, dds, phd, Elif Sepet, prof dr, Tam Avshalom, msc, Vitaly Gutkin, msc &  Doron Steinberg, prof, phd

Abstract: Purposes: (1) To determine the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and acidulated phosphate fluoride (APF) on S. mutans viability, (2) to observe their effects on biofilm structure, and (3) to examine the element content of the hydroxyapatite (HA) surfaces after exposure to CPP-ACP and APF. Methods: HA discs were coated with: CPP-ACP (GC Tooth-Mousse), APF, CPP-ACP+APF (1/1). Uncoated HA discs were used as control. Following application of the materials, the discs were immersed in human saliva and incubated with S. mutans ATCC (27315) for 24 hours. Growth of bacteria on the discs was evaluated by microbial culturing methods. The structure of the biofilm was examined with confocal laser scanning microscope (CLSM). The change in element content of HA surfaces (without biofilm) was evaluated with energy-dispersive x-ray spectroscopy (EDS). The values were statistically analyzed using Kruskal-Wallis and Dunn’s test. Results: The total number of bacteria of APF and CPP-ACP+APF applied groups were found significantly lower than the control group (P< 0.05). All specimens showed similar microbial colonization structure. No statistically significant differences were observed in O, F, Na, P, Ca content on HA surfaces after exposure to the tested agents, although fluoride concentration of the APF treated HA surfaces were increased compared to CPP-ACP, CPP-ACP +APF. (Am J Dent 2011;24:119-123).

Mail: Dr. Arzu Pinar Erdem, Istanbul University, Faculty of Dentistry, Department of Pedodontics, Capa/Istanbul 34093 Turkey. E-mail: pinararzuerdem@yahoo.com

Research Article

Strength and wear resistance of a dental glass-ionomer cement with a novel nanofilled resin coating

Ulrich Lohbauer, msc, phd, Norbert KrÄmer, dmd, phd, Gustavo Siedschlag, dmd, Edward W. Schubert, dmd, Brigitte Lauerer, dmd, Frank A. MÜller, msc, phd, Anselm Petschelt, dmd, phd  &  Johannes Ebert, dmd

Abstract: Purpose: To evaluate the influence of different resin coating protocols on the fracture strength and wear resistance of a commercial glass-ionomer cement (GIC). Methods: A new restorative concept [Equia (GC Europe)] has been introduced as a system application consisting of a condensable GIC (Fuji IX GP Extra) and a novel nanofilled resin coating material (G-Coat Plus). Four-point fracture strength (FS, 2 x 2 x 25 mm, 14-day storage, distilled water, 37°C) were produced and measured from three experimental protocols: no coating GIC (Group 1), GIC coating before water contamination (Group 2), GIC coating after water contamination (Group 3). The strength data were analyzed using Weibull statistics. Three-body wear resistance (Group 1 vs. Group 2) was measured after each 10,000 wear cycles up to a total of 200,000 cycles using the ACTA method. GIC microstructure and interfaces between GIC and coating materials were investigated under SEM and CLSM. Results: The highest FS of 26.1 MPa and the most homogenous behavior (m = 7.7) has been observed in Group 2. The coated and uncoated GIC showed similar wear resistance until 90,000 cycles. After 200,000 wear cycles, the coated version showed significantly higher wear rate (ANOVA, P< 0.05). The coating protocol has been shown to determine the GIC fracture strength. Coating after water contamination and air drying is leading to surface crack formation thus significantly reducing the FS. The resin coating showed a proper sealing of GIC surface porosities and cracks. In terms of wear, the coating did not improve the wear resistance of the underlying cement as similar or higher wear rates have been measured for Group 1 versus Group 2. (Am J Dent 2011;24:124-128).

Address: Dr. Raluca Pecie, Division of Cariology and Endodontology, University of Geneva, Rue Barthélemy-Menn 19, CH-1205 Geneva, Switzerland.  Email:  raluca.pecie@unige.ch