February 2011


Research Article

3D-FEA of stress levels and distributions for different bases under a Class I composite restoration

Yan Wang,  Zhengyu Liao,  Dan Liu, md,  Zhan Liu, phd,  Grant T. McIntyre, phd,  Fan Jian,Wei Lv, Jinbo Yang, phd,  Zhihe Zhao, phd   &   Wenli Lai, phd


Abstract: Purpose: To investigate the level and distribution of stresses in composite-restored mandibular first molars with various combinations of base materials. Methods: The finite element package Abaqus was used for the stress analysis. Several different base materials were evaluated [light-cured glass ionomer (LC-GI), chemically-cured calcium hydroxide (CC-CH), and light-cured calcium hydroxide (LC-CH)] in combination with light-cured composite (LC-CP). Four models of restored molars with Class I deep cavity preparations were simulated, including (1) LC-GI/LC-CP, (2) CC-CH/LC-CP, (3) CC-CH/LC-GI/LC-CP, and (4) LC-CH/LC-GI/LC-CP. A 250N static single-point load was applied vertically on the central fossa of the tooth to simulate physical loading conditions. Results: In each case, the peak stresses were found to be concentrated mainly at the interfaces between the various materials and the dental tissues. In the residual tooth structures, the maximum Von Mises stresses were 20.01 MPa in model LC-GI/LC-CP, 23.85 MPa in model CC-CH/LC-CP, 23 MPa in model CC-CH/LC-GI/LC-CP and 21.83 MPa in model LC-CH/LC-GI/LC-CP. In the LC-CP restorations, the maximum Von Mises stresses were 43.68 MPa in model LC-GI/LC-CP, 42.24 MPa in model CC-CH/LC-CP, 42.29 MPa in model CC-CH/LC-GI/LC-CP and 42.55 MPa in model LC-CH/LC-GI/LC-CP. In the bases, the maximum Von Mises stresses were 5.71 MPa in model LC-GI/LC-CP, 0.85 MPa in model CC-CH/LC-CP, 4.69 MPa in model CC-CH/LC-GI/LC-CP, and 4.93 MPa in model LC-CH/LC-GI/LC-CP. (Am J Dent 2011;24:3-7).


Clinical significance: This study supports the conclusions that (1) peak stresses in restored molars were mainly concentrated at the interfaces between the various materials and the dental tissues; (2) no clinically important differences were found in the stress levels and distributions within composite restored molars based with different combinations of glass-ionomer or calcium hydroxide.


Address: Dr. Wenli Lai, State Key Laboratory of Oral Diseases, Department of Orthodontics, West China College of Stomatology, Sichuan University, Chengdu 610041, China. Dr. Zhihe Zhao, State Key Laboratory of Oral Diseases, Department of Orthodontics, West China College of Stomatology, Sichuan University, Chengdu 610041, China. Email:




Research Article

Degree of conversion of dual-cure resins light-cured through glass-fiber posts


Francesca Cerutti, dmd,  Pier Antonio Acquaviva, dmd, Massimo Gagliani, md, dds,  Marco Ferrari, md, dds,Francesco Mangani, md, dds,  Laura E. Depero, prof  &  Antonio Cerutti, md, dds


Abstract: Purpose: To evaluate the degree of conversion (DC) of dual-curing materials used to lute glass-fiber posts in a simulated root canal polymerized by two different modalities. Methods: Artificial root canals were used to simulate a clinical condition to lute 45 posts by three different dual curing luting cements (Calibra, Multilink Automix and Variolink II). Two light cure modalities were chosen for each luting cement: standard (S group) 400 mW/cm2 for 120 seconds and high-power (H group) 1200 mW/cm2 for 40 seconds. Raman spectra were collected at different positions in the post surface (1, 3, 5 and 7 mm from the coronal-most portion of the post covered in cement) and the percentage degree of conversion was computed. The data were analyzed using ANOVA and post-hoc Student-Neuman-Keuls t-test (P= 0.05). Results: The DC of the tested luting composites decreased progressively while increasing the distance from the light tip. Regardless of the polymerization modality (H or S) applied. Conversely, the curing modality significantly influenced the DC of the tested materials, evidencing different responses to the same energy density: Calibra seemed to be less dependent on light-curing than the other tested materials, showing a constant behavior. Multilink Automix reached the highest DCs in the S group compared to the H mode. Variolink II showed an interesting drawback in DC at 7 mm when cured in the H model. Dual-cure materials show adequate monomer conversion but when the distance from the curing light increased, a variable, but significant lowering in conversion rate was observed. In addition, the time and power of curing appeared to be material-dependent and should be calibrated individually. (Am J Dent 2011;24:8-12).


Clinical significance: To obtain the best performances with dual curing luting materials, a careful choice of the polymerization modality should be taken into account and it could be provided by manufacturers.


Address: Dr. Francesca Cerutti, Department of Materials for Engineering, University of Brescia, Italy. Email:


Research Article

Morphology and microtensile bond strength of adhesive systems to in situ-formed caries-affected dentin after the use of a papain-based chemomechanical gel method


FlÁvia  Lucisano  Botelho  Amaral, dds, ms,  Flávia  MartÃo  FlÓrio, dds, ms scd, Glaucia Maria Bovi Ambrosano, agr eng, ms, scd  &  Roberta Tarkany Basting, dds, ms, phd


Abstract: Purpose: To evaluate the microtensile bond strength of adhesive systems to caries-affected dentin formed in situ after the use of a papain-based chemomechanical removal method. Methods: 84 human dentin specimens (5 x 5 x 3 mm) were sterilized and randomly distributed on palatal devices of 14 volunteers. Each palatal device, containing six dentin slabs, was used for 14 days according to a caries induction design involving plaque accumulation and sucrose use. After this, fragments were removed from devices and randomly assigned to two groups according to the caries removal method: (1) Chemomechanical (papain-based gel followed by curette), or (2) Mechanical (curette - control group). Specimens were subdivided into three subgroups according to the adhesive system tested: (SB) a two-step etch-and-rinse (Adper Single Bond 2); (SE) a two-step self-etching adhesive (Clearfil SE Bond) and (TriS) a one-step self-etching adhesive (Clearfil Tri-S Bond) and subsequently restored with microhybrid composite resin. After 24 hours, resin-tooth blocks were sectioned into 0.9 mm thick slabs, with one slab of each block being prepared for adhesive interface analysis by scanning electron microscopy, and the remaining blocks were sectioned into 0.8-mm2 sticks that were subjected to tensile stress (0.5 mm/minute). Data were subjected to two-way ANOVA and Tukey’s test at a 5% level of significance. Results: The application of the chemomechanical and mechanical methods to demineralized dentin did not affect the bond strength values. SB and SE adhesives promoted statistically similar and significantly higher bond strength values than the TriS. SEM analysis showed no interference of papain-based gel in the formation of hybrid layer; SB showed the thickest hybrid layer with presence of numerous tags; SE showed an intermediate hybrid layer thickness and quantity of tags and the TriS showed no evidence of tag formation. (Am J Dent 2011;24:13-19).


Clinical significance: The papain-based chemomechanical method did not affect the bond to caries-affected dentin, but the use of a one-step self-etching adhesive system should be avoided.


Address: Prof. Dr. Roberta Tarkany Basting, Faculty of Dentistry and Center for Dental Research São Leopoldo Mandic, Department of Restorative Dentistry - Operative, Rua José Rocha Junqueira, 13, Bairro Swift, Campinas – SP CEP: 13045-755, Brazil.  Email:

Research Article

New method of measuring water permeability of adhesive resin films


Rhoda J. Sword, dmd,  Jeremy J. Sword,  William W. Brackett, dds, msd,  Franklin R. Tay, bdsc, phd, David H. Pashley, dmd, phd   &   Franklin GarcÍa-Godoy, dds, ms


Abstract: Purpose: To adapt a simple gravimetric method to measuring the permeability of adhesive resin films to liquid water, and to compare this to the water vapor permeability of the same resins. Methods: Using commercially-available permeability cups designed for industrial permeability testing, the loss of mass of water vapor or liquid water from a stainless steel cup sealed with a resin film was measured over 1-2 days. The permeabilities of Parafilm (control), Clearfil SE Bond adhesive, Xeno IV and One-Up Bond F were compared. Results: The lowest resin film permeability was obtained with Clearfil SE Bond adhesive films.  The permeabilities of Xeno IV and One-Up Bond F to liquid water were 2.76 and 3.27-fold higher (P< 0.001) than that of Clearfil SE Bond adhesive.  Liquid water permeability was always 2.8-3.8-fold higher (P< 0.05) than water vapor transmission rate. It was concluded that quantitative comparisons of the permeability properties of resin films can be made gravimetrically. The large permeability cups that are available commercially may be reduced in size in the future for measuring dentin adhesive films with smaller surface areas that are less liable to contain imperfections. (Am J Dent 2011;24:20-26).


Clinical significance: The permeability to liquid water of adhesive resin films shows promise as a means of screening for adhesives too permeable to form durable dentin bonds.


Address: Dr. William W. Brackett, Department of Oral Rehabilitation, School of Dentistry, Medical College of Georgia, Augusta, Georgia 30912-1260, USA.  Email:


Research Article

Comparison between water and ethanol wet bonding of resin compositeto root canal dentin


Salvatore Sauro, phd, Simona Di Renzo, dds, Raffaella Castagnola, dds, Nicola M. Grande, dds, phd, Gianluca Plotino, dds, phd, Federico Foschi, dds, phd  &  Francesco Mannocci, md, dds, phd


Abstract: Purpose: To evaluate the bond strength of resin dentin interfaces created with adhesives applied on root dentin using the water wet or ethanol wet bonding technique. The morphology of resin dentin interfaces was evaluated using confocal microscopy. Methods: Four experimental resin adhesives (R#A to R#D) and one commercial three-step/etch and rinse adhesive were applied to the root canal dentin of endodontically treated single canal incisors using the water (control) or ethanol wet bonding technique. The ethanol wet bonding substrate was achieved by keeping the root canal immersed in absolute ethanol (100%) for 3 minutes. The root dentin bonded specimens were sectioned into beams, stored in distilled water (24 hours) and finally tested for microtensile bond strengths (µTBS). Additional dentin surfaces were conditioned and bonded as previously described. They were prepared for the microscopy study and finally observed using confocal microscopy. Results: The ethanol wet bonding technique gave higher bond strength values for all the adhesives tested: in Group 1 (water wet bonding technique) no significant difference was found between the resins tested; the only exception being the most hydrophilic Resin #4 showing the highest bond strength values (P< 0.05). In Group 2 (ethanol wet bonding technique) no statistical differences were present between Resin #A and Resin #D. Resin #C showed the highest bond strength values. Confocal microscopy showed better resin diffusion and hybrid layer formation when the ethanol wet bonding was used. (Am J Dent 2011;24:25-30).




Clinical significance: The use of the ethanol wet bonding technique resulted in higher bond strength values with all the adhesives tested. This technique also offers the possibility to bond using resin adhesives containing no hydrophilic and/or acidic monomers to root dentin.


Address: Dr. Salvatore Sauro, Biomaterials, Biomimetics & Biophotonics, King’s College London Dental Institute at Guy’s, King’s College and St. Thomas’ Hospitals, Floor 17, Guy’s Hospital, London, UK.  Email:



 Research Article

Influence of salivary enzymes and alkaline pH environment on fatigue behavior of resin composites


Hesam  Mirmohammadi, dds, phd,  Cornelis  J.  Kleverlaan, phd,  Moustafa  N.  Aboushelib, dds, msc, phd &  Albert  J.  Feilzer, dds, phd


Abstract: Purpose: To evaluate the effect of enzymatic activity and alkaline medium on flexural strength and rotary fatigue resistance of direct and indirect resin composite restorative materials. Methods: Three direct resin composite materials Filtek Z100, Filtek Z250 and Filtek Silorane (3M ESPE), and two indirect resin composite materials; Sinfony (3M ESPE) and an experimental composite (Heraeus Kulzer) were used to fabricate bar-shaped specimens (2 x 2 x 25 mm; n = 10) to determine the flexural strength (Fs) by means of a 3-point bending test according to ISO 4049. Additional specimens of the same dimensions (n = 20) were used to prepare hour-glass shaped specimens which were immersed in distilled water for 48 hours, transferred to one of five aqueous media at 37°C for 2 weeks; phosphate buffer, distilled water, 0.1N NaOH, 1 unit/ml Amylase, 0.1 unit/ml Esterase, and a group in 0.1N NaOH at 60°C. Rotary fatigue resistance (RFR) was determined in a rotating-bending cantilever test with the highest stress located at the constriction of the hour glass. The rotary fatigue resistance tests were conducted according to the staircase approach (104 cycles, 1.0 Hz) and the mean RFR was calculated using logistic regression analysis. Results: NaOH produced a significant decrease in Fs of all materials. The effect of enzymatic biodegradation on Fs of Filtek Z100 and Filtek Z250 was found to be significant, however, for Silorane and indirect composites it was not significant. Except for NaOH the influence of the different aqueous solutions on RFR was not significant for all tested materials. For all materials the RFR was about 22-53% lower than the corresponding Fs. (Am J Dent 2011;24:31-36).


Clinical significance: Beside the deteriorating effect of fatigue, the mechanical properties of resin composites are also affected by the chemical and biological degradation in the oral environment.


Address: Prof. Dr. A.J. Feilzer, ACTA, Department of Dental Materials Science, Louwesweg 1, 1066 EA Amsterdam, The Netherlands. Email:


Research Article

Shortest exposure time possible with LED curing lights


Inga Busemann, dr med dent,  Claudia Lipke,  Anke schattenberg, dr med dent, Brita Willershausen, prof, dr med dent   &  Claus-Peter Ernst, prof, dr med dent


Abstract: Purpose: To investigate the shortest exposure time of different light emitting diode (LED)-curing devices for different resin composites in a clinically relevant laboratory model. Methods: Nine LED curing devices (Bluephase, Bluephase 16i, Bluephase G2, Bluephase 20i/Ivoclar Vivadent, DEMI/sds Kerr, Elipar FreeLight 2, Elipar S10/3M ESPE, Radii plus/SDI, mini LED Autofocus/Satelec) were investigated to polymerize Tetric EvoCeram (TEC) and Filtek Supreme XT B (FS) in the shades A1, A2, A3, A3.5, and A4. The Bluephase 20i was investigated in its high power and turbo modes. Stainless steel molds (Ø = 5 mm, h = 6 mm, six resin composite test samples per curing device, material, and shade) were filled in three increments of 2 mm thickness each and incrementally exposed with the light guide tip in a 7 mm distance from the bottom side to simulate a Class II curing situation. Surface hardness was measured 10 minutes post exposure at bottom surfaces of resin samples (n= 3 per sample). A bottom/top-surface hardness ratio of 80% of a reference surface hardness cured at a zero-distance (40 seconds) was defined as clinically acceptable for safe curing. A statistical analysis (Excel) was carried out. Results: To ensure a ratio in surface hardness of at least 80% the minimal exposure time(s) were: Elipar FreeLight 2, DEMI: TEC and FS: 10 seconds for all shades, except DEMI FS A4: 20 seconds. Elipar S10: 10 seconds for both, TEC and FS shades A2-A4 but 5 seconds for shades A1. Bluephase, Bluephase 16i and Bluephase G2: FS: 10 seconds for shades A1-A3.5; 20 seconds for shade A4. TEC: Bluephase: A1-A3.5: 10 seconds, A4: 20 seconds. Bluephase 16i: A1-A3: 10 seconds; A3.5 + A4: 30 seconds. Bluephase G2: A1-A3: 10 seconds; A3.5 + A4: 20 seconds. Bluephase 20i-HIP: 10 seconds for all shades of TEC and FS, Bluephase 20i-Turbo: 10 seconds for all shades of TEC but 5 seconds for all shades of FS: Radii plus: TEC A1-A3: 10 seconds; A3.5+A4: 20 seconds. FS A1, A2 and A4: 10 seconds; A3+A3.5: 20 seconds. Mini LED Autofocus: TEC A1, A3, A3.5: 10 seconds; A2: 15 seconds; A4: 20 seconds. FS A1: 5 seconds; A2-A4: 10 seconds. In its turbo mode with a 5-second exposure time, the Bluephase 20i was able to polymerize all shades of FS, but not of TEC. For the Elipar S10 and the Mini LED Autofocus this was also possible for the A1 shade of FS; for Elipar S10 additionally for TEC. The higher power of the Bluephase G2 and the S10 LED allowed the use of an enhanced light guide tip diameter while the exposure time was not affected compared to their predecessors equipped with an 7.5 or 8 mm light guide tip diameter respectively. Nevertheless, 10 seconds should be the minimal exposure time recommended for lighter shades under optimal circumstances. (Am J Dent 2011;24:37-44).


Clinical significance: When using darker shades clinicians should increase the exposure time to improve the degree of conversion and the mechanical properties of the resin composite. Additionally, an enhanced light guide tip with an adequate power density should be preferred to avoid many overlapping polymerization cycles. A possible 5-second polymerization as claimed by some manufacturers should be employed carefully.


Address: Dr. Inga Busemann, Department for Operative Dentistry, University Medical Center, Johannes Gutenberg University Mainz, Augustusplatz 2, 55131 Mainz, Germany. Email:



Research Article

Relationship between caries and dental plaque composition  

Sule Bayrak, dds, phd,  Zeynep Ökte, dds, phd  &  Ulvi Reha Fidanci, dvm, phd


Abstract: Purpose: To evaluate the relationship between dental caries and the biochemical composition of dental plaque and to determine the effect of a 10% sucrose solution on the biochemical structure of dental plaque in children. Methods: 60 children grouped according to caries status took part in this study [Caries-free (CF), DMFS= 0, df-s= 0; Caries-positive (CP), DMFS ≥ 10, df-s ≥ 10]. Dental plaque samples were collected before (baseline) and at 3 and 30 minutes after a 1-minute rinse with 10% sucrose. Fluoride (F), calcium (Ca), and inorganic phosphorus (Pi) levels were determined using ion chromatography, and insoluble polysaccharide (IEPS) concentrations were determined using colorimetric analysis. Results: Although the mean baseline Ca and Pi levels in plaque were higher in the CF group than in the CP group, these differences were not statistically significant. Baseline IEPS levels were significantly higher in the CP group than in the CF group. Following exposure to sucrose, plaque F, Ca and Pi concentrations decreased significantly in both groups. However, insoluble polysaccharide concentrations increased significantly in the CF group only. (Am J Dent 2011;24:45-48).


Clinical significance: Insoluble extracellular polysaccharide concentration in dental plaque may be a marker of dental caries.


Address: Dr. Sule Bayrak, Department of Pediatric Dentistry, Faculty of Dentistry, University of Ondokuz Mayıs, 55139, Kurupelit, Samsun, Turkey.   Email:



Research Article

Effect of different concentrations of carbamide peroxide on microhardness of dental ceramics


SÉrgio  A.M.  Ourique, dds, ms,  Jovana  P.S.  Magdaleno, dds,  Cesar  A.G.  Arrais, dds, ms, phd &  JosÉ  A.  Rodrigues, dds, ms, phd


Abstract: Purpose: To evaluate the effect of 10% and 16% carbamide peroxide bleaching agents on microhardness of dental ceramics after different periods of bleaching treatment. Methods: 15 specimens with 5 x 3x 1 mm3 were created with four dental ceramics following manufacturers' instructions: IPS Classic (Ivoclar-Vivadent); IPS d.Sign (Ivoclar-Vivadent); EX3 (Noritake); VMK-95 (Vita). A microhardness tester with a Knoop diamond with a 100 g load was used to evaluate the baseline microhardness values of all ceramics. Afterwards, the specimens were submitted to 6-hour daily bleaching treatments with 10% or 16% carbamide peroxide (Whiteness Perfect - FGM) for 21 days, while control groups from each ceramic system were maintained in artificial saliva. The microhardness of all groups was evaluated at 18, 42, 84, and 126 hours of bleaching treatment. The mean value of five indentations performed at each specimen in each time was obtained and all data were submitted to two-way repeated measures ANOVA and Tukey’s post-hoc test (α=0.05). Results: No significant differences in ceramic microhardness were observed among either bleaching intervals or bleaching treatments. Ceramic restorations are not affected by carbamide peroxide 10% or 16% gel during bleaching treatment. (Am J Dent 2011;24:57-59).


Clinical significance: This study provided evidence that at-home bleaching systems do not cause detrimental effects on dental ceramics.


Address: Cesar Augusto Galvão Arrais, Praça Tereza Cristina, 229 – Centro,  Guarulhos -SP, CEP: 07023-070, Brazil.  Email:


Research Article

Removal of dental plaque from different regions of the mouth after a 1-minute episode of mechanical oral hygiene


Kakarla V.V. Prasad, bds, mph,   Prem K. Sreenivasan, phd,   Subhash Patil, mds,  Kumar G. Chhabra, mds , Shivalingappa B. Javali, phd  &   Wiliam DeVizio, dmd


Abstract: Purpose: To assess dental plaque on different regions of the dentition prior to and immediately after toothbrushing. Methods: Subjects refrained from oral hygiene for 22-26 hours prior to baseline whole mouth plaque assessments by the Turesky modification of the Quigley-Hein Index (TMQH). All subjects brushed with a marketed soft-bristled toothbrush and a fluoride dentifrice for 1 minute prior to post-brushing plaque assessments similar to baseline. One calibrated clinical examiner conducted all measurements. Results: 30 subjects (mean age 23 years) completed the study. Irrespective of arch, posterior teeth harbored higher frequencies for scores of 3-5 than corresponding anterior teeth prior to brushing. In comparison to the pre-brushing examination, scores of 0-1 were more common in the post-brushing evaluation, however, greater frequencies of higher plaque were observed on posterior than on anterior regions. Irrespective of gender, subject or arch, anterior teeth harbored lower mean amounts of plaque than posterior teeth by ANOVA at both clinical examinations (P< 0.0001). Additionally, irrespective of arch, lower mean scores for plaque were observed on anterior teeth than from posterior teeth or the whole mouth at both examinations (P< 0.001). Lingual and molar surfaces consistently harbored large densities of plaque and represented areas with the least plaque removal after toothbrushing. Mid-vestibular sites represented the areas with the highest percent removal of plaque at 65% and harbored significantly lower levels of plaque than proximal sites during all phases of the study (P≤ 0.0059). (Am J Dent 2011;24:60-64).


Clinical significance: Anterior teeth and mid-vestibular surfaces consistently harbored significantly lower amounts of dental plaque in contrast to higher amounts on molar, lingual and posterior regions. Significant differences between the dentition for plaque deposits underscore reasons to evaluate teeth including those accumulating more dental plaque during oral hygiene examinations.


Address: Dr. Prem K. Sreenivasan, Colgate-Palmolive Company, 909 River Road, Piscataway, NJ 08855, USA.  Email:




Review Article


Noncarious cervical lesions  – A clinical concept based on the literature review. Part 1: Prevention


Raluca Pecie, dr, Ivo Krejci, prof dr med dent, Franklin Garcia-Godoy, dds, ms  &  Tissiana Bortolotto, dr, phd


Abstract: Purpose: Due to an increased prevalence of non-carious cervical lesions (NCCL), a clinical strategy for this lesion type should be considered. Previous reviews focused mainly on etiology and prevalence. In Part 1 of this paper, an evidence-based support for a preventive strategy of NCCL was elaborated. Methods: Literature over the last 10 years available in the MEDLINE database was reviewed in order to find clinical evidence for a preventive approach to NCCL. Recommendations were based primarily on systematic reviews, clinical evaluations and a monograph. Results: The etiology of NCCL is currently considered to be rather multifactorial, as clinical investigations found multiple factors associated with this type of lesions and due to the lack of evidence to support exclusively one or another factor. Based on the hypothesis of multifactorial origin, a preventive protocol has been established. No clinical research exists with respect to the prevention of NCCL and long-term clinical evaluations of the proposed preventive measures are needed. (Am J Dent 2011;24:49-56).


Clinical significance: The slow progression, the high capacity of self-defense by producing sclerotic dentin, and the lack of evidence for tooth weakening in the absence of a restoration are evidence-based findings supporting a “wait and see” philosophy. Restoration could be postponed in the absence of esthetic demands, sensitivity or threat to the integrity of the tooth. Restoration should not always be the first treatment of choice, although there still remains to be established to what extent prevention could replace restoration.


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



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