Abstracts of the February 2008 Issue

Is surface roughness of resin composites affected by operator’s performance?

 Martin  Jung, dds , phd,  Andreia  Otte, dds   &  Joachim  Klimek, dds , phd

   Abstract: Purpose: To assess intra-individual and inter-individual differences in applying finishing diamonds and rubber polishers to composite specimens with special reference to surface roughness. Methods: The composite Herculite XRV was used to fabricate 120 specimens. Four human operators with varying experience (Operators 1 to 4) and an automatic mechanical device (Operator 5) were selected for the task of preparation. At baseline, six specimens were prepared by each operator using a 30 µm finishing diamond and six other specimens were prepared by each operator using Astropol polishing cups. After 48 hours, the entire procedure was repeated using new specimens and instruments. All the specimens were assessed for surface roughness by optical profilometry. Average roughness (Ra) and profile-length ratio (LR) were calculated. Intra-individual (baseline/48 hours) and inter-individual (Operators 1 to 5) differences were statistically analyzed by two-way and one-way ANOVA. Results: With respect to finishing, there was a significant inter-individual effect between the four human operators and the mechanical device in terms of Ra (P= 0.007) but not in terms of LR. With respect to polishing, the five test groups had a significant effect on Ra and LR values (P< 0.001 in both cases). Overall, finishing and polishing performed at baseline or after 48 hours had no significant effect on surface roughness values. (Am J Dent 2008;21:3-6).

 *: Prof. Dr. Martin Jung, Justus-Liebig-University, Faculty of Dentistry, Policlinic for Operative and Preventive Dentistry, Schlangenzahl 14, D-35392 Giessen , Germany .  E-*: martin.jung@dentist.med.uni-giessen.de

Improving the completeness and transparency of reports of randomized trials in oral health: The CONSORT Statement

Ian  Needleman, phd, fdsrcs (eng),  Helen   Worthington , phd,  David  Moher, phd,  Ken  Schulz, phd &  Douglas  G.  Altman, dsc

 Abstract: Purpose: Randomized trials provide essential evidence of the effect of interventions in oral health. Such trials need to be appraised by readers in order to decide whether to incorporate new findings into clinical practice and policy in a timely manner. The CONSORT (Consolidated Standards of Reporting of Trials) Statement is a guidance to facilitate reporting of randomized controlled trials (RCTs) and was first introduced in 1996. The purpose of this article is to highlight the importance of rigorous reporting of trials in oral health and to discuss the impact of CONSORT on trial reporting. Results: Empirical studies demonstrate that key aspects of trial methods influence the size of estimates of studied interventions and bias is a plausible mechanism for some of this effect. Complete and transparent reporting of these methods allows appraisal of the value of trials to be undertaken and the potential for bias to be estimated. Systematic reviews have shown that the reported quality of trials in dentistry is poor, thus hindering the understanding of the value of individual trials. Since 1996, CONSORT has been adopted by hundreds of medical journals, international editorial groups, and five dental journals. A systematic review has shown that the quality of reporting of trials improves in journals that have adopted this guidance, although with significant variation, most likely due to differing levels of editorial adherence to it. (Am J Dent 2008;21:7-12).

 *: Dr. Ian Needleman, International Centre for Evidence-Based Oral Health, Unit of Periodontology, UCL Eastman Dental Institute, 256 Gray’s Inn Road, London WC1X 8LD, United Kingdom.  E-*:  I.Needleman@eastman.ucl.ac.uk

 Toothbrushing before or after an acidic challenge to minimize tooth wear? An in situ/ex vivo study  

Annette Wiegand, dr med dent ,  Sebastian Egert  cand med dent    &  Thomas Attin, prof dr med dent  

Abstract: Purpose: To evaluate whether patients should be advised to perform toothbrushing before or after an acidic challenge to minimize enamel and dentin wear by brushing abrasion. Methods: The study was a two-period crossover design (A and B, each 14 days) in which three enamel and dentin specimens were fixed in intraoral appliances of 10 volunteers. The following regimens were performed three times a day with at least 4 hours in between: A: 20-second brushing treatment in an automatic brushing machine, 5 minutes intraoral exposure of the specimens, extraoral erosion of enamel and dentin specimens for 40 seconds or B: Extraoral erosion for 40 seconds, 5 minutes intraoral exposure of the specimens, 20-second brushing treatment in an automatic brushing machine. Enamel and dentin loss at the end of each 14-day regimen was assessed by profilometry and statistically analyzed by t-test. Results: For all volunteers, mean enamel and dentin wear was significantly lower when brushing treatment was performed before erosion (A: enamel: 2.3 ± 1.0 μm, dentin: 4.1 ± 1.6 μm) than when brushing was applied after erosion (B: enamel: 6.4 ± 3.0 μm, dentin: 15.3 ± 6.8 μm). It was concluded that patients awaiting an erosive attack should perform toothbrushing prior to rather than after an acidic challenge to minimize enamel and dentin wear. (Am J Dent 2008; 21:13 -16).

 *: Dr. Annette Wiegand , Clinic for Preventive Dentistry, Periodontology and Cariology, University of Zürich, Plattenstrasse 11, CH-8032 Zürich, Switzerland.  E-*: annette.wiegand@zzmk.unizh.ch

Comparison of two low sensitivity whiteners

Richard S. Callan, dmd, William D. Browning, dds , ms , Mary C. Downey , rdh , ma , Martha G. Brackett, dds , ms   &  William W. Brackett, dds , msd  

Abstract: Purpose: To evaluate two commercially available doctor-supplied, patient-applied, bleaching systems for their ability to whiten the maxillary anterior teeth while at the same time not causing sensitivity. Methods: 46 participants were randomly assigned to one of two groups: One group received Rembrandt Xtra-Comfort and the other group Nite White Excel 2Z. Bleaching stents were fabricated and the bleaching systems were used following manufacturers’ instructions. Participants recorded tray use and any sensitivity on a daily basis. Participants bleached for 2 weeks followed by 2 weeks of no bleaching. Color was evaluated at the first, second and fourth week following the initial delivery of bleaching trays. Color change was measured using the Vita Classic Shade Guide arranged by value. Results: As a group, participants in the NW2Z group bleached for 302 days with a total of 48 days (16%) of sensitivity recorded. The Rembrandt Xtra Comfort group bleached for 313 total days with 97 days (31%) of sensitivity recorded. The difference in sensitivity between the two products proved to be statistically significant (Chi-square analysis, P≤ 0.0001). The median shade change for both products following 2 weeks of active treatment was six tabs. At the 4-week evaluation, the median shade change was 5.5 and 6.0 tabs respectively for Rembrandt and Nite White. There was no statistical difference between the products in respect to shade change. (Am J Dent 2008; 21:17 -20).  

 *: Dr. Richard S. Callan, 1120 15th Street , AD2211, Augusta , GA 30912-1260 , USA . E-*: rcallan@mail.mcg.edu

Opinions of dental professionals from a large American insurance system on outcome of non-surgical root canal treatment  

Ilan  Rotstein, dds   &  Robert Salehrabi, dds  

Abstract: Purpose: To assess the opinions of dental professionals working within the Delta Dental insurance system regarding the predictability of initial endodontic treatment, expected long-term outcome and the importance of placing a coronal coverage after completion of treatment. Methods: An eight-item questionnaire was distributed among participants attending a continuing education course. The questionnaire included four items on practice profile and demographics and four multiple-choice questions regarding participants’ opinions on endodontic treatment outcome. Results: 51% of participants responded that the expected retention rate of teeth 5-10 years after endodontic treatment was more than 90%. Sixty-eight percent of participants responded that the need for additional treatment was expected to occur within the first 3 years after initial endodontic treatment. 87% of participants responded that placing coronal coverage after completion of endodontic treatment was very important for long-term tooth retention. Ninety-three percent of participants responded that overall, endodontic treatment was a predictable procedure with long-term tooth retention rate. Statistically significant associations were found between (1) year of experience and expected rate of retention (P< 0.01); (2) participants’ years of experience and their responses regarding the need for additional treatment (P< 0.05); and (3) their opinions that endodontic treatment was a predictable procedure with long-term tooth retention rate (P< 0.05). (Am J Dent 2008; 21:21 -24).  

 *: Dr. Ilan Rotstein, University of Southern California , School of Dentistry , 925 West 34th Street, Suite 310 , Los Angeles , CA 90089-0641 , USA .  E-*: ilan@usc.edu

 Comparison of visual inspection, radiographic examination, laser fluorescence and their combinations on treatment decisions for occlusal surfaces  

Fabiano  Bassalobre Valera, dds , msc ,  Juliano  Pelim  Pessan, dds , msc , Rubens  Carneiro  Valera, dds , msc , phd, José  Mondelli, dds , msc , phd   &   Célio  Percinoto, dds , msc , phd  

Abstract: Purpose: To compare visual inspection (VI), radiographic examination (RX) and the laser fluorescence device DIAGNOdent (L), as well as their combinations in vitro regarding treatment decisions for occlusal surfaces. Methods: 72 extracted human permanent teeth (molars and premolars) were used. Treatment decisions were recorded by three calibrated examiners, and the options available were fissure sealant and conservative restoration. For validation of treatment decisions, the teeth were sectioned and examined in a stereomicroscope. Thereafter, dental slices were scanned and the images were edited to facilitate classification of existing carious lesions. Intra and inter-examiner reproducibility for the determination of treatment plans were calculated using Cohen’s kappa test (95%-CI). Sensitivity, specificity, positive and negative predictive values, and the area under the ROC curve were also calculated. Results: VI and L provided on average the greatest intra- and inter-examiner reproducibility, respectively. Although the combination of diagnostic methods may decrease both intra- and inter examiners reproducibility, combination of VI, L and RX resulted in the greatest sensitivity, being statistically superior to RX and L. There was more inter-examiner agreement for the option of restorative treatment, while the use of sealants as a treatment option yielded the lowest values. Negative predictive values were numerically inferior to positive predictive values, indicating that the examiners preferred not to restore a carious tooth than to proceed operatively in an intact tooth. The combination of the three methods studied showed the best results in determining treatment plans for occlusal surfaces, when compared to the other types of exams. On the other hand, radiographic examination and laser fluorescence were less efficient when used alone. (Am J Dent 2008; 21:25 -29).  

 *: Dr. Célio Percinoto, Department of Pediatric and Social Dentistry, Araçatuba Dental School, São Paulo State University, Rua José Bonifácio, 1193, Araçatuba, SP 16015-050, Brazil.  E-*: percinoto@foa.unesp.br

 Early and 24-hour bond strength and degree of conversion of etch-and-rinse and self-etch adhesives  

Fernanda Tranchesi Sadek, dds , phd, Fernanda Calabró Calheiros, dds , phd, Paulo Eduardo Capel Cardoso, dds , phd, Yoshio Kawano, mchem, phd, Franklin Tay , bdsc (hons), phd  &  Marco Ferrari, md, dds , phd  

Abstract: Purpose: To evaluate early and 24-hour microtensile bond strength (µTBS) and the degree of conversion (DC) of one representative adhesive system from each of the four current bonding approaches. Methods: 40 human molars were sectioned occluso-gingivally into two halves. Resin composite was bonded incrementally to flat, mid-coronal dentin, using the adhesives Adper Scotchbond MP (MP); Adper Scotchbond 2 (SB); Clearfil SE Bond (SE); and Adper Prompt L-Pop (LP) according to the respective manufacturer’s instructions (n= 10). One half was immediately sectioned into sticks and subjected to µTBS test. As the sectioning process took approximately 1 hour, the results were designated as 1-hour bond strengths. The other half was stored in distilled water at 37°C for 24 hours before being sectioned and tested. The DC of these systems was measured using Fourier Transform-Raman spectroscopy in three periods: immediately, 1 and 24 hours after polymerization. Data were analyzed with ANOVA and Tukey’s tests. Results: There were no significant differences between the 1-hour and 24-hour bond strengths (P> 0.05), or among the DC measured immediately, 1 hour and 24 hours after polymerization (P> 0.05). However, significant differences were observed among adhesives (P< 0.05). µTBS values obtained, in MPa (1 hour/24 hour), were: SB (48.6 + 1.3/48.4 + 3.5) = SE (51.9 + 4.7/53.3 ± 2.9) > MP (35.3 ± 10.9/38.6 + 6.7) > LP (25.5 + 1.1/26.0 + 1.5). The DC, in percentage (immediately/1hour/24 hour), were: SE (81/82/87) > MP (79/77/81) > SB (60/63/65) > LP (39/37/42). (Am J Dent 2008; 21:30 -34).  

  *: Dr. Fernanda Tranchesi Sadek , Department of Dental Materials, Av. Professor Lineu Prestes 2227, CEP: 05508-900 São Paulo , SP, Brazil .  E-*:  fernandasadek@gmail.com

 The effects of ozone gas application on shear bond strength of orthodontic brackets to enamel  

Amna Hassan Al Shamsi, bds ,  James Leo Cunningham, phd, ceng, csci, Fimmm, Philip-John Lamey, bsc , bds , mbchb, dds , fds , rcps, ffd , rcsi, fds rcs &  Edward Lynch, bdentsc , ma , phd, fdsrcslond, fadfe  

Abstract: Purpose: To investigate the possibility that ozone may have an adverse effect on the bond strength of orthodontic brackets and to determine the area of residual adhesive on teeth after the debonding of brackets. Methods: 60 extracted premolars teeth were used in this study. Resin coated APC brackets (3M) were bonded according to the manufacturers’ instructions. Bonded teeth were randomly divided into two groups. The teeth in Group 1 were subjected to a 10-second dosage of ozone from the HealOzone unit (Kavo) after etching and to a further 10 seconds of ozone after bonding the brackets using a 5 mm delivery cup. Teeth in Group 2 were used as a control. Debonding was carried out using a testing instrument at a cross-head speed of 1 mm/minute. Results: The Mann-Whitney test revealed no significant differences in shear bond strength between the two groups (P= 0.337). The mean shear bond strength (11.66 MPa) of Group 1 (subjected to ozone) was not significantly different than the mean shear bond strength (10.88 MPa) of Group 2 (not subjected to ozone). A Pearson Chi-square test of the Adhesive Remnant Index ( ARI ) revealed no significant difference in residual adhesive among the groups tested. (Am J Dent 2008; 21:35 -38).  

*: Amna Hassan Al Shamsi, Restorative Department, School of Dentistry , Queen's University, Grosvenor Rd. , Belfast , Northern Ireland   BT12 6BP , United Kingdom .  E-*: alshamsiamna@hotmail.com

 The effect of a chlorhexidine containing cavity disinfectant on the clinical performance of high-viscosity glass-ionomer cement following ART : 24-month results  

Nazan Kocatas Ersin, phd, dds ,   Arzu Aykut, dds ,   Umit Candan, dds ,  Özant Önçağ, phd, dds , Cemal Eronat, phd, dds    &  Timur Kose, phd, dds  

Abstract: Purpose: To evaluate the effect of a chlorhexidine-gluconate-based cavity disinfectant on the clinical performance of high viscosity glass-ionomer cement following the ART approach under field conditions after 24 months. Methods: 126 school children 6-8 years old who had bilateral matched pairs of carious Class I and II primary molars were included. A split mouth design was used in which Ketac Molar was randomly placed with or without the use of chlorhexidine-gluconate-based cavity disinfectant on contralateral sides by three dentists. The restorations were evaluated after 6, 12 and 24 months by two experienced examiners using USPHS-Ryge criteria. Results: The 24-month mean cumulative survival rates of Ketac Molar without the use of disinfectant were 97.7% and 69.4% while in the disinfectant group, the survival rates were 95.2% and 63.9% in Class I and II restorations, respectively with no significant difference between the groups in both class types. In the non-disinfected group, large Class II cavities had significantly better survival rates than did small Class II cavities (P= 0.023). In the disinfected group, the failure rates in mean cumulative survivals from 6 to 12 months and 12 to 24 months significantly increased with time (P= 0.004 and P= 0.016 respectively). (Am J Dent 2008; 21:39 -43).  

 *: Dr. Nazan Kocatas Ersin, Department of Pediatric Dentistry, Ege University , Bornova-Izmir, 35100 Turkey .  E-*: nazan.ersin@ege.edu.tr

 Influence of dentin acid-etching and NaOCl-treatment on bond strengths of self-etch adhesives  

Maria   Carolina  G.  Erhardt, dds , ms, phd,  Estrella  Osorio , dds , phd,  Fátima  S.  Aguilera, dds , phd, Jatyr  P.  Proença, dds ,  Raquel  Osorio, dds , phd  &  Manuel  Toledano, md, bds  

Abstract: Purpose: To determine the microtensile bond strength (µTBS) of one- and two-step self-etch adhesives bonded to sound dentin conditioned or not with phosphoric acid (H₃PO₄) and sodium hypochlorite (H₃PO₄ + NaOCl). Methods: Extracted human third molars had their crowns transversally sectioned to expose flat dentin surfaces that were divided into four groups, and bonded as follow: (1) according to the manufacturers’ directions, (2) acid etched with 36% H₃PO₄, and (3) 10% NaOCl treated for 2 minutes, after H₃PO₄ etching. Two two-step self-etching primers (Clearfil SE Bond/ SEB and Resulcin/RE), and two one-step adhesives (One-Up Bond F/OUB and Etch & Prime 3.0/EP) were examined. Composite build-ups were constructed incrementally with Tetric Ceram. The specimens were stored in humidity for 24 hours at 37°C and sectioned into beams of 1.0 mm² cross-sectional area. Each beam was tested in tension in an Instron machine at 0.5 mm/minute, and mean µTBS data (MPa) were analyzed by 2-way ANOVA and post-hoc multiple comparisons tests (P< 0.05). Results: The two-step adhesive SEB exhibited the highest bond strength when bonded to smear layer-covered dentin, whereas RE was not affected by all dentin surface conditions. H₃PO₄ and H₃PO₄ + NaOCl pretreatments significantly increased bonding efficacy of the one-step adhesives OUB and EP, respectively. (Am J Dent 2008; 21:44 -48).  

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

 A clinical evaluation of a resin composite and a compomer in non-carious Class V lesions. A 3-year follow-up  

Sarah Pollington, bds , mmedsci, mfds rcps  &  Richard van Noort, bsc , dphil  

Abstract: Purpose: To compare the clinical performance of a resin composite and a polyacid-modified resin composite (compomer) in non-carious cervical lesions using a one-step self-etch adhesive. Methods: Thirty patients, each with two non-carious cervical lesions (60 restorations), received one composite (Pertac-II) restoration and one compomer (Hytac) restoration, both used in conjunction with a self-etch adhesive (Prompt L-Pop) and placed following the manufacturer’s instructions. Evaluations were at baseline, 6, 12 and 36 months after placement for retention, margin adaptation, marginal discoloration, anatomic form, secondary caries and postoperative sensitivity. Statistical analysis with the Pearson Chi-square test was undertaken. Results: Retention rates were 86.6% for composite and 86.7% for compomer at 36 months. 3.3% of composite and 6.7% of compomer restorations showed a deficiency in marginal adaptation. Both materials showed a slight marginal discoloration of 7.7%. More deterioration in anatomic form occurred with the compomer (11.5%) than the composite (3.8%). None of the restorations exhibited secondary caries or postoperative sensitivity problems. There was no significant difference in performance between the materials in any of the categories evaluated (Am J Dent 2008; 21:49 -52).  

 *: Dr. Sarah Pollington, Department of Adult Dental Care, School of Clinical Dentistry, University of Sheffield , Claremont Crescent , Sheffield , South Yorkshire , S10 2TA  United Kingdom .  E-*:  s.pollington@sheffield.ac.uk

 Flowable composites as intermediate agents without adhesive application in resin composite repair  

Federica  Papacchini, dds , msc , phd, Ivana  Radovic, dds , msc , Elisa  Magni, dds , msc , Cecilia  Goracci, dds , msc , phd,  Francesca  Monticelli , dds , msc , phd,  Nicoletta  Chieffi, dds , msc ,phd, Antonella  Polimeni, md, dds   &   Marco  Ferrari, md, dds , phd  

Abstract: Purpose: To evaluate the effect of different intermediate resin agents on composite-to-composite microtensile bond strength (µTBS). Methods: Composite disks (8 x 4 mm) of Gradia Direct Anterior (N=15) and Filtek Supreme XT (N=15), stored in a saline solution at 37°C for 1 month, were sandblasted (Microetcher, 50 μm-Al₂O₃), cleaned (35% H₃PO₄), and randomly divided into five groups (N=3) according to the intermediate agent applied. Two flowable composites (Gradia LoFlo; Filtek Supreme XT Flow) and two adhesives (Adper Scotchbond 1XT, Scotchbond Multi-Purpose) were used. As a control, no intermediate agent was applied. Each disk was incrementally repaired (8x8 mm) with the same resin as the respective substrate. By serially cutting each repaired specimen, multiple sticks of about 0.8 mm² in cross-section were obtained and loaded in tension until failure at a cross-head speed of 0.5 mm/minute. Data were statistically analyzed. Failure mode was examined by stereo- and scanning electron-microscopy ( SEM ). Additional specimens were prepared to morphologically evaluate the composite-to-composite interfacial quality by SEM analysis. Results: Composite substrate and intermediate agent were significant factors (Two-way ANOVA, P< 0.001). Bond strengths achieved with Gradia Direct Anterior were higher than Filtek Supreme XT. The application of flowable composites resulted in statistically superior µTBS than adhesives and control (Tukey test, P< 0.001). Failure mode was predominantly cohesive (flowable composites), cohesive/adhesive (adhesives) and adhesive (no treatment). Flowable composites and adhesives showed a good interfacial quality. (Am J Dent 2008; 21:53 -58).

 *: Prof. Marco Ferrari, University of Siena, School of Dental Medicine, Department of Dental Materials and Restorative Dentistry, Policlinico “Le Scotte”, Viale Bracci, Siena, 53100, Italy.  E-*: md3972@mclink.it

 Wetting ability of single-component self-etching adhesives on enamel and dentin  

Tissiana  Bortolotto, phd, dr med dent ,  Marco  Ferrari, md, dds , phd   &  Ivo  Krejci, prof, dr med dent  

Abstract: Purpose: To assess the contact angle, volume loss and nanoleakeage profile of five one-component self-etching adhesive formulations that differed in their HEMA content, on enamel and dentin. Methods: Contact angles of drops from each adhesive system were measured over 40 enamel and dentin flat surfaces. Volumetric changes were measured as well. The adhesives were then applied over repolished surfaces according to manufacturers’ recommend-dations, covered with a microfilled restorative composite and the samples were silver infiltrated and prepared for evaluation in a scanning electron microscope. Results: On enamel and dentin surfaces, the contact angles decreased with increasing HEMA content. A correlation was observed between contact angle, volume loss and HEMA content on both substrates. (Am J Dent 2008; 21:59 -63).  

 *: Prof. Dr. Ivo Krejci, Division of Cariology and Endodontology, School of Dentistry , University of Geneva , 19, Rue Barthélemy-Menn, CH-1205 Geneva , Switzerland .  E-*:  Ivo.Krejci@medecine.unige.ch

Effect of resin coating on dentin bond durability of a resin cement over 1 year  

Toru Nikaido, dds , phd, Yuichi Kitasako, dds , phd, Michael F. Burrow, mds , phd, med , Ayuko Umino, dds , phd, Rena  Maruoka, dds , phd, Masaomi Ikeda, dt  &  Junji Tagami, dds , phd  

Abstract: Purpose: To evaluate the effect of resin coating of bonded dentin on the micro-tensile bond strengths of a resin cement to dentin over 1 year. Methods: Human molars were ground to obtain flat dentin surfaces and divided into three groups. The dentin surfaces were left as a control, or resin-coated with a combination of a dentin bonding system, Clearfil SE Bond (SE), and one of two lining materials: Protect Liner F (PLF) (SE/PLF) or Ionosit Micro Spand (IMS). The dentin surfaces with or without resin coating were covered with a temporary filling material (Cavit-G) and stored in water for 1 day. After removal of Cavit-G, an indirect composite block (Estenia) was bonded with Panavia F following the manufacturer’s instructions. The specimens were stored in water for 1 day, 6 months or 1 year in 37°C water. Micro-tensile bond strength was measured at a crosshead speed of 1 mm/minute. There were 10 slices each group. Data were analyzed with two-way ANOVA and Fisher’s PLSD test (P< 0.05). Results: ANOVA indicated that resin coating and storage period significantly influenced the micro-tensile bond strengths (P< 0.0001). The bond strengths of SE/PLF, SE/IMS and the control after 1 day were 27.5 ± 5.1, 15.7 ± 3.2 and 10.6 ± 4.9 MPa, respectively. The bond strengths of SE/PLF significantly decreased over 1 year (P< 0.05), while there were no significant differences in bond strengths for SE/IMS (P> 0.05). The bond strengths of SE/PLF were significantly higher than those of the control over 1 year (P< 0.05). (Am J Dent 2008;21:64-68).  

 *: Dr. Toru Nikaido, Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School , Tokyo Medical and Dental University , 5-45 Yushima 1-chome, Bunkyo-ku, Tokyo 113-8549, Japan. E-*: nikaido.ope@tmd.ac.jp