December 2010

Research Article

Effect of bonded area and/or fiber post placement on the fracture strengths of resin-core reconstructions for pulpless teeth


Masatoshi Nakajima, dds, phd,  Tama Kanno, dds, phd,  Wataru Komada, dds, phd, Hiroyuki Miura, dds,  phd, Richard M. Foxton, bds, phd, mfds rcs (ed), fhea  &  Junji Tagami, dds, phd


Abstract: Purpose: To compare the fracture strengths of pulpless teeth restored using resin cores with and without fiber posts, and with and without bonding adhesive in the post cavity. Methods: Human extracted roots were prepared with post cavities and divided into four experimental groups: Groups 1 and 2 – after application of adhesive to both the top surface of the root and the inner surface of the post cavity, DC core Automix was injected into the post space with or without fiber-post placement; Groups 3 and 4 – adhesive was applied to the top surface of the root only, with or without post placement. Resin-cores were then built-up. Teeth prepared for full crowns served as controls. After water storage at 37°C for 24 hours, the all specimens were embedded in acrylic resin at 2 mm below CEJ, and loaded at 45 degrees to the long axis of the tooth using a universal testing machine until fracture. The data were analyzed by one-way ANOVA (α= 0.05). Results: The fracture loads were, Group 1: 1832 ±240 N, Group 2: 1815 ±347 N, Group 3: 1626 ±396 N, Group 4: 1810 ±332 N, Control Group: 1622 ±274 N. There were no significant differences among all the groups (P> 0.05). (Am J Dent 2010;23:300-304).


Clinical significance: This study showed that the absence of fiber posts and/or adhesion in the post cavity did not affect the fracture strengths of resin-core reconstructions of pulpless teeth.



Address: Dr. Masatoshi Nakajima, Cariology and Operative Dentistry, Department of Restorative Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan. E-mail:


Research Article

Plaque and gingivitis reduction efficacy of an advanced Pulsonic

toothbrush: A 4-week randomized and controlled clinical trial


Naresh  C.  Sharma, dds,  Jimmy  G.  Qaqish, bsc,  Tao  He, dmd, phd,  Patricia  A.  Walters, rdh, msdh, msob, Julie  M.  Grender, phd  &  Aaron  R.  Biesbrock, dmd, phd, ms


Abstract: Purpose: To compare the safety and efficacy of a novel sonic power toothbrush and a manual toothbrush in the reduction of gingivitis and plaque over a 4-week period. Methods: This study employed a randomized two treatment, examiner-blinded, parallel group design. Subjects with evidence of gingivitis were randomly assigned to 4 weeks’ twice daily home use of either the Oral-B Pulsonic sonic toothbrush or an ADA reference manual toothbrush. At baseline (Visit 1) and again after product use at Week 4, subjects received gingivitis evaluations with the Modified Gingival Index (MGI) and Gingival Bleeding Index (GBI) examinations, followed by plaque assessment using the Rustogi Modified Navy Plaque Index (RMNPI). For 12 hours before both visits, subjects abstained from all oral hygiene, and ceased eating, drinking and smoking 4 hours prior. Results: Both brushes significantly reduced gingivitis, gingival bleeding and plaque compared with baseline, and were well-tolerated by the 129 subjects completing the study. The sonic toothbrush was statistically significantly (P< 0.0001) more effective than the manual brush, with greater relative mean reductions in MGI, GBI and RMNPI of 11.9%, 62.3% and 46.5%, respectively. (Am J Dent 2010;23:000-000).


Clinical significance: After 4 weeks of twice daily unsupervised brushing, the new advanced sonic toothbrush provided statistically significantly superior reductions relative to a manual toothbrush in all three measured clinical parameters (gingivitis, gingival bleeding and plaque removal) with notable anti-plaque efficacy in interproximal regions, indicating this is a highly effective new tool to improve oral health.


Address: Dr. Tao He, Procter & Gamble Health Care Research Center, 8700 Mason-Montgomery Road, Mason, OH 45040, USA. E-mail:



                                                                                                                                           Research Article

Efficacy of a pit and fissure sealant in arresting dentin non-cavitated caries: A 1-year follow-up, randomized, single-blind, controlled clinical trial


Boniek Castillo Dutra Borges, Giordano Bruno Paiva Campos, Ana Daniela Silva da Silveira, dds, ms, Kenio Costa de Lima, dds, ms, phd  &  Isauremi Vieira de AssunÇÃo Pinheiro, dds, ms, phd


Abstract: Purpose: To evaluate the efficacy of conservative treatment of dentin non-cavitated caries using a resin-based fluoride-containing pit and fissure sealant. Methods: In this controlled clinical trial, 60 teeth with clinically non-cavitated occlusal caries radiographically located beneath the enamel-dentin junction (radiolucent area) were selected among patients presenting a moderate to high caries risk. The teeth were randomly divided into two groups of 30 teeth each: an experimental group receiving an application of Fluorshield (Dentsply) sealant and a control group not submitted to any clinical intervention. Caries progression was monitored by clinical and radiographic examination at 4-month intervals over a period of 1 year. In addition, marginal integrity of the sealant was evaluated in the experimental group. Results: Clinical and radiographic caries progression was significantly more frequent in control teeth when compared to the experimental group (P< 0.05). (Am J Dent 2010;23:311-316).


Clinical significance: The pit and fissure sealant was found to be effective in arresting the carious lesions evaluated, suggesting that this intervention may replace the invasive treatment traditionally used for teeth with dentin non-cavitated caries.


Address: Dr. Boniek Castillo Dutra Borges, Rua Minas Novas, 390, cs 18, Neopolis, Natal/RN, CEP: 59.088-725, Brazil.  E-mail:



                                                                                                                                         Research Article

Clinical and microbiological studies of children and adolescents

receiving orthodontic treatment


Rodrigo O. Rego, CD, MS, PhD,  Cristiane A. Oliveira, CD, MS, PhD,  Ary dos Santos-Pinto, CD, MS, PhD, Shawn F. Jordan, DDS, MS,  Joseph J. Zambon, dds, phd,  Joni A. Cirelli, CD, MS, PhD  &   Violet I. Haraszthy, dds, ms, phd


Abstract: Purpose: This case-controlled study examined clinical and microbiological parameters in Brazilian children and adolescents receiving orthodontic treatment using fixed orthodontic appliances or removable orthodontic appliances. Methods: The plaque index, gingival index, number of decayed, missing and filled teeth, and probing pocket depth was measured on each fully erupted tooth in 30 patients treated with fixed orthodontic appliances and an equal number of age and sex-matched control subjects. The same parameters were also measured in 18 patients treated with removable orthodontic appliances and an equal number of age and sex-matched control subjects. In the patients treated with fixed orthodontic appliances, subgingival plaque samples were collected from four teeth with orthodontic brackets and from four teeth with orthodontic bands. In the patients with removable appliances, subgingival plaque samples were collected from clasped maxillary permanent first molar teeth and from four unclasped permanent teeth. Samples of unstimulated whole saliva and samples from the dorsal surface of the tongue were also obtained from each subject. Each sample was analyzed for the presence of 19 target bacteria by dot blot. A subset of samples was examined by direct amplification of bacterial nucleic acids. Results: Compared to their respective age and sex-matched controls, whole mouth means for plaque index and gingival index were significantly elevated in both the fixed and removable orthodontic groups. There was no difference in the DMFT. Subjects with fixed orthodontic appliances had a higher prevalence of each of the target species except for L. fermentum, Neisseriaceae and S. mutans. The prevalence of A. naeslundii and Streptococcus sp. was significantly higher on teeth with orthodontic brackets alone compared to teeth with both orthodontic bands and brackets. Subjects with removable orthodontic appliances had a higher prevalence of A. actinomycetemcomitans, C. rectus, E. corrodens, L. fermentum, Neisseriaceae, and spirochetes. The prevalence of Neisseriaceae was significantly higher on unclasped teeth compared to clasped teeth. There was no difference between sample sites for the target bacteria except for A. actinomycetemcomitans that was detected less frequently in saliva. Orthodontic patients demonstrated higher proportions of gram negative species by direct amplification of nucleic acids including species frequently associated with periodontal disease as well as rarely cultivable or non-cultivable species such as Abiotrophia defectiva, Gemella haemolysans, Granulicatella adiacens, Lautropia sp., Terrahaemophilus aromaticivorans, and TM7 bacterium. (Am J Dent 2010;23:317-323).


Clinical significance: Both fixed and removable orthodontic appliances can cause alterations in oral biofilms resulting in increased gingival inflammation and which necessitate meticulous oral hygiene during orthodontic treatment.


Address: Dr. Joseph J. Zambon, Department of Periodontics and Endodontics, University at Buffalo, School of Dental Medicine, 3435 Main Street, Buffalo, NY, 14214, USA.  E-mail:




Research Article

Effect of an 8.0% arginine and calcium carbonate in-office desensitizing

paste on the shear bond strength of composites to human dental enamel


Alexander  GarcÍa-Godoy, bs   &  Franklin  GarcÍa-Godoy, dds , ms


Abstract: Purpose: To evaluate the effect of 8.0% arginine and calcium carbonate, in-office desensitizing paste (Colgate Sensitive Pro-Relief Desensitizing Paste) on the shear bond strength of composites to human dental enamel. Methods: Two resin composites (Filtek Supreme, Premise) and human dental enamel were used. 16 samples per composite were prepared. Caries-free extracted human molars, not older than 3 months, and stored in distilled water were used for this portion of the experiment. Buccal and lingual surfaces were polished with high polishing pastes to create a uniform flat surface area to which the cylindrical composite samples were bonded. After polishing, the samples were rinsed in tap water and stored at 100% relative humidity. The resin composites were used to form cylindrical samples 3 mm x 1.6 mm, which were light-cured with a Demetron curing light according to the manufacturers’ instructions. For each composite, 32 surfaces were used; 16 were a control group with the enamel polished with a water slurry of flour of pumice. The experimental group had the enamel polished with the 8.0% arginine and calcium carbonate desensitizing paste, using disposable latex free prophy cups with a slow speed hand piece at 3,000 rpm using moderate to light pressure, according to manufacturer’s instructions. The composite cylinders were bonded to the enamel with their respective etching agents and adhesives and left in distilled water for 48 hours, after which the samples were sheared with an Instron testing machine at 0.5 mm/minute. After shearing, all samples were analyzed with a stereo microscope to evaluate failure pattern (failure at the enamel surface, failure at the composite surface, or mixed failure, at both enamel and composite surfaces). SEM images of selected surfaces were made to depict the overall morphology of the surface of dental materials used after 8.0% arginine and calcium carbonate desensitizing paste, application and shear strength tests. ANOVA and Student-Newman-Keuls tests (P< 0.05) were used to evaluate the difference among the groups. Results: The 8.0% arginine and calcium carbonate  desensitizing paste did not have a significant effect on the shear bond strength of the composites tested to enamel. (Am J Dent 2010;23: 324-326).


Clinical significance: The 8.0% arginine and calcium carbonate in-office desensitizing paste did not affect the shear bond strength to enamel of the composites tested.


Address: Dr. Franklin Garcia-Godoy, College of Dentistry, University of Tennessee Health Science Center, 875 Union Avenue, Memphis, TN 38163, USA. E-mail:



                                                                                                                                             Research Article

Influence of enzymatic and chemical degradation on zirconia

resin bond strength after different surface treatments


Hesam Mirmohammadi, dds, phd,  Mostafa N. Aboushelib, dds, msc, phd,   Ziad Salameh, , dds, msc, phd, Cornelis J. Kleverlaan, phd   &  Albert J. Feilzer, dds, phd


Abstract: Purpose: To investigate the influence of chemical and enzymatic degradation on the stability of zirconia resin bond strength using micro-shear bond strength test. Methods: Zirconia discs were airborne particle abraded (SB) or selective infiltration etched (SIE) while no surface treatment served as control. Resin composite (Filtek Z250) micro-discs were bonded to zirconia using self-adhesive universal resin cement (RelyX UniCem). Micro-shear bond strength (μSBS) test was conducted after immersion in the following degrading media: 24 hours and 2 weeks of water storage, and 2 weeks in NaOH, alcohol, or esterase enzyme (n=10). Results: There was a significant influence of the surface finish (P< 0.001, F=154.5), biodegradation medium (P< 0.001, F=52.9), and their interaction (P< 0.001, F=6.0) on zirconia resin bond strength. In general SIE group revealed the highest μSBS values (8.1 - 34.5 MPa) after degradation in different media, followed by SB group (8.7 - 28.5 MPa), while the control group showed significantly lower bond strength (0.4 - 9 MPa). (Am J Dent 2010;23:327-330).





Clinical significance: Within the limitations of this study, long term performance of zirconia resin bond strength is influenced by accelerated chemical and enzymatic degradation.





Address: Dr. S.H. Mirmohammadi, ACTA, Department of Dental Materials Science, Louwesweg 1, 1066 EA Amsterdam, The Netherlands. E-mail:



                                                                                                                                             Research Article

Effect of light-curing units on the thermal expansion

of resin nanocomposites


Jeong-Kil  Park, dds, phd,  Bock  Hur, dds, phd,  Ching-Chang  Ko, dds, phd,  Franklin  GarcÍa-Godoy, dds, ms, Hyung-Il  Kim, dds, phd  &  Yong  Hoon  Kwon, phd


Abstract: Purpose: To examine the thermal expansion of resin nanocomposites after light-curing using different light-curing units. Methods: Four different resin nanocomposites and four different light-curing units [quartz-tungsten-halogen (QTH), light emitting diode (LED), laser, and plasma arc] were chosen. Metal dies were filled with resin to make specimens and light-cured. The light intensity and light-curing time of the QTH and LED light-curing units were 1000 mW/cm2 and 40 seconds, 700 mW/cm2 and 40 seconds for the laser, and 1600 mW/cm2 and 3 seconds for the plasma arc. The coefficient of thermal expansion (CTE) was evaluated using a thermomechanical analyzer (TMA) at temperatures ranging from 30-80°C. Results: The CTE of the resin nanocomposites tested ranged from 28.5 to 65.8 (×10-6/°C), depending on the product and type of light-curing unit used. Among the specimens, Grandio showed the lowest CTE. The specimens cured using the plasma arc unit (Apollo 95E) showed the highest CTE. There was a linear correlation between the CTE and filler content (vol%) (R: -0.94~-0.99 depending on the light-curing unit). The results may suggest a careful selection of the light-curing unit because there was more expansion in the specimens cured using the plasma arc unit than those cured by the other units. (Am J Dent 2010;23:331-334).


Clinical significance: Within the limitations of this study, the resin nanocomposites evaluated showed much higher CTE than the enamel and dentin. The plasma arc unit produced a significantly higher CTE than the other units due to the incomplete polymerization of the materials.


Address: Prof. Yong Hoon Kwon, Department of Dental Materials, College of Dentistry, Pusan National University, Busan 602-739, Korea. E-mail:




                                                                                                                                             Research Article

Nanoleakage and microtensile bond strength at the adhesive-dentin

interface after different etching times


San-jun Zhao, dds, phd,  Ling Zhang, dds, phd,   Li-hui Tang, dds, phd   &   Ji-hua Chen, dds, phd, 


Abstract: Purpose: To evaluate the effect of etching time on the nanoleakage and microtensile bond strength (µTBS) at the interface between etch-and-rise adhesives and dentin. Methods: Eighty molars were sectioned to expose the superficial dentin and randomly divided into four groups according to the adhesives used: OptiBond Solo (OB), Single Bond (SB), One-Step (OS), and Prime&Bond NT (PB). Within each group, a total-etching technique was applied, and the dentin surfaces were etched for 0, 15, 30 or 60 seconds. Each treated tooth was then sectioned into sticks. A non-trimming µTBS test and TEM observation for nanoleakage were sequentially performed. Results: The degree of nanoleakage increased as etching time increased (P< 0.05). For the OS and PB groups, the highest µTBS values were achieved with 15 seconds of etching, followed by 30, 60 and 0 seconds. For the OB and SB groups, the µTBS values for 15- and 30-second etching times were similar and were both significantly higher than those of 0 and 60 seconds (P< 0.05). (Am J Dent 2010;23:000-000).


Clinical significance: Prolonged etching time produced extensive nanoleakage and reduced bond strength when etch-and rinse adhesives are used for dentin.


Address: Prof. Ji-hua Chen, Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Xi’an, 710032, China.  E-mail:


                                                                                                                                             Research Article

Influence of CAD/CAM scanning method and tooth-preparation design

on the vertical misfit of zirconia crown copings


Raquel Castillo OyagÜe, dds, phd, MarÍa Isabel SÁnchez-Jorge, dds, phd  &  AndrÉs SÁnchez TurriÓn, md, phd


Abstract: Purpose: To evaluate the influence of scanning method, finish line type and occlusal convergence angle of the teeth preparations on the vertical misfit of zirconia crown copings. Methods: 20 standardized stainless-steel master dies were machined simulating full-crown preparations. The total convergence angle was 15º or 20º (n=10 each). Two of the finish line types: a chamfer (CH) and a shoulder (SH) were prepared around the contour of each abutment. Over these dies, 20 structures were made by CAD/CAM (Cercon, Dentsply). An optical laser digitized the wax patterns of 10 single-unit copings (WS), and 10 abutments were direct-scanned to design the cores by computer (DS). Zirconia milled caps were luted onto the models under constant seating pressure. Vertical discrepancy was assessed by SEM. Misfit data were analyzed using ANOVA and Student-Newman-Keuls (SNK) test for multiple comparisons  at α= 0.05. Results: Vertical gap measurements of WS copings were significantly higher than those of DS frames (P< 0.0001). SH exhibited statistically higher discrepancies than CH when combined with a 15-degree occlusal convergence angle regardless of the scanning method (P< 0.05). The taper angle of the preparation (15º vs. 20º) had no effect on the marginal adaptation of chamfered samples. (Am J Dent 2010;23:341-346).


Clinical significance: Vertical misfit of zirconia structures depended on the digitizing technique. Precision was higher when direct scanning of the abutments was performed instead of wax-up digitization. The presence of sharp axiogingival line angles at the preparations’ margins resulted in higher vertical discrepancies, even when the marginal gaps of all the copings tested were within the range of clinical acceptance.


Address: Dr. Raquel Castillo de Oyagüe, Department of Prosthodontics, Faculty of Dentistry, Complutense University of Madrid, U.C.M., Pza. Ramón y Cajal, nº 3, 28040, Madrid, Spain.  E-mail:





                                                                                                                                             Research Article

Microtensile bond strength of three different veneering porcelain systems

to a zirconia core for all ceramic restorations


Giovanni  Fazi, dds, ms,  Alessandro  Vichi, dds, phd  &  Marco  Ferrari, md, dds, phd


Abstract: Purpose: This study investigated the microtensile bond strength of three different ceramic veneering systems to one type of zirconia substrate. Methods: Bilayered zirconia veneer discs were fabricated of a LAVA zirconia core and three different veneering ceramics (VITA VM9, Lava Ceram, Creation ZI) using a conventional layering technique. Discs were cut into microbars of 6 mm x 1 mm x 1 mm. Microtensile bond strength between veneer and core was measured. Surfaces of fractured specimens were examined with scanning electron microscopy (SEM). Results: The mean microtensile bond strengths were respectively VITA VM9 23.52 MPa (8.33), Creation ZI 18.35 MPa (6.40), and Lava Ceram 14.76 MPa (4.00). The differences were statistically significant. Failures were mainly interfacial in all tested groups. (Am J Dent 2010;23:347-350).


Clinical significance: Important variations in terms of veneer/core bond strength can occur by applying different veneering systems to the same zirconia core. Careful selection of a veneering system to a given zirconia substrate could be of importance in achieving adequate bond strength to avoid delamination of bilayered zirconia based restorations.


Address: Dr. Giovanni Fazi, Via A Lamarmora 22, 50121 Firenze, Italy. E-mail:





Research Article

Effect of tooth type and ferrule on the survival of pulpless teeth restored with fiber posts: A 3-year clinical study


Juan  Carlos  Mancebo, md, dds, phd,  Emilio  JimÉnez-Castellanos, md, dds, phd   &  Diego  CaÑadas,  md, dds, phd


Abstract: Purpose: To determine, in a 3-year clinical trial, whether tooth type and ferrule significantly affect the survival of pulpless teeth restored with fiber posts. Methods: A sample of 87 teeth in 87 patients (32 men and 55 women, age ranged from 23 to 78) were restored using Snowpost: 34 incisors, 12 canines, 25 premolars and 16 molars. The posts were cemented with RelyXUnicem and the core was made with a resin composite (Dentocore Automix). Every tooth was covered with a metal-ceramic or all ceramic crown. Two experimental groups, according to the presence or absence of ferrule, were defined: A) 45 teeth with ferrule (>2 mm height); and B) 42 teeth without ferrule (<2 mm height). Patients were reevaluated every 6 months. Results: 14 of the total restorations failed (16.1%). The failure modes were caries (n= 4), post fracture (n= 4), root fracture (n= 2), and marginal gap, post cement failure, crown cement failure, and periapical lesion (n= 1 respectively). In Group A the failure observed was 6.67% and in Group B it was 26.20%. The log-rank test showed statistically significant differences between both groups. According to the type of tooth, the incisors were the teeth with the highest failure rate (73.52%), but Chi-square test showed no statistically significant differences among the four tooth types, perhaps because of the low number of the sample. (Am J Dent 2010;23:351-356).


Clinical significance: In endodontically treated teeth restored with adhesive techniques and fiber posts, the presence of ferrule results in better clinical survival after 3 years of clinical service.




Address:  Dr. Juan Carlos Mancebo, c/ Avicena s/n, Facultad de Odontología, Sevilla. Spain .   E-mail:


                                                                                                                                               Research Article

Comparison of an analytical expression of resin composite curing

stresses with in vitro observations of marginal cracking


Bill  Kahler, d clin dent, phd,   Michael  V.  Swain, bsc, phd   &   Andrei  Kotousov, b eng, phd


Abstract: Purpose: To observe the marginal failure at the enamel-resin composite interface upon curing, and utilize a recently developed analytical model for curing stresses to relate to the extent of interfacial failure. Methods: Occlusal cavity preparations were restored with Heliomolar, Filtek Z100 or UltraSeal XT Plus resin composites. Teeth were restored with either bulk or incremental placement. The control group was not restored. Teeth were placed in an acrylic ring and embedded in cold mounting epoxy resin and the crown sectioned so that the tooth/restoration interface and cavosurface margin could be visualized with an optical microscope. A recently developed simplified analytical approach was utilized to evaluate the composite-enamel interface tensile stresses for these materials theoretically and thereby the fracture susceptibility of the resin-enamel interface during polymerization. Results: White lines, enamel cracks and interfacial failure of the bond were evident for all three materials evaluated (P< 0.01). Gaps at the enamel-composite interface measured 1-10 µm and were more evident for Ultra Seal XT Plus and Z100 than Heliomolar. Conversely, cracking of the enamel adjacent to the interface was more evident for Heliomolar. Statistical analysis showed that enamel cracking and interfacial failure was significant for all groups (P< 0.01). An inverse relationship was noted between enamel cracking and interfacial failure (P< 0.05). The predictions for the extent of cracking from the mathematical modeling match the experimental data and prior studies. (Am J Dent 2010;23:357-364).


Clinical significance: It has been stated that interfacial failure of the adhesive bond and cracking of enamel may be clinically relevant with regard to hypersensitivity, secondary caries and restoration failure. However, few studies have focused specifically on the role of material properties of the restorative materials in such failures. The present work provides evidence that restorative material properties, such as Young’s modulus and polymerization shrinkage, are a major factor contributing to interface failure, and that a simplified analytical model is useful for assessing the likelihood of interface failures during curing.  The study has important clinical applications and can be utilized for the develop-ment of new and improved materials used in adhesive restoration and for comparative assessment of currently used resin composites.


Address: Dr. Bill Kahler, School of Dentistry, University of Queensland, Australia. E-mail:



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