American Journal of Dentistry
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Abstracts of the August 2007 Issue


Clinical reversal of root caries using ozone: 6-month results


Aylin Baysan, bds, msc, phd, mfds, rcsed & Edward Lynch, ma, bdentsc, fds, phd


Abstract: Purpose: To assess the safety and efficacy of ozone either with or without a root sealant, for the management of leathery root caries. Methods: 79 subjects with 220 root caries lesions were recruited into four study groups in this randomized, controlled trial. At baseline and after 1, 3, and 6 months, the ECM III and DIAGNOdent were employed. Subsequently, the root caries lesions were clinically assessed for color, hardness, cavitation, dimensions, distance from the gingival margin, and severity index. Modi­fied USPHS criteria were also performed after 1, 3, and 6 months. These groups were as follows: Group 1: Ozone applica­tion was performed for a period of 10 seconds on caries lesions; Group 2: There was neither ozone nor root sealant appli­cation on root caries; Group 3: Ozone treatment and a root sealant were applied to root caries lesions; and Group 4: Only root sealant was applied to root caries. Results: At the 6-month recall, 78 subjects were examined. There were no observed adverse events. 38.1% of lesions became hard in the ozone only group, while none of the lesions became hard in the con­trol group (P< 0.001). Noncavitated lesions were more likely to reverse than cavitated lesions. 38.4% of noncavitated lesions became hard, while only 5.7% of cavitated lesions became hard in the ozone only group. Modified USPHS criteria revealed that there were 66.6% intact sealants in the ozone and sealant group and 45.5% intact sealants in the sealant only group (P< 0.05). After 1, 3, and 6 months, the ECM and DIAGNOdent readings showed improvements in the ozone only group when compared to the control group (P< 0.001). The ozone and sealant group also had greater improvements in the ECM and DIAGNOdent values when compared to the sealant only group (P< 0.05). (Am J Dent 2007;20:203-208).

Clinical significance: The clinical implications of the ECM and DIAGNOdent are promising for detecting the se­verity of root caries lesions. Noncavitated leathery root caries lesions can be treated non-operatively by the employment of ozone for a period of 10 seconds. The root sealant showed a reduced retention at 6 months but was retained better on ozone-treated root caries lesions.

Address: Dr. Aylin Baysan, Adult Oral Health, The Institute of Dentistry, Barts and The London Queen Mary's School of Medicine and Dentistry, Turner Street, London E1 2AD, United Kingdom. E-:


Desensitizing efficacy of a new toothpaste containing 5.5% potassium citrate: A 4-week clinical study


Rafaella Docimo, md, dds, Luigi Montesani, md, dds, Paolo Maturo, dds, Micaela Costacurta, dds,

Martina Bartolino, dds, William DeVizio, dmd, Yun Po Zhang, msc, phd & Serge Dibart, dmd


Abstract: Purpose: To evaluate the desensitizing capabilities of a new toothpaste containing 5.5% potassium citrate (Colgate Sensitive Multi Protection Toothpaste) to another toothpaste containing 3.75% potassium chloride (Sensodyne Total Care F Toothpaste). Methods: A 4-week clinical study was conducted in 75 subjects at the University of Rome, at Tor Vergata, in Rome, Italy, using a double blind, stratified, two treatment design. Tactile sensitivity as well as air blast sensitivity assessment was used to compare the efficacy of the two products. Results: There was no statistically significant difference in tactile sensitivity scores and air blast sensitivity scores between the tested toothpastes at baseline, 2 weeks and 4 weeks. Both toothpastes provided statistically significant improvement in tactile sensitivity scores and air blast sensitivity scores after 2 weeks of use and 4 weeks of use as compared to baseline scores. (Am J Dent 2007;20:209-211).


Clinical significance: Colgate Sensitive Multi Protection Toothpaste was as effective as Sensodyne Total Care F Toothpaste in decreasing dentin hypersensitivity and providing subjects relief.


Address: Dr. Serge Dibart, Boston University School of Dental Medicine, 100 East Newton Street, Suite G-217, Boston, MA 02118, USA. E-:


Effect of dentifrice containing 5000 ppm fluoride on non-cavitated

fissure carious lesions in vivo after 2 weeks


Jörg Fabian Schirrmeister, dds, dr med dent, Jens Peter Gebrande, dds, Markus Jörg Altenburger, dds, dr med dent, Jürgen Schulte Mönting, prof, dr rer nat & Elmar Hellwig, dds, prof, dr med dent


Abstract: Purpose: This randomized clinical trial compared the ability of two dentifrices, one containing 5000 ppm fluoride (Duraphat) and the other 1450 ppm fluoride (Caries Protection, control) to reverse non-cavitated fissure carious lesions. Methods: 30 adults having occlusal lesions with DIAGNOdent values between 10 and 20 were randomly assigned to two groups of 15 participants each. DIAGNOdent measurements were performed after cleaning the teeth with cleaning brushes and after additional cleaning using an airflow device. The participants were instructed to brush their teeth three times a day for 3 minutes after the meals with a 2 cm line of their assigned dentifrice. After a period of 2 weeks, the teeth were cleaned again with the airflow device and laser fluorescence measurement was performed. Results: The group using the dentifrice containing 5000 ppm showed a significantly higher decrease in laser fluorescence (21%) over the test period than the control group (4%; P< 0.001; repeated measures ANOVA). The decrease in laser fluorescence in the test group was significant (P< 0.001; Wilcoxon signed-rank test). The difference between cleaning the teeth with cleaning brushes and additional cleaning with airflow before DIAGNOdent measurement was not statistically different (P> 0.05; Wilcoxon signed-rank test). (Am J Dent 2007;20:212-216).


Clinical significance: The dentifrice containing 5000 ppm fluoride was significantly better than the dentifrice containing 1450 ppm fluoride regarding reversal of non-cavitated fissure carious lesions.


Address: Dr. Jörg F. Schirrmeister. Department of Operative Dentistry and Periodontology, Albert-Ludwigs-University Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany. E-:



Treatment of root sensitivity after periodontal therapy


Maria F. Fiocchi, dds, ms, ms, Antonio J. Moretti, dds, ms, John M. Powers, phd & Terry Rives, drph


Abstract: Purpose: To compare the effectiveness of an agent that promotes deposition of amorphous calcium phosphate (Quell Desensitizer) to a commonly used product, sodium fluoride solution (Nupro Neutral), in the reduction of root sensitivity after periodontal therapy, in a prospective, convenient sample, double-blind clinical trial. Methods: Thirty patients were enrolled and treated, resulting in 40 teeth treated with the test product and 40 teeth treated with the control product. The clinical parameters tested at baseline and in the follow-up visits (1, 2, and 4 weeks after treatment) were the following: plaque index, gingival index, gingival recession, and response to mechanical and cold stimulation with airblast and ice. Patients were also asked to report the grade of pain response on a Visual Analogue Scale (VAS) on the same schedule as the clinical parameters. Results: Plaque index and gingival index were not significantly different between test and control groups throughout the study. Most recession was observed on midbuccal surfaces. Buccal surfaces evoked higher pain response compared to lingual surfaces. It was concluded that both control and test treatments reduced root sensitivity response reported with mechanical or cold stimulation. No statistically significant differences were observed when the data of both groups were compared by a Student’s t-test at the 0.05 level of significance. (Am J Dent 2007;20:217-220).


Clinical significance: There was no difference between test and control treatment (i.e. amorphous calcium phosphate and sodium fluoride) in reducing root sensitivity after scaling and root planing.


Address: Dr. Maria F. Fiocchi, 6516 M.D. Anderson Blvd., Suite 306, Houston, TX 77030 USA. E-:


Penetration of radiopaque dental restorative materials

using a novel ultrasound imaging system


Rahul S. Singh, phd, Martin O. Culjat, phd, Jason C. Cho, bs, Ratnakar R. Neurgaonkar, phd,

Douglas C. Yoon, dds, Warren S. Grundfest, md, Elliot R. Brown, phd & Shane N. White, bdentsc, phd


Abstract: Purpose: To determine whether a novel ultrasound imaging system could detect 25 µm thick cracks beneath gold, silver amalgam, and porcelain restorations on tooth phantoms. Methods: Tooth phantoms were constructed using acoustically-matched composite to simulate dentin, with 25 µm thick water-filled cracks located ~ 1 mm inside the simulated dentin. Porcelain and gold restorations were bonded using resinous cement, and an amalgam restoration was attached using mechanical retention. A portion of the gold restoration was left unattached to simulate cement washout. A novel monostatic pulse-echo ultrasound system with a 19 MHz single-element PLZT transducer, custom transmit/receive electronics and signal processing with a Ga-In alloy couplant was used to measure the relative return echo amplitude from restoration surfaces, simulated dentin/restoration interfaces, and cracks. Extracted teeth were also used to demonstrate that the system was capable of detecting cracks in real teeth. Results: Cracks were detected beneath porcelain and amalgam, and within a human molar. Cracks were not detected in simulated dentin beneath gold; however, simulated cement washout directly beneath gold was identified. The ability to detect defects in the phantom was dependent on the acoustic reflection coefficient between interfaces, the attenuation of each material, acoustic clutter within the phantom, and geometry. Gold restorations transmitted minimal acoustic energy due to their large acoustic impedance; however, the ability to distinguish the gold/cement interface from the gold/washout interface indicated that ultrasound can detect density changes immediately below restorations, such as caries, fractures, or debonding. The ability to penetrate resin-composite was also demonstrated. (Am J Dent 2007;20:221-226).


Clinical significance: The ability to detect cracks or cement washout beneath radiopaque restorations would greatly aid dentists in diagnosis and in providing appropriate clinical interventions.


Address: Dr. Shane N. White, UCLA School of Dentistry, CHS 23-010, Los Angeles, CA 90095-1668, USA. E-:


Extrinsic stain removal efficacy of a dual-phase dentifrice


YuCheng Li, dds, Tao He, dds, phd, Lili Sun, ms, Yuqing Zhang, ms, Xin Li, bs, Yan Wang, dds, Shouliang Zhao, dds & RongYin Tang, dds


Abstract: Purpose: To evaluate the extrinsic stain removal benefit of a sodium hexametaphosphate containing dual-phase dentifrice (Crest Vivid White) relative to a marketed negative control (Colgate Cavity Protection). Methods: This was a parallel groups, examiner-blind, randomized and controlled clinical trial. A total of 200 healthy adults with natural stain on their anterior teeth were enrolled into the study. Following baseline examination, subjects were randomly assigned to one of the two treatment groups based on baseline Lobene composite scores, smoking status (yes/no), tea/coffee consumption (yes/no), and gender. Subjects brushed twice daily, at least 1 minute every time over 6 weeks. Clinical examinations including extrinsic stain evaluation and oral soft tissue examination were conducted at BL, Weeks 3 and 6. Extrinsic stain removal was evaluated on the anterior teeth by a dental examiner using Lobene stain index. Results: Of the 200 subjects who were randomized to treatment, 195 were available for the 3-week examination and 193 subjects completed the study. The dual-phase dentifrice exhibited a statistically significant (P< 0.01) reduction in Lobene stain composite scores when compared to the negative control dentifrice at Week 6. Adjusted mean Lobene composite reduction for the dual-phase dentifrice group (0.32) was twice as big as the negative control group (0.16). Change in Lobene stain extent (area) contributed primarily to the overall composite score reduction. All test products were well tolerated over the 6-week treatment period. (Am J Dent 2007;20:227-230).


Clinical significance: The research demonstrated the superior extrinsic stain removal efficacy of the dual-phase dentifrice relative to a negative control dentifrice.


Address: Dr. RongYin Tang, College of Stomatology, Fourth Military Medical University, Xi’an, China. E-:


Effect of adhesive systems and surface treatment of methacrylate

resin-based fiber posts on post-resin-dentin bonds


Francesca Monticelli, dds, ms, phd, Raquel Osorio, dds, phd, Alberto Albaladejo, dds, phd, Fátima S. Aguilera, dds, phd, Franklin R. Tay, bdsc(hons), fadm, phd, Marco Ferrari, md, dds, phd & Manuel Toledano, md, dds, phd


Abstract: Purpose: To evaluate the effect of different fiber post surface treatments on bond strength. Methods: Extracted endodontically-treated premolars were prepared for the cementation of a methacrylate resin-based fiber post (FRC Postec). The posts received one of the three surface pre-treatments: silane application; hydrofluoric acid-etching and silane application or no treatment. A light-cured composite was used with one of the three dentin adhesives for luting: Single Bond; Clearfil Photo Bond and Clearfil New Bond, followed by a light-cured composite core build-up. Specimens were serially sliced into 0.8 x 0.8 mm-thick beams and loaded in tension until failure. Results: Significant differences in bond strengths were recorded among the dentin adhesives (P< 0.05). However, post pre-treatment did not affect the bonding efficacy of the adhesives except for Clearfil New Bond. (Am J Dent 2007;20:231-234).


Clinical significance: Adhesion of luting composites to methacrylate resin-based fiber posts can be improved by the application of dentin adhesives. The interface between resin and intraradicular dentin still remains the weakest bond.


Address: Prof. Manuel Toledano, Avda. de las Fuerzas Armadas n. 1, 1°B, 18014 Granada, Spain. E-:



Dental enamel dissolution after alendronate treatment


Maria G. Gandolfi, bd, phd, Cesare Nucci, md, dds, phd, Carlo Prati, md, dds, phd & Romano Mongiorgi, ms


Abstract: Purpose: To evaluate the effect of treatment with a bisphosphonate (alendronate) on human dental enamel dissolution in vitro. Methods: The dissolution of each enamel sample was evaluated by monitoring the calcium release in 0.1M lactic acid solution at pH 4.5 (acidic solution) during dissolution tests, after topical alendronate treatment with 0.1M alendronate solutions at pH 5.0, pH 7.4 and pH 9.0. Results: Data showed that alendronate treatment, both at pH 5.0 and pH 7.4, obtained a statistically significant reduction of enamel demineralization during dissolution test reaction time (45 minutes). The protective effect was not present after treatment at pH 9. (Am J Dent 2007;20:235-240).


Clinical significance: Resulting data concerning the reduction of demineralization in acidic environment suggest the possible inclusion of alendronate in formulations of oral hygiene products to prevent enamel demineralization.


Address: Dr. Maria G. Gandolfi, Piazza di Porta San Donato 1, 40126 Bologna, Italy. E-


Recovery of genomic DNA from lingual mucosal cells in sufficient

quantity and quality


Yasuhiro Imamura, phd, Syuhei Usui, dds, Yuriko Oomori, dds, Yoshihisa Fujigaki, dds, Norio Ota, dds, phd

& Pao-Li Wang, dds, phd


Abstract: Purpose: To investigate whether genomic DNA can be purified in sufficient quantity and quality from the oral cavity. Methods: One milliliter of peripheral blood and saliva were collected. The buccal and lingual mucosal cells were also obtained using 10 strokes with a swab or a toothbrush, respectively. All materials were centrifuged and the cells were lysed by adding sodium dodecyl-sulfate and proteinase K. The DNAs were extracted with phenol and precipitated with ethanol followed by electrophoresing on 0.8% agarose gel. The purified DNAs were digested with restriction enzyme Dpn I and Mbo I, respectively. Amplification of the IL-1A gene by PCR was carried out using the purified DNAs and electrophoresing on polyacrylamide gel. Results: DNA was obtained from lingual mucosal cells collected with a toothbrush. Only about one-thirtieth of the recovered DNA was of non-human origin (bacterial contaminants from the oral cavity). Judging from the PCR amplifications of the IL-1A gene, the DNA extracted from lingual cells was of sufficient quality, in all respects indistinguishable from the DNAs extracted from the other specimen, such as peripheral blood, saliva and buccal mucosal cells collected with a swab, and in sufficient quantity. Our results indicate that it is possible to purify DNAs from lingual mucosal cells collected with a toothbrush in a simple and safe manner. Compared to DNA samples from patients by blood extraction, the described method also had the advantage of being painless and not inducing mental distress. (Am J Dent 2007;20:241-245).


Clinical significance: To obtain genomic DNAs from subjects will be very important for analyzing single nucleotide polymorphisms and gene diagnosis. Purification of the DNA by this method can be performed simply and safely at chair side, without mental distress or bodily pain for subjects.


Address: Prof. Pao-Li Wang, Department of Pharmacology, Matsumoto Dental University, 1780 Gohbara, Hiro-oka, Shiojiri-city, Nagano 399-0781, Japan. E-:


Effect of bleaching on the cemento-enamel junction


Roberta Esberard, dds, msc, Renata R. Esberard, dds, Roberto M. Esberard, dds, phd,

Alberto Consolaro, dds, phd & Cornelis H. Pameijer, dmd,mscd, dsc, phd


Abstract: Purpose: To evaluate the effect of various bleaching agents on the cemento-enamel junction (CEJ) of human teeth by scanning electron microscopy (SEM) analysis. Methods: 30 intact teeth were selected and longitudinally sectioned, yielding 60 specimens. Thirty specimens served as controls; the other 30 were divided into six groups with five specimens each (n= 5) and bleached according to six protocols (Group 1: External bleaching with 10% carbamide peroxide; Group 2: External bleaching with 35% hydrogen peroxide; Group 3: External bleaching with 35% hydrogen peroxide; Group 4: Internal/external bleaching with 35% hydrogen peroxide; Group 5: Internal/external bleaching with 35% hydrogen peroxide; and Group 6: Intracoronal bleaching with a paste of sodium perborate mixed with 9% hydrogen peroxide). After treatment the specimens were prepared and examined in a scanning electron microscope. Results: The bleaching agents used in this study caused morphological changes in the CEJ and increased dentin exposure. (Am J Dent 2007;20:245-249).


Clinical significance: Depending on the type of bleaching agent, there appears to be an effect on the CEJ when extracted teeth are exposed to various external and internal bleaching protocols. This information may be helpful to explain post-bleaching sensitivity symptoms.


Address: Dr. Roberta Esberard, Department of Pathology, Bauru Dental School, University of Săo Paulo, Al. Octávio Pinheiro Brisola, 9-75, Bauru , SP - 17012-901, Brazil. E-:


Influence of thermal and mechanical load cycling on the microtensile

bond strength of self-etching adhesives


Ali I. Abdalla, dds, phd, Ahmed A. El Zohairy, dds, phd, Moustafa M.N. Aboushelib, dds

& Albert J. Feilzer, dds, phd


Abstract: Purpose: To evaluate the influence of thermal and mechanical load cycling on the microtensile dentin bond strength of two self-etching and one total-etch adhesives. Methods: The adhesive materials were: a two-step self-etch adhesive (Clearfil SE Bond), a one-step self-etch adhesive (Hybrid Bond), and a total-etch one-step adhesive (Admira Bond). Sixty freshly extracted human third molars were used. In each tooth, a Class I cavity (4 x 4 mm) was prepared in the occlusal surface with the pulpal floor extending about 1 mm into dentin. The teeth were divided into three groups (n=20). Each group was restored with the resin composite Clearfil APX using one of the adhesives. After restoration, 10 teeth in each group were thermocycled between 5şC and 55şC, (dwell time 3 minutes, 5,000 cycles). The same teeth were then mounted in a fatigue loading machine to receive an intermittent load of 125 N at 52 cycles/minute for 4,000 cycles. Subsequently, each tooth was sectioned longitudinally, bucco-lingually and mesio-distally to get rectangular slabs 1–1.2 mm in thickness for the microtensile test. Each slab was then placed in a universal testing machine and tensile load was applied at a cross-head speed of 0.05 mm/minute. Results: Without loading procedures, there was no significant difference in the bond strength of the tested adhesives. In contrast to Admira Bond and Clearfil SE Bond, fatigue loading resulted in a significant reduction of the bond strength for Hybrid Bond when compared to the unloaded restorations. (Am J Dent 2007;20:250-254).


Clinical significance: The total-etch and the two-step self-etch adhesives used in this study showed better tolerance to thermal and mechanical loading compared to the one-step self-etch system.


Address: Dr. Ali I. Abdalla, Department of Restorative Dentistry, Faculty of Dentistry, University of Tanta, Tanta, Egypt. E-:


Effect of LED curing modes on the microleakage of a pit and fissure sealant


Adil Nalçacı, dds, phd, Nuran Ulusoy, dds, phd & Çiğdem Küçükeşmen, dds, phd


Abstract: Purpose: To evaluate in vitro the curing effect of a very high intensity light-emitting diode (LED) unit and a conventional LED unit (including “soft-start” modes) on the microleakage of a pit and fissure sealant. Methods: 120 intact caries-free human molars were randomly divided into six groups (n=20), sealed with Fissurit-F and polymerized using either a conventional halogen unit (Optilux) (Control group) in standard mode (40 seconds @ 600 mW/cm2); a very high intensity LED unit (Mini LED) in fast (10 seconds @ 1,100 mW/cm2) or soft-start mode (pulse mode: ten 1-second flashes @ 1,100 mW/cm2; exponential mode: exponential increase from 0 to 1,100 mW/cm2 within 10 seconds followed by 10 seconds @1,100 mW/cm2); or a conventional LED unit (Elipar Freelight) in standard (40 seconds @ 400 mW/cm2) or exponential mode (exponential increase from 0 to 400mW/cm2 within 12 seconds followed by 28 seconds @ 400 mW/cm2). Restored specimens were stored in distilled water at 37°C for 24 hours. Specimens were then immersed in a 0.5% fuchsin dye solution for 24 hours, with half of the specimens from each group subjected to thermocycling (5/55°C; x1000) prior to dye immersion. After removal from the dye solution, specimens were sectioned and the degree of dye penetration scored. Data was statistically analyzed using the Kruskal-Wallis H test and the Mann-Whitney U-test (P< 0.05). Results: There was no statistically significant difference in microleakage of pit and fissure sealant polymerized using various curing techniques. Thermocycling regimens had no effect on either LED- or halogen-cured specimens. (Am J Dent 2007;20:255-258).

Clinical significance: High-power LED lights are an effective means of providing a strong marginal seal with pit and fissure sealants and may therefore be preferred for the overall time savings as well as reduced chair time.


Address: Dr. Adil Nalçacı, Kennedy Caddesi, 23/1, 06680, Kavaklıdere, Ankara, Turkey. E-:


Microtensile bond strength of self-etching adhesive systems to

differently prepared dentin


Benyarat Pangsrisomboon, dds, Choltacha Harnirattisai, dds, phd, Kanitha Nilsri, dds & Michael F. Burrow, bds, mds, phd


Abstract: Purpose: To evaluate the microtensile bond strength (µTBS) of three self-etching adhesive systems with dif­ferent degrees of acidity (Clearfil SE Bond, One-Up Bond F, and Xeno III) to dentin prepared with three different methods. Methods: Forty-five extracted human third molars were ground flat to expose occlusal dentin and polished with 600-grit abrasive paper. All teeth were randomly divided into three groups according to the preparation method: baseline surface (AP#600), steel fissure bur (SB) and regular grit diamond bur (DB). Dentin surfaces were bonded with one of the three ad­hesive systems; then resin composite was incrementally built up. After storage in 37°C water for 24 hours, specimens were cut and trimmed to create an hourglass shape with cross sectional area of approximate 1 mm2. All specimens were subjected to microtensile bond strength testing. The bond strength data were analyzed with one and two-way ANOVA and Dunnett Multiple comparisons test at P< 0.05. Results: For Xeno III and One-Up Bond F, the µTBS to dentin prepared with the different methods were not significantly different. However, the µTBS of Clearfil SE Bond to dentin prepared with the diamond bur was significantly lower than the other preparation methods. Xeno III produced the lowest µTBS that were statistically different from the other adhesive systems when each preparation method was compared (P< 0.01). SEM observation of the prepared dentin surfaces showed that the diamond bur group produced a thicker smear layer that fol­lowed by steel bur and 600-grit paper. Therefore, the smear layer from diamond burs had a greater influence in decreasing µTBS of Clearfil SE Bond that has the weakest acidity self-etching adhesive systems evaluated. (Am J Dent 2007;20:259-262).


Clinical significance: When using the self-etching adhesive system tested to bond to dentin, a higher bond strength was obtained when the dentin surface was prepared using steel bur which produced a thinner smear layer compared with that of a diamond bur.


Address: Dr. Choltacha Harnirattisai, Department of Operative Dentistry, Faculty of Dentistry, Mahidol University, 6 Yothee Road, Rajthewee, Bangkok 10400, Thailand. E-:


Quality of curing in relation to hardness, degree of cure and

polymerization depth measured on a nano-hybrid composite


Nicoleta Ilie, grad eng, dr rer hum biol & Reinhard Hickel, dds, prof dr med dent


Abstract: Purpose: To analyze the curing behavior and the curing quality of a nano-hybrid composite material (Tetric EvoCeram) in relation to degree of cure, variation of hardness with depth and polymerization depth. Methods: The composite was evaluated after polymerizing the material with 13 different curing regimens of two LED devices and one halogen curing unit by assessing in real time the degree of cure at depths of 2 and 6 mm, the variation of hardness with depth and the polymerization depth. The sample preparation simulated the clinical incremental technique as well as a bulk fill procedure. Results: No correlation was found for the tested curing regimens between polymerization depth and surface hardness respectively between surface hardness and radiant exposure, whereas the polymerization depth was strongly dependent on polymerization time and radiant exposure. It can be therefore concluded that the surface hardness is not a reliable indicator of the quality of curing. The degree of cure was strongly influenced by depth and curing time, whereas the influence of the curing regimen and of the interaction products between these three factors was low. The higher effect on the variation of the Vickers hardness, measured 24 hours after polymerization, was exercised also by the depth, followed by curing regimen and curing time. (Am J Dent 2007;20:263-268).


Clinical significance: The increase of polymerization time considerably improved the polymerization depth for all curing units without changing the surface hardness. Considering a short polymerization time (10 seconds), the highest depth of cure was reached by using the warmer halogen curing unit and the pulse program of a LED curing unit, whereas the polymerization depth after curing with the other units did not exceed 2.5 mm. An incremental reconstruction will be necessary for deeper cavities. Extending the polymerization time (40 seconds), layers up to 5.2 mm were cured, however, a potential increase of shrinkage stress at the interfaces in a clinical situation must be taken into consideration.


Address: Dr. Nicoleta Ilie, Department of Restorative Dentistry, Dental School of the Ludwig-Maximilians-University, Goethestr. 70, 80336 Munich, Germany. E-:


Effect of post-retained composite restorations and amount of coronal

residual structure on the fracture resistance of endodontically-treated teeth


Roberto Sorrentino, dds, phd, Francesca Monticelli, dds, phd, Cecilia Goracci, dds, phD,

Fernando Zarone, md, dds, Franklin R. Tay, bdsc (Hons), fadm, phd, Franklin García-Godoy, dds, ms

& Marco Ferrari, dds, phd


Abstract: Purpose: To compare the fracture resistance and failure patterns of endodontically-treated teeth with a progressively reduced number of residual walls restored using resin composites, with or without translucent glass fiber posts. Methods: Ninety extracted human single-rooted maxillary premolars were used. After endodontic treatment, the following groups were created: Group 1 (control group): endodontically-treated single-rooted maxillary premolars with four residual walls; Group 2: three residual walls; Group 3: two residual walls; Group 4: one residual wall, and Group 5: no residual wall. Groups 2-5 were each divided into two subgroups: subgroups “a” were restored with resin composites, while subgroups “b” were restored with translucent glass fiber posts and resin composites. Static fracture resistance tests and statistical analyses (P= 0.05) were performed. Results: The mean failure loads (N) were 502.4±152.5 (Group 1), 416.4±122.2 (Group 2a), 423.0±103.3 (Group 2b) 422.1±138.9 (Group 3a) 513.2±121.7 (Group 3b), 488.7±153.7 (Group 4a) 573.4±169.2 (Group 4b), 856.7±112.2 (Group 5a) and 649.5±163.5 (Group 5b), respectively. The samples restored with fiber posts exhibited predominantly restorable fractures. The number of residual cavity walls influenced the mechanical resistance of endodontically-treated teeth. (Am J Dent 2007;20:269-274).


Clinical significance: The results of the present study would allow clinicians to make an informed choice from among available materials to restore endodontically-treated teeth, in order to decide in which clinical situations it would be advisable to use fiber posts.


Address: Prof. Marco Ferrari, Department of Dental Sciences, School of Dental Medicine, University of Siena, Policlinico Le Scotte, Viale Bracci, 53100 Siena, Italy. E-:



Extent of polymerization of dental bonding systems on bleached enamel


Lorenzo Breschi, dds, phd, Milena Cadenaro, dds, phd, Francesca Antoniolli, DEng,

Erika Visintini, dds, Manuel Toledano, dds, phd & Roberto Di Lenarda, dds, phd


Abstract: Purpose: To analyze the extent of polymerization of four adhesive systems on whitened enamel immediately after bonding or delayed for 24 hours and 2 weeks. The effect of prolonged light-curing was also analyzed. Methods: One adhesive of each class was investigated: Adper Scotchbond Multi-Purpose (three-step etch-and-rinse), One-Step (two-step etch-and-rinse), Clearfil Protect Bond (two-step self-etching) and Xeno III (one-step self-etching). Enamel fragments were treated with Opalescence Xtra Boost for 30 minutes, powdered and pressed into aluminum pans. Specimens were bonded immediately after bleaching, after 24 hours or after 14 days of storage in 100% humidity at 37°C. Unbleached enamel powder was prepared as control. Extent of polymerization of bonded interfaces was obtained with differential scanning calorimetry (DSC) at 20, 40 and 60 seconds and data were statistically analyzed with 3-way ANOVA and Tukey’s post-hoc test. Results: The extent of polymerization obtained from DSC exotherms of adhesives applied immediately after bleaching was significantly lower compared to controls. Increased extent of polymerization after storage was confirmed for all adhesives and no difference with controls was found after 14 days. Prolonged irradiation time increased curing rate for all the tested adhesives. This study supported the hypothesis that polymerization of the adhesive is reduced after enamel bleaching and delayed adhesive application reverses the polymerization inhibition. Prolonged polymerization intervals may counteract the inhibition of polymerization due to the bleaching procedure; nevertheless further clinical studies should validate this hypothesis. (Am J Dent 2007;20:275-280).


Clinical significance: This in vitro study supported the hypothesis that adhesive restorations should not be performed immediately after enamel bleaching and that dental adhesives should be polymerized for longer curing times than those recommended by manufacturers.


Address: Prof. Lorenzo Breschi, Division of Dental Sciences and Biomaterials, Department of Biomedicine, University of Trieste, Via Stuparich 1, 34129 Trieste, Italy. E-:

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