Abstracts of the February 2006 Issue

Effects of sonic energy on monospecific biofilms of cariogenic microorganisms.

E. Brambilla, M.G. Cagetti, G. Belluomo, L. Fadini & F. García-Godoy 

ABSTRACT: Purpose: To evaluate the in vitro differential effect of sonic energy, delivered by Sonicare Advance, on cariogenic and non-cariogenic bacteria biofilms. Methods: A wild strain of Streptococcus mutans, Lactobacillus acidophilus, Streptococcus salivarius and Veillonella alcalescens was isolated from human dental plaque. For each of the four microorganisms a biofilm adherent to bovine enamel disks, coated with artificial saliva, was obtained. Biofilms were divided into four groups and were exposed to acoustic energy delivered by Sonicare for 0 (control group), 5, 15 and 30 seconds. The distance between the end of the bristles and the disk surface was set to 7 mm, to ensure that the biofilm removal was simply due to fluid forces and not to the contact with the bristle tips during the brushing cycle. A colorimetric technique (MTT assay), based on the reduction of a yellow tetrazolium salt to a purple formazan, was used to evaluate the reduction of the adherent biomass after the exposure to the sonic energy. Results: ANOVA results showed that sonic energy exposure significantly reduced the biomass of S. mutans and S. salivarius adherent to the disks, while L. acidophilus and V. alcalescens seemed to remain basically unaffected. In the two streptococcal groups, the increase of the exposure time led to different reduction trends; while S. salivarius exhibited a progressive decrease over time, S. mutans showed a rapid reduction of the adherent biomass after a 15-second exposure to Sonicare. (Am J Dent 2006;19: 3-6). 

CLINICAL SIGNIFICANCE: Sonic energy delivered by Sonicare Advance had greater effect on streptococcal species than Lactobacillus acidophilus and Veillonella alcalescens. Since Streptococcus mutans is considered the major caries pathogen, an oral hygiene device able to selectively influence its concentration in plaque could be the best choice in the treatment of high caries risk subjects.  

Correspondence: Prof. Eugenio Brambilla, University of Milan, Department of Medicine, Surgery and Dentistry, San Paolo Dental Clinic, Via Beldiletto 1/3, Milan 20142, Italy. E-mail: Eugenio.Brambilla@unimi.it 

Proliferative response of gingival cells to ultrasonic and/or vibration toothbrushes.

H. Kusano, T. Tomofuji, T. Azuma, T. Sakamoto, T. Yamamoto  &  T. Watanabe

ABSTRACT: Purpose: To evaluate the effects of ultrasonic and/or vibration toothbrushes on cell proliferation and collagen synthesis. Methods: In eight dogs, teeth and gingivae were stimulated once a day as follows: the first quadrant with an ultrasonic toothbrush (1.6 MHz); the second one with a mechanical vibratory toothbrush (141 Hz); and the third one with a toothbrush generating both the ultrasound and the vibration. The fourth quadrant served as a control. Proliferative activity and collagen synthesis of gingival cells were evaluated by assaying the expression of proliferating cell nuclear antigen (PCNA) and procollagen type I C-peptide (PIP), respectively. Results: After 5 weeks, ultrasonic or vibratory toothbrushes increased the numbers of PCNA-positive fibroblasts and PIP-positive fibroblasts. Toothbrushing with a combination of ultrasound and mechanical vibration increased the numbers of PIP-positive fibroblasts, total fibroblasts and vascular endothelial cells to a greater extent than the one with only ultrasound alone. Vibratory toothbrush, but not the ultrasonic one, induced an increase in collagen density without gingival overgrowth. (Am J Dent 2006;19:7-10). CLINICAL SIGNIFICANCE: A mechanical vibratory and ultrasonic toothbrush can stimulate cell proliferative and collagensynthetic activities in gingivae, which effects ascribe to vibratory action of the bristles and may contribute to healing of gingival inflammation. 

Correspondence:  Dr. Tatsuo Watanabe, Department of Oral Health, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama 700-8525, Japan. E-mail: wyobou@md.okayama-u.ac.jp

Microvessel density and vascular endothelial growth factor (VEGF) expression in human radicular cysts.

F. Graziani, M. Vano, P. Viacava, A. Itro, G. Tartaro  &       M. Gabriele

ABSTRACT: Purpose: To assess vascular endothelial growth factor (VEGF) expression and microvessel density (MVD) by immunohistochemistry and to relate them to the inflammatory status in a sample of radicular cysts. Methods: Specimens of 24 human radicular cysts were examined by immunohistochemistry using antibodies anti-VEGF and anti- CD34 and to evaluate vascular density. Integrity of the epithelium and inflammatory state of the connective tissues were evaluated and related with the immunohistochemical findings. A Spearman correlation test was utilized to compare the means of each parameter. Results: VEGF immunoreactivity was detected in both epithelial and connective tissues of radicular cysts. Stromal cells showed higher levels of VEGF expression when compared to epithelial cells. MVD proved to be related to VEGF expression levels (P¡Ü 0.01). In addition, increased MVD was associated with high levels of inflammation (P¡Ü 0.01). Most of the specimens showed a massive inflammatory infiltrate in the connective tissue. The integrity of the cystic lining tend to decrease with increased inflammation. (Am J Dent 2006;19: 11-14). CLINICAL SIGNIFICANCE: The present study indicates that radicular cysts express VEGF both in the epithelium and in the connective tissues. VEGF expression may play an important role in the pathogenesis and enlargement of these lesions. A better understanding of cyst growth process will suggest new therapeutic opportunities as the anti-angiogenic treatment. 

Correspondence:  Dr. F. Graziani, Department of Neurosciences, Section of Oral Surgery, University of Pisa, Pisa, Italy. E-mail : f.graziani@med.unipi.it

Ability of quantitative light-induced fluorescence (QLF) to assess the activity of white spot lesions during dehydration.

M. Ando, G.K. Stookey  &  D.T. Zero

ABSTRACT: Purpose: To determine the ability of QLF to assess the activity of white spots using visual examination (VE) as the gold standard. Methods: Thirty-four specimens were prepared from extracted human permanent posterior teeth presenting natural white spots on the approximal surface. Fluorescence images were acquired at 1-second intervals for the first 10 seconds and every 5 seconds thereafter to 45 seconds. During image acquisition, specimens were dehydrated with compressed air. QLF variables of fluorescence loss (.F [%]), lesion size (S [mm2]), and .Q (.F¡¿S [%¡¿mm2]), were determined. Change in QLF variables per second (.QLFD: .FD, .SD, .QD) was determined using the following equation: (subsequent QLF-variables . baseline QLF-variables)/dehydration time. Five experienced dentists independently conducted VE under standardized conditions using a dental unit¡¯s light, compressed air, with an explorer, used only to check surface structure. Prior to VE, examiners had participated in a half-day training seminar on VE. After drying the specimens, examiners graded the lesions according to dullness of surface, roughness and presence of microcavitation. Agreement by at least three of them determined the activity status of lesions. Results: .QLFD values of Active white spot group (n=7) were compared with those of Inactive white spot group (n=27) using a two-sample t-test. In general, the active group presented larger values of .QLFD than the inactive group; however, there were no differences in .FD and .SD. There were significant differences in .QD up to 6 seconds of dehydration (P< 0.05), and no differences after 7 seconds. The results suggest that .QD can differentiate between active and inactive white spot lesions using QLF during the first few seconds of dehydration. (Am J Dent 2006;19: 15-18). CLINICAL SIGNIFICANCE: Change in .Q per second [.QD, (fluorescence loss ¡¿ lesion size)/second (% ¡¿ mm2/second)] during dehydration may be able to assess activity of white spot lesions using the quantitative light-induced fluorescence technique at the time of examination.

Correspondence:  Dr. Masatoshi Ando, Department of Preventive and Community Dentistry, Oral Health Research Institute, Indiana University School of Dentistry, Indianapolis, Indiana 46202-2876, USA. E-mail : mando@iupui.edu

Use of high-powered magnification to detect occlusal caries in primary teeth.

F.M. Mendes, E. Ganzerla, A.F. Nunes, A.V.C. Puig &    J.C.P. Imparato

ABSTRACT: Purpose: To evaluate if high-powered magnification could improve the performance of visual inspection and compare with other methods to detect occlusal caries lesions in primary teeth. Methods: 110 suspected sites were analyzed by two examiners with four methods: visual inspection, visual inspection aided with high-powered magnification (x20), laser fluorescence (DIAGNOdent) and radiographs. The first examiner performed the examinations in a second session to assess the intra-examiner reproducibility. Then, the teeth were cut and the sections were evaluated in stereomicroscope. Sensitivity, specificity and accuracy were calculated at enamel and dentin caries thresholds, and compared using McNemar change test. The ROC analysis was performed and the mean of areas under ROC curves were compared using ANOVA and Student-Newman-Keuls test. Inter- and intra-examiner reproducibility was assessed by calculating Cohen's Kappa. Results: The visual inspection with magnification did not change the accuracy and reproducibility of the visual inspection alone. The best caries detection method was laser fluorescence, and the least accurate was with radiographs. (Am J Dent 2006;19: 19-22). CLINICAL SIGNIFICANCE: The use of high-powered magnification did not improve the performance of the unaided visual inspection to detect occlusal caries in primary teeth. The use of laser fluorescence was the most accurate method.

Correspondence:  Dr. Fausto Medeiros Mendes, Departamento de Odontopediatria, Faculdade de Odontologia da Universidade de São Paulo, Av. Lineu Prestes, 2227, 05508-900 São Paulo, SP, Brazil. E-mail: medeirosmendes@uol.com.br

Effect of filler addition on the bonding parameters of dentin bonding adhesives bonded to human dentin.

Y-K. Lee, L.M. Pinzon, K.L. O’Keefe & J.M. Powers

ABSTRACT: Purpose: To determine the effect of filler addition on two total-etch, single component bonding systems on the bond strength, displacement at debonding, stiffness of debonding and energy absorbed to debonding of resin composites to human dentin. Methods: Two dentin bonding systems with no-filler (OS and SB) and filler-added (OSP and SBP) versions were studied. The dentin surfaces of human teeth were exposed with 600-grit SiC. TPH Spectrum A2 was used to bond to the dentin surfaces in the form of a truncated cone, 3 mm in diameter at the bonding surfaces and 5 mm in diameter at the base. Bonded specimens were stored in distilled water at 37°C for 24 hours. They were then debonded in tension with a universal testing machine at a cross-head speed of 0.5 mm/minute. Displacement at debonding, stiffness and energy to debonding were calculated based on the stress-displacement curve. Results: Bond strength, displacement at debonding and energy to debonding (measured and elastic) were influenced by the brand of the adhesive (OS/OSP vs. SB/SBP), but were not influenced by the filler addition based on two-way analysis of variance. Bond strength was in the range of 24.4-30.1 MPa, and there were significant differences between the bond strengths of OS and SB. Displacement and energy to debonding (measured and elastic) were different between the adhesives. Bond strength, bond stiffness and energy to debonding (measured) showed significant correlations. (Am J Dent 2006;19: 23-27). CLINICAL SIGNIFICANCE: Filler addition in dentin bonding adhesives did not change the bonding parameters such as bond strength, bond stiffness and energy to debonding. 

Correspondence: Dr. Yong-Keun Lee, Department of Dental Biomaterials Science, Dental Research Institute, College of Dentistry, Seoul National University, 28 Yeongeon-dong, Jongro-gu, Seoul, Korea. E-mail: ykleedm@snu.ac.kr

Effects of saliva contamination on shear bond strength of compomer to dentin in primary teeth.

L. Özer, N. Özalp, Z. Ökte  &  D. Öztas

ABSTRACT: Purpose: To investigate the effects of saliva contamination on the bond strengths of two compomers applied to primary teeth dentin during different bonding stages. Methods: 30 extracted human non-carious primary molars were prepared for shear bond-strength testing. Specimens were randomly divided into three groups of 10. Prime & Bond NT (acetone-based) and Futura Bond A & B (water-based) adhesives were tested under the following conditions: (a) non-contaminated conditions; (b) after contamination of the dentin surface with fresh whole saliva for 20 seconds and removal of excess saliva before adhesive application; and (c) contamination of the dentin surface with fresh whole saliva for 20 seconds and removal of excess saliva after adhesive curing. Following adhesive application Dyract AP or Glasiosite was applied via a polytetrafluroethylene split mould and light-cured to the dentin surface. Shear bond strengths were measured using an Instron Universal testing machine running at a crosshead speed of 1mm/minute. After measuring shear bond strengths, specimens were prepared for SEM evaluation and identification of failure type. Results were analyzed by two-factor experiment with repeated measures as one factor. Results: No statistically significant differences were found among the shear bond strengths (P> 0.05) of the groups. The results revealed that saliva contamination of dentin surfaces before or after adhesive application did not affect the shear bond strength of either compomer. (Am J Dent 2006;19: 28-30). CLINICAL SIGNIFICANCE: Saliva contamination before adhesive application or after adhesive curing did not affect the shear bond strength of (acetone-based) Prime & Bond NT or (water-based) Futura Bond A & B to primary dentin. 

Correspondence: Dr. Zeynep Ökte, Ankara Universitesi, Dis Hekimligi Fakültesi, Pedodonti Anabilim Dali, 06500 Besevler-Ankara, Turkey. E-mail : zokte62@yahoo.com

Hardness and wear resistance of two resin composites cured with equivalent radiant exposure from a low irradiance LED and QTH light curing units.

L.C. Ramp, J.C. Broome & M.H. Ramp

ABSTRACT: Purpose: To measure and compare three-body wear and Vickers hardness at depths of 0 mm and 2 mm in two composite resin materials cured with either a low irradiance light emitting diode (LED) or a quartz tungsten halogen (QTH) light-curing unit (LCU) in which exposure duration with the LED was increased to deliver equivalent radiant exposure in the 450-490 nm wavelength range. Methods: The VIP QTH and Freelight LED LCU’s were obtained and the emission spectrum of each was determined using a Spectra Pro 750 spectrograph. Irradiance in the 450-490 nm range for each LCU was determined by calculating the area under the spectral curve. Curing of two composite resins (Z100 and Esthet-X) with equivalent radiant exposure within this prescribed wavelength range was achieved by increasing the irradiation time of the LED 33% from 30-40 seconds to compensate for its lower irradiance (Table 1). The resulting radiant exposure of 8.40 J/cm2 was roughly equivalent to the radiant exposure produced in 30 seconds by the QTH LCU (8.67 J/cm2). The cured specimens were polished with progressively fine wet silicon carbide papers to 600 grit and stored in distilled water at 37°C for 24 hours prior to evaluating hardness and wear. Indentations for Vickers hardness testing were produced by applying a 0.5 kg load with a 15-second dwell time. Equivalent degree of cure was established indirectly through Vickers hardness numbers for the top and bottom surface of 2 mm thick disks of each material cured with each light (N= 3/group). Hardness ratios were computed by dividing mean bottom hardness by mean top hardness within each group. Three-body wear testing (N= 10/group) was performed on similarly fabricated specimens with a mechanical wear device using 44 µm unpolymerized PMMA beads as a simulated food bolus. The composite resin samples opposed spherical, stainless steel styli. A 75 N contact force was applied at 1.2 Hz for 100,000 cycles. Profilometry was used to quantify localized wear of the resin. Multivariate ANOVA and the Tukey-Kramer post hoc test (á= 0.05) were used to assess differences in hardness and wear of the materials. Results: With respect to hardness, no difference was noted between top and bottom specimen sides based on material or curing method. Specimens cured using the LED exhibited hardness ratios approaching unity. No significant difference in hardness was found for the main effect of light used, but the main effect of material was highly significant. This was primarily because Z100 cured with the LED demonstrated statistically higher hardness than the other three groups, which were statistically similar. No significant difference in wear was found based on the light used, with the lowest mean wear seen in Z100 cured with the LED. Overall, Z100 exhibited significantly greater surface hardness (P< 0.001) and significantly less wear (P< 0.01) compared to Esthet-X. (Am J Dent 2006;19: 31-36). CLINICAL SIGNIFICANCE: Within the parameters of this study, lower irradiance LED curing is an acceptable alternative to QTH curing when equivalent radiant exposure within the appropriate wavelength range is used. Due to the lower irradiance of the Freelight, a 33% (10 seconds) increase in exposure duration was necessary to obtain a radiant exposure approximately equivalent to the VIP. Higher irradiance LED units now available may not require this adjustment.

Correspondence: Dr. Lance C. Ramp, Department of Prosthodontics, University of Alabama School of Dentistry, SDB 77, 1919 7th Ave. S., Birmingham, Alabama 35294, USA. E-mail: lramp@uab.edu

Influence of different tests used to measure the bond strength to dentin of two adhesive systems.

L.M.A. Cavalcante, M.C.G. Erhardt, A.K.B. Bedran-de-Castro, L.A.F. Pimenta & G.M.B. Ambrosano

ABSTRACT: Purpose: To investigate the behavior of two bonding systems: self-etching primer Clearfil Liner Bond 2V (CLB) and total-etch Single Bond (SB) when submitted to two bond strength tests: shear bond strength (SBS) and microtensile (MTBS). Methods: Flat dentin surfaces were obtained at the facial surface of extracted bovine incisors. µTBS started with adhesive application and incremental resin composite insertion. Samples were then sliced into 1 mm slabs parallel to the long axis of the tooth. Half of the specimens from each group were trimmed in order to obtain dumbbell-shaped (D) specimens with a cross-sectional area of 1 mm2, and in the other half of the group, the slabs were cut into beams (B) with a cross section of 1 mm2 area. Specimens were individually fractured on a microtensile apparatus. For SBS, crown segments were embedded in polyester resin and a flat dentin surface was exposed for bonding. After adhesive and restorative procedures were accomplished, the specimens were kept in water for 24 hours prior to bond testing. The tests were performed in a universal testing machine. MPa values were analyzed by Tukey’s test (P< 0.05), two-way ANOVA (µTBS) and Student’s t-test (SBS). Results: Mean values (SD) on µTBS were: SB/B: 42.6 (15.1), SB/D: 35.4 (6.8), CLB/B: 14.3 (10.3) and CLB/D: 27.0 (7.9). SBS values (SD) were: SB: 17.3 (5.6) and CLB 15.9 (7.2). Beam specimens bonded with CLB presented the lowest results. SBS did not show statistical differences between groups. The results showed that the shear bond test seemed to lack the sensitivity that is required to detect subtle differences between bonding agents or procedures. (Am J Dent 2006;19: 37-40). CLINICAL SIGNIFICANCE: The “self etch” adhesive system Clearfil Liner Bond showed the lowest bond strength values independently of the test used, when compared to the “total etch/one bottle” adhesive system Single Bond. The clinician should be aware of the methodologies used to evaluate adhesive systems to make the decision of which one to use in their patients. 

Correspondence: : Prof. L.A.F. Pimenta, Piracicaba School of Dentistry – UNICAMP, Av. Limeira, 901 Caixa Postal 52, 13414-018 Piracicaba, SP, Brazil. 

E-mail: lpimenta@fop.unicamp.br

Five-year clinical evaluation of Dyract in small Class I cavities.

M. Demirci &  H.Ş. Sancakli

ABSTRACT: Purpose: To evaluate the 5-year clinical performance of Dyract in small Class I cavities in non stressbearing areas. Methods: On 36 patients, 87 restorations needing small cavity preparations were performed. The lesions were diagnosed macroscopically with a probe. They involved shallow fissures, and had reached dentin but the lateral spread was limited and localized in dentin. Cavities were designed to be on non stress bearing areas. Cavities’ average facio-lingual width were prepared to be 1/3 or less than the intercuspal width. At baseline, 1-, 2-, 3-, 4- and 5-year recalls, the restorations were evaluated according to the modified Ryge criteria by two calibrated, experienced examiners. Results: None of the restorations was lost and retention rate was 100% at the end of 1 year. After 2 years, one restoration (1.2%) had to be replaced due to caries lesion adjacent to its margin and the rate of retention was 98.8%. At the 3-year recall, four restorations, at the 4-year, one restoration and at the 5-year, one restoration had caries lesions adjacent to their margins and the cumulative retention rates were 94.2%, 92.9% and 91.5% respectively. Significant differences were detected between all of the evaluation periods in regard to color match rate (P= 0.00001), with the exception of rate between the baseline and 1 year evaluations. In regard to the marginal discoloration rates, there were statistically significant differences (P= 0.00001) between all of the evaluation periods with the exception of rates between the baseline and 1-year, 3- and 4-year, and 4- and 5-year results. Except for the failed restoration, no other restoration was clinically unacceptable in regard to color match, wear or loss of anatomic form, marginal discoloration, caries, marginal adaptation and surface texture. (Am J Dent 2006;19: 41-46). CLINICAL SIGNIFICANCE: Dyract’s 5-year clinical performance was satisfactory when used in small and non stress bearing Class I cavities and suggests that the material is reliable.

Correspondence: Dr. Mustafa Demirci, Faculty of Dentistry, Department of Conservative Dentistry, Istanbul University, Çapa, Istanbul, 34390 Turkey. 

E-mail: demirci.md@superonline.com

Bond strengths and adhesive remnant index of self-etching adhesives used to bond brackets to instrumented and uninstrumented enamel.

D.E. Ritter, A.V. Ritter, G. Bruggeman, A. Locks & J.F.C. Tulloch

ABSTRACT: Purpose: This study evaluated bond strengths of orthodontic brackets to instrumented and uninstrumented enamel using self-etching adhesive systems when compared to a total-etch adhesive system. The adhesive remnant index (ARI) was also determined after debonding. Methods: 140 bovine incisors were included in acrylic resin, and divided randomly in two groups: instrumented vs. uninstrumented enamel. For the instrumented enamel, specimens had their facial enamel ground flat to 600-grit. In each group, specimens were subdivided into four experimental subgroups according to the adhesive technique used: Transbond Plus, Adper Prompt L-Pop, iBond, and Adper Single Bond, applied following manufacturers¡¯ instructions. Orthodontic brackets were bonded to the treated instrumented or uninstrumented enamel with Transbond XT light-cured resin-based composite cement, and the bond strength was tested in shear mode after 7 days. One group where no etch and no adhesive were used served as a control. ARI scores were determined after debonding. Results: There was no statistically significant difference in mean bond strengths between instrumented and uninstrumented enamel for any of the adhesive systems (P¡Ý 0.05). No significant differences were observed for bond strengths among the adhesives tested (P= 0.308), and all experimental groups resulted in mean bond strengths significantly higher than the controls (P< 0.05). Statistically significant differences were identified when ARI scores were compared, with less adhesive remnants being observed for iBond (uninstrumented enamel) and the control groups (P< 0.05). (Am J Dent 2006;19: 47-50). CLINICAL SIGNIFICANCE: Self-etching adhesives can be used to bond orthodontic brackets to uninstrumented enamel.

Correspondence: Dr. André V. Ritter, The University of North Carolina at Chapel Hill, 302 Brauer Hall, Chapel Hill, North Carolina 27599-7450 USA. E-mail : rittera@dentistry.unc.edu

Regional bond strengths of a dual-cure resin core material to translucent quartz fiber post.

J. Aksornmuang, M. Nakajima, R.M. Foxton   &  J. Tagami

ABSTRACT: Purpose: To evaluate the microtensile bond strength (ƒÊTBS) of a dual-cure resin core material to different regions of translucent quartz fiber post in a post cavity using different surface treatments. Methods: 30 translucent quartz fiber posts (Light-Post) were used and divided into six groups according to the surface treatments: (1) no surface treatment (Control); (2) photo-cure bonding agent, Clearfil Liner Bond 2V Bond A (PLB); (3) dual-cure bonding agent, Clearfil Liner Bond 2V Bond A+B (DLB); (4) BdA+B followed by light-cured for 20 seconds (DLB&LC); (5) silane coupling bonding agent, Clearfil Photobond with Porcelain Bond Activator (PB+PBA); (6) PB+PBA followed by lightcure for 20 seconds (PB+PBA&LC). Treated post were cemented into artificial post cavities using a dual-cure composite core material (Clearfil DC Core) and light-cured for 60 seconds from the top of the cavity. After 24-hour storage in water, each specimen was serially sliced into twelve 0.6 �~ 0.6 mm-thick beams for the ƒÊTBS test. The data were divided into three regions (upper/middle/bottom) and analyzed using two-way ANOVA and Dunnet's T3 multiple comparisons (ƒ¿= 0.05). Results: The highest bond strength was present in the silane coupling bonding agent group for all regions (P< 0.05). Application of the bonding agent to the post surface significantly improved the bond strength compared with control (P< 0.05). There were no significant differences in ƒÊTBS at all regions between the photo and dual-cure type bonding agents (P< 0.05). The bond strength significantly decreased at the bottom region when the post surface was treated with bonding agents (P< 0.05), whereas no regional differences in bond strength were found in the silane coupling bonding agent group (P> 0.05). (Am J Dent 2006;19: 51-55). CLINICAL SIGNIFICANCE: Application of a silane coupling bonding agent improved the bond strength of resin composite to translucent quartz fiber post. Regional differences were found in resin/post bond strengths when the post surface was treated with the photo and dual-cure bonding agents.

Correspondence: Dr. Juthatip Aksornmuang, Department of Prosthetic Dentistry, Faculty of Dentistry, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. 

E-mail : juthatip.a@psu.ac.th

Clinical evaluation of a resin-modified glass-ionomer liner for cervical dentin hypersensitivity treatment.

D. Tantbirojn, S. Poolthong, C. Leevailoj, S. Srisawasdi, J.S. Hodges & R.C. Randall

ABSTRACT: Purpose: To evaluate the effectiveness of two agents for treating cervical dentin sensitivity associated with gingival recession or noncarious cervical lesions. Methods: 44 patients with at least mild sensitivity affecting cervical dentin were enrolled in a longitudinal randomized clinical trial. A resin-based desensitizer or an experimental glassionomer was assigned to treat at most two teeth from each side of the mouth. Sensitivity was assessed by tactile and cold tests, measured with a Visual Analogue Scale at baseline, after treatment, and at 1 week, 1, 3, 6, and 12 months after treatment. Other noteworthy clinical observations were recorded. Results: Both treatments effectively reduced dentin sensitivity (mixed linear model analysis). Sensitivity score for the glass-ionomer was significantly lower than for the resin-based desensitizer after treatment and at all follow-up periods (P< 0.0001). Some overhanging margins were observed in the glass-ionomer group, which could accumulate plaque and cause gingivitis. Despite material loss from some teeth treated with the glass-ionomer, the follow-up sensitivity scores were still lower than baseline scores. (Am J Dent 2006;19: 56-60). CLINICAL SIGNIFICANCE: Both resin-based desensitizer and experimental glass-ionomer significantly reduced cervical dentin sensitivity up to 12 months. The experimental glass-ionomer was more effective in reducing sensitivity. Overhanging margins of the glass-ionomer in the gingival area must be removed to avoid plaque accumulation that can lead to gingivitis. 

Correspondence: Dr. Daranee Tantbirojn, 16-212 Moos Tower, 515 Delaware St. SE, Minneapolis, Minneapolis 55455, USA. E-mail: tant0002@umn.edu

Clinical performance of posterior compomer restorations over 4 years.

N. Krämer, F. García-Godoy, C. Reinelt  & R. Frankenberger

ABSTRACT: Purpose: To clinically evaluate two polyacid-modified resin composites (Hytac and Dyract AP) for the restoration of posterior teeth over a 4-year period and to investigate accessible margins by light microscopy. Methods: In a controlled prospective clinical study, 71 cavities (21 occlusal, 41 MO/OD, 9 MOD) in 30 patients were restored with compomers by three dentists. Thirty-eight restorations were placed with the combination OSB/Hytac, the same patients received 33 restorations with Prime&Bond 2.1/Dyract AP. Enamel margins of the cavities were etched with phosphoric acid. At baseline, after 12, 24, and 48 months, the restorations were examined by two independent investigators according to modified USPHS-criteria. Focusing on the 40 restorations available at all recalls, a semiquantitative margin analysis was carried out at each recall using replicas and light microscopy at x130 magnification. Results: Twenty restorations were not investigated at the 4-year recall (drop-out). After 48 months, 11 restorations (Hytac: n=8, Dyract AP: n=3) had to be replaced due to tooth fracture (n=4), gap formation (n=5), and adhesive failure (n=2). Forty restorations were still in function after 4 years (overall failure rate 16%; Hytac: 21%; Dyract: 9%). Between the recalls, statistically significant differences were detected for the criteria marginal integrity (Alpha dropping from 76% at baseline to 32% after 4 years), restoration integrity (Alpha ratings at baseline 99% vs. 40% after 4 years), and occlusion (100% vs. 24%). For the criteria surface roughness (from the 6-month recall) and anatomical shape (after 4 years), a significant difference between the materials was evident in favor of Dyract AP. Except gap-free margins, the predominant criterion in the microscopic analysis at baseline was marginal overhang (24%) and 30% negative step formation after 4 years. (Am J Dent 2006;19: 61-66). CLINICAL SIGNIFICANCE: Dyract AP achieved a 91% success rate after 4 years when enamel margins were etched. Facing a 21% failure rate after 4 years of clinical service, the compomer material Hytac did not fulfill the ADA criteria for direct posterior restorative materials. 

Correspondence: Prof. Dr. Norbert Krämer, Glueckstrasse 11, D-91054 Erlangen, Germany. E-mail: kraemer@dent.uni-erlangen.de

The impact of ozone treatment on enamel physical properties.

P. Celiberti, P. Pazera  &  A. Lussi

ABSTRACT: Purpose: To assess the effects of the highly reactive molecule of ozone on sound enamel physical properties and its effects on sealing ability. Methods: The effect of ozone on sealant tag length, microleakage and unfilled area proportion were evaluated on intact and prepared sound molar fissures. Microhardness, contact angle and acid resistance tests were performed on ground sound smooth surfaces. The samples were treated with ozone for 40 seconds (HealOzone). Control samples were treated with air (modified HealOzone) or left untreated. Results: No statistically significant difference was observed between the control and ozone treated samples in all tests. Prepared fissures exhibited no unfilled areas and a statistically significantly lower microleakage compared to intact fissures. Ozone was shown to dehydrate enamel and consequently enhance its microhardness, which was reversible. (Am J Dent 2006;19: 67-72). CLINICAL SIGNIFICANCE: The results indicate that ozone did not influence the studied enamel physical properties and neither enhanced nor harmed the sealing ability.

Correspondence: Dr. Paula Celiberti, Department of Operative, Preventive and Pediatric Dentistry, Freiburgstrasse 7, 3010 Bern, Switzerland. E-mail : paulaceliberti@hotmail.com