Tooth bleaching and pit and fissure stain

David Scott Falconer, James C. Hamilton, dds , Kenneth W. Stoffers, dmd, ms  &  William  A. Gregory, dds , ms  

Abstract: Purpose: To investigate if tooth whitening had any effect on the shade of occlusal pit and fissure stains and whether reservoirs in bleaching trays affected bleaching of occlusal pit and fissure stains. Methods: 96 extracted molars were randomly divided into three paired groups for whitening using a 10% carbamide peroxide solution (Opalescence) or a 22% carbamide peroxide solution (Nite White Excel 3), or tap water for a control. One of each pair utilized reservoirs in their custom bleaching trays. Three dentists evaluated the shade of a specified occlusal area of pit and fissure stain twice before bleaching and twice after bleaching. Results: Pit and fissure stain showed significant lightening of shade for either of the bleaching systems (P< 0.0005) but not the control (P= 0.816). There was no significant difference in pit and fissure stain shade lightening following treatment between those groups utilizing reservoirs in the custom trays and those without reservoirs (P= 0.658). (Am J Dent 2008;21:71-73).  

*: Dr. James C. Hamilton, Department of Cariology, Restorative Sciences and Endodontics, University of Michigan, 1011 N. University, Ann Arbor, MI 48109, USA. E-*: jchamilt@umich.edu

 

Treating sensitive cervical areas with ozone. A prospective controlled clinical trial  

Jan  Eric  Dähnhardt, dr med dent ,  Markus  Gygax, dr med dent ,  Bernhard  Martignoni, dr med dent , Peter  Suter, dr med dent   &  Adrian  Lussi, dipl chem, dr med dent  

Abstract: Purpose: To determine whether the treatment of hypersensitive teeth with gaseous ozone (Healozone, KaVo 1600 ppm) for 60 seconds reduces pain immediately after treatment and in the longer term. Methods: In three private practices in Switzerland , 31 subjects suffering from hypersensitive teeth were treated with gaseous ozone over a period of 54 weeks (one test and one control tooth in each subject). A cross-over design was chosen. The pain level was measured with a Visual Analogue Scale before and after the treatment. Results: The subjects’ pain level was reduced by 55% ± 5.5% immediately after the ozone treatment. Over time, the pain level decreased significantly in all groups: The pain level in the test teeth was significantly reduced in Weeks 0-22 (treatment group, P< 0.001) compared to the pain level before treatment. The pain level in the control group was also reduced significantly over time in Weeks 0-22 (no-treatment, P= 0.025) and in Weeks 22-54 (treatment group, P= 0.0065). Comparing test and control teeth over time, there was no statistically significant difference in pain reduction (P= 0.58). (Am J Dent 2008;21:74-76).

   

   

*: Prof. Dr. Adrian Lussi, Department of Preventive, Restorative and Pediatric Dentistry, School of Dental Medicine, University of Bern , Freiburgstrasse 7, 3010 Bern , Switzerland . E-*: adrian.lussi@zmk.unibe.ch

 

Influence of a desensitizing agent on efficacy of a paint-on bleaching agent  

Dirk  Ziebolz, dr med dent , Christian  Hannig, dr med dent  &   Thomas  Attin, dr med dent  

Abstract: Purpose: To evaluate the influence of a desensitizing agent (VivaSens) on efficacy of a paint-on bleaching agent (VivaStyle Paint On Plus). Methods: Bleaching was performed for 7 days with VivaStyle Paint On Plus. The varnish was applied twice a day for 10 minutes each. 80 subjects were included in the study and randomly distributed in two groups (n= 40) according to exposed cervical dentin and perceived hypersensitivities. Group A used VivaStyle without VivaSens while Group B used VivaStyle Paint On Plus after a single application of VivaSens. Tooth color was assessed on facial surfaces of first upper incisors with Vita shade guide at baseline and 10 days after bleaching therapy. Sensitivity, with intensity graded from 0 (no sensitivity) to 10 (high sensitivity), was assessed chair-side using a blow of air at baseline, at the end of therapy (7 days) and 10 days after bleaching therapy. Statistical evaluation was performed with non parametric ANOVA. Results: Thirteen subjects dropped out of the study; six due to gingival burning sensation (A: 3; B: 3) related to the bleaching regimen and seven due to lack of compliance. Directly after completion of bleaching therapy, tooth color had changed significantly compared to baseline in both treatment groups without difference among the groups. Color changes (∆) according to Vita shade guide were as follows (mean ± standard deviation): Group A: ∆ 2.7 ± 1.0, Group B: ∆ 2.8 ± 0.9. After bleaching (7 days) the intensity of tooth hypersensitivity (mean ± standard deviation) was increased significantly compared to baseline in both groups (P< 0.05): Group A: 1.58 ± 1.91 (baseline: 0.4 ± 0.5); Group B: 1.3 ± 1.8 (baseline: 0.5 ± 0.7). The number of subjects reporting tooth hypersensitivity increased in Group A by 5 (n=13) and in Group B by 1 (n=10) subject. Although degree of hypersensitivities and number of subjects with hypersensitivities were lower in Group B, there was no significant difference between the groups. (Am J Dent 2008;21:77-82).

   

*: Dr. Dirk Ziebolz, Department of Operative Dentistry, Preventive Dentistry and Periodontology, Robert-Koch Str. 40, D-37075 Göttingen , Germany . E-*: dirk.ziebolz@zm-goettingen.de

Clinical evaluation of the effects of a sonic toothbrush with ultrasound waveguide in disrupting plaque with and without bristle contact

 

Aaron  R.  Biesbrock, dmd, phd, ms,   Tao  He, dds , phd,   Patricia  A.  Walters, rdh, msdh, msob &   Robert  D.  Bartizek , ms

   

Abstract: Purpose: To assess the in vivo plaque removal efficacy of the newly marketed sonic/ultrasonic toothbrush. Plaque removal resulting from the toothbrush being held approximately 3 mm from the tooth surface was compared versus a no brushing control. Also, plaque removal resulting from the brush being used according to the manufacturer’s instructions was compared versus a control of using the brush (with power turned off) like a manual toothbrush would be used. Methods: This was a replicate use, four-treatment, examiner-blind, randomized, eight-period crossover design single brushing plaque study involving 31 subjects. The four treatment regimens consisted of (1) brushing for 2 minutes with the Ultreo powered toothbrush according to manufacturer’s instructions, (2) brushing for 2 minutes with the Ultreo toothbrush (power turned off) using the brush like a manual toothbrush, (3) having a trained dental hygienist hold the Ultreo toothbrush head 3 mm from tooth surfaces for a total of 2 minutes, or (4) swishing with a dentifrice slurry for 1 minute in the absence of toothbrushing. For each subject, an experienced, calibrated plaque examiner performed the Turesky Modified Quigley-Hein Plaque Index prior to brushing and following brushing. The difference (baseline minus post-regimen) in average scores was calculated for each subject. The difference scores were analyzed for treatment regimen differences using a mixed model ANCOVA (with baseline whole-mouth average score as the covariate and subjects considered random) for a crossover design. Results: Adjusted mean plaque removal scores (baseline plaque score minus post-brushing plaque score) were 0.052 for swishing with a dentifrice slurry, 0.058 for the dental hygienist holding the Ultreo toothbrush approximately 3 mm from tooth surfaces, 0.536 for the Ultreo toothbrush used according to manufacturer’s instructions and 0.666 for the Ultreo toothbrush (power turned off) used like a manual toothbrush. The difference between the Ultreo toothbrush held approximately 3 mm from tooth surfaces and swishing with a dentifrice slurry was not statistically significant (P= 0.808). The adjusted mean plaque removal score for the Ultreo toothbrush (power turned off) used like a manual toothbrush was statistically significantly (P< 0.001) greater than the corresponding score for the Ultreo toothbrush used per manufacturer’s instructions. Ultreo used like a manual toothbrush had an adjusted mean plaque removal score that was 12.4% greater than that for Ultreo used per manufacturer’s instructions. Finally, plaque removal scores for the Ultreo toothbrush used per manufacturer’s instructions and used like a manual toothbrush were statistically significantly (P< 0.001) greater than plaque removal scores for the non-brushing treatment regimens. (Am J Dent 2008;21:83-87).

   

   

*: Dr. Aaron R. Biesbrock, The Procter & Gamble Company, 8700 Mason-Montgomery Rd., Mason , OH 45040 , USA . E-*: biesbrock.ar@pg.com

 

Influence of cementation variables on fatigue of simulated two-unit

cantilever resin-bonded fixed partial dentures

 

Andy  van Dalen, dds , phd,  Albert  J.  Feilzer, dds , phd  &   Cornelis  J.  Kleverlaan, phd

 

Abstract: Purpose: To determine the influence of various combinations of surface pretreatment and luting cement on flexural fatigue limits of two-unit CoCr cantilever resin-bonded fixed partial dentures. Methods: Cyclic fatigue tests were performed at 1 Hz on an ACTA fatigue tester. The staircase test method was used on CoCr beams, simulating cantilever resin-bonded fixed partial dentures, using flat ground bovine teeth as substrate. Two series of tests have been executed: (1) 10⁴ cycles, and (2) 10⁵ cycles. Prior to cementation, the CoCr beams were subjected to either sandblasting or Rocatec or Silicoater treatments. Three commercially available resin luting cements were used. Fatigue tests were performed 72 hours after cementation and storage in 37°C tap water. Each possible combination of cement and 

pretreatment (n = 20) was tested. Results: One cement, UniFix, showed hardly any debondings with any of the three surface pretreatments. The other two cements, RelyX ARC and Panavia, both showed significantly better performance with Rocatec than when pretreated with sandblasting or Silicoater. (Am J Dent 2008;21:88-92).

 

 

*: Dr. Andy van Dalen, Department of Dental Materials Science, Academic Centre for Dentistry, Louwesweg 1, 1066 EA Amsterdam, The Netherlands. E-*:  a.dalen@acta.nl

 

Effect of different surface treatments on the repair bond strength

of indirect composites

 

Evelise  M.  Souza, dds , mds , phd,  Carlos  E.  Francischone, dds , mds , phd,  John  M.  Powers, phd, Rodrigo  N.  Rached, dds , mds , phd   &  Sergio  Vieira, dds , mds , phd

 

Abstract: Purpose: To evaluate the tensile bond strength of indirect composites repaired with different surface treatments and direct composites. Methods: 180 specimens were prepared with Targis, belleGlass HP and Sculpture indirect composites, light-activated and post-cured according to the manufacturers’ recommendations. The specimens were stored in distilled water for 24 hours at 37°C. The bonding surfaces were prepared with air abrasion, hydrofluoric acid or hydrofluoric acid followed by a neutralizing solution. All the treated surfaces were subject to the application of a silane and a bonding agent before the repair procedures with Tetric Ceram and Tetric Flow for the Targis specimens, Herculite XRV and Revolution for the belleGlass HP specimens and Sculp-It and Flow-It for Sculpture specimens. The tensile bond strength tests were carried out using a universal testing machine at cross-head speed of 0.5 mm/minute. The type of fracture was observed under a light microscope at x40 magnification. Data were analyzed by a two-way ANOVA and Tukey’s post-hoc tests (P< 0.05). Results: Targis showed a statistically higher repair bond strength than belleGlass HP and Sculpture, which were not significantly different from each other. Air abrasion increased the repair bond strength of belleGlass HP and Sculpture. For Targis, all the surface treatments resulted in similar repair bond strength. The different viscosity of repair composites did not affect the repair of indirect composites. Fractured surfaces showed mostly adhesive failures, mainly with hydrofluoric acid treatment. (Am J Dent 2008;21:93-96).  

 

   

* Dr. Evelise M. Souza, R. Simão Bolivar 429, Apt. 204 , Curitiba , PR, Brazil . E-*:  evesouza@yahoo.com

 

Fracture resistance and microtensile bond strength of maxillary premolars restored with two resin composite inlay systems

 

Ya-Shou Sun , dds , ms,  Ya-Ming Chen, dds , ms,  Roger J. Smales, mds (hons), ddsc  &   Kevin H-K. Yip, bds , med , mmedsc, phd

 

Abstract: Purpose: To compare the in vitro fracture resistance and the microtensile bond strength (µTBS) of premolar teeth restored with two light-cured resin composite inlay systems. Methods: 50 sound human maxillary premolars were divided randomly into five equal groups. Four groups received mesial-occlusal-distal (MOD) inlay preparations. Restorative treatments comprised: Group 1 (Renew direct resin composite), Group 2 (Renew direct resin composite inlay), Group 3 (Tescera indirect resin composite inlay), Group 4 (non-restored), Group 5 (intact). All teeth were loaded axially until fracture. The same resin-based materials as used in Groups 1-3 were bonded to the superficial coronal dentin of 15 teeth. Beams approximately 1.0 mm x 1.0 mm were prepared and tested in microtensile mode. Results were compared using one-way ANOVA and Tukey’s multiple comparison tests. Results: Mean fracture strengths (KN): Group 1, 2.06 (0.76); Group 2, 2.30 (0.49); Group 3, 2.62 (0.68); Group 4, 1.24 (0.44); Group 5, 2.40 (0.71). Group 4 was significantly weaker that the other four groups, P< 0.01. Mean µTBSs (MPa): Group 1, 33.38 (6.24); Group 2, 20.38 (6.24); Group 3, 20.87 (4.62). Group 1 was significantly stronger than the other two groups, P< 0.01. (Am J Dent 2008;21:97-100).

 

 

*: Dr. Ya-Ming Chen, College of Stomatology , Nanjing Medical University , Nanjing , PR China. E-*: yaming_chen@yahoo.com

 

Influence of oil contamination on in vitro bond strength of bonding agents to dental substrates

 

Adriana Bona Matos, dds , ms, phd, Denise Cerqueira Oliveira, dds , ms, phd,

Samuel Nilo Vieira,   Narciso Garone Netto, dds , ms , phd  &  John M. Powers, phd

 

 

Abstract: Purpose: To evaluate the influence of cleaning procedures (pumice, anionic detergent and both procedures together) on the tensile bond strength of etch-and-rinse and self-etch adhesive systems to bovine enamel and dentin in vitro. Methods: Eighty non-carious, bovine incisors were extracted, embedded in acrylic resin to obtain enamel/dentin specimens. Flat bonding surfaces were obtained by grinding. Groups were divided according to substrate (enamel or dentin), adhesive system [etch-and-rinse, Adper Single Bond 2 (SB) or self-etch, Clearfil Protect Bond (PB)]; and cleaning substances (pumice, anionic detergent and their combination). The teeth were randomly divided into 20 groups (n=8): G1 - Enamel (E) + SB; G2 –E + oil (O) + SB; G3 – E + O + Pumice (P) + SB; G4 – E + O + Tergentol (T) + SB; G5 – E + O + P + T + SB; G6 – E + PB; G7 – E + O + PB; G8 – E + O + P + PB; G9 – E + O + T + PB; G10 – E + O + P + T + PB; G11 – Dentin (D) + SB; G12 D + SB + O; G13 – D + SB + O + P; G14 – D + SB + O + T; G15 – D + SB + O + P + T; G16 – D + PB; G17 – D + O + PB +; G18 – D + O + P + PB; G19 – D + O + T + PB; G20 – D + O + P + T + PB. Specimens were contaminated with handpiece oil for 5 seconds before bonding. Adhesive systems and resin composite were applied according to manufacturers' instructions. Specimens were tested in tension after 24 hours of immersion using a universal testing machine at a crosshead speed of 0.5 mm/minute. Bond strengths were analyzed with ANOVA. Failure sites were observed and recorded. Results: Tensile bond strength in MPa were: G1 (23.6 ± 0.9); G2 (17.3 ± 2.2); G3 (20.9 ± 0.9); G4 (20.6 ± 0.5); G5 (18.7 ± 2.3); G6 (23.0 ± 1.0); G7 (21.5 ± 2.4); G8 (19.9 ± 1.3); G9 (22.1 ± 1.2); G10 (19.1 ± 1.2); G11 (18.8 ± 1.3); G12 (15.7 ± 2.1); G13 (17.8 ± 3.3); G14 (15.3 ± 2.9); G15 (15.6 ± 1.9); G16 (14.7 ± 2.3); G17 (5.5 ± 0.9); G18 (19.3 ± 1.8); G19 (15.6 ± 1.6); G20 (20.3 ± 3.9). Statistical analysis showed that the main factors substrate and cleaning were statistically significant, as well as the triple interaction between factors of variance. However, the factor adhesive system did not show statistical difference. Oil contamination reduced bond strengths, being less detrimental to enamel than to dentin. Etch-and-rinse (SB) and two-step self-etch (PB) systems had similar bond strengths in the presence of oil contamination. For etch-and-rinse (SB), the cleaning procedures were able to clean enamel, but dentin was better cleaned by pumice. When self-etch (PB) system was used on enamel, anionic detergent was the best cleaning substance, while on dentin the tested procedures were similarly efficient. (Am J Dent 2008;21:101-104).  

 

   

*: Prof. Dr. Adriana Bona Matos, Department of Restoratve Dentistry, Faculty of Dentistry of the University of São Paulo (USP), Av. Prof. Lineu Prestes, 2227 - Cidade Universitária, CEP: 05508-900, São Paulo, SP, Brazil.  E-*:  bona@usp.br

 

Influence of timing of coronal preparation on retention of two types

of post cores

 

Gülbin  Saygılı, dds , phd,  Sevil  Şahmalı, dds , phd  &  Figen  Demirel, dds , phd

 

Abstract: Purpose: To compare the effect of coronal preparation on retention of cemented cast (Cr-Ni) and IPS post core systems. Methods: Cr-Ni and IPS post and cores were placed in 48 extracted single rooted human teeth with two different cements (dual-cure resin and glass-ionomer cement) and randomly divided into four groups of 12 specimens each. twelve of each post-core system were cemented with dual-cure cement and the other 12 of each system were cemented with glass-ionomer cement. Twelve specimens of each post core system were subjected to an axially directed removal force using a universal testing machine. Four groups of 12 specimens were divided into subgroups and subjected to preparation of their cores at 15 minutes and 24 hours after cementation. The specimens were tested at 24 hours having been stored in water at 37°C for the waiting period. The forces required for dislodgement of the posts from their prepared spaces were recorded. Data were statistically analyzed using ANOVA and the Newman-Keuls multiple comparison test. Results: Retention generally increased with time following cementation for both groups. The specimens cemented with glass-ionomer cement revealed less retention compared with specimens cemented with resin cement. Preparation of cemented post cores using a high speed handpiece had a significantly negative effect on retention when carried out 15 minutes and 24 hours after cementation. (Am J Dent 2008;21:105-107).

 

 

*: Dr. Gülbin Saygili, Department of Prosthetic Dentistry, Faculty of Dentistry, Hacettepe University , 06100 Ankara , Turkey . E-*: fdemirel@dr.com

 

Changes in surface contour of resin composites after light-curing

 

Yong-Keun   Lee , dds , phd

 

Abstract: Purpose: To determine the changes in free surface contour and volume of resin composites during light-curing by irradiating on half area of a specimen, using a 3-dimensional profilometer. Methods: Resin composite was packed into a metal mold (9 mm in inner diameter and 2 mm in thickness) after applying a lubricant to the mold. Both sides of the specimens were flattened. Light-curing was done on half area of a specimen for 40 seconds. Then, the entire area of the specimens was cured again with the same irradiation condition. Upper surface profile of a cured specimen in the mold was scanned with a three-dimensional profilometer. The changes in the shape of the free surface of resin composite in a simulated cavity after light-curing were determined as the changes in the height of the material under the condition that the height of the material at the non-irradiated margin was set as a reference point (0 mm). Height was calculated at 0, 2, 4, 6 and 8 mm from the irradiated margin. The elevated volume in the central 1.8 mm-thick section of the specimen was calculated at 2 mm intervals from the irradiated margin with the same reference point. Differences in height and volume by the resin composite were analyzed with repeated measures, one-way analysis of variance at the significance level of 0.05. Results: Height of the irradiated margin was the height and gradually decreased toward the non-irradiated margin. Surface contour change during light-curing was influenced by the distance from the irradiated margin and the brand of resin composite (P< 0.05). Height at the irradiated margin was 113.2-212.4 μm. Total changed volume, compared with the flat uncured surface, was 8.87-17.27x106 μ³. Contour of free surface varied by the resin composite, but showed similar pattern. (Am J Dent 2008;21:108-112).

 

 

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

 

Impact of fluoride, milk and water rinsing on surface rehardening

of acid softened enamel. An in situ study

 

Annette  Wiegand, dr med dent ,  Inga  Müller,  dr med dent ,  Jürgen  Dieter  Schnapp,  pd dr Ing , Carola  Werner, dr Rer nat   &  Thomas  Attin, prof, dr med dent

 

Abstract: Purpose: To evaluate the impact of fluoride, milk and water rinsing on surface rehardening of acid softened enamel in situ. Methods: Ten subjects performed six tests of 4 hours each. In each test, three softened enamel samples were attached to intraoral appliances. For softening, samples were immersed extraorally in an acidic beverage for 120 seconds. Subsequently, specimens were worn intraorally for 5 minutes (Tests 1-3) or 30 minutes (Tests 4-6). Thereafter, the volunteers rinsed with a 250 ppm SnF₂/Olaflur solution (Tests 1 and 4), milk (Tests 2 and 5) or non-carbonated mineral water (Tests 3 and 6) for 60 seconds. At each test, one sample was covered with tape during intraoral rinsing and thus, served as control. After rinsing, both test and the control samples were exposed to the oral cavity for up to 4 hours after demineralization. Surface microhardness (SMH) of the specimens was assessed at baseline, immediately after softening and 4 hours after softening. For each subject, the secretion rate of resting and stimulated saliva, buffering capacity and pH-value as well as calcium and phosphate concentration of saliva were measured. Statistical analysis was performed by ANCOVA followed by stratified analyses with Bonferroni correction. Results: Baseline Knoop Hardness (mean ± S.D.) amounted to 403.1 ± 39.4. Immediately after softening, mean SMH was reduced to 214.4 ± 24.1 KHN. Rinsing with 250 ppm fluoride, milk or water after 5 minutes or 30 minutes intraoral exposure of softened samples had a significant effect on rehardening. The increase of SMH (ΔKHN) was highest after rinsing with fluoride (5 minutes: 95.0 ± 18.3; 30 minutes: 94.2 ± 24.3) followed by milk (5 minutes: 77.1 ± 14.1; 30 minutes: 80.3 ± 18.7) and water (5 minutes: 49.0 ± 9.9; 30 minutes: 47.0 ± 14.1), but did not achieve baseline values. It is concluded that a single rinse with a 250 ppm SnF₂/Olaflur solution, milk or water increases rehardening of previously acid softened enamel. (Am J Dent 2008;21:113-118).

 

 

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

 

Susceptibility of a polycaprolactone-based root canal filling material to degradation using an agar-well diffusion assay

 

Noriko  Hiraishi, dds , phd,  Fernanda T.  Sadek, dds , phd,  Nigel  M.  King, bds , msc , phd,

Marco Ferrari, dds , phd,  David  H.  Pashley, dds , phd   &   Franklin  R. Tay, bdsc(hons), fadm, phd

 

Abstract: Purpose: To examine whether Resilon, a polycaprolactone-based thermoplastic root filling material was susceptible to biodegradation by cholesterol esterase using agar-well diffusion assay of serially-diluted aqueous Resilon emulsions that were dispersed in agar. Methods: Emulsions of Resilon and polycaprolactone were prepared and dispersed in agar on culture plates. Two different concentrations of a cholesterol esterase (0.3 and 1.2 U/mL) were prepared and fed to wells prepared in the agar plates using an agar-well diffusion assay for examination of the degradation of polymeric materials. Results: Degradation of the emulsified Resilon was manifested as the formation of clear zones of different sizes around the agar wells. No clear zones were observed in agar wells that contain sterile distilled water as the negative control. (Am J Dent 2008;21:119-123).

   

   

*: Dr. Franklin R. Tay, Department of Oral Biology and Maxillofacial Pathology, School of Dentistry, Medical College of Georgia, Augusta , GA 30912-1129 , USA .  E-*:  ftay@mcg.edu

 

 

Influence of water flow rate on shear bond strength of resin composite to Er:YAG cavity preparation

 

Vivian  Colucci, dds ,  Marília  Pacífico  Lucisano,  Flávia  Lucisano  Botelho  do  Amaral, dds , Jesus  Djalma  Pécora, dds , ms , phd,  Regina   Guenka  Palma-Dibb, dds , ms , phd &  Silmara  Aparecida  Milori  Corona, dds , ms, phd

 

Abstract: Purpose: To evaluate in vitro the influence of water flow rate on shear bond strength of a resin composite to enamel and dentin after Er:YAG cavity preparation. Methods: Ten bovine incisors were selected and roots removed. Crowns were sectioned in four pieces, resulting in 40 samples that were individually embedded in polyester resin (n=10), and ground to plane the enamel and expose the dentin. The bonding site was delimited and samples were randomly assigned according to cavity preparation: (1) Er:YAG/1.0 mL/minute; (2) Er:YAG/1.5 mL/minute; (3) Er:YAG/2.0 mL/minute and (4) High speed handpiece/bur (control group). Samples were fixed to a metallic device, where composite resin cylinders were prepared. Subsequently, they were stored for 24 hours and subjected to a shear bond strength test (500N at 0.5 mm/minute). Results: Means (MPa) were: enamel: 1: 12.8; 2: 16.8; 3: 17.5; 4: 36.0 and Dentin: 1: 13.6; 2: 18.7; 3: 12.1; 4: 21.3. Data were submitted to ANOVA and Tukey’s test. Adhesion to enamel was more efficient than for dentin. The cavities prepared with conventional bur (control) presented higher statistically significant bond strength values (P< 0.05) than for Er:YAG laser for both enamel and dentin. No significant differences were observed between water flow rates employed during enamel ablation. For dentin, the shear bond strength of 2.0 mL/minute water flow rate was lower than for 1.5 mL/minute and 1.0 mL/minute rates. The Er:YAG laser adversely affected shear bond strength of resin composite to both enamel and dentin, regardless of the water flow rate used. (Am J Dent 2008;21:124-128).

   

 

*: Dr. Silmara Aparecida Milori Corona, Department of Restorative Dentistry, Faculty of Dentistry, University of São Paulo , Av. do Café, S/N, Monte Alegre CEP: 14040-904, Ribeirão Preto , SP, Brazil . E-*: silmaracorona@uol.com.br

 

Long-term evaluation of the remineralization of interproximal caries-like lesions adjacent to glass-ionomer restorations: A micro-CT study

 

Hyeok- Sang Lee , dds , msd, Joel H. Berg, dds , msd, Franklin García-Godoy, dds , msd &  Ki-Taeg  Jang, dds , ms, phd

 

Abstract: Purpose: To compare the remineralization of incipient artificial interproximal caries in the presence of three glass-ionomer cements (highly-filled glass-ionomer cement, compomer, resin-modified glass-ionomer cement) and a resin composite (control). Methods: Proximal restorations were simulated by placing tooth specimens and the various glass-ionomer cements in closed containers with artificial saliva at 37°C and pH 7.0 for 30 days with constant circulation. Tomographic images were obtained with a micro CT scanner at 90, 180, and 270 days, and density-measuring software was used to calculate the micro-density of artificial caries lesions in the specimens. The mean density changes were compared between groups in order to evaluate the effects of remineralization. All data were analyzed using one-way ANOVA and the post-hoc Tukey multiple comparison test at P< 0.05. Results: While the density of artificial caries lesions increased for all treatments, the increases for the three glass-ionomer groups were significantly higher than that for the resin group in each 3-month period. As time increased, the amount of density also increased for the glass-ionomer groups, and significant differences were found between the remineralization effects of the glass-ionomer groups. The micro CT proved to be an effective evaluation method. (Am J Dent 2008:21:129-132).

   

   

*: Dr. Ki-Taeg Jang, Dental Research Institute and Department of Pediatric Dentistry, College of Dentistry, Seoul National University, 28-2, Yeongun-dong, Chongno-ku, Seoul 110-744, Korea.  E-*: jangkt@snu.ac.kr