Abstracts of the December 2006 Issue

Erosive tooth wear: Diagnosis, risk factors and prevention

Adrian Lussi, dds, ms, Elmar Hellwig, dds, Domenick Zero, dds, ms, & Thomas Jaeggi, dds

Abstract: Purpose: To provide an overview on diagnosis, risk factors and prevention of erosive tooth wear, which is becoming an increasingly important factor when considering the long term health of the dentition. Results: Awareness of dental erosion by the public is still not widespread due to the cryptic nature of this slowly progressing condition. Smooth silky-glazed appearance with the absence of perikymata and intact enamel along the gingival margin, with cupping and grooving on occlusal surfaces are some typical signs of enamel erosion. In later stages, it is sometimes difficult to distinguish between the influences of erosion, attrition or abrasion during a clinical examination. Biological, behavioral and chemical factors all come into play, which over time, may either wear away the tooth surface, or potentially protect it. In order to assess the risk factors, patient should record their dietary intake for a distinct period of time. Based on these analyses, an individually tailored preventive program may be suggested to patients. It may comprise dietary advice, optimization of fluoride regimes, stimulation of salivary flow rate, use of buffering medicaments and particular motivation for non-destructive tooth brushing habits. The frequent use of fluoride gel and fluoride mouthrinse in addition to fluoride toothpaste offers the opportunity to minimize abrasion of tooth substance. (Am J Dent 2006;19:319-325).

Clinical significance: Since erosion, attrition and abrasion often occur simultaneously, all causative components must be taken into consideration when planning preventive strategies.

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

Fracture behavior of structurally compromised non-vital maxillary premolars restored using experimental fiber reinforced composite crowns

Wietske A. Fokkinga, dds, Cees M. Kreulen, dds, phd, Anna-Maria Le Bell-Rönnlöf, dds, Lippo V.J. Lassila, dds, msc, Pekka K. Vallittu, dds, phd, cdt & Nico H.J. Creugers, dds, phd

Abstract: Purpose: To study the fracture behavior of direct resin composite crowns with or without experimental fiber reinforcement. Methods: Clinical crowns of single-rooted maxillary premolars were cut off at the cemento-enamel junction. Canals were prepared with Gates Glidden drills up to size 4. No additional post-space preparations were made. Roots were embedded in acrylic and canal entrances were standardized (depth 2 mm, diameter 1.75 mm). Three groups of 14 samples were treated as follows: (1) custom-made glass FRC post (EverStick Post); fibers 5 mm deep in the canal, (2) similar post-system as (1) with incorporation of a new type of glass fiber fabric, (3) no fiber reinforcement (control). Posts were cemented with resin cement (Panavia F). Resin composite crowns (Filtek Z250) were made using an anatomically formed mold. Static load until fracture was applied using a universal loading device with a cylindrical bar (diameter 2 mm) with a crosshead speed of 5 mm/minute (loading angle: 30 degrees to the tooth long-axis). Failure modes were categorized as favorable and unfavorable failures. Results: There was no significant difference in mean failure loads among the four groups (P> 0.05). Favorable failures occurred significantly more often in Group 2 than in the other groups (P< 0.05). The results suggest that an incorporated glass fiber fabric does not affect the load-bearing capacity of resin composite complete crowns on structurally compromised and non-vital premolars. Incorporation of a glass fiber fabric, however, has a beneficial effect on the failure mode. (Am J Dent 2006;19:326-332).

Clinical significance: The resin composite complete crown on a structurally compromised tooth, with or without fiber reinforcement, might be a viable alternative for the conventional cast crown.

*: Wietske A. Fokkinga, College of Dental Science, Department of Oral Function and Prosthetic Dentistry, Radboud University Nijmegen Medical Centre, P.O Box 9101, 6500 HB Nijmegen, The Netherlands. E-*: w.fokkinga@dent.umcn.nl

Effect of the seating pressure on the adhesive bonding of indirect restorations

Nicoletta Chieffi, dds, ms, phd, Stefano Chersoni, dds, ms, phd, Federica Papacchini, dds, ms, phd, Michele Vano, dds, ms, Cecilia Goracci, dds, ms, phd, Carel L. Davidson, md, phd, Franklin R. Tay, bdsc (hons), phd & Marco Ferrari, md, dds, phd

Abstract: Purpose: To evaluate the effect of two different techniques of seating pressure application on the adhesive-dentin bond of indirect restorations. Methods: Eight non-carious human third molars were randomly divided in two treatment groups (four teeth each). Cylindrical composite blocks were luted with a resin cement (Panavia F). In Group 1, the seating pressure was applied for 5 seconds. In Group 2, the resin cylinder was maintained under constant pressure during the entire 3-minute polymerization period of the resin cement. After storing in distilled water for 24 hours, 0.9 x 0.9 mm sticks were produced from these luted specimens for microtensile bond testing and SEM examination. Results: The Student t-test showed a significant difference (P< 0.05) in bond strength between Groups 1 and 2. SEM revealed the presence of structural defects and resin globules on the seating surface of the composites. These features were exclusively identified from Group 1 specimens and were probably caused by fluid transudation from the underlying dentin through the simplified self-etch adhesive (ED primer). (Am J Dent 2006;19:333-336).

Clinical significance: Pressure application during the entire course of setting of the dual-cured resin cement improved the bond strength and reduced fluid interference from the bonded dentin.

: Prof. Marco Ferrari, University of Siena, School of Dental Medicine, Department of Dental Sciences, Policlinico Le Scotte, Viale Bracci, Siena, 53100, Italy. E-: ferrarimar@unisi.it

Marginal quality in enamel and dentin after preparation and finishing with an Er:YAG laser

Carl Bader, med dent & Ivo Krejci, prof dr med dent

Abstract: Purpose: To find the most appropriate Er:YAG laser parameters for an optimal marginal adaptation of Class V restorations in enamel and dentin. Methods: Six saucer-shaped mixed Class V cavities were prepared in each of the eight experimental groups with an Erbium:YAG hard laser (Opus Duo) on extracted human molars in near contact mode with a conical 800 µm sapphire tip under continuous water spray by using different pulse energy and pps (pulse per second) parameters. The cavities were restored under the simulation of dentin fluid with Clearfil SE Bond and Clearfil APX PLT composite applied in two layers and light-cured. Marginal adaptation in enamel and dentin was quantified before and after simultaneous thermal (5-50-5°C, 2 minutes each) and mechanical (max. 49N; 1,200,000 cycles) stresses by using the replica technique in a SEM under x200 magnification. Results: With the exception of dentin margins before loading, significant differences for percentages of “continuous margin” and “enamel fractures” were detected before and after loading (P< 0.05, ANOVA, Student’s t-test). A pulse energy of 100 mJ both on dentin and enamel was found optimal for finishing and smoothing the preparation margins after cavity preparation with 500 mJ or more. (Am J Dent 2006;19:337-342).

Clinical significance: After efficient cavity preparation with 500 mJ per pulse by using an Er:YAG laser the finishing with 100 mJ/pulse optimized marginal adaptation in mixed Class V cavities restored with a self-etching adhesive system and composite.

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: Dr. Ivo Krejci, Prof. Dr. med. dent., Division of Cariology and Endodontology, School of Dentistry, University of Geneva, Rue Barthélemy-Menn 19, CH-1205 Geneva, Switzerland.

E-: ivo.krejci@medecine.unige.ch

Stain retention and surface characteristics of posterior composites polished by one-step systems

L. Şebnem Türkün, dds, phd & E. Ali Leblebicioğlu, dds, phd

Abstract: Purpose: To compare susceptibility to stain of three posterior composite surfaces polished with two one-step polishing systems, to test the efficiency of the re-polishing to remove the stain formed and to analyze the polished surfaces by SEM. Methods: The resin composites tested were Clearfil Photo Posterior, SureFil and Filtek P60. The polishing systems used were Sof-Lex Brush and PoGo. Twenty-two discs of each material were fabricated and divided into two treatment groups of 11. Out of the latter, six were used for SEM evaluation for surface morphology and five for stain retention testing. The discs were roughened with silicon paper and polished for 30 seconds with each system. Specimens were immersed in coffee and distilled water for 7 days. Color measurements were made at baseline and after 1,3,5, and 7 days with a spectrophotometer. The specimens were then re-polished with the same systems and their colors re-measured. All comparison of color change and re-polishing were subjected to repeated measures ANOVA with a Bonferroni post hoc test (P≤ 0.05). Results: After 1 week, the coffee stained all the resin composites. Clearfil Photo Posterior was the least stained composite while Filtek P60 was the most. Regardless of the materials, PoGo polishing was less susceptible to staining (P≤ 0.05). The color change could be partially removed with re-polishing. The surfaces of Sof-Lex Brush polished samples, except the Clearfil group, were scratched and thus more susceptible to stain retention. (Am J Dent 2006;19:343-347).

Clinical significance: The re-polishing procedure was partially effective in the restitution of the original color changed by coffee staining for the packable composites tested. PoGo polished surfaces had less staining and smoother surfaces.

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: Dr. L. Şebnem Türkün, Department of Restorative Dentistry and Endodontics, Ege University School of Dentistry, 35100 Izmir, Turkey. E-: sebnemturkun@hotmail.com

Effect of antioxidant on coronal seal of dentin following sodium-hypochlorite and hydrogen-peroxide irrigation

Tijen Pamir, phd, dds, Murat Türkün, phd, dds, Ayşegül Demirbaş Kaya, phd, dds & Figen Sevgican, phd, dds

Abstract: Purpose: To reduce the microleakage of a self-etching priming dentin adhesive with the use of antioxidant or bur finishing after sodium-hypochlorite or hydrogen-peroxide irrigation. Methods: 70 single-root canals were enlarged and seven different treatment protocols were applied throughout the root canal treatment: The roots in Groups 1, 2, and 3 were irrigated with sodium-hypochlorite. Group 1 was used as the negative control with only sodium-hypochlorite irrigation whereas in Group 2, sodium-ascorbate was applied as an additional irrigation agent following sodium-hypochlorite. Irrigation procedure in Group 3 was same as in Group 1, however, after the roots in this group were obturated, cavities were cleaned off with a carbide bur (bur-finishing) to remove the effect of sodium-hypochlorite. Hydrogen-peroxide irrigation was used in Groups 4, 5 and 6; the procedural steps were similar to those of Groups 1, 2 and 3: hydrogen-peroxide in Group 4, sodium-ascorbate application in Group 5, and bur-finishing in Group 6. Group 7 was the positive control with saline irrigation alone. All roots were obturated with Diaket sealer and gutta-percha cones using cold lateral condensation technique immediately after irrigation. A self-etching priming adhesive plus resin composite was applied after the endodontic treatment. The microleakage of dentin margins was determined using dye-penetration technique with clearing process. Results: The Kruskal-Wallis followed by Mann-Whitney test showed that both sodium-hypochlorite and hydrogen-peroxide deteriorated the marginal seal of the dentin adhesive (P< 0.05), however, following both irrigation solutions the use of sodium-ascorbate reduced the microleakage (P< 0.05). Additionally, when sodium-ascorbate or bur-finishing was applied to remove the deterioration caused by sodium-hypochlorite or hydrogen-peroxide, the microleakage scores obtained were not different from that of the positive control (P> 0.05). (Am J Dent 2006;19:348-352).

Clinical significance: The adverse effects of sodium-hypochlorite and hydrogen-peroxide irrigation on marginal seal of the dentin adhesive might be alleviated with the application of sodium-ascorbate as an additional irrigation agent.

: Dr. Tijen Pamir, Department of Restorative Dentistry and Endodontics, Ege University School of Dentistry, 35100 Bornova, İzmir, Turkey. E-: tijenpamir@yahoo.com

Cleaning effectiveness and shaping ability of rotary ProTaper compared with rotary GT and manual K-Flexofile

Sheng-bo Liu, mds, Bin Fan, dds, Gary S.P. Cheung, dds, Bing Peng, dds, phd, Ming-wen Fan, dds, phd, James L. Gutmann, dds, Ya-ling Song, dds, phd, Qiang Fu, mds & Zhuan Bian, dds, phd

Abstract: Purpose: To compare the cleaning efficacy and shaping ability of engine-driven ProTaper and GT files, and manual preparation using K-Flexofile instruments in curved root canals of extracted human teeth. Methods: 45 canals of maxillary and mandibular molars with curvatures between 25ºand 40º were divided into three groups. The groups were balanced with regard to the angle and the radius of canal curvature. Canals in each group were prepared to an apical size of 25 with either the rotary ProTaper or GT system, or manually with K-Flexofile using the modified double-flared technique. Irrigation was done with 2 mL 2.5% NaOCl after each instrument and, as the final rinse, 10 mL 2.5% NaOCl then 10 mL 17% EDTA and finally 5 mL distilled water. The double-exposure radiographic technique was used to examine for the presence of apical transportation. The time required to complete the preparation, as well as any change in working length after preparation were recorded. The roots were then grooved and split longitudinally. The amounts of debris and smear layer were evaluated at the apical, middle and coronal regions under the scanning electron microscope. Data were analyzed either parametrically with the F-test or non-parametrically using the Kruskal-Wallis test, where appropriate. Results: Two GT files but none of the K-Flexofile and ProTaper instruments separated. For debris removal, the ProTaper group achieved a better result than GT (P< 0.05) but not the K-Flexofile group at all three regions (apical, middle and coronal). K-Flexofiles produced significantly less smear layer than ProTaper and GT files only in the middle third of the canal (P< 0.01). Both NiTi rotary instruments maintained the original canal shape better than the K-Flexofiles (P< 0.05) and required significantly less time to complete the preparation. (Am J Dent 2006;19:353-358).

Clinical significance: ProTaper instruments allowed significantly better removal of debris than GT files but not K-Flexofiles. The ProTaper system took less time than GT files or K-Flexofiles to complete the instrumentation.

: Dr. Zhuan Bian, Department of Endodontics, School and Hospital of Stomatology, Wuhan University, 237 Luoyu Road, Wuhan 430079, China. E-: kqyywjtx@public.wh.hb.cn

Survival of self-etch adhesive Class II composite restorations using ART and conventional cavity preparations in primary molars

Ece Eden, dds, phd, Asli Topaloglu-Ak, dds, phd, Jo E. Frencken, dds, msc, phd & Martin van’t Hof, phd

Abstract: Purpose: To test the null-hypothesis that there was no difference in the survival percentages of Class II composite restorations in primary teeth produced through either ART or conventional approaches after 2 years. Methods: 157 children with 325 Class II cavitated dentin lesions were included in a split-mouth study design. A computer program randomly assigned cavitated dentin lesions to treatment groups stratified for gender, operator, upper/lower jaw and left/right side of the mouth. Three operators placed resin composite (Pertac II) restorations using a self-etch adhesive (Prompt L-Pop). Two independent examiners evaluated the restorations after 0.5, 1 and 2 years using the modified Ryge criteria. A modification of the actuarial survival method was applied to estimate survival percentages. Results: There was no statistically significant difference (P> 0.05) observed between the cumulative survival percentages of Class II composite restorations in primary teeth produced by the two approaches after 2 years (ART: 34.9% ± 4.7%; conventional: 35.1% ± 4.7%). The cumulative survival percentages of ART and conventional Class II restorations of one of the operators were lower than for ART restorations of the other two operators and for conventional restorations of one of the operators (P≤ 0.001). The main reason for Class II composite restorations to fail over the 2-year period was complete loss of retention; ART: 75%; conventional: 77%. The null-hypothesis was accepted as there was no difference in the cumulative survival percentages of ART and conventional Class II composite restorations in primary teeth after 2 years. It appears that the low survival results obtained may have been caused by poor bonding of the self-etch adhesive. (Am J Dent 2006;19:359-363).

Clinical significance: The use of a self-etch adhesive system and resin composite did not provide high restoration survival percentages in Class II preparations in primary teeth

: Dr. J.E. Frencken, WHO Collaborating Centre for Oral Health Care Planning and Future Scenarios, Radboud University Medical Centre, College of Dental Sciences, P.O. Box 9101, 6500 HB Nijmegen, the Netherlands. E-: j.frencken@dent.umcn.nl

In vitro wear evaluation of dental materials in primary teeth

Marcia Regina Bernardi da Cunha, dds, ms, phd, Regina Maria Puppin-Rontani, dds, ms, phd, Jack L. Ferracane, ms, phd & Lourenço Correr-Sobrinho, dds, ms, phd

Abstract: Purpose: To evaluate the effect of dental materials on primary enamel wear. Methods: Four composites (Filtek Z250, Heliomolar, Point 4, SureFil), two compomers (Dyract AP, F2000) and a resin-modified glass-ionomer (Vitremer) were placed into box-shaped preparations in buccal surfaces of primary molars and stored for 24 hours in water at 37°C. The specimens (n = 6) were subjected to abrasive three-body wear against a primary enamel cusp. Material wear, enamel wear (adjacent to the material), and wear on enamel cusps were estimated by profilometry and video-analysis software. Results were compared with ANOVA and Tukey's tests (P< 0.05). Results: Vitremer showed the highest wear (P< 0.05), followed by Dyract AP and F2000, which were not statistically different (P> 0.05). There was no significant difference between Filtek Z250 and Dyract AP (P> 0.05). Filtek Z250, Heliomolar, Point 4 and SureFil, showed the lowest wear values and there was no difference among them (P> 0.05). The highest wear values on the enamel adjacent to the material were found with Dyract AP (P< 0.05) and the lowest next to Point 4 and SureFil (P< 0.05). There was no difference in the wear of the enamel next to Vitremer, F2000, Heliomolar and Filtek Z250 (P> 0.05). Vitremer and F2000 caused the highest wear on enamel cusps (P< 0.05), and there was no statistically significant difference (P> 0.05) between them; SureFil caused the lowest wear (P< 0.05) on the opposing enamel. There was a correlation (r= 0.85) between wear of materials and wear on the enamel cusps, but not (r= 0.53) for the wear on enamel besides the restoration and wear on enamel cusps. SEM micrographs showed different surface characteristics of the materials after the wear test. (Am J Dent 2006;19:364-369).

Clinical significance: The selection of materials for use in primary molar teeth should be done taking into consideration the wear in both the primary enamel and the restorative material.

: Prof. Dr. Marcia Regina Bernardi da Cunha, Rua Alexandre Herculano 64, Bairro Jardim Nossa Senhora Auxiliadora, Campinas, SP 13075-260, Brazil. E-: dacunhamrb@yahoo.com.br

Migration and particle clearance from hard-setting Ca(OH)₂ and self-etching adhesive resin following direct pulp capping

Yuichi Kitasako, dds, phd, Shunichi Shibata, dds, phd & Junji Tagami, dds, phd

Abstract: Purpose: To evaluate the migration and particle clearance from a hard-setting calcium hydroxide (HSCH) and self-etching adhesive resin (SEAD) following direct pulp capping using the light and electron microscope. Methods: Exposed monkey pulps were capped with a hard-setting calcium hydroxide (Dycal) or adhesive resin (Clearfil SE Bond), and histopathologically evaluated at 14 and 21 days using light and transmission electron microscopy (n=14). Results: At 14 days, both HSCH and SEAD materials showed no severe inflammatory reactions of the pulp (necrosis and abscess formation). The main reaction was slight inflammatory cell infiltration consisting of leukocytes. A number of HSCH particles were entrapped by macrophages and observed in the small capillaries similar to blood or lymphatic vessels. For SEAD, slight hemorrhage was observed at the exposed surface. At 21 days, for both HSCH and SEAD, a few cases showed minimal inflammatory response which was limited to the area beneath the exposure. Some macrophages entrapping the HSCH particles in vacuoles within the cytoplasm were arranged at the surface of the capping layer. HSCH particles were also observed in the vessels similar to blood or lymphatic vessels. A few macrophages entrapped filler-like particles of SEAD adjacent to the capping material, but there was no evidence of any SEAD in the vessels. (Am J Dent 2006;19:370-375).

Clinical significance: Both the hard-setting calcium hydroxide and self-etching adhesive resin materials migrated into the exposed pulp, and macrophages contributed to the process of their clearance. However, the pulp healing activity of small capillaries similar to blood or lymphatic vessels might depend on the type of capping material.

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

Clinical evaluation of a polyacid-modified resin composite (Dyract AP) in Class I cavities: 3-year results

Mustafa Demirci, dds, phd & Ömer Uysal, phd

Abstract: Purpose: This study evaluated the 3-year clinical performance of the polyacid-modified resin composite Dyract AP in restorations for Class I carious lesions. Methods: 108 Class I cavities in 21 subjects were restored with Dyract AP. The lesions, which were diagnosed macroscopically with a probe, involved fissures and had reached the dentin, while lateral spread was limited and localized to the dentin. The average facio-lingual width of the cavities was equal to or less than one-third the intercuspal width. Restorations were evaluated clinically by two experienced, calibrated examiners at baseline and at 1, 2, and 3 years, according to the modified Ryge criteria, (color match, marginal discoloration, wear or loss of anatomical form, caries, marginal adaptation, and surface texture). Results: None of the restorations failed at the end of the first year. At 2 years, two restorations required immediate replacement due to caries lesions adjacent to the margins. At 3 years, six restorations had caries lesions adjacent to their margins, and the cumulative rate of success was 93.4%. Color changes and marginal discolorations were found to be statistically significant (P< 0.001) at 3 years, although none of the restorations needed to be replaced. Significant differences were also observed in the caries rate (P< 0.001) at 3 years. Aside from the eight failed restorations, the degrees of color matching, marginal discoloration, wear or loss of anatomical form, caries, marginal adaptation, and surface texture were clinically acceptable at 3 years post-treatment. (Am J Dent 2006;19:376-381).

Clinical significance: The results of this study showed that after 3 years, Dyract AP exhibited an adequate clinical success rate in the treatment of Class I caries lesions .

: Dr. Mustafa Demirci, Department of Conservative Dentistry, Faculty of Dentistry, Istanbul University, Çapa, Istanbul 34390, Turkey. E-: demirci.md@superonline.com

Clinical and microbiological effect of calcium hydroxide protection in indirect pulp capping in primary teeth

Alice Souza Pinto, dds, ms, Fernando Borba de Araújo, dds, ms, phd, Renata Franzon, dds, Marcia Cançado Figueiredo, dds, ms, phd Sandra Henz, dds, ms, Franklin García-Godoy, dds, ms & Marisa Maltz, dds, ms, phd

Abstract: Purpose: To evaluate clinically and microbiologically the effect of calcium hydroxide (CH) on carious dentin on primary teeth submitted to indirect pulp capping (IPC). Methods: Twenty 4-7 year-old subjects with 42 treated teeth participated in the study. The treatment consisted of incomplete excavation of the demineralized dentin, application of a CH or gutta-percha (GP) layer and sealing with a resin-based composite for 4-7 months. After cavity preparation and sealing, the dentin was evaluated clinically (color and consistency) and microbiologically. Dentin samples were cultured on blood agar under aerobic and anaerobic conditions, in Mitis Salivarius agar and Rogosa SL agar. Results: 39 teeth (20 in the CH Group and 19 in the GP Group) were reopened 4-7 months post-treatment for clinical and microbiological evaluation. In all teeth, the initial demineralized dentin was wet and soft or leathery. In the CH Group, 10% of the lesions were yellow, 80% light brown and 10% dark brown and in the GP Group, 94.7% were light brown and 5.3% dark brown. After treatment, the dentin was dry, 90% (Group CH) and 84.2% (Group GP) were dark brown. The final consistency was either leathery or hard. Three samples in the CH Group and five in Group GP changed from soft to leathery; only one sample (GP) remained leathery. 85% in the CH Group and 68.4% in GP Group turned hard after treatment. All bacterial counts decreased significantly by the end of treatment. In the CH Group, the bacterial (Log¹⁰ CFU + 1) anaerobic growth decreased from 4.84 ± 1.31 to 1.35 ± 1.54, aerobic from 4.09 ± 1.04 to 0.92 ± 1.30 and lactobacilli from 3.24 ± 1.22 to 0.36 ± 0.89, respectively; the mutans streptococci from 2.05 ± 1.84 to 0.14 ± 0.60. In GP Group, anaerobic growth decreased from 5.22 ± 0.96 to 2.02 ± 1.65 and aerobic from 4.23 ± 1.37 to 1.08 ± 1.29 and lactobacilli from 2.06 ± 1.81 to 0.00 ± 0.00, respectively; the mutans streptococci from 3.16 ± 1.59 to 0.28 ± 0.84. (Am J Dent 2006;19:382-387).

Clinical significance: The resin-based composite sealing of dentin caries lesions in primary teeth, with or without calcium hydroxide liner over the infected remaining tissue, may help preserve dental tissue as well as pulp vitality.

 Prof. Fernando Borba de Araújo, Department of Pediatric Dentistry, Faculty of Dentistry, UFRGS, Rua Ramiro Barcelos, 2492, Bom Fim, Porto Alegre, Rio Grande do Sul, Brazil. E-: fernando.araujo@ufrgs.br

Effect of tooth-bleaching on the tensile strength and staining by caries detector solution on bovine enamel and dentin

Morakot Piemjai, dds, mdsc, phd & Janya Surakompontorn, dds

Abstract: Purpose: To evaluate the tensile strength and staining of enamel and dentin after extracoronal or intracoronal bleaching using conventional bleaching agents. Methods: Extracted bovine incisors were divided into eight groups of 10 specimens. Individual groups were treated by extracoronal bleaching (E) using in-office and home techniques with different concentrations of hydrogen peroxide (H₂O₂) and carbamide peroxide (CP); no bleaching (EN), 35% H₂O₂ and 10% CP (E35H-10C), 35% H₂O₂ and 20% CP (E35H-20C), 35% CP and 10% CP (E35C-10C), 35% CP and 20% CP (E35C-20C). Intracoronal “walking bleaching” (I) was performed after 24 hours of root canal treatment in the three remaining groups; no bleaching (IN); sodium perborate dissolved in 35% H₂O₂ (ISP-35H); and sodium perborate in distilled water (ISP-W). Mini dumbbell shapes of enamel and dentin with central cross-section diameters of 1.5 x 0.5 mm and 3 x 1 mm respectively were prepared for tensile testing using an Instron machine. Fracture surfaces were examined using SEM. Bleached enamel and dentin specimens were stained and evaluated using Caries Detector solution. Staining scores were analyzed using Kruskal-Wallis H and Mann-Whitney test (P< 0.05). Results: Tensile strengths (mean ± SD) of enamel and dentin respectively for each group in MPa were: EN = 30.5 ± 3.3 and 85.4 ± 3.0, E35H-10C = 14.8 ± 2.3 and 58.9 ± 2.0, E35H-20C = 10.6 ± 2.6 and 55.5 ± 2.2, E35C-10C = 25.4 ± 3.4 and 70.8 ± 2.5, E35C-20C = 20.3 ± 4.1 and 67.2 ± 3.3, IN = 26.5 ± 4.1 and 85.9 ± 2.5, ISP-35H = 13.6 ± 3.1 and 46.7 ± 2.3, ISP-W = 21.7 ± 3.3 and 68.3 ± 4.4. ANOVA and Tukey HSD test found statistically significant differences among and between groups respectively (P< 0.05). No significant difference was found between non-bleached groups (IN and EN) of enamel and dentin. Mean tensile strengths of all bleached groups were significantly lower than those of non-bleached groups. Fracture surfaces demonstrated the different morphologies for bleached and non-bleached enamel and dentin. (Am J Dent 2006;19:387-391).

Clinical significance: Extracoronal and intracoronal bleaching decreased the tensile strength of both enamel and dentin. Home-bleaching 8 hours/day for 4 days using 10% carbamide peroxide could decrease the tensile strength of both enamel and dentin. In-office bleaching using 35% H₂O₂ for 10 minutes had more effect than 35% CP for 30 minutes, and had much greater effect than that of home bleaching using 10% CP 8 hours/day for 4 days. Tooth-bleaching oxidized tooth components, and led to increased roughness and porosity which was easily stained by a caries detector.

: Dr. M. Piemjai, Department of Prosthodontics, Faculty of Dentistry, Chulalongkorn University, Henri-Dunant Road, Pratumwon, Bangkok 10330, Thailand. E-: tmorakot@chula.ac.th