RenÉ F.M. van Oers, phd & Albert J. Feilzer, dds, phd
Abstract: Purpose: To uncover design principles for the abutment-fixture complex that reduce the stress concentration on the bone. Methods: A 3-dimensional finite element model was used to vary shape, elasticity, and connectivity of the abutment-fixture complex. We compared peri-implant bone stress of these designs. Results: Peri-implant bone stress was increased when the abutment could slide frictionless along the rim of the fixture, allowing the abutment to "lean into" the fixture rim and transfer loads near the bone crest. Conversely, bone stress was reduced when no motion was allowed (or no contact was made at all) between the abutment and the fixture rim. Bone stress was also reduced when the fixture was stiffer and thus more resistant to deformation, or when the fixture was wider. (Am J Dent 2015;28:247-250).
Mail: Prof. Dr. Albert J. Feilzer, ACTA, Gustav Mahlerlaan 3004, 1081LA Amsterdam, The Netherlands. E-mail: email@example.com
preparation instruments on fiber post retention
Nino Tsintsadze, dds, Maria Garcia, dds, Simone Grandini, dds, msc, phd, Cecilia Goracci, dds, msc, phd & Marco Ferrari, md, dds, phd
Abstract: Purpose: To assess the effect of three different drills used for post space preparation on fiber post retention after Reciproc endodontic treatment. Methods: 30 human upper incisors were endodontically treated using Reciproc and warm vertical gutta-percha compaction. Teeth were sealed coronally using Fuji VII, then stored in 0.5% T chloramine solution at 4°C. After 1 week, teeth were randomly assigned to three groups (n=10) that differed for the drill type used for post space preparation: Group 1: Calibrated drill; Group 2: Largo drill; Group 3: MTwo drill. Illusion posts were luted into the root canals using Gradia Core. After 24 hours, posted roots were transversally cut into 1 mm-thick slices for thin-slice post push-out testing. Two slices per apical, middle, and coronal thirds were obtained, resulting in a total of 6 slices per tooth. Thin-slice push-out test was conducted using a universal testing machine. Post push-out strength was measured in MPa. For the fracture analysis, the specimens were observed using a stereomicroscope at ×40 magnification and classified as adhesive [between post-cement (P-C) or dentin-cement (D-C) interface], cohesive (within the post or adhesive cement) and mixed (adhesive and cohesive fractures occurred simultaneously). Between-group differences in post retentive strength were statistically analyzed (Kruskal-Wallis ANOVA, Dunn’s Multiple Range test, P> 0.05). Differences in push-out strength among root levels within each group (one-way ANOVA or Kruskal-Wallis ANOVA, depending on the normality of data distribution, P> 0.05) and in failure mode distribution were also statistically evaluated (Fisher’s Exact Test, P> 0.05). Results: For each group the mean of MPa values was: (1) 10.41 ± 3.56, (2) 10.98 ± 3.96, and (3) 12.11 ± 1.65. Failure mode was distributed as follows: Adhesive: (1) P-C - 23.3%, D-C - 21.7%; (2) P-C - 20%, D-C – 10%; (3) P-C - 46.7%, D-C – 13.3%; Cohesive: (1) 0.0%, (2) 3.3%; (3) 0.0%; Mixed: (1) 55.0 %; (2) 66.7%; (3) 40.0%. The statistical analysis revealed the existence of significant between-group differences (P= 0.002). Group 3 measured significantly higher push-out strengths than Groups 1 and 2, which were comparable. Statistically significant between-group differences emerged also in failure mode distribution (P= 0.004). In Group 3 post-cement adhesive failures were significantly more frequent and mixed failures were significantly less frequent than in Group 2. No statistically significant differences emerged among the different root levels of the tested groups (P> 0.05). (Am J Dent 2015;28:251-254).
Mail: Dr. Nino Tsintsadze, Department of Dental Materials and Fixed Prosthodontics, University of Siena, Viale Bracci, Policlinico Le Scotte, 53100, Siena, Italy. E-mail: firstname.lastname@example.org
Eugenia Baena, dds, phd, Valeria Vignolo, dds, phd, Maria Victoria Fuentes, dds, phd & Laura Ceballos, dds, phd
Abstract: Purpose: To investigate the effect of different repair procedures and storage time on microtensile bond strength (µTBS) of a resin composite to an older one from a simulated previous restoration. Methods: Composite disks were made by layering 2 mm-thick increments of a nanohybrid composite (Grandio) shade A1 in a Teflon mold (4×8 mm). Afterwards, they were light-cured and stored (37ºC/7 days) in a saline solution. Specimens were randomly divided into groups according to the surface treatment applied: (1) Composite surface was roughened with a bur (Cimara) and Solobond Plus adhesive was applied; (2) Sandblasting with 27 µm aluminum oxide particles (KaVo Rondoflex), and adhesive application; (3) Air-abrasion with 30 µm alumina particles coated with silica (CoJet Sand), silane (Monobond-S) and adhesive application; (4) Negative control group with only adhesive application. Afterwards, Grandio composite (shade A3.5) was packed incrementally on the treated surface obtaining another disk (4×8 mm). Repaired blocks were stored (24 hours or 6 months) and afterwards µTBS test was performed and failure mode was evaluated. Also, beams obtained from 8 mm-high composite blocks without any surface treatment were immediately submitted to µTBS test to determine Grandio composite cohesive bond strength (positive control group). Data were analyzed using ANOVA and Tukey´s test (P< 0.05). Results: The repair procedure affected µTBS values (P< 0.001) while neither storage time nor interactions did (P> 0.05). All repair procedures achieved bond strength values higher than the negative control group but they did not reach the composite’s cohesive bond strength. The overall conclusion was that an increased superficial roughness by means of a bur, silica coating or alumina sandblasting improved µTBS of the repaired composite and bond strength remained stable after 6 months. (Am J Dent 2015;28:255-260).
Mail: Dr. Eugenia Baena, Avda. Atenas s/n, Alcorcón, Madrid 28922, Spain. E-mail: email@example.com
Robson Tetsuo Sasaki, dds, ms, Anderson Catelan, dds, ms, phd, Carlos Eduardo dos Santos Bertoldo, dds, ms, Paulo César Venâncio, pharmd, phd, Francisco Carlos Groppo, dds, ms, phd, Gláucia Maria Bovi Ambrosano, ms, phd, Giselle M. Marchi, dds, ms, phd, Débora Alves Nunes Leite Lima, dds, ms, phd & Flávio Henrique Baggio Aguiar, dds, ms, phd
Abstract: Purpose: To determine the microhardness, color change, surface roughness, and micromorphology of tooth enamel submitted to bleaching treatment with 7.5% hydrogen peroxide (HP) with added calcium, amorphous calcium phosphate, sodium fluoride (NaF), and hydroxyapatite (HA). Methods: 80 enamel slabs were used (n= 10). Three commercial agents [Pola Day 7.5%, Day White ACP 7.5% (DW-ACP), and White Class Calcium 7.5% (WC-Calcium)], three experimental (7.5% HP+NaF, 7.5% HP+HA, and 7.5% PH+NaF+HA), a positive control (with HP), and a negative control (without HP) groups were assessed. The commercial products were applied according to manufacturers’ recommendations and the experimental ones were applied for 1.5 hours daily. During and after treatment, specimens were stored in artificial saliva. Tests were performed at baseline, 7, 14, 21, 28, and 35 days. Data were analyzed by ANOVA and Tukey’s test (α=0.05). Results: DW-ACP presented lower microhardness and HP+HA presents the highest values (P< 0.05); only the experimental group presented color change similar to the commercial agents (P> 0.05). Overall, roughness increased with time (P< 0.05) and porosities, and deposition of crystalline structures in groups HP+HA and HP+NaF+HA were noted. The HP+HA agent was capable of reducing the loss of enamel microhardness due to bleaching and also present color change similar to the commercial products. (Am J Dent 2015;28:261-267).
Mail: Dr. Flávio Aguiar, Department of Restorative Dentistry, Piracicaba Dental School, UNICAMP. Av. Limeira, 901, Areião, P.O. Box 52, Zip code 13414-903, Piracicaba, SP, Brazil. E-mail: firstname.lastname@example.org
An in vitro white light interferometer study
Maria Nakamura, dds, Yuichi Kitasako, dds, phd, Syozi Nakashima, phd, Alireza Sadr, dds, phd & Junji Tagami, dds, phd
Abstract: Purpose: To evaluate the influence of brushing using toothpastes marketed under different categories on abrasion of sound and eroded enamel in vitro at nanometer scale using a white light interferometer (WLI). Methods: Enamel surface of resin-embedded bovine incisors were fine polished with diamond slurry and divided into testing area (approximately 2 mm × 4 mm) and reference area using a nail varnish. The enamel specimens were randomly assigned to 10 groups (n=10 each); six of which were subjected to erosive challenge. The testing area in these eroded groups was exposed to 10 ml of Coca-Cola for 90 seconds and then rinsed for 10 seconds in deionized water (DW). Enamel specimens, except for those in one eroded group, were brushed by an automatic brushing machine with 120 linear motion strokes in 60 seconds under load of 250 g with/without toothpaste slurry. After the toothbrushing abrasion, each specimen was rinsed for 10 seconds with DW followed by immersion in artificial saliva for 2 hours. Toothpaste slurries were prepared containing one of the four toothpastes used and DW in a ratio of 1:2. The erosion-abrasion cycle was repeated three times. Then, the nail varnish was removed and enamel surface loss (SL) was measured by the WLI. Data were statistically analyzed by one-way ANOVA followed by Bonferroni’s correction at significance level of 0.05. Results: For eroded specimens, the mean SL values of groups not brushed and brushed with no toothpaste were not significantly different, but were significantly lower than those of whitening, anti-erosion and anti-caries toothpaste groups (P< 0.001). The whitening toothpaste group showed significantly higher SL than all other groups (P< 0.001). For sound enamel specimens, SL was not measured except for the whitening toothpaste group. (Am J Dent 2015;28:268-272).
Mail: Dr. Yuichi Kitasako, Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan. E-mail: email@example.com
Malgorzata Klukowska, phd, dds, C. Ram Goyal, dds, Deepa Khambe, ms, Michael Cannon, phd, Melanie Miner, bs, ba, Nataliya Gurich, phd, Ben Circello, phd, Tom Huggins, phd, Matthew L. Barker, phd, Carrie Furnish, bs, Erinn Conde, bs, Phyllis Hoke, ba, med, Chris Haught, phd, Sancai Xie, phd & Donald J. White, phd
Abstract: Purpose: To compare the clinical, microbiological and metabonomic profiles of subjects with high and low levels of chronic gingival bleeding during a controlled oral hygiene regimen intervention including sequential phases of rigorous therapeutic oral hygiene followed by experimental gingivitis (EG). Methods: Two cohorts of qualified study subjects with differences in gingival bleeding on probing levels at their baseline clinical examination were entered into the study. These two cohorts were followed through three separate study phases including a 1-week baseline phase, a 2-week phase of rigorous oral hygiene including dental prophylaxis, and a 3-week EG phase of no oral hygiene to encourage relapse of gingivitis. The 58 subjects were assessed during each phase of the study for clinical presentation of gingivitis and concurrently had plaque sampled for real-time polymerase chain reaction (RTPCR) microbiological characterization and salivary lavage samples for ‘systems biology’ metabonomics assessment by 1H-NMR. Results: Subjects presenting with different levels of gingival bleeding on probing when they entered the study responded differently to rigorous oral hygiene and EG. Specifically, the high bleeding cohort responded sluggishly to rigorous oral hygiene and exhibited markedly greater relapse to gingivitis during EG. RTPCR analysis showed changes in bacterial populations that were associated with study phases, particularly the increases in putative periodontal pathogens during EG. However, the microbiological profiles of high- and low-susceptibility gingival bleeding patients were largely similar. Metabonomic analysis likewise revealed significant changes in metabolite composition during study phases associated with differences in plaque toxicity, especially the short chain carboxylic acids propionate and n-butyrate, which tracked clinical changes in gingivitis severity. Systems analysis of metabonomic changes suggested differences between cohorts, although analysis to date has not elucidated whether these differences are causative (population predictive) or simply diagnostic of clinical status within populations. (Am J Dent 2015;28:273-284).
Mail: Dr. Malgorzata Klukowska, Procter & Gamble, 8700 Mason-Montgomery Road, Mason, OH, USA. E-mail: firstname.lastname@example.org.
thicknesses in vitro
Onjen Tak, dds, phd & Aslihan Usumez, dds, phd
Abstract: Purpose: To evaluate the in vitro diffusion of 2-hydroxyethyl methacrylate (HEMA) from the resin cements through different thicknesses of dentin using high-performance liquid chromatography (HPLC) at two time intervals. Methods: 60 freshly extracted caries- and restoration-free human third molar teeth were used in this study. Standardized box-shaped Class I inlay cavities (6 mm long, 3 mm wide and 2 mm deep) were prepared in all teeth with a high-speed handpiece mounted on a standard cavity machine. The remaining dentin thickness (RDT) between the pulpal wall of the cavity and the roof of the pulp chamber was measured at multiple points for each tooth so that two main groups of 30 teeth each were prepared with an RDT range 0.5-1.9 and 2.0-3.5 mm, respectively. Each of these main groups was divided into three subgroups (n= 10), according to the resin cements tested (RelyX ARC, Panavia F 2.0, Multilink Automix). Lithium disilicate-based ceramic inlays (IPS Empress 2) were manufactured to restore the prepared cavities. A polypropylene chamber containing 1 ml distilled water was attached to the cemento-enamel junction of each tooth. Then, ceramic inlays were cemented with resin cements according to the manufacturers’ instructions. Water elutes were analyzed by HPLC at 4.32 minutes and 24 hours. HEMA diffusion amounts were analyzed using three-way ANOVA and Tukey’s HSD tests (P< 0.05). Results: HEMA was detected in the pulp chamber elutes of all the teeth. The amounts of released HEMA did not significantly differ between time periods. The diffused HEMA amounts were significantly different between the RDT of 0.5-1.9 and 2.0-3.5 mm (P< 0.05) and between resin cements tested (P< 0.05). Decreasing RDT substantially increased the amount of HEMA that diffused through the dentin to the pulp space. (Am J Dent 2015;28:285-291).
Mail: Dr. Onjen Tak, Department of Prosthodontics, Faculty of Dentistry, University of Kocaeli, Yuvacık-Basiskele, Kocaeli, Turkey. E-mail:email@example.com
César PomacÓndor-HernÁndez, dds, phd, Raquel Osorio, dds, phd, FÁtima S. Aguilera, dds, phd, Inmaculada Cabello, dds, phd, Mario de Goes, dds, phd & Manuel Toledano, dds, phd
Abstract: Purpose: To evaluate changes in the physicochemical properties, water sorption (WS), solubility (SO), modulus of elasticity (E), ultimate tensile strength (UTS), and microhardness (MH) tests were undertaken in zinc-doped dental adhesives. Methods: Two bonding resins, Adper Single Bond Plus (SB) and Clearfil SE Bond (SEB), were zinc-doped by mixing them with 5, 10 or 20wt% of ZnO powder, or with 1 or 2wt% ZnCl2. Resin disks were made of each adhesive blend for the evaluation of WS, SO, and MH, and dumbbell-shaped specimens were prepared for E and UTS testing. Results: An increase in WS and SO was observed for adhesives doped with ZnCl2. A reduction in WS was observed for the adhesive blends containing 10% or 20wt% ZnO, while the SO was not altered in any of the ZnO-doped adhesives. An increase in E values was observed only for the SB adhesive doped with ZnCl2. For SEB-blends, the incorporation of zinc compounds did not alter the E values. UTS values decreased when SEB was doped with ZnO. SB-blends doped with 20wt% ZnO significantly increased their MH, and the addition of zinc to the SEB-blends augmented the MH values in all cases. (Am J Dent 2015;28:292-296).
Mail: Dr. Manuel Toledano, Faculty of Dentistry, Campus de Cartuja s/n, University of Granada, E-18071 Granada, Spain. E-mail: firstname.lastname@example.org
Raquel Marianna Lopes, dds, msc, Miriam Lacalle Turbino, dds, msc, phd, Denise Maria Zezell,,dds, msc, phd, Tais Scaramucci, dds, phd & Ana Cecilia Corrêa Aranha, dds, msc, phd
Abstract: Purpose: To evaluate the effect of desensitizing dentifrices on dentin erosive wear, using a 5-day erosion-abrasion-remineralization cycling model. The effect of the dentifrices on dentin’s tubule occlusion was also investigated. Methods: 30 samples of root dentin were randomly divided into three groups (n=10): (1) Colgate Total 12 Clean Mint (control, 1,450 ppm F); (2) Colgate Sensitive Pro-Relief (1,450 ppm F, Pro-Argin); and (3) Sensodyne Repair&Protect (1,450 ppm F, Novamin). Erosion was performed with a cola drink, for 5 minutes, 4×/day. Toothbrushing with the slurry dentifrices (1:2) was performed 2×/day, with electric toothbrushes, using standard pressure for 15 seconds. Surface loss (SL) was determined with optical profilometry at baseline and after the first, third and fifth days of cycling. Before treatment and in the end of the cycling, the amount of opened dentin tubules per area was evaluated in three randomly selected specimens from each group, by environmental scanning electron microscopy. The relative dentin abrasitivity (RDA) of the dentifrices was also measured. Data were statistically analyzed (α= 0.05). Results: All the dentifrices showed a progressive increase in SL over time. However, no significant differences in SL among the dentifrices were observed at any time studied. Sensodyne Repair&Protect significantly reduced the number of opened dentin tubules when compared to the other groups. Colgate Total 12 Clean Mint showed the highest RDA, followed by Sensodyne Repair&Protect and then by Colgate Sensitive Pro-Relief. The desensitizing dentifrices tested produced a similar rate of erosive dentin wear to the conventional dentifrice; however, only Sensodyne Repair&Protect was able to promote tubule occlusion. (Am J Dent 2015;28:297-302).
Mail: Prof. Ana Cecilia Corrêa Aranha, Department of Restorative Dentistry; School of Dentistry, University of São Paulo, Prof. Lineu Prestes, 2227 Cidade Universitária, São Paulo, 05508-000, SP, Brazil. E-mail: email@example.com
and desensitizing agent application
Min-Ho Kim, dds, Ryan Jin-Young Kim, dds, phd, Woo-Cheol Lee, dds, phd & In-Bog Lee, dds, phd
Abstract: Purpose: To evaluate the effects of lasers (Nd:YAG and Er:YAG) and of topical desensitizing agents on dentin tubule occlusion by measuring real-time dentin fluid flow (DFF). Methods: 32 molars were prepared with V-shape cavity at the cervical area, acid-etched, water rinsed, blotted dry, and treated with (1) Nd:YAG laser; (2) Er:YAG laser; (3) SuperSeal, a desensitizing agent; (4) ClinproXT, a resin-modified glass-ionomer (RMGI) varnish (n= 8 each). A real-time fluid flow measuring instrument (nano-Flow) was used to measure the DFF throughout the procedures. The DFF rates before and after the treatment were compared. Moreover, the surface topography of dentin tubules after each desensitizing method was examined using SEM. Results: DFF varied among the groups. The DFF rate was significantly reduced after laser irradiation/application of the desensitizing agents (P< 0.05). ClinproXT showed the greatest reduction of DFF rate (71.9%), followed by the SuperSeal (34.8%) and laser groups (P< 0.05). However, there was no significant difference between the Nd:YAG (24.1%) and Er:YAG (20.6%) groups (P> 0.05). In SEM images, narrowed dentin tubules were observed in both lased groups and SuperSeal group. In the ClinproXT group, the occluded dentin tubules by the RMGI covering were observed. (Am J Dent 2015;28:303-308).
Mail: Dr. In-Bog Lee, Department of Conservative Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, 110 Daehak-ro, Jongno-gu, Seoul, 110-744, South Korea. E-mail: firstname.lastname@example.org