Advertisements
October 2015 Abstracts
Abutment-to-fixture load transfer and peri-implant bone stress
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).
Clinical significance: Overloading of bone surrounding
dental implants is a potential cause of peri-implant
bone loss and subsequent implant failure. Reduction of stress concentrations on
the bone is therefore an important consideration for dental implant design.
Mail: Prof. Dr. Albert J. Feilzer,
ACTA, Gustav Mahlerlaan 3004, 1081LA Amsterdam, The
Netherlands. E-mail: a.feilzer@acta.nl
Effect of Reciproc endodontic treatment with three different post space
preparation instruments on fiber post retention
Nino Tsintsadze, dds, Maria Garcia, dds, Simone Grandini, dds, msc, 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).
Clinical significance: This study showed that when
shaping the root canal with reciprocating instruments, MTwo drills were less aggressive than Largo drills and/or calibrated drills, and
greater post retention was achieved when MTwo drills were
used.
Mail: Dr. Nino Tsintsadze, Department of Dental Materials and Fixed Prosthodontics, University of Siena, Viale Bracci, Policlinico Le Scotte, 53100, Siena, Italy. E-mail: ninotsintsa@yahoo.de
Influence of repair procedure on composite-to-composite microtensile
bond strength
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).
Clinical significance: Composite-to-composite bond
strength repair was improved by increasing the superficial roughness either by
means of a bur, silica coating or alumina sandblasting. However, none of these
methods yielded the cohesive strength of the original resin composite.
Mail: Dr.
Eugenia Baena, Avda. Atenas s/n, Alcorcón, Madrid 28922, Spain. E-mail:
eugenia.baena@urjc.es
Effect of 7.5% hydrogen
peroxide containing remineralizing agents on hardness,
Robson Tetsuo Sasaki, dds, ms, Anderson Catelan, dds, ms, phd, Carlos Eduardo dos Santos Bertoldo, dds, ms,
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).
Clinical significance: Home-use bleaching agent with
7.5% hydrogen peroxide containing remineralizing compo-nents minimized microhardness decrease during bleaching and increased surface roughness of human enamel,
mostly due to deposition of mineral crystals remaining even after bleaching
treatment, with whitening effectiveness similar to commercial products.
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:
aguiar@fop.unicamp.br
Impact of toothpaste on abrasion of sound and eroded
enamel:
An in vitro white light interferometer study
Maria Nakamura, dds, Yuichi Kitasako, dds, phd, Syozi Nakashima, phd, Alireza Sadr, 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).
Clinical significance: Clinicians must be careful when
selecting a toothpaste, especially for patients at high risk of erosion.
Certain types of toothpaste may accelerate the abrasion of dental hard tissue
especially after erosion, depending on their physical and chemical
characteristics.
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:
kitasako.ope@tmd.ac.jp
Response of chronic
gingivitis to hygiene therapy and experimental gingivitis.
Malgorzata Klukowska, phd, dds, C. Ram Goyal, dds, Deepa Khambe, ms, Michael Cannon, 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).
Clinical significance: There is clear susceptibility of
some individuals to more aggressive gingival inflammation associated with
common levels of microbial plaque and plaque toxins. Changes in oral hygiene
toward “healthy” or “non healthy” conditions
produced significant changes in short chain carboxylic acids, specifically,
propionate and n-butyrate, and re-established the significance of these
metabolites in the etiology of gingivitis. Systems analysis ‘metabonomics’ and specific metabolite assessments show
promise as a method for characterization of virulence changes with oral hygiene measures and possibly with
characterization of factors responsible for disease expression in populations.
Mail: Dr. Malgorzata Klukowska,
Procter & Gamble, 8700 Mason-Montgomery Road, Mason, OH, USA. E-mail:
klukowska.m@pg.com.
Diffusion of HEMA from resin cements through
different dentin
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).
Clinical significance: The HEMA was detected in the
pulp chamber elutes of all the teeth in all groups, however, the highest amount
of eluted HEMA detected was not viewed as critical for pulp tissue since the
diffused HEMA amounts were below the level of cytotoxicity,
according to the literature.
Mail: Dr. Onjen Tak, Department
of Prosthodontics, Faculty of Dentistry, University
of Kocaeli, Yuvacık-Basiskele, Kocaeli, Turkey. E-mail:onjentak@hotmail.com
Effect of zinc-doping in physicochemical properties
of dental adhesives
César PomacÓndor-HernÁndez, dds, phd, Raquel Osorio, dds, phd, FÁtima S. Aguilera, 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).
Clinical significance: The addition of 20wt% ZnO particles to adhesive blends is preferred as it
decreased water sorption and increased microhardness of the tested adhesives. No deleterious effect was encountered on the other
tested properties.
Mail: Dr. Manuel Toledano, Faculty of Dentistry, Campus de Cartuja s/n, University of Granada, E-18071 Granada, Spain.
E-mail: toledano@ugr.es
The effect of desensitizing dentifrices on dentin
wear and tubule occlusion
Raquel Marianna Lopes, dds, msc, Miriam Lacalle Turbino, dds, msc, phd, Denise
Maria Zezell,,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).
Clinical significance: 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.
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:
acca@usp.br
Evaluation of dentin tubule occlusion after laser
irradiation
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).
Clinical significance: The fluid flow measuring
instrument clearly showed the changes of DFF rate during laser
irradiation/application of the desensitizing agents in real-time. ClinproXT, a RMGI varnish and SuperSeal,
an oxalate-based desensitizing agent showed better results than did the Nd:YAG and Er:YAG lasers in the
reduction of DFF rate.
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: inboglee@snu.ac.kr
