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December 2010
Research Article
Effect of bonded area and/or fiber post placement on
the fracture strengths
Masatoshi Nakajima, dds, phd, Tama Kanno, dds, phd, Wataru Komada, dds, phd, Hiroyuki Miura, dds, phd,
Abstract: Purpose: To compare the fracture strengths of pulpless teeth restored using resin cores with and without fiber posts, and with and
without bonding adhesive in the post cavity. Methods: Human extracted roots were prepared with post cavities and
divided into four experimental groups: Groups 1 and 2 – after application of
adhesive to both the top surface of the root and the inner surface of the post
cavity, DC core Automix was injected into the post
space with or without fiber-post placement; Groups 3 and 4 – adhesive was
applied to the top surface of the root only, with or without post placement. Resin-cores
were then built-up. Teeth prepared for full crowns served as controls. After
water storage at 37°C for 24 hours, the all specimens were embedded in acrylic
resin at 2 mm below CEJ, and loaded at 45 degrees to the long axis of the tooth
using a universal testing machine until fracture. The data were analyzed by
one-way ANOVA (α= 0.05). Results: The fracture loads were, Group 1: 1832 ±240 N, Group 2: 1815 ±347 N, Group 3:
1626 ±396 N, Group 4: 1810 ±332 N, Control Group: 1622 ±274 N. There were no
significant differences among all the groups (P> 0.05). (Am J Dent 2010;23:300-304).
Clinical significance: This study showed that the
absence of fiber posts and/or adhesion in the post cavity did not affect the
fracture strengths of resin-core reconstructions of pulpless teeth.
Address: Dr. Masatoshi Nakajima, Cariology and Operative Dentistry, Department of Restorative
Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima,
Bunkyo-ku, Tokyo 113-8549, Japan. E-mail: nakajima.ope@tmd.ac.jp
Research Article
Plaque
and gingivitis reduction efficacy of an advanced Pulsonic
toothbrush:
A 4-week randomized and controlled clinical trial
Naresh C. Sharma, dds, Jimmy G. Qaqish, bsc, Tao He, dmd, phd, Patricia A. Walters, rdh, msdh, msob,
Abstract: Purpose: To compare the safety and efficacy of a novel sonic
power toothbrush and a manual toothbrush in the reduction of gingivitis and
plaque over a 4-week period. Methods: This study employed a randomized two treatment, examiner-blinded, parallel
group design. Subjects with evidence of gingivitis were randomly assigned to 4
weeks’ twice daily home use of either the Oral-B Pulsonic sonic toothbrush or an ADA reference manual toothbrush. At baseline (Visit 1)
and again after product use at Week 4, subjects received gingivitis evaluations
with the Modified Gingival Index (MGI) and Gingival Bleeding Index (GBI)
examinations, followed by plaque assessment using the Rustogi Modified Navy Plaque Index (RMNPI). For 12 hours before both visits, subjects
abstained from all oral hygiene, and ceased eating, drinking and smoking 4
hours prior. Results: Both brushes
significantly reduced gingivitis, gingival bleeding and plaque compared with
baseline, and were well-tolerated by the 129 subjects completing the study. The
sonic toothbrush was statistically significantly (P< 0.0001) more effective
than the manual brush, with greater relative mean reductions in MGI, GBI and
RMNPI of 11.9%, 62.3% and 46.5%, respectively. (Am J Dent 2010;23:000-000).
Clinical significance: After 4 weeks of twice daily unsupervised brushing, the new advanced sonic
toothbrush provided statistically significantly superior reductions relative to
a manual toothbrush in all three measured clinical parameters (gingivitis,
gingival bleeding and plaque removal) with notable anti-plaque efficacy in interproximal regions, indicating this is a highly
effective new tool to improve oral health.
Address: Dr. Tao He, Procter
& Gamble Health Care Research Center, 8700 Mason-Montgomery Road, Mason, OH
45040, USA. E-mail: he.t@pg.com
Research Article
Efficacy of a pit and fissure sealant in
arresting dentin non-cavitated caries:
Boniek
Castillo Dutra Borges, Giordano Bruno Paiva Campos, Ana
Daniela Silva da Silveira, dds, ms,
Abstract: Purpose: To evaluate the efficacy of conservative treatment of dentin non-cavitated caries using a resin-based fluoride-containing
pit and fissure sealant. Methods: In
this controlled clinical trial, 60 teeth with clinically non-cavitated occlusal caries radiographically located beneath the enamel-dentin junction
(radiolucent area) were selected among patients presenting a moderate to high
caries risk. The teeth were randomly divided into two groups of 30 teeth each:
an experimental group receiving an application of Fluorshield (Dentsply) sealant and a control group not submitted
to any clinical intervention. Caries progression was monitored by clinical and
radiographic examination at 4-month intervals over a period of 1 year. In
addition, marginal integrity of the sealant was evaluated in the experimental
group. Results: Clinical and
radiographic caries progression was significantly more frequent in control
teeth when compared to the experimental group (P< 0.05). (Am J Dent 2010;23:311-316).
Clinical
significance: The pit and fissure sealant was found to be effective in arresting the carious
lesions evaluated, suggesting that this intervention may replace the invasive
treatment traditionally used for teeth with dentin non-cavitated caries.
Address:
Dr. Boniek Castillo Dutra Borges, Rua Minas Novas, 390, cs 18, Neopolis,
Natal/RN, CEP: 59.088-725, Brazil. E-mail:
boniek.castillo@gmail.com
Research Article
Clinical and microbiological studies of
children and adolescents
receiving orthodontic treatment
Rodrigo O. Rego, CD, MS, PhD, Cristiane A. Oliveira, CD, MS,
PhD, Ary dos Santos-Pinto, CD, MS,
PhD,
Abstract: Purpose: This
case-controlled study examined clinical and microbiological parameters in
Brazilian children and adolescents receiving orthodontic treatment using fixed
orthodontic appliances or removable orthodontic appliances. Methods: The plaque index, gingival index,
number of decayed, missing and filled teeth, and probing pocket depth was
measured on each fully erupted tooth in 30 patients treated with fixed
orthodontic appliances and an equal number of age and sex-matched control
subjects. The same parameters were also measured in 18 patients treated with
removable orthodontic appliances and an equal number of age and sex-matched
control subjects. In the patients treated with fixed orthodontic appliances, subgingival plaque samples were collected from four teeth with
orthodontic brackets and from four teeth with orthodontic bands. In the
patients with removable appliances, subgingival plaque samples were collected from clasped maxillary permanent first molar
teeth and from four unclasped permanent teeth. Samples of unstimulated whole saliva and samples from the dorsal surface of the tongue were also
obtained from each subject. Each sample was analyzed for the presence of 19
target bacteria by dot blot. A subset of samples was examined by direct
amplification of bacterial nucleic acids. Results: Compared to their respective age and sex-matched controls, whole mouth means
for plaque index and gingival index were significantly elevated in both the
fixed and removable orthodontic groups. There was no difference in the DMFT.
Subjects with fixed orthodontic appliances had a higher prevalence of each of
the target species except for L. fermentum, Neisseriaceae and S. mutans. The prevalence of A. naeslundii and Streptococcus sp. was significantly higher on teeth with orthodontic
brackets alone compared to teeth with both orthodontic bands and brackets.
Subjects with removable orthodontic appliances had a higher prevalence of A. actinomycetemcomitans, C. rectus, E. corrodens, L. fermentum, Neisseriaceae, and spirochetes.
The prevalence of Neisseriaceae was significantly higher on unclasped teeth compared to clasped teeth. There
was no difference between sample sites for the target bacteria except for A. actinomycetemcomitans that was detected less frequently in saliva. Orthodontic patients
demonstrated higher proportions of gram negative species by direct
amplification of nucleic acids including species frequently associated with
periodontal disease as well as rarely cultivable or non-cultivable species such
as Abiotrophia defectiva, Gemella haemolysans, Granulicatella adiacens, Lautropia sp., Terrahaemophilus aromaticivorans,
and TM7 bacterium. (Am J Dent 2010;23:317-323).
Clinical
significance: Both fixed and removable orthodontic appliances can cause alterations in oral biofilms resulting in increased gingival inflammation and
which necessitate meticulous oral hygiene during orthodontic treatment.
Address: Dr. Joseph J. Zambon, Department of Periodontics and Endodontics, University at Buffalo, School of Dental Medicine, 3435 Main
Street, Buffalo, NY, 14214, USA. E-mail: jjzambon@buffalo.edu
Research Article
Effect of an 8.0% arginine and calcium carbonate in-office desensitizing
paste on the shear bond strength of composites to human
dental enamel
Alexander GarcÍa-Godoy, bs & Franklin GarcÍa-Godoy,
Abstract: Purpose: To evaluate the effect of 8.0% arginine and calcium carbonate, in-office desensitizing
paste (Colgate Sensitive Pro-Relief Desensitizing Paste) on the shear bond
strength of composites to human dental enamel. Methods: Two resin composites (Filtek Supreme, Premise) and human dental enamel were used.
16 samples per composite were prepared. Caries-free extracted human molars, not older than 3
months, and stored in distilled water were used for this portion of the
experiment. Buccal and lingual surfaces were polished
with high polishing pastes to create a uniform flat surface area to which the
cylindrical composite samples were bonded. After polishing, the samples were
rinsed in tap water and stored at 100% relative humidity. The
resin composites were used to form cylindrical samples 3 mm x 1.6 mm, which
were light-cured with a Demetron curing light
according to the manufacturers’ instructions. For each composite, 32 surfaces
were used; 16 were a control group with the enamel polished with a water slurry of flour of pumice. The experimental group
had the enamel polished with the 8.0% arginine and calcium carbonate desensitizing
paste, using disposable
latex free prophy cups with a slow speed hand piece
at 3,000 rpm using moderate to light pressure, according to manufacturer’s
instructions. The composite cylinders were bonded to the enamel
with their respective etching agents and adhesives and left in distilled water
for 48 hours, after which the samples were sheared with an Instron testing machine at 0.5 mm/minute. After shearing, all samples were analyzed
with a stereo microscope to evaluate failure pattern (failure at the enamel
surface, failure at the composite surface, or mixed failure, at both enamel and
composite surfaces).
Clinical
significance: The 8.0% arginine and calcium carbonate in-office desensitizing
paste did
not affect the shear bond strength to enamel of the composites tested.
Address:
Dr. Franklin Garcia-Godoy, College of Dentistry, University of Tennessee Health
Science Center, 875 Union Avenue, Memphis, TN 38163, USA. E-mail:
fgarciagodoy@gmail.com
Research Article
Influence of enzymatic and chemical degradation on zirconia
resin bond strength after different surface treatments
Hesam Mirmohammadi, dds, phd, Mostafa N. Aboushelib, dds, msc, phd, Ziad Salameh, , dds, msc, phd,
Abstract: Purpose: To investigate the
influence of chemical and enzymatic degradation on the stability of zirconia resin bond strength using micro-shear bond
strength test. Methods: Zirconia discs were airborne particle abraded (SB) or
selective infiltration etched (SIE) while no surface treatment served as
control. Resin composite (Filtek Z250) micro-discs
were bonded to zirconia using self-adhesive universal
resin cement (RelyX UniCem).
Micro-shear bond strength (μSBS) test was
conducted after immersion in the following degrading media: 24 hours and 2
weeks of water storage, and 2 weeks in NaOH, alcohol,
or esterase enzyme (n=10). Results: There was a significant influence of the surface finish (P< 0.001, F=154.5),
biodegradation medium (P< 0.001, F=52.9), and their interaction (P< 0.001,
F=6.0) on zirconia resin bond strength. In general
SIE group revealed the highest μSBS values (8.1 -
34.5 MPa) after degradation in different media,
followed by SB group (8.7 - 28.5 MPa), while the control
group showed significantly lower bond strength (0.4 - 9 MPa).
(Am J Dent 2010;23:327-330).
Clinical significance: Within the limitations of this
study, long term performance of zirconia resin bond
strength is influenced by accelerated chemical and enzymatic degradation.
Address: Dr. S.H. Mirmohammadi, ACTA,
Department of Dental Materials Science, Louwesweg 1, 1066
EA Amsterdam, The Netherlands. E-mail: hmirmoha@acta.nl
Research Article
Effect of light-curing units on the thermal
expansion
of resin nanocomposites
Jeong-Kil Park, dds, phd, Bock Hur, dds, phd, Ching-Chang Ko, dds, phd, Franklin GarcÍa-Godoy, dds, ms,
Abstract: Purpose: To examine the thermal expansion
of resin nanocomposites after light-curing using
different light-curing units. Methods: Four different resin nanocomposites and four
different light-curing units [quartz-tungsten-halogen (QTH), light emitting
diode (LED), laser, and plasma arc] were chosen. Metal dies were filled with
resin to make specimens and light-cured. The light intensity and light-curing
time of the QTH and LED light-curing units were 1000 mW/cm2 and 40 seconds, 700 mW/cm2 and 40
seconds for the laser, and 1600 mW/cm2 and
3 seconds for the plasma arc. The coefficient of thermal expansion (CTE) was
evaluated using a thermomechanical analyzer (TMA) at
temperatures ranging from 30-80°C. Results: The CTE of the resin nanocomposites tested ranged
from 28.5 to 65.8 (×10-6/°C), depending on the product and type of
light-curing unit used. Among the specimens, Grandio showed the lowest CTE. The specimens cured using the plasma arc unit (Apollo
95E) showed the highest CTE. There was a linear correlation between the CTE and
filler content (vol%) (R: -0.94~-0.99 depending on the
light-curing unit). The results may suggest a careful selection of the
light-curing unit because there was more expansion in the specimens cured using
the plasma arc unit than those cured by the other units. (Am J Dent 2010;23:331-334).
Clinical significance: Within the limitations of this
study, the resin nanocomposites evaluated showed much
higher CTE than the enamel and dentin. The plasma arc unit produced a
significantly higher CTE than the other units due to the incomplete
polymerization of the materials.
Address: Prof. Yong Hoon Kwon, Department of Dental Materials, College of
Dentistry, Pusan National University, Busan 602-739,
Korea. E-mail: y0k0916@pusan.ac.kr
Research Article
Nanoleakage and microtensile bond strength at the adhesive-dentin
interface after different
etching times
San-jun Zhao, dds, phd, Ling
Zhang, dds, phd, Li-hui Tang, dds, phd & Ji-hua Chen, dds, phd,
Abstract: Purpose: To
evaluate the effect of etching time on the nanoleakage and microtensile bond strength (µTBS) at the
interface between etch-and-rise adhesives and dentin. Methods: Eighty molars were sectioned
to expose the superficial dentin and randomly divided into four groups
according to the adhesives used: OptiBond Solo (OB),
Single Bond (SB), One-Step (OS), and Prime&Bond NT (PB). Within each group, a total-etching technique was applied, and the
dentin surfaces were etched for 0, 15, 30 or 60 seconds. Each treated tooth was
then sectioned into sticks. A non-trimming µTBS test and TEM observation for nanoleakage were sequentially performed. Results: The degree of nanoleakage increased as etching time increased (P<
0.05). For the OS and PB groups, the highest µTBS values were achieved with 15
seconds of etching, followed by 30, 60 and 0 seconds. For the
Clinical
significance: Prolonged etching time produced extensive nanoleakage and reduced bond strength when etch-and rinse adhesives are used for dentin.
Address:
Prof. Ji-hua Chen, Department of Prosthodontics,
School of Stomatology, Fourth Military Medical
University, Xi’an, 710032, China. E-mail:
jhchen@fmmu.edu.cn
Research
Article
Influence of CAD/CAM scanning method and
tooth-preparation design
on the vertical misfit of zirconia crown copings
Raquel Castillo OyagÜe, dds, phd, MarÍa Isabel SÁnchez-Jorge, dds, phd & AndrÉs SÁnchez TurriÓn, md, phd
Abstract: Purpose: To evaluate the influence of
scanning method, finish line type and occlusal convergence angle of the teeth preparations on the vertical misfit of zirconia crown copings. Methods: 20 standardized stainless-steel master dies were machined
simulating full-crown preparations. The total convergence angle was 15º or 20º
(n=10 each). Two of the finish line types: a chamfer (CH) and a shoulder (SH)
were prepared around the contour of each abutment. Over these dies, 20
structures were made by CAD/CAM (Cercon, Dentsply). An optical laser digitized the wax patterns of 10
single-unit copings (WS), and 10 abutments were direct-scanned to design the
cores by computer (DS). Zirconia milled caps were luted onto the models under constant seating pressure.
Vertical discrepancy was assessed by SEM. Misfit data were analyzed using ANOVA
and Student-Newman-Keuls (SNK) test for multiple
comparisons at α= 0.05. Results: Vertical gap measurements of
WS copings were significantly higher than those of DS frames (P< 0.0001). SH
exhibited statistically higher discrepancies than CH when combined with a
15-degree occlusal convergence angle regardless of
the scanning method (P< 0.05). The taper angle of the preparation (15º vs. 20º) had no effect on the marginal
adaptation of chamfered samples. (Am J Dent 2010;23:341-346).
Clinical significance: Vertical misfit of zirconia structures depended on the digitizing technique.
Precision was higher when direct scanning of the abutments was performed
instead of wax-up digitization. The presence of sharp axiogingival line angles at the preparations’ margins resulted in higher vertical
discrepancies, even when the marginal gaps of all the copings tested were
within the range of clinical acceptance.
Address: Dr. Raquel Castillo de Oyagüe, Department of Prosthodontics,
Faculty of Dentistry, Complutense University of
Madrid, U.C.M., Pza. Ramón y Cajal,
nº 3, 28040, Madrid, Spain. E-mail:
siete_rosas.rc@hotmail.com
Research Article
Microtensile bond strength of three different veneering
porcelain systems
to a zirconia core for all
ceramic restorations
Giovanni Fazi, dds, ms, Alessandro Vichi, dds, phd & Marco Ferrari, md, dds, phd
Abstract: Purpose: This
study investigated the microtensile bond strength of three
different ceramic veneering systems to one type of zirconia substrate. Methods: Bilayered zirconia veneer discs
were fabricated of a LAVA zirconia core and three
different veneering ceramics (VITA VM9, Lava Ceram, Creation ZI) using a
conventional layering technique. Discs were cut into microbars of 6 mm x 1 mm x
1 mm. Microtensile bond strength between veneer and
core was measured. Surfaces of fractured specimens were examined with scanning
electron microscopy (SEM). Results: The mean microtensile bond strengths were
respectively VITA VM9 23.52 MPa (8.33), Creation ZI
18.35 MPa (6.40), and Lava Ceram 14.76 MPa (4.00). The differences were statistically significant.
Failures were mainly interfacial in all tested groups. (Am J Dent 2010;23:347-350).
Clinical
significance: Important
variations in terms of veneer/core bond strength can occur by applying
different veneering systems to the same zirconia core. Careful selection of a veneering system to a given zirconia substrate could be of importance in achieving adequate bond strength to avoid delamination of bilayered zirconia based restorations.
Address:
Dr. Giovanni Fazi, Via A Lamarmora 22, 50121 Firenze, Italy. E-mail: fazi_90211@yahoo.com
Research Article
Effect of tooth type and ferrule on the survival of pulpless teeth restored with fiber posts: A 3-year clinical study
Juan Carlos Mancebo, md, dds, phd, Emilio JimÉnez-Castellanos, md, dds, phd & Diego CaÑadas, md, dds, phd
Abstract: Purpose: To determine, in a 3-year clinical trial, whether tooth
type and ferrule significantly affect the survival of pulpless teeth restored with fiber posts. Methods: A sample of 87 teeth in 87 patients (32 men and 55 women, age ranged from 23 to
78) were restored using Snowpost: 34 incisors, 12
canines, 25 premolars and 16 molars. The posts were cemented with RelyXUnicem and the core was made with a resin composite (Dentocore Automix). Every tooth
was covered with a metal-ceramic or all ceramic crown.
Two experimental groups, according to the presence or absence of ferrule, were
defined: A) 45 teeth with ferrule (>2 mm height); and B) 42 teeth without
ferrule (<2 mm height). Patients were reevaluated every 6 months. Results: 14 of the total restorations
failed (16.1%). The failure modes were caries (n= 4), post fracture (n= 4),
root fracture (n= 2), and marginal gap, post cement failure, crown cement
failure, and periapical lesion (n= 1 respectively). In Group A the failure
observed was 6.67% and in Group B it was 26.20%. The log-rank test showed
statistically significant differences between both groups. According to the
type of tooth, the incisors were the teeth with the highest failure rate
(73.52%), but Chi-square test showed no statistically significant differences
among the four tooth types, perhaps because of the low number of the sample. (Am J Dent 2010;23:351-356).
Clinical significance: In endodontically treated teeth restored with adhesive
techniques and fiber posts, the presence of ferrule results in better clinical
survival after 3 years of clinical service.
Address: Dr. Juan Carlos
Mancebo, c/ Avicena s/n, Facultad de Odontología, Sevilla.
Research
Article
Comparison of an analytical expression
of resin composite curing
stresses with in vitro observations of marginal cracking
Bill Kahler, d clin dent, phd, Michael V. Swain, bsc, phd & Andrei Kotousov,
b eng, phd
Abstract: Purpose: To
observe the marginal failure at the enamel-resin composite interface upon
curing, and utilize a recently developed analytical model for curing stresses
to relate to the extent of interfacial failure. Methods: Occlusal cavity preparations
were restored with Heliomolar, Filtek Z100 or UltraSeal XT Plus resin composites. Teeth
were restored with either bulk or incremental placement. The control group was
not restored. Teeth were placed in an acrylic ring and embedded in cold
mounting epoxy resin and the crown sectioned so that the tooth/restoration
interface and cavosurface margin could be visualized
with an optical microscope. A recently developed simplified analytical approach
was utilized to evaluate the composite-enamel interface tensile stresses for
these materials theoretically and thereby the fracture susceptibility of the
resin-enamel interface during polymerization. Results: White lines, enamel cracks and interfacial failure of the
bond were evident for all three materials evaluated (P< 0.01). Gaps at the
enamel-composite interface measured 1-10 µm and were more evident for Ultra
Seal XT Plus and Z100 than Heliomolar. Conversely,
cracking of the enamel adjacent to the interface was more evident for Heliomolar. Statistical analysis showed that enamel
cracking and interfacial failure was significant for all groups (P< 0.01).
An inverse relationship was noted between enamel cracking and interfacial
failure (P< 0.05). The predictions for the extent of cracking from the
mathematical modeling match the experimental data and prior studies. (Am J Dent 2010;23:357-364).
Clinical
significance: It
has been stated that interfacial failure of the adhesive bond and cracking of
enamel may be clinically relevant with regard to hypersensitivity, secondary
caries and restoration failure. However, few studies have focused specifically
on the role of material properties of the restorative materials in such
failures. The present work provides evidence that restorative material
properties, such as Young’s modulus and polymerization shrinkage, are a major
factor contributing to interface failure, and that a simplified analytical
model is useful for assessing the likelihood of interface failures during
curing. The study has important clinical
applications and can be utilized for the develop-ment of new and improved materials used in adhesive restoration and for comparative
assessment of currently used resin composites.
Address:
Dr. Bill Kahler, School of Dentistry, University of
Queensland, Australia. E-mail: w.kahler@uq.edu.au
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