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Abstract 24
1 Internalized discoloration of dentin under porcelain crowns
2 Ceramic Pressed to Metal Versus Feldspathic Porcelain
3 Effect of two connector designs on the fracture resistance
4 Relationship between Post endodontic Pain,Tooth Diagnostic Factors,
and Apical Patency
Internalized discoloration of dentin under porcelain crowns:
A clinical report
Heather J. Conrad DMD, MSa, , and James R. Holtan DDSb
aAssistant Professor, Division of Prosthodontics,
Department of Restorative Sciences. School of Dentistry,
University of Minnesota, Minneapolis, Minn
bAssociate Professor, Director of Graduate Program in
Prosthodontics,, Department of Restorative Sciences.
School of Dentistry, University of Minnesota, Minneapolis, Minn
Available online 20 February 2009.
This clinical report describes the situation of a patient who was
concerned about the appearance of porcelain crowns that were
placed on the maxillary incisors 4 years prior. The
mechanicochemical gingival retraction technique combining the use
of ferric sulfate and knitted retraction cord is described as a
possible etiology of internalized discoloration of the dentin in
this situation. The hypothesis is explained by the high acidity of
gingival retraction fluids (GRFs) and the high affinity of iron
for hard tooth tissues, resulting in an interaction with bacterial
byproducts and precipitation of insoluble ferric sulfide in the
porous demineralized dentin.
A prospective clinical trial is warranted to track the effects of
GRFs on tooth structure. This article describes the treatment of
internalized discoloration of dentin under porcelain crowns.
(J Prosthet Dent 2009;101:153-157)
Ceramic Pressed to Metal Versus Feldspathic
Porcelain Fused to Metal: A Comparative Study of Bond Strength
International Journal of Prosthodontics
January/February 2009
Volume 22 , Issue 1
Bhavani Venkatachalam, DMD, MS/Gary R. Goldstein, DDS/
Mitchell S. Pines, DDS/Eugene L. Hittelman, MA, EdD
Purpose: The aim of this study was to compare the debond/crack
initiation strength (D/CIS) of a leucite-based low-fusing ceramic
pressed (PC) to metal and feldspathic porcelain (FP) fused to metal.
Materials and Methods: Forty rectangular metal specimens,
20 noble alloy (NA; gold-palladium) and 20 base metal alloy
(BA; cobalt-chromium) were fabricated per ISO 9693:1999 standards
(25.0 mm 3 0.5 mm 3 3.0 mm). Ten samples in each group received
FP and the remaining 10 received PC. The samples in the PC group
underwent wax pattern build-ups and subsequent investing and
casting. The ceramic dimensions in all four groups were 8.0 mm
3 1.0 mm 3 3.0 mm. The final metal-ceramic specimen thickness
was 1.5 mm. All specimens were subject to the Schwickerath
crack-initiation three-point bending test at a crosshead speed
of 1.5 mm/min. Metal-ceramic fracture loads were recorded in
Newtons and D/CIS was calculated using the formula:
tb = k × Ffail. Results: Mean D/CIS were as follows:
BA-FP: 36.11 ± 2.31 MPa, NA-FP: 42.64 ± 1.94 MPa,
BA-PC: 37.47 ± 6.02 MPa, and NA-PC: 47.94 ± 3.92 MPa.
A 2-way ANOVA revealed no significant difference in D/CIS values
between the four groups. A statistically significant difference
was noted when comparing the mean D/CIS values obtained between
the two metal alloys used (NA: 45.29 MPa and BA: 36.79 MPa).
Conclusion: No differences (P > .05) in mean D/CIS were found
between the low-fusing ceramic pressed to metal and the FP fused
to metal. A higher mean D/CIS (P > .05) was found for the NA
compared to the BA, with both ceramics tested.
Int J Prosthodont 2009;22:94 100.
Effect of two connector designs on the fracture resistance of
all-ceramic core materials for fixed dental prostheses
Kwansiri Plengsombut DDS, MSa, , , Jane D. Brewer DDS, MSb,
Edward A. Monaco Jr DDSc and Elaine L. Davis PhDd
aFormer Resident, Department of Prosthodontics; private practice,
Bangkok, Thailand, School of Dental Medicine, State University
of New York at Buffalo, Buffalo, New York
bClinical Associate Professor, Department of Restorative
Dentistry, School of Dental Medicine, State University of
New York at Buffalo, Buffalo, New York
cProgram Director, Advanced Education in Prosthodontics,
Department of Restorative Dentistry, School of Dental Medicine,
State University of New York at Buffalo, Buffalo, New York
dAssociate Professor, Department of Oral Diagnostic Sciences;
Associate Dean for Student Affairs, School of Dental Medicine,
State University of New York at Buffalo, Buffalo, New York
Available online 20 February 2009.
Statement of problem
Most all-ceramic fixed dental prostheses (FDPs) fail at the
connectors.
Purpose
The purpose of this study was to determine the effect of
2 connector designs on the fracture resistance of core
materials used for all-ceramic FDPs.
Material and methods
Three materials were tested:
(1) heat-pressed lithium disilicate glass ceramic
(IPS e.max Press (Press)),
(2) milled lithium disilicate glass ceramic (IPS e.max CAD (CAD)),
and (3) milled yttrium-stabilized tetragonal zirconia polycrystals
(Y-TZP) (IPS e.max ZirCAD (ZirCAD)). Specimens were made into
30 × 4 × 4-mm bars to represent 3-unit FDPs. Two connector designs,
round (0.60 ±0.01-mm radius of curvature) and sharp
(0.06 ±0.001-mm radius of curvature), with a 3.00 ±0.05-mm
cross-section for each connector, were studied (n=5). Each specimen
was loaded to fracture in a universal testing machine with a
crosshead speed of 0.1 mm/min. Data were analyzed with a 2-way
univariate ANOVA and Tukey HSD test (a=.05).
Results
Mean (SD) failure loads for round connector designs were 684.2
(70.1) N for ZirCAD, 260 (7.8) N for CAD, and 172.9 (35.5)
N for Press. Mean (SD) failure loads for sharp connector designs
were 386.3 (51.5) N for ZirCAD, 87.9 (7.0) N for CAD, and 125.1
(15.1) N for Press. The 2-way univariate ANOVA indicated
statistically significant differences (P<.005) for material and
connector design, and, also, a significant interaction between
material and connector design. Higher maximum failure loads were
found for the round connector design when compared to the sharp
connector design, for ZirCAD and CAD. However, this difference
was not statistically significant for the Press groups.
SEM subjective assessment of the fractured specimens revealed that
the fracture initiated from the gingival surface (tensile) of the
connector toward the pontic (central loading point).
Conclusions
Fracture resistance of ceramic core materials is affected by
fabrication technique and connector design. Connector design
affected fracture resistance of the milled ceramic, but not
the pressed ceramic. (J Prosthet Dent 2009;101:166-173)
Relationship between Post endodontic Pain,
Tooth Diagnostic Factors, and Apical Patency
Ana Arias DDS, Dr. Odont, Magdalena Azabal MD, DDS, Dr. Med†,
Juan J. Hidalgo MD, DDS, Dr. Odont and
José C. de la Macorra MD, DDS, Dr. Med, ,
Private practice, Madrid, Spain
Department of Conservative Dentistry, Faculty
(Estomatologia II) of Odontology,
Complutense University of Madrid, Madrid, Spain
Available online 21 January 2009.
Abstract
This study compares the incidence, degree, and length of
postoperative pain in 300 endodontically treated teeth,
with and without apical patency, in relation to some diagnostic
factors (vitality, presence of preoperative pain, group, and
mandible of treated tooth). Of the questionnaires received back,
apical patency was maintained during shaping procedures with
a #10 K-file in one group (n = 115) and not in the other
(n = 121). There was significantly less postendodontic pain
when apical patency was maintained in nonvital teeth. If pain
appeared, its duration was longer when apical patency was
maintained in teeth with previous pain or located in the
mandible. Maintenance of apical patency does not increase the
incidence, degree, or duration of postoperative pain when
considering all variables together.
Key Words: Apical patency; postendodontic pain;
postoperative pain
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