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Assessment of convergence angles of tooth preparations for complete crowns among dental students.
J Dent. 2005 Sep;33(8):633-8.
Ayad MF, Maghrabi AA, Rosenstiel SF.
OBJECTIVES: Convergence angles for complete crown preparations have been recommended at
4-12 degrees . However, practitioners have difficulty meeting these recommendations.
This study measured and compared the convergence angles of tooth preparations for complete
crowns prepared at three Colleges of Dentistry: the University of Tanta, Egypt,
King Abdulaziz University, Saudi Arabia, and The Ohio State University, Columbus,
Ohio METHODS: The convergence angles of 499 tooth preparations for complete crowns were
evaluated. These comprised of a random sample of 262 teeth prepared by third-year dental
students at the University of Tanta on extracted molars under normal preclinical conditions,
37 preparations on molar teeth on typodonts done by first-year dental students.
The Ohio State University and 200 molar typodont complete crown preparations done
by fourth-year dental students at King Abdulaziz University, Saudi Arabia.
The bucco-lingual and mesio-distal convergence angles of each preparation
were measured with a goniometer microscope. Mean convergence angles were calculated,
and differences between groups were tested for statistical significance with
analysis of variance (ANOVA) at 5% level of confidence. RESULTS: Convergence
angle measurements were significantly different between the groups and the
dimensions (P<0.001). The greatest convergence value (19.8+/-10.0) was for
bucco-lingual measurements prepared by Egyptian dental students.
The smallest convergence value (14.1+/-3.8) was for mesio-distal
measurements prepared by Saudi dental students. CONCLUSIONS: This
study emphasized the difference between what is taught at dental schools
(what is theoretically possible) and the school results of actual practice.
There was a considerable disparity between the convergent angles recorded in
this study and the ideal configurations recommended in fixed prosthodontic
textbooks and the dental literature.
The effect of a layer of resin luting agent on the biaxial flexure strength of two all-ceramic systems.
J Prosthet Dent. 2005 May;93(5):459-66.
Pagniano RP, Seghi RR, Rosenstiel SF, Wang R, Katsube N.
STATEMENT OF PROBLEM: The influence of a layer of resin luting agent on the longevity of
glass-ceramic crowns has been demonstrated in some laboratory and clinical studies.
The mechanisms of glass-ceramic crown failure and the influence of the resin luting agent
layer are still not clearly understood. PURPOSE: The objectives of this study were to
examine the difference in biaxial flexure strength between 2 glass-ceramic dental materials
and to examine the influence of a layer of resin luting agent on the characteristic strength
of these materials. MATERIAL AND METHODS: Thirty-seven disks, 15 mm x 1.5 mm, each of
IPS Empress and IPS Empress2, were fabricated according to the manufacturer's recommendations.
The surface of each disk underwent acid etching and silanation. The disks from each group
were arbitrarily divided into 2 subgroups. One subgroup of each material type was selected
to receive a thin (approximately 0.1 mm) layer of resin luting agent (Nexus 2),
whereas the other subgroups remained unaltered. Each disk was loaded, with the treated
surface down, using a ball-on-ring biaxial configuration in a universal testing machine.
The failure loads (N) were recorded, and the biaxial flexure strength for each disk was
calculated. Characteristic Weibull parameters and a +/-95% confidence interval were
determined. A 2-way analysis of variance (alpha=.05) on transformed fracture strength
data was used to determine significant differences between groups. RESULTS: The Weibull
characteristic strength of IPS Empress2 (213 MPa) was 75% higher than IPS Empress
(122 MPa). The results also show that the application of a thin layer of resin luting
agent significantly increased (P <.001) the characteristic strength of both IPS Empress
and IPS Empress2 by 45.6% and 47.6%, respectively. The higher strength of the
resin-coated specimens cannot be explained in terms of standard fracture mechanics
alone. CONCLUSION: Results suggested that IPS Empress had significantly
lower characteristic strength than IPS Empress2. A relatively thin layer of resin luting agent bonded to both IPS Empress and IPS Empress2 significantly
increased the characteristic strength of the ceramics.
Dentists' molar restoration choices and longevity: a web-based survey.
J Prosthet Dent. 2004 Apr;91(4):363-7.
Rosenstiel SF, Land MF, Rashid RG.
STATEMENT OF PROBLEM: The increasing trend toward esthetics has led to controversy as
to the longevity of esthetic restorations and the wisdom of having traditional restorations
replaced for esthetic reasons. With the assumption that the way dentists treat their own
teeth may be a good indication of the accumulated wisdom of the profession, knowledge of
dentists' own restorative choices may provide guidance in selecting the most appropriate
restorations. PURPOSE: The purpose of this article was to determine restorative choices
of dentists for personal molars and estimate restoration longevity. MATERIAL AND METHODS:
Information about dentists' molars was obtained from a Web-based survey designed to
receive dentists' demographic data and charting of 8 molar teeth with estimated longevity.
Approximately 12,000 e-mails asking to access the website were sent to dentists'
addresses randomly selected from a commercial database. Nonrespondents received 1
reminder. The responses were statistically analyzed with a chi-square analysis
(alpha=.05). RESULTS: Seven hundred fifty-seven valid replies provided information
for 6,034 teeth (22% unrestored, 75% restored, 2% missing). Restorations reported
included amalgam (36%), gold inlay/onlay (13%), complete veneer crown (CVC) (10%),
metal-ceramic crown (MCC) (8%), and composite (7%). Other esthetic options
accounted for less than 3%. Restorations with more than 20 years longevity
included amalgam restorations (58%), gold inlays/onlays (48%) and crowns (23%).
Fifty-six percent of esthetic restorations and 5% of amalgams were placed in
the last 5 years. The following restorations were placed in the last year (n=186):
38% esthetic, 29% crowns (18% MCC; 11% CVC), and 17% gold inlay/onlay or amalgam.
Significant differences (P<.001) were identified for dentist's gender, year of
graduation and practice location. CONCLUSIONS: Most dentists have not replaced
traditional metallic restorations with esthetic alternatives. Dentists still
choose nonesthetic options for significant numbers of their own restorations.
Postcementation hypersensitivity: scientific data versus dentists' perceptions.
J Prosthodont. 2003 Jun;12(2):73-81.
Rosenstiel SF, Rashid RG.
PURPOSE: The purpose of this article was to obtain dentists' opinions via an Internet
survey as to the prevalence, causes, and prevention of postcementation sensitivity and
compare their responses with published data on the problem. MATERIALS AND METHODS:
Information as to respondents opinions of postcementation sensitivity was obtained from
an Internet survey asking about their experience and for a ranking of the importance of
each of 15 factors. RESULTS: A total of 466 valid responses were received. The incidence
of postcementation sensitivity was estimated to be less than 2% by more than 2/3 of the
dentists. The factors considered "very important" in reducing sensitivity by more than 50%
of the respondents were desiccation, luting agent, occlusion, provisional, and water spray.
CONCLUSIONS: Comparing respondents' opinions with published clinical studies, the incidence
of postcementation sensitivity appears to be underestimated. There is little published
evidence to support the importance of antimicrobials, desensitizing, or bonding agents,
although these are considered effective by some dentists. Many respondents consider luting
agent to be an important variable.
Clinical diagnosis of dental caries: a North American perspective.
J Dent Educ. 2001 Oct;65(10):979-84.
Rosenstiel SF.
This paper summarizes current trends in the clinical diagnosis of occlusal caries in response
to the RTI/UNC review and reflects the dilemma felt by many dentists who understand the
difficulty in accurately assessing the extent and activity of pit and fissure caries in
many of their patients. They are unsure if they should be aggressive in instrumenting
suspicious lesions and provide small restorations, some of which may not be indicated.
Alternatively, should they wait until signs are more clear-cut and provide larger
restorations? Discussed here is the advantage of practicing dentists who obtain immediate
false-positive feedback when they instrument a tooth with no clinical caries and
false-negative feedback when a recall patient exhibits progression of an equivocal lesion.
They should be encouraged to use this feedback as part of their diagnostic procedure
and explain to their patients
the difficulty of providing an accurate and precise diagnosis with existing tests.
Dental luting agents: A review of the current literature.
J Prosthet Dent. 1998 Sep;80(3):280-301.
Rosenstiel SF, Land MF, Crispin BJ.
STATEMENT OF PROBLEM: The practice of fixed prosthodontic has changed dramatically
with the introduction of innovative techniques and materials. Adhesive resin systems
are examples of these changes that have led to the popularity of bonded ceramics and
resin-retained fixed partial dentures. Today's dentist has the choice of a water-based
luting agent (zinc phosphate, zinc polycarboxylate, glass ionomer, or reinforced zinc
oxide-eugenol) or a resin system with or without an adhesive. Recent formulations of
glass ionomer luting agents include resin components (resin-modified glass ionomers),
which are increasingly popular in clinical practice. PURPOSE: This review summarizes
the research on these systems with the goal of providing information that will help
the reader choose the most suitable material. MATERIAL: The scientific studies have
been evaluated in relation to the following categories: (1) biocompatibility, (2)
caries or plaque inhibition, (3) microleakage, (4) strength and other mechanical
properties, (5) solubility, (6) water sorption, (7) adhesion, (8) setting stresses,
(9) wear resistance, (10) color stability, (11) radiopacity, (12) film thickness or
viscosity, and (13) working and setting times. In addition, guidelines on luting-agent
manipulation are related to available literature and include: (1) temporary cement
removal, (2) smear layer removal, (3) powder/liquid ratio, (4) mixing temperature
and speed, (5) seating force and vibration, and (6) moisture control. Tables of
available products and their properties are also presented together with current
recommendations by the authors with a rationale.
Randomized clinical trial of the efficacy and safety of a home bleaching procedure.
Quintessence Int. 1996 Jun;27(6):413-24.
Rosenstiel SF, Gegauff AG, Johnston WM.
The safety and efficacy of a home-use carbamide peroxide tooth-whitening procedure
were evaluated in a double-blind experimental design. Fifty-two adults were randomly
assigned to experimental and control (placebo gel) groups. The products were applied
in a custom-fitted tray and used for 5 consecutive nights in accordance with the
manufacturer's recommendations. Tooth color changes from baseline were measured
with a small-area colorimeter. Concurrently, electric pulp test and periodontal
indices were measured. At the end of 6 months, the teeth in the active group had
a statistically significant greater mean color change that did the placebo controls.
The mean color change differed significantly by tooth type. No statistically significant
changes in vitality,
sulcus depth, or Gingival Index were found in the treatment group.
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