J. Nihon.
Univ.
Sch.
Wear Part
Dent.,
Vol.
34, 249-264,
of Denture
3: Abrasive
1992
Teeth
by Use
of Metal
Wear of Posterior Teeth Opposing Metal Plates
Plates
and Wear
of
Yoshinori SATOH 1, Eiichi NAGAI 1, Kengo MAEJIMA 1, Tetsuo OHYAMA 1, Sukehiro ITO 1, Hitoshi TOYOMA 1, Masaaki OHWA 1, Eisaku KOBAYASHI1, Katsuzo OHM 1, Masahiro KAKETANI 2 and Minoru NISHIYAMA 2 (Received24 December1991and accepted17 March 1992) Key words:
artificial denture teeth, plastic denture teeth, abrasive wear resistance, removable partial denture Abstract
An in vitro evaluation of abrasive wear resistance of high-strength denture (HS) teeth and wear of metal plates (Pd alloy) on the opposing side was conducted. A total of 8 types of teeth were used in the experiments including 3 types of HS teeth, 3 types of conventional plastic denture (PL) teeth, porcelain teeth and metal teeth (Pd alloy). Sliding-induced wear tests were conducted by sliding these teeth over the metal plates. Abrasive wear resistance of the teeth was evaluated in terms of wear depth and weight loss. A comparison of wear depth showed that the abrasive wear resistance of HS teeth was 4.7 times that of PL teeth, 0.7 times that of porcelain teeth and 8.3 times that of metal teeth. Weight loss showed that the abrasive wear resistance of HS teeth was 3.3 times that of PL teeth, 0.2 times that of porcelain teeth and 11.4 times that of metal teeth. The weight loss of the metal plates was minimal when they slid over HS teeth, but increased in the order PL teeth, porcelain teeth and metal teeth. Introduction The purpose of removable partial dentures as a posterior prosthesis is reconstruction of occlusion with artificial teeth. That is, posterior artificial teeth are designed to maintain the form and function of the stomatognathic system including restoration of masticatory function, maintenance of the vertical dimension and prevention of temporomandibular joint dysfunction caused by occlusal disharmony. Plastic and porcelain materials have been used conventionally for posterior artificial teeth. High-strength denture teeth have been developed, which retain some of the advantages of plastic teeth, such as easy occlusal adjustment and cost, 佐 藤 吉則,永 井栄 一,前 島健 吾,大 山哲 生,伊 東 祐 博,豊 間 掛 谷 昌宏,西 山 實
均,大 輪正 昭,小 林 栄 作,大 木 一 三,
1 Department of Removable Partial Denture Prosthodontics, Nihon University School of Dentistry 2 Department of Dental Materials, Nihon University School of Dentistry To whom all correspondence should be addressed: Dr. Yoshinori SATOH, Department of Removable Partial Denture Prosthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101, JAPAN.
250
while achieving Findings
improved of basic
hardness
studies
impact resistance[4], bonding
and abrasive
on these
strength
wear resistance[1-3].
HS teeth
have
with denture
and wear resistance of anterior teethm. However studies on the abrasive wear resistance of posterior Therefore, wear
we
conducted
resistance
made
of
wear
of
Pd-Au-Ag
depth
weight
profile
of
vitro
of
alloy.
and
roughness
in
8 types
We
teeth
the
abrasive
In
metal
addition,
we
A
total
of
3 types
(PL)
teeth,
1).From
8 types of
each
of
alloy
whose
type,
5 upper
contact
were with
heat-treated pm
for with
40 made
the
artificial
and
order by
to
wear
to have denture
evaluate
sliding
evaluated
the
them
on
resistance the
wear
been few teeth[8.9].
of
abrasive
metal
plates
the
depth
teeth
and
by
surface
Methods
waterproof
and
and
shape
was
right
first
plates
match
bucco-lingual aging
were (HS)
teeth
metal to
teeth denture
porcelain
alloy,
Accordingly,
Ag
of
high-strength
1 type
Pd-Au-Ag
teeth.
0.1
of
Materials
teeth,
of
in terms
plates. Materials
1.
reported
there seem high-strength
in
denture
evaluated
loss. the
experiments
posterior
been
base resin[5,6], hardness[1-3,5,6],
sandpaper
in
of
of
to
the
reduce and
Table
1
of
of
posterior surface
teeth
porcelain
The
roughness
made
teeth
totaling mm
teeth, teeth.
posterior plastic
metal
chosen,
posterior
as
conventional
15•~15•~2
the
buff
that
were
measuring of
experiments
custom-made to
premolars
number
our
3 types
comparable
cusps finished
1 type
each
the
used teeth,
40 made
and
posterior of
used
metal (Ra)
(Table
Pd-Auto
make
plates
were
to
than
less
polishing.
Materials
2. Methods 1) A total of 30 teeth consisting of HS teeth and PL teeth were immersed in distilled water prior to the wear test. Water sorption was measured every 48 h for about 3 months according to JIS T 6508. Wear tests were conducted when each of the posterior teeth reached a constant weight. Wear tests were conducted with a sliding-induced wear testing apparatus (Tokyo Giken). Each metal plate was fixed with a jig to the upper holder of the testing apparatus, while the posterior tooth was fixed to the lower holder, enabling
251
both
the
plate.
bucco-lingual
Both
upper
the
upper
holder
strokes
to
to the
stroke
Wear
depth
was
strokes,
cusp
depth
was
at
a
were
and
depth
of
fixed
before
contact
in was
posterior
distilled to
under of
the
metal
water,
and
apply
200,000
conditions
the
of
300
1 kgf/tooth.
teeth of
50,000
with
moved
loading
initiation
strokes,
make
direction
constant the
to
immersed
was
mesio-distal
mm
using
CCD
TV
rior
tooth
point
was
the
strokes,
0
this,
wear
test
100,000
to
ratio
the of
3)
the
20
mean to
(at
0
stroke),
strokes
and
and
200,000
calculated
for
after
a
each
given
The
of
weight
measured
loss
after
1,
loss
of
lingual
0.3
at
Then using
of
the
a
poste-
binary
each
a
Seimi-
mm/s.
image to
that
with
Tokyo
PIAS)
subjected and
of
strokes
weight
loss
metal
image of
after
a
of
length
of
200,000
19
speed
The
was
the
picture
measurement
given
all
was
synthesized 2 pixels
from
from
number
these then
lines
by
two
lingual
cusp
of
strokes
in
were
divided
the
the
measured
the
a to
enlargement
value.
dividing
and
A,
(LA-500,
PIASP01.
the
tip
mean
by
of
5
on
lengths
after
number
Measurement
cusp
weight
tooth
head
increments
measurement
of
of direction
2000
system
point
in
the
made
completion
a tracing
at 0 stroke
based
This
of was
Surfcom
x V512,
profile
tooth.
lingual
the
The
a bucco-lingual
analysis
tooth
drawn
length.
Measurement
upon
the
Then
obtain
Measurement
4)
was
direction.
and
measurement
each
in
(Surflyzer
H512
of
manner.
times
image
measured
a line
stroke
bucco-lingual calculate
each image
was
20
pm,
an
pixels
for
depth For
at
at the
50
into
(PX-370,
then
following
of
of
fed
synthesized
Wear images.
was
entered and
the
apparatus
diameter
image camera
analysis,
in
enlargement
measuring
a probe
traced
measured an
roughness
each
and
wear
tooth
plate
in
3.0
10,000
was
traced
surface
and
holders
metal
measured
of
posterior
respectively. Wear
tsu)
the
lower
tooth
of
completion
of
the
length
Measurement
upon
tip
and
which
posterior
stroke/min, 2)
cusps
the
strokes,
strokes
for
the by of
plates wear
posterior
10,000
teeth 50,000 each
difference
the
strokes
weight
weights
loss at
0
was stroke
gravity.
plates
which strokes
100,000
The
between
specific
metal
strokes,
tooth.
had as
slid
over
as
after
well
the
denture
teeth
completion
of
was
20•~104
strokes. The given by
weight
of
number
of
dividing 5)
profile
of
denture
using
a probe made
6)
Olympus)
loss
surface
5 pm
cuspal at •~2.5
was
weight
surface was in
after
measured
Then by
of
measured
with
and
of
magnification of
wear
of
posterior
cuspal
after surfaces
plates
which
a surface
test as
and
after
the
volume
metal
opposed
measurement of
4.0
mm.
to
the device
Measurement
strokes.
forms were
were
roughness length
wear
of
posterior
observed
completion of
stroke
calculated
a
plates
metal
20•~104
teeth
wear
was
gravity.
a measurement of
observations
the loss
metal
roughness
diameter
before weight
specific of
completion
forms
the
the
roughness
teeth
only
Observations
plates strokes.
of
Microscopic The
7)
of
The types
was
the
Profile
the
wear
of tooth
using 200,000 cusps
teeth a wear
microscope strokes.
(BH,
8
252
For analysis of the wear surface of metal tooth cusps, two-dimensional Fourier transformation was performed in order to identify any cyclic or specific wear pattern in the image as physical information obtained from the original image. The wear surface of the metal tooth was transmitted from a microscope (BH, Olympus) to an image analysis system (LH-500, PIAS). The image was then analyzed with software (PIAS) designed for two-dimensional Fourier transformation. Results 1. Wear depth of posterior teeth Table 2 and Figure 1 show the wear depth of teeth after 10,000, 50,000, 100,000 and 200,000 strokes. 2. Weight loss of posterior teeth Table 3 and Figure 2 show the weight loss of each tooth after completion of 10,000, 50,000, 100,000 and 200,000 strokes.
Table
3.
Weight
loss
Table 20•~104
4
wear
completion 4.
of
Figure had
slid
Figure slid
20•~104
shows PL
3 types the teeth,
Wear
show
the
of posterior
wear
sample of
sample porcelain
weight
4 shows
teeth
HS
the
loss
weight
of loss
metal of
plates teeth
after
and
metal
1, 5,
10
plates
and after
strokes.
roughness a
depth
plates 3
Figure
surface
5 shows over
6 over
metal Figure
strokes. of
Profile
of
and
2
of
metal
profile teeth profile teeth
plates
of after of and
surface 0
and
surface metal
roughness 20•~104
roughness teeth
of
sliding of after
metal strokes,
metal 20•~104
plates sliding
plates
which
respectively. which strokes.
had
253
Table
Table
3
Weight
4
Weight
loss of posterior
loss of metal
teeth
plates
5.
Microscopic observations of cuspal forms of posterior teeth Figure 7 shows the cuspal forms of 3 types of HS teeth, and Fig. 8 shows that of 3 types of PL teeth. Figure 9 shows the cuspal forms of metal teeth. 6. Observations of wear surface of metal tooth cusps With regard to the wear surface of metal teeth cusps, Fig. 10 shows the original
image
and
the image
after two-dimensional
Fourier
transformation.
254
Fig. 1
Wear depth of posterior
teeth
Fig.
Weight
teeth
2
loss
of posterior
255
Fig.
Fig.
4
Weight
loss
of
3
posterior
Weight
teeth
loss
and
of metal
metal
plates
plates
after
20•~104
strokes
256
Fig. 5
Profile of surface roughness
(metal
plates)
Fig. 6
Profile of surface roughness
(metal
plates)
257
a) ED
b) DD
c) SR Fig.
7
Cuspal
forms
of three
types
of HS
teeth
258
a) AR
b) WL
c) BB Fig.
8
Cuspal
forms
of three
types
of PL teeth
259
a) MT
b) BA Fig. 9
Cuspal
forms of metal and porcelain
teeth
260
a) Original Fig. 10
image Two-dimensional
Fourier
b) Fourier transformation transformation (metal teeth)
Discussion Dentures with PL teeth show significant wear at an early stage due to mastication and swallowing in comparison with dentures with occlusal surfaces restored using other materials. Porcelain teeth, on the other hand, show little wear themselves, but clinically it is often observed that they cause wear of opposing teeth. Since the clinical use of HS teeth has been increasing, we considered it important to evaluate the abrasive wear resistance of these teeth. Experiments were therefore conducted, using PL teeth, porcelain teeth and custom-made metal teeth as control materials. The cuspal inclination of these artificial teeth was based on the functional cusp angle usually employed in partial dentures. 1. Method for measurement of weight loss Types of wear test apparatus used for evaluation of the abrasive wear resistance of artificial teeth differ according to the objectives of study and among laboratories. The extent of abrasive wear found in the mouth is influenced by various factors including occlusal biting force[11,12],friction with food1131,individual masticatory efficiency, type of occlusion and type of retainer used1141 . Therefore SAToH1151 has claimed that an in vitro test method which is easy to perform and highly reproducible has yet to be established. With this in mind , we used a sliding-induced wear test apparatus which reproduces sliding-induced wear . In conducting wear tests, the metal plate and the posterior teeth maintained very close contact during the sliding motion, so that it was difficult to place an intermediary material between them[16'171. The two-body abrasion method was adopted for this reason, and also in order to eliminate any influence of an intermediary material on wear behavior. With regard to the experimental conditions of the wear test, stroke length was set at 3.0 mm in line with previous studies and reports on mastication[181,and the number of strokes was set at 200,000, which is clinically comparable to the number
261
of
chewing
strokes
reference
to
As
to
tracing
cusp
that
2.
of
of
the
Wear
was
as
wear
weight
than
0.0ƒÊm
the
the
times
the
wear
which
was
teeth
was As
mean
other
the
value
for
wear
i.e.
weight
depth
of
8.3
the
teeth
showed
3.3
times
was comparable The
abrasive
result HS
than
agrees
teeth
is
that
when
with
of
opposed
ness[22]. teeth.
It
teeth
has
contact It
is
our
In
wear
all
occlusal
the
time,
and
teeth
strokes PL was
was
4.7
42
depth
or
HS
of
pm,
metal
was
teeth
and
cm3
that
the
of
in
teeth.
the
and
with
a
HS
This
result
teethE71.
teeth
. This
occlusal
wear
significantly
less
porcelain low
is slight
Vickers
resistance
greater
range teeth
artificial
that
wear
the
metal
porcelain
of
the
considering
respectively.
PL
wear
resin
compared by
teeth
teeth
suffer
we
of anterior
abrasive
teeth
2),
than
porcelain
metal
hard-
than
abrasive
on
metal
wear
due
to
food
the
our
was
surface
of
removed
a
significant
sliding-induced the
during
wear
metal
plate
sliding,
so
and that
strong[23].
lower
oily
metals
during
were was
and or
thick
thick
metals
between that
A
A
upper
saliva
of
times
cohesion
300
two
the
wear
which
wear
porcelain
that
suggested
about
the
however,
teeth.
50•`73ƒÊm.
strokes
YoKoYAmA[14]
greater
that is
100•`200
between
reality,
contact
about
A
of
metals[23].
It
layer
layer
adhesive
of
0.2
of
metal
therefore,
a contaminating oxide
that
strokes.
,000 of
Fig.
wear
resistance of
as
times
200
the
291.9•~10-5
indicating
such 11.4
experiment[23].
in
teeth
types
porcelain
resistance
was
that
100,000
of
3 and
3 types
and
wear
a report
materials
conceivable,
in
,
decrease
porcelain
220•`364ƒÊm,
200,000
teeth,
wear
teeth
and
and
whereas
the
PL cm3
than
type
the
cusps
teeth.
findings
greater
same
and of
the
depth
of
(Table
for
for
HS
of
of
abrasive
reported
the
HS
loss
clinical
showed
been
with
factor test,
with
HS
loss[21]
working
different
a wear
teeth,
teeth
6.0•~10-5
and
the
teeth
the
depth
HS
of
HS
completion
depth wear
of
those
of
the
teeth,
wear
for abrasive
slightly
PL
after showed
The
Weight
resistance
weight
i.e.
30 ,000
among
completion
greater
to that wear
also
after
cm3,
with
consideration
calculated
of
10,000,
teeth
that
whereas
60.6•`100.5•~10-5
teeth,
3 types
made
posterior
teeth.
of In
we
tooth
a
times
tooth
cm3,
HS
depth
of
1 .0 kgf/tooth
teeth
1) of
be
teeth.
wear
loss
each
22.2•`26.4•~10-5 were
the
artificial
of
each of
HS
at
performed.
posterior
Fig.
showed
of
times
527ƒÊm, to
for
hand,
depth
0.7
of
not
3 types
set
determination
dimension,
completion
values
The
was
depth.
could
mean
compared.
wear,
of
vertical
2 and
after
of
cusps
loss
(Table
evaluation
on
posterior
teeth
residue
do
is usually
not
maintain
present
on
close the
metal
surface. These
opposing observed 3.
of
less
teeth,
an
loss
depth
were
of
a tips
load
al. [20]
conventionally
in
and
constant et
amount
been lingual
wear
Therefore
the
upper
The
comparative
the
of have
cusp
depth
The
HARRISON
the
clinically
height
of
profile
wear
results
yearr193.
report
measurement
of
fact
per
the
Weight The
adhesive
materials
surfaces[231, in
this loss
weight
so
that
will the
serve wear
as
lubricant
behavior
agents could
between
the
two
be
different
from
that
and
posterior
teeth
after
study. of loss
metal of
plates metal
plates
(Table
4 and
Fig.
3)
262
20•~104
sliding
plates
(Figs. The
range
5,
6)
weight
was
mately
were
This
the of
of
change.
was
metal There
metal
plates
had
13.01•~10-5 son
the
is
which
of
of
turn
that
teeth
metal
was
opposed former
in
the
with was
was
PL
approxi-
opposed than
for
HS
teeth
strokes.
teeth
in
the
a
with It
both
showed
On
showed
teeth.
were
other
significant
the
result
is assumed
that
the
with
HS
comparison
two
in
of
for
porcelain
teeth
HS
Compari-
teeth.
specimens
Table
which
2,
were
was
revealed
whereas
opposed
very
deep
with
and
porcelain
limited. tip
wear
surface
on
the
the
greater
of
of the
wear[23],
made
teeth
HS
which
was
is
in
also
wear the
The
weight
143.50•~10-5
It
metal was
by
Therefore wear.
teeth.
same
rough
plates[ml.
resulting
metal
that
surfaces
was
metal the
with
than
adhesive
with that
the
shown
opposed
two
wear
comparison
greater
cusp
greater
the
of
teeth
HS
PL
quite
the
were
in of
plates
strokes,
times
roughness
3 types
PL
with
as
porcelain
sliding
significant
surface
se, meatl
wear
which
before,
cm3,
considered,
contact
clearly
as
with
each
evident
in
the
of
the
roughness. of
wear
surfaces
of
Fourier
of
image,
HS
surface
20 x 104
between
per
increased
Two-dimensional
the
of
the
of
with
6 times
in
of
66
surfaces
of
loss.
roughness
the
of
Observations
wear
roughness
plates
with
and
which
about
area
about
generated
profile
Thus
profile
contact
plates
teeth
plates
mentioned
cm3.
3 types
weight
that
number
was
other
in
metal
which
metal
difference with
observed
the
the
loss
surface
suggested
strokes, greater
of
was
although It
surface
3 types
of
opposed
opposed
of
metal
the
stroke
were
greater
was
wear
0 wear
range
which
porcelain
in
opposed
of
of
significant teeth,
the
profile
wear
of
with that
were
a significant
were
loss
cm3,
of
little
also
in
weight
evident
which
a wider
resulting The
opposed whereas
which
between
was which
teeth,
also plates
plates
plates
profile
5.61•~10-5•`7.62•~10-5
metal
metal
sample
plates cm3,
change
the
the
latter.
tendency
significant
and
metal
range
the
The
hand,
in
4)
determined.
loss
in
1/3
specimens.
4.
(Fig.
1.65•~10-5•`2.67•~10-5
teeth
no
strokes
metal
teeth
using
an
specific
wear
pattern
of
aligned
in
a mesio-distal
metal
teeth
transformation in
order
image
to
analysis
scratches
was
identify system
generated
direction
on
by the
performed
any
cyclic
(Fig. sliding
cuspal
for or
10).
The
contact surfaces
analysis
specific
wear
results with
of
revealed
the
metal
pattern
metal
a plates
teeth.
Conclusion This used of for
as
study
porcelain
The
teeth
of
1.
A
metal
4.7
1 type
tests,
of
using
abrasive
evaluate Three
conclusions the
the types
abrasive
of
HS
custom-made metal
plates
were
obtained
wear
wear
teeth,
metal made
teeth of
from
resistance
of
resistance
3 types were
Pd-Au-Ag the
of PL
used
HS
teeth, as
teeth 1 type
specimens
alloy.
findings
posterior
of
teeth
of and
comprehensive wear
of
the
of
HS
plates:
comparison was
to teeth.
and
following
opposing
conducted
artificial
sliding-induced
evaluation
teeth
was
posterior
of times
that
wear of
depth PL
teeth,
showed 0.7
that times
the that
abrasive of
porcelain
wear
resistance teeth,
and
8.3
times
263
that
of
resistance teeth 2.
metal
teeth.
of and
The
showed
HS
11.4
times
weight
loss
a minimum The
metal
Comparison
teeth
was that of
plates
5.61•~10-5•`7.62•~10-5 and
metal
teeth
of
which cm3,
showed
times
metal
metal
value
of
3.3
plates of
weight that
loss of
PL
showed teeth,
were
weight
the
times
abrasive
that
of
wear
porcelain
teeth. which
were
opposed
1.65•~10-5•`2.67•~10-5
whereas
that 0.2
opposed the losses
with
3 types
of
HS
teeth
cm3.
with
PL
metal
plates
of
13.01•~10-5
teeth
showed
opposed cm3
with and
a weight porcelain 143.50•~10-5
loss
of
teeth cm3,
respectively. References
[1] TAKAHASHI, Y., HASEGAWA, J., HIRANUMA, K., MORI,H. and HASEGAWA, A.: Properties of experimental high abrasion resistance plastic teeth, Aichi Gakuin J. Dent. Sci., 28, 271-281, 1990 (in Japanese) [2] SAITO,S.: A high-strength denture teeth, Dental Diamond, 3, 146-149, 1990 (in Japanese) [3] HASEGAWA, J.: The Endura-anterio high-strength denture teeth, Dental Diamond, 3, 104107, 1990 (in Japanese) [4] SuzuKi, S., SAKOH, M. and SHIBA, A.: The evaluation of the impact resistance of crosslinked plastic denture teeth, J. Jpn. Prosthodont. Soc., 32, 780-786, 1988 (in Japanese) [5] SuzuKi,S., KUNESHITA, H. and SHIBA, A.: The evaluation of adhesive bonding of the denture base resin to the hard resin teeth, J. Jpn. Prosthodont. Soc., 32, 37-42, 1988 (in Japanese) [6] YAMAUCH, M., OKUMURA, K., SASAKI, M., ANDO,M., KAWANO, J. and YOKOI,K.: Bonding strength of the hardened plastic teeth to the denture base acrylic resin, J. Jpn. Prosthodont. Soc., 32, 1278-1282, 1988 (in Japanese) [7] SATOH, Y., OHTANI, K., MAEJIMA, K., MORIKAWA, M., MATSUZU, M., NAGAI,E., TOYOMA, H., OHKI,K. and NISHIYAMA, M.: A study on high-strength denture teeth, J. Jpn. Prosthodont. Soc., 34, 148-153, 1990 (in Japanese) [8] FRAUNHOFER, J. A. V., RAZAVI,R. and KHAN,Z.: Wear characteristics of high-strength denture teeth, J. Prosthet. Dent., 59, 173-175, 1988 [9] WHITMAN, D. J., MCKINNEY, J. E., HINMAN, R. W., HESBY, R. A. and PELLEU, G. B.: In vitro wear rates of three types of commercial denture tooth materials, J. Prosthet. Dent., 57, 243-246, 1987 [10] SATOH, Y., KIMURA, K. and OHKI,K.: Application of an image-analysis system to prosthodontics, J. Nihon Univ. Sch. Dent., 30, 237-243, 1988 (in Japanese) [11] LAMBRECHT, P., BRAEM,M. and VANHERLE, G.: Evaluation of clinical performance for posterior composite resins and dentin adhesive, Operat. Dent., 12, 53-78, 1987 [12] LUTZ,F., PHILLIPS, R. W., ROULET, J. F. and SETCOS, J. C.: In vivo and in vitro wear of potential posterior composite, J. Dent. Res., 63, 914-920, 1984 [13] JORGENSEN, K. D. and ASMUSSEN, E.: Occlusal abrasion of a composite restorative resin with ultra-fine filler, Quintessence International, 6, 73-78, 1978 [14] YOKOYAMA, M.: The evaluation of posterior plastic teeth, Practice in Prosthodont., 19, 163-171, 1986 (in Japanese) [15] SATOH, M.: The occlusal wear of posterior composite resins, Operat. Dent., 33, 345-385,1990 (in Japanses) [16] MCKINNEY, J. E. and Wu, W.: Relationship between subsurface damage and wear of dental restorative composites, J. Dent. Res., 61, 1083-1088, 1982 [17] ROULET, J. F.: Degradation of Dental Polymers, S. Karger, Basel, Switzerland, 60-66, 1987 [18] Ai, M.: A study of the masticatory movement at the incision inferius, J. Jpn. Prosthodont. Soc., 6, 164-200, 1962 (in Japanese) [19] SOLTESZ, V. U., KLAIBER, B., PERGANDE, C. H. and RICHTER, H.: Vergleichende untersuchungen -Etherdas abrasionsverhalten von composite-fullungsmaterialien, Dtsch. Zahndrztl. Z., 34, 406-412, 1979
264
[20] HARRISON, A. and LEWIS, T. T.: The machine for dental materials, J. Biomed. Mater. Res., 9, 341-353, 1975 [21] MANASKY, G. E. and TAYLOR, D. F.: Studies on the wear of porcelain, enamel, and gold, J. Prosthet. Dent., 25, 299-306, 1971 [22] TAKARABE, M.: An experimental study on sliding-induced abrasion of natural teeth and materials used for crowns, J. Tokyo Dental College Soc., 82, 949-1004, 1982 (in Japanese) [23] SODA,N.: The Friction, 1-180, Iwanami Shoten, Tokyo, Japan, 1988 (in Japanese)
Univ.
Sch.
Wear Part
Dent.,
Vol.
34, 249-264,
of Denture
3: Abrasive
1992
Teeth
by Use
of Metal
Wear of Posterior Teeth Opposing Metal Plates
Plates
and Wear
of
Yoshinori SATOH 1, Eiichi NAGAI 1, Kengo MAEJIMA 1, Tetsuo OHYAMA 1, Sukehiro ITO 1, Hitoshi TOYOMA 1, Masaaki OHWA 1, Eisaku KOBAYASHI1, Katsuzo OHM 1, Masahiro KAKETANI 2 and Minoru NISHIYAMA 2 (Received24 December1991and accepted17 March 1992) Key words:
artificial denture teeth, plastic denture teeth, abrasive wear resistance, removable partial denture Abstract
An in vitro evaluation of abrasive wear resistance of high-strength denture (HS) teeth and wear of metal plates (Pd alloy) on the opposing side was conducted. A total of 8 types of teeth were used in the experiments including 3 types of HS teeth, 3 types of conventional plastic denture (PL) teeth, porcelain teeth and metal teeth (Pd alloy). Sliding-induced wear tests were conducted by sliding these teeth over the metal plates. Abrasive wear resistance of the teeth was evaluated in terms of wear depth and weight loss. A comparison of wear depth showed that the abrasive wear resistance of HS teeth was 4.7 times that of PL teeth, 0.7 times that of porcelain teeth and 8.3 times that of metal teeth. Weight loss showed that the abrasive wear resistance of HS teeth was 3.3 times that of PL teeth, 0.2 times that of porcelain teeth and 11.4 times that of metal teeth. The weight loss of the metal plates was minimal when they slid over HS teeth, but increased in the order PL teeth, porcelain teeth and metal teeth. Introduction The purpose of removable partial dentures as a posterior prosthesis is reconstruction of occlusion with artificial teeth. That is, posterior artificial teeth are designed to maintain the form and function of the stomatognathic system including restoration of masticatory function, maintenance of the vertical dimension and prevention of temporomandibular joint dysfunction caused by occlusal disharmony. Plastic and porcelain materials have been used conventionally for posterior artificial teeth. High-strength denture teeth have been developed, which retain some of the advantages of plastic teeth, such as easy occlusal adjustment and cost, 佐 藤 吉則,永 井栄 一,前 島健 吾,大 山哲 生,伊 東 祐 博,豊 間 掛 谷 昌宏,西 山 實
均,大 輪正 昭,小 林 栄 作,大 木 一 三,
1 Department of Removable Partial Denture Prosthodontics, Nihon University School of Dentistry 2 Department of Dental Materials, Nihon University School of Dentistry To whom all correspondence should be addressed: Dr. Yoshinori SATOH, Department of Removable Partial Denture Prosthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101, JAPAN.
250
while achieving Findings
improved of basic
hardness
studies
impact resistance[4], bonding
and abrasive
on these
strength
wear resistance[1-3].
HS teeth
have
with denture
and wear resistance of anterior teethm. However studies on the abrasive wear resistance of posterior Therefore, wear
we
conducted
resistance
made
of
wear
of
Pd-Au-Ag
depth
weight
profile
of
vitro
of
alloy.
and
roughness
in
8 types
We
teeth
the
abrasive
In
metal
addition,
we
A
total
of
3 types
(PL)
teeth,
1).From
8 types of
each
of
alloy
whose
type,
5 upper
contact
were with
heat-treated pm
for with
40 made
the
artificial
and
order by
to
wear
to have denture
evaluate
sliding
evaluated
the
them
on
resistance the
wear
been few teeth[8.9].
of
abrasive
metal
plates
the
depth
teeth
and
by
surface
Methods
waterproof
and
and
shape
was
right
first
plates
match
bucco-lingual aging
were (HS)
teeth
metal to
teeth denture
porcelain
alloy,
Accordingly,
Ag
of
high-strength
1 type
Pd-Au-Ag
teeth.
0.1
of
Materials
teeth,
of
in terms
plates. Materials
1.
reported
there seem high-strength
in
denture
evaluated
loss. the
experiments
posterior
been
base resin[5,6], hardness[1-3,5,6],
sandpaper
in
of
of
to
the
reduce and
Table
1
of
of
posterior surface
teeth
porcelain
The
roughness
made
teeth
totaling mm
teeth, teeth.
posterior plastic
metal
chosen,
posterior
as
conventional
15•~15•~2
the
buff
that
were
measuring of
experiments
custom-made to
premolars
number
our
3 types
comparable
cusps finished
1 type
each
the
used teeth,
40 made
and
posterior of
used
metal (Ra)
(Table
Pd-Auto
make
plates
were
to
than
less
polishing.
Materials
2. Methods 1) A total of 30 teeth consisting of HS teeth and PL teeth were immersed in distilled water prior to the wear test. Water sorption was measured every 48 h for about 3 months according to JIS T 6508. Wear tests were conducted when each of the posterior teeth reached a constant weight. Wear tests were conducted with a sliding-induced wear testing apparatus (Tokyo Giken). Each metal plate was fixed with a jig to the upper holder of the testing apparatus, while the posterior tooth was fixed to the lower holder, enabling
251
both
the
plate.
bucco-lingual
Both
upper
the
upper
holder
strokes
to
to the
stroke
Wear
depth
was
strokes,
cusp
depth
was
at
a
were
and
depth
of
fixed
before
contact
in was
posterior
distilled to
under of
the
metal
water,
and
apply
200,000
conditions
the
of
300
1 kgf/tooth.
teeth of
50,000
with
moved
loading
initiation
strokes,
make
direction
constant the
to
immersed
was
mesio-distal
mm
using
CCD
TV
rior
tooth
point
was
the
strokes,
0
this,
wear
test
100,000
to
ratio
the of
3)
the
20
mean to
(at
0
stroke),
strokes
and
and
200,000
calculated
for
after
a
each
given
The
of
weight
measured
loss
after
1,
loss
of
lingual
0.3
at
Then using
of
the
a
poste-
binary
each
a
Seimi-
mm/s.
image to
that
with
Tokyo
PIAS)
subjected and
of
strokes
weight
loss
metal
image of
after
a
of
length
of
200,000
19
speed
The
was
the
picture
measurement
given
all
was
synthesized 2 pixels
from
from
number
these then
lines
by
two
lingual
cusp
of
strokes
in
were
divided
the
the
measured
the
a to
enlargement
value.
dividing
and
A,
(LA-500,
PIASP01.
the
tip
mean
by
of
5
on
lengths
after
number
Measurement
cusp
weight
tooth
head
increments
measurement
of
of direction
2000
system
point
in
the
made
completion
a tracing
at 0 stroke
based
This
of was
Surfcom
x V512,
profile
tooth.
lingual
the
The
a bucco-lingual
analysis
tooth
drawn
length.
Measurement
upon
the
Then
obtain
Measurement
4)
was
direction.
and
measurement
each
in
(Surflyzer
H512
of
manner.
times
image
measured
a line
stroke
bucco-lingual calculate
each image
was
20
pm,
an
pixels
for
depth For
at
at the
50
into
(PX-370,
then
following
of
of
fed
synthesized
Wear images.
was
entered and
the
apparatus
diameter
image camera
analysis,
in
enlargement
measuring
a probe
traced
measured an
roughness
each
and
wear
tooth
plate
in
3.0
10,000
was
traced
surface
and
holders
metal
measured
of
posterior
respectively. Wear
tsu)
the
lower
tooth
of
completion
of
the
length
Measurement
upon
tip
and
which
posterior
stroke/min, 2)
cusps
the
strokes,
strokes
for
the by of
plates wear
posterior
10,000
teeth 50,000 each
difference
the
strokes
weight
weights
loss at
0
was stroke
gravity.
plates
which strokes
100,000
The
between
specific
metal
strokes,
tooth.
had as
slid
over
as
after
well
the
denture
teeth
completion
of
was
20•~104
strokes. The given by
weight
of
number
of
dividing 5)
profile
of
denture
using
a probe made
6)
Olympus)
loss
surface
5 pm
cuspal at •~2.5
was
weight
surface was in
after
measured
Then by
of
measured
with
and
of
magnification of
wear
of
posterior
cuspal
after surfaces
plates
which
a surface
test as
and
after
the
volume
metal
opposed
measurement of
4.0
mm.
to
the device
Measurement
strokes.
forms were
were
roughness length
wear
of
posterior
observed
completion of
stroke
calculated
a
plates
metal
20•~104
teeth
wear
was
gravity.
a measurement of
observations
the loss
metal
roughness
diameter
before weight
specific of
completion
forms
the
the
roughness
teeth
only
Observations
plates strokes.
of
Microscopic The
7)
of
The types
was
the
Profile
the
wear
of tooth
using 200,000 cusps
teeth a wear
microscope strokes.
(BH,
8
252
For analysis of the wear surface of metal tooth cusps, two-dimensional Fourier transformation was performed in order to identify any cyclic or specific wear pattern in the image as physical information obtained from the original image. The wear surface of the metal tooth was transmitted from a microscope (BH, Olympus) to an image analysis system (LH-500, PIAS). The image was then analyzed with software (PIAS) designed for two-dimensional Fourier transformation. Results 1. Wear depth of posterior teeth Table 2 and Figure 1 show the wear depth of teeth after 10,000, 50,000, 100,000 and 200,000 strokes. 2. Weight loss of posterior teeth Table 3 and Figure 2 show the weight loss of each tooth after completion of 10,000, 50,000, 100,000 and 200,000 strokes.
Table
3.
Weight
loss
Table 20•~104
4
wear
completion 4.
of
Figure had
slid
Figure slid
20•~104
shows PL
3 types the teeth,
Wear
show
the
of posterior
wear
sample of
sample porcelain
weight
4 shows
teeth
HS
the
loss
weight
of loss
metal of
plates teeth
after
and
metal
1, 5,
10
plates
and after
strokes.
roughness a
depth
plates 3
Figure
surface
5 shows over
6 over
metal Figure
strokes. of
Profile
of
and
2
of
metal
profile teeth profile teeth
plates
of after of and
surface 0
and
surface metal
roughness 20•~104
roughness teeth
of
sliding of after
metal strokes,
metal 20•~104
plates sliding
plates
which
respectively. which strokes.
had
253
Table
Table
3
Weight
4
Weight
loss of posterior
loss of metal
teeth
plates
5.
Microscopic observations of cuspal forms of posterior teeth Figure 7 shows the cuspal forms of 3 types of HS teeth, and Fig. 8 shows that of 3 types of PL teeth. Figure 9 shows the cuspal forms of metal teeth. 6. Observations of wear surface of metal tooth cusps With regard to the wear surface of metal teeth cusps, Fig. 10 shows the original
image
and
the image
after two-dimensional
Fourier
transformation.
254
Fig. 1
Wear depth of posterior
teeth
Fig.
Weight
teeth
2
loss
of posterior
255
Fig.
Fig.
4
Weight
loss
of
3
posterior
Weight
teeth
loss
and
of metal
metal
plates
plates
after
20•~104
strokes
256
Fig. 5
Profile of surface roughness
(metal
plates)
Fig. 6
Profile of surface roughness
(metal
plates)
257
a) ED
b) DD
c) SR Fig.
7
Cuspal
forms
of three
types
of HS
teeth
258
a) AR
b) WL
c) BB Fig.
8
Cuspal
forms
of three
types
of PL teeth
259
a) MT
b) BA Fig. 9
Cuspal
forms of metal and porcelain
teeth
260
a) Original Fig. 10
image Two-dimensional
Fourier
b) Fourier transformation transformation (metal teeth)
Discussion Dentures with PL teeth show significant wear at an early stage due to mastication and swallowing in comparison with dentures with occlusal surfaces restored using other materials. Porcelain teeth, on the other hand, show little wear themselves, but clinically it is often observed that they cause wear of opposing teeth. Since the clinical use of HS teeth has been increasing, we considered it important to evaluate the abrasive wear resistance of these teeth. Experiments were therefore conducted, using PL teeth, porcelain teeth and custom-made metal teeth as control materials. The cuspal inclination of these artificial teeth was based on the functional cusp angle usually employed in partial dentures. 1. Method for measurement of weight loss Types of wear test apparatus used for evaluation of the abrasive wear resistance of artificial teeth differ according to the objectives of study and among laboratories. The extent of abrasive wear found in the mouth is influenced by various factors including occlusal biting force[11,12],friction with food1131,individual masticatory efficiency, type of occlusion and type of retainer used1141 . Therefore SAToH1151 has claimed that an in vitro test method which is easy to perform and highly reproducible has yet to be established. With this in mind , we used a sliding-induced wear test apparatus which reproduces sliding-induced wear . In conducting wear tests, the metal plate and the posterior teeth maintained very close contact during the sliding motion, so that it was difficult to place an intermediary material between them[16'171. The two-body abrasion method was adopted for this reason, and also in order to eliminate any influence of an intermediary material on wear behavior. With regard to the experimental conditions of the wear test, stroke length was set at 3.0 mm in line with previous studies and reports on mastication[181,and the number of strokes was set at 200,000, which is clinically comparable to the number
261
of
chewing
strokes
reference
to
As
to
tracing
cusp
that
2.
of
of
the
Wear
was
as
wear
weight
than
0.0ƒÊm
the
the
times
the
wear
which
was
teeth
was As
mean
other
the
value
for
wear
i.e.
weight
depth
of
8.3
the
teeth
showed
3.3
times
was comparable The
abrasive
result HS
than
agrees
teeth
is
that
when
with
of
opposed
ness[22]. teeth.
It
teeth
has
contact It
is
our
In
wear
all
occlusal
the
time,
and
teeth
strokes PL was
was
4.7
42
depth
or
HS
of
pm,
metal
was
teeth
and
cm3
that
the
of
in
teeth.
the
and
with
a
HS
This
result
teethE71.
teeth
. This
occlusal
wear
significantly
less
porcelain low
is slight
Vickers
resistance
greater
range teeth
artificial
that
wear
the
metal
porcelain
of
the
considering
respectively.
PL
wear
resin
compared by
teeth
teeth
suffer
we
of anterior
abrasive
teeth
2),
than
porcelain
metal
hard-
than
abrasive
on
metal
wear
due
to
food
the
our
was
surface
of
removed
a
significant
sliding-induced the
during
wear
metal
plate
sliding,
so
and that
strong[23].
lower
oily
metals
during
were was
and or
thick
thick
metals
between that
A
A
upper
saliva
of
times
cohesion
300
two
the
wear
which
wear
porcelain
that
suggested
about
the
however,
teeth.
50•`73ƒÊm.
strokes
YoKoYAmA[14]
greater
that is
100•`200
between
reality,
contact
about
A
of
metals[23].
It
layer
layer
adhesive
of
0.2
of
metal
therefore,
a contaminating oxide
that
strokes.
,000 of
Fig.
wear
resistance of
as
times
200
the
291.9•~10-5
indicating
such 11.4
experiment[23].
in
teeth
types
porcelain
resistance
was
that
100,000
of
3 and
3 types
and
wear
a report
materials
conceivable,
in
,
decrease
porcelain
220•`364ƒÊm,
200,000
teeth,
wear
teeth
and
and
whereas
the
PL cm3
than
type
the
cusps
teeth.
findings
greater
same
and of
the
depth
of
(Table
for
for
HS
of
of
abrasive
reported
the
HS
loss
clinical
showed
been
with
factor test,
with
HS
loss[21]
working
different
a wear
teeth,
teeth
6.0•~10-5
and
the
teeth
the
depth
HS
of
HS
completion
depth wear
of
those
of
the
teeth,
wear
for abrasive
slightly
PL
after showed
The
Weight
resistance
weight
i.e.
30 ,000
among
completion
greater
to that wear
also
after
cm3,
with
consideration
calculated
of
10,000,
teeth
that
whereas
60.6•`100.5•~10-5
teeth,
3 types
made
posterior
teeth.
of In
we
tooth
a
times
tooth
cm3,
HS
depth
of
1 .0 kgf/tooth
teeth
1) of
be
teeth.
wear
loss
each
22.2•`26.4•~10-5 were
the
artificial
of
each of
HS
at
performed.
posterior
Fig.
showed
of
times
527ƒÊm, to
for
hand,
depth
0.7
of
not
3 types
set
determination
dimension,
completion
values
The
was
depth.
could
mean
compared.
wear,
of
vertical
2 and
after
of
cusps
loss
(Table
evaluation
on
posterior
teeth
residue
do
is usually
not
maintain
present
on
close the
metal
surface. These
opposing observed 3.
of
less
teeth,
an
loss
depth
were
of
a tips
load
al. [20]
conventionally
in
and
constant et
amount
been lingual
wear
Therefore
the
upper
The
comparative
the
of have
cusp
depth
The
HARRISON
the
clinically
height
of
profile
wear
results
yearr193.
report
measurement
of
fact
per
the
Weight The
adhesive
materials
surfaces[231, in
this loss
weight
so
that
will the
serve wear
as
lubricant
behavior
agents could
between
the
two
be
different
from
that
and
posterior
teeth
after
study. of loss
metal of
plates metal
plates
(Table
4 and
Fig.
3)
262
20•~104
sliding
plates
(Figs. The
range
5,
6)
weight
was
mately
were
This
the of
of
change.
was
metal There
metal
plates
had
13.01•~10-5 son
the
is
which
of
of
turn
that
teeth
metal
was
opposed former
in
the
with was
was
PL
approxi-
opposed than
for
HS
teeth
strokes.
teeth
in
the
a
with It
both
showed
On
showed
teeth.
were
other
significant
the
result
is assumed
that
the
with
HS
comparison
two
in
of
for
porcelain
teeth
HS
Compari-
teeth.
specimens
Table
which
2,
were
was
revealed
whereas
opposed
very
deep
with
and
porcelain
limited. tip
wear
surface
on
the
the
greater
of
of the
wear[23],
made
teeth
HS
which
was
is
in
also
wear the
The
weight
143.50•~10-5
It
metal was
by
Therefore wear.
teeth.
same
rough
plates[ml.
resulting
metal
that
surfaces
was
metal the
with
than
adhesive
with that
the
shown
opposed
two
wear
comparison
greater
cusp
greater
the
of
teeth
HS
PL
quite
the
were
in of
plates
strokes,
times
roughness
3 types
PL
with
as
porcelain
sliding
significant
surface
se, meatl
wear
which
before,
cm3,
considered,
contact
clearly
as
with
each
evident
in
the
of
the
roughness. of
wear
surfaces
of
Fourier
of
image,
HS
surface
20 x 104
between
per
increased
Two-dimensional
the
of
the
of
with
6 times
in
of
66
surfaces
of
loss.
roughness
the
of
Observations
wear
roughness
plates
with
and
which
about
area
about
generated
profile
Thus
profile
contact
plates
teeth
plates
mentioned
cm3.
3 types
weight
that
number
was
other
in
metal
which
metal
difference with
observed
the
the
loss
surface
suggested
strokes, greater
of
was
although It
surface
3 types
of
opposed
opposed
of
metal
the
stroke
were
greater
was
wear
0 wear
range
which
porcelain
in
opposed
of
of
significant teeth,
the
profile
wear
of
with that
were
a significant
were
loss
cm3,
of
little
also
in
weight
evident
which
a wider
resulting The
opposed whereas
which
between
was which
teeth,
also plates
plates
plates
profile
5.61•~10-5•`7.62•~10-5
metal
metal
sample
plates cm3,
change
the
the
latter.
tendency
significant
and
metal
range
the
The
hand,
in
4)
determined.
loss
in
1/3
specimens.
4.
(Fig.
1.65•~10-5•`2.67•~10-5
teeth
no
strokes
metal
teeth
using
an
specific
wear
pattern
of
aligned
in
a mesio-distal
metal
teeth
transformation in
order
image
to
analysis
scratches
was
identify system
generated
direction
on
by the
performed
any
cyclic
(Fig. sliding
cuspal
for or
10).
The
contact surfaces
analysis
specific
wear
results with
of
revealed
the
metal
pattern
metal
a plates
teeth.
Conclusion This used of for
as
study
porcelain
The
teeth
of
1.
A
metal
4.7
1 type
tests,
of
using
abrasive
evaluate Three
conclusions the
the types
abrasive
of
HS
custom-made metal
plates
were
obtained
wear
wear
teeth,
metal made
teeth of
from
resistance
of
resistance
3 types were
Pd-Au-Ag the
of PL
used
HS
teeth, as
teeth 1 type
specimens
alloy.
findings
posterior
of
teeth
of and
comprehensive wear
of
the
of
HS
plates:
comparison was
to teeth.
and
following
opposing
conducted
artificial
sliding-induced
evaluation
teeth
was
posterior
of times
that
wear of
depth PL
teeth,
showed 0.7
that times
the that
abrasive of
porcelain
wear
resistance teeth,
and
8.3
times
263
that
of
resistance teeth 2.
metal
teeth.
of and
The
showed
HS
11.4
times
weight
loss
a minimum The
metal
Comparison
teeth
was that of
plates
5.61•~10-5•`7.62•~10-5 and
metal
teeth
of
which cm3,
showed
times
metal
metal
value
of
3.3
plates of
weight that
loss of
PL
showed teeth,
were
weight
the
times
abrasive
that
of
wear
porcelain
teeth. which
were
opposed
1.65•~10-5•`2.67•~10-5
whereas
that 0.2
opposed the losses
with
3 types
of
HS
teeth
cm3.
with
PL
metal
plates
of
13.01•~10-5
teeth
showed
opposed cm3
with and
a weight porcelain 143.50•~10-5
loss
of
teeth cm3,
respectively. References
[1] TAKAHASHI, Y., HASEGAWA, J., HIRANUMA, K., MORI,H. and HASEGAWA, A.: Properties of experimental high abrasion resistance plastic teeth, Aichi Gakuin J. Dent. Sci., 28, 271-281, 1990 (in Japanese) [2] SAITO,S.: A high-strength denture teeth, Dental Diamond, 3, 146-149, 1990 (in Japanese) [3] HASEGAWA, J.: The Endura-anterio high-strength denture teeth, Dental Diamond, 3, 104107, 1990 (in Japanese) [4] SuzuKi, S., SAKOH, M. and SHIBA, A.: The evaluation of the impact resistance of crosslinked plastic denture teeth, J. Jpn. Prosthodont. Soc., 32, 780-786, 1988 (in Japanese) [5] SuzuKi,S., KUNESHITA, H. and SHIBA, A.: The evaluation of adhesive bonding of the denture base resin to the hard resin teeth, J. Jpn. Prosthodont. Soc., 32, 37-42, 1988 (in Japanese) [6] YAMAUCH, M., OKUMURA, K., SASAKI, M., ANDO,M., KAWANO, J. and YOKOI,K.: Bonding strength of the hardened plastic teeth to the denture base acrylic resin, J. Jpn. Prosthodont. Soc., 32, 1278-1282, 1988 (in Japanese) [7] SATOH, Y., OHTANI, K., MAEJIMA, K., MORIKAWA, M., MATSUZU, M., NAGAI,E., TOYOMA, H., OHKI,K. and NISHIYAMA, M.: A study on high-strength denture teeth, J. Jpn. Prosthodont. Soc., 34, 148-153, 1990 (in Japanese) [8] FRAUNHOFER, J. A. V., RAZAVI,R. and KHAN,Z.: Wear characteristics of high-strength denture teeth, J. Prosthet. Dent., 59, 173-175, 1988 [9] WHITMAN, D. J., MCKINNEY, J. E., HINMAN, R. W., HESBY, R. A. and PELLEU, G. B.: In vitro wear rates of three types of commercial denture tooth materials, J. Prosthet. Dent., 57, 243-246, 1987 [10] SATOH, Y., KIMURA, K. and OHKI,K.: Application of an image-analysis system to prosthodontics, J. Nihon Univ. Sch. Dent., 30, 237-243, 1988 (in Japanese) [11] LAMBRECHT, P., BRAEM,M. and VANHERLE, G.: Evaluation of clinical performance for posterior composite resins and dentin adhesive, Operat. Dent., 12, 53-78, 1987 [12] LUTZ,F., PHILLIPS, R. W., ROULET, J. F. and SETCOS, J. C.: In vivo and in vitro wear of potential posterior composite, J. Dent. Res., 63, 914-920, 1984 [13] JORGENSEN, K. D. and ASMUSSEN, E.: Occlusal abrasion of a composite restorative resin with ultra-fine filler, Quintessence International, 6, 73-78, 1978 [14] YOKOYAMA, M.: The evaluation of posterior plastic teeth, Practice in Prosthodont., 19, 163-171, 1986 (in Japanese) [15] SATOH, M.: The occlusal wear of posterior composite resins, Operat. Dent., 33, 345-385,1990 (in Japanses) [16] MCKINNEY, J. E. and Wu, W.: Relationship between subsurface damage and wear of dental restorative composites, J. Dent. Res., 61, 1083-1088, 1982 [17] ROULET, J. F.: Degradation of Dental Polymers, S. Karger, Basel, Switzerland, 60-66, 1987 [18] Ai, M.: A study of the masticatory movement at the incision inferius, J. Jpn. Prosthodont. Soc., 6, 164-200, 1962 (in Japanese) [19] SOLTESZ, V. U., KLAIBER, B., PERGANDE, C. H. and RICHTER, H.: Vergleichende untersuchungen -Etherdas abrasionsverhalten von composite-fullungsmaterialien, Dtsch. Zahndrztl. Z., 34, 406-412, 1979
264
[20] HARRISON, A. and LEWIS, T. T.: The machine for dental materials, J. Biomed. Mater. Res., 9, 341-353, 1975 [21] MANASKY, G. E. and TAYLOR, D. F.: Studies on the wear of porcelain, enamel, and gold, J. Prosthet. Dent., 25, 299-306, 1971 [22] TAKARABE, M.: An experimental study on sliding-induced abrasion of natural teeth and materials used for crowns, J. Tokyo Dental College Soc., 82, 949-1004, 1982 (in Japanese) [23] SODA,N.: The Friction, 1-180, Iwanami Shoten, Tokyo, Japan, 1988 (in Japanese)
