Pulsedoscillationtechniquefor assessingthe mechanicalstate of the dental implant-boneinterface T.Kaneko Research
Center,
(Received
24
Nikon
July
Corporation,
1989:
Nishi-ohi
accepted
l-6-3,
16 May
Shmagawa-ku,
Tokyo
140,
Japan
1990)
The sensitivity of a vibrational test for in viva assessing the interfacial rigidity of a biocompatible dental root implant was studied using models. Aluminium alloy rods of 4 mm diameter and 7 mm long were root implant models. Cyanoacrylate and epoxy adhesives were hard interface models. Soft interfaces were modelled in a soft silicone adhesive, a gel, adhesive tapes and direct loose contact. Blocks of bovine and canine jaw-bones chemically treated and dried were models of a human alveolar bone. It was found that the minimum average thickness of a soft interface layer distinguishable from a hard interface depends on load directions and positions and ranges from 0 to 160 pm. The sensitivity was rather low in the direction for which a normal load was applied to the bone, reflecting a mechanical difference of the surrounding bone and/or the interface. Therefore, it is desirable that the assessment by the vibrational test is done in the direction, too, for which a shearing load is applied to the interface. Keywords:
Various
Dental
materials
implant,
which
interface,
show
with bone have been applied
excellent
to dental
success of such an implant depends state
of
the
vibrational
implant-bone
techniques
objectively:
(a)
waveform
(c) the
measurement
based
glass-coated
based
on the
the
alumina15);
based on the frequency
and
it the
(b) the
(e)
spectrum
the
should
be mentioned
the above
method
with
increasing
Figure
direction;
bottom.
interface
suggests
loosened
It
from
tendency, range were of POWF
in the implant-embedded
was made of a bioactive
The figure
became
a similar
and frequency
metal and had the shape of a tapered round
titanium”,
the implant
rigidity.
obtained
7 shows clinical examples
meta13-‘); time
by the pulsed
interfacial signals
(a) also suggested amplitude
and low-frequency
induced
that vibrational
though their maximum quite different’.
amplitude
vibration
signals taken from a root implant
13, 14); (d) the forced
impedance
of the implant
measure-
contact
(for apatite-coated on
on
fact3,4; the maximum
components
force tend to decrease
several
titanium’);
and apatite”,
based
(for
method
(for bioactive method
(ILCT method) method
measurement method
load
load
based on the waveform
’ ‘, titanium”-‘*
alumina”, oscillation
Recently,
(for alumina’,
method
method)
impact
The clinical
largely on the mechanical
interface.
impact
measurement
ment (POWF
empirical
biocompatibility
implants.
have been tried in order to estimate
the
pulsed oscillation
v/brat/on
at an
glass-coated
hollow cylinder
with a
that the implant-bone early
stage
and
then
spectrum impact
load
measurement
(for
carbon16). The
merits
of the
POWF
method3,“,18
force acting on the implant-bone the duration
of the force application
small, (d) the measurement therefore
information
tions, (e) an implant mucous
membrane,
can be examined and
The POWF
Correspondence
to Dr T. Kaneko
Butter-worth-Helnemann
(f) the method
are (a) the
is very small, (b)
is short, (c) the probe is
is not limited
can be obtained
inexpensive.
8 1991
interface
to a direction
from different
and direc-
under the protection
apparatus is based
is simple
of and
on the following
imme+iately F/gore
1
VIbrational
signals
diter taken
from
imp a bloactive
:antat.lon root
implant
Ltd. 0142-9612/91/060555-06 Btomatenals
199 1, Vol
12 August
555
Pulsed oscillation technique: T. Kaneko
became rigid with time. However, the assessment is not beyond doubt, because recent model experiments have suggested the following possibility”, ‘s. First, a signal which isdetectedfroman implantsurrounded byaverythinfibrous capsule may be similar to that from an implant rigidly bonded with bone. Second, a detected signal will depend on the density of the surrounding bone to some extent. Such unfavorable possibility for the assessment of the interface itself seems to exist in all the vibration-based tests. Therefore, the sensitivity of the POWF test, especially the minimal detectable thickness of a soft interface layer (MDTSIL), has been examined by using models. The results are presented in this paper.
MEASURING
SYSTEM AND EXPERIMENTAL
MODELS
Figure 2 shows the measuring system of the POWF test used. Each of AED (acoustoelectric driver) and AER (acoustoelectric receiver) consists of a piezoelectric element and a puncture needle3,“. The measurement is done as follows. A pulsed force of about 1 kHz in repetition rate, which is a multifrequency force, is applied to an implant by lightly contacting AED. The pulsed force induces the implant vibration chartacteristic of the mechanical state of the implant-bone interface. The vibrational signal is picked up and transformed to an electric signal by AER. The electric signal is amplified to 60 dB with 20 kHz bandwidth and displayed on the oscilloscope screen. Cylindrical aluminium alloy (AA) rods with a fairly flat bottom, 7 mm long and 0.2 g mass, were used as root implant models. Hard interface models were a cyanoacrylate adhesive (CAd) and an epoxy adhesive (EAd). Soft interface models were a soft silicone adhesive (SAd) named KE 44RTV (Shin-etsu, Tokyo), a gel couplant (GCo) named Ultra/Phonic Conductivity Gel (Pharmaceutical Innovation, New Jersey), adhesive tapes of 0.09 mm thick (09ATa) and 0.16 mm thick (16ATa) named STR Tape (Shinto Chemitron, Tokyo) and direct loose contact, Blocks of bovine and canine jaw-bones chemically defatted and dried were models of a human alveolar bone.
\1
+
AED
- Amplifier
\1
AER
Oscilloscope
mplant -_
Bone
Figure (POWF)
556
2
Experimental test.
AED,
Biomaterials
arrangement
acoustoelectric
199 1, Vol
for the pulsed driver;
12 August
AER,
oscillation
acoustoelectric
waveform receiver.
RESULTS AND DISCUSSION We will specify each POWF signal shown below by a symbol such as (1 iiP). The number in the parentheses denotes that of the sample which AED and AER were contacted with. The material of the sample is designated by the letter b for bone and i for implant model or tooth. The letter P (parallel to bone), U (upper) or L (lower) means that AED and AER were contacted in the corresponding direction shown in Figure 9. If the above letter is unwritten, AED and AER are meant to have been contacted in direction S (‘senkrecht’ to bone), namely, in the implant-embedded direction. Figure 3 shows POWF signals taken from AA rods in the holes drilled in a bovine bone and from the bone itself. The soft interface model was SAd. The rods were 3.70 mm diameter. The holes were about 3.80 mm diameter and 4 mm deep. The compact bone around the rods was about 0.5 to 3 mm thick. The waveform difference of samples 1 and 3 (hard interfaces) from samples 2 and 4 (soft interfaces) is clear. Therefore, MDTSIL is < 50pm in direction P. We see that (1 ii), (5bb) and (7bb) are larger in the maximum amplitude than (3ii). (6bb) and (8bb), respectively. This is because the compact bone around samples I,5 and 7 is thinner and therefore the average bone density around them is lower. Figure 4 shows POWF signals taken from AA rods (samples 1 and 2) in the holes drilled in a canine bone and a natural tooth (sample 3). The soft interface model was GCo. The rods were 3.70 mm diameter. The holes were about 3.76 mm diameter and 4 mm deep. A waveform difference between sample 1 (hard interface) and sample 2 (soft interface) is clear. Therefore, MDTSIL is < 30pm in direction P. The signal (3ii) is smaller in the amplitude than (2ii); this is partly because sample 3 does not have a soft root membrane as a result of the chemical treatment and partly because sample 3 is very different in size and material from sample 2. Unlike (1 ii), (1 iiP) is larger in the amplitude than the corresponding hard signals shown in Figure 3. This is probably because the average bone density around sample 1 is lower in direction P than that in Figure 3. Figures 5 and 6 show POWF signals taken from AA rods in the holes drilled in a compact bovine bone. Soft interface models were GCo in Figure 5 and SAd in Figure 6. The rods were 3.70 to 3.80 mm in diameter. The holes were about 3.80 mm in diameter and 4 mm deep. The bones around the rods were 7 to 10 mm thick. We see that the signal amplitude obtained in direction P tends to decrease with decreasing thickness of the soft interface. In Figure 5 a waveform difference between sample 5 (soft interface) and sample 7 (hard interface) is vague. This means that a thin soft interface is estimated to be rigid or slightly rigid in the POWF test. Waveform differences both between (4iiP) (soft interface) and (7iiP) and between (6iiL) (soft or hard interface) and (7iiL) are clear. Therefore, MDTSIL is about 1 Oprn in direction P (2 V input) and Oprn in direction L (10 V input). This difference in MDTSIL suggests that to make a sensitive assessment, the measurement should be done nearer to the interface and/or under a larger input voltage. The amplitude of (7iiL) is as small as that of (7iiP). This means that the interface and the bone are fairly rigid and inelastic. In Figure 6, a waveform difference between sample 2 (soft interface) and sample 3 (hard interface) is clear. Therefore, MDTSIL is < 15pm in direction P. Figure 7 shows POWF signals taken from AA rods in the holes drilled in an entirely cancellous bovine bone. Soft interface models were SAd (sample 1) and direct loose
Pulsed
5
12
3
(4ii)
/-
F/gore 0 5-3
3
Aluminium
mm. Interface:
contact
(sample
holes were
alloy rods in a dried
see that MDTSIL SAd interface. Figure
3.80
is < 25pm
(sample
waveform clear
difference
in direction
However, figure
1). The
a waveform
and sample
were hard
difference
Figure
9 shows the
POWF
SAd
soft and
(tjbb)
09ATa
sample
2 in this
between
(1 ii) and (2ii),
distinct between
to
test. We see that,
between
soft
and
L than in direction
tape.
waveform
U.
Figure
A
3.7 mm
were 6) and
diameter.
The
and sample
a waveform
but the difference,
is indistinct.
partly
3
difference
especially
This is because
with
bone.
However,
(1 iiL) and (2iiL) difference
in the
the SAd
S for the soft interface
comparison
between
8 and (1 ii) in Figure
to an implant particularly
(1 ii) and (4ii), but not
MDTSIL
is about 160 ,um
modelled (3ii)
9 suggests
the bone itself,
Biomaterrals
in the adhesive
in Figure
7,
the following
in the POWF
when
a waveform
is very clear. We see a
between
( 1 ii) and (5ii). Therefore,
the load applied
and
4 and
1 (hard interface)
of which
flattened
the rods:
models
(samples
recognize
signals taken from AA rods on was
around
respecnvely.
2 was so thin that the bottom of the rod may
between
in direction
hard
also
amplitude,
difference
S.
have
can
contacted
be
may
16ATa
rods were
sample
between
7 is fairly large in direction 2
5). The
We
layer in sample
between
3).
is clear.
have
bone
adhesrves
bone around the rods was 4 mm thick. A waveform
is
< 160 pm.
2 and
(sample
compact
of the compact
and soft silicone
using a paper file. Soft interface
and soft interfaces is
-(5bb)
Thickness
cyanoacrylate
(samples
difference model was
for the holes.
maximum
MDTSIL
in direction
surface
smoothened
sample
7, a discrimination
bone
mm
3 V CAd and SAd,
A
to be slightly rigid in the POWF is more distinct
Input:
diameter.
considered
a bovine
of
3.7 mm
for the rods, 3.80
We
L.
7. The soft interface rods
3 in Figure
r
30-psec
The
U and L for the between
the
interfaces
mm
mm diameter.
Therefore,
as in Figure
3.70
5 to 8: bone
and 4 mm deep.
in direction
Therefore,
interface
i7bb)
Ii ii
signals taken from AA rods on
between S.
Diameter: Samples
in directions
POWF
the same bone as in Figure 16ATa
3.75
a discrimination
is more distinct
8 shows
bone.
mm diameter
However,
hard interfaces
bovine
(31 CAd, (4) SAd.
2). The rods were
about
,-
L
(1) CAd, (2) SAd,
T Kaneko
photograph
/-(211P)
\I
techmoue:
46
X-ray ,(Zii)
oscillat/on
in
point;
test will vibrate
the implant
199 7, Vol
(2ii)
is supported
12 August
557
Pulsed oscillation technique: T. Kaneko
,(2ii)
/.(ZiiP)
(lii)
1
_ 30 psec
Figure 4 Aluminium alloy rods in a dried canine bone. Diameter: 3.70 mm for the rods, 3.76 mm for the hales. Interface: ( 1) cyanoacrylate adhesive, (2) gel couplant. Sample 3: natural tooth Input: 3 V for signals (ii), 2 V for signals (iiP).
(2iiP)
(3iiP)
/
~
(lii)
(4iiP)
(Zii)
(3ii)
(7ii)
(5iiP)
(7iiL) (5ii)
(7iiP)
I(6iiP) 30psec
Figure 5 A~urn~fl~urnalloy rods in a dried compact bovine bone. Diameter (in mmJ of the rods: ( I) 3.70, (ZJ 3.75. (313.77, (4J 3.78. (Sj 3.79. (6J 3.80. (7) 3.70. Diameter of the hoies: 3.80 mm. Bone thickness around the mds: 7 to 10 mm. Interfece: (1) to (6J gel couplam? (7) c~ano~~late adhesive. Input: 2 V for signals [iiJ and (iif), 10 V for signals (iiL).
Figure 6 Aluminium aljoy rods in the same bone as in Figure 5. Diameter (in mm) of the rods: It/ 3.75, (2) 3.77. (3J 3.70. Diameter of the holes: 3.80 mm. Interface: (IJ and (2J silicone adhesive, (3J cyanoactylate adhesive. Input: 2 V
558
Biomaterials
f991,
Vol 12 August
Pulsed
osnllation
technique:
(lii)
T. Kaneko
(1iiL)
L(3ii)
&
-(3iiU)
( 3ilL)
30-m Figure
7
(2J direct
Alomirwm loose
alloy
contact,
(3j
rods
in a dried
cyanoacrylate
cancellous adhesive.
bovine Input:
bone.
Diameter:
3.75
mm
for the
rods,
3.80
mm
for the
holes.
Interface:
(1) silxone
adhesive,
1.5 V
rJ
~j/(lllL)
(11111)
(2llL)
(2iiU) 30-&c FIgwe
8
Alumvwm
alloy
rods
on the same
bone
as in
Flgure 7. Interface:
(1)
a sheet
of 0.16
(Iii)
mm
thxk
adhesive
tape,
(2)
epoxy
adhesive.
11
(Zil)
Input.
1.5 V
(3ii)
d
(3iiU)
(2liU)
(4ii)
(611
j
(311L)
30-psec Figure
9
adhesive, (Sii),
Alumrntum (4) a sheet
3 V for the
alloy rods on a dried of 0.16
mm
thick
compact
adhesive
bovine
tape,
bone.
(5) a sheet
Bone
thickness
of 0.09
mm
around thick
the rods: 4 mm. Interface:
adhesive
tape,
(6) two sheets
f 1) cyanoacrylate
adhesive,
(2) and (31 sjlicone
of 0.16
adheswe
tape.
mm
thick
Input.
1 V for
others.
B/omaterials
199 1, Vol
12 August
559
Pulsed oscillation technique: T Kaneko
only by a cancellous bone. A comparison between (1 ii) in Figure 8 and (4ii) in Figure 9 also suggests it. It is evident from the above results that the POWF test depends on load directions and positions. It is rather lowsensitive in the direction for which the interface and the surrounding bone are compressed over a wide area. This is because a mechanical difference of the surrounding bone and/or the interface is reflected. It is worth noting here that a similar direction dependence of the sensitivity is found for the ILCT test using Periotest (Siemens, Bensheim)‘g-24. Therefore, it is desirable that the vibrational test is done in the direction, too, for which a shearing load is applied to the interface. Only the test in such a direction will distinguish an implant rigidly bonded with bone from an implant only contacted with it.
implantanon. Jpn. J. Oral Maxillofac. Surg. 1986, (in Japanese) 6
7
a
9
10
11
CONCLUSIONS The sensitivity of the POWF test has been examined by using aluminium alloy rods, 4 mm diameter and 7 mm long, as root implant models. Hard interfaces have been modelled in cyanoacrylate and epoxy adhesives. Soft interfaces have been modelled in a soft silicone adhesive, a gel, adhesive tapes and direct loose contact. A human alveolar bone has been modelled in blocks of bovine and canine jaw-bones chemically treated and dried. The sensitivity has been shown to depend on load directions and positions and be rather low in the direction for which only a normal load is applied to the interface. The minimum average thickness of a soft interface layer distinguishable from a hard interface has been found to range from 0 to 160pm in the present experiment. It is desirable that the POWF test is done in the direction, too, for which a shearing load is applied to the interface.
12
13
14
15
16
17
ia
REFERENCES Scholz. F.. Bewegungsverhalten bei Stossanregung des Tiibinger lmplantates im Vergleich sum naturlichen Zahn, Dtsch. ZahnBrztl. Z. 198 1, 36, 567-570 Yamane, S., Nakagawa, S., Shimogoryo, R. and Tsuda, T., Percussron sound of ITI implant, J. Jap. Sot. Oral lmplantol. 1988, 1, 240-244 (in Japanese) Kaneko, T., Nagar, Y.. Ogino, M.. Futami, T. and Ichimura. T., Acoustoelectric technique for assessing the mechanical state of the dental implant-bone interface, J. Biomed. Mater. Res. 1986, 20, 169-176 Miyasawa, M., Kudo, K., Fuj1oka.Y.. Shioyama.T., Nakano, K., Seino, Y. and Kaneko, T.. Clinical application of dental root implants of bioactive glass. Part 1. Assessment of bonding states by means of an acoustoelectric technique, Annual Meeting of rhe Japanese Stomatological Society, Fukuoka, May 15-l 6, 1986 (in Japanese) Kudo. K.. Fujioka, Y., Miyasawa, M., Ishibashi, K.. Shioyama, T., Ishikawa. F., Kamegai, T., Nakano, H. and Seino, Y., Clinical application of dental root implant coated with bioglass. Part 1. Result of
560
Biomaterials
199 1, Vol 12 August
19
20
21
22 23 24
32, 2083-2089
Kudo, K., Ishibashi, K. and Kamegai, T., Application of bioactive glass to the dental root implant, in Bioceramics -Development and Clinical Applications (Eds H. Aoki and J. Niwa), Quintessence, Tokyo, 1987, pp 193-l 96 (in Japanese) Sugihara, K. and Yamashita, S., Clmical application of dental root implant coated with bioglass. Part 1. Procedure of implantation, J. Jpn. Stomatol. Sot. 1987, 36, 96-105 (in Japanese) Kamegai. T., Ishikawa, F., Nakano. H., Seino, Y., Fujioka. Y., Kudo, K., Miyasawa, M.. Ishibashr, K. and Shioyama, T., Clinical applications and their short term results of dental root implantation using materials coated with bioactive glass, 3rd International Congress of lmplantology and Biomaterials in Stomatology, Osaka, Apnl 28-29, 1988, B-29 Fujino, M.. Sakaizumi, K., Senuma, S., Sate. K. and Ogino, M., Clinical application of the dental root implant coated with bioactive glass, 3rd International Congress of lmplantology and Biomaterials in Stomatology, Osaka, April 28-29, 1988, B-33 Schulte. W.. Messung des Dampfungsverhaltens enossaler Implantate mit dem Periotestverfahren, Dtsch. Z. Zahnlrztl. lmplantol. 1986,2, 11-12 lijima. T. and Takeda, T.. Changes in the surrounding bones caused by an implant as monitored using Periotest, Part 1,3rd international Congress of lmplantology and Biomaterials in Stomatology, Osaka, April 28-29, 1988, B-3 Yamane, S., Shimogoryo, Ft.and Tsuda, T.. Mobility of the bridge with implant abutments, J. Jap. Sot. Oral lmplantol. 1989, 2. 34-38 (m Japanese) Ogiso. M., Kaneda. H., Shiota, M., Mitsuwa,T., Wakuda.T., Aikawa, S., Uoshima, K.. Masuda. T., Kaneda, FL, Tomizuka, K., Tabata, T. and Sugimoto, H., Apatite implant, 2-piece implant system, J. Dent. Med. 1987, 25, 617-633 (in Japanese) Takigawa, H., Yamauchi, M.. Nigauri, A., Satoh, F., Shimrzu, M. and Kawano, J., Evaluation of Periotest for prosthetrc clinical application, J. Jpn. Prosthodont. Sot. 1988, 32, 189-l 98 (In Japanese) Saratani. K., Yoshida, S., Oka, H. and Kawazoe, T., Climcal applrcatron of biomechanical mobility measurement to implant body. 3rd International Congress of lmplantology and Biomaterials in Stomatology, Osaka, April 28-29, 1988, B-2 Sairenji, E. and Yanagisawa, S., Specificities of dentoosseous Interface and induction of the mimic structure, 3rd International Congress of lmplantology and Biomaterials in Stomatology, Osaka, April 28-29, 1988, Symposium-4 Kaneko, T.. Assessment of the interfacial rigidrty of bone implants from vrbrational signals, J. Mater. Sci. 1987, 22, 3495-3502 Kaneko, T., Comparrson between acoustic and mechanical tapping methods for assessing the interfacial states of bone implants, J. Mater. Sci. 1989, 24. 2820-2824 K&nig, M., Lukas, D., Quante, F., Schulte, W. and Topkaya, A., Messverfahren zur quantitativen Beurteilung des Schweregrades van 1981, 36, Parodontopathien (Penotest), Dfsch. Zahnlrzrl. Z. 451-454 Schulte. W.,d’Hoedt, B., Lukas, D., Mtihlbradt, L.,Scholz, F., Bretschi, J., Frey, D., Gudat, H.. Konig. M.. Markl. M., Quante, F.. Schief, A. and Topkaya, A., Penotest - neues Messverfahren der Funktion des Parodontiums, Zahr&ztl. Mitt, 1983, 73, 1229-l 240 d’Hoedt, B.. Lukas, D., Muhlbradt, L., Scholz, F., Schulte, W., Quante. F. and Topkaya. A., Das Periotestverfahren Entwicklung und klinische Prufung. Dtsch. ZahndrztI. Z. 1985, 40, 1 13-l 25 Schulte, W.. Was leistet das Periotestverfahren heute? Dtsch. Zahnlrztl. Z. 1985. 40. 705-706 Schulte, W., Der Periotest - Parodontalstatus,Zahndrzf/. Mitt. 1986, 76, 1409-1414 Kohno, S., Sate. T. and Tabata, T., Periotest - A new measuring instrument of the dynamic periodontal function and the gurde to Its applrcation. Quintessence 1987, 6, 187-l 95 (in Japanese)
Center,
(Received
24
Nikon
July
Corporation,
1989:
Nishi-ohi
accepted
l-6-3,
16 May
Shmagawa-ku,
Tokyo
140,
Japan
1990)
The sensitivity of a vibrational test for in viva assessing the interfacial rigidity of a biocompatible dental root implant was studied using models. Aluminium alloy rods of 4 mm diameter and 7 mm long were root implant models. Cyanoacrylate and epoxy adhesives were hard interface models. Soft interfaces were modelled in a soft silicone adhesive, a gel, adhesive tapes and direct loose contact. Blocks of bovine and canine jaw-bones chemically treated and dried were models of a human alveolar bone. It was found that the minimum average thickness of a soft interface layer distinguishable from a hard interface depends on load directions and positions and ranges from 0 to 160 pm. The sensitivity was rather low in the direction for which a normal load was applied to the bone, reflecting a mechanical difference of the surrounding bone and/or the interface. Therefore, it is desirable that the assessment by the vibrational test is done in the direction, too, for which a shearing load is applied to the interface. Keywords:
Various
Dental
materials
implant,
which
interface,
show
with bone have been applied
excellent
to dental
success of such an implant depends state
of
the
vibrational
implant-bone
techniques
objectively:
(a)
waveform
(c) the
measurement
based
glass-coated
based
on the
the
alumina15);
based on the frequency
and
it the
(b) the
(e)
spectrum
the
should
be mentioned
the above
method
with
increasing
Figure
direction;
bottom.
interface
suggests
loosened
It
from
tendency, range were of POWF
in the implant-embedded
was made of a bioactive
The figure
became
a similar
and frequency
metal and had the shape of a tapered round
titanium”,
the implant
rigidity.
obtained
7 shows clinical examples
meta13-‘); time
by the pulsed
interfacial signals
(a) also suggested amplitude
and low-frequency
induced
that vibrational
though their maximum quite different’.
amplitude
vibration
signals taken from a root implant
13, 14); (d) the forced
impedance
of the implant
measure-
contact
(for apatite-coated on
on
fact3,4; the maximum
components
force tend to decrease
several
titanium’);
and apatite”,
based
(for
method
(for bioactive method
(ILCT method) method
measurement method
load
load
based on the waveform
’ ‘, titanium”-‘*
alumina”, oscillation
Recently,
(for alumina’,
method
method)
impact
The clinical
largely on the mechanical
interface.
impact
measurement
ment (POWF
empirical
biocompatibility
implants.
have been tried in order to estimate
the
pulsed oscillation
v/brat/on
at an
glass-coated
hollow cylinder
with a
that the implant-bone early
stage
and
then
spectrum impact
load
measurement
(for
carbon16). The
merits
of the
POWF
method3,“,18
force acting on the implant-bone the duration
of the force application
small, (d) the measurement therefore
information
tions, (e) an implant mucous
membrane,
can be examined and
The POWF
Correspondence
to Dr T. Kaneko
Butter-worth-Helnemann
(f) the method
are (a) the
is very small, (b)
is short, (c) the probe is
is not limited
can be obtained
inexpensive.
8 1991
interface
to a direction
from different
and direc-
under the protection
apparatus is based
is simple
of and
on the following
imme+iately F/gore
1
VIbrational
signals
diter taken
from
imp a bloactive
:antat.lon root
implant
Ltd. 0142-9612/91/060555-06 Btomatenals
199 1, Vol
12 August
555
Pulsed oscillation technique: T. Kaneko
became rigid with time. However, the assessment is not beyond doubt, because recent model experiments have suggested the following possibility”, ‘s. First, a signal which isdetectedfroman implantsurrounded byaverythinfibrous capsule may be similar to that from an implant rigidly bonded with bone. Second, a detected signal will depend on the density of the surrounding bone to some extent. Such unfavorable possibility for the assessment of the interface itself seems to exist in all the vibration-based tests. Therefore, the sensitivity of the POWF test, especially the minimal detectable thickness of a soft interface layer (MDTSIL), has been examined by using models. The results are presented in this paper.
MEASURING
SYSTEM AND EXPERIMENTAL
MODELS
Figure 2 shows the measuring system of the POWF test used. Each of AED (acoustoelectric driver) and AER (acoustoelectric receiver) consists of a piezoelectric element and a puncture needle3,“. The measurement is done as follows. A pulsed force of about 1 kHz in repetition rate, which is a multifrequency force, is applied to an implant by lightly contacting AED. The pulsed force induces the implant vibration chartacteristic of the mechanical state of the implant-bone interface. The vibrational signal is picked up and transformed to an electric signal by AER. The electric signal is amplified to 60 dB with 20 kHz bandwidth and displayed on the oscilloscope screen. Cylindrical aluminium alloy (AA) rods with a fairly flat bottom, 7 mm long and 0.2 g mass, were used as root implant models. Hard interface models were a cyanoacrylate adhesive (CAd) and an epoxy adhesive (EAd). Soft interface models were a soft silicone adhesive (SAd) named KE 44RTV (Shin-etsu, Tokyo), a gel couplant (GCo) named Ultra/Phonic Conductivity Gel (Pharmaceutical Innovation, New Jersey), adhesive tapes of 0.09 mm thick (09ATa) and 0.16 mm thick (16ATa) named STR Tape (Shinto Chemitron, Tokyo) and direct loose contact, Blocks of bovine and canine jaw-bones chemically defatted and dried were models of a human alveolar bone.
\1
+
AED
- Amplifier
\1
AER
Oscilloscope
mplant -_
Bone
Figure (POWF)
556
2
Experimental test.
AED,
Biomaterials
arrangement
acoustoelectric
199 1, Vol
for the pulsed driver;
12 August
AER,
oscillation
acoustoelectric
waveform receiver.
RESULTS AND DISCUSSION We will specify each POWF signal shown below by a symbol such as (1 iiP). The number in the parentheses denotes that of the sample which AED and AER were contacted with. The material of the sample is designated by the letter b for bone and i for implant model or tooth. The letter P (parallel to bone), U (upper) or L (lower) means that AED and AER were contacted in the corresponding direction shown in Figure 9. If the above letter is unwritten, AED and AER are meant to have been contacted in direction S (‘senkrecht’ to bone), namely, in the implant-embedded direction. Figure 3 shows POWF signals taken from AA rods in the holes drilled in a bovine bone and from the bone itself. The soft interface model was SAd. The rods were 3.70 mm diameter. The holes were about 3.80 mm diameter and 4 mm deep. The compact bone around the rods was about 0.5 to 3 mm thick. The waveform difference of samples 1 and 3 (hard interfaces) from samples 2 and 4 (soft interfaces) is clear. Therefore, MDTSIL is < 50pm in direction P. We see that (1 ii), (5bb) and (7bb) are larger in the maximum amplitude than (3ii). (6bb) and (8bb), respectively. This is because the compact bone around samples I,5 and 7 is thinner and therefore the average bone density around them is lower. Figure 4 shows POWF signals taken from AA rods (samples 1 and 2) in the holes drilled in a canine bone and a natural tooth (sample 3). The soft interface model was GCo. The rods were 3.70 mm diameter. The holes were about 3.76 mm diameter and 4 mm deep. A waveform difference between sample 1 (hard interface) and sample 2 (soft interface) is clear. Therefore, MDTSIL is < 30pm in direction P. The signal (3ii) is smaller in the amplitude than (2ii); this is partly because sample 3 does not have a soft root membrane as a result of the chemical treatment and partly because sample 3 is very different in size and material from sample 2. Unlike (1 ii), (1 iiP) is larger in the amplitude than the corresponding hard signals shown in Figure 3. This is probably because the average bone density around sample 1 is lower in direction P than that in Figure 3. Figures 5 and 6 show POWF signals taken from AA rods in the holes drilled in a compact bovine bone. Soft interface models were GCo in Figure 5 and SAd in Figure 6. The rods were 3.70 to 3.80 mm in diameter. The holes were about 3.80 mm in diameter and 4 mm deep. The bones around the rods were 7 to 10 mm thick. We see that the signal amplitude obtained in direction P tends to decrease with decreasing thickness of the soft interface. In Figure 5 a waveform difference between sample 5 (soft interface) and sample 7 (hard interface) is vague. This means that a thin soft interface is estimated to be rigid or slightly rigid in the POWF test. Waveform differences both between (4iiP) (soft interface) and (7iiP) and between (6iiL) (soft or hard interface) and (7iiL) are clear. Therefore, MDTSIL is about 1 Oprn in direction P (2 V input) and Oprn in direction L (10 V input). This difference in MDTSIL suggests that to make a sensitive assessment, the measurement should be done nearer to the interface and/or under a larger input voltage. The amplitude of (7iiL) is as small as that of (7iiP). This means that the interface and the bone are fairly rigid and inelastic. In Figure 6, a waveform difference between sample 2 (soft interface) and sample 3 (hard interface) is clear. Therefore, MDTSIL is < 15pm in direction P. Figure 7 shows POWF signals taken from AA rods in the holes drilled in an entirely cancellous bovine bone. Soft interface models were SAd (sample 1) and direct loose
Pulsed
5
12
3
(4ii)
/-
F/gore 0 5-3
3
Aluminium
mm. Interface:
contact
(sample
holes were
alloy rods in a dried
see that MDTSIL SAd interface. Figure
3.80
is < 25pm
(sample
waveform clear
difference
in direction
However, figure
1). The
a waveform
and sample
were hard
difference
Figure
9 shows the
POWF
SAd
soft and
(tjbb)
09ATa
sample
2 in this
between
(1 ii) and (2ii),
distinct between
to
test. We see that,
between
soft
and
L than in direction
tape.
waveform
U.
Figure
A
3.7 mm
were 6) and
diameter.
The
and sample
a waveform
but the difference,
is indistinct.
partly
3
difference
especially
This is because
with
bone.
However,
(1 iiL) and (2iiL) difference
in the
the SAd
S for the soft interface
comparison
between
8 and (1 ii) in Figure
to an implant particularly
(1 ii) and (4ii), but not
MDTSIL
is about 160 ,um
modelled (3ii)
9 suggests
the bone itself,
Biomaterrals
in the adhesive
in Figure
7,
the following
in the POWF
when
a waveform
is very clear. We see a
between
( 1 ii) and (5ii). Therefore,
the load applied
and
4 and
1 (hard interface)
of which
flattened
the rods:
models
(samples
recognize
signals taken from AA rods on was
around
respecnvely.
2 was so thin that the bottom of the rod may
between
in direction
hard
also
amplitude,
difference
S.
have
can
contacted
be
may
16ATa
rods were
sample
between
7 is fairly large in direction 2
5). The
We
layer in sample
between
3).
is clear.
have
bone
adhesrves
bone around the rods was 4 mm thick. A waveform
is
< 160 pm.
2 and
(sample
compact
of the compact
and soft silicone
using a paper file. Soft interface
and soft interfaces is
-(5bb)
Thickness
cyanoacrylate
(samples
difference model was
for the holes.
maximum
MDTSIL
in direction
surface
smoothened
sample
7, a discrimination
bone
mm
3 V CAd and SAd,
A
to be slightly rigid in the POWF is more distinct
Input:
diameter.
considered
a bovine
of
3.7 mm
for the rods, 3.80
We
L.
7. The soft interface rods
3 in Figure
r
30-psec
The
U and L for the between
the
interfaces
mm
mm diameter.
Therefore,
as in Figure
3.70
5 to 8: bone
and 4 mm deep.
in direction
Therefore,
interface
i7bb)
Ii ii
signals taken from AA rods on
between S.
Diameter: Samples
in directions
POWF
the same bone as in Figure 16ATa
3.75
a discrimination
is more distinct
8 shows
bone.
mm diameter
However,
hard interfaces
bovine
(31 CAd, (4) SAd.
2). The rods were
about
,-
L
(1) CAd, (2) SAd,
T Kaneko
photograph
/-(211P)
\I
techmoue:
46
X-ray ,(Zii)
oscillat/on
in
point;
test will vibrate
the implant
199 7, Vol
(2ii)
is supported
12 August
557
Pulsed oscillation technique: T. Kaneko
,(2ii)
/.(ZiiP)
(lii)
1
_ 30 psec
Figure 4 Aluminium alloy rods in a dried canine bone. Diameter: 3.70 mm for the rods, 3.76 mm for the hales. Interface: ( 1) cyanoacrylate adhesive, (2) gel couplant. Sample 3: natural tooth Input: 3 V for signals (ii), 2 V for signals (iiP).
(2iiP)
(3iiP)
/
~
(lii)
(4iiP)
(Zii)
(3ii)
(7ii)
(5iiP)
(7iiL) (5ii)
(7iiP)
I(6iiP) 30psec
Figure 5 A~urn~fl~urnalloy rods in a dried compact bovine bone. Diameter (in mmJ of the rods: ( I) 3.70, (ZJ 3.75. (313.77, (4J 3.78. (Sj 3.79. (6J 3.80. (7) 3.70. Diameter of the hoies: 3.80 mm. Bone thickness around the mds: 7 to 10 mm. Interfece: (1) to (6J gel couplam? (7) c~ano~~late adhesive. Input: 2 V for signals [iiJ and (iif), 10 V for signals (iiL).
Figure 6 Aluminium aljoy rods in the same bone as in Figure 5. Diameter (in mm) of the rods: It/ 3.75, (2) 3.77. (3J 3.70. Diameter of the holes: 3.80 mm. Interface: (IJ and (2J silicone adhesive, (3J cyanoactylate adhesive. Input: 2 V
558
Biomaterials
f991,
Vol 12 August
Pulsed
osnllation
technique:
(lii)
T. Kaneko
(1iiL)
L(3ii)
&
-(3iiU)
( 3ilL)
30-m Figure
7
(2J direct
Alomirwm loose
alloy
contact,
(3j
rods
in a dried
cyanoacrylate
cancellous adhesive.
bovine Input:
bone.
Diameter:
3.75
mm
for the
rods,
3.80
mm
for the
holes.
Interface:
(1) silxone
adhesive,
1.5 V
rJ
~j/(lllL)
(11111)
(2llL)
(2iiU) 30-&c FIgwe
8
Alumvwm
alloy
rods
on the same
bone
as in
Flgure 7. Interface:
(1)
a sheet
of 0.16
(Iii)
mm
thxk
adhesive
tape,
(2)
epoxy
adhesive.
11
(Zil)
Input.
1.5 V
(3ii)
d
(3iiU)
(2liU)
(4ii)
(611
j
(311L)
30-psec Figure
9
adhesive, (Sii),
Alumrntum (4) a sheet
3 V for the
alloy rods on a dried of 0.16
mm
thick
compact
adhesive
bovine
tape,
bone.
(5) a sheet
Bone
thickness
of 0.09
mm
around thick
the rods: 4 mm. Interface:
adhesive
tape,
(6) two sheets
f 1) cyanoacrylate
adhesive,
(2) and (31 sjlicone
of 0.16
adheswe
tape.
mm
thick
Input.
1 V for
others.
B/omaterials
199 1, Vol
12 August
559
Pulsed oscillation technique: T Kaneko
only by a cancellous bone. A comparison between (1 ii) in Figure 8 and (4ii) in Figure 9 also suggests it. It is evident from the above results that the POWF test depends on load directions and positions. It is rather lowsensitive in the direction for which the interface and the surrounding bone are compressed over a wide area. This is because a mechanical difference of the surrounding bone and/or the interface is reflected. It is worth noting here that a similar direction dependence of the sensitivity is found for the ILCT test using Periotest (Siemens, Bensheim)‘g-24. Therefore, it is desirable that the vibrational test is done in the direction, too, for which a shearing load is applied to the interface. Only the test in such a direction will distinguish an implant rigidly bonded with bone from an implant only contacted with it.
implantanon. Jpn. J. Oral Maxillofac. Surg. 1986, (in Japanese) 6
7
a
9
10
11
CONCLUSIONS The sensitivity of the POWF test has been examined by using aluminium alloy rods, 4 mm diameter and 7 mm long, as root implant models. Hard interfaces have been modelled in cyanoacrylate and epoxy adhesives. Soft interfaces have been modelled in a soft silicone adhesive, a gel, adhesive tapes and direct loose contact. A human alveolar bone has been modelled in blocks of bovine and canine jaw-bones chemically treated and dried. The sensitivity has been shown to depend on load directions and positions and be rather low in the direction for which only a normal load is applied to the interface. The minimum average thickness of a soft interface layer distinguishable from a hard interface has been found to range from 0 to 160pm in the present experiment. It is desirable that the POWF test is done in the direction, too, for which a shearing load is applied to the interface.
12
13
14
15
16
17
ia
REFERENCES Scholz. F.. Bewegungsverhalten bei Stossanregung des Tiibinger lmplantates im Vergleich sum naturlichen Zahn, Dtsch. ZahnBrztl. Z. 198 1, 36, 567-570 Yamane, S., Nakagawa, S., Shimogoryo, R. and Tsuda, T., Percussron sound of ITI implant, J. Jap. Sot. Oral lmplantol. 1988, 1, 240-244 (in Japanese) Kaneko, T., Nagar, Y.. Ogino, M.. Futami, T. and Ichimura. T., Acoustoelectric technique for assessing the mechanical state of the dental implant-bone interface, J. Biomed. Mater. Res. 1986, 20, 169-176 Miyasawa, M., Kudo, K., Fuj1oka.Y.. Shioyama.T., Nakano, K., Seino, Y. and Kaneko, T.. Clinical application of dental root implants of bioactive glass. Part 1. Assessment of bonding states by means of an acoustoelectric technique, Annual Meeting of rhe Japanese Stomatological Society, Fukuoka, May 15-l 6, 1986 (in Japanese) Kudo. K.. Fujioka, Y., Miyasawa, M., Ishibashi, K.. Shioyama, T., Ishikawa. F., Kamegai, T., Nakano, H. and Seino, Y., Clinical application of dental root implant coated with bioglass. Part 1. Result of
560
Biomaterials
199 1, Vol 12 August
19
20
21
22 23 24
32, 2083-2089
Kudo, K., Ishibashi, K. and Kamegai, T., Application of bioactive glass to the dental root implant, in Bioceramics -Development and Clinical Applications (Eds H. Aoki and J. Niwa), Quintessence, Tokyo, 1987, pp 193-l 96 (in Japanese) Sugihara, K. and Yamashita, S., Clmical application of dental root implant coated with bioglass. Part 1. Procedure of implantation, J. Jpn. Stomatol. Sot. 1987, 36, 96-105 (in Japanese) Kamegai. T., Ishikawa, F., Nakano. H., Seino, Y., Fujioka. Y., Kudo, K., Miyasawa, M.. Ishibashr, K. and Shioyama, T., Clinical applications and their short term results of dental root implantation using materials coated with bioactive glass, 3rd International Congress of lmplantology and Biomaterials in Stomatology, Osaka, Apnl 28-29, 1988, B-29 Fujino, M.. Sakaizumi, K., Senuma, S., Sate. K. and Ogino, M., Clinical application of the dental root implant coated with bioactive glass, 3rd International Congress of lmplantology and Biomaterials in Stomatology, Osaka, April 28-29, 1988, B-33 Schulte. W.. Messung des Dampfungsverhaltens enossaler Implantate mit dem Periotestverfahren, Dtsch. Z. Zahnlrztl. lmplantol. 1986,2, 11-12 lijima. T. and Takeda, T.. Changes in the surrounding bones caused by an implant as monitored using Periotest, Part 1,3rd international Congress of lmplantology and Biomaterials in Stomatology, Osaka, April 28-29, 1988, B-3 Yamane, S., Shimogoryo, Ft.and Tsuda, T.. Mobility of the bridge with implant abutments, J. Jap. Sot. Oral lmplantol. 1989, 2. 34-38 (m Japanese) Ogiso. M., Kaneda. H., Shiota, M., Mitsuwa,T., Wakuda.T., Aikawa, S., Uoshima, K.. Masuda. T., Kaneda, FL, Tomizuka, K., Tabata, T. and Sugimoto, H., Apatite implant, 2-piece implant system, J. Dent. Med. 1987, 25, 617-633 (in Japanese) Takigawa, H., Yamauchi, M.. Nigauri, A., Satoh, F., Shimrzu, M. and Kawano, J., Evaluation of Periotest for prosthetrc clinical application, J. Jpn. Prosthodont. Sot. 1988, 32, 189-l 98 (In Japanese) Saratani. K., Yoshida, S., Oka, H. and Kawazoe, T., Climcal applrcatron of biomechanical mobility measurement to implant body. 3rd International Congress of lmplantology and Biomaterials in Stomatology, Osaka, April 28-29, 1988, B-2 Sairenji, E. and Yanagisawa, S., Specificities of dentoosseous Interface and induction of the mimic structure, 3rd International Congress of lmplantology and Biomaterials in Stomatology, Osaka, April 28-29, 1988, Symposium-4 Kaneko, T.. Assessment of the interfacial rigidrty of bone implants from vrbrational signals, J. Mater. Sci. 1987, 22, 3495-3502 Kaneko, T., Comparrson between acoustic and mechanical tapping methods for assessing the interfacial states of bone implants, J. Mater. Sci. 1989, 24. 2820-2824 K&nig, M., Lukas, D., Quante, F., Schulte, W. and Topkaya, A., Messverfahren zur quantitativen Beurteilung des Schweregrades van 1981, 36, Parodontopathien (Penotest), Dfsch. Zahnlrzrl. Z. 451-454 Schulte. W.,d’Hoedt, B., Lukas, D., Mtihlbradt, L.,Scholz, F., Bretschi, J., Frey, D., Gudat, H.. Konig. M.. Markl. M., Quante, F.. Schief, A. and Topkaya, A., Penotest - neues Messverfahren der Funktion des Parodontiums, Zahr&ztl. Mitt, 1983, 73, 1229-l 240 d’Hoedt, B.. Lukas, D., Muhlbradt, L., Scholz, F., Schulte, W., Quante. F. and Topkaya. A., Das Periotestverfahren Entwicklung und klinische Prufung. Dtsch. ZahndrztI. Z. 1985, 40, 1 13-l 25 Schulte, W.. Was leistet das Periotestverfahren heute? Dtsch. Zahnlrztl. Z. 1985. 40. 705-706 Schulte, W., Der Periotest - Parodontalstatus,Zahndrzf/. Mitt. 1986, 76, 1409-1414 Kohno, S., Sate. T. and Tabata, T., Periotest - A new measuring instrument of the dynamic periodontal function and the gurde to Its applrcation. Quintessence 1987, 6, 187-l 95 (in Japanese)
