Experimental study of the damping behaviour of IMZ implants

Journal of Oral Rehabilitation 1999 26; 19–24

Experimental study of the damping behaviour of IMZimplantsR . H A A S , T . B E R N H A R T, O . D O R T B U D A K & G . M A I L AT H Department of Oral Surgery,School of Dentistry of the University of Vienna, Austria

SUMMARY Measurements of the damping behaviour

of dental implants with the Periotest® device are

considered to be an objective means to assess the

mobility of implants. The effects of the position of

an implant in the maxilla or mandible, the period

of time passing between the measurements and

implant placement and the height at which the

Periotest® measurements are performed on the

damping behaviour of implants have been discussed

controversially. This experimental study examined

the influence of the use of different measuring

devices, the measuring height and the embedding

depth on the damping behaviour of IMZ implants.

The implants were embedded in resin at different

depths and damping measurements were carried out

at different measuring heights. It was found that the

values rose with an increasing measuring height and

a decreasing embedding depth. Analysis of variance

was used to assess the influence of the embedding

depth and revealed that the embedding depth had

a significant impact on the measuring values at each

Introduction

Ankylotic anchorage of the implant in bone isconsidered an essential criterion for the success of animplant (Albrektsson et al., 1981; Brånemark, Zarb &Albrektsson, 1985). For a long time, the mobility of animplant was assessed through subjective palpitation.Later, attempts were made to use the dampingcharacteristics for an objective evaluation of the bondbetween the implant and bone.

© 1999 Blackwell Science Ltd 19

measuring height, above 6 mm. Moreover, it was

found that the higher the measuring height, the

higher the measured values and the greater the

differences between the values obtained at the

individual depths. The different measuring devices

had no influence on the measuring results (P J 0·79).

The results of this study suggest that a longitudinal

follow-up of the peri-implant residual bone height

around individual implants is possible. Single

measuring values by themselves do not allow any

conclusions about the prognosis of an implant. The

assessment of the peri-implant bone height through

Periotest® measurements is conceivable only when

a table of damping values taking into account the

physical length of the implant, the embedding depth

and the measuring height for the examined implant

system is available. In cylindrical implants, the head

of the available prefabricated measuring post can be

recommended as a constant measuring point for

further studies, especially when the results are to be

compared with those obtained by other study

groups.

The Periotest® method (Schulte et al., 1983; D’Hoedtet al., 1985) was designed for the objective evaluationof the periodontal health status of natural teeth. ThePeriotest® device consists of a handpiece connected toa unit, which analyses the braking time of a rod appliedto a tooth or an implant surface. The rod, which islocated inside the handpiece and held in low frictionbearings, is accelerated until it reaches a constant speedof 0·2 m/s, which is maintained to compensate forfriction and gravitation until contact is made with the

20 R . H A A S et al.

Table 1. Range of PTV of implant systems

Implant type Author Location Range of PTV Reference

Brånemark Teerlinck et al., 1991 mand 1 max 25/15 21

mand 24/12

Olive & Aparicio 1990 max 20·8/12 13

mand 22/16

Haas et al., 1995b mand 25/15 8

max 28/19

Tricio et al., 1995 mand 26/14 22

max 26/15·5

IMZ Schramm-Scherer 1987 mand 1 max 25/18 15

Haas et al., 1995a mand 27/17 7

max 25/17

ITI Schramm-Scherer 1987 max 1 mand 25/1515

Mericske-Stern et al., 1995 max 1 mand 28/21 12

TPS D’Hoedt & Schulte 1989 max 1 mand 26/18 10

Tubingen Schramm-Scherer 1987 max 1 mand 25/15 15

surface being tested. The deceleration of the rod when

tapping the surface is recorded by a miniature

accelerometer contained in the tapping head. The

information is analysed by the measuring unit and

tabulated as contact time (CT) and given as the

Periotest® value (PTV) (Schulte & Lukas, 1992). Several

reports on measurements carried out in different

implant systems are available (Table 1).

Various authors (Olive & Aparicio, 1990; Cramer,

1992; Schulte & Lukas, 1993; Haas et al., 1995a)

observed PTVs of 1 8 and higher in clinically mobile

implants that had to be removed. Therefore, implants

with a PTV of more than 1 8 should be subject to

further investigation.

Aside from fibrous encapsulation, other factors have

been reported to affect the damping behaviour of

implants:

(i) After an initial rise following second-stage

surgery, the PTV values of an implant show a

tendency to drop, corresponding to increasing

ankylosis of the implant (Schramm-Scherer,

1987; van Steenberghe et al., 1995).

(ii) Maxillary implants show higher values than

mandibular ones because of the different bone

qualities in these regions (Olive & Aparicio,

1990; Buser, Weber & Lang, 1990; Salonen

et al., 1993; Haas et al., 1995a,b; Tricio et al.,

1995).

© 1999 Blackwell Science Ltd, Journal of Oral Rehabilitation 26; 19–24

(iii) An implant may show varying PTVs,

depending on the point in which the

measurements are carried out (Tricio et al.,

1995; Derhami et al., 1995).

The measuring heights used for Periotest®

measurements vary considerably between the

individual study groups and for different implant

systems. For example, measurements of Brånemark

implants were performed at the upper abutment margin

(Teerlinck et al., 1991; Tricio et al., 1995; van

Steenberghe et al., 1995), at the closest point to the

junction (Olive & Aparicio, 1990) or at a height of

3 mm in a gold cylinder. In IMZ implants, measurements

were carried out either at the crown equator or as

close to the gingival margin as possible (Haas et al.,

1995a) or at the measuring post (Schramm-Scherer,

1987). A measuring point located in the middle of the

implant head was used for TPS screws (Schramm-

Scherer, 1987). Some authors do not give the exact

measuring height (Mericske-Stern et al., 1995). Because

different measuring points have been used for different

implant systems and for measurements carried out in

one and the same implant system, a comparison of the

results is not possible. Therefore, no definite statements

can be made about factors influencing the PTVs of

implants.

This experimental pilot study therefore aimed to

examine the impact of the measuring height and the

D A M P I N G B E H AV I O U R O F I M Z I M P L A N T S 21

embedding depth on the Periotest® values of IMZ

implants.

Materials and methods

Ten plasma-flame-sprayed IMZ implants* with a

diameter of 4 mm and a length of 15 mm were used

for the present study. The implants were embedded in

autopolymerizing methyl methacrylate† , each one at a

different depth, i.e. at 1, 2, 3, 4, 5, 6, 8, 10, 12,

and 14 mm, beginning from the tip of the implant.

Therefore, only 1 mm of the first implant was apically

anchored in the resin, whereas the last implant was

fully submerged in the embedding material, except for

a 1 mm portion. The selected embedding material has

an E-modulus of 3353 6 235 N/mm2 and is thus within

the range of 2000 N/mm2 and 4000 N/mm2 of

cancellous bone (Staudter, 1992). The mixing ratio used

to produce the resin block was 2 units powder and 1

unit liquid. The resin was applied in two layers to

guarantee homogenous curing. The curing time was

5–10 min. Prefabricated measuring posts for the IMZ

implant system with a total length of 11 mm above the

upper implant margin were then placed and fixed with

20 Ncm. The resin block was fixed in such a way that

the fixtures were perpendicular to the floor.

Three different Periotest® devices‡ were used during

all experiments and were calibrated individually before

the actual measurement was started. All registrations

were performed by the same investigator. A series of

seven measurements per measuring height and

measuring device was carried out in each implant. The

handpiece of the Periotest® device was held in such a

way that the horizontally swinging rod hit the implant

surface from a distance of 2 mm. Because of the

dimensions of the handpiece, the PTV measurements

began at 3 mm above the resin and then continued at

1 mm increments until the end of the post was reached.

Statistical data analysis

Each measurement was repeated seven times per device

to achieve a greater measuring accuracy and only the

mean value of each series of measurements was used for

further analysis. A repeated measures ANOVA (Crowder &

Hand, 1990) was carried out with the SAS procedure

*Friatec, Friedrichsfeld, Germany.†Technovit 4071, Kluzer, Germany.‡Periotest®; Siemens, Benzheim, Germany.


GLM to analyse the impact of the embedding depth as

well as of the measuring height and the three measuring

devices, which were defined as repeated factors. A

Huynh/Feldt correction ( Huynh & Feldt 1970) was used

because several measurements of the same implant at

increasing heights and with three different devices result

in specific dependencies. Since a completely crossed

design was needed in order to evaluate interactions in

the ANOVA, only measurements carried out at measuring

heights between 3 mm and 12 mm were used.

To assess the impact of the embedding depth at

different measuring heights, additional subgroup

analyses were carried out using repeated measures

ANOVA (Crowder & Hand, 1990). P-values , 0·05 were

considered statistically significant.

Results

The mean values of the PTVs of the three devices

and corresponding standard deviations for the different

embedding depths and measuring heights are listed in

Table 2. All values ranged between –8 and 125·7 PTV.

The lowest values were found near the embedding

margin and in implants embedded at the greatest depth.

The use of the three different devices had no

significant influence on the measuring values (P 5 0·79).

The analysis clearly revealed that the embedding

depth (P 5 0·0005) and the measuring height (P 5

0·0001) had a significant influence on the PTVs. A

linear and quadratic trend was observed with respect

to the measuring height. The subgroup analyses for

each measuring height that were carried out because

of significant interactions (P 5 0·0001), showed that

the embedding depth had a significant influence on

the values in measuring heights above 6 mm. No

statistically significant linear trend was observed below

this measuring height. The deeper the implant was

embedded, the lower the measuring value.

The higher the measuring height, the greater the

differences between the measuring results obtained at

the different embedding depths.

Although the statistical statements are based on the

data obtained for measuring heights between 3 and

12 mm only, Table 2 seems to indicate that these

statements apply also to greater measuring heights.

Discussion

Periotest® measurements have been recommended in

the literature as a valid tool to judge osseointegration


Table 2. Mean periotest values of three devices with regard to different embedding depths and measuring heights for 15 mm IMZ

plasma-flame sprayed implants. The values in parentheses denote the standard deviation

Measuring Embedding depths (mm)

height

(mm) 1 2 3 4 5 6 8 10 12 14

3 26·3 (0·5) 26·3 (0·5) 27·0 (0·0) 28·0 (0·0) 28·0 (0·0) 28·0 (0·0) 25·8 (1·0) 27·3 (0·5) 27·0 (0·0) 27·3 (0·5)

4 26·1 (0·7) 26·6 (0·5) 27·0 (0·1) 28·0 (0·0) 28·0 (0·0) 24·6 (2·8) 25·0 (0·0) 26·0 (0·0) 27·0 (0·0) 27·0 (0·1)

5 26·8 (0·2) 0·3 (6·3) 27·5 (0·5) 27·9 (0·1) 28·0 (0·0) 24·5 (2·7) 25·0 (0·0) 26·0 (0·0) 27·0 (0·0) 27·0 (0·0)

6 0·8 (6·7) 0·4 (6·4) 27·8 (0·2) 22·3 (4·9) 25·6 (4·0) 23·0 (0·0) 23·4 (4·8) 26·0 (00) 26·3 (1·1) 26·0 (0·0)

7 4·3 (0·7) 4·6 (0·5) 24·7 (4·9) 2·6 (1·5) 0·4 (2·6) 23·0 (0·0) 23·0 (0·0) 25·3 (0·5) 24·6 (0·5) 25·6 (0·5)

8 3·4 (0·5) 4·1 (0·7) 2·9 (2·0) 1·8 (1·6) 0·6 (1·5) 21·0 (1·7) 21·6 (1·1) 24·0 (0·0) 24·3 (1·1) 25·0 (0·0)

9 4·2 (1·4) 4·8 (0·7) 3·1 (0·7) 0·0 (0·1) 20·8 (0·2) 21·6 (1·1) 20·5 (0·8) 23·3 (0·5) 23·3 (1·1) 24·3 (1·1)

10 5·0 (0·0) 4·7 (0·2) 1·3 (1·5) 2·6 (2·2) 0·3 (2·3) 0·3 (0·2) 0·3 (1·5) 23·0 (0·0) 23·0 (1·0) 3·0 (0·0)

11 5·0 (1·1) 5·3 (1·5) 4·0 (0·4) 3·0 (2·7) 3·4 (0·5) 1·3 (1·4) 1·8 (1·0) 21·6 (0·5) 21·0 (1·7) 23·0 (0·0)

12 5·6 (1·8) 7·4 (3·6) 4·0 (2·6) 5·9 (1·7) 3·1 (0·2) 2·3 (0·5) 2·5 (0·5) 21·0 (0·0) 20·3 (0·5) 23·0 (0·0)

13 7·8 (1·3) 8·1 (3·0) 5·2 (1·1) 7·5 (2·9) 4·4 (2·1) 3·9 (0·8) 3·3 (1·8) 0·3 (1·1) 0·0 (1·0)

14 11·2 (2·3) 10·7 (3·5) 5·0 (1·0) 9·2 (3·4) 5·3 (0·5) 4·4 (0·5) 3·6 (1·1) 1·0 (0·0) 0·3 (0·5)

15 11·0 (0·5) 11·1 (3·5) 6·9 (2·0) 10·3 (3·3) 5·6 (0·5) 4·9 (0·1) 5·0 (0·1) 1·5 (0·5)

16 12·6 (1·2) 13·5 (3·3) 8·3 (2·7) 11·8 (3·2) 6·2 (0·4) 6·0 (0·8) 5·3 (0·5) 2·2 (0·4)

17 13·9 (2·2) 14·6 (2·5) 8·4 (2·4) 12·4 (2·9) 8·8 (2·4) 6·0 (1·0) 5·6 (1·5)

18 14·8 (2·8) 17·0 (3·7) 11·4 (2·3) 14·9 (3·4) 11·5 (1·5) 7·4 (0·7) 6·0 (0·0)

19 16·4 (3·3) 16·3 (2·4) 12·9 (2·0) 16·4 (3·8) 12·7 (1·5) 8·3 (0·5)

20 18·8 (5·1) 19·9 (2·1) 13·4 (2·8) 17·4 (2·6) 13·4 (0·5)

21 20·5 (4·2) 20·1 (2·3) 17·0 (2·0) 19·4 (1·2)

22 22·4 (3·3) 20·7 (0·3) 18·9 (1·4)

23 23·6 (3·2) 23·4 (0·5)

24 25·7 (1·1)

(Cramer, 1992; Haas et al., 1995a; van Steenberghe

et al., 1995). Values between –7·0 and 17 are considered

normal values. However, because the measuring heights

used by the different authors often vary considerably,

the results obtained in different implant centres cannot

be compared. The aim of this experimental study was

to examine factors that might influence the PTV.

The use of three different measuring devices had no

statistically proved influence on the measuring values.

This is in accordance with the results of other authors

obtained on screw-shaped implants (Derhami et al.,

1995).

Variable measuring heights and embedding depths

were examined to simulate the effects of peri-implant

bone resorption on the damping behaviour of IMZ

implants.

When the findings of this study are transferred to

in vivo conditions, it should be taken into account that

variable bone qualities were not simulated. Moreover,

the examinations were based on the assumption that

the implants are fully ‘osseointegrated’ in the part

covered by the resin.


The results of the study show that the embedding

depth and the measuring height have a significant

influence on the PTV. The measuring results were the

higher, the higher the point at which the measurements

were carried out and the less deep the implant was

anchored. The differences between PTVs obtained at

the same level but in implants submerged into the resin

at differing depths were more pronounced at higher

measuring heights than near the embedding margins.

For example, the mean values of the measurements

carried out at 3 mm were between –8·0 and –5·8,

whereas those obtained at a measuring height of

11 mm were between –3·0 and 5·3 (Table 2). A linear

trend of the individual embedding depth was confirmed

statistically in measuring heights above 6 mm.

The present results confirm the findings of Derhami

who observed that the measuring height had an

influence on the PTVs of screw-shaped implants placed

in different regions of the facial bones of a human

cadaver (Derhami et al., 1995). This fact had not been

stated for IMZ implants so far.

Clinical experience has shown that implants with a

D A M P I N G B E H AV I O U R O F I M Z I M P L A N T S 23

PTV of more than 17 up to 18 can be considered afailure. Table 2 shows that this value corresponds to a6-mm-long implant anchored within bone when themeasurements are carried out 10 mm above the edgeof the implant (measuring height 19). On the otherhand, this critical value is achieved if a 2-mm portionof the implant is still anchored within bone and themeasurements are carried out at the upper edge ofthe implant (measuring height 13, embedding depth2 mm).

The different conclusions about the influence of theimplant portion still anchored within bone drawn bydifferent authors might be due to the fact that theyused different measuring points:

Cramer (1992), for example, found that peri-implantbone resorption had an influence on the PTV whencarrying out measurements at the crown of single-toothrestorations on Tubingen implants. In contrast, Haaset al. (1995a) did not observe any such influence whenthey carried out Periotest® measurements at the sitewhere the implant passes through the mucousmembrane in 392 IMZ implants.

Therefore, a standardized measuring point forPeriotest® measurements of implant mobility is requiredto allow a comparison of the results of different studygroups.

A prefabricated measuring post is available for theIMZ system. The centre of this measuring post is located10 mm above the edge of the implant. In the presentexperimental design, the lowest possible measuringresult for 15-mm-long IMZ implants would be a PTVof –3 (measuring height 11 mm). A PTV of 18, whichhas shown to be the threshold value for normallyfunctioning implants in clinical routine, was obtainedat an embedding depth of 6 mm in the present study.Increasing bone resorption would also affect the apicalperforation of the implant and have a negative effecton possible attempts to restore peri-implantitis. Thismeasuring point therefore seems to be very suitable forthe implant length examined.

In summary, the following conclusions can be drawnfrom the results of this study:

(i) A standardized measuring point, which

constitutes an essential criterion in PTV

measurements, should be established as

reference value for the respective implant

system examined.(ii) Measurements carried out at changing

measuring heights are not suitable to follow-

up an implant.


(iii) Single PTVs do not allow any conclusions

about the state of peri-implant bone resorption

because of a lack of experimental data.

(iv) Standardized measuring sites would allow a

longitudinal follow-up of single implants. The

head of the measuring post is suitable as

constant measuring point for the assessment

of 15-mm-long IMZ implants.

(v) Further experimental PTV measurements will

be needed to obtain analogous tables for all

available implant lengths and diameters of the

different implant systems used throughout the

world.

It is conceivable that single measurements carried

out at a standardized measuring height allow relevant

conclusions about the state of peri-implant bone

resorption if the above criteria are fulfilled.

Acknowledgments

The authors wish to express their gratitude to Dr M.

Mittlbock and Mag. A. Kaider, Department of Medical

Computed Sciences of the University of Vienna, for

their valuable assistance in the statistical data analysis.

References

ALBREKTSSON, T., BRÅNEMARK, P.-I., HANSSON, H.-A. & LINDSTROM, J.

(1981) Osseonintegrated titanium implants. Requirements for

ensuring a long-lasting, direct bone-to-implant anchorage in

man. Acta Odontologica Scandinavia, 52, 155.

BRÅNEMARK, P.-I., ZARB, G. & ALBREKTSSON, T. (1985) Tissue Integrated

Prostheses: Osseointegration in Clinical Dentistry, 1st edn, pp. 11–

76. Quintessence Publishing, Chicago.

BUSER, D., WEBER, H.-P. & LANG, N.P. (1990) Tissue integration of

non-submerged implants. 1-year results of a prospective study

with 100 ITI hollow-cylinder and hollow-screw implants. Clinical

Oral Implants Research, 1, 33.

CRAMER, A. (1992) Periotestwerte der Tubinger Implantate aus

Aluminiumoxidkeramik. Dissertation, 1st edn, University of

Tubingen, Tubingen.

CROWDER, M.J. & HAND, D.J. (1990) Analysis of Repeated Measures,

1st edn. Chapman & Hall, London.

DERHAMI, K., WOLFAARDT, J.-F., FAULKNER, G. & GRACE, M. (1995)

Assessment of the periotest device in baseline mobility

measurements of craniofacial implants. International Journal of

Oral and Maxillofacial Implants, 2, 221.

D’HOEDT, B. & SCHULTE, W. (1989) A comparative study of results

with various endosseous implant systems. International Journal

of Oral and Maxillofacial Implants, 4, 95.

HAAS, R., SABA, M., MENSDORFF-POUILLY, N. & MAILATH, G. (1995a)

Examination of the damping behavior of IMZ implants.

International Journal of Oral and Maxillofacial Implants, 4, 410.


HAAS, R., SABA, M., MENSDORFF-POUILLY, N., SCHIEBEL, H. & MAILATH,

G. (1995b) Einflußfaktoren auf das Dampfungsverhalten von

IMZ- und Brånemark-Implantaten. Zeitschrift fur Zahnarztliche

Implantologie, 11, 15.

D’HOEDT, B., LUKAS, D., MUHLBRADT, L., SCHOLZ, F., SCHULTE, W.,

QUANTE, F. & TOPKAYA, A. (1985) Das Periotestverfahren –

Entwicklung und klinische Prufung. Deutsche Zahnarztliche

Zeitschrift, 40, 113.

HUYNH, H. & FELDT, L.S. (1970) Conditions under which mean

square ratios in repeated measurements designs have exact F-

distributions. Journal of the American Statistic Association, 65, 1582.

MERICSKE-STERN, R., MILANI, D., MERICSKE, E. & OLAH, A. (1995)

Periotest measurements and osseointegration of mandibular ITI

implants supporting overdentures. Clinical Oral Implants Research,

6, 73.

OLIVE, J. & APARICIO, C. (1990) The periotest method as a measure

of osseointegrated oral implant stability. International Journal of

Oral and Maxillofacial Implants, 5, 390.

SALONEN, M., OIKARINEN, K., VIRTANEN, K. & PERNU, H. (1993)

Failures in the osseointegration of endosseous implants.

International Journal of Oral and Maxillofacial Implants, 8, 92.

SCHRAMM-SCHERER, B. (1987) Untersuchungen zum Damp-

fungsverhalten von Metall und Keramikimplantaten. Zeitschrift

fur Zahnarztliche Implantologie, 3, 22.

SCHULTE, W., D’HOEDT, B., LUKAS, D., MUHLBRADT, L., SCHOLZ, F.,

BRETSCHI, J., FREY, D., GUDAT, H., KONIG, M., MARKL, M., QUANTE,


F., SCHIEF, D. & TOPKAYA, A. (1983) Periotest – ein neues

Meβverfahren und Gerat zur Messung der Funktion des

Parodontiums. Zahnarztliche Mitteilungen, 73, 1229.

SCHULTE, W. & LUKAS, D. (1992) The Periotest method. International

Dental Journal, 42, 433.

SCHULTE, W. & LUKAS, D. (1993) Periotest to monitor

osseointegration and to check the occlusion in oral implantology.

Journal of Oral Implantology, 19, 23.

STAUDTER, M. (1992) Verformungsmessungen und Verformungs-

berechnungen an Zahnimplantaten. Diplomarbeit. Mannheim.

VAN STEENBERGHE, D., TRICIO, J., NAERT, I. & NYS, M. (1995) Damping

characteristics of bone-to–implant interfaces. Clinical Oral

Implants Research, 6, 31.

TEERLINCK, J., QUIRYNEN, M., DARIUS, P. & VAN STEENBERGHE, D.

(1991) Periotest: an objective clinical diagnosis of bone

apposition toward implants. International Journal of Oral and

Maxillofacial Implants, 6, 55.

TRICIO, J., LAOHAPAND, P., VAN STEENBERGHE, D., QUIRYNEN, M. &

NAERT, I. (1995) Mechanical state assessment of the implant-

bone continuum: A better understanding of the Periotest

method. International Journal of Oral and Maxillofacial Implants,

10, 43.

Correspondence: Dr Robert Haas, Department of Oral Surgery,

School of Dentistry of the University of Vienna, Wahringerstraße

25a, A-1090 Vienna, Austria.

Documents

Experimental study of the damping behaviour of IMZ implants