Analysis of stress on a fixed partial denture with a blade-vent implant abutment Noriaki Takahashi, D.D.S.,” Tetsuya Kitagami, Tomio Komori, D.D.S., Ph.D.*** Osaka Dental University,
D.D.S., Ph.D.,**. and
Osaka, Japan
D
ental implants are being used more frequently, with many histologic studies having been reported,‘-’ but only a few studies have been made that deal with physical problems. Yet more importance should be given to investigations dealing with physical forces that stabilize dental implants in a functional state. Tesk and associates’ reported stress distribution in the bone arising from loading on endosteal implants, and Weinstein and associates” reported stress analysis of porous rooted implants. However, there is no literature on stress analysis of dental implants with superstructures. A study of stress distribution of dental implants imbedded in the bone is described, with special reference to the model mandibular posterior fixed partial denture constructed on a natural tooth and a blade-vent implant abutment. The results were compared with the findings of a fixed partial denture constructed on two natural tooth abutments. A finite element method was employed for a stress analysis. This method was invented to analyze aeronautical structures in 1956,” and it has been a part of many reports about mechanical problems in dental restorations.
tium were based on the previous literature.‘.” The thickness of the periodontium was 0.4 mm at the cervical part, 0.2 mm at the mid part, and 0,25-0.30 mm at the apical part. The thickness of the periimplantium was 0.4 mm. It was assumed that the bone was isotropic and homogeneous. A finite element model of the fixed partial denture constructed on the second premolar and implant abutments consisted of 428 triangular elements and 259 nodal points (implant fixed partial denture) (Fig. 1). A model of the fixed partial denture constructed on the second premolar and the second molar abutments consisted of 342 triangular elements and 212 nodal points (natural tooth fixed partial denture) (Fig. 2). The physical properties of each material, based on the previous literature, are given in Table I.“‘-” It was considered that the peripheral lines of the bone were fixed for support. A vertical load and an inclined load 45 degrees distal to the vertical axis were created at the pontic with a 1 kg weight. Deflections and stresses under each condition were computed mathematically with a two-dimensional finite element method.
MATERIALS
RESULTS
AND METHODS
A blade-vent implant was imbedded at the site of the mandibular second molar, and a fixed partial denture was constructed on the second premolar and the molar implant abutments. As a control a fixed partial denture was constructed on the second premolar and the second molar; each pontic was a sanitary type. The size of the abutment tooth and the thickness of the periodontium and periimplan*Senior, Graduate School of Osaka Dental University. **Assistant Professor, Department of Prosthodontics. ***Professor, Department of Prosthodontics.
186
AUGUST
1978
VOLUME
40
NUMBER
2
The deffection field of the implant fixed partial denture under the vertical load is seen in Fig. 3. The fixed partial denture unit was depressed by loading. A principal stress distribution under the same eondition is shown in Fig. 4. Stress concentration was markedly found in the pontic, at the implant neck, and at the mesial and distal parts of the premolar retainer. Stresses below 0.2 kg/mm2 were omitted in all principal stress distribution figures. The deflection field of the natural tooth fixed partial denture under the vertical load is seen in Fig. 5. The fixed partial denture unit was depressed by
0022-3913/78/024M)1~~.~/OQ
1978 The C. V. Mosty
Co.
STRESS
ANALYSIS
ON
BLADE-VENT
ABUTMENT
Fig. 1. Mathematical model of a fixed partial denture constructed on the secondpremolar and implant abutments (implant fixed partial denture). Triangular elements,428; nodal points, 259.
of a fixed partial denture constructed oh the second premolar and second molar abutments (natural tooth fixed partial denture). Triangular elements,324; nodal points, 212.
‘\ ’ VI
-------
UNLOADED LOADED
Fig. 3. Deflection field of an implant fixed
partial
denture under vertical load.
Fig. 2. Mathematical model
loading. Fig. 6 shows a principal stressdistribution under that samecondition. Stressconcentration was markedly found in the pontic, at the mesial and distal parts of the premolar retainer, and at the mesial part of the posterior retainer. Higher stresses were induced in the premolar abutment than in the posterior abutment. The deflection field of the implant fixed partial denture under the inclined load is shown in Fig. 7. Following rotational movement of the implant, the fixed partial denture unit was moved along the loading direction and the distal shoulder of the implant was elevated. A principal stressdistribution under that condition is seen in Fig. 8. Stress concentration was markedly found in the pontic, at the implant neck, and at the mesial and distal parts of the premolar retainer. The deflection field of the natural tooth restoration under the inclined load is depicted in Fig. 9. The
THE
JOURNAL
OF FROSTHETJC
DENTISTRY
Fig. 4. Principal stressdistribution of an implant fixed partial denture under vertical load (stressesbelow 0.2 kg/
mm2were omitted).
Table I. Physical properties of each material FObSOI?‘S
M&&d Implant metal Casting metal Bone Dentin Periodontium Periimplantium
Y4l&S
“)
rath,
2oooo.00
0.33
9500.00
0.33
2oc!o.00
0.30 0.30
1200.00 1.00
0.45
1.00
0.45
fixed partial denture unit was moved along the loading direction. Fig. 10 shows a principal stress distribution under the same condition, Stress was markedly concentrated in the pontic, the me&al and distal parts of the premolar retainer, and the mesial part of the posterior retainer. Higher stresseswere induced in the premolar abutments than in the posterior abutment.
187
TAKAHASHI,
\ U\ I
-------
Fig. 6. Principal stress distribution fixed partial denture under vertical 0.2 kg/mm2 were omitted).
of a natural tooth load (stresses below
stress: It is f&wed by the shearing-strain energy and given by following formula: Equivalent stress = J(S: - S, S, + S:) where S, = maximum principal stress and S, = minimum principal stress.
188
KOMORI
implant
fixed
partial
tooth fixed partial
Table II shows absolute quantities of deflection at five reference points under each condition, i.e., the premolar cusp, the center of the premolar cervix, the apex of the premolar, and the central fossa of the posterior retainer. The implant restoration revealed less deflection than the natural tooth restoration in the vertical and inclined load. Table III shows equivalent stresses* at the surrounding bone around the premolar under each
*Equidmt theory
AND
UNLOADED LOADED
Fig. 7. Deflection field of an denture under inclined load. Fig. 5. Deflection field of a natural denture under vertical load.
KITAGAMI,
Fig. 8. Principal stress distribution of an implant fixed partial denture under inclined load (stresses below 0.2 kg/ mm’ were omitted). condition. The surrounding bone was divided into three parts-the mesial, apical, and distal. Equivalent stresses placed on the implant restoration tended to be less than those placed on the natural tooth restoration. This trend was found in the vertical and inclined loads at each part of the surrounding bone. Table IV shows equivalent stresses at the surrounding bone around the posterior abutment under each condition (dotted area in Fig. 11). The surrounding bone was divided into three parts-the mesial, apical, and distal parts. In the apical part equivalent stresses placed on the implant abutment were less than those placed on the natural tooth abutment. But in the mesial and distal parts of the bone, as well as the total bone, equivalent stresses were higher than those placed on the natural tooth
:
AUGUST
1978
VOLUME
40
NUMBER
2
STRESS
ANALYSIS
ON
BLADE-VENT
ABUTMENT
Fig. 9. Deflection field of a natural denture under inclined load.
tooth fixed partial
Fig. 10. Principal stress distribution fixed partial denture under inclined 0.2 kg/mm? were omitted).
Table II. Quantities
at the
Table III. Equivalent
reference
points
of deflection (pm)
bone around Inclined load
Vertical load Reference points Bicuspid cusp Center of biscuspid cervix Apex of bicuspid Center of pontic Central fossa of posterior retainer
Natural posterior abutment
Implant posterior abutment
Natural posterior abutment
Implant posterior abutment
Areas of surrounding bone
4.4
3.2
5.2
4.7
3.8 3.5 8.3
3.5 2.8 6.3
6.2 2.1 7.0
5.6 2.0 6.3
Mesial part Apical part Distal part Total
6.7
3.6
6.1
5.1
DISCUSSION In previous reports 13. ‘-I stresses and deflections of a blade-vent implant without superstructures were studied and some results obtained about the basic behavior of an implant under loading. However, it is clinically necessary to construct superstructures, e.g., fixed partial dentures on an implant abutment. When a fixed partial denture is constructed on a root implant and natural tooth abutments it is important to investigate stresses induced in the surrounding bone supporting an implant fixed partial denture as
OF PROSTHETIC
DENTISTRY
stresses at the surrounding the premolar (kg/mm’) Inclined load
Vertical load
abutment; such findings were found with both the vertical and inclined loads. These results indicated that stress became higher around the posterior abutment and lower around the premolar abutment in the implant restoration as compared to the natural tooth restoration.
THE JOURNAL
of a natural tooth load (stresses below
Natural posterior
Implant poswior
Natural posterior
dw&ment abutment 3.748 0.2400 0.220 4.208
2.786 0.196 0.201 3.183
Implant posterior
t abutarent 3.123 0.171 0.343 3.637
2.789 0.160 0.130 3.259
compared to stresses produced with a conventional fixed partial denture constructed OR natural tooth abutments. In this study the physical properties of materials given in Table I were used. Only a few studies about the periodontium and periimplantium have been reported from a physical viewpoint, while there have been many such reports about other materials. It is necessary to consider the physical properties of the periodontium and periimplantium in relation to their mechanical behavior.‘” The fixed partial dentures were loaded at the center of the pontic with a 1 kg weight. It is possible to proportionally calculate deflections and stresses under any magnitudes of load because this stress analysis was made within the proportional limit. Therefore it was suggested that the results obtained be qualitatively reviewed and that a quantitative review be avoided. From Table II it is obvious that deflections of the
189
TAKAHASHI,
KITAGAMI,
AND
KOMOKI
Table IV. Equivalent bone around
stresses at the surrounding the posterior abutment (kg/mm’) Vertical
Areas of surrounding bone Mesial part Bottom Distal part Total
Fig, 11. Surrounding bone for comparison of stresses under each condition (dotted area in Fig. 11). The left side of the model was omitted. implant fixed partial denture were less than those of the natural tooth fixed partial denture in each loading. It was suggested that these findings might be caused by the wide base of a blade-vent implant. But a more advanced three-dimensional analysis is desirable at this point because the thickness of a blade implant greatly differs from that of the natural tooth. Regarding Tables II and III, equivalent stresses induced in the surrounding bone became higher around the posterior abutment and became lower around the premolar abutment in the implant fixed partial denture than in the natural tooth fixed partial denture. Therefore it was suggested that occlusal forces have to be more concentrated on the premolar abutment in the implant restoration to relieve stress in the bone around the implant abutment. It is recommended that two premolar abutments be used and the occlusal contacts of a posterior retainer be reduced.
inclined
load
Natural posterior abutment
Implant posterior abutment
Natural posterior abutment
Implant posterior abutment
0.090 0.861 0.229 1.180
0.436 0.665 0.490 1.591
0.098 0.406 0.107 0.611
0.245 0.304 0.236 0.875
pontic and the mesial and distal parts of the premolar retainer in both restorations and the implant neck in the implant fixed partial denture. 3. In the implant fixed partial denture, stresses induced in the surrounding bone became higher around the posterior abutment and became lower around the premolar retainer than the stresses produced with the natural tooth fixed partial denture. 4. Therefore it was suggested that, to relieve stress to the surrounding bone around the implant abutment, occlusal forces loaded to the implant fixed partial denture have to be more concentrated on the premolar abutment than do forces loaded to the natural tooth fixed partial denture.
REFERENCES 1.
Bodine, R. L., Melrose, R. J., and Grenoble, D. E.: Longterm implant denture histology and comparison with previous reports. J PROSTHET DENT 35:665, 1976.
Piliero, S. J., Schnitman, P., Pentel, L., Cranin, A. N., and Dennison, ‘P. A.: Histopathology of oral endosteal metallic implants in dogs. J Dent Res 52:1117, 1973. 3. Peters, W. J., and Jackson, R. W.: Reaction of bone to 2.
4
CONCLUSION Using a two-dimensional finite element method, a study was made that compared the behavior of a model mandibular posterior fixed partial denture constructed on the second premolar abutment and a blade-vent implant imbedded at the site of the second molar with the behavior of a fixed partial denture constructed on the second premolar and second molar abutments. The following were the results: 1. Deflections of the implant fixed partial denture were less than those of the natural tooth fixed partial denture in vertical and inclined loads. 2. Stress concentration was markedly found in the
load
5
6
7.
8.
9. 18.
implanted materials. Oral Sci Rev 5:56, 1974. Tesk, J. A., and Widera, 0.: Stress distribution in bone arising from loading on endosteal dental implants. J Biomed Mater Res 4:251, 1973. Weinstein, A. M., Klawitter, J. J., Anand, S. C., Scheussler, R.: Stress analysis of porous rooted dental implants. J Dent Res 55:772, 1976. Turner, M. J., Clough, R. W., Martin, H. C., and Topp, I,. J.: Stiffness and deflection analysis of complex structures. J Aero Sci 23:805, 1956. Picton, D. C. A., Johns, R. B., Wills, D. J., and Davies, W. I. R.: The relationship between the mechanisms of tooth and implant support. Oral Sci Reviews 5:3, 1974. Linkow, L. I., Chercheve, R., and Jones, M.: Theories and Techniques of Oral Implantology. St. Louis, 1970, The C. V. Mosby Company, pp 81-133. Fujita, K., and Kirino, T.: Oral Anatomy. Tokyo, 1967, Kanehara Publishing Company, pp 60-62, 74-87. Stanford, J. W., Weigel, K. V., Paffenbarger, G. C., and Sweeney, W. T.: Compressive properties of hard tooth tissues
AUGUST1978
VOLUME40
NUMBER2
STRESS
11.
12. 13.
14.
ANALYSIS
ON BLADE-VENT
ABUTMENT
M.,
and some restorative materials. J Am Dent Assoc 60:746, 1960. Howen, R. I.., and Rodriguez, M. S.: Tensile strength and modulus of elasticity of tooth structure and several restorative materials. J Am Dent ALVOC 64:378, 1962. Smith. 1). C.: Materials used for construction and fixation of implants. Oral Sci Rev 523, 1974. Komori, T., Kitagami, ‘I‘.. Takahashi, N., Tsuji, I., Amari, M., Taniguchi, T., and Otani, M.: Stress analysis of blade implant. J Osaka Odont Sot 39:810, 1976. Komori, T., Kitagami, T., Takahashi, N., Suese, K., Amari,
ARTICLES The &ect
of oral hygiene
D.D.S., A. J. Hickey, D.M.D.,
Obturator-overdentures MacEntee,
Hlstul@c waveform
on stomatitis
retained
K.,
and
Suginaka,
DR. N~RIAKI
TAKAHASEU
HIGASHI-KU OSAKA,
JAPAN
ISSUES in patients
receiving
cancer
and J. B. Drane, D.D.S.
by nonrigid
of electrosurgery
Facial pains and anxiety
Maury
attachments
with
varying
frequency
and
levels:
Considerations
for treatment
D.D.S., James A. Lipton, D.D.S., Pamela B. Lund, M.A., Ph.D., and Terry Blank, D.D.S.
dentistry:
Mechanical
The problem
properties
of tissue conditioners.
Part II:
crown
John W. McLean, O.B.E., D.Sc., M.D.%, L.D.S., Edmund Howard Bruggers, D.D.S., and David B. Lynn, D.D.S.
OF PROSTHETK
Creep characteristics
D.D.Sc., and J. B. Moser, M.S., Ph.D.
A new me&ceramic
JOURNAL
D.D.S.,
Massler, D.D.S., M.S.
J. A. McCarthy,
THE
of
l-47 KYCBASHI
W. L. Maness, D.D.S., MS., F. W. Rober, B.S., R. E. Clark, Ph.D., E. Cataldo, D. Riis, D.M.D., and A. W. Haddad, D.M.D.
Geriatric
Stress analysis
L.D.S.
evaluation
Joseph J. Marbach, Frances Delahanty,
K.:
Rcprmt requests to.
TO APPEAR IN FUTURE
S. F. Lindquist,
Michael
15.
Sakaguchi,
blade implant. J Osaka Odont Sot 4&l 12: 1977. Huang, H. K., and Ledley, R. S.: Numerical experiments with a linear force-displacement tooth model. ,I Dent Res 48:X?, 1969.
DENTISTRY
E. Jeansonne,
D.D.S.,
191
D.D.S., Ph.D.,**. and
Osaka, Japan
D
ental implants are being used more frequently, with many histologic studies having been reported,‘-’ but only a few studies have been made that deal with physical problems. Yet more importance should be given to investigations dealing with physical forces that stabilize dental implants in a functional state. Tesk and associates’ reported stress distribution in the bone arising from loading on endosteal implants, and Weinstein and associates” reported stress analysis of porous rooted implants. However, there is no literature on stress analysis of dental implants with superstructures. A study of stress distribution of dental implants imbedded in the bone is described, with special reference to the model mandibular posterior fixed partial denture constructed on a natural tooth and a blade-vent implant abutment. The results were compared with the findings of a fixed partial denture constructed on two natural tooth abutments. A finite element method was employed for a stress analysis. This method was invented to analyze aeronautical structures in 1956,” and it has been a part of many reports about mechanical problems in dental restorations.
tium were based on the previous literature.‘.” The thickness of the periodontium was 0.4 mm at the cervical part, 0.2 mm at the mid part, and 0,25-0.30 mm at the apical part. The thickness of the periimplantium was 0.4 mm. It was assumed that the bone was isotropic and homogeneous. A finite element model of the fixed partial denture constructed on the second premolar and implant abutments consisted of 428 triangular elements and 259 nodal points (implant fixed partial denture) (Fig. 1). A model of the fixed partial denture constructed on the second premolar and the second molar abutments consisted of 342 triangular elements and 212 nodal points (natural tooth fixed partial denture) (Fig. 2). The physical properties of each material, based on the previous literature, are given in Table I.“‘-” It was considered that the peripheral lines of the bone were fixed for support. A vertical load and an inclined load 45 degrees distal to the vertical axis were created at the pontic with a 1 kg weight. Deflections and stresses under each condition were computed mathematically with a two-dimensional finite element method.
MATERIALS
RESULTS
AND METHODS
A blade-vent implant was imbedded at the site of the mandibular second molar, and a fixed partial denture was constructed on the second premolar and the molar implant abutments. As a control a fixed partial denture was constructed on the second premolar and the second molar; each pontic was a sanitary type. The size of the abutment tooth and the thickness of the periodontium and periimplan*Senior, Graduate School of Osaka Dental University. **Assistant Professor, Department of Prosthodontics. ***Professor, Department of Prosthodontics.
186
AUGUST
1978
VOLUME
40
NUMBER
2
The deffection field of the implant fixed partial denture under the vertical load is seen in Fig. 3. The fixed partial denture unit was depressed by loading. A principal stress distribution under the same eondition is shown in Fig. 4. Stress concentration was markedly found in the pontic, at the implant neck, and at the mesial and distal parts of the premolar retainer. Stresses below 0.2 kg/mm2 were omitted in all principal stress distribution figures. The deflection field of the natural tooth fixed partial denture under the vertical load is seen in Fig. 5. The fixed partial denture unit was depressed by
0022-3913/78/024M)1~~.~/OQ
1978 The C. V. Mosty
Co.
STRESS
ANALYSIS
ON
BLADE-VENT
ABUTMENT
Fig. 1. Mathematical model of a fixed partial denture constructed on the secondpremolar and implant abutments (implant fixed partial denture). Triangular elements,428; nodal points, 259.
of a fixed partial denture constructed oh the second premolar and second molar abutments (natural tooth fixed partial denture). Triangular elements,324; nodal points, 212.
‘\ ’ VI
-------
UNLOADED LOADED
Fig. 3. Deflection field of an implant fixed
partial
denture under vertical load.
Fig. 2. Mathematical model
loading. Fig. 6 shows a principal stressdistribution under that samecondition. Stressconcentration was markedly found in the pontic, at the mesial and distal parts of the premolar retainer, and at the mesial part of the posterior retainer. Higher stresses were induced in the premolar abutment than in the posterior abutment. The deflection field of the implant fixed partial denture under the inclined load is shown in Fig. 7. Following rotational movement of the implant, the fixed partial denture unit was moved along the loading direction and the distal shoulder of the implant was elevated. A principal stressdistribution under that condition is seen in Fig. 8. Stress concentration was markedly found in the pontic, at the implant neck, and at the mesial and distal parts of the premolar retainer. The deflection field of the natural tooth restoration under the inclined load is depicted in Fig. 9. The
THE
JOURNAL
OF FROSTHETJC
DENTISTRY
Fig. 4. Principal stressdistribution of an implant fixed partial denture under vertical load (stressesbelow 0.2 kg/
mm2were omitted).
Table I. Physical properties of each material FObSOI?‘S
M&&d Implant metal Casting metal Bone Dentin Periodontium Periimplantium
Y4l&S
“)
rath,
2oooo.00
0.33
9500.00
0.33
2oc!o.00
0.30 0.30
1200.00 1.00
0.45
1.00
0.45
fixed partial denture unit was moved along the loading direction. Fig. 10 shows a principal stress distribution under the same condition, Stress was markedly concentrated in the pontic, the me&al and distal parts of the premolar retainer, and the mesial part of the posterior retainer. Higher stresseswere induced in the premolar abutments than in the posterior abutment.
187
TAKAHASHI,
\ U\ I
-------
Fig. 6. Principal stress distribution fixed partial denture under vertical 0.2 kg/mm2 were omitted).
of a natural tooth load (stresses below
stress: It is f&wed by the shearing-strain energy and given by following formula: Equivalent stress = J(S: - S, S, + S:) where S, = maximum principal stress and S, = minimum principal stress.
188
KOMORI
implant
fixed
partial
tooth fixed partial
Table II shows absolute quantities of deflection at five reference points under each condition, i.e., the premolar cusp, the center of the premolar cervix, the apex of the premolar, and the central fossa of the posterior retainer. The implant restoration revealed less deflection than the natural tooth restoration in the vertical and inclined load. Table III shows equivalent stresses* at the surrounding bone around the premolar under each
*Equidmt theory
AND
UNLOADED LOADED
Fig. 7. Deflection field of an denture under inclined load. Fig. 5. Deflection field of a natural denture under vertical load.
KITAGAMI,
Fig. 8. Principal stress distribution of an implant fixed partial denture under inclined load (stresses below 0.2 kg/ mm’ were omitted). condition. The surrounding bone was divided into three parts-the mesial, apical, and distal. Equivalent stresses placed on the implant restoration tended to be less than those placed on the natural tooth restoration. This trend was found in the vertical and inclined loads at each part of the surrounding bone. Table IV shows equivalent stresses at the surrounding bone around the posterior abutment under each condition (dotted area in Fig. 11). The surrounding bone was divided into three parts-the mesial, apical, and distal parts. In the apical part equivalent stresses placed on the implant abutment were less than those placed on the natural tooth abutment. But in the mesial and distal parts of the bone, as well as the total bone, equivalent stresses were higher than those placed on the natural tooth
:
AUGUST
1978
VOLUME
40
NUMBER
2
STRESS
ANALYSIS
ON
BLADE-VENT
ABUTMENT
Fig. 9. Deflection field of a natural denture under inclined load.
tooth fixed partial
Fig. 10. Principal stress distribution fixed partial denture under inclined 0.2 kg/mm? were omitted).
Table II. Quantities
at the
Table III. Equivalent
reference
points
of deflection (pm)
bone around Inclined load
Vertical load Reference points Bicuspid cusp Center of biscuspid cervix Apex of bicuspid Center of pontic Central fossa of posterior retainer
Natural posterior abutment
Implant posterior abutment
Natural posterior abutment
Implant posterior abutment
Areas of surrounding bone
4.4
3.2
5.2
4.7
3.8 3.5 8.3
3.5 2.8 6.3
6.2 2.1 7.0
5.6 2.0 6.3
Mesial part Apical part Distal part Total
6.7
3.6
6.1
5.1
DISCUSSION In previous reports 13. ‘-I stresses and deflections of a blade-vent implant without superstructures were studied and some results obtained about the basic behavior of an implant under loading. However, it is clinically necessary to construct superstructures, e.g., fixed partial dentures on an implant abutment. When a fixed partial denture is constructed on a root implant and natural tooth abutments it is important to investigate stresses induced in the surrounding bone supporting an implant fixed partial denture as
OF PROSTHETIC
DENTISTRY
stresses at the surrounding the premolar (kg/mm’) Inclined load
Vertical load
abutment; such findings were found with both the vertical and inclined loads. These results indicated that stress became higher around the posterior abutment and lower around the premolar abutment in the implant restoration as compared to the natural tooth restoration.
THE JOURNAL
of a natural tooth load (stresses below
Natural posterior
Implant poswior
Natural posterior
dw&ment abutment 3.748 0.2400 0.220 4.208
2.786 0.196 0.201 3.183
Implant posterior
t abutarent 3.123 0.171 0.343 3.637
2.789 0.160 0.130 3.259
compared to stresses produced with a conventional fixed partial denture constructed OR natural tooth abutments. In this study the physical properties of materials given in Table I were used. Only a few studies about the periodontium and periimplantium have been reported from a physical viewpoint, while there have been many such reports about other materials. It is necessary to consider the physical properties of the periodontium and periimplantium in relation to their mechanical behavior.‘” The fixed partial dentures were loaded at the center of the pontic with a 1 kg weight. It is possible to proportionally calculate deflections and stresses under any magnitudes of load because this stress analysis was made within the proportional limit. Therefore it was suggested that the results obtained be qualitatively reviewed and that a quantitative review be avoided. From Table II it is obvious that deflections of the
189
TAKAHASHI,
KITAGAMI,
AND
KOMOKI
Table IV. Equivalent bone around
stresses at the surrounding the posterior abutment (kg/mm’) Vertical
Areas of surrounding bone Mesial part Bottom Distal part Total
Fig, 11. Surrounding bone for comparison of stresses under each condition (dotted area in Fig. 11). The left side of the model was omitted. implant fixed partial denture were less than those of the natural tooth fixed partial denture in each loading. It was suggested that these findings might be caused by the wide base of a blade-vent implant. But a more advanced three-dimensional analysis is desirable at this point because the thickness of a blade implant greatly differs from that of the natural tooth. Regarding Tables II and III, equivalent stresses induced in the surrounding bone became higher around the posterior abutment and became lower around the premolar abutment in the implant fixed partial denture than in the natural tooth fixed partial denture. Therefore it was suggested that occlusal forces have to be more concentrated on the premolar abutment in the implant restoration to relieve stress in the bone around the implant abutment. It is recommended that two premolar abutments be used and the occlusal contacts of a posterior retainer be reduced.
inclined
load
Natural posterior abutment
Implant posterior abutment
Natural posterior abutment
Implant posterior abutment
0.090 0.861 0.229 1.180
0.436 0.665 0.490 1.591
0.098 0.406 0.107 0.611
0.245 0.304 0.236 0.875
pontic and the mesial and distal parts of the premolar retainer in both restorations and the implant neck in the implant fixed partial denture. 3. In the implant fixed partial denture, stresses induced in the surrounding bone became higher around the posterior abutment and became lower around the premolar retainer than the stresses produced with the natural tooth fixed partial denture. 4. Therefore it was suggested that, to relieve stress to the surrounding bone around the implant abutment, occlusal forces loaded to the implant fixed partial denture have to be more concentrated on the premolar abutment than do forces loaded to the natural tooth fixed partial denture.
REFERENCES 1.
Bodine, R. L., Melrose, R. J., and Grenoble, D. E.: Longterm implant denture histology and comparison with previous reports. J PROSTHET DENT 35:665, 1976.
Piliero, S. J., Schnitman, P., Pentel, L., Cranin, A. N., and Dennison, ‘P. A.: Histopathology of oral endosteal metallic implants in dogs. J Dent Res 52:1117, 1973. 3. Peters, W. J., and Jackson, R. W.: Reaction of bone to 2.
4
CONCLUSION Using a two-dimensional finite element method, a study was made that compared the behavior of a model mandibular posterior fixed partial denture constructed on the second premolar abutment and a blade-vent implant imbedded at the site of the second molar with the behavior of a fixed partial denture constructed on the second premolar and second molar abutments. The following were the results: 1. Deflections of the implant fixed partial denture were less than those of the natural tooth fixed partial denture in vertical and inclined loads. 2. Stress concentration was markedly found in the
load
5
6
7.
8.
9. 18.
implanted materials. Oral Sci Rev 5:56, 1974. Tesk, J. A., and Widera, 0.: Stress distribution in bone arising from loading on endosteal dental implants. J Biomed Mater Res 4:251, 1973. Weinstein, A. M., Klawitter, J. J., Anand, S. C., Scheussler, R.: Stress analysis of porous rooted dental implants. J Dent Res 55:772, 1976. Turner, M. J., Clough, R. W., Martin, H. C., and Topp, I,. J.: Stiffness and deflection analysis of complex structures. J Aero Sci 23:805, 1956. Picton, D. C. A., Johns, R. B., Wills, D. J., and Davies, W. I. R.: The relationship between the mechanisms of tooth and implant support. Oral Sci Reviews 5:3, 1974. Linkow, L. I., Chercheve, R., and Jones, M.: Theories and Techniques of Oral Implantology. St. Louis, 1970, The C. V. Mosby Company, pp 81-133. Fujita, K., and Kirino, T.: Oral Anatomy. Tokyo, 1967, Kanehara Publishing Company, pp 60-62, 74-87. Stanford, J. W., Weigel, K. V., Paffenbarger, G. C., and Sweeney, W. T.: Compressive properties of hard tooth tissues
AUGUST1978
VOLUME40
NUMBER2
STRESS
11.
12. 13.
14.
ANALYSIS
ON BLADE-VENT
ABUTMENT
M.,
and some restorative materials. J Am Dent Assoc 60:746, 1960. Howen, R. I.., and Rodriguez, M. S.: Tensile strength and modulus of elasticity of tooth structure and several restorative materials. J Am Dent ALVOC 64:378, 1962. Smith. 1). C.: Materials used for construction and fixation of implants. Oral Sci Rev 523, 1974. Komori, T., Kitagami, ‘I‘.. Takahashi, N., Tsuji, I., Amari, M., Taniguchi, T., and Otani, M.: Stress analysis of blade implant. J Osaka Odont Sot 39:810, 1976. Komori, T., Kitagami, T., Takahashi, N., Suese, K., Amari,
ARTICLES The &ect
of oral hygiene
D.D.S., A. J. Hickey, D.M.D.,
Obturator-overdentures MacEntee,
Hlstul@c waveform
on stomatitis
retained
K.,
and
Suginaka,
DR. N~RIAKI
TAKAHASEU
HIGASHI-KU OSAKA,
JAPAN
ISSUES in patients
receiving
cancer
and J. B. Drane, D.D.S.
by nonrigid
of electrosurgery
Facial pains and anxiety
Maury
attachments
with
varying
frequency
and
levels:
Considerations
for treatment
D.D.S., James A. Lipton, D.D.S., Pamela B. Lund, M.A., Ph.D., and Terry Blank, D.D.S.
dentistry:
Mechanical
The problem
properties
of tissue conditioners.
Part II:
crown
John W. McLean, O.B.E., D.Sc., M.D.%, L.D.S., Edmund Howard Bruggers, D.D.S., and David B. Lynn, D.D.S.
OF PROSTHETK
Creep characteristics
D.D.Sc., and J. B. Moser, M.S., Ph.D.
A new me&ceramic
JOURNAL
D.D.S.,
Massler, D.D.S., M.S.
J. A. McCarthy,
THE
of
l-47 KYCBASHI
W. L. Maness, D.D.S., MS., F. W. Rober, B.S., R. E. Clark, Ph.D., E. Cataldo, D. Riis, D.M.D., and A. W. Haddad, D.M.D.
Geriatric
Stress analysis
L.D.S.
evaluation
Joseph J. Marbach, Frances Delahanty,
K.:
Rcprmt requests to.
TO APPEAR IN FUTURE
S. F. Lindquist,
Michael
15.
Sakaguchi,
blade implant. J Osaka Odont Sot 4&l 12: 1977. Huang, H. K., and Ledley, R. S.: Numerical experiments with a linear force-displacement tooth model. ,I Dent Res 48:X?, 1969.
DENTISTRY
E. Jeansonne,
D.D.S.,
191
