- Email: [email protected]
Biometric design of complete dentures related to residual ridge resorption
EGometric resorption
design of complete
Esa Klemetti, DDS, PhD,a Lippo University of Kuopio, Kuopio, Finland
Lassila,
dentures BDSb
and Veijo
related Lassila,
DDS,
to residual
ridge
PhDc
The aim of this study was to determine whether the location of the incisive papilla, the extent of the alveolar bone remaining on the facial side of the palatal-gingival margin in the canine region, and the height of the palatal vault in the molar region are associated with factors that may affect the volume of the residual ridges in an edentulous maxillae. Results suggest that duration of the edentulousness and skeletal mineral status are important factors in the resorption of the residual ridges in the maxillae. The location of the incisive papilla and the thickness of the ridge on the facial side of the palatal-gingival margin are associated with these two factors. CJ PROSTKET
DENT
199@75:281-4.)
Af
ter extraction of teeth, anatomic changes inevitably take place in the alveolar ridges of the jaws. Biometric guides for the design of complete dentures based on the measurements and publications of Watt and othersld4 have been presented. These authors believed that the incisive papilla and the palatal-gingival margin (the remnant of the gingival margin on the palatal side of the dental arch, which after tooth extractions often remains visible as a cordlike elevation) work as landmarks for estimating the preextraction dimensions of the ridge and they also stated that in the area of the vault in the premolar-molar region there is an area that is not affected by residual ridge resorption (RRR). This study tested whether (1) the location of the incisive papilla, (2) the width of the alveolar bone remaining on the facial side of the palatal-gingival margin in the canine region, or (3) the height of the palatal vault in the molar region is associated with three factors that may affect the volume of the residual ridge in the edentulous maxillae5-7: (1) the duration of edentulousness in the maxillae, (2) skeletal mineral status, and (3) the size of the individual as indicated by the body mass index (BMI).
MATERJAL
AND
MF,THODS
and clinical examinations were conducted on 230 postmenopausal women 48 to 56 (mean 53.3) years old, living in or near Kuopio, Finland. All of these women were participating in a 5year study on osteoporosis and its risk factors and prevention (OSTPRE, University of KuoAnamnestic
aDepartment Dentist, Department of Prosthodontics and Stomatognathic Physiology. ‘Student, Department of Prosthodontics and Stomatognathic Physiology. cProfessor of Dentistry, Department of Prosthodontics and Stomatognathic Physiology. Copyright @ 1996 by The Editorial Council of THE JOURNAL OF PROSTHETICDENTISTRY. OOZZ-3913/96/$5.00 + 0. 10/l/69123
MARCH
1996
1. Occlusal view of plaster cast on which measurements were made in canine region (C@ and molar region (MR). Palatal length from labial edge of incisive papilla to foveolae (FPI was divided into three parts. Fig.
pio and Kuopio University Hospital), and all were edentulous in the maxillae. The location of the incisive papilla was determined from plaster casts of the edentulous maxillae. The subjects were classified into three groups on the basis of the location of the middle of the incisive papilla: (1) clearly on the labial side, (2) on the crest with a margin of 1 mm, or (3) clearly on the palatal side of the crest of the alveolar ridge. The bone width laterally from the palatal-gingival margin was measured in the canine region, which, according to Watt and MacGregor,’ is penetrated by a transverse slice that is tangential to the palatal edge of the incisive papilla (Fig. 1). The difference between the greatest width and the width between the palatal-gingival margins was divided in half to represent the average bone width of one side (Fig. 3. The length of the palate from the anterior edge of the in-
THEJOURNAL,OFPROSTKETICDEIWISTRY
281
THE JOURNAL
OF PROSTRETIC
DENTISTRY
KLEME’lTI,
Table I. Distribution
Trzinsverse
Mean
through the maxilla in the canine region
I
7’6 - L-G B = B8B*‘. Fig. 2. Difference
of total breadth (TB) of maxillae and breadth between lingual gingival margins (L-G B) in canine region (divided by 2) represents labial bone breadth.
cisive papilla to the fovea palatinae was divided into three equal parts. Vault height of the palate was measured in the midline one third the distance anterior from the distal edge of the hard palate (Figs. 1 and 3). The date the last tooth in the maxillae was lost was recorded. The skeletal mineral status of each women was determined on the basis of the bone mineral density in the femoral neck (BMDN) and lumbar regions L2 to L4 (BMDL)’ and on the age of the subject. The mineral status was classified as either better or worse than the mean on the basis of tables for normal BMDN and BMDL values of Finnish women in different age groups (Fig. 4).s Of those two bone mineral density values, the one that belonged to the more advanced osteoporotic group was used. This classification was previously presented in more detail5 The values for BMDN and BMDL were determined by a dual radiographic absorptiometry apparatus (Lunar DPX, Lunar Corp., Madison, Wise.). The body mass index (BMI) of each subject was calculated by dividing the height (in meters) of the subject by the square of her weight (in kilograms). The plaster casts were measured twice, each time by a different researcher. Measurements ofbone width and vault height were recorded within 0.1 to 0.5 mm of accuracy, respectively. Reproducibility of the measurements was excellent. To test the normality of the distribution of the measurements, the Kolmogorov-Smirnov test for accuracy of fit was used, Depending on the type of variables, the Mann-Whitney test, chi square test, or analysis of variance was used to estimate associations between variables.
RESULTS For one test subject measurement of skeletal bone density was not successful. Three subjects did not want to be weighed, and the location of the incisive papilla could not be determined for one subject because the papilla was de-
282
AND LASSILA
of variables
slice
TB
LASSILA,
Duration of edentulousness b-1 Body mass index (m/kgz) Buccal bone breadth (mm) Palatal vault height (mm) Skeletal mineral status lower than mean Skeletal mineral status higher than mean Incisive papilla clearly on anterior side of ridge Incisive papilla on top of ridge Incisive papilla clearly on palatal side of ridge
SD
N
29.9
7.4
230
26.4 1.5 12.5
4.1 1.1 2x5 121
227 227 229
108 26 118 55
formed and almost invisible. For three subjects it was impossible to discover the location of the palatal-gingival margin, and for one subject measurement of the height of the palatal vault was not successful because of an extensive defect of the ridge in the molar region. The distribution of variables is presented in Table I. Location of the incisive papilla was significantly dependent on the duration of the edentulousness in the maxillae. The longer the teeth had been absent, the more anteriorly the papilla was situated because of the flatness. The thickness of the remaining facial bone in the canine region was also significantly dependent on the duration of the edentulousness (Table II). The facial bone also depended on skeletal mineral status. For those women whose bone mineral level was below the mean, the residual ridges in the canine region of the maxillae were significantly thinner (Table II). The height of the palatal vault did not correlate with the length of time of edentulousness, skeletal mineral status, or BMI. None of the variables of the maxillae were associated with BMI (Table II).
DISCUSSION After the teeth are extracted, resorption is most rapid in the labial and buccal bone.4 According to Watt and MacGrego6 the palatal-gingival margin moves outward during the edentulous years so that it lies facially and superiorly to the position occupied by palatal-gingival margins in the dentulous mouth. The anterior movement of the incisive papilla caused by progressive RRR also originates from this flattening. However, in an edentulous jaw the incisive papilla and the palatal-gingival margin represent anatomic formations that, for the dentate ridge, are situated near the ridge crest. In addition, the size of the jaws varies. One millimeter of bone loss in a wide jaw may indicate something quite
VOLUME
75
NUMBER
3
RLEME’ITI,
LASS&$
THE JOURNAL
AND LASSILA
Ridge
\
Fig.
3. Measurement
of vault
height
Table II. Dependencies between changes in maxillae and variables associated with residual ridge resorption Buccal Location of incisive
papilla
Duration of edentulousness in maxilla
p = 0.001
z=-3.27 (M-W)
Skeletal
mineral
status
NS
bone left
mass in canine lX?giOTl
p = 0.003 z= -2.99
of
mass
index
M - W, Mann-Whitney
NS nonparametric
1996
Vault height in molar region
values for BMD spine in Finnish
women
height in molar region
NS
(M-W) p = 0.028
NS
NS
test; NS, nonsignificant
o.g-.
NS
.
_.
0.7 -7 20
_
_
_.
_
30
_
.
40
probability.
different for a narrow alveolar ridge. On the other hand, clinically significant osteoporosis is more common in short childless women with low weights than in tall heavy women who have had children.’ This finding is also associated with the alveolar ridges; subjects with small jaws are more disposed to severe RRR. In this study the weight of the subjects was not considered in the results of bone mineral density measurements in the femur and vertebra. When dual-energy x-ray absorptiometry is used to measure bone mineral density, the thicker the bone, the greater is the measured density.g However, when the weight factor is not considered, the differences in bone loss become clearer because women with low weight and small bones are more predisposed to bone loss. In this study the BMI did not correlate with landmarks of ridge resorption and thus demonstrated that the positive association between skeletal mineral status and bone width was not caused by the size of the subjects. When teeth are extracted in the canine region, there is always a danger of loss of the labial cortical plate. In this
MARCH
top
region.
Normal lumbar
the
DENTISTRY
Vault
z =-2.20 (M-W Body
in molar
OF PROSTHETIC
_
.
_
_
_
50
_
60
70
60
Age
of
Normal femoral
the
values for BMD neck in Finnish
women
d-2 _.__..._____.._-..__...__
0.7
30
20
40
50
60
70
I 80
Age
Krdger
et
al.
(1992)
Fig. 4. Normal values for bone mineral density (B&ID) in femoral collum and lumbar spine among Finnish women, on which classification into two bone loss groups was based.
283
THE JOURNAL
OF PROSTHETIC
DENTISTRY
KLEMElTI,
study neither this bone loss nor differences in the size ofthe subjects (Table II) affected the influence of time and skeletal bone mineral density on the amount of bone in that region. In the canine region it is usually easy to determine the most prominent part of the ridge. The positive correlation between bone width and the time elapsed since the last extractions in the maxillae was expected. It was reported previously that in the regions of the jaws where RRR is clearly taking place and muscle function is not able to provide the bony tissues with enough stimulation the amount of lost bone depends on the length of time the jaw has been edentulous.5$ i” The bone width was also significantly dependent on the mineral status of the skeleton, which has been confirmed by previous reports. 5-7This correlation was not due to the differences in the sizes of the subjects because BMI did not correlate with the variables in the maxillae. According to the findings of this study the palatal-gingival margin can be used as a reference when the resorption of the facial ridge is measured. Measurement of horizontal ridge resorption in the molar region is difficult. In these subjects the slope of the buccal bone in the molar region was gradual enough to destroy all undercuts. In the agrarian areas of middle Finland only a few decades ago it was almost a tradition to extract teeth during young adulthood. Often the surgeon was not a dentist, and much alveolar bone was destroyed. Approximately half the subjects in this study had lost all maxillary teeth before reaching the age of 30 years. The molar teeth were probably lost first from caries. Therefore most subjects had been edentulous for more than 20 years, and almost all the resorption in the molar region had already occurred. The alveolar ridges in the molar regions of the sample in this study may be called “terminal stage ridges,” and the differences in the height of the palatal vault were usually the result of variations in the original anatomic form of the palatal vault. Therefore
Availability
LASSD&
AND LASSILA
the height of the vault was not associated with any other variables.
CONCLUSIONS In conclusion, this study demonstrated that duration of edentulousness and skeletal mineral status were important factors in the resorption of the residual ridges in the maxillae. The location of the incisive papilla and the thickness of the ridge on the labial side of the palatal-gingival margin are both associated with these factors ofRRR. REFERENCES 1. Watt DM, MacGregor AR. Designing complete dentures. 2nd ed. Bristol, United Kingdom: Wright, 1986. 2. Watt DM, Durran CM, Adenubi JO. Biometric guides to the design of complete maxillary dentures. Dent Magn Oral Top 1967;84:109-13, 3. Likeman PR, Watt DM. Morphological changes in the maxillary denture bearing area. Br Dent J 1974;136;500-3. 4. Watt DM, Likeman PR. Morphological changes in the denture bearing areas following the extraction of maxillary teeth. Br Dent J 1974; 136:225-35. 5. Klemetti E, Vainio P. Effect of bone mineral density in skeleton and mandible on extractions of teeth and clinical alveolar height. J PROSTITET DENT 1993;70:21-5.
6. Von Wowern N, Hjorting-Hansen E. The mandibular bone content in relation to vestibulolingual sulcoplasty: a Z-year PROSTHET DENT 1991;65:804-S. 7. Kribbs PJ, Chestnut CH, Ott SM, Kilcoyne RF, Relationship mandibular and skeletal hone in an osteoporotic population,
mineral study. J between J PROS-
THET DENT 1989;6%703-7.
8. Kroger H, Heikkinen J, Laitinen, Kotaniemi A. Dual-energy x-ray absorptiometry in normal women: a cross-sectional study of 71’7 Finnish volunteers. Osteoporos Int 1992;2:135-40. 9, Krijger H, Kotaniemi A, Vainio P, Alhava E. Bone densitometry of the spine and femur in children by dual-energy x-ray absorptiometry. Bone Miner 1992;17:75-85. 10, KIemetti E, Vainio P, La&a V. Mineral density in the mandibles of partially and totally edentate women. Stand J Dent Res 1994;102z64-7. Reprint
requests
to:
DR. ESA KLEMETTI DEPAFLTNWT OF PROSTHETICS AND STOMATOGNATHICF'HYSIOLOGY UNIVERSITY OFKUOPIO P.O.B. 1627 SF-70211, KUOPIO FINLAND
of JOURNAL Back
Issues
As a service to our subscribers, copies of back issues of THE JOURNAL OF PROSTHETIC for the preceding 5 years are maintained and are available for purchase from the publisher, Mosby, at a cost of $9.00 per issue. The following quantity discounts are available: 25% off on quantities of 12 to 23, and one third off on quantities of 24 or more. Please write to Mosby, Subscription Services, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, or call (800)453-4351 or (314)453-4351 for information on availability of particular issues. If unavailable from the publisher, photocopies of complete issues are available from University Microfilms International, 300 N. Zeeb Rd., Ann Arbor, MI 48106, (313)761-4700. DENTISTRY
284
VOLUME
7'5 NLJMRER3
design of complete
Esa Klemetti, DDS, PhD,a Lippo University of Kuopio, Kuopio, Finland
Lassila,
dentures BDSb
and Veijo
related Lassila,
DDS,
to residual
ridge
PhDc
The aim of this study was to determine whether the location of the incisive papilla, the extent of the alveolar bone remaining on the facial side of the palatal-gingival margin in the canine region, and the height of the palatal vault in the molar region are associated with factors that may affect the volume of the residual ridges in an edentulous maxillae. Results suggest that duration of the edentulousness and skeletal mineral status are important factors in the resorption of the residual ridges in the maxillae. The location of the incisive papilla and the thickness of the ridge on the facial side of the palatal-gingival margin are associated with these two factors. CJ PROSTKET
DENT
199@75:281-4.)
Af
ter extraction of teeth, anatomic changes inevitably take place in the alveolar ridges of the jaws. Biometric guides for the design of complete dentures based on the measurements and publications of Watt and othersld4 have been presented. These authors believed that the incisive papilla and the palatal-gingival margin (the remnant of the gingival margin on the palatal side of the dental arch, which after tooth extractions often remains visible as a cordlike elevation) work as landmarks for estimating the preextraction dimensions of the ridge and they also stated that in the area of the vault in the premolar-molar region there is an area that is not affected by residual ridge resorption (RRR). This study tested whether (1) the location of the incisive papilla, (2) the width of the alveolar bone remaining on the facial side of the palatal-gingival margin in the canine region, or (3) the height of the palatal vault in the molar region is associated with three factors that may affect the volume of the residual ridge in the edentulous maxillae5-7: (1) the duration of edentulousness in the maxillae, (2) skeletal mineral status, and (3) the size of the individual as indicated by the body mass index (BMI).
MATERJAL
AND
MF,THODS
and clinical examinations were conducted on 230 postmenopausal women 48 to 56 (mean 53.3) years old, living in or near Kuopio, Finland. All of these women were participating in a 5year study on osteoporosis and its risk factors and prevention (OSTPRE, University of KuoAnamnestic
aDepartment Dentist, Department of Prosthodontics and Stomatognathic Physiology. ‘Student, Department of Prosthodontics and Stomatognathic Physiology. cProfessor of Dentistry, Department of Prosthodontics and Stomatognathic Physiology. Copyright @ 1996 by The Editorial Council of THE JOURNAL OF PROSTHETICDENTISTRY. OOZZ-3913/96/$5.00 + 0. 10/l/69123
MARCH
1996
1. Occlusal view of plaster cast on which measurements were made in canine region (C@ and molar region (MR). Palatal length from labial edge of incisive papilla to foveolae (FPI was divided into three parts. Fig.
pio and Kuopio University Hospital), and all were edentulous in the maxillae. The location of the incisive papilla was determined from plaster casts of the edentulous maxillae. The subjects were classified into three groups on the basis of the location of the middle of the incisive papilla: (1) clearly on the labial side, (2) on the crest with a margin of 1 mm, or (3) clearly on the palatal side of the crest of the alveolar ridge. The bone width laterally from the palatal-gingival margin was measured in the canine region, which, according to Watt and MacGregor,’ is penetrated by a transverse slice that is tangential to the palatal edge of the incisive papilla (Fig. 1). The difference between the greatest width and the width between the palatal-gingival margins was divided in half to represent the average bone width of one side (Fig. 3. The length of the palate from the anterior edge of the in-
THEJOURNAL,OFPROSTKETICDEIWISTRY
281
THE JOURNAL
OF PROSTRETIC
DENTISTRY
KLEME’lTI,
Table I. Distribution
Trzinsverse
Mean
through the maxilla in the canine region
I
7’6 - L-G B = B8B*‘. Fig. 2. Difference
of total breadth (TB) of maxillae and breadth between lingual gingival margins (L-G B) in canine region (divided by 2) represents labial bone breadth.
cisive papilla to the fovea palatinae was divided into three equal parts. Vault height of the palate was measured in the midline one third the distance anterior from the distal edge of the hard palate (Figs. 1 and 3). The date the last tooth in the maxillae was lost was recorded. The skeletal mineral status of each women was determined on the basis of the bone mineral density in the femoral neck (BMDN) and lumbar regions L2 to L4 (BMDL)’ and on the age of the subject. The mineral status was classified as either better or worse than the mean on the basis of tables for normal BMDN and BMDL values of Finnish women in different age groups (Fig. 4).s Of those two bone mineral density values, the one that belonged to the more advanced osteoporotic group was used. This classification was previously presented in more detail5 The values for BMDN and BMDL were determined by a dual radiographic absorptiometry apparatus (Lunar DPX, Lunar Corp., Madison, Wise.). The body mass index (BMI) of each subject was calculated by dividing the height (in meters) of the subject by the square of her weight (in kilograms). The plaster casts were measured twice, each time by a different researcher. Measurements ofbone width and vault height were recorded within 0.1 to 0.5 mm of accuracy, respectively. Reproducibility of the measurements was excellent. To test the normality of the distribution of the measurements, the Kolmogorov-Smirnov test for accuracy of fit was used, Depending on the type of variables, the Mann-Whitney test, chi square test, or analysis of variance was used to estimate associations between variables.
RESULTS For one test subject measurement of skeletal bone density was not successful. Three subjects did not want to be weighed, and the location of the incisive papilla could not be determined for one subject because the papilla was de-
282
AND LASSILA
of variables
slice
TB
LASSILA,
Duration of edentulousness b-1 Body mass index (m/kgz) Buccal bone breadth (mm) Palatal vault height (mm) Skeletal mineral status lower than mean Skeletal mineral status higher than mean Incisive papilla clearly on anterior side of ridge Incisive papilla on top of ridge Incisive papilla clearly on palatal side of ridge
SD
N
29.9
7.4
230
26.4 1.5 12.5
4.1 1.1 2x5 121
227 227 229
108 26 118 55
formed and almost invisible. For three subjects it was impossible to discover the location of the palatal-gingival margin, and for one subject measurement of the height of the palatal vault was not successful because of an extensive defect of the ridge in the molar region. The distribution of variables is presented in Table I. Location of the incisive papilla was significantly dependent on the duration of the edentulousness in the maxillae. The longer the teeth had been absent, the more anteriorly the papilla was situated because of the flatness. The thickness of the remaining facial bone in the canine region was also significantly dependent on the duration of the edentulousness (Table II). The facial bone also depended on skeletal mineral status. For those women whose bone mineral level was below the mean, the residual ridges in the canine region of the maxillae were significantly thinner (Table II). The height of the palatal vault did not correlate with the length of time of edentulousness, skeletal mineral status, or BMI. None of the variables of the maxillae were associated with BMI (Table II).
DISCUSSION After the teeth are extracted, resorption is most rapid in the labial and buccal bone.4 According to Watt and MacGrego6 the palatal-gingival margin moves outward during the edentulous years so that it lies facially and superiorly to the position occupied by palatal-gingival margins in the dentulous mouth. The anterior movement of the incisive papilla caused by progressive RRR also originates from this flattening. However, in an edentulous jaw the incisive papilla and the palatal-gingival margin represent anatomic formations that, for the dentate ridge, are situated near the ridge crest. In addition, the size of the jaws varies. One millimeter of bone loss in a wide jaw may indicate something quite
VOLUME
75
NUMBER
3
RLEME’ITI,
LASS&$
THE JOURNAL
AND LASSILA
Ridge
\
Fig.
3. Measurement
of vault
height
Table II. Dependencies between changes in maxillae and variables associated with residual ridge resorption Buccal Location of incisive
papilla
Duration of edentulousness in maxilla
p = 0.001
z=-3.27 (M-W)
Skeletal
mineral
status
NS
bone left
mass in canine lX?giOTl
p = 0.003 z= -2.99
of
mass
index
M - W, Mann-Whitney
NS nonparametric
1996
Vault height in molar region
values for BMD spine in Finnish
women
height in molar region
NS
(M-W) p = 0.028
NS
NS
test; NS, nonsignificant
o.g-.
NS
.
_.
0.7 -7 20
_
_
_.
_
30
_
.
40
probability.
different for a narrow alveolar ridge. On the other hand, clinically significant osteoporosis is more common in short childless women with low weights than in tall heavy women who have had children.’ This finding is also associated with the alveolar ridges; subjects with small jaws are more disposed to severe RRR. In this study the weight of the subjects was not considered in the results of bone mineral density measurements in the femur and vertebra. When dual-energy x-ray absorptiometry is used to measure bone mineral density, the thicker the bone, the greater is the measured density.g However, when the weight factor is not considered, the differences in bone loss become clearer because women with low weight and small bones are more predisposed to bone loss. In this study the BMI did not correlate with landmarks of ridge resorption and thus demonstrated that the positive association between skeletal mineral status and bone width was not caused by the size of the subjects. When teeth are extracted in the canine region, there is always a danger of loss of the labial cortical plate. In this
MARCH
top
region.
Normal lumbar
the
DENTISTRY
Vault
z =-2.20 (M-W Body
in molar
OF PROSTHETIC
_
.
_
_
_
50
_
60
70
60
Age
of
Normal femoral
the
values for BMD neck in Finnish
women
d-2 _.__..._____.._-..__...__
0.7
30
20
40
50
60
70
I 80
Age
Krdger
et
al.
(1992)
Fig. 4. Normal values for bone mineral density (B&ID) in femoral collum and lumbar spine among Finnish women, on which classification into two bone loss groups was based.
283
THE JOURNAL
OF PROSTHETIC
DENTISTRY
KLEMElTI,
study neither this bone loss nor differences in the size ofthe subjects (Table II) affected the influence of time and skeletal bone mineral density on the amount of bone in that region. In the canine region it is usually easy to determine the most prominent part of the ridge. The positive correlation between bone width and the time elapsed since the last extractions in the maxillae was expected. It was reported previously that in the regions of the jaws where RRR is clearly taking place and muscle function is not able to provide the bony tissues with enough stimulation the amount of lost bone depends on the length of time the jaw has been edentulous.5$ i” The bone width was also significantly dependent on the mineral status of the skeleton, which has been confirmed by previous reports. 5-7This correlation was not due to the differences in the sizes of the subjects because BMI did not correlate with the variables in the maxillae. According to the findings of this study the palatal-gingival margin can be used as a reference when the resorption of the facial ridge is measured. Measurement of horizontal ridge resorption in the molar region is difficult. In these subjects the slope of the buccal bone in the molar region was gradual enough to destroy all undercuts. In the agrarian areas of middle Finland only a few decades ago it was almost a tradition to extract teeth during young adulthood. Often the surgeon was not a dentist, and much alveolar bone was destroyed. Approximately half the subjects in this study had lost all maxillary teeth before reaching the age of 30 years. The molar teeth were probably lost first from caries. Therefore most subjects had been edentulous for more than 20 years, and almost all the resorption in the molar region had already occurred. The alveolar ridges in the molar regions of the sample in this study may be called “terminal stage ridges,” and the differences in the height of the palatal vault were usually the result of variations in the original anatomic form of the palatal vault. Therefore
Availability
LASSD&
AND LASSILA
the height of the vault was not associated with any other variables.
CONCLUSIONS In conclusion, this study demonstrated that duration of edentulousness and skeletal mineral status were important factors in the resorption of the residual ridges in the maxillae. The location of the incisive papilla and the thickness of the ridge on the labial side of the palatal-gingival margin are both associated with these factors ofRRR. REFERENCES 1. Watt DM, MacGregor AR. Designing complete dentures. 2nd ed. Bristol, United Kingdom: Wright, 1986. 2. Watt DM, Durran CM, Adenubi JO. Biometric guides to the design of complete maxillary dentures. Dent Magn Oral Top 1967;84:109-13, 3. Likeman PR, Watt DM. Morphological changes in the maxillary denture bearing area. Br Dent J 1974;136;500-3. 4. Watt DM, Likeman PR. Morphological changes in the denture bearing areas following the extraction of maxillary teeth. Br Dent J 1974; 136:225-35. 5. Klemetti E, Vainio P. Effect of bone mineral density in skeleton and mandible on extractions of teeth and clinical alveolar height. J PROSTITET DENT 1993;70:21-5.
6. Von Wowern N, Hjorting-Hansen E. The mandibular bone content in relation to vestibulolingual sulcoplasty: a Z-year PROSTHET DENT 1991;65:804-S. 7. Kribbs PJ, Chestnut CH, Ott SM, Kilcoyne RF, Relationship mandibular and skeletal hone in an osteoporotic population,
mineral study. J between J PROS-
THET DENT 1989;6%703-7.
8. Kroger H, Heikkinen J, Laitinen, Kotaniemi A. Dual-energy x-ray absorptiometry in normal women: a cross-sectional study of 71’7 Finnish volunteers. Osteoporos Int 1992;2:135-40. 9, Krijger H, Kotaniemi A, Vainio P, Alhava E. Bone densitometry of the spine and femur in children by dual-energy x-ray absorptiometry. Bone Miner 1992;17:75-85. 10, KIemetti E, Vainio P, La&a V. Mineral density in the mandibles of partially and totally edentate women. Stand J Dent Res 1994;102z64-7. Reprint
requests
to:
DR. ESA KLEMETTI DEPAFLTNWT OF PROSTHETICS AND STOMATOGNATHICF'HYSIOLOGY UNIVERSITY OFKUOPIO P.O.B. 1627 SF-70211, KUOPIO FINLAND
of JOURNAL Back
Issues
As a service to our subscribers, copies of back issues of THE JOURNAL OF PROSTHETIC for the preceding 5 years are maintained and are available for purchase from the publisher, Mosby, at a cost of $9.00 per issue. The following quantity discounts are available: 25% off on quantities of 12 to 23, and one third off on quantities of 24 or more. Please write to Mosby, Subscription Services, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, or call (800)453-4351 or (314)453-4351 for information on availability of particular issues. If unavailable from the publisher, photocopies of complete issues are available from University Microfilms International, 300 N. Zeeb Rd., Ann Arbor, MI 48106, (313)761-4700. DENTISTRY
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