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The relationship between clinical denture tooth abrasion and morphologic features of the mandible
The r e l a t i o n s h i p b e t w e e n clinical d e n t u r e t o o t h a b r a s i o n and m o r p h o l o g i c f e a t u r e s of the m a n d i b l e C o n H. J o o s t e , M C h D , P h D , a A n g e l a M. H a r r i s , B C h D , M C h D , b a n d L a u r i e P. A d a m s , M S c , P h D c
University of Stellenbosch, Tygerberg, and University of Cape Town, Rondebosch, South Africa B i o s t e r e o m e t r i c e v a l u a t i o n of denture tooth w e a r in 25 subjects w a s u s e d to d e t e r m i n e w h e t h e r there w a s a relationship b e t w e e n the gonial angle, m a n d i b u l a r length, F r a n k f o r t - m a n d i b u l a r angle, and a b r a s i o n of denture teeth. The results of this study i n d i c a t e d no correlation could be d e m o n s t r a t e d b e t w e e n any of the factors. (J PROSTHET DENT 1995;73:26-30.)
A
strong correlation has been demonstrated between the gonial angle of the mandible and biting forces generated by the natural dentition. 1 The forces applied by a d u l t humans with a deep occlusion were considerably higher t h a n those of persons with an open occlusion and investigators have ascribed this phenomenon to the direction and inherent strength of the mandibular elevator muscles in the two groups. 2 Concern has been expressed about greater stresses on the residual alveolar ridges and the abrasion of denture teeth in patients with low Frankfort mandibular plane angles who undergo prosthodontic treatment. 3 An investigation of 22 denture wearers indicated a m a r k e d association between alveolar bone resorption and m a n d i b u l a r morphologic features. 4 However, recent reports t h a t studied edentulous persons over a period of 20 years did not support these findingsfi 6 This study investigated the relationship, if any, between the clinical abrasion of denture teeth and three morphologic features of the edentulous mandible. MATERIAL
AND
METHODS
Twenty-five adult men 34 to 65 years of age were provided with new complete dentures. There were no symptoms of m a n d i b u l a r dysfunction present and all
Presented at the International Association for Dental Research Meeting, Glasgow, Scotland, 1992. aProfessor, Department of Prosthodontics, University of Stellenbosch. bAssociate Professor/Senior Lecturer, Department of Orthodontics, University of Stellenbosch. cprofessor, Department of Bio-Medical Engineering, University of Cape Town. Copyright | 1995 by The Editorial Council of THE JOURNALOF PROSTHETIC DENTISTRY. 0022-3913/95/$3.00 + 0. 10/1/58846
26
THE J O U R N A L OF P R O S T H E T I C D E N T I S T R Y
patients were from a group of vegetable farmers from the same region with similar diets and local conditions. All patients were treated with nonanatomic denture occlusions composed of either polymethyl methacrylate or polymethyl methacrylate opposed by porcelain (Vitapan Zahnfabrik, Badsiickingen, Germany) and a shortened occlusal table was used to avoid placement of denture teeth over an incline. 7 At denture insertion, a clinical remount was done to ensure bilateral posterior occlusal contact and removal of anterior and lateral occlusal interferences. After a period of adaptation, a baseline cast was made of the m a n d i b u l a r dentures with a polysiloxane impression material (XPress, 3M Dental Products, St. Paul, Minn.) and improved die stone (Fujirock GC, G. C. Dental Industrial Corp., Tokyo, Japan), which was used for the biostereometric analysis of tooth abrasion, s Three stainless steel markers had been inserted in the m a n d i b u l a r dentures, one behind the incisors and one each posterior to the molars on either side. These served as fixed points to which subsequent biostereometric surveys of tooth surfaces could be related. The dentures were worn for 3 years, after which casts were again made with the same materials. 9 The reflex microscope (Reflex Measurement Ltd., Walter Lane, Butleigh, Somerset, United Kingdom) 1~ is an optical plotter that allows direct, three-dimensional measurement of objects. An accuracy of 2 tLm for the x and y coordinates and 4 to 8 #m for the z coordinates has been shown. 11 Contour plots of the tooth surfaces were generated. T h e computer program has the ability to verify the position of the three baseline markers before test measurement to ensure repeatability of the subsequent readings. Each contour plot was related to the three baseline markers, which enabled the computer program to produce areas and volumes of each tooth and material lost relative to the baseline markers during 3 years of clinical wear (Fig. 1). The morphologic features of 25 subjects were obtained
V O L U M E 73
NUMBER 1
J O O S T E , H A R R I S , AND A D A M S
THE J O U R N A L OF P R O S T H E T I C D E N T I S T R Y
461v45
~986
v=55-56
a=38.9]
481v45
1986 3 D vkew
A
f~ 461v45
1989
v=34.92
9 a=38.9~
461v45
1989 3 O v i e w
38.91
461v45
1986-1989
B
461v45
~986--89 v = 2 0 . 6 4
3 D view
C F i g . 1 A - C, Contour plots and three-dimensional representations of tooth surfaces for baseline (1986) and 1989 and difference between these two showing volumetric loss of tooth material over same area.
from routine lateral cephalograms taken at baseline. The gonial angle was defined as the angle between a line drawn tangent to the posterior border of the ramus and the mandibular plane (line tangent to the lower border of the man-
J A N U A R Y 1995
dible), 12 mandibular length as a line t h a t connected the deepest point on the concavity of the sigmoid notch to gnathion, and the F r a n k f o r t - m a n d i b u l a r angle as the angle between the F r a n k f o r t horizontal plane and the mandibu-
27
THE JOURNAL OF PROSTHETIC DENTISTRY
~ \ \
JOOSTE, HARRIS, AND ADAMS
\ ~Mandibular length
Gnathion
F i g . 2. Gonial angle and m a n d i b u l a r length.
T a b l e I. Gonial angle, m a n d i b u l a r length, F r a n k f o r t m a n d i b u l a r angle, and abrasion in each subject Genial Mandibular Frankfortangle length mandibular Abrasion (ram 3 Subject (degrees) (ram) angle (degrees) per mm 2)
T a b l e II. Descriptive statistical d a t a for gonial angle, m a n d i b u l a r length, a n d F r a n k f o r t - m a n d i b u l a r angle for t h e 25 p a t i e n t s Gonial angle Mandibular (degrees)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
132 122 131 124 133 138 119 131 135 133 118 119 115 133 122 113 117 126 121 128 112 127 137 129 144
92 93 90 86 88 96 96 99 90 103.5 91 90.5 95 96 87 96 94 95 106.5 98 96 96.5 95 87 87.5
17.5 18 27 24 28 36 26 27.5 28 31.5 23 20 20 23 26.5 14 16.5 27 10 32 17 22 19.5 36 40
0.5340 0.1753 0.6234 0.2348 0.2035 0.1149 0.2419 0.1572 0.0360 0.4490 0.35~0 0.0121 0.1952 0.3050 0.0138 0.0399 0.2132 0.3755 0.0624 0.0297 0.3688 0.1200 0.2074 0.1793 0.0495
lar plane (Figs. 2 a n d 3). All tracings of the c e p h a l o g r a m s were d r a w n on acetate p a p e r in a d a r k e n e d r o o m by one o b s e r v e r and r e t r a c e d on a second occasion u n d e r similar conditions.
28
Average Median Mode Standard deviation Standard error Minimum Maximum Range Lower quartile Upper quartile
126.36 127 133 8.43 1.69 112 144 32 119 133
Frankfortmandibular
l e n g t h (ram) a n g l e ( d e g r e e s )
93.78 95 96 5.06 1.01 86 106.5 20.5 90 96
24.4 24 23 7.28 1.46 10 40 30 19.5 28
T h e S t a t g r a p h i c s p r o g r a m (version 5, S T S C Inc., Rockville, Md.) was used to test for statistically significant associations b e t w e e n t h e morphologic characteristics and d e n t u r e t o o t h abrasion. RESULTS T h e gonial angle, m a n d i b u l a r length, F r a n k f o r t - m a n dibular angle, and t h e abrasion of t h e d e n t u r e t e e t h for each p a t i e n t are p r e s e n t e d in T a b l e I a n d descriptive statistics of these d a t a in T a b l e II. T h e r e were no statistically significant linear correlations b e t w e e n any of t h e t h r e e m o r p h o l o g i c characteristics and d e n t u r e t o o t h abrasion (Table III) or b e t w e e n combina-
VOLUME73 NUMBER1
JOOSTE,
HARRIS,
AND
ADAMS
THE
Porion_
JOURNAL
OF PROSTHETIC
DENTISTRY
i i
i~I~
~kJ
Fig. 3. Frankfort-mandibular plane angle (FMA).
q
I
0.8
-, . . . . . . . . . .
,. . . . . . . . . . .
i ..........
~
........
0.8
i 84
0.6
0.6
Abrasion
(~'n~/r.m2)
factor
Abrasion
i.
(~.3/mm')
factor
i9
0.4
0.4
0.2
-:
....
._ . "
_ _:
..............
._ _
_
_._ . . . . . . . . . . .
0.2
:
i
:
....... :?...................................... 110
120
130
140
90
150
86
gonial
angle
(degrees)
98 94
Mandibular
106 102
length
110
(mm)
Fig. 4. Scatter plot of association between gonial angle and abrasion factor of dentures.
Fig. 5. Scatter plot of association between mandibular length and abrasion factor.
tions of any two of the characteristics and denture tooth abrasion (analysis of variance tests, p > 0.05).
Table I shows gonial angles ranging from 113 to 144 degrees, mandibular lengths from 86 mm to 106.5 mm, and Frankfort-mandibular angles from 14 to 40 degrees relative to the highest abrasion factor of 0.6234 mm3/mm 2 as opposed to the lowest of 0.0121 mm3/mm 2. Tables II and III illustrate the probability levels of each morphologic feature related to abrasion and clearly show no correlation between the aspects that were examined. In Figs. 4 through 6, scatter plots also show the absence of any relationships between the various factors.
DISCUSSION Earlier reports have demonstrated increased biting forces related to facial types in the natural dentition, 1 and it was assumed that higher biting forces would be applied to prostheses in similar edentulous patients. 3 Previous reports have related residual ridge resorption to morphologic aspects of the mandible. 46
JANUARY
1995
29
THE JOURNAL OF PROSTHETIC DENTISTRY
JOOSTE, HARRIS, AND ADAMS
L
0.8
.............
: .......
i ............
i
i .......
!-
in
'
'
,
9
0.6
Abrasion factor
(mr.3/rr~2)
0.4
0.2 9
,
10
9
9
15
20
25
9
9
30
35
40
FMA (degrees)
Fig. 6. Scatter plot of association between Frankfort-mandibular angle (FMA) and abrasion factor.
Table III. Linear regression analysis Dependent variable Abrasion
Independent variable Gonial angle Mandibular length F r a n k f o r t - m a n d i b u l a r angle
Correlation coefficient p Value 0.047 0.028 -0.063
0.8232 0.8933 0.7662
This study failed to demonstrate any correlation between denture tooth abrasion and three morphologic characteristics of the mandible. REFERENCES 1. Paolini DA. A study on the method of recording and the difference in maximal biting force between extremes of vertical facial types [Thesis]. Pittsburgh, Pa.: University of Pittsburgh, School of Dental Medicine, 1970. 2. Sassouni V. Orthodontics in dental practice. 1st ed. St. Louis: CV Mosby, 1971:124-8. 3. Di Pietro GJ, Moergeli JR. Significance of the Frankfort-mandibular plane angle to prosthodontics. J PROSTHETDENT 1976;36:624-35.
30
4. Tallgren A. Alveolar bone loss in denture wearers as related to facial morphology. Acta Odontol Scand 1970;28:251-70. 5. Unger JW, Ellinger CW, Gunsolley JC. An analysis of the relationship between mandibular alveolar bone loss and a low Frankfort-mandibular plan e angle. J PROSTHETDENT 1991;66:513-6. 6. Unger JW, Ellinger CW, Gunsolley JC. An analysis of the effect of mandibular length on residual ridge loss in the edentulous patient. J PROSTHET DENT 1992;67:827-30. 7. Jooste CH, Thomas CJ. Complete mandibular denture stability when posterior teeth are placed over a basal tissue incline 8. Adams LP, Jooste CH, Thomas CJ. Accuracy of a replication technique for biostereometric evaluation of clinical tooth wear. J Dent Assoc S Afr 1991;46:363-4. 9. Adams LP, Jooste CH, Thomas CJ. An indirect in vivo method for quantification of wear of denture teeth. Dent Mater 1989;5:31-4.. 10. Scott PJ. The reflex plotters: measurement without photographs. Photogrammetric Records 1981;10:4350-446. 11. Adams LP, Wilding RC. A stereometric technique for measuring residual alveolar ridge volumes. J PROSTHETDENT 1988;60:388-93. 12. Lindeg~rd B. Variations in human body-build. Acta Psychiatr 1953; (Suppl)86:51-96. Reprint requests to: DR. CON H. JOOSTE UNIVERSITYOF STELLENBOSCH PRIVATE BAG X1 TYGERBERG 7505 SOUTH AFRICA
VOLUME 73 NUMBER 1
University of Stellenbosch, Tygerberg, and University of Cape Town, Rondebosch, South Africa B i o s t e r e o m e t r i c e v a l u a t i o n of denture tooth w e a r in 25 subjects w a s u s e d to d e t e r m i n e w h e t h e r there w a s a relationship b e t w e e n the gonial angle, m a n d i b u l a r length, F r a n k f o r t - m a n d i b u l a r angle, and a b r a s i o n of denture teeth. The results of this study i n d i c a t e d no correlation could be d e m o n s t r a t e d b e t w e e n any of the factors. (J PROSTHET DENT 1995;73:26-30.)
A
strong correlation has been demonstrated between the gonial angle of the mandible and biting forces generated by the natural dentition. 1 The forces applied by a d u l t humans with a deep occlusion were considerably higher t h a n those of persons with an open occlusion and investigators have ascribed this phenomenon to the direction and inherent strength of the mandibular elevator muscles in the two groups. 2 Concern has been expressed about greater stresses on the residual alveolar ridges and the abrasion of denture teeth in patients with low Frankfort mandibular plane angles who undergo prosthodontic treatment. 3 An investigation of 22 denture wearers indicated a m a r k e d association between alveolar bone resorption and m a n d i b u l a r morphologic features. 4 However, recent reports t h a t studied edentulous persons over a period of 20 years did not support these findingsfi 6 This study investigated the relationship, if any, between the clinical abrasion of denture teeth and three morphologic features of the edentulous mandible. MATERIAL
AND
METHODS
Twenty-five adult men 34 to 65 years of age were provided with new complete dentures. There were no symptoms of m a n d i b u l a r dysfunction present and all
Presented at the International Association for Dental Research Meeting, Glasgow, Scotland, 1992. aProfessor, Department of Prosthodontics, University of Stellenbosch. bAssociate Professor/Senior Lecturer, Department of Orthodontics, University of Stellenbosch. cprofessor, Department of Bio-Medical Engineering, University of Cape Town. Copyright | 1995 by The Editorial Council of THE JOURNALOF PROSTHETIC DENTISTRY. 0022-3913/95/$3.00 + 0. 10/1/58846
26
THE J O U R N A L OF P R O S T H E T I C D E N T I S T R Y
patients were from a group of vegetable farmers from the same region with similar diets and local conditions. All patients were treated with nonanatomic denture occlusions composed of either polymethyl methacrylate or polymethyl methacrylate opposed by porcelain (Vitapan Zahnfabrik, Badsiickingen, Germany) and a shortened occlusal table was used to avoid placement of denture teeth over an incline. 7 At denture insertion, a clinical remount was done to ensure bilateral posterior occlusal contact and removal of anterior and lateral occlusal interferences. After a period of adaptation, a baseline cast was made of the m a n d i b u l a r dentures with a polysiloxane impression material (XPress, 3M Dental Products, St. Paul, Minn.) and improved die stone (Fujirock GC, G. C. Dental Industrial Corp., Tokyo, Japan), which was used for the biostereometric analysis of tooth abrasion, s Three stainless steel markers had been inserted in the m a n d i b u l a r dentures, one behind the incisors and one each posterior to the molars on either side. These served as fixed points to which subsequent biostereometric surveys of tooth surfaces could be related. The dentures were worn for 3 years, after which casts were again made with the same materials. 9 The reflex microscope (Reflex Measurement Ltd., Walter Lane, Butleigh, Somerset, United Kingdom) 1~ is an optical plotter that allows direct, three-dimensional measurement of objects. An accuracy of 2 tLm for the x and y coordinates and 4 to 8 #m for the z coordinates has been shown. 11 Contour plots of the tooth surfaces were generated. T h e computer program has the ability to verify the position of the three baseline markers before test measurement to ensure repeatability of the subsequent readings. Each contour plot was related to the three baseline markers, which enabled the computer program to produce areas and volumes of each tooth and material lost relative to the baseline markers during 3 years of clinical wear (Fig. 1). The morphologic features of 25 subjects were obtained
V O L U M E 73
NUMBER 1
J O O S T E , H A R R I S , AND A D A M S
THE J O U R N A L OF P R O S T H E T I C D E N T I S T R Y
461v45
~986
v=55-56
a=38.9]
481v45
1986 3 D vkew
A
f~ 461v45
1989
v=34.92
9 a=38.9~
461v45
1989 3 O v i e w
38.91
461v45
1986-1989
B
461v45
~986--89 v = 2 0 . 6 4
3 D view
C F i g . 1 A - C, Contour plots and three-dimensional representations of tooth surfaces for baseline (1986) and 1989 and difference between these two showing volumetric loss of tooth material over same area.
from routine lateral cephalograms taken at baseline. The gonial angle was defined as the angle between a line drawn tangent to the posterior border of the ramus and the mandibular plane (line tangent to the lower border of the man-
J A N U A R Y 1995
dible), 12 mandibular length as a line t h a t connected the deepest point on the concavity of the sigmoid notch to gnathion, and the F r a n k f o r t - m a n d i b u l a r angle as the angle between the F r a n k f o r t horizontal plane and the mandibu-
27
THE JOURNAL OF PROSTHETIC DENTISTRY
~ \ \
JOOSTE, HARRIS, AND ADAMS
\ ~Mandibular length
Gnathion
F i g . 2. Gonial angle and m a n d i b u l a r length.
T a b l e I. Gonial angle, m a n d i b u l a r length, F r a n k f o r t m a n d i b u l a r angle, and abrasion in each subject Genial Mandibular Frankfortangle length mandibular Abrasion (ram 3 Subject (degrees) (ram) angle (degrees) per mm 2)
T a b l e II. Descriptive statistical d a t a for gonial angle, m a n d i b u l a r length, a n d F r a n k f o r t - m a n d i b u l a r angle for t h e 25 p a t i e n t s Gonial angle Mandibular (degrees)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
132 122 131 124 133 138 119 131 135 133 118 119 115 133 122 113 117 126 121 128 112 127 137 129 144
92 93 90 86 88 96 96 99 90 103.5 91 90.5 95 96 87 96 94 95 106.5 98 96 96.5 95 87 87.5
17.5 18 27 24 28 36 26 27.5 28 31.5 23 20 20 23 26.5 14 16.5 27 10 32 17 22 19.5 36 40
0.5340 0.1753 0.6234 0.2348 0.2035 0.1149 0.2419 0.1572 0.0360 0.4490 0.35~0 0.0121 0.1952 0.3050 0.0138 0.0399 0.2132 0.3755 0.0624 0.0297 0.3688 0.1200 0.2074 0.1793 0.0495
lar plane (Figs. 2 a n d 3). All tracings of the c e p h a l o g r a m s were d r a w n on acetate p a p e r in a d a r k e n e d r o o m by one o b s e r v e r and r e t r a c e d on a second occasion u n d e r similar conditions.
28
Average Median Mode Standard deviation Standard error Minimum Maximum Range Lower quartile Upper quartile
126.36 127 133 8.43 1.69 112 144 32 119 133
Frankfortmandibular
l e n g t h (ram) a n g l e ( d e g r e e s )
93.78 95 96 5.06 1.01 86 106.5 20.5 90 96
24.4 24 23 7.28 1.46 10 40 30 19.5 28
T h e S t a t g r a p h i c s p r o g r a m (version 5, S T S C Inc., Rockville, Md.) was used to test for statistically significant associations b e t w e e n t h e morphologic characteristics and d e n t u r e t o o t h abrasion. RESULTS T h e gonial angle, m a n d i b u l a r length, F r a n k f o r t - m a n dibular angle, and t h e abrasion of t h e d e n t u r e t e e t h for each p a t i e n t are p r e s e n t e d in T a b l e I a n d descriptive statistics of these d a t a in T a b l e II. T h e r e were no statistically significant linear correlations b e t w e e n any of t h e t h r e e m o r p h o l o g i c characteristics and d e n t u r e t o o t h abrasion (Table III) or b e t w e e n combina-
VOLUME73 NUMBER1
JOOSTE,
HARRIS,
AND
ADAMS
THE
Porion_
JOURNAL
OF PROSTHETIC
DENTISTRY
i i
i~I~
~kJ
Fig. 3. Frankfort-mandibular plane angle (FMA).
q
I
0.8
-, . . . . . . . . . .
,. . . . . . . . . . .
i ..........
~
........
0.8
i 84
0.6
0.6
Abrasion
(~'n~/r.m2)
factor
Abrasion
i.
(~.3/mm')
factor
i9
0.4
0.4
0.2
-:
....
._ . "
_ _:
..............
._ _
_
_._ . . . . . . . . . . .
0.2
:
i
:
....... :?...................................... 110
120
130
140
90
150
86
gonial
angle
(degrees)
98 94
Mandibular
106 102
length
110
(mm)
Fig. 4. Scatter plot of association between gonial angle and abrasion factor of dentures.
Fig. 5. Scatter plot of association between mandibular length and abrasion factor.
tions of any two of the characteristics and denture tooth abrasion (analysis of variance tests, p > 0.05).
Table I shows gonial angles ranging from 113 to 144 degrees, mandibular lengths from 86 mm to 106.5 mm, and Frankfort-mandibular angles from 14 to 40 degrees relative to the highest abrasion factor of 0.6234 mm3/mm 2 as opposed to the lowest of 0.0121 mm3/mm 2. Tables II and III illustrate the probability levels of each morphologic feature related to abrasion and clearly show no correlation between the aspects that were examined. In Figs. 4 through 6, scatter plots also show the absence of any relationships between the various factors.
DISCUSSION Earlier reports have demonstrated increased biting forces related to facial types in the natural dentition, 1 and it was assumed that higher biting forces would be applied to prostheses in similar edentulous patients. 3 Previous reports have related residual ridge resorption to morphologic aspects of the mandible. 46
JANUARY
1995
29
THE JOURNAL OF PROSTHETIC DENTISTRY
JOOSTE, HARRIS, AND ADAMS
L
0.8
.............
: .......
i ............
i
i .......
!-
in
'
'
,
9
0.6
Abrasion factor
(mr.3/rr~2)
0.4
0.2 9
,
10
9
9
15
20
25
9
9
30
35
40
FMA (degrees)
Fig. 6. Scatter plot of association between Frankfort-mandibular angle (FMA) and abrasion factor.
Table III. Linear regression analysis Dependent variable Abrasion
Independent variable Gonial angle Mandibular length F r a n k f o r t - m a n d i b u l a r angle
Correlation coefficient p Value 0.047 0.028 -0.063
0.8232 0.8933 0.7662
This study failed to demonstrate any correlation between denture tooth abrasion and three morphologic characteristics of the mandible. REFERENCES 1. Paolini DA. A study on the method of recording and the difference in maximal biting force between extremes of vertical facial types [Thesis]. Pittsburgh, Pa.: University of Pittsburgh, School of Dental Medicine, 1970. 2. Sassouni V. Orthodontics in dental practice. 1st ed. St. Louis: CV Mosby, 1971:124-8. 3. Di Pietro GJ, Moergeli JR. Significance of the Frankfort-mandibular plane angle to prosthodontics. J PROSTHETDENT 1976;36:624-35.
30
4. Tallgren A. Alveolar bone loss in denture wearers as related to facial morphology. Acta Odontol Scand 1970;28:251-70. 5. Unger JW, Ellinger CW, Gunsolley JC. An analysis of the relationship between mandibular alveolar bone loss and a low Frankfort-mandibular plan e angle. J PROSTHETDENT 1991;66:513-6. 6. Unger JW, Ellinger CW, Gunsolley JC. An analysis of the effect of mandibular length on residual ridge loss in the edentulous patient. J PROSTHET DENT 1992;67:827-30. 7. Jooste CH, Thomas CJ. Complete mandibular denture stability when posterior teeth are placed over a basal tissue incline 8. Adams LP, Jooste CH, Thomas CJ. Accuracy of a replication technique for biostereometric evaluation of clinical tooth wear. J Dent Assoc S Afr 1991;46:363-4. 9. Adams LP, Jooste CH, Thomas CJ. An indirect in vivo method for quantification of wear of denture teeth. Dent Mater 1989;5:31-4.. 10. Scott PJ. The reflex plotters: measurement without photographs. Photogrammetric Records 1981;10:4350-446. 11. Adams LP, Wilding RC. A stereometric technique for measuring residual alveolar ridge volumes. J PROSTHETDENT 1988;60:388-93. 12. Lindeg~rd B. Variations in human body-build. Acta Psychiatr 1953; (Suppl)86:51-96. Reprint requests to: DR. CON H. JOOSTE UNIVERSITYOF STELLENBOSCH PRIVATE BAG X1 TYGERBERG 7505 SOUTH AFRICA
VOLUME 73 NUMBER 1