The Vascularity of Dental Pulp in Cats N. VONGSAVAN and B. MATTHEWS'
Department ofPhysioloy Univerijty of Bristo4 Univerity Walk,Bristol BS8 1D Engand The fiction of the volume of the coronal pulp of cat canines that is occupied by blood vessels was estimated by measurement of the cross-sectional areas of all the vessels in a complete transverse section of the pulp from each offour teeth. The sections were taken 0. 5 mm fom the pulp cornu. Overall, 14.4% ofthe area of the pulp was occupied by vessels. In the core of the pulp, the average value was 42 9%, and superficially, near the odontoblast layer it was between 5 and 10%. The average capillary density was 1402 nmm, which is higher than in most other tissues. Laser Doppler flow meters can be used for recording blood flow from the coronal pulp of intact teeth, but these instruments are linear only if the moving blood cells occupy no more than 1% of the tissue volume. The present results suggest that this figure is exceeded in pulp
montage was traced on a digitizing pad. The geometric center ofthe pulp was calculated and for each vessel the following data were computed: its cross-sectional area, the distance of its center ftom the center ofthe pulp, the ratio fits shortest to its lest diameter,
and its average diameter (calculated as the diameter of a circle with the same area as that of the vessel).
Resuts. The montage formed from a transverse section of the pulp of one tooth is show in Fig. 1. The frequency distribute n ofthe diameters of the vessels in l four teeth is shown in Fig. 2, and Table 1 gives a summary ofthe numbers ofvessels ofdi&ffrent sizes in each tooth. Vessels with diameters of under 10 pm were classified as capillaries, and overall these formed 77% ofthe total. The capillary density J Dent Res 71(12)*1913-1915, Dem ber, 1992 ranged from 1264 to 1613/mm (average, 1402) Some of the larger vessels contained some smooth muscle in their walls, but it was difficult to direntiate arterioies from venues. Details of the total cross-sectional areas of the vessels in each Introduction. tooth are given in Table 2, and the same data have been expressed Pulpal blood flow can be recorded from intact teeth by means oflaser as percentages of the total cross-sectional area of the pulp in Table Doppler flow meters, but these instruments give linear results only 3. Overall, 14.4% of the area of the pulp was occupied by vessels. when recording from tissues in which moving blood cells occupy no As illustrated in Fig. 1, only capillaries (diameters under 10 gm) more than 1% of the tissue volume Vongsavan and Matthews were present in and close to the odontoblast layer. Otherwise, there 1992ab). Although dental pulp is usually considered to he a very was a tendency for the largest vessels to be near the center of the xascular tissue, there appear to be no data from which to deter ne pulp, and there were relatively few capillaries in this central region. whether this figure of 1% is likely to be exceeded. The present Fig. 3 shows the relationship in one tooth between the diameter of experiments were therefore carried out to provide an estimate ofthe each vessel and the distances ofthe centers of the vessels from the faction of the volume of dental pulp normally occupied by blood. centers ofthe pulp A similar relationship was present in the other The coronal pulp of cat canine teeth was examined, and the volume three teeth. of the blood vessels was estimated from measurements ofthe crossIn view of this uneven distribution of the vessels, the proportion sectional areas of the vessels in fixed tissue of the cross-sectional area which they occupied was computed for each of a series of concentric annual of 10 pm width around the center ofthe pulp. The results for one tooth are shown in Fig 4. The Materials and methods. average figure for the central, 100-pm -diameter, core of the pulp in Four upper canine teeth from four cats were examined. The the fou teeth was 42.9% (SD, 15.4). In the superficial part of the animals, aged 10-15 months, were anesthetized with sodium pulp, the proportion was between 5 and 10%. It was difficult fbr a pentbarbitone (42 mg/kg i;p.. then 3 mg/kg i.v as reqred) ard m re prece figure fbr thi 1at a perfused with fixatives through both common carotid arteries by ter area to be calculated from means of a two-stage procedure (Forssmann et al., 1977). The final the pooled data, because the fixative solution contained 3% glutaraldehyde, 3% formaldehyde pulps were not a of the same 0.05% picnic acid, and 2.5% polyvinylpyrrolidine (all wv) in 0.1 moP diameter and they were not L phosphate buffr. The tip ofthe cusp (length, 4 mm) ofeach tooth circular. was removed with a diamond disc under Ringes solution, then Almost all the vessels had decalcified and processed for electronmicroscopy by means of a lumens which were close to cirprocedure which was essentially the same as that described by cular,indicatingthattheywere Holland et al. (1987). Each specimen was osmicated and embedded arranged longitudinally in the in Epon, and the block was trimmed to enable a complete transverse tooth. No lymph vessel of the section ofthe pulp to be obtained approximately 0.5 mm from the tip type described by Bishop and of the pulp corn. At this level, the diameter of the pulp was fom Malhotra (1990) was found. 0.32 to 0.38 mm. The sections (thickness, 70-90 nm) were stained with lead acetate and uranyl acetate and examined in a Philips 300 Discssion. electron microscope, For each tooth, a montage (overall magnification, X1000) was The results support the widely formed from a series of electronmicrographs taken from a typical held view that dental pulp is a Fig. I-Montage of a cross-sec section. The outline ofthe pulp and the lumen ofevery vessel in each relatively vascular tissue. The tion through the pulp ofone tooth (no. densityofcapillariesinthecoro- 2)O mm from the pulp coma. The nal pulp of the cat canine is perimeter of the section is formed by Received for publication July 12, 1991 comparable with that in the dentin withtheunderlyingpredentin Accepted for publication August 5, 1992 T whom correspondence and report requests should be addressed tongue and in the most vascu- and odortoblast layer. Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on March 11, 2015 For personal use only. No other uses without permission.
1.913
a) c C(
Q)
>
J Dent Res December 1992
VONGSAVAN & MATTHEWS
1914 40
TABLE 2 TOTAL CROSS-SECTIONAL AREAS (pm2) OF BLOOD VESSELS IN CAT DENTAL PULP
F
30
~0 -0
Vessel Diameter (pm) 20 k
z
Tooth No.
4-10
10-20
20-30
. 30
Total
1
5268
3252
2187
2695
13402
2
4585
4834
6291
6147
21857
3
3652
3503
2095
1177
10427
4
3316
2509
3544
0
9369
Mean
4206
3524
3529
2504
13763
a)
CD >
10
F
a)
,L 0 5
10
15
20 25 30 35 40 45 50 Diameter (,tm) Fig. 2-Frequency distribution of the internal diameters of the pulp blood vessels in four cat canine teeth. In each tooth, the measurements were made on a section taken 0.5 mm from the pulp cornu. The error bars show the standard deviations ofthe average number ofvessels in each bin, except where that number was less than 3. For each vessel, the diameter used in plotting this histogram was the diameter of a circle of the same area as the
vessel.
lar parts of the brain ofthe cat. It is greater than that in most other tissues in the cat, except the heart and kidney (for review, see HudlikA, 1984). In contrast, there are between 20 and 149 capillaryloops (i.e., 40298 capillaries) per mm2 in the superficial layers of human skin in different parts of the body (Ryan, 1973), with an average of 130per mm2 in the skin of the back of the hand (Wetzel and Zotterman, 1926). With this density, the volume fraction ofblood cells in a plane through the capillaries will be less than 1% (Nilsson et al., 1980). We estimate that the volume fraction of red cells is also likely to be just less than 1% in the superficial part ofthe pulp. This is based on our finding that all the vessels in this region are capillaries and that they occupy up to 10% of the tissue volume. From studies on other tissues, the ratio ofthe hematocrit in the capillaries to that in large vessels is likely to be approximately 0.2 (Zweifach and Lipowsky, 1984). Therefore, ifthe large vessel hematocrit was 45%, the volume fraction of red cells in the superficial pulp would be up to 0.9%. However, by the same argument, the average red cell volume fraction in the core (diam., 100 pm ) ofthe pulp will be about 8%. In this region, the vessels accounted for about 43% ofthe tissue volume on average, and most ofthe vessels had diameters between 20 and 47 pm, in which the hematocrit ratio is likely to be between 0.3 and 0.6 (Zweifach and Lipowsky, 1984). Therefore, within individual vessels of this size, the red cell volume fraction will be up to 27%.
TABLE 3 TOTAL CROSS-SECTIONAL AREAS OF BLOOD VESSELS IN CAT DENTAL PULP EXPRESSED AS PERCENTAGES OF THE CROSS-SECTIONAL AREA OF THE PULP Vessel Diameter (pm)
Tooth No.
4-10
10-20
20-30
> 30
Total
1
5.9
3.6
2.4
2.9
14.8
2
3.9
4.2
5.5
5.4
19.0
3
4.2
4.1
2.4
1.4
12.1
4
4.0
3.0
4.3
0
11.3
Mean
4.5
3.7
3.7
2.4
14.4
These figures are well outside the range over which laser Doppler flow meters would be expected to give a linear response (see Vongsavan and Matthews, 1992a,b). These instruments are capable of detecting flow in vessels in the center of the pulp cavity (Vongsavan and Matthews, 1992b). Our evidence indicates, therefore, that they cannot be used reliably to make quantitative measurements of blood flow in teeth and that, for example, a doubling of the signal obtained does not necessarily indicate that the blood flow through the tooth has also doubled. They provide a valuable method of studying pulpal blood flow non-invasively, but the results
TABLE 1 NUMBERS OF BLOOD VESSELS OF DIFFERENT DIAMETERS AND THE TOTAL PULPAL AREA IN A TRANSVERSE SECTION OF CAT DENTAL PULP Vessel Diameter( m) Tooth No.
4-10
10-20
20-30
2 30
Total No.
1
145
22
5
2
174
89907
2
104
32
14
5
155
114689
3
93
21
4
1
119
86346
4
104
17
7
0
128
82382
Total Pulpal Area (pm2)
111 Mean 23 7 2 144 93331 In Tables 1-3, each bin contains values greater than or equal to the lower limit of its range but less than the upper limit. Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on March 11, 2015 For personal use only. No other uses without permission.
Vol. 71 No. 12
PULP VASCULARIY IN CATS
1915
50 1 00 _ 40
L0
E
30
80
0
60
c)
Q)
%
0
U)
0
20
U) U)
U)
40
0
U)
U)
10
l *
: .6;
%
00
I01
20
-
0-
0
1 2*0S-0 00 1 50 50 Distance of Centre of Vessel from Centre of Pulp (am)
Fig. 3-Scatter diagram showing the relationship between the diameter ofeach vessel in one tooth (no. 2) and the distance ofits center from the center of the pulp. The vessel diameters were calculated as in Fig. 2.
0
50
1 00
1 50
200
Distance from Centre of Pulp (am) Fig. 4-Histogram showing, for each of a series of concentric annuli of 10 pm width around the center of the pulp of one tooth (no. 2), the percentage of the total area of each annulus that was occupied by blood vessels. Fig. 3 shows the diameters of the vessels at different distances from the center of the pulp in the same tooth.
obtained must be interpreted with care. REFERENCES The largest vessels were slightly smaller than those observed by intra-vital microscopy in the pulp of rat incisors (see Kim et al., Bishop MA, Malhotra M (1990). An investigation of lymphatic vessels in the 1984). Also, many very small capillaries were found with diameters feline dental pulp. Am JAnat 187:247-253. of 4-5 pm, which were halfthe size ofthose reported in studies on rat Forssmann WG, Ito S, Weihe E, Aoki A, Dym M, Fawcett DW (1977). An incisor pulp. The average diameter ofacat red cell is 5.7 Pm (Windle improvedperfusion fixation method forthe testis. AnatRec 188:307-314. et al., 1940). Gray SJ, Sterling K (1950). The tagging ofred cells and plasma proteins with radioactive chromium. J Clin Invest 29:1604-1613. The distribution of vessels in the cornu of cat pulp corresponds generally with that seen in the models of Takahashi et al. (1982), Holland GR, Matthews B, Robinson PP (1987). An electrophysiological and although we did not encounter as many radially-arranged vessels morphological study of the innervation and reinnervation ofcat dentine. J Physiol (Lond) 386:31-43. (which would have had elongated profiles) as those models suggest. There are three main sources of error in our measurements: the Hudlika 0 (1984). Development of microcirculation: capillary growth and inclusion of vessels that were not perfused with blood in vivo, the adaptation. In: Renkin EM, Michel CC, Geiger SR, editors. Handbook of physiology: The cardiovascular system. Vol. IV, pt. 1. Bethesda (MD): distention of the vessels during perfusion, and the shrinkage of the American Physiological Society, 165-216. specimens during subsequent processing. We have no estimate of the proportion of unperfused vessels in normal pulp, although, as in Kim S, Lipowsky HH, Usami S, Chien S (1984). Arteriovenous distribution other tissues, it is likely that some ofthe capillaries would not have ofhemodynamic parameters in the rat dental pulp. MicrovascRes 27:28been open in vivo. The amount by which the vessels were distended 38. during perfusion cannot be estimated, but it is likely to be less than Nilsson GE, Tenland T, Oberg PA (1980). Evaluation of a laser Doppler flowmeter for measurement of tissue blood flow. IEEE Trans Biomed in most other tissues, on account of the low compliance of the pulp chamber. From measurements ofthe external dimensions of teeth Eng 27:597-604. before and after processing, we estimate that the linear shrinkage Ryan TJ (1973). Structure and shape of blood vessels of skin. In: Jarret A, of the dentin was less than 5%. The presence of a small number of editor. The physiology and pathophysiology of the skin. London (UK): vessels that were not sectioned transversely will not have affected Academic Press, 619-625. our estimate of the volume ofthe pulpal blood vessels, although we Takahashi K, Kishi Y, Kim S (1982). A scanning electron microscope study ofbloodvessels ofthe pulp usingcorrosionresincasts. JEndodont8:131will have overestimated their average diameters. No correction was made to allow for these in the distribution of vessel diameters, since 135. there were so few of them. Vongsavan N, Matthews B (1992a). Some aspects ofthe use oflaser Doppler An alternative method of estimating the mean red cell volume flow meters for recording tissue blood flow. Exp Physiol (in press). fraction of pulp would be to use 51Cr-labeled red cells (Gray and Vongsavan N, Matthews B (1992b). In vitro experiments on the use oflaser Doppler techniques for recording blood flow in teeth. Arch Oral Biol (in Sterling, 1950). The number of erythrocytes in the pulp could be determined by ligation of the pulp near the apical foramen in vivo, press). extraction of the tooth, then freezing it to prevent blood being lost Wetzel NC, Zotterman Y (1926). On differences in the vascular colouration of various regions of the normal human skin. Heart 13:357-369. from the pulp while it was being dissected out before counts were Windle WF, Sweet M, Whitehead WH (1940). Some aspects of prenatal and made on the tissue. postnatal development of the blood in the cat. Anat Rec 78:321-332. Zweifach BW, Lipowsky HH (1984). Pressure-flow relations in blood and Acknowledgment. lymph microcirculation. In: Renkin EM, Michel CC, Geiger SR, editors. Handbook of physiology: The cardiovascular system. Vol. 4, pt. 1. We are grateful to Mr. G. Harrison for carrying out the electronBethesda (MD): American Physiological Society, 251-307. microscopy.
Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on March 11, 2015 For personal use only. No other uses without permission.
Department ofPhysioloy Univerijty of Bristo4 Univerity Walk,Bristol BS8 1D Engand The fiction of the volume of the coronal pulp of cat canines that is occupied by blood vessels was estimated by measurement of the cross-sectional areas of all the vessels in a complete transverse section of the pulp from each offour teeth. The sections were taken 0. 5 mm fom the pulp cornu. Overall, 14.4% ofthe area of the pulp was occupied by vessels. In the core of the pulp, the average value was 42 9%, and superficially, near the odontoblast layer it was between 5 and 10%. The average capillary density was 1402 nmm, which is higher than in most other tissues. Laser Doppler flow meters can be used for recording blood flow from the coronal pulp of intact teeth, but these instruments are linear only if the moving blood cells occupy no more than 1% of the tissue volume. The present results suggest that this figure is exceeded in pulp
montage was traced on a digitizing pad. The geometric center ofthe pulp was calculated and for each vessel the following data were computed: its cross-sectional area, the distance of its center ftom the center ofthe pulp, the ratio fits shortest to its lest diameter,
and its average diameter (calculated as the diameter of a circle with the same area as that of the vessel).
Resuts. The montage formed from a transverse section of the pulp of one tooth is show in Fig. 1. The frequency distribute n ofthe diameters of the vessels in l four teeth is shown in Fig. 2, and Table 1 gives a summary ofthe numbers ofvessels ofdi&ffrent sizes in each tooth. Vessels with diameters of under 10 pm were classified as capillaries, and overall these formed 77% ofthe total. The capillary density J Dent Res 71(12)*1913-1915, Dem ber, 1992 ranged from 1264 to 1613/mm (average, 1402) Some of the larger vessels contained some smooth muscle in their walls, but it was difficult to direntiate arterioies from venues. Details of the total cross-sectional areas of the vessels in each Introduction. tooth are given in Table 2, and the same data have been expressed Pulpal blood flow can be recorded from intact teeth by means oflaser as percentages of the total cross-sectional area of the pulp in Table Doppler flow meters, but these instruments give linear results only 3. Overall, 14.4% of the area of the pulp was occupied by vessels. when recording from tissues in which moving blood cells occupy no As illustrated in Fig. 1, only capillaries (diameters under 10 gm) more than 1% of the tissue volume Vongsavan and Matthews were present in and close to the odontoblast layer. Otherwise, there 1992ab). Although dental pulp is usually considered to he a very was a tendency for the largest vessels to be near the center of the xascular tissue, there appear to be no data from which to deter ne pulp, and there were relatively few capillaries in this central region. whether this figure of 1% is likely to be exceeded. The present Fig. 3 shows the relationship in one tooth between the diameter of experiments were therefore carried out to provide an estimate ofthe each vessel and the distances ofthe centers of the vessels from the faction of the volume of dental pulp normally occupied by blood. centers ofthe pulp A similar relationship was present in the other The coronal pulp of cat canine teeth was examined, and the volume three teeth. of the blood vessels was estimated from measurements ofthe crossIn view of this uneven distribution of the vessels, the proportion sectional areas of the vessels in fixed tissue of the cross-sectional area which they occupied was computed for each of a series of concentric annual of 10 pm width around the center ofthe pulp. The results for one tooth are shown in Fig 4. The Materials and methods. average figure for the central, 100-pm -diameter, core of the pulp in Four upper canine teeth from four cats were examined. The the fou teeth was 42.9% (SD, 15.4). In the superficial part of the animals, aged 10-15 months, were anesthetized with sodium pulp, the proportion was between 5 and 10%. It was difficult fbr a pentbarbitone (42 mg/kg i;p.. then 3 mg/kg i.v as reqred) ard m re prece figure fbr thi 1at a perfused with fixatives through both common carotid arteries by ter area to be calculated from means of a two-stage procedure (Forssmann et al., 1977). The final the pooled data, because the fixative solution contained 3% glutaraldehyde, 3% formaldehyde pulps were not a of the same 0.05% picnic acid, and 2.5% polyvinylpyrrolidine (all wv) in 0.1 moP diameter and they were not L phosphate buffr. The tip ofthe cusp (length, 4 mm) ofeach tooth circular. was removed with a diamond disc under Ringes solution, then Almost all the vessels had decalcified and processed for electronmicroscopy by means of a lumens which were close to cirprocedure which was essentially the same as that described by cular,indicatingthattheywere Holland et al. (1987). Each specimen was osmicated and embedded arranged longitudinally in the in Epon, and the block was trimmed to enable a complete transverse tooth. No lymph vessel of the section ofthe pulp to be obtained approximately 0.5 mm from the tip type described by Bishop and of the pulp corn. At this level, the diameter of the pulp was fom Malhotra (1990) was found. 0.32 to 0.38 mm. The sections (thickness, 70-90 nm) were stained with lead acetate and uranyl acetate and examined in a Philips 300 Discssion. electron microscope, For each tooth, a montage (overall magnification, X1000) was The results support the widely formed from a series of electronmicrographs taken from a typical held view that dental pulp is a Fig. I-Montage of a cross-sec section. The outline ofthe pulp and the lumen ofevery vessel in each relatively vascular tissue. The tion through the pulp ofone tooth (no. densityofcapillariesinthecoro- 2)O mm from the pulp coma. The nal pulp of the cat canine is perimeter of the section is formed by Received for publication July 12, 1991 comparable with that in the dentin withtheunderlyingpredentin Accepted for publication August 5, 1992 T whom correspondence and report requests should be addressed tongue and in the most vascu- and odortoblast layer. Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on March 11, 2015 For personal use only. No other uses without permission.
1.913
a) c C(
Q)
>
J Dent Res December 1992
VONGSAVAN & MATTHEWS
1914 40
TABLE 2 TOTAL CROSS-SECTIONAL AREAS (pm2) OF BLOOD VESSELS IN CAT DENTAL PULP
F
30
~0 -0
Vessel Diameter (pm) 20 k
z
Tooth No.
4-10
10-20
20-30
. 30
Total
1
5268
3252
2187
2695
13402
2
4585
4834
6291
6147
21857
3
3652
3503
2095
1177
10427
4
3316
2509
3544
0
9369
Mean
4206
3524
3529
2504
13763
a)
CD >
10
F
a)
,L 0 5
10
15
20 25 30 35 40 45 50 Diameter (,tm) Fig. 2-Frequency distribution of the internal diameters of the pulp blood vessels in four cat canine teeth. In each tooth, the measurements were made on a section taken 0.5 mm from the pulp cornu. The error bars show the standard deviations ofthe average number ofvessels in each bin, except where that number was less than 3. For each vessel, the diameter used in plotting this histogram was the diameter of a circle of the same area as the
vessel.
lar parts of the brain ofthe cat. It is greater than that in most other tissues in the cat, except the heart and kidney (for review, see HudlikA, 1984). In contrast, there are between 20 and 149 capillaryloops (i.e., 40298 capillaries) per mm2 in the superficial layers of human skin in different parts of the body (Ryan, 1973), with an average of 130per mm2 in the skin of the back of the hand (Wetzel and Zotterman, 1926). With this density, the volume fraction ofblood cells in a plane through the capillaries will be less than 1% (Nilsson et al., 1980). We estimate that the volume fraction of red cells is also likely to be just less than 1% in the superficial part ofthe pulp. This is based on our finding that all the vessels in this region are capillaries and that they occupy up to 10% of the tissue volume. From studies on other tissues, the ratio ofthe hematocrit in the capillaries to that in large vessels is likely to be approximately 0.2 (Zweifach and Lipowsky, 1984). Therefore, ifthe large vessel hematocrit was 45%, the volume fraction of red cells in the superficial pulp would be up to 0.9%. However, by the same argument, the average red cell volume fraction in the core (diam., 100 pm ) ofthe pulp will be about 8%. In this region, the vessels accounted for about 43% ofthe tissue volume on average, and most ofthe vessels had diameters between 20 and 47 pm, in which the hematocrit ratio is likely to be between 0.3 and 0.6 (Zweifach and Lipowsky, 1984). Therefore, within individual vessels of this size, the red cell volume fraction will be up to 27%.
TABLE 3 TOTAL CROSS-SECTIONAL AREAS OF BLOOD VESSELS IN CAT DENTAL PULP EXPRESSED AS PERCENTAGES OF THE CROSS-SECTIONAL AREA OF THE PULP Vessel Diameter (pm)
Tooth No.
4-10
10-20
20-30
> 30
Total
1
5.9
3.6
2.4
2.9
14.8
2
3.9
4.2
5.5
5.4
19.0
3
4.2
4.1
2.4
1.4
12.1
4
4.0
3.0
4.3
0
11.3
Mean
4.5
3.7
3.7
2.4
14.4
These figures are well outside the range over which laser Doppler flow meters would be expected to give a linear response (see Vongsavan and Matthews, 1992a,b). These instruments are capable of detecting flow in vessels in the center of the pulp cavity (Vongsavan and Matthews, 1992b). Our evidence indicates, therefore, that they cannot be used reliably to make quantitative measurements of blood flow in teeth and that, for example, a doubling of the signal obtained does not necessarily indicate that the blood flow through the tooth has also doubled. They provide a valuable method of studying pulpal blood flow non-invasively, but the results
TABLE 1 NUMBERS OF BLOOD VESSELS OF DIFFERENT DIAMETERS AND THE TOTAL PULPAL AREA IN A TRANSVERSE SECTION OF CAT DENTAL PULP Vessel Diameter( m) Tooth No.
4-10
10-20
20-30
2 30
Total No.
1
145
22
5
2
174
89907
2
104
32
14
5
155
114689
3
93
21
4
1
119
86346
4
104
17
7
0
128
82382
Total Pulpal Area (pm2)
111 Mean 23 7 2 144 93331 In Tables 1-3, each bin contains values greater than or equal to the lower limit of its range but less than the upper limit. Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on March 11, 2015 For personal use only. No other uses without permission.
Vol. 71 No. 12
PULP VASCULARIY IN CATS
1915
50 1 00 _ 40
L0
E
30
80
0
60
c)
Q)
%
0
U)
0
20
U) U)
U)
40
0
U)
U)
10
l *
: .6;
%
00
I01
20
-
0-
0
1 2*0S-0 00 1 50 50 Distance of Centre of Vessel from Centre of Pulp (am)
Fig. 3-Scatter diagram showing the relationship between the diameter ofeach vessel in one tooth (no. 2) and the distance ofits center from the center of the pulp. The vessel diameters were calculated as in Fig. 2.
0
50
1 00
1 50
200
Distance from Centre of Pulp (am) Fig. 4-Histogram showing, for each of a series of concentric annuli of 10 pm width around the center of the pulp of one tooth (no. 2), the percentage of the total area of each annulus that was occupied by blood vessels. Fig. 3 shows the diameters of the vessels at different distances from the center of the pulp in the same tooth.
obtained must be interpreted with care. REFERENCES The largest vessels were slightly smaller than those observed by intra-vital microscopy in the pulp of rat incisors (see Kim et al., Bishop MA, Malhotra M (1990). An investigation of lymphatic vessels in the 1984). Also, many very small capillaries were found with diameters feline dental pulp. Am JAnat 187:247-253. of 4-5 pm, which were halfthe size ofthose reported in studies on rat Forssmann WG, Ito S, Weihe E, Aoki A, Dym M, Fawcett DW (1977). An incisor pulp. The average diameter ofacat red cell is 5.7 Pm (Windle improvedperfusion fixation method forthe testis. AnatRec 188:307-314. et al., 1940). Gray SJ, Sterling K (1950). The tagging ofred cells and plasma proteins with radioactive chromium. J Clin Invest 29:1604-1613. The distribution of vessels in the cornu of cat pulp corresponds generally with that seen in the models of Takahashi et al. (1982), Holland GR, Matthews B, Robinson PP (1987). An electrophysiological and although we did not encounter as many radially-arranged vessels morphological study of the innervation and reinnervation ofcat dentine. J Physiol (Lond) 386:31-43. (which would have had elongated profiles) as those models suggest. There are three main sources of error in our measurements: the Hudlika 0 (1984). Development of microcirculation: capillary growth and inclusion of vessels that were not perfused with blood in vivo, the adaptation. In: Renkin EM, Michel CC, Geiger SR, editors. Handbook of physiology: The cardiovascular system. Vol. IV, pt. 1. Bethesda (MD): distention of the vessels during perfusion, and the shrinkage of the American Physiological Society, 165-216. specimens during subsequent processing. We have no estimate of the proportion of unperfused vessels in normal pulp, although, as in Kim S, Lipowsky HH, Usami S, Chien S (1984). Arteriovenous distribution other tissues, it is likely that some ofthe capillaries would not have ofhemodynamic parameters in the rat dental pulp. MicrovascRes 27:28been open in vivo. The amount by which the vessels were distended 38. during perfusion cannot be estimated, but it is likely to be less than Nilsson GE, Tenland T, Oberg PA (1980). Evaluation of a laser Doppler flowmeter for measurement of tissue blood flow. IEEE Trans Biomed in most other tissues, on account of the low compliance of the pulp chamber. From measurements ofthe external dimensions of teeth Eng 27:597-604. before and after processing, we estimate that the linear shrinkage Ryan TJ (1973). Structure and shape of blood vessels of skin. In: Jarret A, of the dentin was less than 5%. The presence of a small number of editor. The physiology and pathophysiology of the skin. London (UK): vessels that were not sectioned transversely will not have affected Academic Press, 619-625. our estimate of the volume ofthe pulpal blood vessels, although we Takahashi K, Kishi Y, Kim S (1982). A scanning electron microscope study ofbloodvessels ofthe pulp usingcorrosionresincasts. JEndodont8:131will have overestimated their average diameters. No correction was made to allow for these in the distribution of vessel diameters, since 135. there were so few of them. Vongsavan N, Matthews B (1992a). Some aspects ofthe use oflaser Doppler An alternative method of estimating the mean red cell volume flow meters for recording tissue blood flow. Exp Physiol (in press). fraction of pulp would be to use 51Cr-labeled red cells (Gray and Vongsavan N, Matthews B (1992b). In vitro experiments on the use oflaser Doppler techniques for recording blood flow in teeth. Arch Oral Biol (in Sterling, 1950). The number of erythrocytes in the pulp could be determined by ligation of the pulp near the apical foramen in vivo, press). extraction of the tooth, then freezing it to prevent blood being lost Wetzel NC, Zotterman Y (1926). On differences in the vascular colouration of various regions of the normal human skin. Heart 13:357-369. from the pulp while it was being dissected out before counts were Windle WF, Sweet M, Whitehead WH (1940). Some aspects of prenatal and made on the tissue. postnatal development of the blood in the cat. Anat Rec 78:321-332. Zweifach BW, Lipowsky HH (1984). Pressure-flow relations in blood and Acknowledgment. lymph microcirculation. In: Renkin EM, Michel CC, Geiger SR, editors. Handbook of physiology: The cardiovascular system. Vol. 4, pt. 1. We are grateful to Mr. G. Harrison for carrying out the electronBethesda (MD): American Physiological Society, 251-307. microscopy.
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