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A pilot study of mineralization distribution in the cortical bone of the human mandible
ARCHIVES OF
PERGAMON
Archives of Oral Biology 43 (1998) 633±639
ORAL BIOLOGY
A pilot study of mineralization distribution in the cortical bone of the human mandible R.S. Hobson Department of Child Dental Health, Newcastle Dental School, Framlington Place, Newcastle-upon-Tyne, NE2 4BW, UK Received 24 February 1998; accepted 7 April 1998
Abstract Twenty-three specimens from immediately anteroinferior to the mental foramen were obtained from male and female, dentate and edentate, human mandibles. Planoparallel 80 mm thick sections were prepared from the mandibular specimens and computerized quantitative microradiography undertaken, which allowed the production of mineralization frequency distruction curves and mean mineralization. No dierences in mean mineralization with age, sex, presence or absence of dentition were found, but mineralization distribution curves indicated dierences between males and females. Within the age range and small sample size examined (40±90 years) there were no agerelated dierences. There was a lower level of mineralization distribution in the edentulous than the dentate mandible. # 1998 Elsevier Science Ltd. All rights reserved. Keywords: Human mandible; Microradiography; Mineralization; Dentition
1. Introduction Changes that occur in the human mandible after the loss of the dentition are well known and are characterized by the loss of the alveolar ridge. The associated decrease in bit forces accompanying tooth loss may account for the `disuse atrophy' of the alveolus (Devlin and Ferguson, 1991), yet with the loss of the alveolar ridge a greater proportion of occlusal forces has to be absorbed by the mandibular basal bone. The forces exerted upon a bone and the distribution of stress within it will have an eect upon remodelling. Nidelman and Bernick (1978) reported that a thinning of the cortical plates of the mandible followed the loss of teeth. This thinning was associated with an increased porosity of mandibular bone with age (Atkinson and Woodhead, 1968), yet they found no dierences in relation to tooth loss. In biomechanical terms the mandible is a complex structure, possessing two separate load-bearing joints with the masticatory muscles attached on the widely separated rami. In the dentate state, forces are transmitted from the teeth through the alveolar bone into
the basal bone, which undergoes tensile, compressive and torsional loading. Loss of the teeth results in disuse resorption of the alveolar bone, but the mandible is still subject to these various loads. There have been few systematic studies on bone mass in the adult mandible. Atkinson and Woodhead (1968) demonstrated that the porosity of the mandible increases with age, being more pronounced in the alveolar than the basal bone, although the distribution of porosity bore no relation to tooth loss or resorption of alveolar bone. In 1986, Von Wowern reviewed her series of studies on mean mandibular bone mineralization. She concluded that there is a dierence in bone mineral content between males and females, and that there is an increase in cortical porosity in those over the age of 50 years, which is more pronounced in females. She also concluded that bone mass in the mandible is independent of the presence or absence of the dentition. The purpose of this pilot study was to investigate the changes that might occur within the mandibular cortical plate as assessed by mineralization distribution and mean mineralization using the technique of com-
0003-9969/98/$19.00 # 1998 Elsevier Science Ltd. All rights reserved. PII: S 0 0 0 3 - 9 9 6 9 ( 9 8 ) 0 0 0 4 9 - 1
634
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
Table 1 Distribution of donors (age in parentheses)
Dentate Edentate
Female
Male
2 (40, 76) 7 (40, 74, 82, 82, 84, 84, 89)
4 (66, 69, 72, 72) 10 (55, 58, 60, 61, 68, 71, 72, 77, 77, 81) Total male 14
Total female 9
puterized quantitative microradiography (Hobson and Beynon, 1997). 2. Materials and methods Autopsy specimens of mandibular bone were obtained with an 8 mm bone trephine. The construction of the trephine was such that the body separated, so avoiding damage to the specimen that can occur in designs where the bone core is pushed out with a plunger. Strict criteria for the acceptance of autopsy material avoided any with disease of skeletal development or metabolism. The cause of death had to have been sudden and medical records were checked to ensure that there was no history of disease that might have aected bone metabolism, and that any inpatient care
Total dentate 6 Total edentate 17 Total 23
before death had not been for more than 7 days (Jowsey, 1973). In any study on bone it is also necessary to ensure that the material is within the normal range for the individual's age. This was con®rmed by iliac-crest biopsy and the results compared with normal values for age and sex (Melsen et al., 1978). Nine individuals were found to have been osteoporotic and were excluded from the study. This screening resulted in 23 specimens for analysis, four from dentate males, two from dentate females, ten from edentate males and seven from edentate females, with an age range between 40 and 89 years (Table 1). A dentate donor was de®ned as having more than four teeth in all four quadrants; the edentate had no standing teeth. Transverse cortex-to-cortex bone samples were taken from the body of the mandible immediately anteroinferior to the mental foramen. This site was chosen as it
Fig. 1. Mineralization frequency distribution for males and females.
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
635
Fig. 2. Mineralization frequency distribution for dentate males and females.
is the most consistently reproducible anatomical site in the mandible (Morrant, 1936). Von Wowern (1977) has also de®ned it as the site of choice in studies comparing dierent mandibles. The buccal-plate core sample was removed from the trephine and embedded in paran wax. A section was then cut through the middle of the core of bone at right angles to the lower border of the mandible. Specimens were prepared to a planoparallel thickness of 80 mm and computerized microradiography undertaken as described by Hobson and Beynon (1997). Microradiographs were prepared using an aluminium step-wedge with a base foil 31.4 mm thick and ®ve stepped foils of 8.9 mm each, producing a maximum thickness of 75.9 mm. This wedge was exposed alongside the specimen on Kodak high-resolution plates using a Phillips PW 1008 X-ray diraction generator, with a 20 mm thick nickel ®lter to produce monochromatic X-rays of between 1.5±1.6 AÊ. Lindstrom and Philipson (1969) reported a system error of less than 2% for quantitative microradiography. The resultant microradiograpy was analysed with a Leitz MPV microphotometer linked directly to a microcomputer, which was used to calculate and record the percentage mineral (Angmar et al., 1963) at 400 sites on each specimen. The application of point counting from stereological principles (Weibel and
Elias, 1967) allowed the calculation of the mineralization frequency distribution as follows. First, the volume of bone occupied by mineralized tissue at each of the 400 sample sites was determined and expressed as a percentage. These values were then ranked into 26 groups from 0 to 50% bone mineralization in 2% increments. The mineralization frequency distribution is the plot showing the number of samples recorded in each 2% increment. Mean mineralization is the average mineralization of the 400 sample sites recorded on the specimen. Data were analysed with the student paired t-test and the Kolmogorov±Smirnov two-sample test, which tests whether two independent samples have been drawn from populations with the same distributions and is ideal for examination of the mineralized frequency distribution data. 3. Results The eect of sex on the summed mean mineralization of males and females (male 36.58% SD 2.5; female 32.99% SD 3.9) gave a t-test value of 0.7939 ( p>0.05). However, the mineralization distributions (Figs. 1 and 2) showed a pronounced sex dierence, with males having a large, bimodal shift to higher
636
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
Fig. 3. Mineralization frequency distribution for edentate males and females.
Fig. 4. Mineralization frequency distribution for dentate and edentate.
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
Fig. 5. Mineralization frequency distribution for male dentate and edentate.
Fig. 6. Mineralization frequency distribution for female dentate and edentate.
637
638
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
levels of mineralization than females. A Kolmogorov± Smirnov test value of 13.277 ( p < 0.01) con®rmed that there was a signi®cant dierence in the mineralization distributions. As it was found that there were dierences due to the presence or absence of the dentition (see later), distribution curves for males and females in dendate and edentate mandibles were examined separately (Figs. 3 and 4). No dierence was found between the mean mineralization in dentate males and females ( p>0.05) or edentate males and females ( p>0.05). The Kolmogorov±Smirnov test found signi®cant dierences in the distribution between dentate ( p < 0.001) and edentate ( p < 0.001) males and females. This suggests that males have a dierent mineralization distribution from females in dentate and edentate mandibles. The data for age were divided into age groups, and ANOVA used (Table 1). The F-values showed that there were no signi®cant dierences between mean mineralization associated with age. However, the sample size, especially in younger age groups, was small. Analysis of the summed results for dentate and edentate individuals gave a t-value of 0.1515 ( p>0.05) for the mean mineralization of mandibles. The mineralization distribution curves (Fig. 5) also showed similar distributions of mineralization. Because of the earlier ®nding that there were sex dierences, further analysis for the eect of the presence or absence of teeth on mineralization distribution in mandibles was made separately for males and females. The distribution curves for males and females (Fig. 6 and 7) showed the dierences in their mineralization levels. In males (Fig. 6) a bimodal distribution was seen in both dentate and edentate mandibles, with edentate mandibles having a higher proportion of mineralized tissue than dentate, the dierences in the curves being con®rmed by Kolmogorov±Smirnov test value of 10.684 ( p < 0.01). Female dentate and edentate mandibles did not exhibit the bimodal distribution seen in males, but the higher mineralization levels were again seen in edentate mandibles compared with dentate, con®rmed by a Kolmogorov±Smirnov value of 8.267 ( p < 0.01). This indicates that there are dierences in the mineralization distribution in edentate and dentate mandibles. 4. Discussion These data are from a small pilot study. The results from computerized quantitative microradiography suggest that there is no sex dierence in the mean mineralization of the mandible, in agreement with Wowern and Stoltze (1978, 1979). However, signi®cant dierences in mineral distribution were found between males and females. These dierences might be
explained by the slower secondary mineralization that occurs in women over 40 years of age, producing an apparent increase in the number of slightly mineralized osteons (Jowsey, 1968; Pavlova and Poliaknov, 1971). Amprino (1952) was the ®rst to use quantitative microradiography to examine how mineralization distribution changes with age. With a limited sample of only three individuals, aged 7, 20 and 87 years, he reported changes in mineral distribution that he proposed re¯ected a decreased bone turnover with age. Reid and Boyde (1987), using back-scattered electron imaging in the scanning electron microscope on rib cortices, reported that the proportion of more highly mineralized tissue increased with age, but was stable in the age range 40±90 years. The present results con®rm Reid's ®ndings. Previous studies (Von Wowern and Stoltze, 1978, 1979; Von Wowern, 1977, 1982; Atkinson and Woodhead, 1968) of bone porosity have found no dierence between dentate and edentate mandibles. The present ®nding that there is no dierence in the mean mineralization level in relation to the presence or absence of the dentition agrees with those studies. However, all these results are based upon mean data from sections and none takes into account the subtle dierences that occur within osteons and interstitial bone. The use of computerized quantitative microradiography as described here allows examination of the dierences in mineralization distribution. It con®rms previous ®ndings (Amprino, 1952; Sissons et al., 1060a,b; Hobson and Beynon, 1997) that quantitative microradiography is capable of examining the dierences in mineralization distribution of bone. Computerization of the technique provides the opportunity to examine in detail the changes that can occur.
References Amprino, A., 1952. Rapport fra processi di ricostruzione e distrbuzione dei minerali nelle ossa. Z. Zellforschung 37, 144±183. Angmar, B., Carlstrom, D., Glas, J.E., 1963. Studies on the ultrastructure of dental enamel IV: the mineralization of normal human enamel. J. ultrastructure Res. 8, 12±23. Atkinson, P.J., Woodhead, C., 1968. Changes in the human mandibular structure with age. Arch. oral Biol. 13, 1453± 1463. Devlin, H., Ferguson, M.W.J., 1991. Alveolar ridge resorption and mandibular atrophy. A review of the role of local and systemic factors. Brit. Dent. J. 170, 101±104. Hobson, R.S., Beynon, A.D., 1997. Variation of mineralisation distribution within human mandibular bone associated with the loss of the dentition. Arch. oral Biol. 42, 497± 503.
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639 Jowsey, J., 1973. The microradiographic assessment of bone structure. Triangle 12, 93±101. Jowsey, J., 1968. Age and species dierences in bone. Cornell Vet. 58: (Suppl.), 74±94. Lindstrom, B., Philipson, B., 1969. Densometric evaluation of quantitative microradiography. Histochemie 17, 194±200. Melsen, F., Melsen, B., Mosekilde, L., Bergman, S., 1978. Histomorphometric analysis of normal bone from iliac crest. Acta Pathol, Microbiol Scand. 86, 70±81. Morant, G.M., 1936. A biometric study of the human mandible. Biometrika 28, 84±112. Nidelman, C.I., Bernick, S., 1978. The signi®cance of age changes in human alveolar mucosa and bone. J. Pros. Dent. 39, 495±501. Pavlova, M.N., Poliaknov, A.N., 1971. Age changes of mineralisation of the human femur according to quantitative microradiography. Arkh. Anat. Gistol. Embriol. 61, 83±88. Reid, S.A., Boyde, A., 1987. Changes in the mineral density distribution in human bone with age: image analysis using backscattered electrons in the SEM. Bone Mineral Research 2 (1), 13±22. Reid, D.J., Wilson, P.R., Beynon, A.D., 1985. A rapid method for preparing plano-parallel sections of human teeth, and tests of abrasive particle size on surface pro®le and ®nish. J. Dent. Res. 64, Abst No. 238.
639
Sissons, H.A., Jowsey, J., Stewart, L. 1960a. Quantitative microradiography of bone tissue. In X-ray microscopy and X-ray microanalysis. Proceedings of the 2nd international symposium. Eds A. Engstrom, V. Cosslett, H. Pattee. Sissons, H.A., Jowsey, J., Stewart, L. 1960b. The microradiographic appearance of normal bone tissue at various ages. In X-ray microscopy and X-ray microanalysis. Proceedings of the 2nd international symposium. Eds A. Engstrom, V. Cosslett, H. Pattee. Von Wowern, N., 1977. Variations in bone mass within the cortices of the mandible. Scand. J. Dent. Res. 85, 444±455. Von Wowern, N., 1982. Microradiographic and histomorphometric indices of mandibles for diagnosis of osteopenia. Scand. J. Dent. Res. 90, 46±73. Von Wowern, N., 1986. Bone mass of mandibles. Danish Med. Bull. 33, 23±44. Von Wowern, N., Stoltze, K., 1978. Sex and age dierences in bone morphology of mandibles. Scand. J. Dent. Res. 86, 478±485. Von Wowern, N., Stoltze, K., 1979. Age dierences in cortical width of mandibles determined by histoquantitation. Scand. J. Dent. Res. 87, 225±233. Weibel, E.R., Elias, H., 1967. Introduction to stereological principles. In: E.R. Weibel, H. Elias (Ed.). Quantitative Methods in Morphology. Springer.
PERGAMON
Archives of Oral Biology 43 (1998) 633±639
ORAL BIOLOGY
A pilot study of mineralization distribution in the cortical bone of the human mandible R.S. Hobson Department of Child Dental Health, Newcastle Dental School, Framlington Place, Newcastle-upon-Tyne, NE2 4BW, UK Received 24 February 1998; accepted 7 April 1998
Abstract Twenty-three specimens from immediately anteroinferior to the mental foramen were obtained from male and female, dentate and edentate, human mandibles. Planoparallel 80 mm thick sections were prepared from the mandibular specimens and computerized quantitative microradiography undertaken, which allowed the production of mineralization frequency distruction curves and mean mineralization. No dierences in mean mineralization with age, sex, presence or absence of dentition were found, but mineralization distribution curves indicated dierences between males and females. Within the age range and small sample size examined (40±90 years) there were no agerelated dierences. There was a lower level of mineralization distribution in the edentulous than the dentate mandible. # 1998 Elsevier Science Ltd. All rights reserved. Keywords: Human mandible; Microradiography; Mineralization; Dentition
1. Introduction Changes that occur in the human mandible after the loss of the dentition are well known and are characterized by the loss of the alveolar ridge. The associated decrease in bit forces accompanying tooth loss may account for the `disuse atrophy' of the alveolus (Devlin and Ferguson, 1991), yet with the loss of the alveolar ridge a greater proportion of occlusal forces has to be absorbed by the mandibular basal bone. The forces exerted upon a bone and the distribution of stress within it will have an eect upon remodelling. Nidelman and Bernick (1978) reported that a thinning of the cortical plates of the mandible followed the loss of teeth. This thinning was associated with an increased porosity of mandibular bone with age (Atkinson and Woodhead, 1968), yet they found no dierences in relation to tooth loss. In biomechanical terms the mandible is a complex structure, possessing two separate load-bearing joints with the masticatory muscles attached on the widely separated rami. In the dentate state, forces are transmitted from the teeth through the alveolar bone into
the basal bone, which undergoes tensile, compressive and torsional loading. Loss of the teeth results in disuse resorption of the alveolar bone, but the mandible is still subject to these various loads. There have been few systematic studies on bone mass in the adult mandible. Atkinson and Woodhead (1968) demonstrated that the porosity of the mandible increases with age, being more pronounced in the alveolar than the basal bone, although the distribution of porosity bore no relation to tooth loss or resorption of alveolar bone. In 1986, Von Wowern reviewed her series of studies on mean mandibular bone mineralization. She concluded that there is a dierence in bone mineral content between males and females, and that there is an increase in cortical porosity in those over the age of 50 years, which is more pronounced in females. She also concluded that bone mass in the mandible is independent of the presence or absence of the dentition. The purpose of this pilot study was to investigate the changes that might occur within the mandibular cortical plate as assessed by mineralization distribution and mean mineralization using the technique of com-
0003-9969/98/$19.00 # 1998 Elsevier Science Ltd. All rights reserved. PII: S 0 0 0 3 - 9 9 6 9 ( 9 8 ) 0 0 0 4 9 - 1
634
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
Table 1 Distribution of donors (age in parentheses)
Dentate Edentate
Female
Male
2 (40, 76) 7 (40, 74, 82, 82, 84, 84, 89)
4 (66, 69, 72, 72) 10 (55, 58, 60, 61, 68, 71, 72, 77, 77, 81) Total male 14
Total female 9
puterized quantitative microradiography (Hobson and Beynon, 1997). 2. Materials and methods Autopsy specimens of mandibular bone were obtained with an 8 mm bone trephine. The construction of the trephine was such that the body separated, so avoiding damage to the specimen that can occur in designs where the bone core is pushed out with a plunger. Strict criteria for the acceptance of autopsy material avoided any with disease of skeletal development or metabolism. The cause of death had to have been sudden and medical records were checked to ensure that there was no history of disease that might have aected bone metabolism, and that any inpatient care
Total dentate 6 Total edentate 17 Total 23
before death had not been for more than 7 days (Jowsey, 1973). In any study on bone it is also necessary to ensure that the material is within the normal range for the individual's age. This was con®rmed by iliac-crest biopsy and the results compared with normal values for age and sex (Melsen et al., 1978). Nine individuals were found to have been osteoporotic and were excluded from the study. This screening resulted in 23 specimens for analysis, four from dentate males, two from dentate females, ten from edentate males and seven from edentate females, with an age range between 40 and 89 years (Table 1). A dentate donor was de®ned as having more than four teeth in all four quadrants; the edentate had no standing teeth. Transverse cortex-to-cortex bone samples were taken from the body of the mandible immediately anteroinferior to the mental foramen. This site was chosen as it
Fig. 1. Mineralization frequency distribution for males and females.
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
635
Fig. 2. Mineralization frequency distribution for dentate males and females.
is the most consistently reproducible anatomical site in the mandible (Morrant, 1936). Von Wowern (1977) has also de®ned it as the site of choice in studies comparing dierent mandibles. The buccal-plate core sample was removed from the trephine and embedded in paran wax. A section was then cut through the middle of the core of bone at right angles to the lower border of the mandible. Specimens were prepared to a planoparallel thickness of 80 mm and computerized microradiography undertaken as described by Hobson and Beynon (1997). Microradiographs were prepared using an aluminium step-wedge with a base foil 31.4 mm thick and ®ve stepped foils of 8.9 mm each, producing a maximum thickness of 75.9 mm. This wedge was exposed alongside the specimen on Kodak high-resolution plates using a Phillips PW 1008 X-ray diraction generator, with a 20 mm thick nickel ®lter to produce monochromatic X-rays of between 1.5±1.6 AÊ. Lindstrom and Philipson (1969) reported a system error of less than 2% for quantitative microradiography. The resultant microradiograpy was analysed with a Leitz MPV microphotometer linked directly to a microcomputer, which was used to calculate and record the percentage mineral (Angmar et al., 1963) at 400 sites on each specimen. The application of point counting from stereological principles (Weibel and
Elias, 1967) allowed the calculation of the mineralization frequency distribution as follows. First, the volume of bone occupied by mineralized tissue at each of the 400 sample sites was determined and expressed as a percentage. These values were then ranked into 26 groups from 0 to 50% bone mineralization in 2% increments. The mineralization frequency distribution is the plot showing the number of samples recorded in each 2% increment. Mean mineralization is the average mineralization of the 400 sample sites recorded on the specimen. Data were analysed with the student paired t-test and the Kolmogorov±Smirnov two-sample test, which tests whether two independent samples have been drawn from populations with the same distributions and is ideal for examination of the mineralized frequency distribution data. 3. Results The eect of sex on the summed mean mineralization of males and females (male 36.58% SD 2.5; female 32.99% SD 3.9) gave a t-test value of 0.7939 ( p>0.05). However, the mineralization distributions (Figs. 1 and 2) showed a pronounced sex dierence, with males having a large, bimodal shift to higher
636
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
Fig. 3. Mineralization frequency distribution for edentate males and females.
Fig. 4. Mineralization frequency distribution for dentate and edentate.
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
Fig. 5. Mineralization frequency distribution for male dentate and edentate.
Fig. 6. Mineralization frequency distribution for female dentate and edentate.
637
638
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639
levels of mineralization than females. A Kolmogorov± Smirnov test value of 13.277 ( p < 0.01) con®rmed that there was a signi®cant dierence in the mineralization distributions. As it was found that there were dierences due to the presence or absence of the dentition (see later), distribution curves for males and females in dendate and edentate mandibles were examined separately (Figs. 3 and 4). No dierence was found between the mean mineralization in dentate males and females ( p>0.05) or edentate males and females ( p>0.05). The Kolmogorov±Smirnov test found signi®cant dierences in the distribution between dentate ( p < 0.001) and edentate ( p < 0.001) males and females. This suggests that males have a dierent mineralization distribution from females in dentate and edentate mandibles. The data for age were divided into age groups, and ANOVA used (Table 1). The F-values showed that there were no signi®cant dierences between mean mineralization associated with age. However, the sample size, especially in younger age groups, was small. Analysis of the summed results for dentate and edentate individuals gave a t-value of 0.1515 ( p>0.05) for the mean mineralization of mandibles. The mineralization distribution curves (Fig. 5) also showed similar distributions of mineralization. Because of the earlier ®nding that there were sex dierences, further analysis for the eect of the presence or absence of teeth on mineralization distribution in mandibles was made separately for males and females. The distribution curves for males and females (Fig. 6 and 7) showed the dierences in their mineralization levels. In males (Fig. 6) a bimodal distribution was seen in both dentate and edentate mandibles, with edentate mandibles having a higher proportion of mineralized tissue than dentate, the dierences in the curves being con®rmed by Kolmogorov±Smirnov test value of 10.684 ( p < 0.01). Female dentate and edentate mandibles did not exhibit the bimodal distribution seen in males, but the higher mineralization levels were again seen in edentate mandibles compared with dentate, con®rmed by a Kolmogorov±Smirnov value of 8.267 ( p < 0.01). This indicates that there are dierences in the mineralization distribution in edentate and dentate mandibles. 4. Discussion These data are from a small pilot study. The results from computerized quantitative microradiography suggest that there is no sex dierence in the mean mineralization of the mandible, in agreement with Wowern and Stoltze (1978, 1979). However, signi®cant dierences in mineral distribution were found between males and females. These dierences might be
explained by the slower secondary mineralization that occurs in women over 40 years of age, producing an apparent increase in the number of slightly mineralized osteons (Jowsey, 1968; Pavlova and Poliaknov, 1971). Amprino (1952) was the ®rst to use quantitative microradiography to examine how mineralization distribution changes with age. With a limited sample of only three individuals, aged 7, 20 and 87 years, he reported changes in mineral distribution that he proposed re¯ected a decreased bone turnover with age. Reid and Boyde (1987), using back-scattered electron imaging in the scanning electron microscope on rib cortices, reported that the proportion of more highly mineralized tissue increased with age, but was stable in the age range 40±90 years. The present results con®rm Reid's ®ndings. Previous studies (Von Wowern and Stoltze, 1978, 1979; Von Wowern, 1977, 1982; Atkinson and Woodhead, 1968) of bone porosity have found no dierence between dentate and edentate mandibles. The present ®nding that there is no dierence in the mean mineralization level in relation to the presence or absence of the dentition agrees with those studies. However, all these results are based upon mean data from sections and none takes into account the subtle dierences that occur within osteons and interstitial bone. The use of computerized quantitative microradiography as described here allows examination of the dierences in mineralization distribution. It con®rms previous ®ndings (Amprino, 1952; Sissons et al., 1060a,b; Hobson and Beynon, 1997) that quantitative microradiography is capable of examining the dierences in mineralization distribution of bone. Computerization of the technique provides the opportunity to examine in detail the changes that can occur.
References Amprino, A., 1952. Rapport fra processi di ricostruzione e distrbuzione dei minerali nelle ossa. Z. Zellforschung 37, 144±183. Angmar, B., Carlstrom, D., Glas, J.E., 1963. Studies on the ultrastructure of dental enamel IV: the mineralization of normal human enamel. J. ultrastructure Res. 8, 12±23. Atkinson, P.J., Woodhead, C., 1968. Changes in the human mandibular structure with age. Arch. oral Biol. 13, 1453± 1463. Devlin, H., Ferguson, M.W.J., 1991. Alveolar ridge resorption and mandibular atrophy. A review of the role of local and systemic factors. Brit. Dent. J. 170, 101±104. Hobson, R.S., Beynon, A.D., 1997. Variation of mineralisation distribution within human mandibular bone associated with the loss of the dentition. Arch. oral Biol. 42, 497± 503.
R.S. Hobson / Archives of Oral Biology 43 (1998) 633±639 Jowsey, J., 1973. The microradiographic assessment of bone structure. Triangle 12, 93±101. Jowsey, J., 1968. Age and species dierences in bone. Cornell Vet. 58: (Suppl.), 74±94. Lindstrom, B., Philipson, B., 1969. Densometric evaluation of quantitative microradiography. Histochemie 17, 194±200. Melsen, F., Melsen, B., Mosekilde, L., Bergman, S., 1978. Histomorphometric analysis of normal bone from iliac crest. Acta Pathol, Microbiol Scand. 86, 70±81. Morant, G.M., 1936. A biometric study of the human mandible. Biometrika 28, 84±112. Nidelman, C.I., Bernick, S., 1978. The signi®cance of age changes in human alveolar mucosa and bone. J. Pros. Dent. 39, 495±501. Pavlova, M.N., Poliaknov, A.N., 1971. Age changes of mineralisation of the human femur according to quantitative microradiography. Arkh. Anat. Gistol. Embriol. 61, 83±88. Reid, S.A., Boyde, A., 1987. Changes in the mineral density distribution in human bone with age: image analysis using backscattered electrons in the SEM. Bone Mineral Research 2 (1), 13±22. Reid, D.J., Wilson, P.R., Beynon, A.D., 1985. A rapid method for preparing plano-parallel sections of human teeth, and tests of abrasive particle size on surface pro®le and ®nish. J. Dent. Res. 64, Abst No. 238.
639
Sissons, H.A., Jowsey, J., Stewart, L. 1960a. Quantitative microradiography of bone tissue. In X-ray microscopy and X-ray microanalysis. Proceedings of the 2nd international symposium. Eds A. Engstrom, V. Cosslett, H. Pattee. Sissons, H.A., Jowsey, J., Stewart, L. 1960b. The microradiographic appearance of normal bone tissue at various ages. In X-ray microscopy and X-ray microanalysis. Proceedings of the 2nd international symposium. Eds A. Engstrom, V. Cosslett, H. Pattee. Von Wowern, N., 1977. Variations in bone mass within the cortices of the mandible. Scand. J. Dent. Res. 85, 444±455. Von Wowern, N., 1982. Microradiographic and histomorphometric indices of mandibles for diagnosis of osteopenia. Scand. J. Dent. Res. 90, 46±73. Von Wowern, N., 1986. Bone mass of mandibles. Danish Med. Bull. 33, 23±44. Von Wowern, N., Stoltze, K., 1978. Sex and age dierences in bone morphology of mandibles. Scand. J. Dent. Res. 86, 478±485. Von Wowern, N., Stoltze, K., 1979. Age dierences in cortical width of mandibles determined by histoquantitation. Scand. J. Dent. Res. 87, 225±233. Weibel, E.R., Elias, H., 1967. Introduction to stereological principles. In: E.R. Weibel, H. Elias (Ed.). Quantitative Methods in Morphology. Springer.