Objective:

To test the hypothesis that immunohistochemical changes in expression of basic fibroblast growth factor in the periodontal ligament do not change with age.

Materials and Methods:

Thirty male Wistar-ST rats were divided into growing groups (5, 9, and 15 weeks of age) and aging groups (6, 12, and 18 months of age). Serial sagittal sections (5 µm thick) were cut parallel at the distobuccal roots of the maxillary first molar. Paraffin-embedded tissue sections were stained with hematoxylin and eosin and rabbit polyclonal antibodies to basic fibroblast growth factor.

Results:

The number and the area of basic fibroblast growth factor–immunoreactive cells in the periodontal ligament of the maxillary first molar decreased with age. The number of basic fibroblast growth factor–immunoreactive cells was much greater in the root furcation area, which experiences the greatest effect of occlusal force. Regardless of age, the production of basic fibroblast growth factor in the periodontal ligament may occur subject to functional demand.

Conclusions:

The hypothesis is rejected. The expression of basic fibroblast growth factor in the periodontal ligament decreased with age.

bFGF, Aging, Periodontal ligament, Rat molar, Occlusal force

In recent years, more adults and people over 50 years of age have undergone orthodontic treatment. Orthodontic tooth movement in the elderly is more complex than that of younger people. This is because adults who have periodontal problems risk permanent periodontal ligament damage.1 To improve the results of treatment, comprehension of the alteration of periodontal tissue with growth and age is important.

Aging results in various effects on periodontal tissue. The morphology of the periodontal ligament changes as age increases. The periodontal ligament width becomes smaller and more irregular in older animals.2 The maximum shear stress and stiffness of the rat molar periodontal ligament decrease with age.3 In older animals the proliferative rate of periodontal ligament cells4 and collagenous fibers2 is reduced, and an elevation of the physiologic threshold against mechanical stress5 and an inactivity of osteoblasts and osteoclasts occurs histologically.6 

Periodontal tissue, in particular the periodontal ligament, plays an important role in bone remodeling at the periodontal ligament–alveolar bone interface during orthodontic force application. Tooth movement is also affected by age. The biologic response to orthodontic stimuli is delayed in adults.4,7 Age affects proliferative activity of the periodontal ligament and tooth movement in the initial phase.8 

During remodeling of the periodontal ligament, the proliferation, differentiation, and apoptosis of various cells are modulated by several hormones and growth factors, such as fibroblast growth factor. Fibroblast growth factor (FGF) is known as one of the growth factors in periodontal ligament. Twenty-two kinds of FGF family members have been identified so far. FGF adjusts the connection with FGF-receptors (FGFR) by interaction with heparitin sulfate proteoglycans.9,10 Basic fibroblast growth factor (bFGF, FGF-2) appears in the periodontal ligament.11 bFGF transmits signals with the aid of FGFR on the surface of the target cells.

bFGF promotes wound healing and vascularization and controls bone mass and bone formation.12 bFGF increases the activity of osteoclasts and decreases the production of type I collagen and suppresses alkaline phosphatase activity.13 It prevents periodontal ligament cells from cyto-differentiating into mineralized tissue-forming cells. During orthodontic force application, the expression of bFGF was inhibited on the side of the periodontal ligament that received tensile force.14 

Cytokines play important roles for orthodontic treatment in the elderly. Therefore, it is important in orthodontics to clarify the age effect on the expression of bFGF in periodontal ligament. Nevertheless, it remains unclear whether growth and age affect the expression of bFGF in periodontal ligaments. In our study, we used immunohistochemistry to investigate the effects of the expression of bFGF in periodontal ligament with growth and age using rats.

Animal and Tissue Preparation

Thirty male Wistar-ST rats (Sankyo Lab Service, Tokyo, Japan) ranging in age from 5 weeks to 18 months were used. Five rats were used at each time point. They had free access to food and water.

Rats at 5 and 9 weeks of age have not completed the root formation. At 5 weeks of age, two-thirds of the root is developed. At 9 weeks of age, three-quarters of the root is developed. The root formation is fully developed at 15 weeks of age. Rats at 5, 9, and 15 weeks correspond to adolescent humans at 9, 15, and 18 years of age, respectively. Rats at 6, 12, and 18 months of age are equivalent to adult humans at 20, 35, and 50 years of age, respectively.15,16 

At 5, 9, and 15 weeks of age and at 6, 12, and 18 months of age, after administering inhalant anesthesia, all rats were perfused intracardially through the left ventricle with 4% paraformaldehyde in an 0.1 M phosphate-buffered saline solution (pH 7.4). The maxillary specimens were removed en bloc, immersed in the same fixative at 4°C for 24 hours, and decalcified in 10% ethylenediaminetetraacetic acid solution for 5 weeks; the specimens were then embedded in paraffin using conventional methods. Serial sagittal sections (5 µm thick) were cut (RM2155; LEICA, Nussloch, Germany) parallel to the long axis of the mesial and distal roots of the rat maxillary first molar (M1) and mounted on glass slides coated with poly-l-lysine (Matsunami Glass, Osaka, Japan) (Figure 1A,B). At each time point eight serial sections per animal were analyzed.

Figure 1
Figure 1. Area of investigation. (A) Areas of 100 × 200 µm of the distal root mesial surface of the maxillary first molar (M1) located superiorly from the middle of the root length; the root furcation and root apical were used for observation. (B) Diagram showing a horizontal view of M1. Serial sagittal sections were cut parallel to the long axis of the mesialbuccal root and distobuccal root of M1.
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Area of investigation. (A) Areas of 100 × 200 µm of the distal root mesial surface of the maxillary first molar (M1) located superiorly from the middle of the root length; the root furcation and root apical were used for observation. (B) Diagram showing a horizontal view of M1. Serial sagittal sections were cut parallel to the long axis of the mesialbuccal root and distobuccal root of M1.

Figure 1
Figure 1. Area of investigation. (A) Areas of 100 × 200 µm of the distal root mesial surface of the maxillary first molar (M1) located superiorly from the middle of the root length; the root furcation and root apical were used for observation. (B) Diagram showing a horizontal view of M1. Serial sagittal sections were cut parallel to the long axis of the mesialbuccal root and distobuccal root of M1.
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Area of investigation. (A) Areas of 100 × 200 µm of the distal root mesial surface of the maxillary first molar (M1) located superiorly from the middle of the root length; the root furcation and root apical were used for observation. (B) Diagram showing a horizontal view of M1. Serial sagittal sections were cut parallel to the long axis of the mesialbuccal root and distobuccal root of M1.

Close modal

The distopalatal root was selected for observation. In order to examine the changes in the periodontium of the rat maxillary molar, hematoxylin and eosin staining of the deparaffinized sections was performed; the stained sections were then observed by light microscopy.

Animal protocols were approved by the Institutional Animal Care and Use Committee of Tokyo Medical and Dental University. The experiments were carried out under the control of the University's Guidelines for Animal Experimentation.

Immunohistochemistry

The deparaffinized sections were immersed in 0.05 M Tris-HCl (pH 7.6) for 5 minutes and then immersed in 0.04% proteinase K for 7 minutes to activate antigen. After antigen activation, the sections were immersed in methanol containing 3% hydrogen peroxide for 30 minutes at 37°C to block endogenous peroxide activity and were then rinsed with 0.01 M phosphate-buffered saline solution. After pretreatment, the sections were incubated with the rabbit polyclonal antibody to bFGF (diluted at 1∶100, Santa Cruz Biotechnology, Santa Cruz, Calif) in phosphate-buffered saline solution containing 0.5% normal goat serum for 30 minutes at 37°C. After primary antibody response, the sections were incubated with anti-rabbit biotin-labeled antibody for 10 minutes at 37°C and then reacted with peroxidase-labeled streptavidin for 10 minutes at 37°C following the manual of LSAB method (DAKO LSAB 2kit; Dako, Carpinteria, Calif). Finally, the sections were stained with 3,3′-diaminobenzidine.

Quantitative Analysis

The observation area was photographed using a light microscope (Nikon Microphoto-FXA, Nikon, Tokyo, Japan) equipped with a digital camera (DXm1200, Nikon). The length of the periodontal ligament of the M1 was measured using image analysis software (NIS elements, Nikon). The areas comprising 100 × 200 µm of the distal root mesial surface of the maxillary first molar, which were located superiorly from the middle of the root length, the root furcation, and root apex, respectively, were used for the investigation. These areas were chosen because the functional structural stability of the periodontal ligament fibers of each part was thought to be different. In particular, the periodontal ligament of the distal root at the mesial surface located superiorly from the middle of the root length is the last part that receives stimuli from gingivitis.17 

According to the histological observations and preliminary data, the number and the area of bFGF-immunoreactive cells per unit area were recorded using image analysis software (Scion Image Beta 4.02; Scion Corporation, Frederick, Md).

Statistical Analysis

Data are expressed as the mean ± standard deviation and are analyzed by analysis of variance followed by Tukey's Honestly Significant Difference test (P < .05) using SPSS version 14.0 software (SPSS for Windows, version 14.0; SPSS Inc, Chicago, Ill).

Hematoxylin and Eosin Staining

At 5 weeks, the length of the root of the rat maxillary first molar (M1) is shorter than at the other ages (Figure 2A).The root apical of the M1 is still open at 5, 9, and 15 weeks (Figure 2A–C). The dental pulp cavity is thick at 5 and 9 weeks. The width of the periodontal ligament narrowed after the age of 6 months. Cementum increased around the root with age after 6 months (Figure 2D–F).

Figure 2
Figure 2. Light micrographs of 5-µm sagittal sections of M1 (hematoxylin and eosin staining). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; C, cementum; and PDL, periodontal ligament. Bar  =  100 µm; original magnification 20×.
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Light micrographs of 5-µm sagittal sections of M1 (hematoxylin and eosin staining). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; C, cementum; and PDL, periodontal ligament. Bar  =  100 µm; original magnification 20×.

Figure 2
Figure 2. Light micrographs of 5-µm sagittal sections of M1 (hematoxylin and eosin staining). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; C, cementum; and PDL, periodontal ligament. Bar  =  100 µm; original magnification 20×.
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Light micrographs of 5-µm sagittal sections of M1 (hematoxylin and eosin staining). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; C, cementum; and PDL, periodontal ligament. Bar  =  100 µm; original magnification 20×.

Close modal

Immunostaining for bFGF

bFGF-immunoreactive cells were found in all areas of the periodontal ligament and were especially abundant in the root furcation area (Figure 3). We observed three parts of the periodontal ligament: the root furcation, the mesial region of the distopalatal root, and the root apical area of the maxillary M1.

Figure 3
Figure 3. Immunostaining of basic fibroblast growth factor (bFGF) in the root furcation of the maxillary first molar (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; and PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).
View largeDownload slide

Immunostaining of basic fibroblast growth factor (bFGF) in the root furcation of the maxillary first molar (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; and PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).

Figure 3
Figure 3. Immunostaining of basic fibroblast growth factor (bFGF) in the root furcation of the maxillary first molar (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; and PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).
View largeDownload slide

Immunostaining of basic fibroblast growth factor (bFGF) in the root furcation of the maxillary first molar (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; and PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).

Close modal

The number and area of bFGF-immunoreactive cells per unit area on the mesial region of the distopalatal root decreased significantly with age. The number of bFGF-immunoreactive cells per unit area was much greater in the periodontal ligament of the root furcation and much smaller in that of the root apical area. The surge of apical after 18 months meant there was no difference because there was no significant difference statistically between the results at 18 months and results at all of the other time points (Figures 6 and 7). The bFGF-immunoreactive cells could be observed clearly at 5, 9, and 15 weeks, but bFGF decreased at 6, 12, and 18 months in the mesial region of the distopalatal root (Figure 4). There were no obvious changes in the number and area of bFGF-immunoreactive cells per unit area in the root apical area with age (Figure 5).

Figure 4
Figure 4. Immunostaining of basic fibroblast growth factor (bFGF) in the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; and PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).
View largeDownload slide

Immunostaining of basic fibroblast growth factor (bFGF) in the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; and PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).

Figure 4
Figure 4. Immunostaining of basic fibroblast growth factor (bFGF) in the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; and PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).
View largeDownload slide

Immunostaining of basic fibroblast growth factor (bFGF) in the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; B, alveolar bone; and PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).

Close modal
Figure 5
Figure 5. Immunostaining of basic fibroblast growth factor (bFGF) in the root apical area of the maxillary first molar (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).
View largeDownload slide

Immunostaining of basic fibroblast growth factor (bFGF) in the root apical area of the maxillary first molar (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).

Figure 5
Figure 5. Immunostaining of basic fibroblast growth factor (bFGF) in the root apical area of the maxillary first molar (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).
View largeDownload slide

Immunostaining of basic fibroblast growth factor (bFGF) in the root apical area of the maxillary first molar (the area shown in Figure 1A). bFGF-immunoreactive cells are stained with brown (arrowheads). (A) Five weeks old. (B) Nine weeks old. (C) Fifteen weeks old. (D) Six months old. (E) Twelve months old. (F) Eighteen months old. D indicates dentin; PDL, periodontal ligament. A′–F′ indicate higher magnification of the boxed area. Bar  =  100 µm; original magnification 100× (A–F); 200× (A′–F′).

Close modal
Figure 6
Figure 6. Quantitative analysis of the number of cells labeled by immunohistochemistry for basic fibroblast growth factor (bFGF). (A) Quantitative analysis of the root furcation. (B) Quantitative analysis of the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length. (C) Quantitative analysis of the root apical. The number of bFGF-immunoreactive cells was measured. Data are presented as the mean ± standard deviation from five rats in each group. * P < .05; ** P < .01.
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Quantitative analysis of the number of cells labeled by immunohistochemistry for basic fibroblast growth factor (bFGF). (A) Quantitative analysis of the root furcation. (B) Quantitative analysis of the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length. (C) Quantitative analysis of the root apical. The number of bFGF-immunoreactive cells was measured. Data are presented as the mean ± standard deviation from five rats in each group. * P < .05; ** P < .01.

Figure 6
Figure 6. Quantitative analysis of the number of cells labeled by immunohistochemistry for basic fibroblast growth factor (bFGF). (A) Quantitative analysis of the root furcation. (B) Quantitative analysis of the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length. (C) Quantitative analysis of the root apical. The number of bFGF-immunoreactive cells was measured. Data are presented as the mean ± standard deviation from five rats in each group. * P < .05; ** P < .01.
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Quantitative analysis of the number of cells labeled by immunohistochemistry for basic fibroblast growth factor (bFGF). (A) Quantitative analysis of the root furcation. (B) Quantitative analysis of the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length. (C) Quantitative analysis of the root apical. The number of bFGF-immunoreactive cells was measured. Data are presented as the mean ± standard deviation from five rats in each group. * P < .05; ** P < .01.

Close modal
Figure 7
Figure 7. Quantitative analysis of the cell area labeled by immunohistochemistry for basic fibroblast growth factor (bFGF). (A) Quantitative analysis of the root furcation. (B) Quantitative analysis of the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length. (C) Quantitative analysis of the root apical. The area of the bFGF-immunoreactive cells was measured. Data are presented as the mean ± standard deviation from five rats in each group. * P < .05; ** P < .01.
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Quantitative analysis of the cell area labeled by immunohistochemistry for basic fibroblast growth factor (bFGF). (A) Quantitative analysis of the root furcation. (B) Quantitative analysis of the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length. (C) Quantitative analysis of the root apical. The area of the bFGF-immunoreactive cells was measured. Data are presented as the mean ± standard deviation from five rats in each group. * P < .05; ** P < .01.

Figure 7
Figure 7. Quantitative analysis of the cell area labeled by immunohistochemistry for basic fibroblast growth factor (bFGF). (A) Quantitative analysis of the root furcation. (B) Quantitative analysis of the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length. (C) Quantitative analysis of the root apical. The area of the bFGF-immunoreactive cells was measured. Data are presented as the mean ± standard deviation from five rats in each group. * P < .05; ** P < .01.
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Quantitative analysis of the cell area labeled by immunohistochemistry for basic fibroblast growth factor (bFGF). (A) Quantitative analysis of the root furcation. (B) Quantitative analysis of the distal root mesial surface of the maxillary first molar located superiorly from the middle of the root length. (C) Quantitative analysis of the root apical. The area of the bFGF-immunoreactive cells was measured. Data are presented as the mean ± standard deviation from five rats in each group. * P < .05; ** P < .01.

Close modal

bFGF plays a critical role in cell proliferation and synthesis of proteins and other components of the extracellular matrix. The interaction of bFGF and bFGF receptors (FGFR) in the periodontal ligament promotes the proliferation of most cells associated with wound healing and plays an important role in differentiation of mesenchymal cells into fibroblasts, angiogenesis, and formation of extracellular matrix.

In our study, bFGF-immunoreactive cells were observed throughout the areas of the periodontal ligament. Root furcation area and mesial region of the distopalatal root showed a higher level of bFGF-immunoreactive cells. The mesial region of the distopalatal root exhibited attenuation of bFGF immunoreactivity in aged rats. Nevertheless, the root apical area exhibited little age-related change in the overall profile of regional distribution of bFGF immunoreactivity (Figures 6 and 7).

bFGF is produced primarily by fibroblasts and endothelial cells in the periodontal ligament.18 The observed age-related decline in bFGF expression in the mesial region of distopalatal root may be related to the age-related decrease of expression of fibroblasts and endothelial cells.19,20 

The area of bFGF-immunoreactive cells was much greater in the root furcation area (Figure 7). This area may receive a greater effect of occlusal force than all the other regions in the periodontal ligament.21 Occlusal stimuli regulate bFGF expression. The lack of occlusal stimuli caused atrophic changes in the periodontal ligament with a decreased expression of bFGF. This atrophic change can be recovered by occlusal stimuli; the expression of bFGF was enhanced in the recovery process.22,23 The expression of bFGF in the root furcation area may be up-regulated to occlusal force. In brief, regardless of age, the production of bFGF in the periodontal ligament may occur subject to functional demand.

Human periodontal ligament cells express FGFR-1 and FGFR-2. The region in which FGFR-1 and FGFR-2 are produced has not been reported. Periodontal ligament cells alter the responsiveness to bFGF by changing the density of FGFR.24 bFGF acts on the immature periodontal ligament cells at the early stage of wound healing. It enhances the healing process and accelerates periodontal regeneration by enhancement of the proliferation of periodontal ligament cells and inhibition of the alkaline phosphatase activity and collagen I synthesis.12,13 

bFGF down-regulates the alkaline phosphatase activity of periodontal ligament cells and suppresses the cytodifferentiation of periodontal ligament cells into mineralized tissue-forming cells.12 The expression of bFGF was inhibited on the side of the periodontal ligament that received tensile force during tooth movement.14 Age-related decreases in the expression of bFGF may delay the regeneration of the periodontal ligament. Such an effect may act unfavorably in the case of tooth movement. It was suggested that the expression of bFGF in the periodontal ligament changed with age. The demands of orthodontic treatment for the elderly have been increasing. Therefore, it is necessary to investigate the effects of cytokines related to remodeling in periodontal ligaments.

  • The expression of bFGF in the periodontal ligament decreased with age.

  • The expression of bFGF is greater in the periodontal ligament of root furcation, which may be much more affected by occlusal force than are all the other regions in the periodontal ligament.

  • The effect of aging on the periodontal ligament is different on each part of the observed sites.

This study was partly supported by Grant-in-Aids for Scientific Research (18791547 and 20592393) from the Japanese Ministry of Education, Culture, Sports, Science and Technology of Japan. This article will be submitted to the Graduate School, Tokyo Medical and Dental University, in partial fulfillment of the requirement for the PhD degree.

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Author notes

a

PhD graduate student, Orofacial Development and Function Orthodontic Science, Tokyo Medical and Dental University, Tokyo, Japan

b

Assistant Professor, Orofacial Development and Function Orthodontic Science, Tokyo Medical and Dental University, Tokyo, Japan

Part of this study was presented at the 68th Annual Meeting of the Japanese Orthodontic Society (Fukuoka, Japan, November 2009).

The EH Angle Education and Research Foundation, Inc.
2010