J Oral Maxillofac Surg 50:354-358,199Z
Effect of Salivary Gland Hypofunction on the Healing of Extraction Wounds: A Histomorphometric Study in Rats D. DAYAN,
DMD, MSc,*
L. BODNER,
DMD,t
AND I. HOROWITZ,
DMD, MDT
The effect of salivary gland hypofunction (SGH) on oral wound healing is not well established. The present study evaluates the healing of extraction wounds in a SGH rat model. Experimental rats underwent removal of the submandibular and sublingual glands and ligation of the parotid ducts. Maxillary left first molars were extracted and healing was determined at 0, 1, 3, 5, 7, 10, 14, and 21 days after extraction. Salivary gland hypofunction caused a significant delay in socket healing. The inflammatory process was more intense and of longer duration. The formation of fibrous connective tissue and bone was relatively slow among the experimental rats. The results suggest that SGH patients undergoing oral surgery may have prolonged wound healing.
application of epidermal growth factor (EGF) or nerve growth factor (NGF) to the skin wound of sialadenectomized mice restored most of the contraction delay observed after sialadenectomy, suggesting that EGF and NGF may be among wound healing factors in saliva.“*‘* Dental caries leading to extraction of teeth is a common clinical situation among SGH patients.2,‘3 Wound healing after tooth extraction has been extensively studied in humans’4*‘5 and experimental animals,16‘18 and has been shown to be altered following ligation of salivary glands in rats. l9 However, the effect of SGH on extraction wound healing has not been fully investigated. This study was designed to evaluate the healing of extraction wounds in a SGH rat model.
Normal salivary gland function is mandatory for the maintenance of oral health. Reduction of salivary secretion can result from therapeutic interventions, such as pharmacological agents,’ irradiation to the head and neck,2,3 or cancer chemotherapy,4,5 as well as from obstructive, inflammatory, or systemic diseases affecting the salivary glands.‘j A diminished salivary flow rate associated with changes in salivary composition is considered to be salivary gland hypofunction (SGH).’ Salivary gland hypofunction results in alterations in all physiological functions of saliva, such as lubrication and protection of oral mucosa, mechanical cleansing of teeth and mucosa, pH regulation, maintenance of tooth integrity, and antibacterial activity. 1,7-9 Saliva also has an effect on wound healing. This effect was first shown using a back skin wound in sialadenectomized mice. lo The contraction rate of skin wounds was delayed if licking was avoided. Topical
Materials and Methods Eighty male Sprague-Dawley rats, 2 months old and weighing approximately 200 g, were randomly divided into experimental and control groups. The experimental group underwent sialadenectomy of the submandibular and sublingual glands and ligation of the parotid ducts bilaterally through a midventral incision.*’ The control group was subjected to a sham operation involving full exposure of the glands and subsequent incision closure with 3-O silk. In both groups, the maxillary left first molars were extracted by a specially adapted mosquito forceps 2 weeks after surgery in the neck. Rats were fed a standard Purina Lab Chow (Tel
Received from the Maurice and Gabriela GoldschIeger School of Dental Medicine. Tel Aviv University, Tel Aviv, Israel. * Senior Lecturer, Department of bral Pathology and Oral Medicine. t Lecturer, Department of Oral and Maxillofacial Surgery. Address c&re&ndence and reprint requests to Dr Dayan: Section of Oral Patholow and Oral Medicine, The Maurice and Gabriela Goldschleger S&o1 of Dental Medic&, Tel Aviv University, Ramat Aviv 69978, Tel Aviv, Israel. 0 1992 American
Association
of Oral and Maxillofacial
Surgeons
0278-2391/92/5004-0008$3.00/O
354
355
DAYAN. BODNER. AND HOROWITZ
tologic parameter was evaluated as part of the whole socket area by a point counting method” in which each point was an intersection of perpendicular lines in the grid. The data were presented as mean percentage of each histologic parameter in relation to the socket area. The relative standard error was calculated as previously described2’ and presented as mean + standard error. The graphs were drawn by adequate equipment connected to the computer. Student’s t test was used to analyze the data.
Results Animals tolerated the surgery well. Food intake, body weight, and activity were maintained normally
FIGURE 1. Photomicrograph of mesiodistal view of a rat molar socket immediately after extraction. Note that the section includes full length of the socket (hematoxylin-eosin, original magnification X40).
Aviv, Israel) and water ad libitum. Five rats from each group were killed at 0, 1, 3, 5, 7, 10, 14, and 2 1 days following extraction. The maxillae were dissected and fixed in 10% formalin. Paraffin blocks were prepared after decalcification in 18% EDTA for 2 weeks. Serial sections, 6 pm thick, were cut in a plane mesiodistal to the maxillary molars. Only sections including the full length of the socket were stained with hematoxylin and eosin and examined with light microscopy (Fig 1). Histomorphometry. Quantitative microscopy was performed on a Visopan projection microscope (Reichert, Austria) at a magnification of X 160. A systemic grid was overlayed on the projection screen. The area of each square in the grid was 10 mm2. The areas of inflammation and connective tissue and bone formation in the socket were analyzed as follows: 1) the area of inflammation was measured by counting chronic and acute inflammatory cells in the socket; 2) connective tissue areas were estimated by the amount of collagen fibers and ground substance formation; and 3) areas of new bone formation were traced by recording bone formation from the apical part of the socket up to the coronal area. The relative area of each his-
FIGURE 2.
Photomicrograph of the socket 7 days after extraction.
A, Experimental group. B, Control group. AB, Alveolar bone; I, in-
flammation; or, connective tissue. The inflamed area in the experimental socket is much greater than in controls (hematoxyhn-eosin, original magnification X40).
WOUND HEALING IN XEROSTOMATIC
RATS
Discussion Sialadenectomy of the submandibular and sublingual glands, and ligation of the Stenson’s duct, result in an obvious diminution’ of salivary secretion. The SGH rat model is left with only the secretion of the minor salivary glands, which usually contribute less than 5% of the total salivary volume.23 The extraction wound was used as a model because it involved a simple and reproducible wound, relevant to the clinical situation in patients with SGH. The healing process found in the extraction sockets of control rats was in agreement with earlier reports.i6,” The
PIGURE 3. Histomorphometric presentation of area of inflammation as function oftime after extraction. Values are means 2 SEM of five rats. *P < .05. **P < .Ol. Cl, Control; IS, experimental.
throughout the study, and the rats appeared undisturbed by the wounds. Macroscopic observations. The oral cavity of the SGH rats was dry and small pieces of debris were found adjacent to the teeth and the extraction site. Otherwise, no other differences could be observed between experimental and control sockets throughout the experiment. Histomorphometric observations. The histology of the socket wound healing followed the classical morphologic kinetics. Inflammation was observed earlier in experimental animals than in the control animals. The decrease in inflammation was about the same in both groups. However, the area of inflammation was significantly greater (P < .05 to P -E .Ol) in the experimental group than in the control group between days 1 and 14 (Fig 2). This difference were not significant by day 21 (Fig 3). The formation of connective tissue and bone was quantitatively estimated and used as a parameter of tissue repair. Generally, connective tissue and bone formation were delayed in the socket of experimental rats. At day 7 and 14 after extraction, the fraction area of connective tissue in experimental sockets was significantly smaller (P < .05 to P < .Ol) compared with controls (Fig 4). No difference was observed by day 2 1 (Fig 5). Bone formation at days 14 and 2 1 appeared to be more rapid (P < .05) in the control group compared with the experimental group (Fig 6).
Photomicrograph of the socket 14 days after extraction. AB, alveolar bone; I, inflammation; CT, connective tissue. The area of the connective tissue in the control is much greater than in the experimental socket, which still shows marked inflammation (hematoxylin-eosin, original magnification X40). FIGURE 4.
A, Experimental group. B, Control group.
357
DAYAN, BODNER, AND HOROWITZ
3-week follow-up period demonstrated all the histologic steps from blood clot to bone formation. Healing in the SGH rats was generally delayed. The inflammatory process was more intense and of longer duration following sialadenectomy, which is in agreement with Wade and Fleming. l9 This could be a result of reduced antimicrobial substances, such as lysozyme, immunoglobulins, lactofenin, and peroxidase, normally present in saliva.9,24Salivary gland hypofunction also appeared to slow the formation of fibrous connective tissue and bone. This is consistent with Shen et al,25 who report that sialadenectomy altered gingival surface wound healing. Diminution of saliva has little effect on wound healing by first intention and a significant effect on healing by second intention.25 Extraction wound healing is by second intention and is, therefore, sensitive to salivary gland hypofunction. The exact mechanism of the effect of saliva on wound healing is unknown. However, saliva contains several factors that might contribute to the process. A number of growth-promoting factors, such as EGF and NGF, and transforming growth factor have been isolated from animal and human salivary glands.“y’2,26 The oral cavity of the SGH rat was isolated from all antimicrobial enzymes and growth-promoting factors, and this could lead to the delay in extraction wound healing. If the results in rats can be extrapolated to humans, it is possible that SGH patients undergoing oral surgery might also have slower wound healing.
: :
FIGURE 6. Histomorphometric presentation of area fraction of bone formation as a function of time after extraction. Values are mean + SEM of five rats. *P -L.05.0, Control; El, experimental.
Acknowledgment This study was partially supported by a grant from The Sackler Faculty of Medicine Fund (Dr Schauder), Tel Aviv University to Dr D. Dayan and Dr L. Bodner, and cartied out in the Alpha Omega Research Laboratories, The Maurice and Gabriela Goldschleger School of Dental Medicine.
References
FIGURE 5. Histomorphometric presentation of area fraction of connective tissue as a function of time after extraction. Values are mean + SEM of five rats. *P c .05. **P < .Ol. 0,Control; IB, experimental
1. Mandel ID, Wotman S: The salivary secretion in health and disease. Oral Sci Rev 825, 1976 2. Dreizen S, Brown LR, Daly TE, et al: Prevention of xerostomiarelated caries in irradiated cancer patients. J Dent Res 56:99, 1977 3. Bodner L, Kuyatt BL, Hand AR, et al: Rat parotid cell function in vitro following X-irradiation in vivo. Radiat Res 97:386, 1984 4. Dreizen S: Stomatoxic manifestations of cancer chemotherapy. J Prosthet Dent 40:650, 1978 5. Baum BJ, Bodner L, Fox PC, ‘etal: Therapy induced dysfunction of salivary glands: Implication for oral health. Special Care Dent 5~274, 1984 6. Mandel ID: Sialochemistry in diseases and clinical situations affecting salivary glands. CRC Critical Rev Clin Labor Sci 12: 321, 1980 7. Sreebny LM: Recognition and treatment of salivary induced conditions. Int Dent J 39: 197, 1989 8. Tabak LA, Levine MJ, Mandel ID, et al: Salivary mucins in protection of oral cavity. J Oral Pathol 11:1, 1982 9. Mandel ID: The function of saliva. J Dent Res 66:623, 1987 10. Hutson JM. Niall M. Evans D. et al: Effect of salivarv alands on wound contraction in mice: Nature 279:793, 197911. Li AKC, Korolg MJ, Schattenkerk ME, et al: Nerve growth factor. Acceleration of the rate of wound healing in mice. Proc Nat1 Acad Sci USA 77:4379, 1980 12. Niall M, Ryan GB, O’Brien BM: The effect of epidermal growth factor on wound healing in mice. J Surg Res 33:164, 1982
358 13. Green CS: Prevention and treatment of caries in adults with xerostomia. J Prev Dent 6:2 15, 1980 14. Amler MH, Johnson PL, Salman I: Histological and histochemical investigation of human alveolar socket healing in undisturbed extraction wound. J Am Dent Assoc 61:32, 1960 15. Boyne PJ: Osseous repair of post-extraction alveolus in man. Oral Surg Oral Med Oral Path01 21:805, 1966 16. Tennenbaum R, Shklar G: The effect of an anabolic steroid on the healing of experimental extraction wound. Oral Surg Oral Med Oral Path01 30:824, 1970 17. Neville S: A comparative histological and radiographic study of extraction socket healing in the rat. Aust Dent J 27:250, 1974 18. Kurita K, Hashimoto Y, Takei T, et al: Changes in collagen types during the healing of rabbit tooth extraction wounds. J Dent Res 64:28, 1985 19. Wade GW, Fleming HS: Salivary gland ligation extraction wound healing. IADR Prog Abst 40~690, 196 1 (abstr 140)
WOUND HEALING IN XEROSTOMATIC
RATS
20. Bowen WH, Pearson SK, Young DA: The effect of desalivation on coronal and root caries in rats. J Dent Res 67:21, 1988 2 1. Bellhouse DR: Area estimation by point counting techniques. Biometrics 37:303, 198 1 22. Williams MA: Quantitative methods in biology, in Glanert Am (ed): Practical Methods in Electron Microscopy, vol 6. Amsterdam, North-Holland, 1977 23. Young JA, Schneyer CA: Composition of saliva in mammalia. Aust J Exp Biol Med Sci 59:1, 1981 24. Tenuvuo J, Lehtonen OJ, Altonen AS: Antimicrobial factors in whole saliva of human infants. Infect Immun 5 1:49, 1986 25. Shen L, Ghavamzadeh G, Shklar G: Gingival healing in sialadenectomized rats. J Periodontol 50~533, 1979 26. Spom MB, Roberts AB, Shull JH: Polypeptide transforming growth factors isolated from bovine sources and used for wound healing in vim. Science 2 19:1329, 1982
Effect of Salivary Gland Hypofunction on the Healing of Extraction Wounds: A Histomorphometric Study in Rats D. DAYAN,
DMD, MSc,*
L. BODNER,
DMD,t
AND I. HOROWITZ,
DMD, MDT
The effect of salivary gland hypofunction (SGH) on oral wound healing is not well established. The present study evaluates the healing of extraction wounds in a SGH rat model. Experimental rats underwent removal of the submandibular and sublingual glands and ligation of the parotid ducts. Maxillary left first molars were extracted and healing was determined at 0, 1, 3, 5, 7, 10, 14, and 21 days after extraction. Salivary gland hypofunction caused a significant delay in socket healing. The inflammatory process was more intense and of longer duration. The formation of fibrous connective tissue and bone was relatively slow among the experimental rats. The results suggest that SGH patients undergoing oral surgery may have prolonged wound healing.
application of epidermal growth factor (EGF) or nerve growth factor (NGF) to the skin wound of sialadenectomized mice restored most of the contraction delay observed after sialadenectomy, suggesting that EGF and NGF may be among wound healing factors in saliva.“*‘* Dental caries leading to extraction of teeth is a common clinical situation among SGH patients.2,‘3 Wound healing after tooth extraction has been extensively studied in humans’4*‘5 and experimental animals,16‘18 and has been shown to be altered following ligation of salivary glands in rats. l9 However, the effect of SGH on extraction wound healing has not been fully investigated. This study was designed to evaluate the healing of extraction wounds in a SGH rat model.
Normal salivary gland function is mandatory for the maintenance of oral health. Reduction of salivary secretion can result from therapeutic interventions, such as pharmacological agents,’ irradiation to the head and neck,2,3 or cancer chemotherapy,4,5 as well as from obstructive, inflammatory, or systemic diseases affecting the salivary glands.‘j A diminished salivary flow rate associated with changes in salivary composition is considered to be salivary gland hypofunction (SGH).’ Salivary gland hypofunction results in alterations in all physiological functions of saliva, such as lubrication and protection of oral mucosa, mechanical cleansing of teeth and mucosa, pH regulation, maintenance of tooth integrity, and antibacterial activity. 1,7-9 Saliva also has an effect on wound healing. This effect was first shown using a back skin wound in sialadenectomized mice. lo The contraction rate of skin wounds was delayed if licking was avoided. Topical
Materials and Methods Eighty male Sprague-Dawley rats, 2 months old and weighing approximately 200 g, were randomly divided into experimental and control groups. The experimental group underwent sialadenectomy of the submandibular and sublingual glands and ligation of the parotid ducts bilaterally through a midventral incision.*’ The control group was subjected to a sham operation involving full exposure of the glands and subsequent incision closure with 3-O silk. In both groups, the maxillary left first molars were extracted by a specially adapted mosquito forceps 2 weeks after surgery in the neck. Rats were fed a standard Purina Lab Chow (Tel
Received from the Maurice and Gabriela GoldschIeger School of Dental Medicine. Tel Aviv University, Tel Aviv, Israel. * Senior Lecturer, Department of bral Pathology and Oral Medicine. t Lecturer, Department of Oral and Maxillofacial Surgery. Address c&re&ndence and reprint requests to Dr Dayan: Section of Oral Patholow and Oral Medicine, The Maurice and Gabriela Goldschleger S&o1 of Dental Medic&, Tel Aviv University, Ramat Aviv 69978, Tel Aviv, Israel. 0 1992 American
Association
of Oral and Maxillofacial
Surgeons
0278-2391/92/5004-0008$3.00/O
354
355
DAYAN. BODNER. AND HOROWITZ
tologic parameter was evaluated as part of the whole socket area by a point counting method” in which each point was an intersection of perpendicular lines in the grid. The data were presented as mean percentage of each histologic parameter in relation to the socket area. The relative standard error was calculated as previously described2’ and presented as mean + standard error. The graphs were drawn by adequate equipment connected to the computer. Student’s t test was used to analyze the data.
Results Animals tolerated the surgery well. Food intake, body weight, and activity were maintained normally
FIGURE 1. Photomicrograph of mesiodistal view of a rat molar socket immediately after extraction. Note that the section includes full length of the socket (hematoxylin-eosin, original magnification X40).
Aviv, Israel) and water ad libitum. Five rats from each group were killed at 0, 1, 3, 5, 7, 10, 14, and 2 1 days following extraction. The maxillae were dissected and fixed in 10% formalin. Paraffin blocks were prepared after decalcification in 18% EDTA for 2 weeks. Serial sections, 6 pm thick, were cut in a plane mesiodistal to the maxillary molars. Only sections including the full length of the socket were stained with hematoxylin and eosin and examined with light microscopy (Fig 1). Histomorphometry. Quantitative microscopy was performed on a Visopan projection microscope (Reichert, Austria) at a magnification of X 160. A systemic grid was overlayed on the projection screen. The area of each square in the grid was 10 mm2. The areas of inflammation and connective tissue and bone formation in the socket were analyzed as follows: 1) the area of inflammation was measured by counting chronic and acute inflammatory cells in the socket; 2) connective tissue areas were estimated by the amount of collagen fibers and ground substance formation; and 3) areas of new bone formation were traced by recording bone formation from the apical part of the socket up to the coronal area. The relative area of each his-
FIGURE 2.
Photomicrograph of the socket 7 days after extraction.
A, Experimental group. B, Control group. AB, Alveolar bone; I, in-
flammation; or, connective tissue. The inflamed area in the experimental socket is much greater than in controls (hematoxyhn-eosin, original magnification X40).
WOUND HEALING IN XEROSTOMATIC
RATS
Discussion Sialadenectomy of the submandibular and sublingual glands, and ligation of the Stenson’s duct, result in an obvious diminution’ of salivary secretion. The SGH rat model is left with only the secretion of the minor salivary glands, which usually contribute less than 5% of the total salivary volume.23 The extraction wound was used as a model because it involved a simple and reproducible wound, relevant to the clinical situation in patients with SGH. The healing process found in the extraction sockets of control rats was in agreement with earlier reports.i6,” The
PIGURE 3. Histomorphometric presentation of area of inflammation as function oftime after extraction. Values are means 2 SEM of five rats. *P < .05. **P < .Ol. Cl, Control; IS, experimental.
throughout the study, and the rats appeared undisturbed by the wounds. Macroscopic observations. The oral cavity of the SGH rats was dry and small pieces of debris were found adjacent to the teeth and the extraction site. Otherwise, no other differences could be observed between experimental and control sockets throughout the experiment. Histomorphometric observations. The histology of the socket wound healing followed the classical morphologic kinetics. Inflammation was observed earlier in experimental animals than in the control animals. The decrease in inflammation was about the same in both groups. However, the area of inflammation was significantly greater (P < .05 to P -E .Ol) in the experimental group than in the control group between days 1 and 14 (Fig 2). This difference were not significant by day 21 (Fig 3). The formation of connective tissue and bone was quantitatively estimated and used as a parameter of tissue repair. Generally, connective tissue and bone formation were delayed in the socket of experimental rats. At day 7 and 14 after extraction, the fraction area of connective tissue in experimental sockets was significantly smaller (P < .05 to P < .Ol) compared with controls (Fig 4). No difference was observed by day 2 1 (Fig 5). Bone formation at days 14 and 2 1 appeared to be more rapid (P < .05) in the control group compared with the experimental group (Fig 6).
Photomicrograph of the socket 14 days after extraction. AB, alveolar bone; I, inflammation; CT, connective tissue. The area of the connective tissue in the control is much greater than in the experimental socket, which still shows marked inflammation (hematoxylin-eosin, original magnification X40). FIGURE 4.
A, Experimental group. B, Control group.
357
DAYAN, BODNER, AND HOROWITZ
3-week follow-up period demonstrated all the histologic steps from blood clot to bone formation. Healing in the SGH rats was generally delayed. The inflammatory process was more intense and of longer duration following sialadenectomy, which is in agreement with Wade and Fleming. l9 This could be a result of reduced antimicrobial substances, such as lysozyme, immunoglobulins, lactofenin, and peroxidase, normally present in saliva.9,24Salivary gland hypofunction also appeared to slow the formation of fibrous connective tissue and bone. This is consistent with Shen et al,25 who report that sialadenectomy altered gingival surface wound healing. Diminution of saliva has little effect on wound healing by first intention and a significant effect on healing by second intention.25 Extraction wound healing is by second intention and is, therefore, sensitive to salivary gland hypofunction. The exact mechanism of the effect of saliva on wound healing is unknown. However, saliva contains several factors that might contribute to the process. A number of growth-promoting factors, such as EGF and NGF, and transforming growth factor have been isolated from animal and human salivary glands.“y’2,26 The oral cavity of the SGH rat was isolated from all antimicrobial enzymes and growth-promoting factors, and this could lead to the delay in extraction wound healing. If the results in rats can be extrapolated to humans, it is possible that SGH patients undergoing oral surgery might also have slower wound healing.
: :
FIGURE 6. Histomorphometric presentation of area fraction of bone formation as a function of time after extraction. Values are mean + SEM of five rats. *P -L.05.0, Control; El, experimental.
Acknowledgment This study was partially supported by a grant from The Sackler Faculty of Medicine Fund (Dr Schauder), Tel Aviv University to Dr D. Dayan and Dr L. Bodner, and cartied out in the Alpha Omega Research Laboratories, The Maurice and Gabriela Goldschleger School of Dental Medicine.
References
FIGURE 5. Histomorphometric presentation of area fraction of connective tissue as a function of time after extraction. Values are mean + SEM of five rats. *P c .05. **P < .Ol. 0,Control; IB, experimental
1. Mandel ID, Wotman S: The salivary secretion in health and disease. Oral Sci Rev 825, 1976 2. Dreizen S, Brown LR, Daly TE, et al: Prevention of xerostomiarelated caries in irradiated cancer patients. J Dent Res 56:99, 1977 3. Bodner L, Kuyatt BL, Hand AR, et al: Rat parotid cell function in vitro following X-irradiation in vivo. Radiat Res 97:386, 1984 4. Dreizen S: Stomatoxic manifestations of cancer chemotherapy. J Prosthet Dent 40:650, 1978 5. Baum BJ, Bodner L, Fox PC, ‘etal: Therapy induced dysfunction of salivary glands: Implication for oral health. Special Care Dent 5~274, 1984 6. Mandel ID: Sialochemistry in diseases and clinical situations affecting salivary glands. CRC Critical Rev Clin Labor Sci 12: 321, 1980 7. Sreebny LM: Recognition and treatment of salivary induced conditions. Int Dent J 39: 197, 1989 8. Tabak LA, Levine MJ, Mandel ID, et al: Salivary mucins in protection of oral cavity. J Oral Pathol 11:1, 1982 9. Mandel ID: The function of saliva. J Dent Res 66:623, 1987 10. Hutson JM. Niall M. Evans D. et al: Effect of salivarv alands on wound contraction in mice: Nature 279:793, 197911. Li AKC, Korolg MJ, Schattenkerk ME, et al: Nerve growth factor. Acceleration of the rate of wound healing in mice. Proc Nat1 Acad Sci USA 77:4379, 1980 12. Niall M, Ryan GB, O’Brien BM: The effect of epidermal growth factor on wound healing in mice. J Surg Res 33:164, 1982
358 13. Green CS: Prevention and treatment of caries in adults with xerostomia. J Prev Dent 6:2 15, 1980 14. Amler MH, Johnson PL, Salman I: Histological and histochemical investigation of human alveolar socket healing in undisturbed extraction wound. J Am Dent Assoc 61:32, 1960 15. Boyne PJ: Osseous repair of post-extraction alveolus in man. Oral Surg Oral Med Oral Path01 21:805, 1966 16. Tennenbaum R, Shklar G: The effect of an anabolic steroid on the healing of experimental extraction wound. Oral Surg Oral Med Oral Path01 30:824, 1970 17. Neville S: A comparative histological and radiographic study of extraction socket healing in the rat. Aust Dent J 27:250, 1974 18. Kurita K, Hashimoto Y, Takei T, et al: Changes in collagen types during the healing of rabbit tooth extraction wounds. J Dent Res 64:28, 1985 19. Wade GW, Fleming HS: Salivary gland ligation extraction wound healing. IADR Prog Abst 40~690, 196 1 (abstr 140)
WOUND HEALING IN XEROSTOMATIC
RATS
20. Bowen WH, Pearson SK, Young DA: The effect of desalivation on coronal and root caries in rats. J Dent Res 67:21, 1988 2 1. Bellhouse DR: Area estimation by point counting techniques. Biometrics 37:303, 198 1 22. Williams MA: Quantitative methods in biology, in Glanert Am (ed): Practical Methods in Electron Microscopy, vol 6. Amsterdam, North-Holland, 1977 23. Young JA, Schneyer CA: Composition of saliva in mammalia. Aust J Exp Biol Med Sci 59:1, 1981 24. Tenuvuo J, Lehtonen OJ, Altonen AS: Antimicrobial factors in whole saliva of human infants. Infect Immun 5 1:49, 1986 25. Shen L, Ghavamzadeh G, Shklar G: Gingival healing in sialadenectomized rats. J Periodontol 50~533, 1979 26. Spom MB, Roberts AB, Shull JH: Polypeptide transforming growth factors isolated from bovine sources and used for wound healing in vim. Science 2 19:1329, 1982
