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Morphological characterization and permeability of attrited human dentine
archives of oral biology 53 (2008) 14–19
available at www.sciencedirect.com
journal homepage: www.intl.elsevierhealth.com/journals/arob
Morphological characterization and permeability of attrited human dentine Pisol Senawongse a,*, Masayuki Otsuki b, Junji Tagami b, Ivar A. Mjo¨r c a
Department of Operative Dentistry, Faculty of Dentistry, Mahidol University, 6 Yothi Street, Phayathai, Bangkok 10400, Thailand Cariology and Operative Dentistry, Tokyo Medical and Dental University, 5-45 Yushima 1-Chome, Bunkyo-ku, Tokyo 113-8549, Japan c College of Dentistry, University of Florida, P.O. Box 100415, Gainesville, FL 32610, USA b
article info
abstract
Article history:
Objective: Dentine is a vital tissue that can be changed by physiological and pathological
Accepted 27 July 2007
condition. The purpose of this study was to clarify the morphology and permeability of dentine that changed by wearing process.
Keywords:
Methods: Twenty extracted human molars with enamel attrition and dentine was exposed
Wear
and 20 intact human extracted third molars that had not reached occlusion were used. Ten
Transparent dentine
teeth per each group were observed under light microscope (LM) and transmission electron
Reactionary dentine
microscope (TEM). Remaining 10 teeth per each group were subjected for evaluation of
Light microscope
dentine permeability.
Transmission electron microscope
Results: Under LM, the transparent dentine and reactionary dentine were found in the
Permeability
attrition group but were not found in the group unaffected by attrition. When the transparent dentine were examined under the TEM, it was found that dentinal tubules were partially or completely occluded by growth of peritubular dentine or by precipitation of needle-like or rhombohedral crystals in transparent dentine. In reactionary dentine, tubular dentine structures that were comparable to those in secondary physiologic dentine were observed whereas atubular dentine demonstrated occlusion of tubules by high mineral substances or by peritubular dentine under the TEM. Permeability of dentine from worn teeth was less than those from unoccluded teeth significantly. Conclusion: Change in dentine by wear resulted in the formation of reactionary dentine and transparent dentine that illustrated various types and degrees of tubular occlusion. These decrease the dentine permeability. # 2007 Elsevier Ltd. All rights reserved.
1.
Introduction
Increase human life span calls for increasing attention to geriatric dentistry.1,2 Excessive wear may cause of tooth loss in elderly patients.3,4 Tooth wear is a normal physiological process. However, when self-adaptive capabilities are exceeded, the physiological process becomes a pathological problems5–7 and restorative treatment is requirement.
The attrition of teeth allows changes in morphological characterization of dentine such as transparent dentine formation and production of reactionary dentine.8–12 These morphological changes might affect the permeability of dentine. Few studies have been published on the morphology of dentine and its permeability during the progression of wear. Such knowledge is important for understanding dentine reaction under clinical condition.
* Corresponding author. Tel.: +66 2 644 8644; fax: +66 2 354 8510. E-mail address: [email protected] (P. Senawongse). 0003–9969/$ – see front matter # 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.archoralbio.2007.07.010
archives of oral biology 53 (2008) 14–19
15
Fig. 1 – Experimental apparatus for dentine permeable test. Red arrows demonstrate the direction of fluid flow. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
2.
Materials and methods
2.1.
Morphological study
Twenty human teeth were included in this study; 10 extracted molars from elderly individuals with enamel attrition and exposed middle 1/3 of dentine and 10 extracted intact third molars that had not reached occlusion were used in this study. These intact teeth will be referred as unaffected teeth. All teeth were extracted and the patients were informed and agreed that their teeth will be used for this investigation. The ages of subjects ranged from 55 to 65 years for elderly patients (worn teeth) and 18 to 25 years for adolescent patients (intact teeth). The extracted teeth were kept in physiological saline solution at 5 8C within 2 months prior to processing. The teeth were sectioned axiobuccolingually with a highspeed diamond saw (Leitz 1600, Leica Instruments, Heidelberg, Germany) to create a 150 mm thick section from the centre of teeth. The 150 mm thick slabs were reduced to approximately 100 mm with silicon carbide papers by hand lapping. The specimens were examined under a transmission light microscope (Vanox AHBS3, Olympus, Tokyo, Japan). The morphological structures identified were mantle dentine, globular dentine, primary and physiologic secondary dentine, transparent dentine, and tertiary reactionary dentine.13 Based on the light microscope examination, small areas were dissected out and processed for a transmission electron microscopy. Ultrathin sections were cut with a diamond knife and collected on carbon-coated grids. The section were examined under a transmission electron microscope (TEM) operated at 80 kV (Hitachi 300 TEM, Hitachi Co., Tokyo, Japan)
2.2.
Dentine permeable study
The dentine permeability was measured by the means of hydraulic conductance. Additional 10 extracted molars from elderly individuals with enamel attrition and exposed dentine
and 10 extracted intact third molars that had not reached occlusion were used. Flat dentine discs with 0.7 mm thick from outer 1/3 of occlusal dentine were prepared by cutting with a low speed diamond saw (Isomet, Buehler, IL, USA) perpendicular to long-axis of teeth and polished with wet silicon carbide papers (600 grit down to 1000 grit). The smear layers created by polishing were removed with 10% phosphoric acid for 10 s. The test method and apparatus (Fig. 1) were derived from the study of Puapichartdumrong et al.14 The rate of fluid movement pass through circular areas with 6 mm diameter of the dentine disc was measured by monitoring the movement of a small air bubble under the pressure that was comparable to pulpal pressure (1.47 kPa or 15 cm H2O)15 at the rate of 0.2 mL/min. The system used in the present study consisted four parts: a source of pressure, a pressurized chamber, a system to measure the displacement of bubble (50 mL micro-syringe), and a specimen holder. The data were converted into the hydraulic conductance (Lp; mL cm2 min115 cm H2O1):
Lp ¼
Jv P
Jv (mL cm2 min1 cm H2O1) is the fluid flux that was calculated by Jv = Q/At [Q (mL) is the fluid shift, A (cm2) the area of dentine and t (min) is the diffusion time]. P (cm H2O) is the applied hydrostatic pressure.14
3.
Results
3.1.
Morphological study
Morphological features of dentine of worn and unaffected teeth were studied by examined ground sections under the transmission light microscope. The attrition resulted in various changes in dentine. Globular dentine was observed normally in unaffected teeth (Fig. 2A), but was rarely noted
16
archives of oral biology 53 (2008) 14–19
dentine and reactionary dentine (Fig. 3C). At this location, a change in the direction and number of dentinal tubules was frequently noted (Fig. 3D). At the other part of the pulp chamber, no marked reduction in the number of dentinal tubules was observed when passing from physiologic secondary dentine to reactionary tertiary dentine. In some of the teeth, the incremental lines were observed, particularly in the tertiary dentine underlining worn dentine. The transparent dentine of exposed dentine had different appearances in TEM. Some dentinal tubules were occluded by high electron-dense materials. The material seems to be a continuous growth of peritubular dentine (Fig. 5A), which always found at the subsurface of wear. Some tubules were occluded with extremely fine crystals (Fig. 5B), others with large rhombohedral crystals (Fig. 5C), which always found on the surface of attrited dentine. Dentinal tubules occluded with fine needle-like crystals, or rhombohedral crystals mixed with substrates including peritubular dentine were demonstrated (Fig. 5D). Occluded tubules were rarely identified in the normal teeth unaffected by attrition. The dentinal tubules of unaffected teeth were empty. The tubules were surrounded by peritubular dentine, which was more highly minerized than the surrounding intertubular dentine (Fig. 4A). The reactionary tertiary dentine had various appearances. Comparatively large areas with no tubules and areas with tubules of different diameters were observed. Areas with tubular structures (Fig. 5E) demonstrated morphology similar to that of physiologic secondary dentine (Fig. 4A). Areas devoid of tubules; atubular structure had the same appearance as regular intertubular dentine with minerized fibres. Typical cross-banding of the collagen fibres could be discerned (Figs. 4 and 5). The occluded tubules had a high mineral content than the intertubular dentine. In the unaffected teeth, the areas closed to pulp chamber demonstrated low mineralization of intertubular dentine and the peritubular dentine was rarely identified (Fig. 4B). Fig. 2 – Ground section of unaffected third molar reviewed in the transmitted light microscope: (A) demonstrates mantle dentine (M), globular dentine (G), and physiologic primary dentine (S) (magnification 40T); (B) demonstrates tubular structure of physiologic primary and secondary dentine (magnification 100T); (C) shows calcospherite dome shape structure of newly developed secondary dentine (magnification 100T).
3.2.
Hydraulic conductance of dentine discs from unaffected third molars (group 1) and from worn molars (group 2) is demonstrated in Fig. 6. The hydraulic conductance of dentine discs from worn molars (1.998 1.604) was significantly ( p < 0.001) less than that of unaffected third molars (12.537 1.004).
4. subjacent to worn teeth (Fig. 3A). Transparent dentine was typically observed in the worn teeth (Fig. 3B). The physiologic secondary dentine of worn teeth (Fig. 2B) had structure similar to that of unaffected teeth (Fig. 2B), however, it was wider in the unaffected teeth (Figs. 2A and 3B). Reactionary tertiary dentine was only observed in worn teeth. Two types of reactionary dentine: tubular and atubular dentine were observed (Fig. 3B). A transition zone was observed in worn teeth at the junction between physiologic secondary
Dentine permeable study
Discussion
The primary dentine and physiologic secondary dentine of worn teeth demonstrated transparent dentine that conformed to the previous studies.12,16 The transparent dentine is likely to be a result of the attrition since we found this dentine only subjacent to the worn areas. The physiological wear from mastication confirms the deposition of apatite crystal in the tubules.9,10,17 These depositions were similar to those shown in exposed, sensitive dentine.18–20 These crystalline depositions caused a decrease in the diameters
archives of oral biology 53 (2008) 14–19
17
Fig. 3 – Ground section of worn tooth reviewed in the transmitted light microscope (no wear facet is showed): (A) area of globular dentine that is rarely noted subjacent to attrited dentinal tubules (magnification 40T); (B) demonstrates transparent dentine (TR), tubular (T) and atubular (A) reactionary dentine (magnification 40T); (C) demonstrates transition zone between physiologic secondary dentine and reactionary dentine (magnification 100T); (D) demonstrates change in direction and number of dentinal tubules at transition zone (magnification 40T).
of dentinal tubules or obturation of tubules in the worn teeth. The tubules were occluded by mainly four kinds of materials: (1) high electron-dense materials continuous with peritubular dentine, (2) fine needle-like crystals not continuous with peritubular dentine, (3) large rhombohedral crystals, and (4) a mixed form of previous matters. This was in the line with previous studies.19,21 The hydraulic conductance of unaffected teeth was comparable to that of the normal teeth from a previous study.14 The hydraulic conductance of transparent dentine from worn teeth was comparable to that of caries-affected dentine from a previous study.14 The occluded tubules of this area might result in reduction of the dentine permeability in worn teeth confirmed by the results in this study. Since the permeability of dentine has been demonstrated as an important factor in the bonding process, the reduction of dentine permeability is likely to have a direct effect on the penetration of adhesive resin into the deep part of dentine and
the ultimate bond strength between restorative materials and dentine.22,23 Tertiary reactionary dentine was observed predominantly in worn teeth. The ‘‘interface dentine’’13 was identified at the junction of physiologic secondary and reactionary dentine and it was only seen in the worn teeth. These results agree with a previous report.12 This zone might demonstrate as a ‘‘barrier effect’’ in the defence mechanisms of the tooth.13 There was a wide range in the thickness of reactionary dentine. These differences may be caused by different degrees of stimulation that could not be controlled.7 It has been proposed that the milder the insult to the teeth, the longer the period of time before reactionary dentine formation begin.24 The atubular dentine in the worn teeth was generally found in the areas closed to the pulp. The atubular structures probably react as the defence mechanism against physiological wear that reduces the dentine permeability.22 This mechanism is an important factor in protecting the pulp from noxious irritation.12
18
archives of oral biology 53 (2008) 14–19
Fig. 4 – Electron micrographs of unaffected third molar dentine: (A) secondary dentine illustrates dentinal tubules (DT), peritubular dentine (PD), and intertubular dentine (ID) (magnification 5000T) and (B) newly developed secondary dentine close to predentine with low mineralization of intertubular dentine and lack of highly mineralized peritubular dentine (magnification 5000T).
Fig. 5 – Electron micrographs of worn transparent dentine and reactionary dentine; transparent dentine: (A) partly or completely occluded dentinal tubules with peritubular dentine (magnification 5000T); (B) partially obturation of dentinal tubules with needle-shaped crystals (magnification 40,000T); (C) partial obturation of dentinal tubules with rhombohedral crystals (magnification 8000T); (D) obturation of dentinal tubules with combination of growth of peritubular dentine and deposition of various crystals (magnification 8000T) and reactionary dentine: (E) tubular reactionary dentine including peritubular dentine, intertubular dentine, and dentinal tubules (magnification 5000T) and (F) atubular reactionary dentine including occluded tubules and an areas devoid of tubules. Occluded tubules have a higher mineral content than the intertubular dentine (magnification 5000T).
archives of oral biology 53 (2008) 14–19
Fig. 6 – Hydraulic conductance (Lp) of dentine discs from extracted molars of worn teeth and unaffected teeth.
5.
Conclusion
Change in dentine by wear was a main factor that caused the formation of transparent dentine and reactionary dentine with various degrees of tubular occlusion. These responses reduced the dentine permeability.
references
1. Berkey D, Berg R. Geriatric oral health issues in the United States. Int Dent J 2001;51:254–64. 2. Nitschke I. Geriatric oral health issues in Germany. Int Dent J 2001;51:234–46. 3. Naidonis JA, Richards LC, Townsend GC. Abrasion: an evolutionary and clinical view. Aust Prosthodont J 1992;6:9–16. 4. Mair LH, Stolarski TA, Vowles RW, Lloyd CH. Wear: mechanisms, manifestations and measurement. J Dent 1996;24:141–8. 5. Mongini F. Dental abrasion as a factor in remodeling of the mandibular condyle. Acta Anat 1974;92:292–300. 6. Ingle JI. Alveolar osteoporosis and pulpal death associated with compulsive bruxism. Oral Surg Oral Med Oral Pathol 1960;13:1371–81. 7. Owen CP, Wilding RJ, Morris AG. Change in mandibular condyle morphology related to tooth wear in a prehistoric human population. Arch Oral Biol 1991;36:799–804. 8. Tronstad L, Langeland K. Electron microscopy of human dentine exposed by attrition. Scand J Dent Res 1971;79:160–71.
19
9. Tronstad L. Scanning electron microscopy of attrited dentinal surfaces and subjacent dentin in human teeth. Scand J Dent Res 1973;81:112–22. 10. Mendis BN, Darling AI. A scanning electron microscope and microradiographic study of the closure of human coronal dentinal tubules related to occlusal attrition and caries. Arch Oral Biol 1979;24:715–33. 11. Luke DA, Lucas PW. The significance of cusps. J Oral Rehabil 1983;10:197–206. 12. Stanley HR, Pereira JC, Spiegel E, Broom C, Schultz M. The detection and prevalence of reactive and physiologic sclerotic dentin, reparative dentin and dead tracts beneath various types of dental lesions according to tooth surface and age. J Oral Pathol 1983;12:257–89. 13. Mjo¨r IA. Normal structure and physiology. Pulp–dentin biology in restorative dentistry. Carol Stream, IL: Quintessence Publishing; 2000. p. 1–23. 14. Puapichartdumrong P, Ikeda H, Suda H. Facilitation of iontophoretic drug delivery through intact and cariesaffected dentine. Int Endod J 2003;36:674–81. 15. Vongsavan N, Matthews B. Fluid flow through cat dentine in vivo. Arch Oral Biol 1992;37:175–85. 16. Weber DF. Human dentin sclerosis: a microradiographic survey. Arch Oral Biol 1974;19:163–9. 17. Isokawa S, Kubota K, Kuwajima K. Scanning electron microscope study of dentin exposed by contact facets and cervical abrasion. J Dent Res 1973;52:170–4. 18. Yoshiyama M, Masada J, Uchida A, Ishida H. Scanning electron microscopic characterization of sensitive vs insensitive human radicular dentin. J Dent Res 1989;68: 1498–502. 19. Yoshiyama M, Noiri Y, Ozaki K, Uchida A, Ishikawa Y, Ishida H. Transmission electron microscopic characterization of hypersensitive human radicular dentin. J Dent Res 1990;69:1293–7. 20. Hiatt WH, Johansen E. Root preparation. I. Obturation of dentinal tubules in treatment of root hypersensitivity. J Periodontol 1972;43:373–80. 21. Mjo¨r IA. Human coronal dentine: structure and reaction. Oral Surg Oral Med Oral Pathol 1972;33:810–23. 22. Tagami J, Hosoda H, Burrow MF, Nakajima M. Effect of aging and caries on dentin permeability. Proc Finn Dent Soc 1992;88:149–54. 23. Yoshiyama M, Sano H, Ebisu S, Tagami J, Ciucchi B, Carvalho RM, et al. Regional strength of bonding agents to cervical sclerotic root dentin. J Dent Res 1996;75:1404–13. 24. Stanley HR, White CL, McCray L. The rate of tertiary (reparative) dentin formation in the human tooth. Oral Surg Oral Med Oral Pathol 1966;21:180–9.
available at www.sciencedirect.com
journal homepage: www.intl.elsevierhealth.com/journals/arob
Morphological characterization and permeability of attrited human dentine Pisol Senawongse a,*, Masayuki Otsuki b, Junji Tagami b, Ivar A. Mjo¨r c a
Department of Operative Dentistry, Faculty of Dentistry, Mahidol University, 6 Yothi Street, Phayathai, Bangkok 10400, Thailand Cariology and Operative Dentistry, Tokyo Medical and Dental University, 5-45 Yushima 1-Chome, Bunkyo-ku, Tokyo 113-8549, Japan c College of Dentistry, University of Florida, P.O. Box 100415, Gainesville, FL 32610, USA b
article info
abstract
Article history:
Objective: Dentine is a vital tissue that can be changed by physiological and pathological
Accepted 27 July 2007
condition. The purpose of this study was to clarify the morphology and permeability of dentine that changed by wearing process.
Keywords:
Methods: Twenty extracted human molars with enamel attrition and dentine was exposed
Wear
and 20 intact human extracted third molars that had not reached occlusion were used. Ten
Transparent dentine
teeth per each group were observed under light microscope (LM) and transmission electron
Reactionary dentine
microscope (TEM). Remaining 10 teeth per each group were subjected for evaluation of
Light microscope
dentine permeability.
Transmission electron microscope
Results: Under LM, the transparent dentine and reactionary dentine were found in the
Permeability
attrition group but were not found in the group unaffected by attrition. When the transparent dentine were examined under the TEM, it was found that dentinal tubules were partially or completely occluded by growth of peritubular dentine or by precipitation of needle-like or rhombohedral crystals in transparent dentine. In reactionary dentine, tubular dentine structures that were comparable to those in secondary physiologic dentine were observed whereas atubular dentine demonstrated occlusion of tubules by high mineral substances or by peritubular dentine under the TEM. Permeability of dentine from worn teeth was less than those from unoccluded teeth significantly. Conclusion: Change in dentine by wear resulted in the formation of reactionary dentine and transparent dentine that illustrated various types and degrees of tubular occlusion. These decrease the dentine permeability. # 2007 Elsevier Ltd. All rights reserved.
1.
Introduction
Increase human life span calls for increasing attention to geriatric dentistry.1,2 Excessive wear may cause of tooth loss in elderly patients.3,4 Tooth wear is a normal physiological process. However, when self-adaptive capabilities are exceeded, the physiological process becomes a pathological problems5–7 and restorative treatment is requirement.
The attrition of teeth allows changes in morphological characterization of dentine such as transparent dentine formation and production of reactionary dentine.8–12 These morphological changes might affect the permeability of dentine. Few studies have been published on the morphology of dentine and its permeability during the progression of wear. Such knowledge is important for understanding dentine reaction under clinical condition.
* Corresponding author. Tel.: +66 2 644 8644; fax: +66 2 354 8510. E-mail address: [email protected] (P. Senawongse). 0003–9969/$ – see front matter # 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.archoralbio.2007.07.010
archives of oral biology 53 (2008) 14–19
15
Fig. 1 – Experimental apparatus for dentine permeable test. Red arrows demonstrate the direction of fluid flow. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
2.
Materials and methods
2.1.
Morphological study
Twenty human teeth were included in this study; 10 extracted molars from elderly individuals with enamel attrition and exposed middle 1/3 of dentine and 10 extracted intact third molars that had not reached occlusion were used in this study. These intact teeth will be referred as unaffected teeth. All teeth were extracted and the patients were informed and agreed that their teeth will be used for this investigation. The ages of subjects ranged from 55 to 65 years for elderly patients (worn teeth) and 18 to 25 years for adolescent patients (intact teeth). The extracted teeth were kept in physiological saline solution at 5 8C within 2 months prior to processing. The teeth were sectioned axiobuccolingually with a highspeed diamond saw (Leitz 1600, Leica Instruments, Heidelberg, Germany) to create a 150 mm thick section from the centre of teeth. The 150 mm thick slabs were reduced to approximately 100 mm with silicon carbide papers by hand lapping. The specimens were examined under a transmission light microscope (Vanox AHBS3, Olympus, Tokyo, Japan). The morphological structures identified were mantle dentine, globular dentine, primary and physiologic secondary dentine, transparent dentine, and tertiary reactionary dentine.13 Based on the light microscope examination, small areas were dissected out and processed for a transmission electron microscopy. Ultrathin sections were cut with a diamond knife and collected on carbon-coated grids. The section were examined under a transmission electron microscope (TEM) operated at 80 kV (Hitachi 300 TEM, Hitachi Co., Tokyo, Japan)
2.2.
Dentine permeable study
The dentine permeability was measured by the means of hydraulic conductance. Additional 10 extracted molars from elderly individuals with enamel attrition and exposed dentine
and 10 extracted intact third molars that had not reached occlusion were used. Flat dentine discs with 0.7 mm thick from outer 1/3 of occlusal dentine were prepared by cutting with a low speed diamond saw (Isomet, Buehler, IL, USA) perpendicular to long-axis of teeth and polished with wet silicon carbide papers (600 grit down to 1000 grit). The smear layers created by polishing were removed with 10% phosphoric acid for 10 s. The test method and apparatus (Fig. 1) were derived from the study of Puapichartdumrong et al.14 The rate of fluid movement pass through circular areas with 6 mm diameter of the dentine disc was measured by monitoring the movement of a small air bubble under the pressure that was comparable to pulpal pressure (1.47 kPa or 15 cm H2O)15 at the rate of 0.2 mL/min. The system used in the present study consisted four parts: a source of pressure, a pressurized chamber, a system to measure the displacement of bubble (50 mL micro-syringe), and a specimen holder. The data were converted into the hydraulic conductance (Lp; mL cm2 min115 cm H2O1):
Lp ¼
Jv P
Jv (mL cm2 min1 cm H2O1) is the fluid flux that was calculated by Jv = Q/At [Q (mL) is the fluid shift, A (cm2) the area of dentine and t (min) is the diffusion time]. P (cm H2O) is the applied hydrostatic pressure.14
3.
Results
3.1.
Morphological study
Morphological features of dentine of worn and unaffected teeth were studied by examined ground sections under the transmission light microscope. The attrition resulted in various changes in dentine. Globular dentine was observed normally in unaffected teeth (Fig. 2A), but was rarely noted
16
archives of oral biology 53 (2008) 14–19
dentine and reactionary dentine (Fig. 3C). At this location, a change in the direction and number of dentinal tubules was frequently noted (Fig. 3D). At the other part of the pulp chamber, no marked reduction in the number of dentinal tubules was observed when passing from physiologic secondary dentine to reactionary tertiary dentine. In some of the teeth, the incremental lines were observed, particularly in the tertiary dentine underlining worn dentine. The transparent dentine of exposed dentine had different appearances in TEM. Some dentinal tubules were occluded by high electron-dense materials. The material seems to be a continuous growth of peritubular dentine (Fig. 5A), which always found at the subsurface of wear. Some tubules were occluded with extremely fine crystals (Fig. 5B), others with large rhombohedral crystals (Fig. 5C), which always found on the surface of attrited dentine. Dentinal tubules occluded with fine needle-like crystals, or rhombohedral crystals mixed with substrates including peritubular dentine were demonstrated (Fig. 5D). Occluded tubules were rarely identified in the normal teeth unaffected by attrition. The dentinal tubules of unaffected teeth were empty. The tubules were surrounded by peritubular dentine, which was more highly minerized than the surrounding intertubular dentine (Fig. 4A). The reactionary tertiary dentine had various appearances. Comparatively large areas with no tubules and areas with tubules of different diameters were observed. Areas with tubular structures (Fig. 5E) demonstrated morphology similar to that of physiologic secondary dentine (Fig. 4A). Areas devoid of tubules; atubular structure had the same appearance as regular intertubular dentine with minerized fibres. Typical cross-banding of the collagen fibres could be discerned (Figs. 4 and 5). The occluded tubules had a high mineral content than the intertubular dentine. In the unaffected teeth, the areas closed to pulp chamber demonstrated low mineralization of intertubular dentine and the peritubular dentine was rarely identified (Fig. 4B). Fig. 2 – Ground section of unaffected third molar reviewed in the transmitted light microscope: (A) demonstrates mantle dentine (M), globular dentine (G), and physiologic primary dentine (S) (magnification 40T); (B) demonstrates tubular structure of physiologic primary and secondary dentine (magnification 100T); (C) shows calcospherite dome shape structure of newly developed secondary dentine (magnification 100T).
3.2.
Hydraulic conductance of dentine discs from unaffected third molars (group 1) and from worn molars (group 2) is demonstrated in Fig. 6. The hydraulic conductance of dentine discs from worn molars (1.998 1.604) was significantly ( p < 0.001) less than that of unaffected third molars (12.537 1.004).
4. subjacent to worn teeth (Fig. 3A). Transparent dentine was typically observed in the worn teeth (Fig. 3B). The physiologic secondary dentine of worn teeth (Fig. 2B) had structure similar to that of unaffected teeth (Fig. 2B), however, it was wider in the unaffected teeth (Figs. 2A and 3B). Reactionary tertiary dentine was only observed in worn teeth. Two types of reactionary dentine: tubular and atubular dentine were observed (Fig. 3B). A transition zone was observed in worn teeth at the junction between physiologic secondary
Dentine permeable study
Discussion
The primary dentine and physiologic secondary dentine of worn teeth demonstrated transparent dentine that conformed to the previous studies.12,16 The transparent dentine is likely to be a result of the attrition since we found this dentine only subjacent to the worn areas. The physiological wear from mastication confirms the deposition of apatite crystal in the tubules.9,10,17 These depositions were similar to those shown in exposed, sensitive dentine.18–20 These crystalline depositions caused a decrease in the diameters
archives of oral biology 53 (2008) 14–19
17
Fig. 3 – Ground section of worn tooth reviewed in the transmitted light microscope (no wear facet is showed): (A) area of globular dentine that is rarely noted subjacent to attrited dentinal tubules (magnification 40T); (B) demonstrates transparent dentine (TR), tubular (T) and atubular (A) reactionary dentine (magnification 40T); (C) demonstrates transition zone between physiologic secondary dentine and reactionary dentine (magnification 100T); (D) demonstrates change in direction and number of dentinal tubules at transition zone (magnification 40T).
of dentinal tubules or obturation of tubules in the worn teeth. The tubules were occluded by mainly four kinds of materials: (1) high electron-dense materials continuous with peritubular dentine, (2) fine needle-like crystals not continuous with peritubular dentine, (3) large rhombohedral crystals, and (4) a mixed form of previous matters. This was in the line with previous studies.19,21 The hydraulic conductance of unaffected teeth was comparable to that of the normal teeth from a previous study.14 The hydraulic conductance of transparent dentine from worn teeth was comparable to that of caries-affected dentine from a previous study.14 The occluded tubules of this area might result in reduction of the dentine permeability in worn teeth confirmed by the results in this study. Since the permeability of dentine has been demonstrated as an important factor in the bonding process, the reduction of dentine permeability is likely to have a direct effect on the penetration of adhesive resin into the deep part of dentine and
the ultimate bond strength between restorative materials and dentine.22,23 Tertiary reactionary dentine was observed predominantly in worn teeth. The ‘‘interface dentine’’13 was identified at the junction of physiologic secondary and reactionary dentine and it was only seen in the worn teeth. These results agree with a previous report.12 This zone might demonstrate as a ‘‘barrier effect’’ in the defence mechanisms of the tooth.13 There was a wide range in the thickness of reactionary dentine. These differences may be caused by different degrees of stimulation that could not be controlled.7 It has been proposed that the milder the insult to the teeth, the longer the period of time before reactionary dentine formation begin.24 The atubular dentine in the worn teeth was generally found in the areas closed to the pulp. The atubular structures probably react as the defence mechanism against physiological wear that reduces the dentine permeability.22 This mechanism is an important factor in protecting the pulp from noxious irritation.12
18
archives of oral biology 53 (2008) 14–19
Fig. 4 – Electron micrographs of unaffected third molar dentine: (A) secondary dentine illustrates dentinal tubules (DT), peritubular dentine (PD), and intertubular dentine (ID) (magnification 5000T) and (B) newly developed secondary dentine close to predentine with low mineralization of intertubular dentine and lack of highly mineralized peritubular dentine (magnification 5000T).
Fig. 5 – Electron micrographs of worn transparent dentine and reactionary dentine; transparent dentine: (A) partly or completely occluded dentinal tubules with peritubular dentine (magnification 5000T); (B) partially obturation of dentinal tubules with needle-shaped crystals (magnification 40,000T); (C) partial obturation of dentinal tubules with rhombohedral crystals (magnification 8000T); (D) obturation of dentinal tubules with combination of growth of peritubular dentine and deposition of various crystals (magnification 8000T) and reactionary dentine: (E) tubular reactionary dentine including peritubular dentine, intertubular dentine, and dentinal tubules (magnification 5000T) and (F) atubular reactionary dentine including occluded tubules and an areas devoid of tubules. Occluded tubules have a higher mineral content than the intertubular dentine (magnification 5000T).
archives of oral biology 53 (2008) 14–19
Fig. 6 – Hydraulic conductance (Lp) of dentine discs from extracted molars of worn teeth and unaffected teeth.
5.
Conclusion
Change in dentine by wear was a main factor that caused the formation of transparent dentine and reactionary dentine with various degrees of tubular occlusion. These responses reduced the dentine permeability.
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