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Morphological Study of Calcospherites in Rat and Rabbit Incisor Dentin

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Morphological Study of Calcospherites in Rat and Rabbit Incisor Dentin Scanning Microscopy Volume 5 Number 3 Article 15 7-11-1991 Morphological Study of Calcospherites in Rat and Rabbit Incisor Dentin H. Mishima Nihon University T. Sakae Nihon University Y. Kozawa Nihon University Follow this and additional works at: https://digitalcommons.usu.edu/microscopy Part of the Biology Commons Recommended Citation Mishima, H.; Sakae, T.; and Kozawa, Y. (1991) "Morphological Study of Calcospherites in Rat and Rabbit Incisor Dentin," Scanning Microscopy: Vol. 5 : No. 3 , Article 15. Available at: https://digitalcommons.usu.edu/microscopy/vol5/iss3/15 This Article is brought to you for free and open access by the Western Dairy Center at DigitalCommons@USU. It has been accepted for inclusion in Scanning Microscopy by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. Scanning Microscopy, Vol. 5, No. 3, 1991 (Pages 723-729) 0891-7035/91$3 .00+ .00 Scanning Microscopy International, Chicago (AMF O'Hare) , IL 60666 USA MORPHOLOGICAL STUDY OF CALCOSPHERITES IN RAT AND RABBIT INCISOR DENTIN H. Mishima*, T. Sakae and Y. Kozawa Department of Anatomy, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271, Japan (Received for publication March 10, 1991, and in revised form July 11, 1991) Abstract Introduction Calcospherites from incisors of rats and rabbits were The scanning electron microscope (SEM) can be studied, by means of secondary and backscattered elec­ used to obtain various signals, such as secondary, Auger tron images, using scanning electron microscopy . Part and backscattered electrons, cathodoluminescence, char­ of each incisor specimen was made anorganic to allow acteristic X-rays and continuous X-rays, etc.. Electron observation of the surface of the mineralization front by signals usually are used to study the morphology of ir­ scanning electron microscopy; the other part was ground regular surfaces of samples. Backscattered electron im­ on one side for observation by scanning electron micros­ ages have been used to study tissues stained by heavy copy with a backscattered electron image detector. In metals [l, 2, 17], immunohistochemistry studies [6, 18, both species the labial mineralization front was wavy and 19] and to investigate calcification pattern of hard tissues the image showed fused calcospherites, whereas the lin­ [4]. Jones and Boyde [7] reported that the backscattered gual mineralization front appeared to consist of a com­ electron image provided new information about the min­ bination of linear and globular forms. In rat labial eralization front and crystal orientation of calcified tis­ dentin the calcospherites were large and globular form, sues. Several attempts have been made to observe the but they did not develop in the lingual dentin and were three-dimensional structure of calcospherites, after sodi­ small and oval. The shape and size of rabbit incisor cal­ um hypochlorite (NaOCl) treatment [3, 9, 16]. Compar­ cospherites varied from the pulp horn to the root apex. ison of the backscattered with the secondary electron There were great differences between rats and rabbits image after NaOCl treatment may, therefore, provide with respect to the size and shape of the calcospherites new information about the nature of calcospherites. at the mineralization front. This may be due to species Mishima et al. [12] divided rat incisor dentin into differences and possibly the differing rates of dentino­ enamel-covered labial dentin and cement-covered lingual genesis in rats and rabbits. dentin. They demonstrated that the histological structure of labial and lingual dentin differed and that the shape of the calcospherites in predentin differed from those in dentin. The incisors of rats and rabbits grow continu­ ously and are enamel-covered on the labial side and ce­ Key Words: Rat, rabbit, incisor, labial dentin, lingual ment-covered on the lingual side [15]. However, little dentin, calcospherites, mineralization front has been reported on the morphology of calcospherites in rabbit predentin. This study was designed to charac­ terize the morphology of the mineralization front and the calcospherites of the labial and lingual dentin of rat and rabbit incisors using combined backscattered and second­ ary electron images. * Address for correspondence: H. Mishima Material and Methods Department of Anatomy, Nihon University School of Dentistry at Matsudo, Bilateral incisors were extracted from 10 male 2-870-1 Sakaecho-Nishi, Wistar-strain rats (200 to 400 g each) and 5 male Matsudo, Chiba 271, Japan Japanese white rabbits (2.5 to 3.5 kg each). Each Phone No. 0473-68-6111 Ext. 386 incisor was fixed in 2 % glutaraldehyde fixative solution 723 H. Mishima, T. Sakae, And Y. Kozawa (pH 7.4, 0.1 M phosphate buffer solution) for 24 hours Rabbit incisor dentin. The calcospherites in the prior to use. Some samples were fixed in 10 % neutral mineralization front of rabbit incisor labial dentin were formalin for 24 hours . globular (Fig. 3). They were small (8 to 15 µm) com­ After fixation, one of each pair of incisor specimen pared with those in rat labial dentin and contained 2-9 was cut transversely into three portions with a Torx dentinal tubules. The size of the calcospherites de­ dental turbine (Morita Co. Ltd., Tokyo) equipped with creased and their shape changed from globular to mul­ a diamond disc. These portions were divided further, berry-like towards the incisor pulp horn (Fig. 4). In with the same turbine, into separate labial and lingual rabbit lingual dentin, the fused calcospherites were · regions, prior to NaOCl treatment to expose the mineral­ ridge-like (Fig. 5) and were smaller (0.9 to 3 µm) than ization front. For this treatment the specimens were those in rabbit labial dentin and rat lingual dentin. kept in fresh 10% NaOCl solution for 30 minutes at These calcospherites accumulated in the direction of the room temperature with mild vibration, rinsed well with longitudinal axis of the tooth, their shape changed from distilled water and dehydrated with an alcohol series, ridge-like to oval (Fig. 6), and their size increased (1.5 after which the alcohol was substituted by isoamyl ace­ to 4 µm) towards the incisal pulp horn region. The cal­ tate and the specimens were subjected to critical-point cospherites' shapes also varied from the incisal pulp drying with liquid carbon dioxide. The pulpal surfaces horn to the root apex (Table 1). In the labial dentin the were gold-coated for morphological examination (sec­ calcospherites changed from globular to mulberry-like ondary electron image) of the mineralization front, and at the incisal pulp horn, moreover, the calcospher­ which was observed from a direction perpendicular to ites appeared as very small granules (0.3-0 .9 µm). In the tooth's longitudinal axis, with a JSM-T200 SEM the lingual dentin the calcospherites changed shape from (Japan Electron Optics Laboratory Co. Ltd., Tokyo) . small and granular to oval, and at the incisal pulp horn The other incisors were halved parallel to their lon­ they resembled small granules. gitudinal axes using an Isomet low-speed saw (Buehler, Co.), after fixation. The cut surface was ground with a whetstone initially and then with diamond paste (0.25 Observation using backscattered electron images µm particle diameter), after which the specimen were subjected to ultrasonic cleaning for 3 minutes, washed Rat incisor dentin. Backscattered electron images (BEI) were remarkably similar to microradiography well with distilled water, followed by dehydration and critical-point drying as described above. The polished images. The mineralization front in the labial dentin was visualized clearly and had an undulating appearance surfaces were carbon-coated in a TB-500 carbon coater (Fig. 7), with fused calcospherites. The peritubular den­ (EMSCOPE Laboratories Ltd.), and backscattered elec­ tron images were observed with a JSM-T200 SEM. tin was highly calcified, and poorly calcified interglobu­ lar dentin occurred sporadically. Globular calcospheri tes (6 to 20 µmin size) were present in the predentin (Fig. Results 8), and there were Tomes' fibers (odontoblastic proc­ Secondary electron images after anorganic treatment esses) in the dentinal tubules. The mineralization front of rat lingual dentin ap­ The morphological characteristics of calcospherites peared to consist of combined linear and globular forms at the mineralization front from the incisal pulp horn to (Fig. 9). The calcospherites in the predentin were flat the root apex of the incisor were observed . The results compared with those in the labial dentin, they were not presented here are mainly for the calcospherites at the differentiated clearly from the surrounding tissue, and intermediate region between the root apex and the incisal were arranged parallel to the longitudinal axis of the pulp horn. incisor. Rat incisor dentin. Secondary electron images of Rabbit incisor dentin. The backscattered electron the mineralization front of anorganically-treated incisors image showed the mineralization front in the labial den­ showed that rat labial dentin contained large globular tin of rabbit incisor clearly (Fig. 10). It was wavy, sim­ calcospherites, which ranged in size from 7 to 31 µm ilar to that in rat labial dentin . The calcospherites were (Fig. 1), and each contained 2-16 dentinal tubules. The slightly smaller than those of rat incisors. calcospherites in the lingual dentin were oval and The mineralization front of rabbit lingual dentin was smaller (7-20 µm) than those in the labial dentin (Fig. interrupted by calcospherites (Fig. 11). The calcospher­ 2), and each in the lingual dentin contained 2-8 dentinal ites in the predentin were flat, smaller than those of rat tubules. The calcospherites were arranged with their lingual and rabbit labial dentin, and were arranged paral­ longitudinal axes parallel to the longitudinal axis of the lel to the longitudinal axis of the incisor. incisor. 724 Calcospherites in Rat and Rabbit Dentin Root apex ◄ ----1►• Incisal pulp horn Labial: large globular ._. small globular -◄-►- mulberry- ◄◄a---t1►► very small like granules Lingual: small granular ◄ ► ridge-like oval ◄◄..--ti►► very small ◄ ► granules Table 1.
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