TGF-ß in dentin matrix extract induces osteoclastogenesis in vitro.

Previously, we have demonstrated that the extracellular matrix from dentin affects osteoclastic activity in co-culture between osteoclast and osteoblast-rich fraction from mouse marrow cells. In the present study, we aimed to investigate the mechanisms of dentin matrix extract-induced osteoclastogenesis in mouse bone marrow macrophages (BMMs). Dentin proteins were extracted from bovine incisor root dentin using 0.6 M HCl. BMMs were cultured in α-MEM containing macrophage colony-stimulating factor/receptor activator of nuclear factor kappa-B ligand in the presence or absence of dentin matrix extract. Tartrate-resistant acid phosphatase (TRAP)-positive cell number, total TRAP activity, and the mRNA levels of osteoclast-related genes, assayed by real-time RT-PCR, were determined as markers of osteoclastogenesis. A neutralizing antibody against transforming growth factor-ß1 (TGF-ß1), SB431542, a TGF-ß receptor inhibitor, and ELISA were used to determine the role of TGF-ß1. We observed increases in TRAP-positive cell number, TRAP activity, and the mRNA levels of osteoclast-related genes of BMMs cultured with dentin extract. The use of a neutralizing antibody against TGF-ß1 or SB431542 inhibited the inductive effect of dentin extract, suggesting TGF-ß1 involvement. The addition of exogenous TGF-ß1, but not bone morphogenic protein-2, also increased osteoclastogenesis, corresponding to the ELISA determination of TGF-ß1 in the dentin extract. In conclusion, our results indicate that proteins from dentin matrix have an inductive effect in osteoclastogenesis, which is mediated, in part, by TGF-ß1.

The effect of chewing exercise in preschool children on maximum bite force and masticatory performance.

BACKGROUND: Mastication is a developing function affected by various factors. There is a need for further research on methods of promoting masticatory function in young children. AIM: The aim of this study was to evaluate the effects of gum chewing exercise on the maximum bite force (MBF) and the masticatory performance of preschool children. DESIGN: The study population included 98 preschool children age 4-6years. MBF was measured by Occlusal Force-Meter(®) , and masticatory performance values were evaluated by using the colour-changeable chewing gum. The examinations were performed four times with an interval of 4weeks. An exercise group of 70 subjects was instructed to chew the exercise gum twice daily for 5min during a 4-week period. The chewing gum used for this study was specially developed with the physical property of maintaining hardness during chewing. A control group of 28 subjects was instructed not to chew any gum during the study period. RESULTS: No significant differences were found between the exercise group and the control group in MBF and a* values at the start of the study. After 4weeks of chewing exercise, MBF and a* values were significantly increased in the exercise group compared with those of the control group. These increases were maintained for 4weeks after exercise had finished. CONCLUSIONS: Gum chewing exercise is effective to increase MBF and a* values of preschool children and the effects are maintained after exercise completion.

Objective assessment of internal stress in children during dental treatment by analysis of autonomic nervous activity.

AIMS: The aim of this study was to assess the internal stress of children during dental treatment based on autonomic nerve activity and facial muscle activity. METHODS: We recorded the electrocardiogram of children during the treatment of composite resin restoration and analysed autonomic nerve activity by means of power spectral analysis of heart rate variability. Simultaneously, electromyography (EMG) activity of the corrugator muscle was recorded in children during dental treatment, and the relationship between sympathetic nerve activity and corrugator EMG activity was analysed. RESULTS: In all subjects, the mean sympathetic nerve activity was significantly higher during oral examination and after treatment compared with pre-treatment. Depending on the sympathetic nerve responses to the other treatment procedures, the subjects could be classified into two groups: the stress group and the nonstress group. Sympathetic nerve activity was significantly higher during infiltration anaesthesia and cavity preparation compared with pre-treatment activity in the stress group, whereas it was consistently lower than the pre-treatment levels during most treatment procedures in the nonstress group. The mean amplitudes of the averaged corrugator muscle EMG during dental treatment did not differ between the stress and nonstress groups. CONCLUSION: The present results suggest that the measurement of autonomic nervous activity, especially sympathetic nervous activity, is quite useful in assessing the internal stress of children, even when no expressed sign of unease are present during dental treatment.

Wear of resin composites and primary enamel and their applicability to full crown restoration of primary molars.

PURPOSE: To determine whether resin composites are appropriate for full crown restoration of primary molars by evaluating their wear characteristics. Specifically, the wear properties of resin composite specimens and the opposing enamel surfaces were characterized by means of impacting-sliding wear testing. METHODS: Three types of light-cured resin composites (Estelite Sigma quick, Litefill IIP, and Metafil C), one type of chemical-cured resin composite (Clearfil FII), and a hybrid composite (Estenia C&B) were tested in this study. The enamel sample was used as the control. The hemispherically prepared specimens were subjected to impacting-sliding wear testing against the flattened enamel of primary molars. The worn surfaces were examined by laser scanning microscopy and scanning electron microscopy. The volumetric loss was estimated by using micro-CT images. The areas of worn enamel surfaces were measured by 3D color laser microscopy. On most of the worn enamel surfaces, cracks appeared. Scatter plot analyses between their width and depth were carried out. Data for each specimen were statistically analyzed by multiple comparisons among the means of treatment by Bonferroni's method (P< 0.01). RESULTS: Clearfil showed significantly higher surface area wear, volumetric loss, and worn enamel surface area than did the other resin composites and the control enamel (P< 0.01). There was no significant difference among the worn surface areas ofEstelite, Litefill, Metafil, and Estenia (P< 0.01). The control enamel showed significantly lower worn surface area than did the resin composites (P< 0.01). There was no significant difference in volumetric loss and worn enamel surface areas among Estelite, Litefill, Metafil, Estenia, and the control enamel (P< 0.01). Cracks larger than that on the control enamel were seen on the worn enamel surface opposing Estenia.

Three-Dimensional Comparison in Palatal Forms Between Modified Presurgical Nasoalveolar Molding Plate and Hotz's Plate Applied to the Infants With Unilateral Cleft Lip and Palate.

The presurgical nasoalveolar molding plate appliance with stent (PNAM) extended from the palatal molding plate; to correct the nostril shape of infants with cleft lip and palate is well known. The PNAM appliance is based on the finding that a high degree of plasticity is maintained in the cartilage of infants during the first 6 weeks after birth. However, on the current PNAM protocol described by Grayson et al. the nasal stent is supposed to be an adjunct to the palatal molding plate after reducing the severity of the alveolar cleft width. We have used the modified Hotz's plate from the setup model and built up the nasal stent even before reducing the severity of the alveolar deformity. In this study we assess the effects of the modified Hotz's plate and the modified PNAM appliance for the alveolar and palatal form. The lateral deviation of the incisal point, the width of the palatal cleft, and the degree of curvature of the palatal vault were first evaluated on plaster models. The PNAM group is smaller on the lateral deviation of the incisal point than the modified Hotz's group. The decreased average width of the palatal cleft and curvature of the palate, was almost the same in both the modified Hotz's and PNAM groups. In comparison with the modified Hotz's plate, the modified PNAM appliance also improves the molding of the alveolar segments and reduces cleft width.

Absolute transmitted light plethysmography for assessment of dental pulp vitality through quantification of pulp chamber hematocrit by a three-layer model.

After confirming that the gingival circulation had little effect on transmitted light plethysmography measurement in the upper central incisor in both in vivo experiments and numerical Monte Carlo simulation studies, a three-layer model comprising of a pulp chamber sandwiched between two dentin layers has been introduced to quantify the pulp chamber hematocrit (Hctp) from the measured optical density. Two-flux theory was utilized to derive a mathematical equation for transmitted intensity in terms of tooth dimensions, Hctp, and light-source wavelength. Each layer was assumed homogeneous so as to represent its optical properties by the bulk absorption and scattering constants. The mean error between the Hctp estimate based on the three-layer-model equation and the Hctp actual in the extracted model tooth was -0.00115 with standard deviation (SD) of 0.00733 at 522 nm wavelength, while for 810 nm +0.09157 and 0.02493. The Hctp estimate of the upper central incisor in 10 young volunteers at 522 nm using the three-layer model ranged from 0.002 to 0.061 with the mean of 0.032. The Hctp change reflects blood volume shift in the pulp microcirculation to possibly indicate dental pulp vitality.

Effect of turpentine-induced fever during the enamel formation of rat incisor.

OBJECTIVE: Some epidemiological studies have indicated that diseases resulting in prolonged and sustained fever, such as exanthemata, respiratory infections and otitis media in infantile period or childhood are likely to have a marked deleterious effect on enamel formation, but the relationship between fever and enamel defects is unknown. The purpose of the present study was to induce a persistent high fever and examine the effects on the developing tooth enamel. METHODS: Twenty male Wistar rats weighting 140+/-10 g were used in this study. For the experimental group, a dose of 2.3 ml/kg steam-distilled turpentine was subcutaneously injected into both hind limbs five times at 12h intervals. Control rats received 2.3 ml/kg of sterile saline into the same injection site. The rectal temperatures of animals were measured at the febrile period. After constant periods, the animals were sacrificed, and the mandibular incisors were examined by contact microradiography (CMR) and histological observation. RESULTS: The febrile state lasted for 57 h and the average temperature rose 1.51 degrees C higher than that of the control group. The ground sections, semi-thin and ultra-thin sections of mandibular incisors were prepared and the enamel was observed. The microradiographs showed a radiolucent line along with the incremental line in the enamel. Moreover, microscopic examination indicated disorientation of enamel prism and crystal-free area within this radiolucent lesion. CONCLUSIONS: Persistent high fever pattern was established firmly by the turpentine injections and the process of enamel formation was influenced by the febrile period.

[Inspection by infection control team of the University Hospital, Faculty of Dentistry, Tokyo Medical and Dental University].

Factors affecting infection are the existence of infectious microorganisms, sensitivity of hosts, number of microorganisms, and infectious routes. Efforts to prevent infection focus on not allowing these factors to reach the threshold level. Inspection by an infection control team (ICT) of a hospital is one countermeasure for preventing nosocomial infection. We summarize here the problems for complete prevention of nosocomial infection based on the results of inspection by our ICT, so that staff working in the hospital can recognize the importance of preventing nosocomial infection. The following were commonly observed problems in our clinics found by the ICT : (1) incomplete practice of standard precautions and/or isolation precautions, (2) noncompliance with guidelines for the prevention of cross-infection, and (3) inappropriate management of medical rejectamenta. Infection control can be accomplished by strictly observing the standard precautions and isolation precautions. The ICT inspection round in the hospital could be an effective metaff working in the hod to clarify and overcome the problems involved in infection.

Effects of laser irradiation on tensile strength of bovine dentin.

OBJECTIVE: The purpose of the present study was to investigate the tensile strengths of dentin after laser irradiation using three kinds of dental lasers to elucidate the laser-irradiation effect on dentin properties. BACKGROUND DATA: Different kinds of laser devices have been developed in dentistry. The characteristics of each laser are determined by its original wavelength; however, one common feature is to generate heat in irradiated tissues, and such heat possibly affects dentin collagen, which contributes to tensile strength of the tissues. MATERIALS AND METHODS: Er:YAG, CO2, and diode (GaAlAs) lasers were used to irradiate bovine dentin. Subsequently, tensile test specimens were made from the irradiated dentin and tensile tests were conducted. The tensile strengths were analyzed using the paired-t test and Weibull analysis. Irradiated dentin was also observed transversally using light microscopy. RESULTS: The tensile strengths of the lased dentin and the control group for the Er:YAG, CO2, and diode lasers were 73.1 and 78.5, 70.3 and 74.3, and 64.3 and 71.0 MPa, respectively. The tensile strength of the dentin had a tendency to decrease with laser irradiation. Weibull analysis indicated that the laser influence was different among the three kinds of laser apparatuses and seemed to correspond to the depths the laser beam reached, which were suggested by light microscopy observation. CONCLUSION: Laser irradiation could possibly decrease dentin tensile strength, which suggests the importance of careful use of laser for hard tissue treatment, considering its energy-transforming characteristics.

[Career history and perceptions of dental hygiene education programs--questionnaire mail-in survey of alumni of the School of Dental Hygiene in Tokyo Medical and Dental University].

This study was conducted to investigate the career history and perceptions about dental hygiene education programs among the alumni (1952-1999 graduates) of the School of Dental Hygiene in Tokyo Medical and Dental University. A questionnaire containing demographic, practice characteristics and views on the programs was mailed to 997 alumni in 1999, and 576 alumni (57.8%) responded. Three hundred and forty-one respondents worked as dental hygienists. The majority who responded were in clinical practice. One hundred and thirty-one of the respondents worked in private clinics, 76 in public health centers, and 72 in clinics in companies. The rate of them who worked in public health centers was much higher than the national average cited in the Statistical Report on Public Health Administration and Services. Two hundred and ninety-one respondents reported inadequate programs. The rate of them who reported inadequate programs was significantly higher in alumni who were working than in alumni who were not. The items cited as insufficiently taught at the school were clinical practice, instrumentation, foreign language, psychology, counseling, and nursing related subjects. Thus, many alumni suggested the need for better programs and continuing education. From these results, it was suggested that dental hygienists need to change their education programs in order to meet the present and future needs of more diversified society. This view was particularly prevalent among alumni who were working. The result showed that dental hygiene educators and dental hygienists urgently need to reconsider the professionalism of their field.

Octacalcium phosphate-based cement as a pulp-capping agent in rats.

OBJECTIVE: The purpose of this study was to evaluate the pulpal response to an octacalcium phosphate (OCP)-based cement used as a pulp-capping material. STUDY DESIGN: The pulps of 60 maxillary first molars of male Sprague-Dawley rats were exposed and then capped directly by using either OCP-based cement or a calcium hydroxide slurry (control). Histologic examinations were performed at 1, 2, and 5 weeks after the surgical procedure, and the results were analyzed statistically by using the Mann-Whitney U test (P<.05). RESULTS: One week after pulp capping, the initial formation of reparative dentin in the exposed areas was more notable in the calcium hydroxide group than in the OCP-based cement group. At 2 weeks, reparative dentin covered by a layer of odontoblast-like cells was observed in both groups. However, at 5 weeks, reparative dentin consisting of regular dentinal tubules was observed more frequently in the OCP-based cement group. CONCLUSION: OCP-based cement allowed favorable healing processes to occur in the dental pulp.

Gene expression of bone matrix proteins in a calcified tissue appeared in subcutaneously transplanted rat dental pulp.

Dental pulp self-mineralizes or induces calcified tissue formation, when it is subcutaneously transplanted. This study aims to clarify the nature and process of this tissue calcification by using histochemical techniques and in situ hybridization methods. The dental pulps of incisors from Sprague-Dawley strain rats were homogeneously transplanted into the subcutaneous tissue of the head of another rat. On the 1st day of transplantation, the mRNAs of type I collagen (COL I) and bone sialoprotein (BSP) were expressed in the transplant. On the 5th to 7th days after transplantation, von Kossa-positive, calcified tissues appeared in the transplanted tissues. The mRNAs of COL I, BSP and osteopontin (OPN) were expressed with the same distributions as those of the von Kossa-positive areas, but those of type II collagen (COL II) and bone morphogenic protein 2 (BMP-2) were not expressed in the transplant. When the cellular incorporation of BrdU was examined after its subcutaneous injection into the animals, positive cells were present in the von Kossa-positive calcified foci as well as in their surrounding areas. These results indicate that the transplanted dental pulp possesses the ability to induce cell proliferation resulting in the synthesis of several bone matrix proteins and the formation of calcified tissue. This may give us an insight into the nature and processes of pulp obliteration, which occurs in a human tooth following an episode of trauma.

Pulpal blood flow in vital and nonvital young permanent teeth measured by transmitted-light photoplethysmography: a pilot study.

PURPOSE: The purpose of this study was to record transmitted-light photoplethysmography (TLP) from young permanent teeth and examine its applicability to pulp vitality assessment. METHODS: Twenty-six healthy and 7 nonvital upper maxillary incisors in 17 children (ages 7 years, 3 months to 14 years, 8 months) were examined. Recordings of TLP were made with and without opaque black rubber dam application in a darkened room. Finger photoplethysmography (FPP) of the participants was simultaneously recorded. RESULTS: (1) Pulse waves synchronous with FPP were recorded from all healthy teeth, whereas no pulse signals were recognized in nonvital teeth. (2) The signal amplitude in the TLP was not significantly affected by the opaque dam application. (3) In the healthy teeth, there was a significantly negative correlation between the TLP pulse amplitude and the age of the subjects. CONCLUSIONS: TLP can detect pulpal blood flow in young permanent teeth. This technique is considered to be applicable in the assessment of pulp vitality.

Relationship between formation and eruption of permanent mandibular buccal dentition and vertical height of the mandibular body: longitudinal study of Japanese boys from 4 to 9 years of age.

AIM: To examine the relationship between the formation and eruption (vertical tooth movement in and through the alveolar bone) of the permanent mandibular buccal dentition and vertical height of the mandibular body. METHOD: Mandibular morphology and tooth formation and eruption were analyzed from cephalograms taken annually on each birthday month from 4 to 9 years of age. RESULTS: From 4 to 6 years of age, before active tooth eruption, there was a significant positive correlation between the vertical height of the mandibular body and the distance from the permanent mandibular buccal dentition to the occlusal plane. There was a significant positive correlation between the vertical height of the mandibular body at 6 years of age and the subsequent annual amount of tooth eruption in the mandibular buccal dentition. Simple linear regression equations were obtained to predict the amount of mandibular buccal tooth formation and eruption from the vertical height of the mandibular body at 6 years of age. CONCLUSION: The larger the mandibular vertical height, the larger the distance from the buccal dentition to the occlusal plane before active eruption, and the larger the amount of tooth eruption during the active eruption period. The vertical mandibular morphology is useful to predict the formation and eruption of the mandibular buccal dentition.

[Application of a CO2 laser for oral soft tissue surgery in children in Sri Lanka--introduction of a laser through activities of aid to a developing country].

The objective of this study was to clarify the effect of CO2 laser irradiation on oral tissue problems in children in Sri Lanka, through the activities of aid to a developing country by the Japan International Cooperation Agency. This study took about six months, during two times periods: from November 2000 to February 2001, and from July 2001 to October 2001, in the paedodontic clinic of the Faculty of Dental Science, University of Peradeniya, in Sri Lanka. A CO2 laser was used on 48 subjects (51 cases), aged between 1 and 15 years, having main indications for labial frenectomy, frenectomy in ankyloglossia, and excision of mucocele. The results indicated that the CO2 laser had the following advantages. 1. Soft tissue cutting was efficient, with no bleeding, giving a clear operative field during operation. 2. There was no need to use sutures. 3. The surgery itself was simple and less time-consuming. Hence, there was no need for general anesthesia for such cases as tongue tie operation in small children. 4. There was no postsurgical infection. As a result, there was no need for analgesics or antibiotics, as post-surgical pain and infection were prevented. 5. Wound contraction and scarring were decreased or eliminated. Considering the above advantages, the use of a CO2 laser proved to be very safe and effective for soft tissue surgery, especially for children in developing countries such as Sri Lanka.

Characterization of pulp and follicle stem cells from impacted supernumerary maxillary incisors.

PURPOSE: The purpose of this study was to characterize dental pulp and dental follicle stem/progenitor cells (DPSCs and DFSCs) from the same impacted supernumerary maxillary incisors (ISMIs). METHODS: DPSCs and DFSCs were obtained from ISMIs of healthy children (six to 12 years old) by the outgrowth culture method and were compared for proliferation, colony-forming capacity, gene expression, cell surface markers, and trilineage differentiation capacity. RESULTS: The volume of follicle tissue obtained was much larger than that for pulp tissue. DPSCs and DFSCs showed fibroblast-like morphology, expressed the stem cell-associated genes, OCT4 and NANOG, and were positive for CD146, CD90, and CD105 but negative for CD45. The cell proliferation rate and colony-forming capacity of DFSCs were significantly higher than those for DPSCs. Under inductive culture conditions, DPSCs and DFSCs differentiated into osteogenic, adipogenic, and chondrogenic lineage cells. CONCLUSIONS: These results demonstrated that dental pulp and dental follicle stem/progenitor cells have similar mesenchymal stem cell characteristics, but DFSCs are easily accessible for cell culture and have a higher proliferation capacity than DPSCs. It also appears that dental follicle stem/progenitor cells might have some advantages as a stem cell resource for regenerative medicine.

Detection of occlusal caries in primary teeth using swept source optical coherence tomography.

This study aimed to investigate swept source optical coherence tomography (SS-OCT) as a detecting tool for occlusal caries in primary teeth. At the in vitro part of the study, 38 investigation sites of occlusal fissures (noncavitated and cavitated) were selected from 26 extracted primary teeth and inspected visually using conventional dental equipment by six examiners without any magnification. SS-OCT cross-sectional images at 1330-nm center wavelength were acquired on the same locations. The teeth were then sectioned at the investigation site and directly viewed under a confocal laser scanning microscope (CLSM) by two experienced examiners. The presence and extent of caries were scored in each observation. The results obtained from SS-OCT and conventional visual inspections were compared with those of CLSM. Consequently, SS-OCT could successfully detect both cavitated and noncavitated lesions. The magnitude of sensitivity for SS-OCT was higher than those for visual inspection (sensitivity of visual inspection and SS-OCT, 0.70 versus 0.93 for enamel demineralization, 0.49 versus 0.89 for enamel cavitated caries, and 0.36 versus 0.75 for dentin caries). Additionally, occlusal caries of a few clinical cases were observed using SS-OCT in vivo. The results indicate that SS-OCT has a great detecting potential for occlusal caries in primary teeth.

Efficacy of platelet-rich plasma gel and hyaluronan hydrogel as carriers of electrically polarized hydroxyapatite microgranules for accelerating bone formation.

The technology for electrical polarization and characterization of hydroxyapatite (HA) microgranules has been developed. This study aimed to examine and compare the efficacy of composites comprising electrically polarized HA (pHA) microgranules and platelet-rich plasma (PRP) or hyaluronan (HAN) in osteoconductivity. Composites of HA microgranules with or without electrical polarization and either PRP or HAN (PRP+pHA, PRP+HA, HAN+pHA, and HAN+HA, respectively), as well as pHA and HA microgranules were implanted randomly into holes created in the medial femoral condyle or tibial tuberosity of rabbits. As a control, PRP or HAN gel alone was implanted, or the bone holes were left empty. Each group included six animals. After 6 weeks, histological examination was performed, and osteoclastic and osteoblastic cell activities were assessed by cell counting. Although PRP alone could not induce bone formation, PRP+pHA and PRP+HA composites, especially the former, activated osteogenic cells and enhanced bone formation. This effect was not prominent in the HAN+pHA and HAN+HA composites. PRP+HA composites formed a gel in which the ceramic particles were dispersed and entrapped in the fibrin network of PRP. It is assumed that these particles provide scaffolds for osteogenic cells, and when electrically polarized, can activate the cells in co-operation with the positive effects of the PRP, resulting in enhanced bone formation. Conversely, it is conceivable that this composite gel cannot act as an accelerator for woven bone formation, because HAN with low viscoelasticity is absorbed rapidly after implantation, the hydrated network containing HA microgranules is destroyed, and the HA microgranules effuse with HAN from the bone hole.

Self-sealing ability of OCP-mediated cement as a deciduous root canal filling materia.

The densification process and canal sealing ability of octacalcium phosphate (OCP)-mediated cement were investigated for developing biocompatible and biodegradable root canal filling material for deciduous root. The results of the characterization revealed that the starting paste, which consisted of monocalcium phosphate monohydrate, calcium carbonate, and α-tricalcium phosphate, gradually transformed into carbonate apatite for 6 weeks of immersion in medium with 30% fetal bovine serum (MEM30). The canal sealing ability was estimated by dye penetration test. Three kinds of conditions were chosen for the test: one was the cement just after filling the single-rooted extracted human roots; the others were the cement aged in MEM30 for 1 and 6 weeks after filling, respectively. All roots were then immersed in India ink for 3 days. The penetration depth of OCP-mediated cement decreased significantly with time. This demonstrates that OCP-mediated cement has self-sealing ability.

Bovine dentine organic matrix down-regulates osteoclast activity.

Physiological root resorption is a phenomenon that normally takes place in deciduous teeth; root resorption of permanent teeth occurs only under pathological conditions. The molecular mechanisms underlying these processes are still unclear. Our previous study showed that osteoclasts cultured on deciduous dentine exhibited a higher degree of resorption and higher levels of cathepsin K and MMP-9 mRNA than osteoclasts cultured on permanent dentine. These results could be because of different susceptibilities to acid and the different organic matrices between deciduous and permanent dentine. Thus, the purpose of this study was to investigate the effect of dentine extracts from bovine deciduous and permanent dentine on osteoclast activity. Osteoclasts, obtained from mouse bone marrow cells co-cultured with an osteoblast-rich fraction in the presence of 1,25-(OH)(2)-vitamin D3 and PGE2, were incubated with or without 0.6 M HCl extracts from bovine deciduous or permanent dentine for 48 h. TRAP positive cell number, TRAP activity, the areas of resorption pits, and mRNA levels of TRAP, v-ATPase, calcitonin receptor, cathepsin K, and MMP-9 were examined. The results illustrated that TRAP activity, the resorbed area, and the mRNA levels of osteoclast marker genes seemed to be suppressed by both deciduous and permanent dentine extracts. These findings indicate that some factors that suppress osteoclast activity are contained in both deciduous and permanent dentine extracts. Although there was no significant difference in osteoclast activity between deciduous and permanent dentine extracts, osteoclasts incubated with permanent dentine extracts tend to exhibit less resorption activity than those incubated with deciduous dentine extracts. However, we could not clearly explain the causes of this.