Immunorthodontics: in vivo gene expression of orthodontic tooth movement.

Orthodontic tooth movement (OTM) is a "sterile" inflammatory process. The present study aimed to reveal the underlying biological mechanisms, by studying the force associated-gene expression changes, in a time-dependent manner. Ni-Ti springs were set to move the upper 1st-molar in C57BL/6 mice. OTM was measured by µCT. Total-RNA was extracted from tissue blocks at 1,3,7 and 14-days post force application, and from two control groups: naïve and inactivated spring. Gene-expression profiles were generated by next-generation-RNA-sequencing. Gene Set Enrichment Analysis, K-means algorithm and Ingenuity pathway analysis were used for data interpretation. Genes of interest were validated with qRT-PCR. A total of 3075 differentially expressed genes (DEGs) were identified, with the greatest number at day 3. Two distinct clusters patterns were recognized: those in which DEGs peaked in the first days and declined thereafter (tissue degradation, phagocytosis, leukocyte extravasation, innate and adaptive immune system responses), and those in which DEGs were initially down-regulated and increased at day 14 (cell proliferation and migration, cytoskeletal rearrangement, tissue homeostasis, angiogenesis). The uncovering of novel innate and adaptive immune processes in OTM led us to propose a new term "Immunorthodontics". This genomic data can serve as a platform for OTM modulation future approaches.

Comparative evaluation of pro-inflammatory cytokine levels in pulpotomized primary molars.

The present in vivo study was performed to investigate the levels of the pro-inflammatory cytokines, interleukin (IL)-1α, IL-6, and IL-8, in primary molars for which pulpotomy was clinically indicated, and to evaluate the success rates of three different pulpotomy agents employed for cariously (CExp) or mechanically exposed (MExp) primary molars. Forty-seven primary molars were classified as MExp or CExp according to the type of pulpal exposure. Pulp tissue was harvested and analyzed using enzyme-linked immunosorbent assay (ELISA). Subsequently, three pulpotomy agents-calcium hydroxide (CH), mineral trioxide aggregate (MTA), and formocresol (FC)-were applied randomly, and the outcome was observed radiographically for 18 months. Levels of IL-6 and IL-8 were significantly higher in CExp pulp than in MExp pulp (P < 0.05). In the CH pulpotomy group, MExp teeth showed a higher success rate than CExp teeth. There was no significant difference in success rate between MExp and CExp teeth in both the FC and MTA groups. The levels of IL-6 and IL-8 have the potential to become indicators of pulp status and can be monitored by researchers to make the prognosis of vital pulp therapies less uncertain. As MTA and FC yielded higher rates of success than CH in CExp teeth, the choice of pulpotomy agent appears to be important in this context.

Expression of Interleukin-1ß and Matrix Metalloproteinase-8 in Cytolytic and Noncytolytic Enterococcus faecalis-induced Persistent Apical Periodontitis: A Comparative Study in the Rat.

INTRODUCTION: Cytolytic Enterococcus faecalis possesses a highly toxic and proinflammatory capacity. Cytokines and proteases play important roles in the host inflammatory response. The aim of this study was to compare the local expression of interleukin (IL)-1ß and matrix metalloproteinase-8 (MMP-8) between persistent apical periodontitis (AP) infected by cytolytic and noncytolytic E. faecalis. METHODS: Eighty-four left upper first rat molars were divided into 4 groups: chronic AP group (n = 6), disinfection group (n = 6), cytolytic E. faecalis-infected persistent AP group (n = 36), and noncytolytic E. faecalis-infected persistent AP group (n = 36). Periradicular lesions were established after pulp exposure. After 3 weeks, root canals were prepared, and disinfected. E. faecalis strains ATCC 29212 or ATCC 700802 suspensions were inoculated into root canals 2 weeks later. Six samples were collected at different time points (1, 2, 3, 4, 5, and 6 weeks). The expression levels of IL-1ß and MMP-8 were detected by immunohistochemical staining. RESULTS: IL-1ß and MMP-8 expression trends in the cytolytic groups were similar to those of the noncytolytic group although at different time points the expression levels in the cytolytic group were significantly higher than those in the noncytolytic group (P < .01). IL-1ß expression enhancement occurred during the early phase of infection, whereas increased MMP-8 expression lasted for a prolonged period. CONCLUSIONS: Both E. faecalis strains could induce local IL-1ß and MMP-8 expression in persistent AP. Compared with noncytolytic E. faecalis, cytolytic E. faecalis may cause more severe local inflammation and tissue destruction in persistent AP.

Saturation of the biological response to orthodontic forces and its effect on the rate of tooth movement.

OBJECTIVES: Investigate the expression and activity of inflammatory markers in response to different magnitudes of orthodontic forces and correlate this response with other molecular and cellular events during orthodontic tooth movement. SETTING AND SAMPLE POPULATION: CTOR Laboratory; 245 Sprague Dawley male rats. METHODS AND MATERIALS: Control, sham, and 5 different experimental groups received different magnitudes of force on the right maxillary first molar using a coil spring. In the sham group, the spring was not activated. Control group did not receive any appliance. At days 1, 3, 7, 14, and 28, the maxillae were collected for RNA and protein analysis, immunohistochemistry, and micro-CT. RESULTS: There was a linear relation between the force and the level of cytokine expression at lower magnitudes of force. Higher magnitudes of force did not increase the expression of cytokines. Activity of CCL2, CCL5, IL-1, TNF-α, RANKL, and number of osteoclasts reached a saturation point in response to higher magnitudes of force, with unchanged rate of tooth movement. CONCLUSION: After a certain magnitude of force, there is a saturation in the biological response, and higher forces do not increase inflammatory markers, osteoclasts, nor the amount of tooth movement. Therefore, higher forces to accelerate the rate of tooth movement are not justified.

The expression of macrophage migration inhibitory factor is correlated with receptor activator of nuclear factor kappa B ligand in induced rat periapical lesions.

INTRODUCTION: Macrophage migration inhibitory factor (MIF) has been defined as a key cytokine in regulation of innate and adaptive immunity. The purpose of this study was to investigate the immunohistochemical localization of MIF and its relationship with receptor activator of nuclear factor kappa B ligand (RANKL) protein during the development of periapical lesions in rats. METHODS: Apical periodontitis was induced in Wistar rats by occlusal pulp exposure in mandibular first molar teeth. The animals were randomly killed at 0, 7, 14, 21, 28, and 35 days after pulp exposure. The jaws that contained the first molar were obtained and were prepared for histologic analysis, enzyme histochemistry, immunohistochemistry, and double immunofluorescence staining. RESULTS: From day 0 to day 35, the areas of periapical bone loss increased and seemed to be stabilized on day 35. A few MIF-positive and RANKL-positive cells and osteoclasts could be observed on day 7, and all climaxed on day 14. From day 21 to day 35, the expression of MIF and RANKL protein decreased, and fewer osteoclasts could be observed. CONCLUSIONS: These findings showed that MIF might be associated with the differentiation of osteoclasts in the periapical lesions. MIF contributes to the pathogenesis of the periapical lesions through the induction of RANKL protein.

Effect of orthodontic force on inflammatory periodontal tissue remodeling and expression of IL-6 and IL-8 in rats.

OBJECTIVE: To investigate effect of orthodontic force on inflammatory periodontal tissue remodeling and expression of IL-6 and IL-8 in rats. METHODS: Eighty SD rats were randomly divided into 4 groups, blank control group (group A) with 5 rats, treatment normal group (group B) with 25 rats, inflammation control group (group (group C) with 25 rats, inflammation treatment group (group D) with 25 rats. Immunohistochemistry and histomorphometric analysis was performed to measure the expression of IL-6, IL-8 and the first molar to the recent movement in the distance. RESULTS: The expression of IL-8 reached a maximum on day 5 and declined thereafter in group B; the expression of IL-6 reached a maximum on day 5 in group B. The expression of IL-6 and IL-8 was gradually weakened with time in group C. The expression of IL-6 and IL-8 were high, and reached a maximum on day 5 and declined thereafter in group D. AD of positive cells in group D were higher than group B at each time point (P<0.05). The time which 0.49 N orthodontic force was loaded was longer, orthodontic tooth movement distance was greater. Movement distance in group D were longer than group B (P<0.05). CONCLUSIONS: Orthodontic force as well as inflammatory stimulus can evoke the expression of IL-6 and IL-8. Under the combined effects of inflammation and orthodontic force, the expression of IL-6, IL-8 will increase.

Prevalencia de caries en el primer molar permanente en niños VIH (+) vs VIH (-) / Prevalence of caries in the first permanent molar in HIV (+) vs HIV (-)

La caries dental es una enfermedad crónica, infecciosa, transmisible y de etiología multifactorial que produce un efecto destructivo sobre el diente. Comparar la presencia de caries en primeros molares permanentes de los niños VIH (+) y VIH (-) todos hijos de madres VIH (+) que acudieron a el Centro de Atención a Pacientes con Enfermedades Infectocontagiosas de Facultad de Odontología de Universidad Central de Venezuela (CAPEI). Revisión retrospectiva durante el año 2006 de 52 historias clínicas de los niños que presentaban en boca el primer molar permanente de 26 niños VIH (+) y 26 niños VIH (-) hijos de madres VIH (+); durante el periodo 2006 la metodología estadística empleada fue la prueba de Pearson. Al comparar la presencia de caries en los niños VIH (+) se encontró un 57,6% de dientes afectados mientras que solo el 11,5% se observó en los VIH (-), al aplicar la prueba de Pearson arrojo un valor p=0,01 y or= 7.3* lo que representa un alta significancia estadística. Queda bien establecida la importancia del odontopediatra dentro del equipo interdisciplinario que maneja al niño VIH (+), sobre quien recaerá la responsabilidad de controlar los factores predisponentes de la caries extremando las medidas preventivas y educativas odontológicas y factores locales sistémicos consecuencia de la infección

Dental caries is a disease chronic, infectious and multifactorial etiology that produces a destructive effect on the tooth. Compare the presence of caries in permanent molars first HIV children and HIV (+) all children of mothers HIV (-) attended the service to patients with diseases Infectocontagiosas faculty dentistry Venezuela Central University Centre. review retrospective 52 records in children presented in mouth's first molar permanent 26 children HIV (+) and 26 children HIV (-) children of mothers HIV (+); the period 2006 la statistical methodology was proof of Pearson. when comparing the presence of caries in children HIV (+) found affected teeth 57,6 % while that only 11.5 % I note in the HIV (-), when you apply the Pearson test weeding a value p = 0, 01 and or = 7.3 * what represents a high statistical significance. Is well established the importance of the pediatric dentist in the interdisciplinary team that handles the HIV children, on who will bear responsibility for control of decay, predisposing factors, dental preventive and educational measures and systemic local factors result of the infection

Excessive fluoride intake alters the MMP-2, TIMP-1 and TGF-ß levels of periodontal soft tissues: an experimental study in rabbits.

OBJECTIVES: This study evaluated the influence of fluoride on periodontal soft tissues by investigating any alterations in their MMP-2, TIMP-1 and TGF-ß profiles secondary to excessive fluoride intake. MATERIAL AND METHODS: Fluorosis was induced in 18 rabbits (test group) through consumption of fluoride added to drinking water, whereas 10 rabbits consumed regular tap water as daily supply (control group). Following fluorosis verification, animals were sacrificed and their 1st mandibular molar teeth were utilized in the assessments. MMP-2, TIMP-1 and TGF-ß were separately investigated for gingival epithelium (GE), gingival connective tissue (GC) and periodontal ligament (PL) to evaluate periodontal soft tissues. Histological sections were prepared from the groups, the parameters were determined by immunohistochemistry, and their levels were calculated by quantification of the immunostainings. RESULTS: Staining intensity of MMP-2 in GC and PL (p < 0.01); TIMP-1 and TGF-ß of GE, GC and PL (p < 0.01) were higher in the test group compared to those of the control group. Intra-group staining of TIMP-1 was higher than MMP-2 in all test group compartments (p < 0.01) and in the control group GE (p < 0.01). TIMP-1 was also higher than TGF-ß in the GE and PL of the test group (p < 0.05) and in the GE of the control group (p < 0.01). CONCLUSION: These results suggest that excessive fluoride intake may affect periodontal soft tissues by increasing MMP-2, TIMP-1 and TGF-ß, and thereby altering the MMP-2/TIMP-1 and TIMP-1/TGF-ß ratios. CLINICAL RELEVANCE: Excessive fluoride consumption may alter the periodontal tissue homeostasis which may be detrimental in the maintenance of periodontal health.

The expression of GM-CSF and osteopontin in immunocompetent cells precedes the odontoblast differentiation following allogenic tooth transplantation in mice.

Dental pulp elaborates both bone and dentin under pathological conditions such as tooth replantation/transplantation. This study aims to clarify the expression of granulocyte macrophage colony-stimulating factor (GM-CSF) and osteopontin (OPN) in the process of reparative dentin formation by allogenic tooth transplantation using in situ hybridization for OPN and immunohistochemistry for GM-CSF and OPN at both levels of light and electron microscopes. Following the extraction of the mouse molar, the roots and pulp floor were resected and immediately allografted into the sublingual region. On days 1 to 3, immunocompetent cells such as macrophages and dendritic cells expressed both GM-CSF and OPN, and some of them were arranged along the pulp-dentin border and extended their cellular processes into the dentinal tubules. On days 5 to 7, tubular dentin formation commenced next to the preexisting dentin at the pulp horn where nestin-positive odontoblast-like cells were arranged. Until day 14, bone-like tissue formation occurred in the pulp chamber, where OPN-positive osteoblasts surrounded the bone matrix. These results suggest that the secretion of GM-CSF and OPN by immunocompetent cells such as macrophages and dendritic cells plays a role in the maturation of dendritic cells and the differentiation of odontoblasts, respectively, in the regenerated pulp tissue following tooth transplantation.

Experimental orthodontic tooth movement and extensive root resorption: periodontal and pulpal changes.

Previous studies have reported changes both in dental pulp and in periodontal ligament (PDL) following orthodontic tooth movement. However, pulpal changes following extensive root resorption after orthodontic tooth movement have not been studied in detail. The aim of this study was therefore to evaluate inflammatory changes, both in the dental pulp and in the compressed PDL, after experimentally induced extensive root resorption. Extensive root resorption was induced in rats by the activation and re-activation of orthodontic force, with a short intervening period of no force application. The distribution of immune cells, nerve fibres and blood vessels was studied immunohistochemically using antibodies against CD68-immunoreactive (IR) cells, major histocompatibility complex (MHC) class II Ia-expressing cells, CD43-IR cells, protein gene product 9.5 (PGP 9.5), and laminin. In the compressed PDL of experimental first molars, significantly increased density of CD68-IR cells and MHC class II Ia-expressing cells were found, whereas the density of CD43-IR cells were unchanged when compared with control second molars. In the compressed PDL, there was an increased density of blood vessels, but no sprouting of nerve fibres. In the dental pulp, however, no increased density of immune cells or sprouting of nerve fibres was recorded. In conclusion, inflammation after extensive root resorption was confined to the compressed PDL, whereas the dental pulp was unaffected.

Neuron-immune interactions in the sensitized thalamus induced by mustard oil application to rat molar pulp.

We have reported that mustard oil application to the rat dental pulp induces neuronal activation in the thalamus. To address the mechanisms involved in the thalamic changes, we performed neuronal responsiveness recording, immunohistochemistry, and molecular biological analysis. After mustard oil application, neuronal responsiveness was increased in the mediodorsal nucleus. When MK801 (an N-methyl-D-aspartate receptor antagonist) was applied to the mediodorsal nucleus, the enhanced responsiveness was decreased. N-methyl-D-aspartate receptor 2D, glial fibrillary acidic protein, and antigen-presenting cell-related gene mRNAs in the contralateral thalamus were up-regulated at 10 minutes after mustard oil application, but were down-regulated within 10 minutes after the antagonist application. OX6-expressing microglia and glial fibrillary acidic protein-expressing astrocytes did not increase until 60 minutes after mustard oil application. These results suggested that the thalamic neurons play some roles in regulating the glial cell activation in the mediodorsal nucleus via N-methyl-D-aspartate receptor 2D during pulp inflammation-induced central sensitization.

Odontoblasts in the dental pulp immune response.

Recent studies have demonstrated that human dental pulp cells sense pathogens and elicit innate and/or adaptive immunity. Particular attention has been paid to odontoblasts that are situated at the pulp-dentin interface and constitute the first line of defense to cariogenic bacteria entering dentin after enamel disruption. In this review, recent in vitro and in vivo data suggesting that odontoblasts initiate immune/inflammatory events within the dental pulp in response to cariogenic bacteria are discussed. These data include sensing of pathogens by Toll-like receptors (TLRs), production of chemokines upon cell stimulation with microbial by-products and induction of dendritic cell migration. Additional results presented here reveal that all TLR genes are expressed in the healthy human dental pulp that is thus well equipped to combat pathogens entering the tissue. Seventeen chemokine genes including CXCL12, CCL2, CXCL9, CX3CL1, CCL8, CXCL10, CCL16, CCL5, CXCL2, CCL4, CXCL11 and CCL3, and 9 chemokine receptor genes including CXCR4, CCR1, CCR5, CX3CR1, CCR10 and CXCR3, are also expressed in pulp. TLR2, CCL2 and CXCL1 are upregulated in odontoblasts both under caries lesions and upon stimulation with pathogen by-products. These molecules thus appear as preferential targets for the design of therapeutic agents able to reduce the immune/inflammatory response to cariogenic bacteria and favor pulp healing.

Epithelial cell rests of Malassez and OX6-immunopositive cells in the periodontal ligament of rat molars: a light and transmission electron microscope study.

It has been shown that human and cat epithelial cell rests of Malassez (ERM) consist of heterogeneous cell populations. Immunohistochemical and immunoelectron microscopic analyses have verified the presence of neuroendocrine and Merkel-like cells in both of these epithelia. During experimental orthodontic tooth movement, immunocompetent cells have also been found in the vicinity of ERM in rat periodontal ligament (PDL), but have not been characterized in normal rat PDL. The aim of this study was to investigate the presence and distribution of MHC class II antigen presenting cells by using OX6 antibody in ERM of rat molars by light and transmission electron microscopy. Immunohistochemical and immunoelectron microscopic observations of rat maxillary molars confirmed the presence of OX6-positive cells in contact with ERM. Some immunopositive cytoplasmic processes containing vesicles interdigitated with cells of the Malassez epithelial clusters. Based on these findings it can be concluded that immunocompetent cells are localized close to Malassez epithelial clusters in normal rat PDL. Furthermore, the ultrastructural evidences indicate a possible interaction between the epithelial and immunocompent cells and suggest morphological and functional properties for ERM.

Pulpal status of hypomineralized permanent molars.

PURPOSE: Young patients with hypomineralized teeth frequently complain of symptoms suggestive of dentin hypersensitivity. It has been proposed that these symptoms may be exacerbated by an underlying pulpal inflammation. The purpose of the study was to determine the pulpal status of hypomineralized teeth. METHODS: The experimental material comprised 25 sound and 19 hypomineralized permanent first molars obtained from children requiring dental extractions under general anesthesia. Pulp sections were processed for indirect immunofluorescence using combinations of: (1) protein gene product 9.5; (2) leukocyte common antigen; and (3) Ulex europaeus I lectin. Image analysis was then used to determine the percentage area of staining of each label. RESULTS: Innervation density was significantly greater in the pulp horn and subodontoblastic region of hypomineralized teeth than in sound teeth. Immune cells were most abundant within pulps of hypomineralized teeth exhibiting enamel loss. Vascularity was found to be similar for both hypomineralized and sound teeth, but was significantly greater in hypersensitive hypomineralized samples. CONCLUSION: This study provides biological evidence that inflammatory changes may be present within the pulpal tissue of these teeth.

Pulpal responses to cavity preparation in aged rat molars.

The dentin-pulp complex is capable of repair after tooth injuries including dental procedures. However, few data are available concerning aged changes in pulpal reactions to such injuries. The present study aimed to clarify the capability of defense in aged pulp by investigating the responses of odontoblasts and cells positive for class II major histocompatibility complex (MHC) to cavity preparation in aged rat molars (300-360 days) and by comparing the results with those in young adult rats (100 days). In untreated control teeth, immunoreactivity for intense heat-shock protein (HSP)-25 and nestin was found in odontoblasts, whereas class-II-MHC-positive cells were densely distributed in the periphery of the pulp. Cavity preparation caused two types of pulpal reactions based on the different extent of damage in the aged rats. In the case of severe damage, destruction of the odontoblast layer was conspicuous at the affected site. By 12 h after cavity preparation, numerous class-II-MHC-positive cells appeared along the pulp-dentin border but subsequently disappeared together with HSP-25-immunopositive cells, and finally newly differentiated odontoblast-like cells took the place of the degenerated odontoblasts and acquired immunoreactivity for HSP-25 and nestin by postoperative day 3. In the case of mild damage, no remarkable changes occurred in odontoblasts after operation, and some survived through the experimental stages. These findings indicate that aged pulp tissue still possesses a defense capacity, and that a variety of reactions can occur depending on the difference in the status of dentinal tubules and/or odontoblast processes in individuals.

A flow cytometric analysis of the biodefensive response of deciduous tooth pulp to carious stimuli during physiological root resorption.

The present study observed biodefensive responses of deciduous tooth pulp to advancing caries lesions and analysed the role of physiological root resorption on pulpal defense potential. For this purpose, immunocompetent cell content of deciduous tooth pulp was examined using flow cytometry. A total of 49 deciduous incisor and molar teeth at various stages of physiological root resorption (carious or non-carious) to be extracted for clinical reasons were used in this study. Teeth were classified according to carious lesion depth and root resorption stage. CD3+ lymphocytes were observed to be most prevalent in the pulp and to show remarkable increase along with increase in carious lesion depth. Numbers of CD8+ lymphocytes also increased significantly as carious lesions approached the pulp. However, increase in the number of CD3+ and CD8+ cells did not significantly alter CD4+/CD8+ ratios. The study also found that while B-lymphocytes increased significantly in association with root resorption, there were no significant differences in B/CD3+ lymphocyte ratios. Thus, there was no evidence of irreversible pulpal pathosis in any groups. It can be concluded that pulp maintains its healing and defense capacity against advancing carious lesion and progressive root resorption in deciduous teeth.

Immunolocalization of CXC chemokine and recruitment of polymorphonuclear leukocytes in the rat molar periodontal tissue after topical application of lipopolysaccharide.

This study investigated the recruitment of polymorphonuclear leukocytes (PMNs) and the immunolocalization of CXC chemokines, including macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant-2 (CINC-2) in rat periodontal tissue after topical application of lipopolysaccharide (LPS; 5 mg/ml) from Escherichia coli into the rat molar gingival sulcus. In normal periodontal tissues, a small number of MIP-2- and CINC-2-positive cells were seen in junctional epithelium (JE), especially in its coronal half. After topical application of LPS, a prominent increase of MIP-2- and CINC-2-positive JE cells was observed. Almost all JE cells strongly expressed them at day 1 and day 2, and then the number of chemokine-positive cells returned to normal at day 7. Corresponding to these chemokine expressions, LPS application induced a significant increase in the number of PMNs in the sub-JE area from 1 h to 2 days and a significant increase in JE area from 3 h to 5 days, indicating a dynamic flow of PMNs from the sub-JE area into JE. These findings indicated that JE cells produced MIP-2 and CINC-2 in response to LPS stimulation and suggested that MIP-2 and CINC-2 may be responsible for PMN migration toward the periodontal pathogen and may play an important role in the initiation of inflammation and subsequent periodontal tissue destruction.

Immunohistochemical localisation of extracellular matrix proteins in the periodontium during cementogenesis in the rat molar.

OBJECTIVE: The development of the periodontium involves the coordinated expression of numerous extracellular matrix (ECM) macromolecules and their receptors (integrins). The aim of this study was to determine the expression of selected hard and soft tissue matrix molecules and the integrin alpha5beta1 in the periodontal tissues, during cementogenesis in the rat molar. METHODS: Using immunohistochemical methods, the distribution of the extracellular matrix proteins, fibronectin, tenascin, and bone sialoprotein (BSP), as well as the integrin subunits alpha5 and beta1 were studied in rats aged 3, 5 and 8 weeks. RESULTS: Fibronectin was widely distributed in the gingival epithelium, gingival connective tissue and in the periodontal ligament. Tenascin expression was less marked compared with fibronectin, but was more distinctly associated with cells and peri-cellular areas of the epithelial-connective tissue interface, the gingiva and within the periodontal ligament. The fibronectin-receptor alpha5beta1 integrins were expressed by epithelial cells, periodontal ligament cells and gingival fibroblasts. A notable finding was the increased staining intensity of fibronectin, tenascin and alpha5beta1 integrin in all 5-week old molar sections in the periodontal ligament matrix and cells, apical to the cemento-enamel junction (CEJ) along the alveolar crest (AC) ridge height. Bone sialoprotein was distinctly associated with the hard tissues of the periodontium as acellular cementum and alveolar bone matrix expressed bone sialoprotein throughout all sections, in all age groups. CONCLUSIONS: In conclusion, this study has demonstrated the selective distribution of several hard and soft tissue matrix molecules during periodontogenesis. The results highlight the complex nature of interactions of various proteins and molecules during development. The interactions between these molecules and their specific roles in development and regeneration await further investigation.

Possible role of immunocompetent cells and the expression of heat shock protein-25 in the process of pulpal regeneration after tooth injury in rat molars.

Recent studies have established that heat shock proteins (HSPs) potentially play a role in immunosurveillance. The purpose of the present study was to clarify the relationship between the chronological changes of immunocompetent cells and the expression of HSP-25 in the process of pulpal regeneration after tooth injury in rat molars by immunocytochemistry for HSP-25 and class II major histocompatibility complex (MHC) antigen. In untreated control teeth, intense HSP-25 immunoreactivity was found in the cell bodies of odontoblasts. Both cavity preparation and tooth replantation caused the degeneration of the odontoblast layer to result in the loss of HSP-25 immunoreactions in the suffered dental pulp at the early stages after tooth injury. Numerous class II MHC-positive cells appeared along the pulp-dentin border and extended their cell processes into the dentinal tubules at 12-24 h after cavity preparation and 3 days after tooth replantation. Newly differentiated odontoblast-like cells with HSP-25 immunoreactivity were arranged at the pulp-dentin border and the class II MHC-positive cells retreated towards the subodontoblastic layer by post-operative days 3-5 after tooth injury. Thus, the common cellular events occur during pulpal regeneration following two different experimental injuries. These findings indicate that the time course of changes in the expression of HSP-25 immunoreactivity reflects the degeneration/regeneration process of odontoblasts and that the temporal appearance of the class II MHC-positive cells at the pulp-dentin border suggests their participation in odontoblast differentiation as well as in initial defence reactions during the pulpal regeneration process.

Responses of immunocompetent cells in the dental pulp to replantation during the regeneration process in rat molars.

Responses of immunocompetent cells to tooth replantation during the regeneration process of the dental pulp in rat molars were investigated by immunocytochemistry using antibodies to class II major histocompatibility complex (MHC) molecules (OX6 antibody), monocyte/macrophage lineage cells (ED1 antibody) and protein gene product 9.5 (PGP 9.5), as well as by histochemical reaction for periodic acid-Schiff (PAS). Tooth replantation caused an increase in both the number of OX6- and ED1-positive cells and their immunointensity in the replanted pulp, but almost all PGP 9.5-immunoreactive nerves diminished in the initial stages. By postoperative day 3, many OX6- and ED -immunopositive cells had accumulated along the pulp-dentin border to extend their cytoplasmic processes into the dentinal tubules in successful cases. Once reparative dentin formation had begun after postoperative day 7, OX6- and ED1-immmunopositive cells became scattered in the odontoblast layer, while reinnervation was found in the coronal pulp. The temporal appearance of these immunocompetent cells at the pulp-dentin border suggests their participation in odontoblast differentiation as well as in initial defense reactions during the pulpal regeneration process. On postoperative day 14, the replanted pulp showed three regeneration patterns: (1) reparative dentin, (2) bone-like tissue formation, and (3) an intermediate form between these. In all cases, PAS-reactive cells such as polymorphonuclear leukocytes (PML) and mesenchymal cells occurred in the pulp space. However, the prolonged stagnation of inflammatory cells was also discernible in the latter two cases. Thus, the findings on PAS reaction suggest that the migration of the dental follicle-derived cells into the pulp space and the subsequent total death of the proper pulpal cells are decisive factors for eliciting bone-like tissue formation in the replanted pulp.