Dentin phosphoprotein inhibits lipopolysaccharide-induced macrophage activation independent of its serine/aspartic acid-rich repeats.

OBJECTIVE: The objective of this study was to investigate the effects of dentin phosphoprotein (DPP) on lipopolysaccharide-induced inflammatory responses of macrophages in vitro. DESIGN: Wildtype and mutant recombinant dentin phosphoprotein (rDPP) proteins were generated using a mammalian expression system. Macrophages, phorbol 12-myristate 13-acetate-differentiated THP-1 cells, were stimulated with lipopolysaccharide in the absence or presence of rDPP proteins. After the 24-hr incubation, the inflammatory gene expression levels were examined by quantitative reverse-transcription polymerase chain reaction and the amount of secreted TNF-α protein was evaluated by enzyme-linked immunosorbent assay. Furthermore, the subcellular localization of exogenously added rDPP was examined by immunocytochemistry, and the direct binding of rDPP to lipopolysaccharide was quantified by solid-phase binding assay. RESULTS: rDPP dose-dependently reduced the expression of lipopolysaccharide-induced inflammatory genes, such as TNFα, IL-1ß, and IL-8, and TNF-α protein secretion from the macrophages. Furthermore, mutant rDPP having a shortened serine/aspartic acid-rich repeats (SDrr) was also able to inhibit lipopolysaccharide-induced inflammatory responses of macrophages. rDPP was localized adjacent to the cellular membrane rather than in the cytoplasm, and rDPP was able to bind to lipopolysaccharide. These results suggested that rDPP inhibited lipopolysaccharide-induced inflammatory responses by binding to lipopolysaccharide. CONCLUSIONS: In addition to the well-known functions of DPP for dentin mineralization that depend on the SDrr, we demonstrated that DPP possesses anti-inflammatory effects on lipopolysaccharide-stimulated macrophages that are independent of the SDrr.

Comprehensive Characterization of 2 Immature Teeth Treated with Regenerative Endodontic Procedures.

INTRODUCTION: Regeneration of the pulp-dentin complex is the penultimate goal of regenerative endodontic procedures (REPs). Histological outcomes have demonstrated reparative tissue formation in human teeth extracted post-REPs. However, lack of accurate characterization has precluded identification of the true nature of tissues formed post-REP. METHODS: Here, we present 2 case reports of tooth #29 and #9 treated with REPs and demonstrate their clinical, radiographic, and histological outcomes. RESULTS: Clinical outcomes revealed healing of apical periodontitis in both teeth and re-establishment of vitality responses in tooth #29. Moreover, radiographic assessments using 2D and 3D-volumetric analyses demonstrate considerable increase in root development for both teeth. Further, histological outcomes evaluated using Hematoxylin and Eosin and immunohistochemical staining demonstrates presence of vascular and lymphatic structures as well as immune cell markers indicative of regeneration of an immunocompetent pulp. Lastly, examination of hard tissue deposition shows dentin-like tissue in parts of tooth #29 demonstrating for the first time, regeneration of a pulp-dentin complex post-REP. CONCLUSIONS: Collectively, this is the first study demonstrating recapitulation of several tissues commonly found as part of a pulp-dentin complex in teeth treated with REPs.

Circulating dentinal antigen-antibody immune complexes during orthodontic tooth movement in rats.

BACKGROUND: The immunogenic potential of dentin has been reported through dentin-reactive autoantibodies detection in human and animal model. This study aimed to investigate the formation and diagnostic value of immune complexes formation after autoantibodies production, and soluble dentin antigens levels associated to root resorption, in the course of orthodontic tooth movement, in rat experimental model. METHODS: Forty Wistar rats (n = 8 for each group) were submitted to orthodontic tooth movement, in which the maxillary right first molar was mesially moved by applying of 55 g of force for 3, 7, 14, or 21 days. Untreated group was used as control. Circulating autoantibodies to rat dentinal extract, immune complexes, and soluble dentinal antigen levels were determined by immunoenzyme assays. Additionally, dentinal antigens were analyzed by immunoblot. RESULTS: Higher serum dentin-reactive IgG and immune complex levels were detected in the 14- and 21-day groups (p < 0.05 and p < 0.001 respectively) but not in circulating dentinal antigen levels (p > 0.05), as compared to the control group. Reactivity was found to dentinal components with molecular mass (MM) ~120 and ~150 kDa, by immunoblot. CONCLUSION: This work represents the first evidence of immune complexes formation and circulating soluble dentin antigens associated to root resorption in orthodontic tooth movement. Immune complexes formation could be used to early diagnosis of external root resorption.

Immunolocalization and distribution of proteoglycans in carious dentine.

BACKGROUND: Collagen type I, proteoglycans (PG) and non-collagenous proteins represent important building blocks of the dentine matrix. While different PGs have been identified in dentine, changes in the distribution of these macromolecules with the progression of caries have been poorly characterized. The aim of this study was to compare the immunolocalization of three small collagen-binding PGs (biglycan, fibromodulin and lumican) as well as collagen (types I and VI) in healthy versus carious dentine. METHODS: Longitudinal demineralized sections of extracted teeth were stained with antibodies recognizing specific PG core proteins and collagens, as well as glycosaminoglycans (GAGs) with toluidine blue. RESULTS: In healthy dentine, PGs appeared to be more abundant near the tubule walls and directly under the cusps. Conversely, in carious dentine, specific locations appeared to be more prone to PG degradation than others. These degradation patterns were well correlated with the progression of caries into the tissue, and also appeared to trigger interesting morphological changes in the tissue structure, such as the deformation of dentine tubules near highly infected areas and the lower concentration of PG in tertiary dentine. CONCLUSIONS: This study presents new insights into the involvement of PGs in the progression of caries.

Anti-dentine Salivary SIgA in young adults with a history of dental trauma in deciduous teeth.

Anti-dentin autoantibodies are associated with inflammatory root resorption in permanent teeth and are modulated by dental trauma and orthodontic force. However, it is not known whether deciduous tooth trauma can stimulate the development of a humoral immune response against dentin. The aim of this study was to evaluate the levels of salivary SIgA reactivity against human dentin extract in young adults with a history of trauma in the primary dentition. A sample of 78 patients, aged 18 to 25, who had completed an early childhood (0 to 5 years old) caries prevention program years earlier at the Universidade Estadual de Londrina Pediatric Clinic, underwent radiographic examination and salivary sampling. Anti-dentin SIgA levels were analyzed by immunoenzymatic assay and Western blotting. Although dental trauma to deciduous teeth had occurred in 34 (43.6%) of the patients, no differences in SIgA levels were detected between individuals who had experienced trauma and those who had not (p > 0.05). Multivariate regression analysis showed no association between dental trauma and SIgA levels (p > 0.05). Patients with a history of deciduous trauma presented low levels of anti-dentin antibodies, associated with orthodontic root resorption (p < 0.05). Western blot analysis showed that salivary antibodies recognized a single band of approximately 45 kDa in dentin extract. We concluded that salivary SIgA recognizes a specific component of the dentin matrix and that anti-dentin antibodies were not triggered by trauma to primary teeth. However, trauma to deciduous teeth may down-modulate SIgA in response to orthodontic root response.

Anti-dentine Salivary SIgA in young adults with a history of dental trauma in deciduous teeth

Anti-dentin autoantibodies are associated with inflammatory root resorption in permanent teeth and are modulated by dental trauma and orthodontic force. However, it is not known whether deciduous tooth trauma can stimulate the development of a humoral immune response against dentin. The aim of this study was to evaluate the levels of salivary SIgA reactivity against human dentin extract in young adults with a history of trauma in the primary dentition. A sample of 78 patients, aged 18 to 25, who had completed an early childhood (0 to 5 years old) caries prevention program years earlier at the Universidade Estadual de LondrinaPediatric Clinic, underwent radiographic examination and salivary sampling. Anti-dentin SIgA levels were analyzed by immunoenzymatic assay and Western blotting. Although dental trauma to deciduous teeth had occurred in 34 (43.6%) of the patients, no differences in SIgA levels were detected between individuals who had experienced trauma and those who had not (p > 0.05). Multivariate regression analysis showed no association between dental trauma and SIgA levels (p > 0.05). Patients with a history of deciduous trauma presented low levels of anti-dentin antibodies, associated with orthodontic root resorption (p < 0.05). Western blot analysis showed that salivary antibodies recognized a single band of approximately 45 kDa in dentin extract. We concluded that salivary SIgA recognizes a specific component of the dentin matrix and that anti-dentin antibodies were not triggered by trauma to primary teeth. However, trauma to deciduous teeth may down-modulate SIgA in response to orthodontic root response.

Inflammation and regeneration in the dentin-pulp complex: a double-edged sword.

Dental tissue infection and disease result in acute and chronic activation of the innate immune response, which is mediated by molecular and cellular signaling. Different cell types within the dentin-pulp complex are able to detect invading bacteria at all stages of the infection. Indeed, at relatively early disease stages, odontoblasts will respond to bacterial components, and as the disease progresses, core pulpal cells including fibroblasts, stems cells, endothelial cells, and immune cells will become involved. Pattern recognition receptors, such as Toll-like receptors expressed on these cell types, are responsible for detecting bacterial components, and their ligand binding leads to the activation of the nuclear factor-kappa B and p38 mitogen-activated protein (MAP) kinase intracellular signaling cascades. Subsequent nuclear translocation of the transcription factor subunits from these pathways will lead to proinflammatory mediator expression, including increases in cytokines and chemokines, which trigger host cellular defense mechanisms. The complex molecular signaling will result in the recruitment of immune system cells targeted at combating the invading microbes; however, the trafficking and antibacterial activity of these cells can lead to collateral tissue damage. Recent evidence suggests that if inflammation is resolved relatively low levels of proinflammatory mediators may promote tissue repair, whereas if chronic inflammation ensues repair mechanisms become inhibited. Thus, the effects of mediators are temporal context dependent. Although containment and removal of the infection are keys to enable dental tissue repair, it is feasible that the development of anti-inflammatory and immunomodulatory approaches, based on molecular, epigenetic, and photobiomodulatory technologies, may also be beneficial for future endodontic treatments.

Dentin as a suitable bone substitute comparable to ß-TCP--an experimental study in mice.

Microvascular supply is of fundamental importance to the survival and integration of grafting. Since the autogenous bone is still the gold standard for osseous augmentation, the aim of this study was to analyze the initial osseous, angiogenic and inflammatory response and subsequent osseointegration after implantation of dentin and beta-tricalcium phosphate (ß-TCP) scaffolds into the calvaria chamber of balb/c mice comparing with bone. The vascularisation of perforated implants of dentin (n=8), ß-TCP (n=8) and isogenic calvarial bone (n=8) displaying pores similar in size and structure was analyzed in vivo using intravital fluorescence microscopy. In additional animals (n=24) the osseointegration of dentin, ß-TCP and bone implants was assessed by fluorochrome sequential labelling of growing bone for up to 12 weeks. Animals without implants served as controls. Intravital fluorescence microscopy revealed that implantation of bone substitutes caused an only mild inflammatory response. Comparable to isogenic bone both dentin and ß-TCP scaffolds were found nearly completely vascularized by day 22 and osseointegrated within 12 weeks. In conclusion, dentin and ß-TCP scaffolds are similar to isogenic bone in terms of inflammatory and neovascularization response, highlighting their potential utility in regeneration of bone defects.

Anti-dentine antibodies with root resorption during orthodontic treatment.

The aim of this study was to analyse serum IgG levels and salivary secretory IgA (sIgA) levels in human dentine extract (HDE) before (T0) and 6 months after (T6) orthodontic treatment and to correlate anti-HDE autoantibodies to root resorption. Fifty orthodontic patients were selected, 19 males (15.6 ± 8.5 years) and 31 females (21.4 ± 11.2 years), 19 in the mixed dentition (10.3 ± 1.9 years) and 31 in the permanent dentition (24.6 ± 9.9 years). Fifty individuals not undergoing orthodontic treatment matched by gender and age were selected as the controls. Periapical radiographs of the upper central incisors and saliva sampling were obtained of all patients at T0 and T6. Serum samples were collected from the permanent dentition patients (n = 31). Antibody levels were determined by means of immunoenzyme assay. At T6, root resorption was classified as grade 0 (no resorption), grade 1 (slight resorption), and grade 2 (moderate to severe resorption). Differences between antibody levels at T0 and T6 and among different grades of resorption were determined by paired t- and Kruskal-Wallis tests, respectively. Spearman's rank correlation coefficient was applied to detect correlation between sIgA and IgG levels, and logistic regression to determine the association of root resorption grade and the studied variables. Differences were considered significant at P < 0.05. Serum anti-HDE IgG levels decreased (P < 0.01) in grade 2 root resorption patients during treatment and was not correlated to salivary sIgA levels or other variables. Patients who had grade 2 root resorption at T6 showed higher levels of anti-HDE sIgA (P < 0.001). Anti-HDE sIgA levels at T0 and root shape were the main factors associated with the degree of root resorption. The results suggest that variations to systemic and local humoural immune response to dentine antigens may occur during orthodontic treatment. High levels of salivary sIgA before treatment were associated with more advanced lesions after 6 months of treatment.

Inflammation-regeneration interplay in the dentine-pulp complex.

OBJECTIVES: Dental tissue disease and trauma provides an excellent model for the interaction between tissue defence and regenerative processes and has application to many of the body's other tissues. Following dental tissue infection, characterised by caries, the molecular and cellular mediators of the immune/inflammatory processes clearly impact on the dental tissues' natural regenerative responses. This review of the literature was performed to better understand how these two processes interact and identify whether cross-talk may provide novel areas for future research and subsequent translation into clinical application. DATA AND SOURCES: A review of the literature was performed using the PubMed database resource and this was followed by extensive hand searching using reference lists from relevant articles. CONCLUSIONS: Frequently, the dental tissue inflammatory and regenerative processes are seen as both distinct and antagonistic and subsequently have often been studied in isolation; however, both direct and indirect data are now emerging which indicate significant inter-relationship. Whilst the ensuing inflammatory process will result in dental tissue breakdown and molecular signalling which may impede regeneration, low grade inflammation, potentially induced by mechanical trauma and tissue necrosis, may promote regenerative mechanisms, including angiogenic and stem cell processes. Notably, the locally derived growth factors, neuropeptides, cytokines and chemokines, released from the host dentine matrix and by resident pulpal cells, immune cells, neurons and/or dying cells, will modulate defence and repair processes within the tissue.

Immunohistochemical identification of MMP-2 and MMP-9 in human dentin: correlative FEI-SEM/TEM analysis.

Matrix metalloproteinases (MMPs) are a family of peptidases trapped within mineralized dentin matrix and involved with degradation of the extracellular matrix components in hybrid layers and caries. Despite their identification through indirect evidences and biochemical assays, MMP-2 and -9 have not been localized within the human dentin extracellular organic matrix. Thus, this study aimed to assess the localization and distribution of MMP-2 and -9 in human dentin organic matrix by employing a correlative field emission in-lens-scanning electron microscopy (FEI-SEM) and transmission electron microscopy (TEM) immunohistochemical approach. Dentin specimens were submitted either to a preembedding or to a postembedding immunolabeling technique using primary monoclonal antibodies anti-MMP-2 and anti-MMP-9 and exposed to a secondary antibody conjugated with gold nanoparticles. MMP-2 and -9 labelings were identified in the demineralized dentin matrix as highly electron-dense gold particles dispersed on the collagen fibrils. Correlative FEI-SEM/TEM observations confirmed that MMP-2 and MMP-9 are endogenous components of the human dentin organic matrix and revealed the three-dimensional relationship between these proteinases and the collagen fibrils, showing that both antibodies yielded a similar labeling pattern. In conclusion, the results of the study contribute to reveal distinct distribution pattern of gelatinases and support the hypothesis that these enzymes are intrinsic constituents of the dentin organic matrix after decalcification.

Differential regulation of immune responses by odontoblasts.

Odontoblasts (OBs) are cells lining the inner surface of the tooth. Their potential role in host defenses within the tooth is suggested by their production of antimicrobial beta-defensins, but their role needs confirmation. The present study sought to define the roles of human OBs in microbial recognition and innate host responses. Toll-like receptor 2 (TLR2) and TLR4, as well as CCR6, were immunolocalized in human OBs and their dentinal processes in situ. To examine OB function we used organotypic tooth crown cultures to maintain human OBs within their dentin scaffold. Cells in the OB layer of cultured and non-cultured crown preparations expressed mRNA for several markers of innate immunity including chemokine CCL20, chemokine receptor CCR6, TLR2, TLR4 and the OB marker dentin sialophosphoprotein (DSPP). Expression of human beta-defensin 1 (hBD1), hBD2, hBD3, interleukin-8 (IL-8), and CCL20 increased with time in culture. Tooth crown odontoblast (TcOB) cultures were stimulated with agonist that was specific for TLR2 (Pam3CSK4) or TLR4 [Escherichia coli lipopolysaccharide (LPS)]. Nuclear factor-kappaB assays confirmed the TLR2 activity of Pam3CSK4 and the TLR4 activity of LPS. LPS up-regulated IL-1beta, tumor necrosis factor-alpha (TNF-alpha), CCL20, hBD2, IL-8, TLR2 and TLR4; however, Pam3CSK4 down-regulated these mRNAs. IL-1beta, TNF-alpha, CCL20 were also up-regulated from six-fold to 30-fold in TcOB preparations from decayed teeth. Our results show for the first time that OBs express microbial pattern recognition receptors in situ, thus allowing differential responses to gram-positive and gram-negative bacteria, and suggest that pro-inflammatory cytokines and innate immune responses in decayed teeth may result from TLR4 signaling.

The pulpal origin of immunoglobulins in dentin beneath caries: an immunohistochemical study.

Immunoglobulins localized in uninfected dentin beneath caries are thought to be protective, but their origin remains controversial. We reasoned that the localization and dominance of serum IgG1 would support the pulpal origin of the immunoglobulins while a predominance of secretory component (SC) bearing IgA1 and IgA2 would support their salivary origin. The prevalence and staining intensity of IgG1, IgA1, IgA2, IgM, and SC in uninfected dentinal tubules beneath shallow, deep caries, and noncaries teeth were examined immunohistologically. SC was only localized in caries, and IgG1 was the predominant subclass in uninfected dentinal tubules beneath shallow and deep caries, followed by IgA1. In noncaries teeth, IgG1 was localized on the pulpal end. The intensity of IgG1 was significantly higher than either IgA1 or IgA2 in both shallow and deep caries. Our data support the serum origin of immunoglobulins in uninfected dentin beneath caries.

Lipoteichoic acid increases TLR and functional chemokine expression while reducing dentin formation in in vitro differentiated human odontoblasts.

Gram-positive bacteria entering the dentinal tissue during the carious process are suspected to influence the immune response in human dental pulp. Odontoblasts situated at the pulp/dentin interface are the first cells encountered by these bacteria and therefore could play a crucial role in this response. In the present study, we found that in vitro-differentiated odontoblasts constitutively expressed the pattern recognition receptor TLR1-6 and 9 genes but not TLR7, 8, and 10. Furthermore, lipoteichoic acid (LTA), a wall component of Gram-positive bacteria, triggered the activation of the odontoblasts. LTA up-regulated the expression of its own receptor TLR2, as well as the production of several chemokines. In particular, an increased amount of CCL2 and CXCL10 was detected in supernatants from LTA-stimulated odontoblasts, and those supernatants augmented the migration of immature dendritic cells in vitro compared with controls. Clinical relevance of these observations came from immunohistochemical analysis showing that CCL2 was expressed in vivo by odontoblasts and blood vessels present under active carious lesions but not in healthy dental pulps. In contrast with this inflammatory response, gene expression of major dentin matrix components (type I collagen, dentin sialophosphoprotein) and TGF-beta1 was sharply down-regulated in odontoblasts by LTA. Taken together, these data suggest that odontoblasts activated through TLR2 by Gram-positive bacteria LTA are able to initiate an innate immune response by secreting chemokines that recruit immature dendritic cells while down-regulating their specialized functions of dentin matrix synthesis and mineralization.

Humoral immune response of patients with dental trauma and consequent replacement resorption.

Replacement dental resorption may be a consequence of trauma and may cause dental transplants or reimplants to fail. Previously, we demonstrated the participation of the immunopathological response in inflammatory dental resorption. The induction mechanisms of the two types of dental resorption are well known to be different. The aim of the present study was to observe the immune response of patients who suffered dental trauma with subsequent replacement dental resorption. Four patients with replacement radicular resorption and four healthy individuals with no evidence of radicular resorption participated in the study. The results of ELISA demonstrated that serum from patients with replacement dental resorption contained larger amounts of IgG and smaller amounts of IgM anti-total human-dentin extract and anti-fractions of extract than did serum from control individuals. These results signal the hypothesis that dentin is immunogenic and the serological profile of patients with replacement dental resorption may be identified through biochemical analysis of their blood. Precise screening by this method may allow early diagnosis of dental resorption before it becomes visible radiographically.

Cytokine and chemokine response of bone cells after dentin challenge in vitro.

OBJECTIVE: The aim of this study was to characterize the effects of dentin extracts on cytokine, chemokine and nitric oxide (NO) production by primary rat bone cells. STUDY DESIGN: Osteoblastic bone marrow cultures were exposed to particulate (D-part), non-particulate (D-n-part) and demineralized dentin extracts and evaluated for proliferative activity, cell morphology, alkaline phosphatase activity and bone-like nodule formation. Cytokine production was assessed by enzyme-linked immunosorbent assay and NO release by the Griess method. RESULTS: The dentin extracts did not affect osteoblast numbering. Conversely, they up regulated in a dose-dependent manner the production by the osteoblasts of the pro-inflammatory interleukin-1beta (IL-1beta), tumor necrosis factor-alpha, IL-6, cytokine-induced neutrophil chemoattractant-1, and of the anti-inflammatory cytokine, IL-10. The NO production was stimulated only by D-n-part. CONCLUSION: These results demonstrate that dentin induces the production of inflammatory cytokines by osteoblasts and suggest that pro-resorptive pathways might be stimulated when dentin molecules come into contact with bone cells during pathological processes associated with dentin and bone matrix dissolution.

Porphyromonas gingivalis 67-kDa fimbriae induced cytokine production and osteoclast differentiation utilizing TLR2.

Porphyromonas gingivalis, a major etiological agent of adult periodontitis, has two distinctly different types of fimbriae on the cell surface. The major fimbriae, which consist of a 41-kDa fimbrillin of P. gingivalis ATCC 33277, have been known to induce inflammatory cytokine production in murine peritoneal macrophages. In this study, we examined the effects of the minor fimbriae of P. gingivalis, composed of a 67-kDa fimbrillin, on cytokine production in murine peritoneal macrophages and the ability to induce osteoclast differentiation. Murine peritoneal macrophages were stimulated with P. gingivalis 67-kDa minor fimbriae for 24 h, then the levels of interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha and IL-6 production were determined by enzyme-linked immunosorbent assay (ELISA). To estimate osteoclast differentiation, mouse osteoclast precursors were placed on dentine slices, and cultured with or without P. gingivalis 67-kDa minor fimbriae for 7 days. P. gingivalis 67-kDa minor fimbriae clearly induced IL-1beta, TNF-alpha and IL-6 production in mouse macrophages. Furthermore, pit formations on the dentine slices were significantly extended when the osteoclast precursors were incubated with P. gingivalis 67-kDa minor fimbriae. Pretreatment with anti-Toll-like receptor 2 (TLR2) antibody significantly inhibited IL-1beta, TNF-alpha and IL-6 induction (P<0.05) in mouse macrophages and pit-forming activity of osteoclast precursor cells stimulated with P. gingivalis 67-kDa minor fimbriae. These results suggest that P. gingivalis 67-kDa minor fimbriae may provoke host inflammatory response and be involved in periodontal tissue breakdown.

Immunocytochemical analysis of dentin: a double-labeling technique.

Immunocytochemical analysis is a fundamental and selective technique for identifying different molecular components of human dental structure. The hypothesis tested here is that the application of different etching solutions on dentin does not hinder collagen fibrils and proteoglycans from maintaining their immunochemical antigenicity. Human dentin disks were treated with 0.5M of EDTA, citric acid, maleic acid, or phosphoric acid (for 15 or 30 s). A double-immunolabeling technique was performed to identify, simultaneously, collagen fibrils and chondroitin sulfate. The use of different acids resulted in different degrees of labeling. Maleic and citric acids revealed a diffuse and intense labeling for both collagen fibrils and proteoglycans. The use of phosphoric acid on dentin showed a massive coagulation of the proteoglycans (15 s) or very low labeling (30 s). These data clarify that the use of acids on dentin components is able to modify their antigenicity. Moreover, the double-labeling immunocytochemical technique allows understanding of the spatial relationships between the collagen fibrils and proteoglycans of the dentin matrix.

High-sucrose diet reduces defensive reactions of the pulpo-dentinal complex to dentinal caries in young rats.

The significance of systemic dietary effects on the response of the pulpo-dentinal complex to dentinal caries was examined. Weanling rats were divided into high sucrose or control diet groups both with and without cariogenic bacterial inoculation. At the onset, tetracycline was injected to mark the dentin formation during the experiment. After 5-6 week, mandibular molars were sectioned sagittally. The areas of dentin formed during the experiment and those of dentinal caries were quantified separately in the first and second molars. In the control diet groups the area of dentin was significantly greater under carious fissures, whereas in the high sucrose diet groups the area of dentin formed did not differ between intact and carious fissures. The high sucrose diet resulted in a significantly smaller area of dentin formation than did the control diet. The high sucrose diet with cariogenic bacterial inoculation resulted in the greatest area of dentinal caries. With the control diet a positive response against dentinal caries occurs, but the high dietary sucrose content impairs the defensive reactions of pulpo-dentinal complex against dentinal caries. These findings add further evidence of the importance of the local endogenous factors of caries progression.