Differential Responses of Human Dental Pulp Stromal Cells to Bioceramic Materials: A Comparative In Vitro Study

AIM

The aim of this study was to compare the effects of white MTA-Angelus (wMTA), Biodentine® (Biodentine) and TotalFill® BC Root Repair Material^TM putty (TotalFill) on human dental pulp stromal cells (hDPSCs) in vitro.

MATERIALS AND METHODS

hDPSCs were isolated from third molars of healthy young adults. Material elutes at different concentrations were prepared. Cells were exposed to the eluates for 1, 3, and 7 days. Cell proliferation was evaluated using 3-(4,5-dimethyl-thiazoyl)-2, 5-diphenyl-tetrazolium bromide assay. The expression of alkaline phosphatase (ALP), osteoprotegerin (OPG), osteocalcin (OC), collagen1A (Col1A), runt-related transcription factor 2 (RUNX2), vascular endothelial growth factor-A (VEGF-A), fibroblast growth factor-1 (FGF-1), interleukin 6 (IL6), tumor necrosis factor alpha (TNFα), and interleukin-1-beta (IL1β) was determined by reverse transcription-polymerase chain reaction (RT-PCR). VEGF-A protein levels and ALP activity were quantified in the culture supernatant. Data were analyzed by two-way analysis of variance (ANOVA). p values <0.05 were considered statistically significant.

RESULTS

hDPSC proliferation was decreased in a dose-related manner for all materials on day 3. The same effect was observed with wMTA and TotalFill on day 7. RT-PCR showed that Biodentine increased the expression of the osteogenic markers ALP, OPG, and OC. TotalFill decreased the ALP expression and activity, enhanced the production of angiogenic VEGF-A, and downregulated the inflammatory IL6 on day 7.

CONCLUSION

Although the tested materials are used interchangeably in vital pulp therapy, the findings showed varied hDPSC responses. Biodentine did not affect cell proliferation and increased the expression of osteo-/odontogenic markers compared to wMTA and TotalFill, whereas TotalFill decreased cell proliferation and exhibited enhanced angiogenic and anti-inflammatory effects over time.

CLINICAL SIGNIFICANCE

The clinical significance of the results needs further investigation in an attempt to provide recommendations on the selection of bioceramic pulp capping material under different scenarios of pulpal pathosis.

Comparison of bone regenerative capacity of donor-matched human adipose-derived and bone marrow mesenchymal stem cells

Adipose-derived stem cells (ASC) have been used as an alternative to bone marrow mesenchymal stem cells (BMSC) for bone tissue engineering. However, the efficacy of ASC in bone regeneration in comparison with BMSC remains debatable, since inconsistent results have been reported. Comparing ASC with BMSC obtained from different individuals might contribute to this inconsistency in results. Therefore, this study aimed to compare the bone regenerative capacity of donor-matched human ASC and BMSC seeded onto poly(l-lactide-co-ε-caprolactone) scaffolds using calvarial bone defects in nude rats. First, donor-matched ASC and BMSC were seeded onto the co-polymer scaffolds to evaluate their in vitro osteogenic differentiation. Seeded scaffolds and scaffolds without cells (control) were then implanted in calvarial defects in nude rats. The expression of osteogenesis-related genes was examined after 4 weeks. Cellular activity was investigated after 4 and 12 weeks. Bone formation was evaluated radiographically and histologically after 4, 12, and 24 weeks. In vitro, ASC and BMSC demonstrated mineralization. However, BMSC showed higher alkaline phosphatase activity than ASC. In vivo, human osteogenesis–related genes Runx2 and collagen type I were expressed in defects with scaffold/cells. Defects with scaffold/BMSC had higher cellular activity than defects with scaffold/ASC. Moreover, bone formation in defects with scaffold/BMSC was greater than in defects with scaffold/ASC, especially at the early time-point. These results suggest that although ASC have the potential to regenerate bone, the rate of bone regeneration with ASC may be slower than with BMSC. Accordingly, BMSC are more suitable for bone regenerative applications.

Evaluation of Apical Dimension, Canal Taper and Maintenance of Root Canal Morphology Using XP-endo Shaper

AIM

To evaluate the shaping ability of the XP-endo shaper file system in maxillary molars, representing root canals with variation in morphology.

MATERIALS AND METHODS

Twenty maxillary molars were instrumented according to recommended protocols. Pre- and postoperative microcomputed tomography (CT) scans were performed and the root canals classified according to canal type and curvature. The volume change, number of strokes needed to prepare the canals and the size of the 0.04-tapered gutta-percha cone that was adapted in the canal were recorded.

RESULTS

XP-endo shaper created a significant change in volume after instrumentation in all the canals, with the biggest change found in the DB canals, followed by the MB1 and the P canals, both at full length and in the apical 4 mm. The number of strokes needed to achieve working length and final shape did not differ between the various root canals. Although not significant, the number of strokes needed to prepare the root canal increased with severity of the curvature, but the severity of the curvature did not result in increased removal of dentin in the apical 4 mm. It was possible to achieve a final root canal size where a 0.04-tapered gutta-percha cone could be adapted.

CONCLUSION

The XP-endo shaper was a safe and effective instrument to achieve a root canal preparation of at least size 30 and a 0.04 taper.

CLINICAL SIGNIFICANCE

The clinical performance of XP-endo shaper was to some extent dependent on preoperative volume and curvature of the root canal.

Adipose-derived and bone marrow mesenchymal stem cells: a donor-matched comparison

Background

Adipose-derived stem cells (ASCs) have been introduced as an alternative to bone marrow mesenchymal stem cells (BMSCs) for cell-based therapy. However, different studies comparing ASCs and BMSCs have shown conflicting results. In fact, harvesting ASCs and BMSCs from different individuals might influence the results, making comparison difficult. Therefore, this study aimed to characterize donor-matched ASCs and BMSCs in order to investigate proliferation, differentiation potential and possible effects of donor variation on these mesenchymal stem cells (MSCs).

Methods

Human bone marrow and adipose tissue samples were obtained from nine donors aged 8–14. ASCs and BMSCs were isolated and characterized based on expression of surface markers using flow cytometry. The proliferation up to 21 days was investigated. Multi-lineage differentiation was induced using osteogenic, chondrogenic and adipogenic differentiation media. Alkaline phosphatase (ALP) activity was monitored and collagen type I formation was evaluated by immunofluorescence staining. In vitro multi-potency was studied using tissue-specific stains and lineage-specific gene expression. In addition, the osteogenic lineage was evaluated at protein level.

Results

Isolated ASCs and BMSCs from all donors demonstrated morphologic and immunophenotypic characteristics of MSCs, with expression of MSCs markers and negative expression of hematopoietic markers. Unlike BMSCs, ASCs showed high expression of CD49d and low expression of Stro-1. In general, ASCs showed significantly higher proliferation and adipogenic capacity with more lipid vesicle formation and expression of the adipogenesis-related genes than BMSCs. In contrast, BMSCs showed significantly higher osteogenic and chondrogenic capacity compared to ASCs. BMSCs had earlier and higher ALP activity, calcium deposition, and expression of the osteogenesis- and chondrogenesis-related genes and the osteogenesis-related protein osteopontin. Proliferation and differentiation capacity of ASCs and BMSCs varied significantly among the donors.

Conclusions

ASCs and BMSCs showed tissue-specific differentiation abilities, but with significant variation between donors. The similarities and differences in the properties of ASCs and BMSCs should be taken into consideration when planning stem cell-based therapy.

Human dental pulp stromal cell conditioned medium alters endothelial cell behavior

Background

Angiogenesis is of utmost importance for tissue regeneration and repair. Human dental pulp stromal cells (hDPSCs) possess angiogenic potential, as they secrete paracrine factors that may alter the host microenvironment. However, more insight into how hDPSCs guide endothelial cells (ECs) in a paracrine fashion is yet to be obtained. Therefore, the current study aimed to investigate the effect(s) of conditioned medium derived from hDPSCs (hDPSC-CM) on EC behavior in vitro.

Methods

hDPSCs were harvested from third molars scheduled for surgical removal under informed consent. The angiogenic profile of hDPSC-CM was identified using human angiogenesis antibody array and enzyme-linked immunosorbent assay (ELISA). Using real-time reverse transcription-polymerase chain reaction (RT-PCR) and ELISA, the mRNA and protein expression level of specific angiogenic biomarkers was determined in human umbilical vein endothelial cells (HUVECs) exposed to hDPSC-CM. The effect of hDPSC-CM on HUVEC attachment, proliferation and migration was evaluated by crystal violet staining, MTT, transwell migration along with real-time cell monitoring assays (xCELLigence; ACEA Biosciences, Inc.). A Matrigel assay was included to examine the influence of hDPSC-CM on HUVEC network formation. Endothelial growth medium (EGM-2) and EGM-2 supplemented with hDPSC-CM served as experimental groups, whereas endothelial basal medium (EBM-2) was set as negative control.

Results

A wide range of proangiogenic and antiangiogenic factors, including vascular endothelial growth factor, tissue inhibitor of metalloproteinase protein 1, plasminogen activator inhibitor (serpin E1), urokinase plasminogen activator and stromal cell-derived factor 1, was abundantly detected in hDPSC-CM by protein profiling array and ELISA. hDPSC-CM significantly accelerated the adhesion phases, from sedimentation to attachment and spreading, the proliferation rate and migration of HUVECs as shown in both endpoint assays and real-time cell analysis recordings. Furthermore, Matrigel assay demonstrated that hDPSC-CM stimulated tubulogenesis, affecting angiogenic parameters such as the number of nodes, meshes and total tube length.

Conclusions

The sustained proangiogenic and promaturation effects of hDPSC-CM shown in this in vitro study strongly suggest that the trophic factors released by hDPSCs are able to trigger pronounced angiogenic responses, even beyond EGM-2 considered as an optimal culture condition for ECs.

Conditioned medium from human bone marrow stromal cells attenuates initial inflammatory reactions in dental pulp tissue

AIM

To evaluate the effect of MSC-conditioned medium (CM) on the secretion of pro- and anti-inflammatory cytokines from dental pulp cells (hDPC) in vitro, and on the gene expression in vivo after replantation of rat molars.

MATERIALS AND METHODS

hDPC were cultured in CM for 24 h, and the concentration of interleukin IL-10, IL-4, IL-6, and IL-8, regulated on activation, normal T Cell expressed and secreted (RANTES), and prostaglandin E₂ (PGE₂ ) in the media were measured by multiplex assay and ELISA, respectively. Expression of cyclooxygenase-2 (COX-2) was also examined by Western blot analysis after 24 h. Left and right maxillary first rat molars (n = 20) were elevated for 2 min and then replanted with or without application of CM into the tooth sockets. Levels of IL-1β, IL-10, IL-4, IL-6, and IL-8, and tumor necrosis factor-alpha (TNF-α) mRNA were evaluated by real-time qRT-PCR 3 and 14 days following tooth replantation.

RESULTS

The production of IL-8, IL-10, and IL-6, RANTES and PGE₂ by cells cultured in CM was significantly higher than production by cells cultured in standard medium (DMEM). At day 3 following replantation in vivo, the levels of IL-1β and IL-6, and TNF-α mRNA were significantly lower in the CM-treated replanted teeth compared with control teeth. Further, at day 3, the IL-6/IL-10 ratio was significantly lower in the CM-treated replanted teeth compared with control. At day 14 following replantation, no differences in the mRNA ratios were detected between the pulp tissues of replanted and control teeth.

CONCLUSIONS

These findings indicated that CM promotes secretion of pro- and anti-inflammatory cytokines from hDPCin vitro and attenuates the initial inflammatory response in the rat dental pulp in vivo following tooth replantation.

Conditioned media from hypoxic-cultured human dental pulp cells promotes bone healing during distraction osteogenesis

Distraction osteogenesis (DO) is a surgical procedure used to correct various skeletal disorders. Improving the technique by reducing the healing time would be of clinical relevance. The aim of this study was to determine the angiogenic and regenerative potential of conditioned media (CMs) collected from human dental pulp cells (hDPCs) grown under different culture conditions. CM collected from cells under hypoxia was used to improve bone healing and the DO procedure in vivo. The angiogenic potentials of CMs collected from hDPCs grown under normoxic (−Nor) and hypoxic (−Hyp) conditions were evaluated by quantitative PCR (VEGF‐A, angiopoietin‐1, angiopoietin‐2, interleukin‐6 (IL‐6) and CXCL12), ELISA assays (VEGF‐A, Ang‐2), tube‐formation and wound‐healing assays, using human umbilical vein endothelial cells. The results demonstrated that hypoxic CM had significantly higher angiogenic potential than normoxic CM. Human fetal osteoblasts (hFOBs) were exposed to CM, followed by alizarin red staining, to assess the osteogenic potential. It was found that CM did not enhance the mineralization capacity of hFOBs. DO was performed in the tibiae of 30 mice, followed by a local injection of 20 µl CM (CM–Nor and CM–Hyp groups) or serum‐free DMEM (control group) into the distraction zone every second day. The mice were sacrificed at days 13 and 27. The CM–Hyp treatment revealed a higher X‐ray density than the control group (p < 0.05). Our study suggests that the angiogenic effect promoted by hypoxic culture conditions is dependent on VEGF‐A and Ang‐2 released from hDPCs. Furthermore, CM–Hyp treatment may thus improve the DO procedure, accelerating bone healing. © 2015 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons, Ltd.

Bone marrow stromal cell paracrine factors direct osteo/odontogenic differentiation of dental pulp cells

Growth factors play an important role in osteo/odontogenic differentiation of human dental pulp cells (hDPCs). The aim of this in vitro study was to compare the biological effects of recombinant human growth differentiation factor 5 (rhGDF-5) alone and a cocktail of soluble growth factors (conditioned medium) released from human bone marrow mesenchymal stem cells (hBMMSCs) on the morphology, proliferation and osteo/odontogenic differentiation potential of hDPCs. Passage 4 hDPCs were harvested for culture in four different media: (a) DMEM with 10% FBS, (b) odontogenic induction medium (OM), (c) OM plus 500 ng/mL rhGDF-5, and (d) OM plus conditioned medium (CM). Morphological changes at 48 and 120 h were determined by crystal violet staining. The proliferation rates at 3, 24, 48, and 120 h were assayed by MTT. Using real-time reverse transcription-polymerase chain reaction (RT-PCR), the mRNA levels of dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP1), collagen type I (Col 1), Runt-related transcription factor 2 (Cbfa1/Runx2), alkaline phosphatase (ALP), osteocalcin (OC), β3 tubulin (TUBB3), glial cell-derived neurotrophic factor (GDNF), angiopoietin-1 (Ang1), and vascular endothelial growth factor A (VEGFA), were determined at 2, 5, and 9 days. Protein expression of dental sialoprotein (DSP), DMP1, OC, and TUBB3 was recorded at 5 days, using western blot and immunocytochemistry. The effect of the different culture media on mineralization was determined by ALP staining at day 5 and Alizarin red S staining at days 7 and 14. In response to the different culture media, the shape of the hDPCs varied from spindled to polygonal and cuboidal. CM inhibited the cellular proliferation rate, while rhGDF-5 had no effect at early time points, but promoted cellular proliferation at 120 h of culture. In the CM group, the mRNA levels of Cbfa1/Runx2, Col 1, ALP, VEGFA, Ang1, and TUBB3 decreased and the levels of GDNF and OC increased. The mRNA levels of DSPP and DMP1 were inconsistent at the time points evaluated. The staining assays also demonstrated that compared with the other groups, the CM group exhibited lower expression of ALP and higher mineralization levels. Protein expression of DSP, DMP1, OC, and TUBB3 was pronounced by the CM-treated cells. It is concluded that under these in vitro conditions, CM released from hBMMSCs have a greater osteo/odontogenic inductive effect on hDPCs than rhGDF-5.

Mesenchymal stem cells induce endothelial cell quiescence and promote capillary formation

Introduction

Rapid establishment of functional blood vessels is a prerequisite for successful tissue engineering. During vascular development, endothelial cells (ECs) and perivascular cells assemble into a complex regulating proliferation of ECs, vessel diameter and production of extracellular matrix proteins. The aim of this study was to evaluate the ability of mesenchymal stem cells (MSCs) to establish an endothelial-perivascular complex in tissue-engineered constructs comprising ECs and MSCs.

Methods

Primary human ECs and MSCs were seeded onto poly(L-lactide-co-1,5-dioxepan-2-one) (poly(LLA-co-DXO)) scaffolds and grown in dynamic culture before subcutaneous implantation in immunocompromised mice for 1 and 3 weeks. Cellular activity, angiogenic stimulation and vascular assembly in cell/scaffold constructs seeded with ECs or ECs/MSCs in a 5:1 ratio was monitored with real-time RT-PCR, ELISA and immunohistochemical microscopy analysis.

Results

A quiescent phenotype of ECs was generated, by adding MSCs to the culture system. Decreased proliferation of ECs, in addition to up-regulation of selected markers for vascular maturation was demonstrated. Baseline expression of VEGFa was higher for MSCs compared with EC (P <0.001), with subsequent up-regulated VEGFa-expression for EC/MSC constructs before (P <0.05) and after implantation (P <0.01). Furthermore, an inflammatory response with CD11b + cells was generated from implantation of human cells. At the end of the 3 week experimental period, a higher vascular density was shown for both cellular constructs compared with empty control scaffolds (P <0.01), with the highest density of capillaries being generated in constructs comprising both ECs and MSCs.

Conclusions

Induction of a quiescent phenotype of ECs associated with vascular maturation can be achieved by co-seeding with MSCs. Hence, MSCs can be appropriate perivascular cells for tissue-engineered constructs.

Instrument fracture in root canals - where, why, when and what? A study from a student clinic

AIM

To investigate the incidence of instrument fracture during nonsurgical root canal treatment performed by undergraduate dental students and to assess the outcome of the treatment if the remaining fragment was left or removed from the root canal.

METHODOLOGY

A retrospective analysis was performed by reviewing assessment forms (n = 3854) filled out for each root canal treatment over a 10-year period (1997-2006) at the University of Bergen, Norway. Based on the assessment forms, all instrument fractures and data concerning type and dimension of the fractured instruments were identified. Moreover, the affected tooth, root, root curvature and the vertical level of the fragment in the root canal were recorded. To assess the outcome of the root canal treatment, radiographs taken at follow-ups were evaluated by two individual examiners.

RESULTS

The overall incidence of instrument fracture during the period was 1.0% on a tooth level. Instrument fracture occurred significantly more often in molars and in teeth rated as difficult preoperatively. Of all instrument fractures, 39.5% were located in the mesio-buccal canals of molars, and 76.5% of the fragments were located apically. A significant high percentage of instruments of small apical diameter (sizes 006-015) fractured in relative straight root canals. The treatment was successful in 71.4% of the cases where the instrument fragment was removed, but only in 56.5% of the cases where the fragment remained in the root canal. Significantly more instruments were removed from teeth with a primary infection (P ≤ 0.05). The success rate for teeth with instrument fracture was 72.7% for vital teeth, 58.3% for primary infected teeth and 42.9% in retreatment cases.

CONCLUSIONS

Within the limits of the present study, the results indicate that the preoperative diagnosis is important for the final treatment outcome and that removal of the fragment is important in cases with primary infection.

Endothelial microvascular networks affect gene-expression profiles and osteogenic potential of tissue-engineered constructs

Introduction

A major determinant of the potential size of cell/scaffold constructs in tissue engineering is vascularization. The aims of this study were twofold: first to determine the in vitro angiogenic and osteogenic gene-expression profiles of endothelial cells (ECs) and mesenchymal stem cells (MSCs) cocultured in a dynamic 3D environment; and second, to assess differentiation and the potential for osteogenesis after in vivo implantation.

Methods

MSCs and ECs were grown in dynamic culture in poly(L-lactide-co-1,5-dioxepan-2-one) (poly(LLA-co-DXO)) copolymer scaffolds for 1 week, to generate three-dimensional endothelial microvascular networks. The constructs were then implanted in vivo, in a murine model for ectopic bone formation. Expression of selected genes for angiogenesis and osteogenesis was studied after a 1-week culture in vitro. Human cell proliferation was assessed as expression of ki67, whereas α-smooth muscle actin was used to determine the perivascular differentiation of MSCs. Osteogenesis was evaluated in vivo through detection of selected markers, by using real-time RT-PCR, alkaline phosphatase (ALP), Alizarin Red, hematoxylin/eosin (HE), and Masson trichrome staining.

Results

The results show that endothelial microvascular networks could be generated in a poly(LLA-co-DXO) scaffold in vitro and sustained after in vivo implantation. The addition of ECs to MSCs influenced both angiogenic and osteogenic gene-expression profiles. Furthermore, human ki67 was upregulated before and after implantation. MSCs could support functional blood vessels as perivascular cells independent of implanted ECs. In addition, the expression of ALP was upregulated in the presence of endothelial microvascular networks.

Conclusions

This study demonstrates that copolymer poly(LLA-co-DXO) scaffolds can be prevascularized with ECs and MSCs. Although a local osteoinductive environment is required to achieve ectopic bone formation, seeding of MSCs with or without ECs increases the osteogenic potential of tissue-engineered constructs.

Osteogenic stimulatory conditions enhance growth and maturation of endothelial cell microvascular networks in culture with mesenchymal stem cells

To optimize culture conditions for in vitro prevascularization of tissue-engineered bone constructs, the development of organotypic blood vessels under osteogenic stimulatory conditions (OM) was investigated. Coculture of endothelial cells and mesenchymal stem cells was used to assess proangiogenic effects of mesenchymal stem cells on endothelial cells. Four different culture conditions were evaluated for their effect on development of microvascular endothelial cell networks. Mineralization, deposition of extracellular matrix, and perivascular gene expression were studied in OM. After 3 days, endothelial cells established elongated capillary-like networks, and upregulated expression of vascular markers was seen. After 15 days, all parameters evaluated were significantly increased for cultures in OM. Mature networks developed in OM presented lumens enveloped by basement membrane-like collagen IV, with obvious mineralization and upregulated perivascular gene expression from mesenchymal stem cells. Our results suggest osteogenic stimulatory conditions to be appropriate for in vitro development of vascularized bone implants for tissue engineering.

Lymphangiogenesis Is Induced during Development of Periodontal Disease

Lymphangiogenesis, the formation of new lymphatics, is associated with chronic inflammation and tissue injury, and its role is to enhance lymphatic flow, immune cell transport, and antigen clearance. It is unknown if lymphangiogenesis takes place during periodontal disease development, and we hypothesized that growth of lymphatic vessels occurs in gingiva during development of periodontitis in mice. Inflammation was induced in gingiva with Porphyromonas gingivalis gavage, and bone resorption was verified after 42 days. Growth of lymphatic and blood vessels was measured after immunofluorescent staining with LYVE-1 and CD31. Expression of vascular endothelial growth factors and 2 inflammatory cytokines was investigated 10 days post-infection. Gingival lymphangiogenesis was found 10 days and 42 days post-infection, but proliferation of vessels was observed only in the shortest observation period. Epithelial expression of vascular growth factors (VEGF) A, C, and D was observed in gingiva, and increased numbers of immune cells expressing VEGF-C were found after infection, along with up-regulation of IL-1β and TNF-α at protein levels. We conclude that lymphangiogenesis takes place in gingiva during periodontal disease development, and that up-regulation of vascular growth factor C in recruited immune cells is likely important for the growth of lymphatic vessels.

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.

Systemic chemical desensitization of peptidergic sensory neurons with resiniferatoxin inhibits experimental periodontitis

Background and objective:

The immune system is an important player in the pathophysiology of periodontitis. The brain controls immune responses via neural and hormonal pathways, and brain-neuro-endocrine dysregulation may be a central determinant for pathogenesis. Our current knowledge also emphasizes the central role of sensory nerves. In line with this, we wanted to investigate how desensitization of peptidergic sensory neurons influences the progression of ligature-induced periodontitis, and, furthermore, how selected cytokine and stress hormone responses to Gram-negative bacterial lipopolysaccharide (LPS) stimulation are affected.

Material and methods:

Resiniferatoxin (RTX; 50 μg/kg) or vehicle was injected subcutaneously on days 1, 2, and 3 in stress high responding and periodontitis-susceptible Fischer 344 rats. Periodontitis was induced 2 days thereafter. Progression of the disease was assessed after the ligatures had been in place for 20 days. Two h before decapitation all rats received LPS (150 μg/kg i.p.) to induce a robust immune and stress response.

Results:

Desensitization with RTX significantly reduced bone loss as measured by digital X-rays. LPS provoked a significantly higher increase in serum levels of the pro-inflammatory cytokine tumour necrosis factor (TNF)-α, but lower serum levels of the anti-inflammatory cytokine interleukin (IL)-10 and the stress hormone corticosterone.

Conclusions:

In this model RTX-induced chemical desensitization of sensory peptidergic neurons attenuated ligature-induced periodontitis and promoted a shift towards stronger pro-inflammatory cytokine and weaker stress hormone responses to LPS. The results may partly be explained by the attenuated transmission of immuno-inflammatory signals to the brain. In turn, this may weaken the anti-inflammatory brain-derived pathways.

Importance of lymph vessels in the transcapillary fluid balance in the gingiva studied in a transgenic mouse model

The gingiva is frequently challenged by oral bacterial products leading to inflammatory responses such as increased fluid filtration and edema formation. The role of initial lymphatics for transcapillary fluid balance in the gingiva is unknown and was therefore investigated in genetically engineered K14-VEGF receptor 3-Ig (K14) lymphedema mice. The mutant mice demonstrated a total lack of lymphatics in the gingiva, whereas lymphatics were found in the submucosal parts of the alveolar mucosa, although they were almost completely absent in the mucosa. In wild-type (WT) mice, lymphatic vessels were detected in mucosal and submucosal parts of the alveolar mucosa. Interstitial fluid pressure (Pif) measured with micropipettes was increased in the gingiva of K14 mice in the normal situation ( P < 0.001) and after inflammation ( P < 0.01) induced by lipopolysaccharide from the oral bacteria Porphyromonas gingivalis compared with WT littermates. Fluid volume expansion caused a >75% increase in interstitial fluid volume followed by a drop in Pif after recovery in both strains. Continuous measurements during the expansion showed an increase in Pif followed by a decline, suggesting that compliance is increased after the disruption of the extracellular matrix during edema formation. In the alveolar mucosa, no strain differences were observed in Pif in the normal situation or after fluid volume expansion, suggesting that lymph vessels in the mucosa are not critical for tissue fluid regulation in any situation. Our study demonstrates an important role of gingival lymphatics in transcapillary fluid balance in the steady-state condition and during acute perturbations.

Sensory pulpal nerve fibres and trigeminal ganglion neurons express IL-1RI: a potential mechanism for development of inflammatory hyperalgesia

AIM

To localize interleukin-1 receptor type I (IL-1RI) in rat dental pulp and trigeminal ganglion (TG) and to test the hypothesis that pulpal inflammation increases neuronal expression of IL-1RI.

METHODOLOGY

Female Wistar rats were subjected to unilateral pulp exposures in the maxillary and mandibular first molars, whereas the contralateral jaws served as untreated controls. Seven days later the animals were transcardiacally perfused and the jaws and the TGs were removed and prepared for immunohistochemistry. Immunoreactivity for IL-1RI was examined alone (DAB) and together with calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), CD31 or CD34 by multiple-labelling immunofluorescence. Quantification of IL-1RI-immunoreactive (-IR) cells in the maxillary and mandibular division of the ganglion was performed in parasagittal immunoreacted sections of the right and left TGs. Data were analysed with Mann-Whitney Rank Sum test (P < 0.05).

RESULTS

Interleukin-1 receptor type I was found on sensory (CGRP-IR) and sympathetic (NPY-IR) nerve fibres and on blood vessels (CD31- and CD34-IR) in the dental pulp. It was also localized on sensory neurons and axons in the TG. Pulpal inflammation significantly increased the expression of IL-1RI in the TG (P < 0.001).

CONCLUSIONS

The localization of IL-1RI on sensory nerve fibres and its up-regulation in TG neurons during pulpal inflammation may imply a direct effect of IL-1 in pulpal nociception. The presence of IL-1RI on sympathetic nerve fibres and on blood vessels may indicate a vasoactive role of the same cytokine in the pulp.

Cytokine signalling in rat pulp interstitial fluid and transcapillary fluid exchange during lipopolysaccharide-induced acute inflammation

The dental pulp consists of loose connective tissue encased in rigid dentinal walls. Because of its topography the tissue has low interstitial compliance and limited capacity to expand during fluid volume changes. Due to limitations regarding access to interstitial fluid, basic knowledge on transcapillary fluid transport parameters is lacking for this organ. The scope of this project was dual: first we aimed at establishing a method for isolation of pulp interstitial fluid (IF), and second we applied the method in rats subjected to lipopolysaccharide (LPS)-induced endotoxaemia. The aim was to measure colloid osmotic pressure (COP) and pro-inflammatory cytokines in the pulp IF during acute inflammation. Fluid volumes and pulpal blood flow (PBF) were measured to obtain more information about microcirculatory changes that take place in this pulpitis model. By centrifugation of incisor pulp at 239 g we were able to extract fluid representative for IF. Pulp IF had a relative high control COP (approximately 83% of plasma COP) and was similar to plasma COP 3 h after LPS challenge. The pulp exhibited a high content of IF (0.60 +/- 0.03 ml (g wet weight)(-1)) and a vascular volume of 0.03 +/- 0.01 ml (g w.w.)(-1) No differences were observed in the distribution of fluid volumes after 1.5 and 3 h LPS exposure. PBF and systemic blood pressure dropped significantly after LPS administration. PBF remained low whereas systemic blood pressure was re-established during the 3-h period, implying organ dysfunction. There was a differential pattern of cytokine expression in pulp IF and serum with cytokines such as IL-1alpha, IL-1beta and TNF-alpha locally produced, whereas others such as IFN-gamma and IL-6 were produced systemically and probably spilled over to the pulp IF after LPS exposure. Our findings show that pulp IF can be isolated by centrifugation and that this method is useful when studying fluid balance and extracellular signalling mechanisms in the dental pulp in normal and pathological conditions.

Delta (delta) opioid receptors in small and medium-sized trigeminal neurons supporting the dental pulp of rats

The control of pain perception is a challenge in clinical dentistry, most prominent during tooth pulp inflammation. The tooth pulp is a well-defined target, and is densely supplied by a sensory trigeminal innervation. Opioids are signaling molecules that are suggested to participate in pain perception. Here we analysed the presence of delta opioid receptor (DOR) in trigeminal neurons innervating the tooth pulp of rat molars. Immunohistochemical and ultrastructural analysis revealed that DOR was identified in peripheral nerves in the molar dental pulp, both in the root and the coronal pulpal parts, with branching in the highly innervated subodontoblast layer. DOR was localised in about one third of all the trigeminal dental neurons, identified by means of retrograde neuronal transport of fluorogold (FG) from the dental pulp. Of the DOR-labeled neurons, nearly all were small and medium-sized (147.5-1,810.2 microm(2), mean 749.1 +/- 327.3 microm(2)). Confocal microscopy confirmed that DOR-immunoreactivity was distributed as granules in the neuronal cytoplasm. Approximately 70% of the DOR-immunoreactive neurons were also immunopositive for vanilloid receptor 1 (TRPV1). Ultrastructural analysis demonstrated DOR-immunoreactivity in the unmyelinated and in some of the myelinated nerve fibers in the dental pulp. These results indicate that DOR may influence the function in a subset of small and medium-sized trigeminal sensory neurons supporting the tooth, which are mainly known for their ability to mediate nociceptive stimuli. Agonists, acting on DOR, may thus have an influence on a subpopulation of nociceptive neurons supporting the rat tooth.

Effect of electrical tooth stimulation on blood flow and immunocompetent cells in rat dental pulp after sympathectomy

Previous experiments show that nerves have effect on the emigration of immunocompetent cells during acute neurogenic inflammation. The present study aims to determine whether the sympathetic or sensory nerves are responsible for emigration of CD43+ and I-A antigen-expressing cells in the dental pulp after electrical tooth stimulation. Wistar rats were used. Experimental rats (n = 6) had the right superior cervical ganglion removed (SCGx), whereas control rats (n = 6) had sham surgery. Fourteen days later, electrical stimulation of the right maxillary 1st molar was performed in both groups for 20-25 s every 5th min for a total period of 4 h. Changes in pulpal blood flow (PBF) were recorded with a laser Doppler flowmeter. All rats were transcardiacally perfused and processed for immunohistochemistry using antibodies against neuropeptides and immune cells. Intermittent electrical stimulation consistently increased PBF and depleted sympathetic and sensory neuropeptides in the dental pulp. The increase in PBF gradually decreased and approached control values at the end of the 4 h stimulation period. A significant increase in the number of I-A antigen-expressing dendritic cells was found in both the SCGx (P < 0.001) and control rats (P < 0.007). In contrast, tooth stimulation did not increase the number of CD43+ cells in the SCGx rats compared to the unstimulated contralateral control molar. Significantly more CD43+ PMN cells (P < 0.01) were found in the control rats after stimulation. It is concluded that stimulation of sympathetic nerves causes recruitment of CD43+ PMN cells, whereas stimulation of sensory nerves causes emigration of I-A antigen-expressing dendritic cells in the dental pulp.

Glial cell line-derived neurotrophic factor (GDNF) from adult rat tooth serves a distinct population of large-sized trigeminal neurons

Glial cell line-derived neurotrophic factor (GDNF) mediates trophic effects for specific classes of sensory neurons. The adult tooth pulp is a well-defined target of sensory trigeminal innervation. Here we investigated potential roles of GDNF in the regulation of adult trigeminal neurons and the dental pulp nerve supply of the rat maxillary first molar. Western blot analysis and radioactive 35S-UTP in situ hybridization revealed that GDNF in the dental pulp and its mRNAs were localized with Ngf in the coronal pulp periphery, in particular in the highly innervated subodontoblast layer. Retrograde neuronal transport of iodinated GDNF and Fluorogold (FG) from the dental pulp indicated that GDNF was transported in about one third of all the trigeminal dental neurons. Of the GDNF-labelled neurons, nearly all (97%) were large-sized (> or =35 microm in diameter). Analysis of FG-labelled neurons revealed that, of the trigeminal neurons supporting the adult dental pulp, approximately 20% were small-sized, lacked isolectin B4 binding and did not transport GDNF. Of the large-sized dental trigeminal neurons approximately 40% transported GDNF. About 90% of the GDNF-accumulating neurons were negative for the high-temperature nociceptive marker VRL-1. Our results show that a subclass of large adult trigeminal neurons are potentially dependent on dental pulp-derived GDNF while small dental trigeminal neurons seems not to require GDNF. This suggests that GDNF may function as a neurotrophic factor for subsets of nerves in the tooth, which apparently mediate mechanosensitive stimuli. As in dorsal root ganglia both small- and large-sized neurons are known to be GDNF-dependent; these data provide molecular evidence that the sensory supply in the adult tooth differs, in some aspects, from the cutaneous sensory system.

Nonsurgically retreated root filled teeth--radiographic findings after 20-27 years

AIM

To identify periapical changes in nonsurgically retreated root-filled teeth 20-27 years after root canal treatment.

METHODOLOGY

From an original material of 429 roots, retreated by undergraduate students in a teaching clinic, 112 roots in 70 individuals could be evaluated radiographically 20-27 years after treatment. The same roots had been studied 10-17 years earlier. The periapical condition was registered and compared by three observers in two series of intraoral radiographs taken 10-17 and 20-27 years after treatment. A retrospective analysis was performed to gain information about probable endodontic and nonendodontic reasons for extractions of lost roots, by evaluating their periapical status immediately after retreatment and at the 10-17-year follow-up.

RESULTS

Favourable outcomes were observed in 11 roots that had radiolucencies at the 10-17-year follow-up. Eight of these roots had periapical pathosis preoperatively, five of them filled with surplus root filling material. The percentage of cases recorded as normal condition at the final follow-up was 95.5%, including five cases initially recorded with increased width of the apical periodontal space. Delayed healing as a result of surplus root filling material explained most of the cases with favourable outcome assessed many years after treatment. Twenty-eight roots were lost because of extraction during the observation period, 17 during the last 10 years. Based on status at previous follow-ups, endodontic failure seems to represent a minor reason for extraction in the material.

CONCLUSION

Late periapical changes, with more successful cases, were recorded when a 10-17-year follow-up after root canal treatment was extended for another 10 years. Persistent asymptomatic periapical radiolucencies, especially those with overfill, should generally not be classified as failures, as many of them will heal after an extended observation period.

CGRP1 and NK1 receptors in postnatal, developing rat dental tissues

There is little evidence that neuropeptides such as substance P (SP) and calcitonin gene-related peptide (CGRP) participate in the regulation of tooth development. The aim of this study was to analyse the expression of their respective receptors, neurokinin (NK) 1 and CGRP1 receptor, in postnatal developing rat molars and supporting tissues, thereby localizing the target areas for neuropeptide activity. Mol:WIST rats were killed at 7, 14 and 21 d after birth and upper and lower jaws were processed for immunohistochemistry. At early crown stage (P7), only a few individual cells in the dental follicle were receptor positive. At the onset of root formation (P14), post-secretory ameloblasts, cells in the stratum intermedium, the reduced enamel epithelium and the developing alveolar bone demonstrated both NK1 and CGRP1 receptor immunoreactivity. The CGRP1 receptor sites were occasionally evident on cells in the odontoblast layer. At advanced root development (P21), neuropeptide receptor expression was evident on cells close to the developing dentin, cementum and alveolar bone. These data demonstrate dynamic changes in the localization of NK1 and CGRP1 receptors in developing rat dental tissues and indicate an active role for their ligands in the regulation of crown and root development.

Sympathectomy causes increased root resorption after orthodontic tooth movement in rats: immunohistochemical study

Accumulating evidence suggests that the sympathetic nervous system modulates inflammatory responses and bone remodeling. We have studied the effects of sympathectomy and orthodontic tooth movement (OTM) on root resorption, immunocompetent cell recruitment, neuropeptide, neurokinin-1 receptor (NK1-R), and interleukin 6 (IL-6) expression. Experimental rats (n=8) had the right superior cervical ganglion surgically removed, whereas control rats (n=6) underwent sham surgery. Three days later, all rats had the right maxillary first molar moved mesially by an orthodontic appliance. The rats were perfused 13 days later, and the right maxillae were processed for immunohistochemistry by using primary antibodies directed against ED1 antigen, CD43, substance P (SP), NK1-R, neuropeptide Y (NPY), and IL-6. Following OTM, sympathectomized (SCGx) rats had significantly more root resorption (P<0.01) and SP-immunoreactive (IR) fibers (P=0.01) in the compressed periodontal ligament (PDL) compared with control rats. There was a significant decrease in recruitment of CD43+ cells in the pulp after OTM in SCGx rats compared with control rats (P=0.02). An upregulation of NK1-R immunoreactivity was observed surrounding the hyalinized tissue, and an increase in the number of NK1-R IR cells and density of SP-IR fibers was present in first molar pulp of all rats. NPY-IR fibers were absent in the compressed PDL of SCGx and control rats. Thus, OTM induces remodeling not only around the periodontal tissues, but also in the dental pulp. The sympathetic nerves have an inhibitory effect on hard tissue resorption and a stimulatory effect on CD43+ cell recruitment after OTM.

NK1, NK2, NK3 and CGRP1 receptors identified in rat oral soft tissues, and in bone and dental hard tissue cells

The distribution of the tachykinin receptors neurokinin-1 (NK1), neurokinin-2 (NK2) and neurokinin-3 (NK3), and the calcitonin gene-related peptide-1 (CGRP1) receptor were examined in rat teeth and tooth-supporting tissues by immunohistochemical methods and light and confocal microscopy. Western blot analysis was performed to identify the NK1- and the CGRP1-receptor proteins in the dental pulp. The results showed that odontoblasts and ameloblasts, cementoblasts and cementocytes, osteoblasts and osteocytes are all supported with the tachykinin receptors NK1 and NK2, but a distinct, graded cellular labeling pattern was demonstrated. The ameloblasts were also positive for CGRP1 receptor. Blood vessels in oral tissues expressed the tachykinin receptors NK1, NK2 and NK3, and the CGRP1 receptor. Both gingival and Malassez epithelium were abundantly supplied by NK2 receptor. Pulpal and periodontal fibroblasts demonstrated NK1 and NK2 receptors. Western blot analysis identified both the NK1- and the CGRP1-receptor proteins in the dental pulp. These results clearly indicate that the neuropeptides substance P, neurokinin A, neurokinin B and CGRP, released from sensory axons upon stimulation, directly modulate the function of the different types of bone and dental hard tissue cells, and regulate functions of blood vessels, fibroblasts and epithelial cells in oral tissues.

Prodromal herpes zoster--a diagnostic challenge in endodontics

This case report highlights the diagnostic challenge that herpes zoster represents if pain develops in the prodromal stage. A 58-year-old male presented with pain in the left maxilla. The symptoms had lasted for 7 months. The first premolar had been extracted soon after the onset, and the second premolar root filled shortly thereafter. Symptoms were experienced as sudden pain attacks lasting for several hours and analgesics gave some pain relief. Clinical examination showed that the second premolar was tender to percussion. No sinus tract or swelling were present. Radiographic examination showed previously root-filled second premolar and first molar teeth, and no evidence of apical pathosis. Due to the uncertainty about the quality of the root filling in the second premolar and incomplete root filling in the first molar, retreatment was started prior to prosthetic treatment in the region. The pain continued and became more intense during the treatment. A diagnosis of herpes zoster was determined, when an acute attack with oedema and vesicles occurred, 2 months after retreatment was started. In the present case, therefore, the primary attack presented itself after months and the herpes zoster diagnosis could not be made until then. points. Key learning points. * A long lasting prodromal stage is an unusual event. * Symptoms combined with inadequate technical standard of root fillings may confuse the diagnostics. * No available data support or suggest the use of antiviral treatment as a diagnostic tool.

Periapical changes following root-canal treatment observed 20-27 years postoperatively

AIM

The aim of the present study was to identify periapical changes 20-27 years after root-canal treatment.

METHODOLOGY

The periapical condition of 265 roots filled by undergraduate students was evaluated in two series of intraoral radiographs taken 10-17 and 20-27 years after treatment. Roots (72) not recorded with a normal periapical situation on both occasions by two observers, were re-evaluated by other two examiners, separately and jointly. Final decisions about diagnoses were made by all four examiners. A strict definition was used for the identification of cases with an unfavourable outcome.

RESULTS

Favourable outcomes were observed in 6.4% of the roots that had radiolucencies at the 10-17-year follow-up. Periapical radiolucencies after 20-27 years appeared in 1.5% of all other roots. The radiographic failure frequency for the total material was 4.9%. The percentage of cases with normal periapical findings at the final follow-up was 86.4%, whilst 8.7% were recorded with increased width of the apical periodontal space. Delayed healing owing to surplus root-filling material explained nearly all of the cases with favourable outcome assessed many years after treatment.

CONCLUSIONS

Late periapical changes, with more successes than failures, were recorded when a 10-17-year follow-up period after root-canal treatment was extended for another 10 years.

Diagnosing periapical lesions--disagreement and borderline cases

AIM

The aim of this paper is to present a selection of disagreement and borderline cases from a methodological study on the radiographic diagnosis of periapical disease.

METHODOLOGY

Thirty-two roots, 12% of the material in an earlier study, were subjected to joint discussion because of diagnostic problems. The aim was consensus. Six cases representing different teeth/roots illustrating typical problems are presented.

RESULTS

The varying morphology of apical areas and varying density of surrounding bone present a number of challenges. Even so, the joint discussion resulted in an agreement for all the cases. Twenty-five diagnoses were established and seven cases were not diagnosed owing to substandard radiographs.

CONCLUSION

A detailed analysis of the periodontal ligament space, the lamina dura, trabecular pattern and bone marrow spaces is mandatory for the radiographic diagnosis of periapical disease

Incompletely fractured teeth associated with diffuse longstanding orofacial pain: diagnosis and treatment outcome

AIM

To evaluate the diagnostic value of different clinical findings, and analyse the symptoms experienced from teeth with incomplete dentinal fractures in patients with diffuse orofacial pain. Secondly, to present the outcome of different treatment modalities in these patients.

METHODOLOGY

Thirty-two patients, referred to the teaching clinic at the Faculty of Dentistry, University of Bergen, with poorly localized orofacial pain, were finally diagnosed with 46 incompletely fractured teeth. The distribution and pattern of pain was thoroughly recorded for each patient. The final diagnosis, incompletely fractured tooth, was obtained after removal of fillings and direct inspection of possible fracture lines.

RESULTS

Many of the patients had suffered diffuse orofacial pain for more than 1 year, and had earlier consulted dental and medical expertise. Direct inspection of fracture lines, combined with staining solution and transillumination proved to be the best diagnostic tools. The longer the duration of pain before the diagnosis of an incompletely fractured tooth was established, the more diffuse was the distribution of pain. Endodontic or restorative treatment relieved the symptoms in 90% of the patients, whilst persisting symptoms in 10% were considered part of an orofacial pain complex of obscure aetiology.

CONCLUSION

This study shows that the diagnosis of the incompletely fractured teeth in patients with longstanding diffuse orofacial pain symptoms are time consuming and represent a diagnostic problem. With appropriate endodontic and/or restorative treatment, symptoms were relieved in the majority of cases.

Long-term reliability and observer comparisons in the radiographic diagnosis of periapical disease

AIM

The aim of this study was to evaluate and compare the long-term diagnostic consistency of two examiners, an endodontist and a radiologist, and to make comparisons with findings recorded by an observer with more recent scientific and clinical experience in endodontics.

METHODOLOGY

Three groups, each consisting of 20 full mouth series of intraoral radiographs, with 79, 93 and 85 endodontically-treated roots, respectively, were successively evaluated for periapical disease. Evaluations were at first performed separately by the three observers. Disagreement and difficult, borderline cases were subjected to joint evaluation. Intra- and interexaminer comparisons were made. For two of the observers the observations were compared with findings recorded several years before for the same cases in the same radiographs.

RESULTS

The intra- and interobserver long-term reliability of the two original examiners resulted in 83% overall agreement, the kappa values were 0.54, 0.57 and 0.53. Comparisons between all three observers disclosed 82%, 85% and 86% agreement and kappa values 0.55, 0.58 and 0.60. The joint evaluations and decisions did not indicate a dominating influence from any of the observers.

CONCLUSIONS

The long-term reliability of the two original observers was judged as being satisfactory. All three observers judged the overall disease status of the material in the same way. The joint discussions of selected cases might reduce observer variation to an acceptable level, avoid a number of false recordings and increase the reliability and validity of the findings.

Upregulation of growth associated protein 43 expression and neuronal co-expression with neuropeptide Y following inferior alveolar nerve axotomy in the rat

Growth associated protein 43 (GAP 43) is an acidic membrane-bound phosphoprotein produced at high levels in developing and regenerating neurons. It is a substrate for protein kinase C and suggested to be involved in calcium-regulated release of axonal vesicular-contained neurotransmitters. Expression of GAP 43 has been demonstrated in the uninjured cat dental pulp which receives its sensory nerve supply from the trigeminal ganglion. The aim of this study was a detailed mapping of the spatial and time-dependent expression of GAP 43 and co-expression of neuropeptide Y (NPY) in dental peripheral target tissues and trigeminal neurons subsequent to inferior alveolar nerve (IAN) axotomy in rats, as background for later low-level laser studies. Unilateral sectioning of IAN, resulting in an almost complete loss of sensory nerve fibers in the ipsilateral dental pulp of the first molar, was performed. The avidin biotin complex (ABC) method was used to evaluate peripheral changes in GAP 43 expression at 4, 7 and 10 days. Ganglionic changes in GAP 43 and co-localization of neuronal NPY expression was examined at 4, 10 and 21 days using either the ABC method or double immunofluorescence labelling techniques and confocal microscopy. Axotomy resulted in an early upregulation and change in the peripheral distribution of GAP 43 in nerve profiles already 4 days post IAN axotomy suggesting a Schwann cell origin. Ten days post axotomy a pronounced upregulation of GAP 43 immunoreactivity could be demonstrated in neurons located in the mandibular region of the trigeminal ganglion, compared to the contralateral uninjured side. The peripheral and ganglionic upregulation of GAP 43 continued to persist at 21 days. A concomitant time-delayed shift and co-expression of NPY was demonstrated throughout in the GAP 43-upregulated ganglion cells 10 days post axotomy. Furthermore, confocal microscopy indicated that the intraneuronal distribution of NPY and upregulated GAP 43 expression showed a similar conformity and distribution in both perinuclear regions and cell periphery.

Lateral breakdown of nonendodontic origin adjacent to maxillary left incisors

CASE REPORT

A 16-year-old female presented with a labial fistula located between the central and lateral left maxillary incisors. The teeth had normal colour, responded positively to pulp testing, demonstrated negative percussion tests and had no evidence of periodontal pockets. The patient reported no history of trauma, but mentioned that she had received orthodontic treatment. Radiographic examination showed bone loss between these two teeth. Explorative surgery followed by antibiotic treatment was performed, but a fistula reappeared after 22 months. Surgical retreatment combined with antibiotic treatment resulted in gradual healing over a three-year period. No root canal treatment was performed. Aetiological considerations connected to tissue injury and inflammation are discussed. Inflammation induced disturbances in local homeostasis may possibly explain the lateral breakdown of bone. Such areas of reduced resistance may, under unfavourable conditions, be infected by blood-born pathogens. Information about such aberrant cases is important in endodontic decision making.

Neurokinin-1 receptor expression in the mature dental pulp of rats

Substance P induces inflammatory reactions in peripheral tissues including the dental pulp, but its regulatory effects in target tissues are dependent on receptor signalling. Here the expression of the substance-P receptor neurokinin-1 (NK1) in the mature molar pulp of the rat was examined in order to localize the main target areas for substance P. A polyclonal antibody directed against the C-terminal of the receptor was used, and immunohistochemistry was performed by the avidin-biotin peroxidase complex method. The results showed that the NK1 receptor was intensely expressed along vessel-like structures in the odontoblast and subodontoblast layer. A granulated and diffusely distributed NK1-receptor labelling was found along larger blood vessels in the root pulp and pulp proper. NK1 receptor-positive cells were frequently observed in the cell-rich zone beneath the odontoblast layer. The results indicate that, in the mature rat molar pulp, the main targets for substance P acting through the NK1 receptors are tissues related to blood vessels in the odontoblast and subodontoblast area. Furthermore, the expression of NK1 receptors on cells located in the subodontoblast area could indicate that substance P also affects cell functions in this area.

Root resorption and apical breakdown during orthodontic treatment of a maxillary lateral incisor with dens invaginatus

A 13-year-old girl was referred for endodontic treatment of a maxillary right lateral incisor with root resorption and apical radiolucency after orthodontic treatment. Radiographically the tooth had an invagination canal (Oehlers' Type III) and responded positively to pulp testing. The invagination canal extending to the lateral resorption was opened. Vital bleeding tissue was found, and the canal was cleaned and obturated. The pulp in the main root canal remained vital. The radiolucent lesion gradually decreased during the 3-year follow-up. The bone resorption seen here, despite vital tissue in the invagination canal, was probably due to osteoclastic activity caused by a low grade chronic infection, influenced by an injury-induced inflammation in the periodontium during orthodontic treatment.

Nerve fibers immunoreactive to calcitonin gene-related peptide, substance P, neuropeptide Y, and dopamine beta-hydroxylase in innervated and denervated oral tissues in ferrets

The effect of sensory and sympathetic denervation on the localization and distribution of nerve fibers immunoreactive (IR) to calcitonin gene-related peptide (CGRP), substance P (SP), neuropeptide Y (NPY), and dopamine beta-hydroxylase (DBH) was studied in the dental pulp, periodontal ligament (PDL), and gingiva in ferrets. Unilateral axotomy was performed by resection of the inferior alveolar nerve (IAN) 10 days before the experiment (Group 1); sympathectomy, by unilateral removal of the cervical ganglion 5 days before the experiments (Group 2). Immunohistochemistry was performed on free-floating sections by the avidin-biotin-peroxidase technique. A considerably higher density of sensory fibers IR to CGRP and SP was found in the dental pulp than in PDL and gingiva. The majority of pulpal fibers were located in the walls of blood vessels. A subodontoblastic network of fibers IR to CGRP and SP was lacking in incisors and canines and was found only in the coronal pulp in premolars and molars. Sympathetic fibers were sparsely distributed in the pulp, and they were mainly confined to large vessels running centrally in the root pulp as well as the larger vessels in apical PDL and alveolar bone. Gingiva was well supplied with CGRP- and SP-IR nerves, and some NPY and DBH fibers were located in association with larger vessels. Round cell-like structures within the basal part of the epithelium were CGRP-IR. Axotomy induced a complete loss of CGRP- and SP-IR fibers in the anterior part of the jaws, whereas sympathectomy caused a reduction, but not a total loss, of NPY- and DBH-IR nerves. It is concluded that, except for some distributional differences, the oral tissues in the ferret have an abundant sensory innervation similar to that found in other species.

Coexpression of vasoactive intestinal polypeptide and substance P in reinnervating pulpal nerves and in trigeminal ganglion neurones after axotomy of the inferior alveolar nerve in the rat

The effect of this axotomy on the expression of vasoactive intestinal polypeptide (VIP) in trigeminal ganglion neurones and nerve fibres in the first molar was examined immunohistochemically 3 weeks postsurgically in rats. A distinct upregulation of VIP-like immunoreactivity was found in 3 to 4% of the neurones (mean dia., 20.9 +/- 0.45 microns; mean cross-sectional area, 367 +/- 13.2 microns 2) in the mandibular region after axotomy. An almost complete coexpression was registered in neurones upregulated for VIP and growth-associated protein 43. Coexpression of VIP and substance P (SP) was found in a small number of the immunoreactive (IR) small-sized neurones, mainly in those in which VIP and SP were both weakly immunoreactive. In the uninjured ganglion, weakly labelled VIP-positive granules were frequently traced at high magnification in the cytoplasm of small neurones. No VIP-IR fibres were found in the control molar pulp, except for a few in the root pulp near the apex. However, 3 weeks after axotomy, a number of VIP-containing nerve fibres were found in the molar pulp and apical periodontium. Coarse VIP-IR fibres directed towards the odontoblast layer were a common finding. In some of these fibres VIP was shown to colocalize with SP. These results indicate that VIP is clearly expressed and transported in regenerating primary afferent neurones after axotomy of the inferior alveolar nerve.

Dental innervation: functions and plasticity after peripheral injury

Oral tissues including the periodontal ligament, gingiva, and tooth pulp have a relatively dense sensory innervation and a rich vascular supply. Teeth and supporting tissues are susceptible to tissue injury and inflammation, partly due to lack of collateral blood and nerve supply and to their low compliance. This review focuses on dental nerve functions and adaptive changes in the trigeminal ganglion and tooth pulp after peripheral injuries. An overview of the peptidergic innervation of oral tissues is presented, followed by a discussion of plasticity in neuropeptide expression in trigeminal peripheral neurons after local insults to teeth and peripheral nerve injuries. The functional implications of these adaptive changes are considered, with special reference to nerve regeneration, inflammation, and hemodynamic regulation.

Effect of intermittent long-lasting electrical tooth stimulation on pulpal blood flow and immunocompetent cells: a hemodynamic and immunohistochemical study in young rat molars

Release of sensory neuropeptides after stimulation of afferent nerve fibers has previously been shown to induce vasodilation and increased vascular permeability in the dental pulp, a condition recognized as neurogenic inflammation. In the present study a possible role for the sensory neuropeptides in transendothelial migration of immunocompetent cells was investigated. The dental pulp is an isolated tissue densely innervated with sensory fibers containing neuropeptides, and following electrical stimulation of the crown, the effect on pulpal blood flow and immunocompetent cells can be studied in a noninvasive model. A laser Doppler flowmeter was used to measure relative changes in pulpal blood flow during long-lasting intermittent stimulation of innervated and denervated rat first molars. In the innervated teeth, stimulation promptly increased pulpal blood flow by on average 45% at the start of the experiment, whereas almost no blood flow increase was recorded after 4 to 5 h stimulation. Surgical sectioning of the inferior alveolar nerve abolished blood flow increase upon stimulation. After stimulation, a quantitative analysis of CD43+, CD4+, CD11+, and I-A antigen-expressing cells was performed, and the effect of stimulation on calcitonin gene-related peptide (CGRP)-immunoreactive and substance P (SP)-immunoreactive (IR) nerve fibers was studied. Immunohistochemistry was performed by the avidin-biotin peroxidase method. Stimulation resulted in an almost complete depletion of CGRP- and SP-IR nerve fibers in the first molar pulp, whereas nerve fibers in the gingiva and neighboring teeth were unaffected. A significant increase in the number of CD43+ cells was found in the innervated tooth after stimulation compared to the stimulated denervated (P < 0.01) and unstimulated control (P < 0.05) first molars. For I-A antigen-expressing cells a significant increase (P < 0.05) was found between the innervated stimulated and unstimulated control, but not between the innervated and denervated stimulated first molars. Hence, from the present experiment it is concluded that the pulpal nerves participate in and facilitate transendothelial migration of CD43+ cells during acute neurogenic inflammation.

Neuropeptide Y expression in the trigeminal ganglion and mandibular division of the trigeminal nerve after inferior alveolar nerve axotomy in young rats

Neuropeptide Y (NPY) is a 36-amino-acid peptide residing in sympathetic nerve terminals, originating from the superior cervical ganglion in oral tissues. NPY exerts vasoconstrictor action together with noradrenalin and has been found to inhibit the release of neurotransmitters from primary afferent fibers. During regeneration of the axotomized inferior alveolar nerve (IAN), NPY-immunoreactive (IR) nerve fibers have been shown in the odontoblast layer and dentin, an area normally innervated by afferent nerve fibers. The dynamic shift in neuropeptide expression in the trigeminal ganglion and in the dental pulp was studied by immunohistochemistry 1, 2, 3, and 8 weeks after IAN axotomy. In the ipsilateral first mandibular molar a temporal loss of pulpal sensory nerves lasting for approximately 1 week was found after axotomy. An upregulation of NPY was shown in neurons located in the mandibular area of the trigeminal ganglion, concomitant to a reduction in number of neurons expressing substance P (SP). To study an alternate and possible trigeminal origin of some of the peripheral nerve fibers IR to NPY in the dental pulp, double immunofluorescence labeling was performed for NPY and calcitonin gene-related peptide (CGRP). Coexistence of NPY and CGRP was shown in neurons located in the trigeminal ganglion and in nerve fibers in the tooth pulp during IAN regeneration. Furthermore, retrograde tracing with Fluorogold revealed NPY-IR neurons projecting to the first molar pulp 3 weeks after axotomy. Hence, we conclude that after IAN axotomy NPY is produced in trigeminal ganglion neurons and transported in afferent regenerating fibers to the dental pulp. These results add further evidence for a plasticity in peptide transcription in sensory neurons after nerve injury and indicate a trigeminal origin of at least some of the pulpal NPY-IR fibers during nerve regeneration.

Effect of inferior alveolar nerve axotomy on immune cells and nerve fibres in young rat molars

Denervation has been a useful approach to the investigation of interactions between nerve fibres and the pulp-dentine complex. Information on the immunological implications of axotomy is still lacking. The effect of axotomy on CD43+, CD4+, CD11b+ and I-A antigen-expressing cells in both the distal segment of the cut inferior alveolar nerve and in the first molar pulp of young rats was evaluated. Nerve fibres immunoreactive to protein gene product (PGP) 9.5, the neuropeptides substance P and calcitonin gene-related peptide (CGRP), and neuropeptide Y were visualized also by use of the avidin-biotin peroxidase complex method. Recruitment of macrophages was found in the distal segment of the sectioned inferior alveolar nerve 2 days after axotomy, with a further increase in number during the 6-day observation period. However, in the dental pulp, the number of CD43+, CD4+, CD11b+ and I-A antigen-expressing cells was almost unaffected. An almost complete sensory denervation of the first mandibular molar pulp was obtained 2 days after axotomy. After 6 days, the mesial part of the coronal pulp still remained denervated, while regenerated nerve fibres had reached both the root pulp and the distal part of the coronal pulp. Nerve fibres immunoreactive to neuropeptide Y were slightly reduced in density 2 days after axotomy, and after 6 days the localization of neuropeptide Y-immunoreactive fibres was changed compared to the control, with fibres also distributed in the odontoblast layer close to dentine. Hence, following axotomy in young rats, an almost complete sensory denervation is achieved in the first molar, whereas nerve fibres immunoreactive to neuropeptide Y change their distribution pattern, with fibres located close to the dentine after 6 days. Due to the almost unchanged number and distribution of immunocompetent cells in the pulp after axotomy, the young rat molar pulp may represent a suitable and useful experimental model to study neuro-immune interactions.

Recruitment of immunocompetent cells after dentinal injuries in innervated and denervated young rat molars: an immunohistochemical study

The dental pulp represents a peripheral end-organ deprived of a collateral nerve supply. After inferior alveolar nerve (IAN) axotomy, rat molar pulp is denervated over a period of at least 6 days. Therefore, rat molar pulp was used as an experimental model to study the effect of sensory nerve fibers on influx of immunocompetent cells after dentinal injury. In the present study we performed a quantitative analysis of CD43+, CD4+, CD11b+, and I-A antigen-expressing cells subjacent to dentinal cavities in denervated and innervated first mandibular molars. For visualization of nerve fibers, antibodies to protein gene product (PGP) 9.5, the sensory neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP), and the sympathetic neuropeptide Y (NPY) were used. Immunohistochemistry was performed by the avidin-biotin-peroxidase method. In the innervated teeth, a correlation between increased sensory nerve density and influx of immunocompetent cells was found. Compared to the contralateral innervated molars, a significant reduction in recruitment of immunocompetent cells was found in the denervated pulp tissue subjacent to the dentinal cavities. The rat molar represents a unique model to illustrate the influence of sensory nerves and neuropeptides on inflammation and recruitment of immunocompetent cells.

Nerve fibres and cells immunoreactive to neurochemical markers in developing rat molars and supporting tissues

The distribution of nerve fibres immunoreactive to calcitonin gene-related peptide (CGRP), substance P (SP) and neuropeptide Y (NPY) was compared to the general neurochemical markers for nerves and neuroendocrine cells protein gene product 9.5 (PGP 9.5) and neurone-specific enolase (NSE), by use of the avidin-biotin peroxidase complex method in developing dental structures in rats aged 13 to 27 days. A substantially greater part of the nerve fibres was immunoreactive to CGRP and SP than to NPY. In the bell stage, nerve fibres immunoreactive to PGP 9.5, CGRP and SP were found in the dental follicle but not in the dental papilla and stellate reticulum. In the advanced bell stage, after initiation of dentine and enamel formation, PGP 9.5, CGRP- and SP-immunoreactive fibres were found in the dental papilla, while the first NPY-immunoreactive fibres were observed in the papilla when root formation started. Concomitant with the beginning of root development, a subodontoblastic nerve plexus was gradually formed and PGP 9.5-, CGRP- and SP-immunoreactive fibres were found within the dentinal tubules. From the start of root formation, CGRP-, SP- and NPY-immunoreactive nerves were shown in the developing periodontal ligament, although a mature distribution pattern was not observed until root formation was nearly completed. Ameloblasts, odontoblasts and cell-like structures in the outer enamel epithelium and within the dental lamina were PGP 9.5-immunoreactive at the bell stage. As the tooth matured, the immunolabelling gradually decreased, but was still present in some odontoblasts after tooth eruption. NSE-immunoreactive, cell-like structures were found in the periphery of the dental follicle, and persisted close to alveolar bone in the periodontal ligament when the tooth reached occlusion. Hence, it may be concluded that sensory nerves containing SP and CGRP are present in the pulp in advance of sympathetic nerves immunoreactive to NPY.