Regeneration of the cementum and periodontal ligament using local BDNF delivery in class II furcation defects.

Periodontal furcation defects are usually addressed by the placement of a physical barrier which may limit the regenerative potential of periodontal wounds. This study morphometrically quantified the regenerative effect of brain-derived neurotrophic factor (BDNF) in furcation defects in a non-human primate model. Grade II furcation defects (with and without induced inflammation prior to surgery) were created on the first and second molars of eight non-human primates. Defects were treated with open flap debridement and subsequently filled with either: Group A; BDNF (500 µg mL-1 ) in high-molecular weight-hyaluronic acid (HMW-HA), Group B; BDNF (50 µg mL-1 ) in HMW-HA, Group C; HMW-HA acid only, Group D; unfilled defect, or Group E; BDNF (500 µg mL-1 ) in saline. Periodontal wound healing was observed every 2 weeks by computed-tomography. At 11 weeks all animals were sacrificed and maxillary and mandibular block biopsies were referred for nondecalcified histology. Linear measurements of new cementum (cellular and acellular) and periodontal ligament (PDL) formation were performed. Computerized-tomography reconstruction and software quantification demonstrated successful bone fill for all groups. However, histometric assessment demonstrated significantly higher level of total periodontal regeneration for the 500 µg mL-1 BDNF HMW-HA relative to all other groups. No significant differences in cementogenesis were observed among groups. Significantly higher acellular cementum formation was observed for sites where inflammation was not induced prior to surgical procedures. While all groups experienced similar bone fill and cementogenesis, the 500 µg mL-1 BDNF HMW-HA appeared to most effectively repair PDL (minimum increase of ∼22% relative to all groups; over 200% relative to unfilled defects). © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1611-1617, 2018.

GDNF From Human Periodontal Ligament Cells Treated With Pro-Inflammatory Cytokines Promotes Neurocytic Differentiation of PC12 Cells.

Glial cell line-derived neurotrophic factor (GDNF) is known to mediate multiple biological activities such as promotion of cell motility and proliferation, and morphogenesis. However, little is known about its effects on periodontal ligament (PDL) cells. Recently, we reported that GDNF expression is increased in wounded rat PDL tissue and human PDL cells (HPDLCs) treated with pro-inflammatory cytokines. Here, we investigated the associated expression of GDNF and the pro-inflammatory cytokine interleukin-1 beta (IL-1ß) in wounded PDL tissue, and whether HPDLCs secrete GDNF which affects neurocytic differentiation. Rat PDL cells near the wounded area showed intense immunoreactions against an anti-GDNF antibody, where immunoreactivity was also increased against an anti-IL-1ß antibody. Compared with untreated cells, HPDLCs treated with IL-1ß or tumor necrosis factor-alpha showed an increase in the secretion of GDNF protein. Conditioned medium of IL-1ß-treated HPDLCs (IL-1ß-CM) increased neurite outgrowth of PC12 rat adrenal pheochromocytoma cells. The expression levels of two neural regeneration-associated genes, growth-associated protein-43 (Gap-43), and small proline-rich repeat protein 1A (Sprr1A), were also upregulated in IL-1ß-CM-treated PC12 cells. These stimulatory effects of IL-1ß-CM were significantly inhibited by a neutralizing antibody against GDNF. In addition, U0126, a MEK inhibitor, inhibited GDNF-induced neurite outgrowth of PC12 cells. These findings suggest that an increase of GDNF in wounded PDL tissue might play an important role in neural regeneration probably via the MEK/ERK signaling pathway. J. Cell. Biochem. 118: 699-708, 2017. © 2016 Wiley Periodicals, Inc.

The Role of a Platelet Lysate-Based Compartmentalized System as a Carrier of Cells and Platelet-Origin Cytokines for Periodontal Tissue Regeneration.

Currently available clinical therapies are not capable to regenerate tissues that are lost by periodontitis. Tissue engineering can be applied as a strategy to regenerate reliably the tissues and function of damaged periodontium. A prerequisite for this regeneration is the colonization of the defect with the adequate cell populations. In this study, we proposed a bilayered system composed of (1) a platelet lysate (PL)-based construct produced by crosslinking of PL proteins with genipin (gPL) for the delivery of rat periodontal ligament cells (rat-PDLCs); combined with (2) an injectable composite consisting of calcium phosphate cement incorporated with PL-loaded poly(d, l-lactic-co-glycolic acid) microspheres. This system was expected to promote periodontal regeneration by the delivery of adequate progenitor cells and providing a stable system enriched with adequate cytokines and growth factors for the orchestration of tissue regrowth in periodontal defects. The bilayered system was tested in a three-wall intrabony defect in rats and the healing of periodontal tissue was assessed 6 weeks after surgery. Results showed that the bilayered system was able to promote the regrowth of functional periodontal tissues, both with (cells + gPL) and without the loading of PDLCs (gPL). Significant connective tissue attachment (45.0 ± 15.0% and 64.0 ± 15.0% for gPL and cells + gPL group, respectively) and new bone area (33.8 ± 21% and 21.3 ± 3% for gPL and cells + gPL group, respectively) were observed. Nevertheless, rat PDLCs delivered with gPL construct in the defect area were hardly visible 6 weeks after surgery and did not contribute for the regeneration of new periodontal tissue. Overall, our findings show that the bilayered system promotes the stabilization of PL proteins on the root surface and has a positive effect in the repair of periodontal tissues both in quality and in quantity.

Cementum and Periodontal Ligament Regeneration.

The unique anatomy and composition of the periodontium make periodontal tissue healing and regeneration a complex process. Periodontal regeneration aims to recapitulate the crucial stages of wound healing associated with periodontal development in order to restore lost tissues to their original form and function and for regeneration to occur, healing events must progress in an ordered and programmed sequence both temporally and spatially, replicating key developmental events. A number of procedures have been employed to promote true and predictable regeneration of the periodontium. Principally, the approaches are based on the use of graft materials to compensate for the bone loss incurred as a result of periodontal disease, use of barrier membranes for guided tissue regeneration and use of bioactive molecules. More recently, the concept of tissue engineering has been integrated into research and applications of regenerative dentistry, including periodontics, to aim to manage damaged and lost oral tissues, through reconstruction and regeneration of the periodontium and alleviate the shortcomings of more conventional therapeutic options. The essential components for generating effective cellular based therapeutic strategies include a population of multi-potential progenitor cells, presence of signalling molecules/inductive morphogenic signals and a conductive extracellular matrix scaffold or appropriate delivery system. Mesenchymal stem cells are considered suitable candidates for cell-based tissue engineering strategies owing to their extensive expansion rate and potential to differentiate into cells of multiple organs and systems. Mesenchymal stem cells derived from multiple tissue sources have been investigated in pre-clinical animal studies and clinical settings for the treatment and regeneration of the periodontium.

The clinical meaning of external cervical resorption in maxillary canine: transoperative dental trauma

External Cervical Resorption in maxillary canines with pulp vitality is frequently associated with dental trauma resulting from surgical procedures carried out to prepare the teeth for further orthodontic traction. Preparation procedures might surgically manipulate the cementoenamel junction or cause luxation of teeth due to applying excessive force or movement tests beyond the tolerance limits of periodontal ligament and cervical tissue structures. Dentin exposure at the cementoenamel junction triggers External Cervical Resorption as a result of inflammation followed by antigen recognition of dentin proteins. External Cervical Resorption is painless, does not induce pulpitis and develops slowly. The lesion is generally associated with and covered by gingival soft tissues which disguise normal clinical aspects, thereby leading to late diagnosis when the process is near pulp threshold. Endodontic treatment is recommended only if surgical procedures are rendered necessary in the pulp space; otherwise, External Cervical Resorption should be treated by conservative means: protecting the dental pulp and restoring function and esthetics of teeth whose pulp will remain in normal conditions. Unfortunately, there is a lack of well-grounded research evincing how often External Cervical Resorption associated with canines subjected to orthodontic traction occurs.

A reabsorção cervical externa em caninos superiores com vitalidade pulpar em sua quase totalidade está associada a traumatismo dentário decorrente de procedimentos cirúrgicos associado à preparação desse dente para ser tracionado ortodonticamente. Nessa preparação pode se manipular cirurgicamente a junção amelocementária ou luxar o dente com forças excessivas ou com testes de movimentação além dos limites de tolerância estrutural do ligamento periodontal e tecidos cervicais. A exposição dentinária na junção amelocementária é o estopim para se iniciar uma reabsorção cervical externa a partir de uma inflamação induzida na região seguida de reconhecimento antigênico das proteínas dentinárias. A reabsorção cervical externa é indolor, não induz pulpites e tem uma evolução lenta. Em geral, a lesão está associada e recoberta por tecidos moles gengivais que mantêm, por longos períodos, os aspectos clínicos normais, induzindo diagnósticos tardios, quando o processo se aproxima dos limites pulpares. O tratamento endodôntico está indicado apenas em função de procedimentos operatórios que se fazem necessários no espaço pulpar; caso contrário, a reabsorção cervical externa deve ser tratada de forma conservadora, protegendo a polpa dentária e restaurando a função e estética do dente que permanecerá com sua polpa normal. Infelizmente, não sabemos, com base em pesquisas de casuísticas bem estabelecidas, qual é a frequência da reabsorção cervical externa associada a caninos ortodonticamente tracionados.

Microscopic evaluation of induced tooth movement after subluxation trauma: an experimental study in rats

OBJECTIVE: The objective of this study was to assess the histological alterations that occurred in the periodontal area of rat molars submitted to induced tooth movement (ITM) right after an intentional trauma (subluxation). METHODS: Forty adult male Wistar rats (Rattus norvegicus albinus) were selected. The animals were divided into eight groups (n = 5), according to the combination of variables: Group 1 - control (neither trauma nor ITM); Group 2 - ITM; Groups 3, 4, 5 and 6 - dentoalveolar trauma groups corresponding, respectively, to 1, 3, 8 and 10 days after trauma; Groups 7 and 8 - the animals' molars were subjected to a 900 cN impact and, one and three days after the trauma event, tooth movement was induced. The rats' maxillary first molars were mesially moved during seven days with a closed coil (50 cN). After the experimental period of each group, the animals were sacrificed by anesthetic overdose and the right maxillas were removed and processed for histological analysis under light microscopy. RESULTS: In the animals of group 3, 4, 5 and 6, the histological alterations were not very significant. Consequently, the effect of induced tooth movement right after a subluxation event (groups 7 and 8) was very similar to those described for Group 2. CONCLUSION: There was no difference in the quality of periodontal repair when ITM was applied to teeth that had suffered a subluxation trauma. .

OBJETIVO: avaliar as alterações histológicas ocorridas na área periodontal de molares de ratos submetidos à movimentação dentária induzida (MDI), logo após um trauma intencional (subluxação). MÉTODOS: quarenta ratos Wistar machos adultos (Rattus norvegicus albinus) foram selecionados. Os animais foram divididos em oito grupos (n = 5), de acordo com a combinação das variáveis: Grupo 1 - controle (sem trauma e sem MDI); Grupo 2 - MDI; Grupos 3, 4, 5 e 6 - grupos de trauma dentoalveolar correspondendo, respectivamente, para 1, 3, 8 e 10 dias após o trauma; Grupos 7 e 8 - os molares murinos foram submetidos a um impacto de 900cN e, de um e três dias após o evento trauma, o movimento do dente foi induzido. Os primeiros molares superiores dos animais foram movidos mesialmente durante sete dias, com uma mola fechada (50cN). Após período experimental de cada grupo, os animais foram sacrificados por overdose anestésica e as maxilas direitas foram removidas e processadas para análise histológica qualitativa. RESULTADOS: nos animais dos grupos 3, 4, 5 e 6, as alterações histológicas não foram muito significativas. Consequentemente, o efeito do movimento dentário induzido logo após um evento de subluxação (grupos 7 e 8) foi muito semelhante ao descrito para o grupo 2. CONCLUSÃO: não houve diferença na qualidade do reparo periodontal quando a MDI foi aplicada aos dentes que sofreram um trauma de subluxação. .

Coronal reconstruction following anterior teeth traumatism: multidisciplinary treatment.

This study describes how periodontology, endodontology, and dentistry were integrated for the coronal reconstruction of anterior teeth extensively destroyed by dental trauma. A 15-year-old girl suffered a bicycle accident that resulted in the fracture of teeth No. 8 and 9. Clinical and radiographic examinations confirmed coronal fracture in both teeth, in addition to compromised pulp vitality, invasion of the biologic periodontal space, and loss of coronal space due to mesialization of the neighboring teeth. The protocol consisted of endodontic treatment for the fractured teeth, periodontal surgery to augment the clinical crown and gingival recontouring, intracanal cementation of esthetic glass fiber posts, and coronal reconstruction with resin composite. At a longitudinal follow-up visit 1 year later, clinical and radiographic examinations revealed successful rehabilitation of the fractured teeth.

Histological and immunohistochemical analyses of the chronology of healing process after immediate tooth replantation in incisor rat teeth.

Dental tissues have special characteristics, and its regenerative capacity is noteworthy. However, understanding the circumstances that lead to regeneration is challenging. In this study, the chronology of the healing process after immediate replantation of rat incisor teeth was examined by histological and immunohistochemical analyses within a 60-day period. Thirty-six male Wistar rats had their maxillary right incisors extracted and replanted after 15 min in saline storage. The rats were sacrificed immediately 3, 7, 15, 28, and 60 days after replantation. The histological analysis showed rupture of the periodontal ligament and formation of a blood clot, which started being replaced by a connective tissue after 3 days. At 7 days, the gingival mucosa epithelium was reinserted and areas of root resorption could be seen. At 15 days, the periodontal ligament was repaired. At 3 days, the pulp presented an absence of the odontoblast layer, which started being replaced by a connective tissue. This tissue suffered gradual calcification, filling the root canal at 28 and 60 days. The root ends were closed. The immunohistochemical analysis revealed greater expression of OP, OPG, and RANK proteins in the initial periods (0 and 3 days), while TRAP expression predominated at 28 and 60 days (P < 0.05). In conclusion, in delayed tooth replantation, there is great new bone formation activity in the earlier periods of the repair process, while a predominance of bone resorption and remodeling is observed in the more advanced periods.

Clinical fracture site, morphologic and histopathologic characteristics of cemental tear: role in endodontic lesions.

INTRODUCTION: Clinical research regarding the clinical and histopathologic characteristics of cemental tear is limited in the endodontic literature. The objective of this study was to evaluate the morphology, apicocoronal location, and the histologic characteristics of cemental tear. METHODS: The material was collected during 1987-2009 and consisted of 54 teeth that were presented with cemental tears by histologic examination. To investigate the atypical prospects among the groups of each variable, a series of the Poisson χ(2) goodness-of-fit tests were conducted to test for a fit of a discrete, uniform distribution. RESULTS: Cemental tear occurred mainly in incisors (74.1%), proximal root surfaces (79.6%), male patients (74.1%), and patients older than 60 years (72.3%). They were noted often in the middle third of root (45.3%), but 41.5% of cemental tears were noted over the apical region. The morphology of cemental tear was either small/thin piece-shaped (77.4% cases) involving 1 root surface or U-shaped (22.6%) involving >1 root surface. The size of cemental tear had an average length of 3.8 mm, width of 2.2 mm, and thickness of 0.9 mm. The separations of cemental tears occurred at cementodentinal junction (77.6%) relative to cementum (22.4%). The adhered soft tissue was either granulation tissue (92.3%) or cyst (7.7%). CONCLUSIONS: Cemental tear mainly occurs in incisors of male and older persons. It is also popularly noted in the apical region mimicking an endodontic lesion and some with cystic change. Clinically, endodontists should know this disease entity, make accurate early diagnosis, and totally remove the cemental tear during apical surgery to improve the prognosis.

Dentists' level of knowledge of the treatment plans for periodontal ligament injuries after dentoalveolar trauma

This study investigated the level of knowledge held by dentists about the possible treatment plan procedures for periodontal ligament injuries after dentoalveolar trauma. A 5-item self-applied questionnaire was prepared with questions referring to the professional profile of the interviewees and to the treatment plan they would propose for periodontal ligament injuries secondary to dentoalveolar trauma. The questionnaires were filled out by 693 dentists attending the 23rd Annual Meeting of the Brazilian Society for Dental Research, and the data obtained were subjected to descriptive analysis. Either the chi-square test or Fisher's exact test was applied to assess associations among variables, at a 5 percent level of significance. The results revealed that dentists experienced difficulty in establishing a treatment plan for subluxation, and for extrusive, lateral and intrusive luxations. In general, holding a dental specialty degree had no influence on the knowledge about treatment plan procedures for the most severe injuries. It could be concluded that the dentists participating in this study, whether specialists or not, did not have sufficient knowledge to treat most of the periodontal ligament injuries resulting from dentoalveolar trauma adequately.

Effects of traumatic dental injuries to primary teeth on permanent teeth--a clinical follow-up study.

AIM: This study evaluated the prevalence of developmental sequelae to permanent teeth (DSP) after traumatic dental injuries to primary teeth (TDI-1) and their association with age, gender, type of injury, recurrence of injury and post-traumatic damage to primary teeth. MATERIALS AND METHODS: Dental records of 2725 children treated from February 1993 to December 2008 in a private pediatric dental clinic were examined. A total of 308 records had 412 primary teeth that sustained traumatic injuries. Age at the time of injury ranged from 4 months to 7 years. A chi-squared test and logistic regression were used for statistical analyses. RESULTS: One hundred forty-eight children (241 teeth) were followed up until the eruption of the permanent successor. The prevalence of DSP was 22.4%. Discoloration and hypoplasia were the most frequent abnormalities (74.1%), followed by eruption disorders (25.9%). Age at the time of TDI-1 was the only variable significantly associated with DSP. Sequelae were most prevalent among children who suffered an injury between 1 and 3 years of age. CONCLUSIONS: Children who sustain traumatic dental injuries should be followed up regularly for an early diagnosis and treatment of possible DSP.

Disruption of periodontal integrity induces expression of apin by epithelial cell rests of Malassez.

BACKGROUND AND OBJECTIVE: It has been suggested that epithelial cell rests of Malassez (ERM) may express enamel matrix proteins and play an important role in periodontal regeneration. Two novel proteins, apin (APIN) and amelotin (AMTN), produced by maturation-stage ameloblasts and junctional epithelium, have recently been identified. The objective of this study was to evaluate whether the ERM express APIN and AMTN under normal conditions and after periodontal challenge. MATERIAL AND METHODS: Gingivectomy and orthodontic tooth movement were carried out on the left side of the maxillae of rats. The control group included the untreated contralateral side of these animals and the maxillae of normal, untreated rats. Animals were sacrificed by intracardiac perfusion on days 3 and 5 after the experimental procedures and maxillary molars were decalcified and processed for paraffin embedding. Immunohistochemistry was used to evaluate the expression of various ameloblast products, including APIN, AMTN, ameloblastin (AMBN) and amelogenin (AMEL). RESULTS: At 3 and 5 days after periodontal challenge, ERM were more evident in the periodontal ligament along the root surface and in the root furcations. Immunodetection of APIN, but not of the other three proteins, was observed in the ERM following the disruption of periodontal integrity. No immunolabeling for APIN, AMTN, AMBN and AMEL was detected in the ERM under normal conditions. CONCLUSION: The expression of APIN at an early time-point following disruption of periodontal integrity suggests that this protein may be part of the cascade of events leading to the activation of ERM during periodontal healing and regeneration.

Autotransplantation of teeth in 215 patients. A follow-up study.

OBJECTIVE: To evaluate the success rate of autotransplantation of teeth in consecutive patients and to analyze factors affecting the outcome. MATERIALS AND METHODS: The subjects consisted of 215 consecutive patients (101 women and 114 men; aged 9.1-56.4 years, median age 15.2 years [P(10) = 11.4, P(90) = 19.7]) who had undergone transplantation of a total of 269 teeth, all by the same surgeon. In patients with multiple transplants, only the first transplant was included, to ensure that all transplanted teeth were independent units. The transplants were recorded as unsuccessful if the tooth had been extracted or was surviving but with root resorption or ankylosis. The interval between transplantation and final follow-up was a median 4.8 years (P(10) = 2.0, P(90) = 5.5) for successful transplants and a median of 2.4 years (P(10) = 0.4, P(90) = 7.7) for unsuccessful transplants. RESULTS: One-hundred seventy-five (81%) of the transplantations were recorded as successful and 40 (19%) as unsuccessful. Twenty-five teeth had been extracted and 15 had survived but did not fulfill the criteria for success. CONCLUSIONS: The success rate of 215 consecutively transplanted teeth was 81%. The highest success rate was for transplantation of premolars to the maxillary incisor region (100%). Complications at surgery such as difficult extraction, deviant root anatomy, or damaged root periodontium affected the outcome. During growth, a successful transplant preserves alveolar bone.

Cementum, pulp, periodontal ligament, and bone response after direct injury with orthodontic anchorage screws: a histomorphologic study in an animal model.

PURPOSE: To assess the histologic response of the periodontium, cementum, and pulp after intentional root injury with titanium screws. MATERIALS AND METHODS: Three female beagle dogs were used, and a total of 60 self-drilling/self-tapping miniscrews were manually inserted into the maxilla and the mandible with the intention of placement in close proximity or in direct contact with the roots. Digital radiographs were taken to select the sites with root injuries. After a 3-month period, the animals were killed and serial nondecalcified histologic sections were obtained with the miniscrew in place. RESULTS: Sixteen sites with significant root injury were identified. Four sites presented with cementum abrasion, 7 sites had dentin penetration up to 50% of the diameter of the screw, and 5 sites had miniscrew penetration into the pulp space with root fragmentation. At all damaged sites, continuous cementum repair could be observed. There was no evidence of external resorption or pulpal necrosis and/or inflammatory infiltrate. Point ankylosis was seen only in cases of severe injury with root fragmentation. Finally, woven bone was present along the miniscrew threads. CONCLUSION: When titanium screws penetrate root cementum or dentin, pulpal necrosis and/or inflammation was not observed at 12 weeks in an animal model. Cementum regenerates at every injury site, but ankylosis can occur with root fragmentation. Woven bone is present at the screw-bone interface even with root contact suggesting osteointegration.

Stem cell regulatory gene expression in human adult dental pulp and periodontal ligament cells undergoing odontogenic/osteogenic differentiation.

INTRODUCTION: During development and regeneration, odontogenesis and osteogenesis are initiated by a cascade of signals driven by several master regulatory genes. METHODS: In this study, we investigated the differential expression of 84 stem cell-related genes in dental pulp cells (DPCs) and periodontal ligament cells (PDLCs) undergoing odontogenic/osteogenic differentiation. RESULTS: Our results showed that, although there was considerable overlap, certain genes had more differential expression in PDLCs than in DPCs. CCND2, DLL1, and MME were the major upregulated genes in both PDLCs and DPCs, whereas KRT15 was the only gene significantly downregulated in PDLCs and DPCs in both odontogenic and osteogenic differentiation. Interestingly, a large number of regulatory genes in odontogenic and osteogenic differentiation interact or crosstalk via Notch, Wnt, transforming growth factor beta (TGF-beta)/bone morphogenic protein (BMP), and cadherin signaling pathways, such as the regulation of APC, DLL1, CCND2, BMP2, and CDH1. Using a rat dental pulp and periodontal defect model, the expression and distribution of both BMP2 and CDH1 have been verified for their spatial localization in dental pulp and periodontal tissue regeneration. CONCLUSIONS: This study has generated an overview of stem cell-related gene expression in DPCs and PDLCs during odontogenic/osteogenic differentiation and revealed that these genes may interact through the Notch, Wnt, TGF-beta/BMP, and cadherin signaling pathways to play a crucial role in determining the fate of dental derived cell and dental tissue regeneration. These findings provided a new insight into the molecular mechanisms of the dental tissue mineralization and regeneration.

Effects of heparin-binding epidermal growth factor-like growth factor on cell repopulation and signal transduction in periodontal ligament cells after scratch wounding in vitro.

BACKGROUND AND OBJECTIVE: A growing amount of attention has been placed on periodontal regeneration and wound healing for periodontal therapy. This study was conducted in an effort to determine the effects of heparin-binding epidermal growth factor-like growth factor on cell repopulation and signal transduction in periodontal ligament cells after scratch wounding in vitro. MATERIAL AND METHODS: Human periodontal ligament cells were acquired from explant tissue of human healthy periodontal ligament. After the wounding of periodontal ligament cells, the change in expression of heparin-binding epidermal growth factor-like growth factor and epidermal growth factor receptors 1-4 mRNA was assessed. The effects of heparin-binding epidermal growth factor-like growth factor on periodontal ligament cell proliferation and repopulation were assessed in vitro via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and by photographing the injuries, respectively. Extracellular signal-regulated kinase (Erk)1/2, p38 and Akt phosphorylation was characterized via western blotting. RESULTS: Scratch wounding resulted in a significant up-regulation of heparin-binding epidermal growth factor-like growth factor mRNA expression, whereas wounding had no effect on the expression levels of epidermal growth factor receptors 1-4. Interestingly, no expression of epidermal growth factor receptors 2 and 4 was detectable prior to or after wounding. Heparin-binding epidermal growth factor-like growth factor treatment promoted the proliferation and repopulation of periodontal ligament cells. The scratch wounding also stimulated the phosphorylation of Erk1/2 and p38, but not of Akt, in periodontal ligament cells, and heparin-binding epidermal growth factor-like growth factor treatment applied after wounding amplified and extended the activations of Erk1/2 and p38, but not of Akt. Furthermore, Erk1/2 inhibition blocked the process of cell repopulation induced by heparin-binding epidermal growth factor-like growth factor, whereas the inhibition of p38 delayed the process. CONCLUSION: These results indicate that heparin-binding epidermal growth factor-like growth factor may constitute a critical factor in the wound healing of human periodontal ligament cells by a mechanism that requires the activation of Erk1/2 via specific interaction with epidermal growth factor receptor 1.

The behavior of stem cells and progenitor cells in the periodontal ligament during wound healing as observed using immunohistochemical methods.

BACKGROUND AND OBJECTIVE: The aim of this study was to identify stem cells or progenitor cells in the periodontal ligament and to investigate their behavior during wound healing of bone defects created experimentally in the alveolar process. MATERIAL AND METHODS: Intradentinal cavities were created in the mesial root of the first molar of 25 adult male rats that were killed 1, 3, 5, 7 and 14 d after surgery. At each time-point, sections were stained immunohistochemically for CD44s (standard), CD34, c-KIT, PCNA, Cbfa-1 and 5-bromo-2-deoxyuridine using primary antibodies. For morphometric analysis, the ratios of Cbfa-1 and PCNA-positive cells were calculated from the total number of positive cells/10(4) microm(2) in the cavities. RESULTS: 5-Bromo-2-deoxyuridine-positive cells were observed in the periodontal ligament and had migrated into the wound areas. A small number of CD44s-, CD34- and c-KIT-positive cells were observed in the bone marrow, but none were observed in the periodontal ligament. CD44s-positive cells were only observed in the alveolar bone cavity at 5 d after surgery. CD34- and c-KIT-positive cells were only observed in the dentin cavity at 7 d after surgery. Cbfa-1 and PCNA scores tended to show an increase 7 d after surgery. CONCLUSION: Mesenchymal stem cells and hematopoietic stem cells in the bone marrow are not involved in the regeneration of the periodontium. Cells that migrated from the residual periodontal ligament regenerated new alveolar bone at the early stage, and the regeneration around the dentin in the cavity was later than in other parts.

Dental trauma involving root fracture and periodontal ligament injury: a 10-year retrospective study

The purpose of this retrospective study was to analyze the cases of traumatic dental injuries involving root fracture and/or periodontal ligament injury (except avulsion) treated at the Discipline of Integrated Clinic, School of Dentistry of Araçatuba, São Paulo State University (UNESP), Brazil, from January 1992 to December 2002. Clinical and radiographic records from 161 patients with 287 traumatized teeth that had sustained root fracture and/or injuries to the periodontal ligament were examined. The results of this survey revealed that subluxation (25.09 percent) was the most common type of periodontal ligament injury, followed by extrusive luxation (19.86 percent). There was a predominance of young male patients and most of them did not present systemic alterations. Among the etiologic factors, the most frequent causes were falls and bicycle accidents. Injuries on extraoral soft tissues were mostly laceration and abrasion, while gingival and lip mucosa lacerations prevailed on intraoral soft tissues injuries. Radiographically, the most common finding was an increase of the periodontal ligament space. The most commonly performed treatment was root canal therapy. Within the limits of this study, it can be concluded that traumatic dental injuries occur more frequently in young male individuals, due to falls and bicycle accidents. Subluxation was the most common type of periodontal ligament injury. Root canal therapy was the type of treatment most commonly planned and performed.