Reactions In Periodontal Tissues Research Articles

The Impact of Orthodontic Extrusion on Keratinized Gingiva.

Background and Objectives: The key factor that enables osteoblastic activity and the formation of new bone, as well as gingiva, during orthodontic tooth extrusion (OE) is the periodontal ligament. The reaction of periodontal tissues associated with changes in the gingiva is a part of orthodontic tooth displacement. The aim of this study was to examine the effect of OE on the width of the zone of the keratinized and attached gingiva, the position of the mucogingival junction, and the height of the interdental papillae in the region where the OE was performed as well as in the adjacent region. Materials and Methods: This research included 28 adult patients (both orthodontically treated and untreated). The treated group included 15 patients, in whom orthodontic extrusion of the upper or lower frontal teeth was indicated and performed. The untreated group included 13 patients, with no previous or undergoing orthodontic treatment. Patients with periodontal disease and periodontal pockets in the frontal region and patients allergic to iodine were excluded from the study. Gingivomorphometric measurements were performed on two occasions in three groups of teeth (24 extruded and 30 agonist teeth in the treated patients; 66 teeth in the untreated patients). Statistical analysis of the obtained data was performed using the software package SPSS version 26.0. Results: Orthodontic extrusion induced changes in the position of the mucogingival line and an increase in the width of the keratinized gingiva. There were no statistically significant effects on the depth of the gingival sulcus, the attached gingiva width, or the height of the interdental papillae. Conclusions: Orthodontic tooth extrusion has an effect on the periodontium in the observed region. Vertical orthodontic force, directed towards the coronal plane, affects the surrounding soft oral tissues.

КЛИНИЧЕСКАЯ ОЦЕНКА РЕЗУЛЬТАТОВ ПОДГОТОВКИ К НЕСЪЁМНОМУ ПРОТЕЗИРОВАНИЮ ПОСЛЕ ПРОВЕДЕНИЯ ДЕНТАЛЬНОЙ РЕПЛАНТАЦИИ

After dental replantation surgery, it is necessary to take measures to promote the healing of the replanted tooth. In almost 100% of cases, clear signs of an acute inflammatory reaction of periodontal tissues are diagnosed. The effectiveness of combined preparation and pharmacological therapy in the prevention of the inflammatory process of periodontal tissues after tooth replantation was assessed. The condition of the periodontal mucosa and periodontal ligamentous apparatus in the area of supporting teeth was studied in preparation for orthopedic treatment of dentition defects, after the operation of their dental replantation. To solve the set tasks, research methods were used in the work: visual, palpation, instrumental, and statistical analysis of the research results. The patients are divided into two groups. Drug therapy was carried out using traditional medications: antiseptics, antibacterial drugs, biogenic stimulants, etc. Drug therapy used to treat patients in group 1 and group 2 was identical in the list of medications used. Patients of the 2nd group underwent complex treatment of inflammatory phenomena of the desmodontal structures and periodontal mucosa that occur after replantation surgery. In addition to pharmacological drugs, exposure to modulated red light was used using a Stomasvet physiotherapeutic device with a wavelength of 328 nm, a pulse modulation frequency of 76 Hz, and a radiation power of up to 30 mW. On the first day of the study, patients of group 1 and group 2 were characterized by hyperemia of the periodontal mucosa in the area of the replantation, swelling, and pain. By the fourth day, in patients of group 2, the inflammatory phenomena completely disappeared. In patients of group 1, inflammatory phenomena completely disappeared only by the eighth day. An integrated approach to the diagnosis and treatment of periodontal pathologies that arise after dental replantation will reduce the preparatory period for subsequent orthopedic correction of dentition defects, reduce the duration of patient adaptation to the structures used, and also increase the overall level of orthopedic treatment in dentistry.

Influence of antiresorptive/antiangiogenic therapy on changes in periodontal and oral tissue structures: a histomorphometrical analysis in rats

ObjectiveThe objective of this study was to investigate the influence of various antiresorptive and antiangiogenic medications on morphological changes in periodontal and oral tissue structures.Materials and methodsFifty-five Wistar rats randomly received dual application (i.e., at baseline and after 12-weeks) one of the following medications: (1) amino-bisphosphonate [zoledronate (Zo)], (2) RANKL inhibitor [denosumab (De)], (3) antiangiogenic [bevacizumab (Be)], (4) Zo + Be, (5) De + Be or (6) no medication [Control (Co)]. Periodontal and oral tissue biopsies were obtained at 17 (n = 21 animals, Phase 1, (De = 3, De + Be = 3, Zo = 5, Be = 3, Zo + Be = 2, Co = 5) and 29 (n = 34 animals, (De = 8, De + Be = 6, Zo = 2, Be = 7, Zo + Be = 4, Co = 7, Phase 2) weeks after the second drug application. The following outcomes were histomorphometrically assessed: periodontal space width in the coronal (PLS-C, mm) and apical sections (PLS- A), number of empty alveolar bone lacunae in the coronal, apical sections and at the apex at respective tooth sites (EL – C, EL- A, EL- Ap), mucosal thickness at edentulous alveolar ridge areas (MT, mm), and, when present, associated areas of inflammatory cell infiltrates (ICI, mm2).ResultsComparable mean PLS-C, PLS-A, ET-A, ET-C, ET-Ap, and MT values were observed in all experimental groups after Phases 1 and 2. The presence of ICI was identified in 3 animals in the Co group (Phase 1: 1, Phase 2: 2), and 17 animals in the test groups (Phase 1: 4; Phase 2: 14). The estimated ICI surface area was significantly higher in the Zo + Be group, followed by the Zo and Be groups compared to that measured in the Co group. The time (i.e., Phases 1 and 2) was not found to be a predictor for the extent of the ICI area. In all groups, the EL-C, EL-A, and EL-Ap values were significantly higher after Phase 2 compared to those assessed after Phase 1. The MT values were significantly reduced in all groups after Phase 2 compared to those measured after Phase 1.ConclusionsThe present evaluation was not able to find any morphological effects of different antiresorptive and antiangiogenic medications on periodontal and oral tissue structures. The presence of inflammatory cell infiltrates was more frequently observed in the animals administered with antiresorptive and antiangiogenic medications as well as combinations thereof.Clinical relevanceAdministration of antiresorptive and antiangiogenic medications may be capable of inducing inflammatory reactions in periodontal tissues.

Role of biologic modifiers in periodontal regeneration- A review

Regenerative techniques, which aim to replace damaged periodontal ligament, bone, cementum, and connective tissue, are newer approaches to periodontal care. In periodontology and oral implantology, the development of molecular mediators has accelerated substantially over the last decade. At various cellular levels, different growth agents cause distinct reactions in periodontal tissues. The potency of biologics in regenerating the periodontal tissues is the call attention in this review paper, in which it discusses the structure, mechanism of action, indication and FDA (Food and Drug Administration) approval to use in regenerating periodontal tissues. The working activity of biologic agents together with reasons for utilizing them in regenerating tissues of periodontium lost due to disease are discussed, as well as the expected benefits as compared to traditional approaches.

FEA analysis of Normofunctional forces on periodontal elements in different angulations.

In the literature, the periodontal tissue reaction to dissimilar occlusal stress has been described, including clinical and histologic changes caused by stresses in periodontal structures. With respect to occlusal forces, periodontal assembly demonstrates varying adaptive capacity from individual to individual and period to period within the same individual. Unfortunately, these occlusal stresses are yet to be quantified. As a result, determining the effect of normal occlusal force on periodontal elements in various angulations is of interest. Based on CBCT images, one FEA of the maxillary First molar was created, consisting of tooth pulp, periodontal ligament (PDL), and alveolar bone; the effect of normal occlusal force on the pdl in alternate angulations was assessed. Occlusion will occur at three contact areas representing the centric occlusion contact points, each of which will share a 150 N force. The analysis was performed for four force inclinations (0, 22.5°, 45°, and 90°). Maximum stresses are observed in cases of 90-degree loading. These stresses, however, are insignificant and will not cause the periodontal components to rupture. These tensile stresses, which are concentrated in the apical and cervical regions, may obstruct blood flow, resulting in tooth decay or, in some cases, periodontal breakdown in PDL. There have been attempts to express numerical data of stress to be provided for normal and hyper function loads to simulate occlusal situations at various angulations that are known to be accountable for healthy and diseased periodontium.

Periodontal Tissue Reaction Consecutive Implantation of Endodontic Materials and Subsequent Integration of Complex Oral Rehabilitation Treatments

Oral rehabilitation is a main branch of dentistry focused on diagnosing the patient’s problem and creating a treatment plan to restore aesthetics, recondition morphologically all components, and recover the functionality of the oral cavity. Biological compatibility of the materials used has a major importance, due to the direct contact with essential tissues, such as the soft and hard tissue of the periodontium and the potential influence on the outcome of the treatment. The present material aims to assess the inflammatory response after subcutaneous implantation of three materials frequently used in endodontics (Mineral Trioxide Aggregate—MTA, DiaRoot BioAggregate, and Sealapex). The evaluation of the reparative tissue reaction after 7, 30, and 60 days, respectively, subsequent to in vivo implantation, was carried out through electron microscopy imaging. Moreover, evaluation of the dynamics of the osteogenesis process was an indicator for the maintenance of internal homeostasis in the context of complex intraoral rehabilitation treatments that include fixed prosthodontics correlated with the particular periodontal-aesthetic aspects and completed by cranio-mandibular repositioning. Our study showed increased absolute values of alkaline phosphatase in all material-implanted cases (more pronounced in MTA and Bio Aggregate), highlighting that this enzyme could be an effective indicator of bone formation, which takes place after the material implantation, with the most significant elevated values at 30 days postoperatively.

INVESTIGATION OF SPECIES COMPOSITION OF MICROFLORA IN PERIODONTAL POCKETS IN PATIENTS WITH GENERALIZED PERIODONTITIS AND METABOLIC SYNDROME

Among dental diseases, periodontal diseases rank one of the leading places and are considered as the most pressing issues of modern dentistry. The presence of concomitant somatic pathology, in particular, cardiovascular, endocrinological, autoimmune diseases is an important factor that considerably determines the course and prognosis of periodontal disease. Metabolic syndrome is regarded as an urgent social and medical issue due to its high prevalence among the general population and its contribution to the development and progression of cardiovascular disease. The number of reports and scientific interest in the metabolic syndrome has grown up significantly in recent years, but despite the significant number of studies, the oral microbiome in patients with periodontal disease and underlying metabolic syndrome is still remaining insufficiently studied. The aim of this work was to investigate the species composition of the microflora in periodontal pockets and the frequency of excretion of certain types of microorganisms in the acute generalized periodontitis in patients with metabolic syndrome. A microbiological study was performed in 30 people with metabolic syndrome and generalized periodontitis, who formed the main group, and in 30 people with generalized periodontitis without endocrinological pathology, who formed a comparison group. The results of microbiological examination indicate pathological changes in the oral microbiome in the patients with metabolic syndrome demonstrating a predominance of periodontal pathogens. It can be assumed that the components of the metabolic syndrome can initiate and support microbial invasion thus resulting in the inflammatory reaction of periodontal tissues. There is a similarity between pathogenetic mechanisms of metabolic syndrome and periodontal disease that lead to the impairment of all types of metabolism: protein, lipid, mineral, carbohydrate. As a consequence, this contributes to the progressive destruction of oral tissues. The obtained data enable to suggest the dependence between the presence of the patient's metabolic syndrome and the development of intensive damage to periodontal tissues.

CLINICAL COURSE OF PERIODONTAL DISEASES IN PATIENTS WITH POSTMENOPAUSAL OSTEOPOROSIS TREATED WITH BISPHOSPHONATES

The aim of the study was to assess the state of the clinical course of periodontal diseases in patients with postmenopausal osteoporosis (OP), depending on the long-term oral administration of various groups of bisphosphonates (BP). The study included 120 women aged 55–65 years with postmenopausal OP for at least three years who took complex antiosteoporetic therapy, including BP in tablet form. The dental examination included an examination of the oral cavity, the study of the pH of the oral fluid, the hygienic state of the mouth (the "Florida Probe" system). According to the results of the study, it was revealed that prolonged treatment of BP in tablets can provoke the development of inflammatory reactions in periodontal tissues. This phenomenon is associated with a shift in the pH of saliva to the acidic side, at which its buffer properties change.

MODERN SCIENTIFIC VIEW ON THE OPTIMIZATION OF TREATMENT OF PERIODONTAL DISEASES

The article presents a retrospective review of professional domestic and foreign literature on modern aspects of treatment of inflammatory periodontal diseases, including vector therapy, plasmalifting, which can be used in various forms of this pathology. Periodontal diseases are one of the most pressing problems of dentistry, which has not only general but also great social significance, due to the high prevalence, intensity of the process, the subsequent formation of chronic odontogenic foci of infection, tooth loss at a young age and adverse effects on the body. Treatment of periodontal disease is a complex and lengthy process that includes general methods of influencing the pathophysiological processes occurring in the body, both local - therapeutic, orthopedic and surgical measures. Before planning treatment, the dentist should determine the patient's medical and dental history, conduct clinical and radiological examinations, determine the degree of loss of the alveolar ridge, functional disorders of the dental system and the possibility of their correction. Depending on this, determine the plan of treatment and rehabilitation measures, the sequence of medical interventions. The main task of periodontal treatment is to optimize the conditions for maintaining a healthy dentition and restoring its physiological functions. The difficulty of treating inflammatory periodontal diseases is that known and standard methods (antibacterial therapy and courses of local therapy) do not always give a positive result and a long period of remission. Therefore, to improve the quality of medical care for patients with periodontal pathology, it is necessary to introduce new innovative methods of treatment in dental practice. Given the patterns of pathophysiological processes occurring in periodontal tissues and bone tissue of the alveolar process, to date, several stages of treatment and rehabilitation measures have been proposed. The first stage is the elimination of the pathogenic action of microbial factors and inflammatory processes in periodontal tissues. Microbial invasion and the inflammatory reaction of periodontal tissues caused by it activate the processes of osteoclastical bone resorption. The task of the second stage of treatment and rehabilitation measures is to restore the physiological structure of gums and bone by normalizing metabolic processes in periodontal tissues, reducing the activity of resorption processes and stimulating reparative osteogenesis in the bone tissue of the alveolar process and the body in general, surgical treatment. At the third stage of treatment and rehabilitation measures, teeth with a significant degree of atrophy of the alveolar process are removed, which cannot be used for prosthetics. To restore the integrity of the dentition, even distribution of masticatory load, appropriate prosthetics are performed. The use of the latest methods contributes to the effective treatment of periodontal disease in the early stages, stabilization of the process at deeper stages, in some cases helps to avoid surgery.

Clinical and histological reaction of periodontal tissues to subgingival resin composite restorations

To compare the clinical and histological response of supracrestal periodontal tissues to subgingival composite restorations versus natural root surfaces MATERIAL AND METHODS: In 29 subjects with a single tooth requiring subgingival restorations, a deep margin elevation (DME) procedure with composite resin was applied. Full-mouth plaque score (FMPS), full-mouth bleeding score (FMBS), and focal probing depth (PD) were measured at baseline, before DME, and after 3months. The distance between the coronal marked (CM) point to the apical margin of the composite reconstruction (AMR), at baseline, and to the tip of the periodontal probe inserted to reach the bottom of the sulcus (APP), 3months later, was measured. An all-around secondary flap, harvested to ensure the subsequent single-crown prosthetic rehabilitation was histologically processed. The histological inflammation degree was evaluated in areas of gingival tissues adjacent to the composite (group B) and adjacent to the natural surface of each single tooth (group A). Significant FMPS, FMBS, and PD decreases were observed (p < 0.05). CM-AMR and CM-APP were significantly different (p < 0.05), suggesting an attachment gain after 3-months. The inflammation level of gingival tissue was similar in groups A and B (p > 0.05). For the first time, this topic was clinically and histologically studied in humans. Subgingival restorations resulted compatible with gingival health, with levels similar to that of untreated root surfaces. Deep margin elevation procedure produces favorable clinical and histological outcomes allowing a routine utilization in reconstructive dentistry.

CHARACTERISTICS OF KEY FACTORS AFFECTING THE QUALITY OF FIXATION AND DURABILITY OF THE FUNCTIONING OF ARTIFICIAL CROWNS

Introduction. Odontopreparation is an integral step in orthopedic dental treatment with non-removable orthopedic constructions. Correctly performed this stage in the treatment of artificial crowns is a guarantee of the quality of orthopedic treatment. Ensuring a stable geometry of the stump, a ledge of sufficient width on the abutment and the absence of defects on its surface, the clarity of the preparation margin and the correct ratio with marginal periodontal tissues are the most significant criteria for the quality of the intervention. In addition, the quality of the odontopreparation of the orthopedic profile is influenced by the clarity of adherence to the selected algorithm of preparation and the properties of the rotary tool used. The available literature data indicate numerous deviations in the practice of dentistry from the recommended methodology of odontopreparation, which can be explained by the relatively high frequency of complications of treatment with non-removable orthopedic structures. The purpose of the article is to analyze the key factors affecting the quality of fixation and the durability of the functioning of artificial crowns, based on an assessment of the basic principles of odontopreparation for this type of orthopedic structures and the reaction of periodontal tissues based on an analytical review of the literature. Materials and methods. The article presents the data of the literature review on the main factors that are of great importance as the fixation and durability of the functioning of artificial crowns on the stumps of dissected teeth while observing step-by-step odontopreparation algorithms with provision of proper functional and desired aesthetic requirements without negative influence on the condition of the tissue. Conclusion. Based on the analysis of literary sources, it was concluded that the key factors affecting the quality of the formation of the tooth stump to be prosthetized, subject to step-by-step odontoperational algorithms with the creation of conditions for high-quality fixation and durability of the functioning of the artificial crown, ensuring the proper functional and desired aesthetic requirements without negative impact periodontal tissues can significantly reduce the manifestation of unwanted complications, and as a result to increase the effectiveness of prosthetics with artificial crowns.

Microstructural changes of periodontal tissue under the action of opioid analgesics in the early stages

The objective of the study is to determine the peculiarities of pathomorphological features of the periodontal tissue complex under conditions of inoculation of opioid analgesics in small doses for 4 weeks.Material and methods. The study was conducted on 16 outbred sexually mature white male rats which were injected Nalbuphine in a daily dose from 0.212 mg/kg to 0.252 mg/kg for 28 days. Amputated maxillary segments and exarticulated mandibular segments have been used for histological study.Results. The development of the inflammatory process was accompanied by epithelial cell layers damage, their marked hypertrophy, the phenomena of desquamation, keratosis and hyperkeratosis. Invasion of epithelium in swollen lamina propria and initial signs of the destruction of the epithelial attachment have been detected in the region of the gingival sulcus. Polymorphic cell infiltration is moderately marked in the lamina propria of the gingival mucosa and periodontium. Changes in the microcirculatory bloodstream of the connective tissue were manifested by plethora, phenomena of angiomatosis and dilatation of venules. Osseous tissue of the slightly mineralized. Сementum of the tooth root was non-homogeneously mineralized.Conclusions. Initial changes in cell injuries prevailed in interfacial layers of periodontal soft tissues with subsequent spread of the pathological process in deeper periodontal layers where the osseous tissue, periosteum and cementum of the tooth root remained almost intact. The compensatory-adaptive reactions in periodontal tissues were sufficiently developed in the early stages of opioid exposure along with alterations of the inflammatory character.

Effect of hyperfunctional occlusal loads on periodontium: A three-dimensional finite element analysis.

Introduction:The periodontal tissue reaction to variations in occlusal forces has been described in the literature wherein clinical and histologic changes are discussed that produced due to stresses in the periodontal structures. Unfortunately, these stresses are not quantified.Aim:The aim of this study is to determine the stress produced on various periodontal tissues at different occlusal loads using finite element model (FEM) study.Materials and Methods:Four FEMs of maxillary incisor were designed consisting of the tooth, pulp, periodontal ligament (PDL), and alveolar bone at the various level of bone height (25%, 50%, and 75%). Different occlusal load (15 and 29 kg) at an angle of 50° to the long axis of the tooth was applied on the palatal surface at the level of middle third of the crown. All the models were assumed to be isotropic, linear, and elastic, and the analysis was performed on a Pentium IV processor computer using the ANSYS software.Results:At normofunction load, the stresses were maximum on the mesial side near the cervical region at point D for tooth (−10.93 Mpa) for PDL (−4.06 Mpa) for bone (−4.3 Mpa) with normal bone levels as the bone levels decreased the stresses increased and the stresses tend to concentrate at the apical region. At any given point, the stresses were increased by 90% at hyperfunctional load.Conclusion:Based on the findings of the present study, there is reasonably good attempt to express numerical data of stress to be given normal occlusal and hyperfunctional loads to simulate clinical occlusal situations which are known to be responsible for healthy and diseased periodontium.

One hundred years of orthodontic history.

The special section, “100 years of orthodontic history,” published in the December 2015 issue of the AJO-DO, delineates the important events in the past 100 years of orthodontics and provides a rich perspective to young orthodontists on how the field has developed. The timeline shows how far the practice of orthodontics has evolved; moreover, these major events could serve as building blocks to push the boundaries in the future. Two clinician-scientists, Kaare Reitan and Per Rygh, who fundamentally contributed to the biology of tooth movement, are missing in the history timeline. 1951 Kaare Reitan Histological analyses of periodontal tissue reaction in response to orthodontic tooth movement 1973 Per Rygh Ultrastructure changes in periodontium as a function of orthodontic tooth movement Reitan (1903-2000) and Rygh (1930-2008) extensively studied the histology of tooth movement in humans and rodents.1Reitan K. The initial tissue reaction incident to orthodontic tooth movement as related to the influence of function: an experimental histologic study on animal and human material.Acta Odontol Scand Suppl. 1951; 6: 1-240PubMed Google Scholar, 2Rygh P. Hyalinization of the periodontal ligament incident to orthodontic tooth movement.Den Norske Tannlaegeforenings Tidende. 1951; 84: 352-357Google Scholar Their findings partly defined the principles of tooth movement biology: the core of our daily orthodontic practice. In my opinion, we should add these 2 people to the list. Editor's note: Both Kaare Reitan and Per Rygh are included in another Centennial Special Section, “100 years of publishing, 100 people of influence,” in the May 2015 issue of the Journal (Am J Orthod Dentofacial Orthop 2015;147 (Suppl 2):S147-54). 100 years of orthodontic historyAmerican Journal of Orthodontics and Dentofacial OrthopedicsVol. 148Issue 6Preview Full-Text PDF

Onychophagia and postorthodontic isolated gingival recession: Diagnosis and treatment

This clinical report describes the diagnosis and the management of isolated-type recession defects of complex etiology in 2 healthy postorthodontic patients. The lesions were confined to 1 mandibular incisor and were associated with an abnormal buccolingual inclination of the affected tooth despite a lingual retainer made with a round stainless steel twisted wire. After careful questioning, it was determined that the recession defects were indirect effects of habitual onychophagia. The concomitant fingernail-biting habit and the lingual bonded retainer led to the indirect development of bone dehiscence and, consequently, gingival recession.

Transplanted Human Bone Marrow Mesenchymal Stem Cells Seeded onto Peptide Hydrogel Decrease Alveolar Bone Loss

Alveolar bone loss can be caused by periodontitis or periodontal trauma. We have evaluated the effects of transplanted undifferentiated human mesenchymal stem cells (hMSCs) on alveolar bone reaction and periodontal ligament healing in an experimental periodontal wound model. The hMSCs seeded onto a self-assembling peptide hydrogel in combination with collagen sponge were implanted into the right mandible of 12 rats and followed for 1 (n=6) or 4 weeks (n=6) postoperatively. The other 12 sham-treated rats were used as controls. Histological and histomorphometrical methods were used to assess the periodontal tissue reaction. The alveolar bone volume density was significantly higher at 1 week after surgery, and the osteoclast number was significantly lower at both 1 week and 4 weeks postoperatively in the mandibles treated with hMSCs. The implanted cells were detected only at 1 week after surgery. In conclusion, transplanted hMSCs can contribute to alveolar bone preservation after a periodontal surgical trauma at least by decreasing local osteoclast number.

Periodontal tissue reaction to customized nano-hydroxyapatite block scaffold in one-wall intrabony defect: a histologic study in dogs

PurposeThis study evaluated histologically the tissue responses to and the effects of a customized nano-hydroxyapatite (n-HA) block bone graft on periodontal regeneration in a one-wall periodontal-defect model.MethodsA customized block bone for filling in the standardized periodontal defect was fabricated from prefabricated n-HA powders and a polymeric sponge. Bilateral 4×4×5 mm (buccolingual width×mesiodistal width×depth), one-wall, critical-size intrabony periodontal defects were surgically created at the mandibular second and fourth premolars of five Beagle dogs. In each dog, one defect was filled with block-type HA and the other served as a sham-surgery control. The animals were sacrificed following an 8-week healing interval for clinical and histological evaluations.ResultsAlthough the sites that received an n-HA block showed minimal bone formation, the n-HA block was maintained within the defect with its original hexahedral shape. In addition, only a limited inflammatory reaction was observed at sites that received an n-HA block, which might have been due to the high stability of the customized block bone.ConclusionsIn the limitation of this study, customized n-HA block could provide a space for periodontal tissue engineering, with minimal inflammation.

Periodontal tissue reaction during orthodontic relapse in rat molars

Relapse after orthodontic tooth movement (OTM) is an undesirable outcome that involves a number of factors. This study investigated the remodelling of the alveolar bone and related periodontal structures during orthodontic relapse in rat molars. The maxillary right first molars of 35 Wistar rats were moved mesially by a fixed orthodontic appliance for 10 days and the contralateral molars served as controls. The appliances were removed and six animals killed. The molars were allowed to relapse, and the remaining animals were sacrificed at 1, 3, 5, 7, 14, and 21 days. The jaws were sectioned and stained with haematoxylin and eosin and tartrate-resistant acid phosphatase (TRAP). One day after appliance removal, the molars relapsed to a mean 62.5 per cent of the achieved OTM and then steadily relapsed to 86.1 per cent at 21 days. The number of osteoclasts situated along the alveolar bone of the first molars was highest at the end of active treatment and significantly decreased during the relapse period. In the OTM group, osteoclasts were most numerous in the pressure side of the periodontal ligament (PDL). As the molars relapsed over time, the osteoclast distribution shifted, and after 7 days of relapse, TRAP-positive cells were registered in previous pressure and tension sides of the first molars. After 21 days, these cells were concentrated in the distal parts of the PDL of all three maxillary right molars. These results indicate that orthodontic relapse in the rat model occurs rapidly and remodelling of the alveolar bone and PDL plays a central role in the relapse processes of both actively moved and adjacent teeth.

An in vivo experimental model to assess furcal lesions as a result of perforation

To design and validate a rat molar model of furcal perforation to allow investigation of the biological phenomena that follow and to explore its potential for evaluating repair materials under standardized conditions. Eighteen male Wistar rats were used. Surgical aseptic procedures were carried out in order to open the pulp chamber of a first molar tooth. A cavity was prepared on the floor of the pulp chamber using a (1/4) round bur that created a communication between the furcation and the periodontal tissues. Six animals for each time point were sacrificed on days 14, 21 and 28 to assay morphological changes at the furcation region of molars. Maxillary bone was processed, removed and sectioned. Cellular infiltration, collagen deposition and bone resorption were assessed by histological analysis. Cellularity in the lesion area was determined by morphometric analysis. Data were analysed using parametric Student's t-test. A furcal perforation model was standardized in which both radiological outcome and periodontal tissue reactions could be assessed through evaluation of cellularity, osteoclast activity and collagen deposition. The morphometric analysis revealed a greater number of cells 21 day post-surgery when compared with 14 days. This animal model was suitable for radiological and histological evaluation of the processes that accompany surgical furcal perforation.

RANK/RANKL/OPG during orthodontic tooth movement

Orthodontic tooth movement is induced by mechanical stimuli and facilitated by remodeling of the periodontal ligament (PDL) and alveolar bone. A precondition for these remodeling activities, and ultimately for tooth displacement, is the occurrence of an inflammatory process. This review covers current knowledge regarding the role of the receptor activator of nuclear factor-kappa (RANK), receptor activator of nuclear factor-kappa ligand (RANKL), and osteoprotegerin (OPG) in periodontal tissue reactions, in response to orthodontic forces. It has been found that concentrations of RANKL in GCF increased during orthodontic tooth movement, and the ratio of concentration of RANKL to that of OPG in the GCF was significantly higher than in control sites. In vivo studies have shown the presence of RANKL and RANK in periodontal tissues during experimental tooth movement of rat molars, and that PDL cells under mechanical stress may induce osteoclastogenesis through upregulation of RANKL expression during orthodontic tooth movement. Considering the importance of RANK, RANKL, and OPG in physiologic osteoclast formation, it is reasonable to propose that the RANKL/RANK/OPG system plays an important role in orthodontic tooth movement.