Compression loading of osteoclasts attenuated microRNA-146a-5p expression, which promotes angiogenesis by targeting adiponectin.

Osteoclastogenesis in alveolar bone induced by compression stress triggers orthodontic tooth movement. Compression stress also stimulates angiogenesis, which is essential for osteoclastogenesis. However, the effects of osteoclastogenesis induced by compression on angiogenesis are poorly understood. In vivo, we found the markers of angiogenesis increased during orthodontic bone remodeling. In vitro, osteoclast-derived exosomes increased proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs), as well as expression of vascular endothelial growth factor and CD31. The promotive effects of exosomes derived from compressed osteoclasts were greater than those derived from osteoclasts without compression. Next, we analyzed changes in the microRNA transcriptome after compression stress and focused on microRNA146a-5p (miR-146a), which was significantly decreased by compression. Transfection of an inhibitor of miR-146a stimulated angiogenesis of HUVECs while miR-146a mimics repressed angiogenesis. Adiponectin (ADP) was confirmed to be a target of miR-146a by dual luciferase reporter assay. In HUVECs treated with exosomes, we detected increased ADP which promoted angiogenesis. Knockdown of ADP in HUVECs reduced the promotive effects of exosomes. Our results demonstrate that the decreased miR-146a observed in osteoclasts after compression promotes angiogenesis by targeting ADP, suggesting a novel method to interfere with bone remodeling induced by compression stress.

Cementum thickening leads to lower whole tooth mobility and reduced root stresses: An in silico study on aging effects during mastication.

In the course of a lifetime the crowns of teeth wear off, cementum thickens and the pulp closes-in or may stiffen. Little is known about how these changes affect the tooth response to load. Using a series of finite element models of teeth attached to the jawbone, and by comparing these to a validated model of a 'young' pig 3-rooted tooth, the effects of these structural changes were studied. Models of altered teeth show a stiffer response to mastication even when material properties used are identical to those found in 'young' teeth. This stiffening response to occlusal loads is mostly caused by the thicker cementum found in 'old' teeth. Tensile stresses associated with bending of dentine in the roots fall into a narrower distribution range with lower peak values. It is speculated that this is a possible protective adaptation mechanism of the aging tooth to avoid fracture. The greatest reduction in lateral motion was seen in the bucco-lingual direction. We propose that greater tooth motion during mastication is typical for the young growing animal. This motion is reduced in adulthood, favoring less off-axis loading, possibly to counteract natural bone resorption and consequent compromised anchoring.

Cambios morfofuncionales en el periodoncio asociados al movimiento dentario por tratamiento ortodóncico / Morfofunctional changes in the periodontium associated to the teeth movement due to orthodontic treatment

Los cambios morfofuncionales que se producen en las estructuras de soporte dentario durante el movimiento ortodóncico involucran procesos bioquímicos, histológicos y fisiológicos. Desde hace más de un siglo, existen disímiles teorías que tratan de explicarlos; sin embargo, todavía se siguen realizando estudios a fin de comprenderlos más a fondo. En la presente comunicación se ofrece una actualización secuencial y resumida de dichos episodios, con el propósito de incrementar el nivel de conocimientos sobre el tema y mejorar la calidad en la atención ortodóncica.

Morfofunctional changes which take place in the supporting structures during the orthodontic movement involve biochemical, histological and physiologic processes. For more than one century, dissimilar theories exist that try to explain to them; however, studies are still being carried out in order to understand them thoroughly. In the present communication a sequential and summarized updating of these episodes, with the purpose of increasing the knowledge on the topic and improving the quality in the orthodontic care.

A cross-sectional, clinical study to evaluate mobility of teeth during pregnancy using periotest.

BACKGROUND AND OBJECTIVE: Over a century, an increased prevalence of gingival diseases associated with increasing plasma sex steroid hormone levels has been reported. These situations present unique challenges to the oral health-care professional. It is believed that hormonal fluctuations such as those associated with pregnancy, menstruation, and use of hormonal contraceptives lead to an increase in tooth mobility. However, this effect of female sex hormones on periodontal ligament and tooth-supporting alveolar bone has rarely been investigated. Hence, this study was conducted to understand the effect of hormonal changes during pregnancy on tooth mobility. MATERIALS AND METHODS: Mobility of index teeth 16, 13, 21, 23, 24, 36, 33, 41, 43, and 44 was measured with periotest for fifty pregnant females at first trimester (12th week), second trimester (24th week), and third trimester (35th week). Simplified oral hygiene index, plaque index, Gingival index (GI), and probing depth were also evaluated during the three trimesters of pregnancy for each subject participating in the study. STATISTICAL ANALYSIS: The results of the study were subjected to statistical analysis. Data analysis was done by applying Z-test for comparing difference between two sample means. RESULTS: A small but statistically significant influence on the periotest value was seen during the three trimesters of pregnancy. GI scores significantly increased throughout pregnancy despite no significant change in plaque levels. CONCLUSION: Pregnancy had a significant influence on tooth mobility. Highest value of tooth mobility was seen in the last month of pregnancy. The maximum severity of gingivitis was also seen during the third trimester of pregnancy.

Study of force loss due to friction comparing two ceramic brackets during sliding tooth movement.

OBJECTIVE: To compare the percentage of force loss generated during canine sliding movements in newly introduced ceramic brackets with metal brackets. MATERIALS AND METHODS: Two types of ceramic brackets, namely polycrystalline alumina (PCA) ceramic brackets (Clarity Advanced) and monocrystalline alumina (MCA) ceramic brackets (Inspire Ice) were compared with stainless steel (SS) brackets (Victory Series). All bracket groups (n = 5 each) were for the maxillary canines and had a 0.018-inch slot size. The brackets were mounted on an Orthodontic Measurement and Simulation System (OMSS) to simulate the canine retraction movement into the first premolar extraction space. Using elastic ligatures, 0.016 × 0.022″ (0.40 × 0.56 mm) stainless steel archwires were ligated onto the brackets. Retraction force was applied via a nickel-titanium coil spring with a nearly constant force of approximately 1 N. The OMSS measured the percentage of force loss over the retraction path by referring to the difference between the applied retraction force and actual force acting on each bracket. Between group comparisons were done with one-way analysis of variance. RESULTS: The metal brackets revealed the lowest percentage of force loss due to friction, followed by the PCA and MCA ceramic bracket groups (67 ± 4, 68 ± 7, and 76 ± 3 %, respectively). There was no significant difference between SS and PCA brackets (p = 0.97), but we did observe significant differences between metal and MCA brackets (p = 0.03) and between PCA and MCA ceramic brackets (p = 0.04). CONCLUSION: PCA ceramic brackets, whose slot surface is covered with an yttria-stabilized zirconia-based coating exhibited frictional properties similar to those of metal brackets. Frictional resistance resulted in an over 60 % loss of the applied force due to the use of elastic ligatures.

Evaluation of Qualitative Changes in Simulated Periodontal Ligament and Alveolar Bone Using a Noncontact Electromagnetic Vibration Device with a Laser Displacement Sensor.

Evaluating periodontal tissue condition is an important diagnostic parameter in periodontal disease. Noncontact electromagnetic vibration device (NEVD) was previously developed to monitor this condition using mechanical parameters. However, this system requires accelerometer on the target tooth. This study assessed application of laser displacement sensor (LDS) to NEVD without accelerometer using experimental tooth models. Tooth models consisted of cylindrical rod, a tissue conditioner, and polyurethane or polyurethane foam to simulate tooth, periodontal ligament, and alveolar bone, respectively. Tissue conditioner was prepared by mixing various volumes of liquid with powder. Mechanical parameters (resonant frequency, elastic modulus, and coefficient of viscosity) were assessed using NEVD with the following methods: Group A, measurement with accelerometer; Group B, measurement with LDS in the presence of accelerometer; and Group C, measurement with LDS in the absence of accelerometer. Mechanical parameters significantly decreased with increasing liquid volume. Significant differences were also observed between the polyurethane and polyurethane foam models. Meanwhile, no statistically significant differences were observed between Groups A and B; however, most mechanical parameters in Group C were significantly larger and more distinguishable than those of Groups A and B. LDS could measure mechanical parameters more accurately and clearly distinguished the different periodontal ligament and alveolar bone conditions.

Recombinant osteoprotegerin effects during orthodontic movement in a rat model.

BACKGROUND AND OBJECTIVES: Anchorage is one of the most challenging sides in orthodontics. The use of biological modulators that inhibit osteoclasts could be a solution to address these problems and provide new adjunctive approaches. The aim of this study was to assess the effectiveness of recombinant osteoprotegerin fusion protein (OPG-Fc) in orthodontic anchorage. MATERIALS AND METHODS: Two groups of male Sprague-Dawley rats were utilized. The animals in the experimental group received twice-weekly injections with high dose of OPG-Fc (5.0mg/kg) in mesial and distal mucosa of the first molars, and those in the control group received no drugs. Right first maxillary molars were mesialized using a calibrated nickel-titanium spring connected to an anterior mini-screw. Tooth movement was measured by two blinded observers using scanned and magnified stone casts. Receptor activator of nuclear factor κB (RANK), run-related transcription factor 2 (Runx2), type I collagen, vimentin, matrix metalloproteinases 2 and 9, S100 protein and the putative mechanoproteins acid-sensing ion channel (ASIC2) and transient receptor potential vainilloid 4 (TRPV4) were evaluated using immunohistochemistry. RESULTS: OPG-Fc group showed an important decreased in mesial molar movement with only 52%, 31%, and 22% of the total mesial molar movement compared with control group at Days 7, 14, and 21, respectively (P < 0.001). RANK ligand and Runx2 positive cells were severely reduced after OPG-Fc treatment. Periodontal ligament architecture, cell arrangement, and immunohistochemical patter for vimentin, type I collagen and the mechanoproteins TRPV4 and ASIC2 were altered by tooth movement and all these parameters altered by the applied treatment. CONCLUSIONS: OPG-Fc effectively inhibits osteoclastogenesis resulting in improved bone quantity and orthodontic anchorage. Based on present results, OPG-Fc could have clinical utility in preventing undesired tooth movements.

Maturogenesis of an Early Erupted Immature Permanent Tooth: A Case Report With 7-Year Follow-Up.

The main objective of treatment of an undeveloped tooth (immature) is to provide vital pulp therapy to allow continued development of root dentin. A case report is presented that demonstrates the use of calcium hydroxide (CaOH2) as an indirect pulp-copping material for the purpose of continued maturogenesis of an early-erupted permanent tooth with severe mobility and almost-begun root formation. Seven-year radiographic and clinical follow-up demonstrated a vital pulp and physiologic root development without any endodontic failure clinically or radiographicaly.

Finite element simulation of the behavior of the periodontal ligament: a validated nonlinear contact model.

Due to its significance in tooth movement, the stress/deformation field of periodontium and the alveolar bone remodeling process, periodontal ligament (PDL) cannot be excluded from the studies investigating dental biomechanics regarding its excessive deformability. Therefore, many analytical and numerical researches are carried out to simulate its response and to create a constitutive model via experiments intending to discover the material properties of PDL. The aim of this study is to formulate a user specified contact model that can be used in conjunction with finite element (FE) software and reflects PDL's influence on neighboring structures based on the currently available information, without requiring an actual volumetric finite element mesh of ligament. The results show good agreement with available experimental tooth mobility data. Smooth stress fields are obtained on the tooth root and alveolar bone, which is a significant aspect in bone-remodeling studies. The advantage of simulating PDL as a contact model at the interface of tooth root and the alveolar process instead of a solid-meshed FE model with poor geometric morphology and/or very dense mesh is expected to save pre/post-processing workforce, to increase the accuracy and to contribute to the smoothness of interface stress distributions.

Experiment and hydro-mechanical coupling simulation study on the human periodontal ligament.

In this paper, a new method involving an experiment in vivo and hydro-mechanical coupling simulations was proposed to investigate the biomechanical property of human periodontal ligament (PDL). Teeth were loaded and their displacements were measured in vivo. The finite element model of the experiment was built and hydro-mechanical coupling simulations were conducted to test some PDL's constitutive models. In the simulations, the linear elastic model, the hyperfoam model, and the Ogden model were assumed for the solid phase of the PDL coupled with a model of the fluid phase of the PDL. The displacements of the teeth derived from the simulations were compared with the experimental data to validate these constitutive models. The study shows that a proposed constitutive model of the PDL can be reliably tested by this method. Furthermore, the influence of species, areas, and the fluid volume ratio on PDL's mechanical property should be considered in the modeling and simulation of the mechanical property of the PDL.

Numerical simulation and biomechanical analysis of an orthodontically treated periodontally damaged dentition.

BACKGROUND AND OBJECTIVE: Once periodontitis has been completely resolved, one common follow-up method is to carry out orthodontic treatment to take advantage of the residual bone, i.e., via tooth intrusion. In this study, the biomechanical behavior of teeth in a reduced periodontium was studied by numerically simulating upper-incisor intrusion accomplished with various orthodontic mechanics. MATERIALS AND METHODS: Using the finite element method, a patient-customized 3D model of a periodontally reduced dentition was generated in order to simulate tooth movement. The morphology of this upper-jaw model was derived from cone-beam computed tomography (CBCT) datasets of four patients. Material parameters were adopted from previous investigations, including teeth (E=20 GPa), periodontal ligament (PDL) (bilinear elastic; E1=0.05 MPa; E2=0.20 MPa; ε12=7%), and bone (homogeneous, isotropic; E=2 GPa). Two intrusion scenarios were used, the first drawing from Burstone's segmented-arch technique to intrude four splinted incisors at a time, and the second one using cantilevers to intrude single incisors. The aforementioned PDL material parameters were varied in several ways to simulate different biological and biomechanical states of PDL. All simulations were recalculated with an idealized, periodontally intact model to assess the effect of bone loss by way of comparison. RESULTS: Single-tooth intrusion via cantilever mechanics was accompanied by less rotation than the segmented-arch approach. Both intrusion systems involved significantly greater degrees of tooth displacement and PDL load in the periodontally reduced model. CONCLUSION: Periodontally reduced dentitions are associated with an increased load on periodontal tissue. This can be counteracted by reducing orthodontic force levels and by selecting mechanics that do not harm the tissue. In so doing, the use of numerical methods may greatly facilitate individualized computer-aided treatment-planning strategies.

Finite element analysis of equine incisor teeth. Part 2: investigation of stresses and strain energy densities in the periodontal ligament and surrounding bone during tooth movement.

This study investigated the hypothetical contribution of biomechanical loading to the onset of equine odontoclastic tooth resorption and hypercementosis (EOTRH) and to elucidate the physiological age-related positional changes of the equine incisors. Based on high resolution micro-computed tomography (µCT) datasets, 3-dimensional models of entire incisor arcades and the canine teeth were constructed representing a young and an old incisor dentition. Special attention was paid to constructing an anatomically correct model of the periodontal ligament (PDL). Using previously determined Young's moduli for the equine incisor PDL, finite element (FE) analysis was performed. Resulting strains, stresses and strain energy densities (SEDs), as well as the resulting regions of tension and compression within the PDL and the surrounding bone were investigated during occlusion. The results showed a distinct distribution pattern of high stresses and corresponding SEDs in the PDL and bone. Due to the tooth movement, peaks of SEDs were obtained in the PDL as well as in the bone on the labial and palatal/lingual sides of the alveolar crest. At the root, highest SEDs were detected in the PDL on the palatal/lingual side slightly occlusal of the root tip. This distribution pattern of high SEDs within the PDL coincides with the position of initial resorptive lesions in EOTRH affected teeth. The position of high SEDs in the bone can explain the typical age-related alteration of shape and angulation of equine incisors.

[Biomechanical basis splinting of loose teeth while preserving their mobility at physiological].

The aim of this study was biomechanical rationale for splinting mobile teeth with periodontitis according to the height and slope of teeth crowns, their degree of mobility, and type of occlusion. The research studied the effect of axial vertical and horizontal loads on the functioning of the proposed method of splinting. Set clear indications and contraindications for the use of the method of splinting. Biomechanically proven unreasonableness includes teeth with III degree of mobility in the splinted construction. Clinical variant of splinting is only possible at the height of the anatomical crowns of the teeth of at least 7 mm, otherwise the preferred laboratory methods for the manufacture of tires.

Material properties of periodontal ligaments.

The mechanism of orthodontic teeth movement is not entirely explained. The principal reaction on tissues at the cellular and molecular level is initiated by the force applied to the tooth crown and transferred in turn upon the periodontal ligament (PDL). It seems, therefore, that the PDL and particularly its properties play a key role in bone remodelling. One of the more commonly used methods, which is capable of analysis of a wide range of orthodontic movements or distribution of stress and strain within teeth and periodontium, is the finite element method (FEM). Aiming to achieve the FEM model as close as possible to in vivo conditions, it is necessary to account for accurate material properties. The aim of the present study is to compare particular studies and descriptions of material characteristics of the PDL. The analysis of available articles shows how imperfect modern descriptions of PDL material properties available today are, which in the precise method could allow the analysis of the occurrences within the in vivo processes in a non-destructive manner. The complicated anatomy and physiology of PDL, which incur significant parameter changes with age and disease susceptibility, make the accurate description of this material so difficult. The available study results show that those characteristics should be precise and complicated, which undoubtedly impedes the calculation processes but generates reliable results.

Changes in masticatory performance and quality of life in individuals with chronic periodontitis.

BACKGROUND: This study evaluates the effect of periodontitis on masticatory performance and quality of life index. METHODS: Patients (n = 24; 23 to 76 years of age) with periodontal conditions ranging from healthy to generalized disease categorized by the alveolar bone height-to-tooth length (AB/T) ratio were separated into the following two groups: control (AB/T >50%) and test (AB/T <50%). The masticatory performance was evaluated through continuous mastication of a special device called a biocapsule. The Brazilian Oral Health Impact Profile (OHIP-14Br) questionnaire was used to assess the oral health-related quality of life. The Student t test was applied for independent samples (P <0.05) to evaluate the masticatory performance, and the Mann-Whitney U test was used to determine quality of life (P <0.05). RESULTS: There was a statistically significant difference in masticatory efficiency between groups (P = 0.006). Statistically significant differences were also observed in the following parameters: 1) physical pain (P = 0.003); 2) psychologic discomfort (P = 0.008); 3) physical disability (P = 0.033); and 4) OHIP-14Br total score (P = 0.001). The control group achieved the best indicators. Both the masticatory performance and quality of life indicators showed significant correlation with the alveolar bone height. CONCLUSION: The loss of periodontal supporting structures has negative effects on the masticatory performance and quality of life.

Current concepts in hypophosphatasia: case report and literature review.

BACKGROUND. Hypophosphatasia (HP) is characterized by defective mineralization of bone and teeth because of deficient alkaline phosphatase activity. There are generally six recognized clinical forms, of which the most severe is often lethal prenatally or early in life. In milder forms, such as odontohypophosphatasia (OHP), premature exfoliation of primary teeth may be the only clinical manifestation. CASE REPORT. A 20-month-old girl was referred to the Specialist Paediatric Salaried Dental Service within the Harrogate and District NHS Foundation Trust with mobility of tooth numbers 71 and 81. Clinical examination revealed grade III mobile 71 and 81, with minimal gingival inflammation and plaque deposits. There were no other dental findings and no significant medical history. Tooth numbers 71 and 81 exfoliated prematurely with no evidence of root resorption, shortly after presentation. Haematological and urinary investigations showed no abnormalities. Histological examination showed a complete absence of cementum. A diagnosis of OHP was made. After 10 months of dental follow-up, no further teeth have increased mobility. CONCLUSION. Odontohypophosphatasia should be included as a differential diagnosis in children presenting with early loss of primary teeth. The dentist may be the first health care professional to whom the patient presents.

[Periodontal tissue spectral assessment].

The periodontal condition was investigated by means of tooth natural frequency assessment. The correlation between tooth natural frequency and mobility was found out. The comparative estimation of percussion and spectral methods for natural frequency assessment revealed the percussion method to be more complicates because the initial acoustic signal is disturbed by external noises and hammer sound. The spectral method allows receiving reliable and reproducible results when using modified two-parametrical periodontometer.

Early prognostic indicators and outcome prediction model for replanted avulsed teeth.

AIM: To identify early clinical variables that are most predictive of treatment outcome and to develop a model that will allow prediction of treatment outcomes based on these variables. STUDY DESIGN AND METHODS: A dental trauma database was used to randomly identify patients who had received treatment for avulsed teeth between 1998 and 2007. A data extraction form was designed and completed for each tooth. Demographic, diagnostic and treatment information recorded in the patient's records, in addition to radiographs, were viewed retrospectively. STATISTICS: The significance and the predictive power for each early clinical variable were assessed using a univariate logistic regression model. Only significant variables (p<0.05) were considered eligible for the prediction model and a c-index was then constructed for their respective predictive power (0.5 = no predictive power, 1.0 = perfect prediction). RESULTS: Of the original sample of 213 patients who had received treatment for avulsed teeth between 1998-2007 only 105 fulfilled the criteria for evaluation. Two models ('At first visit' and 'at initial treatment visits') were produced with a total of five variables that were significant and holding the greatest predictive power (high c-index): patient age (p=0.001, c=0.80); stage of root formation (p=0.001, c=0.76); storage medium (p=0.047, c=0.58); tooth mobility after dressing (p=0.001, c=0.70); and tooth mobility after splinting (p=0.003, c=0.70). These variables underwent multi-variate analysis and the final models had good predictive abilities (c-index of 0.80 and 0.74). CONCLUSION: These predictive models based on patient age, stage of root formation, storage medium, tooth mobility after dressing and tooth mobility after splinting were shown to have high predictive value and will enable a clinician to estimate the long term prognosis of avulsed and replanted teeth. It will enable planning for further treatment with a realistic view of outcome at an early stage.