The bone morphogenetic protein (BMP) family is an important factor in the regulation of cell ular life activities and in the development of almost all tissues. BMP-mediated signaling plays an important role in tooth root development, which is a part of tooth development. Epithelial and mesenchymal interactions are involved in tooth root development, but the BMP signaling pathway has a different effect on tooth root development in epithelial and mesenchymal. This review summarizes the advances of BMP signaling in tooth root development.
Bone Morphogenetic Protein 2 ; Bone Morphogenetic Protein 7 ; Bone Morphogenetic Proteins ; physiology ; Odontogenesis ; Signal Transduction ; Tooth ; Tooth Root ; growth & development

Tooth eruption is a series of complicated physiological processes occurring once the crown is formed completely, as well as when the tooth moves toward the occasion plane. As such, the tooth moves through the alveolar bone and the oral mucosa until it finally reaches its functional position. Most studies indicate that the process of tooth eruption involves the alveolar bone, dental follicles, osteoclasts, osteoblasts, and multiple cytokines. Dental follicles regulate both resorption and formation of the alveolar bone, which is required for tooth eruption. Furthermore, root formation with periodontal ligament facilitates continuous tooth eruption. However, the exact mechanism underlying tooth eruption remains unclear. Hence, this review describes the recent research progress on the cellular and molecular mechanisms of tooth eruption.
Dental Sac ; Humans ; Osteoblasts ; Osteoclasts ; Periodontal Ligament ; Tooth ; Tooth Eruption ; physiology ; Tooth Root

Cementum is critical for anchoring the insertion of periodontal ligament fibers to the tooth root. Several aspects of cementogenesis remain unclear, including differences between acellular cementum and cellular cementum, and between cementum and bone. Biomineralization is regulated by the ratio of inorganic phosphate (Pi) to mineral inhibitor pyrophosphate (PPi), where local Pi and PPi concentrations are controlled by phosphatases including tissue-nonspecific alkaline phosphatase (TNAP) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (NPP1). The focus of this study was to define the roles of these phosphatases in cementogenesis. TNAP was associated with earliest cementoblasts near forming acellular and cellular cementum. With loss of TNAP in the Alpl null mouse, acellular cementum was inhibited, while cellular cementum production increased, albeit as hypomineralized cementoid. In contrast, NPP1 was detected in cementoblasts after acellular cementum formation, and at low levels around cellular cementum. Loss of NPP1 in the Enpp1 null mouse increased acellular cementum, with little effect on cellular cementum. Developmental patterns were recapitulated in a mouse model for acellular cementum regeneration, with early TNAP expression and later NPP1 expression. In vitro, cementoblasts expressed Alpl gene/protein early, whereas Enpp1 gene/protein expression was significantly induced only under mineralization conditions. These patterns were confirmed in human teeth, including widespread TNAP, and NPP1 restricted to cementoblasts lining acellular cementum. These studies suggest that early TNAP expression creates a low PPi environment promoting acellular cementum initiation, while later NPP1 expression increases PPi, restricting acellular cementum apposition. Alterations in PPi have little effect on cellular cementum formation, though matrix mineralization is affected.
Alkaline Phosphatase ; metabolism ; Animals ; Cell Line, Transformed ; Dental Cementum ; cytology ; metabolism ; physiology ; Gene Expression Profiling ; Humans ; Mice ; Models, Animal ; Phosphoric Diester Hydrolases ; metabolism ; Pyrophosphatases ; metabolism ; Tooth Root ; metabolism ; physiology ; X-Ray Microtomography

Formation of the periodontium begins following onset of tooth-root formation in a coordinated manner after birth. Dental follicle progenitor cells are thought to form the cementum, alveolar bone and Sharpey's fibers of the periodontal ligament (PDL). However, little is known about the regulatory morphogens that control differentiation and function of these progenitor cells, as well as the progenitor cells involved in crown and root formation. We investigated the role of bone morphogenetic protein-2 (Bmp2) in these processes by the conditional removal of the Bmp2 gene using the Sp7-Cre-EGFP mouse model. Sp7-Cre-EGFP first becomes active at E18 in the first molar, with robust Cre activity at postnatal day 0 (P0), followed by Cre activity in the second molar, which occurs after P0. There is robust Cre activity in the periodontium and third molars by 2 weeks of age. When the Bmp2 gene is removed from Sp7(+) (Osterix(+)) cells, major defects are noted in root, cellular cementum and periodontium formation. First, there are major cell autonomous defects in root-odontoblast terminal differentiation. Second, there are major alterations in formation of the PDLs and cellular cementum, correlated with decreased nuclear factor IC (Nfic), periostin and α-SMA(+) cells. Third, there is a failure to produce vascular endothelial growth factor A (VEGF-A) in the periodontium and the pulp leading to decreased formation of the microvascular and associated candidate stem cells in the Bmp2-cKO(Sp7-Cre-EGFP). Fourth, ameloblast function and enamel formation are indirectly altered in the Bmp2-cKO(Sp7-Cre-EGFP). These data demonstrate that the Bmp2 gene has complex roles in postnatal tooth development and periodontium formation.
Actins ; analysis ; Activating Transcription Factor 2 ; genetics ; Age Factors ; Ameloblasts ; pathology ; Amelogenesis ; genetics ; Animals ; Bone Morphogenetic Protein 2 ; genetics ; Cell Adhesion Molecules ; analysis ; Cell Differentiation ; genetics ; Cementogenesis ; genetics ; Dental Cementum ; pathology ; Dental Pulp ; blood supply ; Fluorescent Dyes ; Green Fluorescent Proteins ; Male ; Mice ; Mice, Knockout ; Microvessels ; pathology ; Molar ; growth & development ; Molar, Third ; growth & development ; NFI Transcription Factors ; analysis ; Odontoblasts ; pathology ; Odontogenesis ; genetics ; Periodontal Ligament ; growth & development ; Sp7 Transcription Factor ; Stem Cells ; physiology ; Tooth Root ; growth & development ; Transcription Factors ; genetics ; Vascular Endothelial Growth Factor A ; analysis ; Zinc Fingers ; genetics

One-step apexification using mineral trioxide aggregate (MTA) has been reported as an alternative treatment modality with more benefits than the use of long-term calcium hydroxide for teeth with open apex. However, orthograde placement of MTA is a challenging procedure in terms of length control. This case series describes the sequence of events following apical extrusion of MTA into the periapical area during a one-step apexification procedure for maxillary central incisor with an infected immature apex. Detailed long-term observation revealed complete resolution of the periapical radiolucent lesion around the extruded MTA. These cases revealed that direct contact with MTA had no negative effects on healing of the periapical tissues. However, intentional MTA overfilling into the periapical lesion is not to be recommended.
Adolescent ; Adult ; Aluminum Compounds ; adverse effects ; Apexification ; methods ; Calcium Compounds ; adverse effects ; Dental Fistula ; therapy ; Dental Pulp Necrosis ; therapy ; Drug Combinations ; Female ; Follow-Up Studies ; Foreign Bodies ; etiology ; Gutta-Percha ; therapeutic use ; Humans ; Incisor ; pathology ; Longitudinal Studies ; Male ; Oxides ; adverse effects ; Periapical Abscess ; therapy ; Root Canal Filling Materials ; adverse effects ; Root Canal Obturation ; adverse effects ; Root Canal Preparation ; methods ; Silicates ; adverse effects ; Tooth Apex ; pathology ; Treatment Outcome ; Wound Healing ; physiology

The root is crucial for the physiological function of the tooth, and a healthy root allows an artificial crown to function as required clinically. Tooth crown development has been studied intensively during the last few decades, but root development remains not well understood. Here we review the root development processes, including cell fate determination, induction of odontoblast and cementoblast differentiation, interaction of root epithelium and mesenchyme, and other molecular mechanisms. This review summarizes our current understanding of the signaling cascades and mechanisms involved in root development. It also sets the stage for de novo tooth regeneration.
Cell Differentiation ; genetics ; Dental Cementum ; physiology ; Epithelium ; physiology ; Humans ; Mesoderm ; physiology ; Molecular Biology ; Odontoblasts ; physiology ; Odontogenesis ; genetics ; Signal Transduction ; genetics ; Tooth Root ; embryology ; growth & development

OBJECTIVETo investigate the effect of the continuous light force to the donor teeth on the periodontal healing after transplantation.

METHODSThirty-two maxillary and mandibular incisors in four 10-month-old male Beagle dogs were autotransplanted. The pulps were removed in all teeth. The teeth were divided into four groups, one control and three experimental groups. In control group (group 1), the teeth were unloaded. In the other three experimental groups, continuous force (0.49 N) was applied in the 1st (group 2), 2nd (group 3) and 4th (group 4) week, respectively. The dogs were sacrificed in the 8th week. The tissue blocks were demineralized and sectioned perpendicular to the long axis of the teeth. The histological analysis was made.

RESULTSHistomophometric analysis revealed a significantly lower occurrence of replacement root resorption in the group 3 (2.1%) than in the control group (12.5%, P < 0.05). The significant lower incidence of replacement root resorption, and a higher surface and inflammatory root resorption were found in group 2 (6.3% and 68.8%) than in the control group (12.5% and 41.7%, P < 0.05). No significant difference was found between group 4 and control group (P > 0.05).

CONCLUSIONSThe orthodontic force promoted the regeneration of the periodontal ligament and prevented dentoalveolar ankylosis, whereas excessive initial force might cause root and bone resorption.

Animals ; Dogs ; Incisor ; transplantation ; Male ; Orthodontic Extrusion ; Periodontal Ligament ; physiology ; Root Resorption ; etiology ; Tooth Replantation ; adverse effects ; Transplantation, Autologous ; Wound Healing

Epithelial-mesenchymal interactions (EMIs) are critical for tooth development. Molecular mechanisms mediating these interactions in root formation is not well understood. Laser capture microdissection (LCM) and subsequent microarray analyses enable large scale in situ molecular and cellular studies of root formation but to date have been hindered by technical challenges of gaining intact histological sections of non-decalcified mineralized teeth or jaws with well-preserved RNA. Here,we describe a new method to overcome this obstacle that permits LCM of dental epithelia,adjacent mesenchyme,odontoblasts and cementoblasts from mouse incisors and molars during root development. Using this method,we obtained RNA samples of high quality and successfully performed microarray analyses. Robust differences in gene expression,as well as genes not previously associated with root formation,were identified. Comparison of gene expression data from microarray with real-time reverse transcriptase polymerase chain reaction (RT-PCR) supported our findings. These genes include known markers of dental epithelia,mesenchyme,cementoblasts and odontoblasts,as well as novel genes such as those in the fibulin family. In conclusion,our new approach in tissue preparation enables LCM collection of intact cells with well-preserved RNA allowing subsequent gene expression analyses using microarray and RT-PCR to define key regulators of tooth root development.
Animals ; Dental Cementum ; cytology ; metabolism ; Epithelial-Mesenchymal Transition ; physiology ; Gene Expression Regulation, Developmental ; Laser Capture Microdissection ; Mice ; Mice, Inbred Strains ; Odontoblasts ; metabolism ; Oligonucleotide Array Sequence Analysis ; Reverse Transcriptase Polymerase Chain Reaction ; Tooth Germ ; metabolism ; Tooth Root ; growth & development

This experiment was aimed to shed light on the correlation and quantitative relationships between the width of bovine periodontal ligament (PDL) and the elastic modulus and, more over, between the width of bovine PDL and the capacity ratio of collagen fibers. The width and length of periodontal ligament of PDL were determined by stereomicroscope, and the elastic modulus by the materials testing systems. The collagen fibers in cross section of the specimen were stained with 1% Sirius Red F3B in saturated carbazotic acid, and the photo of stained PDL was collected by stereomicroscope. Image pro plus6.0 image analysis software was used to measure and calculate the capacity ratio of collagen fibers. It was found that there is a negative correlation between the width of bovine periodontal ligament and elastic modulus. The correlation coefficient is -0.21 and the simple linear regression model is Y = 71. 681-0.021x (Width of PDL); there is a positive correlation between capacity ratio of collagen fibers and elastic modulus. The coefficient correlation is 1.583 and the simple linear regression model is Y = -34.944 + 1.583x (The percentage of collagen fibers). Thus, the elastic modulus of bovine PDL increases while the width of bovine PDL decreases, and it increases while the capacity ratio of collagen fibers increases.
Animals ; Cattle ; Collagen ; chemistry ; Elastic Modulus ; Periodontal Ligament ; physiology ; Tensile Strength ; Tooth Root ; anatomy & histology

BACKGROUNDAnimal models are needed for the study of rapid tooth movement into the extraction socket through distraction osteogenesis of the periodontal ligament.

METHODSModified distraction devices were placed on eight dogs between the first and third mandibular premolars on the left sides; similar placement of traditional straight wise appliances on the right sides served as the control. The experimental distractors were activated (0.25 mm/d) twice a day and the control devices were activated (100 g) for two weeks with consolidation periods at weeks two, three, six, and ten. Two dogs were sacrificed at each consolidation time point; rates and patterns of tooth movement, loss of anchorage, and periapical films were evaluated, and the affected premolars and surrounding periodontal tissues were decalcified and examined histologically. General observations, X-ray periapical filming and histology examination were performed.

RESULTSDistal movement ((3.66+/-0.14) mm) measured two weeks after modified distraction exceeded that achieved using the traditional device ((1.15+/-0.21) mm; P<0.05). Loss of anchorage was minimally averaged (0.34+/-0.06) mm and (0.32+/-0.07) mm in the experimental and control sides, respectively. By radiography, apical and lateral surface root resorptions on both sides were minimal. Alveolar bone lesions were never evident. Fibroblasts were enriched in periodontal ligaments and bone spicules formed actively along directions of distraction.

CONCLUSIONSThe canine model is suitable for the study of rapid tooth movement through distraction osteogenesis of the periodontal ligament. The technique accelerates tooth movement, periodontal remodeling, alveolar bone absorption, and may induce fibroblast formation, as compared to the traditional orthodontic method, without adversely affecting root absorption, bone loss, tooth mobility and anchorage loss.

Animals ; Dogs ; Male ; Osteogenesis, Distraction ; methods ; Periodontal Ligament ; physiology ; surgery ; Root Resorption ; etiology ; Tooth Movement Techniques ; methods