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Aim: The model of the unopposed rodent molar was used to study the morphologic and genetic mechanisms of tooth eruption. Methods: Left maxillary molar teeth of 12-day-old Swiss-Webster mice were extracted under anesthesia, and mandibular molars were allowed to supererupt. To trace areas of tissue remodeling and to determine areas of new tissue formation, mice were injected with fluorescent dyes, tetracycline, alizarin red, and calcein blue. Subsequent to sacrifice, mandibular tissue blocks were prepared for ultrathin ground sections, fluorescent microscopy, and von Kossa's mineral detection procedure. A second set of specimens was prepared for RNA extraction and microarray analysis. Results: The data established significant eruption of first and second mandibular mouse molars 12 days after complete extraction of antagonists, exceeding the control side by 0.13 mm. Labeled tissue sections revealed significant amounts of new bone and cementum apposition on the unopposed side compared to the control side, as revealed by fluorescent markers and ultrathin ground sections. Microarray transcript level comparisons between the experimental and the control groups demonstrated significant (more than twofold) increase in gene expression of elastin and tenascin C extracellular matrix proteins; brevican, lumican, and biglycan proteoglycans; as well as fibroblast growth factor 9. Conclusion: In this study, the authors have established the unopposed mouse molar as a model to study tissue dynamics during the axial movement of teeth. The data indicated significant new formation of bone and cementum in tandem with increased expression of extracellular matrix-related genes. [ABSTRACT FROM AUTHOR]

Background: There is growing concern that titanium particles may play a role in peri-implant breakdown. Ultrasonic scalers are routinely used in the debridement of peri-implant lesions. This in vitro study is designed to evaluate if titanium particles are produced when an ultrasonic scaler is used on an implant.Methods: New sandblasted, large grit, acid etched (SLA) coated implants were subjected to ultrasonic scaling with stainless steel, titanium, and PEEK plastic tips. The implants were placed in a holding device and the ultrasonic scaler was positioned on the SLA surface under 25 grams of pressure. The implants were subjected to 30 scaling motions. The ultrasonic coolant water was collected and the number of metallic particles were counted under a light microscope. The particles were confirmed to be titanium via elemental analysis. The implants were visually evaluated for damage to the SLA coating.Results: No metallic particles were detected in the water supplied to the ultrasonic scalers (passive control). Metallic particles were detected when implants were subjected to the ultrasonic coolant water only without the scaler tip touching the implant (active control). All implants that were scaled produced metallic particles and showed easily detectable damage to the SLA layer.Conclusions: All ultrasonic scaling caused the production of titanium particles and caused damage to the SLA coating of the implant. Ultrasonic scalers should be used with great caution in the treatment of peri-implant conditions and care should be taken to not touch the SLA surface of the implant. [ABSTRACT FROM AUTHOR]

We here explore for the very first time how an advanced multiscale mathematical modeling approach may support the design of a provenly successful tissue engineering concept for mandibular bone. The latter employs double-porous, potentially cracked, single millimeter-sized granules packed into an overall conglomerate-type scaffold material, which is then gradually penetrated and partially replaced by newly grown bone tissue. During this process, the newly developing scaffold-bone compound needs to attain the stiffness of mandibular bone under normal physiological conditions. In this context, the question arises how the compound stiffness is driven by the key design parameters of the tissue engineering system: macroporosity, crack density, as well as scaffold resorption/bone formation rates. We here tackle this question by combining the latest state-of-the-art mathematical modeling techniques in the field of multiscale micromechanics, into an unprecedented suite of highly efficient, semi-analytically defined computation steps resolving several levels of hierarchical organization, from the millimeter- down to the nanometer-scale. This includes several types of homogenization schemes, namely such for porous polycrystals with elongated solid elements, for cracked matrix-inclusion composites, as well as for assemblies of coated spherical compounds. Together with the experimentally known stiffnesses of hydroxyapatite crystals and mandibular bone tissue, the new mathematical model suggests that early stiffness recovery (i.e., within several weeks) requires total avoidance of microcracks in the hydroxyapatite scaffolds, while mid-term stiffness recovery (i.e., within several months) is additionally promoted by provision of small granule sizes, in combination with high bone formation and low scaffold resorption rates. [ABSTRACT FROM AUTHOR]

Magnesium ion (Mg2+) is the fourth most common cation in the human body, and has a crucial role in many physiological functions. Mg2+ homeostasis is an important contributor to bone development, however, its roles in the development of dental mineralized tissues have not yet been well known. We identified that transient receptor potential cation channel, subfamily M, member 7 (TRPM7), was significantly upregulated in the mature ameloblasts as compared to other ameloblasts through our whole transcript microarray analyses of the ameloblasts. TRPM7, an ion channel for divalent metal cations with an intrinsic serine/threonine protein kinase activity, has been characterized as a key regulator of whole body Mg2+ homeostasis. Semi-quantitative PCR and immunostaining for TRMP7 confirmed its upregulation during the maturation stage of enamel formation, at which ameloblasts direct rapid mineralization of the enamel matrix. The significantly hypomineralized craniofacial structures, including incisors, molars, and cranial bones were demonstrated by microCT analysis, von Kossa and trichrome staining in Trpm7Δkinase/+ mice. A previously generated heterozygous mouse model with the deletion of the TRPM7 kinase domain. Interestingly, the skeletal phenotype of Trpm7Δ1kinase/+ mice resembled those found in the tissue-nonspecific alkaline phosphatase (Alpl) KO mice, thus we further examined whether ALPL protein content and alkaline phosphatase (ALPase) activity in ameloblasts, odontoblasts and osteoblasts were affected in those mice. While ALPL protein in Trpm7Δ1kinase/+ mice remained at the similar level as that in wt mice, ALPase activities in the Trpm7Δkinase/+ mice were almost nonexistent. Supplemented magnesium successfully rescued the activities of ALPase in ameloblasts, odontoblasts and osteoblasts of Trpm7Δ1kinase/+ mice. These results suggested that TRPM7 is essential for mineralization of enamel as well as dentin and bone by providing sufficient Mg2+ for the ALPL activity, underlining the key importance of ALPL for biomineralization. [ABSTRACT FROM AUTHOR]

Erupting teeth are some of the oldest witnesses of developmental processes in the vertebrate fossil record and provide an important resource for vertebrate cladistics. Here, we have examined a mosasaur jaw fragment from central Texas using ultrathin ground section histology and 3D tomographic imaging to assess features critical for the cladistic placement of mosasaurs among varanoids vs. snakes: (i) the orientation of replacement teeth compared to the major tooth axis, (ii) the occurrence of resorption pits, and (iii) the mode of tooth implantation/attachment to the tooth bearing element (TBE). The replacement tooth studied here developed in an inclined position slightly distal of the deciduous parent tooth, similar to another varanoid squamate, the Gila monster Heloderma suspectum. Ground sections and tomographs also demonstrated that the replacement tooth attachment apparatus was entirely intact and that there was no evidence of mechanical deformation. Sections and tomographs further illustrated that the replacement tooth was located within a bony crypt and the inclination of the crypt matched the inclination of the replacement tooth. These preparations also revealed the presence of a resorption pit within the boundaries of the deciduous tooth that surrounded the developing replacement tooth. This finding suggests that developing mosasaur teeth developed within the walls of resorption pits similar to varanoid tooth germs and unlike developing snake teeth which are surrounded by fibrous connective tissue integuments. Finally, mosasaurs featured pseudo-thecodont tooth implantation with teeth anchored within a socket of mineralized tissue by means of a mineralized periodontal ligament. Together, these data indicate that the moderate inclination of the erupting mosasaur tooth studied here is neither a result of postmortem displacement nor a character representative of snakes, but rather a shared character between Mosasaurs and other varanoids such as Heloderma. In conjunction with the presence of resorption pits and the evidence for pseudothecodont tooth implantation, the tooth eruption and implantation characters described in the present study either place mosasaurs among the varanoids or suggest convergent evolution mechanisms between both clades, with mosasaurs evolving somewhat independently from a common varanoid ancestor. [ABSTRACT FROM AUTHOR]

Background: This report is the second part of the previously published study on the impact of light/chemical hardening technology and a newly formulated composite graft material for crestal augmentation during immediate implant placement.Methods: A total of 48 implants were placed into the sockets of the mesial roots of freshly extracted mandibular premolar teeth in three minipigs. Crestal areas and intrabony spaces were randomly augmented with light-hardened graft materials including a composite graft consisting of polymethylmethacrylate, polyhydroxylethylmethacrylate, and calcium hydroxide (PPCH) plus polyanhydride (PA); PPCH graft; and PA graft, or left untreated. Distal sockets not receiving implants and the sockets of first molars (n = 60) were randomly treated with one of the graft materials or left empty. In addition, two molar sockets were treated with the original PPCH graft material. Quantitative microcomputed tomography (micro-CT) was used to assess alveolar bone structure and tissue compositions. Histologic evaluations included descriptive histology to assess the peri-implant wound healing, as well as histomorphometric measurements to determine bone-to-implant contact (BIC).Results: Both trabecular and cortical bone measurements by micro-CT did not reveal any significant differences among the groups. Sites augmented with PPCH+PA resulted in significantly greater BIC surface than PPCH alone and no-graft-treated implants (P <0.05) histologically. Stained ground sections showed complete bone formation between bone and implant surface in the PPCH+PA group, whereas sites without augmentation showed large gaps between bone and implant surfaces, indicating a slower bone apposition and less BIC surface compared to all other groups. Similar to implant sections, all materials showed positive outcome on trabecular and cortical bone formation in extraction sockets with an intact crestal cortical bone.Conclusion: Histologic evaluations supported the previous findings on implant stability and function and confirmed that PPCH+PA provides a greater BIC with a well-organized implant-bone interface and is useful in crestal augmentation during immediate implant placement. [ABSTRACT FROM AUTHOR]

Freeze-drying is an effective means to control scaffold pore size and preserve its composition. The purpose of the present study was to determine the applicability of lyophilized Platelet-rich fibrin (LPRF) as a scaffold for craniofacial tissue regeneration and to compare its biological effects with commonly used fresh Platelet-rich fibrin (PRF). LPRF caused a 4.8-fold ± 0.4-fold elevation in Runt-related transcription factor 2 (Runx2) expression in alveolar bone cells, compared to a 3.6-fold ± 0.2-fold increase when using fresh PRF, and a more than 10-fold rise of alkaline phosphatase levels and mineralization markers. LPRF-induced Runx2 expression only occurred in alveolar bone and not in periodontal or dental follicle cells. LPRF also caused a 1.6-fold increase in osteoblast proliferation (p < 0.001) when compared to fresh PRF. When applied in a rat craniofacial defect model for six weeks, LPRF resulted in 97% bony coverage of the defect, compared to 84% for fresh PRF, 64% for fibrin, and 16% without scaffold. Moreover, LPRF thickened the trabecular diameter by 25% when compared to fresh PRF and fibrin, and only LPRF and fresh PRF resulted in the formation of interconnected trabeculae across the defect. Together, these studies support the application of lyophilized PRF as a biomimetic scaffold for craniofacial bone regeneration and mineralized tissue engineering. [ABSTRACT FROM AUTHOR]