Hematopoietic Stem Cells as a Novel Source of Dental Tissue Cells.

While earlier studies have suggested that cells positive for hematopoietic markers can be found in dental tissues, it has yet to be confirmed. To conclusively demonstrate this, we utilized a unique transgenic model in which all hematopoietic cells are green fluorescent protein (GFP). Pulp, periodontal ligament (PDL) and alveolar bone (AvB) cell culture analysis demonstrated numerous GFP cells, which were also CD45 (indicating hematopoietic origin) and co-expressed markers of cellular populations in pulp (dentin matrix protein-1, dentin sialophosphoprotein, alpha smooth muscle actin [ASMA], osteocalcin), in PDL (periostin, ASMA, vimentin, osteocalcin) and in AvB (Runx-2, bone sialoprotein, alkaline phosphatase, osteocalcin).

Correlation of changes in the mandible and retina/choroid vasculature of a rat model of BRONJ.

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) causes bones of the mandible and maxilla to become necrotic and protrude into the oral cavity. Compromised blood supply to bone is also a feature of BRONJ. The design of this study was first to use our established technique of molar extraction and IV bisphosphonate injection to produce features of BRONJ in rats that mimic the human disease; second to confirm vascular changes in the mandible and eye using micro-CT of vascular casts, and image analysis of retina/choroid images; and third to show parallel bisphosphonate-induced changes in the structure and markers of the vasculature of the bone and eye.

Mechanical Stretching of Mouse Calvarial Osteoblasts In Vitro Models Changes in MMP-2 and MMP-9 Expression at the Bone-Implant Interface.

Bone to mechanical loading elicits a biological response that has clinical significance for several areas in dental medicine, including orthodontic tooth movement, tempromandibular joint disease, and endosseous dental implant osseointegration. Human orthopedic studies of failed hip implant sites have identified increased mRNA expression of several collagen-degrading matrix metalloproteinases (MMPs), while in vitro experiments have shown increases in MMP secretion after exposure to inflammatory mediators. This investigation evaluates the effects of mechanical deformation on in vitro osteoblasts by assessing changes in MMP gene expression and enzyme activity.

In vitro study of the adverse effect of nicotine and physical strain on human gingival fibroblasts as a model of the healing of wounds commonly found in the military.

Background: Significant adverse effects on fibroblast growth and metabolism are observed with nicotine. We investigated the synergistic effects of nicotine and cyclical mechanical strain (CMS) on human gingival fibroblasts (HGFs) in a wound-healing model.

Methods: HGFs were isolated and grown in Dulbecco's modified Eagle's medium.

Effect of metformin on periimplant wound healing in a rat model of type 2 diabetes.

Purpose: To investigate the effects of hyperglycemia and metformin (a popular biguanide antidiabetic) on periimplant healing.

Methods: Thirty-six male rats were assigned to 3 groups: (1) nondiabetic Wistar-Kyoto rats (controls), (2) Goto-Kakizaki (GK) spontaneously diabetic rats (GK group), and (3) GK rats were fed metformin (100 mg/kg body weight per day) in their water for 4 weeks (GK + Met group). The right maxillary first molars were extracted and sites were allowed 1 month to heal.

Vascular alterations in the sprague-dawley rat mandible during intravenous bisphosphonate therapy.

Long-term use of intravenous bisphosphonates, such as zoledronic acid (zoledronate), has been linked to bisphosphonate-related osteonecrosis of the jaw (BRONJ). Invasive dental surgery seems to trigger the bone necrosis in most cases. To determine the effects of zoledronic acid on the vascular structure of the rat mandible.

Preparation, physical-chemical characterization, and cytocompatibility of polymeric calcium phosphate cements.

Aim. Physicochemical mechanical and in vitro biological properties of novel formulations of polymeric calcium phosphate cements (CPCs) were investigated. Methods.

Development of a rat model of bisphosphonate-related osteonecrosis of the jaw (BRONJ).

The purpose of this study was to develop a rat model predictive of bisphosphonate-related osteonecrosis of the jaw (BRONJ) after exodontias. Thirty female rats were randomized into 2 groups, control and experimental. The experimental group received 2 intravenous injections of zoledronate (20 μg/kg).

Polymeric-calcium phosphate cement composites-material properties: in vitro and in vivo investigations.

New polymeric calcium phosphate cement composites (CPCs) were developed. Cement powder consisting of 60 wt% tetracalcium phosphate, 30 wt% dicalcium phosphate dihydrate, and 10 wt% tricalcium phosphate was combined with either 35% w/w poly methyl vinyl ether maleic acid or polyacrylic acid to obtain CPC-1 and CPC-2. The setting time and compressive and diametral tensile strength of the CPCs were evaluated and compared with that of a commercial hydroxyapatite cement.

Advanced glycation endproducts and rat dental implant osseointegration.

Advanced glycation endproducts (AGEs) are a diverse group of molecular adducts formed in environments high in reducing sugars that accumulate with aging and in diabetes. This study tests the hypothesis that AGEs inhibit the stabile osseointegration of dental implants through tissue interactions that interfere with bone turnover and compromise the biomechanical properties at the bone-implant interface. Maxillary first molars were extracted from 32 rats and allowed to heal for 4 weeks.

Effect of systemic parathyroid hormone (1-34) and a beta-tricalcium phosphate biomaterial on local bone formation in a critical-size rat calvarial defect model.

Objective: The objective of this study was to evaluate local bone formation following systemic administration of parathyroid hormone (1-34) (PTH), a surgically implanted synthetic beta-tricalcium phosphate (beta-TCP) bone biomaterial serving as a matrix to support new bone formation.

Materials And Methods: Critical-size, 8 mm, calvarial through-and-through osteotomy defects were surgically created in 100 adult male Sprague-Dawley rats. The animals were randomized into five groups of 20 animals each to receive one of the following treatments: PTH (15 microg PTH/kg/day; subcutaneously), PTH/beta-TCP, beta-TCP, or particulate human demineralized freeze-dried bone (DFDB), and sham-surgery controls.

Cytotoxicity, calcium release, and pH changes generated by novel calcium phosphate cement formulations.

Few published studies describe the biological properties of calcium phosphate cements (CPCs) for dental applications. We measured several biologically relevant properties of 3 CPCs over an extended (8 wk) interval. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light-activated modified polyalkenoic acid, or 35% w/w polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs, respectively.

Rat model for studying tissue changes induced by the mechanical environment surrounding loaded titanium implants.

Purpose: This study presents a new rat oral implant model for assessing histologic changes in the mechanical environment surrounding loaded and unloaded dental implants.

Materials And Methods: The maxillary left first molar from retired breeder rats was extracted, and the site was allowed to heal for 1 month. A titanium miniscrew implant was then placed into the site and allowed to heal for 21 days.

Tensile strain-induced Ets-2 phosphorylation by CaMKII and the homeostasis of cranial sutures.

Background: Mechanotransduction underpins the homeostasis of musculoskeletal tissues, including cranial sutures. Intracellular calcium, [Ca 2+]ic, and protein phosphorylation are two intermediate variables in signal relay during mechanotransduction. This project establishes a chain of cause and effect, linking cellular strain to substrate phosphorylation, and identifies the agent and target sites of phosphorylation.

Effect of ovariectomy and alendronate on implant osseointegration in rat maxillary bone.

Bisphosphonates such as alendronate (ALD), although controversial, are worthy of investigation for the enhancement of implant osseointegration in patients with low bone mass who are already taking bisphosphonates for osteoporosis. These patients may receive additional benefits and be acceptable candidates for dental implants without needing to change their medication regimen and possibly as a result of their medication regimen. The purpose of this study was to compare implant osseointegration in maxillary bone of normal rats with a rat model of postmenopausal estrogen deficiency (ovariectomized [OVX]), with and without ALD.

Effects of induced premaxillary suture fusion on the craniofacial morphology in growing rats.

Objective: Due to premaxillary rapid development and fusion with the maxilla at the fetus stage, the functions of the premaxillary suture still remain unclear. This study was designed to explore the effect of artificial induced premaxillary suture fusion on craniofacial morphology.

Methods: Thirty Sprague Dawley rats were divided into control and experimental groups, with 3 week, 5 week and 8 week subgroups of five animals each.

Net expansion of dried demineralized dentin matrix produced by monomer/alcohol saturation and solvent evaporation.

The purpose of this work was to determine if nonaqueous methacrylate monomer/alcohol mixtures could expand dried collapsed demineralized dentin matrix. Thin disks (ca. 200 microm) of human dentin were demineralized and placed in wells beneath contact probes of linear variable differential transformers.

Infiltration/evaporation-induced shrinkage of demineralized dentin by solvated model adhesives.

During dentin bonding, solvated adhesive comonomers are applied to water-saturated decalcified dentin matrices. When alcohol-solvated hydrophilic or hydrophobic methacrylate monomers are applied, they chemically remove water and cause matrix shrinkage during comonomer infiltration. Evaporation of solvent induces further shrinkage.

Fractal analysis of the PDL-bone interface and implications for orthodontic tooth movement.

Background: The periodontal ligament (PDL) is a soft tissue interposed between the tooth and the alveolar bone. It is responsible for transmission of forces in vivo; this promotes bone remodeling. The purpose our study was to use fractal analysis to quantify the complex morphology of the PDL-bone interface.

Brief synopsis of cranial sutures: optimization by adaptation.

This article reviews the form and function of cranial sutures across the temporal and spatial scales. The temporal scale spans 530 million years, from ostracoderms to contemporary humans. The spatial scale spans eight orders of magnitude, from the macroarchitectural level (the entire cranium), through the mesoarchitectural (the local/regional bone-suture-bone complex) and microarchitectural levels (tissues and cells), to the nanoarchitectural level (molecules within and outside the cells).

An evaluation of the origin of trabecular bone patterns using visual and digital image analysis.

Objective: The purpose of this research project was to investigate the origin of the anatomical structures interpreted as trabecula bone on dental radiographic images.

Study Design: Mandible sections were cut sagitally into halves. Trabecular bone was removed from each section in 4 stages.

Tension-induced reduction in connexin 43 expression in cranial sutures is linked to transcriptional regulation by TBX2.

Cranial sutures produce bone at precisely the right rate and time to maintain homeostasis. Connexin 43 (CX43), a protein important for communication in bone, is downregulated during cell proliferation and is released from suppression or upregulated during differentiation. Our previous studies have shown that binding sites for the transcription regulatory protein TBX2 are located in the promoter sequence, upstream of the Cx43 gene.

Digital image analysis of cadaver mandibular trabecular bone patterns.

Background: The purpose of this study was to investigate the source of radiographic trabecular patterns by removing trabecular bone in four sequential steps from six cadaver mandible sections, radiographing the sections after each removal, and using four digital-image analysis methods to quantify any resulting changes to the radiographs.

Methods: Mandible sections were cut sagittally into halves. Trabecular bone was removed from each section in four stages.