based on the attachment of human teeth is described as_because_
Answers
Answer:
plants make their own food with the help of light water and sunlight
Explanation:
Abstract
In this study, a comparison between structure, chemical composition and mechanical properties of collagen fibers at three regions within a human periodontium, has enabled us to define a novel tooth attachment mechanism. The three regions include 1) the enthesis region: insertion site of periodontal ligament fibers (collagen fibers) into cementum at the root surface, 2) bulk cementum and 3) the cementum dentin junction (CDJ). Structurally, continuity in collagen fibers was observed from the enthesis, through bulk cementum and CDJ. At the CDJ the collagen fibers split into individual collagen fibrils and intermingled with the extracellular matrix of mantle dentin. Under wet conditions, the collagen fibers at the three regions exhibited significant swelling suggesting a composition rich in polyanionic molecules such as glycosaminoglycans. Additionally, site-specific indentation illustrated a comparable elastic modulus between collagen fibers at the enthesis (1 – 3 GPa) and the CDJ (2 – 4 GPa). However, the elastic modulus of collagen fibers within bulk cementum was higher (4 – 7 GPa) suggesting presence of extrafibrillar mineral.
It is known that the tooth forms a fibrous joint with the alveolar bone which is termed a gomphosis. Although narrower in width than the periodontal ligament space, the hygroscopic CDJ can also be termed as a gomphosis; a fibrous joint between cementum and root dentin capable of accommodating functional loads similar to that between cementum and alveolar bone. From an engineering perspective, it is proposed that a tooth contains two fibrous joints that accommodate the masticatory cyclic loads. These joints are defined by the attachment of dissimilar materials via graded stiffness interfaces, such as; 1) alveolar bone attached to cementum with the PDL and 2) cementum to root dentin with the CDJ. Thus, through variations in concentrations of basic constituents, distinct regions with characteristic structures and graded properties allow for attachment and the load bearing characteristics of a tooth.
1. INTRODUCTION
Biomechanical function of a load bearing system is defined by the physical properties of the tissues and their interfaces (interphases). However, inflammation due to disease progression leads to degraded physical properties resulting in loss of attachment and function. This study was performed to provide a foundation for tissue engineering formulations for tooth attachment by defining physical characteristics of tissues and interfaces within the human periodontium.
The periodontium of a human tooth includes three mineralized tissues: alveolar bone, cementum and root dentin, of which cementum and alveolar bone interface with a soft fibrous tissue; the periodontal ligament (PDL), forming a fibrous joint or gomphosis [1, 2]. Periodontal fibers and Sharpey’s fibers in acellular cementum seemingly attach to root dentin [3–5]. Additionally, they were reported to be calcified in acellular cementum [3, 4]. In addition, the acellular cementum fibers intermingle with the dentin matrix [6]. More recently, similar observations on acellular cementum were reported [7]. Although not clear in studies by Dewey, 1926 [5], results presented to date were only on acellular cementum.
Cementum is attached to root dentin via a hydrophilic fibrous cementum-dentin junction (CDJ) [8]. The CDJ is also known as the innermost cementum layer, intermediate cementum or collagen hiatus and consists of collagen fibrils and remnants of epithelial cells of Hertwig’s Epithelial root sheath (HERS) [9]. Additionally, it was suggested not to be a distinct matrix layer but a composite of non-collagenous proteins and collagen fibrils [10]. Despite the existing theories and these observations, no physical property associations between the fibrous CDJ and the PDL insertions into cementum, also known as Sharpey’s fibers (SFs) have been made.
In this study the attachment of bulk cementum to root mantle dentin was investigated with respect to the periodontal ligament (PDL) and previously reported hydrophilic CDJ [8]. This study sought to demonstrate that the collagen fibers within the CDJ are continuous with the Sharpey’s fibers in human cellular cementum, using various high-resolution imaging techniques and histology. The structure at micro- and nano-scales was investigated using light and atomic force microscopy techniques and the site-specific mechanical properties were studied using AFM-based nanoindentation.
2. MATERIALS AND METHODS