Cementum is a thin layer of hard, mineralized tissue that covers the surface of the tooth root.
Characteristics of Cementum
Organic matrix: composed of a framework of densely packed collagen fibers together by the gellike extracellular ground substanceMicroscopic anatomy of cemntum
Mineralized portion: made up of hydroxyapatite crystals (calcium and phosphate C. Contains no blood vessels or nerves (Hypersensitivity of the root surface occurs when the cementum is removed exposing the dentin. It is the dentin that is sensitive to brushing or the touch of a dental instrument.)
Types of Cementum
Acellular cementum \primary Contains no cementocytes within its mineralized tissue First to be formed and covers approximately the cervical third or half of the root No new acellular cementum is produced during the life of the tooth Thickness ranges from 30 to 60 u,m Sharpey's fibers make up most of the structure of acellular cementumCellular cementum\secondary 1. Contains cementocytes within its mineralized tissue 2. Formed after the tooth has erupted and is less calcified than acellular cementum 3. Deposited in intervals throughout the life of the tooth (thickness increases with age) 4. Thickness ranges from 150 to 200 u m 5. Sharpey's fibers make up a smaller portion of cellular cementum Cementoenamel Junction.
The cementum covering the root may have any one of three relationships with the enamel of the tooth crown. In order of frequency, the cementum may overlap the enamel, meet the enamel, or there is a gap between the cementum and enamel. This order of frequency is known as the OMG (overlap, meet, gap).
Overlap: in 60% of all cases, the cemehtum overlaps the enamel for a short distance. B. Meet: in 30% of all cases, the cementum meets the enamel. C. Gap: in 10% of all cases, there is a small gap between the cementum and enamel (exposing the dentin in this area). The patient may experience discomfort (dentinal sensitivity) during instrumentation. The use of local anesthesia maybe helpful during instrumentation, and desensitization of sensitive areas should be performed following instrumentation.
is the bone of the upper or lower jaw that surrounds and supports the roots of the teeth.
The existence of alveolar bone is dependent on the presence of teeth; when teeth are extracted, in time, the alveolar bone resorbs. If teeth do not erupt, the alveolar bone does not develop..The alveolar bone forms the bony sockets that provide support and protection for the roots of the teeth.
the alveolar process is composed of three layers of hard tissue and covered by a thin layer of connective tissue.
The alveolar bone proper (or cribriform plate) is the thin layer of bone that lines the socket to surround the root of the tooth: 1. The alveolus is the bony socket; a cavity in the alveolar bone that houses the root of a tooth (alveolus, singular; alveoli, plural). 2. The alveolar bone proper has numerous holes that allow blood vessels from the cancellous bone to connect with the vessels of the periodontal ligament space. 3. The ends of the periodontal ligament fibers are embedded in the alveolar bone proper.
The cortical bone is a layer of compact bone that forms the hard, outside wall of the mandible and maxilla on the facial and lingual aspects. This cortical bone surrounds the alveolar bone proper and gives support to the socket: 1. The buccal cortical bone is thin in the incisor, canine, and premolar regions; cortical bone is thicker in molar regions. 2. Since the cortical plate is only on the facial and lingual sides of the jaw, it will not show up in a radiograph; only the cancellous bone and the alveolar bone proper can be seen on a radiograph.
The alveolar crest is the most coronal portion of the alveolar process. a. In health, the alveolar crest is located 1 to 2 mm apical to (below) the CEJ of the teeth . b. When viewed from the facial or lingual aspect, the alveolar crest meets the teeth in a scalloped (wavy) line that follows the contours of the CEJs.
The cancellous bone (or spongy bone) is the latticelike bone that fills the interior portion of the alveolar process (between the cortical bone and the alveolar bone proper). The cancellous bone is oriented around the tooth to form support for the alveolar bone proper.
The periosteum is a layer of connective soft tissue covering the outer surface of bone; it consists of an outer layer of collagenous tissue and an inner layer of fine elastic fibers. Endostium :covers marrow spaces, contain osteoblast.