GLOSSARY OF PERIODONTAL TERMINOLOGY

Acellular cementum
Cementum that does not contain any cementocytes. [Back to text]

Active eruption
The process whereby a developing tooth bodily moves through the jaw bone and overlying mucosa to its functional position in the oral cavity. [Back to text]

Afibrillar cementum
Cementum with a matrix that is devoid of fibrillar type I collagen. [Back to text]

Alveolar bone
The bone of the alveolar process. [Back to text]

Alveolar bone proper
The thin cribriform plate that lines the alveoli. [Back to text]

Alveolar crest
The most coronal portion of the alveolar process. [Back to text]

Alveolar mucosa
The lining mucosa that covers the alveolar process. It consists of a non-keratinized lining epithelium and the subjacent alveolar submucosa. [Back to text]

Alveolar process
The portion of the jawbone that houses the alveoli and the roots of the teeth. [Back to text]

Alveolar submucosa
The loose connective tissue between the alveolar process and the overlying lining epithelium. [Back to text]

Alveolus (plural: alveoli)
The root-shaped depression in the jaw bone that contains the root of a tooth. [Back to text]

Ameloblasts
Highly specialized cells, derived from the inner enamel epithelium and pre-ameloblasts, that are responsible for enamel synthesis and maturation.  After amelogenesis is completed, they contribute to the formation of the reduced enamel epithelium. [Back to text]

Anastomosis (plural: Anastomoses)
Refers to the linkage between adjacent blood vessels. [Back to text]

Anchoring fibrils
Short, striated fibrils that extend from the lamina densa into the adjacent lamina propria. They are composed of type VII collagen and are thought to play a role in the attachment of the epithelium to the connective tissue. [Back to text]

Ankylosis
The fusion of any part of the tooth with bone. [Back to text]

Apical
Toward the tip of the root. [Back to text]

Attached gingiva
Refers to that portion of the gingiva attached to the tooth or alveolar bone, as determined by probing. NOTE: Anatomically, this terminology is incorrect as the probe often severs the dentoepithelial junction. This results in an underestimation of the actual width of the attached gingiva. [Back to text]

Basal lamina
A product of epithelial cells that mediates the attachment of the cell to adjacent structures such as the lamina propria or a tooth surface. It is composed of a lamina densa and a lamina lucida. The internal basal lamina refers to the basal lamina between the junctional epithelium or reduced enamel epithelium and the tooth. The external basal lamina refers to the basal lamina at the junction of the connective tissue with the junctional epithelium or reduced enamel epithelium. [Back to text]

Buccal
The surface of a tooth that faces toward the cheeks. [Back to text]

Cell rests of Malassez
Epithelial cell remnants from the breakup of Hertwig's epithelial root sheath that remain in the periodontal ligament close to the cementum surface. [Back to text]

Cellular cementum
Cementum that contains cementocytes in their lacunae. [Back to text]

Cemento-enamel junction
The linear junction between the apical border of the enamel cap and the root cementum. [Back to text]

Cementum
The mineralized tissue covering the root dentin that serves to anchor periodontal ligament fibers.  It is classified into acellular and cellular cementum, depending on whether it is cell-free of contains lacunae with cementocytes. It is also classified into fibrillar and afibrillar cementum, depending on whether its organic matrix contains fibrillar collagen or is devoid of fibrils. Coronal cementum is found on the crowns of teeth and radicular cementum on the roots. [Back to text]

Cementoblast
Cell found on the surface of cementum and responsible for its synthesis. [Back to text]

Cementocyte
Cell found within the lacunae of cellular cementum. [Back to text]

Cervical
Pertaining to the cervix or neck of the tooth. [Back to text]

Col (gingival)
That portion of the interdental gingiva of molar teeth that is located between the oral and the vestibular papillae. [Back to text]

Collagen
A molecule characterized by a triple helical structure and a high content of glycine, proline and hydroxyproline. It is a major constituent of connective tissue fibers, the organic matrix of bone, dentin and cementum, and basal laminas. [Back to text]

Compact bone
Dense bone devoid of marrow spaces. [Back to text]

Coronal
Toward the crown end of a tooth. [Back to text]

Coronal cementum
Cementum located over the enamel of the crown. [Back to text]

Cribriform plate
A plate of compact bone with numerous perforations that allow blood vessels and or nerves to pass through it. [Back to text]

Crown
The part of the tooth covered by enamel is referred to as the anatomic crown. The clinical crown refers to any part of the tooth that sticks out into the oral cavity. It may be shorter or longer than the anatomic crown. [Back to text]

Dental cuticle
An amorphous, non-mineralized layer of organic material located between the junctional epithelium and the tooth surface.  It most likely represents an accumulation of basal lamina material or possibly the product of an inflammatory exudate. [Back to text]

Dental follicle
The ectomesenchymal tissue immediately surrounding the enamel organ.  It gives rise to cementum,  the periodontal ligament and the alveolar bone proper. [Back to text]

Dental lamina
The ectodermal link between the dental organ and the ectodermal lining of the oral cavity. [Back to text]

Dental papilla
The ectomesenchymal component of the tooth germ that gives rise to the dental pulp. [Back to text]

Dentoepithelial junction
The interface between the junctional epithelium and the tooth surface.  The term is synonymous with "epithelial attachment". [Back to text]

Desmosome (or Macula adherens)
The most common intercellular junction in stratified, squamous epithelia. It is a disk-like structure composed of specialized membranous contributions from adjacent cells. Tonofibrils that extend from the desmosome into the adjacent cytoplasm form a cytoskeleton that dissipates mechanical forces applied to the intercellular junction. [Back to text]

Digestive vacuole
Cytoplasmic vesicle that contains phagocytosed material together with lysosomal enzymes. [Back to text]

Distal
The surface of a tooth that faces away from the midline, along the dental arch. [Back to text]

Ectomesenchymal cells
Primitive cells derived from the migration of neural crest cells into the branchial arches.  These cells serve as precursors for most of the connective tissue cells in the gingiva. [Back to text]

Elastic fibers
A connective tissue fiber composed of elastin and fibrillin.  It provides connective tissues with their elastic properties. [Back to text]

Enamel organ
The ectodermally derived structure that gives rise to the enamel and Hertwig's epithelial root sheath. It assumes different shapes during tooth development, including the bud, cap and bell stages. [Back to text]

Enamel space
The empty space seen in demineralized histological sections formerly occupied by the enamel prior to histologic processing. [Back to text]

Epithelial attachment
The structural complex that mediates the attachment of the reduced enamel epithelium or junctional epithelium to the tooth, namely the internal basal lamina and hemidesmosomes.   The primary epithelial attachment refers to the attachment of reduced enamel epithelium to the tooth.  The secondary epithelial attachment refers to the attachment of the junctional epithelium to the tooth. [Back to text]

Epithelial diaphragm
The apical prolongation of Hertwig's epithelial root sheath that separates the dental papilla within the developing root from the surrounding dental follicle. [Back to text]

External resorption
Refers to the removal by odontoclasts of tooth structure from outside the tooth, as contrasted to internal resorption where the resorptive process starts in the pulp. [Back to text]

Extrinsic fibers
Extrinsic fibers of cementum are principal fibers of the periodontal ligament that became incorporated into cementum as part of the mineralized matrix. They are mainly the product of periodontal ligament fibroblasts and are orientated perpendicular to the cementum surface. [Back to text]

Fibrillar cementum
Cementum with a matrix that contains readily detectable fibers of type I collagen. [Back to text]

Fibroblast
Connective tissue cell responsible for the synthesis and remodeling of non-mineralized connective tissues. [Back to text]

Filaggrin
A histidine-rich protein found in keratohyalin granules that serves as a cementing matrix for the densely packed tonofilaments in the stratum corneum. [Back to text]

Free gingiva
A clinical term that refers to that portion of the gingiva believed to be "free," that is, not attached to the tooth. NOTE: Since the determination is made by probing, a procedure that often severs the junctional epithelium,  the extent of unattached gingival tissue is generally overestimated from an anatomical point of view (see Attached gingiva). [Back to text]

Fundus
The bottom of a pocket or an alveolus. [Back to text]

Furcation
The space just apical to the junction of multiple roots.  [Back to text]

Gingiva
The gingiva forms a collar around the tooth, 1-9 mm wide, that is attached in part to the tooth and in part to the alveolar process. With the exception of the palatal gingiva, its apical border is the mucogingival junction that separates it from adjacent lining mucosa. [Back to text]

Gingival epithelium
The epithelium that lines the external surfaces of the gingiva (oral epithelium) and the gingival sulcus (sulcular epithelium) and mediates the coronal junction of the gingiva to the tooth (junctional epithelium). [Back to text]

Gingival groove
Linear indentation along the oral or vestibular surface of the marginal gingiva that parallels the gingival margin. It is located at about the same level as the apical border of the junctional epithelium. Note: its level does not correspond to that of the bottom of the anatomic sulcus. [Back to text]

Gingival margin
The most coronal portion of the gingiva. [Back to text]

Gingival sulcus
A shallow groove between the marginal gingiva and the tooth surface, bound by sulcular epithelium laterally and junctional epithelium apically. [Back to text]

Hemidesmosomes
Specializations of the epithelial cell membrane for attachment to the adjacent basal lamina and adjacent structures.  [Back to text]

Hertwig's epithelial root sheath
The collar of odontogenic epithelium, initially formed from the apical margin of the enamel organ, that surrounds the developing root and guides its morphologic development. [Back to text]

Incisive canal
A passage located in the midline of the anterior maxilla through which the anterior palatal nerve passes from the floor of the nose into the oral cavity. [Back to text]

Incisive foramen
The palatal orifice of the incisive canal. [Back to text]

Incisive papilla
An oval mucosal protuberance just palatal to the maxillary incisors. It covers the approximate opening of the incisive foramen. [Back to text]

Inner enamel epithelium
The inner epithelial layer of the dental organ that gives rise to the ameloblasts. [Back to text]

Interdental col (see Col)

Interdental papilla
A pyramid-shaped section of gingiva that occupies the interdental space anterior to the molars.  In the molar region the interdental space may have an oral as well as a vestibular papilla joined by a "col." [Back to text]

Interdental gingiva
The gingiva that occupies the interdental spaces coronal to the alveolar crest. [Back to text]

Internal resorption
Refers to the removal by odontoclasts of tooth structure from the pulpal side of the tooth, as contrasted to external resorption where the resorptive process starts from outside the tooth. [Back to text]

Intrinsic fibers
Intrinsic fibers of cementum are fibers produced by cementoblasts of the periodontal ligament. Unlike extrinsic fibers, that are orientated perpendicular to the cementum surface, intrinsic fibers run in a plane parallel to the cementum surface. [Back to text]

Junctional epithelium
That portion of the gingival epithelium that is attached to the tooth on one side and to the gingival connective tissue on the other.  Its coronal end lines the bottom of the gingival sulcus. [Back to text]

Keratinized mucosa
A mucosa with a keratinizing epithelial surface. [Back to text]

Keratinization
The process that leads to the differentiation of superficial epithelial cells into a cornified layer. It provides increasing resistance to environmental injuries. [Back to text]

Keratinocytes
True epithelial cells capable of undergoing keratinization under the right conditions.   [Back to text]

Keratohyalin granules
Electron-dense granules found in the cytoplasm of cells within the stratum granulosum of keratinizing epithelia. They are composed of the protein filaggrin. [Back to text]

Labial
The surface of a tooth that faces toward the lips. [Back to text]

Lacuna
Cavity within mineralized tissues such as bone and cementum that contains individual cells such as osteocytes and cementocytes. [Back to text]

Lamina densa
The electron-dense, approximately 60 nm thick, amorphous layer on the distal aspect of the basal lamina.  It is primarily composed of type IV collagen. Together with the lamina lucida (see below) it forms the basal lamina. [Back to text]

Lamina lucida
The electron-lucent layer, approximately 40 nm thick layer located between the lamina densa (see above) and the cell membrane. It is primarily composed of the glycoprotein laminin. Together with the lamina densa it forms the basal lamina. [Back to text]

Lamina propria
The dense connective tissue beneath the masticatory mucosa. It consists of 2 distinct layers: the papillary layer which forms finger-like extensions in the depressions delineated by the rete ridges and the reticular layer that is located beneath the rete ridges. [Back to text]

Leukocytes
White blood cells.  They include 2 broad categories, polymorphonuclear leukocytes and round cells.  Polymorphonuclear leukocytes comprise a variety of cell types, such as neutrophils, eosinophils, basophils and some of their immature forms. Round cells include lymphocytes, monocytes and plasma cells and some of their immature forms. [Back to text]

Lining mucosa
The non-keratinized mucosa that lines most of the oral cavity, with the exception of the gingiva, anterior palate and dorsum of the tongue. [Back to text]

Lymphocyte
A leukocyte often found in dense aggregates in chronically inflamed tissues. It is an important cell in immune-mediated inflammatory reactions. [Back to text]

Lysosome
Intracytoplasmic organelle containing  mediators of inflammation as well as numerous enzymes able to break down various tissue components. [Back to text]

Macrophage
A tissue cell responsible for the removal of dead cells and debris from the tissues by phagocytosis. It also plays important roles in immune-mediated reactions. [Back to text]

Macula adherens (see Desmosome)

Marginal gingiva
That portion of the gingiva just apical to the gingival margin. It has no distinct limits. [Back to text]

Mast cell
Connective tissue cell with prominent cytoplasmic granules that store heparin, assorted proteolytic enzymes and vasoactive substances, including histamine. [Back to text]

Masticatory mucosa
The keratinized oral mucosa of the gingiva and the hard palate. [Back to text]

Melanin
Brown to black pigment synthesized by melanocytes in the gingival epithelium and stored as melanosome granules in melanocytes as well as keratinocytes. [Back to text]

Melanocytes
Cells of neural crest origin, closely associated with the basal epithelial cell layer, that synthesize melanin pigment in the form of melanosomes or pigment granules. [Back to text]

Melanosome
A cytoplasmic inclusion, found in melanocytes as well as associated keratinocytes, that consists of membrane- bound granules of melanin synthesized by the melanocytes. [Back to text]

Mesial
The surface of a tooth that faces toward the midline. [Back to text]

Mesial drift
The slow, continuous movement throughout life of teeth in the intact dental arch toward the midline, i.e. in a mesial direction.  This physiologic movement allows the tooth contacts to remain tight despite interproximal wear. [Back to text]

Mixed fiber cementum
Cementum that contains a mixture of extrinsic and intrinsic fiber cementum. [Back to text]

Mucogingival junction
The linear junction between the lining mucosa of the vestibule and the masticatory mucosa of the gingiva. [Back to text]

Neutrophil
Polymorphonuclear leukocyte characterized by azure staining cytoplasmic granules (or lysosomes) containing a wide variety of hydrolytic enzymes. [Back to text]

Occlusal
Toward the biting surface of a tooth. [Back to text]

Odontoblast
The cells in the dental papilla and dental pulp responsible for the synthesis of dentin. [Back to text]

Odontoclast
Multinucleated giant cell that plays a primary role in the resorption of tooth structure.  It is structurally and functionally indistinguishable form osteoclasts. [Back to text]

Oral epithelium (of the gingiva)
That portion of the gingival epithelium that lines the external surface of the gingiva. [Back to text]

Orthokeratinization
A form of keratinization where the cells of the stratum corneum become very flat, loose their nuclei and cytoplasmic organelles and are now composed of densely packed tonofilaments cemented by filaggrin. [Back to text]

Osteoblast
Bone cells located on the surface of bone that are responsible for its deposition and remodeling. [Back to text]

Osteoclast
Multinucleated giant cell that plays a primary role in bone resorption.  It is structurally and functionally indistinguishable form odontoclasts. [Back to text]

Osteocyte
Bone cells located within individual lacuna in bone that are responsible for maintaining calcium and phosphate homeostasis through remodeling of the lacunar walls. [Back to text]

Osteoid
Incompletely mineralized, newly formed bone. [Back to text]

Outer enamel epithelium
The outer epithelial layer of the dental organ. [Back to text]

Oxytalan fibers
They are a form of immature elastic fiber, composed of microfilaments only, and unique staining characteristics. [Back to text]

Palatal rugae
Mucosal ridges on either side of the midline of the anterior palate.  They are phylogenetically related to the baleens of whales. [Back to text]

Papilla (see Interdental papilla)

Papillary layer of the lamina propria (see Lamina propria). [Back to text]

Papillary layer of the reduced enamel epithelium
This term is synonymous with the outer layer of the reduced enamel epithelium, which often exhibits papillary, or bulbous projections on its outer aspect. [Back to text]

Parakeratinization
A pattern of keratinization characterized by incomplete keratinization of the cells in the stratum corneum. The cells are flattened and composed primarily of packed tonofilaments. However, the cells may retain remnants of nuclei and other organelles. [Back to text]

Passive eruption
The process whereby the clinical crown of a tooth increases in size because of   apical recession of the surrounding tissues, rather than bodily movement of the tooth. [Back to text]

Periodontal
Belonging to or characteristic of the periodontium. [Back to text]

Periodontal ligament
The thin ligament that attaches the cementum layer to the adjacent alveolar bone. [Back to text]

Periodontium
The tissue complex participating in the support of the tooth. The tissues include the gingiva, periodontal ligament, cementum and alveolar bone proper. [Back to text]

Plasma cell
An inflammatory cell frequently found as dense aggregates in chronically inflamed tissues.  It has a characteristic structure that includes a round eccentric nucleus and a basophilic cytoplasm rich in rough-surfaced endoplasmic reticulum. It is responsible for the localized production of antibody. [Back to text]

Polymorphonuclear leukocyte
Type of white blood cell characterized by a lobulated nucleus and a granular cytoplasm. It includes neutrophils, which make up the majority of the polymorphonuclear leukocytes, as well as eosinophils and basophils. [Back to text]

Pre-ameloblasts
Precursor cells of ameloblasts, derived from the inner enamel epithelium.  Unlike ameloblasts that can no longer divide, these cells are still able to undergo cell division. [Back to text]

Predentin
The non-mineralized layer of freshly synthesized dentin located between the odontoblasts and the mineralized dentin. [Back to text]

Principal fibers
The major fiber groups found in different parts of the periodontium, such as the gingiva and the periodontal ligament.

The principal fibers of the gingiva include the following:  Alveologingival, dentogingival, dentoperiosteal, circumferential (or circular), intergingival, semicircular, transgingival, and transseptal fiber groups.

The principal fibers of the periodontal ligament include the following: Alveolar crest, horizontal, oblique, periapical and interradicular fiber groups. [Back to text]

Probing depth
The distance between the gingival margin and the tip of a periodontal probe during periodontal probing. [Back to text]

Radicular cementum
The cementum layer covering the root. [Back to text]

Reduced enamel epithelium
The thin, multilayered epithelium that covers the enamel following its formation.  It is derived primarily from the ameloblast and stratum intermedium layers of the enamel organ, but may include cell remnants from the stellate reticulum and outer enamel epithelium. [Back to text]

Rete peg
The histologic appearance of a Rete ridge in cross-section. [Back to text]

Rete ridges
The ridge-like structures on the underside of the epithelium that abut the lamina propria. [Back to text]

Reticular fibers
Thin collagen fibers found in proximity to epithelia and vascular basal laminas.  They tend to stain readily with silver stains, hence they are also referred to as argyrophilic fibers. [Back to text]

Reticular layer of the lamina propria (see Lamina propria)

Retrocuspid papilla
A small mucosal tag occasionally detected on the lingual aspect of the mandibular canines.  It has no clinical significance, but merely represents a localized anatomic variation. [Back to text]

Reversal line
A distinct line in stained sections of bone that indicates the location where bone resorption gave way to bone apposition. [Back to text]

Root cementum (See Radicular cementum)

Rugae (See Palatal rugae)

Sharpey's fibers
These are mineralized collagen fibers within bone or cementum that help to anchor tendons or ligaments to the mineralized tissue.  They are originally part of the tendon or ligament, but become incorporated into and part of the mineralized tissue. [Back to text]

Smear layer
A granular layer seen at the junction between an instrumented tooth surface and new cementum.  It is the result of mechanical scraping during therapeutic procedures aimed at gaining new attachment. [Back to text]

Stellate reticulum
The network of star-shaped cells in the dental organ located between the stratum  intermedium and outer enamel epithelium. [Back to text]

Stratum basale (or Basal layer)
The most proximal epithelial cell layer, in direct contact with the basal lamina. [Back to text]

Stratum corneum (or Cornified layer)
The outermost layer of stratified, squamous, keratinizing epithelia, consisting of flattened keratinized cells. [Back to text]

Stratum granulosum (or Granular layer)
The epithelial cell layer located immediately distal to the stratum spinosum. It is characterized by the presence of electron-dense keratohyalin granules. [Back to text]

Stratum intermedium (or Intermediate layer)
The epithelial layer of the dental organ that is immediately adjacent to the inner enamel epithelium or ameloblasts. [Back to text]

Stratum spinosum (or Spinous layer)
The major component layer of stratified, squamous epithelium. It is located between the stratum basale (basal layer) and the stratum granulosum (granular layer). [Back to text]

Sulcular epithelium
The epithelium lining the gingiva within the gingival sulcus. [Back to text]

Tomes' granular layer
A granular layer in the peripheral dentin close to the dentino-cemental junction. [Back to text]

Tonofibril
A bundle of tonofilaments. [Back to text]

Tonofilaments
Filamentous proteins in the cytoplasm of epithelial cells that serve as a major precursor of keratin. [Back to text]

Vestibular
The surface of a tooth that faces toward the vestibule. [Back to text]

Vestibule
The space between the dental arch and the lips and cheeks. [Back to text]