Gingiva

Shalu  Bathla

1Normal Periodontium2

➢ Gingiva
➢ Periodontal Ligament
➢ Cementum
➢ Alveolar Bone
➢ Aging and Periodontium

GingivaCHAPTER 1

Bathla S

Chapter Outline

❒ Introduction
❒ Definition
❒ Macroscopic Features
❒ Microscopic Features
❒ Microcirculation
❒ Nerve Supply
❒ Clinical Criteria
❒ Related Landmark Studies

INTRODUCTION

Oral mucosa consists of the masticatory mucosa, which includes the gingiva and the covering of the hard palate; the specialized mucosa, which covers the dorsum of the tongue; and the lining mucosa which covers the remaining part of the oral cavity. The gingiva is that part of the masticatory mucosa which covers the alveolar process and protect the underlying tissues. The attachment apparatus of periodontium consists of periodontal ligament, cementum and alveolar bone.

DEFINITION

Gingiva is the part of oral mucosa that covers the alveolar processes of the jaws and surrounds the necks of the teeth.¹ Gingiva acts as a seal to teeth by firmly encircling them. This oral soft tissue is tightly bound to the underlying bone both maxilla and mandible.

MACROSCOPIC FEATURES

Anatomically, the gingiva is divided into the following three domains (Flowchart 1.1 and Fig. 1.1)

Marginal Gingiva/Free Gingiva

Marginal gingiva is the terminal edge of the gingiva that covers the teeth in collar-like fashion.² It is also termed as the free or unattached gingiva as it is not fixed to the basal periosteum of alveolar bone. It is usually 1 mm wide and forms the soft tissue wall of gingival sulcus.

Gingival Sulcus

Gingival sulcus is a narrow space between the tooth and free gingival margin. This V-shaped groove extends from junctional epithelium (JE) at base up to the free marginal gingiva. So functionally one of its soft-tissue walls is formed by the free marginal gingiva. These are specialized tissues that separate tooth from the normal gingival tissues. Gingival sulcus barely permits the entry of a periodontal probe and its probing depth is 2–3 mm (Fig. 1.2).

Free Gingival Groove

Marginal gingiva is separated from an attached gingiva by a shallow line called as free gingival groove. This indentation is located at a level corresponding to the level of cementoenamel junction (CEJ) (Fig. 1.1). Free gingival groove is present in only about 30–40% of adults.³

Flowchart 1.1: Division of gingiva

The presence or absence and the location of the gingival 4groove depend on the distinctness of the fan-shaped arrangement of the supra-alveolar collagenous fibers running from the cementum into the gingiva.

Fig. 1.1: Schematic representation showing macroscopic features of gingiva

Fig. 1.2: Clinical picture showing normal clinical gingival sulcus depth

Fig. 1.3: Clinical picture showing absence of interdental papilla in the diastema

Interdental Gingiva

Interdental gingiva, also known as the interdental papilla, is a portion of the gingiva which is located in the space between two adjacent teeth. However, interdental gingiva is not seen in cases of diastema (Fig. 1.3).

Col

It is a valley-like depression of the interproximal contact areas connecting lingual and buccal interdental papilla (Fig. 1.4).⁴ It is lined by nonkeratinized epithelium, which is gradually replaced by continuing cell division. Epithelium lining of col is similar to junctional epithelium as both have the same origin, i.e. from the dental epithelium.

Significance

As col has nonkeratinized epithelium, it is anatomically predisposed to growth of oral microorganism and susceptible to inflammation and disease progression.

Attached Gingiva

Attached gingiva is the part of the gingiva which is tightly attached to the underlying periosteum of alveolar bone and cementum by connective tissue fibers. It is firm, resilient and hence immovable portion of the gingiva. The attached 5gingiva is thus, firmly entrenched between two movable structures: the marginal gingiva coronally and the alveolar mucosa apically (Table 1.1). Attached gingiva is different from keratinized gingiva and should not be confused with it. Keratinized part of the gingiva usually includes all, i.e. attached gingiva, marginal gingiva, and central portion of the interdental gingiva (Fig. 1.5).

Width of the attached gingiva is measured as the distance between mucogingival junction (MGJ) and the projection on the external surface of the bottom of gingival sulcus/periodontal pocket. The dimensions of the attached gingiva vary from the anterior to the posterior teeth. The width of the attached gingiva is generally wider in the maxilla than in the mandible. The narrowest zone of the gingiva is found in the region of the maxillary and mandibular 1st premolars and usually in connection with frenum and muscle attachments (Table 1.2). The pattern of variation is approximately the same in deciduous and permanent teeth.

Width of the attached gingiva is wider in the supraerupted teeth.⁵ It also increases with age.⁶ This increase in dimension occurs as a result of an increase in the height of the alveolar process, which in turn, is the result of passive eruption.

Significance of Attached Gingiva

It gives support to the marginal gingiva.

It provides attachment or a solid base for the movable alveolar mucosa for the action of lips, cheeks and tongue.

Fig. 1.4: Schematic representation showing col and peaks

Fig. 1.5: Schematic representation showing keratinized gingiva

Table 1.1 Differences between alveolar mucosa and attached gingiva

	Alveolar mucosa	Attached gingiva
Color	Red	Pink
Surface texture	Smooth and shiny	Stippled
Epithelium	Thinner Nonkeratinized Rete pegs absent	Thicker Parakeratinized Rete pegs present
Connective tissue	More loosely arranged More blood vessels	Not so loosely arranged Moderate blood vessels

Table 1.2 Dimensions of attached gingiva (on facial aspects)²

Region	Dimensions (mm)
Maxillary incisor region	3.5–4.5
Mandibular incisor region	3.3–3.9
Maxillary 1st premolar	1.9
Mandibular 1st premolar	approx 1.8

It can withstand frictional and functional stresses of mastication and toothbrushing. When the marginal tissue is the alveolar mucosa, it does not resist the functional stresses of toothbrush trauma imposed on it. Frequently, the result is apical shifting of the marginal tissue and additional recession. Attached gingiva is tightly attached to underlying periosteum and the alveolar bone with the densely organized 6connective tissue. Consequently, it is more resistant to the functional stresses placed upon it. Alveolar mucosa is thin, delicate tissue, poorly attached to bone and cementum and is not capable of withstanding this same functional stresses.
It acts as a barrier for passage of inflammation. In the presence of microbial flora, tooth having alveolar mucosa at its margin shows more clinical signs of inflammation than corresponding tooth that has a sufficient band of the attached gingiva. Such marginal tissue appears to be more susceptible to the products of inflammation that may result in pocket formation or apical migration of both attachment apparatus and marginal tissues.
It provides resistance to tensional stresses. Attached gingiva serves as a buffer between the mobile free gingival margin and mobile alveolar mucosa. There are skeletal muscle fibers within the alveolar mucosa that exert a force in an apical direction on the attached gingiva. This force is dissipated by bound down keratinized tissue.

Measurement of Width of Attached Gingiva

Anatomically: Lip or cheek is stretched to delineate the mucogingival line and at the same time place your probe into the pocket to measure the depth. To determine the width of the attached gingiva, measure the total width of the gingiva (gingival margin to mucogingival line) and subtract pocket depth from it.
Functionally:
- Tension test: Stretch the lip or cheek outward and forward to mark the mucogingival line. Now to calculate the width of the attached gingiva, first measure the total width of the gingiva from gingival margin to mucogingival line. Subtracting the sulcus or pocket depth from total width of the gingiva gives the width of the attached gingiva.
- Roll test: In order to conduct the roll test, first mark the mucogingival line by pushing the adjacent mucosa coronally with a dull instrument. Measure the total width of the gingiva, i.e. distance from gingival margin to mucogingival line. Now subtract the sulcus or pocket depth from this total width of the gingiva to get width of the attached gingiva.⁷ A more reliable method of identifying the MGJ would be to take the side of a periodontal probe or similar blunt instrument and jiggle the alveolar mucosa in an apicoronal direction. Since the alveolar mucosa is mobile, it will roll up ahead of the blunt instrument.
Histochemically: Iodine staining test is one of the histochemical test useful to calculate the width of the attached gingiva. In this test, initially you have to paint the gingiva and oral mucosa with Schiller's or Lugol's solution (iodine and potassium iodide solution). Presence of glycogen content in the alveolar mucosa imparts it brown color. However, attached gingiva stays unstained as it is glycogen free. Measuring the total width of this unstained gingiva and subtracting the sulcus or pocket depth from calculated total width gives us width of the attached gingiva.

Mucogingival Junction

Mucogingival Junction is the important landmark between the coronally positioned attached gingiva and the apically placed alveolar mucosa. It remains stationary throughout life. This anatomical feature is located on the three gingival surfaces, namely (1) facial gingiva of the maxilla and (2) facial and (3) lingual gingiva of the mandible. However, MGJ is absent on the palatal gingiva of the maxilla due to an absence of a freely movable alveolar mucosa on the palate. Palatal gingiva of the maxilla extends with palatal tissue and bound to underlying palatal bones.

Gingival Biotype

Gingival thickness is an important determinant of periodontal health. Gingival phenotype or biotype has been classified by Eger and Muller into thick and thin.⁸ Thick gingival phenotype seems to be more conducive to periodontal health. A thin gingival phenotype predisposes to gingival recession and increased tendency to gingival inflammation (Fig. 1.6).

Fig. 1.6: Clinical picture showing thin gingival phenotype

MICROSCOPIC FEATURES

Histological examination of gingiva exhibited following structures:

Gingival epithelium
Epithelium-connective tissue interface
Gingival connective tissue or lamina propria.

Gingival Epithelium

Normally, the gingival epithelium is divided into three types (Fig. 1.7 and Table 1.3):

Oral epithelium
Sulcular epithelium
Junctional epithelium.

Fig. 1.7: Schematic representation showing gingival epithelium: (A) Oral epithelium, (B) Sulcular epithelium and (C) Junctional epithelium (JE)

Table 1.3 Differences between oral, sulcular and junctional epithelium (JE)

	Oral	Sulcular	Junctional epithelium (JE)
Keratinization	Keratinized	Nonkeratinized	Nonkeratinized
Rete pegs	Present	Absent	Absent
Strata granuloma and corneum	Present	Lacking	Lacking
Merkel cells	Present	Absent	Absent
Langerhans cells (LCs)	Present	Few	Absent
Type IV collagen in basal lamina	Present	Absent	Absent
Tight junctions	More	Few	Few
Acid phosphatase activity	Present	Lacking	Lacking
Glycolytic enzyme activity	High	Lower	Lower
Intercellular space	Narrower	Narrower	Wider

Oral Epithelium

Oral epithelium, also called as an outer epithelium, is a keratinized stratified squamous type of epithelium. It covers the crest and outer surface of marginal gingiva and surface of the attached gingiva.

Oral epithelium consists of following types of cellular layers (Figs 1.8A to D):³

Stratum basale: The cells of stratum basale are either cylindrical or cuboid. The basal cells are found immediately next to the connective tissue and are separated from connective tissue by a basement membrane. It is the germinative layer and hence can divide. When two daughter cells have been formed by cell division, an adjacent older basal cell is pushed into the spinous cell layer and starts as a keratinocyte to traverse the epithelium. It takes approximately 1 month for a keratinocyte to reach the outer epithelial surface, where it is shed from the stratum corneum.

Figs 1.8A to D: Schematic representation showing cell of various layers of stratified squamous epithelium: (A) Stratum corneum, (B) Stratum granulosum, (C) Stratum spinosum and (D) Stratum basale

8
Stratum spinosum: It is a prickle cell layer in which large polyhedral cells with short cytoplasmic processes are present. The uppermost cells from this layer contain granules called as keratinosomes or Odland bodies. These are modified lysosomes, which contain a large amount of enzymes acid phosphatase that is involved in the destruction of organelle membranes.
Stratum granulosum: Cells of this layer are flattened in plane parallel to the gingival surface. Keratohyalin granules, which are associated with keratin formation, are (1 μm in diameter) round in shape and appear within the cytoplasm of the cell.
Stratum corneum: It consists of closely packed, flattened cells that have lost nuclei and the most other organelles as they become keratinized. The cells are densely packed with tonofilaments. Clear, rounded bodies probably representing lipid droplets appear within the cytoplasm of the cell.

Sulcular Epithelium

Sulcular epithelium is a nonkeratinized, stratified squamous epithelium usually lines the gingival sulcus. It covers the area from the crest of the gingival margin up to the coronal end of the junctional epithelium.

Junctional Epithelium

Junctional epithelium (JE) is composed of collar-like band of stratified squamous nonkeratinized epithelium. It usually consists two strata namely stratum basale and stratum suprabasale. The normal length of JE is 0.25–1.35 mm. JE is composed of 15–30 cell layers coronally while only 1–3 cell layers apically and hence taper in apical direction.¹

Development of junctional epithelium: Before the eruptive movements of tooth begin, the crown of the tooth is lined with a double layer of epithelial cells. The inner layer of cells is called as ameloblasts. It complete its formative function and develops hemidesmosomes and gets tightly bound to the enamel surface. The outer layer consists of more flattened cells, the remnants of all the remaining layers of the dental organ. These two layers in combination are termed as “reduced enamel epithelium”. Once the process of tooth eruption starts in the oral cavity, the connective tissue present between reduced enamel epithelium and the overlying oral epithelium begins to breakdown and degenerates.⁹ The basal cells from the oral epithelium as well as the cells of the outer layer of the reduced enamel epithelium start to proliferate and migrate into the degenerative connective tissue. In the end, they blend to form a mass of epithelial cells over the erupting tooth. Cell death in the middle of this epithelial plug leads to the formation of an epithelium-lined canal through which the tooth erupts without hemorrhage. From this mass of an epithelium along with the remaining reduced dental epithelium, the epithelial component of dentogingival junction is established. The reduced ameloblasts which have lost and do not regain the ability to divide change their morphology and are transformed into squamous epithelial cells that retain their attachment to the enamel surface. The cells of the outer layer of the reduced enamel epithelium retain their ability to divide and become basal cells of a forming JE.

Initially, it was first named as epithelial attachment (Epithelansatz) by Gottlieb. However, later it was examined electron microscopically and renamed as junctional or attachment epithelium by Stern. This epithelium synthesizes the material that attaches it to the tooth. Now this material, its morphology and mode and mechanism of function is called as the epithelial attachment. Thus, the cellular structure is referred to as junctional or attachment epithelium and its extracellular tooth attaching substance is called as the epithelial attachment.¹⁰

Junctional epithelium has three zones namely (1) coronal, (2) middle, and (3) apical zones. The coronal zone is the most permeable zone of JE. Middle zone has the maximum adhesiveness among all the three zones.

Fig. 1.9: Schematic representation showing junctional epithelium (JE)

Junctional epithelium has three surfaces: (1) internal surface facing the tooth surface; (2) external surface 9facing the gingival connective tissue and (3) coronal surface forming the base of the sulcus. JE is bound to the tooth surface with internal basal lamina and to gingival connective tissue with external basal lamina (Fig. 1.9).¹¹ The JE is attached to the tooth by means of the epithelial attachment apparatus. Ultramicroscopic examination of this apparatus reveals the presence of hemidesmosomes at the plasma membrane of the cells that directly attached to the tooth (DAT cells), and a basal lamina like an extracellular matrix called as the internal basal lamina on the tooth surface.¹²

Junctional epithelium is easily penetrated because of the following factors:

Along the JE, subepithelial vessels run parallel to the surface and consist mostly venules rather than capillaries. These venules have a greater disposition towards increased permeability as compared to capillaries and arterioles, and they are more susceptible to hemorrhage and thrombosis.
Few intercellular tight junctions
Minimal cytoplasmic filaments
Higher number of intercellular spaces
Lower number of desmosomes.

Functions: Junctional epithelium serves many roles in regulating tissue health:

It provides attachment to the tooth.
It acts as an epithelial barrier against the plaque bacteria. External basement membrane laterally forms an effective barrier against invading microbes.
Rapid cell division and funneling of junctional epithelial cells towards the sulcus hinder bacterial colonization and repair of damaged tissue occurs rapidly.
Junctional epithelium allows two-way movement of variety of substances:
- From connective tissue into crevice: Gingival fluid exudates, polymorphonuclear leukocytes (PMN), immunoglobulin (Ig), complement and various cells of immune system.
- From crevice to connective tissue: Foreign materials, such as carbon particles and trypan blue.
- Active antimicrobial substances are produced by junctional epithelial cells. These are defensins, lysosomal enzymes, calprotectin and cathelicidin.
- Junctional epithelial cells which get activated by microbial substances secrete chemokines such as interleukins (IL-1, IL-6, IL-8) and tumor-necrosis factor-alpha (TNF-α) that attract and activate professional defense cells such as lymphocytes and PMNs.¹³

Cells Present in the Gingival Epithelium

Cells present in the gingival epithelium are namely keratinocytes and nonkeratinocytes.

Keratinocytes: These make up 90% of the total gingival cell population. They originate from the ectodermal germ layer. Structurally, they are like any other cells having cell organelles like nucleus, cytosol, ribosomes and golgi apparatus. They have melanosomes, which are the pigment-bearing granules present within these cells only and not in the other cells of the periodontium. The main function of the gingival epithelium, i.e. protection and barrier against the oral environment is achieved by the proliferation and differentiation of the keratinocytes.¹⁴

Keratinization: It is defined as the transformation of living cells into horny material. Keratinocytes have to move from basal to superficial layers of the epithelium as the process of differentiation occurs in a basocoronal direction culminating in the formation of a keratin barrier. The microfilaments present in the keratinocytes help in cell motility and maintenance of the polarity.¹⁵

Keratinocyte motility requires the following steps:

Development of lamellipodia, i.e. extensions on the leading edge of the cell towards the direction of movement.
Attachment of this portion of the cell to the substratum.
Movement of the cytosolic material towards the leading edge of the cell.
Detachment of the rear end.

Nonkeratinocytes: The various nonkeratinocytes or clear cells are langerhans cells (LCs), merkel cells and melanocytes.

Langerhans cells: They are modified monocytes belonging to reticuloendothelial system, which reside chiefly in suprabasal layers. Paul Langerhans used gold impregnation technique 100 years ago to visualize LCs. Langerhans cells can move in and out of the epithelium unlike melanocytes. They are responsible for communication with immune system by acting as antigen—presenting cells for lymphocytes and expressing receptors for C3 and Fc portion of immunoglobulin G (IgG). These cells contain specific elongated granules called as Birbeck's granules and have marked adenosine triphosphatase activity.¹⁶
10Merkel cells: They are usually found in the basal cell layer of the gingival epithelium. These cells either appears individually or in clusters. These are not dendritic cells as melanocytes and LCs.¹⁷ These cells possess keratin tonofilaments and occasional desmosomes, which link them to adjacent cells. These cells are sensory in nature and respond to touch.¹⁸
Melanocytes: They have their origin from neural crest cells located in the stratum basale of the oral gingival epithelium. Oral mucosal melanocytes were identified in the gingiva by Laidlaw and Cahn in 1932. Long dendritic processes from these cells are interposed between the keratinocytes of the epithelium. They lack tonofilaments and desmosomal connection to adjacent keratinocytes. Melanocytes are responsible for the barrier to ultraviolet (UV) damage and synthesize melanin, which is accountable for providing color to the gingiva. Melanin is synthesized in organelle called premelanosomes or melanosomes in melanocytes from amino acid called phenylalanine.¹⁹ Melanosomes are transported along microtubules and actin filaments to the cell periphery. Melanocytes bind to the plasma membrane and transfer the melanosomes to adjacent keratinocytes (Fig. 1.10). The precise mechanism is unknown, but has been described as cytocrine secretion. Sometimes in the connective tissue, macrophages take up the melanosomes produced by melanocytes in the epithelium and are called as melanophages or melanophores. Melanocytes may be classified as active or inactive, depending on presence or absence of mature melanosomes. The ratio of melanocytes-to-keratinocytes producing epithelial cells is approximately 1: 36 cells.

Epithelium-Connective Tissue Interface

It is the boundary where epithelial tissue meets with connective tissue. Deep extensions of an epithelium that reach down into the connective tissue are called as epithelial ridges or rete pegs. Finger-like extensions of connective tissue that extend up into the epithelium are called as connective tissue papillae (Fig. 1.11).

Ultrastructurally, epithelial-connective tissue interface is composed of lamina lucida and lamina densa. Lamina lucida is an electrolucent zone of 25–45 nm width and composed of glycoprotein laminin. Lamina densa is an electrodense zone of 40–60 nm where type IV collagen is present.²⁰

Fig. 1.10: Schematic representation showing mechanism of melanosome transport

Fig. 1.11: Schematic representation showing epithelium-connective tissue interface

Fig. 1.12: Schematic representation showing basal lamina

From the lamina densa so-called, anchoring fibrils project in a fan-shaped fashion into the connective tissue (Fig. 1.12). These anchoring fibrils are of approximately 750 nm in length and form loops around collagen fibers.11

Junctional Complexes

The various junctional complexes present in the gingiva are:²¹

Tight/occluding junctions are formed by the fusion of external leaflets of adjacent cell membranes at series of points.
Adhesive junctions:
- Cell to cell:
  - Zonula adherens
  - Desmosomes: It is the most common type of junction, which consists of two adjacent attachment plaques one from each cell that are separated by an interval of approximately 30 nm.
- Cell to matrix:
  - Focal adhesions
  - Hemidesmosomes
Communicating (gap) junctions: They have intercellular pipes/channels that apparently bridge both the adjacent membranes and intercellular space. The intercellular space in gap junction is approximately 3 nm and is the major pathway for direct intercellular communication.

Gingival Connective Tissue or Lamina Propria

The gingival connective tissue, also called as lamina propria, is composed of gingival fibers, various cells and ground substance.

Gingival Fibers

Human gingival fibers consist of collagen, reticulin and elastin. Collagen fibers constitute more than 50% of the volume of the human gingiva. Collagen fiber types I, III, IV, V, VI are commonly found in the gingiva.²² Type I collagen predominates. The structural formula for type I collagen is [α1(I)]_2'α2(I). Type III collagen is fetal collagen, which is important in the early phases of wound healing and remains in an unmineralized form. Type III collagen in the gingiva is partly responsible for the maintenance of space in the healing matrix. Lamina densa layer of the basement membrane of the epithelium consisted type IV collagen. Type VI collagen is distributed with the elastin fibers along the blood vessels. Type VI collagen fibers impart rigidity required to maintain the elastic blood vessel wall from undergoing permanent deformation. Type VII collagen acts as anchoring fibrils and helps to reinforce epithelial attachment to the underlying connective tissue.²³

Fig. 1.13: Schematic representation showing gingival fibers

Functions of gingival fibers:

To stabilize the attached gingiva to the alveolar process.
To stabilize the attached gingiva to the tooth.
Helps to maintain the epithelial seal to the tooth.
To provide stability to the tooth.
To brace marginal (free) gingiva firmly against the tooth and adjacent attached gingiva.
To provide rigidity to withstand forces of mastication without being deflected away from the tooth surface.

Types of gingival fibers: Gingival fibers are arranged into following groups (Fig. 1.13):²⁴

Dentogingival group: These fibers extend from the cementum apical to JE and course laterally and coronally into lamina propria of the gingiva. These fibers provide gingival support.
12Alveologingival group: These fibers arise from the alveolar crest and insert coronally into lamina propria of the gingiva. These fibers connect the attached gingiva to the alveolar bone.
Circular group: This group of fibers surrounds the teeth in a ring-like fashion. Such encircling of fibers help to maintain position and contour of the marginal gingiva.
Transseptal fibers: These are the groups of prominent horizontal fibers. These are placed interproximally and extend from cementum of one tooth to the cementum of adjacent tooth. This helps to maintain a relationship of adjacent teeth and protects interproximal bone. The transseptal fibers collectively form an interdental ligament connecting all the teeth of the arch. Though this ligament belongs to the supra-alveolar fiber apparatus but appears to be uniquely important in maintaining the integrity of the dental arch. It is rapidly reformed after excision. Residual portions of transseptal fibers are seen even in advanced stages of resting periodontal disease.
Dentoperiosteal group: On the oral and vestibular surfaces of jaws, dentoperiosteal group of fibers extends from the tooth and passes over the alveolar crest to blend with fibers of the periosteum of the alveolar bone. These fibers anchor tooth to bone and protect periodontal ligament.
Semicircular group: These are group of fibers, which are attached at the proximal surface of a tooth immediately below the CEJ and go around the facial or lingual marginal gingiva of the tooth and get attach on the other proximal surface of the same tooth.
Transgingival group: These fibers are usually attached in the proximal surface of one tooth, transverse the interdental space diagonally, go around the facial or lingual surface of the adjacent tooth, again traverse diagonally the interdental space and attach in the proximal surface of the next tooth. They secure alignment of teeth in the arch.
Intergingival group: These fibers run parallel to dentition on vestibular and oral surfaces. They provide contour and support for the attached gingiva.
Interpapillary group: They are seen in the interdental gingiva extending in a faciolingual direction. They provide support for interdental gingiva.

Dentogingival, dentoperiosteal and alveologingival fibers group provide the attachment of the gingiva to the tooth and to the bony structure. Fibers of circular, semicircular, transgingival, intergingival and transseptal bundles connect teeth to one another.

Cells Present in Gingival Connective Tissue

Fibroblasts: These are derived from the undifferentiated progenitor mesenchymal cells that are present in the follicle.²⁵ These are elongated or spindle-shaped cells having prominent golgi apparatus, rough endoplasmic reticulum, mitochondria, vacuoles and vesicles. Fibroblasts synthesize and secrete various cytokines, growth factors and metabolic products. All these play a vital role in the development, maintenance and repair of the gingival connective tissue.²⁶
Mast cells: These are positioned perivascularly. They are identified by their unique cytoplasmic granules, which produce heparin and histamine.
Other cells: They are eosinophils, macrophages, adipose and inflammatory cells (neutrophils, plasma cells and lymphocytes).

Ground substance: The cells, fibers, nerves and vessels of the gingiva are embedded in a gel-like, viscous ground substance. The ground substance is composed of proteoglycans and glycoproteins, which facilitate cell movement and diffusion of various biologically active substances.

Proteoglycans present in the gingival connective tissues are decorin, versican, biglycan and syndecan.
Glycoproteins present in gingival connective tissue are fibronectin, osteonectin, tenascin and laminin.²⁷

MICROCIRCULATION

Microcirculation to the gingiva, i.e. blood and lymph flow through the smallest blood vessels, is mediated through microcirculatory tracts, blood vessels and lymphatic vessels. Microcirculation plays a vital role in tissue fluid drainage and spread of inflammation. The methods commonly employed to detect microcirculation are immunohistochemical reactions, histoenzymatic reactions, perfusion of dyes, scanning electron microscopy and laser Doppler flowmetry.

Arterial Supply

There are three sources of blood supply to the gingiva namely supraperiosteal arterioles, vessels of periodontal ligament and arterioles emerging from the crest of the interdental septa (Fig. 1.14). Supraperiosteal arterioles mainly supply free gingiva and gingival sulcus. These arterioles are the terminal branches of sublingual artery, mental artery, buccal artery, facial artery, greater palatine artery, infraorbital artery and posterior superior dental artery. Vessels of periodontal ligament mainly supply col area. Arterioles emerging from the crest of the interdental septa mainly supply attached gingiva.

Fig. 1.14: Schematic representation showing gingival blood supply which derives from: (a) Periodontal ligament (b), Supraperiosteal vessels and (c) Alveolar bone

Dentogingival plexus are plexus of blood vessels beneath JE. The blood vessels in this plexus have a thickness of approximately 40 μm, which means that these are mainly venules. No capillary loops occur in a healthy gingiva. Subepithelial plexus are plexus of blood vessels beneath oral epithelium of free and attached gingiva and yield thin capillary loops of 7 μm to each connective tissue papilla.³

The venous and lymphatic vessels follow a course closely parallel to that of arterial supply. Lymphatic drainage starts in the connective tissue papillae and drains into regional lymph nodes. Buccal gingiva of maxilla, buccal and lingual gingiva of mandibular premolar and molar region drains into submandibular lymph nodes. Mandibular incisor region drains into submental lymph nodes whereas 3rd molars’ region drains into jugulodigastric lymph nodes.³ Their main function is to return fluids and filterable plasma components to the blood via the thoracic duct.

NERVE SUPPLY

The various regions of the gingiva are innervated by end branches of trigeminal nerve. The gingiva on the labial aspects of maxillary incisors, canines and premolars are innervated by the superior labial branches from infraorbital nerve. Buccal gingiva in the maxillary molar region is innervated by branches from the posterior superior dental nerve. Palatal gingiva is innervated by greater palatal nerve except incisors area, which is innervated by sphenopalatine nerve. Lingual gingiva in the mandible is innervated by sublingual nerve, a branch of lingual nerve. Gingiva on the labial aspects of mandibular incisors and canines is innervated by mental nerve. Buccal aspect of molars is innervated by buccal nerve. Innervation of mandibular premolars is by both mental and buccal nerves. Krause type end bulbs, Meissner type tactile corpuscles and encapsulated spindles are the types of neural terminals, which are present, mainly within the connective tissue but only a few endings occur between epithelial cells.²⁸

Table 1.4 Clinical criteria

Clinical feature	Appearance in health
Color	• Coral or pale pink
Surface texture	• Free gingiva: Smooth • Attached gingiva: Stippled
Contour	• Marginal gingiva: Knife-edged • Attached gingiva: Festooned
Shape	• Interdental papilla: Pointed, pyramidal
Size	• Fits snugly around the tooth
Consistency	• Attached gingiva: Firm, resilient
Position	• Fully erupted tooth: Margin is 1–2 mm above cementoenamel junction (CEJ)

CLINICAL CRITERIA

Following are the clinical criteria of normal gingiva¹(Table 1.4).

Color

Color of the gingiva is described as coral pink, which depends upon vascular supply, thickness of epithelium, degree of keratinization of epithelium and presence of pigment containing cells (Fig. 1.15).

A variation in gingival pigmentation is not produced by variation in the number of pigment forming melanocytes but by genetically determined variation in their pigment-producing capacity. Thus, variations in gingival pigmentation are related to complexion and race. It is lighter in blond individuals with a fair complexion as compared to dark complexion individuals. In the Caucasian 14individuals, pigmentation is minimal, in African or Asian individuals brown or blue-black areas of pigmentation are seen, while in Mediterranean people occasional patches of pigmentation are found.

Fig. 1.15: Schematic representation showing generalized melanin pigmentation

Melanin Index for Gingival Pigmentation:¹⁹

Category 0: No pigmentation.
Category 1: Solitary unit(s) of pigmentation in the papillary gingiva without formation of continuous ribbon between solitary units.

Category 2: At least 1 unit of formation of continuous ribbon extending from two neighboring solitary units.

Surface Texture

Free gingival surface is smooth while attached gingival surface is stippled. Pitted surface texture giving orange-peel appearance is called as stippling, which is more prominent on the labial than the lingual gingival surfaces. Stippling is normally present on attached gingiva and center of the interdental papilla (Fig. 1.16). Intensity of stippling on an average is approximately 2.6 depressions/mm². It is best viewed by drying the gingiva and switching off the chair light. Stippling is more prominent in the maxillary labial area, and its intensity differs within different areas of the dentition. It varies with age also. It appears usually in children of about 5 years and increases with age but absent in old age. Stippling reflects the contours of the epithelial connective tissue boundary in the healthy gingiva. In erythematous tissue, stippling may disappear, although it may be present in thick fibrotic tissue, which is diseased. It is not an absolute sign of health, and its absence is not necessarily a sign of disease.

Fig. 1.16: Clinical picture showing stippling on attached gingiva and center of interdental papilla

Histologically: The bottom of the pits corresponds to deep ridges or projections of the epithelium into lamina propria of the connective tissue. The protruding parts correspond to a thinner epithelium over ridges or projections of the connective tissue. The ridge and the peg arrangements between the epithelium and connective tissue provide excellent mechanical stability between the two tissue components as well as large contact interphase for metabolic interchange.

Contour

The marginal gingiva follows a scalloped outline normally and straight line along teeth with relatively flat surfaces. Attached gingiva has festooned appearance with intermittent prominence corresponding to contour of roots. When the teeth are placed more labially, the normal arcuate contour is accentuated, and gingiva is located further apically. When teeth are lingually placed, the gingiva is horizontal and thickened. Thus, contour of the gingiva depends upon shape and alignment of the teeth in the arch. Gingival contour also varies with the position and size of the area of proximal contacts along with dimensions of the embrasures.

Shape

Contour of the proximal tooth surface, shape and position of the proximal contact and dimensions of the gingival embrasures are important determinant of shape of the interdental gingiva.

Fig. 1.17: Schematic representation showing four stages of passive tooth eruption

15In normal contact areas and in anterior regions, the interdental papilla is usually pointed and pyramidal. However, it is flat- or saddle-shaped in spaced teeth and in molar regions.

Size

The sum total of the bulk of cellular and intercellular elements and their vascular supply gives the size of the gingiva.

Consistency

On palpation with a blunt instrument, healthy attached gingiva should be firm, resilient and tightly attached to the underlying bone. The presence of abundant collagen fibers and the noncollagenous protein in combination impart firm consistency to the gingiva.

Position

Gingival position usually corresponds with the level of attachment of gingival margin to the tooth. When the tooth erupts into the oral cavity, the margin and sulcus are at the tip of the crown. As the eruption progresses, they are seen closer to the root.

Continuous Tooth Eruption

Concept of continuous tooth eruption states that the process of eruption remains continues throughout the life and does not stop even when teeth meet their functional antagonists. The process of continuous eruption involves two phases, like active and a passive phase.

Active eruption: This phase involves the development of the teeth in the direction of the occlusal plane.

Passive eruption: It takes place due to apical migration of the gingiva. This phase is divided into four stages (Fig. 1.17):¹⁰

Stage 1: The teeth reach the line of occlusion with JE and the base of the gingival sulcus, both are on the enamel.
Stage 2: The JE proliferates with its part both on the cementum and enamel. The base of the sulcus is still on the enamel.
Stage 3: The entire JE is on the cementum while the base of the sulcus is at the cementoenamel junction. As the JE starts to proliferate from the crown onto the root, it does not remain at the cementoenamel junction any longer than at any other area of the tooth.
Stage 4: The JE has proliferated further on the cementum. The base of the sulcus is on the cementum, a portion of which is exposed. Proliferation of the JE onto the root is accompanied by degeneration of gingival and periodontal ligament fibers and their detachment from the tooth.

RELATED LANDMARK STUDIES

Width of Attached Gingiva on Supraerupted Teeth

In 1978, Ainamo A and Ainamo J conducted a study to verify the relationship between the anatomical width of attached gingiva and the amount of past tooth eruption.⁵ The study was based upon the hypothesis that the anatomical width of the attached gingiva is directly proportional to amount of past tooth eruption. For particular study, an 16anatomical width was considered as the distance between mucogingival junction (MGJ) to cementoenamel junction. The study was conducted in men with supraerupted teeth, i.e. tooth eruption beyond the occlusal plane in the lack of antagonists. Short pieces of metal wires were used to highlight first and second maxillary MGJ in 28 maxillary cases and orthopantomograms were captured. For the control, the distances from MGJ to the floor of nasal cavity and to the CEJ were calculated. Normally, occluding teeth were compared with the supraerupted teeth.

The anatomical width of the attached gingiva was found to be 3.7 mm wider in the supraerupted teeth compared to normal occluding teeth. This confirmed that even during marked supraeruption cases the teeth prone to erupt along with their investing tissues keeping the location of the MGJ as constant. This study result is of particular interest as it helps to manage cases of too narrow zone of the attached gingiva. It can be achieved by grinding the tooth out of occlusion and then permitting it along with its gingival margin to erupt.

Role of Sulcular Environment in Controlling Epithelial Keratinization

In 1979, a study by Caffesse RG et al. demonstrated the role of sulcular environment in controlling the epithelial keratinization in the animal tooth. This animal study involved three young rhesus monkeys. Total 40 mucoperiosteal flaps were raised, inverted and sutured in order to bring the outer surface epithelium in contact with tooth surface. The study time interval varies in between 1 hour to 60 days. Before scarification, all monkeys were administered with H₃ thymidine. Both histological and radioautographic examinations were carried out to study epithelial morphology. On coming in contact with tooth, the outer surface epithelium transformed from keratinized to nonkeratinized epithelium with the absence of the rete pegs. These morphological changes resembled with the anatomical characters usually found in sulcular epithelium.

Thus the study suggested two important points:

Sulcular epithelium plays the significant role in controlling keratinization of outer surface gingival epithelium.
Constant irritation due to bacterial plaque and its products lead to premature desquamation of sulcular epithelium and inhibit its full differentiation.²⁹

Characteristics of Periodontal Biotype, Its Dimensions, Associations and Prevalence: a Systematic Review

A recently conducted systematic review by Zweers J et al.³⁰ identified the characteristics of periodontal biotype and its prevalence in the population. The review was aimed to understand the following objectives:

Identifying the characteristics that would help to define different forms of periodontal biotypes.
Determining their anatomical dimensions in relation to the definition.
Evaluating the possible link between these characteristics and periodontal biotypes.
Estimating prevalence of various forms of periodontal biotypes in the population.

The respective review was conducted by searching literature from PubMed-MEDLINE, the Cochrane-CENTRAL and EMBASE. Total 2,581 related articles were studied of which 12 publications were included in review. Gingival thickness (GT), gingival morphotype (GM), tooth dimension (TD), keratinized tissue (KT) and bone morphotype (BM) were identified characteristics that would help to define different forms of periodontal biotypes. Thin scalloped, thick flat and thick scalloped were three periodontal biotypes found among the population. Positive link was found between GT, KTs and BM. However, dental, gingival and osseous dimensions demonstrated weak-to-moderate association with these biotypes.³⁰

POINTS TO PONDER

The pH of the gingiva ranges from 6.5 to 8.5.
Junctional epithelium and gingival fibers together form a functional unit called as dentogingival unit.
Junctional epithelium is the only attachment in the body between soft tissue and a calcified tissue which is exposed to the external environment.
Gingival fiber groups enable the gingiva to form a rigid cuff around the tooth that adds stability, especially when a significant portion of the periodontal ligament and alveolar support is lost. This explains that the increased mobility in periodontally involved teeth immediately after surgical procedures (as these procedures disrupt or remove the gingival fiber groups).

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Chapter Notes

GingivaCHAPTER 1

POINTS TO PONDER