Periodontics › Foundations
The Normal Periodontium
High-yield revision notes with linked practice questions, written for dental students and candidates preparing for the ADC and other licensing examinations.
High-yield notes
Major cell types in the gingiva are keratinocytes. Non kerationcytes are also known as the clear cells. They are Merkel cells, Langerhans cells (remember not the Langhan cells), and the melanocytes.
Melanocytes are found in Basal and spinous layer
Langerhans cells are found in Supra basal layer and act as antigen presenting cells to lymphocytes(Absent in junctional epithelium)
Merkel cells are found in Deep layer (Absent in sulcular epithelium)
Gingiva in children is Less keratinized, less stippled
Attached gingiva: 3.9 mm in mandible), and narrower in the posterior segments (1.9 mm in maxillary and 1.8 mm in mandibular first premolars)
- greatest in the incisor region (3.5 to 4.5 mm in maxilla, 3.3 to
- Least width of attached gingiva is found in First premolar
- The palatal surface of the attached gingiva in the maxilla blends imperceptibly with the equally firm and resilient palatal mucosa.
Mucogingival junction Remains stationary throughout age hence, changes in the width of the attached gingiva are caused by modifications in the position of its coronal portion. The width of the attached gingiva increases with age and in supraerupted teeth.
Shape of the interdental gingiva is PYRAMIDAL if the tip of one papilla is located immediately beneath the contact point.
The area of periodontium more susceptible to tissue break down is Interdental col as it has a non keratinized epithelium.
Gingiva is attached to the tooth by:
- Junctional epithelium
- Internal Basal lamina
- Hemidesmosomes
- Epithelial attachment
Dentogingival unit comprises of the Gingival fibres and junctional epithelium
Gingiva is supplied by
- Supraperiosteal vessels
- Vessels arising from the crest of interdental septa
- Anastomosing arterioles from the periodontal ligament
Length of junctional epithelium is 0.25-1.35 mm
The distance between the apical end of the junctional epithelium and the crest of the alveolus remains constant throughout continuous tooth eruption (1.07 mm)
depth of the gingival sulcus in adult 1.8 mm
- clinical probing depth: 2-3 mm
- histological depth (indicated by the FREE GINGIVAL GROOVE):
- ideal condition: 0 mm
Keratin k19 polypeptides are present in junctional epithelium but absent in keratinized epithelium.
Keratinization of the oral mucosa varies in different areas in the following order: palate (most keratinized), gingiva, ventral aspect of the tongue, and cheek (least keratinized)
Orthokeratinized is the most keratinized epithelium
Parakeratinized epithelium has pyknotic nucleus in the stratum corneum and also lacks Stratum Granulosum.
Keratolinin and involucrin protein are precursors of a chemically resistant structure (the envelope) located below the cell membrane whereas keratohyalin granules disappear and give rise to filaggrin, which forms the matrix of the most differentiated epithelial cell, the corneocyte.
Concentration of glycogen in normal gingiva is inversely related to the degree of keratinization and inflammation.
The transformation of the REE into a junctional epithelium takes between 1 and 2 years
Eulanin fibres are found in Periodontal ligament
Oxytalan fibres run parallel to the blood vessels and are thought to regulate the blood flow
Stippling:
- Orange peel like appearance of gingiva (peau d' orange)
- Present on the attached gingiva and central portion of the interdental papillae but not the marginal gingiva
- less prominent on lingual surfaces and posteriorly
- absent in infancy, appears at about 5 years of age, increases until adulthood, and frequently begins to disappear in old age.
- produced by alternate rounded protuberances and depressions in the gingival surface
- depression causing stippling are 50 µm in diameter
- form of adaptive specialization or reinforcement for function
- presence of stippling indicates a healthy gingiva
- loss of stippling in disease state is reversible and hence reappears once the gingiva returns the healthy state
Basal lamina
- consists of Type-IV collagen except for the internal basal lamina of the junctional epithelium which contains Type VIII collagen
- 300 to 400 Å thick, lying approximately 400 Å beneath the epithelial basal layer
- consists of lamina lucida and lamina densa
- Hemidesmosomes of the basal epithelial cells abut the lamina lucida which is mainly composed of glycoprotein laminin
- Connected to underlying connective tissue by anchoring fibrils of 750 nm length.
The main component of keratins in the stratum corneum is K1 keratin polypeptide (68KD)
Type IV collagen fibres demonstrate "Chicken wire" configuration.
Periodontal ligament
- varies in thickness between 0.1-0.25 mm (average: 0.2 mm)
- has hour glass shape
- is thinner mesially and thicker distally
- narrowest at the fulcrum of the rotation (at the middle third of the root)
Odland bodies are seen in Stratum spinosum
Odland bodies are modified lysosomes and contain acid phosphatases
The turnover time for junctional epithelium is 1-6 days
On average, the oral epithelium is 0.2 to 0.3 mm in thickness
The arrangement of the principal fibers is similar to a suspension bridge or hammock.
Periodontal ligament fibres
- Transeptal group
- are reconstructed even after destruction of the alveolar bone resulting from periodontal disease
- Have no osseous attachment
- Transseptal fibers connect two adjacent teeth.
- Common to both gingival and periodontal fibres
- First formed periodontal ligament fibres
- Give the bony hard like consistency when doing curettage procedures
- alveolar crest fibers prevent the extrusion of the tooth and resist lateral tooth movements
- most pdl fibres are activated when resisting the Vertical Forces.
- oblique group of fibers are the largest group and resist vertical masticatory forces
Small collagen fibers associated with the larger principal collagen fibers in PDL run in all directions, forming a plexus called the indifferent fiber plexus
Thickness of PDL varies on person's age, stage of eruption, function of the tooth, history of any trauma.
Orthodontic treatment is possible because the PDL continuously responds and changes as the result of the functional requirements imposed upon it by externally applied forces.
Cementicles are small calcified structures deriverd from HERS.
Cemental tears occurs in trauma.
Cementum: 1.49 mm. (may increase with age to an average of 2.81 mm)
- Cellular intrinsic fibres cementum fills the resorption lacunae in humans
- Primary cementum is formed before the tooth completes its eruption
- The distance between the crest of the alveolar bone and the cementoenamel junction in young adults varies between 0.75 and
- Types of the CEJ and their prevalence are: (mnemonics: OMG)
Cementum overlapping the enamel (60%)
Edge to edge relation/ Marginal (30%)
Gap junction (10%) (reason for the post scaling sensitivity)
Enamel overlapping the cementum is found rarely.
- Collagen fibres are absent in Acellular afibrillar cementum
- Thickness of cementum on the coronal half of the root: 16 to 60 Am, (or about the thickness of a hair).
- Greatest thickness:150 to 200 Am in the apical third and in the furcation areas.
- thicker in distal surfaces than in mesial surfaces
- Acellular extrinsic fibre cementum is mainly found in the cervical third of the root.
- Hypercementosis of the entire dentition may occur in patients with Paget's disease
Alveolar bone:
- Predominantly compact(due to endosteum and periosteum)
- Interdental septa is cancellous
- least stable of the periodontal tissues because its structure is in a constant state of flux
- Leukemia inhibiting factor (LIF), secreted by osteoblasts, coalesce monocytes into multinucleated osteoclasts, which then resorb bone, releasing calcium ions from hydroxyapatite into the blood.
- Isolated areas in which the root is denuded of bone and the root surface is covered only by periosteum and overlying gingiva are termed fenestrations. In these instances the marginal bone is intact.
- When the denuded areas extend through the marginal bone, the defect is called a dehiscence
- Such defects occur on approximately 20% of the teeth; they occur more often on the facial bone than on the lingual, are more common on anterior teeth than on posterior teeth, and are frequently bilateral.
Practice questions
Select an option to check your answer. Answers are shown below each question.
Which of the following is stippled?
- AMarginal gingiva
- BAttached gingiva
- CMarginal borders of the interdental papillae
- DBoth b and c
Masticatory mucosa is present in
- Agingiva
- BCovering of hard palate
- Cdorsum of tongue
- DBoth a and b
The temperature receptors of gingiva are
- AArgyrophilic fibers
- BMeissner type corpuscles
- CKause type end bulbs
- DAll of the above
Melanin pigmentation of gingiva starts appearing
- AIn first trimester
- BIn second trimester
- Cin third trimester
- Dafter birth
The attached gingiva is attached to
- ARoot
- BPeriosteum
- Cboth of above
- DIt is a misnomer as it has no attachment.
Internal basal lamina of junctional epithelium has
- Atype IV collagen
- Btype VII collagen
- Ctype VIII collagen
- Dtype I collagen
Odland bodies are absent in
- Astratum spinosum
- Bjunctional epithelium
- Corthokeratinization
- Dparakeratinizatiion
which of the following is not a clear cell?
- AKeratinocyte
- BMerkel cell
- CLangerhan cells
- DMelanocytes
lamina densa is composed of
- AType I Collagen
- BType IV Collagen
- CType III Collagen
- DType VII Collagen
Gingiva is supplied by
- ASupraperiosteal vessels
- BSubperiosteal vessels
- CApical vessels
- DAll of the above
Cementum is
- AVascular
- BAvascular
- Cvascular in some parts and avascular in some
- DNone
The main form of cementum found on the cervical third of the root
- AAcellular afibrillar cementum
- BAcellular extrinsic fibre cementum
- CCellular mixed stratified cementum
- DCellular intrinsic fiber cementum
Cementum found in resorption lacunae
- AAcellular afibrillar cementum
- BAcellular extrinsic fiber cementum
- CCellular mixed stratified cementum
- DCellular intrinsic fiber cementum(Carranza 11th ed page-34)
Which of the following is not a cause of hypercementosis?
- APaget's disease
- Bperiapical infection
- Cmissing antagonist
- DScleroderma
Collagen fibers are absent in
- Aacellular extrinsic fiber cementum
- Bacellular afibrillar cementum
- CMixed stratified cementum
- DIntermediate cementum
The least stable periodontal tissue is
- AGingiva
- BPeriodontal ligament
- CCementum
- DAlveolar bone
Cribriform plate is formed due to
- AVascular channels
- BSharpey's fibers
- CCollagen fibrils
- DNerve fibrils
Dehiscence is
- AA vertical defect of alveolar bone
- BInfluences progression of disease
- CIs common in anterior teeth with prominent roots
- DAll of the above
Dehiscence occur more frequently on
- Alabial side
- Blingual side
- Cmesial side
- Ddistal side
These notes are compiled from standard periodontology texts for study purposes. They are a revision aid, not a substitute for your own reading or current clinical guidelines. If you spot an error, please leave a comment.