Gingiva divided into

1. Marginal 
2. Attached
3. Interdental papilla
   

Marginal gingiva 

1. Demarcated from attached gingiva by free gingival groove – this is also called marginal groove 
2. Width = 1 mm 
3. Gingival Zenith = most apical point on the marginal gingival scallop 
4. It’s dimensions vary between 0.06 to 0.96 mm

GINGIVAL SULCUS 

1. V shaped space/ Crevice 
2. On one side – there is tooth tooth, on other side – gingival epithelium 
3. Depth
   1. Ideal = 0 mm – germ free individuals and controlled environment 
   2. Histological sections = 1.8mm [ 0-6mm]
   3. Probing depth at apical termination of probe = 2-3mm 

ATTACHED GINGIVA 

1. Firm and resilient 
2. Demarcated from alveolar mucosa by – mucogingival junction
3. Width of attached gingiva
   1. Greatest in maxillary incisors 3.5 -4.5 mm and mandibular incisors 3.3 – 3.9 mm 
   2.  Least in maxillary premolars 1.9 mm and mandibular premolars 1.8mm
   3. Width of attached gingiva increases with age in supraerupted teeth 

INTERDENTAL GINGIVA / PAPILLA

1. Occupies gingival embrasure 
2. Shape can be pyramidal/col 
3. Col covered by non keratinized epithelium 

MICROSCOPIC FEATURES OF GINGIVA 

Composed of epithelium and connective tissue 

Gingival epithelium 

1. Type = stratified squamous epithelium 
2. Cells
   1. Principal cells = Keratinocytes = bulk 
   2. Melanocytes 
   3. Langerhans cells 
   4. Merkel cells 
   5. B,c,d = non keratinocytes 
3. Four layers 
   1. Stratum corneum 
   2. Stratum granulosum 
   3. Stratum spinosum 
   4. Stratum basale 
4. Three types of epithelium on basis of differentiation
   1. ORTHOKERATINIZED
      1. Stratum corneum = NO Nucleus 
      2. Keratin hyaline granules are evenly dispersed in Stratum granulosum
   2. PARAKERATINIZED
      1. No Stratum granulosum 
      2. Stratum corneum = retains PYKNOTIC nuclei 
   3. NON-KERATINIZED
      1. 2 layers are present = basale and spinosum 
      2. Upper most cells = retain VIABLE nucleus 

KERATINOSOMES OR ODLAND BODIES

1. Modified lysosomes 
2. Found in Stratum spinosum 

MELANOCYTES 

1. Found in basal layer and spinosum layer
2. Function = production of melanin 

LANGERHANS CELLS 

1. Seen in suprabasal level
2. Antigen presenting cells 
3. Part of reticuloendothelial system 
4. Contain birbeck granules 

MERKEL CELLS 

1. Basal and Spinosum = deep layers
2. Act as tactile receptors 

BASAL LAMINA

1. Connecting link between epithelium and connective tissue 
2. Thickness – 300 to 400 A and lies 400 A beneath the epithelial basal layer 
3. Consists of two layers
   1. Lamina lucida
      1. Rich in laminin protein
   2. Lamina densa
      1. Rich in collagen type 4
4. Basal lamina is connected to connective tissue by Hemidesmosomes ** and Anchoring Fibrils (750 nm)

KERATINIZATION OF ORAL MUCOSA IN DECREASING ORDER 

1. HARD PALATE = most keratinized 
2. Buccal mucosa = least keratinized 

OUTER EPITHELIUM 

1. Covers the crest or outer surface of marginal gingiva and attached gingiva 
2. 0.2-0.3 um

SULCULAR EPITHELIUM 

1. Lines gingival sulcus 
2. Non keratinized**
3. Semi permeable 

KERATINS

1. K1, k2, k10-k12 = epidermal type differentiation 
2. K6 and k16 = proliferation specific 
3. K5 and k14 = Stratification specific 
4. K19 = present in parakeratinized epithelium and absent in orthokeratinized epithelium 

JUNCTIONAL EPITHELIUM 

1. Non keratinized 
2. Langherhans cells are absent 
3. Thickness
   1. Early – 3-4 cells 
   2. Later – 10 – 20 cells 
4. Length = 0.25 – 1.35 um 
5. Formed by REE + OE
6. Attachments
   1. Attached to tooth by internal basal lamina 
   2. Attached to CT by external basal lamina 
7. Produces = Laminin from lamina lucida of basement membrane 
8. Dentogingival unit
   1. Junctional Epithelium + Gingival fibers 
   2. Function = brace gingiva against tooth 

BLOOD SUPPLY TO THE GINGIVA 

1. Supraperiosteal arterioles 
2. Arterioles emerging from interdental septa 
3. Vessels of periodontal ligament 

GINGIVAL FIBERS 

1. Dentogingival group
   1. Found in maximum number 
2. Alveologingival group 
3. Circular group 
4. Dentoperiosteal 
5. Transeptal fiber group 

SUPRACRESTAL FIBERS 

1. Type of transseptal fibers
2. Important fibers during relapse of orthodontic treatment 

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PERIODONTAL LIGAMENT

PERIODONTAL FIBERS

1. Principal fibers
   1. made up of collagen type 1 
   2. Produced by fibroblasts 
2. Transseptal fibers
   1. Gingival + periodontal 
   2. Reconstructed even after bone loss**
3. Alveolar crest fibers
   1. Prevent extrusion 
   2. Resist lateral forces 
4. Horizontal fibers
5. Oblique fibers
   1. Largest group of fibers 
   2. Resist vertical forces
6. Apical fibers = absent in incomplete roots 
7. Interradicular fibers 

RESISTANCE TO IMPACT OF OCCLUSAL FORCES (SHOCK ABSORPTION)

1. TENSIONAL THEORY 
   1. Major importance to PDL
   2. Best forces = longitudinal forces 
   3. Worst forces = torsional forces 
2. VISCOELASTIC THEORY 
   1. Dental fluids helps in transfer of forces 

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CEMENTUM 

1. Avascular tissue
2.  Forms the outer covering of anatomical root 
3. Two types
   1. Primary cementum
      1. Acellular cementum
      2. Forms before eruption
      3. Covers 1/3rd of root 
   2. Secondary cementum
      1. Cellular cementum
      2. Formed after eruption 
      3. Covers apical third of root 
4. Main sources of collagen fibers in cementum
   1. Extrinsic fibers
      1. Produced by fibroblasts – called as Sharpey’s fibers**
   2. Intrinsic fibers
      1. Produced by cementoblasts
5. Cementum classification by schroeder**
   1. Acellular afibrillar cementum
      1. No cells/fibers
      2. Formed by cementoblasts 
      3. Found as coronal cementum 
      4. Thickness – 1 to 15um 
   2. Acellular extrinsic fiber cementum
      1. Contain only sharpey fibers and lack cells 
      2. Formed by both fibroblasts and cementoblasts 
      3. Found in cervical third of roots 
      4. Thickness = 30 to 230 um 
   3. Cellular mixed stratified cementum
      1. Both intrinsic and extrinsic fibers + cells 
      2. Formed by both fibroblasts and cementoblasts 
      3. Present in apical third of roots and furcation
      4. Thickness = 100 to 100um
   4. Cellular intrinsic fiber cementum
      1. Cells 
      2. Formed by cementoblasts 
      3. Fills resorption lacunae

1, 4 = produced by cementoblasts only 

2 and 4 = cementoblasts + fibroblasts 

INTERMEDIATE CEMENTUM 

1. Poorly defined zone near Cementodentinal junction
2. Contains remnants of HERS embedded in calcified ground substance 

INORGANIC CONTENT OF CEMENTUM (45-50%)

1. Bone = 65 – 70%
2. Enamel = max content = 92- 96%
3. Dentin = 50 – 60%

CEMENTOENAMEL JUNCTION 

1. 60 – 65% = C overlaps E
2. 30% = butt joint = C and E just meet 
3. 5 – 10% = C and E does not meet

CEMENTODENTINAL JUNCTION 

1. When RCT is performed, the obturating material should be at the CDJ 
2. CDJ is 2 – 3 um wide 

ANKYLOSIS 

1. Resorption of PDL
2. Direct connection between tooth and bone 
3. Cementum resorption is present 

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ALVEOLAR PROCESS 

1. External plate of thick cortical bone 
2. Inner socket wall of compact bone = also called alveolar bone proper 
3. Seen as Lamina dura in radiographs 
4. Histologically
   1. Series of openings = cribriform plates
   2. Through which neurovascular bundles pass 
5. Supporting alveolar bone = made up of cancellous bone
6. Basal Bone = unrelated to teeth but it is the most apical part of alveolar bone/jaw 
7. Interdental septum consists of cancellous supporting bone which is enclosed within a compact border