৪৮তম স্পেশাল বিসিএস ডেন্টাল ⎯ মডেল টেস্ট [Archived]

Sharpey’s fibers are collagen fibers from the PDL that embed into cementum to anchor the tooth.

Tomes' processes form during the secretory stage to shape enamel rods, but they disappear during the maturation stage when ameloblasts focus on mineralizing the matrix.

Enamel rods are analogously shaped like keyholes: their heads point toward the crown, tails toward the root, optimizing structural integrity.

Striae of Retzius are incremental (rest-state) lines visible under polarized light that reflect disturbances in ameloblast activity and mineralization.

After enamel breakdown, acid follows the path of dentinal tubules—caries spreads from dentin surface toward the pulp.

Cementum is thickest (150–200 µm) near the apex and thinnest (20–50 µm) near the cervical region.

Enamel is a semi-permeable barrier—not watertight, but selective. Fluid and ions can traverse micro-channels under certain conditions.

~20–30% of dentin by weight is organic, with ~90% of that being collagen—primarily Type I, with trace Type III/V
Special note: Korff fibers—Type III collagen—appear during dentinogenesis, winding through predentin and marking early dentin formation

Hypercementosis is a non-neoplastic condition involving excessive secondary cementum buildup along the roots, often seen as bulbous apices on radiographs.

Orthodontic force induces localized PDL hyalinization and ischemic necrosis, triggering inflammatory-mediated clastic resorption of the root surface.

Also known as transparent dentin, sclerotic dentin results from peritubular dentin thickening and tubule occlusion due to aging or slow caries progression.

It's a granular zone just underneath root dentin, caused by looping of dentinal tubules before cementum formation

Cementum lays down these hypermineralized rest-period lines, parallel to the root’s long axis

These corkscrew-shaped type III collagen bundles originate in the dental papilla and form the scaffold of mantle dentin. They mark the earliest recognizable dentin matrix—like the building blocks of your tooth foundation.

Fine (~4–8 µm apart) incremental lines perpendicular to dentinal tubules, reflecting daily odontoblastic activity.

Dental lamina:

At 7th week of IUL, primary epithelium band divide into 2 layer- a) outer vestibular band[ forms lip& check from future alveolar process] b) inner dental lamina.

Dental lamina is destined for tooth germs of future deciduous &permanent dentition.

Remnants of this dental lamina may persist as Epithelial pearls. 

**Epithelial sheath of Hertwing /Root sheath of Hertwing -Forms root of the tooth. Remnant of root sheath of Hertwing is called Epithelial rests of Malassez.

**Primary enamel organ - Tooth germs for deciduous &permanent teeh are collectively  called primary enamel organ.

**Reduced enamel epithelium - Remnants of enamel organ[ tooth bud in  the cap stage of tooth development]

ref: A K DAS

The central region of both the coronal and the radicular pulp contains large nerve trunks and blood vessels.Peripherally it is composed of odontoblasts, cell free zone (WEIL'S zone) and the cell rich zone.The network of nerves located adjacent to the cell rich zone is called the parietal layer ( or) t he plexus of Rashkow

Large myelinated fibres mediate the sensation of pain.
Unmyelinated fibres are associated with blood vessels of pulp and are sympathetic in nature. They are the majority of nerve fibres ent ering the pulp.

The parasympathetic (secretomotor) supply toSubmandibular and sublingual salivary glands is throug h chordatympanic nerve and that of parotid gland is through glossopharyngeal nerve.
Parasympathetic stimulation produces copious, watery saliva while the sympathetic stimulation produces thicker, and less quantity of saliva.

Myoepithelial cells:
• Related to secretory and intercalated duct cells
• Contains cytokeratin intermediate filament and
contractile actin filaments
Functions
• Contractile process
• Accelerate outflow of saliva from acini
• Shorten and widen intercalated ducts
• Supports parenchyma
• Contribute to secretory pressure in the acini or duct.

[Orban's 1tth ed 297 / 12th ed 234/ 13th ed 254)
Dendritic cells >>>>>> Synthesize melanin melanocytes
Langerhans cell  >>>>>Immune response
Merkel cell >>>>>>>>>>Neural pressure sensitive
receptor cell.

[Orban's 11th ed 310/ 12th ed 241/ 13th ed 273]
After the ameloblasts finish formation of the enamelmatrix, they leave a thin membrane on the surface ofthe enamel ca lled primary enamel cuticle. After thisthe epithelial enamel organ is reduced to a few layersof cells called reduced enamel epithelium; whichcover the entire enamel. Once the tip of the crown hasemerged, the reduced enamel epithelium is termed as primary attachment epithelium

Sharpey's fibers, which anchor the tooth to the jawbone, are derived from the dental follicle during tooth development. Specifically, cells within the dental follicle differentiate into fibroblasts that secrete collagen, forming these fibers. These collagen bundles then embed into the developing cementum of the tooth root and the alveolar bone, creating a strong attachment.

Congenital syphilis : maternal infection or late fetal infection can cause characteristics dental deformity in newborn.  

1. Only permanent teeth are affected.
 
2. Characteristics defects are seen in upper central incisors called Hutchinson's incisors. Teeth are small,barrel/peg shaped with tapering towards the tip. Crescentic notch or deep fissure in incisal edge forms before eruption & can be seen radioghiphically. 

3.Dome shaped  (Moon's molars) or rough pitted occlusal surface with compressed nodules in  instead of cusp(mullberry molars) in 1st molars are also seen.

ref: Cawson

Function of teeth :
Helps in mastication
Adds in articulation and speech
Gives shape & beauty to the face 
May use for self protection &attack.

Specific tooth function :

Incisor- Incisal edge act as a cutting blade. Helps in cutting of food

Canine: Sharp pointed cusp helps in tearing of food. Used for seizing,digging,slashing, piercing& fighting in animal Kingdom. 

Premolar: Helps in chopping of food

Molar : Helps in grinding of food 

ref: AK DAS

The mucosa of the cheek is non-keratinised. Minor salivary glands are found between bundles of buccinator muscle. The cheek, lateral to the corner of the mouth, contain isolated sebaceous glands called Fordyce's spots

The basal lamina is made up of a clear zone (lamina lucida) present just below the epithelial cells,a dark zone (lamina densa) beyond lamina lucida and connective tissue. Lamina densa contains type IV collagen and lamina lucida contains laminin

Sulcular epithelium, junctional epithelium and
interdental epithelium  are non-keratinised areas in gingiva.Sulcular epithelium lacks retepegs.

Stages of Tooth development :

A.Bud stage- Initiation.
B.Cap stage - Proliferation 
C. Bell stage-
      a) early bell stage : Histo-differentiation

Elongated crowns or apically displaced furcation  resulting in increased apico-occlusal height of the pulp chamber.This condition resembles teeth of a bull typical is known as taurodontism. 

It is commonly associated with Klinefelter Syndrome & Down Syndrome. 


Ref: Nisha Garg 

Absence of few tooth is called hypodontia or oligodontia. Absence of one or two teeth[isolated ogilodontia] is relatively common &hereditary. 

Disorder associated with oligodontia commonly seen in Down syndrome. Absence of one or more 3rd molar is seen 90% cases in this syndrome. Absence of individual tooth also common. 

Less frequent disorder with oligodontia include 
1.Cleft lip &palate 
2 Chondroectodermal  dysplasia
3. Oro-facial-digital syndrome 

ref: Cawson

Pit: pointed depression in the enamel. Situated at the junction of developmental groove or at terminal at these groove

Lingual pit- Found in lingual surface of upper permanent lateral incisor. 

Mesial &Distal pit- Found in occlusal surface of deciduous molar and permanent premolar & molar teeth.

Central pit - Found in permanent molar teeth.

ref: A K DAS

Orban's 12th ed 240-41/ 13th ed 277]
The part of the tooth covered by enamel is called anatomic crown and the part of the tooth exposed in the oral cavity is called clinical crown. In gingival recession the root is exposed making anatomic crown
shorter than clinical crown.

Cementicles are calcified bodies fo und in the periodontal ligament. They are seen in older individuals. They remain free in the connective tissue. When they are adherent to the cementum, they form excementoses.

nerve supply for circumvallate papillae, which are located on the posterior third of the tongue, is primarily through the glossopharyngeal nerve (CN IX) according to Kenhub and StatPearls. This nerve carries both general sensory and special sensory (taste) information from this region.

Transseptal fibres extend! interproximally from cementum to cementum of adjacent teeth over the alveolar crest. They are reconstru cted even after the destruction of the alveolar bone due to periodontal diseases.

Permanent 1st molar - known as six year tooth because they erupt at 6 years of age.

Permanent 2nd molar- Known as twelve year tooth because they usually erupt at 12 years of age.

ref: A K DAS

Most frequently missing teeth are

3rd molars,2nd premolars, maxillary lateral incisor.

ref: Cawson

Indomethacin is potent and associated with a greater decline in renal prostaglandin synthesis, increasing the risk of acute renal impairment, especially in vulnerable patients

Denture stomatitis is typically fungal (Candida) in origin—nystatin is the standard topical antifungal of choice .

A rinse of 0.5 mg dexamethasone per 5 mL, used four times daily for two minutes, is recommended for pain relief and inflammation control (eg. aphthous ulcers)

These antibiotics inhibit warfarin metabolism, raising anticoagulant effects and bleeding potential.

Lower pH in inflamed areas shifts the anesthetic equilibrium toward the ionized form, reducing membrane penetration and delaying onset.

Classification: amides (lidocaine, bupivacaine, articaine) undergo hepatic metabolism; esters (procaine, benzocaine) are degraded by plasma cholinesterases.

This antioxidant preserves the stability of epinephrine, which is prone to oxidation, but it may cause allergic reaction.

Early CNS toxicity typically presents with lightheadedness, sensory disturbances, slurred speech, visual and auditory changes, drowsiness—but respiratory depression and coma occur later, after seizures or severe CNS involvement.

A good disinfectant should be non-toxic, non-corrosive, inexpensive and fast-acting. Corrosive agents (like formalin) are avoided where metal tools are involved.

Chlorine releases hypochlorous acid, which oxidizes cell components—kills bacteria, viruses, spores. Used in water tanks, dental suction systems.

3% H₂O₂ is safe as an oral rinse, but >6% can damage tissue. Also, oxygen bubbles may delay healing.

Aluminum chloride acts as an acidic astringent: it constricts tissues, reduces bleeding, and stabilizes the retracted gingiva—but its acidity can irritate sensitive tissues.

Reusable eye protection must be disinfected between patients. Gloves are single-use; scrubs shouldn’t leave clinic .

Use spray disinfection per manufacturer instructions to avoid distortion—immersion risks swelling

NaOCl dissolves tissue, and EDTA removes the smear layer to expose dentinal tubules and enhance sealer adaptation. The sequence matters for effective disinfection and seal.

Mixing NaOCl + CHX forms an orange-brown precipitate that contains parachloroaniline (PCA)—potentially toxic and carcinogenic. Rinse with saline between irrigants.

Ledermix = triamcinolone (steroid) + demeclocycline (antibiotic). It helps control inflammation and root resorption, especially in trauma cases.

Triple antibiotic paste (TAP) = metronidazole + ciprofloxacin + minocycline. It's used in regenerative endo but minocycline stains teeth—alternatives like double antibiotic paste (DAP) are preferred now.

Humectants like glycerin, sorbitol, and propylene glycol retain moisture and maintain paste consistency, preventing it from becoming crumbly or drying out.

A bisbiguanide with lasting attachment and major plaque reduction.

Fluoride replaces hydroxide in hydroxyapatite, creating fluoroapatite, which is less soluble and more resistant to acid dissolution, lowering the enamel’s critical pH from ~5.5 to ~4.5.

Mummifying agents desiccate and preserve the remaining pulp, creating resistance to infection when complete removal is unfeasible.

Desensitizing agents work via physical occlusion, chemical precipitation, or nerve action. Immune response is not a factor in desensitization.

Gluma not only desensitizes but also improves bonding by reducing post-op sensitivity. It's applied before adhesives in restorative procedures. Contains glutaraldehyde and HEMA.

The walking bleach method involves placing a mix of sodium perborate and hydrogen peroxide inside the pulp chamber, sealing it, and allowing gradual internal bleaching over multiple visits.

Nutrient artery enters via the nutrient foramen, supplying medullary cavity, endosteum, inner compact bone. Supplemented by periosteal and metaphyseal vessels.

Flat bones—like those of the skull and mandible form directly from mesenchyme in intramembranous ossification.

The temporomandibular joint—between mandibular condyle and temporal bone—is bicondylar with hinge+gliding movements.

The masseter powerfully elevates the mandible for chewing;
Lateral pterygoid depresses/ protrudes;
Digastric/Geniohyoid depress.

The submental nodes (under chin) receive drainage from the lower lip and chin.

Treacher‑Collins syndrome includes first‑arch defects like mandibular hypoplasia and cleft palate.

The retina is the light-sensitive inner layer converting photons into nerve impulses.

The zona glomerulosa, the outer cortical layer, secretes aldosterone; the fasciculata and reticularis secrete glucocorticoids and androgens respectively.

Cranial sutures are fibrous joints that gradually ossify (synostosis). Gomphoses (e.g. tooth sockets) are different fibrous joints.

Filiform papillae lack taste buds and are keratinized, serving only mechanical functions. Taste buds are found on fungiform, foliate and circumvallate papillae.

CN VII exits via the stylomastoid foramen and innervates muscles of facial expression.

The angular artery (from facial artery) connects to dorsal nasal branches (ICA) – this facial–ophthalmic link opens a route to the cavernous sinus.

The maxillary artery, major supplier of deep face, stems from external carotid.

IX handles both taste and general sensation for posterior 1/3 of tongue.

Elastic cartilage (with elastin) provides flexibility — e.g. in epiglottis and external ear; hyaline cartilage covers joints.