NEET MDS Dental Anatomy Syllabus

What are mamelons and on which teeth are they seen?

Mamelons are three rounded projections on the incisal edge of newly erupted permanent incisors; they represent the developmental lobes and wear away with use.

How many developmental lobes form an incisor, and what does each represent?

Four lobes: three labial lobes (forming the mamelons) and one lingual lobe (forming the cingulum).

What is the 'Curve of Spee'?

The Curve of Spee is the anteroposterior curvature of the occlusal plane, a concave curve beginning at the canine cusp tip and following the buccal cusps of the posterior teeth in the sagittal plane.

What is the 'Curve of Wilson'?

The Curve of Wilson is the mediolateral (transverse) curve formed by the buccal and lingual cusp tips of posterior teeth on both sides, concave for the mandibular arch.

What is the Sphere of Monson?

The Sphere of Monson is a theoretical sphere (~4-inch / ~8 cm radius) with its center at the glabella, whose surface touches the cusp tips and incisal edges, combining the curves of Spee and Wilson.

Define 'centric occlusion' (maximum intercuspation).

Centric occlusion is the occlusion of opposing teeth when the mandible is in maximum intercuspation, giving the greatest number of tooth contacts, independent of condylar position.

What is 'centric relation'?

Centric relation is the maxillomandibular relationship in which the condyles are in their most superoanterior position in the glenoid fossae against the articular eminences, independent of tooth contact.

What is 'canine guidance' (canine-protected occlusion)?

Canine guidance is a form of mutually protected occlusion in which the canines disclude the posterior teeth during lateral excursions, protecting them from lateral forces.

What is 'group function' occlusion?

Group function is a lateral occlusal scheme where multiple teeth on the working side contact simultaneously during lateral excursion, distributing occlusal load over several teeth.

What is the chemical and percentage composition of mature enamel?

Enamel is about 96% inorganic (hydroxyapatite), 1% organic matrix, and 3% water by weight; it is the hardest, most highly mineralized tissue in the body.

What is the basic structural unit of enamel and its approximate shape?

The enamel rod (prism), with a keyhole/fish-scale shaped cross-section, running from the dentinoenamel junction toward the tooth surface.

Name three incremental/structural lines or markings seen in enamel.

Striae of Retzius (incremental growth lines), Hunter-Schreger bands (alternating light/dark bands from rod direction), and enamel lamellae/tufts/spindles (hypomineralized defects).

What is the chemical composition of dentin by weight?

Dentin is approximately 70% inorganic (hydroxyapatite), 20% organic (mainly type I collagen), and 10% water by weight.

What are dentinal tubules and what do they contain?

Dentinal tubules are tubular spaces traversing the dentin from the pulp to the DEJ, containing odontoblastic processes (Tomes' fibers) and dentinal fluid.

Differentiate primary, secondary, and tertiary dentin.

Primary dentin forms before root completion; secondary dentin forms slowly throughout life after root completion; tertiary (reparative/reactionary) dentin forms locally in response to stimuli like caries or attrition.

What is the composition of cementum and what is its main function?

Cementum is about 45-50% inorganic and 50-55% organic/water; it covers the root surface and provides attachment for the periodontal ligament fibers (Sharpey's fibers).

Differentiate acellular (primary) from cellular (secondary) cementum.

Acellular cementum lacks cementocytes, forms first, covers the cervical/coronal two-thirds of the root, and is the main anchoring cementum; cellular cementum contains cementocytes, forms later, and is found mostly at the apical third and furcations.

What are the four zones of the dental pulp, from periphery to center?

Odontoblastic layer, cell-free zone of Weil, cell-rich zone, and the pulp core (central pulp).

List the four main functions of the dental pulp.

Formative (dentin formation by odontoblasts), nutritive (supplies nutrients to dentin), sensory (pain perception), and defensive/protective (tertiary dentin and immune response).

What is a 'pulp stone' (denticle)?

A pulp stone is a discrete calcified mass within the pulp; it may be true (dentin-like) or false (concentric calcification), and free, attached, or embedded.

What is dens in dente (dens invaginatus) and which tooth is most commonly affected?

Dens in dente is a developmental anomaly with invagination of the enamel organ into the dental papilla, producing a 'tooth within a tooth'; it most commonly affects the maxillary lateral incisor.

What is dens evaginatus?

Dens evaginatus is a developmental anomaly with an accessory cusp/tubercle of enamel and dentin (often containing pulp) projecting from the occlusal or lingual surface, commonly on premolars (talon cusp on anteriors).

Define 'fusion' and 'gemination' and how to tell them apart by tooth count.

Fusion is the union of two separate tooth germs (results in one less tooth in the arch); gemination is incomplete division of a single germ into two (normal tooth count when the anomalous tooth is counted as one).

What is 'taurodontism'?

Taurodontism is a morphological anomaly with an enlarged, elongated pulp chamber and apically displaced furcation, giving a 'bull-like' tooth; classified as hypo-, meso-, and hypertaurodont.

What is dilaceration?

Dilaceration is an abnormal angulation or sharp bend in the crown or root of a tooth, usually caused by trauma during tooth development.

What is the difference between amelogenesis imperfecta and dentinogenesis imperfecta?

Amelogenesis imperfecta is a hereditary structural defect of enamel formation (hypoplastic/hypocalcified/hypomaturation types); dentinogenesis imperfecta is a hereditary defect of dentin giving opalescent teeth with obliterated pulp chambers.

What are Turner's tooth and Hutchinson's incisors?

Turner's tooth is localized enamel hypoplasia of a permanent tooth from infection/trauma of its predecessor; Hutchinson's incisors are screwdriver-shaped, notched incisors seen in congenital syphilis.

What is the crown-root ratio and why is it clinically important?

The crown-root ratio is the ratio of the tooth length occlusal to the alveolar crest versus the length within bone; a favorable (smaller) ratio indicates better support and prognosis for restorations and prostheses.

What is the formula for the mesiodistal crown-width (tooth size) component of Bolton's analysis (anterior ratio), and its mean value?

Bolton's anterior ratio = (sum of mandibular 6 anterior widths ÷ sum of maxillary 6 anterior widths) × 100; the mean is about 77.2%.

What is Bolton's overall ratio, including its formula and mean value?

Bolton's overall ratio = (sum of mandibular 12 teeth ÷ sum of maxillary 12 teeth) × 100, with a mean of about 91.3%; it assesses tooth-size discrepancy between arches.

In the context of restorative dentistry, what is the 'biologic width'?

Biologic width is the dimension of soft tissue (junctional epithelium plus connective tissue attachment, ~2.04 mm on average) attached to the tooth coronal to the alveolar bone; it must be respected when placing restoration margins to avoid periodontal inflammation.