NEET MDS Orthodontics Syllabus

What are the main components ('the four parts') of a fixed appliance?

Brackets (and molar tubes/bands), archwires, ligatures/modules, and auxiliaries (elastics, springs, chains, hooks). These work together to deliver three-dimensional control of tooth position.

Differentiate the Begin, Edgewise and Straight-wire (pre-adjusted) appliance systems.

Begin uses round wires and light forces with differential tooth movement and tipping/uprighting (Australian wire). Standard Edgewise uses rectangular slots requiring wire bends for each tooth. Straight-wire (Andrews) builds tip, torque and in-out into the brackets, minimizing wire bending.

How do functional appliances correct Class II malocclusion?

They posture the mandible forward, using the resulting muscle and soft-tissue forces to be transmitted to the dentition and (in growing patients) to encourage condylar growth/glenoid fossa remodeling, while restraining maxillary growth and producing dentoalveolar changes.

Give examples of removable and fixed functional appliances.

Removable functional: Activator, Bionator, Frankel (FR), Twin-block (most popular). Fixed functional: Herbst appliance, Forsus, Jasper Jumper, MARA.

State the four classical types of orthodontic tooth movement.

Tipping, bodily movement (translation), rotation, torque (root movement / controlled inclination), and intrusion/extrusion. Each requires different force systems and produces distinct centers of rotation.

What are the optimum force levels (per Proffit/Storey-Smith) for tipping versus bodily movement?

Approximately: tipping 35-60 g, bodily movement 70-120 g, root uprighting 50-100 g, rotation 35-60 g, extrusion 35-60 g, and intrusion 10-20 g (lightest forces).

Describe the pressure-tension theory of orthodontic tooth movement.

On the pressure (compression) side of the PDL, blood flow decreases, osteoclasts resorb bone (frontal resorption with light force, undermining/hyalinized resorption with heavy force). On the tension side, the stretched PDL stimulates osteoblastic bone deposition, allowing the tooth to move in the direction of force.

What is hyalinization in orthodontic tooth movement and what causes it?

Hyalinization is a sterile, cell-free, glass-like degeneration (necrosis) of compressed PDL tissue caused by excessive force occluding blood supply. It delays tooth movement until the area is removed by undermining resorption from adjacent marrow spaces.

Define anchorage in orthodontics.

Anchorage is the resistance to unwanted tooth movement; it is the source against which orthodontic force reacts (per Newton's third law) so that the reactive forces do not move the anchor unit while the target teeth are moved.

Classify anchorage according to the number of anchor units and direction.

By site: intraoral (intra-maxillary, inter-maxillary), extraoral, muscular. By number of units: simple, compound, reinforced, stationary, reciprocal. By manner: cortical, multiple. Tweed classified anchorage demand as A (maximum), B (moderate), and C (minimum).

State Angle's classification of malocclusion based on first permanent molar relationship.

Class I: mesiobuccal cusp of maxillary first molar occludes in the buccal groove of mandibular first molar (normal AP). Class II: buccal groove is distal to the cusp (mandible retruded). Class III: buccal groove is mesial to the cusp (mandible protruded).

Differentiate Angle's Class II Division 1 from Division 2.

Both are Class II molar relationships. Division 1: proclined (labially tipped) maxillary incisors with increased overjet. Division 2: retroclined maxillary central incisors (often with proclined laterals) and deep overbite, usually minimal overjet.

What is the difference between dental and skeletal malocclusion?

Dental malocclusion involves misalignment of teeth on normal-sized, normally positioned jaws (e.g., crowding, spacing). Skeletal malocclusion arises from a discrepancy in the size or position of the jaw bases (e.g., maxillary or mandibular prognathism/retrognathism).

List the broad categories of etiology of malocclusion (Graber's general and local factors).

General factors: heredity, congenital anomalies, environment (prenatal/postnatal), nutrition, metabolic/endocrine disorders, trauma, posture, and habits. Local factors: anomalies of tooth number, size, shape, abnormal frenum, premature loss/prolonged retention of teeth, ectopic eruption, ankylosis, and caries.

Name common oral habits that cause malocclusion and a typical malocclusion each produces.

Thumb sucking → anterior open bite, proclined upper incisors, posterior crossbite. Tongue thrust → anterior open bite, proclination. Mouth breathing → narrow maxilla, adenoid facies, increased lower face height. Lip biting → increased overjet.

What is the difference between interceptive and corrective orthodontics?

Interceptive orthodontics recognizes and eliminates potential irregularities in a developing dentition (e.g., space maintenance, habit breaking, serial extraction). Corrective orthodontics treats an established malocclusion that already exists, using removable, fixed, or surgical means.

What is serial extraction and what is the usual sequence?

Serial extraction is a guided, planned removal of certain primary and permanent teeth in arch-length-deficient cases to relieve crowding and allow self-alignment. Classic sequence (Tweed/Dewel): extract primary canines first, then primary first molars, then the first premolars as they erupt (C–D–4).

How does adult orthodontic treatment differ from adolescent/growing-patient treatment?

Adults have no growth potential (skeletal changes need surgery, not growth modification), slower tooth movement, more periodontal/restorative concerns, higher prevalence of missing teeth, greater esthetic demands, and reduced cellular response—so treatment is often more limited, slower, and interdisciplinary.

What are the three categories of adult orthodontic treatment?

(1) Adjunctive (limited) treatment to facilitate other dental care (e.g., uprighting molars, intrusion for restorations), (2) Comprehensive treatment to correct the full malocclusion, and (3) Surgical-orthodontic treatment for skeletal discrepancies.

Give examples of interdisciplinary orthodontic treatment scenarios.

Ortho-perio (forced eruption, intrusion of mobile teeth), ortho-prostho/restorative (space management for implants, uprighting molars before crowns), ortho-surgical (orthognathic surgery), and ortho-endo (forced eruption of fractured teeth for crown lengthening).

What are the main indications for orthognathic (surgical-orthodontic) treatment?

Severe skeletal discrepancies beyond the limits of growth modification or dental camouflage—e.g., severe Class II/III skeletal malocclusion, vertical maxillary excess/deficiency, severe asymmetry, large anterior open bite, and obstructive sleep apnea—usually in non-growing patients.

Name the common surgical procedures used to correct mandibular and maxillary discrepancies.

Mandible: Bilateral Sagittal Split Osteotomy (BSSO) for advancement/setback; vertical/inverted-L ramus osteotomy; genioplasty for the chin. Maxilla: Le Fort I osteotomy (advancement, impaction, downgraft); Le Fort II/III for midface; SARPE for transverse expansion.

What are the goals of pre-surgical orthodontics?

To remove dental compensations and decompensate the incisors to their correct positions over basal bone, align and level arches, coordinate arch widths, eliminate occlusal interferences, and create the planned surgical occlusion so the jaws can be placed in their correct skeletal relationship.

What does post-surgical orthodontics aim to accomplish?

To detail and finalize the occlusion—closing residual spaces, settling the bite into maximum intercuspation, correcting minor discrepancies—and then to retain the result. It usually begins a few weeks after surgery once initial healing has occurred.

Why is decompensation necessary before orthognathic surgery, especially in Class III cases?

Dental compensations mask the true skeletal discrepancy (in Class III the lower incisors are retroclined and uppers proclined). Decompensation removes this masking so the full skeletal correction can be achieved surgically; paradoxically it temporarily worsens the malocclusion ('worse before better').

Define retention in orthodontics and state why it is needed.

Retention is the holding of teeth in their corrected positions for the period necessary to maintain the result after active treatment. It is needed because of reorganization of gingival and periodontal fibers, continued growth, soft-tissue/occlusal forces, and the inherent tendency for relapse.

Name the common types of orthodontic retainers.

Removable: Hawley retainer, vacuum-formed (Essix/clear) retainer, Begg wrap-around retainer. Fixed: bonded lingual/palatal wire retainer (commonly canine-to-canine). Active/special: positioner.

List the principal factors that influence orthodontic relapse.

Periodontal and gingival fiber recoil (especially supracrestal/transseptal fibers), continued/late growth, soft-tissue pressures and muscle balance, occlusal forces, failure to achieve correct intercuspation, expansion beyond stable limits, and rotations corrected late. Tooth size/arch-length discrepancies also contribute.

What are Temporary Anchorage Devices (TADs) and what is their main advantage?

TADs are small titanium/stainless-steel mini-implants or miniplates temporarily fixed to bone to provide skeletal (absolute) anchorage. Their main advantage is eliminating the need for patient compliance and avoiding reactive movement of anchor teeth, enabling movements like molar intrusion and en-masse retraction.

What are the components of digital orthodontics and how do clear aligners achieve tooth movement?

Digital orthodontics uses intraoral scanning, CBCT, 3D treatment-planning/setup software, and CAD/CAM (custom brackets, indirect bonding, 3D-printed models/aligners). Clear aligners are a series of thermoplastic trays, each slightly different, that apply light continuous forces to move teeth incrementally (typically ~0.25 mm per aligner) toward the planned final position.