Dental Occlusion and Anatomy

Class 1 Occlusion

• Anatomical Definition: Mesiobuccal cusp of the permanent 1st molar aligns with the buccal groove of the mandibular 1st molar.
• Without 1st Molars: Maxillary canine fits into the facial embrasure between mandibular canine and 1st premolar.

Overjet and Overbite

• Overjet: Horizontal overlap of maxillary and mandibular teeth.
• Ideal Overjet: Maxillary teeth labial to the incisal edges of mandibular teeth.
• Overbite: Vertical overlap of maxillary and mandibular teeth.
• Ideal Overbite: Incisal edge of maxillary incisors overlap the incisal third of mandibular incisors.

Maximum Mouth Opening

• Measurement: Ability to position three fingers (index, middle, ring) of the nondominant hand into the mouth.
• Interincisal Opening Range: 40 to 50 mm.

Malocclusion

• Can occur in mouths of all class jaw relationships.
• Types:
  • Labioversion: Tooth alignment towards the labial/buccal.
  • Linguoversion: Tooth alignment towards the lingual.
  • Torsiversion: Twisted/rotated tooth.
  • Supraeruption: Over-erupted tooth (abnormally long).
  • Infraocclusion: Under-erupted tooth (abnormally short).
  • Ankylosis: Root cementum fuses with alveolar bone, preventing eruption.

Crossbites

• Posterior Crossbites: Mandibular posterior teeth are buccally positioned. Defined by lingual cusps occluding in central fossae of maxillary teeth.
• Anterior Crossbites: Mandibular anteriors are facial to maxillary anteriors.

Other Occlusal Conditions

• Severe Overbite: Maxillary anteriors completely cover mandibular anteriors.
• Anterior Open Bite: Posterior teeth occlude but anterior teeth do not.
• Severe Overjet: Maxillary anterior teeth are considerably anterior to mandibular incisors.

Class II Malocclusion (Retrognathic Profile)

• Definition: Mandible is positioned distal from ideal occlusion.
• Anatomical Definition: Distobuccal cusp of maxillary first molar aligns with buccal groove of mandibular 1st molar.
• Divisions:
  • Division 1: Severe horizontal overjet with flared maxillary incisors.
  • Division 2: Retruded maxillary central incisors with slightly flared lateral incisors.

Class III Malocclusion (Prognathic Profile)

• Definition: Mandible is positioned facially from ideal occlusion, also known as underbite or anterior crossbite.

Temporomandibular Joint (TMJ)

• Components: Mandibular condyle articulating with the articular fossa of the temporal bone.
• Structure Between: Articular joint disc padded with fibrous tissue.
• Conditions:
  • Condylar Subluxation: Dislocation in upper joint compartment.
  • Mandibular Movements: Protrusion, lateral translation (deviation).

Oral and Cellular Biology

Cellular Functions and Structures

• Desmosome: Intercellular junction; junctions reattach during tissue injury.
• Hemidesmosome: Cell attachment to a noncellular surface.
• Cell Membrane Functions: Exocytosis, endocytosis, phagocytosis.
  • Exocytosis: Active transport from cell into the extracellular environment.
  • Endocytosis: Uptake from extracellular environment into cell.
  • Phagocytosis: Engulfing and enzymatic digestion of waste/foreign materials.

Organelles and Their Functions

• Nucleolus: Produces rRNA and nucleotides of RNA.
• Mitochondria: Chief energy source; site of Kreb’s cycle (ATP production).
  • Cristae: Increase surface area.
• Ribosomes: Produced in nucleolus, found in mitochondria, cytoplasm.
• Endoplasmic Reticulum (ER):
  • Smooth ER: Produces steroids.
  • Rough ER: Produces proteins.
  • Primary Functions: Modification, storage, segregation, transport of proteins.
• Golgi Complex: Modifies and packages proteins for exocytosis.

Cytoskeleton Components

• Microfilaments: Stabilize cytoplasm.
• Intermediate Filaments: Form keratin and intercellular junctions.
• Microtubules: Maintain cell shape, transport materials; form framework for cilia, flagella.

Phases of Cell Cycle

• Interphase: G1 (resting/growth), S (DNA duplication), G2 (growth).
  • Replication: Produces two DNA copies; critical for mitosis.

Tissue Types in the Body

Connective Tissue

• Fibroblasts: Synthesize protein fibers, intercellular substances.
• Blood Cells: White (immune response), Red (oxygen transport), Platelets (clotting).
• Cartilage Cells: Chondroblasts and chondrocytes maintain matrix.

Bone

• Functions: Movement, support, protection, blood cell production, mineral storage.
• Bone Cells: Osteoblasts (formation), Osteocytes (maintenance), Osteoclasts (resorption).
• Bone Composition: 60% inorganic material - calcium hydroxyapatite.

Blood and Immunity

• Components: RBCs, WBCs, plasma.
  • RBCs: Transport gases.
  • WBCs: Inflammatory and immune response.
• Immune Cells: B cells (mature in bone marrow), T cells (mature in thymus), NK cells.

Nervous System

• Neuron Components: Axon (impulses away), Dendrite (towards cell body), Cell body.
• Synapse: Junction for neural impulse transmission.
• Nervous System Divisions: CNS (brain and spinal cord), PNS (includes ANS).
• Autonomic Nervous System:
  • Sympathetic: Fight-or-flight response.
  • Parasympathetic: Rest-and-digest response.