Introduction to Orthodontics I - Week 12

Introduction to Orthodontics I - 1602305 Dental Occlusion and Temporomandibular Joint Disorders

• Course offered by Zarqa University, Faculty of Dentistry
• Course code: 1602305
• Semester: 1st, 2024/2024
• Instructor: Dr. Yousef Herzallah
• Week 12

Orthodontics Definition

• Derived from Greek words: "orthos" (meaning normal, correct, or straight) and "dontos" (meaning teeth)
• Focuses on correcting or improving tooth position and malocclusion (bad bite).

Ideal Occlusion and Malocclusion

• Ideal Occlusion: Teeth in optimal anatomical position.
  • Intramaxillary: within each arch
  • Intermaxillary: between both arches
• Malocclusion: Dental and occlusal traits that deviate from ideal occlusion, representing a variety of anomalies.

Important Terminology - Anchorage

• Resistance to reactionary forces during treatment.
• Based on Newton's third law - for every action, there's an equal and opposite reaction.

Important Terminology - Cephalometry

• Analysis and interpretation of standardized radiographs of facial bones.
• Almost always performed on a lateral view.

Important Terminology - A Point (A), B Point (B)

• A Point (A): Deepest concavity on the anterior profile of the maxilla.
• B Point (B): Deepest concavity on the anterior surface of the mandibular symphysis.

Important Terminology - Nasion (N)

• Most anterior point on the frontonasal suture (junction of nasal and frontal bones.)
• If difficult to locate directly, the deepest concavity point where frontal and nasal bones intersect can be used.

Important Terminology - Frankfort Plane

• Plane joining the porion (earlobe, external opening of the ear canal) and the orbitale (eye socket).
• Difficult to accurately measure due to inherent problems defining these points.

Important Terminology - Angulation

• Degree of tip of a tooth in the mesiodistal plane (front-back).
• Sometimes referred to as "tooth tip".

Important Terminology - Inclination

• Degree of tip of a tooth in the labiopalatal plane (side to side).
• Sometimes referred to as "tooth torque".

Important Terminology - Buccal Crossbite

• Buccal cusps of lower premolars and/or molars occlude buccally to the buccal cusps of the upper premolars and/or molars.

Important Terminology - Lingual Crossbite

• Buccal cusps of lower premolars and/or molars occlude lingually to the lingual cusps of the upper premolars or molars.

Important Terminology - Overbite and Overjet

• Overbite: Vertical overlap of upper and lower incisors, graded as 1/3 to 1/2 of lower incisor coverage. Increased is > 1/2 of lower incisor coverage, and reduced is < 1/3 of lower incisor coverage
• Overjet: Horizontal distance between upper and lower incisors (typically 2-4 mm).

Important Terminology - Crowding and Spacing

• Crowding: Insufficient space for teeth to align perfectly in an arch or segment.
• Spacing: Gaps between teeth; may be localized or generalized.

Important Terminology - Ectopic Tooth

• Tooth in the incorrect position due to development or eruption in the wrong position.

Important Terminology - Transposition

• Interchange in position of two teeth.

When to Treat

• Reasons for orthodontic treatment include:
  • Improving dentofacial appearance
  • Correcting occlusal function of teeth
  • Eliminating anomalies that pose a risk of damage to teeth or supporting structures

Need vs Demand

• Need: Based on realistic health and well-being.
• Demand: Does not necessarily reflect need as it may simply be patient's demand

Indices of Need - IOTN

• Origin: Developed through UK government initiative to allocate/ration orthodontic treatment based on need.
• Criticised for: Does not incorporate functional issues; low grading for overbites; subjectivity of the Aesthetic component.
• Components: Dental Health Component and Aesthetic Component, assessing occlusal traits affecting function, missing teeth, overjet, crossbite etc. and aesthetic handicap assessment (images scored on a 1-10 scale).

Indices of Need - IOFTN

• Origin: To overcome limitations of IOTN. Takes functional issues into greater account particularly in surgical cases, important in sleep apnoea cases and skeletal issues due to trauma, asymmetry, or gingival exposures

Classifying Malocclusions / Angle's Classification

• Based on relative anteroposterior positions of first permanent molars to establish dental arch relationships.
• Classified into class I, II and III. Further division of class II and III into specific subtypes can be done based on incisor relationships.

Classifying Malocclusions / British Standards Institute Classification

• Primarily based on incisor relationships.
• More widely used than Angle's classification.

What to do we treat to / Andrews Six Keys

• Define ideal static occlusion, covering critical aspects of occlusal patterns in normal occlusion, using 120 non-orthodontic patients as case study.
• Emphasises six aspects (key elements): key 1 - molar relationship, key 2 - crown angulation and other measurements, key 3 - crown inclination details, key 4 - rotations of teeth, key 5 - spacing, and key 6 - occlusal plane

Risks of Orthodontic Treatment

• I. Demineralization: Appliance can cause plaque build-up.
• II. Root Resorption: Inevitable loss of 1mm of root length with treatment. Risk factors vary from existing root problems, trauma and prolonged time.
• III. Loss of Periodontal Support: Gingival inflammation (common due to poor hygiene) leading to possible hyperplasia and periodontal issues.
• IV. Enamel damage: Enamel may be damaged by bracket or band removers, or through wear from opposing teeth. 
• V. Intra-oral soft tissue damage: Ulcerations and rare allergic reactions.
• VI. Extra-oral damage: Re-positioning may lead to retruded facial profile

This quiz covers key concepts from Week 12 of the Introduction to Orthodontics I course, including ideal occlusion, malocclusion, and important terminologies such as anchorage. Enhance your understanding of dental occlusion and temporomandibular joint disorders. Test your knowledge and prepare for the challenges ahead in orthodontics.