Headgear is an extraoral orthodontic appliance used to correct dental and skeletal discrepancies, particularly in growing patients. It is designed to apply forces to the teeth and jaws to achieve specific orthodontic goals, such as correcting overbites, underbites, and crossbites, as well as guiding the growth of the maxilla (upper jaw) and mandible (lower jaw). Below is an overview of headgear, its types, mechanisms of action, indications, advantages, and limitations.

Types of Headgear

1. Class II Headgear:

   • Description: This type is used primarily to correct Class II malocclusions, where the upper teeth are positioned too far forward relative to the lower teeth.
   • Mechanism: It typically consists of a facebow that attaches to the maxillary molars and is anchored to a neck strap or a forehead strap. The appliance applies a backward force to the maxilla, helping to reposition it and/or retract the upper incisors.

2. Class III Headgear:

   • Description: Used to correct Class III malocclusions, where the lower teeth are positioned too far forward relative to the upper teeth.
   • Mechanism: This type of headgear may use a reverse-pull face mask that applies forward and upward forces to the maxilla, encouraging its growth and improving the relationship between the upper and lower jaws.

3. Cervical Headgear:

   • Description: This type is used to control the growth of the maxilla and is often used in conjunction with other orthodontic appliances.
   • Mechanism: It consists of a neck strap that connects to a facebow, applying forces to the maxilla to restrict its forward growth while allowing the mandible to grow.

4. High-Pull Headgear:

   • Description: This type is used to control the vertical growth of the maxilla and is often used in cases with deep overbites.
   • Mechanism: It features a head strap that connects to the facebow and applies upward and backward forces to the maxilla.

Mechanism of Action

• Force Application: Headgear applies extraoral forces to the teeth and jaws, influencing their position and growth. The forces can be directed to:
  • Restrict maxillary growth: In Class II cases, headgear can help prevent the maxilla from growing too far forward.
  • Promote maxillary growth: In Class III cases, headgear can encourage forward growth of the maxilla.
  • Reposition teeth: By applying forces to the molars, headgear can help align the dental arches and improve occlusion.

Indications for Use

• Class II Malocclusion: To correct overbites and improve the relationship between the upper and lower teeth.
• Class III Malocclusion: To promote the growth of the maxilla and improve the occlusal relationship.
• Crowding: To create space for teeth by retracting the upper incisors.
• Facial Aesthetics: To improve the overall facial profile and aesthetics by modifying jaw relationships.

Advantages of Headgear

1. Non-Surgical Option: Provides a way to correct skeletal discrepancies without the need for surgical intervention.
2. Effective for Growth Modification: Particularly useful in growing patients, as it can influence the growth of the jaws.
3. Improves Aesthetics: Can enhance facial aesthetics by correcting jaw relationships and improving the smile.

Limitations of Headgear

1. Patient Compliance: The effectiveness of headgear relies heavily on patient compliance. Patients must wear the appliance as prescribed (often 12-14 hours a day) for optimal results.
2. Discomfort: Patients may experience discomfort or soreness when first using headgear, which can affect compliance.
3. Adjustment Period: It may take time for patients to adjust to wearing headgear, and they may need guidance on how to use it properly.
4. Limited Effectiveness in Adults: While headgear is effective in growing patients, its effectiveness may be limited in adults due to the maturity of the skeletal structures.

Ashley Howe’s Analysis of Tooth Crowding

Introduction

Today, we will discuss Ashley Howe’s analysis, which provides valuable insights into the causes of tooth crowding and the relationship between dental arch dimensions and tooth size. Howe’s work emphasizes the importance of arch width over arch length in understanding dental crowding.

Key Concepts

Tooth Crowding

• Definition: Tooth crowding refers to the lack of space in the dental arch for all teeth to fit properly.
• Howe’s Perspective: Howe posited that tooth crowding is primarily due to a deficiency in arch width rather than arch length.

Relationship Between Tooth Size and Arch Width

• Howe identified a significant relationship between the total mesiodistal diameter of teeth anterior to the second permanent molar and the width of the dental arch in the first premolar region. This relationship is crucial for understanding how tooth size can impact arch dimensions and overall dental alignment.

Procedure for Analysis

To conduct Ashley Howe’s analysis, the following measurements must be obtained:

1. Percentage of PMD to TTM
   PMD X 100
         TTM
2. Percentage of PMBAW to TTM
   PMBAW X 100
       TTM

3. Percentage of BAL to TTM: [ \text{Percentage of BAL} = \left( \frac{\text{BAL}}{\text{TTM}} \right) \times 100 ]

Where:

• PMD = Total mesiodistal diameter of teeth anterior to the second permanent molar.
• PMBAW = Premolar basal arch width.
• BAL = Basal arch length.
• TTM = Total tooth mesiodistal measurement.

Inferences from the Analysis

The results of the measurements can lead to several important inferences regarding treatment options for tooth crowding:

1. If PMBAW > PMD:

   • This indicates that the basal arch is sufficient to allow for the expansion of the premolars. In this case, expansion may be a viable treatment option.

2. If PMD > PMBAW:

   • This scenario can lead to three possible treatment options:
     1. Contraindicated for Expansion: Expansion may not be advisable.
     2. Move Teeth Distally: Consideration for distal movement of teeth to create space.
     3. Extract Some Teeth: Extraction may be necessary to alleviate crowding.

3. If PMBAW X 100 / TTM:

   • Less than 37%: Extraction is likely required.
   • 44%: This is considered an ideal case where extraction is not necessary.
   • Between 37% and 44%: This is a borderline case where extraction may or may not be required, necessitating further evaluation.

Wire Characteristics

• Resilience: Area under stress-strain curve up to proportional limit; energy storage capacity
• Formability: Permanent deformation before failure
• Ideal wire properties: High strength, low stiffness, high range, high formability
• Nomograms: Developed by Kusy for wire comparison
• Shape memory & superelasticity: Unique to NiTi alloys

Wire Types & Inventors

Elgiloy Color Coding

Metallurgical Concepts

• Passivation: Cr₂O₃ layer from chromium prevents corrosion
• Sensitization: Loss of passivation due to chromium carbide formation (400 – 900° C)
• Cold working: Increases hardness/strength, decreases elongation
• Annealing: Reverses strain hardening; temp = 1/2 melting point

Anchorage in orthodontics refers to the resistance that the anchorage area offers to unwanted tooth movements during orthodontic treatment. Proper understanding and application of anchorage principles are crucial for achieving desired tooth movements while minimizing undesirable effects on adjacent teeth.

Classification of Anchorage

1. According to Manner of Force Application

• Simple Anchorage:

  • Achieved by engaging a greater number of teeth than those being moved within the same dental arch.
  • The combined root surface area of the anchorage unit must be at least double that of the teeth to be moved.

• Stationary Anchorage:

  • Defined as dental anchorage where the application of force tends to displace the anchorage unit bodily in the direction of the force.
  • Provides greater resistance compared to anchorage that only resists tipping forces.

• Reciprocal Anchorage:

  • Refers to the resistance offered by two malposed units when equal and opposite forces are applied, moving each unit towards a more normal occlusion.
  • Examples:
    • Closure of a midline diastema by moving the two central incisors towards each other.
    • Use of crossbite elastics and dental arch expansions.

2. According to Jaws Involved

• Intra-maxillary Anchorage:
  • All units offering resistance are situated within the same jaw.
• Intermaxillary Anchorage:
  • Resistance units in one jaw are used to effect tooth movement in the opposing jaw.
  • Also known as Baker's anchorage.
  • Examples:
    • Class II elastic traction.
    • Class III elastic traction.

3. According to Site

• Intraoral Anchorage:

  • Both the teeth to be moved and the anchorage areas are located within the oral cavity.
  • Anatomic units include teeth, palate, and lingual alveolar bone of the mandible.

• Extraoral Anchorage:

  • Resistance units are situated outside the oral cavity.
  • Anatomic units include the occiput, back of the neck, cranium, and face.
  • Examples:
    • Headgear.
    • Facemask.

• Muscular Anchorage:

  • Utilizes forces generated by muscles to aid in tooth movement.
  • Example: Lip bumper to distalize molars.

4. According to Number of Anchorage Units

• Single or Primary Anchorage:

  • A single tooth with greater alveolar support is used to move another tooth with lesser support.

• Compound Anchorage:

  • Involves more than one tooth providing resistance to move teeth with lesser support.

• Multiple or Reinforced Anchorage:

  • Utilizes more than one type of resistance unit.
  • Examples:
    • Extraoral forces to augment anchorage.
    • Upper anterior inclined plane.
    • Transpalatal arch.

Mouth Breathing

Mouth breathing is a condition where an individual breathes primarily through the mouth instead of the nose. This habit can lead to various dental, facial, and health issues, particularly in children. The etiology of mouth breathing is often related to nasal obstruction, and it can have significant clinical features and consequences.

Etiology

• Nasal Obstruction: Approximately 85% of mouth breathers suffer from some degree of nasal obstruction, which can be caused by:
  • Allergies: Allergic rhinitis can lead to inflammation and blockage of the nasal passages.
  • Enlarged Adenoids: Hypertrophy of the adenoids can obstruct airflow through the nasal passages.
  • Deviated Septum: A structural abnormality in the nasal septum can impede airflow.
  • Chronic Sinusitis: Inflammation of the sinuses can lead to nasal congestion and obstruction.

Clinical Features

1. Facial Characteristics:

   • Adenoid Facies: A characteristic appearance associated with chronic mouth breathing, including:
     • Long, narrow face.
     • Narrow nose and nasal passage.
     • Short upper lip.
     • Nose tipped superiorly.
     • Expressionless or "flat" facial appearance.

2. Dental Effects (Intraoral):

   • Protrusion of Maxillary Incisors: The anterior teeth may become protruded due to the altered position of the tongue and lips.
   • High Palatal Vault: The shape of the palate may be altered, leading to a high and narrow palatal vault.
   • Increased Incidence of Caries: Mouth breathers are more prone to dental caries due to dry oral conditions and reduced saliva flow.
   • Chronic Marginal Gingivitis: Inflammation of the gums can occur due to poor oral hygiene and dry mouth.

Management

1. Symptomatic Treatment:

   • Gingival Health: The gingiva of mouth breathers should be restored to normal health. Coating the gingiva with petroleum jelly can help maintain moisture and protect the tissues.
   • Addressing Obstruction: If nasal or pharyngeal obstruction has been diagnosed, surgical intervention may be necessary to remove the cause (e.g., adenoidectomy, septoplasty).

2. Elimination of the Cause:

   • Identifying and treating the underlying cause of nasal obstruction is crucial. This may involve medical management of allergies or surgical correction of anatomical issues.

3. Interception of the Habit:

   • Physical Exercise: Encouraging physical activity can help improve overall respiratory function and promote nasal breathing.
   • Lip Exercises: Exercises to strengthen the lip muscles can help encourage lip closure and discourage mouth breathing.
   • Oral Screen: An oral screen or similar appliance can be used to promote nasal breathing by preventing the mouth from remaining open.

• First orthodontic appliance: Bandelette
• Term "Orthodontics" coined by: Lefoulon
• Vital staining introduced by: John Hunter
• Cephalometric radiography developed by: Broadbent & Hofrath (1931)
• IOTN (Index of Orthodontic Treatment Need): Brook & Shaw
• Begg appliance: Modification of Angle's ribbon arch
• Light wire technique: Raymond Begg
• MBT bracket system: McLaughlin, Bennett & Trevisi