Angle’s Classification of Malocclusion

Malocclusion refers to the misalignment or incorrect relationship between the teeth of the two dental arches when they come into contact as the jaws close. Understanding occlusion is essential for diagnosing and treating orthodontic issues.

Definitions

• Occlusion: The contact between the teeth in the mandibular arch and those in the maxillary arch during functional relations (Wheeler’s definition).
• Malocclusion: A condition characterized by a deflection from the normal relation of the teeth to other teeth in the same arch and/or to teeth in the opposing arch (Gardiner, White & Leighton).

Importance of Classification

Classifying malocclusion serves several purposes:

• Grouping of Orthodontic Problems: Helps in identifying and categorizing various orthodontic issues.
• Location of Problems: Aids in pinpointing specific areas that require treatment.
• Diagnosis and Treatment Planning: Facilitates the development of effective treatment strategies.
• Self-Communication: Provides a standardized language for orthodontists to discuss cases.
• Documentation: Useful for recording and tracking orthodontic problems.
• Epidemiological Studies: Assists in research and studies related to malocclusion prevalence.
• Assessment of Treatment Effects: Evaluates the effectiveness of orthodontic appliances.

Normal Occlusion

Molar Relationship

According to Angle, normal occlusion is defined by the relationship of the mesiobuccal cusp of the maxillary first molar aligning with the buccal groove of the mandibular first molar.

Angle’s Classification of Malocclusion

Edward Angle, known as the father of modern orthodontics, first published his classification in 1899. The classification is based on the relationship of the mesiobuccal cusp of the maxillary first molar to the buccal groove of the mandibular first molar. It is divided into three classes:

Class I Malocclusion (Neutrocclusion)

• Definition: Normal molar relationship is present, but there may be crowding, misalignment, rotations, cross-bites, and other irregularities.
• Characteristics:
  • Molar relationship is normal.
  • Teeth may be crowded or rotated.
  • Other alignment irregularities may be present.

Class II Malocclusion (Distocclusion)

• Definition: The lower molar is positioned distal to the upper molar.
• Characteristics:
  • Often results in a retrognathic facial profile.
  • Increased overjet and overbite.
  • The mesiobuccal cusp of the maxillary first molar occludes anterior to the buccal groove of the mandibular first molar.

Subdivisions of Class II Malocclusion:

1. Class II Division 1:
   • Class II molars with normally inclined or proclined maxillary central incisors.
2. Class II Division 2:
   • Class II molars with retroclined maxillary central incisors.

Class III Malocclusion (Mesiocclusion)

• Definition: The lower molar is positioned mesial to the upper molar.
• Characteristics:
  • Often results in a prognathic facial profile.
  • Anterior crossbite and negative overjet (underbite).
  • The mesiobuccal cusp of the upper first molar falls posterior to the buccal groove of the lower first molar.

Advantages of Angle’s Classification

• Comprehensive: It is the first comprehensive classification and is widely accepted in the field of orthodontics.
• Simplicity: The classification is straightforward and easy to use.
• Popularity: It is the most popular classification system among orthodontists.
• Effective Communication: Facilitates clear communication regarding malocclusion.

Disadvantages of Angle’s Classification

• Limited Plane Consideration: It primarily considers malocclusion in the anteroposterior plane, neglecting transverse and vertical dimensions.
• Fixed Reference Point: The first molar is considered a fixed point, which may not be applicable in all cases.
• Not Applicable for Deciduous Dentition: The classification does not effectively address malocclusion in children with primary teeth.
• Lack of Distinction: It does not differentiate between skeletal and dental malocclusion.

Lip Bumper

A lip bumper is an orthodontic appliance designed to create space in the dental arch by preventing the lips from exerting pressure on the teeth. It is primarily used in growing children and adolescents to manage dental arch development, particularly in cases of crowding or to facilitate the eruption of permanent teeth. The appliance is typically used in the lower arch but can also be adapted for the upper arch.

Indications for Use

1. Crowding:

   • To create space in the dental arch for the proper alignment of teeth, especially when there is insufficient space for the eruption of permanent teeth.

2. Anterior Crossbite:

   • To help correct anterior crossbites by allowing the anterior teeth to move into a more favorable position.

3. Eruption Guidance:

   • To guide the eruption of permanent molars and prevent them from drifting mesially, which can lead to malocclusion.

4. Preventing Lip Pressure:

   • To reduce the pressure exerted by the lips on the anterior teeth, which can contribute to dental crowding and misalignment.

5. Space Maintenance:

   • To maintain space in the dental arch after the premature loss of primary teeth.

Design and Features

• Components:

  • The lip bumper consists of a wire framework that is typically made of stainless steel or other durable materials. It includes:
    • Buccal Tubes: These are attached to the molars to anchor the appliance in place.
    • Arch Wire: A flexible wire that runs along the buccal side of the teeth, providing the necessary space and support.
    • Lip Pad: A soft pad that rests against the lips, preventing them from exerting pressure on the teeth.

• Customization:

  • The appliance is custom-fitted to the patient’s dental arch to ensure comfort and effectiveness. Adjustments can be made to accommodate changes in the dental arch as treatment progresses.

Mechanism of Action

• Space Creation:

  • The lip bumper creates space in the dental arch by pushing the anterior teeth backward and allowing the posterior teeth to erupt properly. The lip pad prevents the lips from applying pressure on the anterior teeth, which can help maintain the space created.

• Guiding Eruption:

  • By maintaining the position of the molars and preventing mesial drift, the lip bumper helps guide the eruption of the permanent molars into their proper positions.

• Facilitating Growth:

  • The appliance can also promote the growth of the dental arch, allowing for better alignment of the teeth as they erupt.

Anterior Crossbite

Anterior crossbite is a dental condition where one or more of the upper front teeth (maxillary incisors) are positioned behind the lower front teeth (mandibular incisors) when the jaws are closed. This misalignment can lead to functional issues, aesthetic concerns, and potential wear on the teeth. Correcting anterior crossbite is essential for achieving proper occlusion and improving overall dental health.

Methods to Correct Anterior Crossbite

1. Acrylic Incline Plane:

   • Description: An acrylic incline plane is a removable appliance that can be used to guide the movement of the teeth. It is designed to create a ramp-like surface that encourages the maxillary incisors to move forward.
   • Mechanism: The incline plane helps to reposition the maxillary teeth by providing a surface that directs the teeth into a more favorable position during function.

2. Reverse Stainless Steel Crown:

   • Description: A reverse stainless steel crown can be used in cases where the anterior teeth are significantly misaligned. This crown is designed to provide a stable and durable solution for correcting the crossbite.
   • Mechanism: The crown can be adjusted to help reposition the maxillary teeth, allowing them to move into a more normal relationship with the mandibular teeth.

3. Hawley Retainer with Recurve Springs:

   • Description: A Hawley retainer is a removable orthodontic appliance that can be modified with recurve springs to correct anterior crossbite.
   • Mechanism: The recurve springs apply gentle pressure to the maxillary incisors, tipping them forward into a more favorable position relative to the mandibular teeth. This appliance is comfortable, easily retained, and predictable in its effects.

4. Fixed Labial-Lingual Appliance:

   • Description: A fixed labial-lingual appliance is a type of orthodontic device that is bonded to the teeth and can be used to correct crossbites.
   • Mechanism: This appliance works by applying continuous forces to the maxillary teeth, tipping them forward and correcting the crossbite. It may include a vertical removable arch for ease of adjustment and recurve springs to facilitate movement.

5. Vertical Removable Arch:

   • Description: This appliance can be used in conjunction with other devices to provide additional support and adjustment capabilities.
   • Mechanism: The vertical removable arch allows for easy modifications and adjustments, helping to jump the crossbite by repositioning the maxillary teeth.

Steiner's Analysis

Steiner's analysis is a widely recognized cephalometric method used in orthodontics to evaluate the relationships between the skeletal and dental structures of the face. Developed by Dr. Charles A. Steiner in the 1950s, this analysis provides a systematic approach to assess craniofacial morphology and is particularly useful for treatment planning and evaluating the effects of orthodontic treatment.

Key Features of Steiner's Analysis

1. Reference Planes and Points:

   • Sella (S): The midpoint of the sella turcica, a bony structure in the skull.
   • Nasion (N): The junction of the frontal and nasal bones.
   • A Point (A): The deepest point on the maxillary arch between the anterior nasal spine and the maxillary alveolar process.
   • B Point (B): The deepest point on the mandibular arch between the anterior nasal spine and the mandibular alveolar process.
   • Menton (Me): The lowest point on the symphysis of the mandible.
   • Gnathion (Gn): The midpoint between Menton and Pogonion (the most anterior point on the chin).
   • Pogonion (Pog): The most anterior point on the contour of the chin.

2. Reference Lines:

   • SN Plane: A line drawn from Sella to Nasion, representing the cranial base.
   • ANB Angle: The angle formed between the lines connecting A Point to Nasion and B Point to Nasion. It indicates the relationship between the maxilla and mandible.
   • Facial Plane (FP): A line drawn from Gonion (Go) to Menton (Me), used to assess the facial profile.

3. Key Measurements:

   • ANB Angle: Indicates the anteroposterior relationship between the maxilla and mandible.
     • Normal Range: Typically between 2° and 4°.
   • SN-MP Angle: The angle between the SN plane and the mandibular plane (MP), which helps assess the vertical position of the mandible.
     • Normal Range: Usually between 32° and 38°.
   • Wits Appraisal: The distance between the perpendiculars dropped from points A and B to the occlusal plane. It provides insight into the anteroposterior relationship of the dental bases.

Clinical Relevance

• Diagnosis and Treatment Planning: Steiner's analysis helps orthodontists diagnose skeletal discrepancies and plan appropriate treatment strategies. It provides a clear understanding of the patient's craniofacial relationships, which is essential for effective orthodontic intervention.
• Monitoring Treatment Progress: By comparing pre-treatment and post-treatment cephalometric measurements, orthodontists can evaluate the effectiveness of the treatment and make necessary adjustments.
• Predicting Treatment Outcomes: The analysis aids in predicting the outcomes of orthodontic treatment by assessing the initial skeletal and dental relationships.

SEQUENCE OF ERUPTION OF DECIDUOUS TEETH

Upper/Lower   A B D C E 

SEQUENCE OF ERUPTION OF PERMAMENT TEETH 

Upper:   6 1 2 4 3 5 7           Lower:    6 1 2 3 4 5 7   
      
or       6 1 2 4 5 3 7              or  6 1 2 4 3 5 7 
 

ANTHROPOID SPACE / PRIMATE SPACE / SIMIEN’S SPACE  

The space mesial to upper deciduous canine and distal to lower deciduous  canine is characteristically found in primates and hence it is called primate space.  

INCISOR LIABILITY 

When the permanent central incisor erupt, these teeth use up specially all the spaces found in the normal dentition. With the eruption of permanent lateral incisor the space situation becomes tight. In the maxillary arch it is just enough to accommodate but in mandibular arch there is an average 1.6 mm less space available. This difference between the space present and space required is known as incisor liability. 
These conditions overcome by;  

      1. This is a transient condition and extra space comes from slight increase in arch width.   
      2. Slight labial positioning of central and lateral incisor. 
      3. Distal shift of permanent canine.        

      
LEE WAY SPACE (OF NANCE)  

The combined mesiodistal width of the permanent canines and pre molars is usually less that of the deciduous canines and molars. This space is 
called leeway space of Nance.     

Measurement of lee way space: 
 
Is greater in the mandibular arch than in the maxillary arch  It is about 1.8mm [0.9mm on each side of the arch] in the maxillary arch. 
And about 3.4mm [1.7 mm on side of the arch] in the mandibular arch. 
 
Importance:  

 This lee way space allows the mesial movement of lower molar there by correcting flush terminal plane.     
 LWS can be measure with the help of cephalometry.    

FLUSH TERMINAL PLANE (TERMINAL PLANE RELATIONSHIP) 

Mandibular 2nd deciduous molar is usually wider mesio-distally then the maxillary 2nd deciduous molar. This leads to the development of flush terminal plane which falls along the distal surface of upper and lower 2nd deciduous molar. This develops into class I molar relationship. 

Distal step relationship leads to class 2 relationship.
Mesial step relationship mostly leads to class 3 relationship.  

FEATURE OF IDEAL OCCLUSION IN PRIMARY DENTITION 

1. Spacing of anterior teeth. 
2. Primate space is present. 
3. Flush terminal plane is found. 
4. Almost vertical inclination of anterior teeth. 
5. Overbite and overjet varies.  

UGLY DUCKLING STAGE  

Definition:  
Stage of a transient or self correcting malocclusion is seen sometimes is called ugly duck ling stage. 
 
Occurring site: Maxillary incisor region 

Occuring age: 8-9 years of age.  

This situation is seen during the eruption of the permanent canines. As the developing p.c. they displace the roots of lateral incisor mesially this results is transmitting of the force on to the roots of the central incisors which also gets displaced mesially. A resultant distal divergence of the crowns of the two central incisors causes midline spacing.  

This portion of teeth at this stage is compared to that of ugly walk of the duckling and hence it is called Ugly Duckling Stage. 

Described by Broad bent. In this stage children tend to look ugly. Parents are often apprehensive during this stage and consult the dentist.  

Corrects by itself, when canines erupt and the pressure is transferred from the roots to the coronal area of the incisor.  
IMPORTANCE OF 1ST MOLAR
 
1. It is the key tooth to occlusion. 
2.  Angle’s classification is based on this tooth. 
3.  It is the tooth of choice for anchorage. 
4.  Supports occlusion in a vertical direction. 
5.  Loss of this tooth leads to migration of other tooth. 
6.  Helps in opening the bite.   

The Nance Appliance is a fixed orthodontic device used primarily in the upper arch to maintain space and prevent the molars from drifting forward. It is particularly useful in cases where there is a need to hold the position of the maxillary molars after the premature loss of primary molars or to maintain space for the eruption of permanent teeth. Below is an overview of the Nance Appliance, its components, functions, indications, advantages, and limitations.

Components of the Nance Appliance

1. Baseplate:

   • The Nance Appliance features an acrylic baseplate that is custom-made to fit the palate. This baseplate is typically made of a pink acrylic material that is molded to the shape of the patient's palate.

2. Anterior Button:

   • A prominent feature of the Nance Appliance is the anterior button, which is positioned against the anterior teeth (usually the incisors). This button helps to stabilize the appliance and provides a point of contact to prevent the molars from moving forward.

3. Bands:

   • The appliance is anchored to the maxillary molars using bands that are cemented onto the molars. These bands provide the necessary anchorage for the appliance.

4. Wire Framework:

   • A wire framework may be incorporated into the appliance to enhance its strength and stability. This framework typically consists of a stainless steel wire that connects the bands and the anterior button.

Functions of the Nance Appliance

1. Space Maintenance:

   • The primary function of the Nance Appliance is to maintain space in the upper arch, particularly after the loss of primary molars. It prevents the adjacent teeth from drifting into the space, ensuring that there is adequate room for the eruption of permanent teeth.

2. Molar Stabilization:

   • The appliance helps stabilize the maxillary molars in their proper position, preventing them from moving forward or mesially during orthodontic treatment.

3. Arch Development:

   • In some cases, the Nance Appliance can assist in arch development by providing a stable base for other orthodontic appliances or treatments.

Indications for Use

• Premature Loss of Primary Molars: To maintain space for the eruption of permanent molars when primary molars are lost early.
• Crowding: To prevent adjacent teeth from drifting into the space created by lost teeth, which can lead to crowding.
• Molar Stabilization: To stabilize the position of the maxillary molars during orthodontic treatment.

Advantages of the Nance Appliance

1. Fixed Appliance: As a fixed appliance, the Nance Appliance does not rely on patient compliance, ensuring consistent space maintenance.
2. Effective Space Maintenance: It effectively prevents unwanted tooth movement and maintains space for the eruption of permanent teeth.
3. Minimal Discomfort: Generally, patients tolerate the Nance Appliance well, and it does not cause significant discomfort.

Limitations of the Nance Appliance

1. Oral Hygiene: Maintaining oral hygiene can be more challenging with fixed appliances, and patients must be diligent in their oral care to prevent plaque accumulation and dental issues.
2. Limited Movement: The Nance Appliance primarily affects the molars and may not be effective for moving anterior teeth.
3. Adjustment Needs: While the appliance is generally stable, it may require periodic adjustments or monitoring by the orthodontist.