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.   

Orthodontic Force Duration

1. Continuous Forces:

   • Definition: Continuous forces are applied consistently over time without interruption.
   • Application: Many extraoral appliances, such as headgear, are designed to provide continuous force to the teeth and jaws. This type of force is essential for effective tooth movement and skeletal changes.
   • Example: A headgear may be worn for 12-14 hours a day to achieve the desired effects on the maxilla or mandible.

2. Intermittent Forces:

   • Definition: Intermittent forces are applied in a pulsed or periodic manner, with breaks in between.
   • Application: Some extraoral appliances may use intermittent forces, but this is less common. Intermittent forces can be effective in certain situations, but continuous forces are generally preferred for consistent tooth movement.
   • Example: A patient may be instructed to wear an appliance for a few hours each day, but this is less typical for extraoral devices.

Force Levels

1. Light Forces:

   • Definition: Light forces are typically in the range of 50-100 grams and are used to achieve gentle tooth movement.
   • Application: Light forces are ideal for orthodontic treatment as they minimize discomfort and reduce the risk of damaging the periodontal tissues.
   • Example: Some extraoral appliances may be designed to apply light forces to encourage gradual movement of the teeth or to modify jaw relationships.

2. Moderate Forces:

   • Definition: Moderate forces range from 100-200 grams and can be used for more significant tooth movement or skeletal changes.
   • Application: These forces can be effective in achieving desired movements but may require careful monitoring to avoid discomfort or adverse effects.
   • Example: Headgear that applies moderate forces to the maxilla to correct Class II malocclusions.

3. Heavy Forces:

   • Definition: Heavy forces exceed 200 grams and are typically used for rapid tooth movement or significant skeletal changes.
   • Application: While heavy forces can lead to faster results, they also carry a higher risk of complications, such as root resorption or damage to the periodontal ligament.
   • Example: Some extraoral appliances may apply heavy forces for short periods, but this is generally not recommended for prolonged use.

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.

Key Cephalometric Landmarks

1. Sella (S):

   • The midpoint of the sella turcica, a bony structure located at the base of the skull. It serves as a central reference point in cephalometric analysis.

2. Nasion (N):

   • The junction of the frontal and nasal bones, located at the bridge of the nose. It is often used as a reference point for the anterior cranial base.

3. A Point (A):

   • The deepest point on the maxillary arch, located between the anterior nasal spine and the maxillary alveolar process. It is crucial for assessing maxillary position.

4. B Point (B):

   • The deepest point on the mandibular arch, located between the anterior nasal spine and the mandibular alveolar process. It is important for evaluating mandibular position.

5. Pogonion (Pog):

   • The most anterior point on the contour of the chin. It is used to assess the position of the mandible in relation to the maxilla.

6. Gnathion (Gn):

   • The midpoint between Menton and Pogonion, representing the most inferior point of the mandible. It is used in various angular measurements.

7. Menton (Me):

   • The lowest point on the symphysis of the mandible. It is used as a reference for vertical measurements.

8. Go (Gonion):

   • The midpoint of the contour of the ramus and the body of the mandible. It is used to assess the angle of the mandible.

9. Frankfort Horizontal Plane (FH):

   • A plane defined by the points of the external auditory meatus (EAM) and the lowest point of the orbit (Orbitale). It is used as a reference plane for various measurements.

10. Orbitale (Or):

    • The lowest point on the inferior margin of the orbit (eye socket). It is used in conjunction with the EAM to define the Frankfort Horizontal Plane.

11. Ectocanthion (Ec):

    • The outer canthus of the eye, used in facial measurements and assessments.

12. Endocanthion (En):

    • The inner canthus of the eye, also used in facial measurements.

13. Alveolar Points:

    • Points on the alveolar ridge of the maxilla and mandible, often used to assess the position of the teeth.

Importance of Cephalometric Landmarks

• Diagnosis: These landmarks help orthodontists diagnose skeletal and dental discrepancies, such as Class I, II, or III malocclusions.
• Treatment Planning: By understanding the relationships between these landmarks, orthodontists can develop effective treatment plans tailored to the individual patient's needs.
• Monitoring Progress: Cephalometric landmarks allow for the comparison of pre-treatment and post-treatment radiographs, helping to evaluate the effectiveness of orthodontic interventions.
• Research and Education: These landmarks are essential in orthodontic research and education, providing a standardized method for analyzing craniofacial morphology.

Anterior bite plate is an orthodontic appliance used primarily to manage various dental issues, particularly those related to occlusion and alignment of the anterior teeth. It is a removable appliance that is placed in the mouth to help correct bite discrepancies, improve dental function, and protect the teeth from wear.

Indications for Use

1. Anterior Crossbite:

   • An anterior bite plate can help correct an anterior crossbite by repositioning the maxillary incisors in relation to the mandibular incisors.

2. Open Bite:

   • It can be used to help close an anterior open bite by providing a surface for the anterior teeth to occlude against, encouraging proper alignment.

3. Bruxism:

   • The appliance can protect the anterior teeth from wear caused by grinding or clenching, acting as a barrier between the upper and lower teeth.

4. Space Maintenance:

   • In cases where anterior teeth have been lost or extracted, an anterior bite plate can help maintain space for future dental work or the eruption of permanent teeth.

5. Facilitation of Orthodontic Treatment:

   • It can be used as part of a comprehensive orthodontic treatment plan to help achieve desired tooth movements and improve overall occlusion.

Design and Features

• Material: Anterior bite plates are typically made from acrylic or thermoplastic materials, which are durable and can be easily adjusted.
• Shape: The appliance is designed to cover the anterior teeth, providing a flat occlusal surface for the upper and lower teeth to meet.
• Retention: The bite plate is custom-fitted to the patient’s dental arch to ensure comfort and stability during use.

Mechanism of Action

• Repositioning Teeth: The anterior bite plate can help reposition the anterior teeth by providing a surface that encourages proper occlusion and alignment.
• Distributing Forces: It helps distribute occlusal forces evenly across the anterior teeth, reducing the risk of localized wear or damage.
• Encouraging Proper Function: By providing a stable occlusal surface, the bite plate encourages proper chewing and speaking functions.

Management and Care

• Patient Compliance: For the anterior bite plate to be effective, patients must wear it as prescribed by their orthodontist. This may involve wearing it during the day, at night, or both, depending on the specific treatment goals.
• Hygiene: Patients should maintain good oral hygiene and clean the bite plate regularly to prevent plaque buildup and maintain oral health.
• Regular Check-Ups: Follow-up appointments with the orthodontist are essential to monitor progress and make any necessary adjustments to the appliance.

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.