SOLUTION

The reason is found in the concept of "dental compensation for skeletal discrepancy.  This can occur naturally as well as being created by orthodontic camouflage treatment.

In mandibular prognathism, for instance, as the individual grows the upper incisors tend to protrude while the lower incisors incline lingually.

By the time growth is completed, the dental discrepancy usually is smaller than the jaw discrepancy. 

Tooth position has compensated at least partially for the jaw discrepancy.

Solution

The following are the effects when Herbst appliance used for treatment of Class II malocclusion:
1. Class I molar relation or over-corrected Class I molar relation.
2. Increased mandibular growth
3. Distal driving of maxillary molars which helps to achieve molar relation.
4. Reduction of overjet by increasing mandibular length and proclination of mandibular incisors.
5. Inhibitory effect on sagittal maxillary growth
6. Weislander suggested double contour of glenoid fossa which indicates anterior transformation of glenoid fossa
7. Increased SNB angle and decreased SNA angle.

ankylosed teeth are also known as submerged teeth.
submerged teeth are decidous teeth most commonly mandibular second molars
Most common permanant tooth found to be ankylosed is premolars.

SOLUTION
Simon used the orbital plane (a plane perpendicular to the F-H plane at the margin of the bony orbit directly under the pupil of the eye).

According to Simon, in normal arch relationship, the orbital plane passes through the distal axial aspect of the maxillary canine

Malocclusions described as anteropostenor deviations based on their distance from the orbital plane are as follows:

1. Protraction: The teeth, one or both, dental arches, andYor jaws are too far forward, i.e. placed forward or anterior to the plane as compared to the normal where the plane passes through the distal incline of the canine.

2. Retraction: The teeth, one or both dental arches and/or jaws are too far backward, i.e. placed posterior to the plane than normal

Ashley-Howe Model Analysis

The Ashley-Howe model analysis is a method used in orthodontics to assess the relationship of the dental arches and the position of the teeth, particularly in the context of planning orthodontic treatment. This analysis is particularly useful for evaluating the transverse dimension of the dental arches and understanding how the maxilla (upper jaw) and mandible (lower jaw) relate to each other.

Measurement Parameters:

• The analysis involves measuring specific distances and angles on dental casts or models. Key measurements may include:
  • Intercanine Width: The distance between the cusp tips of the canines.
  • Interpremolar Width: The distance between the cusp tips of the first premolars.
  • Intermolar Width: The distance between the cusp tips of the first molars.
• These measurements help in determining the transverse relationships of the dental arches.

Classification:

• The results of the Ashley-Howe analysis can help classify the dental arch relationships into different categories, such as:
  • Normal: Where the measurements fall within the expected range.
  • Narrowed: Indicating a constricted arch that may require expansion.
  • Widened: Indicating a broader arch that may need to be reduced or managed differently.

Clinical Application:

• The Ashley-Howe model analysis is particularly useful in treatment planning for orthodontic cases involving:
  • Crossbites: Where the upper teeth are positioned inside the lower teeth.
  • Crowding: Where there is insufficient space for teeth to erupt properly.
  • Expansion Needs: Determining if a patient requires arch expansion to correct transverse discrepancies.

Treatment Implications:

• Based on the analysis, orthodontists can decide on appropriate treatment modalities, which may include:
  • Orthodontic Appliances: Such as expanders to widen the arch.
  • Extraction: In cases of severe crowding or when space needs to be created.
  • Comprehensive Orthodontic Treatment: To align the teeth and improve occlusion.