Biomechanics of tooth movement

Gian sagar dental college and hospital

Submitted by: Nivedita sharma (45)

Preeti jolly (46) Priyanka goyal (47)

Priyanka wadhawan (48)

Contents:Types of tooth movementTissue response of orthodontic tooth

applicationAge factor in orthodontics

Cardinal Rule – Before doing any tooth movement there should be no inflammation in the periodontal attachment.

Tooth movement

Various kinds of tooth movement

1. Extrusion

2. Intrusion

3. Tipping – Uncontrolled

- Controlled

4. Bodily movement

EXTRUSION

Least hazardous kind of tooth movement as far as periodontium is considered.

Extrusion followed by equilibration of the clinical crown has been shown to reduce infrabony defects and pockets.(Ingber JS, J Periodontol 1974)

INTRUSION

Controversial –

Most authors – Intrusion results in deepening of infrabony pockets, root resorption, bone defects

Birte Melsen (AJODO 1989. Vol.96)

No increase in bone defects/ improvement in bony defects

TIPPING

UNCONTROLLED TIPPING in all cases causes heavy forces at the alveolar crest resulting in severe destruction of the epithelial attachment and crestal bone loss

Bone loss & Center of Resistance of a tooth

CONTROLLED TIPPING also produces high forces in the periodontal ligament as the fulcrum shifts more and more apically with increasing amounts of bone loss

Infact cases have been documented where a gingival lesion has been converted into a periodontal lesion by the injudicious use of tipping moments.

Mild gingival changes associated with orthodontic appliances are transitory. These cause no periodontal damage and resolve on their own.

BODILY MOVEMENT

Moving a tooth bodily into a periodontal defect has been believed to ‘carry the bone’ along with the tooth resulting in improvement of the defect.

However recent studies have shown that this only an illusion because it causes only an improved connective tissue attachment and infact worsens the bony defect. Hence until new evidence surfaces this is contraindicated.

FORCE

TISSUE RESPONSE

STRONG/ HEAVY FORCE (Forces far exceeding capillary blood pressure)

PDL on pressure side ischemia & degeneration of PDL = hyalinization = more delay in tooth movement

MODERATE FORCE (Force exceeding capillary blood pressure)

PDL strangulation resulting in delay in bone resorption

LIGHT FORCE (Force less than capillary blood pressure )

PDL ischemia with simultaneous bone resorption and formation = more continuous tooth movement

PERIODONTAL TISSUE RESPONSE TO ORTHODONTIC FORCE

EQULIBRIUM CONCEPTIt is not only the forces of the musculature that help

in maintaining tooth position.

In certain areas of the dentition like the mandibular anteriors the pressure from the tongue within is more than the pressure from the extroral muscles. Here the metabolic activity of the periodontal ligament helps in maintaining tooth position

Various studies have shown that -

Alveolar bone height reduced in areas of increased over jet

Gingivitis is generally associated with crowding Level of bacteria is higher in areas of crowding

compared with normal areas in same patient

TOOTH MOVEMENT AND AGE

The age related factors affecting tooth movement are as follows:

1. Vitality of tissues2. Role of growth3. Role of apical foramen4. Density of bone

1. Vitality of tissues:

Orthodontic tooth movement is most effectively carried out in young patients.

Young patients exhibit increased vascularity and cellularity of periodontal membrane and bone as compared to older individuals.

Hence, patients of younger age group are more responsive to orthodontic treatment.

2. ROLE OF GROWTH:

Most orthodontic corrections are effectively carried out during the growth period.

Young patients react more favourably to orthodontic forces.

3. ROLE OF APICAL FORAMEN

In adults, the apical foramen is narrow where as in young patients it is wider.

In young patients , there are lesser chances of pulpal damage because of wider apical foramen.

In adult patients, there are more chances of root resorption, non-vitality and ankylosis of teeth due to narrow apical foramen.

4. DENSITY OF BONE:

Orthodontic tooth movement is much slower in adults because of greater density of bone.

YOUNG VERSUS ADULT PATIENTS

1. GROWTH TO WORK WITH: In a child patient the orthodontist has

growth to work with where as the adults lack growth.

Most orthodontic treatments are carried out using growth potential of the patient.

2. PERIODONTAL PROBLEMS:

Periodontal problems occur more commonly in adults.

Periodontally involved teeth move more readily and offer poor anchorage.

3. TISSUE VITALITY:

Because of high vascularity and cellularity, the younger patients are more responsive to orthodontic forces as compared to the older patients.

4. PATIENT MOTIVATION AND COOPERATION:

Adult patients are well motivated as compared to children.

Adult patients are more cooperative too.

5. TREATMENT APPRECIATION:Adult patients are more appreciative of the

treatment results than a child patient.

PRE & POST TREATMENT COMPARISON

Comparison of pre and post treatment OPG note the amount of bone is maintained if not reduced and significant amount of bone formation in upper anterior segment due to tooth Moving closer to each other

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