Physiology of tooth movement and appliances overview Flashcards

Question

cause and prevalance of ectopic canines

Answer 1

genetic 1-2% variation in difficulty to fix

Answer 2

CBCT ## Footnote check position, damage/resorption (follicle can dissolve away bone and cementum)

Answer 3

Ignore ectopic canines – obvious * One thing wrong with development likely to have other issues go through methodically * No additional teeth * Caries – BW follow up * Roots * Lower right E – distal root partly resorbed, mesial root large – take long time to resorb * 45 root is ½ - 2/3 formed – extract deciduous * Same lower left E now maxillary ecotopic canines * Palatally positioned – magnified (closer to midline) * Follicle larger – cystic change * No appearance of resorption of lateral – see full lamina dura * Remove Cs – come into correct position * Follicle pulls through bone

Answer 4

* height * closeness to midline * angle

Answer 5

High – above central apex Good angle – compare to mid sagittal line (vertical plane), under 30 degrees = good Midline - Doesn’t overlap adjacent incisor by more than half Favourable -\> interception will work, lining teeth up more successful

Answer 6

Still high Angle now poor very close to midline – fully covering lateral no cystic change * now need surgery and 2-3 years ortho tx

Answer 7

mandible than maxilla ## Footnote 6 drift forward 5, 4, 3 still waiting to erupt – no space, reduced

Answer 8

Unusual tooth movement following interceptive extraction Lower right buccal segment * 46 * Submerging 85 * 45 – horizontal, no hope Place a space maintainer – band and loop * Within 6 months change position * 2 years of space maintenance – erupt into space Follicle pulling tooth through bone – not apical end

Answer 9

* if an external force is applied to a tooth, the tooth will move as the bone around it remodels * bony remodelling is mediated by the periodontal ligament * If a tooth has no PDL or is ankylosed, it will NOT move * Cause intrusion of adj teeth with healthy PDL

Answer 10

Cementum is much more resistant to resorption than bone (1mm thick) * although some degree of root resorption after orthodontics should be expected

Answer 11

osteoclasts (usually in lacunae) and osteoblasts appear

Answer 12

Manages the growth and development of the teeth, face and jaws Corrects irregularities in these structures using * Appliances to transmit force to PDL and bone * ‘osteoclast herder’ * Thousands of workers, 24 hour shifts, no pay, no superannuation, no complaints, no sickness… * Work not up to standard or any signs of slacking, macrophage will phagocytose!

Answer 13

* Differential pressure theory * Piezoelectric pressure theory * Mechno-chemical pressure theory

Answer 14

Pressure on tooth (e.g. here retrocline) Tension on one side of PDL Compression on other side of PDL Tension = bone deposition Compression = bone resorption

Answer 15

Piezoelectric currents are generated when crystalline structures, such as bone, are deformed These currents have been suggested as a mechanisms by which tooth movement is modulated * Compression = + * Tension = - * May result in cells being recruited to sites (osteoclasts +, osteoblasts -) Forces so small – unlikely alone

Answer 16

Mechanical stress on tooth and bone -\> Release of neuropeptides from nerve endings -\> Stimulate fibroblasts, endothelial cells and alveolar bone -\> Fibroblast also communicate with osteoblasts and osteoclasts -\> Alveolar bone and periodontal ligament remodelling -\> Tooth movement

Answer 17

* removable (URA) * functionals * fixed

Answer 18

* tipping * bodily movement * intrusion * extrusion * rotation * torque - root not crown

Answer 19

tipping centre of rotation moves up as tipped

Answer 20

flat anterior bite plane – best, most efficient way at reducing overbite in growing pt * Common URA and lower fixed – overbite reduced, and reduced the amount of time with fixed upper as start with URA

Answer 21

* The mandible is postured away from its normal rest position * Skeletal Changes - growth backwards (red arrows) * The facial musculature is stretched which generates forces transmitted to the teeth and alveolus * Dental changes * Careful not to over procline lower anterior * Posterior open bite – close naturally * There may be an effect on facial growth * E.g. class II cases * Restrict maxillary growth * Promote mandibular growth * Remodel the glenoid fossa

Answer 22

growth backwards (red arrows) mandible is postured away from its normal rest position

Answer 23

* The mandible is postured away from its normal rest position * Skeletal Changes - growth backwards (red arrows) * The facial musculature is stretched which generates forces transmitted to the teeth and alveolus * Dental changes * Careful not to over procline lower anterior * Posterior open bite – close naturally

Answer 24

E.g. class II cases * Restrict maxillary growth * Promote mandibular growth * Remodel the glenoid fossa

Answer 25

*Significant jaw discrepancy – try and grow their jaw to save from surgery*

Answer 26

* Large 11mm overjet* * 9months constant wearing functional appliance* * 18 months after start Tx – wearing at night*

Answer 27

* Skeletal change (30%), growth of mandible, restraint of maxilla * Dentoalveolar change (70%), retroclination of upper teeth, proclination of lower teeth * Mesial migration of the lower teeth * Distal migration of the upper teeth Combination of the above achieves class I

Answer 28

Note that there is a coordinated bone modelling and remodelling response leading and trailing the moving tooth. * This mechanism allows a tooth to move relative to basilar bone while maintaining a normal functional relationship with its periodontium * Osteoclastic and osteoblastic activity are in red and blue, respectively* More deposition on the outside of alveolus too – distant from tooth * Secondary remodelling

Answer 29

* bodily movement * intrusion * extrusion * rotation * torque

Answer 30

must be active cannot be bendy - tooth slides along

Answer 31

* Pressure on the supporting structures is evenly distributed and bone resorption is necessary, particularly at the apical area at the alveolar crest

Answer 32

* Tension is induced in the supporting structures and bone deposition is necessary to maintain tooth support

Answer 33

* Need a force couple – 2 forces in opposing directions

Answer 34

* Apical root torque * Hard to deliver – root moves most * root uprighting

Answer 35

Hyperaemia within the periodontal ligament on both pressure and tension side * Appearance of osteoclasts and osteoblasts Resorption of lamina dura from pressure side (osteoclasts) *frontal resorption* Apposition of osteoid on tension side (osteoblasts) *deposition* **Remodelling of socket – “frontal resorption”** Periodontal fibres reorganise Gingival fibres appear not to become reorganised but remain distorted

Answer 36

Occlusion of vessels of periodontal ligament on pressure side Hyperaemia of vessels of periodontal ligament on tension side Cell free areas on pressure side (**hyalinisation**) * Period of stasis * not dead - but nothing happening Increased endosteal vascularity – “**undermining resorption**” **Relatively rapid movement of tooth with bone deposition on the tension side** – tooth may become slightly loose Healing of periodontal ligament – reorganisation and remodelling

Answer 37

* Necrosis * Undermining resorption * Resorption of root surfaces * Pain * Permanent change Extensive lateral root resorption (RR) and undermining resorption (UR), just to the left of an area of PDL necrosis (N), is associated with the lag phase of tooth movement

Answer 38

* magnitude * duration * age * anatomy

Answer 39

* Light forces – consistent movement* * Heavy forces – no change for while as undermining resorption and then sudden* * moderate and high forces – not wanted, bad histological movement process * Main problem of heavy force – anchorage teeth are moving but not desired tooth so excessive movement by them*

Answer 40

*Constant 24hrs of force to prevent teeth moving back into old position*

Answer 41

works at any age maybe slower in older ages

Answer 42

* no bone * wasting/cleft * e.g. alveolar encking - not possible to do ortho on as thin dence cortical plate bone * soft tissues * tongue * anterior open bite * mid-palatal suture

Answer 43

* 7, 5, 4* * 6 extracted long time ago* * 5 drifted mesial as no 6* * Alveolar bone cortex plates together – knife edge* * *_Hard to move through as dense_*

Answer 44

## Footnote *No pathology = no problem as ortho deals with PDL*

Answer 45

* Pain and mobility * Pulpal changes * Root resorption * Loss of alveolar bone support * relapse

Answer 46

1mm per month treatment time 24 months for fixed appliances

Answer 47

* Remodelling of the alveolar bone * Role of dental follicle * Elongation of the root * Pressure against the root surface in the apical part of the root pushing it towards the oral cavity * Reorganisation of the periodontal membrane fibres * Role of the fibroblasts both with their contractile properties and their ability to quickly turn over collagen fibres

Answer 48

mechano-chemical theory

Answer 49

tipping forces Functional can also act on MOM set up forces that influences dentition and growth of jaws

Answer 50

all forces * tipping * bodily movement * intrusion * extrusion * rotation * torque (uprighting root on top of crown)

Answer 51

Bodily 2 sides * One deposition one resorption Tipping * Areas – not whole length

Answer 52

* magnitude * light - most efficient, get frontal resorption * moderate - slower, get undermining resorption * heavy/excessive - necrosis, root resorption, pain, loss of vitality (rare), alveolar bone loss (rare) * duration * most efficient with (light) continuous force * age * maybe sligtly slower in adults * anatomy * volume of bone * effects of tongue * digit habits