Space Maintenance in transition from primary to permanent dentition

Question 1

The two ways of managing early loss of deciduous teeth is by balancing or compensating extraction. Define both.

Answer 1

Balancing extraction = extraction of contralateral tooth (usually to preserve midline)

Compensating extraction = extraction of opposing tooth (usually to preserve occlusal relationships

Question 2

Which deciduous teeth should you most/least worry about the early loss of?

(incisors, upper canine, 2nd molars)

When is compensation indicated?

Answer 2

primary incisors → little effect on dentition, not necessary to balance or compensate

upper canines → likely to have most effect on centreline, consider balancing

compensation is NOT indicated in primary dentition

never balance the extraction of a primary 2nd molar, consider fitting a space maintainer

Question 3

What does the OPG show?

Answer 3

over-retained canine which has caused shift in midline

Question 4

When does crown formation of permanent 1st molars happen and what does that make them susceptible to?

Answer 4

timing around birth making susceptible to hypomineralisation/hypoplasia (10-30% prevalence) → makes them more suspectible to caries

Question 5

What can be done for a 1st perm molar with poor prognosis?

Answer 5

exo and aim to get 2nd molar to erupt as suitable replacement and then ultimately 3rd molar to complete the molar dentition

but MUST be timed correctly

Question 6

When should exo of 1st perm molar with poor prognosis be done?

Answer 6

upper: not as time critical, age 8-10 generally ok
lower: ideally immediately after calcification of bifurcation of lower 2nd molar (radiographically detected)

Question 7

What might you need to do for opposing molar after exo of 1st perm molar?

Answer 7

compensating if remaining molar will be out of occlusion to prevent overeruption

(but in full unit class II, possible that upper molar is in contact with lower deciduous 2nd molar then leaving it would be fine)

Question 8

Why shouldn’t exo of poor prognosis 1st perm molars be delayed past appropriate time?

Answer 8

difficult to close space after exo as lower 7s are quite resistant to moving after roots are fully formed

Question 9

Why shouldn’t exo of poor prognosis 1st perm molars be delayed past appropriate time?

Answer 9

difficult to close space after exo as lower 7s are quite resistant to moving after roots are fully formed (big anchors in the mouth)

(always check and refer in 8-10 yr olds as this is very difficult to do in older)

Question 10

About 2% of children are missing congenitally missing 2nd premolars. What is a problem encountered by this?

Answer 10

job of E is to hold upper 6 back in its position to allow space for 5 to erupt, so if 5 is congenitally missing, could extract E to allow for mesial drift of 6 to come in and fill the space

(but need to consult an ortho as there sometimes can be adverse effects on occlusion, Es if left could also be replaced with implant when adult when exfoliated)

Question 11

Describe how teeth transition from primary to permanent dentition and how space is used.

Answer 11

• spacing is normal and desirable in anterior primary teeth
• primate (anthropoid spaces) are found in mx and md arches

Question 12

What kind of spacing is normal in primary teeth? (2)

Answer 12

• spacing in anteriors is normal and desirable
• primate (anthropoid) spaces in both mx and md arch → M to upper deciduous canine and D to lower deciduous canine

Question 13

What is incisor liability? (1) And how much is it (2), why is it greater in upper arch? (1)

Answer 13

difference between combined widths of permanent and decidous incisors

~ 7.5mm upper, 6mm lower

primate space included in uppers but not lowers

Question 14

How is incisor liability overcome in the maxilla? (5)

Answer 14

1. anterior interdental spaces
2. primate space
3. labial eruption of incisors increasing arch length and circumference
4. increased inter-canine width
5. reduced inter-incisal angle (perms more proclined than deciduous, making more space)

Question 15

How is incisor liability overcome in the mandible?

Answer 15

1. anterior interdental spaces
2. increased inter-canine width
3. reduced inter-incisal angle

Question 16

What difference between upper and lower incisor liability is shown in the image?

Answer 16

upper perms erupt more labially than their predecessors whereas lowers dont have as signficant of a difference

Question 17

How can/can’t you describe occlusion in primary posteriors? (1, 3)

Answer 17

DO NOT use Angle’s classification in deciduous molars, use:

• flush terminal plane
• mesial step
• distal step

Question 18

Define flush terminal plane, mesial step and distal step. State which is normal and give approximate incidence of each. (3, 1, 3)

Answer 18

Flush terminal plane (76%) = Distal surfaces of md and mx molars in same vertical plane, NORMAL molar relationship in primary dentition

Mesial step (14%) = D surface of md 2nd molar is M to D surface of mx 2nd deciduous molar

Distal step (10%) = D surface of md 2nd molar is D to D surface of mx 2nd deciduous molar

Question 19

How does the shift in molar relationship from flush terminal plane to class I molar relationship happen? (3)

Answer 19

can occur in 3 ways (or combination)

1. early shift
2. late shift
3. differential jaw growth

Question 20

What is early shift?

Answer 20

if MANDIBULAR primate space is available during eruption of perm molars, lower perm molars move forward into class I relationship (upper primate space obliterated, stay same position)

Question 21

What is late shift?

Answer 21

uses leeway space = space difference between posterior primary teeth and the permanents which replace them

upper ~ 1.5mm per side

lower ~ 2.5mm per side

→ allows lower molars to move further forward than upper molars (& go into class I)

Question 22

What is differential jaw growth?

Answer 22

if md grows more forward than mx, it carries md teeth further forward relative to mx teeth

md usually grows more forward relative mx in transition from mixed dentition to early permanent dentition

Question 23

What permanent molar relations are likely to be caused by the different deciduous relations? (4)

Answer 23

distal step → class II

flush terminal → class I

mesial step → class I, possibly slight class III

Question 24

Name and define the 3 space management strategies for transition from primary to perm dentition? (3) Which one is proactive, reactive and retroactive? (3)

Answer 24

Space management = hold space before primary teeth are lost (proactive)

Space maintenance = maintain space after premature loss of primary tooth (reactive)

Space regaining = regaining space after loss of primary tooth once space has been used up - usually by mesial drift of buccal segments (retroactive)

Question 25

How can we do space management (proactive)? What appliance is used?

Answer 25

if molars are in class I relationship, leeway space can be used to resolve crowding

(upper~3mm, lower~5mm)

Lingual holding arch

(holds 1st molars back when they try to come forward)

Question 26

Outline the components of Lingual Holding arch (2) When is it contraindicated til? (1)

Answer 26

1. bands on 1st perm molar
2. the wire rests on lingual surfaces of anteriors

contraindicated until permanent incisors erupted (bcos permanent lower incisors erupt lingual to the deciduous then move forward - could interfere with eruption)

Question 27

What is shown in the image?

Answer 27

perm incisors crowding and 1st molar erupted

still have deciduous canine and 2 molars

leeway space used for space management to resolve crowding

Question 28

What can be used for space management (of leeway space) for upper teeth?

Answer 28

• lingual arch (similar design)
• trans-palatal arch (TPA) - doesnt rest on anteriors
• Nance appliance - rests on palate instead of anteriors

Question 29

Why should you be careful with space management?

Answer 29

if you use leeway space in lower arch but not upper, upper molars may still come forward and cause class II occlusion

(even if no crowding in upper, may still use lingual arch in upper)

Question 30

What can you do for premature loss of primary incisors (space maintenance)?

Answer 30

no treatment necessary

replacement would mainly be for aesthetic concerns (usually not the childs)

→ fixed lingual arch off deciduous 2nd molars (fixed denture)

Question 31

What can be done for the loss of primary canines? (2)

Answer 31

balancing extractions

and

lower lingual arch can prevent space loss caused by retraction of incisors (due to action of lower lip, usually blocked by canines)

Question 32

What are some appliances for premature loss of primary molars? (3)

Answer 32

1. lingual arch resting against incisor
2. band and loop appliance
3. distal shoe

Question 33

How does a lingual arch resting against incisors help premature loss of primary molars? When is it contraindicated? how long does it take?

Answer 33

if deciduous molar is lost, lingual arch resting against incisors holds perm 1st molar from moving forward into the space, allowing space for the premolars to erupt

CONTRAINDICATED in primary incisors

2 visit appt, lab needed

Question 34

How can a band and loop appliance be used? (single vs bilateral, what is an issue? how long does it take?)

Answer 34

generally used for single tooth (band around molar and loop than comes forward and rests against abutment) → stops it from moving forward and holds space

can be used bilaterally before eruption of permanent incisors

issue: can still cause loss of space once abutment tooth exfoliates

can be fabricated and placed chairside at same visit as exo

Question 35

How can a distal shoe be used for premature loss of primary molars?

Answer 35

not commonly used anymore

if primary 2nd molar is lost before eruption of 6, it will still drift mesially within alveolar bone

can’t put lingual arch or loop or band due to lack of 1st perm molar, distal shoe uses band around primary 1st molar (D) and a shoe which goes subgingival and rests against M surface of erupting 6

use to maintain space before eruption of 2nd perm molar

→ may cause occlusal problems as acts as cantilever

Question 36

How might restoring primary teeth be used for space maintenance?

Answer 36

mesial shift of 1st molar will occur if there is any space in dental arch, this includes space lost from interproximal caries, filling fallen out or badly broken down tooth

→ restoring deciduous molars is part of space maintenance

Question 37

Why should space maintenance be done early after extraction and not later on?

Answer 37

pointless, space already lost

Question 38

Why might space maintenance not be appropriate for all children?

Answer 38

the main cause of early loss of deciduous dentition is caries, appliance may increase risk of caries especially when it is needed for a long period of time

e.g. 7 year old loses primary molars early due to decay, still 3-4 years until pms erupt (11)

Question 39

How is crowding commonly experienced after early loss of deciduous teeth?

Answer 39

usually last tooth to erupt will experience crowding and be disaplced (either 5s - palatally or canines - buccally)

Question 40

SUMMARY

Answer 40

• early loss off deciduous teeth is usually result of extraction, trauma or failure to restore teeth
• can have effect arch symmetry and future space distribution of permanent teeth
• earlier the tooth is prematurely lost, more potential for crowding
• assymetric loss of primary canines have greatest effect on midline
• early loss of deciduous 2nd molars have greatest effect on space loss