Space Maintenance in transition from primary to permanent dentition Flashcards
The two ways of managing early loss of deciduous teeth is by balancing or compensating extraction. Define both.
Balancing extraction = extraction of contralateral tooth (usually to preserve midline)
Compensating extraction = extraction of opposing tooth (usually to preserve occlusal relationships
Which deciduous teeth should you most/least worry about the early loss of?
(incisors, upper canine, 2nd molars)
When is compensation indicated?
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
What does the OPG show?
over-retained canine which has caused shift in midline
When does crown formation of permanent 1st molars happen and what does that make them susceptible to?
timing around birth making susceptible to hypomineralisation/hypoplasia (10-30% prevalence) → makes them more suspectible to caries
What can be done for a 1st perm molar with poor prognosis?
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
When should exo of 1st perm molar with poor prognosis be done?
upper: not as time critical, age 8-10 generally ok
lower: ideally immediately after calcification of bifurcation of lower 2nd molar (radiographically detected)
What might you need to do for opposing molar after exo of 1st perm molar?
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)
Why shouldn’t exo of poor prognosis 1st perm molars be delayed past appropriate time?
difficult to close space after exo as lower 7s are quite resistant to moving after roots are fully formed
Why shouldn’t exo of poor prognosis 1st perm molars be delayed past appropriate time?
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)
About 2% of children are missing congenitally missing 2nd premolars. What is a problem encountered by this?
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)
Describe how teeth transition from primary to permanent dentition and how space is used.
- spacing is normal and desirable in anterior primary teeth
- primate (anthropoid spaces) are found in mx and md arches
What kind of spacing is normal in primary teeth? (2)
- 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
What is incisor liability? (1) And how much is it (2), why is it greater in upper arch? (1)
difference between combined widths of permanent and decidous incisors
~ 7.5mm upper, 6mm lower
primate space included in uppers but not lowers
How is incisor liability overcome in the maxilla? (5)
- anterior interdental spaces
- primate space
- labial eruption of incisors increasing arch length and circumference
- increased inter-canine width
- reduced inter-incisal angle (perms more proclined than deciduous, making more space)
How is incisor liability overcome in the mandible?
- anterior interdental spaces
- increased inter-canine width
- reduced inter-incisal angle
What difference between upper and lower incisor liability is shown in the image?
upper perms erupt more labially than their predecessors whereas lowers dont have as signficant of a difference
How can/can’t you describe occlusion in primary posteriors? (1, 3)
DO NOT use Angle’s classification in deciduous molars, use:
- flush terminal plane
- mesial step
- distal step
Define flush terminal plane, mesial step and distal step. State which is normal and give approximate incidence of each. (3, 1, 3)
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
How does the shift in molar relationship from flush terminal plane to class I molar relationship happen? (3)
can occur in 3 ways (or combination)
- early shift
- late shift
- differential jaw growth
What is early shift?
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)
What is late shift?
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)
What is differential jaw growth?
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
What permanent molar relations are likely to be caused by the different deciduous relations? (4)
distal step → class II
flush terminal → class I
mesial step → class I, possibly slight class III
Name and define the 3 space management strategies for transition from primary to perm dentition? (3) Which one is proactive, reactive and retroactive? (3)
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)
How can we do space management (proactive)? What appliance is used?
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)
Outline the components of Lingual Holding arch (2) When is it contraindicated til? (1)
- bands on 1st perm molar
- 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)
What is shown in the image?
perm incisors crowding and 1st molar erupted
still have deciduous canine and 2 molars
leeway space used for space management to resolve crowding
What can be used for space management (of leeway space) for upper teeth?
- lingual arch (similar design)
- trans-palatal arch (TPA) - doesnt rest on anteriors
- Nance appliance - rests on palate instead of anteriors
Why should you be careful with space management?
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)
What can you do for premature loss of primary incisors (space maintenance)?
no treatment necessary
replacement would mainly be for aesthetic concerns (usually not the childs)
→ fixed lingual arch off deciduous 2nd molars (fixed denture)
What can be done for the loss of primary canines? (2)
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)
What are some appliances for premature loss of primary molars? (3)
- lingual arch resting against incisor
- band and loop appliance
- distal shoe
How does a lingual arch resting against incisors help premature loss of primary molars? When is it contraindicated? how long does it take?
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
How can a band and loop appliance be used? (single vs bilateral, what is an issue? how long does it take?)
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
How can a distal shoe be used for premature loss of primary molars?
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
How might restoring primary teeth be used for space maintenance?
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
Why should space maintenance be done early after extraction and not later on?
pointless, space already lost
Why might space maintenance not be appropriate for all children?
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)
How is crowding commonly experienced after early loss of deciduous teeth?
usually last tooth to erupt will experience crowding and be disaplced (either 5s - palatally or canines - buccally)
SUMMARY
- 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
