MIH Flashcards
Which cells form enamel?
ameloblasts
what is the stimulus that triggers ameloblasts to form enamel ?
dentine deposition
what happens when ameloblasts are triggered?
they secrete matrix proteins and then they become calcified to about 20% (initial calcification)
what function change do ameloblasts go through after the matrix proteins secretion phase?
they secrete enzymes which remove organic component and allows full mineralisation to 99% (maturation stage)
How does removing the organic content allow full mineralisation?
- the crystals are trying to expand and the organic component is takin gum loads if room and preventing the expansion (Maturation stage) = 99% mineralisation
which three stages do we see problems occurring ?
- secretion of matrix proteins
- calcification stage
- maturation stage
what happens when you have a disruption during the laying down of the enamel matrix
HYPOPLASTIC DEFECT due to ….
- physical disruption
- less enamel matrix
- matrix will be mineralised normally but we will have less of it
- reduced bulk or thickness of enamel
- enamel never formed
what happens if the problem occurs in early initial calcification stage or maturation stage?
HYPO MINERALISATION due to…
- disturbance of enamel formation therefore reduced mineral content
- less mineral in enamel therefore less calcification
- AKA hypocalcifiaction or hypo maturation
how can enamel defects be classified?
systemic or local
List the different ways in which we can get local enamel defects.
- trauma
- infection
list the different ways which we can get systemic enamel defects.
- environmental
- genetic = amelogenic imperfecta
what can environmental defects be further classified into?
- CHRONOLOGICAL = this defect has occurred at a very specific point in time as that enamel forms therefore specific teeth are affected. eg. MIH
- GENERALISED = the insult has been there for a longer amount of time eg. fluorosis
how can we describe enamel defects? (3)
- DEMARCATED = distinct, clear boundary, yellow, white or brown
- DIFFUSE = no clear boundary; lines patches
- HYPOPLASTIC = loss of enamel, pits and grooves
Give an eg of demarcated defects?
MIH
give an eg of diffuse defects?
fluorosis
Give eg of hypoplastic defects?
localised legions
give an eg of a condition which have all 3 defects ?
ameleogensis imperfecta
define MIH?
hypo mineralisation of systemic origin of one or more first permanent molars as well as affected incisors
what 2 things are we looking for when diagnosing MIH?
demarcation
first permanent molars
what are some other terms for MIH?
- molar hypomineralisation (MH)
- incisor hypominerlisation (IH)
- deciduous molar hypomineralisation (DMH) (ppl use this term as second primary molars can be affected)
list some histological and biochemical analysis of MIH
- abnormal enamel either full thickness or inner enamel only
- discolouration/ breakdown associated with porosity = MOST porous
- brownish/ yellow - LESS porous
- carbon concentration higher in affected enamel
why Is it important to identify hypo mineralised molars ? (5)
- these teeth go thru POST ERUPTIVE BREAK DOWN
- SENSITIVE
- softer so more susceptible to CARIES
- DECAY FASTER
- DIFICULT TO RESTORE
Prevalence of MIH?
5-25% in uk
what disruption may be the cause of MIH?
ameloblast disruption
how do we treat?
- start with molars
- what is the long term prognosis
how do we judge long term prognosis
what orthodontic considerations do we need to think about when extracting MIH teeth?
why is timing important when extracting MIH teeth?
- if we extract at the right time and right age = gives us best chance of the second permanent molars moving forward in to that space
- lower arch = if we take 6 out when child is aged 8-9 = give us best chance of 7 moving into that space
- upper arch = timing less critical, space closure likely if extracted before 11/12 yrs
what is a compensating extraction?
-when we need to extract a lower 6
- upper 6 will over erupt
- even if upper 6 has a good prognosis we would still extract that tooth
THIS DOESNT WORK THE OTHER WAY ROUND (as lower 6’s don’t overerupt)
what happens if we decide that these teeth can be restored or maintained?
when do we use tooth mouse and what are the benefits?
- use for sensitivity
- used at home
- pleasant for children
when do we use fissure sealant ?
- if we feel enamel is nicely intact and we don’t see caries in BWs
- no sensitivity
when do we use plastic fillings ? how do we do it ?
- when we need to restore
- remove caries
- remove defective enamel (obvs not the dentine)
- therefore we get shallow cavities and need to be particular when choosing restorative material
why would we not use amalgam?
when do we use GIC?
- temp measure
what is the best restorative material for MIH?
composite
indications and contraindiactions for composite ?
when do we use stainless steel crowns ?
- good at addressing sensitivity
- very extensive defects
what are the disadvantages of stainless steel crowns ?
(gingival quality is poor due to poorly adapted margins of MIH)
what are the different ways in which we can restore incisors ?
- micro abrasion
- bleaching
- resin infiltration
- COMPOSITE VENEERS (best)
- porcelain veneers (contraindicated in children)
pros and cons of microabrasion?
- only used for subsurface defects but we know MIH is full thickness of enamel or in the inner layer of enamel
- very easy to do
- easy for pt and parents
- very conservative
what is con of bleaching ?
- lightens whole tooth not just defects
when do we use resin infiltrations ?
for white defects
why is it better for child to grow and then get composite veneers?
- when tooth erupts fully you will see the margin of the veneer showing through
