Developmental abnormalities Flashcards
List developmental defects affecting tooth number
Hypodontia
Oligodontia
Anodontia
Supernumerary teeth
Define: hypodontia
Congenital absence of 1-6 teeth excluding the third molars
Which teeth are most commonly missing due to hypodontia?
Upper second premolars
Upper lateral incisors
Lower second premolars
Lower central incisors
Define: oligodontia
More than 6 congenitally missing teeth
Define: Anodontia
Complete congenital absence of one or both dentitions
Define: Supernumerary teeth
Addition to the normal series of tooth
What would multiple supernumerary teeth indicate?
Disease or syndrome e.g. CLP, Gardner syndrome or Ehlers-Danlos
What is the most common supernumerary tooth?
Mesiodens
List the types of supernumerary teeth
Supplemental
Conical
Tuberculate
Odontome
Define: supplemental tooth
Extra tooth of normal form occurring at the end of a series (most commonly lateral incisor)
Where do conical supernumerary teeth occur
Anterior maxilla in the midline (mesiodens)
When will a conical supernumerary remain unerupted
If it is inverted
Where do tuberculate supernumary teeth occur
In the anterior maxilla on the palatal aspect of central incisors
What is an odontome?
Benign tumour linked to tooth development
What are the types of odontomes
Complex
Compound
Define: Complex odontome
Calcified structure with no resemblence to the anatomical arrangement of dental tissues
Define’ Compound odontome
Calcified structure made up of rudimentary teeth
What is thought to be the developmental issue causing hypodontia
Defect in dental epithelial growth
What stage of development does anodontia occur?
Dental lamina formation stage
What is the developmental issue causing supernumerary teeth
Disturbance during initiation and proliferation stages
What are the theories of supernumerary teeth
- Dichotomy (division) of tooth buds
- Organised hyperactivity of the dental lamina
Define: peg laterals
Small tapered maxillary lateral incisor
What stage is important for peg lat formation
Morphodifferentiation stage
Define: microdontia
Teeth smaller than nrmal
Define: macrodontia
Teeth larger than usual
What stage is implicated in macrodontia
Disturbance in initiation and proliferation stages
Morphodifferentiation stages
Define: Taurodontism
Multirooted teeth with a long body and pulp chamber and short roots. The Pulp chambers are elongated and the pulp is apically displaced
Which teeth are often implicated in Taurodontism
Mandibular molars
Hypothesised cause of taurdontism
Disturbance in growth of hertwig’s epithelial root sheath or morphodifferentiation stage
Define: dens envaginates
Formation of an accessory cusp whose morphology is described as tubercle, elevation, protruberance, extrusion or bulging.
What makes up the dens envaginates
Enamel covering a dentine core and pulp tissue
Which teeth are often implicated in dens envaginates
Anterior teeth (lingual or palatal aspect) Occlusal surface of premoalrs
What stage is implicated in dens envaginates formation
Organic matrix apposition and primary mineralisation stage
Define: dens invaginatus (Dens in dente)
Infolding of enamel into dentine
Where is dens in dentine more common
Maxillary lateral incisors, central incisors, canines then molars
Stage implicated in dens in dente
Morphodifferentiation
Define: dilaceration
Deviation or bend in the linear relationship of the crown relative to the root
Which type of dilaceration is more common
Root dilaceration > crown dilaceration
Where do root dilacerations occur
Posterior region of permanent dentition
Where do crown dilacerations occur
Permanent maxillary and mandibular teeth
Cause of dilaceration
Trauma to primary tooth causing damage to permanent predecessor
Define: Fusion
Two normally seperate adjacent tooth germs fuse into one large tooth, sharing the same enamel and dentine
When does complete fusion occur
If fusion occurs before calcification stage
When does incomplete fusion occur
If fusion occurs later on (after calcification stage)
What stage is implicated in fusion
Initiation and proliferation stages
Define concresence
Cemental union of adjacent teeth without confluence of dentine, they have separate pulp chambers and root canals
Which teeth are often implicated in concresence
Posterior maxillary teeth, often 7s
What is the cause of developmental concresence
Close proximity of developing roots of adjacent teeth
Define germination
Two teeth from the same follicle attempt to divide, but division is incomplete thus forming an abnormally large tooth
Which teeth are often affected by germination
Anterior teeth
What are enamel pearls
Localised formation of enamel on the root of a tooth
What is the cause of enamel pearls
Continued formation of Hertwig’s epithelial root sheath
Define amelogenesis imperfecta
Group of inherited enamel disorders leading to altered enamel morphology, alongisde normal dentine and pulp formation
What are the types of AI
Hypoplastic
Hypocalcified/hypomineralised
Hypomatured
Define hypoplastic enamel
Reduction in the amount of enamel matrix protein secretion thus causing thin enamel, surface pitting or vertical grooves
Define hypomineralised enamel
Normal enamel matrix present but the enamel is deficiently mineralised causing soft enamel
Define hypomatured enamel
Normal enamel matrix present but the enamel lacks hardness forming opaque, discoloured enamel that easily fractures
Define dentinogenesis imperfecta
Genetic disturbance of dentine formation leading to altered morphology of dentine
Features of dentiogenesis imperfecta
Brown, opalescent discolouration and fracture of overlying enamel
Rapid wear/attrition of teeth
Progressive pulp obliteration
What is regional odontodysplasia
Hypoplastic and hypocalcified enamel and dentine
Features of regional odontodysplasia
Small, brown teeth with large pulp chambers and root canals
Define: molar-incisor hypomineralisation
Developmental defect resulting in 1-4 hypomineralised permanent first molars, frequently associated with similarly affected permanent incisors
What is the prevalence of MIH
2.8-40%
What are the stages of amelogenesis
Secretory
Transition
Maturation
Which stage of enamel formation is associated with enamel hypoplasia
Secretory
Which stages of enamel formation are associated with hypomineralised/hypomatured enamel
Transition
Maturation
Aetiology of MIH
Unknown
Possibly systemic in origin
What age is the critical period for enamel defects in incisors and 6s ? WHY?
1yo - as it coincides with early maturation phase
Proposed etiological factors of MIH
- Maternal illness, diabetes, medicines or pyrexia
- Complicated delivery, c section, hypoxia, premature
- ENT infections, respiratory problems, antibiotics, chickenpox/measles/mumps
Stages of management of MIH
Early diagnosis Risk identification Remineralisation & desensitisation Prevent caries + PEB Restorative care/extractions Maintenance
Presentation of MIH
- 1-4 permanent molars (or incisors) with signs of hypomineralised enamel e.g. opacities
- Post eruptive enamel breakdown
- Atypical caries pattern
What are the consequences of MIH
- Caries
- PEB
- hypersensitivity and difficulty obtaining LA
- Frequent restorative failure
What are the features of the hypomineralised lesions
- Clear demarcated opacities which -
1 - Vary in colour - white, cream, yellow or brown
2- Vary in size
What is post-eruptive enamel breakdown (PEB)
Severely affected enamel subject to masticatory forces results in rapid breakdown, exposure of dentine and rapid caries development soon after eruption
What type of prevention is required in MIH ptsq
ENHANCED PREVENTION - includes high dose fluoride, frequent recalls, dietary advice
What remineralisation products can be used for MIH
- CPP-ACP
- Enamelon
- Novamin
How does CPP-ACP work
Incr bioavailability of calcium and phosphate within saliva and prevents spontaneous precipitation, thus encouraging remineralisation deep into lesions and desensitisation
What are the two options to prepare MIH affected teeth for restorative tx
- Remove all defective enamel until sound surface reached
- Remove porous enamel only until resistance to the bur is felt
Disadvantages of a minimally invasive approach in MIH
- Since not all the defective enamel is removed, the tooth is still susceptible to breakdown thus restorative failure
What does restorative tx for MIH depend on?
- Cooperation of patient
- Longevity required
- Extent of PEB (cuspal involvement, restorable?)
- Orthodontic needs
Methods for restoring MIH 6s
Direct - RMGIC as temporary, Composite
Indirect - Crowns or cast onlays
Indications for planned loss of 6s
- Poor long term prognosis
- Underlying malocclusion
- Extent and location of crowding
- No missing teeth (8s present)
- Correct timing
- Which 6s are affected
When is the ideal timing for extraction of 6s ?
DPT showing calcification of the bifurcation of 7s
Why is timing important in planned loss of 6s
Provides good prognosis for the 7s replacing the position of the 6s
Are balancing / compensating extractions done in MIH
- balancing to prevent asymmetry
- Compensating is not recommended
When is timing of planned loss of 6s most important?
for MANDIBULAR 6s
Why is timing of planned loss of 6s not a big concern in the maxilla
The 7 usually takes up a good occlusal position anyway
What is the most favourable age for planned loss of 6s?
8-10
After laterals erupt but before 7s and/or 5s
What happens if planned loss of 6s occurs too early
Loss of space due to 5 drifting distally, retroclination of labial segments and incr overbite
What happens if planned loss of 6s occurs too late
7s are well formed and will not erupt into the space of the 6
Risk of mesial tilt or rotation of 7s
Risk of 5s drifting distally
Explain MIH and LA issues
Hypomineralised enamel is a poor insulator therefore the pulp is not well protected and becomes hypersensitive and difficult to numb up
Options to treat MIH incisors
Bleaching Resin infiltration Microabrasion Composite restorations/veneers Porcelain veneers
Timing of treatment of MIH incisors
Aesthetic tx should be postponed until older as immature teeth have large and sensitive pulps
What is resin infiltration
Hcl as an etchant and low viscosity resin to penetrate demineralised enamel
What is microabrasion
Removal of a small layer of superficial enamel using abrasion and erosion with 18% hcl and pumice
Age and bleaching
GDC states products containing 0.1-6% hydrogen peroxide cannot be used on under 18s unless wholly intended to prevent/treat disease
Differential diagnosis of MIH
Fluorosis
AI
WSL
Traumatic hypomineralisation
