Epidemiology:

• 0.2 – 0.8% primary teeth
• 1.5 – 3.5% permanent teeth ( male : female ratio 2:1)

The supernumerary may be described according to their form and their positions:

Form:

• Conical (peg shaped)
• Tuberculate
• Supplemental
• Odontome

Position:

• Mesiodens (in the midline)
• Distomolar (distal to the arch)
• Paramolar (lingual or buccal to the arch)

Primary Tooth Hypodontia:

• 0.1 – 0.9% Caucasian population, more common in the maxilla and equal between male:female
• 30 – 50% of cases of primary hypodontia will be followed by permanent dental anomalies

Permanent Tooth Hypodontia:

• Prevalence is between 3.5-6.5% (excluding wisdom teeth)
• Equal frequency Maxilla:Mandible
• Female: Male 4:1
• The type of tooth to be absent varies widely especially between racial groups

Severity Of Hypodontia:

• Mild <3 absent teeth
• Moderate 3-6 absent teeth
• Severe >6 absent teeth

Size

1. Macrodont

• Larger than normal sized tooth is described as a megadont or macrodont
• Megadont often affect maxillary permanent incisors and mandibular second premolars
• Prevalence in the UK is approx. 1.1% in the permanent dentition

2. Microdont

• Teeth which are smaller than normal
• More common in females
• Not common in the primary teeth, prevalence 0.2 – 0.5%
• Permanent teeth prevalence is 2.5% and generalised microdontia is 0.2%

Tooth Shape

Abnormalities in shape can originate during the morphodifferentiation stage of tooth development which leads to alteration in crown and root form.

Double teeth: Germination or fused teeth:

• Prevalence in the primary dentition 0.5 – 1.6%
• Less common in the permanent dentition 0.1 – 0.2%
• Male and females are equally affected with these dental anomalies

a) Concrescence:

• Fusion of two or more teeth by cementum

b) Germination:

• Occurs when one tooth bud attempt to split into two
• Tooth count is normal
• There is one main crown with a cleft within the cervical third of the crown

c) Fusion:

• Arises through union of two normally separated tooth germs
• Depending upon the stage of development of the teeth at the time of union, it may be either complete or incomplete.
• Two canals are usually present.
• The number of teeth in dentition is normally reduced by one unit.

Accessory Cusp:

a) Dens Invaginatus

• Dental anomalies which occur due to a result of invagination of the epithelium into the dental papilla during development. Clinically, this may present as deep cingulum pit especially seen on maxillary lateral incisors. Dens is more common in the permanent teeth and in females (2:1).

b) Dens Evaginatus

• This anomaly is more common in the premolars and presents as a projection arising from the occlusal surfaces in the central fissure.
• More common in the Asian population with a prevalence of 1 – 4%
• The projection consists of enamel, dentine and pulp.

c) Tauradontism

• Describes molar teeth in which the body of the tooth is enlarged vertically at the expense of the root
• Clinically teeth appear as normal and usually detected radiographically
• Frequency: 6 – 10% in permanent
• Aetiology: late invagination or failure of Hertwig’s root sheath, during the stage of root formation

d) Talon cusp

• The talon cusp is an exaggerated cingulum of the maxillary, usually permanent incisors

Disturbances in Eruption:

Eruption pattern of primary and permanent teeth can vary. Racial variation in eruption dates have been noted.

Premature Eruption:

Natal teeth are teeth that are present at birth and those that erupt in the first 30 days of birth are called Neonatal teeth. This most commonly affects lower incisors. Concerns related to these teeth include:

• Feeding difficulties
• May be mobile and therefore potential risk to airways

Delayed Eruption:

Delay in eruption can occur in both the primary and permanent teeth.

Local causes of delayed eruption include crowding, supernumeries and impaction e.g. ectopic first permanent molars. Dilaceration can also cause a delay or failure of teeth to erupt.

There are a number of systemic causes of delayed eruption including some syndromes that are commonly linked to delayed eruption- Down Syndrome and Turner Syndrome. In additional nutritional deficiencies, hypothyroidism and hypopituitarism have also been implicated.

Premature Exfoliation:

Early exfoliation of primary teeth is invariably associated with systemic conditions. Causes can be differentiated into:

• Periodontal disease e.g. leucocyte adhesion defect, papillon-Lefèvre syndrome
• Metabolic conditions e.g. hypophosphatasa
• Connective tissue disorder e.g. Ehlers-Danlos syndrome
• Neoplasia e.g. Langerhans cell histocytosis
• Self-inflicted trauma

Delayed Exfoliation:

Often caused by infraocclusion:

• An infraoccluding tooth lies below the occlusal plane as a result of ankylosis
• The primary tooth remains static while eruption of adjacent teeth continues
• May be bilateral or unilateral
• May affect both maxilla and mandible
• X 10 times more common in the primary dentition
• Usually develops during the early mixed dentition
• Prevalence 9% (Kurol, 1981) and may have a familial link
• Can cause a delay in exfoliation of the primary teeth

What Are The Causes of Infraocclusion?

• Ankylosis
• Other less common causes:
  • Disturbed local metabolism
  • Gaps in the periodontal membrane
  • Local mechanical trauma
  • Local Infection
  • Chemical or thermal irritation
  • Local failure of bone growth
  • Abnormal tongue pressure
  • Disturbance in interaction between normal resorption and hard tissue repair
  • Radiation

(Lewis Hua, BDJ 2019)

Consequences Of Infraocclusion:

• Delayed exfoliation
• Denuding of proximal root surface
• Increased difficulty of extraction
• Reduced alveolar bone support
• Progression of submergence
• Tipping of adjacent teeth
• Delayed eruption of successor
• Overeruption
• Malocclusion
• Tongue habits and open bite
• Damage to adjacent teeth
• Retained root fragments

(Teague et al 1999)

How does ankylosis occur?

Damage to Hertwigs epithelial root sheath leads to a break in continuity of the periodontal membrane, causing direct contact of cementum or dentine with bone.

Enamel Defects

Defective enamel may present as either hypoplasia, due to defective matrix production (quantitative defect) or hypomineralisation from imperfect mineralization of the matrix proteins (qualitative defect).

Hypoplastic enamel may appear as grooves or pitting in the enamel. Hypomineralisation may appear as opacities or mottling in the enamel.

Chronological Disturbances

Developmental defects can be acquired or inherited, localised to single tooth or more generalised. Systemic disturbances may affect ameloblast function resulting in abnormality in the secretion of enamel proteins, interrupted calcifications or maturation of the enamel, resulting in dental anomalies in the enamel or dentine.

Fluorosis

This may range from very mild white flecking to severe staining (mottling) or hypoplasia depending on the dosage and exposure of fluoride.

Molar Incisor Hypomineralisation (MIH)

Hypomineralisation of systemic origin of 1 to 4 first permanent molars (FPM) and frequently incisors.

Despite the definition, it is felt that Hypomineralisation affecting the second deciduous molars (Deciduous molar hypomineralisation) is an indicator that there is increased possibility of having hypomineralisation of the first permanent molars (MIH).

Clinical features:

• Prevalence 3.6%-25%
• Large, demarcated opacities, whitish-yellow or yellowish-brown in colour
• Maybe associated with post-eruptive breakdown (PEB) resulting in exposed dentine and sensitivity
• Incisors often have well demarcated opacities, but do not always exhibit PEB as there is less occlusal forces.

Aetiology:

Disturbance during the maturation phase of amelogenesis which is clinically visible as an enamel opacity.

Thought to occur between birth and 18 months.

Associated with the following:

• Asthma
• Pneumonia
• Otitis media
• Antibiotics
• Tonsillitis
• Dioxins in breast milk
• Hypoxia at birth

Treatment:

Patients will benefit from intensive prevention advice including the use of de-sensitising toothpaste and the use of fluoride varnish. If the long term prognosis of the first permanent molars are poor, extraction of these teeth may need to be considered at an ideal stage of development if asymptomatic or earlier.

Permanent molars:

• Fissure sealing – if tooth intact and no sensitivity
• Amalgam –non-adhesive, best avoided (Restriction of use in children under 15)
• Glass Ionomer Cement – interim restoration, poor wear resistance
• Composite – good aesthetics/superior wear resistance and adhesion
• Stainless Steel Crowns – if PEB (post-eruptive breakdown), cuspal involvement
• Cast gold/composite/ceramic onlays

Incisors:

• Microabrasion in shallow defects – Acid-pumice abrasion with 0.2% hydrofluoric acid
• ICON Resin Infiltrate– Lesions look white due to scattering of light at the subsurface of the demineralised enamel underlying remineralised enamel.
  • Etch to remove the outer layer of remineralised enamel.
  • Apply drying agent and then resin infiltrate on demineralised enamel.
• Composite Veneers
• Porcelain Veneers in late adolescence

Amelogensis imperfecta (AI)

AI describes a range of inherited enamel defect affecting both dentitions. Transmission may be autosomal dominant, autosomal recessive or sex-linked. There are numerous classifications of AI but it can be described as:

• Hypoplastic (Quantitative defect). There is generalised thin enamel which can be rough or smooth or pitted
• Hypomineralisation (Qualitative defect). The enamel is initially normal in form but softer. It is often discoloured (yellow/brown)
• Clinically AI is commonly described as hypoplastic, hypomaturation or hypocalcified.

HYPOPLASTIC FORM: REDUCTION IN THE QUANTITY OF THE ENAMEL MATRIX USUALLY WITH NORMAL MINERALISATION.	HYPOMATURATION FORM: DEFECT IN THE QUALITY OF MINERALISATION PROCESS WITH NORMAL QUANTITY OF MATRIX FORMATION.	HYPOCALCIFIED FORM: DEFECT IN THE QUALITY OF THE MINERALISATION PROCESS WITH NORMAL QUANTITY OF MATRIX FORMATION.
Clinical appearance:
Reduced thickness of enamel.	Normal thickness of enamel.	Normal thickness of enamel with loss of translucency.
Enamel is well mineralised and is therefore less prone to attrition than the other forms of of AI.	Enamel is hypomineralised and prone to post eruptive breakdown and attrition.	Enamel is very hypomineralised and often of a soft cheesy consistency. Prone to early rapid post eruptive breakdown and attrition.
The colour can vary from normal colour and translucency to a yellow to dark brown colour, depending on how thin the enamel is and the degree of shine through of the underlying dentine.	Colour may be affected by post-eruptive uptake of staining from the oral environment and the degree of post-eruptive breakdown. It can vary broadly from mottled opaque white to yellow/brown or red/brown discolouration.	Colour may be affected by post-eruptive uptake of staining from the oral environment and the degree of post-eruptive breakdown and exposure of underlying dentine. Teeth tend to be darker in colour than other types of AI.
Spacing between teeth as thinner enamel often reduces tooth size.
Rough, irregular, or pitted, with or without vertical ridges or grooves.
Radiographic appearance:
Enamel contrasts normally from dentine.	Enamel has similar radiodensity as dentine.	Enamel is less radiopaque than the dentine.

Management:

Management can be complex but the principles are:

• Intensive preventive advice will need to be provided.
• Composite resin can be used but bonding can be difficult depending on the nature and extent of the defect.
• Stainless Steel crowns/cast restorations can be use useful on posterior teeth to maintain vertical dimension of the occlusion and preserve further enamel loss.
• Advanced restorative work with porcelain can be considered in adolescence/adulthood.

Dental Anomalies In Dentine

Dentinogenesis Imperfecta (DI) Type I:

Seen in patients with osteogenesis imperfecta (OI) type 1. Discolouration of teeth, enamel chipping and extreme attrition of dentine are common. OI is typically associated with bone fragility and patients have a distinct blue sclera and may have other issues such as hearing loss.

Dentinogenesis Imperfecta Type II

• All teeth are affected in both the primary and permanent dentition
• Teeth have a distinct bluish or brownish colour
• Primary teeth can be more severely affected
• Enamel chips away easily causing the dentine to wear rapidly. Consequently, infections can readily arise from non-carious teeth
• Crowns appear more bulbous radiographically with the roots being short and thin.The pulp canal can be obliterated

Management of DI

Similarly to AI, there are multiple challenges

• Intensive prevention advice is essential.
• Primary molars can be restored with Stainless steel crowns.
• Permanent molars can have Stainless Steel crowns or be restored with cast coverage.
• Permanent incisors could be restored with direct or indirect composite veneers.

Dentine Dysplasia type I (radicular dentine dysplasia, rootless teeth)

Both dentitions are affected with the discolouration varying from bluish to brownish tinge.

Dentine Dysplasia type II (coronal dentine dysplasia)

• Disparity on effects upon the primary and permanent teeth.
• In the permanent teeth, the colour maybe normal but radiographically there is usually a thistle or flame shaped pulp chamber partly occluded by pulp stones.

Regional Odontodysplasia

Often described as ‘ghost teeth’, this is a rare condition characterised by abnormal development of both enamel and dentine localised one or several teeth. The aetiology is unknown.

Willmott N.S Bryan R.A, Duggal M.S (2008) Molar–Incisor-Hypomineralisation: a literature review. European Archives of Paediatric Dentistry 9:172-9

Paediatric Dentistry Text book 4th Edition by Welbury

M. Patel, S.T McDonnell, S. Iram and M.F.W-Y Chan (2013) Amelogenesis imperfect-lifelong management. Restorative management of the adult patient. British Dental Journal Volume 215

Kurol, J., 1981. Infraocclusion of primary molars: an epidemiologic and familial study. Community dentistry and oral epidemiology, 9(2), pp.94-102.

Hua, L., Thomas, M., Bhatia, S., Bowkett, A. and Merrett, S., 2019. To extract or not to extract? Management of infraoccluded second primary molars without successors. British dental journal, 227(2), pp.93-98.

Teague, A.M., Barton, P. and Parry, W.J., 1999. Management of the submerged deciduous tooth: 1. Aetiology, diagnosis and potential consequences. Dental update, 26(7), pp.292-296.