Dra. Mariana Costa

Dentist

Hypomineralisation

Molar Incisor

HPA Magazine 19

Tooth enamel (the outermost layer of the tooth) is made up of approximately 96% minerals, primarily calcium and phosphorous, that bond together to form hard crystallites. During their development, these cells are extremely sensitive to systemic and local changes, resulting in various types of anomalies.
These anomalies can occur at different stages of amelogenesis (enamel formation process) and can be classified into hypoplasia and hypomineralization, which in turn are subdivided; the hypoplasias in imperfect amelogenesis and Turner's hypoplasia, molar incisor hypomineralizations and fluorosis.

Among these changes, Molar Incisor Hypomineralization (MIH) stands out as it is quite challenging for the Dentist. This dental anomaly described as a qualitative defect of systemic origin, occurs during the maturation phase of the enamel, resulting in insufficient mineralization characterized by an alteration in its translucency, affecting one or even the four first molars. It can also be associated with changes in the incisors. Its causes are still not fully understood.
Tooth enamel is thus more fragile and porous, which makes it more likely to fracture and more likely to develop tooth caries. Therefore, an early diagnosis is essential, since the patient's quality of life depends on the treatment.
There is a range of treatments for this condition, and the treatment of choice must be defined according to the degree, location of the MIH and the patient. The decision is made by the Dentist after a careful evaluation.

CAUSES
The causes of MIH are multifactorial. 
The legions observed are the result of a variety of factors that act on a systemic level, including prenatal factors.
Such as smoking and diseases during pregnancy, perinatal (neonatal complications, premature birth and low body weight).
Post-natal (malnutrition and respiratory diseases), diseases in the first three years of life. 
Such as otitis, tonsillitis, high fever and gastrointestinal diseases, due medication during the period of odontogenesis (tooth formation period), child malnutrition or even environmental exposure in individuals with a genetic predisposition.
It is also known that children who present this type of alteration in deciduous (baby) teeth are more likely to develop MIH in the permanent teeth.

CLINICAL CHARACTERISTICS
Clinically, the appearance of the affected teeth appears in the form of opacities and are asymmetric, mainly affecting the occlusal 2/3 of the crown and the buccal surface of the tooth. 
The colour of the enamel is directly associated with the porosity of the tooth and can vary from white/opaque, yellow or yellow-brown, where the darker lesions have a higher degree of porosity.
Consequently, the more porous enamel is more fragile and can fracture easily when chewing, it has a greater predisposition to caries.
It is submitted to reinterventions due to difficulty in the adhesion of restorative materials, dental hypersensitivity and aesthetic alterations. 
HOW IS MIH CLASSIFIED?
Despite the lack of a universal classification, this alteration can usually be classified as mild, moderate or severe. It is considered to be mild when the tooth is discoloured, but enamel fragmentation or discomfort is not observed. 
The most severe degree also presents discolorations, but the enamel also presents fragmentation, spontaneous and persistent hypersensitivity and caries. 

WHAT TYPE OF TREATMENTS ARE AVAILABLE?
Currently, treatment possibilities are diverse and depend on a number of factors; the severity of the lesion, stage of the tooth eruption, socio-economic background of the child/parents and their expectations, age and patient cooperation, desired aesthetic results, material resistance and occlusal balance. These possibilities can range from prevention to restoration or even extraction of the tooth.
Preventive measures in the early stages when only demarcated and hypersensitivity-free opacities are observed and as a first-line treatment, it is necessary to instruct and explain oral hygiene habits to reduce the risk of caries and sensitivity, reinforcing the importance of brushing with a fluoride toothp aste with a fluoride concentration of at least 1000 ppm associated with a non-cariogenic diet.
Fissure sealants are recommended for intact posterior teeth that have not suffered any type of fracture. This is a valid option, as it aims to prevent caries. 
In teeth that sometimes present spontaneous tooth sensitivity, the application of a fluoride varnish can be an effective measure in controlling sensitivity.
Sometimes, when a tooth does not have sufficient conditions to support resin restorations, steel crowns are an option to help control sensitivity and prevent tooth loss. In more critical cases, after evaluating several factors, such as the degree of destruction, the patient’s age, number of teeth involved, the most appropriate solution is to extract the tooth. 
However, the possibility of future complications related to orthodontic treatment must always be taken into account, therefore a prior appointment with the Orthodontist is necessary.
When this hypomineralization affects anterior teeth, it is necessary to assess the degree of aesthetic involvement/compromise and decide on the best approach. 
Currently, an ICON resin infiltration has been shown to be a good treatment option for superficial enamel lesions.It is important to evaluate each child in order to choose the best technique to be implemented and to advise periodic check-ups with the Dentist.

CONCLUSION
During teeth eruption, the hypomineralized surface is very susceptible to caries and erosion, and therefore early diagnosis and explain to parents that molar incisor hypomineralization is important, so that correct measures of oral hygiene can be implemented as well as a diet consisting of non-cariogenic food to permit the remineralization of the dental surfaces.
Although cases of MIH have increased in recent years, its causes are still to be clarified as is the protocol is to be followed. 
It is the Dentist who must define the treatment after a careful examination and evaluation of the various factors that may impair the choice and consequently the success of treatment.
It is known that children with MIH should be considered patients at high risk of developing caries and may sometimes exhibit problems of behaviour,  related to fear and anxiety of going to the dentist, due to dental treatments, since in these cases, local anaesthesia does not provide a minimally adequate blockade of the nervous structures and subsequently results in pain. 
It is sometimes necessary to resort to conscious sedation as an adjuvant in the treatment.
All children should be monitored regularly through dental check-ups with the Dentist. 
However, patients who have a problem with MIH, monitoring control and check-ups is more demanding.  Strick oral hygiene measures must be implemented to achieve the child’s collaboration and a greater control of this pathology.