WHAT CAUSES ENAMEL DEFECTS? TYPES, SYMPTOMS, TREATMENTS, AND MORE

The dental enamel is the outermost layer covering the crown surface of the tooth. It is the hardest substance in the human body, owing to the presence of more than 96% minerals in its composition. During the development of the tooth, the enamel layer is laid down by specialized cells known as ameloblasts. This hardest layer is known to protect underlying tissues-dentin and pulp-from decay.

The process of laying down the enamel is influenced by various genetic and acquired factors. During tooth development, any abnormalities observed during enamel formation can lead to permanent enamel defects. Enamel defects are common in children and effect both primary and permanent dentitions. 

The enamel defects cause structural changes on the tooth surface, increasing the risk of tooth sensitivity and decay. Moreover, the presence of defects in the teeth can impact aesthetics, potentially lowering the individual’s self-esteem and escalating the financial burden required for restoring the teeth. 

In this article, we discuss the various types of enamel defects, their causes, symptoms, diagnosis, and treatment.

Types of Enamel Defects

In general, enamel formation can be divided into an initial stage that involves the production of matrix proteins, such as amelogenin, ameloblastin, and enamelin, which aid in the deposition of the enamel matrix. This is followed by later stages that encompass the mineralization and maturation of the laid-down enamel matrix. Disturbances reported in different stages of enamel production can cause defects in the enamel, which can be expressed in two types: Enamel hypoplasia and Enamel hypomineralization (or enamel hypocalcification)

• Enamel hypoplasia: Enamel hypoplasia causes a reduction in the quantity of enamel tissue due to disturbances during the formation of the enamel matrix. Clinically, hypoplastic enamel may exhibit white spots, grooves, and a pitted appearance on the surface. Additionally, some tooth surfaces may display yellow or brownish discoloration. Moreover, a thin layer of enamel or its complete absence may be observed. This defect can occur in both primary and permanent dentition.
• Enamel Hypomineralization: Hypomineralization (also known as hypocalcification) leads to a reduction in the deposition of minerals in the enamel matrix due to disturbances in the mineralization or maturation phase of enamel formation. This defect makes the enamel soft and porous; however, the thickness of the enamel remains normal. Clinically, teeth with altered translucency and diffuse or well-defined opacities (cloudiness) can be observed. Also, the tooth surface may appear creamy white, yellow, or discolored.

Causes of Enamel Defects

Enamel defects are caused by several factors, including genetic and acquired conditions (both local and systemic). As enamel lacks the ability to regenerate, these defects are usually considered to be the result of insults suffered by the tooth during the development of enamel in both primary and permanent dentition. The details of the causative factors are given below:

A. Genetic conditions: Enamel defects due to genetic conditions may involve only dental enamel or may be part of a generalized systemic syndrome. 

i. Amelogenesis imperfecta is a genetic disorder that influences the development of tooth enamel. This disorder impacts the shape and appearance of almost all teeth in both primary and permanent dentition. It is inherited as an X-linked, autosomal dominant, or autosomal recessive trait and is mainly caused by variation or mutation in specific genes (e.g., AMEL, ENAM, FAM83H, WDR72, KLK4, and MMP20). According to the National Organization for Rare Diseases, it is reported in 1 of 14,000 to 1 of 16,000 children in the US. 

Clinically, amelogenesis imperfecta may present as both enamel hypoplasia and hypomineralization. It is divided into 4 main types and 20 subtypes. 

• Type I: Hypoplastic - Small to normal crowns with the presence of off-white to yellow-brown surface discoloration. Enamel thickness can be thin or normal, and upper and lower teeth do not meet, resulting in an open bite.
• Type II: Hypomaturation - Enamel with normal thickness and creamy white to yellow-brown discoloration on the surface. An open bite is evident, and affected teeth tend to chip easily.
• Type III: Hypocalcified - Teeth may be tender and have creamy white to yellow-brown rough enamel surface. The presence of mineralized hard material or calculi may be evident on tooth surfaces.
• Type IV: Hypomaturation/hypoplasia - Teeth are small with thin enamel, and white to yellow-brown discoloration along with pits is evident on teeth surfaces.

Signs and symptoms of amelogenesis imperfecta

• Teeth with defective or missing tooth enamel
• Cracked/fragile tooth 
• Increased early tooth decay or tooth loss
• Increased tooth sensitivity to anything hot or cold due to exposed inner (dentin) layer
• Increased tooth wear
• Discolored or spaced teeth 
• Increased risk of tartar formation, resulting in periodontal diseases (a condition involving tooth-supporting tissues) 

ii. Among genetic conditions, enamel defects can also be a part of several systemic syndromes. These include:

• Usher syndrome (a condition that involves hearing loss, retinitis pigmentosa, and enamel hypoplasia)
• Seckel syndrome (a condition that involves cognitive delay, small head, and enamel hypoplasia)
• Ellis Van Creveld syndrome (a condition that involves skeletal and cardiac defects along with enamel defects)
• Treacher-Collins syndrome (a condition that involves deformities of the ears, eyes, cheekbones, and chin alongside enamel hypoplasia)
• Velocardiofacial syndrome (a condition that involves deformities of the heart, nervous system, and endocrine system, cleft palate, rheumatoid arthritis, and enamel hypoplasia)
• Heimler syndrome (a condition that involves hearing loss, amelogenesis imperfecta, nail abnormalities, and retinal pigmentation)

B. Acquired conditions: Several systemic and local acquired conditions occurring during prenatal, perinatal, or postnatal stages of development can disrupt the normal growth of enamel, leading to enamel defects. These conditions may affect either deciduous or permanent teeth and can involve a single tooth instead of the entire set of teeth.

1. Prenatal conditions: Prenatal factors result in enamel defects in portions of the enamel formed before birth. Research indicates a higher risk of enamel defects in children who experienced intrauterine malnutrition, inadequate nutrition during fetal development, or those affected by the rhesus (Rh) incompatibility factor. Additionally, conditions such as Zika virus infection, congenital rubella infection, vitamin D deficiency, low calcium levels, increased maternal weight gain, urinary tract infections, gestational diabetes, smoking during pregnancy, bleeding, maternal psychological stress, hypertension, excessive exposure to ultrasonic scans during the last trimester, and maternal consumption of drugs such as Tylenol, antibiotics, antiepileptic drugs, or alcohol during pregnancy are associated with enamel defects.
2. Perinatal conditions: Perinatal or neonatal health factors can lead to enamel defects in portions of the enamel formed at birth or during early infancy. Factors associated with a higher prevalence of enamel defects include delivery complications such as non-progressive labor, umbilical cord issues, abnormal fetal heart rate, placenta previa, preterm birth, and low birth weight. Additionally, infants subjected to tracheal intubation (insertion of a tube into the windpipe) or prolonged mechanical ventilation are at an increased risk of enamel defects. Furthermore, deficiencies in vitamins D and A, low calcium levels, infections such as syphilis, or infections caused by cytomegalovirus (CMV) also elevate the risk of enamel defects.
3. Postnatal conditions: Postnatal conditions such as medical conditions, trauma, or severe diseases can cause enamel defects between the ages of 0 and 3 years. Examples of postnatal conditions include vitamin D deficiencies, low calcium levels, presence of chicken pox, high fever, ear infections, renal disorders, thyroid dysfunction, intestinal infections, celiac disease, vomiting, diarrhea, cerebral palsy, children on antiviral therapy, or specific antibiotics (e.g., Tetracyclines). Enamel defects are also prevalent in children undergoing anticancer therapy or radiotherapy. Moreover, the presence of several respiratory distress syndromes, malnutrition, cleft palate, traumatic injuries to the teeth, or periapical infections (infections around the tooth root), and long-term exposure to lead or excess fluoride intake (>1.5 parts per million) can increase the risk of enamel defects. Research suggests that prolonged breastfeeding (>8 months) without solid supplementation also increases the risk of enamel defects.

Turner’s tooth: Turner’s tooth is a localized type of hypoplastic defect that involves a single permanent tooth. It is mainly caused by the presence of local infection or trauma. For instance, if a primary tooth is severely decayed or traumatized and remains untreated for long, infection around the tooth root may impact the formation of the enamel on the developing permanent tooth.

Clinically, white or yellow discoloration may be seen on the affected tooth surface, affecting the aesthetics. Moreover, this condition tends to increase the risk of tooth sensitivity and decay.

Signs and Symptoms of Enamel Defects

Here are some of the signs and symptoms of enamel defects:

• Discoloration (white, yellow, or brown) on the tooth surface.
• Pits or grooves (depressions) on the enamel surface.
• Irregularly shaped teeth with surface roughness.
• Increased sensitivity to cold, hot, and acidic food and drinks.
• Increased risk of decay and tooth wear due to compromised enamel quality, which serves as a protective barrier.

Diagnosis of Enamel Defects

• In a dental clinic, the dentist will examine the teeth under direct operatory light after cleaning the surfaces with dry dental gauze.
• All tooth surfaces will be evaluated to identify any changes in color, translucency (opacity), and surface defects.
• The dentist may recommend radiographs to evaluate the thickness and degree of mineralization (quantity of mineral content) of enamel. Moreover, radiographs will also aid in identifying other defects, if any.
• The dentist will thoroughly assess the family history of enamel defects, any history of trauma, infections, irradiation, fluoride intake, chemical toxicity, exposure to antineoplastic agents, or antibiotics such as tetracyclines to identify the root cause of enamel defects.
• The dentist may also recommend necessary laboratory tests to confirm the diagnosis.

Management of Teeth Affected by Enamel Defects

Early detection of enamel defects and implementation of preventive care are essential in the early management of enamel defects. According to the American Academy of Pediatric Dentists, the first oral examination of a child's mouth can be performed at 12 months of age.

Here are some ways to manage enamel defects:

• Topical fluoride therapy: Enamel defects increase the risk of decay. To reduce this risk, dentists recommend professionally applied fluoride therapy, such as gels or varnishes, at regular intervals. Additionally, the application of remineralizing agents like 10% casein phosphopeptide amorphous calcium phosphate (CPP-ACP) can help reverse early decay on tooth surfaces.
• Desensitizing agents: Resin-bonded sealants are recommended to alleviate sensitivity associated with enamel defects.
• Tooth fillings: For small lesions in primary teeth, resin-modified glass-ionomer cements and polyacid-modified composite resins are recommended. Amalgam fillings and resin-based composite fillings are suggested for decayed areas in permanent teeth.
• Crowns: Stainless steel crowns are recommended for severely affected primary or permanent teeth as they provide protection against further damage.
• Mouthguards: Mouthguards may be recommended for children who grind their teeth to prevent excessive wear on the tooth surface.
• Full mouth rehabilitation: Children with severe enamel defects involving multiple teeth may be referred to a pediatric dentist for full mouth rehabilitation under general anesthesia.

Preventive Measures

Here are some tips to prevent cavities, tooth sensitivity, and excessive tooth wear in children with enamel defects:

• Regular check-ups and appointments with dentists should be maintained.
• Parents should be informed about teeth with enamel defects and the associated risks.
• Parents should be advised to replace sugary, sticky, and chewy snacks with healthy foods to reduce the risk of decay. Additionally, acidic foods and beverages should be avoided to prevent tooth surface erosion.
• Brush teeth with a soft toothbrush and rinse with lukewarm water twice daily to reduce sensitivity.
• Dentists may recommend topical fluoride application at regular intervals to decrease the risk of decay.

Conclusion

Enamel defects may arise from both genetic and acquired conditions, increasing the risk of decay and sensitivity along with aesthetic concerns among children. Besides, the presence of enamel defects can be an indicator of systemic health issues. Therefore, prompt diagnosis and application of preventive measures are prerequisites in the early management of enamel defects.

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