Enamel is a highly mineralized dental tissue, organized, and structured in hydroxyapatite crystals. It is secreted by ameloblasts in a protein-containing organic matrix. Because it is an acellular tissue, enamel does not have the capacity to repair itself when it is altered extrinsically or intrinsically (1). Alterations of enamel development can cause amelogenesis imperfecta (AI), a widespread hereditary condition that affects the structure of dental enamel of deciduous and permanent dentitions in quantity and quality (2).

The color of the teeth in people with AI varies according to the phenotype and occurs in different shades from light yellow to brown. Patients experience high sensitivity to thermal changes during the intake of beverages and food, which does not allow them to have adequate oral hygiene habits, causing a greater predisposition to cavities, dental fractures, and tooth loss (3). AI patients, due to aesthetic alterations, may suffer from low self-esteem (2). AI is caused by mutations in genes such as AMEL (amelogenin), ENAM (enamelin), MMP20 (matrix metalloproteinase-20), and KLK4 (kallikrein-4), which code for proteins involved in the formation of tooth enamel (4,5,6,7,8 ), and FAM83H, a gene that codes for a protein apparently involved in the organization of ameloblast desmosomes (9). AI has also been associated with other clinical alterations such as dental agenesis, taurodontism, and anterior open bite, and systemic alterations such as nephrocalcinosis, tricho-dento-osseous syndrome and Jalili syndrome (10,11,12,13).

AI is classified according to its phenotype and mode of inheritance into 14 subtypes. Based on the phenotype, it is classified as hypoplastic, hypocalcified, hypomadurative, and hypomadurative-hypoplastic with taurodontism. According to its inheritance pattern, AI is classified as autosomal dominant, autosomal recessive, and linked to the X chromosome (14). Radiographic examination of some phenotypes may show lack of contrast between enamel and dentin. It is also possible to observe some associated anomalies that are not clinically visible, such as pulp calcifications, dental agenesis, and apical dilacerations (15).

Research on the prevalence of AI is limited. In the international context, studies carried out in Switzerland by Backman and Holm (1986) stand out. They found 1:700 individuals affected with AI (16). The proportion of impacts was 1:14,000-1:16,000 in the United States (14), 1:8,000 in Israel (Jerusalem) (17) and 1:10,000 in Pakistan (18).

In Colombia, clinical and molecular studies of AI in families have been carried out. Different phenotypic, dental, and skeletal characteristics have been found, as well as genes involved with this anomaly (19,20,21,22,23). However, to date, prevalence studies have been limited to describing developmental enamel defects, such as hypoplasia, hypomineralization, and opacities (24,25,26,27). Even in the 4th National Oral Health Study (ENSAB IV, 2013-2014) (28), AI was not specifically reported. For this reason, it is relevant to know the frequency, magnitude, and distribution of this pathology and its behavior in the different regions of the country. The research question of this study was: What is the prevalence of AI in Colombian patients who attended the dental clinics of the Pontificia Universidad Javeriana from Bogotá, between January 2015 and December 2017? This prevalence study is the first one carried out in Colombia on AI. The findings provide initial evidence to plan preventive actions for caries, periodontal disease, and associated complications, and corrective actions to improve functionality and aesthetics (16). They also represent the basis to carry out similar studies in other Colombian regions.

This is a descriptive study with retrospective cross-sectional observational design. The study was approved by the Ethics and Research Committee of the Pontificia Universidad Javeriana’s Dental School, through Resolution OD-0218 of 28 July 2017, minute 010B. It adheres to the standards of Resolution 008430 of 1993 and Resolution 2378 of 2008, according to which it was classified as a risk-free study.

This study aimed to determine the prevalence of AI in patients who attended the clinics of the Pontificia Universidad Javeriana’ Dental School from Bogotá, between January 2015 and December 2017. 1,394 medical records were analyzed. To date, few studies describe the prevalence of AI in some populations (14,16,17,18). Shokri et al. (2014) (18) evaluated the prevalence of all types of dental anomalies in 1,640 Iranians, including AI, aged between 7 and 35 years, by means of panoramic radiographs. They found a prevalence of AI of 0.24 %, that is, 4 individuals.

Gupta et al. (2011) (29) reported a prevalence of 0.27 % in 3 people in the Indian population. More recently, Harini & Don (2019) (30), in the same population, reported a prevalence of 0.6 %. In the present study, the prevalence of AI in the Colombian population was also 0.6 %. Such data coincide with those found by Witkop et al. (1988), Shokri et al. (2014), and Gupta et al. (2014) (14,18,29). However, the prevalence is lower than that described in studies from Switzerland (16) and Jerusalem (17).

Regarding age, it was found that AI was diagnosed in the group aged 10 to 19 years, n = 8 (Table 4). This finding coincides with that described in studies of populations from Switzerland (16), Michigan (14), and Jerusalem (17). This could suggest that, at these ages, since permanent teeth are erupting or already erupted, the AI is more visible since this pathology is more serious in permanent teeth than in temporary ones. This aspect could suggest that AI in primary teeth sometimes goes unnoticed and may be underdiagnosed. On the other hand, it is also possible that a differential diagnosis has not been made with other enamel defects such as incisor-molar hypomineralization and fluorosis.

In this study, 7 patients presented hypoplastic phenotype (87.50 %) and one hypocalcified (Table 2). This suggests that the hypoplastic phenotype could influence its mainly autosomal dominant segregation, in which the enamel formation process (amelogenesis) is interrupted in the first stage (secretory). Likewise, the presence of a family history of AI was understood as an important sociodemographic factor since it is a hereditary disorder (2).

On the other hand, the 8 individuals affected by AI came from the lower-middle socioeconomic background and their origin was mainly urban. This could suggest that environmental aspects could be part of the etiology of AI. For example, taking antibiotics was found in 12.5 % of cases (Table 7). More specific studies must be carried out to clarify whether antibiotics play a role in the etiology of AI.

The Colombian population analyzed in this study was represented in its majority (55.31 %) by the female sex (n = 771), although the reported cases of AI showed a 1:1 relationship in both sexes (Table 3). The same was observed in clinical and molecular studies carried out in Colombians (19,22), in which AI has presented indistinctly in men and women, especially the hypoplastic phenotype, which was one of the most frequent in these studies. These findings also coincide with those of Gupta et al. (2011) (29) in Indian population, who evaluated 1,123 patients, 572 men and 551 women. They found that two men and one woman were affected by AI. Similarly, Shokri et al. (2014) (18) and Harini & Don (2019) (19), in Indian population, found a total of 4 people (2 men and 2 women) affected by AI.

Regarding the contrast between enamel and dentin, in the present study an absence of said contrast was evidenced in patients with hypoplastic AI (75 %), a characteristic that is more marked in the hypocalcified phenotype that was identified in 1 of the 8 individuals who presented AI. Another relevant radiographic characteristic was taurodontism, which was observed in all patients affected by AI. However, despite taurodontism being described more frequently than other abnormalities studied (3.7 %), the differences were not statistically significant (Table 6). These results coincide with those of Collins et al. (1999) (10), who analyzed dental anomalies associated with AI in panoramic radiographs. They found that in people with AI, taurodontism was present in 9 of 23 (39 %), a proportion that is similar to that of individuals without AI (10 of 24 cases, 42%).

Similarly, it was observed that in patients affected by AI with a hypoplastic phenotype, the enamel density was quantitatively lower than in those with a hypocalcified phenotype. This was also reported by Witkop in 1988 (14), who showed that the density in the hypoplastic phenotype is highly variable in its mineral content, while in the hypocalcified one this decrease is more constant.

Finally, this study is the first approximation to determine the prevalence of AI and, in turn, of dental anomalies in a Colombian population of patients from the dental clinics of the Pontificia Universidad Javeriana from Bogotá in a period of two years. The data collected allow us to see a trend in the distribution of AI and provide the basis for further studies with a larger population to implement preventive actions and establish therapeutic programs involving different disciplines.

A prevalence of 0.6 % (n = 8) of AI was found in Colombian patients who attended the dental clinics of the Pontificia Universidad Javeriana from Bogotá, attended between January 2015 and December 2017. This prevalence is similar to that described in other populations.

This is the first study of the prevalence of AI carried out in Colombia and shows a trend in magnitude, frequency, and distribution, as well as associated characteristics of this pathology. Taurodontism was the most frequent associated characteristic (100 %).

No predilection for AI was identified with respect to the sex variable.

Family history was important as AI presented more frequently in an autosomal dominant form, closely related to the hypoplastic phenotype.

Continue conducting AI prevalence studies with a larger population that includes different regions of Colombia.

Include this pathology in the National Oral Health Studies of Colombia.

Perform updates in the unification of diagnostic criteria for AI with respect to phenotype and associated dental and skeletal abnormalities bearing in mind this pathology can often be underdiagnosed.

Conduct trainings on differential diagnosis criteria with other enamel defects (hypomineralization, hypoplasia, incisor-molar syndrome and fluorosis).