The use of DAI index has been applied globally for its’ simplicity of application, validity and for being easy to use, allowing comparations between different cultures and ethnic groups, however, it has limitations [16]. One of the limitations pointed to DAI is the fact that it does not account for occlusal anomalies such as: crossbites, impacted teeth, midline deviations, overbites and absent molars. Although the presence or absence of diastema between the teeth and crowding are accounted for, this index does not allow distinctions between various degrees of dentomaxillary discrepancy and is therefore a limitation [20].

The age range was chosen because the DAI index lose validity in individuals with deciduous dentition, and according to Anita et al. (2013), the malocclusions are totally manifested during these ages and, because, at advanced ages, the prevalence of tooth loss is higher [18].

In this investigation, the first component of the DAI evaluated was dental absences, where 91.2% of the participants did not present any type of absence. These results are in line with the results obtained by Sanadhya et al. (2014) in India, where about 89.5% of the 947 children aged between 12 and 15 years did not have dental absences. Rwakatema et al. (2007) in Tanzania observed the prevalence of malocclusions and the need for orthodontic treatment in 289 children aged 12 to 15 years, determined that only about 5.1% and 6.9%, respectively, had absences. Muasya et al. (2013) in Kenya assessed patterns of malocclusion with DAI in 1382 children aged 12 to 15 years in which 94.9% had no absences. Slightly higher values were found by Bauman et al. (2018) in Brazil, where 5,539 children aged 12 years were observed with 96.8% without absences in the upper arch and 97.3% in the lower arch. Singh et al. (2019) in India obtained 98.8% and 96.7% of participants without absences in the upper and lower arch, respectively, of the 902 children observed aged between 12 and 15 years [20-24].

Evaluating crowding, this was not present in 66.3% of the children, a similar situation reported by other authors [20-24]. Evaluating the spacing, this was present in 33.8% of the children observed in this study, values in consonance found by other authors [20-23]. Another parameter evaluated in this investigation was the presence of interincisive diastema in which the percentage of children with this characteristic was much higher than those found in the studies [20-24]. Evaluating the anterior misalignment in the maxilla, in this investigation, only 15% of the children were observed, a situation opposite to the other studies that observed higher values [20-24]. The 6^th DAI parameter assesses previous mandible misalignments, in this investigation 18.7% of the children observed presented this occlusal problem, a similar result found by Bauman et al. (2018), higher values were reported by other authors [20-24]. Maxillary overjet occurred in 70.0% of the children evaluated, most with 1mm (24.4%) or 4mm (23.9%). Sanadhya et al. (2014) found that 36.1% of the children had maxillary overjet of 1 mm and 12.7% of 4 mm. In the studies that analyzed only the highest overjet value, i.e., 4 mm, they found values slightly higher than those determined in this investigation [20-23]. Mandibular overjet in this investigation was present in only 2.7% of children, equally low percentages obtained in different studies [20-24].

The presence of anterior open bite in this investigation was observed in 40.6% of the children, a situation totally opposite to the other investigations, all with much lower values [20-24]. The last parameter of the DAI evaluates the molar relationship, in this investigation the normal molar relationship predominated, a situation also found in the studies mentioned above [20-24].

Analyzing the parameters of gender and age, the results obtained in this study as well as in the studies mentioned above did not present results with statistical significance, except in the analysis of the crowding regarding age in the investigation of Sanadhya et al. (2014), having been higher in individuals aged 12 years in one and in both regions (p=0.000). In the same study they determined that spacing, interincisive diastemas and anterior maxillary misalignment are less prevalent with advancing age, making it difficult to specify the relationship between their occurrence and age [20].

 It should be noted that in the study developed by Singh et al. (2019), in the analysis of mandibular overjet there were no differences between the ages studied and in the open bite component they observed the same percentage in all ages except at 15 years where there was no open bite [24].

After categorizing the DAI index, the results obtained in this investigation determined that 62.5% of the children observed present normal occlusion so, without the need for treatment or slight need for treatment. In the distribution of malocclusions, 11.3% corresponded to defined malocclusion, with elective need for orthodontic treatment, 4.3% corresponded to severe malocclusion with a highly desirable need for orthodontic treatment and 21.9% of very severe malocclusion, and priority treatment was considered mandatory. According to other authors, the result obtained in normal occlusion is similar to those found in this investigation. Comparing malocclusion, most studies found slightly higher values for defined occlusion and severe occlusion and lower values of very severe malocclusion [20-24]. Analyzing the occlusion averages, it can be seen that Angola is statistically within the normal occlusion average of the countries analyzed and out of the average of malocclusions compared to these countries. (Table 4)

Table 4: Comparison of the percentage of occlusion between Angola and other countries.