This is the first survey exploring the knowledge, perception and clinical experience on MIH among Portuguese dentists. Overall, the knowledge on MIH was considered low (average of 41.3 on a scale of 20 to 60), while perception and clinical experience were different between PDs and non-PDs practitioners (GDPs and ODSs). In general, around 75% of the respondents view MIH as a public health problem, only PDs reported to be confident diagnosing and managing MIH cases. In addition, most respondents (overall 94.9%, PDs 70.8%) did not received information about MIH and the majority would be interested in receiving more information on diagnosis, etiology and treatment, showing the need to implement continuing education in the diagnosis and treatment of MIH.
Overall, the average KS from the present study was lower than other counterparts from Australia , Chile  and Hong Kong . This score proposed by Gambetta-Tessini  allows the comparison of knowledge among different groups (either geographic location or dental specialties) as well monitoring its evolution along with education measures (such as, continuing education programs or improvements to curricular contents of Pediatric Dentistry regarding MIH). These results may pave the way for the need to critically appraise both the curricular content among Portuguese dental schools (in undergraduate and specialty graduate programs) and cutting-edge unique courses to meet needs throughout the career.
Similarly to the reports from Australia, Chile and Hong Kong [12, 18], all PDs reported to have found MIH cases in clinical practice. Furthermore, although PDs did report being aware of all phenotypes of MIH (in molars, incisors or premolars), they were not aware of canine-affected MIH cases . Likewise, when asked if MIH was found in primary second molars, highly reported in literature [9, 20], the majority of GDPs and ODSs reported to have not observed such cases, as well as a remarkable 16.7% of PDs.
Considering the latest estimated MIH global prevalence of 13.5% , the cross-country variety may range from 2.8 to 40.2% . The prevalence of MIH in Portugal has never been estimated, therefore we used the worldwide estimated result of 13.5%, yet 32.7% of the participants believe that this may range between 5 and 10%. From the PDs view, the prevalence of MIH has been increasing, in line with the views from Spanish counterparts .
In what the etiology of MIH concerns, the majority of PDs (75%) report to be unknown, contrasting, for example, with New Zealand counterparts that attribute the etiology to medical conditions because of their great experience on MIH cases in populations with compromised health . In addition, surveys from Hong Kong, Iraq, Australia and Chile report that chronic and acute conditions that affect the mother and child are the most relevant etiological factors of MIH [12, 16, 18]. Considering that the etiology of MIH is still unknown, possibly multifactorial, and far from fully understood, these variations are understandable and warrant a particular focus on future research.
Most GDPs reported yellow or brown opacities as the major manifestations of MIH defects mostly found in their clinical practice, similarly to reports from Australia, Spain and Hong Kong [11, 13, 18]. PDs simultaneously reported white, yellow and brown opacities and post-eruptive fractures as the most common findings, showing a relatively higher awareness of the diversity of MIH phenotypes [11, 18]. GDPs showed a lack of recognition ability towards MIH diagnosis, particularly regarding opacities or post-eruptive fractures. Despite this, both PDs and GDPs attested knowing that MIH and other dental developmental defects differ, namely amelogenesis and hypoplasia. Surveys carried out in the United Kingdom, Spain and Malaysia, showed difficulties from dentists in distinguishing MIH from other enamel defects [11, 15, 17].
In what treatment of MIH concerns, PDs reported glass ionomer (75.0%), preformed crown (70.8%) and composite resins (58.3%) as the preferred treatment options. These results contrasted with the reports from GDPs and ODSs, that reported to prefer composite resins (54.6% for GDPS and 57.3% for ODSs), infiltrating resins (39.2% for GDPs and 29.1% for ODSs), and glass ionomer (36.9% for GDPS and 30.1% for ODSs). The variety of materials used in the treatment of teeth affected by MIH possibly denotes the lack of evidence-based guidelines, excluding composite resins that are recommended in moderate MIH lesions [11, 19]. Therefore, further research on the physical properties and clinical performance of restorative materials is recommended to fill this gap of knowledge . The persistence of absent clinical decision-trees and best evidence consensus regarding restorative materials will contribute to enduring difficulties in the clinical management of MIH teeth. Although there are general indications on which professionals can rely, perhaps the lack of dissemination and information is reflected in the use of different materials for the treatment of teeth with MIH, which was observed in this study. Comparing these results with other countries, Australian and Chilean dentists reported glass ionomer as the treatment of choice [12, 19], in Spain the resin-modified glass ionomer cement and composite resins were preferred . Particularly in post-eruptive fractures, surveys from Hong Kong and New Zealand reported preformed crowns as the treatment of choice [13, 18]. According to Elhennawy and Schwendicke, glass ionomer and amalgam restorations have a higher failure rate, opposite to the higher successful rates of composite restorations and preformed crowns .
About the received information on MIH, the results point to a gap in the training of medical dentists. Similarly to Portugal, dentists from Malaysia and Hong Kong also reported that they did not receive information about MIH [17, 18]. Spanish and Hong Kong GDPs received less training than PDs. However, Australian and Chilean reported to have received more information about MIH, which was conveyed to have increased their awareness and knowledge [11,12,13, 18]. Access to information is essential to enhance an early diagnosis of MIH and adequate patient monitoring. This not only allows for the application of preventive measures to minimize post-eruptive sensitivity and fractures, but also allows a strict control of the affected teeth . Therefore, the availability of information on MIH is key to a future coordinated public health response with a multidisciplinary engagement from all specialties in Dentistry.
As such, these results may be the first line of evidence on the level of PDs, GDPs and other specialists regarding this condition, and what gaps of knowledge and opportunities are needed to be filled in the upcoming years in Portugal. Nevertheless, this study presented a low response rate, which may limit the generalizability to the whole country.