Despite the high prevalence and increased incidence of MIH in Spanish pediatric patients, this study is the first to provide information on the perception and knowledge of the etiology and diagnosis of MIH, and strategies in patient management of Spanish dentists, GDPs and PDs.
We used an online survey to avoid the low response rate obtained in postal survey 23. The response rate was 18.6%, despite a reminder sent at two weeks, which was similar to that recorded in studies in other countries 8,13,16,19,21.
In Spain, dentistry is mostly private, which is reflected by the responders (84.58% private), unlike countries such as Norway 14 or Australia and Chile 19 where most of the dentists were public workers. We found that 69.16% of participants were GDPs and 30.84% PDs. PD training in Spain is not specialized, as in most European Union countries, but is a postgraduate master type of training. In both groups of dentists, the majority (74.30%) of practitioners were licensed in Dentistry, with mean age of 31–40 years (44.86%) and with more than 15 years of professional experience (39.72%). The professional profiles found in other studies vary in age and years of experience, with the study conducted in Hong Kong having the oldest professionals and the greatest professional experience 8.
We found that PDs had twice the perception of patients with MIH lesions compared with GDPs, a situation reflected in countries such as Iraq15, Malaysia22, Australia-New Zealand 18, Saudi Arabia 17, China 8 and the UK 20, where the prevalence of MIH is similar to Spain. Both in Spain and in other countries 15,17,18, the general perception of dentists is that there is an increase in the incidence of MIH, although in our case the perception is significantly higher in PDs than in GDPs. Thus, 59.45% of GDPs responded that the prevalence of MIH patients is < 10%. GDPs from countries such as the USA 21 India 16 and China 8 estimated the prevalence at < 5%. These results are closely related to the training of dentists and their diagnostic ability: 59.09% of PDs claimed to have training in MIH compared with 23.8% of GDPs. In addition, this training was received in continuous education courses, compared with the online self-training described by GDPs. In other countries, the training of PDs in MIH shows similar results, although GDPs had less training in MIH (7–8.8%) (16, 30). Despite these results, both PDs and GDPs in Spain require ongoing training courses on MIH 8,15,16, 19.
The most recognized MIH lesion in both study groups was yellow/brown lesions, as it was in other countries 13,15−18. This may be because white-cream lesions can be mistaken for other lesions such as fluorosis or white spot cavities 20, 24. The percentage of post-eruptive enamel fractures was low, possibly because they may be confused with extensive cavity lesions, with atypical restorations typical of this pathology, since the enamel breaks quickly after rupture 15, 25, or with enamel hypoplasia, although in this case the edges of the lesion are not as irregular as in MIH 20.
In 2012, hypomineralization of the primary teeth was described, mainly in the second primary molars (HSPM) 2. This is known to be associated with an increased risk of hypomineralization in the permanent molars 2, although the absence of HSPM does not exclude future MIH. Most of our respondents report detecting HSPM less frequently, with no differences between the two groups, as is the case in studies in the USA 21, Kuwait 13, Saudi Arabia 17 and Australia-Chile 19, even though PDs have greater access to pediatric populations, where the diagnosis should be more common.
In general, and as in other studies 8, 15–18,21, dentists' responses reflect the hypothesis that the etiology may be multifactorial, with a diversity of responses. Most studies, when describing etiological factors, attribute MIH primarily to "chronic and acute medical conditioners affecting the mother and child" 8, 15, 16, 19. In our study, 42.78% of dentists attributed the etiology to these factors, lower than the 80–100% found in other studies 8, 18. The second cause, according to the dentists in our study, was the consumption of antibiotics by the child or mother during pregnancy (24.78%), figures similar to the Iran study 15 but below the studies in Hong Kong 8 and Australia-New Zealand 18. Environmental pollutants were considered causal agents by 11.6%, with a different perception between GDPs and DPs.
A significant percentage of both GDPs and PDs responded that they found the management of MIH "somewhat difficult". This is because these patients have increased anxiety 26 and tooth hypersensitivity, even after local anesthesia. In fact, anesthesia is one of the procedures that mark significant differences between dentists, with GDPs finding it more difficult to achieve good anesthesia than PDs.
Achieving correct restoration and long-term success is what worries dentists the most (48.83%). It is known that etching with orthophosphoric acid creates faulty etched patterns 27, that resin penetration is defective and the adhesion force of the composite resins to the enamel affected by MIH is low 28, and that there is a high failure rate of this type of materials in molars with MIH 29; in fact, the second most relevant factor in the choice of material by our dentists is the adhesion of the material (23.74%).
There are many reported treatment options for the restoration of teeth with MIH lesions: fluoride and/or CPP-ACP remineralization systems, silver diamine fluoride, pit and fissure sealants, resin infiltrations, conventional and modified glass ionomers with resin, resin composite, amalgam, preformed crowns, and even extractions, always depending on the severity of the lesion 30.
The potential for remineralization of material in restoration is the most relevant factor in the choice of materials (23.5%), significantly worrying GDPs more than PDs. In fact, the most commonly used material to restore post-eruptive fractures is RMGIC, followed by composite and both are used equally by GDPs and PDs. GIC is the third material of choice and is used proportionally more by PDs than GDPs. This may be because they treat younger children and use it as filling material in atraumatic restorative treatments or for interim restorations. Durability, which is one of the most relevant factors in material choice, is therefore significantly less decisive for PDs than for GDPs.
There are studies using GIC (81%) more than RMGIC (44.3%), which is justified by the greater fluoride release 18. However, a recent systematic review shows that the rate of failures in restoration materials in the treatment of MIH is higher with the use of amalgams and glass ionomers, and the highest success rate is achieved with indirect restorations, preformed stainless steel crowns (SSC) and composite restorations 43. In other studies, composite was the material of choice 8, 13, 17, 18, and was recommended by Lygidakis et al. 25 in moderate lesions. In our study, the number of SSCs was very low, compared with other studies 8, 16, 18 in which it was the treatment of choice in fractures for most PDs. Some authors recommend them for moderate and severe MIH lesions instead of GIC and RMGIC 25.
With respect to enamel opacity, the materials chosen were the same in both groups, first RMGIC followed by composite. However, in incisor lesions, composite was the material of choice, due to aesthetic concerns, followed by RMGIC and resin infiltrations. PDs use significantly more RMGIC to restore incisor enamel lesions.
The adhesion, durability and potential for remineralization were also decisive in the choice of material by most professionals from other countries 8, 16, 18. We left open the possibility of "other materials" where dentists could introduce other options used in combination with those defined in the survey. However, there were only 1.81–3.45% of responses. In contrast, in the Hong Kong study, 96.3% of PDs used fluoride varnishes and 64% pit fissure sealants 8.
In clinical case 1 (Fig. 1), where a post-eruptive enamel fracture was presented in a semi-erupted tooth, the material selected by both groups for treatment was GIC, followed by composite, similar to the results of the Norwegian study14. Difficult moisture control in a semi-erupted molar and fluoride release were the main reasons for choosing GIC. The limited mechanical properties of GIC mean it should be considered an interim therapeutic restoration and that must be replaced by another, definitive material (composite or preformed crowns) when eruption is complete 26.
In clinical case 2, the preferred option for GDPs was to remove the tissue seemingly most affected and restore with glass ionomer, compared with PDs whose option was to not to remove any dental tissue and use glass ionomer to restore. This shows a trend towards less invasive treatment by PDs, as described by other reports 14.