The management of teeth with MIH lesions is a clinical problem due to its high prevalence, multiple clinical manifestations, young age of patients, severe dental sensitivity, and post-eruptive breakdown [20]. Although preformed metal and cast metal crowns are appropriate restorative options for severe MIH cases, the extensive preparation of complete crowns may not be a justification for the rehabilitation of all cases [21].
Scheduled extractions are also indicated for teeth with significant breakdown, or for those that are pulpally involved or associated with a dental abscess or facial cellulitis. In severe cases, consideration should also be given to the long-term prognosis of the tooth, the likelihood of repeated dental interventions and the psychological impact on the child [22]. Extraction may be the best option in these cases but complete spontaneous space closure is not guaranteed, even if performed at the ideal time of 8–10 years of age [23].
Clinical studies on the evaluation of the clinical performance of direct resin composite restorations are few and limited, hence this study was conducted to evaluate the clinical performance of indirect resin composite in the restoration of MIH first permanent molars during a 12-month follow-up period.
Resin composite was selected to restore MIH first permanent molars because it requires conservative preparation and is the first choice in restoring molars affected by MIH, especially if the lesion includes one or two surfaces [24]. ICRRs were adopted instead of ceramic restorations, as they allow their application with smaller thicknesses and the possibility of fixing it inside the mouth [13].
In the ICRR, the restorations were made by the dentist on the gypsum samples, and the adhesion was performed using self-adhesive resin cement, but selective enamel etching was undertaken for 30 s, where both Goracci et al., and de Goes et al., showed an increase in the bond strength after selective enamel etching [25, 26].
A self-adhesive resin cement was used to shorten the etching, washing, and drying stages as it has good mechanical properties, including its low solubility in oral fluids. It also has good flowability due to its low viscosity, and thus it achieves the lowest possible cement thickness between the restoration and the tooth surface [27]. This cement hardening begins with the transformation of monomers into polymers as soon as it is exposed to light, and the light-curing time is 40 s, and this process continues by the chemical method, and this ensures complete hardening of the cement [28].
The resin composite was applied in both application methods (direct and indirect) with a layering technique so that the thickness of the layer does not exceed 2 mm to harden the entire layer of the resin composite [29]. The inner surface of ICRR was sandblasted with 50 μm aluminum oxide at a distance of 10 ml and a pressure of 2.5 bar for 10 s, which leads to an increase in the roughness of the inner surface of the restoration and thus increases the bonding surface and bonding strength [30].
Silane was applied after sandblasting the inner surface of ICRR to increase the bond strength as an additional covalent interaction occurs between the methacrylate group in the resin cement and the silane particles during the hardening process [30]. An additional silicone was used as it is the most accurate impression material, is hydrophilic, and reduces problems resulting from lack of good isolation [31], which makes it particularly suitable in children for ICRR.
The results of this study supported the first null hypothesis, as there were no significant differences in terms of the clinical performance of DCRR and ICRR in the restoration of MIH first permanent molars. It is possible to apply the indirect resin composite in the restoration according to the results recorded in this study, which may help to overcome the problems associated with the application of direct restorations in children such as polymerization shrinkage and post-operative sensitivity [32].
Despite the need for an additional session in ICRR, the shortness in the duration of the treatment session compared to the DCRR in one was more desirable for the child, as the second null hypothesis was rejected. The results of the assessment of the child’s satisfaction with the ICRR technique were (50% agree and 45% strongly agree) higher than DCRR (60% agree and 20% strongly agree) and this plays a role in gaining the child’s cooperation for dental procedures [33]. Statistically significant differences were found in favor of ICRR, where reducing the treatment time session played an important role in evaluating the child’s acceptance of the treatment technique, and this in turn was reflected clinically in the child’s satisfaction with the treatment provided, which may favor these treatments in children.
No loss of restorative material was observed during follow-up periods in both techniques, this indicates that the resin restorations have good retention and stability towards masticatory forces, and this is consistent with the Dhareula et al. study which evaluated metal and indirect resin onlays in the rehabilitation of first permanent molars affected with MIH in children aged 8–13 years old, the study was performed on 30 children. 42 teeth were equally divided into two groups (n = 21)., and Lygidakis et al. study evaluated direct resin composite in the restoration of molars affected with MIH in children aged 8–10 years old [15, 34].
The presence of secondary caries was examined using the probe, and the results of this study showed there were no secondary caries in 90% of DCRR and 95% of ICRR after 12 months of follow-up without significant differences between these two types of restorations. This could be attributed to the removal of all affected enamel and the placing of the restoration margins on sound enamel. This is consistent with the study of de Souza et al. [20] which evaluated the clinical performance of resin composite restorations with two different adhesive systems for molars affected with MIH in children aged 6–8 years old according to the modified US Public Health Service (USPHS) criteria. The results of the present study also differed from the study of Sönmez and Saat in terms of secondary caries which evaluated deproteinization and different cavity designs on resin restoration performance in 95 MIH-affected molars in children aged 8–12 years. The difference may be attributed to the fact that we have used a self-adhesive bond, while Sönmez and Saat used the traditional bond system for DCRR [17]. Secondary caries for ICRR were consistent also with Dhareula et al. [15].
Comparing the anatomical form changes in the DCRR and ICRR, the results showed no change in the anatomical form of 85% and 95% in both DCRR and ICRR, respectively. This is consistent with the study of Dhareula et al. and Sönmez and Saat studies [15, 17]. Our findings were also different from those of de Souza et al., who were unable to evaluate 6 cases at the end of 12 months out of 21 cases, while in our study there were no withdrawal cases during the follow-ups [20].
As for the surface texture, the DCRR showed an enamel-like surface in 60% of cases compared to 85% for the ICRR without statistically significant differences. This can be explained by the fact that the ICRR contains a larger percentage of filler particles, which makes it less susceptible to surface changes [35, 36].
In this study, it was observed that there was no marginal discoloration and closely marginal adaptation in 75 and 80% of cases respectively, while in the ICRR group, the closely marginal adaptation and no marginal discoloration reached 80% with no statistically significant difference between the two groups. This could be attributed to the application of both resin composite restorations with a layering technique to overcome the polymerization shrinkage by reducing the C-factor [37].
Through the results of this study, it was observed that there was no post-operative sensitivity in the DCRR group 70%, 80%, and 85% during 3, 6, and 12 months respectively, compared to 80%, 90%, and 95% for the ICRR group. These results may be attributed to the strict adherence to rubber dam isolation and adhesive ICRR by dual-cure resin cement, which achieves better sealing of the dentin canals and bypasses the two stages of etching and drying of the dentin. The results of this study are consistent with Lygidakis et al., study regarding post-operative sensitivity [34], while the results differed with the Sönmez and Saat study and this can be attributed to the use of self-adhesive bond while the conventional bond system was used in this study [17].
This is the first study that evaluated ICRR in the first permanent molars affected with MIH. It has included good sample size and good follow-up periods, but we recommend in the future to conduct further studies with longer follow-up periods to confirm these results. Treatment decisions were made on a subjected criteria based on defect size, cooperation, patient needs, and this is the major limitation of the study. This is because there is not a standardized protocol.
