## 4 Discussion
We speculate that a possible cause of the necrotic areas is premature death or dedifferentiation of the odontoblasts and the consequent disappearance of the cytoplasmic process [19]. When treating children with OI, attention should be given to preventing enamel attrition and rapid wear of the poorly mineralized dentin, as well as preventing caries and periodontal disease. The American Academy for Paediatric Dentistry guideline recommends that children affected with DGI should undergo intensive preventive interventions, among which fluoride application and desensitizing agents that reduce tooth sensitivity have been shown to be effective [24]. Restorative care is frequently needed and should be carried out prior to excessive tooth wear and the loss of vertical dimension. For severe cases of type II DGI, [PERSON] et al. suggested that primary incisors and canines should be restored with composite restorations, while molars should be protected with preformed crowns [25]. However, in light of the observations of our study, it should be considered that the adhesion of composite restorations placed on primary teeth in OI patients may be compromised due to the altered structure of collagen fibers. When placing composite restorations, the mineral component of the superficial layer of dentin is removed by acid etching in etch-and-rinse adhesives, or with acidic primers in self-etch adhesives. This procedure leaves behind an exposed collagen matrix, which is then infiltrated with adhesive resin monomers, leading to the creation of a hybrid layer--a structure whose integrity is essential for the durability of the restorations. Even in favorable clinical situations where a sound collagen structure is present, adhesive monomers are not able to entirely infiltrate the exposed collagen matrix, thus leaving unprotected collagen fibrils at the bottom of the hybrid layer [1]. Degradation of the hybrid layer is a result of the presence of endogenous enzymes and the consequent hydrolysis of collagen fibers which are not completely embedded in polymerized adhesive resins. Hydrolytic processes contribute to the weakening of the adhesive joint between the resin material and dentin and are responsible for the loss of bond strength over time [26; 27; 28]. Due to the presence of altered collagen fibrils, adhesive procedures applied on the teeth in OI-affected children could result in the formation of a weaker hybrid layer. The laxed and unorganized collagen fibrils which are infiltrated by resin monomers within the hybrid layer may be more susceptible to micromechanical disruption during occlusal loads. This mechanical aspect of hybrid layer degradation, combined with the above described hydrolytic processes and their possible impact on the clinical performance of composite restorations, should be kept in mind while attending to OI patients. Moreover, the use of cross-linkers--molecules that have the ability to create chemical bonds between the collagen molecules and thereby render collagen more mechanically resistant--should be considered in patients with OI. These molecules have been widely investigated in healthy permanent teeth [29; 30], and their efficacy in structurally altered OI-affected teeth should be studied further. Finally, the potential limitations of the study should be taken into consideration. In this research, no quantitative data were used and, consequently, no statistical analysis was performed due to the nature of the study. Instead, a descriptive approach was used when analyzing representative images of teeth from both healthy and OI donors, similarly to previously published studies [11; 15; 16]. In order to eliminate the risk of bias, two experienced researchers observed and described the images independently from each other, after which they discussed them together. Even though no statistical analysis was performed, this type of qualitative analysis allowed us to establish fine distinctions on the ultrastructural level between teeth from healthy and OI children.