Molar-incisor hypomineralization: treatment decision assisted by optical coherence tomography – MICHOCO

At least 15% of the world's population, especially children, are affected by white to yellow-brown spots on the molars and incisors, characteristic of enamel hypomineralization associated with a systemic mineralization deficit. Molar and Incisor Hypomineralization (MIH) is characterized by well-defined opacities that begin at the enamel-dentine junction, may extend through the enamel thickness, and sometimes result in loss of enamel substance. Teeth affected by MIH require 11 times as many restorative dental treatments and three times as many reoperations as unaffected teeth, resulting in a negative psychological and economic impact on society. Treatment varies according to the severity of the condition, ranging from preventive/interventional, to aesthetic, to more invasive (removal of altered tissue followed by restoration or even extraction).
Numerous studies show that tissues affected by MIH have an altered structure and composition compared to healthy tissues, but clinicians have no information during treatment (apart from haptic feedback from the burr) to define the limits of tissue to be removed for long-term restoration. In this project, we propose to use non-invasive technologies to characterize, in a few seconds and in vivo, the depth and extent of the lesion (Optical Coherence Tomography, OCT) as well as the quality of the tissue (Raman spectroscopy) to help the clinician define his treatment plan.
The first in vitro phase of the project is to improve our knowledge of tissues affected by MIH. Tissues will be characterized at different levels (physicochemical, microstructural, mechanical) and scales (from 10-100 nm to mm) using tools that can be applied in the clinic (Raman, OCT), but also complementary laboratory equipment (micro-CT, SEM, TEM). The aim is to create a structured database that will make it possible to understand the origin of variations in signals accessible in vivo.
The second part proposes a pilot clinical study to acquire OCT and Raman signals on the patient, with the aim of defining indicators correlated with the therapeutic choice.
The last part deals with adhesion failures. Similar to MIH tissues, the properties of the bonding interface will be studied at different scales and using complementary experimental tools. The influence of different bonding steps on roughness, substrate physicochemistry, and adhesive penetration depth will be studied. The tensile strength of the interface as a function of the severity of MIH damage to the substrate will be evaluated using micro-tensile tests combined with image correlation and finite element modeling (FEM) to limit experimental bias. These tests will also allow us to identify, using an inverse method, a more representative traction-separation law for the interfaces that will feed a FEM of a restored MIH cavity. The parameters with the greatest influence on the mechanical strength of the restoration (e.g. cavity dimensions, proportion and mechanical properties of the MIH tissues around the cavity) will be identified through a sensitivity study using this model.
By combining in vivo and in vitro characterization, we hope to gain a better understanding of the parameters that are essential for treatment selection and success, and to translate them into easily objectified indicators. In addition to the planned national and international publications in the fields of materials, biomechanics and clinical practice, we intend to organize a workshop for clinicians to share the results of our study and play an active role in improving the diagnosis and treatment of MIH pathology.