This single armed cohort study is aimed to assess the acceptance, durability and efficiency of glass-Ionomer sealing technique on hypersensitive MIH molars (TNI-3 & 4a/b/c) clinically shortly (15 minutes) after the application and after a time period of 3 months.

The main assumption of the study is that sealing of hypersensitive MIH molars (TNI-3 & 4a/b/c) using glass-ionomer cement reduces the degree of hypersensitivity after direct placement and within a period of time. Moreover, glass-ionomer sealing has a good durability in hypomineralized teeth and is known to be acceptable due to it's easy and fast application.

The aim of this study is to assess the change in the degree of hypersensitivity in the sealed MIH (molar incisor hypomineralisation) tooth / teeth (IonoStar Plus, VOCO-Germany) in the same visit (15 Minutes after the application) and in the 3 months' recall-visit according to Schiff Cold Air Sensitivity (SCASS) Test and the self-report of the patient using Wong- Baker Faces Rating Scale.

This single armed cohort study will be undertaken at the Department of Preventive and Pediatric Dentistry at the University of Greifswald from approximately May 2023 to Autumn 2024. After assessment of eligibility and informed consent for participation in the study, hypersensitivity of the affected MIH permanent molars will be assessed using air blast before the treatment using SCASS (Schiff cold air sensitivity Scale) and VAS (Visual analogue scale) in order to record the degree of sensitivity and pain perception of the child. After initial assessment, the affected teeth are prepared to receive a Glass- Ionomer cement fissure sealant (IonoStar Plus, VOCO GmbH Germany).

The level of tooth sensitivity will be assessed again 15 minutes after the treatment and in the regular 3 months follow up via air blast test (Schiff Cold Air Sensitivity Scale), the pain perception is being recorded with VAS (Visual analogue scale) by an independent observer, dental assistant and the operating dentist. The independent observer will assess the cooperation and behaviour of the child throughout the treatment using FBRS (Frankl behavioural rating scale) and FIS (Facial image scale).

The durability of the fissure sealant will be assessed using the modified USPHS criteria in the 3 months' follow-up. After the dental visit, the participating child the accompanying parent or caregiver, the dental operator receives a short questionnaire to be filled out.

Inclusion Criteria:

• Self-reported hypersensitive MIH molar (MIH-TNI 3 & 4a/b/c).
• Children & adolescents without systematic health diseases.
• No sealing therapy or application of desensitizing agent on the MIH-teeth within 1 month before participation in the study.
• Agreement to voluntary participation in the study.

Exclusion Criteria:

• Patients with acute pain/ patients with signs or symptoms to be treated.
• Patients with systemic disease that require special attention during their dental treatment.
• Parents / children who refused to participate in the study. - MIH teeth with signs of irreversible pulpitis.
• Allergy against any ingredients of the material.