This clinical study main goal is to investigate the effectiveness of nano hydroxy apatite crystal varnish and potassium nitrate gel as a non invasive approach in managing MIH-affected teeth.

This randomized clinical trial study aims to investigate the effectiveness of nano-hydroxy apatite crystal varnish, and potassium nitrate gel compared to fluoride varnish, in reducing dentin hypersensitivity, improving a child's oral hygiene, and gingival health, oral health-related quality of life, preventing post-eruptive enamel breakdown, and dental caries, along with economic evaluation.

The research unit of this study will be the MIH-affected permanent tooth, in children aged from six to ten years, from either gender.

Inclusion criteria:

Participants related criteria:

1. Children aged from six to ten years old.
2. Medically free children according to the history taken from their parents.
3. Children who are categorized as Class I or II according to the American Society of Anaesthesiologists (ASA).
4. Children whom their parents accept to comply with the follow-up visits.
5. Children who accept, and their guardians, to participate in the study by signing the informed consent.
6. Children with no more than four cavitated primary teeth.

Tooth related criteria:

1. The diagnosis of MIH will be done as per the Wurzburg concept, 2023 MIH diagnostic criteria:

The child will be confirmed to have MIH if any of the following characteristics are apparent:

• affected teeth show a clearly defined opacity at the occlusal and buccal surfaces of a tooth,

• defects vary in shape, size, and pattern,

• white, cream-colored, or yellow-brown color deviations are recognizable,

• defects variably vary in size,

• teeth with hypersensitivity are present,

• teeth have an atypical restoration,

• permanent teeth for (suspected) MIH reasons are missing (extractions),

• combinations of the above characteristics are present.

  1. MIH-affected permanent teeth, suffering from dentin hypersensitivity, (MIH-TNI 3, 4a).

  2. Positive Schiff Cold Airblasting Sensitivity score (score 1, 2, or 3).

     • Exclusion criteria:

Participants related criteria:

1. Children with severe behavioral or emotional disabilities.
2. Children who received analgesics within the last 24 hours before the procedure.15
3. Patients who are using chlorhexidine-based gels or mouthwashes.

Tooth related criteria:

1. A tooth with signs and symptoms of irreversible pulpitis.
2. A tooth with signs and symptoms of necrotic pulp.
3. Sealing therapy or application of desensitizing agent on the MIH teeth within one month before participation in the study.
4. Presence of dental caries on the MIH-affected permanent tooth.
5. Presence of restoration(s) on MIH-affected permanent tooth.

the assessment of outcomes will be performed with two investigators other than the main investigator, who will not be aware of the type of the intervention carried out on the assessed child.