The goal of this observational study is to investigate periodontal inflammatory mediators in systemically healthy children aged 8-13 years with and without molar-incisor hypomineralization (MIH) who require initial periodontal treatment due to gingivitis.

The main questions it aims to answer are:

Are the levels of periodontal inflammatory mediators in gingival crevicular fluid different between children with MIH and those without MIH? Is the presence and severity of MIH associated with clinical periodontal parameters and dentin hypersensitivity?

Researchers will compare children with MIH to children without MIH to determine whether MIH is associated with changes in periodontal inflammatory mediator levels and periodontal clinical findings.

Participants will:

Provide written informed consent from their parent or legal guardian before enrollment.

Complete a dental and oral hygiene history questionnaire. Undergo a comprehensive oral examination, including assessment of MIH severity using the MIH Treatment Need Index (MIH-TNI), dentin hypersensitivity using the Schiff Cold Air Sensitivity Scale, plaque index, gingival index, bleeding on probing, and periodontal probing depth.

Provide gingival crevicular fluid samples collected using Periopaper® strips for analysis of periodontal inflammatory mediators.

The following clinical indices and assessment criteria will be used during the clinical examination.

Gingivitis Classification

Participants will be classified as having gingivitis according to the following criteria:

• Localized gingivitis: Bleeding on probing (BOP) affecting 10-30% of sites and probing pocket depth (PPD) ≤3 mm in the absence of periodontitis.
• Generalized gingivitis: BOP affecting >30% of sites and PPD ≤3 mm in the absence of periodontitis.

MIH will be assessed under adequate illumination using a dental mirror, periodontal probe, and air syringe.

The examination will evaluate:

• Presence or absence of MIH.
• Demarcated opacities on the occlusal and/or buccal surfaces.
• Defects of different shapes, sizes, and patterns.
• White-creamy or yellow-brown discolorations.
• Defect size (defects <1 mm will not be recorded).
• Presence of dentin hypersensitivity.
• Presence of atypical restorations.
• Teeth extracted or suspected to have been extracted because of MIH.
• Any combination of the above findings.

Examinations will begin in the maxillary right quadrant and proceed clockwise. The highest MIH-TNI score recorded within each quadrant will be used.

MIH-TNI Scores Grade 0: No MIH. Grade 1: No hypersensitivity; no enamel defect. Grade 2: No hypersensitivity; enamel defect present. 2a: Defect involves <1/3 of the tooth surface. 2b: Defect involves 1/3-2/3 of the tooth surface. 2c: Defect involves >2/3 of the tooth surface, is close to the pulp, includes an atypical restoration, or extraction due to MIH.

Grade 3: Hypersensitivity present; no enamel defect. Grade 4: Hypersensitivity present; enamel defect present. 4a: Defect involves <1/3 of the tooth surface. 4b: Defect involves 1/3-2/3 of the tooth surface. 4c: Defect involves >2/3 of the tooth surface, is close to the pulp, includes an atypical restoration, or extraction due to MIH.

Dentin hypersensitivity will be assessed using the Schiff Cold Air Sensitivity Scale.

Score 0: No response to the air stimulus. Score 1: Responds to the stimulus but does not request discontinuation. Score 2: Responds to the stimulus and requests discontinuation or attempts to avoid the stimulus.

Score 3: Responds to the stimulus, considers it painful, and immediately requests discontinuation.

After isolating adjacent teeth, a continuous air blast from the dental unit syringe will be applied to the exposed dentin surface from a distance of 2-3 mm at a 90° angle for 2-3 seconds with an air pressure of 45-60 psi. The air temperature will be approximately 20°C. Pain response will be scored by the examiner according to the Schiff scale.

Plaque Index (Silness and Löe, 1964) Score 0: No plaque. Score 1: A thin film of plaque at the gingival margin detectable only by probing.

Score 2: Moderate accumulation of visible plaque along the gingival margin. Score 3: Abundant plaque covering the tooth surface and gingival margin.

Gingival Index (Löe and Silness, 1963) Score 0: Healthy gingiva with no inflammation. Score 1: Mild inflammation characterized by slight color change and edema without bleeding on probing.

Score 2: Moderate inflammation with redness, edema, and bleeding on probing. Score 3: Severe inflammation with marked redness, edema, ulceration, and possible spontaneous bleeding.

Bleeding on Probing (BOP) (Ainamo and Bay, 1975)

Bleeding on probing will be assessed using a blunt periodontal probe at six sites per tooth with a probing force of approximately 25 g. Bleeding occurring within 10-15 seconds after probing will be recorded as positive.

The percentage of bleeding sites will be calculated as follows:

(Number of bleeding sites / Total number of examined sites) × 100. Scoring 0: No bleeding.

1: Bleeding present.

Periodontal Probing Depth (Glavind and Löe, 1967)

Periodontal probing depth will be defined as the distance from the gingival margin to the base of the gingival sulcus or periodontal pocket.

Measurements will be obtained at six sites per tooth. Mesial and distal measurements will be taken from the buccal aspect as close as possible to the contact points. Mid-buccal and mid-lingual/palatal measurements will be recorded along the long axis of the tooth. In multirooted teeth, buccal and lingual/palatal measurements will be performed on the mesial roots to avoid furcation areas.

The periodontal probe will be positioned parallel to the long axis of the tooth, and a probing force of approximately 10 g will be applied during measurement.

Inclusion Criteria:

• Systemically healthy children aged 8-13 years (both sexes).
• Children who demonstrate adequate cooperation for dental treatment and study procedures (Frankl Behavior Rating Scale score ≥3).
• Study group: Children with molar-incisor hypomineralization (MIH) affecting at least three permanent first molars and requiring initial periodontal treatment for gingivitis.
• Control group: Children without molar-incisor hypomineralization who require initial periodontal treatment for gingivitis.
• Presence of gingivitis requiring initial periodontal therapy.

Exclusion Criteria:

• Use of antibiotics within the previous 1 month.
• Radiographic evidence of periodontal destruction.
• History of periodontal treatment within the previous 3 months.
• Presence of systemic, chronic, or metabolic diseases.
• Ongoing active orthodontic treatment.
• Developmental enamel defects other than molar-incisor hypomineralization.
• History of premature birth.

Systemically healthy children aged 8-13 years with gingivitis requiring initial periodontal therapy. The study includes children with molar-incisor hypomineralization (MIH) affecting at least three permanent first molars (study group) and age-matched children without MIH (control group).