This clinical study was conducted to compare two different dental materials used in the treatment of children who have a condition called molar-incisor hypomineralization (MIH). MIH affects the quality of the enamel in permanent molars and can cause sensitivity, pain, and rapid tooth breakdown. In this study, children between the ages of 8 and 13 who had MIH in at least two molars received two types of onlay restorations: one made from a hybrid composite block and the other from a hybrid ceramic block. Both restorations were designed and manufactured using a digital system called CAD/CAM, which allows for more precise and efficient dental treatment.

Each child received both types of restorations-one on each side of the mouth-in a split-mouth design. The goal was to see how well each material worked over a period of six months. The restorations were evaluated by trained dentists using clinical criteria, and the children were also assessed for tooth sensitivity using a cold air test.

The main purpose of this study was to find out which material provides better clinical performance and reduces tooth sensitivity more effectively.

Molar-Incisor Hypomineralization (MIH) is a developmental enamel defect that primarily affects the first permanent molars and frequently the incisors. It is characterized by hypomineralized enamel with increased porosity, discoloration, and a high risk of post-eruptive enamel breakdown. Affected teeth often present with significant sensitivity, posing difficulties in achieving adequate anesthesia and effective bonding during restorative procedures. As a result, the management of MIH-affected molars in pediatric patients is both complex and clinically significant.

This prospective, randomized, split-mouth clinical study was designed to compare two different CAD/CAM materials used in semi-direct onlay restorations for the treatment of MIH-affected molars in children aged 8 to 13 years. The materials under investigation were a nano-hybrid composite block (Grandio blocs, VOCO) and a polymer-infiltrated ceramic network (PICN) hybrid ceramic block (VITA Enamic, VITA Zahnfabrik).

The study enrolled 20 pediatric patients, each presenting with at least two permanent first molars affected by MIH (classified as score 2b/c or 4b/c according to the MIH-TNI criteria). Using a split-mouth design, each patient received both interventions-one molar restored with a hybrid composite block and the other with a hybrid ceramic block. Randomization was performed using a computer-generated sequence. All procedures were carried out by a trained pediatric dentistry resident under rubber dam isolation, following a standardized adhesive protocol.

The restorative process was completed in a single session and followed a fully digital workflow. Teeth were scanned intraorally using the CEREC system, and restorations were designed and milled chairside. Immediate dentin sealing (IDS) was applied prior to cementation. The internal surfaces of the restorations were prepared using appropriate surface treatments such as sandblasting or hydrofluoric acid etching followed by silane application, in accordance with the manufacturers' guidelines. Final cementation was performed using a dual-cure resin cement.

Follow-up evaluations are planned at 6, 12, and 18 months post-operatively. At each time point, clinical assessments are conducted by two calibrated, blinded evaluators using modified United States Public Health Service (USPHS) criteria. These include evaluations of marginal adaptation, surface integrity, anatomical form, marginal discoloration, and the presence of secondary caries. Additionally, thermal sensitivity is assessed using the Schiff Cold Air Sensitivity Scale to monitor changes in dentin hypersensitivity over time.

This study aims to provide comparative data on the mid-term clinical performance of two innovative restorative materials applied in MIH-affected molars using a minimally invasive, digital workflow.

Inclusion Criteria:

• Children aged between 8 and 13 years
• Presence of at least two permanent first molars affected by MIH
• MIH-affected molars classified as score 2b, 2c, 4b, or 4c according to the MIH-TNI index
• Symmetrical molars suitable for split-mouth comparison
• Cooperative behavior sufficient to allow treatment under local anesthesia
• Signed informed consent obtained from parent or legal guardian

Exclusion Criteria:

• Presence of systemic or syndromic diseases affecting enamel development
• History of bruxism or parafunctional habits
• Presence of pulp involvement, fistula, or periapical pathology in the target teeth
• Allergies to dental materials used in the study (e.g., resin-based composites, adhesives)
• Participation in another clinical trial within the past 30 days
• Inability to attend scheduled follow-up appointments at 6, 12, and 18 months

Use of medication affecting pain perception or healing process

De-identified individual participant data (including intraoral photographs and clinical evaluation scores) may be shared in scientific publications or presentations. Data will be limited to information relevant for scientific analysis and will not include any personal identifiers.

De-identified individual participant data (IPD), along with supporting documents such as the study protocol and statistical analysis plan, will be available beginning 6 months after publication of the primary study results and will remain available for 5 years following the publication date.

Requests for access to de-identified individual participant data and supporting documents will be considered for academic or scientific research purposes. Interested researchers must submit a written proposal detailing the planned analysis, including objectives and statistical methods. Requests will be reviewed by the principal investigator and institutional review board (IRB) representatives to ensure ethical compliance and scientific merit. A data use agreement must be signed prior to data release. Requests can be submitted via email to the corresponding author listed in the publication.