Occlusal Changes After Modified Hall Technique in Molars Affected by Molar-Incisor Hypomineralization

The aim of this study is:

* to evaluate the occlusal adaptation process following SSC placement using the modified Hall technique in first permanent molars affected by MIH. * to quantify three-dimensional occlusal changes, including cusp displacement, occluso-vertical dimension changes, and occlusal contact area alterations over time using digital model superimposition. * to investigate the potential effects of this treatment on surrounding structures by assessing temporomandibular joint function and periodontal parameters.

MIH is a developmental enamel defect primarily affecting permanent first molars and often leading to hypersensitivity, rapid post-eruptive enamel breakdown, and significant coronal destruction. Recent literature has increasingly recommended biologically oriented and minimally invasive approaches for restoring MIH-affected molars, including the Hall technique and its modifications, which allow SSC placement without conventional tooth preparation. Although SSC placement is clinically successful, it may temporarily increase the occluso-vertical dimension and alter occlusal contacts. While clinical observations suggest that occlusal relationships gradually adapt over time through dentoalveolar compensation, no studies to date have quantitatively evaluated three-dimensional occlusal adaptation following SSC placement in MIH-affected permanent molars.

This prospective longitudinal clinical study will include 46 children with MIH-affected first permanent molars requiring SSC restoration. SSCs will be placed using the modified Hall technique.

Teeth will be equally distributed between maxillary and mandibular arches (23 maxillary and 23 mandibular molars), with only one tooth included per participant. Eligibility for SSC placement will be determined using the MIH-TNI index; teeth with scores 2 and 4 will be considered for inclusion. In cases where more than one first permanent molar meets the inclusion criteria within the same patient, the tooth showing the greatest degree of coronal breakdown will be selected for SSC placement. If multiple teeth present with similar severity level, tooth selection will be determined by computer-generated randomization. To minimize potential occlusal interference during treatment, all other necessary restorative procedures will be completed before SSC placement. Any additional teeth requiring SSC restoration will receive caries management during initial visits, while crown placement for those teeth will be postponed for three months to avoid interference with occlusal assessment.

In cases with tight proximal contacts, orthodontic separators will be placed prior to the procedure and left in situ for 3-5 days to achieve adequate interproximal space. At the SSC placement visit, lip and cheek retractors will be positioned to facilitate clear visualization of the teeth and surrounding soft tissues. Saliva will be removed using high-volume suction, and the tooth surfaces will be dried with an air syringe. Intraoral digital scans of both arches, together with the intercuspal occlusal relationship, will be obtained using a standardized scanning protocol.

Local anesthesia will be administered when clinically indicated. Unsupported hypomineralized enamel and defective restorations will be removed while maintaining a minimally invasive approach and avoiding conventional tooth preparation. Carious dentin will be removed according to selective caries removal principles: to firm dentin in shallow and moderately deep lesions and to soft dentin in deep lesions in order to prevent pulpal exposure.

An appropriately sized SSC (KidsCrown Permanent Molar SSC; Shinhung Co., Ltd., Korea) will be selected and tried in. Marginal adaptation and crown seating will be evaluated, and adjustments will be performed if necessary. The tooth will then be cleaned, dried, and isolated with cotton rolls. A glass ionomer cement (Ketac Cem Easymix; 3M ESPE, USA) will be prepared according to the manufacturer's instructions and placed inside the crown. The crown will be seated using finger pressure, and the patient will be asked to bite on a cotton roll until complete seating is achieved. Excess cement will be removed and interproximal remnants will be cleared using dental floss.

Following SSC placement, intraoral scanning will be repeated. Marginal adaptation of the crown will be verified using a bitewing radiograph obtained as part of the routine post-placement clinical assessment.

Occlusal changes following SSC placement will be monitored using digital models obtained at T0 (immediately before crown placement), T1 (immediately after crown placement), T2 (two weeks after crown placement), T3 (one month after crown placement), and T4 (three months after crown placement). In addition, temporomandibular joint examination and periodontal evaluation of the tissues surrounding the crowned tooth will be performed at T0, T2, T3, and T4 follow-up visits, and the findings will be recorded.

• Change in Maximum Occlusal Contact Area (Surface Area Measurement in mm²) [Time frame: From crown placement to 3 months post-placement]
• Assessment of Temporomandibular Joint Function (Helkimo Dysfunction Index Score) [Time frame: From crown placement to 3 months post-placement]
• Assessment of Gingival Status (Gingival Index Score) [Time frame: From crown placement to 3 months post-placement]
• Assessment of Plaque Accumulation (Plaque Index Score) [Time frame: From crown placement to 3 months post-placement]
• Assessment of Probing Depth (Linear Measurement in mm) [Time frame: From crown placement to 3 months post-placement]