Hall Technique is a non-invasive restorative approach for managing carious primary molars, increasingly used in pediatric dentistry due to its simplicity and patient tolerance. This study aims to evaluate and compare the occlusal changes that occur following Hall crown placement on different primary molar groups (maxillary first molar, maxillary second molar, mandibular first molar, mandibular second molar) using digital model analysis.

The aim of this clinical study is:

• to evaluate the occlusal changes that occur following the Hall Technique in different primary molar groups.
• to investigate whether the molar group (first vs. second) and jaw location (maxilla vs. mandible) influence the degree or pattern of occlusal adaptation.

A total of 60 healthy children aged between 7 and 10 years will be recruited from the Pediatric Dentistry Clinic at Ankara Yıldırım Beyazıt University, Faculty of Dentistry. Patients must have at least two primary molars requiring restorative treatment and meet all inclusion criteria.

After obtaining informed consent from parents and assent from the child, one eligible primary molar per participant will be randomly selected for Hall crown placement using a computer-generated allocation system. Based on the selected tooth, participants will be stratified into four groups: Group 1 (Maxillary first primary molar), Group 2 (Maxillary second primary molar), Group 3 (Mandibular first primary molar), and Group 4 (Mandibular second primary molar). Following group allocation, all other necessary dental treatments-including conventional restorations, endodontic procedures, and preventive interventions-will be completed to eliminate potential occlusal interferences.

One week after the completion of all dental treatments other than the Hall Technique, a baseline digital intraoral scan will be obtained using the Trios 3 scanner (3Shape, Copenhagen, Denmark), prior to crown placement on the designated primary molar. The Hall Technique will then be applied without local anesthesia or any caries removal. Debris will be gently cleared from the cavity, and airway protection will be ensured using gauze or elastoplast fixation. An appropriately sized preformed stainless-steel crown will be filled with glass ionomer cement (3M Ketac Cem) and seated on the tooth. The child will be instructed to bite firmly to ensure crown placement, or finger pressure will be used if necessary. Excess cement will be removed and interproximal contacts will be cleaned with dental floss. Digital intraoral scans will be repeated at three additional time points: immediately after crown placement (T1), at two weeks (T2), and at one month (T3) post-treatment. Superimposition and occlusal analysis will be conducted using Trios CAD (Computer-Aided Design) software to evaluate changes in occlusal parameters over time.

Following parameters will be quantitatively assessed:

• Positional change (in mm) between the mesiobuccal, distobuccal, mesiolingual/palatal, and distolingual/palatal cusp tips of the Hall-treated tooth, as well as the cusp tips of the opposing teeth in maximum intercuspation with this tooth.
• Positional change (in mm) of the cusp tip of the maxillary primary canine on the same side as the treated tooth
• Positional change (in mm) between the mesiobuccal cusp tips of all permanent first molars,
• Change in anterior occluso-vertical dimension (in mm)
• Change in posterior occluso-vertical dimension (in mm)
• Change (in mm²) in the surface area of maximum occlusal contact regions, based on digital bite registration records.

Statistical analysis will involve comparing changes in linear (mm) and surface area (mm²) measurements across the four study groups at multiple time intervals (T0-T1, T0-T2, T0-T3, T1-T2, T1-T3, and T2-T3). Data distribution will be assessed using the Shapiro-Wilk test. Group comparisons will be performed using ANOVA, Kruskal-Wallis, chi-square, and two-way mixed ANOVA or F1-LD-F1 design, as appropriate. Bonferroni correction will be applied for post hoc tests, and p ≤ 0.05 will be considered statistically significant. Analyses will be conducted using SPSS v.23 and R software.

Inclusion Criteria:

Inclusion Criteria for Participants

• No skeletal or dental anomalies,
• ASA (American Society of Anesthesiologists) physical status classification of I or II ,
• Frankl Behavior Rating Scale score of 3 or 4,
• In the mixed dentition stage,
• Fully erupted permanent first molars in occlusal contact at maximum intercuspation
• No acute dental pain or need for emergency treatment,
• Presence of at least two primary molars with carious lesions scored as 3, 4, or 5 according to the ICDAS (International Caries Detection and Assessment System),
• Presence of an antagonist tooth for the molar planned to receive Hall Technique,
• Provision of verbal and written informed consent by the participant and legal guardian after reading or listening to the consent form and fully understanding its content.

Inclusion Criteria for Tooth

Based on Clinical Examination:

• No history of prolonged pain in response to thermal or chemical stimuli, or spontaneous pain suggestive of irreversible pulpitis,
• No sensitivity to percussion or palpation,
• Absence of both pathological and physiological mobility,
• No signs of swelling, fistula, or discoloration,
• Sufficient remaining tooth structure to retain a preformed stainless steel crown.

Based on Radiographic Examination:

• Radiolucent lesion associated with dental caries located within the outer one-third to two-thirds of the dentin, with a visible band of normal dentin between the lesion and the pulp,
• At least two-thirds of root length present,
• No signs of internal or external pathological or physiological root resorption,
• Intact lamina dura and normal periodontal ligament space,
• No periradicular bone loss surrounding the roots,
• No calcified masses in the pulp chamber.

Exclusion Criteria:

• Individuals with serious systemic or psychological conditions
• Participants who fail to attend follow-up appointments
• Those who exhibit excessive fear or anxiety reactions and are unable to cooperate during treatment

The biostatistician performing the data analysis will be blinded to group allocation. The clinician performing treatment and model analysis will not be blinded.