Molar-incisor hypomineralization (MIH) frequently affects permanent first molars and increases the risk of rapid post-eruptive breakdown and restorative failure. Stainless steel crowns (SSCs) are considered a reliable treatment option for severely affected molars; however, SSC placement may temporarily alter the occlusal vertical dimension and occlusal contacts. Quantitative evidence describing the occlusal adaptation process following SSC placement in MIH-affected permanent molars is limited. This prospective longitudinal clinical study aims to evaluate occlusal adaptation after SSC placement using the modified Hall technique in MIH-affected permanent first molars. Forty-six children will be included. Intraoral scans will be obtained at baseline, immediately after treatment, and during follow-up visits up to 3 months. Digital models will be superimposed to measure three-dimensional changes in cusp position, occluso-vertical dimension, and occlusal contact area. Temporomandibular joint function and periodontal parameters will also be assessed. The results are expected to provide quantitative evidence on occlusal adaptation following SSC treatment in MIH-affected molars.
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.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
46
A preformed SSC will be placed on the selected MIH-affected first permanent molar using the modified Hall technique. The procedure will involve selective caries removal while maintaining a minimally invasive approach and avoiding conventional tooth preparation. Local anesthesia will be administered only when clinically indicated. Digital Scan and Bite Registration Schedule * T0 (Baseline): Immediately before crown placement * T1 (Immediate): Immediately after crown placement * T2 (Two Weeks): Two weeks after crown placement * T3 (One Month): One month after crown placement * T4 (Three Months): Three months after crown placement. At each time point (T0-T4), digital scans of both the maxillary and mandibular arches will be obtained, and a buccal bite registration will be recorded. 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.
Ankara Yıldırım Beyazıt University Faculty of Dentistry
Ankara, Keçiören, Turkey (Türkiye)
Cusp Tip Displacement (Linear Measurement in mm)
Positional changes of the mesiobuccal, mesiolingual/palatal, distobuccal, and distolingual/palatal cusp tips of all first permanent molars, including the crowned tooth, will be measured and recorded in millimeters using digital model superimposition across time points. In cases where one or more cusp tips of the crowned tooth are absent due to coronal breakdown, the distances between the corresponding cusp tips of the stainless-steel crown and their projected anatomical locations on the original tooth surface will be measured.
Time frame: From crown placement to 3 months post-placement
Anterior Vertical Distance (Linear Measurement in mm)
The vertical distance between the cusp tips of the maxillary and mandibular primary/permanent canines located on the same side as the crowned tooth will be measured at each time point: 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). Measurements will be compared across time points to evaluate potential anterior vertical positional changes associated with SSC placement. If the canine on the treated side is not clinically visible in the oral cavity, the measurement will be performed between the opposing canines in the contralateral arch.
Time frame: From crown placement to 3 months post-placement
Posterior Vertical Distance (Linear Measurement in mm)
The vertical distance between the mesiobuccal cusp tips of the maxillary and mandibular first permanent molars on both the right and left sides will be measured and recorded in millimeters. Measurements will be obtained at each time point (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) and compared across time points to evaluate posterior vertical positional changes.
Time frame: From crown placement to 3 months post-placement
Change in Maximum Occlusal Contact Area (Surface Area Measurement in mm²)
The change in maximum occlusal contact areas (in mm²) will be analyzed based on bite registration records. Since the 3Shape software does not allow direct quantitative measurement of occlusal contact areas, the analysis will be performed using the color-coded occlusal contact maps generated by the software. Specifically, the red zones representing the areas of maximum contact will be identified from the screenshots, and their surface areas will be measured using the ImageJ software. This analysis will be two-dimensional, based on calibrated screenshots, and will provide a comparative assessment of occlusal contact area changes across different time points: 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.
Time frame: From crown placement to 3 months post-placement
Assessment of Temporomandibular Joint Function (Helkimo Dysfunction Index Score)
Temporomandibular joint (TMJ) function will be assessed at predefined follow-up time points: T0 (baseline, immediately before crown placement), T2 (two weeks after crown placement), T3 (one month after crown placement), and T4 (three months after crown placement) using a pediatric-adapted modification of the Helkimo Clinical Dysfunction Index. The index includes five parameters: maximum mouth opening, deviation during opening, joint function impairment, TMJ pain on palpation, and masticatory muscle pain. Each parameter is scored as 0 (none), 1 (mild), or 2 (severe), and the total composite dysfunction score (range: 0-10; higher scores indicate worse dysfunction) is obtained by summing all parameters. Scores will be categorized as 0 = no dysfunction, 1-4 = mild (Grade I), 5-9 = moderate (Grade II), and ≥10 = severe dysfunction (Grade III), and recorded and compared across time points to evaluate changes in TMJ function associated with SSC placement.
Time frame: From crown placement to 3 months post-placement
Assessment of Gingival Status (Gingival Index Score)
The gingival status of the tissues surrounding the SSC-treated teeth will be evaluated at each time point: T0 (immediately before crown placement), T2 (two weeks after crown placement), T3 (one month after crown placement), and T4 (three months after crown placement). The clinical condition of the gingival tissues will be assessed using the Löe and Silness Gingival Index. Gingival conditions will be assessed at the marginal gingiva and proximal surfaces using a periodontal probe. Scores are defined as follows: 0 = normal healthy gingiva; 1 = mild inflammation (slight color change and edema, no bleeding on probing); 2 = moderate inflammation (redness, edema, glazing, bleeding on probing); 3 = severe inflammation (marked redness and edema, ulceration, possible spontaneous bleeding). Index scores will be recorded and compared across time points to evaluate changes in gingival health associated with SSC placement.
Time frame: From crown placement to 3 months post-placement
Assessment of Plaque Accumulation (Plaque Index Score)
Plaque accumulation around the SSC-treated teeth will be evaluated at each time point: T0 (immediately before crown placement), T2 (two weeks after crown placement), T3 (one month after crown placement), and T4 (three months after crown placement).Plaque accumulation will be assessed using the Silness and Löe Plaque Index. Assessments will be performed at the marginal gingiva and proximal surfaces using a periodontal probe. Scores are defined as follows: 0 = no plaque; 1 = plaque detectable only by probe or disclosing, not visible clinically; 2 = visible plaque limited to the gingival margin; 3 = abundant plaque accumulation along the gingival margin, including interproximal areas. Index scores will be recorded and compared across time points to evaluate changes in plaque accumulation associated with SSC placement.
Time frame: From crown placement to 3 months post-placement
Assessment of Probing Depth (Linear Measurement in mm)
The periodontal status of the tissues surrounding the SSC-treated teeth will be evaluated at each time point: T0 (immediately before crown placement), T2 (two weeks after crown placement), T3 (one month after crown placement), and T4 (three months after crown placement). Probing depth will be measured in millimeters using a periodontal probe at four sites (mesiobuccal, distobuccal, mesiolingual/palatal, and distolingual/palatal) around each SSC-treated tooth. The recorded measurements will be compared across time points to evaluate potential changes in periodontal tissue status associated with SSC placement.
Time frame: From crown placement to 3 months post-placement
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