Influence of Clinical Crown Length and Alignment Method on Accuracy and Buccal Occlusal Scanning Time in Maxillo-Mandibular Registration Using an Intraoral Scanner.

OBJECTIVES

To evaluate how clinical crown length and alignment method affect the accuracy and buccal occlusal scan time required for digital maxillomandibular relationship registration.

METHODS

Four maxillary-mandibular cast pairs with clinical crown lengths of 2, 4, 6, or 8 mm (G2-G8) were fabricated. Each pair was mounted in maximum intercuspation and scanned with a desktop scanner to generate reference models. Corresponding scans were obtained with an intraoral scanner (TRIOS 5). Ten occlusal records per group were registered using automatic and manual alignment. For G2, buccal occlusal scans of shorter durations that did not trigger automatic registration were additionally performed and manually aligned. Trueness was assessed by measuring positional deviations of reference cubes between test and reference datasets.

RESULTS

Crown length significantly affected registration trueness, which decreased as clinical crown length decreased (p < 0.05), whereas automatic and manual alignment showed comparable accuracy within all groups. Shorter crowns (G2 and G4) produced greater dentition distance deviations than longer crowns (G6 and G8) (p < 0.05). The scan time required to trigger automatic registration increased as crown length decreased, reaching up to five times longer in G2 than G8 (p < 0.05). In G2, shortening the buccal occlusal scan duration and subsequently performing manual alignment did not significantly affect registration accuracy (p > 0.05).

CONCLUSION

Reduced clinical crown length may compromise the overall trueness and efficiency of digital maxillomandibular registration, although regional deviations do not necessarily increase uniformly across the dental arch. Manual alignment achieves comparable accuracy with shorter scanning time, particularly in dentitions with markedly reduced clinical crown exposure.

CLINICAL SIGNIFICANCE: For patients with short clinical crowns, manual alignment may shorten buccal occlusal scanning time without compromising registration accuracy, potentially reducing the risk of artifacts related to patient movement.