Contact Area Indicates Masticatory Performance for Neutro-Occlusion, not for Malocclusion

Objectives: Occlusal contact area (OCA) has long been recognized as an indicator of masticatory performance (MP), but historically required individual and laborious measurement. Meanwhile, digital design software could allow automatic quantification based on digitized dental casts, and thus provide routine, built-in prediction of MP. For this purpose, we aimed to determine the optimal evaluation strategy, including patients with dentofacial deformities, where optimization of MP is a main therapeutic goal.
Methods: A cross-sectional study involved 40 subjects (mean age = 28, n females = 29), including 22 subjects with neutro-occlusion and 18 dysgnathic patients with indication for surgical intervention. During the study appointment, MP was measured by comminution of standardized test food (Optosil, Kulzer) using digital sieving method. For OCA, dental impressions were taken (Flexitime Dynamix Putty, Kulzer). Gypsum casts were digitized and aligned in maximum intercuspidation using CAD software. The maxilla was enlarged with offsets between 100 and 800 µm in 50 µm increments to simulate different interocclusal areas. OCA was calculated from the interpenetration of the occlusal surfaces in 2D and 3D projections. Spearman correlations between MP and OCA were investigated.
Results: Evaluation strategies resulted in significantly different OCAs (range 11-355 mm²). Masticatory performance was lower in dysgnathic patients (X50 mean 5.35, range 4.72-5.91) than in controls (X50 mean 4.62, range 3.57-5.14). For control group, contact area correlated significantly with masticatory performance for distances up to 800µm, with strongest correlation at 200µm in combination with 3D projection (r=-0.74). For dysgnathic patients, only weak, non-significant correlations were observed.
Conclusions: Considering the limitations of a young population with intact, unworn dentition and solid test food, OCA appears a suitable indicator of MP in individuals with neutro-occlusion and could be routinely used as such in dental design software. For dysgnathia patients, the concept does not seem valid as other factors seem more determinant.