Digital Quantification of Occlusal Contacts: A Methodological Study.

OBJECTIVE: To compare the reliability of digital occlusal contacts quantification and the validity of digital occlusal contacts quantification with traditional methods used for occlusal contact determination. SUBJECTS AND METHODS: Thirty participants, all of whom were students at the Sahlgrenska Academy, University of Gothenburg in Gothenburg, Sweden, were included in the study. Three different methods were used to evaluate occlusal contacts: (I) a digital examination of the patients' casts, using the Ortho 3D Models (O3DM) software and measuring the total occlusal contact area in square millimeters (DE); (II) an examination involving the measurement of the total number of occlusal contacts on stone casts mounted in an articulator (AE); and (III) a clinical examination with the measurement of the total number of occlusal contacts with 8 µm-thick articulating foil (CE). RESULTS: The repeated digital measurements (same casts scanned multiple times) showed a significant correlation of 0.85 (p < 0.01), which shows a diagnostic consistency. Furthermore, there was a significant correlation between the results obtained with the DE method and the AE of 0.41 (p < 0.05), and between those acquired with the AE method and the CE of 0.37 (p < 0.05). However, no significant correlation was found between the DE method and the CE method with a correlation coefficient of 0.10 (p > 0.05). CONCLUSIONS: Digital casts can be used for quantification of the total occlusal contact area (in mm2) owing to the high reliability of repeated measurements and the strong validity of the method compared to traditionally employed stone cast measurements.

Can We Rely on the Activated Clotting Time to Measure Heparin Anticoagulation? A Clinical Evaluation of Two ACT Monitors.

The sensitivity to heparin during cardiopulmonary bypass (CPB) is determined by patient-specific characteristics and is assessed by the whole blood activated clotting time (ACT). We aimed to examine reliability measures between two different ACT monitors using Bland-Altman analysis: bias should not exceed 50 ± 50 seconds for measurements performed during CPB or 10 ± 10 seconds before and after CPB. The ACT response should be linear in relation to the concentration of heparin in plasma. Twenty patients (n = 20) aged 20-80 years and admitted for coronary artery bypass surgery were enrolled to this clinical observational study. ACT values and antifactor Xa were sampled: 1) before induction of anesthesia, 2) after heparin bolus, 3) during CPB at the start of rewarming, 4) at weaning from CPB, and 5) after heparin reversal. The evaluation comprised the Hemostasis Management System Plus™ (HMS, Medtronic Inc., Minneapolis, MN) and i-STAT™ (Abbott, Point of Care Inc., Princeton, NJ). Bias for the HMS Plus™ vs. i-STAT™ was +105 ± 119 seconds for measurements during CPB and +2.8 ± 11.7 seconds before and after CPB. Associated limits of agreement for the observed bias were ±235 and ±23 seconds, respectively. Inter-device correlation of ACT values was .46 (p < .001) during CPB; otherwise .48 (p = .02). Both devices produced ACT values unrelated (<10%) to the measured heparin concentration. The use of multivariable regression analysis demonstrated an independent association between the ACT measurement and hematocrit, however, not with the plasma concentration of heparin. ACT monitors demonstrate unacceptable bias differences, combined with wide limits of agreement. The ACT response correlated with hematocrit, but not with the actual heparin concentration.