Compressibility of two polyvinyl siloxane interocclusal record materials and its effect on mounted cast relationships.

STATEMENT OF PROBLEM: Addition silicones (polyvinyl siloxanes) are universally accepted as accurate and stable impression materials. They have also gained popularity as interocclusal record materials. However, it has not been defined if it is possible to work with polyvinyl siloxanes without changing the recorded maxillomandibular relations. PURPOSE: This study examined the compressibility of 2 addition silicones as interocclusal record materials, analyzing the changes of maxillomandibular relations at the condyle region when different compressive forces are used to stabilize articulated casts. MATERIAL AND METHODS: Sixteen interocclusal records, obtained from the same patient (8 of each polyvinyl siloxane, Blu-Mousse, Fast Set), were interposed between the patient casts in a new measuring system obtaining 48 curves of load versus maxillomandibular positional changes in 3 axes (x, y, z). These curves were compared with curves obtained with the casts in maximum intercuspation without interocclusal records (reference curves). Analysis of variance was used to compare maxillomandibular positional changes among the 3 groups (n = 48 each): Blu-Mousse, Fast Set, and control group or maximum intercuspation without interocclusal record. RESULTS: There was no significant change in maxillomandibular relations when forces up to 1 kgf were applied to stabilize the casts related by means of Blu-Mousse and Fast Set addition silicone interocclusal records. CONCLUSION: It is possible to use these polyvinyl siloxanes as interocclusal record materials without changing the recorded maxillomandibular relations.

Reproducibility and condylar position of a physiologic maxillomandibular centric relation in upright and supine body position.

Better understanding of the physiologic features of the masticatory system has led to the evolution of the concept of maxillomandibular centric relation from the mechanical to physiological bases. However, the reproducibility of physiologic methods for centric relation determination has been criticized. In this clinical study the swallowing technique was modified to establish a physiologic centric relation in a reproducible manner. Condylar and disk positioning and reproducibility of the proposed modified swallowing technique (MST) were compared with the same parameters of a traditional technique, namely, the chin point guidance technique (CGT). Both techniques were studied with the patient in the upright and supine positions. Three interocclusal records were obtained for each technique-position combination for each of the 30 patients. The recorded maxillomandibular relations were analyzed on the three-dimensional analyzer. MST positioned the condyles in a more superoanterior position than did CGT, which was interpreted as a better seating of the condyles and disk in the articular fossae. There was no significant difference in reproducibility between MST and CGT on x, y, or z axes (p > 0.05), indicating that it is possible to establish a physiologic centric relation in a reproducible manner. The term "functional centric area" was proposed in this study to define a neuromuscularly determined centric occlusal scheme.