Formation of carbonates in the Tatahouine meteorite.

The Tatahouine meteorite, in southern Tunisia, shows terrestrial contamination that developed during 63 years of exposure on Earth's surface. Samples collected on the day of the fall in 1931 contained fractures, with no secondary minerals, whereas samples collected in 1994 contain calcite aggregates (70 to 150 micrometers) and rod-shaped forms (100 to 600 nanometers in length and 70 to 80 nanometers in diameter) on the fractures. Carbon isotope analysis of the carbonates within the Tatahouine meteorite [delta13C = -2.0 per mil Pee Dee belemnite standard (PDB)] and the underlying ground (delta13C = -3.2 per mil PDB) confirm their terrestrial origin.

Asymptomatic morphologic variations in the mandibular condyle-ramus region.

The subjects in this study exhibited considerable condylar anatomic abnormalities and discrepancies in the absence of subjective symptoms. Differences in the mandibular condyle-ramus length from one side of the mandible to the other were found. Enlargements and bony irregularities in the region of the mandibular angle were observed and appear to be associated with increased muscular activity. All these anatomic changes are visible on routine panoramic radiographs and may be predisposing factors for subjective symptoms, especially when alteration of maxillomandibular relations are made.

Subluxation of the temporomandibular joint.

The temporomandibular joint in actual function does not resemble other joints in the body in that the condyles leave their fossae with maximal opening and in some subjects with only a 35 mm. opening. The term subluxation, with its implication of abnormality, does not seem applicable to a normal movement. While significant problems, such as dislocation, locking, and loud clicking, can occur with such anterior-to-the-fossae movements, they are relatively rare. Most temporomandibular problems are associated with confinment of the condyles to their fossae with limited or no translatory condylar movement. A recognition of the normal range of condylar movement would lessen iatrogenic abuse of this area.

The relationship of vertical dimension of atypical swallowing with complete dentures.

A number of subjects were studied cineflourographically during swallowing, and their vertical dimensions of occlusion were clinically evaluated. The subjects who had reduced vertical dimensions of occlusion were older than those with normal vertical dimensions, their dentures were older, their total years with complete dentures were more, and the tendency to swallow without opposing tooth contact was greater. The cumulative evidence indicates that such aberrant muscle activity might contribute to the regressive changes found in complete denture wearers.

Characteristics of temporomandibular joint problems.

A review of the characteristics of 145 patients with temporomandibular joint and myofascial pain-dysfunction syndrome is presented. The material includes both temporomandibular and myofascial involvements. The evidence supports the psychophysiologic etiology theory for most patients. This does not exclude anatomic abnormalities which may be present in such patients nor anatomic abnormalities which may be present without psychogenic causes. The lack of awareness of the range of condylar movement is contributory to iatrogenic trauma. A classification of etiologic factors is proposed. The superimposition of one upon another can create a severe problem. The superimposition of two upon a third can create an unusually severe problem.

Vertical dimension measurements.

Changes in the vertical dimension of mandibular rest position for 50 subjects wearing complete dentures were measured on cephalometric radiographs between lead markers attached to the face and between skeletal landmarks. Measurements between the landmarks were compared on radiographs made without (edentulous) and with (edentoprosthetic) the dentures in the mouth. The findings support the following statements. The facial structures tended to mask the positional changes of the mandible. The rest position of the edentulous mandible tended to vary within the time frame of the cephalometric examination. The range of measurements of the skeletal rest position appeared greater with greater denture age and experience of the subjects. The rest position of the edentoprosthetic mandible (with dentures in the mouth) was more frequently constant when measured skeletally than when measured facially and more frequently constant than the edentulous mandibular rest position. The edentulous mandibular rest position of most subjects was increased upon insertion of dentures. The rest position was decreased for the remainder of the subjects. As a group, those subjects whose mandibular rest position decreased (up-shifted) with insertion of dentures had older dentures and more years of denture-wearing experience than subjects whose mandibular rest position increased (down-shifted) with insertion of dentures. The edentulous mandibular rest position does not seem particularly suitable for determination of the vertical dimension of occlusion and appears somewhat less suitable when facial measurements are used.