R. Ernest Clark

Comparative Distortion in Three-Unit Fixed Prostheses Joined by Laser Welding, Conventional Soldering, or Casting in One Piece

This study was conducted to evaluate objectively the relative distortion in three-unit bridges joined by laser welding, soldering, or one-piece casting techniques, Each procedure was replicated five times. Laser welding and one-piece castings of three units were found to be significantly superior to soldering. The laser welding was most reliable.

Anatomic basis for disk displacement in temporomandibular joint (TMJ) dysfunction.

This study was designed to investigate the site of lateral pterygoid muscle insertion into the temporomandibular joint (TMJ) disk, and the relationship between that attachment and the disk displacement. One hundred and ten TM joints from 78 cadavers were collected and sectioned in the sagittal plane. Sixty-two unilateral specimens were available and 16 additional specimens were selected randomly from the remaining cadavers in which both condyles were available. Thus statistical comparisons were not confounded by autocorrelation and were based on 78 independent specimens. The sites of muscle attachment in relation to the disk were identified histologically. Of the 78 joints 49 had anterior disk displacement. Of the 42 cases with insertion directly into the disk, 30 had anterior disk displacement. In contrast, only 19 of the 36 disks without direct muscle insertion were displaced. This finding indicated a statistically significant relationship between functional muscle attachment and disk displacement (chi 2 = 9.28, df = 1, p = 0.006). However, the superior head of the lateral pterygoid muscle (SLP) may not be the precipitating factor for anterior disk displacement even though it does coordinate disk movement on closure. Since other factors (e.g., trauma) can result in disk displacement, the SLP can maintain disk displacement only when it inserts directly into the disk. In cases of normal disk arrangement and condylar attachment, the muscle may not play a clinically significant role in disk displacement because disk attachment at the medial and lateral poles of the condyle allows the disk to move freely with the condyle.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative description of the shape of the mandible

The purpose of this study was to provide quantitative data on the shape of the mandible at the period around the pubertal growth spurt and to test the hypothesis that early mandibular shape may influence the amount and direction of subsequent mandibular growth. Longitudinal data from lateral cephalograms of 55 white female and 39 white male subjects were used. The mandibular outline from articulare to gnathion was analyzed into cosine curves, according to the Fourier equation. The resulting Fourier coefficients, representing mandibular outline shape, were analyzed statistically in relation to age, sex, craniofacial pattern, and mandibular growth rotation. Statistically significant growth changes of the Fourier coefficients were observed, especially during the postpubertal period, indicating a decrease in the gonial angle with age. Sex-related differences in shape were observed at all ages, male subjects showing a more rounded shape of the mandible than female subjects. Mandibular shape, as represented by the Fourier coefficients, was correlated to cephalometric variables, indicating mandibular inclination, but only poorly to cephalometric variables, indicating anteroposterior jaw relation. Total rotation of the mandible during growth could not be predicted by mandibular shape.

Differential accuracy of silicone-body and self-curing resin interocclusal records and associated weight loss

Abstract Two types of one brand of silicone-body impression material and two brands of self-curing resin were tested as interocclusal recording materials to evaluate their dimensional stability and associated weight losses due to volatiles. Silicone-body interocclusal records were shown to be more reliable than self-curing resin records. However, all of the materials tested exhibited some degree of weight loss and dimensional change over time.

Differential accuracy of silicone-body interocclusal records and associated weight loss due to volatiles

Summary Three brands of silicone-body impression material were tested to evaluate dimensional stability and associated weight loss due to volatiles. The three materials displayed weight losses over time which were generally proportional to their respective dimensional changes.

Determination of the accuracy of laminated wax interocclusal wafers

The variables that were selected as relevant factors in the production of inaccuracy in laminated wax interocclusal wafers were found to be highly significant statistically, mostly with confidence levels greater than 99%. These confidence levels, however, relate to experimental comparisons in the absence of any absolute standard. Clinical impact is difficult to assess without such standards. Laminated wax interocclusal wafers are highly technique sensitive. Variations in treatment and handling procedures are important factors in assessing their accuracy. Wafers that were both laminated and metalized were found to be the most accurate and dimensionally stable. However, exact reproductions of the original wax recordings are unlikely and were not achieved in this investigation.

Pulp Reaction to a Resin-Bonded Quartz Composite Material

Pulp responses induced by a resin-bonded quartz composite material, with and without liners, were compared with those induced by zinc oxide-eugenol at 7, 28, and 84 days after Class V cavity preparations were made in 96 intact dog teeth. Only the unlined composite material elicited a significant inflammatory response.

Affecting Upper Extremity Strength by Changing Maxillo-Mandibular Vertical Dimension in Deep Bite Subjects

Abstract The effect of vertical dimension of occlusion (VDO) on maximizing isometric deltoid strength (IDS) was measured in subjects with deep overbite. Sixteen female dental students with deep dental overbite and no history of temporomandibular joint disorder (TMD) were used as their own control and tested for isometric strength of the deltoid muscles, using a hand held strain gauge. Measurements were taken under four mandibular conditions: 1. habitual occlusion; 2. mandibular rest position; 3. biting on a bite elevating appliance set to the functional criterion of peak IDS; and 4. biting on a placebo appliance. Results showed that in deep bite subjects, isometric deltoid strength in habitual occlusion was significantly less than in the mandibular rest position. Isometric deltoid strength with the bite elevating appliance was significantly greater than isometric deltoid strength in habitual occlusion, as well as in the mandibular rest position. Isometric deltoid strength achieved in habitual occlusion and placebo did not differ. Results of this study support previous findings indicating that a change in the VDO will affect isometric strength of the upper extremities.

Telemetric comparison of centric relation and centric occlusion reconstructions

Abstract Two complete fixed prostheses built with the occlusion in centric relation and with occlusion in the subjects existing centric occlusal position were tested with telemetry under conditions of actual use. The findings indicate that the subject did not use the centric relation position but accepted the prosthesis built to her preexisting centric occlusion. These findings are consistent with our previous results of telemetric studies conducted on patients with three-unit fixed prostheses.

Apparent Digital Vasomotor Hypotonicity in the Remission Stage of Acute Necrotizing Ulcerative Gingivitis

Longitudinal studies were performed on patients with recurrent attacks of acute necrotizing ulcerative gingivitis (ANUG) during remission. Their psychophysiologic responses to standardized stress procedures (cold-pressor stimulation, breath holding, and immersion of the fifth digit in ice water) were tabulated. The data suggested that a peripheral vasomotor defect in ANUG may be reflected in elevated digital temperatures and general hypotonicity of the digital vasomotor system.