William C. Murphy

Magnetic resonance imaging findings in asymptomatic volunteers and symptomatic patients with temporomandibular disorders

Internal derangement has been suggested to be a cause of temporomandibular disorders. This study compared magnetic resonance imaging findings in 82 asymptomatic volunteers and 263 symptomatic patients. Disk displacement was observed in 33% of the asymptomatic volunteers and 84% of the symptomatic patients. The prevalence of trauma, headache, and other joint problems was more common in symptomatic patients. A history of general anesthesia and orthodontic treatment was not increased in the symptomatic population compared with asymptomatic volunteers. This study suggests that disk displacement is more common in symptomatic subjects.

Prevalence of dental occlusal variables and intraarticular temporomandibular disorders: Molar relationship, lateral guidance, and nonworking side contacts

STATEMENT OF PROBLEM The association between dental occlusion and the development of intraarticular temporomandibular disorders remains unclear. PURPOSE This study evaluated the prevalence of molar relationship, lateral guidance and nonworking side contacts and intraarticular temporomandibular disorders. MATERIAL AND METHODS Eighty-two asymptomatic volunteers and 263 symptomatic temporomandibular disorder (TMD) patients completed a subjective questionnaire that documented the absence of jaw pain, joint noise, locking, and a positive history for TMD. Participants also underwent clinical and dental examination for signs and symptoms commonly associated with TMD or internal derangements. RESULTS The most prevalent molar relationship was Class I. Symptomatic patients had a higher prevalence of Class II, Division 1 relationships on the left side compared with the asymptomatic volunteers with normal joints. There was a higher prevalence of canine guidance (52.04%; P <.005) on the right side in the symptomatic patients with disk displacement (DD). Volunteers with normal joints had a higher prevalence of 1 or more nonworking side contacts compared with symptomatic patients with normal joints (P <.001) and symptomatic patients with DD (P <. 001). CONCLUSION This study suggests there are no systematic dental occlusal differences that clearly separate symptomatic from asymptomatic patients. Results indicate that it is unclear as to the relationship of the 3 analyzed factors and of intraarticular TMDs.

Theory of laser-simulated surface processes

Abstract Theoretical techniques for describing laser-stimulated surface processes in a vacuum and at a gas-surface interface are presented. For adspecies-surface systems, the laser excitation of vibrational degrees of freedom is considered, and quantum-mechanical and classical models and also an “almost first-principles” treatment of the competition between multiphoton absorption and multiphonon relaxation are discussed. The laser excitation of electronic degrees of freedom is considered with respect to surface states of semiconductors and metals, for the predissociation of diatomic adspecies on metal substrates, for ionization, and for resonance fluorescence of a gaseous atom near a metal. In connection with gas-surface interactions, the influence of laser radiation on diffraction patterns and energy transfer in atom-surface scattering is explored. Collisional ionization and ion neutralization in the presence of laser radiation are discussed. The roles of partial pressure and surface coverage in laser-stimulated surface processes are analyzed. Finally, some ideas on surface waves and annealing are presented.

Association between dental occlusal variables and intraarticular temporomandibular joint disorders: Horizontal and vertical overlap ☆ ☆☆ ★ ★★ ♢ ♢♢ ♦

STATEMENT OF PROBLEM It has been suggested that dental occlusion may play a role in the development of intraarticular temporomandibular joint disorders. PURPOSE This study evaluated the relationship between horizontal and vertical overlap and intraarticular temporomandibular joint disorders. MATERIAL AND METHODS Vertical and horizontal overlap of the anterior teeth of 82 asymptomatic volunteers and 263 symptomatic patients were examined. RESULTS Fifty-five (67%) of the asymptomatic volunteers had normal joints and 27 (33%) had disk displacement. Two hundred and twenty-one patients (84%) had disk displacement and 42 (16%) had bilateral symptomatic normal joints. Horizontal overlap equal to or greater than 4 mm was more prevalent in the symptomatic patient group as compared with the asymptomatic volunteer group (p < 0.05). Vertical overlap equal to or greater than 4 mm demonstrated no significant differences. CONCLUSION Horizontal overlap equal to or greater than 4 mm was greater in symptomatic patients with intraarticular temporomandibular joint disorders.

Laser Excitation of Surface Electronic States for a One-Dimensional Semiconductor.

Abstract : A semiconductor modeled by a finite one-dimensional chain is shown to have either a continuous or discrete number of surface states. The exact number is determined by the choice of phase factors. Laser-induced charge transfer of electrons from the bulk to these surface states is also shown to be a maximum at the band edge. (Author)

Computed tomographic evaluation of the density of the temporomandibular joint meniscus

Pathologic alteration of the articular disk, including moderate calcification within the meniscus proper, has been reported to occur in many cases of TMJ dysfunction with chronic anterior meniscal displacement. The purpose of this investigation was to measure, by means of direct sagittal computed tomographic scanning technology, the density (x-ray attenuation) of the meniscus. Fifty-two joints, shown to have meniscus displacement with or without reduction (MD/MDR), and 24 symptomatic joints with normal tomograms were evaluated with the use of a GE 8800 CT scanner. Mean attenuation values were extrapolated with the use of a symmetrical (1 to 9 pixels) region-of-interest (ROI) cursor. Density gradients of the masseter muscle, lateral pterygoid fat pad, and lateral pterygoid muscle were also obtained. The results of this study showed that the mean meniscal density values were 116.7 +/- 4.2 Hounsfield units (HU) for MD subjects, 111.3 +/- 4.6 HU for MDR subjects, and 82.4 +/- 2.9 HU for subjects with symptoms. The MD and MDR density group means were significantly different (p less than 0.001) from the normal group means. A relative comparison of the meniscus density with that of the lateral pterygoid muscle, its fat pad, and the masseter muscle showed a consistent mean difference when the paired t test was used. Meniscal displacement was found to be associated with an increase in density gradient, which suggests histologic alteration.

Multiphoton-multiphonon theory of laser-stimulated surface processes

A theoretical model for multiphoton laser-excitation and multiphonon (t1) and phase (T2) relaxation of molecules adsorbed on a solid surface is developed. The ensemble-averaged excitation number for the infrared-active adspecies is obtained within a Heisenberg-Markovian approximation. The selective nonthermal excitation is sensitive to the mass ratio of the surface atoms and the adspecies, the order of the multiphonon excitation and the duration of the laser pulse.

Neutralization of ions at an electronically excited semiconductor surface

Abstract Neutralization of positive ions colliding with a semiconductor surface is studied. It is shown that the neutralization probability can be significantly enhanced if the surface exposed to the impinging ions is electronically excited. The basic reason behind this is that the impinging ions have easier access to the excited surface electrons than to bulk electrons.

Rerandomization tests for analyzing correlated data from dental studies

Dental research studies often produce relatively small data sets in which observations are serially or spatially correlated. Rerandomization tests are presented as alternatives to analysis of variance and multivariate analysis for assessing group differences using such data. Rerandomization tests are particularly useful when the investigator is unwilling to make strong assumptions about the nature of the serial correlation or the distribution of the data. Two examples are discussed that demonstrate these techniques.

Laser-induced surface migration via surface plasmons

Abstract : A classical model coupling a charged adspecies to a laser-induced surface plasmon is presented. Such coupling can enhance the rate and specify the direction of surface migration. For the particular case of an atomic oxygen ion of charge -1 adsorbed on aluminum which is exposed to CO2 laser radiation of intensity 1 W/sq cu, the velocity of migration (61.3 micrometers/sec) is five orders of magnitude greater than the usual thermal velocities observed at room temperature.