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Biomedical subjects

R DeLong

Publications and source records attributed to R DeLong.

At least 37 records · Page 2Linked to original sources
PubMed1992

A piezoelectric film transducer for dental occlusal analysis.

Occlusal load, contact sequence and location are necessary parameters for the study of dental biomechanics, simulation and clinical treatment planning. A piezoelectric film transducer for dental occlusal analysis was developed and in vitro evaluations of the transducer were conducted in a servohydraulically driven artificial mouth. The transducer is designed to provide occlusal contact force information. The transducer thickness (9 mum) minimizes interference with normal mandibular closure. Voltage outputs from the sensor as a result of occlusal contacts generated in the artificial mouth were sampled through a computer controlled data acquisition system. The transducer output recorded by the data acquisition system was calibrated to the applied load in the artificial mouth. The output of the piezoelectric film was evaluated during varying loads, cycling frequencies, surface areas of contact, and transducer surface areas. The preliminary studies indicate that the piezoelectric film holds out considerable promise and with further development may be well suited as a diagnostic tool in dental occlusal analysis.

Biomechanical Phenomena↗
PubMed1991

Independent movement of cusps during occlusal loading.

An integrated experimental and theoretical approach is proposed for the evaluation of stress within a natural tooth during bruxing. A physical model was developed that used strain gauges bonded to the buccal and lingual heights of contour of extracted, intact maxillary premolar teeth for the validation of a two-dimensional finite element model of a natural, intact maxillary premolar tooth. Results from the finite element model were in good agreement with the experimental results. The tooth exhibits "cuspal independence", which describes the relative independence of the loaded cusp from the remaining cusp that is not loaded. In other words, the control cusp does not demonstrate significant strain when the adjacent cusp is loaded. The overall stiffness of the tooth does not appear to be significantly affected by separation of the enamel of the two cusps and appears to be primarily a function of the dentin.

Bicuspid↗
PubMed1991

An artificial oral environment for testing dental materials.

Two servo-hydraulic actuators were combined to produce the force movement cycle of human mastication. A closed-loop method of control was used which functions in a manner similar to the human neuromuscular system. The horizontal closed-loop uses a linearly variable differential amplifier (LVDT) to monitor the position. The vertical closed-loop uses both an LVDT to monitor position and a load cell to monitor force with a "mode switch" being made between the two mechanisms of control. A function generator is used to produce a sine wave which is modified to produce the movement and force programs for the two servo-hydraulic actuators. An acrylic chamber was constructed which contains the test samples and maintains an environment similar to that which occurs in the mouth. Natural or artificial saliva maintained at 37 degrees C is continuously circulated through the chamber. The time to complete a single chewing cycle was decreased by eliminating that part of the cycle where no force is produced. This enables the chewing rate to be increased to four cycles per second. The wear produced in the artificial mouth was found to have a high correlation with clinical wear if 250,000 cycles in the artificial mouth are assumed to be equivalent to one year in the human mouth.

Dental Materials↗
PubMed1990

Enamel abrasion from ceramic orthodontic brackets under an artificial oral environment.

The purpose of this investigation was to examine the potential enamel abrasion on contact with stainless steel and various ceramic orthodontic brackets under a simulated oral environment. Three groups of eight lower premolar ceramic brackets and one group of eight stainless steel brackets were used from four different manufacturers. An upper premolar was brought in contact with the bracket bonded to a lower premolar tooth and subjected to a lateral excursion type of movement by the artificial oral environment. A constant load of approximately 2 lb was used for the masticatory force. The rate of chewing was 1 cycle/sec. The teeth were subjected to 15, 60, and 100 masticatory cycles. The before-and-after occlusal surfaces of the upper premolars were compared by means of a computerized profiling system and the enamel volume loss was calculated. Qualitative changes, such as rate of enamel wear, were examined visually by means of computer graphics and the scanning electron microscope. Abrasion scores (mean +/- SD) in mm3 were 0.015 +/- 0.01 from the metal brackets and 0.135 +/- 0.103, 0.255 +/- 0.242, and 0.581 +/- 0.524 from the three ceramic bracket groups. The abrasion scores were significantly different at p less than 0.05. Ceramic brackets caused significantly greater enamel abrasion than stainless steel brackets. Artificial mouth in vitro testing gave a good indication of clinical performance of orthodontic brackets.

Aluminum↗
PubMed1989

The wear of enamel when opposed by ceramic systems.

The wear of enamel when opposed by different ceramic systems was investigated by use of an artificial oral environment. Cerestore, Dicor, and Ceramco discs were opposed by recently extracted natural teeth. The samples were exposed to 300,000 defined masticatory cycles under physiologic conditions. It was found that the wear mechanisms for Cerestore and Ceramco porcelains were similar, but were distinctly different from that of Dicor. The total volume loss of enamel was 50% less when opposed by Dicor, than when opposed by either the Cerestore or Ceramco porcelains. None of the samples had any external shade applied to their surfaces.

Aluminum↗
PubMed1989

Enamel surface abrasion from ceramic orthodontic brackets: a special case report.

The purpose of this report is to present a dramatic case of enamel abrasion from ceramic orthodontic appliances that was discovered only after appreciation of the initial findings of a study underway at the Department of Orthodontics, University of Minnesota. An artificial oral environment used in this study to simulate mastication also is described. The potential detrimental effects of ceramic appliances on tooth contact are discussed. All aspects of any new material should be investigated before its clinical application to prevent undesired side effects.

Adult↗
PubMed1988

The effect of the resilient-layer distal-extension partial denture on movement of the abutment teeth: a new methodology.

The new methodology presented in this article is simple, reliable, and accurate. The testing casts represented a reasonable simulation of human dentition. The artificial mouth reproduced major mandibular movement in a physiologic manner and applied controlled load instead of static load. The abutment movement sensor and the strain-gauge configurations suggested showed a higher level of sensitivity, accuracy, and reproducibility. This method was intended to be used for in vitro studies of RPD designs. It allowed recording of occlusal forces around the abutment tooth in the three axes of motion simultaneously.

Alveolar Process↗