Investigation of the effect of magnetic retention systems used in prostheses on buccal mucosal blood flow.

The purpose of this study was to investigate the probable effects of the magnetic field produced by dental magnets on neighboring capillary circulation. Ten subjects were used. Transparent acrylic resin devices were prepared to receive the dental magnets and were used continually by subjects except during sleep. The maxillary buccal mucosal blood flow was measured on both sides (control and experimental) in the same subjects before the use of dental magnets and after 3, 7, 15, 30, and 45 days by the 133Xe clearance technique. Upon analysis it was found that the difference in blood flow between the control and experimental sides was insignificant (P greater than .05). The decrease in blood flow as time progressed was attributed to the pressure exerted by the oral devices rather than by the effect of the magnetic field.

Effect of a dilacerated root on stress distribution to the tooth and supporting tissues.

The configuration of the root of a prospective abutment tooth has a significant influence on its potential load-bearing capacity. Dilaceration is an angulation in the root or crown. This abnormality may also affect the stability and longevity of an abutment. Finite element stress analysis was used to investigate the effect of a root dilaceration on stress distribution to the tooth and its supporting structures. A normal and a dilacerated single-rooted tooth under three loads (axial, distooblique, and mesio-oblique) were analyzed and compared. The results indicated that a dilaceration concentrates the stresses in the supporting structures and may be taken into consideration as a risk factor in abutment selection.

Effect of splinting on abutment tooth movement.

The effect of splinting on abutment tooth movement was investigated in an in vitro study. An acrylic resin mandibular model with missing molars and a removable partial denture framework were constructed. The roots of the premolars and edentulous ridges were coated with silicone rubber. A modified Ney surveyor was used for load application, and abutment tooth movement measurements were made with a macroperiodontometer. Four conditions were tested by applying unilateral loadings: 1. Single abutments of both sides 2. Load side double abutment 3. Nonload side double abutment 4. Double abutments of both sides The results showed that a significant decrease in the magnitude of movement resulted when the abutment teeth were splinted.

Effect of a resilient layer in a removable partial denture base on stress distribution to the mandible.

The results of two-dimensional finite element analyses of a mandible indicate that a resilient layer within a denture base can act as an effective "shock absorber" and may slow down ridge resorption. Finite element models of similar types can easily be used to further investigate various applications of resilient layers. The magnitudes and distributions of stresses generated in the mandible by force application to two types of a distal extension denture base were determined and compared. The results were obtained by using the finite element method of stress analysis. In the first analysis, a conventional distal extension denture base resting on the mandible was simulated. In the second analysis, the same testing force was applied to a distal extension denture base with a resilient layer between the teeth and the basal seat. The results indicated that the stress distribution was more uniform during occlusal loading through a resilient layer. The vertical displacement of the alveolar ridge under the denture base with a resilient layer was far less than that of the conventional denture base.