Biomedical subjects

C P Fernandes

Publications and source records attributed to C P Fernandes.

9 recordsLinked to original sources

PubMed1998

The significance of major connectors and denture base mucosal contacts on the functional strain patterns of maxillary removable partial dentures.

The purpose of this study was to investigate the biomechanical significance of major connectors and base mucosal contacts on the mechanical behaviour of maxillary removable partial dentures in vivo. Six subjects wearing maxillary dentures retained by conical crowns were selected for the study. Reflective photoelasticity and strain gauges were used to monitor the development of strain/stress during functional loading. Loading tests were performed initially with a denture design including a palatal major connector and denture bases and then repeated after removal of the major connectors and denture base alveolar muccosa contacts. The palatal major connector and the denture bases mucosal contacts contribute significantly to the rigidity and stability of removable partial dentures retained by conical crowns.

Aged↗

PubMed1994

Jaw-closing muscles: electromyographic activity of human subjects with reduced periodontal support.

The aim of this study was to compare the electromyographic (EMG) activity of jaw-closing muscles of individuals with normal and reduced periodontal bone support. Fourteen adult subjects with more than 24 remaining teeth and low levels of periodontal inflammation, were selected for the study. Subjects of the control group had 90% of the periodontal bone support left, while other subjects presented a reduction of 52% of the original periodontal bone. Chewing experiments were performed using silicone tablets, carrots and white bread. The EMG of masseter and anterior temporal muscles was performed bilaterally, using bipolar surface electrodes, and the EMG amplitude was full wave rectified, integrated and the area extension under the curve was used to access muscle activity. The results of the chewing experiments did not show any statistically significant difference in the EMG activity of the study groups, irrespective of the chewing stuff. The height of periodontal bone support did not seem to influence the electroactivity of jaw-closing muscles, indicating that reduced periodontal support might equally be able to withstand masticatory loads. Hence, individuals with reduced periodontal bone support revealed a similar EMG activity compared to subjects with normal periodontal bone support.

Alveolar Bone Loss↗

PubMed1993

Effect of plasma treatment on the wettability of elastomeric impression materials.

This study investigated the effect of "plasma treatment" on the wettability of impression materials and void formation in die stone casts. Four addition reaction silicones, one condensation reaction silicone, and one polyether impression material were used. Wettability was determined before and after plasma treatment by contact angle registration of a saturated aqueous solution of calcium sulfate (CaSO4) on flat surfaces made from the tested impression materials. Two groups of surfaces were used for each material. The surfaces in one of the groups were exposed to saliva for 5 minutes. The same impression materials were used to produce four groups of die stone casts from a master die. Two groups were produced from impressions that had been exposed to milk. One group from the exposed and one from the bare surfaces were plasma-treated before pouring. Voids in the stone casts were counted under a stereoscopic microscope. The results indicated that after plasma treatment, the drop of CaSO4 solution completely spread over the addition type silicone surfaces. The corresponding die stone casts were found to be void free. It was concluded that plasma treatment produced high-energy impression surfaces that result in void-free die stone casts from the addition type silicone materials.

Adult↗

PubMed1993

Accuracy, detail reproduction, and hardness of gypsum casts produced from silicone impressions treated with glow discharge.

Plasma treatment has been reported to improve the wettability of silicone impression materials. This study investigated whether plasma treatment of silicone impressions influenced the linear dimensional accuracy, detail reproducibility, and surface hardness of models produced from a type IV dental die stone. Five silicone impressions materials were used in this study. Linear dimensional accuracy and detail reproduction were tested according to ISO standards. Surface hardness was evaluated with a Vickers hardness test. The results indicated that plasma-treated impressions from Xantopren and Provil silicone impression materials had significantly smaller dimensional change than their respective controls, and the other materials were not influenced. The detail reproduction was superior in casts produced from plasma-treated impressions from President silicone. Surface hardness was not influenced by the treatment. Plasma treatment of silicone impressions has no negative influence on the tested physical properties of die stone models.

Analysis of Variance↗

PubMed1993

Surface properties of elastomeric impression materials.

This study investigated the wettability of commonly used elastomeric impression materials and their gypsum castability. The wettability was evaluated by determining the contact angles of drops of a CaSO4 aqueous solution on flat impression surfaces. Gypsum castability was determined by counting the number of voids formed in die stone casts made from impressions of a critical die. All specimens used in this study were exposed to saliva to simulate clinical conditions, where materials spontaneously acquire salivary origin biofilms. The results indicate that the condensation silicones and conventional addition silicones exhibited the largest contact angles and the highest number of voids. The new generation of 'hydrophilic' addition silicones had higher wettability than the conventional silicones and an improved gypsum castability, comparable to that of the polyether materials.

Adult↗

PubMed1993

Masticatory efficiency of patients treated with implant retained fixed bridges in the upper jaw over a 2-year period.

The aim of this study was to investigate the effect of the rehabilitation of the upper jaw with a fixed bridge supported by Brånemark implants upon patient's masticatory efficiency. Five patients wearing complete dentures in the upper jaw were selected for the study. Chewing tests using Optosil tablets were performed before fixture installation, immediately after bridge connection and 2 years after bridge delivery. The results indicated that treatment with fixed bridges retained by osseointegrated implants did not give immediate improvements in masticatory efficiency. Only after the subjects had enough time to adapt to the reconstruction was an improvement in the masticatory efficiency index observed.

Adaptation, Physiological↗

PubMed1993

Effect of salivary films on the surface properties of elastomeric impression materials.

Impression materials exposed to the oral cavity are subjected to spontaneous adsorption of salivary films. The aim of this study was to evaluate the effect of adsorbed salivary films on some surface properties of one condensation, four addition silicone and one polyether impression materials. The results showed that adsorbed salivary films caused an increase in the critical surface tension and in the polarity ratios for all materials tested. A reduction in the number of voids in die stone casts was also noticed, along with an improvement in the gypsum compatibility with the impression materials tested. It can be concluded that the presence and effect of salivary films should be taken into consideration when studying the surface properties of elastomeric impression materials.

Calcium Sulfate↗

PubMed1992

Surface properties and castability of elastomeric impression materials after plasma cleaning.

The wettability of impression materials is an important requirement for accurate reproduction of intraoral structures. The aims of this study were to evaluate the effect of plasma cleaning on critical surface tension and die stone castability of five silicone impression materials. Critical surface tension was calculated using a contact angle analysis according to Zisman (1964), before and after plasma cleaning. Die stone casts were produced from impressions of a master die and the area extension of the reproduction was measured planimetrically. The results showed a general increase in the critical surface tension and in the polar force component of the composite free energy for materials treated with plasma cleaning. An improvement in castability of all materials was also noted.

Analysis of Variance↗

PubMed1991

The orientation and direction of rods in dental enamel.

Enamel rods are commonly accepted as perpendicularly oriented to the tooth surface and this concept has influenced the design of cavity preparations. This investigation studied the orientation and direction of enamel rods at the outer third of the enamel plate. Fifteen human molars were randomly selected and sectioned in the buccolingual, mesiodistal, and coronal directions. Angulations of the rods at the outer surface were measured by use of a protractor superimposed on the micrographs taken by scanning electron microscope. The mean angulation for axial surfaces was 60 degrees. The enamel rods were consistently parallel to the long axis of the tooth with 55-degree mean angulation. The conclusion was that enamel rods are not perpendicular to the surface except at the edge of the cusps and occasionally at the cervical area.

Acid Etching, Dental↗