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Biomedical subjects

C J Andres

Publications and source records attributed to C J Andres.

At least 37 records · Page 2Linked to original sources
PubMed1996

An evaluation of microwave-polymerized resin bases for removable partial dentures.

PURPOSE: The hardness, porosity, and adaptation of removable partial dentures fabricated with one heat-polymerized denture base resin and two resins designed for microwave polymerization were evaluated. MATERIALS AND METHODS: Five prostheses were evaluated for each resin. Adaptation of the denture bases to the master cast was evaluated by spatial orientation and mean weight of residual impression material. The prostheses were than embedded in epoxy resin and sectioned for evaluation of resin hardness (Knoop hardness) and microporosity. RESULTS: There were no significant differences in the adaptation of the acrylic resin bases for Acron MC and Ch Lucitone. There was no significant difference in the mean Knoop hardness values for any of the resin bases near and away from the metal. None of the denture bases showed porosity greater than 100 microns. CONCLUSIONS: Both resin bases formulated for microwave polymerization were effectively polymerized around metal frameworks without adverse effects on resin hardness or porosity. Justi Denture Base material had poorer base adaptation than the other two resins.

Acrylic Resins↗
PubMed1996

The art of crown preparation: a review of principles.

The following paper consists of a literature review related specifically to the biomechanical principles that determine the design and preparation of teeth: Retention and Resistance form. Magnitude of forces, geometry of tooth preparation, taper, stress concentration, the influence of luting agents and the clinical implication of these factors upon retention and resistance are presented and discussed from the point of view of several authors from the early 1900s until the present.

Biomechanical Phenomena↗
PubMed1995

A comparison of three methods for preparing reversible hydrocolloid duplicating material.

This study compared the effects of repeated microwave oven and double-boiler liquefactions and prolonged autoduplicator storage on four physical properties of one reversible hydrocolloid duplicating material. No significant differences were observed between the linear dimensional change and detail reproduction of the three liquefaction techniques. Tear strength differences most clearly distinguished the techniques and effects of aging. Fifteen double-boiler remeltings produced tear strength values lower than those recorded for material stored in an autoduplicator for 2 weeks. Thirty microwave melting cycles still produced tear strength values equivalent to that of the autoduplicator material. After 30 melting cycles the compressive strengths of the microwave and double-boiler materials were inferior to that of the stored autoduplicator material.

Alginates↗
PubMed1995

Unusual fracture of a maxillary second premolar.

Root fractures of posterior teeth are rare and occur as a result of severe trauma. This study describes a horizontal root fracture of a maxillary second premolar discovered during routine full-mouth radiographic examination. The tooth was asymptomatic and responded positively to electric pulp testing. The patient had no recollection of a causative event nor was there physical evidence of previous trauma. It is speculated that the fracture was caused when overzealous force was used in seating an overcontoured complete gold crown restoration of an adjacent tooth.

Aged↗
PubMed1993

Influence of porcine somatotropin on endocrine and histological variables in gilts.

Thirty-six crossbred gilts (71.7 +/- .9 kg and 140.1 +/- .9 d) were assigned to one of three doses (0, 35, or 70 micrograms.kg BW-1 x d-1) of recombinant porcine somatotropin (rpST). The doses of rpST were adjusted weekly, and i.m. injections continued until d 50. Gilts were pen fed (six gilts/pen) a 17% CP corn-soybean diet (1.2% lysine and 3.2 Mcal of ME/kg). At d 50, feed intake, feed:gain ratios (P = .02), and blood urea nitrogen were decreased (P < .001) by increasing rpST doses, whereas ADG was increased (P = .04) by increasing rpST doses. Injections of rpST did not affect (P > .05) conception rate, age, or weight at puberty. Numbers of blastocysts or corpora lutea observed at d 10.4 +/- 1.5 of gestation (42.2 d after final rpST injection) were unaffected (P > .05) by rpST treatment. Anterior and posterior pituitary weights were increased (P < or = .003) linearly with rpST dose. However, liver, adrenal, and heart weights were unaffected (P > .05) by rpST. After a withdrawal period of 42.2 +/- 2.0 d, rpST increased (P < or = .02) the estimated percentage of lean by 5.8% and longissimus muscle area by 10.4%. Eighteen hours before the initial rpST injection (d 0), 10 gilts per rpST dose were catheterized. Catheterizations were repeated on d 40. The rpST or diluent was given i.m. in the extensor muscle of the neck 1 h after initiation of blood collection. Adrenocorticotropic hormone (1.4 IU/kg BW) was administered through the catheter 3 h after initiation of blood collection.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1992

Effects of environmental factors on maxillofacial elastomers: Part IV--Optical properties.

The optical properties of four currently used and two recently introduced maxillofacial prosthetic materials were evaluated after the materials were subjected to the following seven environmental variables: natural weathering; normal aging; two types of adhesives; two types of cleaning agents; and cosmetics. Optical density and color changes were evaluated. The currently used silicones Silastic 4-4210 and Silastic 4-4515, Medical Adhesive type A material, and polyurethane all showed more changes in color and optical density than the newly introduced silicone A-102 material.

Analysis of Variance↗
PubMed1992

Orbital prosthesis following temporal muscle or forehead flap reconstruction: use of optics and illusions.

Temporalis myocutaneous flap reconstruction of orbital defects may cause difficulty with fabrication of esthetic orbital prostheses because of limited space. Two patient treatments are presented to show the wide variation in defect size that may be encountered after surgical reconstruction. Methods for using optics and illusions to enhance the esthetic result are also presented.

Adult↗
PubMed1992

Effects of environmental factors on maxillofacial elastomers: Part I--Literature review.

Part I of a four-part report presents a comprehensive review of the literature pertaining to physical property testing of materials for facial and somatoprostheses. The report was conducted in preparation for testing four current maxillofacial elastomers: MDX 4-4210, Silastic 4-4515, Medical Adhesive type A, and Epithane-3, and two recently introduced materials: Silicone A-2186 and Silicone A-102.

Biocompatible Materials↗
PubMed1992

Effects of environmental factors on maxillofacial elastomers: Part III--Physical properties.

The physical properties of four currently used and two recently introduced maxillofacial prosthetic materials were evaluated after the materials were subjected to the following seven environmental variables: natural weathering, normal aging, two types of adhesives, two types of cleaning agents and cosmetics. Ultimate tensile strength, percent elongation, tear strength, and Shore A hardness were evaluated. The physical properties recorded for the currently used materials were consistent with previous studies. Although the properties of the recently introduced materials were similar to those currently in use, one of the new materials, A-2186, showed high strength values, although it was one of the softest materials tested. Unfortunately, this new material lost these advantageous characteristics as it was weakened and made harder by most of the tested environmental variables.

1-Propanol↗
PubMed1992

Effects of environmental factors on maxillofacial elastomers: Part II--Report of survey.

Part II of a four-part report presents an international survey that was conducted to determine the most frequently used materials in the fabrication of facial and somatoprostheses. The survey also solicited information about advantages and disadvantages, methods of coloring, and the perceived properties of an "ideal" material. The results of the survey indicated that the majority of prosthodontists and prosthetists are using room temperature-vulcanized silicone products, intrinsically colored with dry earth pigments or artist's pigments. The need for further research in materials for external prostheses was clearly indicated.

Color↗
PubMed1991

Influence of daily injections of porcine somatotropin on growth, puberty, and reproduction in gilts.

To determine whether recombinant porcine somatotropin (rpST) alters reproduction, 40 crossbred gilts weighing 59.1 +/- .5 kg at 125 +/- 1 d of age were assigned randomly to an experiment arranged as a 2 x 2 factorial. Eight gilts were given daily injections of diluent until they reached 104 kg BW (DW), and eight received diluent injections until puberty (DP). Twelve gilts were given rpST (4 mg/d) until 104 kg BW (PW) and 12 were given rpST injections until puberty (PP). All gilts were individually fed on an ad libitum basis an 18% CP corn-soybean meal diet (1.2% lysine and 3.1 Mcal/kg of ME). Beginning at 5 mo of age, gilts were exposed 20 min daily to mature boars. Serum concentrations of progesterone were measured weekly from 5 to 8 mo of age to verify age of puberty. Gilts observed in pubertal estrus were mated to two different boars 10 h apart. At 47 +/- 1 d of gestation, gilts were slaughtered to assess fetal development. After 60 d of treatment, serum LH and FSH profiles were determined in blood samples drawn at 20-min intervals for 4 h from eight diluent- and eight rpST-treated gilts fitted with indwelling jugular catheters. By 28 d, feed intake, feed/gain, and blood urea nitrogen were decreased (P less than .005) by rpST. Treatments did not affect (P greater than .05) the proportion of gilts attaining first ovulation (DW = 6/6; DP = 10/10; PW = 7/9; PP = 14/14) or conception rate (DW = 5/6; DP = 7/10; PW = 4/6; PP = 11/12).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Principles governing the prosthodontic treatment of patients with cardiac transplants.

As the survival rate of patients with cardiac transplants improves, it is more likely that dentists will have to provide extensive dental care and it is important to know the special precautions that must be taken when treating these patients. In this report on the prosthodontic treatment of a patient with a cardiac transplant and an unstable medical history, specific dental management guidelines are proposed. The treatment illustrates an alternative to complex and prolonged restorative treatment for patients with compromised post-transplant recovery.

Anti-Bacterial Agents↗
PubMed1989

Influence of sulfate in drinking water on mouse reproduction during two parities.

Field studies have suggested that high levels of sulfate in drinking water may alter water consumption and have an adverse effect on animal reproduction. This study was conducted to determine whether sulfate in the drinking water affects the reproductive performance of female mice during gestation and lactation over two parities. Sixty random-bred albino mice were randomly assigned to six sulfate treatments. Sodium sulfate was added to deionized distilled water to give sulfate levels in ppm as follows: (1) 0 (control); (2) 0 (Na control); (3) 625; (4) 1,250; (5) 2,500 and (6) 5,000. Treatments 2 to 6 contained the same Na content (2,392 ppm) by varying Na bicarbonate content. Mice receiving only the deionized distilled water drank less (P less than .05) than mice receiving the other treatments at all times measured. Animals offered the 0 (Na control) water drank more (P less than .05) water than mice on the other sulfate treatments. There was no difference (P greater than .10) in litter size, litter weaning weight, or gestational and lactational weight gain of the dam among water treatments. Although levels of sulfate up to 5,000 ppm and 2,392 ppm Na in the drinking water cubicly altered water consumption, they did not affect litter size, litter weaning weight, or gestational and lactational weight gain of the dam when sulfate ingestion was continued over two parities.

Animals↗
PubMed1987

A custom speech valve retainer for the laryngectomee.

A technique is presented for the fabrication of a custom silicone speech valve retainer that is easily fabricated, may be tinted to match the skin tone, is well tolerated, noninvasive, and functions well in patients who can generate sufficient air pressure to close the valve. This device can greatly improve the quality of life for laryngectomees by allowing hands-free, alaryngeal oral speech.

Colloids↗
PubMed1986

Customized valve housing.

Numerous remarkable advancements have been made in the area of voice prosthetics. A significant, persistent problem, however, has been the development of air leaks around the tracheostome housing. This problem is particularly apparent with patients having deeply recessed, irregular stomas. This paper describes a customized tracheostome valve housing that is fabricated to minimize or alleviate difficulties associated with maintenance of an airtight seal. Our experience with 12 patients revealed that they maintain adequate seals for 72 hours and enjoy the functional benefits provided by the customized housing.

Humans↗