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Biomedical subjects

H R Stanley

Publications and source records attributed to H R Stanley.

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

Biological evaluation of dental materials.

Dental materials and devices are being treated more like drugs and now have to meet the safety and efficacy requirements of drugs and medical devices. Biocompatibility is the key word. The history of the development of controls, standards, and guidelines began almost 500 years ago and is detailed in a chronological fashion up to the present time. An outline of the latest revised draft of the international document (ISO Technical Report No. 7405), to be completed hopefully by 1993 in time for the harmonization of the European Standards within the EC, is presented. The types of tests (initial, secondary, and preclinical usage tests) are listed and described. No amount of experimental study can guarantee absolute safety for any substance. However, toxicological investigations provide data from which reasonable projections and predictions can be made about the conditions under which the product can be safely used. It is the intent that this Technical Report be reviewed regularly and revised, with the ultimate objective of converting it to an International Standard.

Animals↗
PubMed1991

Biocompatibility of a glass ionomer luting agent. 2. Crown cementation.

In this experiment, 64 crown preparations were made in four primates. Final impressions, die fabrication, wax patterns and castings were achieved using conventional established clinical and laboratory techniques. Vented and unvented crowns were cemented with a glass ionomer cement (GI) and a zinc phosphate cement (ZOP). Some preparations were protected with calcium hydroxide liquid. On the same animals, in teeth not used for crowns, Class V cavities were prepared and GI and ZOP inserted by means of a pressure technique imitating hydraulic pressure generated during crown cementation. After periods of 5 and 60 days, the animals were sacrificed, the jaws dissected, fixed in formalin and prepared for histological evaluation. Of the 64 cemented crowns, one was unaccounted for. Of the unvented crowns with GI (5 days), vented crowns with GI (60 days), unvented crowns with ZOP (60 days), Class V with ZOP (5 days) and GI (60 days) with a remaining dentin thickness (RDT) of less than 1 mm, inflammatory responses of greater than or equal to 1 degree (on a scale 1-4 degrees) were observed. The use of liquid calcium hydroxide reduced the intensity of the reactions, in particular when small RDTs were present. It can be concluded that when RDTs of 1 mm or more were present, the cements in all groups were non-toxic. When it is estimated that the RDT is less than or equal to 1 mm, the use of a calcium hydroxide liner is recommended. Placement of luting agents in Class V preparations with pressure resulted in reactions resembling crown cementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

Pulpal responses to ionomer cements--biological characteristics.

When glass ionomer cements were initially introduced, the pulpal responses were considered milder relative to other cements. However, the results mainly came from the application of glass ionomer cements as restorative materials. When ultimately tested with the basic laws of biocompatibility required of other cements, especially a luting agents, little difference has been shown. The judicious use of calcium hydroxide is highly recommended.

Biocompatible Materials↗
PubMed1989

Pulp capping: conserving the dental pulp--can it be done? Is it worth it?

Emphasis has shifted from the "doomed" organ concept of an exposed pulp to one of hope and recovery. The era of vital-pulp therapy has been greatly enhanced with the introduction of calcium hydroxide (CH) products. The sequence of events leading to dentinal bridge formation with various CH formulas is detailed. Those factors usually considered liabilities to direct pulp capping (pulps cariously exposed, contaminated by saliva, previously carious or restored, periodontally involved, or from older patients and primary teeth) are disputed. Those factors that must be considered to improve the success rate of pulp capping are emphasized: control bleeding, make certain the CH contacts vital-pulp tissue, minimize dentinal chip invasion, avoid embolization of CH particles, and be aware of the depth of penetration of the chemical cautery effect.

Calcium Hydroxide↗
PubMed1989

Pulpal and micro-organism responses to two experimental dental bonding systems.

Several new bonding systems have been reported that promote strong adhesion. This in vivo study involves treatment with two experimental bonding systems of Class V cavity preparations in the teeth of three Macaca fascicularis primates and reports the pulpal responses and degree of micro-organism invasion associated with each treatment. In each monkey, the teeth in the upper left quadrant were treated with the experimental solution, containing 2.5% aluminum nitrate + 1.5% oxalic acid + 4.9% NPG, followed by application of PMDM and Silux XL composite. The lower right quadrant was treated with the experimental solution, containing 5.7% NPG + 2.4% nitric acid, followed by PMDM and Silux XL composite. The upper right and lower left quadrants were treated with clinical materials to establish positive and negative controls. After four, 25, and 59 days, the teeth were removed and underwent routine histological and bacteriological evaluation. Slight pathological conditions were noted for superficial and deep responses, but all values approached 0.0 by the 59th day. Micro-organisms were seen under only 12% of the restorations. Both experimental systems appear to be safe for human clinical trials.

Animals↗
PubMed1989

Clinical biocompatibility of an experimental dentine-enamel adhesive for composites.

Previous studies have shown that sequential application of an acidified solution of ferric oxalate, N-phenylglycine and PMDM (the reaction product of pyromellitic dianhydride and hydroxyethyl methacrylate) yields strong adhesive bonding of composite resins to both dentine and enamel. The purpose of this study was to evaluate the clinical characteristics and the biocompatibility of this system in human teeth scheduled for extraction in the course of orthodontic treatment. Controls were light-cured Scotch-bond or ZOE in contralateral teeth. Evaluation criteria, which included clinical feasibility, patient acceptability, retention, margin aesthetics and human pulp response, were met. Within the 4-241 day observation periods, there was no postoperative sensitivity, pain, loss of retention, staining or discolouration. All pulp responses (double-blind pulp analysis including all teeth) were acceptable. With mean (+/- SD) remaining dentine thickness (RDT) of 0.67 +/- 0.35 mm, all indicators of pulp inflammation (displacement, superficial response, deep response etc.) averaged between none and slight, under 1 on a 0-4 scale. Both controls gave similar results. Linear regression analysis indicated low responses at all RDTs. The experimental material is safe and effective; further unrestricted clinical evaluations in teeth to be retained are indicated.

Adhesives↗
PubMed1988

Pathological sequelae of "neglected" impacted third molars.

An NIH conference on "Removal of Third Molars" debated the need for removal of asymptomatic impacted teeth with no evidence of pathology but stressed the need for long-range studies. The assumption is that "neglected" impacted third molars (ITMs) will sometime cause serious pathology. Examination of panoramic radiographs of 11,598 patients revealed 1,756 patients with 3,702 impacted teeth; average age 47 years, and an average retention period approximately 27 years. Dentigerous cystic changes occurred in about 30 ITMs (0.81%), internal resorption in 16 (0.43%), periodontal ligament damage and bone loss distal to the 2nd molar 166 times (4.48%), and pressure resorption of the 2nd molar 113 times (3.05%). No great surge in pathology occurred with increasing age. Some type of pathological change can be expected eventually in approximately 12.0% of an impacted 3rd molar population and 1.82% of the general population. A reappraisal of routine removal of ITMs might be indicated.

Adult↗
PubMed1987

Residual alveolar ridge maintenance with a new endosseous implant material.

In an effort to maintain the height of the residual alveolar ridge, Bioglass cones were placed in fresh sockets after tooth extraction. Today the emphasis is on maintaining the residual alveolar ridge instead of letting it resorb and subsequently resorting to heroic efforts for augmentation. To date, 242 cone implants have been placed in 29 patients. Implant follow-up observation time ranged from 12 to 32 months with an average of 19.9 months. Twenty-seven patients have been fitted with dentures. To date seven implants (2.9%) have been lost. The Bioglass implants appear to be highly biocompatible as evidenced by absence of infection, normal mucosal healing, and radiographic evidence of bone healing around the implants. Evaluation of several implants reexposed surgically revealed new bone in direct contact with the immobile implants circumferentially. The problem of implant dehiscence that started to occur after approximately 10 months in other investigations had not manifested itself in the Bioglass implant patients who have been wearing their dentures for at least 12 months.

Alveolar Process↗
PubMed1986

In vitro antimicrobial activity of six pulp-capping agents.

The antimicrobial activity of six commonly used pulp-capping agents was compared to reagent Ca(OH)2 by means of an in vitro microbiologic assay. Microbial samples were collected from deep carious lesions in each of twelve teeth and plated onto T-soy blood agar. Uniform disks of each pulp-capping agent were pressed slightly below the surface of each agar dish, and zones of bacterial inhibition were measured at 24 hours to the nearest 0.1 mm. All agents, including IRM, demonstrated significantly more antimicrobial activity than reagent Ca(OH)2 with the exception of Pulpdent. This tends to indicate that the antibacterial properties associated with these capping compounds are not entirely due to the high pH associated with Ca(OH)2.

Bacteria↗
PubMed1983

Cervical resorption in bleached teeth.

A case of cervical resorption in a bleached, pulpless tooth is reported. The tooth has not been traumatized, and no other reason for the resorption could be found except the possible effects of a caustic bleaching agent. This case further supports the evidence in the literature that a cause-and-effect relationship exists between Superoxol bleaching and cervical resorption.

Female↗