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Biomedical subjects

N G Schaaf

Publications and source records attributed to N G Schaaf.

At least 19 recordsLinked to original sources
PubMed1997

Custom surgical stent for naris stenosis.

A technique has been described that allows accurate fabrication of a surgical nasal stent, made preoperatively, based on a mirror image of the shape of the normal naris. The advantage to the surgeon is a surgical stent that has the greatest accuracy possible preoperatively, plus the ability to remake the stent postoperatively with even more accuracy should it be needed. This stent can then be worn long term with minimal visibility and maximum patient acceptance during the critical months postoperatively when relapse is most likely.

Constriction, Pathologic↗
PubMed1994

The use of a photoprotective agent to increase the color stability of a tinted extraoral prosthetic silicone.

PURPOSE: This study investigated the use of ultraviolet-absorbing or photoprotective agents as a method of decreasing the color changes caused by ultraviolet radiation on an intrinsically tinted facial prosthetic material. MATERIALS AND METHODS: Silastic MDX 4-4210 (Dow Corning Corp, Midland, MI) was the facial prosthetic material studied. It was intrinsically tinted with talc and nylon flock to approximate the color of skin. Three brands of commercially available sunscreens with sun protective factor (SPF) of 15 were placed on the surface of the cured silicone samples. The samples were rotated in an ultraviolet radiation chamber for 300 hours. A control group was placed in the dark for 300 hours. The second phase of the experiment had para-aminobenzoic acid (PABA) added to the tinted silicone. All samples were measured with a spectrophotometer at the beginning and at the end of 300 hours, and a delta E was obtained. RESULTS: None of the sunscreens provided any ultraviolet radiation protection to the silicone. The addition of PABA caused a significant color degradation of the silicone. CONCLUSIONS: No photoprotective agent tested provided any significant level of ultraviolet radiation protection for silastic MDX 4-4210.

Humans↗
PubMed1992

Trends in prosthodontic treatment of cleft palate patients at one institution: a twenty-one year review.

This 21-year retrospective study evaluated the trends observed in the prosthodontic treatment of 269 patients. The patients were divided into three groups. The speech aid group consisted of 203 patients and showed a significant decrease in numbers over time. The maxillary obturator group consisted of 24 patients and did not show a significant change. The infant feeding prosthesis group consisted of 42 patients and showed a significant increase in numbers. Possible reasons for the trends observed are discussed.

Adolescent↗
PubMed1992

Visualization and initial characterization of the titanium boundary of the bone-implant interface of osseointegrated implants.

A simple procedure has allowed consistent visualization of the titanium boundary of the bone-implant interface of osseointegrated titanium implants at the electron microscope level. This was accomplished by embedding the intact bone-implant specimen block with low-viscosity resin prior to removal of the device in preparation for sectioning. The titanium boundary consisted of either a thin, compact amorphous electron dense layer, a broad layer of dense amorphous granules, or both. This material was removed by decalcification in formic acid (prior to embedding) and did not diffract electrons (ie, was noncrystalline). Scanning-transmission electron microscopy-EDX analysis indicated the presence of titanium, calcium, and phosphorus in the electron dense material. Field emission scanning electron microscopy-EDX dot-mapping analysis confirmed the presence of these elements and mapped them to the same locations at the implant-interface boundary.

Animals↗
PubMed1991

Microscopic observations of the bone/implant interface of surface-treated titanium implants.

Light microscopy, and transmission and scanning electron microscopy were used to evaluate osseointegration of extraoral titanium implant surfaces treated by either autoclaving, exposure to ultraviolet light (UV), or radiofrequency glow discharge (RFGD). Ultraviolet and RFGD-treated implants showed faster healing in the initial 5-week to 3-month period. By 6 months of healing, no structural differences were found at the bone/implant interface among the different treatments. It was concluded that UV or RFGD surface treatment of titanium implants may shorten the time interval between placement and loading.

Animals↗
PubMed1990

Dynamic ultraviolet sterilization of different implant types.

This paper investigates the use of the dynamic ultraviolet sterilization process with various dental implants, stainless steel orthopedic cortical bone screws, and polysulfone polymer healing caps. These biomaterials were inoculated with the spores of Bacillus subtilis and Bacillus stearothermophilus. They were then exposed to dynamic ultraviolet radiation in the chamber of a BUD Ultraviolet Device. Samples were incubated in trypticase soy broth at 37 degrees C and 56 degrees C, and they were subcultured onto an enriched agar medium. Results indicate that 16 seconds of dynamic ultraviolet radiation is effective in sterilizing these materials. This is significantly less time than other sterilization techniques presently used.

Bacillus subtilis↗
PubMed1989

Comparison of weight reduction in different designs of solid and hollow obturator prostheses.

Seven types of the partially edentulous maxillectomy arches based on Aramany's classification were designed to evaluate the weight reduction of hollow obturator prostheses. Six obturator prostheses were made for each type of maxillary defect, three of the solid type and three of the hollow type. The weight of each of the 42 obturator prostheses was measured and all of the data were collected and statistically analyzed. The results showed that the hollow obturator prostheses had significantly increased weight reduction, from 6.55% to 33.06% depending on the size of the defect.

Maxilla↗
PubMed1989

Effects of pretreatment sterilization and cleaning methods on materials properties and osseoinductivity of a threaded implant.

A new endosseous titanium implant has been designed to replace skin adhesives as a method of retention of maxillofacial prostheses. The effects of various methods of preimplantation preparation on surface characteristics of the implant were analyzed with electron spectroscopy for chemical analysis. Having undergone one of several pretreatment protocols, fixtures were implanted in the crania of Yucatan miniature hairless swine. Both argon radiofrequency glow discharge and ultraviolet chamber treated implants were associated with the rapid ingrowth and maturation of new bone around the fixture. Conventional steam sterilization was associated with a paucity of neo-osteogenesis accompanied by the production of thick collagen slings at the interface. Apparently, the bulk material, fixture design, and method of surface preparation all contribute to the ultimate clinical fate of an implant.

Animals↗
PubMed1989

Dynamic sterilization of titanium implants with ultraviolet light.

All implantable devices must be sterile. However, autoclaves produce poor surface properties that jeopardize the integration process. The application of a modified ultraviolet light source has proven to enhance bioreactivity by controlling surface properties, but it lacks validation of its sterilization capabilities. Forty-eight titanium implants were contaminated with spores of the biological indicator Bacillus stearothermophilus and subjected to "dynamic sterilization" by ultraviolet light. Forty-seven of the implants were successfully sterilized, as indicated by not producing turbidity in a suitable growth medium. This sterilization technique only requires a 20-second exposure to achieve sterility.

Dental Implantation, Endosseous↗
PubMed1984

Maxillofacial prosthetics and the head and neck cancer patient.

The rehabilitation of cancer patients has been an important aspect of patient care in recent decades. Disabilities resulting from acquired surgical defects in the head and neck area frequently are corrected by using nonliving substitutes or prostheses. A number of specialists in the prosthetic reconstruction of head and neck patients, namely maxillofacial prosthodontists, have been trained over the past 20 years. Now more large metropolitan areas have these services available for cancer patients. In addition, pertinent research in materials and design has resulted in a whole array of possible prostheses that can be constructed to meet specific patient needs. Both the current state of the art in maxillofacial prosthetics and recent advances are highlighted in this paper. The areas covered are: extraoral (facial) prostheses, intraoral prostheses, implant prostheses, and treatment prostheses. The multidisciplinary nature of head and neck cancer patient rehabilitation is also reviewed.

Dentures↗
PubMed1983

Controlling the porosity and density of silicone rubber prosthetic materials.

The chemical components of the four silicone rubber polymers were reviewed. Methods of controlling the porosity and density of both the one-component semisolid prepolymer and the two-component fluid prepolymer systems were evaluated. The variables examined were deairing of the fluid systems; trial packing, pressure sealing, and processing of the semisolid materials; injection versus hand packing of the mold; the effects of moist-heat versus dry-heat application during processing; and the need for investment of the mold within the confines of a closed flask. It can be concluded that porosity of medical-grade silicone rubber polymers may be totally prevented, or accurately controlled, by proper handling techniques.

Chemical Phenomena↗
PubMed1982

Evaluation of mandibular movements in the horizontal plane made by partial mandibulectomy patients--a pilot study.

The purpose of this pilot study of the partial mandibulectomy patient was to make ttracings of their mandibular movement in a horizontal plane of orientation in the hope that the results would provide information regarding the prosthetic rehabilitation of these patients. The anterior part of a pantograph recording unit was used in making the tracings. The results of the study indicate that racings on partial mandibulectomy patients are diagnostic in nature regardless of the range and extent of movement seen. As has been stated by other authors who have studied this type of patient, more clinical research should be undertaken before a full understanding of the ramifications of prosthetic rehabilitation of the partial mandibulectomy patient can be realized.

Aged↗