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Biomedical subjects

R M Pilliar

Publications and source records attributed to R M Pilliar.

At least 91 records · Page 5Linked to original sources
PubMed1976

The rate of bone ingrowth into porous metal.

Experiments have been devised to study the rate of ingrowth of bone into porous metal with pore sizes up to 100 mu and to study the significance of a gap between the porous metal surface and bone. When the porous coat was in direct apposition with bone, the implant was firmly locked in place after a three week period and the plateau value of implant-tissue shear strength was reached at four weeks. A gap of 1.5 mm between the bone and the implant was bridged by new bone within four weeks.

Animals↗
PubMed1976

Carbon fiber-reinforced bone cement in orthopedic surgery.

A tougher, more fatigue-resistant bone cement consisting of short, highmodulus carbon fibers dispersed randomly in normal ply(methyl methacrylate) bone cement has been developed. Fatigue and impact tests are reported that demonstrate the superior fracture resistance and prolonged load-carrying ability of this system. The use of this carbon fiber-reinforced bone cement in the treatment of a pathological fracture of the femur associated with neoplastic disease of the bone is reported. The tougher cement has provided long-term stability of the fracture.

Bone Cements↗
PubMed1975

Porous surface layered prosthetic devices.

The method of fabrication and properties of a dual structured implant system consisting of a metallic porous surface layer is described. The ingrowth of bone tissue into the outer porous surface layer results in part fixation, while the solid inner core region provides the necessary mechanical strength for a device used for the replacement of heavy load bearing joint regions such as the hip and knee. Additionally, novel implant systems are suggested using the porous coating concept.

Animals↗
PubMed1975

Use of polymethylmethacrylate to enhance screw fixation in bone.

Pull-out testing of screws inserted into cement and bone under various conditions showed that the cement-screw complex was significantly stronger when the screw was placed in soft cement and the cement was allowed to polymerize without further manipulation. When screw fixation in osteoporotic bone was reinforced with cement, the bone was the weakest component in the system. Fixation under these conditions should be enhanced by increasing the area of contact between the cement and bone. By cooling the cement to prolong its working time, it could be injected with a syringe in such a way that maximum endosteal and periosteal contact was provided.

Bone Cements↗
PubMed1975

Iatrogenic subcapital fracture of the hip: a new complication of intertrochanteric fractures.

A recently recognized complication of intertrochanteric fracture is a subcapital fracture occurring at the tip of the blade of an intertrochanteric fracture fixation blade plate. Histological examination reveals that this is not a fatigue fracture but is the result of stress concentration effects of a stiff metalic device. This fracture may be prevented by using a blade plate with a long blade which is well seated in the head, and by removing the metallic device as soon as it is safe to do so. Ultimate prevention lies in using a more compatible material for the internal fixation of fractures.

Aged↗
PubMedDate not supplied

The fatigue strength of porous-coated Ti-6%Al-4%V implant alloy.

The fatigue behaviour of Ti-6Al-4V (extra low interstital) alloy coated with Ti-6Al-4V powder was investigated using rotating bending fatigue testing. It was found that the high cycle fatigue strength of porous coated specimens exhibited a substantial decrease compared to uncoated specimens of the same microstructure. Chemical analysis of the sintered surface revealed significant increases of interstitials compared to the bulk analysis, but it is concluded that this would not adversely affect the fatigue strength. Scanning electron microscopy revealed crack initiation close to particle/substrate contact interfaces and it is concluded that stress intensification due to these interface regions are major sources of weakness with respect to fatigue strength. Finally it was found that subjecting a polished Ti-6Al-4V specimen to the heat treatment required for sintering resulted in delineation of prior beta grain boundaries and it is suggested that this also contributes to the inferior fatigue strength of porous coated Ti-6Al-4V.

Absorption↗
PubMedDate not supplied

Threaded versus porous-surfaced designs for implant stabilization in bone-endodontic implant model.

An endodontic implant model system was used to compare the effect of implant design on stabilization in bone. Specifically a porous-surfaced design was compared to conventional threaded and smooth-tapered endodontic implant designs. All implants were placed in immediate function thereby assessing the effect of early limited movement on the fixation achieved. A total of eighty-three endodontic implants were inserted in the mandibles of six adult mongrel dogs. Animals were sacrificed immediately after implantation and after 3, 6, and 12 months. Implants were evaluated by clinical and radiographic examination and after animal sacrifice by pull-out tests of the implant from the tissues, SEM examination of the pulled-out implants and, finally, histology. The pull-out test results indicated increasing shear strength with implantation time for the porous-surfaced implants in contrast to the gradual loss of fixation for the threaded implants and the continuous low shear strength for the smooth implants. Histological studies and SEM examination indicated the reason for these changes. Smooth implants became encapsulated by fibrous connective tissue from early post-implantation time periods. Threaded implants, although initially mechanically interlocked with bone, developed a fibrous connective tissue capsule that gradually thickened with time until, by 6 months, little mechanical interlock of bone and implant was present. It was assumed that this fibrous capsule thickening was caused by implant movement. The porous-surfaced implants, however, became stabilized by bone ingrowth and showed more extensive bone formation within the surface pores with time. It is concluded that for implants that are made functional immediately after implantation, as in this study, porous-surfaced implants can become strongly fixed by bone ingrowth, in contrast to conventional threaded or smooth-surfaced designs, thus presenting a more favourable long term prognosis.

Alloys↗
PubMedDate not supplied

Analytical and structural electron microscopy of chromium carcinogenesis in vitro.

Syrian hamster embryo cells have been grown in culture on thin (10-50 nm), evaporated substrates of chromium, and examined by analytical transmission electron microscopy. After 10 d exposure, significant metal uptake was observed and numerous cell colonies showed the physical characteristics of carcinogenic transformation. The majority of the ingested chromium appeared to be associated with nucleic acid complexes. As a control, cells grown on titanium showed no signs of metal uptake and had morphologies very similar to cells grown on conventional carbon substrates.

Animals↗
PubMedDate not supplied

A prospective human clinical trial of Endopore dental implants in restoring the partially edentulous maxilla using fixed prostheses.

This is the first report of a group of 50 partially edentulous patients who received a total of 151 Endopore dental implants in the maxilla. A mean implant length of 8.7 mm was used, and 76.8% of implants were placed in the posterior maxilla. At re-entry, all implants appeared to be osseointegrated and were used to support fixed prostheses. Approximately half of the crowns (57%) in these prostheses were splinted to one another, while the remainder (43%) were not. At the time of this report, the mean functional time was 34.6 months and the cumulative survival rate was 97.3% (4 implants had failed). Analysis of carefully standardized sequential radiographs indicated no significant changes in mean crestal bone levels between baseline and any of the examination times (after 6 months, 1 year, and 2 years in function). There were no detectable correlations between crestal bone loss and the factors implant length (7, 9, or 12 mm); implant diameter (3.5, 4.1, or 5.0 mm); implant position anteriorly or posteriorly in the maxilla; or whether or not the implant-supported crowns were splinted.

Adult↗
PubMedDate not supplied

Managing the posterior mandible of partially edentulous patients with short, porous-surfaced dental implants: early data from a clinical trial.

Forty-eight Endopore dental implants were placed in the posterior mandibles of 24 partially edentulous patients. Seventeen of these implants replaced premolar teeth, while 31 replaced molars. Only 7-mm and 9-mm implants were used, and the majority of prosthetic restorations (83%) were single crowns. After a mean functional time of 32.6 months (range, 8.2 to 50.3 months), the implant survival rate was 100% and assessment of available radiographic data showed minimal to no crestal bone loss.

Adult↗
PubMedDate not supplied

The optimum pore size for the fixation of porous-surfaced metal implants by the ingrowth of bone.

For a study on the effects of pore size variation on the rate of bone growth into porous-surfaced metallic implants and on the strength of fixation resulting from this ingrowth, 4 distinct pore size ranges were prepared on cobalt-base alloy implants with cobalt-base alloy powder particles of different dimensions. The porous implants were placed into canine femurs for periods of 4, 8, and 12 weeks. Mechanical tests were performed to measure the shear strength of fixation of the implants to cortical bone. For implants with powder-made porous surfaces, a pore size range of approximately 50 to 400 microns provided the optimum or maximum fixation strength (17 MPa) in the shortest time period (8 weeks).

Animals↗
PubMedDate not supplied

Fracture toughness ov conventional or photopolymerized glass ionomer/dentin interfaces.

Several new light-cured glass-ionomer materials have been developed for restorative use. It is not yet clear, however, whether the ability of the conventional glass ionomers to bond chemically to dentin has been preserved in the new light-cured glass ionomers whose chemical compositions have been modified. The fracture toughness test was recently introduced as an appropriate method of measuring the fracture resistance of an interface. We have applied this test to the glass ionomer/dentin interface for the first time. Ten mini short-rod fracture-toughness specimens were fabricated for each group. Each specimen contained a chevron-shaped glass ionomer/dentin interface along its midplane. After 24 hours in 37 degrees C water, the specimens were tested by loading at 0.5 mm/min. The interfacial Kic results (MPa X m (1/2)) (SD), analyzed by ANOVA and Fisher's LSD test (P<0.05), were: Chem-fil II, 0.17 (0.04); Vitremer, 0.18 (0.15); Fuji II LC, 0.33 (0.16). There were no significant differences in interfacial Kic between the conventional and light-cured glass ionomers. Interfacial Kic's for a light-cured glass ionomer were, however, significantly higher when an intermediary dentin bonding agent was used. SEM examinations of the fractured surfaces indicated that crack propagation generally occurred along the bond interface, and indicated the formation of a resin-infiltrated layer when the dentin bonding agents were used. It was concluded that the fracture-toughness test could be a useful measure of the integrity of the glass ionomer/dentin interface. The clinical effect of an intermediary layer between the glass ionomer and the tooth structure is, however, unknown and requires further investigation.

Aluminum Silicates↗