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Biomedical subjects

R E Holmes

Publications and source records attributed to R E Holmes.

At least 37 records · Page 2Linked to original sources
PubMed1989

Quantification of bone in dental implant sites after composite grafting of the mandible: report of a case.

The amount of viable bone in a composite graft that consisted of autogenous iliac bone marrow, allogenic rib, and porous hydroxyapatite was quantified using standard histologic techniques and an optical insert disk prior to placement of endosteal implants in an augmented mandible. It is suggested that this technique could be used in such cases before deciding whether to proceed with implant insertion.

Bone Regeneration↗
PubMed1989

Surgical retrieval and histologic evaluation of an endosteal implant: a case report with clinical, radiographic and microscopic observations.

An uncommon opportunity to study an endosteal implant after four months of normal healing is presented. After placement of titanium plasma-spray-coated, apical-vent implants in the mandibular molar area, a 55-year-old female reported discomfort around one implant. This implant was removed, despite normal healing, because of continued symptomatology. Radiologic findings, and remission of symptoms after surgical removal, supported the possible etiologic mechanism of canal roof compression. Histologic preparation and imaging of the specimen permitted the evaluation and measurement of the bone growth between the apical vents and bone apposition against the internal vent surfaces. The bone growth was fiber bone, well-mineralized, and occupied 33.8% of the area within the implant perimeter. The bone apposition against the titanium coating was intimate, and 41.1% of the internal vent surfaces were covered with bone ingrowth. The presence of bone healing sufficient to absorb the loads of prosthetic abutment reconstruction is supported by these histologic and histometric findings.

Bone Regeneration↗
PubMed1988

Bone ingrowth into porous calcium phosphate ceramics: influence of pulsing electromagnetic field.

The effect of a pulsing electromagnetic field (PEMF) on bone ingrowth into porous hydroxyapatite (HA) and porous tricalcium phosphate (TCP) implanted in rabbit tibiae was studied. To quantitate the biological response, a recently developed method of surface measurement using a scanning electron microscope was used. The morphometrical findings in the HA pores demonstrated a significantly greater amount of bone and thicker bone trabeculae in the PEMF group as compared with the nonpulsed control group at 3 to 4 weeks postimplantation. No significant differences for these parameters were found in the TCP pores. Histologically, more bone and wider bone trabeculae were observed in the HA implants for the PEMF-treated animals at the early time periods when compared with those of the control animals. Alternatively, the histological findings of the TCP implants were similar between these two groups. These histological results tended to correlate with the morphometrical data. Together, these results suggest that accelerated bone formation and bone maturation occurred in response to PEMF in the HA pores but was without effect in the TCP pores. This stimulatory effect is most significant after 3-4 weeks of PEMF stimulation.

Animals↗
PubMed1988

Hydroxylapatite as a bone graft substitute in orthognathic surgery: histologic and histometric findings.

The use of porous hydroxylapatite (HA) as a substitute for bone in grafting associated with orthognathic surgical procedures was studied histologically and histometrically. The surgical procedures included maxillary downgrafting, advancement, setback, superior repositioning with expansion, and mandibular advancement and chin augmentation. Seventeen biopsies were obtained from nine patients after successful healing from 4.7 to 16.4 months postoperatively. Anatomic sites of the biopsies included maxillary wall, interdental region, palatal midline, chin, and mandible. In addition, nine implants representing six planned and three unplanned exposures were retrieved from nine patients. One biopsy from a successful implant was decalcified and thin-sectioned to provide better cell detail of the antral lining of the implant. The remaining biopsies were sectioned undecalcified to permit backscattered electron imaging with a scanning electron microscope. Each of the 17 biopsy specimens contained bone ingrowth. The decalcified specimen showed an intact submucosa with loss of the mucosal epithelium due to prolonged acid exposure. The biopsies were composed of 48.5% HA matrix, 18.0% bone ingrowth, and 33.5% soft tissue or vascular space. The HA matrix surface area averaged 9.4 mm2/mm3 with 62.1% of the surface covered by appositional bone ingrowth. The nine exposed implants contained connective tissue ingrowth only at their margins, with little or no bone being present. This graft-like biologic response to a porous HA matrix confirmed its ability to serve as a bone graft substitute in clinical applications. The absence of any decrease over time confirmed the relative permanence of the HA matrix. The lack of inflammatory cells in the biopsies, along with the formation of a connective tissue protective barrier in the exposed specimens, suggests that host responses to contamination were not impaired by the porous HA matrix.

Adolescent↗
PubMed1988

Porous hydroxyapatite as a bone graft substitute in cranial reconstruction: a histometric study.

To assess the potential of a porous hydroxyapatite matrix to serve as a bone graft substitute, bilateral 15 X 20 mm craniectomy defects were reconstructed in 17 dogs with blocks of implant and split-rib autografts. Specimens were retrieved at 3, 6, 12, 24, and 48 months, and undecalcified sections were prepared for microscopy and histometry. The implant and graft cross-sectional areas did not change with time, documenting their equivalent ability to maintain cranial contour. Bone ingrowth extended across the implant from one cranial shelf to the other in 15 specimens. Little apparent bone ingrowth was seen in most graft specimens. Two implants and three grafts were nonunited, possibly due to lack of fixation or the orientation of the histology sections. The implant specimens were composed of 39.3 percent hydroxyapatite matrix, 17.2 percent bone ingrowth, and 43.5 percent soft-tissue ingrowth. The graft specimens were composed of 43.7 percent bone and 56.3 percent soft tissue. This study supported the thesis that a porous hydroxyapatite matrix may function in part as a bone graft substitute. The brittle hydroxyapatite matrix undoubtedly became stronger with bone ingrowth, but the degree of cranial protection achieved was not measured in this study. The size of the cranial defect used in this study did not permit estimation of the distance over which bone ingrowth may be reliably expected. There remains a need for greater understanding of the causes of nonunion, the extent of predictable ingrowth depth, and the strength of the resultant implant-bone composite.

Animals↗
PubMed1987

Thick-section histometry of porous hydroxyapatite implants using backscattered electron imaging.

A histometry system has been developed to measure bone ingrowth into porous hydroxyapatite implants utilizing the backscattered electron image of thick sections. The system consists of a scanning electron microscope (SEM) with backscattered electron detector, digital beam controller, minicomputer based image digitization, and microcomputer based image processing, point counting, and lineal analysis. The SEM backscattered electron imaging mode yields high tissue contrast and sharp tissue boundaries, substantially reducing the lost cap and projection effect errors of thick sections. High-resolution digitization of the image substantially reduces the standard error of the estimates. By using the digitized image the tedious process of filtering artifacts and recording actual point counts, intersections, and intercept lengths is delegated to computer software. Performance of this system in a recent study demonstrated substantial ease of operator use and speed of measurement. In the absence of a digital beam controller an inexpensive video digitizer circuit board may be used to digitize photographic prints of the SEM images. The combination of increased accuracy, precision, operator ease, and speed suggests that this system can be useful for soft tissue-bone-implant histometry.

Animals↗
PubMed1987

Porous hydroxyapatite as a bone graft substitute in diaphyseal defects: a histometric study.

Porous hydroxyapatite (IP200), formed by conversion of the Poritidae porites exoskeleton, has pores averaging 230 microns and pore interconnections averaging 190 microns in diameter. In the distal radial diaphyses of 14 dogs, bilateral 7.5 X 20 mm cortical windows were created and fitted with 5 X 7.5 X 20 mm blocks of IP200 implants and iliac autografts. Both implanted and contralateral grafted radius specimens were retrieved at 3, 6, 12, 24, and 48 months. Unstained undecalcified sections were examined by microradiography and UV epi-illumination. Stained undecalcified sections were examined by light microscopy and quantitated by histometric methods. Implant specimens demonstrated good union and bone ingrowth at all time intervals. The implant specimens were composed of (mean +/- SE) 10.6% +/- 1.0% soft tissue, 51.2% +/- 1.3% bone, and 38.2% +/- 1.0% IP200. The graft specimens showed good union with little apparent ingrowth at 3 months, followed by progressive appositional closure of cancellous spaces. The graft specimens contained 21.9% +/- 0.9% bone at 3 months with increases at each time interval to 73.1% +/- 8.7% at 48 months. The volume fraction and mean width of IP200 did not change with time, confirming the absence of implant biodegradation. The volume fraction and mean width of bone remained stable in the implant but increased in the graft specimens, corresponding to graft neocortex formation. It is concluded that implants initially filled in with bone while grafts initially replaced much of their spongiosa and subsequently filled in with bone. Histometry of untreated defects and measurement of mechanical properties are suggested for further study.

Animals↗
PubMed1987

Porous hydroxylapatite as a bone graft substitute in mandibular contour augmentation: a histometric study.

The buccal contour of the mandible was augmented in 17 dogs with 5 X 7.5 X 20 mm blocks of porous hydroxylapatite (HA) on one side and two-layered split rib autografts on the other. Both specimens were retrieved at three, six, 12, 24, and 48 months. Undecalcified sections were prepared for microradiography, light and UV microscopy, and histometry. A transmitted light video image digitizing system was used to trace implant and graft perimeters and calculate cross sectional areas. This system was also used to measure graft density and calculate bone and soft tissue compositions. The HA matrix, bone and soft tissue compositions of implant specimens were measured with a backscattered scanning electron microscope imaging digitizing system. All grafts became increasingly resorbed with time whereas all implants remained intact. Mature osteotonic bone ingrowth was present in all implants except one which failed to unite with the mandibular cortex. The mean graft areas decreased from 30.8 mm2 at three months to 0.7 mm2 at 48 months, while the implant areas averaged 35.5 mm2 and remained stable. The graft specimens were composed of 46.6% bone and 53.4% soft tissue or fluid space. The implant specimens were composed of 34.5% HA matrix, 28.6% bone, and 33.9% soft tissue. The HA matrix had a surface area of 9.8 mm2/mm3 that was 61.9% covered with bone ingrowth and 38.1% covered with soft tissue or fluid space. In contrast to the rapid resorption of graft onlays, the porous HA matrix demonstrated a long-term permanence with maintenance of contour and osseous incorporation over the four-year duration of this study.

Animals↗
PubMed1987

Porous hydroxyapatite as a bone graft substitute in alveolar ridge augmentation: a histometric study.

Following bilateral alveolectomy, the ridge form was restored in 10 dogs with blocks of porous HA matrix and bicortical iliac autografts. The specimens were retrieved after 11 to 17 months and undecalcified sections were prepared for microscopy and histometry. Within the HA implants, bone ingrowth extended throughout the pores. This bone appeared mature and well vascularized. The autografts united to the mandible. However bone ingrowth into the cancellous spaces of the grafts was minimal or absent. Measurement of implant and graft cross-sectional areas showed the maintenance of alveolar ridge form to be equally permanent for the 2 materials over the 1.5 year duration of the study. The implant specimens were composed of 43.1% HA matrix, 45.2% bone and 11.7% soft tissue. The HA matrix had a surface area averaging 9.3 mm2/mm3 that was 91.1% covered with bone ingrowth. Although this study supported the thesis that a porous HA matrix can function as a bone graft substitute, it is noted that the unyielding nature of the implant blocks, compared to granules, requires a solution to the challenge of long-term denture support without ulceration before it can be used with clinical confidence.

Alveolar Ridge Augmentation↗
PubMed1987

Coralline hydroxyapatite bone-graft substitutes in a canine diaphyseal defect model. Radiographic-histometric correlation.

Radiographic and histometric evaluation of a new form of bonegraft substitute derived from reef-building sea coral was performed in a canine diaphyseal defect model. Comparably sized blocks of this material and iliac crest autograft were placed into bilateral surgically created cortical windows in the distal radial diaphyses of 14 dogs. Representative graft specimens of both types underwent densitometric radiography and harvesting at 3, 6, 12, 24, and 48 months. Histometric analysis of implant specimens revealed satisfactory union and native osseous ingrowth at all time intervals. Graft specimens exhibited adequate union with scant host bone ingrowth at three months, but subsequent progressive appositional closure of cancellous spaces during the ensuing 45 months. Volume fraction and mean width of host bone remained stable in the implants but increased in the grafts due to neocortex formation. Stereologic distribution of bone was homogeneous in both implant and graft specimens, and no evidence for biodegradation of the former was observed. Corrected transmission density determinations accurately reflected these differences but correlated significantly with volume fractions and tissue widths of bone and soft tissue only in the autografts. These results support the successful early application of coralline hydroxyapatite bone graft substitutes as an alternative to autogenous grafting in the clinical setting and emphasize the potential role of noninvasive densitometric techniques in monitoring the incorporation of bone-graft materials.

Absorptiometry, Photon↗
PubMed1987

The role of public opinion polling in health legislation.

Two public opinion polls, in Los Angeles and Michigan, on smoking in public places contradicted findings from other major surveys. Both were commissioned by the tobacco interests during consideration of non-smoking legislation to measure opinion and influence the outcome. Analysis reveals the two polls to be remarkably similar and in violation of basic principles of survey research. Response categories lacked objective or parallel phrasing, response lists were not rotated, and the ordering of items appeared prejudicial. Both polls were effectively countered and the legislation passed.

California↗
PubMed1987

Hydroxyapatite and tricalcium phosphate bone graft substitutes.

Autografts have consistently outperformed calcium phosphate implants in most experimental models and clinical applications. However, human trials in metaphyseal defects demonstrate comparable results with autograft, hydroxyapatite, and TCP. Diaphyseal fractures and segmental defects represent more challenging problems, with less predictable results achieved with the synthetic bone graft substitutes. Improvements in the pore configuration, mechanical properties, and osteoinductive capacity of these implants should widen their future clinical application.

Adolescent↗
PubMed1986

Coralline hydroxyapatite bone graft substitutes in a canine metaphyseal defect model: radiographic-biomechanical correlation.

Radiographic and biomechanical assessment of a new type of bone graft substitute derived from reef-building sea coral was performed in a canine metaphyseal defect model. Blocks of this material and autogenous iliac crest graft were implanted, respectively, into the right and left proximal tibial metaphyses of eight dogs. Qualitative and quantitative radiographic evaluation was performed in the immediate postoperative period and at 6 months after surgery. Biomechanical testing was carried out on all grafts following harvest at 6 months, as well as on nonimplanted coralline hydroxyapatite and autogenous iliac cancellous bone. In contrast to autografts, incorporation of coralline implants was characterized by predictable osseous growth and apposition with preservation of intrinsic architecture. Greater percent increase in radiographic density, higher ultimate compressive strength, and lower stiffness with incorporation were documented advantages of coralline hydroxyapatite over autogenous graft. Densitometric measurements correlated moderately with strength for both types of graft material (r = -0.65). These promising results have important implications to the clinical application of coralline hydroxyapatite bone graft substitutes as an alternative to autogenous grafting.

Absorptiometry, Photon↗
PubMed1986

Coralline hydroxyapatite bone graft substitutes in a canine diaphyseal defect model: radiographic features of failed and successful union.

Radiographic and densitometric evaluation of a new type of bone graft substitute derived from reef-building sea coral via a hydrothermal chemical exchange process was undertaken in a canine diaphyseal defect model. Comparably sized blocks of this material and autogenous iliac cortical-cancellous graft were implanted into the respective radial diaphyses of seven dogs. Qualitative and quantitative radiographic assessment was performed during the immediate postoperative period and at 3 months following surgery. Significant complications were observed radiographically in over half of the coralline implanted limbs, including failed union, graft fracture, and loosening of internal fixation hardware. No significant difference was noted in degree of native osseous in-growth between the implants and the autografts, and the latter exhibited a higher success rate. Radiographic film densitometry was found not to be reliably predictive of coralline implant behavior in the individual case. It is concluded that coralline hydroxyapatite bone graft substitutes appear to offer no particular advantage over autogenous grafts in the management of diaphyseal defects, although further investigation is warranted since other factors may be responsible for the unfavorable findings in this study.

Absorptiometry, Photon↗
PubMed1986

Coralline hydroxyapatite bone-graft substitutes in a canine metaphyseal defect model. Radiographic-histometric correlation.

Radiographic and histometric evaluation of a new form of bone-graft substitute derived from reef-building sea coral was performed in a canine metaphyseal defect model. Blocks of this material were implanted into the proximal tibial metaphyses of eight dogs, with radiographic densitometry and harvesting performed at two, four, six, and 12 months. Histometric analysis demonstrated progressive apposition of host compact bone at the margins and trabecular bone at the interior of the implants with time following surgery. Corrected transmission density determinations correlated significantly with degree of osseous ingrowth (R = -0.78), void volume fraction (R = 0.88), and postoperative interval (R = 0.88). These results support the successful early application of coralline hydroxyapatite bone-graft substitutes as an alternative to autogenous grafting in the clinical setting, and indicate that the course of incorporation into host bone can be noninvasively monitored using densitometric techniques.

Absorptiometry, Photon↗
PubMed1986

Coralline hydroxyapatite bone graft substitutes: preliminary report of radiographic evaluation.

A new bone graft substitute made by conversion of the calcium carbonate exoskeleton of reef-building sea coral into hydroxyapatite has recently become clinically available. The normal radiographic appearance of two forms of this material is described. In the immediate postoperative period, the exoskeletal architecture of these implants is readily appreciated. With graft incorporation over the ensuing months, their intrinsic structure is gradually lost in association with poor marginal definition. Evolving radiographic findings reflect the biocompatible nature of these implants, which provides the potential for ingrowth of native bone with preservation of the coralline scaffold, resulting in enhanced biomechanical properties.

Adolescent↗
PubMed1986

Porous hydroxyapatite as a bone-graft substitute in metaphyseal defects. A histometric study.

Porous hydroxyapatite (Interpore 500) formed by conversion of the Porites goniopora coral exoskeleton has pores averaging 600 micrometers and pore interconnections averaging 260 micrometers in diameter. In the proximal tibial metaphysis of eight dogs, a defect one cubic centimeter in size was created unilaterally and was fitted with a block of Interpore 500. Both proximal tibial metaphyses were retrieved at two, four, six, and twelve months. Stained undecalcified sections were examined by light microscopy and quantitated by histometric methods. The implant-side specimens contained compact bone along the external surface and trabecular bone interiorly. The interior of these specimens was composed of 51.9 +/- 1.3 per cent soft tissue, 13.0 +/- 1.2 per cent bone, and 35.1 +/- 1.2 per cent Interpore 500 (mean and standard error). The interior of the normal specimens was composed of 79.7 +/- 1.4 per cent soft tissue and 20.2 +/- 1.4 per cent bone. The allocation of implant pore space between bone and soft tissue was proportional to that of bone and soft tissue in the normal tibiae. The stereological distribution of regenerated bone in the porous hydroxyapatite was also the same as in the normal tibiae. The appositional process of incorporation of the implant was confirmed by the finding that 66.5 per cent of the surface of the Interpore 500 was covered with bone ingrowth at twelve months.

Animals↗