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Biomedical subjects

I M Brook

Publications and source records attributed to I M Brook.

At least 19 recordsLinked to original sources
PubMed2001

In vitro and in vivo evaluation of e-PTFE and alkali-cellulose membranes for guided bone regeneration.

Guided bone regeneration (GBR) is employed to encourage the formation of new bone in osseous defects by restricting the infiltration of soft tissues. While a variety of membranes have been evaluated for this surgical procedure, the non-resorbable material of choice is currently expanded polytetrafluoroethylene (e-PTFE). A new alkali-cellulose membrane produced by a biotechnological process has been developed as an alternative to e-PTFE for GBR. In this study, the biocompatibility of this novel alkali-cellulose membrane and e-PTFE was compared using tissue culture and an in vivo GBR model. In vitro both materials supported the attachment, migration and differentiation of osteoblast-like cells in culture for up to 3 weeks. The in vivo model was based upon full-thickness transcortical bone defects in the mandibular rami of Sprague-Dawley rats. The right rami were used as controls, contralateral defects being covered bucally and lingually with either e-PTFE or alkali-cellulose membranes. Pathological and histomorphometric analysis was undertaken at 4 and 10 weeks post-implantation. Bone regeneration associated with alkali-cellulose membranes was predominantly endochondral in type in contrast to e-PTFE which induced direct bone formation (intramembranous ossification). The amount of new bone formed in defects was similar for both types of membrane, but alkali-cellulose membranes induced significantly greater inflammatory response; characterized by lymphocytes, macrophages and multinucleated giant cells. Degradation and possible exposure of individual cellulose fibres may account for the poor performance of alkali-cellulose membranes in vivo. This animal and in vitro study indicates that when choosing a non-resorbable membrane for GBR, e-PTFE membranes are likely to perform better than those produced from alkali-cellulose.

Alveolar Bone Loss↗
PubMed1999

Glass-ionomer cement: evaluation as an orbital implant.

BACKGROUND: To assess the potential of a porous glass-ionomer cement (GIC) as an alternative material for spherical orbital implants, the handling, side effects and rates of fibrovascular ingrowth of this material were compared with those of a synthetic hydroxyapatite (HA) implant. METHOD: Twenty-one GIC and 8 HA uncovered 14-mm spheres were implanted into the orbits of New Zealand albino rabbits. Postoperative reactions, animal's behaviour, weight increase and socket conditions were monitored. Light and electron microscopy of the exenterated orbits were performed 2, 3 and 6 months after primary insertion. RESULTS: Implanting of GIC was easier than HA. Postoperatively all animals did well. Three HA and 1 GIC implant caused conjunctival dehiscences, but no implant extrusion was observed. Histologically, both materials caused mild inflammation in the surrounding connective tissue capsule, decreasing with time. GIC implants proved to be not truly porous, with only peripheral pores partly occupied by relatively acellular collagenous connective tissue. Free glass particles were observed in both the connective tissue and giant cells, occupying the partly filled pore spaces. HA implants showed extensive ingrowth of vital host tissue from the beginning. CONCLUSIONS: Considering the clinical findings and the mild inflammation in the connective tissue capsule surrounding both materials, they would appear to be equally well tolerated at the implant site. The significantly different microstructure and the histological results make GIC, despite better handling, less suitable as an orbital implant.

Animals↗
PubMed1998

Plasma copolymer surfaces of acrylic acid/1,7 octadiene: surface characterisation and the attachment of ROS 17/2.8 osteoblast-like cells.

The purpose of this study was: (a) to examine the effect of plasma-gas composition on plasma polymer oxygen/carbon (O/C) ratio, functional group composition and stability in water, and then (b) to examine cell attachment to surfaces containing different concentrations of O/C and functional groups. Oxygen-functionalised surfaces were deposited by means of the plasma copolymerisation of acrylic acid/1,7-octadiene. The use of a diluent hydrocarbon allowed the deposition of surfaces with a range of O/C concentrations. Plasma copolymer surfaces were characterised by X-ray photoelectron spectroscopy (XPS). Changes in functional group composition with % acrylic acid monomer and the non-dispersive and dispersive parts of the surface energy of these plasma copolymers were measured. The solubility of the plasma copolymers was assessed by means of XPS. The degree of attachment of ROS 17/2.8 osteoblast-like cells to plasma copolymer surfaces deemed to be 'stable' in aqueous medium was measured. Tissue culture polystyrene (TCPS) was included as a control. Attachment was found to be greatest to the plasma copolymer surface with an O/C of 0.11. This surface had a carboxylic acid concentration of ca. 3%. Attachment did not correlate with increased surface wettability (i.e. the non-dispersive component of the surface energy).

Acrylates↗
PubMed1998

Glass-ionomers: bioactive implant materials.

Glass-ionomer cements (GICs) originally designed for use as dental materials have a number of advantages over acrylic bone cements. These include lack of exotherm during setting, absence of monomer and improved release of incorporated therapeutic agents; this has resulted in the development of GICs for biomedical applications. Major landmarks in this history are the formulation of defined-composition ionomer glasses and an improved understanding of the biological and material properties of GICs. Following implantation, GICs can form a stable integration with bone, and affect the growth and development of bone, both adjacent to their surface and systemically, through an ion release mechanism. The 'non-inert' nature of this group of materials is also demonstrated by their adverse effects on neural tissue. Successful clinical use of GICs, both as bone cements and as preformed implants for hard tissue replacement, have been reported in the fields of otologic surgery (Cochlear implant fixation, repair of the tympanic chain, eustation tube obliteration and as ear ossicles), and oral and reconstructive surgery. The use of GICs in situations where they will come into contact with nerves or neural tissue is contraindicated.

Animals↗
PubMed1997

Role of exchanged ions in the integration of ionomeric (glass polyalkenoate) bone substitutes.

Ionomeric (glass polyalkenoate) implants are synthetic materials which can be used for repairing bone defects. It has been suggested that ions are leached from these implants during healing and that they influence cellular activity in the surrounding tissues. Morphological, immunohistochemical and microanalytical techniques were used to compare the osteogenic capacity of implants which eluted aluminium ions with implants which did not elute aluminium ions. The extracellular matrix molecules fibronectin and tenascin were located upon the surface of both implanted materials. Thick seams of lamellar bone were apposed to implants containing labile aluminium ions, but the bone was poorly mineralized. At the same time, transient increases were apparent in osteoblast activity on periosteal and endosteal surfaces and in chondrocyte activity in the growth plate and articular cartilages. In contrast, small amounts of mineralized lamellar bone were apposed to substituted implants (without aluminium) and the growth plate and articular cartilages remained normal in thickness and morphology. These results suggest that exchanged ions can influence the amount and quality of bone apposed to the implant. They also suggest that the effect of the ions depends upon their concentration and the state of differentiation of osteogenic cells.

Aluminum↗
PubMed1994

The response of cultured bone cells to resorbable polyglycolic acid and silicone membranes for use in orbital floor fracture repair.

Two membranes intended for use in repairing fractures of the orbital floor--reinforced silicone and biodegradable polyglycolic acid (PGA)--were evaluated in vitro using a rat bone cell culture model. After two weeks in culture, cells had colonised the surface of both materials. Bone cells penetrated the weave of the PGA membrane after three weeks in culture, forming a calcified collagenous bone-like tissue within the weave of the PGA at the same time as there was evidence of resorption of the PGA. In contrast, cells could easily be dislodged from the surface of the reinforced silicone membrane and there was less evidence of mineralised extra cellular matrix production. The production of a bone-like tissue within the weave of the PGA membrane supported previous reports of osteoconductive activity of this material.

Animals↗
PubMed1993

X-ray microanalytical detection of iron in pigmentation of oral mucosa.

A patient was referred to the Charles Clifford Dental Hospital with a grey metallic pigmentation of the hard palate. Conventional histopathological examination was inconclusive, suggesting the presence of either an ephelis (freckle) or pigmentation resulting from a stainless steel upper denture. Material from the pathological specimen was dewaxed and reembedded in Spurr's resin. Examination in the TEM revealed electron dense deposits in the cytoplasm of macrophages. Energy dispersive X-ray microanalysis demonstrated that these inclusions contained iron. The results suggested that the iron was in a form similar to haemosiderin and had arisen from the steel denture.

Dentures↗
PubMed1992

Characterisation of the ultrastructure of glass-ionomer (poly-alkenoate) cement.

Set glass-ionomer cements were sectioned with a diamond knife and examined in the transmission electron microscope. Their appearance was in accordance with the theoretical structure of these materials, close examination revealing glass particles surrounded by a siliceous layer set in a hydrogel matrix. The elemental composition of each region was determined by X-ray microanalysis (energy dispersive). The results of microanalysis supported the ultrastructural observations, with ions that originated from the glass particles being detected throughout the matrix of the set cement. It was suggested that the mobility of these ions in the matrix phase was important in determining the biocompatibility and adhesive properties of glass-ionomer cements.

Electron Probe Microanalysis↗
PubMed1992

Bone cell interactions with a granular glass-ionomer bone substitute material: in vivo and in vitro culture models.

The interface between bone and a synthetic bone substitute constructed from glass-ionomer cement (ionomeric microimplant) was studied in diffusion chambers implanted in a primate baboon model (Papio ursinus) and in in vitro primary bone organ cultures derived from neonate rat calvaria. In both models osteoblast-like cells colonized the surface of the implant producing a collagenous extracellular matrix. An electron-dense bonding zone similar to that reported for hydroxyapatite and titanium was seen in both models but was a more constant feature of the tissue/implant interface in calvarial culture.

Animals↗
PubMed1991

Oxygen saturation during third molar removal with local anaesthetic alone and in combination with intravenous sedation.

Oxygen saturation was recorded in 96 adults undergoing removal of third molar teeth in the dental surgery. Half the patients received local anaesthetic alone; the remainder received, in addition, intravenous midazolam. Patients receiving sedation sustained the greatest falls in oxygen saturation. However, in 10 out of 48 patients undergoing third molar removal with LA alone, oxygen saturations in the range of 93-89% were recorded. The results of this study suggest that all patients undergoing removal of third molars are at risk of hypoxia. Short episodes of hypoxia may be of little consequence in healthy patients, but in compromised patients early detection may avoid serious complications.

Adult↗
PubMed1991

Controlled intraoral delivery of hydrocortisone sodium succinate.

Controlled release of hydrocortisone sodium succinate from a device consisting of a drug containing a core of polymethyl methacrylate was achieved by the use of a design incorporating impermeable barriers to drug diffusion and the use of a semipermeable membrane. Initial in vivo study showed sustained intraoral delivery of hydrocortisone sodium succinate during a 6-day period.

Administration, Oral↗
PubMed1991

In vitro interaction between primary bone organ cultures, glass-ionomer cements and hydroxyapatite/tricalcium phosphate ceramics.

Primary organ cultures derived from neonate rat calvaria were maintained for 2 wk and used to study in vitro response of osteoblast and periosteal cells to the component and composite forms of three different glass-ionomer (polyalkenoic) cements, comparing them to densely sintered hydroxyapatite and tricalcium phosphate ceramics. Qualitative analysis by scanning and transmission electron microscopy revealed that osteoblasts colonized all the solid test materials, although there was a less favourable response to materials with a rough surface topography and to unset and fluoride-containing glasses. On solid materials migrated cells maintained their tessellated morphology and exhibited numerous micro-appendages anchoring them to the surface of the test materials. A collagen-containing extracellular matrix was elaborated on to the ceramics and set glass-ionomer cements, except for one (AquaCem). Mineralization of the extracellular matrix was seen adjacent to hydroxyapatite and tricalcium phosphate ceramics, that adjacent to the latter morphologically resembling bone.

Animals↗
PubMed1991

Management of the atrophic anterior maxilla by combined hydroxyapatite augmentation and vestibuloplasty: a pilot study.

A technique is described to overcome the problem of the grossly resorbed maxillary alveolus and improve denture wear, by combining augmentation and increased soft tissue cover of the alveolar ridge. Manipulation and placement of the hydroxyapatite was facilitated by use of a hydroxyapatite/collagen composite (HAC) block. The procedure has been carried out in ten patients where extensive resorption contraindicated the use of permucosal implants. Six cases have been followed up for 2 to 3 years. After some initial compaction of HAC the improvement in ridge height has been maintained and long term improvement in denture function obtained.

Alveolar Bone Loss↗
PubMed1991

Initial in-vivo evaluation of glass-ionomer cements for use as alveolar bone substitutes.

The response of rat femora to implantation of four glass-ionomer (polyalkenoic) cements (GIC) compared to that seen following implantation of densely sintered hydroxyapatite (Ha) ceramic was evaluated for periods up to 12 weeks. Light and transmission electron microscopic analysis of the GIC/bone interface revealed direct bonding of the GIC G338 and Ketac Cem (both based on fluoro-alumino-silicate) glasses to bone, with a mineralized collagen-containing extra-cellular matrix deposited on the surface of the GIC. AquaCem and the fluoride-free GIC based on MP4 glass showed incomplete osseointegration.

Alveolar Ridge Augmentation↗
PubMed1990

Inhibition of tissue prostaglandin synthesis during third molar surgery: use of preoperative fenbufen.

Preoperative administration of a non-steroidal anti-inflammatory drug (fenbufen) reduced immediate postoperative pain in a group of 38 patients undergoing removal of mandibular third molars, compared to placebo. However, overall pain experience and morbidity were not significantly improved suggesting that there was no clinical benefit derived from interference with tissue prostaglandin synthesis at the time of surgery.

Adult↗