Contour analysis of an implant--soft tissue interface.

BACKGROUND AND OBJECTIVE: Studies of peri-implant soft tissue on in vivo models are commonly based on histological sections prepared using undecalcified or 'fracture' techniques. These techniques require the cutting or removal of implant during the specimen preparation process. The aim of this study is to explore a new impression technique that does not require any cutting or removal of implant for contour analysis of soft tissue around four types of titanium (Ti) surface roughness using an in vitro three-dimensional oral mucosal model (3D OMM). METHODS: The 3D OMM was constructed by co-culturing a keratinocyte cell line TR146 and human oral fibroblasts on to an acellular dermis scaffold. On the fourth day, a Ti disk was placed into the model. Four types of Ti surface topographies, i.e. polished, machined, sandblasted and anodized were tested. After 10 d of culture, the specimens were processed based on undecalcified (ground sectioning), electropolishing and impression techniques for contour analysis of the implant-soft tissue interface. RESULTS: Under light microscopic examination of the ground and electropolishing sections, it was found that the cell line-based oral mucosa formed a peri-implant-like epithelium attachment on to all four types of Ti surfaces. In contour analysis, the most common contour observed between the cell line-based oral mucosa and Ti surface was at an angle ranging between 45° and 90°. CONCLUSION: The in vitro cell line-based 3D OMM formed a peri-implant-like epithelium at the implant-soft tissue interface. The contour of the implant-soft tissue interface for the four types of Ti surface was not significantly different.

Comparison of in vitro and in vivo bioactivity of SrO-CaO-ZnO-SiO2 glass grafts.

A range of calcium-strontium-zinc-silicate glass grafts are developed. Following characterization, their ability to form an apatite layer in simulated body fluid (SBF) is evaluated. Concurrently, their in vivo biocompatibility is determined. These glasses are incapable of forming an apatite layer in SBF. However, in vivo, each glass is well tolerated with new bone formation apparent in close apposition to implanted particles and no evidence of an inflammatory response. Such results are contrary to much of the literature and indicate that forecasting a materials ability to bond to bone based on SBF experiments may provide a false negative result.

Tissue-engineered oral mucosa: a review of the scientific literature.

Tissue-engineered oral mucosal equivalents have been developed for clinical applications and also for in vitro studies of biocompatibility, mucosal irritation, disease, and other basic oral biology phenomena. This paper reviews different tissue-engineering strategies used for the production of human oral mucosal equivalents, their relative advantages and drawbacks, and their applications. Techniques used for skin tissue engineering that may possibly be used for in vitro reconstruction of human oral mucosa are also discussed.

In vitro biocompatibility of fluorcanasite glass-ceramics for bone tissue repair.

Fluorcanasite glass-ceramics were produced by controlled two stage heat-treatment of as-cast glasses. These glasses were modified from stoichiometric fluorcanasite composition by either adding P(2)O(5) or altering the molar ratios of Na(2)O and CaO. Commercial bioactive 45S5 Bioglass(R) was also prepared in-house to evaluate the relative in vitro biocompatibility of fluorcanasite glass-ceramics. The scanning electron microscopy (SEM) images showed that cells had colonized the surfaces of fluorcanasite glass-ceramics to form a confluent sheet. Quantitative MTT assay results were in good agreement with the qualitative SEM observations. It was concluded that incorporation of excess calcium oxide or P(2)O(5) in stoichiometric glass composition improved in vitro biocompatibility. Controlled heat-treatment further improved the biological response of cultured bone cells to modified fluorcanasite glass-ceramics when compared with their parent glasses. Ion release and pH data suggested a strong correlation between solubility (in particular, Na ion release) and biocompatibility. Reduced solubility, Na ion release, and related pH effects appeared to be the principal mechanisms responsible for improvement in in vitro biocompatibility.

Biocompatibility of glass-ionomer bone cements.

Glass-ionomer cements (GIC) have been extensively used in dentistry for over 30 years. Due to their excellent biocompatibility in dental applications GIC have been formulated for medical applications. The past decade has seen some impressive advances in the development of medical GICs, however these advances have been matched by serious critical problems. This review examines the properties of GICs, which can influence their behaviour in a biological environment. The progress made and the problems encountered in the development of these bone cements will also be addressed. The review will conclude with the research currently being employed to optimise the biocompatibility of these important biomaterials. There is little doubt that GICs compare favourably with alternative bone cements for specific applications, based on in vitro and in vivo studies. There is however, a degree of risk inherent in the use of any medical device or biomaterial. GICs must therefore be used carefully and in accordance with the instructions that are based on a significant body of research data.

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.

Drug release from acrylic polymers via channels and cracks: in vitro studies with hydrocortisone.

Release of hydrocortisone sodium succinate from acrylic resin was found to occur readily on elution in water at 37 degrees C. Increasing the degree of hydration of the acrylic resin by the addition of hydroxyethyl methacrylate impaired rather than enhanced the release of drug. The mechanism for the release of drug is believed to be surface release and drug dissolution into and diffusion via cracks and channels which are formed by incorporation of the drug, producing a 'drug-modified polymer'. Diffusion through the polymer matrix is believed to be insignificant. The results obtained are discussed in relation to this proposed model for drug release. A simple method for the manufacture of the core of an intra-oral insert capable of delivering drugs with MW greater than 400 for systemic and topical oral drug delivery is described.

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.

Controlling drug release from acrylic polymers: in vitro studies with potential oral inserts.

The use of a drug modified polymer system which can release drugs such as hydrocortisone sodium succinate and chlorhexidine acetate has been explored. By partially coating the drug loaded acrylic, such that it acts as a core with an impermeable membrane covering most of the surface, the rapid releases of the drug can be prevented and near zero-order rates of release achieved. For chlorhexidine acetate the release time was extended from around 20 d to 80 d with at least 60% of the drug being released. A similar potential for the controlled release of hydrocortisone sodium succinate is described and represents an important stage in the development of an intra-oral insert for drug delivery.

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.

Tissue response to subperiosteal implantation of dense hydroxyapatite: case report.

Hydroxyapatite is becoming a popular implant material, yet reports on the tissue response it evokes in humans have been few in number and are based on relatively short periods of implantation. In the present case, implant material became available when it proved necessary to modify an alveolar ridge augmentation procedure carried out 18 month previously. Histology showed that whilst some parts of the implanted material were embedded only in fibrous tissue, others had become fully integrated within partly remodelled bony trabeculae. These findings confirm the status of hydroxyapatite as a biocompatible implant material and provide further evidence of its bone-bonding and osteoconductive capacities.

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.

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).

Bone healing following the use of hydroxyapatite or ionomeric bone substitutes alone or combined with a guided bone regeneration technique: an animal study.

The healing of standardized bone defects grafted with either particulate ionomeric or hydroxyapatite bone substitutes was compared in the mandibular ramus of 30 Sprague-Dawley rats. The possible additional response achieved when combining these materials with a guided bone regeneration (GBR) technique was also evaluated. Three groups of 10 animals received either no implant material or ionomeric or hydroxyapatite bone substitute in defects in the right ramus. The left mandibular defects received the same treatment, except that the operation site was covered by a membrane (GBR technique). Half of the animals were sacrificed at 4 and 10 weeks following surgery, and the inflammatory response at the implant site and the amount of new bone formed in the defects were determined histomorphometrically. Defects implanted with ionomeric bone substitute exhibited more bone formation (4 weeks = 3.19 +/- 0.35 mm2, 10 weeks = 5.35 +/- 0.26 mm2) than both defects that received no treatment (4 weeks = 0.88 +/- 0.35 mm2, 10 weeks = 2.1 +/- 0.49 mm2), membrane alone (4 weeks = 1.21 +/- 0.05 mm2) or hydroxyapatite bone substitute (4 weeks = 1.41 +/- 0.46 mm2, 10 weeks = 3.34 +/- 0.41 mm2) at 4 weeks (P < or = .01) and at 10 weeks (P < or = .05). The use of a GBR technique did not increase the amount of bone formed, compared to the use of bone substitutes alone. Hydroxyapatite and ionomeric bone substitutes used alone were more effective in inducing repair of the defects than was GBR membrane alone. The use of hydroxyapatite was associated with a greater inflammatory reaction (P < or = .01) than was ionomer in this model.

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.

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.

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.

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.

Self-reinforced polyglycolic acid membrane: a bioresorbable material for orbital floor repair. Initial clinical report.

A self-reinforced polyglycolic acid membrane has been used successfully to repair 15 orbital floor fractures in 12 consecutive patients. As polyglycolic acid is absorbable it does not cause the complications of long-term infection and migration associated with non-absorbable bioinert alloplastic repair materials.

Inhalation of a denture fragment complicating facial trauma.

A case of facial trauma is presented, which was complicated by a denture fragment lodged in the larynx. This potentially life threatening event caused minor symptoms only. Its diagnosis and management are reported.