Tetracycline-encapsulated P(3HB) microsphere-coated 45S5 Bioglass(®)-based scaffolds for bone tissue engineering.

Bioglass(®)-based scaffolds for bone tissue engineering have been developed, which can also serve as carriers for drug delivery. For this, P(3HB) microspheres (PMSs) loaded with tetracycline were fabricated and immobilised on the scaffold surfaces by a modified slurry dipping technique. The sustained drug delivery ability in simulated body fluid was confirmed by using UV-Vis absorption spectroscopy measurements. The MTT assay using mouse fibroblast cells provided evidence that the tetracycline loaded microspheres produced in this study show limited cytotoxicity. The scaffolds developed in this work provide mechanical support, adequate 3D surface roughness, bioactivity and controlled drug delivery function, and are thus interesting candidates for bone tissue engineering applications.

Ultramorphology and dentine permeability changes induced by prophylactic procedures on exposed dentinal tubules in middle dentine.

OBJECTIVES: The purpose of this study was to evaluate the changes in dentinal permeability (i.e. hydraulic conductance) after prophylactic treatment performed using prophy-powders with air-polishing system or prophy-pastes applied on exposed middle dentine. The changes in dentine morphology were evaluate by SEM. STUDY DESIGN: Several prophylactic pastes or air-polishing powders were tested in this study. Dentine discs from human third molars were used to study the quantitative reduction of the dentine permeability under simulated pulpal pressure (20 cm H2O). Further specimens were gold-coated and observed with the use of a SEM. RESULTS: The results of this study showed different reductions of dentin permeability effects based on the type of product employed (i.e. prophylactic paste or air-polishing powders). The use of Sylc bioactive glass and sodium bicarbonate were the most effective in reducing dentine permeability of the specimens etched with the phosphoric. The air-polishing procedures performed with Sylc bioactive glass created a dentine surface devoid of exposed dentinal tubules due to the presence of a compact multilayered smear layer. Colgate Sensitive Pro-Relief and Nupro NU-Solution reduced the dentine permeability up to 69.8% and 66.9% respectively. CONCLUSION: Although all the tested products are able to statistically reduce dentine permeability, Sylc bioactive glass is an innovative and effective product suitable for the reducing of the dentine permeability during prophylactic procedures of air-polishing.

Prospective cohort comparison of bioactive glass implants and conchal cartilage in reconstruction of the posterior canal wall during tympanomastoidectomy.

OBJECTIVE: To compare the effectiveness of bioactive glass implants and conchal cartilage in reconstructing the posterior canal wall during tympanomastoidectomy. STUDY DESIGN: Prospective cohort clinical study. SETTING: Teaching hospital. PATIENTS: Patients with clinically diagnosed chronic suppurative otitis media and cholesteatoma awaiting tympanomastoidectomy were recruited. INTERVENTION: All patients underwent tympanomastoidectomy by the same surgeon. A first cohort of 12 patients underwent posterior canal wall reconstruction with autogenous conchal cartilage. A second cohort of 12 patients underwent such reconstruction with prefabricated bioactive glass. MAIN OUTCOME MEASURES: Primary- All patients underwent out-patient review at 1, 3, 6 and 12 months postoperatively, after which a second-look procedure was performed. Reconstructions were inspected for evidence of epithelialization, granulation, infection, stenosis, depression and extrusion. Secondary- All patients had perioperative serial pure-tone audiometry to check for any change in hearing levels upto 1 year postoperatively. RESULTS: By 1 year postoperatively, both reconstructive graft materials showed good epithelialization, no granulation, no infection, no ear canal stenosis, no depression and no extrusion. At operative second-looks, bioactive glass particularly showed good tissue bonding, including both neovascularization and connective tissue integration. Overall clinical outcome was equivalent for both materials. Both graft materials showed no statistically significant difference in postoperative hearing levels. CONCLUSIONS: Bioactive glass and conchal cartilage showed equivalent clinical outcome in reconstructing the posterior canal wall without significantly affecting hearing levels. As bioactive glass does not require second site morbidity and thus also reduces operative time, we prefer it for reconstructing the posterior canal wall following tympanomastoidectomy.

Mechanical behaviour of zirconia and zirconia-toughened alumina in a simulated body environment.

The mechanical properties of a zirconia-toughened alumina (ZTA) and three tetragonal zirconia polycrystal ceramics (TZPs), together with a biograde alumina, have been assessed in a simulated body solution (Ringer's solution). The hardness and fracture toughness of these materials were unchanged from the values in air when the tests were carried out in Ringer's solution; there was an instantaneous fall in strength in Ringer's solution but this was considered acceptable. However, ageing for long periods in Ringer's solution promoted a surface layer of monoclinic zirconia. This was accompanied by a strength decrement and it is concluded that these yttria-stabilized ZTA and TZP materials are unsuitable as implant materials.

Silver enhancement of polymerised diaminobenzidine: increased sensitivity for immunoperoxidase staining.

Unambiguous identification of lymphocytes is sometimes difficult because of weak immunostaining of the cell membrane immunoglobulins. A simple method of intensifying the diaminobenzidine (DAB) peroxidase reaction was therefore devised. Paraffin wax sections of formalin fixed tonsils and lymphomas were digested with trypsin and immunostained for kappa and lambda light immunoglobulin chains and CD3 antigen by various peroxidase linked detection systems. After reaction with hydrogen peroxide and DAB the sections were immersed in methenamine silver solution at 60 degrees C for three to seven minutes. The light brown stain on the cell membranes of the mantle zone lymphocytes became dark brown and the stronger stain of the plasma cells became black. Mantle zone B lymphocytes and CD3 positive T lymphocytes were precisely outlined even at low magnification and the lymphomas were easily classified as monoclonal or polyclonal. At high magnification, staining was clearer than with the immunogold-silver stain. Cryostat and paraffin wax sections of other tissues immunostained for various antigens showed similar intensification. Silver methenamine provides an easy means of increasing the sensitivity and visual impact of an immunoperoxidase/DAB reaction in any preparation.

Manufacture and release characteristics of Elvax polymers containing glutamate receptor antagonists.

Implantable sustained-release polymers offer an alternative to osmotic minipumps for the local delivery of drugs to specific brain areas. Here we describe the production of Elvax polymers containing a range of glutamate receptor antagonists and the quantitative characterization of their release properties. Sections of Elvax (200 or 400 microns), prepared by a dimethyl sulphoxide-based method, containing the NMDA antagonist MK-801 or the non-NMDA antagonist CNQX exhibited similar release profiles: an initial 2-week burst followed by a slow decline in release rate over the next 6 weeks. Differences in slice preparation method and thickness or drug concentration and solubility all led to alterations in the level of drug release, but not the overall exponential nature of the release curve. Elvax sections prepared by an aqueous method containing the NMDA antagonists CPP or APV displayed more constant but much lower levels of release than those from the dimethyl sulphoxide-based method. The in vitro release characteristics were compared with in vivo release of MK-801 and the close correspondence observed indicates that the in vitro release data is an accurate predictor of the drug release behaviour of implanted Elvax slices.

Evaluation of Bioglass/dextran composite as a bone graft substitute.

Allogenic and alloplastic bone graft substitutes serve either as bioinert or bioactive osteoconductors. Bioglass is a bioactive osteoconductor and also shows osteoproductive effects due to its high level of bioactivity. However, the material lacks some cohesiveness when used in augmenting certain bony surfaces, i.e. large or pleomorphic defects. The addition of medium molecular weight dextran modifies the particulate to a putty consistency and improves the handling characteristics. The objective of this study is to evaluate the influence of dextran upon the bioactive properties of Bioglass. Standardized bony defects in the lateral femoral condyles in adult New Zealand white rabbits were filled with one of five material groups: (1) autogenous bone; (2) Bioglass particulate; (3) Bioglass particulate mixed with dextran to a putty-like consistency; (4) a mixture of Bioglass and autogenous bone; (5) a mixture of Bioglass putty with autogenous bone. Postoperative healing was observed after periods of 2 days, 1, 2, 3, 6 and 12 weeks. Results showed no evidence of toxicity in the dextran-containing materials, and defects in all test groups showed 100% bony ingrowth within 6 weeks. The addition of medium molecular weight dextran did not appear to alter the bioactive properties of Bioglass and had no adverse influence upon the ingrowth of bone into the defect sites.

Hemangiomatous ameloblastoma: Clinical, radiologic, and pathologic features.

A hemangiomatous ameloblastoma was present in the third molar region of the left mandible of a 26-year-old woman. The histology and radiologic features of this tumor differed from those of a conventional ameloblastoma. Its histologic features were consistent with those of a hemangiomatous ameloblastoma, and its standard radiologic features and computed tomography mimicked that of fibro-osseous lesions, whereas magnetic resonance imaging suggested a vascular lesion. The behavior and prognosis of the hemangiomatous ameloblastoma are uncertain because of the small number of documented cases and lack of long-term follow-up, but are thought to be similar to those of the conventional type. The relevant clinical, radiologic, and pathologic features of this case are presented.

Exhumation following incorrect identification. A case report.

The exhumation of two victims of a light aircraft accident was performed in February 1991 at Oudtshoorn, Cape. The exhumation was ordered by the magistrate on request of the parents of one of the victims who suspected that their son had been wrongly identified at the postmortem examination. At the pre-burial autopsy all the victims were positively identified, but the identity of two of the victims was subsequently reconsidered and reversed because one of them wore a silver bracelet. Burial then took place. The exhumation was ordered one month after the accident at which stage the bodies were in an advanced state of decomposition. Oral autopsies were performed on each of the victims, the jaws were radiographed and postmortem dental records drawn up. Dental records were obtained from the dentists who treated them and the information from these records was used to draw up ante-mortem dental records. A comparison between the postmortem and ante-mortem records showed that the victims were incorrectly identified and reburial in the correct graves was subsquently carried out. This case again emphasies the importance of dental identification in cases of severe burning, multilation or decomposition in order to avoid mistaken identity and incorrect burial in the future.

A bitemark case with a twist.

This is a case report in which the bite patterns of two suspects were compared to a bitemark on the breast of a murder victim. Each suspect had sufficient concordant features to have been found guilty of producing the bitemark. The irony in this case is that the bitemark was not inflicted by the murderer.

Mechanical properties of bioactive glasses, glass-ceramics and composites.

The application of bioactive glass and glass-ceramics has been widely documented over the past twenty years but the high modulus and low fracture toughness has made them less applicable for clinical, load bearing, applications. The development of non-resorbable polyethylene and polysulphone matrices for these materials has improved the mechanical properties. However, the primary concern of whether the bioactivity of the composites is reduced is still unresolved. The more recent development of resorbable carrier systems, dextran and collagen, for bioactive glasses does not introduce such problems, hence making this form of composite suitable for novel soft tissue applications. The development of a simple quality index has enabled some of the materials described within this paper to be ranked by their ability to replace bone, thus enabling possible new research directions to be emphasized.

Periurethral polytetrafluoroethylene injections for post-prostatectomy incontinence.

Incontinence following prostatectomy is relatively common and produces well-known social and pathologic consequences. Previous reports have shown that periurethral injections of polytetrafluoroethylene (PTFE or Teflon) can provide continence in many patients with a variety of etiologies. Politano's group has shown about 50% of his incontinence radical prostatectomy patients to be cured or improved by these injections. Our experience with 10 patients found that overall, six of 10 were cured or improved. Five of six radical prostatectomy patients were cured or improved after radical prostatectomy and radiation therapy. One patient has subsequently undergone artificial sphincter placement without difficulty. PTFE injections may be a low morbidity procedure for the treatment of post-prostatectomy incontinence and still allow for later artificial sphincter placement if required.

An experimental cyst model established from human unkeratinized vaginal mucosa.

Because of the scarcity of sizeable specimens of normal oral mucosa and the availability of human vaginal mucosa, which resembles the lining mucosa of the mouth, we used the latter to establish a human cyst model. Fragments of vaginal mucosa, removed during corrective procedures, were sutured around 2 mm glass balls and implanted into the flanks of nude mice. Thirty-seven specimens were implanted and 31 harvested after 3, 6, 9 and 12 weeks. At 6 weeks the wall of the implanted cyst consisted of recognizable unkeratinized vaginal mucosa but had not healed completely at the sutured edges. From 9 weeks the cyst cavities were healed and the lumens lined by unkeratinized stratified squamous vaginal epithelium. The enclosing connective tissue had retained the characteristics of the lamina propria of the vaginal mucosa and could be distinguished from mouse tissue.

Recurrent unicystic ameloblastoma of the maxilla.

A previously reported unicystic ameloblastoma, showing luminal plexiform epithelial proliferation and the presence of small islands of odontogenic epithelium in the connective tissue of the cyst wall, recurred 5 years after conservative surgery. The tumour was nucleated and since the epithelial islands were confined to its fibrous capsule a conservative approach was regarded as adequate. In view of the later experience it is now proposed that where cystic ameloblastomas depict epithelial infiltration into the capsule a second excision be considered and that such surgical material be thoroughly examined for signs of epithelial infiltration. Whatever type of treatment the surgeon decides to perform, it is essential to have a long postoperative period of monitoring. Because the presence of islands of odontogenic epithelium in the cyst wall influences the surgical approach, it is recommended that pathologists carefully examine cystic ameloblastoma surgical specimens for their presence. Multiple, even serial sections are required for such examinations. The pathology report should include a description of the islands with an indication of their site in the capsule of the tumour.

Odontoameloblastoma: a case report.

Confusion in the early literature regarding the odontoameloblastoma, resulted in this tumour being reported under a variety of names. Many of the reported cases fail to meet the clinical and histological criteria required for classification as odontoameloblastomata. This article attempts to present a case with clinical, radiological and histological features that meet the required criteria. In this case the ameloblastic component intermingled with the dental hard tissues.

In vitro effect of air-abrasion operating parameters on dynamic cutting characteristics of alumina and bio-active glass powders.

Minimally invasive dentistry advocates the maintenance of all repairable tooth structures during operative caries management in combination with remineralization strategies. This study evaluated the effect of air-abrasion operating parameters on its cutting efficiency/pattern using bio-active glass (BAG) powder and alumina powder as a control in order to develop its use as a minimally invasive operative technique. The cutting efficiency/pattern assessment on an enamel analogue, Macor, was preceded by studying the powder flow rate (PFR) of two different commercial intraoral air-abrasion units with differing powder-air admix systems. The parameters tested included air pressure, powder flow rate, nozzle-substrate distance, nozzle angle, shrouding the air stream with a curtain of water, and the chemistry of abrasive powder. The abraded troughs were scanned and analyzed using confocal white light profilometry and MountainsMap surface analysis software. Data were analyzed statistically using one-way and repeated-measures analysis of variance tests (p=0.05). The air-abrasion unit using a vibration mechanism to admix the abrasive powder with the air stream exhibited a constant PFR regardless of the set air pressure. Significant differences in cutting efficiency were observed according to the tested parameters (p<0.05). Alumina powder removed significantly more material than did BAG powder. Using low air pressure and suitable consideration of the effect of air-abrasion parameters on cutting efficiency/patterns can improve the ultraconservative cutting characteristics of BAG air-abrasion, thereby allowing an introduction of this technology for the controlled cleaning/removal of enamel, where it is indicated clinically.

Minimally invasive caries removal using bio-active glass air-abrasion.

OBJECTIVES: Alumina air-abrasion has been used to clean teeth and shown to over-prepare access cavity preparation to caries. This study investigated the working hypothesis that bio-active glass air-abrasion is more self-limiting than alumina for minimally invasive caries removal. METHODS: Human extracted molars were scored visually using ICDAS II criteria, divided into sound and carious groups and air-abraded with alumina (n=10) and bio-active glass (n=10) in each group, using identical operating parameters. The amount of enamel removed was semi-quantitatively assessed using scanning electron microscopy. Operating time was recorded. RESULTS: Bio-active glass abrasion removed extrinsic stain and substantial quantities of enamel from all carious fissures but not from sound, where only minimal microscopic surface modifications were observed. Alumina air-abrasion resulted in faster extrinsic stain and clinically substantial enamel removal in both sound and carious groups equally. CONCLUSIONS: Bio-active glass air-abrasion appeared to show a significant self-limiting tendency towards demineralised enamel and extrinsic stain removal but was slower in comparison to alumina air-abrasion. Self-limiting bio-active glass air-abrasion could be used clinically to clean teeth, detect caries and minimally prepare carious enamel as part of MI caries access or placing a sealant restoration.

A clinical evaluation and comparison of bioactive glass and sodium bicarbonate air-polishing powders.

OBJECTIVE: Compare clinical effectiveness of sodium bicarbonate and bioactive glass powders used for dental prophylaxis. METHODS: 25 patients were allocated to either good or poor oral hygiene subgroups (n=50). Using a double-blind, split-mouth model, all patients underwent prophylaxis treatment on mandibular teeth; maxillary teeth were untreated controls. Bioactive glass (Sylc, OSspray Ltd., UK) and sodium bicarbonate (Prophy Jet, Dentsply, UK) were applied randomly to opposite sides of each mouth. Sensitivity to cold air/ethyl chloride, dental shade change and procedural comfort were measured. All parameters were recorded immediately pre- and post-treatment and at 10-day recall. RESULTS: Bioactive glass air-polishing, in both subgroups, reported a 44% (0.80+/-0.10, p<0.05) decrease in dental sensitivity, against controls, immediately after application, and a 42% (0.85+/-0.05, p<0.05) decrease at 10-day recall when stimulated with cold air. Ethyl chloride stimulation showed a 10% (3.05+/-0.17, p<0.05) and 22% (2.64+/-0.33, p<0.05) reduction in sensitivity immediately post-op and at 10-day recall. Application of sodium bicarbonate powders increased sensitivity, 17% (1.76+/-0.3, p<0.05), at 10 days when stimulated with cold air. Both powders showed variation between subgroups in colour change, bioactive glass powder 1 and 4 shades whiter, sodium bicarbonate 1 and 2 shades whiter in good and poor oral hygiene groups, respectively. Patients in both subgroups reported a 46% (7.9+/-1.4, p<0.05) increase in comfort of procedure with the bioactive glass over that when using sodium bicarbonate. CONCLUSIONS: Bioactive glass air-polishing was more clinically and statistically effective at desensitising both good and poor oral hygiene groups, and removing stain in the poor oral hygiene patient subgroup. Bioactive glass also provided better overall patient comfort during the procedure.

Dental implants and squamous cell carcinoma in the at risk patient--report of three cases.

Osseointegrated dental implants are increasingly used in the rehabilitation of the dental patient. They have a particular role in dental rehabilitation following treatment for oral cancer. Data is presented that suggests that, in the at risk patient, squamous cell carcinoma may develop in association with dental implants.

Dissolution characteristics of extrusion freeformed hydroxyapatite-tricalcium phosphate scaffolds.

The dissolution behaviour of calcium phosphate filaments made by extrusion freeforming for hard tissue scaffolds was measured. The solubility of filaments with different HA/beta-TCP ratios sintered at temperatures from 1,100 to 1,300 degrees C was measured under simulated physiological conditions (tris buffer solution: tris(hydroxyl) methyl-aminomethane-HCl), pH 7.4, 37 degrees C). Calcium and phosphate concentrations were measured separately by inductively coupled plasma (ICP) atomic emission spectroscopy. Surface morphologies and composition before and after immersion were analyzed by SEM and EDS. The results clearly show that as the beta-TCP content increased, the dissolution increased. Higher sintering temperatures, with consequent closure of surface pores, resulted in lower dissolution. Examination of the surface suggested dissolution on preferred sites by pitting.