Osseointegrated implants in a patient with osteoporosis: a case report

OBJECTIVE: To evaluate the performance of in situ piezolectric extracorporeal shock-wave lithotripsy (ESWL) in the middle part of the ureter. MATERIAL AND METHODS: 36 consecutive patients presenting with stones of the middle part of the ureter were treated by in situ piezoelectric ESWL (EDAP LT 02). The maximal dimensions of the stones ranged from 5 to 14 mm (m = 7.8). Moderate or severe ureterohydronephrosis was present in 19 cases (53%) and a double J stent had been previously implanted in 6 cases (17%). The ESWL sessions were performed in the ventral supine position without any anaesthesia or systematic premedication, but an IM injection of 100 mg of pethidine was administered during poorly tolerated treatments. RESULTS: The stone was located easily in 23 cases (64%) and with greater difficulty in 13 cases (36%), as an intraoperative intravenous injection of contrast agent was performed in 6 cases (17%). The number of sessions per patient ranged from 1 to 2 (m = 1.16). The complete sucess rate was 75%, with a 64% success rate after a single ESWL session. The performances were statistically independent of stone dimensions and the degree of obstruction of the urinary tract. The complication rate was 5.5%, but no ancillary endoscopic or percutaneous treatment was required. CONCLUSION: In situ piezoelectric ESWL allows effective management of most stones of the middle part of the ureter. However, the treatment of stones with a maximal diameter < 5 mm, especially poorly radiopaque stones, can raise problems of localization. Very large or impacted stones, especially when complicated by urinary tract infection, should be preferably treated by first-line ureteroscopy.     

Materials for endosseous dental implants

Melatonin production by isolated pineal glands from guinea pigs was examined under conditions that affect membrane potential or the firing of action potential-like spikes. In glands from superior cervical ganglionectomized animals, depolarization resulting from increasing extracellular potassium concentration to 100 mM did not initiate melatonin production, and it delayed the response to the beta-adrenoceptor agonist orciprenaline. In glands from intact animals melatonin production was initiated by exposure to 100 mM potassium with a time-course similar to the response to orciprenaline. A proportion of this response was propanol resistant, suggesting that the normal control of melatonin production may involve a neurotransmitter in addition to norepinephrine. Exposure to verapamil or nifedipine, or removal of extracellular calcium, previously shown to eliminate action potential-like spikes, did not substantially affect the increase in melatonin production induced by orciprenaline. Phenylephrine, which stimulates spiking, produced only a slight increase in melatonin production. It is concluded that the depolarization and the spiking are not closely related to the stimulation of melatonin production, but may relate principally to the secretion of a substance other than melatonin.     

Variability of hydroxyapatite-coated dental implants

Uniformity, surface roughness, and chemical phase structure are all important features of implant coatings. While the first two variables are important for implant placement, the phase structure affects implant fixation. This study examined the coating morphology and the amount, size, and distribution of crystalline regions of press-fit and screw-type dental implants. Implants obtained from five commercial vendors were sectioned sagittally, mounted, and polished to reveal the coating microstructure. The crystalline phase content varied depending on the implant supplier; however, general trends were observed. Amorphous regions were predominantly found at the metal interface and decreased toward the outside of the coating, producing a crystallinity graded coating. The distal end of the implant, where heat build-up was more likely during the coating procedure, displayed a higher crystalline content and larger crystalline regions. Similarly, the thread apex consisted of more of a crystalline phase. The results of this study of coating microstructure may be used to improve the quality and performance of implants and may help to explain different in vivo responses to the many available varieties of hydroxyapatite-coated dental implants.     

Osseointegrated endosseous implants, University of Liège concepts. Various clinical applications

The occurrence of optic neuropathy in patients with MS-like disorders who carry one of the pathogenetically significant LHON mutations as well as the higher incidence of maternal transmission in familial cases of MS support the hypothesis that mitochondrial genes may be implicated in susceptibility to MS. We sequenced the entire mtDNA of six children with MS who developed optic neuritis as early and prominent visual involvement. The analysis revealed a high degree of nucleotide variations relative to the standard mtDNA sequence. After excluding various synonymous nucleotide changes and common neutral polymorphisms, eight discrete novel missense mutations within the protein coding, tRNA or rRNA genes were detected. None of the eight polymorphic sites were found in common between the patients with MS. Of particular interest was the observation that five of six children carried a total of nine secondary LHON mutations at nucleotide positions 4216, 4917 or 13708. We conclude that variation in mtDNA is unlikely to contribute to genetic predisposition for MS. However, secondary LHON mutations may be regarded as additional risk factor for developing prominent optic nerve involvement. The association of individual sets of mtDNA variations with phenotypic presentation in certain subgroups of MS patients remains to be clarified.     

Educating a patient with dental implants

A functional dentition can be restored for edentulous and partially edentulous patients through the placement of dental implants. Dental assistants have a significant role in the education of implant patients so that meticulous oral self-care can be accomplished. Only through the combined team efforts of the dental office staff and patients themselves will the continued success of dental implantology be insured.     

Biomimicry, dental implants and clinical trials

The overall objective of this study was to develop pluronic F127 (PF127)-containing formulations of pilocarpine hydrochloride (PHCL) suitable for controlled-release ocular delivery of PHCL. Various aqueous formulations were evaluated containing 1% w/v PHCL and 25% w/v PF127 alone or with one of the following additives present: poly(ethylene glycol) 4600 (PEG), poly(vinylpyrrolidone) 10,000 (PVP), poly(vinyl alcohol) 10,000 (PVA), methylcellulose 15 cP (MC), and hydroxypropyl methylcellulose 80-120 cP (HPMC). The in vitro dissolution of the PF127 formulations and the pilocarpine release profiles from them were obtained simultaneously at 34 degrees C and room temperature using a membraneless in vitro model. It was observed that the PEG- and PVP-containing PF127 formulations of PHCL dissolved the quickest and released the drug at a significantly faster rate than the control PF127 formulation, which had no additive present. The PF127 formulations of PHCL containing MC or HPMC exhibited the slowest dissolution rates and released the drug the slowest. The same rank order was observed at each temperature for the dissolution and PHCL release profiles of each formulation. On the basis of the in vitro results, the PF127 formulations of PHCL containing MC or HPMC as an additive showed potential for use as controlled-release ocular delivery systems for PHCL.     

Stress in bone adjacent to dental implants

Finite element analysis (FEA) was employed to assess patterns of stress in bone adjacent to an implant after application of loads through an attached distal extension cantilever. Under all loading conditions, the highest stresses occurred at the distal cervical bone margin adjacent to the cantilever. In clinical studies, this is not consistently the site of the greatest bone changes seen radiographically. This suggests that extrapolation of FEA studies to clinical implantology should be approached with caution until further data become available on both mechanical properties of bone and patterns of bone remodelling induced by defined functional stresses in mandible and maxillae.     

Dry-process surface modification for titanium dental implants

Because dental implants contact many different tissues, the implant material must have optimum surface compatibility with the host bone tissue, subepithelial connective tissue, and epithelial tissue. In addition, dental implant surfaces exposed to the oral cavity must remain plaque-free. Such materials can be created under well-controlled conditions by modifying the surfaces of metals that contact those tissues. “Tissue-compatible implants,” which are compatible with all host tissues, must integrate with bone tissue, easily form hemidesmosomes, and prevent bacterial adhesion. This research was aimed at developing such tissue-compatible implants by modifying titanium surfaces using a dry process for closely adhering to the titanium substrate and ensuring good wear resistance. The process includes ion beam dynamic mixing (thin calcium phosphates), ion implantation (Ca⁺, N⁺, F⁺), titania spraying, ion plating (TiN, alumina), and ion beam mixing (Ag, Sn, Zn, Pt) with Ar⁺. At the bone tissue/implant interface, a thin calcium phosphate coating and rapid heating with infrared radiation were effective in controlling the dissolution without cracking the coating. This thin calcium phosphate coating may directly promote osteogenisis, but it may also enable immobilization of functional proteins or drugs. At the oral fluid/implant interface, an alumina coating and F⁺ implantation were responsible for inhibiting the adhesion of microbial plaque. In conclusion, dry-process surface modification is useful in controlling the physicochemical nature of surfaces, including the surface energy and the surface electrical charge, and in developing tissue-compatible implants.     

The mechanical behavior of LTI carbon dental implants

LTI pyrolytic carbon blade-type dental implants consisting of a graphite substrate and an LTI pyrolytic carbon coating have a strength that increases with the coating thickness. For implants having a coating thickness of about 0.03 in., average fracture loads of about 1500 lb and 230 lb were obtained in axial compressive loading and eccentric loading (e.g., axial compressive loading plus a bending moment), respectively. Depending on the type of loading, the maximum stresses in the graphite substrate were calculated to be very close to its compressive or tensile fracture strength. Also studied was the effect of a variety of defects on the overall strength of the implants.     

Study of mechanical properties of micromachined dental implants

Advancements in technologies and techniques within the dental industry have given rise to new and effective tooth replacement procedures for damages resulting from causes such as trauma or aging. While these treatments are widely available for patients, they remain highly expensive, preventing patients from much-needed dental care. The elevated cost of dental implants is in part associated with their components that are mainly available through third-party companies at a premium cost. To be cost effective, dental laboratories are exploring the option of producing their own dental implant components, and are therefore acquiring knowledge of manufacturing techniques and quality assurance expertise to produce quality components. In order to ensure high quality and reliability, the fabricated components must be tested and benchmarked against current implants on the market. The present study examines the micro machining process of dental implants, specifically for the abutments and screws, and its impact on the mechanical properties of the components. To achieve this, dental implant abutment and screw prototypes were fabricated, experimentally tested, and compared. The impact of different machining processes on the mechanical properties of the implants was comparatively determined and analysed. The fabricated implant testing results show coherent mechanical properties displayed by good hardness, and material microstructures similar to market components, indicating a high level of prototype quality.     

Influences of smoking on the periodontium and dental implants

The purpose of this article is to review current information on the role of smoking in destructive periodontal disease and in increasing the likelihood of failure of endosseous dental implants. Practical recommendations are made on the role of the dental health professional in everyday dealings with patients who smoke.     

Hard-tissue augmentation for the placement of anterior dental implants

Dental implants have become a popular alternative for replacing missing teeth in every region of the oral cavity. In the anterior zone, special esthetic concerns require not only a stably anchored implant for long-term success, but also the presence of adequate hard and soft peri-implant tissues. Anterior tooth loss is often accompanied by considerable loss of alveolar bone, so augmenting hard tissue before or in combination with implant placement becomes a critical part of therapy. One of the most successful augmentation techniques is guided bone regeneration (GBR). Thus far, augmentation procedures using expanded polytetrafluoroethylene membranes (ePTFEa) have proved to be the most efficient and predictable surgical technique to enhance deficient bone sites. This article discusses some critical biological and clinical/technical aspects of GBR and describes techniques for anterior hard-tissue augmentation with the photographic documentations of three clinical cases.     

Crevicular fluid enzymes from endosseous dental implants and natural teeth

Several neutrophil-derived enzymes that are present in the gingival crevicular fluid have been evaluated for use as risk markers for periodontal disease progression. However, very little information is available about the presence of these enzymes in peri-implant tissues. The purpose of this cross-sectional study was to compare levels of enzymes in gingival crevicular fluid between natural teeth and endosseous dental implants and between well-integrated and failing implants. Scores of plaque and gingivitis were recorded for 68 integrated implants, five failing implants, and 34 natural teeth in 12 completely edentulous and 18 partially edentulous subjects. Samples of gingival crevicular fluid were obtained from these sites using filter paper strips and were assayed for levels of neutral protease, neutrophil elastase, myeloperoxidase, and beta-glucuronidase. Neutral protease levels were higher (P = .066) at moderately to severely inflamed implant sites (Gingival Index of 2, 3) compared to mildly or noninflamed sites (Gingival Index of = 0, 1). Despite the small number (n = 5) of failing implants evaluated in this study, levels of neutrophil elastase, myeloperoxidase, and beta-glucuronidase were significantly higher (P < or = .001) around failing implants compared to successful implants. Neutral protease levels were also elevated around failing implants, but the difference was not statistically significant. Results of this study indicate that neutrophil elastase, myeloperoxidase, and beta-glucuronidase levels in GCF appear to be good candidates for study as risk markers of implant failure.