Management of a complication with a fractured zirconia implant abutment in the esthetic zone

Technical complications in implant prosthetic cases represent a major challenge in dentistry. This case report describes minimally invasive management to recover an implant with a fractured remnant of a zirconia abutment, including provisional rehabilitation during a sequential treatment protocol in the esthetic zone. A patient was treated with a screw-retained one-piece implant-supported reconstruction made of a customized zirconia abutment with direct ceramic veneering in the maxillary right central incisor position. During the prosthetic try-in, a fracture in the apical portion of the abutment was evident. The first rescue attempt led to fracture of the retrieval instrument. Immediately, an individualized wired construction was applied to bond the existing fractured reconstruction to the neighboring teeth to maintain the peri-implant mucosal architecture. Because the implant screw canal was blocked, a customized round bur had to be manufactured and was placed in the implant axis with a specific bracket tool from the service set to protect the interior implant threads. Then, the drills of the service set were guided by the newly created access to remove the fractured remnants. The implant screw was retapped and the area rinsed with chlorhexidine solution. All remnants were removed without the need for surgical intervention. Neither the implant connection nor the bone-to-implant interface was damaged. The stepwise treatment approach with the customized round bur combined with the system-specific drills of the service set saved the blocked implant so that the patient could be successfully rehabilitated with a new implant reconstruction.

Zirconia-Based Screw-Retained Prostheses Supported by Implants: A Retrospective Study on Technical Complications and Failures

BACKGROUND Little information is yet available on zirconia-based prostheses supported by implants. PURPOSE To evaluate technical problems and failures of implant-supported zirconia-based prostheses with exclusive screw-retention. MATERIAL AND METHODS Consecutive patients received screw-retained zirconia-based prostheses supported by implants and were followed over a time period of 5 years. The implant placement and prosthetic rehabilitation were performed in one clinical setting, and all patients participated in the maintenance program. The treatment comprised single crowns (SCs) and fixed dental prostheses (FDPs) of three to 12 units. Screw-retention of the CAD/CAM-fabricated SCs and FDPs was performed with direct connection at the implant level. The primary outcome was the complete failure of zirconia-based prostheses; outcome measures were fracture of the framework or extensive chipping resulting in the need for refabrication. A life table analysis was performed, the cumulative survival rate (CSR) calculated, and a Kaplan-Meier curve drawn. RESULTS Two hundred and ninety-four implants supported 156 zirconia-based prostheses in 95 patients (52 men, 43 women, average age 59.1 ± 11.7 years). Sixty-five SCs and 91 FDPs were identified, comprising a total of 441 units. Fractures of the zirconia framework and extensive chipping resulted in refabrication of nine prostheses. Nearly all the prostheses (94.2%) remained in situ during the observation period. The 5-year CSR was 90.5%, and 41 prostheses (14 SCs, 27 FDPs) comprising 113 units survived for an observation time of more than 5 years. Six SCs exhibited screw loosening, and polishing of minor chipping was required for five prostheses. CONCLUSIONS This study shows that zirconia-based implant-supported fixed prostheses exhibit satisfactory treatment outcomes and that screw-retention directly at the implant level is feasible.

Myocardial injection of skeletal myoblasts impairs contractility of host cardiomyocytes

BACKGROUND: Mechanisms underlying improvement of myocardial contractile function after cell therapy as well as arrhythmic side effect remain poorly understood. We hypothesised that cell therapy might affect the mechanical properties of isolated host cardiomyocytes. METHODS: Two weeks after myocardial infarction (MI), rats were treated by intramyocardial myoblast injection (SkM, n=8), intramyocardial vehicle injection (Medium, n=6), or sham operation (Sham, n=7). Cardiac function was assessed by echocardiography. Cardiomyocytes were isolated in a modified Langendorff perfusion system, their contraction was measured by video-based inter-sarcomeric analysis. Data were compared with a control-group without myocardial infarction (Control, n=5). RESULTS: Three weeks post-treatment, ejection fraction (EF) further deteriorated in vehicle-injected and non-injected rats (respectively 40.7+/-11.4% to 33+/-5.5% and 41.8+/-8% to 33.5+/-8.3%), but was stabilised in SkM group (35.9+/-6% to 36.4+/-9.7%). Significant cell hypertrophy induced by MI was maintained after cell therapy. Single cell contraction (dL/dt(max)) decreased in SkM and vehicle groups compared to non-injected group as well as cell shortening and relaxation (dL/dt(min)) in vehicle group. A significantly increased predisposition for alternation of strong and weak contractions was observed in isolated cardiomyocytes of the SkM group. CONCLUSION: Our study provides the first evidence that injection of materials into the myocardium alters host cardiomyocytes contractile function independently of the global beneficial effect of the heart function. These findings may be important in understanding possible adverse effects.

Bonding of restorative materials to dentin with various luting agents

The aim was to compare eight types of luting agents when used to bond six indirect, laboratory restorative materials to dentin. Cylinders of the six restorative materials (Esteticor Avenir [gold alloy], Tritan [titanium], NobelRondo [feldspathic porcelain], Finesse All-Ceramic [leucite-glass ceramic], Lava [zirconia], and Sinfony [resin composite]) were ground and air-abraded. Cylinders of feldspathic porcelain and glass ceramic were additionally etched with hydrofluoric acid and were silane-treated. The cylinders were luted to ground human dentin with eight luting agents (DeTrey Zinc [zinc phosphate cement], Fuji I [conventional glass ionomer cement], Fuji Plus [resin-modified glass ionomer cement], Variolink II [conventional etch-and-rinse resin cement], Panavia F2.0 and Multilink [self-etch resin cements], and RelyX Unicem Aplicap and Maxcem [self-adhesive resin cements]). After water storage at 37°C for one week, the shear bond strength of the specimens (n=8/group) was measured, and the fracture mode was stereomicroscopically examined. Bond strength data were analyzed with two-factorial analysis of variance (ANOVA) followed by Newman-Keuls' Multiple Range Test (?=0.05). Both the restorative material and the luting agent had a significant effect on bond strength, and significant interaction was noted between the two variables. Zinc phosphate cement and glass ionomer cements produced the lowest bond strengths, whereas the highest bond strengths were found with the two self-etch and one of the self-adhesive resin cements. Generally, the fracture mode varied markedly with the restorative material. The luting agents had a bigger influence on bond strength between restorative materials and dentin than was seen with the restorative material.

Internal vs. external connections for abutments/reconstructions: a systematic review

The objectives of the review were (1) to evaluate the accuracy of implant-level impressions in cases with internal and external connection abutments/reconstructions, and (2) to evaluate the incidence of technical complications of internal and external connection metal- or zirconia-based abutments and single-implant reconstructions.

Excision of high and mid cervical spinal cord arteriovenous malformations by anterior operation

Symptomatic cervical spinal arteriovenous malformations (AVMs) located on the anterior aspect of the spinal cord are rare and surgical removal of these AVMs presents considerable challenges and risks. Surgical techniques to date have usually been by posterior approach and lateral dissection around the cord or via midline myelotomy, both approaches involving cord manipulation and retraction and in the latter, dissection through the spinal cord. We present two teenage patients with symptomatic anteriorly placed mid to high cervical spinal AVMs and associated aneurysm in which excision of the AVMs and aneurysm was performed by an anterior approach using vertebrectomy/corpectomy. The first case had a small perimedullary glomus-type AVM with an aneurysm on the anterior aspect of the cord at the C3/4 level; excision was performed using a single level vertebrectomy/corpectomy, the patient remaining neurologically intact. The second case had a medium-sized juvenile AVM with an aneurysm, both perimedullary and intramedullary, centred at the C5/6 level; excision was performed using a two-level vertebrectomy/corpectomy with no deterioration in the marked pre-operative tetraparesis, which at long-term follow up had improved and stabilised. Anterior approaches have been recently described for treatment of anteriorly placed cervical arteriovenous fistulas (AVFs) and an intramedullary haemangioblastoma, but not as yet for spinal AVMs. These are the first two reported cases of anteriorly situated cervical AVMs successfully removed surgically by an anterior approach and with good neurological outcomes.

Biomechanical comparison of different surface modifications for dental implants

Purpose: A satisfactory clinical outcome in dental implant treatment relies on primary stability for immediate load bearing. While the geometric design of an implant contributes to mechanical stability, the nature of the implant surface itself is also critically important. Biomechanical and microcomputerized tomographic evaluation of implant osseointegration was performed to compare alternative structural, chemical and biochemical, and/or pharmaceutical surface treatments applied to an identical established implant design. Materials and Methods: Dental implants with the same geometry but with 6 different surface treatments were tested in vivo in a sheep model (pelvis). Peri-implant bone density and removal torque were compared at 2, 4, and 8 weeks after implantation. Implant surfaces tested were: sandblasted and acid-etched titanium (Ti), sandblasted and etched zirconia, Ti coated with calcium phosphate (CaP), Ti modified via anodic plasma-chemical treatment (APC), bisphosphonate-coated Ti (Ti + Bisphos), and Ti coated with collagen containing chondroitin sulfate (CS). Results: All dental implants were well integrated at the time of sacrifice. There were no significant differences observed in peri-implant bone density between implant groups. After 8 weeks of healing, removal torque values for Ti, Ti + CaP, Ti + Bisphos, and Ti + collagen + CS were significantly higher than those for zirconia and Ti + APC. Conclusions: Whereas the sandblasted/acid-etched Ti implant can still be considered the reference standard surface for dental implants, functional surface modifications such as bisphosphonate or collagen coating seem to enhance early peri-implant bone formation and should be studied further.

Differential influence of arterial blood glucose on cerebral metabolism following severe traumatic brain injury

INTRODUCTION: Maintaining arterial blood glucose within tight limits is beneficial in critically ill patients. Upper and lower limits of detrimental blood glucose levels must be determined. METHODS: In 69 patients with severe traumatic brain injury (TBI), cerebral metabolism was monitored by assessing changes in arterial and jugular venous blood at normocarbia (partial arterial pressure of carbon dioxide (paCO2) 4.4 to 5.6 kPa), normoxia (partial arterial pressure of oxygen (paO2) 9 to 20 kPa), stable haematocrit (27 to 36%), brain temperature 35 to 38 degrees C, and cerebral perfusion pressure (CPP) 70 to 90 mmHg. This resulted in a total of 43,896 values for glucose uptake, lactate release, oxygen extraction ratio (OER), carbon dioxide (CO2) and bicarbonate (HCO3) production, jugular venous oxygen saturation (SjvO2), oxygen-glucose index (OGI), lactate-glucose index (LGI) and lactate-oxygen index (LOI). Arterial blood glucose concentration-dependent influence was determined retrospectively by assessing changes in these parameters within pre-defined blood glucose clusters, ranging from less than 4 to more than 9 mmol/l. RESULTS: Arterial blood glucose significantly influenced signs of cerebral metabolism reflected by increased cerebral glucose uptake, decreased cerebral lactate production, reduced oxygen consumption, negative LGI and decreased cerebral CO2/HCO3 production at arterial blood glucose levels above 6 to 7 mmol/l compared with lower arterial blood glucose concentrations. At blood glucose levels more than 8 mmol/l signs of increased anaerobic glycolysis (OGI less than 6) supervened. CONCLUSIONS: Maintaining arterial blood glucose levels between 6 and 8 mmol/l appears superior compared with lower and higher blood glucose concentrations in terms of stabilised cerebral metabolism. It appears that arterial blood glucose values below 6 and above 8 mmol/l should be avoided. Prospective analysis is required to determine the optimal arterial blood glucose target in patients suffering from severe TBI.

New means in spinal pedicle hook fixation. A biomechanical evaluation

Pedicle hooks which are used as an anchorage for posterior spinal instrumentation may be subjected to considerable three-dimensional forces. In order to achieve stronger attachment to the implantation site, hooks using screws for additional fixation have been developed. The failure loads and mechanisms of three such devices have been experimentally determined on human thoracic vertebrae: the Universal Spine System (USS) pedicle hook with one screw, a prototype pedicle hook with two screws and the Cotrel-Dubousset (CD) pedicle hook with screw. The USS hooks use 3.2-mm self-tapping fixation screws which pass into the pedicle, whereas the CD hook is stabilised with a 3-mm set screw pressing against the superior part of the facet joint. A clinically established 5-mm pedicle screw was tested for comparison. A matched pair experimental design was implemented to evaluate these implants in constrained (series I) and rotationally unconstrained (series II) posterior pull-out tests. In the constrained tests the pedicle screw was the strongest implant, with an average pull-out force of 1650 N (SD 623 N). The prototype hook was comparable, with an average failure load of 1530 N (SD 414 N). The average pull-out force of the USS hook with one screw was 910 N (SD 243 N), not significantly different to the CD hook's average failure load of 740 N (SD 189 N). The result of the unconstrained tests were similar, with the prototype hook being the strongest device (average 1617 N, SD 652 N). However, in this series the difference in failure load between the USS hook with one screw and the CD hook was significant. Average failure loads of 792 N (SD 184 N) for the USS hook and 464 N (SD 279 N) for the CD hook were measured. A pedicular fracture in the plane of the fixation screw was the most common failure mode for USS hooks.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical outcome of single porcelain-fused-to-zirconium dioxide crowns: a systematic review

STATEMENT OF PROBLEM The increasing demand by patients for esthetic and metal-free restorations has driven the development of ceramic restorations with good esthetic and mechanical stability. Recent clinical studies have investigated the use of zirconium dioxide as a core material for complete crowns and computer-aided-design/computer-aided-manufacturing fabricated restorations. PURPOSE The aim of this systematic review was to evaluate the clinical survival rates of porcelain-fused-to-zirconia (PFZ) single crowns on anterior and posterior teeth and to compare them with metal ceramic (MC) crowns. MATERIAL AND METHODS A systematic search was conducted with PubMed and manual research to identify literature written in English that refers to in vivo studies published from January 1, 1950 through July 1, 2011. Clinical trials that evaluated PFZ and MC single crowns on natural teeth were selected for further analysis. Titles and/or abstracts of articles identified through the electronic searches were reviewed and evaluated for appropriateness. In addition, a hand search of relevant dental journals was peformed, and reference lists of culled articles were screened to identify publications. RESULTS The search resulted in a total of 488 initial matches. Nineteen studies with a total of 3621 crowns met the inclusion criteria. The survival rates of PFZ crowns (total 300) ranged from 92.7% to 100% for a follow-up time of 24 to 39 months, whereas those of MC crowns (total 3321) ranged from 70% to 100% for a follow-up time of 12 to 298 months. Studies that reported long-term results were found only for the MC crown group. CONCLUSIONS The scientific clinical data available to compare PFZ and MC crowns are limited. The survival rates may well be influenced by the selection and appropriate use of the veneering ceramic, and, therefore, additional prospective long-term clinical trials are necessary to draw reliable conclusions.

Dentinhaftung von Zementen. Der Haftverbund von Zementen mit Dentin in Kombination mit verschiedenen indirekten Restaurationsmaterialien

Einleitung: Die Anzahl zahnärztlicher Zemente sowie Restaurationsmaterialien steigt stetig. Die richtige Zementwahl für einen zuverlässigen Haftverbund zwischen Restaurationsmaterial und Zahnsubstanz ist von Interesse für den Kliniker. Ziel der vorliegenden in vitro-Studie war es daher, den Dentinhaftverbund von verschiedenen Zementen in Kombination mit verschiedenen indirekten Restaurationsmaterialien zu untersuchen. Material und Methoden: Zylindrische Probekörper aus sechs Restaurationsmaterialien (Goldlegierung, Titan, Feldspat-Keramik, Leuzit-Glaskeramik, Zirkon sowie Komposit) wurden an einem Ende plangeschliffen und sandgestrahlt. Die Zylinder aus Feldspat-Keramik und Leuzit-Glaskeramik wurden zusätzlich mit Flusssäure geätzt und silanisiert. Die Zylinder wurden anschliessend mit acht Zementen auf plangeschliffenes Dentin extrahierter menschlicher Zähne zementiert (ein Zink-Phosphatzement (DeTrey Zinc), ein konventioneller Glasionomerzement (Fuji I), ein kunststoffmodifizierter Glasionomerzement (Fuji Plus), ein "etch-&-rinse" Kompositzement (Variolink II), zwei "self-etch" Kompositzemente (Panavia F2.0 und Multilink) und zwei "self-adhesive" Kompositzemente (RelyX Unicem Aplicap und Maxcem)). Nach einwöchiger Wasserlagerung bei 37°C wurden die Dentinhaftwerte der Zylinder (n=8 pro Gruppe) mittels Scherkraft-Test gemessen. Zusätzlich wurde das Frakturmuster unter dem Lichtmikroskop bestimmt. Die Haftwerte wurden mittels zweifaktorieller ANOVA und einem post hoc-Test analysiert (Signifikanzniveau α = 0.05). Resultate: Sowohl das Restaurationsmaterial wie auch der Zement hatten einen statistisch signifikanten Effekt auf den Haftverbund. Der Zink-Phosphatzement sowie beide Glasionomerzemente zeigten die niedrigsten Haftwerte. Die höchsten Haftwerte wurden mit beiden "self-etch" und einem der zwei "self-adhesive" Kompositzementen erzielt. Im Allgemeinen variierte das Frakturmuster deutlich je nach Zement und Restaurationsmaterial. Schlussfolgerungen: Der Dentinhaftverbund wurde stärker vom Zement beeinflusst als vom Restaurationsmaterial. Die Kompositzemente erzielten im Grossen und Ganzen die höchsten Haftwerte.

The antimalarial drugs quinine, chloroquine and mefloquine are antagonists at 5-HT 3 receptors

Background and Purpose: The antimalarial compounds quinine, chloroquine and mefloquine affect the electrophysiological properties of Cys-loop receptors and have structural similarities to 5-HT3 receptor antagonists. They may therefore act at 5-HT3 receptors. Experimental Approach: The effects of quinine, chloroquine and mefloquine on electrophysiological and ligand binding properties of 5-HT3A receptors expressed in HEK 293 cells and Xenopus oocytes were examined. The compounds were also docked into models of the binding site. Key Results: 5-HT3 responses were blocked with IC50 values of 13.4 μM, 11.8 μM and 9.36 μM for quinine, chloroquine and mefloquine. Schild plots indicated quinine and chloroquine behaved competitively with pA2 values of 4.92 (KB=12.0 μM) and 4.97 (KB=16.4 μM). Mefloquine displayed weakly voltage-dependent, non-competitive inhibition consistent with channel block. On and off rates for quinine and chloroquine indicated a simple bimolecular reaction scheme. Quinine, chloroquine and mefloquine displaced [3H]granisetron with Ki values of 15.0, 24.2 and 35.7 μM. Docking of quinine into a homology model of the 5-HT3 receptor binding site located the tertiary ammonium between W183 and Y234, and the quinoline ring towards the membrane, stabilised by a hydrogen bond with E129. For chloroquine, the quinoline ring was positioned between W183 and Y234 and the tertiary ammonium stabilised by interactions with F226. Conclusions and Implications: This study shows that quinine and chloroquine competitively inhibit 5-HT3 receptors, while mefloquine inhibits predominantly non-competitively. Both quinine and chloroquine can be docked into a receptor binding site model, consistent with their structural homology to 5-HT3 receptor antagonists.

Cessation and resuming of alglucosidase alfa in Pompe disease: a retrospective analysis.

Enzyme replacement therapy (ERT) with recombinant human alglucosidase alfa (rhGAA) in late-onset Pompe disease is moderately effective. Little is known about the clinical course after treatment termination and the resumption of ERT. In Switzerland, rhGAA therapy for Pompe disease was temporarily withdrawn after the federal court judged that the treatment costs were greatly out of proportion compared to the benefits. Re-treatment was initiated after the therapy was finally licensed. We retrospectively analysed seven Pompe patients, who underwent cessation and resumption of ERT (median age 43 years). The delay from first symptoms to final diagnosis ranged from 4 to 20 years. The demographics, clinical characteristics, assessments with the 6-min walking test (6-MWT), the predicted forced vital capacity (FVC) and muscle strength were analysed. Before initiation of ERT, all patients suffered from proximal muscle weakness of the lower limbs; one was wheelchair-bound and two patients received night-time non-invasive ventilation. Initial treatment stabilised respiratory function in most patients and improved their walking performance. After treatment cessation, upright FVC declined in most and the 6-MWT declined in all patients. Two patients needed additional non-invasive ventilatory support. Twelve months after resuming ERT, the respiratory and walking capacity improved again in most patients. However, aside for one patient, none of the patients reached the same level of respiratory function or distance walked in 6 min, as at the time of ERT withdrawal. We conclude that cessation of ERT in Pompe disease causes a decline in clinical function and should be avoided. Resuming treatment only partially recovers respiratory function and walking capacity.

Retention of Root Canal Posts: Effect of Cement Film Thickness, Luting Cement, and Post Pretreatment.

The aim of this study was to investigate the effect of the cement film thickness of a zinc phosphate or a resin cement on retention of untreated and pretreated root canal posts. Prefabricated zirconia posts (CosmoPost: 1.4 mm) and two types of luting cements (a zinc phosphate cement [DeTrey Zinc] and a self-etch adhesive resin cement [Panavia F2.0]) were used. After removal of the crowns of 360 extracted premolars, canines, or incisors, the root canals were prepared with a parallel-sided drill system to three different final diameters. Half the posts did not receive any pretreatment. The other half received tribochemical silicate coating according to the manufacturer's instructions. Posts were then luted in the prepared root canals (n=30 per group). Following water storage at 37°C for seven days, retention of the posts was determined by the pull-out method. Irrespective of the luting cement, pretreatment with tribochemical silicate coating significantly increased retention of the posts. Increased cement film thickness resulted in decreased retention of untreated posts and of pretreated posts luted with zinc phosphate cement. Increased cement film thickness had no influence on retention of pretreated posts luted with resin cement. Thus, retention of the posts was influenced by the type of luting cement, by the cement film thickness, and by the post pretreatment.

Standardised animal models of host microbial mutualism.

An appreciation of the importance of interactions between microbes and multicellular organisms is currently driving research in biology and biomedicine. Many human diseases involve interactions between the host and the microbiota, so investigating the mechanisms involved is important for human health. Although microbial ecology measurements capture considerable diversity of the communities between individuals, this diversity is highly problematic for reproducible experimental animal models that seek to establish the mechanistic basis for interactions within the overall host-microbial superorganism. Conflicting experimental results may be explained away through unknown differences in the microbiota composition between vivaria or between the microenvironment of different isolated cages. In this position paper, we propose standardised criteria for stabilised and defined experimental animal microbiotas to generate reproducible models of human disease that are suitable for systematic experimentation and are reproducible across different institutions.