Influence of repeated implant-abutment manipulation on the prevalence of peri-implant diseases in complete arch restorations. A retrospective analysis.

PURPOSE: To evaluate the effects of repeated abutment manipulation on the prevalence of peri-implant diseases. MATERIALS AND METHODS: A total of 27 edentulous patients (n = 108 implants) immediately restored with double-crown retained implant-supported prostheses were identified for this retrospective study. The test included the one-abutment, one-time care concept (n = 18 patients, n = 72 implants, OAOT) and the control abutment replacement (n = 9 patients, n = 36 implants, AR). A mixed effects model regression was conducted for the variable diagnosis (healthy, peri-implant mucositis, and peri-implantitis) with predictors abutment replacement (presence/absence), number of abutment replacement, category of keratinized mucosa (KM) (2 < KM ≥2 mm), and radiographic bone loss (BL). RESULTS: After 3-15 years (mean 10.2 ± 2.8 years), the prevalence of peri-implant mucositis and peri-implantitis in patients in the AR group was 11.1% and 88.9%, corresponding to 22.2% and 55.6% at the implant level, respectively. In OAOT group, none of the implants showed peri-implant mucositis, whereas the prevalence for peri-implantitis at patient and implant level amounted to 5.6% and 5.6%, respectively. The increased number of abutment replacements was significantly associated with the increased probability to diagnose peri-implant mucositis and peri-implantitis (OR: 6.13; 95% CI [2.61, 14.39]) (p < 0.001), whereas the presence of keratinized mucosa was not founded as a significant cofounder. The estimated mean BL in AR group was 1.38 mm larger than in OAOT group (p = 0.0190). CONCLUSIONS: The OAOT concept was associated with a lower prevalence of peri-implant diseases.

Long-term behavior of double crown retained dentures with metal and metal-free secondary crowns and frameworks made of Vectris(©) on all-ceramic primary crowns: a prospective, randomized clinical trial up to 14 years.

OBJECTIVES: This prospective randomized clinical trial aimed to evaluate the long-term behavior of metal-free double crown retained dentures with secondary crowns and dental frameworks made of the fiber-reinforced composite Vectris(©) on all-ceramic primary crowns (IPS Empress 2(©)) over a period of up to 14 years and to subsequently evaluate patient satisfaction. For the control group, electroplated gold copings and metal frameworks were used. MATERIALS AND METHODS: A total of 29 patients were treated with a total of 37 prostheses on 165 primary crowns. Of these 37 prostheses, 27 were allotted to the control group and 10 to the test group. The mean observation time was 91 ± 57 months; patient satisfaction surveys were conducted over 77 ± 59 months. RESULTS: Success rates in both groups were compared using Kaplan-Meier survival curves and log-rank test. Up to about 3 years, both types of prostheses exhibited similar success rates. Afterwards, a massive decrease in the Vectris(©) curve could be noted, whereas the metal curve dropped only slightly. This difference was also statistically significant (p = 0.032361). There was a comparable susceptibility to damages in both groups: 88.9 % (control) and 90 % (test), respectively, of the prostheses had to be repaired within the period of investigation (p = 0,121). Damages of the Vectris(©) secondary crowns could be detected significantly more often compared to the electroformed gold copings (p < 0.00005). Patient satisfaction with the restorations was comparably high in both groups. CONCLUSION: Metal-free secondary crowns and denture frameworks made with the glass fiber-reinforced composite material Vectris(©) showed a lower survival rate than the electroplated gold copings and metal frameworks. Primary crowns made of IPS Empress 2(©) had insufficient stability. Exclusively high-strength zirconia ceramics should be recommended for this indication. CLINICAL RELEVANCE: Both clinical and statistical data indicated the superiority of the restorations made with electroplated secondary crowns and metal framework. Therefore, the use of Vectris(©) cannot be recommended for the fabrication of double crown retained removable dentures as permanent restorations.

Simultaneous quantification of fludarabine and cyclophosphamide in human plasma by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

Fludarabine and cyclophosphamide are anticancer agents mainly used in the treatment of hematologic malignancies. We have developed and validated an assay using high-performance liquid chromatography (HPLC) coupled with electrospray ionization tandem mass spectrometry for the quantification of fludarabine in combination with cyclophosphamide in human heparin and human EDTA plasma. Sample pre-treatment consisted of a protein precipitation with cold acetonitrile (-20 degrees C) using 250 microL of plasma. Separation was performed on an Extend C18 column (150 x 2.1 mm i.d.; 5 microm) with a stepwise gradient using 1 mM ammonia solution and acetonitrile at a flow rate of 400 microL/min. The analytical run time was 12 min. The triple quadrupole mass spectrometer was operated in the positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over a concentration range of 1 to 100 ng/mL for fludarabine and cyclophosphamide in human heparin and human EDTA plasma. The coefficients of variation were <13.9% for inter- and intra-day precisions. Mean accuracies were also within the designated limits (+/-15%). The analytes were stable in plasma, processed extracts and in stock solution under all relevant conditions.

Elevated alpha-1-acid glycoprotein reduces the volume of distribution and systemic clearance of saquinavir.

The purpose of this study was to characterize the relationship between plasma protein binding and the pharmacokinetic disposition of saquinavir during a normal and elevated alpha-1-acid glycoprotein condition. The extent of plasma binding of [14C]saquinavir to human plasma, human albumin, and human alpha-1-acid glycoprotein was also assessed. Transgenic mice, which overexpress plasma alpha-1-acid glycoprotein, and control mice were given a single intravenous injection of saquinavir (10 mg/kg) and plasma samples were harvested as a function of time. The extent of [14C]saquinavir (0.5-30 microg/ml) plasma protein binding in each group of mice was determined by ultrafiltration. Plasma saquinavir concentrations from in vivo administration were determined by high performance liquid chromatography with tandem mass spectrometry. Saquinavir binding in human plasma and control mouse plasma was similar (approximately 3% unbound). In contrast, the extent of binding was significantly increased in transgenic mice (1.5% unbound). Furthermore, saquinavir was more extensively bound to alpha-1-acid glycoprotein than to albumin (2.1 versus 11.5% unbound). The systemic clearance and volume of distribution of saquinavir were significantly reduced in transgenic mice compared with control mice. The results of this study show that alpha-1-acid glycoprotein is the predominant plasma protein to which saquinavir binds. In addition, elevations in plasma alpha-1-acid glycoprotein considerably alter the pharmacokinetic disposition of saquinavir. This is consistent with the observations that systemic exposure to saquinavir in human immunodeficiency virus patients is greater than that in healthy volunteers and that alpha-1-acid glycoprotein levels increase with the degree of HIV infection.

The disposition of saquinavir in normal and P-glycoprotein deficient mice, rats, and in cultured cells.

Protease inhibitors are very effective in treating patients infected with HIV. However, many drugs in this class penetrate poorly into the central nervous system (CNS) and may permit this site to be a sanctuary from which resistant virus can emerge. Previous studies have shown that the protease inhibitor saquinavir (SQV) interacts with the multidrug transport system, P-glycoprotein (P-gp), expressed in epithelial cells in the gut mucosa and at the blood-brain barrier, and thus might affect both the oral absorption and the penetration of SQV into the CNS. To determine whether SQV is a substrate for P-gp, its uptake was determined in cancer cells, which do (Dx5) and do not (MES-SA) express P-gp. The distribution of SQV between brain tissue and plasma was also investigated in rats and in normal and P-gp-deficient mdr1a(-/-) mice. The distribution ratio of SQV in plasma:brain:cerebrospinal fluid was approximately 100:10:0.2 in rats. The accumulation of SQV was enhanced in MES-SA cells (P-gp-negative) versus Dx5 cells (P-gp-positive). Bolus i.v. injection of [(14)C]SQV (2 and 5 mg/kg) into mdr1a(-/-) and normal mice (n = 3 or 4) resulted in 3-fold higher radioactivity in brains from mdr1a(-/-) mice. Similarly, oral administration of [(14)C]SQV (500 mg/kg) resulted in a 5-fold increase in systemic exposure and a 10-fold increase in brain levels in mdr1a(-/-) mice. These data demonstrate that saquinavir is a substrate for P-gp and that this transport system may play a role in limiting oral absorption and CNS exposure to this protease inhibitor.

Advanced biomaterials used for a new telescopic retainer for removable dentures.

Removable dentures supported by cast-metal telescopic crowns often exhibit an unpredictable increase or decrease in retentive force after being in clinical use for some time. The objective of the present in vitro study was to develop a new retainer for removable dentures and to evaluate its tribological properties. The new retainer is based on a tapered crown design and consists of a conical all-ceramic abutment crown and a coping made of electroplated gold. It was compared with conventional telescopic retainers made of cast metal. There were 30 specimens in groups of equal size by material used (abutment crown/coping): Group 1, gold/gold; Group 2, titanium/titanium; Group 3, ceramic/electroplated gold. Each specimen consisted of 2 conical-shaped abutment crowns (alpha =4 degrees; h = 6 mm; O(base) = 4,5 mm); their copings were rigidly connected at 25 mm intervals. Retentive forces were measured with a universal testing machine following axial loading to 5-400 N. Wear was simulated by 500-100, 000 joining and separating cycles in the presence of artificial saliva. Metallographic cross-sections were made to evaluate the specimens' fit and surfaces with an SEM. Retentive forces in Groups 1 and 2 increased with load, exhibiting nondirectional changes after induced wear. Sometimes the alloys' functional surfaces showed considerable tracks of wear. Neither load nor wear had any effect on Group 3 retentive forces (mean(force) = 5.03 N). The functional ceramic and gold surfaces showed no traces of wear and the best fit (median(gap) = 4.9 microm). Replacing cast metals by ceramics and electroplated gold results in retainers with clinically advantageous tribological effects, implying, in particular, high wear resistance.

Advanced biomaterials used for a new telescopic retainer for removable dentures.

Telescopic retainers with conical ceramic abutment crowns and electroplated gold copings define a new retainer for removable dentures exhibiting favorable tribological properties that could offer clinical advantages. The objective of this study was to evaluate the clinical effects of this retainer. To do so, a novel treatment modality was developed based on intraoral bonding of the copings to the framework in order to be able to realize, in a clinical setting, the retainer function based on a precision fit. A total of 32 patients wearing 33 dentures (16 mandibular, 17 maxillary; period of risk [months]: minimum = 3; maximum = 58; mean = 27.6), supported by 147 abutments (83 natural teeth, 64 implants) with ceramic abutment crowns (IPS Empress 1, IPS Empress 2, InCeram, Procera, CerAdapt; CeraBase) were followed at 6-month intervals. The ceramic abutment crowns showed low plaque accumulation (mean PI = 17.3%). The gingival tissues around natural abutments were generally free of inflammation; so was the mucosa around the implants (mean SBI = 4.9%). Denture adhesion and occlusion did not change, and there were no rocking movements. The mobility (as determined by Periotest) of 29 teeth was reduced in a highly significant manner within 6 months (t test, p < 0.001). Osseointegration was preserved for all implants. One abutment loosened. Six Empress 1 ceramic copings failed (94.6% Kaplan-Meier survival rate), and one abutment tooth was lost (99.2% survival rate). All patients reported problem-free handling, no rocking movements, and constant adhesion. The adhesive strength of one denture was too low at insertion. 94% of the patients experienced no problems with oral hygiene. The retainer examined has relevant clinical advantages and meets geriatric requirements for removable dentures.

Machinability of IPS Empress 2 framework ceramic.

Using ceramic materials for an automatic production of ceramic dentures by CAD/CAM is a challenge, because many technological, medical, and optical demands must be considered. The IPS Empress 2 framework ceramic meets most of them. This study shows the possibilities for machining this ceramic with economical parameters. The long life-time requirement for ceramic dentures requires a ductile machined surface to avoid the well-known subsurface damages of brittle materials caused by machining. Slow and rapid damage propagation begins at break outs and cracks, and limits life-time significantly. Therefore, ductile machined surfaces are an important demand for machine dental ceramics. The machining tests were performed with various parameters such as tool grain size and feed speed. Denture ceramics were machined by jig grinding on a 5-axis CNC milling machine (Maho HGF 500) with a high-speed spindle up to 120,000 rpm. The results of the wear test indicate low tool wear. With one tool, you can machine eight occlusal surfaces including roughing and finishing. One occlusal surface takes about 60 min machining time. Recommended parameters for roughing are middle diamond grain size (D107), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 1000 mm/min, depth of cut a(e) = 0.06 mm, width of contact a(p) = 0.8 mm, and for finishing ultra fine diamond grain size (D46), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 100 mm/min, depth of cut a(e) = 0.02 mm, width of contact a(p) = 0.8 mm. The results of the machining tests give a reference for using IPS Empress(R) 2 framework ceramic in CAD/CAM systems.

Myocardial-infarction after adjuvant chemotherapy for resected stage-ii nonseminomatous testicular cancer.

Although acute toxicity of cisplatin-based chemotherapy of germ cell tumors is considerable, major vascular complications have been reported infrequently. This report describes the case of a 36-year-old man developing myocardial infarction after the first cycle of adjuvant cisplatin-based chemotherapy for resected stage II testicular cancer. A close temporal association between the administration of chemotherapy and the vascular event suggests a cause and effect relationship. A drug-induced endothelial cell damage may be an important pathogenetic factor. Although reports on vascular accidents following treatment of testicular cancer raise concern with regard to the safety of chemotherapy, at present the very low incidence of such complications should not enter into therapeutic decisions.

[The use of the "cine-technic" in the MRT diagnosis of the temporomandibular joint]. / Die Anwendung der "Cine-Technik" in der MRT-Diagnostik des Kiefergelenkes.

A new cine-technique in a prospective study using rapid gradient echo sequences was evaluated for the MRT investigation of the temporo-mandibular joint. A newly developed hydraulic apparatus was used to produce progressive opening of the jaw and MRT appearances were recorded during predetermined points of mandibular movement. The investigation included 16 normals and 34 patients. A modified gradient echo sequence was combined with an optimised surface coil or a special double coil and this provided good spatial resolution of the articular disc and of the muscular and bony structure. Amongst the abnormal findings were luxation of the disc (15 cases), tears in the disc (5 cases), late effects of internal derangements (12 cases) and condylar hypermotility (7 cases). The new cine-technique provides specific images in any chosen position of the mandible depending on the clinical disability of the patient.

Is resistance to ischaemia of motor axons in diabetic subjects due to membrane depolarization?

The reasons for the resistance to ischaemia of peripheral nerves in diabetics are not well understood. We have now explored whether axonal depolarization underlies this phenomenon, as has previously been proposed. Resistance to ischaemia was determined by the new method of "threshold tracking". This method revealed an increase in excitability of the peroneal nerve at the popliteal fossa during ischaemia, and a decrease in excitability in the post-ischaemic period. The extent of these alterations in 28 type 1 diabetics without peripheral neuropathy showed a strong correlation with the mean blood glucose concentrations during the last 24 h before examination. To test whether the ischaemic resistance was related to membrane potential, we also measured axonal superexcitability in 11 selected diabetics, since it has been shown that post-spike changes in excitability depend on membrane potential. Changes in excitability of the peroneal nerve were measured in the period between 10 and 30 msec following a conditioning supramaximal compound action potential. Under resting conditions, no differences in the post-spike superexcitability were found between controls and diabetics, despite striking differences in their responses to a 10-min pressure cuff. These observations indicate that membrane depolarization is not involved in the resistance to ischaemia of motor axons in diabetic subjects.

Threshold tracking provides a rapid indication of ischaemic resistance in motor axons of diabetic subjects.

An early abnormality in the peripheral nerves of patients with diabetes mellitus is that it takes a long period of limb ischaemia to block conduction. As a diagnostic test, however, the procedure is time consuming (30 min of ischaemia). We have now used an electronic feedback system to track threshold changes in human motor axons during and after a short period of ischemia (10 min) induced by a pressure cuff. The strength of stimulus current applied over an appropriate nerve was adjusted to maintain a constant amplitude of muscle action potential. This method reveals an increase in excitability during the first few minutes of ischaemia, and a post-ischaemic depression. Both changes in excitability were consistently much reduced in diabetic subjects compared with normal controls.