ITP in dynamically double-coated fused-silica capillaries

Bidirectional ITP in fused-silica capillaries double-coated with Polybrene and poly-(vinylsulfonate) is a robust approach for analysis of low-molecular-mass compounds. EOF towards the cathode is strong (mobility >4.0 x 10(-8) m(2)/Vs) within the entire pH range investigated (2.40-8.08), dependent on ionic strength and buffer used and, at constant ionic strength, higher at alkaline pH. Electrokinetic separations and transport in such coated capillaries can be described with a dynamic computer model which permits the combined simulation of electrophoresis and electroosmosis in which the EOF is predicted either with a constant (i.e. pH- and ionic strength-independent) or a pH- and ionic strength-dependent electroosmotic mobility. Detector profiles predicted by computer simulation agree qualitatively well with bidirectional isotachopherograms that are monitored with a setup comprising two axial contactless conductivity detectors and a UV absorbance detector. The varying EOF predicted with a pH- and ionic strength-dependent electroosmotic mobility can be regarded as being realistic.

Clinical evaluation of 3 overdenture concepts with tooth roots and implants: 2-year results

PURPOSE: In the present cohort study, overdentures with a combined root and implant support were evaluated and compared with either exclusively root- or implant-supported overdentures. Results of a 2-year follow-up period are reported, namely survival of implants, root copings, and prostheses, plus prosthetic complications, maintenance service, and patient satisfaction. MATERIALS AND METHODS: Fourteen patients were selected for the combined overdenture therapy and were compared with 2 patient groups in which either roots or implants provided overdenture support. Altogether, 14, 17, and 15 patients (in groups 1, 2, and 3, respectively) were matched with regard to age, sex, treatment time, and observation period. The mean age was around 67 years. Periodontal parameters were recorded, radiographs were taken, and all complications and failures were registered during the entire observation time. The patients answered a 9-item questionnaire by means of a visual analogue scale (VAS). RESULTS: One implant failed and 1 tooth root was removed following longitudinal root fracture. Periodontal/peri-implant parameters gave evidence of good oral hygiene for roots and implants, and slight crestal bone resorption was measured for both. Technical complications and service performed were significantly higher in the first year (P < .04) in all 3 groups and significantly higher in the tooth root group (P < .03). The results of the VAS indicated significantly lower scores for satisfaction, speaking ability, wearing comfort, and denture stability with combined or exclusive root support (P < .05 and .02, respectively). Initial costs of overdentures with combined or root support were 10% lower than for implant overdentures. CONCLUSION: The concept of combined root and implant support can be integrated into treatment planning and overdenture design for patients with a highly reduced dentition.

Design of custom-shaped vascularized tissues using microtissue spheroids as minimal building units

Tissue engineering strategies are gathering clinical momentum in regenerative medicine and are expected to provide excellent opportunities for therapy for difficult-to-treat human pathologies. Being aware of the requirement to produce larger artificial tissue implants for clinical applications, we used microtissues, produced using gravity-enforced self-assembly of monodispersed primary cells, as minimal tissue units to generate scaffold-free vascularized artificial macrotissues in custom-shaped agarose molds. Mouse myoblast, pig and human articular-derived chondrocytes, and human myofibroblast (HMF)-composed microtissues (microm3 scale) were amalgamated to form coherent macrotissue patches (mm3 scale) of a desired shape. Macrotissues, assembled from the human umbilical vein endothelial cell (HUVEC)-coated HMF microtissues, developed a vascular system, which functionally connected to the chicken embryo's vasculature after implantation. The design of scaffold-free vascularized macrotissues is a first step toward the scale-up and production of artificial tissue implants for future tissue engineering initiatives.

Tissue-transplant fusion and vascularization of myocardial microtissues and macrotissues implanted into chicken embryos and rats

Cell-based therapies and tissue engineering initiatives are gathering clinical momentum for next-generation treatment of tissue deficiencies. By using gravity-enforced self-assembly of monodispersed primary cells, we have produced adult and neonatal rat cardiomyocyte-based myocardial microtissues that could optionally be vascularized following coating with human umbilical vein endothelial cells (HUVECs). Within myocardial microtissues, individual cardiomyocytes showed native-like cell shape and structure, and established electrochemical coupling via intercalated disks. This resulted in the coordinated beating of microtissues, which was recorded by means of a multi-electrode complementary metal-oxide-semiconductor microchip. Myocardial microtissues (microm3 scale), coated with HUVECs and cast in a custom-shaped agarose mold, assembled to coherent macrotissues (mm3 scale), characterized by an extensive capillary network with typical vessel ultrastructures. Following implantation into chicken embryos, myocardial microtissues recruited the embryo's capillaries to functionally vascularize the rat-derived tissue implant. Similarly, transplantation of rat myocardial microtissues into the pericardium of adult rats resulted in time-dependent integration of myocardial microtissues and co-alignment of implanted and host cardiomyocytes within 7 days. Myocardial microtissues and custom-shaped macrotissues produced by cellular self-assembly exemplify the potential of artificial tissue implants for regenerative medicine.

Osseointegration of hollow cylinder based spinal implants in normal and osteoporotic vertebrae: a sheep study

INTRODUCTION: Osteoporosis is not only responsible for an increased number of metaphyseal and spinal fractures but it also complicates their treatment. To prevent the initial loosening, we developed a new implant with an enlarged implant/bone interface based on the concept of perforated, hollow cylinders. We evaluated whether osseointegration of a hollow cylinder based implant takes place in normal or osteoporotic bone of sheep under functional loading conditions during anterior stabilization of the lumbar spine. MATERIALS AND METHODS: Osseointegration of the cylinders and status of the fused segments (ventral corpectomy, replacement with iliac strut, and fixation with testing implant) were investigated in six osteoporotic (age 6.9 +/- 0.8 years, mean body weight 61.1 +/- 5.2 kg) and seven control sheep (age 6.1 +/- 0.2 years, mean body weight 64.9 +/- 5.7 kg). Osteoporosis was introduced using a combination protocol of ovariectomy, high-dose prednisone, calcium and phosphor reduced diet and movement restriction. Osseointegration was quantified using fluorescence and conventional histology; fusion status was determined using biomechanical testing of the stabilized segment in a six-degree-of-freedom loading device as well as with radiological and histological staging. RESULTS: Intact bone trabeculae were found in 70% of all perforations without differences between the two groups (P = 0.26). Inside the cylinders, bone volume/total volume was significantly higher than in the control vertebra (50 +/- 16 vs. 28 +/- 13%) of the same animal (P<0.01), but significantly less (P<0.01) than in the near surrounding (60 +/- 21%). After biomechanical testing as described in Sect. "Materials and methods", seven spines (three healthy and four osteoporotic) were classified as completely fused and six (four healthy and two osteoporotic) as not fused after a 4-month observation time. All endplates were bridged with intact trabeculae in the histological slices. CONCLUSIONS: The high number of perforations, filled with intact trabeculae, indicates an adequate fixation; bridging trabeculae between adjacent endplates and tricortical iliac struts in all vertebrae indicates that the anchorage is adequate to promote fusion in this animal model, even in the osteoporotic sheep.

Immediate loading of implants with 3-unit fixed partial dentures: a 12-month clinical study

PURPOSE: The aim of the present clinical trial was to evaluate the 12-month success rate of titanium dental implants placed in the posterior mandible and immediately loaded with 3-unit fixed partial dentures. MATERIALS AND METHODS: Patients with missing mandibular premolars and molars were enrolled in this study. To be included in the study, the implants had to show good primary stability. Implant stability was measured with resonance frequency analysis using the Osstell device (Integration Diagnostics). Implants were included in the study when the stability quotient (ISQ) exceeded 62. Clinical measurements, such as width of keratinized tissue, ISQ, and radiographic assessment of peri-implant bone crest levels, were performed at baseline and at the 12-month follow-up. The comparison between the baseline and the 12-month visits was performed with the Student t test for paired data (statistically significant at a level of alpha = 0.05). RESULTS: Forty implants with a sandblasted, large grit, acid-etched (SLA) surface (Straumann) were placed in 20 patients. At 12 months, only 1 implant had been lost because of an acute infection. The remaining 39 implants were successful, resulting in a 1-year success rate of 97.5%. Neither peri-implant bone levels, measured radiographically, nor implant stability changed significantly from baseline to the 12-month follow-up (P > .05). DISCUSSION: The immediate functional loading of implants placed in this case series study resulted in a satisfactory success rate. CONCLUSION: The findings from this clinical study showed that the placement of SLA transmucosal implants in the mandibular area and their immediate loading with 3-unit fixed partial dentures may be a safe and successful procedure.

The effect of rhBMP-2 around endosseous implants with and without membranes in the canine model

BACKGROUND: Bone morphogenetic protein (BMP) is a potent differentiating agent for cells of the osteoblastic lineage. It has been used in the oral cavity under a variety of indications and with different carriers. However, the optimal carrier for each indication is not known. This study examined a synthetic bioabsorbable carrier for BMP used in osseous defects around dental implants in the canine mandible. METHODS: Twelve canines had their mandibular four premolars and first molar teeth extracted bilaterally. After 5 months, four implants were placed with standardized circumferential defects around the coronal 4 mm of each implant. One-half of the defects received a polylactide/glycolide (PLGA) polymer carrier with or without recombinant human BMP-2 (rhBMP-2), and the other half received a collagen carrier with or without rhBMP-2. Additionally, one-half of the implants were covered with a non-resorbable (expanded polytetrafluoroethylene [ePTFE]) membrane to exclude soft tissues. Animals were sacrificed either 4 or 12 weeks later. Histomorphometric analysis included the percentage of new bone contact with the implant, the area of new bone, and the percentage of defect fill. This article describes results with the PLGA carrier. RESULTS: All implants demonstrated clinical and radiographic success with the amount of new bone formed dependent on the time and presence/absence of rhBMP-2 and presence/absence of a membrane. The percentage of bone-to-implant contact was greater with rhBMP-2, and after 12 weeks of healing, there was approximately one-third of the implant contacting bone in the defect site. After 4 weeks, the presence of a membrane appeared to slow new bone area formation. The percentage of fill in membrane-treated sites with rhBMP-2 rose from 24% fill to 42% after 4 and 12 weeks, respectively. Without rhBMP-2, the percentage of fill was 14% rising to 36% fill, respectively. CONCLUSIONS: After 4 weeks, the rhBMP-2-treated sites had a significantly higher percentage of contact, more new bone area, and higher percentage of defect fill than the sites without rhBMP-2. After 12 weeks, there was no significant difference in sites with or without rhBMP-2 regarding percentage of contact, new bone area, or percentage of defect fill. In regard to these three outcomes, comparing the results with this carrier to the results reported earlier with a collagen carrier in this study, only the area of new bone was significantly different with the collagen carrier resulting in greater bone than the PLGA carrier. Thus, the PLGA carrier for rhBMP-2 significantly stimulated bone formation around dental implants in this model after 1 month but not after 3 months of healing. The use of this growth factor and carrier combination appears to stimulate early bone healing events around the implants but not quite to the same degree as a collagen carrier.

Effect of Bio-Oss on osseointegration of dental implants surrounded by circumferential bone defects of different dimensions: an experimental study in the dog

OBJECTIVES: This study was designed to evaluate the effect of gap width and graft placement on bone healing around implants placed in simulated extraction sockets of various widths in four Labrador dogs. MATERIALS AND METHODS: Five Osseotite implants per dog were placed in the mandible of four dogs. Two implants were inserted into sites with a 2.37 mm and two with a 1 mm gap present between the implants and bone around the coronal 6 mm of the implants in each dog. For one of each gap sizes, the gap was filled with Bio-Oss, and the other two with blood alone. A fifth implant was inserted without a gap and used as a control. Ground sections were prepared from biopsies taken at 4 months and histometric measurements of osseointegration and bone between the threads made for the coronal 6 mm. RESULTS: The medians for osseointegration ranged from 5.2 mm for control to 1-2.6 mm for the test modalities. There were significant differences for linear measurements of osseointegration (chi(2) 18.27; df 4; P=0.0011) and bone area within threads (chi(2) 23.4; df 4; P=0.0001) between test modalities. CONCLUSIONS: The results suggest that the wider the gap around the implants, the less favourable the histological outcome at short time intervals following treatment. They also infer that bone grafting with an organic bovine bone xenograft seems to lead to a more favourable histological outcome for wider circumferential defects but not for narrower defects.

Significance of primary stability for osseointegration of dental implants

AIM: To investigate the significance of the initial stability of dental implants for the establishment of osseointegration in an experimental capsule model for bone augmentation. MATERIAL AND METHODS: Sixteen male rats were used in the study. In each rat, muscle-periosteal flaps were elevated on the lateral aspect of the mandibular ramus on both sides, resulting in exposure of the bone surface. Small perforations were then produced in the ramus. A rigid, hemispherical Teflon capsule with a diameter of 6 mm and a height of 4 mm and with a hole in its middle portion, prepared to fit the circumference of an ITI HC titanium implant of 2.8 mm in diameter, was fixed to the ramus using 4 mini-screws. On one side of the jaw, the implant was placed through the hole in such a way that its apex did not make contact with the mandibular ramus (test). This placement of the implant did not ensure primary stability. On the other side of the jaw, a similar implant was placed through the hole of the capsule in such a way that contact was made between the implant and the surface of the ramus (control). This provided primary stability of the implant. After placement of the implants, the soft tissues were repositioned over the capsules and sutured. After 1, 3, 6 and 9 months, four animals were sacrificed and subjected to histometric analysis. RESULTS: The mean height of direct bone-to-implant contact of implants with primary stability was 38.8%, 52.9%, 64.6% and 81.3% of the implant length at 1, 3, 6 and 9 months, respectively. Of the bone adjacent to the implant surface, 28.1%, 28.9%, 52.6% and 69.6%, respectively, consisted of mineralized bone. At the test implants, no bone-to-implant contact was observed at any observation time or in any of these non-stabilized specimens. CONCLUSION: The findings of the present study indicate that primary implant stability is a prerequisite for successful osseointegration, and that implant instability results in fibrous encapsulation, thus confirming previously made clinical observations.

Tactile sensibility of single-tooth implants and natural teeth

AIM: The purpose of this randomized split-mouth clinical trial was to determine the active tactile sensibility between single-tooth implants and opposing natural teeth and to compare it with the tactile sensibility of pairs of natural teeth on the contralateral side in the same mouth (intraindividual comparison). MATERIAL AND METHODS: The hypothesis was that the active tactile sensibilities of the implant side and control side are equivalent. Sixty two subjects (n=36 from Bonn, n=26 from Bern) with single-tooth implants (22 anterior and 40 posterior dental implants) were asked to bite on narrow copper foil strips varying in thickness (5-200 microm) and to decide whether or not they were able to identify a foreign body between their teeth. Active tactile sensibility was defined as the 50% threshold of correct answers estimated by means of the Weibull distribution. RESULTS: The results obtained for the interocclusal perception sensibility differed between subjects far more than they differed between natural teeth and implants in the same individual [implant/natural tooth: 16.7+/-11.3 microm (0.6-53.1 microm); natural tooth/natural tooth: 14.3+/-10.6 microm (0.5-68.2 microm)]. The intraindividual differences only amounted to a mean value of 2.4+/-9.4 microm (-15.1 to 27.5 microm). The result of our statistical calculations showed that the active tactile sensibility of single-tooth implants, both in the anterior and posterior region of the mouth, in combination with a natural opposing tooth is similar to that of pairs of opposing natural teeth (double t-test, equivalence margin: +/-8 microm, P<0.001, power >80%). Hence, the implants could be integrated in the stomatognathic control circuit.

Immediate bacterial colonization of titanium implants

Background: The information on bacterial colonization immediately after dental implant insertion is limited. Aims: (1) to assess the early colonization on titanium implants immediately post placement through the first12 post-surgical weeks , (2) to compare the microflora at interproximal subgingival implant and adjacent tooth sites. Material and Methods: Subgingival plaque samples from implant and neighbouring teeth were studied by checkerboard DNA-DNA hybridization before, 30 min. after implant placement , 1 week, 2 weeks, 4 weeks, 8 weeks, and 12 weerks after surgery. Results: Comparing bacterial loads at implant sites between 30 min. after placement with one week data showed that only the levels of V.parvula (p<0.05) differed with higher loads at week 1. Week 12 data demonstrated significantly higher bacterial loads for 15/40 species at tooth sites compared to pre-surgery (p < values varying between 0.05 and 0.01). Between immediately post-surgery and week 12 at implant sites 29/40 species were more commonly found at week 12. Included among these bacteria at implant sites were P.gingivalis (p< 0.05), T.forsythia, (p < 0.01), and T denticola (p<0.001). Immediately post-surgery 5.9% of implants, and 26.2% of teeth and at week 12, 15.0 % of implants, and 39.1% of teeth harbored S.aureus. Comparing tooth and implant sites, significantly higher bacterial loads were found at tooth sites for 27/40 species at the 30 minutes after placement interval. This difference increased to 35/40 species at week 12. Conclusions: The colonization of bacteria occurs within 30 minutes. Colonization patterns differed between implants and tooth surfaces.