Effect of ultraviolet photofunctionalization of dental titanium implants on osseointegration.

OBJECTIVE: The aim of the current study was to evaluate the effect of ultraviolet (UV) photofunctionalization of dental titanium implants with exposure to the oral cavity on osseointegration in an animal model. METHODS: Forty-eight titanium implants (Camlog® Conelog® 4.3 mmx9.0 mm) were placed epicrestally into the edentulous jaws of three minipigs and implant stability was assessed by measuring the implant stability quotient (ISQ). Prior to implantation half of the implants were photofunctionalized with intense UV-light. After three months, the implants were exposed and ISQ was measured again. After six months of implant exposure, the minipigs were sacrificed and the harvested specimens were analyzed using histomorphometric, light, and fluorescence microscopy. MAIN RESULTS: Forty-two of 48 implants osseointegrated. The overall mean bone-implant contact area (BIC) was (64±22)%. No significant differences were found in BIC or ISQ value (multivariate analysis of variance (MANOVA), P>0.05) between implants with and without exposure to UV photofunctionalization. CONCLUSIONS: No significant effects were observed on osseointegration of dental titanium implants nine months after exposure of UV photofunctionalization.

Influence of Four Different Abutment Materials and the Adhesive Joint of Two-Piece Abutments on Cervical Implant Bone and Soft Tissue.

PURPOSE: The main aim of this study was to evaluate the influence of four different abutment materials and the adhesive joint of two-piece abutments on the cervical implant bone and soft tissue. MATERIALS AND METHODS: Sixty-four titanium implants (Camlog Conelog; 4.3 ± 9 mm) were placed bone level into the edentulous arches of four minipigs. Four different types of abutments were placed at implant exposure: zirconium dioxide, lithium disilicate, and titanium bonded to a titanium luting base with resin cement; one-piece titanium abutments served as the control. The animals were sacrificed 6 months after implant exposure, and the bone-to-implant contact (BIC) area, sulcus depth, the length of the junctional epithelium and the connective tissue, the biologic width, and first cervical BIC-implant shoulder distance were measured using histomorphometry and light and fluorescence microscopy. RESULTS: Overall, 14 implants were lost (22%). At exposure, the implant shoulder-bone distance was 0.6 ± 0.7 mm. Six months later, the bone loss was 2.1 ± 1.2 mm measured histomorphometrically. There was a significant difference between the two measurements (P ≤ .0001). No significant influence could be found between any of the abutment materials with regard to bone loss or soft tissue anatomy (P > .05), with the exception of zirconium dioxide and onepiece titanium abutments when measuring the length of the junctional epithelium (P ≤ .01). The maxilla provided significantly more soft tissue and less bone loss compared with the mandible (P ≤ .02). CONCLUSION: All tested abutment materials and techniques seem to be comparable with regard to soft tissue properties and the cervical bone level.

Can one-wall bone defects be augmented with xenogenic bone grafting material alone?

OBJECTIVES: The main aim of this study was to evaluate the impact of xenogenic bovine bone grafting material particle size, addition of harvested autogenic bone as well as the influence of a periosteum on growth of newly formed bone, bone marrow, residual bone grafting material and connective tissue of one-wall defects. METHODS: Overall 32 augmentation sites were placed on the frontal skull of four minipigs and covered with titanium pin immobilized absorbable porcine membranes. After a 6 month healing period the harvested specimens were analyzed using light- and fluorescence microscopy. RESULTS: In the augmented areas 47%-57% bone, 14%-34% bone marrow, 10%-20% residual xenogenic bone grafting material and 4.5%-10% connective tissue were found. Admixture of autogenic bone resulted in statistically significantly more newly formed bone, more bone marrow, less residual xenogenic bone grafting material and less connective tissue (P ≤ 0.03). CONCLUSIONS: While augmenting one-wall defects seems to be possible with xenogenic grafting material and absorbable membranes alone, the addition of autogenic bone seems to benefit the augmentation site.

Periodontal regeneration employing gingival margin-derived stem/progenitor cells in conjunction with IL-1ra-hydrogel synthetic extracellular matrix.

AIM: This study investigated the periodontal regenerative potential of gingival margin-derived stem/progenitor cells (G-MSCs) in conjunction with IL-1ra-releasing hyaluronic acid synthetic extracellular matrix (HA-sECM). MATERIALS AND METHODS: Periodontal defects were induced at four sites in eight miniature pigs in the premolar/molar area (-4 weeks). Autologus G-MSCs were isolated from the free gingival margin and magnetically sorted, using anti-STRO-1 antibodies. Colony formation and multilineage differentiation potential were tested. The G-MSCs were expanded and incorporated into IL-1ra-loaded/unloaded HA-sECM. Within every miniature pig, four periodontal defects were randomly treated with IL-1ra/G-MSCs/HA-sECM (test group), G-MSCs/HA-sECM (positive-control), scaling and root planing (SRP; negative control-1) or left untreated (no-treatment group; negative control 2). Differences in clinical attachment level (ΔCAL), probing depth (ΔPD), gingival recession (ΔGR), radiographic defect volume (ΔRDV), and changes in bleeding on probing (BOP) between baseline and 16 weeks post-transplantation, as well as periodontal attachment level (PAL), junctional epithelium length (JE), connective tissue adhesion (CTA), cementum regeneration (CR) and bone regeneration (BR) at 16 weeks post-transplantation were evaluated. RESULTS: Isolated G-MSCs showed stem/progenitor cell characteristics. IL-1ra loaded and unloaded G-MSCs/HA-sECM showed higher ΔCAL, ΔPD, ΔGR, PAL, CR and BR as well as a lower JE compared to their negative controls and improved BOP. CONCLUSION: G-MSCs in conjunction with IL-1ra-loaded/unloaded HA-sECM show a significant periodontal regenerative potential.

Transapical mitral valved stent implantation: computed tomographic evaluation of different prototype designs.

AIMS: The evaluation of in vivo shaping of mitral valved stent prototypes using cardiac computed tomography (CT) was the focus of this study. METHODS AND RESULTS: Twelve pigs received a self-expanding mitral valved stent, composed of an atrial element connected to a tubular ventricular body at a modified angle (45°, 90°, 110°) resulting in three designs. Cardiac CT was performed three weeks after implantation, with focus placed on stent design-related parameters: possible left ventricular outflow tract obstruction and stent shaping. CT was successfully conducted in 11/12 animals showing correct stent position within the mitral annulus and no obstruction of the left ventricular outflow tract in 9/11 animals. Minor radial deformations of the stent body were detected. At the atrioventricular junction, deformations of the stent structure were observed in all cases. Stents with a 45° angle exhibited the greatest deflection (≤56.4°±14.5°). CONCLUSIONS: The effectiveness of cardiac computed tomography in the development process of valved stents to provide essential information and quantitative data about the in vivo stent geometry was demonstrated. The in vivo mechanical deformations of the stent were quantified, identifying critical design areas: a larger preset angle leads to less deflection and improved alignment and hence reduces the mechanical load.

Transapical mitral valved stent implantation: enhanced survival and decreased paravalvular leakages.

BACKGROUND/OBJECTIVES: This study presents the recent results of transapical implantation of a new design of a mitral valved stent with up to three months follow-up. METHODS: A self-expanding re-designed mitral valved stent was implanted via transapical approach into the beating heart of eight pigs. Echocardiographic- and hemodynamic parameters were assessed before (n=8), at 1h (n=8), at one month (n=6), at two months (n=2), and at three months (n=1) after implantation and a cardiac CT was conducted. RESULTS: The stent was successfully deployed in all animals. Two animals died within the first month due to incorrect fixation force. Echocardiographic evaluation showed low gradients (3.9 ± 1.4 mm Hg and 1.9 ± 0.8 mm Hg across the valved stent and aortic valve) and a normal mitral annular plane systolic excursion (1.1 ± 0.2 cm) after one month. No paravalvular leakages (PVL) were detected after 1h. The pulmonary artery pressure did not increase after valved stent implantation (p ≥ 0.106). The pulmonary capillary wedge pressure (PCWP) slightly increased to 16 ± 3 mm Hg after one month (p=0.033). The left ventricular end-diastolic pressure was mildly elevated (15.8 ± 8.6 mm Hg) after one month. CONCLUSIONS: Secure deployment and correct position of the valved stents were reproducibly achieved in the off-pump implantation procedure. No paravalvular leakages after 1h as well as low gradients, few stent fractures and a normal longitudinal function after one month were achieved with this newly developed and well-aligned prototype. However, a number of challenges have been identified during this study and potential for improvement has been identified.

Off-pump tricuspid valved stent implantation: the next step.

OBJECTIVES: Off-pump transcatheter valved stent implantation could be a treatment option for patients suffering from symptomatic tricuspid regurgitation (TR) who are classified as inoperable. In this study, we present our recent short-term results of transventricular tricuspid valved stent implantation and compare different stent types for atrial anchorage. METHODS: Fifteen pigs received a self-expandable valved stent implantation off-pump via a transventricular access. Successfully implanted pigs were observed over a period of 6 h (n = 9), 48 h (n = 1) and 4 weeks (n = 1). Haemodynamic and full transoesophageal echocardiographic (TOE) evaluations were done before, 1 h, 3 h (n = 11; all successfully implanted pigs), and 6 h (n = 9; acute group) after implantation. Nine days postimplantation, one pig received additional angiography, computed tomography (CT) and transthoracic echocardiography (TTE). Post-mortem, gross examination was conducted to analyse the stent position and deformation. In two pigs (48 h and 4 weeks survival) histological staining and immunohistochemistry of surrounding myocardium was performed. RESULTS: The heart rate significantly increased in all pigs postimplantation from 66.8 ± 13.6 to 101.8 ± 24.6 bpm, whereas cardiac output and pressure levels remained unchanged. Orthotopic positioning was reproducibly achieved. TOE showed an efficient reduction of paravalvular leakages from a mean grade of 1.4 1 h postimplantation to a mean of 0.9 at 6 h postimplantation due to a special sealing pouch. The ratio early and late ventricular filling velocities remained constant and the valvular gradient across the valved stent stayed low during the observation period. Angiography, CT and TTE confirmed orthotopic positioning and mild grade of paravalvular leakage after 9 days (n = 1). Only mild TR was observed here. The ventricular part of the stent was deformed to an oval shape in 7 of 14 animals as shown via post-mortem examination. The surrounding tissue after 1 month (n = 1) showed normal morphology, without inflammation or calcification. CONCLUSION: This study shows the feasibility of catheter-based replacement of the tricuspid valve by a valved stent in an off-pump procedure. The successive enhancements in this tricuspid valved stent design lead to a prototype being ready for mid- to long-term evaluations.

Transapical mitral valved stent implantation: comparison between circular and D-shaped design.

AIMS: In this study two designs of a self-expanding valved stent were compared after off-pump implantation into the mitral valve to identify the superior one. METHODS AND RESULTS: Two designs of a mitral valved stent were tested. The first design is composed of a circular atrial element connected to a tube-shaped ventricular element. In the second design, the atrial element is D-shaped to achieve better anatomical alignment. Prior to in vivo testing, the area with the highest risk of PVL was identified in a hydrostatic in vitro set-up. Subsequently, eight pigs received stents (circular, n=5; D-shaped, n=3) via apical access in the beating heart. Positioning and haemodynamics were evaluated by TEE and invasive pressure measurement pre-implantation, after 1 hr, and at two and four weeks. In vitro testing showed less PVL in the anteromedial region in D-shaped design stents (p<0.001). All stents were successfully deployed in vivo and six animals maintained normal haemodynamics for two weeks or longer. Rotational reorientation of all stents with D-shaped elements was observed. Both groups indicated no clinically relevant gradients over the mitral valved stent. CONCLUSIONS: This study demonstrates that the circular design was superior to the D-shaped model after rotational reorientation of the latter occurred.