Discrete Crystalline Deposition Research Articles

Modulation of evaporation-affected crystal motion in a drying droplet by saline and surfactant concentrations

Crystallization of evaporating droplets has attracted intense interests thanks to its broad applications in bioengineering, coating technologies and pharmaceutical industries. We investigate the effects of saline and surfactant concentrations on the evaporative dynamics and crystallization patterns of sessile droplets. The droplet exhibits three regimes during evaporation. In regime I, the droplet transits from pinning to depinning, and then the commence of crystallization near the contact line launches regime II, during which the crystal exhibits more or less inward motion. In regime III, the crystal becomes immobilized until the evaporation completes. In the surfactant-free saline droplet, the crystal exhibits a weak gathering motion towards the center at a low saline concentration, resulting in the mild discrete crystalline deposition. Whereas the crystal movability is highly enhanced that they gather as a chunk at a high saline concentration, resulting from the larger droplet contact angle and higher supersaturation at the beginning of crystallization, and the higher liquid-vapor surface tension. These factors increase the horizontal component of the capillary force and solutal Marangoni force which drive crystals inwards. In the presence of surfactant, the crystals stay almost immobilized in regime II compared to the ones of the surfactant-free droplet, leading to discrete crystal morphologies. Surfactant reduces the liquid-vapor surface tension and the contact angle at the beginning of crystallization which are responsible for the smaller inward driving force.

Relative contributions of implant hydrophilicity and nanotopography to implant anchorage in bone at Early Time Points

To compare the contributions of implant hydrophilicity and nanotopography on anchorage in bone. The effect of elevated calcium surface chemistry on bone anchorage was also investigated. A full factorial study design was implemented to evaluate the effects of ultraviolet (UV) light and/or sodium lactate (SL) and discrete crystalline deposition of nanocrystals (DCD) treatments on the osseointegration of dual acid-etched (AE) titanium alloy (Ti6Al4V) and grit blasted and AE (BAE) commercially pure titanium (CpTi) implants. Sodium hydroxide (NaOH)-treated CpTi implants were immersed in simulated body fluid (SBF) to increase calcium surface chemistry. Implants were placed in the femora of Wistar rats and tested using pull-out testing (BAE implants: 5, 9, 14days) or tensile testing (AE implants: 9days, NaOH implants: 28days). Ti6Al4V-AE implants with DCD- and UV-treated surfaces significantly increased bone anchorage compared with untreated Ti6Al4V-AE alloy implants. Pull-out testing of BAE-CpTi implants with the DCD treatment showed increased disruption force values compared with surfaces without the DCD treatment at 5, 9 and 14days by 4.1N, 13.9N and 15.5N, respectively, and UV-treated implants showed an increase at 14days by 8.4N. No difference was found between NaOH+SBF and NaOH+H2 O groups. Bone anchorage of implants was found to be improved by UV-treating implants or nanotopographically complex surfaces. However, implant nanotopography was found to have a greater contribution to the overall bone anchorage and is more consistent compared with the time-dependent nature of the UV treatment.

Sequential morphometric evaluation at UnicCa® and DCD® implant surfaces. An experimental study in the dog.

To study tissue components adjacent to implants with nanotechnologically modified surfaces at different periods of healing. In 12 beagle dogs, two different implant systems with different surface configurations were randomly installed in the edentulous premolar regions of the mandible. One surface was first acid-etched and subsequently, nanotechnologically modified with calcium ions (UnicCa® ), while the other was first sandblasted and acid-etched, and then additionally treated with a nanometer calcium phosphate deposition (discrete crystalline deposition; DCD® ). The implants were fully submerged; surgeries and sacrifices were planned to harvest biopsies after 1, 2, 4 and 8weeks of healing (n=6 per period). A morphometric evaluation of percentages of new and old bone, bone debris/particles and clot, new soft tissues (provisional matrix and immature marrow), mature bone marrow and vessels was performed in the spongiosa compartment adjacent to the implant surface up to a distance of about 0.4mm from the surface. After 2weeks of healing, the soft tissues were represented by 41.0% at the UnicCa® and 37.9% at the DCD® surfaces, in both cases mainly being composed of provisional matrix. These percentages decreased over time, being composed of greater amounts of immature bone marrow, and disappeared after 8weeks. New bone increased progressively between 1 and 8weeks of healing from 9.7±6.3% to 70.0±8.4% and from 8.2±3.5% to 67.0±6.1% at the UnicCa® and DCD® surfaces, respectively. Pristine bone was progressively resorbed. Throughout the periods of healing observed, the formation of a provisional matrix followed by the formation of new bone and marrow was revealed in a similar fashion as for other modified surface configurations.

Impact of Dental Implant Surface Modifications on Osseointegration.

Objective. The aim of this paper is to review different surface modifications of dental implants and their effect on osseointegration. Common marketed as well as experimental surface modifications are discussed. Discussion. The major challenge for contemporary dental implantologists is to provide oral rehabilitation to patients with healthy bone conditions asking for rapid loading protocols or to patients with quantitatively or qualitatively compromised bone. These charging conditions require advances in implant surface design. The elucidation of bone healing physiology has driven investigators to engineer implant surfaces that closely mimic natural bone characteristics. This paper provides a comprehensive overview of surface modifications that beneficially alter the topography, hydrophilicity, and outer coating of dental implants in order to enhance osseointegration in healthy as well as in compromised bone. In the first part, this paper discusses dental implants that have been successfully used for a number of years focusing on sandblasting, acid-etching, and hydrophilic surface textures. Hereafter, new techniques like Discrete Crystalline Deposition, laser ablation, and surface coatings with proteins, drugs, or growth factors are presented. Conclusion. Major advancements have been made in developing novel surfaces of dental implants. These innovations set the stage for rehabilitating patients with high success and predictable survival rates even in challenging conditions.

Biomechanical Testing of Microblasted, Acid-Etched/Microblasted, Anodized, and Discrete Crystalline Deposition Surfaces: An Experimental Study in Beagle Dogs

Modifications in implant surface topography and chemistry may alter the early bone response at different levels. This study characterized four implant surfaces and evaluated the biomechanical fixation and histologic response at early implantation times in a canine radius model. External-hexagon Branemark-type implants were used with four experimental surfaces: microblasted (MI), acid-etched and microblasted (AAM), anodized (A), and discrete crystalline deposition (DCD). Surface topography was assessed by scanning electron microscopy, interferometry, and x-ray photoelectron spectroscopy. The implants were placed in the central region of the radii of eight beagle dogs and remained in vivo for 10 or 30 days. The implants were torqued to interface failure, and a general linear statistical model with torque as the dependent variable and implant surface and time in vivo as independent variables was used. All surfaces presented were textured, and different surface chemistries were observed. No significant differences between implant surfaces were observed for torque at 10 days. However, at 30 days, the AAM surface presented significantly higher torque values compared to the DCD and A surfaces. Significantly higher torque values were observed at 30 days compared to 10 days (P < .001). Significantly different biomechanical fixation dependent on surface preparation was observed after 30 days, and all surfaces were biocompatible and osteoconductive.

Evaluation of Bacterial Adhesion on Machined Titanium, Osseotite® and Nanotite® Discs

Bacterial adhesion and colonization play a crucial function in the pathogenesis of peri-implant tissue infection, which is considered the main cause of fixture loss. The aim of this study is to evaluate the differences in bacterial adhesion between a machined titanium surface, a double acid etched surface (Osseotite®) and an Osseotite surface with Nanometer-scale Discrete Crystalline Deposition (DCD™) of calcium phosphate (CaP)(Nanotite®). Surface roughness properties of each sample were determined by a laser profilometer and scanning electron microscopy (SEM) observation. Bacterial adhesion on machined, Osseotite®, and Nanotite® discs were performed using the following bacterial strains: Streptococcus mutans CCUG 35176, Streptococcus sanguis CCUG 17826, Streptococcus salivarius CCUG 11878, Actinobacillus actinomycetecomitans CCUG 37002, Porphyromonas gingivalis CCUG 2521. The assessment of bacterial adhesion was performed by comparing two methods: Total Viable Count (TVC) estimation and Confocal Laser Scanning Microscopic (CSLM) studies. The surface roughness parameter increased as follows: machined<Nanotite®<Osseotite®. The attachment of all bacterial strains performed by both methods showed a significant reduction on Osseotite® and even higher on Nanotite® in comparison to machined surfaces (p<0.05). The reduction in bacterial attachment was more significant on Osseotite® and Nanotite® for A. actinomycetecomitans, S. mutans and S. sanguis than for P. gingivalis and S. salivarius strains. Nanotite® samples showed the lowest amount of bacterial contamination in comparison to the smoother machined and rougher Osseotite® surfaces.

Short implants with a nanometer‐sized CaP surface provided with either a platform‐switched or platform‐matched abutment connection in the posterior region: a randomized clinical trial

To assess the performance of short nanorough implants (8.5 mm in length) provided with either a platform-matched or a platform-switched implant-abutment connection, placed in the resorbed posterior region of partially dentate patients. A total of 149 implants with a dual-acid surface and a discrete crystalline deposition of nanometer-sized CaP particles, with either a platform-matched (control) or a platform-switched implant-abutment connection (test) were placed (randomly assigned) in 92 patients. Follow-up visits were conducted 1 month and 1 year after placing the implant crown. Outcome measures were implant survival, radiographic peri-implant bone loss, clinical parameters, and patient's satisfaction. One year after loading, 6 of 76 implants in the control group (survival 92.1%) and 3 of 73 implants in the test group (survival 95.9%) were lost (P = 0.33). Radiographic bone loss around test implants (0.50 ± 0.53 mm) was significantly less than around control implants (0.74 ± 0.61 mm; P < 0.005). With regard to implant survival, clinical parameters, and patient's satisfaction, no significant differences were observed between test and control group. For teeth replacements in the resorbed posterior region of partially dentate patients, short implants with a platform-switched implant-abutment connection showed significantly less peri-implant bone loss after 1 year in function, while implant survival, clinical parameters, and patient's satisfaction were independent of the implant-abutment connection design.

Buccal and lingual bone level alterations after immediate implantation of four implant surfaces: a study in dogs

Bone formation and maintenance around implants placed immediately after tooth extraction may be affected by implant surface treatment and compromise long-term esthetic results. This study morphometrically evaluated buccal bone loss and bone-to-implant contact (BIC) of four implant systems placed immediately after tooth extraction in a dog model. The premolars of eight beagle dogs were bilaterally extracted with a full-thickness flap, and root-form dental implants were placed on the root extraction socket. Implants (n = 16 each) with different surface treatments were placed from sites 1 to 4 and alternated between animals to allow evaluation of the same number of implants at sites and evaluation time points. Implant surface treatments were as follows: anodized, discrete crystalline deposition, SLActive, and microblasted. The left and right side provided implants that stayed for 2 and 4 weeks, respectively. Submerged healing was allowed and bone-to-implant contact (BIC) and buccal bone loss were morphometrically measured. Linear mixed models (P < 0.05) were used to assess differences between groups, across time, and their interaction. Buccal bone loss was observed to approximately double between 2 and 4 weeks (P = 0.01). BIC also increased between 2 and 4 weeks, by 20-25% (P = 0.01). These changes were statistically similar for each surface. When placed immediately after tooth extraction, the evaluated histomorphometric parameters vary only with time.

Biomechanical Evaluation of Endosseous Implants at Early Implantation Times: A Study in Dogs

This study tested the null hypothesis that differences in surgical instrumentation, macrogeometry, and surface treatment imposed by different implant systems do not affect early biomechanical fixation in a canine mandible model. The lower premolars of 6 beagle dogs were extracted and the ridges allowed to heal for 8 weeks. Thirty-six (n = 12 each group) implants were bilaterally placed, remaining for 1 and 3 weeks in vivo. The implant groups were as follows: group 1, Ti-6Al-4V with a dual acid-etched surface with nanometer scale discrete crystalline deposition (Nanotite; Certain Biomet-3i, West Palm Springs, FL); group 2, Ti-6Al-4V with a titanium oxide-blasted fluoride-modified surface chemistry (Osseospeed 4.0 S; Astra Tech, Mölndal, Sweden); group 3: Ti-6Al-4V with a bioceramic microblasted surface (Ossean; Intra-Lock International, Boca Raton, FL). Following euthanasia, implants were torqued to interface failure and histologically evaluated. General linear modeling (ANOVA) at 95% level of significance was performed. Histology showed that interfacial bone remodeling and initial woven bone formation were observed around all implant groups at 1 and 3 weeks. Torque values were significantly affected by time in vivo, implant group, and their interaction (P = .016, P < .001, and P = .001, respectively). Regarding torque values, group 3, group 2, and group 1 ranked highest, intermediate, and lowest, respectively. Early biomechanical fixation at 1 and 3 weeks was affected by surgical instrumentation, macrogeometry, and surface treatment present for one of the implant systems tested. The null hypothesis was rejected.

Vitamin D and Bone Physiology: Demonstration of Vitamin D Deficiency in an Implant Osseointegration Rat Model

The patient population varies in nutritional deficiencies, which may confound the host response to biomaterials. The objective of this study was to evaluate the effect of a common deficiency of vitamin D on implant osseointegration in the rat model. Male Sprague-Dawley rats were maintained under the cessation of vitamin D intake and UV exposure. The serum levels of 1,25(OH)(2)D(3), 25 OHD(3), Ca, and P were determined. Miniature cylindrical Ti6Al4V implants (2-mm long, 1-mm diameter) were fabricated with double acid-etched (DAE) surface or modified DAE with discrete crystalline deposition (DCD) of hydroxyapatite nanoparticles. DAE and DCD implants were placed in the femurs of vitamin D-insufficient and control rats. After 14 days of healing, the femur-implant samples were subjected to implant push-in test and nondecalcified histology. The surfaces of recovered implant specimens after the push-in test were further evaluated by scanning electron microscopy (SEM). The decreased serum level of 25 OHD(3) demonstrated the establishment of vitamin D insufficiency in this model. The implant push-in test revealed that DAE and DCD implants in the vitamin D-insufficient group (15.94 +/- 8.20 N, n = 7; 15.63 +/- 3.96 N, n = 7, respectively) were significantly lower than those of the control group (24.99 +/- 7.92 N, n = 7, p < 0.05; 37.48 +/- 17.58 N, n = 7, p < 0.01, respectively). The transcortical bone-to-implant contact ratio (BIC) was also significantly decreased in the vitamin D-insufficient group. SEM analyses further suggested that the calcified tissues remaining next to the implant surface after push-in test appeared unusually fragmented. The effect of vitamin D insufficiency significantly impairing the establishment of Ti6Al4V implant osseointegration in vivo was unexpectedly profound. The outcome of Ti-based endosseous implants may be confounded by the increasing prevalence of vitamin D insufficiency in our patient population.

Early healing of implants placed into fresh extraction sockets: an experimental study in the beagle dog. II: ridge alterations

To describe the early phases of healing at the alveolar ridge around dental implants placed into fresh extraction sockets and to study whether (i) the dimension of the socket and (ii) a new implant surface nano-topography may have any influence. Sixteen beagle dogs received 64 test (new surface) and control implants randomly placed at the distal socket of 3P3 and 4P4. The implant shoulder was levelled with the marginal buccal bone crest. Animals were sacrificed at 4 h, 1, 2, 4 and 8 weeks for histological examination. Bone loss occurred at the buccal crest between the 4-h and 1-week healing intervals, being more pronounced at the third premolar site [vertical bone loss between day 0 and 8 weeks 1.1 (0.5) mm]. The corresponding loss at the fourth premolar site was 0.3 (0.5) mm. Test sites containing implants with discrete crystalline deposition nano-particles' surface exhibited less buccal bone resorption than control sites at 8 weeks. Dimensions of the socket influenced the process of wound healing of implants placed into fresh extraction sockets, with more bone loss in the narrower sockets; however, the implant surface nano-topography seemed to have a limited effect in the healing of this implant surgical protocol.

Discrete calcium phosphate nanocrystalline deposition enhances osteoconduction on titanium‐based implant surfaces

We sought to assess the ability of nanotopographically complex titanium surfaces to accelerate osteoconduction. For this, 130 miniature bone ingrowth chambers (called "T plants"), fabricated from either commercially pure titanium (cpTi) or titanium alloy (Ti6Al4V or Ti64), with microtopographically complex surfaces were used in the study, of which 50 were further modified by the discrete crystalline deposition (DCD) of calcium phosphate (CAP) nanoparticles that superimposed a nanotopographic complexity on each implant surface. Thus, four experimental groups were generated (cpTi, cpTi-DCD, Ti64, and Ti64-DCD), and the Tplants were implanted bilaterally in the femora of Wistar rats for 9 days. After harvesting, the femora were trimmed, and multiple-mounted samples were embedded in PMMA. The blocks produced were ground and block faces observed by back-scattering electron imaging (BSEI) at different planes through the chambers. Osteoconduction was assessed, as a function of bone-implant contact, on a total of 1087 BSEI micrographs and submitted to rigorous statistical analyses. Our results showed both the important effects of anatomic location on bone ingrowth and the significant increase in osteoconduction (p < 0.001) as a function of the enhanced surface nanotopography obtained by the CAP nanocrystals.

The effect of discrete calcium phosphate nanocrystals on bone-bonding to titanium surfaces

We sought to address the question: Can metallic surfaces be rendered bone-bonding? We employed dual acid-etched (DAE) commercially pure titanium (cpTi) and titanium alloy (Ti6Al4V) custom-made rectangular coupons (1.3 mm×2.5 mm×4 mm) with, or without, further modification by the discrete crystalline deposition (DCD) of calcium phosphate (CAP) nanocrystals. A total of 48 implants comprising four groups were placed bilaterally in the distal femur of male Wistar rats for 9 days. After harvesting, the bone immediately proximal and distal to the implant was removed, resulting in a test sample comprising the implant with two attached cortical arches. The latter were distracted at 30 mm/min, in an Instron™ machine, and the disruption force was recorded. Results showed that alloy samples exhibited greater disruption forces than cpTi, and that DCD samples had statistically significantly greater average disruption forces than non-DCD samples. The bone-bonding phenomenon was visually evident by fracture of the cortical arches and an intact bone/implant interface. Field emission scanning electron microscopy showed the bone/implant interface was occupied by a bony cement line matrix that was interlocked with the surface topographical features of the implant. We conclude that titanium implant surfaces can be rendered bone-bonding by an increase in the complexity of the surface topography.