Retracted: A new cervical implant design compared with standard design in order to increase peri-implant hard and soft tissue behavior: histomorphometric and histological study in dogs.

OBJECTIVE: The aim of this study was to evaluate a new design of the cervical portion of dental implant with the objective to increase the volume of peri-implant tissues in the crestal area. MATERIALS AND METHODS: Forty-eight tapered dental titanium implants with internal conical connection were implanted in healed alveolar sites of six dogs. Twenty-four conventional implants design (C1 implant) formed the control group, and 24 new implant design (V3 implant) formed the test group. The groups were randomized. Histological, histomorphometric, and implant stability quotient were performed. After 12 weeks of healing period, histomorphometric analyses of the specimens were carried out to measure the crestal bone level values and the tissue thickness in the cervical implant portion. The data were compared using statistical tests (α = 5%). RESULTS: The mean of the measurements in the buccal and lingual aspects measured of crestal bone level was 0.31 ± 0.24 mm and 0.30 ± 0.19 mm in the control group, respectively, and 0.71 ± 0.28 and 0.42 ± 0.30 mm in the test group, respectively, whereas the mean of the tissue thickness was 1.63 ± 0.33 mm and 2.04 ± 0.23 mm in the control group, respectively, and 2.11 ± 0.35 mm and 2.51 ± 0.41 mm in the test group. CONCLUSIONS: Within the limitations of this study, our findings suggest that more thickness of peri-implant hard and soft tissues may be expected in this new implant design. However, the control group with traditional implant design was found to have more height values of the crestal bone compared with new V3 implants.

Role of mechanical compression on bone regeneration around a particulate bone graft material: an experimental study in rabbit calvaria.

PURPOSE: This experimental study was designed to analyze the effect of different compressive forces on the bone regeneration around a particulate bone graft material. MATERIAL AND METHODS: Eighty 6-mm-diameter defects were created in the calvaria of 20 New Zealand rabbits (4 defects per rabbit calvaria). All the defects were filled with particles of synthetic bone. Two standardized compressive forces were then applied, 4.1 g to half the defects (Test A) and 8.2 g to the other half (Test B), all for 1 min. The graft sites were allowed to heal for 6 weeks, after which the rabbits were euthanized. The calvarium vault of each animal was extracted, radiographed, and prepared for histomorphometric analysis. The percentage of defect fill, bone density, new bone formation, and residual bone graft material were recorded, and the results were subjected to statistical analysis. RESULTS: Histological evaluation found that defect closure among the Test A (lower compression) group ranged from 38.34 (95% lower CI) to 55.8 (95% upper CI) (mean 47 ± 8.5%), while among the Test B group (higher compression), it ranged from 81.26 (95% lower CI) to 95.32 (mean 88 ± 7.3%). Significantly more closure was achieved for the Test B group (P < 0.05). Histomorphometric comparison of the two groups found significantly more new bone formation, higher bone density, and a higher percentage of defect fill in the defects subjected to the higher compression level (P < 0.05). CONCLUSIONS: Increasing the compressive force applied to bone graft particulate used to fill small defects created in rabbit calvaria appears to be beneficial.

Bone neoformation of a novel porous resorbable Si-Ca-P-based ceramic with osteoconductive properties: physical and mechanical characterization, histological and histomorphometric study.

OBJECTIVE: The aims of the present work were to study a new porous Nurse's A ceramic (Si-Ca-P-based material) bone substitute and examine its mechanical properties in vitro and the biocompatibility, osteoconductivity and resorption process in vivo. MATERIALS AND METHOD: Porous ceramic scaffolds were prepared by solid-state reaction and implanted in critical-sized defect created in 15 NZ rabbits. Strength values were determined by the diametrical compression of disk test. Weibull analyses were performed following the European Standard for technical ceramics EN-843-5: 1996, considering 90% of confidence intervals. Results were correlated with scanning microscope observations of fracture surfaces. Implanted scaffolds were characterized by histological and histomorphometric point of view. RESULTS: The parameters of the Weibull distribution of strength, determined by diametrical compression of disks, were modulus m = 13, and characteristic strength σ0  = 0.60 MPa (90% confidence limit: m = 7.2-17.6, σ0  = 0.570-0.578). Porous calcium silicophosphate scaffolds showed significantly more bone formation in the pores and in the periphery of the implant than the control group. Histomorphometric analysis revealed that the ceramic scaffold (62.23 ± 0.34*) produced higher values of bone-to-implant contact (BIC) percentages (higher quality, closer contact); moreover, defect closure was significative in relation with control group. CONCLUSIONS: The porous calcium silicophosphate ceramic is biocompatible, partially resorbable and osteoinductive material. This rabbit study provides radiological and histological evidences confirming the suitablity of this new material for bone tissue regeneration on critical defects.

Topical applications of vitamin D on implant surface for bone-to-implant contact enhance: a pilot study in dogs part II.

OBJECTIVE: The aim of this study was to evaluate the effect of topical application of vitamin D over implant surface, placed immediately to the extraction, throughout histological and histomorphometric analysis of peri-implant tissue. MATERIAL AND METHODS: Six American foxhound dogs were used in the study. Mandibular premolar distal roots were extracted. Twenty-four immediate conical C1 implants (MIS, Barlev, Israel) were randomly assigned to the distal site on each site of the mandible in three groups: (Group CI) 12 titanium implants alone; (Test Group DI) 12 titanium implants supplemented with vitamin D. Prior to implanting, test implants (DI) were submerged in vitamin D 10% solution. No treatment was applied at control implants (CI). After 12 weeks, animals were sacrificed. Block sections were obtained and processed for mineralized ground sectioning. Bone-to-implant contact (Total BIC and BIC%), new bone formation (NBF), interthread bone (ITB), and histological linear measurements (HLM) were analyzed. RESULTS: At 12 weeks, all implants were clinically stable and histologically osseointegrated. BIC evaluation showed Total BIC mean and SD values for DI (48.96 ± 2.14), CI (44.56 ± 1.75) (P < 0.05), BIC% DI (43.59 ± 0.98), and CI (42.67 ± 9.26) (P > 0.05). For interthread bone formation, values were as follows: DI (15.21 ± 3.87), CI (14.79 ± 1.45) (P > 0.05), no statistically differences. Regarding peri-implant new bone formation, no statistically differences could be found between the two groups DI (31.87 ± 1.23), CI (27.18 ± 2.38) (P > 0.05). For linear measurements, test group (DI) showed statistically significant less buccal crestal bone loss (CBL) DI (0.37 ± 0.12)*, CI (1.26 ± 0.8) (P < 0.05), and vitamin D implants showed less lingual junctional epithelium DI (1.58 ± 0.43)*, CI (2.18 ± 0.48) (P < 0.05). No differences were observed in the buccal mucosa. CONCLUSION: With the limitation of animal studies, topical application of vitamin D on dental implants could reduce crestal bone loss and increase 10% more bone-to-implant contact at 12-week follow-up period.

Influence of hydroxyapatite granule size, porosity, and crystallinity on tissue reaction in vivo. Part A: synthesis, characterization of the materials, and SEM analysis.

OBJECTIVE: The aim of this study was the synthesis and analysis of the tissue reaction to three different Hydroxyapatite (HA)-based bone substitute materials differing only in granule size, porosity, and crystallinity through an animal experimental model at 60 days. MATERIALS AND METHODS: Three different HA-based biomaterials were synthesized and characterized by X-ray diffraction, SEM, and EDS analysis, the resultant product was ground in three particle sizes: Group I (2000-4000 µm), Group II (1000-2000 µm), and Group III (600-1000 µm). Critical size defects were created in both tibias of 15 rabbits. Four defects per rabbit for a total of 60 defects were grafted with the synthesized materials as follows: Group I (15 defects), Group II (15 defects), Group III (15 defects), and empty (15 defects control). After animals sacrifice at 60 days samples were obtained and processed for SEM and EDS evaluation of Ca/P ratios, elemental mapping was performed to determine the chemical degradation process and changes to medullary composition in all the four study groups. RESULTS: The tendency for the density was to increase with the increasing annealing temperature; in this way it was possible to observe that the sample that shows highest crystallinity and crystal size corresponding to that of group I. The SEM morphological examination showed that group III implant showed numerous resorption regions, group II implant presented an average resorption rate of all the implants. The group I displayed smoother surface features, in comparison with the other two implants. CONCLUSION: The data from this study show that changing the size, porosity, and crystallinity of one HA-based bone substitute material can influence the integration of the biomaterials within the implantation site and the new bone formation.

Bone response to collagenized xenografts of porcine origin (mp3(®) ) and a bovine bone mineral grafting (4BONE(™) XBM) grafts in tibia defects: experimental study in rabbits.

OBJECTIVES: This study aimed to carry out the evaluation of bone response of new bone formation to two different xenografts (bovine and porcine) biomaterials inserted in rabbit tibiae. MATERIALS AND METHODS: The study used a total of 20 male New Zealand albino rabbits. They received a total of 40 grafts in the proximal metaphyseal areas of both tibiae. Two biomaterials were evaluated: 20 porcine xenografts, as a bone granulate (OsteoBiol(®) MP3(®) ; Tecnoss srl, Giaveno, Italy), were placed in the proximal metaphyseal area of the right tibia, 20 anorganic bovine bone mineral grafting (4BONE(™) XBM, MIS Implants Inc., BARLEV, Israel) were placed in the left tibia. Following graft insertion, the animals were sacrificed in two groups of 10 animals, after 1 and 4 months, respectively. For each group, biomaterials were analyzed: newly formed bone, residual graft materials and the connective tissue. Histomorphometric, EDX analysis and element mapping were performed at 1 and 4 months after graft insertion. RESULTS: At 4 months after treatment, the bone defects displayed radiological images that showed complete repair of osseous defects. Histomorphometric evaluation showed that for the porcine xenograft, the study averages for newly formed bone represented 84.23 ± 2.9%, while bovine matrix was 79.34 ± 2.1%. For residual graft material, the porcine biomaterial had 11.23 ± 1.7% and the bovine graft 31.56 ± 2.3%. Finally, the connective tissue for MP3 was 10.33 ± 1.8%, while for the 4BONE(™) XBM we obtained 14.34 ± 2.9%. Element analysis revealed higher percentages of Ca (54 ± 9%) and P (35 ± 6%) in the group B than group A and control group (P < 0.05). CONCLUSIONS: Defects of a critical size in a rabbit tibia model can be sealed using a bovine porous biphasic calcium phosphate and MP3 material; this supports new bone formation, creates a bridge between borders, and facilitates bone ingrowth in both biomaterials. Furthermore, this study observed partial dissolution of the mineral phase of four bone graft and complete resorption of porcine MP3 biomaterial and its incorporation into the surrounding bone. Depending on clinical needs, each biomaterial could be useful in daily clinical practice.

Bone neo-formation and mineral degradation of 4Bone.(®) Part I: material characterization and SEM study in critical size defects in rabbits.

OBJECTIVE: This study reports the characterization process and in vivo application of a new high-porosity biphasic calcium phosphate (4Bone(®) - HA 60%/ß-TCP 40%) inserted into the critical size defect of a rabbit tibiae. MATERIAL AND METHODS: Two critical size defects of 6 mm diameter were created in each tibia of 15 New Zealand rabbits, and a total of 60 defects were divided into a test group filled with 4Bone(®) (n = 30) and a control group (n = 30). The material and the implants were characterized by scanning electron microscope (SEM) fitted with energy-dispersive X-ray spectroscopy (EDX). RESULTS: The biomaterial's grain size decreased progressively with the graft integration process over the 60-day study period. Element analysis revealed increased percentages of Ca/P (2.86 ± 0.32 vs. 1.97 ± 0.59) in new bone and at the interface (P < 0.05). Element mapping showed that Ca and P were concentrated in the medullary and cortical zones in the test group but were concentrated only in cortical zones in the control group. CONCLUSIONS: Critical size defects in a rabbit tibia model can be sealed using this highly porous biphasic calcium phosphate; it supports new bone formation, creates a bridge between defect borders, and facilitates bone in growth.

Peri-implant tissue reactions to immediate nonocclusal loaded implants with different collar design: an experimental study in dogs.

PURPOSE: The aim of this study was to evaluate bone remodelling and soft tissue reactions around immediate nonocclusal loaded implants with different collar configuration in beagle dogs. MATERIAL AND METHODS: The mandibular bilateral second, third and fourth premolars of six beagle dogs were extracted. After 3 months of healing, four implants were placed in the mandibles of each dog. Randomly, two implants with a 1.5 mm polished surface collar (TSA, control group) and two implants with a 0.7 mm polished surface collar and 2.5 mm microthreaded area (TSAA, test group) were inserted. Both groups were treated with a minimal mucoperiosteal flap elevation approach. Impressions were taken and two single screw-retained restorations were inserted in each hemi-mandible 2 days after the implant placement. The animals were sacrificed at 1, 2 and 3 months (two specimens each), and biopsies were obtained. Samples were processed for ground sectioning. Histomorphometric analysis was carried out to compare buccal and lingual bone height loss and soft tissue behaviour between the two groups. RESULTS: Crestal bone resorption was significantly higher in the control group (P > 0.05). The establishment of the biological width showed similar outcomes for both groups. Only the distance from the top of the peri-implant mucosa to the apical portion of the barrier epithelium at lingual aspect was significantly more pronounced in the control group (P > 0.05). CONCLUSIONS: The alterations that occurred in the peri-implant tissues were related to the adaptation that occurred after the loading conditions in both groups. The microthread design might have an effect in maintaining the marginal bone loss against loading.

Clinical and radiographic evaluation of osseotite-expanded platform implants related to crestal bone loss: a 10-year study.

OBJECTIVE: The aim of this prospective clinical study was to evaluate the survival rates at 10 years of expanded platform implants placed in the anterior zone of the maxilla and immediately restored with single crowns. MATERIALS AND METHODS: Implants incorporating the platform-switching concept were placed in fresh extraction sockets in the maxillary arch, with each patient receiving a provisional restoration immediately after implant placement. After 15 days, final screwed restorations were inserted. Mesial and distal bone heights were evaluated using digital radiography on the day following implant placement and at 1, 5, 7, and 10 years. Primary stability was measured with resonance frequency analysis (RFA) using the Osstell Mentor device. Eighty-six implants were placed in 32 men and 32 women ranging in age between 29 and 60 (mean, 39.64 ± 5.16 years). RESULTS: Marginal bone loss from implant collar to bone crest between baseline and 10 years follow-up was 1.01 mm ± 0.22. Mesial site crestal bone loss ranged from 3.57 mm ± 1.1 at baseline to 3.77 mm ± 0.7 at 10-year. Distal site crestal bone loss ranged from 3.49 mm ± 0.8 at baseline to 3.73 mm ± 0.7 at 10 year. CONCLUSION: The platform-switched implants remained stable over the course of 10 years and had an overall survival rate of 97.1%.

Biodegradation process of α-tricalcium phosphate and α-tricalcium phosphate solid solution bioceramics in vivo: a comparative study.

This article reports the structure and morphology of the in vivo interface between implants composed of either a tricalcium phosphate (αTCP) or αTCP doped with 3.0 wt% dicalcium silicate (αTCP(ss)) ceramic, and natural bone of rabbit tibias. Both interfaces developed a new bone layer in direct contact with the implants after 4 and 8 weeks of implantation. The specimens were examined using analytical scanning and transmission electron microscopy, up to the lattice plane resolution level. Degradation processes of the implants developed at the interfaces encouraged osseous tissue ingrowth into the periphery of the material, changing the microstructure of the implants. The ionic exchange initiated at the implant interface with the environment was essential in the integration process of the implant, through a dissolution­precipitation­transformation mechanism. The interfaces developed normal biological and chemical activities and remained reactive over the 8-week period. Organized collagen fibrils were found at the αTCP(ss)/bone interface after 4 weeks, whereas a collagen-free layer was present around the Si-free αTCP implants. These findings suggest that the incorporation of silicate ions into αTCP ceramic promotes processes of the bone remodeling at the bone/αTCP(ss) interface, hence the solubility rate of the aTCP(ss) material decreased.

Nurse's A-Phase-Silicocarnotite Ceramic-Bone Tissue Interaction in a Rabbit Tibia Defect Model.

Calcium phosphate materials are widely used as bone substitutes due to their bioactive and biodegradable properties. Also, the presence of silicon in their composition seems to improve the bioactivity of the implant and promote bone tissue repair. The aim of this study was to develop a novel ceramic scaffold by partial solid-state sintering method with a composition lying in the field of the Nurse's A-phase-silicocarnotite, in the tricalcium phosphate-dicalcium silicate (TCP-C2S) binary system. Also, we evaluated its osteogenic and osteoconductive properties after being implanted into tibia defects in New Zealand rabbits. X-ray, microcomputer tomography, and histomorphometry studies demonstrated that this porous ceramic is highly biocompatible and it has excellent osteointegration. The material was being progressively reabsorbed throughout the study and there was no unspecified local or systemic inflammatory response observed. These results suggest that ceramic imitates the physicochemical characteristics of bone substitutes used in bone reconstruction.

A New Biphasic Dicalcium Silicate Bone Cement Implant.

This study aimed to investigate the processing parameters and biocompatibility of a novel biphasic dicalcium silicate (C2S) cement. Biphasic α´L + ß-C2Sss was synthesized by solid-state processing, and was used as a raw material to prepare the cement. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid (SBF) and human adipose stem cell cultures. Two critical-sized defects of 6 mm Ø were created in 15 NZ tibias. A porous cement made of the high temperature forms of C2S, with a low phosphorous substitution level, was produced. An apatite-like layer covered the cement's surface after soaking in SBF. The cell attachment test showed that α´L + ß-C2Sss supported cells sticking and spreading after 24 h of culture. The cement paste (55.86 ± 0.23) obtained higher bone-to-implant contact (BIC) percentage values (better quality, closer contact) in the histomorphometric analysis, and defect closure was significant compared to the control group (plastic). The residual material volume of the porous cement was 35.42 ± 2.08% of the initial value. The highest BIC and bone formation percentages were obtained on day 60. These results suggest that the cement paste is advantageous for initial bone regeneration.

Bone Ceramic® at Implants Installed Immediately into Extraction Sockets in the Molar Region: An Experimental Study in Dogs.

PURPOSE: The aim of this paper was to study the healing of 1-1.4 mm wide buccal defects at implants placed immediately into extraction sockets (IPIES) filled with a mixture of synthetic hydroxyapatite (HA) 60% and beta-tricalciumphosphate (TCP) 40% or left with the clot alone and both covered with collagen membranes. MATERIAL AND METHODS: Eight Labrador dogs were used and implants were placed immediately into the extraction sockets of the first molar bilaterally. A mixture of synthetic HA 60% and beta-TCP 40% at the test or the clot alone at the control sites were used to fill the defects. All surgical sites were subsequently covered by a resorbable collagen membrane and a non-submerged healing was allowed. After 4 months, the animals were euthanized, biopsies harvested and processed for histomorphometric analysis. RESULTS: At the time of installation, residual buccal defects occurred that were 1.1 mm and 1.4 mm wide and 3 mm and 4 mm deep at the control and test sites, respectively. After 4 months of healing, the top of the bony crest and the coronal level of osseointegration were located respectively at 0.1 ± 1.8 mm and 1.5 ± 1.8 mm at the test, and 0.6 ± 1.6 mm and 1.2 ± 0.7 mm at the control sites apically to the implant shoulder. Bone-to-implant contact at the buccal aspect was 34.9 ± 25.9% and 36.4 ± 17.3% at the test and control sites, respectively. No statistically significant differences were found between test and control sites for any of the variables analyzed at the buccal aspects. CONCLUSIONS: The use of a mixture of synthetic HA 60% and beta-TCP 40% to fill residual buccal defects 1-1.4 mm wide at IPIES did not improve significantly the results of healing.

αTCP ceramic doped with dicalcium silicate for bone regeneration applications prepared by powder metallurgy method: in vitro and in vivo studies.

This study reports on the in vitro and in vivo behavior of α-tricalcium phosphate (αTCP) and also αTCP doped with either 1.5 or 3.0 wt % of dicalcium silicate (C2 S). The ceramics were successfully prepared by powder metallurgy method combined with homogenization and heat treatment procedures. All materials were composed of a single-phase, αTCP in the case of a pure material, or solid solution of C2 S in αTCP for the doped αTCP, which were stable at room temperature. The ceramics were tested for bioactivity in simulated body fluid, cell culture medium containing adult mesenchymal stem cells of human origin, and in animals. Analytical scanning electron microscopy combined with chemical elemental analysis was used and Fourier transform infrared and conventional histology methods. The in vivo behavior of the ceramics matched the in vitro results, independently of the C2 S content in αTCP. Carbonated hydroxyapatite (CHA) layer was formed on the surface and within the inner parts of the specimens in all cases. A fully mineralized new bone growing in direct contact with the implants was found under the in vivo conditions. The bioactivity and biocompatibility of the implants increased with the C2 S content in αTCP. The C2 S doped ceramics also favoured a phase transformation of αTCP into CHA, important for full implant integration during the natural bone healing processes. αTCP ceramic doped with 3.0 wt % C2 S showed the best bioactive in vitro and in vivo properties of all the compositions and hence could be of interest in specific applications for bone restorative purposes.

Physical properties, mechanical behavior, and electron microscopy study of a new α-TCP block graft with silicon in an animal model.

This study reports the characterization process and in vivo application of a new block bone graft of α-TCP with silicate in three different percentages in the aim of determining the influence of the silicate. Three groups of cylindrical implants (6 ± 0.01 mm diameter, 8 ± 0.01 mm length) with varying Si composition were studied: A: 3 wt % C(2) S; B: 1.5 wt % C(2) S; C: 100 wt % TCP-0 wt % C(2) S. These were implanted randomly in critical size defects in New Zealand rabbits. X-ray diffraction analysis was performed to determine the crystalline phases of the different compositions. Histomorphometric analysis produced one measurement of bone-to-implant contact. Comparing the α-TCPss ceramics, the trial found improved mechanical properties due to the silicon content in solid solution as well as densification. Previous studies have shown that the mechanical strengths of sintered ceramics correlate to densification as well as grain size and mechanical properties. Because of its mechanical and biological behavior, the study has shown α-TCP with C(2) S to be an alternative to other bone graft substitutes for use in bone reconstructive surgery in the fields of veterinary, medicine, and oral and maxillofacial surgery.