Hard and soft tissue healing around implants with Ag coating: An experimental study in dogs.

Introduction The purpose of this randomized controlled canine experimental study was to evaluate peri­implant hard and soft tissue healing around implants with silver coating. Methods All mandibular premolars and molars of five male beagle dogs were extracted. 25 test and 25 control implants were randomly installed and connected with the healing abutments. After 2 and 4 month healing period, implants with soft and hard tissues were obtained for histologic and histomorphometric analysis. Results In mesio-distal sections, supracrestal tissue attachment dimensions were 4.03±0.48 mm and 4.25±0.66 mm for test and 4.34±0.6 mm and 5.21±0.72 mm for control implants at 2 and 4 month healing time. The respective crestal bone loss values were 1.10±0.69 mm and 0.74±0.67 mm for test and 1.13±0.48 mm and 1.49±0.65 mm for control implants. The differences were statistically significant only in the 4-month healing period. In buccolingual sections, supracrestal tissue attachment height at 2 and 4 month healing periods were 4.09±0.64 mm and 4.5±0.8 mm for test implants and 4.17±0.76 mm and 4.48±0.76 mm for control implants. The respective mean values for crestal bone loss were 1.31±0.6 mm and 1.02±0.58 mm for test implants, and 1.28±0.61 mm and 1.29±0.69 mm for control implants. No statistical significant differences were recorded, apart from the height of connective tissue at the 2 month healing group. No significant difference in terms of BIC between implants or healing periods was recorded. Conclusions The Ag implant coating resulted in smaller supracrestal tissue attachment dimensions and less bone loss. Within the limits of a canine study, prevention of crestal bone loss along with the effectiveness of Ag antimicrobial properties in dental implantology is demonstrated.

Comparison of histomorphometry and microradiography of different implant designs to assess primary implant stability.

OBJECTIVES: To contribute toward optimizing the long-term stability of dental implants. Our working hypothesis was that the degrees of immediate implant-bone contact, and hence of primary stability, would demonstrably differ between implant systems due to their different external geometries and thread designs (macro-design). This demonstration was provided in a bovine model (ex vivo) by employing and comparing histomorphometry and microradiography as evaluation methods. MATERIALS AND METHODS: A total of 120 implants, representing six different implant thread designs, were inserted following the recommended surgical protocol in ribs of freshly slaughtered cattle. Twenty specimens of implants with surrounding bone were prepared per system and were divided into two equally sized groups of 60 specimens for analysis by either histomorphometry or micro-computed tomography. Data were analyzed by Mann-Whitney U test (P ≤ .05). RESULTS: One of the implant systems, featuring a slight tapered external geometry and a progressive thread design, consistently revealed the most favorable bone-implant contacts in both histomorphometric and microradiographic evaluations. Overall, consistently higher values of bone-implant contact were obtained with the microradiographic than the histomorphometric approach, and this difference reached statistical significance in three of the six implant systems tested. CONCLUSIONS: Progressive threads offering a bone-condensing effect can significantly help to maximize implant-bone contact percentages. Compared to histomorphometry, microradiography is likewise a suitable method to evaluate bone-implant contact, offering the additional benefits of being noninvasive and less time consuming.

Effect of clopidogrel in bone healing-experimental study in rabbits.

BACKGROUND: Clopidogrel is a widely prescribed drug for prevention of myocardial infarction and stroke in patients at risk. It inhibits thrombus formation via inhibition of the P2Y12 purinergic receptor on platelets, which is important in their activation by ADP. However, the P2Y12 receptor has also been found to be expressed in both osteoblasts and osteoclasts. Accumulated evidence suggests that purinergic receptors regulate important functions of bone turnover. Previous studies on the effect of clopidogrel on bone metabolism indicated potential harmful effects, but their results remain conflicting. Thus, clopidogrel treatment may affect bone healing, but it has not yet been studied. AIM: To evaluate if continuous perioperative clopidogrel treatment has any negative effect on bone healing in the rabbit calvarial defect model. METHODS: Sixteen male white New Zealand rabbits were randomly assigned in two groups: One group received daily 3 mg/kg of clopidogrel per os and the other group received the vehicle alone for a week prior to the surgical procedures; the treatments were continued for another 6 wk postoperatively. The surgical procedures included generation of two circular calvarial defects 11 mm in diameter in every animal. After the 6-wk period of healing, postmortem radiographic and histomorphometric evaluation of the defects was performed. RESULTS: Both the surgical procedures and the postoperative period were uneventful and well tolerated by all the animals, without any surgical wound dehiscence, signs of infection or other complication. New bone was formed either inwards from the defect margins or in the central portion of the defect as separated bony islets. While defect healing was still incomplete in both groups, the clopidogrel group had significantly improved radiographic healing scores. Moreover, the histomorphometric analysis showed that bone regeneration (%) was 28.07 ± 7.7 for the clopidogrel group and 19.47 ± 4.9 for the control group, showing a statistically significant difference between them (P = 0.018). Statistically significant difference was also found in the defect bridging (%), i.e. 72.17 ± 21.2 for the clopidogrel group and 41.17 ± 8.5 for the control group, respectively (P = 0.004), whereas there was no statistical difference in bone tissue density between the groups. CONCLUSION: Our results indicate that maintenance of perioperative clopidogrel treatment does not negatively affect bone healing but rather promotes it. Further research is needed in order to find useful applications of this finding.

Top-Cited Articles in Implant Dentistry.

PURPOSE: Citation analysis is the field of bibliometrics that uses citation data to evaluate the scientific recognition and the influential performance of a research article in the scientific community. The aim of this study was to conduct a bibliometric analysis of the top-cited articles pertaining to implant dentistry, to analyze the main characteristics, and to display the most interesting topics and evolutionary trends. MATERIALS AND METHODS: The 100 top-cited articles published in "Dentistry, Oral Surgery, and Medicine" journals were identified using the Science Citation Index Database. The articles were further reviewed, and basic information was collected, including the number of citations, journals, authors, publication year, study design, level of evidence, and field of study. RESULTS: The highly cited articles in implant dentistry were cited between 199 and 2,229 times. The majority of them were published in four major journals: Clinical Oral Implants Research, International Journal of Oral & Maxillofacial Implants, Journal of Clinical Periodontology, and Journal of Periodontology. The publication year ranged from 1981 to 2009, with 45% published in a nine-year period (2001 to 2009). Publications from the United States (29%) were the most heavily cited, followed by those from Sweden (23%) and Switzerland (17%). The University of Göteborg from Sweden produced the highest number of publications (n = 19), followed by the University of Bern in Switzerland (n = 13). There was a predominance of clinical papers (n = 42), followed by reviews (n = 25), basic science research (n = 21), and proceedings papers (n = 12). Peri-implant tissue healing and health (24%), implant success/failures (19.2%), and biomechanical topics (16.8%) were the most common fields of study. CONCLUSION: Citation analysis in the field of implant dentistry reveals interesting information about the topics and trends negotiated by researchers and elucidates which characteristics are required for a paper to attain a "classic" status. Clinical science articles published in high-impact specialized journals are most likely to be cited in the field of implant dentistry.

Bone reactions around dental implants subjected to progressive static load: an experimental study in dogs.

OBJECTIVE: To evaluate histologically and histomorphometrically, the peri-implant bone reaction around implants subjected to controlled progressive orthodontic loading. MATERIALS AND METHODS: In three beagle dogs, bilateral edentulous flat alveolar ridges were created in the maxillary area posterior to the canines. After 8 weeks of healing, 24 implants (Biomet 3i) were inserted in the edentulous sites. Two experimental groups were created. Progressive loading group: Twelve implants were left to heal for 8 weeks uncovered, and abutments were adapted and connected by pairs with Ni-Ti orthodontic springs. A gradual static force of 100, 200 and 300 g was applied for a 3-week period each. Thus, a total progressive loading period of 9 weeks was exercised. Unloaded control group: Twelve implants were left to heal undisturbed. At the end of the experimental period, all implants of both groups were removed with the surrounding bone. Histologic and histomorphometric analyses were performed, and the following parameters were measured: bone-to-implant contact, bone density 1 and 2 mm distant to the implant threads and crestal bone resorption. Median regression models are used for statistical analysis. RESULTS: Implants of the progressive loading group exhibited significantly higher percentage of bone-to-implant contact compared to the unloaded control implants (P = 0.018). Bone density 1 and 2 mm distant to the threads was found to be the same between the two groups (P = 0.734 and P = 0.961, respectively). Crestal bone resorption did not differ between loaded and unloaded implants (P = 0.813). CONCLUSION: The application of progressive loading by controlled orthodontic force on osseointegrated implants provoked significant increase in the percentage of bone-to-implant contact of the low-density bone of the dog maxilla.

Bone lesions in a Late Pleistocene assemblage of the insular deer Candiacervus sp.II from Liko cave (Crete, Greece).

Candiacervus sp.II is one of the deer species that inhabited the island of Crete during the Late Pleistocene. The species evolved on the island under a prolonged period of isolation and, as a consequence, developed a high degree of endemism. Fossils of this species have been discovered at many Cretan sites, including Liko cave (an attritional accumulation of several thousand fossils). In this paper, we present the results of a systematic analysis of the prevalence and anatomical distribution of bone lesions of Candiacervus sp.II, from that cave. We identified one metapodial with a healed fracture and nine (various) specimens with moderate to severe degenerative lesions of osteoarthritis. The lesions were evaluated macroscopically and radiographically, and they were classified as traumatic or degenerative. Degenerative lesions that affected adult individuals had prevalence rates below 5% and were attributed to environmental or nutritional causes. Representative bones were sampled for histological evaluation, to provide essential baseline data on possible underlying disorders. The aims of this study are to provide evidence for bone disease contributing to species morbidity, and to shed new light on causes and potential palaeoecological significance.

Evaluation of Vertical Bone Regeneration Using Block and Particulate Forms of Bio-Oss Bone Graft: A Histologic Study in the Rabbit Mandible.

The aim of the present study was to evaluate histologically vertical bone regeneration outcomes after using bovine bone graft material in block and granular forms. The buccal bony plates of the outer mandibles of 10 New Zealand rabbits received Bio-Oss blocks that were immobilized using orthopedic mini-plates, and another 10 received granular forms that were gently packed and stabilized into the custom-made perforated metallic cubes. The mean graft area (GA), new bone area (NBA), bone-to-graft contact (BGC), and maximum vertical height reached by the new bone development (MVH) were histometrically evaluated and showed no significant differences between 2 graft types. The new bone was observed mostly close to the basal bone and developed penetrating the trabecular scaffold in the form of seams that covered the intralumen surfaces of the block type graft, while in the granular graft type the new bone was observed to grow between the graft particles usually interconnecting them. Either form of Bio-Oss was capable of providing considerable vertical bone augmentation.

Evaluation of peri-implant marginal bone loss using modified abutment connections at various crestal level placements.

The purpose of this study was to evaluate crestal bone loss around 282 two-piece implants with straight (n = 193) and platform-switched (n = 89) abutment connections after placement at various crestal levels. Implants were assigned into two groups according to straight and platform-switched abutment connections. Each group was further subdivided into three groups depending on the location (supracrestal, crestal, or subcrestal) of the implant cervical platform. Linear measurements of bone resorption were made from the implant's platform to the first point of bone-to-implant contact at the time of implant placement and 2 years postrestoration. Data were statistically analyzed. Statistically significant differences were found between subgroups in both straight and platform-switched categories. The only nonstatistically significant difference (P = .341) arose when comparing the supra- and subcrestal locations in the straight abutment connection group. The platform-switched group exhibited significantly less bone loss (P = .046) only in subcrestal locations. The platform-switched concept was not beneficial during the overall comparison, but it was for the subcrestal location of the abutment connection. Crestal placement of the implant-abutment connection resulted in higher marginal bone resorption in both straight and platform-switched abutments.

Bone regeneration using beta-tricalcium phosphate in a calcium sulfate matrix.

The aim of the study was the histomorphometric comparison of the osteogenic potential of beta-tricalcium phosphate (beta-TCP) alone or in a calcium sulfate matrix. Three round defects, 10 mm (diameter) x 5 mm (depth), were created on each iliac crest of 4 dogs. The defects were divided into 3 groups. Ten defects were filled with beta-TCP in a calcium sulfate (CS) matrix (Fortoss Vital; group A), 10 defects were filled with beta-TCP alone (Fortoss Resorb; group B), and 4 defects were left ungrafted to heal spontaneously (group C). All defects were left to heal for 4 months without the use of a barrier membrane. Histologic evaluation and morphometric analysis of undecalcified slides was performed using the areas of regenerated bone and graft remnants. All sites exhibited uneventful healing. In group A sites (beta-TCP/CS), complete bone formation was observed in all specimens, graft granules dominated the area, and a thin bridge of cortical bone was covering the defect. Group B (beta-TCP) defects were partially filled with new bone, the graft particles still dominated the area, while the outer cortex was not restored. In the ungrafted sites (group C), incomplete new bone formation was observed. The outer dense cortical layer was restored in a lower level, near the base of the defect. The statistical analysis revealed that the mean percentage of new bone regeneration in group A was higher than in group B (49.38% and 40.31%, respectively). A statistically significant difference existed between the 2 groups. The beta-TCP/CS group exhibited significantly higher new bone regeneration according to a marginal probability value (P = .004 < .05). The use of beta-TCP in a CS matrix produced significantly more vital new bone fill and preserved bone dimensions compared with the use of beta-TCP alone.

Evaluation of the osteogenic potential in experimental defects, with and without bone marrow, in the rabbit tibia: a pilot study.

PURPOSE: The influence of bone marrow in the osteogenic potential of bone has not been evaluated in the rabbit tibia model. Previous studies employed this model extensively to test the osteogenic capabilities of bone grafts. The primary aim of the present study was to assess the role of bone marrow in the healing of experimental defects in the rabbit tibia model. MATERIALS AND METHODS: Ten New Zealand rabbits were divided into two groups of five each. In the first experimental test group (PoP), the marrow cavity was emptied completely under a 6-mm defect in the rabbit tibia metaphysis; the marrow was replaced by plaster of Paris, and a round piece of lyophilized collagen membrane was placed in contact with the endosteum and rested on the plaster. In the second experimental group (control), similar artificial defects were made, but the marrow was left intact. After 8 weeks, the animals were sacrificed and prepared for histologic and histomorphometric analysis. RESULTS: There was a statistically significant difference (P = .016) in newly formed bone area between the control group (mean, 68.08% +/- 12.09%) and the PoP group (mean, 54.02% +/- 13.93%). Similarly, there was a statistically significant difference in new bone density (P < .001) between the control group (mean, 95.99% +/- 1.74%) and the PoP group (mean, 75.37% +/- 13.27%). CONCLUSIONS: The current study confirms the significant effect that bone marrow has in bone regeneration and also the true regenerative capabilities of the osseous walls of the defects. The proposed experimental model may be a more reliable method of investigating and comparing the potential of different graft materials and methods.

Osseointegration of Osseotite and machined-surfaced titanium implants in membrane-covered critical-sized defects: a histologic and histometric study in dogs.

The texture of an implant's surface can influence the rate and extent of bone fixation as expressed by the amount of linear bone-to-implant contact (BIC). The purpose of this study was to compare the bone density and linear BIC between Osseotite and machined-surface implants placed in bony defects without graft material and covered by a membrane. Thirty 2 mm diameter, 10 mm length custom implants were prepared for this study having a 'split surface,' with one side having the acid-etched surface and the opposite side having a machined surface. Defects were created in the iliac wing of three adult mongrel dogs where a 6-mm-diameter drill was used to generate a 5-mm-deep defect. The implants were inserted into the center of the defect with 5 mm secured into the bone leaving 5 mm free in the defect with a 2 mm gap between the implant and surrounding bone. Expanded polytetrafluroethelyene membranes were placed over the defect sites stabilized with Biotack pins. The healing times were 2, 3, and 5 months. Histologic and histometric analysis showed significantly lower BIC in the defect region as compared with the portion of implant placed into native bone for both implant surfaces in all groups. There was no difference in BIC values at 2- and 5-month periods between the two surfaces in the regenerated area, while BIC values for Osseotite surfaces were significantly higher than the machined surfaces at 3 months' healing time. Changes in bone density, observed between the three groups, affected correspondingly the BIC values in both implant surfaces, the effect being more pronounced in the Osseotite surface.

Bone regeneration around implants using spherical and granular forms of bioactive glass particles.

PURPOSE: It has been reported that previous Biogran (3i Implant Innovations, Inc., Palm Beach Gardens, FL) can be converted in vitro into hydroxyapatite (Biogran II) to accelerate new bone formation. The purpose of this study was to evaluate the bone regeneration around implants placed in critical-sized defects in rabbit tibia using granular and spherical forms of Biogran II in regards to implant contact, bone-to-graft contact, bone graft area, and total bone volume. MATERIALS AND METHODS: Twelve adult New Zealand rabbits were used, offering 24 surgical sites (1 in each tibia), where 6-mm round defects were created allowing the homocentric insertion of a screw type experimental implant with Osseotite (3i Implant Innovations, Inc.) surface. Half of the defects (group A) were filled up with spherical and half (group B) with granular forms of Biogran II. Ossix (3i Implant Innovations, Inc.) membranes covered the surgical sites. RESULTS: The histological evaluation after 8 weeks showed new bone formation in both groups, without any statistically significant differences in regards to bone-to-implant contact, bone-to-graft contact, bone graft area, and bone volume. Both dissolution of the outer shell and inner silica gel of the particles were observed mostly in spherical particles. In addition, new bone formation within the protected pouch interconnected with the surrounding new bone was observed exclusively in spherical particles of Biogran II. CONCLUSION: Faster dissolution of both outer and inner portions of spherical particles of Biogran II led to better integration with the surrounding new bone during an 8-week period of healing.

Effect of autogenous harvest site location on the outcome of ridge augmentation for implant dehiscences.

Treatment planning for the placement of an implant in a site with a thin crestal ridge should address the probability that a buccal dehiscence will result. The aim of the present investigation was to perform guided bone regeneration (GBR) around implants with buccal dehiscences and evaluate the outcomes of using autogenous bone grafts harvested from three different intraoral sites. Forty-six Osseotite implants, 4 mm in diameter, were placed in thin crestal ridges, resulting in an uncovered implant surface from the buccal aspect. The lengths of the buccal dehiscences ranged from 3 to 7 mm as measured from the implant cervix to the most apical extent of the uncovered threads. A standard GBR technique was carried out to augment the bone defect around the buccal implant surface immediately after implant placement. The cases were divided into three groups according to receipt of an autogenous bone graft from the ramus, tuberosity, or mandibular symphysis. In all cases, e-PTFE membranes were used to cover the grafted areas. Grafted sites were exposed after 6 months, membranes were removed, and residual distance between the implant cervix and most uncovered thread was recorded. All grafting materials were able to produce a certain degree of bone regeneration. In terms of bone change level, the three groups were not equal. The mandibular symphysis group exhibited the highest mean bone growth level, followed by the ramus group. The tuberosity produced the poorest result. Mandibular and ramus autogenous bone grafts represent the best choice in materials for GBR procedures around implants, while tuberosity bone grafts can be used as an alternative.

Osseointegration of Osseotite and machined titanium implants in autogenous bone graft. A histologic and histomorphometric study in dogs.

It has been shown that a roughened implant surface results in a higher percentage of bone to implant contact (%BIC) than a machined one. A modified implant surface using a dual thermo-acid etching process (Osseotite) has been introduced and evaluated clinically, mechanically and histologically. The aim of the present study was the histological evaluation of the %BIC between the Osseotite or machined surfaces and the autogenous bone graft. Twenty-two custom-made split-type 10-mm-long implants having two opposing surfaces (Osseotite and machined) were placed between the cranial and caudal dorsal iliac spine at the iliac wing of two adult mongrel dogs. An artificial bone defect was created leaving a 2 mm empty space around the coronal 5 mm of the implants, while the apical 5 mm was stabilized in the existing basal bone. The defects around the implants were filled with particulate autogenous bone graft, covered by an Osseoquest membrane, and left to heal for 5 months. All inserted implants showed a complete integration in the bone tissue. It was found that the resulting %BIC at the Osseotite surface was significantly higher than at the machined one in both regenerated (46.44+/-15.81% vs. 28.59+/-12.04%) and basal bone areas (32.32+/-15.09% vs. 17.25+/-7.40%). The findings of this study imply that the use of autogenous bone graft resulted in significantly higher %BIC values in the regenerated area than in the basal bone area itself, for both implant surfaces.