Peri-implant bone tissues around retrieved human implants after time periods longer than 5 years: a retrospective histologic and histomorphometric evaluation of 8 cases

Identifying an optimal approach for the placement of pterygoid implants: A 3D finite element analysis

STATEMENT OF PROBLEM

A consensus on the optimal approach to the placement of pterygoid implants is lacking.

PURPOSE

The purpose of this finite element analysis study was to determine the optimal approach to the placement of pterygoid implants by comparing biomechanical behavior.

MATERIAL AND METHODS

An edentulous and moderately atrophic maxilla with the anatomic structure of the pterygomaxillary region was constructed. Complete arch restorations with 4 standard anterior implants and pterygoid implants in 3 approaches were simulated: L70, long pterygoid implants (4.1×18 mm) inclined at 70 degrees relative to the Frankfort horizontal plane with anchorage in the pterygoid process; L45, long pterygoid implants (4.1×20 mm) inclined at 45 degrees with anchorage in the pterygoid process; and S45, shorter pterygoid implants (4.1×13 mm) inclined 45 degrees without apical anchorage. The L70, L45, and S45 groups were classified as D or S depending on the bone quality: D3 (dense trabecular bone) or D4 (sparse trabecular bone). A total of 6 finite element models were built. The bone failure theory, based on the von Mises theory, was used to judge yielding of the trabecular bone. The von Mises stress (σVM) distribution was measured in the cortical bone, the trabecular bone, and on the implant surface. Deformation (DF) distribution was obtained for the entire bone (DFB) and bone surrounding the pterygoid implant (DFP).

RESULTS

L70 showed a lower maximum σVM value (maxσVM), more uniform σVM distribution in the cortical bone, trabecular bone, and on the implant surface and a lower maximum DFp value (maxDFp), especially in the D4 bone. The biomechanical behaviors were similar in L45 and S45 with no stress distribution in the pterygoid process. In the D4 bone, L70, L45, and S45 exceeded the limited stress of the bone failure theory by 50%, 130%, and 130%, while all values were under the limit in D3 bone.

CONCLUSIONS

The approach of pterygoid implants inclined at 70 degrees relative to the Frankfort plane with anchorage in the pterygoid process was optimal, providing improved biomechanical behavior. Clinically, in the case of D4 bone, the inclined angulation of pterygoid implants should be 70 degrees to minimize the risk of failure.

Exploring the Importance of Corticalization Occurring in Alveolar Bone Surrounding a Dental Implant

Several measures describing the transformation of trabecular bone to cortical bone on the basis of analysis of intraoral radiographs are known (including bone index or corticalization index, CI). At the same time, it has been noted that after functional loading of dental implants such transformations occur in the bone directly adjacent to the fixture. Intuitively, it seems that this is a process conducive to the long-term maintenance of dental implants and certainly necessary when immediate loading is applied. The authors examined the relationship of implant design features to marginal bone loss (MBL) and the intensity of corticalization over a 10-year period of functional loading. This study is a general description of the phenomenon of peri-implant bone corticalization and an attempt to interpret this phenomenon to achieve success of implant treatment in the long term. Corticalization significantly increased over the first 5-year functional loading (CI from 200 ± 146 initially to 282 ± 182, p < 0.001) and maintained a high level (CI = 261 ± 168) in the 10-year study relative to the reference bone (149 ± 178). MBL significantly increased throughout the follow-up period—5 years: 0.83 ± 1.26 mm (p < 0.001), 10 years: 1.48 ± 2.01 mm (p < 0.001). MBL and radiographic bone structure (CI) were evaluated in relation to intraosseous implant design features and prosthetic work performed. In the scope of the study, it can be concluded that the phenomenon of peri-implant jawbone corticalization seems an unfavorable condition for the future fate of bone-anchored implants, but it requires further research to fully explain the significance of this phenomenon.

Hybrid Funnel Technique: A Novel Approach for Implant Site Preparation: A Pilot Study

(1) Background: Different techniques and tools have been developed for implant site preparation. In this clinical scenario, Hybrid Funnel Technique (HFT), a novel osteotomy procedure, has been proposed. (2) Aim: The aim of this retrospective observational study was to consider the different responses to compression of the histological bony compartments (cancellus and cortical). HFT involves the use of multiple drills for the cortical layer preparation and of an osteotome for the osteocompaction of the cancellous bone. (3) Materials and Methods: Following computer-supported implant planning and guided surgery, 10 osteotomies with HFT were performed and 10 implants with the same length and diameter were placed in seven healthy and no daily smoking patients. Periapical X-ray and intraoral photographs were performed at baseline and after 12 months of follow-up to evaluate marginal bone level (MBL) changes and aesthetic results obtained from implant prosthetic rehabilitation. (4) Results: At 1 year of follow-up, 100% of the implants were successfully integrated, MBL change mean value was 0.17 mm ± 0.21. No differences in terms of MBL were noted between thin and thick biotypes. Pink esthetic score (PES) and white esthetic score (WES), assessed one year after definitive restoration placement, were 7.5 ± 2.3 and 8.5 ± 1.1, respectively. (5) Conclusions: Based on the findings of this preliminary clinical study, HFT has led to stability of peri-implant tissues and could represent a reliable technique for surgical preparation of the implant site.

Micro/nanostructural properties of peri-implant jaw bones: a human cadaver study

PURPOSE

Many points concerning the structure of osseointegration and the surrounding jaw bone remain unclear, and its optimal histological form has yet to be identified. The aim of this study was to clarify the structural characteristics of peri-implant jaw bone on the micro- and nano-scales by quantitatively evaluating bone quality.

METHODS

Five samples of human mandibular bone containing dental implants and one dentate sample that had been in place for some years while the donors were still alive were collected. Bulk staining was performed, and 100-μm-thick polished specimens were prepared. The osteon distributions in peri-implant bone and mandibular cortical bone were measured, after which alignment analysis of biological apatite (BAp) crystallites and anisotropy analysis of collagen fiber orientation using second-harmonic generation imaging were carried out.

RESULTS

Osteons in the vicinity of the implant body ran parallel to it. In the cortical bone at the base of the mandible, however, most osteons were oriented mesiodistally. The preferential alignment of BAp crystallites was generally consistent with osteon orientation. The orientation of collagen fibers in peri-implant jaw bone resembled the concentric rings seen in normal cortical bone, but there were also fibers that ran orthogonally across these concentric fibers.

CONCLUSIONS

These results suggest that the mechanical strain imposed by implants causes the growth of cortical bone-like bone in areas that would normally consist of cancellous bone around the implants, and that its structural characteristics are optimized for the load environment of the peri-implant jaw bone.

Biomechanics of Implant Fixation in Osteoporotic Bone

PURPOSE OF REVIEW

The purpose of this review is to critically evaluate the current literature regarding implant fixation in osteoporotic bone.

RECENT FINDINGS

Clinical studies have not only demonstrated the growing prevalence of osteoporosis in patients undergoing total joint replacement (TJR) but may also indicate a significant gap in screening and treatment of this comorbidity. Osteoporosis negatively impacts bone in multiple ways beyond the mere loss of bone mass, including compromising skeletal regenerative capacity, architectural deterioration, and bone matrix quality, all of which could diminish implant fixation. Recent findings both in preclinical animal models and in clinical studies indicate encouraging results for the use of osteoporosis drugs to promote implant fixation. Implant fixation in osteoporotic bone presents an increasing clinical challenge that may be benefitted by increased screening and usage of osteoporosis drugs.

A Narrative Review of the Histological and Histomorphometrical Evaluation of the Peri-Implant Bone in Loaded and Unloaded Dental Implants. A 30-Year Experience (1988-2018)

Background: The aim of the present review was to assess the histological and histomorphometrical data from the paper published by our Laboratory on peri-implant bone in dental implants in different loading conditions. Methods: The papers published in different implant loading conditions, in dental implants retrieved from humans, and in the Hard Tissues Research Center of the University of Chieti-Pescara, Italy, were screened on MEDLINE/PubMed, Embase, Scopus, and other electronic databases until 31 December 2018. Only articles that reported the histological and histomorphometrical values of the Bone-Implant Contact (BIC) were selected. Results: The system selection provided a total of 155 papers. The manuscripts included for the narrative review were 57. These papers provided histological and histomorphometrical data. Conclusions: The bone remodeling around dental implants was found to be a dynamic process; loading changed the microstructure of the peri-implant bone; and implants were found to provide a successful function, over several decades, with different range of degrees of BIC in vivo (varying from a little more than 30% to a little more than 90%). Loaded implants presented a 10%-12% higher BIC values when compared to submerged, unloaded implants, and rougher surfaces had, on average, about a 10% higher BIC than machined surfaces.

Mechanical aspects of dental implants and osseointegration: A narrative review

With the need of rapid healing and long-term stability of dental implants, the existing Ti-based implant materials do not meet completely the current expectation of patients. Low elastic modulus Ti-alloys have shown superior biocompatibility and can achieve comparable or even faster bone formation in vivo at the interface of bone and the implant. Porous structured Ti alloys have shown to allow rapid bone ingrowth through their open structure and to achieve anchorage with bone tissue by increasing the bone-implant interface area. In addition to the mechanical properties of implant materials, the design of the implant body can be used to optimize load transfer and affect the ultimate results of osseointegration. The aim of this narrative review is to define the mechanical properties of dental implants, summarize the relationship between implant stability and osseointegration, discuss the effect of metallic implant mechanical properties (e.g. stiffness and porosity) on the bone response based on existing in vitro and in vivo information, and analyze load transfer through mechanical properties of the implant body. This narrative review concluded that although several studies have presented the advantages of low elastic modulus or high porosity alloys and their effect on osseointegration, further in vivo studies, especially long-term observational studies are needed to justify these novel materials as a replacement for current Ti-based implant materials.

Immediate and delayed loading of fixed dental prostheses supported by single or two splinted implants: A histomorphometric study in dogs

To evaluate presumptive differences in osseointegration at implants supporting crowns that are physiologically loaded either immediately or 3 months after installation. All premolars and first molars were extracted bilaterally in six dogs. After 3 months of healing, three implants were installed on the premolar region and two in the molar region in one side of the mandible. Likewise, after another 3 months, five implants were installed in the contralateral side, and impressions were taken bilaterally. Within 48 hours, two single crowns were screwed bilaterally onto two implants in the premolar region, and two splinted crowns reproducing the shape of the first molar were screwed bilaterally onto the implants in the molar region. The mesial implants were used as no-loaded controls. Sacrifices were performed after 3 months, and histological analyses were performed. At the premolar sites, mineralised bone-to-implant contact (MBIC%) was 78.0 ± 4.0% and 70.9 ± 7.9% at the delayed and immediately loaded sites, respectively. This difference was statistically significant. At the control implants, MBIC% was 61.4 ± 14.7% and 63.1 ± 13.1% at the delayed and the immediately loaded sites, respectively. At the molar sites, MBIC% was 79.2 ± 10.9% and 61.1 ± 10.3% at the delayed and immediately loaded sites, respectively. Applying a delayed loading to fixed dental prostheses supported by single or two splinted implants yielded higher proportions of bone-to-implant contact (osseointegration) compared to immediately loaded implants. Moreover, both types of loading protocols yielded a higher rate of osseointegration compared to unloaded implant sites after 3 months following implant installation.

Periimplant Bone Response in Human-Retrieved, Clinically Stable, Successful, and Functioning Dental Implants After a Long-Term Loading Period: A Report of 17 Cases From 4 to 20 Years

OBJECTIVE

This study aimed at a histologic and histomorphometric analysis of the periimplant tissues and bone-titanium interface reactions in successfully osseointegrated, clinically stable, and immobile human titanium dental implants retrieved after a long loading period.

MATERIALS AND METHODS

In the last 30 months (2013-2015), 21 implants, retrieved from individuals for different causes after a loading period ranging from 4 to 20 years, were sent to the Implant Retrieval Center, University of Chieti-Pescara, Italy. In 4 cases, almost all the bone had been lost during the retrieval, whereas in the remaining 17 cases, mineralized bone was still present.

RESULTS

Around the majority of the implants, mature compact bone with few marrow spaces was found. The trabecular bone, constituted by a few thin bone trabeculae, was in a periimplant location around only a few implants. A high percentage of bone-implant contact (BIC) (comprised between 32 ± 4.1% and 83 ± 2.9%) was present. In almost all implants, the space within the threads was almost completely filled by compact lamellar bone or by a thin layer of bone. Close and tight contact between bone and implant surface was observed in all specimens with no gaps or connective tissue at the interface.

CONCLUSIONS

All implants appeared to be well integrated in the surrounding mineralized bone, and all of them showed adequate bone-to-implant contact percentages.

Osseointegration of Plateau Root Form Implants: Unique Healing Pathway Leading to Haversian-Like Long-Term Morphology

Endosteal dental implants have been utilized as anchors for dental and orthopedic rehabilitations for decades with one of the highest treatment success rates in medicine. Such success is due to the phenomenon of osseointegration where after the implant surgical placement, bone healing results into an intimate contact between bone and implant surface. While osseointegration is an established phenomenon, the route which osseointegration occurs around endosteal implants is related to various implant design factors including surgical instrumentation and implant macro, micro, and nanometer scale geometry. In an implant system where void spaces (healing chambers) are present between the implant and bone immediately after placement, its inherent bone healing pathway results in unique opportunities to accelerate the osseointegration phenomenon at the short-term and its maintenance on the long-term through a haversian-like bone morphology and mechanical properties.

Osseointegration: hierarchical designing encompassing the macrometer, micrometer, and nanometer length scales

OBJECTIVE

Osseointegration has been a proven concept in implant dentistry and orthopedics for decades. Substantial efforts for engineering implants for reduced treatment time frames have focused on micrometer and most recently on nanometer length scale alterations with negligible attention devoted to the effect of both macrometer design alterations and surgical instrumentation on osseointegration. This manuscript revisits osseointegration addressing the individual and combined role of alterations on the macrometer, micrometer, and nanometer length scales on the basis of cell culture, preclinical in vivo studies, and clinical evidence.

METHODS

A critical appraisal of the literature was performed regarding the impact of dental implant designing on osseointegration. Results from studies with different methodological approaches and the commonly observed inconsistencies are discussed.

RESULTS

It is a consensus that implant surface topographical and chemical alterations can hasten osseointegration. However, the tailored combination between multiple length scale design parameters that provides maximal host response is yet to be determined.

SIGNIFICANCE

In spite of the overabundant literature on osseointegration, a proportional inconsistency in findings hitherto encountered warrants a call for appropriate multivariable study designing to ensure that adequate data collection will enable osseointegration maximization and/or optimization, which will possibly lead to the engineering of endosteal implant designs that can be immediately placed/loaded regardless of patient dependent conditions.

Progressive plateau root form dental implant osseointegration: A human retrieval study

Although preclinical and sparse human histology retrieval studies have shown that the interface between implant and bone is constantly remodeling, no human retrieval database has been developed to determine the effect of functional loading time and other clinical/implant design variables on osseointegration. The present study tested the hypothesis that bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) increase over functional loading time around dental implants. Due to prosthetic retreatment reasons, 93 human implant retrievals from the same manufacturer (Bicon LLC, Boston, MA, USA) were obtained over a period of approximately 15 years. The retrieved implants were under functional loading from 120 days to ∼18 years and were histomorphologic/metrically evaluated. BIC/BAFO were assessed as a function of multiple independent variables: implant surface type, diameter, length, jaw (maxilla/mandible), region (anterior/posterior), and time of functional loading. The results showed that both BIC and BAFO increased over time independently of implant design/clinical variables, supporting the postulated hypothesis.

Latham J, G. Dunlop D, Oreffo RO. Bone and metal: an orthopaedic perspective on osseointegration of metals

The area of implant osseointegration is of major importance, given the predicted significant rise in the number of orthopaedic procedures and an increasingly ageing population. Osseointegration is a complex process involving a number of distinct mechanisms affected by the implant bulk properties and surface characteristics. Our understanding and ability to modify these mechanisms through alterations in implant design is continuously expanding. The following review considers the main aspects of material and surface alterations in metal implants, and the extent of their subsequent influence on osseointegration. Clinically, osseointegration results in asymptomatic stable durable fixation of orthopaedic implants. The complexity of achieving this outcome through incorporation and balance of contributory factors is highlighted through a clinical case report.