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

Mineralization and morphology of peri-implant bone around loaded and unloaded dental implants retrieved from the human mandible

PURPOSE

Limited data is reported regarding the bone mineralization around dental implants in the first months from insertion. The study analyzed the peri-implant bone around loaded and unloaded implants retrieved from human mandible after 4 months from placement.

METHOD

The composition and mineralization of human bone were analyzed through an innovative protocol technique using Environmental-Scanning-Electron-Microscopy connected with Energy-Dispersive-X-Ray-Spectroscopy (ESEM/EDX). Two regions of interest (ROIs, approximately 750×500 μm) for each bone implant sample were analyzed at the cortical (Cortical ROI) and apical (Apical ROI) implant threads. Calcium, phosphorus, and nitrogen (atomic%) were determined using EDX, and the specific ratios (Ca/N, P/N, and Ca/P) were calculated as mineralization indices.

RESULTS

Eighteen implant biopsies from ten patients were analyzed (unloaded implants, n=10; loaded implants, n=8). For each ROI, four bone areas (defined bones 1-4) were detected. These areas were characterized by different mineralization degree, varied Ca, P and N content, and different ratios, and by specific grayscale intensity detectable by ESEM images. Bony tissue in contact with loaded implants at the cortical ROI showed a higher percentage of low mineralized bone (bone 1) and a lower percentage of remodeling bone (bone 2) when compared to unloaded implants. The percentage of highly mineralized bone (bone 3) was similar in all groups.

CONCLUSION

Cortical and apical ROIs resulted in a puzzle of different bone "islands" characterized by various rates of mineralization. Only the loaded implants showed a high rate of mineralization in the cortical ROI.

ESEM-EDX Mineralization and Morphological Analysis of Human Retrieved Maxillary Sinus Bone Graft Biopsies before Loading

This study aimed to analyze the morphology of bone graft granules, the presence of granule demineralization, and bone morphology in retrieved human maxillary sinus bone graft biopsies. Healthy patients underwent sinus bone augmentation using lateral access. Two different dimensions of the antrostomy were performed, a 4 mm or 8 mm height. After 6 months, all sites received one implant using a flap technique, crestal positioning, and submerged healing. Implant biopsies were retrieved after 3 months and were histologically processed. The ESEM analysis was performed on the entire portion of the peri-implant bone (up to 750 µm from the implant thread). Three different regions of interest (ROIs) were selected: the coronal, middle, and apical portions of the implant. In these areas, EDX was performed, and calcium (Ca), phosphate (P), nitrogen (N), and their atomic ratios (Ca/P, Ca/N, and P/N) were calculated. Different bone tissue electron-dense areas were detected through grayscale intensity quantification of ESEM images with different organic (N) or inorganic (Ca,P) compositions. A total of 16 biopsies from 16 healthy patients were analyzed. Bone graft granules were mostly detected in the apical ROI. New bone tissue bridges were detected in the apical and middle ROI. These structures, with lower Ca/N and P/N ratios, were connected and enveloped the bone graft granules. Cortical ROI revealed the most mineralized bone tissue. Conclusions: After 9 months, bone graft resorption was only partially completed and new bone tissue appeared less mineralized in the middle and apical ROI than in the coronal ROI.

Human Histological Analysis of Early Bone Response to Immediately Loaded Narrow Dental Implants with Biphasic Calcium Phosphate® Grid-Blasted Surface Treatment: A Case Report

Implant surface topography using bioactive material provides faster bone-to-implant healing. This histological report described the analysis of human bone tissue around an immediately loaded implant, with BPC^® (Biphasic Calcium Phosphate) grit-blasted surface treatment, after two months of healing. Two temporary mini-implants (2.8 × 10 mm) with BPC^® grit-blasting surfaces were placed and immediately loaded to retain a complete interim denture. After a 60-day healing period, one mini-implant was removed for histologic analysis. The ground section showed the whole implant surrounded by healthy peri-implant tissues. Implant surface presented a close contact with newly formed bone, showing some areas of osteoblasts secreting mineral matrix. The ground section depicted a bone contact of 60.3 + 8.5%. The BPC^® grit-blasted surface was biocompatible and enabled the osseointegration process after a short-term period.

Nanostructured Calcium-Incorporated Surface Compared to Machined and SLA Dental Implants-A Split-Mouth Randomized Case/Double-Control Histological Human Study

Background: Implant surface topography is a key element in achieving osseointegration. Nanostructured surfaces have shown promising results in accelerating and improving bone healing around dental implants. The main objective of the present clinical and histological study is to compare, at 4 and 6 weeks, (w) bone-to-implant contact in implants having either machined surface (MAC), sandblasted, large grit, acid-etched implant surface (SLA) medium roughness surface or a nanostructured calcium-incorporated surface (XPEED®). Methods: 35 mini-implants of 3.5 × 8.5 mm with three different surface treatments (XPEED® (n = 16)—SLA (n = 13)—MAC (n = 6), were placed in the posterior maxilla of 11 patients (6 females and 5 males) then, retrieved at either 4 or 6w in a randomized split-mouth study design. Results: The BIC rates measured at 4w and 6w respectively, were: 16.8% (±5.0) and 29.0% (±3.1) for MAC surface; 18.5% (±2.3) and 33.7% (±3.3) for SLA surface; 22.4% (±1.3) and 38.6% (±3.2) for XPEED® surface. In all types of investigated surfaces, the time factor appeared to significantly increase the bone to implant contact (BIC) rate (p < 0.05). XPEED® surface showed significantly higher BIC values when compared to both SLA and MAC values at 4w (p < 0.05). Also, at 6w, both roughened surfaces (SLA and XPEED®) showed significantly higher values (p < 0.05) than turned surface (MAC). Conclusions: Nanostructured Calcium titanate coating is able to enhance bone deposition around implants at early healing stages.

Management and sequelae of dental implant removal

Inappropriate and unnecessary implant therapy driven by an erroneous belief that dental implants provide enhanced function and esthetics over diseased or failing teeth has led to a growing burden of implant complications across the globe. Specifically, esthetic and biological complications frequently lead to the unfavorable prognosis of dental implants. Often, these cannot be managed predictably to improve the condition or satisfy patients' demands. In such circumstances, implant removal needs to be considered. Currently, minimally invasive methods based on reverse torque engineering are key to preserve peri-implant soft and hard tissues. Implant replacement is now feasible, as evidenced by the high survival rates of implants placed at previously failed sites. Notwithstanding these data, clinicians should still consider carefully the expendability of an implant and whether its replacement will satisfy the prosthetic, biomechanical, and esthetic demands of the patient. In the scenario where future implant placement is desired, protocols undertaken for soft/hard tissue grafting and implant placement should be based upon defect morphology and soft and hard-tissue characteristics. Currently, however, a lack of knowledge of the biological events and dimensional changes that arise following implant removal renders decision-making complex and challenging, and recommendations remain largely based upon empirical speculation. This chapter will review the indications for implant replacement for prosthetic, biomechanical, and esthetic complications, alongside considerations in decision-making, planning, implementation, and outcomes of implant replacement.

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.

Influence of mini-screw diameter and loading conditions on static and dynamic assessments of bone-implant contact: An animal study

OBJECTIVES

The goal was to compare static versus dynamic bone-implant interface histology of mini-screws and to evaluate its relation to diameter and load.

SETTING AND SAMPLE POPULATION

Canine animal model.

MATERIAL AND METHODS

Custom-machined, titanium alloy (Ti6AI4V) mini-screws (n = 70) of 1.60, 2.00, 3.00 and 3.75 mm diameter were placed into edentulous sites in five skeletally mature beagle dogs. Using a split-mouth design, no load (NL) was applied to one side while a 2N load (L) was applied by calibrated coil springs on the other side. Intravenous bone labels were administered 21 and 7 days prior to sacrifice. Dogs were euthanized 90 days after screw placement. Bone sections were analysed under bright-field and epifluorescent light. The region of interest was defined as the bone within the threads of the screws. The following parameters were quantified: (a) Static-bone volume/tissue volume (BV/TV %) and bone-implant contact (BIC, %); (b) Dynamic-labelled bone/bone volume (LB/BV, %), and dynamic BIC (DBIC, %).

RESULTS

BV/TV ranged from 71.2% to 85.0% of the screw surface. BIC ranged from 45.7% to 55.4% of the screw surface and was not affected by diameter (P = 0.66). In contrast, the percentage of DBIC did not vary with the applied load (P = 0.41); however, it correlated significantly with the diameter of the screw (P = 0.001).

CONCLUSION

The percentage of DBIC that is actively remodelling increases with increasing diameter of the screw. Dynamic histomorphometry is more sensitive to detecting changes in bone-implant contact when compared to static measurements.

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.

Formation of hydroxyapatite on titanium implants in vivo precedes bone-formation during healing

The bone material interface has been an area of intense study over many decades, where studies of the healing process ranging from simple mineral deposition in vitro to actual healing in vivo have given important clues to the importance of calcium minerals in the bone/implant interface. Here, the authors use a combination of in vitro cell culture methods and in vivo implantation to study how the role of the spontaneously formed hydroxyapatite layer on Ti-implants for the in vivo-healing into the bone tissue of rat tibia. Initial experiments were made in reduced systems by incubation of TiO₂ in cell culture medium and analysis by time of flight secondary ion mass spectrometry (ToF-SIMS) and energy-dispersive x-ray spectroscopy followed by subsequent exposure of human embryological stem cells analyzed by von Kossa staining and environmental scanning electron microsopy. In vivo studies of the bone-material interface was analyzed by ToF-SIMS depth profiling using both C₆₀⁺ ions as well as a gas cluster ion source beam, Ar₁₅₀₀⁺ as sputter source. The low ion yield of the Ar₁₅₀₀⁺ for inorganics allowed the inorganic/organic interface of the implant to be studied avoiding the erosion of the inorganic materials caused by the conventional C₆₀⁺ beam.

Histological Evidence of the Osseointegration of Fractured Direct Metal Laser Sintering Implants Retrieved after 5 Years of Function

Background

Direct metal laser sintering (DMLS) is an additive manufacturing technique that allows the fabrication of dental implants layer by layer through the laser fusion of titanium microparticles. The surface of DMLS implants is characterized by a high open porosity with interconnected pores of different sizes; therefore, it has the potential to enhance and accelerate bone healing. To date, however, there are no histologic/histomorphometric studies in the literature evaluating the interface between bone and DMLS implants in the long-term.

Purpose

To evaluate the interface between bone and DMLS implants retrieved after 5 years of functional loading.

Methods

Two fractured DMLS implants were retrieved from the human jaws, using a 5 mm trephine bur. Both the implants were clinically stable and functioned regularly before fracture. The specimens were processed for histologic/histomorphometric evaluation; the bone-to-implant contact (BIC%) was calculated.

Results

Compact, mature lamellar bone was found over most of the DMLS implants in close contact with the implant surface; the histomorphometric evaluation showed a mean BIC% of 66.1% (±4.5%).

Conclusions

The present histologic/histomorphometric study showed that DMLS implants were well integrated in bone, after 5 years of loading, with the peri-implant bone undergoing continuous remodeling at the interface.

Histological and Histomorphometrical Analysis on a Loaded Implant With Platform-Switching and Conical Connection: A Case Report

The association of Morse taper implant-abutment design with the use of a smaller abutment diameter (platform switching) may improve dental implant success rate and prevent peri-implant bone loss. The aim of the present study was to histologically and histomorphometrically evaluate the behavior of peri-implant tissues around an implant with a conical connection associated with platform switching. A platform-switched Morse-cone connection implant was inserted in the left posterior mandible of a 61-year-old patient. The implant was inserted at the level of the alveolar crest. After 11 months from placement and 6 months of loading, the implant was retrieved for psychological reasons and processed for histological evaluation. The retrieved implant was wholly surrounded by bone tissue, except for a small area in the apical portion. At higher magnification, in the coronal portion of the implant, it was possible to observe bone directly at the implant platform level. No resorption of the coronal bone was present, except for 0.2 mm on the vestibular aspect. Crestally, bone remodeling with areas of newly formed bone was detected; the bone-implant contact was 73.9%. Apposition of bone was detected even upon the platform. Peri-implant crestal bone preservation can be achieved with the combination of Morse taper conical internal implant-abutment connection with the use of a smaller abutment diameter (platform-switching).

Early Bone Formation around Immediately Loaded Transitional Implants Inserted in the Human Posterior Maxilla: The Effects of Fixture Design and Surface

Aim. To evaluate the effects of fixture design and surface on the early bone formation around immediately loaded implants inserted in the human posterior maxilla. Materials and Methods. Ten totally edentulous subjects received two transitional implants: one tapered implant with knife-edge threads/nanostructured calcium-incorporated surface (test: Anyridge®, Megagen, Gyeongbuk, South Korea) and one cylindrical implant with self-tapping threads/sandblasted surface (control: EZPlus®, Megagen). The implants were placed according to a split-mouth design and immediately loaded to support an interim complete denture; after 8 weeks, they were removed for histologic/histomorphometric analysis. The bone-to-implant contact (BIC%) and the bone density (BD%) were calculated. The Wilcoxon test was used to evaluate the differences. Results. With test implants, a mean BIC% and BD% of 35.9 (±9.1) and 31.8 (±7.5) were found. With control implants, a mean BIC% and BD% of 29.9 (±7.6) and 32.5 (±3.9) were found. The mean BIC% was higher with test implants, but this difference was not significant (p = 0.16). Similar BD% were found in the two groups (p = 0.9). Conclusions. In the posterior maxilla, under immediate loading conditions, implants with a knife-edge thread design/nanostructured calcium-incorporated surface seem to increase the peri-implant endosseous healing properties, when compared to implants with self-tapping thread design/sandblasted surface.