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.

Measures of Corticalization

After the insertion of dental implants into living bone, the condition of the peri-implant bone changes with time. Implant-loading phenomena can induce bone remodeling in the form of the corticalization of the trabecular bone. The aim of this study was to see how bone index (BI) values behave in areas of bone loss (radiographically translucent non-trabecular areas) and to propose other indices specifically dedicated to detecting corticalization in living bone. Eight measures of corticalization in clinical standardized intraoral radiographs were studied: mean optical density, entropy, differential entropy, long-run emphasis moment, BI, corticalization index ver. 1 and ver. 2 (CI v.1, CI v.2) and corticalization factor (CF). The analysis was conducted on 40 cortical bone image samples, 40 cancellous bone samples and 40 soft tissue samples. It was found that each measure distinguishes corticalization significantly (p < 0.001), but only CI v.1 and CI v.2 do so selectively. CF or the inverse of BI can serve as a measure of peri-implant bone corticalization. However, better measures are CIs as they are dedicated to detecting this phenomenon and allowing clear clinical deduction.

Early Bone Healing on Hydroxyapatite-Coated and Chemically-Modified Hydrophilic Implant Surfaces in an Ovine Model

Implant topography affects early peri-implant bone healing by changing the osteoconduction rate in the surrounding biological environment. Implant surfaces have been designed to promote faster and stronger bone formation for rapid and stable prosthesis loading. Early peri-implant bone healing has been observed with a sandblasted, acid-etched implant that was chemically modified to be hydrophilic (cmSLA). The present study investigates whether early peri-implant bone healing extends to a rough surface implant with a high crystalline hydroxyapatite surface (TSV MP-1 HA). Three implants were randomly placed in porous trabecular bone within both medial femoral condyles of 10 sheep. Early peri-implant bone stability was measured at 3- and 6-weeks healing time following implant insertion. Results indicated a similar implant stability quotient between the implants at insertion and over time. The significant increase over time of reverse torque values with respect to insertion torque (p < 0.001) did not differ between the implants. However, the bone-to-implant contact of TSV MP-1 HA was significantly higher than that of cmSLA implants at 6 weeks (p < 0.01). These data validate previous findings of a hydrophilic implant surface and extend the observation of early osseointegration to a rough surface implant in porous trabecular bone.

Peri-implant bone alterations under the influence of abutment screw preload stress. A preclinical vivo study

OBJECTIVES

The study purpose was to examine peri-implant bone alternations around osseointegrated implants caused solely by abutment screw preload stress using different tightening torque values.

MATERIALS AND METHODS

Twenty 20- to 22-week-old Japanese white rabbits received two implants each in right and left femurs. Implants were randomly assigned to one of three tightening torque groups or the control (Cont) group. After 8 weeks, 35 Ncm torque was delivered to abutment screws in the recommended torque (RT) group (n = 16). Other screws received 70 Ncm torque as the high torque (HT) group (n = 16). Temporary tightening (TT) groups (n = 8) received only 70 Ncm torque without preload stress as screws were untightened immediately. Cont group (n = 40) remained in situ. Animals were euthanized at 4, 6, 8, and 10 weeks after torque application. Micro-CT images were then taken, and undecalcified ground sections were stained with toluidine blue.

RESULTS

Cross-sections of cortical bone showed remodeling activities adjacent to the implant in all groups. While bone marrow spaces appearance was relatively small in Cont and TT groups, RT and HT groups showed large bone marrow spaces and extensive remodeling activity. Bone-to-implant contact was significantly less in RT and HT groups compared with Cont and TT groups at different time points (p ˂ .05). Furthermore, RT and HT groups showed significantly less bone volume and area (p ˂ .05).

CONCLUSION

Results suggested that preload stress without any occlusal loading might negatively affect peri-implant bone stability and initiate bone remodeling. This could alter bone mechanical properties, subsequently influencing long-term implant success.

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.

Osseointegration of titanium dental implant under fluoride exposure in rabbits: Micro-CT and histomorphometry study

OBJECTIVE

This study aims to investigate the influence of fluoride exposure on implant osseointegration.

METHODS

A total of 24 male New Zealand white rabbits were randomly divided into the control group and the fluoride exposure group. Rabbits in the control group were fed with tap water, while those in the fluoride exposure group were given 200 mg/L sodium fluoride solution. After 2-month feeding, implants were inserted into the extraction socket immediately after extraction of rabbit mandibular anterior teeth. Four rabbits in each group were sacrificed to collect the implants samples at 1, 2, and 3 months post-implantation, respectively. Radiographic and histomorphometry examinations were performed to evaluate the condition of implant osseointegration.

RESULTS

Bone volume around the implants increased in a time-dependent manner in both groups. Micro-CT images illustrated that the bone mineral density (BMD) in the fluoride exposure group was significantly lower than that in the control group after implantation for 2 and 3 months. The bone-implant contact ratio (BIC) in the fluoride exposure group was much lower than that of the control group at 3 months post-implantation according to histomorphometry examination.

CONCLUSIONS

In rabbit animal model, high fluoride exposure affected the quality of bone surrounding the implant and significantly reduced bone integration of the implant, especially in the late stage of osseointegration.

Histopathological comparative analysis of periimplant bone inflammatory response after dental implant insertion using flap and flapless surgical technique. An experimental study in pigs

AIM

To evaluate by histopathological analysis the peri-implant bone inflammation degree, in certain time intervals (7, 14, 21 and 28 days), following mini-incision flapless and flap implant placement.

MATERIAL AND METHODS

The experiment was conducted on four domestic pigs. Nine weeks prior to implant insertion, second and third mandibular premolars were extracted. Each animal received six implants in lower jaw. On one randomly chosen side of jaw flapless technique using mini-incision was performed, while on the other side implants were inserted after flap raising. After 7, 14, 21, and 28 days, the experimental animals were sacrificed. Following mandibular resection and decalcification, the samples for histopathological analysis of the peri-implant bone were obtained in the empty implant bed area, from the buccal side of the mandible, adjacent to implant neck region and parallel to crestal edge of implant bed. The degree of inflammatory response of the peri-implant bone was estimated through ordinal scores from 0 to 2.

RESULTS

Seven days after the surgery all samples in the flap group had score 2 indicating high inflammation degree, in contrast to lower inflammatory reaction in flapless group. On the 14th and 21st postoperative day decreasing of inflammation degree was noted in all samples of the flapless group (score 1), while in flap group samples presented scores 1 and 2. Twenty-eight days after the implant placement, further reduction of inflammation in the flapless group (33% of samples had score 0) was observed.

CONCLUSION

Flapless technique in comparison to conventional flap procedure minimizes postoperative bone inflammatory reactions.

Influence of immediate and early loading on bone metabolic activity around dental implants in rat tibiae

OBJECTIVES

The aim of this study was to examine the influence of immediate and early loading on dynamic changes in bone metabolism around dental implants using bone scintigraphy.

MATERIAL AND METHODS

Two titanium implants were inserted in the right tibiae of 21 rats. Closed coil springs with 4.0-N loads were applied parallel to the upper portion of the implants for 35 days. According to the load application timing, rats were divided into three groups: immediate loading (IL) group, early loading 1 day after implant insertion (1-D early loading [EL]) group, and loading 3 days after implant insertion (3-D EL) group. Rats were intravenously injected with technetium-99 m-methylene diphosphonate (Tc99 m-MDP) (74 MBq/rat) and scanned by bone scintigraphy at 1, 4, 7, 11, 14, 21, 28, and 35 days after load application. The ratio of accumulation of Tc99 m-MDP around the implants to that of a reference site (uptake ratio) was calculated to evaluate bone metabolism.

RESULTS

In every group, the uptake ratio increased until 7 days after load application and then gradually decreased. It was significantly higher than baseline at 4, 7, 11, and 14 days (P < 0.001). The uptake ratio in the 1-D EL and 3-D EL groups were significantly higher than that in the control group and also that in the IL group (P < 0.001).

CONCLUSIONS

Bone metabolism initially increased and then gradually decreased to baseline despite differences in load timing. Increases in bone metabolic activity differed according to load application timing; the later the load application, the more enhanced the bone metabolism.

Bone healing with or without platelet-rich plasma around four different dental implant surfaces in beagle dogs

PURPOSE

Surface development is one of the major aims in dental implant engineering. Additive application of substances could possibly improve the new bone formation around dental implants. The present study evaluated the bone reaction on four different implant surfaces with or without platelet-rich plasma (PRP).

MATERIALS AND METHODS

Four self-tapping titanium screw implants (Brånemark MK III [Nobel Biocare, Göteborg, Sweden], Osseotite [3i, Miami, FL, USA], Xive [Densply Friadent, Mannheim, Germany], and Compress [IGfZ eG, Diez, Germany]) with different surfaces were inserted in each hemimandible of 12 female beagle dogs; the implant positions and the application of PRP were randomized. After intravital fluorochrome staining, sacrifices and biopsies harvesting were performed after 6 weeks (five dogs; one dog died before) and 12 weeks (six dogs) and the respective specimens were analyzed.

RESULTS

The only significant difference in bone remodeling was found for the Compress implants with increased bone formation compared with the Brånemark implants at 12 weeks (sign test, p = .03). Comparing the histological and histomorphometric specimens of all other implant surfaces with respect to peri-implant bone remodeling and the resulting bone-implant contact rates (BICRs), no statistically significant differences were seen in the PRP or non-PRP groups (sign test, all p values ≥ .063).

CONCLUSIONS

This study found no significant differences in the BICR for roughened implant surfaces compared with machined surfaces. In this animal model, the addition of PRP did not demonstrate evidence of faster bone formation or the resulting BICR.