Vittoria Perrotti

Maxillary Sinus Augmentation With Different Biomaterials: A Comparative Histologic and Histomorphometric Study in Man

Objective:Rehabilitation of the edentulous posterior maxilla with dental implants can be difficult because of insufficient bone volume caused by pneumatization of the maxillary sinus and crestal bone resorption. Different biomaterials have been used for sinus augmentation. The aim of the study was to compare different materials in maxillary sinus augmentation in man. Methods:A total of 94 patients participated in this study. Inclusion criteria were maxillary partial (unilateral or bilateral) edentulism involving the premolar/molar areas, and the presence of 3–5-mm crestal bone between the sinus floor and alveolar ridge. A total of 362 implants were inserted. There were 9 biomaterials used in the sinus augmentation procedures. Each patient underwent 1 biopsy after 6 months. A total of 144 specimens were retrieved. Results:None of the 94 patients had complications. All implants were stable, and x-ray examination showed dense bone around the implants. Mean follow-up was 4 years. There were 7 implants that failed. Histologic resultsshowed that almost all the particles of the different biomaterials (i.e., autologous bone, demineralized freeze-dried bone allograft Biocoral® [Inoteb, St. Gonnery, France], Bioglass® [US Biomaterials, Alachua, FL], Fisiograft® [Ghimas, Bologna, Italy], PepGen P-15TM [Dentsply Friadent CeraMed, Lakewood, CO], calcium sulfate, Bio-Oss® [Geistlich Pharma AG, Wohlhusen, Switzerland], and hydroxyapatite) were surrounded by bone. Some biomaterials were more resorbable than others. Included are the histomorphometry clarified features of the newly formed bone around the different grafted particles. Conclusion:All biomaterials examined resulted in being biocompatible and seemed to improve new bone formation in maxillary sinus lift. No signs of inflammation were present. The data are very encouraging because of the high number of successfully treated patients and the good quality of bone found in the retrieved specimens.

Bacterial Leakage in Implants With Different Implant–Abutment Connections: An In Vitro Study

BACKGROUND Two-piece implants present gaps and cavities between the implant and the abutment, and these hollow spaces can act as a trap for bacteria. The aim of the present in vitro study was to evaluate the migration of two different microbial species from the inside to the outside of the implant-abutment assembly in three different connection types. METHODS A total of 30 implants (10 implants per group) were used. The implants presented a screwed trilobed connection (group 1), a cemented connection (group 2), and an internal conical connection (group 3). The inner parts of five implants, per group, were inoculated with Pseudomonas aeruginosa suspension and the remaining five implants, per group, with Aggregatibacter actinomycetemcomitans. The penetration of bacteria into the surrounding solution was determined by the observation of turbidity of the broth. RESULTS In group 1, bacterial contamination was found in six of 10 implants. In group 2, no contaminated samples were found. In group 3, bacterial contamination was found in one implant of 10. Statistically significant differences were detected between group 1 versus group 3 (P <0.05) and between group 1 versus group 2 (P <0.01), whereas no significant differences were found when comparing group 2 versus group 3 (P >0.05). CONCLUSION The present study confirms previous results about the hermeticity of the cement-retained implant-abutment assembly, the very low permeability to bacteria of the conical implant-abutment connection, and the high prevalence of bacterial penetration of screw-retained implant-abutment assemblies.

Comparative Analysis of Immediate Functional Loading and Immediate Nonfunctional Loading to Traditional Healing Periods: A 5-Year Follow-Up of 550 Dental Implants

BACKGROUND Clinical, radiographical, and histological findings have shown that immediately loaded implants show the presence of mineralized tissues at the interface. PURPOSE The aim of this study was to compare an immediate loading protocol with a two-staged one using an implant with a square thread design. MATERIALS AND METHODS One hundred fifty-five consecutive patients (71 men, 84 women), aged between 18 and 78 years (mean: 54 years) participated in this study. A total of 550 implants (Maestro; BioHorizons, Birmingham, AL, USA) were inserted. In group A, 264 implants were inserted in 82 patients with immediate functional loading with occlusal contact if the patients were completely edentulous, or with immediate nonfunctional loading without occlusal contact if the patients were partially edentulous. In group B, 286 implants were inserted in 73 patients with a one-stage or two-stage surgical procedure. All patients were followed for at least 5 years. RESULTS In the immediately loaded implants group, three implants failed, all in posterior mandibular sites, with an overall 98.8% 5-year survival rate. In the control group, no implant failed, with a 100% 5-year survival rate. No statistically significant differences were found in the survival rates of the implants in the two groups. DISCUSSION A very high implant survival rate was also present in our series for the immediately loaded implants. All the three failed implants were retrieved from the same patient, who had poor oral hygiene, after a loading period of 5 years. These data can suggest that, from a clinical point of view, an abbreviated healing period is compatible with the development and maintenance over a longer time period (5 years) of mineralized tissues at the interface with dental implants. CONCLUSION We can then conclude that shorter healing periods can be highly satisfactory from a clinical point of view.

Bone Remodeling in Immediately Loaded and Unloaded Titanium Dental Implants: A Histologic and Histomorphometric Study in Humans

Remodeling is thought to prevent microdamage accumulation caused by repetitive loading and to increase the fatigue life of bone. The bone remodeling rate (BRR) is the period of time needed for new bone to replace the existing bone and to allow for the adaptation of bone to its environment. BRR is expressed as a percentage or volume of new bone within a specific time period. The aim of the present study was to evaluate bone remodeling events on submerged and immediately loaded dental implants. Twelve patients with edentulous mandibles participated in this study. All patients were rehabilitated with fixed mandibular prostheses, with 10 dental implants per patient. An additional implant was inserted in the most distal posterior mandibular jaw region. In 6 patients, these additional implants were loaded with a fixed provisional prosthesis the same day of the implant surgery and loaded. In the other 6 patients, the additional implants were left submerged and not loaded. After 6 months, all the additional implants were retrieved with a trephine. The percentage of woven and lamellar bone, number of osteoclasts and osteoblasts, and percentage of bone labeled by tetracycline at 0.5 mm and 2 mm from the implant surface were evaluated. The percentage of lamellar bone, number of osteoblasts, and percentage of bone tetracycline labeling was significantly higher in the loaded implants than in the unloaded implants (P =.0001). Also in the loaded implants, the percentage of woven and lamellar bone, number of osteoclasts and osteoblasts, and percentage of bone tetracycline labeling was significantly higher at 0.5 mm than at 2 mm from the implant surface (P =.0001). No such differences were found in unloaded implants (P =.377). In conclusion, we found that (1) loading appeared to stimulate bone remodeling at the interface, (2) a higher percentage of lamellar bone was found in loaded implants, (3) the percentage of bone labeling was higher at the interface of loaded implants, (4) no differences were found in the BRRs between immediately loaded and unloaded implants, and (5) immediate loading had not interfered on the lamellar bone formation at the interface and had not produced formation of woven bone at the interface.

Is insertion torque correlated to bone–implant contact percentage in the early healing period? A histological and histomorphometrical evaluation of 17 human‐retrieved dental implants

OBJECTIVE A precise and scientifically established method for the evaluation of the bone quality/primary stability is the measure of the insertion torque (IT). The aim of this study was a comparison between the IT values and the bone-implant contact percentage (BIC) of human implants retrieved after a 4/8-week healing period. MATERIALS Seventeen implants, all with a sandblasted and acid-etched surface, were evaluated in the present study. METHODS The implants had been retrieved for different causes, after 4/8 weeks, with a 5 mm trephine bur, and immersed in 10% buffered formalin to be processed for histology. RESULTS A not statistically significant correlation was found between IT and BIC (P<or=0.892). CONCLUSIONS In the present study on human-retrieved implants, no statistically significant correlation was found between the IT values and BIC. These results could be due to a lack of relationship between bone structure and IT, or to the fact that primary stability may not only be influenced by bone volumetrical density and/or bone trabecular connectivity but also by the thickness and density of the cortical layer. Moreover, the present knowledge of the bone microstructure is not enough to explain the relationship of bone quality and primary implant stability.

Alveolar Ridge Regeneration with Equine Spongy Bone: A Clinical, Histological, and Immunohistochemical Case Series

BACKGROUND In the case of localized ridge atrophy, a ridge augmentation procedure, with the use of bone substitutes and barrier membranes, may then be necessary. PURPOSE The aim of the present study was a clinical, histological, and immunohistochemical evaluation of an equine spongy bone in alveolar ridge augmentation procedures. MATERIALS AND METHODS Five patients showing horizontal mandibular ridge defects participated in this study. A ridge augmentation was performed through an onlay apposition of equine bone covered by a titanium-reinforced membrane. After 6 months of healing, five bone cores from nonaugmented sites (control) and five from augmented sites (test) were retrieved. RESULTS In test sites, no postoperative complications occurred. Horizontal bone width increased from 24 to 37 mm. In control sites, the newly formed bone represented 33%, and in test sites, 35% of the total area. The mean value of the microvessel density was 25.6 +/- 3.425 per mm(2) in controls, while 33.3 +/- 2.5 vessels per mm(2) in the test sites were found (p < .05). Both groups showed a high intensity (++) of vascular endothelial growth factor expression in the newly formed bone, while a low intensity (+) was found in the mature bone. CONCLUSION Equine bone appeared to be biocompatible and to be associated with new vessel ingrowth. Within the limits of the small sample size, the present study indicated that equine bone could be used in mandibular ridge augmentations.

Maxillary Sinus Augmentation Using an Engineered Porous Hydroxyapatite: A Clinical, Histological, and Transmission Electron Microscopy Study in Man

Porous hydroxyapatite (HA) is a calcium-phosphate-based material that is biocompatible, nonimmunological, and osteoconductive, and has a macroporosity of about 200 to 800 microm. The pores seem to be able to induce migration, adhesion, and proliferation of osteoblasts inside the pore network and to promote angiogenesis inside the pore system. The aim of this study was to evaluate the clinical behavior and the histological and ultrastructural aspects of porous HA in maxillary sinus augmentation procedures. Twenty-four patients (19 men, 5 women; average age 53.4 years) in good general physical and mental health and with partially or completely edentulous maxillae were selected for this study. Six months after sinus floor elevation, at the time of dental implant placement, biopsies were carried out under local anesthesia. These bone cores were cut in half and were processed for light and transmission electron microscopy. After a mean 3 years after implantation, all implants are clinically in function and no surgical or prosthetic complications have occurred. Under light microscopy, newly formed bone was 38.5% +/- 4.5%, whereas the residual biomaterial represented 12% +/- 2.3% and the marrow spaces represented 44.6% +/- 4.2%. In addition, in the majority of cases, the biomaterial particles were in close contact with the bone, which appeared compact with the characteristic features of well-organized lamellar bone. A cement-like line was slightly visible at the bone-biomaterial interface, but there were no gaps or interposed connective tissue in between. A high quantity (about 40%) of newly formed bone was present. Bone was closely apposed to the biomaterials particles as shown in light microscopy and transmission electron microscopy. Moreover, no signs of inflammatory cell infiltrate or foreign body reaction were present. Also, most of the biomaterial was resorbed and only a small quantity (a little more than 10%) was still present. The results of our study show that porous HA can be a suitable synthetic material for bone regeneration in maxillary sinus augmentation procedures.

Bone response to submerged, unloaded implants inserted in poor bone sites: a histological and histomorphometrical study of 8 titanium implants retrieved from man.

An important parameter that influences the long-term success of oral implants is the bone quality of the implant bed. Posterior areas of the jaws have been avoided in implant dentistry because of their poor bone quality, higher chewing forces, and presumed higher implant failure rates. Several researchers have deemed soft bone implant sites to be a great potential risk situation, and most failures have been found in sites where the bone density was already low. The inferior success rates in the posterior maxilla have been attributed to a lower bone density and a lesser bone-implant interface. The aim of the present study was a histological and histomorphometrical analysis of the bone response to submerged implants inserted in posterior areas of the human jaws and retrieved, for different causes, after healing periods varying from 6 weeks to 12 months. Eight submerged implants that had been retrieved for different causes after different healing periods were evaluated in the present study. All implants were submerged and unloaded. Three implants had been removed for inadequate patient adaptation, 2 for inability of the implant to meet changed prosthetic needs, 1 for not optimal position from esthetic and hygiene aspects, and the last 2 for pain and dysesthesia. All the implants were retrieved with a 5-mm trephine bur. Newly formed peri-implant bone was found in all implants even after shorter healing periods. The bone-implant contact percentage varied from 30% to 96%. In conclusion, some surfaces have an improved characteristic of contact osteogenesis in soft bone, with coverage of the implant surface with a bone layer as a base for intensive bone formation and remodeling. We documented osseointegration of implants with a rough surface even after an insertion period of less than 2 months, both in the mandible and in the maxilla. From these results, we tentatively extrapolate that these implants might be carefully loaded after 2 months of healing, even when inserted in soft bone. A higher removal torque value might lead to a more predictable use of shorter implants, to a support of a prosthesis with fewer implants, or to shorter healing periods.

Equicrestal and Subcrestal Dental Implants: A Histologic and Histomorphometric Evaluation of Nine Retrieved Human Implants

BACKGROUND Stability of peri-implant crestal bone plays a relevant role relative to the presence or absence of interdental papilla. Several factors can contribute to the crestal bone resorption observed around two-piece implants, such as the presence of a microgap at the level of the implant-abutment junction, the type of connection between implant and prosthetic components, the implant positioning relative to the alveolar crest, and the interimplant distance. Subcrestal positioning of dental implants has been proposed to decrease the risk of exposure of the metal of the top of the implant or of the abutment margin, and to get enough space in a vertical dimension to create a harmoniously esthetic emergence profile. METHODS The present retrospective histologic study was performed to evaluate dental implants retrieved from human jaws that had been inserted in an equicrestal or subcrestal position. A total of nine implants were evaluated: five of these had been inserted in an equicrestal position, whereas the other four had been positioned subcrestally (1 to 3 mm). RESULTS In all subcrestally placed implants, preexisting and newly formed bone was found over the implant shoulder. In the equicrestal implants, crestal bone resorption (0.5 to 1.5 mm) was present around all implants. CONCLUSION The subcrestal position of the implants resulted in bone located above the implant shoulder.

Human osteoclast formation and activity on a xenogenous bone mineral.

To date, the majority of studies on bone substitute materials have investigated their regenerative properties; however, little is known about their resorption processes, forasmuch as it is believed that the ideal biomaterial for bone regeneration must be completely resorbable. This study is aimed at defining the in vitro resorption potential of human osteoclasts (OCLs) on a xenogenous bone mineral (XBM). Peripheral blood mononuclear cells from healthy volunteers were used to generate OCLs in vitro in the presence of macrophage colony stimulating factor and receptor activator of NF-kappaB ligand on bovine bone slices and XBM. By using morphologic and biochemical methods, we observed that OCL formation occurred on XBM and these cells were positive for the major OCL markers. Regarding OCL activity, resorption pits were detected on XBM by reflection and confocal microscopy. However, biochemical analysis revealed that collagen degradation at day 14 and 21 was significantly lower in XBM supernatants when compared to bovine bone, suggesting that XBM underwent a much slower resorption over time. These findings demonstrate that OCLs are generated on, attach to, and resorb XBM though more slowly than native bone, and suggest that cultured human OCLs could be used as a model for comparing resorption rates of bone substitute materials.