Giovanna Iezzi

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.

Influence of implant surfaces on osseointegration

The biological fixation between the dental implant surfaces and jaw bones should be considered a prerequisite for the long-term success of implant-supported prostheses. In this context, the implant surface modifications gained an important and decisive place in implant research over the last years. As the most investigated topic in, it aided the development of enhanced dental treatment modalities and the expansion of dental implant use. Nowadays, a large number of implant types with a great variety of surface properties and other features are commercially available and have to be treated with caution. Although surface modifications have been shown to enhance osseointegration at early implantation times, for example, the clinician should look for research evidence before selecting a dental implant for a specific use. This paper reviews the literature on dental implant surfaces by assessing in vitro and in vivo studies to show the current perspective of implant development. The review comprises quantitative and qualitative results on the analysis of bone-implant interface using micro and nano implant surface topographies. Furthermore, the perspective of incorporating biomimetic molecules (e.g.: peptides and bone morphogenetic proteins) to the implant surface and their effects on bone formation and remodeling around implants are discussed.

A 16-year study of the microgap between 272 human titanium implants and their abutments.

A microgap has been described at the level of the implant-abutment connection. This microgap can be colonized by bacteria, and this fact could have relevance on the remodeling of the peri-implant crestal bone and on the long-term health of the peri-implant tissues. The authors report on 272 implants with screw- or cement-retained abutments retrieved from humans for different causes during a 16-year period. In the implants with screw-retained abutments, a 60-microm microgap was present at the level of implant-abutment connection. In some areas the titanium had sheared off from the surface and from the internal threads. The contact between the threads of the implant and those of the abutment was limited to a few areas. Bacteria were often present in the microgaps between implant and abutment and in the internal portion of the implants. In implants with cement-retained abutments, a 40-microm microgap was found at the level of the implant-abutment connection. No mechanical damage was observed at the level of the implant or of the abutment. All the internal voids were always completely filled by the cement. No bacteria were observed in the internal portion of the implants or at the level of the microgap. The differences in the size of the microgap between the two groups were statistically significant (P < .05). In conclusion, in screw-retained abutments the microgap can be a critical factor for colonization of bacteria, whereas in cement-retained abutments all the internal spaces were filled by cement. In these retrieved implants, the size of the microgap was markedly variable and much larger than that observed in vitro.

Vertical ridge augmentation of the atrophic posterior mandible with interpositional bloc grafts: bone from the iliac crest vs bovine anorganic bone. Clinical and histological results up to one year after loading from a randomized-controlled clinical trial.

OBJECTIVES To compare two different techniques for vertical bone augmentation of the posterior mandible: bone blocs from the iliac crest vs. anorganic bovine bone blocs used as inlays. MATERIALS AND METHODS Ten partially edentulous patients having 5-7 mm of residual crestal height above the mandibular canal had their posterior mandibles randomly allocated to both interventions. After 4 months implants were inserted, and after 4 months, provisional prostheses were placed. Definitive prostheses were delivered after 4 months. Histomorphometry of samples trephined at implant placement, prosthesis and implant failures, any complication after loading and peri-implant marginal bone-level changes were assessed by masked assessors. All patients were followed up to 1 year after loading. RESULTS Four months after bone augmentation, there was statistically significant more residual graft (between 10% and 13%) in the Bio-Oss group. There were no statistically significant differences in failures and complications. Two implants could not be placed in one patient augmented with autogenous bone because the graft failed whereas one implant and its prosthesis of the Bio-Oss group failed after loading. After implant loading only one complication (peri-implantitis) occurred at one implant of the autogenous bone group. In 16 months (from implant placement to 1 year after loading), both groups lost statistically significant amounts of peri-implant marginal bone: 0.82 mm in the autogenous bone group and 0.59 mm in the Bio-Oss group; however, there were no statistically significant differences between the groups. CONCLUSIONS Both procedures achieved good results, but the use of bovine blocs was less invasive and may be preferable than harvesting bone from the iliac crest.

Bone regeneration with calcium sulfate: evidence for increased angiogenesis in rabbits.

Autologous bone is the preferred bone graft material because it carries proteins as bone-enhancing substrates, minerals, and vital bone cells. Calcium sulfate (CS) is a well-tolerated, biodegradable, osteoconductive bone graft substitute and is a reasonable alternative to autogenous bone graft. Blood vessels are an important component of bone formation and maintenance. The process of vascular induction is called angiogenesis, and it plays a key role in all regenerative processes. Bone tissue differentiation is related to the local presence of blood vessels. One method to evaluate the presence of blood vessels in a tissue is to count the microvessels to evaluate microvessel density (MVD). The aim of the present study was to conduct a comparative evaluation of microvessel density in sites treated with CS and autologous bone in rabbits, with or without e-PTFE nonresorbable membranes (Gore-Tex, Flagstaff, Ariz). Nine New Zealand rabbits, each weighing about 2.5 kg, were used in this experiment. Three 6-mm wide defects were created in each tibial metaphysis. The defects were filled in a random way. The defects of group 1 (3 rabbits) were filled with CS granules (Surgiplaster, Classimplant, Rome, Italy) and covered with e-PTFE membranes. The defects in group 2 (3 rabbits) were filled with CS granules (Surgiplaster). The defects in group 3 (3 rabbits) were filled with autologous bone. A total of 54 defects were filled (18 with CS and e-PTFE membranes, 18 with CS alone, and 18 with autologous bone). No postoperative deaths or complications occurred. All nine animals were sacrificed at 4 weeks. MVD results were as follows: in the first group, 9.88 +/- 4.613; in the second group, 7.92 +/- 1.998; and in the third group, 5.56 +/- 1.895. P = .000 was highly significant. Statistically significant differences were found between groups 1 and 3, 1 and 2, and 2 and 3. The presence of more blood vessels in the sites treated with CS could help to explain the good results reported in the literature with the use of CS.

Osteolipoma of the tongue

Lipomas are common, benign tumours located in any part of the body in which fat is normally present. Some variants of lipoma have been described according to the type of tissue present. A rare variant consists of a lipoma with osseous or cartilaginous metaplasia. These lesions have been called chondrolipoma, osteolipoma, lipoma with chondroid or osseous metaplasia, lipoma with cartilaginous or osseous change, or ossifying lipoma. We present the case of an osteolipoma of the tongue in a 49-year-old female who was referred for a painless mass on the left lateral margin of the tongue, and present for about 8 years. Osteolipomas have been reported in middle-aged or elderly patients with a very long clinical history. These tumours tend to be large and to arise from the deep soft or subcutaneous tissues. The cartilage and bone is probably produced by metaplasia of fibroblasts in chondroblasts or osteoblasts. These lesions are benign and do not recur.

Vertical ridge augmentation of the atrophic posterior mandible with sandwich technique: bone block from the chin area versus corticocancellous bone block allograft--clinical and histological prospective randomized controlled study.

The aim of the present study is to compare the histological aspects of bone formation in atrophic posterior mandibles augmented by autologous bone block from chin area with corticocancellous bone block allograft used as inlays with the sandwich technique. Materials and Methods. Sixteen patients with bilateral partial edentulism in the posterior mandible were selected. The residual bone height, preliminarily measured by computed tomography scans, ranged between 5 and 7 mm from the inferior alveolar nerve. All patients required regeneration procedure with autologous bone block from chin area (control group) versus bone block allograft Puros (Zimmer Dental, 1900 Aston Avenue, Carlsbad, CA, USA) (test group). Histological and histomorphometric samples were collected at the time of implant positioning in order to analyze the percentage of newly formed bone, the residual graft material, and marrow spaces/soft tissue. Results. No statistically significant differences between the two groups were found regarding the percentage of newly formed bone. The percentage of residual grafted material was significantly higher in the test group, whilst the percentage of marrow spaces was higher in control group. Conclusions. In conclusion, both procedures supported good results, although the use of bone blocks allograft was less invasive and preferable than harvesting bone from the mental symphysis.

Human Dental Pulp Stem Cells Hook into Biocoral Scaffold Forming an Engineered Biocomplex

The aim of this study was to evaluate the behavior of human Dental Pulp Stem Cells (DPSCs), as well as human osteoblasts, when challenged on a Biocoral scaffold, which is a porous natural hydroxyapatite. For this purpose, human DPSCs were seeded onto a three-dimensional (3D) Biocoral scaffold or on flask surface (control). Either normal or rotative (3D) cultures were performed. Scanning electron microscopic analyses, at 8, 24 and 48 h of culture showed that cells did not adhere on the external surface, but moved into the cavities inside the Biocoral structure. After 7, 15 and 30 days of culture, morphological and molecular analyses suggested that the Biocoral scaffold leads DPSCs to hook into the cavities where these cells quickly start to secrete the extra cellular matrix (ECM) and differentiate into osteoblasts. Control human osteoblasts also moved into the internal cavities where they secreted the ECM. Histological sections revealed a diffuse bone formation inside the Biocoral samples seeded with DPSCs or human osteoblasts, where the original scaffold and the new secreted biomaterial were completely integrated and cells were found within the remaining cavities. In addition, RT-PCR analyses showed a significant increase of osteoblast-related gene expression and, above all, of those genes highly expressed in mineralized tissues, including osteocalcin, OPN and BSP. Furthermore, the effects on the interaction between osteogenesis and angiogenesis were observed and substantiated by ELISA assays. Taken together, our results provide clear evidence that DPSCs differentiated into osteoblasts, forming a biocomplex made of Biocoral, ECM and differentiated cells.

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.

Implant periapical lesion: a clinical and histologic case report.

A new pathologic entity called implant periapical lesion has been recently described. This lesion could be produced by contamination of the implant surface, overheating of bone, overloading of the implant, presence of a pre-existing bone pathology, presence of residual root fragments and foreign bodies in bone, implant placement in an infected maxillary sinus, implant placement in a poor bone quality site, or lack of biocompatibility. A 49-year-old female patient underwent the placement of a screw-shaped titanium dental implant in the premolar region of the right mandible Six months after implant insertion, the patient presented with a persistent pain resistant to analgesics. No fistula was present at a clinical intraoral examination. A periapical x-ray showed the presence of a radiolucency at the apical portion of the implant; this image was confirmed by a CT Scan. The implant was removed. After implant removal, the pain disappeared completely. The specimen was processed to obtain thin ground sections. The histologic examination showed the presence of necrotic bone in the external and apical portion of the antirotational hole of the implant. The etiology of the implant failure in this instance could be related, probably, to an implant contamination of the apical portion of the implant.