Adriano Piattelli

Direct laser metal sintering as a new approach to fabrication of an isoelastic functionally graded material for manufacture of porous titanium dental implants

OBJECTIVES This work focuses on a titanium alloy implants incorporating a gradient of porosity, from the inner core to the outer surface, obtained by laser sintering of metal powder. Surface appearance, microstructure, composition, mechanical properties and fractography were evaluated. METHODS All the specimens were prepared by a selective laser sintering procedure using a Ti-6Al-4V alloy powder with a particle size of 1-10 microm. The morphological and chemical analyses were performed by SEM and energy dispersive X-ray spectroscopy. The flexure strength was determined by a three-point bend test using a universal testing machine. The surface roughness was investigated using a confocal scanning laser microscope. The surface roughness variation was statistically evaluated by use of a Chi square test. A p value of <0.05 was considered statistically significant. RESULTS The original surface microstructure consisted of roughly spherical particles, diameter range 5-50 microm. After exposure to hydrofluoric acid some of these were removed and the microsphere diameter then ranged from 5.1 microm to 26.8 microm. Following an organic acid treatment, particles were replaced by grooves 14.6-152.5 microm in width and 21.4-102.4 microm depth. The metal core consisted of columnar beta grains with alpha and beta laths within the grains. The alloy was composed of 90.08% Ti, 5.67% Al and 4.25% V. The Youngs modulus of the inner core material was 104+/-7.7 GPa; while that of the outer porous material was 77+/-3.5 GPa. The fracture face showed a dimpled appearance typical of ductile fracture. SIGNIFICANCE In conclusion, laser metal sintering proved to be an efficient means of construction of dental implants with a functionally graded material which is better adapted to the elastic properties of the bone. Such implants should minimize stress shielding effects and improve long-term performance.

High-precision, cost-effective cutting system for producing thin sections of oral tissues containing dental implants

A new high-precision, cost-effective cutting system, able to produce thin (20-30 microns) sections of oral tissues, containing dental implants, is presented. With this system the authors have been able to obtain, in a reproducible and consistent way, thin slides containing biomaterials and biological tissues. Very high cellular detail was possible, even at high magnifications (x 1200). Histochemical reactions (e.g. acid and alkaline phosphatases) have also been obtained in a reproducible way, without sputter ground staining. The time involved in specimen cutting was significantly reduced, and about five slides per specimen were obtained with minimal loss of tissue. In almost all cases it has been possible to eliminate the grinding process with its inherent problems, such as formation of ledging at the bone-titanium interface. With this system it was also possible to obtain thin slides of soft tissue lesions (i.e. benign mucous membrane pemphigoid).

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.

Comparison of bone regeneration with the use of mineralized and demineralized freeze-dried bone allografts: a histological and histochemical study in man

Mineralized (FDBA) and demineralized freeze-dried bone allografts (DFDBA) have been proposed as substitutes for autologous bone in oral surgery. The demineralization process has been shown, in rodents, to determine osteoinduction in tissues other than bone. Other investigators have reported poor clinical results, in man, with the use of DFDBA. The aim of the present study was a comparative light microscopical and histochemical analysis of bone regeneration processes, in man, with the use of FDBA and DFDBA. Our histological results showed that in DFDBA only the particles near the host bone were involved in the mineralization processes, while in FDBA even the particles that were farthest from the host bone were lined by osteoblasts, actively secreting osteoid matrix and newly formed bone. These results probably point to a more osteoconductive effect of FDBA. No osteoinduction was observed with FDBA or DFDBA.

Expression of proliferating cell nuclear antigen in ameloblastomas and odontogenic cysts

The identification of the proliferative activity in tumours may be useful to predict the biological behaviour of different lesions. Proliferating cell nuclear antigen (PCNA) has been used for the evaluation of the proliferative ability of many lesions. In this study 22 ameloblastomas (4 follicular, 5 plexiform, 4 acanthomatous, 5 unicystic, 4 recurrent), 12 odontogenic keratocysts (OKC), 8 dentigerous cysts (DC), and 12 radicular cysts (RC) were analysed. PCNA+ cells were present in all cyst types but the OKC contained the highest number of PCNA+ cells. In OKC the location of PCNA+ cells was mainly suprabasal. In ameloblastoma PCNA+ cells were located mainly in the peripheral portion of the tumour islands. Statistical analysis showed that ameloblastoma had higher PCNA+ cell counts than OKC (P < 0.0001); OKC had higher values than DC and RC (P < 0.0001). Recurrent ameloblastoma presented higher PCNA+ cell counts than other types of ameloblastoma, while unicystic ameloblastoma showed lower values than acanthomatous, plexiform and follicular ameloblastomas (in this latter case the difference was not statistically significant). These data could help to explain the different biological behaviour of these lesions.

Warthin's tumour: a study of 78 cases with emphasis on bilaterality, multifocality and association with other malignancies

The authors reviewed the clinical records and the histopathological preparations of 78 cases of Warthins tumours (WTs), treated at the Department of Dental Sciences, Centre for the Study of Oral Tumours, of the University of Bari. All the surgical specimens had been fixed in neutral buffered formalin, sampled according to the step-serial, whole-specimen sectioning technique, embedded in paraffin and stained with haematoxylin-eosin, periodic acid Schiff and Gomoris reticulin. The results showed that Warthins tumours characteristically affect the parotid gland, and most frequently arise in adults (mean age=57 years) and in males (95%). Multiple tumours were detected in 16 cases (20.5%), and five of these were bilateral (6.5%). One of the multifocal tumours involved an intra-parotideal lymph node and the laryngeal piriform sinus. In addition, 13 cases (16.6%) were associated with other malignancies. These data indicate that multiple (synchronous or metachronous) WTs may occur more frequently than previously reported. The high rate of multiple WTs detected in the current study may result from extensive and accurate sampling of these neoplasms for histopathological evaluation. Consequently, complete preoperative work-up of patients harbouring parotideal tumours consistent with or suspicious for WT is necessary. The work-up should include CT scans and/or magnetic resonance imaging of both parotid glands, to exclude the occurrence of multiple tumours, which may be clinically undetectable. Also, fine needle aspiration biopsy may be an accurate tool for excluding malignant neoplasms and for better planning subsequent surgical procedures. These usually consist in (bilateral) superficial parotidectomy and should be followed by long term follow up of the patients, in view of possible metachronous WTs, even after prolonged time intervals.

Clinical and histologic aspects of biphasic calcium phosphate ceramic (BCP) used in connection with implant placement.

A granulate of biphasic calcium phosphate ceramic (BCP), composed of 50% hydroxyapatite and 50% beta-tricalcium phosphate, was used, in man, to fill defects resulting from cyst enucleation. The defects were covered with e-PTFE membranes, and at the re-entry procedure after six months, it was possible to see that the defects were filled by a newly formed tissue with the macroscopic features of mature bone. Smooth titanium implants were inserted in the newly regenerated tissue. Histological examination of this tissue showed that most of the particles were lined by newly formed bone. Some particles were undergoing resorption processes and were being gradually substituted by newly formed bone. No inflammatory infiltrate was present. Our results point, in conclusion, to a good biocompatibility and osteoconductivity of this material.

Clinical and histological results in alveolar ridge enlargement using coralline calcium carbonate.

A very important parameter during the insertion of dental implants is the amount of bone present in a site. A regenerative procedure to increase the width and the height of bone is proposed with the use of occlusive barrier membranes and biomaterials. The authors used, in six patients with deficient alveolar ridges, prior to implant insertion, Biocoral gel particles in connection with expanded polytetrafluoroethylene membranes. After 6 months it was observed that a tissue similar to mature bone had regenerated under the membrane and microscopically it was observed that the Biocoral particles were still present and almost all were completely surrounded by mature bone.

10‐Year Follow‐Up of Immediately Loaded Implants with TiUnite Porous Anodized Surface

BACKGROUND The immediate loading of implants with a porous anodized surface is a well-described technique. Few data are however available on the long-term outcomes. PURPOSE The aim of this prospective study was to assess the 10-year performance of TiUnite implants supporting fixed prostheses placed with an immediate loading approach in both postextractive and healed sites. MATERIALS AND METHODS All patients received a fixed provisional restoration supported by immediately loaded parallel design, self-tapping implants with a porous anodized TiUnite surface, and an external-hexagonal connection. Both healed and postextractive cases were included. Success and survival rate for restorations and implants, changes in marginal peri-implant bone level, probing depth measurements, biological or technical complications, and any other adverse event were recorded at yearly follow-up up to 10 years after surgery. RESULTS A total of 210 implants fulfilled the inclusion criteria and were consecutively placed in 59 patients. Forty-seven (22.38%) implants were lost because of the recalled patient refused to attend the planned 10-year follow-up. Five over 210 (2.38%) implants were lost. At the final follow-up, the accumulated mean marginal bone loss and probing depth were, respectively, 1.93 mm (SD 0.40) and 2.54 mm (SD 0.44) for the implants placed in healed sites (n = 84); 1.98 mm (SD 0.37) and 2.63 mm (SD 0.39) for the implants placed in postextractive sites (n = 74). The restorations examined achieved a cumulative 65.26% success rate and 97.96% survival rate. The implants placed in healed and postextractive sites, respectively, achieved a 98.05% and a 96.52% cumulative survival rate. CONCLUSIONS Positive results in terms of bone maintenance in the long-term perspective are to be expected using immediately loaded implants with a TiUnite porous anodized surface in both postextractive and healed sites when adequate levels of oral hygiene are kept.

Evaluation of guided bone regeneration in rabbit tibia using bioresorbable and non-resorbable membranes

The aim of this study was an evaluation of the possibility of bone regeneration in connection with implant placement, using a new bioresorbable membrane (Guidor Matrix Barrier) used previously in periodontal tissues regeneration. The study compared the bone regeneration obtained around Bonefit-ITI implants inserted in rabbit tibia using Guidor membranes, Gore-Tex membranes and in control sites. Microscopic analysis was performed after 6, 9 and 12 weeks. It was possible to see that the amount of bone around implants covered by Guidor and Gore-Tex membranes was roughly equivalent in all experimental sites at the 6-, 9- and 12-week time intervals. Also, all control sites healed completely. It could be concluded from this study that: (1) rabbit tibia cannot be recommended in research connected with guided bone regeneration, as all control sites healed in the same way as the test sites; (2) in no case did the presence or the degradation of the resorbable membrane prevent the formation of new bone; (3) no inflammatory reaction was present around the bioresorbable and the non-resorbable membranes; (4) bone formed in all cases on the outer surface of the non-resorbable membranes; (5) large Guidor membrane fragments were present in the 6-week specimens, while in the 12-week specimens only small fragments were recognizable; (6) Guidor membranes can be used in guided bone regeneration.