Healing outcomes at implants installed in grafted sites: an experimental study in dogs

Aim: To evaluate the integration of implants installed using a surgical guide in augmented sites with autologous bone or deproteinized bovine bone mineral (DBBM) blocks, concomitantly with a collagen membrane.Material and methods: Mandibular molars were extracted bilaterally in six Labrador dogs, the buccal bony wall was removed, and a box-shaped defect was created. After 3 months, flaps were elevated, a bony graft was harvested from the ascending ramus, and secured to the lateral wall of the defect by means of screws. In the left mandibular side, a DBBM block was fixed into the defect. A resorbable membrane was applied at both sides, and the flaps were sutured. After 3 months, flaps were elevated, and a customized device was used as surgical guide to prepare the recipient sites in the interface between grafts and parent bone. One implant was installed in each side of the mandible. After 3 months, biopsies were harvested, and ground sections were prepared for histologic evaluation.Results: One autologous bone block graft was lost before implant installation. The width of the alveolar crest at the test sites (DBBM) was 5.4 +/- 1.2 mm before, 9.4 +/- 1.2 mm immediately after grafting, and 9.3 +/- 1 mm at implant installation. At the control sites (autologous bone), the corresponding values were: 5.2 +/- 1, 9 +/- 1.2, and 8.7 +/- 0.9 mm, respectively. All implants installed were available for histologic evaluation (n = 5). The autologous bone grafts, rich in vessels and cells, were integrated in the parent bone, and only little non-vital bone was found. The BIC% was 56.7 +/- 15.6% and 54.2 +/- 13.2% at the buccal and lingual aspects, respectively. At the test sites, the DBBM appeared to be embedded into connective tissue, and very little newly formed bone was encountered within the grafts. The BIC% was 5.8 +/- 12.3% and 51.3 +/- 14.2% at the buccal and lingual aspects, respectively.Conclusions: Autologous bone blocks used to augment the alveolar bony crest horizontally allowed the complete osseointegration of implants installed after 3 months of healing. However, similar blocks of DBBM did not promote osseointegration, although the installed implants were stable owing to the osseointegration in the sites of the parent bone.

Bioactive coating on titanium implants modified by Nd:YVO4 laser

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dosimetry and cost of imaging osseointegrated implants with film-based and computed tomography

Thermoluminescent dosimeters were used to measure radiation doses at craniofacial sites in a tissue-equivalent phantom during film-based multidirectional tomography with the Tomax Ultrascan (Incubation Industries, Ivyland, Pa.) and during computed tomography with the Elscint Excel 2400 (Elscint Corp., Tel Aviv, Israel). Mean absorbed doses for presurgical mandibular and maxillary canine and molar implant assessments were converted to equivalent doses, which were then multipied by published weighting factors and summed to give effective doses. The computed tomgraphy device consistently delivered higher doses than the Tomax Ultrascan to all anatomic locations; the differences were most pronounced when only one or two implant sites were evaluated. The reasons for the dose disparities are considered both anatomically and procedurally. A survey of examination cost revealed film-based multidirectional tomography to be less expensive than computed tomography.

A study of different calcification areas in newly formed bone 8 weeks after insertion of dental implants in rabbit tibias

In orofacial implantology there are many types of implants for the different systems. Among these is the implant surface type, e.g., a screw type, cylindrical and laminar. Furthermore, the implants are different in their dimensions, their metal composition, their surface condition, such as smooth, grit or layered surfaces and in their methods of application. Two different self-tapping implants, one smooth and the other grit-blasted, are screwed into the bone, and another one with a plasma of titanium coating, which is also in a screw form but with greater spaces between the screw threads are compared. The greatest amount of bone deposition in the bone/implant interface was encountered in the latter one, the smooth surfaced implant being in second place. All of these systems can alter the implant healing process and to demonstrate this, we injected bone markers in the rabbits over different periods of time so as to observe the different areas of bone deposition in the tibias where the implants had been inserted. The bone tracers used were Alizarin, Calcein and Xylenol-orange. The amount of deposition was calculated by using the method of surface morphometry.

Maxillary and mandibular width changes studied using metallic implants.

The purpose of this implant study was to evaluate the transverse stability of the basal maxillary and mandibular structures. The sample included 25 subjects between 12 and 18 years of age who were followed for approximately 2.6 years. Metallic implants were placed bilaterally into the maxillary and mandibular corpora before treatment. Once implant stability had been confirmed, treatment (4 first premolar extractions followed by fixed appliance therapy) was initiated. Changes in the transverse maxillary and mandibular implants were evaluated cephalometrically and two groups (GROW+ and GROW++; selection based on growth changes in facial height and mandibular length) were compared. The GROW++ group showed significant width increases of the posterior maxillary implants (P <.001) and the mandibular implants (P =.009); there was no significant change for the anterior maxillary implants. The GROW+ group showed no significant width changes between the maxillary and mandibular implants. We conclude that (1) there are significant width increases during late adolescence of the basal mandibular and maxillary skeletal structures and (2) the width changes are related with growth potential.

Hydroxylapatite implants with or without collagen in the zygomatic arch of rats. Histological study.

The authors studied the behavior of calcium phosphate materials used as inlay implants into bone cavities prepared in the zygomatic arch of rats. Fifty male albino rats were divided into four groups as follows: group I-preparation of bone cavities which did not receive any implant material as controls; group II-implants of Interpore 200; group III-implants of experimental hydroxylapatite; group IV-implants of experimental hydroxylapatite combined with collagen. The animals were sacrificed after 5, 15, 30, 60 and 120 days and the specimens were submitted to histological analysis. Results showed that the experimental hydroxylapatite used in group III presented better osteogenic properties compared to the other materials. All tested materials were biocompatible, although group IV presented a more intense inflammatory response.

Use of dental implants in children: A literature review

The aim of this literature review is to discuss the use of dental implants in growing patients and the influence of maxillary and mandibular skeletal and dental growth on the stability of those implants. It is recommended to wait for the completion of dental and skeletal growth, except for severe cases of ectodermal dysplasia.

Dental implants: Surface modification of cp-Ti using plasma spraying and the deposition of hydroxyapatite

The commercial pure titanium (cp-Ti) is currently being used with great success in dental implants. In this work we investigate how the cp-Ti implants can be improved by modifying the metal surface morphology, on which a synthetic material with properties similar to that of the inorganic part of the bone, is deposited to facilitate the bone/implant bonding. This synthetic material is the hydroxyapatite, HA, a calcium-phosphate ceramic. The surface modification consists in the application of a titanium oxide (TiO2) layer, using the thermal aspersion - plasma spray technique, with posterior deposition of HA, using the biomimetic method. The X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) and Diffuse Reflectance Infrared Fourier Transform (DRIFT) techniques have been used for characterizing phases, microstructures and morphologies of the coatings. The TiO2 deposit shows a mixture of anatase, rutilo and TiO2-x phases, and a porous and laminar morphology, which facilitate the HA deposition. After the thermal treatment, the previously amorphous structured HA coating, shows a porous homogeneous morphology with particle size of about 2-2.5 μm, with crystallinity and composition similar to that of the biological HA.

The influence of diabetes mellitus and insulin therapy on biomechanical retention around dental implants: a study in rabbits.

The oral rehabilitation by dental implants in patients with diabetes remains a controversial issue. The aim of this study was to evaluate the influence of diabetes mellitus and insulin therapy on the bone healing around dental implants using torque removal. Twenty-seven rabbits were randomly divided into 3 groups with 9 animals each: control (C) group, induced diabetic (D) group, and insulin-treated diabetic (ITD) group (10 U/day). After 1 week, one implant was inserted at the tibial metaphysis of the animals. The glucose levels were periodically evaluated through the glucose-oxidase enzymatic method. The animals were killed at 4, 8, and 12 weeks after surgery and the biomechanical test was performed using a torque manometer. Statistically significant differences regarding the removal torque of the implant could not be found at 4 weeks (P = 0.2) among groups. Group C showed statistically higher values than groups D and ITD at the experimental periods of 8 (P = 0.0001 and P = 0.0002, respectively) and 12 weeks (P = 0.0053 and P = 0.001, respectively). There were no statistical differences between D and ITD groups in any of the experimental periods. Diabetes mellitus has negatively influenced the mechanical retention of implants placed at the tibial metaphysis of rabbits. Therapy with insulin did not induce any changes.

Naso-orbicular tissue necrosis by Streptococcus parasanguis in a patient with Fanconi anemia: Clinical and laboratory aspects

Fanconi anemia (FA) is a rare autosomal recessive disorder, characterized by pancytopenia and progressive hypoplasia of the bone marrow. A 23-year-old woman with FA showed severe pancytopenia and developed an abscess on the infraorbicular region on the right side of the face that progressed to phlegmon and caused tissue necrosis of the nostrils, nasal septum, nasal fossa, and posterior orbital region. Laboratory examination showed Streptococcus parasanguis as the etiologic agent of the phlegmon. Supportive treatment was recommended due to donor incompatibility for bone marrow transplant. The intraoral examination showed spontaneous gingival bleeding, edema of the interdental papillae, hematomas on the superior and inferior lips, bacterial and fungal infections, and adequate oral hygiene. The patient was treated with the administration of an antibiotic (imipenem), an antifungal (amphotericin B), and mouth washing with antiseptic solutions. Periodontal prophylaxis and orientation to and control of oral hygiene and diet were also used during the remission period. For functional and esthetic rehabilitation of the alar regions and nasal dorsum, an acrylic resin nasal prosthesis was made, supported by a spectacle frame.

Evaluation of transfer impressions for osseointegrated implants at various angulations

The accuracy of impressions that transfer the relationship of the implant to the metal framework of the prosthesis continues to be a problem. This study was designed to evaluate the accuracy of the transfer process under variable conditions with regard to implant analog angulations, impression materials, and techniques. Replicas (n = 60) of a metal matrix (control) containing four implants at 90°, 80°, 75°, and 65° in relation to the horizontal surface were obtained by using three impression techniques: T1 - indirect technique with conical copings in closed trays; T2 - direct technique with square copings in open trays; and T3 - square copings splinted with autopolymerizing acrylic resin; and four elastomers: P-polysulfide; I-polyether; A-addition silicone; and Z-condensation silicone. The values of the implant analog annulations were assessed by a profilometer to the nearest 0.017°, then submitted to analysis of variance for comparisons at significance of 5% (P < .05). For implant analog at 90°, the material A associated with T2 and material Z with T3 behaved differently (P < .05) from all groups. At 80°, all materials behaved differently (P < .01) with T1. At 75°, when T1 was associated, materials P and A showed similar behavior, as well as materials I and Z; however, P and A were different from I and Z (P < .01). When T3 was associated, all experimental groups behaved differently among them (P < .01). At 65°, the materials P and Z behaved differently (P < .01) from the control group with T1, T2, and T3; the materials I and A behaved differently from the control group (P < .01) when T1 and T2, respectively, were associated. The more perpendicular the implant analog annulation is in relation to the horizontal surface, the more accurate the impression. The best materials were material I and A and the most satisfactory technique was technique 3.

Interleukin-2 and interleukin-6 gene promoter polymorphisms, and early failure of dental implants

Single nucleotide polymorphisms in the promoter region of the human interleukin (IL)-2 (T-330G) and IL-6 (G-174C) genes have modified the transcriptional activity of these cytokines and are associated with several diseases. The aim of this study was to investigate the possible relationship between these single nucleotide polymorphisms and early implant failure. A sample of 74 nonsmokers was divided into 2 groups: test group comprising 34 patients (mean age 49.3 years) with ĝ‰¥1 implants that failed and control group consisting of 40 patients (mean age 43.8 years) with ĝ‰¥1 healthy implants. Genomic deoxyribonucleic acid from oral mucosa was amplified by polymerase chain reaction and analyzed by restriction fragment length polymorphism. Monte Carlo simulations (P < 0.05) were used to assess differences in allele and genotypes frequencies of the single nucleotide polymorphisms between the 2 groups. No significant differences were observed in the allele and genotypes distribution of both polymorphisms when the 2 groups were compared. The results indicate that polymorphisms in the IL-2 (T-330G) and IL-6 (G-174C) genes are not associated with early implant failure, suggesting that the presence of those single nucleotide polymorphisms does not constitute a genetic risk factor for implant loss in the studied population. Copyright © 2005 by Lippincott Williams & Wilkins.

Evaluation of the biocompatibility of root canal sealers using subcutaneous implants

The purpose of this study was to evaluate in vivo the biocompatibility of Endométhasone, Pulp Canal Sealer EWT and AHPlus root canal sealers after implantation in rat connective tissue. Twenty-four Wistar-Furth rats were used. Polyethylene tubes were filled with the sealers and implanted into specific dorsal subdermal tissue sites of the rats. Implants were removed after 3, 7 and 30 days, fixed and processed for glycol methacrylate-embedding technique to be examined microscopically. On the 3rd day, there was a mild inflammatory reaction to Pulp Canal Sealer EWT implants, but a severe response to the other sealers with presence of acute inflammatory cells. On the 7th day, tissue organization was more evident with attenuation of the inflammatory reaction, especially for the AH-Plus implants. On the 30th day, connective tissue with few inflammatory cells was observed in contact with all sealer implants. In this time interval, the tissue in contact with Pulp Canal Sealer EWT implants was more organized, while the tissue close to Endométhasone and AH-Plus implants showed a mild persistent inflammatory reaction and had similar results to each other. In conclusion, the sealers had a similar pattern of irritation, which was more severe in the beginning and milder with time, in such a way that all sealers showed a persistent mild reaction. Pulp Canal Sealer EWT yielded better tissue organization than Endométhasone and AH-Plus, which, in turn, showed similar results to each other.

Compressive fatigue in titanium dental implants submitted to fluoride ions action

The aim of this study was to assess the influence of a fluoridated medium on the mechanical properties of an internal hexagon implant-abutment set, by means of compression, mechanical cycling and metallographic characterization by scanning electronic microscopy. Five years of regular use of oral hygiene with a sodium fluoride solution content of 1500 ppm were simulated, immersing the samples in this medium for 184 hours, with the solutions being changed every 12 hours. Data were analyzed at a 95% confidence level with Fisher's exact test. After the action of fluoride ions, a negative influence occurred in the mechanical cycling test performed in a servohydraulic machine (Material Test System-810) set to a frequency of 15 Hz with 100,000 cycles and programmed to 60% of the maximum resistance of static compression test. The sets tended to fracture by compression on the screw, characterized by mixed ruptures with predominance of fragile fracture, as observed by microscopy. An evidence of corrosion by pitting on sample surfaces was found after the fluoride ions action. It may be concluded that prolonged contact with fluoride ions is harmful to the mechanical properties of commercially pure titanium structures.

Immediate X delayed loading dental implants: An overview

The aim of this investigation was to accomplish an overview about the principles of the indication and of the success parameters involving immediate and delayed loading dental implants procedures. Studies about the philosophies (immediate and delayed loading dental implants) and their clinical indications will be discussed in order to overview the rules for the clinical success in both techniques. In addition, studies regarding the criteria for immediate loading implants as primary stabilization, surface treatments and bone density and amount will be also analyzed. More important than the philosophy selection, is how and when to use it according to biomechanical rules and principles. Among the vast limitations pointed by the literature regarding procedures of immediate and delayed loading are evidenced the parafunctional habits, primary stabilization, bone quality, surface treatments and the number of dental implants. The anterior region of the jaw seems to be associated with a major percentage of satisfactory results, regardless of rehabilitation procedures. Although several studies have demonstrated high success rates for the immediate loading dental implants, several aspects remain without an explicit definition and further studies are needed to elucidate some reservations.