Bone reformation and implant integration following maxillary sinus membrane elevation: An experimental study in primates

Background: Recent clinical studies have described maxillary sinus floor augmentation by simply elevating the maxillary sinus membrane without the use of adjunctive grafting materials. Purpose: This experimental study aimed at comparing the histologic outcomes of sinus membrane elevation and simultaneous placement of implants with and without adjunctive autogenous bone grafts. The purpose was also to investigate the role played by the implant surface in osseointegration under such circumstances. Materials and Methods: Four tufted capuchin primates had all upper premolars and the first molar extracted bilaterally. Four months later, the animals underwent maxillary sinus membrane elevation surgery using a replaceable bone window technique. The schneiderian membrane was kept elevated by insertion of two implants (turned and oxidized, Brånemark System®, Nobel Biocare AB, Göteborg, Sweden) in both sinuses. The right sinus was left with no additional treatment, whereas the left sinus was filled with autogenous bone graft. Implant stability was assessed through resonance frequency analysis (Osstell™, Integration Diagnostics AB, Göteborg, Sweden) at installation and at sacrifice. The pattern of bone formation in the experimental sites and related to the different implant surfaces was investigated using fluorochromes. The animals were sacrificed 6 months after the maxillary sinus floor augmentation procedure for histology and histomorphometry (bone-implant contact, bone area in threads, and bone area in rectangle). Results: The results showed no differences between membrane-elevated and grafted sites regarding implant stability, bone-implant contacts, and bone area within and outside implant threads. The oxidized implants exhibited improved integration compared with turned ones as higher values of bone-implant contact and bone area within threads were observed. Conclusions: The amount of augmented bone tissue in the maxillary sinus after sinus membrane elevation with or without adjunctive autogenous bone grafts does not differ after 6 months of healing. New bone is frequently deposited in contact with the schneiderian membrane in coagulum-alone sites, indicating the osteoinductive potential of the membrane. Oxidized implants show a stronger bone tissue response than turned implants in sinus floor augmentation procedures. © 2006 Blackwell Publishing, Inc.

A new device in immediately loaded implant treatment in the edentulous mandible

Purpose: This article reports preliminary clinical results of the Speed Master system, a method for immediate loading of implants for the treatment of mandibular edentulism. Materials and Methods: Fifteen patients with edentulous mandibles were consecutively included in the study. Each received 4 implants between the mental foramina placed using the system's surgical guides. Permanent fixed prostheses fabricated over premanufactured titanium bars were attached to the implants on the day of implant placement. The patients were followed for 15 to 27 months (mean, 19 months). Peri-implant tissues were periodically evaluated. Marginal bone loss was monitored with periapical radiographs using a computerized technique. Satisfaction was assessed by means of a questionnaire. Results: The overall implant and prosthetic survival rates were 100%. At the time of the final follow-up visit, mean marginal bone loss was 1.11 mm, and bleeding on probing was not observed. Only 6.7% of the patients reported any discomfort during treatment, and all patients would recommend the procedure to others. Discussion: The immediate loading of implants placed in the edentulous mandible with the Speed Master surgical and prosthetic protocol reduces treatment time and number of surgical procedures in comparison to classic delayed loading protocols. Conclusion: The rehabilitation of the mandible with an immediately delivered occlusally loaded hybrid prosthesis supported by 4 implants does not appear to jeopardize the success of the osseointegration and represents a viable treatment option.

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.

Influence of length and diameter of implants associated with distal extension removable partial dentures

PURPOSE

Accuracy of impression techniques for implants. Part 1 - Influence of transfer copings surface abrasion

Purpose: This study evaluated the influence of surface abrasion of transfer copings to obtain a precise master cast for a partially edentulous restoration with different inclinations. Materials and Methods: Replicas (N = 30) of a metal matrix (control group) containing two implants at 90° and 65° in relation to the benchtop were obtained using a polyether impression material and three impression techniques: square impression copings splint with dental floss and autopolymerizing acrylic resin (TRS), square impression copings abraded with aluminum oxide (TA), and square impression copings abraded with aluminum oxide and adhesive-coated (TAA). The replicas obtained in type V stone were digitalized, and the images were exported to AutoCAD software to perform the readings of possible degree alterations in implant inclinations. The results were submitted to analysis of variance (ANOVA) and Tukey test (α < 0.05). Results: Comparing the techniques with regard to the 90° implant inclination, no statistical difference was observed between the three techniques and the control group. Analyzing the three techniques with regard to the 65° implant inclination, no significant difference was seen between technique TA and the control group. Conclusions: Technique TA presented more accurate master casts than TRS and TAA techniques. The angulated implant (65°) tended to generate more imprecise master casts than implants perpendicular to the surface. © 2008 by The American College of Prosthodontists.

In vivo evaluation of porous titanium implants with biomimetic coating

The osseointegration of porous titanium implants was evaluated in the present work. Implants were fabricated from ASTM grade 2 titanium by a powder metallurgy method. Part of these implants were submitted to chemical and thermal treatment in order to deposit a biomimetic coating, aiming to evaluate its influence on the osseointegration of the implants. The implants were characterized by Scanning Electron Microscopy (SEM), Electron Dispersive X-Ray Spectroscopy (EDS) and Raman Spectroscopy. Three coated and three control (uncoated) implants were surgically inserted into thirty albino rabbits' left and right tibiae, respectively. Tibiae samples were submitted to histological and histomorphometric analyses, utilizing SEM, optical microscopy and mechanical tests. EDS results indicated calcium (Ca) and phosphorous (P) at the surface and Raman spectra exhibited an intense peak, characteristic of hydroxyapatite (HA). Bone neoformation was detected at the bone-implant interface and inside the pores, including the central ones. The mean bone neoformation percentage in the coated implants was statistically higher at 15 days, compared to 30 and 45 days. The mechanical tests showed that coated implants presented higher resistance to displacement, especially after 30 and 45 days.

Biological response to wollastonite doped α-tricalcium phosphate implants in hard and soft tissues in rats

The biological response following subcutaneous and bone implantation of β-wollastonite(β-W)-doped α-tricalcium phosphate bioceramics in rats was evaluated. Tested materials were: tricalcium phosphate (TCP), consisting of a mixture of α- and β-polymorphs; TCP doped with 5 wt. % of β-W (TCP5W), composed of α-TCP as only crystalline phase; and TCP doped with 15 wt. % of β-W (TCP 15), containing crystalline α-TCP and β-W. Cylinders of 2×1 mm were implanted in tibiae and backs of adult male Rattus norvegicus, Holtzman rats. After 7, 30 and 120 days, animals were sacrificed and the tissue blocks containing the implants were excised, fixed and processed for histological examination. TCP, TCP5W and TCP15W implants were biocompatible but neither bioactive nor biodegradable in rat subcutaneous tissue. They were not osteoinductive in connective tissue either. However, in rat bone tissue β-W-doped α-TCP implants (TCP5W and TCP 15W) were bioactive, biodegradable and osteoconductive. The rates of biodegradation and new bone formation observed for TCP5W and TCP15W implants in rat bone tissue were greater than for non-doped TCP.

A modified method of immediate occlusal loading using a reinforced framework denture: A case report

The technique presented in this article presents a protocol for treatment that reduces the time required for the fabrication and placement of an implant supported prosthesis. It also offers improved patient comfort at a lower cost when compared to conventional technology.

Histological findings following the use of a space-making device for bone reformation and implant integration in the maxillary sinus of primates

Background: Previous studies have shown that membrane elevation results in predictable bone formation in the maxillary sinus provided that implants can be placed as tent poles. In situations with an extremely thin residual crest which impairs implant placement, it is possible that a space-making device can be used under the sinus membrane to promote bone formation prior to placement of implants. Purpose: The present study was conducted to test the hypothesis that the use of a space-making device for elevation of the sinus membrane will result in predictable bone formation at the maxillary sinus floor to allow placement of dental implants. Materials and Methods: Eight tufted capuchin primates underwent bilateral sinus membrane elevation surgery, and a bioresorbable space-making device, about 6 mm wide and 6 mm in height, was placed below the elevated membrane on the sinus floor. An oxidized implant (Nobel Biocare AB, Gothenburg, Sweden) was installed in the residual bone protruding into the created space at one side while the other side was left without an implant. Four animals were sacrificed after 6 months of healing. The remaining four animals received a second implant in the side with a space-making device only and followed for another 3 months before sacrifice. Implant stability was assessed through resonance frequency analysis (RFA) using the Osstell™ (Osstell AB, Gothenburg, Sweden) at installation, 6 months and 9 months after the first surgery. The bone-implant contact (BIC) and bone area inside the threads (BA) were histometrically evaluated in ground sections. Results: Histologically there were only minor or no signs of bone formation in the sites with a space-making device only. Sites with simultaneous implant placement showed bone formation along the implant surface. Sites with delayed implant placement showed minor or no bone formation and/or formation of a dense fibrous tissue along the apical part of the implant surface. In the latter group the apical part of the implant was not covered with the membrane but protruded into the sinus cavity. Conclusions: The use of a space-making device, with the design used in the present study, does not result in bone formation at the sinus floor. However, membrane elevation and simultaneous placement of the device and an implant does result in bone formation at the implant surface while sites with implants placed 6 months after membrane elevation show only small amounts of bone formation. It is suggested that lack of stabilization of the device and/or a too extensive elevation of the membrane may explain the results. © 2009, Wiley Periodicals, Inc.

SEM-EDS and biomechanical evaluation of implants with different surface treatments: An initial study

Aim: Alterations in implant surfaces can affect periimplant bone formation and shorten the healing time. The goal of the present study was a comparative scanning electron microscopy (SEM)/energy dispersive spectrometry (EDS) and biomechanical evaluation of implants subjected to different surface treatments. Materials and Methods: Four implant surfaces were analyzed in the present study: machined commercial implants (TU); porous-surfaced commercial implants blasted with Al2O3 microspheres and acid-etched (TJA); laser beam-irradiated experimental implants (Laser) and laser beam-irradiated experimental implants with hydroxyapatite coating (HA). One sample for each surface underwent pre-surgery SEM/EDS analysis. Thirty-two implants (8 for each surface treatment) were then inserted into the tibia of 4 rabbits. After 8 weeks, the animals were euthanized and the implants retrieved by reverse torque and processed for post-surgery SEM/EDS analysis. Results: HA implants presented higher removal torque values when compared to Laser, TJA and TU groups. Post-surgery SEM micrographs clearly showed bone formation on all the examined surfaces; however, in the TU group bone covered only some areas of the implant surface, while in TJA, Laser and HA groups the entire implant surfaces were overlaid by newly formed bone. EDS analysis supported the results obtained by SEM and removal torque, showing that concentration of Ca and P increased from TU to TJA, Laser and HA implants. Conclusions: Implants with surfaces modified by laser beam with or without apatite coating showed more promising results.

Influence of implant positioning in extraction sockets on osseointegration: Histomorphometric analyses in dogs

Aim: To evaluate the influence of implant positioning into extraction sockets on osseointegration. Material and methods: Implants were installed immediately into extraction sockets in the mandibles of six Labrador dogs. In the control sites, the implants were positioned in the center of the alveolus, while in the test sites, the implants were positioned 0.8 mm deeper and more lingually. After 4 months of healing, the resorptive patterns of the alveolar crest were evaluated histomorphometrically. Results: All implants were integrated in mineralized bone, mainly composed of mature lamellar bone. The alveolar crest underwent resorption at the control as well as at the test sites. After 4 months of healing, at the buccal aspects of the control and test sites, the location of the implant rough/smooth limit to the alveolar crest was 2±0.9 mm and 0.6±0.9 mm, respectively (P<0.05). At the lingual aspect, the bony crest was located 0.4 mm apically and 0.2 mm coronally to the implant rough/smooth limit at the control and test sites, respectively (NS). Conclusions: From a clinical point of view, implants installed into extraction sockets should be positioned approximately 1 mm deeper than the level of the buccal alveolar crest and in a lingual position in relation to the center of the alveolus in order to reduce or eliminate the exposure above the alveolar crest of the endosseous (rough) portion of the implant. © 2009 John Wiley & Sons A/S.

Influence of high insertion torque on implant placement - an anisotropic bone stress analysis

The aim of this study was to evaluate the influence of the high values of insertion torques on the stress and strain distribution in cortical and cancellous bones. Based on tomography imaging, a representative mathematical model of a partial maxilla was built using Mimics 11.11 and Solid Works 2010 softwares. Six models were built and each of them received an implant with one of the following insertion torques: 30, 40, 50, 60, 70 or 80 Ncm on the external hexagon. The cortical and cancellous bones were considered anisotropic. The bone/implant interface was considered perfectly bonded. The numerical analysis was carried out using Ansys Workbench 10.0. The convergence of analysis (6%) drove the mesh refinement. Maximum principal stress (σ max) and maximum principal strain (ε max) were obtained for cortical and cancellous bones around to implant. Pearson's correlation test was used to determine the correlation between insertion torque and stress concentration in the periimplant bone tissue, considering the significance level at 5%. The increase in the insertion torque generated an increase in the σ max and ε max values for cortical and cancellous bone. The σmax was smaller for the cancellous bone, with greater stress variation among the insertion torques. The ε max was higher in the cancellous bone in comparison to the cortical bone. According to the methodology used and the limits of this study, it can be concluded that higher insertion torques increased tensile and compressive stress concentrations in the periimplant bone tissue.