The International Journal of Oral & Maxillofacial Implants, 03/2011

Purpose: The purpose of this study was to investigate the cellular activities of MG63 osteoblast-like cells on modified titanium surfaces. Materials and Methods: MG63 osteoblast-like cells were cultured on titanium disks (n = 20 in each group) with turned, resorbable blast media (RBM)--treated, or anodized surfaces. The surfaces of commercially available implants of Osstem (Osstem Implant) were reproduced for the titanium disks. The morphology of cells cultured on these disks was examined using scanning electron microscopy. X-ray photoelectron spectroscopy (XPS) was employed for the analysis of surface chemistry. Specimens were also evaluated with an initial cell adhesion assay to compare initial adhesion, with a methyl tetrazol sulfate (MTS) assay to compare the proliferation ability, and with an alkaline phosphatase (ALP) assay to compare the differentiation ability. Statistical significance of the differences was determined using the Kruskal-Wallis test for the cell adhesion assay and analysis of variance for the MTS and ALP assays. Results: Attached cells with more defined lamellopodia and flattened morphology were observed on the anodized and RBM surfaces than on the turned surfaces. The titanium surfaces were all oxidized as titanium oxide and polluted by carbon determinants, as determined by XPS. Anodized titanium surfaces exhibited calcium and phosphorus peaks. Initial cell attachment activity, cell proliferation activity, and ALP activity were higher on the anodized surfaces than on the other surfaces. Cell differentiation on the anodized surfaces at culture day 10 was significantly higher (P .05) than on the other surfaces. Conclusions: Surface treatment by anodization may improve initial attachment of cells, proliferation ability, and differentiation activity, which play important roles in providing better osseointegration of implants. More rapid and stronger osseointegration of implants may make it possible to offer the best anchorage and shorten the healing time required prior to functional loading. Keywords: dental implants, surface properties, titanium, x-ray photoelectron spectroscopy

Purpose: The objective of this study was to evaluate, using three-dimensional finite element analysis (3D FEA), the stress distribution in peri-implant bone tissue, implants, and prosthetic components of implant-supported single crowns with the use of the platform-switching concept. Materials and Methods: Three 3D finite element models were created to replicate an external-hexagonal implant system with peri-implant bone tissue in which three different implant-abutment configurations were represented. In the regular platform (RP) group, a regular 4.1-mm-diameter abutment (UCLA) was connected to regular 4.1-mm-diameter implant. The platform-switching (PS) group was simulated by the connection of a wide implant (5.0 mm diameter) to a regular 4.1-mm-diameter UCLA abutment. In the wide-platform (WP) group, a 5.0-mm-diameter UCLA abutment was connected to a 5.0-mm-diameter implant. An occlusal load of 100 N was applied either axially or obliquely on the models using ANSYS software. Results: Both the increase in implant diameter and the use of platform switching played roles in stress reduction. The PS group presented lower stress values than the RP and WP groups for bone and implant. In the peri-implant area, cortical bone exhibited a higher stress concentration than the trabecular bone in all models and both loading situations. Under oblique loading, higher intensity and greater distribution of stress were observed than under axial loading. Platform switching reduced von Mises (17.5% and 9.3% for axial and oblique loads, respectively), minimum (compressive) (19.4% for axial load and 21.9% for oblique load), and maximum (tensile) principal stress values (46.6% for axial load and 26.7% for oblique load) in the peri-implant bone tissue. Conclusion: Platform switching led to improved biomechanical stress distribution in peri-implant bone tissue. Oblique loads resulted in higher stress concentrations than axial loads for all models. Wide-diameter implants had a large influence in reducing stress values in the implant system. Keywords: biomechanics, dental implants, finite element analysis, platform switching, prosthesis

Purpose: Polished and machined collars have been advocated for dental implants to reduce plaque accumulation and crestal bone loss. More recent research has suggested that a roughened titanium surface promotes osseointegration and connective tissue attachment. The purpose of this research was to compare crestal bone height adjacent to implants with laser-microtextured and machined collars from two different implant systems. Materials and Methods: Four implants, two with laser-microtextured collars and two with machined collars, were placed in the anterior mandible to serve as overdenture abutments. They were placed in alternating order, and the distal microtextured- and machined-collar implants were loaded with ball abutments. The mesial implants were left unloaded. The distal implants were immediately loaded with prefabricated dentures. Plaque Index, Bleeding Index, and probing depths (PDs) were measured after 6 and 12 months for the loaded implants. Bone loss for both groups (loaded and unloaded) was evaluated via standardized radiographs. Results: Plaque and bleeding values were similar for both implant types. The microtextured-collar implants showed shallower PDs (0.36 ± 0.5 mm and 0.43 ± 0.51 mm) than those with machined collars (1.14 ± 0.77 mm and 1.64 ± 0.93 mm; .05 for 6 and 12 months, respectively). At 6 and 12 months, respectively, the microtextured implants showed less crestal bone loss for both loaded (0.19 ± 0.15 mm and 0.42 ± 0.34 mm) and unloaded groups (0.15 ± 0.15 mm and 0.29 ± 0.20 mm) than the machined implants for both the loaded (0.72 ± 0.5 mm and 1.13 ± 0.61 mm) and unloaded groups (0.29 ± 0.28 mm and 0.55 ± 0.32 mm). Conclusion: Application of laser-microtextured grooves to the implant collar resulted in shallower PDs and less peri-implant crestal bone loss than that seen around implants with machined collars. Keywords: biologic width, crestal bone, implant collar, tissue engineering

Implant dentistry has come a long way since 1981, with great improvements made to achieve primary implant stability and improve bone-to-implant contact. The focus has since shifted toward creating an esthetic restoration that is indistinguishable from natural teeth and is stable over time. This paper proposes a management triad that enhances soft tissue thickness around implant-supported restorations while discussing distinct differences between thin and thick tissue biotypes. In addition, the effect of tissue biotype on implant esthetics is highlighted. Keywords: biologic width, implant esthetics, interproximal papilla, peri-implant mucosa

Purpose: To compare in vitro the attachment and proliferation of human osteoblast-like cells (MG63) on tissue culture plates and guided bone regeneration (GBR) membranes in the absence or presence of nicotine. Materials and Methods: Membrane samples were fixed to wells and the cell number (CN) was counted after 24 hours (attachment assay) or 5 days (proliferation assay). The ratio of cell count (RCC) (CN at 5 days/CN at 24 hours) was calculated. The study had three parts: First, five different resorbable GBR membranes were compared (Resolut Adapt LT [RALT], Biocollagen [BC], Bio-Gide [BG], OsseoGuard [OG], and Demokritos Human Tissue Bank [DEM]). Next, cells were cultured on tissue culture plates with five different concentrations of nicotine. Finally, cells were cultured on the membrane that had demonstrated the highest RCC and CN in part 1 with four different concentrations of nicotine. Results: At 24 hours, BG showed the highest CN and OG showed the lowest CN. At 5 days, BG showed the highest CN. The order of RCC was BG > OG > DEM > RALT ~ BC. At 24 hours, lower nicotine concentrations (0.3 and 3 µg/mL) showed higher CNs versus the control, whereas CNs for high nicotine concentrations (30 and 300 µg/mL) were lower than for the control. CN at 5 days and RCC were lowest with 300 µg/mL nicotine. At 24 hours and 5 days, all differences among wells with membrane were statistically insignificant. Nevertheless, CN at 5 days and RCC were highest with the lowest nicotine concentration (3 µg/mL) and lowest with high concentrations. Conclusions: Membrane materials influence attachment and proliferation of bone cells and, therefore, could affect the outcomes of GBR. On both tissue culture plates and membranes, there is a tendency toward a biphasic effect of nicotine, with stimulatory effects at low concentrations and inhibitory effects at high concentrations. Keywords: cell attachment, cell proliferation, guided bone regeneration, membrane, nicotine, osteoblast

Purpose: To determine and compare the accuracy of an advanced surgical template based on computer-aided design/computer-assisted manufacture (CAD/CAM) with the conventional surgical template in different respects such as entry point, length, and osteotomy angle. Materials and Methods: Computed tomography (CT) scanning of a dentate epoxy mandible was performed and its three-dimensional computerized model was simulated. Sixteen rapid-prototyped models were fabricated and divided into two groups. In the first group, a radiographic template was fabricated and placed on the model during CT scanning and then was modified to the conventional surgical template form. In the second group, a coordinate measuring machine was used to reformat a nonanatomic radiographic template fabricated by a stereolithographic machine, and four implants were planned and then placed in the jaw. The differences between planned and actual mesiodistal and buccolingual entry points, lengths, and angles of the implants were measured. Statistical analysis was performed with the Mann-Whitney and Friedman tests to detect differences between groups. Results: The average differences between the planned and actual entry points in the mesiodistal and buccolingual directions, lengths, and angles of the implants and the osteotomy showed a considerable reduction in the CAD/CAM group versus the conventional group (P .005). Conclusion: The accuracy of implant placement was improved using an innovative CAD/CAM surgical template. Keywords: computed tomography, computer-aided design, coordinate measuring machine, dental implants, stereolithography, surgical templates

Purpose: To provide a preliminary understanding of the biomechanics with respect to the effect of cusp inclination and occlusal loading on the mandibular bone remodeling. Materials and Methods: Three different cusp inclinations (0, 10, and 30 degrees) of a ceramic crown and different occlusal loading locations (central fossa and 1- and 2-mm offsets horizontally) were taken into account to explore the stresses and strains transferred from the crown to the surrounding dental bone through the implant. A strain energy density obtained from two-dimensional plane-strain finite element analysis was used as the mechanical stimulus to drive cancellous and cortical bone remodeling in a buccolingual mandibular section. Results: Different ceramic cusp inclinations had a significant effect on bone remodeling responses in terms of the change in the average peri-implant bone density and overall stability. The remodeling rate was relatively high in the first few months of loading and gradually decreased until reaching its equilibrium. A larger cusp inclination and horizontal offset (eg, 30 degrees and 2-mm offset) led to a higher bone remodeling rate and greater interfacial stress. Conclusions: The dental implant superstructure design (in terms of cusp inclination and loading location) determines the load transmission pattern and thus largely affects bone remodeling activities. Although the design with a lower cusp inclination recommended in previous studies may reduce damage and fracture failure, it could, to a certain extent, compromise bone engagement and long-term stability. Keywords: bone-implant interface, bone remodeling, cusp inclination, dental implant, occlusal load

Purpose: The purpose of this in vitro study was to compare the dimensional accuracy of the pickup impression technique using a modular individual tray (MIT) and using a standard individual tray (ST) for multiple internal-connection implants. The roles of both materials and geometric misfits were considered. Materials and Methods: First, because the MIT relies on the stiffness and elasticity of acrylic resin material, a preliminary investigation of the resin volume contraction during curing and polymerization was done. Then, two sets of specimens were tested to compare the accuracy of the MIT (test group) to that of the ST (control group). The linear and angular displacements of the transfer copings were measured and compared during three different stages of the impression procedure. Experimental measurements were performed with a computerized coordinate measuring machine. Results: The curing dynamic of the acrylic resin was strongly dependent on the physical properties of the acrylic material and the powder/liquid ratio. Specifically, an increase in the powder/liquid ratio accelerated resin polymerization (curing time decreases by 70%) and reduced the final volume contraction by 45%. However, the total shrinkage never exceeded the elastic limits of the material; hence, it did not affect the coping's stability. In the test group, linear errors were reduced by 55% and angular errors were reduced by 65%. Conclusions: Linear and angular displacements of the transfer copings were significantly reduced with the MIT technique, which led to higher dimensional accuracy versus the ST group. The MIT approach, in combination with a thin and uniform amount of acrylic resin in the pickup impression technique, showed no significant permanent distortions in multiple misalignment internal-connection implants compared to the ST technique. Keywords: acrylic resin, direct implant impression, implant connection, individual tray, pickup impression technique, splinted implant impression

Purpose: The objective of this study was to assess the use of ion beam polishing for preparing cross sections suitable for high-resolution scanning electron microscope (SEM) investigation of dental implants with a brittle porous oxide layer and of bone/implant interfaces. Materials and Methods: Thirteen Nobel Biocare TiUnite implants were placed in minipigs. After 4 weeks, the implant and surrounding bone were removed en bloc and the implant was cut axially into two halves. The cross section was then polished with an argon ion beam. Additionally, ion beam-polished cross sections were prepared from four as-received implants. Ion beam-polished surfaces were studied with a field emission SEM (FE-SEM). Results: With FE-SEM, up to 1 mm along the interface of ion beam-polished implant surfaces can be studied with a resolution of a few nanometers. Filled and unfilled pores of the porous TiUnite coating can be distinguished, providing information on pore accessibility. Implant-bone interfaces can be analyzed using backscattered electron images, where titanium, the oxide layer, mineralized extracellular matrix, and osteocyte lacunae/resin/soft tissue can easily be distinguished as a result of atomic number contrast and the sharp boundaries between the different materials. Filled and unfilled pores can be distinguished. Characterization of local chemistry is possible with energy dispersive X-ray spectrometry, and bone growth into small pores ( 1 µm) can be unambiguously confirmed. Conclusion: FE-SEM complements the established methods for the characterization of interfaces and bridges the wide gap in accessible length scale and resolution between the observations of mechanically polished interfaces by optical or scanning electron microscopes and the observation of focused ion beam-milled sections in a transmission electron microscope. Keywords: dental implant, interface, ion beam, osseointegration, surface properties

Purpose: Peri-implantitis is an inflammatory disease due to bacteria and plaque formation on implant surfaces which can lead to bone resorption and loss of osseointegration. Biomaterial strategies to prevent or eliminate initial bacterial attachment, in favor of host tissue attachment may have a positive effect on decreasing peri-implantitis, particularly for at risk patient goups. This study provides a brief overview of some of the experimental biomaterial strategies aimed at suppressing or inhibiting bacterial colonization of implant surfaces in favor or host cells and tissues. Materials and Methods: These biomaterial strategies have different mechanisms of action from interfering with bacterial adhesion by modifying surface energies, immobilizing antimicrobials on implant surfaces, creating photocatalytic surfaces, as well as modifying surfaces to deliver antimicrobial agents either prophylactically or in response to bacterial challenge. This is not a comprehensive review, rather a review of studies that serve to illustrate many of the different approaches being investigated. Results: While many of these strategies have demonstrated the potential to significantly reduce bacterial attachment on implant surfaces in vitro, it is unclear if these same reductions will be adequate clinically since even a few adhering bacteria may over time develop into inflammatory inducing biofilms or plaque. Also, data on the ability of the antibacterial modified biomaterials to support osseointegration and permuosal seal formation is still needed. Conclusion: Given the complex and multivariate causes of peri-implant disease, it is likely that combinations of these strategies (eg, antimicrobial surfaces and or delivery mechanisms coupled with methods to favor stable osseointegration and permucosal seal) will be most effective in developing implants resistant to peri-implant disease. Keywords: antimicrobial, biomaterials, dental implants, peri-implantitis, peri-mucositis, surfaces

Purpose: Anorganic bovine hydroxyapatite matrix (ABM), when coupled with synthetic cell-binding peptide (P15), mimics the cell-binding region of type 1 collagen and is commercially available suspended in a sodium hyaluronate carrier. The aim of the present study, therefore, was to test the efficacy of ABM/P-15 Putty (DENTSPLY Friadent CeraMed) as a sole graft material for sinus augmentation in patients with severely resorbed posterior maxillae. Materials and Methods: Sinus augmentation was performed in 10 patients using ABM/P-15 Putty and two provisional dental implants (3.0 mm in diameter). The graft and implants were placed simultaneously with the aid of a surgical stent. After 8 or 16 weeks, the implants were removed using a 4.25-mm trephine bur; this was followed by immediate placement of wider-diameter (5.5-mm) implants. All 20 implants were scanned by microcomputed tomography to determine bone mineral density (BMD), percent bone volume (PBV), and percent bone contact (PBC). Results: There was a significant increase in the BMD of bone around the implants at 8 weeks and 16 weeks compared to native residual (control) bone. There was no significant difference in PBV or PBC between 8 weeks and 16 weeks. The average increase in bone height at 16 weeks was 9.63 ± 1 mm. Microcomputed tomographic images and histologic sections showed dense graft particles surrounded by vital trabecular bone. Conclusion: BMD increases as early as 8 weeks and does not show an additional increase after 16 weeks. PepGen P-15 Putty was found to be a promising osteoconductive graft for sinus augmentation, supporting immediate placement of implants. Keywords: anorganic bone matrix, cell-binding peptide, microcomputed tomography, sinus augmentation

Purpose: The aim of this study was to evaluate changes in subjective oral health among patients receiving single dental implants in different anatomic locations. Materials and Methods: Subjective oral health was surveyed with the Oral Health Impact Profile 14 (OHIP-14) questionnaire after implant placement but prior to uncovering and 3 months after the completion of treatment. The locations of the implants and age and gender of the patients were recorded. Mean OHIP-14 severity scores were compared before and after treatment (paired t test). Results: Ninety consecutive self-referred patients were enrolled in the study, and 80 of them (28 men and 52 women) completed the OHIP-14 both before and after treatment. The mean age of the patients at the time of surgery was 52 years (range, 24 to 75 years). The patients received a total of 131 commercially available dental implants (Astra Tech) and appropriate prosthetic constructions. The mean OHIP-14 severity score decreased significantly, from 10.4 before treatment to 3.1 after treatment (P .001). The drop was from 13.4 to 1.5 (P .001) if the missing tooth was replaced with an implant in the anterior area, from 11.2 to 4.3 (P .001) if it was replaced in the premolar area, and from 6.5 to 3.0 (P = .085) if it was replaced in the molar area. In general, both before and after treatment, women reported subjective oral impacts approximately three times more often than men did. Conclusion: Replacement of missing teeth with single dental implants in anterior and premolar areas, but not necessarily in molar areas, may significantly improve subjective oral health, especially among women. Keywords: oral health-related quality of life, single implants, subjective oral health

Purpose: The appearance of the peri-implant soft tissue is a crucial factor in the success of implant therapy. However, no effective objective method exists to observe and document this factor over the long term. The aim of this clinical trial was to determine whether oral photographs can be used for peri-implant soft tissue data collection by observing peri-implant soft tissue alterations after placement of a single-tooth implant in the esthetic zone and to determine whether the pink esthetic score (PES) reflects patient satisfaction with the peri-implant soft tissue esthetic result. Materials and Methods: Twenty-eight consecutive patients received single implants in the esthetic zone. Clinical photographs were taken to collect data on the peri-implant soft tissue at baseline (crown placement) and again 3 months later. Two observers assigned PES values to the peri-implant soft tissue in the photographs. Changes in the PES value from baseline to the 3-month follow-up were calculated. Patient satisfaction was measured using a visual analog scale (VAS) at the 3-month follow-up appointment. The correlation between the VAS and PES scores was calculated. Results: The mean PES value (± SD) was 8.68 ± 2.69 at baseline and 10.37 ± 2.13 at follow-up (P .01). VAS values ranged from 72.5 to 100. A significant correlation was found between VAS and PES values. The linear regression of patient satisfaction and PES values was significant. Conclusions: Oral photographs can be used to collect PES data on peri-implant soft tissue. The esthetic result of peri-implant soft tissue is markedly improved 3 months after restoration of the implant with a porcelain-fused-to-metal crown. The PES value generally reflects the degree of patient satisfaction with the peri-implant soft tissue esthetic result. Keywords: esthetic zone, oral photograph, patient satisfaction, pink esthetic score, single-tooth implant

Purpose: The purpose of this retrospective investigation was to evaluate the influence on the adjacent cervical bone of moving the implant-abutment microgap inward from the outer edge of an internal-hex implant platform (ie, a platform-switched configuration). Materials and Methods: A convenience sample of 26 patients received 42 Frialit-2 (Dentsply-Friadent) implants for single tooth replacement and were divided into two groups. One group followed the original protocol (control group), and the other (study group) received narrower replaceable components. Follow-up time varied between 6 and 60 months (mean, 33.45 months). Results: The control group showed noticeable bone remodeling (mean bone loss = 2.30 mm), and all the remodeled crests were apical to the implant platform. In contrast, all patients in the study (platform-switched) group showed stable levels (mean bone loss = 0.27) of the peri-implant crestal bone, coronal to the implant platform. Conclusion: The relocation of the implant-abutment microgap through platform switching with Frialit-2 System implants seems to be an effective means to minimize marginal bone loss in all circumstances employed. Keywords: marginal bone level, peri-implant bone loss, platform switching

Purpose: The present paper demonstrates a new technique and long-term results of a treatment concept that uses four implants placed in the anterior mandible that are connected to prefabricated telescopic abutments and immediately loaded with removable restorations. Materials and Methods: The present retrospective study included 488 implants (Ankylos, Dentsply) placed in 122 patients (mean age: 65.2 ± 9.8 years) with clinical and radiographic evaluation for a period of at least 1 year. Eighty-four implants were placed in fresh extraction sockets and combined in the restorations with implants placed in healed ridges. All implants were placed 2 mm subcrestally (based on chart documentation, measured from the midfacial bone level). The implants were connected immediately after surgery to conical prefabricated abutments (angle of 4 to 6 degrees) using a final torque of 15 Ncm. Secondary prefabricated copings that fit the abutments were placed over the abutments after abutment connection, and the complete denture of each patient was relined chairside with methyl methacrylate resin. The prosthetic restorations were to remain in place for 10 days to ensure that the implants remained immobile. Results: After a mean of 79 ± 29.8 months (range, 17 to 129 months) only eight implants failed (1.6%). Twenty-one implants (4.3%) showed crestal bone loss greater than 2 mm relative to the implant position at the time of implant insertion. Therefore, the failure rate was 5.94% for the entire observation period. The success rate for the evaluated implants was 94.06%. The patients were satisfied with the stability of their prostheses, and no prosthetic or peri-implant problems were observed. Conclusions: These telescopic implant-supported restorations with immediate loading seem to be an alternative prosthetic solution for the edentulous patient, providing long-term implant stability. Keywords: dental implant, prosthesis, telescopic attachments

Purpose: Implant success, peri-implant conditions, and prosthodontic maintenance requirements were evaluated and compared for mandibular overdentures supported by two implants and retained with ball or resilient telescopic crown attachments during a 5-year period. Materials and Methods: Twenty-five patients with an edentulous mandible each received two root-form dental implants in the mandibular interforaminal (canine) region. The type of denture attachment was chosen randomly; 13 patients received ball attachments and 12 patients received resilient telescopic crowns. Implant success and peri-implant conditions (bone resorption, pocket depth, Plaque Index, Gingival Index, Bleeding Index) as well as prosthodontic maintenance and patient satisfaction were evaluated annually during a 5-year follow-up period and compared with respect to the two retention modalities used. Results: Implant success, peri-implant conditions, and subjective patient satisfaction scores did not differ between the two retention modalities used. However, during the 5-year observation period, significantly more postinsertion complications/interventions for maintenance purposes were registered in the ball group (87 interventions, 61.1%) than in the telescopic crown group (53 interventions, 37.9%; P .01). Differences in prosthodontic maintenance efforts were most significant in the second and third years (P .05) of the follow-up period but were similar at the end of the study for both anchorage systems. Conclusion: Both ball attachments and resilient telescopic crowns on isolated implants in the atrophic mandible are viable treatment options for implant-supported overdentures. No implant losses, good peri-implant conditions, and general patient satisfaction were noted. Although the frequency of technical complications was initially higher with ball attachments than with resilient telescopic crowns over a 5-year period, similar frequencies of maintenance efforts may be anticipated for both retention modalities. Keywords: ball anchors, implant-retained prostheses, mandibular overdentures, prosthodontic maintenance, telescopic crowns

Purpose: Since the introduction of endosseous dental implants, the treatment concepts for management of the edentulous mandible have changed drastically. Reconstructive, preprosthetic surgery has changed from surgery aimed to provide a sufficient osseous and mucosal support for a conventional denture into surgery aimed to provide a sufficient bone volume enabling placement of dental implants at the, from a prosthetic point of view, optimal position. Moreover, the currently applied implant based prosthodontic concepts for the edentulous mandible are based on prospective randomized clinical trials comparing the treatment outcome of a variety of treatment modalities. This study reviews the various treatment concepts that are currently in use to rehabilitate the extremely atrophied mandible. Materials and Methods: A comprehensive review of human studies published in the international peer-reviewed literature up to March 2010 regarding procedures related to implant treatment in the extremely atrophied edentulous mandible was made. A MEDLINE search was completed, along with a manual search, to locate relevant literature. Results: There are advantages and disadvantages that are specific to removable implant-supported overdentures and fixed implant-supported full prostheses. The choice of an overdenture or a fixed full-arch prosthesis should be made on an individual basis. Once this choice has been made, the surgical procedure and the number of implants to be placed have to be determined. Conclusion: On the basis of the best evidence currently available, a treatment concept is proposed on how to deal with the edentulous mandible in order to provide patients with a mandibular overdenture supported by endosseous implants. Keywords: atrophied mandible, bone augmentation, bone resorption, dental implant, denture problems, review

Purpose: This study sought to determine whether there was a correlation between bone resorption and individual bone patterns in patients treated with implants restored conventionally or using the platform-switching concept. Materials and Methods: Ten patients (24 implants) were randomly assigned to receive implants with different platform diameters (3.8, 4.3, 4.8, or 5.5 mm), all of which were restored with standard 3.8-mm-diameter abutments. Biopsy specimens were obtained prior to implant placement, and histologic and immunohistochemical analyses were performed. Standardized radiographs were made at each site after implant placement and at 36 months after prosthetic loading and bone levels were determined. Results: One patient dropped out, resulting in a total of 9 patients and 22 implants. Mean bone resorption was 1.358 mm for non-platform-switched implants; mean resorption was 0.832, 0.486, and 0.375 mm for implant platforms of 4.3, 4.8, and 5.5 mm, respectively. After standardization of peri-implant bone remodeling values, a borderline direct correlation between peri-implant bone changes and levels of biglycans was found. At the same time, a borderline indirect correlation between bone changes and levels of tumor necrosis factor-α was found. Conclusions: Within the limit of this study, which was conducted in a small patient sample over a short observation period, an individual resorption trend was detected and paralleled by immunohistochemical findings. Individual local bone structure and quality seemed to be correlated to peri-implant bone resorption. Correlations between biglycan and tumor necrosis factor-α and bone resorption should be confirmed by a larger patient sample. Keywords: biglycans, bone biomarkers, bone level, bone loss, dental implants, implant design, platform switching, tumor necrosis factor-α

Purpose: A single-blind randomized controlled split-mouth trial was performed to compare the 36-month outcomes of machined and titanium oxide-anodized (ADZ) dental implant surfaces immediately loaded with fixed partial dentures in the posterior mandible. Materials and Methods: Ten patients with bilateral partial edentulism in the posterior mandible received 42 implants; 20 were placed on the test side (ADZ) and 22 were placed on the control (machined) side. The implants were loaded within 24 hours after placement. Changes in the radiographic bone level (RBL) were measured on standardized periapical films at baseline, 12 months, and 36 months. The mean changes in RBL were compared using a paired t test, and the mean changes in RBL with regard to implant position and implant surface type were compared via two-way analysis of variance. Results: After 36 months of functional loading, the overall cumulative success rate for all implants was 95%. The mean change in RBL at 36 months was 0.35 mm and 0.32 mm for ADZ and machined implants, respectively (not statistically significantly different between groups; P = .88). A reduction in RBL was observed for both machined and ADZ implants between 12 and 36 months, but only the machined implants demonstrated a statistically significant decrease in RBL during the observation period. Conclusions: No statistically significant differences in RBL change were found between machined and ADZ implant surfaces after 36 months in function, and both surfaces demonstrated minimal marginal bone remodeling. As such, immediate loading of ADZ and machined dental implants supporting fixed partial dentures may be a suitable long-term treatment option in the posterior mandible. Keywords: dental implant, immediate loading, machined surface, partially edentulous mandible, randomized controlled trial, titanium oxide surface

Purpose: The aim of this retrospective study was to evaluate the outcomes, after 5 years of functional loading, of four different types of implants supporting prostheses in the posterior maxilla and mandible. Materials and Methods: Patients missing posterior teeth were treated with implants between 1998 and 2004. The implants were evaluated by clinical and radiographic parameters and Plaque Index, Sulcus Bleeding Index (BI), peri-implant probing depths (PD), and marginal bone loss (MBL) were recorded. Repeated-measures analysis of variance, Kruskal-Wallis, and Wilcoxon signed rank tests were used for statistical analysis. Results: In all, 244 implants were placed in 83 patients: 86 Straumann implants, 35 Swiss Plus implants, 90 Camlog implants, and 33 Frialit implants. Patients received 93 single crowns and 71 fixed partial dentures (FPDs). Nine FPDs were cemented to both implants and natural teeth, and 62 FPDs were supported by implants only. At the 5-year recall, plaque accumulation was significantly higher than at baseline for all groups (P = .01). Mean PD was 1.8 mm in the maxilla and 1.6 mm in the mandible. The mean PD values were 1.77 ± 0.52 mm for Straumann, 1.87 ± 0.64 mm for Swiss Plus, 2.33 ± 0.58 mm for Camlog, and 2.29 ± 0.46 mm for Frialit. MBL was 0.19 ± 0.07 mm for Straumann, 0.27 ± 0.06 mm for Camlog, 0.26 ± 0.07 mm for Swiss Plus, and 0.24 ± 0.07 mm for Frialit. The mean MBL of Straumann implants was significantly lower than that seen in the other groups (P = .001). Conclusion: The four types of implants resulted in similar clinical success after 5 years. Keywords: osseointegration, partial edentulism, posterior mandible, posterior maxilla, titanium implants

Purpose: To analyze maintenance service of fixed maxillary prostheses and overdentures based on conventional gold bars or titanium bars and frameworks fabricated with computer-aided design/computer-assisted manufacture (CAD/CAM) technology. Materials and Methods: Forty-one patients participated; 16 received an implant overdenture with a gold bar (gold OD), 12 received a CAD/CAM-fabricated implant OD with a titanium bar (Ti OD), and 13 received a CAD/CAM implant-supported fixed prosthesis (IFP). The bars and frameworks were screw-retained at the implant level. Maintenance service performed during the first 2 years was recorded and compared between the three groups. After this 2-year period, the Oral Health Impact Profile (OHIP) was administered. Results: For ODs (gold, Ti) most service consisted of activation of the matrices. Fractures of matrices and bar extensions occurred only in the gold OD group, and 65% of these patients exhibited hyperplasia of the peri-implant mucosa. The maintenance rates were 1.24 (gold OD), 1.36 (Ti OD), and 0.98 (IFP). These differences were not statistically significant. Retightening of occlusal screws was not necessary in any group. The probability that a complication occurred in the first year was high (60% to 70%) and statistically not different between the three groups. The probability that a second complication occurred was significantly lower for the IFP group versus the gold OD group. The mean OHIP values were 1.7 (IFP), 6.7 (gold OD), and 7.3 (Ti OD); ratings in the IFP group were significantly better. Conclusions: Maintenance service was typical for implant prostheses in the edentulous maxilla. Direct screw retention at the implant level without abutments had a favorable effect in all groups. A trend toward a reduction in problems was observed with the CAD/CAM superstructures. The OHIP confirmed high satisfaction, but quality of life appeared to be slightly higher with fixed prostheses. Keywords: computer-aided design/computer-assisted manufacture, edentulous maxilla, fixed prosthesis, overdenture, prosthetic maintenance

Purpose: Retrievability, connecting strength, and ease of laboratory work are important but conflicting prerequisites for the success of an implant superstructure, particularly with regard to immediate function. To resolve this issue, a telescopic magnetic attachment system has been developed for implant-supported removable dentures. The splinting effect of the attachment was evaluated for stress distribution and elevation with an in vitro model of three implants in an edentulous mandible. Materials and Methods: Two types of telescopic magnetic attachments were prepared; the inclination angles of the axial wall of the abutment were 2.5 and 6.0 degrees. Three types of three-unit superstructures-a screw-retained superstructure and two telescopic magnet-retained superstructures-were fabricated. Static loads of 24.5, 49, and 98 N were applied vertically at three loading points on one side of each occlusal table. The elevation was measured as the height at which the magnet-retained superstructure detached from the abutment (on the other side of the prosthesis). In addition, by means of strain gauges, the stress distribution around the implants was evaluated and compared among the superstructures with the same three loads applied at six different points. Results: The magnet-retained superstructure with the axial wall inclined at 2.5 degrees did not detach from the abutment. The differences in stress distribution between the screw-retained and magnet-retained superstructures with a 2.5-degree inclination were found to be statistically insignificant. The magnet-retained superstructure with a 6-degree inclination detached from the abutment, and the stress was concentrated during loading to a cantilever site. Conclusion: Because of its stress distribution and elevation, the new telescopic magnetic attachment, which has properties such as splinting the implants, ease of fabrication, and retrievability, is expected to be a viable alternative for the retention of implant-supported removable dentures. Keywords: implant, magnetic attachment, splint effect, stress distribution, telescopic

Purpose: To report on the clinical outcome of 150 extrasinus zygomatic implants placed lateral to the maxillary sinus and combined with conventional implants in the anterior maxilla for the implant-supported rehabilitation of the edentulous maxilla. Materials and Methods: All patients included in this study presented with completely or partially edentulous maxillae with any remaining teeth indicated for extraction. Indications for extractions in partially edentulous patients included longitudinal fractures, periodontal disease, endodontic failure, perforated roots, and prosthetic convenience. All patients showed severe resorption of the posterior maxilla. Each patient was treated with at least four implants, with a minimum of one zygomatic implant. No bone grafting was performed. The zygomatic implants were placed outside the sinus, lateral to the maxillary sinus. The patients were followed with standardized clinical and radiographic examinations. Results: Seventy-five patients with severely atrophic maxillae (mean age, 52 years) were treated between 2003 and 2006. In all, 436 implants (150 zygomatic implants and 286 conventional implants) were placed. Two conventional implants failed during the study period, and two zygomatic implants were removed. All the prostheses were successful. No patients presented sinusitis. No loosened or fractured screws on any implants were recorded. Conclusion: Extrasinus zygomatic implants, when combined with conventional implants in the anterior maxilla, represent a predictable treatment option for the atrophic edentulous maxilla. Further studies are necessary to evaluate the long-term prognosis of these implants. Keywords: atrophic maxilla, dental implants, maxillary sinus, zygomatic implants