The International Journal of Oral & Maxillofacial Implants, 04/2012

The topographic and physicochemical features of implant surfaces influence the process of osseointegration. The biologic properties of implant surfaces have been considered to remain stable over time, ie, the capability of osseointegration of implant surfaces presumably does not change over time after manufacturing. However, recent reports have demonstrated that titanium surfaces undergo a progressive change in their biologic characteristics over time, resulting in a significant decrease in osseointegration capability. In comparison to newly prepared titanium surfaces, 4-week-old titanium surfaces (ie, stored for 4 weeks after processing) required more than twice as much healing time to achieve a similar strength of osseointegration. The boneimplant contact percentage for the 4-week-old surfaces was less than 60%, as opposed to more than 90% for the new surfaces. In vitro, the 4-week-old surfaces showed only 20% to 50% of the levels of recruitment, attachment, settlement, and proliferation of osteogenic cells versus new surfaces. On the other hand, a series of recent papers reported the generation of highly cell-attractive and osteoconductive titanium surfaces by ultraviolet (UV) light treatment. The phenomenon, defined as photofunctionalization, caused a fourfold acceleration in the process of osseointegration and resulted in nearly 100% bone-implant contact. Remarkably enhanced behavior and response of osteogenic cells around UV-treated surfaces exceeded the levels observed for the newly prepared surfaces. These studies indicated that UV treatment reverses the time-dependent biologic degradation of titanium and even enhances the surface beyond its innate potential. The present paper summarizes the findings about the aging-like time-dependent biologic degradation of titanium surfaces as well as about the discovery of UV photofunctionalization as a solution for this phenomenon. It also provides a novel understanding of osseointegration and calls for immediate attention to a new avenue of exploration in the science and therapeutics of implant dentistry. Keywords: bone-titanium integration, dental implants, orthopedic implants, photofunctionalization, superosseointegration

Purpose: This study analyzed the concentrations of platelets and growth factors in platelet-rich plasma (PRP), which are likely to depend on the method used for its production. Materials and Methods: The cellular composition and growth factor content of platelet concentrates (platelet-rich plasma) produced by six different procedures were quantitatively analyzed and compared. Platelet and leukocyte counts were determined on an automatic cell counter, and analysis of growth factors was performed using enzyme-linked immunosorbent assay. Results: The principal differences between the analyzed PRP production methods (blood bank method of intermittent flow centrifuge system/platelet apheresis and by the five point-of-care methods) and the resulting platelet concentrates were evaluated with regard to resulting platelet, leukocyte, and growth factor levels. The platelet counts in both whole blood and PRP were generally higher in women than in men; no differences were observed with regard to age. Statistical analysis of platelet-derived growth factor AB (PDGF-AB) and transforming growth factor ß1 (TGF-ß1) showed no differences with regard to age or gender. Platelet counts and TGF-ß1 concentration correlated closely, as did platelet counts and PDGF-AB levels. There were only rare correlations between leukocyte counts and PDGF-AB levels, but comparison of leukocyte counts and PDGF-AB levels demonstrated certain parallel tendencies. Conclusions: TGF-ß1 levels derive in substantial part from platelets and emphasize the role of leukocytes, in addition to that of platelets, as a source of growth factors in PRP. All methods of producing PRP showed high variability in platelet counts and growth factor levels. The highest growth factor levels were found in the PRP prepared using the Platelet Concentrate Collection System manufactured by Biomet 3i. Keywords: growth factors, leukocyte, platelet concentrate, platelet-rich plasma, production process

Purpose: To evaluate three-dimensionally the bone change following ridge preservation procedures (RPP) using computed tomography (CT). Materials and Methods: Subjects in need of implant therapy were enrolled in the study. The teeth were extracted, and sockets underwent RPP with a bioactive glass (Inion BioRestore, Inion Oy). The patients were scanned with CT within 1 week and 3 months after surgery. Horizontal and vertical radiographic measurements were performed on superimposed CT scans to evaluate bone changes in the alveolar sites during the 3-month period. Results: Thirteen subjects participated, and 32 teeth were extracted and treated with grafting. Alveolar sites treated with RPP demonstrated a preservation of about 77% of the original width dimensions, with a mean loss of 1.8 ± 1.1 mm in width. Moreover, it was observed that the vertical loss of buccal bone was 2.7 ± 1.1 mm, while the loss of lingual bone was 1.9 ± 1.2 mm. Conclusions: The CT evaluation was helpful to assess that the bone loss in width was less than the vertical bone loss of both walls 3 months after RPP. Keywords: alveolar ridge preservation, bioactive glass, bone morphometry, computed tomography, graft material

Purpose: This study was conducted to evaluate alkali- and heat-treated titanium implant material. Materials and Methods: Ninety-eight square plates of commercially pure titanium were divided into three groups. Group 1 plates were left untreated, and groups 2 and 3 were subjected to anodization and alkali treatment for 24 and 48 hours, respectively. Treated specimens were then subdivided into three equal subgroups (a, b, and c), which were heat treated for 1 hour at temperatures of 500°C, 700°C, and 800°C, respectively. Changes in the crystalline structure were analyzed using x-ray diffractometry. Surface roughness was measured using a surface roughness tester. Selected specimens were immersed in a specially prepared simulated body fluid for 10 days. Calcium and phosphorous deposition on the specimens was detected using energy dispersive x-ray analysis. Results: Increasing the alkali treatment period and heat treatment temperature positively affected surface roughness and formation of a bioactive sodium titanium oxide (sodium titanate) layer on the titanium surface, especially after heat treatment at 800°C. There was a significantly higher calcium deposition on specimens of group 3 in comparison with those of groups 1 and 2. The results of pH and ion concentration changes of the used simulated body fluid confirmed the results of energy dispersive x-ray analysis. Conclusion: Alkali and heat treatment of titanium implant materials created better treatment conditions for obtaining a bioactive implant material. Keywords: alkali treatment, bioactivity, heat treatment, implant materials, titanium

Purpose: Yttria-stabilized zirconia (ZrO2-Y2O3) ceramics have received increasing attention in recent years because of their stress-induced tetragonal-to-monoclinic (martensitic) transformation. This unique process acts as a toughening mechanism, imparting strength and toughness to the ceramic alloy. This property, along with well-documented biocompatibility, is now being exploited in an increasing number of medical applications, including implant dentistry. To prevent clinical problems and predict their behavior and physical limitations, a characterization of the ceramic elements used in dental restorations is essential. The aim of the present study is to characterize the crystal structure, elemental composition, and micr ostructure of asreceived ZiReal Post (Biomet 3i) zirconium oxide abutments, as well as specimens coated with a first layer of a low-fusing fluoroapatite ceramic. Materials and Methods: Zirconium oxide abutments, both as-received and porcelain-coated, were studied using the following techniques: x-ray diffraction, x-ray fluorescence, energy dispersive x-ray spectroscopy, optical microscopy, and scanning and transmission electron microscopy. Results: X-ray analyses detected only the presence of Zr, O, Y, and hafnium (Hf), in an amount of 3% to 4% molecular weight Y2O3-ZrO2. X-ray diffraction measurements showed that the ceramic abutment crystallizes mainly in the tetragonal phase, with some residual monoclinic phase. The microstructure is characterized by a rather homogenous grain distribution, formed by equiaxed and fine grains with a mean size of 0.30 µm. Conclusions: Compositional and diffraction results are consistent with polycrystalline yttria-stabilized tetragonal zirconia. The material is susceptible to undergoing the stress-induced transformation toughening mechanism because of the very fine grain size. Except for machining ring marks, the surfaces exhibit an excellent finishing quality. No structural modifications were observed in the fluoroapatite ceramic-coated abutments because of the relatively low temperatures used for ceramization compared with the phasetransformation temperatures used for zirconia. Keywords: ceramics, dental implants, microstructure, zirconia

Purpose: This study sought to evaluate the influence of methodologic aspects on variations in the findings of in vitro microleakage studies of the implant-abutment interface. Materials and Methods: The MEDLINE, EMBASE, and Cochrane Library databases were consulted for in vitro studies published between 1990 and August 2011. Date from the studies that met the inclusion and exclusion criteria were arranged in tables and subjected to descriptive analysis. Results: Twenty-one studies were found to be eligible for the analysis after application of the inclusion/exclusion criteria. Sixteen studies used bacteria (76.2%), one used a bacterial toxin (4.76%), one used saliva (4.76%), two employed dyes (9.52%), and one used a combination of dyes and bacteria (4.76%). Eight studies evaluated microleakage from the inner portion of the implant to the external portion (38.1%) and nine examined the reverse (42.85%), while four studies investigated the relationship between them (19.05%). The volume inoculated inside the implants ranged from 0.1 to 5.0 mL. The bacterial concentrations used in the tests ranged from 2.41 × 106 to 8 × 108 colony-forming units/mL. Oral bacterial flora; mixtures of bacteria, toluidine blue, and gentian violet; and lipopolysaccharide of Salmonella enterica bacterial toxins were used. The monitoring period of test results ranged from 24 hours to 11 weeks for bacteria, 5 minutes to 7 days for dye, and 7 days for bacterial toxins. In four studies, microleakage was correlated with the size of the implant-abutment microgap. The external-hexagon implant configuration showed the greatest microleakage, followed by internal-trilobe, internal-hexagon, and internal-taper configurations. Conclusion: The lack of standardization hinderd comparisons of the studies and could explain the divergent results. It is suggested for future studies that special emphasis be placed upon inoculation and analysis of the specific volume for each system, lower concentrations of inoculated bacterial suspensions, and shorter follow-up time when using bacteria. Keywords: implant-abutment interface, literature review, microleakage

Purpose: To assess the effects of a recently developed ultrasonic scaler tip, composed mainly of copper, on the surfaces of several dental materials. Materials and Methods: Representative samples of dental materials, including titanium, type II gold, cobalt-chromium alloy, zirconia, and porcelain, were prepared. Three ultrasonic scaler tips of conventional metal (CM), carbon composite (CC), and copper alloy (CA) were prepared. To simulate ultrasonic scaling in an oral environment, 30 g of force was applied using a doublepan balance, and the scaler tip was allowed to move horizontally 5 mm for three consecutive cycles of 20 seconds each. The power of the scaler tip was set to intermediate according to the manufacturer's advice. The surface morphology of each dental material was examined using scanning electron microscopy and confocal laser scanning microscopy. Statistical analysis was performed through one-way analysis of variance and post hoc Scheffé test. All values were considered significant when P .05. Results: Surface alterations of titanium, type II gold, and cobalt-chromium alloy by the CM tip were much greater than those caused by the CC and CA tips. No alterations were created on the zirconia surface by the CM, CC, or CA tips. On the porcelain surface, surface roughness (Ra) induced by the CM tip was 1.86 and 1.72 times higher than that produced by the CC and CA tips, respectively (P .001). Conclusions: Within the limitations of this study, the surface alterations induced by CC and CA tips on the surfaces of dental materials were comparable. Therefore, this novel ultrasonic copper alloy scaler tip may possibly be used for the maintenance of implant prostheses. Keywords: confocal laser microscopy, profilometry, surface alteration, surface topography, ultrasonic instrumentation, ultrasonic scaler tip

Purpose: The aim of the present in vivo study was to examine alterations of the microbial community structure in biofilms on different dental implant surfaces over the time. Materials and Methods: Zirconium nitride-coated glass (ZrN-glass) and ZrN-coated polished titanium (ZrN-Ti) disks were used as substrates and polished titanium (Ti-pol) was used as a control. The specimens were mounted on removable intraoral splints in one adult. After 24 hours and 14 days of intraoral exposure, the microbial biofilms were analyzed by generating 16S rRNA gene clone libraries. Results: ZrN coating of a Ti surface altered the microbial composition early on (24 hours), with a tendency to augment Lactobacillus-related phylotypes later. Long-term exposure (14 days) of dental implant surfaces to microbes resulted in a significantly different composition of the biofilm on all three tested surfaces. Conclusions: This preliminary study showed that a ZrN-Ti disk surface harbors a significantly different microbial composition from a polished Ti surface. Further improvement of ZrN physical vapor deposition coatings might help to influence the adhesion of bacteria that are less pathogenic, thereby reducing the risk of peri-implantitis. Keywords: bacterial adhesion, biofilm, dental implants, DNA cloning, titanium hard coatings, zirconium nitride

Purpose: One of the most common types of failure in dental implants is fracture of the abutment screw, after which the remnant is usually not easily removed. The purpose of this study was to investigate the effect of abutment screw length on the amount of screw resistance load and strain after loading. Materials and Methods: Twenty-one implants and straight abutments were prepared. The implants were placed in acrylic resin blocks at an angle of 30 degrees relative to the long axis. The abutment screws were prepared and classified into seven groups based on length (n = 3 abutments per group). The implants and abutments were joined with a torque of 30 Ncm. Strain gauges were attached to the abutments, and the implant-abutment assemblies were compressed. Curves of strain over time, peak load, and load at fracture were measured. Linear models of the variables over the abutment screw length were analyzed. Results: The break and peak loads were significantly associated with abutment screw length. However, all measured break and peak loads were greater than the maximal occlusal force. There were no significant changes in peak or break strain values associated with screw length (P > .05). Conclusions: Clinically, fractured abutment screws may be replaced by shorter abutment screws without removal of the broken screw remnant. Keywords: abutment, dental implant, fracture, load, screw length, strain

Purpose: An in vitro model was developed and tested to evaluate the precision of guided implant systems. The accuracy of dental implants placed with a flapless technique was analyzed using a stereolithographic template in vitro. Differences between the virtual and actual positions of the implants were measured. Materials and Methods: Six polyurethane mandibles with artificial silicone gums were fabricated, and each was fitted with an individual computed tomography (CT) guide. Stereolithographic guides were created using computer-aided design/computer-assisted manufacturing technology and virtual planning software. All stereolithographic guides had four holes for stabilization pins and three holes for cylindric implants. After implant placement, the mandibles were subjected to another CT scan to compare the actual implant positions with the planned positions. The pre- and postimplantation CT images were superimposed using digital processing image software to evaluate the linear and angular deviations between the virtual planning data and the surgical results. Results: The mean angular discrepancy between the virtual and actual positions of the 18 placed implants was 2.16 ± 0.92 degrees. Among the placed implants, 66.7% were situated a mean of 0.38 ± 0.03 mm apical to the planned vertical position, and 33.3% were situated 0.39 ± 0.03 mm coronal to the planned position. Conclusions: Within the limitations of the present study, this tool showed promising accuracy in virtual implant placement. Keywords: accuracy of computer-generated templates, computed tomography, dental implants, flapless surgery

Purpose: This study sought to determine an optimal postinsertion retorque protocol to maintain implantsuprastructure joint stability after being subjected to a 1-year in vitro masticatory simulation. Materials and Methods: Ten mandibular implant-supported dentures were manufactured and 20 epoxy resin models were obtained for two fit levels: passive fit and misfit. Eight groups (n = 20) were created on the basis of vertical fit (passive or misfit) and prosthetic screw material (titanium or gold). The single-screw test was performed and the vertical misfit was quantified using an optical microscope. Loosening torque was measured after simulations of two types of clinical use: (1) 6 months of use, torque loosening, retightening, another 6 months of use, and loosening torque; and (2) 1 year of use followed by loosening torque. Data were analyzed by means of two-way analysis of variance and the Tukey test. Results: The factors of cycling time and condition use (fit level and screw type), as well the interaction between these factors, significantly influenced the loosening torque (P .05). After 6 months and another 6 months of clinical use simulation, titanium screws showed higher loosening torque values than did gold screws for the same fit level (P .05). After 1 year of clinical use simulation, titanium and gold screws in passively fit dentures showed higher loosening torque values than they did in misfit dentures (P .05). The titanium screws presented a decrease in the loosening torque after 1 year in misfit dentures. Conclusions: The stability of titanium screws was higher than that of gold screws after 6 months of simulation because of their lower plastic deformation. When the cycling time was analyzed, titanium screws were less stable after 1 year of simulation because of loss of torque in the presence of misfit. Keywords: cyclic loading, implant prosthesis, loosening torque, prosthetic screw

Purpose: Zirconia implant abutments offer enhanced esthetics and promote biologic sealing; however, the effect of laboratory or intraoral preparation on the mechanical stability of zirconia has not been investigated. The purpose of the study was to evaluate the influence of the preparation mode and depth on the fracture strength of zirconia abutments restored with lithium disilicate crowns. Materials and Methods: To replace a maxillary central incisor (11.0 mm in height and 8.0 mm in width), 35 lithium disilicate crowns were cemented onto zirconia abutments on 4.5- × 15-mm titanium implants. Lithium disilicate implant crowns were divided into five study groups (n = 7) according to the abutment preparation mode (milling by the manufacturer or milling by the Celay System [Mikrona] [P]) and preparation depth (0.5 mm [A], 0.7 mm [B], or 0.9 mm [C]). All groups were subjected to quasi-static loading (S) at 135 degrees to the implant axis in a universal testing machine. Results: Mean fracture strengths were: group SA, 384 ± 84 N (control); group SB, 294 ± 95 N; group SPB, 332 ± 80 N; group SC, 332 ± 52; group SPC, 381 ± 101 N. All specimens presented a typical fracture mode within the implant/abutment internal connection. Multiple regression analysis revealed that preparation depth up to 0.7 mm statistically influenced the fracture strength (P = .034), whereas the preparation mode did not seem to play an important role (P = .175). Conclusion: Regardless of preparation mode, circumferential preparation of zirconia abutments might negatively affect the fracture strength of adhesively cemented singleimplant lithium disilicate crowns. Keywords: abutment, fracture mode, fracture strength, implant, internal-connection implants, lithium disilicate, preparation, zirconia

Purpose: This study investigated the effect of enamel matrix derivative (EMD) on spreading, proliferation, and differentiation of osteoblasts cultured on zirconia disks with smooth and rough surfaces. Materials and Methods: EMD was added to the culture medium or coated on zirconia disks that had machined (smooth) or sandblasted (rough) surfaces. The effects of EMD on cell proliferation of MC3T3-E1 osteoblastic cells were examined using a hemocytometer. Osteoblastic differentiation was examined by histologic analysis of alkaline phosphatase (ALP) activity and the degree of mineralization. ALP activity was also measured quantitatively. Scanning electron microscopic analysis was performed to observe cell morphology. Enzyme-linked immunosorbent assay of osteocalcin and reverse-transcriptase polymerase chain reaction of osteocalcin, osteopontin, and type 1 collagen were performed to investigate the expression of osteoblast-related genes. Results: The addition of EMD to the medium enhanced the spreading, proliferation, and differentiation of osteoblasts cultured on zirconia. However, when it was coated on zirconia, EMD reduced osteoblastic spreading and adhesion in the early stage of culture, although it enhanced proliferation and differentiation of osteoblasts in later stages. A promotive effect of EMD on osteocalcin mRNA expression, mineralization, and ALP activity of osteoblasts cultured on the rough surface was observed. Conclusions: EMD may contribute to treatment with zirconia implants via its promotion of osteoblastic proliferation and activity. However, the procedure for application of EMD may be a crucial factor for the outcome of implants. Keywords: dental implants, enamel matrix derivative, osteoblasts, zirconia

Purpose: To investigate different techniques used by dentists when luting an implant-supported crown and to evaluate the application of cement quantitatively and qualitatively. Materials and Methods: Participants were given a bag containing cement sachet, mixing pad, spatula, a variety of application instruments, and a polycarbonate crown form. The participants were instructed with a standardized audio-video presentation to proportion the cement, mix it, and apply it to the intaglio of the crown as they would if they were to cement it onto an implant abutment in a clinical situation. The crowns were weighed, first unfilled and then again once the applied cement had set. The mean weights of fully-loaded crowns (n = 10) were used as a control group. The patterns of cement loading were recorded. The weights of collected cement-loaded crowns were compared to those of the control group and analyzed statistically. Results: Four hundred and one dentists in several different geographic locations were surveyed. Three distinct cement loading patterns were observed: gross application (GA), brush-on application (BA), and margin application (MA). The mean weights for each cement loading pattern were 242.2 mg for the GA group, 59.9 mg for the BA group, and 59.0 mg for the MA group. The weight of cement in the GA group was significantly higher than that in the other groups. No statistically significant difference between groups BA and MA was seen. Conclusions: The diversity of the cement loading patterns disclosed in this study indicates that there is a lack of uniformity and precision in methods and a lack of consensus in the dental community regarding the appropriate quantity of cement and placement method for a cement-retained implant crown. Keywords: cement-retained implant crown, cement volume, dental cement, luting cement application

Purpose: The aim of this systematic review was to assess the methodologic and statistical quality of prospective case series of treatment interventions of dental implant surgery and prosthodontics published between 2004 and 2008. Materials and Methods: Prospective case series were identified following detailed searches of the Medline, EMBASE, and CINAHL databases. Identified studies were independently assessed by two nonblinded reviewers for 10 key methodologic and statistical domains. Information was collected using a customized data collection sheet. Results: The initial search yielded 1,484 studies. Following application of inclusion criteria, 31 prospective case series reports that did not present the same patient material were identified for this review. Interexaminer agreement was assessed for all domains (median kappa score, 0.84). All disagreements were resolved by discussion. The source of funding was unclear in 20 studies (65%). Treatment protocol was adequately described in 21 studies (68%), and eligibility criteria were adequately reported in 24 studies (77%). Only two studies (6.5%) tested the intraexaminer/interexaminer reliability of at least one outcome of interest. Inferential statistical analysis was presented in 21 studies. However, this analysis was only considered appropriate in 12 studies (57%). Confidence intervals were reported in four studies (13%). Conclusions: Prospective case series of treatment interventions of dental implant surgery and prosthodontics are poorly analyzed and rarely test the reliability of outcome measures. These particular studies have limited external validity and appear to provide little unbiased evidence to support clinical decision-making. Keywords: prospective case series, quality assessment, systematic review

Purpose: To estimate the applicability of potential sites for insertion of orthodontic mini-implants (OMIs) by a systematic review of studies that used computed tomography (CT) or cone beam CT to evaluate anatomical bone quality and quantity parameters, such as bone thickness, available space, and bone density. Materials and Methods: Medline and the Cochrane Database of Systematic Reviews were searched to identify all relevant papers. Several key words were used, such as computerized/computed tomography, mini-implants, and OMIs. The anatomical variables that were assigned in each article to a specific site suggesting it as the ideal or best alternative were assessed separately and evaluated with a scoring system. Results: Twenty-two articles were included in the study. The most favorable areas for OMI insertion in the maxilla are proposed between the first and second molars buccally and palatally. The best area in the mandible is also between the first and second molars, both buccally and lingually. In the palate, the paramedian area 3 to 6 mm posterior to and 2 to 9 mm lateral to the incisive foramen was identified as the best site for OMI placement. Conclusions: Despite the heterogeneity of the studies, there was considerable agreement regarding the optimal site for OMI insertion among most studies that investigated anatomical hard tissue parameters based on CT or CBCT data. In this respect, the posterior area from the second premolar to the second molar is the best option for OMI placement in alveolar bone. Keywords: anatomical parameters, computed tomography, mini-implants, orthodontic mini-implants

Purpose: Osteoporotic patients require particular attention during implant placement, and insertion torque (IT) has been established as a simple and noninvasive method to assess local bone quality and primary implant stability. This study aimed to test the hypothesis that IT was not significantly correlated with bone density, as assessed with computed tomography, in a group of osteopenic and osteoporotic patients. In addition, the hypothesis that IT was not significantly correlated with implant length was tested. Materials and Methods: Fifty-three completely edentulous patients with compromised bone mineral density (osteoporotic or osteopenic) who required treatment with complete maxillary dentures and complete mandibular implantsupported overdentures participated in the study. Each patient received two screw-shaped self-tapping implants (Brånemark Mark III TiUnite) at the mandibular canine regions. The IT of each implant during placement was recorded. The Pearson correlation between IT and implant site bone density (Hounsfield unit) obtained from presurgical computed tomographic scans was analyzed. The relationship between IT and implant length was also studied. Results: IT was significantly correlated to implant site bone density but not to implant length. Conclusion: IT can be a viable and practical means to assess mandibular bone quality in patients with compromised general bone density. Keywords: bone quality, dental implants, insertion torque, osteoporosis

Purpose: The aim of this article is to discuss the current literature available on the etiology and management of biomechanical complications of dental implant treatment. Materials and Methods: An electronic search of the PubMed database for English-language articles published before May 31, 2011, was performed based on a focus question: "How can biomechanical implant treatment complications be managed and identified?" The key words used were "dental implant", "etiology", "management", "excessive occlusal forces", "occlusal forces", "occlusion", "parafunctional habits", "biomechanical failure", "biomechanical complications", and "occlusal overloading". Clinical trials with a minimum of 10 implants followed for at least 1 year after functional loading were included. Results: The initial electronic search identified 2,087 publications, most of which were eliminated, as they were animal studies, finite element analyses, bench-top studies, case reports, and literature reviews. After the titles, abstracts, and full text of 39 potentially eligible publications were reviewed, 15 studies were found to fulfill the inclusion criteria. Conclusion: Occlusal overloading was thought to be the primary etiologic factor in biomechanical implant treatment complications, which commonly included marginal bone loss, fracture of resin/ceramic veneers and porcelain, retention device or denture base fracture of implant-supported overdentures, loosening or fracture of abutment screws, and even implant failure. Occlusal overloading was positively associated with parafunctional habits such as bruxism. An appreciation of the intricacy of implant occlusion would allow clinicians to take a more preventive approach when performing implant treatment planning, as avoidance of implant overloading helps to ensure the long-term stability of implant-supported prostheses. Keywords: biomechanics, dental implants, implant complications, implant prosthesis, overload

Purpose: To evaluate the use of the buccal fat pad flap (BFPF) technique as an option to prevent complications in the treatment of patients with atrophic maxillae rehabilitated after complex zygomatic implant surgery. Materials and Methods: A retrospective study was made of completely edentulous patients submitted to zygomatic implant surgery between May 2005 and November 2007. Patients with severely atrophic maxillae received conventional and zygomatic implants and were followed after the implants were loaded. Preoperative evaluation included panoramic radiography and computed tomographic scans of the maxilla to identify the anatomic conditions and presence of pathology. Results: Eight male patients with a mean age of 57 years and atrophic maxillae were rehabilitated with zygomatic implants placed using the BFPF technique. The BFPF technique was used in complex situations, including oroantral communication-associated sites, areas that had lost the sinus wall, and extrasinus implant placement. A total of 16 conventional implants, 4 long (21-mm) tilted implants, and 22 zygomatic implants was placed. The patients were rehabilitated with fixed prostheses and were followed for a minimum of 15 months. None of the conventional implants failed and none of the zygomatic implants failed or presented with soft tissue complications. Conclusion: The BFPF presented a high success rate, demonstrating that it is a viable and predictable treatment option to prevent and treat soft tissue complications in complex zygomatic implant surgery. Keywords: buccal fat pad flap technique, complication prevention, zygomatic implants

Purpose: The purpose of this controlled prospective study was to compare the satisfaction of patients rehabilitated with an immediately loaded implant-supported prosthesis and patients rehabilitated with a conventional denture in the mandible. Materials and Methods: Selected mandibular partially or totally edentulous patients were included in this prospective study. Patients' mandibles were completely rehabilitated with immediately loaded implants supporting a screw-retained full-arch prosthesis (test group) or with a conventional denture (control group). The Satisfaction Profile (SAT-P), which investigates a number of psychologic aspects related to the function and esthetics of the stomatognathic apparatus, was administered to each patient 1 month before and 3 months after provisional prosthetic rehabilitation. The questionnaire comprised four different SAT-P items: quality of eating, eating behavior, mood, and self-confidence. A visual analog scale was used to elicit patient responses. SAT-P item scores were analyzed statistically by means of the Student t test and the chi-square test (or the Mann-Whitney nonparametric test), with P .05 considered significant. Results: Forty-one patients were consecutively treated with 205 immediately loaded implants supporting a screw-retained full-arch prosthesis (test group); 38 patients were consecutively treated with a conventional denture (control group). Statistically significant differences were observed between the test and control groups for all four SAT-P items. The test group reported greater satisfaction for all items versus the control group. In both groups, the differences between pre- and postrehabilitation values were statistically significant. Conclusions: Each patient was satisfied with their treatment outcomes, but patients who received an implant-supported prosthesis were more satisfied than the patients who received a conventional denture. The results suggest that a screw-retained full-arch prosthesis on immediately loaded implants is a predictable means of enhancing patient satisfaction. Keywords: conventional denture, full-arch prosthesis, immediate loading, patient satisfaction

Purpose: To explore the possibility and evaluate the clinical outcome of accomplishing maxillary internal sinus floor augmentation through the use of a piezoelectric osteotome in conjunction with dental implant placement and to discuss this technique. Materials and Methods: Patients attending the outpatient clinic of the Department of Dental Implantology, Hospital of Stomatology, Tongji University, between July 2007 and September 2009, who had insufficient bone volume to harbor endosseous implants at least 8 mm long in the lateral/posterior maxilla because of sinus pneumatization were enrolled in the study. Sinus augmentations were accomplished with a piezoelectric osteotome, followed by implant placement, either immediately or delayed (6 months after augmentation, if the residual ridge height was less than 4 mm). Results: Thirty patients with 36 maxillary molar sites with insufficient alveolar bone height as a result of pneumatization of the sinus were included in this study. The residual vertical bone height ranged from 2 to 8 mm. Twenty-eight implants were placed into 24 patients immediately after sinus augmentation. Another eight implants were placed into 6 patients 6 months after sinus augmentation. Only one sinus membrane perforated (failure rate: 2.78%). Only one implant was lost during the observation period. No other implant mobility or rapid bone loss was seen during a follow-up period of 5 to 27 months. Conclusions: Application of a piezoelectric osteotome for internal sinus elevation simplified manipulation of the membrane and greatly reduced the chance of perforation. The pressure gradient between sinus and implant cavity was helpful in accomplishing this technique. Keywords: dental implants, internal sinus elevation, maxillary sinus, piezoelectric ultrasonic osteotome

Purpose: This prospective randomized matched-pair controlled trial aimed to evaluate marginal bone levels and soft tissue alterations at implants restored according to the platform-switching concept with a new inwardinclined platform and compare them with external-hexagon implants. Materials and Methods: Traditional external-hexagon (control group) implants and inward-inclined platform implants (test group), all with the same implant body geometry and 13 mm in length, were inserted in a standardized manner in the posterior maxillae of 40 patients. Radiographic bone levels were measured by two independent examiners after 6, 12, and 18 months of prosthetic loading. Buccal soft tissue height was measured at the time of abutment connection and 18 months later. Results: After 18 months of loading, all 80 implants were clinically osseointegrated in the 40 participating patients. Radiographic evaluation showed mean bone losses of 0.5 ± 0.1 mm (range, 0.3 to 0.7 mm) and 1.6 ± 0.3 mm (range, 1.1 to 2.2 mm) for test and control implants, respectively. Soft tissue height showed a significant mean decrease of 2.4 mm in the control group, compared to 0.6 mm around the test implants. Conclusions: After 18 months, significantly greater bone loss was observed at implants restored according to the conventional external-hexagon protocol compared to the platform-switching concept. In addition, decreased soft tissue height was associated with the external-hexagon implants versus the platformswitched implants. Keywords: bone resorption, dental implants, follow-up studies, implant connection, implant platform, platform switching

Purpose: The aim of this retrospective study was to evaluate the long-term survival rates and the frequency of complications associated with single implants and their associated restorations. Materials and Methods: A retrospective cohort study was performed in patients who received dental implants between 1997 and 2007. The cohort included patients who had a single implant restored with a cemented or screwed restoration that had been in function for more than 2 years. The cumulative implant survival rates and peri-implant conditions (marginal bone loss, pocket depth, and plaque, gingival, and bleeding indices), as well as prosthodontic maintenance requirements, were evaluated. Descriptive statistics, the chi-square test, and regression models were used. Results: Seventy-three implants were placed in 44 patients (32 women, 12 men; mean age, 48 years). All implants were available for follow-up after 2 to 13 years (mean follow-up, 60 months). The overall cumulative 5-year survival rates for implants were 95.9%, and most of the prostheses (98.6%) remained functional throughout the observation period. The overall frequency of complications was 29.6% (4.3% inflammatory, 22.5% prosthetic, 2.8% operative). The average peri-implant marginal bone loss was 1.8 mm. Peri-implant soft tissue conditions such as plaque and bleeding indices and pocket depths were also satisfactory. However, the presence of inflammation was significantly associated with pocket depth and gingival keratinized mucosa. The need to retighten loose abutment screws (21%) was the most frequent prosthodontic maintenance performed. However, all loose abutment screws occurred in prostheses retained with titanium screws, and 92.9% of the prostheses had a UCLA-type abutment. Conclusion: The implants and the associated prosthetic constructions used in this study showed excellent survival rates. However, there was a high frequency of prosthetic complications associated with titanium screws and UCLA cast abutments. Other prosthetic components may have yielded different results. Keywords: complications, dental implants, long-term survival rates, retrospective follow-up study, singletooth dental implants

Purpose: The primary goal of this stratified randomized controlled trial (SRCT) was to compare the stability of dental implants placed under three different loading regimens during the first 16 weeks of healing following implant placement. Implants were loaded immediately, early (6 weeks), or with conventional/delayed timing (12 weeks). Secondary outcomes were to compare marginal bone adaptation for 3 years after placement. Materials and Methods: Single posterior implant sites in the maxilla or mandible were examined. The insertion torque value was the primary determinant of load assignment. Resonance frequency analysis was performed at follow-up appointments for the first 16 weeks (with results provided as implant stability quotients [ISQs]). Marginal bone levels were assessed via radiographs. Results: Forty patients each received a single 4.0-mmdiameter dental implant between 2004 and 2007. One implant failure occurred in Lekholm and Zarb type 4 bone with insertion torque value (ITV) of 8.1 Ncm; the cumulative success rate was 97.5%. All implants, when classified by bone and loading type, increased in stability over time, with a minor reduction of 1.3 ISQ units seen at 4 weeks in the immediate loading group. The mean marginal bone loss over 3 years was 0.22 mm. The mean ITVs at implant placement for bone types 1 and 2 (grouped together), 3, and 4 were 32, 17, and 10, respectively, and were significantly different (P .05). Conclusions: ITV was a good objective measure of bone type. Using an ITV of 20 Ncm as the determinant for immediate loading and an ITV of 10 Ncm or greater as the determinant for early loading provided long-term success for this implant and led to no negative changes in tissue response. All bone type groups and loading groups showed no reduction in stability during the first 4 months of healing. Keywords: dental implants, immediate loading, implant stability, randomized controlled clinical trial, resonance frequency analysis, single-tooth replacement

Purpose: The aim of this study was to investigate peri-implant bone remodeling as a response to biomechanical factors, including implant size and contour, magnitude of occlusal load, and properties of osteogenic bone grafts through the use of a computational algorithm. Materials and Methods: A bone-remodeling algorithm was incorporated into the finite element method, where bone remodeling takes place as a result of the biomechanical alteration caused by dental implant placement and continues until the difference between the homeostatic state and the altered state is minimized. The site-specific homeostatic state was based on a model consisting of a natural tooth. Three long (11-mm) implants and two short (5-mm) implants were investigated. A three-dimensional segment of the mandible was constructed from a computed tomographic image of the premolar region, and an extraction socket was filled with bone graft. Results: Generally, the extent of bone loss in the cortical region was greater and denser bone developed at both the implant crest and apex with increased occlusal loads. The areas between implant threads were prone to bone resorption. Bone graft materials that were relatively stiff and that had high equilibrium stimulus values appeared to cause increased bone loss. Conclusions: Short implants are better for conserving the mechanotransductive signaling environment of the natural tooth than long implants. Also, short implants are predicted to lead to less interfacial bone loss at high loads over the long term, while long implants are associated with a more consistent level of bone loss for different amounts of loading. It is also predicted that in the long term, bone grafts with relatively low elastic modulus lead to lower levels of interfacial bone loss. Keywords: bone grafts, bone remodeling, dental implants, extraction socket, site-specific stimulus, wide implants

Purpose: The objective of this study was to analyze and compare the stresses in two different bone-implant interface conditions in anisotropic three-dimensional finite element models (FEMs) of an osseointegrated implant of either commercially pure titanium or yttrium-partially stabilized zirconia (Y-PSZ) in combination with different superstructures (gold alloy or Y-PSZ crown) in the posterior maxilla. Materials and Methods: Three-dimensional FEMs were created of a first molar section of the maxilla into which was embedded an implant, connected to an abutment and superstructure, using commercial software. Two versions of the FEM were constructed; these allowed varying assignment of properties (either a bonded and or a contact interface), so that all experimental variables could be investigated in eight groups. Compact and cancellous bone were modeled as fully orthotropic and transversely isotropic, respectively. Oblique (200-N vertical and 40-N horizontal) occlusal loading was applied at the central and distal fossae of the crown. Results: Maximum von Mises and compressive stresses in the compact bone in the two interfaces were lower in the zirconia implant groups than in the titanium implant groups. A similar pattern of stress distribution in cancellous bone was observed, not only on the palatal side of the platform but also in the apical area of both types of implants. Conclusion: The biomechanical parameters of the new zirconia implant generated a performance similar to that of the titanium implant in terms of displacement, stresses on the implant, and the bone-implant interface; therefore, it may be a viable alternative, especially for esthetic regions. Keywords: dental implants, finite element method, stress, zirconia