The International Journal of Oral & Maxillofacial Implants, 05/2012

Purpose: To evaluate the combination of fractal dimension (FD), lacunarity, and Feret diameter (FeD) to quantitatively characterize structural changes of mandibular alveolar bone around dental implants during initial healing. Materials and Methods: Three standard-sized regions of interest (ROIs) (mesial and distal crest and apical area) around implants and three ROIs of the same size in the alveolar bone on the contralateral side were analyzed on digital panoramic images. FD was calculated using the box-counting method, and lacunarity was calculated using the FracLac plugin of Image J software. FeD was measured in the same ROIs. Comparisons of the groups were done with the Dunnett test. Results: Forty-two implants in the posterior mandibles of 21 patients were used for FD measurements. A total of 189 ROIs was segmented into binary images. Mean FD values for mesial, distal, and apical ROIs around implants were 1.26, 1.36, and 1.4, respectively. The mean FD of alveolar bone around premolars/molars was 1.39 for all ROIs. The mean FeD for mesial, distal, and apical ROIs around implants was 7.63, 7.86, and 8.02, respectively, whereas it ranged between 7.88 and 8.13 for premolar teeth. Mean lacunarity values for mesial, distal, and apical ROIs around implants were 0.53, 0.51, and 0.48, respectively. Lacunarity values for ROIs around premolars ranged between 0.45 and 0.50. No significant differences were observed in FD, FeD, or lacunarity measurements between ROIs around implants and around teeth. Conclusions: The satisfactory healing of bone following implant placement may be monitored by calculating FD, lacunarity, and FeD using digital panoramic images. Although preliminary, these values may alert the practitioner to any implants with loss of stability. Keywords: dental implants, Feret diameter, fractal dimension, lacunarity, panoramic radiography

Purpose: Implant placement in the edentulous anterior mandible is frequently performed to stabilize prosthetic superstructures. The position of the inferior alveolar nerve (IAN), especially in an atrophic mandible, has to be considered to position implants properly. In this study, the prevalence of looping of the IAN was retrospectively determined to assess the need for imaging prior to implant placement in the anterior mandible. Materials and Methods: Cone beam computed tomography scans of consecutive patients were evaluated to assess the prevalence and size of IAN looping. The results were compared with respect to patient age and sex as well as degree of atrophy and bone height at the mental foramen. Results: Scans of 1,010 patients were obtained. IAN loops were found in 31% of the patients, with a significantly higher prevalence in male patients (33.1%) than in female patients (28.1%). The average size of loops was 1.4 ± 0.70 mm, with a maximum of 4.6 mm. For male patients, the average loop size was 1.6 ± 0.74 mm (maximum 4.6 mm), and for female patients an average dimension of 1.4 ± 0.63 mm (maximum 4.4 mm) was recorded. This difference was significant (t test). A significant difference with respect to the various classes of atrophy up to class 4 was not found. Conclusion: Loops of the IAN occur in about one third of patients and vary in size from 0.7 to 4.6 mm. Large anterior loops put the IAN at risk when interforaminal implants are placed. Either a sufficient safety distance or three-dimensional imaging procedures should be used to detect loops and locate the incisive canal, which could be harmed during the interforaminal implant placement. Keywords: anterior loop, cone beam computed tomography, dental implants, dental radiography, mental foramen, nerve alteration

Purpose: In current practice, two types of burs are typically used: stainless steel (SS) and alumina-toughened zirconia (ATZ). The present study evaluated the durability of these two burs in relation to osteotomy creation for implant placement. In addition, the effects of the two types of burs on a bone model were examined. Materials and Methods: SS and ATZ burs were compared under controlled conditions in a swine rib osteotomy. The heat generated and time necessary for perforation were measured and analyzed with repeated-measures one-way analysis of variance. The burs and bone samples were evaluated using scanning electron microscopy. Results: New ATZ and SS burs showed greater bone disruption compared to burs that had been used 80 times. Brand new burs of either material showed small manufacturing defects, which increased in number with use. No clinically or statistically significant differences were found between burs with respect to temperature and time for perforation. Conclusions: SS and ATZ burs can be used several times for implant site preparation under controlled conditions without reaching a temperature that is harmful to the bone. Both burs wear under repeated use, but not to an excessive degree. The duller burs produced smoother perforations than did the new ones. Keywords: burs, dental implants, heat, osteotomy, stainless steel, temperature, zirconia

Purpose: This study investigated the influence of smooth, roughened, and tricalcium phosphate (TCP)-coated roughened titanium-aluminum-vanadium (Ti-6Al-4V) surfaces on the osteogenic potential of rat bone marrow stromal cells (BMSCs). Methods: Machined smooth (MS), grit-blasted roughened (MT), and roughened surfaces coated with TCP were prepared from Ti-6Al-4V. Plastic surfaces were used as a control. Surface topography and chemical characteristics were determined. Cell attachment, morphology, proliferation, and temporal expression of mRNA and protein markers associated with bone healing were examined. Results: Roughness values were 0.09 ± 0.02 µm, 2.71 ± 0.24 µm, and 6.08 ± 0.62 µm for MS, MT, and TCP, respectively. Cell attachment was similar on all surfaces. The cell expansion phase occurred during days 1 to 3 on MS surfaces and days 3 to 5 on MT and TCP surfaces. The earlier onset of differentiation on MS surfaces versus MT and TCP surfaces was evidenced by: high mRNA expression peak for Runx2 at day 5 on MS (day 7 on MT and TCP); higher mRNA expression for osteopontin, osteonectin, bone sialoprotein (BSP), osteocalcin, type 1 collagen, and alkaline phosphatase over days 5 to 12 on MS compared with MT and TCP; higher levels of bone matrix proteins on MS compared with MT, with only BSP detected on TCP; cell morphology consistent with descriptions of differentiating osteoblasts apparent at day 5 on MS and absent on MT. Compared to plastic surfaces, Ti-6Al-4V appeared to suppress mRNA for interleukin 1ß, tumor necrosis factor alpha, and peroxisome proliferator-activated receptor gamma expression and upregulate osteoprotegerin. Conclusions: Cell expansion was delayed on roughened Ti-6Al-4V surfaces, impeding osteoblast differentiation and bone matrix synthesis. These results disagree with a number of published studies examining pure titanium. Ti-6Al-4V surfaces appear to assist in the resolution of proinflammatory cytokines and inhibit BMSC differentiation toward adipocytes. Keywords: calcium phosphate, osseointegration, osteoblasts, titanium

Purpose: To review the literature on decontamination of titanium implant surfaces following peri-implantitis and the effect of various cleaning methods on re-osseointegration. Materials and Methods: An electronic search of the literature at PubMed was conducted on the studies published between 1966 and October 2010. In vitro, animal, and clinical studies were included. Results: Of 597 studies retrieved, 74 manuscripts were selected for the review. Various implant surface decontamination methods using various chemical and mechanical agents have been suggested for treatment and re-osseointegration following periimplantitis. It has been shown that re-osseointegration of contaminated implant surfaces is possible; this largely depends upon the surface of the implant and the types of decontamination techniques and bone regenerative materials used. Complete re-osseointegration cannot be achieved by surface decontamination alone. Titanium implants with titanium plasma-sprayed or sandblasted and acid-etched surfaces may be effectively decontaminated by applying chlorhexidine and saline-soaked gauze or by repeated rinsing with these solutions. Conclusions: Both mechanical and chemical decontamination techniques should be applied alongside regenerative surgical procedures to obtain optimum re-osseointegration and successfully treat peri-implantitis. In recent years, lasers and photodynamic therapy have shown minor beneficial results, which need to be confirmed by long-term clinical studies with comparable groups. Keywords: biofilm removal, chemical and mechanical cleaning, laser, peri-implantitis, photodynamic therapy, re-osseointegration

Purpose: To evaluate the implant-abutment interface area and the abutment screw loosening value when diamondlike carbon (DLC)-coated or titanium screws were used before and after cyclic loading. Materials and Methods: Thirty-six implants were divided into four groups according to the type of connection (external hexagon [EH] or internal hexagon [IH]) and the type of abutment screw (with [EHD/IHD] or without [EHT/IHT] DLC coating). The implants were placed in epoxy resin-glass fiber composite, and crowns cast in a metal alloy were screwed to the implants. The implant-abutment interface was measured before (VG1) and after (VG2) cyclic loading. The removal torque values were recorded. Results: In groups with titanium screws, there was an increase in the implant-abutment interface area from VG1 to VG2, whereas in groups with DLC-coated screws, the interface area was reduced (EHT = 4.49%, IHT = 24.32%, EHD = -1.05%, IHD = -9.95%). In the IHT group only, the implant-abutment interface area showed a statistically significant difference between VG1 and VG2. The Pearson correlation indicated no significant differences among the studied factors, where r = -0.11 for EHT, 0.14 for EHD, 0.07 for IHT, and 0.43 for IHD. Conclusions: The implant-abutment interface areas in groups with an EH connection were larger than those in groups with an IH connection, regardless of the type of screws used. The screw loosening values decreased in all groups after cyclic loading. No correlation between the implant-abutment interface area and the screw loosening value was seen. Keywords: dental implants, implant screw, marginal adaptation

Purpose: Different surface treatments have been developed in attempts to prevent the loosening of abutment screws. The aim of the current study was to compare the effectiveness of titanium alloy screws with tungsten-doped diamond-like carbon (W-DLC) coating and uncoated screws in providing stability to zirconia (ZrO2) ceramic abutments after cyclic loading. Materials and Methods: Twenty prefabricated ZrO2 ceramic abutments on their respective external-hex implants were divided into two groups of equal size according to the type of screw used: uncoated titanium alloy screw (Ti) or titanium alloy screw with W-DLC coating (W-DLC/Ti). The removal torque value (preload) of the abutment screw was measured before and after loading. Cyclic loading between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants at a frequency of 15 Hz. A target of 0.5 × 106 cycles was defined. Group means were calculated and compared using analysis of variance and the F test (α = .05). Results: Before cyclic loading, the preload for Ti screws was significantly higher than that for W-DLC/Ti screws (P = .021). After cyclic loading, there was no significant difference between them (P = .499). Conclusions: Under the studied conditions, it can be concluded that, after cyclic loading, both abutment screws presented a significant reduction in the mean retained preload and similar effectiveness in maintaining preload. Keywords: abutment screws, cyclic loading, implant preload, screw coating surface, zirconia abutment

Purpose: This study tested the effects of phosphate treatment of titanium on bone volume fraction (BV/TV) at 30 to 60 µm from the implant surface using microcomputed tomography to analyze the mineralized tissue. Materials and Methods: Electrolytically phosphated (50/100 volts [T1/T2]) or nonphosphated 3.3- × 8-mm titanium implants (C) with sandblasted acid-etched surfaces were placed in 40 mandibular sites in five foxhounds 6 weeks after the extraction of the premolars. After 4 weeks, the animals were sacrificed, and BV/TV was analyzed using microcomputed tomography. Results: The mean BV/TV (± standard deviation) of the control implants was 31.4% ± 15.3% (range, 10.9% to 55.3%). For the T1 implants, a mean BV/TV of 38.4% ± 10.7% (range, 21.6% to 57.3%) was seen, and for T2 implants, the mean BV/TV was 40.3% ± 15.1% (range, 16.5% to 61.1%). Mean BV/TV values for the groups were not significantly different. For all groups (C, T1, and T2), there were no significant differences in BV/TV at the most coronal slices. For all groups, there was a positive slope showing more bone apposition as the slices moved from coronal to apical. The T2 group showed significantly increased mineralized tissue moving from the coronal to the apical section of the implant, compared to the control and T1 implants. Conclusion: Access to better blood supply and bone cells from the marrow spaces in the apical regions may lead to a better trabecular bone response. Increased mineralized tissue apposition may allow for accelerated loading and more predictable implant placement in sites with poorquality bone or patients with compromised bone healing. Keywords: acid etching, dental implant, microcomputed tomography, osseointegration, phosphate, surface properties, titanium

Purpose: A number of environmental and patient-related factors contribute to implant failure. A significant fraction of these failures can be attributed to limited osseointegration resulting from poor bone healing responses. The overall goal of this study was to determine whether surface treatment of a titaniumaluminum- vanadium alloy (Ti-6Al-4V) implant material in combination with a biomimetic protein coating could promote the differentiation of attached osteoblastic cells. The specific aims of the study were to investigate whether osteoprogenitor cells cultured on a rigorously cleaned implant specimen showed a normal pattern of differentiation and whether preadsorbed fibronectin accelerated or enhanced osteoblast differentiation. Materials and Methods: Ti-6Al-4V disks were rigorously cleaned, passivated in nitric acid, and dry heat- sterilized; some of the disks were then coated with 1 nmol/L fibronectin. MC3T3 osteoprogenitor cells were then cultured on the pretreated disks for several weeks. Quantitative real-time polymerase chain reaction was performed to measure changes over time in the mRNA levels of osteoblast genes. Results: Fibronectin increased the peak expression of all analyzed osteoblast gene markers. "Early" genes that normally mark the proliferative phase (0 to 10 days) of osteoblastic development showed peak expression within the first 10 days after cell attachment to the titanium alloy. In contrast, "late" genes that normally mark the differentiation (10 to 20 days) and mineralization (20 to 36 days) phases of osteoblastogenesis achieved peak expression only after approximately 3 to 4 weeks of culture. Conclusions: Osteoprogenitors cultured on a rigorously cleaned Ti-6Al-4V alloy were found to demonstrate a normal pattern of osteoblast differentiation. Preadsorbed fibronectin was observed to stimulate osteoblast differentiation during the mineralization phase of osteoblastogenesis. Keywords: coatings, differentiation, fibronectin, metal oxides, osteoblast, real-time polymerase chain reaction

Purpose: The aim of this study was to compare, in vitro, external-hexagon and Morse taper implant systems with respect to bacterial sealing between implants and abutments using a new methodology. Materials and Methods: Two groups of implants were tested. Group 1 implants had an external-hexagon implant-abutment interface (Neodent) and group 2 implants featured a Morse taper (Neodent) interface. The implants were perforated apically with a 1-mm bur until the bur reached the internal chamber. Prosthetic components were adapted with the recommended torque (32 and 10 Ncm, respectively) for each group. The implants were attached to an assay vial, with the abutment end positioned into the tube. With a sterilized syringe, the assay vials were filled with liquid culture medium (brain heart infusion broth). All the specimens were sterilized by gamma radiation. After the efficacy of sterilization had been confirmed using control samples, the apical hole was carefully opened and inoculated with Escherichia coli. Results: Samples were examined daily for evidence of contamination. Within a 14-day period, 60% of the samples of group 1 were contaminated and 30% of group 2 samples were contaminated. After this period there was no further contamination in either group. Conclusion: Although both systems exhibited bacterial contamination, the Morse taper implants of the system used in this study provided a better bacterial seal than external-hexagon implants of the same system. Keywords: contamination, dental implants, microbiology

Purpose: Different synthetic and natural biomaterials have been used in bone tissue regeneration. However, several limitations are associated with the use of synthetic as well as allogenous or xenogenous natural materials. This study evaluated, in an in vitro model, the behavior of rat osteoblastic cells cultured on a human globin scaffold. Materials and Methods: Rat osteoblastic cells were isolated from the calvaria of 21-day-old fetal Sprague-Dawley rats. They were then grown in the presence of globin. Real-time polymerase chain reaction (RT-PCR) was performed to study the expression of cyclin D1, integrin ß1, Msx2, Dlx5, Runx2, and osteocalcin on days 1, 5, and 9. Moreover, alkaline phosphatase activity was measured on days 1, 3, 5, and 7. Alizarin red staining was performed on day 9 to observe calcium deposition. Results: Cells were able to adhere, proliferate, and differentiate on globin scaffolds. Moreover, RT-PCR showed that globin may stimulate some key genes of osteoblastic differentiation (Runx2, osteocalcin, Dlx5). Globin had an inhibitory effect on alkaline phosphatase activity. Calcium deposits were seen after 9 days of culture. Conclusions: These results indicate that purified human globin might be a suitable scaffold for bone tissue regeneration. Keywords: bone regeneration, differentiation, globin, in vitro model, osteoblasts

Purpose: To evaluate the influence of abutment height and thermocycling on the retrievability of cemented implant crowns. Materials and Methods: Ninety tapered titanium abutments (6 degree taper, 4.3 mm diameter, 8.5 mm height) were shortened to 2, 3, or 4 mm, respectively. Ninety crowns were designed and manufactured using CAD/CAM techniques and laser sintering a CoCr alloy. The crowns were cemented either with a glass-ionomer, a polycarboxylate, or a composite resin cement followed by 3-day storage in demineralized water without thermocycling or 150-day storage with 37,500 thermal cycles. The force (in N) and the number of attempts needed to remove the crowns using a universal testing machine (UTM) or a clinically used removal device (Coronaflex) were recorded. Statistical analysis at a level of significance of P = .05 was conducted using the Kruskal-Wallis and Mann-Whitney U tests (Coronaflex) and three-way and two-way ANOVA, Tukey's HSD post hoc tests, and t tests (UTM). Results: Regardless of whether the crowns were retrieved with Coronaflex or UTM, the crowns cemented with the glass-ionomer cement were significantly easier to retrieve followed by the polycarboxylate and the resin cement, both of which differed significantly from each other (P = .001). With both retrieval methods, the cement, abutment height, and thermocycling were significantly influential (P = .0001). Significant interactions could be found for retrieval with UTM between the abutment height and thermocycling, between the cement and thermocycling, and between all three factors (P = .05). Conclusions: Glass-ionomer cement may be used for retrievable cementation of implant restorations, whereas polycarboxylate cement and especially composite resin cement should be used for a nonretrievable permanent cementation. Keywords: abutment, cement, crown, implant, retention, retrievability

Purpose: To show the presence and direction of the collagen fiber orientation around platform-switched (PS) and non-platform switched (NPS) implants at the crestal bone level. Materials and Methods: Twelve implants (six PS and six NPS implants) were placed with single-stage surgery in three dogs. The implant abutments were disconnected and reconnected after 8, 10, 12, and 14 weeks. The animals were sacrificed in the 18 week. The specimens were stained with hematoxylin and eosin and examined using polarized light microscopy. Results: The PS implant specimens showed circular fiber orientation at the implant platform level and the NPS implants showed similar fiber orientation at the bone level of the first implant thread. All specimens demonstrated a circular fiber orientation of the collagen fibers at the crestal bone level. Conclusions: The discrepancy in implantabutment diameter involving a change from a wider implant platform to a smaller abutment diameter, described as platform switching, seems to provoke a circular fiber orientation at the implant platform level. Similar circular fiber orientation was found at the first implant thread bone level for regular implants without platform switching. The histologic results support the hypothesis that platform switching can reduce crestal bone loss and can serve as a "mechanical retention factor" for periodontal fiber orientation. More clinical and histologic studies are needed to corroborate this preliminary finding. Keywords: bone preservation, circular fibers, collagen fibers, implants, platform switching, soft tissue stabilization, transversal fibers

Purpose: To evaluate treatment outcomes of hydroxyapatite-coated implants in comparison to nonhydroxyapatite- coated implants. Materials and Methods: A comprehensive electronic search was performed through MEDLINE, EMBASE, the Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), the UK National Research Register, and Conference proceedings citation index up to June 2011. Additionally, several journals, bibliographies of selected articles, and relevant reviews were manually searched. Results: A total of seven studies (one randomized, four prospective, and two retrospective) were included. The quality of the studies was assessed "better" for the randomized and prospective and "fair" for the retrospective. Over a mean observation period of at least 5 years, the survival rates ranged from 77.8% to 98.1% for the hydroxyapatite-coated implants and from 77.1% to 95.2% for the nonhydroxyapatitecoated implants, with no significant differences observed. Hydroxyapatite-coated implants were associated with lower but insignificant failure risk compared with nonhydroxyapatite-coated implants (risk ratio of 0.68; 95% CI 0.33 to 1.41; P = .30). Marginal bone loss quantified in a single study was significantly higher around hydroxyapatite implants (1.51 ± 2.71 mm versus 0.55 ± 1.04 mm; P .001). Conclusions: Hydroxyapatitecoated implants demonstrate short-term survival outcome up to 5 years, which is comparable to that of nonhydroxyapatite-coated implants. The long-term success of hydroxyapatite-coated implants using welldesigned clinical trials remains lacking in the literature. Keywords: hydroxyapatite-coated implants, meta-analysis, systematic review

Purpose: The use of distal cantilevers in fixed implant-supported prostheses is often discussed in dental literature in relation to implant restorations. The aim of this study was to conduct a systematic review of the literature in an effort to identify factors related to the long-term success of distal cantilevers. In addition, a more traditional review was conducted to determine complications associated with this type of prosthetic design. Material and Methods: A systematic literature review was conducted of all published articles identified through a search of MEDLINE from January 1980 through June 2011 using the terms "crestal bone loss," "dental implants," "distal cantilevers," "marginal bone loss," and "periodontal disease." An initial review was conducted of titles and a second review was performed using full abstracts. Articles were thus identified to assess studies that met the inclusion criteria that described fixed complete dental prostheses utilizing distal cantilevers. In vivo studies were included for data extraction while in vitro and animal studies were used for descriptions of clinical or mechanical performance. Results: Following the method described, from an initial identification of 49 studies, a total of 14 human clinical studies were found that met the inclusion criteria and provided data associated with clinical performance. An additional 5 studies detailed in vitro research. It was noted that the majority of studies lacked specific data but, nonetheless, provided subjective and objective information regarding the use of cantilevers. The follow-up period of human studies ranged from 1 to 10 years. Weighted averages demonstrate a prosthetic survival rate of 95% during a follow-up period of 7.3 ± 2.6 years. The descriptive studies demonstrate that the most frequent complication was screw loosening, which was observed equally in virtually all studies, even if controlled torque was used to connect abutments and prostheses. Porcelain chipping and esthetic veneer fracture were described, although data associated with these occurrences were not available for systematic review. Conclusions: Based on 19 articles (including 14 human studies), it was difficult to derive data-based conclusions regarding the use of cantilever prostheses other than an approximate 95% prosthetic survival rate. Subjective and objective information from these studies demonstrated a distinct preference for the use of distal cantilever prostheses, as few risks are associated with these prostheses. Careful evaluation of the studies shows that cantilevers provide a treatment option without a high risk of complications. Keywords: complications, crestal bone loss, distal extension, implant-retained prostheses

Purpose: To evaluate the radiographic crestal bone level changes around immediately restored dental implants up to 5 years after insertion in patients with a history of periodontitis. Materials and Methods: Patients previously treated for chronic periodontitis who required a fixed full-arch restoration for the maxilla or mandible or a fixed partial restoration in the esthetic zone were treated. Implant surgery included extraction of hopeless teeth, debridement around remaining adjacent teeth, and implant insertion guided by a surgical stent. A prefabricated screw-retained provisional restoration was immediately placed on selected implants. Periapical radiographs were taken at implant placement, 6 and 12 months postsurgery, and annually thereafter. The distance between the alveolar crest and the implant shoulder was measured at the mesial and distal aspects of each implant. Bone changes (BC) and annual rate of bone change (Rate) were calculated for the first year and the following 4 years. Results: Total BC (mean ± standard deviation) from baseline to 5 years (BCt0-t5) was -1.41 ± 0.67 mm. First-year BC (BCt0-t1) was -1.14 ± 0.86 mm, and BC in years 2 to 5 (BCt1-t5) was -0.27 ± 0.69 mm. Ratet0-t1 was -0.98 ± 0.79 mm/year and ratet1-t5 was -0.06 ± 0.17 mm/year. Fifty-seven of 61 available implants met the criterion of cumulative bone loss of no more than 1.5 mm for the first year and 0.2 mm/year for the following years. Four implants (7%; 95% confidence interval: 0.4% to 13.6%) failed the criterion. Conclusions: Dental implants in patients with a history of periodontitis showed radiographic bone changes similar to previous reports in the literature. After the first year, immediately restored implants exhibited crestal bone loss rates similar to those seen for conventionally restored implants. Keywords: bone loss, dental implants, immediate loading, periodontal disease

Purpose: The aim of this clinical study was to compare a hand mallet with an electric mallet in osteotomeassisted sinus elevation. Materials and Methods: Eighty patients, all of whom were edentulous in the maxillary premolar and molar regions, were included in this prospective study. The patients were divided into two groups. In one group (40 patients, control group) sinus floor elevation was performed with an osteotome pushed by a hand mallet, and in the second group (40 patients, test group) sinus floor elevation was performed with the use of an electric mallet. One-hundred twenty dental implants (60 test, 60 control) were positioned. Intraoral digital radiographic examinations were made at baseline and at 6, 12, and 24 months after implant placement. Alveolar bone height was measured and reported at 6, 12, and 24 months. Results: After 24 months, a survival rate of 98.33% was reported. Three control group patients developed benign paroxysmal positional vertigo following the use of osteotomes and percussion with the hand mallet. The mean alveolar bone gain at 6 months after implant placement was 2.64 ± 1.21 mm in the control group and 2.45 ± 1.55 mm in the test group. After 12 months, the bone height had increased in both groups, and at 24 months it was stable (4.17 ± 1.70 mm in the control group and 4.07 ± 1.03 mm in the test group). No statistically significant differences were seen between groups. Conclusions: A significant increase in bone height was achieved between 6 and 12 months, and bone levels remained stable at 2 years. The use of an electric mallet provided some essential advantages during surgery in comparison with the hand mallet. Keywords: dental implant, electrical mallet, sinus elevation

Purpose: The aims of the present study were to compare a novel biphasic calcium phosphate (BCP) with deproteinized bovine bone (DBB) for maxillary sinus floor augmentation in a split-mouth design and to perform a clinical follow-up of dental implants placed in the augmented sinuses. Materials and Methods: Partially or completely edentulous patients requiring bilateral sinus augmentation were included in the study. The patients were randomized for augmentation with BCP (test) and DBB (control) in the contralateral side. Eight months after grafting, dental implants were placed. After 3 years of graft healing, core biopsy specimens were obtained from the grafted areas for histologic and histomorphometric analyses. After 3 years of functional implant loading, implant survival/success rates and clinical indices were assessed and radiographic examination and resonance frequency analysis were performed. Results: Nine completely edentulous patients and two partially edentulous patients (mean age, 67 years) who required bilateral sinus augmentation were included in the study, and 62 implants were placed. The mean values for the area of newly formed bone in the retrieved specimens were 29% ± 14.3% and 32% ± 18.0% for BCP and DBB, respectively; the percentage of graft particles in contact with bone was 38% ± 10.9% in the BCP group and 44% ± 12.1% in the DBB group (no statistical significant differences between groups). The mean values for the area of BCP particles and DBB particles were 20% ± 7.5% and 24% ± 13.5%, respectively (difference not significant). One dental implant was lost from each group, resulting in an overall implant survival rate of 96.8% after 3 years of loading. Conclusion: After 3 years, a similar amount of newly formed bone was present regardless of the biomaterial used. The choice of biomaterial did not seem to influence implant survival rates. Keywords: biphasic calcium phosphate, deproteinized bovine bone, histology, implants, sinus floor augmentation

Purpose: The aim of the present study was to evaluate marginal bone loss (mBL) adjacent to dental implants with a machined surface with at least 5 years of function. Materials and Methods: Machined-surface implants with a minimum follow-up of 5 years were included in the study. Recorded clinical parameters included plaque and gingival bleeding indices, smoking habit (nonsmoker, 0 to 10 cigarettes/day, or more than 10 cigarettes/ day), presence of periodontal disease (healthy or periodontally compromised), and compliance with periodontal maintenance. Marginal bone loss (mBL) was assessed radiographically around the implants using the long-cone parallel technique. Results: Sixty-eight participants who received 217 implants were included in the study. No late failures occurred. The mean duration of follow-up was 6.7 years (range, 5 to 9 years). The mean mBL after 5 to 9 years was 0.43 threads (± 1.12 threads) (0.26 mm). Thirteen implants (6.0%) showed a mBL of at least three threads. Multiple linear regression (R2 = 0.229) showed that implants in patients with poor periodontal maintenance and implants placed in periodontally compromised patients were significantly associated with greater mBL (P .005). Female gender and follow-up time were also associated with greater mBL. Conclusions: Limited long-term mBL was associated with machined-surface implants. Regular periodontal maintenance visits every 3 to 6 months, especially in periodontally compromised patients, have to be considered paramount to maintain peri-implant bone levels over the long term. Keywords: alveolar bone level, dental implants, periodontal maintenance, Plaque Index, risk factors, smoking

Purpose: Implant-supported rehabilitation of the atrophic posterior maxilla often necessitates maxillary sinus surgery to augment existing bone volumes. Recent systematic reviews have reported implant survival rates above 90% following sinus elevation. However, statistical assessment of the effect of anatomic factors, implant design and surface, individual risk factors, and complications related to sinus floor elevation procedures on implant survival through analyzing patient data has not yet been performed. The aim of this study is to identify risk factors that might affect implant survival following sinus elevation. Materials and Methods: Three centers were involved in this retrospective multicenter study; 106 patients were treated with 144 sinus elevation procedures and received 328 implants. The mean follow-up was 48.4 months, and the longest follow-up period was 72 months. The analysis considered patient age, gender, health status, and smoking habit; implant size, shape, and surface; residual ridge height; timing of implant placement with respect to grafting; graft material; and the occurrence of surgical complications. For quantitative variables, the Pearson correlation was used. The chi-square test and Fisher exact test (for samples smaller than five units) were used for qualitative variables. Results: The cumulative implant survival rate was 93.0% up to 5 years. Complications occurred in 41 patients. Intraoperative sinus membrane perforation occurred in 40 sinuses (28%) and was not a significant risk factor for implant survival. Six patients experienced postoperative infection leading to graft failure, and two patients had considerable intraoperative bleeding. Smoking more than 15 cigarettes/day and a residual ridge height 4 mm were significantly associated with reduced implant survival. Conclusions: Smoking habits and residual ridge height should be evaluated carefully prior to sinus elevation procedures. Keywords: atrophic maxilla, maxillary sinus elevation, residual ridge, sinus membrane perforation, smoking

Purpose: There is a growing pressure in implant dentistry to perform implant rehabilitations in difficult conditions, such as fresh extraction sockets, periodontally compromised sites, or sites with low bone density and quantity that imply a high likelihood of dehiscences or fenestrations. The aim of this study was to document complete rehabilitations in both jaws through the so-called All-on-Four concept (ie, four implants with the posterior implants placed at an angle) using immediate function implants inserted in "nonideal" conditions (eg, implants inserted with dehiscences or fenestrations, in periodontally compromised sites, or in fresh extraction sockets). Materials and Methods: This prospective cohort study included patients with immediately functioning implants placed in difficult conditions to support fixed full-arch maxillary and mandibular prostheses. Results: One hundred forty-two patients received 227 implants. A total of seven implants failed in six patients (three implants in three patients in the maxilla and four implants in three patients in the mandible), for cumulative patient and implant survival rates of 96.2% and 97.7% for the maxilla and 94.7% and 94.8% for the mandible, respectively, after 2 years (Kaplan-Meier). The average (standard deviation) peri-implant bone resorption after 1 year and 3 years in the maxilla was 1.3 mm (0.4 mm) and 1.6 mm (0.4 mm), respectively; in the mandible, the average (standard deviation) peri-implant bone resorption at 1 year and 5 years was 1.4 mm (0.3 mm) and 1.7 mm (0.6 mm), respectively. Conclusions: The results support the conclusion that the four-implant ("All-on-Four") immediate-function concept in completely edentulous maxillae and mandibles using implants inserted in difficult conditions is a viable concept in the short term. Keywords: All-on-Four, dehiscence, fenestration, immediate function, periodontally compromised, postextraction

Purpose: Today patients are living longer and demanding more stable prostheses to replace lost teeth. The restoration of the mandibular dentition with metal-acrylic resin implant-supported fixed complete prostheses via an immediate loading protocol allows patients to have an immediate definitive restorative solution. However, little is known about the patient experience and satisfaction with this protocol. The aim of this study was to determine patient experiences and satisfaction with metal-acrylic resin implant-fixed complete prosthesis fabricated according to the Ohio State University protocol. Materials and Methods: The records of patients who had received full-arch implant-supported restorations in a 7-year period were examined; patients who met the inclusion criteria were sent a questionnaire. Patients were given an opportunity to rate their postoperative experience using a visual analog scale and to agree or disagree with regard to their overall satisfaction with the surgical and prosthetic treatment. Results: The records of 82 patients were initially examined; 61 patients were retained after the inclusion criteria were applied. The questionnaire was sent to the 61 patients, and 24 returned their surveys. Data from the written questionnaires revealed that patient postoperative experiences were not considered severe and that the patients were generally very pleased with treatment and the outcome. Conclusions: The results of this questionnaire-driven study suggest that delivering the definitive fixed metal-acrylic resin prosthesis immediately after implant placement is a successful and patient-approved treatment approach for mandibular edentulism. Keywords: immediate load, metal-acrylic resin implant-supported fixed complete prosthesis, patient satisfaction

Purpose: Immediate loading has become a widely reported practice in implant dentistry. The aim of this study is to report on the 10-year clinical and radiographic outcomes of an immediate-loading treatment protocol that included flapless surgery. Materials and Methods: Forty-six patients were treated with 97 immediately loaded Mk IV implants (Nobel Biocare) with machined surface in the maxilla. Presurgically, a three-dimensional model of each patient's soft tissue and underlying alveolar bone anatomy was created and a surgical template was fabricated. A circular mucotome was used to punch out a 5-mm hole in the mucosa to avoid flap elevation. Control examinations were performed on the day of surgery and at 1, 2, 3, 6, 8, and 10 years after surgery. Results: All prepared implant sites had intact buccal and lingual bone walls. The prefabricated provisional restorations showed excellent fit. Nine implants failed within 8 weeks of loading, resulting in a cumulative survival rate of 91% after 10 years of loading. The survival rates were 94% for implants supporting partial prostheses and 81% for implants supporting single restorations. Average marginal bone resorption was 1 mm during the first year, 0.4 mm during the second year, and 0.1 mm during the third year and after 10 years. Conclusions: The unchanged survival rate and the low average bone loss after 10 years confirm the feasibility of an immediate loading treatment protocol in the maxilla that included flapless surgery. Keywords: dental implants, flapless surgery, immediate loading, machined surfaces, poor bone quality

Purpose: The aim of this retrospective study was to evaluate results and complications in sinus floor augmentations performed in the presence of antral pseudocyst. Materials and Methods: Two hundred thirtyfive sinus floor augmentation procedures performed in 179 patients (102 men and 77 women; mean age, 46.3 years; range 24 to 77 years) were included in the study. All patients had been admitted between 2007 and 2010 and treated with sinus augmentation in a single-stage or two-stage procedure using lateral sinus floor elevation (LSFE) or in a single stage via osteotome sinus floor elevation (OSFE). Results: A total of 29 (16.2%) patients had 32 (13.6%) sinus floor augmentation procedures performed in the presence of an antral pseudocyst. Faint dome-shaped radiopacities were detected at the floor of the antrum of these patients. No sinus membrane tears occurred during elevation in the LSFE group. Two patients in the LSFE group and one patient in the OSFE group developed acute sinusitis during the postoperative period and were treated with medical therapy. No symptoms of acute sinusitis or any other complications were encountered in the remaining patients after an average 17-month follow-up period. Conclusions: Pseudocysts of the maxillary sinus may not be a contraindication for sinus augmentation by OSFE or LSFE techniques. However, detailed evaluation of patients is crucial to prevent undesirable complications. Further studies of larger patient populations are needed to reach definitive conclusions. Keywords: maxillary sinus, pseudocyst, sinus elevation

Purpose: The present article sought to evaluate the effectiveness of a piezoelectric surgical unit for maxillary sinus augmentation surgeries in avoiding perforation of the sinus membrane and other possible procedural complications in patients with anatomical variations of the sinus. Materials and Methods: Twentyfive patients presenting sinus anatomical variations, who were indicated for a total of 40 sinus grafting procedures performed by the lateral window approach with a piezoelectric device, were analyzed. After 6 months of healing, implants were placed. Information collected included clinical and computed tomographic information on anatomical variations in the sinus bone walls, in the size of the sinus, and in the thickness of the sinus membrane. Occurrence of sinus membrane perforation and computed tomographic measurements of the amount of bone height gained with the grafting procedures were also recorded. Results: Only two patients presented a small perforation (less than 5 mm in diameter) of the sinus membrane, which occurred only after osteotomies of the lateral windows and did not compromise the surgical outcome. No implants were lost during a mean follow-up period of 19 months. Conclusion: The use of piezoelectric surgery allowed for the accomplishment of all rehabilitation treatments within the follow-up period of this study. Keywords: lateral window approach, maxillary sinus, piezoelectric surgery, sinus anatomical variations, sinus elevation

Purpose: The purpose of this retrospective chart-review study was to compare the early success rate and the crestal bone changes of dental implants in patients taking oral bisphosphonates at the time of implant placement to those of patients who had never taken bisphosphonates. Materials and Methods: A retrospective chart review of 100 women (153 implants) taking oral bisphosphonates at the time of implant placement (test group) and 100 women (132 implants) who had never taken bisphosphonates (control group) was performed to examine overall implant success at the time of stage-two surgery. Radiographic images, which were available for 73 patients in each group and were taken at the time of implant placement and at stage-two surgery, were analyzed to assess and compare crestal bone changes around the implants. Results: There was no significant difference between groups in the success rates of dental implants at stagetwo surgery (test 93.5%, control 95.5%). The change in crestal bone height was statistically significant from the time of placement to stage-two surgery within both groups but was not significantly different between groups (means ± standard deviations: test, 0.66 ± 0.70 mm; control: 0.80 ± 0.65 mm). Conclusions: In this study, the use of oral bisphosphonates at the time of implant placement and during healing did not affect early implant success rates or crestal bone changes up to the time of stage-two surgery. In addition, the implant location and the duration of drug therapy at the time of placement were not significant factors in the success rate or bony changes. These conclusions must be viewed in the context of the limitations of the retrospective study design and should be confirmed in longer, more rigorously designed studies. Keywords: bisphosphonates, dental implants

Purpose: Sinus elevation through the crestal approach has become a routine procedure for implant placement in the posterior edentulous maxilla. The combination of flapless surgery and crestal sinus elevation with simultaneous placement of implants is an attractive surgical approach for implant grafting in the posterior maxilla, but its efficacy and safety have seldom been studied. The aim of this study is to evaluate retrospectively the outcomes of flapless crestal sinus floor elevation using piezosurgery and a hydraulic sinus elevation system with simultaneous implant placement. Materials and Methods: Between October 2009 and August 2010, flapless implant surgery using a crestal approach, accompanied by simultaneous hydraulic sinus elevation and grafting, was performed. Patients were followed up clinically and with intraoral and panoramic radiographs. Any postoperative complications, including swelling, discomfort, infection, fractures, and implant loss, were recorded, and sinus bone gain was measured. Results: Thirty-one sinuses were elevated and 35 implants were placed. Patients were a mean of 41.2 ± 6.69 years old, and 45% were women. The sinus was elevated to 7 to 15 mm, and no membrane perforations were noted. The mean follow-up period was 21 weeks. The mean bone gain under the maxillary sinus was 12.03 ± 2.1 mm, and all implants displayed primary stability with a mean insertion torque >= 15 Ncm. No postoperative discomfort, swelling, hematoma, infection, or bone fenestration was noted. One patient experienced prolonged edema in the lower eyelid region, and another lost an implant. Conclusion: In this retrospective analysis, flapless crestal sinus floor elevation was safe and effective, decreasing surgical discomfort and trauma and early implant failures. Keywords: crestal approach, flapless dental implant placement, hydraulic sinus elevation, piezosurgery, posterior maxillary implant

Purpose: The aim of this study was to evaluate the influence that lateral window dimensions may have on maxillary sinus augmentation outcomes. Materials and Methods: Patients requiring maxillary sinus augmentation by a lateral window approach and delayed implant placement were recruited in this study. Approximate window dimensions (AWD) were calculated in mm2 at the time of the surgical intervention. In all cases, a mixture of cortical and cancellous allograft particles was used as the sole grafting material. Patients were followed for 6 months. At the time of implant placement, bone core biopsies were harvested. Transversal circular samples were histomorphometrically analyzed. Proportions of vital bone (VB), remaining allograft particles (RA), and nonmineralized tissue (NMT) were quantified. Analysis of correlation of AWD with %VB, %RA, and %NMT was performed using a statistical model. Results: A total of 24 maxillary sinus augmentation procedures were performed in 21 patients. One patient developed an infection after grafting and was excluded. Histomorphometric analysis showed that mean %VB was 21.69% ± 16.30%, %RA was 23.51% ± 16.33%, and %NMT was 55.08% ± 8.52%. A strong negative correlation was observed between AWD and %VB (r = -0.621; P = .0007), a marked positive correlation was found between AWD and %RA (r = 0.565; P = .002), and a minimal positive correlation, without statistical significance, was found between AWD and %NMT (r = 0.076; P = .365). Conclusions: The results of this study suggest that AWD may have an important influence on the maturation and consolidation of a mixture of cortical and cancellous allograft in the maxillary sinus. Keywords: bone grafting, dental implants, maxillary sinus

Purpose: This prospective clinical study evaluated an experimental custom-made zirconia abutment with respect to peri-implant hard and soft tissue reaction in narrow implants. Materials and Methods: Patients were treated with prefabricated titanium implants and custom-made zirconia abutments. All-ceramic crowns were fabricated and cemented with resin cement. Clinical parameters such as Plaque Index, Sulcus Bleeding Index, peri-implant probing depth, and radiographic marginal bone loss levels were recorded, along with any biologic and mechanical complications, at baseline and up to 5 years. Results: Twelve patients with missing maxillary lateral incisors treated with a total of 23 implants were evaluated. Thirteen Straumann Narrow Neck Solid Screw implants with a diameter of 3.3 mm and 10 Astra MicroThread implants with a diameter of 3.5 mm were used. Six patients with 11 implants were treated with custom-made zirconia abutments and prefabricated metal abutments were used in the control group. Implant and abutment success at 5 years was 100%. No abutment fractures occurred. Abutment screw loosening was reported for one restoration at the 1-year recall. Mean marginal bone loss measured 0.21 mm after 5 years of functional loading. Conclusion: Custom-made zirconia abutments offered sufficient stability to support all-ceramic restorations over narrow implants in anterior regions over a 5-year period. The soft and hard tissue reactions to zirconia were favorable. Keywords: clinical follow-up, full ceramic crowns, narrow implants, zirconia abutment

Purpose: To evaluate the influence of sex, implant characteristics, and bone grafting on the survival rate of dual acid-etched (DAE) implants. Materials and Methods: Patients treated with internal-hex DAE implants for singletooth replacement in a military dental clinic between January 2005 and December 2010 were included in this study. Clinical data related to implant characteristics, implant location, presence of grafted bone, and implant failures were collected. The primary outcome was implant loss. The survival rate was analyzed using the Kaplan- Meier method. Cox regression modeling was used to determine which factors would predict implant failure. Results: DAE implants were evaluated in a total of 988 patients (80.3% men). Twenty-four (2.4%) implants failed, most were cylindric (54.2%) with regular platforms (70.8%) and were 10 mm long (58.3%). The failure rate was 2.4% for the anterior maxilla, 3.3% for the posterior maxilla, 1.6% for the anterior mandible, and 2.0% for posterior mandible. The cumulative survival rate was 97.6%. The failure rate was 8.8% in implants placed after sinus augmentation, 7.3% in bone block-grafted areas, and 1.6% in native bone. Based on multivariable analysis (Cox regression), sinus augmentation and bone block grafting had a statistically significant effect on implant failure; the hazard ratios were 5.5 and 4.6, respectively. Conclusion: The results revealed that DAE implants had high survival rates, and no influence of sex, location, shape, diameter, or length on failure rates could be observed. However, a significant association was observed between failure and presence of bone graft in the implant area. Keywords: clinical trial, dental implants, retrospective studies, survival rate

Purpose: Buccal bone responses following dental implant placement are considered significant determinants of esthetic outcomes. The aim of this pilot study was to evaluate whether cone beam computed tomography (CBCT) could be used to measure buccal alveolar bone changes following implant placement. The second aim of this investigation was to determine both qualitatively and quantitatively if changes could be determined 1 year postoperatively at the buccal aspect of implants placed in healed ridges or extraction sockets. Materials and Methods: Twenty patients in need of a single tooth in the maxillary anterior or first premolar region were recruited under an institutional review board-approved protocol. Patients were allocated into two groups: those missing a tooth with a healed alveolar ridge and those needing an extraction. Following treatment planning, implants were placed and immediately loaded. Zirconia abutments and all-ceramic crowns were delivered 16 weeks following implant placement. CBCT images of the maxilla were obtained at three different time points; 2 weeks before surgery, immediately after surgery, and 12 months after implant placement. A single examiner measured each implant three times in four different sites. The data between different implants or subjects were compared among groups by the nonparametric sign test. Results: Evaluation of the CBCT images revealed that it was possible to discern the presence or absence of the buccal bone plate both prior to and 1 year following implant placement in the majority of subjects. The median alteration after 1 year for the vertical distance from the abutment/implant interface to the buccal alveolar bone crest for all subjects was -1.12 mm (P = .018). The horizontal alteration of the buccal bone measured 1 mm apical to the implant/abutment interface was -0.62 mm (P = .004). At the midimplant and apical regions of the implants, the 1-year horizontal bone alteration was -0.57 mm (0.004) and -0.19 mm (P = .059), respectively. Conclusions: Buccal bone and alterations following implant placement may be visualized by CBCT in both extraction sockets and healed ridges. When the implant was appropriately displaced from the buccal wall of the socket, bone changes could be qualitatively evaluated by CBCT 1 year following placement. Keywords: bone resorption, CBCT, dental implant, immediate provisionalization

Purpose: To evaluate the performance of a computer-aided three-dimensional planning protocol in combination with previously inserted reference mini-implants and CAD/CAM technology to restore completely edentulous patients. The study evaluated implant and superstructure survival in a prospective clinical trial. Materials and Methods: The plan protocol called for treatment of 35 patients who were edentulous in either arch. Miniimplants were used to establish a platform for computed tomography and fixation of the surgical template. The planning software based on three-dimensional simulation was used to plan ideal implant placement, digitally integrating the future prosthetic and anatomical situations to design the definitive superstructure. Results: A total of 35 patients, 20 with edentulous maxillae, 10 with edentulous mandibles, and 5 patients with edentulism in both arches were treated. All patients received definitive prostheses on the day of surgery. The majority of patients treated in maxilla underwent a sinus graft procedure to achieve sufficient bone to place implants. A total of 40 superstructures were inserted and immediately loaded. Of the 240 inserted implants, 229 (95.4%) survived, with 146 (93.6%) and 83 (98.8%) implants in the maxillary and mandibular arches, respectively. Of the 10 implants that failed in the maxilla, 9 occurred in patients with an augmented sinus. All definitive restorations demonstrated clinically acceptable fit. Conclusions: When evaluating implant and superstructure survival, reference-based guided surgery seems to be a reliable treatment option for edentulous patients. The CAD/CAM superstructure, inserted and loaded immediately after guided implant insertion, demonstrated acceptable fit to the underlying implants. Keywords: computed tomography, computer-assisted surgery, dental implant, edentulism, surgical guide, surgical template, three-dimensional planning

Purpose: To examine the relationship between dental cone beam computed tomography (CBCT) gray scale values and Hounsfield units (HU), and whether the gray values of edentulous sites correlate with the subjective clinical bone quality assessed at surgery. Materials and Methods: Two radiographic phantoms containing varying concentrations of either dipotassium hydrogen phosphate or calcium hydroxyapatite (HA) were imaged using multislice CT or CBCT. Reconstructed DICOM data were analyzed to examine the relationship between CBCT gray values and HU. Presurgical CBCT scans from 52 patients who underwent implant placement in the posterior sextants were used. The gray values of the edentulous implant sites were measured and compared with the subjective bone quality assessed at surgery. Results: There was a strong correlation between CBCT gray values and HU. CBCT gray values increased linearly with increasing calcium HA or bone equivalent density material. CBCT gray values measured at edentulous implant sites ranged from -455 to 642, with a trend of decreasing gray values with bone quality type. The median gray values for the four subjective bone types were: 362 (type 1), 214 (type 2), 76 (type 3), and -454 (type 4). Conclusions: CBCT gray values can be used to infer bone density and may provide a valuable aid to predict bone quality at potential implant sites. Keywords: cone beam computed tomography, endosseous implants, radiographic bone density

Purpose: The aim of this study was to analyze and compare the level and distribution of peri-implant bone stresses associated with mandibular two-implant overdentures with different implant positions. Materials and Methods: Mathematical models of mandibles and overdentures were designed using finite element analysis software. Two intraosseous implants and ball attachment systems were placed in the interforaminal region. The overdenture, which was supported by the two implants, was designed to withstand bilateral and unilateral vertical masticatory loads (total 100 N). In all, eight types of models, which differed according to assigned implant positions, height of attachments, and angulation, were tested: MI (model with implants positioned in the lateral incisor sites), MC (implants in canine sites), MP (implants in premolar sites), MI-Hi (greater height of attachments), MC-M (canine implants placed with mesial inclination), MC-D (canine implants placed with distal inclination), MC-B (canine implants placed with buccal inclination), and MC-L (canine implants placed with lingual inclination). Results: Peri-implant bone stress levels associated with overdentures retained by lateral incisor implants resulted in the lowest stress levels and the highest efficiency in distributing peri-implant stress. MI-Hi showed increased stress levels and decreased efficiency in stress distribution. As the implants were inclined, stress levels increased and the efficiency of stress distribution decreased. Among the inclined models, MC-B showed the lowest stress level and best efficiency in stress distribution. Conclusion: The lowest stress and the best stability of implants in mandibular two-implant overdentures were obtained when implants were inserted in lateral incisor areas with shorter attachments and were placed parallel to the long axes of the teeth.

Purpose: The aim of the present study was to compare the biomechanical effects of different lengths of implants in an immediate loading condition in mandibular and fibular bone. Three-dimensional (3D) nonlinear finite element analysis (FEA) was used to examine the complex irregular structures. The variables of this research were the two different bone types (mandible and fibula) and three different implant lengths. Materials and Methods: Simplified half models were constructed for 3D FEA. Three different implant lengths (6 mm, 10 mm, and 15 mm) were inserted into the mandibular and fibular bone models, which were made to simulate immediate implant loading conditions. A load of 125 N was applied to the center of the suprastructure at a 45-degree angle relative to the long axis of the implant, and the resultant maximum von Mises equivalent (EQV) stresses, stress distribution, strain energy, and micromotion were measured. Results: In the mandible, the maximum EQV stresses were 115.636 MPa, 155.943 MPa, and 157.105 MPa with the 6-mm, 10-mm, and 15-mm implants, respectively. The mean EQV stresses were 64.145 MPa, 77.925 MPa, and 78.500 MPa, respectively. In the fibula, the maximum EQV stresses were 174.04 MPa, 157.456 MPa, and 144.353 MPa with the 6-mm, 10-mm, and 15-mm implants, respectively. The mean EQV stresses were 82.329 MPa, 73.526 MPa, and 74.050 MPa, respectively. Conclusion: The micromotion in the fibula models was lower than that seen in the mandible models. EQV stress in the fibular bone was different from that in the mandible. Short implants can be an option for oral rehabilitation in the mandible; however, implants in the fibula should probably have bicortical engagement.

In the past, the Brånemark Novum protocol for the immediate functional loading of a mandibular fixed implantsupported prosthesis provided an effective alternative for select patients. However, the manufacwturer has discontinued this design, and only a few selected prosthetic-related replacement components are currently available. This clinical report presents the loss of an implant associated with a discontinued system. To take advantage of all of the preexisting components, it proposes a rescue procedure that allows continuous use of the original fixed restoration during the restoration of the tripod support at the implant level.

Extraoral implants have been used for many years to anchor silicone nasal prostheses. This report describes the design and use of a specially engineered bifunctional implant, which is placed via an intraoral approach, to simultaneously anchor nasal and oral prostheses for an edentulous patient who has undergone a complete rhinectomy. The bifunctional implant was designed and milled from commercially pure titanium using computer-aided design/computer-assisted manufacturing (CAD/CAM) technology. The nasal part of the implant was designed to fit through the prepared site and protrude into the piriform aperture. A hex attachment was orientated perpendicular to the axis of the implant on this extension. The intraoral head of the implant was provided with a standard Brånemark hex configuration. Implants were placed using the guide and associated instrumentation. This case demonstrates the potential for CAD/CAM technology to produce bespoke implantable components at low cost. In this report, the implant greatly facilitated the surgical and prosthetic management for the simultaneous provision of nasal and oral prostheses.

Obtaining an accurate impression of facial tissues with undercuts and extraoral implants has always been a challenge for both clinicians and patients. This report describes a three-step, two-piece technique that enables an accurate and comfortable impression of undercut tissues and extraoral implants in an orbital defect. An impression of the basal tissue surface of the defect area was made using a medium-body polyether impression material followed by an impression of the entire face of the patient made with a polyvinyl siloxane (PVS) impression material. First, the PVS impression material was removed; second, the impression posts were removed from the magnets; and third, the polyether impression was removed from the defect. The impression posts were attached to the implant analogs and placed in the negative spaces in the polyether impression. The polyether impression, which carries the implant analogs and impression posts, was placed in the PVS impression through the negative spaces. This technique minimizes trauma to the soft tissues and implants during impression making and also does not require additional materials.