The International Journal of Oral & Maxillofacial Implants, 03/2019

Purpose: To report the performance of a repair service set for the retrieval of fractured screws and to compare three clinical assessments to an in vitro assessment to verify the completeness of removal of the fractured screws. Materials and Methods: Twelve clinicians were asked to remove fractured implant abutment screws from prepared specimens by means of a repair service set. The completeness of the removal of any abutment screw material was measured by the fit of an impression post, a dental surgery microscope, and the use of an elastomeric impression material. Results: After the participants attempted to remove the fractured screw with the repair service set, 100%, 83.3%, 66.7%, and 75% of the fractured screws were considered successful in the impression post, dental surgery microscope, silicone replica, and stereomicroscope assessments, respectively. Conclusion: The retrieval of fractured screws succeeded in 75% of the cases. The silicone replica technique and the dental surgery microscope had similar diagnostic values to the stereoscopic microscope assessment. Keywords: dental abutments, dental implants, dental restoration failure

Purpose: To investigate the histologic differences between immediate implants placed in chronically infected sites and noninfected sites in a canine model. The histologic results of immediate implant placement also were evaluated on the basis of healing time and implant surface modification. Materials and Methods: Chronic endodontic-periodontic combined lesions were induced on the second, third, and fourth premolars of the hemimandible in six dogs, with the contralateral teeth as controls. Implants were immediately placed following the infected and noninfected tooth extractions using implants with a machined surface, sandblasted with alumina and acid-etched surface, and chemically modified sandblasted with alumina and acid-etched with calcium solution surface. After 1 and 3 months, three dogs were euthanized and the bone-to-implant contact, bone area fraction occupied, buccal and lingual first bone-to-implant contact from the implant platform, and buccal and lingual marginal bone loss were calculated. Results: On histologic evaluation, no inflammation was observed around implants placed in the infected or noninfected sockets. At 1 month, no statistically significant differences were observed between the infected and noninfected sockets in buccal marginal bone loss in the machined implant group (P = .046), lingual first bone-to-implant contact from the implant in the sandblasted with alumina and acid-etched group (P = .046), lingual marginal bone loss in the sandblasted with alumina and acid-etched implant group (P = .028), buccal first bone-to-implant contact from the implant platform in the chemically modified sandblasted with alumina and acid-etched with calcium solution group (P = .028), and lingual first bone-to-implant contact from the implant platform in the chemically modified sandblasted with alumina and acid-etched with calcium solution group (P = .046). At 3 months, no statistically significant differences were observed in parameters between the infected and noninfected sockets for three implant surfaces. Differences between the infected and noninfected sockets were observed between the machined and sandblasted with alumina and acid-etched implant at 1 month (P = .023). Conclusion: Immediate implant placement in an infected socket did not lead to any differences compared with placement in a noninfected socket when sufficient healing time was provided. Keywords: bone healing, histomorphometric, immediate placement, periodontitis, surface

Purpose: To evaluate differences in implant placement accuracy depending upon the presence or absence of metal restorations, as well as between distal extension and tooth-end cases. Materials and Methods: Five experimental groups were designed with mandibular models exhibiting the following dental statuses: six anterior teeth and bilateral second molars, with bilaterally edentulous sites between them (group NN); six anterior teeth (group NDE); identical to group NN, with the six anterior teeth restored with metal crowns (group MN); identical to group NDE, with the six anterior teeth restored with metal crowns (group MDE); identical to group NN, with all remaining teeth restored with metal crowns (group MM). Six implants were placed on the bilateral first and second premolars and first molars; the linear and angular deviations between the preoperatively planned and actually placed implant positions were computed. Results: Implant position errors were 0.55 to 0.87 mm and 0.53 to 0.80 mm at the entry point and apex, respectively, and were 0.35 to 0.71 mm and 2.02 to 3.12 degrees in depth and angular deviations, respectively. Significant differences were observed between groups NN and MM in overall deviations at the entry point (P = .009) and apex (P = .026), as well as in depth deviation (P = .008). Conclusion: The presence of metal restorations on all anterior and posterior remaining teeth resulted in significant differences in linear deviation at the entry point and apex between preoperatively planned and actually placed implant positions, compared with natural teeth without restorations. No significant differences were observed in placement accuracy between distal extension and tooth-end cases. Keywords: cone beam computed tomography, dental implantation, dental models, dental prosthesis, radiation scattering

Purpose: This study assessed the ability of resonance frequency measurements to differentiate the stability of implants with different lengths and diameters, and in different densities of bone. Another objective was to identify an alternative parameter capable of quantifying dental implant stability, thus facilitating greater sensitivity for efficacious detection of compromised or failing implants. Materials and Methods: Implants of two different diameters (4 and 5 mm) and six different lengths were individually placed in synthetic bone blocks of three different densities (15, 40/20, and 40 pounds per cubic foot) in combination with two different abutments (short and tall) to evaluate their stability. Resonance frequency measurements were obtained via Osstell ISQ and experimental modal analysis. The resonance frequency measurements were further confirmed via finite element analysis using commercially available software ANSYS. Results: Resonance frequencies measured via Osstell ISQ and experimental modal analysis did not change with respect to the length of the implants. The finite element analysis also confirmed the measured results. Finite element analysis simulations further indicated that angular stiffness at the neck of the implant (ie, the base of the abutment) varied considerably with respect to the implant length and diameter. Moreover, the calculated angular stiffness was independent of the type of abutment used. Conclusion: The results obtained from resonance frequency analyses did not accurately represent dental implant stability. Changes to implant length and diameter did not affect resonance frequencies. In contrast, angular stiffness at the neck of the implant represented a superior index for quantifying dental implant stability. It not only successfully differentiated stability of implants of both varying lengths and diameters, but also produced quantitative data that were independent of the type of abutments used. Keywords: angular stiffness, dental implant, experimental modal analysis, finite element analysis, natural frequency, stability

Purpose: Dental implant placement in atrophic ridges is challenged by availability of bone and proximity to vital structures. Although short dental implants have been considered favorable, there is no consensus regarding their long-term survival and factors affecting it. This systematic review addressed the focused question, "What is the survival rate of short dental implants (SDI; length ≤ 6.5 mm) placed in posterior edentulous ridges without any ridge augmentation procedures and followed up for 12 months post-prosthetic loading, and what are the factors affecting their survival rate?" Materials and Methods: Based on a search of the indexed literature, 51 studies fulfilling the inclusion criteria were quantitatively reviewed. Overall SDI survival and factors influencing survival, such as anatomical location, surgical protocol, time of loading, type of prosthesis retention, nature of prosthesis, implant stability, crown-to-implant ratio (C/I ratio), and marginal bone loss at follow-up were evaluated. SDI survival based on clinical factors was compared to overall survival using odds ratio (OR), and continuously distributed data were evaluated using Pearson's correlation (P .05). Results and Conclusion: Based on this review, SDI placed in edentulous posterior regions of the maxilla and mandible have survival rates (96.45%) similar to those of conventional-length implants after a follow-up period of 12 months post-prosthetic loading. Except for smaller implant diameter (OR = 1.59, 95% confidence interval [CI] = 1.03-2.43, P .05), screwretained restorations (OR = 2.11, 95% CI = 1.25-3.57, P .01), and C/I ratio ≥ 2 (Pearson's R = -0.694, P .01), other variables relating to implant surgery, prosthetic loading, nature and type of prosthesis, and follow-up did not significantly affect SDI survival. Keywords: dental implants, extra-short implants, extremely short implants, implant survival, osseointegration, short implants

Purpose: The purpose of this study was to compare the fracture resistances and the fracture types of titanium, zirconia, and ceramic-reinforced polyetheretherketone (PEEK) implant abutments supporting computer-aided design/computer-aided manufacturing (CAD/CAM) monolithic lithium disilicate ceramic crowns after in vitro dynamic loading and thermocycling aging. Materials and Methods: Three implant abutment (SKY Implant) groups-titanium (group Ti, control); zirconia with titanium base (group Zr); and ceramic-reinforced PEEK (BioHPP) with titanium base (group RPEEK); n = 12 each-were used. Thirty-six CAD/CAM monolithic lithium disilicate crowns (IPS e.max CAD) in the form of a maxillary central incisor were cemented with Panavia V5 on the abutments. The specimens were subjected to dynamic loading and thermocycling. Fracture resistances of the restorations were tested with a universal testing machine (0.5 mm/min), and their fracture patterns were analyzed. One-way analysis of variance (ANOVA) and Tukey post hoc test were used for statistical analyses (α = .05). Results: All samples survived after aging. The fracture strength values (mean ± standard deviation) of the groups were as follows: group Ti, 787.8 ± 120.9 N; group Zr, 623.9 ± 97.4 N; and group RPEEK, 602.9 ± 121 N. The fracture strengths were significantly higher in group Ti compared to groups Zr and RPEEK (P = .001). No significant difference was observed between groups Zr and RPEEK. Failures generally occurred due to fracture of the screw in group Ti, abutment and crown in group Zr, and crown in group RPEEK. Conclusion: Ceramic-reinforced PEEK abutments may be an alternative to zirconia abutments with a titanium base for single-implant restorations in the anterior region. However, there is need for further in vitro and clinical studies to evaluate the long-term performance of ceramic-reinforced PEEK abutments. Keywords: ceramic-reinforced polyetheretherketone, chewing simulator, dental implant abutments, fracture resistance, lithium disilicate crowns, titanium, zirconia

Purpose: The aim of this work was to prove the synergic complementarity of attenuated total reflection Fourier transform infrared microspectroscopy (micro-ATR FTIR), scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDS), and x-ray microcomputed tomography (micro-CT) by studying implant samples with bone affected by peri-implantitis. Materials and Methods: Six samples of implanted bone affected by peri-implantitis and one control healthy bone were analyzed. Thick bone sections included in epoxy-resin and removed implants were analyzed by micro-ATR FTIR, SEM-EDS, and micro-CT. Results: Micro-ATR FTIR revealed the complex nature of the bone composition. Vibrational bands characteristic of both mineral bone phase (acidic phosphates, CO₃^2- groups) and organic bone phase (mostly collagen) could be recognized, and their proportion could be seen to change accordingly with the bone degradation. Similarly, SEM-EDS clearly revealed the cortical nature of the control mandible and its homogenous mineral composition. On the contrary, EDS analyses performed over relevant portions of pathologic samples revealed that defective areas were almost Ca and P free. Micro-CT data showed that the morphology of the interface was smooth and linear in the physiologic peri-implant bone, while in the pathologic samples, an altered morphology was evident. Conclusion: This study demonstrated that morphologic, elemental, and biochemical modifications of peri-implant bone can be studied using micro-ATR FTIR, SEM-EDS, and micro- CT. The complement of these techniques can be considered a new multipurpose approach to investigate bone affected by peri-implantitis. Keywords: bone-implant interactions, CT imaging, surface chemistry

Purpose: The increased use of cell phones has raised many questions as to whether their use is safe for patients with dental implants. This study aimed to assess the consequences of cell phone-emitted radiation on bone-to-implant osseointegration during the healing phase. Materials and Methods: Twelve rabbits were grouped into three groups of four. Group 1 (control) was not exposed to electromagnetic radiation; group 2 (test) was exposed for 8 hours/day in speech mode and 16 hours/day in standby mode; and group 3 (test) was exposed for 24 hours continuously in standby mode for 3 months. Forty-eight implants were placed in the tibia and femur bone of rabbits, and after 90 days, the rabbits were sacrificed and bone surrounding the implant was retrieved. Histopathologic evaluations of the specimens were done using a transmitted light microscope. The differences among the three groups were statistically analyzed with analysis of variance (ANOVA) and pairwise comparisons via Fisher's exact test. Results: Significantly less bone-to-implant contact and bone area surrounding implant threads were found in the test groups compared with the control group. There was a significant difference in regular bone formation (P .001) among the three groups. Conclusion: Implants exposed to cell phone radiation showed more inflammatory reaction compared with the nonexposed implants, thus indicating that cellular phone overuse could affect the maturation of bone and thus delay osseointegration. Keywords: cell phones, dental implants, nonionizing radiation, osseointegration

Purpose: The purpose of this in vitro study was to examine the effect of dissociated soft tissue on bone marrow cell proliferation and differentiation under osteogenic conditions. Materials and Methods: Rat bone marrow cells were cultured to assess the stimulation of cell proliferation and differentiation. Harvested palatal mucosa was dissociated using a device (Rigenera, Human Brain Wave), and the dissociated soft tissue was cultured with rat bone marrow cells. Cell proliferation, differentiation, and mineralized nodule formation were assessed after 2 or 5 days of culturing. Bone marrow cell proliferation was assessed by quantifying the absorbance of a water-soluble tetrazolium salt using a cell proliferation assay kit. Bone marrow cell differentiation was assessed by alkaline phosphatase staining and real-time polymerase chain reaction. Mineralized nodule formation was assessed by Alizarin red staining. Results: At day 2, cell proliferation, osteoblast-specific gene expression, and mineralized nodule formation were significantly higher in the experimental group than in the control group. Alkaline phosphatase staining was also higher in the experimental group on day 2. Mineralized nodule formation area and osteoblast-specific gene expression were also statistically higher in the experimental group on day 5. Conclusion: This study demonstrates that dissociated soft tissue elevates bone marrow cell proliferation and differentiation under osteogenic conditions. Keywords: bone regeneration, dissociated soft tissue solution, in vitro study, palatal mucosa

Purpose: This histologic study aimed at assessing bone healing after treatment with simvastatin in association with low-level laser therapy (LLLT). Materials and Methods: Twenty-four male rats (Wistar) were submitted to surgery to create a bone defect of 5 mm in diameter in the parietal bone. These rats were randomly and equally divided into four treatment groups (n = 6): control (C), in which no treatment was performed; simvastatin (SIM), in which rats received daily subcutaneous doses of 2.5 mg/kg of simvastatin; LLLT, which was daily applied to the bone defect; and SIM-LLLT, in which both SIM and LLLT were daily applied. All laser irradiations were carried out with a 830-nm infrared diode laser (GaAlAs) with maximum output of 100 mW and a dose of 4 J, totaling 16 J per session. Rats were euthanized on the 12th postoperative day. Formalinfixed paraffin-embedded bone samples were obtained and stained with hematoxylin-eosin (HE) and toluidine blue for optical microscope analysis. Degree of inflammation, new vascular formation, tissue repair, and osteoblastic activity were assessed. Results: Categorical analysis of the histologic slides revealed newly formed bone reaching the center of the surgical wound in two animals from the SIM group, two from the LLLT group, and three from the SIM-LLLT group. Greater new bone formation and a lower degree of inflammation were observed in the animals that had bone neoformation at the center of the defect, especially in the LLLT and SIM-LLLT groups. SIM and C groups presented greater angiogenesis than LLLT and SIM-LLLT. SIMLLLT therapy showed a statistically significant reduction in the degree of inflammation compared with the control group (P .05). Conclusion: Within the limitations of this study, the present results suggest that a combination of simvastatin and low-level laser therapy may stimulate better bone formation. Keywords: biomaterials, bone repair, histology, low-level laser, simvastatin, surgery

Purpose: To assess the reliability and accuracy of linear measurements on three-dimensional (3D) crosssectional images, both acquired with cone beam computed tomography (CBCT) and multidetector row CT (MDCT). Bone thickness was evaluated with regard to image-guided planning of craniofacial implant surgery. Materials and Methods: Five dry human skulls were used. Cuts were made with a circular bone saw at the ideal implant positions in the nasal, orbital, and temporal regions prior to acquisition of CBCT and MDCT scans. After imaging examination, bone width was assessed by three independent observers using a caliper and defined as a reference. In the next step, cross-sectional images of the regions with the aforementioned cuts were reconstructed from 3D virtual models generated from the digital DICOM datasets with the use of 3D image-based planning software. Subsequently, linear measurements were performed. The systematic difference and interobserver and intraobserver variation of MDCT and CBCT linear measurements were compared with the physical measurements at different locations in the nasal, orbital, and temporal regions, respectively. Also, the potential influence of different gray-level values was investigated. The quantitative accuracy of distance measurements was performed using a two-way analysis of variance (ANOVA) and variance component analyses. Only differences with P values .05 were considered significant. Results: All radiologic measurements showed a significant overestimation of the bony dimensions, reaching more than the used voxel sizes of 0.3 mm for CBCT and 0.5 mm for MDCT. For CBCT, an average measurement bias of 0.39 to 0.53 mm and for MDCT of 0.57 to 0.59 mm was found. MDCT images showed less interobserver variation in linear measurements on cross-sectional images from 3D virtual models compared with CBCT images. Contrast settings statistically significantly influenced linear measurements of bone width for CBCT images (P .0015) and interobserver variation on MDCT imaging (P .029). Conclusion: Both CBCT images (KaVo 3D eXam Imaging System, KaVo Dental) and MDCT images (Aquilion ONE, Toshiba) showed a highly consistent submillimeter overestimation of the anatomical truth in assessing bone thickness of nasal, orbital, and temporal regions of ex vivo specimens. When using CBCT and MDCT images for presurgical assessment, one should be aware of the overestimation of the cortical bone thickness. Keywords: 3D, implant planning, maxillofacial, radiology

Purpose: To evaluate the effects of different titanium particle concentrations on the viability of human calvarial osteoblasts and human gingival fibroblasts. Materials and Methods: Primary human calvarial osteoblasts (HCO, 3H Biomedical) and human gingival fibroblasts (HGF-1, ATCC) were cultivated and allowed to adhere for 24 hours. Titanium powder concentrations (0.01 to 1.0 mg/mL) were added, and samples were analyzed at three time points (24 hours, 7 days, 21 days). Cell viability was analyzed using living cell count, proliferation (MTT) assay, and live/dead staining. Cytotoxic effects were evaluated using lactated dehydrogenase assay. Qualitative analysis of cell viability was performed. In addition, scanning electron microscopy (SEM) analysis was performed. Release of interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) was estimated with human IL-6/human TNF-α ELISA. Results: Titanium concentrations of 0.1 mg/mL and 1.0 mg/mL showed medium- and long-term effects on cell growth and proliferation rates. Cytotoxic effects by release of lactate dehydrogenase were observable during the first 24 hours. Human gingival fibroblast cells showed a release factor between 2.6 and 3.4. Titanium powder seemed to be more cytotoxic to human gingival fibroblast cells than to human calvarial osteoblast cells. For human calvarial osteoblasts, only the highest concentration showed cytotoxic effects with a release factor of 2.7. Human calvarial osteoblasts secreted IL-6 only during the first 24 hours and only in the highest titanium concentration, whereas human gingival fibroblasts secreted IL-6 during the entire period. The lowest titanium concentration showed stronger secretion of IL-6 compared with the control. Incorporation of smaller and single titanium particles by cells was identified under SEM analysis. Conclusion: Cell viability is negatively correlated with titanium concentration. Further, titanium debris might lead to an inflammatory biologic response of dental peri-implant tissue. Also, cells interact with the debris, eg, with incorporation of particles. Keywords: human gingival fibroblasts, human osteoblasts, primary cell culture, titanium debris, titanium particles

Purpose: Scientific publications have recently found that bone graft quality and implant survival rates were not influenced by antrostomy membrane coverage during maxillary sinus floor augmentation with a lateral approach. The aim of this study was to evaluate the stability of the bone substitute after a maxillary sinus floor augmentation procedure with or without using a covering membrane. Materials and Methods: This retrospective study evaluated all patients who were enrolled between April 2016 and January 2017. The stability of the bone graft inside the sinus cavity and at the level of the lateral bone window was assessed through preoperative and postoperative cone beam computed tomography images up to 6-month follow-up. The clinical postoperative morbidity was evaluated following a visual analog scale protocol. Results: Maxillary sinus floor augmentation with a lateral approach was performed in 41 patients. In 17 cases (10 women/7 men, mean age: 55.4 years), a barrier membrane was used to cover the lateral bone window (control group), and in 24 cases (13 women/11 men, mean age: 56.2 years), no membrane was used (test group). The bone graft dislodgment within the buccal mucosa at 6 months postoperative ranged from 0 to 12.2 mm (mean ± SD value: 3.8 ± 3.1 mm) in the test group and from 0 to 2.3 mm (mean ± SD value: 0.5 ± 0.4 mm) in the control group. The postoperative pain and swelling complications were significantly more important for the test group (3.3 ± 1.4/4.3 ± 4.5, respectively) than for the control group (2.1 ± 0.9/2.7 ± 0.9). Conclusion: On the basis of this preliminary study, it appears that the use of a barrier membrane to cover the lateral bone window during maxillary sinus floor augmentation surgery with a lateral approach reduces the postoperative dislodgment of the bone graft throughout the sinus antrostomy and prevents the bone substitute particles from penetrating within the buccal mucosa, which is related to postoperative morbidity. Keywords: barrier membranes, bone substitutes, computed tomography, sinus floor elevation, sinus membrane

Purpose: To examine human mandibular angle integrity alterations accompanying a mandibular body block graft harvest surgical procedure. Materials and Methods: Hemimandibles from 24 human cadavers were resected and sorted into one of three groups by residual dental status. The height of each hemimandible body was obtained and recorded. Acrylic bone cement was utilized to mount the hemimandibles at the mandibular condyle. Using standard surgical instruments and techniques, cortical bone of the mandibular body buccal plate was resected from the right hemimandibles. Left hemimandibles were used as a control. Each hemimandible was secured in an Instron 5565 mechanical unit. With forces placed on and perpendicular to the occlusal plane, each hemimandible underwent sequential loading until osseous fracture occurred. Descriptive statistics between grouped data were compared and discussed in terms of mean, minimum, and maximum. The statistical relationship between the maximal load, sex, and mandibular body height were identified. Results: Donor and control hemimandible maximal load mean values were 423.63 N and 957.90 N, respectively. A statistically significant difference was present between maximal loads of donor and control hemimandibles (P .0001). Correlations of statistical significance were present between mandibular bone height and maximal load in the control hemimandibles (P = .009). Correlations of statistical significance were not found between mandibular bone height, displacement at maximal load, and maximal load in the grafted hemimandibles (P > .05). No statistically significant correlation between dental status and sex was found in the donor and control hemimandibles (P > .05). Conclusion: After being subjected to a typical block graft harvest surgical procedure, the human mandible's integrity is significantly altered. Sex, dental status, and mandibular bone height do not correlate with maximal load, and thus, integrity, of donor and control mandibles. Keywords: human mandible, mandible integrity, mandibular body block graft, osteotomy

Purpose: The objective was to measure the implant-prosthodontic discrepancy of complete-arch implant-supported frameworks made of cobalt-chromium (Co-Cr) fabricated using selective laser melting (SLM) additive manufacturing technologies. Materials and Methods: A completely edentulous maxillary cast with seven implant replicas was obtained. Co-Cr SLM frameworks (n = 9) from three different providers (SLM-1, SLM-2, SLM-3) were manufactured. A coordinate measuring machine was selected to measure the implant-prosthodontic discrepancy (μm) on the x-, y-, and z-axes and the 3D gap (3D = √x2 + y2 + z2 where implants were considered as the statistical unit (n = 7). One-way analysis of variance (ANOVA), Student-Newman- Keuls, and Tukey tests were used to analyze the data (α = .05). Results: The mean 3D implant-prosthodontic discrepancy (μm) was higher for SLM-1 (73.77 ± 27.94) than for SLM-2 (47.54 ± 22.63) and SLM- 3 (47.26 ± 22.57). At the x-axis, SLM-2 showed a significantly smaller gap (16.21 ± 9.6) than SLM-3 (32.92 ± 27.77) and SLM-1 (34.77 ± 21.85). At the y-axis, however, SLM-3 presented a significantly smaller gap (27.97 ± 9.49) than SLM-2 (38.84 ± 27.82) and SLM-1 (54.35 ± 29.89). Similarly, at the z-axis, SLM-3 (4.01 ± 2.29) showed the least gap, followed by SLM-2 (9.09 ± 7.63), which was significantly smaller than that of SLM-1 (16.14 ± 21.09). Conclusion: The three SLM additive manufacturing technologies tested showed implant-prosthodontic discrepancies ranging from 4.01 to 54.35 μm, which could be considered in the clinically acceptable range. Distortion at the z-axis was significantly less compared with the x- and y-axes in all the groups tested. Keywords: 3D printing, additive manufacturing technologies, chrome-cobalt, implant-prosthodontic gap, selective laser melting

Purpose: The purpose of this prospective randomized clinical trial was to test the hypothesis that narrow-diameter titanium-zirconium (Ti-Zr) alloy implants with a chemically modified hydrophilic surface are not inferior in regard to crestal bone level change compared to standard-diameter implants with the same implant surface and material. Materials and Methods: This multicenter study included 50 patients in need of a single tooth replacement in the anterior (canine to canine) or premolar region of the mandible or maxilla. Patients were included if the site could accommodate a 4.1-mm-diameter implant. Implants were temporarily restored at 3 to 4 weeks after placement. Definitive restorations were delivered 4 to 6 months after placement. Patients returned 1 year after implant loading for clinical measurements and radiographic examination. The primary outcome was mean crestal bone level changes measured between implant loading and 12 months postloading. Secondary outcomes included implant success, survival, gingival recession, and patient satisfaction. Results: Fifty patients were enrolled; 47 completed the study. Twenty-three patients were in the narrow-diameter implant group (test), and 24 patients were in the standard-diameter implant group (control). The success and survival rates at 12 months postloading were 100% for both groups. The change in the mean crestal bone level from implant loading to 12 months postloading around narrowdiameter implants was -0.27 ± 0.34 mm. For the standard-diameter implants, the change was significantly higher at -0.48 ± 0.67 mm (P = .02). No significant difference was found in gingival recession and patient satisfaction. Conclusion: The results of this prospective randomized clinical trial suggest noninferiority of the narrow- vs standard-diameter Ti-Zr implant. In addition, bone remodeling was less pronounced for the narrow-diameter implants. Keywords: dental Implant, marginal bone level, prospective study, randomized clinical trial, single implant, soft tissue

Purpose: To evaluate the clinical and radiographic outcomes of full-arch mandibular rehabilitation with fixed prostheses supported by three immediately loaded implants after at least 5 years of follow-up. Materials and Methods: The sample comprised 58 patients who underwent treatment with immediate loading. Radiographic evaluation of bone loss was carried out in Adobe Photoshop CS5 by a single calibrated examiner using digitized panoramic radiographs. Clinical examination of the technical conditions of the prosthetic device assessed the condition of the acrylic resin base, dental occlusion, metal framework, presence of cover screws, screw fixation of the prosthesis and abutments, and length of cantilever and resistance arms. Results: Five implants in four patients failed, for an overall success rate of 97.13%. Mean bone loss was 2.65 ± 1.06 mm around central implants and 2.11 ± 0.84 mm around distal implants. The most common complication was loss of abutment torque. Half of all patients in the sample experienced some prosthetic complication. There was no evidence of a statistically significant relationship of cantilever length with bone loss or prosthetic complications. Conclusion: The immediately loaded three-implant-supported fixed prosthesis protocol tested in this study proved to be a viable therapeutic strategy for mandibular rehabilitation in edentulous patients, with favorable outcomes after 5 years of clinical and radiographic follow-up. Keywords: dental implants, edentulism, implant-supported dental prosthesis, mandibular prosthesis

Purpose: Different navigation markers in dynamic guided implant surgery could cause different degrees of artifacts, which would affect the accuracy and efficiency of the implant navigation system. This study aimed to quantify artifacts caused by navigation markers made of different materials and to evaluate their effects on registration accuracy under various oral conditions. Materials and Methods: Four U-shaped tubes with different navigation markers (440c stainless steel, silicon nitride, zirconium oxide, and aluminum oxide) were produced by three-dimensional printing. Four kinds of maxillary plaster models were prepared to simulate four tooth crown conditions. U-shaped tubes combined with different tooth models were scanned using cone beam computed tomography. The size of artifacts from different navigation markers and registration rate were measured. Abrasion performance of navigation markers was evaluated by scanning electron microscopy images. Results: Aluminum oxide navigation markers showed the fewest artifacts. Silicon nitride markers caused fewer artifacts than zirconium oxide and 440c stainless steel ones (P .05) and had the best registration performance under all tooth crown conditions with the lowest volume of abrasion. Registration data suggested aluminum oxide worked badly under artificial crown and natural tooth conditions for its lower radiopacity, and zirconium oxide worked undesirably in edentulous conditions. 440c stainless steel was worst in all dental conditions. Conclusion: Navigation markers made of silicon nitride have the best overall performance and perform the best in registration under all circumstances owing to less artifact generation, better radiopacity, and desirable abrasion resistance. Silicon nitride can be regarded as an ideal material, including but not limited to oral implant navigator-guided surgery. Keywords: artifacts, cone beam computed tomography, dental implants, dynamic guided, navigation marker, registration

Purpose: This study uses intentionally tilted implants with a moderate insertion torque to retain an immediately loaded fixed full-arch implant-retained prosthesis using four implants. The aims of this study were to determine the likelihood that this type of implant-retained prosthesis can be predictably provided on the day of implant placement, the survival rate when providing immediate load, and the importance of insertion torque on the survival of the implants. Materials and Methods: All implants that were placed after August 1, 2015 and before December 31, 2016 at the ClearChoice Dental Implant Center of Minneapolis were recorded. The performance of these implants was followed to determine the success rate in the category of "intention to treat" where the treatment is provided on the same day as implant placement. Insertion torque was recorded for all implants. Implants were followed to determine survival of the implants and complications observed. Results: Between August 1, 2015 and December 31, 2016, a total of 1,903 implants were placed. These implants were utilized to support 441 prostheses, with 440 actually being restored with a provisional prosthesis on the day of implant placement. Mean follow-up time was 484 days with a maximum of 972 days and a median of 474 days. A total of 36 implants failed to achieve osseointegration, resulting in an overall survival rate of 98.1% with a confidence interval (CI) of 98.7% to 97.5%. Survival was 97.6% in the maxilla and 98.9% in the mandible. Insertion torque of less than 15 Ncm (n = 80, 77 survival), between 15 and 34 Ncm (n = 122, 120 survival), and greater than 35 Ncm (n = 1,701, 1,670 survival) demonstrated no difference in implant survival. Conclusion: Based on this study of 1,903 implants placed between August 1, 2015 and December 31, 2016, the following observations were made: (1) this surgical/prosthetic treatment approach succeeded in the "intention to treat" category with 440/441 (99.8%) prostheses inserted on the day of implant surgery; (2) overall implant survival was 98.1%; (3) insertion torque appeared to have no effect on implant survival. Keywords: angled, immediate loading, implant survival, insertion torque, intent to treat, tipped, zirconia

Purpose: The aim of this study was to examine the long-term results of implants in orbital reconstruction after exenteration. Materials and Methods: From 1998 to 2012, patients undergoing implant-supported rehabilitation after subtotal or total exenteration due to a tumor were included in a retrospective study. All the patients were evaluated for soft tissue reconstruction, irradiation, complications, abutments, hygiene index, implant mobility, and long-term success. Results: Forty-eight patients (aged between 27 and 81 years) were selected. A total of 187 implants were inserted. All the patients were supplied with epitheses after implantation in the long term. Of the 187 implants, nine implants placed on five patients were lost. The mean follow-up period was 34 months (ranging from 6 to 144 months). The 5-year survival rate was 88%. Conclusion: On the basis of this retrospective study of 48 patients with 187 implants, the following observations were made: (1) the 5-year survival of implants in nonradiated bone was 92%, and (2) the 5-year survival of implants in radiated bone was 86%. Extraoral implants should be presented as an option in orbital rehabilitation after exenteration. Keywords: epithesis, exenteration, implants, orbit, reconstruction

Purpose: The aim of this study was to assess the visual effects of pink-neck implants and pink abutments with respect to the color of natural gingiva. The distribution pattern and magnitude of CIELAB color difference coordinates were studied. Materials and Methods: Forty subjects with a tooth in the maxillary esthetic zone deemed hopeless were recruited. Patients were randomized to either a conventional gray implant or a pink-neck implant. The hopeless tooth was removed, and patients received an immediate implant along with an immediate customized provisional prosthesis. The provisional was maintained for 3 months to allow for complete healing of the implants. Two identical computer-aided design/computer-aided manufacturing (CAD/CAM) titanium abutments only differing in color (gray and pink) were fabricated along with an all-ceramic zirconia crown. The gray abutment was delivered first with a zirconia crown, and it was replaced with the pink abutment 3 weeks later. Three weeks after insertion of each abutment with the zirconia crown, a spectrophotometer was used to collect the color of the peri-implant mucosa and natural gingiva, so the difference between the two sites could be calculated (ΔL* [difference in lightness], Δa* [difference in green-red axis], Δb* [difference in blue-yellow axis]). The natural gingiva measured was the gingiva of a contralateral or adjacent unrestored tooth. The effect of implant color and abutment on the color difference between peri-implant mucosa and natural gingiva was investigated with a linear regression model using a generalized estimating equation approach. Results: Raw data demonstrated statistically insignificant smaller ΔL*, Δa*, and Δb* between peri-implant soft tissue and natural gingiva when the implant was pink vs gray. Further, there were statistically insignificant smaller ΔL* and Δb* between peri-implant soft tissue and natural gingiva when the abutment was pink vs gray. Δa* between peri-implant soft tissue and natural gingiva was significantly smaller when using a pink abutment regardless of the implant type (P .05). Conclusion: Using an anodized pink abutment and/or a pink-neck implant minimizes the color difference observed between the peri-implant mucosa and the natural gingiva in the redness spectrum. These advances in technology assist in helping the peri-implant mucosa appear more natural by minimizing the color variance. Keywords: dental implant, flapless procedure, immediate placement, implant esthetics

Purpose: This pilot study evaluated and compared the degree of new bone formation following maxillary sinus graft using three different bone graft materials. Materials and Methods: Patients with an edentulous posterior maxilla (unilateral or bilateral) were included in this study and underwent a two-stage procedure. Each sinus was randomly assigned one of the three graft materials: anorganic bovine bone mineral (ABBM), anorganic equine bone mineral (AEBM), or mineralized cancellous bone allograft (MCBA). Bone core samples were obtained from the lateral wall of the grafted sites at least 8 months after maxillary sinus graft. Bone quality was evaluated during bone core retrieval. The samples were histomorphometrically analyzed using Kruskal-Wallis and Dunn-Bonferroni tests at the significance level of α = .05. Results: A total of 28 sinuses (14 unilateral and 7 bilateral) from 21 subjects, with a mean age of 61.5 (range: 33 to 75) years, were included in the study. Twenty-eight bone cores (ABBM [n = 9], AEBM [n = 9], and MCBA [n = 10]) were obtained at a mean healing time of 9.1 (range: 8 to 12) months. Six maxillary sinus membrane perforations (≤ 5 mm) were noted and repaired during surgery (21.4%). Histomorphometric analysis of the harvested bone cores revealed statistically significant differences in the percentage of vital bone, residual bone materials, and connective tissue/marrow among the different graft materials (Kruskal-Wallis; P .05). The percentage of vital bone in the MCBA group (32.0% ± 12.4%) was significantly greater than those in the ABBM (10.9% ± 8.9%) and AEBM (9.1% ± 5.9%) groups (P .05). The percentage of residual bone materials in the MCBA group (5.5% ± 5.7%) was, however, significantly less than those in the ABBM (34.3% ± 12.1%) and AEBM (38.9% ± 5.3%) groups (P .05). There were no significant differences in the percentage of vital bone and residual bone materials between ABBM and AEBM (P = 1.0). Newly formed bone and residual graft materials were integrated into the surrounding tissue with no sign of inflammation or foreign-body reaction. Conclusion: Within the confines of the study, MCBA has significantly greater new bone formation than ABBM and AEBM. AEBM showed comparable histomorphometric results in all parameters (percentage of vital bone, residual bone materials, and connective tissue/marrow) to ABBM. Keywords: bone formation, bone graft materials, histomorphometric analysis, maxillary sinus graft

Purpose: To investigate whether MMP-13 g.-77 A > G (rs2252070) gene polymorphism is associated with early implant loss. Materials and Methods: Two hundred nonsmoking volunteers in good oral health, > 18 years of age, and found to be periodontally healthy by clinical examination were matched by age, sex, and implant position and separated into two groups: control group (100 patients with one or more healthy implants for a minimum of 1 year) and test group (100 patients who had suffered early implant loss, considered when implants presented mobility and/or pain before or during abutment connection, requiring their removal). Genomic DNA from saliva was genotyped by PCR-RFLP. Statistical analysis of the results was done using Mann-Whitney U and chi-square tests, with a significance level of 5%. Results: A significant difference in the presence of the different alleles and genotype was found between groups for the MMP-13 g.-77 A > G (rs2252070) gene polymorphism (P = .0161, OR 95% = 0.57 [0.37 to 0.89]; P = .007, OR 95% = 0.44 [0.25 to 0.78]). The A allele increased susceptibility to early implant loss and appeared to be a genetic risk factor. Conclusion: The findings suggest that MMP-13 g.‐77 A > G (rs2252070) polymorphism may contribute to early implant loss. Keywords: implant loss, metalloproteinase, polymorphism, risk factor

Purpose: To investigate the implant stability quotient (ISQ) values of implants placed in bone with and without dehiscence bone defects over 12 weeks and to compare the ISQ values between the two groups. Materials and Methods: Twenty-two patients with an edentulous area at the posterior mandible were enrolled. Thirty OsseoSpeed EV Astra Tech implants (Dentsply Sirona), 4.2 mm in diameter, were placed. Twenty implants were placed without bone regeneration (no dehiscence group), while 10 presented with favorable bone defects and received simultaneous guided bone regeneration with dental implant placement (dehiscence group). At the time of implant placement, 2, 4, 8, and 12 weeks, resonance frequency analysis was utilized. The changes in ISQ values within group were analyzed with repeated-measures analysis of variance (ANOVA), and the mean ISQ values between the no dehiscence and dehiscence groups were compared using unpaired t tests. Results: All implants were successfully integrated without complication. The no dehiscence group demonstrated mean ISQ values of 74.30 ± 6.01, 69.58 ± 5.30, 71.10 ± 5.80, 75.08 ± 3.93, and 77.85 ± 3.18 at baseline, 2, 4, 8, and 12 weeks, respectively. The dehiscence group demonstrated mean ISQ values of 69.85 ± 7.00, 63.40 ± 8.47, 59.90 ± 10.23, 72.55 ± 3.10, and 76.20 ± 2.68 at baseline, 2, 4, 8, and 12 weeks, respectively. The dehiscence group showed significantly lower mean ISQ values at 2 weeks (P = .021) and at 4 weeks (P = .007) after implant placement compared with those of the no dehiscence group. Conclusion: Within the 12-week healing period, all implants demonstrated successful osseointegration and achieved stability in favorable bone defects. Nevertheless, clinicians should consider that significantly lower implant stability can occur in the first month. Keywords: dental implant, favorable bone defect, guided bone regeneration, implant stability quotient, resonance frequency analysis

Purpose: This study investigated the effect of implant length, diameter, and surface contact on the stresses developed in a fibular free flap. Materials and Methods: Finite element models for dental implants placed in a patient-specific fibula were created using a patient-specific fibula computed tomography scan and geometry files of commercially available dental implants. The finite element models involved nine dental implants of different lengths and diameters: 3.5, 4.3, and 5.0 mm in diameter and 10.0, 11.5, and 13.0 mm in length. Three contact conditions between the implant and the fibular flap were investigated: complete fusion, friction, and smooth contact, representing complete osseointegration, a rough implant-bone interface, and no osseointegration, respectively. Finite element analysis was performed to examine the average von Mises stresses around the local implant-fibula interface within the fibula under a load of 500 N along the long axis of the implant and posterior-anterior and medial-lateral directions. Results: Both the level of osseointegration and implant size had noticeable effects on the mechanical stress inside the fibula. The stress introduced to the fibula gradually decreased as the implant osseointegrated into the bone. An optimal implant size existed where the internal stresses were minimized; this trend was seen when investigating both the implant diameter and length. In this study, an implant with a diameter of 4.3 mm and length of 10 mm produced the lowest mechanical stresses overall. Conclusion: Both implant length and diameter were influential; stresses were seen to decrease to a minimum then subsequently increase as either dimension increased. Additionally, stresses in bone introduced by an implant decreased as the degree of interaction between the implant and fibula increased. Complete fusion between the implant and bone yielded the lowest stresses.

Purpose: This review article evaluated biomechanical studies, finite element analyses, and clinical papers on the prosthetic and surgical principles for the survival of implants when reconstructing the edentulous mandible, including the use of a three-implant-supported fixed prosthesis. Materials and Methods: A comprehensive search of studies published from 1983 to December 2017 listed in the PubMed/MEDLINE databases was performed. Relevant studies were selected according to predetermined inclusion and exclusion criteria. Results: The initial database search yielded 942 titles. After filtering, 157 abstracts were selected, with 68 articles considered relevant and included. Consensus among authors was identified in regard to the number and the distribution of implants, limiting or eliminating distal cantilevers, and the principles of biomechanical loading of a cross-arch splinted prosthesis. Conclusion: The result of this review suggests that reconstruction of the edentulous mandible with a fixed prosthesis using three, four, or six implants is a viable treatment option. However, when using three implants, wider-diameter implants are recommended for favorable force control. Keywords: ad modum Brånemark, biomechanics, graftless solution, implant, mandible

Purpose: The aim of this study was to analyze stress distribution on four different implant designs and four different qualities of cortical bone surrounding the implant crest modules using three-dimensional finite element analysis. Materials and Methods: Four different implant designs of the same diameter and length (3.75 × 11.5 mm) were used. Rhinoceros 4.0 3D modeling software was used for preparing the four types of bone quality (D1, D2, D3, and D4). Mandibular second premolar crowns were constructed as prosthetic superstructures of the implants, and a total force of 300 N was vertically applied to the crowns. Stress distribution on dental implants and cortical bone of D1, D2, D3, and D4 bone quality was evaluated. Results: Among all of the implants, the maximum von Mises stress value on cortical bone surrounding the neck region of the implants was found in D4 bone quality, while the minimum stress was detected in D1 bone quality. The stress distribution on the threads of dental implants exhibited the most homogenous distribution in D1 bone quality, while higher von Mises stress values were observed in the apical blade segment of the implants in D3 and D4 bone quality. Conclusion: It was found that the maximum stress of cortical bone surrounding the implant crest module decreased as the bone density increased. The microthreads on the implant crest module might cause an increase in stress to cortical bone surrounding the neck region of implants. Keywords: bone quality, dental implant design, stress distribution