The International Journal of Oral & Maxillofacial Implants, 06/2018

Purpose: To evaluate the biomechanical behavior between two different micro conical abutments: two-piece and one-piece abutments. Materials and Methods: Four groups were divided according to the prosthetic connection (internal or external hexagon) and abutment type. The vertical misfit between the abutment and implant was evaluated under stereomicroscope. Next, the implants were divided into pairs and embedded in polyurethane to receive two-element prostheses. The initial removal torque was measured for abutments and for prosthesis fixation. The samples were mechanically cycled (200 N, 2 Hz, 2 × 10⁶ cycles) before measuring the torque loss in the same regions. For stress verification, a finite element analysis was used. Results: For vertical misfit, one-piece (4.70 ± 0.26 μm) two-piece (16.8 ± 0.32 μm). For preload in abutment screw, two-piece = one-piece. For prosthetic screw, a higher percentage of preload was found for two-piece, but no statistical difference was observed after fatigue cycling between the groups. For stress analysis, no difference (10%) was observed for abutments, retention screw, or for the bone. Conclusion: The one-piece abutment maintained even amounts of preload after cyclic loading and presented less vertical misfit in comparison with the two-piece abutment for both implant connections. The use of one-piece abutments did not increase the stress and strain concentration, suggesting acceptable biomechanical behavior. Keywords: abutments, finite element analysis, dental implants, implant-abutment interface, nonlinear analysis, torque loss

Purpose: This study aimed to evaluate the effects of leucocyte- and platelet-rich fibrin (L-PRF) on the inflammatory process, tissue repair, and expression of vascular endothelial growth factor (VEGF) on bone defects in the calvaria of rats. Materials and Methods: L-PRF was obtained from three animals submitted to cardiac puncture to prepare the membranes. Two noncritical defects with a diameter of 2 mm were created in the calvaria of 15 Wistar rats. The defects on the right side were filled with a blood clot (CTRL) and the left side with L-PRF. After 5, 15, and 30 days, the animals were euthanized and the specimens processed for histologic, histomorphometric, and immunohistochemical analyses. In order to measure the intensity of the inflammatory infiltrate and VEGF expression, scores were assigned from 0 to 3, with 0 being no expression, 1 discrete (up to 25%), 2 moderate (between 25% and 50%), and 3 intense (> 50%) expression. The area of bone neoformation at the edges of the defects was also quantified. Results: A less intense inflammatory infiltrate was observed in the defects filled with L-PRF compared with CTRL at all times analyzed (P .05). At 5 days, no bone neoformation was observed in any of the groups evaluated. After 15 and 30 days, greater bone neoformation was observed in the group treated with L-PRF compared with the CTRL group (P .05). At 15 days, 3,871.8 (1,070.15) μm² were recorded for the CTRL and 49,978.5 (14,360.7) μm² in the L-PRF. At 30 days, 62,284.5 (3,579.5) μm² were observed in the CTRL and 154,076.6 (31,464.9) μm² in the L-PRF. At all evaluated times, a lower inflammatory infiltrate was observed in the group treated with L-PRF compared with the CTRL. VEGF expression was observed in the initial phase and throughout the tissue repair process in both groups. At 5 days, there was no difference in VEGF expression between the groups. VEGF was present at the initial phase and throughout the tissue repair process in both groups. In the L-PRF group, a decrease in VEGF expression was observed at 15 and 30 days compared with the CTRL group. Conclusion: L-PRF had a positive effect on the regenerative process of bony defects, with a reduced inflammatory response and greater bone neoformation. Keywords: bone regeneration, fibrin, L-PRF, platelet-derived growth factor, VEGF

Purpose: Computer-aided surgery under navigation system guidance is widely applied in dental implant procedures. However, the accuracy of drilling with such navigation systems has not been comparatively evaluated alongside those of laboratory guide-based and freehand drilling. Therefore, this study aimed to compare the accuracies of these three drilling systems. Materials and Methods: A navigation system, a laboratory guide, and freehand drilling were used to drill 150 holes on 30 cast models. Two master models- one each for the maxilla and mandible-were prepared with the idea of placing five implants per cast. After drilling five holes on each cast, postoperative cone beam computed tomography images were acquired to measure the magnitude of errors. Results: The navigation system and laboratory guide were more accurate than freehand placement with respect to total errors at the entry and apex, lateral error at the apex, and angular error. The navigation system was more accurate than the laboratory guide with respect to angular error. Laboratory guide-based drilling was more accurate than freehand drilling in terms of lateral error at entry. Conclusion: In comparison with the laboratory guide and freehand placement, the navigation system exhibited lower angular and axial errors. Despite its higher accuracy, the navigation system requires the operator to pay greater attention. Keywords: computer-aided surgery, dental implant, hand drilling, laboratory guide, navigation system

Purpose: This research aimed to propose a three-dimensional (3D) augmented reality navigation method with point cloud-based image-patient registration that could merge virtual images in the real environment for dental implants using a 3D image overlay and to evaluate its feasibility. Materials and Methods: A total of 12 rapid prototyping mandibular models were fabricated using a 3D printing method and were divided into two groups: 3D augmented reality-guided group and traditional two-dimensional (2D) image-guided group. A point cloud-based preoperative image-to-patient registration method was introduced to replace the traditional point-to-point registration. After the registration, dental implant surgery was performed in the two model groups using an augmented reality-guided navigation method and a traditional two-dimensional image-guided navigation method. The planned and actual postoperative implant positions were compared for measuring positional implantation errors. The surgery time was also recorded and compared between the two groups. Results: In the model experiment, the root-mean-square deviation of registration was 0.54 mm, and the implant surgery results showed 1.5-mm mean linear deviation and 5.5-degree angular deviation. The augmented reality-guided implantation showed smaller horizontal, vertical, and angular errors in the apical areas of the central incisor and the canine region. The surgery time using the augmented reality-guided navigation method was significantly shorter than that using the two-dimensional (2D) image-guided navigation method (P .05). Moreover, the volunteer experiment demonstrated that the preoperative 3D models in situ accurately overlaid onto the surgical site. Conclusion: The proposed point cloud-based registration method can achieve excellent registration accuracy. Dental implant placement guided by the proposed 3D augmented reality navigation method showed better accuracy and applicability, as well as higher efficiency, than the traditional 2D image navigation method. Keywords: 3D augmented reality, dental implant, operative time consumption, point cloud registration, surgery accuracy, surgical navigation

Purpose: In addition to original componentry, clinicians can choose to restore an implant using third-party parts claimed to be compatible with the original implant system. The goal of these in vitro experiments was to evaluate the performance of a selection of original and clone titanium abutments available for a widely used implant system with an internal conical connection. Materials and Methods: Six groups of original and clone abutments compatible with NobelActive implants were compared based on the following parameters: dimensional accuracy, gap formation, circumferential strain, abutment screw preload, micromotion, abutment settling, median fatigue limit (MFL), and bacterial leakage. Each parameter was analyzed separately and compared with the original (reference) abutment applying a variety of statistical tests (α = .05). Results: Overall, the results obtained in the different experiments showed considerable deviation from the reference abutment. Deviations in interface geometry of the abutments were inconsistent and reached up to 56.26%. Gap measurements performed on cross sections of implant-abutment assemblies were not sensitive enough for detecting consistent differences. Development of circumferential strain at the implant shoulder reached up to 1,389.30 μm/m. Abutment screw preload ranged from 285.25 N to 397.70 N, while micromotion at the implant-abutment interface ranged from 61.68 μm to 79.69 μm. Abutment settling resulting from screw fixation was greater compared with settling caused by dynamic loading, reaching up to 0.09 mm. The MFL ranged from 246.00 N to 344.00 N. All implant-abutment combinations showed bacterial leakage after 6 days of incubation. Conclusion: While clone abutments may look similar to the original component, they display considerable differences and variations in their physico-mechanical characteristics detectable by advanced testing methods. How much these differences affect reliability and longevity of the restoration's clinical performance should be investigated in clinical studies. Keywords: abutment connection, compatible abutment, dental implants, implant-abutment interface

Purpose: This bibliometric study analyzed English language dental implant literature from 2007 to 2016 to evaluate and identify the terms, authors, and journals concerning dental implant articles with high citation count and the structure of their bibliometric networks. Materials and Methods: The Web of Science database was searched to identify articles on the topic of dental implants published under the Web of Science category of Dentistry, Oral Surgery & Medicine from 2007 to 2016. The articles were first assessed using descriptive analysis concerning the authors, organizations, countries/territories, and journals. Afterward, VOSviewer was used to visualize the term map, author network, and journal network consisting of the most highly cited entities. CiteSpace II was used with default settings to identify keywords that experienced a large increase in citations received within the surveyed period of time. Results: The citation analyses were based on 12,114 dental implant articles published during the survey period. The top five highly cited terms with > 500 publication counts were peri-implantitis (a mean of 20.17 citations per surveyed article [CPA]), survival rate (19.02 CPA), survival (18.74 CPA), implant failure (16.58 CPA), and success rate (16.53 CPA). The top five authors with highest average citations authored 80 papers (80/12,114 = 0.7%) that received 5,962 citations (5,962/151,404 = 3.9%) among the highly cited authors' network. Clinical Oral Implants Research had the largest total number of citation links (19,283), and hence, was in the center of the journal network, with a mean of 21.47 citations per surveyed article. Conclusion: The terms with high impact were related to implant success, survival, failure, and peri-implantitis. Clinical Oral Implants Research and The International Journal of Oral & Maxillofacial Implants were in the center of the journal citation network. Keywords: bibliometrics, dental implants, journal impact factor, library science, literature, publications

Purpose: The aim of this vitro study was to reproduce and evaluate the response of bone and bacteria to traditional and innovative implant surfaces with difference wettability. Materials and Methods: Two hundred fifty-two samples made of grade 4 titanium with different coating (machined [MAC]; double-etched, Ti-AE; zirconium nitride [Ti-ZrN]) were used for this in vitro study. Disks were divided into test (bioactivated using plasma of argon) and control group (untreated). To assess the surface morphology of the specimens, representative images were acquired via scanning electron microscopy (SEM). Murine preosteoblasts (MC3T3-E1) were used to study the biologic response in vitro, while the quantification of protein adsorption was achieved through the incubation of the titanium samples in a 2% solution of fetal bovine serum (FBS) in phosphate-buffered saline (PBS). The sterilized titanium disks were then colonized by bacterial species from a single sputum sample obtained from a healthy volunteer. For every analysis, 24 disks were used (12 for each group). Results: SEM and topographic analyses demonstrated a Sa value of 0.33 (Ti-ZrN), 0.34 (MAC), and 0.62 (Ti-AE). Compared with the control groups, plasma treatment significantly increased the protein adsorption level on all the different titanium surfaces (5.88 ± 0.21 vs 7.85 ± 0.21, 7.13 ± 0.14 vs 9.74 ± 0.65, 4.41 ± 0.62 vs 6.13 ± 0.52, respectively, for MAC, Ti-treated, and Ti-ZrN). Similar behavior was described for cell adhesion (27.67 ± 2.03 vs 58.00 ± 20.13, 116.67 ± 12.02 vs 159.33 ± 8.09, 52.00 ± 4.73 vs 78.33 ± 4.67, respectively, for MAC, Ti-treated, and Ti-ZrN). Plasma treatment significantly augmented the number of CFU only in MAC and ZrN samples. Conclusion: With the limitations of this in vitro study, the following conclusions could be drawn: (1) rough implant surfaces present a higher adhesion and proliferation of preosteoblastic cells and bacterial biofilm; (2) rough implant surfaces benefited the most by the plasma of argon treatment. Keywords: cell adhesion, implant surfaces, microbiologic growth, plasma of argon, protein adsorption, zirconium nitride

Purpose: The aim of this study was to systematically analyze the effect of growth factors, particularly recombinant human platelet-derived growth factor-BB (rhPDGF-BB) and bone morphogenetic proteins (BMPs), on volumetric and histomorphometric changes after socket augmentation in comparison with the natural healing sockets. Materials and Methods: An electronic search of four databases (1965 to February 2017) and a hand search of peer-reviewed journals for relevant articles were performed. Human clinical trials that reported quantitative and qualitative outcomes of soft and hard tissues in socket augmented sites with the use of rhPDGF-BB or BMPs, with a minimum five samples per group, were included. Results: Eight studies, including six randomized controlled trials and two case series, were selected. Five of them used BMPs, and three used rhPDGF-BB. Regarding linear bone width change, the weighted mean difference (WMD) between the sites with and without the use of BMPs was 1.66 mm (95% confidence interval = 0.29 to 3.02 mm, P = .02), favoring the BMP group. In terms of histomorphometric outcome, the WMD of the percentage of vital bone between the sites with the use of rhPDGF-BB and with grafting materials alone was 2.16% (95% confidence interval = -4.61% to 8.93%, P = .53). Conclusion: This systematic review revealed that the use of BMPs in socket augmentation yields better ridge width in comparison with a natural healing socket. However, more studies are needed to warrant the effectiveness when using rhPDGF-BB in socket augmentation procedures. Keywords: alveolar ridge augmentation, bone morphogenetic proteins, bone regeneration, growth factors, tissue preservation, tooth extraction

Purpose: The goal of this study was to foresee the fatigue life of two implant connections, evaluate the failure probability with several bone levels, and compare the in vitro test results with finite element results. Materials and Methods: Mechanical tests were done with 60 implants (Ø3.50 mm), and abutments were used. These implants were divided into two groups with 30 implants each: internal hexagon and Morse taper. Three bone levels and 10 implants for each level were analyzed. The first level was considered at the platform level, the second at 3 mm, and the last level at 5 mm above the platform resin. A quasi-static loading at 30 degrees was applied to the axis of the implant in a universal machine. Six models were created and assembled to reproduce the conditions used in the laboratory testing. All models had restricted all displacement at the bone (bottom and lateral). Loads employed in the numerical test were obtained experimentally. Loads and material properties were supposed to be random. Then, failure probability was calculated by the probabilistic methodology. Results: The internal hexagon group obtained the following mean fracture strengths: 2,092 N at the first level, 1,041 N at the second level, and 898 N at the third level. The mean fracture strengths for the Morse taper group were as follows: 1,687 N at the first level, 1,644 N at the second level, and 1,159 N at the third level. Results obtained by the finite element analysis are in accordance with the in vitro mechanical test results. The Morse taper group obtained a better behavior at bone levels 2 and 3 than the internal hexagon group. An important dependency between failure probability and bone level was found in the internal hexagon group. However, a similar behavior in levels 2 and 3 was obtained for the Morse taper group. Conclusion: In view of the mechanical results, the Morse taper group has a better behavior in bone levels 2 and 3 than the internal hexagon group. This is also in accordance with the probabilistic fatigue outcomes. Keywords: abutment, bone level, dental implant, failure probability, fracture strength, probabilistic approach

Purpose: To evaluate whether removing a fractured abutment screw with a specific rescue device negatively affects the success of a new restoration in terms of early abutment loosening. Materials and Methods: Implants (n = 10) with a regular platform of 4.1 mm (tissue level [TL]) and implants (n = 10) with a reduced diameter of 3.3 mm (bone level [BL]) were used. The screws of eight respective abutments for both implant types were artificially weakened in order to fracture during torque application for abutment insertion. The fractured abutment screws were removed applying a specific rescue kit. The implant inner threads were cleaned and remodeled with a system-specific tapper. New abutments were inserted, and computer-aided design/computer-aided manufactured (CAD/CAM) full zirconia crowns were luted. Aging by thermal cycling and mechanical loading was performed with a customized masticator simulator, and the number of crown and/ or abutment loosenings was determined. In cases in which no loosening was observed, sawing and grinding were performed to determine the contact zone between the inner implant thread and abutment screw. Data were compared with a control group, eg, unmodified implant-abutment connections. Results: No abutment loosening was observed. All crowns were in function after mastication simulation. The inner thread contact zones of both test groups were generally smaller than in the control group, with a mean contact area of 448.6 μm and 459 μm for BL implants, and 608.8 μm and 620.5 μm for the TL implants in test and control groups, respectively. Conclusion: Removing a fractured abutment screw with a specific rescue device and modifying the inner thread seems not to negatively affect the functional connection between a new abutment and the implant. Keywords: CAD/CAM, mastication, screw, torque, zirconia crowns

Purpose: The aim of this study was to investigate the influence of the abutment material and the connection geometry on deformation and wear at the internal implant-abutment connection area (IAC), using an optical scanner. Materials and Methods: Thirty-two internal conical titanium implants, and two types of prefabricated abutments (zirconia or titanium), each (n = 8) with different connection geometries (hexagon or nonhexagon) were prepared. The inner surfaces of the implants were optically scanned before and after loading for 100,000 cycles in a simulated wet environment. The scanned data were superimposed to calculate potential three-dimensional (3D) deviations. Surfaces of the two respective implants in each group were examined using scanning electron microscopy to observe fretting wear patterns. A two-way analysis of variance (ANOVA) was used for the statistical analysis. Results: The 3D deviation (deformation) was detected at the IAC in relation to the loading direction. The average 3D positive deviation and maximum positive and negative deviations at the IAC were significantly higher with zirconia abutments than with titanium abutments, regardless of connection geometries (all P .05). However, the average 3D negative and standard 3D deviations were similar between the two materials (both P > .05). The effect of connection geometry was not significant (P > .05). After cyclic loading, an irregular wave-pattern furrow was observed on the connection area of the implant with the titanium abutment, whereas a long and straight groove was detected on that with the zirconia abutment. Conclusion: Based on this analysis, the deformation and the wear at the IAC could be significantly affected by the material of the prefabricated abutment. Keywords: deformation, implant-abutment connection, prefabricated abutment, titanium, wear, zirconia

Purpose: The aim of this work was a finite element analysis of the effect of a sloped platform in tilted implants in the All-on-4 treatment concept on the level of maximum stresses in compact bone. Materials and Methods: Finite element modeling of the stresses at tilted microthread implants with standard and sloped abutment platform under four loading conditions and two levels of osseointegration was performed. Results: The sloped abutment platform in tilted implants positioned at rim bone level resulted in a two to four times reduction of the maximum von Mises stresses in the adjacent cortical bone compared with the standard platform. These stresses were well below the yield stress of the cortical bone. The main importance of the proposed sloped platform in tilted implants is substantial stress reduction in the case of immediate loading. The stress reduction also results in the reduction of the deformation of the framework of the All-on-4 concept. Conclusion: The suggested modification of the slope of the abutment platform on tilted implants is recommended as a technically simple and highly effective solution for significant reduction of maximum stresses in the cortical bone around the implant. Keywords: All-on-4 concept, FEA, sloped abutment configuration, tilted implant

Purpose: To investigate cone beam computed tomography (CBCT) accuracy in measuring facial bone height and detecting dehiscence and fenestration defects around teeth. Materials and Methods: Patients who were treatment planned for periodontal flap or dental implant surgeries were enrolled (n = 25). CBCT imaging (Carestream CS 9300) was obtained at 0.09-mm voxels (n = 10 patients, 23 teeth) and at 0.18-mm voxels (n = 15 patients, 33 teeth). Facial bone height measurements, from cusp tip to crest of bone height along the long axis of the tooth, and presence or absence of dehiscence or fenestration defects were recorded from CBCT images in triplicates independently by two examiners. The corresponding clinical measurements were made at the time of surgery. Comparisons of CBCT and clinical measurements were made using paired t tests for teeth: anterior and posterior, maxillary and mandibular, with or without restorations, or root canal therapy. Level of agreement between investigators was assessed by concordance correlation coefficients (CCC), Pearson's correlation coefficient (PCC), and Cohen's Kappa. Results: Comparing mean CBCT and clinical measurements, statistically significant differences were noted for 0.09-mm and 0.18-mm voxel sizes, for anterior and posterior teeth, for maxillary and mandibular teeth, for teeth with or without restorations, and for teeth without root canal therapy (P .05). Clinical and CBCT measurements were similar for teeth with crowns and with root canal therapy (P > .05). CBCT measurements underestimated mean facial bone height from 0.33 ± 0.78 to 0.88 ± 1.14 mm (mean ± SD) and absolute facial bone height values from 0.56 ± 0.35 to 1.08 ± 0.92 mm. Intraexaminer and interexaminer reliability for measuring facial bone height ranged from poor to substantial (PCC = 0.78 to 0.97 and CCC = 0.63 to 0.96, respectively). Interexaminer reliability for detection of dehiscence and fenestration defects ranged from poor to moderate (Cohen's Kappa = -0.09 to 0.66). Conclusion: CBCT imaging underestimated facial bone height and overestimated the presence of dehiscence and fenestration defects. Keywords: bone, cone beam computed tomography, diagnostic imaging, radiography

Purpose: To evaluate the effectiveness and predictability of a novel biomechanical, minimally invasive bone instrumentation technique that enhances bone density through compaction grafting, called osseous densification, and allows for transcrestal sinus membrane elevation and augmentation with simultaneous implant placement. Materials and Methods: Patients who were consecutively treated with the bone densification and transcrestal sinus augmentation technique and were followed up in three treatment centers between May 2012 and September 2017 were included in this retrospective study. The summary statistics are presented as means for continuous variables and percentages for categorical variables. Results: In total, 222 patients with 261 implants were included in the final clinical analysis. The included follow-up period ranged from 6 to 64 months with a mean of 35 months. The subsinus residual bone height at baseline was 5.4 mm (SD: 1.9). Following the sinus augmentation, a significant vertical increase of 7 mm (SD: 2.49) was observed. No sinus membrane perforations and no late implant failures were observed from 6 up to 64 months follow-up, yielding a cumulative implant survival rate of 97%. Conclusion: This osseous densification technique for maxillary implant site preparation with transcrestal sinus augmentation and simultaneous implant placement led to favorable clinical outcomes with up to 64 months of follow-up. Keywords: atrophic maxilla, bone substitutes, compaction autografting, densifying burs, maxillary sinus, osseous densification, sinus augmentation, sinus elevation procedure

Purpose: The rate of dental implant failures ranges from 3% to 8%, with that number increasing as the number of implants placed increases. When an implant fails, the survival rate drops significantly when a second or third attempt is performed. The aim of this study was to evaluate the survival rate of an implant placed in a previously failed implant site and to explore the risk factors that might affect the outcome of the second procedure. Materials and Methods: A retrospective chart review was conducted for patients receiving dental implants at the University of Texas, School of Dentistry from 1985 to 2017. Exclusion criteria included patients with genetic diseases, radiation and chemotherapy, or an age less than 18 years. Data on age, sex, race, tobacco use, diabetes, cardiovascular, osteoporosis, implant brand, anatomical location of the implant, implant length and width, respective information on the replacement implant, and professional maintenance were collected for analysis. Results: A total of 1,234 patients with 2,742 implants were included. A chart review found that of the 247 failed implants, replacement of implants was performed in 85 patients with 99 implants. More than half of the initial implants failed within the first year of placement. Based on the 12-month performance of each brand, the initially failed implants were categorized as high, medium, or low survival rates. Based on this categorization, the replacement implants that belonged to the medium survival rate category showed higher survival rates than the high survival group of the initially failed implants. Conclusion: The cumulative survival rates of the replacement implants were 91% at 1 year, 88% at 5 years, and 83% at 10 years. Implant failures were more common prior to functional loading. Keywords: dental implant, retrospective study, survival rate

Purpose: Maxillary sinus augmentation has been a predictable procedure. However, in-depth analysis of tissue healing after sinus grafting with simultaneous implant placement is limited. This study aimed to compare histologic outcomes after sinus grafting with a synthetic bone graft compared with a xenograft. Materials and Methods: A randomized controlled split-mouth study was conducted to compare bone formation around microimplants (2.00 mm, Dentium) placed at the time of maxillary sinus augmentation with a synthetic material (Osteon, Dentium) (OST) and deproteinized bovine bone (Bio-Oss) (BIO) as the control group. Four microimplants per subject (n = 13) were placed bilaterally for intrasubject comparison (two implants per side/patient). Bone cores with osseointegrated microimplants were harvested for histomorphometric analysis 6 to 8 months after sinus augmentation surgery. Results: Histologic analysis revealed newly formed bone deposited on the microimplant surface and bridging to bone graft material in both groups. Further, there was no histologic evidence of signs of inflammation in all specimens. In general, bone-to-implant contact was comparable and ranged from 6.1% to 67.0% with a mean of 38.4% ± 11.61% in OST and from 10.5% to 57.0% with a mean of 34.58% ± 12.55% in BIO. However, a significantly higher percentage of bone-to-implant contact in the first four threads of the grafted area was noted in OST compared with BIO (P = .016). Conclusion: The synthetic OST was found to be equivalent to BIO in new bone formation and clinical success after sinus augmentation in conjunction with microimplant placement. Although there are some statistically significant differences in the histologic outcomes, the clinical relevance of these needs to be further evaluated. Nevertheless, the findings of this study indicate that this synthetic alloplast would be a viable alternative to an allograft material. Keywords: allografts, dental implants, sinus floor augmentation, treatment outcome, xenografts

Purpose: The aim of this study was to determine the possibility and extent of artifact reduction by an optimized use of cone beam computed tomography (CBCT) parameter configuration (geometric resolution, implant geometric parameters, and image analyses). It furthermore sought to determine the distance from correctly reproduced bone tissue to an implant, where the grayscale values are equal to the pre-implantation values. Materials and Methods: Titanium implants were inserted into pig tibia under standardized conditions. CBCT investigations in the form of bone density mapping were performed under various CBCT settings and implantation situations. The circumference of the implants was measured in order to determine the extent of metal artifacts. This was done by determining grayscale and comparing it to the bone area prior to implantation. Results: Using CBCT to determine bone density postimplantation showed a correlation in dependence of CBCT parameter configuration. Higher resolution led to a better detection of correct bone density values in the peri-implant region. Normal bone density values can be recognized at a distance of 370 μm from the implant surface, when the spatial resolution is 125 μm. Therefore, higher resolution in CBCT is accompanied by an improved bone detection in peri-implant bone, despite the presence of metal artifacts. Peri-implant bone defects that extend 400 μm around implants were reliably detected by using a spatial resolution of 125 μm. In specimens, where multiple implants are present in one line, pronounced artifact formations were present. The artifacts were visible as a combination of streak-like hardening and extinction effects. Conclusion: Bone geometric data and density values may be determined correctly in close proximity to the implant surface, and can detect peri-implant bone defects. When multiple implants are placed, the implant radiation direction geometry must be considered. Keywords: CBCT, grayscale, implant, metal artifact, peri-implant defects, spatial resolution

Purpose: The All-on-4 treatment concept has been shown to be an effective clinical procedure; however, to date, no studies have analyzed the subgingival microbiota present in these restorations. The purpose of this study was to evaluate the microbial profile of the subgingival biofilm around dental implants placed in the All-on-4 protocol and compare the microbial profile around axial and tilted implants. Materials and Methods: Fourteen subjects treated by the All-on-4 concept were evaluated clinically and microbiologically. Subgingival biofilm was collected from each patient, and the amount of 40 species of bacteria was assessed using the checkerboard DNA-DNA hybridization technique. Results: The results for the indices of probing depth (PD), bleeding on probing, marginal bleeding, and visible plaque were 2.32 mm, 46%, 60%, and 57%, respectively. Tilted implants presented a significantly higher mean PD and Plaque Index compared with axial implants (P .05). Fusobacterium nucleatum ssp vincentii, Veillonella parvula, and Fusobacterium nucleatum ssp polymorphum were found in higher levels; however, no difference in the microbial composition was observed between tilted and axial implants (P > .05). Tilted implants presented statistically higher mean levels for the orange complex in relation to the axial implants (P .05). Conclusion: Despite the clinical success rate of the All-on-4 protocol, the subgingival biofilm of tilted implants presented a higher proportion for the orange complex pathogens in comparison to axial implants. These data could suggest that subjects with this modality of implant-supported restoration must be aware that they need a more rigorous maintenance protocol. Keywords: All-on-4, dental implant, microbiota, prosthesis, subgingival biofilm

Bovine-derived bone mineral demonstrated good osteoconductive properties as grating material for maxillary sinus floor elevation, but the long-term behavior of this material has not been reported. The purpose of this report was to analyze and compare histomorphometric measurements of new bone, bone graft, and medullar spaces 6 months, 12 months, and 20 years after grafting. In the grafted area, the amount of mineralized bone was 16.96% at 6 months, 22.53% at 12 months, and 22.05% at 20 years, respectively. The amount of bovine-derived bone mineral ranged from 35.87% to 4.85% in the same period. The volume of the newly formed mineralized bone does not increase over time, conversely to nonmineralized bone. Keywords: bovine bone, histomorphometry, long term, maxillary sinus grafting

Purpose: To evaluate the 5-year clinical outcomes for implants placed in a staged sinus floor elevation (SFE) procedure and to compare three patient groups with sinus grafts with three different ratios of bovine bone mineral (BBM) and autogenous bone (AB) mixture. Materials and Methods: A 5-year prospective cohort study was conducted on 81 patients with 119 staged SFEs non-randomly distributed to three groups based on the origin of the AB and the mixture ratio with BBM: group 1 (locally harvested AB [LHB] from osteotomy sites + BBM, ratio: 1:10), 31 patients, 37 SFEs; group 2: (LHB + intraorally harvested peripheral AB [IHPB] from retromolar/chin region + BBM, ratio: 1:4), 22 patients, 29 SFEs; and group 3 (LHB + extraorally harvested peripheral AB [EHPB] from iliac crest/tibia + BBM, ratio 1:1), 28 patients, 53 SFEs. After graft healing (5 to 7 months), 284 dental implants (group 1: 76, group 2: 61, group 3: 147 [overall: 2.3 implants/sinus]) were placed. After an additional healing period (5 to 7 months), all implants placed were functionally loaded and prospectively followed by clinical and radiographic evaluations assessing implant survival/success rate as well as peri-implant marginal bone level (MBL) alteration at 1, 3, and 5 years postloading. Results: A total of 76/81 patients with 267/284 implants were followed for up to 5 years (dropouts: 5 patients/ 15 implants; implant loss = 2). The 5-year implant survival and implant success rate (group 1: 100%/98.6%; group 2: 98.3%/96.6%; group 3: 99.3%/95.7%) did not differ between the three graft mixture groups. The peri-implant marginal bone alteration (reduction) averaged over all 5 years was 1.40 ± 0.29 mm for group 1, 1.41 ± 0.22 mm for group 2, and 1.46 ± 0.46 mm for group 3 (P = .187). However, over time, a continual and significant MBL reduction (P = .045) was noted for all groups presenting peri-implant MBL changes between 1 year and 5 years of -0.17 mm (group 1), -0.12 mm (group 2), and -0.24 mm (group 3), respectively. Conclusion: According to the clinical results obtained, dental implants inserted in grafted (staged) SFE using a mixture of BBM with a minimal amount of AB harvested from local sites provide for similarly high 5-year implant/augmentation success rates as graft mixtures with AB harvested from peripheral intraoral or extraoral donor sites, confirming no need for additional bone harvesting. Keywords: 3 different bone ratios, implant survival/success, staged maxillary sinus augmentation

Purpose: This study evaluated the effect of the level of the prosthetic construction on the marginal bone stability around extra-short implants (≤ 6.5 mm in length) supporting a fixed prosthesis. Materials and Methods: This retrospective study was performed at a private dental clinic. The patient charts were reviewed to select those who had an extra-short implant (≤ 6.5 mm in length) supporting a fixed prosthesis. A transmucosal abutment (transepithelial Multi-Im, BTI Biotechnology Institute) was used in those implants that were restored at the gingival level. Otherwise, the implants were restored at the platform level. Demographic data and implant-related and prosthesis-related variables were obtained. Results: Thirty-three extra-short implants in 17 patients were assessed. The patients' mean age was 61 ± 12 years at the time of surgery. The prosthetic reconstruction was done at the platform level in 18 implants and at the gingival level (via transmucosal abutment) in 15 implants. Considering the use or not of a transmucosal abutment, there were no statistically significant differences in all studied variables except bone stability. The extra-short implants that were restored at the platform level experienced more crestal bone loss (P = .024). Conclusion: The extra-short implant restoration at the gingival level would increase the stability of the marginal bone. Keywords: dental prosthesis, fixed prosthesis, implant survival, marginal bone loss, short dental implants

Purpose: This pilot study investigated the retrospective outcomes of implants placed immediately or with a delayed protocol in revascularized free fibula flaps (FFF). Materials and Methods: Patients undergoing FFF between 2014 and 2017 were included in the study. Implants were inserted either immediately or 23.63 ± 10.61 months after reconstructive surgery. Resonance frequency analyses were recorded at the time of implant placement (first control) and 4 months postoperatively while uncovering and screwing the gingiva formers (second control). The statistical significance level was set at P .05. Results: Eight patients (four men, four women, mean age: 46.75 ± 12.96 years) were included in the study. Twenty-six implants were placed in FFF (14 immediate, 12 delayed), and 28 were placed in the alveolus. All implant stability quotient (ISQ) scores were in high stability ranges. Statistically significant differences were observed between delayed (79.25 ± 4.77) and immediate implant placement (73.14 ± 7.42) at first controls, but not at second controls (79.17 ± 3.59 and 76.00 ± 6.18). The ISQ values of immediate implant placement significantly increased from first to second controls (P = .018). Bicortically placed implants showed significantly higher scores than unicortical implants (P .05). ISQ values of FFF and alveolar bone groups were similar (P > .05). Conclusion: High stability scores similar to alveolar bone could be achieved by both immediate and delayed implant placement. Bicortical implantation results in better implant stability. Keywords: dental implant, implantation times, resonance frequency analyses, revascularized free fibula flap

Purpose: This within-subject comparison tested the null hypothesis that there is no difference in patient satisfaction and oral health-related quality of life when an individual with an edentulous mandible is rehabilitated with a two-implant overdenture or a three-implant-supported fixed dental prosthesis. Materials and Methods: Twelve subjects with an edentulous mandible or failing dentition were rehabilitated with the use of endosseous dental implants. Three implants were placed, and were immediately loaded with a provisional fixed prosthesis with minimal cantilever. After healing for 4 months, two Locator attachments were inserted and an overdenture was trialed; then, after a further 4 months, a fixed prosthesis was placed on the three implants. The fixed prosthesis was fabricated using computer-assisted design, and a titanium framework was manufactured with a resin base and teeth. Patient satisfaction and oral health-related quality of life was assessed before treatment, after wearing the provisional, and after each treatment option using a seven-item visual analog scale and a modified version of the 49-item oral health impact profile. Results: Of the 12 subjects, 11 chose the fixed over the removable prosthesis. A statistically significant (P .05) and positive effect on the overall score of both assessment tools was reported for both treatment modalities (when compared with pretreatment scores). Although no significant difference (P > .05) was found between the two options in overall scores of both surveys or in any of the seven domains of the modified oral health impact profile, the fixed prosthesis had a statistically higher score for stability, retention, and ease of chewing on a visual analog scale. Conclusion: Both treatment modalities provided a significant and similar improvement in patient satisfaction and oral health-related quality of life compared with a conventional complete mandibular removable dental prosthesis; however, a statistically significant higher score was reported for stability, retention, and ease of chewing for the fixed dental prostheses. Based on the 12 participants in this study, greater stability and ease of chewing with the fixed prosthesis likely influenced patient preference in most but not all subjects. Keywords: fixed, implants, mandible, overdenture, patient satisfaction, quality of life, removable

Purpose: The aim of this paired clinical study was to evaluate psychometric parameters (patient satisfaction and masticatory ability) and masticatory efficiency in elderly people before and after oral rehabilitation by a single-implant overdenture. Materials and Methods: This study included elderly individuals with residual alveolar bone height classified as Class III or IV according to the American College of Prosthodontics, and who wore clinically unsatisfactory complete dentures. Subjects first received new maxillary and mandibular conventional complete dentures. After 2 months of patient adaptation to the new complete dentures, subjective and objective variables were measured. Satisfaction with the new complete dentures was verified by applying a visual analog scale to rate patient satisfaction with stability, comfort, ability to chew, ability to speak, ease of cleaning, esthetics, and general satisfaction of their new complete dentures. Masticatory ability was assessed by asking participants to rate on a visual analog scale their ability to chew foods with different roughness and consistencies. Masticatory efficiency was measured by the sieving method using a siliconebased artificial test food. After evaluations were completed, each participant received one implant, which was placed in the symphysis region. After 3 months of implant osseointegration, the conventional complete dentures were transitioned to mandibular single-implant overdentures through placement of a low-profile attachment on the intaglio surface of the prostheses. Subjects used the single-implant overdentures for 2 months, and then all variables were reevaluated. Parametric t test and nonparametric Wilcoxon statistical tests were used to analyze data. Results: Participants reported increased satisfaction with stability of their mandibular single-implant overdentures compared with their new conventional complete dentures. However, satisfaction with the esthetics decreased when the new complete denture was converted into the singleimplant overdenture (P .05). Masticatory ability with the rehabilitation was not different between the new conventional complete dentures and the single-implant overdentures; however, transition to the single-implant overdenture greatly increased masticatory efficiency (P .0001). Conclusion: Single-implant overdentures changed the patient perceptions, improving their satisfaction with stability, although decreasing satisfaction with esthetics. Despite that, masticatory efficiency of elderly individuals with decreased residual bone height was greatly improved after single-implant overdenture use. Keywords: edentulous mandible, implant, mastication, overdenture, patient satisfaction

Purpose: The aim of this clinical study was to determinate if patients allergic to penicillin present a higher incidence of dental implant failure compared with nonallergic patients. Materials and Methods: This crosssectional clinical study analyzed patients rehabilitated with endosseous dental implants between September 2011 and July 2015, at the University Dental Clinic, School of Dentistry, International University of Catalonia (UIC). Prophylactic antibiotic therapy was prescribed for all patients: a single dose of 2 g of amoxicillin taken orally 1 hour before implant surgery for non-penicillin-allergic patients, and 600 mg of clindamycin taken orally 1 hour before the implant surgery for penicillin-allergic patients. Postsurgical antibiotics were prescribed to prevent early implant failures and postoperative infections: amoxicillin 750 mg three times a day for 7 days for nonallergic patients, and in patients with penicillin allergy, 300 mg clindamycin every 6 hours for 7 days. Implant failure was defined as the removal of the implant for any reason and was classified as early or late failure. Results: A total of 1,210 patients' files were analyzed; 8.03% of nonallergic patients and 24.68% of penicillin-allergic patients presented at least one implant failure. In penicillin-allergic patients, 21.05% were classified as late implant failure and 78.95% as early implant failure, with a lack of osseointegration (80%) being the mean reason for an early implant failure. Penicillin-allergic patients demonstrated a higher risk of implant failure with a risk ratio of 3.84 (95% CI) compared with nonallergic patients. Conclusion: Penicillinallergic patients treated with clindamycin presented almost four times the risk of suffering dental implant failure, although other variables such as implant brand, location, and the surgeon's skill might have influenced these results. Keywords: clindamycin, dental implant, implant failure, implant osseointegration, penicillin allergy

Explantation of fully or partially osseointegrated titanium implants is a complex procedure for myriad reasons and often results in major bone loss and pronounced defects of the hard and soft tissues. This may require more elaborate surgical interventions in cases of re-implantation. In this patient case, an osseointegrated titanium implant with some visible bone loss, missing attached mucosa at the buccal aspect, and a nonideal three-dimensional (3D) position had to be explanted. For this, the implant's inner connection was heated using a CO2 laser, which resulted in localized laser-induced thermo-necrosis at the bone-to-implant contact. One week following laser application, explantation could be performed easily with a torque slightly more than 35 Ncm. No complications occurred during the healing period. The result was a very easily performed explantation while preserving a maximum of the surrounding bony structure. Healing was uneventful, and no further visible bone loss could be observed during the healing time. Keywords: CO2 laser, explantation, implant, induced osteonecrosis, removal