The International Journal of Oral & Maxillofacial Implants, 01/2017

Purpose: It is essential to have sufficient bone bulk and density at the implant site in order to achieve good boneto- implant contact and primary stability, which are crucial for osseointegration. A new osteotomy preparation technique was recently introduced that uses a bone preservation method that creates a layer of compacted bone along the surface of the osteotomy. The hypothesis of this study was that this novel technique would increase primary implant stability, bone mineral density, and the percentage of bone at the implant surface compared with drilling technique. Materials and Methods: A total of 72 osteotomies were created in porcine tibial plateau bone samples using three preparation techniques: standard drilling; osseous extraction drilling with a new tapered, multi-fluted bur design; and osseous densification with the same multi-fluted bur rotating in a reversed direction that preserved and created a compacted layer of bone. The surgical process (temperature increase, drilling force, and torque), mechanical stability during the insertion and removal of 4.1-mm and 6.0- mm diameter implants (implant torque and stability quotient), and bone imaging (scanning electron microscopy, microcomputed tomography measurement of bone mineral density, and histomorphology) were compared among the three preparation techniques. Results: Osseous densification significantly increased insertion and removal torques compared to standard drilling or extraction drilling. No significant differences in implant stability quotient readings or temperature increases were demonstrated among the three groups. Although the same bur was used for extraction drilling and osseous densification techniques, the osseous densification osteotomy diameters were smaller than both the extraction drilling and standard drilling osteotomies due to the spring-back effect of bone elastic strain created. Imaging methods documented a layer of increased bone mineral density around the periphery of osseous densification osteotomies. The percentage of bone at the implant surface was increased by approximately three times for implants prepared with osseous densification compared with standard drilling. Conclusion: This study confirmed the hypothesis that the osseous densification technique would increase primary stability, bone mineral density, and the percentage of bone at the implant surface compared with drilling. By preserving bulk bone, it is hypothesized that the healing process will be accelerated due to the bone matrix, cells, and biochemicals that are maintained in situ and autografted along the surface of the osteotomy site. The healing response requires further study in vivo. Keywords: autografting, biomechanics, bone mineral density, compaction, implant fixation, osseodensification, primary stability

Purpose: The aims of this study were to evaluate the ability of a stepped osteotomy to improve dental implant primary stability in low-density bone sites and to investigate possible correlations between primary stability parameters. Materials and Methods: The study was performed on fresh humid bovine bone classified as type III. The test group consisted of 30 Astra Tech EV implants inserted following the protocol provided by the manufacturer. The first control group consisted of 30 Astra Tech EV implants inserted in sites without the underpreparation of the apical portion. The second control group consisted of 30 Astra Tech TX implants inserted following the protocol provided by the manufacturer. Implant insertion was performed at the predetermined 30 rpm. The insertion torque data were recorded and exported as a curve; using a trapezoidal integration technique, the area underlying the curve was calculated: this area represents the variable torque work (VTW). Peak insertion torque (pIT) and resonance frequency analysis (RFA) were also recorded. Results: A Mann-Whitney test showed that the mean VTW was significantly higher in the test group compared with the first control and second control groups; furthermore, statistical analysis showed that pIT also was significantly higher in the test group compared with the first and second control groups. Analyzing RFA values, only the difference between the test group and second control group showed statistical significance. Pearson correlation analysis showed a very strong positive correlation between pIT and VTW values in all groups; furthermore, it showed a positive correlation between pIT and RFA values and between VTW and RFA values only in the test group. Conclusion: Within the limitations of an in vitro study, the results show that stepped osteotomy can be a viable method to improve implant primary stability in low-density bone sites, and that, when a traditional osteotomy method is performed, RFA presents no correlation with pIT and VTW. Keywords: dental implants, primary stability, resonance frequency analysis, surgical technique, variable torque work

Purpose: A novel approach for the study of early bone formation around dental implants in the miniature pig was evaluated. In addition to the traditional histologic and histomorphometric analysis, the expression of the osteogenic genes was analyzed both at the messenger ribonucleic acid (mRNA) and protein level. Materials and Methods: Mandibular premolars and the first molar were extracted in six miniature pigs. After 3 months of healing, 36 specially designed bone chamber implants were placed. Three different implant surface configurations were used: titanium SLA, titanium SLActive, and titanium zirconium SLActive (Roxolid). Each hemi-mandible received three randomly allocated implants (one for each surface type) on both sides of the arch, in a split-mouth design. Three animals were sacrificed after 3 days and another three after 2 weeks of healing post-implant insertion. For each animal the right hemi-mandible underwent qualitative histologic and quantitative histomorphometric analysis. The left hemi-mandible underwent immunohistofluorescence (IHF) analysis. β-catenin, Runx2, osteopontin, and osteocalcin were analyzed by IHF; osterix, and osteocalcin mRNA expression was also evaluated by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Results: At 3 days after the implantation, all implants were surrounded by blood clot. No provisional matrix or bone was observed inside the chamber. Infection or degenerative lesions were absent. At 2 weeks, the histomorphometric analysis showed no significant difference between the groups concerning the bone area. qRT-PCR showed that Ti SLActive had the highest osteocalcin mRNA expression followed by Ti SLA and Roxolid SLActive. Osterix mRNA expression was higher on Ti SLA and Roxolid SLActive compared to Ti SLActive. The differences were not statistically significant. IHF was only found positive for osteocalcin at 2 weeks. At 3 days, osteocalcin was detected only on native bone. At 2 weeks, osteocalcin was expressed highest by Ti SLActive followed by Roxolid SLActive and TiSLA; however, there was no statistically significant difference between the groups in the osteocalcin expression level. Conclusion: The present methodology allowed evaluation of changes in gene expression during the early phase of osteogenesis that seem to be related to the quality of the surface. Further studies with higher power and more specific antibodies are needed to confirm these preliminary findings. Keywords: bone healing, dental implant, miniature pig

Purpose: Ultraviolet (UV)-mediated photofunctionalization has earned considerable attention for the enhancement of the biologic capabilities of titanium. The effects of photofunctionalization on bone augmentation and gap closure were examined using titanium implants and mesh in a rat femur model. Materials and Methods: An acid-etched titanium implant (4-mm length, 1-mm diameter) was placed in the gluteal tuberosity that resembles a knife-edge-like edentulous ridge. The lower half of the implant was located in a 2-mm-diameter defect created in the bone without cortical bone support; the upper half was exposed and covered with a titanium mesh to provide augmentation space. After 12 and 24 days of healing, specimens were subjected to microcomputed tomography (micro-CT)- and histology-based bone morphometry in three zones of analysis: augmentation, cortical bone-implant gap, and bone marrow. A biomechanical push-in test was performed to examine the strength of bone-implant integration. Photofunctionalization was performed by treating titanium implants and mesh with UV light for 12 minutes. Results: Photofunctionalized titanium mesh and implants were hydrophilic, whereas untreated controls were hydrophobic. Bone volume was significantly greater in photofunctionalized implants and mesh than in untreated implants in all zones on days 12 and 24. Bone-to-implant contact of photofunctionalized implants was greater than that of untreated implants, not just in the bone marrow but also in the gap and augmented zones. The strength of osseointegration was three times greater for photofunctionalized implants than for untreated implants. Conclusion: Use of photofunctionalized titanium mesh and implants effectively enhanced vertical bone augmentation, cortical bone-implant gap closure, and osseointegration without innate bone support. Keywords: bone engineering, osseointegration, photofunctionalization, titanium mesh, ultraviolet

Purpose: Reinforcement of maxillary implant overdentures is necessary not only for preventing prosthetic complications but also for protecting underlying structures, as it makes the denture base more rigid. However, few studies have investigated the effects of reinforcement on the underlying structure. The purpose of this study was to examine the effects of reinforcement on implant stress under various implant configurations and denture designs. Materials and Methods: A maxillary edentulous model with implants and experimental overdentures with and without palatal coverage and three types of cast reinforcement was fabricated. Four strain gauges were attached to the implants in the anterior, premolar, and molar areas. A vertical occlusal load of 98 N was applied through the mandibular complete denture, and the strain on the implants was compared using one-way analysis of variance (P = .05). Results: In dentures with palatal coverage, reinforcement significantly decreased the strain on the anterior and molar implants. In palateless dentures, reinforcement with a palatal bar decreased the strain most on the anterior and molar implants. Conclusion: Reinforcement of maxillary implant overdentures decreased the strain on underlying implants, regardless of the denture design and implant configurations. Keywords: implant, load, maxillary implant overdenture, palateless denture, strain

Purpose: To compare the three-dimensional (3D) accuracy of conventional direct implant impressions with digital implant impressions from three intraoral scanners, as well as different implant levels-bone level (BL) and tissue level (TL). Materials and Methods: Two-implant master models were used to simulate a threeunit implant-supported fixed dental prosthesis. Conventional test models were made with direct impression copings and polyether impressions. Scan bodies were hand-tightened onto master models and scanned with the three scanners. This was done for the TL and BL test groups, for a total of eight test groups (n = 5 each). A coordinate measuring machine measured linear distortions (dx, dy, dz), global linear distortion (dR), angular distortions (dϴy, dϴx), and absolute angular distortions (Absdϴy, Absdϴx) between the master models, test models, and .stl files of the digital scans. Results: The mean dR ranged from 35 to 66 μm; mean dϴy angular distortions ranged from -0.186 to 0.315 degrees; and mean dϴx angular distortions ranged from -0.206 to 0.164 degrees. Two-way analysis of variance showed that the impression type had a significant effect on dx, dz, and Absdϴy, and the implant level had a significant effect on dx and Absdϴx (P .05). Among the BL groups, the mean dR of the conventional group was lower than and significantly different from the digital test groups (P = .010), while among the TL groups, there was no statistically significant difference (P = .572). Conclusion: The 3D accuracy of implant impressions varied according to the impression technique and implant level. For BL test groups, the conventional impression group had significantly lower distortion than the digital impression groups. Among the digital test groups, the TR system had comparable mean linear and absolute angular distortions to the other two systems but exhibited the smallest standard deviations. Keywords: accuracy, coordinate measuring machine, digital, implant impression, three-dimensional, 3D

Purpose: The objective of this study was to evaluate the osteogenic and osseointegration capability of the Ce-tetragonal zirconia polycrystal (TZP)-based nanostructured zirconia/alumina composite (Ce-TZP/Al2O3) that was treated with hydrofluoric acid (HF). Materials and Methods: Osteogenic MC3T3-E1 cells were cultured on acid-etched titanium (AETi) disks and Ce-TZP/Al2O3 disks without HF treatment (Zr[0%]), with 4% HF treatment (Zr[4%]), or with 55% HF treatment (Zr[55%]) for 24 hours, and biologic responses were compared among four conditions in vitro. Miniature implants of AETi and Zr(55%) were surgically placed in the femora of rats. Osseointegration was evaluated by a biomechanical push-in test after 2 and 4 weeks of healing. Results: The surface of Zr(55%) rendered nanofeatured topography with a greater surface area and roughness, and extensive geographical undercut as ceria-zirconia crystal disappeared from the superficial layer and was similar to the surface morphology of biomineralized matrices. Culture studies showed that the attachment, proliferation, spread, and functional phenotypes of osteogenic cells, such as alkaline phosphatase activity and bone-related gene expression, were remarkably increased on the Zr(55%) surface. The strength of osseointegration measured using the biomechanical push-in test in a rat model was stronger for Zr(55%) implants than for AETi implants by 1.6 fold. Conclusion: The nanostructured Ce-TZP/ Al2O3 surface substantially enhanced the osteogenic response in vitro and the osseointegration capability in vivo, which suggest its potential clinical application as a novel implant material. Keywords: bone-implant integration, Ce-TZP/Al2O3, surface topography, zirconia implant

Purpose: The aim of this prospective study was to determine platform and angle accuracy for dental implants using dynamic navigation, a form of computer-assisted surgery. Three hypotheses were considered: (1) the overall accuracy for implant placement relative to the virtual plan is similar to that of static tooth-borne computerized tomography (CT)-generated guides; (2) the dynamic system is more accurate than freehand methods; and (3) there is a learning curve associated with this method. Materials and Methods: This study involved three surgeons placing implants in the mandible and maxilla of patients using a dynamic navigation system (X-Guide, X-Nav Technologies). Virtual implants were placed into planned sites using the navigation system computer. Post-implant placement cone beam CT scans were taken on all patients. For each patient, this scan was mesh overlayed with the virtual plan and used to determine platform and angular deviations to the virtual plan. The primary outcome variables were platform and angular deviations comparing the actual placement to the virtual plan. Secondary analyses included determination of accuracy related to case experience and freehand placement of implants. Comparisons to published accuracy studies were made for implant placement using static guides. Results: Accuracy deviations from the virtual plan were similar to those reported for static tooth-based guides using literature references as the comparison. The accuracy of dynamic navigation was superior compared to freehand implant placement. The three surgeons had similar accuracies after their learning curve was achieved. Proficiency based on case series was achieved by the 20th surgical procedure. Conclusion: Dynamic navigation can achieve accuracy of implant placement similar to static guides and is an improvement over freehand implant placement. In addition, there was a learning curve to achieve proficiency. Keywords: accuracy, implants, navigation

Purpose: Osseointegration has been defined in many ways, from both basic science and clinical perspectives, but generally represents the restoration of bony homeostasis following implant placement and is usually judged by some form of bone/implant disruption test. In this study, bone anchorage to two different implant surfaces, in tensile and shear modes, was compared to investigate the relation between implant surface topography and osseointegration over time. The purpose was to determine if mathematical parameters could be derived that would reflect the biologic relevance of the implant surface design. Materials and Methods: Rectangular titanium implants (n = 244) were placed in the distal femora of 122 male Wistar rats proximal to the knee joint. Implants were either microsurfaced (MS) or nanosurfaced (NS). Animals were euthanized at one of six time points ranging from 5 days to 6 months, and the force required to disrupt the bone implant interface, in either shear or tension, was measured using an Instron machine. Data were analyzed by fitting the function F = C (1-e-x/τ), where F is the measured disruption force, C is the predicted average maximum disruption force, x is the time postimplantation, and τ is a time constant defined as the time required for F to reach 63.2% of C. Results: Analysis showed that shear testing resulted in significantly larger values of C than seen in tension, but no significant difference was observed when comparing the values of C for NS and MS implants in shear (P = .7). Thus, in accord with clinical reports, both implants performed equivalently at longer implantation periods. The differences in C were significant in tension (P .05). Importantly, NS implants had a significantly smaller τ than the MS implants (P .01, in shear), but no significant differences were observed in τ due to mechanical testing vector. The disruption force values reached a plateau with time, representing bony homeostasis as a result of osseointegration. With time, both implant surfaces reached the same maximum (C) values, in shear. However, the value of τ was smaller in NS compared to MS implants, which represented a higher rate of osseointegration. Conclusion: Thus, τ emerges as a measureable and biologically relevant parameter that can be employed to compare the osseointegration potential of putative implant surfaces. Keywords: bone anchorage, homeostasis, implant surface, mathematical modeling, nanotopography, new parameter, osseointegration, surface roughness, tau

Purpose: This study aimed to evaluate the radiographic bone level changes of implants positioned via the split-crest procedure both in the maxilla and mandible at a long-term follow-up. Materials and Methods: Seventy-one patients were retrospectively enrolled in the study. The placement of 137 dental implants was performed in the edentulous premolar or molar region after a split-crest ridge expansion procedure. Implants followed a delayed loading protocol. Intraoral digital radiographs were performed at baseline, upon implant placement, at 70 days (following placement of the provisional prosthesis), and on a yearly basis during followup. Crestal bone levels were evaluated at the baseline, upon provisional prosthesis placement, at 12, 36, and 60 months, and at the long-term follow-up of healing from implant placement. Results: The patients underwent a mean follow-up of 6.54 ± 1.32 years, from which the implant survival rate was reported at 98.54%. Within the first year from implant placement, a bone loss resulted at a mean value of -1.11 ± 0.44 mm. After almost 3 years from implant placement, a mean bone gain of +0.89 ± 0.39 mm was reported, which was statistically significant compared with 12-month values (P .05). From this point, bone levels remained stable, reporting similar values over time, with no significant differences (P > .05). Conclusion: A mean vertical bone gain of +0.89 ± 0.39 mm was observed after almost 36 months after implant positioning. Keywords: bone level, dental implant, split crest

Purpose: The aim of this study was to compare solvent dehydrated human allograft (SDHA; Puros Allograft) and freeze-dried human allograft (FDHA; MinerOss) in order to determine if the allogeneic bone preservation process influences the amount of remaining particles and newly formed bone in maxillary sinus augmentation. Materials and Methods: Subjects requiring maxillary lateral sinus augmentation with ridge height 5 mm were included in this study. Maxillary sinuses were randomly assigned to be grafted with a 1:1 ratio of cortical and cancellous bone, either SDHA or FDHA. In both groups, the graft material was mixed with autogenous bone graft at a ratio of 1:1. Morphologic and histomorphometric analyses were completed 6 months after the grafting procedure. Results: Thirty-four subjects were included in this study. All subjects showed similar demographic characteristics at baseline. Half of the sinuses were grafted with SDHA; the remaining half were grafted with FDHA. Histomorphometric analysis of bone core biopsy samples showed no statistically significant difference between the SDHA or FDHA allogeneic bone substitutes (P = .365), with a mean value of 39.54% ± 0.05% and 31.96% ± 0.08% of mineralized tissue for SDHA and FDHA, respectively. However, a slightly higher mean value of remaining particles was obtained for the FDHA compared with SDHA (18.91% ± 0.09% vs 8.65% ± 0.06%, respectively), although the difference was not statistically significant. Additionally, FDHA demonstrated statistically significantly higher osteoblast, fibroblast, and inflammatory cell numbers. Conclusion: Regardless of the preservation process subtype, allogeneic bone grafting material, in combination with autogenous bone, was demonstrated to be effective for maxillary sinus augmentation bone by means of cellular, vascular, and histomorphometric behavior. Nonetheless, FDHA demonstrated higher cellularity compared to SDHA, suggesting accelerated turnover activity for the latter grafting material. Keywords: alveolar ridge augmentation, bone, dental implant, grafting, maxillary ridge augmentation

Purpose: The purpose of this study was to evaluate patient satisfaction and clinical outcomes among subjects with mandibular overdentures supported by one or two immediately placed dental implants 5 years after loading. Materials and Methods: Thirty-six subjects (16 men and 20 women) received one or two dental implants in the anterior mandible, and all implants were loaded the day of surgery. Subjects were scheduled for follow-up 3-, 6-, and 12 months after implant placement and thereafter annually for 4 more years. Patient satisfaction scores were measured with the Oral Health Impact Profile-EDENT (OHIPEDENT) questionnaire. Results: Seventeen subjects (7 male and 10 female) with a mean age of 59.4 years (range, 44 to 74 years) were available for the 5-year follow-up examination. Nine subjects with 10 failing implants were excluded during the first year and nine subjects were lost to follow-up. No implants failed between the 12- and 60-month follow-up examinations, and the need for denture maintenance was low. Mean peri-implant bone change was 0.92 mm, and the Spearman test failed to show correlation between the insertion torque value and implant stability quotient. Patient satisfaction scores increased significantly when compared with baseline values and continued to be high for both groups, with no significant differences. Conclusion: Ten implants in nine subjects failed early, but no failures were observed after the 12-month examination. No significant differences were found between subjects in the two groups with respect to implant survival rates and peri-implant bone loss, and patient satisfaction scores continued to be high. Although patient satisfaction and implant success were high during the 12- to 60-month period, the results should be interpreted with caution because of the high number of failing implants and patients lost to followup. More research is needed to study outcomes of treatment with immediately loaded mandibular implant overdentures. Keywords: dental implants, overdenture, patient satisfaction, peri-implant bone loss

Purpose: The aim of this retrospective study was to compare long-term (≥ 5 years) outcomes of implants placed in patients treated for chronic periodontitis versus those placed in periodontally healthy patients. In both groups, the implants were placed in alveolar ridges that were laterally augmented with autogenous bone block grafts using a split bone block technique. Materials and Methods: Two hundred ninety-two patients were screened in the course of supportive periodontal treatment examinations. Nonsmoking patients without any severe systemic diseases who had adhered to regular supportive periodontal treatment for a minimum of 5 years after undergoing autogenous lateral grafting (using the split bone block technique), implant placement, and prosthetic reconstructions were classified into two groups based on their presurgical status: periodontally healthy patients (PHP) and periodontally compromised patients (PCP). Results: Clinical outcomes for 77 patients, 38 PHP and 39 PCP, were examined. All had been successfully treated for severe lateral atrophy and received a total of 241 endosseous implants between 2002 and 2008. At the final examination, mean bleeding on probing was 7.08% ± 7.27% in PHP and 14.49% ± 18.14% in PCP, a statistically significant difference. Significantly higher Plaque Index and more recession were associated with a narrow ( 2 mm) width of keratinized mucosa. Conclusion: Implants in alveolar ridges laterally augmented using a split bone block technique revealed similar clinical peri-implant conditions in both PHP and PCP. Using autogenous bone block grafts without biomaterials resulted in long-term peri-implant tissue stability. Keywords: autogenous bone augmentation, CIST, lateral augmentation, peri-implant disease, periodontally compromised patients, split bone block grafting

Purpose: The present study aimed to explore the association between marginal bone loss and type of peri-implant bony defect determined using a new peri-implant bony defect classification system. Materials and Methods: A total of 110 patients with implant-supported mandibular overdentures were involved. Clinical information was collected, including gender, age, smoking habit, and the overdenture attachment system used. Peri-implant bony defect types and marginal distances (ie, distance between the marginal bone level and the top of the implant shoulder) of all sites were identified on panoramic radiographs by a single experienced observer. The associations between marginal distance and peri-implant bony defect type, gender, age, smoking habit, attachment system, and time after implantation were investigated using marginal generalized linear models and regression analysis. Results: A total of 83 participants were included in the final sample with a total of 224 implants involving 3,124 implant sites. The mean observation time was 10.7 years. All peri-implant bony defect types except Type 5 (slit-like) were significantly related to marginal distance in all models (P .01). Smoking and time after implantation were significantly related to marginal distance while gender, age, and the overdenture attachment system used were not. Conclusions: The periimplant bony defect type, determined using the new classification system, is associated with the extent of marginal bone loss. Keywords: bone morphology, dental implant, marginal bone loss, peri-implant bone defect

Purpose: To assess the influence of anodized titanium and zirconium dioxide abutments and peri-implant soft tissue thickness on the optical outcome of implant-supported lithium disilicate single crowns. Materials and Methods: Twenty patients with a missing maxillary single incisor, canine, or first premolar received an endosseous implant after a two-stage surgery protocol. After healing and soft tissue conditioning, peri-implant soft tissues were reproduced in the impression, and the thickness was measured. Customized abutments were made of titanium, gold-anodized titanium, pink-anodized titanium, and zirconium dioxide. The definitive prosthesis was a lithium disilicate crown stratified by feldsphatic porcelain. Customized abutments were screwed (35 Ncm), and the crown was temporarily placed on the abutment with a try-in paste. Color measurements were made using a spectrophotometer. CIELab color scale was employed following the formula: ΔE = (ΔL)2 + (Δa)2 + (Δb)2. Data were analyzed using repeated-measures analysis of variance (ANOVA), Bonferroni and Pearson's correlation tests (α = .05). Results: Abutment material type significantly affected the ΔE values at both the periimplant soft tissue (P = .0001) and coronal level (P = .001). The lowest ΔE values were obtained with zirconia abutments at both soft tissue (6.06 ± 3.2) and coronal level (5.76 ± 2.9) compared with those of other abutments (soft tissue: 8.96 ± 3.1 to 11.56 ± 3.4; coronal: 8.66 ± 6.1 to 10.42 ± 6.3). Mean soft tissue thickness (1.63 ± 0.64 mm) affected the ΔE values at the peri-implant soft tissue level for only titanium and pink-anodized titanium abutments (P = .024 and P = .048, respectively). In all conditions, correlation coefficients between ΔE and the abutment materials were higher for titanium (r = -0.544; P = .024) and the least for zirconia (r = -0.313; P = .238) and gold-anodized titanium (r = -0.393; P = .119) abutments. Conclusion: All abutment types demonstrated noticeable color difference at both the soft tissue and coronal levels. Zirconia abutments showed the lowest ΔE values at both measurement zones. Soft tissue thickness did not affect the ΔE values at the periimplant soft tissue level. Keywords: color, implant abutments, lithium disilicate, oral implants, soft tissue, spectrophotometer, titanium, zirconia

Purpose: The objectives of this study were to evaluate implant survival and success in the elderly population and to assess indicators and risk factors for success or failure of dental implants in older adults (aged 60 years and older). Materials and Methods: This historical prospective study was developed from a cohort of patients born prior to 1950 who received dental implants in a single private dental office. Implant survival and marginal bone levels were recorded and analyzed with regard to different patient- and implant-related factors. Results: The study examined 245 patient charts and 1,256 implants from one dental clinic. The mean age at the time of implant placement was 62.18 ± 8.6 years. Smoking was reported by 9.4% of the cohort studied. The overall survival rate of the implants was 92.9%; 7.1% of the implants had failed. Marginal bone loss depicted by exposed threads was evident in 23.3% of the implants. Presenting with generalized periodontal disease and/or severe periodontal disease negatively influenced the survival probability of the implant. Implants placed in areas where bone augmentation was performed prior to or during implant surgery did not have the same longevity compared with those that did not have augmentation prior to implantation. Conclusion: The overall findings concluded that implants can be successfully placed in older adults. A variety of factors are involved in the long-term success of the implant, and special consideration should be taken prior to placing implants in older adults to limit the influence of those risk factors. Keywords: bone loss, dental hygiene, gingival health, maintenance, plaque, prevention

Purpose: The aim of this prospective study was to establish if ultrashort implants are a reliable therapeutic solution by evaluating their effect on mean crestal bone loss and assessing their survival and success rates. Materials and Methods: Patients were treated using 6-, 9-, and 11-mm-long implants with sandblasted and acid-etched surfaces and fitted with fixed partial prostheses. Clinical and radiographic examinations were scheduled yearly. Data collected included the implant positioning site, implant length and diameter, peri-implant bone loss (PBL), and clinical and anatomical C/I ratios. Results: One hundred eleven implants (6-mm-long, 30.6%) were positioned; two implants were lost before loading. During the 36-month followup, no other implants were lost (98.2% survival rate, 100% from loading), but four implants did not meet the criteria for success, due to excessive crestal bone loss, resulting in a 94.6% success rate, 96.3% from loading. Success rates and peri-implant bone loss were not significantly different among implants with different lengths. No correlation was observed between implant length and bone resorption. Conclusion: Six-millimeter-long implants did not show different results in comparison with 9- and 11-mm-long implants. They can be considered a reliable solution for implant prosthetic rehabilitation and a dependable and minimally invasive therapeutic option in areas showing severe bone resorption. Keywords: crown-implant ratio, implant length, implant success rate, prospective study, ultrashort implants

Purpose: To evaluate whether primary implant stability could be used to predict bone quality, the association between the implant stability quotient (ISQ) value and the bone type at the implant site was evaluated. Materials and Methods: Ninety-five implant sites in 50 patients were included. Bone type (categorized by Lekholm and Zarb) at the implant site was initially assessed using presurgical dental radiography. During the preparation of the implant site, a bone core specimen was carefully obtained. The bone type was assessed by tactile sensation during the drilling operation, according to the Misch criteria. The primary stability of the inserted implant was evaluated by resonance frequency analysis (RFA). The ISQ value was recorded. The bone core specimen was then examined by stereomicroscopy or microcomputed tomography (micro- CT), and the bone type was determined by the surface characteristics of the specimen, based on Lekholm and Zarb classification. Agreement between the bone quality assessed by the four methods (ie, presurgical radiography, tactile sensation, stereomicroscopy, and micro-CT) was tested by Cohen's kappa statistics, whereas the association between the ISQ value and the bone type was evaluated by the generalized linear regression model. Results: The mean ISQ score was 72.6, and the score was significantly influenced by the maxillary or mandibular arch (P = .001). The bone type at the implant sites varied according to the assessment method. However, a significant influence of the arch was repeatedly noted when using radiography or tactile sensation. Among the four bone-quality assessment methods, a weak agreement existed only between stereomicroscopy and micro-CT, especially in the maxilla (κ = 0.469). A negative association between the ISQ value and the bone type assessed by stereomicroscopy or by micro-CT was significant in the maxilla, but not in the mandible, after adjustments for sex, age, and right/left side (P = .013 and P = .027 for stereomicroscopy and micro-CT, respectively). Conclusion: The ISQ value was weakly associated with the bone type when assessed by stereomicroscopy or micro-CT in the maxilla. Caution is necessary if RFA is used as a tool to evaluate bone quality at the implant site, especially in the mandible. Keywords: bone, dental implants, diagnosis, microcomputed tomography, resonance frequency analysis, structural biology

Purpose: The histomorphometric results of sinus floor augmentation with deproteinized bovine bone (DBB) and a new fully synthetic bone substitute, poly(lactic-co-glycolic acid/hydroxyapatite) (PLGA/HA), were compared in humans. Materials and Methods: Twelve maxillary sinuses of eight patients requiring major maxillary sinus floor augmentation and free of concomitant conditions (ASA scores 1 and 2) were studied. Lateral sinus augmentation was performed using DBB or PLGA/HA grafts; sites were randomly assigned to control or test groups. Patients were reexamined approximately 6 months after grafting using cone beam computed tomography scans, and biopsy samples were harvested from implant sites. Total bone volume, residual graft material volume, and new bone volume were assessed. Results: Healing times were similar between groups. Measurable biopsy specimens were available from four of the test sites and six of the control sites. PLGA/HA grafts showed no trace of graft material, whereas DBB grafts had a mean graft area of 16.5% (P .05). Mean percent newly formed bone tended to be greater for PLGA/HA (44.45%) than for DBB (27.51%). Mean total volume percent did not differ significantly: PLGA/HA = 44.45%, DBB = 44.10%. Conclusion: DBB and PLGA/HA produced similar total bone volumes. PLGA/HA appeared to be completely resorbed, whereas DBB presented residual graft material. With the limitations due to the small sample size, both materials were suitable for sinus floor augmentation. Keywords: bone graft, histomorphometry, in vivo, PLGA, sinus elevation, tissue engineering

Purpose: Collagen barrier membranes were first introduced to regenerative periodontal and oral surgery to prevent fast ingrowing soft tissues (ie, epithelium and connective tissue) into the defect space. More recent attempts have aimed at combining collagen membranes with various biologics/growth factors to speed up the healing process and improve the quality of regenerated tissues. Recently, a new formulation of enamel matrix derivative in a liquid carrier system (Osteogain) has demonstrated improved physico-chemical properties for the adsorption of enamel matrix derivative to facilitate protein adsorption to biomaterials. The aim of this pioneering study was to investigate the use of enamel matrix derivative in a liquid carrier system in combination with collagen barrier membranes for its ability to promote osteoblast cell behavior in vitro. Materials and Methods: Undifferentiated mouse ST2 stromal bone marrow cells were seeded onto porcine-derived collagen membranes alone (control) or porcine membranes + enamel matrix derivative in a liquid carrier system. Control and enamel matrix derivative- coated membranes were compared for cell recruitment and cell adhesion at 8 hours; cell proliferation at 1, 3, and 5 days; and real-time polymerase chain reaction (PCR) at 3 and 14 days for genes encoding Runx2, collagen1alpha2, alkaline phosphatase, and bone sialoprotein. Furthermore, alizarin red staining was used to investigate mineralization. Results: A significant increase in cell adhesion was observed at 8 hours for barrier membranes coated with enamel matrix derivative in a liquid carrier system, whereas no significant difference could be observed for cell proliferation or cell recruitment. Enamel matrix derivative in a liquid carrier system significantly increased alkaline phosphatase mRNA levels 2.5-fold and collagen1alpha2 levels 1.7-fold at 3 days, as well as bone sialoprotein levels twofold at 14 days postseeding. Furthermore, collagen membranes coated with enamel matrix derivative in a liquid carrier system demonstrated a sixfold increase in alizarin red staining at 14 days when compared with collagen membrane alone. Conclusion: The combination of enamel matrix derivative in a liquid carrier system with a barrier membrane significantly increased cell attachment, differentiation, and mineralization of osteoblasts in vitro. Future animal testing is required to fully characterize the additional benefits of combining enamel matrix derivative in a liquid carrier system with a barrier membrane for guided bone or tissue regeneration. Keywords: bone graft, emdogain, enamel matrix derivative, enamel matrix proteins, periodontal regeneration

Purpose: Parathyroid hormone (PTH) plays an important role in the treatment of osteoporosis due to its anabolic effect. In this study, PTH was administered intermittently to rats with ovariectomy-induced osteoporosis, titanium implants were placed into the rat maxillae, and the response of surrounding bone was evaluated. Materials and Methods: A total of 30 female 8-week-old Sprague-Dawley rats were either ovariectomized to induce osteoporosis or sham operated. After 8 weeks, the upper right first molar was extracted and after a 4-week healing period an implant was placed. The animals were then divided into three groups: the PTH group (n = 10), which had been ovariectomized and received postimplant PTH; the OVX group (n = 10), which had been ovariectomized but did not receive postimplant PTH; and the control group (n = 10), which had been sham operated only (n = 10). Following implant placement, the rats in the PTH group received intermittent doses (three times a week) of PTH (30 μg/kg) subcutaneously in the dorsum. All the rats were sacrificed 4 weeks after implantation and specimens of the peri-implant maxillary bone were harvested, including the implant. Samples were evaluated by histomorphometric analysis and three-dimensional microcomputed tomography. Results: Histomorphometric results showed that the mean bone area per tissue area (BA/TA) was 54.16% ± 2.2% in the PTH group and 45.24% ± 6.3% in the OVX group. The percentage of bone-to-implant contact (BIC) was 45.58% ± 9.4% in the PTH group and 32.00% ± 10.9% in the OVX group. Mean BA/TA and mean BIC values in the PTH group were higher than those in the OVX group; however, the differences were not statistically significant (P > .05). Microstructural data also showed differences between the groups. Bone volume was greater and trabecular bone was thicker in the PTH group than in the OVX group and more trabeculae were found in the PTH group. Bone mineral density was also higher in the PTH group. However, statistical analysis failed to show a significant difference between these two groups in any parameters other than trabecular thickness (P = .023). Conclusion: Despite the limitations of this study, intermittent PTH administration in humans may be helpful in accelerating new bone formation around implants. PTH treatment could improve clinical outcomes when dental implants are placed in jaws with low-quality bone. Keywords: bone regeneration, dental implants, osteoporosis, parathyroid hormone

Purpose: The purpose of this study was to review and evaluate the characteristics of the 300 most-cited articles that have been published in the most important implant dentistry journals. Materials and Methods: A search and selection of the most-cited articles up to October 2014 was conducted for implant journals with the highest impact factors, according to the ISI Web of Science. The 300-most-cited articles were evaluated according to the most commonly studied topics and methodological designs used. The most-cited journals and the number of articles cited by year were calculated. Descriptive statistics were used to summarize the results. Results: The most-cited topics consisted of implant success/survival and guided bone regeneration, and the most-cited methodological designs were case series and cohort studies. The most frequently referenced journal was The International Journal of Oral and Maxillofacial Implants, with 47% of the citations, and the period with the most citations was 1996 to 2000. Conclusion: Longitudinal studies of success and survival have had great scientific impact on the practice of implant dentistry. Awareness of the most-cited articles in implant dentistry will contribute to scientific advances, as it serves to identify the most researched areas, the most frequently used study designs, and areas that require further research. Keywords: dental implants, evidence-based dentistry, impact factor, journal article, MEDLINE

Purpose: This systematic review and meta-analysis was aimed at evaluating the longitudinal effect of platform switching on implant survival rates as well as on soft and hard tissue outcomes. Materials and Methods: An electronic search of the databases of the National Center for Biotechnology Information, PubMed, Ovid (MEDLINE), EMBASE, Web of Science, and Cochrane Collaboration Library was conducted in February 2015. Studies published in English with at least 10 human participants and a 12-month postloading follow-up were included. Random effects meta-analyses of selected studies were applied to compare the primary and secondary outcomes of platform-switched (PS) and regular-platform (RP) implants, as well as the experimental designs and clinical outcomes. Results: A total of 26 studies involving 1,511 PS implants and 1,123 RP implants were evaluated. Compared to RP implants, PS implants showed a slight increase in vertical marginal bone loss (VMBL) and pocket depth reduction (weighted mean differences were -0.23 mm and -0.20 mm, respectively). The PS implants had a mean VMBL of 0.36 ± 0.15 mm within the first year of service. The meta-regression suggested a trend of decreased bone resorption at sites with thick soft tissues at baseline. Conclusion: This study suggested that platform switching may have an indirect protective effect on implant hard tissue outcomes. Keywords: implant, marginal bone resorption, meta-analysis, platform switching, tissue biotype

Purpose: The purpose of this meta-analysis was to assess and compare clinical outcomes of short implants versus long implants placed in conjunction with a bone augmentation procedure. Materials and Methods: The eligible studies were searched from PubMed, Embase, Springer link, and the Cochrane library databases up to 23 January 2015. Prosthesis failures, implant failures, complications, and marginal bone loss were the clinical outcomes measured. The pooled weighted mean difference (WMD) or risk ratios (RRs) and their 95% confidence intervals (CIs) were used to measure the effect size of continuous variables and dichotomous variables, respectively. A random-effects model was performed to assess the effect size. Results: Nine eligible studies including 480 short implants (≤ 8 mm) and 503 long implants (≥ 9.3 mm) were selected for this meta-analysis. Compared with the long-implant group, a notable decrease in the short-implant group was found for complications at the 5-year follow-up (RR = 0.34, 95% CI: 0.15 to 0.79, P .05) and for marginal bone loss at the 1-year (WMD = -0.08, 95% CI: -0.15 to -0.02, P .05), 3-year (WMD = -0.43, 95% CI: -0.63 to -0.23, P .05), and 5-year (WMD = -0.57, 95% CI: -1.10 to -0.04, P .05) followups. No significant differences were found between the short-implant and long-implant groups for other variables (P > .05). Moreover, the results were not obviously changed when stratified by implants placed in the mandible and maxilla. Conclusion: Implants ≤ 8 mm in length are considered to be a suitable alternative treatment when bone height is not adequate for standard implants. Keywords: dental implants, meta-analysis, randomized controlled trial

Purpose: This study aimed to investigate the effects of titanium surface topography and simvastatin on growth and osteogenic differentiation of human bone marrow stromal cells (hBMSCs) in estrogen-deprived (ED) cell culture. Materials and Methods: Human BMSCs were seeded on cell culture plates, smoothsurface titanium (Ti) disks, and sandblasted with large grits and acid etched (SLA)-surface Ti disks; and subsequently cultured in regular (fetal bovine serum [FBS]), ED, and ED-with 100 nM simvastatin (ED-SIM) culture media for 14 to 21 days. Live/dead cell staining, scanning electron microscope examination, and cell viability assay were performed to determine cell attachment, morphology, and growth. Expression levels of osteoblast-associated genes, Runx2 and bone sialoprotein and levels of alkaline phosphatase (ALP) activity, calcium content, and osteocalcin in culture media were measured to determine osteoblastic differentiation. Expression levels of bone morphogenetic protein-2 (BMP-2) were investigated to examine stimulating effects of simvastatin (n = 4 to 5, mean ± SD). In vitro mineralization was verified by calcein staining. Results: Human BMSCs exhibited different attachment and shapes on smooth and SLA titanium surfaces. Estrogendeprived cell culture decreased cell attachment and growth, particularly on the SLA titanium surface, but cells were able to grow to reach confluence on day 21 in the ED-osteogenic (OS) culture medium. Promoting effects of the SLA titanium surface in ED-OS were significantly decreased. Simvastatin significantly increased osteogenic differentiation of human BMSCs on the SLA titanium surface in the ED-OS medium, and the promoting effects of simvastatin corresponded with the increasing of BMP-2 gene expression on the SLA titanium surface in ED-OS-SIM culture medium. Conclusion: The ED cell culture model provided a welldefined platform for investigating the effects of hormones and growth factors on cells and titanium surface interaction. Titanium, the SLA surface, and simvastatin synergistically promoted osteoblastic differentiation of hBMSCs in ED condition and might be useful to promote osteointegration in osteoporotic bone. Keywords: estrogen-deprived, osteogenic differentiation, sandblasted and acid etched, simvastatin, titanium surfaces

Purpose: To examine early bone tissue healing in dental implants incorporating StemBios cell therapy. Materials and Methods: SLAffinity samples were examined by scanning electron microscopy and atomic force microscopy. The clinical trial comprised 11 patients, who each received a dental implant in the mandible. Only one of these 11 patients received StemBios cell therapy in combination with the dental implant. The patients continued to be observed over a 4-month period after implantation using computed tomography and resonance frequency analysis. Results: It was found that StemBios cell therapy promoted bone tissue healing in the case of the treated dental implant. The data indicated that stress altered more smoothly and declined faster in the patient who received the StemBios cell therapy than those without StemBios cell therapy over 4 months. Conclusion: A dental implant with SLAffinity surface treatment, in combination with StemBios cell therapy, significantly promoted bone tissue healing, especially at early osseointegration compared with that of implants without StemBios cell therapy when monitored over a 4-month period. Keywords: biocompatibility, dental implant, early osseointegration, stress