The International Journal of Oral & Maxillofacial Implants, 04/2020

Purpose: The purpose of this in silico study was to determine appropriate implant treatment planning using three implant diameters and four different superstructures in enlarged mandibular first molar areas. Materials and Methods: A mandibular bone block was constructed, and four configurations using three implants (2.9 × 10 mm, 4.1 × 10 mm, and 4.8 × 10 mm) were created for the first molar area. The four superstructures were designed as one large crown for a widediameter implant, a crown with a cantilever for a wide-diameter implant, two splinted crowns of one standard-diameter and one narrow-diameter implant, and two separate crowns of one standard-diameter and one narrow-diameter implant. Vertical loads of 200 N and oblique loads of 100 N were applied to various predetermined spots on the occlusal surfaces of these superstructures. Principal and von Mises stresses were analyzed on both the cortical bone and implant structures. Results: Stresses were intensified in the cortical bone around the implant neck and implant-abutment interface. The highest compressive (36.97 MPa) and von Mises (265.71 MPa) stress values were noted in the model with standardand narrow-diameter implants supporting two separate crowns. The lowest compressive (15.86 MPa) and von Mises (16.36 MPa) stress values were observed in the model with a distally positioned wide-diameter implant supporting the crown with a cantilever. Conclusion: In an enlarged first molar area, a configuration with a wide-diameter implant near the second molar and a cantilevered crown might distribute stresses more favorably than other configurations. Keywords: crown, dental implant, finite element analysis, mandible, molar

Purpose: To evaluate the implant and prosthetic outcomes and biologic and technical complications of tooth-implant– supported fixed dental prostheses (TISFDPs) in comparison with implant-supported fixed dental prostheses (ISFDPs). Materials and Methods: A comprehensive electronic search was performed by two independent reviewers up to February 2019. A hand search in relevant dental journals was also performed. The search identified a total of 175 citations, and 160 were excluded. Of the remaining 15 articles, seven were included in the review. Results: The implant failure rate was between 0% and 9% for the TISFDPs and between 0% and 13% for the ISFDPs, and the prosthesis failure rate was between 0% and 13% for the TISFDPs and between 0% and 17% for the ISFDPs; no significant differences were observed within 24 to 120 months of follow-up. Less peri-implant marginal bone loss was observed in the TISFDPs (MD: –0.29; 95% CI: –0.58, 0.00; P = .05), but the difference was marginally significant. Abutment tooth intrusion rate was 3%, while abutment tooth fracture rate was between 0% and 4%. No significant differences in the technical complications were observed, although the TISFDPs had higher failure rates in framework fracture and abutment/prosthesis screw loosening, while ISFDPs had a higher failure rate in porcelain fracture. Conclusion: The TISFDPs could be an alternative treatment option to ISFDPs for the partially edentulous patient with both treatments achieving comparable implant, prosthetic, biologic, and technical outcomes. Keywords: meta-analyses, systematic reviews, tooth-implant–supported fixed dental prostheses

Purpose: This study was designed to evaluate the effects of four different surgical techniques on the primary stability of short implants in two sizes (4-mm and 6-mm length) through resonance frequency analysis and insertion torque measurement in vitro. Materials and Methods: Forty implant site preparations and implant insertions were performed in pig ribs. Guided surgery, bone condensing, conventional drilling, and undersized preparation surgical techniques were used five times in each bone block to prepare 4-mm/6-mm-length implant beds. The maximum insertion torque and implant stability quotient (ISQ) values were recorded for each implant. Results: Both the ISQ and torque differed significantly for various surgical techniques (P = .009 and P < .001). The conventional technique had higher ISQ (79.00), whereas the condenser technique had higher torque (48.00 Ncm) than did the other techniques. The mean torque was significantly higher in all surgical techniques other than the guided surgery group regardless of implant length (P < .01 for all). Implant lengths were not significantly different in terms of ISQ and torque in all surgical techniques. Conclusion: There are significant correlations between the implant bed preparation technique and primary implant stability when using short implants. Conventional surgery and the bone condensing technique are favorable alternatives with higher primary stability and torque values in short implants. Keywords: dental implants, oral surgery, osseointegration, resonance frequency analysis

Purpose: The purpose of this study was to provide sufficient information on the clinical outcome of zirconia implants, mainly observing the survival rate and marginal bone loss (MBL), with a minimum follow-up of 12 months, to verify the adoption of ceramics as a rational possibility for dental implants. Materials and Methods: A systematic electronic search through the PubMed (MEDLINE) and EMBASE databases was performed by two independent reviewers to identify clinical studies published between January 2005 and April 2019 containing a minimum of 10 patients per study and 12 months of follow-up after functional loading. References from the selected articles were manually reviewed for further studies. Results: From the initial 1,225 articles retrieved, 19 met all the inclusion criteria. The marginal bone remodeling accounted for mean losses of 0.8 mm (95% CI: 0.60 to 1.00 mm) and 1.01 mm (95% CI: 0.72 to 1.29 mm) at 1 year and 2 years postloading, respectively. The failure rate of 6.8% was calculated for a mean follow-up period of 2.75 years, where the prevalence of early failure, late failure, and implant fracture was 3.4%, 1.7%, and 1.7%, respectively. The meta-analysis associated with the survival rate of one- and two-piece zirconia dental implants was hindered due to the lack of confidence interval or standard deviation information in most of the included articles. Conclusion: Zirconia implants presented MBL values consistent with the standard in the global consensus, high survival rates, and considerable clinical results at short-term observation periods following prosthetic delivery. Keywords: dental implants, marginal bone loss, survival rate, zirconium

Purpose: The aim of this study was to explore the effect of preventing first-stage wound dehiscence with new types of incision and flap design and to evaluate the effect of wound dehiscence on the bone resorption of the autogenous bone ring graft. Materials and Methods: In six beagle dogs, the second and fourth premolars on the bilateral mandible were extracted. After 3 months, on the left extraction sites, conventional alveolar crest incisions were made and the full-thickness flaps were elevated. However, on the right sites, the incisions were made at the mucogingival junction, the split-thickness flaps were elevated toward the lingual side, and the periosteum was elevated toward the buccal side. Then, Straumann implants (Ø 3.3, length 8 mm) were placed with simultaneous autogenous bone ring grafting. Next, the wounds on the left side were closed with periosteal releasing on buccal flaps conventionally, but the semi-thickness flaps on the right side were sutured with the elevated periosteum. After 3 months, the animals were euthanized, and the harvested samples were analyzed using microcomputed tomography and histology. Results: The incidence rate of wound dehiscence in the new incision group was 16.7%, which was significantly lower than that in the conventional incision group (75%). There was hardly any vertical bone loss of the bone ring in the samples without wound dehiscence, but in wound dehiscence samples, severe bone loss, 2.47 ± 0.17 mm, was found on the buccal side of the bone ring, which was significantly higher than that on the lingual, mesial, and distal sides, 1.37 ± 0.14 mm, 1.00 ± 0.15 mm, and 1.03 ± 0.05 mm, respectively. Conclusion: The use of a mucogingival junction incision and split-thickness flap design can effectively prevent first-stage wound dehiscence in autogenous bone ring grafting, which plays a key role in bone resorption of the graft. Keywords: animal experiment, bone ring, incision design, vertical bone resorption, wound dehiscence

Purpose: To evaluate the influence of bioactivation with argon plasma of a xenograft used as graft material for sinus floor augmentation. Materials and Methods: Sinus floor elevation was performed in 20 rabbits using a deproteinized bovine bone mineral as graft material. The xenograft used in the test sites was bioactivated with argon plasma (plasma group), while that used in the control sites was left untreated (control group). Collagen membranes were used to cover the antrostomy. The rabbits were euthanized after 2 and 10 weeks, in groups of 10 each. A histomorphometric analysis was performed in various regions of the elevated space. Results: After 2 weeks of healing, a similar pattern of healing was observed in both groups. New bone fractions were 5.2% ± 2.9% in the plasma group and 5.0% ± 3.5% in the control group (P = .795). In this period, higher amounts of new bone were found in the region close to the sinus bone walls. After 10 weeks of healing, the amounts of new bone within the elevated space increased to 23.5% ± 7.0% and 21.3% ± 7.3% (P = .176) in the plasma and control groups, respectively. The only statistically significant difference was found in the central region, with 20.4% ± 9.7% in the plasma group and 13.2% ± 10.5% in the control group (P = .037). Conclusion: The bioactivation of a xenograft using argon plasma improved bone formation within an augmented sinus, especially in the central regions, far from osteogenic sources. Keywords: animal study, argon plasma, bone healing, sinus floor elevation, xenograft

Purpose: To compare the osseointegration at the portion of the implant within the elevated space after sinus elevation using different sizes of xenograft. Materials and Methods: Eighteen New Zealand rabbits were selected, antrostomies were prepared bilaterally through the nasal dorsum, and the sinus mucosa was elevated. Deproteinized bovine bone mineral with granules of either 1 to 2 mm (large sites) or 0.250 to 1.0 mm (small sites) were randomly used to fill the elevated space of the two sinuses. Subsequently, mini-implants were placed through the antrostomy, one in each sinus. The animals were euthanized 2, 4, and 8 weeks after surgery, six animals for each group. Microcomputed tomography (micro-CT) and histologic analyses were performed. Results: In the elevated space, at the histologic analysis after 2 weeks of healing, new bone formed on the implant surface was found in fractions of 18.8% ± 6.8% and 15.8% ± 9.6% in the large and small sites, respectively (P = .249). After 4 weeks, the respective fractions of new bone were 20.3% ± 3.5% and 23.3% ± 5.6% (P = .249). After 8 weeks, the proportions reached 33.9% ± 9.5% and 28.5% ± 10.3% (P = .173), respectively. At the micro-CT analysis, bone-to-implant contact percentage (BIC%) was 21.0% ± 2.3% and 21.2% ± 2.4% in the large and small sites, respectively (P = 1.000). The respective proportions of BIC% at the large and small sites were 20.5% ± 3.3% and 23.4% ± 5.4% after 4 weeks (P = .463), and 23.0% ± 2.7% and 25.8% ± 4.1% after 8 weeks (P = .249). Conclusion: The use of xenograft granules of different dimensions resulted in similar amounts of bone-to-implant contact at implants placed simultaneously with sinus floor augmentation. Keywords: biomaterials, bone graft, histology

Purpose: The aim of this study was to evaluate 141 zygomatic implants for the reconstruction of severely atrophic maxillae. Materials and Methods: In this retrospective case series study, zygomatic implants were placed under general anesthesia. Inclusion criteria were as follows: ASA I or ASA II, age older than 18 years, inadequate bone for restoration with conventional implants, alternative augmentation procedures considered either inappropriate or contraindicated, absence of a medical condition related to implant failure, and providing written consent. Zygomatic implants used in the study consisted of three different brands: NobelZygoma, Southern Implants System, and Implantswiss. Results: The study included 45 patients, in whom 141 zygomatic implants were placed. The mean age of the patients was 51.76 (range: 23 to 72) years. Three patients were rehabilitated with removable prostheses, 19 patients with fixed prostheses, and 23 patients with hybrid prostheses. The overall complication rate was 5.67% (two zygomatic implants developed infection [1.4%], one zygomatic implant developed peri-implantitis [0.7%], three zygomatic implants developed sinusitis [2.1%], and two zygomatic implants showed unsuccessful prosthetic rehabilitation [1.4%]). The follow-up period ranged from 6 to 36 months. Conclusion: Clinical complications of zygomatic implants are acceptable, and their survival rates are similar to those of endosteal implants. Zygomatic implants can contribute to prosthetic rehabilitation. Keywords: atrophic maxilla, survival rate, zygomatic implant

Purpose: The aim of this retrospective study was to report the survival rate of a novel hybrid hydrophilic dental implant design for all bone types. Materials and Methods: This study evaluated the data collected from patients who received at least one implant to support a full-arch, partial, or single-crown dental rehabilitation in the maxilla or mandible. Implant survival rate was evaluated according to the clinical area and bone type, loading protocol, implant length and diameter, and placement torque. Results: A total of 453 tapered hybrid implants placed in 101 patients (mean age: 56.39 ± 12.98 years) were evaluated, and the survival rate was 99.6%. The follow-up period was up to 24 months. Regarding bone quality, types I, III, and IV presented a 100% survival rate, whereas type II presented a 99.3% survival rate. The vast majority of implants were immediately loaded (443 implants), which achieved placement torques between 32 and 60 Ncm or higher, and presented an implant survival rate of 99.5%. Conclusion: An overall survival rate of 99.6% was found for hydrophilic hybrid dental implants when placed in all bone types, and no statistically significant difference was observed between them. However, further studies should be necessary to confirm these preliminary results. Keywords: dental implants, primary stability, prosthodontics, retrospective study, survival rate

Purpose: Dental anxiety causes patients to avoid or delay dental treatments. This delay leads to more serious dental problems, which can then lead to more invasive and expensive treatment with possible emergency situations. The purpose of this study was to determine the most successful and effective kind of music to lessen the anxiety of patients during dental implant surgery. Materials and Methods: This study was a prospective observational randomized controlled study. Eighty dental implant surgery patients aged between 40 and 70 years were chosen for the study. Patients were divided into four groups: group 1—classic Turkish music group (Saba or Rast Tune); group 2—classical music (Vivaldi); group 3—slow rock music; and group 4—control group. Blood pressures, heart rate, and O2 saturations of the patients were evaluated along with Corah's Dental Anxiety Survey (CDAS) at admittance. After 5 minutes of music in the room, the same evaluations were recorded, and the survey was repeated. Results: All the groups with music treatment had a significant decrease in anxiety levels. It was observed that listening to music had a positive effect on dental anxiety regardless of the kind of music. There were significant differences in CDAS values postoperatively. Turkish music and classical music were much more effective in diminishing dental anxiety compared with soft rock music (P = .000 and .002, respectively). Conclusion: This study indicated that regardless of the kind of music, listening to music diminishes dental anxiety significantly; Turkish music and classical music were the most effective kinds of music. Keywords: dental anxiety, dental implant, music effect, music genres

Purpose: To present functional and esthetic success of a well-defined protocol for rehabilitation with implant-supported complete-arch prostheses in the treatment of patients with maxillary edentulism. Materials and Methods: Medical records of patients treated from 1990 to September 2014 were reviewed. This clinic history should include clinical, anatomicalfunctional, and esthetic data for at least the first 5 years of follow-up. Results: Two hundred eighty-two implants were inserted into the pterygomaxillary-pyramidal region in 141 edentulous patients using cylindrical osteotomes to form bone sites and thereby minimize the use of drills in bone preparation. Also, 580 implants were inserted in the premaxilla using lyophilized bone of bovine origin as a graft material and platelet-rich plasma for repairing small bone defects around implants and as a volume-generating material to support perioral structures. Of the 282 implants placed in the pterygomaxillary-pyramidal region, 272 survived (96.1% survival rate). The 10 failures occurred after being subjected to functional load. Of the 580 implants placed in the premaxilla, 19 implants failed; thus, the survival rate was 96.7%. Moreover, from the results obtained in the study sample, it was observed that the retention and stability obtained with the implant-supported prosthesis helps improve the ability to speak, swallow, and chew, which improves patient comfort and satisfaction. Conclusion: The rehabilitation of total maxillary edentulism with an implant-supported complete-arch prosthesis achieves a high level of functional and esthetic success, which is reflected directly in oral health and patient satisfaction. Keywords: full edentulism, platelet-rich plasma, prostheses, pterygoid implants

Purpose: Surface treatments may significantly affect physical-chemical properties and surface biologic responses. This study aimed to investigate the influence of alterations in the physical-chemical properties of pure titanium with different surface topographies on biocompatibility and early microbiologic response. Materials and Methods: Titanium disks were exposed to five different surface treatments created through acid etching and anodizing methods. Surface morphology, 2D and 3D roughness, wettability, biocompatibility, and cell viability were evaluated. Osteoblast adhesion and bacterial adhesion tests were also executed. Data were statistically analyzed using analysis of variance followed by Tukey test, roughness (P < .05), and bacterial proliferation (P < .05). Results: Five different surface morphologies were developed; double acid etching was shown to be significantly rougher than the others. The 2D roughness measurements were shown to be less consistent than the 3D measurements. All surfaces presented biocompatibility to allow cell behavior and differentiation. Osteoblasts presented better evolution in terms of adhesion and behavior in the nanomorphologies. High roughness significantly increased bacterial adhesion. Conclusion: Surface treatments may critically alter titanium properties and morphology. Therefore, roughness measurements with a wide area should be used in their evaluation. Nanotextured surfaces show a positive effect on bone cells and antibacterial response; their application is suggested when considering surface texturization for biomedical implants. Keywords: biocompatibility, biomedical implant, roughness, surfaces, TiO2 nanotubes, topography

Purpose: The autogenous bone block graft is regarded as the gold standard material due to reported osteoconductive, osteoinductive, and osteogenic properties. Various intraoral donor sites for autogenous block grafts are presented in the literature. The aim of this study was to radiographically evaluate the maximum dimensions, volume, and bone quality values of these sites. Materials and Methods: According to the inclusion criteria, 50 cone beam computed tomography (CBCT) images from 50 subjects were evaluated. The maximum length, width, height, and volume of autogenous regions where block grafts could be harvested were measured. Radiographic bone quality was calculated by using Hounsfield units derived from CBCT (CBCT-HU). Results: The mean age of 50 subjects (19 men and 31 women) was 55.84 ± 15.9 years. In this study, the symphysis was the largest potential donor site (3.14 ± 1.05 cm3), while maxillary tuberosity was the smallest (0.53 ± 0.34 cm3). These results correlated with bone density values, where the symphysis retained the highest values (937.31 ± 160.59 CBCT-HU) and the maxillary tuberosity had the lowest values (360.87 ± 141.48 CBCT-HU). Conclusion: Intraoral bone blocks have restrictions due to surrounding vital anatomical structures. The surgeons should consider these vital structures using accurate CBCT evaluation. The volume and density of the maximal bone harvest from the symphysis was statistically higher in comparison with ramus, palatal, and maxillary tuberosity bone blocks. Keywords: augmentation, density, dental implant, imaging, tomography, volume

Purpose: To analyze risk factors affecting sinus membrane perforation (SMP) during sinus floor elevation (SFE) procedures using the lateral window technique (LWT). Materials and Methods: For patients with SFEs using the LWT, patient-related risk factors (age/sex/smoking/diabetes) and surgical-anatomical–related risk factors (stage approach/sinus side/residual ridge height/sinus membrane thickness/previous surgical interventions) were compared between perforated and nonperforated sites and were evaluated for their influence affecting SMP. Additionally, SMPs were further subdivided into small/moderate (< 10 mm) or large (≥ 10 mm) in dimension, which were also analyzed for risk factors and consecutively for their influence on perforation. Results: The study sample comprised 434 SFE procedures in 355 patients; 94/355 patients (26.5%) presented SMP in 103 of 434 SFE procedures (23.8%). SFE procedures with (n = 103) and without (n = 331) SMP did not differ for patient-related risk factors but differed significantly (P = .001) for surgical-anatomical factors as follows: residual ridge height (3.05 ± 1.35 mm vs 4.15 ± 1.46 mm), sinus membrane thickness (1.2 ± 0.5 mm vs 2.6 ± 1.1 mm), prevalence of staged procedures (78.6% vs 57.7%), presence of maxillary sinus septa (75.7% vs 14.2%), presence of thin (< 1.5 mm) mucosa biotype (62.1% vs 29%), and previous oral surgical interventions (37.9% vs 16.3%). In the multivariate analysis, significant associations of SMP were found with the presence of sinus septa (odds ratio [OR] = 31.992; P = .001), residual ridge height (OR = 1.563; P = .007), sinus membrane thickness (OR = 1.057; P = .001), presence of thin (< 1.5 mm) sinus biotype (OR = 8.883; P = .001), previous surgical interventions (OR = 4.689; P = .002), and smoking habits (OR = 2.238; P = .030). For inducing a large (≥ 10 mm) SMP, the presence of thin sinus membrane thickness/thin sinus membrane biotype (OR = 5.319; P = .006; OR = 22.222; P = .001) and reduced alveolar ridge height (OR = 0.629; P = .026) were assessed as being significant risk factors. Conclusion: In general, the presence of sinus septa, thin sinus mucosa, staged procedures, and previous surgical interventions are the main risk factors inducing SMP for SFE using the LWT. In particular, the presence of thin sinus membrane in conjunction with a staged procedure significantly increases the risk for a large SMP. Keywords: lateral window, membrane perforation, perforation size, risk factors, sinus elevation

Purpose: This study assessed a novel treatment protocol for immediate implant placement in defective fresh extraction sockets. Materials and Methods: A single-arm clinical study was conducted including 12 fresh extraction sockets divided into two groups: those with intact and those with a deficient facial plate of bone. Hopeless teeth were atraumatically extracted, a vestibular access horizontal incision was made 3 to 4 mm apical to the mucogingival junction, a mucoperiosteal tunnel was created from the labial orifice of the socket, a slowly resorbing membrane shield was stabilized under the tunnel, implants were placed using a surgical guide, and a subepithelial connective tissue graft was harvested and secured over the membrane shield. Definitive restorations were delivered at 3 months postoperatively. Cone beam computed tomography (CBCT) scans were taken at baseline and after 6 and 13 months to measure facial bone thickness and height. Pink esthetic score (PES) was recorded at 6 and 13 months. Results: At 6 months, the mean ± SD facial bone thickness was 1.88 ± 0.73 mm for sockets with intact facial bone compared to 0.76 ± 0.42 at baseline and 2.34 ± 0.78 mm for sockets with deficient facial bone compared with 0 ± 0 at baseline, whereas at 13 months, the thickness was 1.84 ± 0.74 and 2.18 ± 0.73 mm, respectively. The facial bone crest coincided with the implant platform in sockets with an intact facial bone plate and those with a deficient facial bone plate at 6 months, whereas at 13 months, the distance for sockets with a deficient facial bone plate increased to 0.20 ± 0.13 mm. The mean PES at 6 and 13 months was 11.33 for both groups out of a maximum score of 14. Conclusion: The proposed technique provided a minimally invasive treatment with predictable esthetic outcome allowing immediate implant placement in sockets with intact and with deficient facial plates. Keywords: bone grafting, facial bone plate, fresh extraction socket, immediate implant, xenograft

Purpose: Evidence suggests that maxillary sinus floor augmentation via a lateral approach can be performed without positioning a bone graft inside, when one or more implants can be placed simultaneously. The aim of this study was to test if the placement of a porcine cortical bone layer underneath the sinus membrane can increase bone formation and implant stability. Materials and Methods: One hundred seventy-two patients with posterior maxilla atrophy needing implant rehabilitation were selected. Two hundred six sinus augmentation procedures were performed via a lateral approach, and 295 implants were placed in the same session of the sinus elevation surgery. In all the surgeries, a porcine cortical bone layer was placed underneath the sinus membrane, without using any graft material. After 6 to 7 months of healing, the implants were uncovered, then restored with porcelain-fused-to-metal crowns and monitored with a followup of 1 to 5 years. Results: The implant cumulative success rate was 95.2%, while the residual bone crest height changed from 2.67 ± 1.11 mm to 12.54 ± 1.42 mm, with an increase of 9.87 mm on average. Marginal bone resorption was 0.83 mm on average after 1 year of loading, while the mean implant stability measured at the moment of implant placement and 6 to 7 months later increased from an implant stability quotient (ISQ) of 62.61 ± 5.7 to an ISQ of 70.07 ± 8.2. Conclusion: This study confirms the validity of the graftless sinus elevation surgery when simultaneous implant placement is performed. The use of a porcine cortical bone layer seems to increase, from a radiologic point of view, the amount of bone around the implants, reducing healing time, cost, and biologic complications for the patient. Keywords: cortical bone layer, implant, posterior maxilla, sinus elevation, sinus graft, sinus membrane

Purpose: The aim of this preliminary study was to evaluate maxillary bone resorption with conventional dentures and implant-supported prostheses opposed by distal-extension removable partial dentures (RPDs). Materials and Methods: Fifteen patients (seven women and eight men) with totally edentulous maxillary ridges and partially edentulous mandibular ridges (Class I Kennedy classification) received maxillary fixed prostheses on four implants and mandibular distal-extension RPDs (study group). The control group consisted of 15 patients who received conventional maxillary dentures and distal-extension mandibular RPDs without any implant treatment but were matched to the study group and acted as a historical group. Evaluation of vertical maxillary bone resorption for both groups was made at the time of prosthesis insertion (T0) and 5 years later (T2) using the proportional area measurements made on digital panoramic radiographs for anterior and posterior areas. Results: The control group showed significantly higher vertical bone loss than the test group (P < .001). The control group had 0.270 higher maxillary bone loss than the test group. For both groups, anterior maxillary areas showed significantly higher bone loss than posterior areas (P < .003). Anterior maxillary areas had 0.122 higher bone loss compared with posterior areas. Women had 0.035 higher maxillary bone loss compared with men. Conclusion: Within the limitations of this study, implant-supported fixed prostheses for the edentulous maxilla opposed by remaining mandibular anterior teeth reduce maxillary anterior and posterior alveolar bone loss compared with conventional dentures. However, they do not prevent maxillary bone loss. Keywords: All-on-4, bone resorption, combination syndrome, partial dentures

Purpose: A barrier membrane consisting of an equine-derived, demineralized cortical bone sheet has been made available, yet evidence of its effectiveness is currently only anecdotal. This study aimed to obtain preliminary evidence concerning the medium-term prosthetic and implant success rates that may be achieved when such a membrane is used in combination with an equine, enzyme-treated bone graft, concomitantly to implant placement in the esthetic zone. Materials and Methods: Records of patients who had one or two implants placed in the anterior sectors of the two arches and had peri-implant bone regeneration carried out using the equine-derived membrane and equine-derived collagen-preserving bone granules were retrospectively collected. Peri-implant marginal bone loss (MBL) was used to assess implant survival. When available, histologic data concerning the equine membrane and cone beam computed tomography (CBCT) scans were analyzed as well. Results: Records of 32 patients (ages 36 to 73 years), corresponding to 44 implants placed, were retrieved and analyzed. The mean follow-up was 113.9 ± 10.2 months. Two implants failed. The implant success rate was 90.9%. Twelve membrane samples could be retrieved and analyzed, showing the membrane was still occlusive at 4.2 ± 1.1 months and only beginning to undergo remodeling. Twelve CBCT scans showed that 65.1 ± 9.8 months after surgery, a newly formed cortical layer could be observed in the zone that had undergone grafting. Conclusion: The equine cortical bone membrane and the enzyme-treated bone graft used in this case series achieved a medium-term implant and prosthetic success rate that was not dissimilar to that of other resorbable membranes and grafts for peri-implant guided bone regeneration augmentation. Preliminary medium-term histologic and CBCT data suggest that the membrane may be occlusive for a period of at least 4 months and may contribute to preserve the ridge thickness over time. Keywords: barrier membrane, bone collagen, cortical bone, equine bone, equine membrane, guided bone regeneration

Purpose: A prospective cohort multicenter study was undertaken to identify risk factors for implant survival, complications, and patient-centered outcomes following single-tooth immediate implant placement and loading in esthetic areas. Materials and Methods: Consecutive immediate implants placed in incisors, canines, and premolar sites were included. Variables recorded as possible risk factors included smoking habit, systemic conditions or therapies, previous assumption of bisphosphonates, inability to take amoxicillin, untreated periodontitis, thin periodontium, parafunctional habits, suppuration, bone dehiscences, and buccal bone fracture during implant insertion. Outcome variables included implant survival, recession, other complications, and patient satisfaction. Results: Data of 215 implants in 215 patients were collected in 15 centers in 2 years. One implant was seated with a torque < 30 Ncm and was not immediately loaded. It was successfully loaded 10 weeks after placement and was healthy 2 years later. This implant was excluded from subsequent analysis. Potential risk factors were identified in 116 patients (54.21%). There were 11 dropouts after 1 year and 37 after 2 years. Failures were relatively frequent (14.6%) before the delivery of the definitive prosthesis. No significant association was observed between early failures and risk factors. One failure and six recessions were observed after the definitive prosthesis. High satisfaction scores (mean score of 9.47/10 and 9.55/10 for esthetics and function, respectively) were recorded at 2 years. No recession occurred in the no-risk group. Five mucositis cases and one peri-implantitis case were observed in the 2-year follow-up. Conclusion: Failures were frequent before the definitive restoration and could not be explained by specific risk factors. Tissues appeared stable after the definitive restoration. Patients were very satisfied during the follow-up. Keywords: cohort study, dental implants, esthetics, osseointegration, tissue preservation, tooth extraction

Purpose: This nonrandomized, retrospective multicenter study aimed to evaluate success rates, peri-implant marginal bone loss, and clinical parameters around single implants with and without laser-microgrooved collars placed and loaded using different protocols after 7 to 10 years of function. Materials and Methods: A chart review was used to select patients treated at five private dental clinics with single dental implants with and without laser-microgrooved collars. Cumulative success rates, peri-implant marginal bone loss, probing depth, Plaque Index, bleeding on probing, and gingival recession were recorded at baseline examinations (ie, definitive restoration delivery) and at each year during the follow-up period. Results: Three hundred single implants (140 without laser-microgrooved collars and 160 with 1.7-mm laser-microgrooved collars) in 300 patients were selected. At the completion of the study period, 26 patients and 26 implants (17 with and 9 without a laser-microgrooved collar) were classified as "dropouts." Implants and restorations were categorized into two subgroups each for a total of four study groups: group 1, immediate implant placement; group 2, delayed implant placement; group 3, immediate nonocclusal loading of prostheses; and group 4, delayed loading of prostheses. Nineteen implants (6.9%) failed clinically (4 [2.7%] with and 15 [11.4%] without a laser-microgrooved collar). The difference in cumulative success rates was statistically significant (P < .05). Radiographically, at the end of the follow-up period, the laser-microgrooved group showed a mean peri-implant marginal bone loss of 0.64 mm compared with 1.82 mm for the non–laser-microgrooved group. At the same time point, a mean probing depth of 0.76 mm was observed for the lasermicrogrooved group compared with 2.75 mm for the non–laser-microgrooved group. A statistically significant difference in peri-implant marginal bone loss and probing depth between the two types of implant collars was evident (P < .05). No statistically significant correlation was noted between the types of implant placement/prosthetic restoration and clinical parameters. Conclusion: Implants with a laser-microgrooved collar appear to influence the peri-implant soft and hard tissue stability, reducing the probing depth levels and the peri-implant marginal bone loss by more than 50% after 10 years of function, regardless of the type of implant placement and loading protocol. Keywords: delayed loading, delayed placement, immediate non-occlusal loading, immediate placement, laser-microgrooved

Purpose: The purpose of the three-dimensional (3D) finite element analysis study was to compare the use of titaniumzirconium (Ti-Zr) narrow-diameter implants as an alternative to titanium (Ti) or Ti-Zr standard-diameter implants in the posterior jaw regions. Materials and Methods: Ti-Zr and Ti standard-diameter implants (4.1 mm) and Ti-Zr narrow-diameter implants (3.3 mm) in cylindrical (parallel) macrodesign were simulated in the mandibular and maxillary first premolar area. Forces of 100 N were applied to the crowns in a vertical and oblique (45-degree angle to the long axis) direction. The von Mises stresses and fatigue strength values of the implants and principal stresses in the bone structures were evaluated. Results: In vertical and oblique force application, stress data in cortical and trabecular bone structures were found to be higher in 3.3-mm Ti-Zr narrow-diameter implant models than 4.1-mm Ti-Zr and Ti standard-diameter implant models. Also, the von Mises stress data of the 3.3-mm Ti-Zr narrow-diameter implants were higher than the 4.1-mm Ti-Zr and Ti standard-diameter implants. The shortest cycle of fatigue failure and estimated duration of clinical success (years) results were found in the mandibular 3.3-mm Ti-Zr implant model under oblique force, and these results remained below the identified 30-year critical threshold. Conclusion: Considering all implant models, Ti-Zr narrow-diameter implants exhibited higher stress values than Ti-Zr and Ti standard-diameter implants. In the premolar region, care should be taken biomechanically when using Ti-Zr narrow-diameter implants as an alternative to standard-diameter implants. Further comparative and in vivo studies are needed to examine the long-term success of Ti-Zr narrow-diameter implants as an alternative to standard-diameter implants. Keywords: failure analysis, finite element analysis, narrow-diameter implant, standard-diameter implant

Purpose: This three-dimensional finite element analysis study aimed to compare the stresses transmitted to short, tilted, and vertical implants used in different configurations and to the surrounding peri-implant bone in the atrophic mandible. Materials and Methods: A three-dimensional model of an atrophic mandible was made using customized computer software. Four models including short, tilted, and vertical implants were constructed with and without cantilever extension. Four or six implants in different configurations were placed into the models and mounted with the same fixed prosthesis. An oblique force of 200 N was bilaterally applied to the most distal part of the fixed denture. Von Mises stress values on implants and minimum and maximum principal stress values transmitted to peri-implant bone were analyzed. Results: The highest stress values recorded in the tilted implants (von Mises: 129 MPa), in the peri-implant bone around the tilted implants (minimum principal stress: –40 MPa), and overall stress values were found to be higher in the model including tilted implants with cantilever extensions. Distally placed short implants, with consequent elimination of the cantilevers, resulted in decreased stress values for all of the treatment variabilities of an atrophic mandible. Von Mises stress values were found as 129 MPa in tilted (model I), 48 MPa in short (model II), 47 MPa in short (model III), and 57 MPa in vertical (model IV) at the most distal implant location. Lower compressive stress values were noted in the bone around straight and short implants compared with the tilted implants in all models (model I, tilted: –40 MPa; model II, short: –34 MPa; model III, short: –33 MPa; model IV, vertical: –25 MPa). Conclusion: Distally placed short implants contributed to the reduction of stress values of the implants and the surrounding bone. The combination of two short and four straight implants without cantilevers may be a beneficial design in the rehabilitation of posteriorly atrophic mandibles. Keywords: atrophic mandible, bone, finite element analysis, short implant, stress, tilted implant