The International Journal of Oral & Maxillofacial Implants, 04/2019

Purpose: Fast wound healing after abutment connection may reduce infectious complications. Cold atmospheric pressure plasma can increase the hydrophilicity of abutment surfaces, and therefore, the cell attachment, cell density, and sealing could help hamper microbial penetration into the wound cavity. In this in vitro study, the effect of three different plasma devices and common antiseptics on cell growth after treatment on zirconia ceramic and titanium disks was analyzed. Materials and Methods: Specimens were treated for 5 minutes with the plasma devices kINPen 08, kINPen 09, or kINPen Chamber and for 15 minutes with the antiseptics chlorhexidine digluconate (0.2%), octenidine (0.1%), and ethanol (70%). After treatment, primary human fibroblast cells (HGF-1) were seeded and incubated for 1 and 24 hours. The cell area after 1 hour and cell density after 24 hours were analyzed by scanning electron microscopy images. Results: Water contact angles of both surfaces (95/96 degrees) were significantly reduced to 26 to 36 degrees (titanium) or 9 to 28 degrees (zirconia ceramic) after plasma treatment. On titanium only, the average cell area was significantly increased after 1 hour of cell incubation following kINPen 08 and kINPen 09 treatment. No significant differences between all three plasma devices and the untreated control were determined on both materials after 24 hours, whereas octenidine and chlorhexidine reduced cell surface covering. The cell density was significantly lower for all treatment regimens except octenidine on zirconia ceramic compared with titanium. Conclusion: Plasma reduced the water contact angle and supported cell covering on titanium in the early stage. Plasma devices had no discernible influence on cell covering after 24 hours of cell incubation, whereas chlorhexidine and octenidine hampered cell covering on both abutment surfaces. Keywords: abutment, chlorhexidine, cold atmospheric pressure plasma, ethanol, fibroblast, octenidine, surface treatment, titanium, zirconia ceramic

Purpose: To evaluate healing after sinus floor augmentation at antrostomies prepared with either a drill or a sonic instrument. Materials and Methods: Sinus mucosa elevation was performed bilaterally in 18 rabbits. The antrostomy was prepared with either a drill or a sonic instrument. The elevated space was filled with a collagenated porcine bone, and the access antrostomy was covered by a collagen membrane. The animals were euthanized in groups of six after 2, 4, and 8 weeks of healing. Microcomputed tomography and a histologic analysis were performed. Results: After 8 weeks of healing, remaining defects occupying about 28.9% and 26.0% of the antrostomy were found in the microcomputed tomography analysis. In the histologic analysis, new bone was formed from the margins of the antrostomy, reaching the central region over time. After 8 weeks of healing, 29.1% ± 18.6% and 28.4% ± 15.6% of new mineralized bone was occupying the analyzed zone in the antrostomy at the drill and sonic sites, respectively. Conclusion: The use of a sonic device to prepare the antrostomy resulted in similar healing outcomes in both the antrostomy and the elevated regions. Keywords: animal study, bone healing, histology, morphometry, sinus floor elevation, xenograft

Purpose: The purpose of this study was to investigate the effects of celecoxib and ibuprofen on the proliferation, viability, and migration of MC3T3-E1 cells cultured on titanium surfaces. Materials and Methods: MC3T3-E1 cells were cultured on sandblasted titanium disks and allocated to one of the following six groups: (a) control (untreated); (b) celecoxib (5 μM and 10 μM); (c) ibuprofen (5 μM and 10 μM); and (d) prostaglandin E₂ (10 μM). Proliferation of attached cells was assessed over 9 days using an alamarBlue assay. A trypan blue exclusion test was conducted to assess cell viability; the relative percentages of live and dead cells were quantified using a hemocytometer over 2 days. A Boyden-Chamber Assay was utilized to assess cell migration over 3 days. Results: The proliferation of cells treated with any intervention was not significantly different than that of the untreated group throughout the treatment period. However, celecoxib and ibuprofen significantly decreased the percentage of viable cells in a dose-dependent manner. Specifically, celecoxib (10 μM) and ibuprofen (5 μM and 10 μM, respectively) on day 1 and celecoxib (10 μM) on day 2 showed significantly higher percentages of dead cells compared to the untreated cells. There was a significant increase in migration of cells treated with ibuprofen (5 μM) compared to untreated cells on day 1; however, the migration of cells treated with any of the interventions was not significantly different from that of untreated cells on day 3. Conclusion: Nonsteroidal anti-inflammatory drugs at therapeutic doses did not significantly affect osteoblast proliferation and migration. However, higher dosages of celecoxib (10 μM) significantly reduced the cell viability and therefore can potentially affect the process of osseointegration. Keywords: celecoxib, ibuprofen, nonsteroidal anti-inflammatory drug, osseointegration, osteoblast, titanium implant

Purpose: This study aimed to investigate the in vitro and in vivo bone-forming potential of a sandblasted, large-grit, acid-etched (SLA) titanium (Ti) surface treated with a laminin-derived functional peptide, PPFEGCIWN (DN3). Materials and Methods: Human osteoblast-like MG63 cells were cultured with SLA Ti disks that were untreated or treated with DN3 or a control scrambled peptide. Cell adhesion, spreading, and viability on the disks were tested. Alkaline phosphatase gene expression and enzyme activity were also evaluated. Four DN3-coated SLA Ti implants and four untreated implants were placed into the tibiae of two rabbits (two implants/tibia). Ten days later, the bone-implant interfaces were subjected to histomorphometry to measure the bone response. The surface properties of the disks and implants were determined using scanning electron, widefield confocal, and confocal laser microscopy and x-ray photoelectron spectroscopy. Results: The peptide-treated and untreated disks and implants were similar in terms of physical surface properties, but the peptide-treated surfaces had significantly higher nitrogen levels (P < .05). The DN3 peptide promoted cell adhesion, spreading, and alkaline phosphatase expression and enzyme activity (P < .05). Histomorphometry of the harvested implants showed rapid bone formation and affinity of the motif. Conclusion: This study suggests that treatment with the cell adhesion peptide DN3 promotes bone healing at the SLA Ti surface. Keywords: functional peptide, large-grit and acid-etched, osseointegration, PPFEGCIWN, sandblasted, titanium

Purpose: Among all platelet concentrates, platelet-rich fibrin has been shown to possess fibrin, leukocytes, and a variety of growth factors that could promote wound healing. The purpose of this study was to compare the bone healing in natural healing sockets (control group) versus that in sockets under ridge preservation with platelet-rich fibrin alone (test group). Materials and Methods: Searches were conducted via electronic and manual approaches for randomized controlled trials and controlled clinical trials published up to May 2018 that evaluated alveolar ridge outcomes (at least 1-month follow-up) in both natural healing sites and sites with platelet-rich fibrin placement alone for ridge preservation. Changes of ridge height and width, osteoblastic activity, and the number of sites were extracted from original articles for meta-analyses. Weighted mean difference and 95% confidence interval were calculated using a random-effects model. Results: Eight human studies (six randomized controlled trials and two controlled clinical trials) that fulfilled the inclusion criteria were included in the study. Data obtained in the study showed a favorable outcome in platelet-rich fibrin for socket preservation, although the difference was not statistically significant when compared to the natural healing group with regard to alveolar bone height change (weighted mean difference: -0.28 mm, 95% confidence interval: -0.55 to 0.00, P = .051), alveolar bone width change (weighted mean difference: -1.73 mm, 95% confidence interval: -3.58 to 0.12, P = .067), or osteoblastic activity (weighted mean difference: -0.01 [unit], 95% confidence interval: -0.50 to 0.49, P = .982). Conclusion: This study revealed that platelet-rich fibrin alone in ridge preservation does not provide significant additional benefit when compared to natural healing sockets with regard to bone volume, bone density, and osteoblastic activity. Keywords: bone healing, extraction socket, meta-analysis, platelet-rich fibrin, ridge preservation, systematic review

Purpose: The leukocyte- and platelet-rich fibrin block (L-PRF block) is a composite graft that combines a xenograft that is acting as a scaffold with L-PRF membranes that serve as a bioactive nodule with osteoinductive capacity. This study evaluated the properties of the L-PRF block and its components in terms of release of growth factors, cellular content, and structure. Materials and Methods: The concentration of transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor (VEGF), platelet-derived growth factor-AB (PDGF-AB), and bone morphogenetic protein-1 (BMP-1) released by an L-PRF membrane and an L-PRF block were examined with ELISA for five time intervals (0 to 4 hours, 4 hours to 1 day, 1 to 3 days, 3 to 7 days, 7 to 14 days). Those levels in L-PRF exudate and liquid fibrinogen were also evaluated. The cellular content of the liquid fibrinogen, L-PRF membrane, and exudate was calculated. The L-PRF block was also analyzed by means of a microcomputed tomography (micro-CT) scan and scanning electron microscopy (SEM). Results: TGF-β1 was the most released growth factor after 14 days, followed by PDGF-AB, VEGF, and BMP-1. All L-PRF blocks constantly released the four growth factors up to 14 days. L-PRF membrane and liquid fibrinogen presented high concentrations of leukocytes and platelets. The micro-CT and SEM images revealed the bone substitute particles surrounded by platelets and leukocytes, embedded in a dense fibrin network. Conclusion: The L-PRF block consists of deproteinized bovine bone mineral particles surrounded by platelets and leukocytes, embedded in a fibrin network that releases growth factors up to 14 days. Keywords: blood platelets, cell count, fibrinogen, growth factors, scanning electron microscopy, tissue engineering

Purpose: It remains unclear whether estrogen deficiency affects the ultrastructure and tissue-level mechanical properties of the maxilla. The hypothesis of this study was that the ovariectomized rat could induce tissue-level changes of the maxilla. Materials and Methods: Twelve 3-month-old female Sprague Dawley rats were acquired and randomly divided into two groups: ovariectomized and SHAM (control) (n = 6 for each group). Three months after the ovariectomy, implants were placed; the animals were sacrificed at day 28, and then samples were collected and prepared according to the previously established protocols. Advanced analytical equipment including scanning electron microscope with energy-dispersive spectrometry, transmission electron microscope, and nanoindentation were used to analyze bone quality. Results: The results showed that the mature bone areas in the ovariectomized group were significantly affected in the mineral crystal and the microstructure. The micromechanical properties of the mature bone were also affected, showing significantly increased hardness (H) and reduced modulus (Er) in ovariectomized rats compared with the normal rats (P < .05). Differences in H and Er in new bone areas between the normal and ovariectomized rats were less significant. Conclusion: Ovariectomy affected maxilla bone tissue-level quality; however, the effects mainly existed in the mature bone areas, which were characterized by higher crystalline mineralization, hardness, and modulus. Keywords: bone, maxilla, nanoindentation, osteoporosis, ovariectomy

Purpose: To evaluate, through a systematic review of the literature, the published data regarding marginal bone loss, implant failure proportion, biologic and prosthetic complications, and risk factors associated with short (≤ 8 mm) implants supporting fixed or removable full-arch restorations in the edentulous mandible. Materials and Methods: Two reviewers performed a search of five databases, with handsearching through the reference lists and gray literature. Controlled clinical trials and prospective cohort studies were selected in a two-phase process. The data were independently gathered by the same two reviewers. Quality assessment of the studies was done using the Cochrane Handbook for Systematic Reviews of Interventions for Randomized Clinical Trials and the Newcastle-Ottawa Scale for Prospective Cohort Studies. Marginal bone loss and implant failure proportion were meta-analyzed using random and fixed-effects models, respectively, with 95% confidence intervals. A descriptive analysis was performed of the prevalence of biologic and prosthetic complications. Meta-regression analysis was run as fixed-effect models for risk factors. Results: Six studies met the eligibility criteria and had data extracted. A total of 291 short implants (lengths 5 to 8 mm) were placed in 122 patients (82 women; mean age, 64.7 ± 10.8 years) supporting 23 fixed and 99 removable full-arch restorations. The pooled marginal bone loss overall was 0.12 mm (0.07 to 0.17 mm). Marginal bone loss for fixed full-arch restorations was 0.11 mm (0.01 to 0.21 mm) and for removable full-arch restorations was 0.14 mm (0.07 to 0.21 mm). The pooled overall implant failure proportion was 2.0% (1.0% to 5.0%) for the studies. Implant failure proportion for fixed and removable restorations was 2.0% with confidence intervals of 0.0% to 9% and 0.0% to 6%, respectively. The prevalence of prosthetic complications was 34.5% for fixed restorations and 2.6% for removable restorations. No biologic complications were found for fixed restorations, while 13.1% of removable restorations did have biologic complications. Risk factors did not demonstrate statistical differences regarding implant failure proportion and marginal bone loss. All included studies demonstrated a high methodologic quality. Conclusion: Findings from this systematic review and meta-analysis suggest that full-arch restorations supported by short implants in atrophic edentulous mandibles might be a viable treatment option, presenting minimal marginal bone loss and implant failure in the short term. However, further well-performed prospective clinical trials with long-term observation are needed. Keywords: edentulous patients, meta-analysis, short implants, systematic review

Purpose: The purpose of this in vitro study was to determine the minimum placement torque required to attach the transducer (measuring peg) to the implant to provide an accurate assessment of implant stability using resonance frequency analysis. Materials and Methods: One hundred 4 × 11-mm screw-shaped titanium implants were inserted into a uniform polyurethane block with similar density to bone in a standardized surgical protocol. The implants were distributed into 10 groups, with 10 implants each (G1 to G10). In G1, the transducer was manually attached by a female operator and in G2 by a male operator using the manual connector provided by the manufacturer. For the remaining groups (G3 to G10), the transducers were placed using a connector adapted to a digital torque wrench with different torque settings: 3 Ncm (G3), 4 Ncm (G4), 5 Ncm (G5), 6 Ncm (G6), 10 Ncm (G7), 13 Ncm (G8), 17 Ncm (G9), and 20 Ncm (G10). Stability was measured for all groups using the Osstell equipment (Diagnosis of Integration) and the implant stability quotient (ISQ) annotated for statistical comparison between the groups. Results: The mean ± standard deviation ISQ values for groups G1 to G10 were 9.50 ± 5.54, 19.05 ± 2.67, 29.25 ± 4.22, 26.55 ± 5.37, 40.90 ± 0.99, 69.60 ± 2.41, 71.30 ± 0.82, 71.20 ± 1.32, 72.40 ± 0.97, and 70.90 ± 0.88, respectively. Statistical comparisons determined that the amplitudes of the confidence intervals, relative to the standard deviations, were lowest for groups G5, G7, G8, G9, and G10. For the means, the lowest amplitudes of the confidence intervals were observed in G6, G7, G8, G9, and G10. When checking the conjugated confidence intervals (mean and standard deviation), the results were homogenous for G7, G8, G9, and G10. When the torque of 20 Ncm was reached, the connection between the transducer and the implant failed. Conclusion: In this in vitro model experiment, transducer torques between 10 and 17 Ncm appear to be adequate for accurate measurement of implant stability, allowing more precise comparisons without damaging the prosthetic connection in the implant. Keywords: dental implants, in vitro techniques, primary implant stability, resonance frequency analysis

Purpose: There are currently no clear guidelines on the reuse of metal implant impression copings and scanbodies in implant dentistry. Manufacturers generally recommend single use, which has cost and ecologic implications. The objectives of this study were to examine the effect of multiple use of implant impression copings and scanbodies on the accuracy of partially dentate implant casts. Materials and Methods: Ten direct polyether impressions were made of a partially dentate mandibular acrylic resin master model fitted with two internal connection implants (Straumann RC bone level) in the positions of right first premolar and molar, to produce 10 dental stone casts. A single set of impression copings was utilized for the 10 impressions. The sample casts and the master model were digitized using a laboratory scanner. Ten digital scans were then performed on an implant stone cast with two bone-level internal connection implant analogs using one set of scanbodies to produce scans 1 to 10. Measurements were made on all the digitized casts using computer software and discrepancies calculated in the x-, y-, and z-axes, and in the overall three-dimensional position (R). Data were statistically analyzed using paired t tests (α = .05), and P values were adjusted using Holm- Bonferroni sequential correction. Results: The outcomes were mixed, in that no significant differences were found between the casts or scans produced by reusing impression copings (P > .05) and scanbodies (P > .005), respectively, in all dimensions, for most repetition cycles; however, significant differences were noted in the y-axis for cast 6, and in relation to R, for casts 2, 4 (P < .05), and 8 (P < .005), and the scanbody reuse elicited significant differences in 3D(R) with scan 2 alone (P < .005). Conclusion: Reuse of impression copings and scanbodies up to 10 times did not seem to consistently affect the accuracy of partially dentate multi-implant dental casts and digital models. Keywords: CAD/CAM, dental implant, dental impression technique, dental models, digital scans, impression accuracy, reuse, scanbodies

Purpose: The purpose of this study was to evaluate the biomechanical effects of bone loss on peri-implant bending strain underneath overdentures. Materials and Methods: One mandibular and one maxillary edentulous model were created and covered with 2 to 4 mm of silicone rubber to simulate the oral mucosa. Four strain gauges were attached to four sides of each implant. In the mandibular model, two implants were inserted, and the implant was placed bilaterally in the area between the mandibular canines and lateral incisors. A maxillary conventional denture and mandibular overdenture were fabricated with acrylic resin to fit the edentulous models. Five bone loss levels were created: no bone loss, 0.8 mm bone loss on only the left implant, 0.8 mm bone loss bilaterally, 1.5 mm bone loss on only the left implant, and 1.5 mm bone loss bilaterally. Magnetic attachments were used to retain the denture. The bending strains generated from three types of unilateral loading were measured by a sensor interface, and the data were analyzed using the Kruskal-Wallis test and Bonferroni's post hoc test. Results: Bending strain increased with decreasing bone levels on the loading side. On the nonloading side, bending strains were greater at even bone loss (0.8 mm or 1.5 mm bone loss bilaterally) than at uneven bone loss (0.8 mm or 1.5 mm bone loss on only the left implant). Strains under loading at the left first premolar were approximately equal to that under loading with a cotton roll; these strains were higher than those generated with loading at the left first molar. Conclusion: Peri-implant bending strains rapidly increased on the loading side as bone loss levels increased. Peri-implant bending strains on the nonloading side were higher at bilaterally even bone loss than at unilateral bone loss. Keywords: bending strain, implant overdenture, magnetic attachment, marginal bone level

Purpose: This study evaluated the micro shear bond strength of resin cement to an yttria-stabilized zirconia ceramic and the survival probability of zirconia abutments and crowns after different surface treatments through a fatigue test. Materials and Methods: The study was divided into two parts. For part 1, 95 zirconia disks were divided into five groups (n = 19): control, untreated, airborne particle abrasion with Al2O3 particles before sintering, airborne particle abrasion with Al2O3 particles after sintering, silicatization before sintering, and silicatization after sintering. Three samples of each group were used for evaluation of surface roughness by confocal laser scanning microscopy and afterward were prepared for surface microstructural analysis by scanning electron microscopy. Ten samples of each group were subjected to micro shear bond strength testing, and the interfaces of the remaining six were examined by scanning electron microscopy. In part 2, 70 external hex zirconia abutments and copings were made by computer-aided design/computeraided manufacturing (n = 14). Marginal fit of abutment/coping was measured in a confocal laser scanning microscope. Afterward, a fatigue test was carried out with progressive load of 80 up to 320 N (40 N steps), 5 Hz frequency, and 20,000 cycles at each step. Thermal cycling was simultaneously performed (5°C to 55°C). Results: The group treated after sintering with SiO achieved statistically higher micro shear bond strength (P < .01). Higher failure loads were associated with a combined failure. The surface changes in the group treated with SiO before sintering suggest silica deposition, and there was a lack of homogeneity, which was more evident on the surface of the groups treated before sintering. The marginal gap was higher for the group treated before sintering with SiO (P < .01), and the survival probability of the sets was similar for all tested groups (P = .57). Conclusion: The micro shear bond strength to zirconia was improved after silicatization after sintering, but the survival probability of crown/abutment/implant sets was not affected by different surface treatments. Keywords: marginal gap, surface treatment, thermomechanical fatigue, zirconia

Purpose: The purpose of this prospective, randomized, clinical pilot study was to compare the threedimensional changes of grafted maxillary sinuses when deproteinized bovine bone (DBB) or cortical mineralized allogeneic bone (MAB) was used. Materials and Methods: Seventeen patients were randomly assigned to receive either DBB or MAB for lateral-approach maxillary sinus augmentation. Cone beam computed tomography (CBCT) scans were performed preoperatively (T0), immediately after (T1), and at approximately 6 months postoperatively (T2). Three-dimensional analysis of the radiographic volumetric changes was performed for DBB and MAB by measuring the difference in unoccupied sinus volumes at T1 and T2. Results: In the DBB group, a statistically significant increase in unoccupied sinus volume was found at T2 when compared to T1 (P = .001), representing a mean resorption rate of 23.8% ± 15.9%. Similarly in the MAB group, a statistically significant increase in unoccupied sinus volume was found at T2 when compared to T1 (P = .007); the mean resorption rate in the MAB group was 19.5% ± 10.1%. There was no statistically significant difference between the contraction of DBB (23.8%) and MAB (19.5%) (P = .52). Conclusion: Both DBB and MAB showed sufficient volume stability at T2 (mean: 6.3 ± 1.6 months) postoperatively for 10- to 13-mm-implant placement without the need for additional grafting. Keywords: bone remodeling, bone substitute, dental implants, maxillary sinus

Purpose: Vertical and horizontal guided bone regeneration with nonresorbable membranes is a regenerative alternative for treating bone defects in edentulous zones. Its indication and good outcomes have been confirmed by different authors; however, this procedure remains highly technique sensitive and might lead to complications. The purpose of this study was to describe the management of complications such as exposures and infections following vertical and horizontal guided bone regeneration with titaniumreinforced high-density polytetrafluoroethylene (d-PTFE) nonresorbable membranes carried out using a new management protocol for complications related to this type of membrane. Materials and Methods: Complications in vertical and horizontal guided bone regeneration were evaluated by the same surgeon in a private practice between 2010 and 2017. They were classified and managed according to whether they were exposures and/or infections, and also according to their size, sagittal location, and coronal position of the alveolar ridge of the exposures. Descriptive analyses were conducted to evaluate the influence of age, sex, clinical characteristics of the complication, time of appearance, location, membrane size, anatomical and sagittal location, pink ceramic use, and definitive restoration, both before and after management protocol application. Results: Eighty complications were evaluated. The sextant with the highest number of complications was the anterior maxilla (35/80, 43.75%), followed by the mandibular left side area (16/80, 20.00%). The majority (56/80, 70.00%) of all complications appeared before 2 months. In relation to the sagittal location of exposures, 43.64% (24/55) were located coronal to the alveolar ridge. Statistically significant differences were found between exposures with or without purulent exudate, related to the coronal location of the exposure (P < .05). Conclusion: A new protocol for managing complications with titanium-reinforced high-density PTFE nonresorbable membranes is proposed based on the follow-up of 80 complications. These steps can help prevent total graft loss, allowing patients to reach final rehabilitation without multiple additional surgeries. Infections continue to be the most common cause of bone loss in guided bone regeneration. Long-term results and follow-up studies are necessary to assess the stability of soft and hard tissues in patients rehabilitated using this complication management protocol. Keywords: complications, d-PTFE membrane, nonresorbable membrane, vertical ridge augmentation

Purpose: The aim of this study was to compare the clinical outcomes of four-implant-supported overdentures retained by stud or bar attachments for patients with an edentulous maxilla. Materials and Methods: From January 2008 to December 2014, patients with maxillary edentulism were enrolled in this retrospective study. The insertion of four maxillary dental implants was followed by restoration with either stud-retained or barretained overdentures. The characteristics of the subjects and implants were recorded. Implant survival rates, marginal bone loss, peri-implant clinical parameters, prosthetic maintenance efforts, and patient satisfaction score were evaluated at the last follow-up time. The data were statistically analyzed, and the level of significance was set at α = .05. Results: A total of 132 implants were placed in 33 patients, of whom 18 were restored with four-implant-supported overdentures retained by stud attachments, and the other 15 with four-implant- supported overdentures retained by bar attachments. Thirty-one patients and 124 implants were available for the entire follow-up. During a mean follow-up period of 77 months (range: 36 to 111 months), five among 72 implants failed for three patients in the stud-retained group and two among 60 implants failed for two patients in the bar-retained group, resulting in estimated cumulative implant survival rates of 81.4% and 86.2% for the stud-retained group and the bar-retained group, respectively. Except for the modified Plaque Index (P = .035), no significant differences were indicated between the two attachment groups in terms of implant survival rate, marginal bone loss, peri-implant clinical parameters, or prosthetic maintenance treatment. Peri-/inter-implant gingival hyperplasia occurred only with implants under bar attachments. Patients in both groups reported a high degree of satisfaction. Conclusion: Within the limitations of this study, no significant differences were indicated between the clinical outcomes of maxillary four-implant-supported overdentures with either stud or bar attachments, although a higher modified Plaque Index was observed for the bar-retained group. Furthermore, prostheses with stud attachments were advantageous for their convenient cleaning and repair. Keywords: bar, dental implants, edentulous maxilla, overdenture, stud, survival rate

Purpose: To analyze peri-implant bone loss around two types of tissue-level implants (convergent and divergent transmucosal morphology) placed in the same region of either the maxilla or mandible in a single surgical session. Materials and Methods: This prospective study included 21 patients who each received two implants, one with a convergent transmucosal collar (n = 21) and the other with a divergent collar (n = 21). Implants were placed in a single surgical session, by the same clinician, in the same clinical setting at the Prosthodontic and Occlusion Unit, University of Valencia (Spain). The implants (n = 42) were restored with splinted crowns screwed directly onto the prosthetic platforms. Bone loss analysis consisted of measurements taken from periapical radiographs 24 months after loading. Statistical analysis evaluated the homogeneity of the groups using Pearson's chi-square test; bone loss was compared with the Wilcoxon test. Statistical significance was set at 5% (α = .05), with a confidence interval of 95% and a power of 57%. Results: Implants with convergent transmucosal morphology presented less mean peri-implant bone loss (0.29 ± 0.34 mm) than those with divergent transmucosal morphology (0.60 ± 0.63 mm), with a statistically significant difference between the two types of implants (P = .031). Conclusion: Less peri-implant bone loss occurs around supracrestal implants with convergent transmucosal morphology than divergent transmucosal morphology. Keywords: dental implant abutment, dental implant bone loss, dental prosthesis retention, supracrestal dental implant

Purpose: The purpose of this study was to assess the effect of different loading protocols (immediate or delayed) on bone volume remodeling of an immediate implant-supported single crown in the maxilla with a follow-up from 2 to 3 years. Materials and Methods: Patients presenting a failing tooth were rehabilitated with implant-supported single crowns. Data of patients with a survey from 2 to 3 years after baseline surgery were retrospectively acquired. One implant per patient was randomly selected during data analysis and assigned to one of two predictor groups: the loading protocol, 9 immediate vs 13 delayed loading; and tooth position, 9 incisors vs 9 canines. Cumulative survival rates were recorded; loss of crestal bone volume was assessed with cone beam computed tomography (CBCT) by means of software that superimposed the preoperative and postoperative CBCT scan data (Matrix Laboratory) and by dentascan software. Results: Twenty-two patients were enrolled. No postoperative complications or implant failures were recorded. Bone volume loss from the 2- to 3-year follow-up period ranged between 19.1% and 22.0%, without significant differences between the two loading protocols. Irrespective of the tooth site, intragroup analyses revealed the presence of significant differences between preoperative and postoperative time evaluations for all the analyzed groups and subgroups. Volumes at baseline (ranging between 0.546 and 0.553 mL) recorded significant loss of approximately 110 mm3 (P values ≤ .0001) for both loading protocols. The volume at the postoperative evaluation ranged between 0.428 and 0.442 cm3. Considering tooth site in the analysis, the subgroups showed similar behaviors at the crestal bone level. However, bone loss at the apex of the implant appeared to be lower for incisors than canines. Conclusion: This study attested that the loss of crestal bone around an immediate implant-supported single crown depended on neither the loading protocol nor the tooth site. Keywords: cone beam computed tomography imaging, extraction socket, fixed implant prosthesis, immediate loading, immediate placement

Purpose: To analyze peri-implant bone loss around six different types of implant-prosthetic connections over a 2-year follow-up period. Materials and Methods: A total of 120 implants were divided into six groups (n = 20), three with crestally and three with supracrestally placed implants, with different internal connections, placed in posterior sectors (molar and premolar), and bearing one-piece computer-aided design/computer-aided manufacturing (CAD/CAM) restorations screwed directly to each implant's prosthetic platform. Bone height was measured from parallelized periapical radiographs taken at the moment of loading and 2 years later. Results: The patient sample included 61 subjects, 36 men and 25 women. Significant differences were found in bone loss between groups, with the implant with internal hex and convergent transmucosal collar showing the least bone loss (P < .001) in comparison with the other designs. Supracrestally placed implants underwent less bone loss than crestally placed implants (P = .025). Conclusion: Peri-implant bone loss is influenced by the level of implant placement in relation to the bone crest (crestal or supracrestal) and by the morphology of the prosthetic platform. Keywords: crestal bone loss, dental implants, internal connection, prosthetic platform, supracrestal

Purpose: This study assessed the survival and marginal bone loss of single-unit short implants (≤ 8 mm in length) in the premolar-molar area. It also compared cemented with screw-retained restorations. Materials and Methods: In this clinical retrospective study, short implants supporting a single crown in the premolarmolar region were selected. Demographic-, surgical-, implant-, and prosthesis-related data were obtained. The predictor variable was the type of prosthesis retention. The principal variables were survival rate and marginal bone loss. The secondary variables were prosthesis survival and technical and biologic complications. Results: A total of 113 patients (56 ± 11 years of age) with 128 short implants were assessed. The mean follow-up time from implant insertion was 25.47 ± 14.95 months. Fifty-one crowns were cemented and 77 were screw-retained. No failure events were recorded for the implants and the prostheses. The distal marginal bone loss was significantly lower in the screw-retained crowns than in the cemented crowns. Marginal bone loss ≥ 2 mm as a biologic complication was more frequent in the cemented crowns. Two screw-loosening events were observed in the screw-retained restorations. These events were resolved by screw retightening. Conclusion: Short implants could be an effective option to support a single-unit prosthesis in the premolar-molar areas of the maxillae. Keywords: cement, crown, screw, screw-retained, short dental implants, single-unit

Purpose: To evaluate the outcome of a clinical study on telescopic-crown-retained removable dental prostheses (TCR-RDPs) on implants or implants and teeth after 8 to 12 years. Materials and Methods: Between 1999 and 2002, 39 (41 arches) patients received implant- or combined tooth-implant-supported TCR-RDPs in the maxilla and/or mandible. One-stage surgery was performed, and after a conventional healing period, TCR-RDPs were inserted. Thirty-one patients (33 prostheses) were available for annual follow-up investigations with a standardized protocol from 2010 until 2013. Cumulative survival and success of the abutments were estimated using the Kaplan-Meier method, and a Cox regression model was used to identify potential predictors for abutment complications. Patients' oral health-related quality of life (OHRQoL) was measured by means of the Oral Health Impact Profile (OHIP). Results: After a mean observation period of 11.3 ± 1.1 years, all restorations were still functioning successfully. Two implants and 10 abutment teeth were lost, leading to significantly different implant and tooth survival rates of 97.6% (SE ± 1.7%) and 81.8% (SE 5.3%; P = .007). Implants placed in the mandible and those in the group with a higher number of abutments (five to six vs two to four) showed higher success rates. The success rates of abutment teeth were not influenced by location (mandible vs maxilla) or number of abutments (five to six vs two to four). Conclusion: Implant- or combined tooth-implant- supported TCR-RDPs provided a satisfying treatment option for patients with severely reduced dentition in the long term. Due to the small sample size, the results presented should be interpreted with caution. Keywords: complication, double crown, implant-retained prosthesis, removable dental prosthesis, survival rate, telescopic crown

Purpose: The aim of this retrospective study was to analyze complications, risk factors, and corresponding treatment regarding the medial approach to harvesting tibial bone. Materials and Methods: Consecutive cases at Yokohama City University Hospital were analyzed for complications of tibial particulated bone and marrow harvesting with the medial approach. The condition of bone marrow, duration of harvesting, and complications were evaluated. The complication rate and correlations between bone marrow conditions and duration of bone harvesting were assessed. The corresponding treatments for the complication were also observed. Results: Thirty cases of tibial particulated bone and marrow harvesting for alveolar ridge or sinus floor augmentation before implant therapy from 2005 to 2014 were analyzed. Twenty-one patients had healthy bone marrow, whereas nine patients had fatty bone marrow. The duration of operation in patients who had both spontaneous pain and gait disturbance was approximately 56 minutes, which was significantly longer than that (approximately 40 minutes) in patients who had only gait disturbance (P < .05). A strong correlation between fatty bone marrow condition and bone harvesting time was seen. The correlation between bone marrow condition and bone harvesting time for fatty marrow was stronger than that for healthy marrow with a trend to significant difference (P = .082). The minor and major complication rate was 96.7% and 6.6%, respectively. Two patients showed postoperative infection on the tibial harvesting site. One of them, who had fatty bone marrow, showed methicillin-resistant Staphylococcus aureus-caused osteomyelitis of the tibia, which needed to be debrided and reconstructed with vancomycin-containing bone cement. Conclusion: A duration of less than 40 minutes for harvesting time may decrease the risk of minor complications. Bone marrow condition influenced tibial bone harvesting duration, which may result in increasing the risk of complications. Regarding major complications, it was considered that wound protection was more important even if the marrow condition was healthy. Keywords: bone augmentation, cancellous bone and marrow, complication, morbidity, tibial bone harvesting

Purpose: To evaluate the influence of the crown-to-implant ratio (CI) on marginal bone loss (MBL) around short dental implants placed in the posterior mandible. Materials and Methods: All patients treated with short implants (7-mm length) in the posterior mandible between 1994 and 2003 at the Dental Clinic of the Department of Neuroscience of the University of Padua (Italy) were retrospectively included in the analysis. MBL and clinical CI (cCI) were measured on the radiographs. Implant characteristics including implant diameter, prosthetic type, retention mode, antagonist type, veneering material, and implant surfaces were retrieved from local medical records. A generalized linear mixed model was estimated to identify the predictors of MBL. Results: A total of 108 dental implants placed in 51 patients were included in the analysis. Mean follow-up was 16 years (range: 11 to 20 years). Mean cCI was 2.21 (SD = 0.31) with a mean crown height of 10.86 mm (SD = 0.99). Mean MBL was 1.42 mm (SD = 0.38). At multivariable analysis, cCI ≥ 2 was associated with higher MBL (regression coefficient: 0.27; 95% CI: 0.15 to 0.40), while implant characteristics, follow-up, and site were not associated with MBL. The effect of a cCI ≥ 2 was estimated in an increase of 0.28 mm in MBL (95% CI: 0.14 to 0.43 mm). Conclusion: Higher cCI was associated with greater MBL of implant-supported fixed dental prostheses in short dental implants placed in the posterior mandible, while implant characteristics, follow-up, and site were not associated with MBL. However, the increase of 0.28 mm of MBL in patients with a cCI ≥ 2 may not be clinically relevant. Keywords: crown-to-implant ratio, implant-supported dental prosthesis, marginal bone loss, prosthetic parameters, short implant

Purpose: The aim of this long-term retrospective study was twofold: (1) to evaluate the survival and success rates of stepped-screw titanium implants with an airborne particle-abraded and acid-etched surface, and (2) to assess the influence of hypothetical predictors of implant failure on the survival rate. Materials and Methods: From 75 possible candidates, 67 patients contributing 346 Frialit-2 implants (DPS Frialit-2 implant system, Friadent) placed between 1997 and 2005 were retrospectively evaluated. The inclusion criteria consisted of implants placed in either native or augmented bone, rehabilitated with an implantsupported prosthesis, and radiographically documented at the time of prosthetic loading (T0). At the followup recall performed between January and October 2018 (T1), clinical and radiologic examinations were conducted to evaluate the survival and success rates. The influences of specific variables on the survival rate were subsequently investigated, including gender and smoking habits, location and size of the implants, and bone augmentation procedures. Cox regression and shared frailty models were used, with the patient representing the statistical unit. Results: A survival rate of 91.62% over a median observation time of 189 months with a range of 11 to 20 years was observed. A total of 14 out of 29 implants failed before delivery of the provisional prosthesis. Overall, the median marginal bone loss was 1.25 mm, with an annual increase of 0.12 mm. Different from the other variables, the results of the multivariate model indicated that smoking was strongly correlated with implant failure (P = .002). Conclusion: Considering the limitations of this study, stepped-screw titanium implants with an airborne particle-abraded and acid-etched surface provided a good survival rate. Smoking might be considered a relevant risk factor for implant failure. Keywords: dental implants, implant-supported prosthesis, retrospective study, rough surface, survival rate

Purpose: To assess the three-dimensional (3D) accuracy of multi-implant impressions for complete arches obtained using 3D-printing technology, and to determine the clinical feasibility of this approach by comparing the results obtained with those obtained with conventional impression techniques. Materials and Methods: A maxillary model matrix with four implant analogs was used to fabricate 10 stone reference models (control) to simulate edentulous patients. Ten 3D-printed impressions were made using polylactic acid custom open trays with component splinting (3D-printed group). To make 10 conventional impressions of the reference models, the poly(methyl methacrylate) open trays with splinting technique was used (conventional group). Impressions were poured with a type IV dental stone, which had been digitalized utilizing a high-resolution laboratory scanner after connecting the polymer scan bodies. Standard tessellation language (STL) datasets from the two groups of stone models were superimposed with the corresponding reference models. The interimplant distances and interimplant angulations for each implant pair were measured for the reference models and for the two test groups' definitive models, to assess 3D deviations. In addition, the mechanical properties of polylactic acid and poly(methyl methacrylate) tray materials were compared by means of threepoint loading and tensile bond tests. The Student t test was used to compare the differences in implant position and mechanical properties between the two groups, while implant angulations were analyzed with Wilcoxon's rank-sum test, at P = .05. Results: There was less implant-position deviation for the 3D-printed group (mean ± SD: 56.37 ± 12.52 μm) than for the conventional group (71.94 ± 18.86 μm) (P = .014). No significant differences were found in angular deviation between the two groups (P > .05). Flexural strength results suggested that polylactic acid (112.7 ± 1.62 MPa) was stronger than poly(methyl methacrylate) (104.0 ± 2.17 MPa; P < .0001). The tensile bond strength of polylactic acid (0.07 ± 0.005 MPa) was higher than that of poly(methyl methacrylate) (0.03 ± 0.004 MPa; P < .0001). Conclusion: The 3D-printing multi-implant impression technique could be an alternative to conventional impression techniques for complete arches. Keywords: 3D printing, accuracy, CAD/CAM, edentulous, impression techniques, polylactic acid

Purpose: Achieving successful and predictable alveolar ridge augmentation in the vertical dimension is extremely challenging. Several materials have been investigated to achieve vertical ridge augmentation; however, the results are highly unpredictable. The collaborative team presenting this research has developed brushite- and monetite-based grafts that incorporate in their matrix a novel bone anabolic conjugate (C3) of a bisphosphonate and a potent bone-activating EP4 receptor agonist. The study objective was to investigate the potential of these graft formulations to achieve rapid, enhanced, and clinically significant bone regeneration in the vertical dimension. Materials and Methods: Brushite and monetite grafts were fabricated and characterized for phase purity, porosity, compressive strength, and microstructural morphology. They were implanted in 12 rabbit calvaria for 12 weeks. The groups (each group n = 6) were: brushite control, brushite with C3, monetite control, and monetite with C3. Postmortem samples were retrieved and processed for analysis. The percentage bone volume, vertical bone height gained, and graft resorption were calculated and assessed. Results: The brushite and monetite grafts containing C3 integrated well onto the calvarial bone surface, with new bone extending through the graft area (36% and 80%, respectively), while the C3 lacking grafts showed decreased surface integration and bone infiltration (28% and 38%, respectively). The C3 containing brushite and monetite grafts demonstrated bone growth vertically (1.8 mm and 2.7 mm, respectively) and improved graft resorption. Conclusion: The brushite- and monetite-based grafts loaded with the C3 conjugate resulted in greater de novo bone formation in the vertical dimension when compared with the grafts without the drug. However, the monetite grafts produced much more and predictable vertical height gain than was achieved with brushite grafts. The advantages of this new graft drug formulation in the future would be to provide more predictable vertical bone regeneration, which will ultimately benefit patients undergoing dental implant placement. Keywords: anabolic conjugates, bone regeneration, bone substitutes, dicalcium phosphates, vertical bone augmentation

Purpose: To compare implant survival, marginal bone loss, peri-implant clinical parameters, and complications in dental implants placed in the posterior maxilla in native bone or after grafting using the open sinus lift technique. Materials and Methods: A search was made of two electronic databases (MEDLINE via PubMed and the Cochrane Oral Health Group Trials Register [CENTRAL]), complemented by a manual search. The study included randomized clinical trials, non-randomized clinical trials, and observational studies such as cohort studies and case-control studies conducted on a prospective or retrospective basis and comparing the placement of standard-length implants (≥ 10 mm) in native bone or after grafting using the sinus lift procedure. Risk of bias was evaluated with the Cochrane risk of bias assessment tool and the methodological index for non-randomized studies (MINORS). Results: The search yielded 51 studies, of which 23 were included. Two studies were evaluated with the Cochrane risk of bias assessment tool, with neither being identified as presenting a low risk of bias. Twenty-one studies were evaluated by the MINORS, yielding a mean score of 15.76 points out of 24. The implant survival rate in the control group was 90% to 100% versus 75.3% to 100% in the test group over a follow-up period of 6 to 120 months. Most studies revealed no statistically significant differences. In most of the publications, marginal bone loss was greater in the test group than in the control group, though without reaching statistical significance. Similar results were obtained in both groups with regard to the peri-implant clinical parameters. There were more surgical complications in the test group than in the control group-such complications being inherent to the sinus lift procedure. Conclusion: Implant placement after sinus lift affords results in terms of implant survival, marginal bone loss, and peri-implant clinical parameters similar to those obtained with conventional implant placement in native bone. However, there is a greater incidence of surgical complications associated with the sinus lift procedure. Keywords: complications, dental implants, implant survival, marginal bone loss, native bone, pristine bone, sinus lift