The International Journal of Oral & Maxillofacial Implants, 01/2018

Purpose: The aim of this in vitro study was to verify whether or not stock and computer-aided design/ computer-aided manufacturing (CAD/CAM) abutments show similar precision in the connection with the respective implants. Materials and Methods: Ten CAD/CAM titanium abutments were compared with 10 stock titanium abutments. Each abutment fit a regular-platform implant (Institute Straumann). Implants and abutments were measured independently and then connected. During the connection procedure, the torque was measured using a six-axes load cell. Then, outer geometric features of the implant-abutment connection were measured again. Finally, the assembly was sectioned to provide the analysis of inner surfaces in contact. The geometric measurements were performed using a multisensored opto-mechanical coordinate measuring machine. The following parameters were measured and compared for the CAD/CAM and stock titanium abutment groups, respectively: width of interference and interference length between the conical surfaces of the implant and abutment; and volume of material involved in the implant-abutment connection. Results: Interference width mean ± SD values of 18 ± 0.5 and 14 ± 0.5 μm were calculated for the stock and CAD/CAM titanium abutment groups, respectively. The difference was statistically significant (P = .02). Furthermore, the interference length mean ± SD values of 763 ± 10 and 816 ± 43 μm were calculated for stock and CAD/CAM titanium abutment groups, respectively. The difference was also statistically significant (P = .04). Finally, the volume of material involved in the implant-abutment connection was compared between stock and CAD/CAM titanium abutment groups; the mean ± SD values of 0.134 ± 0.014 and 0.108 ± 0.023 mm3 were significantly different (P = .009). Conclusion: Both standard and CAD/CAM abutment groups showed a three-dimensional (3D) seal activation after the screw tightening. Nevertheless, stock titanium abutments showed a significantly higher volume of material involved in the implant-abutment connection compared with that of CAD/CAM titanium abutments. Keywords: CAD/CAM abutments, implant-abutment connection, stock titanium abutments

Purpose: To evaluate the effect of repeated screw joint closing and opening cycles and cyclic loading on abutment screw removal torque and screw thread morphology using scanning electron microscopy (SEM). Materials and Methods: Three groups (n = 10 in each group) of implant-abutment-abutment screw assemblies were created. There were also 10 extra abutment screws as new screws in group 3. The abutment screws were tightened to 12 Ncm with an electronic torque meter; then they were removed and removal torque values were recorded. This sequence was repeated 5 times for group 1 and 15 times for groups 2 and 3. The same screws in groups 1 and 2 and the new screws in group 3 were then tightened to 12 Ncm; this was also followed by screw tightening to 30 Ncm and retightening to 30 Ncm 15 minutes later. Removal torque measurements were performed after screws were subjected to cyclic loading (0.5 × 106 cycles; 1 Hz; 75 N). Moreover, the surface topography of one screw from each group before and after cyclic loading was evaluated with SEM and compared with an unused screw. Results: All groups exhibited reduced removal torque values in comparison to insertion torque in each cycle. However, there was a steady trend of torque loss in each group. A comparison of the last cycle of the groups before loading showed significantly greater torque loss value in the 15th cycle of groups 2 and 3 compared with the 5th cycle of group 1 (P .05). Nonetheless, torque loss values after loading were not shown to be significantly different from each other. Conclusion: Using a new screw could not significantly increase the value of removal torque. It was concluded that restricting the amount of screw tightening is more important than replacing the screw with a new one when an abutment is definitively placed. Keywords: dental implants, preload, screw loosening, torque loss

Purpose: The rate of developing soft tissue complications that accompany guided bone regeneration (GBR) procedures varies widely, from 0% to 45%. The present review was conducted to investigate the rate for resorbable versus nonresorbable membranes and the timing of soft tissue complications. Materials and Methods: Electronic and manual literature searches were conducted by two independent reviewers using several databases, including MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Cochrane Oral Health Group Trials Register, for articles published through July 2015, with no language restriction. Articles were included if they were clinical trials aimed at demonstrating the incidence of soft tissue complications following GBR procedures. Results: Overall, 21 and 15 articles were included in the qualitative and quantitative synthesis, respectively. The weighted complication rate of the overall soft tissue complications, including membrane exposure, soft tissue dehiscence, and acute infection/abscess, into the calculation was 16.8% (95% CI = 10.6% to 25.4%). When considering the complication rate based on membrane type used, resorbable membrane was associated with a weighted complication rate of 18.3% (95% CI: 10.4% to 30.4%) and nonresorbable membrane with a rate of 17.6% (95% CI: 10.0% to 29.3%). Moreover, soft tissue lesions were reported as early as 1 week and as late as 6 months based on the included studies. Conclusion: Soft tissue complications after GBR are common (16.8%). Membrane type did not appear to significantly affect the complication rate, based on the limited number of data retrieved in this study. Technique sensitivity (ie, soft tissue management) may still be regarded as the main component to avoid soft tissue complications and, hence, to influence the success of bone regenerative therapy. Keywords: alveolar ridge augmentation, guided bone regeneration, soft tissue complication, systematic review

Purpose: The prevalence of peri-implantitis has increased significantly, forcing clinicians to search for ways to prevent it. Laser-microtextured surfaces promote soft tissue attachment and provide a tight seal around implants. Hence, the aim of this study was to examine the clinical, radiographic, and histologic features of ligature-induced peri-implantitis, as well as the effect of surgical treatment of these induced peri-implantitis lesions on laser-microtextured implants in a controlled animal model. Materials and Methods: Six mini-pigs (three males/three females) received 6 implants each (3 resorbable blast textured [RBT] implants and 3 laser-microtextured [LM] implants) in mandibular premolar sites, for a total of 36 implants. Two groups were identified based on the time point of sample analysis. After osseointegration was achieved, metal wire ligatures were placed and left for 12 weeks. Group 1 samples were then obtained, and group 2 samples received rescue therapy following a guided bone regeneration (GBR) protocol. Sample collection in group 2 was completed 12 weeks after the samples were submerged and treated. All samples were analyzed histologically and measurements were taken. Results: Four implants (three RBT, one LM) were lost at early time points because of implant instability. Interimplant distances and soft tissue thicknesses varied subtly between groups. More notable was the mean (± standard error of the mean) crestal bone loss (group 1: 1.860 ± 1.618 mm [LM] and 2.440 ± 2.691 mm [RBT]; group 2: 2.04 ± 1.613 mm [LM] and 3.00 ± 2.196 mm [RBT]) (P .05), as demonstrated by a paired t test. Histologic pocket depth was also greater at RBT sites than at LM sites (4.448 ± 2.839 mm and 4.121 ± 2.251 mm, respectively, in group 1; and 3.537 ± 2.719 mm and 2.339 ± 1.852 mm, respectively [P .005] in group 2). Conclusion: LM implants had less crestal bone loss and shallower histologic pocket depth compared with their RBT counterparts. Also, LM implants had higher bone fill when a rescue therapy (GBR) was performed. Keywords: implant surface, microtextured implant surface, peri-implantitis

Purpose: To compare the qualitative and quantitative profile of Epstein-Barr virus (EBV) at external and internal implant surfaces between participants with peri-implantitis and healthy peri-implant tissues and to quantitatively assess the relation between EBV and periopathogens inside the microbiologic profile associated with peri-implantitis. Materials and Methods: Microbiologic specimens were retrieved from 84 patients wearing 190 implants to estimate the levels of EBV and 10 periopathogens in the peri-implant pocket and internal-implant connection using quantitative polymerase chain reaction. Results: The study sample consisted of 113 healthy and 77 peri-implantitis-affected implants. Statistical significance was not reached in EBV prevalence between peri-implantitis and healthy controls. EBV-positive participants demonstrated higher levels of Prevotella intermedia (Pi) and Campylobacter rectus (Cr) compared with EBV-negative participants. A positive correlation was demonstrated among EBV and Tannerella forsythia (Tf), Parvimonas micra (Pm), Fusobacterium nucleatum (Fn), and Cr levels in peri-implantitis-affected implants, while healthy controls demonstrated a positive correlation between EBV and Aggregatibacter actinomycetemcomitans (Aa), Pi, and Pm. Conclusion: EBV cannot be considered as a microbiologic marker of peri-implantitis. However, EBV could be considered as a risk factor and a peri-implantitis enhancer based on its positive correlations with pathogens associated with peri-implantitis. Keywords: Campylobacter rectus, Epstein-Barr virus infections, Fusobacterium nucleatum, peri-implantitis, Prevotella intermedia

Purpose: The aim of this study was to evaluate the effect of implant inclination and cantilever length on the stress distribution in mandibular cortical bone, implant, abutment, prosthetic framework, and prosthetic screw via three-dimensional (3D) finite element analysis (FEA). Materials and Methods: Four different finite element models (0-0, 17-17, 30-30, 45-30) were designed according to the tilting angle (0, 17, 30, and 45 degrees) of the posterior implant and angle of multiunit abutments (0, 17, and 30 degrees). Screw-retained fixed prostheses with different cantilever lengths in accordance with implant inclination were modeled. A foodstuff was used for the 100-N load application. Maximum principal (Pmax) and minimum principal (Pmin) stresses were calculated for cortical bone, and von Mises stress values were calculated for the implant, abutment, metal framework, and prosthetic screw. Results: The highest stress values were observed in the anterior implant, surrounding bone, and prosthetic components of the 0-0 configuration. Pmin stress values in bone were gradually decreased with the increasing inclination of both anterior and posterior implants. Peak Pmax stress values were detected in the 0-0 group. For the cortical bone around the posterior implant, the 30-30 group showed the lowest Pmax value. The highest von Mises stress on implants was found at the posterior implant of the 30-30 group. The stress values on abutments gradually decreased with the increase of the angulation of the posterior implants. For prosthetic screws, the 30-30 and 45-30 groups exhibited lower stress values, and for the metal framework, the 30-30 group exhibited lower stress values. Conclusion: Biomechanical comparison via 3D FEA revealed that decreasing the cantilever length by tilting the posterior implants resulted in a reduction in stress values in the peri-implant bone, abutment, prosthetic screw, and metal framework. The groups with 30- and 45-degree tilted posterior implants and shorter cantilever lengths showed better stress distributions in comparison to the straight and 17-degree tilted groups. Keywords: All-on-4, edentulous mandible, finite element analysis, multiunit abutments, stress distribution, tilted implants

Purpose: Implant-supported dental prostheses are based on the principle of osseointegration, and the success of dental implantation depends on adequate formation of this intimate bone-to-implant contact. The application of heat during the drilling procedure leads to a rise in intraosseous temperature at the prospective implant site, which may result in various complications. The purpose of the present study was to compare the ability of thermocouples and infrared thermography to detect changes in intraosseous temperature during dental implant site preparation. Materials and Methods: Standardized bovine costae bone blocks were used to simulate the cortical bone of the human mandible. Steel implant form drills with a diameter of 3.0 mm were used. Two types of irrigation systems were used (external cooling only and combined internal and external cooling). Drilling was performed at a constant speed (1,200 rpm). Changes in intraosseous temperature were evaluated using Type T Cu-CuNi thermocouples and an infrared thermography camera system at contact pressures of 5 and 20 N. Results: Infrared thermography detected significantly greater increases in intraosseous temperature (ΔT) than thermocouples for all tested combinations of cooling system and contact pressure (P ≤ .0001). Conclusion: These results suggest that thermography more accurately reflects intraosseous temperature changes during implant site preparation than thermocouples. Keywords: bone, drilling, implant, temperature, thermocouple, thermography

Purpose: The aim of this study was to examine the deformation modality of palateless maxillary implant overdentures using isolated attachments under various implant configurations. Materials and Methods: A maxillary edentulous model with implants inserted in the anterior, premolar, and molar areas was fabricated, and three types of unsplinted attachments-ball, locator, and magnet-were set on the implants distributed in various configurations. Experimental palateless dentures were fabricated, and two strain gauges were attached at the anterior midline of the labial and palatal sides. A vertical occlusal load of 98 N was applied, and the shear strains of dentures were measured. The measurements of strains were compared with the Kruskal-Wallis test (P = .05). Results: The strains of the labial side were much larger than those of the palatal side except for those using the ball attachment. The strains using the magnet attachment on anterior implants were significantly larger than those using other attachments (P .05). Those using anterior implants were significantly smaller than those using premolar or molar implants (P .05). Conclusion: The strains of palateless overdentures were different according to the attachments and implant distribution. However, when using molar implants, there was no significant difference among the three attachments. Keywords: ball attachment, implant configuration, locator attachment, magnet attachment, maxillary implant overdenture, palateless denture

Purpose: The aim of this meta-analysis was to evaluate different methods for guided bone regeneration using collagen membranes and particulate grafting materials in implant dentistry. Materials and Methods: An electronic database search and hand search were performed for all relevant articles dealing with guided bone regeneration in implant dentistry published between 1980 and 2014. Only randomized clinical trials and prospective controlled studies were included. The primary outcomes of interest were survival rates, membrane exposure rates, bone gain/defect reduction, and vertical bone loss at follow-up. A meta-analysis was performed to determine the effects of presence of membrane cross-linking, timing of implant placement, membrane fixation, and decortication. Results: Twenty studies met the inclusion criteria. Implant survival rates were similar between simultaneous and subsequent implant placement. The membrane exposure rate of cross-linked membranes was approximately 30% higher than that of non-crosslinked membranes. The use of anorganic bovine bone mineral led to sufficient newly regenerated bone and high implant survival rates. Membrane fixation was weakly associated with increased vertical bone gain, and decortication led to higher horizontal bone gain (defect depth). Conclusion: Guided bone regeneration with particulate graft materials and resorbable collagen membranes is an effective technique for lateral alveolar ridge augmentation. Because implant survival rates for simultaneous and subsequent implant placement were similar, simultaneous implant placement is recommended when possible. Additional techniques like membrane fixation and decortication may represent beneficial implications for the practice. Keywords: alveolar ridge augmentation, barrier membranes, collagen membranes, decortication, guided bone regeneration, membrane fixation

Purpose: The aim of this systematic review was to analyze the accuracy of implant placement using computerguided surgery and to compare virtual treatment planning and outcome in relation to study type (in vitro, clinical, or cadaver). A further objective was to compare the accuracy of half-guided implant surgery with that of full-guided implant surgery. Materials and Methods: A PubMed search was performed to identify studies published between January 2005 and February 2015, searching the keywords "reliability AND dental implant planning" and "accuracy dental implant planning." Inclusion criteria were established a priori. Horizontal coronal deviation, horizontal apical deviation, angular deviation, and vertical deviation were analyzed. Results: A total of 186 articles were reviewed, and 34 fulfilled the inclusion criteria. Information about 3,033 implants was analyzed in 8 in vitro studies (543 implants), 4 cadaver studies (246 implants), and 22 clinical studies (2,244 implants). Significantly less horizontal apical deviation and angular deviation were observed in in vitro studies compared to clinical and cadaver studies, but there were no statistically significant differences in apical coronal deviation or vertical deviation between the groups. Compared to half-guided surgery, full-guided implant surgery showed significantly less horizontal coronal deviation for cadaver studies, significantly less horizontal apical deviation for clinical studies, and significantly less angular deviation for both clinical and cadaver studies. Conclusion: Implant placement accuracy was lower in clinical and cadaver studies compared with in vitro studies, especially in terms of horizontal apical deviation and angular deviation. Full-guided implant surgery achieved greater accuracy than half-guided surgery. Keywords: computer-guided accuracy, computer-guided precision, computer-guided surgery, planning in implant dentistry

Purpose: To investigate the force absorption capacity of implant-supported crowns made of different restorative materials and connected to abutments with different luting agents. Materials and Methods: Molar crowns were milled of different computer-aided design/computer-aided manufacture materials (n = 8 crowns per material): polymethyl methacrylate, polyether ether ketone, composite, lithium disilicate, titanium, and zirconia. Crowns were mounted on titanium implant replicas using different luting agents: uncemented, temporarily cemented (zinc oxide-eugenol cement), conventionally cemented (zinc oxide phosphate cement), and adhesively bonded. As a reference, one implant replica was tested without a crown. Force absorptions of the different combinations of crown materials and luting agents were determined by applying an increasing force (0 to 250 N) on the occlusal crown surface and measuring the resulting force below the implant. Mean curves of applied and resulting forces up to 200 N were determined (six measurements per group), and slopes were calculated. Statistical analysis was performed (one-way analysis of variance, Bonferroni post hoc test, α = .05). Results: Significant (P .001) differences in the applied and resulting forces were found between the crown materials that were uncemented, temporarily cemented, cemented, and adhesively bonded. Materials with higher moduli of elasticity (ceramics, titanium) showed steeper slopes of the force curves and lower shock-absorbing capacity than resin-based materials, but were influenced more by the luting agents. The damping effects of resin-based materials were higher in combination with all cementation and luting modes. Conclusion: Shock absorption tests exhibited a strong material-dependent damping behavior of implant-supported crowns. The shock-absorbing capacity of crown materials with high moduli of elasticity may benefit from conventional cementation. Keywords: CAD/CAM, crown, implant, luting agent, resin-based materials, shock absorption

Purpose: The aim of this study was to evaluate the effect of sealing agents on preload maintenance of screw joints. Materials and Methods: A total of four groups (n = 10 in each group) of abutment/implant systems, including external hexagon implants and antirotational UCLA abutments with a metallic collar in cobalt-chromium alloy, were assessed. In the control group (CG), no sealing agent was used at the abutment screw/implant interface. In the other groups, three different sealing agents were used at the abutment screw/implant interface: anaerobic sealing agent for medium torque (ASMT), anaerobic sealing agent for high torque (ASHT), and cyanoacrylate-based bonding agent (CYAB). All abutments were attached to the implants at 32 ± 1 N.cm. After 48 ± 2 hours of initial tightening, loosing torque (detorque) was measured using a digital torque wrench. Data were analyzed using Shapiro-Wilk, Wilcoxon, and Kruskal-Wallis tests, at 5% level of significance. Results: In the CG and ASMT groups, detorque was lower than the insertion torque (24.6 ± 1.5 N.cm and 24.3 ± 1.1 N.cm, respectively). In the ASHT and CYAB groups, mean detorque increased in comparison to the insertion torque (51.0 ± 7.4 N.cm and 47.7 ± 15.1 N.cm, respectively). Conclusion: The ASHT was more efficient than the other sealing agents, increasing the remaining preload (detorque value) 58.88%. Although the cyanoacrylate-based bonding agent also generated high detorque values, the high standard deviation suggested its lower reliability. Keywords: detorque, implant-supported restorations, preload, screw joint

Purpose: To measure the microgap between dental implants and custom abutments fabricated using different computer-aided design/computer-aided manufacture (CAD/CAM) methods before and after mechanical cycling. Materials and Methods: CAD software (Dental System, 3Shape) was used to design a custom abutment for a single-unit, screw-retained crown compatible with a 4.1-mm external hexagon dental implant. The resulting stereolithography file was sent for manufacturing using four CAD/CAM methods (n = 40): milling and sintering of zirconium dioxide (ZO group), cobalt-chromium (Co-Cr) sintered via selective laser melting (SLM group), fully sintered machined Co-Cr alloy (MM group), and machined and sintered agglutinated Co-Cr alloy powder (AM group). Prefabricated titanium abutments (TI group) were used as controls. Each abutment was placed on a dental implant measuring 4.1 × 11 mm (SA411, SIN) inserted into an aluminum block. Measurements were taken using scanning electron microscopy (SEM) (×4,000) on four regions of the implant-abutment interface (IAI) and at a relative distance of 90 degrees from each other. The specimens were mechanically aged (1 million cycles, 2 Hz, 100 N, 37°C) and the IAI width was measured again using the same approach. Data were analyzed using two-way analysis of variance, followed by the Tukey test. Results: After mechanical cycling, the best adaptation results were obtained from the TI (2.29 ± 1.13 μm), AM (3.58 ± 1.80 μm), and MM (1.89 ± 0.98 μm) groups. A significantly worse adaptation outcome was observed for the SLM (18.40 ± 20.78 μm) and ZO (10.42 ± 0.80 μm) groups. Mechanical cycling had a marked effect only on the AM specimens, which significantly increased the microgap at the IAI. Conclusion: Custom abutments fabricated using fully sintered machined Co-Cr alloy and machined and sintered agglutinated Co-Cr alloy powder demonstrated the best adaptation results at the IAI, similar to those obtained with commercial prefabricated titanium abutments after mechanical cycling. The adaptation of custom abutments made by means of SLM or milling and sintering of zirconium dioxide were worse both before and after mechanical cycling. Keywords: CAD/CAM, dental implant, external abutment connection, implant-abutment interface, microgap, misfit

Purpose: To evaluate the peri-implant soft and hard tissues of dental implants placed in vertically regenerated posterior mandibles with intraoral onlay block bone grafts and patient satisfaction at 3-year follow-up. Materials and Methods: A retrospective study of patients with dental implants placed in posterior mandibular sites vertically augmented with intraoral onlay block bone grafts was carried out between 2005 and 2009 at the University of Valencia. The outcomes assessed at the 3-year follow-up visit were the peri-implant soft tissues (Plaque Index and Bleeding Index, probing depth, keratinized mucosa width, and recession), implant survival and success rates, marginal bone loss, and patient satisfaction. Results: Sixteen patients with 36 implants were included. The mean Plaque Index and Bleeding Index scores were ≤ 0.4. The mean band of facial keratinized mucosa was ≥ 3 mm in 52.7% of implants; 38.8% of the implants showed facial recession. The mean midfacial recession was -0.31 ± 0.75 mm. Implant survival reached 100%, while the success rate was 85%, and the mean marginal bone loss was 1 ± 1.03 mm (range: 0.1 to 5.3). Good quality of life (9.19 ± 0.40) was reported for all patients, and the overall general satisfaction score was 8.07 ± 1.04 (mucosa esthetics: 7.71 ± 1.45; prosthesis esthetics: 8.42 ± 0.6; chewing: 8.68 ± 0.94; ease of cleaning: 8.01 ± 1.03). Conclusion: Considering the limitations of the study, implants in vertically augmented posterior mandibular areas with intraoral onlay block bone grafts showed good soft tissue levels and high patient satisfaction. No implants were lost at 3 years postloading, though one-fifth of the patients showed a statistically significant marginal bone loss. Keywords: atrophied mandible, block bone graft, intraoral graft, onlay graft, soft tissues, vertical augmentation

Purpose: To evaluate the number of patients with dental implants who present to a dental school clinic for screening and to report the prevalence of peri-implant bone level change detected on digital panoramic radiographs of those subjects. Materials and Methods: Patient screening files for 9,422 patients over a 2-year period were examined to see how many patients presented with dental implants. Those patients with at least one implant were further evaluated by measuring the bone level on the mesial and distal sides of the implant using the screening radiograph. Results: A total of 187 patients (2%) had at least one implant. In regard to implants, 423 were examined and 146 (33%) had no detectable bone loss defined as bone level below the top of the implant. When thresholds of bone loss were evaluated, 109 implants (25%) had ≥ 2 mm of bone loss on either the mesial or distal sides or both. The median bone loss was 1.74 mm for the 277 implants with detectable bone loss and 2.97 mm for the 109 implants that had ≥ 2 mm bone loss. Interestingly, patients who were ≥ 70 years of age had significantly (P = .03) more bone loss in the mandible compared with the maxilla, while patients who were 60 to 69 years of age had significantly greater loss in the maxilla. Conclusion: These data reveal that for patients presenting to the dental school for a screening over a 2-year period, 1.98% had one or more dental implants. Furthermore, those patients with implants had a minimum amount of bone loss as measured from the top of the implant. Keywords: alveolar bone level, dental implants, dental school, screening

Purpose: The aim of this pilot study was to evaluate clinical outcomes of implant treatment in periodontally compromised patients. Materials and Methods: Partially edentulous patients who were diagnosed and treated for chronic periodontitis and later rehabilitated with implant-supported single crowns or fixed partial dentures were enrolled in this study. At the final follow-up, data on probing pocket depth and bleeding on probing were collected, and changes in peri-implant bone levels were assessed on periapical radiographs. Accordingly, patients were categorized into peri-implant disease-free (PID-free), peri-implant mucositis (PIM), or peri-implantitis (PI) groups. Additionally, information on the history of systemic diseases was obtained and correlated with the findings. Results: Seven females and six males with a mean age of 55.2 (standard deviation [SD] ± 8.38) years were included in this study. Fifty-five implants were placed in 13 partially edentulous patients with a history of chronic periodontitis. The mean follow-up in the study was 35.1 (SD ± 2.40) months. No implants were lost in the 13 patients, for a cumulative survival of 100%. PI was confirmed in 3 patients and PIM in 8 patients, while 2 patients were found to be PID-free. Diabetes and hypertension were found to be the predominant systemic factors among patients affected by peri-implant diseases. Conclusion: Patients with a history of periodontitis are at considerable risk of being affected by peri-implant mucositis, if not by peri-implantitis. Keywords: dental implants, peri-implantitis, peri-implant mucositis, periodontitis

Purpose: The purpose of this study was to develop a probabilistic estimation of the strength of risk factors associated with early dental implant failure and rank them by importance. Materials and Methods: A systematic literature search was performed on PubMed, Web of Knowledge, Scopus, Cochrane Central Register of Controlled Trials, and grey literature up to April 2017. A total of 368 records were identified. Following the removal of duplicate and irrelevant records, 56 were screened. Eight studies met the inclusion criteria, in which seven statistically significant risk factors for early failure were selected and used to build a conceptual simulation model. Selected risk factors were, namely, "male sex," "smoking," "bone quality," "short implants," "wide implants," "adjacent teeth," and "periodontitis." Monte Carlo simulation with 100,000 iterations and a sensitivity analysis were performed to evaluate the risk estimates of these risk factors and to identify which of the risk factors are more important in influencing the model, respectively. Results: The performed simulation model has shown a significant difference in terms of estimated effects of the risk factors on early failure rate. As a result, the most sensitive risk factor was found to be "periodontitis" with the second being "adjacent teeth" and the third "smoking." The least sensitive factor for early failure was "wide implants." Conclusion: This study develops a better understanding of the importance of risk factors for early dental implant failure by an estimated ranking. Keywords: dental implants, Monte Carlo method, risk factors, treatment failure

Purpose: This study evaluated the effect of low-level laser therapy (LLLT) on the healing of bone defects filled with autogenous bone or bioactive glass. Materials and Methods: A critical size defect with 5-mm diameter was created on the calvaria of 60 adult male rats divided into 6 groups (n = 10): group C (control), group LLLT (LLLT - GaAlAs, wavelength of 780 nm, power of 100 mW, energy density of 210 J/cm2 per point during 60 seconds/ point, in five points, only once, after creation of the surgical defect), group AB (autogenous bone), group AB+LLLT (autogenous bone + LLLT), group BG (bioactive glass), group BG+LLLT (bioactive glass + LLLT). All animals were sacrificed at 30 days after surgery. The areas of newly formed bone (ANFB) and areas of remaining particles (ARP) were calculated in relation to the total area (TA). Results: The highest mean ± SD ANFB was observed for group LLLT (47.67% ± 8.66%), followed by groups AB+LLLT (30.98% ± 16.59%) and BG+LLLT (31.13% ± 16.98%). There was a statistically significant difference in relation to ANFB between group C and the other groups, except for comparison with group BG (Tukey test, P > .05). There was no statistically significant difference in ANFB values between group AB and the other study groups (Tukey test, P > .05), group AB+LLLT and groups BG and BG+LLLT (Tukey test, P > .05), and between groups BG and BG+LLLT (Tukey test, P > .05). The highest mean ± SD ARP was found for group BG (25.15% ± 4.82%), followed by group BG+LLLT (17.06% ± 9.01%), and there was no significant difference between groups (t test, P > .05). Conclusion: The LLLT, in the present application protocol, did not increase the area of new bone formation when associated with autogenous bone or bioactive glass. Keywords: biomaterials, bone substitute, lasers

Purpose: Sinus membrane thickness has been associated with the incidence of membrane perforation during the sinus elevation procedure. Understanding the sinus membrane thickness is essential for prevention of this specific surgical complication. Therefore, the aim of this retrospective study was to investigate the impact of sex, age, and season on the membrane thickness. Materials and Methods: The charts of 144 healthy patients were included in the study. Cone beam computed tomography (CBCT) images from these patients were analyzed to determine the sinus membrane thickness in the coronal and sagittal views. Sex, age, and season were correlated with the membrane thickness. Results: The mean thickness of the sinus membrane was 1.81 ± 1.66 mm (range: 0.47 to 9.49 mm). In 22.12% of the CBCT images, the sinus membrane was not visible. Membrane thickness of less than 2 mm was found in 70.8% of the cases. Age was found to be strongly correlated (P .05) with sinus membrane thickness but not sex or season. Conclusion: Based on CBCT assessment, age was found to be a factor influencing sinus membrane thickness but not sex or season. Keywords: maxillary sinus, nasal mucosa, sinus floor augmentation

Purpose: To evaluate histologically and histomorphometrically the effect of a delayed load on healing at implants with a moderately rough surface. Materials and Methods: Two solid titanium screw-shaped devices, 5 mm long and 3.5 mm in diameter, were inserted in the distal segments of the alveolar ridge of 16 volunteer patients in a nonsubmerged fashion. After 2 months, one implant was loaded, while the other was left unloaded. After 2 months, the two implants were collected from 10 patients using a sonic instrument, and ground sections were prepared from the biopsy specimens. Histomorphometric analyses were performed. Results: After 4 months of healing, biopsy specimens from 10 patients were available for analyses (n = 10). The total bone-to-implant contact percentage was 86.8% ± 6.5% and 84.6% ± 3.7% for loaded and unloaded implants, respectively. New bone was represented by 85.5% ± 6.7% and 83.4% ± 3.9% at the loaded and unloaded sites, respectively. A very small amount of old parent bone was found. The density of the mineralized bone was 76.8% ± 8.3% for the loaded sites and 74.1% ± 10.5% for the unloaded sites. The percentages of new and old bone densities were 69.0% ± 8.3% and 7.8% ± 3.9% at the loaded sites, and 65.9% ± 10.3% and 8.2% ± 4.5% at the unloaded sites, respectively. No statistically significant differences were disclosed. Conclusion: Applying a delayed load to implants supporting single crowns did not yield statistically significant differences, and only a tendency of higher osseointegration and bone density was observed at loaded sites compared with the unloaded sites. Keywords: delayed load, dental implants, histometry, human study, morphometry, prosthetic reconstruction

Purpose: The aim of this study was to evaluate the clinical performance of one-piece, screw-retained implant crowns based on hand-veneered computer-aided design/computer-aided manufacture (CAD/CAM) zirconium dioxide abutments with a crossfit connection at least 1 year after insertion of the crown. Materials and Methods: Consecutive patients who had received at least one Straumann bone level implant and one-piece, screw-retained implant crowns fabricated with CARES zirconium dioxide abutments were reexamined. Patient satisfaction, occlusal and peri-implant parameters, mechanical and biologic complications, radiologic parameters, and esthetics were recorded. Results: A total of 50 implant crowns in the anterior and premolar region were examined in 41 patients. The follow-up period of the definitive reconstructions ranged from 1.1 to 3.8 years. No technical and no biologic complications had occurred. At the reexamination, 100% of the implants and reconstructions were in situ. Radiographic evaluation revealed a mean distance from the implant shoulder to the first visible bone-to-implant contact of 0.06 mm at the follow-up examination. Conclusion: Screw-retained crowns based on veneered CAD/CAM zirconium dioxide abutments with a crossfit connection seem to be a promising way to replace missing teeth in the anterior and premolar region. In the short term, neither failures of components nor complications were noted, and the clinical and radiographic data revealed stable hard and soft tissue conditions. Keywords: biologic complications, dental implant, screw retention, single crown, technical complications, zirconia abutment

Purpose: The aim of this 1-year randomized trial was to determine the stability and the magnitude of the effect of converting patients' conventional mandibular dentures to implant overdentures (IODs) on their satisfaction and oral health-related quality of life (OHRQoL). The IODs were retained either with two immediately loaded interconnected standard-diameter implants or with four immediately loaded mini dental implants (MDIs). Materials and Methods: Fifty completely edentulous subjects complaining about insufficient retention of their mandibular dentures were randomly assigned to two groups; 25 patients received IODs retained with four MDIs and 25 patients received IODs retained with two standard-sized tissue level (STL) interconnected implants. All IODs were opposed by conventional maxillary dentures. Patients rated their satisfaction on a 100-mm visual analog scale (VAS) and their quality of life on a denture-specific short version of the oral health impact profile (OHIP-20) before assignment, and after 3 and 12 months. A two-way mixed analysis of variance (ANOVA) was conducted to assess the change in time and its interaction with treatment mode on patients' overall satisfaction ratings, the total OHIP-20, and their specific domain scores. Results: Immediate loading was possible for all the patients who received the MDIs. By contrast, the immediate loading protocol could be followed for only 15 of the patients allocated to the STL implant group. For the remaining patients, a delayed loading protocol was applied. There was a significant improvement in patients' general satisfaction between baseline and 3 months and between baseline and 12 months postoperatively (F2,44 = 81.006, P .001). This increase did not differ between the treatment groups (F4,90 = 1.838, P = .128). The results also showed a decrease in mean overall OHIP score (F2,43 = 46.863, P .001) between baseline and 3 months and between baseline and 12 months postoperatively, indicating a higher level of OHRQoL. In addition, patients scored lower 3 and 12 months after treatment than at baseline for all seven domains. This decrease did not differ between the treatment groups (F4,88 = 0.608, P = .658). Conclusion: The results suggested that in terms of patient-based outcomes, mandibular overdentures retained by immediately loaded MDIs can offer an improvement of equal magnitude with that achieved by overdentures retained by standard-sized implants. Keywords: immediate loading, mini dental implants, OHIP-20, VAS

Purpose: This randomized controlled clinical trial compared the stability of augmented bone between a synthetic resorbable membrane and a collagen resorbable membrane with guided bone regeneration (GBR) simultaneous with dental implant placement in the esthetic zone in terms of facial bone thickness. Materials and Methods: A total of 60 dental implants from patients requiring implant placement with simultaneous GBR in the esthetic zone were equally allocated to the test group or control group by block randomization. Biphasic calcium phosphate ceramic bone was used in combination with either a polylactic acid (PLA) membrane (test group, 30 implants) or a resorbable collagen membrane (control group, 30 implants). Cone beam computed tomographic (CBCT) images were used to assess the facial bone thickness postimplantation and then 6 months later at four levels: implant platform and 2 mm, 4 mm, and 6 mm apical to the implant shoulder. Results: All implants were osseointegrated, and no implant loss was found during this study. Facial bone was detected in all cases; however, the thickness of the facial bone was reduced at the 6-month follow-up in both groups. The percentage of facial bone thickness reduction was 34.30%, 27.94%, 24.25%, and 19.81% in the test group and 34.80%, 24.06%, 19.52%, and 20.45% in the control group at the level of the implant platform and at 2 mm, 4 mm, and 6 mm apical to the implant shoulder, respectively. Nevertheless, there was no statistically significant difference between the groups (P > .05). Conclusion: A synthetic resorbable membrane revealed an amount of stable augmented bone similar to that of a collagen resorbable membrane. Keywords: cone beam computed tomography, dental implant, facial bone thickness reduction, guided bone regeneration, resorbable membrane, stability of augmented bone

Purpose: No consensus regarding the efficacy of zirconia implants in maintaining peri-implant hard and soft tissue health has yet been obtained. The aim of this retrospective follow-up study was to gain knowledge about peri-implant bone behavior and about implant survival and success after treatment with zirconia dental implants in patients with normal and compromised soft and hard tissue conditions. Materials and Methods: This follow-up study involved 86 patients with 123 zirconia implants (Straumann PURE Ceramic Implant) that were radiographically investigated directly after implant placement (day 0), 3 months after placement, and 1 year after the definitive implant crown placement. The clinical assessment was done at the 1-year postloading appointment and also included the modified Plaque Index, modified Sulcus Bleeding Index, and sulcus pocket depths. Eighteen patients with periodontally compromised conditions were compared to 68 patients with healthy periodontal conditions. Results: The survival rate was 100% and success rate was 94.5%, with no differences between the two groups. The alveolar crest around the ceramic implants showed no significant difference between day 0 and 1 year postloading for both groups (P > .05). There was also no significant difference at 1 year postloading between the groups in the distance from the implant shoulder to the peri-implant bone crest (P = .67) or in pocket depth (P = .07). Conclusion: No significant peri-implant bone loss was observed in the first year. The survival and success rates showed no differences between the periodontally healthy and periodontally compromised groups; however, only a limited number of patients with periodontally compromised conditions were included in this study. Keywords: alveolar crest, esthetics, gingiva, zirconia implants

Purpose: One of the suggested methods for enhancing osseointegration is the local application of drug agents around implant surfaces. The aim of this review was to evaluate the methods most commonly used for local drug and chemical compound delivery to implant sites and assess their influence on osseointegration. Materials and Methods: An electronic search was undertaken in three databases (PubMed, Scopus, Embase). The search was limited to animal experiments using endosseous implants combined with local drug delivery systems. Meta-analyses were performed for the outcome bone-to-implant contact (BIC). Results: Sixty-one studies met the inclusion criteria. Calcium phosphate (CaP), bisphosphonates (BPs), and bone morphogenetic proteins (BMPs) were the most commonly used chemical compounds. There were two main methods for local drug delivery at the bone-implant interface: (1) directly from an implant surface by coating or immobilizing techniques, and (2) the local application of drugs to the implant site, using carriers. There was a statistically significant increase in BIC for both local drug delivery methods (P = .02 and P .0001, respectively) compared with the control methods. There was a statistically significant increase in BIC when CaP (P = .0001) and BMPs (P = .02) were either coating implants or were delivered to the implant site, in comparison to when drugs were not used. The difference was not significant for the use of BPs (P = .15). Conclusion: It is suggested that the use of local chemical compound delivery systems around implants could significantly improve implant osseointegration in animal models. It is a matter of debate whether these in vivo results might have some significant effect in the human clinical setting in the long term. Keywords: animal models, bone-to-implant contact, dental implants, drug delivery, meta-analysis, osseointegration, systematic review

The socket-shield technique described 7 years ago has since grown in its reporting in the literature as a valid method of ridge preservation at immediate implant placement. To date, large clinical cohorts with up-to-4-year follow-up have been reported. Additionally, evidence of tissue histology at the dental implant and socket-shield has been demonstrated in the animal model. However, human histologic evidence has not yet been available, and the clinician's uncertainty regarding the tissues that may form between the socket-shield and dental implant may remain unanswered until now. This case report presents the first human histologic evidence that bone may entirely fill the space between root dentin and an osseointegrated implant surface. Keywords: dental implant, implantology, partial extraction therapies, ridge preservation, socket-shield