The International Journal of Oral & Maxillofacial Implants, 01/2022

Purpose: This in vitro study evaluated technical outcomes of monolithic zirconia implant-supported fixed dental prostheses (iFDPs) supported by different designs of titanium base abutments after aging and static load testing. Materials and methods: Sixty three-unit monolithic zirconia (yttrium oxide partially stabilized tetragonal zirconia polycrystals; Y-TZP)iFDPs were produced and divided into four groups: group A-conical titanium base abutments for the prosthesis; group B-cylindrical titanium base abutments for the crown; group C-conical titanium base abutment for the prosthesis and cylindrical titanium base abutment for the crown; group D-cylindrical titanium base abutments for the prosthesis. The samples were subjected to an aging protocol and to continuous static loading until failure and analyzed visually and with specific software. The technical outcomes comprised the occurrence of debonding, screw loosening, deformation and fracture, abutment deformation and fracture, implant deformation and fracture, zirconia chipping and fracture, and bending moments. The Pearson chi-squared test (χ²) and Fischer exact test were used to compare the outcomes. The Kolmogorov-Smirnov test was used to evaluate data distribution of the bending moments. Analysis of variance (ANOVA) was used for the analysis of parametric data distribution, and the Kruskal-Wallis test was used for nonparametric data distribution. Results: After aging, a higher percentage of debonding (P = .042) and micromovement (P = .034) was recorded in group C (P = .042). The conical titanium base abutments had a higher debonding (P = .049) and a higher macromovement rate (P = .05). The static load test showed higher bending moments in group D (P = .001) and lower bending moments in group A (P = .001). Debonding was highest in group C (P = .001) and lowest in group A (P = .002). Complete loss of retention rate was highest in group C (P = .001). The conical titanium base abutment had the highest debonding rate (P = .001) and complete loss of retention (P = .001). The micromovement rate was the highest for cylindrical titanium base abutments for the crown (P = .001). The lowest screw loosening, zirconia chipping, and fracture rate (P = .001) and the highest screw deformation (P = .004) were recorded in group A. The screw deformation rate was lowest in the cylindrical titanium base abutments for the crown (P = .008). Conclusion: The mixed titanium base abutment design comprising one conical and one cylindrical abutment in Y-TZP iFDPs led to the highest debonding rate. The cylindrical titanium base abutment for the prosthesis provided a lower percentage of debonding and the highest load resistance. Keywords: bending moments, debonding, implant-supported fixed dental prostheses, monolithic zirconia, technical complications, titanium base abutment

Purpose: To evaluate the influence of using different fabrication techniques, including intraoral scans, CBCT scans of patients' existing dentures, or denture duplicates, on the accuracy of radiographic scan templates. The influence of selecting different segmentation threshold values during reconstruction of CBCT data was also evaluated. Materials and methods: A reference model was obtained by scanning five pairs of maxillary and mandibular acrylic complete dentures using a desktop laboratory laser scanner (DWOS 7Series, Dental Wings). Test scans were obtained from intraoral scans of dentures, CBCT scans of dentures and denture duplicates reconstructed at different grayscale segmentation thresholds, and a laboratory scan of denture duplicates. The resultant STL scan files were imported to an open source and cloud storage software (Medit Link) for the accuracy measurements by calculating root mean square estimate (RMSE) between reference and test scans. Collected data were then analyzed. Qualitative analysis was also performed using 3D color maps. Results: The lowest RMSE (352.7) was found with intraoral denture scans. The highest RMSE (1,336.3) was found with the CBCT scans of the denture duplicates at segmentation threshold of -700 grayscale level. Qualitative analysis revealed that the intraoral denture scans exhibited the most homogenous deviation pattern relative to reference lab scans. Conclusion: Within the limitations of this study, the intraoral scans of the patients' existing dentures resulted in the fabrication of the most accurate radiographic scan templates. The improved accuracy of scan templates fabricated using the intraoral scanners can eliminate the possible laboratory errors associated with the conventional technical procedures as well as reduce the inaccuracies resulting from the image processing and segmentation of CBCT data. Keywords: accuracy, CBCT scans, computer-guided implant placement, intraoral scans, radiographic template, scan template

Purpose: The aim of this study was to compare the trueness and precision of four intraoral scanners (IOSs) and splinted open-tray conventional implant impression (SOCI) in partial and total edentulism. Materials and methods: Four gypsum models (Model A-implants at mandibular right second molar, right second premolar, and right canine; Model B- implants at mandibular right canine, left central incisor, and left canine; Model C-implants at mandibular right second molar, right second premolar, right canine, left central incisor, and left canine; and Model D-implants at mandibular right second molar, right second premolar, right canine, left central incisor, left canine, left second premolar, and left second molar) were prepared, and four different IOSs (Aadva IOS, CS 3600, Trios 3, and Emerald) and one polyvinyl siloxane (PVS) were used. Reference models were digitized with a high-resolution industrial scanner, and data were superimposed. Root mean square (RMS) values were calculated by software and defined as deviation values after superimposition. The oneway analysis of variance (ANOVA) test and Tukey honest significant difference (HSD) test were performed to analyze the data (P < .05). Results: For Models A and B, the truest impressions were made with Aadva, followed by CS 3600, PVS, Trios 3, and Emerald, respectively, while for Model C, the truest impressions were made with CS 3600, followed by Aadva, PVS, Trios 3, and Emerald, and for Model D, the truest impressions were made with Aadva, followed by CS 3600, PVS, Emerald, and Trios 3 (P < .05). There was no statistical difference between groups for precision in Models A, B, and C (P > .05); however, PVS showed lower precision values than other groups in Model D (P < .05). Conclusion: In partial edentulism, IOSs are true and precise as SOCI except Emerald. However, the trueness of IOSs is not favorable in total edentulism cases. SOCI with PVS in total edentulism treated with implants is less precise than IOSs. Keywords: accuracy, conventional impression, digital impression, implant impression, intraoral scanner, trueness

Purpose: To examine the influence of posterior residual ridge resorption (PRRR) and relining on bending strain around implants under an overdenture. Materials and methods: Maxillary and mandibular edentulous models were made and covered with white silicone. Four strain gauges were placed on four sides of each implant. Two tissue-level implants were placed bilaterally in the part between the lateral incisors and canines of the mandible. A maxillary conventional denture and a mandibular overdenture were fabricated to fit the models. Three levels of bone resorption around the implant were created: 0, 0.8, and 1.5 mm. The surface of the residual ridge was uniformly removed from the area near the distal side of the implant to the retromolar section, and three levels of PRRR were created (0, 1, and 1.5 mm). After the measurement, the experimental denture of the PRRR of 1 mm and 1.5 mm were relined. Locator attachments were used. A 98-N occlusal force was applied, and bending strains around the implant were measured. The Kruskal-Wallis test and Bonferroni correction were employed to analyze the data. Results: Without relining, at each bone resorption level around the implant, the bending strain was smallest with PRRR of 0 mm and largest with PRRR of 1.5 mm. The bending strain after relining was smaller than the bending strain with ridge resorption. Bending strains after relining were smaller than bending strains with no ridge resorption, but there was no significant difference in bending strain between these three groups. Conclusion: As PRRR increased, the bending strain increased without relining. As bone resorption around the implant progressed, PRRR enhanced the increase in the peri-implant bending strain. Bending strain was reduced when relining was performed. Keywords: bending strain, bone resorption around implant, implant overdenture, posterior residual ridge resorption, relining

Purpose: The aim of this ex vivo study was to assess the ability to remove oral biofilm by different combinations of mechanical and chemical treatments on smooth and rough titanium surfaces, as well as their impact on osteoconduction. Materials and methods: Forty-eight sandblasted acid-etched (SLA) and 48 machined titanium disks were contaminated with oral bacterial biofilm and exposed to the following treatments: (1) titanium brush (TB), (2) TB + 40% citric acid (CA), (3) TB + 5.25% sodium hypochlorite (NaOCl), (4) air polishing with glycine powder (AP), (5) AP + 40% CA, and (6) AP + 5.25% NaOCl. Residual bacteria and chemical contamination were assessed using viable bacterial count assay, scanning electron microscopy (SEM), and x-ray spectroscopy (XPS). Human primary osteoblast (hOB) adhesion and osteocalcin (OC) release were also evaluated. Results: The microbiologic, SEM, and XPS analysis indicate a higher biofilm removal efficiency of combined mechanical-chemical treatments compared with exclusively mechanical approaches, especially on SLA surfaces. SEM analysis revealed significant alterations of surface microtopography on the disks treated with TB, while no changes were observed after AP treatment. OC release by hOBs was mainly decreased on disks treated with CA and NaOCl. Conclusion: The combination of mechanical and chemical treatments provides effective oral biofilm removal on both SLA and machined implant surfaces. NaOCl and CA may have a negative effect on osteoblasts cultured on SLA samples. Keywords: antiseptics, implant decontamination, peri-implantitis, surface decontamination

Purpose: Investigate the effects of three different complete-arch digital implant scanning techniques used with a combined healing abutment-scan body (CHA-SB) system on the accuracy (trueness and precision) and scan time. Materials and methods: A poly(methyl methacrylate) master model simulating an edentulous maxilla was fabricated with four parallelly inserted dental implants. A CHA-SB system was attached to each implant. The model surface was scanned using a structured blue light industrial extraoral scanner to achieve a reference model standard tessellation language file (MRM-STL). Three different scanning techniques-(1) conventional technique with unmodified master model, (2) scan body splinting technique using orthodontic elastic ligatures and plastic splint materials, and (3) land-marking technique using pyramid-shaped glass-ceramic markers-were performed. Fourteen consecutive digital scans were made by using an intraoral scanner (IOS) for each technique, converted to an STL file, and superimposed on the MRM-STL. Trueness and precision were calculated for each technique. The scan time was also recorded. The data were analyzed with one-way analysis of variance (ANOVA) and Tukey honest significant difference (HSD) tests (α = .05). Results: Effects of different scanning techniques on the trueness (distance and angular deviations; P < .001) and scan time (P = .002) were statistically significant. For precision, different scanning techniques had only a significant effect on the distance deviation (P < .001). Conclusion: Regarding trueness and precision, none of the scanning techniques was superior to others. The scan body splinting technique led to significantly less scan time. Keywords: accuracy, implant impression, landmark, precision, splinting, trueness

Purpose: To achieve high plaque removal around peri-implant tissues, noninvasive cleaning methods that guarantee the long-term success and survival of titanium implants should be established. This systematic review aimed to systematically evaluate in vitro investigations assessing different treatment modalities to decontaminate titanium surfaces, with special focus on the most effective cleaning procedures. Materials and methods: PRISMA guidelines were adopted in an electronic search conducted through MEDLINE, Scopus, and Google Scholar databases to identify studies on mechanical, chemical, or laser decontamination modalities up to November 2019. Results: The search resulted in 326 articles; after removing duplicates and reading titles, abstracts, and full texts, 38 articles were ultimately processed for data extraction. Mechanical decontamination provided better results in comparison to laser and chemical procedures. Among mechanical modalities, air abrasion showed the best cleaning effectiveness. Conversely, upon comparison of the chemical methods, chlorhexidine demonstrated comparable results with all tested substances and even with photodynamic therapy. Among different lasers, the results showed that the diode was more promising compared with the other tested lasers. Conclusion: This review demonstrated that there is still no consensus on which technique performs better. However, mechanical decontamination yielded more favorable results than laser and chemical methods. This aspect would support the hypothesis that decontamination procedures adopted in a combination fashion, which includes mechanical procedures, may provide better clinical results than when used alone. Keywords: chemical decontamination, cleaning efficacy, dental implants, laser decontamination, mechanical decontamination

Purpose: The aim of this study was to coat titanium substrate with bioactive glass nanoparticles and characterize the deposited surface coat. Materials and methods: Amorphous bioglass nanoparticles < 20 nm in diameter were prepared using a modified sol-gel technique followed by a ball-milling process. The prepared nanoparticles were used to coat airborne particle-abraded titanium disks. The in vitro bioactivity of the bioglass nanopowder was confirmed using simulated body fluid. Coated surfaces were characterized in terms of microstructure, composition, thickness, phase structure, surface roughness, wettability, and tissue behavior in a rabbit model. Results: Bioglass nanoparticles showed apatite formation under a scanning electron microscope (SEM) after 5 days, confirming that bioactivity was enhanced with increasing degradation rate for up to 2 weeks. An optimized deposition technique and heat-treatment process produced a homogenous coating with a uniform thickness of 32 to 39 μm. Chemical analysis confirmed the presence of silicon and calcium on the coated disks. Amorphous coated surfaces exhibited porous nano/microroughness with microcracks and super-hydrophilicity. The interface of the coated disks with subcutaneous tissue revealed good tissue adhesion, high cellular activity, and rich vascularization, with multinucleated cells in the microenvironment surrounding the coat, as confirmed using histomorphometric analysis. Conclusion: The results of this study show that it is feasible to coat titanium surfaces with bioactive glass nanoparticles with super-hydrophilicity and high biologic activity. These particles may promote the regenerative environment around dental implants. Keywords: bioactive coating, hydrophilic surface, nanoparticles, silicate bioglass, titanium implant

Purpose: After tooth extraction, a modeling and remodeling phase of bone and soft tissues occurs. It has been fully demonstrated that bone resorption as high as 50% can take place regarding ridge width and a variable amount concerning ridge height, making it difficult to perform implant surgery. Materials and methods: Active members of the Italian Academy of Osseointegration (IAO) participated in this Consensus Conference, and three systematic reviews were conducted before the meeting to provide guidelines on alveolar ridge preservation procedures. The systematic reviews covered the following topics: (1) What material best preserves the dimensions of the ridge horizontally and vertically?; (2) what material favors the formation of the highest quantity of new bone?; (3) which technique would best seal the socket?; and (4) what effect does alveolar ridge preservation have on soft tissues? Results: The main conclusions reached by the assembly were that alveolar ridge preservation is advisable after dental extraction, particularly in esthetic areas, in proximity of anatomical structures (ie, maxillary sinus, inferior alveolar nerve, and mental foramen), whenever the treatment plan requires delayed placement, and whenever patients ask to postpone implant insertion for various reasons. Socket debridement is advised before the use of a "regenerative material," and xenograft is considered the gold standard material to maintain ridge dimensions. Another indication is antibiotic therapy, which is recommended in the case of alveolar ridge preservation (amoxicillin 2 g 1 hour before the intervention and 1 g every 12 hours for 6 days). A membrane or autologous soft tissue should be used to seal the socket and protect the regenerative material, and the indicated reentry time (implant insertion) is 4 to 6 months. Conclusion: This Consensus Conference agreed that the adoption of alveolar ridge preservation can effectively prevent physiologic bone loss, especially in esthetic areas. It is recommended to cover the xenograft material with a membrane or autologous soft tissue, and antibiotic therapy is advisable. Keywords: antibiotics, bone regeneration, dental implants, postextraction site, surgery

Purpose: Implant surgical guides are often fabricated using CBCT technology. In this study, an alternative technique is proposed. The aim of this in vitro study was to compare the accuracy of the guide sleeve corrections of a geometric approach to guided surgery to the accuracy of in vitro studies of stereolithographic guides. Materials and methods: Four arch forms were milled from acrylic blocks each with 12 root form sites. Root form inserts were made. Holes were milled in the inserts at arbitrary angles. Guide posts were placed in these sites. Guide sleeves were placed on the posts and connected with light-cured resin to form verification jigs. The goal was to correct the angles of the guide sleeves to a vertical position 90 degrees from the base of the arch forms. The initial angles from the vertical and horizontal positions of the center of each guide sleeve were determined radiographically and geometrically. Horizontal and angle corrections were made using two-piece guide posts. Guide sleeves placed over the corrected guide posts were connected with light-cured resin, forming new verification jigs. The accuracy of the angle correction and the coronal horizontal and apical horizontal deviations of the 3-mm guide sleeves were determined. The experimental sites were divided into two groups to determine if the size of the initial angles of the guide sleeves had any effect on the accuracy of the corrections. Results: The initial angles of the guide sleeves before corrections revealed the mean difference between the two methods of measurements in groups 1 and 2 as 0.36 degrees (P = .14) and 0.69 degrees (P = .07), respectively. A comparison of the angle error measurements from 90 degrees after corrections between the two groups in the mesiodistal and buccolingual planes was not significant. The coronal and apical horizontal deviations after corrections revealed a significant difference between the two groups at the coronal level (P = .005) but not at the apical level (P = .14). In comparison of the methods of the two measurements of the angle error from vertical after corrections, the mean difference was 1.23 degrees (P = .01) and 0.69 degrees (P = .02). Conclusion: The in vitro accuracy of the guide sleeve corrections made with the geometric approach for implant guidance was compared to the results of the meta-analyses of in vitro studies of implant placement with stereolithographic guides. The mean errors were smaller and within the recommendations of the EAO Consensus Conference of 2012. Keywords: guidance, guidepost, single implant, surgical guide, surgical procedure

Purpose: The stability and density of the grafted bone in the maxillary sinus are essential for dental implant survival. This study aimed to compare bone density following mineralized allogeneic bone and deproteinized bovine bone and evaluate the volumetric changes as the secondary outcome. Materials and methods: In this prospective cohort study, subjects were randomly allocated into two groups of mineralized bone and deproteinized bone to augment the maxillary sinus. Subjects underwent CBCT immediately after augmentation and 9 months later. The relative bone density was the primary outcome, and the volumetric change after 9 months was the secondary outcome of the study. The authors used an independent t test for assessing the bone density and volumetric change between the two groups. Results: Fifty patients were studied (n = 25 in each group). At 9 months after sinus elevation, the mean bone density was 237.20 ± 55.72 Hounsfield units (HU) in group 1 (mineralized bone) and 634.8 ± 166.11 HU in group 2 (deproteinized bone). There was a substantial difference statistically for the mean of HU between groups 1 and 2 (P < .001). The mean volume change was 0.25 ± 0.13 cm³ in group 1 (mineralized bone) and 0.06 ± 0.05 cm³ in group 2 (deproteinized bone). Assessment of the data showed a substantial difference in the mean volume change at 9 months after sinus elevation between groups 1 and 2 (P < .001). Conclusion: Considering the results of this study, the deproteinized bone was associated with higher relative bone density than the mineralized bone 9 months after sinus elevation. The volume change of the deproteinized bone was less than the mineralized bone in the study time. Keywords: bone substitutes, cone beam computed tomography, maxillary sinus, sinus floor augmentation

Purpose: Bone level tapered implants have an advantage in terms of stability and less need for additional bone augmentation procedures in healed sites, which might be advantageous for the esthetic zone. The aim of this study was to assess the clinical, radiographic, and esthetic performance of bone level tapered implants placed in healed sites in the maxillary esthetic region during a 1-year evaluation period. Materials and methods: Thirty participants (15 male, 15 female) with a single-tooth diastema that had healed without an alveolar ridge preservation procedure received a bone level tapered implant. Buccal bone augmentation procedures were performed at implant placement if the labial bone wall thickness was < 2 mm. A provisional crown was connected after a healing phase of 3 months. A definitive crown was placed 3 months after the provisional restoration. Implant stability, peri-implant soft and hard tissue health, esthetics, and patient-reported outcomes were recorded. Results: All the placed implants demonstrated good stability. A labial bone augmentation technique was needed in 23 of the 30 cases. The median implant stability quotient value was 73 (68;76) at implant placement and had increased to 79 (76;81) when the definitive restoration was inserted (P < .005). All patients were present at the 1-year evaluation, and none had lost an implant. The mean loss of marginal bone was 0.07 ± 0.10 mm. The midbuccal mucosa-level recession was 0.14 ± 0.40 mm. There was an overall gain in papilla height: +0.05 ± 0.60 mm mesially and +0.06 ± 0.53 mm distally. Median values of the pink esthetic score and white esthetic score were 6 (4;7 interquartile range) and 8 (7;8.3 interquartile range), respectively. The participants' mean overall satisfaction was 90.1 ± 6.5 on a visual analog scale. No complications occurred. Conclusion: It can be concluded from a 1-year followup that treatment with the bone level tapered implant system resulted in good implant stability, healthy peri-implant soft and hard tissues, satisfying esthetics, and good patient-reported outcomes. Keywords: esthetic region, healed site, single-tooth, tapered implants

Purpose: Knowledge of the early mortality patterns in edentulous implant patients is limited. This study aimed to report patient mortality within the first year after surgery and compare the cause of death with preexisting conditions reported before surgery. Materials and methods: In this retrospective cohort study, data from the Swedish National Death Register on patients, consecutively treated in the edentulous arch between 1986 and 2013, were compared with information from the patient files regarding the preexisting health conditions of the deceased patients. One-year survival rates were calculated and compared with expected mortality in a Swedish reference population based on three age groups: young (< 45 years of age), middle-aged (45 to 64 years of age), and old patients (> 64 years of age). Proportions of mortality between study groups and reference populations were tested by means of a log-rank test, and agreement between diagnoses before surgery and cause of death was tested by means of kappa test. Results: Altogether, 3,877 patients were included, of whom 60 patients died within 1 year after implant surgery (1.5%). The expected mortality in the Swedish reference population was 2.1% (P < .05). Mortality was higher for middle-aged (P = .02) but lower for old patients (P = .0001) compared with the Swedish reference populations. Eight of the deceased patients (13%) had no preexisting conditions, while 48 patients reported a health diagnosis before implant surgery. The most common of these were related to the circulatory system (ICD 10-I), which was the cause of death for 30 patients. A "none to slight agreement" between presurgical diagnoses and cause of death was observed in the population (kappa: 0.152). Conclusion: Edentulous implant patients presented overall lower mortality than expected in the general population during the first year after surgery. However, middle-aged patients showed a higher proportion of deceased patients compared with control people of the same age. Cardiovascular diseases were the cause of death in 50% of the group, and the agreement between presurgical and cause of death diagnoses was poor. Keywords: age at surgery, causes of death, dental implant, early mortality, edentulous

Purpose: Primary stability is the most important prognostic index for predicting osseointegration. It is generally thought that to achieve high primary stability, it is necessary to insert an implant with a high insertion torque (IT). To date, it has not yet been determined whether IT and implant stability quotient (ISQ) values are correlated. The primary aim of the study was to determine the correlation between IT and ISQ values at the time of implant insertion (T0); at 2 months, the time of healing (T1); and at 6 (T2) and 12 months (T3) after loading. The secondary aims were to determine the influence of different macroscopic implant designs and of a different insertion arch on this correlation; and to assess whether implants inserted with a high IT, that is, > 50 Ncm, had higher levels of implant stability at 2-, 6-, and 12-month follow-ups. Materials and methods: STROBE guidelines were followed. Partially or monoedentulous patients were randomly assigned to receive taper thread on straight-body implants with microthreads (group A) or without microthreads (group B). At implant insertion, IT and ISQ values were recorded. At 2-, 6-, and 12-month follow-ups, the ISQ values were recorded. A spring-style torque wrench was used to assess the IT. The Osstell device was used to determine the ISQ values. Descriptive statistics, Pearson correlation, and t test were used. P was set at ≤ .005. Results: Two hundred fifty subjects were assessed; 142 were included. Two hundred sixty-eight implants were inserted (group A, 137 implants; group B, 131 implants). No subject dropped out, and no implant failed. A statistically significant correlation between ISQ and IT was determined at the time of implant insertion (T0; P = .000). The implant morphology and arch did not influence the correlation. An IT > 50 did not determine a higher secondary stability. Conclusion: There is a strong correlation between IT and primary stability, but IT is not correlated with the secondary stability. A different implant macroscopic design and a different arch of insertion did not influence this correlation. Moreover, implants inserted with IT > 50 Ncm do not result in greater secondary stability. Keywords: dental implant, dental prosthesis implantation, implant loading, insertion torque, osseointegration, resonance frequency analysis

Purpose: Cone beam computed tomography (CBCT) image quality is known to be affected by artifacts produced by metal restorations, causing image deterioration via bright streaks and loss of gray values in the vicinity of the metallic structure. The aim of the study was to determine the impact of progressively increasing metal artifacts on the measurement accuracy of commonly evaluated points in implant treatment planning. Materials and methods: Holes were drilled into porcine mandibles at known distances from the alveolar crest on the buccal and lingual surfaces and filled with gutta-percha. Repeated CBCT images were taken, with progressively increasing amalgam restorations and stainless steel crowns (up to a total of eight restorations per jaw). The imaging field of view (FOV) was of a single site (5 × 5 cm²) in two different locations in the mandible, as well as a full-arch FOV (10 × 5 cm²). Images were taken using clinical settings, and with increased kVp and exposure time, without metal artifact reduction (MAR) corrections. Measurements between the buccal and lingual gutta-percha points on the mandible were performed using a digital caliper and compared to the same measurements taken digitally on the CBCT images. Measurements were obtained with no restorations (baseline) and compared with increasing number of restorations. Results: Comparison between caliper measurements and baseline CBCT with no metal artifact demonstrated differences ranging from 0 to 1.7 mm, with no clear detectable pattern of change related to the restorations. Compared to baseline measurements, scans with amalgam and stainless steel restorations showed a maximum difference of 0.54 ± 0.64 mm and 0.62 ± 0.64 mm, respectively, with no significant differences with increasing metal restorations. Conclusion: There may be a variation of up to 1.7 mm between measured anatomical points and CBCT imaging under commonly used settings. While this result may be clinically important, it does not appear to be affected by increasing metal artifact due to amalgam restorations or stainless steel crowns. The findings of this study support current clinical practices accounting for a safety margin of up to 2 mm with any CBCT image, and not limiting CBCT scans for patients with multiple metal restorations. Keywords: dental cone beam computed tomography, measurement accuracy, metal artifact

Purpose: Strains transferred to the supporting simulated bone structure by implant-supported full-arch fixed dental prostheses (FAFDPs) were analyzed by digital image correlation (DIC). Materials and methods: Polyurethane models were made using 3.75 × 11-mm implants and divided into the following groups with different implant numbers and design: EH5 (five implants/external hexagon), MT5 (five implants/internal taper), EH4 (four implants/external hexagon), and MT4 (four implants/internal taper). Both qualitative and quantitative (one-way analysis of variance [ANOVA] statistical comparison) analyses were performed by the DIC method after the application of a 250-N load in the central fossa of the mandibular first molar. Different regions of interest were selected in the polyurethane model for comparison between groups. Results: Compressive strains were found in the cervical region of the models, and tensile strains were found in the apical region of the models. Significant differences were found in the different analyzed regions of interest for the different number of supporting implants and implant designs (P < .05). Conclusion: Groups with five implants showed more regions with less strain concentration compared to groups with four implants, but strain distribution was similar between groups. The different tested implant designs showed similar strain concentration and distribution to the supporting structures. Keywords: dental implants, digital image correlation method, full-arch fixed dental prostheses, stress analysis

Purpose: The goal of this study was to assess the effect of a liquid platelet-rich fibrin (PRF)-coated implant surface (double acid-etched) on osseointegration, analyzing the stability and the possibility of shortening the rehabilitation period. Materials and methods: Initially, the blood was centrifuged to obtain the liquid PRF (2,000 revolutions per minute [rpm], 10 minutes), dividing a sample to be analyzed by Luminex, and another was applied onto the implant surface. Fifteen patients (30 implants) were divided into two groups (control and liquid PRF). Following the recommendation provided by the manufacturer, within a controlled torque at a maximum of 34 N.mm, the implant was placed. All patients had 1 year of follow-up. Results: Eleven analytes were identified for the sample characterization (IP-10, eotaxin, RANTES, macrophage inflammatory protein 1-beta [MIP-1β], VEGF, PDGF-BB, bFGF, IFN-γ, interleukin [IL]-5, IL-10, and IL-15). Regarding clinical evaluation, for control and liquid PRF groups, respectively, (1) the mean torque for implant placement was 26.67 and 27.27 N.mm; (2) the initial stability (implant stability quotient [ISQ]) was 64.87 (SD ± 6.01) and 67.36 (SD ± 7.21); (3) the final ISQ was 67.67 (SD ± 6.13) and 70.14 (SD ± 6.40); (4) it took an average 73 and 71 days to reestablish the masticatory function; (5) the survival rate was 93.3% and 86.6%; and (6) the marginal bone loss was up to 1.0 mm after 1 year (control)-for two patients, it was between 1.0 and 2.0 mm, and for another two subjects, it was up to 1 mm (liquid PRF). No statistical significance was observed for all parameters analyzed (P > .05). Conclusion: Within the limitations of this study, the results indicated that there was no statistical significance when liquid PRF was applied on the implant surface, for all parameters. Keywords: autologous platelet concentrate, clinical trial, implants, osseointegration, platelet-rich fibrin, surface

Purpose: The aim of this pilot study was to compare three surgical techniques (bicortical fixation, unicortical fixation, and indirect sinus elevation) for implant placement in the posterior maxilla with limited alveolar bone height. This 2-year follow-up assessment on the implants of a previously published prospective clinical trial compared (1) restoration/implant stability among the three surgical groups, (2) intrasinus bone formation between the bicortical fixation and indirect sinus elevation groups, and (3) implant and prosthetic complications reported among the three groups. Materials and methods: For the original prospective study, 38 patients were recruited, exhibiting 7 to 11 mm of alveolar bone coronal to the sinus floor as confirmed by preoperative CBCT, and 45 implants were placed using three randomly assigned surgical techniques. No patient received more than two implants, which were placed in opposite sides of the maxilla and using different surgical techniques. At the 2-year follow-up assessment, 32 patients with 37 implants were evaluated. The 2-year follow-up restoration/implant stability was measured with the Periotest stability measuring device. Intrasinus bone formation was measured from the 2-year follow-up CBCT in comparison to the preoperative CBCT. Clinical examination was also performed to identify loose implants and/or implant crowns and signs of peri-implantitis. Patients were interviewed regarding complications experienced with the study implants/restorations, and electronic charts were thoroughly reviewed to identify records of complications. Results: No significant difference in restoration/implant stability (Periotest value [PTV]) was seen between the bicortical fixation, unicortical fixation, and indirect sinus elevation groups (-1.69 [0.80], -1.76 [0.80], -2.22 [0.60], respectively, P = .76) at the 2-year follow-up. The indirect sinus elevation group showed more intrasinus horizontal (1.99 [0.17] vs 1.47 [0.16] mm, P = .03) and vertical (3.15 [0.43] vs 2.35 [0.38] mm, P = .13) bone gain compared with the bicortical fixation group. Conclusion: Within the limitations of this study, placing implants using a bicortical fixation surgical technique in moderately limited alveolar bone height (7 to 11 mm) was not significantly different from the other two techniques and may be a feasible option with limited risks while allowing longer implant placement and negating the need for indirect sinus augmentation, which is accompanied by additional expense and surgical morbidity to the patient. Keywords: bicortical fixation, intrasinus bone formation, sinus elevation

Purpose: This study aimed to evaluate clinical and prosthetic outcomes of metal-ceramic and polyether ether ketone (PEEK) fixed prostheses supported by four maxillary implants and opposed by distal extension removable partial dentures. Materials and methods: Thirty participants with edentulous maxillary and distal extension mandibular ridges received four implants according to the All-on-4 treatment concept. The implants were immediately loaded by fixed acrylic prostheses. After 6 months, patients received either metal frameworks covered with porcelain teeth (metal group) or PEEK framework veneered with composite teeth (PEEK group). Plaque Index (PI), Gingival Index (GI), pocket depth (PD), implant stability quotient (ISQ), peri-implant marginal bone loss (MBL, using digital periapical radiographs), and implant survival were measured at baseline, 1 year, and 3 years. Prosthetic complications were measured on the patient and implant levels after 3 years. Results: No implant failures occurred after insertion of the definitive prosthesis, and the implant survival rate was 100% in both groups. PI, GI, PD, ISQ, and MBL increased significantly with time. The most frequent complications were veneer fracture for the PEEK group and prosthetic screw loosening for the metal group. The metal group showed significantly higher PI, PD, and MBL than the PEEK group after 3 years. PEEK was associated with significantly higher veneer fracture than metal, while metal was associated with significantly higher prosthetic screw loosening than PEEK. Conclusion: Within the limitations of this study, the PEEK framework veneered with composite may be a suitable alternative to a metal porcelain prosthesis for All-on-4 implant rehabilitation in patients with maxillary edentulous arches opposed by distal extension mandibular ridges, as it was associated with favorable clinical and prosthetic outcomes after 3 years. However, it was associated with an increased rate of veneer or artificial gingiva fracture. Keywords: All-on-4, fixed prosthesis, implant, metal ceramic, PEEK

Purpose: To evaluate the short-term effect of dental implant placement, mucosa thickness, and their combined effects (initial biologic width) on marginal bone loss. Materials and methods: This was a retrospective study on patients who received implant surgery in the posterior region without bone augmentation surgery between 2012 and 2016, and implants had been loaded for more than 12 months. Each patient received radiographic examination before and after implant surgery, before the stage-two surgery, and during the 1- to 5-year follow-up. The thickness of mucosa, depth of dental implant placement, and crestal bone loss were evaluated on digital radiographs. The interaction was discussed by defining the combination of initial mucosal thickness and implantation depth as the initial biologic width. The implants were divided into four study groups based on the quartile of the initial biologic width. Results: This study included 266 patients (94 male and 172 female, 22 to 85 years of age, mean age: 51.43 years), with 413 dental implants placed including 239 Straumann implants and 174 Ankylos implants. The average follow-up was 21.50 months. After 1 to 5 years, the median crestal bone loss around implants was 0.35 mm (0.30 mm for Straumann BL and 0.40 mm for Ankylos). The implants were divided into four groups: group A (≤ 2.85 mm), group B (2.85 to 3.40 mm), group C (3.40 to 3.97 mm), and group D (> 3.97 mm). Group B showed significantly less crestal bone loss than group A (0.38 mm vs 0.25 mm; P < .05) and group C (0.25 mm vs 0.40 mm; P < .05) during the follow-up. Significantly more crestal bone loss around implants was observed in the thin mucosa group than in the thick mucosa group (0.50 mm vs 0.30 mm; P < .001), while implants placed beneath the bone level displayed a significantly higher amount of marginal bone loss than implants placed even with the bone crest (0.50 mm vs 0.10 mm; P < .001). Conclusion: The initial biologic width has an effect on crestal bone loss. When the initial biologic width was between 2.85 and 3.40 mm, the marginal bone loss was lowest. Based on radiographic evaluation, implants placed in thick gingiva and even with the bone level showed less alveolar marginal bone loss compared with implants placed in thin gingiva and below the crestal bone level. Keywords: biologic width, marginal bone loss, mucosal thickness, placement level

Purpose: The aim of this clinical study was to verify the predictability of the rehabilitation of extremely atrophic jaws with immediately loaded short implants and evaluate posterior mandibular regrowth. Materials and methods: A cohort of consecutive fully edentulous patients wearing complete dentures in both arches was enrolled. Periodically, implant survival and prosthetic success were assessed. After informed consent, a subsample of 10 patients who had preoperative CBCT underwent a postoperative CBCT 1 year after immediate implant loading, and 3D superimpositions of pre- and postoperative images were performed. Linear measurements of bone height were performed at two sites in each hemimandible and, on the same sections, bone density according to the qualitative gray values (GVs) was analyzed in an area of 3 mm² including the cortical mandibular bone. Results: Fifty-nine fully edentulous patients (31 females, 28 males) with Class VI atrophic mandibles according to Cawood and Howell were rehabilitated with the insertion of four to five short implants (4-mm diameter, 7- or 8.5-mm long). Overall, 251 implants were immediately loaded with a fixed hybrid prosthesis. Four patients did not show up for recall visits, bringing the final number down to 55 patients (31 females, 24 males) and 231 implants. In up to 14 years of follow-up, a total of 4 implant failures were recorded (cumulative survival rate, 98.4%). The biologic complications included 9 mucositis (3.9%) and 3 peri-implantitis (1.3%) at implant-level analysis. Mechanical complications involved 9 chippings of the prosthetic restorations (17.0%). In the 10-patient subsample, the analysis showed bone growth (average of 1.2 ± 0.7 mm) in the posterior areas of the mandible. In addition, bone density was found to increase 17% to 27% with reference to the preoperative CBCT. Conclusion: The immediate loading of short implants may represent a feasible therapeutic option for the treatment of fully edentulous patients with severely atrophic mandibles. Bone regrowth in the posterior areas and an increase in bone density of the mandible may occur. Keywords: atrophic mandibles, immediate implant loading, implant survival

Purpose: The purpose of this study was to show the full evolution of bone anchorage caused by the growth of secondary stability and to determine which empirical model would provide the best quantitative description of this growth. Materials and methods: The retention and anchorage of machined (M), grit-blasted and dual acid etched (BAE), and BAE implants with discrete crystals of calcium phosphate (+DCD) were evaluated with both ex vivo and in vivo methods. Ex vivo evaluation of implant retention was tested by measuring the force required to pull implants out of blood-filled osteotomies formed in bovine bone for up to 1 hour. In vivo measurements of bone anchorage were evaluated by reverse torque testing of implants placed in the proximal metaphysis of rat tibiae up to 28 days after initial placement. Four models were fit to the reverse torque results, and fits were evaluated by Bayesian and Akaike information criteria (BIC and AIC) and analysis of variance (ANOVA). Results: AIC and BIC were 655.53 and 684.78, 472.53 and 512.74, 477.40 and 513.96, and 470.60 and 507.16 for the monomolecular, Richards, Gompertz, and logistic curves, respectively. Comparison of the Richards and logistic curves by analysis of variance (ANOVA) resulted in a P value of .78. A comparison of the three implant types using the logistic curve found that M implants had an earlier inflection point compared with BAE implants (P = .038), and the BAE+DCD implants had the greatest peak anchorage and were significantly greater than both M (P < .0001) and BAE implants (P = .005). Conclusion: Bone anchorage was found to follow sigmoidal growth, which was best described by the logistic function. Further comparison of the fit values for the logistic curve shows that both overall anchorage and timing of bone anchorage are influenced by implant surface topography. Keywords: bone anchorage, empirical modeling, implant topography, mechanical testing, remodeling

Purpose: To summarize the methodologic quality and outcome measures from systematic reviews and meta-analyses evaluating the efficacy of different nonsurgical therapies for the treatment of peri-implant diseases. Materials and methods: Two review authors independently searched for systematic reviews and meta-analyses evaluating the efficacy of different nonsurgical therapies for treatment of peri-implant diseases in three different databases: MEDLINE, Embase, and the Cochrane Library. In addition, journals with a high impact factor in the fields of periodontics, prosthodontics, oral maxillofacial surgery, and implant dentistry were analyzed for potential reviews. The search was implemented from January 2010 through August 2020. Eligible reviews were screened and assessed to determine the characteristics and outcome measures. Furthermore, two review authors independently evaluated the methodologic quality by using the AMSTAR tool and the checklist proposed by Glenny et al. The interrater agreement was assessed by using the Cohen kappa coefficient. The assessment of correlation between the findings of the AMSTAR tool and Glenny et al checklist was performed by using the Spearman correlation. Results: Fifteen systematic reviews and 12 meta-analyses were evaluated based on the inclusion criteria. One review investigated the efficacy of growth factors and another investigated glycine powder air polishing, 5 evaluated the role of antimicrobial photodynamic therapy, 8 assessed the effect of laser therapy, and 13 compared the different nonsurgical therapies with the surgical therapies for the treatment of peri-implant diseases. The quality assessment score evaluated by the AMSTAR checklist ranged from 5 to 11 with a mean of 7.5 ± 1.8, whereas the score evaluated by the Glenny et al checklist ranged from 3 to 14 with a mean of 9.7 ± 2.8. Spearman correlation analysis between these two tools reported a high correlation (r = 0.91) that was statistically significant (P < .001). Conclusion: The summarized evidence of this overview shows that the different nonsurgical therapies are effective for the treatment of peri-implant mucositis. The lack of sufficient long-term data involving large datasets results in their inconclusive efficacy in the treatment of peri-implantitis. However, the summary is determined from the moderate quality of evidence. Hence, future well-designed high-quality trials are encouraged to reassess the findings. Keywords: AMSTAR, dental implant, evidence-based dentistry, Glenny, nonsurgical therapy, peri-implantitis, systematic review

Purpose: To investigate whether titanium mesh exposure is influenced by the type of titanium mesh, the type of bone graft material, or the associated employment of absorbable membranes. Materials and methods: Electronic literature searches were conducted using four databases: PubMed, EMBASE, Web of Science, and Cochrane. Articles reporting titanium mesh exposure rates were included, and exposure rates in different subgroups were compared to determine whether a factor significantly influenced titanium mesh exposure. The review protocol was registered in the PROSPERO registry (CRD42020210187). Results: Twenty and 12 articles were included in the qualitative and quantitative synthesis, respectively. The weighted exposure rates of employing conventional titanium mesh or 3D-customized titanium mesh were 19.9% and 15.2% (P = .34). When employing autogenous bone combined with anorganic bovine bone material as bone graft material, the weighted exposure rate was 21.7%, whereas when using other bone graft material, the exposure rate was 23.5% (P = .74). The weighted exposure rate of using titanium mesh associated with absorbable membranes is 23.9%, while the weighted exposure rate of using titanium mesh without absorbable membranes is 20.2% (P = .36). Meta-regression showed that when analyzing one factor, the other two confounding factors did not influence the result (P = .28). Conclusion: It seemed that the type of titanium mesh, the type of bone graft material, or the combined employment of absorbable membranes did not statistically significantly influence the titanium mesh exposure rate in guided bone regeneration. Keywords: exposure, guided bone regeneration, influence factor, systematic review, titanium mesh