The International Journal of Oral & Maxillofacial Implants, 03/2022

Purpose: The results of trials can inform health care decisions. However, this is dependent on both clear and transparent reporting. The aim of this study was to assess the reporting quality of split-mouth trials in implant dentistry in relation to the CONSORT extension checklist for reporting within-person randomized clinical trials (RCTs). Materials and methods: Split-mouth trials published between January 1, 1997, and September 30, 2020, were identified from four databases. Study characteristics at the level of each trial were extracted. Each trial was assessed against a 37-item checklist and assigned one of four categories. Descriptive statistics and the frequencies of the ratings per checklist item were calculated. A percentage score was calculated per study. Linear regression assessed associations between the aggregate score and the study characteristics. Results: Two hundred forty-four trials were analyzed. More than 50% of the RCTs were published between 2016 and 2020, were published in specialty journals (81.2%), and were interventional-type RCTs (98.4%). Generally, the reporting of checklist items was suboptimal in many areas. The reporting score was predicated by the number of authors (> 7 vs baseline [1 to 4] authors: β: 6.00; 1.48, 10.52; P = .01), authors' continent (Europe vs Americas: β: 5.30; 0.85, 9.74; P = .02), and the number of participants (per-unit increase: β: .07; 0.01, 0.12; P = .02). Conclusion: The reporting of split-mouth trials in implant dentistry seems to be suboptimal. The endorsement and adherence to the CONSORT extension for the within-person trials checklist by journal editors and investigators could improve reporting quality and transparency. Keywords: data reporting, dental implants, methods, randomized controlled trial, research design

Purpose: To assess the cumulative failure rate of 4,842 implants comprising six commercial implant brands in a university setting, and to evaluate the influence of different risk factors on the implant failure rate. Materials and methods: A retrospective chart review was conducted in patients receiving dental implants at the School of Dentistry of the International University of Catalonia (Barcelona, Spain) from 2011 to 2018. The inclusion criterion was patients presenting at least one failed implant. Results: The cohort study included 1,510 patients who received a total of 4,842 implants. The cumulative failure rate was 4.9% and 10.8% at the implant and patient levels, respectively. The multiple regression analysis showed that for the same number of implants per patient, variables such as age and sex were not associated with higher implant failure rates. Furthermore, in considering the combination of arch-sector, a statistically significant reduction in failure rate was observed in the posterior maxilla (OR = 0.66, P = .038) and in the posterior mandible (OR = 0.64, P = .037). The results showed all implant brands offering high implant survival rates (> 91%). Nobel Biocare and Straumann implants significantly reduced the risk of implant failure (OR = 0.37, P = .021 and OR = 0.53, P = .024, respectively), while no significant differences were recorded among Klockner (2.8%), MIS (5.4%), Biomet 3i (7.1%), and Astra Tech (8.4%; P ≥ .05). No association was found between implant loss and bone augmentation, time of implant placement, smoking, and history of periodontal disease. Conclusion: The implant failure rates obtained in a university setting resulted in overall cumulative rates of 4.9% and 10.8% at the implant and patient levels, respectively, over a 7-year period. Male sex and implants placed in the anterior mandible may be associated with a higher risk of implant failure. Nobel Biocare and Straumann implants seem to positively affect implant survival rate. Keywords: adult, dental implants, retrospective studies, risk factors, survival rate

Purpose: The aims of this study were to determine the accuracy and repeatability of CBCT for assessing gingival thickness (GT) as compared to transgingival probing and to investigate the correlation between GT and labial bone defects. Materials and methods: This cross-sectional study comprised 37 patients who underwent CBCT imaging. A total of 111 sites were examined, and measurements were obtained from the same points on selected index teeth. The GT was measured, and the presence of dehiscence and fenestration defects was evaluated on the CBCT scans. Transgingival probing was performed at the same points as those used on the scans. Intraexaminer reliability for clinical and radiographic measurements and interexaminer reliability for radiographic measurements were tested. Agreement between the measurement methods and the correlations between GT and labial bone defects were assessed using intraclass correlation coefficient (ICC) and chi-square test, respectively. Results: The agreement between both measurement methods was excellent and statistically significant (ICC = 0.888; P < .001), with a bias of 0.04 (95% CI: 0.01 to 0.08). Significant differences in the occurrence of fenestration (P = .023) and dehiscence defects (P < .001) between the thin and thick gingival phenotypes were observed, and the defects were positively correlated with the thin gingival phenotype. Conclusion: CBCT demonstrated high diagnostic accuracy for GT measurements, with minimal discrepancies from the transgingival method. The presence of dehiscence and fenestration defects was positively correlated with thin gingival phenotype. Keywords: cone beam computed tomography, dehiscence, fenestration, gingival phenotype, gingival thickness, transgingival probing

Purpose: The aim of this retrospective study was to introduce a novel technique of a double-scan protocol with markerfree registration and compare it to the already-used techniques regarding the accuracy of registration. Materials and methods: Fifty-nine fully edentulous patients underwent double-scan procedures by three different methods: the barium sulfate method for 11 patients; the gutta-percha method for 26 patients; and the marker-free method for 22 patients. Point-to-point registration of the two scans was followed by a voxel-based surface "best fit" registration. The mean registration error of each case was digitally recorded. Differences in registration error between groups were evaluated using one-way analysis of variance (ANOVA). Results: The accuracy of the registration showed no significant differences according to the method (P = .719). Conclusion: The marker-free procedure was presented as a novel technique for registration of the scans in the double-scan protocol. There was no significant difference in the accuracy of the registration between the three techniques: marker-free, gutta-percha markers, and fully radiopaque barium sulfate scan appliance. Therefore, the marker-free technique might be a viable option for the double-scan protocol. Keywords: 3D, CAD, computer-guided surgery, prosthetic procedure, radiology

Purpose: The increasing popularity of desktop 3D printers makes guided surgery more accessible. The aim of this in vitro study was to evaluate the accuracy of single-tooth guided implant surgery by means of a 3D-printed tooth-supported guide. Materials and methods: Fifteen implants were virtually planned to replace a missing first mandibular molar, using planning software for guided implant surgery (Exoplan, Exocad). A tooth-supported guide was designed and manufactured using a desktop 3D printer (Asiga MAX UV). The implants were placed fully guided in resin casts, and a digital impression was taken to register their position. This scan was compared with the virtual implant position in the planning software, and the internal fit of the guides was evaluated using metrology software. One planning was executed six times for measuring precision. Results: For trueness, the mean angular deviation was 2.63 degrees (SD: 1.69 degrees; range: 0.38 to 5.99 degrees), the mean coronal deviation was 0.52 mm (SD: 0.25; range: 0.09 mm to 1.07 mm), and the mean apical deviation was 0.90 mm (SD: 0.47; range: 0.14 to 1.74 mm). The absolute apical mean deviation in the buccolingual direction (x-axis) was 0.70 mm (SD: 0.42, 0.12 to 1.65 mm; P < .001); in the mesiodistal direction (y-axis), it was 0.34 mm (SD: 0.26; range: 0.01 to 0.80 mm; P = .650); and in the vertical direction (z-axis), it was 0.32 mm (SD: 0.27; range: 0.02 to 1.00 mm; P = .010). The mean internal fit of the guides was 79.5 μm (SD: 19.6 μm; range: 51 to 118 μm). Conclusion: Desktop 3D-printed tooth-supported guides demonstrate an acceptable fit and acceptable level of accuracy for single implant placement. Keywords: 3D printing, 3D-printed surgical guide, accuracy, dental implants, edentulous mandibular, guided surgery, intraoral scan, single implant

Purpose: Poor alveolar bone quality and quantity may cause low insertion torque during implant placement; therefore, a delicate occlusal design is important for the immediate loading procedure. This retrospective clinical study aimed to investigate (1) the proportion of implants with a low insertion torque between the maxilla and mandible, (2) factors affecting implants with a low insertion torque, and (3) survival rates of implants with a low insertion torque value (< 35 Ncm) using different occlusal designs with full-arch fixed prostheses supported by immediately loaded implants. Materials and methods: Between 2013 and 2017, patients who received full-arch reconstructions were treated with immediately loaded one-piece fixed prostheses supported by four to six implants. Full-arch fixed prostheses with at least one immediately loaded regular implant with a low insertion torque value were included in this study. The fixed provisional acrylic prosthesis with a rigid framework was delivered within 3 to 5 days after surgery. According to the distribution of implants with low insertion torque, provisional prostheses were divided into three groups with different occlusal schemes. Definitive prostheses were fabricated after 3 months of loading. Results: A total of 144 patients were treated; 608 and 304 regular implants were inserted in 118 maxillae and 76 mandibles, respectively. Moreover, 42 patients (11 men and 31 women) with 39 maxillae and 4 mandibles were included in this study. The proportion of implants with low insertion torque values in the maxilla was significantly greater than that in the mandible (10.5% vs 1.6%, respectively, P < .001). Implant length and low insertion torque value had no significant correlation (P = .948). Implants with a 3.3-mm diameter (narrow platform) had a greater proportion of low insertion torque values than 4-mm-wide implants (P = .002). Implants placed in a fresh socket had a greater proportion of insertion torque values ≥ 35 Ncm (P = .023). The overall cumulative implant survival rate was 98.6%. Groups 1, 2, and 3 had 14, 23, and 6 provisional prostheses, respectively. The survival rates for implants with insertion torque values < 35 Ncm and ≥ 35 Ncm were 98.4% and 98.7%, respectively, and were not significantly different (P = .866). All prostheses were still functioning during the mean follow-up of 3.7 ± 1.2 years. Conclusion: The high cumulative implant survival rate indicated that implants with a low insertion torque in immediately loaded full-arch provisional prostheses did not jeopardize the outcomes after a corresponding occlusal scheme was used. Keywords: dental implant, full-arch fixed prosthesis, immediate loading, low insertion torque, occlusal scheme

Purpose: This study examined the effect of dental implant rehabilitation on masticatory function following jaw reconstruction. Materials and methods: Patients who received dental rehabilitation after jaw reconstruction with a fibular or iliac bone flap from 2012 to 2018 were examined for masticatory efficiency, electromyographic (EMG) activity of the masticatory muscles, and the distribution of occlusal force. The masticatory efficiency was measured by a spectrophotometer. The asymmetry index of the masticatory muscle was calculated by EMG measurement, and the asymmetry index of the occlusal force was calculated by T-scan analysis. Results: A total of 32 patients were examined, 13 with implant-retained fixed dental prostheses, 9 with implant-retained removable dental prostheses, and 10 with removable dental prostheses. Masticatory efficiency was significantly lower in the removable dental prosthesis group (2.29 ± 0.19) than in the implant-retained removable dental prosthesis (2.45 ± 0.03, P < .05) and implant-retained fixed dental prosthesis groups (2.45 ± 0.03, P < .05). Moreover, the asymmetry index of the masticatory muscle while chewing and clenching was significantly higher in the removable dental prosthesis group (0.099 ± 0.046 and 0.107 ± 0.042, respectively) than in the implant-retained removable dental prosthesis (0.032 ± 0.019 and 0.035 ± 0.021, respectively; P < .01) and implant-retained fixed dental prosthesis groups (0.038 ± 0.021 and 0.046 ± 0.023, respectively; P < .01). The asymmetry index of the occlusal force was also significantly higher in the removable dental prosthesis group than in the implant-retained removable dental prosthesis (0.38 ± 0.08, P < .01) and implant-retained fixed dental prosthesis groups (0.36 ± 0.11, P < .05). Conclusion: The results of this study suggest that dental implant prostheses have a greater effect on masticatory function following jaw reconstruction, improving masticatory efficiency, EMG activity of the masticatory muscles, and occlusal force. Keywords: dental implants, dental rehabilitation, jaw reconstruction, masticatory function

Purpose: The aim of this study was to investigate the association of hypertension and antihypertensive drugs with the failure of osseointegrated dental implants. Materials and methods: This study conformed to STROBE Guidelines regarding retrospective studies. Data from 602 medical records of patients who received rehabilitation treatment with osseointegrated implants between 2000 and 2017, completed at least 6 months before the study, were analyzed. Data on age, sex, presence or absence of hypertension, use or not of antihypertensive drugs, number of placed and lost implants, and type of prosthetic rehabilitation were collected. Statistical chi-square tests and the Fisher exact test were used to analyze the variables with implant loss, using a significance level of P < .05. Results: One thousand eight hundred eighty-seven implants were placed with a success rate of 97.51% (47 implants lost in 41 patients). Of the 602 patients, 71.43% (432) were normotensive and 28.36% (171) were hypertensive. The success rate of implants in the normotensive group was 93.28%, and in the hypertensive group, it was 92.99%, with no statistical difference between the groups (P = .958). Of these patients, the success rate among the hypertensive group was similar for medication users (92.5%) and for nonusers (94.1%), with no statistically significant difference (P = .939). Conclusion: The presence of hypertension, as well as the use of antihypertensives, could not be associated with the failure of osseointegrated implants. Keywords: antihypertensive agents, dental implantation, hypertension, survival rate

Purpose: The aim of this pilot exploratory cohort study was to assess the value of buccal augmentation in immediate implant placement and immediate restoration of anterior teeth in maxillae with missing buccal lamellar bone with regard to esthetic parameters, as well as soft and hard tissue level changes. Materials and methods: This study compared three groups of 10 patients each with immediate implant placement and immediate restoration in the anterior maxilla: (1) patients with partially to totally missing buccal bone with simultaneous augmentation with bovine collagen (test group augmented [TGA]); (2) patients with partially to totally missing buccal bone without augmentation (test group nonaugmented [TNA]); and (3) patients with intact buccal lamellar bone (control group [CG]). The pink esthetic score (PES) and the course of the peri-implant bone level after 1, 3, and 12 months were used as assessment criteria. Results: After 12 months, the PES in the TGA was assessed as being better than it was preoperatively (mean ± SD: 8 ± 3.09 vs 9.25 ± 3.01, respectively, P = .8243), while it remained almost identical in the other two groups (TNA = 8.75 ± 2.7 vs 8.6 ± 3.3, P = .4098; CG = 10.6 ± 2.41 vs 10.6 ± 2.22, P = .7085). A significant difference among the PES values of the three groups was not observed at any point in time (preoperative: P = .118, 12 months: P = .383). In total, the TNA and CG showed an improvement in 3 out of 7 parameters of the PES after 12 months, while this was the case in 5 out of 7 parameters in the TGA. No significant difference among the three groups could be seen at any time point regarding peri-implant bone level. In the CG and TGA patients, a nonsignificant improvement in peri-implant bone level was seen after 12 months (respectively: 1.6 mm to 0.99 mm; P = .08068; 1.89 mm to 1.73 mm; P = .5866). In contrast, TNA patients showed a nonsignificant deterioration vs the postoperative situation (1.16 mm to 1.45 mm; P = .08208). Conclusion: Within the limitations of this pilot study, it can be concluded that a missing buccal lamellar bone appears to be no contraindication for immediate implant placement and immediate restoration, provided the baseline esthetic situation is accepted. As compared to the nonaugmented defect group or the group with intact lamellar bone, neither the esthetic nor the radiologic results could be improved significantly by augmentation with bovine collagen. Keywords: buccal bone defects, esthetic zone, flapless implant surgery, immediate implants, immediate loading, maxilla

Purpose: The aims of this study were: (1) to quantify the marginal bone loss (MBL) of 3.3-mm narrow-diameter, bonelevel, titanium-zirconia (Ti-Zr) implants with two different surfaces in single restorations after a 1-year follow-up; (2) to analyze the combinations of different variables that may influence MBL; and (3) to record the Pink Esthetic Score (PES) value and its correlation with MBL. Materials and methods: This is a prospective longitudinal clinical study with a 1-year follow-up after crown placement. Two different implant surfaces (sandblasted acid-etched and modified sandblasted acid-etched) were used. All bone-level and bone level-tapered implants had a diameter of 3.3 mm. Different healing and prosthetic abutments were used. Clinical, radiographic, and photographic records were taken 6 months and 1 year after placement of the restorations, and the survival rate, MBL, PES, clinical parameters, and biologic and/or mechanical complications were assessed. The correlations between the variables and MBL were verified. Results: A total of 30 narrowdiameter implants were placed in 30 patients; 18 implants had a sandblasted acid-etched surface, and 12 implants had a modified sandblasted acid-etched surface. The measured MBL at 1 year after implant function had a mean value of -0.36 mm, ranging from 0 mm to -1.77 mm. There was no implant loss. A statistically significant relationship was observed between implant shape (design and length), implant placement level, healing abutment, prosthetic abutment size, gingival thickness, and MBL. The mean PES values recorded at the beginning and end of the study were 7.58 and 11.37, respectively. Conclusion: Narrow-diameter implants showed reduced MBL values, with the surrounding tissues remaining stable after 1 year of follow-up. The MBL did not show different values on two implant surfaces. MBL does not seem to influence esthetic outcome. Keywords: dental implants, marginal bone loss, narrow-diameter implants, pink esthetic score

Purpose: This study aimed to assess the influence of implant diameter and taper on the proximity of virtually planned maxillary central incisor implants to the nasopalatine canal and adjacent anatomical structures. Materials and methods: Virtual implant planning was performed in the maxillary central incisor position. The distance between the implant and the incisive canal (IC) and the thickness of the surrounding buccal and palatal bone walls were measured. Implants were categorized as having an exposed implant surface, thin bone, or moderate/thick bone. Measurements were repeated for regular-/narrow-diameter and parallel/tapered implants. Results: A total of 60 patients were included, and 240 implants (60 of each type: 3.3-bone level [BL], 3.3-bone level tapered [BLT], 4.1-BL, and 4.1-BLT) were planned. The percentages of implants with between 0 and 0.5 mm of remaining bone in the coronal aspect of the IC were 31.6% for 4.1-BL/BLT and 6.6% for 3.3-BL/BLT (P < .001). The percentage of implants with IC exposure was 13.3% for 4.1-BL/BLT and 6.6% for 3.3-BL/BLT (P < .001). The frequency of sites that required bone augmentation at the coronal facial aspect (< 1 mm) was 52.6% and 33.9% for 4.1-BL/BLT and 3.3-BL/BLT, respectively. At the apical portion, the percentages of sites requiring bone augmentation at the facial aspect were 59.9%, 49.9%, 31.6%, and 23.3% for 4.1-BL, 3.3-BL, 4.1-BLT, and 3.3-BLT, respectively (P < .001). Conclusion: The proximity of the nasopalatine canal is often < 0.5 mm from regular-diameter virtually planned implants at the most coronal aspect in the maxillary central incisor position. In these situations, the selection of narrowdiameter implants significantly lowers the incidence of implant exposure and the need for additional management of the nasopalatine canal and also results in greater residual buccal and lingual bone thicknesses surrounding the implant. As expected, tapered implants reduced the risk of implant exposure through the buccal cortex at the apical aspect. Keywords: diagnostic procedure, epidemiology, single implant, virtual reality

Purpose: To determine the fracture strength and stress distribution of esthetic dental implant abutments. Materials and methods: Fifty specimens were prepared. Four hybrid abutment groups with titanium bases (zirconia [Z], lithium disilicate [L], ceramic-reinforced polymer [B] and [BC]) and a custom titanium abutment control group (T) were restored with monolithic zirconia crowns except BC, which was crowned with layered composite. Ceramic abutments were cemented on Ti bases with a self-curing resin cement. Polymer abutments were cemented on Ti bases with an adhesive resin cement. All crowns for T, Z, and L were cemented with another self-adhesive resin cement, while the B and BC groups were cemented with the same adhesive resin cement for the polymer. Fatigue testing was performed by a chewing simulator (CS-4.2, SD, 50 N, 240,000 cycles) followed by fracture strength testing (0.5 mm/min, 5,000 N). Failure type analysis was made by a stereomicroscope. Statistical analyses were made (SPSS 25.0, analysis of variance [ANOVA], Tukey honestly significant difference [HSD], 95% CI). Complementary finite element analyses (FEAs) were performed (Algor Fempro). Results: Mean ± SD fracture strengths for T, Z, L, B, and BC were 1,522.67 ± 190.77, 1,207.76 ± 89.03, 818.81 ± 109.96, 1,126.23 ± 142.23, and 899.08 ± 60.36, respectively (P < .05). Abutment screw flexure and/or cracks or crown material fractures for T, Z, L, and B occurred, while no implant and/or abutment fractures were observed for BC except for crown fracture and Ti base flexure. FEA exhibited similar stress concentrations. Conclusion: Monolithic zirconia crowns on titanium abutments and hybrid zirconia abutments exhibited the highest fracture strengths. Lithium disilicate and BioHPP abutments had the lowest fracture strength, while no fractures were observed on the implant, abutment, or screw. Keywords: chewing simulator, dental implant, finite element analysis, fracture strength, hybrid abutment

Purpose: The primary stability of dental implants is one of the most crucial factors for providing long-term success of osseointegration. Vertical deficiencies, such as those due to maxillary sinus pneumatization, may cause a severe vertical limitation to residual bone height. This study aimed to examine the primary stabilization of implants without apical contacts. Materials and methods: Eighty bone-level implants (4.1-mm diameter/10-mm length) were placed into polyurethane test blocks without apical contacts. According to coronal bone-to-implant contact, groups were set as 4, 6, 8, and 10 mm, respectively. Resonance frequency analysis (RFA) using a SmartPeg was performed separately toward the transversal and horizontal axes by two independent researchers. Data were statistically compared for interobserver and among groups. Results: Interobserver reliability varied from moderate to excellent (intraclass correlation coefficient [ICC]: 0.629 to 0.985). There were no significant differences among the 6 mm, 8 mm, and 10 mm groups, although the 4 mm group showed the significantly lowest stability (P < .001). Transversal and longitudinal measurements of the same groups did not show a parallel correlation statistically. Conclusion: RFA values may be affected by the finger torque in tightening of the SmartPeg among different researchers. Fully placed implants did not significantly show the highest stability among various apically contactless groups. Consequently, RFA should not be used alone to evaluate primary stability for implants without an apical contact. Keywords: apically contactless, dental implant, primary stability, resonance frequency analysis

Purpose: The objectives of this in vitro study were to evaluate changes in the retention force of the indexed conometric system subjected to repeated insertion-removal cycles and to examine the elements (matrix and patrix) that cause retention changes in the system as a result of repeated cycles. Materials and methods: Monolithic zirconia crowns were cemented on 24 matrixes and 24 patrixes fixed on the implant analog. The pull-out test was performed with 12 matrixes and 12 patrixes attached, and the initial retention forces were recorded. Six of them were subjected to five insertion-removal cycles (5-cycle group), and the other six samples to 15 cycles (15-cycle group), and the final retention forces were calculated. Then, in both groups, an element of each pair exposed to the cycle was matched by an exchanging with new pieces: 5 cycles of matrix-new patrix (5M/0P), 5 cycles of patrix-new matrix (5P/0M), 15 cycles of matrix-new patrix (15M/0P), and 15 cycles of patrix-new matrix (15P/0M); thus, subgroups were created. A pull-out test was applied to these subgroups, and retention forces were recorded. Data were subjected to a paired-samples t test (α = .05). Two specimens from the 15-cycle group were randomly selected and analyzed by scanning electron microscopy. Results: In the 5-cycle group, the mean initial retention force was 153.13 ± 7.08 N, and the mean final retention force was 111.59 ± 18.30 N. In the 15-cycle group, the mean initial retention force was 143.30 ± 15.46 N, and the mean final retention force was 78.55 ± 17.03 N. There was a statistically significant loss of retention in both groups (P < .05). The change in retention in the 5P/0M and 15P/0M subgroups was not statistically significant (P > .05). However, significant loss of retention was found in the 5M/0P and 15M/0P subgroups (P < .05). Conclusion: There was a significant loss of the retention force after insertion-removal cycles. The increase in these cycles caused a further decrease in retention force. The decrease in the retention force of this system mainly resulted from the changes in the surface characteristic of the frictional surfaces of the matrix. Keywords: conometric concept, double crown, insertion-removal cycle, matrix, patrix, retention

Purpose: The aim of this study was to measure and compare the retention degrees of different attachment systems before and after 1 year of mastication and removal/insertion simulations. Materials and methods: A 4 × 10-mm implant embedded in self-curing acrylic resin was placed inside a rectangular metal frame installed in a plastic container with artificial saliva at 37°C. Three different attachment systems were connected to the implants: Dalbo Classic, Locator (with blue, pink, and clear inserts), and Klockner Rotula. A loading test at 100 N and 1.25 Hz frequency was repeated 10 times for each attachment (changing the matrix component or plastic insert) until a total of 300,000 cycles and 1,095 removal/ insertion sequences. The retention force was assessed at baseline until the end of the test (1 year) after 3-month intervals of simulation. One-way analysis of variance (ANOVA) and post hoc Tukey test (P < .05) were performed for statistical analyses. Results: Klockner Rotula showed the highest retention values at the beginning (69.6 ± 9.2 N; 7.1 ± 0.9 kg) and the end of the test (51.4 ± 5.4 N; 5.2 ± 0.6 kg), while Dalbo Classic showed the lowest values both at the beginning (13.1 ± 1.7 N; 1.3 ± 0.2 kg) and the end of the test (6.7 ± 1.6 N; 0.7 ± 0.2 kg). Locator with clear insert exhibited the lowest retention loss ratio (20.4%), while Locator with blue insert showed the highest (50.8%). At the end of the test, all attachment systems showed a significant decrease in retention force in comparison with the initial retention (P < .001). Conclusion: Locator attachments with clear and pink inserts and the Klockner Rotula attachment system showed retention forces > 20 N (2 kg) after 1 year of mastication and prosthesis insertion/removal simulation. All attachment systems showed a progressive loss of retention, which was higher for Locator attachments with blue and pink inserts and Dalbo Classic. The Klockner Rotula attachment system showed the highest retention values both at the beginning and the end of the test. Keywords: attachment, dental implants, overdenture, retention

Purpose: To determine the von Mises stress values of extramaxillary implants anchored in zygomatic bone, known as zygomatic implants, abutments, superstructures, and principal stress values of bone under occlusal forces and to compare them with tilted implants and sinus elevation concepts. The hypothesis of the study was that there would be higher stress on zygomatic implants under occlusal forces compared with tilted implants and the sinus elevation technique due to the more angled placement of the zygomatic implants. Materials and methods: Finite element analysis (FEA) was used to apply a force of 600 N (75 N premolars and 150 N first molar) vertically and at an angle of 20 degrees to the hybrid prosthesis with three different concepts-zygomatic implants, tilted implants, and sinus elevation-in D2 bones in six separate models. The posterior implants were tilted in zygomatic implant models (45 degrees) and tilted implant models (30 degrees). The von Mises and principal stress values formed in the models were compared by FEA. These values were also compared with the physiologic stress limit of the bone. Results: In the zygomatic implant models, the von Mises stress values on both anterior and posterior implants were less than other models under both loading conditions. In addition, the lowest principal stress values were seen in these models. The highest von Mises stress among all models was found to be posterior implants in tilted implant models under oblique loading. In addition, the highest principal stress values were seen at posterior implants in the sinus elevation model under oblique loading. Vertical loading was found to induce less stress than loading at a 30-degree angle. Conclusion: Although zygomatic implants have a more angled placement, the stress values on the bone and implants are lower. Keywords: finite element analysis, sinus elevation, tilted implant, zygomatic implant

Purpose: To evaluate the effects of vertical compressive cyclic load on abutment screws and the stability of screw-retained splinted fixed dental prostheses supported by bone-level nonengaging and partially engaging abutments. Materials and methods: Ten standardized two-unit prostheses integrated with nonengaging and partially engaging abutments were 3D-printed and cast in nonprecious metal and attached to two implant analogs with conical connections angled 15 degrees toward the vertical axis in a resin bock. The common path of insertion for the prosthesis with partially engaging abutments to angled implant analogs was created by selectively reducing the abutment surface that obstructed the implant housing. A 500-N average load was applied to each sample while oscillating 30 degrees from the vertical axis at 60 Hz to failure. Prosthesis stability was measured by deflection from the initial position using a linear displacement measuring device. Sample groups were assessed using the independent-samples t test and one-way repeated-measures analysis of variance (ANOVA) with post hoc tests. Results: The mean cycles to failure for nonengaging and partially engaging abutment groups were 27,180 ± 29,420 and 457,890 ± 265,734, respectively. Failed nonengaging samples had 9 out of 10 abutment screws fracture inside the implant housing but with minimal wear to the top of the implant analog. For partially engaging samples, 8 out of 10 implant housings and 7 out of 10 abutment screws fractured at test endpoints. There was no difference in initial deflections between groups. Prostheses supported by nonengaging abutments failed before deflection measurements could be taken after loading. Prosthesis displacement of partially engaged abutments decreased significantly from the initial position after 300,000 load cycles. Conclusion: Under the experimental conditions, screw-retained splinted fixed dental prostheses supported by partially engaging abutments are 17 times more stable than prostheses supported by nonengaging abutments. Abutment screw fractures are the most prevalent mode of failure for nonengaging abutments at significantly lower cycles with minimal wear on implant analogs. Partially engaging abutment groups failed from implant housing and abutment screw fractures at higher cycles. Loading appears to concentrate preferentially on the medial side on all angled implant components. Selective removal of the abutment obstruction allows a common path of insertion for multiple implants and partial engagement to implant housings. Keywords: common path of insertion, compressive cyclic fatigue loading, engaging abutment, nonengaging abutment, prosthetic stability, screw-retained fixed dental prosthesis

Purpose: Proximal contact loss (PCL) between implant-supported fixed dental prostheses (FDPs) and adjacent teeth has been reported as a common complication of implant therapy. The prevalence of PCL and its potential risk factors have been extensively studied. However, few studies have discussed the recurrent PCL after intervention to restore the proximal contacts. Thus, this retrospective study aimed to evaluate the recurrence rate of PCL and its potential risk factors. Materials and methods: This study included 41 patients (with 45 implants in the posterior region), who had experienced PCL between implant restorations and adjacent teeth and had received contact repair. Recurrent PCL was recorded and evaluated during routine follow-ups with an interval of 6 to 12 months. The recurrence rates and time were measured. The potential influential factors of PCL were also assessed. Fisher exact test, t test, univariate logistic regression analyses, and multivariate logistic regression model were utilized to identify factors influencing PCL. Results: The recurrence rates of mesial PCL were high (> 50%) and the recurrence time became progressively rapid after each repair (5, 3.2, and 2.2 years). Implants with the first PCL recurrence were more likely to be splinted than those implants without recurrence (54.5% vs 18.8%; P = .032). In addition, patients with the first recurrence were slightly older than those without recurrence (55.8 vs 50.1 years; P = .087). Age, implant restoration (splinted vs single), frequent use of interdental brushes, and time to first complaint were the candidate factors associated with recurrent PCL in the univariate logistic regression analysis. The multivariate logistic regression model revealed that only splinted implant restoration was independently associated with a higher risk of recurrence (odds ratio 4.99; 95% confidence interval 1.02-24.31; P = .047). Conclusion: The recurrence rates of mesial PCL were high and associated with the splinted-type design. Also, the recurrence time of PCL accelerated after each repair. Therefore, routine follow-up monitoring PCL and carefully assessing patient compliance after implant therapy are recommended. Keywords: implant complication, implant prosthesis, proximal contact loss, recurrence rate, risk factors

Purpose: The increasing use of dental implants in oral rehabilitation has contributed to the increase of cases of peri-implantitis, a complex clinical condition that persists without an ideal treatment protocol. Therefore, this study aimed to verify the decontaminating action of the sodium bicarbonate jet in vitro, using different protocols, and the presence of visible changes on the surface of dental implants. Materials and methods: Sixteen titanium implants (BioHE, Bioconnect) were used, divided into four groups (four implants per group): sterile implants (S)-negative control; implants contaminated with oral biofilm (C)-positive control; and implants contaminated with oral biofilm and decontaminated with a sodium bicarbonate jet for 30 seconds (J30) or 60 seconds (J60). The implants of groups C, J30, and J60 were contaminated in vitro with oral biofilm, then groups J30 and J60 received the respective decontamination treatments. Microbiologic analysis was performed by counting the colony-forming units (CFUs), and a qualitative descriptive analysis of the implant surface was performed after microbiologic analysis using scanning electron microscopy (SEM). Statistical analysis included one-way analysis of variance (ANOVA) and Tukey tests and the independent t test, with a .05 significance level. Results: There was a significant reduction (P < .01) in the number of CFUs in groups J30 (3.63 × 10⁶ ± 0.32) and J60 (2.74 × 10⁶ ± 0.21) compared with group C (5.05 × 10⁶ ± 0.43). Both decontaminated groups were statistically different from group S, which did not show bacterial growth (P < .01). When groups J30 and J60 were compared, there was also a significant difference between them (P < .01), and the group J60 showed greater decontaminating potential. The descriptive qualitative analysis did not show any visible changes on the surface of the implants. Conclusion: The sodium bicarbonate jet was effective in decontaminating titanium implants in vitro, causing no visible damage to the implant surface. Keywords: decontamination, dental implants, peri-implantitis, scanning electron microscopy, sodium bicarbonate

Purpose: The objective of this study was to compare the osseodensification drilling technique used with Densah implant drills (Versah) to standard drilling by evaluating their contribution to primary implant stability. Materials and methods: A total of 21 mandibles dissected from cadavers were selected. Axiom drills (Anthogyr) were used for 29 standard drilling (SD) protocols in the control group. In the test group, the Densah profile drills were used to perform 29 osteotomies (OD). Implant placement was performed for 58 of these procedures. The insertion torque (IT) and implant stability quotient (ISQ) were recorded. High-resolution CBCT allowed for a postoperative analysis of the peri-drilling bone tissue. For 16 osteotomies without implant placement, Mann-Whitney U test was used for comparison of IT and ISQ values between groups. Spearman rank correlation coefficient was used between IT and ISQ values. The significance level was α = .05. Results: The IT values for OD and SD were, respectively, 34.9 Ncm ± 19.1 and 23.6 Ncm ± 9.8. The IT was significantly higher in the OD group compared to the SD group (P = .036). A moderate positive correlation (ρ = 0.527) between IT and ISQ was observed, as well as a significant increase (P = .026) in bone density. Conclusion: There was a significant increase in IT and bone density following an osseodensification procedure compared to standard drilling. Keywords: bone density, implant primary stability, insertion torque, osseodensification, resonance frequency analysis

Purpose: Internal and marginal fit accuracy of an implant-supported fixed partial denture (I-FPD) along with passive fit are required for long-term clinical success. This study compared the fit accuracy of three-unit CAD/CAM-fabricated cementretained I-FPDs milled from pre-sintered cobalt-chromium (Co-Cr) and zirconia (Zr) and evaluated the effect of applying porcelain. Materials and methods: Two implant analogs were positioned parallel at first premolar and first molar sites in an acrylic model. Their corresponding abutments were tightened with 25-Ncm torque force. Four groups were designed: two groups of I-FPD frameworks with pre-sintered Zr (ZrF) and soft millable Co-Cr alloy (SF) blocks, and two groups by applying porcelain to the Co-Cr (SP) and Zr (ZrP) frameworks (n = 4 in each group). Absolute marginal gap (AMG), marginal gap (MG), and internal discrepancies were measured. Kolmogorov-Smirnov, Levene, one-way analysis of variance (ANOVA), and Scheffe tests were used for statistical analysis using SPSS software version 22 at a significance level of .05. Results: All measured criteria were significantly different from each other (all P values < .001). The rankings from the lowest gap to the highest gap for the main criteria were as follows: MG: SF < SP < ZrF < ZrP; AMG and internal discrepancies: SF < SP < ZrP < ZrF. Comparing molars and premolars, molars had smaller MGs, larger internal discrepancies, and smaller AMG in ZrP but larger AMG in SP. Conclusion: All three-unit CAD/CAM-fabricated cement-retained I-FPDs were in the clinically acceptable range of fit accuracy. The lowest and highest misfit values were observed in the SF and ZrF groups, respectively. Keywords: cobalt-chromium, computer-aided design and computer-aided manufacturing, fixed dental prosthesis, marginal gap, pre-sintered materials, zirconia

Purpose: The aim of the study was to analyze the microchemistry of human bone in different regions of interest (ROIs) on histologic samples of implants retrieved postmortem by the innovative use of an environmental scanning electronic microscope (ESEM) connected to energy-dispersive x-ray spectroscopy (EDX). Materials and methods: Maxillary and mandibular bone blocks with inserted implants (n = 12) were obtained postmortem from a patient. The histologic samples were observed uncoated using ESEM in quadrant backscattered condition. Two ROIs (approximately 750 × 500 μm) for each implant were analyzed corresponding to the cortical thread (cortical ROI) and the middle part of each implant (approximately 3.0 mm below; middle ROI). Different electron-dense bone tissue areas were detected through grayscale intensity quantification of ESEM images. Calcium (Ca), phosphorous (P), and titanium (Ti; atomic %) were evaluated by EDX, and Ca/P ratios were calculated and used as the index to identify areas with different mineralization. The presence of Ti contaminants was investigated by EDX microanalysis. Additional ROIs approximately 2.0 mm from the implant interface and not in connection with the implant surface were analyzed as the control. Results: Four bone areas (BAs) with different degrees of mineralization (from 1 as the lowest mineralized to 4 as the highest mineralized) were identified by Ca and P content and by tissue electron density. BA1 (bone marrow areas) and BA2 (areas with active bone remodeling) proved to have low levels of Ca and P, while BA3 (mineralized new bone areas) and BA4 (control cortical bone) had higher content of Ca and P and higher electron density. Mandibular ROIs displayed higher percentages of BA3 and BA4, while maxillary ROIs revealed a greater presence of BA2 and moderate presence of BA1. Control bone showed a high percentage of BA4. Cortical and middle ROIs showed similar BA distribution within mandibular bone, whereas in maxillary bone, a slightly higher presence of BA1 was observed. Ti ions were detected in ROIs of all specimens; the atomic % significantly decreased in the most distant areas. Ti particles were observed close to the implant interface. Analyses 2.0 mm distant from the implant thread revealed low traces of Ti in healthy bone tissue. Conclusion: The high percentage of BA3 and BA4 in mandibular blocks associated with low presence of BA2 suggested the fast formation of compact bone tissue after 7 months from the implant placement. The presence of BA2 in maxilla blocks suggested active bone remodeling still present after 7 months. Ti particles were observed throughout the ROIs with and without bone remodeling activity. ESEMEDX resulted as a suitable technique to obtain more complete information on microchemistry composition and density/mineralization of bone around implants. For clinical significance, maxillary and mandibular peri-implant bone revealed different mineralization patterns, which means different healing times. The presence of Ti particles at the bone-implant interface and ion translocation, likely due to wear forces in the times following the implant insertion, do not affect the bone remodeling process. Keywords: bone block biopsies, Ca/P ratio, EDX microanalysis, ESEM micromorphology, ESEM-EDX, interface bone mineralization, metal contaminants, retrieved dental implants