The International Journal of Oral & Maxillofacial Implants, 06/2024

Purpose: To conduct a systematic review and meta-analysis to examine the impact of titanium (Ti) base–supported single-implant restorations on peri-implant conditions. Materials and Methods: Six randomized controlled trials (RCTs) comprising 274 implants met the inclusion criteria and were chosen for data analysis. A random-effects model was employed for the meta-analysis. Results: Data from this study revealed that the Ti-basegroup exhibited a small but statistically significant increase in peri-implant marginal bone loss (MBL; mean difference = 0.088 mm; 95% CI = 0.003 to 0.17; P = .041) compared to the one-piece abutment group. These effects were consistent in the subgroup analysis of regularly threaded implants compared to the microthreaded subgroup. No significant differences were observed between the Ti-base group and the abutment group concerning probing depth (PD), bleeding on probing (BoP), and the risk of prosthetic-related complications. Conclusions: The use of a Ti-base in a single implant-supported restorationis associated with a slight increase in peri-implant MBL, while other peri-implant health parameters show no significant correlation. Therefore, the evidence of the impact that Ti-bases have on the peri-implant conditions of single implant-supported restorations is insufficient based on the findings of the present meta-analysis. Keywords: clinical trials, meta-analysis, peri-implant conditions systematic review, Ti-base, titanium base, single-implant restorations

Purpose: To identify the technical complications associated with maxillary complete-arch implant-supported fixed prostheses (ISFPs) and to evaluate the survival rates of both dental implants and prostheses. In addition, we sought to analyze the impact that the presence of cantilevers, the type of prosthetic abutment, and the number of implants have on the occurrence of complications. Materials and Methods: Data were obtained from standardized clinical assessments carried out in a single appointment by two calibrated professionals (F.B.A. and I.A.Y.) using information from dental records. Results: The sample consisted of 64 patients rehabilitated with ISFPs classified as hybrid prostheses (metal-resin). The survival rate for implants was 98.6% after 1 to 12 years (5.2 years ± 36.6 months) and was 100% for the prostheses after a follow-up of 12 to 144 months (mean: 48.1 ± 33.94 months). The most frequent complications were occlusal wear (82.8% of patients) as well as loosening of prosthetic screws (16.6%) and abutments (8.1%). The screw loosening frequency was significantly greater in 30-degree abutments compared with straight abutments (P = .008), but no significant difference was found between 17-degree and 30-degree abutments. Prostheses with a higher occurrence of screw loosening had a greater average cantilever length/anteroposterior spread (CL/AP) ratio (0.9 ± 0.5). In addition, abutments placed on distal implants were more likely to loosen (P < .001). The absence of mutually protected occlusion did not significantly influence the loosening of prosthetic screws and abutments. Conclusions: Implant-supported fixed maxillary complete-arch rehabilitations have high survival rates but are subject to technical complications.  Keywords: dental implants, follow-up, maxillary edentulism, mechanical outcomes, screw loosening

Primary failure of eruption (PFE) is a rare, nonsyndromic condition in which non-ankylosed teeth fail to erupt either fully or partially due to malfunction of the eruption mechanism. Three young patients are presented in this article with features consistent with a diagnosis of PFE. The features of this condition are described together with different modalities of treatment planning for such patients. The following is a discussion about zygoma implants as a new approach to treatment for patients with PFE requiring full-mouth rehabilitation.  Keywords: full-mouth rehabilitation, immediate loading, overretained primary teeth, primary failure of eruption, PFE, zygoma Implants

Purpose: To investigate whether the wettability of two zirconia (Zr) implant disk surfaces is affected by glycine and erythritol air polishing using the following wetting solutions as test mediums: saline, bovine serum albumin (BSA), bovine thrombin, and bovine artificial blood. Materials and Methods: The two types of Zr disks used were SDS (Swiss Dental Solutions; n = 6) and Patent (Zircon Medical AG; n = 6). Surface parameters (Sa, Sz, Sdr, Ssk, Sku, and Spd) were measured to determine their initial surface roughness. Air polishing was completed using glycine or erythritol powders using the AIRFLOW PERIO device (EMS Dental). The wettability of the disk surfaces was evaluated by the contact angle analysis applied to the treated and untreated disks using four wetting solutions, including saline, BSA, bovine thrombin, and bovine artificial blood. In total, 720 contact angle measurements were completed with n = 30 per group. Statistical analysis was performed using one-way ANOVA and the post-hoc Tukey HSD test. Results: The results indicate that SDS has a greater wettability than Patent before and after air polishing. The wettability of surfaces treated with glycine was hydrophobic in some cases. Erythritol increased the surface wettability of Zr disks more than glycine. BSA and bovine artificial blood had lower contact angles than saline and bovine thrombin for both types of untreated disks. Conclusions: The initial wettability of Zr disks differs between manufacturers, and air polishing with erythritol powder increases the wettability of Zr implant disks for saline, bovine serum, bovine thrombin, and bovine artificial blood. Keywords: contact angle, erythritol, glycine, wettability, zirconia

Purpose: To conduct a longitudinal evaluation of sites grafted with autogenous bone prior to implant placement using a dental cast with a 3D modeling system. Materials and Methods: A total of nine patients underwent implant treatment with bone grafting for anterior missing teeth. Informed consent was obtained from each patient. Casts were made and evaluated at three time periods, including before bone grafting (Pre BG), 4 or 5 months after grafting (Post BG), and 4 or 5 months after implant placement (Post IP). 3D data of these casts were acquired using a 3D digital scanner and then superimposed with reference to the remaining teeth. The volume of the anterior area of the cast was evaluated Pre BG and Post BG. Results: Accuracy of superimposition on the remaining teeth was between 20 and 50 µm. Horizontal differences Post BG and Post IP were 0.1 to 1.6 mm. The volume Post IP decreased by 14% to 38% compared to the volume Post BG. Conclusions: This 3D modeling technique allowed 3D evaluation before and after bone grafting. Results suggested that the volume of the maxilla was sequentially decreased after bone grafting. Keywords: bone graft, bone loss, 3D digital evaluation

Purpose: To present a sling suture technique used to stabilize a collagen membrane against the lateral bone window to improve bone substitute stability inside the sinus cavity. Materials and Methods: Maxillary sinus floor augmentation was performed on 17 patients (8 women and 9 men; mean age 58.2 years) using a lateral approach with the sling suture technique to maintain a collagen membrane against the lateral bone window. Postoperative CBCT images were captured at 6-month follow-up of each patient to monitor the bone graft stability at the level of the lateral antrostomy. Clinical postoperative pain and swelling were assessed via visual analog scale (VAS) questionnaire, measured from level 1 (low) to level 5 (acceptable) to level 10 (high) at 1 week postoperative. Results: No bone substitute displacement was observed in any clinical cases on the CBCT images at 6 months postoperative. The pain and swelling levels observed 1 week postoperatively were significantly low (mean ± SD; 1.6 ± 1.0 and 2.1 ± 0.9, respectively). Conclusions: The use of the sling suture technique to maintain a barrier membrane at the level of the lateral bone window in cases of maxillary sinus floor augmentation using a lateral approach is a predictable protocol to prevent bone substitute displacement outside the sinus cavity.  Keywords: bone substitute, case series, CBCT collagen membrane, sinus floor elevation, suture

Purpose: To examine the impact of two implant designs that promote different insertion torque values on implant stability and to histomorphometrically evaluate the bone healing after immediate implant placement in fresh sockets in a sheep model. Materials and Methods: Twelve female sheep (mean weight: 35.0 ± 5.0 kg) were included in the study. Additionally, 48 conical Morse taper dental implants were included, comprising two groups (n = 24 per group): Group 1, where the implant design can provide high insertion torque values; and Group 2, where the implant design can provide low insertion torque values. Both had the same surface treatment and dimensions (4.0 × 10 mm). The mandibular first and second molars on both sides were extracted carefully. Sequentially, osteotomies were made in the mesial socket of each molar tooth. The final implant position was 2 mm below the buccal bone crest level. On the right side, a Group 1 implant was placed anteriorly, with a Group 2 implant in the posterior position; on the left side, the Group 2 implant was anterior and the Group 1 implant was posterior. A digital torque meter was used to measure the maximum final insertion torque value (f-IT). The initial implant stability quotient (ISQ) was measured immediately after implant insertion (T0) and immediately after the euthanasia and removing the mandibles. The animals were euthanized (n = 6 animals/ time) at 21 days (T1) and 35 days (T2). To compare statistical differences for each analyzed intragroup parameter, t-test was used. Pearson’s correlation was used to analyze possible correlations: f-IT and percentage of bone-to-implant contact (%BIC), f-IT and ISQ, and ISQ and %BIC. Results: Group 1 presented higher insertion torque values than Group 2, with a statistically significant difference (P < .0001). The ISQ mean values were higher in the buccolingual direction than those obtained in the mesiodistal direction for both groups. Higher %BIC measurements were seen in Group 2 than Group 1 samples at both times and in both directions. There were statistical differences between groups for new bone, medullary spaces, and collagen matrix at each evaluation time. Conclusions: Using implants with a modified macrogeometry plays a significant role in implant stability and bone tissue healing around the implant. It is important for clinicians to carefully consider implant macrogeometry when planning implant surgery to achieve optimal implant stability and successful osseointegration, mainly in cases of immediate implant placement.  Keywords: dental implants, histomorphometry, macrogeometry, preclinical study

Purpose: To investigate the effect of lateral sinus floor elevation (LSFE) on sinus membrane (SM) thickness and sinus health in mucosa thickness < 5 mm and > 5 mm. Materials and Methods: LSFE was performed in a prospective controlled clinical trial on two groups with < 5 mm and > 5 mm SM thickness (Groups A and B, respectively) and followed for 6 months. Using preoperative and 6-month postoperative CBCT scans and clinical evaluation, SM thickness changes (primary outcome variable), sinus health, augmented bone height and length (augmentation adequacy), membrane-related variables, and operation time were measured. Results: Forty unilateral sinus augmentations (n = 20 for both groups) were performed on 40 subjects (72.5% men, mean age of 48.8 ± 7.6 years), and 52 implants were simultaneously placed. The mean preoperative and 6-month SM thicknesses were 1.4 ± 0.9 mm and 1.3 ± 0.6 mm in Group A, respectively, and were 6.8 ± 1.0 and 3.4 ± 1.7 mm in Group B, respectively. The mean postoperative SM thickness significantly decreased (P < .001) only in Group B. The mean SM thickness changes also revealed a noticeable difference between the two groups (P < .001). Augmentation adequacy and membrane perforation rate were similar in both groups. Clinical and radiographic rhinosinusitis was not detected in any of the patients. Bleeding during separation and resistance to elevation were significantly higher in Group B than in Group A (P = .003, P = .001). Surgical time was longer in Group B (12.08 ± 8.26 minutes) than in Group A (8.64 ± 3.70 minutes), without reaching significance (P = .097). Conclusions: LSFE in thickened mucosa (< 10 mm) and thinner mucosa (< 5 mm) does not cause abnormal changes in the SM and sinus health. LSFE in thickened mucosa results in adequate sinus augmentation. The thickened membrane does not appear to be a contraindication to LSFE. Keywords: mucosal thickness, ostium patency, sinus floor elevation, sinus membrane

Purpose: To summarize and analyze all the evidence available concerning marginal bone loss (MBL) and implant failure between tilted and axial implants. Materials and Methods: An electronic literature search was conducted without any language restrictions, and only systematic reviews with meta-analysis or meta-analysis studies were included. Relative risks (RRs) and the differences in mean (MD) were calculated with 95% confidence intervals (CIs) for the assessed outcomes (in mm) of implant failure and MBL. Results: In total, eight studies were included. Based on the short-term results, a nonsignificant mean difference (MD = 0.00; 95% CI; –0.01–0.02; P value = .75) was recorded between tilted and axial implants supporting full-arch dentures. A significant mean difference was recorded at 3-year follow-up (MD = 0.08 95% CI= 0.05–0.11; P value < .00001) and at long-term follow-up (MD = 0.18; 95% CI = 0.15–0.20; P value < .00001). A nonsignificant difference was observed between tilted and axial implants regarding implant failure (RR = 1.02; 95% CI = 0.85–1.23;P value = .81). Conclusions: Based on the high- and moderate-quality studies with low risk of bias included in this review, no significant difference in outcome regarding implant failure was observed between tilted and axial implants supporting full-arch or fixed partial dentures. Keywords: axial implant, dental implant, implant failure, marginal bone loss, tilted implant

Purpose: To evaluate over 5 years the mesial, distal, palatal, and buccal bone levels as well as the buccal bone thickness surrounding scalloped implants that were immediately placed and loaded with provisional crowns fixed on final prefabricated abutments. Materials and Methods: A total of 18 implants were placed and immediately loaded using CAD/CAM technology in 18 patients to replace a single tooth in the anterior maxilla. The marginal bone levels around the scalloped implant necks were measured mesially and distally using intraoral standardized radiographs after crown placement as well as at the 1-, 3-, and 5-year follow-ups. CBCT para-axial cut images were used to measure the bone level buccally and palatally from the implant neck to the bone-to-implant contact (BIC) 5 years after loading. These images were used to evaluate the thickness of the buccal bone at the implant neck and 4 mm apically both immediately after implant placement (T0) and 5 years later. Results: All implants were assessed clinically and radiologically after 5 years. No implant failure was recorded, and the average marginal bone variation for mesial and distal sites was as follows: 0.114 ±0.135 mm at crown cementation, 0.239 ± 0.158 mm 1 year later, 0.233 ± 0.182 mm 3 years later, and 0.180 ± 0.182 mm 5 years later. Our findings indicate that at T0, the average thickness of the buccal bone was 2.27 mm at the implant neck (M0; ranging from 1.9 to 2.4 mm) and 2.33 mm at 4 mm apical to the implant neck (M1; ranging from 1.9 to 2.9 mm). At 5 years postoperative (T4), the mean had decreased to 1.94 mm at M0 (ranging from 1.7 to 2.3 mm) and 2.14 mm at M1 (ranging from 1.8 to 2.4 mm). After 5 years of functional loading, the mean changes at the buccal and palatal bone for all implants were +0.187 ± 0.52 mm and +0.06 ± 0.38 mm, respectively. Minor prosthetic problems were observed over the 5 years, including incisal ceramic chipping in two crowns and replacement of two crowns due to esthetic reasons after 1 year. No loosening of crowns or abutments was reported. Conclusions: Scalloped-neck implants demonstrated a comparable behavior to regular-neck implants with similar designs in immediate placement and temporization protocol over a 5-year period. Keywords: buccal bone thickness, CAD/CAM, immediate loading, immediate placement, marginal bone level, maxilla, scalloped neck

Purpose: To explore the contribution of paired-related homeobox 1-positive (Prrx1+) cells to the implant-induced osseointegration process in adult alveolar bone and the potential underlying mechanisms. Materials and Methods: Crerecombinase-induced lineage tracing and cell ablation were conducted in a murine dental implant model. Scratch and transwell assays were used to assess MC3T3-E1 cell migration after paired-related homeobox 1 overexpression. Single-cell RNA sequencing was applied to identify potential genes involved in Prrx1+ cell–driven osteogenesis. Results: Prrx1+ cells were observed to accumulate in the peri-implant area in a time-dependent manner; the number of these cells was found to reach its maximum on day 14. Osseointegration in mice was noticeably impaired after ablation of Prrx1+ cells. Further, it was discovered that Prrx1 promotes MC3T3-E1 cell migration, a process which is indispensable for sound healing of peri-implant tissue. Finally, semaphorin 3C (Sema3C) was detected exclusively and abundantly expressed by Prrx1+ cells. Knockdown of Sema3C in Prrx1+ cells significantly weakened their osteogenic potential. Conclusions: Our data suggest that Prrx1+ cells contribute to the osseointegration process under stress stimulation and Sema3C may play a critical role in Prrx1+ cell–driven osteogenesis. Prrx1 could significantly promote MC3T3-E1 cell migration.  Keywords: alveolar bone, paired-related homeobox 1-positive cells, osseointegration, semaphorin 3C

Purpose: To determine the esthetic success of single-tooth implant restorations (STIRs) through pink and white esthetic scores (PES/WES). This study aimed to utilize PES/WES to (1) establish threshold scores based on detectability and acceptability of a STIR by layperson perception, (2) evaluate the difference in the ability of laypeople and dentists to detect the presence of a STIR, and (3) assess the pink and white deficiencies in relation to the detectability of a STIR. Materials and Methods: A total of 38 calibrated photographs of STIRs in the anterior region were scored with PES/WES by three prosthodontists. Next, 100 laypeople and 60 dentists were instructed to identify the STIR among the anterior teeth and provide reasoning behind the identification (based on pink and white esthetic criteria). The acceptance of the STIR was recorded. A receiver operating characteristics (ROC) analysis was performed to determine the threshold scores. Results: At the PES/WES score of 17, 71% of laypeople could not correctly identify the STIR, and at the PES/WES score of 12, 80% of laypeople accepted the implant. Out of 3,800 occasions, laypeople correctly identified the STIR in 1,770 (46.58%) of those occasions. Among the correctly identified STIRs, 751 (42.43%) of those occasions were identified with pink deficiencies and 1,019 (57.57%) of those occasions were identified with white deficiencies. Out of 2,280 occasions, dentists correctly identified the STIR in 1,869 (81.98%) of those occasions. Conclusions: A PES/WES score of 12 indicates the clinically acceptable threshold, and a score of 17 indicates the detectable threshold for an exceptional esthetic outcome. Laypeople tend to accept the implant despite its detectability. For both laypeople and dentists, root convexity/soft tissue color and texture are the most focused criteria of PES/WES, followed by overall white deficiencies, which remain influential. Compared to laypeople, dentists tend to have a higher ability to detect STIRs.

Purpose: To evaluate the clinical performance of implant-prosthetic rehabilitations carried out using ceramic-coated CAD/CAM titanium abutments. Materials and Methods: Thirty implants were placed in 30 patients and rehabilitated with 30 single crowns attached to CAD/CAM titanium abutments. A conventional procedure was applied, implants were placed after postextraction socket healing, and prosthetic restorations were placed after implant healing. Implant lengths ranged from 6 to 15 mm, and widths were 3.6, 4.2, and 4.8 mm. At the time of prosthesis delivery (T0), after 2 years (T1), and after 5 years (T2), the Plaque Index (PI), bleeding on probing (BoP), pocket probing depth (PPD), marginal bone level (MBL), and pink/white esthetic scores (PES/WES) were evaluated for each implant. Results: No patient dropped out of the study during the follow-up period. All 30 implants were clinically successful 5 years after prosthesis delivery (survival rate: 100%) and showed no signs of peri-implant infection. Peri-implant soft tissues were in good health (BoP at T2: 0% in 73% of patients; 25% in 13% of patients; 50% in 10% of patients; and 75% in 3% of patients). The mean PPD was 2.05 ± 0.56 mm at T0, 1.992 ± 0.6 mm at T1, and 1.867 ± 0.439 mm at T2. The mean MBL was 0.413 ± 0.440 mm at T0, 0.306 ± 0.388 mm at T1, and 0.263 ± 0.368 mm at T2. The mean PES, WES, and PES/WES indices (7.43 ± 1.04, 7.57 ± 0.82, and 15.00 ± 1.17, respectively) indicate good integration of soft tissues, satisfactory esthetics, and overall positive outcomes. Conclusions: The success rates, maintenance of MBLs, and periodontal and esthetic indices suggest the validity of implant-prosthetic rehabilitations with CAD/CAM abutments in cases of single crowns. Keywords: Implant-prosthetic rehabilitation; CAD/CAM abutments; Single crowns; Clinical performance; Peri-implant soft tissues

Purpose: To evaluate the feasibility of reversing a primary failure through therapeutic mechanical stimulation induced by transcutaneous application of acoustic waves (extracorporeal shockwave therapy [ESWT]) in the peri-implant tissues. Materials and Methods: This clinical report evaluates the outcome of a new protocol proposed to treat a primary failure (loosened oral implant): application of three cycles of ESWT (one session per week for 3 consecutive weeks) with an equivalent positive energy of 0.18 mJ/mm² (therapeutic dose: 2,000 pulses, 8 Hz, 4.0 bar). Standardized intraoral radiographs and CBCT scans were taken, the implant stability quotient (ISQ) was determined, and clinical evaluations were performed. Results: It was possible to verify a progressive increase in ISQ values after the ESWT protocol: 17 initially, 46 at 2 months, and 68 at 4 months. This led to successful implant prosthetic rehabilitation (35 Ncm). Follow-up evaluations at 6 years confirm that the new bone-implant interface is preserved and that ESWT is a safe, noninvasive treatment. Conclusions: In the context of the new dynamic model of osseointegration (the foreign body equilibrium), this represents the first report of a host-implant equilibrium reestablished after an early implant failure process. However, more studies are needed to determine both the medical device and the most effective therapeutic range for clinical applications of this technology in oral implantology. Keywords: case report, ESWT, oral implant, osseointegration, osteoimmunology, primary failure

Purpose: To examine the mechanical influence of edentulous mandible morphology on peri-implant bone in implant prosthetics via finite element analysis (FEA). Materials and Methods: Computed tomographic (CT) data from 25 patients with edentulous mandibles were selected. Measurements such as the radius of mandibular curvature and the height of the mandible at the midline were taken to clarify the morphologic characteristics of the mandible. From the measurements, two patients with the smallest and largest radii of the mandible were selected. Two types of 3D finite element models were created from the two selected edentulous mandibles (small and large radius), and they included superstructures (a cantilever bridge), implants, and abutments. In both models, four implants were placed between the right and left mental foramina. The upper surface of the mandibular condyle was constrained, and a vertical load of 100 N was applied on the occlusal surface of the right first molar. 3D FEA of each model was performed to examine the mechanical influence of the edentulous mandible morphology on the peri-implant bone. Results: The mandibular morphology measurement in the CT images indicated that the smaller the mandibular height, the larger the radius of the anterior mandibular curvature. FEA revealed that higher equivalent stress was generated in the model of the peri-implant bone with a larger radiusof curvature than that of the model with a smaller radius of curvature. The highest equivalent stress in the mandible was generated in the distal margin of the peri-implant bone posterior to the loaded side of the large-radius model. Conclusions: The mandibular morphology had a mechanical influence on the peri-implant bone. Keywords: edentulous mandible, height of mandible, mandibular morphology, radius of mandibular curvature

Purpose: To perform a finite element analysis (FEA) and an in vitro experiment to investigate and compare the loading effects (effects on the implant and surrounding bone) of various customized angled abutments to commercial 15-degree angled abutments (control). Materials and Methods: Four customized angled abutment models (21.9, 24.15, 20.22, and 33 degrees) were developed using CBCT images of incisor inclination measurements from patients of various age groups (20 to 23, 24 to 39, and 40 to 65 years). 3D maxillary bone models were created from the CBCT images of four individual patients: One patient from each age group with the respective average incisor inclination measurement and another patient with the overall average were selected. Then, FEA and in vitro strain gauge experiments were conducted by applying 100 N or 50 N of axial or oblique force to each model in order to assess the differences in stress/strain between the customized angled abutments (test) and the control in both the implants and surrounding bone. Results: Under axial loading, the stress values in the implant and surrounding bone were elevated due to the relatively higher angles of the customized angled abutments (21.9, 24.15, 20.22, and 33 degrees) compared to the control angled abutments. Under oblique loading, the control angled abutments exhibited higher stress values in both the implant and surrounding bone. For the in vitro experiment, there was no statistically significant difference in bone strain between the customized (21.9 degree) and the control angled abutments in axial loading. Nevertheless, the control angled abutment with oblique loading induced greater bone strains. Conclusions: Customized angled abutments offer lower stress/strain under oblique loads but higher stress/strain under axial loads compared to the control abutments. Therefore, in the design and application of angled abutments, careful consideration of the occlusal load direction is important for achieving the biomechanical success of an implant. Keywords: customized angled abutments, finite element analysis, immediate implant placement, maxillary incisor region, in vitro strain gauge experiment

Purpose: To analyze the effect of scanning modes on the accuracy of the Trios intraoral scanner (IOS) for full-arch digital implant impressions. Materials and Methods: The trueness and precision of the intraoral scanning mode (IOSM) and the intraoral edentulous scanning mode (IOEM) of the Trios IOS were evaluated in three edentulous models, each featuring four, six, and eight implant analogs. Reference scanning data were obtained by scanning each model with a desktop scanner. Each model was scanned 10 times using the IOSM and IOEM modes of the Trios IOS to establish the test groups. The scan bodies in the test and reference scans were isolated and exported in the reverse engineering program. The scan bodies in each group were superimposed with the corresponding reference scan (trueness) or with each other (precision). The overall 3D deviation between the aligned scan bodies was computed by the root mean square (RMS) values. Results: No significant difference was found between scanning modes in any of the models. When comparing models, the eight- implant model showed significantly lower trueness than the four-implant model. However, it exhibited significantly higher precision than the four-implant and six-implant models. There were no significant differences in other pairwise comparisons between the models. Conclusions: Trueness and precision values were similar between the IOSM and IOEM groups across all the models. An increase in the number of implants in completely edentulous arches may have a negative impact on digital impression accuracy. Keywords: digital implant impression, full-arch, intraoral scanner, scanning mode

Purpose: To investigate the rotational load fatigue performance of different implant diameters and abutment platforms of a one-size implant-abutment (OSIA) connection system. Materials and Methods: Narrow-, regular-, and wide-diameter implants were tested with regular base (RB/WB) abutments of an OSIA system (BLX, Straumann). Wide-diameter implants (WDIs) were also tested with wide base (WB) abutments. This resulted in four test groups: (1) narrow-diameter implants (NDIs; 3.5 mm) with RB/WB abutments, (2) regular-diameter implants (RDIs; 4.0 mm) with RB/WB abutments, (3) WDIs (5.0 mm) with RB/WB abutments, and (4) WDIs (5.0 mm) with WB abutments. Each group tested five of their respective implants (n = 5). A rotational load fatigue machine applied a sinusoidally varying stress at a 45-degree angle, producing an effective bending moment of 35 Ncm at a frequency of 10 Hz in 20ºC air. The number of cycles to failure was recorded, and the results were evaluated using two-way ANOVA. Failed specimens were examined with a scanning electron microscope (SEM) to evaluate the failure mode. Pristine specimens were sectioned to examine the implant-abutment connection. Results: All specimens in three of the test groups with RB/WB abutments failed within the range of 558,750 cycles to 4,497,619 cycles, while the WDI-WB test group reached the upper limit of 5 million cycles without failure. A significant difference was found between abutment platforms (P < .001). There were no significant differences found for implant diameters (P = .857). However, with a greater implant diameter, implant fracture was less common, and the failure location was more coronal. It was consistently at the implant platform level for the abutment and at the screw neck. Conclusions: For WDIs, WB abutments exhibited superior fatigue performance compared to RB/WB abutments and would be preferred in situations of high mechanical risk. Increasing the implant diameter, when used with RB/WB abutments, did not improve fatigue performance due to the one-size prosthetic connection; however, failures were less catastrophic and coronally located, which may be advantageous in managing failures. Keywords: failure analysis, implant-abutment connection, implant fracture, load fatigue

Purpose: To evaluate the response of human peri-implant soft tissue (PIST) to different healing abutment materials 24 hours after positioning by assessing the expression of genes related to the early connective tissue wound healing response. Materials and Methods: The following four materials were used to create experimental abutments that were mounted on implants placed in five patients (four different abutments in each patient): group A—grade 4 titanium (Ti), group B—grade 5 Ti, group C—zirconia (Zr), and group D—polyetheretherketone (PEEK). Before implant placement, a gingival biopsy (control, CT) sample was obtained using a 2-mm-diameter punch (T0). After 24 hours, PIST biopsy samples were collected using a specifically designed custom-made cutting device. Real-time polymerase chain reaction (PCR) was performed to analyze the expression of the following genes: COL-I, COL-III, MMP-1, TIMP-1, TGF-β1, FN, ITGA4, ITGA5, ITGB1, RAC-1, COL-IV, αSMA, IL-6, and CXCL-1. Results: Gene expression analysis showed some differences between CT and the experimental groups; however, no significant differences were detected when comparing the experimental groups. COL-I was significantly downregulated in groups A and C compared to CT. Expression of MMP-1 and TIMP-1 increased in all the experimental groups but to a lesser extent in group A. FN, RAC-1, COL-IV, and αSMA were downregulated, especially ingroup A, in which CXCL-1 and IL-6 showed the lowest expression. Conclusions: The results of grade 4 Ti and Zr abutments seem to be promising, because a lower expression of genes related to inflammation, myofibroblast activation, and extracellular matrix remodeling was observed when compared with grade 5 Ti and PEEK, without triggering a profibrotic response in the early phases of PIST repair. Keywords: gene expression analysis, PEEK, peri-implant soft tissue, titanium, wound healing, zirconia