The International Journal of Oral & Maxillofacial Implants, 01/2024

In order to keep clinical norms aligned with evidence-based practices, dental researchers need to be equipped to read and evaluate meta-analyses. Moreover, clinician scientists in dentistry should be prepared to lead investigations that incorporate meta-analysis. This article provides an overview of the principles and practices that will equip dental researchers to engage in meta-analysis work. Six elements of meta-analysis are addressed: formulating a research question, searching the literature, collecting the data, aggregating the data, analyzing the data, and interpreting results and drawing generalizations. Readers are guided through each of these stages of research so that they can recognize and implement robust, reproducible meta-analysis work. Keywords: guide, review (systematic), statistical methods

Purpose: To assess the handling properties and clinical function of a new class of material, a so-called mineral-organic bone adhesive (Tetranite; TN), which as yet has no precedent in orthopedic or oral and maxillofacial surgery, for clinically unstable implants placed in immediate extraction sockets and immediately temporized in the anterior maxilla. Materials and Methods: A cohort of up to 15 patients requiring between one and four immediate dental implants placed into maxillary extraction sockets from canine to canine were eligible for inclusion. Implants had to be unstable with an insertion torque of < 15 Ncm. Implants were then stabilized using TN, which was allowed to set before reassessing stability using both torque and resonance frequency measurements. Implant stability quotients (ISQs) taken after TN setting were compared to ISQs taken prior to its application, and the implants had to demonstrate resistance to a forward torque of 20 Ncm to be considered stable. ISQs were monitored at 1 week and 1, 3, 7, and 12 months postplacement. In addition, peri-implant tissue health was monitored, adverse events were recorded, and implant success was determined at 1 year postplacement. Results: Eleven patients received a total of 14 implants. Three out of the first six implants failed within 1 month (50%), and thus a protocol amendment was made to remove steps considered potentially destructive to the bonding process. As a result of these amendments, only one further failure was experienced for the next eight implants placed (12.5%). Mean ISQ data averaged for buccolingual and mesiodistal measurements demonstrated a baseline value before TN application of 59.1 Ncm (SD: ± 9.7; range: 40.5 to 73.0). After final setting of the TN, mean ISQ measured 71.9 Ncm (± 6.5; 56.0 to 80.0). At 3 months, just prior to restoration placement, mean ISQ measured 71.0 Ncm (± 6.6; 57.0 to 78.0). Thereafter, the mean ISQ continued to increase at both the 7- and 12-month follow-ups with scores of 78.9 (± 4.6; 72.0 to 84.5) and 80.3 (± 3.8; 74.5 to 85.0), respectively. The surviving 10 implants went on to be fully restored and remained in function beyond the end of the study period to yield a final success rate of 71.4%. Conclusions: The purpose of a first-in-human study is to demonstrate an extrapolation of preclinical data into the controlled human clinical arena. It is an opportunity to learn what does and does not translate well from experimental data. In that regard, the current pilot study can be deemed a complete success. The implant survival rate of 71.4%, while disappointing, should be considered in light of the protocol amendments identified, the user handling experience learned, and the opportunity to modify the material to better perform in the human patient, as all represent important lessons learned. The notable increase in ISQ sheds light on the nature by which the glue was substituted for bone to yield a stable implant by the end of the study period. Keywords: bone glue, mineral-organic bone adhesive, Tetranite, dental implant, primary stability

Purpose: To assess the pain, swelling, infection, and alteration in sensation following the flapless placement of zygomatic implants guided by dynamic navigation. Materials and Methods: A randomized controlled trial was conducted on 20 patients. In group 1, the placement of the zygomatic implants was carried out without reflecting a mucoperiosteal flap (flapless). In group 2, a mucoperiosteal flap was raised (flapped). Two zygomatic implants were placed in each patient (one on each side) under local anesthesia, guided by dynamic navigation. Postoperative evaluations included pain (using the visual analogue scale [VAS]), swelling (using standard measurements), maxillary sinus infection, and alteration of sensation (using mechanical stimuli, thermal threshold detection, and a two-point discrimination test). The assessments were carried out at 2 days, 1 week, and then 1, 2, and 3 months postoperatively. Results: In group 1, all implants except for one were successfully osseointegrated. Immediate postoperative pain and swelling were both significantly greater in group 2 (P < .01). No alteration in sensation was detected in any case in the two groups. There were a total of three cases of chronic sinusitis: one in group 1 and two in group 2. Conclusions: The flapless placement of zygomatic implants guided by dynamic navigation and under local anesthesia improves postoperative recovery. Keywords: dynamic navigation, flapless, pain, swelling, zygomatic implant

Purpose: To evaluate the effect of supraphysiologic administration of testosterone in an early and late model of implant osseointegration in rat tibiae. Materials and Methods: A total of 40 rats were randomly allocated into four groups (n = 10/ group), which were divided according to the type of experiment and time of osseointegration: (1) vehicle (14 days), (2) testosterone (14 days), (3) vehicle (42 days), and (4) testosterone (42 days). Testosterone cypionate (7.5 mg/kg) administration started 4 weeks before implant placement, and the injections were performed daily until euthanasia. Machined-surface titanium implants (2.2 mm in diameter and 4 mm high) were placed bilaterally in the tibia of animals 28 days after the first testosterone injection. At days 14 and 42 after implant placement, euthanasia was performed and the tibiae were harvested to perform biomechanical evaluation and histomorphometric analysis of bone-to-implant contact (BIC%) and bone between the threads (BBT%). Results: There was no statistical difference in the removal torque of the implants between the groups treated with the vehicle (control group) or testosterone (P > .05). At 14 days of osseointegration, the BIC% and BBT% did not differ between vehicle or testosterone groups (P > .05), while at 42 days, both the BIC% and BBT% were significantly reduced by testosterone compared to the vehicle group (P < .05). Conclusions: Testosterone cypionate in supraphysiologic dose impaired late-phase osseointegration in rat tibiae. Keywords: androgens, testosterone, dental implants, osseointegration

Purpose: To demonstrate a modified surgical approach for horizontal ridge augmentation that allows for safe manipulation and predictable management of the buccal plate and avoids creation of a secondary surgical site. Materials and Methods: This pilot randomized controlled clinical trial included 24 patients who required horizontal alveolar ridge augmentation. Patients were assigned to one of the three groups: Group A was treated with the buccal plate repositioning (BPR) technique and grafted with silica calcium phosphate nanocomposite (SCPC) graft, group B was similarly managed and grafted using demineralized freeze-dried bone allograft (DFDBA), and group C was augmented using mandibular ramus autogenous bone block graft (ABBG). The primary outcome was the coronal crest width, which was measured at 6 months using CBCT. Results: The BPR technique resulted in horizontal augmentation with a mean of 4.30 ± 0.94 mm for group A, showing no significant difference from either group B (4.98 ± 1.13 mm) or group C (3.68 ± 0.27 mm). All augmented ridges allowed for successful implant placement with good primary stability. Conclusions: The BPR technique resulted in horizontal bone gain in extremely narrow alveolar ridges. It allowed for implant placement in a vascular cancellous bed protected by intact cortical plate. Different types of bone grafts, whether alloplast or allograft, resulted in successful augmentation comparable to that gained from autogenous block grafting. Keywords: alveolar ridge augmentation, mandibular atrophy, horizontal augmentation, ridge splitting, silica calcium phosphate, allograft

Purpose: To review experimental peri-implantitis studies using rat models and summarize different peri-implantitis induction techniques and evaluate their effectiveness. Materials and Methods: Electronic searches were conducted by two independent examiners to address the following issues. Meta-analyses explored the marginal bone loss (MBL) of four types of peri-implantitis induction methods in rats. The detailed induction tactics—such as the implant design, implant size, surgical process, time cost, induction methods, and endpoint measurements—were summarized. Results: Of the 18 included studies, 38.9% of the studies placed implants at the maxillary first molar, and 44.4% placed them at the alveolar ridge region anterior to the maxillary first molar. As for the induction method, the numbers of published studies on ligature methods, bacterial inoculation, and bacterial lipopolysaccharide inoculation were equally high among all selected studies. The total implant survival rate at the end was 160 out of 213 implants (75.11%). Eight studies with high pooled heterogeneity (I2 = 98, P < .01) in the meta-analysis reported an overall MBL (μ-CT) of 0.47 mm (95% CI = 0.14 to 0.81). A subgroup analysis estimated an MBL of 0.31 mm (95% CI = 0.12 to 0.50) for bacterial inoculation and 0.66 mm (95% CI = 0.07 to 1.26) for the ligature method. Histopathologic analysis revealed that peri-implantitis in rats was similar to peri-implantitis lesions in humans. Conclusions: Implant placement at the maxillary first molar with bacterial inoculation and the silk ligature method to build peri-implantitis rat models is reliable to use for research on peri-implantitis. Keywords: bacteria, bone loss, implant, ligature, peri-implantitis, rat

Purpose: To evaluate the influence of initial implant protrusion within the subantral space on hard tissue gain for implants placed simultaneously with transcrestal sinus floor elevation (TSFE) with a biomaterial. Materials and Methods: A total of 50 implants were placed after TSFE in 44 patients using either a human demineralized bone matrix or a deproteinized bone mineral matrix. Intraoral radiographs were obtained before and immediately after surgery. CBCT scans were obtained at the last follow-up (mean: 6.6 years). Results: The initial bone crest height was 4.6 ± 1.4 mm, and the initial protrusion of the implants above the sinus floor was 3.5 ± 1.4 mm. At the follow-up assessments, the hard tissue mean gain was 2.5 ± 1.5 mm, resulting in a mean residual protrusion of 1.1 ± 1.3 mm. Only 10 implants did not protrude above the apical level of hard tissue. Positive correlations were found between hard tissue gain and initial protrusion (r = 0.55; 95% CI: 0.32 to 0.72; P = .0001), between the initial and final protrusions (r = 0.38; 95% CI: 0.10 to 0.60; P = .007), and between the follow-up period and final protrusion (r = 0.35; 95% CI: 0.07 to 0.58; P = .012). Conclusions: The higher the initial protrusion was, the higher were the hard tissue gain and the final protrusion of the implant above the apical level of the hard tissue. Keywords: maxillary sinus, biomaterial, dental implant, CBCT, sinus augmentation

Purpose: To investigate the possible antimicrobial activity of glycine air polishing by comparing peri-implant microbiota before and after treatment. Materials and Methods: A total of 15 patients who received implant-supported full-arch fixed rehabilitations were included. After prosthesis removal (T0), Plaque Index (PI), probing depth (PD), and bleeding on probing (BOP) were recorded. In each hemiarch, the implant with the highest PD score was selected for microbiologic sample collection from the peri-implant sulcus (T0). All patients received two different hygienic protocols (randomly administered, one per each hemiarch): glycine air-polishing (G) and cleansing with cotton pellets soaked in saline (C). At 7 days (T1) and 3 months (T2) after the intervention, PI and BOP were recorded, and new microbiologic samples were taken. Traditional polymerase chain reaction (PCR) and quantitative PCR real-time were employed for microbiologic analysis to investigate how the presence of different bacterial species varied according to the hygienic treatment performed. Results: Treatment G provided a significantly higher PI score reduction around implants compared to treatment C (P = .015). No statistical difference was found in the microbial population around G and C implant sites, with Tannerella forsythia being the most commonly detected bacterial species in both G and C groups. No statistical differences were found between the antimicrobial activity of treatments C and G. Conclusions: Glycine powder air polishing is a valid method for professional hygienic care of implants and was more effective in PI reduction compared to the control treatment. However, its antimicrobial efficacy cannot be confirmed by the outcomes of the present study. Keywords: dental implants, microbiota, peri-implantitis, air polishing, glycine

Purpose: To determine the accuracy of dental implant placement using haptic robotic guidance in a large clinical series. Materials and Methods: In a prospective single-arm clinical study, 108 patients received 273 individual endosteal implants. A virtual preoperative restorative and surgical plan was created from a CBCT scan and matched to the surgical workspace on the day of surgery via either a tooth-based or bone-based fiducial splint. Intraoperatively, the surgeon manipulated a handpiece attached to a haptic robotic guidance arm. A variety of drills and implants were used. Both the osteotomy and the implant placement were guided by 3D haptic constraints according to the virtual plan. Postoperative CBCT scans permitted the calculation of the actual implant placement deviations compared to the plan for accuracy. Precision was calculated by comparing SDs from published literature. Results: The implants were evenly distributed by arch, with 47% placed in the maxilla and 53% in the mandible. The mean ± SD signed depth deviation was 0.14 ± 0.87 mm proud. The global angular deviation averaged 1.42 ± 1.53 degrees, with 95% confidence limits of 1.24 and 1.60 degrees. The crown of the actual placed implant showed an average deviation from the plan of 1.10 ± 0.69 mm and the apex of the placed implant showed a deviation of 1.12 ± 0.69 mm. Haptic robotic guidance showed greater precision than freehand, static computerguided, and dynamic computer-guided implant placement. Conclusions: This large clinical series of 273 implants shows a high accuracy of implant placement compared to the published accuracy for angular deviations for any technology, as well as demonstrating statistically greater precision. Long-term clinical studies are necessary to establish the true effect of increased accuracy on clinical outcomes. Using haptic robotic guidance provides accurate implant placement while allowing additional benefits compared to computer-guided surgery, namely full visualization of the surgical field and the ability to change the plan intraoperatively. Keywords: robotics, dental implant, haptics, accuracy

Purpose: To evaluate the impact of different approaches to sinus membrane perforation (SMP) repair on bone formation, postoperative complications, and implant loss risk. Materials and Methods: Electronic searches on PubMed, Web of Science, Scopus, Embase, and Cochrane Library databases were conducted for publications up to February 2021. All included articles reported SMPs submitted for repair. The proportion of implant loss in repaired SMP sites was calculated using a random-effects model meta-analysis. Results: A total of 130 studies reporting SMP repair protocols were included in the systematic review, with 20 selected for meta-analysis. A total of 1,972 sinuses that were perforated and repaired during sinus elevation using different approaches were included in the qualitative analysis. The resorbable collagen membrane was the most commonly reported treatment. The presence of sinusitis was the most frequently described complication. Regarding bone parameters, the majority of studies described no differences between perforated and repaired sinuses and intact membranes. No difference in the implant loss proportion was observed between sites with repaired SMP compared to undetected SMP. The proportion of implant loss in repaired sinuses membrane sites (independent of the material or implant placement time) was 4% (95% CI: 2.0 to 8.0). In meta-regression analysis, no association was observed between the SMP size and implant loss proportion (P = .86). Conclusions: The materials and techniques indicated for SMP management seem to securely seal the maxillary sinus, without a negative effect on the ultimate survival of the implants placed in the affected sinuses. Keywords: sinus elevation, sinus membrane perforation, sinus membrane repair

Purpose: This in vitro study investigated the effect of implant geometry and diameter on the rotational load fatigue performance of an implant system with an internal conical connection with microthreads. Materials and Methods: Regular (4.2 mm) and wide-diameter (4.8 mm) Astra Tech EV implants with straight (S) and conical (C) geometries were tested with their corresponding titanium abutments, comprising four test groups: 4.2-mm S (Group 1), 4.2-mm C (Group 2), 4.8-mm S (Group 3), and 4.8-mm C (Group 4). Five samples were included in each group. Customized brass implant holders and abutment holders were machined. A rotational load fatigue machine was used to apply a sinusoidally varying load to the implant-abutment interface at an angle of 45 degrees to produce an effective bending moment of 35 Ncm at a frequency of 14 Hz (air temperature: 20ºC). The number of cycles to failure was recorded, with the upper limit set at 5 × 106 cycles. Results were analyzed using ANOVA. Failed samples were examined with a scanning electron microscope to evaluate the mode of failure. Results: Of the 20 total samples, 2 failed, with Groups 1 and 2 each reporting one failure. Abutment and abutment screw fracture were observed in the failed sample in Group 1, while implant and abutment screw fracture occurred in the failed sample in Group 2. All wide-diameter implants ran beyond the cut-off without failure, but abutment screw loosening was noted in one sample in Group 3. No significant difference was found between implant groups of different geometries and diameters. Damage to the abutments and the implant internal surface were noted in all failed samples. Conclusions: While no significant differences were found between the test groups, failures were observed only in the regular-diameter group. The abutment and abutment screw fractured deep within the implant, and the implant fractured below the simulated bone level. These modes of failure may pose a significant clinical challenge during retrieval of these components. Keywords: implant-abutment connection, implant fracture, load fatigue

Purpose: To evaluate the precision and efficiency of a novel guide system for single implant placement in the mandibular symphyses and to evaluate whether the outcome is affected by the level of operator experience. Materials and Methods: A total of 90 implants were placed in three different mandibular cast types (Cawood and Howell class III, IV, and V). For each model, a complete denture was 3D printed. A polyether ether ketone rail with a guide sleeve was embedded in the middle of the denture. To determine the ideal implant position, the sleeve could be moved in a buccolingual direction. Adjustment of implant angulation was possible, and an angle correction of 0, 12, or 24 degrees was available. A total of 30 clinicians were divided into three groups: group 1 (experienced, n = 10), group 2 (beginner, n = 10), and group 3 (inexperienced, n = 10). Each clinician was asked to plan and perform a guided flapless implant placement in the mandibular symphysis. Two preoperative CBCT scans were taken; the first was to verify the planning, and the second was to adjust the planning if needed. Finally, a postoperative CBCT scan was taken to compare the planning to the final implant position. Results: Based on the first CBCT, the clinicians adjusted their planning by an average of 1.66 ± 1.65 mm coronally, 2.41 ± 2.44 mm apically, and by a mean angular correction of 6.08 ± 0.77 degrees. After implant placement, the mean deviation from the planned implant position was 0.87 ± 0.58 mm at the coronal aspect and 0.98 ± 0.64 mm at the apical aspect. The mean angular deviation was 6.05 ± 0.71 degrees. Overall, there were no significant differences in coronal and apical deviation (P > .05) based on the level of experience. In terms of angulation, a significant difference was found in both planning (P = .049) and placement (P = .038) between beginners and experienced clinicians. Conclusions: Guided implant placement of a single implant in the mandibular symphysis using a removable denture with guide sleeve had an acceptable level of accuracy. Clinicians with limited experience spent more time on the procedure, resulting in less angular deviation during implant planning and placement compared to experienced clinicians. Keywords: dental implants, edentulous mandible, guided surgery, overdenture, single implant

Purpose: The present study describes a new presurgical soft tissue technique in oral/maxillary bone reconstructive surgery for reducing the risk of soft tissue dehiscence and its related complications. Materials and Methods: Ten consecutive patients with Cawood and Howell type V atrophy were scheduled for CAD/CAM titanium mesh bone reconstructive surgery after applying the vascular delay technique 21 days before regenerative surgery. The surgical and healing complications were clinically assessed at nine time points, ranging from the time of bone regenerative surgery to 9 months after surgery. Surgical complications included flap damage and neurologic and vascular complications. Healing complications were subdivided into four classes. These classes comprised Class I: small membrane exposure (≤ 3 mm) without purulent exudate; Class II: large membrane exposure (> 3 mm) without purulent exudate; Class III: membrane exposure with purulent exudate; and Class IV: abscess formation without membrane. Results: The study sample included seven men and three women (mean age: 48.2 ± 3.5 years) with seven mandibular cases and three maxillary cases. The defect length ranged from three to six teeth, with a mean mesiodistal distance of 29.9 ± 8.5 mm and a mean volume augmentation of 2.03 ± 0.9 cm³. There were no surgical complications. One patient presented a Class I healing complication that did not affect the regeneration outcome. Conclusions: The vascular delay technique appears to reduce the risk of soft tissue dehiscence and exposure in bone regenerative surgery, though randomized studies involving larger samples and longer follow-up periods are needed in order to draw firm conclusions. Keywords: delay phenomena, guided bone regeneration, ischemic preconditioning

Purpose: Patients with systemic scleroderma (SSc) often suffer from premature tooth loss. The aim of this study was to radiologically investigate bone loss at dental implants in patients with SSc and compare it with data from the literature on healthy patients. Materials and Methods: Mesial and distal bone level changes at implants were independently determined on panoramic and intraoral radiographs. They were double-checked after determination of evaluability by three different raters. Cohen’s kappa was used to test for interrater reliability. Mean bone loss was estimated using linear regression analysis considering the patient as a random-effect implant and performed separately in predefined implant regions for different time points and for the mesial and distal sides of the implants. Results: Mesial and distal bone level changes were analyzed in 61 implants using periapical and panoramic radiographs. In total, 114 radiographs from 18 patients were evaluable in both the mesial and distal regions. After a maximum observation period of 60 months, the mean peri-implant bone loss was 1.68 mm (range: 0.83 to 2.54 mm) at the distal aspect and 1.65 mm (range: 0.81 to 2.48 mm) at the mesial aspect in the right posterior mandible (region 44 to 47 [FDI numbering system]), whereas in the left posterior maxilla (regions 24 to 27), the mean peri-implant bone loss was 0.61 mm (range: 0.32 to 0.91 mm) at the distal aspect and 0.59 mm (range: 0.16 to 1.03 mm) at the mesial aspect. The mean bone loss 60 months after surgery was 1.05 mm (range: 0.85 to 1.25 mm). Conclusions: Marginal bone loss at implants in patients with SSc is comparable to data from the literature collected in healthy subjects. Keywords: systemic scleroderma, rare disease, dental implant, radiographic analysis

Purpose: To evaluate the usefulness of ridge augmentation using a customized titanium mesh (CTM) that was preformed by trimming and bending the commercial titanium mesh on a virtually reconstructed 3D acrylic resin model using clinical, radiologic, histologic, and histomorphometric analyses. Materials and Methods: This study was designed prospectively for patients who required vertical ridge augmentation using a staged approach before implant surgery. After installation of the CTM, grafting was performed using deproteinized porcine bone mineral covered with an absorbable membrane. Computed tomography was performed preoperatively and 6 months after simultaneous/staged guided bone regeneration to measure planned, reconstructed, and lacking bone volume, and the reconstruction rate was calculated based on these values. Clinical complications were also recorded, particularly the mesh exposure rate. At re-entry, the bone core was obtained using a trephine bur, and histologic and histomorphometric analyses were performed. Results: A total of 10 sites in eight patients were used for the study analysis. The mean planned bone volume was 1.15 cm3 (range: 0.78 to 1.56 cm³), mean lacking bone volume was 0.13 cm³ (range: 0 to 0.59 cm3), and mean reconstructed bone volume was 1.02 cm³ (range: 0.56 to 1.43 cm³). The exposure rate was 30% (3 out of 10 sites). The reconstruction rate was over 80%, except for one case that showed suppuration. From histomorphometric analysis, 27.52% ± 16.87% of new bone, 7.62% ± 5.19% of residual graft, and 64.86% ± 23.76% of connective tissue were observed. The core biopsy samples demonstrated different pseudoperiosteum layer appearances based on the healing stage of the augmented sites. In the premature bone, the inner osteogenic layer consisted of multiple layers of osteoblast cells with adjacent large blood vessels. However, in the mature augmented site, there was no specific inner osteogenic layer, and the outer fibrous layer was dominant. Conclusions: The fabrication of CTM based on the application of the 3D-printing technique makes vertical ridge augmentation easier and can reduce complications and achieve target bone acquisition. In addition, it is expected that quantitative analysis of the pseudoperiosteum layer will be facilitated using the CTM. Keywords: 3D printing, surgical mesh, alveolar ridge augmentation, bone substitutes

Purpose: To report the prevalence of early implant failure and evaluate factors that contribute to the early failure of dental implants placed at a teaching clinic. The study also aims to identify risk indicators for early implant loss to better predict and prevent early implant loss in the future. Materials and Methods: This retrospective study included all patients with a dental implant placed by the Section of Oral Surgery and Oral Medicine, Department of Clinical Dentistry, University of Bergen, between January 2011 and December 2018. All information was collected from operation logbooks and from patient records. A failed implant in this study was defined as an implant lost before functional loading. Results: A total of 1,005 dental implants were placed in the studied time period, of which 54 failed early, giving an early failure rate (EFR) of 5.4%, with functional loading obtained for the remaining 94.6%. Analysis showed an increased hazard for early implant failure among smokers, men, and younger patients. With an age increase of 10 years, the risk of implant failure was reduced by 14% (hazard ratio [HRR] = 0.86, P = .037). A higher failure rate was found in anterior maxillary implants than in posterior maxillary implants (7.79% vs 3.29%, respectively; HRR = 0.47; P = .041). The probability for early failure in the posterior mandible was significantly increased compared to the posterior maxilla (HRR = 3.68, P = .005). If the first implant failed, it was more likely that the consecutive implant would also fail (HRR = 1.82). In the study, 53.4% of the placed implants were Straumann (EFR = 5.2%), 30.3% were Nobel Biocare (EFR = 7.2%), and 16.3% were Astra Tech (EFR = 2.5%). Conclusions: This study found that younger, male, and smoker patients were associated with an increase in early failure of dental implants. Significantly increased failure rates were also seen for implants placed in the mandible, and there were differences with respect to implant system. Although differences were found in early failure both for patient- and implant-related factors, the overall early failure rate (5.4%) in this study was low. Keywords: complications, dental implants, early implant failure, risk indicators

Purpose: To determine the characteristics of dental implant transmucosal surfaces that influence soft tissue attachment and marginal bone loss (MBL). Materials and Methods: The PubMed, Embase, and Cochrane Library electronic databases were searched based on predefined PICO eligibility criteria. Data from animal studies that compared junctional epithelium and connective tissue attachment and MBL from 4 days to 72 weeks were analyzed. The risk of bias was performed with the Systematic Review Centre for Laboratory Animal Experimentation tool. A rank analysis evaluation of data was performed, and the most frequently appearing materials/surfaces for each tissue compartment were identified. Results: The search identified 3,549 studies, 28 of which were eligible for analysis, with an average risk of bias of 28% ± 10%. Machined, polished, etched, sandblasted, or coated titanium and zirconia materials/surfaces were most frequently examined. Several studies investigated lithium disilicate, polyether ether ketone (PEEK) or polyether ketone ketone (PEKK), aluminum oxide, and gold. Based on ranking and frequency of use at different time points, titanium grade IV (Ti-4) microthreads with a polished neck area most frequently supported natural tooth-like junctional epithelial attachment (≤ 1.5 mm), while machined Ti-4 and machined titanium grade V (Ti-5) most frequently supported connective tissue attachment (≤ 1.25 mm) and led to the least MBL (≤ 0.75 mm). Conclusions: Analyzed data suggest that Ti-4 microthreads with a polished neck area and machined Ti-4 and Ti-5 were the materials/surfaces of choice for the transmucosal part of implants. However, the extensive heterogeneity in reported studies precludes solid identification of the best materials/surfaces. Keywords: abutment surfaces, bone loss, dental implants, soft tissue attachment, transmucosal implants