The International Journal of Oral & Maxillofacial Implants, 04/2021

Purpose: To evaluate the effect of bovine-derived anorganic bone graft (ABB) in combination with hemostatic plant extract (ABS) on bone regeneration. Materials and methods: Three bone defects were created via an extraoral approach on the mandibles of nine domestic pigs. The first defects were filled with ABS solution (0.3 mL/defect) in a transporting agent of ABB (0.3 cc/defect), whereas the second defects were filled with ABS (0.3 mL/defect) in microcapsules for controlled drug release, combined with ABB (0.3 cc/defect) again. The third defects were left empty. After a 10-week healing period and the sacrification, undecalcified sections were prepared for histomorphometric analysis. Results: The mean total area of hard tissue was 29.54% ± 3.2% in the control group, 59.78% ± 5.4% in the conventional group, and 63.67% ± 4.2% in the microsphere group (P < .001). The mean area of newly formed bone was 29.54% ± 3.2% in the control group, 34.79% ± 3.9% in the conventional group, and 37.95% ± 5.3% in the microsphere group (P = .003). The mean residual graft area was 24.99% ± 2.4% in the conventional group and 25.71% ± 4.4% in the microsphere group (P = .730). Conclusion: The combined usage of ABS and ABB in both ways increased bone regeneration statistically. However, there was no significant difference between the two methods for ABS delivery systems in terms of new bone regeneration. Keywords: bovine-derived anorganic bone graft, controlled release, hemostatic plant extract, histomorphometry

Purpose: The aim of this study was to determine the effect of solid (one-piece) and two-piece abutments on the stress profile of narrow implants with marginal bone loss. Materials and methods: Solid and two-piece abutments were connected to a conical internal octagon-connection implant (3.3 mm in diameter, 10 mm in length) and restored with a single crown. Three-dimensional finite element analysis was used to simulate the stress distribution in implant models with different levels of marginal bone resorption (0, 1, 2, and 3 mm). The effect of the design variables under increased bone resorption scenarios, including abutment screw length and diameter, was assessed. Static loading was applied to determine the mechanical response of the implant and cortical and trabecular bone. Results: Marginal bone resorption levels dominated the mechanical response under static loading conditions. A marginal bone loss of 3 mm significantly increased stress values in the implant vicinity and abutment screw. Both abutment designs displayed similar stress distribution in the surrounding bone, but lower stress values were observed in the implant body with two-piece abutments. The abutment screw length was more effective in the resultant stress, as the longer screws reduced the stress in the implants. Conclusion: Marginal bone resorption magnitude is the crucial parameter in biomechanics to determine the mechanical behavior. As bone loss increases, resultant stress around implants under mastication forces may lead to implant failure, regardless of abutment type. Keywords: dental implants, finite element analysis, marginal bone loss

Purpose: To evaluate whether a hydrophilic surface treatment compared with a hydrophobic implant surface can enhance osseointegration by analysis of calcium deposition, bone-to-implant contact (BIC), bone volume (BV), and upregulation of genes involved in bone formation. Materials and methods: Sixty implants (n = 60) with a hydrophobic (SAE) or hydrophilic (SAE-HD) surface treatment were placed bilaterally in each femur of 3-month-old male mice (n = 30). Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) were utilized for quantifying the presence of calcium on the implant surface 7 days after implant placement. The specimens were analyzed after 14 and 21 days for BIC and BV by Nano CT scanning followed by histologic evaluation. Additionally, 1, 3, and 7 days postsurgery, femurs were harvested, implants were explanted, and gene expression (Sp7, Bsp, Sost, IL-1α, and IL-10) by quantitative real-time polymerase chain reaction was studied. Moreover, implants were characterized for surface roughness area. Data were statistically analyzed with two-way analysis of variance (ANOVA) followed by the Tukey test (P < .05). Results: The amount of calcium on the surface was higher for SAE-HD after 7 days. Nano CT revealed significantly more BV in the SAE-HD than the SAE surface. The histologic assessment showed increased BIC in SAE-HD in comparison to SAE. SAEHD showed significantly increased levels of genes involved in bone formation. Conclusion: Both surfaces were able to modulate bone responses toward osteoblast differentiation. SAE-HD presented a better response compared with SAE. Keywords: bone-to-implant contact, dental implant, hydrophilicity, osseointegration, surface chemistry

Purpose: To examine the reaction of mucosa over time to a close contact with biomaterial after sinus elevation performed with deproteinized bovine bone mineral (DBBM) granules of two different sizes. Materials and methods: Bilateral sinus mucosa elevation was performed in 18 New Zealand rabbits through access on the nasal dorsum. DBBM with granule dimensions of either 1 to 2 mm (large group) or 0.250 to 1.0 mm (small group) were used to randomly fill the subantral hollow spaces. Biopsy specimens of the experimental sites from six animals in each group were obtained 2, 4, and 8 weeks after the surgery. Results: The integrity of the sinus mucosa was clinically evaluated during surgery using a ×2.5 magnifying visual device. The sinus mucosa in contact with the biomaterial granules was found to be thinned compared with the pristine mucosa in all periods examined. Three hundred fifty-two thinned zones were found considering all 36 sinuses treated. Perforations of the sinus mucosa with extrusion of granules toward the sinus were observed, increasing in number over time. In the 8-week healing period, five perforations in three sinuses and eight perforations in four sinuses were found in the large and small groups, respectively. No differences were seen between the large and small groups. The differences between 2 and 8 weeks were statistically significant for the thinned mucosa width in both the large and the small groups and for the number of sinuses and perforations for the small group. Conclusion: Thinning zones and perforations of the sinus mucosa were seen increasing in number over time in regions in contact with graft granules in both the large and small groups. Keywords: animal study, bone healing, sinus floor elevation, xenograft, perforation

Purpose: The aim of this systematic review with meta-analysis was to compare the survival rate of single crowns supported by extra-short implants (≤ 6 mm) to those supported by conventional implants, with or without previous maxillary sinus augmentation. The proportion of failures was described according to the type of complication and follow-up periods. Materials and methods: Randomized and prospective clinical trials were selected from six databases and gray literature. The risk of bias was evaluated by Joanna Briggs Institute Critical Appraisal Checklist, and the certainty of the evidence was analyzed with Grading of Recommendations Assessment, Development, and Evaluation. Meta-analyses were processed with RevMan and MedCalc Statistical Software. Results: Single crowns supported by extra-short implants had a similar risk of failure to those supported by conventional implants, regardless of previous maxillary sinus augmentation (P > .05). Overall failure proportion of extra-short implants was 5.19%, but it varied according to follow-up (1.18% before loading, 1.56% at 12 months, 1.20% at 24 months, 2.10% at 48 months). Biologic failure complications were 37.90% for bleeding on probing, 22.45% for peri-implantitis, and 11.29% for infection. Prosthodontics failure complications were 14.88% for abutment failures and 14.73% for prosthetic screw loosening. Considering the risk of bias, most studies were classified at moderate risk. Conclusion: The risk of failure of single crowns supported by extra-short implants is similar to those supported by conventional implants, regardless of previous maxillary sinus augmentation or follow-up period. The most frequent biologic and prosthetic complications were bleeding on probing and abutment failures, respectively. Keywords: dental implants, meta-analysis, short implants, single crowns, systematic review

Purpose: To determine the profile of gene expression of soft connective tissue covering bone grafted with deproteinized bovine bone mineral (DBBM) or demineralized freeze-dried bone allograft (DFDBA) in comparison to that without grafting. Materials and methods: Calvaria defects of mice were created and treated as follows: (1) defect without a graft as a control, (2) grafted with DBBM, or (3) grafted with DFDBA. After 1 month, the animals were sacrificed. Soft connective tissue covering the defect area was collected by a punch technique. RNA was isolated and processed to cDNA. Gene expression was evaluated with the microarray technique. Pathway analyses were performed via the PANTHER Overrepresentation test and WikiPathway analysis. Inflammatory marker genes were chosen for mRNA expression using reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR). Tissue sections were used for the histologic and immunohistologic evaluation. Results: The numbers of genes that were significantly differently expressed were 312 (DBBM vs control), 82 (DFDBA vs control), and 113 (DBBM vs DFDBA). Inflammation-related genes were upregulated in DBBM vs control (16 genes), DFDBA vs control (3 genes), and DBBM vs DFDBA (15 genes). Two of these genes, Bcl2a1 and Cxcl9, were significantly upregulated in both the DBBM and DFDBA groups compared with the control. Pathway analysis indicated that Bcl2a1 and Cxcl9 are dominantly expressed in inflammation-related pathways. RT-qPCR and immunohistochemistry showed upregulation of Bcl2a1 and Cxcl9 in DBBM compared with the control and DFDBA groups. Cxcl9 showed a significantly higher expression in the DBBM group. Bcl2a1 at the protein level was equally expressed in all groups. Any sign of inflammation, however, was not seen by histology in any of the groups. Conclusion: After a 1-month healing period, soft tissue covering bone grafted with DBBM expressed a higher number of inflammation-related genes compared with those non-grafted or grafted with DFDBA. DFDBA resulted in a decreased expression of inflammation-related genes. Keywords: bone graft, gene expression, immunohistochemistry, inflammation, microarray, RT-qPCR

Purpose: To evaluate the impact on healing of bioactivation with argon plasma of a xenogeneic graft with adequate fixation but poor adaptation to the native host bone. Materials and methods: Xenogeneic grafts were either treated with argon plasma or left untreated and randomly secured with a titanium screw to both lateral aspects of the mandible angle of rabbits. A discrepancy was obtained between the xenograft and the mandible due to the convexity of the recipient site. Collagen membranes were placed on the grafts. Thirty animals were included and euthanized in groups of 10 after 2, 6, and 10 weeks, respectively. Histomorphometric evaluations were performed on ground sections. Newly formed bone was the primary outcome, while the distance between the peak of new bone inside the graft and the upper surface of the graft, the xenograft percentages, and the area of the xenograft were considered as secondary variables. The Wilcoxon test was applied for statistical analyses. Results: After 2 weeks of healing, gaps of ~0.5 mm were observed at the interface between the graft and the recipient sites, and new bone was mainly located in the interface and within the inferior regions of the grafts. New bone increased over time in all regions, including those in the upper zones of the graft, reaching proportions of 20.3% ± 6.5% and 19.3% ± 7.4% (P = .484) after 10 weeks in the plasma and control groups, respectively. The mean distance between the peak of new bone inside the graft and the upper surface of the graft decreased between 2 and 10 weeks of healing from 1.4 mm to 0.4 mm and from 1.7 mm to 0.3 mm at the plasma and control sites, respectively. Conclusion: The xenogeneic grafts of both groups were incorporated into the recipient sites by newly formed bone that presented a growth close to the upper surface of the graft. The bioactivation with argon plasma did not improve healing. Keywords: argon plasma, biomaterials, bone graft, histology, surgical procedure

Purpose: To evaluate the influence of age and trabecular microstructure on peri-implant strain in aging and young mice models under compressive load. Materials and methods: Eighteen 4-week-old female C57BL/6 mice (n = 6) were subjected to a 1.2% calcium content diet (young normal calcium group), and 7-month-old mice (n = 12) were randomly subjected to 0.01% and 1.2% calcium content diets (aging low and normal calcium groups, respectively) for 3 weeks. Histomorphometric and microcomputed tomography (micro-CT) analyses were used to investigate local alveolar bone microstructure. One maxilla segment from each group was reconstructed using micro-CT images to highlight the trabecular microstructure. A finite element analysis based on a computational model of the maxilla segment was performed to investigate peri-implant strain. Implants with three different diameters (0.3, 0.4, and 0.5 mm) were analyzed in these models. Results: The aging low calcium group showed worse cancellous microstructure in hematoxylin and eosin (HE) staining, significantly increased osteoclast numbers (P < .05), and reduced bone volume fraction and trabecular thickness compared with the aging normal calcium group (P < .05). However, the young normal calcium group presented no difference in trabecular microstructure and osteoclast numbers compared with the aging normal calcium group. The aging low calcium group demonstrated increased strain intensity compared with the aging normal calcium group, whereas the young normal calcium and aging normal calcium groups showed comparable strain magnitude. The strain intensity of peri-implant bone increased with worse cancellous microstructure. When the diameter increased from 0.3 mm to 0.4 mm, the percentages of pathologic overload decreased regardless of bone microstructure. Conclusion: Deteriorated bone microstructure induced by a low calcium diet determined higher strain intensity, whereas, whenever age had no significant effect on trabecular microstructure, consequently, there was no substantial influence on strain. An increase of implant diameters can improve the strain distribution. Clinical decision-making should take into consideration the patient-specific and site-specific trabecular microstructure in preoperative assessment. Keywords: aging, dental implants, finite element analysis, strains, x-ray microtomography

Purpose: To assess the impact of abutment angulation on loosening torque, torque loss, and percentage of torque loss in the prosthesis and abutment screws after aging of the implant-supported prosthesis. Materials and methods: Fifty epoxy maxillary casts with missing central, lateral, and canine teeth were used, and each cast received two implants. All casts were divided into five groups (n = 10): (1) both implants received straight abutments (0-0); (2) the central implant received a straight abutment and the canine implant received a 17.5-degree angled abutment (0-17.5); (3) the central implant received a straight abutment and the canine implant received a 35-degree angled abutment (0-35); (4) both implants received 17.5-degree angled abutments (17.5-17.5); and (5) both implants received 35-degree angled abutments (35-35). For each cast, a three-unit zirconia restoration was fabricated, and a torque meter was utilized to tighten the abutment screw (25 Ncm) and prosthesis screw (18 Ncm). The reverse torque value was recorded for each screw. All restorations were subjected to 3,500 thermal cycles between 5°C and 55°C and load cycled for 150,000 cycles with 50-N load. After the loosening torque was measured for each screw, the torque loss and percentage of torque loss were calculated. Results: There was a statistically significant difference in the torque loss of the central prosthesis screw (P < .001) and canine prosthesis screw (P < .001) between study groups. The 35-35 group showed the highest percentage of torque loss, while the 0-0 group showed the lowest value. A significant difference was found regarding the torque loss of the central abutment screw (P < .001) and canine abutment screw (P < .001). The abutment screws of the 35-35 group showed the highest percentage of torque loss, while the 0-0 groups showed the lowest percentage of torque loss. Conclusion: Screw loosening of the prosthesis and abutment screws increases with increasing abutment angulation after aging. In the same fixed prosthesis, the torque loss in the prosthesis and abutment screws was higher in canine screws employing different angled abutments. Keywords: cyclic loading, fixed partial denture, monolithic, thermocycling, zirconia

Purpose: The objective of this study was to identify the highly cited references that drove the research on implant dentistry with CBCT. Materials and methods: The literature database Web of Science Core Collection was accessed to identify a collection of papers on this theme. Cited reference analysis was conducted with the aid of CRExplorer, dedicated bibliometric software. Results: The analysis succeeded in identifying the papers that introduced the very first CBCT machines in the Asian and European markets, respectively; papers that proved the CBCT measurement accuracy, its ability to visualize sinus floor penetration, and its reduced metal artifact relative to conventional CT; papers that gave imaging guidelines for implant cases; and papers reporting bone remodeling at extraction sockets and the possibility of grafting at sites with inadequate bone. Conclusion: These publications together provided solid evidence to support subsequent dental implant research and evaluation by CBCT. Keywords: bibliometric, CBCT, image artifact, implant, spectroscopy, sinus grafting

Purpose: The aim of this study was to determine whether the Periotest device could be used to reliably and reproducibly determine the prosthetic readiness of one-piece ceramic implants. Materials and methods: Periotest values were measured on one-piece ceramic implants from two manufacturers, CeraRoot and Straumann PURE. Measurements were taken at the time of placement and up to 9 months after placement. The survival of the implants was assessed up to 12 months following placement. Data were modeled on R software utilizing the Cox Proportional Hazards model and Generalized Additive Model (GAM) regression. Results: In all, stability testing was performed on 320 placed implants in 202 patients. The overall implant survival rate after 12 months of follow-up was 96.9%. The mean Periotest value (PTV) at the time of placement was -2.0 for the surviving implants, while it was only +0.6 for the failed implants. The PTV showed a gradual and steady increase leading up to 12 to 16 weeks. The mean PTV recorded at 12 weeks was -3.2. The Periotest device provided accurate and reproducible stability measurements following the prescribed protocol, thus helping to determine readiness for prosthetic loading. Conclusion: Within the limitation of this study, the preliminary findings suggest that the Periotest is an objective tool for stability assessment of one-piece ceramic implants. Further follow-up is needed to evaluate whether the Periotest can be suggested as a monitoring device of stability after the prosthetic phase of the implants is completed. Keywords: ceramic implants, implant stability, Periotest

Purpose: This study evaluated the long-term survival and success rates of dental implants placed with autogenous onlay block bone grafts harvested from the mandibular ramus. Materials and methods: Patients treated with onlay bone graft from the mandibular ramus due to a severe vertical alveolar defect from 2001 to 2017 were included in this study. The marginal bone loss, success, and survival time of the implants were recorded and analyzed with clinical factors, such as time from bone graft to implant placement, type of implant prosthesis connection, history of periodontitis, and insertion depth. Results: Seventy-five implants in 40 onlay bone-grafted areas of 38 patients were included, with a mean follow-up period of 102 months (range: 14 to 192 months). Two grafts were removed before implant placement. Of the 75 implants, 11 implants were lost. History of periodontitis and marginal bone loss at 6 months after implant placement were significantly associated with implant success. The receiver operating characteristic curve showed that a marginal bone loss of 0.75 mm after 6 months of implant placement was related to implant success, with a sensitivity of 72.2% and specificity of 89.6%. Conclusion: Implants placed with onlay bone graft from ramal bone had more frequent biologic complications, and failures may be predicted by measuring the amount of implant bone loss after 6 months of placement. Keywords: dental implant, mandibular ramus, onlay bone graft, vertical bone deficit

Purpose: The study aimed to evaluate the outcomes of flapless guided surgery related to surgery, patient, operator, assistant, and advisor, comparing it with conventional surgery performed by undergraduate students who had never placed implants in patients. Materials and methods: A randomized controlled split-mouth clinical trial was carried out. Ten patients with bilateral mandibular posterior tooth loss received an implant on each side with conventional flap surgery or flapless guided surgery that was performed by undergraduate students. Surgery time, pain, patient satisfaction, quantity of consumed medications, time of procedure, ease of procedure, anxiety, and stress were assessed. Results: Conventional surgery showed statistically significantly inferior results compared with flapless guided surgery in terms of procedure time (56 minutes, 36 seconds ± 8 minutes, 38 seconds vs 30 minutes, 1 second ± 6 minutes, 2 seconds), consumption of analgesic medications (49 tablets vs 15 tablets), intraoperative (1.75 ± 1.56 vs 0.65 ± 0.64) and postoperative pain (4.62 ± 2.17 vs 1.17 ± 0.72), and operator anxiety (4.76 ± 1.66 vs 3.47 ± 1.50), respectively. Conclusion: Flapless guided implant surgeries performed by individuals with no previous clinical experience showed reduced surgery time and delivered better patient-reported outcomes both in the intraoperative and postoperative periods; reduced medication consumption; and showed better results in the operator and assistant perspectives. Keywords: 3D, computer-guided surgery, dental implant, flapless procedure, surgical guide

Purpose: The aim of this study was to investigate the influence of different clinical parameters on the primary stability of a variable thread tapered implant system with a focus on surgical undersizing protocols. Materials and methods: This retrospective study evaluated patients who received NobelActive implants in a single institution. The relationship between the independent variables, bone quality, implant diameter, implant length, implantation time, region of the jaw, and surgical undersizing protocol, and the dependent variable, maximum insertion torque, was investigated. Statistical analysis was conducted using analysis of variance (ANOVA) and multiple linear regression. Results: A total of 1,292 implants placed in 574 fully or partially edentulous patients were evaluated. For the total sample size, without further differentiation between bone qualities, statistically significantly higher primary stability values were shown for an 8% to 9% undersized group (50.33 ± 17.16 Ncm), compared with a 16% undersized group (41.88 ± 17.63 Ncm), a 20% undersized group (33.65 ± 15.78 Ncm), a 26% to 28% undersized group (34.53 ± 15.49 Ncm), and a 35% to 44% undersized group (32.78 ± 18.80 Ncm). No statistical differences were found for undersizing protocols in bone quality 4. Bone quality had the highest influence on primary stability (Welch-Test F(3, 65.57) = 119.48, P < .001, η² = .20). Contrary to the other investigated independent variables, no statistically significant differences in primary stability were found for the different implantation times. Conclusion: Undersizing protocols exceeding 8% to 9% do not seem to enhance primary stability values. Further studies are needed to investigate the biologic consequences of undersizing, including the impact of implant design characteristics. Keywords: bone quality, primary stability, tapered dental implant, undersized drilling protocol

Purpose: This study aimed to investigate the influence of oversized drilling on the stability of the implant and the bone response during osseointegration. Materials and methods: The trial was designed as a prospective, parallel-group randomized controlled clinical trial with 20 implants placed in the posterior region of the maxilla. The sample size was divided into two groups, 10 each, with implants being placed with manufacturer-recommended implant osteotomy preparation according to the manufacturer guidelines in one group (MR group) vs oversized osteotomy preparation (3 to 5 mm) in the other group (oversized drilling [OD] group). The implant stability was monitored for 3 months by means of resonance frequency analysis, while the crestal bone levels were recorded using parallel technique periapical radiography for 6 months. Patient-reported outcomes including pain, swelling, satisfaction, and implant survival were all monitored throughout the study. Results: In the MR group, a mean decrease in implant stability quotient (ISQ) values was detected during the first 4 weeks, after which a gradual increase in values was recorded. In comparison, the OD group showed a rapid increase in ISQ value over the entire follow-up period from baseline and up to week 12. Regarding crestal bone level, follow-up showed a significant difference when comparing baseline and 6-month radiographs (P = .00) between the OD group, 0.908 mm ± 0.343, and the MR group, 1.3 ± 0.23 mm. Conclusion: Within the limitations of this study, the results suggest that the oversized osteotomy technique may lead to earlier implant stability and postsurgical recovery compared with the manufacturer-recommended technique for osteotomy preparation. However, further studies are needed to confirm these findings. implant stability, osseointegration, oversized drilling protocol, undersized drilling protocol

Purpose: The aim of this retrospective study was to evaluate the clinical performance of two implants supporting mandibular overdentures by means of clinical and radiologic parameters, and also to explore the relationship of marginal bone loss with implant-/patient-related factors and soft tissue parameters. Materials and methods: Data of patients who had undergone insertion of two implants into the interforaminal region between November 2012 and December 2016 using three different implant systems were retrieved from the archival records. Age, sex, implant length, implant diameter, observation period, mobility, and soft tissue parameters were recorded. Marginal bone levels and interimplant distances were measured with computer software on panoramic radiographs obtained at 3 months and at the recall session. Results: A total of 43 patients with 86 implants were included in the study. Patients were evaluated with an average observation period of 41.79 months. Among the evaluated parameters, Gingival Index, Bleeding Index, and implant diameter were found to have significant effects on the marginal bone loss (P < .05). However, no significant effects of sex, age, implant length, observation period, and interimplant distance were observed on the marginal bone loss. No implants showed peri-implantitis or mobility, while eight implants showed peri-implant mucositis. Conclusion: Within the limitations of this study, it can be concluded that peri-implant soft tissue health and the diameter of the implant have an important effect on the marginal bone loss as well as the success of two-implant-supported mandibular overdentures. Keywords: edentulous mandible, interforaminal implants, overdenture

Purpose: The aim of this split-mouth randomized clinical trial was to evaluate the primary and secondary stability of implants with hydrophilic surfaces in comparison to implants with conventional surfaces in the posterior region of the maxilla. Materials and methods: Twenty patients with a bilateral edentulous ridge in the posterior area of the maxilla randomly received implants with two types of surfaces: (1) implants with the surface modified by double acid-etching and sandblasting (DAS, n = 20); and (2) implants with the surface modified by double acid-etching and sandblasting, stored in 0.9% saline solution to confer highly hydrophilic properties (DAS-H, n = 20) on the surface. The implants presented the same macrostructure with a hybrid design. The resonance frequency analysis was performed in order to obtain the implant stability quotient (ISQ) using Osstell. The ISQ analyses were performed just after placement of the implant (primary stability) and at 28, 40, and 90 days after the surgical procedure (secondary stability). Results: There were no differences between the DAS and DAS-H surfaces in the primary stability or during the conversion of the primary to the secondary stability; however, there was a reduction in the stability of the implants at 28 days, which increased significantly at 40 and 90 days in both surfaces. Conclusion: It can be concluded that the surface wettability of implants with a hybrid macrostructure did not increase the primary and secondary implant stability in the posterior region of the maxilla. Keywords: dental implants, implant surface, stability

Purpose: The purpose of this cone beam computed tomography (CBCT) study was to investigate the probability of using straight screw-channel screw-retained restorations following an immediate implant placement and provisionalization protocol in maxillary anterior teeth utilizing implant planning software. Materials and methods: A retrospective review of CBCT images was done. The midsagittal images of maxillary anterior teeth (right canine to left canine) were created in implant planning software, screen-captured, and transferred to a presentation program. The digital implant templates were created for 3.5-mm-diameter (used for central and lateral incisors) and 4.5-mm-diameter (used for central incisors and canines) tapered implants with lengths of 13, 15, and 18 mm. The frequency percentages of immediate implant placement and provisionalization and immediate implant placement and provisionalization with straight screw-channel screw-retained restorations were recorded and compared among all maxillary anterior teeth. Results: CBCT images from 1,200 teeth were evaluated. The overall frequency percentages of immediate implant placement and provisionalization and immediate implant placement and provisionalization with straight screw-channel screw-retained restoration were 84% (range = 74% to 92%) and 14% (range = 10% to 24%), respectively. Conclusion: Although the probability of being able to employ immediate implant placement and provisionalization with a straight screw-channel screw-retained restoration in the esthetic zone is low, the use of smaller-diameter implants can substantially increase the probability. Keywords: cone beam computed tomography, dental implantation, dental implants, esthetics, immediate placement, prosthodontics

Purpose: The aim of this study was to evaluate maxillary full-arch implant-supported fixed rehabilitations by identifying biologic complications, implant survival and success rates, and patient satisfaction with treatment. In addition, the study verified the influence of attendance at maintenance appointments on the occurrence of complications. Materials and methods: Data were collected from clinical follow-up appointments. Results: The sample consisted of 52 patients (363 implants) with follow-up of 1 to 12 years (mean: 4.69). The main biologic complication was soft tissue recession (20.8%) at the implant level. Tissue hyperplasia was observed in eight patients (15.4%), and 17 (4.7%) implants had bone loss ≥ 2 mm. The peri-implantitis rate was 3.1% (11 implants). Implant survival and success rates were 97.8% and 93.4%, respectively. Rates of patient satisfaction with treatment were as follows: 21 (40.4%) completely satisfied, 28 (53.8%) satisfied with some complaint, and 3 (5.8%) expected more from treatment. The main complaint was the difficulty of cleaning (64.5%). Patients who attended annual follow-up appointments were associated with less bone remodeling and peri-implant disease, but no significant difference was found in biofilm accumulation. Conclusion: This type of rehabilitation is susceptible to biologic complications, but high survival and success rates and patient satisfaction were found. Periodic maintenance was associated with reduced complications, such as bone loss or peri-implantitis. Keywords: biologic implant complications, follow-up, implant fixed complete dental prostheses, implant survival

Purpose: This cross-sectional study aimed to identify and characterize the pathway for appropriate placement of four zygomatic implants in the severely atrophic maxilla and to group the anatomical variations of the osteotomy trajectory for anterior zygomatic implants. Materials and methods: CBCT images of patients presenting indications for the use of four zygomatic implants to withstand a maxillary rehabilitation were reviewed. Cross-sectional planes corresponding to the implant trajectories, designed according to a zygoma anatomy-guided approach for implants placed in the anterior and posterior maxilla, were assessed separately. The relationship of the implant osteotomy trajectory with the correlated residual alveolar bone, nasal and sinus cavities, maxillary wall, and zygomatic bone anatomies was established. Results: The study population included 122 globally recruited patients, with 488 zygomatic implants, 244 of which had their starting point on the anterior incisor-canine area and 244 on the posterior premolar-molar area. The anatomy of the osteotomy path designed for the anterior implants ("A") was named and grouped into five assemblies from zygomatic anatomy-guided ZAGA A-0 to A-4, representing 2.9%, 4.5%, 19.7%, 55.7%, and 17.2% of the studied sites. Percentages for posterior implant ("P") trajectories of the osteotomy were grouped and named as ZAGA P-0 to P-4, representing 5.7%, 10.2%, 8.2%, 18.4%, and 57.4% of the sites, respectively. Approximately 70% of the population presented anatomical intra-individual differences. Conclusion: The trajectory of the zygomatic implant followed different anatomical pathways depending on its coronal point being anteriorly or posteriorly located, which justifies a new zygoma anatomy-guided approach classification for anteriorly placed zygomatic implants. Topographic characteristics of the anatomical structures that are cut by an anterior oblique plane joining the lateral incisor-canine area to the zygomatic bone, representing the planned anterior osteotomy path in a quadruple-zygoma indication, have not been previously reported. Adaptation of surgical procedures and implant sections/designs to individual patients' anatomical characteristics is essential to reduce early and long-term complications. Keywords: cross-sectional studies, maxillary atrophy, zygoma, zygoma anatomy-guided approach, zygomatic implants

Purpose: This study aimed to investigate whether axial or radial functionally graded root analog implants can optimize the stress and strain distribution near the implant-bone interface in alveolar bone models under static loads using finite element analysis (FEA). Materials and methods: The 3D profile of the root analog implant was captured from a natural tooth in CBCT data. The implant was separated into different layers (3, 5, and 10 layers) to vary the Young modulus axially or radially. The variation in Young modulus was designed to be linear, exponential, or parabolic. Different occlusal loads were applied. The von Mises stress and strain were used to evaluate the system risk of failure. Results: The difference in the numbers of layers had no significant effect on the alveolar bone. In the radial functionally graded implant models, the maximum von Mises stress of the alveolar bone decreased as the outer layer's elastic modulus increased; however, in the vertical functionally graded implants, this stress varied little. The maximum von Mises stress of the cancellous bone changed only slightly, from 2 to 5 MPa in all models. The maximum strain of the alveolar bone varied from 0.001478 mm to 0.003999 mm. Those FEA results were in line with previous findings. Conclusion: The functionally graded root analog implants show no significant biomechanical advantages over dense zirconia implants. Radial functionally graded root analog implants should optimize the peri-implant stresses and are biomechanically favorable for design. Keywords: biomechanics, finite element analysis, functionally graded material, root analog implant, Young modulus

Purpose: To analyze the effect of implant placement and loading protocols (protocol types) on the survival of single implant tooth replacements in different locations. Materials and methods: An electronic search was conducted to identify clinical trials regarding outcomes of single implants subjected to different treatment protocols. A weighted mean survival rate for each protocol type in the anterior maxilla, anterior mandible, posterior maxilla, and posterior mandible was calculated. Study design, sample size, and outcome homogeneity were used to evaluate the validation of each protocol type in different locations. Results: A total of 45 publications (13 RCTs, 21 prospective studies, and 11 retrospective studies) were included. The anterior maxilla was the most reported site (35 studies, 1,391 implants, weighted survival rate: 97.5% to 99.6%). Immediate placement + conventional loading (Type 1C) and late placement + immediate restoration/loading (Type 4A) were scientifically and clinically validated (SCV). For the posterior maxilla (19 studies, 567 implants, weighted survival rate: 85.7% to 100%), Type 1C was SCV. The anterior mandible was the least-reported site (three studies, 42 implants, weighted survival rate: 98.5% to 100%). For the posterior mandible (13 studies, 447 implants, weighted survival rate: 95.0% to 100%), late placement + conventional loading (Type 4C) was SCV. It was not possible to perform a metaanalysis due to the limited number of controlled studies that had the same comparison and considerable heterogeneity in study design. Conclusion: Differences were found in the level of scientific evidence between the anterior and posterior and the maxilla and mandible, indicating that location is a consideration when selecting treatment protocol for a single implant. Keywords: dental implants, placement and loading protocol, single implant

Purpose: The objective of this investigation was to assess the extent of mucosal discoloration caused by different CAD/CAM abutment materials and to determine the influence of mucosa thickness on the subsequent color, with a particular focus on titanium nitride. Materials and methods: In a pig maxilla, a trapdoor-shaped mucosa flap was prepared unilaterally. Several CAD/CAM abutment materials were used to assess a number of clinical scenarios. Varying mucosa thicknesses were simulated by connective tissue grafts harvested at the contralateral side of the palate, resulting in layer thicknesses of 1.5, 2, and 3 mm. Titanium (Ti), zirconia (ZrO₂), and titanium nitride (TiN) served as test specimens with and without ceramic veneering. Color differences (ΔE) and deviations in brightness (L), chroma (C), and hue (H) were determined spectrophotometrically, comparing the measured value of the native tissue and the results obtained with different materials at varying mucosa thicknesses. Results: All tested specimens caused a mucosa discoloration in comparison to the native tissue, diminishing with increasing mucosa thickness. The use of TiN demonstrated the least mucosa discoloration in thin soft tissue of 1.5 mm, with a mean ΔE value of 1.93 (P = .004). While ZrO₂ revealed a comparable ΔE value of 2.13 (P = .022) at a tissue thickness of 1.5 mm, Ti showed the highest mucosa discoloration above the visibility threshold of ΔE = 3.1, with a mean ΔE value of 4.07 (P = .002). Ceramic veneering of the Ti samples led to a considerable reduction in soft tissue discoloration, with a resulting ΔE value of 2.2. The veneering of TiN and ZrO₂ samples with porcelain, on the other hand, had no noticeable effect on the mucosa color. Conclusion: CAD/CAM abutment materials cause an adverse soft tissue color shift that decreases with increasing mucosa thickness. In thin peri-implant mucosa, titanium nitride and zirconia lead to the least discoloration. Due to their positive optical properties and mechanical superiority compared with ceramic abutments, gold-hue titanium nitride-coated CAD/CAM abutments could be a clinical alternative in cases of thin peri-implant mucosa. Keywords: CAD/CAM abutment, gold hue, mucosa discoloration, peri-implant mucosa, spectrophotometer, titanium nitride