The International Journal of Oral & Maxillofacial Implants, 04/2016

Purpose: To evaluate the influence of different implant numbers and connection types on the biomechanical behavior of mandibular full-arch implant-supported rehabilitation. Materials and Methods: Computed tomography-based finite element models comprising a totally edentulous mandible and 3.8 × 13-mmdiameter implants, abutments, abutment screws, bar retaining screw, and bar were constructed. Different implant numbers (three, four, and five implants) and loading conditions (symmetrical/balanced, unilateral, and posterior with diverse loading magnitudes) were simulated for both external hex and Morse-taper connections. The peak equivalent strain (EQV strain) in the bone and the peak of von Mises stress (EQV stress) in the abutment screw and bar retaining screw were evaluated. Results: Lower strain values were observed for a symmetrical loading distribution. Considering the same loading conditions, significantly higher bone strain levels were observed for external hex, compared with the Morse-taper connection. The number of implants had no significant influence on strain levels in bone, irrespective of the connection types. Compared with the external hex connection, the Morse-taper connection type presented significantly lower EQV stress values in abutment screws, but significantly higher stress in the bar retaining screw. Increasing the number of implants significantly reduced the EQV stress in the abutment screw and bar retaining screw. Conclusion: The Morse-taper connection type significantly decreased the strain levels in peri-implant bone, while increasing the stress in bar retaining screws. A smaller number of implants in an inferior full-arch rehabilitation slightly increased the stress in the abutment and bar retaining screws. Balanced adjustments of the loading improve the biomechanics of a mandibular full-arch rehabilitation. Keywords: biomechanics, dental implants, edentulous mandible, finite element analysis

Purpose: The radiologic outcomes of implants placed using static computer-guided surgery have not yet been systematically investigated. The purpose of this study was to evaluate the marginal bone loss (MBL) around dental implants inserted with static computer assistance in healed sites. Materials and Methods: An electronic search of publications in English from three databases (from 2000 to March 2015), including PubMed, Web of Science, and Cochrane Oral Health Group Trials Register, and a hand search of peerreviewed journals for relevant articles were performed. Only clinical human studies, either randomized or nonrandomized, with at least 10 cases and a minimum follow-up time of 12 months, reporting on MBL were included. Results: The search strategy resulted in 18 publications, with 2,675 implants inserted with static computer assistance in healed sites. The pooled mean MBL at 1-year follow-up was 1.06 mm (95% CI: 0.83 to 1.30 mm; heterogeneity: random-effects model, I2 = 99.38%; P < .01). Moreover, when considering studies with a 3-year follow-up only (n = 5; 748 implants), the pooled MBL was 1.48 mm (95% CI: 0.81 to 2.15 mm; heterogeneity: random-effects model, I2 = 99%; P < .01). Conclusion: Within the limitations of this review, the MBL around dental implants placed in healed sites with computer-guided surgery seems to be a well-functioning one-stage alternative to extended two-stage conventional procedures if patients are appropriately selected and an appropriate width of bone is available for implant placement. However, current evidence is limited by the quality of available studies and the lack of comparative long-term clinical trials. Keywords: bone loss, dental implants, flapless, guided surgery, immediate loading, stereolithography

Purpose: Acid etching in conjunction with storage in an aqueous solution can induce nanostructures forming spontaneously on titanium surfaces, but an inevitable biologic degradation is suspected to accompany the evolution of nanostructures. The aim of this study was to investigate whether ultraviolet (UV) irradiation is effective to solve this problem and further enhance the bioactivity. Materials and Methods: Surface characteristics of five groups of titanium implants (SLAnew, SLAold, modSLA, UV-SLA, and UV-modSLA) and their in vivo bone response were analyzed in this study. The surface characteristics were evaluated with contact angle measurements, scanning electron microscopy, and x-ray photon spectroscopy. A total of 160 implants (32 for each group) were inserted into the tibial metaphyses and femoral condyles of 40 rabbits. After 3 and 6 weeks, the rabbits were euthanized for removal torque tests and histomorphometric analysis. Results: Spontaneously formed nanostructures were observed on water-stored surfaces with a size of approximately 15 nm in diameter, and an inevitable contamination of hydrocarbons accompanied the evolution of nanostructures. UV irradiation effectively eliminated hydrocarbon contamination that accompanied nanostructure evolution. UV-modSLA implants showed the highest removal torque value, and UV-irradiated implants exhibited higher bone-to-implant contact and bone area. Conclusion: UV irradiation can effectively eliminate the hydrocarbon contamination accompanying the evolution of nanostructures and further enhance the osseointegration. Nanostructures and UV treatment have combined effects in enhancing the interfacial strength between titanium and bone, while UV photofunctionalization has much more overwhelming effects on histologic and histomorphometric performance. Keywords: biologic aging, contamination of hydrocarbons, osseointegration, spontaneously formed nanostructures, UV photofunctionalization

Purpose: Strains tending to pull the periosteum away from the bone are typically osteogenic. The aim of this study was to assess the influence of periosteum on de novo bone formation in a rat calvaria model of distraction osteogenesis. Materials and Methods: A total of 28 rats were randomized in four experimental groups considering two treatment modalities. Periosteum was either left intact or completely excised. In half of the animals, the distraction plate was covered with a collagen membrane. All animals were subjected to a 7-day latency period and a 10-day distraction period. The samples were harvested after a 2-week consolidation period and analyzed histologically and by means of microcomputed tomography (micro-CT). Results: New bone in all animals originated from the original bone surface. Two groups of animals with periosteum, with membrane (24.56 ± 5.26) and without membrane (21.83 ± 14.04), showed significantly more bone volume compared with groups without periosteum, with membrane (2.72 ± 1.08, P = .003) and without membrane (4.25 ± 2.33, P = .014). There were no significant differences between the four groups in bone mineral density. Groups pooled together for the presence of periosteum demonstrated significantly more bone volume (P < .001) and bone mineral density (P = .028) than groups without periosteum. No differences were found for groups pooled for the barrier membrane application. Conclusion: The periosteum plays an indispensable, but indirect role in the osteogenic process during periosteal distraction osteogenesis. Keywords: animal model, collagen membrane, distraction osteogenesis, periosteum

Purpose: The aim of this study was to evaluate whether the drilling speed used during implant site preparation influences primary stability. Materials and Methods: Eighty tapered designed implants (3.8 × 10 mm) were inserted following osteotomies created in solid rigid polyurethane foam (simulating bone type II) and cellular rigid polyurethane foam (simulating bone type IV). Half were prepared using drilling speeds of 800 rpm (low speed), and the other half were prepared using speeds of 1,500 rpm (high speed). Following insertion, implant primary stability was measured using Periotest and Osstell (resonance frequency analysis [RFA]) devices. Results: Two-way analysis of variance (ANOVA) used for this study found that the drilling speed used to create the osteotomies appeared to have no significant impact on primary stability. Conclusion: The bone quality and not the osteotomy drilling speed seems to influence the implant primary stability. Keywords: dental implants, drilling speed, implant design, primary stability

Purpose: The aim of this study was to evaluate the surface characteristics and gingival fibroblast adhesion of disks composed of implant and abutment materials following brief and repeated instrumentation with instruments commonly used in procedures for implant maintenance, stage-two implant surgery, and periimplantitis treatment. Materials and Methods: One hundred twenty disks (40 titanium, 40 titaniumzirconium, 40 zirconia) were grouped into treatment categories of instrumentation by plastic curette, titanium curette, diode microlaser, rotary titanium brush, and no treatment. Twenty strokes were applied to half of the disks in the plastic and titanium curette treatment categories, while half of the disks received 100 strokes each to simulate implant maintenance occurring on a repetitive basis. Following analysis of the disks by optical laser profilometry, disks were cultured with human gingival fibroblasts. Cell counts were conducted from scanning electron microscopy (SEM) images. Results: Differences in surface roughness across all instruments tested for zirconia disks were negligible, while both titanium disks and titaniumzirconium disks showed large differences in surface roughness across the spectrum of instruments tested. The rotary titanium brush and the titanium curette yielded the greatest overall mean surface roughness, while the plastic curette yielded the lowest mean surface roughness. The greatest mean cell counts for each disk type were as follows: titanium disks with plastic curettes, titanium-zirconium disks with titanium curettes, and zirconia disks with the diode microlaser. Conclusion: Repeated instrumentation did not result in cumulative changes in surface roughness of implant materials made of titanium, titanium-zirconium, or zirconia. Instrumentation with plastic implant curettes on titanium and zirconia surfaces appeared to be more favorable than titanium implant curettes in terms of gingival fibroblast attachment on these surfaces. Keywords: cell attachment, dental implants, fibroblasts, maintenance, surface roughness, titanium

Purpose: This study sought to (1) compare the effects of crown preseating prior to cementation, (2) determine whether maintenance of screw access openings on titanium abutments and open vent holes on cast crowns affects the amount of excess cement at the crown-abutment margin, and (3) analyze the associated tensile force after cementation. Materials and Methods: Three independent variables were tested: (1) abutment screw access (open or closed), (2) crown coping modification (with or without a vent hole in the palatal aspect), and (3) crown preseating on an abutment analog. Ten implant crown copings were cemented using temporary cement on ten straight implant abutments for each combination of the three independent variables. The amount of excess cement at the crown margins was measured by weight. Axial tensile load was measured 24 hours after cementation. Results were statistically analyzed using linear regression and univariate three-way analysis of variance (α = .05). Results: Open screw access, presence of a vent hole on the crown, and preseating of the crown had significant effects on the amount of excess cement at the crown margin (P < .05). Preseating significantly lowered tensile strength values (P = .001), particularly in specimens with preseating and open screw access (P < .001). There was no significant correlation between excess cement at the margins and tensile strength values. Conclusion: Placement of vent holes on the crown or open screw access may be considered for cementing crowns on implant abutments using temporary cement in order to minimize excess cement at the crown margin. A preseating protocol is not advisable, either alone or combined with open screw access, since it significantly reduces the retentive strength of cemented restorations (P < .001). Keywords: crown preseating, excess cement, open screw access, vent hole

Purpose: The aim of this study was to evaluate the removal torque and in vitro biofilm penetration at Morse taper and hexagonal implant-abutment joints after fatigue tests. Materials and Methods: Sixty dental implants were divided into two groups: (1) Morse taper and (2) external hexagon implant-abutment systems. Fatigue tests on the implant-abutment assemblies were performed at a normal force (FN) of 50 N at 1.2 Hz for 500,000 cycles in growth medium containing human saliva for 72 hours. Removal torque mean values (n = 10) were measured after fatigue tests. Abutments were then immersed in 1% protease solution in order to detach the biofilms for optical density and colony-forming unit (CFU/cm2) analyses. Groups of implant-abutment assemblies (n = 8) were cross-sectioned at 90 degrees relative to the plane of the implant-abutment joints for the microgap measurement by field-emission guns scanning electron microscopy. Results: Mean values of removal torque on abutments were significantly lower for both Morse taper (22.1 ± 0.5 μm) and external hexagon (21.1 ± 0.7 μm) abutments after fatigue tests than those recorded without fatigue tests (respectively, 24 ± 0.5 μm and 24.8 ± 0.6 μm) in biofilm medium for 72 hours (P = .04). Mean values of microgap size for the Morse taper joints were statistically signicantly lower without fatigue tests (1.7 ± 0.4 μm) than those recorded after fatigue tests (3.2 ± 0.8 μm). Also, mean values of microgap size for external hexagon joints free of fatigue were statistically signicantly lower (1.5 ± 0.4 μm) than those recorded after fatigue tests (8.1 ± 1.7 μm) (P < .05). The optical density of biofilms and CFU mean values were lower on Morse taper abutments (Abs630nm at 0.06 and 2.9 × 104 CFU/cm2) than that on external hexagon abutments (Abs630nm at 0.08 and 4.5 × 104 CFU/cm2) (P = .01). Conclusion: The mean values of removal torque, microgap size, and biofilm density recorded at Morse taper joints were lower in comparison to those recorded at external hexagon implant-abutment joints after fatigue tests in a simulated oral environment for 72 hours. Keywords: biofilms, dental implants, fatigue, implant-abutment, removal torque

Purpose: The use of the roll pedicle flap has been recommended by various authors, but there are no studies evaluating the stability of the augmented soft tissue in the long term. The aim of this retrospective study was to evaluate the stability of peri-implant soft tissue augmented with the roll flap technique in patients with congenitally missing maxillary lateral incisors after 10 years of function. Materials and Methods: Patients with congenitally missing maxillary lateral incisors restored with dental implants in the period between 2000 and 2002 were invited for reexamination after 10 years. The esthetic of the peri-implant soft tissue was evaluated with Furhauser's pink esthetic score (PES). Results: The peri-implant soft tissue of 21 implants in 17 patients was evaluated at the 10-year follow-up. No implants were lost within the duration. The PES score was slightly improved from 11.43 ± 1.504 at baseline to 11.70 ± 1.793 at the 10-year follow-up examination without a statistically significant difference (P > .05). Conclusion: Within the limitations of this study, the roll flap technique was found to be a sustainable method for the achievement of durable peri-implant esthetics in the anterior maxillary region, especially in terms of variables related to tissue contour and appearance. Keywords: dental agenesis, dental implants, long-term results, pink esthetic score

Purpose: To determine the potential complications and clinical outcomes using the lateral sinus elevation technique with window repositioning. Materials and Methods: One hundred nine sinus elevations were performed on 102 consecutively treated patients. Following lateral window outward fracturing, sinus mucosa was elevated, and the sinus was grafted with anorganic bovine bone. Two hundred five implants were placed: 160 concomitantly with grafting, and 45 six months after grafting. Seventeen implants replaced single missing molars. One hundred eighty-eight implants replaced multiple missing posterior teeth. The bone window was repositioned over the osteotomy site and the flap sutured. Implants were connected at 6 months and followed up from 12 to 60 months (mean: 29.8 months). In 30 cases, biopsy specimens were harvested from the lateral wall of the sinus for histomorphometric analysis. The Fisher exact test and Kruskal-Wallis test followed by the Mann-Whitney test were used for statistical analysis. Results: No clinically significant complications were encountered in using this technique (mucosa tear, intraoperative bleeding, window sequestration). In three cases, the window was separated in two before outfracturing. In 20 cases, it was stabilized with a collagen fleece. Limited sinus mucosa tears occurred in 14 cases during elevation. They were patched with a collagen membrane, and 18 implants were placed in these cases. All of the latter cases osseointegrated at abutment connection with no statistically significant difference in the outcome compared with implants placed with no tear of the membrane (P < .05). The reconstruction of the lateral wall was confirmed in all cases. No significant differences in outcomes were found between the immediately and delayed placed implants (P < .05). One implant failed in the immediately placed group due to a sinus infection. All other implants were loaded and remained in function during the observation period. Conclusion: Lateral sinus elevation with window repositioning is safe and effective with minimal risks, such as mucosal tear, intraoperative bleeding, or window sequestration. The repositioned window can serve as an alternative for collagen membrane in containing the graft. Graft maturation, percent of vital bone formation, and the potential of the window to serve as a source of osteogenic cells need to be confirmed histomorphometrically. This will be reported in a subsequent article. Keywords: lateral approach, posterior maxilla, sinus floor elevation, window repositioning

Purpose: The purpose of this study was to evaluate the various factors that influence the success rate of miniscrew implants used as orthodontic anchorage. Materials and Methods: Potential confounding variables examined were sex, age, vertical (FMA) and sagittal (ANB) skeletal facial pattern, site of placement (labial and buccal, palatal, and retromandibular triangle), arch of placement (maxilla and mandible), placement soft tissue type, oral hygiene, diameter and length of miniscrew implants, insertion method (predrilled or drill-free), angle of placement, onset and strength of force application, and clinical purpose. The correlations between success rate and overall variables were investigated by logistic regression analysis, and the effect of each variable on the success rate was utilized by variance analysis. Results: One hundred fourteen patients were included with a total of 253 miniscrew implants. The overall success rate was 88.54% with an average loading period of 9.5 months in successful cases. Age, oral hygiene, vertical skeletal facial pattern (FMA), and general placement sites (maxillary and mandibular) presented significant differences in success rates both by logistic regression analysis and variance analysis (P < .05). Conclusion: To minimize the failure of miniscrew implants, proper oral hygiene instruction and effective supervision should be given for patients, especially young (< 12 years) high-angle patients with miniscrew implants placed in the mandible. Keywords: clinical success, miniscrew implants, multiple-factor regression, orthodontic anchorage

Purpose: Maxillary sinus membrane elevation is a common procedure intended to increase the volume of the maxillary sinus osseous floor prior to insertion of dental implants. The aim of this study was to evaluate bone formation under a perforated sinus membrane grafted with buccal fat pad (BFP). Materials and Methods: Six consecutive patients (10 sinus augmentations, 24 dental implants) underwent sinus floor elevation, using the lateral window approach. The compartment around the implants under the sinus mucosal lining in the sinus floor was filled with adipose tissues, which were retrieved as free graft from BFP. Clinical and radiologic follow-up was conducted through the healing period; in all cases, samples were taken for biopsy during the stage-two surgery. Results: New bone consolidation in the maxillary sinus was radiologically and histologically observed within an average of 7.2 months after the sinus augmentation. According to the histomorphometric data, 62.8% ± 13.1% vital bone formation was observed. Out of the 24 implants placed, only 1 failed, indicating a 95% overall implant survival rate. Conclusion: Despite the limited size of this case series, BFP can be considered an autologous osteogenic graft material and/or biologic membrane capable of achieving high success rates in sinus elevation procedures. Keywords: buccal fat pad (BFP), sinus augmentation, sinus membrane

Purpose: The aim of this study was to evaluate the necessity for additional regenerative procedures following healing of compromised and noncompromised extraction sockets with alveolar ridge preservation procedures through the use of virtual implant imaging software. Materials and Methods: The cohort was comprised of 87 consecutive patients subjected to a single maxillary tooth extraction with an alveolar ridge preservation procedure for subsequent implant placement. Patients were divided into two main groups based on the integrity of the buccal bone plate following teeth extraction. Patients in the compromised socket (CS) group (n = 52) had partial or complete buccal bone plate loss, and patients in the noncompromised socket (NCS) group (n = 35) exhibited no bone loss of their socket walls following tooth extraction. Following 4 to 6 months of healing, all patients had a cone beam computed tomography (CBCT) study. Root-formed implants were placed virtually in an ideal prosthetic position. The number of implants per group and location (anterior, premolar, molar) exhibiting exposed buccal implant surface was calculated. Results: In the CS group, 5 out of 19 anterior implants (26.3%), 4 out of 14 premolar implants (28.5%), and 7 out of 19 molar implants (36.8%) had exposed buccal surfaces. In the NCS group, 4 out of 9 anterior implants (44.4%), 2 out of 9 premolar implants (22.2%), and 4 out of 17 molar implants (23.5%) had exposed buccal surfaces. There were no statistically significant differences for intragroup and intergroup comparisons (χ2 test, P > .05). Conclusion: This study failed to find statistically significant differences in the frequency of implants with exposed buccal surfaces placed virtually, following treatment of compromised and noncompromised sockets. A high proportion (22% to 44%) of sites had implants that potentially needed additional regenerative procedures. Keywords: bone regeneration, bone resorption, cone beam computed tomography, cone beam virtual implant placement, dental implants, tooth extraction

Purpose: In recent years, dental implants made from zirconia have been further developed and are considered a reliable treatment method for replacing missing teeth. The aim of this study was to analyze dental implants made from zirconia regarding their clinical performance compared with natural teeth (control). Materials and Methods: One hundred six zirconia implants in 38 adults were analyzed in a clinical study after 1 year of loading. The plaque index (PI), bleeding on probing (BOP), probing pocket depth (PPD), probing attachment level (PAL), and creeping or recession (CR/REC) of the gingiva were detected and compared with natural control teeth (CT). Furthermore, the papilla index (PAP), Periotest values (PTV), microbial colonization of the implant/dental sulcus fluid, and patient satisfaction were assessed. Results: The survival rate was 100%. No statistical significance was observed between implants and teeth regarding BOP, PPD, and PAL. A statistical significance was detected regarding PI and CR/REC with significantly less plaque accumulation and recession in the study group. Mean PAP was 1.76 ± 0.55, whereas the mean PTV was -1.31 ± 2.24 (range from -5 to +6). A non-statistically significant higher colonization of periodontitis/peri-implantitis bacteria was observed in the implant group. The questionnaire showed that the majority of the patients were satisfied with the overall treatment. Conclusion: One-piece zirconia dental implants exhibited similar clinical results (BOP, PPD, and PAL) compared with natural teeth in regard to adhesion of plaque (PI) and creeping attachment (CR/REC); zirconia implants performed even better. The favorable results for PA and CR/REC reflect the comparable low affinity of zirconia for plaque adhesion. Patient satisfaction indicated a high level of acceptance for zirconia implants. However, a long-term follow-up is needed to support these findings. Keywords: clinical study, microbial contamination, patient satisfaction, zirconia, zirconia dental implants

Purpose: The aim of this study was to evaluate the degree of resorption that occurs following a period of consolidation in alveolar distraction osteogenesis and assess the amount of overcorrection necessary to achieve the planned height. Materials and Methods: A retrospective observational study was conducted comprising 19 surgically treated patients, where a total of 19 extraosseous distractors were placed. All patients undergoing surgery had a panoramic radiograph and a computed tomography scan, both at the end of distraction and at the end of the consolidation period. To assess the degree of resorption, the distance from the mandibular border, maxillary sinus floor, or nasal floor to the limit of the crestal bone following consolidation was compared with the height recorded at the end of the distraction period. Results: Resorption occurred in all cases ranging from 7% to 25%. Conclusion: The presence of resorption reported from this study indicates that an overcorrection of at least 20% may be necessary when distraction osteogenesis is performed. Keywords: alveolar distraction osteogenesis, bone resorption, overcorrection

Purpose: The purpose of this study was to evaluate the clinical, radiographic, and patient-based outcomes of dental implants placed at an undergraduate student dental clinic. Materials and Methods: A retrospective study was performed to determine the success and survival rates of dental implants placed at the undergraduate dental clinic at Dalhousie University between January 1999 and January 2012. Only patients with a minimum of 1-year follow-up were included. Clinical and radiographic assessments determined implant success and survival rates. Questionnaires recorded patients' satisfaction with esthetics, comfort, and ease of hygiene. Results: Of the 352 patients (n = 591 implants) who received implants over 13 years, 165 patients completed the clinical and radiographic examinations. By the end of the study period, demographic information and implant characteristics were collected for 111 (n = 217 implants; 47.5% in the maxilla, 52.6% in the mandible) of these patients. Of those assessed clinically, 36.4% were males and 63.6% females, with a mean age of 56.1 ± 14.15 years (range, 17 to 86 years) at the time of implant placement. The mean follow-up period was 5.8 years (range, 1 to 13 years). The overall implant success and survival rates were 88.0% and 97.2%, respectively. No observable bone loss was evident in 88.0% of the surviving implants. There were no implant fractures. Most patients (91.2%) were very satisfied with the implant restoration appearance, 88.0% were very comfortable with the implant, 92.6% were very satisfied with their ability to chew, and 84.8% reported easy hygiene maintenance at the implant sites. Conclusion: Implant success and survival in an undergraduate student clinic were comparable to those reported in the literature. It seems that inexperienced students were able to provide restorations that were very satisfying to the patients. Keywords: dental implants, success rate, survival rate

Purpose: Some initial loss of bone around dental implants is generally expected. There is reason to believe that reflecting a mucoperiosteal flap promotes crestal bone loss in the initial phase after an implant has been inserted. The objective of this study was to compare the effect of flapless implant insertion on initial bone loss with that of conventional placement after elevation of a mucoperiosteal flap. Materials and Methods: Eighty patients were randomly assigned either to the flapless group (test) or to the group with a full-thickness flap (control). In total, 195 implants were included in the study: 95 of these were inserted flapless (test group), and 100 were inserted by raising a mucoperiosteal flap (control group). Healing occurred unsubmerged for both groups. To assess changes in the peri-implant bone level, the height of the mesial and distal peri-implant bone was measured on digitally calibrated radiographs taken at the time of implant placement and 12 months afterward. Results: After 1 year, a mean cumulative crestal bone loss of 0.24 ± 0.62 mm was measured. A mean bone loss of 0.55 ± 0.57 mm was found in the group with the mucoperiosteal flap, while a slight mean gain in bone height of 0.09 ± 0.49 mm was found in the test group, a statistically significant difference (P < .001). Conclusion: Flapless implant insertion caused less peri-implant bone loss than implant insertion with flap preparation. Therefore, the flapless procedure represents a protective and promising method in implant surgery. Keywords: dental implants, flapless implant insertion, initial bone loss, taper connection, transgingival healing, transmucosal healing

Purpose: Edentulism usually leads to esthetic, functional, and emotional discomfort resulting in a loss of self-esteem and a decrease of the patient's quality of life. Dental implants provide new possibilities to ensure the comfort and efficacy of prosthetic rehabilitation. The aim of this study was to evaluate the satisfaction level of patients rehabilitated using the Brånemark protocol or overdenture implant-supported prostheses. Materials and Methods: Fifty-two patients were rehabilitated using the Brånemark protocol and 23 using overdenture prostheses. Then, an adapted oral health-related quality of life questionnaire was administered in addition to a clinical exam to determine the condition of the dental implants and prostheses. The results for treatment expectation, understanding of the type of treatment, phonetic function, chewing comfort, pain, and self-esteem improvement were analyzed with Fisher exact test (P ≤ .05). Results: Both treatments presented satisfaction of above 87%, with no statistical difference between them. Eighty-two percent of patients treated with overdenture prostheses and 80.8% of those treated with the Brånemark protocol had no complaint of pain (P = .087). Conclusion: The treatments analyzed in this study were highly satisfactory with regard to functional and esthetic factors, resulting in an increase in self-esteem and quality of life. The psychological factor is a complex variable in patient satisfaction that directly influences quality of life. Considering the desires of patients in choosing the type of prosthesis is critical to treatment success. Keywords: dental implants, edentulous mouth, implant-supported denture, overdenture, patient satisfaction

Purpose: The purpose of this study was to compare the outcome of fixed partial prostheses in the posterior maxilla with two axially placed implants or one implant placed distally tilted and one axially placed implant following an immediate loading protocol. Materials and Methods: A sample of 60 patients was divided into two groups-group 1: 30 patients rehabilitated with one axially placed implant and one implant placed distally tilted in the posterior maxilla; group 2: 30 patients rehabilitated with two axially placed implants in the posterior maxilla. Outcome measures were implant survival based on function, marginal bone resorption, and the incidence of mechanical and biologic complications at 5 years; inferential statistics were used to analyze the intergroup and intragroup differences. The level of significance was set at 5%. Results: No significant differences were found between both groups in survival, complications, or marginal bone resorption. One axially placed implant was lost at 58 months in group 1, rendering a cumulative survival estimate at 5 years of 96.7% and 98.3% in group 1 and the total sample, respectively (P = .317). Mechanical complications occurred in 16 patients (26.7%; n = 8 patients in each group; [P > .999]), consisting of fractures in the provisional prosthesis (n = 8 patients), chipped ceramics of the definitive prosthesis (n = 2 patients), loosening of prosthetic components (n = 5 patients), and fracture of an attachment screw (n = 1 patient). Biologic complications occurred in 5 patients (8.3%; group 1 = 4 patients; group 2 = 1 patient; [P = .161]), consisting of peri-implant pathology. The mean ± SD marginal bone loss was 2.02 ± 0.36 mm and 1.90 ± 0.69 mm for groups 1 and 2, respectively (P = .235). In group 1, the mean ± SD marginal bone loss was 1.92 ± 0.48 mm and 2.11 ± 0.44 mm for the implant placed distally tilted and axially placed implant, respectively; the difference was significant (P < .001). Conclusion: Within the limitations of this study, the use of implants placed distally tilted together with axially placed implants or two axially placed implants in the fixed partial rehabilitation of the posterior maxilla are viable treatment alternatives. Keywords: biomechanical complications, fixed partial rehabilitation, immediate load, implant survival, marginal bone loss, tilted implants

Purpose: To compare long-term survival and marginal bone loss of late interantral implants in the nonaugmented edentulous maxilla subjected to immediate vs delayed loading. Materials and Methods: One hundred twenty-two edentulous patients with implants in native, healed jawbone were subjected to either immediate loading (179 implants) or delayed loading (403 implants) of their four to six interantral implants (part I of 362 graftless maxillary cross-arch rehabilitations performed in the years 2004 to 2013). Kaplan-Meier survival estimates were computed, and marginal bone loss was evaluated in a stratified random sample of 20 patients per group. Results: Fifteen of 582 implants failed within the mean observation period of 4.7 years, and no difference in 8-year survival estimates could be seen between immediate (98.3% [95% CI: 96.4-100.0]) and delayed (96.7% [95% CI: 94.7-98.6]) loading protocols (P = .370). Mean marginal bone resorption following implant insertion did not differ significantly between the groups (1.1 ± 1.3 mm vs 1.4 ± 1.3 mm, P = .490). Conclusion: Immediate loading of interantral implants in the nonaugmented edentulous maxilla yields favorable results comparable to delayed loading and may be considered to shorten periods of removable provisional prostheses in maxillary edentulism. Keywords: complete denture, dental implants, edentulous arch, immediate dental implant loading, implantsupported dental prosthesis, maxilla

Purpose: This intention-to-treat (ITT) non-inferiority multicenter study was performed to evaluate implant system design, surgical and prosthetic aspects, and the effect on marginal bone levels of two related implant systems. Implant design alterations consisted of modifications in implant body shape and abutment connections. Drilling procedures and drill design were adapted to the implant design. Materials and Methods: Five clinics participated in this study; all had institutional review board approval. Two versions of the implant system were used: test and predicate. One hundred twenty partially dentate subjects with healed sites were randomized to either test or predicate implants. Fifty-nine subjects received 79 test implants and 61 received 87 predicate implants. Bone classification, insertion torque values (ITV), and the surgeon's perception of primary stability were recorded. Definitive restorations with a titanium abutment were made approximately 6 to 8 weeks following implant placement. All restorations were cement retained. Marginal bone levels were evaluated on radiographs at implant placement, at restoration, and at 6 and 12 months postloading. Results: Most subjects received one implant placed in the premolar or molar area (95% of sites). Fifty-three percent of the implants were placed in the maxilla. Median ITV at placement was 31 ± 13 Ncm for the test system and 22 ± 9 Ncm for predicate system, respectively. Time to loading was similar (test, 63.1 ± 24.8; predicate, 62.9 ± 26.9 days). Mean marginal bone loss 12 months after functional loading was 0.07 ± 0.73 mm in the test group and 0.03 ± 0.84 mm in the predicate group, with no statistically significant difference (P = .6895). Five implants were lost (four test, one predicate) from implant placement, all within the first 8 weeks following placement; none were restored. The 1-year postloading cumulative implant survival rate was 94.9% (73 implants at risk) for the test system and 98.9% (84 implants at risk) for the predicate system. Conclusion: Treatment with the test implant system, utilizing its bone classification for guidance regarding drilling protocol, resulted in enhanced implant stability. Marginal bone levels were stable 12 months after functional loading. Keywords: bone loss, equivalence, RCT trial, stability

Purpose: Diabetes mellitus (DM) affects the processes of repair, wound healing, and bone remodeling. This study was conducted to evaluate autologous bone graft integration, either with or without guided bone regeneration, through analyzing the expression of bone reabsorption markers and neovascularization in rats suffering from DM. Materials and Methods: Thirty adult Wistar rats were divided into two groups: The DM group received an injection of alloxan monohydrate (150 mg/kg), and the control group received an injection of sterile saline. Fifteen days afterward, an autologous bone grafting was performed in each of their arches, with the insertion of a membrane into the left arch. Euthanasia occurred in 7, 21, or 60 days after the surgery. Bone samples were processed for histomorphometric and immunohistochemical analyses. Results: After a statistical analysis of the data, the presence of DM did not interfere negatively in the bone autograft repair. The collagen membrane favored the graft integration into the recipient bed and the bone neoformation around the graft. Greater vascularization was observed between 21 and 60 days after the surgery, which increased bone formation and resulted in the graft integration. Only the RANK marker showed a significant difference in the glycemic groups. Transglutaminase 2 was significant for the membrane presence and experimental time. Conclusion: It is hence concluded that diabetes mellitus does not interfere with bone reabsorption via the RANK/RANKL/OPG. The graft integration was similar between the groups; however, the results of hyperglycemia with the collagen membrane indicate greater bone growth after graft placement. Keywords: angiogenesis, bone reabsorption, diabetes mellitus, guided bone regeneration, RANK/RANKL/ OPG, transglutaminase 2, VEGF

Purpose: This study investigated the effects of biomimetic deposition on a zirconia surface in simulated body fluid (SBF) and assessed the proliferation and differentiation of human bone marrow mesenchymal stem cells on the SBF-treated zirconia disks. Materials and Methods: Corrected SBF was prepared according to Kokubo's recipe. Eighty yttrium oxide-stabilized tetragonal zirconia polycrystalline disks were prepared and divided into two groups: (1) the test group with SBF-treated disks and (2) the control group with nontreated disks. Zirconia disks were soaked in SBF for 1, 4, 7, and 14 days at 36.5°C, and the hydroxyapatite (HA) precipitation was verified by analyzing the surface morphology. For more in-depth validation of HA formation, the surface roughness, composition, and crystallization of the 7-day treated disks were analyzed. Human bone marrow mesenchymal stem cells were used to further evaluate cell proliferation, alkaline phosphatase activity, and osteoblast gene expression on the 7-day treated zirconia disks. Results: Disks showed different surface morphologies after soaking for different time periods. As the SBF soaking time increased, the amount of HA coverage increased gradually, uniformly covering the disks by day 7. There was no difference in surface roughness between the two groups (P > .05). Cell proliferation was higher on the SBF-treated disks (P < .05). At 9 days, alkaline phosphatase activity was higher on the SBF-treated disks (P < .05). Alkaline phosphatase staining was significant on the SBF-treated disks (P < .05). A gene study revealed that alkaline phosphatase and osteocalcin showed higher expression in SBF-treated disks (P < .05); however, collagen type I and runt-related transcription factor 2 did not show significant differences between the two groups (P > .05). Conclusion: This study demonstrated that biomimetic deposition has an effect on the formation of HA on zirconia disks. The cell attachment, proliferation, and differentiation of SBF-treated zirconia disks was superior to that of nontreated disks, which indicates that SBF-treated zirconia implants have long-term clinical value. Keywords: cell proliferation, human mesenchymal stem cells, hydroxyapatite, osteoblast differentiation, simulated body fluid, zirconia implant

Purpose: Bone tissue adapts its structure and mass to the stresses of mechanical loading. The purpose of this review article was to summarize recent advances on cell signaling relating to the phenomenon of bone remodeling, focused on bone ossification and healing at the interface of dental implants and bone under loading conditions. Materials and Methods: When a dental implant is placed within an osteotomy, osteocytes, osteoblasts, and osteoclasts are all present. As functional loads are imposed, the remodeling processes adapt the peri-implant bony tissues to mechanical stimuli over time and reestablish a steady state. Based on the current literature, this article demonstrates fundamental information to these remodeling processes, such as the conversion of mechanical cues to electrical or biochemical signals. Results: Multiple intracellular signals are involved in cellular mechanotransduction; the two Wnt signaling pathways (the canonical, β-catenin-dependent and the noncanonical, β-catenin-independent Wnt pathway) are particularly significant. Knowledge of how these molecular signaling pathways are translated into intracellular signals that regulate cell behavior may provide new therapeutic approaches to enhancing osteogenesis, especially around implants with immediate function or placed in areas of poor bone quality. New knowledge about the primary cilia as an organelle and bone cellular mechanosensor is critical for endochondral ossification and proper signal transduction. Other mechanisms, such as the expression of sclerostin as a negative regulator of bone formation (due to deactivation of the Wnt receptor) and downregulation of sclerostin under loading conditions, also present new understanding of the cellular and pericellular mechanics of bone. Conclusion: The complexity of the cell signaling pathways and the mechanisms involved in the mechanoregulation of the bone formation provide new technologies and perspectives for mechanically induced cellular response. Future novel therapeutic approaches based on the cell signaling pathways may improve and stimulate osseointegration of dental implants and accelerate the healing mechanisms. Keywords: β-catenin, cell signaling, molecular biology, Wnt signaling

Purpose: Clarification of the protocol for using short implants is required to enable widespread use of short implants as an available treatment option. The purpose of this study was to investigate the influences of implant length and diameter, bicortical anchorage, and sinus augmentation on peri-implant cortical bone stress by three-dimensional finite element analysis. Materials and Methods: For bone models with bone quantity A and C in the maxillary molar region, three-dimensional finite element analysis was performed using different lengths and diameters of implant computer-aided design models, and the degree of maximum principal stress distribution for each model was calculated. Results: For bone quantity A models, the degree of stress distribution of the 4-mm-diameter, 6-mm-length implant was the greatest. For bone quantity C models, the degree of stress distribution of the 5-mm-diameter, 6-mm-length implant with bicortical anchorage was much smaller than that for the 4-mm-diameter, 13-mm-length implant with sinus augmentation. Conclusion: The results of this study suggest that 6-mm-length implants should be selected in cases with bone quantity C where the bone width permits increasing implant diameter from 4 mm to 5 mm. Keywords: biomechanics, dental implants, finite element analysis, sinus floor augmentation

Purpose: Dental implant macrogeometry parameters, such as the prosthetic connection and implant body shape, can influence the biomechanical behavior of the restoration. Using tridimensional finite element analysis (3D-FEA), this study evaluated the biomechanical behavior of two implant macrodesign parameters (prosthetic connection and implant body shape) in low-quality bone. Materials and Methods: Four groups were obtained by the combination of external hexagon and Morse taper connections, and cylindrical and conical body shapes. Implants (4ø × 10-mm) with a microthread collar and triangular thread shape received a single abutment and monolithic zirconia crown on the maxillary first molar. Bone was constructed on the basis of cross-sectional images of the posterior human maxilla obtained by cone beam computed tomography. A 200-N axial loading was distributed on five points of the occlusal surface. Data were acquired as shear stress (τmax, in megapascals) and strain (εmax, in micrometers) in the cortical and trabecular bone. Results: The external hexagon groups generated higher shear stress/strain values compared with Morse taper groups in the cortical bone, regardless of implant body shape. In the trabecular bone, the highest τmax and εmax values were observed in the Morse taper conical implant group (6.94 MPa and 21.926 × 10-4 μm, respectively), and the lowest values were observed in the external hexagon cylindrical implant group (4.47 MPa and 9.3155 × 10-4 μm, respectively). Conclusion: The magnitudes of shear stress and strain in the peri-implant region of low-quality bone was lower with the use of Morse taper connection and cylindrical implants compared with external hexagon connection and conical implants. Keywords: dental implant, finite element analysis, implant body shape, osseointegration, prosthetic connection

This case presentation describes the reconstruction of an extensive maxillary-orbital defect following subtotal resection of the maxilla en bloc with orbital exenteration in a young adult following the diagnosis of chondrosarcoma. A new approach to composite midface reconstruction with dental implants is described, in which computer-guided surgery (CGS) was used to obliquely position dental implants interradicularly in the residual maxilla, such that the implant tips lie in close proximity to the root apices of the remaining teeth. The implants were then used to fixate a milled-titanium bar, fabricated using computer-aided design and manufacture (CAD/CAM), and provided with attachments for the stabilization and retention of a maxillary obturator. Keywords: computer-guided surgery, hemimaxillectomy, overdenture, zygomatic implants, 3D printing

Purpose: The aim of this study was to compare strontium-containing implant (Sr-Ti) surfaces with modified pure Ti (Mod Ti) on the promotion of osteogenesis in vitro and in vivo. Materials and Methods: The Sr-Ti surfaces were fabricated by hydrothermal treatment. The Mod Ti surfaces were used as a control. These surfaces were characterized with scanning electron microscopy, x-ray diffractometer, and x-ray photoelectron spectroscopy. The biologic activity was analyzed by initial adhesion, proliferation, alkaline phosphatase (ALP), osteocalcin, and osteogenesis-related genes in vitro. Hematoxylin and eosin (H&E) staining and immunohistochemistry analysis of tissue adjacent to this implant were used to evaluate osteogenic activity in vivo. Results: The results confirmed multiple nanogranules on the Sr-Ti surface composed of well-crystallized TiO2 and SrTiO3 phases. Long-term release of Sr enhanced mesenchymal stem cell (MSC) initial adhesion, the production of ALP, osteocalcin, and upregulated osteogenesis-related genes. For in vivo osteogenic evaluation, mesenchymal-like cells were adhered on these two surfaces under the electron microscope and transitory hematoma in adjacent bone tissue by H&E staining. The Stro-1-labeled MSCs were noted around the Sr-Ti surface in immunohistochemistry analysis. Conclusion: This study suggests that Sr-Ti surfaces with nanostructures could promote the response of MSCs in vitro, and recruit Stro-1 labeled MSCs in vivo. Keywords: hydrothermal treatment, mesenchymal stem cells, nanostructure, osseointegration, strontium, titanium