The International Journal of Oral & Maxillofacial Implants, 06/2016

Purpose: The purpose of this study was to evaluate fracture resistance of straight and angulated zirconia implant abutments supporting anterior three-unit lithium disilicate fixed dental prostheses (FDPs). Materials and Methods: Four different test groups (n = 8) representing anterior three-unit implant-supported allceramic FDPs were fabricated to fit an in vitro model with two implants. Groups 1 and 2 simulated a clinical situation with an ideal implant position for maxillary left central and right lateral incisors from a prosthetic point of view, which allowed for the use of a straight, prefabricated zirconia and titanium abutment. Groups 3 and 4 simulated a situation with a compromised implant position that required an angulated (15-degree) abutment. Tapered internal-connection implants (Direct's Legacy, 13-mm length, 3.7-mm diameter, Implant Direct) mounted in epoxy resin models were used in this study. Lithium disilicate (IPS e.max press, Ivoclar Vivadent) three-unit FDPs were fabricated and cemented using self-adhesive resin cement. The samples were subjected to thermocycling (2 × 3,000 × 5°C/55°C) and mechanical loading (TCML; 50 N × 600,000 cycles). Fracture resistances were determined for all the samples that survived aging. Kruskal-Wallis analysis of variance and Mann-Whitney U tests were performed to test for differences in fracture strength values at a 5% significance level. Results: All samples subjected to TCML survived without mechanical failure. The highest fracture loads were associated with FDPs supported by implants with 0-degree abutment angulations compared with those FDPs supported by 15-degree abutment angulations (group 1: 538.7 ± 24.77 N; group 2: 542.17 ± 21.64 N; group 3: 523.57 ± 19.71 N; group 4: 528.37 ± 24.57 N). This difference in load-bearing capacity was not statistically significant (P > .05). Conclusion: The use of angulated zirconia abutments for compensation of nonideal implant locations is possible without reducing the load-bearing capacity of implant-supported anterior three-unit lithium disilicate FDPs. Keywords: abutment angulations, all-ceramic FDPs, fracture resistance, zirconia abutment

Purpose: To compile the current evidence on biomechanical, biologic, and clinical outcomes of undersized surgical preparation protocols in dental implant surgery. Materials and Methods: An electronic search using three different databases (PubMed, Web of Science, and Cochrane Library) and a manual hand search were performed including in vitro, animal, and clinical studies published prior to October 2015. Studies in which an undersized drilling protocol was compared with a nonundersized drilling protocol were included. Results: From an initial selection of 1,655 titles, 29 studies met the inclusion criteria, including 14 biomechanical, 7 biologic, 6 biologic and biomechanical, and 2 clinical. Due to methodologic variation, meta-analysis was not performed. Several studies showed that implants inserted with an undersized drilling approach reached a significantly higher insertion torque value than conventional drilling in low-density substrates, while this effect is less evident if a thick cortical layer is present. Similar results in terms of boneto- implant contact (BIC) were achieved in the longer term between implants inserted with undersized and nonundersized protocols. Results in the short term were inconclusive. Clinical studies did not show negative outcomes for undersized drilling, although clinical evidence was sparse. No data are available on marginal bone loss. Conclusion: From the biomechanical standpoint, an undersized drilling protocol is effective in increasing insertion torque in low-density bone. Biologic response in long-term healing after undersized implant placement is comparable to that in the nonundersized surgical drilling protocol. Clinical studies indicate that performing an undersized drilling protocol on low-density bone is a safe procedure; however, more extensive studies are needed to confirm these data. Keywords: dental implant, primary stability, secondary stability, surgical protocol, systematic review, undersized osteotomy

Purpose: The main aim of this study was to evaluate the influence of four different abutment materials and the adhesive joint of two-piece abutments on the cervical implant bone and soft tissue. Materials and Methods: Sixty-four titanium implants (Camlog Conelog; 4.3 × 9 mm) were placed bone level into the edentulous arches of four minipigs. Four different types of abutments were placed at implant exposure: zirconium dioxide, lithium disilicate, and titanium bonded to a titanium luting base with resin cement; one-piece titanium abutments served as the control. The animals were sacrificed 6 months after implant exposure, and the bone-to-implant contact (BIC) area, sulcus depth, the length of the junctional epithelium and the connective tissue, the biologic width, and first cervical BIC-implant shoulder distance were measured using histomorphometry and light and fluorescence microscopy. Results: Overall, 14 implants were lost (22%). At exposure, the implant shoulder-bone distance was 0.6 ± 0.7 mm. Six months later, the bone loss was 2.1 ± 1.2 mm measured histomorphometrically. There was a significant difference between the two measurements (P ≤ .0001). No significant influence could be found between any of the abutment materials with regard to bone loss or soft tissue anatomy (P > .05), with the exception of zirconium dioxide and onepiece titanium abutments when measuring the length of the junctional epithelium (P ≤ .01). The maxilla provided significantly more soft tissue and less bone loss compared with the mandible (P ≤ .02). Conclusion: All tested abutment materials and techniques seem to be comparable with regard to soft tissue properties and the cervical bone level. Keywords: animal study, bone, cell adhesion, cytology, dental implants, minipigs, osseointegration, osteoblasts, osteogenesis, soft tissue

Purpose: The highly porous titanium granules are currently being used as bone substitute material and for bone tissue augmentation. However, they suffer from weak bone bonding ability. The aim of this study was to create a nanostructured surface oxide layer on irregularly shaped titanium granules to improve their bioactivity. This could be achieved using optimized electrochemical anodic oxidation (anodizing) and heat treatment processes. Materials and Methods: The anodizing process was done in an ethylene glycol-based electrolyte at an optimized condition of 60 V for 3 hours. The anodized granules were subsequently annealed at 450°C for 1 hour. Scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) were used to characterize the surface structure and morphology of the granules. The in vitro bioactivity of the samples was evaluated by immersion of specimens in simulated body fluid (SBF) for 1, 2, and 3 weeks. The human osteoblastic sarcoma cell line, MG63, was used to evaluate cell viability on the samples using dimethylthiazol-diphenyl tetrazolium bromide (MTT) assay. Results: The results demonstrated the formation of amorphous nanostructured titanium oxide after anodizing, which transformed to crystalline anatase and rutile phases upon heat treatment. After immersion in SBF, spherical aggregates of amorphous calcium phosphate were formed on the surface of the anodized sample, which turned into crystalline hydroxyapatite on the surface of the anodized annealed sample. No cytotoxicity was detected among the samples. Conclusion: It is suggested that anodic oxidation followed by heat treatment could be used as an effective surface treatment procedure to improve bioactivity of titanium granules implemented for bone tissue repair and augmentation. Keywords: annealing, anodizing, bioactivity, bone substitute material, nanostructures, porous titanium granule

Purpose: To compare the tissue composition of augmented sites after using two different synthetic bone substitute materials, nanocrystalline and nanoporous hydroxyapatite (HA), for sinus floor elevation and augmentation. Materials and Methods: Forty-four patients received 88 titanium screw implants (Camlog Promote plus) of 4.3-mm diameter and 11- or 13-mm length, placed simultaneously during sinus floor elevation and augmentation. Nanocrystalline (Ostim) or nanoporous (NanoBone) HA were used exclusively. Bone substitute materials and implant lengths were allocated by randomization. Bone biopsy specimens were obtained from the former area of the lateral access window at implant exposure during healing abutment placement after 6 months. Biopsy specimens were prepared and examined histologically and histomorphometrically. Results: All implants were osseointegrated at the time of exposure. Clinically and histologically, no signs of inflammation in the augmented sites were present. The histomorphometric analysis of 44 biopsy specimens revealed 31.8% ± 11.6% newly formed bone for sites augmented with nanocrystalline HA and 34.6% ± 9.2% for nanoporous HA (P = .467). The proportion of remaining bone substitute material was 28.4% ± 18.6% and 30% ± 13%, respectively (P = .453). The proportion of soft tissue within the biopsy specimens was 39.9% ± 11.1% and 35.4% ± 6.8%, respectively (P = .064). No significant differences were found between the area fractions of bone, bone substitute material, and soft tissue concerning the bone substitute material utilized. Conclusion: Within the present study, both synthetic bone substitute materials, nanocrystalline and nanoporous HA, were found to support bone formation in sinus floor elevation and augmentation procedures by osteoconductivity. They were not completely resorbed after 6 months. The amounts of newly formed bone, soft tissue, and bone substitute material remnants were found to be similar, indicating that both materials are likewise suitable for sinus floor elevation and augmentation procedures. Keywords: bone substitutes, hydroxyapatite, nanocrystalline, nanoporous, sinus floor augmentation

Purpose: Cyclic loading may cause settling of abutments mounted on dental implants, potentially affecting screw joint stability and implant-abutment micromotion. It was the goal of this in vitro study to compare micromotion of implant-abutment assemblies before and after masticatory simulation. Materials and Methods: Six groups of abutments (n = 5) for a specific tissue-level implant system with an internal octagon were subject to micromotion measurements. The implant-abutment assemblies were loaded in a universal testing machine and an apparatus and extensometers were used to record displacement. This was done twice, in the condition in which they were received from the abutment manufacturer and after simulated loading (100,000 cycles; 100 N). Statistical analysis was based on analysis of variance, two-sample t tests (Welch tests), and Pearson product moment correlation (α = .05). Results: The mean values for micromotion ranged from 33.15 to 63.41 μm and from 30.03 to 42.40 μm before and after load cycling. The general trend toward reduced micromotion following load cycling was statistically significant only for CAD/CAM zirconia abutments (P = .036) and for one type of clone abutment (P = .012), with no significant correlation between values measured before and after cyclic loading (Pearson product moment correlation; P = .104). While significant differences in micromotion were found prior to load cycling, no significant difference among any of the abutment types tested could be observed afterward (P > .05 in all cases). Conclusion: A quantifiable settling effect at the implant-abutment interface seems to result from cyclic loading, leading to a decrease in micromotion. This effect seems to be more pronounced in low-quality abutments. For the implant system tested in this study, retightening of abutment screws is recommended after an initial period of clinical use. Keywords: clone abutments, implant-abutment connection, micromotion, settling effect

Purpose: Studies have recognized the importance of Wnt/β-catenin signals in osteoblastogenesis. Sclerostin is a glycoprotein product of the SOST gene that inhibits Wnt/β-catenin signaling and reduces osteoblastogenesis. To date, there is little evidence regarding the role of the Wnt/β-catenin pathway and its inhibitors in the osseointegration process. Therefore, the aim of this study was to evaluate the expression of sclerostin in bone healing around titanium implants inserted in rats. Materials and Methods: Fifteen Wistar rats received an implant with primary stability in a tibia, while the contralateral tibia received an implant without primary stability, representing experimental models of implant success and failure, respectively. Animals were then euthanized 7, 14, or 21 days later (five each day). Immunohistochemistry was used to evaluate the specimens for sclerostin-positive cells. Results: The proportion of cells positive for sclerostin was significantly higher around implants without primary stability than those with primary stability at 7 and 14 days after implant placement (P < .05). There were no differences between groups for the proportion of cells positive for sclerostin at 21 days after implant insertion (P > .05). Conclusion: Sclerostin expression is upregulated around implants inserted without primary stability, in comparison with that around implants inserted with primary stability, in the tibia of rats. This preliminary evidence reinforces the importance of primary implant stability from the biologic viewpoint. Keywords: dental implants, osseointegration, sclerostin protein, SOST protein

Purpose: The purpose of this systematic review was to evaluate long-term outcomes of regenerative procedures for treating peri-implantitis. Materials and Methods: Electronic searches of five databases and hand searches of journals were performed to identify human trials that had treated more than 10 periimplantitis lesions using a regenerative approach with a follow-up period of at least 36 months. To meet the inclusion criteria, studies had to report at least one of the following parameters: radiographic bone fill (RBF), probing depth (PD) reduction, clinical attachment level gain, bleeding on probing reduction, and mucosal level gain. The pooled weighted mean and the 95% confidence interval (CI) of each variable were estimated. Results: The searches yielded 1,412 records, and after evaluating titles, abstracts, and full texts, 5 case series and 1 controlled trial were included for quantitative data synthesis. Meta-analysis of the studies for the amount of RBF revealed a weighted mean of 2.41 mm (range, 1.46 to 3.30 mm) with 95% CI. For PD reduction, the weighted mean was 3.06 mm (range, 1.24 to 5.21 mm). Conclusion: There is limited evidence in the literature reporting long-term results of the regenerative approach for treating peri-implantitis. Within the limits of this meta-analysis, regenerative treatment of peri-implantitis resulted in a mean radiographic defect fill of 2.41 mm after a minimum healing time of 36 months. However, this finding must be interpreted with caution, since it is difficult to discern between grafting material and newly formed bone. Keywords: alveolar bone reconstruction, dental/oral implants, evidence-based dentistry, guided bone regeneration, peri-implant repair, tissue engineering

Purpose: Information on precision of treatment-effect estimates is pivotal for understanding research findings. In animal experiments, which provide important information for supporting clinical trials in implant dentistry, inaccurate information may lead to biased clinical trials. The aim of this methodological study was to determine whether sample size calculation, standard errors, and confidence intervals for treatmenteffect estimates are reported accurately in publications describing animal experiments in implant dentistry. Materials and Methods: MEDLINE (via PubMed), Scopus, and SciELO databases were searched to identify reports involving animal experiments with dental implants published from September 2010 to March 2015. Data from publications were extracted into a standardized form with nine items related to precision of treatment estimates and experiment characteristics. Data selection and extraction were performed independently and in duplicate, with disagreements resolved by discussion-based consensus. The chi-square and Fisher exact tests were used to assess differences in reporting according to study sponsorship type and impact factor of the journal of publication. Results: The sample comprised reports of 161 animal experiments. Sample size calculation was reported in five (2%) publications. P values and confidence intervals were reported in 152 (94%) and 13 (8%) of these publications, respectively. Standard errors were reported in 19 (12%) publications. Confidence intervals were better reported in publications describing industry-supported animal experiments (P = .03) and with a higher impact factor (P = .02). Conclusion: Information on precision of estimates is rarely reported in publications describing animal experiments in implant dentistry. This lack of information makes it difficult to evaluate whether the translation of animal research findings to clinical trials is adequate. Keywords: animal experimentation, confidence interval, methods, precision, sample size, treatment effect

Purpose: Ultraviolet (UV)-mediated photofunctionalization technology is intended to enhance the osseointegration capability of titanium implants. There are concerns about orthodontic anchor screws loosening under immediate loading protocols in adolescent orthodontic treatment. The purpose of this in vivo study was to evaluate the effects of photofunctionalization on the intrabony stability of orthodontic titanium anchor screws and bone-anchor screw contact under immediate loading in growing rats. Materials and Methods: Custom-made titanium anchor screws (1.4 mm in diameter and 4.0 mm in length) with or without photofunctionalization pretreatment were placed on the proximal epiphysis of the tibial bone in 6-week-old male Sprague-Dawley rats and were loaded immediately after placement. After 2 weeks of loading, the stability of the anchor screws was evaluated using a Periotest device, and the bone-anchor screw contact ratio (BSC) was assessed by a histomorphometric analysis using field-emission scanning electron microscopy. Results: In the unloaded group, Periotest values (PTVs) were ~25 for UV-untreated screws and 13 for UVtreated screws (P < .01), while in the immediate-loading group, PTVs were 28 for UV-untreated screws and 16 for UV-treated screws (P < .05). Significantly less screw mobility was observed in both UV-treated groups regardless of the loading protocol. The BSC was increased ~1.8 fold for UV-treated screws, compared with UV-untreated screws, regardless of the loading protocol. Conclusion: Photofunctionalization enhanced the intrabony stability of orthodontic anchor screws under immediate loading in growing rats by increasing boneanchor screw contact. Keywords: mini-implants, mini-screws, temporary anchorage devices

Purpose: This systematic review aimed to compare immediate protocols with conventional protocols of single-tooth implants in terms of changes in the surrounding hard and soft tissue in the esthetic area. Materials and Methods: Electronic and manual searches were performed in PubMed, EMBASE, Cochrane, and other data systems for research articles published between January 2001 and December 2014. Only randomized controlled trials (RCTs) reporting on hard and or soft tissue characteristics following a single-tooth implant were included. Based on the protocol used in each study, the included studies were categorized into three groups to assess the relationships between the factors and related esthetic indexes. Variables such as marginal bone level changes (mesial, distal, and mean bone level), peri-implant soft tissue changes (papilla level, midbuccal mucosa, and probing depth), and other esthetic indices were taken into consideration. The data were analyzed using RevMan version 5.3, Stata 12, and GRADEpro 3.6.1 software. Results: A total of 13 RCTs met the inclusion criteria. Four studies examined immediate implant placement, five studies examined immediate implant restoration, and four studies examined immediate loading. Comparing the bone level changes following immediate and conventional restoration, no significant differences were found in the bone level of the mesial site (standard mean difference [SMD] = -0.04 mm; 95% confidence interval [CI]: -0.25 to 0.17 mm), the distal site (SMD = -0.15 mm; 95% CI: -0.38 to 0.09 mm), and the mean bone level changes (SMD = 0.05 mm; 95% CI: -0.18 to 0.27 mm). The difference in the marginal bone level changes between immediate and conventional loading was also not statistically significant (SMD = -0.05 mm; 95% CI: -0.15 to 0.06 mm for the mesial site and SMD = -0.02 mm; 95% CI: -0.09 to 0.05 mm for the distal site). Soft tissue changes following immediate and conventional restoration reported no significant differences in the papillae level of the mesial site (SMD = 0.18 mm; 95% CI: -0.00 to 0.37 mm), the papillae level of the distal site (SMD = -0.12 mm; 95% CI: -0.34 to 0.09 mm), and the midbuccal mucosa (SMD = -0.22 mm; 95% CI: -1.29 to 0.85 mm). Conclusion: Within the limitations, it can be concluded that immediately placed, restored, or loaded single-tooth implants in the esthetic zone result in similar hard and soft tissue changes compared with conventional protocols. Keywords: esthetic, immediate implant, immediate loading, immediate restoration, meta-analysis, single implant

Purpose: Tapered implants are thought to result in equivalent long-term stability and marginal peri-implant bone height in comparison to cylindrical implants. The goal of this study was to compare the primary stability and osseointegration of a novel bone-level tapered-wall implant to a control bone-level cylindrical implant with exactly the same surface characteristics, in a direct side-by-side comparison in an animal model. Materials and Methods: Mandibular premolars and first molars were extracted in 11 Göttingen minipigs, and healing was allowed for 3 months. Six implants were placed with a 4-week surgical lag time between hemimandibles (three per side), and either immediately loaded (first implantation time point) or submerged (second implantation time point). Eight-mm-long × 4.1-mm-diameter titanium screw-type bone-level implants with tapered (two per side) and cylindrical bodies (one per side) were used (Institut Straumann); insertion torque and implant stability were measured, and the soft tissue was closed. Standardized radiographs were taken at implant placement and at sacrifice. Following a healing period of 1 month from the last surgical intervention (8 weeks total healing time for loaded implants; 4 weeks total healing time for nonloaded implants), the animals were sacrificed and mandibular blocks were harvested for nondecalcified histologic and histomorphometric analysis. Results: All implants were integrated radiographically and osseointegrated histologically. Maximum insertion torque measurements and implant stability quotient values showed no significant difference between tapered and cylindrical implants. Histomorphometric analysis also resulted in comparable bone-to-implant contact values between the implant types and similarly limited marginal periimplant bone resorption; no significant differences were observed regarding all the evaluated parameters between the groups, regardless of the loading regime. Conclusion: In a direct side-by-side comparison, in an intraoral minipig model, a novel bone-level tapered screw implant with an SLActive surface showed comparable clinical and histologic outcomes to a parallel-walled bone-level screw implant with an SLActive surface. Keywords: bone-level implants, bone remodeling, osseointegration, peri-implant bone level, tapered implant

Purpose: To assess the estimated cumulative survival (ECS) and explore the technical and biologic complications of 256 TiUnite implants (Nobel Biocare) supporting one-piece cast abutment/metal-ceramic implant-supported single crowns (ISCs) in situ for up to 14 years. Materials and Methods: A prospective sequentially recruited cohort of 207 patients received 256 metal-ceramic ISCs on TiUnite implants between 2001 and 2014. All but 24 patients with 27 crowns were clinically evaluated between January 2014 and April 2015 in conjunction with or in addition to their tailored maintenance program. Radiographs were obtained, and any previously recorded treatments associated with the crowns were tabulated. The ECS and standard errors were calculated with the life table actuarial method and Greenwood's formula, respectively. The log rank test was applied to assess differences between anterior and posterior crowns. Complication incidence, severity, and economic burden, measured in time/cost accounting units (TAUs), were tallied and compared descriptively. Independent groups were compared with the Mann-Whitney U test and related groups with the Wilcoxon Signed Rank Test. Results: The mean clinical service time of the crowns was 5.61 years (44 ≥ 10 years). The 14-year ECS was 95.95% ± 3.20% with no significant difference between anterior and posterior prostheses. Only seven implants lost marginal bone ≥ one thread from the time of crown insertion. There were 30 nonterminal complications (16 biologic, 14 mechanical). The associated economic burden was low (n = 35 TAUs). Conclusion: High gold-alloy one-piece cast abutment/metal-ceramic ISCs on TiUnite implants exhibited excellent longevity and few complications over 14 years. Keywords: complications, implant-supported single crowns, prospective studies, survival analysis

Purpose: Short implants (≤ 8.5 mm in length) have presented predictable outcomes. However, there is paucity in the long-term evaluation of immediate loading of short implants. The objective of this study was to assess the effect of the immediate loading of short implants on treatment outcomes. Materials and Methods: Patients having short implants inserted before December 2010 that were immediately loaded were selected. A database was then created to include the patient's data as well as implant- and prostheses-related outcomes. Long implants inserted at the same surgery and immediately loaded by the same prosthesis formed the control group. The proximal bone loss and the survival rates of implants and prostheses were assessed. Results: Forty-nine short and 38 long implants were placed in 30 patients. The mean follow-up time was 5.2 ± 0.8 years after loading, and three implants (two short and one long) failed. The differences in marginal bone loss and implant survival between short and long implants were not statistically significant. Three prosthetic complications occurred. Two prostheses failed, and the survival rate was 95.8%. Conclusion: The immediate loading of short implants is not a risk factor for treatment success. This could be related to the good bone quality and the achievement of adequate primary stability. Keywords: dental prosthesis, immediate loading, implant survival, marginal bone loss, short dental implants

Purpose: The aim of this study was to evaluate and compare the long-term clinical and radiographic outcomes between a bone graft substitute mixture (beta-tricalcium phosphate [β-TCP] and plateletrich plasma [PRP]) and β-TCP bone graft substitute alone used for sinus floor elevation. Materials and Methods: This randomized clinical trial included patients with an atrophic maxilla referred for maxillary sinus floor elevation. The elevated sinus cavities of patients were randomly filled with β-TCP plus PRP (study group) or β-TCP alone (control group). Residual bone crest height, vertical bone height gain, and bone graft resorption were measured on cone beam computed tomography (CBCT) images at 10 days and 6 months postoperatively. Incidence of sinus membrane perforations and maxillary sinus infections were recorded. Paired t and Student t tests were used for intragroup and intergroup comparisons, respectively. Results: The sample was composed of 18 subjects: nine subjects in the control group (mean age, 31.51 years) and nine subjects in the study group (mean age, 34.01 years). The mean residual bone crest height was found to be < 5 mm in both groups (4.88 mm in the control group and 2.70 mm in the study group, with no significant difference). From the 10-day to 6-month postoperative visit, mean vertical bone height gains were changed from 12.48 to 11.59 mm in the study group and from 14.77 to 13.19 mm in the control group, with no significant difference. The mean vertical bone graft resorption was -1.58 mm in the study group and -0.89 mm in the control group, with no significant difference. Sinus membrane perforation was observed in 3 of 18 patients. Conclusion: In this study, PRP plus β-TCP graft substitute did not produce significantly more vertical bone height gain or significantly less vertical bone graft resorption compared with β-TCP graft substitute alone. Within the limitations of this study, however, it can be concluded that both grafting materials produced sufficient vertical bone height gain for safe implant placement. Keywords: beta-tricalcium phosphate, cone beam computed tomography, platelet-rich plasma, sinus floor augmentation

Purpose: The aim of this study was to compare masticatory performance, occlusal force, and oral health- related quality of life (OHRQoL) in patients with mandibular distal-extension edentulism between those with implant-supported fixed prostheses (ISFPs) and those with removable partial dentures (RPDs), and to evaluate relationships among them. Materials and Methods: Subjects were recruited from patients using ISFPs or RPDs for mandibular distal-extension edentulism. Masticatory performance was evaluated based on the glucose extracted from chewed gummy jelly. Occlusal force was measured with a pressure-sensitive sheet, and data were subjected to computer analysis. The Japanese version of the Oral Health Impact Profile (OHIP-J) was used to evaluate OHRQoL. The masticatory performance, occlusal force, and OHIP-J scores of the ISFP and RPD groups were compared using the Wilcoxon rank-sum test. The relationships among the variables were analyzed using the Spearman rank correlation coefficient test. Multivariate logistic regression analysis was employed with the OHIP-J score as a dependent variable. Results: Nineteen patients with ISFPs and 25 patients with RPDs participated in this study. No significant difference was observed between the two groups with regard to masticatory performance and occlusal force. The OHIP-J score was significantly lower in the ISFP group than in the RPD group. The OHIP-J score had no significant correlation with masticatory performance, but was significantly correlated with occlusal force and the prosthetic method. Multivariate logistic regression analysis showed that younger age, RPDs, and lower occlusal force were significantly associated with a higher OHIP-J summary score. Conclusion: The present results suggest that the difference in masticatory performance and occlusal force between ISFPs and RPDs is small, but ISFPs are superior to RPDs with regard to OHRQoL in patients with mandibular distal-extension edentulism. In addition, there appears to be a slight correlation between the OHIP-J and occlusal force in these patients. Keywords: implant-supported fixed prostheses, mandibular distal-extension edentulism, masticatory performance, oral health-related quality of life, removable partial dentures

Purpose: The design of an implant connection that allows prosthetic suprastructures to be attached to implants has long been debated in the dental literature. The goal of this retrospective study was to evaluate the 5-year clinical results for a large number of single implants restored by certified prosthodontists in an attempt to establish whether different clinical outcomes could be detected for external- or internalconnection implants. Materials and Methods: All single implants with internal or external connections inserted in 27 private dental practices from January 1, 2003 to December 31, 2007 were evaluated. An initial statistical analysis was performed to describe the sample population at baseline and then to compare the two types of implant-abutment connection configurations and their clinical outcomes. All data were statistically analyzed with STATA12 (StataCorp). Results: Twenty-eight of the 85 active members of the Italian Academy of Prosthetic Dentistry (AIOP) participated in this study. The sample included 1,159 patients and 2,010 implants. Of the implants, 75 were dropped because there was no information about follow-up. Of the remaining implants, 1,431 (74.0%) were followed for at least 5 years, and 332 implants (17.2%) were followed for more than 8 years. Nearly 99% (98.9%) of the implants survived. The difference between the survival frequencies of the two types of implant-abutment connection configurations was not significant for each negative event (log-rank test, P > .05). There was no difference between the two types of implants regarding restoration fracture, implant screw loosening, and peri-implant disease. Conclusion: Within the limitations of this study, it can be suggested that there is no difference in clinical outcomes of single restorations joined to internal- or external-connection implants. Keywords: external-connection implant, internal-connection implant, single implant restoration

Purpose: This study discussed a 3-year retrospective survey of clinical and esthetic outcomes of immediate implants placed by experienced senior surgeons and residents in implant dentistry. Materials and Methods: The retrospective chart review included patients who received single-tooth extraction and immediate implant placement at the Tuscan Stomatology Institute between 2009 and 2011. Treated independent postextraction areas were divided into two groups according to the operator's experience: expert versus nonexpert group. Patient satisfaction with the esthetic aspect, chewing, speaking, comfort, self-esteem, and ease of cleaning were assessed by visual analog scales. Changes in the marginal bone level and parameters describing the changes of the facial soft tissue and in papilla index were assessed. Proper pairwise comparison tests were applied with a significant level α = .05. Results: Of the 60 selected patients, 31 were in the expert group and 29 in the nonexpert group. At the 3-year follow-up, findings attested to a significantly higher bone loss in the nonexpert group (1.74 ± 0.59 mm) than those registered in the expert group (1.34 ± 0.45 mm), with a P value of .0044. The papilla index (PI) appeared very stable in the group of experts, whereas it showed a significant loss throughout the study in patients in the nonexpert group (PI = 2 at 1 year and PI = 1.5 at 3 years). Moreover, significant recessions at the buccal soft tissue were registered for all groups at both check-ups; however, in the expert group, slight soft tissue recession was evident 3 years later (0.58 ± 0.72 mm), whereas the nonexpert group showed greater recession (1.52 ± 0.74 mm). Patients reported higher overall satisfaction when treated by the group of experts (85.2%) than when treated by the nonexperts (81.1%) with P < .0001. Conclusion: The findings from this study suggested that immediate implant procedures could be considered a successful and satisfying treatment strategy when strict selection criteria together with a high level of surgical expertise are applied. Keywords: clinical competence, delayed dental implant loading, dental prosthesis implant-supported, esthetics dental, single dental implantation

Purpose: This was a retrospective cohort study designed to evaluate the clinical performance of ceramicveneered zirconia frameworks. Materials and Methods: Patients were recruited according to defined inclusion criteria. All patients were checked every 4 months from the time of definitive rehabilitation. At the end of 2013, all patients were rescheduled and rechecked for study purposes. The restorative procedures assessment was performed by previously established methods. The primary outcomes were the survival and success rates of the prosthesis. Descriptive statistics were used for the patient's demographics, implant distribution, and occurrence of complications. To study the survival and success of the prostheses, a Cox Regression analysis was used with a model constructed in a forward conditional stepwise mode. Predictive variables were included in the model, and adjusted survival curves were obtained for each outcome. Results: From 2008 to 2013, 75 patients were rehabilitated with 92 implant-supported, screw-retained, full-arch ceramic-veneered zirconia framework rehabilitations. The range of follow-up was between 6 months and 5 years. From the 92 full implant-supported screw-retained full-arch rehabilitations, Cox regression analysis indicated that within a 5-year time frame, the probability of framework fracture, major chipping, minor chipping, or any of the former combined to occur was 17.6%, 46.5%, 69.2%, and 90.5%, respectively. Conclusion: Results suggest zirconia as a suitable material for framework structure in implant-supported, full-arch rehabilitations. However, it experiences a high incidence of technical complications, mainly due to ceramic chipping. Further clinical studies should aim to ascertain the effects of clinical features and manufacturing procedures on the survival rates of these prostheses. Keywords: clinical research, computer-aided design, dental prosthesis, dental prosthesis design, implant supported, retrospective studies, zirconium oxide

Purpose: The aim of this 4-year retrospective follow-up study was to investigate treatment outcomes, including implant survival rate and marginal bone loss, in patients with maxillary Cawood type VI atrophy pattern who underwent Le Fort I downgrafting and iliac block augmentations for implant rehabilitation. Materials and Methods: Retrognathic edentulous Class III patients with severe maxillary resorption (Cawood VI) were enrolled. Reconstructive procedures performed included Le Fort I maxillary osteotomy, iliac block grafting, labial sulcoplasties, and dental implant placement. Panoramic radiographs were used to assess marginal bone loss. The Nobel Biocare Replace and GMI Frontier dental implant systems and fixed partial dentures were used for dental rehabilitation. Statistical analyses were made using NCSS 2007 statistical software, with significance set at P < .05. Results: Ten patients (six men and four women) with a mean age of 50.4 ± 12.55 years underwent maxillary osteotomy (advancement: 9 ± 1.4 mm; inferior repositioning: 8 ± 1.0 mm) and iliac block sandwich grafting (posterior ilium: n = 3; anterior ilium: n = 7) from 2009 to 2015. Nine patients were treated with a two-stage protocol. The mean graft healing period was 5.9 ± 0.73 months. A total of 98 implants were placed, 80 in maxillae and 18 in mandibles. The Nobel Biocare Replace system was used in two patients (n = 29 implants) and GMI Frontier system was used in eight patients (n = 69 implants). Implant numbers in the maxilla were: 6 implants in 2 patients, 8 implants in 6 patients, and 10 implants in 2 patients. The mean follow-up period was 47.8 ± 3.4 months. The success rate was 93.75%, with a 6.25% fail ratio (n = 9 implants) at a follow-up of 4 years. Marginal bone resorption was 1.8 ± 1.0 mm at the postoperative year 1 and 3.75 ± 0.85 mm at postoperative year 4. Marginal resorption in the 8-implant group was found to be higher than that in the 6-implant group and 10-implant group at the postoperative year 1 (P = .045, P = .026, P < .05, respectively). Conclusion: Le Fort I osteotomy and simultaneous iliac block grafting (downgrafting) is a valuable option for implant rehabilitation in extremely atrophic maxillae (Cawood VI). It showed a high survival rate (93.75%) at 4 years of follow-up in this study. Keywords: atrophy, graft, iliac, implant, Le Fort I osteotomy, maxilla

Purpose: The purpose of this clinical trial was to evaluate the survival rate, bone remodeling, and soft tissue health around sloped marginal contour implants when placed in healed sites posteriorly in the mouth. Materials and Methods: Implants were placed in healed sites at premolar and molar regions. After a 3-month osseointegration period, definitive prostheses were connected. Clinical and radiographic examinations were performed at implant placement and then 1, 3, 6, 12, and 24 months after implant placement. An assessment of implant stability, peri-implant mucosa, level of attached gingivae, occlusion, proximal contact, and marginal bone levels was performed at each respective visit. Results: Fourteen patients were treated and restored with 18 single crowns. The cumulative survival rate was 100% after 2 years. The mean marginal bone remodeling was 0.04 ± 0.26 mm (n = 18). The attached gingival change was +0.33 ± 0.35 mm. Conclusion: The 24-month results indicate that the sloped marginal contour implant performed well in posterior healed sites with a 100% survival rate and good marginal bone maintenance. Keywords: dental implant, marginal bone, sloped marginal contour

Purpose: The objective of this study was to evaluate new bone regeneration around delayed implants positioned in large bone defects, filled with reactive soft tissue, using cone beam computed tomography (CBCT) at a follow-up of 3 years. Materials and Methods: Patients presented large bone defects after tooth extraction. Reactive soft tissue was left in the defects, and no grafts were used. CBCT scans were performed before tooth extraction and upon implant placement (at 3 months after extraction), and bone volume measurements were then evaluated 3 years after implant placement. Results: Three months after extraction, CBCT revealed a bone volume gain both for single-rooted and multirooted sites: an overall mean bone level of 8.34 ± 3.18 mm was calculated, and implants were placed. At the 3-year follow-up, CBCT revealed bone maintenance, with mean levels of 10.47 ± 3.68 mm. Statistically significant differences were not observed between 3-month and 3-year bone levels, both for maxillary or mandibular defects and for sites (single-rooted or multirooted teeth). Conclusion: CT scans presented a successful outcome of delayed implants placed in large bone defects at the 3-year follow-up. Keywords: bone defects, cone beam computed tomography, dental implants, reactive soft tissue

Purpose: This randomized clinical trial aimed to investigate the relationships between insertion torque, implant stability quotient (ISQ), and crestal bone loss (CBL) of implants placed in fresh or 12-week healed extraction sites. Materials and Methods: Forty patients were randomly assigned to one of two groups and had one implant placed immediately (test group, n = 20) or 12 weeks after extraction (control group, n = 20) at premolar or molar sites. For all implants, insertion torque and ISQ scores at insertion and loading were recorded. Patients were followed for up to 12 months. Results: Implant success was 100% in both groups. No differences were observed concerning both ISQ at insertion and ISQ at loading. A stronger correlation was detected between ISQ at insertion and insertion torque in the postextractive group (R = 0.83), than in the delayed group (R = 0.39), while ISQ at loading and insertion torque showed no correlation. CBL at 12 months was significantly different between test (0.68 ± 0.43 mm) and control (0.40 ± 0.26 mm, P = .02) groups. Conclusion: Implant placement timing (immediate or delayed) may affect correlation between insertion torque and ISQ at insertion with ISQ at loading. While insertion torque influences ISQ at insertion, it does not affect ISQ at loading because of successful osseointegration. Postextraction and delayed implants seem to have similar ISQ at insertion and at loading, but different CBL after 12 months of follow-up because of postextraction bone remodeling. Keywords: crestal bone loss, implant stability quotient, implant success, insertion torque, postextraction sites, RFA

This case report describes the clinical application of a real-time surgical navigation system to guide zygomatic implants on their placement. With the assistance of this novel navigation system, constant visualization of the drilling trajectory and exact control of the drilling direction can be achieved, which could minimize the risk of penetration into critical anatomical structures. Moreover, implants might be accurately placed in accordance to the preoperative planned position. In this patient, who had previously undergone a hemimaxillectomy, three zygomatic implants were placed on the unilateral zygoma, and two conventional implants were placed on the unresected maxilla. Measurement of distributive deviation of implants between preoperative planning and the postoperative result showed the mean linear deviations at the entrance and apical point of the implant were 1.07 ± 0.15 mm (range: 0.9 to 1.1 mm) and 1.20 ± 0.46 mm (range: 0.7 to 1.6 mm), respectively. The mean angle deviation between the axes of the planned and the actual implant was 1.37 ± 0.21 degrees (range: 1.2 to 1.3 degrees). Therefore, this surgical navigation system represents a reliable approach to guide the placement of zygomatic implants. Keywords: computer-assisted surgery, minimal invasion, real-time three-dimensional navigation system, zygomatic implant

Purpose: The purpose of this study was to evaluate whether or not bone quality has an effect on the biomechanical behavior of a tooth connected to an implant, when a rigid and a nonrigid attachment are used. Materials and Methods: Models of fixed partial dentures supported by a tooth and an implant were developed. These models were then imported into finite element analysis software to study the impact of forces on different types of attachments (rigid vs nonrigid) and bones (types 1 to 4). Each fixed partial denture was subjected to a vertical load of 200 N on the premolars and 230 N on the molar. The materials were considered linear, isotropic, and homogenous. Eight different scenarios were tested. The von Mises criterion was used to display the stress in five structures: fastening screw, implant, attachment, cortical, and trabecular bone. The displacements of the tooth and the implant were also examined. Results: The calculated maximum observed stress values differed among the simulated scenarios. The biggest values of stress concentrations were observed at the lingual cervical areas, the implant-cortical bone interface, the implant-crown interface, the butt-joint contact of the implant-abutment screw, and the apical parts of the tooth and implant. The main difference between the rigid and nonrigid connection was observed between the natural tooth retainer and the pontic. In the rigid connection, the movement of the natural tooth retainer was smooth. In the nonrigid connection, the attachment exhibited a partial buccal displacement. Von Mises stresses among the different tested structures ranged between 24 and 840 MPa. Conclusion: The quality of the bone and the rigidity of the connection between a natural tooth and an implant influence both the generated stresses and the displacement of the tooth and the implant. The highest stresses for the implanttrabecular bone interface, the neck of the implant, and the fastening screw were observed in type 3 bone when a rigid connection was used. The lowest stresses for the implant-cortical bone interface, the neck of the implant, and the connector were registered in type 1 bone, when a rigid connection was used. The smallest tooth and implant displacement was observed in type 1 bone, when a rigid connection was used, while the biggest tooth and implant displacement was registered in type 4 bone when a nonrigid connection was used. Keywords: biomechanics, bone types, finite element analysis, implant displacement, nonrigid attachment, rigid attachment, tooth displacement, tooth-implant connection

Purpose: This study analyzed the use of bone marrow-derived mesenchymal stem cells and adipose tissue-derived stem cells, associated with xenograft, in appositional reconstructions in rabbit calvaria using histomorphometry. Materials and Methods: Fifteen New Zealand rabbits, weighing 3.5 to 4.0 kg and aged between 10 and 12 months, were randomly divided into three groups. Appositional bone reconstruction situations were created in the calvaria of the animals using titanium cylinders, fitted with titanium occlusive caps. Bone decortication was performed to promote bleeding. Inside the cylinders, only xenograft was positioned in the control group (CG; n = 5); xenograft combined with mesenchymal bone marrow-derived stem cells was positioned in group 1 (G1; n = 5), and a xenograft combined with adult mesenchymal stem cells derived from adipose tissue was positioned in group 2 (G2; n = 5). After 56 days, all rabbits were euthanized and their parietal bones processed for histomorphometric analysis, and the following parameters were evaluated: newly formed bone; residual graft particles; soft tissue; vital bone titanium contact, also called the level of osseointegration; and the level of bone volume contained inside the cylinders, also called the internal bone volume. Results: The histomorphometric study revealed the following for CG, G1, and G2: newly formed bone of 18.96% ± 9.00%, 27.88% ± 9.98%, and 22.32% ± 7.45%; residual graft particles of 28.43% ± 2.44%, 23.31% ± 3.11%, and 27.58% ± 3.98%; soft tissue of 52.61% ± 10.80%, 50.23% ± 8.72%, and 49.90% ± 8.76%; vital bone titanium contact of 4.98% ± 4.30%, 34.91% ± 7.82%, and 20.87% ± 5.43%; and internal bone volume of 88.36% ± 25.97%, 98.73% ± 19.05%, and 98.52% ± 19.87%, respectively. No statistical difference between groups for newly formed bone, residual graft particles, soft tissue, and internal bone volume (P > .05) were verified. Conclusion: Regarding vital bone titanium contact, it was observed that the use of bone marrow mesenchymal stem cells, when compared with the adipose mesenchymal stem cells, showed the highest level of osseointegration, and both of them obtained superior levels to the xenograft alone. Keywords: adipose tissue-derived mesenchymal stem cells, bone marrow-derived mesenchymal stem cells, bone regeneration, cell transplantation

Purpose: Maxillary implant overdentures are often designed without palatal coverage to maximize wearer comfort. Although palateless dentures have been reported to be less rigid than conventional dentures, and require reinforcement to prevent complications, there is little documentation about the effects of such reinforcement. The purpose of this study was to examine the effects of reinforcement on the strain on maxillary implant overdentures supported by implants in a variety of configurations. Materials and Methods: A maxillary edentulous model with implants inserted in the anterior, premolar, and molar area was fabricated. Five types of experimental overdentures, with and without reinforcement, were fabricated, and two strain gauges were attached at the anterior midline of the labial and palatal sides. A vertical occlusal load of 98 N was applied through a mandibular complete denture, and the shear strain on the denture was measured. The measurements were compared using the Kruskal-Wallis test (P = .05). Results: On both the labial and palatal sides, the strain on the palateless dentures with reinforcement was significantly lower than the strain on palateless dentures without reinforcement in all implant configurations (P < .05). The labial strain on the palateless dentures with reinforcement was almost as low as the labial strain on dentures with palatal coverage in most implant configurations. Conclusion: Reinforcement of a palateless implant overdenture with residual ridge reinforcement and a palatal bar could reduce the strain in the anterior midline to almost the same level as a denture with palatal coverage. This type of reinforcement may prevent prosthetic and implant complications. Keywords: implant distribution, implant number, maxillary implant overdenture, palateless denture, reinforcement

Purpose: The purpose of this report is to describe the crestal bone level (CBL) around implants of various designs, describe the peri-implant soft tissue condition, and evaluate the relationship between the two over time. Materials and Methods: This retrospective cohort study reports on 2,060 patients with 4,591 implants evaluated after 3 months; 1, 3, 5, and 7 years; and up to 10 years. Periapical radiographs were used to evaluate changes in CBL. The peri-implant soft tissue was evaluated using a modified Bleeding Index termed the Implant Mucosal Index (IMI) where: 0 = no bleeding; 1 = minimal, single-point bleeding; 2 = moderate, multipoint bleeding; 3 = profuse, multipoint bleeding; and 4 = suppuration. Results: At 3 months, the mean CBL was 0.06 ± 0.22 mm; by 8 to 10 years, it had increased to 0.44 ± 0.81 mm. The median CBL remained stable throughout the study at < 0.1 mm. At 8 to 10 years, 15% of implants exhibited a CBL > 1.02 mm, and 5% exhibited a CBL > 2.28 mm. More than 50% of patients experienced some bleeding, as seen by an IMI ≥ 1 during follow-up. A positive correlation was found between IMI and CBL, as shown by a mean CBL after 4 years of 0.33 mm, 0.71 mm, and 1.52 mm for IMI = 2, 3, and 4, respectively. One exception was between IMI = 0 and IMI = 1, where no significant difference was found and bone loss was minimal. Conclusion: Bone loss, as measured by changes in CBL during the first 10 years of implant life spans, was minimal for most implants. Nevertheless, it is not unusual to observe implants with advanced bone loss. The soft tissue condition is a good indicator of bone loss. Time alone and minimal bleeding did not correlate with bone loss, but care should be taken for implants with profuse bleeding or suppuration. Keywords: bone-implant interface, crestal bone loss, index, inflammation, modified bleeding index, mucositis, peri-implantitis suppuration, retrospective

Purpose: Granulation tissue containing reactive soft tissue with potential multipotent stem cells can help socket healing following extraction. The aim of this study was to assess bone healing of maxillary large bone defects while maintaining reactive soft tissue. Materials and Methods: A total of 32 patients presenting large bone defects were selected for this prospective study. Eight patients (Group A) presented with large bone defects but an intact buccal cortical plate, while 24 patients (Group B) presented with large bone defects lacking a buccal cortical plate. Teeth were extracted, and reactive soft tissue was left in the defects. Bone volume was assessed through cone beam computed tomography (CBCT) both before tooth extraction and at 4 months. A histomorphometric evaluation was performed. Results: CBCT and cylinder bone cores were obtained for histology and histomorphometry analysis. At 4 months after tooth extraction, CBCT showed bone volume preservation and bone formation and no statistically significant difference in bone volume before and after tooth extraction in group A. However, in group B, over the same time period, a statistically significant increase (P < .01) of vertical bone volume was reported. Biopsy specimens showed the presence of vital bone in the defects 4 months later. Conclusion: Reactive soft tissue left in large bone defects after tooth extraction may support a significant bone volume gain and vital bone formation. Keywords: bone defects, cone beam computed tomography, reactive soft tissue