Alberto Barlattani

Randomized controlled trial comparing a variable-thread novel tapered and a standard tapered implant: Interim one-year results

STATEMENT OF PROBLEM A tapered implant with continuously changing threads purported to provide stable tissue support and allow immediate function has been developed. Treatment success and stabilization of supporting tissues over time require documentation. PURPOSE The purpose of this prospective, randomized, controlled, multicenter study was to evaluate changes in bone level and soft tissue behavior between the novel implant (NobelActive/NA) and a standard tapered implant (NobelReplace Tapered Groovy/NR) with regard to immediate function. MATERIAL AND METHODS A total of 177 patients randomly allocated to 3 treatment groups (2 different test implant groups: NA Internal (n=117; internal connection) and External (n=82), and 1 standard treatment group, NR (n=126)) received 325 implants. Implants were placed into healed sites, and all but 6 implants were immediately nonocclusally loaded. Clinical and radiographic evaluations of treatment success, crestal bone levels, and soft tissue changes were performed at the time of placement and after 3, 6, and 12 months. Log-Rank test was used to analyze the differences in survival rate. Marginal bone level was compared using the Kruskal-Wallis test and Mann-Whitney U-test (alpha=.05). RESULTS One-year cumulative survival rates were comparable (96.6% for NA Internal; 96.3% for NA External; 97.6% for NR; P=.852; Log-Rank). Mean (SD) change in bone level was -0.95 mm (1.37) for NA Internal, -0.64 mm (0.97) for NA External, and -0.63 mm (1.18) for NR (P=.589; Kruskal-Wallis). Stable soft tissues and significantly increased papilla scores (P<.001; Wilcoxon signed-rank) were observed for all implant types. CONCLUSIONS The novel implants showed high survival rates as well as stable bone and soft tissue levels after 1 year, and may be recommended for clinical use, even under immediate function.

Clinical and radiological outcomes of two implants with different prosthetic interfaces and neck configurations: randomized, controlled, split-mouth clinical trial.

BACKGROUND Peri-implant bone loss seems to occur following implant placement/loading regardless of all the efforts to eliminate it. Several factors, including surgical trauma, biologic width establishment, lack of passive fit of the superstructures, implant-abutment microgap, and occlusal overloading, may increase peri-implant bone loss. Over the years, new interface designs were introduced and clinical studies suggest that internal conical connection and platform shifting may be advantageous for marginal bone preservation. PURPOSE To compare clinical and radiological outcomes of two implant designs with different prosthetic interfaces and neck configurations in a randomized, controlled, split-mouth clinical trial. MATERIALS AND METHODS Thirty-four partially edentate patients randomly received at least one internal conical connection with back-tapered collar and platform shifting design or external-hexagon implants with flat-to-flat implant-abutment interface. Primary end point was peri-implant bone level changes at different time points, failures of implants and/or prosthesis, any complications, implant stability quotient (ISQ) values, and periodontal parameters. RESULTS No dropout occurred. Marginal bone changes were statistically significantly different with better results for the internal conical connection. No implants and prosthesis failures have been observed, yielding a cumulative survival rate of 100%. A high ISQ value was found for both implants, and no statistically significant difference was found for ISQ mean values between interventions at each time point (p > .05). All implants showed no bleeding on probing and a very slight amount of plaque at the 1-year-in-function visit. CONCLUSIONS Both implant designs investigated performed similarly in terms of failure rates, providing successful results up to 1 year after loading. The back-tapered neck configuration with conical connection and built-in platform shifting showed statistically lower marginal bone loss than straight neck configuration with flat-to-flat implant-abutment interface and external-hexagonal connection.

Minimally invasive treatment of the atrophic posterior maxilla: A proof-of-concept prospective study with a follow-up of between 36 and 54 months

STATEMENT OF PROBLEM In the posterior maxilla, tooth loss is usually associated with alveolar bone resorption and sinus pneumatization, limiting the placement of implants without grafting procedures. PURPOSE The purpose of this study was to evaluate a minimally invasive treatment of the atrophic posterior maxilla, with axial and tilted implants and immediate loading. The research hypothesis was that the combination of a guided, minimally invasive approach and the biomimetic features of computer-aided design and computer-aided manufacturing (CAD/CAM) abutments would be an effective alternative to maxillary sinus floor augmentation procedures with reduced bone resorption around implants. MATERIAL AND METHODS Twenty-seven consecutive participants (female=12, male=15) (mean age 54.18 years) with severe atrophy of the posterior maxilla were treated by using guided surgery with immediately loaded axial (39) and tilted (42) implants supporting CAD/CAM zirconia (39) and titanium (42) abutments (81 total) and partial fixed prostheses. Each participant underwent a computed tomography scan, after which 2 or 3 implants were positioned with a flapless or miniflap approach. The drilling protocol was adapted to the bone density of each implant site to obtain an insertion torque ranging between 40 and 50 Ncm. CAD/CAM customized abutments composed of zirconia or titanium were fixed to the implants with prosthetic screws tightened with a torque of 35 Ncm. An acrylic resin interim restoration reinforced with metal was placed immediately. Five to 6 months after initial loading, a zirconia framework was manufactured, and a definitive prosthesis was placed. Clinical and radiological controls were performed at baseline and after 1 and 3 years to assess implant and prosthesis survival and success rate and compare marginal bone remodeling of axial and tilted implants. Inferential statistics for radiological data were acquired by using the Mann-Whitney U-test. All statistical comparisons were conducted at the .05 significance level. RESULTS The mean follow-up period was 43.3 months (ranging from 36 months to 54 months). The cumulative implant survival rate was 96.3% at 3 years. All prosthetic restorations were stable and in good function, resulting in a cumulative prosthetic survival rate of 100%. Three restorations had chipping of the veneer material; thereafter, the cumulative prosthetic success rate was 91.9%. CONCLUSIONS Treatment of the posterior partially edentulous atrophic maxilla with guided surgery and immediate loading of tilted and straight implants supporting short-span partial fixed dental prostheses is effective.

Monolithic Lithium Disilicate Full-Contour Crowns Bonded on CAD/CAM Zirconia Complete-Arch Implant Bridges With 3 to 5 Years of Follow-Up

This study was carried on to assess the clinical performance of a novel restorative concept consisting in single monolithic lithium disilicate full-contour crowns bonded on computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia complete-arch implant bridges, to overcome the drawbacks related to the chipping of porcelain fused to zirconia restorations. Sixteen patients received 18 implant-supported hybrid screw-cement-retained complete-arch restorations, consisting of single monolithic lithium disilicate full-contour crowns bonded on CAD/CAM zirconia frameworks. The restorations were supported by 4-8 implants. All patients were followed up for at least 3 years on function (range 36 to 60 months, mean 49.3 months). Clinical controls were scheduled every 4 months. The outcomes were implant and prosthetic survival and success rates, any complications, patient satisfaction, and soft tissue parameters. No dropouts occurred. The overall implant and prosthesis survival rates were 100%. One of 18 restorations (1 of 236 dental units) showed a chip-off fracture of the veneering ceramic that was polished intraorally without any additional treatment, scoring a cumulative prosthetic success rate of 100%, according to the California Dental Association index. All patients were functionally and esthetically highly satisfied with their restorations. Successful soft tissue parameters were found around all implants. Single monolithic lithium disilicate full-contour crowns, bonded on CAD/CAM screw-retained complete-arch zirconia frameworks, showed favorable preliminary outcomes with medium-term follow-up. However, randomized controlled studies of this technique are required for further conclusive recommendations.

Mechanical evaluation of an implant-abutment self-locking taper connection: finite element analysis and experimental tests.

PURPOSE To evaluate the mechanical properties and behavior of a self-locking taper connection with three different techniques: three-dimensional finite element analysis (FEA), ultimate failure loading, and cyclic loading analysis. MATERIALS AND METHODS The implant-abutment complex was embedded vertically in the center of an acrylic resin support block (Youngs modulus > 3 GPa). All materials used in this study were assumed to be homogenous and isotropic, but while the resin was assumed to be linearly elastic, the titanium was assumed to have a multilinear behavior to better represent the implant system in its plastic phase and to compare as closely as possible the numeric simulation with the experimental tests. An 800-N 30-degree off-axis load was applied to the occlusal surface of the abutment. In addition to the FEA, static and dynamic tests were carried out. RESULTS The greatest von Mises stresses were concentrated in the coronal portion of the abutments tapered connection, while at the implant neck they were lower and less extensive than the abutment ones. Experimental results confirmed the FEA findings, in which the structural limit of the system was reached, with permanent deformation of the abutment that exceeded a predefined limit, rather than fracture. CONCLUSION Within the limitations of the reported analyses, these static and dynamic tests appear to supply congruent results, thus allowing evaluation of the mechanical behavior of a self-locking tapered-connection implant system. High resistance to an off-axis load was exhibited, exceeding that usually offered by screw-retained implant systems, thus indicating good stability of the implant-abutment connection.

Straight Versus Angulated Abutments on Tilted Implants in Immediate Fixed Rehabilitation of the Edentulous Mandible: A 3-Year Retrospective Comparative Study.

PURPOSE The aim of this study was to evaluate and compare the use of straight versus angulated abutments on tilted implants in the All-on-Four immediate function protocol. MATERIALS AND METHODS A total of 85 patients (36 men and 49 women; mean age 56.5 years) with edentulous mandibles were treated according to the All-on-Four concept using computer-guided implant placement. All patients received immediate interim prostheses screwed onto distal tilted implants by means of angulated (control group, n = 42) or straight abutments (test group, n = 43) and were followed for at least 3 years. Outcome considerations comprised implant and prosthetic survival and success rates, marginal bone level changes, patient satisfaction, and required clinical time. Student t test at a significance level of P < .05 was used to correlate the influence of the prosthetic protocol on marginal bone levels around the implants. RESULTS Overall implant survival rate was 98.21% for the control group and 98.83% for the test group. None of the 85 fixed prostheses were lost during the observation period (prosthetic survival rate of 100%). Statistically significant differences (P = .0068) in marginal bone loss were found between control and test groups. All patients were functionally and esthetically satisfied with their restorations. Required clinical time averaged 50 minutes for the control group and 30 minutes for the test group. CONCLUSION The described simplified and shortened surgical-prosthodontic protocol that avoids use of angulated abutments may be considered a reliable alternative to the traditional All-on-Four protocol.

Salivary miRNAome profiling uncovers epithelial and proliferative miRNAs with differential expression across dentition stages

Saliva’s ability to mirror the internal physiological environment of an organism coupled with its facile accessibility makes it an attractive diagnostic medium. The finding of microRNAs (miRNAs) in saliva has expanded the field of biomarker discovery since these tiny non-coding RNAs affect various physiological processes and diseases. Few reports have linked miRNAs to tooth development and eruption, with none having studied this in humans. As a first initiative to describe miRNAs in saliva whose modulations may reflect developing and erupting teeth, we quantified the levels of 730 miRNAs in the saliva of children of varying dentition stages: edentulous (newborns), deciduous and permanent by megaplex stemloop reverse-transcription quantitative PCR. The three groups expressed 193, 181 and 192 miRNAs, respectively, where 125 miRNAs had consistent expression. The remaining miRNAs had inter-group variations from 5 to hundreds of fold, where most had either an increasing or decreasing trend in going from edentulous to deciduous to permanent. A literature survey of epithelial miRNAs found most were present in saliva. Moreover, most miRNAs with expression differences between groups had previously documented functions in proliferation, cell cycle, apoptosis and other cellular behaviors key to the dynamics of tooth morphogenesis. Lastly, miRNAs of the same family, such as the let-7 and miR-200 families, or transcribed from the same hairpin, had similar expression patterns. The results presented here should serve as a salivary miRNA dictionary for future studies in tooth development as well as in childhood diseases associated with modulations in saliva composition.

A Retrospective 2-Year Clinical Study of Immediate Prosthetic Rehabilitation of Edentulous Jaws with Four Implants and Prefabricated Bars.

PURPOSE The purpose of this retrospective investigation was to evaluate the use of a prefabricated bar system for immediately loaded implants placed and restored according to the All-on-Four concept with up to 24-month follow-up. MATERIALS AND METHODS A total of 51 patients (31 males and 20 females; mean age 63.4 years) presented with edentulous or partially edentulous jaws with severe atrophy of the posterior regions. All patients were treated with full-arch fixed prostheses (28 maxillary, 34 mandibular) each supported by four implants (two vertical, two distally tilted). The implants were immediately loaded with screw-retained full-arch restorations. Each prosthesis was supported by a prefabricated metal bar combined with high-density acrylic resin. Follow-up visits were scheduled at 6, 12, and 24 months after initial prosthetic loading. Intraoral radiographs were obtained immediately after surgery and at each follow-up visit by using a custom radiograph holder and parallel technique. Marginal bone levels were assessed using digital image analysis. Implant and prosthetic survival and success rates were evaluated. Patient satisfaction was further assessed using a 100-mm visual analog scale (VAS). Data were compared by means of the Mantel-Haenszel test. RESULTS No drop-outs occurred. The overall implant survival rates were 100% and 98.38% for the vertical and tilted implants respectively. Two of the 62 definitive fixed prostheses were lost during the observation period due to implant failure. Since restoration replacement due to implant failure was not judged a prosthodontic failure according to the survival criteria provided in this study, the overall prosthetic survival rate was 100%. No statistically significant differences in marginal bone levels between vertical and tilted implants were detected at 24-month follow-up evaluation in either jaw. All participants were functionally and esthetically satisfied with their definitive restorations after 2 years functioning, as confirmed by the average VAS scores (masticatory function: 99.7; phonetic function: 99.5, esthetics: 99.2). CONCLUSIONS The preliminary 24-month results indicate that immediate loading of vertical and tilted implants using the evaluated prefabricated bar system may be a viable solution for edentulous jaw rehabilitation; however, more long-term prospective clinical trials are needed to affirm the effectiveness of this surgical-prosthetic protocol.

Influence of the implant drill design and sequence on temperature changes during site preparation

PURPOSE The purpose of this study was to compare bone temperature changes during implant drilling with two drill designs employed in three different drilling sequences. MATERIALS AND METHODS Two implant drill designs and three drilling sequences were evaluated in vitro using artificial bone cylinders. The evaluated drills were different only in the cutting-surface length (control, 16 mm; test, 4 mm). Three drilling sequences (control A, test B1, and test B2) were evaluated with and without irrigation. Temperatures were measured with thermocouple technology. The temperature changes generated by the final drill of each sequence were recorded as the experimental results and were subjected to the Student t test. RESULTS There were statistically significant differences in temperature changes when comparing the control group A with the test groups B1 (P = .001) and B2 (P = .01) during drilling without coolant. The mean temperature changes were 12.4°C, 6.5°C, and 13.7°C for groups A, B1, and B2, respectively. The Student t test showed statistically significant differences between temperature changes of the control group A and the test groups B1 (P < .01) and B2 (P < .05) during drilling with coolant. The mean temperature changes were 0.9°C, 0.7°C, and 1.9°C for groups A, B1, and B2, respectively. CONCLUSION Reduction in length of the cutting surface of the drill may limit frictional heat. Drills with the same length of cutting surface may induce lower bone temperature changes, when considering a preliminary drilling step with a pilot drill.

Mechanical characterization of an innovative dental implant system

PURPOSE The research presented is aimed at the characterization of the mechanical resistance of an innovative system of an abutment-fixture connection in dental implants. This innovative connection system is composed of a triangular prismatic connection designed to improve the anti-rotational properties of the implant, and to seal any gap between the abutment and the fixture. METHODS The mechanical performances of the dental implant system were investigated by means of static mechanical strength tests, which allowed the identification of the bending, torque and compression resistance of the system, and fatigue testing, according to the practice standard - ISO 14801. Surface finishing was also analyzed by scanning electron microscopy (SEM) observations and laser profilometry tests. RESULTS The analyzed implant exhibited good mechanical characteristics, both in static and in fatigue tests. Moreover, the gap between the fixture and the abutment detected by SEM analyses was restricted, both before and after fatigue tests, being approximately 4 mum in the worst case observed: this is representative of optimal sealing against fluid infiltration. CONCLUSIONS The modification of traditional dental implants with the introduction of a triangular prismatic connection system not only allowed the implant rotational stability and sealing performances to increase, but also conferred optimal mechanical resistance to the implant.