Manufacturing of Metal Frameworks for Full-Arch Dental Restoration on Implants: A Comparison between Milling and a Novel Hybrid Technology.

PURPOSE: To determine the trueness and precision of frameworks manufactured with a selective laser melting/milling hybrid technique (SLM/m) and conventional milling by comparing the implant-platform/framework interface with those of the original computer-aided design (CAD). MATERIALS AND METHODS: Using a virtual 6-implant-supported full-arch framework CAD drawing, 27 titanium replicas were manufactured by 3 independent manufacturing centers (n = 9/center) using a hybrid SLM/m technology (labs 1 and 2) or the conventional milling technique (lab 3). Using an opto-mechanical coordinate measuring machine, the frameworks' misfit distribution and patterns were analyzed, and the position error between paired platform positions within each framework was evaluated to calculate the misfit tendency for each group. A multilevel analysis using a mixed-effects model was conducted (α = 0.05). The trueness was evaluated as the dimensional difference from the original, while the precision as the dimensional difference from a repeated scan. RESULTS: The 3 dimensional misfits differed significantly among the 3 groups, with the milled group exhibiting the least accurate outcome (p = 0.005). The mean 3D positioning errors ranged from 8 to 16 µm and from 9 to 22 µm for the SLM/m technique (labs 1 and 2, respectively), and from 20 to 35 µm for conventional milling (lab 3). Regarding the misfit distribution pattern, the misfit increased with the distance between paired platform positions in all groups. CONCLUSIONS: All groups had 3D misfits well within the error limits reported in the literature. The 3D misfits of new hybrid (SLM/milling) and conventional (milling) procedures differed significantly among them, with the milling technique the less accurate and precise. The largest errors in all groups were found between the most distant implants, resulting in a correlation between the framework span and the inaccuracies.

Implant-abutment connection deformation after prosthetic procedures: an in vitro study.

This study tested the possible damage to the internal implant connection provoked by repeated disconnection and reconnection of prosthetic components. Using a light-structured scanner, connection deformation was inferred by threedimensional (3D) positional changes of a "reference" abutment before and after multiple dis- and reconnections. Measurements were taken after 1, 2, 5, 10, and 20 insertions of titanium abutments in 16 internal hexagon implants. Statistical analysis revealed that multiple dis- and reconnections could cause a deformation in the implant-abutment connection, proportional to the number of insertion procedures. However, below the threshold of 10 cycles, 3D deformation values were minimal.

Impact of plasma of argon cleaning treatment on implant abutments in patients with a history of periodontal disease and thin biotype: radiographic results at 24-month follow-up of a RCT.

BACKGROUND: A lack of evidence is present in literature regarding the clinical relevance of micropollution and bacterial contamination present on customized titanium abutments following laboratory stages and steaming cleaning procedures. To preserve abutments from such pollutants, plasma of argon cleaning of customized abutments was advocated. AIM: The aim of this prospective, randomized, match-paired, triple-blinded, controlled, clinical trial is to longitudinally assess radiographical marginal bone-level changes around implants restored according to the platform switching and "one-abutment-one-time" concepts, using commercially available abutments, with and without plasma of argon cleaning treatment after customization. MATERIALS AND METHODS: Thirty patients with thin gingival biotype, a history of periodontal disease, and in general good health received one implant in the anterior maxilla or premolar region. Patients were randomly assigned to control (abutment subjected only to usually adopted cleaning protocol by steam) and test group (abutment subjected to plasma of argon treatment). Periapical standardized digital radiographs were taken at the time of crown connection (T0), 6 (T1) and 24 months after the final restoration (T2). Average mesial-distal bone-level changes mean values with standard deviations (SD) were calculated. The Mann-Whitney U-test was selected to identify differences in bone-level changes between test and control groups. RESULTS: An average interproximal bone loss of 0.16 mm (SD: 0.17) and 0.07 mm (SD: 0.34) was revealed in the control and test group at 6 months (T1), respectively, while after 24 months, groups showed a mean bone-level changes of 0.38 mm (SD: 0.44) and 0.11 mm (SD: 0.14), respectively. Statistically significant differences among control and test groups were found at both time points. Intergroup comparison relived absence of statistically significant difference. CONCLUSION: Plasma-cleaning treatment of implant titanium abutments, together with platform switching and one-abutment-one-time concepts, could be favorable in terms of hard-tissue-level changes, also in critical conditions such as in patients with a history of periodontal disease, presenting thin gingival biotype.

Zirconia-composite bonding after plasma of argon treatment.

PURPOSE: To compare the shear bond strength (SBS) values of resin cement to zirconia treated with a new activating method. MATERIALS AND METHODS: Forty-five zirconia specimens were divided into three groups: no treatment (group 1), plasma of argon cleaning for 375 seconds (group 2), and plasma of argon cleaning for 750 seconds (group 3). Composite cylinders were bonded with a self-adhesive cement. After 40 days of water storage, specimens were subjected to the SBS test. Data were analyzed with one-way analysis of variance and the Neuman-Keuls multiple comparison test. RESULTS: Test groups obtained SBS values significantly higher (101% for group 2 and 81% for group 3) than controls. CONCLUSION: Plasma of argon appeared to improve bonding between zirconia and resin cement.

Effect of 2 impression techniques on the dimensional accuracy of working implant prosthesis models: an in vitro study.

PURPOSE: Implant impressions and working models form integrated precision systems for registration and transmission of clinical data. The components of implant systems have a dimensional tolerance capable of introducing inaccuracies in the impression, thus in the prosthetic framework. This article aimed at comparing 2 repositioning impression techniques: one using impression copings (conventional technique) and the other using the final abutments as impression copings (interceptive technique). MATERIALS AND METHODS: Two experimental models, one with 4 parallel implants and the other with 4 nonparallel implants, were used to make silicone impressions. Twenty impressions were made with the conventional technique, and a further 20 were made with the interceptive technique. Three-dimensional images acquired with a three-dimensional scanner were measured using a three-dimensional image analysis software, comparing models obtained from the impressions with the experimental models. Data were statistically analyzed by means of confidence intervals calculated with the mean (α = 0.05), descriptive (box plot), and bivariate analyses. RESULTS: Statistic analysis highlighted significant differences among models obtained using both techniques: the interceptive technique generated working models with less distortion and variability. CONCLUSIONS: For internal-connection implants, the interceptive technique provided significantly more precise working models than did the conventional technique.

Shear bond strength of veneering porcelain to zirconia after argon plasma treatment.

PURPOSE: The aim of this study was to investigate if argon plasma cleaning increases the shear bond strength between zirconia and veneering ceramic surfaces. MATERIALS AND METHODS: Ninety tablets of densely sintered yttriastabilized tetragonal zirconia polycrystal were divided into three groups according to cleaning treatment (steam cleaning or plasma of Argon for 375 or 750 seconds). Groups were divided into two subgroups according to the application of a ceramic liner (A = liner, B = no liner). RESULTS: Within subgroup A, argon plasma cleaning significantly decreased shear bond strength. In subgroup B, the plasma treatment increased the shear bond strength, but the differences were not statistically significant. Subgroup A demonstrated lower shear bond strength compared to subgroup B. CONCLUSIONS: Argon plasma cleaning was suggested to improve the bond between ceramic and zirconia surfaces; however, when plasma cleaning was followed by a glassy liner application, the veneering ceramic/zirconia bond was significantly reduced.

The evaluation of marginal gap with and without optical aids: clinicians versus technicians.

PURPOSE: This study investigated the reliability of visual assessment of marginal gaps in relation to the use of magnification and the operator's profession. MATERIALS AND METHODS: A titanium bar was notched, simulating 40 marginal gaps, and 35 operators performed a quantitative evaluation of the incisions. RESULTS: Visual examination was neither sensitive nor specific, as an extreme variability of data was recorded. The precision of readers improved with magnification aids only for clinicians; technicians were significantly more accurate in evaluating the incision's width. CONCLUSION: The visual examinations were inadequate to decide the clinical acceptability of a restoration with regard to its marginal fit.

Microscopical and microbiologic characterization of customized titanium abutments after different cleaning procedures.

AIM: To assess and characterize pollution micro-particles and bacterial growth on customized titanium abutments after steaming, ultrasonic and plasma cleaning treatments. MATERIALS AND METHODS: Thirty commercially available implant abutments, after customization, were randomly divided into 3 groups of 10 and cleansed by steam (considered as control group), ultrasonic cleaning (test group 1) and plasma of Argon (test group 2). For all specimens, SEM analysis and EDAX microanalysis were performed to count and characterize pollution micro-particles, both on the abutment surface and implant-abutment connection. For the control and test groups, mean values and standard deviations were calculated for number and density of micro-particles. Statistical differences were determined by one-way ANOVA with Scheffe multiple comparison test. The level of statistical significance was set at P ≤ 0.05. Additional microbiologic analysis was performed to detect bacterial contamination on the abutment surface. RESULTS: In the control group, the number of micro-particles on average was 117.5, and 14.1, respectively, on the abutment surface and connection. In the test groups, no pollution was revealed on the abutment (average of 1.09 and 1.13 spots, respectively, in test group 1 and test group 2) and connection (1.28 and 1.41, respectively, in test group 1 and test group 2). The analysis of variance (ANOVA) showed a statistically significant difference for all the variables examined. For each variable, at least one of the groups differs from the others. Scheffe multiple comparison test showed that all comparisons for every variables between the control group and both groups are significant, while there were some comparisons between test group 1 and test group 2 that were not significant. EDAX microanalysis identified micro-particles as residual of lubricant mixed with traces of Titanium and other metals. Microbiologic analysis demonstrated the presence of bacterial growth on the abutment surface only in the control group (111.5 ± 11.43 CFU/ml/implant-abutment as mean value). In the test groups, absence of growing microorganisms was found. CONCLUSIONS: This study confirmed that both plasma and ultrasonic treatments can be beneficially adopted for abutment cleaning process after laboratory technical stages, to supposedly favor soft tissue healing and implant-prosthetic connection stability.

Hard tissue response to argon plasma cleaning/sterilisation of customised titanium abutments versus 5-second steam cleaning: results of a 2-year post-loading follow-up from an explanatory randomised controlled trial in periodontally healthy patients.

PURPOSE: The aim of this triple-blinded randomised controlled trial was to test if argon plasma cleaning/ sterilisation of customised abutments can affect peri-implant marginal bone levels when compared to 5 seconds of steam cleaning. MATERIALS AND METHODS: A total of 20 consecutive periodontally healthy patients requiring single implant-supported restorations in the maxillary premolar or anterior area were selected. All patients received a single implant. At abutment connection, customised abutments were randomly allocated to control (subjected only to usually adopted steam cleaning, CG) and test groups (subjected to plasma cleaning/sterilisation, TG). Abutments were screwed in at 32 Ncm, provisional restorations adapted and periapical radiographs were taken using customised film holders. Two weeks later, definitive restorations were placed. Patients were followed-up for 2 years post-loading. Outcome measures were implant/crown success, complications, periapical marginal bone level changes on periapical standardised radiographs, and microbiological analyses of the abutments after customisation and cleaning procedures but before connection. Comparisons between groups were performed by independent sample t tests (significance threshold of P ≤ 0.05). RESULTS: No patient dropped out 2 years after loading. The presence of bacterial growth (staphylococci, including Staphylococcus aureus) was observed only on the CG abutments. No implant failed and no complications occurred. After 2 years of prosthetic loading, radiographic analysis revealed a statistically significantly higher mean bone loss for the CG group (mean difference 0.4 mm; 95% CI 0.08-0.73; P = 0.018). CONCLUSIONS: This study suggests that removal of contaminants from titanium abutments using plasma of argon can allow for better bone level maintenance when compared to 5-second steam cleaning of titanium abutments. It is therefore important to use cleaned and sterilised customised abutments in patients.

Implant abutment screw reverse torque values before and after plasma cleaning.

This in vitro study analyzed the reverse torque (RevT) of abutment screws following different cleaning treatments. A convenience sample of 50 customized titanium abutment screw complexes was divided into five groups: cleaning by steam (control group), cleaning by Argon plasma (test groups 1 and 2 [with chlorhexidine gel]), and replacement of old screws with new ones (test groups 3 and 4 [with chlorhexidine gel]). Abutments were screwed onto implants and tested for RevT. The RevT of the test groups was significantly higher than that of the control group. No statistically significant difference between test groups was noted except between groups 2 and 3.

Microscopical and chemical surface characterization of the gingival portion and connection of an internal hexagon abutment before and after different technical stages of preparation.

AIM: This study was aimed to assess contaminants on the abutment surface close to the implant-abutment interface and the connection, after common technical protocols. MATERIALS AND METHODS: A total of 40 abutments were divided into four groups: control group (abutment removed from the plastic envelop), test group1 (milled), test group2 (milled and polished), test group3 (milled, polished and steamed). Groups were subjected to scanning electron microscope (SEM) analysis. Pollution particles were counted and measured. Mean values and standard deviation (SD) were calculated. To evaluate any difference between groups Wilcoxon Signed Rank Test was conducted. In addition, contaminant chemical characterization was investigated by Energy-dispersive X-ray spectroscopy (EDX). RESULTS: Control group presented minimal amount of pollution (mean value of 2.1 spots [SD: 1.66] covering 0.004% of the surface). On the other hand, SEM analysis revealed on the abutment surface a mean value of 115.9 (SD: 32.27), 162 (SD: 21.17), and 32.5 (SD: 9.73) spots, respectively, in Test group 1, 2, and 3. Micro-particles covered the 0.025%, 0.057%, 0.0404% of the surface, respectively, in Test group 1, 2, and 3. On the connection, SEM analysis revealed a mean value of 61.9 (SD: 9.07), 39 (SD: 12.35), 42.1 (SD: 8.59) spots, respectively, in Test group 1, 2, and 3. Micro-particles covered the 0.0774%, 0.0869%, and 0.0392% of the surface, respectively, in Test group 1, 2, and 3. Spots were identified by EDX as micro-particles of lubricant and titanium smear layer. All differences were statistically significant. CONCLUSIONS: After technical procedures, presence of contaminants on the abutment surface in contact with the peri-implant tissues was confirmed. To prevent that such debris could interfere with biological stability of peri-implant tissues and, thus, enhance the implant-prosthesis integration, different cleaning protocols should be evaluated.

Edentulous site enhancement: a regenerative approach to the management of edentulous areas. Part 2: Peri-implant tissues.

The appearance and long-term stability of peri-implant bone, mucosa, and gingiva determine the success of implant-supported prostheses from both the esthetic and functional standpoints. Any surgical or prosthetic technique that takes into consideration only some variables, or that only intervenes in a limited phase of treatment, is a potential source of a partially successful and/or unpredictable clinical outcome. This article describes the underlying principles and surgical-prosthetic procedures of a systematic regenerative approach, edentulous site enhancement (ESE). The goal of this approach is to improve the anatomy of edentulous sites. Applied to implant dentistry, this approach enables peri-implant tissue to be managed predictably, optimizing the functional and esthetic result of restorations with regard to treatment time, number of surgical stages, long-term prognosis, and incidence of complications. The principles underlying the ESE approach, which are independent of any specific implant system, are applicable in the majority of clinical situations, regardless of the esthetic requirements.

Edentulous site enhancement: a regenerative approach for the management of edentulous areas. Part 1. Pontic areas.

The successful esthetic integration of a prosthesis is dependent on the anatomic site in which the restoration is inserted. Edentulous site enhancement is a regenerative approach based on the following: (1) anatomic evidence that the morphology of soft tissues is dependent on the underlying support (bone, roots, implants) but also significantly influenced by overlying structures (fixed or removable prostheses); (2) histologic evidence of the remarkable regenerative capacity of the newly formed tissue that develops during healing by secondary intention; (3) clinical evidence that it is possible to guide the formation of this new regenerative tissue by creating a support with proper morphology and a highly polished surface; (4) observations that positive pressure exerted by alimentary bolus and negative pressure produced by deglutition affect the growth of this tissue healing by second intention; and (5) the application of appropriate oral hygiene techniques to guide tissue healing and maintain its integrity. The edentulous site enhancement approach is simple, practical, and predictable and offers minimal postoperative complications. This paper describes the edentulous site enhancement approach as applied in the pontic areas.

Morphogenic bone splitting: description of an original technique and its application in esthetically significant areas.

PURPOSE: This article presents a regenerative technique, morphogenic bone splitting (MBS), which overcomes the limitations associated with expansion techniques described to date. MATERIALS AND METHODS: The authors propose a method whereby the bone-mucosa-gingival complex (BMGC) is displaced in its entirety, establishing a new focus for a secondary hinge located in the coronal reaches of the osteotomy. Depending on clinical needs, this approach modifies or eliminates the facially inclined hinge displacement characteristic of ridge expansion techniques. By exploiting the inherent capacity for second intention healing, the regenerative MBS technique avoids the use of graft material, membranes, or mechanical devices. It effectively harnesses the intrinsic regenerative capabilities of the treated site. RESULTS AND CONCLUSIONS: The MBS technique is performed in a single operation. By permitting the insertion of implants of an appropriate size in the optimum position for esthetic and functional requirements, it achieves the desired 3-dimensional reshaping of the BMGC and thereby restores the anatomy of the implant site. This reshaping includes: root prominences, keratinized gingiva, papillae, fornix, and the mucogingival junction. In addition to these esthetically significant issues, it permits implants to be placed at a functionally favorable axial inclination.