Libros

Purpose: Marginal bone resorption (MBR) around dental implants may sometimes be a self-limiting condition due to balancing immunologic reactions against utilized materials rather than a progressive bacterial infection. Contrary to previous assumptions from ligature-induced experimental peri-implantitis studies, a recent 8-week experiment by the present authors showed that marginal ligatures trigger an inflammatory immune response, resulting in bone resorption around implants in the absence of plaque. The present study aimed to investigate whether this inflammatory/immunologic reaction attenuates or progresses toward implant failure after a longer healing time (12 weeks). Materials and Methods: Sterile silk ligatures were placed around the top of titanium (Ti) implants and compressed against the femoral cortical bone plate of six rabbits. A nonligated implant was used as a control. After 12 weeks of submerged healing, ground sections of implants and surrounding tissues were investigated with light microscopy. The marginal soft tissues were also analyzed using selected quantitative polymerase chain reaction (qPCR) markers. Results: Histologically, the ligatures were outlined by immune cells, including multinucleated giant cells (MNGCs), with adjacent fibrous encapsulation and resorbed peripheral bone that contrasted from the osseointegrated nonligated control implants. The difference in expression of qPCR markers was not significant, but > two-fold upregulation of markers CD11b, IL1β, ARG1, NCF1, and CD4 and > twofold downregulation of CD8 indicated a mild, focal inflammatory/immune response against the ligatures compared to controls, with upregulation of M1 and M2 macrophages, neutrophils, and helper T-cells as well as downregulation of killer T cells. Further, the bone formation markers OC and ALPL were > two-fold downregulated (consistent with the lack of osseointegration of the ligatures) compared to control implants. Conclusions: Marginal silk ligatures trigger an inflammatory/immune response and aseptic bone resorption around implants. Compared to the previous 8-week study, the inflammatory reaction against the silk appears to attenuate with time, with only a mild persisting inflammation that may block osseointegration; instead, a fibrous tissue encapsulation–type reaction is maintained. This may explain why traditional ligature experiments have required regular exchange of ligatures for the bone resorption to progress. Palabras clave: bone loss, dental implant, immunology, ligature, osseointegration

Purpose: To compare the inflammatory responses of peripheral blood mononuclear cells (PBMCs) subjected to titanium (Ti) and/or zirconia (Zr) particles while growing on Ti or Zr discs. Materials and Methods: In total, 240 discs were fabricated at a size of 2 mm in height and 5 mm in diameter. Of the 240 discs, 120 discs were made of Ti (commercially pure [CP] grade 4), and 120 discs were made of Zr (3 mol% yttria-stabilized zirconia polycrystals [3Y-TZP]). The PBMCs were cultured on the two-disc materials, and particles with a size up to 20 mm Ti (99.5% Ti) and 0.1 to 0.2 mm Zr (3Y-TZP) were added to the cultures. The concentration levels of inflammatory cytokines in culture supernatants were measured through Bio-Plex assay (Bio-Rad Laboratories), and light microscopic analysis was performed to detect cell attachment and characterize particle shape and cell-particle interaction. Results: The inflammatory responses of PBMCs were generally higher when cells were cultured on a Ti surface compared to a Zr surface. In addition, higher cytokine levels were seen when cells were cultured in the presence of Ti particles compared to Zr particles when no discs were used. However, there were only significantly increased levels for three cytokines (MCP-1, IFN-γ, and TNF-α) when particles were added to Ti discs. Higher release of neutrophil extracellular traps (NETs) from neutrophils were seen in presence of Zr particles compared to Ti particles. A reduction in cell death was observed in the presence of Zr particles compared to Ti particles and unstimulated control samples. Conclusions: The type of growth material and presence of particle affects PBMCs in vitro. Cells seeded on Ti discs and together with Ti particles generated higher levels of inflammatory cytokines compared to the Zr counterparts. Palabras clave: dental implant, PBMCs, titanium, wear particle, zirconia

Purpose: To compare the clinical outcomes of single implants with titanium (Ti) or zirconia (Zr) abutments after up to 5 years in function. Materials and Methods: This study was a retrospective analysis on single implants with screw-retained abutments (Zr or Ti) covered with porcelain veneer placed between 2011 and 2013 at one referral specialist clinic. Clinical data from patient records were collected from 132 patients and 174 implants. Technical complications such as fractures, chipping, and abutment screw loosening were registered. Radiographs were analyzed comparing both annual bone loss and accumulated bone loss at 5 years. In 57 patients with 85 implants, the values of accumulated bone loss at 5 years were compared to baseline. Results: Technical complications occurred in 16 (9%) of the implants, most often during the first year. The following complications were found: fracture of the abutment (n = 1); loosening of the abutment screws (n = 5); and chipping of the porcelain veneer (n = 11). Ti abutments had more complications than Zr abutments (79%). Of all the implants, 45% had an annual bone loss ranging between 0.05 and 2.15 mm, and 59% had an accumulated bone loss at 5 years ranging between 0.05 and 4.25 mm. Zr abutments had a statistically significantly higher amount of yearly and accumulated bone loss at 5 years. Conclusion: Abutment material affected marginal bone loss. The Zr group displayed statistically more bone loss both yearly and after 5 years compared to the Ti group. Technical complications were not affected by abutment material but were affected by age of the patient.

Purpose: After some initial setbacks in the 1970s, ceramic implants seem to be a promising alternative to titanium implants. Since the surface of an implant system represents the interface to surrounding biologic structures, the study focuses on cleanliness and surface topography. Clinical documentation of the corresponding systems completes the picture and allows a better evaluation of zirconia implant systems. Materials and methods: Five different ceramic implant systems were selected randomly and purchased via blind-shopping: Z5s (Z-Systems), ZiBone (COHO), W implant (TAVDental), ceramic. implant (vitaclinical), and BioWin!/Standard Zirkon Implantat (Champions-Implants/ZV3 system). Three samples of each implant system underwent scanning electron microscopy (SEM) imaging and elemental analysis (EDS). Where appropriate, subsequent Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was performed to identify the chemical nature of impurities. Surface topography was evaluated, and a search for clinical trials in the PubMed database, on the websites and by written request to each dental implant manufacturer, was performed. Results: Surfaces of Champions implants (ZV3) and Z-Systems implants were relatively clean, whereas the other investigated surfaces of vitaclinical, TAV Dental, and ZiBone implants all displayed organic contaminations on their surfaces. Four of the investigated ceramic implants showed a moderately rough implant surface. Only the vitaclinical ceramic.implant had minimal surface roughness. Three ceramic designs-vitaclinical, ZV3, and Z-Systems-had clinical trials documented with up to 3 years of follow-up and results varying between 82.5% and 100% survival. TAV Dental W and ZiBone implant systems lacked properly conducted clinical recording of results. Conclusion: The results of this study showed that it is technically possible to produce zirconia implants that are largely residue-free. On the other hand, the variety of significant residues found in this analysis raises concerns, as contamination may lead to undesirable biologic effects. The lack of clinical studies in peer-reviewed journals does not seem to be relevant for the approval of marketing, nor does the lack of surface cleanliness. In the authors' opinion, a critical analysis of these aspects should be included in a more stringent future analysis prior to the marketing of oral implant systems. Palabras clave: ceramic implants, dental implants, implant contamination, implant surface, scanning electron microscopy, surface, surface properties, zirconia

Purpose: To compare clinical and esthetic outcomes between immediately loaded single implants placed with and without a fully guided surgical procedure. Materials and Methods: Patients with a missing maxillary tooth (second premolar to second premolar) were considered for inclusion in this 1-year prospective nonrandomized study. Exclusion criteria were general health contraindications for oral surgery besides the need for bone grafting or ridge augmentation. One group received digital implant planning, fully guided surgery, and immediate loading (DIL). The other group received freehand surgery and immediate loading (IL). Outcome measures were implant survival, marginal bone loss, soft tissue changes, papilla index, pink and white esthetic scores (PES and WES, respectively), and patient-reported outcome measures (PROMs). Results: Two of 21 implants failed in the DIL group soon after placement, resulting in a 1-year implant survival rate of 90.5%, while no implants failed in the IL group. Significantly higher papilla index scores and lower soft tissue changes were found for the DIL group compared to the IL group. No differences were found after 1 year regarding marginal bone loss, PES, WES, or PROMs. Conclusion: Within the limitations of this study, immediate loading in combination with fully guided surgery might negatively affect implant survival. Immediate loading, fully guided surgery, and a digital workflow appear to have a positive effect on early soft tissue adaptation.

Purpose: The purpose of this paper is to present evidence that supports the notion that the primary reason behind marginal bone loss and implant failure is immune-based and that bacterial actions in the great majority of problematic cases are of a secondary nature. Materials and Methods: The paper is written as a narrative review. Results: Evidence is presented that commercially pure titanium is not biologically inert, but instead activates the innate immune system of the body. For its function, the clinical implant is dependent on an immune/inflammatory defense against bacteria. Biologic models such as ligature studies have incorrectly assumed that the primary response causing marginal bone loss is due to bacterial action. In reality, bacterial actions are secondary to an imbalance of the innate immune system caused by the combination of titanium implants and ligatures, ie, nonself. This immunologic imbalance may lead to marginal bone resorption even in the absence of bacteria. Conclusion: Marginal bone loss and imminent oral implant failure cannot be properly analyzed without a clear understanding of immunologically caused tissue responses. Palabras clave: biomaterials, failure analysis, immunologic reactions, peri-implantitis, review (narrative)

This retrospective study sought to compare a new implant (Astra Tech OsseoSpeed EV, Dentsply Sirona) with its predecessor (Astra Tech OsseoSpeed TX) by scanning electron microscopy and interferometry. Radiographic data from 19 patients who underwent implant restoration with EV (n = 49) with a median follow-up of 16 months were evaluated for mean bone level (MBL) changes from delivery of the definitive prosthesis. EV and TX did not differ in surface roughness, and both systems had a tight seal at the implant-abutment interface. The median MBL change of the EV was −0.02 mm mesiodistally after a median follow-up period of 16 months. Greater maintenance of MBL was found in the screw-retained restorations (n = 17) compared to cemented (0.35 ± 0.33 mm and −0.38 ± 0.76 mm, respectively; P = .03). The data suggest that EV shows minimal levels of bone loss and high implant survival.

Purpose: To evaluate the effect of misfit at implant-level fixed partial dentures (ILFPDs) and marginal bone support on the generation of implant cracks. Materials and Methods: This in vitro study included a mechanical fatigue test and finite element analysis. A mechanical cycling loading test was performed using 16 experimental models, each consisting of two parallel implants subdivided into four groups based on the misfit and the supporting bone condition. The framework, firmly seated at implants, was dynamically loaded vertically with a force of 1,600/160 N and 15 Hz for 1 × 10⁶ cycles. Optical microscope, scanning electron microscope (SEM), and computed tomography three-dimensional (CT-3D) analyses were performed to detect impairments. Finite element models, representing the setups in the mechanical fatigue test, were used to represent the fatigue life. Results: None of the mechanical components presented distortion or fracture at the macroscopic level during the test. In a microscopy evaluation, the fatigue test revealed scratches visible in the inner part of the conical portion of the implants regardless of the groups. SEM and CT-3D analysis revealed one implant from the misfit/no bone loss group with a microfracture in the inner part of the conical interface. The simulated effective stress levels in the coronal body were higher in the misfit groups compared with the no misfit groups. The misfit groups presented effective stress levels, above 375 MPa, that penetrated the entire wall thickness. The no bone loss group presented an effective stress level above 375 MPa along its axial direction. In the no misfit group, the area presenting effective stress levels above 375 MPa in the conical connection was larger for the bone loss group compared with the no bone loss group. Conclusion: This study confirmed that implant fracture is an unlikely adverse event. A clear pattern of effective distribution greater than fatigue limit stresses could be noticed when the misfit was present. The dynamic load simulation demonstrated that the crack is more likely to occur when implants are fully supported by marginal bone compared with a bone loss scenario. Within the limitations of this study, it is speculated that marginal bone loss might follow the appearance of an undetected crack. Further research is needed to develop safe clinical protocols with regard to ILFPD. Palabras clave: CAD/CAM, finite element analysis, implant fracture, implant level, misfit