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Manfredini M, Poli PP, Giboli L, Beretta M, Maiorana C, Pellegrini M. Clinical Factors on Dental Implant Fractures: A Systematic Review. Dent J (Basel) 2024; 12:200. [PMID: 39056987 PMCID: PMC11276356 DOI: 10.3390/dj12070200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 06/06/2024] [Accepted: 06/25/2024] [Indexed: 07/28/2024] Open
Abstract
Dental implant fractures pose a significant challenge to long-term treatment success. This systematic review aims to comprehensively examine the clinical factors influencing dental implant fractures (IFs). Furthermore, strategies to choose the right type of implant and prevent this complication are addressed. A systematic search was conducted across PubMed, Scopus, and Web of Science databases. Eligible studies included retrospective case-control, prospective cohort studies, and clinical trials. The initial search yielded 361 articles, of which 312 were excluded being these reviews, case reports, irrelevant, or written in languages other than English. This left 49 articles, with only 6 meeting the eligibility criteria for an in-depth review. These studies, all retrospective case-control, examine implant characteristics, patient demographics, surgical and prosthetic variables, biomechanical and functional factors, clinical and procedural variables, complications and maintenance issues. The risk of bias was assessed as low using the ROBINS-I tool. Key findings suggest a correlation between implant diameter and structural resistance, with wider implants demonstrating reduced fracture risk. Additionally, posterior regions, especially molars and premolars, exhibit higher susceptibility to IFs due to increased masticatory forces. Implant design and material may considerably influence fracture risk, with conical implants and screw-retained prostheses showing higher vulnerability. Biomechanical overload, particularly in patients with bruxism, emerges as a primary contributing factor to IFs. Prosthesis type significantly influences fracture incidence, with cantilever prostheses posing a higher risk due to increased stress. Peri-implant bone loss is strongly associated with IFs, emphasizing the need for meticulous preoperative assessments and individualized management strategies. Future research should prioritize larger and heterogeneous populations with long-term follow-up and standardized methodologies to enhance the generalizability and comparability of findings. Randomized controlled trials and biomechanical studies under controlled conditions are also essential to elucidate the complex interactions contributing to IFs and developing effective prevention strategies. Additionally, integrating patient-reported outcomes may offer a comprehensive understanding of the impact of IFs on quality of life.
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Affiliation(s)
- Mattia Manfredini
- Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20122 Milan, Italy
- Implant Center for Edentulism and Jawbone Atrophies, Maxillofacial Surgery and Dental Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy
| | - Pier Paolo Poli
- Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20122 Milan, Italy
- Implant Center for Edentulism and Jawbone Atrophies, Maxillofacial Surgery and Dental Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy
| | - Luca Giboli
- Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20122 Milan, Italy
- Implant Center for Edentulism and Jawbone Atrophies, Maxillofacial Surgery and Dental Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy
| | - Mario Beretta
- Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20122 Milan, Italy
- Implant Center for Edentulism and Jawbone Atrophies, Maxillofacial Surgery and Dental Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy
| | - Carlo Maiorana
- Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20122 Milan, Italy
- Implant Center for Edentulism and Jawbone Atrophies, Maxillofacial Surgery and Dental Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy
| | - Matteo Pellegrini
- Department of Biomedical, Surgical and Dental Sciences, University of Milan, 20122 Milan, Italy
- Implant Center for Edentulism and Jawbone Atrophies, Maxillofacial Surgery and Dental Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy
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da Rosa LS, Soares PM, Packaeser MG, Chiapinotto GF, Bacchi A, Tribst JPM, Kleverlaan CJ, Pereira GKR. Effect of abutment screw-access hole on the fatigue performance of implant-supported lithium-disilicate luted simplified restorations. J Mech Behav Biomed Mater 2024; 150:106254. [PMID: 38035645 DOI: 10.1016/j.jmbbm.2023.106254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 11/13/2023] [Accepted: 11/15/2023] [Indexed: 12/02/2023]
Abstract
The present study aimed to evaluate the impact of the existence of an abutment screw-access hole and the filling effects on the fatigue mechanical behavior of a luted lithium-disilicate glass-ceramic. Seventy-two discs (Ø = 10 mm, 1.0 mm in thickness) of lithium disilicate (IPS e.max CAD, Ivoclar AG) were obtained from prefabricated blocks. Thirty-six abutment specimens of an opaque zirconia (Yz - IPS e.max ZirCAD, Ivoclar AG) and titanium (Ti - Luminesse Ti-Cam discs, Talladium Inc.) were confectioned, and allocated according to 6 groups: Yz and Ti rigid (without screw access hole); Yz unfilled, Yz filled, Ti unfilled and Ti filled (with the screw access (Ø = 2.5 mm) in the center). For the unfilled groups, only a polytetrafluoroethylene tape was used. Resin composite (Tetric N-Ceram, Ivoclar AG) was applied to the screw access hole for the filled groups (Yz and Ti). A cyclic fatigue test was carried out (load of 200 N, 10,000 cycles each; 20 Hz of frequency, step size of 100 N until failure detection (radial/cone crack). The fatigue failure load (FFL) and number of cycles until failure (CFF) were recorded for statistical purposes. The stress distribution (MPa) was evaluated by finite element analysis. A statistically positive effect of the abutment material and the presence of the screw access hole was observed (p ≤ 0.05). The rigid groups (without screw access holes) depicted almost 100% of survival after the fatigue tests. Among the other groups, the Yz-filled group showed the best performance (p ≤ 0.05), followed by the Yz unfilled group. The Ti groups depicted lower values of FFL and CFF, with the Ti unfilled group showing the most unfavorable fatigue behavior (p ≤ 0.05). The lowest tensile stress concentration in the restorative material was observed with the use of rigid abutments, the filled groups depicted intermediate values, while unfilled groups showed the highest stress concentration (Yz rigid = 306.3 MPa; Ti rigid = 310.4 MPa < Yz filled = 490.7 MPa; Ti filled = 498.9 MPa < Yz unfilled = 707.6 MPa; Ti unfilled = 719.7 MPa). Therefore, the presence of a screw-access hole decreases the mechanical performance of a lithium disilicate ceramic regardless of the abutment material. In the presence of a screw-access hole, zirconia abutments depicted a higher fatigue failure load when compared with titanium. The filling of the abutment screw-access hole with resin composite increased the mechanical performance of the simulated restoration.
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Affiliation(s)
- Lucas Saldanha da Rosa
- Post-Graduate Program in Oral Sciences (Prosthodontics Unit), Faculty of Dentistry, Federal University of Santa Maria (UFSM), Santa Maria, Rio Grande do Sul State, Brazil.
| | - Pablo Machado Soares
- Post-Graduate Program in Oral Sciences (Prosthodontics Unit), Faculty of Dentistry, Federal University of Santa Maria (UFSM), Santa Maria, Rio Grande do Sul State, Brazil.
| | - Maria Gabriela Packaeser
- Post-Graduate Program in Oral Sciences (Prosthodontics Unit), Faculty of Dentistry, Federal University of Santa Maria (UFSM), Santa Maria, Rio Grande do Sul State, Brazil.
| | - Gratcheva Falcão Chiapinotto
- Post-Graduate Program in Oral Sciences (Prosthodontics Unit), Faculty of Dentistry, Federal University of Santa Maria (UFSM), Santa Maria, Rio Grande do Sul State, Brazil.
| | - Atais Bacchi
- Post-Graduate Program in Dentistry, Paulo Picanço School of Dentistry (FACPP), Fortaleza, Ceará State, Brazil.
| | - João Paulo Mendes Tribst
- Department of Reconstructive Oral Care, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Amsterdam, North Holland, the Netherlands.
| | - Cornelis Johannes Kleverlaan
- Department of Dental Materials, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Amsterdam, North Holland, the Netherlands.
| | - Gabriel Kalil Rocha Pereira
- Post-Graduate Program in Oral Sciences (Prosthodontics Unit), Faculty of Dentistry, Federal University of Santa Maria (UFSM), Santa Maria, Rio Grande do Sul State, Brazil.
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Teja Obulareddy V, Dixit A, Takhellambam V, Verma RK, Deepyanti, Kumar S, Kumar A. An In Vitro Investigation of the Role of Implant Abutment Materials on the Fracture Resistance and Failure Mode of Implant-Supported Restorations. Cureus 2024; 16:e54624. [PMID: 38529462 PMCID: PMC10962928 DOI: 10.7759/cureus.54624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 02/14/2024] [Indexed: 03/27/2024] Open
Abstract
BACKGROUND Implant-supported restorations have gained popularity in modern dentistry, and the choice of abutment material is crucial for their long-term success. This in vitro study aimed to evaluate the fracture resistance and failure mode of implant-supported restorations using different abutment materials. METHODS Ninety standardized implant-supported restorations were included in the study. Abutments made of titanium, zirconia, and a hybrid material (titanium base with a zirconia veneer) were evaluated. Standardized abutments were fabricated, and screw-retained restorations were fabricated using a resin-based composite material. Cyclic loading was applied using a universal testing machine to simulate masticatory forces. Fracture resistance was measured in terms of the number of cycles to failure (NCF), and failure modes were analyzed. RESULTS The findings indicate that zirconia abutments exhibited higher fracture resistance compared to titanium and hybrid abutments. Longer implants demonstrated higher fracture resistance, suggesting improved stability and resistance to mechanical forces. Increased loading angles resulted in decreased fracture resistance of implant-supported restorations, emphasizing the need for proper occlusal adjustment. Central loading showed higher fracture resistance than lateral and posterior loading locations. The distribution of failure modes varied among the abutment materials, with bulk prosthesis fracture being the most common in the titanium group, while abutment fracture was predominant in the zirconia and hybrid groups. CONCLUSION This in vitro study demonstrated that the choice of abutment material significantly influenced the fracture resistance and failure mode of implant-supported restorations. Zirconia abutments exhibited the highest fracture resistance, followed by hybrid and titanium abutments. The failure mode analysis revealed different patterns of failure for each abutment material.
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Affiliation(s)
| | - Arti Dixit
- Public Health Dentistry, Vaidik Dental College and Research Centre, Daman, IND
| | | | - Rajnish K Verma
- Pedodontics and Preventive Dentistry, Kalinga Institute of Dental Sciences, Kalinga Institute of Industrial Technology (KIIT) (Deemed to be University), Bhubaneswar, IND
| | - Deepyanti
- Conservative Dentistry and Endodontics, D.Y. Patil Dental College and Hospital, Pune, IND
| | - Sandeep Kumar
- Public Health Dentistry, Rajendra Institute of Medical Sciences (RIMS), Ranchi, IND
| | - Amit Kumar
- Public Health Dentistry, Interdental Multispeciality Dental Clinic, Mumbai, IND
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Strazzi-Sahyon HB, Bergamo ETP, Gierthmuehlen PC, Lopes ACO, Alves LMM, Benalcázar Jalkh EB, Zahoui A, Coelho PG, de Carvalho AM, Bonfante EA. In vitro assessment of the effect of luting agents, abutment height, and fatigue on the retention of zirconia crowns luted to titanium base implant abutments. J Prosthet Dent 2023; 130:739.e1-739.e8. [PMID: 37684141 DOI: 10.1016/j.prosdent.2023.07.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Revised: 07/27/2023] [Accepted: 07/31/2023] [Indexed: 09/10/2023]
Abstract
STATEMENT OF PROBLEM The bonding of implant-supported prostheses is determined by abutment material, convergence angle, height, surface treatment, and luting agents. However, studies evaluating the bonding of luting agents to titanium base abutments with different heights under fatigue conditions are scarce. PURPOSE The purpose of this in vitro study was to evaluate the retention of zirconia crowns bonded with different luting agents to titanium base abutments of different heights before and after fatigue testing. MATERIAL AND METHODS Zirconia crowns were designed, milled, and distributed into 4 experimental groups according to the luting agents (G-Multi Primer/G-Cem LinkForce [MP/GC] and Scotchbond Universal/RelyX Ultimate [SU/RU]) and titanium base abutment heights (2.5 mm and 4 mm) (n=10). Pull-out testing was performed in a universal testing machine at a crosshead speed of 1 mm/min until crown displacement. Fatigue testing was performed by an electric precision fatigue simulator (1×106 cycles; 100 N; and 15 Hz), followed by pull-out testing of fatigued specimens. Collected data were statistically evaluated by using a linear mixed model after post hoc comparisons by the least significant difference test (α=.05). RESULTS Luting agents, abutment heights, and fatigue influenced the bonding retention of zirconia crowns to titanium base abutments. SU/RU agents promoted higher pull-out compared with MP/GC for both abutment heights before and after fatigue. Higher abutment height increased pull-out regarding lower abutment height for SU/RU materials before and after fatigue testing. Although fatigue had no significant effect on the pull-out of MP/GC, lower bond retention was observed for SU/RU after fatigue, regardless of abutment height. CONCLUSIONS Luting agent composition and the interaction with abutment height and fatigue influenced the retention of zirconia crowns to titanium base abutments.
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Affiliation(s)
- Henrico B Strazzi-Sahyon
- Postdoctoral Researcher, Department of Prosthodontics and Periodontology, Bauru School of Dentistry, University of Sao Paulo (USP), São Paulo, Brazil.
| | - Edmara T P Bergamo
- Postdoctoral Researcher, Department of Prosthodontics and Periodontology, Bauru School of Dentistry, University of Sao Paulo (USP), São Paulo, Brazil; Postdoctoral Researcher, Biomaterials Division, New York University College of Dentistry, New York, NY
| | - Petra C Gierthmuehlen
- Professor, Department of Prosthodontics, School of Dentistry, Heinrich-Heine-University, Düsseldorf, Germany
| | - Adolfo C O Lopes
- Postgraduate student, Department of Prosthodontics and Periodontology, Bauru School of Dentistry, University of Sao Paulo (USP), São Paulo, Brazil
| | - Larissa M M Alves
- Postdoctoral Researcher, Department of Prosthodontics and Periodontology, Bauru School of Dentistry, University of Sao Paulo (USP), São Paulo, Brazil
| | - Ernesto B Benalcázar Jalkh
- Postdoctoral Researcher, Department of Prosthodontics and Periodontology, Bauru School of Dentistry, University of Sao Paulo (USP), São Paulo, Brazil
| | - Abbas Zahoui
- Postgraduate student, Department of Prosthodontics and Periodontology, Bauru School of Dentistry, University of Sao Paulo (USP), São Paulo, Brazil
| | - Paulo G Coelho
- Professor, Department of Surgery, University of Miami Miller School of Medicine, Miami, FL
| | - Alexandre M de Carvalho
- Postdoctoral Researcher, Department of Prosthodontics and Periodontology, Bauru School of Dentistry, University of Sao Paulo (USP), São Paulo, Brazil
| | - Estevam A Bonfante
- Professor, Department of Prosthodontics and Periodontology, Bauru School of Dentistry, University of Sao Paulo (USP), São Paulo, Brazil
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López-Píriz R, Goyos-Ball L, Cabal B, Martínez S, Moya JS, Bartolomé JF, Torrecillas R. New Ceramic Multi-Unit Dental Abutments with an Antimicrobial Glassy Coating. MATERIALS (BASEL, SWITZERLAND) 2022; 15:5422. [PMID: 35955356 PMCID: PMC9369483 DOI: 10.3390/ma15155422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 07/24/2022] [Accepted: 08/04/2022] [Indexed: 06/15/2023]
Abstract
The choice of suitable materials and new designs in oral implantology and the subsequent enhancement of the characteristics of the dental implant developed is an important research topic with wide scope. The present work aims to develop a new multifunctional zirconia-ceria/alumina (Ce-TZP/Al2O3) composite with an antimicrobial glass-based coating to be used in multi-unit abutments compatible with commercially available Ti implants for peri-implantitis prevention. An airbrush spraying technique was effectively applied to coat the sintered ceramic composite starting from a glass powder suspension. This deposition technique was appropriate for obtaining continuous antimicrobial glass-based coatings with homogenous thickness (~35 µm) on ceramic dental implant components. The dental implant systems with the antimicrobial glassy coating were subjected to a mechanical integrity test following ISO 14801 to determine their long-term stability. The tested implant-coating structure seems to be stable under in vitro conditions with ultimate applied forces exceeding the maximum physiological occlusal loading force. This paper also presents a pilot clinical case report that shows peri-implant tissue around the mechanically stable glass coating with no signs of inflammation 1 year after implant insertion. This result is a preliminary probe of the durability and biological tolerance of the glassy material by the gingiva, as well as the antimicrobial effect on the peri-implant microbiota displayed by the coating.
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Affiliation(s)
- Roberto López-Píriz
- Instituto de Cirugía Oral Avanzada-ICOA, Calle de Fray Luis de León, 14, 28012 Madrid, Spain
| | - Lidia Goyos-Ball
- Nanoker Research, Pol. Ind. Olloniego, Parcela 22A, Nave 5, 33660 Oviedo, Spain
| | - Belén Cabal
- Nanomaterials and Nanotechnology Research Centre (CINN), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Oviedo (UO), Principado de Asturias (PA), Avenida de la Vega 4-6, 33940 El Entrego, Spain
| | - Susana Martínez
- Nanoker Research, Pol. Ind. Olloniego, Parcela 22A, Nave 5, 33660 Oviedo, Spain
- Nanomaterials and Nanotechnology Research Centre (CINN), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Oviedo (UO), Principado de Asturias (PA), Avenida de la Vega 4-6, 33940 El Entrego, Spain
| | - José S. Moya
- Nanomaterials and Nanotechnology Research Centre (CINN), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Oviedo (UO), Principado de Asturias (PA), Avenida de la Vega 4-6, 33940 El Entrego, Spain
| | - José F. Bartolomé
- Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), 28049 Madrid, Spain
| | - Ramón Torrecillas
- Nanoker Research, Pol. Ind. Olloniego, Parcela 22A, Nave 5, 33660 Oviedo, Spain
- Nanomaterials and Nanotechnology Research Centre (CINN), Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Oviedo (UO), Principado de Asturias (PA), Avenida de la Vega 4-6, 33940 El Entrego, Spain
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Wang D, Dong W. Application Effect of New Material after Surface Modification of Zirconia Ceramics and Analysis of Patient Evaluation. COMPUTATIONAL INTELLIGENCE AND NEUROSCIENCE 2022; 2022:1589209. [PMID: 35837209 PMCID: PMC9276471 DOI: 10.1155/2022/1589209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 06/10/2022] [Accepted: 06/15/2022] [Indexed: 01/10/2023]
Abstract
Objective To explore the application effect of new material after surface modification of zirconia ceramics and patient evaluation. Methods A total of 60 patients with tooth defect treated in our hospital from April 2020 to April 2021 were selected as the study subjects and randomly divided into the control group and experimental group, with 30 cases each. The patients in the control group were treated with glass-ceramics, and those in the experimental group received LiSi surface treatment, so as to compare the application effect and patients' evaluation between the two groups. Results Between the two groups, no obvious differences in surface loss, adhesive strength, and transmittance at 3 months, 6 months, and 1 year were not observed (P > 0.05); and after intervention, the score on dental aesthetics, hardness value, and occlusal force were obviously higher in the experimental group than in the control group (P < 0.001). Conclusion The new material enables forming an acid etchable coating on the zirconia surface, increases the adhesive strength, and achieves an aesthetic degree that is welcomed by the patients; meanwhile, after grinding, the edge is defect free and the tightness is higher. Further research will help to establish a better solution for patients.
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Affiliation(s)
- Dongjiang Wang
- Department of Stomatology, Tianjin Second Hospital, Tianjin 300010, China
| | - Wenjie Dong
- Department of Stomatology, The Second Affiliated Hospital of Mudanjiang Medical College, Mudanjiang 157000, Heilongjiang, China
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Ordoñez Balladares A, Abad-Coronel C, Ramos JC, Martín Biedma BJ. Fracture Resistance of Sintered Monolithic Zirconia Dioxide in Different Thermal Units. MATERIALS 2022; 15:ma15072478. [PMID: 35407810 PMCID: PMC8999687 DOI: 10.3390/ma15072478] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 03/16/2022] [Accepted: 03/22/2022] [Indexed: 01/27/2023]
Abstract
The purpose of this study was to compare the fracture strength of monolithic zirconium dioxide subjected to a sintering process in two different furnaces: InFire HTC Speed and CEREC SpeedFire. Methods: Forty restorations were designed and machined using a computer aided design / computer aidded machine (CAD/CAM) system. The restorations were randomly assigned to two groups of 20 samples each, Group 1 for the SpeedFire furnace (fast sintering) and Group 2 for the InFire furnace (slow sintering). Each of the crowns was subjected to a maximum compression load recorded in Newtons (N) and a displacement control with a speed of 1 mm/min. Results: Group 1 presented an average of 1222.8 N and a standard deviation of 136.91 N. Group 2 obtained a mean of 1068.5 N and a standard deviation of 316.39 N. Conclusions: There were no significant differences between the two groups, and the mechanical strength of the material was not affected, which would imply a saving of clinical and laboratory time when performing rapid sintering on monolithic translucent zirconium dioxide restorations. However, rapidly sintered restorations have limited reliability.
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Affiliation(s)
- Andrea Ordoñez Balladares
- Faculty of Dentistry, Universidad de Guayaquil, Guayaquil 090514, Ecuador;
- Faculty of Dentistry, Universidad de Santiago de Compostela, 15782 Galicia, Spain;
| | - Cristian Abad-Coronel
- Department of Digital Dentistry and CAD/CAM Materials, Faculty of Dentistry, Universidad de Cuenca, Cuenca 010107, Ecuador
- Faculty of Dentistry, Universidad San Francisco de Quito, Quito 170901, Ecuador
- Correspondence:
| | - Joao Carlos Ramos
- Faculty of Medicine, Universidad de Coimbra, 3000-370 Coimbra, Portugal;
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