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Implant Tribune Middle East & Africa Edition No. 2, 2018

Dental Tribune Middle East & Africa Edition | 2/2018 ◊Page D2 IMPLANT TRIBUNE D3 Degradation rates at room or body temperature of Y-TZP ceramics are currently not available, and acceler- ated tests at intermediate tempera- ture (100 to 300 °C) are the only basis for extrapolating an estimate of the transformation rate and, hence, of the product lifetime. This approach relies on the assumption that the transformation rate follows the same Arrhenius-like trend down to room/body temperature. Unfortu- nately, such extrapolation could lead to a signifi cant error in estimating room/body temperature lifetimes.9 Still this is the method that is used in researches. Monzavi M. et al. (2017) examined 36 zirconia implants of four different brands and found that the effect of ageing was minimal in all systems.19 They suggested though that in vivo studies are needed to investigate the effect of mastication force on the extent of LTD and the infl uence of surface changes such as delamination of the grains on sur- rounding hard- and soft-tissue. Still a certain degree of transforma- tion from tetragonal to monoclinic phase can actually improve the me- chanical properties of Y-TZP. Under stress, i.e. at the tip of a crack, the Y- TZP undergoes a phase transforma- tion from tetragonal to monoclinic phase. This phase transformation results in a 3 to 4 per cent volumetric expansion inducing a compressive stress in the area of the crack and theoretically prevents crack propa- gation.1 An implant which exhibits phase transformation in case of microcracks and high forces is desir- able. Still it is not sure whether the already existing microcracks that are produced (for instance, during handling) during mastication or par- afunctional activities, don’t propa- gate, leading to a possible fracture. One- vs two-piece zirconia implants Zirconia appears in two varieties, one- and two-piece implants. One- piece implants offer the absence of a microgap between implant and abutment which seems to be of bene- fi t. The surgical placement of the im- plant, though may not always meet the prosthodontic requirements and angled abutments in order to cor- rect misalignment, is not common. Secondary corrections of the shape by grinding must be avoided, as this severely affects the fracture strength of zirconia.20 Protection by use of splints is also required, though not always possible. So, two-piece im- plants were designed. Designing a zirconia implant should be based on material properties and should sim- plify surgical and prosthetic steps for the doctor. Size limitations should be considered, in order to produce an implant that is not prone to frac- tures. A clinical study by Gahlert et al. (2012) showed a marked tendency of one-piece implants with a narrow di- ameter (3.25 mm) to fracture, with a percentage that reached 92 per cent of the fractured implants.21 Threads and shape of implants should be designed according to the needs, al- ways with respect to material. Size and shape precautions should also be applied to the implant head in order to avoid the risk of creating microcracks during implantation. The implant head if positioned at the gingival level or even higher, could eliminate the need for a sec- ond surgery, as well as to bypass the bacterial growth in the gap between implant and abutment. The decision of choosing between a one- and a two-piece implant could be infl u- enced by the design of the implant, the available space to be installed, and the prosthetic rehabilitation that follows. Implant-abutment connection Connection of the abutment with the implant is performed by three ways: either by screwing, cementing, or even as a combination of both. When screwing, the material of the abutment and the connecting screw is of crucial importance for the im- plant to be intact. As a consequence from titanium knowledge, screwing an abutment made from the same material as the implant was a “natu- ral” step. Screwing though zirconia inside a zirconia, unlike titanium, cannot result in a tight connection, because of the stiffness of the mate- rial. This loosening could possibly result in fracture and if this happens to the implant, it could jeopardise everything. In case of abutment failure, one should estimate the con- venience of removing the abutment screw. A recent in vitro study by Preis et al. (2016) comes to strengthen the aforementioned performance of different implant-abutment con- nections, was investigated in six groups of different two-piece zir- conia implant systems.22 In group 1, the abutments were cemented to an alumina-toughened zirconia implant. In group 2, the abutments were screwed with a carbon fi bre reinforced polymer screw on an alu- mina-toughened zirconia implant. In the remaining four groups, the abutments were screwed with tita- nium screws on tetragonal zirconia polycrystalline implants. A standard screw-retained implant served as the control. The bonded zir- conia system and the titanium refer- ence survived without any failures. Screw-retained zirconia systems showed fractures of abutments and/ or implants, partly combined with screw fracture/loosening. Failures concerning the abutment/implant region around the screw, indicate that the connecting design is crucial for clinical success. titanium Additionally, a study by Neumann et al. (2014) compared the fracture resistance of abutment retention screws made of titanium, poly- (PEEK) and 30 etheretherketone per cent carbon fi bre-reinforced PEEK, using an external hexago- nal implant/UCLA-type abutment interface assembly.23 UCLA-type abutments were fi xed to implants using titanium screws (group 1), polyetheretherketone screws (group 2), and 30 per cent carbon fi bre- reinforced PEEK screws. They found that the titanium screws had higher fracture resistance, compared with PEEK and 30 per cent carbon fi bre- reinforced PEEK screws. Screwing abutments can be the trend, but cementation on the other hand could be a simpler and less time-consuming procedure as it is also shown in the study by Brüll et al. (2014).24 It is closer to the den- tist’s basic education, resembles the procedure of cementing a post in natural endodontically treated teeth and requires no extra instruments. A combination of both screwing and cementing though, could make the procedure more complicated. More studies are required to determine the proper abutment material, ce- mentation method and procedure. The restoration materials that will be used together with their limitations should be studied. Mostly fi xed prosthetics on single crowns or small bridges have been presented. The fracture resistance of two-piece zirconia and titanium im- plant prototypes under forces rep- resentative of a period of fi ve years of clinical loading was tested, during an in vitro experiment by Kohal et al. (2009).25 In this experiment the crown materials had no infl uence on the fracture strength of the zirconia implants. Still, in certain cases such as treating a patient with parafunc- tional chewing, a softer prosthetic material could be a wise choice. The need for further investigation on re- movable prosthetics on zirconia im- plants should be kept in mind, too. Peri-implantitis Peri-implantitis im- plants is a serious and underesti- mated problem involving millions in titanium ÿPage D4 THE ELEVENTH ANNUAL AMERICAN ACADEMY OF IMPLANT DENTISTRY MaxiCourse®- UAE 2018 – 2019 Starts 28 March 2018 A unique opportunity towards becoming an American Board Certified Oral Implantologist* In Fulfillment of the Educational Requirement for the Examination for Associate Fellow Membership and Fellowship for the American Academy of Implant Dentistry The Faculty are as follows: Dr. Shankar Iyer, USA Director, AAID Maxi Course®UAE Diplomate AAID Clinical Assistant Professor,Rutgers School of Dental Medicine. Dr. Frank LaMar, Sn USA Fellow, American Academy of Implant Dentistry Diplomate, American Board of Oral Implantology Dr. Ninette Banday, UAE Co-Director AAID Maxicourse- Abu Dhabi, UAE Academic Associate Fellow AAID Dr. Amit Vora, USA Diplomate of the American Board of Periodontology Professor (partime) ,JFK Hospital and the Veteran Affairs (V.A.) Hospital Dr. Jaime Lozada, USA Director of the Graduate Program in Implant Dentistry Fellow, American Academy of Implant Dentistry Dr. William Locante, USA Diplomate of ABOI Fellow of American Academy of Implant Dentistry Dr. Robert Horowitz, USA Diplomate American Board of Periodontology Clinical Assistant Professor New York University Dr. Frank LaMar Jr. Diplomat American Board of Prosthodontist Dr. John Minichetti, USA Diplomat, American Board of Oral Implantology Honored Fellow, American Academy of Implant Dentistry Dr. Kim Gowey, USA Past President – AAID Diplomate ABOI Dr.Burnee Dunson, USA Fellow, American Academy of Implant Dentistry Diplomate ABOI Dr. Jason Kim, USA Diplomate of ABOI Dr. Ozair Banday, USA Prosthodontist Dr. Stuart Orton-Jones, UK Founder Member, The Pankey Association Member, Alabama Implant Study Group Dr. Robert Miller, USA Board Certified by the American Board of Oral Implantology/Implant Dentistry Honored Fellow American Academy of Implant Dentistry Dr. Philip Tardeu, France Founder and Author, Computer Guided Implantology and the Safe System. Dr. Natalie Wong, Canada Diplomate, American Board of Oral Implantology Fellow, American Academy of Implant Dentistry Dr. Irfan Kanchwala, India Implant Fellowship ( UMDNJ, USA) Diplomate , American Board of Prosthodontics Dr. Jihad Abdallah, Lebanon Diplomate American Board of Oral Implantology Fellow AAID Professor & Head of Implantology Division, Faculty of Dentistry.Beirut Arab University Dr.Bart Silvermann, USA Diplomate, American Board of Oral Implantology Oral & Maxillofacial Surgeon 2016-2017 Program Accredited by Health Authority Abu Dhabi for 228.5 CME Hours. Accredition of 2018 -2019 Program under Process Program Includes placement of upto 10 Implants with all surgical and prosthetic components, all materials for hands – on workshops and lecture handouts plus one complete surgical instrument Kit. MaxiCourse ® Advantage: 300 hours of comprehensive lectures, live surgeries, demonstration and hands-on sessions. In depth review of surgical and prosthetic protocols. Sessions stretch across 5 modules of 6 days. Each session is always inclusive of a weekend. Curriculun taught by over 18 faculty & speakers from the International Community who are amongst the most distinguished names in implantology.. Certificate of completion awarded by the American Academy of Implant Dentistry. Non commercial, non sponsored course covering a wide spectrum of implant types and system. Hands-on patient treatment under direct AAID faculty supervision. Membership for AAID awarded for 2017 – 2018         Registration : Dates: Module 1 March 28th – April 2nd 2018 Module 2 July 5th - 10 th 2018 Module 3 August 23rd – 28th 2018 Module 4 November 1st – 6 th 2018 Module 5 January 24th- 29th 2019 *AAID is the sponsoring organization of ABOI Pre-Registration is Mandatory as it is a limited Participation Program. For further information and registration details visit website: www.maxicourseasia.com or e-mail Dr. Ninette Banday, Co- Director AAID-MaxiCourse UAE at drnbanday@yahoo.com Dr. Mohammed Eid Allahham, Coordinator UAE at: m_eid_1992@hotmail.com or +971-56-7174417

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