March-April 2018 | No. 2, Vol. 8PUBLISHED IN DUBAI www.dental-tribune.me

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researchTitanium and its alloys in dental implantology

case reportRehabilitation of edentulous patients

industryDigital workfl ow: From planning to restoration

implants international magazine of oral implantology

issn 1868-3207 Vol. 18 • Issue 4/2017

4 2017

SUBSCRIBE NOWwww.me.dental-tribune.com/e-paper/Implant Restorations

with CEREC

By Dr Simon Chard, United Kingdom

Dental implants are a fantastic addi-tion to the repertoire of any restora-tive dentist and allow us to provide a tooth replacement in a way that minimises damage to remaining dentition. The restoration of dental implants requires a sound knowl-edge of restorative dentistry, pros-thodontics and periodontology.

Traditionally, this has been carried out with an analogue impression taken with an impression coping either via an open or closed tray im-pression technique. A skilled techni-cian then fabricates this restoration over a 2- to 3-week period. The time

and skill required for these restora-tions both from the clinician and technician command high fees for the patient.

This case report highlights a novel method of restoring implants utilis-ing the modern advances in digital intraoral scanning and chairside milling. It illustrates how an aesthet-ic single implant retained crown can be provided chairside without the need for analogue impressions (Figs. 1 & 2: Pre-operative condition).

Following a discussion of the options for replacement of LR6, the patient elected for an implant retained so-lution. A MegaGen AnyRidge 4 x 10

mm implant was placed utilising a surgical guide for position of the pilot hole. An immediate tempo-rary crown was fabricated using the MegaGen fuse abutment and DMG Luxatemp. A silicone index of the di-agnostic wax-up was fabricated and the temporary crown was polished and taken out of occlusion while the implant fully integrated (Fig. 3).

Following 3 months of integration, the patient attended the practice for the restoration of the implant with a definitive crown. During this period, the soft tissue had been given time to mature and a beautiful molar soft tissue profile had formed (Figs. 4 & 5).

Traditionally, capturing the detail of this soft tissue profile with analogue methods is complicated and time consuming; however, utilising a digi-tal intraoral scan (CEREC Omnicam) a “gingival mask scan” can be taken to accurately replicate this soft tissue and use it to guide the subgingival emergence profile of the restoration (Fig. 6).

Following removal of the temporary crown, a TiBase was placed into the fixture head and a scan body used as a reference point for the scanning of the implant (Figs. 7 & 8).

Following digital intraoral scanning (DIOS) of the opposing arch, working

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arch and buccal bite, a digital design was created using the biogeneric in-dividual design mode. In this design mode on the CEREC Omnicam, the software evaluates the other teeth captured in the DIOS and tries to recreate what it believes to be the

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Dental Tribune Middle East & Africa Edition | 2/2018 IMPLANT TRIBUNED2

closest match to the original missing tooth (Figs. 9–11).

This tooth design is then positioned digitally within an e.max meso block. This meso block has a predetermined hole within it that acts as the access hole for the screw-retained crown, as well as the orifice into which a TiBase will be bonded (Fig. 12).

This restoration is then milled from

the low translucency monolithic e.max CAD Block in its purple phase (taking around 18 minutes) and checked for precision of fit on the TiBase (Figs. 13 & 14).

It is tried in intraorally to assess contacts and occlusion in static and dynamic function (Figs. 15 & 16). The restoration is then stained us-ing Ivoclar e.max Crystall Glaze so as to provide an aesthetically har-

monious restoration and glazed with Glaze Spray. It is placed in an Ivoclar Vi-vadent Programat CS2 fir-ing furnace for 15 minutes to crystalise the ceramic, turning it from purple to tooth-coloured (Fig. 17).The ceramic restoration is then bonded onto the

TiBase extraorally. The fit surface of the ceramic is treated with 5 % Hy-drofluoric acid and silanated with Monobond Plus (Ivoclar Vivadent). The TiBase is sandblasted and also silanated. Finally, the ceramic and TiBase are bonded with multilink hy-brid resin cement (Ivoclar Vivadent; Figs. 18–21).

Following the bonding, the restora-tion is steam cleaned to remove any residue. The final restoration (Fig. 22) is now ready to be inserted, approxi-mately 2 hours after the patient ar-rived in the practice (Fig. 23).

The restoration is finally torqued down to 25 Ncm. Following this, occlusion is rechecked, but no ad-justment is required at this stage following the try-in adjustments.

PTFE is placed in the access cavity and the access hole filled with opa-cious composite (OMC Venus Pearl) and stained with Venus tints (Figs. 24–26).

In conclusion, as you can see in the final result (Figs. 27–29) an aesthetic, biologically designed and durable restoration has been fabricated. The patient has been delivered the final restoration in a single visit without the need for traditional analogue im-pressions.

Editorial note: A list of references is available from the publisher.

The article was originally published in CAD/CAM International Magazine 2/2017.

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Dr Simon Chard BDS(Hons) BSc(Hons) qualified with Hon-ours from King’s Col-lege London Dental Institute in 2012. He is director of member-

ship for the British Academy of Cosmetic Dentistry, was voted the Best Young Den-tist in the Dentistry Awards 2015 and is a member of the Association of Dental Implantology. Dr Chard is very passionate about providing beautiful, healthy smiles for his patients and is a big promoter of using digital technology to simplify cos-metic and implant dentistry.

Dental education is something that is a major part of his professional career and he has dedicated thousands of hours to advanced training from the best dentists around the world.

From titanium to zirconia implantsBy Sofia Karapataki, Greece

Zirconium is a metal with the atom-ic number 40. Zirconium dioxide (ZrO2) or Zirconia is a ceramic ma-terial without any metal properties. It is electrochemically inert causing no galvanising or electro current disturbance effects at an inter- and intracellular level. It is the most bioinert and biocompatible mate-rial currently available in the market, with no detected allergies or intoler-ances. The material exhibits lower surface free energy that leads to hy-drophilic reduced plaque (biofilm) accumulation, so, less inflammation is expected leading to superior soft tissue health.

Zirconia fulfils highly desirable aes-thetic results: healthy, pink and beau-tiful tissue can be created around an implant, with no tissue translucency. Its high aesthetics resembles natural tooth. Unlike titanium, it may stimu-late bone growth in the long-term with ultimate osseointegration for both bone and gum. In addition to the white colour, a low modulus of elasticity and thermal conductivity

have made zirconia implants a very attractive alternative to titanium in implant dentistry.1–4 With its inter-esting microstructural properties, zirconia is the material of choice for the “new generation” of implants. Hashim et al. (2016) made a system-atic review and evaluated the clinical success and survival rates of zirconia ceramic implants after at least one year of functioning.5 They concluded that in spite of the unavailability of sufficient long-term evidence to justify using zirconia oral implants, zirconia ceramics could potentially be the alternative to titanium for a non-metallic implant solution. This is also shown in the review made by Cionca et al. (2017), that through in vitro and in vivo studies, zirconia has managed to earn its place as a valu-able alternative to titanium.6

Mechanical and physical properties Zirconia though, is a totally different material than titanium. The thor-ough knowledge of implantology using titanium is not so easy to be transferred to zirconia, simply due

to different physical and mechanical properties of the materials. Knowl-edge of the potentials of the mate-rial is the key of success and the only chance to minimise failures. Zirconia (ZrO2) is a highly biocompatible ma-terial, but it needs to osseointegrate and withstand masticatory force without fracturing. A good product needs to be fabricated that would ful-fil all the necessary requirements in order to be successfully implanted.

ZrO2 is stable at room temperature at a monoclinic phase. Doped by yttrium oxide, when it cools down from 1,173 °C, a tetragonal phase sta-ble at room temperature (metasta-ble) is produced. This is the material used for implants. It is of major im-portance for the implant to be kept in the tetragonal phase to keep its mechanical and physical properties over time. It is well established that the stability of this phase is affected by several compositional parame-ters, including grain-size, processing conditions and quality control.

Purity or rather contamination with impurities, density and porosity

of the final product as well as pre-sintering and sintering process and time are also some of these param-eters. Environment or conditions (loading-temperature-humidity) in which the product will be used (it makes a difference whether zirconia is produced for a hip prosthesis or for dental implants) are to be kept in mind. And last but not least, han-dling of the material is of outmost importance.7,8 Lughi et al. (2010) sug-gested engineering guidelines for the use of zirconia as dental material.9

Producing zirconia implantsThere are two ways of producing zir-conia implants: through moulding and through milling of prefabricated rods. The first method produces im-plants with specific shape and spe-cific low roughness on their surface. Milling of the rods on the other hand, is done either on partially or fully sintered zirconia. The fabrication of an implant through soft machining of partially sintered ZrO2 provides the advantage of easier milling than the fully sintered ZrO2. It requires less milling time and causes less wear of the cutting tools.10, 11

In hard machining of fully sintered ZrO2, no sintering shrinkage is ex-pected and there is no need for a sin-tering oven. However, microcracks maybe introduced.10 Since diamond zirconia is known as the toughest material existing, only diamond tools are used for cutting sintered zirconia. The grinding of the fully sintered ZrO2 causes a certain degree of transformation (from tetragonal to monoclinic phase) in the surface of this material.12 When comparing

the final surface of the soft machined ZrO2 to the hard machined ZrO2, it is expected that the former will have a more consistent final state, given that it is left intact (no sandblasting or grinding) after the final sintering.13

The implants that are produced need to be roughened in order to be osse-ointegrated. Question arises what is the optimal roughness and surface that is produced after it, in order for zirconia implants to be successfully osseointegrated in any of the afore-mentioned production methods. It seems that the rougher the body, the better the odds for osseointegra-tion.14 This though should not be the goal for the head of the implant in case that it is visible in the mouth—it could favour bacteria colonisation. The best method to achieve the op-timal roughness as well as the mo-ment that this should be realised with respect to the material’s prop-erties is also not established. Finally, depending on the procedure, the roughened surface needs to be to-tally clean, free of all foreign bodies.

Ageing of titanium vs zirconiaAgeing of titanium implants is a not widely known phenomenon and starts four weeks after their produc-tion which decreases dramatically the osseointegration potential.15–18 Ageing of zirconia (Low Temperature Degradation LTD, i.e. the slow trans-formation of the metastable tetrago-nal crystals to the stable monoclinic structure in the presence of water or water vapour) on the other hand is quite well investigated.

ZrO2 is a highly biocompatible material that needs to

osseointegrate and withstand masticatory force without fracturing.

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Dental Tribune Middle East & Africa Edition | 2/2018IMPLANT TRIBUNE D3

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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.

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The Faculty are as follows:

Dr. Shankar Iyer, USA Director, AAID Maxi Course®UAEDiplomate AAIDClinical Assistant Professor,Rutgers School of Dental Medicine.

Dr. Ninette Banday, UAECo-Director AAID Maxicourse- Abu Dhabi, UAEAcademic Associate Fellow AAID

Dr. Amit Vora, USADiplomate of the American Board of PeriodontologyProfessor (partime) ,JFK Hospital and the Veteran Affairs (V.A.) Hospital

Dr. Jaime Lozada, USADirector of the Graduate Program in Implant Dentistry Fellow, American Academy of Implant Dentistry

Dr. William Locante, USADiplomate of ABOIFellow of American Academy of Implant Dentistry

Dr. Robert Horowitz, USADiplomate American Board of Periodontology

Clinical Assistant Professor New York University

Dr. Frank LaMar, Sn USAFellow, American Academy of Implant DentistryDiplomate, American Board of Oral Implantology

Dr. Frank LaMar Jr.Diplomat American Board of Prosthodontist

Dr. John Minichetti, USADiplomat, American Board of Oral ImplantologyHonored Fellow, American Academy of Implant Dentistry

Dr. Kim Gowey, USAPast President – AAID Diplomate ABOI

Dr.Burnee Dunson, USAFellow, American Academy of Implant Dentistry Diplomate ABOI

Dr. Jason Kim, USADiplomate of ABOI

Dr. Ozair Banday, USAProsthodontist

Dr. Stuart Orton-Jones, UKFounder Member, The Pankey AssociationMember, Alabama Implant Study Group

Dr. Robert Miller, USABoard Certified by the American Board of Oral Implantology/Implant DentistryHonored Fellow American Academy of Implant Dentistry

Dr. Philip Tardeu, FranceFounder and Author, Computer Guided Implantology and the Safe System.

Dr. Natalie Wong, CanadaDiplomate, American Board of Oral ImplantologyFellow, American Academy of Implant Dentistry

Dr. Irfan Kanchwala, IndiaImplant Fellowship ( UMDNJ, USA)Diplomate , American Board of Prosthodontics

Dr. Jihad Abdallah, LebanonDiplomate American Board of Oral ImplantologyFellow AAIDProfessor & Head of Implantology Division, Faculty of Dentistry.Beirut Arab University

Dr.Bart Silvermann, USADiplomate, American Board of Oral ImplantologyOral & Maxillofacial Surgeon

2016-2017 Program Accredited by Health Authority Abu Dhabi for 228.5 CME Hours. Accredition of 2018 -2019 Program under Process

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 connectionConnection 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 titanium 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.

Additionally, a study by Neumann et al. (2014) compared the fracture resistance of abutment retention screws made of titanium, poly-etheretherketone (PEEK) and 30

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-implantitisPeri-implantitis in titanium im-plants is a serious and underesti-mated problem involving millions

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Dental Tribune Middle East & Africa Edition | 2/2018 IMPLANT TRIBUNE4

of implants. The prevalence of peri-implantitis according to the review of Zitzmann and Berglund (2008) varies between 12 and 43 per cent of implant sites.26 Many aetiological factors have been implicated, bacte-rial contamination among them. In peri-implantitis, the lesion extended apical to the pocket epithelium con-tains large proportions of plasma cells and lymphocytes but also PMN cells and macrophages in high num-bers.27,28 Peri-implantitis though has hardly been reported on zirconia implants. Zirconia demonstrates a low affi nity to bacterial plaque, small amounts of infl ammatory infi ltrate and good soft tissue integration. These properties might lower the risk for peri-implant diseases.1–3 This hypothesis is strengthened by the re-sults of the study conducted by Nas-cimento et al. (2014), where cast and polished titanium were presented with the highest incidence and to-tal count of bacteria, while zirconia showed the lowest.29

Rosenberg et al. (1991) claimed dis-tinct differences between bacterial profi les of infected and overloaded titanium implants.30 The latter were characterised by the absence of mo-tile rods, spirochetes and classical periodontopathogens, along with a predominance of Gram-positive organisms, similar to what is ob-served in periodontal health. These observations were supported by Quirynen and Listgarten in 1990.31 Failures of zirconia implants due to bacteria, should be differentiated against those of technical reasons

and the microbiota should be inves-tigated. It should be kept in mind that bacterial cells have a net nega-tive charge on the cell wall, although the magnitude of this charge varies from strain to strain. Especially on the Gram-negative bacteria, LPS as a major component of their cell mem-brane increases even more the nega-tive charge.32

Titanium is also negatively charged, thus acting repulsively to bacteria. This could be one of the reasons of success of titanium implantation in

a contaminated environment. Zir-conia though has no electric charge. Depending on the roughness and the hydrophilic surface of every zirconia implant system, contami-nation may be easier to occur and this could be a reason of early fail-ure when zirconia is implanted in a contaminated environment. Studies are needed to clarify whether the lat-ter could affect the osseointegration result and what is the relative danger comparing to titanium. Local disin-fection could minimise the risk in immediate implantation using the

help of ozone and autologous plas-ma. Nutrition and food supplements could also be helpful, too.

Intolerance to titanium and genetic predisposition to infl ammation has been introduced as an additional and independent risk factor (Odds Ratio 12 and Odds Ratio 6 respec-tively) for peri-implantitis.33 The au-thors propose a direct effect of the released microparticles of titanium on the immunological mechanism of the body that could possibly ini-tiate peri-implantitis. Zirconia parti-cles on the other hand have no effect on the release of TNF-a.34 Titanium microparticles are released as a re-sult either of friction, electrochemi-cal corrosion, or the synergistic effect of both and can either be taken up by macrophages, remain in the intercel-lular space near the releasing site, or systemically migrate in organs such as liver, spleen and lung, as Olmedo et al. (2003 and 2002) found.35,36

Same group of authors made a long-term evaluation of the distribution, destination, and potential risk of both TiO2 and ZrO2 microparticles, in an animal study.37 They evaluated:

(a) the presence of particles in blood cells and liver and lung tissue, (b) Ti and Zr deposit quantitation, (c) oxidant-antioxidant balance in tissues, and (d) O2– generation in alveolar mac-rophages.

Ti and Zr particles were detected in blood mononuclear cells and in organ parenchyma. At equal doses and times post administration, Ti content in organs was consistently higher than Zr content. Ti elicited a signifi cant increase in O2– genera-tion in the lung compared to Zr. The consumption of antioxidant en-zymes was greater in the Ti than in the Zr group.

ConclusionScientifi c studies are promptly needed to fulfi l gaps like long-term clinical evaluations of all existing zirconia implant systems. Protocols used to design, manufacture and test titanium implants cannot simply apply to produce and evaluate the zirconia ones. Every step, from pro-duction to surgery and prosthetic reconstruction needs to be carefully planned, with respect to the proper-ties of the new material. Accordingly, the advantages of zirconia would be fully benefi cial and the risk of failure could be minimised.

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Dr Sofi a Karapataki Implant and Periodontal ClinicAdrianeiou 4211525 Athens, GreeceTel.: +30 210 671138-0info@skarapataki.grwww.leadingimplantcenters.com

Microparticles released by titanium on the immunological mechanism of the body

could possibly initiate peri-implantitis.