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ARTICLE IN PRESSBJOM-5652; No. of Pages 9

British Journal of Oral and Maxillofacial Surgery xxx (2019) xxx–xxx

Available online at www.sciencedirect.com

ScienceDirect

istorical development of root analogue implants: review of published papers. Saeidi Pour a, C. Freitas Rafael b, M.L.P.D. Engler b, D. Edelhoff c, G. Klaus d,. Prandtner e, M. Berthold c, A. Liebermann c,∗

Seehofer — Praxis für Zahnmedizin-Implantologie-Kieferorthopädie, Widenmayerstrasse 7, Munich, 80538 GermanyDepartment of Dentistry, Federal University of Santa Catarina, Florianópolis, BrazilDepartment of Prosthetic Dentistry, University hospital, LMU Munich, Goethestrasse 70, Munich, 80336 GermanyAn der Sonnhalde 11b, Herbolzheim, 79336 GermanyPlattform Laboratory, Goethestrasse 47, 80336, Germany

bstract

The timetable for placing a dental implant can be crucial in the reduction of resorption of the socket after an extraction. The associationf immediate implantation with an implant that copies the anatomy of the extracted root seems to add benefits in limiting the hard and softissue changes that may occur. The purpose of this paper is to provide an overview of the historical development of all types of root analoguemplants from their beginning to the present day. To our knowledge the first individualised ones were described in 1969. Later, the use ofitanium instead of the polymers that were used to start with offered better bony integration, and showed that the selection of materials was

key factor in their success. Root analogue implants made from zirconia were also described when attempts were being made to improveesthetics in the anterior regions. The more recent introduction of digital technology such as DICOM has allowed the fabrication of thesemplants in less time, and the combination with digital diagnostic options such as cone-beam computed tomography facilitated the fabricationf some types of implants before extraction that could be inserted immediately into the alveolar socket with optimal and safe 3-dimensional
ositioning. Currently digital planning allows the clinician to design the ideal implant and abutment, which reduces the need for tissue graftingn the surgical phase and gingival conditioning in the prosthetic phase.
2019 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

ograph

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eywords: root analogue implants; CAD/CAM technology; cone beam tom

ntroduction

Please cite this article in press as: Saeidi Pour R, et al. Historical develBr J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.bjoms.2019.

ental implants are an optimal way of replacing missingeeth, as they have good long-term success rates of up to

∗ Corresponding author at: Goethestrasse 70, Munich, 80336 Germany.el.: +49 89 4400 59571; Fax: +49 89 4400 59502.

E-mail addresses: [email protected] (R. Saeidi Pour),[email protected] (C. Freitas Rafael),[email protected] (M.L.P.D. Engler),[email protected] (D. Edelhoff),[email protected] (G. Klaus), [email protected]. Prandtner), [email protected] (M. Berthold),[email protected] (A. Liebermann).

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ttps://doi.org/10.1016/j.bjoms.2019.01.021266-4356/© 2019 The British Association of Oral and Maxillofacial Surgeons. Pu

y; zirconia; titanium

0% or more.1 After a tooth has been extracted there is annevitable remodelling of the socket, which can limit the plac-ng of an implant. The continuous resorption can reach up to3% on horizontal and 11%-22% on vertical alveolar boneithin six months.2 Alterations of the dimensions of the alve-lar socket on the buccal wall are related to the resorption ofhe bundle bone, a tooth-dependent structure that is left afterhe extraction with few or no vessels for its blood supply.2–5

It has been reported that the immediate use of implantsight control these alterations to the ridge by reducing the

6

opment of root analogue implants: a review of published papers.01.021

peed of resorption of the socket. The main advantage ofmmediate implants is that the overall duration of treatment,ost, and number of surgical interventions can be reduced,6

blished by Elsevier Ltd. All rights reserved.

https://doi.org/10.1016/j.bjoms.2019.01.021


http://www.sciencedirect.com/science/journal/02664356

mailto:[email protected]









ARTICLE IN PRESSYBJOM-5652; No. of Pages 9

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ut the operator usually has to face some surgical challengesn this approach, including: difficulty in achieving primarytability and controlling the 3-dimensional position of themplant; discrepancies between the sizes of the implant andhe socket; the poor quality of bone that is often present inhe extraction socket; and the need to prepare the socketith drilling burrs that can overheat the bone. 7–11 These

hallenges are related to the characteristics of conventionalmplants, mainly the standardised sizes and shapes.

To overcome these challenges, the use of an immedi-te implant with the same design as the extracted root ishought to be highly beneficial.8 This patient-individual con-ept, known as root analogue implant, was first describedn 1969,12 and was fabricated from an autopolymerisednd heat-processed poly methylmethacrylate material. How-ver, this approach was considered unsuccessful because themplant became fibrointegrated (or encapsulated) instead ofsseointegrated, and this resulted in the abandonment of thisype of root analogue implant.8–13

The technique was reintroduced in 1992 using differentaterials to fabricate the implant, as well as various methods

f fabrication.13 The use of titanium instead of polymers gaven osseointegration rate of 88%, which highlighted the facthat selection of the material is as important a factor for theuccess of the implant as an optimal fit between the implantnd the socket.

Titanium is nowadays considered to be the material ofhoice for dental implants, but several zirconia-based implantystems are available and a root analogue implant can beabricated from zirconia.8 The choice of zirconia improveshe aesthetic result, particularly in the anterior region, whichvoids the aesthetic impairment often caused by the greyishiscolouration in the soft tissue that is caused by titaniummplants and abutments.8,14 Recently, a technique that used

titanium root and a zirconia abutment was introduced intohe dental market. Besides the possible improvements inesthetics of this design, the zirconia abutment is fused tohe titanium root by a sintering process, which eliminatesny microgap (which has been reported to be a possibleause of appreciable bone loss around the implant duringemodeling).15

As well as the beneficial shape of root analogue implants,he development of techniques such as cone-beam computedomography (CT) and computer-aided design/computer-ided manufacturing (CAD/CAM) offers the fabrication ofuch implants before, and placement immediately after,xtraction. This facilitates the whole procedure by allowingafe 3-dimensional positioning of the implant with optimalesign of the abutment, and the might reduce the need for hardnd soft tissue grafts and the number of appointments for gin-ival conditioning (that may affect the soft tissue surroundinghe implant).8,16,17

Considering that immediate implantation can show some


mportant benefits, some difficulties might be encounteredith the insertion of conventional implants. The use of root

nalogue implants associated with the described preopera-

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Maxillofacial Surgery xxx (2019) xxx–xxx

ive fabrication might turn the surgical and prosthetic phasento a simpler and a more predictable treatment in selectedases. Because of the number of types of implant and fab-ication methods that have been published, the aim of thisrticle was to provide a detailed overview of their historicalevelopment from the first ideas to the current state of affairs,ombined with a special focus on the comparison between theeImplant® System and the modern ReplicateTM System.

istorical overview of root analogue implants

historical overview of root analogue implants includingame, version, material, fabrication process, surface, num-er of parts, clinical applications, insertion technique, andossibility of immediate loading is shown in Fig. 1.

he dental polymer implant concept

he dental polymer implant was the first root polymermplant, and its description was published in 1969.12 Mate-ials for the polymer were selected because: they couldossibly be “tailored” to specific needs through the additionr removal of ingredients to change their physical character-stics; for their ease of handling and accuracy of reproduction;

icrowave or electric current emissions, as with metals, werebsent; they had a better fibrous connective tissue attachment;nd there was the possibility of microscopic evaluation.12

n autopolymerising and heat-processed polymethacrylate,lone or combined with grated cancellous freeze-dried calfone, was used to fabricate the implant, and the processas done after extraction. The tooth was cleaned, and any

urface defect was corrected with wax, then a mould wasade by investing the tooth in stone or plaster, applying a

ydrocolloid separating medium to the plaster, and packinghe polymer into the flask. The heat polymerisation pro-ess was at a temperature and time recommended for thepecific material. The surface was pretreated by airborne par-icle abrasion with corundum and sterilised with a 10-minutemmersion in zephiran chloride®. The size and shape of themplant were compared with those of the tooth, and the replicaould be installed 45 minutes after extraction. The authorsecommended splinting the implant to the adjacent teeth ormplants during healing.12 Over the years, new studies haveeported that the polymethacrylate root analogue implantecame mainly encapsulated by soft tissue (fibrointegration)nstead of osseointegrated, leading to the discontinuation ofhis technique.1,7,8,18

he root analogue titanium implants

oot analogue implants were reintroduced in 1992, this time


ade of pure titanium, and the first research was done inogs.13 The teeth were extracted, and each extracted rootas machine-copied to a titanium analogue. The machine-



R. Saeidi Pour et al. / British Journal of Oral and Maxillofacial Surgery xxx (2019) xxx–xxx 3

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opying process was done according to the techniqueescribed in 198919 and combined the spark erosion with

method of machine duplication for fabrication of therown, which eliminated the inherent errors that resultedrom waxing, investing, and casting.19 After the fabrication,he implants were cleaned manually and ultrasonically in N-utanol for 15 minutes, and then in graded series of ethanol70%-99%) for another 15 minutes, and sterilised in an auto-lave at 135 ◦C for 20 minutes. With the longer fabricationrocess, the implants were then installed two weeks after thextraction by making a ridge incision, followed by mucope-iostal flaps to expose the sockets. The intra-alveolar softissue in the healing phase had to be removed and the rootnalogue implants were put in place.13

It was possible to conclude from clinical and histologi-al findings that the titanium root analogues osseointegratedith a high degree of predictability when implanted into

xtraction sockets during an early stage of healing.13 Theuthors found an osseointegration rate of 88% and noticedhat a good fit between the implant and host bed was anmportant factor for success. For this reason a new approacho inserting the implants by widening the coronal area to


ompensate for the lost periodontium and achieve good con-ruence between the implant and the extraction socket wasefined in 1997.20

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beginning of their development until today.

he ReImplant® system

n 1997, a new model was introduced, and initially testedn monkeys. 20 The extraction was by means of buccal andalatal full thickness flaps and the root of the extracted toothas scanned extraorally with laser. The data obtained were

ransferred to computer software where a design modificationas made on the coronal part of the implant analogue, whichas slightly enlarged circumferentially to promote better

daptation and obtain a good congruence between the implantnd the extraction socket.20 The milling unit then fabricatedhe implant from a cylindrical titanium blank according tohe computer data.

The surface treatment of the root involved air-abrasionith aluminum oxide powder (500 �m) and acid etching,hile the entire part above the alveolar bone was polished.he implantation was inserted six to eight hours after extrac-

ion, and the authors reported that the volume of somemplants was too great to fit into the respective extractionocket, which led to fractures of the thin buccal alveolarall. This minimal difference in volume could be related to

he first generation of the laser-scanner and the milling unit® 20


hat were used to fabricate the ReImplant System. Thet of the implant without macroretentions might be respon-ible for the failure in the intermediate term, which was the



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esult of pressure-induced resorption.1 A case report from997 described the use of this technique to replace an upperateral incisor, and the authors highlighted the simplicity ofhe procedure, the possibility of maintaining the aestheticnterdental papillae, and the advantage of shaping the naturalesign of the root, but they also recommended further basicnd clinical research before recommending the system forse by private practitioners.16

he BioImplantTM

n 2007, the BioImplantTM was described as a new design foroot analogue implants, using zirconia as the material fromhich to fabricate the implant for advanced biocompatibility

nd improved aesthetics.21 Microretentions and macroreten-ions were added to the entire root surface to improve primarytability and therefore osseointegration. In this new design,he diameter of the implant next to the buccal cortical boneas reduced in an effort to avoid fracture of the bony wall

nd pressure-induced bone loss.The tooth was extracted, the socket curetted, and an

odoform-soaked cotton gauze was placed in the extractionocket. The root was scanned with laser, macroretentionsere designed, and a crown stump was created for later

onnection to the crown. The implant was milled from a pre-intered zirconium dioxide blank and sintered into the finaltage and size for eight hours. The surface was roughened bybrasion with airborne particles. Four days after extraction,he implant was placed into the socket by finger pressure andubsequent gentle tapping with a hammer and a mallet.21 In009, this type of implant was used to replace a molar in thepper jaw22 and a right lateral maxillary incisor.23 At twoears follow-up, all variables had successfully been met. Theast two cases using the BioImplantTM were reported in 2016o replace a first premolar and a first molar.24

irect laser metal sintered (DLMS) implants

LMS implants were first described in 200825 using theone-beam CT data and CAD/CAM technology for the directroduction of custom-made root analogue implants in aiocompatible titanium alloy.26 This technique involved aigh-power laser beam focused on a metal powder bed androgrammed to fuse microparticles according to a CAD-file,o build the desired object layer-by-layer.26,27 The implantsnd integrated abutments were produced from DLMS tech-ology (Leader Implants) from Ti-6Al-4 V alloy powder witharticles ranging between 25 and 45 �m in size.25–28 Surfacereatment was by etching with acid through the immersionf the sample in a mixture of oxalic acid (50%) and maleiccid (50%) at 80 ◦C for 45 minutes.26 This implant was fab-icated from cone-beam CT data before extraction, so by the


ime of extraction the implant could be inserted in the sockety finger pressure or tapping. Primary stability of the implantas checked by palpation and percussion. Provisional crowns

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ere cemented on the custom-made abutments.26 The radio-raphic fitting control at the one-year follow-up gave aurvival rate of 100%. However, the authors recommendedhat when an atraumatic extraction is not possible, or if theres loss of any alveolar bony wall, the use of this type of implanthould be avoided and standard implants used. Divergentoots were also a limitation.26

A new method of digital laser metal forming (DLMF) waseported in 2012 in humans. The DLMF technique allowshe fabrication of functionally-graded titanium implants withorous surfaces, which may provide better adaptation ofhe load. 28 These studies highlighted that DLMS/DLMFmplants were successful and had the main advantage of beingabricated before extraction, making immediate placement ofhe root analogue implant possible.28

AD/CAM fabricated titanium root analogue implants

new method of creating single-rooted titanium rootnalogue implants was described in 2013 that also com-ined cone-beam CT 3-dimensional acquisition of data withAD/CAM technology.29 This was described on a deaduman body, and the selected tooth was a lateral lower incisor.irst, the mandible was scanned and the data exported inICOM format. Three-dimensional surface models of the

ooth were created, and the implant was fabricated usingigh-end selective laser melting, by depositing and meltinghin layers of metal powder from a biocompatible titaniumlloy (Ti6Al4V). Optical scanning was used to check theccuracy of the manufactured titanium implant related tohe cone-beam CT 3-dimensional root surface, and goodrecision manufacturing of the implant was achieved. Nohanges were made on the surface of the root. For this rea-on, the authors reported that this implant would not haveufficient primary stability after placement. It was suggestedhat macroretentions or microretentions should be added,nd the surface treated, to give better primary stability andsseointegration.29

he ReplicateTM tooth system

n 2016 a case report described a new technique for theabrication of a root analogue implant through CAD/CAMechnology.15 A cone-beam CT and elastomeric or digitalmpressions were necessary to produce both the root and theoronal part of the implant. This implant can be fabricatedefore extraction and is composed of a titanium root and

zirconia (3Y-TZP) abutment that are fused together by aintering process that generates a one-piece hybrid implant.his procedure avoids there being a microgap between the

oot part and the abutment and reduces the bacterial coloni-ation in this sensitive area, which has been reported to cause


one and soft tissue loss.To fabricate the “ReplicateTM” tooth, impressions were

ade and a cone-beam CT taken. The data to be used to



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alculate the dimensions of the implant were sent to the man-facturer (Natural Dental Implants AG) so that an individualmplant could be fabricated. The CAD procedure consisted ofbtaining the data from the image, and the CAD process. Theone-beam CT 3-dimensional data are received in a singleICOM file format, with the data for impressions or intraoral

cans in an open STL file or CEREC format. The impressionsre then digitalised by a micro-CT device and the surfaceeconstruction of the natural shape of the root and adjacentlveolar bone contours is initiated. At this moment, the den-ists can send their prescriptions, preferences, and treatmentlan. The authors of the case report described,15 opted toesign the implant with an intentional reduction of the coro-al part (first 4 mm of the root) on the buccal side to avoidressure on the thin buccal wall of the socket and to providepace for augmentation of the bone.

The computerised prototype of the ReplicateTM toothystem is created, root anomalies and divergences are cor-ected, the insertion simulated, and the interproximal spacesdjusted. The desired shape, position, and inclination of therown are then also adjusted. The interface between the tita-ium root and the zirconia abutment is defined virtually, and

widening of the root is designed in a mesiodistal directiono make it possible to achieve good primary stability afternsertion. The components of the ReplicateTM tooth systemre then prepared for glass soldering; the zirconia abutment isused to the titanium root with biocompatible glass solder, andhe one-piece hybrid material replicate implant is generated.he margins of the abutment are polished with medium abra-ives (100 and 40 �m grain size),30 while the titanium rootortion is abraided with medical grade corundum and etchedo create micrometered roughness for optimising osseointe-ration. A micro-CT device is used to measure the dimensionf the glass solder interface, and ensure that the microgapetween the implant and the abutment is avoided. The implants inserted by gently tapping it into the socket. To protecthe replicate tooth during healing, a cover shield (a tempo-ary one-wing adhesive zirconia bridge) should be fixed tohe adjacent tooth.15 Fig. 2 A and B illustrate the process ofbtaining the ReplicateTM tooth from planning to the finalroduct.

hree-dimensional printed root analogue implantsfuture perspectives)

lthough titanium is a successful material for fabrication ofmplants it can cause hypersensitivity and corrosion becausef gradual degradation of the material.31–33Zirconia hasherefore been proposed as an alternative, as it has bet-er biocompatibility and aesthetics, and is more resistant toorrosion.33 When these characteristics were combined withhe innovations of 3-dimensional printing, it became possible


o fabricate a 3-dimensional printed zirconia root analoguemplant using digital light processing technology, which wasrst described in 2017.33

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Maxillofacial Surgery xxx (2019) xxx–xxx 5

This is an additional manufacturing technique (Rapidrototyping) in which solid 3-dimensional objects are builtsing a digital light processing projector to translate voxelata, and it is similar to the previously described method torint titanium implants27 (DLMS implants) by which spe-ific geometry is built up layer-by-layer. The images werebtained by cone-beam CT, processed, and converted to

3-dimensional surface model using the marching cubelgorithm and saved in the standardised triangulation lan-uage (STL) file format. A printable 3-dimensional implantas then reconstructed using CAD software and the fab-

ication made using the high-end digital light processing,-dimensional printing technology. The congruity of therinted zirconia implant compared with the CAD model of themplant and the optical scan of the natural tooth, was checkedy superimposition. The authors highlighted that this exper-ment was a first step to 3-dimensional printing of individualirconia implants. However, some divergence was noticed inhe apical area between the scan of the printed implant, theAD model, and the optical scan of the natural tooth.33 This

howed that digital light processing 3-dimensional printingechnology results in less accurate fabrications of implantshan the commercially available additive manufacturing tech-iques for metal such as DLMS.26,33 The authors concludedhat it is feasible to print a 3-dimensional zirconia implant.owever, possible surface modifications would influence thesseointegration, and the peri-implant biology needs furthernvestigation.33

oot analogue zirconia implant (future perspectives)

new method to fabricate root analogue zirconia implantsas described in 2016.34 In this design the surface of the

oot was modified in two ways: first, microretentions weredded to the entire root surface, and macroretentive stepsere added only in the mesiodistal root surfaces. The diam-

ter of the implant was then reduced next to the thin corticallveolar bone to avoid both fracture and pressure-inducedone loss. The implant was used to replace a first premolar.he tooth was then extracted and the socket cleaned. The rootas modified with light-cured composite material to create

post (abutment) to receive a further crown. The macrore-entions were designed, and the modified root was scannedith laser. The replica was milled by CAD/CAM technology

nd the surface treated with abrasion with airborne particlesnd pre-sintering; the zirconia implant was then sintered intohe final size over eight hours. Three days after extraction,he implant was placed in the alveolus by finger pressure andubsequent tapping with a special hammer and a mallet; pri-ary stability was confirmed by palpation and percussion.efinitive restoration was possible after four months. The

ollow-up at 18 months showed that the implant was stable,


he level of the implant marginal bone was unchanged, andomplete apical peri-implant ossification was apparent onadiographs.34



6 R. Saeidi Pour et al. / British Journal of Oral and Maxillofacial Surgery xxx (2019) xxx–xxx

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iscussion

ccording to these published papers it is evident that toothoss predominantly leads to resorption of bone and softissue.4 Immediate implantation in the post-extraction socket

ight reduce, but not avoid, these alterations to the ridge.1–8

n addition, the operation of immediate implantation withonventional implants can be difficult for the operator. Tochieve primary stability, the bone drilling will normallyeed to exceed the apex of the socket in 4-5 mm,11 whichill require a larger quantity of bone that might not be avail-

ble or might be closely related to vital structures such as thenferior alveolar nerve or the maxillary sinus.35 The availableone in a post-extraction socket is often infected, or poorlyascularised, or both.11

Controlling the three-dimensional position of the implants challenging, because it is a symmetrical object that iseing inserted into a non-symmetrical socket with variableorphology.11 The surgeon’s experience is therefore impor-

ant in the 3-dimensional positioning of the implant, whichight be placed too deep or too buccal in the socket, whichould lead to functional and aesthetic problems.8 Anotherifficulty is the incongruence between the sizes of the implantnd the extraction socket that, after placement of the implant,


ay lead to connective tissue or epithelial growth around thearts of the implant that are not in direct contact with the bonyalls. To prevent this, the use of barrier membranes or bone

ct

th implant - from the planning to the final product.

ugmentation between the implant and the socket walls isecommended.20,36 An additional limitation is the cylindricalesign of conventional implants that requires preparation ofhe socket with drilling burrs, which could overheat the bonend lead to damage that might affect osseointegration.37

The use of root analogue implants could be an alterna-ive to improve results with immediate implantation, as theatient’s individual replicate implants have the same designs the natural root, which might reduce the difficulties previ-usly cited when using conventional implants. This techniqueas described for the first time in 196912 and, over theears, several types of implant have been developed. TheeImplant® system, however, was the first one to have aodified root design.16,20This modification was important

o show that changes in volume at the root of an implantight result in better osseointegration with a better fit of the

mplant into the alveolar socket.20 Conversely, the enlarge-ent of the coronal part of the implant often led to fractures

f the buccal wall, and a study showed both excellent primarytability on the one hand, and a highly disappointing failureate of 48% at nine months follow-up on the other.38 The highailure rates led to further modifications of the surface, whichmproved the fit of the implant without generating pressuren the bony wall.


One study described the need to reduce the area that is inontact with the buccal bony wall by 0.1 - 0.3 mm, becausehis might avoid pressure-induced bone loss.39 Another fun-



R. Saeidi Pour et al. / British Journal of Oral and Maxillofacial Surgery xxx (2019) xxx–xxx 7

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ig. 3. Overview of the differences between the systems “Re Implant” and

estoration.

amental influence on the success of immediate implantsegardless of the type of implant being used is the thicknessf the buccal bone at the moment of implantation. Spray etl40 reported a study of more than 3000 implants, and eval-ated the thickness of the buccal plate during implantationnd the second stage of the operation (uncovering). Theyound a small but not significant difference between the suc-essful implants and the ones that failed (0.1 mm less bonehickness). However, a pattern of favourable changes in theesponse of buccal bone, with bone gain after the healingeriod, was found in the implants that had bony thicknesseslose to 1.8 and 2.0 mm. The authors considered 2 mm as acritical thickness” to be available around the implant andhat, when the buccal plate is less than 2 mm, more bone losshould be expected during remodelling.

This is even more important in the case of immediatelacement of implants, as no preparation of the socket iseeded. The thickness of the buccal wall is therefore the onehat was present around the original tooth before extraction.

carefully and minimally invasive extraction is thereforeecessary to preserve bone and, in the case of less than 2 mmhickness, the surface of the implant should be reduced torovide space for a bone graft.

The addition of microretentions or macroretentions waslso reported to improve the desired osseointegration.15 Thepplication of the cone-beam CT and digital technology to theesigning process allows the system to place the retentionsn areas of thicker bone. In the areas of thinner bundle ornterdental bone, pressure is avoided by the reduction of theimensions of the implant (as mentioned before) and also byllowing space for selective bony augmentation to counteractny bony resorption of these areas. An individual implant canherefore be designed, taking the remodelling processes intoonsideration.

The advanced use of digital technology such as theAD/CAM systems combined with cone-beam CT allows

abrication of a root analogue implant before tooth extraction,nd enables the placement of the individual implant immedi-


tely after extraction.15,39 This technique avoids additionalntervention. Fig. 3 summarises and compares the neces-ary treatment steps both for the modern ReplicateTM tooth

atu

ate Implant” according to fabrication method, time of placement, and final

ystem and the ReImplant® system. The treatment time ofhe ReplicateTM tooth system is clearly less than that withhe ReImplant® system (four rather than five interventionalteps). As well as the reduced treatment time, another advan-age of the ReplicateTM system is that it is a hybrid implant,omposed of a titanium root directly fused to a zirconia abut-ent without any microgap that could cause loss of bone and

igher failure rates.15 This version of a root analogue implantan be fabricated before extraction with the aid of modernone-beam CT and CAD/CAM technology, which results inn individual root analogue for the patient, designed and fab-icated in a short period of time. In the ReImplant® system,n impression of the extraction socket after extraction of theooth is needed for further fabrication of the implant, whichesults in a second intervention to insert the ReImplant®

mplant. This is harmful to the ongoing healing process andould lead to reduced success rates.16

Although titanium is widely used for manufacturing den-al implants, its dark colour can become visible in some cases,hich causes a greyish discolouration in the patient’s mucosa,articularly in the aesthetic zone.14,41,42 The zirconia abut-ent of the ReplicateTM implant offers a better aesthetic

esult without compromising the resistance of the set, as 3Y-ZP-zirconia has excellent mechanical properties (flexuraltrength >1000 MPa).43

The ReplicateTM implant also has its surface treated bycid-etching, which consists of increasing the thickness ofhe oxide layer and the surface roughness by immersinghe implant into an acid solution (hydrofluoric acid), whichrodes the surface and produces micropits. This providesomogeneous roughness, increases the active surface area,nd improves cell adhesion.15

There is increasing concern in implantology about aes-hetics, biocompatibility, and the corrosive behaviour ofaterials. Root analogue zirconia implants are becoming a

ood option because they favour aesthetics even in the pres-nce of a thin buccal wall or gingival biotype, are resistant toorrosion, are hypoallergenic, and are bioinert.44 Addition-


lly, studies done with the finite element method have shownhat zirconia implants produce higher stress values on trabec-lar bone, and so protect cortical bone. Conversely, zirconia



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mplants have a smoother surface than titanium implants,nd surface treatments are still limited for zirconia implants,articularly because of the chemical resistance of zirconiaurfaces. This might limit its osseointegration potential whent is compared with titanium. Although the difference insseointegration and bone-to-implant contact was reported asot significant, studies are focussing in new modifications ofhe surface to improve osseointegration of zirconia implantsnd its consequences in the materials’ mechanical behaviourefore use.44

Several different types of implants have been describedver the past decades, which were fabricated in differentonventional and industrial ways with diverse material com-ositions. Yet most of them remain in the past and contributedo the technique being rejected because of high failure ratesr difficulties in the fabrication process. It is important forhe dental team to have a detailed overview of root analoguemplant systems to be able to choose if one will be ableo fulfill aesthetic and functional requirements in specificases, combined with having a simplified and time-savingabrication process.

The implant procedure is technique-sensitive, and shoulde used only with adequate experience. More evidence-basedata from prospective, long-term, clinical studies, however,re necessary to give a better evaluation of the systems avail-ble.

thics approval and patients’ consent

either was required.

onflict of interest

e have no conflicts of interest.

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