3

ABUTMENTS FOR SELECTION AND USE WITH MORSE TAPER IMPLANTS

MORSE TAPERIvete Mattias Sartori*

Sérgio Rocha Bernardes**

Alexandre Molinari***

Caio Hermann****

Geninho Thomé *****

The works initiated by Brånemark enabled the replacement of lost dental elements by titanium anchorages inserted into the bone tissue, used as support for prostheses for the rehabilitation of totally edentulous 1 patients. The technique has a well documented use and the implant and prostheses success rate has been 2,3 satisfactory. Partially edentulous patients can also be rehabilitated with fixed partial prostheses supported by osseointegrated implants. The success rate for this procedure is also high, and it is considered a type of 4,5,6,7 viable clinical procedure. However, as reports of clinical follow-ups have validated the use of implants as an important treatment option, some data have shown mechanical problems, such as screw loosening and breakage, and therefore led to the search of new designs for the prostheticinterface. Among the developments, implant internal unions 8, 9 can be highlighted. The most used examples are internal hexagon and Morse taper. Morse taper is a term which has its origins in the mechanical tools industry, and it designates a fitting mechanism in which two elements develop an action resulting in an intimate contact with friction, when a “male” conical element is installed in an also conical “female” (Figure 1). This kind of fitting was invented by Stephen A. Morse and was widely used to screw a drill or mandrel of cutting machines, for example, drilling machines. The Morse taper angle is determined according to the mechanical properties of each single material, and involves a relation between the angle values and the friction between the pieces. This is a biconical fitting mechanism. In which effectiveness is significantly increased due to the preload generated by the contact surfaces, from the internal cone to the implant and from the abutment screw, resulting in the control, 10, 11 maintenance and torque stability. Mechanical tests in an implants laboratory environment with internal conical union or “Morse taper” have produced excellent prosthetical abutment stability 12,13,14,15,16,17,18,19,20,21,10,22,23,24,25,26. Analytical calculations

about different parameters of implants with Morse taper internal union show that this kind of interface, in theory, could result in great retention and 20,10,27,11,24,29,30,31,32,33 prosthesis stability. In order for the biological advantage of this kind of interface to be expressed, it is necessary that the implant installation respect some features. Morse taper implants installation must be at least 1 to 2 mm inside the bone, especially in aesthetic regions. This maneuver has the objective of optimizing and facilitating the maintenance of the tissues which surround the cervical third of the dental implant. These considerations consequently lead to small modifications in the original protocol ad modum Brånemark. In case of regions where aesthetics are not the main focus and the available bone height is not enough, the implant may be installed in the bone crest level. In these cases, if the quantity of gingival tissue is not enough, the dentist can face situations of exposure of the retention system metal, which will demand special components to enable rehabilitations which do not interfere in aesthetics. An interesting detail which has been added to the Morse taper implant is the presence of threads (Figure 1) up to the region next to the implant top. Studies show that the peri-implant bone loss or saucerization stabilizes and stops, normally, at the level of the first threads of threaded osseointegrated implants 34. Moreover, as this incorporated modification to the design has made the implant body diameter equal along its whole length, it is not necessary to use countersink drills to adapt the implant head. The preparation must only enable adaptation of the cerival portion, which is 1 mm long. This is performed with a pilot drill (same diameter as the implant) (Figure 2).As clinical aspects interfere in the rehabilitation needs, different abutment ideas have been proposed. In order for the correct indication to be made, it is necessary that the local conditions are evaluated and the choice is made exploring indications. For that reason, the objective of this paper is

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to present and clarify clinical sequences to the reader, from the prosthetical point of view, in which Neodent (Curitiba, Brazil) Morse taper® implants are used. The various options of prosthetic components for this kind of implant will be shown, drawing attention to important details in relation to their application and use, in order to facilitate and improve clinical resolutions. During the idealization of components, were considered factors which respected the choice between cemented or screwed, single or multiple prostheses, and also the features of the surrounding tissues, caring to offer concepts already used by the company and options which are easily understood.

GENERAL FEATURES

According to its mechanical project, the Morse taper® implant (Neodent, Curitiba, Brazil) has a special feature: it does not have a “prosthetic platform”. The prosthetic component contacts the implant through its interface, because there is no prosthetic seating area on the top of the implant cervical region, as shown in figure 1. This fact has enabled the idealization of prosthetic components with the same design for all implant diameters. The central hole is the same in all implant diameters in the regular family (Figure 1). WS and zygomatic implants use different abutments because they have a different internal hole (figure 3). When using implant with diameters 3.5, 3.75, 4.0, 4.3 or 5.0, the surgeon does not need to worry about identifying the implant diameter when choosing a prosthetic abutment, since they are compatible for all Morse taper implants, whatever their dimensional features, which facilitates the stock management at the dentist’s office. The Morse taper implants abutments do

not have the screw and the component in two separate pieces; they are always together, but there are two possible versions: single piece abutment or through-bolt abutment. Nevertheless, the screw in the through-bolt version is stuck to the component, there is no possibility of taking off the screw which is housed through the abutment. Figure 4 shows examples of single piece and through-bolt components, focusing on the screw/abutment relation. Neodent Morse taper interface does not have any kind

Detail of the conical “male/female” fitting

used in an implant with Morse taper

prosthetic interface. Notice that the implant

has threads up to the top of the superior part.

Available diameter and their drill profiles

FIGURE 1

FIGURE 2

3Ø. 0mm

17º 30º

Diagrammatic drawing of WS and

Zygomatic implants.

Internal area measurements.

The abutments are specific for these

two models.

Diagrammatic drawings of prosthetic components in the single piece

and through-bolt (straight and angled) families, detail of the relation

between screw and abutment. Angled and customizable abutments will

always have a through-bolt.

FIGURE 3:

FIGURE 4:

implantes WS Zigomáticos

MIN

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AR

CÓ

NIC

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MIN

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CÓ

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ULA

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PIL

AR

CM

MU

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N U

NIV

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SA

L

MU

ÑÓ

N U

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SA

L T

OR

NIL

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MU

ÑÓ

N A

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5

of anti-rotational system, which facilitates the surgical installation, so the surgeon never needs to worry about the place where the implant must be stabilized, but rather about when the primary stability will be achieved which is favorable to the long life of its fixation. From the restorer point of view, this detail enables the installation of the prosthetic component in 360 different positions, which facilitates cases of angled implants. Most of the Morse taper prosthetic components are supplied in two angled options: 17º or 30º, with three options of transmucosal part: 1.5, 2.5 and 3.5 mm. All angled components have a screw which runs through its structure, as do all customizable components, which characterizes the “through-bolt” version.

HEALING SELECTION

TYPES OF ABUTMENTS FOR MORSE TAPER IMPLANTS

When selecting healing, it is necessary to study the tridimensional prosthetic space and the mucous thickness. As the healing has the same design as the abutments in its subgingival portion, it is important that it is selected according to the height of the gingival tissue and has the same diameter as the abutment which will be used later. The available collar heights are: 0.8 to 6.5 mm and the available diameters are 3.3 and 4.5 mm. The healing shape allows the cicatrization of the gingival tissue. The concave area will offer conditions for the tissue growth and the selection of the abutment must respect the outline formed by the healing (figure 5). The heights of the straight abutments vary from 0.8 to 6.5 mm and should be chosen according to the gingival height found. As the internal shape is the same, if the healing transmucosal height chosen is too high, the gingival tissue formed will respect that design. If the abutment collar choice is not compatible (if it is lower), the abutment will apply a lot of pressure on the tissues and the patient will report pain generated by compression (Figure 6). In this case, it is recommended to choose healings of the same diameter as the abutment and the same height as the gingival tissue. The choice of the abutment height must be compatible (Figure 7). When it is chosen at the same height, the final height will be 0.9 mm lower. If the area requires more safety in relation to the subgingival space, an abutment with a lower collar can be chosen, but in this case the anesthesia should be used first, then the abutment can be installed and the torque can only be applied after tissue accommodation.

Appearance of the design of a healing chosen at the same height as

the gingival tissue and its effect on the tissue structure.

Diagrammatic simulation of the choice of an abutment with a collar height lower than the healing collar.The abutment convexity will pressure the soft tissue.healings with 3.3 and 4.5 mm heights / abutment with 3.3 and 2.5 mm heights

Diagrammatic simulation of a situation in which an abutment was

chosen with the same height as the healing. The final height difference

will be 0.9 mm.

healings with 3.3 and 4.5 mm heights / abutment with 3.3 to 4.5 mm

heights

FIGURES 5A AND B:

FIGURAS 6A AND B:

FIGURES 7A AND B:

cicatrizador de 3.3 y 4.5 mm de altura intermediario de 3.3 y 2.5 mm de altura

height difference 0.9 mmpain and edema

pain and edema

In case of rehabilitations, the first decision to be taken will be in relation to the type of prosthesis. They can be cemented or screwed. This decision must be based on the analysis of advantages and 35 disadvantages that they both represent. As Morse taper implants have the feature of screws stability, it is possible to choose cemented prostheses whenever the clinical features point to this option. Screwed prostheses should be chosen, only in cases in which the reversibility factor is important (for example, in partial prostheses or total arch), 1. FOR CEMENTED PROSTHESISThe abutment types for cemented prostheses are: universal post and universal post with a through-bolt.

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UNIVERSAL POST

They have two versions: solid and with a through-bolt. The solid universal post is a single piece component. It should be indicated in situations of well positioned implants, in which there will not be the necessity of component adaptations. The surgeon should choose the collar height, the size and diameter of the coronary portion and the implant angle. The post with a through-bolt has the options of preparing in the whole profile, which enables it to be adapted in cases of inclined implants or in relation to the cervical contour, when one wishes to customize the proximal areas. Besides the transmucosal height options shown previously, this component is also supplied in two diameter options (3.3 and 4.5 mm) and two options of the coronary part length (4 or 6 mm). The selection will be based on the interocclusal space offered and the desired cemented area. The coronary part end has the shape of chamfer and the walls are inclined to optimize the cement outflow. In the case of angled implants, the two options previously cited are also available (17 and 30).

A B

C D

Universal post accessories, available for all height and diameter options.

Intermediate transfersuniversal post

code 108.042 to 108.045

Intermediate replicascode 101.038 to 101.041

Universal post cylinderAcrylic: provisory prosthesis code118.186 to 118.189Calcinable: foundry code 118.181 to 118.184Alumina: metal-free prosthesis code 118.192 to 118.195

AcryliqueCalcinableAlumine

FIGURES 8:

E

F - A F - B

G H I

J - A J - B

L -A L - B

M -A M - B

N - A N - B

Universal post clinical sequence

A and B - height choice with the CM height measurer.

C and D - universal posts installed.

E - occlusal view of provisories.

F A and B - interocclusal registers being obtained.

G - Molding components of universal posts in position.

H - Obtained mold: position the universal post replicas on the molding

abutments.

I - obtained plaster mold.

J A and B - Registers which have been obtained inside the mouth (fig. 7)

positioned on the model, enabling mounting on articulator.

L A and B - Crowns obtained by ceramics application on alumina cylinders.

M A and B - Test of the crowns in the mouth.

N A and B - X-rays obtained at the moment of the test.

FIGURE 9:

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The universal post, as all components which are premade “manufactured abutments”, have accessories available. These are: casting components, replicas, copings for provisory crowns, calcinable copings or copings in Allumina-Zirconium (figure 8). All these accessories are compatible with the universal posts, whatever their groove height, angle, with or without a through-bolt. The casting components are made of plastic and destined for single use. They adapt slightly below the end of the component by means of “claws” which surpass the component cervical design. Therefore, especially in cases when the abutment collar chosen is more than 1 mm under the gingiva, the tissue should be sculpted with provisory material, which results in aesthetic and adaptation of the casting abutment. The casting components should be used for the technique with the closed guard tray. The coping for provisory is made of acrylic resin and the surgeon only needs the premade facets to perform the restoration; this cylinder can also be used for interocclusal register, when necessary. The calcinable cylinder is prepared by the laboratory technician for waxing and ulterior fusion in metal, preferably for ceramics application. For Alumina-Zirconium cylinders, the technician just has to apply the same ceramics which is used on reinforced metal-free copings. Metal-free copings enable the addition of reinforced restored ceramic material (aluminized porcelain, Build-up from Allceram, Dentsply), adapting the clinical case to each special situation, with no risk of breaking the feldspathic porcelain due to the lack of ceramic support. In cases in which preparations are necessary, it would be ideal to use the through-bolt post. This component enables preparation in a laboratory environment. However, if small preparations in the active part are necessary, where the prosthesis is cemented, to solve any problem of interocclusal space limitation, with no need to modify the end, these preparations could be made directly inside the mouth. In this situation, accessories cannot be used by the technician and the preparation must be made before applying the torque.In situations in which the soft tissue from the area which will be rehabilitated has different papillary heights, or in cases in which the height of gingival tissue in the vestibule face requires a collar size that does not seem to be a good option of height in relation to the interproximal bone level (because it results in infraosseous adaptation), the best option is to indicate the use of the post with a through-bolt. This component enables preparation and can offer the control of the end area in the laboratory.Initially, the surgeon will transfer the implant position to

the work model, molding the implant surrounding tissue with the help of a component for closed guard tray, which adapts directly on the Morse taper implant interface. With this model ready, the technician will install the universal post with a through-bolt and prepare it in the laboratory. Notice, on figure 4, that the inferior portion of the Universal Post with a Through-Bolt has a convex shape, different from that of the straight Universal Post. It is this feature which allows its preparation, because there is a large quantity of metal, which accepts a reduction. The prothetist will idealize all the indicated cervical and coronary preparation on the abutment. After the preparation, the technician will make a “transfer guide” in acrylic resin, adapted in the whole preparation and in the occlusal faces of the neighbor teeth. The upper part should be open, enabling the entrance of the driver to remove and install the abutment. Figure 10G shows an example of a guide ready to be used. This is an important step, because the dentist will have a reference which will enable the installation of the prepared post on the patient’s implant in the same position in which it was prepared on the model. In order to facilitate the technique, it is interesting that, when one uses this idea, the infrastructure of the definitive crown is already prepared for testing and remounting, as well as the provisory crown which will be installed, since it is not recommended to remove the abutment after the test. The idealization of the prosthetic infrastructure in the laboratory also means a technical facility for the correct adaptation of the abutment, since it is idealized on top of the prepared abutment itself. It is important to highlight that this component screw has a union

A B

C D

E F

G

I

H

Universal post with a through-bolt

clinical sequence

A - initial clinical situation.

B - post choice with selection kit.

C - post x-ray.

D - implant transfer.

E - transfer + replica set (repositioning)

F - post preparation on model.

G - post installation + positioning

guide (15 N.cm).

H - installed post.

I - finished rehabilitation.

FIGURE 10:

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area of the screw shaft with the thread, made by welding. Thus, both the dentist and the prothetist should be careful when working with it. The recommended torque is from 10 to 15 N.cm. It is enough to offer an excellent interlock and not offer any risks to the integrity of the welded union. In the cases in which it is necessary to angle the component but a cervical preparation is not necessary, the angled universal post can be chosen and installed directly inside the mouth, as shown in figure 11. In this case, the implant was installed in an inclined position, which required the angled abutment. However, the use of a selection component with a 2.5 mm collar showed a good cervical selection with the gingival tissue and the interproximal bone level. This made the cervical preparation unnecessary. Thus, the component can be used directly inside the mouth. As no preparation was made, the work sequence uses the premade components.

A B

C - A C - B

D E

Universal post with through-bolt clinical sequence

A - selection component in position (2.5 mm collar 17º angle).

B - x-ray image of selection component. Enables evaluation of collar in

relation to interproximal bone level.

C A and B - 17º angled universal post installation.

D - provisory crown installed.

E - x-ray image of installed provisory crown.

FIGURA 11:

ANATOMIC POST

An abutment in the same family as the universal post with a through bolt is being created, but with a larger quantity of metal for the preparation creation. This is a component that offers a greater titanium mass for preparation. Ideally, it should be chosen with a collar height which is compatible with the requirement of the proximal areas to the local in question, and the collar can be 1 or 2 mm under the gingiva. The exposed areas in the free faces will then be prepared in the laboratory, in the same manner described for the posts with a through-bolt.It is also possible to use this component clinically. The main feature in relation to the implant position which will lead to its choice will be in cases in which the vestibularization of the crown emergence is desired. It works as if it would extend the cervical area so that the emergence profile can be facilitated. There are also the advantages of enabling adaptations of the coronary and cervical portions and the internal profile. Thus, it can be thoroughly adapted to the indicated place (figure 12).

Anatomic post use clinical

sequence. This component

is being developed and will

soon be available in the

catalogue.

A - occlusal appearance of

installed implant.

B - selection component in position.

C - x-ray appearance of selection component in position.

E - ceramic crown installed.

F - final x-ray appearance.

FIGURE 12:

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Although the necessity of infra-osseous installation of the Morse cone implant is already well established, sometimes that does not happen. The result of a surgery in which the implant has been installed above the bone crest can be the exposure of the implant in the oral cavity. The implant top, when it is above the gingival level, prevents the installation of any of these cited abutments due to the metallic portion, which would be apparent. In this case, the indication of abutment choice would be the customizable Post 0.2. Its use requires from the surgeon the same steps described for the universal

CUSTOMIZABLE POST

MORSE TAPER ABUTMENT

A B

C D

E F

post with a through-bolt family: the implant should be molded. After obtaining the mold, a replica should be installed of the same diameter as the implant which is in place (because, in more extreme cases, the crown adaptation will involve the implant cervical portion) and sent to the laboratory. The prothetist will install the component on the model, make the preparation needed, create the provisory crowns, the definitive crowns infrastructures and the transfer guide which enables the positioning of the component in the mouth in the same position as in the model. The crowns may have their ends positioned in the cervical portion of the implant or, in cases in which the implants are apparent in the mouth, the waxing can involve up to the height marked on the replica, finishing as in a knife blade. Notice that, although this component offers a solution for complex cases, these should ideally not happen. This is the reason for which this component is not in the catalogue: so that the surgeons do not grow accustomed to indicating it and its use is not too widespread. It should be understood as a component which annuls the biological benefit of the Morse taper concept.

2. FOR SCREWED PROSTHESISThe abutments for screwed prostheses with Morse taper interface can be divided in two groups: for unitary or multiple prostheses

0.2 mm customizable post use clinical sequence.A - Morse taper implants with positioning problems.B - molding abutments installed directly on implants.C - positioned model obtained with prepared abutments and resin transfer guide.D - transfer guide positioned enabling abutment transfer.E - cemented crowns.F - x-ray appearance.

FIGURE 13

For screwed unitary rehabilitations, the surgeon will use the Morse taper Abutment® (Neodent, Curitiba, Brazil) on the dental implant, installing it directly in the mouth. It should be recommended in case of posterior unitary prosthesis in which, for any reason, a cemented prosthesis is not desired. It is not recommended for front teeth due to the abutment volume. Also because in front segments, it is recommended to use a cemented prosthesis to enable the achievement of an anatomy which is closer to natural elements which have been lost. As the Morse taper concept is reliable in relation to screw stability, there is no reason not to recommend the cemented prosthesis in an aesthetic area. However, in posterior areas there can be a low interocclusal height or a large mesiodistal distance, jeopardizing the cemented unitary prosthesis stability. Moreover, the Morse taper abutment facilitates the steps to make the prosthesis. However, this abutment does not have any angled options available. This component can be seen in figure 13. It is like the GT abutment adapted to the Morse taper implant. As it is an abutment with a wider diameter, the anti-rotational part is in the cylinder internal design. The prosthetic screw also has a wider diameter, as is therefore more resistant.

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MORSE TAPER MINI-ABUTMENT

FIGURE 14:

Diagrammatic drawing of Morse taper

Abutment

FIGURA 15:Morse taper Abutment clinical sequence.A - occlusal appearance of positioned healing.B - initial x-ray appearance.C - occlusal view showing the appearance of gingival tissue conditioned by healing.D - CM height measurer positioned, enabling evaluation of gingival tissue height.E - use of a component from the CM abutment selection kit, enabling the evaluation of gingival level, relation of height chosen with the proximal bone and implant axial position.F - x-ray appearance of 4.5 mm height component in position, notice the relation between collar and bone level.G - 4.5 mm Morse taper abutment already installed.H - application of recommended torque: 32 N.cm.I - x-ray appearance of installed 4.5 mm Morse taper Abutment.J - A - B - C - transfer technique: x-ray appearance of installed molding component, insertion of molding material and obtained mold.L - metal-ceramic crown on model.M - metal-ceramic crown - vestibular view.N - x-ray appearance after crown installation.

For multiple prostheses, the abutment option is well known: the mini conical abutment (Neodent, Curitiba, Brazil). It is available according to the collar and angle options already cited. There was a special care not to modify the abutment design, so that there was no change either in the concept which was already used in external or internal hexagon implants or in the prostheses production options.After installing the abutment, the sequence to obtain the prosthesis will be the same already used. In relation to the abutment collar height choice, it is recommended to be at gingival level in immediate load cases, and 1 to 2 mm below the gingiva in cases where there are already osseointegrated implants in aesthetic areas. Even in cases of lower total arch prostheses, it is better that the choice is made not to leave the abutments above the gingiva (figure 16). Remember that the Morse taper abutment concave area has the role to enable fibers to fill the area, and they will maintain the gingival tissue height (Figure 17).

FIGURA 16: Choice of mini conical abutment height in case of immediate load: Approximate gingival tissue and calculate the gingival level which will be obtained after suture.

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FIGURA 17:

Gingival height maintained after osseointegration period.

In order to help with the abutment selection, there is a Morse taper height measurer (Figure 18) and the prosthetic selection kit (figure 19). The kit offered by the company is made in titanium, which enables sterilizing and radiological imaging. The following features should be analyzed:A. Unitary or multiple prosthesis.B. Screwed or cemented prosthesis.C. Interocclusal prosthetic space (height and width).D. Need for angle correction or parallelism among components.E. Quantity (height) and quality of transmucosal tissue.F. Distance from the prosthesis end (cement line) to the bone crest around the implant.Feature “F” is especially relevant in cases where there is an aesthetic implication. While selecting the prosthetic abutment, an x-ray should be obtained to evaluate the relation between the prosthesis end and the bone crest, whose distance should be at least 1 mm, but values of 2 or 3 mm are preferable whenit is possible to obtain them. This measure has the objective of maintaining the bone tissue, because it respects the biological space around the implant. Figure 19 shows a clinical case in which this selection was used.

The single piece components should be tightened with a torque of 32 N.cm. The components which have a through-bolt cannot be tightened with more than 15 N.cm. In case of screwed prostheses on mini conical abutment, the torque used is 10 N.cm on the prosthetic retention screw; when the Morse taper post is used, the torque is 20 N.cm (on the prosthetic screw).

Morse taper implants offer prosthetic components options for successful rehabilitation in edentulous spaces, for all clinical realities, with no difference in relation to any other type of implant system. However, as always when introducing a new concept, it is necessary that the surgeons study and get to know the correct recommendations for each abutment. Thus, is also useful that the correct positioning of the implant is obtained, based on correct planning, so that all advantages offered by this new design can be explored and obtained.

AUXILIARY RESOURCES FOR ABUTMENT SELECTION

TORQUE APPLICATION

CONCLUSION

FIGURA 18:

Morse taper height measurer.

Enables analysis of gingival tissue

height.

1 a 1,5mm

1 a 2mm

FIGURA 20:

The position of the universal post cementing line should be at least 1.0

mm below the gingiva and 1.5 mm away from bone tissue, respecting

aesthetics and biological space around the implant.

FIGURA 19:

Morse taper prosthetic

selection kit

xCM Prosthetic Components Selection

Typ

e of

pro

sthe

sis 1. Screwed Unitary Prosthesis

A. Abutment level

Work manner

B. Implant level

Well positioned

Universalpost

Universal post with through-bolt

Inclined or requiring

prosthetic abutment

customization

Implant position Unitary Prosthesis

Implants above the gingiva or at gingival level (with lack of soft tissue) - Customizable post

(0.2 mm).

Multiple Prosthesis

Multiple ProsthesisGT Abutment Mini conical abutment

2. Cemented

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