screw versus cement for implant prosthesis installation. part 2: the game changer the tips the...

Screw Versus Cement For Implant Prosthesis Installation. Part 2: The Game Changer that tips the

balance in Favour of Intra-oral Cementation.

Emil L.A. Svoboda PhD, DDS,Published to www.ReverseMargin.com

Update January 2, 2016

1

© Dr. Emil Svoboda PhD, DDS 2015

2AbstractPart 2: The Game Changer that tips the balance to Favor Intra-oral Cementation. During 100 years of intra-oral cementation, nobody seems to have published on the effect of Gingiva on the flow of cement during the intra-oral

cementation process. Understanding this process is the key to mitigating its negative effects. Dr. Svoboda has created an “in vitro model”, that sheds New Light on the dynamics of intra-oral cementation. This is a “Game Changer”.

Understanding the “Gingival Effects” changes the logic behind the approach to intra-oral cementation. This presentation refers to design features of the abutment-prosthesis complex and the dental cementation process that can make intra-oral

cementation safer. Safer cementation also helps the clinician optimize the fit of the implant-abutment junction, unlike that seen with screw-in prosthesis techniques. The herein described innovations will likely tip the balance in favor of intra-oral cementation and hopefully reduce the incidence of implant treatment failure. Failure is expensive for patients, clinicians and the entire implant industry. It can be especially damaging to the patient-dentist relationship.

Part 1: The Logic Behind the Arguments This subject has been reviewed many times over many years. Some conclusions do not follow from the evidence presented in the articles, or they

simply ignore pertinent evidence from the literature. Ignoring evidence about problems in the system makes it difficult to make informed conclusions.

The reviews are unable to show a difference in survival of implants on the bases of prosthesis insertion technique - screw or cement. It appears to be too difficult to see through the many variables contained in the studies, that are the foundations of the reviews. Let us say the failures using either system, are about 5% for 5 years and 8 % for 10years, and the implants require significant home and professional care to reduce the impact of peri-implant disease.

What is causing the implants attached to Screwed-in Prosthetics to Fail? This is an important question. Let us review some of the less visible causes of these failures. Some appear to be related to implant-abutment misfit and exacerbated by mechanical challenges created by a need for prosthesis retrievability. These problems appear to be very difficult to solve. They are discussed here.

Intra-oral cementation can optimize the fit of the implant-abutment connection. However, subgingival residual excess cement is a known risk factor for peri-implant disease. We know that it can be removed and thus reduce peri-implant disease. Can we prevent it? That could surely reduce implant failure. That is discussed in Part 2 above.

See Both Slide Presentations at www.ReverseMargin.com


http://www.reversemargin.com/

3Residual subgingival cement is a problem with intra-oral cementation of implant prosthetics!

I have already encountered a number of clinicians that feel that they are already using a system of prostheses installation that is best for them and their patients. How can this be true if current reviews show rather frightening peri-implant disease statistics and implant failure rates of about 5% for 5 years and 8% for 10 years, regardless of prosthesis installation technique. I was one of those dentists about 3 years ago.If you are screwing in your implant prosthetics, and do not want to change your technique, you already accept the above complication and failure rates and feel that is good enough. The problems inherent in this installation system are real and have been covered in detail in Part 1.If you are cementing in your implant prosthetics, and do not want to change your technique, you already accept the above complication and failure rates and feel that is good enough.

I hope that the new information I am presenting will change your mind.You can do better! Would the possibility of a 50% decrease in failure rate interest you?

Read On.


© Dr. Em

il Svoboda PhD, DDS 2015

4First the ProblemThis cemented implant crown was removed because of

chronic “Food Impaction” due to an open contact.

The x-ray is clear of visible cement. A hole was drilled into the cemented crown to access the retaining screw for removal.”

© Dr. Em


5Residual Cement is not a MythIt is a Problem!

Loose piece of cement placed

back onto crown

Undersurface of abutment with

biological debris

© Dr. Em


6Residual cement can be hard and smooth and difficult to detect and can go deep into the tissues.

red arrow shows residual acrylic cement

7Being careful is not enough!The flow of excess cement is difficult to control, locate, access, and remove when using stock

abutments and with the use of other predominant intra-oral cementation techniques.

Excess cement can go deep into the peri-implant tissues where it is difficult to see on x-rays and where it can be very hard to remove from the surfaces of the prosthesis, abutment and implant surfaces. Indeed, a bulky and/or

cantilevered prosthesis may even block access to effective instrumentation.

“Better to schedule surgery to locate and remove excess cement!


Cementation in Dental Implantology. An Evidence Based Guide. Edited by Chandur P.K. Wadhwani. Published by Springer 2015.

8Residual subgingival cement is a known risk factor for peri-implant disease and

failure of already osseointegrated dental implants!We must first acknowledge that the great majority of dentists simply do not understand enough

about the dynamics involved the process of intra-oral cementation to make the logical changes to current designs and techniques to make intra-oral cementation safer. Even worse, until the dental schools and KOL’s (Key Opinion Leaders) teach the new information presented, a whole next generation of dentists may continue to perpetuate current systems with current problems. I hope this will begin to change soon! I hope you will help me in this matter.There are some great researchers that have studied intra-oral prosthesis cementation, but no one seems to have studied the effect of abutment-prosthesis complex design and gingiva on the flow of cement during the process of intra-oral cementation. This is the essence of this presentation.


Cementation in Dental Implantology. An Evidence Based Guide. Edited by Chandur P.K. Wadhwani. Published by Springer 2015. The Influence of the cementation margin position on the amount of undetected cement. A prospective clinical study. Tomas Linkevicius et al. Clinical Oral Implants Research. Vol 24,Issue 1, 71-76, Jan 2013. Thomas G Wilson Jr. The Positive Relationship Between Excess Cement and Peri-implant Disease: A Prospective Clinical Endoscopic Study. J. Periodont 2009;1388-1392

9What if we could make intra-oral cementation safer???

© Dr. Em


Then we could achieve an optimal fit of the implant-abutment connection, make prosthesis installation easier and avoid unfavourable cantilevers made necessary by lingual screw access channels. This would have promise

to reduce dental implant failure rates by over 50%*.Would these benefits interest you and your

patients??? • Estimate derived from data of Thomas G Wilson Jr. The Positive Relationship Between Excess Cement and Peri-implant Disease: A Prospective Clinical Endoscopic Study. J. Periodont 2009;1388-1392

• See Slide 12 in Screw Versus Cement For Implant Prosthesis Installation. Part 1: The Logic Behind the Arguments. Emil L.A. Svoboda PhD, DDS, Published to www.ReverseMargin.com. Update January 2, 2016


10


1. It is a hydraulic event*2. It can be difficult to control excess cement**3. Excess cement can go deep into the subgingival spaces*,**4. Excess cement can be difficult to detect and remove** 5. Excess cement can be a longstanding risk factor for

periodontitis and peri-implant disease***6. Excess cement can be accessed and removed by endoscopic

means or after surgical access****Cementation in Dental Implantology. An Evidence Based Guide. Edited by Chandur P.K. Wadhwani. Published by Springer 2015. **The Influence of the cementation margin position on the amount of undetected cement. A prospective clinical study. Tomas Linkevicius et al. Clinical Oral Implants Research. Vol 24,Issue 1, 71-76, Jan 2013. **Thomas G Wilson Jr. The Positive Relationship Between Excess Cement and Peri-implant Disease: A Prospective Clinical Endoscopic Study. J. Periodont 2009;1388-1392

What do we understand about intra-oral cementation???

11New Information about the Flow of Cement During Intra-Oral Cementation


1. It is affected by Margin Design*2. It is affected by its relationship to Gingiva**3. The “Gingival Effects” can be mitigated by the

design of the implant-abutment-prosthesis complex**4. Cement control is enhanced by reducing cementation

pressure*** during the installation process

*The Gingival Effects can increase the problem of Excess Subgingival Cement. An “in vitro” Study. Emil L.A. Svoboda PhD, DDS, Video Published to www.ReverseMargin.com. Aug 13, 2015. **Controlling Excess Cement During The Process of Intra-oral Prosthesis Cementation: Overcoming the Gingival Effects. ELA Svoboda, OralHealth Oct 2015;52-66.***Prosthesis Installation Technique using the Reverse MarginTM Design and Technique. Emil L.A. Svoboda, Published to www.ReverseMargin.com. June 16, 2015.

12

1. Affect of a Common Margin Design

on Direction of Flow of Excess Cement


During the process of intra-oral cementation, excess cement is ejected from between the apposing margins of the retainer and prosthesis. The apposing margins can act as a nozzle that affects the direction of projection of excess cement.Most margins used today direct the cement towards the tissues.When a crown and its retainer have downward directing tapered margins, excess cement is directed downwards – towards the tissues!This is a big problem when margins are subgingival.

13Effect of Different Margin Designs on

the Direction of Cement Flow


A

ChamferMargin

ReverseMargin

TaperedMargin

B

Figure 1 A—Shows 3 aluminum rods with different margin designs. B—Shows the rods with zirconia crowns cemented into place. The arrows indicate the direction of the margins and the cement flow. Note, the Tapered and Chamfer Margin designs direct the cement downwards while the Reverse Margin directs the cement upwards.

Video 1 Demonstrates the “Margin Effects”

on the Direction of Cement Flow …

Now that you understand this, why would you ever choose to use Margin Designs that direct excess

cement towards and into the tissues again??Now you have the choice.

You can choose to redirect cement away from the tissues by using the Reverse Margin ™ Design.


15

2. Gingival Effects Discovered!


16

When Gingiva was present on the model – Excess Cement was still projected under the Gingiva – regardless of Margin Design!

Cementation of a Crown with a Subgingival Margin still resulted in Excess Cement in the Subgingival

Space – Regardless of Margin Design!

This finding was consistent with clinical observations that “Even Retraction Cord” could not stop the flow of Excess cement into the subgingival environment! Cementation in Dental Implantology. An Evidence Based Guide. Edited by Chandur P.K. Wadhwani. Published by Springer 2015.


17

This observation stimulated further study “in vitro”

Gingival Effects Studied


18

Figure 8—A Shows 3 aluminum rods with 3 different margin designs that are 1 mm below the top of the clear Tygon tubes (gingiva) The black electrical tape was placed 1 mm below the margin and is 0.125 mm thick. It fills the space between the tube and the rod. The black arrows indicate the direction of the margins. B—Depicts the zirconia crowns cemented into place. Note the huge amount of sub-margin cement, regardless of margin design.

A

ChamferMargin

ReverseMargin

TaperedMargin

B

Video 2 Shows that Gingiva can have a HUGE EFFECT on Cement Flow!

When the margins of the abutment and the prosthesis are subgingival and the outer contour of the prosthesis engages the gingiva … and thus forms a seal that traps

excess cement … this trapped cement can be driven deep into the peri-implant space where it is difficult to

locate and clean away. Can we prevent this detrimental effect of the Gingiva on

intra-oral cementation??


20

First we must understand more about the Gingival Effects on Cement Flow!

The “Gingival Effects” are comprised of at least 4 Distinct

Effects


21

These Effects are also described in: Controlling Excess Cement During The Process of Intra-oral Prosthesis Cementation: Overcoming the Gingival Effects. ELA Svoboda, OralHealth Oct 2015;52-66 and at www.ReverseMargin.com.

1. Deflection Effect2. Eddy Effect3. Plunger Effect4. Bellows Effect


1. The Deflection EffectIn the case of a subgingival margin, as the cement is extruded from the undersurface of the prosthesis, it can be deflected by adjacent gingiva. The direction of deflection is a function of the angle of the margins that are projecting the excess cement, the position of the gingiva, the rigidity of the gingiva and the forces acting to seat the crown. Most current tissue facing margins would direct the cement towards the tissues and the adjacent gingiva would also deflect the excess cement towards the peri-implant tissues. (Red Arrows)


22

Indeed, the more subgingival the margin, the more the Deflection Effect. It is this effect that usually loads the space between the gingiva and the implant-abutment-prosthesis complex with excess cement. Controlling Excess Cement During The Process of Intra-oral Prosthesis Cementation: Overcoming the Gingival Effects. ELA Svoboda, OralHealth Oct 2015;52-66:Figure 4. Also at www.ReverseMargin.com.The Gingival Effects can increase the problem of Excess Subgingival Cement. An “in vitro” Study. Emil L.A. Svoboda PhD, DDS, Video Published to www.ReverseMargin.com. Aug 13, 2015: Frame 1:42.

2. The Eddy EffectIn the case of a subgingival margin, as the cement is extruded from the undersurface of the prosthesis, it can accumulate in the subgingival space. The cement still coming out of the prosthesis collides with the cement already in the subgingival space, and if the pressure is great enough, it can cause a backflow that tends to push the excess into the tissues.


23

The more fluid the cement, the easier it can escape from the subgingival environment, and the more the resistance to the backflow (the abutment stretching the gingiva) and the lower the pressure of cementation – the less the Eddy Effect. The Eddy Effect can transition into the Plunger Effect as the cement coming out of the prosthesis becomes trapped by the Gingival as it forms a seal against the outer contour of the prosthesis.Indeed, the abutment-prosthesis design, choice of a fluid cement and cementation pressure can be used to minimize and eliminate the negative impact of this effect.


3. The Plunger EffectIn the case of a subgingival margin, as the prosthesis is being pushed into place, the exterior convex contour of the prosthesis can touch and form a seal with the gingiva. (Black arrows) This seal can trap subgingival cement. As the prosthesis continues to be pushed into place and more cement is exiting the prosthesis … the pressure increases.The trapped cement is then plunged into the subgingival environment (Red arrow) … until the back pressure allows some of the excess cement to again escape from between the gingiva and the undersurface of the crown.

24

This Effect can be huge and can easily squirt cement into places that are difficult to access and clean effectively. The Plunger Effect appears to be a major contributor to the Problem of Residual Excess Cement! Overcoming the Gingival Effects by Prosthesis Design. An “in vitro” Study. Emil L.A. Svoboda PhD, DDS, Video Published to www.ReverseMargin.com. Aug 17, 2015. Frame 2:10.


**Overcoming the Gingival Effects by Prosthesis Design. An “in vitro” Study. Emil L.A. Svoboda PhD, DDS, Video Published to www.ReverseMargin.com. Aug 17, 2015. Frame 1:59 – observe cement being sucked down and the air front ahead of the cement filling the space.© Dr. Emil Svoboda PhD, DDS 2015

4. The Bellows EffectIn the case of a subgingival margin,

as the prosthesis is being pushed into place, the wider exterior contour of the prosthesis can push the gingiva in a lateral direction*. (Black arrow) As the gingiva moves laterally it can create a space and a negative pressure that draws excess cement into the tissue spaces – much like a Bellows draws air “in” when it is filled. The flow of cement can also contribute to this effect by pushing the gingiva laterally as it flows down between the gingiva and the implant-abutment-prosthesis complex.**

25

This Effect can be huge and can easily draw cement into places that are difficult to access and clean effectively.

*Controlling Excess Cement During The Process of Intra-oral Prosthesis Cementation: Overcoming the Gingival Effects. ELA Svoboda, OralHealth Oct 2015;52-66 and at www.ReverseMargin.com. Figure 6.



3. Overcoming the “Gingival Effects” by Design


26

NarrowCrown

HybridCrown

WideCrown

A B

Figure 9—A Shows 3 aluminum rods with Reverse Margins that terminate 1 mm below the top of the clear Tygon tubes (gingiva). The black electrical tape was placed at the margin and is 0.125 mm thick. It fills the space between the tube and the rod. There are 3 crown designs, wide, narrow and hybrid. The narrow is smaller in diameter than the tube, and the hybrid has a narrow part sub-gingival tapering to a wider profile 1/2 mm above the tube. B—Depicts the crowns cemented into place. Note the huge amount of sub-margin cement under the wide crown, while the narrow and hybrid crowns did not have any cement that breached the black tape border.

Video 3 shows that the Huge Negative Impact of the Gingival Effects on Cement Flow can be

Changed by Design!

Why would you ever choose to use Abutment-Prosthesis Designs that trap excess cement and force it into the tissues??

You can now choose to allow excess cement to escape from the subgingival space and block it from going past the abutment

margin. Use the design features of the Cement Control System™ to make your intra-oral cementation safer.


28

Design Features are Patent Pending and TM above is also pending.Go to www.ReverseMargin.com to find out how.


In Order to Take Advantage of the Design Features Necessary to

Control Excess Cement …29

*The Evolution from Stock to Custom Abutments Allows for a Better Prosthesis Design that can Control the Gingival Effects and thus the flow of Excess Cement. Emil L. A. Svoboda PhD, DDS, Published to www.ReverseMargin.com. September 4, 2015.


… it is necessary to use “well designed custom abutments and well designed custom prosthetics”.*In a recent review of the subject, a number of authors are recommending the use of customized site specific abutments for intra-oral cementation of implant prosthetics.**

**Cementation in Dental Implantology. An Evidence Based Guide. Edited by Chandur P.K. Wadhwani. Published by Springer 2015.

Overcoming the Gingival Effects by DesignA) Use a “Well Designed” Custom Abutment to Control:

1. Emergence profile – to support shape of the base of the prosthesis (it is like the base of the prosthesis)

2. Margin height – to control the margin position (Supra-, Equi-, Sub- gingival)3. Margin design – to avoid tissue facing margins4. Margin Rim – use a small horizontal rim to stretch the gingiva to form a barrier against the

movement of cement into the tissues, to create a space above the rim o allow excess cement to flow out of the tissue space and make it easier to clean away.

5. Material – Titanium, hybrid Titanium/Zirconia - for biocompatibility and aestheticsB) Use a “Well Designed” Custom Prosthesis to Control:

6. Emergence profile – that works with the well designed custom abutment to allow excess cement to move out of the tissue spaces during the process of intra-oral cementation

7. Margin Design – to compliment the abutment margin and to direct excess cement out of the tissue space

8. Cement Space – to allow for passive fit of prosthesis onto abutments(s). ). This optimizes the implant-abutment fit. The space between the abutment and prosthesis is filled with cement.

9. Material Composition – to meet aesthetic needs of the patient

30

The Evolution from Stock to Custom Abutments Allows for a Better Prosthesis Design that can Control the Gingival Effects and thus the flow of Excess Cement. Emil L. A. Svoboda PhD, DDS, Published to www.ReverseMargin.com. September 4, 2015. Cement Control Features of the Abutment and Prosthesis are Patent Pending. © Dr. Emil Svoboda PhD, DDS 2015

*Based on - Overcoming the Gingival Effects by Prosthesis Design. An “In Vitro” Study. Emil L.A. Svoboda PhD, DDS, Video Published to www.ReverseMargin.com, Aug 17, 2015.Cement Control Features are Patent Pending.

A) Overcoming the Gingival Effects by Abutment Design

Use a “Well Designed” Custom Abutment* to Control: 1. Emergence profile – to support shape of the base of the

prosthesis (it is the base of the prosthesis) and stretch gingiva to form a barrier against excess cement penetration

2. Margin height – to control the margin position (Supra-, Equi-, Sub- gingival) around the entire abutment

3. Margin design – to avoid tissue facing margins4. Margin Rim – use a small horizontal rim to stretch the gingiva

to form a barrier against the movement of cement into the tissues, and to create a space above the rim o allow excess cement to flow out of the tissue space (0.1 – 0.25 mm)

5. Material – Titanium, hybrid Titanium/Zirconia - for biocompatibility and aesthetics


31

1.

2.

3.

4.

“Well Designed” Custom Abutment1. Emergence profile a) It is important that the abutment takes on the shape of the base of the crown so that the abutment can stretch the gingiva and form a barrier against cement penetration during the process of intra-oral cementation. The shape does not have to be so convex as shown, as long as the occlusal aspect of the abutment stretches the gingiva sufficiently at its rim.

b) Its shape should also allow for easy instrumentation of the implant abutment interphase easier removal of excess cement. Some concave profiles may make it more difficult to detect and clean away excess cement.

c) It should be at least as wide or slightly wider than the intended prosthesis, to prevent the “Gingival Effects”. Its shape works together with the prosthesis shape to facilitate the escape of excess cement.


32

“Well Designed” Custom Abutment2. Margin Heighta) It is important that the Margin Height is controlled around the entire perimeter of the abutment. This can only be accomplished consistently with a well designed site specific custom abutment.

b) It should only go subgingival if and where absolutely necessary, and go subgingival to a depth that is simple to access for cleaning away excess cement.

c) Changes in its subgingival position will affect changes in Prosthesis Emergence Profile Design, in order to prevent the “Gingival Effects”.

d) Changes in materials may be necessary to get desired esthetics. It may be desirable to use a hybrid titanium base with zirconium body. This can usually control the grey coloration of the gingiva caused by a solid titanium abutment in the esthetic zone.


33

“Well Designed” Custom Abutment3. Margin Design*a) It is important to use a Margin Design that redirects cement away from and out of the tissue spaces. Use the Reverse Margin™ Design.

b) It should only go subgingival if and where absolutely necessary, and go subgingival to a depth that is simple to access and clean away excess cement.

c) The depth of this margin design can often be used increase the surface area necessary to retain the short crown or bridge.

d) Changes in its subgingival position will affect changes in prosthesis Emergence Profile Design, in order to prevent the “Gingival Effects”.


34

Based on *Effects of Margin Design on the Direction of Flow of Excess Cement “in vitro”. Emil L.A. Svoboda PhD, DDS, Video Published to www.ReverseMargin.com. Aug 13, 2015. Reverse Margin™ Design is Patent Pending.


a) A margin rim of about 0.1 to 0.25 mm is useful for milling purposes to help define the margin height

b) It is also used to stretch the gingiva, and thus to form a barrier against the movement of cement into the tissues.

c) It creates small a space above the rim that keeps the gingiva away from the base of the crown and thus facilitates the flow of excess cement out of the tissue space.

d) The rim makes it easier to feel the margin with an instrument, put a downwards pressure on the instrument and clean away the excess cement.

e) I am sure that one could get a similar effect without the rim by indenting the crown or retainer to lessen its ability to for a seal with the gingiva and thus trap cement. (see under prosthesis design below)

f) This part of the design may vary according to the clinicians’ preference, given they understand and are still able to overcome the Gingival Effects effectively.


35“Well Designed” Custom Abutment4. Margin Rim

a) The custom abutment may be made of various materials that are now available or may be made available in the future. It is the design features that control the flow of cement.

b) Titanium or titanium alloy may be a good choice for biocompatibility, durability and ease of milling into precision shapes.

c) Hybrid custom abutments made up of a Titanium precision milled base with a cemented on Zirconia body may be used to meet the high esthetic demands of the patient. This is meant to eliminate the “grey show through” caused by titanium under thin gingiva and also make the abutment-prosthesis margin less visible in case of gingival recession.


36“Well Designed” Custom Abutment5. Material

“Well Designed” Custom Abutments …

… take the shape of the prosthesis they will retain and have a number of features that can control excess cement during the intra-oral cementation process. These features include a shape that stretches the gingiva, a margin design that redirects cement out of the tissues.


37



“Well Designed” Custom Abutments …

… can be made of different materials such as this hybrid custom abutment with a titanium base with an attached zirconia top. This custom abutment can control cement and meet the aesthetic needs of the patient.


38



Well Designed Custom Abutments Stretch the Gingiva

Stretching the peri-implant gingiva creates a tighter seal that can further resist excess cement injection.

The Reverse Margin Design makes the custom abutment even better, by changing the direction of the excess cement ejection away from the soft tissue.


39

Note the blanching of the tissues – yellow arrows

Look at Custom Abutments from a premium abutment company

a) These are designed with limited control from dentists

b) Margins are positioned subgingival, even where this is not necessary for aesthetics

c) They have tissue facing margins d) They are much narrower than the

emergence profile crowns that will be cemented onto them (cause Gingival Effects)


40

These Abutments have Poor Cement Control Features!

These custom abutments are Poor Choice for Cement Control!

Not much better than a Stock Abutment below, available at “no cost” from another implant company.

During cementation, neither system will control projection of cement into the peri-implant space, or prevent the “Gingival Effects”


41

The Evolution from Stock to Custom Abutments Allows for a Better Prosthesis Design that can Control the Gingival Effects and thus the flow of Excess Cement. Emil L. A. Svoboda PhD, DDS, Published to www.ReverseMargin.com. September 4, 2015.

Where is the value in these custom abutments ????

What is the true cost of poor cement control?

Poor Cement Control

Many implants today still have almost straight walled standard abutments that are designed for

intra-oral preparation and cementation

“It would be difficult to avoid subgingival cement injection using these stock abutments

with or without intra-oral modification!”


42

Figure from “Dental Implant Prosthetics, Carl E. Misch, Elseier Mosby, 2005, Pg 445

Abutment Types and Intra-oral CementationSimpleStock

Pre-shapedStock

Milled UCLA Base With

Cast Retainer

Well Designed Milled

Custom Abutment

Milled Base Yes Yes Yes Yes

Distorted by CastingProcesses

No No *Yes No

Margin type Downwards Downwards/Sideways

**Controlled **Controlled

Prevents Gingival Effects by Design

No No **Yes **Yes

Optimized Implant-Abutment Connection

Yes Yes *No **Yes


43

*The UCLA base is distorted by high temperatures used during the casting process and the removal of investment material from around the milled base of the abutment. This compromises its precision fit.**The Reverse Margin Design and Cement Control Design are Patent Pending … available through licensed Labs . Core3D Centres are licensed in Canada and the USA. Info at www.ReverseMargin.com


Use only “Well Designed Custom Abutments”


44

a) They begin with an optimized implant-abutment interface … specific for the implant brand being used.

b) They are then milled with site specific features that form part of an effective Cement Control System (TM Pending).

c) The Effectiveness of the “Cement Control Features” are Enhanced by the “Prosthesis Design and Installation Technique” using super low cementation pressures.

“An once of prevention is worth a pound of cure” Ben Franklin.

They work best with a “Well Designed Custom Prosthesis”

B) Overcoming the Gingival Effects by Prosthesis Design


45

Use a “Well Designed” Custom Prosthesis* to Control:1. Emergence profile – that works with the well designed custom abutment to

allow excess cement to move out of the tissue spaces during the process of intra-oral cementation

2. Margin Design – to compliment the abutment margin and to direct excess cement out of the tissue space

3. Cement Space – to allow for passive fit of prosthesis onto abutments(s). This optimizes the implant-abutment fit. Space between the abutment and prosthesis is filled with cement.

4. Material Composition – to meet aesthetic needs of the patient5. Cements – This technique is not cement specific. There are many good

cements on the market. The cement I use is Rely-X Ultimate. It has many characteristics that I like and I have learned to work with it. 1

.

4.

3.

2.

Based on *Overcoming the Gingival Effects by Prosthesis Design. An “In Vitro” Study. Emil L.A. Svoboda PhD, DDS, Video Published to www.ReverseMargin.com, August 17, 2015. The Cement Control Features of the Prosthesis are Patent Pending and part of a Cement Control System - Trade Mark Pending.

“Well Designed” Custom Prosthesis

1. Emergence profilea) The prosthesis profile, as it emerges from the well designed custom abutment,

must both avoid the “Gingival Effects” by not forming a tight seal with the surrounding gingiva and also allow excess cement to follow a trajectory up and out of the subgingival tissue space. This profile should continue until about 0.25 mm above the height of the gingiva to help facilate the movement of cement. (shown by red arrow)

b) The shape of this subgingival portion of the prosthesis will thus vary, but can often be perpendicular to the long axis of the abutment until it emerges above the height of the gingiva. Then the shape of the crown can morph to take on the shape of the tooth it is replacing.

c) There are times when the subgingival portion of the prosthesis can be concave to accomplish a) above.

d) The well designed custom abutment should form a seal with the gingiva to prevent the flow of cement past its margin.

a) Be careful that there is no ledge at the prosthesis-abutment interphase that redirects the cement in an unfavourable direction.


46


2. Margin Design a) The margin design should compliment the to compliment the

abutment margin and to direct excess cement out of the tissue space. It is the Reverse Margin™ Design (shown by red arrow).

b) The prosthesis margin touches the abutment margin at the tissue rim of the margin in such a way that forms a nozzle that directs cement out of the tissues and then pinches off the cement to give a minimal cement line.

c) It is important that the margin of the prosthesis does not touch the abutment or the base of the margin. This will give the desired passive fit between the prosthesis and abutment.

d) Be careful that there is no ledge at the prosthesis-abutment interphase that redirects the cement in an unfavourable direction.


47


3. Cement Spacea) The cement space (between the black and yellow line designated by

the red arrow) should be adequate to prevent the prosthesis from touching the abutment, except at the rim of the margin as designated by the purple arrow. This ensures the desired “passive fit” between the prosthesis and the abutment.

b) The cement space should be about 40 to 120 microns to ensure passive fit of the prosthesis on the abutment.

c) Digital cement space parameters are easy to keep consistent once determined according to the desires of the clinician.

d) Smaller cement spaces will probably require intra-oral adjustment to ensure passive fit of components prior to cementation.

e) Be careful that there is no ledge at the prosthesis-abutment interphase that redirects the cement in an unfavourable direction.


48

“Well Designed” Custom Prosthesis4. Material Composition

a) There are many great new and old materials to use for prosthetics on natural teeth and dental implants. They each have their advantages and disadvantages. The concepts discussed in this presentation are not material specific.

b) Most of my work involves the use of zirconia, followed by variations of Emax because it is esthetic and it can be milled to high precision by CAD/CAM techniques. Almost all of my impressions are intra-oral digital scans. This technology is very accurate and results in much less chair side adjustment and stress.

c) I avoid porcelain whenever possible in the posterior and use it for better esthetics on Emax in the anterior. I welcome the introduction of more translucent zirconia.

d) Porcelain fractures in the posterior have been a significant irritation to me and I find that few people are that critical of esthetics in the posterior. They have tolerated gold and amalgam in the posterior for years.

e) Critical porcelain fractures involving contacts and visible cusps are remakes. They are easy to remove by creating a screw access holes. When implants are off angle, the multiunit prosthesis may need to be sectioned to be removed. Any bridge that could be removed by the screw-in technique can also be removed by drilling an access to the screw access holes and unscrewing it.

f) A new impression may be desirable to compensate for tissue shrinkage or to create refinements in the remake.


49

“Well Designed” Custom Prosthesis4. Cement

a) There are many great cements to use for prosthetics on natural teeth and dental implants. New cements are also being developed. The designs used in this document are not cement specific. Cement and excess cement is in red.

b) The cement should support the prosthesis material and retain it in place. In addition it is nice if it did not dissolve or expand.

c) Cement should also fill the entire space between the prosthesis and the retainer and exclude bacteria and not be too irritating to the adjacent tissues.

d) It is nice if they also have great handling characteristics, such as good fluidity and be dual cure. This reduces the need for heavy installation pressures and gives plenty of time to complete the installation before beginning the set of cement with a curing light.

e) The cement I am presently using is Rely-X Ultimate. It has all of the above characteristic and has an impressive compressive strength of 262 MPa.

f) You may have your own favourite cement. You may wish to use it. Understanding the essence of the Cement Control System™ will help you make good choices. I look forward to your feedback.

g) At this time I smear a light coat of Vasaline on peri-implant tissues and adjacent teeth, and my assistant puts it on the outside of the prosthesis. We use small disposable micro-brushes for this purpose. This separator plus a short 4 second preliminary cure time allows for easy removal of excess cement. The small horizontal rim on the abutment gives a defined guide for effective instrumentation to remove excess cement.


50

Prosthesis Installation Technique using the Reverse MarginTM Design and Technique. Emil L.A. Svoboda, Published to www.ReverseMargin.com. June 16, 2015.


The main feature of the prosthesis and its connections to pontics or other retainers is that it should not cause the “Gingival Effects” by blocking the flow of excess cement out from between the prosthesis and the gingiva during the process of intra-oral cementation.Both the Well Designed Custom Abutment and the Well Designed Custom Prosthesis must work together to allow for the optimal control of cement.Together with the “Super Low Pressure Intra-oral Cementation Technique”, the location of subgingival cement can be controlled for easier access and instrumentation and thus its complete removal.


51Video 3 demonstrates how the huge negative impact of the Gingival Effects

on Cement Flow can mitigated by Prosthesis Design

and Complimentary Abutment Design

4) Reducing Cementation PressureDentists use Huge Insertion Pressure to cement crowns and bridges into the

mouth. This behavior is evolved from use of older cements with poor compression, retentive, solubility and handling properties.

Hard Biting 600 N (sometimes used to help seat the prosthesis)

Finger Pressure 40 N * (average seating pressure)

Low Pressure 2.5 N **Super Low Pressure 0.125 N and less ***


52

* Effects of finger pressure applied by dentists during cementation of all-ceramic crowns. M.Zortuk M. et al, Eur J Dent 2010, Oct; 4(4):383-388.

**Low force cementation. Wilson PR. J Dent. 1996 Jul;24 (4):269-73.*** Super Low Cementation Forces. Emil L.A. Svoboda PhD, DDS, Video Published to www.ReverseMargin.com,

July 13, 2015.

http://www.ncbi.nlm.nih.gov/pubmed/?term=Wilson%20PR%5BAuthor%5D&cauthor=true&cauthor_uid=8783532

http://www.ncbi.nlm.nih.gov/pubmed/?term=Wilson%20PR%5BAuthor%5D&cauthor=true&cauthor_uid=8783532

http://www.ncbi.nlm.nih.gov/pubmed/8783532

How is it possible … to reduce cementation pressure by so much??

With the Cement Control System™ and a modern dual cure fluid acrylic based cement, it is simply not necessary to push hard to overcome tight contacts and resistance from gingiva … and do all of this under the added pressure of time to avoid or overcome premature setting of cement.Everything has already been tried in and confirmed .. Fit is good, Contacts are good, Occlusion is good …. Clean and dry, Lubricate … and then gently tap the prosthesis into place … light cure for 4 seconds per side and start cleaning away excess cement ... It is really so easy!

Much better control over the whole cementation process!


53

Super Low Cementation Forces. Emil L.A. Svoboda, Video Published to www.ReverseMargin.com, July 13, 2015. Prosthesis Installation Technique using the Reverse MarginTM Design and Technique. Emil L.A. Svoboda, Published

to www.ReverseMargin.com. June 16, 2015.


The Cement Control System™ includes

Super Low Installation Pressure


55

© Dr. Em


Teflon is easy to place and remove, and it blocks cement from entering, setting and

blocking the screw access channel!56

The Clinician first recommending this useful Teflon technique is unknown to me.

Cut small strips, roll and sterilize

© Dr. Em


Received Prosthesis - Sterilzed & Bagged. Nice and Clean!

58

Can you sterilized pre-assembled prosthetic units? Hard to do without degrading the cement! Are they sterile??

Install Custom Abutment, Fit OK?, Torque, Teflon, Lubricate, Cement, Remove Excess,

Maintain … Great Control of Excess Cement!


59

Intra-oral Cementation using Well Designed Abutments and Prosthesis


60

Intra-oral Cementation using Well Designed Abutment and

Prosthesis


61

Cement Flows Up & Out and is easy to find & remove because it sticks to itself!


62



Cement Flows Up & Out and is easy to find & remove because it sticks to itself!


63



Alternate Means of Cement Control1) Venting the Prosthesis (Reducing Cement Pressure)This is based on an old technique developed to help seat a prostheses onto teeth, to minimize film thickness of the cement and to reduce the amount of cement injected into the subgingival environment. There is extra expense to create and close the vents after the prosthesis was seated. How much venting do you need, to avoid both overfilling or underfilling the prosthesis?

Underfilling leads to voids and possible breading spots for pathogens and overfilling leads to excess cement. This is a problem.

Small volumes of excess cement may be difficult to find and clean away effectively.

© Dr. Em


64

Cementing pressure can be reduced significantly by using a fluid cement with good handling attributes and “Super Low Installation Pressure” as part of the Cement Control System™ herein described.

Effect of implant abutment modification on the extrusion of excess cement at the crown-abutment margin for cement-retained implant restorations. C. Wadhwani et al. The International journal of oral & maxillofacial implants 11/2011; 26(6):1241-6. Cementing an Implant Crown: A Novel Measurement System Using Computational Fluid Dynamic Approach. C Wadhwani, S Goodwin, K Chung. Clinical Implant Dentistry and Related Research, 2014.

http://www.researchgate.net/publication/51876507_Effect_of_implant_abutment_modification_on_the_extrusion_of_excess_cement_at_the_crown-abutment_margin_for_cement-retained_implant_restorations

http://www.researchgate.net/publication/51876507_Effect_of_implant_abutment_modification_on_the_extrusion_of_excess_cement_at_the_crown-abutment_margin_for_cement-retained_implant_restorations

http://www.researchgate.net/researcher/33683104_Chandur_Wadhwani

http://www.researchgate.net/researcher/33683104_Chandur_Wadhwani

Alternate Means of Cement Control2) Cement Volume Reduction How do you estimate exactly how much cement is needed to fill all the space between

the prosthesis and the retainer? Making a model to express excess cement, but not too much! This is only a crude device for reducing cement volume.

In my research, I quickly learned that even a slight tilting of the prosthesis during the cementation process tended to cause the cement to extrude preferentially from one side of the prosthesis or the other. So application of minimal cement can lead to both voids and excess cement. How do you control this? Both overfill and under fill around the same prosthesis? This would be difficult to manage at best.


65

Technique for controlling the cement for an implant crown. C Wadhwani, A Pineyro, Journal of Prosthetic Dentistry:102, no. 1 (2009): 57-58.This technique looks good on the surface but suffers the same problems as venting, except that it may be less labour intensive to make an abutment index to squeeze out excess cement than it is to create and fill vents. Underfill leaves voids for pathogens to inhabit and slight over filling may leave just a little excess cement that is difficult to detect and clean away. “Just a little” is huge at the bacterial level of size!

The alternate means of cement control, try to reduce cement volume and/or pressure, and this leads to the problems of under fill and/or overfill at the margins of the prosthesis. As well these systems completely ignore the effect of gingival on the flow of cement.


66

The Cement Control System™ described in this presentation, is sensitive to the presence of gingiva, and uses design and technique to control the location of the excess cement. We want to overfill the prosthesis because it is easier to confirm that there are no cement voids to harbor periodontal pathogens. The gross overfill is easier to locate and clean away! Cement sticks to itself and can be removed in chunks. You have seen the examples.

Discussion:This presentation gives us a new margin design that redirects cement away from the tissues, and defines the features of “well designed custom abutments and prostheses”. These features tend to block the ingress of cement into the peri-implant tissues and facilitate the egress of cement from the tissues. These features control the location of residual excess cement and thus facilitate its instrumentation and removal. Prior to the process of intra-oral cementation, the abutments are individually installed to optimize their fit, without regard to prosthesis misfits or prosthesis contact with adjacent teeth. The fit of the prosthesis onto the abutment(s) is then confirmed passive, adjusted as necessary, lubricated and cemented intra-orally with super low forces. The excess cement can now be located and cleaned away. This entire process is part of the Cement Control System™ that is designed to eliminate residual excess cement and its inherent problems. If one can extrapolate from the work of *Wilson, this could result in a 60% reduction in implant failures! Such a reduction in failures and peri-implant disease would surely make intra-oral cementation the safer installation technique**.*Thomas G Wilson Jr. The Positive Relationship Between Excess Cement and Peri-implant Disease: A Prospective Clinical Endoscopic Study. J. Periodont 2009;1388-1392. See discussion of Wilson’s results in Screw versus Cement for Implant Prosthesis Installation: Part 1. See next slide.

© Dr. Em


67

**Prosthesis Installation Technique using the Reverse MarginTM Design and Technique. Emil L.A. Svoboda, Published to www.ReverseMargin.com. June 16, 2015.


Conclusions:


68From Part 1 – You should understand that it is not possible to use the “screw-in prosthesis technique” with multiple unit prostheses, without causing implant-abutment misfits and detrimental cantilevers for the purpose of screw access. It is difficult to correct existing problems with this system of installation or further reduce the failure rate resulting from these problems.

From Part 2 – You should understand how to cement your prosthesis into the intra-oral environment safely, by controlling excess cement and thus prevent problems attributed to residual excess cement. You can also reduce or prevent the failures attributed to the misfits and technique driven cantilevers created by the screw-in prosthesis technique. This is great news, as failures are expensive for patients and clinicians and the whole implant industry.I hope this presentation will encourage you to embrace and implement this technique into your

office routine. It does not get better if you don’t make it better!

Screw or Cement??


69

The Cement Control System™ makes

Intra-oral Cementation BETTER

because it 1) Controls Excess Cement

2) Optimizes the Implant-Abutment Connection3) Avoids Cantilevers Created for Screw Access

Next Step is to make this Cement Control System™ available to your patients.

Its Easy. Find Out How at www.ReverseMargin.com

We Partnered with a Large Precision Milling Group to Create Custom

Components for the“Cement Control System™”


70

Workflow – Your Lab or Diamond Dental Studio receives your models and/or digital impressions and sends files to Core 3 D Centres for Design and Precision Milling. Your Lab or Diamond Dental Studio then assembles and further customizes work for delivery to Your Office and your Patients. Contact us at www.ReverseMargin.com

North America

Making It Available


Authors notes


71Over the last 3 years, I have made many refinements to the Cement Control SystemTM as herein described. I expect refinements to continue and indeed, I welcome all of you to contribute to them. My website allows for abundant opportunity to communicate with me. Please be specific with your comments, as I would love to address your specific concerns. Also tell me what you like about this system, as I depend on you to help validate the effects of my work on yours. A little encouragement is also much appreciated. Together we can make our treatment much better for our patients. There may be some details of this presentation, which you may not agree with. For example, you may choose to use a different cement. That is OK. You may already be great at using your favorite one. Cements are evolving all the time and tomorrow there may even be a better one. The system proposed is not cement specific and it is not even material specific. However certain physical and esthetic properties may influence your choice of cement or materials. You may you find some instances where you cannot use all aspects of my system and thus need to modify it to suit a particular situation. Again, that is quite OK. As clinicians, we are rendering treatment that is specific to the needs of our patients. We often have to modify systems to get a great result. Understanding the “Gingival Effects” on cement flow, will already allow you to make better decisions about safe and effective modifications to the proposed system.

USE THE REVERSE MARGIN™ AS PART OF YOUR CEMENT CONTROL SYSTEM™

TO PROTECT THE FOUNDATIONSOF YOUR PROSTHETIC TREATMENT


Go to www.ReverseMargin.com to view supporting information and to find out how to implement these innovations. It is Easy and I will help you.

72


screw versus cement for implant prosthesis installation. part 2: the game changer the tips the...

Health & Medicine