Treatment Planning pt. 7-8

Outline for 1/28/09• Take home messages from last week

• Pick up implant DVD and look over the treatment planning section and single tooth implant section.

• Questions asked during the week

• Ten treatment planning cases

• Single tooth implants

• Implants with removable prosthodontics

Take home messages last week: Tx. Planning with implants

• Understanding the incidence and reason for implant complications is important when you are treatment planning with implants.

• Many of the complications seen with dental implants occur because of a lack of coordination between the restorative dentist, surgeon and laboratory technician. You need to work with people you trust.


• Complications with single tooth implants occur more often in the posterior than anterior part of the arch.

• Screw loosening occurs more often when implants are single units than when implants are splinted together.

• Bruxisim is a big deal- about 20% of the population will brux at some point in their life, and bruxing can increase complications.


• You should know which complications are reversible and which are irreversible.

• You should understand some of the common reasons for material fracture.

• You should understand the basic steps in the fabrication of a surgical guide and understand what a surgical guide does for you and what it does not do for you.

Take home messages last week: treatment planning with implants

• Understand the reversible and irreversible complications with implants.

Questions this week

• Goodacre; clinical complications in fixed prosthodontics

• Fixed dental prostheses; complications caries 18%, need for endo 11%, loss of retention 7%

• Single crowns; complications endo 3%, porcelain fracture 3%, loss retention 2%.

• Why the big difference between FDP and single units- will be on test.

Questions this week

• Why do we use 35 N torque when tightening the screw to the implant abutment crown?

• Answer: You want to create pre-load in the screw to provide what is called clamping force. Pre-load basically means stretching the screw. You want to develop as much pre-load as you can without damaging the screw head. If you use more than 35 N you can damage the screw head.

Questions this week

• Why do we use a torque wrench to tighten abutment screws?

• Answer: With hand tightening you can only develop about 15 N force. Screw loosening is much more likely with 15 N tightening force than 35 N force because of less pre-load or stretching of the screw.

Questions this week

• Why do we have the patient back to re-tighten the implant?

• Answer: After you tighten the screw there is a process of “embedment” which basically is the compression of surface imperfections over time. As the surface imperfections compress, the pre-load of the screw decreases. By having the patient back you can tighten the screw again and have a higher pre-load.

Questions this week

• Why is it that the time necessary for implants to osseointegrate to the bone is so much shorter now (2-3 months rather than 4-6 months)?

• Answer: Implant surfaces have changed from milled titanium to a roughened surface (often by acid etching) that makes the surface more interlocking and bioreactive.

Titanium Implants – Current Surfaces

Methods• Histomorphometric analysis• Shear strength evaluations• Gene expression studies

Clinical studies have implied that the rough Clinical studies have implied that the rough surfaces are superior surfaces are superior particularly the acid particularly the acid etched surfaces. Why are they superior?etched surfaces. Why are they superior?

Mechanical interlockingMechanical interlocking BioreactiveBioreactive

Titanium Implants - Surface Modification2nd Generation

• Surface roughness and the bone appositional index

Initial studies indicated Initial studies indicated that the bone appositional that the bone appositional index achieved is 50% index achieved is 50% greater with rough surfaces greater with rough surfaces as compared to machined as compared to machined surfaces (Buser et al, 1991; surfaces (Buser et al, 1991; Weinlander, 1993; Weinlander, 1993; Hamada, 1995; Nishimura Hamada, 1995; Nishimura and Ogawa, 2000, 2003)and Ogawa, 2000, 2003)

Dual Acid etchedDual Acid etched

Electrolytically enhanceedElectrolytically enhanceed

Sandblast Acid-ethchedSandblast Acid-ethched

**

**

Bone-implantBone-implantcontact ratiocontact ratio

00

2020

W2W2 W4W4

4040

6060

8080

(%)(%)

MachinedMachined

Acid etchedAcid etched

50 µm50 µm50 µm50 µm

Near zone

Far zone

Histomorphometry

Acid etched vs Machine surface

More recent studies (Ogawa and Nishimura, 2000, 2003), reconfirm these findings

Summary of Ogawa’s and Summary of Ogawa’s and Nishimura’s work re: gene Nishimura’s work re: gene

expressionexpression

Summary of Ogawa’s and Summary of Ogawa’s and Nishimura’s work re: gene Nishimura’s work re: gene

expressionexpressionThe placement of implants The placement of implants

induces a phenotypic alteration induces a phenotypic alteration (gene expression) of wound (gene expression) of wound healing cells. healing cells.

The double acid etched surfaces evoked The double acid etched surfaces evoked activation of additional activation of additional selected bone genesselected bone genes,, which may be associated with enhanced interfacial which may be associated with enhanced interfacial strength and accelerated bone formationstrength and accelerated bone formation

Questions this week

• Why is initial stabilization important for the wound healing of implants?

• Answer: If you have very much micromovement the predictability of osseointegration is compromised. Please consider the following graph from my teacher John Beumer at UCLA.

MicromotionTwo types of micromotion: it may be

tolerated , or it may be deleterious

Micromotion appears to permit bone ingrowth,Macromotion appears to preclude it

From Maniatopoulos C, Pilliar RM and Smith DCJ Biomed.Mater Res 1986

150µm 500µm50µm

Tolerated Deleterious

Ten cases

• I want to go through 10 patient treatments with you to highlight and review the treatment planning principals you have learned from lecture, your reading and the DVD.

• Favorable bone width, depth,

• May need crown #2 for vertical height

• Pt preferred chewing• Splinted crowns• Bicuspid size

• Consider shortened dental arch; depend on pt age, chief concern

• If 5.0 mm internal connection then ok with one implant.

• Consider caries history, meds, compliance of pt.

• Pt health

• Function; 6 teeth better than 2 imlants,bar,clip

• Function; 4 implants often better than 2, especially if wide AP spread

• From a functional standpoint, two implants will probably not provide as high a level of function as 6 teeth but 4 implants will allow higher function than anterior teeth and extension partial denture.

• Extract 1,2,31

• Implant #29, consider #19

• Upper partial

• Space measures 14 mm. How many implants?

• Would be 2 implants, perhaps adjusting occlusal plane first.

• Carefully review history

• Is the patient at high risk for caries?

• Will attempts to save the tooth compromise a future implant site? If you did crown lengthening would you later have the vertical height for implants??

• Because opposing a partial denture can use 3 implants to replace 4 teeth.

• Check space to IA nerve

• Check to make sure more than 5 mm to opposing arch

• How does the ridge look?--- narrow

• How long after extraction of 27,28 would you wait for implant placement?

• Part of a 4 unit FDP

• Decay on distal

• Sinus is high

• Extract #3 and use three splinted implants

• Not a new FDP because of high caries risk.

Treatment planning decisions for single tooth implants

• Do I take out or try to restore the tooth?• Do I complete a FPD or implant or RDP? • Do I need site preparation?• Immediate placement or delayed?• Do I use a narrow diameter or wide diameter

implant?• Do I use an internal connection or external

connection implant? Platform switching?• Do I splint the implants?• Do I cement or use screw retained?

Evaluate how much crown lengthening would be necessary if you were to save the tooth.

Determine from the patient history and clinical examination how many implants make sense. If the patient has high biting forces you would need two splinted implants. If the patient is older and has sufficient tooth-to-tooth stops you might consider a SDA. If the patient has low levels of implant loading and a wide arch, you might consider a single wide diameter implant.

• Patient presented with deep caries on the mesial of the first molar.

• Even though RCT is possible, other problems like root proximity are seen.

• Here I would probably proceed with RCT, a build-up and a crown.

• Be sure to check the anatomic limitations before you promise options to a patient. In this situation, make sure you have the vertical space above the IA

• In this example you have adequate tooth stops so SDA would be an option as would a FDP but a single tooth implant would most likely be the best option.

• In this case you have adequate ridge height and width for a wide diameter implant that is more than 10 mm long; so, ask for a 5.0mm diameter implant. Remember in the posterior a wider diameter is better.

• In general, you would not complete high risk procedures like root amputations. Normally, you would complete a single tooth implant if necessary. Why do you think a root amputation was completed here??

• If you did crown lengthening you would compromise an implant site. You probably would not want a FDP because of the caries activity you see on the mesial of the second molar. A single tooth implant is the logical option. However, what does that large facet on the mesial of #31 tell you??


• Do I take out or try to restore the tooth?• Do I complete a FPD, implant or RDP? • Do I need site preparation?• Immediate placement or delayed?• Do I use a narrow diameter or wide diameter



FDP, RDP or implant??

• You know the comparison of an implant, FDP or RDP. The RDP is less expensive, takes less treatment time than an implant, is often less comfortable than an implant but is generally tolerated if not a distal extension. The FDP also takes less treatment time than an implant, is also less expensive than the implant, but has a higher risk of failure if the clinical crown height is not sufficient or if the patient has a high caries risk.

FPD Success Rates

• 87% 10 yr success rate,69% at 15 years

• Failure by recurrent caries (18%),loose retainer (7%), porcelain fracture 6.1%, Endo 5%, Perio 4%.

• Please read Goodacre et al. and Curtis

Implant success rates• Surgical success 92% (Moy)

• Restorative complications; porcelain fracture (12%), screw loosening (7%), screw fractures (4%), metal frame fractures (3%).

• Please read Goodacre et al. and Curtis





Determine what the patient’s expectations from treatment are

Determine where bone might be grafted from.

Then move foreword knowing that much more force will be on the implants because of the lower natural dentition.

1)Complete diagnostic set-up

2)Index teeth

3)Place pins where you want implants

4) Complete 0.060 suck-down

• If you do fixed, then you need to break it into segments; trying to have the prosthesis retrievable.

• Often lip support is less than ideal with a implant supported fixed prosthesis.

Site preparation for implants

OrthodonticsRidge splittingOnlay graftingMembranes

Be sure to get the height of the implants correct; images of CT, pano

• In contrast to the patient case presented this patient did not have any site preparation.

A connective tissue graft was added to hide the margin of the angulated implant.





Dental Implants

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• •

• •

• •

Nevin, MJPerio, 2005

• •

Use open tray, have pre-selected denture tooth, use screw retained, out of occlusion, don’t touch for several months, altering proximal contacts to work papilla.

• •

• •

• •

• •

Immediate or Early LoadingWas it feasible with the original machined surface?

• Blood clot formation• Angiogenesis• Osteoprogenitor cell migration• Woven bone formation• Deposition of lamellar bone• Secondary remodeling of the woven bone

Biologic processes to complete osseointegration*

**In humans these events take about In humans these events take about 4-5 months with machined surfaces 4-5 months with machined surfaces

In most cases no!!! WHY?

Initial Primary Stability(1st few days)

• Function of – Local bone quantity and

quality

– Implant geometry

– Surgical procedure (skill)

Two main factors:1. Amount of initial bone contact2. Lateral compression of the osteotomy creating local compression stresses (hoop stresses)

Courtesy Dr. C. StanfordCourtesy Dr. C. Stanford





Surface Area of ImplantsSurface Area of Implants

DiameterDiameter

•3.753.75

•4mm4mm•5mm5mm•6mm6mm

•2 x 3.75 mm2 x 3.75 mm

Surface AreaSurface Area•Baseline•+8%•+35%•+61%•+100%

What diameter do I use?• Keep 1.5 mm from

adjacent teeth.

• Keep 2.0 mm from adjacent implant

• Error on side of narrow in anterior and wide in posterior

5.0

3.5


• Do I take out or try to restore the tooth?• Do I need site preparation?• Do I complete a FPD, RDP or implant?• Do I use a narrow diameter or wide diameter



Internal vs. External connection• Generally use internal

connection

• Can splint divergent implants up to 40 degrees with both internal/external

• Screw loosening is related more to pre-load than connection type





To splint or not to splint?

Splinting of implants• Assess forces

• Patient factors; wt, gender, skeletal form, bone volume, quality

• Dental factors; proximal teeth, opposing teeth, location in arch

• Implant factors; wide or narrow implant

Splinting of implants• To protect integrity of

prosthesis; less screw loosening or breakage

• For biomechanical reasons to distribute forces to wider area of bone

• Splinting somewhat less comfortable for patients

Splint if bone is grafted, or low density

Internal vs. External connection• Platform surface area

is very similar

Platform switching

4.8 mm

4.1 mm

Platform switching

• Creating horizontal offset

• In theory, less bone loss

• When have to use short implants

4.8 mm

4.1 mm

Platform switching

• Traditionally, you see bone loss to the first or second thread.

• Micrograp; establishing biologic width

• Platform switching is an attempt to minimize the bone loss





Cement or screw retained

• More complications with screw retained

• More retrievable with screw retained


• When tissue is thick consider screw retained

• Need to be very careful to remove all cement if use cement retained

• Remember soft tissue connection is not the same between teeth and implants!!!!!!!!


• When use cement on restoration do not have it very far sub-gingival

• Consider all ceramic abutments


• When use cement on restoration do not have it very far sub-gingival

• Consider all ceramic abutments

• Don’t always try to be first

• Treat every patient as if they were a family member

•Fibers connect soft tissue with bone and cementum

• Fibers only Fibers only circumferential to circumferential to implantimplant

ToothTooth

•Fibers run perpendicular, vertical and circumferential to tooth

ImplantImplant

• Fibers do not insert Fibers do not insert into implantinto implant


• Use cemented when screw access hole is close to facial to avoid porcelain fracture


• Use screw retained with all removable bars

• Use screw retained on cantilevers because higher risk

Other considerations for single tooth implants

• Place implant platform 2-3 mm below adjacent tooth CEJ.

• Remember at least 1.5 mm from proximal teeth


• Often use narrower diameter implant so have at least 1.5 mm proximally to adjacent tooth.


• Seldom will you use an implant diameter greater than standard diameter in the maxillary anterior

• An exception is sometimes the maxillary canine


• In maxillary anterior ask for placement that would allow screw retained; better esthetics, easier provisional, retrievable

Other considerations for single tooth implants• If placed too far to the

palatal will introduce cantilever (A/P) and result in more difficult esthetics because of ridge-lap.


• In maxillary anterior if you have to restore an implant that is facial to the incisal edge you will need a cement on restoration


• Be careful with occlusion

• On implant crowns have very light occlusion when the patient closes hard

• Avoid lateral forces on implants

Please list the mistakes you can see with this implant placement

Patient worries about esthetics; you need to also worry about function

Steps for a single tooth implant

Tell me the steps

What is wrong?

Site preparation may not be necessary if the patient’s smile line is not very high.

My preference is screw retained, using a metal lingual for less bulk and improved contours.

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Treatment Planning pt. 7-8

Education