Occlusal Considerati

ons in Implants

CONTENTS Introduction Terminology Significance of occlusion on osseoitegrated implants. Occlusal goals for implant prosthodontics. Implant protective occlusion(IPO) Occlusal schemes Occlusal adjustment in implant-supported prosthesis Conclusion

INTRODUCTION

For many years, in fact, for more than 100 years, dentists and researchers have

debated how to identify and define concepts of dental occlusion that could be

applied in diagnostic and therapeutic situations.

Occlusion has been, and still is to some extent, a controversial issue in what is

now called conventional removable and fixed prosthodontics, and it is not fully

resolved in implant prosthodontics.

The choice of an occlusal scheme for an implant supported prosthesis is broad

and controversial

Almost all concepts are based on those developed with natural teeth and are

transposed to implant support systems with almost no modification

TERMINOLOGY (GPT 2005)

Occlusion : 1: The act or process of closure or of being closed or shut off. 2: The static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues.

Balanced articulation :

The bilateral, simultaneous, anterior and posterior occlusal contact of teeth in centric and eccentric positions

Lingualized occlusion :

First described by S. Howard Payne, DDS, in 1941, this form of denture occlusion articulates the maxillary lingual cusps with the mandibular occlusal surfaces in centric working and nonworking mandibular positions.

Mutually protected articulation :

An occlusal scheme in which the posterior teeth prevent excessive contact of the anterior teeth in maximum intercuspation, and the anterior teeth disengage the posterior teeth in all mandibular excursive movements.

Group function occlusion:

An occlusal scheme in which lateral pressure are distributed to all working side teeth in contrast MPO where lateral pressure are directed only to the working side canine.

SIGNIFICANCE OF OCCLUSION ON THE OSSEOINTEGRATED IMPLANTS

There are no specific defense mechanisms against occlusal forces in implants: poorly restored occlusion deleterious effect.

Prosthesis must be fabricated as accurately as possible in order to achieve long standing success and occlusion should be key factor in overall success rate.

Haraldson suggested that in pts OIP, occlusal forces are controlled through neuromuscular mechanisms via masticatory muscles.

An impact force can have destructive effects on prosthesis and implants and supporting bone.

Teeth should contact simutaneously when mandible closes into maximum intercuspal position

OCCLUSAL GOALS FOR IMPLANT PROSTHODONTICS

Bilateral simultaneous contact.

No prematurities in retruded contact position. (RCP)

Smooth, even, lateral, excursive movement with no nonworking interferences.

Equal distribution of occlusal forces.

Freedom from deflective contacts in intercuspal position (IP).

Anterior guidance whenever possible

IMPLANT PROTECTIVE OCCLUSION(IPO)

A poor occlusal scheme both increases the magnitude of loads and intensifies

mechanical stresses (and strain) at the crest of the bone.

IPO was previously known as medial positioned-lingualized occlusion. This

occlusal concept refers to an occlusal plane that is often unique and specifically

designed for the restoration of endosteal implant.

A primary goal of IPO is to maintain the occlusal load that has to be

transferred to the implant body within the physiologic limits of each patient.

IPO adresses several conditions to decrease stress to implant interface

Timing of occlusal contacts:

The implant has no periodontal membrane, concerns center around the potential

for the “nonmobile” implant to bear the total load of the prosthesis when joined

to the “mobile” natural tooth.

Four important components may contribute movement to the system:

implant, bone, tooth, and prosthesis.

The initial difference in vertical movement of teeth and implants in the same arch – 28

Initial occlusal contacts should account for this difference or implants will sustain greater loads

Occlusal prematurities are ideally eliminated on teeth

before implant reconstruction.

Thin articulating paper (less than 25m thickness) is then

used for the initial implant occlusal adjustment in centric

relation occlusion under a light tapping force.

The implant prosthesis should barely contact, and the

adjacent teeth should exhibit greater initial contacts. Only

axial occlusal contacts should be present on the implant

crown

Once the equilibration with a light bite force is completed, a

heavier centric occlusal force is applied.

The contacts should remain axial over the

implant body and may be of similar

intensity on the implant crown and the

adjacent teeth under greater bite force to

allow all elements to react similar to the

occlusal load.

Hence to harmonize the occlusal forces

between implants and teeth, a heavy bite

force occlusal adjustment is used because it

depresses the natural teeth, positioning

them closer to the depressed implant

position and equally sharing the load.

The initial lateral movement of healthy anterior teeth ranges from 68 to 108m before secondary tooth movement.

Anterior implant movements are not immediate and range from 10 to 50m.

Because of the greater discrepancies in lateral movement, the occlusal adjustment in this direction is more critical to implant success and survival.

A similar scenario is used for the occlusal equilibration - implants joined to

natural teeth

A light force and thin articulating paper are used, and the implant crown

exhibits minimum contact compared with the natural abutment crown.

A heavy bite force is then used to establish equal occlusal contacts for all

abutments and the entire prosthesis, whether implant or natural.

Influence of surface area: An important part of IPO is the adequate surface area to sustain load

transmission to the prosthesis. Wider diameter root form implants have a greater area of contact at the crest

than narrow implants which reduces the mechanical stress at the crest. When narrow diameter implants are used in regions that receive greater loads,

additional splinted implants are indicated to compensate for the design. Placement of implants in posterior jaws to be staggered to improve

biomechanical loads.

Implant body orientation and

influence of load direction:

Forces acting on dental implants are

referred to as vectors (defined in both

magnitude and direction).

Occlusal forces are typically three-

dimensional, with components

directed along one or more of the

clinical coordinate axes.

Implants are also designed for long axis load. Axial load generates greater proportion of compressive stress than tension and

shear.

Bone mechanics and force direction: Anisotropy refers to the character of bone, whereby its mechanical properties,

including ultimate strength, depend on the direction in which the bone is loaded.

Whenever possible bone should be loaded with compressive load

Strength of cortical load decreases with increasing angle of applied load

The primary component of the occlusal force should therefore be directed along

the long axis of the implant body, not at an angle.

Angled abutments are used only to improve the path of insertion of the

prosthesis or the final esthetic result.

Larger diameter implants or a greater number of implants are indicated to

minimize the crestal bone stress on each abutment.

IPO aims at reducing the force of occlusal contacts, increasing implant number,

and/or increasing implant diameter for implants subjected to angled loads.

Crown cusp angle: Occlusal contact along an

angled cusp result in an angled load to the crestal bone.

Post implant crown should have wider central fossa perpendicular to implant body.

Opposing cusp should be modified to occlude in fossa

Natural tooth 30 deg Wide central fossa

Cantilevers and IPO:

Cantilevers or crowns with less favourable crown/implant ratio also increase

the amount of stress to the implant.

The goal of IPO relative to cantilevers is to reduce the force on the lever or

pontic region compared with that over implant abutments.

In addition no lateral load is applied to the cantilever portion.

Crown height and IPO:

The implant crown height is often greater than the original

natural anatomical crown, even in division A bone.

Crown height with a lateral load may act as a vertical

cantilever and a magnifier of stress at the implant-to-bone

interface.

Therefore the noxious effects of a poorly selected cusp

angle, an angled implant body, or an angled load to the

crown will be magnified by the crown height

measurement

Occlusal contact positions: Determines the direction of force.

The marginal ridge contact is also a cantilever load because the implant is not under the marginal ridge

The ideal implant body position is usually under the central fossa and maybe 1-2mm to the facial aspect (when bone is abundant) to be under the buccal cusp of the mandible and to improve the esthetic emergence of maxillary implant crowns.

The ideal primaty contact should reside within the diameter of an implant.

secondary occlusal contact should remain within 1 mm of the periphery of implant

Marginal ridge and buccal cusp contacts should be avoided.

Implant crown contour: A wide occlusal table favors offset contacts

during mastication or parafunction. Narrower implant bodies are even more

vulnerable to occlusal table width and offset loads.

Wider root form implants can accept a broader range of vertical occlusal contacts while still transmitting lesser forces at the permucosal site under offset loads.

Therefore in IPO the width of the occlusal table is directly related to the width of the implant body.

Restorations mimicking the occlusal anatomy of natural teeth often result in offset loads (increased stress), complicated home care and increased risk of porcelain fracture.

In nonesthetic regions of the mouth, the occlusal table should be reduced in width compared with natural teeth.

Division A Bone: In an edentulous ridge with abundant height and

width and little resorption, the implant may be placed in a more ideal position for occlusion and esthetics.

To load implant in axial direction the primary occlusal contacts should be the central fossa region in div A bone.

Thus for maxillary implant opposing mandibular natural teeth, the mandibular buccal cusp acts as the primary tooth contact.

Canines and premolar – crown contour

Division B Bone : Division B bone has maxillary and mandibular

implants positioned under the lingual cusp when compared with the original natural tooth position.

As a result, mandibular crowns require even more reduced buccal contours to avoid offset occlusal contacts.

The primary contact of occlusion on an opposing natural posterior maxillary tooth is the lingual cusp, which is reshaped to axially load the implant

A Division B maxillary implant is often placed under the palatal cusp region of the original natural tooth.

The maxillary occlusal table cannot always be reduced from the facial aspect for esthetic reasons; therefore the buccal cusp is offset facially but left completely out of occlusion (as with natural teeth) in centric relation occlusion and during all mandibular excursions.

The buccal cusp of the opposing natural tooth is recontoured in width and height to reduce offset loads to the opposing crown on the maxillary implant.

When Division B implants are placed in both

arches, the maxillary and mandibular

prostheses are similar to that described in the

previous scenario.

However, it is usually not possible to load

both arches with an axial load, so the

weakest implant in bone density, width, or

prosthesis type determines the axial load,

because it is the most vulnerable arch.

When further resorption occurs and the ridge evolves into Division C or D, the

maxillary palatal cusp becomes the primary contact area, situated directly over

the implant body.

Hence the occlusal contacts differ from those of a natural tooth and may even

be positioned more medial than the natural palatal cusp when the implant is

placed in Division C or D bone.

Design to the Weakest Arch:

The weakest component philosophy is used when one opposing segment is at

more risk of complications than an opposing area.

The amount of force distributed to a system can be reduced by stress relieving

components that may dramatically reduce impact loads to the implant support.

The soft tissue of a traditional completely removable prosthesis opposing

implant prosthesis is displaced more than 2 mm and is an efficient stress reducer.

Lateral loads do not result with as great a crestal load to the implants because the

opposing prosthesis is not rigid.

The weakest component philosophy also applies to axial occlusal contacts in

implant body in the presence of cantileveres and offset loaded areas.

Absence of centacts during excursion on post cantilevers and ant offset pontics

is recommended which minimizes the loads on the terminal implant abutments

When cantilever pontics are in both arches, they should oppose each other.

If cantilever pontic is present only in one arch it is better for mandibular

cantilever pontics to oppose maxillary implants than the reverse situation.

Full – Arch Fixed Prosthesis:

Fixed prostheses on natural teeth opposing FP-1 to FP-3 implant restorations

should follow mutually protected occlusal schemes whenever possible.

In protrusion, there should be total absence of posterior contacts, especially for

cantilevered posterior units.

The masticatory force generated during lateral excursions is decreased in absence

of posterior contacts. This assists in reducing the noxious effect of lateral forces

on the anterior implants.

Minimal occlusal contact in the cantilevered regions in centric and the total

absence of posterior lateral contacts during excursions are indicated when

opposing the natural dentition or a fixed restorations.

Mandibular flexure distal to mental foramen demands the placement of

implants in two separate units, total of 7-8 implants to support a complete

implant prosthesis in the mandible for a fixed restoration opposing a fixed

prosthesis or natural teeth.

In the edentulous maxilla, flexure of the bone is not a concern. A full arch

prosthesis may be fabricated in one section.

Eight to ten maxillary implants most often are required for a twelve unit fixed

prosthesis opposing a fixed dentition on teeth and / or implants.

Occlusal materials:

The materials selected for the occlusal surface of the prosthesis affect the

transmission of forces and the maintenance of occlusal contacts.

Occlusal material fracture is one of the most common complications for restorations

on natural teeth or implants.

Occlusal material for each individual restoration must be considered.

Occlusal materials maybe evaluated by esthetics, impact force, a static load,

chewing efficiency, fracture, wear, interarch space requirements, and accuracy of

castings.

The three most common groups of occlusal material are porcelain, acrylic and metal.

Therefore when all 8 criteria are evaluated, metal is an excellent occlusal material, with improved properties in accuracy, wear, fracture resistance, abutment retention, and good qualities for impact or static force.

Esthetics is best satisfied with porcelain, which has improved properties compared with acrylic concerning fractures and retention.

OCCLUSAL SCHEMES

Rationale for choice of occlusal scheme:

Occlusal scheme that allows disocclusion of posterior teeth in eccentric

occlusion and reduce lateral stress to dentition, which is accomplisehed by

mandibular and maxillary cuspid.

In group function lateral forces are distributed to all working side teeth.

Although they are seemingly divergent philosophies..

Both philosphies have been helpful in developing occlusal scheme for implant

supported prosthesis.

Implant occlusion in partially edentulous patient:

It is important to differentiate betn ant. Restoration over implants that replace

cuspid and those do not.

Cuspid is not involved: cuspid disocclusion/group function.

Cuspid is involved: group function

Fixed type restorations opposing partially edentulous maxilla: group function.

Post fixed implant prosthesis: cuspid disocclusion.

Singe tooth implant in post segment: cuspid disocclusion.

Implant occlusion in edentulous patient:

No attempt should be made to obtain full balanced occlusion.

Lingualised type of oclusion id preferred.

Totally implant borne prosthesis opposes arch with natural dentition: group

function occlusion

Single tooth restoration:

Centric contact – light in casual intercuspation

equal in max intercuspation.

No contact during excursive movements.

Occlusal surface should be smaller buccolingually.

Single missing molars – 2 implants can be splinted

Occlusal contact should be at centred over implant.

Partially edentulous –multiple units

Post. Partial denture

Centric contact – light in casual intercuspation

equal in max intercuspation.

No contact during excursive movements.

This is possible when there is immediate

disocclusion with natural canine

Anterior fixed partial denture:

Centric contact – light in casual intercuspation

equal in max intercuspation.

The goal should be ant. Grp funcn

Place contact on multiple implants

If missing canine is replaced –avoid immediate disocclusion

Avoid load on single implant during excursive movement or in centric.

Completely edentulous:

Standars for different type of osseoingration treatment

EdentulousClassification

Type of Prosthesis

Optimal Occlusal Scheme

1 Edentulous Fully bone anchored FPD

MPO

2 Edentulous Overdenture Balanced Occlusion

3 Class 3 or 4 partially edentulous

Freestanding FPD

Group Function Occlusion

4 Class 1 or 2 partially

edentulous

Freestanding FPD

MPO

IDJ 2008

OCCLUSAL ADJUSTMENT IN IMPLANT-SUPPORTED PROSTHESIS

This consists of modifying tooth anatomy to obtain a good occlusion.

Occlusal adjustments must be performed in the upper and lower arch jointly at

the same time and on both sides.

All of the following adjustments can be done when checking a case prior to

laboratory work or once it is placed in mouth or in finished cases to readjust

occlusion.

Technique – Double colored thin articulating paper or black marking ribbon and the patient

close from CR to MI several times. Mandible : In normal occlusion (Class 1) the distal lower inclines and the

mesial upper inclines contact in condylar centric relation.

To adjust, we should follow these steps:

Cusp distal inclines Active-cusp outer inclines

Inner inclines

Maxilla:

Mesial cusp inclines Active-cusp outer inclines

Inner inclines

Deepening fossae: maxilla and mandible

If the cusp contacts the floor of the fossa, it will create

large contact surface; avoided.

Spare the lateral cusp marks while eliminating the

intermediate zone, which will cause loss of active

material for chewing and will decrease efficiency.

Deepen the fossa while preserving its lateral aspects,

which will permit preservation of cusp surface.

At the end of this phase of adjustment a great number of black contact points,

not surfaces, will appear on the occlusal surfaces.

The presence or absence of excessive contact in the anterior teeth must be

checked during closure.

It should be done with very thin ribbon, noting slight resistance while pulling it

from the teeth.

Anterior Guidance:

The anterior guidance should be as flat as possible to avoid overload in the

anterior teeth in lateral excursion and in protrusion.

No posterior teeth should contact when the guidance is in function which is

always checked with red ribbon

Eliminating interferences:

(Non physiological contacts that appear in anterior and posterior teeth in lateral

and protrusive excursions)

Using red ribbon have the patient go through working, nonworking and

protrusive movements.

Next place black ribbon and have the patient close to MI.

Eliminate all red marking except the guide marks of anterior disclusion.

CONCLUSION Occlusion has been an important variable in the success or failure of most

prosthodontic reconstruction.

With natural teeth, a certain degree of flexibility permits compensation for

occlusal irregularity. But “Implants Cannot Bail Out Our Faulty Occlusion”…

Therefore occlusion must be more rigorously evaluated with implant supported

prosthesis

BIBLIOGRAPHY Dental implant prosthetics – Misch

Implant supported prosthessis: occlusion, clinical cases, laboratory procedures - Vicente Lopez

Osseointegration and oral rehabilitation – Hobo

Surgical and Prosthetic techniques for dental implant – Ismail,Fagan,Meffert

Clinical decision making and treatment plannning in osseointegration.Engleman MJ.

Implants in dentistry. Black. Kent , Guerra.

Indication for splinting implant restorations. J oral maxillofc surg. 63; 1642;2005.

Guidelines for occlusal strategy in implant borne prosthesis. Idj 2008, 58

Factors to consider in selecting an occlusal concept for pts with implants in edentulous mandible. JPD 1995; 74; 380

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