Jan Lindhe. Clinical Periodontology

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RADIOGRAPHIC EXAMINATION • 847

Fig. 36-16. When a tomographic technique is used with

which thin tomographic layers can be produced, ghost

shadows from surrounding teeth are minimized.

surrounding teeth, particularly if metal crowns or

fillings are present. A technique yielding thin ( 2 mm)

tomographic layers (Fig. 36-16) should be used (Gron

dahl et al. 1996).

In many single implant cases, sufficient informa-

tion about the width and height of available bone

volume can be obtained from a clinical examination

supplemented by intraoral radiography. Tomography

is recommended when patient history, the clinical

examination and intraoral radiographs lead to a sus-

picion of a narrow width of the jaw bone. Tomography

is also recommended when a single implant is to be

placed above the mandibular canal.

Conclusion

The distance between opposing root surfaces is pref-

erably measured in intraoral radiographs. Slight vari-

ations in patient positioning can make such a distance

appear too small or too large in panoramic images.

If tomography is considered necessary, thin to-

mographic layers should be used to avoid disturbing

ghost shadows.

Tomography is recommended when a single im-

plant is to be placed above the mandibular canal.

POSTOPERATIVE RADIOGRAPHY

abutment connection

For some implant systems such as the Branemark

System

it is necessary to control the fit between the

abutment and the implant pillar once the abutment

has been seated. Even a small intermediary gap means

that forces from the suprastructure will not be opti-

mally transferred to the implant pillar. Later, this can

cause a fracture of the abutment screw or of the im-

plant pillar itself. To be able to radiographically dis-

close a small misfit, intraoral radiographs should be

used because of their high geometric resolution. The

irradiation geometry has to be such that the X-ray

beam is directed at a right angle to the longitudinal

axis of the implant. Even small deviations from a

direction of the incident radiation parallel to the upper

surface of the implant and the opposing surface of the

abutment can make a clinically significant gap invis-

ible. Because of less geometric resolution and difficul

ties in individual adjustment of the radiation beam

direction, panoramic images cannot be recommended

for abutment controls.

Following crown-bridge installation

Immediately following the connection of the crowns

the bridgework, radiographs should be taken both to

provide necessary information at this point in time

and

to serve as reference images for subsequent follow-

up radiographs. The information to be obtained

at this

time again concerns the fit between implant and

abutment, but also that between abutment and the

suprastructure. In addition, the level of the marginal

bone must be determined and the conditions of the

bone that surrounds the implant evaluated.

High demands on image quality

To be meaningful, images obtained in conjunction

with crown or bridge installation as well as at sub-

sequent follow-ups must be of the best possible qual-

ity as regards density and contrast as well as radiation

geometry. Most problems concerning density and con

trast depend on suboptimal film developing. Conse-

quently, a strict program for quality maintenance of

the dark-room procedure must be followed. Through-

out the follow-up period the exposure factors (tube

current, tube voltage and focus-to-film distance) must

be kept constant. As regards radiation geometry it is

of the utmost importance that images are taken with

the film placed parallel to the implant and that the

radiation beam is directed perpendicular to the longi-

tudinal axis of the implant (Fig. 36-17). Only then can

a correct estimate of the marginal bone level relative

to some reference point on the implant be obtained.

Furthermore, the bone-implant interface zone cannot

be evaluated in its entirety if the bone, reaching into

the inner parts of the threads, is not visualized. Be-

cause of the high demands made in terms of irradia-

tion geometry and resolution, intraoral radiographs

are to be preferred for all follow-up examinations. In

some cases it is not possible to display the implant in

its entire length when a strict paralleling technique is

used. In the absence of clinical signs and symptoms

this is acceptable, because the significant changes that

848 • CHAPTER 36

Fig. 36-17. For postoperative control radiographs the in

cident X-ray beam should be perpendicular to the lon

gitudinal axis of the implant and the film.

may occur are most often found around the marginal

part of the implant. In the presence of clinical signs

and symptoms, such as pain, suppuration and im-

plant mobility, radiographs obtained with the paral-

leling technique can be supplemented with radio-

graphs obtained with a radiation beam angulation

which visualizes the "apical" part of the implant.

Analysis of postoperative radiographs

In the postoperative radiographs the marginal bone

level is compared with that in radiographs obtained

immediately following crown and bridge installation

(

Bragger 1994). Therefore, the demands on radio-

graphs similar in irradiation geometry, density and

contrast are high (Fig. 36-18). When threaded implants

are used, optimal projections in the vertical plan are

at hand when the threads on both sides of the implant

are clearly seen. Due to the spiral right-turned path of

the threads it is possible to determine how to adjust

the angulation of the X-ray beam if the threads are not

clearly seen on either side. Diffuse threads on the right

side of the implant indicate a direction of the X-ray

beam too much from above while diffuse threads on

the left side indicate a beam direction too much from

below. Corrections of the irradiation geometry are

necessary to make it possible to correctly ascertain any

changes in the marginal bone level over time. Even

relatively moderate variations in irradiation geometry

between radiographs to be compared can lead to dif-

ferences in the bone level estimates. Because the mar

ginal bone often can be relatively thin in the buccolin

gual direction, or less well mineralized in the early

stages of the postoperative phase, a high density of the

radiographs can make it less visible. This can also lead

to erroneous conclusions about bone level changes.

An important aim of the postoperative controls is

to determine lack of osseointegration. Because it

would be both too costly and inconvenient to detach

the bridgework at all postoperative clinical controls,

radiography is the most feasible tool to use. Radiog-

raphically, lack of osseointegration and thus lack of

clinical stability of the implant is indicated by a radi-

olucent line along the implant surface (Fig. 36-19).

However, false-negative diagnoses can be made when

the soft tissue layer surrounding the implant is not

wide enough to overcome the resolution of the radio-

graphic system, including that of the observer. On the

other hand, false-positive diagnoses can be made,

above all due to the presence of a so-called Mach band

effect. This causes a thin area adjacent to an area of a

lower radiographic density, in this case the implant,

to look darker than it is in reality. Although radiogra

phy is not a perfect tool to reveal lack of osseointegra

tion, it has been demonstrated that it performs as well

in this respect as it does for approximal caries diagno

sis (Sunden et al. 1995). However, an important pre-

requisite is radiographs of high quality.

At the postoperative follow-ups the state of the

implant components should also be controlled. Al-

Fig. 36-18. When proper projections are used, the

threads on both sides of the implant are clearly seen.

The marginal bone level can be evaluated relative to a

reference point on the implant.

RADIOGRAPHIC EXAMINATION •

Fig.

36-19.

Postoperative radio-

graph taken in connection with

bridge installation (a) with no

signs of failure. In a radiograph

taken

2 years later (b) the most

posterior implant is surrounded

by a radiolucent zone indicating

lack of osseointegration.

though infrequently, fractures of the abutment screw

(

Fig. 36-20) or the implant pillar itself (Fig. 36-21)

occur. An indirect sign of a fracture of the abutment

screw is the appearance of a gap between abutment

and the implant pillar. An indirect sign of a fracture of

the implant pillar itself is a pronounced, localized

reduction in the marginal bone level. To be able to

directly detect fractures of the implant components,

the density of the radiographs has to be relatively

high. Hence, there are conflicting demands on the

density of the postoperative radiographs.

Subsequent follow-up examinations

Most clinically significant changes occur during the

first year of function. Control radiographs 6-12

months after crown or bridge installation can there-

fore be recommended. When using systems for which

high success rates have been reported, the application

of rigid protocols for subsequent, frequent radio-

graphic examinations can be questioned, once a clini

cian has established that his /her success rate is similar

to that reported from multi-center studies. However,

for a clinician to determine that he/she has reached a

similar, high success rate, control radiography can be

recommended at intervals of 2-3 years. The same is the

case when systems are used for which long-term re-

sults are still lacking. Naturally, any clinical signs and

symptoms which cannot be explained without radi-

ography make this justified at any point in time.

Since pathologic conditions in and around remain

ing teeth can have a negative effect on the fate of the

implants, control radiographs covering the teeth

should also be considered. When and how often these

should be obtained depends on the results of the

clinical examination. However, for conditions for

which the clinical examination gives little guidance,

e.g. periapical lesions, annual radiography can be

Fig.

36-20.

Fracture of the abutment screw (left im-

plant). Notice dislocation of fragments and small gap

between abutment and implant pillar.

Fig.

36-21. Fracture of the implant pillar. Also notice

lack of osseo-integration.

850 • CHAPTER 36

recommended until it is clear that healing is well

under way.

Conclusion

For abutment controls and all follow-up examina-

tions, intraoral radiography should be used.

Reference images should be taken immediately fol-

lowing crown/bridge installation.

The film should be placed parallel to the implant

and the radiation beam be directed perpendicular to

its longitudinal axis. Small deviations from optimal

projections can make small misfits between abutment

and implant or between implant and suprastructure

invisible. They can also cause significant variability in

bone level estimates.

The visibility of the threads can be used to deter-

mine whether proper projections have been used or

not.

A quality assurance protocol should be used to

maintain optimal image quality over time in terms of

density and contrast.

Variations in film density and contrast can lead to

erroneous conclusions regarding bone level changes

over time.

Provided there is proper image quality, lack of

osseointegration can be determined with a reasonably

high accuracy.

A gap between the implant pillar and the abutment

may be an indirect sign of abutment screw fracture.

A pronounced, localized loss of marginal bone may

indicate fracture of the implant pillar.

Most clinically significant changes occur during the

first year of function. Control radiographs should

therefore be taken

6-12

months after crown/bridge

installation.

Subsequent radiographs in asymptomatic patients

should be obtained with intervals of

2-3

years depend

ent on system used and success rates obtained, other

wise when clinically needed.

Remaining teeth should be regularly controlled!

DIGITAL INTRAORAL

RADIOGRAPHY

To avoid problems pertaining to the darkroom proce-

dures it seems tempting to use a digital system for

intra oral radiography. These could also contribute to

lowering of the radiation doses, since all digital

systems require considerably lower exposures than

film (Wenzel & Grondahl 1995, Borg & Grondahl

1996). Because implant radiography requires that

rather thin and thus quite radiolucent structures — the

marginal bone — should be visualized at the same time

as more radiopaque structures — the implant and its

components — a system with a wide dynamic range

can be recommended. Among the systems so far

tested, the image plate systems seem to have the wid-

est dynamic range. They can thus show structures

with a small mass density with the same exposure

with which they can show structures with a consider

ably larger mass density. A wide dynamic range also

means that exposure variations exert a limited influ-

ence on image quality (Borg & Grondahl 1996).

Digital radiographs can be subjected to image proc

essing with which the images can be altered to achieve

task specific image characteristics. For example, den-

sity and contrast can be lowered for evaluations of the

marginal bone and increased for evaluations of the

implant components. It is also conceivable that the

influence of the Mach band effect can be reduced

through image processing. The possibilities of

pseudo-coloring, that is, to assign different colors to

different gray-level values, have been suggested to be

of value in evaluating the bone surrounding the im-

plant. So has the possibility to graphically display the

variations in gray-level values over a distance, e.g. one

that covers the implant-bone interface.

Little scientific evidence of the value of these types

of image processing procedures in implant evaluation

has been presented. However, subtraction of serially

taken radiographs in combination with pseudo-color-

ing has been able to demonstrate changes between

radiographs not readily apparent by unaided visual

observations (Bragger & Pasquali 1989, Bragger et al.

1991). It has also been shown that edge enhancement

can be of value to detect a distance between implant

and surrounding bone that may be undetected in

conventional radiographs (Borg et al.

2000).

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RADIOGRAPHIC EXAMINATION • 851

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CHAPTER 37

The Surgical Site

ULF LEKHOLM

Preoperative examination

Primary judgment

Secondary assessment

Treatment planning

Implant placement

Flap design

Bone drilling

Implant

position Implant

direction

Cortical

stabilization

Implant

selection

Healing time

PREOPERATIVE EXAMINATION

The two main prerequisites for proper implant treat-

ment are: well-performed preoperative examination

and thorough pretreatment planning. In part, the out

come is also dependent on the medical condition of

the patient as well as the local health and bone mor-

phology of the area considered for implants. Conse-

quently, adequate preoperative assessments, adapted

to individual needs, have to be performed before any

implant treatment is offered. When carried out, the

examinations have to be cost effective and mainly

based on conventional techniques, at least in the rou

tine situation. The below protocol, based on experi-

ence of the Branemark implant system, may constitute

one practical way of working in the partially edentu-

lous patient.

essence, the same principles can, of

course, also be valid when working with other oral

implant protocols. The following preoperative exami-

nation levels are thereby recommended:

primary judgment (prosthetic level)

secondary assessment (surgical level)

treatment planning (combined surgical-prosthetic

level)

Primary judgment

When patients are referred – seeking implant treat-

ment – the restorative dentist/prosthodontist must

first of all identify the specific oral problems that the

patient is having. It is also important to discuss his or

her esthetic and functional demands in case of being

treated, i.e. to elucidate what the patient really is

expecting of the treatment. The patient can first then

be presented with alternative prosthetic solutions, im

plant therapy being only one option. If implants are

considered, there should be clear motivations given,

as implant treatment ought not to be routinely offered

just because a tooth or some teeth are missing. Indica

tions for oral implants may, for example, be present

partially edentulous situations, when removable par

tial dentures are not accepted and fixed prosthetic

reconstructions are wanted, but where remaining

teeth are either too few or are so located that they can

not support conventional fixed bridgework. Implants

may also be indicated in connection with single tooth

losses or small gap situations, especially in younger

individuals, in order to avoid unnecessary mutilation

of intact neighboring teeth. Furthermore, if interden-

tal diastemas are to be preserved, only implants seem

to give an acceptable solution.

However, before suggesting any implant treatment

it is important to roughly judge whether it is realistic

to perform the procedure, from both medical and

anatomic points of view. It is also necessary to check

whether the wishes /prerequisites of the patient match

the potentials of the technique offered. Any sign of

unrealistic expectation, including too cosmetically-

oriented demands, must be identified and discussed,

as otherwise problems may later arise in the patient-

doctor relationship or in the patient's appreciation of

performed treatment. Regarding the medical history,

the same principles as in connection with any type of

oral and maxillofacial surgery can be followed. The

anatomic state within the area considered for implants

can roughly be checked with regard to the available

bone volume via palpation and/or probing through

the mucosa, together with evaluation of obtained

panoramic and periapical radiographs (for X-ray

tech-

THE SURGICAL SITE •

niques, see Chapter 36). If implant treatment is re-

garded as possible, the X-rays are also used to study

the health condition of remaining teeth and edentu-

lous areas, as the need for pretreatment must be con

sidered. No ongoing pathology, such as denture-in-

duced stomatitis, candidosis, hyperplasia or similar

mucosal disorders, root remnants, periodontitis, pe-

riapical lesions, residual jaw infections or cysts, be-

nign or malignant tumors, etc. can be accepted at the

time of implant placement. Consequently, the entire

oral situation, and not only the edentulous area aimed

for implants, must be examined and evaluated, i.e. a

total oral rehabilitation plan should be offered to the

patient. Information on possible results and risks with

the treatment, as well as on expected costs and treat-

ment duration, must also be included, before the pa-

tient is left with the decision of whether or not to

accept the offered tentative treatment plan.

Before continuing with secondary assessments,

there should be signs of ongoing healing regarding all

pathology treated. Depending on the nature and ex-

tent of the pretreatment, the time before advancing to

the next level will vary. Mucosal lesions mostly need

few weeks of healing, whereas conditions involving

bone formation may take months to heal, depending

on how much bone restoration is desired. In the case

of tooth extractions, various modalities have been

advocated regarding how soon after the tooth removal

implants can be inserted. Everything from immediate

placement to delayed and/or late insertion of im-

plants has been suggested. The advantages of imme-

diate placement may be that the patient only has to

use provisional removable or fixed constructions for

short period, and that the postextraction resorption

the alveolar bone may be limited. However, various

levels of implant failures (2-7%) have been found with

the immediate implant insertion technique (Krump &

Barnett 1991, Gelb 1993, Watzek et al. 1995), which is

why delayed (5-6 weeks of healing) or even late im-

plant insertion (9-10 months of healing) seem to be

recommended in the long term. In connection with

endodontic treatment of periapical lesions, at least the

beginning of bone fill within the previous defect

should radiographically be detected before implants

are to be inserted, to prevent residual tooth infections

from migrating to and contaminating the inserted

implants during healing. If periodontal treatment is

needed, positive results from that must be recogniz-

able as well, and the patient should be deemed capable

of continuously maintaining good oral hygiene at

remaining teeth and prosthetic constructions, before

any implant surgery is started. Unfavorable plaque

control and ongoing periodontitis may otherwise ad-

versely affect the implant treatment outcome (Ber-

glund 1993, Hardt et al. 2002).

Summary: primary

judgment

The specific oral problems of the patient must first be

identified by the prosthodontist/restorative dentist,

after which different treatment alternatives can be

presented. If implant therapy is preferred, there

should be clear motivations for this, together with a

rough estimation of how realistic it would be to carry

it out. A total treatment plan must always be offered

to the patient, not just implant therapy of edentulous

areas. Unrealistic expectations of the discussed treat-

ment have to be identified and explored in order to

establish a well-functioning future patient-doctor re-

lationship. Any necessary pretreatment must be initi-

ated and signs of healing seen, before continuing to

the second examination level. Furthermore, costs and

timetables for suggested treatment should be indi-

cated before the patient is left with the decision

whether or not to accept the offered tentative treat-

ment plan.

Secondary assessment

Following the primary judgment and suggested pre-

treatment, the patient will advance to secondary as-

sessments, where the medical condition of the patient

as well as the local health and bone morphology of

future implant sites will be analyzed in more detail

from a surgical standpoint.

Medical condition

The patients must meet the physical demands for

surgery in general and have such a psychological

constitution that they can cope with proposed surgical

procedures, i.e. show

general operability.

The same

principles as in connection with any type of oral and

maxillofacial surgery may thereby be followed. So far

no specific condition has been identified which would

exclusively prevent implant surgery, should conven-

tional oral surgery be possible. In connection with this,

patient gender does not seem to have any influence on

the outcome, though theoretically women after meno-

pause are more prone to develop osteoporotic condi-

tions (Lekholm et al. 1994, Friberg et al. 1997, Sennerby

& Rasmusson 2001). Furthermore, age does not seem

to be influential for the establishment of osseointegra

tion, as implants become bone anchored both in young

(Thilander et al. 1994) as well as in elderly individuals

(

Kondell et al. 1988, Jemt 1993). Still, it must be remem

bered that elderly patients are more susceptible to

infections and/or slow healing, and therefore may

constitute potential risks for problems peroperatively

and postoperatively (Sermerby & Rasmusson 2001). It

must also be observed that implants inserted in grow

ing individuals may end up in infra-occlusion (Oil-

man 1994), as they will not follow the growth and

development of the jaws, but rather react like anky-

lotic teeth. Consequently, it is not the chronological

age but rather the dental and skeletal maturation that

must be considered when osseointegrated implants

are to be inserted in adolescents (Thilander et al. 1994).

Individual growth curves should be studied together

with radiographs of the growth zones of the hand

bones, to check that the body growth has ceased or is

854 • CHAPTER 37

close to completion, before any titanium implants are

inserted in adolescents in general. It is only in very

specific situations, and then due to psychosocial rea-

sons mainly, that implants may be inserted in even

younger individuals (Koch et al. 1996).

For implant surgery as well as other types of oral

operations, there are some absolute and relative con-

traindications for treatment that have to be identified.

As examples of absolute contraindications, the follow

ing conditions can be mentioned:

Systemic diseases such as developing cancer and

Aids. Even HIV-positive patients ought not to be

considered, as there may be future complications

due to their impaired immunology defense mecha-

nisms, resulting in increased risks for infections

and impaired healing around the implants.

Cardiac diseases, if not otherwise stated by a re-

sponsible medical doctor. Implant surgery should

be carefully considered in patients with heart valve

replacements and should not be performed on pa-

tients having suffered from recent infarcts, i.e.

within the latest 6-month period.

Deficient hemostasis and blood dyscrasias, such

hemophilia, thrombocytopenia, acute leukemia

and agranulocytosis, are situations which present

risks for bleeding or may limit the healing capacity

of the tissues. If these conditions are suspected, the

patient should be checked via laboratory tests and

the responsible physician consulted.

Anticoagulant medication or any medication lead-

ing to impaired hemostasia, such as ASA, may

result in extended peroperative and postoperative

bleeding as well as enlarged postoperative hema-

toma formation. If anamnestic information regard-

ing such medication is at hand, tests of coagulation

and/or primary hemostasia should be carried out

and the medication be interrupted, if implants are

to be inserted.

Psychological diseases may carry potential risks as

well, as such patients often have difficulties co-op-

erating and/or lack interest in maintaining suffi-

cient oral hygiene. They may also be using medica-

tion which could interfere with the anesthesia

needed during the surgical procedure.

Uncontrolled acute infections, as in the respiratory

tract, may negatively influence the surgical proce-

dure or may affect the treatment result and are thus

a contraindication for surgical treatment.

There are relative contraindications for implant sur-

gery in connection with some medical and clinical

situations as well as chronic health conditions. How-

ever, as long as conventional precautions for the treat

ment of these situations are fully considered during

the surgical interventions, it may still be possible to

perform implant placement.

In the case of diabetes, when there may be an in-

creased risk for infection and reduced healing, it is still

possible to perform implant surgery if the operation

is carried out under antibiotic cover, and provided that

the diabetic condition can be controlled via insulin

medication and/or via the diet (Adell 1992, Sennerby

& Rasmusson 2001). However, if unregulated diabetes

is present, implant surgery ought to be avoided.

Irradiation of the jaw may be another potential risk

factor for implant treatment, specifically if the jaw has

been exposed to irradiation over the level of 50 Gy (

Adamo & Szal 1979, Sennerby & Rasmusson 2001),

due to the risk of developing osteoradionecrosis.

However, it has been suggested that with the use of

hyperbaric oxygen treatment preceding implant ther-

apy, the failure rate can be reduced from around 60%

to about 5% (Granstrom 1992). Furthermore, reports

have indicated (Franzen et al. 1995) a lower risk for

failures if the preoperative irradiation has been less

than 40 Gy and carried out 2 years or more prior to the

implant placement. However, whenever treating irra-

diated patients, a specific follow-up protocol is

strongly recommended postoperatively, in order to

detect possible problems early.

Chemotherapy has been reported (Wolfaardt et al.

1996) to have little effect on the osseointegration of

implants if these have been inserted either before or

after the medication period. However, if the implants

are placed during the medication, or if chemotherapy

given in combination with irradiation, higher failure

rates have been indicated (Wolfaardt et al. 1996).

Smoking has been found to negatively affect the

long-term prognosis of osseointegration as well as the

marginal bone remodeling around implants (Bain &

Moy 1993, Lindqvist et al. 1996). Furthermore, it has

been reported that if the patient can stop smoking just

during healing, the implant survival rate may im-

prove (Bain 1996). Other abuse situations such as the

misuse of alcohol and/or drugs must be discussed

too; there are potential risks for complications in such

patients due to their higher propensity for bleeding,

infections and/or impaired healing. Co-operation is

also often lacking in affected persons, and therefore it

is recommended to refer them to a psychiatrist for

analysis to see if their misuse can be related to the

edentulous state, and if implant treatment can help

them to recover.

The cutaneous lesion lichen planus, especially the

erosive type, has in some single cases resulted in total

implant losses; the reason for this is not fully under-

stood at the present time. Changes in the capacity of

the epithelium to adhere to the titanium surface may

be the problem, as the losses seem to occur first after

some time of clinical function. However, there are also

lichen patients, mainly of the reticular type, in whom

implants have been inserted without creating any late

problems, which is why the condition cannot be re-

garded as an absolute contraindication for implant

treatment. Still, potential implant patients having the

disease should be informed that they might experi-

ence late implant failures if treated. It has to be men-

tioned, too, that conditions such as pemphigus, lupus

erythematosus, erythema multiforme, aphthous sto-

THE SURGICAL SITE •

matitis, herpes zoster and herpes labialis ought to be

handled with caution due to the lack of knowledge

regarding these disorders in combination with oral

implant placement.

Long-standing steroid medication has often been

connected with the gradual development of poor bone

quality, i.e. osteoporosis (Mori et al. 1997), which is

why the medication may also affect the establishment

and/or maintenance of implant osseointegration.

However, patients suffering from severe osteoporosis

have been treated with implants without developing

any negative results in the long term (Friberg et al.

2001, Sennerby & Rasmusson 2001). Therefore, steroid

medication/osteoporosis may not always have a de-

teriorating effect on implant treatment, at least not

when performed in edentulous jaws.

Local health and bone morphology

It is also important to examine the intraoral health

status of the soft and hard tissues as well as of the bone

morphology in future implant areas, i.e. to judge the

local operability.

This is mainly done using both clinical

and radiographic parameters.

The clinical assessments include inspection and

palpation of the edentulous areas considered for im-

plants, in order first of all to decide that no persisting

pathology is present. Via the palpation, a second esti-

mation of the available bone volume is performed,

and any defects should thereby be identified in order

to contemplate the need for augmentation procedures.

If during implant placement, minor fenestrations or

marginal dehiscences would occur, resulting in some

exposed threads, these can in general be left unat-

tended, as in follow-up studies no real adverse mu-

cosal reactions have been observed due to their pres-

ence (Lekholm et al. 1996), at least not as long as good

oral hygiene is provided for in the area. Consequently,

it does not seem necessary to perform bone augmen-

tations just because a few implant threads have be-

come exposed during implant insertion. However, if

the jaws contain defects of such a magnitude that the

implants cannot be placed in favorable positions with

out having major parts of their surfaces exposed, some

kind of guided bone regeneration or local bone graft-

ing procedure might be recommended (Buser et al.

1994, Deporter 2001).

Furthermore, the clinical examination must include

a judgment of the interarch and interdental spaces to

see that there is accessibility for the instruments as

well as for the future prosthetic construction. First of

all, the patient must be able to open up sufficiently to

allow access of the hand piece together with the drills.

When occluding, the minimum interarch distance

must be at least 5 mm to harbor the implant-supported

bridgework. The smallest interdental space that can

be accepted, without damaging the periodontal sup-

port of neighboring teeth, is around 7 mm, if implants

of about 4 mm in diameter are to be used. It is also

important to carefully study the jaw relation, as that

will have an influence on the implant direction (fur-

The 4 different groups of bone

quality

Fig. 37-1. Schematic drawings showing: (a) residual

jaw shape classification, and (b) jaw bone quality classi-

fication, according to Lekholm & Zarb (1985).

ther discussed below). The final step of the clinical

assessment is to take impressions for stone cast mod-

els which will later be used during the treatment

planning and for the possible manufacturing of surgi-

cal position and direction stents.

Based on the radiographic assessments performed

(

for techniques, see Chapter 36) it is possible to also

study the bone volume and the bone quality present

for implants, i.e. to elucidate the

radiographic operabil-

ity. A

grading into five groups depending on the re-

sorption rate (Fig. 37-1a) has been presented for the

residual jaw shape, together with a corresponding

grading into four groups (Fig. 37-1b) regarding the

jaw bone quality (Lekholm & Zarb 1985). Even if not

specifically adapted to the partially edentulous situ-

ation, these classifications may still be roughly ap-

plied also there. The base for the radiographic exami-

nations is mainly the panoramics and the intraoral

apical images from which, besides the shape and qual-

ity parameters, important anatomic landmarks sur-

rounding the edentulous area designated for implants

can be identified. Such structures are, for example, the

floor of sinusal and nasal cavities, incisive nerve, infe-

rior alveolar nerve, roots and apices of neighboring

teeth, and top of the alveolar crest. From the two-di-

mensional pictures it is also possible to get informa-

tion about the height available for implants, but three-

dimensional X-rays, tomographs mainly, are neces-

sary to study the bone volume. Consequently, no final

judgment of the operability can in critical situations

be based on just intraoral radiographs and orthopan-

tomograms, especially not if it is of crucial

importance

856 • CHAPTER 37

Fig. 37-2. Schematic drawings showing minimum bone

volume needed for standard implants of the Brane-

mark System.

to decide the bone volume present for implants. The

location of the inferior alveolar nerve must, for exam-

ple, be studied via tomography in order to avoid

inserting the implants in such a way that the sensation

of the lower lip and neighboring soft tissues is im-

paired. Tomography may also be used when the clini-

cal palpation has indicated that small bone volumes

are present in other areas, e.g. in the lateral or posterior

regions of the maxilla.

The minimum bone volume needed for a standard

Branemark implant (7 mm long and 3.75 mm in di-

ameter) is where the bone height is 7-9 mm and the

buccal-lingual width amounts to at least 4 mm (Fig.

37-2). When working above the inferior alveolar

nerve, a minimum height of 9-10 mm is needed for a

7 mm long implant. If less height is present, no stan-

dard implant can be placed without damaging the

nerve, as the drills extend about 2 mm deeper than the

length of the implant. Heights of 7-9 mm may only be

accepted if working in between the mental foraminae

or when working in the maxillae, where it is possible

to perforate the second cortex without damaging any

important structures.

From the obtained radiographs, it is possible to

discuss tentative locations of the implants as well as

the number and type of implants needed. This can be

done first after having identified where the minimum

bone volume is located in a distal direction (Fig. 37-3),

keeping in mind that each implant needs a gap dis-

tance of about 7 mm. However, no definite decision

regarding the number and type of implants that may

be used should be made preoperatively, but instead

should be made during stage one surgery and after

the implant sites have been finalized (see below).

Following the second assessments, the patient is

again informed about the clinical procedures, possible

risks, costs involved, treatment timing, etc., in order

Fig. 37-3. Schematic drawings indicating location of

minimum bone volume areas in distal directions, and

giving distances needed for various numbers of im-

plants. Arrows indicate prominence and apex of the

nearest tooth.

to make the final decision whether or not to go on with

the implant therapy suggested.

Summary: second assessment

The second level of clinical and radiographic exami-

nations is performed in order to evaluate the operabil-

ity of the patient from medical and anatomic stand-

points. No specific medical condition has so far been

detected that specifically excludes implant surgery.

Consequently, the same absolute and relative contra-

indications for treatment are present when inserting

implants as when performing other types of oral and

maxillofacial surgery. It is recommended when treat-

ing patients at risk that trained specialists work in

collaboration with the physicians responsible for the

treatment of such conditions when performing the

handling. The local health of edentulous areas consid-

ered for implants must be studied too, and no pathol-

ogy in the soft and hard tissues of the jaws can be

accepted at the time of implant placement. Radio-

graphic evaluations are necessary in order to identify

important landmarks, constituting the limits for the

operation, as well as the jaw shape and bone quality

areas considered for implants. Tomography is spe-

cifically needed when working in relation to the infe-

rior alveolar nerve, and when the clinical examination