Dental Implant diagnosis/ practice dentistry

Preoperative diagnosis for
implant patients
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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Contents
Introduction
Ideal properties of implants
Indications
General medical contraindications
Intraoral contraindications
Diagnostic methods for implant patients
Age limitations
Quantitative bone availability
Qualitative bone availability

Radiographic diagnosis
Periapical radiographs
Occlusal radiographs
Lateral cephalometric radiography
Panoramic radiographs
Digital intraoral radiography
Tomography- conventional & computed
3D reconstruction of CT data
Measurement of mucosal thickness
Diagnostic casts
Surgical guides
Conclusion

Introduction
Oral implantology / implant dentistry is the science
and discipline concerned with the diagnosis, design,
insertion, restoration and / or management of
alloplastic or autogenous oral structures to restore the
loss of contour, comfort, function, esthetics, speech
and / or health of partially or completely edentulous
patient.
Oral implant / dental implant is a biologic or
alloplastic biomaterial surgically inserted into soft or
hard tissues of the mouth for functional or cosmetic
problems.

Types of implants
1. Endosteal implants
Root form, blade form, Transosteal implants.
2. Subperiosteal implants
3. Endodontic stabiliser
4. Intramucosal inserts

Ideal properties of implants
Accordind to Branemark, 1969 & Brunski,
1988 :
1.Sterile
2.Made of highly biocompatible material such as
titanium
3.Inserted with atraumatic surgical technique
4.Placed with initial stability
5.Not functionally loaded during the healing
period of 4 to 6 months.

Indications
Patients with partially and fully edentulous
arches as well as patients with maxillofacial
deformities.
Patients who are unable to wear removable
dentures and have adequate bone for
replacement of dental implants.

General Medical Contraindications
Absolute Contraindications :
Systemic diseases such as developing cancer
and Aids.
Even HIV positive patients should not to be
considered.
Cardiac diseases – patients with heart valve
replacements and recent infarcts.
Deficient hemostasis and blood dyscrasias.
Disorders involving erythrocytes – Anemia.

Anticoagulant medication or any medication leading
to impaired hemostasis.
Psychological diseases may carry potential risks.
Uncontrolled infections such as of the respiratory tract
may negatively influence the surgical procedure or
may effect the treatment result.

Relative Contraindications
1. Diabetes.
2. Irradiation of the Jaws. - Specifically if the jaw has
been exposed to irradiation over the level of 50 Gy
(Sennerby & Rasmusson 2001)
Hyperbaric oxygen treatment preceding implant
therapy, the failure rate can be reduced from 60%
to about 5%
(Granstrom 1992)
Reports have indicated a lower risk for failures if
the pre-operative irradiation has been less than 40
Gy and carried out two years or more prior to the
implant placement.

3. Chemotherapy.
If the implants are placed during medication or if the
chemotherapy is given in combination with irradiation higher
failure rates have been indicated. (Wolfhardt et al 1996)
4. Smoking.
If the patient stops smoking during the healing period,
implants survival rate may improve. (Bain 1996)
5. Misuse of alcohol and drugs
6. Long standing steroid medication
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)

Intraoral Contraindications
No Pathologic conditions should be present.
All Oral lesions, including periodontal
inflammation should be treated.
Quantity and quality of soft tissue present in
the anticipated implant site is also important.
Unfavorable intermaxillary relationships.
Problematic occlusal and functional
relationships
Pathologic conditions in alveolar bone.

Pathologic alterations of Oral mucosa.
cutaneous lichen planus
Leukoplakia
Conditions such as pemphigus, lupus erythematosus,
aphthous stomatitis, erythema multiforme, herpes
zoster and herpes labialis should be handled with
caution.
Xerostomia- reduced salivary flow rate is a relative
contraindication for oral implantology. (Matukas
1998)
Macroglossia
Unrestored teeth and poor oral hygiene.

Diagnostic methods
A primary determinant for the long term success of
the endosteal implants is the best possible
anchorage in the bone.
Before attempting any treatment, 3 important
diagnostic procedures must be performed.
1. Analysis of appropriate and adequate radiographs.
2. Measurement of mucosal thickness.
3. Analysis of mounted study models.

Medical and dental histories.
Inspection of the oral cavity - provides information
about
Mucosal situation ( such as width of attached gingiva)
Possible existence of pathological changes
Extent of bone resorption
Intermaxillary relationship
Intraoral bidigital palpation - available bone mass
(width), contour of the alveolar process and thickness
of mucosa.

Functional analyses - examination of the
temporomandibular joints, muscles of mastication
and occlusal relationships.
If functional disturbances of the masticatory system
are present, recreate functional harmony by selective
grinding or fabrication of night guard.

Are there age limitations?
Dental Implants for older patients –
It is the biologic age and not the chronological age
that is important.
Life expectancy of at least 5 years from the time of
implantation.
Elderly patients are more susceptible to infections
and slow healing and therefore may constitute
potential risks for problems preoperatively and
postoperatively.
(Sennerby and Rasmusson 2001)

How early in life can dental implants be placed ?
Age does not seem to influence the establishment of
osseointegration as implants become anchored both in
young as well as elderly individuals.
(Thilander et. al 1994, Kondell et al 1998)
Serious consideration must be given to the possibility
of subsequent esthetic complications as the implants
may end up in Infra occlusion. (Oddman 1994)
Numerous authors have stated that implants should
not be placed before the 15th
or 16th
year of life.

Studies have shown continuation of facial growth into late
teens for women and into twenties for men.
(Bjork 1963, Hunter 1966)
Dental and skeletal maturation that must be considered when
implants are to be inserted in adolescence or growing
individuals. (Thilander et al 1994)
Skeletal age – determined from hand radiograph called the
biological clock.
Only in specific situations such as mainly due to psychological
reasons implants may be inserted even in younger individuals.
(Koch et al 1996)

Anatomic prerequisites
Amount of available bone –
Height
Width
Length
shape

Minimum bone volume needed - bone height is 9-10
mm and where the width is at least 5 mm.
Less height - drills extend about 2mm deeper than the
length of the implant, damaging the nerve.
Heights of 7-9mm may be accepted only when
working between the mental foramina or when
working in the maxilla.

The length of the bone or the minimum
distance required from axis to axis between
two implants is 7 mm.
Depending on the implant diameter this
corresponds to a minimum of 3-4mm distance
between the Implants.
The minimum distance between an implant
and a natural tooth should be 1.25mm.
(Ohrnell 1992)

Maxillary sinuses
As a general rule, the implants should be placed no
closer than 1-2mm from the base of the maxillary
sinus.
Implant crown relationship: The crown to root
implant ratio should be ideally less than 1 or close to
1:1 as possible.

Shape of the jaws :
Tooth extraction leads to a remodeling of the alveolar bone.
Mandible – resorption occurs lingually in premolar areas and
bucally in molar areas.
Maxilla – resorption occurs mainly on the buccal aspect.
This leads to changes in the intermaxillary relationships.
Because of the atrophy of the alveolar ridge, characteristic
shapes result from the resorptive process.

Classification of the residual jaw shape based
on the degree of resorption :
(Lekholm and Zarb, 1985)
Class A: Virtually intact alveolar ridge.
Class B: Minor resorption of the alveolar ridge.
Class C: Advanced resorption of the alveolar
ridge to the base of the dental arch.
Class D: Initial resorption of the base of the
dental arch.
Class E: External resorption of the base of the
dental arch.

Classification of edentulous and partially
edentulous arches - Misch & Judy (1987).
The basis for their classification is the amount
of bone available for endosteal implantation.
The system has been mainly modified for
cylinder & screw form implants.
The Kennedy system was extended to include
the osseous status of the edentulous jaw
segment destined to receive an implant.

Classification for edentulous arches:
Group A: Sufficient quantity of bone is
available for anchoring all types of endosteal
implants in the maxilla and mandible.
Group B: Smaller form of cylinder and screw
implants can be placed in both the maxilla and
mandible.
The prognosis however is also dependant on
the bone quality.
The number of abutments should be increased .

Group C: The amount of available bone is very less.
It may be necessary to relocate the inferior alveolar
nerve.
Ridge augmentation (or) sinus lift procedures may be
attempted.
Group D: In this case, the alveolar process as well as
portions of the basal bony structure are resorbed.
The placement of endosteal dental implants is not
possible in either jaw.

Classification of partially edentulous arches:
Class I & Class II :
Group A: The quantity of available bone is sufficient
implant bone bridges or bridge work extending from natural
teeth to implants.
Group B: The patients in this group exhibit a reduced bone
quality that is however still sufficient for the placement of
smaller screw and cylinder form implants.

CLASS I – II (A &B)www.indiandentalacademy.com

CLASS I-II (C &D)www.indiandentalacademy.com

CLASS III- IV(A&B)www.indiandentalacademy.com

CLASS III-IV (C&D)www.indiandentalacademy.com

Group C: Patients in this category do not have
adequate bone for placement of root form implants.
Exceptional cases of this type can be treated after
sinus lift procedures in the maxilla and after
relocation of inferior alveolar nerve in the mandible.
Group D: There is extremely advanced atrophy of
the alveolar bone.
The use of conventional removable dentures is
indicated,
If there is a risk of mandibular fracture during
implant placement autologous bone may be used for
ridge augmentation.

Class III & Class IV:
Group A:
Sufficient bone available for placement of root form implants.
Number of implants to be placed will depend upon the length
of the edentulous space
Group B:
Bone availability is still adequate .
Very long edentulous spaces can be restored using fixed
bridge work supported by implants.

Group C:
Bone quantity is not adequate for the placement of endosteal
implants in class III.
Maxillary sinus lifting or mandibular nerve relocation
procedures may be employed.
In class IV situations it is possible to use short screw and
cylinder form implants
Group D:
Advanced bone resorption & excludes the possibility of
endosteal implants.
Conventional partial dentures is indicated.
In special cases, ridge augmentation should be done.

Qualitative bone availability:
Bone quality or density reflects the hardness of the bone.
Estimation of the bone quality.
Classification of bone quality (Lekholm and Zarb 1985):
Class I: Jaw consists exclusively of homogenous compact bone.
Class II: Thick compact bone surrounds highly trabecular core.
Class III: Thin cortical bone surrounds highly trabecular core.
Class IV: Thin cortical bone surrounds loose spongy core.

Influence of bone quality on surgical implant placement:
In dense compact alveolar bone, the drilling of the implant bed
must be performed with intermittent up and down movements
using higher rpm, greater force application and the best
possible cooling.
In the loose spongy bone of maxilla surgical bed preparation
must be performed with extreme care and without application
of force.
Jaffin et .al(1991) reported that failure rates were as much as
50% when implants were placed into softer bone or bone of
quality Class IV.

When a tooth is lost, the alveolar bone starts to loose its
dimension and density.
The spacing of trabeculae in relation to variable forces of
mastication was discussed by MacMillan in 1926.
Levels of bone density are directly related to stress.
The greater the physiological stress, the denser is the bone.
When a tooth is lost, stresses are not transmitted to the
alveolar process.
• The longer time span the alveolar bone is edentulous, lesser
the trabeculae that are present.

The thickness of the bone as well as the internal osseous
structure varies in different regions of the maxilla and
mandible.
These structural differences can influence treatment planning
and clinical success with dental implants as they effect the
anchoring of endosteal implants.
Misch 1990, acknowledged this fact in his classification of four
degrees of bone quality.
Each of these four classes is topographically based and
described from the clinical point of view with regard to its
importance and the problem it may present in Implantology.

Classification of bone density (Misch 1990) :
D1 - Thick, dense compact bone
Site: Anterior segment of the atrophic edentulous
mandible
Thick lateral aspects of anterior mandible
Advantages:
1. Provides good primary stability for the implants.
2. More implant bone interface with a percentage of
approximately 80%.
3. Because of this use of shorter implants is possible.
4. It is highly mineralized and able to withstand greater loads.

5. Ensures excellent bone stability even after trauma. A
a result implants can be removed and re-inserted if
necessary during the surgical procedure.
6. Threaded Titanium implants when placed into D1
bone, proved to be very predictable over long term
period with a success rate of above 94%.
(Adell 1981, Babbush 1986)

Disadvantages:
1. Low Vascular supply compared with other bone
categories and healing phase is longer.
2. Bone height is often short and so crown to implant ratio is
increased .
3. Difficult implant bed preparation and may require greater
burr revolutions ( up to 2000 rpm) to obtain adequate
depth penetration and bone is easily over heated.
Healing time is 5 months and immediate loading can be
done

D2 Bone: Thick porous compact bone with coarse
trabecular core.
Site: Anterior and posterior segment of the mandible.
Anterior maxillary segment ( palatal aspect).
Advantages:
1. Provides immediate stability and long term survival.
2. Osseointegration is very predictable.
3. The intrabony bleeding helps control over heating during
preparation.
4. The percentage of bone at bone implant interface is 70%.
5. The excellent blood supply and rigid initial fixation permit
adequate bone healing within 4 months.
 Progressive loading is important.

D3 Bone: Thin porous compact bone with coarse trabecular
core.
Site: Anterior (Facial aspect) and posterior segments of the
maxilla, posterior segments of the mandible,
Condition following osteoplasty of D2 bone
Advantages:
Good blood supply.
Disadvantages
1. Difficult implant bed preparation (widening). The surgeon
must be extremely careful to avoid lateral perforations of the
cortical bone especially on the labial portion of the maxilla.

2. The rotations of the drill may have to be reduced to less than
1000 rpm to improve the tactile sense of the bone
preparation.
3. If the lingual and apical cortical bone are not engaged at the
time of implant placement, less than 50% of the implant
surface may actually contact bone. So optimum usage of
available bone is necessary.
4. Because of reduced implant bone interface, more number of
implants may be necessary.
Time period of healing - 6 months.
Extended gradual loading should be done.

D4 Bone: Fine trabecular bone
Site: Maxillary tuberosity,
condition following osteoplasty of D3 Bone.
Advantages:
None.
Disadvantages:
1. Has very little bone density and little or no crestal cortical
bone.
2. Difficult implant bed preparation. The bone site is easily
distorted resulting in reduced initial stability of the implant.

3. Reduced implant bone interface, so optimum usage of
available bone is necessary.
4. Number of implants to be placed is increased.
5. Obtaining rigid fixation for the implant is very difficult.
A larger diameter implant offers greater surface area for
support, compresses the fine trabecular bone for greater
initial rigidity and has a greater chance to engage the lateral
regions of cortical bone for support.
Up to 8 months of undisturbed healing is suggested.

Progressive bone loading: (Misch)
According to this theory, bone possess the capacity
for functional adaptation that is it responds to changes
in loading with a remodeling of internal structure.
Such adaptation will achieve an optimum
biomechanical situation as long as the loading forces
are not excessive. (Wolf’s Law)

From a practical and clinical point of view,
progressive bone loading is a process where by
intervals of time are inserted intentionally between
the individual prosthodontic treatment steps.
The length of intervals is related to bone quality.
For eg: if the initial situation presents bone of
quality class D4, a waiting time of 4 weeks is
recommended between the individual treatment steps.
Thus the peri implant bone is given a correspondingly
longer period of time for functional adaptation based
on its initial stability.

Radiographic diagnosis
Peri apical radiographs:
Technique of choice is the paralleling technique.
Intra oral radiographs provide valuable information
concerning -
1. The mesiodistal dimension of the region in which implants
are considered.
2. Potentially available bone height
3. To determine whether implant treatment can be performed
after bone augmentation, if available bone volume is less.

Disadvantages :
1. It cannot provide information about the
buccolingual dimension of the bone and whether
implant treatment can be performed.
2. The use of Radio opaque millimeter lines on
periapical radiographs though helpful does not
permit true assessment of bone quantity.
There are many disadvantages to this technique.
The millimeter grid is applied to the x-ray film and
not to the edentulous ridge, as a result the
millimeter lines appear 1mm apart regardless of
foreshortening or elongation of the image.

3. Limited value in determining bone density as a
lateral cortical plates prevent accurate
interpretation.
4. Little use in depicting the spatial relationship
between the critical structures and the proposed
implant site.

Occlusal radiograph:
Can provide information about the cortical and
cancellous bone structure in edentulous jaw segments
i.e., bone quality.
It provides the 3rd
dimension in combination with
other radiographs to clarify the existence and
localization of root tips, cysts, tumors etc.
The disadvantage is that it shows the widest width of
the bone (at the base), rather than the width at the
crest where diagnostic information is needed most.

Panoramic radiograph:
Depicts the body of mandible , maxilla and lower half
of maxillary sinuses in a single image.
Most utilized diagnostic modality in implant dentistry.
However, for pretreatment implant imaging it is not
the most diagnostic as it produces magnification.

Advantages :
1. The opposing landmarks are easily identified.
2. The vertical height of bone can be assessed.
3. Procedure is performed with convenience and speed.
4. Gross anatomy of the jaws and any related
pathologic findings can be evaluated.

Disadvantages :
1. Produces vertical magnification of up to 10 % and
horizontal magnification of up to 20 %.
2. Does not demonstrate bone quality.
3. Does not provide spatial relationship between the
critical structures and the implant site.

Overcoming the shortcomings –
Use of diagnostic templates that have 5mm ball
bearings or wires incorporated around the curvature of
the dental arch when the radiograph is taken can
enable the clinician to determine the amounts of
magnification in the radiograph.
These metal spheres appear radio opaque in the film.
Because their diameter is known, it is easy to calculate
the true bone height.
(Spiekermann 1987)

An example for calculation of the posterior region :
true diameter of the metal spheres (D-real) – 5mm.
Consider its diameter measured on the radiograph
(D-PR) – 6mm
Consider the distance between the alveolar crest and the
mandibular canal measured on the radiograph
(A-PR) – 18mm
To determine the real distance between the alveolar crest
and the mandibular canal (A-real) use the following
equation :-
A-real = A-PR x (D-real) / (D-PR) = 18 x 5/6 = 15mm.

Zone of safety:
A zone of safety for placement of posterior
mandibular endosteal implants was established
by Misch in 1980 by evaluation of 530
consecutive panoramic radiographs of partially
edentulous patients and further confirmed by
Crawford in 1989.
Defined as an area within the bone in which
implants may be placed safely without fear of
impingement on the neurovascular bundle.
Studies indicated radiographic prevalence of
the mandibular canal below the zone of safety.

A Zone of safety was observed in 100% of the
radiographs mesial to the middle of mandibular 1st
molar.
In the region of distal half of the first molar – 97.5%
In the region of mesial half of the second molar –
43%
In the region of distal half of second molar- 5.5%
The most common position of the canal anterior to
the mid first molar region was 2mm or more apical to
the zone of safety representing a gray zone of
additional surgical safety.

Lateral cephalometric radiograph :
Demonstrates a cross sectional image of the alveolus of both
the mandible and the maxilla in the midsagittal plane.
Is more accurate for bone quantity determinations unlike
panoramic or periapical images.
Magnification ranges from 6% to 15%.
Provides information on bone availability in the region of
premaxilla and symphysis of the mandible.

Helps to determine the width of the bone in the symphysis
region and the relationship between the buccal cortex and the
roots of anterior teeth before harvesting bone for ridge
augmentation.
Demonstrates the spatial relationship between the implant site
and critical structures such as the floor of the nasal cavity,
anterior recess of the maxillary sinus and nasopalatine canal.

It can also help to evaluate a loss of vertical
dimension, skeletal arch inter relationship anterior
crown-implant ratio, anterior tooth position in the
prosthesis etc.
As a result cephalometric radiographs are a useful
tool for the development of implant treatment plan
especially for the completely edentulous patient.
The disadvantage is that it does not demonstrate bone
quality and demonstrates only a cross sectional image
of the alveolus.

Digital Intraoral radiography:
Precludes the problems pertaining to dark room procedures.
Lower radiation dose than for the film.
Digital images can be altered to achieve task specific image
characteristics.
For e.g.: density and contrast can be lowered for evaluations of
the marginal bone and increased for the evaluation of implant
components.
Pseudo coloring which is to assign different colors to different
gray level values is helpful in evaluating the bone surrounding
the implant.

Tomography
Conventional Tomography :
It is a technique in which a slice or a section of a given body
structure is made in a predetermined plane.
It is useful for revealing the quality and quantity of bone at
any desired implant location by creating a cross sectional
representation of the jaws.
Planes other than the sections to be projected are blurred.

With the use of conventional tomography, clinician
can accurately evaluate the cortical and trabecular
bone along with vital structures in the region destined
for implant placement.
It also enables to determine the spatial relationship
between the critical structures and the implant site.
Magnification varies from 10% to 30%.

To achieve the desired cross section at specific sites
the patient wears a diagnostic prosthesis which
incorporates ball bearings.
With the use of these metal markers which are seen in
the cross section it is possible to display the bone
precisely in cross section where implants are planned.
The average radiation exposure during a tomographic
series is less than that for a full mouth radiographic
survey
(Richards 1981).

Lingual concavities in the jaw such as submandibular
gland fossa within which a branch from the facial
artery can be found can be detected on the image.
Failure to take account of this cavity can lead to
lingual perforation of the mandible during surgery and
sometimes can damage the artery and the subsequent
bleeding can be life threatening.
This important information about lingual concavity or
lingual inclination can be obtained only through cross
sectional tomography.

This not only prevents serious complications but also provides
information about where sufficient amount of bone can be
found in which the apical part of the implant can be anchored.
Tomographic images which includes the crowns of the teeth in
the maxilla also provide the guidance for an appropriate
buccolingual placement and inclination of the mandibular
implant.
In cases where the mesiodistal distance between the incisive
canal and the intended implant site appears too small in an
Intraoral radiograph, tomography can be used to determine
whether sufficient amount of bone is present buccal to the
canal.

Computed tomography
First introduced to medical field by Hounsfield in 1972.
CT is a digital imaging technique that makes use of a special
software and planes of section in all three dimensions of space
can be produced.
CT enables differentiation of both hard tissues and soft tissues
without performing an invasive procedure such as injection of
contrast media.
Tomographic sections produced are of best image quality due
to less disturbing ghost shadows from adjacent structures.

CT analysis of the jaws is very expensive. Therefore
the technique is used only if additional diagnostic
information is necessary because of anatomic
peculiarities or diagnostic difficulties.
The Images produced are spaced 1mm apart.
CT enables identification of disease, identification of
critical structures at the proposed regions and
determination of bone quantity, quality and
determination of the position and orientation of dental
implants.

Evaluation of Misch’s bone density using CT
number or Hounsfield unit:
Each CT image produced has 2,60,000 pixels
and each pixel has a CT number or
Hounsfield unit (HU) related to the density
of the tissues within the pixel
Higher the CT number, denser is the tissue.
D1 : >1250 HU
D2: 850 HU - 1250 HU
D3: 350 HU – 850 HU
D4: <400 HU

With these values the bone density in different areas
can be determined.
A diagnostic template is used for obtaining the image
at the planned site.
Indicators made of radio opaque acrylic are
incorporated into diagnostic template at sites where an
implant insertion is planned.
Radiologist uses these aids to produce images of the
available bone at that site in all three planes.

Disadvantages:
1. Causes more exposure than conventional
tomography
2. Images may not be of true size and may require
compensation for magnification

3-D reconstruction from CT data :
3-dimensional anatomical models of the jaws and
skulls can be fabricated using CT data.
Such models permit direct preoperative
measurements as well as precise determinations of
the spatial relationships between mandible and
maxilla.

In the craniomaxillo facial region, the fabrication of such
models requires up to 70 layers with layer interval of 1 or 2
mm.
From the available CT data a model can be created from a solid
block of material by means of a computer guided milling
device or with two laser beams. (stereolithography).
In the future these type of 3-D reconstruction may become a
mandatory aid for pre-operative planning in dental implant
cases in situations where difficulties are anticipated.

Advantages:
1. Precise evaluation of the actual osseous condition.
2. Surgical therapy can be precisely planned
preoperatively for determination of the most
favorable implant axis orientation.
3. Helpful for evaluating the relationship of mandible
to maxilla.

Measurement of Mucosal thickness:
A very simple method to evaluate the width of
available bone.
Mucosal thickness is measured using needles with the
patient anaesthetized.
Technique is indicated primarily in the maxilla
The needle is inserted through the mucosa to the bone
surface and a rubber stop marks the position of the
depth.

By subtracting the sum of facial and palatal
mucosal thicknesses from the width of the
entire alveolar ridge, effective bone width can
be calculated (Spiekermann 1987).
A sectioned plaster model of the arch is
fabricated to visualize the mucosal thickness,
the individual measurements are carried over on
to the cut plaster surface.
This provides the good indication of the shape
and width of the bony alveolar process.

Diagnostic casts or study model analysis
For edentulous patients
Study models of edentulous patients mounted in an adjustable
articulator using bite registration enables to determine the
spatial relationship of the mandible to maxilla or inter
maxillary relationship.
A jaw relation has to be studied as it will have an influence on
implant direction.
With increasing resorption of the alveolar process, a greater
divergence between the maxillary and mandibular dental
arches occurs in the vestibulo-oral dimension.

This can manifest in the posterior segments as a cross
bite or anteriorly as a prognathism.
Also because of an increase in inter alveolar distance,
rotation of the mandible around the inter condylar
axis occurs resulting in a combined upward and
forward displacement of the occlusal plane.
With the help of study models the dentist will not
only be able to ascertain the vertical relationships, but
also the saggital relations of the mandible to maxilla
(Angles class I-III)

Because of the varying degrees of alveolar resorption
in the maxilla and mandible, an unfavorable situation
may exist for implant and prosthetic treatment.
For eg: one arch may exhibit a U shaped while the
opposing arch has a V shape.
The placement and orientation of implants in such
cases must be precisely planned to compensate for
these anatomic peculiarities.

There may be situations where the inter arch distance
is not adequate for implant prosthetic restorations.
Many times in such cases the alveolar processes are
narrow and pointed and therefore unfavorable for
implant placement.
Then it is necessary to confirm whether an osteoplasty
can be performed to improve the situation either before
or during the surgery to place the implants.

Edentulous patients with pronounced Angle class II
or III relationships must be viewed as difficult cases
for implant prosthetic procedures.
In such cases fixed bridge work such as utilizing
cantilevered distal extensions is generally to be
avoided and instead over denture treatment is
preferable.
In extreme cases, dental implants should be avoided
altogether

Edentulous jaws that exhibit the Angle class II
relationship (retrognathia) often have advanced
resorption of anterior segment of the mandible with
resulting in pronounced horizontal and vertical
anterior overbite.
In such cases difficulties associated with esthetics
and function are frequently encountered when
attempting to relate the maxillary to mandibular
anterior teeth

In cases that exhibit Angle Class III relationship
(prognathism) one frequently observes resorption of
the anterior segment of the maxillary alveolar
process due to excessive loading.
If an implant retained or implant borne prosthesis is
seated in the mandible this problem in maxilla is
further enhanced.
The differential planning for implant prosthetic
therapy should include a discussion of surgically
repositioning the mandible distally or repositioning
the maxilla in the anterior direction.

If the Angle Class III situation is to be maintained
then the implants will have to be placed with a lingual
orientation for prosthetic reasons.
Tilting the implants lingually or positioning them
bodily towards the lingual can lead to functional
difficulties as the tongue space is impinged upon.
Sometimes an implant emergence profile located in
the anterior area of the floor of the mouth in mobile
mucosa may result.

Study model analysis – partially edentulous patients
The goal of the planning phase is to recreate a balance
between application of force and the ability of implant bone
prosthetic replacements to receive and distribute these forces.
Basic requirements to fulfill this goals include-
Ensuring the most favorable distribution of forces in the bone
by axial loading of the implants.
Viewed from the transverse dimension the axes of the implants
should be oriented towards the cusps of natural teeth in the
opposing arch or towards the middle of alveolar crest, if the
opposing arch is edentulous.

In the saggital plane, the implant axes should
parallel the axes of adjacent natural teeth.
The number of implants to be placed depends on
the surface area of the tooth roots to be replaced.

An analysis of the study models will also clarify
the clinical length of the prosthetic crown that will
be supported by the implant. (Crown-implant ratio)
If the height of the implant borne crown and bridge
is great, every effort should be made to increase
the implant bone contact surface area by either
increasing the number or length of the implants.

If the inter arch distance is very small, it will
necessitate excessively short implant crowns.
It may be possible to adjust the teeth in opposing
arch to increase the inter occlusal distance.

Surgical guides
Partially edentulous patients:
Helps the dentist to position the implants
appropriately from the prosthetic point of view.
In patients with some remaining teeth, these stents can
be fabricated in the form of clasp retained partial
dentures or modified bridge constructions.
Holes are drilled into the acrylic at appropriate
locations with proper axis orientation.

Surgical guides that cover the incisal or occlusal
surfaces of the remaining teeth have the advantage
that they remain secure as the pilot hole is drilled
during surgery.
The ideal implant position and axis orientation are
determined during analysis of the study models.
The holes in the acrylic that guide the pilot drills are
ideally located in the center of the occlusal surface of
the artificial acrylic teeth.

The acrylic stent can be hollowed out from the buccal
or lingual side – a good overview of the surgical field
is insured.
When implants are inserted without guidance (free
hand) the danger exists that the final restoration will
be less than optimal in one or more of the categories
such as function, occlusion, esthetics and hygiene.
In cases where the axes orientation determined by the
prosthodontist cannot be followed accurately the
surgical guide will nevertheless serve to orient the
surgeon and is always an important aid as the
implants are placed.

Edentulous patients
Surgical guide is not necessary if the treatment plan
involves a complete denture retained by 2-4 implants
in the anterior segment of the edentulous maxilla or
mandible.
But if the therapy involves rigid screw fixation
prosthesis then the use of a surgical guide is required
to achieve the best possible treatment result.
The guide is prepared from clear acrylic. It could
even be the patient’s own complete denture.

In the jaw segments, where the implants are to
be placed the guide must be either completely
relieved or have holes drilled in it at the proper
locations.
The guide can be relieved from either the
buccal aspect or palatal and lingual aspects.
Maxillary guides relieved from the palatal
aspect and mandibular guides relieved from the
lingual aspects offer practical advantages with
corresponding incisions.

In this way the surgeon would be able to visualize the course of
the dental arch and can also appreciate the inclination of the
implant axes, which should be parallel to the buccal surfaces of
the anterior and posterior teeth as much as possible.
The occlusal surfaces of the molars should be retained to
permit intraoperative checks of the guide position in centric
occlusion.
Guides must be disinfected in appropriate solutions before
clinical use.

Conclusion
A comprehensive clinical examination must precede
the radiographic examination. Radiographic
examination should be done with techniques yielding
the lowest possible doses.
Failure to diagnose and treat the pathologic
conditions in and around the remaining teeth can
seriously compromise the results of implant therapy.
When panoramic techniques are used, supplementary
intra oral radiographs should always be obtained
when horizontal distances are critical.

In many single implant cases sufficient
information about the width and height of the
available bone volume can be obtained from a
clinical examination supplemented by intra
oral radiography.
Tomography is recommended for the best
estimation of height and width of implant site
when patient history, clinical examination and
intra oral radiographs lead to a suspicion of
narrow width of the jaw bone.
Is also recommended when an implant is to be
placed above the mandibular canal.

Based on the clinical and radio graphical data
collected, a final discussion regarding what is
expected and possible to perform is carried out.
The prosthodontist/restorative dentist conveys to the
surgeon the optimal therapy for the patient so that a
team approach to the treatment planning can be
established.
In order to create an acceptable function and esthetics,
the best position and direction of the implants must be
identified together with the number and type of
implants that can be inserted.

A wax up may then be fabricated in order to
study the suggested treatment result and to
show the patient the presumed outcome.
Based on the wax up a surgical stent may be
fabricated, the design of which should be
simple and possible to sterilize.
After obtaining the consent of the patient, the
implant insertion can finally be executed.

Bibliography
Contemporary Implant Dentistry.
Carl E. Misch; 2nd
edition.
Implantology – Hubertus Spiekermann
Atlas of Oral Implantology.
A. Norman Cranin; 2nd
edition
Clinical Periodontology and Implant Dentistry.
Jan Lindhe; 4th
edition.
Carranza’s Clinical Periodontology.
Takei, Newman, Carranza; 9th
edition.

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