treatment planning for implant and force factor related to patient conditions

1. Treatment Planning: Force Factors
Related to Patient Conditions
Presented By :-
Dr.Mayank Aggarwal

2. Content
• Introduction
• Normal Bite Force
• Parafunction
• Crown Height Space
• Masticatory Dynamics
• Arch Positions
• Nature Of Opposing arch

3. INTRODUCTION
• Biomechanical stress is a significant risk factor in implant dentistry.
• Its magnitude is directly related to force. As a result, an increase in
any dental force factor magnifies the risk of stress-related
complications.
• Different patient conditions place different amounts of force in
magnitude, duration, type, and direction.
• In addition, several factors may multiply or increase the effect of
these other conditions.

5. NORMAL BITE FORCE
• The greatest natural forces exerted against teeth, and thus against
implants, occur during mastication.
• These forces are primarily perpendicular to the occlusal plane in the
posterior regions.
• They are of short duration, occur only during brief periods of the
day, ranges between 5 to 44lbs.
• The actual time during which chewing forces are applied on the
teeth is about 9 minutes each day.
• The perioral musculature and tongue exert a more constant, yet
lighter horizontal force on the teeth or on implants.

7. PARAFUNCTION
• Parafunctional forces on teeth or implants are characterized by
repeated or sustained occlusion .
• Recognized as harmful to the stomatognathic system.
• These forces are also most damaging when applied to implant
prostheses.
• These parafunctional forces are the most common cause of both
early and late implant failure.

8. • Nadler has classified the causes of parafunctional or non-functional
tooth contact into the following six categories.
1. Local :- tooth form or occlusion & soft tissue changes .
2. Systemic :- cerebral palsy, epilepsy, and drug-related dyskinesia.
3. Psychological :- Stress & Anxiety
4. Occupational:- Dentists, athletes, and precision workers, as well as
the seamstress or musician
5. Involuntary :- Provokes bracing of the jaws.
6. Voluntary:- Include chewing gum or pencils & Pipe smoking.

9. Bruxism
• Bruxism is the most common oral habit.
• Bruxism primarily concerns the horizontal, non-functional grinding
of teeth.
• The forces involved are in significant excess of normal physiologic
masticatory loads.
• Sleep clinic studies have evaluated nocturnal bruxism and found
approximately 10% of those observed had obvious movement of
the mandible with occlusal contacts.
• The maximum biting force of bruxing patients is greater than
average.

10. DIAGNOSIS
SYMPTOMS
• May include repeated
headaches.
• History of fractured teeth
or restorations.
• Repeated un-cemented
restorations.
• jaw discomfort upon
awakening.
SIGNS
• Increase in size of the
temporal and masseter
muscles.
• Deviation of the lower jaw on
opening.
• Limited occlusal opening.
• Increased mobility of teeth.
• Cervical abfraction of teeth.

11. • The easiest way to diagnosis bruxism is tooth wear and on the
basis of tooth wear bruxism can be classified into
• Absent
• Mild
• Moderate
• Severe

12. • Posterior wear patterns are more difficult to manage, because this
usually is related to a loss of anterior guidance in excursions.
• once the posterior teeth contact in excursive jaw positions, greater
forces are generated.
• The masseter and temporalis muscles contract when posterior
teeth contact. With incisal guidance and an absence of posterior
contact, two thirds of these muscles do not contract.
• This lead to dramatic loss in bite force.
• Bruxing patients often repeat mandibular movements, which are
different from border movements of the mandible and are in one
particular direction.
• This result in wear of teeth in a particular direction and create a
engram pattern.

13. Guideline to restore reduce crown height
1. Determine the position of the maxillary incisor edge of the anterior
teeth. They may be acceptable (if eruption occurred as they wore) or
need greater coronal length to correct related incisal wear.
2. Determine the desired occlusal vertical dimension.
3. Evaluate and restore the position of the lower anterior teeth where
necessary.
4. The posterior plane of occlusion s then determined. This may be
accomplished by using first the maxillary arch or the posterior
mandibular arch.

14. Fatigue Fractures
• The increase in duration of the force is a considerable problem.
• A bruxing patient is at greater risk of fatigue fractures for two reasons.
– The magnitude of the forces increases over time as the muscles become
stronger.
– the number of cycles increase on the prosthetic components.

15. Occlusal Guards
• The cause of bruxism is multifactorial and may include occlusal
disharmony.
• When an implant reconstruction is considered in a bruxing patient,
occlusal analysis is warranted.
• Premature and posterior contacts during mandibular excursions
increase stress conditions.
• An elimination of eccentric contacts may allow recovery of
periodontal ligament health and muscle activity within 1 to 4 weeks.
• A night guard can be a useful diagnostic tool to evaluate the influence
of occlusal disharmony on nocturnal bruxism.

16. •A night guard can be a useful diagnostic tool to evaluate the influence of
occlusal disharmony on nocturnal bruxism.
•The Michigan night guard exhibits even occlusal contacts around the arch in
centric relation occlusion and provides posterior disocclusion with anterior
guidance in all excursions of the mandible.
•This device may be fabricated with 0.5 to 1 mm colored acrylic resin on the
occlusal surface.
•After 4 weeks of nocturnal wear, if the patient wears this device for an
additional month or more, the influence of occlusion on the bruxism may be
directly observed.

17. Treatment Planning
• The implant treatment plan is modified primarily in two ways when
implants are inserted in the posterior region.
1. Additional implants that are wider in diameter are one method used
to reduce the overload risk.
2. Anterior teeth may be modified to recreate the proper incisal guidance
and avoid posterior interferences during excursions.
• The elimination of posterior lateral occlusal contacts during excursive
movements is recommended.
• This is beneficial in two aspects:
– the elimination of posterior contacts diminishes the negative effect of
angled forces during bruxism
– the absence of posterior contacts will stimulates less fibres of temporalis &
masseter muscle which decrease the applied force on ant implant system
by 2/3rd.

18. Clenching
• Clenching is a habit that generates a constant force exerted from one
occlusal surface to the other without any lateral movement.
• The jaw may be positioned in any direction before the static load;
therefore a bruxing and clenching combination may exist.
• The clench position most often is in the same repeated position.

19. Diagnosis
• The signs for clenching are often less obvious.
• Wearing of the teeth is usually not evident; therefore clenching often
escapes notice during the intraoral examination.
• When a patient has a dental history of muscle tenderness upon
awakening or tooth sensitivity to cold, parafunction is strongly
suspected.
• In the absence of tooth wear, clenching is the prime suspect.
• A physical examination for the implant candidate should include
palpation of the muscles of mastication.
• The lateral pterygoid muscle will be overused by the pt of bruxism &
Clinching.
• The ipsilateral medial pterygoid muscle provides more reliable
information

20. • Deviation to one side during opening
indicates a muscle imbalance on the
same side.
• Increased mobility of teeth may be an
indication of a force beyond physiologic
limits, bone loss, or their combination.
• Cervical erosion is primarily a sign of
parafunctional clenching or bruxism In
the past.
• Other signs of enamel or occlusal
material fatigue encountered in bruxing
or clenching patients include
– occlusal invaginations or pits, stress lines
in enamel,
– stress lines in alloy restorations or acrylic
(lines of Luder), and material fracture
• A common clinical finding of clenching is
a scalloped border of the tongue.

21. Fatigue Fractures
• The increase in force magnitude and duration is a significant problem.
• The clenching patient may suffer from a phenomenon called creep.
• Creep occurs in a material when an increasing deformation is expressed as a
function of time, when subjected to a constant load.

22. Prosthetic Considerations
• The night guard can be relieved around
an intermediate implant, and the teeth
bear the entire load.
• In a full-arch or quadrant implant
restoration, the night guard provides a
biomechanical advantage to reduce the
impact of the force during clenching.
• A removable partial denture over a
healing implant is especially of concern.
The acrylic between the soft tissue–
borne region and metal substructure is
usually less than 1 mm thick.
• 6-mm– diameter hole through the
metal substructure should be prepared.

23. • The prosthesis may be designed to improve the distribution of stress
throughout the implant system with centric vertical contacts aligned with
the long axis of the implant whenever possible.
• Narrow posterior occlusal tables to prevent inadvertent lateral forces and to
decrease the occlusal forces are beneficial.
• Enamoplasty of the cusp tips of the opposing natural teeth is indicated to
help improve the direction of vertical forces.

25. TONGUE THRUST AND SIZE
• Parafunctional tongue thrust is the unnatural force of the tongue against the
teeth during swallowing.
• A force of approximately 41 to 709 g/cm2 on the anterior and lateral areas of
the palate has been recorded during swallowing.
• Six different types of tongue thrust have been identified; anterior,
intermediate, posterior, and either unilateral or bilateral may be found
• The tongue thrust applied less intensity of forces and more in horizontal
direction
• They exert forces on permucosal site of implant which tend to increase the
event of incision line opening and may compromise the soft and hard tissue.
• Tongue thrust also contribute to loosening of tooth and will ultimately inc the
occlusal load on the implant.

26. Diagnosis
• Anterior tongue thrust evaluate by holding the tongue downwards and
asked patient to swallow water but due to abnormal tongue position the
patient is unable to swallow water without closing the lip.
• A posterior tongue thrust is evaluated by retracting one cheek at a time
away from the posterior teeth/ edentulous region with a mirror, injecting
water into the mouth with a water syringe, and asking the patient to
swallow.
• Deglutition may also be accompanied by pressure against the instrument
and confirms a lateral force.

27. Prosthetic consideration
•The posterior tongue thrust may occur in
patients wearing a maxillary denture opposing a
Kennedy Class 1 mandibular arch, without a
mandibular prosthesis replacing the posterior
teeth.
•A potential prosthetic complication for a patient
with a lateral tongue thrust is the complaint of
inadequate room for the tongue once the
mandibular implants are restored.
•The lingual contour of mandibular tooth should
follow the curve of Wilson and proper horizontal
overjet.
•The placement of implants and prosthetic teeth
in such a patient results in an increase in lateral
force, which may be continuous.

28. CROWN HEIGHT SPACE
• A dimension of only one arch does not
have a defined term in prosthetics;
therefore Misch proposed the term
crown height space (CHS).
• It is measured from the crest of the
bone to the plane of occlusion in the
posterior region and incisal edge of the
arch in question in the anterior region.
• The ideal CHS needed for a fixed
implant prosthesis should range
between 8 and 12 mm.
• Removable prostheses often require a
CHS greater than 12 mm

30. Biomechanics Consequences of Excessive Crown
Height Space

31. Excessive Crown Height Space
• CHS greater than 15 mm is excessive.
• It is primarily the result of the vertical loss of alveolar bone from long-
term edentulism.
• Other causes may include genetics, trauma, and implant failure
• .Treatment of excessive CHS before implant placement includes
orthodontic and surgical methods.
• Orthodontics in partially edentulous patients is the method of choice as
other surgical or prosthetic methods are usually more costly and have
greater risks of complications.
• Several surgical techniques may also be considered, including block onlays
bone grafts, particulate bone grafts with titanium mesh or barrier
membranes, interposition bone grafts, and distraction osteogenesis.

32. • Misch presented a unique approach
combining vertical distraction and
horizontal onlays bone grafting to
reconstruct the deficiency three
dimensionally.
• Osseous distraction is performed first to
vertically increase the ridge and expand
the soft tissue volume.
• Secondarily an onlay bone graft is used to
complete the repair of the defect.
• Surgical augmentation of the residual
ridge height will reduce the CHS and
improve implant biomechanics.
• Augmentation will allow the placement of
wider implant and increase surface area
and improved bone implant contact.
• Using gingival colored prosthetic materials
on fixed restorations or changing the
prosthetic design to a removable
restoration should often be considered
when restoring excessive CHS.

33. TREATMENT PLANNING FOR
EXCESSIVE CROWN HEIGHT SPACE
• Because CHS is a considerable force magnifier various methods are adopted
to decrease the stress:
1. Shorten cantilever length.
2. Minimize offset loads to the buccal or lingual.
3. Increase the number of implants.
4. Increase the diameters of implants.
5. Design implants to maximize the surface area of implants.
6. Fabricate removable restorations that are less retentive and incorporate soft
tissue support.
7. Remove the removable restoration during sleeping hours to reduce the
noxious effects of nocturnal parafunction.
8. Splint implants together, whether they support a fixed or removable
prosthesis.
9. Narrow occlusal table (buccal-lingually).
10. Minimal cusp height on prosthesis.
11. Occlusal contacts centred over implants and eliminated over cantilevers

34. Masticatory Dynamics (Patient Size, Gender,
Age, and Skeletal Position)
• Masticatory muscle dynamics are responsible for the amount of force exerted
on the implant system.
• The size of the patient can influence the amount of bite force.
– Large athletic Patient can developed a greater bite force as compared to
slim or weak built patient.
• Sex of patient :-
– In general the forces recorded in women are approximately 20 lb less than
those in men.
– In a clinical report by van Steenberghe et al.,85 partially edentulous men
have a 13% implant failure rate compared with 77% for women.
• Age of patient :
– In a report by Wyatt and Zarb,86 first-year radiograph bone loss was
positively correlated with male sex, younger age, and implants supporting a
distal extension prosthesis.
– Younger patient need implant for long time as compared to old patient so
planning need to be done accordingly.

35. • Skeletal position :-
– The brachiocephalic, with a stout head shape, may generate three times the bite
force compared with a regular head shape.
– The skeletal Class III patient is primarily a vertical chewer and generates vertical
forces with little excursive movement.
• However, some patients appear “pseudo-Class III” as a result of anterior bone
resorption or loss of posterior support and collapse of the vertical dimension
with an anterior rotation of the mandible.
• As a general rule, the implant treatment plan should reduce other force
magnifiers when masticatory musculature dynamics increase.
• The prosthesis may be made removable so nocturnal bruxism is reduced (if
they do not wear their prosthesis).
• The implant number, size, and design may also be increased to increase the
surface area of load.

36. ARCH POSITION
• The maximum biting force is greater in the
molar region and decreases as
measurements progress anteriorly.
• Bite force in various region
– Anterior region :- 35 to 50psi
– Canine region :- 47 to 100psi
– Molar region :- 127 to 250psi
• Mansour et al.87 evaluated occlusal forces
and moments mathematically using a Class III
lever arm, the condyles being the fulcrum
and the masseter and temporalis muscles
supplying the force.
• The anterior biting force is decreased in the
absence of posterior tooth contact and
greater in the presence of posterior occlusion
or eccentric contacts.

37. • Implants in the posterior regions should often be of greater diameter,
especially in the presence of additional force factors. Because the surface
area of natural tooth increase in molar region to accommodate the forces.
• Hence larger implant diameter is required in posterior region.
• The bone density of natural dentition is almost similar throughout the
arch but this is not true for edentulous ridge.
• The posterior regions, in general, form less bone density after tooth loss
than the anterior regions.
• The denser the bone, the greater its resistance to stress applied at the
implant–bone interface.
• As a result the posterior maxilla is the most at-risk arch position, followed
by the posterior mandible, and then the anterior maxilla. The most ideal
region is the mandibular anterior.

38. Opposing Arch
• Natural teeth transmit greater impact forces through occlusal contacts than
soft tissue–borne complete dentures.
• the maximum occlusal force of patients with complete dentures is limited
and may range from 5 to 26 psi.
• The occlusal forces in denture pt decrease with time and muscle atrophy
take place.
• In elderly pt thinning of oral tissue and bone atrophy also occur.
• When the opposing arch is a denture (as depicted in this panoramic
radiograph in the maxilla), the bite forces are less

39. • The opposing arch consists of
natural teeth.
• The cantilever length should be
reduced or the number of implants
increased, compared with an
edentulous opposing arch.
• A complete implant fixed prosthesis
does not benefit from
proprioception as do natural teeth,
and patients bite with a force four
times greater than with natural
teeth.
• In addition, premature contacts in
occlusal patterns or during
parafunction on the implant
prostheses do not alter the pathway
of closure thus a continuous force is
applied and stresses are increased.

40. References
Misch, Dental Implant Prosthesis 3rd &4th Edition.