Transcript PREIMPLANT PROSTHODONTICS

MISCH: CHAPTER 12
PREIMPLANT PROSTHODONTICS
Presented by:Dr.mehrak Amjadi
Supervised by: Dr. Mansour Rismanchian
And Dr.saied Nosouhian
Dental of implantology
Dental implants research center
Isfahan university of mediacal science
PREIMPLANT PROSTHODONTICS
OVERAL EVALUATION, SPECIFIC
CRITERIA, AND PRETREATMENT
PROSTHESIS
Mehrak Amjadi
OVERALL EVALUATION
1) MAXILLARY ANT. TEETH POSITION
 The labial position of the max ant teeth is first
determined with the lip in repose.
 overall support of the maxillary lip and its
relationship to the nose and presence or
absence of a philtrum in the midline
MAXILLARY ANT. TEETH POSITION
 The vertical position of the max ant teeth :
 canine tip is located 1 mm level with the lip in
repose, regardless of age or sex of the patient.
 The centrals are 1 to 2 mm longer than canine.
 If the patient is wearing a maxillary complete
denture,the maxillary anterior tooth position is
often incorrect
2) EXISTING OCCLUSAL VERTICAL
DIMENSION
 OVD: the distance between 2 points (one in max and
the other directly below in the mandible) when the
occluding members are in contact.
 OVD requires clinical evaluation not diagnostic casts.
 OVD is not a precise dimension, because a range of
dimensions is possible without clinical symptoms.
 OVD often decreases over time without clinical
consequence in the dentate or edentulous patients.
OVD
 Any change in OVD affects the CHS.
 Any change in OVD modifies the horizontal
dimensional relationship of the maxilla to the
mandible.  change in OVD will modify anterior
guidance, range of function, and esthetics.
 The most important effect of OVD on tooth / impalnt
= effect on the biomechanics of anterior guidance.
 The more closed OVD  the farther the mandible
rotates  the more CL III the chin appears.
OVD
 In a Class II, division 2 patient, the more
closed the OVO, the steeper the anterior
guidance and the greater the vertical overlap
of the anterior teeth.
Anterior guidance is necessary to maintain
incisal guidance during mandibular
excursions to decrease the risk of posterior
interferences. These conditions will increase
the forces to the anterior teeth.
OVD
 completely edentulous patients restored with
fixed implant prosthodontics Opening OVD
+ decreasing the incisal guidance  increase
force on posterior implants during
mandibular excrusion.
 Change in OVD may affect the sibilant sounds
by altering the horizontal position of the
mandible.
OVD
 Situations that altering OVD is mandatory:
1. Esthetic α incisal edge position, facial
measurements, occlusal plane.
2. Function α canine position, incisal guidance,
angle of load to teeth or implants.
3. Structural needs of the dentition α dimensions
of teeth for restoration while maintaining a
biologic width.
Methods for evaluating OVD
 OBJECTIVE METHODS: use facial dimensions
 SUBJECTIVE METHODS: rely on esthetics, resting arch position,
and closet speaking space.
 OVD = RESTING POSITION – FWS (3 mm)
 The amount of FWS depends on factors like head posture,
emotional state, presence or absence of teeth, parafunction, and
the time of recording.
 The physiologic rest position should not be primary method to
evaluate OVD.
 The speaking method (making S sound) also should not be used
as the only method to establish OVD.
 Experienced clinicians often use subjective
method to assess OVD.
 The objective method is usually the method of
choice to evaluate existing OVD or establish a
different OVD during prosthetic
reconstruction.
 THE GOLDEN RATIO: the length and width of a
golden rectangle as 1 to 0.618.
 Radiographic methods to determine an objective OVD
are also documented in the literature. Tracings on a
cephalometric radiograph is suggested when gross jaw
excess or deficiency is noted.
 Esthetics are influenced by OVD, because of the
relationship to the maxillomandibular positions. The
smaller the OVD, the more Class 1IIthe jaw relationship
becomes; the greater the OVO, the more Class II the
relationship becomes.
The maxillary anterior tooth position is
determined first and is most important for the
esthetic criteria of reconstruction.
 complete maxillary denture opposing a partially
edentulous mandible may result in COMBINATION
(KELLY) SYNDROM:
 Max incisor denture positions up and rotates back
 Lower natural ant teeth overerupt
 Occlusal plane tilted apically in ant and coronally in
post
 Enlarged tuberosities
 Maxillary palatal hyperplasia
 Highly mobile tissue in the premaxilla.
COMBINATION (KELLY) SYNDROM:
 The proper maxillary incisal edge position and OVD are
especially critical for these patients, because of the
incidence of mandibular incisor extrusion beyond the
maxillary occlusal plane.
 To position the maxillary incisors properly, the
mandibular anterior teeth must be repositioned at the
proper incisal plane.Endodontic therapy and crown
lengthening procedures usually precede the restorations
on the lower arch to obtain a retentive and esthetic
restoration.
3) MANDIBULAR INCISOR EDGE
POSITION
 mandibular incisor edge should contact the lingual aspect
of maxillary anterior natural teeth at the desired OVD
position.
 A vertical overlap of 3 to 5 mm is acceptable.
 INCISAL GUIDANCE: influence of contacting surfaces of
the mandibular and maxillary anterior teeth on mandibular
movements.
 CHRISTENSEN’S PHENOMENON: IG is responsible for the
amount of post tooth separation during mandibular
excursions and to do so it should be steeper than condylar
disc assembly.
IG
 IG is evaluated on the mounted diagnostic
casts.
 A steep IG 
1)avoid post interferences during mandibular
excursions,
2) greater forces on anterior crowns
4,5) EXISTING OCCLUSAL PLANES
 The position of occlusal planes relates to the curve of
spee and wilson ( the radius of a 4 inch sphere).
 Ideally, the maxillary posterior occlusal plane should be
parallel to the Camper's plane .
 Odontoplasty, endodontic therapy, or crowns are
indicated to remedy tipping or extrusions of adjacent or
opposing natural teeth.
 A proper curve of Spee and curve of Wilson are also
indicated for proper esthetics and are reproduced in the
compensating curves for complete denture fabrication.
 An occlusal plane analyzer may be used on diagnostic
casts to evaluate pretreatment conditions and assist in
intraoral occlusal plane correction.
 The natural dentition opposing a partially edentulous
ridge also must be carefully examined and often needs
modification before surgical placement of the implants.
 The implant drills and implant body insertion often
require a posterior CHS of more than 8 mm from the
ideal occlusal plane.
 Enameloplasty of the stamp cusps of the opposing teeth
is often indicated to redirect occlusal forces over the long
axis of the implant body.
 The existing tooth and arch relationships do not
need to be perfect before implant treatment.
 The correct tooth positions should be first
determined, so even if the total treatment time
is extended over several years, at least each
segment will aim toward a consistent goal.
SPECIFIC CRITERIA
SPECIFIC CRITERIA
1. Lip line
2. Maxillomandibular arch relationship
3. Existing occlusion
4. CHS
5. TMJ status
6. Existing of hopeless teeth
7. Existing prosthesis
8. Arch form
9. Natural teeth adjacent to implant site.
10. Soft tissue evaluation of the edentulous site.
LIP LINE
 General rule: 1 -2 mm of max ant teeth should display with
the lip at rest.
 But it is better to position the prosthetic teeth in most likely
location for the patient’s natural teeth.
 The average upper lip is 20 to 22 mm for women and 22 to
26 for men.
 The canine position at the corner of the lip is not affected
by the lip bow effect. Thus, it is more consistent position
and usually corresponds to the length of the resting lip
position from the 30 to 60 years of age in both male and
female.
 The low lip line displays no interdental papilla or
gingiva above the teeth during smiling.
 The high lip demonstrates all of the interdental
papilla and more than 2 mm of tissue above the
cervices of the teeth.
 The selection of FP2 or FP3 is often based solely on
the evaluation of the high lip line.
 An FP2 (in low lip line patients) is easier to fabricate
because of fewer porcelain bake cycles.
 In patients with a high lip line who are missing all
their ant teeth, the prosthetic teeth can be made
longer (up to 12 mm) instead of the average 10
mm to reduce gingival display.
 The height of the maxillary ant teeth is
determined by:
1.
2.
3.
Establishing incisal edge by the lip in repose.
The high smile line determines the height of the tooth
(9-12 mm)
The width of the anterior teeth is determined by the
height/width ratios.
Mandibular lip line
 Although the maxillary high lip line is
evaluated during smiling, the mandibular low
lip line is evaluated during speech.
 In pronunciation of sibilants or S some
patients may expose the entire ant mand
teeth.
 An FP3 may be indicated in a patient with low
mandibular lip position.
MAXILLOMANDIBULAR ARCH RELATIONSHIP
 Teeth ext  bone loss  placing implant in
lingual position  facially overcontoured
restoration  cantilever.
 To counteract cantilever effect  increased
implant number, size, design, and change
prosthesis to RP4, and spilinting implants.
MAXILLOMANDIBULAR ARCH RELATIONSHIP
 palatal resorption of the maxilla with the anterior
rotation of the mandible  Class III relationship>> Class III mandibular mechanics do not apply
(no anterior excursions during mastication or
parafunction).
 can contribute significant lateral forces on the
maxillary restoration-> additional splinted /
implants are suggested in the maxilla with the
widest A-P distance available.
EXISTING OCCLUSION
 MI : complete intercuspatin of opposing teeth
independent of condylar position.
 CO : occlusion of opposing teeth when mandible
is in CR.
 The more teeth replaced or restored, the more
likely the patient restored to CR occlusion.
 One tooth replacement MI position.
CROWN HEIGHT SPACE
 CHS= distance between bone level and occlusal
or incisal plane.
 IDEAL CHS for FP1 implant  8 -12 mm.
 Angled force, high CHS, angled implant
placement  force magnifier.
 A 12 degree force o implant increases the force
by 20%
Excessive CHS
 The biomechanics of CHS are related to lever
mechanics.
 CHS is a vertical cantilever and therefore is also a
force magnifier.
 When the direction of a force is in the long axis of
the implant, the stresses to the bone are not
magnified in relation to the CHS
Excessive CHS
 CHS is excessive when more than 15 mm = vertical
cantilever.
 In the case of removable prostheses with mobility
and soft tissue support, two prosthetic levers of
height :
 1. the height of the attachment system to the crest of the
bone. The greater the height distance, the greater the
forces applied to the bar, screws, and implants
 2. the distance from the attachment to the occlusal
plane. This distance represents the increase in prosthetic
forces applied to the attachment.
Excessive CHS
 In crown heights of more than 15 mm :
 no cantilever should be considered unless all
other force factors are minimal.
 The occlusal contact intensity should be reduced
 Occlusal contacts in CR occlusion may even be
eliminated on the most posterior aspect of a
cantilever.
 Treatment plan for Excessive CHS:
 Shorten cantilever length
 Minimize buccal and lingual offset loads.
 Increase diameter and number of implants.
 Improve implant design
 Fabricate removable restoration or hybrid pr.
 Splint implants together
Reduced CHS
 Reduced CHS causes:
 material failure
 increased material flexibility
 Reduction of retention
 It is better to use metal in occluding surfaces in
these cases.
 minimum restoration space required:
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Reduced CHS
 Less than 3 mm of abutment height indicates a screw retained
crown, 3 to 4 mm requires a screw retained or resin-cemented
restoration, and greater than 4 mm of abutment height allows
the operator's preference.
When a screw is used to retain the crown the strength of
occlusal porcelain is reduced by 40%.
 The most common method of retention for a fixed prosthesis
is cement retention. The most common method of bar
retention is screw retention.
 in ideal to excessive CHS situations, the cemented bar should
be considered.
Reduced CHS
 Reduced CHS causes:
 material failure
 increased material flexibility
 Reduction of retention
 It is better to use metal in occluding surfaces in these cases.
 When a screw is used to retain the crown the strength of
occlusal porcelain is reduced by 40%.
 minimum restoration space required:
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