Treatment Planning and Biomechanics of Fixed Partial Dentures Flashcards
What is a fixed partial denture (bridge)?
A dental prosthesis definitively attached to remaining teeth or to dental implants, which replaces one or more missing teeth.
What is an abutment?
Natural tooth or implant serving as attachment for Fixed Partial Denture
What is a retainer?
Extra-coronal restoration cemented to abutment
What is a pontic?
Artificial tooth suspended from abutments
What is a connector?
Rigid (or non-rigid) connecting pontic and retainers
What is an edentulous ridge?
The site of the alveolar bone and its covering soft tissues that remains after tooth loss.
What allows for a state of dynamic equalibrium?
Equal pressures keeping teeth in their locations
What would the consequences be for loss of #19?
-Improper occlusal pressures on #14 and #18
-Food trap #20 and #21 due to drifting
-Lack of inter-occlusal space in area #19
-Occlusal plane is now disrupted and out of harmony
-Excursive movement interferences and possible loss of full range of
movement.
What are the consequences of unrestored tooth loss?
Tooth Movement
-Over-eruption
-Tilting and drifting
-Disruption of occlusion (Pain, TMJ disfunction)
No tooth Movement
-for some reason, some teeth never move after loss of proximal or opposing contact
Occlusal interferences are produced when a FPD is made to the…
over-erupted dentition
How do you prevent interferences with making an FPD to the over-erupted dentition?
Opposing tooth being restored to a corrected occlusal plane
- Odontoplasty, restoration, crown, RCT, crown lengthening, intrusion, or even extraction
Partially Edentulous Patient Treatment Options…
-Removeable Partial denture
-Tooth supported Fixed Partial Denture (Conventional, Resin-Bonded, Cantilever)
-Implant supported Fixed Partial Denture
-Always the option to do nothing.
What are the indications for removeable partial denture?
-Long edentulous spans
-No distal abutment
-Multiple Edentulous spaces
-Abnormal abutments (Tipped, divergent, or few abutments)
-Periodontally weakened primary abutments (Bridge abutments compromised)
-Severe loss of tissue/bone in residual ridge
What information would you need to know to determine the prognosis of a fixed bridge for treatment planning?
X-rays
Perio charting
Decay prevention
Home care
Reason for previous tooth loss
Clencher/grinder?
Finances?
Condition of existing crowns
What are the indications for a fixed partial denture?
-To replace function of missing teeth
-To stabilize occlusion and keep teeth from drifting and extruding
-To create esthetics and phonetics
- Properly distributed abutments
- Abutment strength
What should you be aware of for properly distributed abutments for an FPD?
- Abutment on both ends of the edentulous space
- Span length falls within structural limits
- Straight alignment of restoration (slight variations)
What should you be aware of for abutments strength for an FPD?
- Abutments need to be restorable
- Peridontally sound and stable
- No questionable pathology (PARL, non-vital)
- In Occlusal harmony
What are the contraindications for an FPD?
- excessive loss of alveolar ridge
- abutments not restorable
- abutments are periodontally compromised
What should you be aware of for escessive loss of alveolar ridge for not doing an FPD?
- Difficultly cleaning
- Difficult to make esthetic
What should you be aware of for non restorable abutments for not doing an FPD?
- Short clinical crown
- Heavily restored already
What should you be aware of for abutments that are periodontally compromised for not doing an FPD?
- Loss of bone
- Crown to root ratio
- Span between abutments too long
What does an ideal Fixed Partial Denture look like?
-Periodontally sound abutments
-Tissue follows contour of pontic and connector
-Span is within structural parameters
How do we evaluate Abutments?
-Clinical exam including hard and soft tissues, periodontal exam and occlusal evaluation.
-Radiographic exam
-Diagnostic casts (articulated on full- size articulator w/ facebow if needed)
What are the criteria we use for Abutment evaluation?
- Restorative assessment (coronal tooth structure, previous restorative treatment)
- Endo assessment (pulp status, PARL, previous endo)
- Periodontal assessment (crown/root ratio, root configurations)
- Abutment Positional assessment (tilted tooth, inclined tooth, path of insertion)
- Radiographic assessment (anomalies)
Questions to ask yourself about the teeth being assessed as abutments:
- Adequate retention and resistance form possible?
- Is there adequate wall length?
- Is the tooth restorable as is or is decay present?
- If not, can restorability be gained with foundation or modification of preparation?
- What is the apical extent of caries or restoration?
What do you need to evaluate on the coronal tooth structure of an abutment?
Remove all caries, old restorations, then evaluate:
-Is there a Pulp exposure, symptomatic tooth, or Periapical pathology?
-Proximity of cavity depth to alveolar crest.
—Biologic width violation likely?
-Adequacy of retention/resistance form to support retainer crown.
—Do I have the necessary tooth structure?
What do you do to an abutment with existing RCT?
Assess radiographically first. Is there a PARL present? Is the RCT adequate?
When can you use an abutment with vital pulp?
Ideally tooth is asymptomatic with
sound tooth structure remaining
When can you use an abutment with nonvital pulp?
RCT if sound tooth structure remaining with non-vital tooth.
–Post may be needed
Periodontal health is a prerequisite for any fixed prosthodontic restorations. What do you need to make sure for abutments?
-Need a zone of attached tissue
- No mobility
-Patient home care adequate
–Crown to root ratio, root shape and configuration, periodontal ligament area all need to be assessed and evaluated
What is the crown to root ratio?
The ratio of the portion of the tooth occlusal to the alveolar crest (crown) versus the portion of the tooth embedded in bone (root).
What is the optimum crown/root ratio?
Optimum C:R is 2:3
What is the minimum crown/root ratio?
Minimum C:R is 1:1 for fixed restorations
The ______ root shape diminishes the actual area of support more than expected from the height of the bone
conical
___________ bone loss dramatically reduces supported root surface area
Horizontal
The __________________ (R) moves apically and the lever arm (L) increases, greatly magnifying the forces on the supporting structures.
center of rotation
What are the exceptions for the crown/root ratio rules?
If opposing occlusal forces are diminished such as:
- Artificial teeth (Full denture, RPD)
- Periodontally compromised opposing teeth
What are the best teeth for abutments (multi-rooted or single rooted)?
Multi-rooted teeth are better than single rooted teeth, conical teeth.
What are the best teeth for abutments (widely separated roots or fused roots)?
Widely separated roots are better abutments than fused roots.
What are the best teeth for abutments (long roots or short roots)?
Long roots are better abutments than short roots.
What type of single rooted tooth is good for abutments?
Irregular configurations or curvatures are preferable compared to a perfect taper
The tooth root should be boader FL or MD for an abutment?
FL
What is ante’s law?
The root surface area (embedded in bone) of the abutment teeth should be equal or surpass that of the teeth being replaced with pontics.
Is this ante’s law favorable or unfavorable?
Is this ante’s law favorable or unfavorable?
Is this ante’s law favorable or unfavorable?
What is the principle for any FPD replacing more than 2 posterior teeth has guarded/poor prognosis?
Maxillary arch has longer crowns and less tooth inclinations and therefore can occasionally be acceptable
What is ante’s law not as reliable?
“Occlusion is the key to success. Even the worst cases with doubtful
prognosis had good success rates when occlusion was right.”
-Failure in FPD’s are more due to biomechanical factors like caries, gingival inflammation, poor framework design, poor occlusion and material failure than due to overstressing of periodontal ligaments
-The suggested ratio cannot be made standard for all patients as individual variations in crown root ratio, root morphology and bone exist.
-Occlusal scheme which is the key factor has not been considered at all.
Axial walls of abutment teeth must be aligned without ____________________ for a path of insertion of a bridge
undercuts or interferences
Why is a tipped tooth difficult to prepare?
-often exposes mesial pulp horn
-unfavorable occlusal forces if tilt is too significant
What can you evaluate using casts?
-Edentulous spaces and span length
-Curvature of the arch
-M-D drifting, rotations, F-L displacement of the abutments
-Inclination
-Occlusion and inter-occlusal space
-Path of Insertion
When teeth are not perfectly aligned, a ________ can be used to identify the path of insertion and to help you create the appropriate planes in tooth preparation to create a path of insertion.
surveyor
What do you need to look for on radiographs of abutment teeth?
-Caries – Where and how much
-RCT present? – is it healthy?
-Bone levels – C:R ratio, direction of roots, PDL widened, bone loss
-Maxillary sinus – Is there lack of bone support due to sinus pneumatization
When can you do a resin-bonded fixed partial prosthesis?
-Conservative enamel only preparation
-Used for single missing tooth with slight to moderate tissue resorption in missing tooth area
-Only areas of light occlusal stresses and good alignment with neighboring teeth
-Not indicated for deep vertical overlaps (Deep bite)
-Excellent option in younger patients where age contraindicates implant or bridge
-Most often used to replace missing maxillary lateral incisors
What is a cantilever fixed partial prosthesis?
A fixed partial denture that has an abutment(s) at one end with the pontic remaining unconnected on the other end.
What are the indications for an implant supported FPD?
-Implant abutments must be soundly integrated
-Implant parallelism very important
-Availability of bone to support implant critical
-Patient must demonstrate adequate home care
Why are implant supported FPDs controversial?
–Clear Choice and others fabricate full arch one piece fixed appliance.
–$25,ooo per arch
–Patient cannot remove
–Hygiene is a huge challenge here.
–Need to be replaced around every 10 years with current materials.
What are the limitations of implant placement?
- Amount of bone critical
- Location of bone critical
- Anatomy
–Maxillary sinus
–IAN
–Anterior angulation of bone
