Fundamentals of Occlusion for Fixed Prosthodontics Flashcards
— is a critical factor for all dental restorations and for
the health and longevity of teeth and intraoral structures
Occlusion
* Takes time, effort, and knowledge to assess Occlusion,
Occlusal concepts, and design appropriate occlusion for
restorations
A patient may have an orthodontically ideal
Angles Class I Occlusion. This does not mean that
the patient has (3)
optimal occlusal contacts, optimal
condyle/mandibular position, and ideal/optimal
contacts in excursive movements.
Conversely a patient with a Class II or Class III
occlusion, although not orthodontically ideal, may
in fact have
an acceptable, functional occlusion.
Patients may have a less than ideal occlusion,
HOWEVER, it may still be
(2)
a functionally acceptable occlusion
or
a physiologically acceptable occlusion
Patient’s occlusion may deviate from the ideal
(3)
- is treatment required?
- adaptive capacity of a patient
- if treatment is rendered, what is the optimal position for the joints,
muscles, and teeth
- is treatment required?
(assess the masticatory system for evidence of pathology - tooth
wear, tooth mobility, TMJ dysfunction, muscle dysfunction, etc)
MUTUALLY PROTECTED OCCLUSION
(optimal functional occlusion)
definition
anteriors
posteriors
in excursive movements:
*Multiple, even, bilateral, simultaneous occlusal contacts of
the posterior teeth in MIP with the mandible is CR position
i.e. MIP and CR are coincident.
*The anterior teeth exhibit lighter occlusal contacts as
compared to posterior teeth in MIP.
*Posterior teeth are axially loaded in MIP
*In excursive movements: canine guidance/anterior
guidance occurs
Temporomandibular Joints
The TM Joints are in an optimum, orthopedically stable joint position
when the mandible is in CENTRIC RELATION.
MUTUALLY PROTECTED OCCLUSION
* The posterior teeth
* The anterior teeth
withstand the majority of the load
in MIP, protecting the anterior teeth from high loads.
disclude the posterior teeth in
excursive movements, thereby protecting the posterior
teeth from off-axis loading.
- Posterior teeth can tolerate axial loading well so they
protect anterior teeth, which are not axially loaded, in
MIP. Anterior teeth can tolerate lateral forces in
excursive movements (off-axial loading) since they are
further away from the fulcum and the loads are less.
Evaluation of Occlusion
* Is required at
* Better results if the evaluation of Occlusion has been done at
all phases of the fixed prosthodontic treatment
(diagnosis and treatment)
all stages (even for simple prosthodontic treatments)
Evaluation of Occlusion
Diagnostic Phase
Evaluation is completed in conjunction to (2)
Clinical Examination and
Articulated Casts
Articulation of Casts
(2)
- Maxillary cast is articulated using a fabebow record
- 2 positions to articulate mandibular casts
- 2 positions to articulate mandibular casts
(2)
- Centric Relation (CR)
- Maximum Intercuspation (MIP)
Purpose of a facebow:
Orient the maxillary cast to
the rotational axis in three planes
Kinematic Facebow
This facebow is the most accurate (locates the True Hinge Axis).
Requires training, elaborate instruments, and more time.
Arbitrary Facebow
(3)
- Locates an arbitrary hinge axis by using anatomical landmarks
- Less accurate
- Requires less complicated instruments and less time.
Benefits of a Facebow Record
Using a facebow will result in the path of opening and closure
(arch of closing) being the same on articulator as intraorally.
Centric Relation CR
The position of the mandible in which the condyles are in the most
superior and anterior position in the articular fossae, resting
against the posterior slopes of the articular eminences with the
articular discs interposed.
Centric Relation
recording CR on a dentate pt requires an anterior deprogrammer
Articulation of Casts in CR
(3)
- Interocclusal Record(s)
- The record is made at ↑OVD
- Avoid deflective tooth contacts
Mounting Casts - CR Record
* CR record is made at an — OVD (~ 3mm)
* If an accurate CR record is made, then the
increased
MIP position can be achieved on the articulator
Maximal Intercuspal Position MIP
(also known as Maximum Intercuspation)
(4)
- This is a position in which the maxillary and mandibular teeth make
maximum surface contact with each other. - The mandible is elevated as superiorly as possible in the sagittal plane
- For most patients: MIP and CR are NOT coincident
- “habitual closing” position
Articulation of Casts in MIP
* For most dentate patients:
an interocclusal record(s) should
not be used to articulate the dx casts in MIP
Partially Edentulous Patients
— may be needed (Stabilized Record Bases)
Occlusal Records
Without posterior occlusion / few remaining teeth, casts cannot be related accurately.
Importance of Accurate Articulation
- The casts that are mounted on the articulator need to exhibit
the same occlusal relation as the teeth do intraorally!!!
When to articulate casts using CR record?
(4)
- Diagnose occlusal disease
- Completely edentulous patients
- Partially edentulous patients
- Dentate patients to receive extensive fixed prosthodontic restorations
- Diagnose occlusal disease
(TMD / Occlusal equilibration / Splint / Orthodontic / orthognathic surgery)
- Partially edentulous patients
(when there are few teeth remaining / a stable MIP is not present)
- Dentate patients to receive extensive fixed prosthodontic restorations
(3)
- Occlusion will be altered completely
- The restorations will be made at an increased OVD
- Kinematic facebow recording (hinge axis) necessary
- (Full-size) Transverse hinge axis close to that of patient
- Slight difference in arc of closure between patient and articulator
- (Small) Large difference in arc of closure between patient and
articulator →
centric premature contacts in restorations
Programming the Articulator
- Condylar Elements set with eccentric records
Determinants of Occlusal Anatomy (TMJs)
Opposing cusps will travel through groove pathways without tooth
contact in excursions (posterior teeth disclude during excursive
movements)
Full-size Articulator vs. Hinge Articulator
Discrepancies in occlusal morphology →
interferences on the restoration
(especially on the NW side)
Full-size Articulator vs. Short Hinge Articulator
— impression/articulation recommended:
(3)
Full arch
- More posterior teeth (occlusal surfaces) being restored
- FDPs; multiple crowns
- Group Function (instead of Canine Guidance)
Custom Incisal Guide Table
* Provides record of the
lingual concavity and incisal edge length / position
and therefore anterior guidance for replication when fabricating anterior
indirect restorations.
Occlusion
Treatment Phase
- Articulate working casts
Articulation of the Master Cast (working cast)
(4)
- Ensure accurate tooth to tooth contact
- Verify contact of incisal pin
- Accuracy of mounting is critical to create accurate occlusion on restorations
- Compare intraoral and articulated cast occlusal contacts.
Mounting Casts –MIP Interocclusal Record
*For patients that have a stable — position
*Mount casts with — record at —
MIP
MIP,
OVD
Mounting Casts –MIP Interocclusal Record
Material:
(3)
- No resistance to closure
- Rigid when set
- Dimensional stability / accuracy
Mounting Casts –MIP Interocclusal Record
*Mount casts with MIP record at –
OVD
Concepts of Occlusion (occlusal schemes)
(3)
*Mutually Protected Occlusion
*Group Function (Unilaterally Balanced Occlusion)
*Balanced Occlusion (Bilateral Balanced Occlusion)
Group Function (Unilaterally Balanced Occlusion)
(2)
- Mandible moves laterally it is guided by a group of teeth on the working side.
- Canine, premolars, and MB cusp of 1st molar
Balanced Occlusion (Bilateral Balanced Occlusion)
(5)
- Simultaneous contacts on both sides during lateral movements (W / NW), and between posterior / anterior during protrusive
- Not acceptable for dentate patients
- Promotes tooth wear; NW side contacts destructive
- Acceptable form of occlusion for CD and RPD
- Contact on NW side can help stabilization of the removable prosthesis
Creating the occlusal surface to ensure proper
loading of the tooth(teeth)
(2)
- Cusps and ridges should allow even occlusal contact(s) with opposing teeth
with forces along long axes - Non-centric cusps should overlap horizontally and vertically
Occlusal Surface
Opposing cusps should travel through groove pathways without tooth
contact in excursions
(2)
- Posterior teeth disocclusion
- Avoid interferences
- Curve of Spee (A-P curve):
(2)
- Cusps follow an anteroposterior curve
- Steepness of curve influences the cusp heights
- Curve of Wilson (M-L curve):
(3)
- Mediolateral curve
- Non-functional cusps shorter than functional cusps
- Helps prevent interferences in lateral excursions
Occlusal Surface: Occlusal Contacts
1. Tripodized point contacts on (3)
2. Buccal and lingual cusps lie along —
cusps, fossae / marginal ridges.
a-p lines.
Waxing Technique: Proximal Contact Areas
(3)
- Size and location are established first
- Proper size:
- Location:
- Proper size:
(2)
- Convex oval area
- Not pinpoint or deficient
- Location:
(3)
- Occlusal 1/3
- Distal: more cervically located
- Slightly towards facial
Waxing Technique: Proximal Surfaces
* Proximal surfaces should reflect the
*— from contact area to CEJ
* Proper space for —
emergence profile and contour
gingival to the contact area as it relates to the adjacent tissues
Flat to slightly concave
interdental papilla
Axial Surfaces
(3)
- Shape buccal and lingual surfaces to follow contours of adjacent and
contralateral teeth - Height of contour:
- Emergence profile:
- Height of contour:
Buccal:
Lingual:
cervical 1/3
middle 1/3
- Emergence profile:
(3)
surface apical to height of contour adjacent to gingival soft tissues
* Flat or straight
* Avoid bulky convexity in cervical region
