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45 Cards in this Set
- Front
- Back
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When do you conform or rearrange occlusion?
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Conform when you can
Rearrange when you cant |
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When can you conform?
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1 - When there is stable ICP
To achieve a stable ICP on dental casts,we need occlusal stops that are spreadout around arch with no slide, no rock. It is more common, but not certain, to bestable in Kennedy class III and in shortsaddle Kennedy class IV cases .2 - If we have an occlusal stop (or more than one) ….but the casts are unstable when hand held |
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When do you re-arrange occlusion?
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When you can't conform
1 When there are no occlusal stops The decision to reorganiseshould only be taken if;· There needs to be an increase in OVD - To make space for restorations, or to improveappearance Where the ICP is causing destruction to teeth There has been a history of restorationsrepeatedly failing due to occlusal forces. |
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When are hand articluated models suitable? |
There is a stable ICP The position of the replacement teeth requiresno gude We need to mark the correct occlusion,Check against the patients occlusion,The technician seals the models togetherto our marks So he/she can mount them on anarticulator. |
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When do we use tooth bourne registration? |
Mainly used in crown and bridge work;little use for removable prosthetics. You have to have a good occlusal stop anda pretty stable ICP to use this method. |
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When is mucosa bourne registration suitable? |
There is nota stable ICP on the casts Theposition of the replacement teeth requires a guide |
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How do you do mucosa bourne registration? |
Case where ther is ICP it just rocks - use bite block - Trim the block until there is a slightgap intra orally and then fill with blue moose. Where no ICP - much harder |
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Steps for recordign oclusion when there is no ICP (complete:complete) |
1. measure vertical dimension, e/o,calculate target OVD- First we need to calculate our TARGET OVD- This is usually RVD-3mm….. The 3mm iscalled ‘freeway space’ (FWS) 2. shape upper anterior lip support 3.adjust upper anterior incisal height - discuss w/ pt. guidline of 2mm 4.mark upper anterior mid line 5. adjust occlusal plane to be parallelto interpupillary line 6. adjust occlusal plane to be parallelto ala tragus line - NB not needed if there are enough teeth 7. adjust wax to give position ofposterior teeth/buccal corridor - aim to put teeth in neutral zone - "zone of minimum conflict" between cheeks, lips and tongue 8. insert lower registration block andtrim to give i) target OVD ii)even contact iii)in ICP if conforming, otherwise in RCP 9. Seal blocks together intra orally. - blue mousse it |
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Which articulator for conformatince and re-organised? |
Conformative = average value Reorganised = semi adjustable |
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Why do restorations fail due to occlusion? |
Essentially due to excessive forces or forces in the wrong direction (laterally) - Prematurecontacts - Lateralforces on posterior teeth - Guidanceon vulnerable teeth - Excessiveforces due to parafunction |
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What is intereference? |
An unwanted tooth to tooth interactionthat leads to deviation of the mandible from its expected path •Can occur during any jaw movement• •ICP •RCP •Protrusive •Working side•Non-working side |
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What do ICP intereferences cause? |
•Usually (but not always) feels “high” to the patient•7 •Can lead to pain / mobility / increased toothsensitivity / failure of restoration ••Look for whenever you place any restoration ••Don’t allow the patient to leave until their occlusionis corrected |
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What is shimstock? |
8um thick metal foil |
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Where should lateral guidance be and not be? |
Should always be on……… A healthy canine (canine guidance) - even if its a crown or abutment Or Shared across several posterior teeth(group function) )Should NEVER be on: A root filled tooth A Bridge Pontic |
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What does lateral interference cause? |
•Wear ••Discomfort•Fracture•Increased mobility•Loosening of crown Lateral forces on the working side willaffect•Buccal cusp upper•Lingual cusp lower (BULL) |
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What do you do if canine guidance is lost? |
1.Let Nature takes it’s course – if noteeth have become vulnerable by it’s loss● 2.Reinstate canine guidance•if canines are suitable 3.Carry out occlusal adjustments so thatlateral forces are shared rather than on any one vulnerabletooth (not for beginners!) |
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How do you reinstate canine guidance? |
Must check it can take the job on…..•Periodontal status•Pulp vitality•Periapical radiograph•Periapical status•Root length and angulation•No RCT and definitely no post•Articulated model•Diagnostic wax-up to see if it’s feasible Canine riser - adding composite to repair worn palatal surface |
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What uses are theere for different articualtors? |
From low to high risk of lateral interference being a problem Simple hinge Goodfor ICPBadfor lateral movements Average value Goodfor ICPOKfor lateral movements Semi-adjustable Goodfor ICPBestfor lateral movements |
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Low and high risk of lateral interference being a problem treatments? |
LOW single post crown Pt with canine guidance High RCT canine Bridge in pt with group function Post crown in patient w/ group function Pt with parafunction |
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define canine guidance and it's effect on restorations |
Allteeth except the canines are discluded on eth working and non-working sides. Having canine guidance means that the canines take the majority of any lateralforces. Posterior teeth only meet in ICP and therefore when restoring orchoosing an articulator we are mainlyinterested in looking for interferences in ICP only. |
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Define group function and it's implcations |
This is a catch-all term for anything that is not canineguidance and therefore doesn’t really tell us anything specific about theocclusion, therefore when group function is identified a more detailedinvestigation of how lateral forces may affect the teeth providing guidance isrequired. Forpatients in group function, the BULL rule tells you which cusps may be at risk |
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What is the BULL rule and it's implications |
The BULL rule,(Buccal Upper, Lingual Lower) indicates which cusps may be at risk if they arein heavy lateral guidance and the cusp has been weakened by a restoration inthe tooth. Normally this requires nothing more than monitoring, but if therestoration needs replacing then it may be wise to include some form of cuspalprotection such as an onlay or even a crown |
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What do wear facets indicate and what is important when restoring an area with a wear facet? |
Often a good indicator that parafunction may be occurring.Remember when restoring a tooth that has a wear facet, the facet must berecreated otherwise it will act as an interference. |
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What should happen during protrusion? |
Duringprotrusion there should be even contact between as many anterior teeth aspossible. |
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When is it impotant to check for incisal guidance and how is it done? |
especially important to check after placing any anteriorrestoration including crowns and bridges. Prematureor heavy contacts can be identified by feeling for Fremitus – light fingerpressure distributed across two or more teeth will detect if one of those teethis being displaced slightly during coming together into ICP or duringprotrusion. |
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What does re-organisation of the occlusion include? |
· Increasing OVD · Creation of a new ICP· Alteration of the lateral guidance |
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Describe the different types of articulator |
Simple Hinge Can only open and closearound a fixed hinge axis. No pretention to be anatomically correct. Hold themodels in ICP but cannot undergo lateral excursions. Useful if ICP is the onlyjaw position required to be recreated Average Value Articulator Originally based on Bonwill’sTriangle – an equilateral triangle with 4 inch sides and corners in the centreof each condyle and the lower incisor teeth. Modern average value articulatorsare based on: - intercondylar width of 110mm - condylar guidance angle of 30 degrees - conyle to incisal edge distance 110mm Lateral and protrusivemovements can be carried out though they are an average estimate of thepatients actual jaw movements Adjustable articulators Various settings can be altered to attempt to moreclosely model the actual jaw movements of the patient (dpendds on make) Eg - Denar MarkII articulator has a variable condylar guidance angle, immediate side shift andBennett angle. The Denar 5a has these plus the ability to alter theintercondylar width and various other dimensions of the glenoid fossa. Thesettings very difficult to record clinically and the advantage of doing sois unproven in terms of clinical benefit. The models are positioned inthese articulators with the assistance of a facebow which will lead to a closerapproximation of the patient’s hinge axis and so opening, closing and lateralmovements stand a higher chance of matching those of the patient. |
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When do you use each type of articulator? |
Simple Hinge – If tooth being restored only touches in ICP Average Value – Used for denture cases Semi-Adjustable – If lateral guidance needs to be recreated or altered (build ups/re-organisation) |
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Tips for conformative treatment |
· Try to recreate the originalanatomy, fissures often deeper in reality than in the restoration · Create Adequate occlusalclearance for crowns (Use amalgam packer as a simple guide) · Remember functional cuspbevel · Well-fitting temporary crownwith occlusal hold, replace immediately if comes off mid-treatment · Check impressions for; o Air blows in fissures o Adhering to tray o Occlusal surfaces of teeth necessary forarticulation have been recorded · Check models for o Blobs of plaster o Damage to teeth and preps Winstanley et al 1997 (UK) - 72% of impressions in flexible trays, defects on preparations common Storey 2014 (UK) 65% impressions in flexible trays 32% opposing impressions not adequately fixed to the tray |
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WHat is required for a technician to locate models correctly? |
Maximum Intercuspation (MICP_ |
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How is MICP recoreded in differnt scenarios? |
If odels fit only one way wich matches patient - none If models would have fitted together but you have prepped a tooth making it now not clear how they would fit - blu-mousse over top of prep and get pt to close to ICP Significan wear and no clear position for models - full arch wax/blu-mousse If too many teeth mising and no stable position - wax rims in endentulous spaces + blu-mousse |
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WHat does a facebow do? |
· Relates the position of theteeth to the patients skull · Shows the technician what ishorizontal - Accuracy of locating hinge axis is +/- 5mm |
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Technique for facebow record |
1 soften beauty wax, applay double layer to top surface of bite fork and mark centre line. (bite fork prong must be pointing straight forward below patients eye0 2 soften wax and position the bite fork over teh upper teeth making sure to keep midline in line wiht patients midline. Apply pressure to record cusp tips (not go through wax) 3 remove fork and allow to cool 4 reinsert fork ans get pt to stabilise with their thumbs in premolar area. double check promng is pointing striaght forward bleow right eye. Take out of patients mouth 5 use ruler to mark on right side of nose 42mm above right lateral incisor edge 6- attach jig, ear bow and bite fork 7 - guide bite fork in pts mouth. nurse holds ear bow in pt ears. Tighten ear bow centre piece 8 adjust height so pointer on ear bow is level with mark made earlier on patients nose 9 - ensure interpupillary line and ear bow line are parallel 12 - tighten nut 1 then 2 13 remove from mouth and tighten again - disassemble and disinfect |
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In lateral excursion do the teeth on the working side stay in contact and why? |
Yes because the condyle remains in the glenoid fossa and does not translate. On the non-working side it does |
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WHat can interference cause? |
pain due to overloading of the PDL. wear facets. fracture of teeth and restorations. mobility of the teeth. |
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What is condylar guidance? |
Condylar Guidance is the translational movement of the condyle down the articular eminence on the non-working side. This results in the downwards displacement of this side of the mandible as the patient rotates the mandible laterally. This consequently leads to the downwards displacement and therefore disclusion of the posterior teeth on this side. |
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What movements are facilitated by temporalis? |
Elevation and retraction |
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When is canine guidance not the best option? |
A root filled canine is not ideal for canine guidance BUT small access cavity + minimal root prep = probably strong enough Pt already in group function - may be suitable to change to canine guidance Bone loss due to perio - dpends on amount, if no longer active and suffiecient bone it would be ok Definitely not ok: - cantilever bridge pontic - post retained crown - heavily restored canine |
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WHat are the protective mechanisms in protrusion? |
condylar guidance, when the condyles translate down the articular eminence. incisal guidance. This is the movement of the lower incisors over the palatal aspect of the upper incisors. Preparation of multiple crowns for the upper anterior teeth can lead to the loss of the anterior most protective mechanism, however this can be reproduced or reinstated by asking the technician to create a custom incisal [guidance] [table]. |
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What does masseter facilitate? |
Elevation and protrusion |
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What can lose of lower molars lead to? |
Over eruption of upper molars causing RCP or protrusive intereference |
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HWat do you do if a tooth that is causing intereference needs a crown? |
Can't keep reducing occusal surface (damage pulp) Can't place crown high Answer = adjust intereferences first then carry out crown prep later |
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Features of average value articulator |
•Capable of lateral and protrusivemovement ••Are of an anatomical size ••Do not accept a facebow record ••Condylar angle usually an average value 30 degrees •Intercondylar distance 110mm Condyle to incisal egde distance 110mm ••User-friendly. |
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Features of semi-adjustable articulator |
•Widely used for diagnostic andtreatment procedures ••Anatomical size ••Intercondylar distance similar tothe average patient, not usually adjustable ••Accepts a facebow record ••Capacity to adjust the CondylarAngle, Immediate Side Shift, Progressive Side Shift. They may have two types of anteriorguidance table:•Adjustable flat metal table•Plastic for custom moulding withacrylic resin to mimic palatal surfaces. |
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What is immediate side shift and progressive side shift? |
Immediate - initial lateral only movement Progressive - when combined with protrusion |
