Advanced restorative Flashcards
1
Q
What is an articulator?
Uses?
A
A mechanical device that simulates movements of the mandible, via replication of movement paths of the TMJ.
- Occlusal movements can be reproduced outside the mouth
- Occlusal surface of prosthesis can be constructed extra-orally
- Occlusion can be viewed from the lingual aspect (not possible intra-orally)
- Time efficient and convenient for patients.
They are used for diagnosis and treatment planning, as well as construction of crowns, bridges, fixed and removable prosthesis, as well as occlusal splint.
2
Q
What are the 4 different types of hinges?
A
- Simple hinge
- Average value
- Semi-adjustable
- Fully-adjustable
3
Q
What is a simple hinge articulator?
A
> Cannot simulate excursions or accurately alter vertical dimension
> Can hold and reproduce ICP, cannot reproduce retruded path of closure
> Used for temp crowns or single crown fabrication
4
Q
What is an average value articulator?
A
ASH free plane
Sagittal condylar guidance angle 30*
Vertical height can be varies (OVD changed via incisal pin)
Used for denture construction
5
Q
What is a semi-adjustable articulator?
A
- Closer to the retruded axis position, it is used for most fixed restorative work.
> Arcon (condylar element fixed to lower) = Denark MKII, can adjust the OVD
> As it can adjust the OVD is used for fixed restorative work.
> Non-arcon (fixed to upper) = Dentatus ARH, upper member locked in, used for dentures.
6
Q
What is a fully-adjustable articulator?
A
> Requires high amount of skill, confined for hospital setting mainly.
Used for reorganisation of entire occlusion.
7
Q
What are face bows?
A
Facebows orient the upper model in three dimensions relative to rotational axis of the mandible:
- sagittal axis - lateral excursions
- transverse axis - opening and closing movements
- vertical axis - lateral excursions
Facebows are used to record the relation of the maxilla to the hinge axis rotation of the mandible.
Enables this relationship to be transferred between the maxillary and articular hinge axis.
8
Q
What is a kinematic facebow?
A
Attached to the mandible which is moved through the retruded arc.
> Orients mandible to actual hinge axis.
Adjustments made until rotation only occurs and no translation.
9
Q
What is an average axis facebow?
A
> Most systems use the external auditory meatus as a landmark.
Denar, whipmix and Sam use the EAM
10
Q
What do occlusal bite registrations do?
A
Link the mandibular cast to the maxillary one (RCP).
11
Q
What are inlays?
A
Intra-coronal restorations constructed extra-orally, which are then luted into place.
12
Q
What are onlays?
A
Onlays are inlays with cuspal protection, fabricated extra-orally to cover one or more cusps.
13
Q
What are 3 types of tooth coloured inlays/onlays?
A
- Resin-based materials
- Ceramics
- Zirconium oxide
14
Q
What are the advantages of tooth coloured inlays/onlays?
A
- More conservative than crowns
- Aesthetics
- More resistant to wear than direct restorations
- Strengthen tooth 75%
- Less susceptible to decay
- No mercury
- Decreased # risk as increased resistance to occlusal load.
15
Q
What are disadvantages of inlays/onlays?
A
- # risk of restoration or remaining tooth
- Loss of marginal adaptation
- Cost
- Time consuming
- Technique sensitive
- Extensive tooth preparation
- Cement discrepancy and micro-leakage.
16
Q
When are inlays/onlays used? Tx scenarios
A
- Increased tooth structure loss - 1/3 to 1/2 of the distance from cusp tip to cusp tip.
- Horizontal fracture
- Lack of dentine support under the cusp
- Heavy occlusion, wearing composite restorations
- Carious teeth with short clinical crowns
- Strengthen underlying tooth (RCT)
- Maintaining or restoring vertical dimension
17
Q
What are dental requirements for inlays or onlays?
A
- Moderate to large Class I or II cavity
- Sufficient enamel present for bonding
- Strengthening or protecting of remaining tooth structure required (RCT)
- Maintain or restore the vertical dimension
18
Q
What are the benefits of indirect restorations over direct restorations for onlays/inlays?
A
Large inter-occlusal direct restorations can act as a ‘wedge’ force when under occlusal load.
- This can cause cuspal fractures by forces being transmitted outwards from the occlusal surface.
- Cuspal coverage provides better distribution of occlusal forces.
19
Q
What are contraindications for inlays or onlays?
A
- Excessive tooth wear
- Bruxism
- High caries risk
- Insufficient tooth substructure present for adequate bonding (>1/3r of occlusal surface)
- Young patients with large pulp chambers.
20
Q
What are preparation principles for tooth-coloured inlays?
A
- No undercuts present
- 10-20* flaring of internal walls, ideally 15*
- Rounded internal line and point angles
- All preparation margins in enamel (for optimal bonding)
- Cavo-surface should margin (no bevel as required in gold preps)
- If dentine or undercuts exposed, line and block out respectively with GIC.
21
Q
What are composite onlay preparation rules?
A
- Weak and undermined cusps need reduction by at least 2mm?
- Cusp thickness should be at least 2mm
- Block undercut area e.g. using polyalkenoate cement
- 15* outward wall taper
22
Q
What are similarities and differences in gold onlay and composite onlay preparation?
A
Similarities:
- Both have no undercut areas
- both need to be >2mm wide and deep
Differences
- Composite requires 15* outward taper, gold requires 5-10*
- rounded internal line angles for composite, sharp line angles for gold
- peripheral and occlusal bevel for gold
- cuspal reduction >2mm with composite onlays
- gingival floor rounded for composite, flat with gold
23
Q
How can you verify occlusal clearance of a reduced cusp?
A
Use a wax interocclusal record for the reduced cusp.
- Insufficient thickness of the wax calls for more cuspal reduction.
- The interocclusal record should be 1 or 1.5mm thick with little indentation.
24
Q
What 3 things do you need to send to the lab for inlay/onlay prep?
A
- Full arch impression using elastomer (silicone)
- Opposing arch impression in alginate
- Interocclusal bite record in ICP
25
What materials could you use for temporisation of inlays/onlays?
- Telio
- Soft light-cured resins (Fermit)
- Self-cured acrylic resins
26
What materials are used for inlays/onlays?
- Metal
> gold alloys
- Tooth coloured materials
> resin-based composite
> ceramic
> zirconium oxide
27
What are the advantages and disadvantages of composite inlays over direct composite filling?
Advantages:
- Polymerisation of fit surface possible.
- More efficient overall polymerisation
- Space created by shrinkage takes place on model rather than intra-orally (can replace shrinkage space in lab)
- Better proximal contours, contacts and aesthetics
- Reduced clinical time shaping the restoration.
Disadvantages:
- Bonding to tooth structure very technique sensitive
- Wear
- Overhanging margins
28
What are the advantages of ceramic inlays/onlays over composite?
Better contour and surface characterization possible to composite, fit surface of ceramic pre-treated with hydrofluoric acid (micromechanical retention)
A minimum of 2mm is desired for the restorative material ceramic over the cusps.
29
What are 3 features of fold inlays/onlays?
- Undercut-free preparation
- Maximum height with minimum taper (diverging 10* taper)
- Single path of insertion
30
What are contraindications of gold inlays/onlays?
- Adjacent teeth have dissimilar metallic restorations - galvanic action.
- Where inter-occlusal cavity width >1/3 of occlusal sirface
- Post-endodontic restoration will provide wedging action
- Young dentition with large pulp chambers.
31
Why do inlays and onlays fail?
- Fracture 8.3%
- Occlusal wear in contact areas
- Secondary caries 4.2%
32
What are advantages of restoring edentulous spaces?
Aesthetics
Occlusal stability
Masticatory effect
Speech
Psychological effect
Try and prevent over-eruption of opposing tooth and tilting of adjacent teeth.
33
What are disadvantages of restoring an edentulous space?
- Potential damage (fracture) to abutment tooth and pulp.
- Risk of secondary caries under retainer
- Cost and discomfort
- Periodontal effects
34
What is an bridge abutment tooth?
The tooth to which the bridge is attached
35
What is the bridge retainer?
The restoration that is luted into the abutment tooth.
36
What is a bridge pontic?
The artificial tooth that is carried by the prosthesis to replace the missing tooth.
37
What is the connector?
Connector is the area of the bridge that joins the pontic to the retainer.
38
What factors affect the selection of a bridge prosthesis?
1. General patient factors
> Medical history
> Occupation
> Appearance
2. General dental considerations
> Poor OH is risk for periodontal disease and caries
> Distribution of missing teeth, bridge more suited to single bounded space.
> Occlusion, difficult to provide dentures for Class II div 1 malocclusion
3. Local dental considerations
> Abutment teeth condition and inclination
> Opposing dentition, if over-erupted, tooth wear, occlusal stops or crowding.
> Edentulous ridge
39
What does the operator check before cementing a bridge?
Seating of prosthesis
Marginal quality
Occlusal stop
Interferences in functional movements
40
What can cause failure of a bridge to seat?
1. Clinical faults
- Preparation errors
- Impression errors
- Temporisation errors
2. Laboratory errors
- Case and die --> porosity and damage to the die
- Wax pattern --> distortion from heat, and no die separator or reservoir
- Investment --> setting, hygroscopic and thermal expansion to counter shrinkage.
- Casting
- Finishing and polishing.
41
Why make a temporary bridge?
- Allows minor movement of the teeth and improvement in marginal fit
- Allows patient to inspect the appearance
- Allows dentist to make further adjustments to occlusion and appearance.
42
What can you use to permanently cement a bridge in a. vital abutment teeth. b. non-vital abutments?
Vital abutments
a. Glass ionomer cement (AquaCem)
b. Zinc polycarboxylate (Poly-F)
c. Resin luting materials
d. Resin reinforced GIC (Fuji Plus)
Non-vital abutment
a. Zinc phosphate (irritant to vital pulp)
b. Glass ionomer cement (AquaCem)
c. Zinc polycarboxylate (Poly-F)
d. Resin luting materials.
43
Does Poly F bond to dentine?
NO
44
Does Aquacem bond to enamel and dentine?
yes
45
Does Fuji Plus bind to enamel and dentine?
yes, and it releases fluoride
46
Why are bridges hard to seat?
- High hydrostatic pressure of the cement and the large surface area and parallelism of the preparation.
47
What is a RRB?
- Minimal tooth preparation, made to adhere to tooth via acid etch technique.
- Electrolytically etched NiCr alloy
48
What is a cantilever bridge design?
- Retainer only at one end of the pontic, with a rigid connector.
- Prep of only one abutment, conservative design.
- Leverage forces on the abutment limits span to only 1 pontic.
- No torqueing forces from occlusion can act on pontic
- Construction must be rigid = avoid distortion of bridge and #.
49
What is a fixed-fixed bridge design?
- Retainer either end with a pontic lying in the middle, with rigid connector.
- Robust design for maximum strength and retention, ideal for large spans.
- Disadvantaged due to preparation of two teeth that need to be parallel
- Simplest lab construction
- Cementations problematic due to insertion in one piece.
- Full occlusal coverage of abutment teeth, 3/4 crown minimum preparations.
- The opposing arch must have full occlusal contact, otherwise risk of depressing natural tooth contact.
50
What is a fixed-moveable bridge design?
- Retainer at either end with pontic.
- Rigid connector distally
- Movable connector mesially, stress-redistributing.
- Ideal for divergent abutment teeth.
- Able to lute bridge in two sequential parts.
- Lab construction complicated, and length of span limited (especially perio pts)
- Minor retainer mesially with an intra coronal attachment (ICA) allows movement.
51
What is a spring cantilever design?
- Retainer at one end only, with one pontic with a moveable connector.
- Abutment tooth is a posterior tooth, with flexible connector palatally connected to the pointic.
- Allows spacing between anterior teeth to remain, whilst preserving sound anterior tooth structure.
- Limited to replacing maxillary incisors and can cause trauma.
- Full occlusal coverage of distal abutment tooth.
- Poor tolerance to palatal spring.
52
What is a hybrid design bridge?
Crowned tooth at one end of an edentulous span, with sound tooth at the other end.
53
What materials can be used in bridge construction?
1. All metal
- used where appearance is not vital and function and stability are of concern.
- least destructive conventional material (retained via 135* chamfer)
- chamfer provides slip join, limits microleakage.
2. Porcelain fused to metal (PFM)
- Strength of alloy provides durability, whilst porcelain more aesthetic.
- Used for visible bridges
- Requires butt joint (shoulder margin preparation).
3. All porcelain
- Limited to 3 unit fixed-fixed design
- Pontic out of occlusal contact.
54
What are the biological, mechanical and aesthetic factors that affect pontic design?
Biological factors:
- Maintain and preserve alveolar ridge, abutment teeth, supporting tissues.
- Minimal plaque accumulation
- Light pontic contact
- Must be easy to maintain OH with it in-situ.
Mechanical factors
- Pontic must be able to withstand forces of occlusion and mastication without flexing
- Retainers flexing will result in prosthesis # and displacement of retainers.
Aesthetic factors
- Following XLA there is loss of tooth structure, alveolar bone and dental papillae
- Must deceive observer into believing they see a natural tooth shape.
55
What are 5 different pontic designs?
A. Ridge lap pontic
B. Modified ridge lap pontic
C. Stein pontic
D. Sanitary pontic
E. Ovate pontic
F. Dome pontic
56
When is a hygienic pontic used?
Used only for functional reasons, with no soft tissue contact.
57
When is a dome-shaped pontic used?
- Used where only occlusal 2/3 of pontic visible and gingival part unseen.
58
What is a disadvantage of saddle-shaped/ridge lap pontic used?
Large area of tissue contact on bridge, produces inflammation though.
59
What is an advantage of modified ridge lap pontic?
Allows pontic to resemble tooth, with ridge tissue buccal, has lingual surface cut away to allow access for oral hygiene reasons.
60
What is a resin retained bridge?
A fixed prosthesis that is bonded to one or more unprepared of minimally prepared natural teeth.
Chemical bond between the sand-blasted oxidised metal retainer surface and the resin.
61
What are advantages and disadvantages of RRB?
Advantages:
- Conservative
- Shorter clinical time
- Reversibility
Disadvantages:
- Aesthetics: greying of abutment teeth and metal displaying over incisal edge
- Try in difficulty
- Temporisation difficult
- Risk of debond and failure rate higher than conventional bridge
- Risk of caries is greater if partial debond compared to fixed-fixed design.
62
What are indications for an RRB?
- Single tooth replacement
- Unrestored or minimally restored abutment teeth
- Teeth with sufficient quality enamel
- Retention after orthodontic
- Intermediate prosthesis for young patients prior to implants.
63
What are contraindications to RRB?
- Heavily restored abutments
- Lack of sufficient quality enamel
- Excessive occlusal loading and bruxists
- Poor OH and isolation
- Translucent incisal edge (requires incisal edge bonding
- Small teeth (peg shape)
- Allergy to Nickel
- RCT
64
What are the advantages of an RRB cantilever design and which teeth can these be used for?
- Limited to anterior teeth
- No differential movement issues, therefore less stress on resin lute
- Eliminates partial debonding
65
What factors can increase the survival or an RRB? (5)
1. Cantilever design
2. Greater operator skill and experience
3. Minimal or no preparation
4. Single pontic
5. Not using rubber dam
66
What little prep may be needed for an RRB?
Sharp angles removed
Bulbosities removed
Guide planes may need to be cut
Avoid dentine exposure
Create incisal bevel for anterior teeth
67
Retainer from RRB:
- maximum surface area for bonding.
- aim to achieve "180* wrap around" for aesthetics.
- consider crown lengthening if insufficient clinical crown
- retainer must extent just onto the incisal edge or over posterior cusps
- posterior teeth should have extensive occlusal coverage
- must be rigid to resist flexion and prevent debond
- thickness >0.7mm minimum
68
What materials do RRBs have?
- Nickel-chrome (NiCr) alloy used due to rigidity.
- Cement must incorporate 4-META or phosphate groups.
69
What rotary curettage for soft tissue management?
- Surgical procedure designed to remove the soft tissue lining of the periodontal pocket with a curette.
- Creates a wider gingival sulcus
- Aim to leave only a gingival connective tissue lining.
- Easy to do, cheap and requires no special equipment.
- Difficult to control bleeding, painful, slow healing, minimal tissue removed (unless scalpel).
70
What is electrosurgery soft tissue management?
Indications?
Contraindications?
Advantages?
Disadvantages?
- High frequency radio waves generate heat, causing cell destruction.
- Used for cutting and coagulating tissue.
Indications:
> used for forming a gingival trough
> Crown lengthening
> Gingivectomy and frenectomy (removal of excess tissue)
> Exposing subgingival cavities and unerupted teeth
> Tissue recontouring
Contraindications:
- Poor OH
- Pacemaker present
- Space formation if instrument touches metal
Advantages:
- Dry operating field
- First intention healing
- Post-surgical haemorrhage well controlled provided no tissue inflammation
Disadvantages:
- Bone trauma
- Potential recession post-treatment
- Post-operative pain
71
How do you carry out electrosurgery?
- Anaesthetise patient and instrument selection, earth the patient and set up high volume suction, isolating surgical area. Keep electrode moving, avoiding the same area for 10 secs and avoiding metallic restorations, using lowest setting possible.
72
What are advantages and disadvantages of a retraction cord?
Advantages:
> universal technique using double or single cord.
> various degree of retraction possible.
Disadvantages:
> potential bleeding
> time consuming
> epithelial attachment can be damaged leading to recession
> can slow setting of impression materials
73
What can you dip retraction cord in to help control bleeding?
Dip in a haemostatic agent (15.5% ferric sulphate), blot on gauze and pack using proper instrument.
74
What is Expasyl (Kerr UK)?
Injectable past for gingival retraction.
Made from kaolin, aluminium chloride and water.
Opens gingival sulcus, leaving surgical field dry
Aluminium chloride controls bleeding
75
What are 5 different haemostatic agents?
1. Ferric sulphate: pH 1.2, constricts tissues, turns tissue black, may produce bleeding on removal and inhibits impression material from setting.
2. Aluminium sulphate: pH 3, constricts tubules.
3. Aluminium chloride: pH 3, constricts tubules (least reactive with addition-cured silicone impressions)
4. Zinc Phenol Sulphate: pH 3, constricts tubules.
5. Epinephrine: pH 7, vaso-constrictor (side effects of adrenaline)
76
Why is the restoration fit of a bridge important?
- Direct correlation between poor fit and periodontal disease.
- Defective crown margins and reduction in height of interdental alveolar bone
- Poor fit allows plaque accumulation
- Closest fit with thinnest layer of cement, remove all excess.
77
What is attrition?
Loss of tooth substructure caused by contact with opposing dentition
78
What is erosion?
Progressive loss of hard dental tissue by chemical process
79
What is abrasion?
Loss of tooth substance caused by mechanical action not mastication or tooth-tooth contact.
e.g. tooth brushing, tongue, pen chewing, tongue piercing.
80
What is abfraction?
Loss of hard dental tissue by biomechanical loading of forces
81
What are risk actors for tooth surface loss?
- Incisal position, malocclusion can cause lost of attrition
- Restorations, porcelain crowns particularly destructive
- Habits
- GORD, bulimia, anorexia (intrinsic acid source)
- diet - fizzy drinks (carbonic acid). citrus foods.
82
What are the classifications of tooth wear?
1. Mild/moderate/severe
2. Localised or generalised
3. Basic Erosive Wear Examination (BEWE), ranging from - to 3*
4. Tooth wear index (TWI), ranging from 0 to 4
83
What is BEWE scores?
0 = no erosive wear
1 = initial loss of surface texture
2= distinctive defect, hard tissue loss <50% of surface
3 = hard tissue loss ? 50% of surface area
84
What can cause dental erosion?
Intrinsic acid sources:
1. Rumination, GORD, excessive vomiting, increased gastric pressure.
2. Increased gastric volume
3. Sphincter incompetence
4. GI disorders, eating disorders and drug induced excessive vomiting
Extrinsic acid sources:
1. Dietary, environmental and medication
85
How can you monitor dental erosion?
Ongoing study models, very useful for patients with worn dentition
Photographs
Linear and 3D direct measurements
Keeping up to date classification in medical notes
86
What are indications for restorative intervention in TW pts?
Unacceptable aesthetic appearance
Normal function disrupted
Progressive tooth wear
87
What are restorative treatment options for the worn dentition?
Conventional fixed restorations
- removeable onlay or overlay prosthesis
Minimal preparation adhesive restorations
- orthodontic appliance to prevent grinding??
88
What are challenges restoring the worn dentition?
- Insufficient interocclusal space due to vertical wear.
> Creating of adequate space by increasing OVD via restorations
> Tooth reduction for preparations
> Conform to the reduced space and crown height
> Full mouth rehabilitation can increase the OVD, or orthodontic treatment.
- Dahl appliance to allow increased eruption of the opposite arch
> includes a flat anterior bite plane, causing deliberate posterior disclusion.
> Therefore, it creates anterior interocclusal space.
> Resin bonded palatal metal veneers
> Gold bonded palatal veneers
> Ceramic resin bonded palatal veneers
> Direct composite resin palatal veneers
- Direct and indirect composite resin restorations
> Median survival around 5-6 years.
89
What is a briault probe used for?
> Sharp double ended probe
> Helps in detecting interproximal caries and hidden tartar in periodontal pockets.
90
What is naber's probe used for?
Assess furcation areas of a tooth
3mm marks
91
What is number 9 probe = explorer right angle probe used for?
Detects caries and calculus.
92
What are the measurements on a William's probe?
1, 2, 3, 5, 7, 8, 9, 10
93
What are the measurements on a WHO probe = BPE probe?
0.5mm ball
3.5-5.5mm black band
8.5-11.5mm black band
94
What are the 2 broad types of discolouration?
1. Intrinsic: formation of staining within the tooth structure (pre-eruptive or post-eruptive)
2. Extrinsic: found on the outside of the tooth
95
What are causes of extrinsic staining?
- smoking (tobacco, betel nut)
- medication (tetracyclines)
- plaque and calculus
- chlorhexidine mouthwash (only if diet high in tannins, e.g. tea, coffee etc)
- Dietary (tea, coffee, red wine, curry, beets, pomegranate)
96
What are intrinsic causes of tooth discolouration? (pre-eruptive (6), post-eruptive (7))?
1. Pre-eruptive
> Fluorosis
> Hypoplasia and hypomineralisation
> Amelogenesis imperfecta
> Dentinogenesis imperfecta
> Other inherited enamel defects
> Tetracycline staining
2. Post-eruptive:
> caries
> aging
> restorative materials
> smoking
> tooth wear
> tetracycline staining
> trauma
97
What is used to whiten teeth? concentrations?
1. Carbamide peroxide 10%: approx 3.5% hydrogen peroxide
2. Carbamide peroxide 16%: 5.6% hydrogen peroxide
Higher concentrations are associated with increased risk of experiencing side effects
98
How do you do non-vital whitening?
1. Place rubber dam
2. Removal of GP 2mm below the gingival margin
3. Consider removal of heavily stained dentine
4. Place 1-2mm of GIC over GP
5. Place carbamide peroxide with cotton pledget, seal and leave for 2 weeks.
- Discolouration due to haemoglobin breakdown products from necrotic pulp tissue diffuse into dentinal tubules.
- Walking, inside-outside bleaching and selective reservoir are all treatment options.
99
What types of staining are unable to be whitened? (4)
1. amelogenesis imperfecta
2. dentinogenesis imperfecta
3. enamel hypoplasia
4. root resorption
100
What are 5 side effects of whitening?
1. Sensitivity
2. Gingival irritation
3. Cervical resorption (non-vital whitening)
4. GIC barrier
5. Relapse
101
What is microabrasion treatment used for?
Brown and white stains non-responsive to whitening, involving removal or a small amount of surface enamel.
102
What do you use to carry out microabrasion?
Uses abrasion (pumice) and erosion (18% HCl), with approx 0.1mm of enamel being removed (Hydrochloric-acid-pumice microabrasion)
103
What are indications of microabrasion treatment?
1. Fluorosis
2. Localise hypoplasia
3. Post-orthodontic demineralisation
4. Idiopathic hypoplasia, with limited discolouration to outer enamel layer.
104
Why would you do a RCT for a perfectly fine tooth?
A restoration for a tooth where there is insufficient coronal structure to support a conventional restoration, requires RCT for required support.
- Root canal provides retention for the post, which provides retention for the restoration.
- Core replaces dentine
- Crown restores morphology and function.
105
What are indications for a post crown?
Post RCT single rooted teeth
Insufficient coronal structure to support a conventional crown
- Ferrule present
- PROVE assessment complete
> Periodontal assessment
> Restorative condition
> Occlusion
> Vitality (periapical assessment radiographically)
> Endodontics
106
What are contraindications to a post-crown?
- Active caries or periodontal disease
- Subgingival margins
- Vertical root #
- Very short root length
107
What is a ferrule?
A metal collar of the crown surrounding the parallel walls of dentine.
108
What steps are there in a post-crown?
- 1-2mm of dentine coronal to crown margin.
- Improves fracture resistance and long-term prognosis
- 1mm of root dentine required
- Removal of GP up until 5mm from apex of the tooth
- Cement using zinc phosphate or panavia F2.0
Treatment should be immediately post RCT, with a coronal seal critical to success
109
What are 4 different types of posts?
1. Tapered post
- less risk of perforation during preparation
- can cause wedging effect - root #. Less retentive per unit length
2. Parallel-sided post
- more retentive
- preparation can result in perforation
3. Serrated
- more retentive than smooth. Forms a cement lock between metal post and wall of canal.
- less retentive than threaded
4. Threaded
- Greatest retention of all surfaces
- Stress concentration - root #
110
What are active posts?
Dentatus screws
Parapost threaded
Kurer anchor
Radix anchor
Self-threading or pre-tapped
- they are combined with a luting cement to create a seal.
- however they introduce great stress onto the canal preparation by wedging effect
- greater risk of #
111
What are passive posts?
Cast (indirect and direct) or prefabricated, post is retained in the canal by adhesive lute.
Indirect: impression taken of prepared RCT and coronal dentine.
Direct: acrylic resin pattern of post and core constructed chairside, using Duralay.
112
What are advantages and disadvantages of parapost system: both direct and indirect?
Advantages:
- conservative
- reduced risk of perforation
- removeable
- suitable for flared canals
Disadvantages:
- Wedging effect - root #
- Time consuming
- Additional visit for crown impression
- Temp post-crown may lead to lack of coronal seal
113
What can prefabricated posts be made from?
- Titanium
- Glass fibre
- Ceramic
114
Fibre posts?
Quartz and silica in resin matrix, smooth, elasticity like dentine, bonded to root canal
> Good aesthetics with ceramic crowns
> Immediate placement ensures coronal seal
> Fewer visits, with no temporary post-crown necessary
> However, procedure very technique sensitive, not suitable for flared canals
??
115
How can you remove posts?
Piezo sealer to loosen cement around post then trephine from Masserann kit used to cut 2mm channel around post.
116
how do you place a post crown? steps (6) parapost system
1. Removal of GP
- chemical: oil of eucalyptus or terpentine
- thermal: heated lateral condenser or system B spreader
- mechanical: gates glidden burs or peeso reamers
2. Preparation of canal using Parapost drills
3. Ferrule:
- 1-2mm of dentine coronal to crown margin
4. Length of post
- as long as possible allowing for RCT lenth and curvature of canal
- 4mm short of apex
- Optimum crown:root ratio 1:1.5 (Crown should b x1.5 1/3 diagmeter of root at that depth
6. Antirotation:
- luting cements
> metal post: zinc phosphate cement
> fibre post: dual cure adhesive resin (Panavia or Rely X)
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What is the ferrule effect (ferrule resistance)?
- improves the overall resistance of restoration.
- reinforces root filled teeth
Height of ferrule:
- greater the height of remaining tooth structure, better the fracture resistance
- ferrule height of 1.5-2mm of vertical tooth structure will be the most beneficial
Width of ferrule:
- it is considered too thin if the dentine walls are <1mm in thickness.
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Why must RCT teeth be restored with cuspal coverage?
- Weakened by previous restorations and access cavity.
- Cusp height now from floor of pulp chamber to tip of cusps
- Dentine structure has been altered, making it more brittle
- Alteration to proprioception in PDL, allows greater occlusal forces to be applied.
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What is the objective for restoring RCT teeth?
1. Reinforcement of remaining tooth structure.
2. Replacement of coronal structure
3. Retention for overlying crown
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What are replacement options for RCT to replace core for crown prep?
1. Bonded coronal restoration when adequate core material present.
2. Pinned retained amalgam
3. Amalgam retained with slots and grooves
4. Bonded amalgam
5. RCT post retained amalgam
6. Nayyar core
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What is a Nayyar core?
An amalgam coronal-radicular core technique/or RCT posterior teeth
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What are indications for a nayyar core?
1. Root filled posterior tooth
2. Short or curved root canals
3. Sufficient cervical dentine in coronal area to support final restoration
4. At least one cusp remaining to allow a ferrule
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What are the stages of a Nayyar core preparation?
1. Asses post-operative radiograph
2. Remove all coronal restorative material, render cavity caries free
3. Remove root filling material from pulp chamber
4. Remove 2-3mm of coronal GP in root canals filled (Gates Glidden)
5. Consider placement of additional retention features
6. Apply matrix band
7. Condense amalgam into coronal aspect of root canals
8. Fill pulp chamber and cavity to restore tooth
9. Remove excess amalgam before removing matrix
10. Carve amalgam anatomy
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What are indications for endodontic surgery? (3)
- Extruded material with apical periodontitis over a prolonged period
- Persisting or emerging disease following RCT, when re-treatment is appropriate
- Perforation of the root or floor of pulp chamber
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What are reasons for RCT failure?
1. Microbes persisting within the root canal system
2. Cyst formation (15% prevalence)
3. Extra-radicular infection
4. Foreign body reaction
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What is the PROVE system used for endo???
Periodontal assessment
Restorative condition
Occlusion
Vitality (periapical assessment radiographically)
Endodontics
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What is the prep for a full gold crown?
> Occlusal reduction (1mm on non-functional and 1.5mm on functional)
> Axial reduction (buccal, palatal and interproximal) 0.7mm? with 877 torpedo bur to produce 135* chamfer.
> Retention grooves and boxes
> Cusp bevels
> Retention grooves and boxes
> Margin prep
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What is retention form?
Prevents removal along path of insertion or along the long axis of the tooth
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What is resistance form?
Prevents dislodgement of the restoration by forces directed apically or obliquely
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What is a 3/4 gold crown?
Used where the lingual cusp has been lost and remaining core will be compromised if conventional techniques are used.
- Occlusal groove adds to resistance form and strengthens cast (buccally placed)??
- > Slots and grooves not essential as precious metal can be oxidised and sand-blasted
> Casting can be luted to etched tooth surface via 4-META and Panavia F
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What are indications of veneers? (4)
1. Discoloured, hypoplastic and hypocalcified teeth
2. Alter shape and size of tooth
3. Close diastema
4. Align mis-aligned teeth
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How do you do a veneer prep?
Labial reduction necessary to avoid an over-contoured restoration when veneer placed.
0.5-0.7m
Three plane reductions (gingival, mid-labial and incisal)
Place gingival margin of the prep at the crest of the gingivae
Proximal margin placed just labial to the contact area to preserve the contact points.
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What do each of these features help with:
- Shoulder, chamfer, buccal reduction, bevel, wing?
Shoulder - structural durability
Chamfer - marginal integrity
Buccal reduction - retention and resistance form
Bevel - structural durability
Wing - retention & resistance
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What is an anterior PFM bridge prep?
> Each abutment must be prepared appropriately for individual retainer
> Both abutments must have an appropriate path of insertion
> Together they must have a common path of insertion
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How do you do an anterior PFM bridge prep?
1. Incisal or cuspal reduction - 2mm reduction with inciso-palatal angle of 45° > Reduced surface lies perpendicular to forces of mastication
2. Align mesial and distal surfaces of abutments
3. Align labial and palatal surfaces
> Either winged or winless prep
4. Cingulum reduction
5. Finish line — labial shoulder (> 1.3mm) and palatal chamfer (0.7mm)
6. Final definition and finish
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What do you check intra-orally on a bridge before cementing it?
Appearance
Fit of metal regainer
Occlusion
Contact points
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How can you prep an RRB?
Bonding process??
RRB is decontaminated, removing glycoproteins and mucopolysaccharides from fit surface.
Preparation of fit surface by sandblasting with 50um alumina particles.
Resin lute is chemically, and light activated, sets in absence of oxygen
> Methacryl oxy deccyl dihydrogen phosphate (ionic bonding)
> 2 hydroxyethyl methacrylate resin (covalent bonding)
> Apply Panavia (Oxyguard) to margins of retainers
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What is a benefit of a fixed-fixed bridge?
Fixed-fixed bridges allow stresses to be distributed evenly between the abutment teeth.
> Abutment teeth should be capable of supporting the functional load of missing teeth.
> Good alveolar bone support and healthy supportive tissues are needed.
> Patient motivation and good oral hygiene for successful fixed-fixed posterior bridges.
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What is the rule for root surface area for bridges?
Total root surface area of all the teeth which support a bridge must be equal or exceed the total root surface area of the teeth being replaced.
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What is retention dependant on?
Retention dependant on clinical height of preparation and parallelism of opposing walls (3-5*).
