Operative Flashcards
What is centric occlusion ?
The position of the mandible when the teeth are in maximum intercuspation
Tooth related jaw position
What is centric relation ?
The position of the mandible e when the teeth first come into contact in the return dead position
Jaw related position
The heads of the condyls are in their medially braced uppermost untrained position
Ideal F/F occlusion
What is anterior guidance ?
The pathway of guidance provided by the palatial surfaces of upper anterior teeth during protrusion of the mandible
What is canine guidance ?
The pathway of guidance provided by the palatal surfaces of the upper canines during lateral movement The majority of patients with intact dentition and class 1 occlusion will have canine guidance
What is disclusion ?
The separation of posterior teeth during anterior guidance and the separation of anterior teeth during canine guidance
What is group function ?
Articulation between posterior teeth on the working side during lateral movement of the mandible
Ideal occlusion for full dentures
Which factors determine occlusion ?
Teeth
Left and right tmj
Neuromuscular system
Define caries
A process affecting the mineralised tissues ie denting enamel and cementum caused by the action of microorganisms on fermentable carbohydrates
What are the common sites of caries ?
Pits and fissures
Approximal
Root surfaces
What are the requisites for caries ?
Plaque containing cariogenic bacteria
Substrate eg sugar
Susceptible tooth surface
Time
Which bacteria are involved in the caries process ?
Strep mutants
lactobacillus deep lesions
Actinomyces for cervical caries
What is the microscopic appearance of primary enamel caries ?
Initiation phase
Destruction of enamel
Invasion of enamel by bacteria
Secondary enamel caries
Describe the initiation phase Of primary enamel Caries
Translucent zone
Dark zone
Body of lesion
Surface zone
What is the relative porosity of primary enamel caries ?
Normal enamel is 0.1% Translucent zone is 1% Dark zone is 2-4% Periphery of body is 5% Centre of body is 25% Surface zone is 1%
Describe secondary enamel caries
Enamel next to dentine is more susceptible to caries due to branching of tubules
What is secondary / reactionary dentine ?
Regular is rapid change of direction of dentinal tubules, similar to primary dentine
Irregular is rapid deposition of dentine due to caries, irregular pattern and little tubules
What risk factors are associated with caries ?
Cultural social and economic status Age Systemic and topical fluoride Sugar intake General and dental health knowledge Medical conditions Saliva, plaque and bacterial flora
What are the defence reactions of the pulp dentine complex ?
Tubular sclerosis
Secondary dentine
Pulpitis
What are the principles of cavity design ?
Gain access
Clear caries from adj
Remove unsupported enamel and grossly carious areas
Extend margins to prevent future disease
Consider retention, occlusal strength
Remove debris and dry
What is GV Blacks cavity classification ?
Class I - caries in outs and fissures
Class II - caries on approximal surfaces of posterior teeth
Class III - caries on approximal surfaces of anterior teeth
Class IV - caries on approximal surfaces of anterior teeth including the incisal edge
Class V - carries of the cervical surfaces
Why are crowns placed ?
Protect remaining tooth structure
Prevent drifting, over eruption
Restore occlusal function and arch integrity
Aesthetics
What are the indications for a crown ?
Cusp fracture
Vertical fracture
What are the contra indications of crowns ?
Poor oral hygiene
Insufficient tooth structure
Poor periodontal support
Non vital tooth - untreated periodical disease
What is the diagnostic approach towards crowns ?
History
Intra oral examination
Radiographs
Diagnostic models or face bow record
What type of articulation should diagnostic casts be set up on for crowns ?
Semi adjustable articulator
What are the advantages of diagnostic casts in The process of crown treatment planning ?
Can see edentulous areas
View occlusion from lingual aspect
Assess length of abutment teeth to decide best crown design
Assess abutment teeth drifting, rotation, inclination and buccolingual displacement
What are the biochemical principles of crown preparations ?
Preservation of tooth structure Marginal integrity Retention and resistance Preservation of periodontium Structural durability
What are the consequences of excessive removal of tooth structure during a crown preparation ?
Pulpal inflammation and necrosis
Acceleration of restorative cycle
Define retention
The ability of a crown to resist removal along its pathway of insertion
Define resistance
The ability of a crown to resist removal from apical, oblique or functional directions
What factors contribute to the degree of retention of a crown ?
Degree of taper Length of crown Type of cement Surface area of cement film Amount of cement under shear Roughness of the tooth surface
What is the ideal degree of taper for a crown ?
5-8 degrees up to 16 degrees
State the advantages, disadvantages, occlusal reduction and finish line for a full metal crown
Adv - little tooth preparation, does not wear opposing teeth
Disadvantage - aesthetics
Occlusal reduction is 1 mm non functional cusp, 1.5 mm functional
Finish line is 1 mm champher
State the advantages, disadvantages, occlusal reduction and finish line for an all ceramic crown
Adv- aesthetics
Disadvantages- increased wear of opposing teeth, substantial tooth preparation
Occlusal reduction is 1.5-2mm incisally
Finish line is 1.2-1.5 mm shoulder
State the advantages, disadvantages, occlusal reduction and finish line for a porcelain bonded to metal crown
Adv- aesthetics, reasonable tooth prep
Disadvantage - wear of opposing teeth
Occlusal reduction is 2 mm
Finish line is 1.2 mm shoulder on labial surface and 0.5 mm champher on lingual surface
What is the history of the rubber dam ?
First introduced in 1864 by Dr Sanford Barnum
Clamps in 1870
Harness on 1881
Frame in 1900
What are the advantages of rubber dam ?
Safety
Moisture control
Patient control
What is the role of the rubber dam in protecting soft tissues ?
Liquid etchant can penetrate cotton wool roll leading to gingival ulceration
What are the disadvantages of the rubber dam ?
Damage to gingivae
Feature of tooth or restorations
Allergy
Inhalation or swallowing of clamps
What are the dimensions of the rubber dam ?
15x15 cm , 0.15-0.35 mm thick, 3 year shelf life
What is the difference between a bland and retentive clamp ?
Bland clamps above the gingival margin, retentive clamps below
What is the disadvantage of using a green or blue rubber dam ?
Poor for shade selection
Where should the rubber dam stamp be placed ?
1.5 cm below the top of the dam
Which sized holes are suitable for which teeth when preparing a rubber dam ?
A for mandible are molars and large maxillary molars B for maxillary molars and small molars C for canines and pre molars D for maxillary incisors E for mandibular incisors
What are the relative merits of placing the clamp after the rubber dam ?
Only technique possible for double winged clamps
Restricted to anterior and premolars teeth
What are the relative merits of placing the rubber dam and the clamp together
Ideal for third molar teeth and endodontics
What are the relative merits of placing the rubber dam after the clamp ?
Ideal for posterior teeth but not third molars
Minimises the risk of gingival trauma
What proportion of lesions are due to fissure caries ?
84%
What are the non invasive diagnostic methods for fissure caries ?
Visual, tactile, electrical, magnification, radiographs , trans illumination, caries detection dyes
Why is tactile probing not a suitable method for the diagnosis of fissure caries ?
Can introduce cariogenic bacteria into fragile surface zone
What type of fissure lesion can be seen in a radiograph ?
Occult caries
How can dyes diagnose caries ?
Selectively complex with carious tooth structure which can be detected by fluorescence
Allows quantitative and qualitative assessment of caries
Which dyes are used to detect enamel caries ?
Procion- n2 and oh groups irreversibly bond to caries
Calcein- complexes with calcium
Zyglo- not used in vivo
Brilliant blue - not used in vivo
Which dyes are used to detect dentine caries ?
1% acid red 52 in propylene glycol complexes with dentures dentine
Iodine penetration method measures enamel permeability
What are the disadvantages of caries detection dyes ?
Dye staying and bacterial penetration are independent events
Dye stains food, pellicle, adj
Dye aided caries removal is laborious
How does diode laser fluorescence detect caries ?
680 mm wavelength
Optical tip has one transmission fibre and 8 fibres to detect reflected light
Caries has a different fluorescence than normal tooth structure
80% sensitivity
How do light emitting diode based devices eg vista proof detect caries ?
Violet light 405 nm
Porphyrins metabolites from bacteria are red
Normal tooth structure is green
How do electrical methods diagnose the presence of caries ?
Demineralisation increases tooth porosity
Porosity contains fluid with increased ions
Increases electrical conductivity
Very high sensitivity and can be used to monitor the progression of a lesion
What treatment options are available for fissure caries ?
Observation Laser therapy Ozone treatment Sealant restoration Normal restoration
How does laser therapy treat caries ?
Experimental co2 laser
Re organisation of HA structure
Probably will not raise pulp above 1 degree but no clinical trials
Which materials can be used as sealant restorations ?
Gic, composite, compomer, fissure sealant , dentine adhesive
What are the advantages of the sealant restoration technique in the treatment of fissure caries ?
Little tooth prep
Does not weaken tooth structure
Aesthetic
Preventive
What is a cavity ?
A permanent defect in tooth structure which leads to destruction
What is a tooth preparation ?
Iatrogenic alteration of the tooth structure in order to accommodate filling material to restore the tooth integrity
What is a conventional tooth preparation ?
Follows a specific depth, patter, marginal adaptation and form
For amalgam, metal and porcelain materials
What is a modified preparation ?
Used when bonding of the filling material to tooth structure is possible eg composite, compomer gic
What is the classification of radiographic depth scale ?
E1 is caries confined in the outer 1/2 of enamel
E2 is caries conforms to the inner 1/2 of enamel
D1 is caries 0.5 mm into dentine
D2 is caries more than 0.5 mm into dentine but less than 0.5 mm from pulp
D3 is caries within 0.5 mm of pulp
How long does caries take to reach the adj in deciduous teeth ?
3-4 years
How long does caries take to reach the adj in permanent teeth ?
6 years
Which type of cavity most commonly causes cusp fracture in posterior teeth ?
Mod
What are bonded amalgam restorations ?
A resin or gic based luting cement is placed into the cavity followed by the amalgam before the cement sets
Reduces marginal leakage
Useful for non retentive cavities
Increases cost
What are the indications for posterior composite restorations?
Small or medium class II cavities
Allergy to metals
Non retentive cavity
Where unsupported enamel may be strengthened by composite
What are the contraindications of posterior composite restorations ?
Poor oral hygiene Susceptibility to caries Poor moisture control Multiple large cavities with contact involvement Allergy Bruxing and grinding habits
What problems are associated with large class II composite restorations ?
Micro leakage and secondary caries
Wear and fracture
Cuspal flexure and post op pain
How long on average do amalgam restorations last ?
15 years
How long on average do composite restorations last ?
6 years
