Week 3 Caries, Matrix, Dental Dam Flashcards
T or F Teeth are composed of inorganic elements (96% in enamel, 70% in dentin), organic elements, and water
true
Inorganic elements in teeth
calcium, phosphate, hydroxyl group = hydroxyapatite crystals
What is the Ca/P ratio
2.15
Cariogenic bacteria
strep mutans, lactobacilli, etc
The following factors contribute to demineralization:
Higher oral bacterial load - Results in more acid production
Frequent snacking- Allows less time for remineralization
Poor oral hygiene - Increases plaque and sugar remains longer
Decreased saliva production
Caries formation is positively associated with the following activities:
Frequent or prolonged contact of the teeth with sugary substances.
Consumption of sticky foods.
Regular use of medications that contain sucrose, including some multi-vitamins.
Why does saliva aid in remineralization?
Acts as a buffer to return the pH above the demineralization level, strengthens tooth enamel, and is a fluoride source
Black’s Classification System for caries
- Class I – Occlusal
- Class II – Posterior proximal * Class III – Anterior proximal * Class IV – Incisal
- Class V – Cervical
- Class VI – Caries in cusps
Class IV prep
incisal
Class II prep
posterior proximal
Class I prep
occlusal
Class III prep
anterior interprox only
Class V prep
cervical
Class VI prep
cusp tip
The mechanical alteration of a defective, injured, or diseased tooth in order to best receive a restorative material which will re-establish a healthy state for the tooth including esthetic corrections where indicated, along with normal form and function.
Cavity Preparation
Factors Affecting Tooth Preparation
General Factors
* Diagnosis
* Prevention
* Interception * Preservation * Restoration
Patient Factors
* Economic status
* Age
* Choice of material
Principles of cavity prep
–access and see the diseased tissue
–remove caries lesion
–cut away significantly unsupported enamel
–extend margins so they are accessible for instrumentation and cleaning
Simple tooth preparation
Only one tooth surface is involved
Compound tooth preparation
Only two tooth surfaces are involved
Complex tooth preparation
Involves three or more surfaces
Internal Wall Prep
prepared surface that does not extend to the external part of the tooth surface (including axial and pulpal walls)
Axial Wall of prep
internal wall parallel with long axis of the tooth
Pulpal wall of prep
internal wall perpendicular to the long axis of the tooth and occlusal of the pulp
External wall of prep
the prepared surface that extends to the external tooth surface, including
Floor/Seat
A floor is a prepared wall that is reasonable flat and perpendicular to the occlusal forces that are directed occlusogingivally.
Enamel Wall
A portion of a prepared external wall consisting of enamel.
Dentinal Wall
the portion of a prepared external wall consisting of dentin in which mechanical features can be located.
Where is the pulpsoaxial line angle in a class II prep?
the line where the pulpal wall and axial wall meet, right where the proximal box begins
Cavo-Surface Angle
is the angle of the tooth structure formed by the junction of a prepared cavity wall and the external surface of the tooth.
What class are OL and OB preps?
Class I, if it’s the in the occlusal 2/3 of the B and L surfaces of molars
What class prep are palatal pits of the maxillary incisors?
Class I
Can an anterior tooth be class II prep?
no
Do all class III lesions require a F or L surface?
no, it can be a straight M or D if accessible without a F or L prep
Do class III lesions involve the incisal edge?
no, that would be a class IV
Can class V lesions be proximal?
Yes, carious lesions in the cervical third that do not involve the margin.
Posterior tooth straight mesial prep in the middle third without access in the cervical third or margin would be what class?
I DON’T KNOW
Steps to stage I of the prep
- Obtain outline form and initial depth
- Primary resistance form
- Primary retention form
- Convenience form
Steps stage 2 final tooth prep steps
- Removal of remaining carious dentin
- Providing pulp protection if indicated
- Obtain secondary resistance and retention form * Finishing of enamel walls and margins
- Final procedures; Cleaning, inspecting and sealing.
Features of Resistance Form
-shape and placement of cavity walls
-Box shaped preparation
- Flat pulpal and gingival floor (helps the tooth resist forces)
-Adequate thickness of material to not break the filling or the tooth
-don’t extend too far so the marginal ridges are still strong
-include weak structure so it won’t break
-round internal line angles reduce stress
In resistance form, amalgam requires a minimal thickness of ____
1.5 mm
In resistance form, porcelain requires a minimal thickness of ____
2mm
In resistance form, cast metal requires a minimal thickness of ____
1mm
In resistance form, composite/glass ionomer requires a minimal thickness of ____
2.5mm
Which tooth is the pulpal wall prepped NOT flat?
mand 1st premolar, because the lingual cusp is so small, the pulpal floor is parallel to imaginary line joined the tips of the B and L cusps.
Retention form
Shape and configuration of the tooth preparation that resists the displacement or removal of the restoration from the preparation while under the influence of lifting and tipping during masticatory forces.
Factors affecting retention:
-Amount of stresses falling on the restoration
-Thickness of the restoration
-Total surface area of the restoration exposed to the masticatory forces -Amount of remain tooth structure.
Means of retention for amalgam
Adhesive system provide retention by micromechanically bonding amalgam to tooth structure. Undercut dovetail. 2-5% dentinal walls converge towards the tooth surface.
Means of retention for cast metal
- Close parallelism of the opposing walls with slight occlusal
divergence of 2 – 5% - Making occlusal dovetail to prevent tilting of restoration in class II preparations
- Use of secondary retention (if dentin is thick enough, extra grooves put in to give more surface area) in the form of coves, skirts and dentin slots.
Means of retention for composite
micro mechanical bonding between the etched and primed prepared tooth structure and composite resin, enamel bevels
Convenience form
the form in which the dentist must create to facilitates and provides adequate visibility, accessibility and ease of operation during preparation and restoration of the tooth. (So you can access it)
How does pulpal injury occur during prep?
- Heat production from hand pieces
*Irritating restorative materials - Galvanic currents from dissimilar metals
- Excessive masticatory forces transmitted through restorative materials to the dentin
- Micro-leakage
Pulp protection is achieved by using
liners, varnishes, and bases
Grooves and Coves in Secondary Retentive Form
small depressions and grooves placed into healthy dentin to provide additional retention (slots, locks, skirts)
The final step in tooth preparation is cleansing of the preparation.
- Removal of debris
- Irrigate the prep
- Drying the preparation
- Final inspection before placing restorative materials
- Leaving debris in the preparation may result in microleakage which can result in secondary caries.
- Cleaning of prep can be done by using warm water.
- Immovable particles of debris can be removed with a small cotton
pellet dampened with water or hydrogen peroxide.
Chapter 5 p142
When should cusp reduction be considered
- When the outline form extends half the distance from central groove to cusp tip.
- HIGHLY RECOMMENDED: when 2/3, but maybe not if the cusp is super large and using bonded resin
From the chapter, minimal occlusal thickness of materials amalgam, cast metal, and ceramics
amalgam 1.5mm
cast metal 1-2mm
ceramics 2mm
T or F The material thickness needed is greater in the posterior vs the anteriors
True
T or F Bonding increases resistance form
True
How do affected and infected dentin differ?
Affected: has not lost structural integrity to allow for micro-organisms to readily invade.
Infected: has.
Old restorative material should be removed while prepping if
- esthetic reasons
- old material will compromise bond to tooth
- caries under that material
- tooth pulp was symptomatic before prep
- the old material isn’t totally in tact.
T or F It’s okay to leave old restorative material in a prep
Yes, it can be kept as a base as long as it won’t compromise the new restoration
Pulpal irritation occurs during or after operative procedures may result from:
- heat rotary instruments
- ingredients in materials
- thermal changes in materials
- forces transferred from materials into pulp
- galvanic shock
- ingress noxious products and bacteria through micro leakage.
What is most commonly associated with pulpal response after a prep?
Ingress of bacteria, so completely sealing the dentinal tubules is important
Liners provide
- barrier protecting dentin from noxious agents
- electrical insulation
- thermal protection
Most common: zinc oxide, calcium hydroxide, resin modified glass ionomer RMGI thin film
What are bases?
materials, most commonly cements, that are used in thicker dimensions than liners to provide mechanical, chemical, and thermal protection to the pulp (zinc phosphate, zinc oxide eugenol, polycarboxylate, glass ionomer RMGI)
Calcium hydroxide liner is indicated when the excavation extends within ____mm of the pulp
0.5mm
T or F Calcium hydroxide liners must always be covered with an RMGI to prevent dissolution of the liner over time when used under amalgam
true
Liners are typically ___ thick
0.5mm
Space needed between pulp and metallic restorative material needed
desirable to have 2mm between pulp and metallic restorative material and can be made up of dentin liner and/or base.
T or F Calcium hydroxide liners must always be covered with an RMGI to prevent dissolution of the liner from the etch used for a composite restoration
true
Liners and bases placed in very thin areas or close pulp exposures should be placed without pressure
true
RGMI is used for ____
typically as a base. Effectively bond to tooth, release fluoride, and are strong.
Secondary resistance and retention forms
mechanical prep and treatments of the preparation walls with etching, priming, and adhesive materials.
Mechanical features of secondary resistance and retention forms
Retention grooves and coves–class III and V amalgam and some V composite. Coves for Incisal retention class III
Preparation extensions
Skirts–gold
Beveled Enamel Margins–cast metal and some composite
Pins, slots, steps, and amalgam pins
Enamel walls are etched for bonded restorations that use….
ceramic, composite, and amalgam materials
Objectives of finishing the prepared walls
create optimal margin between restorative material and tooth
smooth marginal junction
maximal strength of. the tooth and material at the margin.
What needs to be considered in finishing of enamel walls and margins
direction of enamel rods
support of the enamel rods at the DEJ and laterally
Type of restorative material
location of margins
smoothness or roughness desired
Which way do enamel rods point
radiate form DEJ perpendicular to tooth surface.
–converge from DEJ toward concave surfaces and diverge outwardly towards convex surfaces
–Rods converge toward center of grooves and diverge cusps and ridges.
–gingival third of enamel of smooth surfaces rods incline slightly apically.
Where is gnarled enamel located? Stronger or weaker than straight?
occlusal surfaces, stronger
T or F Enamel walls should be oriented so rods forming the prepared enamel wall have their inner ends resting on sound dentin
true, but walls no not need to have full length rods
The strongest enamel margin is composed of full length enamel rods supported on the preparation side by shorter enamel rods, all which extend to sound dentin
YES
What cavosurface angle is ideal for amalgam and ceramic due to low edge strength
90 degree
Which burs produce the finest finish with high speed finishing external walls?
plain cut fissure
crosscut
diamonds
carborundum stone
plain cut fissure
T or F In amalgam preps, a rougher prepared wall improves resistance to marginal leakage
true
Bond to drain deteriorates over time as a result of hydrolysis of the adhesive resin component of the hybrid layer and proteolytic degradation of the collagen component of the hybrid later
yes
The precipitation of mineral in the dentinal tubules beneath a caries lesion creates a physical barrier to bacterial ingress and appears ________
transparent appearance
Qualifications for ADA seal
safe and effective
Examples of class I medical decive
ex. prophy paste, brushes
Least regulated. Good manufacturing practices are required
Examples of class II medical device
ex. Composite and amalgam materials
Approval from FDA meeting equivalency to other products: meet performance standards.
Class III medical device
ex. Bone graft material
Most regulated, premarket approval. Must be approved by FDA before being sold. (device supported by data
a denture replaces
missing teeth, bone and gingiva to help with chewing food, speech, and appearance
Cast
a restoration is constructed on the replica
Study model is the same thing as diagnostic cast
true
What are study models used for?
study position of the teeth and as opposing cast to aid in construction of a restoration.
Most models and casts are made with
gypsum materials, similar to plaster of paris
cements as Luting Agents
cementing, gluing two objects together and fills microscopic gaps between the tooth and the crown.
Cements as bases or liners
can be used to protect the pulp from irritating materials or insulating under metal restoration.
Examples of dental preventive materials
sealants, mouthguard, fluoride trays
restorative polishing
remove a thin layer of material
Direct restorative materials
constructed directly in the oral cavity.
Ex. amalgam, composites, glass ionomers
Amalgam
liquid mercury with powdered metals
Composites
esthetic materials that polymerize in the mouth. Chemical reaction
Glass Ionomers and other cements
mortar like materials that set by an acid base chemical reaction in the mouth
indirect restorative materials
fabricated outside the mouth
ex. gold crowns, inlays, ceramic materials, indirect restorative polymers
Another name for temporary restoration
provisional restoration
Interim restoration
long term temp, ex. fractured front tooth but currently in ortho. So they do a very large filling but a crown would be better suited once the ortho is removed.
Dental materials are classified in 3 ways
- where it’s fabricated (intra or extra orally)
- how it’s used.
- longevity
What are all the categories of USE for dental materials?
-Restorations
-Crowns
-Bridges
-Complete and Partial Dentures
-Impressions
-Casts and models
-Cements
-Temporary materials
-preventive materials
-polishing
-implants
-specialty
Categories of location of fabrication of dental materials
Indirect or direct
Categories of longevity of dental materials
permanent, temporary, interim
Are undercuts divergent or convergent?
convergent
Which preps have divergent walls, an amalgam or an inlay?
inlay
Difference between a cast and a diagnostic cast/study model
It is called a cast when the restoration is constructed on the replica. It’s called a study model/diagnostic cast when used to study size and position of the oral tissues
Rubber dam contraindications
severe asthma, claustrophobia, trouble breathing through nose
