Restorative and Oral Rehab Flashcards
T/F:Primary teeth may be more susceptible to restoration failures than permanent teeth
True
Differences between primary and permanent teeth w/ respect to cavity preparation
Primary teeth: restore smaller carious lesions because of
- thinner enamel and dentin;- pulps larger in relation to crown (pulp involvement occurs more rapidly);
- pulp horns closer to DEJ
Also……
- enamel rods in gingival 1/3 extend in occlusal direction (no need to bevel gingival margin)
- greater constriction of crown at CEJ (more prominent cervical constriction, extensive gingival extension can lead to loss of gingival floor)
- broader, flatter contact areas (makes clinical diagnosis of proximal caries more difficult)
- whiter in color (need lighter composite shades)
- shallower pits and fissures
- narrower occlusal table
Incomplete excavation (either one-step or stepwise) results in (fewer/more) pulp exposures and (fewer/more) s/s pulpal disease compared to complete excavation.
Fewer, fewer
Pulp exposure occurred (more/less) frequently from complete excavation compared to stepwise excavation.
More
There is evidence of a (decrease/increase) in pulpal complications and post-op pain after incomplete caries excavation compared to complete.
decrease
T/F: The risk of permanent restoration failure was greater for incompletely excavated teeth compared to completely excavated.
False. Risk for permanent restoration failure similar for incompletely and completely excavated teeth.
T/F: Higher rates of success in maintaining pulp vitality in permanent teeth was found with one-step/partial excavation compared to stepwise/two-step excavation.
True According to Maltz study (RCT) which compared stepwise to partial excavation in permanent molars. Suggests that there is no need to re-open the cavity and perform a second excavation.
Is there evidence to suggest not removing caries at all prior to restoring?
Yes, surprisingly! Two RCTs suggest no excavation can arrest dental caries so long as a good seal of the final restoration is maintained
What % of caries in permanent posterior teeth is in pits/fissures?
80-90% 44% in primary teeth
A Cochrane review found that sealants placed on the occlusals of permanent molars of kids reduced caries up to ___ months compared to no sealant.
48(4 yrs) Overall effectiveness in preventing dental decay – 71%
Sealants result in what % of caries reduction after 1 year?
86% caries reduction after 1 year!
Sealants result in what % caries reduction after 4 years?
58%
Sealants reduce caries risk in permanent 1st molars by what %?
33% (Mehare et al) 50% cochrane review
Sealing both sound surfaces and non-cavitated enamel lesions is warranted because…
Sealants lower the amt of viable bacteria by at least 100 fold and reduced the number of lesions with any viable bacteria by about 50%
T/F: You should not provide sealants if follow-up cannot be ensured.
FalseWhy? Because caries risk for sealed teeth that have lost some or all sealant does NOT exceed the caries risk for never-sealed teeth.
T/F: It is recommended to mechanically prepare the tooth prior to sealant placement.
FALSEIt is NOT RECOMMENDED. There is evidence that mechanical preparation may make a tooth MORE prone to caries in case of resin-based sealant loss. Sealant placement methods should include careful cleaning of the pits and fissures without mechanical tooth preparation.
Which is better – toothbrush prophylaxis or handpiece prophylaxis – to clean the tooth prior to sealant placement?
Toothbrush Evidence shows that teeth cleaned prior to sealant application with a TOOTHBRUSH prophylaxis exhibited SIMILAR OR HIGHER success rate compared to those sealed after handpiece prophylaxis.
How much enamel can be removed through rubber cup prophy?
.6-4.0 microns of the outer enamel
What kind of primers enhance sealant retention?
Acetone or ethanol solvent based primers, especially single bottle system NOT water-based primers – drastically reduce retention of sealants want low-viscosity hydrophilic material bonding layer, as part of or under the sealant – better for long-term retention and effectiveness
T/F: Resin-based sealants have better retention than glass ionomer-based sealants.
True, according to one meta-analysis and a Cochrane review BUT GI sealants exhibit good short-term retention comparable to resin-based at 1 year (therefore may be used as interim when moisture control compromises placement of resin sealants) Also no difference between caries-preventive effects of GI and resin-based sealants.
T/F: There is sufficient data to support use of fissure sealants in primary teeth.
False Insufficient data:76% retention in 2.8 years; retention rate of GI sealants in primary molars 18% in 1.3 years and no difference in caries reduction
What do bonding agents do for sealants?
Increase bond strength minimize leakage
Can you seal over enamel lesions?
Yes. It can arrest the lesion and reduce progression.If caries is into dentin, must be treated.
What are the 3 indications for sealants?
- Previous history of caries/restorations on other occlusal surfaces
- Sound occlusal surface with deep pits and fissures
- Explorer tugback with no demineralization, opacities, or shadowing.
What is Resin infiltration? What acid is used to etch?
Newer approach to treating non-cavitated interproximal lesions (ICON) Goal is to arrest the progression of such lesions. Aim: allow penetration of a low viscosity resin into the porous lesion body of enamel caries Technique:uses a specialized matrix interproximally treat surface with hydrochloric aciddesiccate surface with air, ethanolvia capillary action and 2 application cycles, infiltrate an unfilled fluid resin to the extent of the DEJ or beyondpolymerize resin with light TECHNIQUE SENSITIVEMUST USE RDI NOT RADIOPAQUE
There is evidence in favor of resin infiltration as a treatment option for small, non-cavitated interproximal carious lesions in primary teeth.
False. Evidence in favor of resin infiltration for PERMANENT TEETH. *Most of the RCTs done on resin infiltration have potential conflicts of interest BUT RI versus placebo showed less lesion progression (32% lesion progression versus 70% in one study, another study 7% versus 37%). Potential consistent benefit in slowing the progression or reversing non-cavitated carious lesions
According to the FDA, amalgam is classified as a Class ___ device.
II “having some risk”, therefore designated guidance including warning labels re: possible harm of hg vapors, disclosure of hg content, contraindications for persons with known hg sensitivity; also noted that there is limited info re: dental amalgam and long-term health outcomes in pregnant women, developing fetuses and children <6yo.
There is strong evidence that dental amalgam is efficacious in the restoration of what kinds of cavities in primary and permanent teeth?
Class I and class II Success rates: Class I in primary teeth: 85-96% for up to 7 years, average annual fail rate 3.2% Class I in permanent teeth: 90-99% for up to 7 years Class II in primary teeth: amalgam expected to survive minimum 3.5 years and potentially in excess of 7 years, Class II in permanent teeth: amalgam = to composite in mean annual failure rate (2.3%), medium success rate of composite and amalgam are = after 10 years (92% composite, 94% amalgam)
Amalgam is an alloy of:
Silver tin copper zinc mercury (wetting agent) (50%)
2 phases of amalgam
Gamma-1 : strong Gamma-2 : Sn7-8Hg Very weak, corrosion prone – responsible for early fractures and failures Added copper to change this (Sn7Hg to Cu6Sn5) Tin sets the reaction, controls the dimensional changes
What is ideal % mercury?
42-54% >55% Hg weakens amalgam All mercury is chemically bound and non-reactive after amalgamation All studies show no neurologic effects of dental Hg
Zn in amalgam serves what purpose:
Acts as oxygen scavenger, inhibiting oxide formation with Cu, Ag, Sn
Why would you use a bonding agent with amalgam?
Seal against microleakage, may aid in mechanical retention(?)
What is creep?
Tendency of a material to deform under constant stress. Higher copper means less deformation/less creep
Corrosion
Deterioration (chemical or electrochemical) of amalgam at the surface / subsurfaceHigh copper means less corrosion
Tensile strength of amalgam is high or low?
Low – that’s why you need deeper cavity preparation Compressive strength higher for amalgam
If the prep extends beyond the proximal line angles of a primary tooth, is amalgam a good restoration?
No. Class I, II, V restorations in permanent posteriors Class I, V primary Class II primary where prep does NOT extend beyond the prox line angles
What are the survival rates of amalgam restorations in primary teeth after 2-5 years?
46-66% over 2-5 yrs Mean survival about 5 yrs if placed at age 4-5Younger age at placement => lower mean survival time
Resins have what components?
- Filler particles (hydrophilic) - Matrix = dimethacrylate resin/BisGMA (hydrophobic) - Silane coupling agent (bonds matrix/filler) - Pigments - Stabilizers - Polymerization inhibitor- Photoinitiator - Radioopaquing agents
What size are the filler particles in micro-, mini-, midsize, and macro- filled resins?
Micro <0.1 micron (highest polishability) Mini 0.1–1 micron Midsize 1 – 10 microns Macro 10 – 100 microns (greatest strength) Hybrid resins combine both Filler size affects polishability/esthetics, polymerization depth and shrinkage, and physical properties
Filler functions
- Reduce polymerization shrinkage - Decrease coefficient of thermal expansion - increase hardness (compressive strength) - improve wear - control translucency
4 Contraindications to resins:
- Class II primary tth extending beyond line angles or C II permanent tth extending beyond ½ B-L intercuspal width 2. difficult moisture control 3. kids needing large multisurface restorations in 1˚ molars 4. High risk – multiple caries and/or demin and who exhibit poor OH or poor compliance
What is the polymerization shrinkage of resins?
2.5 – 6% less shrinkage w/ RMGI liner shrink towards the strongest area of the bond bond strength of ≥ 17 mPa needed to overcome shrinkage stress incremental filling reduces stress lower filled resins shrink more
Categories of Resins
Traditional – non-silane treated quartz particles (8-12um); >80% filled Microfilled – silane treated colloidal silica particles (0.04-0.4 um); 50-60% filled Hybrid – silane treated colloidal silical and glass particles of varying sizes (0.04-1.5 um); 50-75% filled Nanofilled – silane treated silica/zirconium particles (0.005-0.01 um);75-80% (highly filled) *trend toward high level of fillers (nano), replacement of traditional monomers with larger m.w. monomers, addition of silorane monomer*bulk fill resins frequently nanofilled, low shrinkage, polymerization depth up to 5 mm
Rank the tensile strengths of small particle, hybrid, nano, traditional, and microfilled composites
Small particle (1-5µ) = hybrid (0.6-1µ) = nano (5-100µ) > traditional (8-12µ) > micro (0.04-0.4µ)
Rank the compressive strengths of small particle, hybrid, nano, traditional, and microfilled composites
Small particle (1-5µ) > hybrid (0.6-1µ) = nano (5-100µ) > micro (0.04-0.4µ) = traditional (8-12µ)
Rank the finishability of small particle, hybrid, nano, traditional, and microfilled composites
Nanofilled > Microfilled > hybrid > small particle > traditional Take homes: Traditional are not strong or polishable – bad Microfilled are not strong but decent polishability Nanofilled are the most polishable and somewhere in the middle for strength Small particle and hybrid are the strongest, with medium polishability Note: Handbook also talks about “fine particle” – high wear resistance, good mechanical properties, rougher surface than microfilled or hybrid
What % filler are flowable resins?
45 – 70% result in: - increased shrinkage - decreased wear resistance - decreased strength - decreased bond strength radio-opacity is an issue, especially if flowable is placed beneath composite in “sandwich” technique
BPA (Bisphenol A) is considered a toxin and it is recommended to minimize exposure to it. Is it present in dental composites and sealants?
Yes, present in most. FDA & ADA conclude that any low-level exposure from dental materials poses no known health threat
BPA can become part of resin/sealant in 3 ways:
- Direct ingredient 2. Degradation by-product of bisGMA or bisDMA 3. trace material Recommendations to reduce BPA exposure: clean/rub new resins with cotton roll, pumice; rinse with water/suction, use RDI Trace amounts of BPA derivatives are released from dental resins thru salivary enzymatic hydrolysis