Choosing the material · Operative Dentistry
Direct Restorative Materials MCQ
Amalgam, composite resin, and glass ionomer / RMGI: properties, indications, and handling, and matching the material to the situation. 25 MCQs and 7 INBDE patient cases.
25 practice MCQsQuick-reference tableMnemonics + clinical pearlsFull distractor explanations
High-yield review
Concept summary and clinical relevance.
Quick-reference structure first, then detailed coverage. Mnemonics in amber, clinical pearls in blue.
The direct restorative materials each have a place, and matching material to the situation (load, esthetics, moisture, and caries risk) is a core operative skill. Amalgam is strong, durable, and forgiving of a wet field but does not bond and is not esthetic. Composite is esthetic and bonds, but it shrinks as it polymerizes. Glass ionomer chemically bonds to tooth and releases fluoride, but it is weaker. There is no single best material, only the best fit.
Direct restorative materials compared
| Material | Key properties | Best use |
|---|---|---|
| Amalgam | Strong, durable, no bond, not esthetic, needs mechanical retention | High-load posterior, hard-to-isolate sites |
| Composite resin | Esthetic, bonds, conservative, polymerization shrinkage | Esthetic and many posterior restorations |
| Glass ionomer | Chemically bonds, releases fluoride, weaker/less wear-resistant | High caries risk, root caries, liners, pediatric |
| RMGI | Resin-modified glass ionomer, light-cured, fluoride release | Liners, Class V, moderate-stress sites |
Amalgam
- Dental amalgam is made by triturating a silver-tin (with copper and zinc) alloy powder with liquid mercury; it sets through reaction phases (gamma, gamma-1, and gamma-2).
- High-copper amalgam is the modern standard because it essentially eliminates the weak, corrosion-prone gamma-2 (tin-mercury) phase, giving greater strength, less corrosion, and less creep (marginal breakdown).
- Amalgam is strong in compression and durable, and it tolerates a less-than-perfect (moist) field, but it does not bond to tooth, is not tooth-colored, and requires mechanical retention; it is brittle (weak in tension), so it needs adequate bulk and a 90-degree margin.
- Mercury is tightly bound in set amalgam; a separate handling concern is delayed expansion, which occurs when a zinc-containing amalgam is contaminated by moisture during placement.
Clinical pearl, Amalgam: strong, forgiving, but mechanical
Amalgam still excels where occlusal load is high and a dry field is hard to keep, because it is strong and technique-tolerant. The modern high-copper formulations removed the weak gamma-2 phase, improving strength and reducing corrosion and creep. Its limits define its preparation: it does not bond (so it needs mechanical retention), it is brittle (so it needs bulk and a butt-joint margin), and a zinc amalgam contaminated by moisture can show delayed expansion.
Composite Resin
- Composite is a resin matrix (such as BisGMA or UDMA), reinforced with filler particles, joined by a silane coupling agent, and set by a photoinitiator (camphorquinone) activated by curing light.
- Higher filler content increases strength and wear resistance and reduces polymerization shrinkage, which is why filler is the key reinforcing component.
- Polymerization shrinkage is composite's major drawback: as it cures, it contracts, creating contraction stress that can pull at the margin, opening gaps that cause microleakage and postoperative sensitivity; placing it in increments helps manage this stress.
- Composite has a higher coefficient of thermal expansion than tooth, so it expands and contracts more with temperature, stressing the margin; its strengths are esthetics, bonding, and conservative preparation.
Clinical pearl, Composite: bonded and beautiful, but it shrinks
Composite's advantages are esthetics, adhesion, and a conservative bonded preparation; its central weakness is polymerization shrinkage, which generates contraction stress that can open the margin and cause sensitivity. Manage it with incremental placement, good isolation, and attention to occlusion. Remember too that composite expands and contracts more than tooth with temperature, another reason a sealed, well-bonded margin matters.
Glass Ionomer and RMGI
- Glass ionomer cement sets by an acid-base reaction between polyacrylic acid and a fluoroaluminosilicate glass; it chemically bonds to tooth structure by ion exchange, without a separate adhesive step.
- It releases fluoride (and can be recharged by topical fluoride), giving it an anticariogenic quality valued in high-caries-risk situations.
- Its indications include high-caries-risk patients, root (Class V) caries, liners and bases, and pediatric or atraumatic restorative treatment (ART); its drawbacks are lower strength and wear resistance and sensitivity to moisture during early set.
- Resin-modified glass ionomer (RMGI) adds a resin component so it is light-cured with improved strength and handling, while still releasing fluoride and bonding to tooth.
Clinical pearl, Glass ionomer: the fluoride-releasing, self-bonding choice
Glass ionomer is the material to reach for when caries risk is high or a root surface is involved, because it chemically bonds to tooth and releases fluoride, and it is also a workhorse liner and base. The trade-off is lower strength and wear resistance, so it is not first choice for high-load occlusal surfaces. RMGI improves strength and handling while keeping the fluoride release, bridging glass ionomer and composite.
Choosing the Material
- Load: high occlusal load favors amalgam or a well-placed composite; glass ionomer alone is not ideal for high-stress occlusal surfaces.
- Esthetics: a visible (anterior or premolar) restoration favors composite, which can be shade-matched and bonded.
- Moisture and isolation: a site that is hard to keep dry favors amalgam (or glass ionomer) over technique-sensitive composite bonding.
- Caries risk: a high-risk patient or a root lesion favors fluoride-releasing glass ionomer or RMGI, and the final choice weighs all of these together.
Clinical pearl, Match the material to structure, force, and field
There is no single best material, only the best fit. Read the case through the structure (how much tooth remains and where), the force (occlusal load), the field (how well it can be isolated and bonded), and the patient's caries risk. Amalgam for high load and a difficult field, composite for esthetics and conservative bonding, glass ionomer or RMGI for high caries risk and root lesions: the SDF lenses turn the choice into a reasoned decision.
Core Recall Check
25 board-style MCQs.
Active recall is the highest-yield study method. Pick an answer, check it, and read why every distractor is wrong.
0 of 25 answered · 0 correct
Keys: A-E or 1-5, Enter to check
- Question 1EasyDental amalgam is produced by triturating an alloy powder with:
- Question 2HardThe advantage of high-copper amalgam over older low-copper amalgam is that it:
- Question 3HardWhich amalgam reaction phase is the weakest and most prone to corrosion?
- Question 4ModerateA key limitation of amalgam compared with composite is that amalgam:
- Question 5ModerateRegarding mercury in a set amalgam restoration:
- Question 6HardDelayed expansion of an amalgam restoration is caused by:
- Question 7ModerateAmalgam is especially well suited to:
- Question 8ModerateComposite resin is composed of a resin matrix, a photoinitiator, and filler particles joined to the matrix by a:
- Question 9ModerateIncreasing the filler content of a composite generally:
- Question 10ModerateThe major drawback of composite resin during placement is:
- Question 11ModeratePlacing composite in increments rather than one bulk mass helps to:
- Question 12ModerateLight-cured composite is set by a photoinitiator, classically:
- Question 13HardComposite has a higher coefficient of thermal expansion than tooth structure, which means it:
- Question 14ModerateComposite resin is the material of choice primarily when the priority is:
- Question 15ModerateGlass ionomer cement sets by:
- Question 16ModerateA distinctive property of glass ionomer is that it:
- Question 17ModerateThe fluoride release of glass ionomer makes it particularly useful for:
- Question 18ModerateA drawback of conventional glass ionomer is that it is:
- Question 19ModerateResin-modified glass ionomer (RMGI) differs from conventional glass ionomer in that it:
- Question 20ModerateGlass ionomer (or RMGI) is commonly used in atraumatic restorative treatment (ART) and pediatric dentistry because it:
- Question 21EasyWhich factor LEAST directly drives the choice among direct restorative materials?
- Question 22HardAmalgam is strong in compression but relatively weak in tension, which means it is:
- Question 23EasyFor a visible anterior restoration where esthetics is the priority, the material of choice is:
- Question 24ModerateFor a high-caries-risk patient with a cervical root lesion, a particularly suitable material is:
- Question 25ModerateThe continuous (matrix) phase of a composite resin, into which the filler is embedded, is the:
Clinical Reasoning Cases
INBDE patient cases.
7 ADA INBDE-format patient cases on direct restorative materials. Each case is a shared patient box plus linked questions with full distractor explanations.
INBDE Patient Cases
Direct Restorative Materials INBDE Patient Cases →
7 patient cases · 35 linked questions
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Author
Dr. Isaac Sun, DDS
Founder, KYT Dental Services. These MCQs are reviewed by a practicing clinician and offered as an educational reference for dental students.
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