Adhesion & Chemistry
Name the primary chemical family of resin-based cements and one inorganic component typically added to improve mechanical properties.
Resin-based cements are primarily composed of methacrylate resins; inorganic fillers (e.g., glass or silica) are added to improve strength and wear resistance.
According to the three-type classification of dental cements, what is Type I?
Type I are luting agents (permanent and temporary cements).
Name three variables that affect the final properties of a mixed dental cement
Powder-to-liquid ratio, mixing time/technique, humidity, temperature, glass slab temperature (for zinc phosphate), and working time.
After cementation of an indirect restoration, what is the immediate patient instruction and why?
Ask the patient to bite on a cotton roll for a few minutes to ensure initial set and proper seating; this helps reduce micro-movement and excess cement flow before final removal.
Name two advantages of resin-modified glass ionomer cements over conventional glass ionomers.
Higher early strength and longer working time; less sensitivity to water contamination and often reduced postoperative sensitivity.
Explain how glass ionomer cements chemically bond to tooth structure.
Glass ionomer cements bond chemically by an acid–base reaction where polyalkenoic acid reacts with fluoroaluminosilicate glass, forming ionic bonds between carboxylate groups and calcium/aluminum in tooth hydroxyapatit
List at least three clinical uses of dental cements.
Examples: luting permanent restorations (crowns, inlays), temporary cementation of provisional coverage, cavity liners/bases, pulp capping, root canal sealing, temporary restorations, core buildup (with appropriate materials), orthodontic band cementation.
Describe the consequence of using an incorrect powder-to-liquid ratio for a cement (e.g., too much powder).
Excess powder makes the mix thicker, reducing flow and potentially increasing brittleness and film thickness, compromising seating of restorations and possibly causing internal stress or incomplete seating.
Describe the clinical steps for removal of excess cement after seating a crown.
After initial set, remove gross excess with an explorer and floss interproximally; use hand instruments and rotary polishing/interproximal instruments as needed to remove marginal cement, then check occlusion and make final adjustments.
What is the principal disadvantage of ZOE as a permanent luting cement?
ZOE lacks long-term strength and durability and can interfere with resin polymerization; therefore it’s generally unsuitable for permanent luting of restorations requiring strong mechanical properties.
Describe how resin-modified glass ionomer (RMGI) differs chemically and in working characteristics from conventional glass ionomer cement.
RMGI contains both the conventional acid–base chemistry and polymerizable resin components (e.g., HEMA), allowing dual-setting (acid–base + light or chemical polymerization), resulting in higher early strength, longer working time, and reduced sensitivity to water.
Which type of cement is commonly recommended for cementation of ceramic veneers and what pre-treatment step is necessary?
Resin-based (composite) cements are commonly used; the tooth and restoration surfaces must be prepared (etching/enamel/dentin and silanation/etching of ceramic or intraoral bonding protocols) to ensure effective micromechanical and chemical adhesion.
For zinc phosphate cement, why is a cool glass slab used during mixing and how does temperature influence the cement?
A cool glass slab slows the exothermic acid-base reaction, extending working time and ensuring better manipulation; warmer temperatures accelerate set and reduce working time, risking incomplete seating and improper film thickness.
When is temporary cementation indicated for an indirect restoration and how does it influence later removal?
Indicated when the dentist anticipates needing to remove the restoration later (sensitivity, diagnostic concerns, provisional), or while waiting for lab work completion; temporary cements are weaker and allow easier retrieval without destruction of restoration or tooth.
Discuss the fluoride-related advantage of glass ionomer cements and its clinical implication.
Glass ionomers release fluoride, which can help reduce secondary caries around margins; clinically this offers cariostatic benefit especially in high caries-risk patients or as liners in restorative procedures
Identify two chemical reasons why zinc oxide–eugenol (ZOE) has a sedative effect on the pulp.
Eugenol provides local analgesic and anti-inflammatory effects by protein denaturation and nerve membrane stabilization; zinc oxide contributes an obtunding physical barrier and neutralizes irritating components.
For which indications is zinc phosphate cement still considered appropriate despite its age, and why might a clinician choose it?
Zinc phosphate (Type I fine grain) is appropriate for permanent cementation of cast restorations (crowns, inlays, bridges) due to its long clinical history, reliable compressive strength, thin film thickness when mixed properly; a clinician may choose it when chemical bonding is not required and reversibility or proven performance is prioritized.
Explain best-practice steps to minimize humidity-related problems when mixing water-sensitive cements (e.g., glass ionomer).
Work in a controlled, low-humidity environment; use freshly opened or properly stored materials; protect mixed cement from moisture contamination during initial set (avoid saliva exposure), follow manufacturer instructions for glazing or protective coatings, and apply quickly to reduce water uptake or loss.
Outline the steps and precautions when cementing an all-ceramic restoration with resin cement to maximize longevity.
Ensure restoration and tooth are clean and dry; etch enamel and dentin per bonding protocol (acid-etch enamel, apply bonding agent to dentin or use appropriate adhesive system), prepare ceramic surface (hydrofluoric acid etch for glass ceramics, silane application), use appropriate resin cement (light/dual cure per restoration opacity), seat, remove excess before final cure, and light-cure as indicated. Take care to avoid contamination and follow manufacturer’s timing for cure and cleanup.
Identify two limitations of resin-based cements and how to mitigate them clinically.
Sensitivity to contamination (moisture and oil) and technique sensitivity in bonding protocols; mitigate by meticulous isolation (rubber dam if feasible), strict adherence to etch/primer/bond steps, and proper surface treatment of ceramic restorations (silanization).
Discuss the role of silane coupling agents in composite resin cements and explain the chemistry by which they improve bond strength between filler particles and the resin matrix.
Silane coupling agents have bifunctional groups: an organofunctional methacrylate (or similar) group that co-polymerizes with the resin matrix and alkoxy groups that hydrolyze and form covalent siloxane bonds with the surface hydroxyl groups of inorganic fillers, improving stress transfer and bond durability.
Match the glass ionomer types I–VI to their primary clinical uses (briefly).
Type I — luting cement for indirect restorations; Type II — restorative for class V/erosion areas; Type III — liners and bases; Type IV — pit and fissure sealants; Type V — cementation of orthodontic bands/brackets; Type VI — core buildup material.
Compare hand-mixing versus encapsulated delivery systems for achieving powder-to-liquid consistency, including advantages and limitations of encapsulation
Hand-mixing allows clinician control and small-batch adjustments but risks operator variability in ratio and mixing technique. Encapsulated systems standardize powder-to-liquid ratios and mixing (mechanical Triturators), improving consistency and reducing contamination risk, but may be less flexible for altered ratios and require device availability and proper capsule storage.
Explain how cement selection should change for a deep preparation near the pulp and justify the choice.
For deep preparations near pulp, choose a nonirritating cement with insulating properties (e.g., polycarboxylate as a base or ZOE for its sedative effect, or a resin-modified glass ionomer liner) to protect the pulp, provide adhesion or seal as needed, and avoid materials with high exotherm or strong acid irritation (unless pulp is protected).
Correctly mixed glass ionomer cement should appear ____________.
shiny