Introduction
Obturatio cavi dentis (Latin: “closing of the cavity of the tooth”, from obturare, to stop up) is the third principle of caries treatment: the prepared (first principle) and medicated (second principle, medicatio cavi dentis) cavity is filled with a restorative material. The material chosen for a given cavity, load and patient largely decides how long the restoration and the tooth survive.
Goals of obturation
The filling must seal the cavity, restore the tooth’s form, function and esthetics, and protect the pulp and periodontium.
- Marginal seal: no microleakage, hence no secondary caries or pulp irritation.
- Anatomical form: contour, contact point and occlusal relief (see contours and contacts).
- Function: chewing and speech; support of the weakened cusps.
- Esthetics: shade and translucency matching the tooth.
- Periodontal health: smooth surface, no overhangs.
Requirements of an ideal filling material
No material meets every requirement; each is a compromise, and the requirements are the yardstick for choosing one.
Filling materials: indications and limitations
Amalgam
- Indications: Class I and II in premolars and molars, especially large cavities under heavy load or where moisture control is poor.
- Limitations: no esthetics; no bond, so it needs mechanical retention form and more tooth is removed; a bulk of at least 1.5–2 mm and butt-joint (90°) margins; conducts heat (deep cavities need a base); corrosion, tooth discoloration, galvanic currents next to other metals.
- Contraindications: esthetic areas; mercury allergy. In the EU it has been excluded since 2018 for primary teeth, children under 15 and pregnant or breastfeeding women, and since 2025 is used only where the dentist judges it strictly necessary for the patient’s medical needs (details: amalgam topic).
Composite resin
- Indications: all classes (I–VI), anterior and posterior; first choice in esthetic areas, the only direct material for Class IV, and the basis of minimally invasive adhesive preparations.
- Limitations: polymerisation shrinkage of about 1.5–3 vol% – contraction stress, marginal gaps, postoperative sensitivity; placed in increments of ≤ 2 mm; technique-sensitive: needs an adhesive system and a dry field (rubber dam); no fluoride; weaker marginal seal on dentin and cementum.
- Contraindications: a field that cannot be kept dry (deep subgingival margins); relatively, very large cavities in bruxists and high caries risk with poor hygiene.
Glass ionomer cement (GIC) and resin-modified GIC
GIC is a fluoroaluminosilicate glass powder mixed with polyalkenoic acid; it sets by an acid–base reaction. Resin-modified GIC (RMGIC) adds resin (HEMA) and light curing: it is stronger, more esthetic and less sensitive to early moisture, but keeps the chemical bond and fluoride release.