Restorative Dentistry

Caries diagnosis begins with visual inspection and tactile exploration: look for white spots (demineralization), brown/black discoloration, or cavitation on proximal (between-teeth) and occlusal (chewing) surfaces. Probe suspicious areas gently; a sticky, catching sensation often indicates caries. Radiographs (bitewings, periapical) reveal interproximal and subsurface caries that are invisible to the naked eye. However, not all demineralization requires a filling: early white-spot lesions can be arrested and remineralized with fluoride and improved home care; only active, cavitated caries require restoration. ICDAS (International Caries Detection and Assessment System) criteria help standardize diagnosis: non-cavitated lesions (confined to enamel, no spread) can be monitored or treated non-operatively; cavitated lesions need filling. Patient risk (high sugar diet, poor oral hygiene, dry mouth, cavity history) guides decisions on aggressive versus conservative treatment. If the patient is young, has good hygiene, and has only one small cavity, a minimally invasive restoration (filling) is appropriate; if the cavity is large or involves multiple surfaces, the tooth may need a crown instead. Some caries are iatrogenic (caused by a previous filling's poor margins or overhang) and can be managed by replacing the old restoration rather than drilling deeper.

Amalgam (a mixture of mercury, silver, tin, and copper) is an older material that is durable, radiopaque, and highly forgiving of moisture; it sets instantly and requires no light curing. It is inexpensive, long-lasting (20–30 years), and excellent for large restorations, especially on molars. Disadvantages: esthetic (silver color, not tooth-colored), requires more tooth removal to achieve mechanical retention, and mercury concerns (though research shows minimal health risk). Composite resin (acrylic polymer filled with glass or ceramic particles) is tooth-colored, bonds chemically to tooth structure, and requires a curing light; can be matched to tooth shade precisely. Advantages: esthetic, conservative (less tooth removal), bonded to tooth. Disadvantages: technique-sensitive (moisture contamination weakens bond), requires strict isolation, less durable in high-stress areas (chewing surfaces), and more time-consuming than amalgam. Modern hybrid and nanofilled composites are stronger than older versions. Current trend is toward composite for anterior teeth (visibility) and increased use of composite in posterior teeth (molars) as material science and technique improve. Amalgam is still used by many dentists for large, deep restorations and posterior restorations in patients with poor oral hygiene, because composite's bond is vulnerable to contamination. Glass ionomer is a third material: weak but releases fluoride, used in pediatric teeth or as a temporary restoration. Resin-modified glass ionomer is stronger and combines benefits of both.

Bonding is the chemical attachment of composite resin to tooth structure (enamel and dentin) via a resin tag system. Steps: (1) Etch: apply phosphoric acid (30–40%) to enamel and dentin for 15–30 seconds, which demineralizes the surface and creates micro-porosities; rinse thoroughly and dry. (2) Prime: apply a hydrophilic resin primer that flows into the microporosities and absorbs into dentin. (3) Bond: apply a hydrophobic bonding agent (resin) that bridges the primer and composite. (4) Apply composite and cure with light. Moisture contamination is the enemy of bonding: saliva, blood, or sweat on the enamel or dentin will cause the etch, primer, or bonding agent to fail, leaving gaps between the restoration and tooth that allow micro-leakage, sensitivity, and recurrent caries. Critical steps: (a) isolate the tooth completely with a rubber dam if possible, or use gauze, cotton rolls, and a retraction cord; (b) dry the tooth thoroughly; (c) do not touch the area with gloved fingers (oils from glove powder contaminate); (d) once the primer is applied, keep the area dry until you flow the composite. If moisture contamination occurs, clean it off, re-etch, and re-prime. Bonding failure is one of the top causes of composite restoration failure. Skill in achieving and maintaining moisture control is the mark of a competent restorative dentist.

Shade matching is part art, part science. Start with a shade guide in natural light, not overhead operatory light, to avoid color distortion. Hold the guide tile against the tooth and look at the middle third (shade guides can be misleading at the edges). Most anterior teeth are in the A1–A3 range (slightly yellow, slightly darker than pure white); posterior teeth are often one shade darker. Take a photograph of the shade guide next to the target tooth if possible. Order composite in that shade. At the operatory light, verify the shade once more on the set composite before curing. Polishing enhances esthetics: a smooth surface reflects light and appears more natural. Use a sequence of finishing burs (12-fluted, 30-fluted, 40-fluted) or diamond burs in decreasing coarseness, starting at high speed with water cooling. Polish the occlusal surface last (chewing surface first often removes the polish). Use polishing cups and brushes with fine pumice or composite polish paste for final luster. A rough composite surface will stain and look dull; polish is non-negotiable for esthetic restorations. Check contacts (contacts between the tooth and adjacent tooth) with an articulating paper (carbon paper) and adjust if too tight or missing. Contacts affect food trapping and esthetics. Check occlusion (bite): mark the contact points with articulating paper and relieve high spots until the restoration has no prematurities (avoids chewing pressure and sensitivity). A well-polished, well-contoured, well-occluded restoration is invisible and lasts.

Composite restorations fail due to: (1) Recurrent caries: improper isolation during bonding, moisture contamination, or patient neglect of home care (no flossing) allows bacteria and decay at the restoration margin. Prevention: perfect bonding technique, excellent isolation, and patient education on flossing. (2) Marginal breakdown: gaps at the margin allow micro-leakage and staining; caused by polymerization shrinkage (composite contracts as it hardens) or poor contouring. Prevention: use incremental layering (small layers cured one at a time to reduce shrinkage stress) and excellent polishing. (3) Bulk fracture: composite is less strong than enamel under high chewing forces; likely on large posterior restorations or in bruxers (teeth grinders). Prevention: crown posterior teeth with large restorations; monitor bruxers and suggest a nightguard. (4) Secondary caries (cavity at another site on the same tooth): patient's poor hygiene causes new cavity next to the restoration. Prevention: patient education, fluoride, and frequent re-evaluation. (5) Sensitivity: exposed dentin or gaps in the restoration irritate the nerve. Prevention: complete sealing, proper depth of restoration, and desensitizing agents. Composite restorations are durable if technique is meticulous, but they are less forgiving than amalgam. Posterior composites on large cavities have a failure rate of 10–15% at 10 years (versus 5% for amalgam), so patient selection and case design matter.

Diagnosis of a crack: ask the patient where it hurts (often when biting down on a specific spot). Transillumination (shining a bright light through the tooth) can reveal cracks. Radiographs may show a vertical fracture line (radiolucent line). Classification: (1) Craze line: enamel only, no treatment. (2) Fractured cusp: piece of tooth breaks off; restore with composite or crown. (3) Crack extending into dentin: may be symptomatic; seal with composite to prevent progression and nerve exposure. (4) Vertical root fracture: extends deep into the root; often requires extraction. Treatment for cracks and fractures: isolate the tooth, remove any loose pieces, and restore with composite or crown. If the crack extends close to the nerve (pulp), monitor for signs of inflammation (pain, swelling) and consider a root canal if pulp becomes infected. For a fractured cusp that is not severe, a composite build-up often works; if the fracture is large or the tooth has prior endodontic treatment (weaker), a full-coverage crown is stronger and more durable. Immediate treatment is critical because a crack will continue to propagate and may lead to splitting of the root, which is irreversible.

A Class II restoration is a filling on a proximal (between-teeth) surface, often on a posterior tooth. Without a matrix band, it is impossible to restore the contact point and anatomy properly. A matrix band is a thin metal or plastic band that wraps around the tooth and holds the composite in place while it hardens, creating a physical barrier to the adjacent tooth. A wedge is a small piece of wood or plastic inserted between the teeth (lingual side) to create pressure and push the band against the tooth, ensuring proper contact and anatomy. Steps: (1) Select appropriate band (size by tooth). (2) Insert the wedge from the lingual side first (gently, to avoid tissue trauma). (3) Slide the band around the tooth with the loop or gate on the facial side. (4) Tighten the band so it is snug. (5) Check the contact with the adjacent tooth (should be tight, not loose). (6) Apply composite incrementally into the cavity and proximal area. (7) Remove the band and wedge after curing. A poor proximal contact leads to food trapping, plaque accumulation, and secondary caries. Skill in matrix band placement is essential for restorative dentistry, especially in pediatric and orthodontic patients.

Postoperative sensitivity is common after cavity treatment because the restoration exposes fresh dentin and creates micro-leakage paths. Prevention: (1) Complete sealing of margins with proper bonding and polishing to eliminate gaps. (2) Avoid overheating the tooth during preparation (use water cooling and intermittent bur contact). (3) Use a base or liner (calcium hydroxide or glass ionomer) under deep restorations to provide insulation and reduce sensitivity. (4) Avoid over-etching dentin (15–20 seconds is adequate; longer causes irritation). If sensitivity occurs: (1) Verify the restoration is not high in the bite (use articulating paper and adjust if needed); occlusal trauma is a common cause. (2) Apply a desensitizing agent (potassium nitrate toothpaste or professional fluoride varnish). (3) Recommend a soft toothbrush and avoid acidic drinks. (4) In severe cases, a dentist-applied resin coating or even a root canal may be necessary if dentin irritation leads to pulp inflammation. Most sensitivity resolves within 2–4 weeks as the dentin tubules remineralize and sensitivity naturally decreases.