Filling Methods

Part of Dentistry

Filling a decayed tooth preserves it for years or decades of additional service. In a rebuilding world where every tooth is irreplaceable, restoring a cavity is always preferable to extraction — if the decay has not yet reached the nerve.

Why Fillings Matter

A small cavity left untreated grows steadily. Bacteria eat through enamel, then the softer dentin, and eventually reach the dental pulp — the nerve and blood vessel center of the tooth. Once bacteria reach the pulp, the tooth becomes infected, an abscess forms, and extraction becomes the only option.

Filling the cavity at an early stage removes the bacteria, seals the hole, and allows the tooth to function normally for years. The Romans filled teeth with gold. Medieval practitioners used lead, tin, and beeswax. Modern dentistry uses amalgam and composite resins. In a rebuilding scenario, several of these materials are accessible.

Assessing the Cavity

Before filling, determine if the tooth is salvageable:

Finding	Meaning	Action
Dark spot, soft to probe	Early to moderate decay	Fill — good prognosis
Deep hole, no pain to probing	Moderate decay, nerve not yet exposed	Fill carefully — avoid penetrating floor
Pain on probing the floor of cavity	Decay approaching the nerve	Fill if possible, but poor prognosis
Spontaneous severe toothache	Nerve likely infected (pulpitis)	Extraction usually necessary
Swelling of gum near tooth root	Abscess — nerve is dead	Extraction required
Tooth fractured to gum line	Insufficient tooth structure to hold filling	Extraction

The Stick Test

Poke the darkened area with a sharpened stick or metal probe. If the probe sticks into soft, leathery dentin, the area needs to be excavated and filled. If the dark area is hard and the probe slides off, it may be a stain rather than active decay — monitor but do not drill.

Cavity Preparation

Removing Decay

All decayed (soft, discolored) tooth material must be removed before filling. Leaving decay beneath a filling allows bacteria to continue destroying the tooth underneath.

Tools:

Tool	Construction	Use
Dental excavator (spoon)	Small spoon-shaped metal instrument, hand-forged	Scooping out soft decay
Small chisel	Flat-tipped thin metal blade	Breaking away unsupported enamel
Drill bit (hand-powered)	Small metal burr in a pin vise or bow drill	Enlarging access to cavity
Files/rasps	Small metal files	Smoothing cavity walls

Procedure:

1. Open access — if the cavity entrance is small but decay extends underneath, carefully chip away overhanging enamel with the chisel to expose the full extent of decay.
2. Excavate soft dentin — use the spoon excavator to scoop out all soft, discolored material. Sound dentin is hard and makes a scraping sound; decayed dentin is soft and comes away in flakes.
3. Shape the cavity — the walls should undercut slightly (wider at the bottom than the top) so the filling is mechanically locked in place. This is called retention form.
4. Test the floor — probe gently. If the floor feels hard throughout, no nerve exposure. If you see a pink spot or the patient feels sharp pain, you may be close to or have exposed the nerve.

Nerve Exposure

If a tiny pink or red spot appears at the deepest point of the cavity, the nerve is exposed. In modern dentistry this receives a calcium hydroxide cap. In a survival scenario, place a small amount of zinc oxide paste (see below) directly over the exposure, then fill normally. If the tooth develops persistent severe pain within days, extraction becomes necessary.

Isolation and Drying

A dry cavity is essential for filling retention. Before placing the filling:

1. Pack small cotton rolls between the cheek and the tooth to absorb saliva.
2. Have the patient tilt their head so gravity drains saliva away from the work area.
3. Blot the cavity dry with cotton or clean cloth.
4. Work quickly — the cavity will re-moisten within minutes.

Filling Materials

Zinc Oxide Eugenol Cement

The most practical filling material for a rebuilding scenario. It combines pain-relieving properties with reasonable durability.

Components:

Component	Source	Preparation
Zinc oxide	Heat metallic zinc in air until white powder forms, OR scrape white coating from galvanized (zinc-coated) iron	Fine white powder
Eugenol (clove oil)	Steam-distil dried clove buds	Clear to pale yellow liquid

Mixing:

1. Place a spoonful of zinc oxide powder on a clean, dry, flat surface (glass, ceramic, or polished stone).
2. Add eugenol drop by drop, mixing with a flat blade after each drop.
3. Continue adding and mixing until the paste reaches a putty-like consistency — it should roll between your fingers without sticking.
4. Working time is approximately 3-5 minutes before it begins to set.

Placement:

1. Press the mixed cement firmly into the dried cavity using a flat instrument or the back of a probe.
2. Overfill slightly and shape the surface to match the tooth’s original contour.
3. Have the patient bite gently on a thin strip of cloth to check the height — if it feels high, carve away excess while still soft.
4. Setting time: 5-10 minutes for initial set, full hardness in 24 hours.

Durability Expectations

Zinc oxide eugenol fillings typically last 6 months to 2 years with normal chewing. They are softer than amalgam and wear faster. Plan to replace fillings periodically, or use this as a temporary filling while sourcing more durable materials.

Dental Amalgam

The gold standard of durable filling material for over 150 years. An amalgam filling can last 15-30 years.

Components:

Metal	Proportion	Source
Silver	50%	Coins, jewelry, recovered electronics
Tin	25%	Tin cans (remove lacquer by heating), solder
Copper	15%	Wire, coins, scrap
Mercury	10% (by separate measure)	Thermometers, barometers, old switches

Preparation:

1. Make alloy filings — melt silver, tin, and copper together in the proportions above. Cast into a small ingot, then file into fine shavings with a metal file.
2. Mix with mercury — place alloy filings in a cloth or leather pouch. Add mercury (approximately equal weight to the filings). Squeeze and knead the pouch for 1-2 minutes until the mixture forms a uniform, clay-like mass.
3. Express excess mercury — squeeze the amalgam through the cloth to remove surplus liquid mercury. The remaining mass should be workable but not runny.

Mercury Safety

Mercury is a cumulative neurotoxin. Always work in ventilated areas. Never heat mercury (vapor is extremely dangerous). Wear gloves or handle through cloth. Despite the risk, dental amalgam has been safely used since the 1830s because the mercury is bound within the alloy once set.

Placement:

1. Pack the amalgam firmly into the cavity in small increments, pressing each layer hard against the cavity floor and walls.
2. Overfill slightly.
3. Carve the surface anatomy using a small blade or shaped instrument before the amalgam fully hardens (working time approximately 5-8 minutes).
4. The patient should avoid hard chewing on that side for 24 hours while the amalgam reaches full hardness.

Glass Ionomer Cement (If Available)

Made from powdered fluoride-containing glass and polyacrylic acid. If you have access to these materials (potentially from salvaged dental supplies), this cement bonds chemically to tooth structure and releases fluoride to prevent further decay. Mix powder and liquid to a paste, place in cavity, and allow to set for 5 minutes.

Emergency Temporary Fillings

When proper materials are unavailable:

Material	Duration	Notes
Beeswax	Days to weeks	Softens with hot food; reapply frequently
Pine resin (tree pitch)	Days to weeks	Hardens well but brittle; mix with beeswax
Gutta-percha (latex)	Weeks to months	If natural rubber trees available
Crusite (calcium sulfate paste)	Weeks	Plaster of Paris mixed thick; weak but seals

Finishing and Adjusting the Bite

Checking Occlusion

After the filling sets:

1. Have the patient bite together slowly and report where contact feels too high.
2. Place a thin strip of cloth between the teeth — if it pulls out easily everywhere except over the filling, the filling is too high.
3. Carefully carve or file the high spot until the bite feels normal.

Why Bite Adjustment Matters

A filling that sits even 0.5 mm too high receives all the biting force that should be distributed across multiple teeth. Within weeks, this causes constant aching, and the tooth may crack under concentrated force. Always verify the bite before dismissing the patient.

Surface Polishing

A smooth filling surface resists plaque buildup. After the filling has fully set:

1. Smooth with progressively finer abrasives — coarse file, then fine file, then cloth with fine sand or pumice.
2. For amalgam, a final burnish with a smooth metal instrument pressed firmly against the surface creates a shiny, glass-like finish.

Aftercare Instructions

Give these instructions to every patient:

1. Do not chew on the filled side for 24 hours (amalgam) or 2 hours (zinc oxide cement).
2. Avoid very hot or cold foods for 2-3 days — the tooth may be sensitive.
3. If sharp pain develops that worsens over days, the nerve may be dying — return for assessment.
4. Mild sensitivity to cold that gradually decreases is normal and expected.
5. If the filling falls out, return promptly — an open cavity re-infects quickly.
6. Clean around the filling daily with a stick or fiber brush.

Common Mistakes

1. Leaving soft decay beneath the filling — the most common error. All discolored, soft dentin must be removed even if it makes the cavity larger. A large clean cavity has a better prognosis than a small one with decay left behind.
2. Placing filling in a wet cavity — moisture prevents bonding and retention. The filling loosens and falls out within days. Take the time to isolate and dry thoroughly.
3. Not checking the bite — an over-high filling causes pain, tooth fracture, and patient loss of trust.
4. Using too much mercury in amalgam — excess mercury weakens the filling and increases toxicity risk. Express surplus mercury thoroughly after mixing.
5. Giving up on a salvageable tooth — if the decay is caught before pulp exposure, a filling saves the tooth. Extraction should be the last resort, not the first.

Summary

Filling Methods — At a Glance

• Fill teeth when decay is moderate and the nerve is not yet exposed — always preferable to extraction
• Remove all soft, decayed dentin before filling; shape cavity with slight undercut for retention
• Zinc oxide eugenol (zinc powder + clove oil) is the most practical survival filling material, lasting 6-24 months
• Dental amalgam (silver-tin-copper + mercury) lasts 15-30 years but requires mercury — handle safely in ventilated areas
• Emergency temporary fillings from beeswax or pine resin buy time until proper materials are sourced
• Always check and adjust the bite after placement — a high filling causes pain and tooth fracture
• Instruct patients to avoid hard chewing for 24 hours and return if pain worsens progressively