Rubber dam is the textbook answer to moisture control, yet many dentists bond composites and cement ceramics without it. This article sets out what the evidence actually shows, how to choose a clamp and place the dam quickly and leak-free, which situations make rubber dam isolation non-negotiable, and when a strict relative isolation protocol is a valid alternative.
Why isolation decides the bond
Resin adhesion needs a tooth surface free of saliva, blood and crevicular fluid. The German S3 guideline on direct composite restorations (AWMF 083-028, January 2024) describes contamination control as a precondition for adhesion, aesthetics and longevity, and distinguishes two approaches: absolute isolation with rubber dam and relative isolation with suction, cotton rolls, isolation devices and controlled air drying.
The invisible enemy is humidity. In a small study by Kameyama and colleagues (2011), the non-isolated mouth reached more than 30 °C and more than 95 % relative humidity. Rubber dam and two suction-based isolation devices lowered both values, which climbed again as soon as the isolation was removed. Haruyama and colleagues (2014) measured 100 % relative humidity with cotton rolls alone, whereas a dam exposing only a single molar brought humidity down to room level. With four teeth exposed, values varied more.
What the evidence shows
The data are weaker than the textbooks suggest, which is worth knowing when you explain your choice to colleagues or patients.
- Cochrane review. Miao and colleagues (2021) included six randomised trials with 1,342 participants, all at high risk of bias. For composite restorations of non-carious cervical lesions, rubber dam improved survival at six months (odds ratio 2.29, 95 % CI 1.05 to 4.99; two studies, 192 participants; low-certainty evidence). At 12 and 18 months there was little to no difference, and the evidence was very uncertain. None of the trials reported adverse effects or costs.
- Cervical restorations. The German guideline draws on, among others, a meta-analysis by Mahn and colleagues (2015): tooth-coloured cervical restorations placed under rubber dam in roughened dentin showed significantly higher retention than those placed without dam or in unprepared dentin.
- Bond strength. In an in-situ study by Falacho and colleagues (2023), 120 enamel surfaces of 30 third molars were bonded while mounted on a splint in a volunteer's mouth. Rubber dam groups reached the highest shear bond strengths with both adhesives tested; without the dam, failures were partly adhesive, with it they were cohesive within enamel only.
- Guideline position. The German guideline's consensus recommendation states that both relative and absolute isolation can be used successfully for direct composites, and that rubber dam could have a positive long-term effect on restoration longevity (strong consensus, 16 votes to 0). It rests on a systematic literature search and the panel's consensus rather than on a formal evidence grade (Sekundo et al. 2024).
In endodontics the picture is different: rubber dam is regarded as the standard of care, and a review by Ahmed and colleagues (2014) argues that a study to prove its benefit would be unnecessary and unethical.
Equipment and preparation
Dam, punch and frame
Non-latex dams are widely available for patients with latex allergy (Nasser 2021). Punch each hole to suit the size of the tooth (Doshi et al. 2023), and mount the dam on a frame.
Choosing a clamp
A clamp is right when its jaws contact the tooth at four points below the height of contour and it does not rock under light pressure. In a randomised trial with 60 patients receiving Class I restorations on molars, wingless clamps caused more gingival trauma and more pain in the first 12 hours, but allowed less fluid seepage. Winged clamps slipped slightly more often, without a significant difference. Both performed acceptably (Doshi et al. 2023).
How many teeth to isolate
Limited procedures need few teeth, quadrant work needs more (Alkhatib et al. 2023). Keep in mind that humidity under the dam may vary more as more teeth are exposed.
Flowable Injection Technique course
Hands-on course in English on the injectable composite technique.
View the coursePlacing the rubber dam step by step
The winged technique carries clamp, dam and frame into the mouth in one movement. Winged clamps are widely used and are considered well suited to beginners (Doshi et al. 2023).
- Check the contacts. Pass floss through the contacts the dam will need to cross, so you know where it will be tight.
- Punch. Mark the teeth and punch a hole of suitable size for each. Correct hole position is what later allows the dam to invert around the necks of the teeth.
- Try in and tie the clamp. Test the clamp on the anchor tooth for four-point contact and stability, then attach the floss ligature.
- Assemble. Mount the dam on the frame and engage the winged clamp in the hole for the anchor tooth.
- Seat. Carry clamp, dam and frame together to the mouth with clamp forceps and seat the clamp.
- Release the dam. Slip the dam off the clamp wings with a blunt instrument so that it hugs the cervical area.
- Work it through the contacts. Stretch the dam over the remaining teeth and take it through the contacts with floss.
- Invert. Tuck the dam edge into the sulcus with air and a blunt instrument. A correctly inverted dam retracts the gingiva and seals (Nasser 2021).
- Stabilise. Where the dam slips back, secure it with a floss ligature around the neck of the tooth, a wedge or a stabilising cord (Alkhatib et al. 2023).
- Check. Confirm that the dam seals at every tooth and that the clamp is stable.
With a wingless clamp, pass the jaws through the hole, seat clamp and dam together, then stretch the dam under the jaws so that it encircles the cervical area (Doshi et al. 2023).
Special situations
Class V restorations
Cervical lesions often extend to or below the gingiva. Owens (2006) describes seating a modified retainer on the tooth first and then placing the dam over retainer and tooth, which retracts the gingiva and keeps the cavity isolated. For cervical restorations Dr Hajtó also uses PTFE cord in the sulcus.
Deep margin elevation
Here rubber dam is not optional. Dr Hajtó elevates a deep subgingival proximal margin with direct composite only when rubber dam can be placed and a matrix adapted tightly, following Magne (2006). If that is not possible, surgical crown lengthening or orthodontic extrusion are the alternatives; see the article on deep margin elevation.
Anterior composites and injection technique
Anterior work often involves several teeth in one session, so the isolation has to include several teeth. When neighbours are restored in separate rounds, PTFE tape keeps etchant and adhesive off the untreated surfaces (Dunn et al. 2004), as described for diastema closure with composite. In the posterior region, injectable composite tabletops follow the same isolation principles.
Bridges and multiple abutments
Full isolation of a long-span bridge is often impractical. Tsuruta and colleagues (2024) report a case in which a split dam combined with PTFE tape in the sulcus controlled saliva, crevicular fluid and humidity in a way similar to full dam isolation and made excess cement easier to remove. As a single case report, it illustrates a technique rather than proving superiority.
Adhesive cementation: rubber dam or relative isolation?
Cementation demands the same as composite bonding: a field without saliva, dry and accessible. Dr Hajtó does not regard rubber dam as a precondition for cementing veneers. He relies on a strict relative isolation protocol instead:
- PTFE tape around the neighbouring teeth, so that etchant, adhesive and luting composite cannot bond there,
- a PTFE cord in the sulcus, in his practice in 0.6, 1.0 and 1.8 mm,
- a small palatal suction tip,
- an assistant who watches the field throughout,
- and zero tolerance for moisture on the bonding surfaces.
Cord and tape come out only after the excess has been removed. The complete sequence is in the veneer cementation protocol, and the handling of the tape in PTFE tape in adhesive dentistry.
| Situation | Isolation | Reason |
|---|---|---|
| Class I and II composite | rubber dam | easy to place, dry cavity, airway protection |
| Class V composite | dam with clamp seated first; Dr Hajtó uses PTFE cord for cervical restorations | higher retention under dam in meta-analysis |
| Deep margin elevation | rubber dam mandatory | only indicated with dam and tight matrix |
| Anterior composite, injection technique | isolation of several teeth, PTFE tape on neighbours | protects adjacent surfaces from etchant and adhesive |
| Veneer cementation | relative isolation with PTFE tape and PTFE cord | sufficient in Dr Hajtó's view if the field stays strictly dry |
Troubleshooting
| Problem | Cause | Fix |
|---|---|---|
| Dam tears during placement | tight contacts | work the dam through the contacts step by step with floss |
| Leakage at the anchor tooth | no four-point contact, dam not inverted | change clamp, invert, add a ligature |
| Clamp rocks or springs off | clamp too small, no hold below the contour | choose another clamp, tie a ligature |
| Sore gingiva afterwards | clamp jaws pressing on the gingiva | choose a clamp that grips tooth, not gum |
| Saliva under the dam | dam not fully through the contacts | rework contacts with floss, ligate |
For patients who cannot tolerate a dam, for example mouth breathers, severe asthmatics or patients with marked claustrophobia, cotton rolls and a lip and cheek retractor are the alternative (Nasser 2021). Vacuum-assisted isolation devices also reduced intraoral humidity markedly and, at high ambient humidity, outperformed rubber dam (Washino et al. 2025).
Practical tip: cleaning clamps
Dr Hajtó cleans soiled rubber dam clamps in two steps: sandblasting with 50 µm particles at 2 bar, then glass bead blasting with 50 µm beads at 2 bar.
Summary
Rubber dam isolation is a routine skill: holes punched to size, a clamp with four-point contact, a floss ligature and a properly inverted dam make it quick and reliable. The evidence favours it, especially for cervical restorations, and it is mandatory for deep margin elevation. For veneer cementation, a disciplined relative isolation protocol with PTFE tape and cord is an alternative that Dr Hajtó uses himself. Rubber dam placement and isolation are part of the practical programme in the Flowable Injection Posteriors hands-on course with David Geštakovski.
Frequently asked questions
Is rubber dam mandatory for composite restorations?
No. The German S3 guideline on direct composites states that both relative and absolute isolation can be used successfully, and that rubber dam could improve longevity in the long term. What matters is that no saliva, blood or crevicular fluid reaches the bonding surfaces during etching, bonding and layering. For deep margin elevation, however, rubber dam is a precondition of the technique.
Which rubber dam clamp should I use on a molar?
Choose a clamp that grips the tooth at four points below the height of contour and stays stable under light pressure. Winged clamps can be carried in together with the dam and caused less gingival trauma in a randomised trial, while wingless clamps sealed better against seepage but pressed more on the gingiva. Whichever you choose, tie floss to it before placing it.
What can I use instead of a latex dam?
Non-latex dams are widely available and handle in the same way, so the placement technique does not change. Ask about latex allergy in the medical history before choosing the material. A genuine allergy is therefore no reason to give up rubber dam isolation, provided a latex-free sheet is in stock.
When is rubber dam not suitable?
It is difficult for patients who rely on mouth breathing, such as severe asthmatics, and for patients with marked claustrophobia, certain disabilities or epilepsy with frequent seizures. In these cases, relative isolation with cotton rolls, high-volume suction and a lip and cheek retractor is the alternative. It requires more attention from dentist and assistant to keep the bonding surfaces uncontaminated.
Does rubber dam really make restorations last longer?
The best evidence is limited. A Cochrane review found low-certainty evidence that rubber dam improved six-month survival of cervical composites, but no clear difference at 12 and 18 months, and all trials had a high risk of bias. A meta-analysis cited in the German guideline found higher retention of cervical restorations under rubber dam, and an in-situ study showed higher enamel bond strength.
