Water Quality in Dental Practice Distilled Water vs Deionized Water

01

Physicochemical Foundations of Water Purification

Water — the vital element of the care chain

Water is involved at every stage of the dental care chain, from tissue irrigation to the reprocessing of medical devices. Mastering its quality is not merely a regulatory requirement — it is a patient safety imperative and a strategy for preserving the technical capital of the practice. Distilled water and deionized water designate distinct technical realities and purity levels that directly influence equipment behaviour.

Distillation — The thermal process

Separation by change of physical state

Water is brought to boiling → steam → condensation in a sterile container
Eliminates virtually all mineral salts, heavy metals, sediments and microorganisms
Boiling acts as an absolute thermal microbiological barrier
Slightly acidic pH (5.5–6) during storage due to re-dissolved CO₂
Key concept: the water is extracted from its contaminants, not the other way around

Deionization — Ion exchange

Cation and anion exchange resins

Captures cations (Ca²⁺, Mg²⁺, Na⁺) and anions (Cl⁻, SO₄²⁻) on specific resins
Very low conductivity: < 1 µS/cm in the most efficient systems
Warning: does not intrinsically eliminate microorganisms or uncharged molecules
Risk of residual bacterial load if stored under non-sterile conditions
Requires 0.2 µm filtration or UV treatment for microbiological guarantee

Reverse osmosis — Membrane filtration

Mechanical pressure above osmotic pressure forces water through a semi-permeable membrane (pore size ≈ 0.0001 µm). It rejects 95% to 98% of dissolved solids, bacteria and viruses. Quality depends heavily on inlet water pressure and temperature. It is the solution of choice for producing large volumes at reduced energy cost.

"Hungry water" — The paradox of ultra-purity Ultra-pure water (fully deionized, devoid of all ions) becomes chemically aggressive. With no ions to satisfy, it seeks to "remineralize" by attacking the metal alloys of pipes and instruments — a phenomenon known as leaching corrosion. Always use conforming purified water that is not corrosively aggressive, and verify material compatibility with the dental unit.

02

Comparative Table of the Three Technologies

Physicochemical comparison — Distilled, deionized and reverse osmosis water

Characteristic	Distilled water	Deionized water (DI)	Reverse osmosis water (RO)
Production principle	Evaporation and condensation	Ion exchange on resins	Membrane filtration under pressure
Mineral salt removal	> 99.9%	99.99%	95–98%
Bacteria removal	Complete (by heat)	Partial (depends on filtration)	High (physical barrier)
Typical conductivity (µS/cm)	0.5 to 5.0	< 1.0	5 to 20
Energy cost	High (heating)	Very low	Moderate (pressure)
Maintenance required	Descaling the tank	Resin replacement	Membrane replacement

03

EN 13060 Standard — Class B Autoclave Requirements

A binding normative framework — Annex C of EN 13060

Water use in a Class B autoclave is not left to the practitioner's discretion. The European standard EN 13060 defines maximum permissible contaminant limits for feed water. Exceeding these thresholds can lead to critical failures and premature wear of internal components as well as damage to instruments.

Maximum threshold table — EN 13060 Annex C

Contaminant	EN 13060 maximum	Consequences of exceedance
Conductivity (at 25°C)	≤ 15 µS/cm	Global indicator of mineral pollution
Evaporation residue	≤ 10 mg/L	Severe scaling of the boiler
Silica (SiO₂)	≤ 1 mg/L	Indelible white stains on instruments
Iron	≤ 0.2 mg/L	Galvanic corrosion and rust pitting
Chlorides	≤ 2 mg/L	Pitting corrosion of stainless steel
Phosphates	≤ 0.5 mg/L	Steam instability, coloured deposits
Total hardness	≤ 0.02 mmol/L	Calcium carbonate crystallization
pH	5 to 7.5	Chemical aggressiveness or alkaline deposits

Silica — The silent enemy of instruments Silica (SiO₂) forms extremely resistant glassy deposits, unlike ordinary limescale which dissolves easily with mild acid. During vaporization, it deposits on instruments as white or bluish stains — easily mistaken for poor sterilization — and can block the hinges of forceps and the internal channels of turbine handpieces.

Softened water — Prohibited despite appearances Water from a domestic salt-based softener replaces calcium ions with sodium ions. "Soft" to the touch, it remains rich in salts that crystallize during vaporization and cause severe electrochemical corrosion. Both tap water and softened water are formally prohibited in autoclaves.

04

Impact on Rotary Instruments and the Dental Unit

Consequences of hard water on rotary instruments

Turbines and contra-angles — concrete clinical risks

Spray nozzle obstruction: asymmetric spray → insufficient cooling → risk of irreversible pulpal heat damage
Bearing wear: mineral particles penetrate ball bearings (up to 400,000 rpm), reducing both power and instrument lifespan
Costly repairs avoidable simply by choosing the appropriate water

Rotary instrument maintenance protocol

Flushing, cleaning and lubrication — the indispensable routine

Channel flushing: run the instrument in air for 30 seconds after each patient to purge stagnant water
Internal cleaning: cleaning sprays (e.g. Spraynet) to remove debris before sterilization
Systematic lubrication before every autoclave cycle to protect bearings from steam moisture

!

Purified water in the dental unit — Independent circuit mandatory

The mains water risk

Mains water running through dental unit tubing introduces hardness, chlorides and microorganisms into irrigation circuits. Any stagnation actively promotes bacterial proliferation.

The recommended solution

Independent irrigation system (separate bottle) filled with purified water + bacteriostatic agent (dilute H₂O₂ or silver ions). Addition of a continuous disinfectant treatment is mandatory.

05

Biofilm in DUWL — Risks and Prevention

Dental Unit Water Lines (DUWL) — An ideal environment for microbial proliferation

The small diameter of the tubing (polyurethane or PVC), low flow rates and stagnation periods promote bacterial adhesion and the formation of a complex biofilm capable of harbouring opportunistic pathogens. The target is to maintain water quality below 500 CFU/mL (ADA/CDC recommendation).

Key pathogens and prevention strategies

Pathogen	Clinical risk	Preventive measure
Legionella spp.	Severe pneumonia via aerosol inhalation	Temperature > 55°C or regular chemical disinfection
Pseudomonas aeruginosa	Wound infections, septicaemia in immunocompromised patients	Terminal filtration at 0.2 µm
Free-living amoebae	Vectors for intracellular bacteria	Regular flushing of all water lines

DUWL biofilm control protocol

Use purified water (distilled or deionized) in an independent circuit isolated from the mains supply
Add a continuous bacteriostatic agent: low-concentration H₂O₂ or silver ions
Flush all water lines at the start of each day (1–2 minutes) before any patient treatment
Flush for 30 seconds after each patient to reduce stagnation
Perform periodic intensive chemical shock disinfection of the circuit per manufacturer recommendations

06

In-Practice Water Production Systems

1

Benchtop electric distiller

Self-contained unit (standard power outlet). Produces ~4 L per 5–6 hour cycle. Microbiological purity guaranteed by boiling.

Drawbacks: high energy consumption (750–1500 W), slow production, limescale accumulation in the tank requiring frequent manual cleaning.

2

Cartridge-based deionizer

Connected directly to mains and autoclave (e.g. MELAdem 40, W&H Multidem). High flow rate (60 L/h), fully automatic autoclave filling.

Drawbacks: recurring cartridge cost, bacterial risk in resins during periods of inactivity. Conductivity must be monitored closely.

3

Professional reverse osmosis unit

Ideal for multi-surgery facilities. Lowest per-litre cost over the long term.

Drawbacks: significant water waste (2–3 L rejected per litre produced), complex installation, delicate membrane maintenance.

!

Selection matrix

< 5 L/day → Benchtop distiller (maximum simplicity, safest economically).

5–20 L/day → Cartridge deionizer (full automation).

> 20 L/day → Reverse osmosis unit (optimal operating cost).

Purification system selection table

Criterion	Distiller	Deionizer	Reverse osmosis
Daily volume	Low (< 5 L)	Moderate (5–20 L)	High (> 20 L)
Automation	None	Full	High
Installation cost	Low	Moderate	High
Operating cost	Electricity	Resins	Water + filters
Microbiological guarantee	Maximum	Partial	High

07

Algerian Context — Hard Water and Local Solutions

ADE water quality — Significant geographic variability

Water distributed by the Algérienne des Eaux (ADE) shows marked regional variation in hardness. In the North-Central and Eastern regions, hardness can exceed 30°f (French degrees), placing it in the "very hard" category. This elevated hardness has direct implications for purification system selection.

!

Hard water vs deionizer — The economic calculation in Algeria

The deionizer trap in hard-water areas

Very hard water saturates resin cartridges in record time. If a single cartridge (~350,000 DA) treats only 200 L of hard water, the cost per litre becomes prohibitive and the system is not economically viable.

The distiller's advantage in hard-water areas

Since electricity is subsidized in Algeria, a distiller is often more cost-effective. Limescale accumulation in the tank is inconvenient to clean but costs nothing to eliminate physically through boiling.

Indicative local market prices — Algeria

Product	Source	Estimated price (DZD)
4 L water distiller (stainless steel)	Ouedkniss / pharmacy	23,500 – 55,000
Deionized water (5 L container)	Retail	150 – 250
Professional deionizer	Import / Dentolink	76,000 – 150,000
Resin cartridge (unit)	Specialist supplier	12,000 – 30,000

Bottled water in Algeria — Do not confuse "pure" with "autoclave-safe" A study from the University of Ouargla highlights that Algerian bottled waters are frequently highly mineralized (elevated TH, dry residue > 500 mg/L), making them entirely unsuitable for use in an autoclave, even when labelled "pure" for drinking purposes. Always verify conductivity before using any water in medical equipment.

08

Preventive Maintenance Protocols

Conductivity monitoring

The only reliable indicator of ionic purity

A calibrated digital conductivity meter is the sole arbiter of water quality

Frequency

Weekly for in-house production systems. With each new batch for water purchased in containers.

Critical thresholds

Safety threshold: 15 µS/cm. Above 50 µS/cm: risk of irreversible corrosion of the autoclave boiler.

Required instrument

Calibrated electronic conductivity meter — the investment pays for itself from the first incident avoided.

Distiller maintenance

Every 10 to 15 uses

Descale the tank with citric acid or specialist powders (e.g. Aquadist)
Replace sediment pre-filters and activated carbon filters every 3–6 months
Monthly storage tank disinfection with dilute sodium hypochlorite or H₂O₂

Deionizer maintenance

Continuous conductivity monitoring

Replace resins as soon as conductivity exceeds 15 µS/cm
After prolonged inactivity: preventive disinfection of the resin circuit
Inspect integrity of seals and hydraulic connections quarterly

09

Strategic Recommendations

Recommended water type by clinical application

Application	Recommended water type	Complementary requirement
Class B autoclave	Distilled or high-quality DI	Conductivity < 15 µS/cm — EN 13060 compliant
Dental unit irrigation (DUWL)	Distilled or deionized	Independent circuit + continuous bacteriostatic agent mandatory
Rotary instruments (PIR)	Purified water	Pre-sterilization lubrication = the #1 longevity factor
Chemical dilutions (NaOCl)	Deionized water	Absence of ions prevents inactivation of active ingredients
Implant / periodontal surgery	Distilled water preferred	Maximum steam sterility — high criticality context

Practice action plan — 4 steps

Needs assessment: calculate weekly purified water consumption. If under 20 L, a benchtop distiller is the simplest and most economically sound solution.
Local water audit: have the tap water hardness tested. If very high, consider a pre-treatment stage (reverse osmosis unit) to protect the purification system.
Investment in measurement: acquire a digital conductivity meter — the only way to reliably validate the quality of purchased or produced water.
Team training: educate dental assistants on the importance of reservoir rinsing and compliance with conductivity thresholds.

10

Clinical FAQ

No, absolutely not. Tap water — however clear it looks — is formally prohibited in Class B autoclaves. Its chloride content causes pitting corrosion of the stainless steel sterilization chamber from the very first cycles. Its limescale content causes rapid boiler scaling. In the event of a stock shortage, it is better to suspend autoclave use entirely than to risk permanent damage to equipment worth millions of dinars.

No. Mineral waters are precisely defined by their mineral content (calcium, magnesium, sodium), which is fundamentally incompatible with EN 13060 requirements. A "light" mineral water may have a conductivity of 200–500 µS/cm — 10 to 30 times above the maximum permitted threshold of 15 µS/cm. A study from the University of Ouargla confirms that Algerian bottled waters, even those labelled "pure," frequently show dry residues exceeding 500 mg/L. The only way to verify any water's suitability is to measure its conductivity with a calibrated meter.

Several causes are possible. First, reservoir contamination: a poorly rinsed container, prior deposits or prolonged storage can introduce ions into distilled water. Second, salt accumulation in the autoclave chamber itself from previous cycles run with borderline water — the rinse cycle redistributes these salts. Third, an ageing distiller with a heavily scaled tank may release salts into the produced water. Solution: rinse the reservoir with fresh distilled water, verify conductivity at the production source, and carry out a full descaling of the distiller with citric acid.

Deionized water is ideal for preparing sodium hypochlorite dilutions. Calcium and magnesium ions in hard water react with NaOCl to form insoluble chlorite and hypochlorite compounds, reducing its active concentration (available chlorine content). With water hardness at 25°f, the available chlorine concentration in a 2% solution can drop by 15–25% within hours. For canal irrigation solutions, deionized water preserves NaOCl's bactericidal efficacy throughout the working period.

Not necessarily. White stains on instruments after sterilization are most often related to mineral or silicate deposits rather than a sterilization problem. Silica (SiO₂) present in inadequately purified water forms resistant glassy deposits resembling white or faintly bluish limescale. Sterility may be perfect despite these deposits. To distinguish: if biological and chemical cycle indicators are correct, sterilization is effective. The solution is to improve water quality (check conductivity, replace resins or the distiller). In the worst case, silica deposits can mechanically block forceps hinges — resolving the water quality issue must be the immediate priority.

Distilled water, pure at the moment of production, does not remain sterile indefinitely once stored. Paradoxically, in the absence of ions, ultra-pure water provides an excellent medium for certain bacteria that do not require mineral nutrients. The recommended maximum storage period is 48 to 72 hours in a clean, hermetically sealed container kept away from light. For autoclave use, using water on the day of production is ideal. Disinfect the storage reservoir monthly with dilute hypochlorite solution or H₂O₂.

Ref

References

Standards and regulations

1

Standard AFNOR. NF EN 13060 — Small steam sterilizers. Annex C: Feed water quality specifications.
boutique.afnor.org — NF EN 13060
2

Recommendation Faculty of Medicine, University of Constantine 3. Asepsis and sterilization in the dental practice.
facmed.univ-constantine3.dz — Sterilization in dental practice

Biofilm and DUWL contamination

3

Study FDI World Dental Federation. Dental unit water lines and microbial contamination.
fdiworlddental.org — DUWL and microbial contamination
4

PMC Comparison of the Efficacies of Disinfectants To Control Microbial Contamination in Dental Unit Water Systems. PMC / J Dent Res.
pmc.ncbi.nlm.nih.gov — Disinfectants and DUWL
5

PMC Optimizing hydrogen peroxide shock treatment frequencies for dental unit waterlines contamination control. PMC / Pilot Study.
pmc.ncbi.nlm.nih.gov — H₂O₂ and DUWL
6

Recommendation Dentsply Sirona. Infection Prevention for Dental Chairs. Independent irrigation system recommendations.
dentsplysirona.com — Infection prevention, dental chairs

Water physicochemistry and purification systems

7

Review B-Autoclave. What water should be put in an autoclave? Complete guide.
b-autoclave.fr — Water for autoclaves
8

Technical document W&H. Multidem — The water demineralizer system. Technical documentation.
wh.com — W&H Multidem
9

Review Dentaltix. Tips for maintaining rotary instruments in your dental practice.
dentaltix.com — Rotary instrument maintenance

Algerian context — Local water quality

10

Algeria Algérienne des Eaux (ADE). Water quality — monitoring data by wilaya.
ade.dz — ADE water quality
11

Algeria University of Ouargla — Sandali B. Hydrochemical analysis and classification of bottled waters in Algeria. DSpace, Kasdi Merbah University Ouargla.
dspace.univ-ouargla.dz — Bottled waters in Algeria
12

Algeria ASJP. Physicochemical study of distributed water in Algeria. Algerian Environmental Sciences Journal.
asjp.cerist.dz — Distributed water quality, Algeria