CATEGORY AUSTRALASIAN DENTIST59 Choosing the Correct Diluent: What Not to Use While discussion often centres around preserved versus non-preserved saline, it is equally important to understand what should not be used. Botulinum toxin must be reconstituted with 0.9% isotonic saline. is is physiologic and compatible with human tissue. Hypertonic saline solutions, such as 3% or 5% saline, must never be used. ese solutions are designed for speci c medical conditions such as hyponatraemia or intracranial pressure management. eir osmotic properties can cause cellular dehydration, vascular irritation, and tissue damage, including the potential for necrosis. ese e ects are entirely inappropriate in aesthetic practice. Similarly, bacteriostatic water should not be used. It is hypotonic and can lead to cellular swelling and rupture, resulting in tissue damage and increased discomfort. Understanding Dilution: Why Volume Matters Beyond the choice of diluent, the volume of reconstitution plays a critical role in how botulinum toxin behaves in tissue. Most botulinum toxin products have a labelled reconstitution of 2.5 mL per vial. is provides a standardised concentration that was used in clinical trials and forms the basis of dosing guidelines. However, in practice, clinicians often adjust dilution depending on treatment goals. Increasing the dilution (using more saline) results in a lower concentration per unit volume, which can: u Increase di usion u Soften the e ect u Be useful in larger or more super cial areas Conversely, using a more concentrated dilution (less saline) results in: u Greater precision u Reduced spread u More targeted e ect in small or delicate areas is concept is often described in terms of the “action halo” – the area over which the toxin exerts its e ect. By altering dilution, the practitioner can in uence the size and intensity of this halo. is is not about changing the total dose administered, but rather about how that dose is distributed within the tissue. Why Changing Dilution Can Be Clinically Useful Adjusting dilution is not simply a matter of preference – it is a tool for re ning outcomes. In areas such as the forehead, where muscle bres are broad and super cial, a slightly more diluted solution may provide a softer, more even result. In contrast, in areas such as the perioral region or around the chin, where precision is critical and functional muscles are involved, a more concentrated solution may reduce the risk of unwanted spread and functional compromise. is ability to tailor di usion characteristics allows for a more nuanced approach to treatment, aligning technique with anatomy and patient goals. However, it is essential that practitioners understand the implications of altering dilution. Changing concentration without adjusting injection technique or dosing strategy can lead to inconsistent or unpredictable outcomes. Safety, Consistency, and Clinical Judgement Ultimately, the choice of diluent and dilution should be guided by a combination of: u Evidence u Clinical experience u Patient comfort u Practice logistics While bacteriostatic saline is widely accepted within community standard, practitioners must recognise that its use is technically o -label, as it falls outside manufacturer guidance. is does not preclude its use, but it does require an understanding of the evidence supporting it and appropriate documentation within clinical practice. Consistency is also important. Using a standard dilution within your clinic allows for reproducibility of results and clearer interpretation of outcomes over time. Final Thoughts Reconstituting botulinum toxin is not a trivial step – it is a critical part of treatment planning that in uences patient experience, product handling, and clinical outcomes. While manufacturers recommend non-preserved saline due to regulatory constraints, the broader scienti c community supports the use of bacteriostatic saline as a safe and e ective alternative that o ers clear advantages in patient comfort and product longevity. At the same time, understanding dilution allows practitioners to move beyond a one-size- ts-all approach, using concentration strategically to control di usion and re ne results. In modern aesthetic practice, these decisions should not be made by habit, but by informed clinical reasoning. By understanding the science, respecting regulatory frameworks, and applying thoughtful technique, practitioners can ensure that even the most routine steps – such as reconstitution – contribute meaningfully to safe, predictable, and highquality patient care. u Regular updates in CPD in cosmetic injectable practice is mandatory to remain compliant with the Cosmetic Guidelines. To undertake training in cosmetic injectable treatments in an accredited practice, please visit www.dermaldistinction.com for more information. CLINICAL
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