Injectable Fillers and the Theory of Persistence with Repeated Treatments
The use of injectable filler materials, despite their relative recent popularity, have been around for a long time. From 1981 to 2002, the only FDA-approved filler was bovine and human-derived collagen. This seemed a perfectly natural filler material as that was ideally what one wanted to replace. But their short persistence and the need for a pre-injection skin test drove these filler products into an historic medical treatment when the much longer-lasting hyaluron-derived fillers became commercially available.
As the hyaluron-based fillers emerged, so has the concept of facial volumetric enhancement. Rather than the original use of collagen for filling lines, todays fillers are placed deeper into the subcutaneous tissues and are about adding volume to provide an outward push. This is really why they should no longer be referred to as ‘dermal fillers’, as they rarely are put into the actual dermis of the skin anymore.
One of the hypothesized benefits of injectable fillers is that they may have a stimulatory effect on collagen formation, resulting in longer lasting effects with repeated use. This phenomenon has been reported and commented on by numerous accounts with the observation that repeated treatments often required less filler product to get the same effect. This suggests that even though all fillers products today are not collagen that they have more of a tissue effect than just filling a space with a hydrophilic gel material. But is this true?
Some theorize that injectable hyaluronic fillers somehow stimulate collagen to form, particularly in sun-damaged and thinning skin. The proposed mechanism is that the tissue expanding effect of the filler stretches the tissues, resulting in fibroblast stimulation and/or proliferation. This is partly an analogy to what is proposed to happen and why hyaluronic acid derivatives are part of many topical skin creams. The absorption of the their molecules (if this really occurs) is believed to stimulate fibroblasts and make it produce collagen, thickening the skin layer.
While we all wish that an injectable filler was more than just a filler, there is little hard science to prove this collagenesis effect
. No study has ever been published that has conclusively demonstrated that this filler effect occurs. Some histologic data has been shown over the years, using fillers alone or in combination with external energy (heat) treatments, but persistent increased skin thickness data has not been forthcoming.
Clearly there are some patients who have reported durations that well exceed what the injectable filler product is known to generally last. But this is observational and it is unknown whether the filler really did last that long or was it just that the patient didn’t notice it had long been resorbed. There is also the known variability in different parts of the face that even the same filler will last different periods of time, a phenomenon well known with fat injections. (lips vs cheek for example)
Until there is more scientific evidence that fillers cause collagen formation (excluding the particulated fillers like Radiesse and Sculptra), we will have to assume that it is a sporadic event and that some patients are more ‘lucky’ than others. The next great evolution in hyaluronic-based injectable fillers will be the addition of a collagen stimulatory agent that does build up the tissues over time.
Dr. Barry Eppley
Indianapolis, Indiana
Dr. Barry Eppley