If you want crisis insurance, beware cheaper amalgams and synthetic composites...

What use is gold? Besides jewelry, outrageous cutlery, money, microchips and a thin veneer for astronauts' visors, gold once got sizeable demand from dentists.

The least reactive of all elements, gold is also highly malleable but very dense. Making it the perfect fit for cavity fillings everywhere.

No more however. "The long-term declining trend in dental demand for gold showed no sign of abating in Q1," said last week's new Gold Demand Trends from market-development organization the World Gold Council.

As recently as the turn of this century, global gold demand for tooth fillings averaged more than 60 tonnes a year. That equalled almost 2.5% of global gold mining output. German dentists alone stuffed 24 tonnes of gold into people's mouths in 1996. But technology, like fashion, moves on.

"I hate gold," said a stockbroker on CNBC last week. Friday saw gold's 8th daily price drop in succession, the worst run since March 2009. The world's two largest gold trust funds shed another 16 tonnes between them last week, taking the combined GLD and IAU outflow to 22% for 2013 so far. And gold is now "a falling knife" on its way to $1100 per ounce reckons Credit Suisse's chief commodities analyst, Ric Deverell.

"Rotation" is one name for what's happening. Because money managers who got round to buying gold - early or late - during the financial crisis are now moving into equities, into higher-risk bonds, and into emerging-market currencies. But it's important not to confuse this with "substitution" such as you might see in physical industries.

"Much of the long run decline [in dental demand] can be attributed to cost," the World Gold Council's report goes on, "with consumers switching to cheaper base metal alternatives" for filling their teeth.

Amongst investors and notably private households, gold is typically used to provide financial insurance. Is there a substitute? Away from the shifting trends in money management and dentists' chairs, gold retains several unique qualities. Rare and tightly supplied, gold tends to rise in real terms when inflation overtakes interest rates on cash in the bank. All-too physical and indestructible (you need cyanide to dissolve it) gold is also immune to banking or credit default.

For anyone wanting to back-stop their savings against currency crisis or financial collapse - whether immediate or long term - that's made gold valuable at pretty much any price over the last decade and more. The finance industry has yet to develop a substitute. Unlike the dental industry. And even there, "Many authorities consider gold the best filling material," says a handy page from Colgate, the toothpaste manufacturer.

"However, [gold] is often the most expensive choice and requires multiple visits."

Investors, you have been told! Composite synthetics simply don't last as long or do the same job. Cheaper amalgams - involving silver, which tends to track gold prices but with greater volatility - will also prove "more noticeable". Both in your portfolio and in your teeth.