If you are using the same dirt and think its contaminated you can always freeze it or bake it to kill most bugs. Freezing being easier. Baking at 325 for 20 min a sure fire way of killing bacteria and bugs. It needs to be properly rehydrated with a surfectant afterward (aloe puree in water if you have a plant, "green" dishsoap works too). Freezing is way easier.
Fresh dirt is ideal. Get some drainage materials too. My favorite is "growstone" expanded glass fake rocks. Its really lightweight and easier on enclosures and my back. Lava rock in the area of 1/2 inch to 3/4 inch can work, hyroton pellets are okay. You want a big rocky one and some little pebbly stuff. Coarse perlite is good and cheap. Medium orchid bark is ok for most. 25% big rocks 25% little rocks (can sub up to 10% orchid bark) 50% dirt. Most plants in that mix that get misted until water runs into their pot will be OK. Adding 3/4 inch of sand will make a bug deterrent, topping with large river stones makes sure the cham can't snack on sand.
Lightbulb Moment.... Get a bag of napa floor dry 100% diatomaceous earth (it's 100% fossilized diatoms, natural and cheap). Used for its absorbing properties. It's great mixed into dirt as a silica source and would make the best bug killing top layer. The really rocky stuff is a good small rock source for soil too.
Sand and diatomaceous earth both work to kill small bugs by cutting their chitin and sucking out the moisture. Burrowing root bugs don't go through it. If they do they die. When wet it doesn't work the same way.
Predatory nematodes will destroy the bugs too. Very common in the agricultural world. Found on the big A with 4 star ratings if your local garden center lacks. Mine carries Natures Control brand and keeps them refrigerated along with lady bugs and mantis ooth's. They die if the soil dries out though. I treat all my 50ish indoor plants with a dose to prevent and or treat at least once a year. One package watered down.
I have a ficus benjamina planted in just small rocks, red lava rock cinders, and a really shallow bonsai pot with river stone cover that's growing fiercely. It sits under a mist nozzle that goes off 2 times a day for 20 min total. All it needs is rocks. No soil, no bugs.