Summary of Significant Accounting Policies - Revenue by Type and Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 8,668	$ 2,107	$ 24,335	$ 4,496
U.S.
Disaggregation of Revenue [Line Items]
Total revenue	7,391	1,113	20,204	2,062
U.S. | System sales and rentals
Disaggregation of Revenue [Line Items]
Total revenue	5,038	646	14,368	1,106
U.S. | Handpieces and other consumables
Disaggregation of Revenue [Line Items]
Total revenue	2,184	451	5,458	930
U.S. | Service
Disaggregation of Revenue [Line Items]
Total revenue	169	16	378	26
Outside of U.S.
Disaggregation of Revenue [Line Items]
Total revenue	1,277	994	4,131	2,434
Outside of U.S. | System sales and rentals
Disaggregation of Revenue [Line Items]
Total revenue	481	369	1,725	1,111
Outside of U.S. | Handpieces and other consumables
Disaggregation of Revenue [Line Items]
Total revenue	666	596	2,159	1,278
Outside of U.S. | Service
Disaggregation of Revenue [Line Items]
Total revenue	$ 130	$ 29	$ 247	$ 45