revenues were $33.9 million, or 70% of net revenue, for the year ended December 31, 2022 compared to $25.4 million, or 65% of net revenue, for the year ended December 31, 2021. International revenues for year ended December 31, 2022 were $14.6 million, or 30% of net revenue, compared to $13.8 million, or 35% of net revenue for year ended December 31, 2021.
Laser system net revenues increased by $6.4 million, or 26%, for the year ended December 31, 2022 compared to the same period in 2021. Consumables and other net revenue, which includes products such as disposable tips and shipping revenue, increased $1.9 million, or 20%, for the year ended December 31, 2022, as compared to the same period in 2021. Services revenue increased $1.0 million, or 21%, for the year ended December 31, 2022, as compared to the same period in 2021.
The increase in year-over-year net revenue primarily resulted from additional adoption of our lasers in dentistry, an increase in consumable sales and the addition of our OEM product at the start of 2022.
Cost of Revenue. Cost of revenue increased by $9.9 million, or approximately 44%, to $32.6 million, or 67% of net revenue for the year ended December 31, 2022, compared to cost of revenue of $22.7 million, or 58% of net revenue, for the same period in 2021. The increase is primarily due to the increase in sales and higher warranty and inventory reserve charges for the year ended December 31, 2022.
Gross Profit. Gross profit as a percentage of revenue typically fluctuates with product and regional mix, selling prices, product costs and revenue levels. Gross profit for the year ended December 31, 2022 was $15.9 million, or 33% of net revenue, a decrease of $0.6 million, or 4%, as compared with gross profit of $16.5 million, or 42% of net revenue, for the same period in 2021. The decrease in gross profit as a percentage of revenue reflects the impact of a $2.7 million charge for inventory. This inventory charge was driven by the supply chain issues that we have encountered requiring us to change to new suppliers along with end of life designation for certain products and components, which resulted in higher inventory reserves and warranty expenses. In addition, lower margin OEM products were launched at the beginning of 2022 and an Employee Retention Credit under the CARES Act of $0.7 million was received during the year ended December 31, 2021 that did not occur in 2022. The decrease was partially offset by the impact of the increase in sales and the favorable absorption of fixed expenses.
Operating Expenses. Operating expenses for the year ended December 31, 2022 were $41.2 million, or 85% of net revenue, an increase of $8.3 million, or 25%, as compared with $33.0 million, or 84% of net revenue, for the same period in 2021. See the following expense categories for further explanations.
Sales and Marketing Expense. Sales and marketing expense for the year ended December 31, 2022 increased by $6.3 million, or 41%, to $21.7 million, or 45% of net revenue, as compared with $15.3 million, or 39% of net revenue, for the same period in 2021. This increase is primarily due to $2.9 million from compensation expense due to no open territories, or no territories without a sales representative in 2022, and commissions and bonus incentives for achieving sales targets, $1.9 million in higher travel and trade show related expenses, $0.7 million in higher supply costs and other expenses, $0.2 million in additional advertising expenses, and $0.6 million from an Employee Retention Credit under the CARES Act received during the year ended December 31, 2021 that did not occur in 2022.
General and Administrative Expense. General and administrative expense for the year ended December 31, 2022 increased by $1.1 million, or 9%, to $12.3 million, or 25% of net revenue, as compared with $11.3 million, or 29% of net revenue, for the same period in 2021. This increase is primarily from $0.8 million in compensation expense for achieving sales targets and filling open positions, $0.5 million for the production of the “Talk Dental To Me” docuseries, and $0.2 million in a higher allowance for doubtful accounts. The increase in general and administrative expenses was partially offset by $0.4 million in severance expense that did not occur in 2022, and $0.2 million from an Employee Retention Credit under the CARES Act received during the year ended December 31, 2021 that did not occur in 2022.
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