ICD-10 codes play a crucial role in dental billing by identifying the patient's diagnosis or condition that justifies the dental procedure being performed. While CDT codes describe what procedure was done, ICD-10 codes explain why it was necessary. Insurance payers often require both to approve claims—especially when dental care is linked to medical necessity, trauma, or systemic conditions. Accurate diagnosis coding can reduce denials and ensure proper reimbursement for medically related dental services.