Written and reviewed by oral and maxillofacial surgery residents and crosschecked with national guidelines and best practices.
What the CBSE is
The Comprehensive Basic Science Examination is an NBME subject exam. NBME describes it as a general, integrated achievement test of the basic science material typically learned in medical school, with a little more emphasis on second-year courses. NBME also says it reflects the content coverage of USMLE Step 1 and uses the same question formats.
Dental students who want to apply to oral and maxillofacial surgery residency take it through AAOMS. AAOMS says it is open to all dental students interested in applying to OMS residency. Many programs look at CBSE results alongside the rest of an application, so check each program's requirements.
Format
AAOMS lists 200 questions over 5 hours and 15 minutes, including an optional 15-minute break, taken at a Prometric testing center. It is a computer-based exam. Starting in 2027 it is offered in May and November, and the dates and registration details are here.
What it covers
NBME organizes the content by organ system. These are NBME's approximate ranges, and NBME says they can change at any time.
| Organ system | Approximate share |
|---|---|
| Reproductive and Endocrine | 12% to 16% |
| Respiratory and Renal/Urinary | 11% to 15% |
| Behavioral Health and Nervous Systems/Special Senses | 10% to 14% |
| Blood and Lymphoreticular/Immune | 9% to 13% |
| Musculoskeletal, Skin and Subcutaneous Tissue | 8% to 12% |
| Multisystem Processes and Disorders | 8% to 12% |
| Cardiovascular | 7% to 11% |
| Gastrointestinal | 6% to 10% |
| Social Sciences: Communication and Interpersonal Skills | 6% to 9% |
| Biostatistics and Epidemiology/Population Health | 4% to 6% |
| Human Development | 1% to 3% |
Questions also test disciplines such as physiology, pathology, pharmacology, microbiology, anatomy and biochemistry, usually inside a clinical scenario instead of as isolated facts.
How dental students prepare
- Start with the content outline. Use NBME's organ-system list to see how the exam is weighted.
- Learn a system, then test it. Reading is not enough. Answer questions on a topic soon after you study it, and review what you miss.
- Look at official material. NBME publishes sample items for the exam and sells a paid self-assessment.
- Practice the full format. A timed, full-length exam shows you pacing and which systems need work. Our CBSE Practice Exam 2026 is 200 original questions in four 50-question blocks with a score report by system.
- Plan the calendar. The free study schedules show 1-year, 18-month and 2-year plans, and this page compares them.
Everyone's results are different, and no practice exam can predict a score. Use practice scores to decide what to study next, not to guess a number.
Where OMS Collective fits
OMS Collective is an independent study resource made by oral and maxillofacial surgery residents. We offer free study guides, a free 10-question renal demo and practice exams you can take online. We are not affiliated with NBME, AAOMS or the ADA.
Frequently asked questions
What is the CBSE for oral surgery residency?
The Comprehensive Basic Science Examination is a 200-question basic science exam from NBME. Dental students applying to oral and maxillofacial surgery residency take it through AAOMS, and many programs look at the score alongside the rest of an application.
How long is the CBSE?
AAOMS lists 200 questions over 5 hours and 15 minutes, including an optional 15-minute break, taken at a Prometric testing center.
When is the CBSE offered in 2027?
Starting in 2027, AAOMS offers the CBSE in May and November instead of February and July. Check aaoms.org for current dates and fees.
Is OMS Collective affiliated with NBME or AAOMS?
No. OMS Collective is an independent study resource and is not affiliated with or endorsed by NBME, AAOMS or the ADA. Every question is original.
OMS Collective is an independent study resource. It is not affiliated with or endorsed by NBME, AAOMS or the ADA. CBSE and NBME are trademarks of the National Board of Medical Examiners. Nothing here predicts or guarantees a score.