Periodontics board practice questions, with answers
Free questions in the style of the ABP Qualifying Exam, each with the answer, a rationale and its source. Start with 11 mixed questions below, one from each domain of the 2027 blueprint, or pick a domain for a short study guide and more questions.
A 58-year-old man has lost 6 teeth over the past 8 years, each extracted for advanced bone loss, abscesses and mobility. He has 22 remaining teeth with 11 opposing pairs and reports comfortable chewing. The worst interdental CAL is 7 mm, bone loss extends past the middle third of several roots, and probing depths reach 7 mm. No remaining tooth has mobility greater than degree 1, and there is no drifting, flaring or bite collapse. Which stage is most appropriate, and why?
Stage III, because no stage IV complexity factor is present
Stage IV, because 5 or more teeth were lost to periodontitis
Stage III, because more than 20 teeth and 10 pairs remain
Stage IV, because interdental CAL is 5 mm or more at the worst site
Stage III, because tooth loss changes the grade but not the stage
Show answer and rationale
Answer: B. Stage IV, because 5 or more teeth were lost to periodontitis
A (incorrect): Complexity factors are not the only route to stage IV. Tooth loss attributable to periodontitis is part of the severity dimension and can modify the stage even when no complexity factor is present.
B (correct): The severity dimension of stage IV includes loss of 5 or more teeth due to periodontitis. Six teeth lost to periodontitis place him in stage IV even though his function and occlusion are currently stable, and that information can modify the stage in the absence of complexity factors.
C (incorrect): Fewer than 20 remaining teeth (10 opposing pairs) is one stage IV complexity factor, but having more than 20 teeth does not exclude stage IV. His tooth-loss history meets stage IV on its own.
D (incorrect): Interdental CAL of 5 mm or more is shared by stages III and IV, so it cannot separate them. The deciding feature here is the number of teeth lost to periodontitis.
E (incorrect): Tooth loss due to periodontitis is a staging criterion (none for stages I and II, 4 or fewer for stage III, 5 or more for stage IV). It is not one of the grade criteria, which are progression evidence and the smoking and diabetes modifiers.
Source: Papapanou PN, Sanz M, Buduneli N, et al. Periodontitis: consensus report of workgroup 2 of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions. J Periodontol. 2018;89(Suppl 1):S173-S182. Table 1A (Tooth loss row) and table footnote, page S175. https://doi.org/10.1002/JPER.17-0721
Question 2Foundational Knowledge
A 38-year-old woman needs a subepithelial connective tissue graft to cover a Cairo RT1 recession on tooth #22. You plan a single-incision harvest from the palate between the mid-palatal aspect of the canine and the second molar. Her palatal vault is of average height, and there is no torus. When you set the apical (medial) limit of the harvest, which landmark best approximates the course of the greater palatine artery?
The midpalatal suture
The level of the palatal cementoenamel junctions of the premolars and molars
The junction of the vertical and horizontal walls of the palatal vault
The crest of the palatal rugae
The palatal root apices of the first molar
Show answer and rationale
Answer: C. The junction of the vertical and horizontal walls of the palatal vault
A (incorrect): The artery does not run near the midline; it lies laterally, at the base of the alveolar process. Extending the harvest toward the suture would carry the incision across the neurovascular bundle rather than stopping short of it.
B (incorrect): This line marks the coronal end of the donor area, not the apical limit. The incision is usually kept a few millimeters apical to the gingival margin to protect the marginal tissue, and the artery lies far more apically than the CEJ.
C (correct): The greater palatine artery emerges from the greater palatine foramen and is generally taken to run forward where the vertical (alveolar) wall of the vault meets its horizontal floor. Graft height is therefore estimated as the distance from the gingival margin to that junction, which in periodontally healthy adults ranged from about 12 mm at the canine to about 14.7 mm at the second molar. In the premolar area, that distance allowed a 5 mm high graft in all patients and an 8 mm graft in 93%.
D (incorrect): The rugae occupy the anterior palate and do not track the greater palatine artery, which runs anteroposteriorly at the base of the alveolar wall. Rugae also make the tissue irregular and are a poor harvest zone.
E (incorrect): Root apices sit within bone and are not visible or palpable landmarks for the vessel. The first molar region is also where the palatal root and thinner tissue limit the harvest, so it is not used to set the apical limit along the whole donor site.
Source: Monnet-Corti V, Santini A, Glise JM, Fouque-Deruelle C, Dillier FL, Liébart MF, Borghetti A. Connective tissue graft for gingival recession treatment: assessment of the maximum graft dimensions at the palatal vault as a donor site. J Periodontol. 2006;77(5):899-902. Abstract, Methods and Results. https://pubmed.ncbi.nlm.nih.gov/16671884/
Question 3Periodontal Therapy: Non-Surgical and Surgical
A periodontal practice plans to add a structured motivational interviewing program, delivered by hygienists after additional training, to its standard oral hygiene instruction for patients beginning periodontitis therapy. Based on current guideline evidence, which result should the practice expect from adding this program?
A clinically relevant fall in plaque scores within 6 months
Greater probing depth reduction after subgingival instrumentation
No significant gain in hygiene over standard instruction
Fewer patients needing step 3 surgery at re-evaluation
Lower cost per patient than standard instruction
Show answer and rationale
Answer: C. No significant gain in hygiene over standard instruction
A (incorrect): The trials, most at high risk of bias, mostly found no significant extra benefit, and the reported effect size was judged not clinically relevant. Expecting a clear plaque reduction overstates the evidence. Standard, repeated, individualized instruction remains the core intervention.
B (incorrect): The evidence addressed oral hygiene behavior, not the pocket response to instrumentation. With no demonstrated improvement in hygiene, there is no basis to expect better probing depth outcomes. Pocket reduction depends mainly on thorough instrumentation and the patient's plaque control.
C (correct): Randomized trials of motivational interviewing and other psychological methods added to oral hygiene instruction have not shown a significant or clinically relevant added effect on oral hygiene performance. The guideline therefore treats this as an unresolved question. Emphasizing oral hygiene and engaging the patient in behavior change remain recommended, but the specific psychological technique has not been shown to add benefit.
D (incorrect): No study linked psychological motivation programs to fewer residual pockets or less surgery. This outcome would require an improvement in hygiene that has not been demonstrated. It is a downstream claim with no supporting data.
E (incorrect): Cost-benefit was not assessed, and the program adds cost because the psychological approach requires special training. A lower cost per patient is the opposite of what would be expected. The practice should weigh added training costs against an unproven benefit.
Source: Sanz M, Herrera D, Kebschull M, et al. Treatment of stage I-III periodontitis: The EFP S3 level clinical practice guideline. J Clin Periodontol. 2020;47(Suppl 22):4-60. Section 5.1, Recommendations 1.2 and 1.3. https://pmc.ncbi.nlm.nih.gov/articles/PMC7891343/
Question 4Treatment Planning and Patient Management
A 47-year-old man is referred by his general dentist with a written prescription for functional crown lengthening on tooth #19 before a new crown; the buccal fracture margin is 1 mm subgingival. He has never had periodontal treatment. Full-mouth charting shows probing depths of 5 to 7 mm in every sextant, bleeding on probing at 60% of sites, a plaque score of 70% and radiographic bone loss to the middle third of the roots. He is a healthy nonsmoker. Which is the most appropriate management?
Perform crown lengthening on #19 as prescribed and recommend a hygiene visit after the crown is seated
Perform crown lengthening on #19 combined with subgingival scaling of the left mandibular sextant only
Return the patient to the general dentist with a note stating that crown lengthening is contraindicated
Explain the full diagnosis, complete steps 1 and 2 of therapy, and re-evaluate before crown lengthening
Prescribe systemic amoxicillin and metronidazole and perform crown lengthening at the next visit
Show answer and rationale
Answer: D. Explain the full diagnosis, complete steps 1 and 2 of therapy, and re-evaluate before crown lengthening
A (incorrect): This treats only the prescribed site and leaves active generalized periodontitis unmanaged. Operating with a 70% plaque score predicts poorer healing, and surgery in patients without adequate plaque control is specifically discouraged. The patient also loses the chance to make an informed decision about his main problem.
B (incorrect): Instrumenting one sextant leaves the other pockets untreated and does nothing for his plaque control. The first two steps of therapy are whole-mouth interventions. Surgery is still premature because oral hygiene has not been established.
C (incorrect): Crown lengthening is not contraindicated here; it is premature. Returning the patient without diagnosis or treatment leaves the periodontitis unmanaged. The periodontist should treat the periodontitis and coordinate the restorative sequence with the referring dentist.
D (correct): Generalized periodontitis with 5 to 7 mm pockets and heavy plaque must be addressed first: the first and second steps of therapy apply to every periodontitis patient, and periodontal surgery is not recommended in patients who are not achieving adequate self-performed oral hygiene. A prescription for one procedure does not remove the specialist's duty to diagnose and inform the patient of the whole condition. Crown lengthening follows once inflammation is controlled and the restorative plan is confirmed with the referring dentist.
E (incorrect): Systemic antibiotics are not recommended for routine adjunctive use and never substitute for plaque control and subgingival instrumentation. They do not make surgery appropriate in a patient with uncontrolled biofilm. This plan adds antibiotic risk without treating the disease.
Source: Sanz M, Herrera D, Kebschull M, Chapple I, Jepsen S, Berglundh T, Sculean A, Tonetti MS; EFP Workshop Participants and Methodological Consultants. Treatment of stage I-III periodontitis: The EFP S3 level clinical practice guideline. J Clin Periodontol. 2020;47(Suppl 22):4-60. doi:10.1111/jcpe.13290. Section 4 (stepwise approach, first and second steps of therapy) and Recommendation 3.6. https://pmc.ncbi.nlm.nih.gov/articles/PMC7891343/
Question 5Implant-Related Therapy
A 52-year-old patient is having a nonrestorable mandibular first premolar extracted and plans to have an implant placed 6 months later. He declines grafting and asks how the ridge will change if the socket heals on its own. Which statement best describes the expected change in the alveolar ridge?
Height will decrease more than width, with the loss spread evenly across the first year
Width will decrease more than height, with most of the change occurring in the first 3 to 6 months
Width and height will decrease by similar amounts, with most of the change after the first 6 months
The overlying mucosa will thin noticeably and add to the loss of the bony contour
Width will be largely maintained because the lingual wall thickens to make up for the buccal plate
Show answer and rationale
Answer: B. Width will decrease more than height, with most of the change occurring in the first 3 to 6 months
A (incorrect): This reverses both the magnitude and the timing of the change. Vertical loss at 6 months is roughly 1.24 mm at the buccal, compared with about 3.79 mm of horizontal loss. Most remodeling happens early rather than evenly over 12 months.
B (correct): Human studies show horizontal loss of 29% to 63% versus vertical loss of 11% to 22% at 6 months after extraction. The reduction is rapid in the first 3 to 6 months and then continues more slowly. This is why the buccolingual dimension is usually the limiting factor at delayed implant sites.
C (incorrect): Horizontal and vertical losses are not similar; width loss is consistently greater. The early phase, not the period after 6 months, accounts for most of the reduction.
D (incorrect): Soft tissue over the healing socket actually gains about 0.4 to 0.5 mm in thickness during the first 6 months. The visible contour loss comes mainly from bone remodeling, not from mucosal thinning.
E (incorrect): The lingual wall does not compensate for buccal resorption. Horizontal loss is the dominant dimensional change after extraction, which is the main reason ridge preservation is considered.
Source: Tan WL, Wong TL, Wong MC, Lang NP. A systematic review of post-extractional alveolar hard and soft tissue dimensional changes in humans. Clin Oral Implants Res. 2012;23 Suppl 5:1-21. Abstract, Results and Conclusions. https://pubmed.ncbi.nlm.nih.gov/22211303/
Question 6Oral Pathology and Oral Medicine
A 36-year-old woman reports a painful patch on the palatal gingiva next to her maxillary premolars that began 2 days after a dental cleaning. She has had similar episodes at the same site about twice a year, and a previous dentist called them canker sores. Examination shows a cluster of 1 to 2 mm shallow ulcers, some coalescing, confined to the attached gingiva and adjacent hard palate. She is afebrile and otherwise well. Which is the most likely diagnosis?
Recurrent minor aphthous stomatitis
Primary herpetic gingivostomatitis
Recurrent intraoral herpes simplex
Necrotizing gingivitis
Erythema multiforme, minor form
Show answer and rationale
Answer: C. Recurrent intraoral herpes simplex
A (incorrect): Aphthae are the usual misdiagnosis here, but they do not typically affect keratinized mucosa such as the attached gingiva and hard palate. Minor aphthae favor nonkeratinized lining mucosa such as the labial and buccal mucosa and ventral tongue. A recurring cluster on attached gingiva points away from aphthae.
B (incorrect): Primary infection is usually seen in children and produces generalized, fiery gingivitis with many vesicles that coalesce into irregular fibrin-coated ulcers, often with fever and lymphadenitis. This patient is an afebrile adult with a localized lesion that recurs at one site. That pattern fits reactivation rather than primary disease.
C (correct): Recurrent intraoral herpes typically affects adults as clusters of small painful ulcers on keratinized, bound-down mucosa such as the attached gingiva and hard palate. Local trauma, such as dental treatment, can trigger reactivation, and episodes tend to recur at the same site. The course is far milder than primary gingivostomatitis, which is why it is often misdiagnosed.
D (incorrect): Necrotizing gingivitis produces punched-out, necrotic interdental papillae with pain and bleeding in a patient with risk factors such as stress, smoking or immunosuppression. It begins at the papilla tips rather than as discrete vesicles on palatal attached gingiva and hard palate. The recurrent site-specific cluster here does not fit.
E (incorrect): Erythema multiforme causes acute erosions mainly of the lips and nonkeratinized mucosa, often with crusted lips and target skin lesions on the distal extremities. Although recurrent erythema multiforme can be triggered by herpes simplex, it does not present as a small cluster of ulcers restricted to the palatal gingiva. The lesion described is the viral lesion itself.
Question 7Etiology of Periodontal and Peri-implant Diseases
A national survey of 12,000 dentate adults finds that, after adjustment for age, sex, education and income, current smokers have about 4 times the odds of periodontitis of never smokers. The odds rise from about 2.8 at 9 or fewer cigarettes per day to about 5.9 at 31 or more per day, and among former smokers the odds fall as years since quitting increase. Which inference about causation do these findings most directly strengthen?
A biological gradient, in which greater exposure yields greater risk
Temporality, because exposure was shown to precede disease onset
Specificity, because smoking produces a unique periodontitis phenotype
Experimental evidence, because cessation was assigned to some participants
Absence of confounding, because adjustment removed the bias
Show answer and rationale
Answer: A. A biological gradient, in which greater exposure yields greater risk
A (correct): Odds that rise steadily with cigarettes per day and fall with time since quitting describe a dose-response (biological gradient). A graded relationship is one of the strongest observational supports for a causal role of smoking in periodontitis.
B (incorrect): A cross-sectional survey measures exposure and disease at the same time, so it cannot establish that smoking preceded the onset of periodontitis. Temporality needs longitudinal data.
C (incorrect): Smoking-associated periodontitis has no unique phenotypic features, which is why it is not a distinct disease in the 2017 classification. The data show magnitude of association, not specificity.
D (incorrect): No one was assigned to quit; former smokers chose to stop. The decline in odds after quitting is observational and supports reversibility, not experimental proof.
E (incorrect): Adjustment for measured covariates reduces confounding but cannot exclude unmeasured factors such as oral hygiene or access to care. Residual confounding remains possible in any observational study.
Source: Tomar SL, Asma S. Smoking-attributable periodontitis in the United States: findings from NHANES III. J Periodontol. 2000;71(5):743-751. Abstract, Results and Conclusions. https://pubmed.ncbi.nlm.nih.gov/10872955/
Question 8Prognosis
A 49-year-old man who does not smoke and has no systemic disease has stage III, grade B periodontitis. After oral hygiene instruction and full-mouth subgingival instrumentation his plaque score is 15%. At re-evaluation, tooth #30 has a 6 mm buccal probing depth with bleeding, a Class II buccal furcation involvement, 35% radiographic bone loss and no mobility. All other sites probe 4 mm or less without bleeding. Using the Kwok and Caton prognosis system, which prognosis best fits tooth #30?
Favorable
Unfavorable
Questionable
Hopeless
Fair
Show answer and rationale
Answer: C. Questionable
A (incorrect): A favorable prognosis means comprehensive treatment and maintenance can be expected to stabilize the tooth's periodontal status. That describes the rest of this dentition, but control of a bleeding 6 mm pocket in a Class II furcation is not yet assured, so favorable is too optimistic.
B (incorrect): Unfavorable is reserved for teeth whose influencing factors cannot be controlled, so that breakdown is likely even with comprehensive treatment. A mandibular buccal Class II furcation in a motivated nonsmoker is amenable to further therapy, so this overstates the risk.
C (correct): Kwok and Caton assign a questionable prognosis when local or systemic factors are present that may or may not be controlled with treatment and patient motivation. A bleeding residual pocket entering a Class II furcation is exactly such a local factor: if further therapy (for example regenerative surgery) and the patient's plaque control bring it under control, the tooth can be stable; if not, breakdown is likely to continue.
D (incorrect): Hopeless teeth are those that must be extracted. With 35% bone loss, a treatable furcation and no mobility there is no basis for planning extraction.
E (incorrect): Fair is a category of the McGuire and Nunn system (good, fair, poor, questionable, hopeless), not of the Kwok and Caton system. Kwok and Caton use four categories: favorable, questionable, unfavorable and hopeless.
Source: Yanni P, Curtis DA, Kao RT, Lin GH. The pattern of tooth loss for periodontally favorable teeth: a retrospective study. Biology (Basel). 2022;11(11):1664. Introduction (description of the Kwok and Caton prognosis categories). https://pmc.ncbi.nlm.nih.gov/articles/PMC9687859/
Question 9Evaluation and Maintenance
A 61-year-old woman completed nonsurgical and surgical therapy for generalized stage III grade B periodontitis 4 years ago and has attended supportive periodontal care (SPC) every 3 months since. She has never smoked and has no systemic disease. Over the last 3 years her full-mouth bleeding on probing (BOP) has stayed between 4% and 7%, no site exceeds 4 mm, no 4 mm site bleeds, and her plaque scores are consistently low. She asks whether she must keep coming every 3 months. Which is the most appropriate response?
Keep a fixed 3-month interval for life, since any periodontitis history requires it
Discharge her to annual general dental recalls without periodontal charting
Lengthen the interval within the 3- to 12-month range, guided by her risk profile
Move to an 18-month interval because she has been stable for more than 3 years
Schedule visits only when she notices bleeding, mobility or discomfort
Show answer and rationale
Answer: C. Lengthen the interval within the 3- to 12-month range, guided by her risk profile
A (incorrect): Three-month SPC suits many patients, but it is not mandatory for life. The interval should be tailored to risk; a patient with years of low BOP, shallow pockets and good plaque control does not need the same frequency as a high-risk patient.
B (incorrect): She remains a periodontitis patient and needs periodic periodontal examination, risk review and professional plaque removal. Annual general recalls without charting would drop the monitoring that detects recurrence early.
C (correct): Treated periodontitis patients stay at risk of recurrence, but the interval is meant to be tailored. Current guidance places SPC visits between 3 months and a maximum of 12 months, set by the patient's risk profile and periodontal condition after therapy. A long-stable, low-risk nonsmoker is a reasonable candidate for a longer interval within that range, reassessed at each visit.
D (incorrect): An 18-month interval exceeds the recommended maximum of 12 months. Stability over 3 years supports lengthening the interval, not leaving the 3- to 12-month window.
E (incorrect): Symptom-triggered care abandons a structured recall system. Recurrent periodontitis is usually painless until late, so waiting for symptoms delays detection of new pockets and attachment loss.
Source: Sanz M, Herrera D, Kebschull M, Chapple I, Jepsen S, Berglundh T, Sculean A, Tonetti MS; EFP Workshop Participants and Methodological Consultants. Treatment of stage I-III periodontitis: The EFP S3 level clinical practice guideline. J Clin Periodontol. 2020;47(Suppl 22):4-60. Section 8.1, Recommendation R4.1. https://pmc.ncbi.nlm.nih.gov/articles/PMC7891343/
Question 10Implant Restorations
A 45-year-old nonsmoker needs extraction of a maxillary right central incisor with a cervical root fracture. CBCT shows intact socket walls with a facial bone wall about 0.5 mm thick, and the gingival phenotype is thin. There is no infection. After flapless atraumatic extraction, a tapered implant is placed in a palatal position with insertion torque of 35 Ncm, leaving a 2.5 mm facial gap. The experienced clinician and the patient elect immediate placement with immediate restoration. Which additional measure is most appropriate to reduce esthetic risk?
Reposition the implant against the facial wall to close the gap
Raise a full-thickness flap to inspect and graft the facial plate
Place the provisional in light centric contact to stimulate bone
Leave the gap ungrafted so that a blood clot can organize
Graft the facial gap and add a connective tissue graft
Show answer and rationale
Answer: E. Graft the facial gap and add a connective tissue graft
A (incorrect): Placing the implant against the facial wall removes the protective gap. A facial gap of more than 2 mm at the implant shoulder is recommended, and its presence is associated with better survival with the Type 1A protocol.
B (incorrect): A minimally traumatic flapless approach is recommended for Type 1A so that bone and soft tissue integrity are preserved. Raising a flap on a thin facial plate adds trauma and resorption risk without a clear benefit here.
C (incorrect): The provisional for Type 1A should have no eccentric contacts and should be protected during function. Deliberate occlusal loading of an immediate provisional is not a recognized way to stimulate bone and increases risk to integration.
D (incorrect): Grafting the gap between implant and facial bone with autogenous bone or a bone substitute is associated with higher pink esthetic scores. Leaving a 2.5 mm gap empty in a thin-wall site invites facial collapse.
E (correct): With a thin tissue phenotype or a facial wall thinner than 1 mm, Type 1A can still be considered, but in addition to grafting the gap, adjunctive soft tissue grafting may be required to offset post-extraction dimensional change. The patient should be told that this raises the complexity of the procedure and the risk of adverse outcomes.
Source: Morton D, Wismeijer D, Chen S, et al. Group 5 ITI Consensus Report: Implant placement and loading protocols. Clin Oral Implants Res. 2023;34(Suppl 26):349-356. Section 5, Clinical recommendations 6, 9 and 10; Consensus statements 3.3.5 and 4.3.3. https://doi.org/10.1111/clr.14137
Question 11Periodontal and Systemic Relationships
A 38-year-old man has generalized stage II periodontitis. He smokes 6 cigarettes per day and has no history of diabetes. His radiographic bone loss relative to age, considered alone, would place him in grade A, and no longitudinal records exist. Which grade should be assigned?
Grade A, because fewer than 10 cigarettes per day does not alter the grade
Grade C, because any current cigarette smoking places the patient in grade C
Grade A, because grading requires direct longitudinal evidence of progression over 5 years
Grade B, because smoking fewer than 10 cigarettes per day modifies the grade to B
Grade C, because periodontitis at his age implies a rapid rate of progression
Show answer and rationale
Answer: D. Grade B, because smoking fewer than 10 cigarettes per day modifies the grade to B
A (incorrect): Light smoking is still a grade modifier. The 2017 framework assigns grade B to patients who smoke fewer than 10 cigarettes per day, so leaving him at grade A ignores a documented risk factor.
B (incorrect): Grade C is reserved for smokers of 10 or more cigarettes per day when smoking is the modifier. Assigning grade C to every smoker overstates his risk and blurs the dose response that the framework is built on.
C (incorrect): Direct longitudinal evidence is preferred, but indirect evidence (bone loss relative to age) is used when records are lacking, and risk factors then modify the grade. Missing records do not freeze the grade at A.
D (correct): Grade modifiers apply regardless of the radiographic grade. Smoking fewer than 10 cigarettes per day corresponds to grade B, so this patient moves from A to B, and cessation counseling becomes part of the treatment plan.
E (incorrect): Age matters only through the ratio of bone loss to age, which here is consistent with grade A. Stage II disease at 38 years does not by itself establish rapid progression.
Source: Karaaslan F, Dikilitas A, Aydin EO, et al. Are there correlations between radiographic grade levels and modified grade levels of periodontitis? J Indian Soc Periodontol. 2021;25(2):102-105. doi:10.4103/jisp.jisp_49_20. Introduction, paragraph on grade modifiers; Methods. https://pmc.ncbi.nlm.nih.gov/articles/PMC8041079/
For exam preparation only, not clinical advice. Periodontics QBank is independent and not affiliated with the American Board of Periodontology or the American Academy of Periodontology.
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