Use these selected concepts to connect clinical findings, treatment decisions and simulated preparation assessment for the Central Regional Dental Testing Service (CRDTS) Dental Examination. Each concept pairs a practical distinction with a resolved example and a specific mistake to avoid. Read the referenced clinical guidance alongside the official examination overview and component manuals, and develop procedural skills through supervised clinical and simulation practice.
Diagnostic assessment and imaging
1. Clinical need determines radiographic selection
Select imaging type and recall intervals from each patient's clinical findings, history, and individual disease risk rather than from the calendar. The ADA's recommendations guide professional judgment; they are not standards of care or regulations. A thorough clinical examination precedes image selection, and radiographs alone cannot establish a complete diagnosis and treatment plan.
Worked example: Two patients arrive on the same morning for routine visits. One presents with generalized gingival bleeding and a history of rapid caries; the other is asymptomatic with low risk. Their differing findings can justify different imaging selections despite the identical appointment date.
Mistake to avoid: Ordering an identical full-mouth series for every patient solely because both are attending a routine recall visit.
Reference: [9]
2. Control exposure through field size and receptor choice
Once imaging is justified, reduce exposure by restricting the beam to the area of interest with rectangular collimation, positioning the patient correctly, and using digital receptors instead of conventional film, which are distinct technologies. Equipment instructions and applicable radiation regulations remain relevant, and no specific exposure settings are prescribed here.
Worked example: A clinician who has justified a necessary periapical image positions the patient carefully and attaches a rectangular collimator so the beam covers only the diagnostic field, choosing a digital receptor rather than conventional film; these steps reduce exposure while the justified image remains diagnostically useful.
Mistake to avoid: Believing that using a lower-exposure technique somehow makes an otherwise clinically unjustified image acceptable to take.
Reference: [9]
3. Reserve CBCT for a diagnostic information gap
CBCT is justified only when lower-exposure planar options cannot provide the necessary diagnostic information and the clinical benefit outweighs the radiation risk. The example assumes the lower-exposure image is diagnostically adequate. Discuss the imaging exam's benefits and associated risks with the patient, and remember this principle establishes no universal CBCT indication.
Worked example: A clinician planning third molar surgery reviews a panoramic image that adequately shows root proximity; because the lower-exposure image answers the treatment question, CBCT is not justified merely because the scanner is available, and the clinician discusses the imaging decision with the patient.
Mistake to avoid: Selecting three-dimensional imaging for a case without first identifying the additional diagnostic information that CBCT must provide.
Reference: [9]
4. Recognize exposure creep in digital imaging
In digital radiography, repeatedly increasing exposure to reduce apparent image noise can produce exposure creep, a gradual rise in patient dose. Digital technology does not by itself prevent unnecessary increases. Manufacturers build tools into equipment to improve detector sensitivity without raising dose, but no device-specific adjustment, acceptable noise level, or exposure setting is prescribed.
Worked example: An operator notices grainy digital images and repeatedly raises exposure settings over several weeks. The supervisor reviews the imaging practice and the detector-sensitivity tools available on the equipment rather than permitting automatic dose escalation.
Mistake to avoid: Assuming that switching to digital technology automatically prevents any unnecessary increase in a patient's radiation exposure.
Reference: [9]
5. Separate oral cavity from oropharyngeal anatomy
The oral cavity and oropharynx border each other yet remain separate, non-overlapping anatomic regions. The anterior two-thirds of the tongue, anterior to the circumvallate papillae, belongs to the oral cavity, while the posterior one-third, or tongue base, belongs to the oropharynx. Correct localization supports assessment, but anatomic position alone never establishes what a lesion is.
Worked example: During a screening examination, a candidate charts an ulcer on the lateral anterior tongue as an oral cavity finding and separately records an incidental tongue-base prominence as oropharyngeal, documenting each region accurately without claiming either finding represents a specific diagnosis.
Mistake to avoid: Recording every tongue lesion as an oral cavity finding regardless of its position relative to the circumvallate papillae.
Reference: [15]
6. Interpret cancer risks in their anatomic context
Tobacco use, alcohol consumption, their combined heavy use, and betel quid chewing are major risk factors for both oral cavity and oropharyngeal squamous cell carcinoma. HPV infection is a major risk factor specifically for oropharyngeal cancer, though it is also associated with a small percentage of other head and neck cancers. Risk factors inform assessment but never establish a diagnosis by themselves.
Worked example: For an adult with a tongue-base lesion and a reported HPV history, a candidate treats HPV as especially pertinent to the assessment, also documents the patient's tobacco and alcohol use, and records that these risks guide, but do not confirm, any diagnosis.
Mistake to avoid: Treating an HPV history as diagnostic proof of oropharyngeal cancer or dismissing its relevance entirely for anterior tongue findings.
Reference: [15]
7. Connect examination findings with diagnostic follow-up
Routine visual and tactile examination is the starting point, not the endpoint, of cancer detection. When a possible sign or symptom of oral cancer is found, the clinician must pursue follow-up until a definitive diagnosis is obtained. Documenting a concerning finding or completing the examination does not resolve the uncertainty that the finding created.
Worked example: After documenting a persistent unexplained mucosal ulcer during a routine examination, a candidate arranges appropriate follow-up so a definitive diagnosis can be obtained, rather than closing the episode once the finding has been examined, described, and recorded in the patient's chart.
Mistake to avoid: Considering the diagnostic process finished once a suspicious lesion has been examined and recorded in the chart.
Reference: [15]
8. Do not let optical or staining adjuncts decide referral
Current evidence does not support using vital staining or light-based adjuncts to determine which lesions require biopsy or specialist referral, and reliance on them may cause unnecessary procedures or delayed diagnosis. This conclusion applies to adults with oral cavity or lip mucosal abnormalities and should not be extended to every diagnostic technology or to cytology.
Worked example: For an adult with an oral mucosal abnormality whose light-based adjunct scan appears reassuring, a candidate proceeds with standard clinical assessment and bases the biopsy or referral decision on the examination findings, ensuring the adjunct result never delays needed diagnostic follow-up.
Mistake to avoid: Allowing a reassuring light-based adjunct result to postpone assessment of an adult's oral mucosal abnormality.
Reference: [15]
Systemic risk and medication decisions
9. Balance bleeding risk against antithrombotic interruption
For most dental patients, anticoagulant or antiplatelet therapy does not need to be altered before dental intervention, because stopping these medicines can raise the risk of thromboembolic events such as stroke or myocardial infarction. Local measures usually control procedural bleeding. Any proposed medication change should be made only in consultation with the patient's physician, particularly when comorbidities increase bleeding risk.
Worked example: A patient taking apixaban for atrial fibrillation who also has kidney failure presents for multiple extractions. The dentist plans local hemostatic measures, reviews the bleeding history, and contacts the physician to coordinate assessment rather than advising any change to the anticoagulant independently.
Mistake to avoid: Telling a patient on warfarin to skip doses before an extraction without consulting the physician, assuming local bleeding control justifies interruption.
Reference: [14]
10. A prosthetic joint does not automatically require prophylaxis
Current guidance finds no association between dental procedures and prosthetic joint infection, so routine antibiotic prophylaxis is generally not recommended for patients with joint implants. Premedication decisions are rare and should arise from shared decision making among the dentist, orthopedic team, and patient, mainly when prior joint-replacement complications exist and invasive procedures are planned.
Worked example: An adult with an uncomplicated total knee replacement and no complication history needs scaling and root planing. The dentist proceeds without premedication, documenting that the implant history alone does not establish a prophylaxis indication under current guidance.
Mistake to avoid: Prescribing prophylactic antibiotics for every patient with an artificial joint before routine restorative care, treating the implant itself as an automatic indication.
Reference: [16]
11. Endocarditis prophylaxis requires patient and procedure eligibility
Infective endocarditis prophylaxis applies only when two conditions coincide: the patient has a cardiac condition associated with the highest risk of adverse outcome, and the planned procedure involves manipulation of gingival tissue or the periapical region or perforation of oral mucosa. An unspecified heart history or an invasive procedure alone does not establish eligibility.
Worked example: A patient with a transcatheter-implanted prosthetic cardiac valve is scheduled for deep scaling with gingival manipulation. Both eligibility conditions are met, so the dentist discusses prophylaxis per applicable guidance while confirming allergy history, without assuming every cardiac murmur qualifies.
Mistake to avoid: Recommending prophylaxis solely because a procedure invades mucosa, without verifying that the cardiac history meets a high-risk category.
Reference: [16]
12. Choose acute pain therapy within patient-specific limits
For adolescents, adults, and older adults, nonopioid medications are recommended as first-line therapy for acute pain after tooth extraction and for temporary toothache management. Opioids are reserved for situations where first-line therapy is insufficient or NSAIDs are contraindicated. Clinicians should review medical history, medications, and contraindications, use shared decision making, and remember that temporary relief does not resolve the underlying cause.
Worked example: An otherwise suitable adult reports severe pain after a surgical extraction. The dentist reviews the medical history and medication list, considers nonopioid therapy first, and discusses expectations through shared decision making, reserving any opioid consideration only if first-line relief proves insufficient.
Mistake to avoid: Interpreting a patient's report of severe post-extraction pain as an automatic opioid indication, skipping review of NSAID suitability.
Reference: [13]
13. NSAID benefits and harms share a prostaglandin pathway
NSAIDs generally inhibit cyclooxygenase, the enzyme that converts arachidonic acid into prostaglandins, mediators of inflammation, fever and pain. Because prostaglandins also protect gastrointestinal mucosa and support renal perfusion, blocking their synthesis can produce gastrointestinal and renal harm, and cardiovascular risk is considered too. Mechanism alone does not determine an individual drug's suitability, and no dose or categorical prescribing decision is specified here.
Worked example: A candidate reviewing pain-control options for a scheduled extraction reads a health history noting reduced kidney function and a prior stomach ulcer; both findings belong in the risk discussion even though the medicine is available without prescription, alongside cardiovascular history.
Mistake to avoid: Assuming that over-the-counter availability by itself proves a medicine carries no systemic risks during assessment.
Reference: [13]
14. Count acetaminophen across combination products
Acetaminophen appears as an active ingredient in many prescription and over-the-counter combination products, including cold and flu remedies, so patients may unknowingly take several acetaminophen-containing drugs at once. Acetaminophen use has been associated with liver toxicity, and no daily amount is presented as universally safe; medication reconciliation should therefore count every product by its active ingredients rather than by product names.
Worked example: During medication reconciliation, a candidate asks a patient about a cold remedy taken this week and a separate dental pain product; comparing both ingredient lists reveals acetaminophen in each, so the review covers prescription and over-the-counter items without naming any universally safe daily amount.
Mistake to avoid: Relying on product names instead of active ingredient lists when reviewing a patient's current medications.
Reference: [13]
15. Recognize opioid sedation and respiratory hazards
Opioids can cause sedation, dizziness, nausea, vomiting, constipation and respiratory depression, and their labels warn about dangers of concomitant use with benzodiazepines or other central nervous system depressants. Risk assessment therefore weighs concurrent medicines and respiratory hazards alongside addiction, misuse and accidental-ingestion risks; no opioid selection, dose or emergency management protocol is supplied here.
Worked example: A candidate reviewing a health history sees a benzodiazepine among current medicines; this finding materially changes opioid risk assessment because combined central nervous system depression is possible, and the review also covers addiction, misuse and accidental-ingestion risks without naming an opioid, dose or emergency protocol.
Mistake to avoid: Evaluating an opioid option only by its expected analgesic benefit while overlooking concurrent depressant medicines.
Reference: [13]
Infection prevention foundations
16. Standard Precautions apply regardless of known infection status
Standard Precautions are the minimum infection prevention practices applying to all patient care regardless of suspected or confirmed infection status; when they alone cannot prevent transmission, Transmission-Based Precautions supplement, never replace, them. Dental settings may lack facilities for some Transmission-Based Precautions, so nonurgent care may be rescheduled and urgent care referred. CRDTS separately requires CDC-recommended infection control during simulated procedures.
Worked example: A clinical patient reports no known infection, yet hand hygiene, PPE and sharps safety still apply; if a transmissible disease were suspected, nonurgent care might be rescheduled or urgent care referred to an appropriately equipped setting.
Mistake to avoid: Reducing precautions because a patient's history appears reassuring, or treating supplemental precautions as full replacements.
17. Gloves do not replace hand hygiene
Hand hygiene is required before putting on gloves and immediately after removing them. Wash with soap and water when hands are visibly soiled with blood or body fluids; otherwise an alcohol-based hand rub may be used, following the product manufacturer's label instructions. Surgical procedures require a surgical hand scrub before sterile surgeon's gloves.
Worked example: After a restorative appointment, a candidate removes gloves and notices visible blood on the hands, so soap-and-water washing is required before donning fresh gloves for the next patient rather than relying on alcohol rub alone.
Mistake to avoid: Skipping hand hygiene between patients because a fresh pair of gloves will be worn over unwashed hands.
Reference: [10]
18. Reduce sharps exposure through controls and disposal
Engineering controls, such as self-sheathing needles and sharps containers, are the primary method for reducing bloodborne pathogen exposures, supplemented by work-practice controls like the one-handed scoop technique. Necessary recapping requires a supported one-handed method or mechanical device, and used sharps belong in puncture-resistant containers located close to the point of use.
Worked example: Following an injection, a candidate recaps the needle with a one-handed scoop technique, then places the syringe into a puncture-resistant container mounted near the operatory chair instead of passing the unsheathed syringe by hand.
Mistake to avoid: Recapping a used needle with both hands so its point aims toward the fingers, instead of using a one-handed scoop.
Reference: [10]
19. Match reprocessing to instrument risk classification
Critical instruments penetrate soft tissue or bone and carry the highest infection risk, so they require heat sterilization. Most semicritical items in dentistry, such as mouth mirrors, are heat-tolerant and should also be heat sterilized. If a semicritical item is heat-sensitive, it should be replaced with a heat-tolerant or disposable alternative; only when none is available is high-level disinfection the minimum fallback.
Worked example: A candidate cleans and heat sterilizes both a periodontal scaler and a mouth mirror between patients rather than wiping the mirror with surface disinfectant, recognizing that semicritical classification does not permit disinfection alone for heat-tolerant items.
Mistake to avoid: Wiping a heat-tolerant mouth mirror with surface disinfectant only, treating its semicritical classification as permission to skip heat sterilization.
Reference: [11]
20. Cleaning and intact packaging support safe instrument reuse
Cleaning must always precede disinfection or sterilization because retained blood and debris can shield microorganisms and compromise processing. After cleaning, dried instruments should be inspected and packaged before heat sterilization, and packs found wet, torn, or punctured during storage require full reprocessing before patient use.
Worked example: A candidate scrubs visible debris from instruments, dries and inspects them, and packages them before sterilization; a stored pack later found wet is cleaned, repackaged, and heat sterilized again rather than accepted because a cycle already ran.
Mistake to avoid: Loading instruments with retained blood and debris into the sterilizer and accepting a wet pack because a cycle already ran.
Reference: [11]
21. Interpret sterilization monitors as complementary evidence
Biological, mechanical, and chemical monitoring each supply different information about sterilization. Mechanical records document cycle parameters, chemical indicators show agent penetration, and weekly spore tests directly confirm lethality. Because mechanical and chemical indicators do not guarantee sterilization, no single monitor proves every processing step succeeded. If an internal indicator's color change fails, the instruments should not be used.
Worked example: A practice runs a weekly spore test and reviews cycle printouts, yet a package's internal indicator shows no color change after processing; the team sets those instruments aside for reprocessing rather than releasing them for patient care.
Mistake to avoid: Treating a changed indicator tape as proof of sterilization and skipping weekly biological monitoring or cycle-record documentation.
Reference: [11]
22. Distinguish clinical contact surfaces from housekeeping surfaces
Clinical contact surfaces, such as light handles, are touched often during care and need barrier protection or cleaning and disinfection between patients. Housekeeping surfaces, like floors and sinks, carry lower transmission risk and can be cleaned with soap and water, but visible blood contamination calls for cleaning and disinfection. A visibly blood-contaminated clinical contact surface needs an intermediate-level, tuberculocidal disinfectant, with labeled contact time observed.
Worked example: After treating a patient, a team member cleans an unprotected operatory light handle and applies an EPA-registered hospital disinfectant, allowing the full labeled contact time before the next appointment begins.
Mistake to avoid: Cleaning an operatory light handle as rarely as the floor and ignoring the disinfectant's labeled contact time before wiping.
Reference: [11]
Endodontic access and treatment decisions
23. Straight-line access concerns an unimpeded path
Straight-line access is defined by an unimpeded path from the occlusal surface to the apex or to the first point of canal curvature. The definition concerns path geometry, not the external size of the opening, and it stops at the first curvature rather than endorsing removal of natural canal curvature.
Worked example: A candidate enlarges an access cavity until the opening looks generous, but a dentin shelf still deflects an instrument before the first canal curvature; the preparation does not meet the unimpeded-path definition despite its size.
Mistake to avoid: Judging straight-line access by the external opening's size alone, or extending preparation beyond the first canal curvature.
Reference: [3]
24. Posterior internal form must preserve access to canal openings
For the Class of 2027 posterior endodontic simulation, satisfactory internal form tapers to the canal opening without ledges. Gouges that do not affect access to the canal orifice(s) may still be acceptable, while excessive ledging or gouges preventing orifice access, or perforation of the crown or pulp-chamber floor, are critically deficient. Defects are judged by their effect on access.
Worked example: A preparation shows a shallow axial gouge that leaves both canal orifices fully visible and reachable, so the internal form may still earn an acceptable rating, whereas a ledge blocking one orifice would be critically deficient.
Mistake to avoid: Rating any gouged preparation as deficient automatically, without assessing whether the defect actually blocks access to the orifices.
Reference: [4]
25. Interpret anterior apical preparation length within its stated bands
For the Class of 2027 anterior simulated procedure, the apical portion is satisfactory when instrumented 0.5–1.0 mm short of the anatomical apex. Preparation more than 1.0–2.0 mm short is substandard; instrumentation beyond the apex or more than 2.0 mm short is deficient. These bands apply only to this examination, not as a universal working-length prescription, and transportation or perforation are judged independently.
Worked example: A candidate instruments an anterior simulated canal so its apical termination sits 0.8 mm short of the anatomical apex, with no transportation or perforation; the apical-portion criterion is rated satisfactory, while remaining criteria are still graded separately.
Mistake to avoid: Grading a preparation 1.5 mm short as deficient instead of substandard, or treating the examination bands as a universal clinical working-length rule.
Reference: [4]
26. Canal transportation is a change in the anatomic pathway
Transportation occurs when over-instrumentation deviates preparation from the canal's natural anatomical pathway. Under the Class of 2027 anterior apical-portion criteria, a transported apical portion that still blends with the anatomical apex is substandard, while one that does not blend is deficient, as is root perforation. A correct endpoint distance therefore never guarantees preserved canal anatomy.
Worked example: A candidate's anterior preparation terminates 0.8 mm short of the anatomical apex, which alone would be satisfactory, but the transported apical portion fails to blend with the apex, so the apical-portion assessment is deficient despite the acceptable length.
Mistake to avoid: Assuming a satisfactory apical length proves the canal pathway is preserved, overlooking transportation that does not blend with the anatomical apex.
27. Isolation quality is a functional assessment
Isolation is judged functionally: an isolation dam is inadequate when inappropriate application, tearing, or leakage permits contamination of the endodontic preparation, or when it renders a Class II composite preparation unsuitable for subsequent material placement. A dam that is merely present but leaking fails this requirement. The cited standard is an examination treatment-management penalty, not a placement technique.
Worked example: During an endodontic simulation exercise, a candidate's dam appears well positioned, but a torn proximal edge lets a stated simulated contaminant reach the access preparation; because contamination occurs, the functional isolation requirement is not met and the examination penalty applies.
Mistake to avoid: Crediting isolation solely because a dam is placed, while ignoring a leak that contaminates the preparation or blocks restorative placement.
Reference: [3]
28. Separate definitive dental treatment from antibiotic indications
For symptomatic irreversible pulpitis, symptomatic apical periodontitis, or localized acute apical abscess in adults who are not severely immunocompromised, the guideline recommends prioritizing definitive dental treatment—pulpotomy, pulpectomy, nonsurgical root canal treatment, or incision and drainage—over routine antibiotics. Antibiotics are indicated when systemic involvement develops, shown by fever or malaise. This summary excludes severely immunocompromised patients and supplies no drug selection or dosing.
Worked example: An adult with symptomatic irreversible pulpitis and localized swelling but no fever or malaise, and with definitive treatment available, receives pulpotomy as the prioritized intervention rather than antibiotics; severe immunocompromise is absent, so the guideline's treatment-first recommendation applies here.
Mistake to avoid: Prescribing antibiotics as a substitute for pulpotomy or drainage in a non-immunocompromised adult lacking fever or malaise.
Reference: [12]
Periodontal assessment and management
29. Periodontitis assessment includes destructive tissue findings
Periodontitis is described as an inflammatory disease of bacterial etiology that produces loss of periodontal tissue attachment and alveolar bone, so assessment pairs inflammatory findings with destructive evidence. Signs such as bleeding on probing indicate inflammation, but the destructive component is identified through documented attachment loss and radiographic bone loss rather than through any single isolated sign.
Worked example: A chart shows bleeding on probing at several sites; the candidate also records documented attachment loss and radiographic bone loss on the molars, pairing inflammatory and destructive findings together when assessing periodontitis rather than relying on bleeding alone.
Mistake to avoid: Recording bleeding on probing as conclusive proof of periodontitis while omitting the documented attachment and radiographic bone loss that show tissue destruction.
Reference: [8]
30. Locate calculus relative to the gingival margin
Calculus is defined as a hard deposit attached to the teeth, usually consisting of mineralized bacterial plaque, and its classification as supragingival or subgingival depends on position relative to the gingival margin. A deposit lying apical to the margin is subgingival even when it sits on a crown surface, so location is judged against the margin rather than the tissue covered.
Worked example: A hard mineralized deposit is found on the crown surface of a lower molar but lies apical to the gingival margin; the candidate classifies it as subgingival because location is referenced to the margin, not to whether the deposit rests on crown tissue.
Mistake to avoid: Classifying a deposit as supragingival simply because it sits on the crown, instead of checking its position relative to the gingival margin.
Reference: [3]
31. Recognize recession from apical margin displacement
Gingival recession is defined as the visible apical migration of the gingival margin, which exposes the cementoenamel junction and root surface. Recognition therefore depends on observing the margin's displaced position together with the exposed junction and root. Recession and probing depths are separately identified examination observations, so visible root exposure does not substitute for a separate probing-depth assessment.
Worked example: On a canine, the gingival margin sits visibly apical to its expected position, exposing the cementoenamel junction and root surface; the candidate records this as recession and separately notes that probing depths on the same tooth are evaluated as a distinct observation.
Mistake to avoid: Treating visible root exposure as a complete periodontal diagnosis and skipping the separate probing-depth evaluation required alongside the recession finding.
Reference: [3]
32. Stage and grade answer different periodontal questions
Under the current classification, staging describes the severity and extent of periodontitis, while grading addresses the potential for disease progression and treatment outcome. Stages I through IV are assigned based on the most severe area of presentation, and grades A through C follow. The two terms answer different questions and should not be used interchangeably.
Worked example: A record documents substantial historical attachment and bone loss, supporting a stage assignment based on the most severe area, while documented rapid progression over recent years informs the grade; the candidate reports the two descriptors as answering separate classification questions.
Mistake to avoid: Using stage and grade interchangeably, or assuming that a severity description alone establishes the disease's progression category without progression evidence.
Reference: [8]
33. Use progression evidence and risk modifiers in grading
Grading reflects the potential for periodontitis progression and is based on supplemental evidence rather than stage alone. Examiners consider direct evidence of progression, indirect evidence such as radiographic bone loss divided by the patient's age, smoking patterns, and diabetes with glycemic control. The percentage-to-age calculation is one input and must be interpreted alongside the other applicable modifiers.
Worked example: A candidate reviewing a 50-year-old smoker with 30 percent radiographic bone loss computes 30 ÷ 50 = 0.60, then weighs that ratio with the smoking history and glycemic status before discussing a grade, without asserting a specific grade threshold.
Mistake to avoid: Assigning a grade from the bone-loss-to-age ratio alone while overlooking the patient's smoking status and diabetes-related glycemic control evidence.
Reference: [8]
34. Separate systemic association from demonstrated causation
Associations between periodontitis and several systemic conditions have been reported, but an observational association does not by itself demonstrate causation or a treatment benefit. Evidence strength varies across conditions; diabetes is described separately as a bidirectional relationship, while cardiovascular findings rely on surrogate outcomes with significant limitations and lack focus on true cardiovascular disease outcomes.
Worked example: When reviewing a patient with periodontitis and hypertension, a candidate explains that an association with cardiovascular disease has been reported, that causation is not established, and that periodontal treatment cannot be presented as preventing myocardial infarction.
Mistake to avoid: Telling a patient that scaling visits will prevent a future heart attack because periodontitis and cardiovascular disease are associated.
Reference: [8]
35. Nonsurgical care combines debridement and maintainable biofilm control
Nonsurgical periodontal therapy is defined as professional removal of supragingival and subgingival biofilm and calculus together with the patient's adoption of a comprehensive daily plaque control routine. It also includes addressing plaque-retentive factors, such as areas where plaque and food debris collect, and treatment selection depends on patient, site, and systemic factors.
Worked example: A candidate plans debridement for a patient with a defective overhanging margin that traps food, noting that calculus removal alone would not complete nonsurgical care until the plaque-retentive factor is also addressed and daily biofilm control is established.
Mistake to avoid: Treating the assigned debridement as the whole plan while ignoring the overhanging margin and the patient's daily biofilm control routine.
Reference: [8]
36. Assess simulated tissue injury by reflection and extent
Class of 2027 criteria distinguish two simulated tissue-trauma findings: a laceration of 3 mm or greater that does not allow reflection of the simulated gingival tissue, which is a scored tissue trauma error, and a laceration of 3 mm or greater that allows reflection, which is a critical error causing examination failure.
Worked example: During a simulated debridement, a candidate documents a 3.2 mm gingival laceration and recognizes that because the tissue can be reflected, the injury meets the critical description rather than being a minor, acceptable trauma error.
Mistake to avoid: Classifying a 3.5 mm laceration as minor based only on its length without checking whether reflection of the tissue is possible.
Reference: [3]
37. Successful periodontal therapy still requires supportive care
A treated periodontitis patient retains the diagnosis and disease susceptibility, so lifelong supportive care remains indicated even after successful active therapy. Maintenance visits may include reviewing home care and risk factors such as tobacco, professional plaque removal, subgingival debridement as needed, and monitoring attachment levels, pocket depths, bleeding, exudation, and mobility, with renewed active therapy considered if recurrence is suspected.
Worked example: A patient who completed scaling and root planing shows reduced probing depths and less bleeding at re-evaluation; the written plan still includes periodontal maintenance with attachment-level and mobility monitoring, because susceptibility persists and recurrence remains possible rather than eliminated.
Mistake to avoid: Discharging a successfully treated periodontitis patient from recall because improved probing depths and the absence of symptoms are mistaken for a cure.
Reference: [8]
Fixed prosthodontic principles
38. Distinguish bridge support from the replacement unit
An abutment is a tooth that provides support or anchorage for a fixed or removable prosthesis, while a pontic is the suspended portion of a fixed bridge replacing missing teeth. In a typical three-unit bridge, the two supporting prepared teeth function as abutments and the middle replacement unit is the pontic.
Worked example: A candidate reviewing a three-unit fixed bridge that replaces one missing premolar between two natural teeth identifies both supporting teeth as abutments providing anchorage and the suspended middle replacement unit as the pontic, without judging whether those abutments are suitable for the design.
Mistake to avoid: Calling the suspended replacement tooth of a three-unit bridge an abutment because every visible component of the prosthesis appears to provide support.
Reference: [3]
39. Retention and resistance address different displacement directions
Retention describes how a preparation keeps a crown seated against removal along its placement path, typically a vertical pull. Resistance addresses stability against tipping, rotation, or other displacement on a different axis. Because the two terms cover different displacement directions, a crown that resists lifting along its seating path is not automatically stable in every other direction.
Worked example: While evaluating a prepared molar for a cast crown, a candidate checks whether the restoration could lift vertically along its seating path, which concerns retention, and separately checks tilting or rotational dislodgement about other axes, which concerns resistance form.
Mistake to avoid: Treating retention and resistance as synonyms and concluding that a crown resisting vertical lift alone is stable against dislodgement in every direction.
Reference: [3]
40. Classify convergence and divergence by projected wall direction
Convergence refers to opposing cavity walls whose extensions, followed in a gingival-to-occlusal direction, would intersect at a point above the occlusal or incisal surface. Divergence refers to walls whose extensions, followed occlusal-to-gingival, would intersect below the crown. Either label is valid only when the projection direction is stated, so geometry should never be named from visual impression alone.
Worked example: In a fictional practice exercise, a candidate sketches a preparation and extends two opposing wall traces that would intersect above the prepared occlusal surface; after stating the gingival-to-occlusal projection direction used, the candidate labels the walls convergent.
Mistake to avoid: Naming prepared walls divergent based on their appearance alone without specifying whether the walls are projected gingival-to-occlusal or occlusal-to-gingival.
Reference: [3]
41. An undercut has different implications for different restorations
The CRDTS glossary gives undercut two meanings: a feature retaining intracoronal restorative material, and an undesirable feature for extracoronal restorations. Retentive undercuts for a filling do not automatically transfer to a crown preparation, which requires an unobstructed seating path along its line of draw. Candidates should judge undercuts against the planned restoration type rather than assuming retention features carry over.
Worked example: A candidate preparing a molar for an intracoronal restoration retains the filling with internal undercuts; later planning a full crown on that tooth, the candidate evaluates the crown's external preparation and seating path rather than presuming the filling's internal geometry blocks seating.
Mistake to avoid: Assuming an undercut that retains an intracoronal filling will also improve retention for a planned extracoronal crown preparation.
Reference: [3]
42. Match each assigned crown preparation to its material
For the Class of 2027, the fixed prosthodontic assignments pair each tooth with a specific material: monolithic zirconia on #3, porcelain-fused-to-zirconia on #5, and anterior lithium disilicate on #9. Each preparation is judged against its own material-specific criteria, so reductions, tapers and finish lines cannot be interchanged between assignments. Schools may also choose bi-layer teeth, so tooth construction can vary by site.
Worked example: A candidate assigned the anterior lithium disilicate crown on tooth #9 applies that material's criteria when checking incisal reduction and finish line placement, rather than borrowing the posterior monolithic zirconia dimensions used for tooth #3, because each assigned material carries its own grading standards.
Mistake to avoid: Grading tooth #9's preparation against monolithic zirconia criteria instead of the assigned anterior lithium disilicate standards.
43. Bridge abutments need a shared preparation relationship
Teeth #3 and #5 are prepared as abutments for the same three-unit bridge, and the manual requires both preparations to be parallel to each other. The Bridge Factor evaluates their shared line of draw, meaning the common direction of seating or withdrawal, rather than each abutment alone.
Worked example: A candidate completes tooth #3 with a distally converging path and tooth #5 with a mesially converging path; although each preparation might be considered separately, the conflicting directions identify a shared-draw problem for the Bridge Factor because the abutments lack a parallel seating path.
Mistake to avoid: Evaluating each bridge abutment's draw separately and overlooking whether the two preparations are parallel to each other.
44. Keep assigned crown margins supragingival
The Class of 2027 crown preparations must carry supragingival margins on the artificial teeth, prepared to within 0.5 mm of the gingival shroud; for the anterior lithium disilicate on #9, margins sit 0.5 mm above the simulated gingiva and criteria are adjusted accordingly. These simulation requirements do not establish universal clinical margin placement.
Worked example: While preparing tooth #9 for the anterior lithium disilicate crown, a candidate places the finish line 0.5 mm above the simulated gingival shroud as specified; positioning it at or below the shroud to mimic a clinical subgingival design would not satisfy the assigned simulation requirement.
Mistake to avoid: Extending the anterior lithium disilicate margin to the gingival shroud, an equigingival position that still differs from the specified supragingival placement.
Reference: [7]
45. Use standardized matrices to assess crown reduction
CRDTS supplies standardized reduction matrices for evaluating occlusal, facial and palatal reduction on Class of 2027 crown preparations because working and scoring articulators can produce occlusal variance. Material-specific numerical reduction requirements remain in the complete criteria, and a single favorable clearance observation does not establish overall preparation quality. Assessment with the supplied matrix supports, and articulator clearance alone does not replace, reduction evaluation.
Worked example: A candidate prepares tooth #5 for the assigned porcelain-fused-to-zirconia crown and observes generous opposing-tooth clearance on the working articulator. Before finishing, the candidate also assesses occlusal, facial and palatal reduction with the supplied CRDTS matrix rather than relying on the articulator observation alone.
Mistake to avoid: Concluding that the preparation's reduction is acceptable solely because opposing teeth clear on the working articulator, without checking the supplied matrix.
Reference: [7]
Removable prosthesis assessment
46. Changing supporting tissues can undermine denture fit
Resorption of residual ridges and other hard and soft tissue changes beneath denture bases can reduce a removable prosthesis's fit, retention, stability and support, and may contribute to tissue inflammation or ulceration. These findings prompt assessment of the patient and prosthesis rather than an automatic treatment choice, and no cancer-causation or fabrication claim is made here.
Worked example: A patient reports that a complete denture that previously felt secure now rocks during chewing although the base shows no cracks. Examination reveals residual ridge resorption, so the dentist reassesses retention, stability and support before discussing whether relining, rebasing or remaking suits this patient.
Mistake to avoid: Assuming an intact, undamaged denture must still fit and recommending a specific treatment without reassessing the patient's changed residual ridge and tissues.
Reference: [17]
47. Evaluate denture replacement from findings rather than a fixed lifespan
There is no evidence establishing a required frequency for denture relines, rebasing or remakes; the decision should follow thorough examination of the patient and prosthesis, assessing retention, fit, support, occlusal vertical dimension, esthetics, phonetics and patient satisfaction. Function beyond five years is an ACP evaluation trigger, not a mandatory replacement interval, and adhesive dependence, irritation or degradation can prompt earlier evaluation.
Worked example: A patient presents with a complete denture worn for six years that retains well and satisfies her esthetically. Rather than automatically remaking it, the dentist examines denture base adaptation, occlusal vertical dimension, phonetics and supporting tissues, then discusses with her whether replacement evaluation is warranted.
Mistake to avoid: Telling every patient that dentures must be replaced after five years, using elapsed time alone as the entire replacement decision.
Reference: [17]
48. Denture biofilm includes surfaces and acrylic porosities
Oral biofilm forms on all surfaces of a removable prosthesis and within acrylic resin porosities, which can make hygiene more challenging and may prevent commercially available denture cleansers from removing biofilm completely. Daily removal and cleaning appropriate to the prosthesis and its materials are therefore supported, without specifying any chemical concentration, soaking protocol or product.
Worked example: A patient shows a denture whose outer surfaces look clean after brushing. Because acrylic porosities can harbor biofilm that a visual check cannot confirm, the dentist reviews daily removal and cleaning methods suited to the prosthesis's materials rather than declaring all biofilm eliminated.
Mistake to avoid: Treating a visually clean denture surface as proof that biofilm within acrylic porosities has been completely removed by a commercial cleanser.
Reference: [17]
Caries and restorative decisions
49. Distinguish carious tissue removal endpoints
Selective removal stops when soft or firm dentin is reached; nonselective removal continues until hard dentin is reached. For moderate or advanced lesions on vital, non-endodontically treated permanent teeth requiring restoration without pulp therapy, the ADA conditionally prioritizes selective removal with very low certainty. Firm dentin does not make removal nonselective, and assigned CRDTS simulated preparations must still include all areas of caries or cavitation.
Worked example: During a vital molar preparation with an ICDAS 4 lesion, the candidate stops excavating once firm dentin is reached and restores without pulp therapy; the endpoint remains selective removal even though the dentin feels firm.
Mistake to avoid: Assuming that firm dentin reached throughout a preparation proves nonselective removal was performed on the qualifying lesion.
50. Match anterior approximal material recommendations to Class III
For moderate or advanced Class III approximal lesions on vital anterior permanent teeth without pulp therapy, the ADA conditionally suggests nanocomposite or hybrid resin composite, assigning no priority between them. This anterior approximal recommendation differs from the cervical and root-surface lists, so both lesion location and surface must be checked before selecting a material category.
Worked example: A patient with an ICDAS 4 approximal lesion on a vital maxillary central incisor is planned for a Class III restoration using nanocomposite, following the anterior approximal recommendation rather than the glass ionomer options listed for cervical surfaces.
Mistake to avoid: Selecting conventional GIC for a Class III lesion because that material appears on the anterior cervical or root-surface recommendation lists.
Reference: [5]
51. Class II material selection includes isolation feasibility
For moderate or advanced Class II lesions on vital posterior permanent teeth requiring restoration without pulp therapy, the ADA conditionally prioritizes amalgam, resin composite, or resin-modified GIC over conventional GIC with very low certainty and no ranking among them. Resin-modified GIC may be preferable when isolation cannot be achieved; amalgam consideration retains FDA cautions. CRDTS simulated Class II restorations are limited to composite or amalgam.
Worked example: For a vital molar with an ICDAS 4 approximal lesion and no pulp therapy, moisture control is difficult clinically, so resin-modified GIC could be favored; the assigned simulated restoration is still completed with composite per CRDTS criteria.
Mistake to avoid: Treating conventional GIC as equally prioritized for Class II restorations, or substituting it into an assigned simulated restoration.
52. Root-surface restorative recommendations differ from coronal Class II
For moderate or advanced root caries lesions on vital, non-endodontically treated permanent teeth requiring restoration without pulp therapy, the ADA conditionally suggests resin-modified GIC or conventional GIC with low certainty and no prioritization between them. This root-surface recommendation differs from the posterior coronal Class II list, so the affected surface, not merely tooth position, determines which material guidance applies.
Worked example: An ICDAS 5 root-surface lesion on a vital, non-endodontically treated premolar requiring restoration without pulp therapy is planned clinically with resin-modified GIC under the root caries recommendation, rather than with the amalgam or composite options prioritized for coronal posterior approximal lesions.
Mistake to avoid: Choosing amalgam or resin composite for a root caries lesion by following the posterior Class II coronal list instead of the root-surface guidance.
Reference: [5]
53. Noncavitated occlusal lesions have sealant-based options
For noncavitated occlusal lesions on permanent teeth, the ADA guideline prioritizes sealants, either alone or combined with 5% sodium fluoride varnish applied every three to six months, over its listed fluoride-only alternatives such as varnish alone, APF gel, or weekly mouthrinse. This strong recommendation carries moderate certainty, and patient preferences, feasibility, and resources still shape implementation.
Worked example: A clinician documents an ICDAS 2 occlusal lesion on a permanent molar and, after discussing options with the patient, plans sealant placement with sodium fluoride varnish rather than assuming the surface requires restorative preparation.
Mistake to avoid: Treating every occlusal lesion as a cavitation that automatically requires preparation, or extending this permanent-tooth sealant pathway to advanced cavitated lesions.
Reference: [6]
54. SDF decisions require disclosure of darkened lesion surfaces
Before silver diamine fluoride is chosen, informed consent should cover all restorative and nonrestorative options together with potential side effects, including blackening of treated surfaces. A patient who values appearance must understand that arrest does not preserve the original look, and eligibility still depends on the applicable tooth, lesion, and patient conditions.
Worked example: An adult concerned about a visible front-tooth lesion asks about SDF; the clinician explains that treated surfaces may darken and discusses restorative and nonrestorative alternatives before the patient decides.
Mistake to avoid: Obtaining a patient's agreement for SDF while omitting the possible blackening of treated surfaces that may matter greatly to that patient.
Reference: [6]
55. Nonrestorative treatment requires continuing lesion assessment
Nonrestorative care does not end when an agent is applied; lesions should be monitored periodically using features such as hardness or texture, color, and radiographs. No single feature or universal interval defines success, and any radiograph needs its own clinical justification that the benefit outweighs radiation risk, so a concerning texture warrants reassessment.
Worked example: At a recall visit, a lesion previously managed nonrestoratively shows changed color, and softened texture is noted, so the clinician reassesses the lesion and considers whether a radiograph is clinically justified rather than ordering one automatically.
Mistake to avoid: Judging lesion arrest from surface color alone or treating one intervention as the final step, without periodic reassessment of texture or justified radiographs.
56. Distinguish an open margin from a sealed marginal deficiency
The CRDTS glossary defines an open margin as restorative material not tightly adapted to the cavity preparation wall, generally detectable when an explorer tine penetrates it. A marginal deficiency differs: the discrepancy does not exceed 0.5 mm and the margin is sealed. This glossary distinction is terminology, not a universal acceptability threshold.
Worked example: During an evaluation, a 0.3 mm marginal discrepancy is found sealed along a restoration's margin, so it is recorded as a marginal deficiency rather than an open margin, pending complete criteria.
Mistake to avoid: Classifying every visible marginal discrepancy as an open margin, or assuming that a sealed defect within 0.5 mm is automatically satisfactory.
Reference: [3]
57. Assess excessive and missing opposing contact separately
Supra-occlusion describes a tooth or restoration with excessive or singular opposing contact in centric or excursions where such contact should not occur, while infra-occlusion describes a tooth or restoration lacking opposing centric contact where contact should be present. Examiners evaluate each condition against the expected occlusal relationship rather than simply checking whether any contact exists.
Worked example: A candidate evaluates a newly placed Class II restoration showing one heavy, isolated centric contact on a marginal ridge and grades it as supra-occlusion, while an adjacent restoration lacking its expected centric contact is separately graded as infra-occlusion.
Mistake to avoid: Grading a restoration as acceptable for occlusion merely because some opposing contact exists, without determining whether that contact is excessive, singular, or absent where required.
Reference: [3]
58. Apply the Class II gingival-clearance bands precisely
For the Class of 2027 Class II preparation, gingival contact must be open. Clearance up to 1.0 mm is satisfactory, above 1.0 up to 1.5 mm is acceptable, above 1.5 up to 2.0 mm is substandard, and above 2.0 mm or a contact that is not open is deficient. Each stated upper boundary is inclusive.
Worked example: A candidate measures 1.3 mm of open gingival clearance between the proximal box floor and the adjacent tooth and records acceptable, recognizing that a closed contact measuring zero gap would instead be deficient under this criterion.
Mistake to avoid: Recording a closed gingival contact as satisfactory because the measured clearance is zero, ignoring that the criterion requires the contact to be open gingivally.
Reference: [4]
59. Read both sides of the Class II isthmus-width criterion
Class of 2027 grades the Class II isthmus width in both directions from the satisfactory 1.5 mm value. Widths above 1.5 up to 2.0 mm are acceptable; 1.0 to less than 1.5 mm and above 2.0 up to 2.5 mm are substandard; below 1.0 mm or above 2.5 mm are deficient.
Worked example: A candidate prepares an isthmus measuring 1.2 mm and records substandard, recognizing that although this width conserves tooth structure, it falls below the satisfactory 1.5 mm band rather than earning a higher grade for being narrow.
Mistake to avoid: Assuming a narrower isthmus always grades better, overlooking that widths below 1.0 mm are deficient and 1.0 to less than 1.5 mm is substandard.
Reference: [4]
60. Balance Class II outline coverage with ridge preservation
The Class of 2027 satisfactory outline is smooth, rounded, and flowing, with the cavosurface margin positioned so the marginal or oblique ridge remains at least 1.5 mm wide. Underextension that omits occlusal pits and grooves is substandard, and unsupported cavosurface margins or ridges narrower than 1 mm are deficient.
Worked example: A candidate extends a Class II outline leaving a 1.2 mm marginal ridge and records substandard, while a separate preparation whose cavosurface margin leaves unsupported enamel is graded deficient even though its measured ridge width appears adequate.
Mistake to avoid: Widening the outline for access while thinning the marginal ridge below 1.5 mm, or leaving required occlusal pits and grooves outside the preparation.
Reference: [4]
Sources
- CRDTS Dental Examination: Current Components and Published Candidate Manuals
- CRDTS Dental Simulated Patient Examination: Overview, Policy and Procedures, Class of 2026
- CRDTS Dental Simulated Patient Examination: Overview, Policy and Procedures, Class of 2027
- CRDTS Class of 2027 Dental Simulated Patient Examination: Summary of Changes
- ADA Restorative Caries Treatments Chairside Guide: Tissue Removal and Direct Restorative Materials for Permanent Teeth
- ADA Nonrestorative Caries Treatments Chairside Guide: Permanent Teeth
- CRDTS Prosthodontic Candidate Manual, Class of 2027: Crown Reduction, Margins, Taper and Bridge Draw
- ADA Oral Health Topics: Periodontitis—Classification, Diagnosis and Treatment
- ADA Oral Health Topics: X-Rays/Radiographs—Patient Selection, Digital Imaging and Radiation Safety
- CDC Standard Precautions in Dental Settings
- CDC Sterilization and Disinfection: Dental Instruments, Devices and Environmental Surfaces
- ADA Antibiotics for Dental Pain and Swelling Guideline: Definitive Treatment and Antibiotic Indications
- ADA Oral Analgesics for Acute Dental Pain: Mechanisms, Selection and Adverse Effects
- ADA Oral Anticoagulant and Antiplatelet Medications and Dental Procedures
- ADA Cancer of the Head and Neck: Risk Factors, Clinical Examination and Diagnostic Follow-up
- ADA Antibiotic Prophylaxis Prior to Dental Procedures: Cardiac and Prosthetic Joint Decisions
- American College of Prosthodontists Position Statement: The Frequency of Denture Replacement