Dental Hygienist Licensing Exam cheat sheet

Enamel is about 96% inorganic by weight, chiefly carbonated hydroxyapatite; dentin is about 70% inorganic with a type I collagen matrix.

Cementum is roughly 45–50% inorganic and becomes more cellular toward the apical third as cellular cementum.

Principal periodontal ligament fiber groups include alveolar crest, horizontal, oblique, apical, and interradicular; the oblique group resists axial occlusal forces.

Caries requires a susceptible tooth, cariogenic biofilm, fermentable carbohydrate, and time; demineralization predominates when plaque pH falls below about 5.5.

Resting saliva pH is about 6.7–7.4; stimulated flow increases bicarbonate buffering and raises pH.

Fluoride reduces demineralization and enhances remineralization by forming fluorapatite and calcium fluoride-like deposits.

Gingival inflammation begins with bacterial biofilm; reversible gingivitis shows bleeding on probing, erythema, and edema without attachment loss.

Periodontitis involves clinical attachment loss and alveolar bone resorption driven by the host inflammatory response to dysbiotic biofilm.

Permanent first molars and central incisors typically erupt at 6–7 years, canines at 11–12 years, and third molars at 17–21 years.

Clinical attachment loss equals probing depth plus recession minus gingival margin position; probing depths of 4 mm or more with bleeding indicate site-specific risk.

A universal curet has a rounded toe and two cutting edges per working end; Gracey curets are area-specific with one cutting edge.

Sickle scalers are designed for supragingival calculus and have a pointed tip; they are not adapted subgingivally.

Correct scaling angulation is 45–90 degrees to the tooth surface; 0 degrees is adaptation and more than 90 degrees can gouge cementum.

Five percent sodium fluoride varnish contains about 22,600 ppm fluoride; 1.23% APF gel contains about 12,300 ppm.

Resin sealants bond to acid-etched enamel by micromechanical retention and physically block pits and fissures from plaque and carbohydrate.

Standard precautions treat all blood, saliva, and body fluids as potentially infectious and include hand hygiene, gloves, masks, eye protection, and safe sharps handling.

Steam autoclave sterilization uses 121°C at 15 psi for 15–20 minutes or 134°C for 3–4 minutes when packaging and load are correct.

Blood pressure of 130–139/80–89 mmHg is stage 1 hypertension under ACC/AHA criteria; 180/120 mmHg or higher with symptoms requires urgent evaluation.

Incidence counts new cases over a period; prevalence counts all existing cases at a point or interval.

Sensitivity equals true positives divided by true positives plus false negatives; specificity equals true negatives divided by true negatives plus false positives.

Positive predictive value depends on disease prevalence and is lower when prevalence is low.

DMFT indexes decayed, missing, and filled permanent teeth; dmft applies the same counting to primary teeth.

Relative risk equals incidence in exposed people divided by incidence in unexposed people; odds ratio approximates relative risk for rare outcomes.

Primordial prevention addresses risk-factor emergence; primary prevents disease onset; secondary detects early disease; tertiary limits disability.

Community water fluoridation is adjusted to 0.7 mg/L in the United States and reduces caries across socioeconomic groups.

Randomized controlled trials provide the strongest causal evidence; cohort studies follow exposed and unexposed groups, and case-control studies compare diseased and nondiseased people.

Reliability is consistency or repeatability of measurements; validity is accuracy in measuring the intended construct.