NZ Dental Hygiene REX cheat sheet

Scope of practice: a dental hygienist works under the HPCA Act 2003 framework; the Dental Council's scope statement defines permitted activities, and anything outside it requires referral or a specified delegation from a dentist.

Informed consent in New Zealand follows Health and Disability Commissioner Code of Health and Disability Services Consumers' Rights Right 7: valid consent requires competence, adequate information, and freedom from coercion; written consent is not itself a legal requirement.

Right 6 of the Code requires disclosure of the nature and purpose of treatment, expected risks and benefits, alternatives (including no treatment), and the likely consequences of declining.

Privacy: the Health Information Privacy Code 2020 governs collection, storage, use and disclosure of health information; disclosure without consent is limited to serious threat to safety, court order, or statutory reporting.

Cultural safety: the HPCA Act requires practitioners to be culturally competent; Nursing Council/Dental Council guidance frames cultural safety as the patient determining whether care is safe, with Te Tiriti o Waitangi obligations underpinning practice.

Mandatory reporting duties: suspected abuse or neglect of a child or vulnerable adult, and privacy breaches likely to cause harm, must be escalated under the relevant legislation (Oranga Tamariki Act 1989, Privacy Act 2020).

Record keeping: clinical records must be accurate, contemporaneous and retained for at least 10 years from the last entry (or until age 25 for children); patients have a right of access under Right 6(1) and the Privacy Act.

Professional boundaries and conflicts of interest must be declared; accepting gifts or personal relationships that could compromise clinical judgement is a boundary violation reportable to the Council.

Infection control and scope breaches are notifiable to the Dental Council under the Health Practitioners Competence Assurance Act; practising outside scope can result in a competence review or disciplinary referral.

Standard precautions apply to all patients regardless of known status: hand hygiene, gloves, eye protection, mask, gown, and safe sharps handling.

Hand hygiene uses the WHO 5 Moments; alcohol-based hand rub is used for non-soiled hands, soap and water when visibly soiled or after contact with spore-forming organisms such as Clostridioides difficile.

Sterilisation: instruments must be cleaned (ultrasonic or washer-disinfector), inspected, packaged, and autoclaved; Class B vacuum autoclaves are required for hollow or wrapped items, with chemical and biological indicators each cycle.

Critical items (surgical, periodontal scalers, probes) must be sterile; semi-critical items (mouth mirrors, impression trays) require high-level disinfection or sterilisation; non-critical surfaces require low-level disinfection.

Sharps: never recap needles by hand; use a one-handed scoop or a sharps container at point of use; containers are replaced when three-quarters full.

Occupational exposure: needlestick or splash to mucous membranes requires immediate washing, reporting, and risk assessment for HBV, HCV and HIV post-exposure prophylaxis within the recommended window.

Immunisation: dental hygienists should be vaccinated against hepatitis B (with post-vaccination serology confirming anti-HBs ≥10 mIU/mL) and be offered influenza and COVID-19 vaccination.

Waste segregation: sharps into rigid yellow containers, infectious clinical waste into yellow bags, amalgam waste into designated amalgam separators and containers under the Resource Management (amalgam) regulations.

Health and Safety at Work Act 2015: the practice has a primary duty of care (PCBU) to eliminate or minimise risks, including ergonomic hazards, latex allergy, and hazardous substances; workers must be consulted.

Enamel is 96% mineral (hydroxyapatite) with 1–2% organic material; rods are oriented perpendicular to the dentine-enamel junction and are aprismatic at the surface.

Dentine is 70% mineral, 20% organic (mostly type I collagen) and 10% water; dentinal tubules radiate from the pulp with a density of 15,000–65,000 per mm².

Pulp is innervated by A-delta fibres (sharp, fast, myelinated) and C fibres (dull, slow, unmyelinated); A-delta fibres respond to dentine fluid movement (hydrodynamic theory).

Periodontal ligament is 0.15–0.38 mm wide, composed of principal fibres (alveologingival, transseptal, oblique, apical, interradicular) that transmit occlusal forces to bone.

Junctional epithelium attaches to the tooth via hemidesmosomes and internal basal lamina; its length is about 1 mm, with 0.5–1 mm of connective tissue attachment and 1–2 mm of biologic width.

Saliva: resting flow 0.3–0.4 mL/min, stimulated 1.5–2.0 mL/min; pH 6.7–7.4; bicarbonate is the principal buffer, with phosphate and proteins contributing.

Tooth eruption: primary teeth begin at 6 months (mandibular central incisors), permanent first molars at 6 years, and third molars at 17–21 years; mixed dentition spans 6–12 years.

Embryology: dental lamina forms at 6 weeks in utero; bud, cap and bell stages occur by 12 weeks; enamel organ derives from ectoderm, dental papilla from neural crest mesenchyme.

Nerve supply: maxillary teeth via the maxillary division (V2) and its branches (posterior, middle, anterior superior alveolar); mandibular teeth via the inferior alveolar nerve (V3), with the lingual nerve supplying lingual mucosa.

Periodontitis is a polymicrobial dysbiosis; the red complex (Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola) is strongly associated with established disease.

2018 classification: staging uses severity (CAL, bone loss, tooth loss) and complexity; grading uses progression rate (A slow, B moderate, C rapid) based on bone loss/age and risk factors such as smoking and diabetes.

Probing depth ≥4 mm with bleeding on probing (BOP) indicates active inflammation; ≥5 mm with BOP suggests need for subgingival debridement; ≥6 mm often requires referral or specialist care.

BOP is the best single predictor of disease progression when absent (negative predictive value high); its presence alone does not confirm progression.

Risk factors: smoking (dose-dependent, reduces BOP and healing), poorly controlled diabetes (HbA1c >7%), stress, medications (calcium channel blockers, phenytoin, ciclosporin causing gingival overgrowth).

Non-surgical periodontal therapy (NSPT) includes oral hygiene instruction, supragingival and subgingival scaling and root debridement, and risk factor modification; re-evaluation typically at 6–8 weeks.

Supportive periodontal care intervals are individualised: 3 months for high-risk (grade C, smokers, diabetes), 6 months for low-risk stable patients.

Aggressive periodontitis (now grade C, stage III/IV) is characterised by rapid attachment loss, familial aggregation, and often a younger age of onset.

Caries is a dynamic, biofilm-mediated, diet-modulated, multifactorial disease; the balance between demineralisation and remineralisation determines lesion progression.

ICDAS scoring: 0 sound, 1–2 early (non-cavitated), 3–4 moderate, 5–6 extensive cavitation; only cavitated lesions typically require restoration.

Caries risk assessment tools (e.g., CAMBRA, Cariogram) consider diet, fluoride exposure, saliva, plaque, past caries experience, medical conditions and socioeconomic factors.

Fluoride: 1,000–1,500 ppm fluoride toothpaste twice daily for adults; children under 6 use 1,000 ppm; high-risk patients may use 2,800–5,000 ppm or professional fluoride varnish (22,600 ppm F) every 3–6 months.

Fluoride varnish is the recommended professional topical for high-risk patients; it reduces caries increment by ~30–40% in primary teeth and ~25% in permanent teeth.

Dietary advice: limit free sugars to <10% of energy intake (WHO), ideally <5%; reduce frequency of sugar exposures rather than total amount; avoid sugary drinks between meals.

Fissure sealants: resin-based sealants reduce caries by ~80% in high-risk molars; apply to permanent molars with deep pits/fissures, especially within 2 years of eruption.

Saliva as a risk factor: hyposalivation (unstimulated <0.1 mL/min) markedly increases caries risk; common causes include medications, radiotherapy, Sjögren's syndrome and diabetes.

Silver diamine fluoride (SDF) 38% arrests active dentinal caries and is useful for high-risk or uncooperative patients; it stains arrested lesions black.

Red flags for referral: ulceration persisting >2 weeks, induration, fixed or non-healing lesions, unexplained bleeding, paraesthesia, neck lump, or unilateral symptoms.

Oral potentially malignant disorders (OPMDs): leukoplakia, erythroplakia, oral submucous fibrosis, actinic cheilitis, and lichen planus; erythroplakia has the highest malignant transformation rate.

Oral squamous cell carcinoma most commonly affects the lateral border of tongue, floor of mouth and retromolar region; risk factors include tobacco, alcohol, betel quid and HPV (oropharyngeal).

Recurrent aphthous stomatitis: minor (<10 mm, heals in 10–14 days), major (>10 mm, scarring), and herpetiform; treat with topical corticosteroids and identify triggers.

Oral candidiasis: pseudomembranous (thrush), erythematous, hyperplastic and angular cheilitis; risk factors include antibiotics, inhaled corticosteroids, xerostomia, diabetes, immunosuppression and dentures.

Oral lichen planus: bilateral, reticular white striae (Wickham striae) on buccal mucosa; erosive forms require biopsy to exclude dysplasia and topical corticosteroid management.

Herpes simplex: primary herpetic gingivostomatitis in children; recurrent herpes labialis triggered by stress, UV, illness; HSV-1 most common.

Medication-related osteonecrosis of the jaw (MRONJ): associated with bisphosphonates, denosumab and anti-angiogenics; presents as exposed bone >8 weeks in the maxillofacial region; avoid elective extractions where possible.

Comprehensive assessment includes medical history, dental history, extraoral and intraoral examination, periodontal charting (PD, CAL, BOP, mobility, furcation), caries charting and radiographs.

Periodontal charting records six sites per tooth (mesiobuccal, midbuccal, distobuccal, mesiolingual, midlingual, distolingual); CAL = PD + recession (or minus hyperplasia).

Instrument selection: sickle scalers for supragingival calculus; universal curettes (Columbia 13/14) for all areas; area-specific Gracey curettes (1/2 anterior, 7/8 posterior buccal/lingual, 11/12 posterior mesial, 13/14 posterior distal).

Gracey curettes have a curved, offset blade with one cutting edge; the terminal shank is angled 70° to the blade face; correct adaptation keeps the terminal shank parallel to the long axis of the tooth.

Working angulation is 45–90° for calculus removal, with light lateral pressure (1–2 N); excessive angulation causes root grooving and tissue trauma.

Powered instrumentation: ultrasonic scalers use magnetostrictive or piezoelectric mechanisms; magnetostrictive tips move in an elliptical pattern, piezoelectric in a linear pattern; use light pressure and keep tips moving.

Polishing: use a rubber cup or brush with prophylaxis paste; avoid on newly erupted teeth, exposed dentine, carious lesions and restorations with poor marginal integrity; air polishing is contraindicated in sodium-restricted patients and communicable disease.

Treatment planning is sequenced: emergency care, disease control (NSPT, caries management), re-evaluation, definitive care (restorative, prosthodontic), and maintenance.

Motivational interviewing (MI) uses open questions, affirmations, reflections and summaries (OARS) to explore ambivalence and build intrinsic motivation; avoid the righting reflex.

The transtheoretical model (Prochaska & DiClemente) stages: precontemplation, contemplation, preparation, action, maintenance, and relapse; interventions are matched to stage.

Health belief model constructs: perceived susceptibility, severity, benefits, barriers and cues to action; self-efficacy added in later versions.

Oral health education should be tailored to health literacy; use teach-back and plain language; avoid jargon and written materials above the patient's reading level.

Community water fluoridation is the most cost-effective population caries prevention measure; in New Zealand it is managed by local authorities under the Health Act 1956 and reduces caries by ~25–40%.

New Zealand's oral health services: children and adolescents up to 17 years receive free care through community oral health services and the Adolescent Oral Health Service; adults pay privately or via WINZ/ACC where eligible.

Te Whare Tapa Whā (Durie) model: taha tinana (physical), taha hinengaro (mental), taha whānau (family), taha wairua (spiritual); used to frame holistic oral health promotion with Māori whānau.

Settings-based health promotion (Ottawa Charter 1986) includes building healthy public policy, creating supportive environments, strengthening community action, developing personal skills and reorienting health services.

ALARA principle: radiation dose should be as low as reasonably achievable, with justification (benefit outweighs risk) and optimisation (lowest dose for diagnostic quality).

Bitewing radiographs detect interproximal caries and crestal bone levels; periapicals show the full tooth and periapical tissues; panoramic (OPG) gives a broad overview but lower resolution.

Intraoral film/sensor positioning: paralleling technique with a holder reduces distortion; bisecting-angle technique is an alternative when paralleling is not possible.

Radiation dose: a bitewing is ~1–5 µSv; an OPG is ~10–20 µSv; background radiation in New Zealand is ~2,000–2,500 µSv per year for comparison.

Pregnancy is not a contraindication to necessary dental radiography; lead apron and thyroid collar are used as standard, and elective radiographs may be deferred.

Radiographic interpretation within scope: identify normal anatomy (enamel, dentine, pulp, lamina dura, PDL space, alveolar bone, maxillary sinus, mandibular canal, mental foramen) and refer suspicious findings.

Common artefacts: cone cutting, elongation/foreshortening, overlapping, movement, film bending; each has a specific cause that should be corrected.

Radiographs must be reported and stored with the clinical record; findings should be recorded contemporaneously and shared with the treating dentist where required.