LDS Part 1 cheat sheet

Tooth numbering: FDI two-digit system - first digit is the quadrant (1 upper right, 2 upper left, 3 lower left, 4 lower right), second digit is the tooth position from the midline (1 = central incisor through 8 = third molar).

Enamel composition by weight: ~96% inorganic (hydroxyapatite), ~1% organic, ~3% water; dentin is ~70% inorganic, ~20% organic (mostly type I collagen), ~10% water.

Setting of zinc phosphate cement is an acid–base reaction between zinc oxide and phosphoric acid; it is exothermic and the set cement is brittle with low pH initially.

Glass ionomer cements bond chemically to tooth structure via carboxylate groups and release fluoride; they are moisture-sensitive during initial set.

Composite resin polymerization shrinkage is a major cause of marginal leakage; shrinkage stress is reduced by incremental placement and by low-shrinkage or bulk-fill formulations.

Amalgam is a silver–tin–copper–mercury alloy; high-copper (>6% Cu) formulations reduce the gamma-2 (Sn7-8Hg) phase and improve corrosion resistance and strength.

Denture base resins are typically heat-cured PMMA; polymerization shrinkage of acrylic resin is compensated by processing techniques such as injection molding or extended curing.

Crown-to-root ratio: a minimum of 1:1 is generally acceptable for a single-rooted tooth; 2:1 crown-to-root is considered favorable for multi-rooted support.

Lichen planus: T-cell–mediated interface mucositis; reticular (Wickham striae) is the most common oral form; erosive/atrophic forms are more symptomatic and carry a small malignant transformation risk.

Leukoplakia is a clinical diagnosis of exclusion (white patch not attributable to another cause); it carries a higher malignant transformation risk than homogeneous lesions when it is non-homogeneous or on the floor of the mouth/ventral tongue.

Odontogenic cysts: radicular (periapical) cyst is the most common; dentigerous cyst surrounds the crown of an unerupted tooth; keratocyst (OKC) has a high recurrence rate and is associated with PTCH1 mutations and nevoid basal cell carcinoma syndrome.

Ameloblastoma is a locally aggressive odontogenic tumor, most often in the posterior mandible, with a classic soap-bubble multilocular radiolucency; it requires wide resection due to high recurrence.

Oral squamous cell carcinoma risk factors include tobacco, alcohol (synergistic), betel quid, HPV-16 (oropharyngeal), and chronic irritation; most common sites are lateral tongue and floor of the mouth.

Periapical abscess vs. granuloma vs. cyst: all may present as a periapical radiolucency; definitive distinction is histologic, and the radiolucency is typically not visible until cortical bone is involved.

Local anesthesia: the inferior alveolar nerve block targets the pterygomandibular space; failure is most often due to accessory innervation, bifid canal, or deposition too anteriorly.

Antibiotic prophylaxis for infective endocarditis is indicated for high-risk cardiac conditions (prosthetic valve, prior endocarditis, certain congenital heart disease) before invasive dental procedures, per current guidelines.