Comprehensive University Study Notes on Odontology, Maxillofacial Surgery, Ophthalmology, and Otorhinolaryngology, and Audiology

Dental Anatomy and Coordinates

Dental coordinates are based on four quadrants. The first digit represents the quadrant, starting from the upper right and moving clockwise: 1 for upper right, 2 for upper left, 3 for lower left, and 4 for lower right. The second digit indicates the specific tooth in a mesio-distal direction. Mesial refers to a position toward the midline, whereas distal refers to a position away from the midline.

The human tooth consists of several distinct components. The corona is the portion of the tooth that develops outside the gingival margin. It is covered by Smalto (enamel), an inorganic tissue composed of $98\,\%$ idrossiapatite that appears radiopaque on imaging. Underlying this is the Dentina (dentin), composed of $70\,\%$ idrossiapatite crystals and $30\,\%$ organic substances. The dentin has a tubular structure containing the cellular extensions of odontotiasts, which are neural-derived cells located at the border between the dentin and the pulp. The Colletto (cervix) is the small groove dividing the crown from the root. The root (Radice) forms the base of the tooth. Its outermost layer is the Cemento (cementum), composed of $40\,\%$ idrossiapatite and $60\,\%$ organic substance, typically yellow in color. At the apex of the root, an opening allows blood vessels and nerves into the pulp chamber, which provides nourishment and sensation. The parodonto is the supporting tissue of the tooth, consisting of the alveolar bone, the periodontal ligament (containing fibroblasts, mesenchymal cells, residues of Malassez, and osteoblasts), and the external gingiva.

Dental eruption begins with the deciduous (primary) dentition, which includes 20 teeth: 8 incisors, 4 canines, and 8 molars. There are no deciduous premolars. The primary eruption sequence occurs between 6 and 30 months of age. Permanent dentition begins with the first lower molar around age 6, followed by the lower incisors. The eruption is driven by the formation of roots at the lower pole of the tooth, which pushes the hard tissue upward, causing the follicle to fuse with the gingiva.

Disodontiasi and Impacted Teeth

Disodontiasi refers to an anomalous and complicated dental eruption. If eruption fails to occur within the normal timeframe, it is classified as dental inclusion (impacted tooth). Clinically, this often presents as pericoronitis, an inflammatory pathology of the pericoronal sac. The most frequently included tooth is the third molar (wisdom tooth), followed by the maxillary canine. Mandibular third molars are more commonly impacted than maxillary ones. Eruption is typically complete by age 20 but may continue until 25.

Etiopathogenesis involves embryonic factors, such as the germ of the third molar arising from the gubernaculum dentis of the second molar, often resulting in an axe oblique to the second molar. Chronological factors follow the Capdepont curve, moving from bottom to top and back to front. Prognostic factors for eruption include the angulation of the tooth (mesio-version, distal-version, vestibular, lingual, or palatal inclination) and the distance between the distal surface of the second molar and the anterior margin of the mandibular ramus. The Pell and Gregory classification stages this space into Class I (equal to crown width), Class II (less than crown width), and Class III (no space).

Pulpitis and Trigeminal Neuralgia Identification

Pulpitis encompasses inflammatory and degenerative processes of the pulp tissue leading to necrosis. Etiology includes caries, physical trauma (orthodontic forces, bruxism), thermal damage (exceeding the $55\,^{\circ}C$ tolerance limit), and chemical factors from filling materials. Evolutionary stages begin with pulp hyperemia (reversible) and proceed to acute serous pulpitis, characterized by protein-poor liquid trasudation and increased pressure. Acute purulent pulpitis follows, where leukocyte enzymes dissolve the tissue into small abscesses. Chronic forms include ulcerative and hyperplastic variants. The terminal stage is pulp necrosis, which can be coagulative (ischemic), colliquative (bacterial/autolytic), or gangrenous.

Clinical presentation of acute serous pulpitis includes non-localized continuous pain that radiates along trigeminal branches (secondary trigeminal neuralgia). Pain increases when lying down or during effort due to blood flow changes. Acute purulent pulpitis features continuous, pulsating pain, aggravated by heat and relieved by cold. Differential diagnosis (DD) with primary trigeminal neuralgia is critical: primary neuralgia typically affects patients aged 60-70, presenting as violental "electric shocks" lasting seconds, often triggered by touching the face or shaving. Pulpitis pain is constant and lacks a specific external trigger. Treatment requires pulp removal or devitalization.

Medication-Related Osteonecrosis of the Jaw (MRONJ)

Osteonecrosis of the jaw (ONJ) is a progressive necrosis of mandibular or maxillary bone in subjects exposed to specific drugs without prior radiation treatment. Two main drug classes are implicated: antiresorptive agents (Bisphosphonates and Denosumab) and antiangiogenic agents. Bisphosphonates (BP) bind to idrossiapatite and induce osteoclast apoptosis, hindering bone remodeling and allowing microfractures from mastication to evolve into infections and necrosis. High-risk BP includes zoledronate ($5\,mg$ every 12 months) or pamidronate. Denosumab (Xgeva at $120\,mg$ or Prolia at $60\,mg$) inhibits RANK-L, reducing bone turnover temporarily. Antiangiogenic agents like VEGF inhibitors (bevacizumab) or Tyrosine Kinase inhibitors (sunitinib) increase risk due to the terminal vascularization of the mandible.

Clinical staging follows the AAOMS 2014 criteria. Stage 0 involves non-specific symptoms without bone exposure. Stage 1 features exposed necrotic bone in asymptomatic patients without infection. Stage 2 includes exposed bone with pain and infection (purulent drainage). Stage 3 involves exposed bone, infection, and complications like pathological fractures, extra-oral fistulas, or oronasal communication. Diagnosis requires a history of drug use, bone exposure persisting $> 8$ weeks, and no history of radiation. Treatment involves strict follow-up, controlling pain, and managing infections with ampicillin-sulbactam or metronidazole. Surgical debridement or sequestrectomy is reserved for extensive cases.

Refractive Errors and Optics

The human eye functions as a dioptric system with a total power of approximately 60 diopters ($40\,D$ from the cornea and $20\,D$ from the crystalline lens). Emmetropia is the condition where light rays from infinity focus perfectly on the retina without corrective assistance. Ametropias include myopia, hypermetropia, and astigmatism.

Myopia occurs when light rays focus in front of the retina, often due to an axial length that is too long. Patients see clearly up close but blurrily at a distance. It is classified as mild ($< 3\,D$), moderate ($3-6\,D$), or high ($> 6\,D$). High myopia is associated with degenerative risks like stafiloma miopico and retinal detachment. Hypermetropia occurs when light rays focus behind the retina because the bulb is too short. Young patients may compensate via accommodation, potentially leading to astenopia or convergent strabismus. Astigmatism results from irregular corneal curvature where different meridians have different refractive powers, resulting in a conoide of Sturm rather than a single focal point. It can be regular (meridians are orthogonal) or irregular (e.g., in cheratocono).

Presbiopia is a physiological age-related loss of accommodation (the ability of the ciliary muscle to increase lens convexity via the Zinn fibers). It typically begins around age 40 with a loss of $1\,D$, reaching $3\,D$ by age 60. Correction involves positive (convergent) lenses for near vision. Amblyopia ("lazy eye") is a reduction in visual acuity (at least $2/10$ difference between eyes) resulting from lack of stimulation during the critical developmental period (0-6 years). Causes include strabismus, anisometropia, or deprivazione (e.g., congenital cataracts). Treatment focus is on occlusion (patching) or penalization of the functioning eye to stimulate the amblyopic eye before age 6.

Glaucoma Pathophysiology and Management

Glaucoma is a chronic degenerative neuropathy of the optic nerve, frequently associated with elevated intraocular pressure (IOP). Normal IOP is defined as $16 \pm 2.5\,mmHg$. Pressure is maintained by the balance of production from the ciliary processes and drainage through the trabecular meshwork (conventional pathway) or the uveoscleral route. Risk factors include age over 40, ethnicity, and family history. Primary Open-Angle Glaucoma (GP AA) is characterized by an open iridocorneal angle ($> 35\,^{\circ}$) but increased resistance in the trabecular meshwork. It is often asymptomatic until severe visual field loss (scotoma) occurs.

Diagnosis involves tonometry (Goldmann applanation is the gold standard), gonioscopy to evaluate the angle, and visual field testing. OCT is used for pre-perimetric diagnosis by measuring the thickness of the retinal nerve fiber layer (RNFL). Treatment focuses on lowering IOP via pharmacological means: prostaglandin analogues (increase uveoscleral outflow), beta-blockers like timolol (decrease secretion), and carbonic anhydrase inhibitors. Surgical options include laser trabeculoplasty or trabeculotomy, which creates a "bozza filtrante" for aqueous humor drainage.

Acute angle-closure glaucoma is an ocular emergency. It occurs when a sudden block (often pupillary block) prevents drainage, causing IOP to spike up to $40-90\,mmHg$. Symptoms include intense pain, halos around lights, nausea, and a stone-hard bulb (ballonamento test). Emergency treatment includes IV mannitol, systemic acetazolamide, and eventually laser iridotomy to equalize pressure between chambers.

Audio-Vestibular Semiotics and Vertigo

Hearing is measured using tonal and vocal audiometry. Tonal audiometry establishes thresholds for air conduction (using headphones) and bone conduction (using a mastoid vibrator). Normoacusia is defined as thresholds below $25\,dB$. Trasmissive hearing loss shows normal bone conduction but impaired air conduction. Neurosensory loss shows both impaired, while mixed loss shows a gap between the two. Recruitment is a sign of cochlear damage where small intensity increases cause large loudness changes (tested via Fowler or SISI tests). Adaptation is a sign of retrocochlear (nerve) damage where sensitivity drops during continuous stimulation (tested via Carhart test).

Vertigo involves an erroneous sensation of movement. Peripheral vertigo (VPPB, Meniere, Neuritis) is distinguished from central vertigo by the nature of nystagmus. Nystagmus has a slow phase (VOR mediated) and a fast phase (saccadic). Vertigine Parossistica Posizionale Benigna (VPPB) is the most common form, caused by otoliths (otoconi) detaching from the utricle into the semicircular canals. Diagnosis involves the Dix-Hallpike maneuver (posterior canal) or McClure-Pagnini (lateral canal). Treatment uses repositioning maneuvers like Semont, Epley, or Lempert/Barbecue. Meniere's disease features a triad: vertigo, tinnitus, and fluctuating low-frequency hearing loss, caused by endolymphatic hydrops. Acoustic Neuroma (schwannoma) is a tumor of the VIII nerve presenting with progressive unilateral neurosensory hearing loss and potential trigeminal involvement.

Pharyngo-Laryngeal Pathologies and OSAS

Faryngotonsillitis can be viral ($50\,\%$, e.g., Adenovirus, EBV/Mononucleosis) or bacterial (Streptococco beta-emolitico group A). Chronic tonsillitis may present with tonsillar hypertrophy or cryptic/caseous debris. Neoplasms of the rhinofaringe (cavum) are often non-keratinizing carcinomas associated with EBV, presenting with unilateral hearing loss or cervical lymphadenopathy. Vocal cord pathologies include nodules (from vocal abuse), polyps (from acute trauma), and Reinke's edema (from chronic smoking). Papillomatosis is linked to HPV 6 and 11.

Obstructive Sleep Apnea Syndrome (OSAS) involves repeated nocturnal respiratory arrests ($> 10\,s$) due to airway collapse. In children, it is primarily caused by adenotonsillar hypertrophy. Diagnosis is made via videopolisonnografia, establishing the Apnea-Hypopnea Index (AHI). Severity in adults is graded as AHI $5-15$ (mild), $15-30$ (moderate), and $> 30$ (severe). Treatment includes weight loss, MAD (mandibular advancement devices), CPAP, or surgical adeno-tonsillectomy. Tracheotomy is a secondary airway opening, performed between the II-III or IV-V tracheal rings, used for long-term ventilation or acute airway obstruction.