• Randomization - participants are allocated by chance, balancing known and unknown confounders
• Control group - provides a baseline for comparison
• Blinding - single-blind (participant unaware) or double-blind (both participant and investigator unaware) reduces measurement bias
• Prospective - participants are followed forward in time after the intervention

• Expensive and time-consuming
• May have strict inclusion/exclusion criteria, limiting generalizability (external validity)
• Ethical constraints may prevent randomization in some scenarios (e.g., you cannot randomize someone to smoke)
• Short follow-up periods may miss long-term effects

Root Canal Treatment (Endodontic Treatment)

What Is It?

Relevant Anatomy

• Crown - the visible part of the tooth, covered by enamel
• Dentin - the layer beneath enamel; microporous, can transmit bacteria and their byproducts to the pulp
• Pulp cavity / Root canal - the hollow space running through the crown and root, housing the dental pulp
• Apical foramen - the opening at the root tip, where nerves and blood vessels enter/exit
• Periodontal ligament, alveolar bone, cementum - the attachment apparatus anchoring the tooth in the jaw

Why It Is Needed - Pathological Progression

1. Dental caries - bacteria (primarily Streptococcus mutans, then lactobacilli) produce acid that demineralizes enamel and penetrates dentin
2. Reversible pulpitis - early inflammation; pulp reacts with hyperemia; pain triggered by temperature/pressure changes, which resolves with stimulus removal
3. Irreversible pulpitis - continued bacterial invasion; pulp cannot repair itself; pain becomes spontaneous, dull, throbbing, and persistent - even without any stimulus
4. Pulp necrosis - total degeneration of pulp tissue; an anaerobic bacterial biofilm colonizes the necrotic root canals
5. Apical periodontitis / Periapical abscess - infection spreads beyond the root tip (apical foramen) into periapical tissues, causing tenderness on percussion, swelling, and suppuration

Indications for RCT

• Irreversible pulpitis (spontaneous, severe, or persistent tooth pain)
• Pulp necrosis
• Periapical abscess or periodontitis
• Deep carious lesion with pulp exposure
• Tooth fracture reaching the pulp
• Before placing a crown over a severely compromised tooth

Procedure - Step by Step

If infection is severe, the tooth may be left open to drain for 1-2 days before the canal is sealed, requiring a second appointment.

Key Points on Antibiotics

Complications of Untreated Pulp Infection

• Periapical abscess with facial swelling
• Spread to deep neck spaces (Ludwig's angina - a life-threatening emergency)
• Osteomyelitis of the jaw
• Cavernous sinus thrombosis (rare)
• As Dermatology 2-Volume Set notes: odontogenic infections can present with skin manifestations requiring incision, drainage, and endodontic therapy or extraction

Prognosis

Root Canal Treatment (RCT)

Indications

• Irreversible pulpitis
• Pulp necrosis
• Periapical abscess / apical periodontitis
• Deep carious lesion with pulp exposure
• Tooth fracture extending to the pulp

Steps of RCT

1. Diagnosis - Clinical exam + periapical X-ray
2. Local anesthesia and rubber dam isolation
3. Access cavity preparation through the crown
4. Pulp extirpation using endodontic files
5. Canal shaping and irrigation (sodium hypochlorite)
6. Obturation - filling with gutta-percha and sealer
7. Restoration - permanent filling or crown placement

Pathological Basis

Key Points

• Antibiotics are NOT routinely prescribed; RCT/extraction is the definitive treatment
• A crown is placed post-RCT to prevent tooth fracture
• Success rate: >90% at 10 years

Root Canal Treatment (RCT) / Endodontic Treatment

Definition

Relevant Anatomy

• Enamel - outermost hard layer covering the crown
• Dentin - microporous layer beneath enamel; transmits bacteria and their byproducts to the pulp
• Pulp cavity - contains the dental pulp (nerves, blood vessels, connective tissue)
• Root canal - the channel running through the root, continuous with the pulp cavity
• Apical foramen - opening at the root tip; entry/exit point for neurovascular supply
• Periodontal ligament + alveolar bone + cementum - the attachment apparatus anchoring the tooth

Etiology and Pathological Basis

Indications for RCT

1. Irreversible pulpitis
2. Pulp necrosis
3. Periapical abscess / apical periodontitis
4. Deep carious lesion with pulp exposure
5. Tooth fracture reaching the pulp
6. Heavily compromised tooth requiring crown placement
7. Symptomatic tooth that fails to respond to conservative management

Clinical Features Suggesting Need for RCT

• Spontaneous, severe, persistent toothache (irreversible pulpitis)
• Pain worse on lying down
• Tenderness on percussion of the tooth (periapical involvement)
• Facial swelling or sinus tract (abscess)
• Well-circumscribed periapical radiolucency on X-ray (granuloma/cyst)
• Non-response to analgesics

Procedure - Step by Step

• Clinical examination + periapical radiograph
• Vitality testing (cold/electric pulp test)
• Percussion and palpation

• Local anesthetic (e.g., lidocaine with epinephrine)
• Rubber dam placed to maintain a sterile, dry operating field

• A hole is drilled through the crown to reach the pulp chamber
• Roof of the pulp chamber is removed to gain straight-line access to canals

• Electronic apex locator and/or periapical X-ray to determine the exact length of each root canal

• Infected/necrotic pulp removed using endodontic files (hand/rotary)
• Canals progressively shaped in a crown-down technique

• Copious irrigation with sodium hypochlorite (NaOCl) - main irrigant
• EDTA used to remove the smear layer
• Final rinse with chlorhexidine or saline

• Calcium hydroxide paste placed in canals between visits for severely infected teeth
• Tooth may be left open to drain for 1-2 days if infection is severe

• Canals dried with paper points
• Filled with gutta-percha cones + root canal sealer (e.g., zinc oxide eugenol)
• Lateral condensation or warm vertical compaction technique

• Temporary or permanent filling placed
• A dental crown is strongly recommended to restore function and prevent fracture of the brittle, non-vital tooth

Post-operative Care

• Mild pain and sensitivity for a few days - managed with NSAIDs (ibuprofen)
• Avoid chewing on the treated tooth until crown is placed
• Follow-up X-ray at 6-12 months to confirm periapical healing

Role of Antibiotics

• Spreading infections (cellulitis, fascial space involvement)
• Systemic signs (fever, trismus, lymphadenopathy)
• Immunocompromised patients

Complications of Untreated Pulp Infection

• Periapical cyst
• Osteomyelitis of the jaw
• Deep neck space infections (e.g., Ludwig's angina - life-threatening)
• Cavernous sinus thrombosis (rare)
• Bacteremia and systemic spread in susceptible individuals

Complications of RCT Itself

• Instrument fracture inside canal
• Ledging or perforation of root
• Underfilling or overfilling
• Missed canals
• Post-operative flare-up
• Reinfection requiring retreatment or apicoectomy

Prognosis

• Success rate: >90% at 8-10 years when properly performed and restored
• Key factors for success: complete canal debridement, tight obturation, and good coronal seal
• Failed RCT can be retreated endodontically or managed with periapical surgery (apicoectomy)

Short Note on Peritonsillar Abscess (PTA) / Quinsy

Definition

Anatomy of the Space

• Pus collects in the potential space between the tonsillar capsule and the superior constrictor/palatopharyngeus muscle
• Fibrous septa direct the infection anteriorly and superiorly
• Infection originates from the Weber glands (minor salivary glands in the superior pole)

Etiology / Microbiology

• Typically polymicrobial (mixed aerobic + anaerobic)
• Most common isolate: Streptococcus pyogenes (Group A Strep)
• Recurrent PTA: high incidence of Fusobacterium
• Preceded by: streptococcal tonsillitis, infectious mononucleosis, dental/periodontal disease, smoking

Clinical Features

Trismus (inability to open mouth) is the hallmark - caused by spasm of the pterygoid muscles, distinguishing PTA from simple tonsillitis.

Diagnosis

• Primarily clinical - bulging anterior pillar + uvular deviation + trismus
• Needle aspiration - both diagnostic and therapeutic (confirms pus vs. cellulitis)
• CT neck with contrast - not routinely needed; indicated if clinical picture is unclear or deep space spread is suspected

Treatment

• Needle aspiration - first choice; wide-bore needle at the point of maximal fluctuation (superior pole)
• Incision and Drainage (I&D) - if aspiration fails or recurrence
• Quinsy tonsillectomy (tonsillectomy during acute attack) - not popular due to risk of pus aspiration

• IV high-dose penicillin or cephalosporin (first line)
• Alternatives: clindamycin (300-450 mg QID x 14 days) or amoxicillin-clavulanate (875 mg BD x 10 days)
• Metronidazole does NOT add benefit in otherwise healthy adults treated with I&D

• IV steroids as adjunct - reduce inflammation, pain, and trismus

• Adequate hydration, analgesics, antipyretics

Interval Tonsillectomy

• Two or more episodes of PTA on the same side
• Background history of recurrent tonsillitis
• Recurrence rate after first PTA: ~17%

Complications

• Rupture - spontaneous pus release into airway (aspiration risk)
• Parapharyngeal abscess - spread to parapharyngeal space; trismus + airway compromise
• Retropharyngeal abscess - posterior spread; mainly in children
• Deep neck space infection / Mediastinitis - life-threatening
• Lemierre's syndrome - septic thrombophlebitis of the internal jugular vein (rare but fatal); caused by Fusobacterium necrophorum; presents with fever, neck mass, septic pulmonary emboli

Short Note on Pure Tone Audiometry (PTA)

Definition

Principle

• A pure tone is presented to the ear at varying intensity levels
• The threshold = the lowest intensity level at which the patient responds correctly at least 50% of the time
• Testing is done by air conduction (AC) and bone conduction (BC)
• Comparison of AC and BC thresholds determines the type of hearing loss

Equipment

• Audiometer - generates calibrated pure tones; types include screening, clinical, and diagnostic
• Earphones (supra-aural or insert) for air conduction
• Bone oscillator - placed on the mastoid process for bone conduction
• Sound-treated booth - required to measure thresholds as low as 0 dB HL
• Calibration must be done at least annually

Audiogram - The Recording Chart

Procedure (Hughson-Westlake Method)

1. Explain the test to the patient; conduct otoscopy first
2. Present a tone well above threshold so patient knows what to listen for
3. Decrease in 10 dB steps until no response
4. Increase in 5 dB steps until response is obtained
5. Threshold = level at which response is obtained on 3 out of 5 (≥50%) ascending trials
6. Test AC first (250-8000 Hz), then BC if AC thresholds ≥15 dB HL

Masking

• Noise introduced into the non-test ear to prevent it from detecting signals intended for the test ear (called crossover)
• The spread of sound energy across the skull is called interaural attenuation
  • AC with supra-aural headphones: 40-65 dB
  • BC: only 0-10 dB (masking almost always needed for BC)
  • Insert earphones: up to 70-90 dB (less crossover risk)
• Masker used: narrow-band noise centred around the test frequency

Grading of Hearing Loss (Shambaugh Classification)

Types of Hearing Loss on Audiogram

Air-Bone Gap = difference between AC and BC thresholds. Indicates a conductive component (outer/middle ear pathology).

Audiometric Configurations (Patterns of Loss)

• Flat - equal loss across all frequencies (e.g., otosclerosis)
• High-frequency sloping - worse at high frequencies (e.g., noise-induced, presbycusis)
• Low-frequency loss - worse at low frequencies (e.g., Meniere's disease - early)
• Cookie-bite / U-shaped - mid-frequency loss (hereditary causes)
• Notch at 4000 Hz - classic pattern in noise-induced hearing loss

Pure Tone Average (PTA)

Limitations

• Subjective - requires patient cooperation and reliable responses
• Not suitable for infants (<3 years) - alternative methods used:
  • 0-6 months: Behavioral Observation Audiometry (BOA)
  • 6 months - 2 years: Visual Reinforcement Audiometry (VRA)
  • 2-5 years: Conditioned Play Audiometry (CPA)
• Cannot differentiate cochlear from retrocochlear SNHL - needs ABR/BERA

Clinical Significance

• Quantifies degree and type of hearing loss
• Guides hearing aid selection and fitting
• Monitors ototoxicity (serial audiograms at 3000, 6000 Hz)
• Provides medico-legal documentation
• Cross-checks speech audiometry results