Changes in Plaque pH After Sucrose Rinse

The pH of dental plaque is a critical factor in the development of dental caries and periodontal disease. Key findings from various studies that investigated the changes in plaque pH following carbohydrate rinses, particularly focusing on sucrose and glucose.

Key Findings from Studies

1. Monitoring Plaque pH Changes:

   • A study reported that changes in plaque pH after a sucrose rinse were monitored using plaque sampling, antimony and glass electrodes, and telemetry.
   • Results:
     • The minimum pH at approximal sites (areas between teeth) was approximately 0.7 pH units lower than that on buccal surfaces (outer surfaces of the teeth).
     • The pH at the approximal site remained below resting levels for over 120 minutes.
     • The area under the pH response curves from approximal sites was five times greater than that from buccal surfaces, indicating a more significant and prolonged acidogenic response in interproximal areas.

2. Stephan's Early Studies (1935):

   • Method: Colorimetric measurement of plaque pH suspended in water.
   • Findings:
     • The pH of 211 plaque samples ranged from 4.6 to 7.0.
     • The mean pH value was found to be 5.9, indicating a generally acidic environment in dental plaque.

3. Stephan's Follow-Up Studies (1940):

   • Method: Use of an antimony electrode to measure in situ plaque pH after rinsing with sugar solutions.
   • Findings:
     • A 10% solution of glucose or sucrose caused a rapid drop in plaque pH by about 2 units within 2 to 5 minutes, reaching values between 4.5 and 5.0.
     • A 1% lactose solution lowered the pH by 0.3 units, while a 1% glucose solution caused a drop of 1.5 units.
     • A 1% boiled starch solution resulted in a reduction of 1.5 pH units over 51 minutes.
     • In all cases, the pH tended to return to initial values within approximately 2 hours.

4. Investigation of Proximal Cavities:

   • Studies of actual proximal cavities opened mechanically showed that the lowest pH values ranged from 4.6 to 4.1.
   • After rinsing with a 10% glucose or sucrose solution, the pH in the plaque dropped to between 4.5 and 5.0 within 2 to 5 minutes and gradually returned to baseline levels within 1 to 2 hours.

Implications

• The studies highlight the significant impact of carbohydrate exposure, particularly sucrose and glucose, on the pH of dental plaque.
• The rapid drop in pH following carbohydrate rinses indicates an acidogenic response from plaque microorganisms, which can contribute to enamel demineralization and caries development.
• The prolonged acidic environment in approximal sites suggests that these areas may be more susceptible to caries due to the slower recovery of pH levels.

Epithelium Types

• Parakeratinized: Retains pyknotic nuclei in stratum corneum
• Orthokeratinized: No nuclei in stratum corneum
• Keratinization order: Palate > Gingiva > Tongue > Cheek (most to least)

Keratin Distribution

• K 1, 2, 10, 12: Orthokeratinized areas
• K 6, 16: Highly proliferative areas
• K 5, 14: Stratification specific
• K 19: Parakeratinized areas

Structural Components

• Stratum spinosum: Contains keratinosomes/Odland bodies (modified lysosomes)
• Basal lamina: 300 – 400 Å thick, joins epithelium to connective tissue
  • Lamina lucida (rich in laminin)
  • Lamina densa (rich in collagen type IV)
• Junctional epithelium: 0.25 – 1.35 mm long, formed by oral + reduced enamel epithelium

Clinical Probing

• Normal probing depth: 2 – 3 mm (requires apical penetration)
• Stippling: Orange peel appearance, restricted to attached gingiva
• Loss of stippling: Early sign of gingivitis

• Perinatal transmission (90%)
• Window phase: HBsAg ↓, anti-HBs ↑
• Infectivity: HBsAg + HBeAg
• First marker post-infection: HBsAg
• IgM anti-HBc = acute infection
• Reverse transcriptase → P gene
  | Hepatitis C | Most chronic & linked to liver disease
  | Hepatitis A | Prophylaxis: Human IgG
  | Hepatitis E | Most epidemic-prone in India
  | Councilman bodies | Seen in acute viral hepatitis

ANUG (Acute Necrotizing Ulcerative Gingivitis)

• Signs: Punched – out crater depressions of interdental papilla
• Symptoms: Metallic foul taste, pasty saliva
• Treatment: 3 visits (2nd visit: 1 – 2 days after 1st; 3rd visit: 5 days after 2nd)

NUG/NUP

• No pocket formation (destroys junctional epithelium)

Primary Herpetic Gingivostomatitis

• Cellular change: Ballooning degeneration → Tzanck cells
• Treatment:
  • Within 3 days: Acyclovir 15 mg/kg × 5 times × 7 days
  • After 3 days: Supportive care with NSAIDs

Leukemic Gingivitis

• Most common in acute monocytic leukemia

Lead Intoxication

• Steel gray linear pigmentation (Burton's line)

Smoking

• Pack years = Packs/day × Years of smoking

Diabetes

• Causes collagen cross – linking via AGEs formation

AIDS

• Most common oral lesion: Candidiasis
• Most common oral malignancy: Kaposi sarcoma

Infection Timeline Post-BMT

Phase I: Pre-engraftment (0-30 days)

• Earliest infection: Herpes Simplex Virus (HSV)
• Other pathogens: Bacteria, Candida, Aspergillus
• Risk factors: Neutropenia, mucositis, central lines

Phase II: Early post-engraftment (30-100 days)

• ~7th week (50 days): Interstitial Pneumonitis peak incidence
• Causes: CMV, Pneumocystis jirovecii, idiopathic
• GVHD: Acute graft-versus-host disease peak

Phase III: Late post-engraftment (>100 days)

• Chronic GVHD: Major concern
• Encapsulated bacteria: Due to functional asplenia
• Varicella-zoster virus: Reactivation common

Specific Infectious Complications

CMV Disease

• Timeline: 30-100 days post-BMT
• High risk: CMV+ recipient or donor
• Manifestations: Pneumonitis, gastroenteritis, retinitis

Interstitial Pneumonitis (IP)

• Peak incidence: ~7th week (50 days) post-BMT
• Types:
  • CMV pneumonitis (most common infectious cause)
  • Idiopathic IP
  • Pneumocystis pneumonia
• Mortality: High, especially CMV pneumonitis

Prophylactic Strategies

• Antibacterial: Fluoroquinolones
• Antifungal: Fluconazole or newer azoles
• Antiviral: Acyclovir for HSV/VZV
• PCP prophylaxis: Trimethoprim-sulfamethoxazole
• CMV monitoring: Pre-emptive therapy based on viral load

GVHD Prevention

• Immunosuppression: Methotrexate + calcineurin inhibitors
• T-cell depletion: In some protocols
• HLA matching: Reduces risk significantly