• Rapid drop in plaque pH after sugar
• Critical pH for enamel demineralization: ~5.5
• Caries-prone individuals:
  • Lower plaque pH
  • Higher Lactobacillus counts

Research Highlights

• Stephan: Rapid pH drop post-carbohydrates
• Caries-free pH: ~7.1
• Caries-active pH: ~5.5
• Maxillary anterior teeth: Greater drop than mandibular
• Stratfors: Lower pH ↔ higher Lactobacillus; plaque buffers better than saliva

Acute suppurative osteomyelitis

• Serious sequela of periapical infection.
• Leads to spread of pus through the medullary cavities of bone.
• Depending upon the main site of involvement of bone, can be of two types-

1. Acute intramedullary
2. Acute subperiosteal

Acute Intramedullary Osteomyelitis

CLINICAL FEATURES:

• Patient experiences dull , continuous pain , indurated swelling forms over the affected region of jaw involving the cheek , febrile.
• When mandible involved, loss of sensation occurs on lower lip on affected side due to involvement of inferior alveolar nerve.
• Teeth become loose later along with tender on percussion
• Pus discharge , trismus , foul smell , regional lymphadenopathy , weakness

RADIOGRAPHIC FEATURES

• Earliest radiographic change is that trabeculae in involved area are thin, of poor density & slightly blurred.
• Subsequently multiple radiolucencies appear which become apparent on radiograph.
• In some cases there is saucer shaped area of destruction with irregular margins.
• Loss of continuity of lamina dura, seen in more than one tooth.

HISTOLOGIC FEATURES:

• Dense infiltration of marrow by polymorphonuclear leukocytes.
• Bone trabeculae in involved site (sequestrum) are devoid of cells in the lacunae.
• separation of considerable portions of devitalized bone.

Acute Subperiosteal Osteomyelitis

CLINICAL FEATURES

• Pain , febrile condition , i/o and e/o swelling , parasthesia
• Bone involvement limited to localized areas of cortex.
• Pus ruptures rapidly through the overlying cortex, tracks along the surface of mandible under the periosteal sheath.
• Elevation of periosteum from cortex is followed eventually by minute cortical sequestration.

Viral Infections

Herpes Simplex Virus (HSV-1)

• Dormancy Sites: Trigeminal > Nodose (Vagus) > Dorsal Root > Brain
• Inclusions: Lipschutz bodies (intranuclear)
• Herpetic Whitlow: Finger lesions in dentists
• Location Difference:
  • Herpangina: Posterior palate
  • Herpes: Anterior palate

Herpes Zoster

• Key Feature: Lesions do not cross midline
• Ramsay Hunt Syndrome: Zoster of geniculate ganglion → facial paralysis

Measles

• Koplik's Spots: Disappear after skin rash onset

Rubella

• First Trimester: Blindness, deafness, cardiovascular defects

Mumps

• Complications: Orchitis, oophoritis (sterility), pancreatitis, meningoencephalitis

 General Features

• Caused by mutation in DSPP gene (dentin sialophosphoprotein).

• Teeth appear translucent or opalescent.

• Enamel fractures easily due to poor dentin support.

• Pulp chambers are obliterated or enlarged depending on type.

• Also called Hereditary Opalescent Dentin or Shell Teeth.

Type II DI

• Pulp chambers are normal but rapidly obliterate.

• Associated with progressive hearing loss.

Type III DI

• Pulp chambers are large and shell-like.

• Seen in Brandywine isolate population.

• Calcifying Odontogenic Cyst (COC) / Gorlin Cyst: Characterized by Ghost Cells.

• Aneurysmal Bone Cyst (ABC): Associated with a "blood-soaked" appearance on gross examination.

• Radicular Cyst - Common Site: Maxillary anterior teeth (due to higher incidence of trauma).

• Odontogenic Keratocyst (OKC) / Keratocystic Odontogenic Tumor (KCOT):

  • Most common site: Posterior mandible (similar to ameloblastoma).

  • Expansion: Tends to expand antero-posteriorly; buccal and lingual expansion seen in late stages.

  • Basal layer histology: Tall columnar cells with palisaded nuclei – "row of tombstones" or "picket fence appearance."

  • Classification: Now considered a benign odontogenic neoplasm (KCOT) in recent WHO classifications.

• Schilling Test: Done to identify the deficiency of either extrinsic (dietary vitamin B12) or intrinsic factor involved in Pernicious Anemia.

• Fanconi's Syndrome: Associated with Aplastic Anemia.

• "Safety-Pin" Cells: Characteristic finding in Thalassemia / Erythroblastic Anemia.

• Radiographic Features of Anemias:

  • "Salt and Pepper" effect (Intraoral Periapical Radiograph): Found in Cooley's Anemia (Thalassemia) and Sickle Cell Anemia.

  • "Hair-on-End" pattern (Skull Radiograph): Found in Thalassemia, Sickle Cell Anemia, Congenital Hemolytic Jaundice, Chronic Iron Deficiency Anemia.

• "Rh Hump" (Erythroblastosis Fetalis): Describes a ring-like defect.

• Plummer-Vinson Syndrome: Associated with Iron Deficiency Anemia.

• Chediak-Higashi Syndrome: Giant abnormal PAS positive granules found in peripheral circulating leukocytes are basically altered lysosomes.

• Philadelphia Chromosome: Translocation of chromosomal material from chromosome 22 to chromosome 9; found in Chronic Myeloid Leukemia (CML).