📌 POINTS TO PONDER 

🔹 1.97 mm ± 33.16% is the distance between apical extent of calculus and alveolar crest. 

🔹0.5–2.7 mm is the distance between attached plaque and alveolar bone. 

🔹Rate of bone loss depends upon the type of disease present and tooth surface. An average of 0.2 mm/year on facial surfaces and 0.3 mm/year on proximal surfaces. 

🔹 The most common bony lesion described and encountered in periodontal disease is the interdental crater. 

🔹 Approximately 1.5–2 mm is the radius of action of bacterial plaque that can induce bone loss. 

🔹 In osteoclastic bone resorption, first there is the solubilization of the mineral content of bone and then is the dissolution of the organic matrix.

📣 Various bone destructive patterns : 

🔹 Horizontal bone loss 

🔹 Vertical or angular defects 

🔹 Interdental osseous craters 

🔹 Bulbous bone contours 

🔹 Reversed architecture 

🔹 Ledges 

🔹 Furcation involvement 

🔹 Fenestration and dehiscence 

🔹 Marginal gutter 

🔹 Irregular bony margins

📌 VIVA VOCE 

Q1. What is the radius of action of bacterial plaque that can induce bone loss? 

Ans. The radius of action of bacterial plaque that can induce bone loss is 1.5–2.5 mm approximately. 

Q2. What is the yearly rate of bone loss when periodontal disease is allowed to progress untreated? 

Ans. Rate of bone loss depends upon the type of disease present: an average of 0.2 mm/year on facial surfaces and 0.3 mm/year on proximal surfaces. 

Q3. What is hemiseptum? 

Ans. The one-wall (1W) vertical defect is called as hemiseptum. 

Q4. What is Moat? 

Ans. When crater-like bone loss involves all the four surfaces of the same tooth, it is called as moat. 

Q5. What is RANKL? 

Ans. Receptor activator of nuclear factor kappa E ligand (RANKL) is a cytokine essential for osteoclastogenesis, which is expressed by osteoblast. Osteoclast precursor express RANK (a receptor of RANKL) and recognizes RANKL expressed by osteoblasts through cell-to-cell interaction and differentiate into osteoclasts in the presence of macrophage colony-stimulating factor (CSF). 

Q6. What is osteoprotegerin? 

Ans. It is a soluble decoy receptor for RANKL, produced mainly by osteoblasts. It blocks osteoclastogenesis by inhibiting RANKL-RANK interaction. 

Q7. What are interdental osseous craters? 

Ans. Interdental osseous craters are concavities in the crest of the alveolar septa centred under the contact point of adjacent teeth. 

Q8. What are the various types of craters? 

Ans. Ochsenbein divided bony craters into three basic types: 1. shallow (1–2 mm); 2. medium (3–4 mm) and 3. deep (5 mm and more). 

Q9. What are ledges? 

Ans. Ledges are plateau-like bone margins caused by resorption of thickened bony plates. 

Q10. Which is the best way to determine the bone defect pattern? 

Ans. Surgical exposure of bone defect through full thickness flap.

📌 MULTIPLE CHOICE QUESTIONS MCQs 

💡 Reversed architecture is: 

A. The level of interdental bone is more apical to radicular bone. 

B. The interdental bone is at the same level to that of radicular bone. 

C. The level of radicular bone is apical to the interdental bone 

D. None of the above

Answer : A 

💡 Mirror image type of bone loss pattern of Arc shaped bone loss around molars is seen in: 

A. Localized aggressive periodontitis 

B. Rapidly progressive periodontitis 

C. Chronic periodontitis 

D. Necrotizing ulcerative periodontitis

Answer : A 

💡 How many osseous walls are present in one – walled vertical defects? 

A. Two walls present 

B. One wall present 

C. Three walls present 

D. Four walls present

Answer : B 

💡 Window – shaped alveolar defect on labial alveolar bone is called 

A. Dehiscence 

B. Crater 

C. Fenestration 

D. Trough

Answer : C

💡 Bony defects which results in plateau–like marginal bone are called 

A. Bulbous adaptive 

B. Ledges 

C. Craters 

D. Trough

Answer : B 

💡 The most potent bone resorbing interleukin is 

A. IL – 8 

B. IL – 1β 

C. IL – 5 

D. IL – 3

Answer : B 

💡 Bone factor concept was given by: 

A. Schluger 

B. Newman 

C. Irving Glickman 

D. None of the above 

Answer : C