Orthopaedic Biomaterials — MCQs
All of the following factors affect osseointegration EXCEPT:
In a functional implant, bone loss seen annually after 1 year is:
Buttressing bone formation is the periodontal tissue response to an increase in occlusal forces seen in
Healing of bone is affected by:
Which prosthesis is shown below in the X-ray?
A 45-year-old was given steroids after renal transplant. After 2 years he had difficulty in walking and pain in both hips. Which one of the following is most likely cause?
What is the primary use of stainless steel in orthodontics?
What is the latent period in distraction osteogenesis?
Bone resorption is enhanced by which of the following?
Which anatomical structure is considered a dynamic stabilizer of the shoulder joint?
Orthopaedic Biomaterials Indian Medical PG Practice Questions and MCQs
Question 1: All of the following factors affect osseointegration EXCEPT:
- A. Biocompatibility of implant material.
- B. Implant design.
- C. Patient's blood type (Correct Answer)
- D. Status of the host bed.
Explanation: ***Patient's blood type*** - A patient's **blood type** (e.g., A, B, AB, O) is determined by antigens present on red blood cells and plays no direct role in the biological processes of bone healing or the integration of a dental implant with bone. - While systemic factors can influence osseointegration, blood type itself does not affect the cellular and molecular mechanisms required for direct bone-to-implant contact. *Biocompatibility of implant material* - The **biocompatibility** of the implant material (e.g., **titanium**) is crucial for osseointegration, as it must not elicit adverse reactions and must permit host bone growth on its surface. - Materials that are cytotoxic or inflammatory will prevent bone apposition and lead to fibrous encapsulation rather than direct bone contact. *Implant design* - **Implant design**, including features like **surface roughness**, thread pitch, and macro-geometry, significantly influences the initial stability and long-term success of osseointegration. - A greater surface area and appropriate surface treatments can enhance bone cell attachment and differentiation, promoting faster and stronger bone integration. *Status of the host bed* - The **status of the host bone bed** refers to its quality and quantity (e.g., bone density, vascularity), which are critical for the biological processes of osseointegration. - Adequate bone volume and good bone quality provide a stable foundation and sufficient blood supply for bone regeneration around the implant.
Question 2: In a functional implant, bone loss seen annually after 1 year is:
- A. 1 to 1.5 mm
- B. Less than 0.1 mm (Correct Answer)
- C. 1 to 2 mm
- D. 1.5 to 2 mm
Explanation: ***Less than 0.1 mm*** - In a functional implant, **crestal bone loss** after the first year of initial healing is expected to be minimal. - This minimal bone loss indicates successful **osseointegration** and long-term stability of the implant. *1 to 1.5 mm* - This amount of annual bone loss is generally considered **excessive** and may indicate issues such as peri-implantitis or improper loading. - Such bone loss could compromise the **long-term prognosis** and stability of the dental implant. *1 to 2 mm* - An annual bone loss in this range would be deemed **unacceptable** for a healthy, functional implant. - This level of bone loss suggests significant **peri-implant inflammation** or biomechanical overload, requiring intervention. *1.5 to 2 mm* - This degree of bone loss is a clear sign of significant **implant pathology** and would likely lead to implant failure if not addressed. - It is far beyond the clinically acceptable limits for bone remodeling around a **stable implant**.
Question 3: Buttressing bone formation is the periodontal tissue response to an increase in occlusal forces seen in
- A. Stage I injury
- B. Stage II repair (Correct Answer)
- C. Stage III repair
- D. None of the options
Explanation: **_Stage II repair_** - In response to increased occlusal forces, buttressing bone formation is a reparative mechanism where the **alveolar bone thickens** to better withstand these forces. - This adaptive change is characteristic of the **Stage II repair phase**, aiming to reinforce the supportive structures around the tooth. *Stage I injury* - This stage typically involves the **initial damage** to the periodontal tissues, such as widening of the periodontal ligament space or increased vascularity. - **Buttressing bone formation** is a reparative, not an initial injury, response. *Stage III repair* - Stage III repair is usually associated with more **severe or chronic injury**, often involving a more pronounced remodeling or even degenerative changes if the forces are persistent and overwhelming. - While repair continues, buttressing bone formation is most characteristic of the **active phase of adaptation** in Stage II. *None of the options* - Buttressing bone formation is a well-documented biological response to increased occlusal forces and is particularly relevant in the context of **periodontal adaptation and repair**. - Therefore, one of the provided stages is the correct answer.
Question 4: Healing of bone is affected by:
- A. Hypoxia
- B. Micromovement
- C. Muscle interposition
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - **Hypoxia**, **micromovement**, and **muscle interposition** are all factors known to impede or negatively affect the normal healing process of a bone fracture. - The successful healing of a bone fracture relies on a series of biological events that can be disrupted by these adverse conditions, leading to delayed union or non-union. *Hypoxia* - **Hypoxia**, or insufficient oxygen supply, impairs the metabolic activity of cells essential for bone healing, such as osteoblasts and chondrocytes. - It interferes with **angiogenesis**, the formation of new blood vessels, which is critical for delivering nutrients and oxygen to the healing bone. *Micromovement* - Excessive **micromovement** at the fracture site prevents the formation of a stable callus and can stimulate the development of fibrous tissue or cartilage instead of bone. - While some motion is beneficial, uncontrolled or excessive micromotion can lead to a **non-union** or pseudarthrosis, as it constantly disrupts the delicate tissue bridges attempting to form. *Muscle interposition* - **Muscle interposition** refers to muscle tissue becoming trapped between the bone fragments, physically separating them and preventing direct bone-to-bone contact. - This physical barrier inhibits the formation of the **fracture hematoma** and subsequent callus, thus mechanically hindering the healing process.
Question 5: Which prosthesis is shown below in the X-ray?
- A. Articular resurfacing
- B. Thompson prosthesis
- C. Austin Moore's prosthesis (Correct Answer)
- D. Birmingham hip replacement
Explanation: ***Austin Moore's prosthesis*** - The image clearly shows a **femoral stem with a long intramedullary component** and an **integrated prosthetic head** that articulates directly with the native acetabulum. This is characteristic of a hemiarthroplasty design, specifically resembling an Austin Moore prosthesis. - This type of prosthesis is commonly used for **femoral neck fractures** in older patients, replacing only the femoral head and neck rather than the entire hip joint. *Articular resurfacing* - **Articular resurfacing** involves capping the femoral head and lining the acetabulum with metallic implants, preserving more bone than a traditional total hip replacement. - The X-ray image does not show a cap on the femoral head or a separate acetabular component, which are features of resurfacing. *Thompson prosthesis* - The **Thompson prosthesis** is another type of hemiarthroplasty, but it typically has a **shorter, bulkier femoral stem** and a **relatively smaller head** compared to the Austin Moore prosthesis shown. - While both Thompson and Austin Moore prostheses are hemiarthroplasties, the specific shape and length of the stem in the X-ray are more consistent with an Austin Moore design. *Birmingham hip replacement* - The **Birmingham hip replacement** is a type of **hip resurfacing arthroplasty**, which, as explained earlier, involves capping the femoral head and is not depicted in this image. - It maintains more of the patient's original bone structure compared to conventional total hip replacement but still requires both femoral and acetabular components.
Question 6: A 45-year-old was given steroids after renal transplant. After 2 years he had difficulty in walking and pain in both hips. Which one of the following is most likely cause?
- A. Tuberculosis
- B. Primary Osteoarthritis
- C. Aluminum toxicity
- D. Avascular necrosis (Correct Answer)
Explanation: ***Avascular necrosis*** - Chronic **steroid use**, especially after organ transplantation, is a major risk factor for avascular necrosis (AVN) due to impaired blood supply to bone, particularly in the femoral head. - **Hip pain** and **difficulty walking** are classic symptoms of AVN, which can lead to collapse of the femoral head if untreated. *Tuberculosis* - While tuberculosis can affect bones and joints (**Pott's disease**), it typically presents with more systemic symptoms like fever, weight loss, and night sweats, which are not mentioned. - Skeletal TB often affects the spine more commonly and usually presents with granulomatous inflammation and bone destruction rather than isolated joint pain in the hips *Primary Osteoarthritis* - Primary osteoarthritis is typically an **age-related degenerative joint disease** occurring in older individuals, and while it causes hip pain, it is not directly linked to steroid use in a 45-year-old. - The onset of pain in this scenario, following long-term steroid use, strongly points away from primary osteoarthritis as the primary driving factor. *Aluminum toxicity* - Aluminum toxicity can occur in patients with **renal failure** and can cause **osteomalacia** or **dialysis encephalopathy**. - Its presentation typically involves bone pain, fractures, and neurological symptoms, but it does not specifically cause avascular necrosis of the femoral head as seen with steroid use.
Question 7: What is the primary use of stainless steel in orthodontics?
- A. To enhance the strength of dental materials
- B. For making clasps in partial dentures
- C. To replace gold restorations in teeth
- D. In the fabrication of orthodontic wires (Correct Answer)
Explanation: ***In the fabrication of orthodontic wires*** - Stainless steel is widely used in orthodontics for **wires** due to its excellent **strength**, **formability**, and corrosion resistance. - Its **elasticity** allows for controlled force application to move teeth effectively and predictably. *To enhance the strength of dental materials* - While stainless steel is strong, its primary orthodontic use is not as an additive to **enhance** other bulk dental materials like composites or ceramics. - Other materials or processing methods are typically used for strengthening restorative or prosthetic dental materials. *For making clasps in partial dentures* - Stainless steel can be used for clasps, but **cobalt-chromium alloys** or **wrought wire clasps** made from other alloys are more common in partial dentures for their specific mechanical properties and biocompatibility. - The context of the question points to a primary orthodontic application beyond general prosthodontics. *To replace gold restorations in teeth* - Stainless steel is not typically used as a direct replacement for **gold restorations** (inlays, onlays, crowns) in permanent dentition due to aesthetic and long-term wear considerations. - While stainless steel crowns are used in pediatric dentistry, they serve a different purpose than replacing gold in adults.
Question 8: What is the latent period in distraction osteogenesis?
- A. 4-6 weeks
- B. 5-7 days (Correct Answer)
- C. 6-8 months
- D. 4 months
Explanation: **Explanation:** **Distraction Osteogenesis** (Ilizarov technique) is a process of growing new bone by mechanically stretching a vascularized callus. The procedure follows a specific chronological sequence: 1. **Latent Period (The Correct Answer):** This is the duration between the corticotomy (surgical bone cut) and the commencement of distraction. It typically lasts **5–7 days**. This period allows for the inflammatory phase of bone healing to occur and for the initial soft tissue/callus bridge to form. Starting distraction too early (before 5 days) can lead to poor callus formation, while starting too late (after 10–14 days) may result in premature consolidation (early fusion). 2. **Distraction Phase:** The bone is stretched at a rate of **1 mm per day**, usually divided into four increments (0.25 mm every 6 hours). 3. **Consolidation Phase:** The period where the newly formed "regenerate" bone mineralizes and hardens. **Analysis of Incorrect Options:** * **A (4-6 weeks):** This is the typical time for clinical union in simple fractures, not the latent period for distraction. * **C & D (6-8 months / 4 months):** These timeframes are more representative of the total duration an Ilizarov fixator might remain on a limb for complex lengthening or non-union treatments. **High-Yield Clinical Pearls for NEET-PG:** * **The Law of Tension-Stress:** Proposed by Ilizarov, stating that gradual traction on living tissues stimulates and maintains the regeneration and growth of those tissues. * **Rate of Distraction:** 1 mm/day is the gold standard. <0.5 mm/day leads to premature fusion; >2 mm/day leads to non-union and nerve damage. * **Most common complication:** Pin tract infection. * **Best site for corticotomy:** Metaphysis (due to superior vascularity and osteogenic potential).
Question 9: Bone resorption is enhanced by which of the following?
- A. PGD2
- B. PDF2
- C. PGE2 (Correct Answer)
- D. PGI2
Explanation: **Explanation:** Bone remodeling is a dynamic process regulated by various systemic hormones and local inflammatory mediators. Prostaglandins, which are derivatives of arachidonic acid, play a significant role in this process. **Why PGE2 is the Correct Answer:** **Prostaglandin E2 (PGE2)** is the most potent stimulator of bone resorption among the prostaglandins. It acts by stimulating the **RANKL (Receptor Activator of Nuclear Factor kappa-B Ligand)** expression in osteoblasts. This RANKL then binds to RANK receptors on osteoclast precursors, leading to their maturation and activation. While PGE2 has a dual role (it can also stimulate bone formation in certain concentrations), its primary clinical significance in inflammatory states (like rheumatoid arthritis or periodontal disease) is the induction of osteoclastogenesis and subsequent bone loss. **Analysis of Incorrect Options:** * **PGD2 (Prostaglandin D2):** Primarily involved in smooth muscle relaxation and allergic responses; it does not have a significant stimulatory effect on bone resorption. * **PGF2α (often mislabeled as PDF2):** While it can influence bone metabolism, it is significantly less potent than PGE2 and is more associated with uterine contraction. * **PGI2 (Prostacyclin):** Mainly acts as a potent vasodilator and inhibitor of platelet aggregation; it has minimal to no role in enhancing bone resorption. **High-Yield Clinical Pearls for NEET-PG:** * **NSAIDs and Bone:** Since NSAIDs inhibit prostaglandin synthesis (COX inhibition), they can theoretically delay fracture healing by reducing PGE2-mediated bone remodeling. * **IL-1 and TNF-α:** These cytokines also enhance bone resorption by stimulating PGE2 production. * **Bisphosphonates:** These are the drugs of choice to *inhibit* bone resorption by inducing osteoclast apoptosis.
Question 10: Which anatomical structure is considered a dynamic stabilizer of the shoulder joint?
- A. Rotator cuff (Correct Answer)
- B. Glenoid labrum
- C. Coracohumeral ligament
- D. Glenohumeral ligament
Explanation: **Explanation:** The stability of the shoulder (glenohumeral) joint is maintained by a complex interplay between static and dynamic stabilizers. **1. Why the Rotator Cuff is correct:** The **Rotator Cuff** (comprising the Supraspinatus, Infraspinatus, Teres minor, and Subscapularis—SITS muscles) is the primary **dynamic stabilizer**. These muscles stabilize the joint through "concavity compression." As they contract, they pull the large humeral head into the shallow glenoid fossa, centering it during movement. Because they require active muscular contraction to provide stability, they are classified as dynamic. **2. Why the other options are incorrect:** * **Glenoid Labrum (B):** This is a fibrocartilaginous rim that deepens the glenoid cavity. It is a **static stabilizer** because it provides structural stability without active contraction. * **Coracohumeral Ligament (C) & Glenohumeral Ligaments (D):** These are capsular thickenings that act as **static stabilizers**. They provide stability only at the end-range of motion when they become taut, preventing excessive translation of the humeral head. **High-Yield Clinical Pearls for NEET-PG:** * **Static Stabilizers:** Include the glenoid labrum, joint capsule, glenohumeral ligaments (Superior, Middle, and Inferior), and negative intra-articular pressure. * **The "Safety Belt" of the Shoulder:** The **Inferior Glenohumeral Ligament (IGHL)** is the most important static stabilizer against anterior dislocation when the shoulder is abducted and externally rotated. * **Long Head of Biceps:** Often considered a secondary dynamic stabilizer, as it depresses the humeral head. * **Rotator Interval:** A triangular space between the Supraspinatus and Subscapularis; it is a common site for pathology in shoulder instability.
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