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25 Terms

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Advantages of MTA

  • biocompatible (highly similar to biological hydroxyapatite)

  • non-toxic/non-mutagenic

  • anti-inflammatory effect on pulp tissue

  • formation of an alkaline pH against bacteria and therefore a biological seal of hydroxyapatite is formed.

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Disadvantages of MTA

  • very long setting time

  • expensive

  • irreversible staining

  • difficulty in handling

  • difficult to remove once placed

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Height Velocity Curve:

three general phases

On the x axis is age and the y axis is height velocity

the first stage is a rapid increase at birth, this is then followed but a rapid and steady decline. Then at age 12 there is a large increase in growth due to puberty

These curves have difference between sexes as the curve occurs later in males

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Factors for Candidosis

  • local =  poorly fitting denture, high carb diet, steroid use, xerostomia

  • systemic =  immunodeficiencies, drugs such as broad spectrum antibiotics, smoking, nutritional deficiencies, endocrine disorders

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Advantages of Ceramics

biocompatible, good aesthetics, high hardness, excellent wear resistance, chemically inert, resistance to corrosion, withstands high temperatures, relatively cheap, high compressive strength, colour stability, can be porous and non-porus

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Disadvantages of Ceramics

brittle (low tensile strength), prone to microcracks but can propagate to fractures, technique sensitivity, surface roughness can increase overtime

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Ideal Properties of Biomaterials:

low thermal conductivity and diffusivity, high fracture toughness, ductility, stress strain, no cytotoxicity or carcinogenicity, biointegration, osseointegration, low cost, aesthetic, relaible, strong bond, ease of manufacture

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Adenoid Cystic Carcinoma

Adenoid cystic carcinoma is a salivary malignancy that consists of basaloid cells. It can have three histological appearances. Slow growing and consists of epithelial and myoepithelial cells that form the three patterns. More common in the 4th to 7th decade and in females. In some countries is the most common. 

  1. Cribriform = epithelial nests are permeated by swiss cheese spaces, contains two cell types ductal epithelial (line true luminal spaces) and small angular myoepithelial cells (form pseudocystic spaces)

  2. Tubular= two layered ductal system composed of inner ductal and outer myoepithelial cells

  3. Solid = solid nests or strands of basaloid myoepithelial cells, has peripheral palisading columnar basaloid cells cellular pleomorphism and increased mitotic activity

Has a marked infiltrative tendency with perineural and perivascular invasion. Survival rate is high for 5 year but low for 10. has distant metastasis to lung, bone and brain.

Management is to remove the lesion, check for metastasis.

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Mucoepidermoid Carcinoma

Mucoepidermoid carcinoma is a salivary malignancy that consists of squamoid, intermediate and mucinoius cells. It is the most common minor salivary gland malignancy. Most common in <20 yr olds, usually diagnosed in the 5th to 6th decades  Clinically it appears as a palatal swelling that is mucin filled and bluish in colour.

Histologically it shows poorly differentiated epithelium and a mature connective tissue. It can also be glandular and mucous secreting.

  • Low grade is cystic, mucous rich and well circumscribed, minimal atypia

  • Middle is more solid

  • High grade is necrosis wit bone/nerve invasion, many mitoses seen

There are cords, strands and islands of epithelium some with an epithelioid appearance.

Management is removal of lesion, has a good prognosis for low not for high.

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Advantages of Titanium Implant

  • Cheap compared to zirconia, expensive compared to PEEK

  • Biocompatible, has osseointegration, non toxic

  • Corrosion resistant, excellent to physiological environments

  • Durable

  • Very strong

  • Lightweight

  • Good fatigue resistance

  • Non-ferromagnetic hence safe for MRI, partially radiolucent in CT

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Disadvantages of Titanium Implant

  • Not aesthetic as can have grey line

  • hypersensitivity allergies to metal particles

  • difficult to customise

  • low modulus of elasticity causes stress shielding

  • release of ions can accelerate gingival retraction cause grey shadow

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Advantages of Zirconia

  • Resists crack propagation

  • High fracture toughness and fracture strength

  • High hardness

  • Biocompatibility, osseointegration

  • Good fatigue resistance

  • High flexural strength

  • Good chemical and dimensional stability once placed, corrosion resistant

  • Customisability

  • Non-conductivity

  • good implant aesthetics

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Disadvantages of Zirconia

  • Unfavorable wear and friction, can chip on crown

  • Strength reduction due to physiological fluids

  • Expensive

  • Limited aesthetics (opaque)

  • Brittle implant

  • As ages become rough, microcracks and strength reduction

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Zirconia vs Alumina

  • Zirconia 2-3 times stronger than alumina

  • Surface of zirconia can be made smooth than aluminum oxide

  • Alumina has lower mechanical strength and is more brittle (lower tensile)

  • Alumina has lower translucency and therefore less aesthetic

  • Alumina has limited bonding capabilities as low surface reactivity and doesn’t etch well with HF

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Advantages of Alumina

  • High density

  • High fracture toughness

  • High compressive strength

  • Corrosion resistance

  • High wear resistance

  • Good biocompatibility

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Disadvantages of Alumina

  • Highly dependent on microstructural refinement

  • Low tensile strength

  • Poor translucency

  • Limited bonding  capabilities

  • Difficult to mill or adjust or polish chairside

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Advantages of Calcium Phosphate

  • stable and significant release of Ca and K ions

  • bioactive - strong direct bonding with bone

  • biocompatible

  • osteoconductive

  • remineralising agent

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Disadvantages of Calcium Phosphate

  • lack of strength (compressive)

  • brittle, low tensile strength

  • limited clinical applications

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Advantages of PEEK

  • less stress shielding as youngs modulus matches bone

  • very good chemical resistance and high mechanical resistance

  • biocompatibility, can be modified to improve oseointegration

  • cheap

  • easier to customise

  • tooth coloured

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Disadvantages of PEEK

  • low osteoinductive ability results in poor osseointegration

  • susceptible to bacterial infection

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Advantages of Endosequence

  • antimicrobial properties pH of 12

  • biocompatible and osteogenic, no cytotoxicity on gingival fibroblast

  • easier to handle

  • no staining

  • metal free

  • great bonding to dentine as hydrophilic

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Disadvantages of Endosequence

  • more bacterial leakage than MTA

  • very expensive

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Cemento Ossifying Fibroma

Benign odontogenic fibroosseous neoplasm arising in the jaws and characterised by production of bone and cementum like calcifications in a fibrous stroma

They are a true neoplasm with a significant growth potential.

Presumed to be odontogenic in origin. Can be associated with hyperparathyroidism jaw tumour syndrome which is an autosomal dominant which is caused by a mutation in TSG CDC73 causing antiproliferative activity through cyclin D1.

epidemiology is 20-30 females, caucasians,

a slow, painless buccolingual expansion of the bone

well demarcated FOL composed of fibrocellular tissue and variable mineralised material, FCT has varying degrees of cellularity usually is hypercellular

hard tissue is bone and osteoid with peripheral osteoblastic rimming. also cementum spehricules with brush border

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Fibrous Dysplasia

Fibrous dysplasia is caused by a post zygotic gene mutation in which bone is replaced by abnormal bone and fibrous tissue during bone growth. GNAS 1 gene mutation that affects the function in proliferation and differentiation of pre-osteoblasts

equal in males and females, no racial predilection

painless swelling ± facial asymmetry, slow growth, teeth might be displaced, pigmentation has well defined but irregular margins, are unilateral tan macule

Histologically there will be irregular bony trabeculae on a fibrous tissue stroma. The trabecular will be V U and W, they will be like chinese characters (curvilinear). Loosely arranged cellular fibrous connective tissue, transitions from cellular to more fibrous over time. Lesion bone fuses directly to normal bone hence it is not well defined

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Measures for Assessing Growth

  • height and weight

  • dental maturation

  • cervical vertebra maturation

  • hand wrist radiograph

  • development of secondary sex characteristics