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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.
Disadvantages of MTA
very long setting time
expensive
irreversible staining
difficulty in handling
difficult to remove once placed
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
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
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
Disadvantages of Ceramics
brittle (low tensile strength), prone to microcracks but can propagate to fractures, technique sensitivity, surface roughness can increase overtime
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
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.
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)
Tubular= two layered ductal system composed of inner ductal and outer myoepithelial cells
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.
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.
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
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
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
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
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
Advantages of Alumina
High density
High fracture toughness
High compressive strength
Corrosion resistance
High wear resistance
Good biocompatibility
Disadvantages of Alumina
Highly dependent on microstructural refinement
Low tensile strength
Poor translucency
Limited bonding capabilities
Difficult to mill or adjust or polish chairside
Advantages of Calcium Phosphate
stable and significant release of Ca and K ions
bioactive - strong direct bonding with bone
biocompatible
osteoconductive
remineralising agent
Disadvantages of Calcium Phosphate
lack of strength (compressive)
brittle, low tensile strength
limited clinical applications
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
Disadvantages of PEEK
low osteoinductive ability results in poor osseointegration
susceptible to bacterial infection
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
Disadvantages of Endosequence
more bacterial leakage than MTA
very expensive
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
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
Measures for Assessing Growth
height and weight
dental maturation
cervical vertebra maturation
hand wrist radiograph
development of secondary sex characteristics