Restorative Flashcards
what are the indications for crowns
improve aesthetics, improve OVD, improve occlusion and function, support reduced tooth tissue, support or retention for RPD or bridgework
what are the contra-indications for crowns
extensive caries and periodontal disease, fracture, when more conservative options are available
what are the principles of crown prep
preserve tooth tissue, structural durability, marginal integrity, preserve periodontal tissue, improve aesthetics
what are the crown prep measurements for a metal only crown
axial - 0.5mm, functional cusp - 1.5mm, non-functional cusp - 0.5mm, margin - chamfer, 0.5mm
what are the crown prep measurements for a metal ceramic crown
if metal only - 0.4mm, if ceramic as well - 0.9mm - 1.3mm
margin - 1.3mm or 0.5mm, chamfer non aesthetic, shoulder for aesthetic. functional cusp - 1.8mm
what types of crowns are there
metal only - gold, metal ceramic crown - metal and porcelain, porcelain jacket - zirconia underneath supporting porcelain, porcelain only
why do functional cusps need more prep
under more force, need more material so its stronger, thicker material - more prep
name 3 types of preformed crowns
polycarbonate, clear plastic, stainless steel
what are the disadvantages of preformed crowns
not an accurate fit, requires a large bank - costly
why is a good provisional crown so crucial
if poor margins - not cleansible, cause inflammation and recession - definitive then wont fit, will also make it more difficult to take impressions
what are indications of a successful provisional crown
good aesthetics, restore function - OVD, reduces sensitivity, easily cleansed - should be exposed to cleansible, margins at access for finish for dentist and clean for patient, above gingiva margin
what are the indications for a veneer
improve aesthetics - shape, colour of teeth
correct peg shaped laterals
reduce or close proximal spaces
improve discolouration
what are the contra-indications for veneers
if too extensive a prep is required - should be in enamel for mechanical retention
gingival recession
caries and perio disease
what is the main failure for RCT
coronal microleakage - ingress of oral bacteria through coronal seal
how do you decide what to restore RCT with
if marginal ridges intact - composite
if intact but discolouration - either composite and bleaching or crown/veneer
if broken down - crown
when is a post-core used
for intra-radicular support when insufficient tooth tissue, gives retention and support for restoration
what is the function of a post
retain and support core build up, extends from root canal
what is the function of a core
retain and support restoration, what prosthesis is fixed to
what is a post and core made of
post - metal, gold - ceramic, zirconia - fibre, glass
core - composite, amalgam, GI
what is a ferrule
a dentinal collar, 1-2mm in vertical axis, circumferentially around cervical aspect of tooth. crown needs to bond on to tooth surface. if no ferrule, increased rate of fracture
what are guidelines for post and core
should have ferrule, post should be tapered at 6 degrees, non-threaded and cemented, should be 3-5mm of GP left apically
give 3 examples of post
smooth tapered, smooth parallel, threaded tapered, threaded parallel
what structures are in the TMJ
cranial base - temporal condyle head of mandible articular disc - with superior and inferior articular space mandibular fossa articular eminence
what are the movements at the TMJ
rotation, translation and lateral translation
describe the rotation movement of TMJ
rotation of condylar head around an imaginary horizontal line - terminal hinge axis. movement fully within fossa, slight opening of 20mm, passive movement, clenching of teeth
what is the facebow used for
to record the relationship of the maxilla with the terminal hinge axis
what is posselts envelope
the border movements of the mandible in the sagittal plane
what are the positions of posselts envelope
ICP - intercuspal position E - edge to edge P - protrusion T - maximum opening R - retruded axis position RCP - retruded contact position
what is the mutually protected occlusion and why is it desired
canine guidance. desired as prevents excess lateral force on teeth caused by occlusion, unwanted tooth contacts can distort the teeth coming into ICP. no posterior teeth contacts - not subjected to lateral force
what is used to record tooth contacts
miller forceps and articulating paper - 40 microns thick
when do you record tooth contacts
before placing a restoration and before removing an old one - want to conform to occlusion
after placing restoration or crown - ensure occlusion is not altered and no heavy contact on restorations
what is static occlusion and how is it recorded
intercuspal position. lingual cusps of upper molars in contact with lower fossa, buccal cusps of lower molars in contact with upper fossa. recorded by tapping teeth together
what are some deviations from ICP
incisor relationship class 2 div 1 - increased overjet div 2 - increased overbite anterior open bite posterior open bite cross bite
what is dynamic occlusion
contacts during movement. lateral movement - working side and non-working side contacts. protrusive movement - posterior contacts
what is the problem with posterior teeth contacts during lateral or protrusive movements
excessive lateral force which teeth are not able to withstand, musculature unable to rest as it should
what would you be looking for when record dynamic occlusion
any marks on posterior teeth - slide marks, during lateral or protrusive movement
what are some pathologies caused by unwanted tooth contacts
bruxism - eccentric or centric
what is the anterior reference point
43mm apically to lateral incisor
what different approaches can be used
conformative or reorganised
what contact is used for designing a reorganised approach
first occlusal contact in Retruded arch of closure - RCP
why might a reorganised approach be used
to increase OVD, when change in aesthetics is desired
what is used to ensure casts are mounted accurately
facebow and intercuspal registration using either wax or paste
what are the different types of discolouration
internal - fluorosis, tetracycline, nonvital tooth
external - tannins (coffee, tea, red wine), smoking, chromogenic bacteria
explain how external bleaching works
hydrogen peroxide oxides high weight molecules to lower weight - less pigmentation
what factors affect external bleaching
time, tooth surface, temperature, concentration
compare at home bleaching with chairside
chairside - dentist in control, can ensure no damage to gingiva etc, however takes time and more expensive. faster results but dont last as long
at home - patient needs good written instructions, trusting them, cheaper, takes longer for results but lasts longer, patient can keep guard in over night
what are some disadvantages of external bleaching
sensitivity, relapse, tooth damage, gingival inflammation, problems with bonding
describe internal bleaching
can only be done on non-vital teeth, gain access to pulp chamber, remove GP 1mm below ACJ, place RMGI, put hydrogen peroxide in, cotton wool and seal with RMGI. Remove in a day and do it weekly
what are the requirements for internal bleaching
non-vital tooth, good RCT, no apical pathology
what is external cervical resorption and how is it caused
odontoclasts breaking down dental hard tissue around cervical junction, caused by H2O2 diffusing through dentinal tubules to periodontal tissues
how can internal and external bleaching be combined
can prepare tooth for internal, put bleach inside but also provide mouth guard and fill with bleach too, leave access cavity open with bleach in, patient has to keep this in 24 hours or will fill with food
when is micro abrasion useful
for removal of discolouration caused by demineralisation, brown/yellow stain
what are the legal requirements regarding bleachin
any hydrogen peroxide over 0.1% can only be sold or prescribed by dental professionals, anything over 6% cannot be sold unless requirement to prevent disease.
