Restorative Dentistry Flashcards
(182 cards)
1
Q
5 causes on instrinsic discolouration of vital teeth
A
- trauma resulting in pulpal death
- fluorosis
- tetracycline staining
- amelogensis imperfecta
- dentinogenesis imperfecta
2
Q
improving tooth colour
methods that need tooth prep
methods that do not need prep
A
methods needing prep
- veneer
- crown
methods not needing prep
- bleaching
- microabrasion
- composite veneers
3
Q
how to remove extrinsic stains from tooth surface
A
polishing the surface with pumice slurry and water or prophylaxis paste
ultrasonic cleaners
bleaching
4
Q
primary dentine
A
formed before eruption or within 2-3 years after eruption and consists mainly of circumpulpal dentine
inc mantle dentine in the crown and the hyaline layer and granular layer in the root
5
Q
secondary dentine
A
regular dentine formed during the life of the tooth and laid down in the floor and ceiling of the pulp chamber
physiological type of denitne after the full length of root has formed
6
Q
tertiary dentine
A
divided into reparative and reactionary denitne - both laid down in response to noxious stimuli
reactionary dentine is laid down in reposne to mild stimuli whereas reparative dentine is laid down directly beneath the path of injured dentinal tubules as a response to stronger stimuli and are irregular
7
Q
difference between internal and external resorption
A
internal resorption starts within the pulp chamber of a tooth
external resorption starts on the surface of the tooth, most commonly the root surface
8
Q
internal resorption in vital or non vital teeth
A
only in vital teeth (or partially vital)
9
Q
external resorption in vital or non vital teeth
A
can occur in both vital and non vital
10
Q
signs of ankylosis
A
- different sound from a normal tooth when it is percussed, often described as a cracked china sound
- lacks periodontal membrane space on a radiograph
- has no physiological mobility
- may become infraoccluded as the jaw grows around it
11
Q
BPE 0
finding on probing
tx
A
coloured area of probe is completely visible, no calculus and no gingival bleeding
no need for tx
12
Q
BPE 1
finding on probing
tx
A
coloured area is completely visible, no calculus but bleeding on probing
OHI
13
Q
BPE 2
finding on probing
tx
A
coloured area is completely visible; supra or sub gingval calculus detected or overhanging restorations
OHI; elimination of plaque retentive areas; professional mechanical plaque removal
14
Q
BPE 3
finding on probing
tx
A
coloured area partially visible
OHI; elimination of plaque retentive factors; PMPR
15
Q
BPE 4
finding on probing
tx
A
coloured area completely disappears indicating proving depth of >5.5mm
referral may be needed
16
Q
general risk factors for periodontal disease
A
- poor access to dental care
- smoking
- systemic disease e.g. diabetes
- stress
- history of periodontal disease
- genetic factors
17
Q
localised factors for periodontal disease
A
- overhanging restorations and defective restoration margins
- partial dentures
- oral appliances
- calculus
18
Q
gingival recession risk factors
A
- trauma - excessive toothbrushing, digging fingernails into gingiva, biting pencils
- traumatic incisor relationship
- thin tissues
- prominent roots
19
Q
fluoride effect on teeth prior to eruption
A
teeth have more rounded cusps and shallower fissures
crystal structure of the enamel is more regular and less acid soluble
20
Q
effect of fluoride on teeth after eruption
A
decreases acid production by plaque bacteria
prevents demineralisation and encourages remineralisation of early caries
remineralised enamel is more resistant to further acid attacks
thought to affect plaque and pellicle formation
21
Q
consequences of fluoride overdose
A
enamel fluorsis
mottling
pitting
GI toxic effect
22
Q
recommended water fluorid conc for optimal caries prevention
A
1ppm in UK
23
Q
safely tolerated dose F
A
1mg/kg body weight
level below which symptoms of toxicity are unlikely to occur
24
Q
potentially lethal dose F
A
5mg/kg body weight
lowest dose associated with fatality
25
certainly lethal dose
32-64mg/kg body weight
at this dose survial is unlikely
26
pulpitis
inflammation of the pulp
27
reversible pulpitis is a X pain
set off by X and is X localised and lasts X
reversible pulpitis is a **SHARP** pain
set off by **HOT/COLD AND SWEET THINGS** and is **POORLY** localised and lasts **SEVERAL SECONDS**
28
irreversible pulpitis is a X pain
set off by X
it is X localised and lasts X
irreversible pulpitis is a **THROBBING** pain
set off by **BITING OR SPONTANEOUSLY**
it is **WELL** localised and lasts **SEVERAL HOURS**
29
nerve fibres found in the pulp
* A beta fibres - large, fast conducting proprioceptive fibres
* A delta fibres - small sensory fibres
* C fibres - small unmyelinated sensory fibres
30
tx for irreversible pulpitis
root canal tx
extraction
31
pts can have thermal sensitivity after placement of a resotration
theory for this
theory of pulpal hydrodynamics
* fluid moves along dentinal tubules and when there is a gap between the restoration and dentine, fluid will slowly flow outwards
* decrease in temperature leads to a sudden contraction in this fluid and so inc flow - pt feels as pain
32
how can restorative techniques limit thermal senstitivty
hydrodynamic theory - aim to seal the dentine and inc the integrity of the interface between the dentine and the resotrative material
33
cavity sealers role
prevent leakage of the interface of the restorative material and the cavity walls and to provide a protective coating to the cavity walls
34
cavity sealers types
* **varnishes** e.g. synthetic resin based material or natural resin or gum
* **adhesive sealers** which also bond at the interface between teh restorative material and cavity walls e.g. GI luting cement
35
what is microleakage
passage of bacteria, fluids, molecules or ions along the interface of a dental resotration and the wall of the cavity preparation
36
consequences of microleakage
* marginal discolouration of restorations
* secondary caries
* pulpal pathology
37
management of pulpal expsoure in a vital tooth
direct pulp capping
1. if tooth not already isolate - isolate with dental dam
2. dry the cavity
3. place CaOH over the exposure
4. cover with cement/liner e.g. Glass ionomer
5. restore as normal
6. inform the pt
7. arrange a review
38
aim after direct pulp cap
what may happen:
* dentine bridge will form
* pulp will remain vital
39
contraindication to pulp capping
* non vital tooth
* history of spontaneous pain - irreverisble pulpitis
* evidence of periapical pathology
* large exposure
* contamination of the exposure with saliva, oral flora or bacteria from teh caries
older the pulp the less likelihood of success
40
adv of rubber dam in restorative dentisty
* isolation and moisture control - esp imp for moisture sensitive techniques e.g. acid etch before composite restoration
* prevention of inhalation of small instruments e.g. during endo tx
* improved access to the tooth - no soft tissues/tongue in way
* pt do not swallow irrigants
* soft tissues protected from potentially noxious materials
41
restorative material able to bone to tooth tissue without surface pretreatment
glass ionomer
42
how can GI adhesion be improved
using a polyalkenoic acid conditioner
43
how does GI bond to teeth
* micromechanical interlocking - hybridisation of the hydroxyapatite coated collagen fibril network
* chemical bonding - ionic bonds form bewtween the carboxyl groups of the polyalkeonic acid and the calcium in HA
44
adv of GI
* bonds to tooth tissue
* releases F
* quick to use as limited pretreatment of teh tooth surface is needed
45
clinical uses of GI
* premanent direct resotrative material in deciduous and permanent teeth
* temporary restoration
* luting cement
* cavity lining or base
* core build up material
* retrograde rooth filing material
* pit and fissure sealant
46
'smear layer'
when tooth tissue is cut the debris is smeared over the tooth surface
this is the smear layer - contains any debris produced by the reduction or instrumentation of dentine, enemal or cementum
calcific in nature or contaminant that precludes the interaction of restorative material with underlying pure tooth tissue
47
dentine can be treated/conditioned with acid
why is this
removes most of the hydroxyapatite and exposes a microporous network of collagen
smear layer is altered or dissolved
bonding that results is diffusion based and relies on the exposed collagen fibril scaffold being infiltrated by the resin
48
why are primers needed
the denture surface after conditioning is difficult to wet with the bonding agents
the primer transforms this surface froma hydrophillic state into a hydrophobic state that allows the resin to wet and penetrate the exposed collagen fibres
49
what is the hybrid layer
hybrid layer is the area in which the resin of the adhesive system has interlocked with the collagen of the dentine, providing micromechanical retention
50
dentine bonding agents role
* form resin tags in the dentinal tubules
* stabilise the hybrid layer
* form a link between teh resin primer and the restorative material
51
aims of obturating a root canals
* prevent reinfection of teh cleaned canal
* prevent periradicular exudate from entering into the root canal
* seal any remaining bacteria in the root canal
52
methods for filling a root canal with GP
* single cone method
* lateral condensation - warm or cold
* thermomechanical compaction
* vertical condensation
* thermoplasticised GP method
* carrier based techniques
53
causes of intra radicular failure of root canal tx
* necrotic material left in the canal
* bacteria left in the root canal system (lateral or accessory canals)
* contamination of the canal during treatment
* loss/lack of coronal seal
* persistent infection after treatment
54
causes of extra radicualr failure of RCT
* root fracture
* radicular cyst
55
indications for apicepctomy (surgical endo)
* infection due to a lesion that requires biopsy e.g. radicular cyst
* instrument stuck in canal with residul infection
* impossible to fill apical third of root canal due to anatomy or pulp calcification
* perforation of root
* post crown with excellent margins but persistent apical pathology
* infected, fractured apical third of root
56
acid etching of enamel
application of mild acid to the surface of enamel causes dissolution of about 10um of the surface organic component, leaving a microporous surface layer up to 50um deep
suface is thus pitted, and the unfilled resin of the restorative material is able to flow into the irregularities to form resin tags that provide micromechanical retention
57
common etchant
30-40% Phosphoric acid
gel or liquid
gel longer to wash away but less likely to run onto areas where etch not wanted
can be combined with dentine conditioner
58
etch applied for
15-20 secs
59
after applying etch
wash away with watwr for at least 15 secs
60
what can damage the etch enamel surface and reduce the efficacy of bonding
blood and saliva, and mechanical damage may occur by probing the area
rubbing cotton wool over it to dry it or by scraping across teh surface with a tip or an instrument
61
total etch technique
involves using an acid to etch the enamel and condition the dentine at the same time
commonly used acids: phophoric acid (10-40%), nitric acid, maleic acid, oxalic acid adn citric acid
62
20 yo women, CO gaps, missing laterals
tx options
* orthodontic tx to close the spaces
* removable partial denture
* adhesive bridges
* conventional bridges
* implants
63
20 yo women, CO gaps, missing laterals
orthodontic tx to close spaces
adv and disadv
adv
* no artifical teeth needed
* pt does not need restorative tx to replace teeth
disadv
* may take long time to complete
* canines may not provide a good contact against the central incisors
* bleaching and restoration of the canines may be needed to make them look like incisors and recontoring of ginigval margin
64
20 yo women, CO gaps, missing laterals
RPD
adv and disadv
adv
* quick
* cheap
* does not require removal of tooth tissue
disadv
* not ideal in young pt
* removable
* may need replacing in long term
* may compromise gingival and oral health if OH and diet not idea
65
20 yo women, CO gaps, missing laterals
adhesive bridges
adv and disadv
adv
* fixed tooth in place
* good aesthetics
* no/min prep of adj teeth
disadv
* may debond
* needs favourable occlusal clearance
* may need replaced
66
20 yo women, CO gaps, missing laterals
conventional bridge
adv and disadv
adv
* fixed tooth in place
* good aesthetics
disadv
* requires destruction of adj teeth
* impairs cleansabilty
* may need replaced
67
20 yo women, CO gaps, missing laterals
implants
adv and disadv
adv
* permanent solution
* good aesthetics
* like having real tooth
disadv
* costly
* may need bone graft
* requires surgery
68
what is composite
type of restorative material
made of: oragnic resin matrix, an inorganic filler and a coupling agent
69
traditional composite
adv and disadv
* good mechnical properties
* surface roughness and difficult to polish
70
microfilled resin composite
adv and disadv
very good surface polish
poor wear resistance
unsuitable for load beading areas
high contraction shrinkage
71
hybrid composites
adv and disadv
good mechancial properties
good surface polish
72
small particle hybrid composites
good mechnical properties
very good surface polush
73
how to finish and polish a composite
involves shaping and smoothing the restoration to teh anatomical form and polishing imparts a shine to the surface
smoothest suface is achived when composite is polymerised against an acetate strip with no polishing - but leaves a surface with a v high resin content that is not resistant to wear
for polishing:
* diamond and carbide burs are used for gross finishing
* rubber cups with abrasive materials of diffreing coarsness
* flexible abrasive discs - most to least (light to dark)
* finishing strips for interproximal areas
74
risk factors for root caries
* exposure of the root surface (pocketing, gingival recession or attachment loss)
* cariogenic diet
* decreased salivary flow (medicaments, previous radiotherpy, drugs, diabetes, ageing)
* poor oral hygiene - inaccessible areas e.g. perio pockets, decreased manual dexterity, lack of access to dental healthcare or dental health low priorty, remoable prosthesis, poor restorations
75
materials commonly used for Class V lesions
GI
RMGI
composite
amalgam
76
management of pt with multiple root caries lesions
elimination of active infection (remove caries and place resotrations) and preventative measures:
1. identify any risk factors that can be corrected
2. oral hygiene advice
3. dietary analysis and advice
4. periodontal tx as necessary
5. F tx in teh surgery (duraphat application) or at home application (rinses)
6. recall
77
adv of bonded amalgam restoration vs non bonded amalgam
* dec in microleakage
* less destructive in tooth tissue
* may limit need for dentine pins
* may inc fracture resistance of restored teeth
* transmits and distributes force better
* less post op sensitivity due to better sealing of the margins
78
materials that can bond to tooth tissue
* GI
* composites
* hybrid restorative materials e.g. RMGI, compomers
* ceramics - using special cements
79
pretreatment of anterior crowns
conventional ceramics that are silica based are tx with **hydrofluoric acid and ammonium bifluoride**
* can also be sandblasted or air arbraded
* often tx with silane coupling agent
alumina and zirconium oxide ceramics are surface roughened with air abrasion and then coated with silicate
80
materials for primary impression complete dentures
alginate
compound - thermoplastic
impression putty
81
hydrocolloid imp materials division
reversible - agar
irreversible - alginate
82
synthetic elastomeric imp materials divided into
elastomers
polysulphides
polyethers
silicones (addition or condensation cured)
83
mucostatic impression
impression with mucosa in its resting state
provides a good fit at rest and therefore good retention
i.e. most of the time but when the pt chews the denture will tend to rock around teh most incompressible areas e.g. palatine torus
84
mucocompressive impression
taken when the denture bearing area is subjected to compressive force
denture is maximally stable during fuction but not at rest
85
RVD
resting vertical dimension
measure of vertical height of the pt lower face and is measures as the distance between two abritary points (one related to maxilla and other mandible) with pt at rest
86
OVD
occlusal vertical dimension
similar measure to RVD but taken when pt teeth in occlusion
87
FWS
freeway space
difference between RVD and OVD - vertical gap between the pt teeth at rest
88
factors that may affect rest jaw position
* stress
* head posture
* pain
* age
* neuromuscular disorders
* bruxism
89
group function
during lateral excursion there is contact between several upper and lower teeth on the working side and no contacts on teh non-working side
90
canine guidance
during lateral excursion there is contact between upper and lower canine teeth on the working side only and no contact on the non working side
91
balanced occlusion
means simultaneous contacts between opposing artifical teeth on both sides of dental arch
92
aim for occlusion in C/C
balanced occlusion
93
difference between balanced occlusion and balanced articulation
balanced articulation is simulatenous contact of opposing teeth in centreal and eccentric positions as the mandible moves
i.e. it is a dynamic relationship
whereas balanced occlusion is a static situ
94
factors affecting occlusion in protrusive movements in C/C
* incisor guidance angle
* cusp angles of posterior teeth
* condylar guidance angle
* orientation of occlusal plane
* promenence of compensating curve
95
immediate dentures
adv and disadv
adv
* pt never without teeth - psychological adv
* aesthetics - pt never without teeth
* artifical teeth can be set in the same position as natural ones
* soft tissue support
* easier to register jaw relations as they are taken when the pt had teeth
* bleeding easier to control after extractions
disadv
* denture may not fit
* will need relining/copying or remaking
* will not fit when the alveolus remodels
* usable to try in
* may need many visits for adjustments
96
flanged immediate denture
flanged periphery like a normal complete denture
good retention and will make future adjustments easier
disadv is that the lip may be over supported/appear too bulbous
97
open faced immediate denture
no buccal flange and the denture teeth sit at the edge on the extraction sockets of the natural teeth
adv is that it can be used when there are large undercuts, often good aesthetics initally
disadv retention is poor and when resorption occurs a gap appears between ginigval margin of the denture teeth and mucosa
98
methods to adjust fit of immediate denture
* relining
* rebasing
* copy dentures
* total remake
99
dental surveyor
and aim of surveying
instrument used to determine relative parallism of 2 or more surfaces of teeth or other parts of the cast of dental arch
aims to identify
* most desirable path of insertion that will eliminate or minimise interference to placement and removal
* tooth and tissue undercuts
* tooth surfaces that are or need to be parallel so that they act as guide planes during insertion and removal
* measure areas of teeth may be used for retention
* whether tooth and bony area of interference need to be eliminated surgically by selecting different paths of insertion
* undesirable tooth undercut that needs t be avoided, blocked out or eliminated
* potential sites for occlusal rests and where they need to be prepared
100
dental articulator
instrument used to reproduce jaw relationships and movements of the lower jaw relativet to the upper jaw
casts of both upper and lower are mounted on
101
facebow
instrument that measures teh relationship of either the maxillary or mandibulr arch to the intercondylar axis and ise used to transfer these measurements to the articulator
means that the articulated casts will have the same relationship to the hinge axis of the articulator as the teeth with the intercondylar axis
102
muscles which may affect the peripheral flanges of a C/C
geniohyoid
orbicularis oris
mentalis
mylohyoid
buccinator
palatpharyngeus
palatoglossus
103
location of posterior margins of upper complete denture usually
anterior to the fovea palatine
104
what is post dam and its role
where is it
raised lip on the posterior boder of the fit surface of an upper complete denture
compresses teh palatal soft tissue to form a border seal
usually lies at the junction of the non-moveable hard palate(anteirorly) and moveable soft palate (posteirorly)
105
neutral zone
area between tongue, lips and cheeks where displacing forces of the muscles is minimal
the ideal area into which a prosthesis should be placed to minimise displacing forces
106
kennedy class I
bilateral edentulous areas located posterior to natural teeth
107
kennedy class II
unilateral edentulous areas located posteriot to the remaining natural teeth
108
kennedy class III
a unilateral edentulous area with natural teeth remaining both anterior and posterior (bounded saddle)
109
kennedy class IV
single, but bilateral (crossing midline) ednetulous area located anterior to remaining natural teeth
110
stages in designing a partial denture
1. outline saddle areas
2. place occlusal rests seats
3. place clasps for direct retention
4. place indirect retainers
5. connect the denture
111
direct retainer in partial denture is
any element of a partial denture that provides resistance to movement of the denture awy from the supporting tissues is a direct retainer
112
2 types of clasp in partial denture
gingivally approaching
occlusally approaching
113
what is in a clasp unit? why?
* clasp
* some form of support, usually an occlusal rest
* some form of reciprocation
support will allow loads to be transferred along the long axis of teeth
also enable the clasp arm to be accurately located in the undercut on the tooth
reciprocation is needed as all clasps on teeth must be balanced by something on the opposite surface to act as a balance - prevent inadvertent force being applied to a tooth in one direction
114
indications for copy dentures
* occlusal wear on a set of previously successful complete dentures
* need for replacement denture base material
* pt was initially given immediate dentures and they need to be replaced
* pt has a set of complete dentures that they have been happy with but are now unretentive/worn, esp elderly pts who may find it hard to adapt to a completely new set of dentures
* make spare set of dentures
115
adv of copy dentures
* simple clinical steps, quicker than starting from scratch
* reduced number of lab steps - no special trays or record blocks
* pt is never without denture
* original dentures not altered in any way
* more predictable pt acceptance
116
X is tooth surface loss from non bacterial X attack. Smooth X surfaces are seen with restorations standing X. Tooth surface loss of the X surfaces of the upper incisors is seen in cases of gastric reflux and vomitting
**erosion** is tooth surface loss from non bacterial **chemical** attack. Smooth **plaque-free** surfaces are seen with restorations standing **proud**. Tooth surface loss of the **palatal** surfaces of the upperincisors is seen in cases of gastric reflux and vomitting
117
X is physical wear of a tooth by an external agent and may result in class V cavities at the X.
**abrasion** is physical wear of a tooth by an external agent and may result in class V cavities at the **gingival margin**.
118
X is physical wear of a tooth by another tooth, and its commonly affects X and X surfaces
**attrition** is physical wear of a tooth by another tooth, and its commonly affects **occlusal** and **interproximal** surfaces
119
abfraction lesions are thought to be due to a combination of X and occlusally-induced tooth X
abfraction lesions are thought to be due to a combination of **abrasion** and occlusally-induced tooth **flexure**
120
possible causes of severe erosion in 16 y.o. girl
* vomitting - bulima nervosa
* excessive fizzy drinks
less likely GORD, pregnancy
121
how to determine working length of a root canal
electronic apex locator
working length radiograph with an intrument in the canal
122
benefits of crown down method for root canal prep
* better access
* flaring of coronal part first removes restrictions and helps prevent instruments binding short of working length
* coronal part is usually where most of the infected material is present
* if removed and cleaned first it limits the chance of spreading the infected material to the apical and periapical tissues
* estimate the working length then change the coronal part of prep it may inadvertently alter the length
* coronal prep first allows irrigants to gain access to more the root canal system
123
commonly used irrigants in RCT
* sodium hypochlorite
* EDTA
* *CHX*
124
ideal properties of root canal filling
* capable of sealing teh canal apically, laterally and coronally
* radiopaque
* bacteriostatic
* not irritate the periradicular tissues
* easy to handle, inert and if needed removable
* impervious to moisture
* dimensionally stable
125
overdenture Vs onlay denture
overdenture derives support from one or more abutment teeth by completely covering them beneath its fitting surface
onlay denture is a partial denture that overlays the occlusal surface of all or some of the teeth - often used to inc OVD
126
overdenture adv
* preservation of alveolar bone around retained roots
* improved stability, retention and support
* preserved proprioception
* decreaded crown-root ratio which reduces damaging lateral forces and reduces mobility in teeth with recued periodontal support
* inc masticatory force
* psychological benefit of not losing all teeth
127
overdentures useful in
* severe tooth wear
* pt with hypodontia
* cleft lip and palate pt
* motivated pts with good OH
128
osseointegration
direct strutural and functional union between ordered living bone and the surface of a load carrying implant
129
factors to consider for abutment teeth selection
* should ideally be bilateral and symmetrical with a min one toooth space between them
* order of preference: canine, molars, premolars, incisors
* healthy attached gingivae and periodontal support, min mobility
* done root surface 2-4mm above gingival margin
* root canal tx may be needed
130
situations that can use implants
* single tooth replacement
* bridge abutment
* support for overdenture
* support facial prosthesis and hearing aids
* orthodontic anchorage
131
pt related factors that may affect the success of implants
* oral hygiene
* periodontal disease
* previous radiotherapy
* smoking
* bisphosphonates
132
anatomical factos that may affect implants
* bone height
* bone width
* bone density or quality
* proximity to inferior dental nerve proximity to maxillary sinus
* tooth position
133
what would you see in a clinically failed implant
* moblity
* pain
* ongoing marginal bone loss
* soft tissue infection
* peri-implantatits
134
constituents of dental amalgam
* silver
* tin
* coppper
* zinc
* mercury
135
what are the gamma, gamma 1 and gamma 2 phases in dental amalgam and what is there importance?
gamma phase is Ag3Sn
gamma 1 is Ag2Hg3
gamma 2 is Sn7Hg
gamma 2 is the weakest of the part of the amalgam - lowest tensile strength and is the softest of the phases
if the amount of gamma 2 phase can be limited in teh final dental amalgam the resulting amalgam will be strongth
136
setting reaction for dental amalgam
Ag3Sn + Hg -\> Ag3Sn + Ag2Hg3 + Sn7Hg
gamma + mercury -\> gamma + gamma1 + gamma2
follwed by
gamma2 + AgCu -\> Cu6Sn5 + gamma1
leaving no/little gamma2
137
lathe cut particales
spherical particles
significance of different types
lathe cut alloy is made by chipping off pieces from a solid ingot of the alloy - results in particles of different shapes and sizes
spherical particles are made by melting the ingredients of the alloy together and spraying them into an inert atomosphere, droplets solidify into spherical pellets that are regular in shape and can be more closely packed together - amalgam needs less condensation force and results in increased strength of amalgam
138
why is it common practice to overfill an amalgam cavity and carve it down
when amalgam is condensed the mercury rises to the surface of the restoration
to try and minimise the residual mercury left in the restoration it is usual to overfil the preparation and the excess mercury-rich amalgam can be carved away leaving the lower mercury containing amalgam which has greater strength and better longevity
139
what are dental ceramics made of
feldspar, silica (quartz) and kaolin
140
3 technical stages in making a porcelin jacket crown
first stage - compaction
* powder is mixed with water and applied to the die so as to remove as musch water as possible and compact the material such that ther is a high density of particles, which minimises firing shrinkage
second stage - firing
* crown is heated in a furnance to allow molten glass to flow between the powder particles and fill the voids
thrid stage - glazing
* done to produce a smooth impervious outer layer
141
adv and disadv of porcelain jacket crown
adv
* excellent aesthetics
* low thermal conductivity
* high resistance to wear
* glazed surface resists plaque accumulation
disadv
* poor strength and very brittle, so often fracture
* firing shrinkage so must be overbuilt
142
how has poorn strength of porcelain jacket crowns been overcome
by fusing the porcelain to metal to produce metal ceramic restorations
by making reinforced ceramic core systems
creating resin bonded ceramics
143
CADCAM stands for
computer assisted/aided design and computer assisted/aided manufacture
144
requirements of metal ceramic alloy
* high bond strength to ceramic
* no adverse reaction with ceramic
* melting temperature must be greater than the firing temperature of the ceramic
* accurate fit
* biocompatible
* no corrosion
* easy to use and cast
* high elastic modulus
* low cost
145
dental cement uses
* luting agents
* cavity lining and bases
* temporary restorations
146
luting agents examples
modified zinc phosphate
zinc oxide adn eugenol
zinc polycarboxylate
glass ionomer
resin modified glass ionomer
compomers
resin cements
147
cavity lining and bases examples
calcium hydroxide
zinc oxide and eugenol
148
temporary restorations examples
zinc oxide and eugenol
glass ionomer
149
which zinc based cement bonds to tooth substances
zinc polycarboxylate
150
how to mix zinc polycarboxylate and why
on a glass slab as it must not be mixed on anything that absorbs water
addtitionally, glass slabs can be cooled and this will inc working time
151
which cement cannot be used under composite restorations and why
zinc oxide and eugenol
eugenol is thought to interfere with teh proper setting of the composite material
152
which material is used for pulp capping and why
calcium hydroxide is extremely alkaline pH11
helps with formation fo reparative dentine
also antibacterial and has a long duration of action
153
which cement is thought to reduce sensitivity of a deep restoration
zinc oxide and eugenol
due to obtundent adn analgesic properties of eugenol
154
indications for anterior veneers
* discolouration of teeth
* for closure of spaces/midline diastema
* hypoplastic teeth
* fracture of teeth
* modifying the shape of a tooth
155
maaterials used for veneers
porcelain
composite (direct/indirect)
156
what would you need to check prior to advising placement of veneers
* discoloration enough to warrant treatment or is it so severe that it will not be masked
* pt smile line - helps determine which teeth need tx if for aesthetic reasons only, placement of cervical margin
* is there enought crown present to support a veneer
* any occlusal restrictions e.g. edge to edge occlusion, imbrication
* any parafunctional activities
* is there an alternative option e.g. balancing
157
what is the thickness of veneers
0.5-0.7mm usually
158
what is the long term prognosis of veneers
what to warn pt
may require replacement in the long term (e.g. approx 4 years for composite veneers) as a result of:
* risk of chipping incisal edge
* debonding
* need to keep good gingival health
159
key points during tooth prep for veneers
* tooth reduction labially - depth cuts are helpful
* chamfer finish line is helpful for the technician
* margin - slightly supragingival unless discolouration, then margin can be subgingval
* extend into embrasure but short of contact point
* incisally either chamfer or wrap over onto palatal surface
160
function of post and core
provides support and retention for the restoration and distributes streses along the root
161
important to check this prior to placement of post and core
condition of the orthograde root filling and the apical condition as placement of the post will make it difficult to redo root canal filling so if necessary repeat orthograed root canal treatment
162
ideal length of post
at least the length of the crown; approx 2/3 of the canal length
apical seal must not be distrubed so at least 4mm of the well condensed GP should be left
163
classfication of post and core system:
* prefabricated or custom made
* parallel sided or tapered
* threaded, smooth or serrated
164
ideal characteristics of a post
post should have
* adequate length
* be as parallel as possible
* have a roughened or serrated surface
* not rotate in the root canal
165
measure that can be taken to avoid post perforation
careful choice of post:
* avoid large diameter post in small tapered roots, instead used tapered post and cement passively
* avoid long post in curved roots
* avoid threaded post which will inc internal stress within root canal
166
how to manage a post perforation
depends on the location of perforation
* if its in the coronal third try to incorporate into the design of the post crown e.g. diaphragm post and core preparation
* for a minimal perforation in teh middle third - seal the perforation (e.g. lateral condensation) and reposition the post
* in apical 2/3s - use a surgical approach to try to reduce the exposed post and seal the perforation
if attempting to repair the perforations, use of MTA is preferable
due to poor long term prognosis, extraaction may be favoured
167
when are posterior crowns used
* bridge abutments
* restoring endodontically treated teeth
* repairing tooth substances lost due to extensive caries/remaining tooth substance requires protection
* fractured teeth
* situations in which it is difficult to produce a reasonable occlusal form in a plastic material
168
principles of posteiror crown prep
* remove enough tooth substance to allow adequate thickness of material
* develop adequate retention and resistance form
* marginal intergrity, supragingival and onto sound tooth where possible
169
tooth reduction needed for different materials for posterior crowns
* full veneer gold crown - 1.5mm on functional cusp, 1mm elsewhere
* porcelain fused to metal crown - same tooth reduction as for gold crown excepth where porcelain covereage is required where more tooth substance must be removed
* occlusal reduction - metal occlusal surface requires same tooth reduction as for gold crown
* all porcelain - occlusal surface 2mm supporting cussps and 1.5mm non suppporting cusps; buccal reduction 1.2-1.5mm; margins 1.2-1.5mm shoulder, if porcelain to tooth margin otherwise chamfer finish as for gold crown
170
what features affect the retention and resistance form of the crown?
retention relies on
* height, diameter and taper of the preparation
* will also be increased by the placement of boxes, grove, pins and suface texturere
resistance relies on
* taper or preparation, height to diameter ratio, correctly aligned and position grooves and boxes
171
adv os partial covereage crown over full coverage crown
* preservation of tooth structure
* less pulpal damage
* margins more likely to be supragingival
* remaining tooth substance can act as a guide for technician
172
21y.o. women presents with gingival recession affecting the lower incisors
how will you manage this
take a thorough history
* CO:
* present concerns, sensitivtiy
* SOCRATES
* HPC
* DH
* toothbrushing - frequency, duration
* interdental
* previous ortho tx or other tx
* SH
* MH
exam - inc asssessment of plaque, recession, probing depth, bleeding on probing, amount of attached gingivae, presence of functional gingivae, tooth mobility, vitality testing, occlusion
173
recession is mild on all bar lower left lateral incisors in 21 y.o. female
how to proceed
taget traumatic tooth brushing and improve plaque control
monitor progression with clinical measurements, photos
treat sensitivity
take impression for study models
174
causes of gingival recession
* traumatic toothbrushing
* incorrect toothbrushing technique
* abrasive toothpaste
* traumatic occlusion/incisor relationship
* tooth out of arch
* orhtodontic movement of tooth labially
* habits such as rubbing of ginvivae with fingernail,pen etc
175
gingival recession continues despite tx and prevention
what other options may be considered
mucogingival surgery to correct recession by a:
* lataeral pedicle graft
* double papilla flap
* coronally repositioned flap
* free gingival graft to provide a wider and functional zone of attached gingivae, taken from palate
* thin acrylic gingival veneer/stent (rarely used)
176
clinical features of necrotizing ulcerative gingivitis
* painful yellowish white ulcer
* inititally involve the interdental papillae
* spread to involve the labial and lingual marginal gingivae
* metallic taste
* regional lymphadenopathy
* fever
* mallaise
* poor oral hygiene
* sensation of teeth biting wedged apart
177
organisms implicated in nectosing ulcerative gingivitis
mixed picture
* fuso-spirochaetal organisms (fusobacterium fusiformis)
* gram negative anaerobes (pophymoonas, treponema, selenomasn, prevotella)
178
risk factors for nectrotising ulcerative gingivitis
* poor oral hygiene
* pre-exisitng gingivitis
* smoking
* stress
* malnourishment an debilitation
* HIV infection
179
tx nectorising ulcerative gingivtis
* local measures
* oral hygiene instructions
* debridement
* chemcial plaque control e.g. CHX
* metronidazole 200-400mg three times daily for 3 days is systemically unwell
* advice on management of risk factors, OHI, nutritional advice
180
how can you classify periodontal disease (10)
1. health
2. plaque induced gingivitis (localised/generalised gingivitis)
3. non plaque induced gingival disease and conditions
4. periodontitis (localised, generalised, molar incisor)
5. necrotising periodontal diseases
6. periodontitis as a manifestation of systemic diseases
7. systemic diseases or conditions affecting periodontal tissues
8. periodontal abscesses
9. periodontal-endodontic lesions
10. mucogingival deformities and conditions
181
juvenile periodontitis define
aggressive periodontitis occurring in an otherwise healthy adolescence characterised by rapid loss of connective tissue attachment and alveolar bone loss
usually localised to the incisors and first molars altough it can be generalised
182
4 indicators for periodontal surgery
* pockets greater than 6mm
* pockets associated with thick fibrous gingivae
* furction involvement
* mucogingival deformitis or extensive periodontitis lesion requiring reconstruction or regenerative tx
* short clinical crwn requiring inc in clincal crown height
* gingival hyperplasia
