9/27 - Crown Fabrication, Screw vs. Cement Retained, Implant Occlusion Flashcards
what mill do we use to create crowns
PM7
what program is used to design implant crowns
dental designer
what program is used to look at 3D model on phone
3shape communicate
how many mills can be created per puck
20 mills
what is the making of solid material into porous mass due to heat and compression
sintering
what are the different types of restorations
screw vs. cement
what is done during pre-treatment evaluation/diagnosis
- patient expectiaons
- systemic eval
- extra/intraoral photographs
- mounted diagnostic casts
- radiographs
- clinical/esthetic examination
when planning crown, what must you make decisions aout
adjacent teeth, ortho, implant position and number, prosthetic design, hard/soft tissue augmentation, provisionalization
distance from tooth to implant for crown
1.5-2mm
distance from implant to implant for crown
3 mm
distance of buccal bone for crown
> 1-1.5mm
what is bare minimum of interoccusal space needed for implant crown
> 5mm
what is a portion of dental implant that serves to support and/or retain a prosthesis
abument
types of implant/abutment junction
external hexagon and internal conical connection
what abutment junction has antirotations part on OUTSIDE of implant
external hexagon
what abutment junction has antirotational component INSIDE implant
internal conical connection
is there always a microgap beteween implant and abutment
yes
order of abutment junctions from most amount of microleakage to least
external hex> inernal trilobe> internal hexagon> internal-taper
what is the shifting of the microgap inwards called
platform switching
what is it called when abutment is smaller than implant platform
platform switching
what is thought to preserve crestal bone and interdental papilla by moving microgap inward
platform switching
advantages of external hex
*Ease of multiunit restorations
-Screw Fracture Retrievability
-Impression coping confirmation
Bar type overdentures, large cases nonparallel implants
advantages of internal conical
-Abutment/implant connection
-Bacterial Seal with Morse Taper
-Single unit less screw/abutment
loosening
-Prevents micro movement (lessened
bone remodeling around implant)
disadvantages of external hex
-Individual: Screw Loosening
*Plastic Deformation
-Bacterial Seal
-Screw fixture attachment
disadvantages of internal conical
-Screw fracture retrieval
-Thinning of implant wall in narrow body
-Radiographic confirmation
what screw strip easily? what do not?
easy strip = hex
not as easy = square
what are the standard square screww sizes
0.050”
what are the standard hex screw sizes
0.035”, 0.048”, 0.050”
advantages of gold screws
- galvanized pure gold deformed during screw tightening, increasing frictional resistance
- initial preload of gold screws is significantly higher compared with titanium screws
what is tension created in a screw when tightened
preload
what torque wrenches produce average torque values close to value of 35Ncm
toggle-type (friction-style) and beam-type (spring-style)
range of values and variability are GREATER with what style wrenches
toggle (friction)
mechanical torque-limiting devices should be checked and calibrated according to instructions how oten
annually
what torque style is better to start off with
spring style/beam
what style of torque
spring style/beam
what style of torque
toggle-type/friction
retighten screw how long after initial torque application
10 minues
what type of restoration has hole thru crown which gives access to abutment screw
screw-retained
where is hole on anterior teeth of screw retained
cingulum
where is hole on posterior teeth of screw retained
central fossa
what type of restoration has crown cemented onto abutment with no direct access to abutment screw
cement retained
where is hole on anterior teeth of cement retained
incisal edge or facial
where is hole on posterior teeth of cement retained
access exits functional cusp
advantages of screw retained restoration
primary: RETRIVABILITY
also limited restorative space (5mm) and no residual cement
disadvantages of screw retained restoration
esthetics and occlusal access hole
advantages of cement retained restoration
esthetics, no access hole, traditional C&B technique, passive fit, mitigate angulation issues
disadvantages of cement retained restoration
primary: RESIDUAL CEMENT
also: retrievability and space contraints (>/= 6mm)
what has a smaller biological width: natural tooth or implant
IMPLANT:
natural tooth = 2.04 mm
implant = 0.75 mm
is there a significant different bectween screw and cement restorations
no
if you choose to cement, must have how many mm space
6 mm
if you choose to cemement what must you do
- have 6 mm space
- choose radio-opaque cement (zinc phosphate and ZOE)
- control margin placement
- choose proper amount of cement
cement technique
put teflon inside crown and seat on abutment. inject PVS into crown. remove PVS and teflon and place cement. seat crown on PVS die and remove excess cement. seat andclean cement
how can you modify abutment
createion of vent hole to allow for excess cement to seep thru
main advantage of custom abutments
control of margin position
(avoid sub-gingival margins, prevent residual cement, optimize abutment design)
what types of custom abutment metal can be milled
- titanium
- gold-shaded
- zirconia
does cement retained crown have occlusal access
no
does cement/screw retained crown have occlusal access
yes! “screw-mented” so retrievable and has no risk of residual cement
which is stronger: titanium or zirconia abutments
zirconia is 10x strnoger
custom castable plastic pre-machined titaniu, gold alloy or chrome cobalt is almost exclusively used for what types of restoration
screw retained
advantages of prefabricated abutments
inexpensive, may prepare
disadvanages of prefabricated abutments
no control of margin placemen and HOC
what abutments to select when provisional is used to sculpt tissue
no tissue displacement and support tissue
implant should be placed how many mm apical to propsed CEJ
3-4 mm
how long for custom abutment fabrication
1 week
how long for abutment supported crown fabrication
2 weeks
advantages of screw-mentable
Retrievable
Prevent residual cement
Milled=fit of custom abutment
Restorative materials
Monolithic zirconia / PFM / Gold
disadvantages of screw-mentable
Extra steps
Access hole binding on driver-
lower torque
values delivered to
abutment screw
Cement interface-modes of
failure
Space constraints (need ≥ 6mm)
difference between natural tooth and implant
Natural tooth: PDL, physiologic movement, decreased stress to bone, and proprioception
Implant: ankylosed, no physiologic movement, higher stress to bone, dull mechanoreception
what has greater width: natural or implant
greater width = natural tooth
narrower width = implant
natural tooth has a greater width and supportive cross-sectional shape, meaning what?
less stress to bone
implant is narrower in width and has a round platform, meaning what?
greater stress to bone
what is stimulation of sensory nerve terminals within tissues that give information concerning movements and the position of the body
proprioception
for implants, does it require a lower or higher level of force to activate patient’s perception of force
HIGHER
perception is from mechanoreceptors in periosteum as a result of what
result of bone deformation
occlusal awareness of tooth:tooth
20 microns
occlusal awareness of tooth:implant
48 microsn
occlusal awareness of implant:implant
64 microsn
occlusal awareness of tooth:implant overdenture
108 microns
magnitude of bite force is dependent on what
age, sex, degree edentulism, bite location, and parafunction (bruxism/clenching)
bite forces on molar, canine, premolar, and incisors
molar: 374-710N
canine/premolar: 424-583N
incisor: 150 N
early signs of occlusal overload on natural tooth
hyperemia, cold sensitivity, and percussion
what is present on natural tooth when occlusal overload is present
widened PDL, mobility, wear facets, stress lines, abfraction
are there any early signs of occlusal overload present on implants?
no - asymptomatic typically
what is present on an implant with occlusal overload
fatigue fracture, biomechanics failures, moat-shaped crestal bone loss, mobility
is there a specific right or wrong way to approach implant occlusion
no (not yet anyways) - there havent been much studies
distinctions for theories of implant occlusion are made according to what
- biomechanical design of implant
- # of implants
- design/fit of prosthesis
- opposing dentition
- supporting bone
- nature of bolus of food
what does IPO stand for
implant protected occlusion
describe IPO
- force along long axis of implant
- avoid non-axial loadings
- stable occlusion with narrow occlusal table
- reduce cusp height and inclines
- avoid splinting implants to natural dentition
- light contact in centric occlusion
T/F: force is along the long axis of a prosthetically driven implant placement
true
5% increase in torque for every ___ increase in implant angulation
10 degree
how do you minimize the occlusal table
- limit width
- select appropriate diameter implant or multiple implants
- avoid cantilevers
- 15% increase in torque for every 1 mm increase in horizontal offset
15% increase in torque for every ___mm increase in horizontal offset
1 mm
what does it mean to limit vertical cantilevers
this results in more prosthetic issues (looks like its being supported only on one end)
5% increase in torque for every ___ mm increase in vertical implant offset
1 mm
do studies show a relationship between crown:implant ratio and marginal bone loss after functional loading?
NO
what does it mean to minimize cusp height and inclines
reduce the lateral stress
30% increase in torque for every ___ increase in cusp inclination
10 degree
what does it mean to address parafunctional habits in regards to implant occlusion
eliminate premature contacts but expect increased risk for prosthetic complications
should you avoid splinting implants to natural dentition? why?
YES! there are differences in physiologic movement where tooth has 10x the mobility causing intrusion of natural tooth
if you have to use an implant split, what should you use
a rigid connector
what occlusal scheme for implant occlusion
canine guidance
what occlusal scheme if implant replaces canine
group function
is there evidence that alteration of current occlusal concepts is necessary when restoring dental implants
no
what should you strive for when looking at implant occlusion
- stable centric
- evenly distributed occlusal contacts
- no interferences during working/nonworking movements
- anterior guidance whenever possible
what is “whether implant is still in mouth”
survival
what is “clinical criteria to include mobility, radiographic assessment, ginigval and plaque indices”
success
what are criteria for implant success
- immobile
- no radiographic PA radiolucency
- vertical bone loss less 1.5 mm during first year, then 0.2 mm anually after 1st year of implant
- absence of persistent or irreversible signs and symptoms
for success, vertiical bone loss should be ___ during first year then ___ annually after 1st year of service of implant
1.5mm; 0.2mm
success rate of ___% at end of 5 year observation, ___% at end of 10 year period
85%, 80%
crestal bone loss may result from what
surgical trauma
what is a primary indicator of need for early intervention if >1mm loss occurs after prosthesis placement
crestal bone loss
do you need to see apex when takign radiograph of implant
not necessary
describe implant radiograph
parallel orientation, clear threads, abutment: implant connection clear and crisp
when to complete radiographs
- baseline - at restoration
- 6 months post-restoration
- 1 year post-restoration
- every 3 years (bare minimum) otherwise indicated due to clinical signs (but can do every year)
why is keratinized tissue desiereable
cleansibility, comfort of cleaning aids, more manageable/predictable esthetically, more resistant to abrasion/recession
describe probe depths of implants
- deeper than natural teeth (2.5-5mm)
- apply less pressure (fragile attachment apparatus)
- less reliable
- reveals tissue consistency, BOP, exudate
- BOP - indicates inflammation
BOP on an implant indicates what
inflammation
what is apparant with implant health
- no pain, purulence, signs of inflammation
- pink, healthy tissues
- probe depths in range of 2.5-5mm without BOP
- normal crestal bone levels
- immobile
what are peri-implant disease etiologies
plaque biofilm and lack of keratinized tissue
what is inflammation confined to mucosa surrounding an implant with no signs of loss of supporting bone
per-implant mucositis
what is inflammation around an implant which includes both soft tissue inflammation and loss of supporting bone
peri-implantitis
what is an implant without mobility, but affected by bone loss and pocketing
ailing
what is similar to ailing, but does not respond to therapy, worsening bone loss and pocketing despite therapeutic measures
failing
what is a mobile implant and must be removed
failed
is peri-implantitis slow or rapid progressing
rapid
what bacteria in peri-implantitis
gram negative anaerobic flora
what are risk factors for implants
smoking, poor oral hygiene, periodontitis
what is done for implant maintenance
plaque index, soft tissue assessment, restoration evaluation, radiographic eval, and scaling and prophy or implant maintenance
how is soft tissue assessment completed during implant maintenance
- palpation
- probing
- periodontal stability
- quality of tissue
what should you evaluate when palpating during implant maintenance
evaluate for presence of inflammation, purulence
how often to probe during implant maintenance
at leaset annually and more frequently in presence of inflammation or bone loss
during implant maintenance, what should you look at during restoration evaluation
stable restoration (absence of movement and residual cement), proximal contact, and oclusion
during implant maintenance, what should you look at during radiographic eval
assess bone levels and pathology
the study spontaneous open contacts shows importance of what
retained or occlusal guard post treatment
what are the specialized instruments used for implant maintenance
titanium scalers/probes
plastic scalers/probes
should proshteses be removed and resinserted; including cleansing of abutments and prostheses during implant maintenance
yes
