Implants Flashcards
Titanium biocompatibility
• Tough, light and durable • TiO2 surface • Low corrosion • Biocompatible • Bioinert or bioactive? • Osseointegrating • Biointeraction? o Protein absorption o Calcium phosphate deposition
Osseointegration from clinical perspective
3 month healing period - can be shorter in mandible as more dense bone
Avoid micro-movement
Can wear prosthesis on top but need to relieve to avoid pressure on implant
Check check stability with radiofrequency analysis (RFA)
Cement retained vs screw retained
Cement retained:
+ Better aesthetics
+ No chipping of access hole
- Associated with peri-implantitis due to cement
Screw retained:
+ Reduced risk peri-implantitis
- Chipping of access hole
- Less aesthetic
Screw retained less aesthetic due to screw hole - can be covered with composite but margins eventually stain. In anterior region this can be overcome by using Omnigrip driver which allows placement of screwdriver into curved channel at 25degrees
Types of implant bridges (3)
Multi-unit abutments
Fixture level screw retention
Cement retained bridge
Multi-unit abutment bridges
+ Allows engagement of internal channel
- Expensive (£180 per abutment)
Divergent implants placed, multi-unit abutment slots on implants, bridge slots on top of abutments and all screwed in through screw hole
(Implant/screw in bone, abutment (crown prep shaped) sits in screw, bridge fits on top of abutment and screwed on)
Having abutments is advantageous as if any issues with implant, can separate components and identify problem without messing around with implant in bone
Fixture-level screw retention
+ Avoids cost of multi-unit abutments
- Does not fully engage internal connection
- Stress on screws
- Bridge sits above implants, then crews pass through crown into implant channel. No anti-rotational device
Wouldn’t work for just one crown as presence of multiple screws/sites prevents crowns spinning
Cement retained
+ Engages with internal connection
+ Similar to standard crown and bridge work in terms of fit
Basically same part/mechanism as multi-unit abutments but final crown is cemented on instead of screw retained
- Cant be unscrewed - any problems, whole thing need to come off
- Risk of cementitis
Types of implant retained dentures
Local abutments
Ball attachments
Milled bar
Magnets
Denture retained good for maintaining OH as comes in and out
Implant retained denture - local abutments
Standard implants allow divergence of 17 degrees
If implants more divergent than this - extended male range allows 30 degrees of divergence
Range can go up to 60 degrees divergence however if this is case - should rethink implant placement
Implant retained denture - ball attachments
Retain denture via ball attachments
Different colours correspond to different degrees of stiffness
Implant retained denture - milled bar
+ Greater stability
- requires more implants
- at least 15-17mm height needed
Implant retained denture - magnets
- Usually solution for poor implant position
- Dont provide much retention
+ able to compensate for significant angulation
+ able to provide low profile if limited vertical space
Guided tissue regeneration
- Collagen is the most widely used membrane material today
- Typically derived from bovine (e.g. Geistlich) or porcine (e.g. Nobel Biocare) sources
- Small risk of adverse reaction and theoretical risk of disease transmission with possibility of religious or ethical objection
Flap design (2)
Papilla sparing/Sclar:
+ doesn’t raise flap papilla to papilla - avoids recession
+ scarring hidden at point of mucogingival junction
Sulcal incision:
+ avoids scarring
- risk of papilla recession
Implant diameters
Narrow platform - maxillary 2
Regular platform - maxillary 1
Wide platform - molars
Cover screw vs healing abutment
Cover screw screwed onto implant then gum stitches over so implant completely buried - protects from external environment, good when concerns about healing e.g. diabetes or case when GBR used. Requires second surgery at later date to change cover screw for healing abutment then further few weeks healing
Healing abutment - transmucosal. Gum heals as collar around tooth
How does the surface of a titanium dental implant differ from the bulk material?
List the materials properties of titanium implants that are associated with good clinical performance
Name a synthetic bone graft substitute
Which material is currently most widely used as a membrane for GTR
Which surgeon scientist is credited with birth of implantology
** Branemark pioneered careful surgery and patient selection, whilst early implants didn’t
Pre-planning: things to consider
Patients desires/expectations Medical history Social history Clinical examination Case-specific considerations Radiographic examination
Patients desires/expectations
Problem in their own words - don’t assume implants only option to satisfy expectations
Patient priority - functional/aesthetic
Patient understanding of risks and timescale involved, smile line etc
Medical history
Bisphosphonates
Steroids - alone no, but can compound effect of bisphosphonates
Diabetes
Immunosupressants
Radiotherapy - if area has undergone more than 60 Grays = higher risk implant failure & osteoradionecrosis - IMRT
Bone diseases - Paget’s, osteoporosis
Bleeding tendencies
Generally, only absolute contraindication is bisphosphonates/denosumab
Social history
20-300% increased risk of implant failure if smoker
Heavy smoker 15/day
Non-smokers failure risk is 3% failure
So max risk for smokers is 9%
However need to be warned of risks and consented
Is not an absolute contraindication but is for providing on NHS
Variation in practitioner acceptance
E/O examination:
ab
Skeletal profile
Smile line - high (upper lip above cervical line), medium (papillary line visible), low (papillary line covered by lip)
I/O:
cdef
c - horizontal and vertical space requirements
Horizontal - at least 3mm between implants, 1.5mm between implant-tooth
Vertical - screw retained = 5mm, cement retained = 7mm
Minimum 15-17mm if milled bar
d - access
Should be able to fit 2 fingers between opposing dentition for access for surgery
e - perio status
BoP, pocketing, review previous perio/recession
Hx of perio increases risk of peri-implantitis
Active disease contraindication for implants
f - 3D assessment of available bone/dimensions
Mesiodistal clinical space and surgical space
Apices of teeth - esp. after ortho if teeth been tilted and roots converge apically
Buccolingual - check by palpating, ridge map (w/callipers) or CBCT to assess buccal-lingual dimension
Vertical - 4mm safety margin for IDN (renton)
Pre-implant surgery - ?
To little bone to support implant in acceptable position
Too much bone - ridge reduction
Done if bone poor quality, make additional restorative space, remove knife edge ridges
Types of augmentation
Autograft - from self
Allograft - from donor
Xenograft - from animal
Inorganic material - HAP, bet TCP
Osseoinductive vs osseoconductive
Inductive - promotes/induces bone formation
Conductive - acts as scaffold for bone formation. Will need something osseoinductive around it to induce the formation
E.g. osseoinductive - bone chips taken from pt
E.g. osseoconductive - bovine particulate (xenograft). Will need addition of other things to induce bone
Techniques for WIDTH: (5)
Guided bone regeneration
Ridge split
Block graft
Narrow/angled implants
Taking study models and waxing up additional thickness needed for bone allows you see whether you’ll need small amount, moderate amount or large amount. This will influence what operation is done
Techniques for HEIGHT:
Onlay graft Inlay graft Osseodistraction Short implants/all on 4 Zygomatic implants
Inadequate width - small amount:
GUIDED BONE REGENERATION
Common and popular
Can be undertaken at same time as implant placement and done in GDP
Works by tricking natural bone into thinking its fractured
Normal fracture site - week 1 haematoma formation + release of inflammatory mediators such as IL-1, IL-6 & proteins e.g. BMP-2, PDGF, TGF-b (cytokines) which induce bone callus formation
Bone chips have large SA releasing these cytokines + introduce osteoblasts into area as matrix for new bone formation
Chips taken from pt = gold standard osseoinductive agent
Bovine derived mineral less soluble than grafted bone chips so combination of these ensures osseoinduction without risk of area resorbing later on
Week 17 - remodeling
Dual layer GBR technique
Bone chips - osseoinductive
Bone substitute e.g. Creos/Bio-oss - osseoconductive
Absorbtion of bone-conditioned blood makes bone substitute osseoinductive
Membrane over top to stop soft tissue contacting and resorbing graft material
Dual layer GBR - flap raised, bur holes aside implant to allow neovascularisation of bone layer as it heals, layer of bone chips on outside layer of implant (layer 1) then bovine particulate (layer 2). Bovine particulate compressed to allow blood from chips to saturate particulate so inflammatory mediators carried into area, membrane over top then close.
Inadequate width: small-mod amount
RIDGE SPLIT OSTEOTOMY
Trapdoor incision - incision across top of ridge then 2 lateral relieving incisions - care not to damage mental nerve
Then follow with standard drilling protocol but size of final osteotomy is undersized compared to width of implant allowing bone to be levered outwards - larger implant in smaller hole - ‘ridge split’
Inadequate width - mod-large amount
BUCCAL ONLAY GRAFT
Bone placed on top of buccal plate - bone harvested either from mandibular symphsis or ramus. Can take from iliac crest if large amount needed but poorer quality
Get recipient site ready to take bone, bur holes to promote angiogenesis over healing period.
Make incision in donor site, harvest bone using saggital saw. Screw hole made in recipient site and trauma screw used to screw donor bone into site.
Risk of mandibular symphysis graft:
Reduced sensitivity over chin
Scarring in buccal sulcus - fraenal tags
Chin ptosis - reduce risk by strapping chin
Damage to incisor/canine region - can accidentally apicect these teeth
Do incision through lower lip, leaving border of muscle above incision to allow muscle-muscle suturing - reduce risk of ptosis
Ensure cuts are below incisor region and leave 5mm safety margin to leave adequate blood supply for lower incisors
When block taken - divide into 2 to reduce risk of fracture if whole piece lifted out as one
Inadequate height
OCCLUSAL ONLAY GRAFT
If whole mandible is edentulous and significant bone needed
Ring of bone used like polo and ‘onlay’ onto ridge, screw into place
Inadequate height: localised defect
OSSEODISTRACTION
Cut made in bone to split bone then osseodistractor used with activator on top. Activator twisted which moves two pieces of bone apart
Favoured to occlusal onlay graft as, as bone moves, moves mucosa with it
Inadequate height: maxilla
SINUS LIFT
Flap raised, piezo used to cut trap door, floor of sinus lifted, particulate bone graft layer
Inadequate height: mandibular canal
NERVE REPOSITION
Mandibular canal can get in way of grafting so can lateralise inferior alveolar nerve to move it out the way so graft can be placed
Post-op testing to ensure no loss of sensation
Alternatives:
All on 4 & zygomatic implants
All on 4: placing implants at an angle posteriorly to avoid structures like mental nerve or maxillary antrum. Implants emerge further back so can place prosthesis further back
Zygomatic implants - when no posterior bone at all in maxilla can get support from zygomatic bones plus combination of anterior traditional implants
Failure modes of implants:
Mechanical/material
Biological
Appearance and function
Mechanical/material failures:
Fractured porcelain Fractured bridgework Screw loosening Fractured abutment Fractured implant - rare Worn/broken clips - common Worn attachments - common
Biological failures
Plaque/calculus Gingival inflammation Gum recession Peri-implantitis Failure of implant to integrate Pocketing Bleeding Pus exudate Bone loss Tooth movement Damage to nerves/teeth
Aesthetic and functional failures:
Poor shape Poor colour Poor position Gum recession Black triangles Can't chew Lisp Pain and discomfort Proprioception
