Implants

Question 1

Titanium biocompatibility

Answer 1

•	Tough, light and durable 
•	TiO2 surface 
•	Low corrosion 
•	Biocompatible 
•	Bioinert or bioactive?
•	Osseointegrating 
•	Biointeraction?
o	Protein absorption 
o	Calcium phosphate deposition

Question 2

Osseointegration from clinical perspective

Answer 2

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)

Question 3

Cement retained vs screw retained

Answer 3

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

Question 4

Types of implant bridges (3)

Answer 4

Multi-unit abutments
Fixture level screw retention
Cement retained bridge

Question 5

Multi-unit abutment bridges

Answer 5

+ 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

Question 6

Fixture-level screw retention

Answer 6

+ 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

Question 7

Cement retained

Answer 7

+ 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

Question 8

Types of implant retained dentures

Answer 8

Local abutments
Ball attachments
Milled bar
Magnets

Denture retained good for maintaining OH as comes in and out

Question 9

Implant retained denture - local abutments

Answer 9

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

Question 10

Implant retained denture - ball attachments

Answer 10

Retain denture via ball attachments

Different colours correspond to different degrees of stiffness

Question 11

Implant retained denture - milled bar

Answer 11

+ Greater stability

• requires more implants
• at least 15-17mm height needed

Question 12

Implant retained denture - magnets

Answer 12

• 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

Question 13

Guided tissue regeneration

Answer 13

• 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

Question 14

Flap design (2)

Answer 14

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

Question 15

Implant diameters

Answer 15

Narrow platform - maxillary 2
Regular platform - maxillary 1
Wide platform - molars

Question 16

Cover screw vs healing abutment

Answer 16

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

Question 17

How does the surface of a titanium dental implant differ from the bulk material?

Question 18

List the materials properties of titanium implants that are associated with good clinical performance

Question 19

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

Answer 19

** Branemark pioneered careful surgery and patient selection, whilst early implants didn’t

Question 20

Pre-planning: things to consider

Answer 20

Patients desires/expectations 
Medical history 
Social history 
Clinical examination 
Case-specific considerations
Radiographic examination

Question 21

Patients desires/expectations

Answer 21

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

Question 22

Medical history

Answer 22

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

Question 23

Social history

Answer 23

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

Question 24

E/O examination:

ab

Answer 24

Skeletal profile

Smile line - high (upper lip above cervical line), medium (papillary line visible), low (papillary line covered by lip)

Question 25

I/O: | cdef

Answer 25

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)

Question 26

Pre-implant surgery - ?

Answer 26

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

Question 27

Types of augmentation

Answer 27

Autograft - from self Allograft - from donor Xenograft - from animal Inorganic material - HAP, bet TCP

Question 28

Osseoinductive vs osseoconductive

Answer 28

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

Question 29

Techniques for WIDTH: (5)

Answer 29

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

Question 30

Techniques for HEIGHT:

Answer 30

``` Onlay graft Inlay graft Osseodistraction Short implants/all on 4 Zygomatic implants ```

Question 31

Inadequate width - small amount:

Answer 31

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

Question 32

Dual layer GBR technique

Answer 32

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.

Question 33

Inadequate width: small-mod amount

Answer 33

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'

Question 34

Inadequate width - mod-large amount

Answer 34

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.

Question 35

Risk of mandibular symphysis graft:

Answer 35

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

Question 36

Inadequate height

Answer 36

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

Question 37

Inadequate height: localised defect

Answer 37

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

Question 38

Inadequate height: maxilla

Answer 38

SINUS LIFT | Flap raised, piezo used to cut trap door, floor of sinus lifted, particulate bone graft layer

Question 39

Inadequate height: mandibular canal

Answer 39

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

Question 40

Alternatives: | All on 4 & zygomatic implants

Answer 40

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

Question 41

Failure modes of implants:

Answer 41

Mechanical/material Biological Appearance and function

Question 42

Mechanical/material failures:

Answer 42

``` Fractured porcelain Fractured bridgework Screw loosening Fractured abutment Fractured implant - rare Worn/broken clips - common Worn attachments - common ```

Question 43

Biological failures

Answer 43

``` 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 ```

Question 44

Aesthetic and functional failures:

Answer 44

``` Poor shape Poor colour Poor position Gum recession Black triangles Can't chew Lisp Pain and discomfort Proprioception ```