Considerations for implant-retained complete denture in the mandible [6]
Ridge thickness
Ridge crestal bone contour - if has ledges or protrusions will need corrective surgery
Mental foramen - superficial will need to be careful, leave a 5mm safety margin between incision and foramen
Muscle attachments
Occlusal stability
Verticle occlusal dimension
The difference in implant placement for crowns/bridges vs complete dentures
Implants for dentures need to be more lingual and parallel
Titanium implants - about the material
BBOLTT Biocompatible Bioinert Osseointegrating Low corrosive, low toxicity (TiO2) Tough, light, durable TiO2 forms within a second
How does osseointegration for implants work
(+HA coating) [6]
- TiO2 surface interacts with the body’s proteins in a normal way e.g. adsorption and desorption
- Proteins that stimulate pre-Ob –> Ob differentiation
- Ob lay down lamina and gets made into new bone
- New bone gets remodelled
- Space between implant and bone gets filled
Coating of hydroxyapatite on the surface of the implant is bioactive/osteoinductive and makes osseointegration happen quicker
Implant components
Implant
Abutment
Screw
Crown
Abutment inserts into the implant (+antirotation device) and the screw holds them together.
Crown screwed/cemented on.
Types of implant failure [4]
Failure to osseointegrate
Peri-implantitis
Cementitis
Mechanical failure (uncommon)
Types of implant systems for crowns/single tooth
Cemented
- Better aesthetics
- No risk of chipping of the access hole
- But can leak/excess can cause cementitious or peri-implantitis if reaches gingiva or implant
Screw retained
- Worse aesthetics if the screw is buccal so need to change the angulation
- Access hole needs a restoration - risk of chipping, need to check occlusion carefully
- But no risk of cementitious/more hygienic
Types of implant systems for bridges/multi-unit
Divergent implants - abutments will need to have a “crown prep” e.g. tapered sides and more allowance so the anti-rotation device can work
Cemented - can engage anti-rotation, but cement risks (cementitious or peri-implantitis) and is harder to remove (can’t unscrew)
Fixture level bridge - screw holds the bridge directly to the implant i.e. no abutment into the crown - screw is carrying all the force so less stress distribution and more likely to cause screw fractures or implant and harder to manage. But cheaper. No anti-rotation but this is fine for bridges.
Types of implant systems for dentures
Milled bar
- Less hygienic and needs enough occlusal verticle height because it is thick
- Needs more implants
- But very retentive and stable - can’t rock or tilt
Locator abutment
- Male piece on the denture fits onto the external and internal parts of the locator abutment on implant (or just external if need more allowance for divergent implants)
- Stable
- Can be removed and cleaned
Ball attachment
Magnet
- Cheaper and easier
- But less good/stable
- For when you don’t have enough occlusal vertical dimension
- For poor implant placement/poor planning
Implant surgery steps (brief)
- Flap
- Papilla sparring has more scaring
- Sulcal has less scarring but more risk of papilla recession - Select implant - wider for posterior, anterior should be narrow to match neck of the tooth.
- Drill - in increasing sizes, use lots of water
- Place implant and cover
- Healing
- Impression
- Of abutment and implant
- Sent to lab and crown made to fit the gingival contours
Healing of an implant
- 3 months
- No occlusal forces, movement or pressure
- Temporary crown but needs to be out of occlusion
- Radiofrequency to see the level of osseointegration of the implant
Types of covers after implant placement surgery
- Cover screw for complete gingival coverage if worried about healing e.g. GTR, diabetes, thin bone. But then will need a healing abutment
- Or a healing abutment with a hole
GTR
Membrane placed between soft tissues and bone/graft to stop the down-growth of the epithelium (which grows faster) and to give time and space for the bone to form.
Resorbable membranes are best bc don’t need a 2nd surgery
What is a dental implant
Metal device surgically placed into the bone to act as an anchor for a crown
Interacts with soft tissues and mineralised tissues
Medical history considerations before implant planning
MRONJ or ORN risk e.g. bisphosphonates Bleeding disorders Mental health Can they withstand long procedures e.g. severe learning disabilities Bone diseases e.g. osteoporosis Immunosuppression Anything that will reduce healing e.g. diabetes, steroids Smokers
Clinical exam (E/O and I/O) before implants (brief)
E/O - smile line and profile
I/O
- verticle and horizontal clinical space for the abutment/crown
- Radiographical verticle and horizontal space for the implant
- Ridge thickness
- Perio disease
- Access for the surgery
Smile line (high, medium, low)
High = gingival showing Medium = just papillary line showing Low = no gum
Space requirements for implants
1.5-2mm of healthy bone all around the implant to provide enough blood supply for healing (double between 2 implants)
OVD space - 5mm for screw-retained, 7.5mm for cement-retained, 15mm for milled bar
Need enough distance from special structures e.g. IAN, sinus - 3-4mm
Need enough verticle distance for the implant (8mm for uppers)
Steps for implant placement
- CBCT/planning beforehand - to see bone and surrounding structures
- Remove soft tissue
- Drill with increasing sizes to the correct depth
- Place implant
- Close
When do u need to do pre-implant surgery
If there’s not enough bone to support the implant in a good position
Or if there’s too much bone
General principles for pre-implant surgery
Plan using CBCT/PA, etc.
Stir up blood by drilling and stimulate healing and integration that way
Fix graft
3-6 months of healing
Types of augmentation techniques for implants
GBR Block grafts Ridge split osteotomy Sinus lift SARME
GBR for increasing bone width before implants
For small increases
Use Osseo-conductive and Osseo-inductive materials together
- Bovine particles or Bio-oss provides a scaffold to stabilise the blood clot and bone grows into it
- Bio-glass/ bone chips attract Ob and BMP = bone formed
Place a membrane on top e.g. resorbable xenograft or collagen membrane to separate the 2 and stop down-growth of scar/epithelial tissues
Can be done at the same time as implant placement
Ridge split osteotomy for increasing bone width before implants
Split ridge where you want to place the implant, with relieving incisions on one side.
Pull this side back and place implant + bone chips
