Implants Flashcards
1
Q
What is an implant?
A
It is a metal device that is surgically placed in the bone and it acts as an anchor for an artificial tooth or teeth. They are unusual as they penetrate the mucosa and interface with both soft and mineralised tissues.
2
Q
What biomaterials/medicinal devices may be used in implant surgery?
A
- Permucosal dental implants are increasingly common
- Bone grafts and/or bone graft substitutes
- Membranes e.g. PTFE or more likely collagen
- Sutures
3
Q
Is dental implantology in the GDCs specialist list?
A
No because of its multifactorial nature. 5 million implants placed in the USA per year.
4
Q
What are the features of titanium as an implant material?
A
- Biocompatible
- TiO2 surface - forms oxide layer on the surface
- Low corrosion due to TiO2 on surface
- Tough, light and durable
- Bioinert or bioactive (tissue bonding)
- Osseointegrating - achieve stable fixation in bone tissue
- Biointeraction - protein adsorption, calcium phosphate deposition
5
Q
What are the options for managing a missing tooth?
A
- Accept gap and leave
- Denture
- Bridge
- Implant
6
Q
What is the structure of an implant?
A
Implants are sometimes called fixtures. There is an internal channel and an abutment (like a post) which slots into the channel. It screws in place and then a crown is screwed on top. Cotton wool pellet or PTFE tape can be placed on the screw to allow it to be unscrewed if required. There is a trichannel system or conical connection. Tri-channel is when the abutment is a triangular shape which prevents rotation once placed in the channel. A conical connection is round at the neck but hexagonal further down to prevent rotation. The circular shape is better for more even stress distribution.
7
Q
What are the biological events at the bone implant interface that are associated with osseointegration?
A
- Protein adsorption
- Protein desorption
- Surface changes
- Inflammatory/connective tissue cells approach the implant
- Possible release of matrix proteins and selected adsorption of proteins e.g. BSP and OPN
- Formation of a lamina limitans/adhesion of osteogenic cells
- Bone deposition on bone and implant surfaces
- Remodelling of newly formed bone
These processes are dependent on whether there is damage when the implant is placed. It is still not certain which of this is the most important for clinical success.
8
Q
What do bioinert and bioactive mean?
A
The terms originally described bone-biomaterial interaction only but now can be used to describe dental materials. Bioinert described a material that once placed in the human body has minimal interaction with surrounding tissue e.g. SS and titanium. Bioactive has an effect on the surrounding tissues. Bioinert is slightly misleading as no material is totally inert following placement into a biological environment. Some authors claim titanium is bioactive.
9
Q
What is hydroxyapatite in bone augmentation?
A
Some materials are bioactive/osteoconductive and hydroxyapatite is a calcium phosphate ceramic that encourages new bone tissue formation/healing following implantation into established bone tissue. Bone forms directly on the surface whereas with other materials you can get a fibrous capsule surrounded by bone. The bone-hydroxyapatite interface is direct, forms relatively quickly and is capable of fixing a medical device in bone tissue (osseointegrating). Calcium phosphates are widely used synthetic bone graft substitutes but not as effective as bone grafts (clinical material of choice for implants). Calcium phosphates are too brittle to be used alone as load bearing implants so they are used in particulates on the surface of metallic devices.
10
Q
What is the clinical perspective on osseointegration?
A
Osseointegration has a 3 month healing period. Micro movement should be avoided due to fibrosis around the implant rather than bone. You can wear a prosthesis over the top but you need to relieve it to avoid pressure on the implant. Due to dense bone in the mandible some clinicians have shorter healing protocols. You can check the stability of the implant with radiofrequency analysis RFA.
11
Q
What is the clinical application of implants?
A
- Crowns
- Bridges
- Dentures
12
Q
What are the types of implant retained crown?
A
Crowns:
- Cement retained are more aesthetic, no chipping of access hole but there is a risk of peri-implantitis as the cement can pass down into the gingiva
- Screw retained - less aesthetic, risk of chipping access hole for screw but reduced risk of peri-implantitis
Screw retained has hole labially. angled screw channel allows screw hole to be palatal/lingual.
13
Q
How can material selection cause implant failure?
A
Implants may fail to osseointegrate (short term) or may fail due to peri-implantitis associated with bacterial colonisation. Some authors claim specific implant surfaces favour/inhibit biofilm formation. Cementitis is peri=implantitis like condition where residual luting cement has caused local inflammation and bone loss. It is associated with reversible cementitis that subsides after removal of the material. No one dental material appears to be soley responsible. Implants can also fail due to other reasons such as mechanical failure but this is a small number.
14
Q
What are the types of implant retained bridge?
A
- Multi-unit abutments - this involves separate abutments and lots of screws, allows non-parallel implants, allows engagement of internal channel, expensive (£180 per abutment)
- Fixture level screw retention - avoid cost of multi-unit abutments, does not fully engage internal connection, stress is placed on screws
- Cement retained bridge - similar to standard crown and bridgework in terms of fit, engages internal connection, cannot be unscrewed so would need to be drilled and new prosthesis made, risk of cementitis
15
Q
What is the role of abutments in stress relief?
A
The abutments distribute the stress around the suprastructure rather than the substructure. So stress distributed to things that can be replaced.
16
Q
What are the types of implant retained denture?
A
- Locator abutments
- Ball attachments
- Milled bar
- Magnets
17
Q
What are locator abutments?
A
These are used to improve retention (mostly) and stability of the denture. They are simple, cheap and effective and work like a press stud. On the underside of the denture there is a male locator unit. It is an internally and externally engaging locator male unit as it attaches to the inside and outside of the female unit on the implant to increase retention. It allows 17 degrees of divergence so is effective if implants are placed in the correct position. There has been the development of extended range males which do not engage the female unit internally and allow 30 degrees of divergence. There are also male units which allow 60 degree divergence.
18
Q
What are ball attachments?
A
Angle isn’t as important so don’t need to worry about divergence. Ball shaped attachment.
19
Q
What is a milled bar?
A
This increases stability whereas previous options mainly help retention. Implants are linked by a parallel bar and there are locator abutments on top. This means there is one path of insertion so lateral forces are resisted and braced by the bar. It requires more implants and the denture requires a minimum of 15-17mm height (depending on attachment height) as it needs to house the abutments and the milled bar. See if patient can tolerate increased OVD, if not you may need to remove bone.
20
Q
What are magnets?
A
They are generally a solution for poor implant placement. They are able to compensate for significant angulation and provide a solution if there is limited vertical space.
21
Q
How is guided bone regeneration used in implant dentistry?
A
It is used in 50% of placements. There may be exposure of parts of the implant (threads). Particulate can be placed over the surface to augment bone. Collagen membrane can be placed over particulate to protect it from fibroblasts from the overlying soft tissue. So the particulate can only be populated by osteoblasts.
22
Q
How are membranes used in implant dentistry?
A
They exclude soft/scar tissue from the site where bone regeneration/healing is needed. It is also called guided tissue regeneration or guided bone regeneration. The materials used all have problems and do not have any intrinsic regenerative properties other than their barrier function. They can be used with bone graft or synthetic bone graft substitute. The types:
- Non-resorbable - Goretex
- Resorbable synthetic - PGA
- Resorbable natural - collagen (market leader)
23
Q
How are collagen membranes used in implant dentistry?
A
It is the widest used membrane material. It is derived from bovine e.g. Gesitlich or porcine e.g. nobel biocare sources. There is a risk of adverse reaction, theoretical risk of disease transmission and religious/ethical objections.
24
Q
What are the flap designs for implant placement?
A
- Papilla sparing - prevents recession of papilla, scarring is hidden at point of mucogingival junction
- Sulcular incision - no scarring, may get recession of papilla due to bone dropping back
25
What are the different implant diameters?
- Narrow 3.5mm
- Regular 4.3mm
- Wide 5mm
Narrow is used for incisors and regular is used for central incisors and canines. Wide is used for molars. There may be an undercut around the crown which can lead to peri-implantitis. Explain cleaning to patient and the importance of this.
26
What is a cover screw and healing abutment and when are they used?
A cover screw is placed into the implant and the suture placed on top. A healing abutment is then placed at a later date. A healing abutment can be placed in most cases straight away. Cover screws are used when healing may be slower e.g. in diabetics so that the implant is completely sealed away.
27
How are impressions taken of implants?
Healing abutment is removed and impression coping screwed into place. An impression is taken of the implant in the same way as for crowns and bridges. You then remove the impression coping and send it to the lab (screw the healing abutment back in). An impression analogue is used in the lab.
28
What should be considered when planning for implants?
- Patient desires/expectations
- Medical history
- Social history
- Clinical examination
- Case specific considerations
- Radiographic examination
29
What should you consider in terms of the patients expectations/desires before implants?
- Problem in patients own words
- Discuss options of gap, denture and bridge
- Patient needs to be aware of timescale and risks
- Take into account patient's smile line
- What is important to the patient - function/aesthetics
- Does the patient have reasonable expectations?
30
What medical history is relevant to implants?
- Bisphosphonates mean there is a risk of osteonecrosis of the jaw
- Poorly controlled diabetes - 2-3% increase in chance of implant failing
- Immunosuppressed - reduced healing capacity
- Steroids - healing is reduced and patient may also be on bisphosphonates
- Bone disease - osteoporosis, Paget's disease - drilling the bone will be difficult and may overheat bone leading to osteonecrosis
- Recent radiotherapy - osteoradionecrosis
- Other general risks related to surgery - bleeding disorder
- Only absolute contraindication is IV bisphosphonates/denosumab
31
What social history is relevant to implants?
- Smoking - 20-300% increase in failure risk (relative risk)
- Healthy non-smoker has a 3% chance of failure (97% success)
- So maximum risk is 9% (91% success)
- It is not an absolute contraindication but it is for NHS
- Heavy smoking is >15 cigarettes a day
- Some practitioners will only accept non-smokers, some <5 and some <15
- Need to warn patient of the risk
32
What should be looked at in a clinical examination for implants?
```
EO:
- Facial profile - skeletal pattern
- Smile line
IO:
- Space available - horizontal and vertical
- Access (two fingers between teeth you have enough room)
- Periodontal support
- 3D assessment of bone available
```
33
How can skeletal pattern affect implants?
Class III tends to be a square jaw which can be an issue. Implants may be placed far forward in the square part of the jaw which may lead to failure.
34
What is the smile line?
It is the relationship between the upper lip and the cervical line. A high smile line is when the upper lip is above the cervical line. A medium smile line is when the cervical line is not exposed but the papillary line is visible. A low smile line is when the upper lip covered the papillary line.
35
What horizontal space requirements are needed?
Horizontally you need a minimum of 3mm between implants and a minimum of 1.5mm between implant and tooth. This is because of the blood supply to the teeth. Implants are dependent on blood filtering between the implants so there needs to be sufficient space. If sufficient space is not left there may be recession, loss of interdental papilla as the bone shrinks back. We need 1.5-2mm between implants and the labial aspect of bone. Implants are about 4mm in width and as we need 1.5mm between teeth, there is 7mm minimum width overall. Mirror handle is about 7mm
36
What vertical space requirements are needed?
For a screw retained restoration you need 5mm and for a cement retained restoration you need 7.5mm. Minimum of 15-17mm height for a milled bar.
37
How do you assess periodontal status before implant placement?
- Bleeding on probing
- Pathological pocketing
- Review previous CPITN/evidence of recession (community periodontal index of treatment need)
- History of periodontitis increases risk of peri-implantitis
- Active disease contraindicates implant placement
38
How do you assess the 3D bone dimensions prior to implants?
- Mesiodistal
- In the mouth - clinical/restorative space
- In the bone - surgical space
- Buccolingual - probably the most critical defining factor for whether implant is feasible in the anterior zone. You can palpate, ridge map (ridge mapping under LA) and get CBCT to asses bucco-lingual dimension
- Vertical
39
Is it easier to place implants in a basal bone or alveolar bone?
When bone resorbs it leaves the basal bone behind. The basal bone will be broader than a little bit of alveolar bone so better for implants. If there is a little alveolar bone you may need to reduce it down.
40
What limits the height of bone in the maxilla and mandible?
The maxillary antrum will limit the height of bone in the maxilla. The minimum height is 8mm for standard implants. For IDN you need a 4mm safety margin. You can go less than 2mm but there is increased risk.
41
How are implants placed?
- Implants have depth markers
- Precision drill is used to mark out the crest so there is accurate placement of drills
- Then use drill with depth markers
- Then choose thickness of implant to use - use narrow and go up to wide so bone doesn't overheat
42
What are the adjuvants to successful placement of implants?
Stents make sure drill goes in the right direction.
| There is CT guided surgery.
43
Why is pre-implant surgery done?
- If there is too little bone to support an implant in an acceptable position
- If there is too much bone - ridge reduction
44
What are the augmentation techniques?
- Sinus lift
- Block graft
- Guided bone regeneration
- Zygomatic implants
- Ridge split
- Use of narrow/short implants
45
What are the augmentation types?
- Autograft - get bone from somewhere else on the patient
- Allograft - take bone from someone else, need to decellularise to prevent rejection
- Xenograft - taking bone from an animal
- Inorganic material - Beta TCP, HAP
46
What is osseoconductive and osseoinductive?
Osseoinductive promotes bone formation. Osseoconductive serves as an insoluble scaffold and doesn't form any bone.
47
What are the techniques for lack of bone width and height?
Width:
- Guided bone regeneration
- Ridge split
- Block graft
- Narrow/angled implants (technique to compensate)
Height:
- Inlay graft (type of block)
- Onlay graft (type of block) not very predictable
- Osseodistraction
- Short implants/all on 4 (technique to compensate)
- Zygomatic implants (technique to compensate)
48
What may cause inadequate width?
Often the buccal plate resorbs causing inadequate width.
49
What are the general principles of augmentation procedures?
- You need to plan using a diagnostic wax up and stents so you know what technique to use
- Raise a flap and distress the bone surface by drilling into it
- This is to stimulate the graft site and there is neovascularisation and angiogenesis. Now there is a path where blood vessels are to provide blood supply to new bone
- It also allows the graft to integrate into the bone
- The fix graft over surface of bone and in 3-6 months place the implant
50
What treatment is done to add a small amount of bone width?
We can use guided bone regeneration. Particulate is placed over the implant and then membrane is placed over this which will dissolve. This protects and stabilises the underlying particulate. It also prevents fibroblasts from the overlying soft tissue from passing into the particulate and causing fibrosis rather than bone formation. There can be apical fenestration or coronal fenestration (implant showing through bone). GBR improves aesthetics with coronal fenestration - black margins.
51
How does bone heal?
There is a fracture of bone and there is clot formation. There is an inflammatory response related to the release of inflammatory mediators from the broken bone surface. The inflammatory mediators are very specific. Initially you get interleukin 1 and 6 IL1/IL6. This is in the inflammatory phase and leads to the recruiting of cells, initiating repair cascade and stimulate angiogenesis. IL6 causes bone resorption. Then there is release of other mediators such as BMP2, PDGF and TGF-B which cause callus formation. The hard callus is wider than the bone. IL1 and IL6 increase again during remodelling.
52
What are bone chips?
It is important to use bone chips to get bone to infuse around the scaffold. We take bone scrapings which have a large surface area of damage to release cytokines and inflammatory mediators. We mix them with blood so that the blood contains lots of inflammatory mediators and it is called preconditioned blood. Now the bone chips and blood are osseoinductive.
53
What is the dual layer guided bone regeneration technique?
The bone chips are placed over the implant. Then we place particulate over the top as the scaffold. The scaffold is compressed to allow blood to leach into the scaffold. Often the scaffold is bathed in the preconditioned blood before being placed. The scaffold cannot be dissolved away so prevents new bone dissolving. Then we place a membrane over the top. The scaffold is xenograft and the bone chips are autograft.
54
What are the aims of the dual GBR technique?
- Bone chips are osseoinductive
- Scaffold/bone substitute is osseoconductive e.g. bio-oss/creos
- Absorption of bone conditioned blood makes bone substitute osseoinductive
- Membrane over the top to prevent soft tissues contacting and resorbing grafted material
55
What is ridge split osteotomy?
It is used to add a small-moderate amount of bone width. It is a process of opening out the bone and making it broader. You make a crestal incision and two lateral incisions to make a trap door. You level the bone buccally and then start drilling for the implant.
56
What is a buccal onlay graft?
It is used to replace a moderate-large amount of bone. This has more morbidity than other techniques. Bone is distressed and bone graft is placed buccally. The bone graft is autograft and can be taken from the mandible. It is often taken from the ramus or mental region (symphysis). The mental nerve and IAN are at risk.
57
What are the mandibular symphysis graft complications?
- Reduction in sensitivity over chin
- Chin ptosis
- Scarring in buccal sulcus - fraenal tags
- Damage to teeth - cut of apices or cause necrosis by cutting off blood supply
Can do iliac crest graft but quality of bone is poorer.
58
What is an occlusal onlay graft?
Augmenting bone height is unpredictable. You take a large amount of bone from the hip or rib (poor quality bone). You add this to bulk out the height of the bone but in general this doesn't work as you are augmenting height and the bone is of poor quality.
59
What is osseodistraction?
This is used for a localised defect of bone height. You cut the bone and separate it from the basal jaw. You leave the bone attached to the mucosa to maintain a blood supply. You attach an osseodistractor to both pieces of bone. You expand the bone rapidly to where it should be by screwing the distractor and moving the bone over a couple of weeks. You can move it 5mm. It acts like an orthodontic expander. Healing bone will chase after the moving block of bone.
60
What is the sinus lift trapdoor technique?
This is an inlay graft into the maxillary sinus. It is more predictable because it is a protected area in the maxillary sinus. You move the sinus lining out of the way and place bone particulates. Piezosurgery device is used for sinus lift.
61
What anatomy may we look at moving prior to implant placement?
Nerve repositioning may be used to move the nerve out of the way. You assess the nerve and lateralise it and place an implant in the bone left behind. It can then go from the crest to the basal bone without damaging the nerve. But his carries a high risk.
62
What are the alternative compensating techniques for bone height?
- All on 4 is when 4 implants are placed with the 2 posterior ones placed at an angle to compensate for where you cannot go due to nerve
- Zygomatic implants - using zygoma to support implant (implant at an angle)
63
What does the McGill consensus statement 2002 say about dentures and implants?
That in the mandible a conventional denture is no longer the first choice of treatment. A two implant overdenture is the first line of treatment.
64
When is an implant retained overdenture suitable on the NHS?
- Instability despite a well adapted set of dentures
- Denture intolerance:
- Severe gag reflex (reduced palatal coverage)
- Ongoing pain with well adapted dentures
65
What should be involved in a clinical assessment for implants?
- Denture in place and outside the mouth
- Residual ridge
- Mental nerve
- Neutral zone
- Radiographic assessment
66
What should be assessed with regards to the denture prior to implants?
- Adaptation to ridge
- Margins
- Occlusal stability
- Overclosure
- Acceptable fit
May need to remake denture
You need to look at the denture thickness:
- Thickness for supragingival component of locator abutment
- Thickness for locator housing
- Thickness for overlying denture
- Height overall should be a minimum of 8.5mm to allow implant retained denture
- When assessing height it is not flange to occlusal tip it is fitting surface to occlusal tip
67
What are the space requirements for the different types of attachment?
- Bar - 15mm
- Ball - 10mm
- Locator - 8.5mm
68
What should be assessed with the residual ridge?
- Buccolingual width - if narrower than implant this is problematic
- Variation in crestal contour - may limit available space for denture components, may need to be addressed surgically
- Mentalis insertions and exostoses - mandible resorbs back to basal bone, anteriorly you get two prominences where the mentalis muscles attach. If you place the implant too far labially you will get ulceration due to muscle.
69
Why does the mental nerve need to be assessed before implants?
- The mental nerve affects how far distally implants can be placed
- Superficial mental foramen means a crestal cut carries a risk of nerve damage
- A radiograph is important
- Place the implant more anterior so you do not need to cut in this area
- Or you can do CT guided surgery
The mental nerve is between lower 4 and 5 in the general population. It is apical to the lower 5 in Chinese subpopulations. The anterior limb of IDN curves back before exits mental foramen so the mental foramen is not the most anterior part of the nerve. Nerve surrounded by periosteum.
70
What radiograph is needed for implants for an overdenture?
An OPG is suitable for a few locator abutments. If the height of the mandible is a little short on the OPT a CT scan can be taken to look in 3D.
71
How are implants positioned for an overdenture?
Positioning of the implants is different than for crowns and bridges. Implants are placed and emerge within the fitting surface of the denture. They should be in the centre of the denture fitting area or slightly lingual. They need to be near parallel to prevent wear of locator male units. A midline orientation marker can be used to ensure parallelism and this is drilled into the midline. Reference points for the orientation marker and placement of implants are nose, philtrum, central incisors, frenum. Precision drill is used and this allows assessment of safety from mental foramen. 5mm anterior to mental foramen is recommended. Make sure driver of drill is parallel to midline orientation marker when placing implant.
72
How do you decide the thickness of the locator abutment?
The healing abutment is changed for a locator abutment. You can use the height of the healing abutment to work this out - add an extra mm or 2. Alternative use a perio probe to measure depth. Depending on how divergent/parallel the implants are we select a locator male or extended range locator male.
73
What is a locator processing pack?
The metal housing is placed in the denture and processed. There are three different options of male unit and try each one to see which fits best. There is the processing insert and O ring spacer.
74
What is done during denture adjustment/chairside reline?
Metal housing is cast into denture. The processing insert fits into the housing when processing is taking place. It is then removed. O ring spacer is placed over locator abutments which protects it and prevents acrylic being pressed around implant. The processing insert is then placed over implant. Separator is painted on fitting surface so that acrylic doesn’t stick to fitting surface. Cold cure acrylic painted into reliefs. Then denture is placed over with acrylic in. processing insert will come off with denture.
75
What affects the success of root canal treatment?
Look at success rates in notes.
Root canal treatment reduces in success by 50% if there is periapical pathology. It reduces a further 14% for every 1% increase in size. It reduces by 12% for every 1mm short of the apex.
76
What are the main determining factors in choosing between treatment options?
- Restorability of the tooth (Tooth restorability index)
- Resistance and retention form for crowns and bridges
- Structural durability of the supporting structures
- Periodontal support and health
- Cleansability and maintenance
- Willingness for surgery and maintenance
- Overall risk
77
Why does resistance and retention form affect your choice of treatment?
Resin cements help overcome problems but a ferrule is still considered critical. A ferrule of 2-3mm is considered critical. It is more important in anterior teeth and on resisting surfaces in guidance (e.g. palatal of uppers). Look at paper - rethinking ferrule.
78
Why does structural durability of supporting structures affect choice of treatment?
A root filled tooth is more likely to fracture at the cervical margin. This becomes more significant when considered cantilevered pontic. A post and core can also predispose to vertical root fracture.
79
Why does periodontal support and health affect the choice of treatment?
Inappropriate support will lead to increased mobility and failure of the rigid components or fracture of abutments. There can be debonding of a retainer and an uneven distribution of loading on the abutment teeth. Abutment teeth are more prone to periodontal inflammation.
80
Why does cleansability and maintenance affect choice of treatment?
Partial dentures are likely to cause root caries in the absence of good oral hygiene. They also accumulate plaque and predispose to gingivitis, but not necessary periodontitis. Peri-implant mucositis and peri-implantitis are huge problems. 60% have peri-implant mucositis and 20% have peri-implantitis. The best treatment for peri-implantitis is open flap debridement.
81
Why does willingness for surgery and maintenance affect choice of treatment?
Patients must be aware how implant therapy works in terms of planning and placement. It normally involves 2 surgeries and sedation can be used. It may require grafting from donor sites. There is rehabilitation and maintenance.
82
What is the effect of partial dentures on oral health?
Look at papers in notes.
Evidence shows they can increase plaque, gingivitis and risk of root caries. There is no clear risk of periodontitis. They can improve quality of life. However they do not necessarily cause the loss of further teeth if well maintained. If OHI well managed they are successful. If partial dentures simply given to patient 57% show higher root caries.
83
How should periodontal health be assessed before confirming the treatment plan?
A full periodontal assessment should be carried out. At a minimum a BPE should be carried out and there should be recent radiographs showing degree of bony support available and whether there is any pathology associated with the standing teeth.
Individual periodontally involved teeth (active disease or advanced bony loss) may not be suitable for supporting crown and bridge work or indeed a tooth borne prosthesis.
84
How should occlusion be assessed before treatment planning?
Clinical assessment of occlusal contacts, guidance patterns and whether there are any occlusal anomalies is important. Helps to determine the risk of rehabilitating with crown and bridge work.
85
Why are teeth retained for overdentures?
- Proprioception
- Increased stability/retention
- Maintenance of alveolar bone height
- Psychological benefit
- Increased biting force and accuracy
- Less mucosal coverage
86
What are the complications of implants?
- Bone loss >2mm over 5 years - 5%
- Screw or abutment loosening over 5 years - 9%
- Loss of retention over 5 years - 4%
- Fracture of veneering material over 5 years - 4%
look at systematic review in notes.
87
What is the difference between long term looseness and immediate loosening of an implant?
If an implant has been loose for a long time it will have been moving back and forth repeatedly leading to fatigue and eventually fracture. The fracture will be unfavourable leading to deformation. If immediate looseness this may be a loose screw which can be fixed. But if it is not fixed quickly there will be fatigue, fracture and deformation. Clicking when chewing may also suggest looseness.
88
What is the structure of an implant?
There is the implant/fixture, abutment screw, abutment, prosthetic screw and crown.
89
Why might the patient be disappointed after placement of the implant and how is this avoided?
They may expect to see a tooth but the healing abutment is placed after implant placement. The patient needs to be informed of this prior to treatment for informed consent.
90
What is the main difference between screwing on the crown vs cementing it?
If it is screwed in it can easily be unscrewed if there is a problem. If it is cemented it will need to be cut off. The design influences the maintenance.
91
How do you examine implants?
History first then clinical examination:
- Soft tissues - inflamed
- Percussion
- Mobility
- Pocketing - may be normal as abutment is coming through mucosa
- Pus - palpate and see if pus comes out
- Radiograph - needs to be parallel to implant and need to see threads to be able to measure bone
92
What are the different failure modes?
- Mechanical/material
- Biological
- Appearance/function
- Patient satisfaction
- Early/during/after/delayed/long term - when it happens is important
93
How can the implant mechanically/material fail?
- Fracture of porcelain
- Fracture of bridgework
- Screw loosening
- Fracture of screw
- Fracture of abutment
- Fracture of implant
- Worn clip
- Worn attachment - locator, magnet
94
How can the implant biologically fail?
- Plaque and calculus accumulation
- Gingival inflammation
- Pocketing
- Bleeding
- Recession
- Pus exudate
- Bone loss
- Peri-implantitis/infection - OHI, smoker
- Damage to nerve/teeth
- Tooth movement
- Failure to integrate
95
How can the implant fail in terms of appearance/function?
- Poor colour
- Poor shape
- Poor position
- Recession
- Black triangles
- Lisp
- Pain and discomfort
- Loss of proprioception
- Can't chew
96
How is the model for implants constructed in the lab?
- There are impression copings in the impression taken
- Silicone separator is applied to impression for rubber gum technique
- Fixture head replicas are screwed onto the copings (don’t use real implants/abutments in lab)
- Rubber gum material added around replicas
- Model cast in die stone
- You then have the model with healing abutments in place
97
What is model verification?
It makes sure the model is the same as the mouth - very important step.
- We use metal components that fit over abutments, screw them down and make sure they fit
- Then build a bridge between replicas using dental floss and then autopolymerising resin to join two components
- Then section the beam/bridge as the resin contracts when it sets
- Then rejoin it so the contraction is only over 0.5mm ish rather than the whole span of the beam, this eliminates the tension
- This produces a passive, fitting verification beam which can be used on clinic
- This can be tried in with light finger pressure only as it is plastic
98
What are the types of fixed beam construction?
- Cast gold alloy beam
| - Procera implant beam
99
What is gold beam construction?
This is a gold beam joining implants for use with dentures. This technique is historical now - use CAD-CAM. Do a tooth try in on the verified model and then a buccal and lingual lab putty indexes to show where teeth are. Than place gold cylinders over implants and duralay pattern is built up over these. Pattern is sectioned and rejoined as before. Finished pattern is waxed over duralay. Weigh it to work about amount of alloy required. Sprue the pattern and then place in metal casting ring and invest. Casting is cleaned. Final wax try in where teeth are re-waxed over metal bar. Converted to acrylic and polished. Protect connections when polishing. Spot grind occlusion ready for polishing.
100
What is procera implant bridge construction?
There is model verification and tooth try in. index with teeth again, duralay pattern within index. The duralay pattern doesn’t need to be that accurate due to CAD-CAM. Then a digital order form is generated using procera system. The model and pattern is sent to Sweden/America. The model and pattern are laser scanned. A beam milled from solid titanium is returned. Check the passivity of fit and then it is ready for insertion.
101
How is ball abutment retained overdenture constructed?
An impression is taken directly over ball abutment. You use stainless steel ball abutment replica and locate the abutment replicas in the impression. The abutment replicas are then in model. There is a retentive element on replica and therefore denture. We don’t tend to verify as there is some give with removable appliance.
102
How is locator abutment retained overdenture constructed?
Impression copings are placed onto model. Aluminium locator abutment replicas placed on impression coping. And then cast to form a model so abutment replicas are in model. There is a male housing with black processing insert. There is blocking out below male housing. Preparing for packing. Fit surface of processed denture. There are different inserts available and a locator core tool. There is removal of processing insert using this. There are different locator male inserts with different retentions. Insert is selected and placed.
