Bone grafting and Implantology

Question 1

What is a Dental implant?

Answer 1

titanium screw inserted into bone (heals via osteointegration)
-> crown inserted on top after healing

Question 2

What is the minimum amount of healthy bone required for a normal dental implant?

Answer 2

10mm

Question 3

What are the types of bone loss?

Answer 3

1. Congenital- born without sufficient bone levels (CLP, hypodontia)
2. Traumatic
3. Pathology
4. Natural- physiological, occurs with age

Question 4

What are the types of bone grafts?

Answer 4

Autogenous- IO/EO

Xenograft (from animals)- as deproteinised bone matrix (bio-oss)

Allograft- irradiated sterilised freeze dried bone blocks

Alloplastic- natural sources and synthetic materials (HA, proplast, TCP, TCS)

Bone bioengineering- bone growth factors (bone morphogenic protein)

Question 5

What are the intraoral sites for autogenous bone grafts?

Answer 5

Chin

Tuberosity

Ramus

Coronoid process

Question 6

What are the EO sites for autogenous bone grafts?

Answer 6

Hip

Calvarium

Question 7

What are the 2 different strategies in bone grafting?

Answer 7

Osteoconduction- replace tissue with scaffold that supports bone forming cells
-> higher risk of infection and loss

Osteoinduction- If material itself can stimulate bone formation- induces undifferentiated mesenchymal cells to change into osteoblasts (form bone)

Question 8

What are the different means of bone augmentation?

Answer 8

Application of grafts- onlay, interpositional, sinus lift

Inferior dental nerve retraction/lateralisation
-> moving nerve during procedure into a new position

Distraction osteogenesis

Zygomatic implants

Question 9

What is an onlay graft?

Answer 9

When grafting material is applied on top of bone

Question 10

What is an interpositional graft?

Answer 10

When graft is applied between 2 pieces/tables of bone
-> increases bone height

-> covered with bio-oss and guided tissue regeneration membrane

Question 11

Why may a sinus lift be used?

Answer 11

 If maxillary sinus occupies most of bone in area of the maxilla you want to place implant (don’t want to perforate)

 Relocate sinus lining/membrane upwards and then graft underneath

Question 12

What are the steps in a sinus lift?

Answer 12

 Expose outer cortex
 Lift sinus mebrane
 Apply bone graft
 Add bio-oss (xenographic)
 Cover everything with guided tissue regeneration membrane

Question 13

How is a bone graft from chin harvested and used for bone augmentation?

Answer 13

 Harvest bone from chin if not enough bone in maxilla
 Raise mucoperiosteal flap, cut outer table of mandible with surgical drill or surgical saw (stay away from mental nerves), take this bone and put in maxilla (reconstruct deficient bone in this region)
 Some can be done with LA but most with GA
 Insert implant when healed

-> same principles apply to outer cortex of mandible (good graft site due to thickness)

Question 14

What part of the hip bone is used in grafts? When is this used?

Answer 14

Medial cortex of the ileac crest

If massive bony deficiency

Question 15

Why is harvesting bone from the skull a good option?

Answer 15

Cortical membranous bone- less chance of infection or resorption is less

Question 16

What is the use of the milling machine when doing bone augmentation?

Answer 16

Produces putty stage used to augment deficient bone

Question 17

What are the steps in in inserting an implant

Answer 17

 Sequence of drills go through bone and then widening
-> Pilot drill, widening drill, then size of drill which is compatible with implant
 Load dental implant (pure titanium)
 Apply healing cap
 After 4-6 months it is ready to receive crown (should last 20 years- success rate is over 90%)

Question 18

What is the issue with bone in hypodontia patients?

Answer 18

Can be deficient- thin and lacking in height

Question 19

What is done to augment bone in hypodontia patients?

Answer 19

Bone augmentation and orthognathic surgeries may both be required

-> graft is taken from chin and covered with GTRM and titanium foil

Question 20

Which condition can result in loss of bone and need for augmentation before placing implants?

Answer 20

Central giant cell granuloma

Question 21

What is the advantage of distraction osteogenesis?

Answer 21

Allows bone lengthening/augmentation without using grafts
-> can be in multiple directions- vertical, horizontal, medial, lateral

Can prevent damage of mental nerve

Question 22

How is distraction osteogenesis carried out?

Answer 22

 Cut bone (osteotomy)
 Wait until blood clot forms at site
 Using distractor device stretch callous between pieces of bone to allow lengthening process to happen (allows remodelling process and bone formation- lengthen callous at rate of 1mm per day)

-> Leave double the lengthening time to allow bone to consolidate after you have achieved desired length

Question 23

When is retraction of IAN considered?

Answer 23

If you cannot augment or use distraction osteogenesis

Question 24

What are the indications for zygomatic implants?

Answer 24

Severe maxillary atrophy

Sinus is large or patient does not want sinus lift

Avoid harvesting of bone graft
-> patient may not want this

Hemimaxillectomy (due to cancer)- patient is missing large parts of their maxilla

For retention of a denture

Question 25

What are the different about zygomatic implants?

Answer 25

They are longer- around 55mm

Question 26

What is BMP? What is its use in implantology?

Answer 26

Cytokine which responds to trauma within bone and cause osteoinduction
-> convert UMCs into osteoblasts AND stimulate angiogenesis

Can be injected into area you want to augment to stimulate bone augmentation

Question 27

Which BMPs induce osteogenesis?

Answer 27

BMP2, 4, 7

Question 28

When may bioengineering using BMPs be utilised?

Answer 28

On patients with CLP who are receiving surgery at a young age
-> other bone augmentation surgeries deemed inappropriate due to age