Introduction to biomaterials and surgery in dental implantology

Question 1

What is unusual about the dental implant compared with other biomaterials used in skeletal tissue repair? (2)

Answer 1

Penetrates the mucosa, interfacing with both soft and mineralised tissues

Question 2

What is a dental implant? (2)

Answer 2

A metal device that is surgically placed in the jawbone. It acts as an anchor for an artificial tooth or teeth.

Question 3

How is implantology growing and evolving? (4)

Answer 3

Pre-1990, majority of implants were placed in a hospital or specialist centre - now in dental practices
Full clinical competency provided by postgrad training, but dental schools are increasing teaching on clinical dental implantology
Not part of GDC’s specialist lists
Over 200 companies manufacture dental implants worldwide

Question 4

How many implants placed in USA per annum? (1)

Answer 4

5 million

European figures similar

Question 5

Types of early implants (3)

Answer 5

Sub-periosteal implants
Bade implants
Trans-osteal implants

Question 6

“Brånemark” osseointegrating implant (3)

Answer 6

Orthopaedic surgeon, 1950s research in bone metabolism
Used viewing chamber made from titanium
Placed 1st set of titanium 2-stage dental implants in pt 1965
Commercial launch 1985
Careful surgery & pt selection

Question 7

Titanium biocompatibility (7)

Answer 7

Tough, light, and durable
TiO2 surface 
Low corrosion (due to TiO2)
-TiO2 more like a ceramic surface than a metal
Biocompatible
Bioinert or bioactive?
Osseointegrating
Biointeraction?:
-protein adsorption
-calcium phosphate deposition

Question 8

Options in managing a missing tooth (4)

Answer 8

Accept gap
Denture
Bridge
Implant

Question 9

Key components of an implant (3)

Answer 9

Crown
Abutment and component screw with cotton??? on top
Implant (or fixture)

Question 10

Engagement of prosthesis into implant (2)

Answer 10

Tri-channel system with anti-rotation device
Conical connection (with anti-rotation hexagonal connection at base of crown)
-more even distribution of stress, better for thin implants

Question 11

Biological events at the bone/ implant interface associated with osseointegration (8)

Answer 11

Be aware that a lot of these studies have been done in vitra (biology) so be cautious about believing everything

(a) Protein adsorption
(b) Protein desorption
(c) Surface changes
(d) Inflammatory/connective tissue cells approach implant
(e) Possible release of matrix proteins and selected adsorption of proteins (e.g. BSP and OPN)
(f) Formation of a lamina limitans/adhesion of osteogenic cells
(g) Bone deposition on bone and implant surfaces
(h) Remodeling of newly formed bone
* *Despite extensive research, it is still not certain which of these is most important with respect to clinical success, and the specific biological events that are most important remain subject to ongoing debate.

Question 12

Terminology: “bioinert” vs “bioactive” (4)

Answer 12

Two terms coined originally to describe bone-biomaterial interaction
They may be applied conceptually to many biomaterials including dental materials (e.g. dental amalgam v. glass-ionomer cement)
They remain slightly misleading terms, with no material being totally inert following placement into the biological environment
Titanium (and TiO2 surface) not usually considered “bioactive”, but this has been claimed by some authors

Question 13

Bone tissue response to “bioactive” HA ceramic vs “bioinert” ceramic (canasite glass ceramic)

Answer 13

The classical response of bone tissue to so-called “bioactive” materials has been well-known for a long time, albeit most data is from animal studies with relatively little histological data from human studies.
HA and bone - bioactive
Bone and canasite - bioinert

Question 14

Hydoxyapatite: A “bioactive” or osteoconductive bioceramic used in bone augmentation (4)

Answer 14

Hydroxyapatite is a calcium phosphate ceramic that encourages new bone tissue formation/healing following implantation into established bone tissue.
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 a bone grafts (clinical material of choice in implant therapy).
Calcium phosphates are too brittle to use alone as load-bearing implants, so they are used as particulates or coatings on metallic devices

Question 15

Osseointegration: a clinical perspective - healing period (5)

Answer 15

3 months

• avoid micro-movement (could lead to fibrosis –> failure)
• can wear prosthesis over top, but need to relieve to avoid pressure on implant
• due to dense bone in mandible, some clinicians have shorter healing protocols
• can check stability with radiofrequency analysis (RFA)

Question 16

Different designs on crowns

Answer 16

Cement retained

Screw retained

Question 17

Cement retained crown (3)

Answer 17

Cemented like an extra-coronal restoration except no cement on top of screw

+ Ideal aesthetics
+ No chipping of access hole

• risk of peri-implantitis / **??cementitis (due to cement leaking)

Question 18

Screw retained crown (3)

Answer 18

Crown itself is small screw hole - one piece solution. Screw crown into implant, then composite restoration on top

+ reduced risk of peri-implantitis

• aesthetics slightly reduced (e.g. for anterior teeth)
• risk of chipping access hole for screw

Question 19

Compensating for poor position (3)

Answer 19

Angled screw channel
Screwdriver at “elbow joint” engages screw at angle
Angulation allows to change by up to 25 degrees for screw retained crowns

Question 20

Material selection and implant failure - what could go wrong (3)

Answer 20

Failure to osseointegrate (short term)
Failure due to peri-implantitis associated with bacterial colonisation
Failure due to “cementitis”

Question 21

Cementitis - describe (3)

Answer 21

“Cementitis” is used to describe a peri-implantitis-like condition where residual luting cement is associated with local inflammation and bone loss.
Biomaterial issue
Mechanical failure a much smaller issue

Question 22

Describe periimplantitis (2)

Answer 22

Microbial colonisation and infection are associated with peri-implantitis, Wilson claimed that residual dental cements were associated with a reversible “cementitis” that subsided after removal of the material.
***

Question 23

Bridges - multi-unit abutments (2)

Answer 23

+ Allows engagement of internal channel
- expensive (£180 per abutment)
Abutments must be convergent for retention
Retained by a screw

Question 24

Bridges - fixture-level screw retention (3)

Answer 24

+ avoids cost of multi-unit abutments

• does not fully engage internal connection
• stress on screws

Question 25

Bridges - cement retained bridge (4)

Answer 25

+ similar to standard crown and bridgework in terms of fit
+ engages internal connection
-cannot be unscrewed (has to be cut off and binned and redone)
-risk of cementitis

Question 26

Options for bridges (3)

Answer 26

Multi-unit abutments
Fixture-level screw retention
Cement retained bridge

Question 27

Denture options

Answer 27

Locator abutments
Ball attachments
Milled bar
Magnets

Question 28

Denture - locator abutments (5)

Answer 28

Go to
Simple, relatively cheap, very successful
Male unit fits over top - male in the sense that it fits into underside of denture is in two parts
-locator males
-externally and internally locator male
Standard males 17 degrees divergence
Extended range 30 degrees divergence

Question 29

Dentures - ball attachments

Answer 29

Choose tension of which you want to retain the denture

Question 30

Dentures - milled bar (3)

Answer 30

+ Much greater stability

• requires more implants
• requires minimum 15-17mm height (depending on attachment type) - may need to cut back bone to increase OVD

Question 31

Dentures - magnets (3)

Answer 31

• generally a solution for poor implant position - you wouldn’t choose to do this
  + able to compensate for significant for significant angulation
  + able to provide low-profile solution if limited vertical space
  Dome type or flat type

Question 32

Guided bone regeneration in how many placements (1) and what is done (2)

Answer 32

About 50%
Add extra bone on top (bucally) to augment what should have been there in the first place
Collagen membrane which protects particulate from fibroblast ingressing, can only be popuated by fibroblasts

Question 33

Membranes in implant surgery - purpose (1)

Answer 33

Employed to exclude soft/scar tissues from site where bone healing or regeneration needed.

Question 34

Membranes in implant surgery - terms (2)

Answer 34

This is termed guided tissue regeneration (GTR) or guided bone regeneration (GBR)

Question 35

Membranes in implant surgery - materials that have been used (3) and function of these (2)

Answer 35

Non resorbable (e.g. GoreTex)
Resorbable synthetic (e.g. PGA)
Resorbable natural (e.g. collagen) - this is material of choice due to ease of use plus resorbable nature
-all have problems, and none yet have intrinsic regenerative properties beyond the barrier function
-may be used with bone graft or synthetic bone graft substitute

Question 36

Collagen membranes for GTW (3)

• use
• derivation
• risks

Answer 36

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 37

Implant surgery - flap design (2)

Answer 37

Papilla-sparing/ “Sclar”

Sulcal incision

Question 38

Papilla-sparing/ “Sclar” flap design (2)

Answer 38

+ avoids papilla recession

-scarring - hidden at point of mucogingival junction

Question 39

Sulca, incision flap design (2)

Answer 39

+avoids scarring

-risk of papilla recession

Question 40

Choice of implant diameter

Answer 40

Narrow platform - 3.5mm width
Regular platform -4.3mm width
Wide platform - 5mm width

Question 41

Impression - closed tray

Question 42

Cover screw vs healing abutment