Biomedical Engineering Reference
In-Depth Information
existing bone (osseintegrates) and encourages new bone growth along
its surface (osteoconductive). Bone bonding is due to the formation of a
calcium phosphate (hydroxycarbonate apatite, HCA) layer on the glass
surface, which happens in the first few hours after implantation. The
HCA layer has a similar composition to natural bone mineral. Collagen
fibrils from host bone are thought to interact, via cellular processes,
with the fine (nano)scale topography of the HCA layer, creating a
strong bond.
The main application for Bioglass is as a synthetic bone graft for
orthopaedic and periodontal use. In both these applications, the glass
is used to regenerate and heal bone defects (holes in bone) that result
usually from trauma or tumour/cyst removal. Periodontal defects are
usually defects in the jaw bone around the tooth root.
Currently, orthopaedic surgeons use autografting, which is the trans-
planting of bone from another part of the body (a donor site) to the
defect site. The donor site is usually the pelvis, or for spinal surgery
it could be bone spurs from the vertebrae. In either case, the amount
of bone is limited in quantity, and harvesting the bone in turn leaves
a defect needing repair at the donor site. The donor site defect causes
substantial pain to the patient and lengthens the recovery time. Com-
plications arising at the donor site can lead to the need for further
(revision) surgery.
Most recently, the original Bioglass can be found as the active ingre-
dient in a leading toothpaste for reducing sensitivity in teeth. Sensodyne
Repair & Protect (GlaxoSmithKline, UK) is available in more than 20
countries and is said to be 'powered by NovaMin' (see Figure 2 in
colour section). NovaMin
®
(GlaxoSmithKline, UK) is a fine particulate
of Bioglass that reduces pain felt in teeth when people eat or drink
hot or cold items. Pain is felt when the dentine is exposed, perhaps as
a result of receding gums. Dentine contains tubules that lead to nerve
endings (Chapter 11). When hot or cold fluid flows down these tubules,
pain is felt. Previous toothpastes for sensitive teeth have used potassium
salts that temporarily desensitise the nerve endings. Clinical trials based
on brushing with NovaMin indicate that the glass particles release ions
and raise pH, causing precipitation of hydroxyapatite-like (HA) mineral
over the tubule ends, blocking the tubules. The mineral has a similar
composition to tooth enamel and therefore is beneficial to the tooth.
Several patents have also been filed from a range of leading international
researchers with the aim of improving further on the performance of
bioactive toothpaste.
