Biomedical Engineering Reference
In-Depth Information
A clinical 2-year study comprising 35 cemented crowns was conducted at Kornberg School
of Dentistry, Temple University, and follow-up data and feedback from participating
dentists were excellent with no failures at all reported (Jefferies et al 2009).
Fig. 8. Cemented ceramic crown (left), and HRTEM of the nanostructure of Ca-aluminate
hydrates, hydrates formed in the interval 10-30 nm(right), bar = 10 nm (Hermansson et al,
2010)
4.1.2 Endodontics
In a review of the biocompatibility of dental materials used in contemporary endodontic
therapy (Haumann and Love, 2003) amalgam was compared with gutta-percha, zinc oxide-
eugenol (ZOE), polymers, glass ionomer cements (GICs), composite resins and mineral
trioxide aggregate (MTA). A review (Niederman, 2003) of clinical trials of
in vivo
retrograde
obturation materials summarized the findings. GIC's appeared to have the same clinical
success as amalgam, and orthograde filling with gutta-percha and sealer was more effective
than amalgam retrograde filling. Retrograde fillings with composite and Gluma, EBA
cement or gold leaf were more effective than amalgam retrograde fillings. However, none of
the clinical trials reviewed in included MTA. In a 12 week microleakage study, the MTA
performance was questioned compared to that of both amalgam and a composite (Alamo et
al, 1999).
The Ca-aluminate-based material discussed in this paper belongs to the same material
group as MTA, the chemically bonded ceramics. MTA is a calcium silicate (CS) based
cement having bismuth oxide as filler material for improved radio-opacity, whereas the Ca-
aluminate material consists of Ca-aluminate phases CA and CA
2
with zirconia as filler
material. MTA is claimed to prevent microleakage, to be biocompatible, to regenerate
original tissues when placed in contact with the dental pulp or periradicular tissues, and to
be antibacterial. The product profile of MTA describes the material as a water-based
product, which makes moisture contamination a non-issue (Dentsply 2003). The CA-cement
materials are more acid resistant than the CS-based materials, and in general show higher
mechanical strength than the CS materials. A two-year and a five-year retrospective clinical
study of Ca-aluminate based material have been conducted (Pameijer et al, 2004, Kraft et al,
2009). The study involved patients with diagnosis of either chronic per apical osteitis,
chronic per apical destruction, or trauma. Surgery microscope was used in all cases. For
orthograde therapy the material was mixed with solvent into appropriate consistency and
put into a syringe, injected and condensed with coarse gutta-percha points. Machine burs
were employed for root canal resection. For the retrograde root fillings, the conventional
surgery procedure was performed. The apex was detected with surgery microscope and
rinsed and prepared with an ultrasonic device. Crushed water-filled CA-tablets were then
inserted and condensed with dental instruments. The patients' teeth were examined with X-
