**4.1.2 Endodontics**

64 Biomaterials – Physics and Chemistry

Compressive strength, MPa

Self-adhesive Resin

Polymerisation

Acidic /neutral

hydrophilic, Hydrophobic

Adhesion / Micromechanical retention

Shrinks Shrinks Non-

Degrades Degrades Degrades Degrades Degrades Stable

Znphosphate cement

material

Acid-base reaction

shrinking


Micromechanical retention

allergenic

OK Acceptable Excellent

Acidic Acidic

Hydrophilic Hydro-philic

Crown retention, Kg/Force

> Ceramir C&B

Ceramicpolymer

Acid-base + cross-linking

/basic

Nonshrinking

Nanostructural integration

Nonallergenic

Film thickness, m

based 4.8 15 196 (at 30days) 38.6 Ketac Cem - 19 - 26.6 RelyX-Unicem - - 157 39.4

> Resin (bonded)

Polymerisation

/neutral

bonding

Hydrophilic Hydrophobic Initially

Adhesion / Micromechanical retention

Irritant Allergenic Allergenic Allergenic Non-

11. Bioactivty No No No No No Bioactive

operation sensitive

Material aspects 4-12 in Table 13 are also relevant for all other Ca-aluminate based dental

Good OK OK OK Good Good

Polymer Monomer Monomer Monomer Inorganic

Material Net setting

Glass Ionomer (GI)

Crosslinking

Nonshrinking

> Hydrophilic

Micromechanical retention, Chemical bonding

3. pH Acidic Acidic Acidic

Ca-aluminate

Material aspects

2. Hardening mechanism

1. Type of material

4. Geometrical stability

5. Stability over time

6. Extra treatment

7. Hydrophilic / phobic

8. Integration mechanism

9. General behaviour

10. Biocompatibility

12. Sealing quality

applications.

time, min

Table 12. Selected properties, Test methods according to SO 9917-1

Resinmodified GI

Polymerisation

Nonshrinking

Micromechanical retention / Chemical bonding / Adhesion

OK OK Good but

Table 13. Overview of dental luting cements (Hermansson et al, 2010)


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 oxideeugenol (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 Caaluminate material consists of Ca-aluminate phases CA and CA2 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-

Nanostructural Chemically Bonded Ca-Aluminate Based Bioceramics 67

the material, but rather to the difficulty of treating and sealing a multi-channelled tooth. The use of CA's as root canal sealers is indirectly supported in "Introduction to Dental Materials" by van Noort (van Noort, 1994), where the following materials characteristics are looked for; biocompatible, dimensionally stable, antibacterial and bioactive. The results in

Already in the 1970s, Calcium aluminate (CA) was suggested as a biomaterial and tested *in vivo*. Hentrich et al (Hentricht et al, 1994) compared CA with alumina and zirconia in an evaluation of how the different ceramics influenced the rate of new bone formation in femurs of rhesus monkeys. Hamner et al (Hamnar and Gruelich, 1972) presented a study in which 22 CA roots were implanted into fresh natural tooth extraction sites in 10 baboons for periods ranging from 2 weeks to 10 months. In both studies CA successfully met the criteria

An important feature of the hydration mechanisms of the Ca-aluminate based materials is the nanostructural integration with and the high shear strength developed towards dental tissue. This makes both undercut (retention) technique and bonding techniques redundant. The Ca-aluminate approach to dental filling technique is new. With this technique, the chemical reactions cause integration when the bioceramic material is placed in the oral cavity at body temperature and in a moist treatment field. Figure 11 shows a TEM (transmission electron microscopy) illustration of the interface between the CA-based material and dentine. This establishes a durable seal between bioceramic and tooth. Whereas amalgam attaches to the tooth by mechanical retention and resin-based materials attach by adhesion, using bonding agents, etchants, light-curing or other complementary techniques, the CA-materials integrate with the tooth without any of these, delivering a

Fig. 11. Nanostructural integration of CAPH-material with dentine (gray particles in the

biocompatibility and mechanical properties (Kraft 2002, Lööf et al 2003).

**4.1.4 Coatings on dental implant and augmentation** 

The general aspects of Ca-aluminate based materials have been presented in two Ph D Thesis-publications. Important aspects of Ca-aluminate materials as dental filling materials are dealt with, such as dimensional stability, acid corrosion and wear resistance, and

For successful implantation of implants in bone tissue, early stabilisation is of great importance (Ellingsen and Lyngstaadas, 2003). This includes both orthopaedic and dental

this study can be interpreted as a success in meeting these materials requirements.

for tissue adherence and host acceptance.

quicker, simpler and more robust solution.

biomaterial are glass particles)

**4.1.3 Dental filling materials** 

ray, and three questions regarding subjective symptoms were put to patients: 1. Have you had any persistent symptoms? 2. Do you know which tooth was treated? 3. Can you feel any symptoms at the tooth apex?

In 13 of the 17 treated patients the diagnosis was chronic perapical osteitis (c p o). These were treated with retrograde root filling (rf) therapy. Three patients suffered from trauma or chronic perapical destruction, and these patients were treated with orthograde therapy. Out of 17 patients (22 teeth) treated, 16 patients (21 teeth) were examined with follow-up x-ray after treatment and also after two years or more. The additional patient was asked about symptoms. The results of both the clinical examination and the subjective symptoms were graded into different groups related to the success of the therapy. The results of the 2-year and the 5-year study are shown in Table 14.


Table 14. Summary of the results (Score 1 and 2 considered successful, score 3 and 4 failure)

Figures 9-10 show examples of the X-ray examination of orthograde and retrograde treatments.

Fig. 9. Tooth 21 (patient14) a) condensing with a Gutta-percha pointer, b) just after treatment and c) at two year control

Fig. 10. Tooth 21 (patient 9) at treatment (left) and at two year control (middle) and at 5 year control (right)

In summary 21 out of 22 treated teeth have acceptable results being either symptom free or judged healed after clinical examination. The single failure can probably not be attributed to the material, but rather to the difficulty of treating and sealing a multi-channelled tooth. The use of CA's as root canal sealers is indirectly supported in "Introduction to Dental Materials" by van Noort (van Noort, 1994), where the following materials characteristics are looked for; biocompatible, dimensionally stable, antibacterial and bioactive. The results in this study can be interpreted as a success in meeting these materials requirements.

Already in the 1970s, Calcium aluminate (CA) was suggested as a biomaterial and tested *in vivo*. Hentrich et al (Hentricht et al, 1994) compared CA with alumina and zirconia in an evaluation of how the different ceramics influenced the rate of new bone formation in femurs of rhesus monkeys. Hamner et al (Hamnar and Gruelich, 1972) presented a study in which 22 CA roots were implanted into fresh natural tooth extraction sites in 10 baboons for periods ranging from 2 weeks to 10 months. In both studies CA successfully met the criteria for tissue adherence and host acceptance.
