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Endodontic treatment in dentistry is a delicate procedure and many treatment attempts fail. Despite constant development of new root canal filling techniques, the clinician is confronted with both a complex root canal system and the use of filling materials that are harmful for periapical tissues. This paper evaluates reported studies on biomaterials used in endodontics, including calcium hydroxide, mineral trioxide aggregate, calcium phosphate ceramics and calcium phosphate cements. Special emphasis is made on promising new biomaterials, such as injectable bone substitute and injectable calcium phosphate cements. These materials, which combine biocompatibility, bioactivity and rheological properties, could be good alternatives in endodontics as root canal fillers. They could also be used as drug-delivery vehicles (e.g., for antibiotics and growth factors) or as scaffolds in pulp tissue engineering.

An injectable bone substitute (IBS) made of a suspension of calcium phosphate ceramic was used to filled dental root canal after removing of canal pulp. Compared with current filling materials, which are toxic to periapical tissues, calcium phosphate materials, due to their biocompatibility and bioactive properties, may be viewed as possible alternatives. The aim of this study was first to determine if an injectable bone substitute could be used to obtain further healing of apical tissue by the neoformation of a mineralized barrier. In the next step, the paper will focus on rheological measurements as a tool for physical characterisation and on the improvement of the injection technique. Rheology concerns the flow and deformation of the suspension and, in particular, its behaviour in the transient area between solids and fluids. The results showed that injection is possible with a good level of BCP granules at the end of the root dental canal with extracted tooth. Other experiments with other animal models closer to a Human model have to be performed before human trials.

An injectable bone substitute (IBS) made of a suspension of Calcium phosphate ceramic was used to filled dental root canal after removing of canal pulp. The aim of this study was to verify the ability of calcium phosphate ceramic suspension to fill the apical zone of teeth ex vivo (n=40) and in vivo in a sheep model (n=8). The results showed that injection is possible with a good level of BCP granules at the end of the root dental canal with extracted tooth. In vivo, the presence of blood pressure due to the pulpectomy is a negative parameter to allow a good filling. The scanning electron microscopy revealed mineral formation at the apex level with mineral tissue conduction between the BCP granules but only one tooth showed a good apical filling with a good sealing. The sealing of the apex seems to depend of the amount of BCP granules. Other experiments with other animal models closer to a Human model have to be performed before human trials.

The use of injectable calcium phosphate (CaP) biomaterials in noninvasive surgery should provide efficient bone colonization and implantation. Two different kinds of injectable biomaterials are presently under development: ionic hydraulic bone cements that harden in vivo after injection, and an association of biphasic calcium phosphate (BCP) ceramic granules and a water-soluble polymer vehicle (a technique particularly investigated by our group), providing an injectable CaP bone substitute (IBS). In our study, we compared these two approaches, using physicochemical characterizations and in vivo evaluations in light microscopy, scanning electron microscopy, and three-dimensional microtomography with synchrotron technology. Three weeks after implantation in rabbit bone, both biomaterials showed perfect biocompatibility and bioactivity, but new bone formation and degradation of the biomaterial were significantly greater for BCP granules than for ionic cement. Newly formed bone developed, binding the BCP granules together, whereas new bone grew only on the surface of the cement, which remained dense, with no obvious degradation 3 weeks after implantation. This study confirms that BCP granules carried by a cellulosic polymer conserve bioactivity and are conducive to earlier and more extensive bone substitution than a carbonated-hydroxyapatite bone cement. The presence of intergranular spaces in the BCP preparation, as shown on microtomography imaging, seems particularly favorable, allowing body fluids to reach each BCP granule immediately after implantation. Thus, the IBS functions as a completely interconnected ceramic with total open macroporosity. This new bone replacement approach should facilitate microinvasive bone surgery and local delivery of bone therapy agents. (C) 2003 Wiley Periodicals, Inc.

Although initial results were promising for an injectable bone substitute (IBS) associating a hydroxypropyl methylcellulose (HPMC) polymer vector (Benecel®, 2 w/w %) with biphasic calcium phosphate (BCP), a sensitization reaction occurred probably related to the degree of polymer purity. In this context, Benecel® and another HPMC, E4M® were investigated in the present study. The expected composition of the polymers was confirmed by gas–liquid chromatography. Studies in the guinea pig showed that Benecel® has strong sensitization capacity and E4M® none. Benecel® manifests impurities (30 times more than E4M®) in individual fibers or rounded clumps that are apparently responsible for extreme sensitization. Purification by ultracentrifugation associated with 0.2 μm filtration can decrease sensitization capacity considerably, though with a slight loss of polymer concentration. Fourier transform infrared (FTIR) analysis showed that the impurities were largely cellulose derivatives. However, extraction by organic solvent, followed by FTIR studies and micro-X analysis, detected an oily substance containing carbon and silicon associated with the cellulose derivatives. E4M®, a polymer with no sensitization capacity, could replace Benecel® and improve results with IBS.

This study investigated the in vivo performance of two composite injectable bone substitutes (IBS), each with different calcium-phosphate particles granulometries [40-80 (IBS 40-80) and 200-500 microm (IBS 200-500)]. These biomaterials were obtained by associating a biphasic calcium-phosphate (BCP) ceramic mineral phase with a 3% aqueous solution of a cellulosic polymer (hydroxy-propyl-methyl-cellulose). Both materials were injected for periods of 2, 3, 8, or 12 weeks into bone defects at the distal end of rabbit femurs. Quantitative results on new bone formation, BCP resorption, and staining for tartrate-resistant acid phosphatase (TRAP) activity were studied for statistical purposes. Measurements with scanning electron microscopy and image analysis showed that the final rates of newly formed bone were similar for both tested IBS after 12 weeks of implantation. Bone colonization occurred more extensively during early implantation times for IBS 40-80 than for IBS 200-500. For the latter, BCP degradation occurred regularly throughout the implantation period, whereas it was very intensive during the first 2 weeks for IBS 40-80. Positive TRAP-stained degradation cells were significantly more numerous for IBS 40-80 than for IBS 200-500 regardless of implantation time. With the granulometry of either mineral phase, both tested IBS supported extensive bone colonization, which was greater than that previously reported for an equivalent block of macroporous BCP. The resorption-bone substitution process seemed to occur earlier and faster for IBS 40-80 than for IBS 200-500. Both tested IBS expressed similar biological efficiency, with conserved in vivo bioactivity and bone-filling ability.

9th European Meeting on Injectable Bone and Joint Substitution Materials, LAUSANNE, SWITZERLAND, MAR 01-02, 1999; This in vivo study investigated the influence of two calcium phosphate particle sizes (40-80 mu m and 200-500 mu m) on the cellular degradation activity associated with the bone substitution process of two injectable bone substitutes (IBS), The tested biomaterials were obtained by associating a biphasic calcium phosphate (BCP) ceramic mineral phase and a 3% aqueous solution of a cellulosic polymer (hydroxypropylmethylcellulose). Both were injected into osseous defects at the distal end of rabbit femurs for 2- and 3-week periods. Quantitative results for tartrate-resistant acid phosphatase (TRAP) cellular activity, new bone formation, and ceramic resorption were studied for statistical purposes. Positive TRAP-stained degradation cells were significantly more numerous for IBS 40-80 than IBS 200-500, regardless of implantation time. BCP degradation was quite marked during the first 2 weeks for IBS 40-80, and bone colonization occurred more extensively for IBS 40-80 than for IBS 200-500, The resorption-bone substitution process occurred earlier and faster for IBS 40-80 than IBS 200-500, Both tested IBS displayed similar biological efficiency, with conserved in vivo bioactivity and bone-filling ability. Differences in calcium phosphate particle sizes influenced cellular degradation activity and ceramic resorption but were compatible with efficient bone substitution, (Bone 25:71S-74S; 1999) (C) 1999 by Elsevier Science Inc, All rights reserved.