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Biomedical subjects

J J Lasfargues

Publications and source records attributed to J J Lasfargues.

At least 19 recordsLinked to original sources
PubMed2000

Bone sialoprotein-induced reparative dentinogenesis in the pulp of rat's molar.

Bone sialoprotein (BSP), an osteogenic protein (OP), mixed with a carrier, was implanted in the pulp of rat first upper molars (OP group). Cavities were prepared with dental burs and pulp perforation was carried out by pressure with the tip of a steel probe. After 8, 14, and 30 days, the rats were killed and the pulps of the OP group were compared with (1) a sham group (S group), (2) a group where the carrier was implanted alone (C group), and (3) capping with calcium hydroxide (Ca group). After 8 days, a few inflammatory cells were seen, mostly located at the pulp surface near the perforation. In the Ca group, a dentin bridge started to form, in contrast to the other groups. After 15 days, globular structures were seen in the pulps of the S and C groups. A reparative osteodentin bridge isolated the pulp from the cavity in the Ca group. Variable reactions were seen in the OP group, with some evidence of cell and matrix alignments or plugs of osteodentin in continuity with an inner layer of reparative dentin. After 30 days, irregular osteodentin formation was observed in the pulps of the S and C groups, with a tendency for globular structures to merge, but with interglobular spaces filled by pulp remnants. In the Ca group, osteodentin was observed in the mesial part of the pulp chamber. In the BSP-implanted group, the osteogenic protein stimulated the formation of a homogeneous dentin-like deposit occupying most of the mesial part of the pulp. Apparently, BSP stimulates the differentiation of cells which secrete an organized extracellular matrix more efficiently than any other capping material used so far. Altogether, the results reported here support that bone sialoprotein displays novel bioactive properties and is capable of stimulating in 1 month's time the development of a thick reparative dentinal tissue in the pulp, occluding the perforation and filling the mesial third of the pulp chamber.

Animals↗
PubMed2000

In vivo study of the pulp reaction to Fuji IX, a glass ionomer cement.

OBJECTIVE: Our aims were to investigate the pulp biocompatibility of Fuji IX, a glass ionomer cement (GIC) used as a restorative material in cavities prepared in rat's upper molars, and to assess the value of this in vivo model for testing dental biomaterials. METHOD: Half-moon class V-like cavities were drilled on the mesial aspect of 26 rat upper first molars. Half of the experimental rats whose molars were restored with the GIC were killed after 8days and the second half after 30days. They were compared with two control groups, also submitted to cavity preparation, but with cavities left unfilled. Again, half of the control rats were killed at 8 days and the second half after 30days. Following intracardiac perfusion with the fixative solution, the specimens were processed to histologic procedures. RESULTS: After 8 days, in both groups a few inflammatory cells were observed. The odontoblastic layer was disrupted and dilated blood vessels were seen in the pulp area related to the cut tubules. The experimental group displayed a moderate inflammatory reaction whereas only a slight reaction was detected in the control group. In few teeth, bacteria were visualized in dentine tubules beneath the GIC restoration. Such colonies were not observed in unfilled molars.After 30days, in both groups, the pulp tissue recovered and displayed a normal appearance. Disruptions of the odontoblast layer were not visible anymore. Bacteria penetration into dentine tubules was reduced compared with the 8-day situation. A thick layer of reparative osteodentine was formed. However no difference in thickness was detected between the experimental and control groups, supporting that the formation of reparative dentine is not impaired. Irregular mineralizations including calcospherites were induced by the GIC. CONCLUSIONS: This study demonstrates that, despite small alterations in the mineralization processes, the GIC Fuji IX has a good biocompatibility and does not induce any harmful effect on pulp cells.

Animals↗
PubMed1995

Pulpo-dentinal complex revisited.

OBJECTIVES AND METHODS: The value of the concept of a pulpo-dentinal complex was assessed on human teeth treated according to the ISO test on biological evaluation. The teeth were extracted after 1 or 3 months and examined histologically. Biochemical and biological data available from the dental literature were also re-examined. RESULTS: During the early development of the tooth, pulp and dentine establish close links and form an undivided organ. However, examination of the tissues at later stages of development casts doubt on the validity of such a concept. Major differences are reviewed in this report between the cells (odontoblasts and heterogeneous pulpal cells) and extracellular matrix (collagens, non-collagenic proteins and phospholipids) located either in the odontoblast-dentine area or in the pulp. It seems also that clear-cut differences are detected during inflammatory and repair processes. CONCLUSION: It is concluded that, although the existence of a dentino-pulpal reaction cannot be denied, the concept of a pulpo-dentinal complex is an oversimplification and should be revisited. This may have implications in the evaluation of restorative treatments and in the design of a tissue repair strategy.

Adolescent↗
PubMed1994

Clinical testing of dental materials--histological considerations.

In order to assess the biocompatibility of dental materials, clinical studies, as well as in vitro studies, are needed. Although no bacteria were detected inside tubules, pulp reactions were observed when either adhesives of the last generation aiming to create an hybrid layer were used or restorative materials controlling the interface between the biomaterial and dental tissues. However, the reactions were feeble to moderate. Reparative dentine seldom appeared after such treatments. Differences between odontoblast and pulp cells, the nature of the lesion (necrosis or apoptosis), and differences between sound experimental and carious teeth seen in the real clinical situation are discussed in the context of in vivo human studies.

Adolescent↗
PubMed1993

Inhibition of prostanoid synthesis depresses alveolar bone resorption but enhances root resorption in the rat.

Tooth drift requires the deformation of the root socket and the adjustment of the other components of the attachment apparatus, namely, the periodontal ligament (PDL) and the cementum. Indomethacin (7.5 mg/kg/d), an inhibitor of prostanoid synthesis, provoked in rats a depression in the bone resorption effecting the deformation of the socket (Lasfargues and Saffar, Anat. Rec., 234:310-316, 1992). In the present paper we examined the consequence of this treatment both on the PDL and the root surface. After 3 days of treatment, when osteoclastic resorption was not yet disturbed, the root had been markedly resorbed (P < 0.05) opposite the resorbing bone surface; at that time the PDL width remained in the normal range. After 7 days, i.e., when the bone resorption was depressed, the PDL was widened as the result of the ongoing root resorption. Despite the extensive root resorption, the anchorage of the PDL fibers appeared to remain effective, suggesting that it was rapidly restored. On day 14 at the time of the bone resorption recovery, cementum was deposited in the root resorption lacunae and the PDL width had returned to its control value. As early as day 3 the daily rate of dentine formation increased in the pulp area subjacent to the root resorption lacunae (P < 0.01). These data demonstrate that i) the responses of the different components of the periodontal apparatus are coordinated to allow for the maintainance of the PDL width so that when bone resorption is disturbed, root resorption compensates for it, and ii) the odontoclasts can differentiate and resorb under prostanoid inhibition whilst osteoclastic resorption of the bone socket is inhibited.

Adaptation, Physiological↗
PubMed1993

[Regulation of osteoclastic resorption by prostanoids in vivo].

Prostanoids, and particularly prostaglandins (PGs) E, are potent mediators of bone resorption. However the actual role(s) of these agents in osteoclastic resorption is (are) not yet known. In an attempt to approach the role of prostanoids in the events leading to resorption itself, we used two different animal models. We showed that indomethacin, an inhibitor of prostanoid biosynthesis, drastically reduced osteoclastic resorption at the dose of 7 mg/kg/d in the two models. This effect was dose-dependent as resorption inhibition increased by increasing the dose of indomethacin. However the effect was already significant at the lower dose (2 mg/kg/d). The total number of osteoclasts in the site was according by reduced, showing the involvement of the prostanoids in the events preceding and/or regulating the fusion of the mononucleated preosteoclasts into multinucleated osteoclasts. The calculation of the ratio active/inactive osteoclasts indicated that the activation (i.e. access to the bone surface) of the osteoclast, was prostanoid-dependent; indeed the ratio systematically decreased in the indomethacin-treated animals in the two models. We also observed that the inhibition was not sustained in time as resorption recovered, probably through the starting of PG-independent metabolic pathways. However this starting was rather slow and these pathways apparently were less affective than the PG-dependent ones since the intrinsic activity of the differentiated osteoclasts was significantly reduced.

Animals↗
PubMed1992

Effects of prostaglandin inhibition on the bone activities associated with the spontaneous drift of molar teeth in the rat.

Little is known about local bone regulation that enables spontaneous molar tooth drift. In this study the role of prostaglandins (PGs) were investigated in the rat by inhibiting PG-synthesis with indomethacin (7 mg/kg/d). Untreated animals were killed at the start of the experiment, while treated ones were killed after 3, 7, or 14 days of treatment. Mandibles were processed for histomorphometry without demineralization. Changes in osteoclasts and extent of the different steps of the bone remodeling sequence (resorption, reversal, and formation) were assessed along the remodeling side of the socket of the buccal root of the first molar. The total number of osteoclasts decreased after 7 days of PG inhibition (P < 0.01 vs controls) and then partially recovered. This change was due to a sharp decrease in active cells on day 7 (P < 0.01), while inactive cells remained unchanged throughout the experimental period. The extent of resorption fell on day 7 (P < 0.01) and then recovered almost to the control level on day 14. Reversal at first increased insignificantly and thereafter decreased (P < 0.02) for the remaining 7 days. Formation was modified only on day 14; at that time it had doubled compared with controls. These results show that PGs are involved in the local regulation of bone remodeling accompanying tooth drift. Resorption inhibition was partial, indicating that other factors participate with PGs in this regulation; in addition, the trend to recovery observed at the end of the experimental period suggests that these factors can take over from PGs to achieve the necessary remodeling of the socket.

Alveolar Process↗
PubMed1990

[Pulpectomy. Why? When?].

There are many circumstances under which the condition of the pulp calls for root canal work, due to the real or potential risk of pain, infection, inflammation or functional difficulties (acute, irreversible pulpitis, chronic pulpitic conditions, necrosis and its consequences, etc.). Other circumstances exist in which injury to the pulp is not necessarily irreversible: initial pulpitis, iatrogenic fracture of the pulp, traumatisms, dystrophic deteriorations. The high success rate for endodontic therapy could argue for elimination of impaired or necrose-prone pulp. In fact, however, unsuccessful pulpectomies often lead to loss of the dental organ and successful endodontic treatment severely weakens the whole tooth structure and often implies prosthetic restoration, with the consequent increase in tissular loss. In order to preserve pulp and crown tissues, pulpal vitality should be protected in all cases where such conservative efforts do not worsen the prognosis for maintaining the tooth on its arch or jeopardize a planned restoration. Solutions are presented for various types of situations, according to the risks encountered.

Contraindications↗
PubMed1990

[Prognosis of canal treatment. Success and failure].

This clinical review confirms the very positive prognosis for endodontic therapy, conditional to strict compliance with imperatives. Endodontics failures are transient and can be remedied. The authors define the attitude to be adopted and the measures to be taken in accordance with the type of difficulty encountered.

Humans↗
PubMed1990

[Conservative restoration of pulpectomized teeth].

In endodontic treatment of teeth, partial or "conservative" crown reconstructions are clinically acceptable where loss of substance is limited and recourse to radicular pivots is contraindicated. Such reconstructions bring into play a variety of currently available biomaterials, including those inserted in the plastic phase. They make it possible to delay a prosthetic solution (full crown restoration) without impinging on the conservation of the devitalized tooth.

Composite Resins↗
PubMed1990

[Preparations for anterior composites].

This paper sets forth and discusses the various preparations used in aesthetic restoration of anterior teeth with composite resins. The clinical description of contours involves treatment of class III and IV carious lesions and correction of aesthetic imperfections which justify resorting to direct techniques of cosmetic dentistry.

Composite Resins↗
PubMed1990

[Marginal adaptation of posterior composites. A complex clinical problem].

In this article, the authors deal with the problem of marginal fit for posterior composites, where direct class-II aesthetic restoration is involved. For different materials, they analyse and discuss the influence of their physicochemical properties, the contour of preparations, and composite handling. Three types of clinical cases are described: preparation using the tunneling technique, adhesive preparation, conventional preparation.

Bicuspid↗
PubMed1990

[Composite resin inlays. Convincing solution or uncertain compromise?].

This is a report on the authors' clinical experience years of using laboratory composites. They describe the contours of composite resin preparations for inlays, discuss the advantages drawbacks of such restorations and provide limited indications. The illustrations also involve specific clinical cases.

Acrylic Resins↗
PubMed1988

[Root reactions during treatment with indomethacin in the rat].

During the course of a study on the effect of indomethacin, an inhibitor of PG-synthesis, on the alveolar bone remodeling associated with the drift of the rat molar, the root profile appeared altered. The perimeter of the buccal root of the lower first molar had increased during the 7-day experimental period (+9%; p less than 0.02) in the treated group. This was due to an increase in the extent of root resorption lacunae (+99%; p less than 0.05). They were located in the disto-buccal aspect of the root, i.e., facing the alveolar wall remodeling area. The periodontal ligament width was also increased (p less than 0.001). This might be an adaptative process to maintain the periodontal ligament width as the drift of the teeth had not ceased while the remodeling had markedly slowed down. These results show that the osteoclastic population responsible for root resorption was not PG-dependent, unlike that active on alveolar wall. In addition, dentin deposition was accelerated in the pulp area underlying the resorption lacunae in the treated group as shown by measuring the distance between two fluorescent labels incorporated in a 6-day interval (p less than 0.05).

Alveolar Process↗