Interest in a new test for caries risk in adolescents undergoing orthodontic treatment.

It has been reported that patients undergoing orthodontic treatment present a high risk of caries. Recently, an immediate chair-side test was proposed, displaying the intra-oral lactic acid production of cariogenic bacteria. The aim of this 12-month follow-up prospective cohort study was to evaluate the association between having a high score on this test and caries occurrence in 110 young patients scheduled for orthodontic treatment. Caries occurrence was studied by Kaplan-Meier curves and Multivariate Cox models allowed the examination of its association with covariates. Fifty four patients developed at least one carious lesion during the follow-up period. At baseline, approximately 70% of the patients presented a high risk of caries according to the test and this number came close to 80% by the study's completion. According to the Kaplan-Meier estimator, 51% (CI(95%) 0.40, 0.60) of the sample would have developed at least one carious lesion during the follow-up. The test score was then associated with age, DMFT, and caries occurrence. This study showed that a high test score at baseline associated with a high DMFT predicted a high risk of caries (RR = 2.6). Taking the patient's age into consideration, an increase of 1 year resulted in a 10% decrease of the risk of caries occurrence (RR = 0.89). Within the limits of this longitudinal study, it may be concluded that this test is useful to evaluate the risk for dental caries in adolescents with orthodontic treatment. Furthermore, the distribution of the lesions in our sample suggests specific clinical approaches for this group of patients.

A proposal for a new classification of lesions of exposed tooth surfaces.

In the presence of improved methods of identification and treatment of lesions on the exposed surfaces of teeth, it should now be acknowledged that the GV Black "classification of carious cavities" is out of date. This paper describes a new system, proposed in 1997, discussed broadly throughout the profession, and eventually modified. The system has been adopted in several regions around the world as being a useful corollary to the current developing concept of minimal intervention dentistry. It is now desirable to adopt a new approach to the identification and recording of the lesions caused by both caries and non-carious tooth loss. A major advantage arising from its adoption would be that it would encourage the profession to minimise the amount of normal healthy tooth structure that is often sacrificed in pursuit of the cavity designs as suggested by Black. The authors are members of a Project Group of the FDI Science Committee, and this paper explains the concept and offers justification for the adoption of the system.

A histometric study of the effect of indomethacin and calcitonin on bone remodelling in hamster periodontitis.

The action on bone remodelling of indomethacin, a potent inhibitor of prostaglandin (PG) synthesis, was determined in hamster periodontitis and compared to that of calcitonin. The two treatments reduced the extent of bone resorption considerably but not significantly (NS). The reversal phase, the intermediate step between resorption and formation, was decreased by 33 per cent (NS) by indomethacin and 75 per cent by calcitonin (p less than 0.02). Bone formation was increased by 270 per cent with indomethacin (p less than 0.05) and by 400 per cent with calcitonin (p less than 0.03), compared with untreated animals. This exceeded the extent of bone formation activity in control animals. These data strongly suggest that PG are involved in the mechanism of bone destruction in hamster periodontitis and that PG are potent in vivo uncouplers of bone remodelling as they participate both in an increase in bone resorption and a decrease in bone formation. A partial decrease in reversal lacunae indicates that other factors, also acting as uncouplers, probably take part in the mechanism of bone destruction.

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.

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.

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.

Minimal intervention dentistry II: part 4. Minimal intervention techniques of preparation and adhesive restorations. The contribution of the sono-abrasive techniques.

The concept of minimal intervention in oral medicine is based on advances in biological sciences applied to the dental organ. Many cultural barriers, economic as well as technical, have thwarted the application of micro-invasive conservative techniques by the general practitioner. Emerging technologies do not remove all obstacles but promote the integration of less invasive techniques in daily practice. Sono-abrasion is a technique for the selective preparation of enamel and dentine offering excellent efficacy, quality and safety. The authors describe the therapeutic principles, the choice of instrumentation and its mode of action and discuss its interest in adhesive restorative dentistry. The illustrated clinical situations focus on the preservation and optimisation of tissue bonding for both initial lesions and advanced lesions.

Minimal intervention dentistry: part 6. Caries inhibition by resin infiltration.

Resin infiltration has made possible an innovative way of treating initial carious lesions that fits perfectly with the concept of minimal intervention dentistry. Infiltration of carious lesions represents a new approach to the treatment of non-cavitated lesions of proximal and smooth surfaces of deciduous and permanent teeth. The major advantage of this method is that it is a non-invasive treatment, preserving tooth structure and that it can be achieved in a single visit. While this therapy can rightly be categorised as minimum intervention dentistry, clinical experience is limited and further controlled clinical trials are required to assess its long-term results. The inhibition of caries progression by resin infiltration should now be considered an alternative to invasive restorations, but involves early detection of lesions and does not allow for appropriate monitoring of the caries risk.

Minimal intervention dentistry: part 4. Detection and diagnosis of initial caries lesions.

The detection of carious lesions is focused on the identification of early mineral changes to allow the demineralisation process to be managed by non-invasive interventions. The methods recommended for clinical diagnosis of initial carious lesions are discussed and illustrated. These include the early detection of lesions, evaluation of the extent of the lesion and its state of activity and the establishment of appropriate monitoring. The place of modern tools, including those based on fluorescence, is discussed. These can help inform patients. They are also potentially useful in regular control visits to monitor the progression or regression of early lesions. A rigorous and systematic approach to caries diagnosis is essential to establish a care plan for the disease and to identify preventive measures based on more precise diagnosis and to reduce reliance on restorative measures.

[Conservative restoration of pulpectomized teeth]. / Restaurations conservatrices des dents dépulpées.

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.

[Root reactions during treatment with indomethacin in the rat]. / Réactions radiculaires au cours d'un traitement à l'indométhacine chez le 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).

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.

[Preparations for anterior composites]. / Les preparations pour composites anterieurs.

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 resin inlays. Convincing solution or uncertain compromise?]. / Incrustations en resine composite. Solution convaincante ou compromis incertain?

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.

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.

Osteogenic proteins (bone sialoprotein and bone morphogenetic protein-7) and dental pulp mineralization.

Bone sialoprotein (BSP) cross-linked to collagen/gelatin was implanted in the pulp of rat's upper molars. Comparison was carried out with a sham group (non implanted), with a group of rats receiving the carrier alone, and a group of molars where the perforated pulps were capped with calcium hydroxide. The cavities were occluded with a glass-ionomer cement (GIC). After 8, 14 and 30 days respectively the rats were killed by intracardiac perfusion of the fixative and processed for light microscopy. Dentin and predentin debris pushed into the pulp during the preparation enhanced self-repair processes, with large pulp remnants. The carrier alone induced slight inflammation, and calcium hydroxide the formation of a reparative dentin bridge. BSP stimulated the recruitment of cells which produced an homogeneous atubular dentin-like structure, filling after one month the mesial third of the crown pulp. Osteogenic protein (OP-1) used in the same experimental conditions induced the formation of osteodentin in the coronal pulp and the radicular part of the pulp was totally filled by a mineralized material. The differences reported here suggest two possible different therapeutic approaches with the two osteogenic proteins, BSP inducing pulp mineralization in the crown part, and OP-1 occluding the root part of the pulp.

Apoptosis in human and rat dental pulp.

Apoptotic cells were visualized in human premolar and rat molar pulps using either the TUNEL method, which stains DNA strand breaks by in situ nick end labeling, or labeling sections with an anti-transglutaminase antibody. Apoptotic cells were evident at the periphery of the pulp, mostly in a sub-odontoblastic location, and were more numerous in the crown than in the root region of the pulp. Most odontoblasts were unlabeled. A few apoptotic nuclei in the pulp of rat molars displayed the characteristics of chromatin condensation, as observed by electron microscopy. Many cell debris resembling apoptotic bodies were also observed. The 3 methods support the occurrence of apoptosis in the dental pulp. As this phenomenon was observed in healthy teeth apoptosis is probably involved in the regulation of the pulp cell population.

[Regulation of osteoclastic resorption by prostanoids in vivo]. / Régulation de la résorption ostéoclastique par les prostanoïdes 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.

[Pulpectomy. Why? When?]. / La dépulpation. Pourquoi? A quel moment?

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.