Dentinal tubules driven wetting of dentin: Cassie-Baxter modelling.

We investigate the wetting properties of dentin surfaces submitted to a phosphoric acid etching followed by an air drying procedure, as in clinical situations of adhesive dentistry. The surface topography of the etched surfaces was characterized by AFM, and the wetting properties of water on these rough and heterogeneous surfaces were studied, by contact angle measurements. We showed that the contact angle increases with the acid exposure time and consequently with both surface roughness and the organicmineral ratio of the dentin components. From the whole results, obtained on dentin and also on synthesized hydroxyapatites samples, we inferred a water contact angle of ~133° on the dentinal tubule. These experimental results may be described by the Cassie-Baxter approach, and it is suggested that small air pockets could be formed inside the dentinal tubules.

Database analysis of a French type 2 diabetic population shows a specific age pattern of tooth extractions and correlates health care utilization.

AIMS: To assess the relationship between type 2 diabetes and tooth loss and the predictive value of health behavior and routine dental care in regard to both dental and medical follow-ups. METHODS: Cross-sectional study from a national database of a French population of railways transport workers was conducted with a descriptive analysis between registered diabetic patients and non-diabetic subjects. The relationship between oral health and diabetes was measured by tooth extraction prevalence in regard to the frequency of scaling-prophylaxis sessions and the number of medical and dental appointments. RESULTS: The prevalence of tooth extractions in the type 2 diabetic population is 1.88 higher than the non-diabetic population. Diabetic patients tend to undergo dental extractions earlier and more often than non-diabetic individuals. They also have more medical appointments and less dental check-ups and scaling sessions than the non-diabetic population. CONCLUSION: Measured by tooth loss, type 2 diabetic patients have a significantly earlier detrimental oral status when compared to the non-diabetic population. They exhibit a different pattern in health care utilization of outpatient medical resources. Oral health surveillance is not correctly addressed by the medical and dental coverage of these diabetic patients. Emphasis should be directed on specific dental care programs aimed at preventing tooth loss.

In vitro study of a Nd:YAP laser in endodontic retreatment.

Nd:YAP laser is a dental laser with a 1340 nm wavelength. The laser beam is carried by a 200 to 300 microns fiberoptic and is suitable for endodontic therapy. We used the Nd:YAP laser in an in vitro experiment to study its effectiveness in endodontic retreatment. Temperature measurements and irradiation parameters were first defined. Then Nd:YAP laser irradiation was used, alone or in combination with hand instruments, to remove various canal sealers and broken instruments. Clinical parameters were monitored and scanning electron microscopic observations were conducted. When used at 200 mJ--with a pulse duration of 150 ms, an exposure time of 1 s and a frequency of 10 Hz--Nd:YAP laser preserved the dentinal walls of the root canal and enabled root canal retreatment without thermic elevation harming periodontal tissue. It is concluded that, in combination with hand instruments, the Nd:YAP laser is an effective device for root canal preparation in endodontic retreatment.

mRNA characterization of human fetal enamel matrix.

Preliminary characterization of the human enamel matrix at 16-18 weeks in utero was performed. Using an homogenizing buffer, the proteins were extracted and analysed by gel electrophoresis. Total cellular RNA was isolated and the cell-free mRNA translated. The major component was a 68,000 protein with an enamelin-like amino-acid composition. Other translation products included a 55,000 polypeptide and lower mol. wt components of 26,000, 22,000 and 20,000 size of amelogenin size. It is suggested that high mol. wt component in the enamelin range is the most prevalent at the early stage of human tooth development.

Immunoblotting and cytochemical characterization of human enamel proteins.

Mature enamel proteins (tuft proteins) and fetal enamel proteins were extracted by an homogenizing buffer method, subjected to SDS-PAGE and immunoblotted with a polyclonal antibody raised against the mature enamel proteins. Both fetal and tuft proteins were recognized by this immunoblotting. With the same antibody, immunolocalization of the developing enamel proteins was done on semi-thin-sections of human fetal tissue at the secretory stage, using an immunoperoxidase technique. Specific labelling of the enamel protein matrix was observed. It is concluded that a polyclonal antibody against mature enamel proteins (anti-tuft) can recognize the developing protein matrix at the secretory stage. This suggests that a common antigenic determinant is maintained throughout the course of amelogenesis in human enamel.

Numb chin syndrome.

Numb chin syndrome reflects an abnormality in the mental nerve or inferior alveolar nerve, or occasionally in a nervous structure located higher up in the body. It manifests as objective and/or subjective sensory disorders in the distribution of the mental nerve or inferior alveolar nerve, represented primarily by half of the lower lip and chin. Although numb chin syndrome falls mainly within the province of dentists and stomatologists, it can reveal a number of neoplastic or other diseases seen by rheumatologists. This article provides background information on numb chin syndrome, discusses its causes (including those seen mainly by dentists and stomatologists), and reviews numb chin syndrome due to generalized malignancies based on 144 cases from the literature and two personal cases.

Mental nerve neuropathy as a result of hepatitis B vaccination.

We describe a 20-year-old woman who presented with polyarthralgia and sensory neuropathy, including mental nerve neuropathy. The symptoms were attributed to hepatitis B vaccination. This unusual cause of mental nerve neuropathy has not been previously described. However, as the use of hepatitis B vaccination is growing, adverse side effects, including mental nerve neuropathy, should be observed with an increased frequency.

Florid cemento-osseous dysplasia: Report of a case documented with computed tomography and 3D imaging.

Florid cemento-osseous dysplasia is an uncommon disease of the jaws. This article reports the case of a 49-year-old black woman who was diagnosed with florid cemento-osseous dysplasia on the basis of conventional radiographic findings. Computed tomography and three-dimensional imaging of the mandible were performed, and they enabled detailed localization of the bone defects. The role of computed tomography in the evaluation of cemento-osseous lesions is discussed.

Factors influencing the long-term results of endodontic treatment: a review of the literature.

The purpose of this review of the literature is to examine the factors and their influence on the outcome of endodontic treatments, and also to attempt to have an authors' consensus concerning the impact of these factors on long-term results. The documentary research was conducted using the meta-analysis principles of critical reading of the literature. Two groups of factors can be identified regarding the outcome of endodontic treatments: those which influence the success of the procedure and those which do not significantly affect the success rate. Agreement is obtained in all studies on two major factors, the preoperative periapical status and the apical limit of the obturation, which appear to strongly influence the success of endodontic therapy. This review highlights the methodological problems of retrospective studies and points out the need for consensus regarding the evaluation criteria of root canal therapy.

[Recent findings in the etiopathogenesis of caries]. / Données récentes sur l'étiopathogénie de la carie.

Caries have three main interrelated etiological factors: 1) a bacteriological factor represented by cariogen oral bacteria, mainly Streptococcus mutans, which adhere to the dental surface and initiate the decalcification of the enamel by producing an acid environment through carbohydrate degradation; 2) the quality of the oral biofilm which is colonized more or less rapidly by bacteria after brushing, leading to an adhesive and aggressive dental plaque; 3) the quality of enamel which is reinforced by fluor ion, and of saliva. The early superficial phase of carie constitution is reversible through remineralisation from calcium, phosphate and fluor ions present in the oral cavity. In the absence of remineralisation the destructive and infectious process extends to the inner part of the tooth leading, to its progressive destruction. Prevention is based upon the following pathophysiological data, mainly: 1) family education on oral hygiene by regular brushing, and avoidance of foods or fluids containing sugars between meals; 2) fluoride intake starting at birth and being adapted to age, the prescription of fluoride supplementation, taking into account possible other sources of fluor (salt, water).

[When to consult an orthodontist?]. / Quand conseiller un orthodontiste?

Orthodontics aims to improve face and teeth harmony and to allow a good development of orofacial and occlusive functions. Orthodontic treatment is adapted to each individual case and may be early or late. Orthodontic indications and management require a collaboration between the paediatrician, the dentist and the orthodontist. The main indications are described.

Adhesion forces between AFM tips and superficial dentin surfaces.

In this work, we study the adhesion forces between atomic force microscopy (AFM) tips and superficial dentin etched with phosphoric acid. Initially, we quantitatively analyze the effect of acid etching on the surface heterogeneity and the surface roughness, two parameters that play a key role in the adhesion phenomenon. From a statistical study of the force-distance curves, we determine the average adhesion forces on the processed substrates. Our results show that the average adhesion forces, measured in water, increase linearly with the acid exposure time. The highest values of such forces are ascribed to the high density of collagen fibers on the etched surfaces. The individual contribution of exposed collagen fibrils to the adhesion force is highlighted. We also discuss in this paper the influence of the environmental medium (water/air) in the adhesion measurements. We show that the weak forces involved require working in the aqueous medium.

Dentin wetting by three adhesive systems: influence of etching time, temperature and relative humidity.

OBJECTIVES: The purpose of this study was to investigate the wetting properties of three adhesives systems on etched dentin surfaces submitted to a brief air-drying procedure, as in clinical conditions. The influence of two clinical parameters (surface temperature and surrounding hygrometry) on wetting was investigated. METHODS: Two total-etch adhesives (Excite Vivapen and Adper Scothbond 1XT) and one self-etching adhesive (GC-G Bond) were used. Superficial and deep dentin slice were obtained from six caries-free extracted third molars. Before the adhesive deposition, the dentin samples were etched with 37% phosphoric acid for different time durations. The surface topography was characterised by atomic force microscopy (AFM) observations and the wetting properties of dentin were studied by contact angle measurements. RESULTS: Unlike clinical expectations, the contact angles increased with the acid exposure time, and consequently with both surface roughness and the organic-mineral ratio of the dentin components. The wetting properties were clearly more sensitive to the surrounding relative humidity than the temperature. The contact angles values were reduced by about 50% when the relative humidity increased from 37% to 80% and by about 15% when the temperature was raised from 25 degrees C to 37 degrees C. CONCLUSION: Acid-etched dentin exposed to a brief air-drying appears as the key parameter to control the wetting properties of total-etch adhesive-dentin systems. The experimental results seem to be well described by the Cassie-Baxter approach, and suggest that dentinal tubules through an adhesive repellent contribution should account for the observed wettability decreases.

The association between periodontal disease and joint destruction in rheumatoid arthritis extends the link between the HLA-DR shared epitope and severity of bone destruction.

OBJECTIVE: To evaluate a possible association between wrist and periodontal destruction in rheumatoid arthritis, and between periodontal destruction, dry mouth, and labial salivary gland biopsy and the contribution of genetic factors (the shared epitope (SE) and IL1B (+3954) or TNFA (-238 or -308) gene polymorphisms). METHODS: 147 patients with rheumatoid arthritis were enrolled. Periodontal damage was defined according to the Hugoson and Jordan criteria on panoramic dental x rays. Typing for the SE and cytokine polymorphisms was undertaken by enzyme linked oligosorbent assay. Odds ratios (OR), relative risk (RR), and chi2 values were calculated to quantify associations. RESULTS: An association was observed between wrist and periodontal bone destruction (chi2=11.82; p<0.001): 63 patients had both wrist and periodontal destruction, 31 had wrist destruction alone, 20 had periodontal destruction alone, and 33 had no destruction at either site. An association was seen between a positive labial salivary gland biopsy and periodontal bone destruction (RR=2.73 (95% CI, 1.35 to 5.51), p<0.01, n=41) or wrist bone destruction (RR=4.52 (1.96 to 10.45), p<0.001, n=41). The SE was associated with wrist bone destruction (OR=2.5 (1.16 to 5.42), p<0.05) and periodontal bone destruction (OR=2.2 (1.04 to 4.84), p<0.05). No association was found between the selected cytokine polymorphisms and bone destruction. CONCLUSIONS: A strong association was found between wrist and periodontal bone destruction. The destruction risk was further increased in patients with sicca syndrome. The SE appears to be a severity genetic marker for both wrist and periodontal bone destruction.

[Histological aspects of tooth bleaching technics]. / Aspect histologique des techniques de blanchiment dentaire.

The chemical principles of tooth bleaching are detailed in order to analyze scanning microscopy data obtained following internal and external bleaching tooth bleaching appears harmless to the enamel structure providing no etching is applied prior to bleaching. Previous enamel undermining appears to increase the porosity along preexisting cracks. Internal bleaching gives way to enamel and dentinal demineralization, which is of particular importance at the dento enamel junction. The biological effects of bleaching on dental hard tissues must be viewed in light of the clinical indications for these procedures.

Student satisfaction with curriculum modifications in a French dental school.

Since 1994, important modifications have been implemented in the dental curriculum in France, and an additional year has been included in the dental curriculum. The 1st year has remained unchanged; it is common to both medical and dental schools and leads to a selection procedure of 1 in 10 dental students. In the new curriculum, the dental student is engaged in a 5-year programme in dental school (years 2 to 6), as opposed to 4 years in the former programme (years 2 to 5). Basically, this new curriculum emphasises research initiation, links with medical training and offers broader clinical experience. During the academic year 1998-1999, dental schools had 2 different types of students: the 4th year students belonging to the new programme along with the 5th year students in their final year of the old curriculum. Using a specially devised questionnaire, we investigated the students' perception of their respective training, their motivation and professional plans. At the Faculty of Odontology in Lyon, the new curriculum is perceived as an increased strain by the dental students.

Outcome assessment of the French internship graduate programme.

In 1995, the first dental postgraduate residency programme was established in France. Selection of the applicants was performed by means of a selective national competitive examination among dental students in the final year of the undergraduate studies. The main objective of this 3-year general practice internship was to provide a clinical training for future academic dentists. This study describes the characteristics and the professional outcome of the student population enrolled in this programme. The French internship programme represents a new and welcome modification on the training of future dental academicians and establishes similarities with other programmes in Europe.

Prenatal diagnosis of trisomy 10 p in a twin pregnancy.

A twin pregnancy with trisomy 10 p due to a paternal 10;12 translocation is reported. The prenatal diagnosis steps followed in twin pregnancies are reviewed and the concordant features of trisomy 10 p seen in both fetuses confirm previous reports on the clinical features of this chromosomal defect.

[Amelogenesis imperfecta and hypothalamo-hypophyseal insufficiency]. / Amelogenèse imparfaite et insuffisance hypothalamo-hypophysaire.

Eleven patients with hypopituitarism, medio-facial hypoplasia and amelogenesis imperfecta were examined. The hypothalamo-pituitary dysfunction affected somatotrophic, gonadotrophic, corticotrophic and thyrotrophic function. The facial anomalies included medio-facial hypoplasia with hypertelorism and amelogenesis imperfecta. The latter--hypoplastic in nature--was noted in all anterior teeth and affected both dentitions. The enamel defect was confirmed on microscopic examination of an impacted tooth. The spectrum of malformation may also present as amelogenesis imperfecta in association with somatotropin deficiency. A genetic mechanism may possibly account for the clinical elements.