Anterior disc displacement with reduction and symptomatic hypermobility in the human temporomandibular joint: prevalence rates and risk factors in children and teenagers

AIMS: To assess the prevalence rates and risk factors of anterior disc displacement with reduction (ADDR) and symptomatic hypermobility in a large sample of children and teenagers. Prevalence rates were also established in samples of young adults and adults. METHODS: Children from 7 Dutch primary and secondary schools (n = 1,833) aged 4 to 18 years (mean age +/- SD 10.8 +/- 3.9 years), 220 dental students aged 19 to 30 years (mean age +/- SD 21.9 +/- 3.6 years), and 100 dental school employees more than 30 years old (mean age +/- SD 43.5 +/- 9.8 years) were examined. The presence of ADDR or symptomatic hypermobility was scored using well-defined clinical criteria. For the children only, an additional standardized oral history and clinical examination were performed to assess possible risk factors. Odds ratios (ORs) were calculated with the use of logistic multivariate regression analysis. RESULTS: The prevalence rate of ADDR in at least 1 of the 2 joints increased during childhood and adolescence and stabilized into adulthood at about 26.6%. In children and teenagers, besides age (OR = 1.06 for boys, OR = 1.23 for girls), risk factors for ADDR were a history of orthodontics (OR = 1.57), an increasing overbite (OR = 1.15), and protrusion (OR = 1.12). In children and teenagers, the prevalence rate of symptomatic hypermobility was higher for girls (13.8%) than for boys (8.2%). Besides gender (OR = 2.07), risk factors for symptomatic hypermobility were race (OR = 2.61 for non-Caucasians), masticatory muscle pain (OR = 1.95), and increasing maximum mouth opening (OR = 1.08). CONCLUSION: In children and teenagers, ADDR and symptomatic hypermobility have different prevalence rates and risk factors.     

Impact of irrigant sequence on mechanical properties of human root dentin

To get the root canal system free of organic debris and the smear layer, it has been recommended to irrigate with a NaOCl solution during instrumentation, followed by a rinse with a chelating agent such as ethylenediaminetetraacetic acid (EDTA) and a final irrigation with NaOCl. However, both hypochlorite and EDTA weaken dentin through dissolution of its organic and inorganic components, respectively. EDTA exposes the organic dentin matrix, which could then be attacked more easily by hypochlorite. It was the aim of this study to assess the impact of different irrigation sequences of NaOCl (2.5% w/v; total exposure time, 24 minutes) and EDTA (17%; 3 minutes) on the elastic modulus and flexure strength of standardized human root dentin bars (n = 11 per group). Exposures to solely EDTA (3 minutes), NaOCl (24 minutes), and water were used as control treatments. Specimens were subjected to 3-point bending tests; modulus of elasticity and flexure strength values were compared between groups with one-way analysis of variance followed by Fisher probable least-squares difference test. The alpha-type error was set at .05. The 24-minute exposure to the hypochlorite solution caused a significant drop in flexure strength compared with water- or EDTA-treated controls (P < .05), whereas the elastic modulus remained unaffected. In contrast, the short exposure to EDTA as is clinically recommended did not affect the mechanical dentin parameters under investigation, regardless of the irrigant sequence that was used.     

Panoramic radiograph as a method for detecting calcified atheroma plaques. Review of literature

Cerebrovascular accident (CVA) is the third cause of death in industrialized countries, following cardiovascular disease and cancer. It is therefore a significant public health issue, not only due to its high incidence, but also to the high costs involved in the physical and psychological rehabilitation of these patients. Dental Practitioners, as health care providers, ought to play their part in this issue and contribute, within their means, to the early detection of patients at risk of having a CVA. Since the eighties, different authors have described the possibility of detecting calcified atheroma plaques located at carotid artery bifurcation through panoramic radiograph. In this way, the Dental Practitioner s possibilities in this field have been extended. However, this new use of panoramic radiograph must overcome certain obstacles before it is implemented as a new screening method for patients at risk of having a CVA. Amongst these, we would have, on the one hand, the assessment of the real clinical significance, as regards prognosis, of atheroma plaque calcification as well as its usefulness as a factor for predicting the appearance of CVA symptoms and, on the other hand, the possibility of making a correct differential diagnosis regarding other calcified structures that may appear on panoramic radiograph.     

Electron microscopic observations of "keratin pools" in chronic hyperplastic oral mucosa.

"Keratin pools," previously characterized clinically and histochemically in the superficial epithelium of chronic hyperplastic oral mucosa, were studied by light and electron microscopy. These occured as small beaded and larger coalescent masses which varied in metachromasia. Ultrastructurally, the "keratin pools" consisted of electron-dense, amorphous or finely-granular material developing and coalescing, chiefly as extracellular deposits. The "pools" frequently possessed a layered arrangement alternating with cells having distinct tonofilaments, desmosomes, and definite cell membranes. Occasional bands of filamentous-like material, possibly representing tonofilament bundles, were observed in some "pools."     

Fracture process characterization of fiber-reinforced dental composites evaluated by optical coherence tomography, SEM and optical microscopy

This study used optical coherence tomography (OCT) compared to scanning electron microscopy (SEM) and optical microscopy (OM) to evaluate qualitatively crack propagation and final fracture in restorative composite materials - Filtek Z250 and Filtek Z350 (3M ESPE) - with fiber reinforcement after cyclic loading. Samples were made using a split mold. Initially, 3-point bending tests were performed to determine the maximum force and tension at the fracture moment using samples without fiber reinforcement. Then, mechanical cycling tests were performed using samples with glass fiber embedded internally. The failures were analyzed using the 3 methods described before. OCT permitted good characterization of internal crack propagation of the dental composites, which, however, could not be visualized by either SEM or OM. OCT was proven to be laboratory research tool that is easy to use, does not require any specific preparation of the samples, and is less expensive than SEM.     

Dietary influences on the formation of dental calculus in rats

Eleven diets were evaluated for their ability to produce dental calculus in albino rats. A diet containing 50 % cornstarch, 32 % nonfat dry milk, 3 % liver powder, 5 % celluflour, 1 % cottonseed oil, 5 % powdered sucrose, 1 % calcium chloride dihydrate, 2.7 % sodium dihydrogen phosphate monohydrate, and 0.3 % magnesium sulfate (Francis and Briner 1969) was remarkably effective. On the basis of a 0–3 calculus scoring system, an average score of 2.36 (S.D. = 0.65) resulted after 4 weeks' exposure to the above diet and, after 8 weeks, the average score was 2.59 (S.D. = 0.56).
While it was found that, in general, high cornstarch and milk powder diets were associated with higher calculus scores, no other diet remotely approached the above diet in calculogenicity.