An ectopic maxillary second molar

A bstract — A rarely encountered ectopic and dilacerate maxillary second molar is described. The tooth was found to be attached to the medial wall of the maxillary sinus. Its location is thought to be due to ankylosis consequent to injury sustained during infancy.     

Subcritical crack growth behavior and life data analysis of two types of dental Y-TZP ceramics

Objectives

The aim of this study was to evaluate the mechanical properties and the subcritical crack growth behavior of a presintered dental Y-TZP (Kavo Everest ZS) and a hot isostatic pressed Y-TZP (Kavo Everest ZH) and to perform life data analysis.

Methods

For each material 150 bending bars were produced. The initial fracture strength was determined in a four-point bending test. The subcritical crack growth parameters n and A were determined in a dynamic fatigue method at four decreasing loading rates from 110 MPa/s to 0.11 MPa/s in distilled water at 38 °C. For each loading rate Weibull statistics were performed and the Weibull moduli m and characteristic strengths σ₀ were calculated. Using these data, strength-fracture probability-life time (SPT) predictions were derived for 1 day, 1 year, 5 years and 10 years, based on a static crack growth mechanism.

Results

The “hipped” Y-TZP ceramic exhibited a higher initial strength (σ_c = 1618.18), characteristic strength (σ₀ = 837.15) and fracture toughness (K_IC = 4.52 MPa/m^1/2) than the pre-sintered ceramic (σ_c = 1431, σ₀ = 745.46 and K_IC = 3.17 MPa/m^1/2, respectively). Fatigue parameters, n and A, were 28.5 and 7.97 × 10⁻²⁴ for Everest ZH and 30.15 and 5.47 × 10⁻²⁰ for Everest ZS. The predicted fracture stress at 5% failure probability for a lifetime of 10 years was 259.34 MPa for Everest ZH and 263.2 MPa for Everest ZS.

Conclusions

Although the “hipped” Y-TZP showed favorable initial mechanical properties, no significant difference could be found in the susceptibility of both ceramics to subcritical crack growth and their long-term strength.     

Identification of cultivable microorganisms from primary endodontic infections with exposed and unexposed pulp space

This study was aimed at comparing the cultivable microorganisms in canals with periapical radiolucencies with exposed and unexposed pulp space. Microbiological samples were taken and analyzed from 45 canals with exposed pulp space, and 43 canals with unexposed pulp space. The canal contents were analyzed by aerobic/anaerobic culture, and conventional identification techniques. There were 211 isolates of bacteria belonging to 28 genera and 55 species recovered from exposed canals. In the unexposed group, 185 isolates of bacteria were recovered, of which 54 species of 28 genera were identified. Among the four most common genera, Prevotella was significantly more common in the exposed group (51/211 in the exposed group versus 30/185 in the unexposed group) (p = 0.049), while there were no differences in prevalence of Actinomyces, Peptostreptococcus, and Campylobacter between two groups of canals. In addition, Fusobacterium nucleatum and Propionibacterium acne were significantly more common in the unexposed canals (p = 0.047 and p = 0.0051, respectively). Similarity in bacterial species in these two groups suggests that pulp space exposure may not be a significant factor in determining the type of bacteria present in infected canals.     

Effect of a peripheral NMDA receptor antagonist on glutamate-evoked masseter muscle pain and mechanical sensitization in women

AIMS: To test the hypothesis that local injection of the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine would significantly attenuate glutamate-evoked masseter mechanical sensitization and muscle pain in healthy young women either taking oral contraceptives (W+OC) or not taking oral contraceptives (W-OC). METHODS: Experimental pain was evoked in 47 healthy female subjects (W+OC, n=25; W-OC, n=22) by 2 injections of glutamate (0.2 mL, 1 mol/L) into the masseter muscle. A first injection of glutamate alone was followed by a second injection, 35 minutes later, of glutamate combined with ketamine (0, 1, or 10 mmol/L). Evoked pain intensity was scored on a 10-cm electronic visual analog scale (VAS). Distribution of perceived pain was drawn on a lateral view of the face (pain drawing). Masseter muscle pressure pain thresholds (PPT) and pressure-pain tolerances (PPTOL) were determined bilaterally before and at regular time intervals after injections. Analyses of variance (ANOVA) were used to test the data. RESULTS: There were no main effects of ketamine on any of the VAS pain parameters or on the pain drawing (ANOVAs: P > .055). Furthermore, there were no differences in PPT, PPTOL, VAS peak pain, duration, overall VAS pain, or pain drawing when W-OC were compared with W+OC (ANOVAs: P > .087). Repeated injection of glutamate alone significantly decreased PPT and PPTOL (ANOVAs: P < .001); however, this effect was not significantly attenuated by ketamine. CONCLUSIONS: Peripherally administered ketamine had no effect on glutamate-evoked masseter muscle pain and sensitization in healthy young women, which contrasts with recent observations in healthy young men. Further studies will be needed to reveal the mechanisms that underlie this apparent sex-related difference in ketamine-mediated analgesia.     

Experimental evaluation of microsurgical repair of the lingual nerve

Epineural microsurgical repair of the lingual nerve has been shown to be effective in leading to return of sensation in an animal model. Cadaver dissections have provided information regarding surgical access to the operative site, some possible anatomic variations that may be encountered, and a method for nerve repositioning to allow a gain in length.     

Age-related changes in the periodontium of pigtail monkeys

Age-related changes in the periodontia of maxillary lateral incisors were studied in the pigtail monkey (Macaca nemestrina) . Transverse sections were obtained from the crestal and apical middle third of the roots from specimens of ages 3 and 4 years (N = 2), 10 years (N = 3), and 20 years (N=3). With increasing age, the roots migrated toward the labial cortical plate, resulting in the development of a bony root prominence on the labial periosteal surface. Quantitative histomorphometric measurements in conjunction with analysis of variance were used to isolate the effects of age and section level on the parameters of interest. The areas of the alveolar socket and cementum increased significantly with age, as did cemental thickness. The width of cementum on the lingual surface was significantly greater than the width on the other surfaces, probably as a response to the labial migration of the tooth. The width and relative area of the periodontal ligament space decreased significantly with age, suggesting that the deposition of cementum proceeded at a rate slightly greater than that at which the socket was enlarging. The number of blood vessels in each quadrant of the periodontal ligament were counted, and no significant difference was found among the different age groups. There were, however, significantly more blood vessels in sections from the crestal third than in those from the apical third of the roots.     

Epilepsy and the dental management of the epileptic patient

AIM: The aim of this article is to educate oral healthcare providers on the diagnosis and treatment of epilepsy and seizure disorders. It also shows the impact of epilepsy on the oral cavity and provides suggestions on the dental management of epileptic patients. REVIEW: Epilepsy and seizure disorders affect 1.5 million Americans. The disease is caused by a number of genetic, physiologic, and infectious disorders as well as trauma. Treatment is primarily pharmaceutical but can also be surgical. The disease itself and the pharmaceutical management often have an impact on the oral cavity. Primary management considerations are the provision of good periodontal care and the restoration of the teeth with stable, strong restorations. CONCLUSIONS: With proper understanding of patients with epilepsy and seizure disorders and their medical treatment, the dental care team can safely and effectively render dental care that will benefit the patient and minimize the risk of oral health problems in the future.     

Molar Distalization with Different Pendulum Appliances: In Vitro Registration of Orthodontic Forces and Moments in the Initial Phase

Abstract. Aim: Registration of the orthodontic forces and moments acting with different types of pendulum appliance for non-compliance upper molar distalization in an in vitro study. Material and Methods: The purpose-designed test set-up comprised the following components: artificial maxilla with anchorage unit and two electrothermodynamic (ETD) molars, electronic measuring unit for temperature control and regulation, and a sensor unit with force-moment sensor, analog/digital converter and data readout unit. This set-up permitted virtually authentic simulation of in vivo conditions on the one hand and precise determination of the force systems on the other.The appliances investigated were the standard pendulum appliance with U-loop activation according to Hilgers and with uprighting activation according to Byloff, the M-pendulum with U-loop activation according to Scuzzo, and the Pendulum K with initial uprighting activation, toe-in bend and incorporated distal screw according to Kinzinger. Results and Conclusions: The effects shown by the standard pendulum appliance and the M-pendulum over a 3 mm simulated distalization increment were a marked decrease in the distally directed forces, and an increase in the intrusive and palatally directed forces as well as in the distoinclinatory, mesially inward, and palatally rotating moments.Activations in the U-loop region of the pendulum springs induced an increase in distally and buccally directed forces and in uprighting and buccally rotating moments as well as a marked rise in extrusive forces. Whereas the activation described by Hilgers led to mesially outward rotating moments, activation according to Scuzzo resulted in a further increase in the mesially inward rotating moments.In the measured standard pendulum appliances, uprighting activation at the end of the pendulum according to Byloff led to an increase in distally and buccally directed as well as in mildly intrusive forces, and to an increase in uprighting as well as in buccally and mesially outward rotating moments.With the Pendulum K according to Kinzinger, the initial toe-in bend and uprighting activation in the region of the end of the pendulum spring together with regular adjustment of the incorporated distal screw permitted virtually translatory molar distalization: constantly distalizing forces with slight intrusive, buccally directed, and rotating side effects.