The effect of the mismatch between the core diameter of self-threading dentine pins and the pinhole diameter

This laboratory study incorporated the use of three different sized twist drills to prepare pinholes in extracted upper molar teeth. The diameter of each pinhole was measured. A pre-measured self-threading pin was then placed in each pinhole. The amount of strain created during pin placement (placement strain), the temperature rise during pin placement, the amount of strain remaining (residual strain) within the tooth structure after pin placement and the removal force (retention) were recorded for each pin. The results showed that, during the placement of a self-threading dentine pin, the difference between the pincore diameter and the pinhole diameter was an important parameter. This difference determined the amount of strain created during pin placement, the temperature rise during pin placement, the amount of strain remaining within the tooth structure after pin placement and the retention of the pin. The placement strain, temperature rise, residual strain and retention were all greater when the pin core diameter exceeded the pin hole diameter.

Glaucoma

The routine, easiest-to-treat adult patients with glaucoma utilize 1.80 office visits, 3.34 prescriptions, and 2.02 medical/surgical procedures during the course of a year. Based on data from the PTE-Registry database, this patient group did not receive any hospital admissions or professional inpatient services. Eye surgery was performed at an average rate of 0.08 times per PTE. About 53.5% of all PTEs were treated without the use of prescription drugs. When a drug was prescribed, beta blockers were used most often. In fact, 74.1% of all PTEs treated with a single drug group used a beta blocker.

Characterization of the development of elasticity in dental luting cements

OBJECTIVES

The development of elasticity of dental luting cements was investigated as an indicator of working and setting time.

METHOD

A displacement rheometer was used to monitor the development of elasticity. Three luting cements were examined.

RESULTS

The initial onset of elasticity in the glass-ionomer and polycarboxylate cements did approximate the manufacturer's quoted working times. The onset of elasticity did not appear to define a clinically useful working time for the zinc phosphate cement.

CONCLUSIONS

The development of elasticity in luting cements as a measure of working time was not universally relevant. The demonstration of the presence of elasticity in some cements may have consequences for cementation and all ceramic crown systems.

Nonmigraine headaches

The easiest-to-treat nonmigraine headaches for the 18-to-64 year old population have an average duration of 60 days. The most common diagnostic imaging test used is the computed tomography scan performed on the head or brain. Two out of 1,000 patients have a hospital admission. About 43% of the PTEs are treated without prescription. When a single prescription drug group is used, 56.7% of the prescriptions are for pain relief drugs. Nonsteroidal anti-inflammatory drugs are the most prescribed single drug group for this condition.

Classification of complex regional pain syndromes. New concepts

A new classification system, termed complex regional pain syndromes types I and II, has been devised to replace the nomenclature of pain disorders previously termed reflex sympathetic dystrophy and causalgia. CRPS type I does not have identifiable major nerve injury, whereas CRPS type II has an identifiable major nerve injury. The classification is based on clinical symptoms and signs without incorporating any mechanistic connotations. These CRPS disorders may have SMP, SIP, or both.

Post-traumatic upper extremity reflex sympathetic dystrophy. Clinical course, staging, and classification of clinical forms

RSD is a symptom complex, representing an exaggerated response to injury or tissue damage. The amplification of the normal responses probably occurs both in the periphery and in the central nervous system. Diagnostic criteria are still under discussion, and treatment modalities are still directed toward the symptoms because the pathophysiology is not known. The pain of the condition may be sympathetically maintained of sympathetically independent (or both), and sympathetic blockade is useful in the former category. Treatment modalities must be directed toward optimizing both comfort and function of the affected extremity. Such treatment programs might occur in a multidisciplinary setting.

The effects of die-spacing on post-cementation crown elevation and retention

This paper reviews the relevant dental literature concerning the effect of die-spacing on crown elevation and pre- and post-cementation crown retention. Techniques of providing die-spacing and measurement of the thickness of die-spacer are discussed. A review of the role of the provision of a cement space in reducing post-cementation crown elevation is presented. Factors which may affect crown retention prior to and following cementation are also reviewed. The influence of variables in techniques and experimental design on the results of the studies reviewed is discussed.

The effect of seating force and die spacing on pulpward cementation pressure transmission: a laboratory study

Pulpward pressure transmission during crown cementation occurs via the dentinal tubules. The present study investigated the effect of crown seating forces and the effect of increasing the die spacing on pulpward pressure transmission. Twenty upper premolars were prepared with 1 mm shoulder margins for non-precious metal full crowns. A 0-104 kPa pressure transducer (Mediamate EA, Data Instruments, Baltimore, MD, USA) was connected, via the sectioned root of the premolar, to the pulp chamber which was perfused with saline at 83 kPa driven by nitrogen gas, for two hours prior to cementation. Crowns with 2 or 6 layers of die-spacing were seated with 25 N or 100 N force using zinc-phosphate cement. The pressure transducer was connected to a Wheatstone bridge (Measurements Group, Instruments Division) and the extent of crown seating and output from the pressure transducer was recorded. Results indicate that 25 N seating force produced a lower mean pulpward pressure (41 +/- 54 Pa) compared to the 100 N seating force (251 +/- 276 Pa). Seating was significantly improved with 6 layers of die-spacing (seating discrepancy 18 +/- 12 mm) compared with 2 layers (139 +/- 111 mm). It is concluded that a higher seating force increases pulpward pressure transmission. Increasing die spacing improved crown seating but did not affect the amount of pressure transmitted.

Natural infection of red deer with bovine tuberculosis

Six bovine tuberculosis-free red deer hinds were introduced in October 1993 to a 1.8 ha enclosure, within a larger field study site known to contain tuberculous possums, and kept there for 9 months. A Mycobacterium bovis-infected possum was found in the vicinity of the deer enclosure 3 weeks after the introduction. Subsequently, a further eleven infected possums were found in the area. The deer were monitored by repeated composite antibody detection ELISA and lymphocyte transformation assays for tuberculosis, interpreted in parallel, by skin testing and by routine culturing of samples collected from potential excretion sites. Lymphocyte transformation assay evidence of M. bovis infection in four hinds was first observed 4 months after introduction. One other hind became bovine tuberculin lymphocyte transformation assay positive in the 5th month. Positive or equivocal bovine reactivity remained evident at most test episodes. A comparative cervical skin test performed in July 1994, shortly before slaughter, was positive in these five hinds. Mycobacterium bovis was recovered off swabs from the oropharyngeal tonsils of two hinds during routine sampling. Detailed necropsy of the six deer revealed a single typical tuberculous lesion in only one, but culturing of various tissue specimens ascertained that the five blood test and comparative cervical skin test-positive animals were all infected. Mycobacterium bovis was cultured from the oropharyngeal tonsils of four and medial retropharyngeal lymph nodes of two of the deer with no typical gross lesions. Six additional tuberculosis-free hinds were introduced to the enclosure in April 1994 and kept there for 12 months. Four of these animals showed a positive lymphocyte transformation assay response to M. bovis after 9 weeks, but no significant reactivity thereafter. Concurrent observational studies suggest that five of the first six deer probably became infected through close inspection and investigation of the tuberculous possums, although the possibility of deer-to-deer transmission cannot be totally excluded. The likely deer-possum contact, and thus exposure to M. bovis, was related to the curiosity and social ranking of the hinds. The second group appear to have had transient exposure to M. bovis, possibly caused by direct contact with the infected hinds introduced earlier. This group never showed any curiosity toward, or interaction with, possums during the periods of observation.

Dressed to heal: new options for graft site dressing

To ensure the close apposition and immobilization required for survival of full thickness skin grafts, the traditional method is to use pexing sutures or tie-over pressure dressings. In certain areas, such as around the eye, other methods are required because either a concave or convex surface prevents adequate pressure, or the use of sutures as ties produces distortion of anatomical free margins. Alternative dressing methods include; telfa chips kept in place by a pressure pad; calcium alginate (which has the advantages of assisting haemostasis and absorbing serous discharge) under a pressure pad; and extra thin hydrocolloid dressings which decrease slough and are less conspicuous than other dressings.

Low force cementation

OBJECTIVES

The marginal adaptation of full coverage restorations is adversely affected by the introduction of luting agents of various minimum film thicknesses during the cementation process. The increase in the marginal opening may have long-term detrimental effects on the health of both pulpal and periodontal tissues. The purpose of this study was to determine the effects of varying seating forces (2.5, 12.5, 25 N), venting, and cement types on post-cementation marginal elevation in cast crowns.

MATERIALS

A standardized cement space of 40 microns was provided between a machined gold crown and a stainless steel die. An occlusal vent was placed that could be opened or closed. The post-cementation crown elevation was measured, following the use of two commercially available capsulated dental cements (Phosphacap, and Ketac-cem Applicap).

RESULTS

The results indicate that only the combination of Ketac-Cem Applicap and crown venting produced post-cementation crown elevation of less than 20 microns when 12.5 N seating force was used. Higher forces (25 N) and venting were required for comparable seating when using Phosphacap (19 microns).

CONCLUSIONS

The amount of force required to allow maximum seating of cast crowns appears to be cement specific, and is reduced by effective venting procedures.

Xylazine and a xylazine/fentanyl citrate/azaperone combination in farmed deer II: Velvet antler removal and reversal combinations

Three studies were undertaken on farmed red and red x wapiti deer to evaluate xylazine and a xylazine/fentanyl citrate/azaperone combination for velvet antler removal. In the first experiment, 30 1-2 year-old red and 25% red x wapiti deer whose velvet was to be removed were given either 5% xylazine alone at 0.5 mg/kg body weight intramuscularly or the same dose rate of a commercially available mixture of 5% xylazine with the addition of 0.4 mg of fentanyl citrate and 3.2 mg of azaperone per ml. Physiological, behavioural and analgesic responses and reversal times after yohimbine or yohimbine and naloxone were monitored. There were no differences in heart rate, respiration rate, sedative or analgesic properties detected between xylazine or the xylazine/fentanyl citrate/azaperone combination. All deer became recumbent, but those given the xylazine/fentanyl citrate/azaperone combination became recumbent more rapidly than those given xylazine alone (9.4 and 12.5 minutes, respectively, p<0.05). The arousal pattern and timing of reversal of xylazine and xylazine/fentanyl citrate/azaperone using yohimbine and yohimbine and naloxone, respectively, were similar. The second experiment evaluated the reversal of the xylazine/fentanyl citrate/azaperone combination with either yohimbine or yohimbine and naloxone in 43 3-year-old red deer stags after velvet antler removal. There were no differences in arousal pattern or time to standing between reversal treatments. Sixteen 1-year-old red and 25% red x wapiti stags were used in the third experiment to evaluate clinically the analgesic properties of xylazine and xylazine/fentanyl citrate/azaperone combination during velvet removal without the application of a local anaesthetic agent. Withdrawal responses were observed in most deer after the xylazine/fentanyl citrate/azaperone combination at dosages containing 0.5, 0.7 and 0.75 mg of xylazine/kg and after xylazine alone at 0.7 mg/kg, indicating that insufficient analgesia was provided by the systemic agent for the surgical procedure of velvet antler removal. These studies have shown that the knock-down effect of the xylazine/fentanyl citrate/azaperone combination was more rapid than that of xylazine alone, but that other physiological, behavioural and analgesic responses at doses used and evaluated by the methods used were similar. Reversal of both the xylazine and xylazine/fentanyl citrate/azaperone combination was similar when using either yohimbine alone for xylazine and the xylazine/fentanyl citrate/azaperone combination or yohimbine and naloxone for the xylazine/fentanyl citrate/azaperone combination. The evaluation of surgical analgesia for antler removal suggested that both xylazine alone and the xylazine/fentanyl citrate/azaperone combination provided insufficient analgesia and that local anaesthetic should be used in all cases.

Differential Rotation and Dynamics of the Solar Interior

Splitting of the sun's global oscillation frequencies by large-scale flows can be used to investigate how rotation varies with radius and latitude within the solar interior. The nearly uninterrupted observations by the Global Oscillation Network Group (GONG) yield oscillation power spectra with high duty cycles and high signal-to-noise ratios. Frequency splittings derived from GONG observations confirm that the variation of rotation rate with latitude seen at the surface carries through much of the convection zone, at the base of which is an adjustment layer leading to latitudinally independent rotation at greater depths. A distinctive shear layer just below the surface is discernible at low to mid-latitudes.

Cementation of vented crowns with low deformation

Crown deformation during cementation was measured with a circumferential strain gauge. The effects of different seating forces (3, 10 and 25 N), three different cements (Phosphacap, Ketac-cem Applicap and Fuji-cap I) and the presence or absence of venting on deformation and seating discrepancy were investigated. Forty microns of cement space was provided for all experiments. Venting increased deformation and reduced seating discrepancy, whilst increased force increased deformation and decreased seating discrepancy. Ketac-cem Applicap allowed the lowest seating discrepancy with median crown deformation. It was possible, by using venting, low forces (10 N) and Ketac-cem Applicap, to achieve a low marginal discrepancy with low crown deformation. Venting also diminished the seating discrepancy to acceptable levels when higher forces (25 N) were used with Phosphacap.