Influence of the inclination of the plate of an intra-oral tracing device on the condylar position registered by tapping movement

The object of this study was to determine the best inclination of the intra-oral tracing device to get optimum condylar position with the registration of tapping movement. Three appliances with different tracing plate inclinations were used in five healthy subjects. The tracing plates were set at 0 degrees to occlusal plane (horizontal); at the angle formed by drawing a line from condylar point to the stylus position at occlusal plane (inclined); then at the angle half to inclined (half-inclined). Subjects made Gothic arch and tapping movements (n = 30) at a 30 mm interincisal distance with the head Camper plane horizontal. The incisal and condylar points were tracked with a 6-degree-of-freedom jaw movement tracking system. The location of gothic arch apex, the distribution and mean position of 30 tapping points from intercuspal position were analyzed in incisal and condylar point between the appliances. Data were analyzed with repeated measures one-way anova. Results showed that mean position of tapping points were significantly different among the appliances. Half-inclined appliance recorded tapping points in a convergent area nearer to intercuspal position (IP) than other appliances. In all appliances, the contact points of the tapping movement were anterior to Gothic arch apex.     

New partition technique for two-chamber pressure casting unit for titanium

Although titanium has been widely used in prosthetic appliances, such as cast removable partial denture frameworks, high quality castings are still difficult to obtain. This study proposes a new partition technique using a metal foil for improving castability of a two-chamber pressure casting unit. The metal foil was formed beforehand to bring it in contact with the mold crucible wall so that no clearance was left behind it. Using this formed foil, the mold cavity can be completely isolated from the upper chamber and can be maintained in a vacuum even after the rupture of the foil. Accordingly, a large casting force is generated very quickly, and as a result, castability is expected to be significantly improved. This expectation was confirmed by the experiments using wax patterns including thin plate and mesh plate.     

Use of industrially available aluminium-bronze alloys for cast restorations. I. Preliminary study

A bstract — A preliminary study of the use of three industrial aluminium bronze alloys and one silicon bronze alloy for dental castings is reported. The results indicate that satisfactory marginal fit was achieved for full crown castings, and further investigation in the use of these alloys is warranted.     

Predictability of treatment outcome in patients with myofascial pain-dysfunction (MPD) syndrome.

Responses to the Minnesota Multiphasic Personality Inventory (MMPI) were used to develop a 29-item scale designed to predict the treatment outcome of 135 patients with Myofascial Pain-Dysfunction (MPD) Syndrome. The results suggested that a single scale to predict treatment outcome would be ineffective due to the absence of consistent personality differences in MPD patients.     

Double-layer porcelain veneers: effect of layering on resulting veneer color

STATEMENT OF PROBLEM: Densely sintered aluminum oxide veneered with feldspathic porcelain seems to be a promising technology for the fabrication of porcelain laminate veneers, which provide both strength and esthetics. To effectively use this approach for porcelain veneers, practitioners should know how the resulting color is affected by adding a layer of veneering porcelain onto the aluminum oxide. PURPOSE: This study compared changes in CIE L*a*b* color coordinates of simulated stained teeth when covered with the aluminum oxide core disks alone and after the disks had been veneered with 3 different shades of porcelain. MATERIAL AND METHODS: Fifteen aluminum oxide disks were divided into 3 groups. Each of 5 disks was veneered with porcelain of the Vita shades A1, A2, and B4, respectively. The colors of the substrate covered with the nonveneered disks and the veneered disks were measured separately, and the color differences were calculated. Measurements of the disks on a white background were also performed and used as controls. The extracted data were compared with Vita shade values available from the literature. RESULTS: Statistically significant differences in color coordinates of dark substrates were recorded between the substrate covered by an aluminum oxide disk and the addition of veneering porcelain to the aluminum oxide disks. Veneering the aluminum oxide disks with A1, A2, and B4 porcelain produced significant differences in the resulting color when placed on a dark substrate. The direction of the color modifications correlated with values obtained from the literature. The resulting color was also affected by the color of the underlying structures. CONCLUSION: Although aluminum oxide alone does have a degree of masking capability, the resulting color of porcelain veneers with the use of this material can successfully be modified with the veneering porcelain.     

Oxygen tension (pO2) in untreated human periodontal pockets

The purpose of this study was to assess the oxygen tension in untreated human periodontal pockets and test the hypothesis that the subgingival environmental is anaerobic in nature. Twenty-six patients with advanced chronic inflammatory periodontal disease participated. A total of 111 untreated pockets, 5 to 10 mm in depth, were selected for the pO2 measurements. Pocket depths, Plaque-Index and Gingival-Index were recorded. The pO2 at the base of the 111 pockets ranged from 5 to 27 mm Hg, with an average of 13.3 mm Hg (1.8% O2). Mean pocket depth was 6.9 mm. Moderately deep pockets (5-6 mm) had a mean pO2 of 15.0 mm Hg, whereas deep pockets (7-10 mm) showed a significantly lower pO2 of 11.6 mm Hg. No correlation was found between the pO2 and the Plaque-Index. Higher Gingival-Index scores tended to be associated with higher pO2 values. The pO2 in untreated periodontal pockets was low. However, it does not represent a completely anaerobic environment. Deep pockets contained less oxygen than moderately deep sites.     

The role of dentist, practice and patient factors in the provision of dental services

OBJECTIVES: Service provision varies by dentist, practice and patient factors. However, limited subsets of these potential influences on service rates have been explored. More comprehensive models could improve our understanding of the factors influencing the pattern of care delivered. The aim of this study was to examine variation in dental services by dentist (treatment choice, practice beliefs, preferences for patients, demographics), practice (type, location, size and volume of practice) and patient (visit, demographic, oral health and socio-economic) characteristics. METHODS: A random sample of Australian dentists was surveyed in 1997-98 (response rate=60.3%). Private general practitioners (n=345) provided dentist and practice data, and service provision and patient variables were collected from a log of a typical clinical day (n=4,115 patients). Multivariate negative binomial regression models were fitted for diagnostic, preventive, restorative, extraction and prosthodontic services. RESULTS: Significant dentist factors included (P<0.05; RR=rate ratio): lower diagnostic rates (RR=0.78) for dentists with stronger practice beliefs for giving information about cost and treatment options; preventive rates were lower (RR=0.74) for male dentists and higher (RR=1.48) for younger dentists aged 20-29 years; restorative rates were higher (RR=1.27) for dentists that rated patient preferences more highly in treatment choice and in the dentist age group 30-39 years (RR=1.25); extraction rates were lower (RR=0.61) for dentists with stronger preferences for patients that would adhere with treatment but higher (RR=1.57) for dentists with stronger preferences for sociable patients; and prosthodontic rates were lower (RR=0.38) for dentists with stronger preferences for adaptable patients who were willing to cooperate when expected to do so. Practice factors included: higher preventive (RR=1.28) and prosthodontic rates (RR=2.07) in solo practice; higher preventive (RR=1.34) but lower prosthodontic rates (RR=0.42) in capital cities; lower diagnostic (RR=0.82) and extraction rates (RR=0.55) in practices with fewer other dentists; higher diagnostic (RR=1.33) and extraction (RR=1.62) rates but lower restorative rates (RR=0.84) in practices with lower patient visits per year. Patient factors included: lower preventive (RR=0.76) but higher extraction rates (RR=1.45) for emergency visits; lower extraction rates (RR=0.60) for the insured; higher diagnostic rates (RR=1.17) for new patients; higher restorative (RR=1.31) but lower prosthodontic rates (RR=0.46) for patients with decayed teeth; higher prosthodontic rates (RR=2.14) for those with dentures; and lower preventive (RR=0.66), but higher extraction (RR=2.22) and prosthodontic rates (RR=1.82) for patients from lower socio-economic status areas. CONCLUSIONS: Dental service rates were influenced by large number of small effects from a wide range of dentist, practice and patient factors. Socio-economic and geographic barriers may need broad policy innovations to be addressed, but factors such as insurance and visit type have the potential to be altered to achieve better service outcomes and there is scope for research into clinical outcomes to improve the knowledge upon which treatment decisions are based.