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.     

Etiology and treatment of idiopathic trigeminal and atypical facial neuralgias.

In a series of sixteen patients with idiopathic trigeminal neuralgia and twenty-one patients with atypical facial neuralgia, it was found that the painful phenomena associated with both disorders were, in nearly all instances, closely related to the presence of maxillary or mandibular bone cavities at previous tooth extraction sites. Standard oral surgical procedures for curettage of the cavities, together with administration of antibiotics, were employed in the successful treatment of both the trigeminal and atypical facial neuralgias, with complete pain remissions for periods varying from 2 months (for most recently treated cases) up to 9 years. The observations and results of this study suggest that dental and oral disorders may play a role in the genesis of trigeminal and atypical facial neuralgias.     

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.     

Influence of professional cleaning and drying of occlusal surfaces on laser fluorescence in vivo

Three dentists recorded laser fluorescence (LF) values on 117 teeth in 70 patients, in the sequence: (1) moist, uncleaned; (2) dried, uncleaned; (3) moist, cleaned; (4) dried, cleaned. LF values varied significantly with surface status (p < 0.01). The optimal cutoffs were up to 5 units lower on uncleaned, moist surfaces compared to the other states. Drying uncleaned surfaces significantly increased LF readings for dentinal caries (p < 0.01). It was concluded that occlusal surfaces should be clean and dry, for precise longitudinal monitoring of caries with LF as well as for detailed visual inspection, which should precede LF measurements.     

Optimum force magnitude for orthodontic tooth movement: a mathematic model.

The aim of this study was to develop a mathematic model to describe the relationship between magnitude of applied force and rate of orthodontic tooth movement. Initially, data were extracted from experimental studies in dogs (beagles), in which controlled, standardized forces were used to move mandibular second premolars distally. Curve-fitting by nonlinear regression analysis provided an equation describing the relationship between force magnitude and rate of tooth movement in beagles. A similar equation was subsequently used to analyze the limited available data from the literature on human canine retraction. The maximum rates of tooth movement in humans and dogs are very similar. A threshold for force magnitude that would switch on tooth movement could not be defined. The model showed that a wide range of forces can be identified, all of which lead to a maximum rate of tooth movement.     

Crouzonodermoskeletal syndrome

Crouzon craniostenosis [MIM 123500], is identified on the basis of the additional phenotypical manifestations of acanthosis nigricans, vertebral changes and cementomas of the jaws. Choanal atresia and hydrocephalus are other features. The molecular defect in CDSS is a point mutation in the FGFR3 gene on chromosome 4p, whereas, the mutation in the Crouzon syndrome is in the FGFR2 gene at 10q25.3-26. An affected girl aged 2 years presented at the UWC dental genetics unit with a prior diagnosis of Crouzon syndrome. Choanal atresia had necessitated a permanent tracheostomy, and hydrocephalus was managed by a shunt operation. Clinical examination revealed acanthosis nigricans in the axilliary regions, a diagnosis confirmed by a biopsy of the lesion. Eruption of the primary dentition was delayed with only six out of twenty teeth present. Radiographic examination conducted shortly after birth revealed the presence of several tooth buds in both the maxillae and the mandible. The delayed eruption of the teeth will be of significance in future orthodontic and maxillofacial measures for the improvement of the patient's facial Crouzonodermoskeletal syndrome (CDSS) was separated from the classical appearance. Molecular investigations in the girl and her parents are underway. If the specific mutation in FGFR3 is observed, a positive diagnosis of CDSS will be confirmed and the status of her parents and other family members will be determined. On this basis, appropriate genetic management can be offered to the kindred.     

Tissue oxygen tension and blood-flow changes in rat incisor pulp with graded systemic hyperoxia

The role of oxygen in the regulation of the pulpal microcirculation is unknown. This investigation is aimed to measure tissue oxygen tension and blood-flow changes in the pulp of rat lower incisors during graded systemic hyperoxia, and to determine the response of the pulpal vasculature to various oxygen tensions. Twenty-four Sprague-Dawley rats were anaesthetized and artificially ventilated with the appropriate gas mixture. Recessed oxygen-sensitive microelectrodes were used to measure pulpal tissue oxygen tension via a small access cavity filled with saline on the labial surface of the incisor. A laser Doppler flowmeter was used to record pulpal blood-flow. Inspired oxygen was increased stepwise from 20 to 100% in 20% steps. Systemic blood-gas concentrations were measured at each step. Systemic arterial oxygen tension at 100% oxygen ventilation reached 481.2 +/- 30.7% of the baseline at 20% oxygen breathing (n=21). Pulpal tissue oxygen tension did not change significantly whereas pulpal blood-flow fell dose-dependently to 74.6 +/- 5.0% at 100% oxygen ventilation (n=21). Systemic hyperoxia, therefore, induces a significant reduction in pulpal blood-flow whereas pulpal tissue oxygen tension remains relatively stable, indicating an oxygen-dependent local regulatory mechanism.