摘要:

A knowledge‐based system for designing removable partial dentures is described in which graphical representations of denture components are manipulated directly by the user to build the required denture design. The arch form of individual patients may be depicted by linear movement and rotation of the icons representing teeth. The size, shape and position of many denture components are determined dynamically to conform to the shape of abutment teeth and to the juxtaposition of other elements. Expert clinical knowledge is used to analyse the developing design and suggest alternate approache

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01595.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

This study represents an attempt to introduce a system for the longitudinal evaluation of the severity and the rate of progression of tooth wear. The material comprised a selected group of 10 males and 10 females, examined twice within an 18‐month period. The subjects were predisposed to advanced occlusal wear and had a mean age of 32 years within the range of 16‐56 years. Evaluation of occlusal wear was performed on a tooth‐by‐tooth basis, on study casts, using two ordinal scales, one for assessing the severity, and the other the progression of occlusal wear. The reliability of the scales was assessed by percentage inter‐observer concordances.The sample exhibited higher occlusal wear scores in the incisor and canine regions compared to the posterior region. It was found that the overall progression in an 18‐month follow‐up period was slow. The inter‐observer concordance in the evaluation of the severity of wear was 88%, and 91% in the progression of wear. Within the limitations of the described system, the scales may be utilized for determining the severity of occlusal wear and the rate of its deterioration in an individual's dentition. From a clinical standpoint, the need for future treatment may be based on such an evaluation of the prog

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01596.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Fourteen dual‐cure luting composites were analyzed for their filler particle shape, predominant and maximum filler size, and filler weight in function of their clinical use. Polished surfaces were etched with an argon ion beam and studied by means of scanning electron microscopy.The type of filler particles, either inorganic or prepolymerized, could clearly be recognized. Their shapes were angular, rounded or spherical, depending on the product. The maximum filler size varied extremely from less than 1 urn to 250 urn. A particle‐size distribution analyser disclosed a bell‐shaped filler‐size distribution. The predominant filler size for all the products was much smaller than the maximum filler size. The filler weight varied from 36 to 77%. After ion etching, some products showed small areas with a low degree of filler loading. A classification of the luting composites based on the maximum filler size is proposed. Since the particle size varies widely within the group of products analyzed, a standard specification for luting composites is urgently

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01597.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The stress distribution in an edentulous mandible provided with two implants in the interforaminal region was calculated by means of three different finite element models. The implants were connected with a bar or remained solitary. The first model was a three‐dimensional representation of the entire mandible, the second model of the interforaminal region of this same mandible, whilst the third model was a two‐dimensional representation of the interforaminal region. The differences in stress distribution around the connected implants and the solitary implants between these three models were analysed.It can be concluded that for a parameter study the stress distribution around the dental implants following from a three‐dimensional finite element model of only the interforaminal region of an edentulous mandible can be used. For such studies therefore, benefit can be gained from the advantages of reduced modelling and calculation

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01598.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

An experimental artificial test food with low fracture strength (Optocal) was compared with Optosil® with respect to the comminution during mastication by complete denture wearers and subjects with natural dentitions. The comminution of both test foods revealed large differences between the denture wearers and the dentate subjects. These differences were larger with Optosil® than with Optocal. The differences in comminution between Optocal and Optosil® were larger in the denture wearers than in the dentate subjects. The differences in comminution between the denture wearers and the dentate subjects as well as the differences in comminution between Optocal and Optosil® within each group were largely established in less than 20 chewing strokes. The results indicate that differences in selection contributed substantially to the differences in comminution. Since Optocal appeared to be much easier to chew than Optosil®, it may be preferred to Optosil® for measuring masticatory performance in complete denture we

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01599.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The effects of the molecular weight of polymer powders, the ethyl alcohol content of the liquids, the type of plasticizer and the polymer powder/liquid ratio on viscoelastic properties during gelation of tissue conditioners were studied with an oscillating rheometer. The results showed that:(i) The gelation time decreased exponentially with increases in molecular weight of the polymer powder and with powder/liquid ratio. There were linear relationships between the log of gelation time, and both the molecular weight of the polymer powder and the powder/liquid ratio.(ii) In general, gelation time decreased exponentially with increases in ethyl alcohol content. However, the relationship between the log of the gelation time and ethyl alcohol content fitted a second‐order polynomial.(iii) The type of plasticizer affected gelation time. The order of gelation times was: benzyl benzoate

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01600.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Tooth mobility was measured mechano‐electronically with the aid of quasi‐static and dynamic methods in 309 patients comprising 2650 teeth being periodontally healthy. Besides, clinical and roentgenographic findings were ascertained to relate functional features to each periodontium. In general the result was that teeth loaded excessively show increased mobility parameters compared to those loaded normally. However, the mobility of teeth loaded poorly or deficiently was even greater compared to teeth stressed excessively. Moreover, follow‐up studies showed that tooth mobility decreases after removal of functional disorders of the masticatory system or an immobilisation of splinted teeth. An experimental trauma of the periodontal ligament also brings on an increased tooth mobility which decreases to the original values some days after the

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01601.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The purpose of this study was to examine the longitudinal changes of torque around the sagittal axis in lower distal‐extension removable partial dentures. The torque transmitted from the denture base to retainers was measured on several separate occasions from the insertion of new dentures to about 2 months after it. The maximal mean value of torque (Max.MT) was calculated from the magnitude of all chewing strokes of the minimum of the interocclusal distance. The integration values of torque (I) and time (T) from initiation of chewing to swallowing were obtained and then the average value of torque (Ave.T) was calculated (Ave.T= I/T).Subjects could be divided into two groups. Max.MT and Ave.T were almost constant in one group while they were remarkably decreased in another. After 1 month of insertion of new dentures the value of both groups was within the range of less than 3 × 10‐3kgm (1 kgm = 9.8 Nm) of Max.MT and less than 1 × 10‐3kgm ss‐

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01602.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Laser‐roughened enamel surfaces have been shown to provide for greater acid‐resistance and enhanced restorative material/enamel bond strength. Extracted tooth enamel was irradiated with several lasers: CO2/Nd:YAG (CW), CO2(RSP), Nd:YAG (CW), Nd:YAG (Q‐switched), Argon (CW), and Ar:F excimer. Additional teeth were acid‐etched. Energy densities were standardized at 25‐47 J/cm2for all mediums. Surface profile analyses were conducted with a profilometer to determine the amount of enamel surface roughness. The acid‐etched samples exhibited both a greater amount of surface roughness and a qualitatively different type of enamel surface morphology than the laser‐treated specimens. Independent use of the CO2and Nd:YAG beams exhibited a moderate amount of roughness, while the coaxial CO2/Nd:YAG beam displayed surface roughness approaching that of the acid‐etch samples. Different laser mediums produce enamel surface morphologies that are characteristic of a variety of inherent la

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01603.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A simple method of estimating traces of chlorhexidine in water using bromothymol blue is described. The procedure involves the extraction of the chlorhexidine/bromothymol blue complex into carbon tetrachloride from a buffered neutral solution and measurement of the absorbances of the extracts in a spectrophotometer.The extracted complex has good colour stability, and the method is accurate, reproducible, and very sensitive, with concentrations of chlorhexidine down to 0.05 μg ml‐1measurab

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01604.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY