ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00290.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Problems that can occur when single implants are utilized to restore first molar teeth include the frequent loosening of screws, as well as screws and/or implant breakage. These may result from torquing and rotational movements of the prosthesis during masticatory and parafunctional mandibular movements. When sufficient bone and mesio‐distal restorative space is present, the placement of two implants should be considere

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00291.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

PurposeThe importance of dentofacial attractiveness to the psychosocial well‐being of an individual has been well established. Very little information is available regarding dental patient perceptions of a pleasing esthetic image. The purpose of this study was to identify factors distinctive to attractive smiles versus unattractive smiles, as perceived by patients.Materials and MethodsStandardized format photographs (5 × 7 in, matte finish, at f‐32 and 1:2 magnification) of eight male and eight female smiles, framing only lips and teeth, were viewed by 297 subjects. The smiles exhibited differences in symmetry, tooth shade, number of teeth displayed, and height of maxillary lip line, and included both restored and unrestored teeth. Respondents ranked the photographs in order from most to least appealing appearance. Respondents viewed each series of photographs in a similar lighting and time period. A questionnaire identified the respondent's age, sex, race, education, income, and home town. Twenty‐five demographic groups were established from the information in the questionnaire. Data were analyzed using stepwise discriminant analysis to determine the combination of smile characteristics that best predicted the ranking.ResultsThe same female smile was chosen as the most attractive by 24 of the 25 demographic groups. This smile is characterized by natural teeth having light shade, high lip line, a large display of teeth, and radiating symmetry. Two female smiles typified by darker shade and asymmetry were rated by all groups as being least attractive. Two male smiles were judged equal as the most pleasing esthetically. Respondents favored those smiles characterized by light shade, a moderate display of teeth, moderate lip line, and a symmetrical arrangement of teeth. One male smile characterized by darker shade was rated as least attractive.ConclusionsIn all cases, tooth shade was the most important factor, followed in sequence by unrestored natural teeth and number of teeth displayed. No correlation was found to exist between specific demographic groups and smile var

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00292.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

PurposeEar‐rod facebow techniques may position casts high or low between the upper and lower members on the articulator when using orbitale or nasion as anterior reference positions. This study assessed the effect of changing the anterior reference position on simulated mountings utilizing simulated ear‐rod facebow.Materials and MethodsTracings from lateral cephalographs made on seven subjects were superimposed with an outline model of a semiadjustable articulator. Three simulated mountings were performed for each subject in which the plane of occlusion was positioned (1) high, (2) midway, and (3) approaching the lower member (low). Maxillary and mandibular occlusal planes representing intercuspal position were determined from the cephalographs and positioned on the articulator model in a simulated centric relation position for each mounting. Condylar guidance was determined from a simulated protrusive position.ResultsAnalysis of the three mounting positions demonstrated no change in intercuspal position within subjects; however, angles formed between upper member and condylar guidance were 14.9% smaller for the mid‐distance mounting, 42.9% smaller for the high mounting, and 13.4% higher for the low mounting positions when compared with a standard Frankfort horizontal plane reference.ConclusionsThe cephalographs showed extreme variability in the position of the ear piece to bony structures of the skull, but this deviation appeared to be compensated by a change in the horizontal condylar guidance relative to mounting. Results also suggest that casts may be mounted in a convenient mid‐position for routine artic

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00293.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

PurposeThis study evaluated the color stability of four stains of a light‐cured porcelain stain system between the light‐cured and fired stages.Materials and MethodsThirty‐six ceramometal discs 20 mm in diameter and 2 mm in thickness were cast to provide the substrate on which Ceramco II porcelain was applied. The porcelain was polished to a uniform thickness of 2 mm, and the samples were divided into four groups and assigned a color (yellow, orange, green, or blue). Orbit LC stain was applied in a thin layer and light‐cured for 40 seconds. After light‐curing, three color readings were made with a Minolta Chroma Meter II. The porcelain discs were then fired in a porcelain oven and three color measurements were again made. The pre‐ and postfired Commission Internationale de I'Eclairage L*a*b* values were recorded and the color difference (ΔDLE) was calculated for each specimen. The clinical significance for the computed ΔDLE ratings was completed according to previously modified criteria.ResultsThe results show that the mean ΔDLE between the light‐cured and fired stages of Orbit LC are clinically acceptable. No statistically significant differences (p<.05) were observed between any of the four groups.ConclusionsA light‐cured porcelain stain system was evaluated for color stability between light‐cured and fired stages. Within the conditions of this study, the following conclusions can be made: (1) There was no clinically significant color difference between light‐cured and fired stages for the stain colors evaluated; and (2) the final color of the restorations altered with light‐cured stains can be

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00294.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

PurposeThe objective of this study was to determine the fatigue resistance of wrought‐steel wire clasps used for removable partial dentures.Materials and MethodsFive wrought‐steel wires with cross‐sectional diameters of 1.2,1.1,1.0, 0.9, and 0.8 mm were tested using a deflection fatigue test with deflections of 0.4 to 0.7 mm. The force and stress required to cause deflection was determined, as well as the number of loading cycles required to cause fatigue fracture. The fracture surfaces of the wrought‐steel wire clasps were examined with a scanning electron microscope.ResultsThe number of loading cycles required to cause fatigue fracture increased with reduced deflection of the wrought wire (p<.005). To obtain fatigue resistance for loading cycles of over 106, the stress in the wrought‐steel wire clasp should remain under 1.0 GPa.ConclusionsThese results suggest that to avoid fractures of wrought‐steel wire clasps caused by bending fatigue, the stress on the clasp during its deflection should be taken i

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00295.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

PurposeTo measure and compare the strains transferred by screw‐fastening one‐piece full‐arch prostheses as cast and after sectioning and soldering.Materials and MethodsPhotoelastic resin was applied directly to five 3.75 × 13‐mm Brånemark implants, situated 7 mm apart, in a silicone mold of an edentulous mandible. Four strain gauge rosettes were also incorporated in the resin to allow strain measurements at four locations. Three frameworks were made from a single master cast produced from an impression of the five‐implant model with 4‐mm abutments. These frameworks were sequentially secured to the master model with five gold slot screws tightened to 10 N cm. Strain indicator readings were recorded at a standardized time following the initial fastening of each prosthesis. The test was repeated three times. Each of the three castings were subsequently sectioned and soldered in two locations, mesial to the two terminal fixtures. After soldering, the three superstructures were returned to the master model for measurement of postsolder strains three times each. A one‐way repeated‐measures ANOVA was performed to determine differences between mean principal strains between the as‐cast and postsoldered groups.ResultsA statistically significant difference was found in the principal strains between the as‐cast and soldered frameworks. Overall, there was a decrease in the magnitude of strain for the soldered frameworks.ConclusionsSectioning and soldering improved the as‐cast accuracy as far as the amount of strain transferr

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00296.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

PurposeThe marginal fit of MOD inlay and full‐crown patterns fabricated from wax, autopolymerized acrylic resin, and two light‐polymerized, diacrylate resin pattern materials was compared on standardized dies.Materials and MethodsFour pattern materials were studied—two light‐polymerized, diacrylate resin materials (Palavit G LC and Triad VLC Burnout Paste), an inlay wax, and an autopolymerized resin (Duralay). Patterns were fabricated using incremental and bulk techniques on stone dies made from addition silicone impressions of American Dental Association MOD and full‐crown master dies. Gaps were measured with a measuring microscope in four marginal areas on the master dies at 1 and 24 hours after fabrication.ResultsFor the MOD inlay patterns, marginal gaps ranged from 7 to 23 μm, and the light‐polymerized, diacrylate resins and autopolymerized acrylic resin material had statistically smaller gaps than the inlay wax. For the full‐crown patterns, marginal gaps ranged from 10 to 23 μm, with the exception of the autopolymerized acrylic resin prepared by the bulk technique (40 to 46 μm). With the incremental technique, the light‐polymerized, diacrylate resins and inlay wax had statistically smaller gaps than the autopolymerized acrylic resin material. Overall, the incremental technique produced equal or smaller marginal gaps than the bulk technique for full‐crown patterns. Generally, the patterns measured at 1 hour had smaller marginal gaps than at 24 hours.ConclusionsWhen measured on intra‐ and extracoronal master dies, the light‐polymerized, diacrylate resins had equal or better marginal fit, compared with wax or autopolymerized acrylic resin, and were less affected by placement technique and storage. The marginal gaps of all four pattern materials ranged from 7 to 46 μ and are within the range

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00297.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

PurposeIn this study, the Periotest instrument was used to measure the precision of fit between cast high noble‐metal frameworks and the supporting implants in a patient‐simulation model. Three framework conditions and three implant‐location variables were used to evaluate the rigidity of the assembly as measured by the Periotest method. The framework variables were (1) one‐piece castings (OPC); (2) sectioned‐soldered inaccurate castings (SSIC); and (3) sectioned‐soldered accurate castings (SSAC). The implant‐location variables were right anterior (RA), center (C), and left anterior (LA).Materials and MethodsThe patient simulation model used consisted of three self‐tapping Brånemark implants in a reasonable arch curvature in bovine bone. Three working casts were fabricated from the patient‐simulation model using polyvinyl siloxane and tapered impression copings. From the working casts, three sets of three frameworks were fabricated as OPCs, SSICs, and SSACs using type 3 high noble alloy. The SSICs were fabricated with a quantitative misfit of 101.6 μm at the facial surface, between the abutment‐to‐gold cylinder interface at the C implant location. Periotest value (PTV) measurements were made at the midfacial surface of the frameworks directly above each abutment‐to‐gold cylinder interface. Three measurements were made for each test condition. The data were analyzed to compare framework condition(s) and implant location(s) using ANOVA and Fisher's Protected Least Significant Difference Comparison Test.ResultsThe ANOVA showed that significant differences exist between the mean PTV data for framework condition and for implant location (p<.01). Significant differences were shown between the mean PTV data for the SSAC assemblies and the OPC and SSIC assemblies. The SSICs displayed a more positive (+) mean PTV than the OPCs. The OPC assemblies had a more positive mean PTV than the SSAC assemblies. The mean PTV data for the SSAC assemblies had a significantly different PTV (p<.01) than the other two framework condition assemblies. The OPC and the SSIC assemblies had PTVs that were not significantly different. The C implant location was significantly different from the RA and the LA implant locations (p<.01). The RA and the LA implant locations were not significantly different from each other. The C implant location always demonstrated the most positive mean PTV regardless of the framework condition being tested.ConclusionsThe Periotest instrument quantified differences in the precision of fit between three framework conditions. The SSAC assemblies were significantly more rigid than the OPC and SSIC assemblies. The OPC and SSIC assemblies' mean PTVs were not significantly different. The mean PTVs for the C implant location and the RA and LA implant locations were significantly different (p<.01). The mean PTVs of the RA and LA implant locations were not significantly different. The implant‐location PTVs followed the same rank order for all three framework conditions. The procedures used to fabricate a more precise fit between the framework and the supporting implants is influenced by the skill of

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00298.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

This article describes a seminar/case‐based, instructional model designed to simulate removable partial denture (RPD) problem‐solving and decision‐making processes encountered in third‐year clinic in dental school and in dental general practice. Groups of approximately 20 second‐year students (in the 3‐year program) meet in a series of six 1‐hour seminars during the first days of the course. Following the seminars, students complete an exercise on mouth preparation and multiple clasp and major connector designs on prototype casts. This is followed by survey‐design exercises on casts of dentitions representing six variations of RPD requirements. Instructors assist students during the practice phase of each class. Each 2‐hour practice session is followed by a 1‐hour practical examination. The last day of the course is devoted to a comprehensive final practical examination on both maxillary and mandibular casts, incorporating any of the design features

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1996.tb00299.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY