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When the dough-molding method is used for processing a trial denture, it is often difficult to remove the processed denture from the flasking stone. The palatal and lingual stone portions contribute to this difficulty. This article describes a procedure that uses metal aluminum plates to facilitate the removal of these stone portions. The plates are placed vertically at the midline and in the palatal and lingual stone mixtures during flasking. The plates, which are removed during deflasking, make deep grooves and allow the stone portions to be pried toward the midline without considerable force during deflasking. The procedure is easy, facilitates the deflasking procedure, reduces the danger of damaging the denture base and the artificial teeth, and saves time.
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The statics of prostheses in complete absence of teeth is discussed with analysis of the effect of the position of the masticating surfaces of artificial teeth on the values of forces disturbing the balance of the prosthesis during mastication. Considering the friction forces active during mastication, the worse fixation of lower prostheses, and the lateral position of the mandible in relation to the maxilla the author describes as optimal such a spatial arrangement of artificial teeth that in centric occlusion the interalveolar line passes through the centre of their masticating surfaces which are perpendicular to it.
STATEMENT OF PROBLEM: One of the most important physical properties of artificial teeth used in the restoration of the edentulous patient is wear resistance, and the ability of these teeth to maintain a stable occlusal relationship over time. PURPOSE: This study compared the in vitro wear of four different resin denture teeth against human enamel. MATERIAL AND METHODS: Five denture tooth samples opposing five enamel abraders were positioned in a mechanical wear testing device for two 5,000 cycle wear periods (total of 10,000 cycles) under a 13.4 N load. All tests were conducted in human saliva, and the wear was measured at the end of each test period. RESULTS: The wear of the Classic and Kenson acrylic resin denture teeth was much greater than the DB Plus and MLI composite teeth after 10,000 cycles. The wear of the KENSON denture tooth was also greater than the Classic tooth. No wear differences were found between the two composite teeth. CONCLUSIONS: The wear of DB Plus and MLI resin denture teeth was approximately 50% less than the wear of Classic and Kenson teeth when opposed by human enamel.
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PURPOSE: To determine whether intercommissural width is a reliable guide for the selection of maxillary denture teeth width. MATERIALS AND METHODS: Casts were made of 160 subjects from 4 different racial groups. Locations of intercommissural width landmarks (the corners of the mouth) were made on the subjects and transferred to the casts. The distances between the corners of the mouth and the distal of the canines were measured on the casts and compared. RESULTS: A weak correlation was found between the distal of the canines and the distance between the corners of the mouth in the 4 racial groups. CONCLUSION: The use of the corners of the mouth for the selection of artificial teeth is generally inaccurate.
There is no definitive method for the arrangement of artificial teeth in complete denture construction. A new method is introduced whereby the maxillary posterior teeth have been set in approximate positions mediolaterally similar to their natural predecessors. The procedure is based on a constant relationship derived from the natural dentition. Its clinical application proved to be suitable for the arrangement of artificial teeth for complete dentures with minimal errors.
Movements of artificial teeth during the wax trial denture stage was investigated in three dimensions by means of a traveling microscope. Fixed points of reference were devised for accurate measurements of teeth movements. Porcelain and plastic anterior and posterior teeth set in five wax trial dentures were tested at 2, 4, 7, and 24 hours. Tooth movements in wax trial dentures invariably occurred and lacked correlation in direction and time.
High-strength denture teeth (HS teeth) were developed in order to improve the hardness and wear resistance of conventional plastic denture teeth (PL teeth), while retaining their feature of easy occlusal adjustment. The objective of this study was to evaluate the abrasive wear resistance of HS teeth. We conducted wear tests and measured surface roughness using six types of anterior artificial teeth, i.e., three types of HS teeth and three types of PL teeth, the latter serving as the control. The results of the toothbrush abrasion test revealed that the HS teeth had about 5 times greater wear resistance than the PL teeth. It was also found that the type of artificial teeth and the number of abrasive wear-testing strokes had a significant (P less than 0.05) influence on the surface roughness of artificial teeth.
When two-layered artificial teeth are used, acrylic resin occlusal parts can be removed from base parts and used directly as resin patterns for casting, which facilitates fabrication of metal occlusal surfaces. Because these teeth were made of acrylic resin, it was easy to modify occlusal morphology before converting to metal. Application of two-layered artificial teeth to achieve lingual contact occlusion brought about sufficient masticatory forces and denture stability and resulted in patient satisfaction.
The aim of the present study was to evaluate clasp-retained removable partial dentures (RPDs) made in the Public Dental Health Service (PDHS) in Orebro County in 1989. Records from all 25 PDHS clinics concerning RPDs from 1989 were collected after eight years and available information was registered. The entire material consisted of 447 RPDs (both attachment-retained and clasp-retained RPDs) in 387 patients. Of the 316 clasp-retained RPDs that were traceable, 208 were followed from 1989 to 1997. In most instances, information on diagnoses, alternative treatments and design of the RPDs was lacking. One hundred and thirty-two (42%) of the 316 clasp-retained RPDs were judged to still be in use in 1997 while 75 were not in use. The main reason for ceased use was dislike by the patient. There were 108 clasp-retained RPDs that were not possible to follow from 1989 to 1997 because there were no notes regarding follow-ups in the records. The most common technical complications noted in the records during the observation period were clasp fractures and loosened artificial teeth.
To improve the quality of the complete denture prosthesis, the bucco-lingual position of the artificial posterior teeth must be determined with consideration of the shape of the maxillary and mandibular residual ridge and the relationship between them. The arrangement of posterior artificial teeth should be considered not only for the denture stability but also for the avoidance of high pressure on the supporting structures. A two-dimensional finite element method program to investigate the statics for the contour of the complete denture and the residual ridge was developed. With this program, the effect of the bucco-lingual position of the artificial posterior teeth under occlusal force on the denture supporting bone could be investigated.
We have developed a visual analysis method to examine the spatial relationship between the edentulous ridges and the bucco-lingual position of the artificial posterior teeth in complete denture fabrication. In this system, a non-contact type shape measurement system is used. We applied this system to the plaster models and the wax dentures of an edentulous patient. Using the measurement data on the upper and lower plaster models, we reconstructed their shape three-dimensionally and determined the points regarded as the ridge crests and the inter-alveolar crest lines in the frontal sections. To generate the upper and lower ridge crest lines which consisted of the points of the ridge crests, interpolation by B-spline curves was applied. Furthermore, the loft surfaces that we regarded as the consecutive inter-alveolar crest lines, were generated between the upper and lower ridge crest lines. The surface models of the plaster models and artificial teeth were displayed on the cathode-ray tube display unit, and the ridge crest lines and the consecutive inter-alveolar crest lines were superimposed on the surface models. This method could be utilized to visualize and examine the bucco-lingual position of the artificial posterior teeth in reference to the inter-alveolar crest lines.
The choice of the size of artificial teeth takes an important place in the treatment of edentulism with removable prosthesis. However, the standards or proportions commonly used as guide have been developed mainly on Caucasian populations. This study have been undertaken to determine some proportions between anterior upper teeth and some maxillo-facial structures in black African subjects. The results suggest that the proportions generally used to choice the anterior upper artificial teeth in Caucasian subjects can not been applied in melanoderme African patients.
The aim of this study was to clarify the influence of working side contacts for masticatory function for a distal extension removable partial denture. Five subjects who had edentulous arches from second premolar to second molar opposing natural teeth participated. Working side contacts were altered by using three types of artificial teeth attached to the denture base. A-form teeth made contact with opposite teeth while acting as the working side in a lateral excursion. The cusp angles of B- and C-form teeth were decreased by 10 degrees and 20 degrees, respectively compared with A-form teeth. B-and C-form teeth discluded with opposite teeth on the working side. Subjects were asked to perform two kinds of masticatory performance test. Obtained data were evaluated by the repeated-measures anova and the Tukey test for multiple comparisons. Results revealed that there was a significant difference (P=0.001) in the three types of teeth in the mixing ability test and the value of A-form teeth was statistically less value than those of the other teeth. However, there was no significant difference in the comminuting ability test. These results suggested that working side contacts between artificial teeth and opposite natural teeth influenced mixing ability, but not comminuting ability.
LITERATURE REVIEW: A ferrule is a metal ring or cap used to strengthen the end of a stick or tube. It has been proposed that the use of a ferrule as part of the core or artificial crown may be of benefit in reinforcing root-filled teeth. A review of the literature investigating this effect is presented. The literature demonstrates that a ferrule effect occurs owing to the artificial crown bracing against the dentine extending coronal to the crown margin. Overall, it can be concluded that a ferrule is desirable, but should not be provided at the expense of the remaining tooth/root structure.
Adhesion, functional adhesion, and observation of mechanical regularities during repair of dentition in patients with complete loss of teeth ensure stability of complete dentures and, hence, their functional value. Since functional adhesion is frequently impossible to provide as far as it concerns the lower denture, such dentures are always liable to the action of dumping force. The authors describe a method for making artificial teeth of complete removable dentures with due consideration for the individual force of occlusion of the jaws and the teeth inclination angle determined individually for each patient.