Complete Denture Base Research Articles

The evolution of the complete denture base. Theories of complete denture retention--a review. Part 1.

The history of denture base materials and the accompanying development of impression techniques are traced from the earliest times to the present day (Part 1) as a prelude to a study (Part 2-4) of the various theories that have been advanced to explain retention of the base without mechanical support. These theories are critically reviewed and tabulated in chronological order. Some areas for further investigation are identified.

Reinforcement of complete denture bases with continuous high performance polyethylene fibers

Clinical literature details the causes for deformation and failure of acrylic resin complete denture bases. These findings are used to select patterns of high performance polyethylene fiber reinforcement that would best use the properties of the material and improve the mechanical behavior of the prostheses. A technique is described for making reinforced maxillary and mandibular bases with the fibers placed as suggested by the analysis. Microscopic observations of cross sections of reinforced bases revealed good fiber/resin integration and polish.

Mechanical property and adaptability of super-plastic titanium alloy denture base

The purpose of this study is to investigate the mechanical property and the adaptability of the upper complete denture bases made by superplastic forming of Ti-6A1-4V alloy plates which have various thicknesses. The strength of the denture base made by superplastic forming using the 0.55 mm thickness plate was lower than that of the base made by Co-Cr alloy casting in the standard form when loaded on the hard metal board. But by increasing the thickness by partial or full diffusion bonding of two Ti-6A1-4V alloy plates, the denture base became stronger than the Co-Cr alloy base. With resin occlusion rims, all the denture bases were reinforced. Moreover, when loaded on the mastermodel covered with rubber in the residual ridge and palate area, the difference of the strain between the thin and the thick bases became small. However, the strain of the thin base increased particularly when the base had a contact with the mastermodel on a small area in the palate. The superplastic forming denture bases revealed a high adaptability with the space less than 0.13 mm on the average between the base and the mastermodel. And increasing the thickness of the base prevented the worsening of the adaptability after curing resin for the denture.

Application to thinning palatal area of upper complete denture base by CF-cloth reinforcement

The acrylic resin denture base is used more than the usual metal denture base because of its low cost, ease of manufacture and ease of rebasing. Because the resin base is weaker than the metal base, the upper resin denture base is three to four times as thick as the metal denture base. So, a study was made to make the upper complete resin denture base thinner while maintaining the strength of the resin denture base currently in use. To make the palatal area of the denture base thinner carbon fiber (CF) cloth reinforcement was used. The resin denture base reinforced by the CF cloth was 0.7 mm thick and was evaluated for the mechanical properties of bending. As a result, it was found that both the stiffness and strength were improved by 10% or more compared with those of the ordinary resin denture bases.

超塑性成形したTi-6Al-4V義歯全部床へのスパッタ蒸着による純Tiの被覆

超塑性成形したTi-6Al-4V義歯全部床へのスパッタ蒸着による純Tiの被覆

Application of superplastic titanium alloy for denture base--Part 1. Adaptability of the titanium alloy denture base

The adaptability of the upper complete denture base made from superplastic alloy 90Ti-6A1-4V was investigated by measuring the space between the master model and the denture base. The denture bases showed a high adaptability with the space less than 0.1 mm, whereas after curing resin for denture, it became worse especially with the heat-curing resin. In addition, the thinnest area of the denture base was observed at the middle of the plate with 38% reduction in thickness, and distortion of the base plate of 0.55mm thickness by curing resin was found to be nearly the same as that of type 304 stainless steel plate of 0.50 mm thickness.

全部床義歯患者の予後に関する臨床的研究 装着５〜１０年の観察 ＩＩＩ 義歯床の適合試験

The purpose of this study was to estimate the clinical condition of complete denture wearers. 72 patients came to our Dental Hospital according to our recall. The examination consisted of a questionnaire and clinical examinations. For objective evaluation, the fitness test of lower complete denture base was taken place and was classified into four groups by the thickness of the white-silicone film (A-zone 0-30 microns, B-zone 30-70 microns, C-zone 70-130 microns, D-zone 130 microns-). Results 1. The average ratio of four groups of the white-silicone film were A-zone 9.3%, B-zone 35.8%, C-zone 24.5% and D-zone 30.4%. 2. The fitness of anterior portion was ill fit in comparison with posterior portion. 3. There was statistically significant difference between the fitness of lower complete denture and dentist's judgment diagnosed as ill fit denture. 4. There was significant difference between the fitness test and the patients who complained about loose fit of the denture.

Effectiveness of Reinforcement by Carbon and Aramid Fiber-cloth to Upper Complete Denture Bases (Part 1)Thinning of Palatal Area and Flexural Strength

Effectiveness of Reinforcement by Carbon and Aramid Fiber-cloth to Upper Complete Denture Bases (Part 1)Thinning of Palatal Area and Flexural Strength

Effectiveness of reinforcement by carbon and aramid fiber-cloth to upper complete denture bases. (Part 2). Fatigue strength

Effectiveness of reinforcement by carbon and aramid fiber-cloth to upper complete denture bases. (Part 2). Fatigue strength

Measurement of facial form using stereo-photogrammetry system

We have been developing a three dimensional measurement system by 35mm non-metric SLR camera and have been applying this system to the measurement of complete denture base surface area and edentulous cast model surface. The purpose of this study was to apply this system to the measurement of the facial form. The subject's head was fixed and 15 control points were arranged around his face. In order to make the process of stereo-matching easier, we projected mesh on the subject's face and took stereoscopic photographs. These photographs were measured by the digitizer and the 3-D coordinates of about 5000 measuring points were calculated by a personal computer. The geometric model of the face was displayed in three dimensional computer graphics. And the model of the face was carved out from the acrylic resin by the NC milling machine from these data.

Pressures on supporting tissues under complete denture during functions. Concerning the effects of the arrangement of artificial posterior teeth

The purpose of this study was to investigate how the arrangement of the artificial posterior teeth of the complete denture influenced pressures of supporting tissues under denture. The eight diaphragm pressure sensors were placed on the lower complete denture base to measure the pressures.The pressures were measured dynamically during mastication.The results were as follows:1. The pressures in tapping movement were much different among subjects, but the pressures of lingual side showed the common tendency to be greater than the pressures of buccal side.2. In the cases of subjects 1 and 2, the difference between the pressures in mastication and those in tapping movement was minimum with the standard arrangement. In the case of subject 3, it was minimum with the lingually shifted arrangement.3. During mastication, total pressures much increased on the chewing side with the buccally shifted arrangement than the standard arrangement, and its difference between on chewing side and non-chewing side got bigger. In the case of the lingually shifted arrangement, its difference got bigger.4. As the above-mentioned showed, the following was found: The arrangement of the artificial posterior teeth of the complete denture influenced the distribution of the pressures of supporting tissues under denture greatly, and especially in the case of the buccally shifted arrangement, the pressures increased.

Investigation into the wettability of poly(methylmethacrylate) in vivo.

Abstract One of the principal sources of complete denture retention is the adhesive action of the thin film of saliva between the palate and the surface of the denture. To produce this adhesive effect the saliva must flow easily over the denture surface to ensure its wetting. It has been observed that the retention of a denture base increases with time of wearing. Also it has been demonstrated that there is an immediate increase in retention when a complete denture base is treated with a ‘molecular bonding agent’ (MBA) such as silicon tetrachloride. The following questions are therefore raised: At what rate and to what extent does wettability of a PMMA specimen increase in vivo? Is routine use of an MBA indicated or desirable? The object of this study was to investigate the wettability of poly( methylmethacrylate) in vivo. Standard squares of denture base PMMA were prepared A square was inserted in each of 10 denture bases after final processing and before their insertion into the mouth. A microscope with a goniometer eye-piece was used to measure the contact angles of distilled water on the specimen after various intervals of time in the mouth to monitor wettability. There was a significant increase in wettability after 24 h intra oral exposure. No further increase was detected after 7 d. In vitro experiments with fresh saliva indicate that the increase in wettability occurred within 5 min. The increase was less than that reported by using MBA. No correlation between water absorption and wettability was detected. It was concluded that the wettability of PMMA increased almost immediately on contact with saliva, presumably due to the formation of a film of a salivary component(s), and that water absorption did not cause a measurable increase in wettability.

３５ｍｍカメラによる三次元形態測定システム ＩＩ 全部床義歯の床内面積の測定

A three dimensional measurement system by 35mm non-metric SLR camera was developed (Part 1).The purpose of this study was to examine the propriety of the application of the above mentioned system with addition of one other instrument, for clinical prosthodontics, especially in the measurement of complete denture base surface area.In this experiment, three dimensional concave and convex curved metal test pieces were used to evaluate the accuracy of measuring curved surface.Additionally, this system was applied to the measurement of complete denture base surface area and edenturous cast model surface.And then the measurements were compared with one previous measurement system for accuracy.From the three dimensional data obtained from this system, three dimensional color photographic representations of measured objects were also attempted.Results were as follows:1. Measurement errors of the test piece surfaces were -1.6% on the average.2. This system was applicable to measure the denture base surface area.3. Measured objects could be represented by three dimensional color photographs (Photo. 6-11).

Diagnosing functional complete denture fractures

Many factors can contribute to the fracture of complete dentures. This article has identified some of these factors and presented some methods that can greatly reduce or eliminate functional complete denture base fractures when used with a thorough diagnosis and treatment plan.

Effect of steel strengtheners on fracture resistance of the acrylic resin complete denture base

Effect of steel strengtheners on fracture resistance of the acrylic resin complete denture base

こう合採得法の相違による水平的下がく位の変動

The purpose of this study was to compare and evaluate the relative reproducibility and equality as well as jaw relationships produced by four jaw guiding methods; the gothic arch tracing, the voluntary tapping, the myomonitor centric and to occlude warm wax bite rim by light habitual closure. Four patients were selected whose remaining teeth had already lost the maximum intercuspation. The intraoral tracer was fixed on upper complete denture base and lower removable partial denture in three cases. Only in one dentulous case needed complete occlusal rehabilitation, the appliance was fixed on transfer coping crowns.The mandibular position guided by each methods was measured to the nearest 0.1mm in laterally and anteroposteriorly (x and y components). The accuracy of this experiment was estimated at 0.22mm (±2σ) or 0.34 mm (±3σ). This error was derive from width of tracing line, area of tapping point, mobility of denture base and mounting on articulator. Within the limits of this investigation, it is concluded that;1. Each guiding methods determined different mandibular position in case 1, 2 and 4. But in case 3, they terminated in the same mandibular position.2. The gothic arch tracing produced the least variable and the voluntary, tapping the most variable. The habitual closure tended toward eccentric position laterally. The myo-monitor centric produced more variable than the gothic arch tracing but less than the habitual closure.3. The estimated region of apex point was 0.57mm in laterally and 0.45mm in anteroposteriorly, the myo-monitor centric showed 0.62mm in laterally and 0.76mm in anteroposteriorly, the habitual closure determined 0.97 mm in laterally and 0.96mm in anteroposteriorly and the voluntary tapping produced 0.95mm in laterally and 1.59 mm in anteroposteriorly in an average of rejection ellipse (α=0.05).4. In an average of mandibular positon in anteroposteriorly, the gothic arch apex was the most retruded. The distance between apex point and the habitual closure was 0.4mm, the myo-centric was 0.7mm and the voluntary tapping was 0.9mm anterior.5. An average distance between apex point and mean points of each methods produced more consistent mandibular position that ranged within 0.15mm in laterally.

Application of carbon fiber (CF)-cloth reinforcement to upper complete denture base.

The acrylic resin denture base is used more than the usual metal denture base because of the low cost, simple process to make and easy rebasing. But, as the strength of the resin is weaker, the upper resin denture base is three to four times as thick as the metal denture base. So, a study was made to make the upper complete resin denture base thinner while maintaining the strength of the resin denture bases currently in use now. To make the palatal area of the denture base thinner was made possible by the application of carbon fiber (CF)-cloth reinforcement. The resin denture base reinforced by the CF-cloth was of a thickness of 0.7 mm and was evaluated for the mechanical properties of bending. As a result, it was found that both the stiffness and strength were improved by 10% or more as compared with those of the ordinary resin denture bases.

Studies on Masticatory Force and E.M.G. of Difference from Border Forms of Complete Dentures

It has been considered that the occlusal aspects of artificial molar teeth, occlusal types, forms and sizes of denture bases are the significant factors, which have direct effects masticatory function of complete denture wearers. According to the serial studies at our department, it is defined that the difference of occlusal forms and occlusal of complete dentures have influence on the masticatory function of complete denture wearers, especially masticatory force and electromyography (EMG).As regarding the effect of the difference in border forms and sizes of complete dentures on the masticatory function, it has been analyzed that using the bite force by Moriya and Okane, using the EMG by Nakano, using the masticatory performance ratio and EMG by Sasaki, using the masticatory performance ratio and the activity of masseter by Yanagida and using the masticatory performance ratio by Kapur and so on.However, there are little studies about the effect of difference in border forms of molar ragion of mandibular complete denture on masticatory function. Then, the author make the following plane to examine about these problems. Two different complete dentures are fabricated. The form and size of the control complete dentures are defined by the functional impression, the subjects are trimed at bilateral buccal shelves, retromylohyoid spaces and retromolar pads. Using these complete dentures, the author examines the masticatory forces and EMG used the semicondoctor element.The outline of the discussion about these studies as follows;1. About the masticatory and antagonic force in various foods, such as peanuts, ham and takuan. The measured values of the control complete denture are the same level with the subject complete denture when the patient masticate peanuts, the control is higher when the patient masticate ham and the control is lower when the patient masticate takuan.2. Concerning the masticatory rhythm and the swallowing pattern in various foods, the duration and a ratio of the duration during electric discharge period on masticatory force for the control complete denture are larger than that of the subject complete denture, and the interval and the cycle for the control are smaller than the subject. On the other hand, the duration, the cycle and a ratio of the duration during electlic discharge period on EMG for the control are smaller than the subject, and the interval for the control are smaller than the subject except ham.3. The integrated masticatory forces in various foods for the control are larger than that of the subject.4. The activities of masticatory muscles in masticating various foods for the control, are smaller than that of the subject.5. The activities of masticatory muscles which are needed for the integrated masticatory force unit and the antagonistic force unit in masticating various foods for the control, are smaller than that of the subject.6. The masticatory force and integrated masticatory force per unit area of complete denture base in masticating various foods the control, are smaller than that of the subject.

繊維強化義歯床の成形法と強度

The fiber-reinforced upper complete denture base was studied to improve the mechanical properties and the performance of the molding of acrylic resin denture base. The carbon and the organic fibers were used to reinforce the upper acrylic resin complete denture bases which are brought about the most high frequency of fracture. The positions of reinforcement were respectively near the front teeth and the palatal area of upper complete denture base. The purpose of such the studies is to strengthen the upper denture base of which the thickness of palatal area is thin. As the applied load on the denture base was assumed as the flexural de formation of the denture base, the four-point loading system was adoptted for these tests. Then, the strain destribution and the stiffness of denture base were examined, and the effec tiveness of reinforcement for the fiber-reinforced denture bases were investigated. And so the flexural deformation and fracture of the upper complete denture base caused with the occlusal force were basically considered, and the progress of fracture and the fracture modes of the denture base were examined.

A Study on the Fitness Test of the Lower Complete Denture Base

A Study on the Fitness Test of the Lower Complete Denture Base