Experimental Denture Base Research Articles

Accuracy and retention of denture bases fabricated by injection molding, milling, and three-dimensional printing

Objective: To compare the accuracy and retention of denture bases fabricated by injection molding, milling, and three-dimensional (3D) printing fabricating, in order to provide some references for clinical practice. Methods: A maxillary edentulous jaw model made was used to duplicated 10 working casts. The casts were numbered and scanned. The wax pattern was designed by digital ways and conventional methods and then the denture bases were fabricated by injection molding, milling, and 3D printing. The tissue surface of experimental denture base was obtained using a dental laboratory scanner. The deviation between the tissue surface of the fabricated denture bases and the working model was evaluated. A digital force gauge was used to measure the traction force. Results: The milling group [(0.076±0.026) mm] was more accurate than the 3D printing group [(0.117±0.041) mm] (P<0.05) and the injection group [(0.120± 0.025) mm] (P<0.05). The accuracy of 3D printing group and that of injection group were not statistically significant (P>0.05). The milling group [(9.55±2.44) N] demonstrated greater retentive force than 3D printing group [(5.19±0.06) N] and injection molding group [(1.52±0.52) N] (P<0.05). Conclusions: The denture base fabricated by milling was more accurate and showed the greatest retentive force than the other groups. And 3D printing group showed better retentive force than the injection molding group. Both digital manufacturing methods can meet the requirements of clinical application.

Accuracy and retention of denture base fabricated by heat curing and additive manufacturing

PurposeThe aim of the present study was to compare the accuracy and retentive force of an experimental denture base fabricated using additive manufacturing and heat curing. MethodsA maxillary edentulous jaw model made of silicon was used. The shape data for the working cast and wax pattern of the experimental denture base were obtained using a dental laboratory scanner. Fabrication of the experimental denture bases was performed using heat curing and additive manufacturing. The shape data for the experimental denture bases was captured using an optical scanner. The shapes of the two experimental denture bases were compared with the shape of the working cast. A digital force gauge was used to measure the traction force. Pulling was maintained until the experimental denture base separated from the elastic model. Retention was set as the maximum value for the traction force. In order to compare the retentive force of the two experimental denture bases. ResultsThe experimental denture base fabricated using additive manufacturing was more accurate than the experimental denture base fabricated using heat curing. The experimental denture base fabricated using additive manufacturing demonstrated greater retentive force than the experimental denture base fabricated using heat curing. ConclusionsIn this study, the experimental denture base fabricated using additive manufacturing was more accurate and obtained greater retentive force than the experimental denture base fabricated using heat curing.

Influence of the mechanical properties of resilient denture liners on the retention of overdenture attachments

Statement of problemInformation is lacking about the selection criteria for silicone resilient denture liners applied as a matrix material for attachments on overdentures. PurposeThe purpose of this in vitro study was to investigate the mechanical properties of silicone resilient denture liners and their influence on the initial retention force of overdenture attachments and the reduction in retention force over time. Material and methodsNine types of silicone resilient denture liner were injected and fixed to the matrix section of an experimental denture base. They were then fitted to an epoxy resin model that simulated the residual ridge with a patrix ball attachment (n=10). The retention force of the denture was measured with a digital force gauge, and the maximum force of traction (N) was regarded as the initial retention force. The retention force reduction (N) after repeated insertion and removal (n=5) was calculated by subtracting the retention force after 3348 cycles (3-year simulated insertion and removal) from the initial retention force. The intaglio of the matrix was observed with a scanning electron microscope (SEM) before and after the 3348 cycles. Four mechanical properties (hardness, strain-in-compression, tensile strength, and arithmetic mean roughness) of the resilient denture liners were measured. One-way ANOVA of the initial retention force of each lining material was performed, followed by the Scheffe test (α=.05). Pearson correlation analysis was used (α=.05) to analyze correlations of the initial retention force with the retention force reduction after insertion and removal and the mechanical properties of each material. Multiple regression analysis with the stepwise method extracted the initial retention force and the retention force reduction as dependent variables, and the resilient denture liner mechanical properties as explanatory variables (α=.05). ResultsThe initial retention force of the resilient denture liners was 1.3 to 5.4 N. Multiple comparisons showed significant differences in some groups (P<.05). The retention force reduction of the resilient denture liners was 0.2 to 1.9 N. Multiple regression analysis with the stepwise method extracted hardness and strain-in-compression as explanatory variables for the initial retention force and the retention force reduction. ConclusionsWithin the limitations of this in vitro study, hardness was found to influence the initial retention force of the overdenture, and strain-in-compression influenced the retention force reduction in the 3-year simulation.

Physical, mechanical, thermal, and dynamic characterization of carbon nanotubes incorporated poly(methyl methacrylate)-based denture implant

The objective of this study was targeted to synthesize and characterize a carbon nanotubes (CNTs) incorporated poly(methyl methacrylate) (PMMA)-based denture polymer. Two experimental denture base polymers were fabricated either by incorporating single-walled CNTs (SWCNTs) (SW-group) or multi-walled CNTs (MWCNTs) (MW-group). In both groups, 0.5 wt% of the CNTs were incorporated into MMA monomer. Using a commercially available heat-cured PMMA (Interacryl Hot, Interdent, Opekarniska, Slovenia), a polymer-to-monomer ratio of 3:1 was used to fabricate the specimens (14 × 14 × 3 mm3 in dimensions) of the control group (without CNTs) (C-group) and the experimental groups (either SWCNT–PMMA or MWCNT–PMMA) ( n = 30, N = 90). Physical, mechanical, thermal, and rheological attributes of the tested materials were assessed. The data were statistically analyzed using SPSS version 21.0 (SPSS®, Chicago, IL, USA) and results were explored with one-way ANOVA. Incorporation of CNTs changed the surface morphology and topography of the PMMA specimens. No thermal changes were observed among C-, SW-, and MW-groups. Conversely, the hardness, elastic modulus and wear resistance were improved in both SW-group and MW-group. Additionally, the dynamic mechanical analyzer showed improvement in storage modulus in SW-group, affirming the load transfer capability of SW–PMMA composite. The CNT–PMMA composite might favorably be used as a potential denture base polymer.

Evaluation of the effect of Poly Vinyl Pyrrolidone addition on the shear bond strength of acrylic resin artificial teeth to heat cured acrylic resin denture base material

Background: The most common materials used for fabrication of denture bases are poly methyl methacrylate (PMMA). Fracture or debonding of plastic teeth from denture base are common clinical problems which are facing both the patient and the dentist. The aim of this study is to evaluate and compare the shear bond strength of acrylic resin artificial teeth treated by different chemical surface treatments (solvents like acetone & thinner) to the experimental prepared material and to the control material before and after thermocycling. Materials and methods: Preparation of modified heat cured denture base acrylic resin was carried out by preparing of (PMMA) (80%) and poly vinyl pyrrolidone (PVP) (20%) and the liquid part composed of methyl methacrylate (MMA) monomer. Control: poly methyl methacrylate (PMMA) + methyl methacrylate ( MMA ) as control group ( 2.5 : 1 ) by weight (1). Experimental: PMMA (80% ) + PVP ( 20% ) + MMA as experimental group ( 2.5 : 1 ) by weight. Sixty artificial acrylic teeth were prepared and cured by control and experimental denture base acrylic resin, then teeth were divided into three groups and treated with different surface treatment; first group received no further treatment (control), second group treated with acetone and third group treated with thinner. The denture teeth were flasked and wax was eliminated with running hot water. Denture resin was packed and cured according to manufacturer's instructions and specimens were deflasked upon the completion of resin processing. Then half of specimens from all surface treatments were tested by using Instron machine and subjected to shear force until failure. The other half of specimens which also include the surface treatments groups were thermocycled. Teeth surfaces after treatment and fracture sites were examined and photographed visually and under reflecting light microscope. Results: The results showed that all surface treatments produced significantly high improvement in shear bond strength (SBS). Control group had shown significantly lower (SBS) than experimental group bonded to artificial acrylic teeth. On the other hand, experimental denture base resin bonded to artificial acrylic teeth were affected more significantly by thermocycling than the same teeth bonded to control denture base resin. Results indicated that thinner treatment for acrylic teeth is recommended prior to denture base processing. Conclusion: higher SBS of artificial acrylic teeth bonded to experimental denture bases rather than to control denture bases.

Influence of anterior palatal coverage on perception and retention in complete dentures

Oral perception is adversely affected by palatal coverage in complete denture wearers. The purpose of this study was to determine whether an opening in an anterior palatal base enhanced oral perception and the effect of the size of the opening on retention. Ten healthy dentate individuals (5 men, 5 women; age range: 22-29 years) participated in the perception test. The time required to sense a nylon thread embedded in test food was measured. The test was performed with 3 types of experimental palatal form: no-opening; small-opening, where the opening was located in the anterior region of the palatal base; and large-opening, where the opening was located between the incisive papilla and the third palatal rugae. No palatal coverage was used as a control. Retention force was measured by pulling and loading tests. In the pulling test, pulling force was applied to 2 points on the experimental denture base, and in the loading test, loading force was applied to 6 points. Response times (sec) and retention forces (N) were analyzed using a 1-way ANOVA for repeated measurements followed by the Bonferroni test for multiple comparisons (α=.05). A significant difference was observed in response time in fiber perception between bases with or without a small opening (P =.017). In the pulling test, retention force with the small-opening type was 4% lower at the molar region, and 35% lower at the center of gravity than in the no-opening type. Retention force in the large-opening type was lower than in the small-opening type. In the loading test, retention force was 13 N or higher in all 3 types. The small-opening type of palatal coverage improved oral perception and demonstrated sufficient retention force.

Fluoride release and recharge characteristics of denture base resins containing surface pre-reacted glass-ionomer filler

The flexural strength, flexural modulus, and the amount of fluoride released from four experimental denture base resins containing 5, 10, 20 and 30 wt% surface pre-reacted glass-ionomer (S-PRG) filler added to the powder were evaluated. The mean flexural strength of the experimental resins, except the 30 wt%, and the flexural modulus of all the resins, complied with ISO 1567 requirements. In the 20 wt% resin, the amount of fluoride released in the initial phase was 1.88 microg/cm2/day, after which the level decreased. After recharging in a 9000 ppm fluoride solution for eight hours, the level of released fluoride increased markedly to 40.21 microg/cm2/16 hrs. Our results show that fluoride levels increased as a function of the S-PRG filler content. After the almost completely discharged resins were recharged, similar fluoride release occurred again. These results suggest that denture base resins containing S-PRG filler have great recharge and release capabilities which may assist in preventing root caries of abutment teeth.

Electron-beam irradiation of experimental denture base polymers

Objective. Since the properties of polymers can be influenced using electron-beam irradiation, the aim of this study was to investigate whether electron-beam post-curing can improve the mechanical properties of experimental denture base polymers. Material and methods. Rectangular specimens of different experimental polymeric blends were electron-beam irradiated (post-cured) with 25 kGy and 200 kGy using an electron accelerator of 4.5 MeV. Fracture toughness, work of fracture, Vickers hardness and colour changes were measured and compared in non-irradiated specimens. Results. The mechanical properties of all the investigated polymers seemed to benefit from low-energy electron-beam irradiation (25 kGy). Using an energy dose of 200 kGy, all blends showed deteriorated mechanical properties resulting from chain breakage. Nevertheless, all investigated polymers had undesirable colour changes after electron-beam irradiation. Conclusions. Mechanical properties of experimental polymethyl-methacrylate could be changed using electron-beam irradiation. Because of discolorations caused by the irradiation levels investigated, these levels cannot be recommended for practical applications.

Effect of continuous pressure on histopathological changes in denture-supporting tissues.

The histopathological changes in denture-supporting tissues were studied in relation to continuous pressure exerted through an experimental denture base. The experimental dentures were designed to load continuous pressures (1.5, 3.4 or 4.9 kPa) to the palate of molar region of rat. Histopathological changes caused by the continuous pressure were observed, and the intensity of the pressure was also estimated. A high correlation was observed between the histopathological changes under the denture base and the intensity of the continuous pressure. In groups exposed to 4.9 and 3.4 kPa, the continuous mechanical pressure caused bone resorption; in 1.5 kPa group, no evidence of bone resorption was observed. The epithelium and lamina propria mucosa under the denture base, which were compressed by the continuous pressure, recovered histopathologically depending on the decrease of the pressure caused by bone resorption; no quantitative recovery of the absorbed bone tissue was observed. No inflammatory change was induced by the continuous pressure. From the histopathological results observed in this study, the possibility of the existence of a threshold for bone resorption induced by continuous pressure was suggested.

The effect of diabetes mellitus on the expression of Argyrophilic nucleolar organizer regions (AgNORs) in mucosal epithelium under experimental denture bases in rats.

Expression of argyrophilic nucleolar organizer regions (AgNOR) was counted on mucosal epithelium to detect whether the AgNOR count (the number of AgNOR per nucleus) is, for 20 weeks, affected by streptozotocin-induced diabetes mellitus. Diabetic rats were applied non-denture wearing, non-pressure contact, continuous pressure (0.5, 1.5 or 3.4 kPa) and intermittent pressure (10.5, 33.0 or 81.7 kPa), respectively. In the non-denture wearing or the non-pressure contact group, AgNOR count was almost constant (ranging 1.86-1.92) without significant difference. Under continuous pressure, AgNOR count significantly decreased at earlier stage and finally recovered to the non-pressure contact group. A similar effect of continuous pressure appeared to manifest itself in intermittent pressure, but to a greater degree. Consequently, AgNOR count under intermittent pressure showed no recovery at 20-week stage. : Diabetes mellitus exerted, by itself, no influence on the cellular proliferative activity under continuous pressure, whereas the activity deteriorated under intermittent pressure.

Histopathological changes in the tissues under a denture base in experimental osteoporosis with a non-pressure covering or bearing continuous pressure.

In this study, the experimental denture base on the hard palate of the molar region of osteoporotic rats was designed to cover without any mechanical pressure or to load continuous pressure (0.5, 1.5 or 3.4 kPa). Experimental osteoporosis was induced by ovariectomy and feeding on a low calcium diet. Histopathological changes induced by non-pressure covering or continuous pressure in the tissues under the experimental denture bases were examined. Regarding the histological changes induced by continuous pressure, this was evaluated in relation to the time course of the intensity of the continuous pressure. In the tissues under the denture base in osteoporotic condition with non-pressure covering, no histopathological changes caused by non-pressure covering were observed except for a transient slight proliferative reaction in the epithelial ridge. The following histopathological changes were observed in the tissues under the denture base in the osteoporotic condition bearing continuous pressure; (i) bone resorption was induced on the periosteal surface (Ps) in the osteoporotic-3.4 kPa group, and on the pressure side of the endocortical surface (p-Ec) in the osteoporotic-1.5 and -3.4 kPa group, (ii) the appearance of osteoclasts on the p-Ec in the osteoporotic-3.4 kPa group was earlier than that on the Ps in a same group, (iii) bone resorption on the pressure side of the Ec in the osteoporotic-3.4 kPa group manifested at the earlier stage than that in the osteoporotic-1.5 kPa group, (iv) bone formation following bone resorption on the p-Ec was observed more markedly than that on the Ps and (v) histopathological changes in the tissues under the denture base in experimental osteoporosis bearing continuous pressure had an intimate relationship with the initial intensity and the time course of continuous pressure.

Changes of blood flow in the mucosa underlying a mandibular denture following pressure assumed as a result of light clenching.

The aim of this study was to investigate the influence of the continuous compression assumed as a result of light clenching on the blood flow of the denture underlying mucosa in tissue-supported or tooth-tissue-supported denture wearers. Measurements were carried out on eight removable partial denture wearers (three males and five females, from 50 to 72 years, mean age: 61.5 years). The blood flow in the denture underlying mucosa was measured at the unilateral mandibular first molar region using an experimental denture base equipped with a laser Doppler flowmeter. The area of the experimental denture base was 2 cm2, and the loading force was 1 kgf. The loading time was set at 5, 10, 20, 30 and 60 s. The blood flow after 20 s loading was <15% in rest. The times from release of loading to the maximum blood flow and from release of loading to recovery up to 110% of the blood flow at pre-loading were significantly prolonged by an increase in the loading time. Even if it is light, a continuous clenching results in ischaemia and delays the recovery of blood flow in the mucosa underlying the denture after release of compression.

A histomorphometric analysis on bone dynamics in denture supporting tissue under continuous pressure in streptozotocin-induced diabetic rat.

The purpose of this study was to investigate bone dynamics in denture supporting tissue under continuous pressure in the diabetic condition by using bone histomorphometry in relation to initial intensity of continuous pressure exerted through the denture base. The experimental denture base, which was designed to load initial continuous pressure of 0.0, 1.0, 10.0 or 20.0 kPa to the denture supporting tissue, was applied to the molar region of hard palate of streptozotocin-induced diabetic rats. Fluorescent labelled palatal bone tissue was stained with Villanueva bone stain and was prepared for the undecalcified grinding section. In 0.0 kPa group, no bone resorption was observed and bone formation was transiently inhibited after the denture insertion. In 1.0 kPa group, although no bone resorption was observed, the beginning of bone formation after the inhibition of bone formation was later than that in 0.0 kPa group and bone formation dynamics after the resumption of bone formation was similar to that in 0.0 kPa group. In 10.0 and 20.0 kPa groups, bone resorption was observed until 3 and 4 weeks, respectively, and the amount of bone resorption for each group was 60 +/- 16 and 87 +/- 18 microm, respectively. The resumption of bone formation in 10.0 and 20.0 kPa groups were observed at the same stage with 1.0 kPa group, and the bone formation dynamics after the resumption of bone formation in 10.0 and 20.0 kPa groups were also similar to that in 0.0 kPa group. From the results of this study, it was revealed that bone formation following bone resorption did not cause equivalent recovery of the bone surface level to the level observed in the case without bone resorption in the diabetic condition.

The effect of diabetes mellitus on histopathological changes in the tissues under denture base bearing masticatory pressure.

The effect of streptozotocin-induced diabetes mellitus on histopathological changes in tissues bearing masticatory pressure exerted through an experimental denture base has been studied in animal specimens. Experimental dentures, which prescribed the masticatory pressure by the amount of subsidence of the denture base (100, 50 or 13 microm), were constructed for the hard palate of the molar regions of rats. It was revealed that streptozotocin-induced diabetes mellitus (1) weakened the intercellular junctions in the epithelium and gradually enhanced this state with time, (2) lessened the atrophic and proliferative reactions in the epithelial ridge and prolonged their appearance period, (3) enhanced the compression of lamina propria mucosae and prolonged the appearance period of this reaction, (4) enhanced the inflammatory change and extended its appearance period, (5) lowered the threshold for the inflammatory reaction induced by the masticatory pressure, (6) increased the number of osteoclasts and prolonged the period of their presence, (7) lowered the threshold for osteoclastic bone resorption induced by the masticatory pressure, (8) inhibited the appearance of osteoblasts following the disappearance of osteoclasts and (9) accelerated the decline rate of masticatory pressure exerted to the denture supporting tissues. Therefore, it can be concluded that the streptozotocin-induced diabetes mellitus in the animals tested deteriorated the tolerance of the denture supporting tissues to masticatory pressure.

The effect of diabetes mellitus on histopathological changes in the denture-supporting tissues under continuous mechanical pressure in rat.

The histopathological changes in denture-supporting tissues of streptozotocin-induced diabetes mellitus rat were studied in relation to continuous mechanical pressure exerted through an experimental denture base. The experimental dentures were designed to load continuous mechanical pressures (3.4, 1.5 or 0.5 kPa) to the hard palate of the molar region of a rat. From the results of this study, the following conclusions were drawn: the streptozotocin-induced diabetic condition (1) tended to prolong the appearance period of a shortened epithelial ridge, and weakened the phenomenon, (2) reduced the appearance period and severity of the compression of epithelium, (3) delayed the time of manifestation of the proliferative change in the recovery process of the shortened epithelial ridge, and weakened the phenomenon, (4) prolonged the appearance period of the compressed lamina propria mucosae, and enhanced the phenomenon, (5) reduced the number of osteoclasts, (6) lowered the threshold for induction of the osteoclastic bone resorption to between 1.5 and 0.5 kPa, (7) inhibited the appearance of osteoblast which follows the disappearance of osteoclasts, (8) did not induce any inflammatory change, and (9) tended to enhance the longitudinal change of the continuous mechanical pressure. The histopathological changes in the denture-supporting tissues of the streptozotocin-induced diabetes mellitus rat related highly to the longitudinal change of the continuous mechanical pressure exerted through the denture base. From the results of this study, it was suggested that the streptozotocin-induced diabetic condition lowers the tolerance of the denture-supporting tissues to continuous mechanical pressure.

The effect of diabetes mellitus on histopathological changes in the tissues under denture base and without mechanical pressure.

Histopathological changes in the tissues under a denture base were studied with respect to the difference between diabetic and normal rats. Diabetes mellitus was induced in Wistar rats by streptozotocin. The experimental denture base was designed to make contact with the palatal mucosa without any continuous nor masticatory pressure. Histopathological observation periods were 1, 2, 4, 8, 12 and 20 weeks after the insertion of the denture base. Histopathological examination revealed that only the transient slight proliferative reaction observed in mucosal epithelium under a denture base in normal non-diabetic rats, was lessened by induced diabetes mellitus. Moreover, covering the palatal mucosa with a denture base without any continuous nor masticatory pressure and with the maintenance of mucosal cleanliness under it and of the denture itself, did not cause any inflammatory change or bone resorption in the tissues under the base.

Effect of continuous pressure on histopathological changes in denture‐supporting tissues

summary The histopathological changes in denture‐supporting tissues were studied in relation to continuous pressure exerted through an experimental denture base. The experimental dentures were designed to load continuous pressures (1.5, 3.4 or 4.9 kPa) to the palate of molar region of rat. Histopathological changes caused by the continuous pressure were observed, and the intensity of the pressure was also estimated. A high correlation was observed between the histopathological changes under the denture base and the intensity of the continuous pressure. In groups exposed to 4.9 and 34 kPa, the continuous mechanical pressure caused bone resorption; in 1.5 kPa group, no evidence of bone resorption was observed. The epithelium and lamina propria mucosa under the denture base, which were compressed by the continuous pressure, recovered histopathologically depending on the decrease of the pressure caused by bone resorption; no quantitative recovery of the absorbed bone tissue was observed. No inflammatory change was induced by the continuous pressure. From the histopathological results observed in this study, the possibility of the existence of a threshold for bone resorption induced by continuous pressure was suggested.

Effect of occlusal pressure on the histopathological changes in denture supporting tissues.

Histopathological changes in the denture supporting tissues in relation to the occlusal pressure exerted through an experimental denture base were studied. An experimental denture, which prescribed the occlusal pressure by the amount of subsidence of the denture base (100, 50 and 13 microns), was constructed for the palate of the molar region of rat. Histopathological changes caused by the occlusal pressure were observed, and the intensity of the pressure was also estimated. In the 100 microns subsidence group, compression of epithelium and lamina propria mucosae, inflammatory change and bone resorption were caused by the occlusal pressure. In the 50 microns subsidence group, compression of epithelium and lamina propria mucosae and bone resorption were observed, while in the 13 microns subsidence group, no evidence of inflammatory change and bone resorption were observed. The epithelium and lamina propria mucosae recovered histopathologically depending on the gradual decrease of the occlusal pressure resulting from bone resorption, whereas no quantitative recovery of the resorbed bone tissue was observed in the 100 and 50 microns subsidence groups. From the results observed in this study, a high correlation was observed between the histopathological changes under a denture base and the intensity of the occlusal pressure, and the possibility of the existence of the threshold for bone resorption induced by occlusal pressure was suggested.

こう合圧が義歯床下組織の初期変化に及ぼす影響に関する研究

Histopathological initial changes in denture supporting tissues, in relation to the changes in intensity of occlusal pressure exerted through the experimental denture base, was studied. The denture base was applied to the palate of the molar region of the rat, and was installed to cover the palatal mucosa without any pressure unless occlusal force was exerted. The defined amount of occlusal pressure was transmitted to denture supporting tissue by allowing the denture base to subside the specified amount into palatal mucosa. The intensity of the occlusal pressure measured immediately after the insertion of the denture were 79.7, 31.7 and 10.7kPa. The animals were sacrificed at 2, 4, 7, 10 and 14 days after the insertion of the denture. Histopathological changes caused by the occlusal pressure were observed, and the changes in intensity of the occlusal pressure was also measured on every histopathological observation periods.Histopathological changes of the denture supporting tissues showed dependence on the intensity of the occlusal pressure, and also showed high correlation with the subsequent gradual changes of the pressure. Compression of lamina propria mucosa, shortening of epithelial ridges, osteoclastic bone resorption, compression of epithelial tissue except for epithelial ridges and inflammatory cell infiltration in the lamina propria mucosa were observed with the elapse of time. These tissue changes came out early and became severe by increasing the occlusal pressure.

自浄作用の欠如に伴う義歯床下骨組織の吸収に関する組織計測的検討

The purpose of the present study was to make a histometrical evaluation of bone formation under the denture base caused by lack of self-cleaning as a result of coverage by the denture base, utilizing a double labeling technique with bone markers.The experimental denture base was designed to make contact with the molar region of the palate of the rat and to transmit no occlusal force to the tissues under the denture base. The denture base was not removed throughout the experimental period. This procedure caused lack of self-cleaning, and it also caused continuous pressure to palatal tissues under the denture base by the accumulation of exfoliative horny cells, which induced bone resorption and formation under the denture base.Five rats of each denture wearing group and control group were sacrificed every week during the observation period of 10 weeks after the insertion of the experimental denture base. Palatal tissues were prestained with Villanueva bone stain, and then processed for undecalcified resin section for quantitative bone histomorphometry. These specimens were analyzed using a two-dimensional graphic analyzing system.The following results were obtained.1. One to three weeks after the insertion of the denture base, bone formation was suppressed or disappeared on the palatal surface of hard palate bone tissue under the denture base.2. A transient but significant increase of bone formation was observed following bone resorption on the palatal surface of hard palate bone tissue under the denture base. And seven to ten weeks after the insertion of the denture base, bone formation was suppressed again.3. On the nasal surface of hard palate bone tissue, increased bone formation was observed simultaneously with bone resorption on the palatal surface.