Dry mouth and denture plaque microflora in complete denture and palatal obturator prosthesis wearers.

OBJECTIVE AND BACKGROUND: The purpose of this study was to investigate the association of dry mouth with denture plaque microflora in patients with palatal obturator prostheses from the viewpoint of infection control. METHODS: Thirty palatal obturator prosthesis wearers were compared with 30 healthy maxillary complete denture wearers. Dry mouth was examined using a moisture-checking device and was diagnosed by the measured moisture levels. Denture plaque was collected by rubbing the mucosal surface of the denture with a swab; collected microorganisms were cultured and identified using culture-dependent methods. The number of colonising microorganisms and prevalence of microorganisms were examined according to the type of prostheses and presence of dry mouth using nonparametric tests and frequency analysis (α = 0.05). RESULTS: The prevalence of Candida spp. and Staphylococcus spp. in palatal obturator prostheses was significantly higher than that in complete dentures. In palatal obturator prostheses, the total number of colonising microorganisms showed no significant differences between the groups with and without dry mouth on each side of the prostheses. However, the prevalence of Candida spp. and Staphylococcus spp. in the group with dry mouth was significantly higher than that in the group without dry mouth. The number of microorganisms and moisture levels of palatal obturator prosthesis wearers showed a significantly negative correlation with Candida spp. and Staphylococcus spp., but a positive correlation with Neisseria spp. CONCLUSION: It was concluded that palatal obturator prosthesis wearers with a dry mouth have greater colonisation by Candida spp. and Staphylococcus spp. than do complete denture wearers.

Influence of an antidiabetic drug on biomechanical and histological parameters around implants in type 2 diabetic rats.

OBJECTIVES: Type 2 diabetes mellitus (DM) has a deleterious effect on dental implant integration into alveolar bone, thought to arise from impaired osteoblast function and consequent reduced bone turnover. However, whether controlling blood glucose with antidiabetic drugs is sufficient to improve implant integration is unclear. This study was designed to evaluate implant integration using diabetic rats with/without an antidiabetic drug. MATERIALS AND METHODS: Titanium screws were surgically implanted in each tibia of 20 Goto-Kakizaki (GK) rats and 5 nondiabetic control rats. After 3 or 9 weeks, osseointegration was determined by testing the removal torque required to displace the screw and by histological analysis of various parameters of bone formation. RESULTS: Removal torque was significantly higher in the nondiabetic control group than in GK rats, irrespective of whether the GK rats had received voglibose. Histology revealed that single-labeled surface area was still high in the GK rats at 9 weeks but had peaked and diminished in control rats. Bone-implant contact area was reduced in GK rats. CONCLUSIONS: Despite controlling blood glucose, voglibose was unable to reverse the bone metabolic effects of DM.

Comparison of a saliva wetness tester and a moisture-checking device in patients with maxillary obturator prostheses.

OBJECTIVE: Examination of dry mouth in postoperative oral tumour patients should ideally be performed simply and quickly at the chair side. Moisture-checking devices and saliva wetness testers are available for such moisture measurement. Previous studies have reported that moisture-checking devices are useful to examine dry mouth in patients with maxillary obturator prostheses. However, because the measurement principles of saliva wetness testers differ from those of moisture-checking devices, diagnosis by the two devices may result in diagnostic disagreement. The purpose of the present study was to compare the usefulness of a saliva wetness tester with a moisture-checking device for patients with maxillary obturator prostheses. METHODS: Oral moisture was measured with a moisture-checking device and a saliva wetness tester in 30 subjects with maxillary obturator prostheses. These measurements were performed five times at the lingual mucosa, and mean values of each measurement were calculated. The reference value for moisture measurements with the moisture-checking device was 29%, and that with the saliva wetness tester was 3 mm. Subjects were classified as having dry mouth when their moisture measurements were less than the reference values. RESULTS: The diagnostic results of the saliva wetness tester were in agreement with those of the moisture-checking device. The respective moisture measurements showed a significant positive correlation (r=0.88, p<0.01). CONCLUSION: The results of the present study demonstrate that saliva wetness testers are as useful as moisture-checking devices to examine dry mouth in patients with maxillary obturator prostheses.

Survival of microorganisms on complete dentures following ultrasonic cleaning combined with immersion in peroxide-based cleanser solution.

OBJECTIVES: To compare ultrasonic cleaning combined with immersion in a commercially available peroxide-based cleanser solution (Polident(®) ) with other denture cleaning methods, we examined the quantity of micro-organisms that survived on dentures before and after various cleaning methods. SUBJECTS AND METHODS: One hundred complete dentures belonging to 50 nursing home residents (mean age, 84.6 years) were randomly assigned to five groups according to the cleaning method employed: (A) immersion in Polident(®) solution alone, (B) brushing with water, (C) ultrasonic cleaning with water, (D) method (A) followed by method (B) and (E) ultrasonic cleaning combined with immersion in Polident(®) solution. Before and after the dentures had been cleaned, denture biofilm was collected from the mucosal surface of each lateral half of the examined dentures. The collected micro-organisms were cultured, presumptively identified by standard methods and quantified. Comparisons between the five cleaning methods were carried out using the Kruskal-Wallis test and Dunn's multiple comparisons test. RESULTS: The denture cleaning methods involving the use of Polident(®) solution (methods A, D and E) were significantly more effective at denture disinfection than the other methods (p < 0.05); in particular, the quantity of Candida spp. was lowest after method E (median, 0.00; significantly lower than those observed after methods A, B and C; p < 0.05). CONCLUSION: It was concluded that ultrasonic cleaning combined with immersion in a peroxide-based cleanser solution effectively reduces the quantity of micro-organisms surviving on dentures and is a suitable method for elderly individuals who find brushing their dentures difficult.

Changes in lip forms on three-dimensional images with alteration of lip support and/or occlusal vertical dimension in complete denture wearers.

PURPOSE: This study aimed to examine changes in the lip form, oral fissure form and vermilion height of complete denture wearers resulting from altered occlusal vertical dimension (OVD) and/or lip support. METHODS: Three-dimensional facial images of 10 edentulous patients (four males and six females) when wearing six experimental record blocks (ExpRBs) with varying OVD and/or lip support were analyzed. Analysis was performed using three landmarks on the mid-line (labrale superius (ls), stomion (sto), and labrale inferius (li)) and two landmarks on the oral fissure (at points 20mm right and left of the midline (r-OFP and l-OFP, respectively)). Curvature of the oral fissure (COF) in the frontal view was evaluated by calculating the difference between sto and the average of r-OFP and l-OFP (avrl-OFP). The vermilion height in the frontal view was calculated as the distance from sto to ls and li. In 10 subjects, comparison between standard ExpRB and test ExpRBs with altered OVD and/or lip support was performed by calculating differences between these data. RESULTS: The ls, sto, and li landmarks changed with alteration of OVD and/or lip support, whereas avrl-OFP changed vertically with alteration of lip support and anteroposteriorly with alteration of OVD and/or lip support. COF and vermilion height were affected by alterations in OVD and/or lip support. CONCLUSION: Deficient OVD with extensive lip support can curve the oral fissure form upward, and deficient OVD with deficient lip support can reduce the vermilion height.

Examination of denture-cleaning methods based on the quantity of microorganisms adhering to a denture.

OBJECTIVES: To investigate effective denture-cleaning methods, we examined the relationships between the quantity of microorganisms adhering to dentures and the use of a denture brush and the frequency of use of a denture cleanser. SUBJECTS AND METHODS: Denture plaque was collected from the mucosal surface of the examined dentures, which were 142 and 80 upper and lower complete dentures, respectively, worn by 96 outpatients (mean age: 71.9 years) of a university hospital and 41 nursing home residents (mean age: 84.8 years). The collected microorganisms were counted in terms of isolated representative colonies that were cultured and identified using standard methods. The use of a denture brush, the frequency of use, and the type and soaking time of denture cleansers as denture-cleaning methods were surveyed. RESULTS: The quantity of microorganisms was significantly lower in dentures of denture brush users than in those of non-users in the outpatients (p < 0.01, Mann-Whitney U test). The quantity of microorganisms was significantly lower in the dentures of outpatients who used a denture cleanser daily or 3-4 times a week than in those who used one once or less per month and in the dentures of nursing home residents who used one daily than in those who used one at other frequencies (p < 0.05, Kruskal-Wallis test, followed by Dunn's Multiple Comparison test). CONCLUSION: Within the limitations of this study, it was concluded that the use of a denture brush and daily use of denture cleanser should be recommended to complete dentures wearers as denture-cleaning methods that effectively reduce the quantity of microorganisms adhering to dentures.

Optimum design for glass fiber-reinforced composite clasps using nonlinear finite element analysis.

The purpose of this study was to design an optimum glass fiber-reinforced composite (FRC) clasp. Three-dimensional finite element models were constructed of FRC circumferential clasp arms and an abutment tooth. The basic clasp arm was half-oval, without a taper, 2.60 mm wide and 1.30 mm thick. Four modified clasp arms were prepared by changing the width or thickness of the basic clasp (width/thickness: 2.60 mm/0.65 mm, 2.60 mm/1.95 mm, 1.30 mm/1.30 mm, and 3.90 mm/1.30 mm). Forced displacements of 5 mm in the removal direction were applied to the nodes at the base of the clasp arm. The retentive forces and maximum tensile stresses of the five FRC clasp arms ranged from 1.00-16.30 N and from 58.9-151 MPa, respectively. Results showed that an optimum FRC clasp was a circumferential clasp with 2.60 mm width and 1.30 mm thickness, which had sufficient retentive force and low risk of tensile failure.

Relationship between symptoms of dryness and moisture levels in patients with maxillofacial prostheses.

PURPOSE: This study aimed to examine the relationship between symptoms of dry mouth and the moisture levels in patients with maxillofacial prostheses. METHODS: Dry mouth of 30 patients with maxillofacial prostheses was examined by direct measurement of oral moisture and subjective symptoms of dry mouth were surveyed using Kakinoki's questionnaire. Oral moisture was measured five times at each of the lingual mucosa and the right and left buccal mucosa using Moisture Checker Mucus and the mean value was calculated. Using a value of 29% as a reference, patients were classified as normal when the moisture value was 29%, or more, or with dry mouth if the value was when less than 29%. RESULTS: The moisture levels of the patients with subjective symptoms of dry mouth were significantly lower than those of the patients without symptoms of dry mouth at each of the lingual and buccal mucosa. The moisture level of the lingual mucosa was significantly lower than that of buccal mucosa in the group reporting subjective symptoms of dry mouth, but not in those without symptoms. CONCLUSION: These results suggest that the symptom of dry mouth is corresponding to the moisture level and the moisture level of the lingual mucosa is associated with symptoms of dryness in patients with maxillofacial prosthesis.

Role of the artificial tooth arch during swallowing in edentates.

PURPOSE: This study aimed to clarify the role of the artificial tooth arch (ATA) during swallowing in edentates. METHODS: The tongue pressures, activities of the masseter and suprahyoid muscles, and laryngeal and mandibular movements when swallowing saliva, water, pudding, and corned beef were measured simultaneously using experimental dentures with and without an ATA. We analysed the maximum magnitudes of muscle activities and tongue pressures (MAmax and TPmax, respectively), the times from reaching MAmax and TPmax to laryngeal movement (TLM-MAmax and TLM-TPmax, respectively), and the vertical mandibular position. RESULTS: The MAmax of the masseter muscle and TPmax were significantly greater with the ATA than without the ATA (p<0.05). However, MAmax of the suprahyoid muscles was not significantly different in the conditions with and without the ATA. TLM-TPmax was significantly longer without the ATA than with the ATA (p<0.05) but the TLM-MAmax of the suprahyoid and masseter muscles were not significantly different with and without the ATA. The MAmax of both suprahyoid and masseter muscles and the TPmax were significantly greater, and TLM-TPmax was significantly longer when swallowing corned beef than other materials (p<0.05). The intermaxillar distance and the range of measured mandibular position at the time of swallowing were shorter and wider in the absence of the ATA than with it. CONCLUSION: The present study shows that during swallowing the ATA supports the function of the tongue to perform skillful movements for the smooth passage of food to the oropharynx and the elevation of the larynx by maintaining the mandible position constant near the intercuspal position.

Osteoblast differentiation is functionally associated with decreased AMP kinase activity.

Osteoblasts, originating from mesenchymal stem cells, play a pivotal role in bone formation and mineralization. Several transcription factors including runt-related transcription factor 2 (Runx2) have been reported to be essential for osteoblast differentiation, whereas the cytoplasmic signal transduction pathways controlling the differentiation process have not been fully elucidated. AMP-activated protein kinase (AMPK) is a serine-threonine kinase generally regarded as a key regulator of cellular energy homeostasis, polarity, and division. Recent lines of evidence have indicated that the activity of the catalytic alpha subunit of AMPK is regulated through its phosphorylation by upstream AMPK kinases (AMPKKs) including LKB1. Here, we explored the role of AMPK in osteoblast differentiation using in vitro culture models. Phosphorylation of AMPKalpha was significantly decreased during osteoblastic differentiation in both primary osteoblasts and MC3T3-E1, a mouse osteoblastic cell line. Conversely, the terminal differentiation of primary osteoblasts and MC3T3-E1 cells, represented by matrix mineralization, was significantly inhibited by glucose restriction and stimulation with metformin, both of which are known activators of AMPK. Matrix mineralization of MC3T3-E1 cells was also inhibited by the forced expression of a constitutively active form of AMPKalpha. Metformin significantly inhibited gene expression of Runx2 along with osteoblast differentiation markers including osteocalcin (Ocn), bone sialo protein (Bsp), and osteopontin (Opn). Thus, our present data indicate that differentiation of osteoblasts is functionally associated with decreased AMPK activity.

Bactericidal efficacy of glycine-type amphoteric surfactant as a denture cleaner and its influence on properties of denture base resins.

The bactericidal efficacy of 1.00-4.50% glycine-type amphoteric surfactant (Gly) was evaluated by measuring its microorganism removal rate in denture plaque. Physical and mechanical properties such as surface roughness, color difference, and bending strength of two different denture base resins were determined before and after cleaning in Gly solutions, a commercial denture cleaner, and tap water. The microorganism removal rates of all the Gly solutions were higher than those of a commercial enzymatic denture cleaner (Polident) (p>0.05). The removal rate of Candida spp. by Polident was not significantly different from the removal rate using water. Changes in the surface roughness and color difference among the specimens were slight. There were no significant differences in the bending strengths of the two resins for all concentrations of Gly solution (p>0.05). These results suggested that glycine-type amphoteric surfactant solution may be effective as a denture cleaner in conjunction with an ultrasonic cleaning device.

Use of a magnetic attachment to retain an obturator prosthesis for an osseous defect.

Tooth loss accompanied by a massive defect of the alveolar bone can cause serious problems such as food deposit and esthetic impairment. This report describes procedures for the fabrication of an osseous defect obturator prosthesis connected to a fixed partial denture by a magnetic attachment along with the clinical outcome.

Relationship between medical treatment and oral dryness diagnosed by oral moisture-checking device in patients with maxillofacial prostheses.

PURPOSE: This study aimed to examine the relationship between oral dryness and medical treatment (medication, radiotherapy) for patients with maxillofacial prostheses. METHODS: Sixteen patients with maxillofacial prostheses were examined according to the following procedure. For evaluating oral dryness, oral moisture was measured at the lingual mucosa and the right and left buccal mucosa using a Moisture Checker Mucus. The mean value of each measurement was recorded as the moisture value (%). A value of 29% was used as a reference value to divide patients into a normal group and an oral dryness group. Patients with a moisture value of more than 29% were classified as normal. The clinical histories of the patients (including their current medication use and radiotherapy history-dose of radiation and period after radiation) were surveyed from their clinical records. Patients rated themselves on their feelings for oral dryness using a faces scale. RESULTS: The moisture value was significantly lower in the oral dryness group than the normal group. There was a significant difference in moisture values between the number of patients with and without radiotherapy, but not patients with and without medications. The moisture value had a significant negative correlation with the dose of radiation and a positive one with the period after radiation. The score of faces scale showed a significant negative correlation with moisture value. CONCLUSION: The patients with maxillofacial prostheses who had undergone radiotherapy need moisture retention because of oral dryness depending on the dose of radiation and the period after radiation.

Stress analysis of clasps made of glass fiber-reinforced composite material using three-dimensional finite element method: influence of shape in cross and longitudinal sections of circumferential clasp arms.

The purpose of this study was to investigate the effects of different cross-sectional shapes and presence of taper on stress distribution in clasp arms made of glass fiber-reinforced composite (FRC) material. Stress analysis of clasps was performed under a constant load (5 N) using a three-dimensional finite element method with due consideration to the anisotropy of unidirectional FRC material. Results were then compared with clasp arms made of metal- an isotropic material. It was found that both FRC clasps and metal clasps yielded similar results. As for the displacement of clasp arms with a basic cross-sectional shape under a load of 5 N, the amount of displacement showed that FRC clasps provided sufficient retentive force required for clinical application.

A three-dimensional analysis method for edentulous mandibular ridge shape.

The aim of this study was to develop a three-dimensional method to analyze edentulous ridge shapes. A laser projection method was used to record the shape of edentulous plaster models. Contour of residual ridge on the reconstructed image was then subdivided into small triangles, and a 'normal line' representing the center of gravity of each triangle was determined buccolingually and anteroposteriorly. Angle between the normal line on the residual ridge and the tentative occlusal plane was calculated for each triangle. These angles were then used to analyze the ridge shape. This method was used to analyze the ridges of 20 edentulous patients with excessive bone resorption. The results suggested that this method was useful for analyzing edentulous ridges regardless of ridge shape and degree of resorption.

Application of a glass fiber-reinforced composite material to clasps--the effects of immersion and repeated loading.

The aim of this study was to investigate the effects of water immersion and repeated loading on the mechanical properties of a glass fiber-reinforced composite (FRC) material. Measurements for three-point flexural tests were made at three different temperatures and cross-head speeds, while measurements for fatigue tests were made under three different loads in air or water at 37 degrees C after each cycle. The flexural strength and elastic modulus of the immersed specimens were significantly lower than those of the dry specimens at the same cross-head speed and temperature. On the whole, the values were inferior to those of metal. The deflection increased significantly as the load increased, but there were no significant differences between the values of dry and immersed specimens. With increasing load and number of cycles, the permanent deformation of both specimens increased significantly. The permanent deformation was similar to that of Co-Cr alloy. Based on the results of this study, it is recommended that more effort be devoted to exploring and devising shapes that would render FRC clasp arms with mechanical and physical properties that differ favorably from those of metal.