Showing papers in "Prosthodontic Research & Practice in 2007"
TL;DR: This randomized controlled clinical trial revealed that a clinician’s experience has an obvious influence on the chair time required for a final impression and the number of visits for denture adjustment.
Abstract: Purpose: The purpose of this study was to demonstrate how a clinician’s experience might affect the complete denture treatment.Methods: A randomized controlled parallel clinical trial at two hospitals was conducted from April 2004 to July 2006. Written informed consent was obtained from the study subjects. Permuted-block randomization was performed with a block size of 4, indicating that not only was the clinician’s experience randomized) but also the denture base materials used (conventional acrylic resin and resilient liner). The chair time required for each step of complete denture treatment was compared between the junior clinician and senior clinician groups. The clinical protocol was carried out as follows: the preliminary impression, final impression, maxillomandibular registration, trial placement, denture delivery, and the number of visits for denture adjustments. Seventy-four subjects were assigned to this trial.Results: Significant differences were observed between the junior clinician and senior clinician groups with regard to chair time required for final impressions and the number of visits required for denture adjustments. There were no differences in chair time required for the other treatment steps.Conclusion: This randomized controlled clinical trial revealed that a clinician’s experience has an obvious influence on the chair time required for a final impression and the number of visits for denture adjustment.
17 citations
13 citations
TL;DR: The hypothesis that dentures might serve as potential reservoirs of organisms causing systemic infections is supported, as a high CFU count of Candida spp.
Abstract: Purpose: The purpose of this study was to investigate denture plaque microflora of geriatric inpatients and maxillary defect patients from the standpoint of infection control in the elderly.Methods: Denture plaque was collected from 80 elderly subjects who were categorized into 3 groups: group A, 21 healthy complete denture wearers; group B, 49 complete denture wearers residing at a geriatric hospital; and group C, 10 complete denture wearers with maxillary defects. The microflora was investigated by counting the total number of microorganisms, including streptococci, staphylococci, and Candida spp.Results: The colony-forming unit (CFUs) count and incidence, particularly those of Candida spp., were significantly higher in group B (P<0.01). The CFUs of staphylococci were significantly higher in group C (P<0.01), and methicillin-resistant Staphylococcus aureus (MRSA) was observed in all Staphylococcus-positive patients. The CFUs of Candida spp. were significantly correlated to those of staphylococci (P<0.01).Conclusion: A high CFU count of Candida spp. and staphylococci (including MRSA) are characteristic of the microflora in geriatric inpatients and maxillary defect patients, respectively. This study supports the hypothesis that dentures might serve as potential reservoirs of organisms causing systemic infections.
10 citations
TL;DR: The original FS is an effective nonverbal method for conveniently assessing the mood of patients with dentures with respect to prosthetic treatment.
Abstract: Purpose: This study aims to examine the reliability, validity, and preference of an original faces scale (original FS) for mood assessment.Methods: The original FS was evaluated by comparing it with a modified faces scale developed by Lorish and Maisiak (modified LM mean age: 68.8 years). We included 32 subjects for reliability and validity analyses, and 34 for analysis of scale preference. The test-retest reliability of the scales was determined by calculating the correlation between two assessments obtained at one-week intervals; the concurrent validity of the original FS, by calculating its correlation with VAS and the modified LM further, the original FS demonstrated the highest Spearman’s rank correlation coefficient (r=0.76). The concurrent validity, measured by the correlation between the original FS and VAS (r=0.70, P<0.01) and the modified L&M FS (r=0.90, P<0.01), was also established. A majority of the subjects preferred the original FS to the other scales.Conclusion: The original FS is an effective nonverbal method for conveniently assessing the mood of patients with dentures with respect to prosthetic treatment.
8 citations
TL;DR: The addition of high-molecular-weight sodium alginate to anAlginate impression material can be effective for increasing the viscosity of the material without deterioration of the properties of thematerial.
Abstract: Purpose: In this study, we investigated the effects of addition of high-molecular-weight sodium alginate to alginate impression materials with the aim of developing a new high-viscosity impression material.Methods: Four experimental alginate impression materials were prepared based on a conventional material (control material) by varying the percentage of addition of high-molecular-weight sodium alginate in the range of 50% to 100%. The viscosity after mixing, setting time, recovery from deformation, strain in compression, compressive strength, and compatibility with dental stones was determined in accordance with the ISO 1563 and ANSI/ADA Specification no. 18. Results were analyzed using ANOVA and linear regression.Results: All the experimental materials exhibited significantly higher viscosity than the control material (P<0.05). A significant and positive relationship was observed between the addition rate and the viscosity (P<0.05). In the specification tests, all the experimental materials were found to be within specification limits, and not significantly different from the corresponding values of the control material.Conclusion: The addition of high-molecular-weight sodium alginate to an alginate impression material can be effective for increasing the viscosity of the material without deterioration of the properties of the material.
8 citations
TL;DR: Findings revealed that changes in the bone structure due to functional loading of implants had negligible or no effect on the ISQ value, and Morphological changes occurred in response tofunctional loading.
Abstract: Purpose: The objective of this study was to clarify the effect of mechanical loading on the trabecular structure of peri-implant bone and determine its correlation with the implant stability quotient (ISQ) value.Methods: This study used 3 immunologically mature male dogs. Three months after bilateral extraction of the mandibular premolars of the dogs, 4 implants were placed in these sites for each dog. After 3 months to allow healing of the implant sites, superstructures were prepared on the right side (loaded side). The implants on the left side were covered with mucosa (non-loaded side). The ISQ values of all implants were measured 3 months after placing the superstructures; subsequently, the animals were sacrificed. After the mandible was excised and fixed, micro-CT images were acquired and three-dimensional analysis, performed.Results: The means and S.D. of the ISQ value for the 12 implants were 69.6±6.2 and 62.9±13.8 for the loaded and non-loaded sides, respectively. No significant difference was noted between the 2 sides. Mean and S.D. of bone volume fraction (BV/TV) were 13.0±6.6 and 9.3±3.8; trabecular thickness (Tb.Th), 97.7±27.7 µm and 91.0 ± 24.0 µm; and trabecular number (Tb.N), 1.24±0.30/mm and 0.99±0.20/mm for the loaded and non-loaded sides, respectively. BV/TV and Tb.N values were higher for the loaded side.Conclusion: Morphological changes occurred in response to functional loading. However, lamellar bone was observed around the implants on both sides. These findings revealed that changes in the bone structure due to functional loading of implants had negligible or no effect on the ISQ value.
7 citations
6 citations
TL;DR: It is suggested that PUO includes several patterns of occlusal states and that not all cases of PUO are morbid and incurable, and it is difficult to predict the prognosis ofPUO only by data concerning clinical history of PUo and Occlusal contacts at the initial examination.
Abstract: Purpose: The aim of this study was to elucidate the features of patients with persistent uncomfortable occlusion (PUO).Methods: Clinical states of 39 patients with PUO that was not improved by dental treatment for six months or more were retrospectively examined.Results: In all patients, the events involved in the onset of the uncomfortable sense were dental treatments. PUO improved in 17 patients after treatment in our clinic but did not change in 22 patients. The mean periods of PUO and the mean numbers of dental clinics visited before visiting our clinic were 40.8 months and 2.3, respectively, in the improved group and 55.5 months and 3.1, respectively, in the non-improved group. However, there was no significant difference between these data in the two groups. No significant relationship was found between treatment results and age, sex, events involved in the onset of the uncomfortable sense, expressions of chief complaints, occlusal contacts and diagnosis of psychiatric disorders. There was a significant relationship between medication with muscle relaxants and treatment results. The following patterns of occlusal states were included in PUO; obvious malocclusion, malocclusion detected by strict examination, malocclusion resulting from patients’ intolerance, malocclusion not associated with patients’ complaint and no observable abnormality of occlusion.Conclusion: The results suggested that PUO includes several patterns of occlusal states and that not all cases of PUO are morbid and incurable. It is difficult to predict the prognosis of PUO only by data concerning clinical history of PUO and occlusal contacts at the initial examination.
6 citations
TL;DR: Moderate-intensity SMF exposure increased mineralized nodule formation in mouse osteoblastic MC3T3-E1 cells, however, gene expression related to decreased cell proliferation and unaltered cell differentiation and bone matrix did not correlate with the long-term effects observed followingSMF exposure.
Abstract: Purpose: The stage at which bone formation was influenced by a static magnetic field (SMF) remains to be elucidated. The purpose of this study was to investigate the initial and long-term effects of moderate-intensity SMF on mouse osteoblastic cells (MC3T3-E1).Methods: MC3T3-E1 osteoblastic cell cultures were exposed to SMF (250 mT, Nd-Fe-B disc magnet). The long-term effect of this exposure was evaluated by measuring mineralized nodule formation. Osteoblastic cell proliferation was assessed using a colorimetric proliferation assay (WST-8); differentiation was evaluated by measuring alkaline phosphatase (ALP) activity; and noncollagenous gene expression was evaluated using real-time PCR to determine the initial and early responses.Results: After a month of continuous SMF exposure, mineralized nodule formation increased significantly. The initial proliferative activity decreased and was not related to apoptotic changes. ALP activity and the gene expression levels of secreted phosphoprotein 1 (SPP1), integrin binding sialoprotein, and bone gla protein were not influenced by the SMF exposure.Conclusion: Moderate-intensity (250 mT) SMF exposure increased mineralized nodule formation in mouse osteoblastic MC3T3-E1 cells. However, gene expression related to decreased cell proliferation and unaltered cell differentiation and bone matrix did not correlate with the long-term effects observed following SMF exposure. The mechanism by which SMF exposure influences osteoblast mineralization remains unknown.
5 citations
TL;DR: Masticatory performance of post-maxillectomy patients with obturator prosthesis could be predicted with high accuracy in patients with soft palate defect limited to the anterior part.
Abstract: Purpose: Little objective investigation has been published regarding factors influencing masticatory performance of post-maxillectomy patients with obturator prosthesis. This study aimed to assess the relationship between masticatory performance and sociological and post-surgical factors, and to develop a theoretical equation predicting masticatory performance using significant factors.Methods: In 37 post-maxillectomy patients with obturator prosthesis, their age, gender, resection of hard and soft palate, number of posterior maxillary teeth, occlusal support, and mouth-opening distance on masticatory performance were investigated, and masticatory performance was measured using a gummy jelly. The influence of these items was evaluated quantitatively using multiple regression analysis (Quantification Method type I). The strength of influence of each explanatory factor on the masticatory performance, identified by the category weight and theoretical value of masticatory performance of each subject, was calculated by totaling the category weights and the constant. Pearson correlation coefficient was used to analyze the correlation between actual values and theoretical values of masticatory performance.Results: The order of strength of influence on masticatory performance was identified by the category weights: extent of hard palate resection (1229.9) > occlusal support (1113.0) > mouth-opening distance (280.8) > age (209.0) > resection of soft palate (194.2) > number of posterior maxillary teeth (186.4). There was a high correlation (R2=0.863, P<0.01) between the theoretical values calculated by the predictive equation and the actual values.Conclusion: Masticatory performance of post-maxillectomy patients could be predicted with high accuracy in patients with soft palate defect limited to the anterior part.
5 citations
TL;DR: The incisal point deviated significantly in the anteroposterior direction due to changes in head and body position, and a set of standards for patient posture was developed.
Abstract: Purpose: The objectives of this study were to determine how changes in body and head position undergoing dental treatment affect mandibular position, and to develop a set of standards for patient posture.Methods: Mandibular position was investigated in 8 subjects with normal occlusion and not suffering any stomatognathic dysfunction. This was done by measuring the location of the tapping point on the incisal point using a Gnathohexagraph (a 3-dimensional jaw movement measurement device with 6 degrees of freedom), with the subject’s head in 4 different positions while sitting, and the body and head in 16 different positions with the subject supine, and then comparing deviation from the reference position in each of these positions. Statistical analysis of data was performed using first, repeated measures of 1-way ANOVA (α=.05), second Bonferroni’s multiple comparison test was undertaken in seated positions. In supine positions, repeated measures of 2-way ANOVA was performed, and followed by Bonferroni’s multiple comparison test was performed.Results: The incisal point deviated significantly in the anteroposterior direction due to changes in head and body position. With the subjects seated, the incisal point tended to move backwards when the subjects were asked to lean backwards from the reference position. The incisal point tended to move forward when the subjects were asked to lean forward. With the subjects in a supine position, the incisal point was inclined backwards. The degree of backwards inclination of the incisal point tended to decline as the head position was varied from 10 degrees backwards to 20 degrees forward, regardless of the degree of backwards inclination of the body.Conclusion: Changes in body and head posture undergoing dental treatment affect incisal point deviation.
TL;DR: Evaluating the reliability and validity of a Japanese short version of the Oral Health Impact Profile (OHIP-JP16) for prostheses showed good measurement properties and might be appropriate for use in the clinical settings.
Abstract: Purpose: The Oral Health Impact Profile (OHIP) is one of the most widely used instruments to measure oral health-related quality of life (OHRQoL). The aim of this study was to evaluate the reliability and validity of a Japanese short version of the Oral Health Impact Profile (OHIP-JP16) for prostheses.Methods: Data were collected by means of self-administered questionnaires from July 2004-November 2005 at 4 dental offices located in Japan. The questionnaires consisted of self-perceived oral health status, need for treatment, and the OHIP-JP16 score. The total target sample consisted of 137 patients, of which 125 patients answered all the 16 items in the questionnaires. The reliability was assessed in terms of internal consistency and reproducibility.Results: Cronbach’s alpha of the OHIP-JP16 subscales ranged from 0.43 to 0.93. The reproducibility of test-retest reliability was analyzed (n=12). The test-retest reliability was measured by the intra-class correlation coefficient (ICC) and kappa index. The ICC ranged from 0.69-0.92 and kappa index ranged from 0.12-0.67. The internal consistency and reproducibility demonstrated quite a good reliability. Discriminative validity was examined by comparing total scores among groups according to the following parameters: number of teeth (more than 24 and less than 23), Eichner index (A, B, and C group), denture wearing (with and without dentures), and self-perceived oral health (good and poor). The patients who had more than 24 teeth, were in group A of the Eichner index, those without dentures, and having good oral health had better OHIP-JP16 total scores (P<0.05).Conclusion: As a result of having examined for behaviormetrics study, OHIP-JP16 showed good measurement properties and might be appropriate for use in the clinical settings.
TL;DR: In the cases of reduced periodontal support or large and/or laterally directed occlusal force, abutments should be splinted in cases of a coincidence of these unfavorable conditions.
Abstract: Purpose: The purpose of this study was to investigate the relationship between the number of splinted teeth and the effect of splinting on the movement of canines as abutments for maxillary distal-extension removable partial dentures.Methods: A three-dimensional finite element method was used for the analysis. Abutments with normal bone height and with bone height lowered by 3 mm were prepared. The numbers of splinted teeth were two, three and six units. A load of 50 N or 200 N was applied in the vertical, buccal-oblique and lingual-oblique directions at the node corresponding to the buccolingual center of the mesial marginal ridge of the left first molar. Different material properties of the mucosa and periodontal ligament were used depending on the amount of loading. The ligament was defined as an orthotropic material.Results: The results showed that horizontal displacement of the canine in the “two-unit splint” model was approximately one-third to one-half of that in the single abutment model. There was little difference in the horizontal displacement between the two-unit splint and “three-unit splint” models. In the “six-unit splint” model, the displacement was reduced to approximately half of that of the two-unit splint model. In all of the splinted models, the vertical displacement was reduced to approximately half of that of the single abutment model.Conclusion: In the cases of reduced periodontal support or large and/or laterally directed occlusal force, abutments should be splinted. In cases of a coincidence of these unfavorable conditions, splinting six anterior teeth was recommended.
TL;DR: Clinicians who treat TMD patients should choose patient education and physiotherapy as their first approach, as the treatment outcome of TMD-C was superior.
Abstract: Purpose: We conducted this study in order to define the methods of treatment that are beneficial for TMD patients by the comparison of the characteristics of TMD patients between prosthodontic clinic (PD-C) and special clinics for TMD (TMD-C). Methods: Clinical records that had been preserved in a database of 253 new TMD patients treated in PD-C were compared with 404 new TMD patients treated in TMD-C. Items of sex, age, chief complaint, present observations, diagnostic categories, treatment methods and treatment outcome were investigated. The chisquare test was used for comparison of the items in two groups (StatMateIII for Windows). Results: The TMD patients in both groups were characterized as being a high female-to-male ratio. Most symptoms were pain of TMJ and masticatory muscles as the chief complaint and present observations. According to the diagnostic categories, there were the most Type I conditions (masticatory muscle disorders) in PD-C and the most Type III conditions (disc disorders) in TMD-C. Treatment consisted of mostly splint therapy (81%) in PD-C, and patient education (67%) and physiotherapy (64%) in TMD-C. Thirty percent of the patients in PD-C and 42% of those in TMD-C were completely healed, thus showing that the treatment outcome of TMD-C was superior. Conclusion: We reached the conclusions that the treatment outcome of TMD patients was superior, as we provided patient education such as prohibition of tooth contact and orofacial parafunctions, and physiotherapy such as jaw opening stretches. Clinicians who treat TMD patients should choose patient education and physiotherapy as their first approach.
TL;DR: The all-ceramic crowns milled from Cadim block CE by using the DENTAL Cadim CAD/CAM system showed a clinically acceptable marginal fit and the fitting accuracy differed significantly among the three sides of the crown.
Abstract: Purpose: This study aimed to measure the marginal discrepancy at the buccal, mesial, and distal sides along the marginal edge of all-ceramic crowns fabricated using the DENTAL Cadim CAD/CAM system and to examine the effect of a post-milling heat treatment for staining on the marginal fit of the all-ceramic crowns.Methods: An 18-8 stainless steel abutment tooth with a height of 5 mm and an occlusal convergence angle of 8° was used as a mold. A cylindrical pattern model was fabricated using a brush stacking method with an autopolymerizing resin. Three-dimensional geometric measurement of the pattern model was performed using a spherical ruby scanning probe. Subsequently, five all-ceramic crowns were milled from Cadim block CE by using the DENTAL Cadim CAD/CAM system. Surface roughness (Ra and Rmax) of the occlusal surface and vertical distances between the marginal edge and the mold before and after the post-milling heat treatment were measured using a profilometer and an X-Y coordinate reading microscope, respectively.Results: The Ra and Rmax significantly decreased after the heat treatment. The vertical distance at the mesial and distal sides of the crowns was approximately 10 μm before and after the heat treatment. This distance at the buccal side was significantly greater (17.1 μm) than that at the mesial and distal sides before heating, and it significantly increased to 22.0 μm after heating.Conclusion: The all-ceramic crowns milled from Cadim block CE by using the DENTAL Cadim CAD/CAM system showed a clinically acceptable marginal fit. We also observed that the fitting accuracy differed significantly among the three sides of the crown. The change in the marginal fit after the post-milling heat treatment was of a clinically acceptable value.
TL;DR: The majority of Japanese dentists seem to believe that overeruption of molars would occur after extraction of antagonists, and that prosthetic interventions are necessary to prevent possible clinical problems.
Abstract: Purpose: The aim of this questionnaire study was to survey Japanese dentists’ perceptions of risks for overeruption of unopposed molars and dentists’ attitudes to prosthetic intervention.Methods: A clinical situation with a 42-year-old male patient who just had lost the left mandibular molars was presented. A series of questions was provided regarding what would most probably occur with the unopposed maxillary molars within a 10-year period, what treatment to propose, and indications for the proposed treatment. The questionnaire was sent to the council members of the Japanese prosthodontic society, doctors of Matsumoto Dental University, members of the Nagano and Niigata prefecture dental societies via letter, facsimile or E-mail.Results: 887 of 1320 (67%) dentists returned completed questionnaires. The great majority believed that overeruption of the unopposed molars would occur within a 10-year period (94%). 87% of respondents wanted to perform prosthetic treatment. In contrast, a “wait-and-see” alternative was chosen by only 12%. The most commonly suggested indications for the treatments were the risk for overeruption (96%) followed by impaired masticatory function (77%) and development of TMD (73%).Conclusion: To date, the majority of Japanese dentists seem to believe that overeruption of molars would occur after extraction of antagonists, and that prosthetic interventions are necessary to prevent possible clinical problems.
TL;DR: Despite the 2 fractures, In-Ceram Alumina crowns with copings fabricated using CAD/CAM (GN-I system) showed excellent results during the observation period.
Abstract: Purpose: This study prospectively evaluated the clinical performance of CAD/CAM-generated In-Ceram alumina core crowns.Methods: The GN-I system was used to fabricate the 101 In-Ceram crowns with aluminum copings placed in 39 patients. Using a modified quality assessment system developed by the California Dental Association (CDA), the crowns were evaluated at baseline and at all follow-up examinations.Results: The mean service time of the crowns was 28.7 months. Six crowns fractured or were removed; a maxillary first molar crown and a mandibular second premolar crown fractured after 17 months and 22 months, respectively. Others were removed due to esthetic complications, endodontic therapy, root fracture, and so on. A small chip was detected in a mandibular canine crown after functioning for 6 months. After 39 months, the cumulative survival rate of the crowns was 93.9%. According to the modified CDA criteria, most crowns were rated as “satisfactory” during the observation period.Conclusion: Despite the 2 fractures, In-Ceram Alumina crowns with copings fabricated using CAD/CAM (GN-I system) showed excellent results during the observation period.
TL;DR: The results of this study suggest mandibular movements in the mixing ability test are partially different from those in masticatory performance test.
Abstract: Purpose: The purpose of this study was to compare mandibular movements in the mixing ability test with those in the masticatory performance test.Methods: Twenty-six dentate subjects (mean age 25.3 years) performed a mixing ability test using a two-colored paraffin wax cube and a masticatory performance test using 3 g peanuts. Mandibular movements during the chewing of each test item were recorded using an opto-electronic system. Twelve parameters of mandibular movements on a mandibular incisal point were measured for each masticatory cycle. The mean from 2nd to 5th cycle in each parameter was employed for paired t-test.Results: 7 of 12 parameters showed significant mean differences between the mixing ability test and the masticatory performance test. Vertical amplitude, anteroposterior amplitude, maximum closing velocity and opening angle for the mixing ability test were significantly greater than for the masticatory performance test (P<0.05). Opening duration and cycle duration for the mixing ability test were significantly longer than for the masticatory performance test (P<0.05). Envelope angle for the mixing ability test was significantly less than for the masticatory performance test (P<0.001).Conclusion: The results of this study suggest mandibular movements in the mixing ability test are partially different from those in masticatory performance test.
TL;DR: The educational methods for delivery of RPDs are thought to be adequate, since it is suggested by an objective assessment of them that they are unsatisfactory.
Abstract: Purpose: The aim of this study was to survey the undergraduate removable partial denture (RPD) clinical program and RPD’s fabricated by students in 2006, and to identify the problems to be solved in the future. Methods: Sixty-nine students in their final semester at Tokyo Medical and Dental University (TMDU) recorded the following preoperative data: age, gender, chief complaint, and Kennedy and Eichner classifica tions. The students were requested to present their treated cases and were subjected to an oral examination by the professor to determine the treatment plan and prosthetic design of denture. Additionally, the students surveyed the chewing function score and visual analogue scale (VAS) regarding esthetics and stability of RPD, and the material used for RPD frameworks was summarized. Results: The patients included 35 men and 34 women, and their chief complaints were mostly dissatisfaction with their current dentures. More than 80% of cases were classified as Kennedy I or II, and about one-fourth were classified as Eichner B4 or C1, in which the occlusal supports could not easily be reconstructed. Chewing function score significantly improved compared to preoperative state (P<0.05) and postoperative VAS was clinically acceptable. 89% of frameworks, were cast with Co-Cr alloy in one piece and a palatal strap or bar and a lingual bar were applied in 77% of treated RPDs. Conclusion: It is thought that our educational methods for delivery of RPDs are adequate. Since it is suggested by an objective assessment of them that they are unsatisfactory, we should deal with that problem without delay.
TL;DR: Although the CT exhibited the greatest retention, the retentive force of each CT specimen varied widely and the coefficient of variation of the CT was also greater.
Abstract: Purpose: Attachments are widely used for the fixation, retention, and stabilization of prostheses. This study assessed the retentive forces of 3 types of attachments for root-retained overdentures.Methods: The patrices of “O” ring plastic pattern anchor (OPA) attachments (No. 2; Inoue Attachments), magnetic attachments (MAs; 3513, Neomax), and coping telescopes (CTs) were cast with an Ag-Au-Pd alloy (Castwell, GC). For the OPA and MA, the “O” ring and magnet were fixed on the post anchor and keeper, respectively, by using autopolymerized polymethyl methacrylate (PMMA) resin (Unifast II, GC). For the CT, autopolymerized PMMA was used to connect the patrix coping and matrix framework. The retentive force (n=5, N) was measured at a crosshead speed of 20 mm/min as the maximum load when the connected patrix and matrix of either single or double retainers (30-mm apart) were separated under both dry and wet conditions. The results were analyzed using ANOVA/Tukey’s HSD test (α=0.05).Results: In the case of a single retainer, the retentive force of the CT was significantly greater than those of the MA and OPA (P<0.05). However, the coefficient of variation of the CT was also greater. In the case of double retainers, the retentive forces of all the attachments were approximately twice the forces of single retainers.Conclusion: Although the CT exhibited the greatest retention, the retentive force of each CT specimen varied widely. Consistent retentive values were obtained for the OPA and MAs because ready-made patterns of these attachments were used.
TL;DR: Dentures and metallic splints prepared with a cap clasp serving as a retainer fit well into the oral cavity of patients, provide excellent occlusal support, and are retained for long periods of time.
TL;DR: The amount of saliva secretion increased during chewing of gummy jelly and affected the assessment of masticatory performance, and this effect was less than 5 % for chewing of up to 20 seconds.
Abstract: Purpose: The purpose of this experiment was to clarify whether the amount of saliva secreted during the chewing gummy jelly affected the assessment of masticatory performance.Methods: Twenty healthy subjects were asked to chew 2 g of gummy jelly for 10, 15, and 20 seconds and the amounts of glucose extraction and saliva secretion were measured. The changes in both glucose extraction and saliva from 10 to 20 seconds were investigated. Next, the amount of glucose extraction excluding the effect of saliva (extraction B) was divided by the amount of glucose extraction measured (extraction A), and the results for the two chewing times were compared.Results: The amount of glucose extraction increased proportionally as the chewing time progressed and the change was significant. Although the amount of saliva secretion increased as the chewing time progressed, the change differed from the proportional change in glucose extraction. The amount of saliva secretion was extensive for the first 10 seconds and increased about 0.1 ml every 5 seconds. The ratio of the extraction B to extraction A was between 1.03 and 1.05, and there was a significant difference between each pair of chewing times.Conclusion: From these results it was concluded that the amount of saliva secretion increased during chewing of gummy jelly and affected the assessment of masticatory performance, and this effect was less than 5 % for chewing of up to 20 seconds.
TL;DR: The results suggest that the bite force and anterior open bite might influence dysphagia in MyD patients; however, this remains a speculation.
Abstract: Purpose: This study aims to investigate the relationship between masticatory function and dysphagia in patients with myotonic dystrophy (MyD).Methods: Eighteen MyD patients with an average age of 54.1 years (SD, 5.7 years) were enrolled as subjects of this study. They were divided into 2 groups: a non-dysphagia group (12 patients) that consumed ordinary rice along with an ordinary supplementary diet and a dysphagia group (6 patients) that consumed semisolid rice along with a chopped supplementary diet. The maximum bite force, activity in the temporal and masseter muscles during 1 chewing cycle, number of food items that were considered as easy to chew, and occlusal contact area were investigated, and the proportion of patients with anterior open bite was analyzed. The results obtained were compared between the groups.Results: The maximum bite force in the dysphagia group was statistically much smaller than that in the non-dysphagia group (P=0.024). On the other hand, the masticatory muscle activity in the dysphagia group was statistically much greater than that in the non-dysphagia group (P=0.048). The proportion of patients with anterior open bite in the dysphagia group was higher than that in the non-dysphagia group.Conclusion: These results suggest that the bite force and anterior open bite might influence dysphagia in MyD patients; however, this remains a speculation. It is necessary to consider masticatory disturbances in MyD patients with dysphagia.
TL;DR: The dimensional accuracy and flexural strength of autopolymerized resins were significantly improved by the application of water pressure during polymerization and the PSRs of Unifast II and Miky Plus were greatly improved by pressure polymerization.
Abstract: Purpose: This study evaluated the effects of water pressure on the mechanical properties and tensile bond strength of autopolymerized resins during polymerization at room temperature using a dental pressure pot with chair-side ease of handling.Methods: Four different autopolymerized resins (Unifast II, Unifast III, Provinice, and Miky Plus) were used. Specimens were fabricated by the brush-on technique. In the pressure group, specimens were polymerized in a dental pressure pot under 0.2 MPa water pressure at room temperature. In the non-pressure group, specimens were polymerized on bench. The 2 groups were compared for dimensional accuracy, 3-point bending, and tensile bond strength. Data were statistically analyzed by two-way analysis of variance (ANOVA) with Tukey’s multiple comparison test at a significance level of α=0.05.Results: Two-way ANOVA indicated that both resin and pressure had significant effects on the polymerization shrinkage rate (PSR). Interaction between resin and pressure was also significant. The PSR was lower in the pressure group than in the non-pressure group. The PSRs of Unifast II and Miky Plus were greatly improved by pressure polymerization. Significant differences in flexural strength were observed between the 2 groups. The flexural strength significantly increased under pressure. No significant differences in tensile bond strength were observed between the 2 groups.Conclusion: The dimensional accuracy and flexural strength of autopolymerized resins were significantly improved by the application of water pressure during polymerization. No significant changes in tensile bond strength were observed following pressure application at room temperature.
TL;DR: Within the limitations of this clinical study, AGCs luted with adhesive resin cement functioned satisfactorily with a relatively low fracture rate compared to porcelain-fused-to-metal (PFM) and all-ceramic crowns.
Abstract: Purpose: Porcelain-fused-to-gold copings prepared by the electroforming technique were introduced as an alternative to conventional metal/ceramic crowns. However, there are few clinical studies that have evaluated this technique. The purpose of this study was to prospectively evaluate the clinical performance of Auro Galvano Crowns (AGCs).Methods: One hundred and twenty-seven AGCs were used to treat patients at the Tsurumi University Dental Hospital from October 2002 to December 2003. All the crowns were evaluated using the modified California Dental Association (CDA) quality assessment system at baseline and at all follow-up appointments.Results: A total of 122, 119, and 72 crowns were examined at the 1-, 2-, and 3-year follow-ups, respectively. During the observation period, four crowns were removed because of partial fracture of the veneered porcelain in premolar and posterior teeth. No chips were detected during this observation period. All of the crowns examined were rated as satisfactory according to the modified CDA quality assessment system. During this period, the cumulative survival rate was 96.1%.Conclusion: Within the limitations of this clinical study, AGCs luted with adhesive resin cement functioned satisfactorily with a relatively low fracture rate compared to porcelain-fused-to-metal (PFM) and all-ceramic crowns. Since the observation period was short, long-term observation will be necessary in order to further evaluate these crowns.
TL;DR: To achieve maximum oral comfort, palatal connectors should be constructed such that their thickness gradually increases from the margin toward the top, and they should be placed in a bilaterally symmetrical position.
Abstract: Purpose: This study assessed the influence of cross-sectional shape of the margin, contour, and positioning of palatal connectors on oral sensation.Methods: The study population comprised six healthy dentulous individuals with an average age of 26 years. Ten types of connectors were fabricated in the form of light-cured resin baseplates; four types had different cross-sectional shapes of the margins, two had different contours of the upper surface (i.e., the surface facing the oral cavity), and four varied in their placement position. The subjects’ feelings when the different types of connectors were placed in their oral cavities were assessed using a questionnaire. The results were analyzed and weighted using the sigma score method, which is a tool used in the field of psychology.Results: The results suggested that the subjects experienced greater comfort with connectors having a knife-edge-shaped margin (P<0.05). Moreover, greater discomfort was reported with bilateral oblique positioning of the connector, while less discomfort was reported with bilateral symmetrical positioning (P< 0.05).Conclusion: We suggest that to achieve maximum oral comfort, palatal connectors should be constructed such that their thickness gradually increases from the margin toward the top, and they should be placed in a bilaterally symmetrical position.
TL;DR: This newly developed classification of condylar dynamics is expected to improve the diagnosis of stomatognathic disorders and design effective treatments for functional occlusal disorders by considering comprehensive mandibular function.
Abstract: Purpose: The purpose of this study was to classify condylar dynamics to understand stomatognathic disorders and design effective treatments for functional occlusal disorders by considering comprehensive mandibular function. This assessment of categorizing of condylar movement in combination with frequency analyses will contribute to the diagnosis and treatment of functional occlusal disorders.Methods: Lateral-border movements with/without tooth contact were recorded from a reference condylar position in 102 patients (30 males and 72 females; mean age, 41.5±15.9 years) by using the CADIAX®III (GAMMA, Klosterneuburg, Austria). After superimposing the two types of movement on both sagittal and horizontal planes, a trace of lateral movement with tooth contact was compared in terms of direction with the trace of the lateral movement without tooth contact. The area in the sagittal view was then classified into the following four categories: no-shift, upward shift, downward shift, and rearward shift. We obtained 10 grinding shift (GS) patterns by combining the four area categories of each condylar movement.Results: The data set of condylar movements—a total of 204 sides of the 102 patients—permitted us to classify the pattern of each subject into 1 of the 10 GS patterns.Conclusion: Since the GS patterns provided an active image of mandibular behavior during grinding movement, this newly developed classification is expected to improve the diagnosis of stomatognathic disorders.
TL;DR: The Japan Prosthodontic Society decided to prepare relining guidelines on the basis of limited evidence obtained by searching for scientific papers and consensus among specialists, which will have to be periodically modified when additional rationales or clinical findings are revealed in scientific clinical studies.
Abstract: With the increasing attention to oral health in recent years, the number of residual teeth retained by individuals has been increasing with each generation. According to the survey of dental diseases in 2005, the percentage of individuals between 80 and 84 years of age retaining 20 or more teeth was 21.1%, thus exceeding 20% for the first time since this survey was started. The survey in 2005, however, showed that there was still a high percentage of individuals with multiple missing teeth, i.e., individuals using dentures. It is well known that the alveolar ridge inevitably undergoes resorption with advancing age, irrespective of whether or not the individual uses dentures. For this reason, dentures are destined to show deterioration in fit no matter how well they are initially prepared. Means available to deal with loss of denture fit are fabricating new dentures or relining. Relining can reduce the frequency of a patient’s visits and medical expenses as compared to fabricating new dentures. Under such circumstances, the Japan Prosthodontic Society decided to prepare relining guidelines. When preparing this set of guidelines, we followed the procedures for preparing evidencebased clinical practice guidelines. However, because of the specific nature of dental treatment and dentistry, it is difficult to conduct studies designed to provide the evidence for each treatment in this field. Because of these limitations, we prepared this set of guidelines on the basis of limited evidence obtained by searching for scientific papers and consensus among specialists. This guideline will have to be periodically modified when additional rationales or clinical findings are revealed in scientific clinical studies.
TL;DR: In this article, the effect of the method of keeper fabrication on the attractive force of the magnetic attachment was evaluated and the results indicated that the flatness and smoothness of the keeper surface may influence the attraction of the magnet attachment.
Abstract: Purpose: This study evaluated the effect of the method of keeper fabrication on the attractive force of the magnetic attachment.Methods: The attractive forces of the keepers of a Hyper Slim 3513 magnetic attachment system (Neomax Material Co. Ltd., Osaka, Japan) and Physio magnetic attachment system 35 (Nissin Co. Ltd., Kyoto, Japan) were measured. Specimens were prepared by the cast-bonding (n=5) and direct-bonding (n=5) techniques. The attractive force was measured using a digital force gauge (FGC-1, Nidec-Shimpo Corporation, Kyoto, Japan). The attractive force was statistically analyzed by the t-test at a significance level of α=0.05.Results: The direct-bonding technique yielded a keeper with significantly greater attractive force than that of the keeper obtained by the cast-bonding technique (P<0.05).Conclusion: Measurement of the attractive force of magnetic attachments fabricated by two different techniques revealed that the magnetic attachment fabricated by direct bonding possessed a significantly greater attractive force than that fabricated by cast bonding. Our results and those of previous studies suggest that the flatness and smoothness of the keeper surface may influence the attractive force of the magnetic attachment.