Three-dimensional photo-elastic stress analysis of maxillary and mandibular complete dentures

Three-dimensional photo-elasticity was used to study the stress distribution in complete dentures in functional positions. A new loading device was developed utilizing a linear motion bearing as its main component and mandibular dentures were evaluated for the first time. The stress concentrations were highest (2.5 fringes) on the working side of the mandibular denture. This was also demonstrated in the maxillary denture; however, the magnitude was less (1.8 fringes). The results indicate that this method could be used to quantitatively evaluate the effect of various occlusal schemes upon the denture bases.     

Improving the speech function of maxillary complete dentures: a pilot study

PURPOSE: The aim of this pilot study was to investigate a universal and easy method for improving the speech function of complete maxillary dentures. Specifically, it was analyzed whether sandblasting could improve speech performance, since this process increases the tactile surface area in the region of tongue-to-denture contact. MATERIALS AND METHODS: Fourteen volunteers with complete maxillary dentures in a geriatric rehabilitation center (7 men, 7 women, mean age 81.2) were recruited. Speech samples (normal conversation, logopedic standard text, and a word list) were recorded for all subjects. In 11 cases, a specific area of the denture was sandblasted, while the remaining 3 cases served as controls. After 1 week of service, the same speech samples were recorded again. The rating of the speech samples was performed by 2 experienced speech therapists. The rater did not know whether the sample was a control case or whether it was before or after intervention. RESULTS: The speech therapists found no difference between the 2 speech samples in all 3 cases in the control group. For 8 of 11 subjects, the speech sample after sandblasting was rated better by both therapists (P = .002). In 2 subjects, no difference was observed, and deterioration was found in only 1 subject by 1 speech therapist. CONCLUSION: Taking into account the limited number of subjects, the results show that sandblasting may lead to moderate improvements in speech performance in most cases. Deterioration is not expected, but in such cases, it is easy to restore the denture with simple polishing.     

Movement of maxillary complete dentures—a Kinesiographic study

A clinical study on the movement of maxillary complete dentures was carried out on ten patients using the Kinesiograph. The results indicated a significant difference in the amount of movement between well-fitting and ill-fitting dentures. A comparison of this method with other methods used as well as the precautions to be taken when using the Kinesiograph are discussed.     

Occlusal contacts of edentulous patients with mandibular hybrid dentures opposing maxillary complete dentures.

The purpose of this study was to evaluate differences between the occlusal contacts of edentulous patients with mandibular implant-supported hybrid dentures opposing maxillary complete dentures and those of patients with conventional maxillary and mandibular complete dentures. Six parameters related to occlusion were measured in the 2 groups (n = 40 for each group) using pressure-sensitive film. The mean values generated by each test group for each parameter were compared using a t test. Pearson's correlation coefficients between occlusal force, age, and time in function were examined. Occlusal force and area in the implant denture wearers were larger than those in the conventional denture wearers. No significant difference was seen in occlusal force balance between the left and right sides. The center of occlusal load in the implant denture wearers was more anterior. The maxillary denture may become more unstable in implant denture wearers. It is suggested that the stability and retention of a maxillary denture be checked and the occlusion be adjusted more frequently in the hybrid denture wearer than in the conventional denture wearer.     

Effect of weight change of mandibular complete dentures on chewing and stability: A pilot study

STATEMENT OF PROBLEM: Little is known as to whether denture weight contributes to the retention and stability of mandibular complete denture. PURPOSE: This study compared the jaw movements and denture retention, stability, and comfort of heavy and light weight mandibular complete dentures. MATERIAL AND METHODS: Mandibular complete dentures of 12 subjects were duplicated using an autopolymerized polymethyl methacrylate (PMMA) resin. The heavy weight denture was set with weights (20 or 60 g) and the lightweight denture was packed with wax instead of weights. Masticatory movements (3 times each) and denture stability (5 times each) were measured. The subjects expressed their denture preference for comfort and chewing. Results were analyzed using ANOVA and Wilcoxon tests at significance level of alpha=.10. RESULTS: Masticatory movements and denture retention were not significantly (P >.10) affected by increasing the weight. Five subjects preferred the heavy denture and 4 subjects preferred light denture for comfort; 3 subjects had no preference. CONCLUSION: The weight of a well-fitting mandibular complete denture did not affect jaw movements, denture stability, or patient preference.     

义齿附着剂增强上下颌总义齿固位的研究

目的：本文对义齿附着剂增加总义齿固位的持久性进行研究，方法：选择临床复诊的总义齿病例12例，在使用biotene义齿附着剂前、使用后即刻和使用后4小时分别用改良Hz-1型固位力测试仪测量上下颌总义齿的固位力。结果：上颌总义齿使用义齿着剂即后即刻的的固位力明显增加，使用4小时后的固位力较即刻时增加明显；下颌总义齿使用义齿附着剂后即的固位力明显增加，但是4小时后较即刻无显著性变化，结论：义齿附着剂可明显增加上下总义齿固位力，上颌总义齿增强效果在4小时后比使用后即刻更明显。     

Processing changes in maxillary complete dentures

A technique that allows for comparison of undercuts palatal thickness, and double curing has been described for measurement of curing changes in acrylic resin dentures. The technique involves a precision cast and denture positioner in front of the x-ray tube and the transfer of a lead foil strip from cast to denture. Radiographs made of this strip are projected at X20 magnification, and subsequent tracings are measured and superimposed to note shrinkage and contour changes.     

Immediate function with fixed implant-supported maxillary dentures: a 12-month pilot study

STATEMENT OF PROBLEM: Immediate occlusal loading of dental implants in the edentulous mandible has proven to be an effective, reliable, and predictable procedure. There is little long-term data available on similar treatments in the edentulous maxilla. PURPOSE: The purpose of this study was to evaluate the 12-month implant survival after immediate loading of 4 to 6 implants with fixed screw-retained prostheses in edentulous maxillae. MATERIAL AND METHODS: Twenty-one patients, edentulous or with remaining teeth to be extracted in the maxilla, received 4 to 6 implants (n=111). The patients were restored with screw-retained fixed provisional prostheses supported by palladium-alloy frameworks within 24 hours after surgery. Insertion torques for implants were at least 40 Ncm. Implants, grouped as tapered or cylindrical screws, were placed in healed bone or extraction sockets. Implants were also classified as either vertical or off-angle. Definitive prostheses were placed after a mean healing time of 18 weeks. Radiographic examinations were made at the time of placement of provisional prostheses and 12 months later. Between-groups bone resorption was compared using 2-way ANOVA (alpha=.05). RESULTS: The mean follow-up time for all of the patients was 20 months (range, 13 to 28 months). The cumulative implant survival rate at the 12-month follow-up visits (after surgery) was 92.8%; the prostheses survival rate was 100%. No significant differences were found between the survival of tapered or cylindrical screw-type implants placed in postextraction sockets versus those in healed edentulous sites or between vertical and off-angle placed implants. Eight implants failed during the first 3 months, 5 of which were the most distal implants. The mean reduction in marginal bone height over the 12-month observation period was 0.84 mm (CI 95%; 0.68-0.99 mm). CONCLUSIONS: In this study with 12-month follow-up, 4 to 6 implants were sufficient to successfully support fixed implant screw-retained prostheses in the edentulous maxillae of 21 patients.     

Clinical deformation of maxillary complete dentures

A study of strain-gauge behaviour in two groups of complete denture wearers was completed. The groups consisted of seven satisfied subjects and eight dissatisfied. Six linear strain gauges were used on each denture and functional strain was recorded in the maxillary dentures during maximum bites and empty-mouth chewing. The strain values reported varied a little between the two groups of subjects. The strain values reported agreed generally with those reported previously and demonstrate the complex straining behaviour of complete dentures in function.     

Cephalometric evaluation of maxillomandibular relationships in patients wearing complete dentures: a pilot study

The purpose of this study was to evaluate the changes in vertical and sagittal maxillomandibular relationship of the patients who had been wearing dentures for an extensive period. Fifteen edentulous patients (seven men and eight women; mean age 63.5 years) who had worn dentures for six to 16 years (mean 10 years) were selected for this study. New prostheses were fabricated by conventional methods, and the patients were evaluated cephalometrically before and after the new prosthesis. The results were compared by Wilcoxon signed rank test (P < .05). Results indicated that a prognathic mandible and a pseudo Class III relationship with a reduced occlusal vertical dimension became a normal Class I maxillomandibular relation when the new prosthesis was inserted. A better facial profile was achieved.     

Comparison of implant-retained mandibular overdentures and conventional complete dentures: a 10-year prospective study of clinical aspects and patient satisfaction

PURPOSE: The aim of this prospective randomized clinical trial was to evaluate 10 years of treatment of patients receiving a mandibular implant-retained overdenture (IRO) or a conventional complete denture (CD). MATERIALS AND METHODS: One hundred twenty-one edentulous patients were treated with an IRO (2 endosseous implants, n = 61) or a conventional CD (n = 60). Clinical aspects and patient satisfaction were evaluated. One year after placement of the denture, unsatisfied patients of the CD group were given the opportunity to receive implants. RESULTS: In the IRO group, 4 implants were lost during the first year and 4 implants were lost during the next 4 years. Between 5 and 10 years, no implants were lost (survival rate: 93%). In the CD group, 24 patients (40%) chose an IRO between 1 and 10 years. DISCUSSION: Patients in the IRO group were significantly more satisfied than patients in the CD group after 1 year (satisfaction score 8.3 versus 6.6 on a scale of 1 to 10), after 5 years (7.4 versus 6.4), and after 10 years (7.7 versus 6.8). CONCLUSION: The mean satisfaction score of the CD group (including patients who later received implants) was still lower than that of the IRO group, in spite of the opportunity for retreatment with IROs. Endosseous implants had a high survival rate after 10 years of follow-up.     

Influence of occlusal factors on treatment outcome: a study of 109 consecutive patients with mandibular implant-supported fixed prostheses opposing maxillary complete dentures

PURPOSE: This study was undertaken to investigate the relationship between occlusal variables and clinical and radiologic findings as well as patient response to treatment outcome in patients with mandibular implant-supported fixed prostheses opposing maxillary complete dentures. MATERIALS AND METHODS: The study group consisted of 109 consecutive patients attending for annual control. They had received their mandibular implant-supported prostheses according to the Br?nemark system on average 8 years previously (range 1 to 27 years). All patients were interviewed with standardized questions by one examiner, who also performed the clinical examination. The questions focused on the patients' opinion on masticatory and prosthetic function and problems. The clinical examination comprised occlusal and prosthetic factors and the health of the oral mucosa. RESULTS: The great majority of the patients were very satisfied with their present dental situation and masticatory function. Two thirds reported no problems with their maxillary complete dentures at all. Balanced occlusion was found bilaterally in 61%, and a further 4% had balanced function on one side. More than one third thus lacked balanced occlusion. Only about 60% had optimal occlusion, and 8% had poor occlusion according to common prosthodontic criteria. This was interpreted as a continuing impairment of the occlusion with time. The mean bone loss was 0.5 mm, according to available radiographs, for a mean observation period of 54 months. There were no or only weak correlations between the variables examined. CONCLUSION: The occlusal factors registered were of limited importance for patient satisfaction and treatment outcome recorded clinically and radiographically at follow-up examination of the actual prosthodontic rehabilitation.     

Kinesiographic study of mandibular movements during functional adaptation to complete dentures

After complete denture insertion, edentulous patients usually present transitory difficulties. This is one of the most critical stages of prosthetic treatment and it is strongly related to the prostheses acceptance. The aim of this study was to evaluate potential changes in the mandibular movement pattern related to insertion of the complete denture during the functional adaptation period. The kinesiograph instrument K6-I (Myotronics Research Inc., Seattle, WA) was used to evaluate eight edentulous patients that received conventional complete denture treatment. Recordings of opening and closure movement limits, movement velocity, postural rest position, chewing cycle and limits of eccentric movements were performed. Each patient was evaluated in four different stages: with the old dentures, immediately after insertion of the new dentures, and 30 days and 6 months after insertion of the dentures. The results showed that there were no remarkable changes in the mandibular motion patterns after insertion of the new dentures. It was suggested that the problems related to the process of utilization of new dentures are not strictly associated to the mandibular movement. Therefore, functional adaptation after denture insertion is not directly related to functional changes, but to the quality of the dentures and to individual features.