Residual Ridge Height Research Articles

Maxillary Sinus in relation to Modern Oral and Maxillofacial Surgery

Maxillary Sinus in relation to Modern Oral and Maxillofacial Surgery

Retrospective Study of Bone Resorption after Maxillary Sinus Bone Graft

Purpose: This research sought to determine the resorption rate of bone grafted to the maxillary sinus according to the grafted material’s type, patient’s age, systemic disease, implant size, site of implant placement, and residual ridge height. Materials and Methods: This research targeted 24 patients who had immediate Osstem ® implant (US Plus ® ) placement after bone graft. The panorama was taken before the surgery, after the surgery, and 6 months after the surgery. Vertical height change and resorption rate of the grafted bone were measured with the same X-rays and compared. The influence of the following factors on the grafted bone material’s resorption rate was evaluated: grafted material type, patient’s age, systemic disease, implant size, site of implant placement, and residual ridge height. Results: Patients in their 40s had 34.0±21.1% resorption rate, which was significantly higher compared to the other age groups (P＜0.05). There was no significant relationship between systemic disease and grafted bone resorption. There was no significant relationship between implant size (diameter, length) and grafted bone resorption. There was no significant relationship between the site of implant placement and grafted bone resorption. The ramal bone-grafted site was significantly more resorbed than the ramal bone/Bio-Oss ® -grafted site, maxillary tuberosity bone/Bio-Oss ® -grafted site, and ramal bone/maxillary tuberosity bone/Bio-Oss ® -grafted site (P＜0.05). There was no significant difference in the grafted bone resorption rate in the sinus between more than 4 mm and less than 4 mm residual ridge heights. After an average of 6 months, a second surgery was done; given an average follow-up of 1.9 years, the success rate and survival rate of the implant were 96.9% and 98.4%, respectively. Conclusion: These results indicate that the bone resorption rate of grafted bone among patients in their 40s is higher compared to patients in their 50s and over, and that only autogenous bone (ramus) shows higher resorption rate than the mixed graft of autogenous bone and xenogenous graft (Bio-oss) after maxillary sinus graft.

Impact of facial form on the relationship between conventional or implant-assisted mandibular dentures and masticatory function

It is not clear if the interaction of craniofacial form with type of prosthetic restoration (conventional or implant-assisted) is related to masticatory function in complete denture patients. The purpose of this study was to investigate the relationships among facial form, skeletal class, alveolar residual ridge heights and masticatory function in subjects treated with implant-assisted or conventional mandibular dentures with lateral cephalometric evaluation. Data from a previously reported randomized controlled clinical trial were accessed to compare treatment success rates, functional and perceptual outcomes, dietary intake, and craniofacial relationships between mandibular complete dentures and implant overdentures in edentulous diabetic subjects. Evaluation of the digitized post-insertion lateral cephalometric radiographs provided measures of facial form (mesocephalic "medium", brachycephalic "broad and square", dolichocephalic "vertical and long"), skeletal class (Class I, Class II, Class III), and alveolar ridge height (mm), which were compared to results of standardized masticatory tests as evaluated using MANOVA and REGW post-hoc evaluation (α=.05). Masticatory performance on the preferred side was slightly reduced in the dolichocephalic group, compared to brachycephalic and mesocephalic groups (P=.085). Swallowing threshold performance was significantly less in skeletal Class II subjects compared to Class I (P=.034). Maxillary residual alveolar ridge height was significantly less in the brachycephalic group compared to the dolichocephalic group (P<.001). No differences in mandibular ridge height were seen associated with facial form or skeletal class groups. Facial form may be related to masticatory function with conventional and implant-assisted mandibular dentures, but larger controlled studies are needed to confirm this relationship. Alveolar ridge height is reduced in edentulous subjects with a brachycephalic facial form.

Atrophic maxillary floor augmentation by mineralized human bone allograft in sinuses of different size: an histologic and histomorphometric analysis

The aims of this work were to histologically examine the healing of mineralized human bone allograft (MHBA) in sinus augmentation for elevating a severe maxillary atrophy ridge (≤2 mm residual ridge height) and to correlate the results to the sinus cavity size. A two-stage protocol was conducted in 23 patients, all having crestal bone ≤2 mm. A mixture of 80/20 cortical/cancellous of MHBA particles was used to augment sinus using the lateral window approach in narrow (NS; <15 mm bucco-palatal distance) and wide (WS; ≥15 mm bucco-palatal distance) sinuses, based upon computerized tomography (CT) assessment. A bone core biopsy was taken at implant placement, 6 and 9 months after surgery. Microradiography, histology and histochemistry of methacrylate-embedded sections were performed to analyze and to evaluate the bone and graft amount. Newly formed bone around MBHA particles was found in all 28 biopsies. Bone showed a woven structure at 6 months after surgery and a lamellar structure 9 months after surgery. At 6 months after surgery, the 13 NS and 15 WS had 30.5±8.8% and 20.7±4.9% mean±SD bone formation, respectively. At 9 months after surgery, it was 38.8±7% (NS) and 30.7±3% (WS). Residual graft was about 16% (6 months) and 6% (9 months), in both NS and WS. The Mann-Whitney test showed a greater bone formation in NS than in WS (P<0.005). The used 80/20 MHBA mixture appears to promote, in the severe atrophic maxilla, a satisfactory bone formation. Our results prove that the larger the sinus, the longer the maturation time needed to achieve a suitable amount of new bone formation.

The retrospective study of survival rate of implants with maxillary sinus floor elevation

Introduction: Maxillary posterior region, compared to the mandible or maxillary anterior region, has a thin cortical bone layer and is largel y composed of cancellous bone, and therefore, it is often difficult to achieve primary stability. In such cases, sinus elevation wit h bone graft is necessary. Materials and Methods: In this research, 121 patients who had implant placement after bone graft were subjected to a follow-up study of 5 years from the moment of the initial surgery. The total survival rate, 5-year cumulative survival rate and the influence of the follo wing factors on implant survival were evaluated; the condition of the patient (sex, age, general body condition), the site of implant placement, diamet er and length of the implant, sinus elevation technique, closure method for osseous window, type of prosthesis and opposing teeth. Results: 1. The 5-year cumulative survival rate of total implants was 90.5%, there was no significant difference between sex, age, the s ite of implant placement, diameter and length of the implant, sinus elevation technique, and the type of opposing teeth. 2. Patients with diabetes mellitus & osteoporosis and smooth-surfaced machined group & hydroxyapatite (HA)-treated group and ho mogenous demineralized freeze dried allogenic bone (DFDB) bone graft only group had significantly lower survival rate. 3. With less than 4 mm of residual alveolar ridge height, lateral approach without closing the osseous window resulted in a sig nificantly lower survival rate. 4. Restoration of a single implant showed a significantly lower survival rate, compared to cases where the superstructure was j oined with several implants in the area. Conclusion: Patients with diabetes or osteoporosis need longer period of time for osseointegration compared to the normal, and the dentists must be prudent when choosing a surface treatment type and the bone graft material. Also, as the vertical dimension of the residual alv eolar ridge can influence the result, staged implant placement should be considered when it seems difficult for the implant to gain primary stability fro m the residual bone with less than 4 mm of vertical dimension. It is recommended to obdurate the bone window and that the superstructure be connected wi th several impants in the peripheral area.

Relationship between the age, the bone density, and the height of mandibular residual ridge in edentulous menopausal women

Good quantity and quality of bones are keys to the success of prosthodontic treatment. The quantity of bones is showed by the height of mandibular residual ridge, whereas the quality of bones is indicated by the bone density.The aim of this study is to investigate the relationship between the age, the bone density, and the height of the mandibular residual ridge. The observation is carried out to six edentulous menopausal women. The height of mandibular residual ridge and the mandibular bone density are measured by using CBCT-3D (Cone Beam Computed Tomography-3 Dimension). Pearson analysis of bivariate correlation is used to determine the relation between variables. As a result, there is a strong correlation between the increased of the age and the decrease of mandibular bone density (r=-0.922 with α=0.009). The study also shows a significant correlation between the decrease of the height of mandibular residual ridge and the decrease of the mandibular bone density (r=0.815 with α=0.048) and between the decrease of the height of mandibular residual ridge and the increase of the age (r=-0.89 with α=0.017).To summarize, the decrease of the height of mandibular residual ridge in this study correlates with the decrease of the mandibular bone density and the age.

The Use of Cancellous Block Allograft for Sinus Floor Augmentation With Simultaneous Implant Placement in the Posterior Atrophic Maxilla

The simultaneous placement of dental implants during sinus augmentation is advocated in cases in which >or=4 to 5 mm of alveolar bone exists coronally to the sinus floor. The aim of the present study was to assess the survival rate of dental implants placed during sinus augmentation and stabilized by the use of cancellous freeze-dried block allograft. Residual alveolar ridge height <or=4 mm was an inclusion criteria. Twenty-eight consecutive patients (13 females and 15 males) aged between 25 and 65 years (mean, 54 +/- 9 years) were referred for implant-supported reconstruction of the posterior atrophic maxillae. Seventy-two implants (two to four per patient) were placed. No case presented difficulty in achieving initial stabilization. Relatively small membrane tears (5 to 10 mm) were observed in 21.4% of the sinuses. There were no other clinically evident complications of the sinuses. Sixty-eight implants were clinically osseointegrated, yielding a 94.4% success rate, whereas four implants were noted to be failed at the second stage. Three months later, implants were inserted at the previously failed implant sites; after 3 additional months, at the second stage, they were diagnosed as osseointegrated. All patients received a fixed implant-supported prosthesis. The mean follow-up was 27 months (range, 11 to 46 months). Radiographs taken at the last follow-up demonstrated that the vertical augmented bone within the sinus ranged from 11 to 14 mm (mean, 12.3 mm). The histologic evaluation showed newly formed bone containing viable osteocytes merged with residual grafted bone, characterized by empty lacunae devoid of osteocytes. The cancellous block allograft seems to possess potential as a grafting material for sinus floor augmentation with simultaneous implant placement.

Ultrasound Transmission Velocity for Noninvasive Evaluation of Jaw Bone Quality In Vivo Before Dental Implantation

For the insertion of dental implants, mechanical bone properties at the implantation site have great impact both for therapeutic regimes as well as for the overall long-term success, making a reliable method for the preoperative assessment of the bone quality desirable. Ultrasound transmission velocity (UTV) has been introduced as a noninvasive method to analyze mechanical properties of bone. The aim of this study was the first intra-oral in vivo assessment of alveolar crest UTV values of edentulous jaws. Partly or fully edentulous patients ( n = 108) were enrolled in this study, taking into account possible influence factors that affect bone quality (osteoporosis, radiation therapy). Six intra-oral measurement points were used: left side region, right side region and frontal region, for upper and lower jaw, respectively. Ultrasound transmission velocity values were measured bicortically (in bucco-oral direction) and correlated to sex, age, measurement site and history of osteoporosis or radiation therapy. We found a minimum mouth opening of 30 mm, as well as a residual alveolar ridge height of 8 mm as thresholds for a reliable intra-oral placement of the device. Xerostomia was no contraindication. Assessment of intra-oral UTV showed significantly higher values both for mandibular side regions (female 1713 ± 153 m/s, male 1734 ± 221 m/s) and the maxillary frontal region (female 1665 ± 189 m/s, male 1648 ± 82 m/s) than for maxillary side regions (female 1538 ± 177 m/s, male 1583 ± 90 m/s). These data were even more clarified by intra-individual correlation of upper and lower jaw side region UTV values. We found no correlation between assessed UTV values and the variables sex, age, osteoporosis or radiation therapy. The use of a small UTV device in this study allowed the recording of intra-oral UTV values in a large and heterogeneous patient collective for the first time. Assessment of alveolar-ridge UTV might offer the possibility to identify critical bone quality before implantation or to monitor bone healing (mineralization) after augmentation procedures. (E-mail: klein@mkg.klinik.uni-mainz.de)

Microvessel Density in Sinus Augmentation Procedures Using Anorganic Bovine Bone and Autologous Bone: 3 Months Results

This study was an immunohistochemical evaluation of microvessel density (MVD) in sinus augmentation procedures with autologous bone and anorganic bone (Bio-Oss). Twenty-four patients (14 men and 10 women - mean age of 48 years with a range from 34 to 53 years) participated in this study. All the patients presented a maxillary partial unilateral edentulism involving the premolar/molar areas, with a residual alveolar ridge height of about 4 to 5 mm. Twelve patients received sinus augmentation procedures with 100% autologous bone; 100% Bio-Oss was used in the other 12 patients. Endosseous implants were inserted after a mean period of 3 months. As control, the portions of preexisting subantral bone were used. The mean value of the MVD in control bone was 23.4 +/- 1.3. The mean value of the MVD in the sinuses augmented with autologous bone was 29.0 +/- 2.4. The mean value of the MVD in the sinuses augmented with Bio-Oss was 23.8 +/- 2.2. The statistical analysis showed that the differences of the MVD between control bone and sinuses augmented with Bio-Oss were not statistically significant (P = 0.52), while the difference of the MVD between sinuses augmented with autologous bone and those augmented with Bio-Oss was statistically significant (P = 0.0008). Autologous bone may act not only as a passive filling material in bone defects but may also release osteogenic growth factors; and particles of autologous bone seem to contain vital osteoprogenitor cells.

客観的評価に基づいた顎堤高さ診査用スケールの有用性に関する研究

To establish a simple and objective assessment of the residual ridge height of edentulous patients, we investigated the utility of a newly developed "examination scale" based on our clinical research. The sites corresponding to the right and left first molars in study models (100 sets) of edentulous maxillae and mandibles were examined. Subjective assessment and assessment with the three-grade examination scale (high, middle, low) were performed by 16 dentists (less than 3 years of clinical experience: 8, more than 7 years of clinical experience: 8). Objective assessment of residual ridge vertical height was performed with digital vernier calipers. Agreement among the subjective assessment, objective assessment, and assessment with the examination scale was analyzed with kappa values. Marked variations were noted in the relation between the subjective assessment and objective assessment regardless of the individual's clinical experience. Agreement between the subjective assessment and objective assessment was low (maxillae: less than 3 years of clinical experience: 0.38, more than 7 years of clinical experience: 0.32, mandibles: less than 3 years of clinical experience: 0.35, more than 7 years of clinical experience: 0.43). However, agreement between the assessment with the examination scale and objective assessment was high (maxillae: less than 3 years of clinical experience: 0.68, more than 7 years of clinical experience: 0.69, mandibles: less than 3 years of clinical experience: 0.57, more than 7 years of clinical experience: 0.60). The assessment by the newly developed examination scale for residual ridge height of edentulous patients agreed well with the objective assessment, indicating the usefulness of this scale.

The Clinical Significance of Sinus Membrane Perforation During Augmentation of the Maxillary Sinus

Augmentation of the maxillary sinus floor is a well-documented technique and is generally accepted as a pure implantology procedure to facilitate placement of dental implants in the posterior atrophic maxilla. The objective of this report was to evaluate the significance of the sinus membrane perforations on the incidence, complications, and success rate of this procedure. Patients who received sinus floor augmentation and simultaneous placement of dental implant were included in this study. Subgroup I consisted of patients who had their sinus membrane perforated and repaired during the procedure with resorbable membrane. Subgroup II consisted of patients whose Schneiderian membrane was not perforated during the procedure. The patients were followed between 1 to 4 years after augmentation. All perforations were classified as class II or III. The success rate of the implants in the perforation group was 94.4%, and that for the nonperforation group was 93.9%. The difference between the 2 study groups was statistically not significant. A significant statistical correlation was found between the residual ridge height and the membrane perforation (P < .01). Mainly due to technical difficulties, maxillary sinus membrane perforation occurs more frequently with a small height of residual alveolar bone. In this study, no statistical difference was observed in the success rate of the immediate implants placed with sinus bone grafting in patients whose membrane was perforated versus those patients in whom an intact membrane was maintained.

無歯顎者の顎堤高さの診査における主観的評価と客観的評価の関係

Appropriate examination of the height of the residual ridge is critical in complete denture treatment. To clarify the possibility of establishing standards for improving the reproducibility of subjective evaluation, the relationship between conventional subjective evaluation by several dentists and objective evaluation by model measurement was evaluated. Locations for evaluation were the sites corresponding to the central fossa of the right and left first molars in study models (100 sets) of edentulous maxillas and mandibles. Subjective evaluation with a three-grade scale was performed by some dentists and objective evaluation was performed with digital vernier calipers. The relationship between objective evaluation and subjective evaluation was studied separately in dentists with less than 3 years of clinical experience and those with more than 7 years. Discrimination values for objective evaluation were determined at changeover points of the rate of subjective evaluation. In addition, we studied the correction between subjective evaluation and objective evaluation with the discrimination values. Marked variations were noted in subjective evaluation depending on the individual and number of years of clinical experience. Discrimination values were obtained from subjective evaluation for dentists with more than 7 years of clinical experience: for the maxilla, "low" and "middle" were 6 mm and "middle" and "high" were 10 mm; for the mandible, "low" and "middle" were 0 mm and "middle" and "high" were 5 mm. The correlation between subjective evaluation and objective evaluation based on these discrimination values was extremely low regardless of the individual's clinical experience. Reproducibility of subjective evaluation of the residual ridge height was low. To improve the universality and reproducibility of the examination, subjective evaluation must be performed by referring to the discrimination values.

Number of teeth and residual alveolar ridge height in subjects with a history of self-reported osteoporotic fractures.

The purpose of this case-control study was to determine if elderly subjects with a history of osteoporotic fractures have fewer teeth and greater residual ridge resorption than subjects without such fractures. Patients older than 60 with a panoramic radiograph were invited to a phone interview. Information was obtained regarding fracture history, smoking, and hormone replacement therapy (HRT). The number of teeth was obtained from the panoramic radiograph. The residual ridge height of the edentulous mandible was measured at the site of the mental foramen. Multiple regression models were used to assess the association between fracture status and number of teeth or residual ridge height (controlling for age, gender, HRT, smoking, height and weight). Cases (n=93) were individuals reporting osteoporotic fractures (fractures occurring after minor impact). Controls (n=394) were individuals reporting traumatic fractures (n=105) or no fractures (n=289). Fracture status in this population affect neither the number of teeth nor the residual ridge height. In the regression model, the variables that had a statistically-significant effect on the number of teeth were age (p<0.0001) and smoking (p<0.0001). There was a dose-effect of smoking on the number of teeth. In the regression model, the variables that had a significantly-significant on residual ridge height (n=95 edentulous subjects) were age and gender. Our conclusion was that in elderly dental-school patients the number of teeth and residual ridge height were not influenced by fracture status. Age and smoking had the most influence; there was no effect from HRT. The clinical implication is that a history of osteoporotic fractures is not an important cause for tooth loss and residual ridge resorption in an elderly dental-school population.

Association of mandibular angle size with cortical thickness and residual ridge height of the edentulous mandible

To evaluate the mandible angle and to investigate the relationship of angle size to gender, age-group, cortical thickness at the mandibular angle (CTMA), height of mandibular residual body, and edentulous period in the elderly edentulous subjects. A total of 356 panoramic radiographs of three groups of subjects were evaluated: the young dentate group, 131 subjects (mean age: 27); the older dentate group, 97 (mean age: 64); and the elderly edentulous group, 128 (ages 76, 81, or 86). Mandibular angle size, CTMA, and height of mandibular residual body were measured from panoramic radiographs. A structured questionnaire was used to determine the history of edentulousness. Difference in angle size was found between dentate men and women (P < 0.05, P < 0.001), but not between the elderly edentulous men and elderly women. The elderly edentulous subjects had larger mandibular angles than did older dentate subjects (P < 0.001). The angle size was negatively related to CTMA only among 76-year-old edentulous women (P < 0.01) and negatively associated with average height of the mandibular residual body in the edentulous men and women (P < 0.01). No association existed between angle size and duration of edentulousness. Elderly edentulous subjects have large mandibular angles and the angle size is correlated with low-height of the mandibular residual body, which suggests that masticatory function of natural dentition and complete denture may influence change of the mandibular angle. The significant relationship of mandibular angle size to CTMA probably indicates the effect of systemic factors on change in the mandibular angle.

RADIOGRAFI UNTUK PERAWATAN IMPLAN GIGI

Dental implants have become an accepted form of permanent tooth replacement. Successful dental implant treatment requires knowledge of the precise location in connection with critical structures in maxillae and mandible. Injurty to the nerve canal or perforation of maxillary antrum can cause paresthesia or antral infection that may lead to failure of the treatment. Measuring the height and width of residual alveolar ridge is necessary to select the appropriately sized implant as well as to assure the adequacy of bone. Presurgical radiographic evaluation of dental implants plays very important role in the success of implant treatment procedure. Various imaging modalities from conventional intraoral radiographs to more sophsticated and modern ones can be used for this purpose. The conventional imaging modalities have very limited diagnostic information in accordance with details and accurate in bone evaluation of the implant sites. On the other hand, modern imaging modalities such as Dental CT have been proven to produce excellent image either for measuring the detailed evauating the sites. Selecting the appropriate imaging modality will be one of the key to success in dental implant treatment.

Degree of the residual alveolar ridge resorption registrated by ortopantomograms among immediate and classic complete denture users

Degree of residual ridge loss is influenced by sistemic phactors, but during the first phase after extraction local phactors are dominant. Patohistological changes of alveolar processus of jaws show the possibility of negative influence of complete dentures on support tissue. In this study, on the chosen sample, the degree of alveolar ridge loss was measured in the group of immediate complete denture users (30 patients) and classical complete denture users ( 30 patients).Height of residual alveolar ridge was measured on ortopantomograms. Localization of referent points proportion was used because of neutralization of shadow distorsion (five in maxilla and five in mandibula). The first ortopantomogram was made at the time of delivering dentures, and the second one six months later. The final measurement of alveolar ridge height is bigger in the group with classical dentures. The reduction degree of residual alveolar ridge is bigger in the group of immediate complete denture users in the first six months.

A new method for the radiological investigation of residual ridge resorption in the maxilla.

To develop a new method for assessing residual ridge resorption in the edentulous maxilla. Defined experimental and reference areas in the maxilla were drawn on transparent film laid over a panoramic radiograph and digitized. Bone areas were measured with an integrated planimetry program and expressed as a ratio R. The effect of positioning errors on reliability of the method was investigated on dry skulls. The correlation between the change in ratio and actual bone loss was examined by progressively reducing the height of an artificial residual ridge on one skull. The coefficient of variation for the absolute ratio in different head positions was < 0.05 and its correlation coefficient of the change in R and the degree of resorption was r2 > or = 98.3%, P = 0.0001. Comparison of the experimental area with the reference area on serial panoramic radiographs appears suitable for the assessment of residual resorption in the maxilla.

フランジテクニックによって製作した総義歯の安定性と咀嚼能に関する臨床的検討

To establish the stability of complete denture during occlusal functions such as mastication is indispensable for complete dentures. The stability should be also established during non-occlusal functions, such as speech. Complete dentures constructed by the flange technique generally exhibit excellence during non-occlusal functions because the polished surface contour of the denture base and the position of the artificial teeth are in harmony with the surrounding contacting tissues, i.e. the tongue, lips, and cheeks. However, it has not yet been clarified whether or not these dentures exhibit good stability during unilateral occlusion. This article investigated stability during unilateral occlusion of the dentures, especially the mandibular dentures, constructed by such a physiological technique, and the masticatory performance of the dentures. The results were as follows : 1) In both the stability group and instability group, as determined in the unilateral occlusal balancing test, the central fossa of the mandibular first molar, which is the center of occlusion for dentures, was positioned buccaly from the interalveolar crest line. This was, however, apt to be located more buccally in the instability group. Still, as for masticatory performance of the denture, no significant difference was found to exist between the groups. 2) The ratio of alveolar residual ridge height to denture height tends to be higher in the stability group, as determined in the unilateral occlusal balancing test, and the HM group, which was able to masticate a wide variety of foods in the masticatory performance test. This ratio tended to be smaller in both the stability group and LM group, which exhibited trouble masticating. 3) There were many cases which exhibited longer flanges of the denture in the stability group and HM group. This was in contrast to the instability group and LM group which exhibited shorter lingual flanges of the lower denture. 4) Comparing to the instability group, the stability group exhibited a gentler slope in the posterior part of the ridge, at about 4°. Also, the HM group which had exhibited better masticatory performance of the dentures tended to exhibit a gentler mesiodistal inclination of the ridge in the sloping posterior part of the LM group. On the basis of the foregoing findings, it appears to be essential to arrange denture molars as far as possible toward the lingual side of the denture space in order to obtain successful function of complete dentures constructed by the physiological technique without having leverage action occurring. Furthermore, it is essential for the lingual flange of lower dentures to be extended as far downward as possible, with consideration being paid to the occlusal relationship of the last molar according to the degree of mesiodistal inclination of the residual ridge toward the retromolar pad.

全部床義歯装着者の義歯支持基盤形態がそしゃく機能に及ぼす影響

To elucidate the relationship between masticatory performance and the size of denture foundations in complete denture wearers, 28 complete denture wearers (average age: 75.6±4.8 yrs) whose dentures were developed by one dentist using the same methods and materials were selected. The size of lower denture foundations in each patient were analyzed by the “replica method” newly developed by our department. Replica of each denture foundation was made by silicone impression material filling in the mucosal surface of the lower complete denture and cutting by rubbing the denture border.The basal area (flat plane cut and rubbed denture border) of residual ridge replica were measured by the digitizer, and volume (weight of replica/specific gravity of silicone impression material) and height (volume/basal area×2) were calculated.Voluntary maximal clenching force, masticatory efficiency, and cross-sectional area of masseter muscle in complete denture wearers were measured by occlusal force meter (Nihon Koden, Co.), sieving method, and CT-scan.The results were as follows:1. The height of residual ridge decreased significantly in relation to aging (p<0.05). But the basal area and volume of residual ridge did not depend on aging.2. When voluntary maximal clenching force and basal area as well as volume and height of residual ridge replica were dependent variables, and masticatory performance was an independent variable, multiple correlation coefficient (R) as a means of multiple regression analysis was 0.834 (p<0.001).Partial correlation coefficients (β) of each dependent variable were 0.640 (voluntary maximal clenching force:p<0.01), 0.531 (basal area of residual ridge:p<0.01), 0.489 (height of residual ridge: p<0.05), 0.321 (volume of residual ridge:p<0.05), and they were significant statistically.3. Voluntary maximal clenching force decreased significantly in relation to aging. The cross-sectional area of masseter muscles by CT-scan did not decrease significantly in relation to aging.

Trabecular bone mineral density of mandible and alveolar height in postmenopausal women

Mineral density of the trabecular bone of the mandible was determined by single-energy QCT (quantitative computed tomography) for 74 totally or nearly edentulous menopausal women. These results were compared with the bone mineral densities (BMD) of their lumbar area (L2-L4) and femoral collum, measured by dual-energy x-ray transmission, Lunar DPX. The remaining height of the residual ridge at the symphysis of the mandible was measured on computed tomography (CT) lateral projection view, and an index of the residual ridge status was introduced. To determine whether general osteoporosis status affects the remaining height of the residual ridges, we compared these values with all results for bone mineral density. The BMD of the lumbar area and that of the femoral collum correlated well with each other, but the BMD of the trabecular bone of the mandible did not correlate with either of the other two BMD measurements. Measurements of residual ridge height did not correlate with any BMD values. The effect of possible bone loss earlier in life is no longer apparent in mandibular height or trabecular BMD over 20 yr after tooth extractions.