Clinical bone densitometric evaluation of the mandible in removable denture wearers dependent on the morphology of the mandibular cortex

STATEMENT OF PROBLEM: Wide normal variations have been found in the structure and density of the human skeleton, as well as of the mandible. PURPOSE: The objective of this study was to determine whether the mandibular bone mineral density is correlated with the classification of the structure of the inferior cortex on panoramic radiographs in complete and removable partial denture wearers. MATERIALS AND METHODS: The mandibular cortical index of 136 randomly selected complete and removable partial denture wearers was evaluated via panoramic radiographs. The criteria for the mandibular cortical index were as follow: category 1, sharp endosteal margin of the inferior cortex; category 2, semilunar defects; and category 3, thick cortical residues on endosteal margin. Forty male patients (mean age 72.7; range 56 to 84 years) and 96 female patients (mean age 69.7; range 48 to 86 years) participated. With a copper stepwedge and DenEx 2001 computer program, the mandibular bone mineral density was investigated densitometrically on dental panoramic radiographs. Four experienced observers and 6 general dental practitioners made the observations on all panoramic radiographs. All bone mineral density values were expressed in equivalents of the actual stepwedge thickness. An independent t test (alpha =.05) was used. RESULTS: The severity of changes in the mandibular cortex was significantly related to all measured mandibular bone mineral density values (t test: P<.01). Mandibular cortical index category 3 had significantly lower bone mineral density values in all measured regions of interest. Interobserver and intraobserver agreement in mandibular cortical index assessment was excellent. CONCLUSION: Patients having lower bone mineral density values in the mandible have much more porous cortical layer of the inferior border of the mandible.     

The effect of the mandibular buccal denture base surface on food retention.

The accumulation of food debris in the buccal vestibule surrounding a mandibular denture flange was studied. This investigation focused on the effect of the thickness, physiologic molding, and slope of the buccal flange of denture base on the patient's ability to expel test-food particles from the area. Experimental denture bases were placed in the mandibular buccal vestibule of subjects having a complete natural dentition. Only the slope of the polished surface of buccal flange was found to have a significant positive correlation with the ability to expel test food from the buccal vestibule.     

Topography of the outer mandibular symphyseal region with reference to the autogenous bone graft

The mandibular symphysis is preferred as a donor site for the relatively small grafts needed for the autogeneous bone graft procedure. This study was undertaken to determine the morphology and composition of the cortical and trabecular bone in the mandibular symphyseal region using 35 mandible specimens from Koreans. The topographical patterns through the thickness of the cortical plate and the width of the trabecular bone were observed. In this study, the labial cortical plate of the mandible became thicker from the superior to the inferior aspects (P < 0.05). However, the trabecular bone width exhibited a different distribution pattern compared to the thickness of the labial cortical plate. This observation concerning the cortical and trabecular bones assists in determination of the depth of osteotomy. The results provide useful information on the mandibular symphysis graft prior to dental implant placement. These results will enable the volume of the cortical plate in the mandibular symphyseal region and its proper size, depth, and location to be predicted when removing a graft block.     

Mandibular movement and velocity in relation to state of dentition and age

Parameters of mastication, such as mandibular displacement, velocity and chewing cycle duration, were investigated in relation to age and rehabilitation with complete dentures. Two groups of elderly subjects (mean age 80 years), one with natural dentition and the other with complete dentures, and one group of young dentate adults (mean age 26 years) participated. Three-dimensional records of masticatory mandibular movements were obtained using the Selspot movement analysis system. There were no differences in the duration of the total or individual components of a chewing cycle, except for the closing phase, which was significantly longer in the complete denture group. Mandibular closing velocity was significantly lower in the two groups of elderly subjects than in the group of young adults. There was a high degree of inter-individual variation in mandibular displacement in all groups, but the mean vertical amplitude was smaller in the elderly groups compared to the group of young adults. For many of the parameters the variation was significantly greater in the groups of elderly subjects than in the younger group. Ageing thus appeared to have a more important effect than the state of the dentition on the parameters studied.     

Changes in Head and Cervical-Spine Postures and EMG Activities of Masticatory Muscles Following Treatment with Complete Upper and Partial Lower Denture

A clinical stomatognathic, cephalometric and electromyographic (EMG) study was performed in relation to 14 subjects (10 women, 4 men), each with an edentulous maxilla and residual mandibular dentition before and six months after treatment with complete upper and partial lower dentures. The mean age of the subjects was 54.4 years (range 43–64 years). The mean period of edentu-lousness and age of dentures were 22.5 years (range 15–33 years) and 14.1 (range 1.5–30 years), respectively. Natural head position was recorded (using a fluid-level method) and measured from cephalograms. EMG activity was measured in relation to masseter and temporal muscles. A decrease in clinical dysfunction index was noted in 12 of 14 subjects (86%). There was no change in cervical inclination, but a slight extension of the head was noted after treatment. Rapid recovery of the masticatory muscles was reflected in increased EMG activity, especially when biting in the maximal intercuspal position. In cases of edentulous maxilla and residual mandibular anterior dentition, treatment with a complete upper and lower partial denture had a favorable effect on craniomandibular disorders and masticatory muscle function.     

无牙下颌角大小与其皮质骨厚度和剩余牙槽骨高度的关系

目的　分析无牙下颌角角度的变化 ,探讨其角度与性别、年龄、下颌角骨皮质厚度、剩余牙槽骨高度及无牙颌时间的关系。方法　年轻有牙组 131例 ,女性 6 8例 ,男性 6 3例 (平均年龄 2 7岁 ) ,年长有牙组 97例 ,女性 5 9例 ,男性 38例 (平均年龄 6 5岁 ) ,老年无牙颌组 12 8例 (平均年龄 80岁 ,76岁者 5 8例 ,81岁者 39例 ,86岁 31例 )。 3组共拍摄 35 6张曲面断层片。分别测量曲面断层片下颌角角度、无牙下颌角区骨皮质厚度和剩余牙槽骨高度。用调查问卷收集无牙颌患者的病史资料。结果　年轻有牙组和年长有牙组的下颌角大小差异无显著性 ,但两组男性下颌角均小于女性下颌角 (P <0 0 5 ,P <0 0 0 1)。老年无牙颌组下颌角为 12 8 4 °± 6 6 °,大于年长有牙组 ( 12 2 8°± 6 6 °) ,二者间差异有极显著性 (P <0 0 0 1)。 76岁无牙女性组 ,下颌角的大小与下颌角区骨皮质厚度呈负相关 (P <0 0 1) ;无牙颌男性和女性下颌角大小均与剩余牙槽骨平均高度呈负相关 (P <0 0 1)。无牙下颌角角度与无牙颌时间无关。结论　无牙患者较有牙者下颌角增大以及剩余牙槽骨越低下颌角越大的结果说明 ,自然牙列和全口义齿的咀嚼功能可能对下颌角的角度有显著影响。无牙下颌角的大小与其骨皮质厚度的显著关系提示 ,系     

Bite force and its correlations in different denture types

Maximal bite force was measured and intraoral condition was examined in 89 patients at the Institute of Dentistry, University of Turku. These patients formed three different denture groups: those with complete dentures, those with full maxillary denture and partial mandibular denture, and those with natural dentition or skeleton-supported partial maxillary denture and partial mandibular denture. There were three age groups: greater than or equal to 70, 60-69, and less than or equal to 59 years old. Maximal bite force was recorded with an appliance at seven different measuring points by placing a biting fork between the antagonistic teeth while at the same time the occlusion was stabilized contralaterally with a plastic tube. Maximal bite force had a correlation with age and sex (P less than 0.01). In partial-denture groups high bite force had a correlation with the breaking of dentures (P less than 0.001 and P less than 0.05, respectively). Satisfied patients had a higher bite force than dissatisfied ones. When there was some disturbance in occlusion, the bite force was smaller, especially in full-denture groups (P less than 0.001). Full-denture wearers also had a good bite force, but the best biting area was located more posteriorly than in patients who still had some natural teeth left in both jaws. Changes in the denture-bearing mucosa in patients with complete dentures and negative height of the mandibular alveolar process decreased the bite force slightly.     

Inferior alveolar nerve canal position: a clinical and radiographic study.

PURPOSE: To document a clinically relevant position of the inferior alveolar nerve (IAN) in dentate patients and identify patient factors associated with IAN position. MATERIALS AND METHODS: The investigators used a cross-sectional study design and a study sample of subjects who had a radiographically identifiable IAN canal and at least 1 mandibular first molar was enrolled. Predictor variables were age, gender, and race. Outcome variables were the linear distances between the buccal aspect of the IAN canal and the outer buccal cortical margin of the mandible, and the superior aspect of the IAN canal and the alveolar crest. Appropriate uni-, bi-, and multivariate statistics were computed. RESULTS: The study sample was composed of 50 patients with a mean age of 42 years, 42.0% were male, and 73.2% were white. On average, the buccal aspect of the canal was 4.9 mm from the buccal cortical margin of the mandible. The superior aspect of the IAN canal was 17.4 mm inferior from the alveolar crest. Age and race were statistically associated with IAN position relative to the buccal cortical mandibular margin (P<.05). None of the demographic variables were associated with vertical position. CONCLUSIONS: The IAN canal was 4.9 mm and 17.4 mm from the buccal and superior cortical surfaces of the mandible, respectively. The bucco-lingual IAN canal position was associated with age and race. Older patients and white patients, on average, have less distance between the buccal aspect of the canal and the buccal mandibular border. To minimize the risk of IAN injury, these variables should be considered when planning mandibular osteotomies or using monocortical plates.     

A Comparative Study of Mandibular Incisor Relation to the Lingual Frenum in Natural Dentition and in Complete Denture Wearers

The determination of the occlusal vertical dimension and proper positioning of the anterior teeth are major factors in making complete dentures which will give optimum service. In this study, efforts were made to evaluate the reliability of measurement of vertical distance between the anterosuperior most point on the lingual frenum and mesioincisal edges of mandibular central incisors in natural dentition among different age groups and in complete denture wearers. Three hundred dentulous subjects belonging to different age groups and hundred edentulous patients wearing complete dentures were selected. The dentulous group was divided into three groups, group I (20–40 years), group II (41–60 years), group III (61 years and above) and the edentulous subjects being group IV ( 40–60 years). Mandibular irreversible hydrocolloid impression (Alginate) was made using modified stock tray. In edentulous subjects impression was made with denture in position. The vertical distance between anterosuperior most point on the lingual frenum and mesioincisal edges of mandibular central incisors was measured on the dentulous casts and casts of complete denture wearer using dental surveyor and the vernier calipers. The values were tabulated and statistically analysed. The mean vertical distance between anterosuperior most point on the lingual frenum and mesioincisal edges of mandibular central incisors among dentulous subjects was 12.3 mm and among complete denture wearers was found to be 13.2 mm. There was no significant variation in the mean vertical distance among dentulous subjects belonging to different age groups. At 5 % significance level, statistically there was a significant difference in the mean vertical distance between group I and group IV; group II and group IV.     

The value of radiographic predictors of the rate of mandibular residual ridge resorption.

This study tested the relationships between the rate of mandibular residual ridge resorption and the following two variables: cortical thickness at the gonion, and the proportion of cortical bone at the symphysis. These parameters were also compared between men and women. Measurements of cortical thickness at the gonion on panoramic radiographs were compared with similar measurements on lateral cephalometric radiographs. The results showed that neither cortical thickness at the gonion nor the proportion of cortical bone at the symphysis could be used as radiographic predictors of the rate of mandibular bone resorption. The rate of resorption was significantly greater in men than in women, while cortical thickness at the gonion in women was significantly less than that in men. Furthermore, the authors concluded that cephalometric and panoramic measurements should not be used interchangeably.     

Retention of complete maxillary dentures as a result of changes in design

The influence of complete maxillary denture design on retention was studied under clinical conditions simulating chewing. Five persons with an edentulous maxilla and a natural dentition of at least 10 teeth in the mandible participated. Retention was measured with a miniature bite force sensor. The occlusal load required to provoke denture dislodgement was recorded. The general principles of denture design were as follows: the bicuspids and molars were set on top of the residual ridge; the thickness of the denture borders was determined functionally; and the palate was covered to the vibration line, without attempts at border compressions. The details that were changed to evaluate their influence on denture retention were as follows: the point of attack of the dislodgement-provoking load alternated between three distinct pits, situated 2 mm apart in the buccopalatal direction on the occlusal surface of the first right bicuspid; the vestibular denture border on the left side was reduced stepwise to 75%, 50%, and 25% of its original thickness; and the distal extension of the palatal denture border was shortened stepwise (2 + 2 mm, as measured in the midline). Measurements pertaining to one specific problem were carried out within a period of 2 h. The results confirmed the concepts that lingualized occlusal contact, functionally determined filling in of the vestibular sulcus, and full palatal coverage to the vibration line all have a positive influence on the retention of complete maxillary dentures.     

Kortikalisdicke am Unterkiefer unter besonderer Berücksichtigung der Miniplattenosteosynthese

Thirty-two human mandibles were marked with three typical fracture lines: a low condylar fracture, a fracture of the mandibular angle, and one through the mental foramen on each side. The mandibles were sectioned at the fixation sites of the miniplate screws. The thickness of the cortical layer was measured with a scaled magnifying glass at the points of anthropological interest and at the marked screw holes. The inferior cortical layer turned out to be thickest in the anterior area. In contrast, it was very thin at the mandibular angle, which might explain the higher complication rate in treating fractures in this region. The thickness of the lingual cortex increased up to the symphysis, whereas the buccal cortical layer showed a decline in size from the mandibular angle up to the chin. The cortical bone at the alveolar ridge was porous. The cortical supply for miniplate osteosynthesis at the condylus ranged from 1.11 mm up to 1.74 mm, which seems to be limited, but due to the small diameter of the condylus most common screws obtain additional anchorage in the inner cortex. The thickness of the cortical layer at the mandibular angle increased from 1.47 mm at the ramus up to 1.97 mm at the beginning of the corpus, reaching 2.14–2.38 mm for the lower plate at the mental foramen. The results for the upper plate were slightly lower.     

Resorbable mesh as a containment system in reconstruction of the atrophic mandible fracture.

PURPOSE: The purpose of this article is to introduce the use of a resorbable material (L-lactide, Co DL-lactide) to help contain the bone graft used during the reconstruction of the edentulous atrophic mandibular fracture. TECHNIQUE: After the mandibular fracture was reduced and fixated with a large reconstruction plate, the resorbable mesh was contoured with scissors and a hot water bath. The mesh was secured into position with 1.5-mm tacks to the inferior border or buccal cortical plate of the mandible. The material was then filled with particulate bone graft harvested from the medial aspect of the anterior iliac crest. RESULTS: Two patients had augmentation of the superior aspect of the mandible and one patient had augmentation of the inferior aspect of the mandible. All patients were augmented at least 10 to 12 millimeters. The mean follow-up was 25 months. All went on to heal to complete bony union. CONCLUSION: This material can be used as a containment system when bone grafting the edentulous atrophic mandible fracture.     

Kinesiographic study of deglutition in dentate individuals and complete denture wearers

Swallowing is used as a clinical method in prosthodontics to determine and record jaw relationships. The aim of this study was to perform a quantitative evaluation, in naturally dentate subjects and complete denture wearers, of three measurements associated with the mandibular position during the act of swallowing water: 1. intermaxillary distance on vertical axis; 2. anteroposterior deviation; and 3. lateral deviation. Two groups were selected: Group I (GI) included 40 subjects with complete dentition (mean age 45.27 yrs) and Group II (GII) included 40 bimaxillary edentate subjects, complete denture wearers (mean age 63.92 yrs). A kinesiographic instrument was used for analysis. Three records were taken for each measurement and a mean value obtained. It was concluded that: 1. intermaxillary distance on vertical axis and horizontal deviation were similar for both groups; 2. there was a significant intermaxillary distance on the vertical axis; and 3. for anteroposterior and lateral axis, results showed moderate deviation in relation to maximal intercuspation (MI).     

Planning the treatment of the complex prosthodontic case.

An approach to planning the treatment of a complete maxillary denture opposing an imperfect mandibular dentition has been described. Maxillary supporting tissues under complete dentures that oppose natural dentitions are often overstressed during function. Generally, as the damage to dentition increases, so do the forces causing thrusting and rotation of the denture. Every effort should be made to develop an occlusal table at the optimal level and in harmony with the patient's condylar guidance and a minimal incisal guidance in the attempt to enhance the stability and retention of the denture and the preservation of the dentition and supporting tissues that remain.     

The influence of selective grinding on the thickness discrimination threshold of patients wearing complete dentures

The influence of selective grinding on the ability of patients wearing complete dentures to discriminate thicknesses occlusally was evaluated. The study included two groups of white Caucasian patients, matched for age, sex and duration of edentulism; 12 wearing traditional complete dentures and 12 wearing maxillary complete denture and mandibular implant-retained overdenture (MIR-OVD). The ability to discriminate thickness was evaluated before and after selective grinding. In both groups, sensitivity improved after selective grinding. Subjects wearing MIR-OVD showed a better ability to discriminate thickness than those rehabilitated with traditional complete dentures. The thickness discrimination threshold might be a suitable method to evaluate complete dentures fit.     

不同垂直骨面型青年女性下颌体形态的测量分析

目的采用锥形束CT（CBCT）分析不同垂直骨面型青年女性患者的下颌体截面的高度和宽度以及下颌体皮质骨厚度,确定不同垂直骨面型患者下颌体形态结构的特点及差异。方法选取在山东大学口腔医院正畸科就诊的女性患者64例,年龄19~40岁,均行CBCT扫描,根据垂直骨面型分为3组,其中低角组14例,均角组31例,高角组19例。测量其下颌体形态,包括下颌体截面高度、宽度及其皮质骨厚度。使用SPSS 16.0软件对测量值进行统计学分析,确定不同垂直骨面型患者下颌体形态结构的特点及差异。结果高角组下颌体截面高度在下颌联合部较低角组大,但低角组在磨牙段较高角组大（P<0.05）。低角组的下颌体截面上1/3宽度在前牙和前磨牙段较高角组宽,而下1/3宽度在下颌联合部、侧切牙段较高角组宽（P<0.05）。除前磨牙段以外,低角组的下颌基底部皮质骨厚度较高角组明显增厚（P<0.05）;低角组颊侧上1/3皮质骨厚度在尖牙、前磨牙以及磨牙段均较高角组厚（P<0.05）,而下1/3皮质骨厚度只在尖牙和第二磨牙段较高角组厚（P<0.05）;低角组舌侧下1/3皮质骨厚度在下颌联合部较高角组厚（P<0.05）,而上1/3皮质骨厚度在前磨牙与磨牙段均较高角组厚（P<0.05）。结论不同垂直骨面型者下颌体截面高度和宽度的差别较下颌体皮质骨厚度的差别明显;下颌体截面高度从前牙段向磨牙段逐渐减小;低角组的下颌体截面宽度较其他两组宽大;下颌体皮质骨厚度从低角、均角到高角组依次变薄。     

Criteria for applying lingualized occlusion by the condition of residual alveolar ridge

Lingualized occlusion is applied to patients with alveolar ridge resorption, and it is considered that this occlusion is functionally useful and should be applied to cases with alveolar ridge resorption. However, selection criteria supported by evidence for what conditions of the alveolar ridge lingualized occlusion should be selected do not exist. For that reason, we conducted an investigation on choosing lingualized occlusion. As a result, no differences were noted in subjects with a good alveolar ridge condition while a sufficient lingualized occlusion effect was obtained in subjects with a poor alveolar ridge condition, suggesting that efficient mastication could be attained. The following indexes were examined as the criteria for applying lingualized occlusion: The ratio of the residual alveolar ridge should be less than approximately 0.5, in which the distance between the inferior border of the mental foramen and the superior border of the mandibular bone should be less than half the distance between the inferior border of the mental foramen and the inferior border of the mandibular bone. The supporting area of the denture base should be less than approximately 2,000 mm(2). Though the effect can be expected when applying lingualized occlusion under these criteria, they are one standard, and cannot be applied in all cases. In clinical cases, it is important to grasp the local and the whole-body conditions of the patient in order to choose denture occlusion.     

Is there a relationship between mandibular cortical bone thickness and orthodontic treatment time?

ObjectivesTo determine whether there was a correlation between patients'' bone thickness and time spent in orthodontic treatment. The secondary aim was to study the influence of Angle classification, extraction treatment, and age on overall treatment duration.Materials and MethodsIn this retrospective study, records of 971 orthodontic patients from two centers were reviewed and 500 subjects were included after imposing inclusion/exclusion criteria. The Mental Index was used to determine patients'' bone density. For the Mental Index, a line perpendicular to the inferior border of the mandible was drawn on a panoramic radiograph so that it intersected the inferior border of the mental foramen. The mandibular cortical thickness was measured along this line. Two-sample t-test or a chi-square test, followed by multiple linear regression, were used to identify the factors affecting treatment duration.ResultsMandibular cortical thickness was negatively associated with treatment time for all subjects (P < .05). After adjusting for covariables, it remained significant for center-1, but non-significant for center-2 subjects. Angle Class II and Class III malocclusion, extraction therapy, and age had significant positive correlations with treatment duration (P < .05).ConclusionsThere is a negative correlation between the mandibular cortical thickness and orthodontic treatment duration. An extraction treatment plan and treatment of Angle Class II and Class III malocclusions significantly increase the duration of orthodontic treatment. Additionally, patients over 12 years of age have shorter treatment times compared to patients under 12 years of age.     

The symphyseal single-tooth implant for anchorage of a mandibular complete denture in geriatric patients: a clinical report

Little information exists to define the minimum number of implants required for sufficient anchorage of mandibular overdentures. To date, 2 implants placed in the interforaminal region have been considered the minimum. The aim of this study was to examine whether a single symphyseal implant would suffice for adequate anchorage of a mandibular complete denture in elderly patients (octogenarians), and whether this surgically, prosthetically, and financially simple concept would also satisfy patients needing replacement of the mandibular dentition. Nine patients with a mean age of 82.2 years underwent placement of a single symphyseal endosseous implant and anchorage of a complete denture using a ball attachment. Standardized recall examinations, including patient response and inspections of the peri-implant soft tissue and bone conditions, were carried out at 3- to 6-month intervals for a period of 1 1/2 years. It was found that anchorage with a single implant led to both a significant improvement in patients' subjective satisfaction (P < .01) and a significant reduction in reported symptoms (P < .01). During the observation phase, pocket depth and bone resorption initially increased around implants but stabilized after the sixth month. Denture management (placement and removal) also improved during the recall period (P < .01). The results of this study indicate that oral rehabilitation by mandibular complete dentures anchored on a single implant can be considered an economical therapeutic alternative to a conventional mandibular complete denture for very old (octogenarian) patients.