On-Bone Fixation of Free Gingival Graft Induces an Osteoinductive Effect in Human Alveolar Bone.

We examined alveolar bone samples in the area of on-bone fixation of a free gingival graft performed during surgery in patients aged 37-55 years with a diagnosis of secondary partial adentia of the upper and lower jaws. Six months after fixation of the graft in the alveolar bone, foci of neoosteogenesis were found in the contact zone. They were characterized by the appearance of appositional lines, cords of basophilic osteoblasts, and growing osteons. An immunohistochemical study revealed an increase in the number of CD44+, CD29+, and osteocalcin+ cells in the layer of the outer circumferential lamellae, primary osteons, and the lining of the Haversian canals. TGF-ß1+ cells were located in the intertrabecular reticular tissue and wall of microvessels. The results indicate activation of mesenchymal stem cells in the area of localization of the graft and differentiating osteoblasts. The observed osteoinductive effect of free gingival graft is associated with its participation in reorganization in MSC and induction of morphogenetic molecules.

Radiographic evaluation of bone density in dentulous and edentulous patients in Riyadh, KSA.

BACKGROUND: The Cone Beam Computed Tomography (CBCT) is currently being used as the most common diagnostic method to evaluate the bone density of the maxilla and the mandible for planning dental implant. Aim: The aim of the study is to check the quantitative alveolar bone density in complete or partial edentulous and dentulous male and female patients among Riyadh sample population in Saudi Arabia. MATERIALS AND METHODS: The study involved a cross-sectional analysis of 231 consecutive CBCT images of 231 different patients (115 males and 116 females). The scans were of Saudi National patients who were partially or completely edentulous without any bone infections in the maxilla and the mandible. The findings are presented as descriptive statistics and inferential statistics: student -t-test for two group means, ANOVA for three groups, Post-hoc LSD test for multiple comparisons, Levene statistics for testing the homogeneity of variances and a statistical significance at 5% level. RESULTS: Comparison of mean alveolar bone density in maxillae of dentulous male smokers showed a statistically significant difference for bucco-cortical plate and cancellous bone among different regions. In dentulous male nonsmokers, no significant difference was observed for maxillary regions, while in mandibular areas, a statistically significant difference was seen for buccal cortex, palatal cortex, and cancellous bone among different regions. While studying the scans of female dentulous patients, a statistically significant difference was observed in alveolar bone density for all the areas. CONCLUSION: Evaluation of bone density is an important step in treatment planning and this study was aimed to provide insight into bone density patterns of population in Riyadh, Saudi Arabia. Further similar studies in different populations can help in planning for more efficient treatment outcomes.

Correlation of cognitive and masticatory function in Alzheimer's disease.

OBJECTIVES: This study investigated chewing function in elderly individuals with Alzheimer's disease (AD) and correlated chewing function with cognitive status. MATERIALS AND METHODS: Sixteen elderly individuals with mild AD (mean age 76.7 ± 6.3 years; 8 men, 8 women) and 16 age and gender-matched healthy controls (mean age 75.23 ± 4.4 years; 8 men, 8 women) were included in this study. All volunteers wore removable prostheses: 11 were totally edentulous and five were partially edentulous in each group. Chewing function was evaluated via masticatory performance (MP) using Optocal chewable test material and a sieve fractionation method. Cognitive functioning was assessed by the Mini Mental State Exam (MMSE), administered by a trained examiner. Data were analyzed by non-paired t test and Pearson's correlation with α = 0.05. RESULTS: Compared to controls, mild AD patients had decreased MP (P < 0.01) and MMSE (P = 0.01). MP showed a moderate negative correlation with MMSE (r = -0.69). CONCLUSIONS: Mild AD was associated with impaired chewing function. CLINICAL RELEVANCE: Knowledge that mild AD has an impact on chewing is important for dental professionals in decision-making related to prosthetics and general dental treatment.

Masticatory function and oral health-related quality of life in patients after partial maxillectomies with closed or open defects.

STATEMENT OF PROBLEM: The healing pattern after surgical resection of tumors of the oral cavity involving the maxilla may vary from one patient to another. The result may be open communication between the oral and nasal cavities (open defect) or complete oronasal separation after healing of the defect area (closed defect). PURPOSE: The purpose of this clinical study was to compare masticatory function and oral health-related quality of life (OHRQoL) between patients with closed and open defects who had undergone a partial maxillectomy and were wearing dentomaxillary prostheses. MATERIAL AND METHODS: Thirty-eight participants who had undergone a partial maxillectomy and who were wearing dentomaxillary prostheses were enrolled between September 2014 and April 2016. Participants were assigned to 2 groups according to the type of defect after healing: 19 participants had a closed defect, and 19 participants had an open defect. Masticatory function was evaluated objectively and subjectively. The objective measurement was food-mixing ability, which was assessed using color-changeable chewing gum. The subjective measurement was perceived mastication ability, rated as a masticatory score based on the patient's responses to a 35-item food intake questionnaire. OHRQoL was assessed using the Geriatric Oral Health Assessment Index (GOHAI). The GOHAI questionnaire consists of 12 items reflecting 3 hypothesized domains of the impact of oral disease: physical function, psychosocial function, and pain or discomfort. Differences in the scores obtained by the 3 measurements were compared between the 2 groups, using the Wilcoxon rank-sum test (α=.05). RESULTS: No significant differences were seen between the 2 groups in objective mixing ability, subjective masticatory score, or GOHAI (P>.05). Regarding the GOHAI physical function domain, only the swallowing item was significantly lower (P=.025) in participants with an open defect than in participants with a closed defect. Regarding the GOHAI psychological function domain, the item related to patients' psychological worries or concerns about their teeth, gingival tissue, or dentures was significantly lower (P=.045) in patients with an open defect than in those with a closed defect. Other items related to physical function, psychological function, and pain or discomfort were not significantly different (P>.05) between the 2 groups. CONCLUSIONS: The closed or open defect in patients who had undergone a partial maxillectomy may not influence patients' masticatory function and overall OHRQoL if they have adequate prosthetic rehabilitation. However, special consideration should be given to patients with an open defect with regard to swallowing function and psychological concerns in order to improve their OHRQoL.

Masticatory efficiency of shortened dental arch subjects with removable partial denture: A comparative study.

OBJECTIVE: The objective of this study was to compare the masticatory efficiency in subjects with shortened dental arch (SDA) before and after restoration with removable partial denture (RPD). MATERIALS AND METHODS: This was a prospective study carried out on 36 consecutive patients. The subjects were asked to chew 5 g of a measured portion of fresh raw carrot for 20 specified numbers of strokes. The raw carrot was recovered into a cup and strained through a standard mesh sieve of 5 mm by 1 mm, it was air dried for 30 min and weighed with FEM digital series weighing scale. The masticatory performance ratio was then determined. RESULT: The age range of the subjects was 34-64 years with the mean age being 52.2 ± 8.2 years. The difference between the total masticatory performance score at the post- and pre-treatment phases was statistically significant (P = 0.001). The improvement in masticatory performance was marked among the younger age groups (P = 0.001), unilateral free end saddle subjects (P = 0.001), and among the male gender (P < 0.05). CONCLUSION: Masticatory performance improved with the provision of RPD. However, the improvement was marked among the younger age groups, unilateral free end saddle subjects, and the male gender; thereby supporting the need for RPDs in patients with SDA.

Objective assessment of mastication predominance in healthy dentate subjects and patients with unilateral posterior missing teeth.

We aimed to investigate mastication predominance in healthy dentate individuals and patients with unilateral posterior missing teeth using objective and subjective methods. The sample comprised 50 healthy dentate individuals (healthy dentate group) and 30 patients with unilateral posterior missing teeth (partially edentulous group). Subjects were asked to freely chew three kinds of test foods (peanuts, beef jerky and chewing gum). Electromyographic activity of the bilateral masseter muscles was recorded. The chewing side (right side or left side) was judged by the level of root mean square electromyographic amplitude. Mastication predominance was then objectively assessed using the mastication predominant score and the mastication predominant index. Self-awareness of mastication predominance was evaluated using a modified visual analogue scale. Mastication predominance scores of the healthy dentate and partially edentulous groups for each test food were analysed. There was a significant difference in the distribution of the mastication predominant index between the two groups (P < 0·05). The mastication predominant score was weakly correlated with self-awareness of mastication predominance in the healthy dentate group, whereas strong correlation was observed in the partially edentulous group (P < 0·05). The results suggest that the individuals with missing unilateral posterior teeth exhibited greater mastication predominance and were more aware of mastication predominance than healthy dentate individuals. Our findings suggest that an objective evaluation of mastication predominance is more precise than a subjective method.

Effect of prosthetic restoration on masticatory function in patients with shortened dental arches: a multicentre study.

The aim of this multicentre study was to investigate the effect of prosthetic restoration for missing posterior teeth on mastication in patients with shortened dental arches (SDAs). Partially dentate patients who had an intact teeth in anterior region and missed distal molar(s) (2-12 missing occlusal units) classified as Kennedy Class I or Class II were recruited from seven university-based dental hospitals in Japan. Of the 125 subjects who underwent baseline (pre-treatment) and follow-up/post-treatment evaluation, 53 chose no replacement of missing teeth and 72 chose treatment with removable partial dentures (n = 53) or implant-supported fixed partial dentures (n = 19). Objective masticatory performance (MP) was evaluated using a gummy jelly test. Perception of chewing ability (CA) was rated using a food intake questionnaire. In the no-treatment group, mean MP and CA scores at baseline were similar to those at follow-up evaluation (P > 0·05). In the treatment group, mean MP after treatment was significantly greater than the pre-treatment mean MP (P < 0·05). However, the mean perceived CA in the treatment groups was similar at pre- and post-treatment (P > 0·05). In a subgroup analysis of subjects in the treatment group, subjects with lower pre-treatment CA showed a significant CA increase after treatment (P = 0·004), but those with higher pre-treatment CA showed a significant decrease in CA (P = 0·001). These results suggest that prosthetic restoration for SDAs may benefit objective masticatory performance in patients needing replacement of missing posterior teeth, but the benefit in subjective chewing ability seems to be limited in subjects with perceived impairment in chewing ability before treatment.

A multifactorial model of masticatory performance: the Suita study.

Previous studies have identified various factors related to masticatory performance. This study was aimed to investigate variations and impacts of factors related to masticatory performance among different occlusal support areas in general urban population in Japan. A total of 1875 Japanese subjects (mean age: 66·7 years) were included in the Suita study. Periodontal status was evaluated using the Community Periodontal Index (CPI). The number of functional teeth and occlusal support areas (OSA) were recorded, and the latter divided into three categories of perfect, decreased and lost OSA based on the Eichner Index. Masticatory performance was determined by means of test gummy jelly. For denture wearers, masticatory performance was measured with the dentures in place. The multiple linear regression analysis showed that, when controlling for other variables, masticatory performance was significantly associated with sex, number of functional teeth, maximum bite force and periodontal status in perfect OSA. Masticatory performance was significantly associated with number of functional teeth, maximum bite force and periodontal status in decreased OSA. In lost OSA, masticatory performance was significantly associated with maximum bite force. Maximum bite force was a factor significantly influencing masticatory performance that was common to all OSA groups. After controlling for possible confounding factors, the number of functional teeth and periodontal status were common factors in the perfect and decreased OSA groups, and only sex was significant in the perfect OSA group. These findings may help in providing dietary guidance to elderly people with tooth loss or periodontal disease.

Oral physiology, nutrition and quality of life in diabetic patients associated or not with hypertension and beta-blockers therapy.

The relationship between type 2 diabetes oral physiology, nutritional intake and quality of life has not been fully elucidated. We assessed the impact of type 2 diabetes - exclusive or associated with hypertension with beta-blockers treatment - on oral physiology, mastication, nutrition and quality of life. This cross-sectional study was performed with 78 complete dentate subjects (15 natural teeth and six masticatory units minimum; without removable or fixed prostheses), divided into three groups: diabetics (DM) (n = 20; 45·4 ± 9·5 years), diabetics with hypertension and receiving beta-blockers treatment (DMH) (n = 19; 41·1 ± 5·1 years) and controls (n = 39; 44·5 ± 11·7 years) matched for gender, age and socioeconomic status. Blood glucose, masticatory performance, swallowing threshold, taste, food intake, stimulated and unstimulated salivary flow, pH and buffering capacity of saliva were assessed. Glycemia was higher in DM than in controls (P < 0·01). No differences were observed between DM and controls for nutrition and quality of life. Both stimulated and unstimulated salivary flow rate were lower in DMH (P < 0·01), which also presented the lowest number of teeth and masticatory units (P < 0·0001), and reduction in the number of chewing cycles (P < 0·01). Controls showed lower Decayed Missing Filled Teeth index (DMFT) scores in comparison with DMH (P = 0·021). Masticatory performance and saliva buffering capacity were similar among groups. Exclusive type 2 diabetes did not alter oral physiology, nutrition or quality of life. However, when hypertension and beta-blockers treatment were associated with diabetes, the salivary flow rate, chewing cycles and number of teeth decreased.

Association between dental status and food diversity among older Japanese.

OBJECTIVE: To investigate the relationship of dental status to food diversity among older Japanese. DESIGN AND SETTING: A community-based cross-sectional study conducted in the town of Tosa, Kochi Prefecture, Japan. METHODS: The study participants were 252 Japanese (84 men and 168 women, average age 81.2 years) and dentate participants were classified into three groups: 1-9 teeth, 10-19 teeth and 20 or more teeth. Food diversity was assessed as a validated measure of dietary quality using the 11-item Food Diversity Score Kyoto (FDSK-11), which evaluates frequency of consumption of 11 main food groups. Multivariable analysis of the differences in FDSK-11 score ranging from 0 to 11, with a higher score indicating greater food diversity, among the three dental status groups was conducted using general linear models. All the performed analyses were stratified by gender. RESULTS: There was no association between dental status and food diversity score in models for men. In contrast, women with ≤ 9 teeth and with 10-19 teeth had significantly lower FDSK-11 scores than women with ≥ 20 teeth after adjusting for confounders (p < 0.001 and p = 0.009, respectively). Additionally, there was a trend toward lower scores for FDSK-11 with fewer teeth (p = 0.001). CONCLUSION: A less varied diet, as indicated by low FDSK-11 score, was observed in female participants with fewer teeth. Tooth loss was associated with poor diet quality among older Japanese women.

The effect of periodontal status and occlusal support on masticatory performance: the Suita study.

AIM: In this study, we investigated the effect of differences in periodontal status in the masticatory performance of dentate subjects with the same occlusal supporting area. MATERIALS AND METHODS: The subjects of the analysis were classified into those of Eichner A1-3 (n = 1094) and Eichner B1-4 (n = 529). Subjects' periodontal status was evaluated on the basis of the Community Periodontal Index (CPI). The number of functional teeth and occlusal support were investigated, the latter on the basis of the Eichner Index. Furthermore, masticatory performance was investigated by means of test gummy jelly. For each group, periodontal status was classified in two different ways, either with/without moderate periodontitis (CPI Code ≤2/≥3) or with/without severe periodontitis (CPI Code ≤3/4), and masticatory performance was compared between the various groups. RESULTS: In subjects who were Eichner A1 and B3, masticatory performance was significantly lower in subjects with moderate periodontitis compared with those without, and in subjects with severe periodontitis compared with those without. CONCLUSION: Periodontal disease affects masticatory performance not only if occlusion is established by natural dentition with no tooth loss but also if occlusal support has decreased.

Implant retainers for free-end removable partial dentures affect mastication and nutrient intake.

OBJECTIVES: This study measured swallowing threshold parameters and nutrient intake in partially dentate subjects rehabilitated by conventional free-end removable partial dentures (RPD) and by RPD over posterior implant retainers and ball attachments (BA). MATERIALS AND METHODS: Eight subjects (two men and six women; mean age 60.1 ± 6.6 years old) received conventional total maxillary dentures and free-end RPD in the mandible. Two months after denture insertion, swallowing threshold and nutrient intake assessments occurred, which included an evaluation of the number of masticatory cycles and medium particle size (X50) of a silicone test material (Optocal). A 3-day food diary verified nutrient intake based on a standard Brazilian Food Composition Table. Then, osseointegrated implants were placed bilaterally in the mandibular first molar region, followed by BA, which was fitted in the RPD bases after healing. After 2 months of the RPD over implants and BA use, variables were again assessed. Wilcoxon signed rank tests evaluated the data (P < 0.05). RESULTS: Masticatory cycles did not differ (P > 0.05); however, subjects showed decreased X50 values at the swallowing moment (P = 0.008) and increased daily energy (P = 0.008), carbohydrate (P = 0.016), protein (P = 0.023), calcium (P = 0.008), fiber (P = 0.016), and iron (P = 0.016) intake with RPD implants and BA inserts. No differences were found in fat consumption (P > 0.05). CONCLUSION: Implants and BA retainers over a free-end RPD resulted in smaller swallowed median particle size and improved nutrient intake.

Maximum bite force following unilateral implant-supported prosthetic treatment: within-subject comparison to opposite dentate side.

Bite force is a significant component of chewing and masticatory function. The literature lacks studies that compare bite force values of implant-supported fixed bridges to natural dentition within same subjects. The objective of the study was to assess maximum occlusal bite force (MBF) among patients with an implant-supported fixed prosthesis and compare it to their opposite dentate side and also to determine the effect of gender, age and Body Mass Index (BMI) on maximum occlusal bite force. Forty patients (20 males and 20 females, mean age = 42.7 ± 9.6 years) with an implant-supported fixed prosthetic rehabilitation on one side and dentate on the other side were recruited into this study. Participants' MBF were measured bilaterally at the first molar region using a digital hydraulic occlusal force gauge (GM10). The measurements were repeated three times (with 45 s intervals between times) for each side, and the highest value of the bite force (MBF) was recorded for each side. The mean MBF was 577.9 N at the implant-supported prosthesis side and 595.1 N at the dentate side. The average MBF was higher at the dentulous side (P < 0.05). Maximum occlusal bite force was higher in males and participants with higher weight and height. However, BMI was not significantly related to MBF values. Maximum occlusal bite force values at the dentate side were slightly (3%) but significantly higher than MBF at implant-supported prosthesis side. Males, taller patients and patients with higher weights had higher MBF values. Body mass index was not significantly related to MBF values.

Influence of posterior dental arch length on brain activity during chewing in patients with mandibular distal extension removable partial dentures.

It is well known that shortened dental arch decreases masticatory function. However, its potential to change brain activity during mastication is unknown. The present study investigates the effect of a shortened posterior dental arch with mandibular removable partial dentures (RPDs) on brain activity during gum chewing. Eleven subjects with missing mandibular molars (mean age, 66.1 years) on both sides received experimental RPDs with interchangeable artificial molars in a crossover trial design. Brain activity during gum chewing with RPDs containing (full dental arch) and lacking artificial molars (shortened dental arch) was measured using functional magnetic resonance imaging. Additionally, masticatory function was evaluated for each dental arch type. Food comminuting and mixing ability and the perceived chewing ability were significantly lower in subjects with a shortened dental arch than those with a full dental arch (P < 0.05). Brain activation during gum chewing with the full dental arch occurred in the middle frontal gyrus, primary sensorimotor cortex extending to the pre-central gyrus, supplementary motor area, putamen, insula and cerebellum. However, middle frontal gyrus activation was not observed during gum chewing with the shortened dental arch. These results suggest that shortened dental arch affects human brain activity in the middle frontal gyrus during gum chewing, and the decreased middle frontal gyrus activation may be associated with decreased masticatory function.

Mastication and jaw motion of partially edentulous patients are affected by different implant-based prostheses.

The main goal of prosthetic treatment is to restore masticatory function. However, insufficient evidence supports the recommendation of one specific prosthetic intervention for partially edentulous patients. Function after the use of three different prostheses by the same partially edentulous subject. Mastication was assessed in 12 subjects (mean age 62.6 ± 7.8 years) after they had used removable partial dentures (RPDs), implant-supported partial dentures (IRPDs) and implant-fixed partial dentures (IFPDs). Masticatory ability (MA) was estimated by visual analogue scale questionnaire, while the mandibular chewing motion was evaluated by kinesiographic device, representing an objective measurement of masticatory function. Data were analysed by repeated-measures anova followed by Tukey-Kramer (P < 0.05). MA improved after IRPD and IFPD use (P < 0.05). Opening, closing and total cycle time duration were reduced after both IRPD and IFPD use (P < 0.05), irrespectively the implant prosthesis type. IFPDs and IRPDs restore the masticatory function of partially edentulous patients better than RPDs.

Occlusal tooth wear in Chinese adults with shortened dental arches.

To assess associations between occlusal tooth wear and shortened dental arches (SDA) in Chinese 40 years and older subjects. From a sample of 1462 urban and rural adults, those presenting with SDA (n = 150) were compared with a control group of 65 randomly selected subjects with complete dentitions (CDA). Occlusal wear was assessed using a modified Smith and Knight index - the occlusal tooth wear index (OWTI) - and analysed using multivariate (logistic) regression. There was no significant effect from SDA on severe occlusal wear (OTWI score 3 or 4: OR = 2.016; 95% CI = 0.960-4.231; P = 0.064). Higher age was associated with severe occlusal wear (P values ≤0.007) and with higher mean OTWI scores; urban had less often severe occlusal wear than rural residents (OR = 0.519; P = 0.008). Higher mean OTWI scores were associated with rural residents, except for anterior teeth. Females had lower mean OTWI score for anterior teeth (effect = -0.153; P = 0.030). Premolars in SDA had higher mean OTWI scores compared with those in CDA (effect = +0.213; P = 0.006). In SDA, more posterior occluding pairs (POPs) were associated with lower mean OTWI sores for anterior teeth (effect: -0.158; P = 0.008) and higher scores for molars (effect: +0.249, P = 0.003). Subjects with SDA or CDA presented comparable occlusal wear, but premolars in SDA tend to have higher probability for having occlusal wear. Fewer numbers of POPs were associated with more wear in anterior teeth.

Influence of implant framework and mandibular flexure on the strain distribution on a Kennedy class II mandible restored with a long-span implant fixed restoration: a pilot study.

STATEMENT OF PROBLEM: The human mandible flexes during different jaw movements. Mandibular flexure is known to be restricted when natural dentition is restored with long-span fixed prostheses, but its effect on implant-supported fixed prostheses is unknown. Restriction of mandibular movement by implant-supported fixed prostheses may lead to excess strain accumulation, which could affect the outcome of implant treatment. PURPOSE: The purpose of this study was to investigate the influence of mandibular flexure on the implant bone interface by measuring the strain distribution in the body of the mandible at the periimplant level and at the implant framework level during the unilateral loading of a long-span implant-supported fixed prosthesis. MATERIAL AND METHODS: A partially edentulous mandible model with the mandibular left premolars and molars missing was fabricated in epoxy resin. Two implants were placed in the edentulous area, one in the position of the first premolar and one in the position of the second molar. Strain gauges were cemented at the implant bone interface parallel to each implant on the body of the mandible and on the framework. Three screw-retained, 3 × 3-mm bar-shaped frameworks were cast from cobalt-chromium alloy. The fit of these frameworks was deemed clinically acceptable with a routine clinical assessment technique. The mandible model was suspended by elastic cords to a universal testing machine. A 50-N load cell was placed on the occlusal surface of the right first molar. The mandible model was then loaded to 50 N on the working side first without any framework and then a second time with the framework in place. Information from the strain gauges were collected with a computer for analysis. RESULTS: When the mandible model was loaded without the implant framework, the buccal aspect of the body of the mandible experienced mainly compression, whereas the lingual aspect was mainly in tension on the working side under unilateral loading. At the implant-bone interface, compression strain was detected on the mesial aspect of the mesial implant. When frameworks were placed and a unilateral load applied, compression was detected on the mesial and buccal aspect of the mesial implant with all 3 frameworks. The amount of strain recorded was higher than that recorded without any framework in place. CONCLUSIONS: Mandibular flexure occurred during unilateral loading. The amount of strain transmitted to the implants increased with the screw-retained fixed-implant frameworks in place. The amount of strain introduced by mandibular flexure under unilateral loading may not be enough to stimulate bone remodeling; however, the accumulative strain generated by mandibular flexure under cyclic loading and its relationship with bone remodeling is unclear.

Tooth displacement in shortened dental arches: a three-dimensional finite element study.

STATEMENT OF PROBLEM: Some patients may opt for a prosthetic rehabilitation without replacing all missing teeth, finishing treatment with a reduced dental arch. This choice may be due to biologic reasons or financial restrictions. It is unclear if a reduced dental arch functions as well as a complete dental arch. PURPOSE: The purpose of this study was to analyze whether shortened dental arches could result in tooth displacement. MATERIAL AND METHODS: Four different 3-dimensional maxillary and mandibular arches with different levels of arch length reduction were created. In all models, anatomic structures that represent the temporomandibular joint, cortical and cancellous bone, enamel, dentin, and periodontal ligament were modeled. Mechanical properties were attributed to each anatomic component, and a total occlusal load of 100 N on masseter, temporal, and medial pterygoid muscles was simulated for each model. The MSC. Patran software was used for the preprocessing and postprocessing of the biomechanical analysis of the models. One complete dental arch was used as the control. RESULTS: The simulations showed that shortened dental arches presented greater tooth displacements than those found in a complete dental arch. The changes in mandibular tooth position were greater than those observed in the maxillary arches. In finite element models 1 and 2, the largest maxillary displacements were found for posterior teeth. CONCLUSIONS: Decreasing numbers of occlusal units resulted in increasing amounts of displacements of the remaining teeth, which may compromise dental stability in patients with shortened dental arches.

Finite element analysis of an implant-assisted removable partial denture during bilateral loading: occlusal rests position.

STATEMENT OF PROBLEM: When implants are incorporated into an existing partial removable dental prosthesis, the acrylic resin base can fracture. It is therefore essential to study the mechanical behavior of partial removable dental prostheses by using stress and deformation analysis. PURPOSE: The purpose of this study was to analyze the effect of the occlusal rest position on the implant-assisted partial removable dental prosthesis by finite element analysis. MATERIAL AND METHODS: A Faro Arm scan was used to extract the geometrical data of a human partially edentulous mandible. A standard plus regular neck (4.8×12 mm) implant and titanium matrix, tooth roots, and periodontal ligaments were modeled by using a combination of reverse engineering in Rapidform XOR2 and solid modeling with the Solid Works CAD program. The model incorporated a partial removable dental prosthesis and was loaded with standard bilateral forces. A uniform pressure was applied on the occlusal surface so as to generate an equivalent net force of 120 N for both the left and right prosthesis. The finite element analysis program ANSYS Workbench was used to analyze the stress and strain distributions in the implant-assisted partial removable dental prosthesis. RESULTS: Maximum stresses were significantly high for the metal framework compared to the acrylic resin surface, and these stresses were different for the mesial and distal arm designs. The maximum stress in the metal framework for the mesial arm design was 614.9 MPa, and it was 796.4 MPa for the distal arm design. The corresponding stresses in the acrylic resin surface were 10.6 and 8.6 MPa. CONCLUSIONS: Within the limitation of this study, it was found that moving the position of the occlusal rest from the mesial to distal side of the abutment teeth improved the stress distribution in the metal framework and acrylic resin denture base structures.

The reliability of computerized condylar path angle assessment.

Recording the track of the mandibular hinge axis and consequently ascertaining the posterior determinants is one of the key requirements for accurately simulating individual oral conditions in the (virtual) articulator. The aim of this study was to determine the reliability of computerized condylar path inclination angle (CPIA) measures and to assess whether the reliability depends on the mandibular dentition. Sagittal and transverse CPIA were measured using computerized axiography (Cadiax Compact 2) at two separate sessions in prosthodontic patients (mean age +/- SD: 64.3 +/- 10.3 years; female: 45%) who were classified into three dentition categories (fully dentate: N = 19, partially dentate: N = 27 and edentulous: N = 19). These measurements were repeated three times at both sessions without removing the computerized axiograph. Reliability was assessed in multilevel analyses using the subject as a grouping variable in linear random-intercept models. Considering all assessment procedures, the patient-specific differences explained 75% of the variance for the sagittal and 38% for the transverse condylar path. This corresponds to the overall reliability of both the sagittal and the transverse CPIA assessment. The dentition had no significant impact on the reliability of the measurements. The sagittal CPIA can be assessed with satisfactory reliability using computerized axiography. It is independent of the status of the dentition, which has no statistically significant impact on the measures. Transverse CPIA measurements have shown poor reliability. Therefore, the electronic determination of the sagittal CPIA is a reliable procedure that can be applied in patients irrespective of the status of the mandibular dentition.