Evaluation of the occlusion vertical dimension of complete dentures after microwave disinfection

doi: 10.1111/j.1741‐2358.2011.00567.x Evaluation of the occlusion vertical dimension of complete dentures after microwave disinfection Objectives: An increase in occlusal vertical dimension (OVD) after microwave disinfection may result in the need for adjustments in the complete dentures. This in vitro study evaluated the increase in OVD of maxillary complete dentures submitted to microwave disinfection protocols. Material and methods: Thirty sets of complete dentures were evaluated as follows: Group 1–15 sets had the maxillary complete dentures submitted to microwave disinfection (650 W/3 min), once a week, for 4 weeks. Group 2–15 sets had the maxillary complete dentures submitted to microwave disinfection (650 W/3 min), three times a week, for 4 weeks. The vertical dimension was measured with a micrometre (in mm) before disinfection protocols (baseline readings) and after each week of disinfection. Data were analysed using Wilcoxon and Friedman tests (α = 0.05). Results: For Group 1, no significant difference was found between the increases in OVD and zero, and no significant difference was found between the weeks. For Group 2, the increases in OVD were significantly greater than zero, and the Friedman test showed that weeks 3 and 4 had significantly greater changes than week 1 and that week 4 had significantly greater change than week 2. Conclusion: Microwave disinfection only promoted significant increase in OVD in Group 2, in which the values increased progressively.     

Reliability and comparison of two facial measurements to detect changes of occlusal vertical dimension in complete denture wearers

Gerodontology 2010; doi: 10.1111/j.1741‐2358.2009.00353.x
Reliability and comparison of two facial measurements to detect changes of occlusal vertical dimension in complete denture wearers Background: Facial measurements are frequently used to determine OVD. However, the reliability of neither the method nor the chosen landmarks has been cleared yet. Objective: This study compares the reliability of two facial measurements, subnasal (SN) to chin (C) and tip of the nose (TN) to C, for determining occlusal vertical dimension (OVD). Materials and methods: Thirty edentulous subjects with adequate neuromuscular co‐ordination, without signs and symptoms of temporomandibular disorders and who had been wearing complete dentures for at least 5 years were enrolled. A modified central bearing device was used to alter the OVD and facial measurements were made with a digital caliper. Student’s t‐test was used to compare the two measurements. Interobserver and intraobserver reliability were evaluated with Spearman’s rho correlation test. Results: TN–C distance had an improved correlation with the changes in intraoral alterations than SN–C distance. While the means of the changes in facial measurements were in good agreement with the intraoral alterations, the ranges were wide. Both interobserver and intraobserver reliability of the measurements were high. Conclusion: While facial measurement is not a good predictor of OVD, TN–C distance appears to be more reliable than SN–C distance.     

Predicting vertical dimension with cephalograms, for edentulous patients

Objectives: To provide information on vertical dimension (VD), occlusal plane (OP), and size of future occlusal rims, through lateral Rx and cephalometric tracings that analyse and compare hard and soft tissue. To show that these measures are compatible with methods routinely used to prescribe for full. Design: Ten patients age range 53–81. Lateral Rx, with and without dentures, were taken and traced cephalograms were used to compare hard and soft tissue angles and planes. Main outcome measures: Based on three cephalometric analyses: Rickets, and McNamara for skeletal, and Legan‐Burstone for soft tissue, to identify the following landmarks: 13 skeletal points: N, ANS, PNS, Me, Xi, Pm, FC, Or, Po, A, B, Co, Gn and four soft tissue points: G, Gv, Sn, Me′; seven skeletal planes: HP, FP, NF, N‐ANS‐Me, A‐B, ANS‐Me, Co‐Gn, and three soft tissue planes: G‐Sn, Sn‐Me′, Sn‐Gv, and six angles: N‐FC‐A, ANS‐Xi‐Pm, 1 NF, 1MP, 6 NF, interincisor angle. Results: Stability in skeletal VD was observed with the proportion of 0.8 ± 0.2 being present, between the middle third and lower third facial heights, N‐ANS/ANS‐Me. In addition, soft tissue proportion remained near 1, G‐Sn,/Sn‐Me. The length and position of first upper molar, upper and lower incisors were used to predict the OP. When compared with cephalograms of the same patient with dentures, similar measurements were observed. Conclusions: It was possible to provide information on skeletal, facial proportions, VD, OP, and rim size using cephalograms for edentulous patients.     

Cast titanium overlay denture for a geriatric patient with a reduced vertical dimension

An older patient reporting to the dental surgery for his/her dental treatment is becoming a common occurrence. Improved oral hygiene has meant that teeth are retained for a longer time, along with the potential problems of attrition, decreased vertical dimension, temporomandibular joint discomfort/strain, and poor aesthetics. The case in question is that of a 65-year-old male patient who had severe attrition in the lower arch, temporomandibular joint pain and reduced vertical dimension. The maxillary arch had previously been restored with a fixed partial prosthesis. For restoration of the lower teeth, a removable cast titanium overlay denture was fabricated incorporating an increased vertical dimension. Porcelain facings were placed to restore the aesthetics of the anterior teeth. The titanium was cast in a semi-automatic electric arc, pressure type casting machine. A titanium overlay denture with porcelain facing on the anterior teeth may provide a means of restoring a patient's concerns regarding aesthetics and function.     

Maxillary complete denture movement during chewing in mandibular removable partial denture wearers

Objectives: To evaluate the pattern of maxillary complete denture movement during chewing for free‐end removable partial dentures (RPD) wearers, compared to maxillary and mandibular complete denture wearers. Materials and methods: Eighteen edentulous participants (group I) and 10 volunteers with bilateral posterior edentulous mandibles (group II) comprised the sample. Measures of mean denture movement and its variability were obtained by a kinesiographic instrument K6‐I Diagnostic System, during the mastication of bread and a polysulphide block. Data were analysed using two‐way anova (α = 0.05). Results: Upper movement during chewing was significantly lower for group II, regardless of the test food. The test food did not influence the vertical or lateral position of the denture bases, but more anterior dislocation was found when polysulphide blocks were chewed. Group II presented lower intra‐individual variability for the vertical axis. Vertical displacement was also more precise with bread as a test food. Conclusion: It can be concluded that mandibular free‐end RPD wearers show smaller and more precise movements than mandibular complete denture wearers.     

The influence of double flask investing on tooth displacement in dentures processed by microwave irradiation

doi: 10.1111/j.1741‐2358.2011.00587.x The influence of double flask investing on tooth displacement in dentures processed by microwave irradiation Objective: This study evaluated the influence of the bimaxillary flask (BMF) and two different investing materials on first molar inclination in dentures processed by microwave irradiation. Background: The BMF may minimise tooth displacement, saving time and improving occlusion. Methods and materials: Forty pairs of dentures were randomised into four groups: stone wall in monomaxillary flask; silicone wall in BMF; stone wall in BMF; acrylic resin retentions and silicone in BMF. Dentures were processed by microwave irradiation. Two referential points were established on tooth surface. A microscope and a digital pachymeter were used to measure the distance between these points, and the angles α (right maxillary molar), β (left maxillary molar), α′ (right mandibular molar) and β′ (left mandibular molar) were calculated by the law of cosines. Data were submitted to Kruskal–Wallis (5% significance). Results: No difference was observed among the groups (p > 0.05). In the intra‐group analysis, α was significantly different for groups I, II and III; α′, for groups II and IV; β, for all groups; β′, for groups III and IV. Conclusion: First molar inclination was similar for monomaxillary and BMFs. The use of stone or silicone as investing materials presented the same effect on tooth inclination.     

The influence of implant number and attachment type on maximum bite force of mandibular overdentures: a retrospective study

doi: 10.1111/j.1741‐2358.2010.00421.x
The influence of implant number and attachment type on maximum bite force of mandibular overdentures: a retrospective study Aim: Assessment of the influence of such factors as attachment type, number of implants, gender and age of patients on maximum bite force (MBF). Material and methods: Sixty‐two edentulous patients (32 females, 30 males; aged 64.03 ± 10.07 years, range 42–90 years) with mandibular implant overdentures with various attachment types were included in the study and their MBFs were recorded. The results were evaluated statistically at a significance level of p < 0.05. Results: The MBF in male patients was found to be statistically significantly (p < 0.05) higher than in female patients. No statistically significant differences (p > 0.05) were found with respect to age groups, attachment types and number of implants supporting the mandibular overdentures. Conclusion: Within the limitations of this study, it is concluded that independent of the number applied, dental implants increase MBF in edentulous patients. While males show higher bite force, patient age and attachment type seem not to play an important role.     

Patient ratings of chewing ability from a randomised crossover trial: lingualised vs. first premolar/canine-guided occlusion for complete dentures

Background: Complex procedures involving a facebow transfer and the use of lingualised teeth are deemed to have a positive influence on the chewing ability with complete dentures. Objectives: To determine if patients’ ratings of their ability to chew depend on the method of complete denture fabrication. Methods: Edentulous patients (n = 20) participated in a within‐subject crossover trial. Each patient received two sets of new complete dentures. One pair was manufactured based on intraoral tracing of centric relation and facebow transfer; semi‐anatomical teeth with lingualised occlusion denture (LOD) were chosen. The second pair was made using a simplified procedure without facebow transfer; jaw relations were recorded with wax occlusion rims, and anatomical teeth with a first premolar/canine‐guidance (CGD) were selected. The dentures were delivered in randomised order, and each was worn for 3 months. Three months after delivery, patients’ ratings of each new prosthesis were recorded on visual analogue scales for their ability to chew seven index foods. Repeated measurements analysis of variance was performed to investigate possible carry‐over effects accounting for confounding by treatment period. Results: When comparing the two treatments, participants rated their ability to chew in general, to masticate carrots, hard sausage, steak and raw apple in particular, was significantly better with the CGD (anatomical teeth) than with the LOD (p < 0.05). Conclusion: Comprehensive methods for the fabrication of complete dentures including semi‐anatomical lingualised teeth and a full registration do not seem to influence the perceived chewing ability, when compared with more simple procedures. Chewing ability for tough foods appears to benefit from the use of anatomical teeth.     

A study on oral rehabilitation in stroke patients: analysis of a group of 33 patients

doi:10.1111/j.1741‐2358.2009.00322.x
A study on oral rehabilitation in stroke patients: analysis of a group of 33 patients Background: Stroke is the third leading cause of death in the world after cardiovascular disease and cancer. This study aimed to investigate the oro‐dental status and removable denture conditions in stroke survivors. Methods: At the Department of Vascular Disease of the Neurological Clinic of the Polyclinic Hospital of Bari, from January 2003 to May 2008, 189 consecutive patients were examined who had had a stroke, to select removable denture wearers. The oro‐dental examination was performed in a period between 12 and 60 months after the stroke and among these 189 patients, 60 were wearing a removable denture, but only 33 participated in our research. All the patients gave written informed consent. Results: It was observed that in 42.4%, removable dentures needed to be remade, in 27.3%, they needed to be rebased and in 30.3%, they were adequate. Conclusion: The role of oral health providers is fundamental in order to maintain good oral health and to avoid oral diseases in stroke patients. They should, indeed, monitor these patients with a regular follow‐up after 1 month and every 3–4 months.     

Electromyographic evaluation of masseter and anterior temporalis muscles in rest position of edentulous patients with temporomandibular disorders, before and after using complete dentures with sliding plates

Objectives: This study was performed with the purpose of investigating electromyographic (EMG) activity of the anterior temporalis and masseter muscles in edentulous individuals with temporomandibular disorder (TMD), before and after using sliding plates on complete dentures in the mandibular rest position. Background: Edentulous patients may present TMD, which is characterised by pain in temporomandibular joints, masticatory and neck muscles, uncoordinated and limited mandible movements, joint sounds and an altered occlusal relationship. It is imperative to offer treatment in order to re‐establish stomatognathic system structures before submitting the individual to any definitive restorative treatment. Materials and methods: The patients were edentulous for at least 10 years. EMG recordings were made before the insertion of the dentures (0 months) and also after using the sliding plates at the fourth month, 9th month and 12th month, using computerised electromyography K6‐I/ EMG Light Channel Surface. EMG evaluations of the muscles were performed under the following clinical conditions: rest position with dentures (R1), rest position without dentures (R2), rest position with dentures post‐activity (chewing) (R3), rest position without dentures post‐activity (chewing) (R4). Results: All patients obtained remission of muscular fatigue and reduced pain in stomatognathic system structures. Temporalis muscle showed significant increase in EMG activity compared with initial values (p < 0.01). Masseter muscles showed significantly lower mean values (p < 0.01) compared with initial values. Conclusion: The sliding plates allowed the process of neuromuscular deprogramming, contributing to muscular balance of the masticatory system, and are therefore indicated to be used before the fabrication of definitive complete dentures in patients with TMD.     

A study of occlusion in elderly Japanese over 80 years with at least 20 teeth

Objectives: The purpose of this study was to identify the occlusal status of elderly Japanese over 80 years with at least 20 teeth. Materials and methods: The study enrolled 76 elderly Japanese (44 male, 32 female) with a mean age of 82 years and an average of 25.7 remaining teeth. The study consisted of intra‐oral examination, intra‐oral and facial photographs, radiographs and impressions for study casts. Results: No gender difference was observed in age or number of remaining teeth. Anteroposterior occlusal relationship was characterised by maxillary protrusion in 67.6%, acceptable overjet in 31.0%, and anterior crossbite in 1.4%. Vertically, deep bite was noted in 33.8%, acceptable overbite in 64.8%, and open bite in 1.4%. Most of the subjects had either Angle class I (68.4%) or class II (25.7%) canine relationship. Only 3.9% of the subjects had upper anterior crowding. Lower anterior crowding was observed in 23.7%, but tended not to be severe. Conclusion: These results indicate that Japanese who attained the goal of ‘8020’ have a relatively good occlusion.     

Comparison between complete denture and implant‐retained overdenture: effect of different mucosa thickness and resiliency on stress distribution

Background: The effect of different mucosa characteristics on stress distribution of complete dentures and overdentures remains unknown. Objective: The aim of this study was to evaluate the effect of different mucosa thickness and resiliency on the stress distribution of complete dentures and implant‐retained overdentures using a two‐dimensional finite element analysis. Material and methods: Representative models of the edentulous mandible were constructed on AutoCAD software according to the groups’ characteristics. In group CD, a model of the edentulous mandible supporting a complete denture was obtained while in group IO, a model of edentulous mandible supporting an overdenture over two unsplinted implants with an o’ ring system was constructed. In each group, mucosa assumed three characteristics of thickness (1, 3 and 5 mm) corresponding to the resiliencies hard, resilient and soft respectively. Evaluation was performed on Ansys software with 100N vertical load applied on central incisor teeth. The principal stress was used as analysis criteria. Results: Group IO showed higher stress values than group CD regardless of mucosal thickness and resiliency. Stress decreased at the supporting tissues in both groups as the thickness and resiliency of mucosa increased. In relation to the supporting tissues, cortical bone showed the highest stress values. Conclusion: It was concluded that the use of an attachment system increases stress values and the thickness and resiliency of mucosa influence more on these values.     

Influence of connection type on the biomechanical behavior of distal extension mandibular removable partial dentures supported by implants and natural teeth

Few studies are performed to evaluate the influence of connection type on the stress distribution of distal extension mandibular removable partial dentures (RPDs) supported by both implants and natural teeth. In this study, five three-dimensional finite element models were prepared to simulate mandibular bilateral partially edentulous arches. Four were RPDs supported by both implants and natural teeth, and the other one was RPDs supported only by natural teeth. The maximum equivalent (EQV) stress values of bone around implants, the abutments, and the mucosa displacements of the related supporting structures were measured. It was found that a non-rigid telescopic coping was more favorable to protect the implant than a rigid telescopic coping. Compared with other connection types, the easy resilient attachment (ERA) system seemed to be effective to associate implant without complications. However, the results obtained in the present study should be cautiously interpreted in the clinic.     

Assessment of changes in oral health‐related quality of life among patients with complete denture before and 1 month post‐insertion using Geriatric Oral Health Assessment Index

doi:10.1111/j.1741‐2358.2009.00323.x
Assessment of changes in oral health‐related quality of life among patients with complete denture before and 1 month post‐insertion using Geriatric Oral Health Assessment Index Objective: Geriatric Oral Health Assessment Index (GOHAI) is a 12‐item measure of “patient‐reported oral functional problems” intended for use in the assessment of the effectiveness of dental treatment. Design and Setting: As there is scanty literature available on GOHAI in the Indian population, the present study was undertaken to assess the changes in GOHAI before and 1 month after placement of dentures in completely edentulous patients reporting to a dental hospital at Indore, India. Measurements: The GOHAI questionnaire was completed by the examiner who interviewed the patients (n = 35) before placement of complete dentures and 1 month later. Mean, median values were calculated and the data were analysed using Wilcoxon signed‐rank test. Results: When overall mean was considered, the GOHAI scores increased from 27.48 to 30.19 (p = 0.002; highly significant). Conclusion: Patients reported improvement in functional changes after placement of complete dentures.     

Stress analysis of a complete maxillary denture under various drop impact conditions: a 3D finite element study

Complete maxillary dentures are one of the most economic and easy ways of treatment for edentulous patients and are still widely used. However, their survival rate is slightly above three years. It is presumed that the failure reasons are not only due to normal fatigue but also emerge from damage based on unavoidable improper usage. Failure types other than long-term fatigue, such as over-deforming, also influence the effective life span of dentures. A hypothesis is presumed, stating that the premature/unexpected failures may be initiated by impact on dentures, which can be related to dropping them on the ground or other effects such as biting crispy food. Thus, the behavior of a complete maxillary denture under impact loading due to drop on a rigid surface was investigated using the finite element method utilizing explicit time integration and a rate-sensitive elastoplastic material model of polymethylmethacrylate (PMMA). Local permanent deformations have been observed along with an emphasis on frenulum region of the denture, regardless of the point of impact. Contact stresses at the tooth–denture base were also investigated. The spread of energy within the structure via wave propagation is seen to play a critical role in this fact. Stress-wave propagation is also seen to be an important factor that decreases the denture's fatigue life.     

A twin study of dental dimension. I. Discordance,asymmetry, and mirror imagery

Bilateral tooth measurements in twins were partitioned into three orthogonal contrasts, each associated with one degree of freedom, to estimate three parameters: discordance, asymmetry, and mirror imagery. The probability levels of the within-pair variance ratios were used to test for significance of these estimates. The results provided strong evidences for the existence of significant genetic determinants of almost all of the individual tooth dimensions, but little or no evidence for a genetic basis of asymmetry. The analysis gave no indication that monozygotic twinning was associated with an increased degree of either fluctuating asymmetry or mirror imagery, when compared to dizygotic twins. The data on monozygotic twins further suggested that for most variables examined, the increment of environmental discordance resulting from the twinning phenomena was greater than the developmental noise that caused asymmetry within individual cotwins.     

FE study of bone quality effect on load-carrying ability of dental implants

Extreme stresses in surrounding bone are among the most important reasons for implant failure. Bone density (quality) is a variable that plays a decisive role in achieving predictable osseointegration and long-term survival of implants. The magnitudes of ultimate occlusal load, which generate ultimate von Mises stress at the critical point of peri-implant area for the spectrum of implants inserted into mandible with four different bone qualities (Lekholm and Zarb classification), were calculated. Geometric models of mandible segment were generated from computed tomography images and analysed with osseointegrated cylindrical implants of various dimensions. Occlusal loads were applied in their natural direction. All materials were assumed to be linearly elastic and isotropic. The investigation suggests that an implant's ultimate occlusal load indicates its load-carrying capacity. As a result, bone loss can be predicted, and viable implants can be selected by comparing the values of their ultimate occlusal load in different clinical conditions.