Trial data for precision analysis of a three-dimensional mandibular mechanical advantage.

The data presented in this manuscript describe craniofacial landmark coordinate values, muscle and load moment arm lengths, and mechanical advantage rates for constructing a three-dimensional model of masticatory muscles. Cone-beam computed tomography scans from 30 subjects (aged 12-19 years, 16 females) were used. Thirty-six craniofacial landmarks were identified. Subsequently, the moment arms for 7 muscles and their corresponding load moment arms at incisor and molar positions were determined. Then, the three-dimensional mechanical advantage for each muscle and tooth position was calculated as the ratio of muscle moment arm to load moment arm. This procedure was repeated three times by a main examiner and once by two other examiners. The Friedman test and the square root of the 'method of moments' variance estimator were used to compare data among examiners and calculate random errors, respectively. Although the values for the craniofacial landmark coordinates and biomechanical variables are very close, differences were found between measurements, especially in the interexaminer comparisons. Values served as the basis for reliability (intraclass correlation coefficient) and errors (average mean of absolute differences) analysis in the research paper titled "A three-dimensional method to calculate mechanical advantage in mandibular function: Intra- and interexaminer reliability study," published in the Journal of Orofacial Orthopedics.

Self-perceived oral health: a study with patients wearing removable dentures

Aim: This study aimed to investigate the relationship between self-perceived oral health and the prosthetic status of individuals who seek care in prosthodontics clinics. Methods: Self-perceived oral health was analyzed through the Geriatric Oral Health Assessment Index (GOHAI). Abutment tooth mobility was assessed, and denture status was determined by clinical assessment of stability, retention, occlusal balance, vertical dimension, and integrity of dentures. The frequency of individuals in each variable was determined for the low and very low GOHAI conditions. Chi-square, Pearson, and stepwise logistic regression tests were used for the statistical analyses (α = 0.05). Results: Ninety wearers of removable dentures with a mean age of 55.1±9.1 years were evaluated. None of the variables was related to GOHAI values (p > 0.05). The regression analysis showed that age predicts (p = 0.006) the variation of GOHAI conditions (OR = 0.924, CI = 0.873- 0.978), showing only 7.6% protective effect against very low GOHAI. Unsatisfactory stability showed the opposite effect (p = 0.034) and the individuals with this characteristic are more likely (OR = 3.055) to have very low GOHAI scores (CI = 1.085- 8.602). Conclusions: The self-perceived oral health of wearers of removable dentures worsens with age and unsatisfactory stability of dentures

A three-dimensional method to calculate mechanical advantage in mandibular function : Intra- and interexaminer reliability study.

PURPOSE: Masticatory muscles are physically affected by several skeletal features. The muscle performance depends on muscle size, intrinsic strength, fiber direction, moment arm, and neuromuscular control. To date, for the masticatory apparatus, only a two-dimensional cephalometric method for assessing the mechanical advantage, which is a measure for the ratio of the output force to the input force in a system, is available. This study determined the reliability and errors of a three-dimensional (3D) mechanical advantage calculation for the masticatory system. METHODS: Using cone-beam computed tomography images from teenage patients undergoing orthodontic treatments, 36 craniofacial landmarks were identified, and the moment arms for seven muscles and their load moment arms (biomechanical variables) were determined. The 3D mechanical advantage for each muscle was calculated. This procedure was repeated by three examiners. Reliability was verified using the intraclass correlation coefficient (ICC) and the errors by calculating the absolute differences, variance estimator and coefficient of variation (CV). RESULTS: Landmark coordinates demonstrated excellent intra- and interexaminer reliability (ICC 0.998-1.000; p < 0.0001). Intraexaminer data showed errors < 1.5 mm. Unsatisfactory interexaminer errors ranged from 1.51-5.83 mm. All biomechanical variables presented excellent intraexaminer reliability (ICC 0.919-1.000, p < 0.0001; CV < 7%). Interexaminer results were almost excellent, but with lower values (ICC 0.750-1.000, p < 0.0001; CV < 10%). However, the muscle moment arm and 3D mechanical advantage of the lateral pterygoid muscles had ICCs < 0.500 (p < 0.05) and CV < 30%. Intra- and interexaminer errors were ≤ 0.01 and ≤ 0.05, respectively. CONCLUSIONS: Both landmarks and biomechanical variables showed high reliability and acceptable errors. The proposed method is viable for the 3D mechanical advantage measure.

Evaluation of the intaglio surface shape of implant-supported complete-arch maxillary prostheses and its association with biological complications: An analytical cross-sectional study.

STATEMENT OF PROBLEM: Whether the shape of the intaglio surface of fixed implant-supported maxillary prostheses is associated with the occurrence of biological is unclear. PURPOSE: The purpose of this cross-sectional study was to evaluate the shape (convex or concave) of the intaglio surface of complete-arch implant-supported maxillary fixed prostheses and to assess the association with biofilm accumulation, hyperemia, bone loss, and patient satisfaction. MATERIAL AND METHODS: Study participants consisted of 56 individuals with fixed complete implant-supported maxillary prosthesis attending follow-up appointments. The 56 prostheses supported by 388 implants had been in place for an average of 5.5 years (range 1-14 years). The intaglio surface was divided into areas corresponding to the cantilever regions and between implants (n=442) and was assessed for shape (concave or convex) and biofilm index (0 to 3). Tissue hyperemia (redness) was assessed as absent or present. Bone loss (mm) was measured from digital periapical radiographs by 2 calibrated evaluators (kappa=94.9%). Study participant satisfaction was investigated by using a visual analog scale. Association assessments (α=.05) between the shape of each area and all these parameters were performed with the Friedman, linear regression, and logistic regression tests. RESULTS: Of the analyzed areas, 58 (13.1%) were concave, and 384 (86.9%) were convex. Biofilm was absent on 3.5% of the concave and 5.5% of the convex areas. Biofilm was detectable with a probe on 12% of the concave and 22.4% of the convex areas and clinically visible in 58.6% of the concave and 57.8% of the convex areas. Abundant biofilm was seen in 25.9% of the concave and 14.3% of the convex areas and was associated with hyperemia (P=.003). A statistically significant association was found between the shape and biofilm accumulation (P=.009). Hyperemia was present in 199 (45%) areas. The association analysis between the shape of the area and the presence of hyperemia was not significant (P>.05). The mean bone loss was 0.71 mm (0.91 mm). Implants placed near concave areas underwent greater bone loss (P=.001). Study participants reported a high level of satisfaction with the esthetics, mastication, speech, and smile provided by the prosthesis, with satisfaction scores ranging between 8.46 and 8.77. However, in relation to ease of cleaning, only 19.6% were fully satisfied. CONCLUSIONS: The shape of the intaglio surface of prostheses influenced the occurrence of biofilm accumulation and bone loss, and concave areas showed greater biofilm accumulation and bone resorption. High rates of satisfaction with treatment were identified.

Effect of potentially chromogenic beverages on shear bond strength of acrylic denture teeth to heat-polymerized denture base resins.

BACKGROUND: Detachment of denture acrylic resin artificial teeth from denture base resin is one of the most common problems presented by denture wearers. PURPOSE: This study investigated the shear bond strength (SBS) and fracture type of bonding interface of two commercial acrylic teeth (Vipi Dent Plus e Biolux) to two denture base resins (Vipi Cril e Lucitone 550) after immersion in potentially chromogenic beverages (coffee, cola soft drink, and red wine) or control solution (distilled water). MATERIALS AND METHODS: Maxillary central incisor acrylic teeth were placed at 45° to denture base resin and submitted to short polymerization cycle according to manufacturers. Specimens were divided according to the combination tooth/resin/solution (n = 8) and submitted to bond strength tests in a universal testing machine MTS-810 (0.5 mm/min). Subsequently, fracture area was analyzed by stereomicroscope at a magnification of ×10 and categorized into adhesive, cohesive, or mixed failure. RESULTS: The bond strength of teeth/denture base resins interface was not significantly affected by tested solutions (P > 0.087), except for Biolux teeth immersed in coffee (P < 0.01). In all conditions, the Vipi Dent Plus teeth showed higher bond strength to Lucitone and Vipi Cril resins when compared to Biolux teeth (P < 0.003). All specimens' failure modes were cohesive. CONCLUSIONS: The SBS of acrylic teeth to denture base resins was not generally influenced by immersion in the tested staining beverages.

O uso da aprendizagem baseada em problemas na Odontologia: uma revisão crítica da literatura / Problem-Based Learning in Dentistry: a critical literature review

A sociedade contemporânea impõe desafios constantes aos setores da saúde e da educação, alicerçada em revisões e reformulações permanentes para formação de recursos humanos. Este artigo promove uma revisão crítica da literatura a respeito da aprendizagem baseada em problemas (Problem Based Learnig - PBL) direcionada ao ensino da Odontologia. As bases de dados consultadas foram Medline (via EBSCO), SCIELO, BBO e LILACS (via BVS). As palavras-chave foram definidas baseadas em artigos previamente selecionados. Esta metodologia se apresenta como uma alternativa para formação e educação em Odontologia. É considerada uma ferramenta de trabalho para professores que buscam desenvolver em seus alunos capacidades cognitivas promotoras do desenvolvimento do raciocínio clínico integrado, com perfil direcionado à educação permanente (AU).

Contemporary society imposes constant challenges in the areas of health and education, founded on permanent revisions and redesigns for training. This article promotes a critical review of the literature on problem-based learning (PBL) directed to the teaching of Dentistry. Data bases consulted were Medline (via EBSCO), SCIELO, BBO and LILACS (BVS). The keywords have been defined based on previously selected articles. The PBL is presented as an alternative methodology for training and education in Dentistry. It isconsidered a working tool for teachers seeking to develop in their students cognitive skills promoting the development of integrated clinical reasoning with the continuing education directed profile (AU).

Overlay removable partial denture as temporary restoration of vertical dimension of occlusion in a bruxist patient / Overlay removível como tratamento provisório para restabelecimento da dimensão vertical de oclusão de paciente bruxista

The reestablishment of the vertical dimension of occlusion is an important phase during prosthodontics treatment. Its reduction can be a consequence of severe bruxism, and patient rehabilitation requires complex, expensive, and long treatments. In this context, an overlay removable partial denture is a viable alternative, as it represents a simple manufactured reversible treatment. As a temporary treatment, it does not require tooth wear, reestablishes vertical dimension of occlusion, and allows the patient to adapt to this new dimension until the definitive rehabilitation treatment can be planned and finished. This case report describes the temporary rehabilitation of a maxillary complete edentulous bruxist patient with excessive tooth wear on his lower jaw, seeking treatment at the Removable Prosthodontics Department at State University of Ponta Grossa to replace his upper complete denture. A new complete denture was made ​​and the implementation of an overlay removable partial denture was proposed to be made to the lower arch, which provided aesthetics and function to the patient until the completion of the definitive work. The patient was instructed and guided about the causal factors and consequences of his parafunctional habit and was taught methods for self-perception to control frequency. For the final rehabilitation, ​​a new maxillary complete denture with metal occlusal surfaces will be made as well as metaloceramic crowns with metal occlusal using intraradicular retention with cast posts. An occlusal splint will be inserted in the lower jaw as supportive therapy to control the parafunctional habit.

O restabelecimento da dimensão vertical de oclusão é uma etapa importante e indispensável durante a realização de trabalhos protéticos. Sua diminuição pode ser consequência do bruxismo severo e a reabilitação dos pacientes exige a realização de tratamentos complexos, de alto custo e tempo prolongado para execução. Neste contexto, a prótese parcial removível overlay é uma alternativa viável, pela reversibilidade do tratamento e simplicidade de execução. Como tratamento provisório, não necessita de preparo dental, restabelece a dimensão vertical de oclusão e permite que o paciente se adapte a esta nova dimensão, até que seja planejado e executado o tratamento reabilitador definitivo. O presente caso clínico descreve a reabilitação provisória de um paciente bruxista, desdentado total superior, com desgaste dental excessivo na arcada inferior que procurou tratamento na Clínica de Prótese Removível da Universidade Estadual de Ponta Grossa para substituição de sua prótese total superior. Uma nova prótese total foi confeccionada e proposta a execução de uma prótese parcial removível overlay para o arco inferior, a qual devolveu estética e função ao paciente até a realização do trabalho definitivo. O paciente foi instruído e orientado sobre os fatores desencadeantes e consequências de seu hábito parafuncional e conscientizado no intuito da autopercepção para controle da frequência. Para a reabilitação final, será confeccionada uma nova prótese total superior com superfícies oclusais metálicas, coroas metalocerâmicas com oclusal em metal utilizando retenção intracanal com núcleos metálicos fundidos. Uma placa miorrelaxante será instalada sobre a arcada inferior como terapia de suporte para controle do hábito parafuncional.

In-office bleaching effects on the pulp flow and tooth sensitivity - case series.

Laser Doppler flowmetry (LDF) is a noninvasive method capable of evaluating variations in pulp blood flow (PBF) and pulp vitality. This method has thus far not been used to assess changes in blood flow after in-office bleaching. The aim of this case series report was to measure changes in PBF by LDF in the upper central incisor of three patients submitted to in-office bleaching. The buccal surfaces of the upper arch were bleached with a single session of 35% hydrogen peroxide gel with three 15-min applications. The color was recorded using a value-oriented Vita shade guide before in-office bleaching and one week after the procedure. The tooth sensitivity (TS) in a verbal scale was reported, and PBF was assessed by LDF before, immediately, and one week after the bleaching session. The lower arch was submitted to dental bleaching but not used for data assessment. A whitening degree of 3 to 4 shade guide units was detected. All participants experienced moderate to considerable TS after the procedure. The PBF readings reduced 20% to 40% immediately after bleaching. One week post-bleaching, TS and PBF were shown to be equal to baseline values. A reversible decrease of PBF was detected immediately after bleaching, which recovered to the baseline values or showed a slight increase sooner than one week post-bleaching. The LDF method allows detection of pulp blood changes in teeth submitted to in-office bleaching, but further studies are still required.

Description of a Rat Palatal Acrylic Plate That Can Be Relined.

PURPOSE: The objective of this article is to describe a method to construct an intraoral acrylic device that permits a reline material to be added to the inner surface of the palatal plate. MATERIALS AND METHODS: Fifteen 60-day-old adult female rats (Rattus Norvegicus Albinus Wistar), weighing 150 to 250 g were used for this study and allocated to three groups (n = 5): G1, animals wearing a heat-polymerized acrylic resin palatal plate (Lucitone 550) for 14 days; G2, animals wearing a heat-polymerized acrylic resin palatal plate (Lucitone 550) relined with Tokuyama Rebase II for 14 days; and G3, animals maintained under the same conditions as the experimental groups, without wearing palatal plates for 14 days. The manipulation of the animals followed the guidelines of the Brazilian College of Animal Experimentation, under the approval of the animal ethics committee of the State University of Ponta Grossa. The palatal plates covered the whole palate, were fixed in the molar region with light-cured resin, and were kept there for 14 days. The animals received a paste diet and water ad libitum. Before and after the trial period, the rats were weighed individually on a precision scale. Statistical analysis was performed using a two-way analysis of variance (α = 0.05) test for comparison of the animals' weight (g) at time 0 and after 14 days of using the palatal plate. RESULTS: No statistical differences were observed regarding the weight of the animals among the experimental groups in the study. CONCLUSIONS: The individual master impressions, the molar teeth coverage, and the method of cementation with nonadhesive composite resin provided good stability for the palatal plate showed in this study, not disturbing the eating habits and nutrition of the animals. This model seems reproducible, offering adequate histopathological evaluation. Differences in tissue morphology exist between the animals that used the palatal plate and the animals that did not use this device. Use of these palatal plates could clarify how prostheses bring changes in the palatal mucosa of users.

In-office bleaching effects on the pulp flow and tooth sensitivity – case series

Laser Doppler flowmetry (LDF) is a noninvasive method capable of evaluating variations in pulp blood flow (PBF) and pulp vitality. This method has thus far not been used to assess changes in blood flow after in-office bleaching. The aim of this case series report was to measure changes in PBF by LDF in the upper central incisor of three patients submitted to in-office bleaching. The buccal surfaces of the upper arch were bleached with a single session of 35% hydrogen peroxide gel with three 15-min applications. The color was recorded using a value-oriented Vita shade guide before in-office bleaching and one week after the procedure. The tooth sensitivity (TS) in a verbal scale was reported, and PBF was assessed by LDF before, immediately, and one week after the bleaching session. The lower arch was submitted to dental bleaching but not used for data assessment. A whitening degree of 3 to 4 shade guide units was detected. All participants experienced moderate to considerable TS after the procedure. The PBF readings reduced 20% to 40% immediately after bleaching. One week post-bleaching, TS and PBF were shown to be equal to baseline values. A reversible decrease of PBF was detected immediately after bleaching, which recovered to the baseline values or showed a slight increase sooner than one week post-bleaching. The LDF method allows detection of pulp blood changes in teeth submitted to in-office bleaching, but further studies are still required.

Histopathological changes by the use of soft reline materials: a rat model study.

AIM: To assess the histopathological changes of rat palatal mucosa exposed to soft reline materials. METHODS: Forty-five adult female Wistar rats with controlled living conditions and fed ad libitum were employed. Palatal appliances of heat-polymerized acrylic resin Lucitone 550 were manufactured and worn by forty animals during 14 days. Five animals did not use the appliances (G1) and were used to control the appliance influence. One experimental group (n = 10) used the appliances without any relining material (G2) to control the material effect. Three experimental groups (n = 10) received the following soft reline materials below appliances: Dentusoft (G3), Dentuflex (G4), and Trusoft (G5). Appliances from half of each experimental group(n = 5) was immersed in water bath at 55°C for 10 min before use. Animals were slaughtered and the palates were fixed in 10% buffered formalin. Hematoxylin and eosin stained sections of 5 µm were analyzed by computerized planimetry. Cellular compartment, keratin and total epithelial thickness, and basement membrane length were measured to histopathological description.Analysis of variance and Tukey post-hoc test were used to data examination(α = 0.05). RESULTS: For heat-treatment groups, G4 showed less elongated ridges at the basal layer interface (p = 0.037) than G2. When comparing the conditions with and without heat-treatment, only G2 showed a significant decrease in the cellular compartment, keratin layer and total epithelium thickness (p<0.05). CONCLUSION: The post-polymerization for Lucitone 550 was an effective method to reduce the changes in the rat palatal mucosa. The soft reline materials tested did not cause significant histopathological changes in the rat palatal mucosa.

Evaluation of different treatment methods against denture stomatitis: a randomized clinical study.

OBJECTIVE: The aim of this clinical study was to determine the efficacy of Uncaria tomentosa (cat's claw) against denture stomatitis (DS). STUDY DESIGN: Fifty patients with DS were randomly assigned into 3 groups to receive 2% miconazole, placebo, or 2% U tomentosa gel. DS level was recorded immediately, after 1 week of treatment, and 1 week after treatment. The clinical effectiveness of each treatment was measured using Newton's criteria. Mycologic samples from palatal mucosa and prosthesis were obtained to determinate colony forming units per milliliter (CFU/mL) and fungal identification at each evaluation period. RESULTS: Candida species were identified with HiCrome Candida and API 20C AUX biochemical test. DS severity decreased in all groups (P < .05). A significant reduction in number of CFU/mL after 1 week (P < .05) was observed for all groups and remained after 14 days (P > .05). C albicans was the most prevalent microorganism before treatment, followed by C tropicalis, C glabrata, and C krusei, regardless of the group and time evaluated. U tomentosa gel had the same effect as 2% miconazole gel. CONCLUSIONS: U tomentosa gel is an effective topical adjuvant treatment for denture stomatitis.

Surface roughness of acrylic and silicone-based soft liners: in vivo study in a rat model.

PURPOSE: The aim of this in vivo animal study was to investigate changes in the surface roughness of soft liners over time. MATERIALS AND METHODS: Forty adult Wistar rats (Rattus norvergicus albinus) were fitted with acrylic custom-made palatal plates relined by dynamic impressions and tested with the following soft liners: Dentuflex (DF), Trusoft (TS), Dentusoft (DS), and Ufi Gel P (UG). Half of the animals for each tested material had the plates fitted during the material reline procedure. Their surface roughness was read immediately (IRa group, n = 5). The other half used the palatal plates for 14 days before roughness readings were performed (FRa group, n = 5). The surface roughness (Ra) of the inner surface from the relined dentures was recorded using a Surftest SJ-401 with eight readings per specimen, and mean values were obtained. Data (µm) were analyzed by two-way ANOVA and Tukey's test (α = 0.05). RESULTS: IRa means (2.92 ± 0.87 µm) and FRa means (3.35 ± 0.65 µm) were significantly different (p = 0.016). UG showed a lower (p = 0.01) Ra mean (2.1 ± 0.52 µm) than DF (3.94 ± 0.81 µm), TS (4.12 ± 0.64 µm), and DS (3.27 ± 0.64 µm). CONCLUSIONS: Ufi Gel P showed the smoothest surface among the materials evaluated. The period of use resulted in changes in the surface roughness of the materials tested.

Relationship between chewing rate and masticatory performance.

The influence of mandibular movement timing on food breakdown remains unclear. The authors, therefore, sought to relate chewing rate with masticatory performance. Chewing rate, defined as the number of masticatory cycles habitually achieved per minute, was measured in 55 healthy dentulous subjects (age, 22.2 +/- 5.0 years). Subjects were grouped according to obtained values (cycles/minute): slower: < 70; middle: 70-90; and faster: > 90. Masticatory performance was determined through the sieve method, and the estimated comminuted median particle size (X50). Data was analyzed using the one-way ANOVA and chi-square tests (alpha = .05). Subjects with slower chewing rates showed higher (p < .05) masticatory performance (X50 = 3.05 +/- 0.77 mm). X50 was associated with chewing rate when subjects were categorized as better or poorer performers (chi-square = 11.25, p < .005). Thus, chewing rate was related to masticatory performance, with smaller food particles being achieved with a slower chewing rate.

Relationship between body fat and masticatory function.

PURPOSE: The aim of this cross-sectional study was to investigate the relationship between body fat and masticatory function. MATERIALS AND METHODS: One hundred dentate and partially edentulous participants (33 male; mean age, 39.7 ± 16.6 years) were selected. Body fat was established through body mass index (BMI). Masticatory function was evaluated by quantifying occlusal pairs and determining masticatory efficiency and swallowing threshold with the sieving method. During the swallowing threshold test, chewing rate was registered. Masticatory ability was also evaluated with a 5-point Likert scale questionnaire. Data were analyzed with Spearman and chi-square tests, as well as binary logistic regression analysis for the presence of increased BMI (α= 0.05). RESULTS: Age (rho = 0.517), occlusal pairs (chi-square = 26.353), masticatory efficiency (chi-square = 30.935), masticatory ability (chi-square = 25.132; p < 0.001), and swallowing threshold (chi-square = 8.730; p < 0.005) were related to BMI. Age (odds ratio, OR = 1.048, 95% CI = 1.008 to 1.089) and lower masticatory efficiency (OR = 4.792, 95% CI = 1.419 to 16.183) were predictive of increased body fat (p < 0.05). Gender (chi-square = 0.402, p= 0.526) and chewing rate (rho =-0.158, p= 0.117) were not related to BMI. CONCLUSIONS: These results suggest that people with lower masticatory efficiency may be at risk for increased body fat.

Montagem de modelos de próteses removíveis em articulador semiajustável / Mounting casts from removable prostheses in semi adjustable articulator

Introdução: O relacionamento dos modelos de diagnóstico ou de trabalho em articulador semiajustável é um dos procedimentos mais importantes no tratamento reabilitador com próteses removíveis parciais ou totais. Objetivo:  Este trabalho descreve as diversas etapas da montagem em articulador semiajustável em situações de dois pacientes com arcos parcial ou totalmente edêntulos. Material e método: Foram discutidos os materiais e as técnicas que são indicados para registro das relações intermaxilares, inclusive em situações diferentes dos casos apresentados. Conclusão: A montagem de modelos de pacientes parcialmente edêntulos em articulador é de grande importância e apresenta uma ampla variação de indicação de acordo com diferentes situações.

Introduction: Articulating preliminary or working casts in semiadjustable articulators is one of the most important procedures in the prosthetic rehabilitation of partially and fully edentulous patients. Objective: This work described the several steps involving mounting casts in semiadjustable articulator in cases of two patients presenting partial and fully edentulous arcs. Material and method: It was discussed the recommended material and techniques for recording the maxilomandibular positions, including a range of situations different from the presented cases. Conclusion: The fitting of models of the edentulous patients in articulator is of great importance and presents a wide range of indication according to different situations.

The effect of long-term disinfection procedures on hardness property of resin denture teeth.

OBJECTIVE: The aim of the study was to evaluate the effect of long-term disinfection procedures on the Vickers hardness (VHN) of acrylic resin denture teeth. MATERIAL AND METHODS: Five acrylic resin denture teeth (Vipi Dent Plus-V, Trilux-T, Biolux-B, Postaris-P and Artiplus-A) and one composite resin denture teeth (SR-Orthosit-O) were embedded in heat-polymerised acrylic resin within polyvinylchloride tubes. Specimens were stored in distilled water at 37°C for 48 h. Measurements of hardness were taken after the following disinfection procedures: immersion for 7 days in 4% chlorhexidine gluconate or in 1% sodium hypochlorite (CIm and HIm group, respectively) and seven daily cycles of microwave sterilisation at 650 W for 6 min (MwS group). In the WIm group, specimens were maintained in water during the time used to perform the disinfection procedures (7 days). Data were analysed with anova followed by the Bonferroni procedure (α = 0.01). RESULTS: Microwave disinfection decreased the hardness of all acrylic resin denture teeth (p < 0.001). Immersion for 7 days in 4% chlorhexidine gluconate or distilled water had significant effect on the hardness of the acrylic resin denture teeth A (p < 0.01), and 1% sodium hypochlorite on teeth T (p < 0.01). All disinfection procedures decrease the hardness of the composite resin denture teeth (p < 0.01). Teeth O exhibited the highest and teeth V the lowest hardness values in the control group (p < 0.01). CONCLUSIONS: Disinfection procedures changed the hardness of resin denture teeth.

Mastication in subjects with extremely shortened dental arches rehabilitated with removable partial dentures.

Mastication was evaluated in subjects presenting extremely shortened dental arches (ESDAs) rehabilitated with mandibular free-end removable partial dentures (RPDs). Subjects were divided into four groups (n = 10): those with a complete dentition, those with ESDAs, and those with ESDAs who were rehabilitated with an RPD, who were evaluated both with and without their prostheses. Mastication was measured through masticatory performance, time, and ability. RPD wearers showed higher masticatory performance (P < .01) and ability (P < .001) and lower masticatory time (P < .001) than when not wearing their prostheses as well as ESDA subjects who had not received RPD therapy. Those with a complete dentition showed the best results (P < .001). It can be suggested that RPDs improve mastication in ESDA subjects but without achieving normal mastication levels.

Reembasamento em prótese total: material resiliente versus material rígido / Rebasing in total prosthesis: resiliente material versus rigid material

A reabsorção óssea do rebordo alveolar é um processo crônico e irreversível. Com o objetivode minimizar estas alterações, tem-se indicado o reembasamento imediato ou mediato das próteses removíveis. Existem estudos que demonstram que este procedimento traz maior qualidade de uso aos pacientes, pois promove uma adaptação mais satisfatória das mesmas com a mucosa. O objetivo deste artigo é comparar as indicações, vantagens e limitações dos materiais, resilientes e rígidos, indicados para o reembasamento imediato de próteses removíveis em consultório, através de dois casos clínicos. Após o acompanhamento destes casos clínicos, pode-se concluir que para obtenção do sucesso do reembasamento é importante que se respeite a indicação clínica, as propriedades físicas e mecânicas de cada material, bem como a proservação do comportamento do material, através de um rigoroso controle clínico. Também que os reembasadores rígidos podem ser utilizados por um maior período em relação aos resilientes, os quais devido às suas limitações devem ser utilizados apenas em condições transitórias.

The alveolar bone resorption is a cronic and irreversible processo In order to minimize thesechanges, it has been indicated the mediate or immediate relining of dentures. Studies have shown that the procedure for rebasing of dentures brings higher quality of use to patients, as this will promote a more satisfying adaptation of the prosthesis with the mucosa. The aim of this paper is to compare the indications, advantages and limitations of relíning materiais, resilient and hard, in office by two clinical cases. After the clinical monitoring of these cases, it can be concluded that to obtain the success of the relining is important to respect the indication, the physical and mechanical prerties of each material, as well as preservation the behavior of the material, through a rigorous clinical control. Also the hard reline can be used for a longer period compared to resilient, which due to their limitations should only be used in transient conditions.

Color stability of resins and nylon as denture base material in beverages.

PURPOSE: Staining of prosthodontic materials may result in patient dissatisfaction and additional expense for replacement. This study aimed to determine the color stability of two heat-cured denture base acrylic (Lucitone 550, Vipi Cril) and one nylon denture base resin (Transflex) after immersion in beverages. MATERIALS AND METHODS: Forty disks of each resin (20.0-mm diameter, 3.0-mm thick) were prepared and stored in distilled water for 24 hours at 37°C. During that time (T(0) ), the color of all specimens was spectrophotometrically measured. Each specimen was immersed in coffee, cola, red wine, and distilled water as a means of control. After 15-day (T(1) ) and 30-day (T(2) ) periods of immersion, the color of the specimens was measured again. The CIE (Commission Internationale de L' Eclairage) L*a*b* system was used to determine mean ΔE (color changes) values for each material and compared statistically with two-way ANOVA and Bonferroni intervals at 0.95. RESULTS: In ΔET(0) T(1) and ΔET(0) T(2) the most severe staining was apparent with red wine (p < 0.001), followed by coffee (p < 0.01), when compared to the specimens stored in distilled water. Transflex also showed significant color change after immersion in cola (p < 0.01). In ΔET(1) T(2) only red wine promoted significant staining of all resins (p < 0.0001). CONCLUSION: Chromatic changes were exhibited by specimens immersed in red wine, followed by coffee. For Transflex, cola also promoted color changes. The values of color changes converted to National Bureau of Standard units showed them to be perceivable to the human eye.