Evaluation of Stress Patterns Produced by Implant-Retained Overdentures and Implant-Retained Fixed Partial Denture

The purposes of this study were to photoelastically measure the biomechanical behavior of 4 implants retaining different cantilevered bar mandibular overdenture designs and to compare a fixed partial denture (FPD). A photoelastic model of a human edentulous mandible was fabricated, which contained 4 screw-type implants (3.75 x 10 mm) embedded in the parasymphyseal area. An FPD and 3 overdenture designs with the following attachments were evaluated: 3 plastic Hader clips, 1 Hader clip with 2 posterior resilient cap attachments, and 3 ball/O-ring attachments. Vertical occlusal forces of 100 N were applied between the central incisor and unilaterally to the right and left second premolars and second molars. Stresses that developed in the supporting structure were monitored photoelastically and recorded photographically. The results showed that the anterior loading, the overdenture with 3 plastic Hader clips, displayed the largest stress concentration at the medium implant. With premolar loading, the FPD and overdenture with 3 plastic Hader clips displayed the highest stresses to the ipsilateral terminal implant. With molar loading, the overdenture with 3 ball/O-ring attachments displayed the most uniform stress distribution in the posterior edentulous ridge, with less overloading in the terminal implant. It was concluded that vertical forces applied to the bar-clip overdenture and FPD created immediate stress patterns of greater magnitude and concentration on the ipsilateral implants, whereas the ball/O-ring attachments transferred minimal stress to the implants. The increased cantilever in the FPD caused the highest stresses to the terminal implant.

Three-Dimensional Finite Element Analysis of Vertical and Angular Misfit in Implant-Supported Fixed Prostheses

Purpose: Three-dimensional finite element analysis was used to evaluate the effect of vertical and angular misfit in three-piece implant-supported screw-retained fixed prostheses on the biomechanical response in the peri-implant bone, implants, and prosthetic components. Materials and Methods: Four three-dimensional models were fabricated to represent a right posterior mandibular section with one implant in the region of the second premolar (2PM) and another in the region of the second molar (2M). The implants were splinted by a three-piece implant-supported metal-ceramic prosthesis and differed according to the type of misfit, as represented by four different models: Control = prosthesis with complete fit to the implants; UAM (unilateral angular misfit) = prosthesis presenting unilateral angular misfit of 100 pm in the mesial region of the 2M; UVM (unilateral vertical misfit) = prosthesis presenting unilateral vertical misfit of 100 pm in the mesial region of the 2M; and TVM (total vertical misfit) = prosthesis presenting total vertical misfit of 100 pm in the platform of the framework in the 2M. A vertical load of 400 N was distributed and applied on 12 centric points by the software Ansys, ie, a vertical load of 150 N was applied to each molar in the prosthesis and a vertical load of 100 N was applied at the 2PM. Results: The stress values and distribution in peri-implant bone tissue were similar for all groups. The models with misfit exhibited different distribution patterns and increased stress magnitude in comparison to the control. The highest stress values in group UAM were observed in the implant body and retention screw. The groups UVM and TVM exhibited high stress values in the platform of the framework and the implant hexagon, respectively. Conclusions: The three types of misfit influenced the magnitude and distribution of stresses. The influence of misfit on peri-implant bone tissue was modest. Each type of misfit increased the stress values in different regions of the system. INT J ORAL MAXILLOFAC IMPLANTS 2011;26:788-796

Photoelastic Analysis of Biomechanical Behavior of Single and Multiple Fixed Partial Prostheses With Different Prosthetic Connections

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Programa de extrações seriadas: variáveis relacionadas com a extração de pré-molares

OBJETIVO: verificar o percentual de pacientes que necessitaram extração de dentes permanentes, pré-molares, dentre aqueles tratados com extração de dentes decíduos para correção do apinhamento primário na dentição mista, bem como analisar as possíveis variáveis relacionadas. MÉTODOS: a amostra foi composta por documentações ortodônticas de 70 pacientes na dentição permanente, cujo tratamento iniciou-se na dentição mista com planejamento de um programa de extrações seriadas (PES). Todos os prontuários foram analisados por um único examinador, no intuito de verificar se o PES havia sido cumprido com a extração de dentes permanentes ou se havia sido realizada apenas extração de dentes decíduos. Verificou-se a associação entre a extração de dentes permanentes e as variáveis padrão facial; relação sagital entre as arcadas dentárias; IMPA; proporção tamanho do segundo molar permanente inferior/espaço retromolar; mecânica de controle de espaço e discrepância de modelo (teste exato de Fisher para as variáveis categóricas e modelo de regressão logística para as variáveis numéricas). Os resultados foram considerados para p<0,05. RESULTADOS: dos pacientes que haviam sido tratados com extração de dentes decíduos para a correção do apinhamento na dentição mista, 70% necessitaram de extração de dentes permanentes. A análise estatística não mostrou associação significativa entre as variáveis estudadas e a necessidade de extração de dentes permanentes, com exceção da variável discrepância de modelo. CONCLUSÃO: a discrepância de modelo representou a principal determinante de extração de pré-molares no PES.

Avaliação ortopantomográfica das angulações mesiodistais de caninos, pré-molares e molares inferiores com e sem a presença dos terceiros molares

OBJETIVOS: comparar os valores médios normais das angulações mesiodistais dentárias, propostos por Ursi, em 1989, com as angulações mesiodistais de caninos, pré-molares e molares inferiores em indivíduos com e sem a presença dos terceiros molares inferiores e idades entre 18 e 25 anos. Além disso, foram comparados os valores das angulações mesiodistais desses dentes nessas duas situações. MÉTODOS: foram utilizadas 40 radiografias ortopantomográficas de indivíduos, de ambos os gêneros, que não receberam tratamento ortodôntico, divididos em dois grupos: Grupo I, constituído por 20 radiografias que não apresentavam os terceiros molares inferiores; e Grupo II, formado por 20 radiografias com os terceiros molares inferiores presentes. RESULTADOS E CONCLUSÕES: a análise dos resultados e a análise estatística permitiram concluir que ambos os grupos exibiram pré-molares e molares inferiores mais angulados em sentido mesial, quando comparados à oclusão normal. Por outro lado, a angulação mesiodistal de caninos inferiores mostrou-se semelhante àquela apresentada em casos de oclusão normal. Os dois grupos, quando comparados entre si, exibiram semelhantes valores angulares dos caninos, pré-molares e molares inferiores, de modo que a presença dos terceiros molares não exerceu influência sobre essas angulações mesiodistais dentárias.

Antimicrobial potential of medicaments used in healing process in dogs' teeth with apical periodontitis

Estudou-se a influência de diferentes irrigantes no potencial antimicrobiano da pasta de hidróxido de cálcio em dentes de cães com periodontite apical. 48 pré-molares de cães adultos tiveram suas câmaras coronárias abertas e expostas à cavidade bucal por 6 meses. Os canais radiculares foram preparados, irrigados e medicados com diferentes substâncias, de acordo com os seguintes grupos: 1) 2,5% NaOCl + CHP; 2) 2% CHX + CHP; 3) vinagre + CHP; 4) vinagre + vinagre. No grupo 4, a solução irrigante e a medicação intracanal utilizada foi o vinagre. Neste grupo, a cada 7 dias, a solução era renovada. Cada amostra foi coletada, mantendo-se o cone de papel esterilizado em posição por 1 min, e a seguir transportado e imerso em 7 mL de Letheen broth, seguido de incubação a 37ºC por 48 h. O crescimento microbiano foi analisado por dois métodos, turbidade do meio de cultura e subcultura em meio nutritivo específico (brain heart infusion). Os resultados mostraram que em todos os grupos experimentais houve crescimento microbiano após 21 dias, em diferentes percentagens: grupo 1 - 30%; grupo 2 - 30%; grupo 3 - 40%; grupo 4 - 60%. Todos os materiais testados apresentaram potencial antimicrobiano. Entretanto, o processo de cura favorecido pela pasta de hidróxido de cálcio não pode ser esquecido, uma vez que muitos estudos já demonstraram sua ação antimicrobiana.

Human pulp responses to in-office tooth bleaching

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Response of human pulps after professionally applied vital tooth bleaching

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Pixel intensity and fractal analyses: detecting osteoporosis in perimenopausal and postmenopausal women by using digital panoramic images

Objective. Pixel intensity values (PI) and fractal dimensions (FD) were compared in selected mandibular regions on digital panoramic images of normal, osteopenic, and osteoporotic perimenopausal and postmenopausal women to evaluate their relative efficacies in detecting osteoporotic-associated bone density changes.Study design. Standardized mandibular angle, body, and canine/premolar (C/PM) regions on 54 charge-coupied device (CCD) digital panoramic images of normal and potentially osteoporotic postmenopausal women were analyzed for PI and FD. Lumbar spine and femoral neck dual-energy x-ray absorptiometry QXA) on each patient served as the reference standard examination. Pearson correlation coefficients and analysis of variance (ANOVA) were performed.Results. There was significant correlation among PI measurements (P < 0.01), and no significant correlation between FD. C/PM had significantly lower PI than control C/PM (P = 0.049).Conclusions. Osteoporotic changes in mandibular C/PM cancellous bone were detected in our study population on CCD digital panoramic images by using a robust image analysis paradigm. Future automated application of such image analysis could enable widespread, cost effective screening for osteoporosis in dental settings.

Comparison between embossed digital imaging and unprocessed film-based radiography in detecting periodontal bone defects: an in vitro study

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Evaluation of collagen-based membranes for guided bone regeneration, by three-dimensional computerized microtomography

Objective. The aim of this study was to evaluate the use of a collagen-based membrane compared with no treatment on guided bone regeneration by 3-dimensional computerized microtomography (mu CT).Study Design. Defects were created between the mesial and distal premolar roots of the second and third premolars (beagle dogs; n = 8). A collagen-based membrane (Vitala; Osteogenics Biomedical Inc., TX, USA) was placed in one of the defects (membrane group; n = 16), and the other was left untreated (no-membrane group; n = 16). Left and right sides provided healing samples for 2 and 16 weeks. Three-dimensional bone architecture was acquired by mu CT and categorized as fully regenerated (F, bone height and width) or nonregenerated (N).Results. Chi-square tests (95% level of significance) showed that tooth did not have an effect on outcome (P = .5). Significantly higher F outcomes were observed at 16 weeks than 2 weeks (P = .008) and in membrane group than in no-membrane group (P = .008).Conclusions. The collagen-based membrane influenced bone regeneration at the furcation. (Oral Surg Oral Med Oral Pathol Oral Radiol 2012;114:437-443)

Recursive hierarchic segmentation analysis of bone mineral density changes on digital panoramic images

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Single crowns versus conventional fillings for the restoration of root filled teeth

BackgroundEndodontic treatment, involves removal of the dental pulp and its replacement by a root canal filling. Restoration of root filled teeth can be challenging due to structural differences between vital and non-vital root filled teeth. Direct restoration involves placement of a restorative material e.g. amalgam or composite directly into the tooth. Indirect restorations consist of cast metal or ceramic (porcelain) crowns. The choice of restoration depends on the amount of remaining tooth which may influence long term survival and cost. The comparative in service clinical performance of crowns or conventional fillings used to restore root filled teeth is unclear.ObjectivesTo assess the effects of restoration of endodontically treated teeth (with or without post and core) by crowns versus conventional filling materials.Search methodsWe searched the following databases: the Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE via OVID, EMBASE via OVID, CINAHL via EBSCO, LILACS via BIREME and the reference lists of articles as well as ongoing trials registries. There were no restrictions regarding language or date of publication. Date of last search was 13 February 2012.Selection criteriaRandomised controlled trials (RCTs) or quasi-randomised controlled trials in participants with permanent teeth which have undergone endodontic treatment. Single full coverage crowns compared with any type of filling materials for direct restoration, as well as indirect partial restorations (e.g. inlays and onlays). Comparisons considered the type of post and core used (cast or prefabricated post), if any.Data collection and analysisTwo review authors independently assessed trial quality and extracted data.Main resultsOne trial judged to be at high risk of bias due to missing outcome data, was included. 117 participants with a root filled premolar tooth restored with a carbon fibre post, were randomised to either a full coverage metal-ceramic crown or direct adhesive composite restoration. At 3 years there was no reported difference between the non-catastrophic failure rates in both groups. Decementation of the post and marginal gap formation occurred in a small number of teeth.Authors' conclusionsThere is insufficient evidence to support or refute the effectiveness of conventional fillings over crowns for the restoration of root filled teeth. Until more evidence becomes available clinicians should continue to base decisions on how to restore root filled teeth on their own clinical experience, whilst taking into consideration the individual circumstances and preferences of their patients.

Er : YAG laser: Antimicrobial effects in the root canals of dogs' teeth with pulp necrosis and chronic periapical lesions

Objective: Our goal in this study was to evaluate the antimicrobial effect of Er:YAG laser applied after biomechanical preparation of the root canals of dog's teeth with apical periodontitis. Background Data: Various in vitro studies have reported effective bacterial reduction in infected root canals using Er:YAG laser. However, there is no in vivo research to support these results. Methods: Forty root canals of dogs' premolar teeth with pulp necrosis and chronic periapical lesions were used. An initial microbiological sample was taken, and after biomechanical preparation was carried out, a second microbiological sample was taken. The teeth were divided into two groups: Group I-biomechanical preparation was taken of root canals without Er:YAG laser application; Group II-biomechanical preparation was taken of root canals with Er:YAG laser application using 140-mj input, 63-mJ output/15 Hz. After coronal sealing, the root canals were left empty for 7 days at which time a third microbiological sample was taken. The collected material was removed from the root canal with a #40 K file and placed in transport media. It was serially diluted and seeded on culture dishes selective for anaerobes, aerobes, and total streptococci. Colony-forming units per milliliter (CFU/mL) were counted. Results: Groups I and II showed an increase of CFU/mL for all microorganisms 7 days after treatment, being statistically significant for anaerobes in Group I and for anaerobes and total streptococci in Group II. When comparing CFU/mL of Groups I and II, there was a statistically significant increase after 7 d for total streptococci in Group II. Conclusion: Er:YAG laser applied after biomechanical preparation did not reduce microorganisms in the root canal system.

Root canal treatment of three-rooted maxillary second premolars: Report of four cases

The aim of this report is to contribute to a better understanding of the radiographic, clinical and anatomic findings in maxillary second premolars. This paper reports the endodontic treatment of two cases of three-rooted three-canal maxillary second premolars in different patients, and two sound maxillary second premolars also with three canals and three independent roots in a sibling of one of the patients. Although the presence of maxillary second premolars with one or two canals and one root is much more common, other anatomic conditions can be found. A correct clinical and radiographic diagnosis based on knowledge of root canal anatomy and critical interpretation of radiographs is necessary for a safer and successful endodontic treatment of these teeth.