Radiographic Appearance of Interocclusal Record Materials for Cone Beam Computed Tomography-Guided Implant Surgeries.

PURPOSE: To select an ideal interocclusal record material for cone beam computed tomography (CBCT)-guided implant surgery based on the material's radiodensity on the scan. MATERIALS AND METHODS: Twelve commonly used interocclusal record materials were used for this investigation: two were waxes, one was polyether, and nine were polyvinyl-siloxane-type materials. A scan template was fabricated by duplicating existing dentures in Ortho-Jet acrylic resin mixed with 30% barium powder for the teeth and 10% barium powder for the denture base between the teeth and the tissue. An interocclusal record was fabricated with each material, and the same template was used to obtain a CBCT scan with an ICAT machine (Imaging Sciences International) at 0.3 voxel and 14-bit depth settings. Twelve CBCT scans were obtained and analyzed. The radiopacity of the barium teeth was used as a control and was compared with the opacity of the 12 materials using a paired t test. A post hoc analysis of variance (ANOVA) test was used to compare the densities of the various materials with each other. RESULTS: There was a statistically significant difference between the radiopacity of barium teeth (gray value: 1,959.475) and that of Modelling Wax (gray value: 750; P = .0026), Aluwax (gray value: 795.22; P = .0022), Blu-Bite CT (gray value: 1,105; P = .005), Ramitec (gray value: 1,105.3; P = .08), Memosil 2 (gray value: 1,202; P = .01) followed by Reprosil (gray value: 1,407.73; P = .01). Compared with the barium teeth, there was no statistically significant difference between the densities of Futar D (gray value: 1,866.5; P = .51), Jet Bite (gray value: 1,660.04; P = .08), Lab-Putty (gray value: 1,402.14; P = .19), and Memoreg 2 (gray value: 1,754.72; P = .1). The highest radiodensity was seen with Blu-Mousse (gray value: 2,949; P = .007) and Take 1 (gray value: 2,229.85; P = .025), which were also significantly different from the density of the barium teeth but in the opposite direction, making them more opaque. CONCLUSION: Within the limitations of this in vitro study, the most radiolucent appearance of Modelling Wax, Aluwax, Memosil 2, Blu-Bite CT, and Ramitec made them the suitable materials of choice of those tested, as the interocclusal registration record during CBCT scanning allowed clear visualization of barium teeth.

Influência do agente cimentante e desajuste interno na adaptação marginal de coroas em resina nanocerâmica / Influence of the cement agent and internal mismatch in the marginal adaptation of nanoceramic resins crowns

A adaptação marginal é um dos requisitos fundamentais para a longevidade e o sucesso das restaurações. O objetivo desse estudo foi avaliar a influência do desajuste interno associado à diferentes agentes cimentantes na desadaptação marginal de coroas em resina nanocerâmica (Lava Ultimate 3M ESPE) confeccionadas pelo sistema CAD-CAM. A partir do escaneamento de um preparo de coroa total em um pré-molar, foram obtidos 36 modelos em metal. Esses foram divididos em seis grupos de acordo com o desajuste interno (70 µm ou 100 µm) e o cimento (Fosfato de zinco- SS White, Cimento de ionômero de vidro- Ketac Cem 3M/ESPE e Cimento resinoso- Relyx Ultimate 3M/ESPE). Após escaneamento de todos os modelos as coroas foram confeccionadas a partir da fresagem de blocos de resina nanocerâmica (Lava Ultimate 3M/ESPE). Com auxílio de microscópio óptico comparador (40X) foram medidas as desadaptações marginais prévia e posteriormente à cimentação, sendo considerados 8 pontos ao longo do término em todas as faces do corpo de prova. Os valores obtidos após serem submetidos aos testes two-way anova e teste t, demonstraram que as coroas confeccionadas com desajuste interno de 70 µm apresentam desadaptação marginal inferior estatisticamente significante às coroas com desajuste interno de 100 µm. Para o desajuste interno de 70 µm o grupo do cimento fosfato de zinco apresentou o menor gap marginal, sendo que este valor não foi estatisticamente diferente em relação ao grupo do Ketac Cem. Ainda com esse desajuste, o grupo do Ketac Cem não apresentou diferença estatística significante em relação ao grupo do Relyx Ultimate, no entanto esse último promoveu "gap" marginal estatisticamente maior em relação ao grupo do cimento fosfato de zinco. Para o desajuste interno de 100 µm não houve diferença estatisticamente significante no "gap" marginal entre os três cimentos avaliados. O presente estudo demonstrou através da metodologia utilizada, que a menor desadaptação marginal observada nas restaurações de Lava Ultimate, foi proveniente do desajuste interno de 70 µm. Neste grupo os cimentos de fosfato de zinco e de ionômero de vidro demonstraram melhor comportamento comparado ao cimento resinoso, embora o cimento de ionômero de vidro numericamente, mas não estatisticamente tenha apresentado resultado inferior ao do fosfato de zinco

The marginal adaptation is one of the basic requirements for the longevity and success of restorations. The aim of this study was to evaluate the influence of the internal imbalances associated with different luting agents on marginal leakage of crowns Nanoceramic resin ( Lava Ultimate 3M ESPE) made by CAD-CAM system. From the scanning of a full crown preparation in a pre molar were obtained 36 metal models. These were divided into six groups according to the internal imbalances ( 70 or 100 micrometres) and cement (SS White Zinc phosphate, glass ionomer cemet Ketac Cem 3M/ Espe and resinous cement Relyx Ultimate 3M / Espe). After scanning all models crowns were made from milling Nanoceramic resin blocks (Lava Ultimate 3M / Espe). With the aid of optical comparator microscope (40X) were measured prior marginal mismatches and after the cementation, being considered 8 points along the end in all specimen faces. The values were submitted to ANOVA two-way test and t test. Results showded that crowns made with internal imbalances of 70 uM show statistically significant lower marginal leakage to the crows with internal imbalances of 100 micrometres. For the internal imbalances 70 uM zinc phosphate cement group showed the lowest "gap" marginal, and this figure does not show a statistically significant difference compared to Ketac Cem gropu. Even with this misfit, Ketac Cem group showed no statistically significant difference in relation to Relyx Ultimate group, though the latter showed a statistically significant difference compared to zinc phosphate cement group. For the internal imbalances of 100 micrometres there was no statistically significant difference in the "gap" marginal among the three cements. This study demostrated through the methodology used, the lower marginal leakage oberved in Lava Ultimate restorations, was from the inner misfit 70 micrometers...

Biomecânica da união dente-implante com plataforma restauradora reduzida, sistema de retenção tipo cone morse e roscas quadradas: uma análise por elementos finitos / Biomechanics of tooth-implant union with restorative platform reduced, restraint system morse cone type and square threads: a finite element analysis

Objetivou-se, a partir do Método dos Elementos Finitos, avaliar a biomecânica da união dente-implante e implante-implante, além de estabelecer uma análise qualitativa com achados fotoelásticos prévios. Foram planejados quatro modelos tridimensionais: dois Modelos Teste (dentes unidos a implantes) e dois Modelos Controle (a mesma condição, porém implanto suportada). Os implantes (ANKYLOS® - Dentsply) apresentaram conexão cônica, roscas quadradas e pilares Switching. Suas dimensões, ângulos externos e pilares protéticos foram obtidos a partir de um projetor de perfil. Já, dentes e próteses, a partir da visão direta, tiveram suas formas externas construídas em plataforma CAD (SOLIDSWORKS). O suporte alveolar foi configurado como um retângulo (68/30/15 mm). Todos os pilares foram posicionados no suporte alveolar, conforme os modelos físicos pré-existentes, gerando modelos sólidos. O ligamento periodontal consistiu de uma camada de 0,25 mm de espessura em poliéter (Impregum Soft, 3M Espe). Os modelos de dentes foram produzidos em dentina, pilares e implantes em titânio puro, próteses em liga Níquel-Cromo (Ni-Cr), e o suporte alveolar em resina fotoelástica (Araldite® - Produtos Químicos Ciba S/A do Brasil). As propriedades da resina foram obtidas por meio de ensaio de tração. Carga pontual, vertical e estática, de 150 N, foi aplicada. Os resultados destes ensaios evidenciaram menor concentração de tensão no aspecto cervical de implantes do grupo teste. Ao se confrontar tais achados com os fotoelásticos anteriormente obtidos, foi possível estabelecer uma relação direta entre as áreas mais solicitadas para os modelos de prótese fixa (PF) de três elementos. Concluiu-se que, para as condições estudadas ¿ conexão cônica, roscas quadradas e restauração com Plataforma Switching ¿, unir dentes a implantes parece ser uma terapia clínica viável, sugerindo, inclusive, ser mais favorável que a união de implantes entre si. Além disso, a partir da afinidade positiva entre os achados das duas técnicas, pôde-se considerar validados os modelos matemáticos de prótese fixa de três elementos

The goal of this study was to evaluate, from the Finite Element Method, the biomechanics of implant-tooth union and implant-implant and to establish a qualitative analysis with previous photoelastic findings. Four three-dimensional models were planned: two Test Models (teeth attached to implants) and two Control Models (the same condition, however implant supported). The implants (ANKYLOS® - Dentsply) showed conical connection, square threads and Switching pillars. Their dimensions, external angles and abutments were obtained from a profile projector. Already, teeth and dentures, from direct view, had their external forms built in CAD platform (SOLIDSWORKS). Alveolar support wasconfigured as a rectangle (68/30/15 mm). All the pillars were placed in the alveolar support, as the pre-existing physical models, generating solid models. The periodontal ligament consists of a layer of 0.25 mm thick in polyether (Impregum Soft, 3M Espe). The models of teeth trumped up of dentin, abutments and implants of pure titanium, prosthetics of Nickel-Chrome (Ni-Cr) alloy and alveolar support in photoelastic resin (Araldite® - Chemicals Ciba S/A of Brazil). The resin properties were obtained by traction tests. Punctual and vertical static load of 150 N was applied. The results of these tests showed lower concentration of tension in the cervical aspect of the test group implants. When comparing these findings with the photoelastic previously found, it was possible to establish a direct relation between the areas most requested for fixed prosthesis (FP) models of three elements. It was concluded that, for the studied conditions tapered connection, square threads and Platform Switching restoration , joining teeth implants seems to be a viable clinical therapy, suggesting, inclusive, to be more favorable than to join implants each other. Moreover, from the positive affinity between the findings of the two techniques, it was possible to consider validated the mathematical models of fixed prosthesis of three elements

Comparison of the accuracy of a 3-dimensional virtual method and the conventional method for transferring the maxillary cast to a virtual articulator.

STATEMENT OF PROBLEM: The currently available virtual articulators fail to locate the digitized maxillary cast at the exact position in the virtual environment. Some locate the casts on a mechanical articulator with a facebow, and this position is then digitized for the virtual environment. PURPOSE: The purpose of this study was to compare the location of the maxillary cast on an articulator by using 2 different procedures: the conventional method and a virtual method. MATERIAL AND METHODS: With the conventional procedure, the kinematic axis of the participant was determined with an axiograph. The location of the maxillary cast in reference to this axis was then physically transferred to a Panadent mechanical articulator. By a virtual procedure, the same kinematic axis and the maxillary cast were transferred directly from the participant to the Panadent virtual articulator by means of reverse engineering devices. The locations obtained with both procedures were compared in a virtual environment with an optical scanner. By calculating the deviation at every point of the occlusal surface, the results obtained with this procedure were then compared with those of the conventional method. RESULTS: The mean deviation on the occlusal surface was 0.752 mm, and the standard deviation was 0.456 mm. CONCLUSIONS: The deviation between the procedures was sufficiently small to allow the methodology for orthodontic purposes. However, the accuracy of the virtual procedure should be improved so as to extend its use to other fields, such as orthognathic surgery or dental restorations, in which the clinical technique requires an articulator.

Prevalence of dental anomalies in Saudi orthodontic patients.

AIM: This study aimed to investigate the prevalence of dental anomalies and study the association of these anomalies with different types of malocclusion in a random sample of Saudi orthodontic patients. MATERIALS AND METHODS: Six hundred and two randomly selected pretreatment records including orthopantomographs (OPG), and study models were evaluated. The molar relationship was determined using pretreatment study models, and OPG were examined to investigate the prevalence of dental anomalies among the sample. RESULTS: The most common types of the investigated anomalies were: impaction followed by hypodontia, microdontia, macrodontia, ectopic eruption and supernumerary. No statistical significant correlations were observed between sex and dental anomalies. Dental anomalies were more commonly found in class I followed by asymmetric molar relation, then class II and finally class III molar relation. No malocclusion group had a statistically significant relation with any individual dental anomaly. CONCLUSION: The prevalence of dental anomalies among Saudi orthodontic patients was higher than the general population. CLINICAL SIGNIFICANCE: Although, orthodontic patients have been reported to have high rates of dental anomalies, orthodontists often fail to consider this. If not detected, dental anomalies can complicate dental and orthodontic treatment; therefore, their presence should be carefully investigated during orthodontic diagnosis and considered during treatment planning.

Error analysis of a CAD/CAM method for unidirectional mandibular distraction osteogenesis in the treatment of hemifacial microsomia.

Our aim was to investigate the errors in a computer-aided design and manufacture (CAD/CAM) method of unidirectional mandibular distraction osteogenesis. Six patients with hemifacial microsomia were selected, and studied on computed tomographic (CT) scans taken at 3 time intervals: preoperatively, at the end of the latent period, and at the end of consolidation. The plan for mandibular distraction osteogeneisis was designed using CT-based 3-dimensional visible software. The osteotomy line and site of the drill were transferred to a rapid prototyping surgical guide. The osteotomy of the mandible and implantation of the distraction device were completed under guidance. The accuracy of the transferred surgical plan was confirmed by fusion of images after the latency period. The 3-dimensional superimposition of the preoperative simulation, and the postoperative actual models at the end of consolidation, showed that the mean (SD) error between the actual and the predicted height of the ramus was 0.6 (0.6) mm. The error between the actual and predicted intercondylar distance was 8.1 (2.1) mm. There was a significant difference in intercondylar distance between the simulated and actual groups (p=0.00024). The 3-dimensional CT-based planning system described in this paper was transferred precisely from the virtual plan to the real-time operation. The planning system also gave a precise prediction of the height of the ramus after mandibular distraction osteogenesis. However, because of the pull of the lateral pterygoid muscle and pseudarthrosis, the intercondylar distance decreased compared with the predicted value. These influencing factors should be considered when the planning system is refined.

Assessment of the reliability and repeatability of landmarks using 3-D cephalometric software.

The aim of this study was to analyze the reliability and repeatability of identification landmarks using 3-D cephalometric software. Ten orthognathic patients were selected for this study and underwent the following protocol: 1. radiographic evaluation (CBCT technique); 2. stone casts; 3. photos; and 4. 3-D cephalometric evaluation. Twenty-one hard tissue landmarks and 14 cephalometric measurements were taken three times (T1, T2, and T3) on each patient, with an interval of one week by two experts in orthodontics (A, B). Standard deviation and Pearson's correlation coefficient were calculated to evaluate intra- and inter-observer repeatability. The results showed a strong correlation for both intra- and inter-observer Pearson's correlation coefficient (>0.7). The current preliminary study showed that the reliability and repeatability of the identification landmarks were very high if the 3-D cephalometric landmarks are defined correctly in the three planes of the space. Further evaluation is necessary to better define the 3-D cephalometric system.

Evaluation of an improved orthognathic articulator system. 2. Accuracy of occlusal wafers.

The errors produced by occlusal wafers constructed on casts of the teeth mounted on a standard articulator and an improved orthognathic articulator were investigated by carrying out simulated orthognathic surgery on plastic skulls. The wafers were used to relocate the position of the maxillae of the skulls. The vertical and horizontal displacements of the maxillae were determined from measurements of the positions of markers on the skull and teeth. Comparison of the magnitudes of the actual and intended movements showed that wafers constructed on the standard articulator had systematic prediction errors of up to 5mm, but the improved orthognathic articulator showed much smaller random errors. There was a statistically significant improvement in overall accuracy in predicting maxillary Le Fort I position with the use of the improved orthognathic articulator which the authors recommend for clinical use.

Evaluation of an improved orthognathic articulator system: 1. Accuracy of cast orientation.

A systematic study was carried out using plastic model skulls to quantify the accuracy of the transfer of face bow registration to the articulator. A standard Dentatus semi-adjustable articulator system was compared to a purpose built orthognathic articulator system by measuring the maxillary occlusal plane angles of plastic model skulls and of dental casts mounted on the two different types of articulators. There was a statistically significant difference between the two systems; the orthognathic system showed small random errors, but the standard system showed systematic errors of up to 28°.

Investigations on the palatal rugae pattern in cleft patients. Part I: A morphological analysis.

The characteristics of the palatal rugae zone (number of rugae, relief type, posterior limitation) were investigated on the maxillary casts of 44 patients with unilateral cleft lip and palate and 28 patients with bilateral clefts by means of reflex microscopy, a three-dimensional, computer-assisted, touch-free measuring system for the metrical registration and analysis of the parameters directly on the maxillary casts for the segments of the 2 cleft groups. The features "number of palatal rugae" and "relief type" (primary rugae) were determined both before and after surgical repair of the cleft palate. Both segments in unilateral cleft lip and palate and both lateral segments in bilateral clefts most commonly had 4 to 5 palatal rugae. The number of rugae in cleft patients is thus in a range that other authors have reported for non-cleft individuals. Following palatal cleft repair, the rugae counts per segment decreased significantly in patients with unilateral and bilateral cleft lip and palate but the 3rd rugae was never lost after surgery. The relief type identified in unilateral and bilateral cleft lip and palate was the same as in isolated cleft palates and did not differ from that in non-cleft subjects. The posterior limitation of the palatal rugae zone was determined both in a tooth-defined manner and as an absolute linear distance (at all time points). The most frequent tooth-defined posterior limitation of the rugae zone in unilateral and bilateral clefts was the second deciduous molar, which is also the position identified for non-cleft individuals. The linear distance from the tuberosity line to the rugae zone increased in all segments of unilateral and bilateral clefts during the interval up to palatal cleft repair, indicating sagittal maxillary development in the posterior area of the palate. Surgical repair of the cleft palate resulted in a significant shortening of the distance in both segments of the unilateral cleft, most likely due to the displacement of mucosa and periosteum required to cover the palatal cleft.

Three-dimensional virtual imaging of facial skeleton and dental morphologic condition for treatment planning in orthognathic surgery.

The improvement of esthetics and function, including the occlusal relationship, needs to be carefully considered in treatment planning for the success of orthognathic surgery. Conventional lateral cephalograms and dental study casts have been used usually for the assessment of skeletal morphologic condition and occlusion, respectively, in planning procedures. However, these traditional techniques do not allow for simultaneous evaluation of the skeletal morphologic condition and the occlusal harmony. A new technique has been developed that combines the conventional clinical diagnostic materials, cephalograms, and dental study casts to produce a 3-dimensional virtual image for routine practice. A 3-dimensional graphic image of dental study casts was generated with a laser surface scanner. A 3-dimensional skeletal image was constructed based on the coordinates of anatomic landmarks registered on frontal and lateral cephalograms. The image of the study cast was then set up with the 3-dimensional skeletal image to create a 3-dimensional dataset of the virtual image. The 3-dimensional virtual image, combining the cephalometric and the dental study cast information, permits simultaneous display of skeletal morphologic condition and occlusal relationship. This 3-dimensional virtual imaging can be helpful in planning orthodontic-surgical treatment and in providing graphic information to the patient. This article describes the technique and outline. A clinical application with this imaging technique is also demonstrated.

Prevalencia de anomalías de malposición dentaria en niños de 7 a 12 años / Prevalence of tooth malposition anomalies in 7-12 year-old children

Las anomalías de malposición dentaria se presentan en un porcentaje muy elevado a nivel mundial. En el Ecuador y especialmente en Guayaquil, según observaciones e información de ortodoncistas, se conoce que existe un elevado porcentaje de anomalías que deben ser analizadas e investigadas. Es conocido por quienes hacemos salud bucal y general, que las anomalías dentomaxilofaciales producen trastornos en la masticación, dicción, deglución, A.T.M. y estética facial. Como consecuencia, producen trastornos funcionales y psicológicos que alteran la salud general. Por esta razón, hemos iniciado un estudio descriptivo de las anomalías de malposición dentaria en niños de 7 a 12 años de zonas urbano marginales en seis escuelas y un sector urbano de la ciudad de Guayaquil, durante los años 1993 a 1996

Suma incisiva superior: estudio en una muestra de la población de Santiago / Upper incisive sum: study of a population sample at Santiago, Chile

Se realiza un estudio en el cual se hacen mediciones en modelos de pacientes atendidos en la sección de Ortodoncia del Servicio Dental del Hospital José Joaquín Aguirre, con el propósito de comparar estos resultados con los índices actualmente utilizados en la clínica. Las mediciones corresponden al ancho mesiodistal de los incisivos superiores e inferiores y se realiza con un compás de punta metálica y un calibrador. Se analiza el tamaño individual de cada diente, se compara con su homólogo y se analiza el Indice Incisivo. Se entregan los resultados con los análisis y se comparan con los de otros autores extranjeros. Se entregan conclusiones del trabajo

A three-dimensional analysis of mandibular arch changes following curve of Spee leveling in nonextraction orthodontic treatment.

The present study was conducted to determine the effects of curve of Spee leveling on three-dimensional arch length and specific components of arch form. The mandibular pretreatment and posttreatment dental casts of 33 patients treated orthodontically without the extraction of teeth were digitized with a three-dimensional positioning transducer integrated with a graphics calculator. Statistical analysis was carried out with general linear models and the calculation of Pearson correlation coefficients of the relationships between the dependent variable of the curve of Spee leveling and the independent variables of arch length, arch depth, and three arch widths. The regression and correlation analyses essentially showed no relationship between the independent variables (arch length, arch depth, and the three arch widths) and the dependent variable (curve of Spee leveling). Although the three-dimensional arch length was increased after leveling of the curve of Spee in 24 of the 33 dental casts evaluated, the results from the statistical analyses indicated that this increased arch length was not necessarily the result of the curve of Spee leveling but may have been caused by other variables.

Enseñanza de la exodoncia complicada sobre modelo figurado / Teaching the complicated tooth extraction using a dental model

Los estudiantes de odontología pueden educarse en las técnicas quirúrgicas bucales utilizando un modelo adaptado previo al manejo de pacientes reales. Esta práctica es un valioso instrumento para ofrecer una atención quirúrgica segura en el consultorio dental. El modelo que aquí se propone se ha utilizado durante 13 años en la planeación y ejecución de exodoncia complicada, transfiriendo los conceptos del aula a la clínica

Auxiliares didácticos en la enseñanza de la endodoncia preclínica / Didactic auxiliaries for the teaching of preclinical endodontics

El adiestramiento preclínico previo a la enseñanza de la endodoncia, está reconocido y aceptado por la mayoría de las facultades y escuelas de odontología del mundo. Su desarrollo exige disponer de espacio, tiempo y aparatología suficientes, lo que crea un verdaero problema cuando la población estudiantil es numerosa. Se describen una serie de dispositivos utilizados como auxiliares didácticos, especialmente para las tomas radiográficas, en la Cátedra de Endodoncia "B" de la Facultad de Odontología de la Universidad Nacional de Córdoba (Argentina), que van desde el clásico maniquí que permite la toma de una sola radiografía por disparo y de un dispositivo que hace posible la toma de 4 a 8 radiografías simultaneamente. Los mismos permiten ventajas tales como: 1) obtener placa de buena definición y escasa distorsión, 2) economizar tiempo, 3) aprovechar al máximo las exposiciones radiográficas con el mínimo desgaste de la aparatología, ya que el número de disparos puede reducirse a una cuarta u octava parte