RESUMEN
Desktop microcomputed tomography (micro-CT) offers a non-invasive 3-dimensional analysis of structures and their physical properties. To date, the use of micro-CT has mostly involved qualitative observations, with the extent of quantitative analysis relying on automated internal calibration by the micro-CT control software. However, the value of such calibration is limited by machine drift. For an accurate quantitative use of micro-CT, it is recognized that external means of calibration are needed. A novel system of calibration standards, also known as 'phantoms', is presented. A range of low mineral concentration phantoms involving triethylene glycol dimethacrylate/glycerolate dimethacrylate resin mixed with commercial pure hydroxyapatite (HAP), from 0.07 to 1.05 g/cm(3), was fabricated. Sintered HAP was impregnated with the same resin, producing phantoms with medium-level mineral concentrations up to 1.90 g/cm(3). These phantoms were easy to create, proved accurate and stable with repeated use, and were found to mimic the composite nature of dental enamel and dentine structures under investigation.
Asunto(s)
Caries Dental/diagnóstico por imagen , Esmalte Dental/diagnóstico por imagen , Hidroxiapatitas/análisis , Fantasmas de Imagen/normas , Microtomografía por Rayos X/instrumentación , Animales , Densidad Ósea , Calibración , Bovinos , Humanos , Estándares de Referencia , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Microtomografía por Rayos X/métodosRESUMEN
Molar crown preparations, as described in the literature, have standard forms dictated by the demands of retention, resistance and the physical properties of materials. Standard designs may not be appropriate for all patients because of ethnic variations in tooth shape, pulp size and dentine thickness. Accurate data on these features could assist clinicians to minimize the risk of accidental pulpal injury. The aim of this study was to compare the first molar crown and pulp dimensions between Asian (Chinese, Korean, Malay) and other ethnic groups, using measurements from the bitewing radiographs of 121 subjects. Comparisons revealed the following significantly different features of Asian first molars: larger total pulp areas in uppers (P < 0.0005); shorter crowns (P < 0.0005); narrower upper teeth at the cervix (P < 0.0005); wider pulps at the cervix of lowers (P < 0.02); more bulbous crowns (P < 0.0005 for uppers; P < 0.01 for lowers), and finally significantly thinner dentine interproximally at the cervix (P=0.001 for uppers; P=0.011 for lowers). Preparations with wide shoulders could pose hazards to the pulps in Asian subjects. This study emphasizes the value of bitewing films in assessing crown and pulp size and shape before making crown preparations. The experienced practitioner may intuitively include tooth and pulp morphology in treatment planning, but this appears not to be taught or documented in textbooks.
Asunto(s)
Coronas , Diente Molar/diagnóstico por imagen , Radiografía de Mordida Lateral/métodos , Preparación Protodóncica del Diente/métodos , Adulto , China/etnología , Esmalte Dental , Pulpa Dental/diagnóstico por imagen , Dentina/diagnóstico por imagen , Etnicidad , Humanos , Indonesia/etnología , Corea (Geográfico)/etnología , Odontometría/métodos , Cuello del Diente/diagnóstico por imagenRESUMEN
AIM: To determine whether metal type, cement type and the use of ultrasonic vibration influence the amount of tensile force required to remove parallel-sided, prefabricated, metal posts from tooth roots. METHODOLOGY: Ninety extracted canine teeth were sectioned horizontally 1-mm coronal to the labial cemento-enamel junction and embedded in acrylic blocks. Standardized post spaces were prepared with a ParaPost no. 5 (1.25 mm) drill to 10 mm and ParaPost XP no. 5 stainless steel and titanium posts were cemented using zinc phosphate, glass ionomer or composite resin cement. Sixty posts were subjected to 16 min of ultrasonic vibration whilst 30 stainless steel posts received no vibration. The force required for post removal was determined using a universal testing machine. Results were analysed using univariate anova. RESULTS: The univariate anova revealed no statistically significant differences between the groups at the P = 0.05 level. CONCLUSIONS: In this in vitro experiment, metal type, cement type and ultrasonic vibration did not influence the force required to remove posts.
Asunto(s)
Aleaciones Dentales/química , Cementos Dentales/química , Desconsolidación Dental , Técnica de Perno Muñón , Análisis de Varianza , Resinas Compuestas/química , Diente Canino , Cementos de Ionómero Vítreo/química , Humanos , Modelos Lineales , Técnica de Perno Muñón/instrumentación , Cementos de Resina/química , Preparación del Conducto Radicular/instrumentación , Acero Inoxidable/química , Estrés Mecánico , Titanio/química , Ultrasonido , Vibración , Cemento de Fosfato de Zinc/químicaRESUMEN
In this in vitro study, properties of a titanium alloy post recently introduced to the market (IntegraPost), were compared with those of a clinically proven stainless steel post (ParaPost). The IntegraPost has a unique, perforated, spherical head and a microknurled shank surface. The posts were tested for rigidity, for retention within the root canals of extracted teeth and for ability to retain composite resin cores. The two post types exhibited similar properties in core and root canal retention, however, the IntegraPost was significantly less rigid than the ParaPost.
Asunto(s)
Técnica de Perno Muñón/instrumentación , Retención de Prótesis Dentales , Análisis del Estrés Dental , Humanos , Docilidad , Acero Inoxidable , Estadísticas no Paramétricas , Resistencia a la Tracción , TitanioRESUMEN
Ceramic root-canal posts offer potential advantages over other types with respect to aesthetics and biocompatibility. Any post must be sufficiently rigid and retentive to withstand functional forces. Ceraposts (1.2 mm coronal diameter, ceramic, tapering, smooth posts) and Paraposts (1.25 mm, stainless-steel, parallel, serrated posts) were tested for rigidity by means of a three-point bending test. To test retention in roots, ceramic posts were cemented using one of three protocols: (1) glass-ionomer cement, (2) silane coupling agent and resin cement, or (3) sandblasted post surface, silane coupling agent, and resin cement. Stainless-steel posts were cemented with resin. The tensile force required to dislodge the posts, following four weeks of storage in water, was recorded. Data were compared using Student's t-test and Mann-Whitney U analysis. Ceraposts were significantly more rigid than Paraposts (p < 0.001). Paraposts cemented with resin were significantly more strongly retained than Ceraposts following any cementation protocol (p < 0.001). Retention of the ceramic posts was significantly greater with a silane coupling agent and resin cement than with glass-ionomer cement (p < 0.001). Sandblasting the ceramic posts produced variable results and needs further investigation before it could be recommended.
Asunto(s)
Cerámica , Retención de Prótesis Dentales , Técnica de Perno Muñón , Grabado Ácido Dental , Materiales Biocompatibles/química , Cementación/métodos , Cerámica/química , Dentina/ultraestructura , Elasticidad , Estética Dental , Cementos de Ionómero Vítreo/química , Humanos , Microscopía Electrónica de Rastreo , Docilidad , Cementos de Resina/química , Silanos/química , Acero Inoxidable/química , Estadística como Asunto , Estadísticas no Paramétricas , Estrés Mecánico , Propiedades de Superficie , Resistencia a la Tracción , Agua/químicaRESUMEN
AIM: The aims of this study were firstly to compare the area of canal occupied by gutta-percha, sealer or voids using the System B heating device with that obtained by a modified vertical condensation technique using the Touch 'n Heat: and secondly to compare the temperature changes at the root canal wall and external root surface during obturation with the above techniques. METHODOLOGY: Forty-five resin blocks, each with a standardized, simulated, prepared main root canal and five lateral canals, were assigned to three equal experimental groups. The canals were obturated using either the System B technique at two different temperature settings, or vertical condensation with a Touch 'n Heat instrument as the heat source. A heat transfer model was used to simultaneously record internal and external root surface temperature elevations during obturation by the three techniques. Data were analysed using unpaired Student's t-test and Mann-Whitney U-test. RESULTS: Both obturation techniques produced root fillings consisting of over 90% gutta-percha at most levels, although the percentages of sealer and voids 2-3 mm from the working length following System B obturation were higher than those found following modified vertical condensation. Modified vertical condensation resulted in more gutta-percha in lateral canals. Obturation was accomplished more quickly using the System B, and temperature elevations produced during obturation with the System B were significantly less (P < 0.001) than with vertical condensation. An elevation of external root surface temperature by more than 10 degrees C occurred during vertical condensation. CONCLUSIONS: The results suggest that the System B may produce an acceptable obturation and that the use of a Touch 'n Heat source during vertical condensation may result in damage to the periodontium.
Asunto(s)
Obturación del Conducto Radicular/métodos , Gutapercha , Humanos , Modelos Dentales , Modelos Estructurales , Porosidad , Materiales de Obturación del Conducto Radicular , Estadísticas no Paramétricas , Temperatura , Cemento de Óxido de Zinc-EugenolRESUMEN
In an in vitro study, the use of sealers and liners (Fuji varnish, Vitrabond, Vitremer, Paama 2, All-Bond 2, or Resinomer) significantly reduced the amount of marginal leakage around amalgam (Permite C or Lojic Plus) and gallium (Galloy) alloy restorations. This reduction in marginal leakage was produced by all sealers and liners tested, and there were no statistically significant differences between these materials. Unlined restorations of Permite C had significantly less marginal leakage than Galloy or Lojic Plus. Unlined Lojic Plus restorations had the greatest amount of marginal leakage. The experimental method used in the present study proved to be suitable for quantitative comparison of marginal leakage of different dental materials.
Asunto(s)
Amalgama Dental , Recubrimiento de la Cavidad Dental , Filtración Dental/prevención & control , Recubrimientos Dentinarios , Análisis de Varianza , Resinas Compuestas , Aleaciones Dentales , Estudios de Evaluación como Asunto , Cementos de Ionómero Vítreo , MetacrilatosRESUMEN
OBJECTIVES: To measure and compare the retention of serrated root canal posts cemented with glass ionomer, resin and resin-modified glass ionomer (hybrid) cements. METHODS: Fifty single-rooted human teeth were decoronated, treated endodontically and then embedded in resin blocks. Standard post-holes, 10 mm long, were prepared to receive 1.5 mm serrated stainless steel posts. Five equal-sized groups of roots had posts cemented using either a glass ionomer cement, one of two resin cements or one of two resin-modified glass ionomer luting cements. The cements were prepared and used according to the manufacturers' instructions. The tensile force required to dislodge the cemented posts in a testing machine was recorded. Statistical analysis was performed using Student's t-test and Mann-Whitney U-tests at the 99.9% confidence level. RESULTS: Statistical analysis revealed that posts cemented with resin A were significantly better retained (340.06 N+/-23.13 N) than those cemented with resin B (212.56 N+/-67.62 N), or either of the two resin-modified glass ionomer cements (53.90 N+/-28.42 N, 25.97 N+/-14.70 N), but not statistically better than posts cemented with the glass ionomer cement (286.16 N+/-38.71 N). The retention of posts cemented with either resin B or the glass ionomer cement was significantly better than with either hybrid cement. There was no significant difference in retention between the hybrid cements. CONCLUSION: The performance of the resin-modified glass ionomer cements was significantly below that of alternative cements in this study. Possible explanations for this finding are discussed. Dentists should be cautious in adopting this new cementing regime.
Asunto(s)
Retención de Dentadura , Cementos de Ionómero Vítreo , Técnica de Perno Muñón , Cementos de Resina , Cementación , Resinas Compuestas/química , Intervalos de Confianza , Diseño de Prótesis Dental , Análisis del Estrés Dental/instrumentación , Cementos de Ionómero Vítreo/química , Humanos , Óxido de Magnesio/química , Ensayo de Materiales , Fosfatos/química , Cemento de Policarboxilato/química , Cementos de Resina/química , Tratamiento del Conducto Radicular , Acero Inoxidable , Resistencia a la Tracción , Raíz del Diente , Óxido de Zinc/químicaRESUMEN
In this in vitro study, where alloys were condensed into unset paste lining materials, shear bond strengths were significantly greater than with the unlined controls. The use of varnish or Paama 2 linings did not significantly increase the shear bond strength of amalgam or gallium alloy restorations. The use of Vitrabond, Vitremer, or Resinomer liners significantly increased the shear bond strength compared to unlined restorations. Permite C restorations lined with Resinomer all showed cohesive failure within the mixed alloy/ liner. Of the unlined restorations, Permite C had significantly higher shear bond strength than Lojic Plus. The experimental method used in the present study proved to be suitable for quantitative comparison of the shear bond strength of different dental materials.
Asunto(s)
Aleaciones Dentales/química , Recubrimiento de la Cavidad Dental , Cementos Dentales/química , Restauración Dental Permanente/métodos , Análisis de Varianza , Resinas Compuestas , Amalgama Dental , Análisis de Falla de Equipo , Cementos de Ionómero Vítreo , Ensayo de Materiales , Metacrilatos , Estadísticas no Paramétricas , Resistencia a la TracciónRESUMEN
OBJECTIVE: To test the rigidity and the retention into roots of parallel root canal posts, one a spiral vented titanium post and the other a spiral serrated, hollow, stainless steel post. A serrated, stainless steel post was used as the control. MATERIALS AND METHODS: A three-point bending test was used to test rigidity. To test retention, ten posts of each type were cemented into the roots of extracted teeth with a resin cement and the tensile loads required to remove them were compared using Student's t and Mann-Whitney U tests. RESULTS: The serrated stainless steel posts were significantly more rigid than either of the other types. The titanium posts and the stainless steel hollow posts were not significantly different in rigidity. The serrated, stainless steel posts were significantly better retained than either of the other types. The titanium posts showed greater retention than the hollow posts. CONCLUSIONS: Within the limits of the study the stainless steel, serrated posts were superior to the two newer types in terms of rigidity and retention into roots.
Asunto(s)
Diseño de Prótesis Dental , Retención de Prótesis Dentales , Técnica de Perno Muñón/instrumentación , Cementación , Análisis del Estrés Dental , Humanos , Docilidad , Cementos de Resina , Tratamiento del Conducto Radicular , Acero Inoxidable , Propiedades de Superficie , Resistencia a la Tracción , Titanio , Raíz del DienteRESUMEN
This report describes three instances of radiodense bone lesions. These lesions are most commonly associated with teeth with pathological pulpal changes, and are believed to represent an osteoblastic response to inflammation. However, they may also be found adjacent to apparently clinically healthy teeth.
Asunto(s)
Enfermedades Mandibulares/diagnóstico , Osteomielitis/diagnóstico , Adulto , Diagnóstico Diferencial , Femenino , Humanos , Enfermedades Mandibulares/etiología , Persona de Mediana Edad , Osteomielitis/etiología , Osteosclerosis/diagnóstico , Osteosclerosis/etiología , Periodontitis Periapical/complicaciones , RetratamientoRESUMEN
The retention in root canals of serrated carbon fibre Composiposts and stainless steel Paraposts was tested under tensile load. Twenty unrestored human roots were endodontically prepared and root filled. Two groups of 10 roots received 1.4-mm Composiposts or 1.25-mm Paraposts luted with a resin cement. The specimens were then embedded in acrylic resin and mounted in an Instron machine. The tensile force (kg) required to dislodge the posts was recorded and analysed with Student's test. The results revealed that there was no significant difference in the retention of either post (P > .05). The rigidty of 10 1.4-mm serrated Composiposts was tested in a three-point bend test in an Instron machine, and the retention of composite cores to 10 of these posts under tensile force was also tested. The results from these tests were compared to previous data from the authors' laboratory and revealed that the serrations significantly reduced the rigidity of the post (P < .001) and increased the retention of a core material (P < .001).
Asunto(s)
Recubrimiento Dental Adhesivo , Técnica de Perno Muñón/instrumentación , Carbono/química , Fibra de Carbono , Resinas Compuestas/química , Diseño de Prótesis Dental , Retención de Prótesis Dentales/instrumentación , Elasticidad , Estudios de Evaluación como Asunto , Humanos , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Docilidad , Cementos de Resina , Acero Inoxidable/química , Resistencia a la TracciónRESUMEN
Two of the main requirements of a root canal post are that it is rigid so as to resist flexing under functional load, and that it is well retained in the root. This study compared these properties in two different 1-mm diameter root canal posts--smooth carbon fibre posts (Endopost) and serrated stainless steel posts (Parapost). Ten posts of each type were tested for rigidity in a three-point bend test. Ten posts of each type were cemented with resin cement into the roots of endodontically treated, extracted teeth. The tensile force required to remove the posts was recorded. The Paraposts proved to be significantly more rigid under load (P < 0.001) and significantly more strongly retained in the tooth roots (P < 0.005). The Parapost appears to be a mechanically superior post for the restoration of root-filled teeth with narrow diameter root canals.
Asunto(s)
Recubrimiento Dental Adhesivo , Diseño de Prótesis Dental , Técnica de Perno Muñón/instrumentación , Carbono/química , Fibra de Carbono , Resinas Compuestas , Retención de Prótesis Dentales , Ensayo de Materiales , Docilidad , Cementos de Resina , Acero Inoxidable/química , Resistencia a la Tracción , Diente no VitalRESUMEN
This in vitro study compared physical properties of root canal posts made of carbon fiber-reinforced epoxy resin with those of stainless steel posts. Three-point bending tests were used to derive the transverse modulus of elasticity of the posts. Resin composite cores on the posts were subjected to tensile forces to test the bonds between the cores and posts. Carbon fiber posts appeared to have adequate rigidity for their designed purpose. The bond strength of the resin composite cores to the carbon fiber posts was significantly less than that to the stainless steel posts.
Asunto(s)
Carbono , Técnica de Perno Muñón/instrumentación , Acero Inoxidable , Fibra de Carbono , Resinas Compuestas , Análisis del Estrés Dental , Elasticidad , Resinas Epoxi , Ensayo de Materiales , Resistencia a la TracciónRESUMEN
This report describes success and failure in the use of fixed bridges supported by Brånemark implants, placed in the mandible bilaterally in one patient and unilaterally in the other. The non-intrusive nature and excellent functional characteristics of such bridges make them an attractive alternative to a removable partial denture in making good the loss of posterior mandibular teeth. However, there are biomechanical principles which must be considered in the design of such appliances. In particular, designs which minimise bending moments should be chosen to avoid the type of failure described in one of our patients. Repeated loosening of screw components should be considered as a possible indicator of bending overload. Where space permits, this problem is most easily overcome by placing three implants in staggered formation.
Asunto(s)
Implantación Dental Endoósea , Implantes Dentales , Dentadura Parcial Fija , Arcada Parcialmente Edéntula/rehabilitación , Adulto , Diente Premolar , Diseño de Prótesis Dental , Análisis del Estrés Dental , Femenino , Humanos , Mandíbula , Diente Molar , Falla de PrótesisRESUMEN
An artificial caries technique was used to produce caries-like lesions in the cavity walls adjacent to microfilled resin restorations with and without dentin bonding agent, and glass-ionomer cement restorations, in the roots of extracted teeth. The lesions had histological characteristics similar to those of natural lesions and to those of the lesions produced by other experimental methods. The zonal pattern of the lesions was examined by means of polarized light microscopy and microradiography, and the depth of the lesions was measured for assessment of the microleakage around the restorations. Three cavity cleaning regimes-water spray alone, 50% citric acid, and a proprietary cleaner-were compared in conjunction with the three restorative methods. Cavity cleaning with the citric acid or the proprietary cleaner, and the use of a fluoride-releasing restorative material, acted to reduce the depths of the lesions. Glass-ionomer cement restorations in cavities cleaned with citric acid showed lesions significantly shallower than those treated with other restorations. The glass-ionomer cement was soluble in the acidic environment but promoted the precipitation of minerals in the lesions. The use of a dentin bonding agent did not affect the depth of demineralization around the microfilled resin restorations.