Magister Scientiae Dentium - MSc(Dent) / NiTi rotary instruments have shape memory and are highly flexible and super-elastic. These properties of the metal alloy allows for ease of root canal preparation to ultimately result in a root canal preparation that has a continuous taper, while canal shape and curvature is maintained. It must be noted that the NiTi rotary instrumentation may have an effect on root canal dentine, which may manifest as dentine damage. Different NiTi rotary systems on the market vary with regards to their design features and kinematics, which may influence dentine damage. The purpose of this in-vitro study was to compare the effect of four different NiTi rotary systems, as well as stainless steel files on root canal dentine. One hundred and eighty permanent human mandibular molar mesial roots were used for the study. The total samples were randomly divided into six groups, where one group (n=30) was left unprepared to serve as the control group. The remaining five groups were randomly assigned to a nickel-titanium rotary instrumentation system and one stainless steel hand file group. Group 1: Control group; Group 2: Stainless steel files group; Group 3: Wave One (Dentsply Maillefer) rotary group; Group 4: ProTaper NEXT (Dentsply Maillefer) rotary group; Group 5: iRaCe (FKG Dentaire) rotary group; Group 6: BT-Race (FKG Dentaire) rotary group.The root canal preparations were carried out according to the manufacturers' recommendations, after decoronation of the tooth crowns. Sodium hypochlorite (5,25%) and 17% EDTA was used as a root canal irrigant and a chelating agent during canal preparation. Each root segment was sectioned at 3mm, 6mm and 9mm from the apex. The root segments were observed under a stereomicroscope at 12x magnification and digital camera at 40 x magnification for the appearance of dentine damage. The images were observed by the author and an impartial second observer. Root segments were observed for the appearance of dentine damage (microcracks, craze lines or fractures), and samples were described as having 'dentine defect' or 'no dentine defect'. Data for the different groups were collected and results were calculated and the total incidence of dentine damage was as follows: Control group = 0% Stainless steel hand files group = 0% Wave One group = 56, 67% ProTaper NEXT group = 60% iRaCe group = 60% BT-Race group = 56, 67% There are no significant differences between the groups: WaveOne, ProTaper NEXT, iRACE and BT-Race. However, there is a significant difference between the four groups and the stainless steel group (p<0.0001).

Foi realizada uma avaliação in vitro da influência de três variáveis sobre a rugosidade, porosidade, microdureza, sorção e solubilidade de uma resina acrílica para coroas provisórias: ambiente de polimerização (ar/água), temperatura e pressão de acordo com 4 técnicas de manipulação, diretas e indiretas. Os corpos de prova foram confeccionados utilizando a resina poli (metilmetacrilato) (PMMA) Dencorcor nº 66. A rugosidade de superfície (Ra) foi verificada por um rugosímetro/perfilômetro. Na análise da porosidade foi utilizado um método quantitativo de contagem dos poros por área delimitada utilizando um microscópio comparador. A análise da microdureza foi feita antes e depois da simulação do desafio ácido ocorrido na cavidade bucal. Para a análise de sorção e solubilidade os espécimes foram submetidos a ciclos de hidratação e ressecamento e através da comparação entre as pesagens iniciais e finais foi possível estabelecer os resultados. Os resultados de Rugosidade foram favoráveis às técnicas indiretas (grupos I e II) com médias de Ra=0,141m e 0,181m, respectivamente, seguidos pelas técnicas diretas (grupos III e IV) com Ra=0,373m e 0,908m. Os resultados de porosidade foram de 0,8 poros por área delimitada para o grupo I, seguido do grupo II com 0,9 poros; grupo III com 7,2 poros e grupo IV com 124 poros. Os resultados de microdureza para todos os grupos evidenciaram diminuição da dureza após a ciclagem ácida com valores que diminuíram de 14,12 para 13,03 no grupo I; de 14,06 para 12,93 no grupo II; de 13,73 para 12,71 no grupo III e de 13,47 para 12,65 no grupo IV. Os resultados de sorção foram de 1,807% para o grupo I; 1,817% para o grupo II; 2,068% para o grupo III e 2,227% para o grupo IV. E os resultados de solubilidade foram 0,036% para o grupo I; 0,054% para o grupo II; 0,184% para o grupo III e 0,212% para o grupo IV. Os maiores valores de rugosidade e porosidade foram alcançados pelos corpos-de-prova confeccionados pelas técnicas diretas e os menores valores se deram nos corpos-de-prova confeccionados segundo as técnicas indiretas e pela técnica do pincel. O desafio ácido reduziu a dureza da resina acrílica, porém não houve diferença nos testes de dureza entre os diferentes grupos. Os espécimes confeccionados pelas técnicas indiretas apresentaram menor sorção e solubilidade quando comparadas às técnicas diretas. Portanto, as técnicas indiretas de confecção de coroas provisórias devem ser preferidas às técnicas diretas. / An in vitro evaluation of the influence of three variables (polymerization medium (air/water), temperature and pressure) on roughness, porosity, microhardness, sorption and solubility of an acrylic resin for provisional crowns was conducted according to 4 techniques (direct and indirect). The samples were prepared using a poly (methylmethacrylate) (PMMA) resin Dencor color No 66. The surface roughness (Ra) was evaluated with a perfilometer. Porosity was analyzed according a quantitative method of counting number of pores per area by using a comparator microscope. Microhardness readings were made before and after acid challenge simulation as in the oral cavity. For sorption and solubility analysis, specimens were subjected to successive cycles of dampening and dehydration to make comparisons of the initial and final weights. Roughness results were lower for indirect techniques (groups I and II) with averages of Ra = 0.141m and 0.181m, respectively, followed by direct techniques (groups III and IV) with Ra = 0.373m and 0.908m. Porosity results were 0.8 pores per area for the group I, 0.9 pores for group II, 7.2 pores for group III and 124 pores for group IV. All groups showed a decrease in hardness after acid cycling with values that ranged from 14.12 to 13.03 in group I, 14.06 to 12.93 in group II, 13.73 to 12.71 in group III, and 13.47 to 12.65 in group IV. Sorption results were 1.807% in group I, 1.817% in group II, 2.068% in group III, and 2.227% in group IV. Solubility results were 0.036% in group I, 0.054% in group II, 0.184% in group III and 0.212% in group IV. Higher values of roughness and porosity were obtained by specimens made by direct technique and lower values were achieved with specimens made by indirect technique and brush technique. The acid challenge statistically decreased hardness of the acrylic resin, but there was no statistical difference among different groups. The specimens prepared by indirect techniques showed lower sorption and solubility when compared to direct techniques. The indirect techniques for making provisional crowns should be preferred compared to direct techniques.

Indiana University-Purdue University Indianapolis (IUPUI) / Objectives: Repair of crown margins may extend the functional life of existing crowns. However, the longevity of such treatment is unknown. This study determined the survival time of crown margin repairs (CMR) with glass-ionomer (GI) and resin-modified glass-ionomer cements. Methods: We queried axiUm (Exan Group, Coquitlam, BC, Canada) database for permanent teeth that underwent CMR in the Graduate Operative Dentistry Clinic, Indiana University School of Dentistry (IUSD), Indianapolis, Ind., USA, from January 1, 2006 through January 1, 2018. Since there is no CDT code for the CMR procedure, CDT codes for resin-composite and GI restorations (D23XX) were queried; these patients also had treatment notes that indicated CMR. The final data set included patient ID, birth date, gender, dates of treatments, CDT codes, tooth type, tooth surface and existing findings. Two examiners developed guidelines for record review and manually reviewed the clinical notes of patient records to confirm CMR. Only records that were confirmed with the presence of CMR were retained in the final dataset for survival analysis. Survival time was calculated by Kaplan-Meier statistics and a Cox Proportional Hazards model was performed to assess the influence of selected variables (p < 0.05). Results: 214 teeth (115 patients) with CMR were evaluated. Patient average age was 69.4  11.7 years old. Posterior teeth accounted for 78.5 percent (n = 168) of teeth treated. CMRs using GI had a projected 5-year survival rate of 62.9 percent (K-M Analysis) and an 8.9 percent annual failure rate. Cox Proportional Hazards Regression analysis revealed that none of the factors examined (age, gender, tooth type) affected time to failure. Conclusion: CMRs may extend the longevity of crowns with defective margins. Larger EHR studies or case control studies are needed to investigate other variables, such as the caries risk status or the severity of defects that may affect the survival rate of CMRs.

Discrimination of different tree crowns based on their 3D shapes is essential for a wide range of forestry applications, and, due to its complexity, is a significant challenge. This study presents a modified 3D shape descriptor for the perception of different tree crown shapes in discrete-return LiDAR point clouds. The proposed methodology comprises of five main components, including definition of a local coordinate system, learning salient points, generation of simulated LiDAR point clouds with geometrical shapes, shape signature generation (from simulated LiDAR points as reference shape signature and actual LiDAR point clouds as evaluated shape signature), and finally, similarity assessment of shape signatures in order to extract the shape of a real tree. The first component represents a proposed strategy to define a local coordinate system relating to each tree to normalize 3D point clouds. In the second component, a learning approach is used to categorize all 3D point clouds into two ranks to identify interesting or salient points on each tree. The third component discusses generation of simulated LiDAR point clouds for two geometrical shapes, including a hemisphere and a half-ellipsoid. Then, the operator extracts 3D LiDAR point clouds of actual trees, either deciduous or evergreen. In the fourth component, a longitude-latitude transformation is applied to simulated and actual LiDAR point clouds to generate 3D shape signatures of tree crowns. A critical step is transformation of LiDAR points from their exact positions to their longitude and latitude positions using the longitude-latitude transformation, which is different from the geographic longitude and latitude coordinates, and labeled by their pre-assigned ranks. Then, natural neighbor interpolation converts the point maps to raster datasets. The generated shape signatures from simulated and actual LiDAR points are called reference and evaluated shape signatures, respectively. Lastly, the fifth component determines the similarity between evaluated and reference shape signatures to extract the shape of each examined tree. The entire process is automated by ArcGIS toolboxes through Python programming for further evaluation using more tree crowns in different study areas. Results from LiDAR points captured for 43 trees in the City of Surrey, British Columbia (Canada) suggest that the modified shape descriptor is a promising method for separating different shapes of tree crowns using LiDAR point cloud data. Experimental results also indicate that the modified longitude-latitude shape descriptor fulfills all desired properties of a suitable shape descriptor proposed in computer science along with leaf-off, leaf-on invariance, which makes this process autonomous from the acquisition date of LiDAR data. In summary, the modified longitude-latitude shape descriptor is a promising method for discriminating different shapes of tree crowns using LiDAR point cloud data.

AbstraktSyfte:Studiens syfte var att utreda maxlasttoleransen mellan yttria-stabiliserad zirkoniumdioxid- (Y-TZP) och metallkeramiska- (MC) molarkronor med en ny design på in vitro belastningsformen. En stålkula användes för att utöva last på kusparna istället för i fissuren för att framställa en sprickbildning liknande den som ses kliniskt. Materialochmetod:26 kronor tillverkades, varav 13 högädla MC och 13presintrade Y-TZP. 7 av MC göts av 50% tidigare icke-gjuten och 50% omgjuten legering medan de kvarvarande 6 göts av 100% tidigare icke gjuten legering. Kronorna täcktes av ett fasadporslinoch cementerades på stansar av ett resinmaterial. Av de 26 kronorna genomgick 24 förbelastingstester och belastades slutligen till fraktur. Resultat: MC klarade signifikant högre belastningar än Y-TZP, P>0,001. Frakturerna skiljde sig också grupperna emellan där MC-gruppen uppvisade enbart adhesiva frakturer av fasadporslinet under det att Y-TZP-gruppen uppvisade kohesiva brott i ytporslinet undantaget en Y-TZP-krona som uppvisade total fraktur. Ingen signifikant skillnad kunde ses mellan MC-kronor bestående av enbart tidigare icke gjuten legering och MC-kronor med 50% omgjuten legering, P=0,370. Konklusion: MC-kronor klararsignifikant högre belastningar än Y-TZP-kronor och testet genererar kliniskt relevanta frakturer av ytporslinet snarare än totala frakturer. Frakturbeteendet skiljer sig mellan MC och Y-TZP där MC uppvisar endast adhesiva fraktureroch Y-TZP främst kohesiva brott av ytporslinet.

Nesta pesquisa, foram avaliados a retenção de coroas cimentadas sobre dentes terceiros molares humanos extraídos, após submetê-los às ciclagens térmica e mecânica, e o tipo de falha dos cimentos. Vinte dentes foram preparados de maneira padronizada, com 4 mm de altura, 8 mm de diâmetro e 20º de expulsividade. Coroas metálicas fundidas em NiCr foram cimentadas sobre os preparos, sendo dez com cimento de fosfato de zinco e dez com cimento resinoso, e armazenadas em água a 37ºC por 24 horas. Aleatoriamente, a metade das amostras de ambos os cimentos foi submetida a termociclagem (5ºC e 55ºC ±1ºC por 700 ciclos), seguida de ensaios mecânicos (freqüência de 2 Hz, carga compressiva de 141N por 200.000 ciclos). A outra metade das amostras (grupo controle) não foi submetida aos testes de fadiga. Realizou-se o teste de tração e os valores obtidos foram tratados estatisticamente pelo teste ANOVA (Tukey-Kramer Multiple Comparisons Test). Os resultados mostraram retenção significativamente superior do cimento resinoso Panavia F (valor médio 569,43 N) sobre o cimento de fosfato de zinco (valor médio 350 N). Os testes de envelhecimentos mostraram-se significantes (p<0,001) na sua influência sobre a retenção das coroas, exceto para o grupo cimentado com fosfato de zinco (p>0,05). A falha do cimento observada foi de natureza adesiva para todos os grupos. / The aim of this study was to evaluate the retention of NiCr cast metal crowns fixed with two different lutting agents after thermocycling and mechanical load. The nature of the cement failure was evaluated too. Twenty natural human molar teeth extracted were selected (Banco de Dentes Permanentes Humanos da Faculdade de Odontologia da Universidade de São Paulo – SP). They were prepared at 4mm height, 8mm diameter and 20º of convergence. The cast crowns were lutted with zinc phosphate cement (n=10) and resin cement (n=10) and stored in water at 37ºC for 24 hours. Randomly the half of the specimens of each cement were thermal (5ºC and 55ºC for 700 cycles) and load cycled (2 Hz, 141 N load for 200.000 cycles). The control group did not perform the thermal or fatigue tests. The pull-out test was performed and the results showed a significant (confidence interval 95%) superior retentive strength for Panavia F resin cement (mean value 569,43 N) when compared with zinc phosphate (mean value 350 N). The aging tests were significant (p<0,001) about their influence over the retention of the crowns. They was no significant difference between control and cycled group for crowns lutted with phosphate cement (p>0,05). Adhesive failure of the cements was observed for all subjects.

Die hier vorliegende Dissertation beschreibt die vergleichenden Untersuchungen zweier Verfahren zur Herstellung vollkeramischen Zahnersatzes. Zur Bewertung der Praxistauglichkeit eines solchen Systems sind mehrere Untersuchungskriterien notwendig. Für einen klinischen Langzeiterfolg sind die marginale und okklusale Präzision von entscheidender Bedeutung. Aus betriebswirtschaftlicher und gesundheitspolitischer Sicht ist für den Zahnarzt aber auch der notwendige zeitliche Aufwand von elementarer Bedeutung. Das Ziel dieser in-vitro-Untersuchung war es, zwei vollkeramische Systeme hinsichtlich ihrer marginalen und okklusalen Präzision zu vergleichen. Zusätzlich wurde der verfahrensbedingte Zeitaufwand zur Herstellung einer vollkeramischen Restauration untersucht.

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Made available in DSpace on 2014-12-17T14:07:07Z (GMT). No. of bitstreams: 1 JulianaCS.pdf: 1007525 bytes, checksum: 74d4bf5035436a1b506b801dce77838f (MD5) Previous issue date: 2006-03-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The metalceramic crowns are usually used in dentistry because they provide a resistant structure due to its metallic base and its aesthetics from the porcelain that recovers this structure. To manufacture these crowns, a series of stages should be accomplished in the prosthetic laboratories, and many variables can influence its success. Changes in these variables cause alterations in the metallic alloy and in the porcelain, so, as consequence, in the adhesion between them. The composition of the metal alloy can be modified by recasting alloys, a common practice in some prosthetic laboratories. The aim of this paper is to make a systematic study investigating metalceramic crowns as well as analyzing the effect of recasting Ni-Cr alloys. Another variable which can influence the mechanism of metalceramic union is the temperature used in firing porcelain procedure. Each porcelain has to be fired in a fixed temperature which is determined by the manufacturer and its change can cause serious damages. This research simulate situations that may occur on laboratory procedures and observe their consequences in the quality of the metalceramic union. A scanning eletron microscopy and an optic microscopy were accomplish to analyse the metal-ceramic interface. No differences have been found when remelting alloys were used. The microhardness were similar in Ni-Cr alloys casted once, twice and three times. A wettability test was accomplished using a software developed at the Laborat?rio de Processamento de Materiais por Plasma, on the Universidade Federal do Rio Grande do Norte. No differences were found in the contact angle between the solid surface (metallic substratum) and the tangencial plane to the liquid surface (opaque). To analyse if the temperature of porcelain firing procedure could influence the contact area between metal and porcelain, a variation in its final temperature was achieve from 980? to 955?C. Once more, no differences have been found / Durante o processo de confec??o de coroas metalocer?micas, ? necess?rio que todas as informa??es passadas pelo fabricante sejam seguidas de forma criteriosa. Caso isto n?o ocorra, podem acontecer altera??es tanto na liga met?lica como na porcelana e como conseq??ncia, na ades?o entre elas. Um fator que deve ser levado em considera??o, consiste em analisar o efeito das refus?es, uma vez que nos laborat?rios prot?ticos torna-se comum a pr?tica do reaproveitamento da ligas. Outro fator importante ao se preparar coroas metalocer?micas ? a temperatura de sinteriza??o da porcelana. Sabe-se que a temperatura de sinteriza??o pode influenciar na microestrutura, afetando diretamente suas propriedades f?sicas e mec?nicas. Nesse trabalho, um estudo sistem?tico ? realizado com o intuito de investigar a ades?o metal-cer?mica em ligas Ni-Cr fundidas sob diferentes graus de reaproveitamento, assim como analisar o efeito de diferentes temperaturas de sinteriza??o da porcelana. Procura-se aqui simular situa??es poss?veis de ocorrer durante procedimentos laboratoriais prot?ticos e observar suas conseq??ncias na qualidade da ades?o metal-cer?mica. Deste modo, coroas de ligas de n?quel-cromo refundidas em 1 e 2 vezes, foram comparadas com aquelas apenas fundidas. Uma an?lise por microscopia ?ptica e eletr?nica foi realizada para se avaliar o contato entre o metal e o opaco da porcelana. Al?m do mais, testes de microdureza sobre a liga met?lica foram executados. Neste estudo, procurou-se tamb?m avaliar a molhabilidade da porcelana sobre ligas met?licas com diferentes estados de fus?o, al?m de realizar uma sinteriza??o da porcelana em diferentes temperaturas (980?C e 955?C). Como resultado encontrou-se que n?o houve diferen?a na interface entre as liga em diferentes est?gios de fus?o e a porcelana. Com rela??o ? microdureza, os resultados indicaram que, na medida em que se aumenta o n?mero de refus?es, os valores de microdureza n?o se alteram e com rela??o ? molhabilidade n?o houve diferen?a estatisticamente significativa entre as amostras. Tamb?m n?o se encontrou diferen?a entre as ?reas de contato formadas entre a porcelana e a liga fundida quando a porcelana foi sinterizada em diferentes temperaturas, mostrando que uma diminui??o de 25?C na temperatura final de sinteriza??o n?o interfere na uni?o metal-cer?mica

Nesta pesquisa, foram avaliados a retenção de coroas cimentadas sobre dentes terceiros molares humanos extraídos, após submetê-los às ciclagens térmica e mecânica, e o tipo de falha dos cimentos. Vinte dentes foram preparados de maneira padronizada, com 4 mm de altura, 8 mm de diâmetro e 20º de expulsividade. Coroas metálicas fundidas em NiCr foram cimentadas sobre os preparos, sendo dez com cimento de fosfato de zinco e dez com cimento resinoso, e armazenadas em água a 37ºC por 24 horas. Aleatoriamente, a metade das amostras de ambos os cimentos foi submetida a termociclagem (5ºC e 55ºC ±1ºC por 700 ciclos), seguida de ensaios mecânicos (freqüência de 2 Hz, carga compressiva de 141N por 200.000 ciclos). A outra metade das amostras (grupo controle) não foi submetida aos testes de fadiga. Realizou-se o teste de tração e os valores obtidos foram tratados estatisticamente pelo teste ANOVA (Tukey-Kramer Multiple Comparisons Test). Os resultados mostraram retenção significativamente superior do cimento resinoso Panavia F (valor médio 569,43 N) sobre o cimento de fosfato de zinco (valor médio 350 N). Os testes de envelhecimentos mostraram-se significantes (p<0,001) na sua influência sobre a retenção das coroas, exceto para o grupo cimentado com fosfato de zinco (p>0,05). A falha do cimento observada foi de natureza adesiva para todos os grupos. / The aim of this study was to evaluate the retention of NiCr cast metal crowns fixed with two different lutting agents after thermocycling and mechanical load. The nature of the cement failure was evaluated too. Twenty natural human molar teeth extracted were selected (Banco de Dentes Permanentes Humanos da Faculdade de Odontologia da Universidade de São Paulo – SP). They were prepared at 4mm height, 8mm diameter and 20º of convergence. The cast crowns were lutted with zinc phosphate cement (n=10) and resin cement (n=10) and stored in water at 37ºC for 24 hours. Randomly the half of the specimens of each cement were thermal (5ºC and 55ºC for 700 cycles) and load cycled (2 Hz, 141 N load for 200.000 cycles). The control group did not perform the thermal or fatigue tests. The pull-out test was performed and the results showed a significant (confidence interval 95%) superior retentive strength for Panavia F resin cement (mean value 569,43 N) when compared with zinc phosphate (mean value 350 N). The aging tests were significant (p<0,001) about their influence over the retention of the crowns. They was no significant difference between control and cycled group for crowns lutted with phosphate cement (p>0,05). Adhesive failure of the cements was observed for all subjects.