Thesis (Ph. D.)--University of Toronto, 1997. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Toronto, 1997. / Includes bibliographical references.

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

Objectives: The present work was under taken to compare osseointegration of immediately and delayed restored implants in a sheep model, and to compare methods of assessing osseointegration. Methods: Twenty wide-platform implants were placed in the posterior mandibles of 10 sheep, 3 months after premolar extractions. Ten were control implants placed and restored after 3 months of submerged healing. Ten were test implants placed contralaterally and immediately restored. Animals were sacrificed after a further 3 months of healing. At each experimental stage implant stability was measured with resonance frequency analysis (RFA) and standardized radiographs were taken. Tissue blocks with the implants were embedded in acrylic resin. The specimens were analysed by three-dimensional micro tomogram (micro-CT) images. Ground sections of the tissue blocks were then prepared for light microscopy and quantitative morphometry. Morphometric parameters computed by both methods were mean percent bone-to-implant contact (BIC) and mean percent bone density (BD). Radiographic, stability and morphometric measurements were compared statistically. Results: The survival rate was 60% (controls) versus 40% (test) (p=0.28). Mean crestal bone levels after three months restoration did not differ significantly between control (5.54 � 0.92) and test groups (4.35 � 1.61) (p=0.56). All surviving implants were stable at stage three and RFA values in implant stability quotient (ISQ) did not differ significantly between the two groups (test 82.3 � 3.9 versus control 78.8 � 4.3, p=0.36). No correlation was found between crestal bone loss and RFA (Spearman�s rho =-0.27, p=0.46). Histomorphometric analysis found no statistical difference (%BIC test 65.65 � 12.7%, control 53.36 � 6.41%, p=0.18; and %BD test 54.84 � 8.45%, control 64.69 � 13.57%, p=0.11). A similar trend was observed for mean micro-CT (%BIC test 65.72 � 72, control 50.84 � 4.19, p=0.11). Histology revealed high density inflammatory infiltrates beneath the sulcular and pocket epithelium. No significant difference was found between histomorphometric (HMA) and microCT analysis (%BIC p=0.08, %BD p=0.08). A statistically significant correlation was observed between HMA and microCT for %BIC (Spearman�s rho = 0.89, p=0.02) but not %BD (Spearman�s rho = 0.51, p=0.30). Conclusions: The results suggest that the sheep mandibular model has limited potential for evaluation of implants designed for poor quality bone and for the assessment of implant loading protocols. This thesis does highlight the potential for the use of this model in peri-implantitis studies. The results suggest that morphometric variables determined by HMA and microCT analysis are comparable, however further studies are required to standardize the microCT protocol to reduce metal artifacts and enhance bone-implant contrast.

Objectives: The present work was under taken to compare osseointegration of immediately and delayed restored implants in a sheep model, and to compare methods of assessing osseointegration. Methods: Twenty wide-platform implants were placed in the posterior mandibles of 10 sheep, 3 months after premolar extractions. Ten were control implants placed and restored after 3 months of submerged healing. Ten were test implants placed contralaterally and immediately restored. Animals were sacrificed after a further 3 months of healing. At each experimental stage implant stability was measured with resonance frequency analysis (RFA) and standardized radiographs were taken. Tissue blocks with the implants were embedded in acrylic resin. The specimens were analysed by three-dimensional micro tomogram (micro-CT) images. Ground sections of the tissue blocks were then prepared for light microscopy and quantitative morphometry. Morphometric parameters computed by both methods were mean percent bone-to-implant contact (BIC) and mean percent bone density (BD). Radiographic, stability and morphometric measurements were compared statistically. Results: The survival rate was 60% (controls) versus 40% (test) (p=0.28). Mean crestal bone levels after three months restoration did not differ significantly between control (5.54 � 0.92) and test groups (4.35 � 1.61) (p=0.56). All surviving implants were stable at stage three and RFA values in implant stability quotient (ISQ) did not differ significantly between the two groups (test 82.3 � 3.9 versus control 78.8 � 4.3, p=0.36). No correlation was found between crestal bone loss and RFA (Spearman�s rho =-0.27, p=0.46). Histomorphometric analysis found no statistical difference (%BIC test 65.65 � 12.7%, control 53.36 � 6.41%, p=0.18; and %BD test 54.84 � 8.45%, control 64.69 � 13.57%, p=0.11). A similar trend was observed for mean micro-CT (%BIC test 65.72 � 72, control 50.84 � 4.19, p=0.11). Histology revealed high density inflammatory infiltrates beneath the sulcular and pocket epithelium. No significant difference was found between histomorphometric (HMA) and microCT analysis (%BIC p=0.08, %BD p=0.08). A statistically significant correlation was observed between HMA and microCT for %BIC (Spearman�s rho = 0.89, p=0.02) but not %BD (Spearman�s rho = 0.51, p=0.30). Conclusions: The results suggest that the sheep mandibular model has limited potential for evaluation of implants designed for poor quality bone and for the assessment of implant loading protocols. This thesis does highlight the potential for the use of this model in peri-implantitis studies. The results suggest that morphometric variables determined by HMA and microCT analysis are comparable, however further studies are required to standardize the microCT protocol to reduce metal artifacts and enhance bone-implant contrast.

Thesis (M. Sc.)--McGill University, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1997. / Includes bibliographical references.

Thesis (M. Sc.)--McGill University, 1998. / Includes bibliographical references.

O objetivo desse trabalho foi avaliar, pelo método fotoelástico, de que maneira cargas aplicadas sobre próteses metalocerâmicas implantossuportadas eram transmitidas a implantes de diferentes comprimentos, e como a proporção coroa/implante influenciaria essa distribuição de tensões. A partir de quatro modelos mestres em resina do tipo policarbonato foram confeccionados quatro modelos em resina fotoelástica (Araldite) simulando extremidade livre mandibular, com o dente 44 em resina (Luxatemp) e os dentes 45, 46 e 47 substituídos por implantes com 4 mm de diâmetro. O grupo 1 (G1) foi formado por 2 implantes de comprimento convencional ou longo (11 mm; Titamax Cortical CM, Neodent) substituindo o 45 e o 46, e 1 implante curto (5 mm; Ws Cortical CM, Neodent) substituindo o 47. O grupo 2 (G2) apresentava 1 implante com 11 mm (45) e 2 implantes com 5 mm (46 e 47). O grupo 3 (G3) foi reabilitado por 3 implantes de 5 mm e o grupo 4 (G4) por 3 implantes de 11 mm de comprimento. Nos grupos com implantes de 5 mm foi simulada reabsorção óssea de 4 mm de altura. Coroas metalocerâmicas unidas foram parafusadas sobre os minipilares intermediários. Foram realizados diferentes carregamentos oclusais sobre as coroas: oclusal balanceado de 150N, puntiforme de 100N na mesial do 45 e puntiforme de 100N na distal do 47. Análise fotoelástica quantitativa determinou a tensão transmitida (MPa) nos grupos: G1 (84.73), G2 (136.36), G3 (126.77) e G4 (164.72) para a carga oclusal balanceada; G1 (91.66), G2 (70.93), G3 (93.08) e G4 (119.82) para a carga na mesial do 45; e G1 (75.22), G2 (70.88), G3 (93.79) e G4 (117.56) para a carga na distal do 47. Para os implantes curtos, em todos os casos, a proporção coroa/implante foi maior que 2,5 e para os implantes de comprimento convencional essa proporção foi 1, em média. Após as análises realizadas, foi possível concluir que os maiores valores de tensões foram encontrados no grupo com 3 implantes longos (G4), e o aumento da proporção coroa/implante não mostrou correlação com maior concentração de tensões. Comparativamente, a utilização de implantes curtos reduziu as tensões transmitidas ao redor dos implantes. / The aim of this study was to evaluate by the photoelastic method, stress transmission to implants of different lengths by metal-ceramic crowns under different loads, and how crown/implant ratio influenced this stress distribution. From four matrixes, four photoelastic models (Araldite) were made simulating free mandibular end, with teeth 44 in resin (Luxatemp) and tooth 45, 46 and 47 replaced by implants with 4 mm in diameter. Group 1 (G1) was formed by two implants with conventional length or long (11 mm; Titamax Cortical CM, Neodent) replacing tooth 45 and 46, and one short implant (5 mm; Ws Cortical CM, Neodent) replacing the 47. Group 2 (G2) had one implant with 11 mm (45) and 2 implants with 5 mm (46 and 47). Group 3 (G3) was rehabilitated by three implants of 5 mm and group 4 (G4) for 3 implants of 11 mm in length. In the groups with 5 mm implants was simulated 4 mm bone resorption in height. Metal-ceramic fixed prosthesis was bolted on the abutments. Different oclusal loads were performed over the crowns, 150N in occlusal balanced, 100N on the 45 mesial, and 100N on the 47 distal. Quantitatively photoelastic analysis determined the stress transmitted (MPa) on the groups: G1 (84.73), G2 (136.36), G3 (126.77) and G4 (164.72) for the occlusal load balanced, G1 (91.66), G2 (70.93), G3 (93.08) and G4 (119.82) for charging on the 45 mesial, and G1 (75.22), G2 (70.88), G3 (93.79) and G4 (117.56) to the load on the 47 distal. Crown/implant ratio for short implants was greater than 2.5 and for long implants was about 1. After analysis, it was concluded that the highest values of strains were found in the group with three long implants (G4), and the increased crown/implant ratio showed no correlation with the highest stress concentration. Comparatively, the use of short implants reduced stress around the implants.

O objetivo desse trabalho foi avaliar, pelo método fotoelástico, de que maneira cargas aplicadas sobre próteses metalocerâmicas implantossuportadas eram transmitidas a implantes de diferentes comprimentos, e como a proporção coroa/implante influenciaria essa distribuição de tensões. A partir de quatro modelos mestres em resina do tipo policarbonato foram confeccionados quatro modelos em resina fotoelástica (Araldite) simulando extremidade livre mandibular, com o dente 44 em resina (Luxatemp) e os dentes 45, 46 e 47 substituídos por implantes com 4 mm de diâmetro. O grupo 1 (G1) foi formado por 2 implantes de comprimento convencional ou longo (11 mm; Titamax Cortical CM, Neodent) substituindo o 45 e o 46, e 1 implante curto (5 mm; Ws Cortical CM, Neodent) substituindo o 47. O grupo 2 (G2) apresentava 1 implante com 11 mm (45) e 2 implantes com 5 mm (46 e 47). O grupo 3 (G3) foi reabilitado por 3 implantes de 5 mm e o grupo 4 (G4) por 3 implantes de 11 mm de comprimento. Nos grupos com implantes de 5 mm foi simulada reabsorção óssea de 4 mm de altura. Coroas metalocerâmicas unidas foram parafusadas sobre os minipilares intermediários. Foram realizados diferentes carregamentos oclusais sobre as coroas: oclusal balanceado de 150N, puntiforme de 100N na mesial do 45 e puntiforme de 100N na distal do 47. Análise fotoelástica quantitativa determinou a tensão transmitida (MPa) nos grupos: G1 (84.73), G2 (136.36), G3 (126.77) e G4 (164.72) para a carga oclusal balanceada; G1 (91.66), G2 (70.93), G3 (93.08) e G4 (119.82) para a carga na mesial do 45; e G1 (75.22), G2 (70.88), G3 (93.79) e G4 (117.56) para a carga na distal do 47. Para os implantes curtos, em todos os casos, a proporção coroa/implante foi maior que 2,5 e para os implantes de comprimento convencional essa proporção foi 1, em média. Após as análises realizadas, foi possível concluir que os maiores valores de tensões foram encontrados no grupo com 3 implantes longos (G4), e o aumento da proporção coroa/implante não mostrou correlação com maior concentração de tensões. Comparativamente, a utilização de implantes curtos reduziu as tensões transmitidas ao redor dos implantes. / The aim of this study was to evaluate by the photoelastic method, stress transmission to implants of different lengths by metal-ceramic crowns under different loads, and how crown/implant ratio influenced this stress distribution. From four matrixes, four photoelastic models (Araldite) were made simulating free mandibular end, with teeth 44 in resin (Luxatemp) and tooth 45, 46 and 47 replaced by implants with 4 mm in diameter. Group 1 (G1) was formed by two implants with conventional length or long (11 mm; Titamax Cortical CM, Neodent) replacing tooth 45 and 46, and one short implant (5 mm; Ws Cortical CM, Neodent) replacing the 47. Group 2 (G2) had one implant with 11 mm (45) and 2 implants with 5 mm (46 and 47). Group 3 (G3) was rehabilitated by three implants of 5 mm and group 4 (G4) for 3 implants of 11 mm in length. In the groups with 5 mm implants was simulated 4 mm bone resorption in height. Metal-ceramic fixed prosthesis was bolted on the abutments. Different oclusal loads were performed over the crowns, 150N in occlusal balanced, 100N on the 45 mesial, and 100N on the 47 distal. Quantitatively photoelastic analysis determined the stress transmitted (MPa) on the groups: G1 (84.73), G2 (136.36), G3 (126.77) and G4 (164.72) for the occlusal load balanced, G1 (91.66), G2 (70.93), G3 (93.08) and G4 (119.82) for charging on the 45 mesial, and G1 (75.22), G2 (70.88), G3 (93.79) and G4 (117.56) to the load on the 47 distal. Crown/implant ratio for short implants was greater than 2.5 and for long implants was about 1. After analysis, it was concluded that the highest values of strains were found in the group with three long implants (G4), and the increased crown/implant ratio showed no correlation with the highest stress concentration. Comparatively, the use of short implants reduced stress around the implants.