Magister Scientiae Dentium - MSc(Dent) / Aim: The aim of this study was to evaluate, in-vitro, the shear bond strength (SBS) and the resultant failure pattern after debonding of metal orthodontic brackets bonded with TransbondTM XT adhesive resin cement and RelyXTM Unicem 2 self-adhesive resin cement to pre-treated (35% ortho-phosphoric acid and silane coupling agent application) IPS eMax and porcelain veneered zirconia crowns. Material and methodology: A Typhodont maxillary lateral incisor was used and prepared in a conventional manner to receive a full ceramic crown. A CAD (computer aided design)/ CAM (computer aided manufacturing) machine was used to scan the prepared tooth and manufacture 40 IPS eMax crowns and 40 porcelain veneered zirconia crowns. Half the number of IPS eMax crown specimens (ie. 20) and half the number of porcelain veneered zirconia crown specimens (ie. 20) were thermocycled (ie. to mimic thermal changes which occur in the mouth), from 5 to 55o for 500 cycles as recommended by the International Organization for Standardization (ISO 6872, 2008). The remaining 20 IPS eMax crown specimens and 20 porcelain veneered zirconia crown specimens remained new and unexposed to thermal changes. The facial surfaces of all the thermocycled and non-thermocycled crown specimens were then etched. Etching of all the ceramic bonding surfaces was performed by the application of 35 per cent ortho-phosphoric acid liquid for 2 minutes, followed by a thin layer of a ceramic primer. A lateral incisor metal bracket with a bracket base area of 9mm2 (as confirmed by the manufacturer) was bonded to each of the etched and silane treated ceramic crown specimens and separated in the following manner: Group 1: (10 thermocycled, etched and silane treated IPS eMax and 10 thermocycled, etched and silane treated porcelain veneered zirconia crown specimens) RelyX™ Unicem 2 self-adhesive resin cement was used to bond the bracket to the ceramic crown specimens, Group 2: (10 thermocycled, etched and silane treated IPS eMax and 10 thermocycled, etched and silane treated porcelain veneered zirconia crown specimens) Transbond™ XT light cure adhesive primer was first applied onto the bonding surface of the crowns and then Transbond™ XT adhesive resin was used to bond the bracket to the ceramic crown specimens, Group 3: (10 non-thermocycled, etched and silane treated IPS eMax and 10 non-thermocycled, etched and silane treated porcelain veneered zirconia crown specimens) RelyX™ Unicem 2 self-adhesive resin cement was used to bond the bracket to the ceramic crown specimens, Group 4: (10 non-thermocycled, etched and silane treated IPS eMax and 10 non-thermocycled, etched and silane treated porcelain veneered zirconia crown specimens) Transbond™ XT light cure adhesive primer was first applied onto the bonding surface of the crowns and then Transbond™ XT adhesive resin cement was used to bond the bracket to the ceramic crown specimens. After bonding all samples were stored in distilled water for 24 hours before being submitted to the shear bond strength test. Debonding forces in Newtons (N) was determined by using a shear testing machine and converted into Mega Pascals (MPa). Results: The results after debonding were compared. The mean shear bond strength for RelyXTM Unicem 2 self-adhesive resin cement bonded to the all ceramic non-thermocycled crowns (Group 3) ranged from a low of 5.1 MPa (45.5 Newtons) when brackets were bonded to the IPS eMax crowns to a high of 5.8 MPa (51.9 Newtons) when brackets were bonded to the porcelain veneered zirconia crowns. The mean shear bond strength for Transbond XT adhesive resin cement bonded to the all ceramic non-thermocycled crowns (Group 4) ranged from a low of 6.4 MPa (57.3 Newtons) when brackets were bonded to the porcelain veneered zirconia crowns to a high of 8.1 MPa (72.7 Newtons) when brackets were bonded to the IPS eMax crowns. The side by side Box-and-Whisker plots of the shear bond strengths show wide and overlapping dispersions of the crown/adhesive resin combinations which consequently lessen the probability of significant differences between the crown/adhesive resin combinations in all 4 groups. According to the Kruskal-Wallis test (p < 0.05), and the Bonferroni Test the non-thermocycled crown/adhesive resin combinations do not differ significantly. Study of the mean ARI (Adhesive Remnant Index) values for the non-thermocycled crown/adhesive combinations shows that brackets bonded with Rely-XTM Unicem 2 to non-thermocycled porcelain veneered zirconia crowns failed entirely at the ceramic/adhesive interface and for all the other non-thermocycled ceramic/adhesive combinations most of the failures of the bond (70%) occurred at the bracket/adhesive interface, ie. cohesive fractures within the composite resin. No cohesive fractures of the porcelain crowns were noted. The results of the thermocycled groups (Group 1 and Group 2) show the TransbondTM XT/non-thermocycled IPS eMax crown combination yielded the highest overall mean shear bond strength of 8.1 MPa (72.7 Newtons) but dropped to a mean shear bond strength of 5.1 MPa (46.1 Newtons) (36.4% drop in shear bond strength) when the crowns were thermocycled prior to bonding. The TransbondTM XT/non-thermocycled porcelain veneerd zirconia crown combination yielded the second highest overall mean shear bond strength of 6.4 MPa (57.3 Newtons) and dropped to a mean shear bond strength of 5.1 MPa (45.8 Newtons) (19.3% drop in shear bond strength) when the crowns were thermocycled prior to bonding. The RelyXTM Unicem 2/non-thermocycled porcelain veneered zirconia crown combination yielded the third highest overall mean shear bond strength of 5.8 MPa (51.9 Newtons) but dropped significantly to a mean shear bond strength of 3.2 MPa (29.1 Newtons) (a significant 43.8% drop in shear bond strength) when the crowns were thermocycled prior to bonding. Lastly, the RelyXTM Unicem 2/non-thermocycled IPS eMax crown combination yielded the fourth highest mean shear bond strength of 5.1MPa (45.5 Newtons) but dropped to a mean shear bond strength of 4.9 MPa (44.5 Newtons) (a drop in shear bond strength of only 3%) when the crowns were thermocyled prior to bonding. Relaxing the significance level (p-value) somewhat demonstrates the negative influence of thermocycling on the shear bond strength of the crown/adhesive combinations. The non-thermocycled all ceramic crown/adhesive combinations showed mean ARI values of between 1.3 and 2.1 indicating cohesive fractures within the composite resin and efficient bonding of the adhesive material to the porcelain surface. However, all the thermocycled all ceramic crown/adhesive treatment combinations showed mean ARI values of between 0 and 0.8 indicating a bond failure between adhesive and porcelain and highlighting the negative influence of thermocycling on bond strength of both adhesive resin cements. Conclusion: Within the limitations of this study, it can be concluded that: 1.There was no significant difference in the shear bond strengths of metal orthodontic brackets bonded with RelyXTM Unicem 2 self-adhesive resin cement and metal orthodontic brackets bonded with TransbondTM XT adhesive resin cement to IPS eMax and porcelain-veneered zirconia crowns which were conditioned with 35 % phosphoric acid and a silane coupling agent. 2. Conditioning the porcelain surface with 35% phosphoric acid and a silane coupling agent (which is safer to use than Hydrofluoric acid) is sufficient for bonding metal orthodontic brackets to all ceramic crowns, and should make it simpler for clinicians to remove the remaining adhesive from the porcelain surface after debonding. 3. The negative influence of thermocycling prior to bonding can be seen on shear bond strength values. 4. Most of the failures of the bond occurred at the ceramic/adhesive interface and cohesive fractures within the composite resin. No cohesive fractures of the porcelain crowns were noted.

As restaurações metalocerâmicas apresentam relatos de sucesso clínico a longo prazo e as características de reforço (cinta lingual e poste proximal) das infra-estruturas metálicas parecem ser de grande importância para este sucesso. Estes reforços freqüentemente estão ausentes nas infraestruturas das restaurações ceramocerâmicas. O objetivo deste estudo foi testar a hipótese nula de que coroas confeccionadas com infra-estruturas cerâmicas com desenho com e sem reforço não resultam em valores de resistência à fratura diferentes de coroas com infra-estruturas metálicas confeccionadas com os mesmos desenhos. Para a realização deste trabalho foram fabricadas 40 coroas, dividas em quatro grupos (n=10): (1) coroas metalocerâmicas - infra-estrutura com reforço; (2) coroas metalocerâmicas - infra-estrutura sem reforço; (3) coroas ceramocerâmicas - infra-estrutura com reforço; e (4) coroas ceramocerâmicas - infra-estrutura sem reforço. Os corpos de prova foram cimentados com ionômero de vidro modificado por resina nos troquéis metálicos e submetidos à análise de resistência à fratura usando uma máquina de teste universal Kratos, a uma velocidade de 0,5 mm/min. Todos os corpos de prova foram mantidos sob pressão até a fratura. Os resultados de resistência à fratura (kgf) foram submetidos à análise de variância (ANOVA) a dois critérios e ao teste de Tukey. O nível de significância considerado em todas as análises foi de 5% (p<0,05). Os valores médios de resistência à fratura foram de 237,637 kgf para as coroas metalocerâmicas com infraestruturas com reforço, 171,738 kgf para as coroas metalocerâmicas com infraestruturas com reforço, 127,588 kgf para as coroas ceramocerâmicas com infra-estruturas com reforço e 93,914 kgf para as coroas ceramocerâmicas com infra-estruturas sem reforço, com diferença estatisticamente significante (p<0,05), entre os quatro grupos. As coroas metalocerâmicas com reforço (Grupo 1) apresentaram o maior valor de resistência à fratura e estatisticamente significante, entre todos os grupos. As coroas confeccionadas com infra-estruturas com reforço apresentaram maior resistência à fratura do que as confeccionadas sem reforço, tanto nas coroas metalocerâmicas como nas ceramocerâmicas. / Metal-ceramic restorations present reports of long-term clinical success, and the characteristics of reinforcement coping (lingual collar and buttressing shoulder) seem to be of great importance for this success. These reinforcements are often absent in all-ceramic coping restorations. The aim of the current study was to evaluate and compare the in vitro fracture resistance of metal-ceramic and In-Ceram Alumina all-ceramic crowns, with and without reinforced coping design. Forty crowns were fabricated and divided into four groups (n=10): group 1, metal-ceramic crown with reinforced coping design; group 2, metal-ceramic crown without reinforced coping design; group 3, allceramic crown with reinforced coping design and group 4, all-ceramic crown with out reinforced coping design. The forty crowns were cemented on stainless steel dies and axially loaded in a universal testing machine until fracture occurred, and the maximum load (kgf) was recorded. Data were analyzed by one-way analysis of variance (ANOVA) and Tukey test (p<0.05) The results showed a statistical significant superiority (p<0.05) of the reinforcement coping groups (237.637 kgf for metalo-ceramic crowns and 127.588 kgf for all-ceramic crowns), regarding to non reinforcement coping groups (171.738 kgf for metalo ceramic crowns and 93.914 kgf for all-ceramic crowns). These founds denote that: (1) crowns made with reinforcement coping had presented greater fracture resistance than those confectioned without it and (2) metal-ceramic crowns had presented greater fracture resistance than all-ceramic crowns.

No description available.

As restaurações metalocerâmicas apresentam relatos de sucesso clínico a longo prazo e as características de reforço (cinta lingual e poste proximal) das infra-estruturas metálicas parecem ser de grande importância para este sucesso. Estes reforços freqüentemente estão ausentes nas infraestruturas das restaurações ceramocerâmicas. O objetivo deste estudo foi testar a hipótese nula de que coroas confeccionadas com infra-estruturas cerâmicas com desenho com e sem reforço não resultam em valores de resistência à fratura diferentes de coroas com infra-estruturas metálicas confeccionadas com os mesmos desenhos. Para a realização deste trabalho foram fabricadas 40 coroas, dividas em quatro grupos (n=10): (1) coroas metalocerâmicas - infra-estrutura com reforço; (2) coroas metalocerâmicas - infra-estrutura sem reforço; (3) coroas ceramocerâmicas - infra-estrutura com reforço; e (4) coroas ceramocerâmicas - infra-estrutura sem reforço. Os corpos de prova foram cimentados com ionômero de vidro modificado por resina nos troquéis metálicos e submetidos à análise de resistência à fratura usando uma máquina de teste universal Kratos, a uma velocidade de 0,5 mm/min. Todos os corpos de prova foram mantidos sob pressão até a fratura. Os resultados de resistência à fratura (kgf) foram submetidos à análise de variância (ANOVA) a dois critérios e ao teste de Tukey. O nível de significância considerado em todas as análises foi de 5% (p<0,05). Os valores médios de resistência à fratura foram de 237,637 kgf para as coroas metalocerâmicas com infraestruturas com reforço, 171,738 kgf para as coroas metalocerâmicas com infraestruturas com reforço, 127,588 kgf para as coroas ceramocerâmicas com infra-estruturas com reforço e 93,914 kgf para as coroas ceramocerâmicas com infra-estruturas sem reforço, com diferença estatisticamente significante (p<0,05), entre os quatro grupos. As coroas metalocerâmicas com reforço (Grupo 1) apresentaram o maior valor de resistência à fratura e estatisticamente significante, entre todos os grupos. As coroas confeccionadas com infra-estruturas com reforço apresentaram maior resistência à fratura do que as confeccionadas sem reforço, tanto nas coroas metalocerâmicas como nas ceramocerâmicas. / Metal-ceramic restorations present reports of long-term clinical success, and the characteristics of reinforcement coping (lingual collar and buttressing shoulder) seem to be of great importance for this success. These reinforcements are often absent in all-ceramic coping restorations. The aim of the current study was to evaluate and compare the in vitro fracture resistance of metal-ceramic and In-Ceram Alumina all-ceramic crowns, with and without reinforced coping design. Forty crowns were fabricated and divided into four groups (n=10): group 1, metal-ceramic crown with reinforced coping design; group 2, metal-ceramic crown without reinforced coping design; group 3, allceramic crown with reinforced coping design and group 4, all-ceramic crown with out reinforced coping design. The forty crowns were cemented on stainless steel dies and axially loaded in a universal testing machine until fracture occurred, and the maximum load (kgf) was recorded. Data were analyzed by one-way analysis of variance (ANOVA) and Tukey test (p<0.05) The results showed a statistical significant superiority (p<0.05) of the reinforcement coping groups (237.637 kgf for metalo-ceramic crowns and 127.588 kgf for all-ceramic crowns), regarding to non reinforcement coping groups (171.738 kgf for metalo ceramic crowns and 93.914 kgf for all-ceramic crowns). These founds denote that: (1) crowns made with reinforcement coping had presented greater fracture resistance than those confectioned without it and (2) metal-ceramic crowns had presented greater fracture resistance than all-ceramic crowns.