Indiana University-Purdue University Indianapolis (IUPUI) / Statement of problem: Yttria-partially stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic restorations have been reported to suffer from chipping or cracking of the veneering porcelain (VP) as the most common complication. There is little information in the literature regarding the influence of surface treatment on VP shear bond strength to Y-TZP after cyclic loading. Purpose of this study: The goals of this study were (1) to investigate the influence of zirconia surface treatments on veneering porcelain shear bond strength and (2) to investigate the influence of cyclic loading on the shear bond strength between VP and Y-TZP. Materials and Methods: 48 cylinder–shaped specimens (6mm in diameter and 4mm in height) were divided into 4 groups containing 12 specimens each according to the surface treatment. As a control group (C), no further treatment was applied to the specimens after grinding. Group H was heat-treated as a pretreatment according to the manufacturer’s recommendations. Group S was airborne-particle abraded with 50 µm alumina (Al2O3) particles under a pressure of 0.4 MPa for 10 seconds. In the group SH, the heat-treatment was performed after the airborne-particle abrasion. A VP cylinder (2.4 mm in diameter and 2 mm in height) was applied and fired on the prepared Y-TZP specimens. The shear bond strength was tested using a universal testing machine. Six specimens from each group were subjected to fatigue (10,000cycles, 1.5Hz, 10N load) before testing. Results: The 3-way ANOVA showed no statistically significant effect of surface treatment and cyclic loading on shear bond strength. The highest mean shear bond strength was recorded for the air-particle abrasion group without cyclic loading (34.1 + 10 MPa). The lowest mean shear bond strength was the air-particle abrasion group with cyclic loading (10.7 ± 15.4 MPa). Sidak multiple comparisons procedure demonstrated cyclic loading specimens had significantly lower shear bond strength than non-cyclic loading specimens after air-particle abrasion without heat treatment (p=0.0126) Conclusion: Within the limitations of this study, (1) Shear bond strength between Y-TZP and VP is not affected statistically by surface treatment using heat treatment, airborne-particle abrasion, and heat treatment after airborne-particle abrasion. (2) There is significant difference in shear bond strength with air-particle abrasion between with and without cyclic loading groups. This difference suggested that air-particle abrasion should be avoided in clinical situations as a surface treatment without heat treatment.

Indiana University-Purdue University Indianapolis (IUPUI) / The objectives: 1. To compare the flexural strength, flexural modulus, and fracture toughness of specimens fabricated from recently marketed translucent full-contour zirconia, traditional zirconia, and lithium disilicate glass ceramic. 2. To compare the load-to-failure of crowns fabricated from recently marketed translucent full-contour zirconia, traditional zirconia, and lithium disilicate glass ceramic at their recommended tooth-reduction thickness. Methodology: Four groups of translucent zirconia (BruxZir, KDZ Bruxer, CAP FZ, Suntech zirconia), one group of traditional zirconia (CAP QZ) and IPS e.maxCAD) were tested. Twelve bars of each material were made and tested for flexural strength, and fracture toughness. Fracture patterns were imaged under SEM. Forty-eight crowns (8 from each group) were fabricated with CAD/CAM technique following manufacturers’ recommendations for the amount of tooth reduction. All the crowns were cemented to prepared epoxy resin dies with RelyX Unicem and tested for static load to failure in a universal machine. Result: In bar-shape samples, CAP QZ (traditional zirconia) showed the highest flexural strength (788.12 MPa), fracture toughness (6.85 MPa.m1/2), and fracture resistance (2489.8 N). All translucent zirconia groups show lower mechanical properties than QZ. However, there were no differences between translucent and traditional zirconia in the fracture resistance of the crown-shape samples. There was no significant difference in fracture resistance between IPS e.max crowns at recommended thickness and other zirconia crowns at recommended thickness. Conclusion: With less reduction of tooth structure, a high inherent strength and chip resistance make full-zirconia crowns a good alternative to porcelain-fused-to-metal crowns and all other ceramic crowns.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: A silorane based resin composite, Filtek LS restorative, has been introduced to overcome the polymerization shrinkage of the methacrylate based resin composite. The repair of resin composite may hold clinical advantages. Currently, there is no available information regarding the repair potential of silorane resin composite with either silorane or methacrylate based resin composite. Objectives: The purpose of this study was to compare the repaired microtensile bond strength of aged silorane resin composite using different surface treatments and either silorane or methacrylate based resin composite. Methods: One hundred and eight silorane resin composite blocks (Filtek LS) were fabricated and aged by thermocycling between 8oC and 48oC (5000 cycles). A control (solid resin composite) and four surface treatment groups (no treatment, acid treatment, aluminum oxide sandblasting and diamond bur abrasion) were tested. Each treatment group was randomly divided in half and repaired with either silorane resin composite (LS adhesive) or methacrylate based resin composite (Filtek Z250/Single Bond Plus). Specimens were 12 blocks and 108 beams per group. After 24 hours in 37oC distilled water, microtensile bond strength testing was performed using a non-trimming technique. Fracture surfaces were examined using an optical microscopy (20X) to determine failure mode. Data was analyzed using Weibull-distribution survival analysis. Results: Aluminum oxide sandblasting followed by silorane or methacrylate based resin composite and acid treatment with methacrylate based resin composite provided insignificant differences from the control (p>0.05). All other groups were significantly lower than the control. Failure was primarily adhesive in all groups. Conclusion: Aluminum oxide sandblasting produced comparable microtensile bond strength compared to the cohesive strength of silorane resin composite. After aluminum oxide sandblasting, aged silorane resin composite can be repaired with either silorane resin composite with LS system adhesive or methacrylate based resin composite with methacrylate based dentin adhesive.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: Since the introduction of glass ionomer cements (GICs) in the 1970s, many attempts have been made to improve them and expand their application in restorative dentistry. Recently, GC America introduced a new glass ionomer restorative system called EQUIA. The manufacturer claims that this material has improved wear resistance by coating the surface of high-strength GIC with a nano-filled resin coating. Objective: The objective of this study was to measure the wear resistance and hardness of EQUIA and to compare it to other current restorative materials. Materials and Methods: Four different materials were used in this study: EQUIA, Fuji IX GP Extra, Fuji II LC and Z-100. Six specimens of each material were made and then tested in a toothbrush abrasion machine for 20,400 cycles, after which the amount of volume loss was calculated. Eight specimens of each material were made and tested in a three-body Alabama wear testing machine under a load of 75 N for 400,000 cycles. Four surface profiles were obtained from each specimen and volume loss was calculated using computer software. Five specimens of each material were made and Knoop microhardness was determined by using the mean of the three values from the top surface of the specimen. Results of each test were collected and compared with the other materials using one-way analysis of variance (ANOVA) at a significance level of 0.05. Results: Wear-resistance results showed that EQUIA has wear-resistance values comparable to composite resin and higher values than those for the high-strength GIC. The results also showed that Fuji II LC had the highest wear among all tested materials. Microhardness results showed that EQUIA has significantly lower microhardness than Fuji IX GP Extra and Z-100. Conclusion: Based on the results of the present study, it can be concluded that coating the surface of glass ionomer restorations with a nano-filled resin coat results in increasing the wear resistance and decreasing the microhardness of the material. Within the limitations of this study, EQUIA has comparable wear resistance to composite resin.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / PURPOSE: To evaluate the effect of aqueous solutions of chlorhexidine digluconate (CHX) in different concentrations on bond strength to eroded dentin up to 6 months, using normal dentin as a control. METHODS: Exposed flat dentin of extracted third molars was only ground with 600-grit SiC paper/1 minute (normal dentin - N), or subsequently eroded by a regular-cola soft-drink (eroded dentin - E). N and E were acid-etched, washed, dried and rehydrated with 1.5 μL, respectively, of distillated water (control - NC / EC); of 0.004% CHX (N0.004% / E0.004%); or of 2% CHX (N2% / E2%). Adper Single Bond 2 was applied in all specimens and resin composite buildups were constructed with Filtek Z350. Specimens were sectioned in beams, which were tested (μTBS) immediately or after 6 months of aging. RESULTS: Microtensile bond strength to eroded dentin was always significantly lower than that to normal dentin. Application of tested CHX solutions did not exert a significant effect immediately; however, after aging, the 2% CHX prevented abrupt bond strength loss both to eroded and normal dentin. / Revisión por pares

<p>Uvod. Usled kompromitovanja strukturnog integriteta, rekonstruktivne procedure na endodontski lečenim zubima moraju se veoma pažljivo isplanirati, pogotovo u specifičnoj grupi zuba kao &scaron;to su premolari. U stomatolo&scaron;koj naučnoj i stručnoj javnosti ne postoji usagla&scaron;en stav o tome koja endodontska instrumentacija i rekonstruktivna procedura primenjena u slučajevima ekstenzivnog gubitka zubne supstance predstavlja metodu izbora sa biomehaničkog aspekta. U okviru prezentovane doktorske disertacije ispitivan je uticaj varijacija u endodontskoj instrumentaciji i restaurativnim procedurama na promene naponskih stanja u zubnim tkivima i rekonstruktivnim materijalima kod premolara sa ekstenzivnim gubitkom zubne strukture. Metode. Osnovni 3D model je kreiran pomoću CT snimaka zdravog drugog gornjeg premolara u SolidWorks programu za modelovanje. Kreirano je 135 različitih modela, u kojima su metodom konačnih elemenata proračunati fon Mizesovi naponi u položaju maksimalne interkuspidacije pod dejstvom sile od 150 N. Statistička analiza je izvr&scaron;ena koristeći Op&scaron;ti linearni model. Rezultati. Indirektne zubne rekonstrukcije imaju povoljniji uticaj na naponska stanja u zubnim tkivima. Ukoliko se koristi direktna restauracija, povoljniji su naponi u dentinu i gleđi ukoliko se redukuje palatinalna kvržca. Upotreba kočića uz ispun snižava napone u zubnim tkivima samo u slučaju MOD kaviteta. Naponi u dentinu su niži pri apikalnom terminusu 0,5 mm i instrumentaciji instrumentima manje veličine (kod modela sa kočićem i indirektnim nadoknadama). Uglavnom procedure koje su povoljne za napone u dentinu, nepovoljne su za napone u zubnoj nadoknadi i obratno. Zaključci. Kod opsežnih MOD kaviteta a samo ukoliko se ne redukuje visina palatinalne kvržice, preporučuje se upotreba kompozitnog kočića. Smanjenje povr&scaron;ine zubnih tkiva u kojima su naponi visoki (iako su najvi&scaron;e vrednosti napona slične), moglo bi da utiče na dugotrajnost endodontski lečenih i rekonstruisanih zuba. Krući rekonstruktivni materijali povoljnije utiču na napone u zubnim tkivima biomehanički kompromitovanih endodontski lečenih zuba. Čini se da je optimalnije, u rekonstruktivnim re&scaron;enjima koja podrazumevaju upotrebu kočića, postaviti apikalni terminus bliže vrhu korena i koristiti instrumente srednje &scaron;irine.</p> / <p>Background. Restoration of an endodontically treated premolar with a wide and deep mesial-occlusal-distal (MOD) cavity is often complex due to biomechanical weakening of the tooth. There are no definitive recommendations on the optimal restoration in these cases. The aim of this study was to determine the effects of different endodontic and restorative procedures on von Mises stress values and distribution in dental tissues and restorative materials using finite element analysis (FEA). Methods. Based on CT scans of an second upper premolar, extracted for orthodontic reasons, 135 3D endodontically treated tooth models were created. Each model was subjected to a summary force of 150 N on the occlusal surface simulating the normal biting pattern and maximal von Mises stresses were calculated. Results. MODP cavity design seems to reduce von Mises stress values in dental tissues and P seems to transfer some of the stresses from dental tissues to the composite filling in the MOD cavity when direct restorations are used. Indirect restorations caused lower stresses within dentin. Apical terminus of 0.5 mm induces lower, while the terminus of 1.5 mm induces the highest stresses in dentin in models restored with direct composite and post. It seems that from the aspect of the tooth tissue, it is more recommended to use smaller endodontic instruments sizes. Conclusions. Stiffer restorative materials cause lower stresses in dentin of an endodontically treated structurally weakened tooth, and if a direct restoration is to be used, palatal cuspal reduction could be beneficial for the longevity of the tooth and the restoration. Further, in a wide and deep MOD cavity, without cuspal reduction, the use of a FRC post is recommended in order to reduce the stresses in the enamel and dentin. Moreover, it seems that it is beneficial for the stresses in the tooth tissue to place the apical terminus closer to the root apex as well as to use smaller size endodontic instruments.</p>

<p>Gubitak tvrdih zubnih struktura usled karijesne lezije, traume ili ekstenzivne preparacije dovodi do smanjenja otpornosti preostalih zubnih struktura na dejstvo sila prilikom žvakanja. Osnovni zadatak restaurativne procedure je da se ponovo uspostavi anatomo-morfolo&scaron;ka funkcija zuba i da se preostale zdrave zubne strukture za&scaron;tite od nepovoljnog odgovora na dejstvo sila. Cilj doktorske disertacije bio je da se ispita uticaj različitih restaurativnih procedura na biomehaničke karakteristike premolara sa ekstenzivnim kavitetima. Materijal i metode: Trodimenzionalni model intaktnog drugog gornjeg premolara kreiran je u SolidWorks računarskom programu, na osnovu snimaka ekstrahovanog zuba primenom vi&scaron;eslojnog spiralnog kompjuterizovanog tomografa. Na osnovu ovog modela potom je kreirano ukupno 48 modela, koji su podeljeni u dve grupe: modeli vitalnog premolara sa MOD kavitetom (I grupa) i modeli premolara sa endodontski lečenim kanalom korena sa MOD kavitetom (II grupa). U svakoj grupi ispitivan je uticaj 4 vrste restaurativnog materijala (direktan kompozitni ispun, direktan kompozitni ispun sa smolom modifikovanim glas-jonomer cementom u vidu podloge, indirektan kompozitni ispun, keramički ispun), 3 dizajna preparacije kaviteta (bez skraćivanja kvržica, sa skraćivanjem palatinalne kvržice 2mm, sa skraćivanjem palatinalne i bukalne kvržice 2mm) i 2 &scaron;irine istmusa (1/2 i 2/3 interkuspalnog razmaka). Primenom metode konačnih elemenata proračunate su vrednosti von Mises napona u zubnim strukturama i ispunu za sve modele pri dejstvu statičke sile od 200N. Rezultati: Dizajn preparacije kaviteta je pokazao najveći uticaj na vrednosti von Mises napona u zubnim strukturama. Pri tome, postupak skraćivanja palatinalne, kao i obe kvržice, doprineo je smanjenju vrednosti von Mises napona u gleđi na modelima obe grupe; dok je postupak skraćivanja bukalne i palatinalne kvržice doprineo smanjenju vrednosti von Mises napona u dentinu na modelima vitalnog premolara. U obe grupe, vrsta restaurativnog materijala pokazala je uticaj na vrednosti von Mises napona u gleđi, pri čemu je keramički ispun doveo do pojave napona značajno manjih vrednosti u odnosu na direktan i indirektan kompozitni ispun.Vrsta restaurativnog materijala je uticala i na vrednosti von Mises napona u dentinu, ali samo na modelima vitalnog premolara; pri tome su indirektni kompozitni i keramički ispun podjednako doprineli pojavi napona manjih vrednosti. &Scaron;irina istmusa je uticala na vrednosti von Mises napona u gleđi i dentinu na modelima vitalnog premolara. &Scaron;irina istmusa 1/2 interkuspalnog razmaka dovela je do pojave napona manjih vrednosti u gleđi, dok je &scaron;irina istmusa 2/3 interkuspalnog razmaka dovela do pojave napona manjih vrednosti u dentinu.</p> / <p>Loss of tooth structure from caries, trauma or extensive preparation decreases fracture resistance of tooth. The main goal of restorative procedure is to rebuild lost structures and to protect remaining tooth structures from unfavorable responses from masticatory forces. Aim of thesis was to investigate the influence of different restorative procedures on biomechanical properties of premolar with extensive cavities. Materials and Methods: Three dimensional model of intact maxillary second premolar, based on computerized tomography scan images of extracted tooth, was designed using SolidWorks software. Using this model, 48 models were designed and divided in two groups: models of vital premolars with MOD cavities (group I), and models of premolars with root canal treatment with MOD cavities (group II). In each group use of four restorative materials (direct composite resin restoration, direct composite resin restoration with resin modified glass-ionomer cement as base, indirect composite resin restoration, ceramic restoration), three cavity preparation designs (without cusp coverage, 2mm palatal cusp coverage, 2mm palatal and buccal cusp coverage) and two isthmus width (1/2 and 2/3 intercuspal width) were simulated. After applying static load of 200N, von Mises stresses in enamel, dentin and restoration were calculated using finite element analysis. Results: Cavity preparation design showed the most significant influence on von Mises stress values in tooth structures. Cusp coverage in general decreased stress values in enamel, while palatal and buccal cusp coverage decreased stress values in dentin only in group I. Restorative material affected stress values in enamel, were ceramic restoration contributed to minimal stress values. In dentin, indirect composite resin and ceramic restoration showed no difference in reducing von Mises stress values, but only for models in group I. Cavity isthmus width had influence on stress values in tooth structures only in group I. 1/2 isthmus width decreased stress values in enamel, while 2/3 isthmus width showed same effect in dentin. Conclusion: In order to provide optimal biomechanical characteristics of tooth structures, premolars with MOD cavity should be restored with ceramic overlay covering both palatal and buccal cusp.</p>

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / PURPOSE: To assess the long-term effect of a 2% aqueous chlorhexidine (CHX) solution on bond strength to artificially eroded dentin compared to sound dentin. MATERIALS AND METHODS: Flat mid-coronal dentin surfaces of extracted third molars (n = 28) were subjected only to grinding with a 600-grit SiC paper for 1 min (sound dentin S, n = 14) or additionally to erosive pH cycling with a cola-based soft-drink (eroded dentin E, n = 14). After acid etching, rinsing, and air drying, S and E were rehydrated with 1.5 μl of 2% CHX (S2%, n = 7; E2%, n = 7) or of distilled water (control SC, n = 7; EC, n = 7). Composite buildups were incrementally constructed with Filtek Z350 following Adper Single Bond 2 application. Specimens were sectioned into beams, which were subjected to microtensile testing immediately or after 6 or 12 months of aging. Fractured surfaces were observed under a digital microscope (50X magnification). Microtensile bond strength (μTBS) (MPa) was analyzed by three-way ANOVA and Tukey's tests (α = 0.05) and failure mode by the Kruskal-Wallis test (α = 0.05). RESULTS: Compared to sound dentin, eroded dentin was consistently related to lower μTBS. Immediately and after 12-month aging, the effect of CHX was insignificant, but it was significant after 6-month aging, when it conserved the bond strength to both eroded and sound dentin. The percentage of adhesive and mixed failures were equivalent, and significantly more frequent than cohesive failures, whether in dentin or in composite. CONCLUSION: The 2% CHX effect on bond strength conservation to both eroded and sound dentin was not found to be persistent. / Revisión por pares

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / PURPOSE: To assess the influence of simulated oral erosive/abrasive challenges on the bond strength of an etch-and-rinse two-step bonding system to enamel using an in situ/ex vivo protocol. METHODS: Bovine enamel blocks were prepared and randomly assigned to four groups: CONT - control (no challenge), ABR - 3x/day-1 minute toothbrushing; ERO - 3x/day - 5 minutes extraoral immersion into regular Coca Cola; and ERO+ABR - erosive protocol followed by a 1-minute toothbrushing. Eight blocks were placed into an acrylic palatal appliance for each volunteer (n = 13), who wore the appliance for 5 days. Two blocks were subjected to each of the four challenges. Subsequently, all the blocks were washed with tap water and Adper Single Bond 2/Filtek Z350 were placed. After 24 hours, 1 mm2 beams were obtained from each block to be tested with the microtensile bond strength test (50 N load at 0.5 mm/minute). The data were statistically analyzed by one-way RM-ANOVA and Tukey's tests (alpha = 0.05). RESULTS: No difference was detected among the ABR, ERO, and CONT groups (P > 0.05). ERO+ABR group yielded lower bond strengths than either the ABR and ERO groups (P < 0.0113). / Revisión por pares