Degree of conversion of 3D printing resins used for splints and orthodontic appliances under different postpolymerization conditions.

OBJECTIVES: To measure the degree of conversion (DC) of different 3D printing resins used for splints or orthodontic appliances under different postpolymerization conditions. MATERIALS AND METHODS: Five 3D-printed photopolymer resins were studied. Each resin was analyzed in liquid form (n = 15), and then cylindrical specimens (n = 135) were additively manufactured and postcured with Form Cure (Formlabs) at different times (10, 60, and 90 min) and temperatures (20 °C, 60 °C, and 80 °C). The DC of each specimen was measured with Fourier transform infrared spectroscopy (FTIR). The data were statistically analyzed using a 3-way ANOVA followed by Tukey's post hoc test. RESULTS: The time and temperature of postpolymerization significantly influenced the DC of each resin: when time and/or temperature increased, the DC increased. For all resins tested, the lowest DC was obtained with a postcuring protocol at 10 min and 20 °C, and the highest DC was obtained at 90 min and 80 °C. However, at 80 °C, the samples showed a yellowish color. CONCLUSIONS: With the Form Cure device, the time and temperature of postcuring could have an impact on the DC of the 3D printing resins studied. The DC of the 3D printing resins could be optimized by adjusting the postpolymerization protocol. CLINICAL RELEVANCE: Regardless of the resin used, when using the Form Cure device, postcuring at 60 min and 60 °C would be the minimal time and temperature conditions for achieving proper polymerization. Beyond that, it would be preferable to increase the postcuring time to boost the DC.

Shear bond strength of a RMGIC for orthodontic bracket bonding to enamel.

OBJECTIVE: To evaluate the shear bond strength (SBS) of a restorative resin-modified glass ionomer cement (RMGIC) for orthodontic bracket bonding. MATERIALS AND METHODS: One hundred twenty-one human teeth were randomly divided into 11 groups (n = 11) according to the surface treatment applied (H3PO4 ± Transbond Plus (TSEP) or Scotchbond Universal (SU)), and the adhesive used (Riva LC HV (RIVA), Fuji Ortho (FUJI), and Transbond XT (TXT)). For each sample, a metal button was bonded. SBS tests were performed at 1 week and debonded specimens were observed for failure modes determination. One-way ANOVA followed by Tukey's post hoc test was used to compare SBS differences and Fisher's exact test to analyze the failure modes (p < 0.05). RESULTS: TSEP + FUJI and H3PO4 + SU + TXT showed the highest SBS values while H3PO4 + TSEP + RIVA showed the lowest value. Cohesive failure and mixed failure were found in the groups with SU and TXT and adhesive failure in the other groups. DISCUSSION/CONCLUSIONS: The bonding of orthodontic attachments to enamel could be performed with any of the three materials studied. The use of a universal adhesive in the bonding protocol could optimize the adhesion values. Clinical studies would be needed to confirm the results obtained.

Analysis of Resin-Based Dental Materials' Composition Depending on Their Clinical Applications.

The objective of this study was to detail the monomer composition of resin-based dental materials sold in the market in 2023 and to evaluate the proportion of bisphenol A (BPA)-derivatives in relation to their applications. A search on manufacturers' websites was performed to reference resin-based dental materials currently on the European market (including the European Union (EU) and United Kingdom (UK). Their monomer composition was determined using material-safety data sheets and was completed by a search on the PubMed database. Among the 543 material compositions exploitable, 382 (70.3%) contained BPA derivatives. Among them, 56.2% contained BisGMA and 28% BisEMA, the most frequently reported. A total of 59 monomers, of which six were BPA derivatives, were found. In total, 309 materials (56.9%) contained UDMA and 292 (53.8%) TEGDMA. Less than one third of materials identified contained no BPA derivatives. These proportions vary a lot depending on their applications, with materials dedicated to the dental care of young populations containing the highest proportions of BPA-derivative monomers. The long-term effects on human health of the different monomers identified including BPA-derivative monomers is a source of concern. For children and pregnant or lactating women arises the question of whether to take a precautionary principle and avoid the use of resin-based dental materials likely to release BPA by opting for alternative materials.

In vitro study evaluating the shear bond strength of metal brackets to lithium disilicate ceramic support using a universal adhesive / Étude in vitro évaluant l'adhérence des attaches métalliques orthodontiques collées à l'aide d'un adhésif universel aux céramiques en disilicate de lithium

Introduction: The number of adult patients who seek an orthodontic treatment is increasing. These patients often have lithium disilicate ceramic restorations. The orthodontist has to find a procedure to bond effectively brackets to these restorations. In 2011, a new family of adhesives was introduced, universal adhesives, which are capable of bonding to ceramic and are said "multi-mode" because they can be used in etching-rinse or self-etching protocol on tooth surface. The objective of this in vitro study was to evaluate the shear bond strength (SBS) of metal brackets to lithium disilicate ceramic support using a universal adhesive. Materials and Methods: Forty machinable lithium disilicate blocks (IPS e.max CAD, Ivoclar) were prepared according manufacturer's instructions. Each specimen was randomly assigned to one of four groups (n=9 or 10) defined by the pretreatment protocol. Protocol 1: Hydrofluoric Acid 9 % (HF) + Silane + Orthodontic adhesive (Transbond™ XT Light Cure Adhesive Primer, 3M ESPE), protocol 2: HF + Universal adhesive (UA) (Scotchbond Universal®, 3M ESPE), protocol 3: UA only, protocol 4 : Monobond Etch & Prime® (Ivoclar) + UA. Then, a bracket of upper cuspid (3M ESPE) was bonded to each specimen with a composite resin (Transbond™ XT, 3M ESPE). SBS was measured between ceramic and bracket with a universal testing machine. A one-way ANOVA (ANalysis Of Variance) followed by Tukey's post-hoc test was performed to investigate SBS differences between groups. Results: Protocol 2 (43 MPa) and protocol 4 (36 MPa) showed the highest SBS values and were statistically different from protocol 1 (25 MPa) and protocol 3 (21 MPa). Conclusion: Despite the lower bond values obtained in the study, but higher than the minimum expected, the application of UA alone appears to be a safe procedure that seems to provide sufficiently strong and resistant bonding between the ceramic and the bracket. However, clinical studies are needed before a recommendation can be made.

Introduction: Les traitements orthodontiques chez l'adulte se démocratisent. Ces patients ont souvent des restaurations en céramique en disilicate de lithium, sur lesquelles l'orthodontiste doit être à même de coller efficacement ses attaches. Or, les adhésifs universels, nouvelle famille d'adhésifs introduite en 2011, présentent un potentiel d'adhésion aux céramiques, en plus de pouvoir être utilisés en mode mordançage-rinçage ou auto-mordançant. L'objectif de cette étude in vitro était d'évaluer l'adhérence d'attaches métalliques à ces céramiques à l'aide d'un adhésif universel. Matériels et méthodes: Quarante blocs de céramique en disilicate de lithium (IPS e.max CAD, Ivoclar) ont été préparés selon les recommandations de cristallisation du fabricant. Chaque échantillon a été ensuite réparti aléatoirement en quatre groupes (n = 9 ou 10) selon le protocole de traitement de surface appliqué. Protocole 1 : Acide Fluorhydrique 9 % (HF) + Silane + Adhésif orthodontique (Transbond™ XT Light Cure Adhesive Primer, 3M ESPE), protocole 2 : HF + Adhésif universel (AU) (Scotchbond Universal®, 3M ESPE), protocole 3 : AU uniquement, protocole 4 : Monobond Etch & Prime® (Ivoclar) + AU. Une attache métallique de canine maxillaire (3M ESPE) a ensuite été collée sur chaque échantillon avec une résine composite (Transbond™ XT, 3M ESPE). La résistance en cisaillement a ensuite été mesurée entre la céramique et l'attache métallique. Une ANOVA (ANalysis Of Variance ou analyse de variance) suivie du test post-hoc de Tukey ont été réalisés pour étudier les différences d'adhérence entre les groupes. Résultats: Les protocoles 2 (43 MPa) et 4 (36 MPa) présentent des valeurs d'adhérence significativement supérieures à celles des protocoles 1 (25MPa) et 3 (21 MPa). Conclusion: Malgré de plus faibles valeurs d'adhérence obtenues dans l'étude, mais supérieures à celles minimales attendues, l'application seule de l'adhésif universel semble être une procédure sans danger qui procure une adhésion suffisamment forte et résistante entre la céramique et l'attache. Des études cliniques sont cependant nécessaires avant d'émettre une recommandation.