Restoration Interface Research Articles

Evolving interfaces: A comprehensive review of implant-abutment connections

Studying the implant-abutment connection is crucial, as it primarily determines the strength and stability of an implant-supported restoration, which, in turn, affects prosthetic stability. Traditionally, Brånemark's external hexagon has been used. However, significant complications such as abutment screw loosening, rotational misfit at the implant-abutment interface and microbial penetration have necessitated modifications of the external hexagon and led to the development of internal implant-abutment connection.This review outlines the evolution of various implant-abutment connections from the traditional external hexagon to advanced internal designs. Internal interface designs offer several advantages over the traditional approach. They reduce the vertical height platform for restorative components and distribute lateral loading deep within the implant. These designs also shield the abutment screw and provide long internal wall engagements that create a rigid, unified body resisting joint opening. Additionally, they feature wall engagement with the implant that buffers vibration, offer the potential for a microbial seal, and provide extensive flexibility. Importantly, they allow for the lowering of the restorative interface to the implant level for better aesthetics. These advancements have significantly enhanced the clinical performance and reliability of implant-supported restorations.

The Adult Orthodontic– Restorative Interface. Part 1: Concepts of Treatment and Presenting Challenges

This is the first article in a three-part series that discusses joint orthodontic–restorative care for the adult patient. Part 1 presents an overview of the clinical presentations, challenges and strategies that may be employed to treat this complex patient group. CPD/Clinical Relevance: The reader should be able to describe a care pathway, with potential associated complications, for the provision of adult orthodontic–restorative treatment.

Laser-texturing and traditional surface modification to improve the adhesion of glass fiber-reinforced composite posts to resin cements

ObjectivesThe aim of this study was to perform an experimental evaluation of the synergistic effects of laser-texturing and different traditional surface modification approaches to improve the adhesion of glass fiber-reinforced composite (GFRC) posts to resin-matrix cements used in endodontically treated teeth rehabilitation. MethodsOne hundred and ten freshly extracted mandibular single-rooted premolars were endodontically treated and groups of specimens were divided according to the GFRC cementation after different surface treatment, as follow (n = 10): silane-based conditioning (SIL); 9.7 % HF acid-etching (HF); 35 % H2O2 etching (H2O2); grit-blasting (GB); HF plus H2O2 etching (HFH2O2); 6 W Nd:YAG laser-texturing (L6W); 4.5 W Nd:YAG laser-texturing (L4.5W); 3 W Nd:YAG laser-texturing (L3W); 3 W Nd:YAG plus 35 % H2O2 (L3WH2O2); 3 W Nd:YAG plus SIL (L3WSIL); and untreated (C). GFRC posts were cemented into the tooth root canals using a dual-cured resin cement. Then, specimens were cross-sectioned and mechanically assessed by push-out bond strength tests. Specimens were inspected by optical microscopy and scanning electron microscopy (SEM) at magnification from × 30 up to × 2000. The failure mode was recorded by microscopic analyses after the bond strenght tests. ResultsSurface analyses of the GFRC posts showed a rough and retentive morphological aspect with a removal of the outer epoxy matrix layer and exposure of glass fibers after laser-texturing, grit-blasting, or etching under 35 % H2O2. The highest bond strength values at 21.8 MPa was recorded for GFRC posts after laser-texturing on 3W plus silane-based conditioning followed by the group etched with 35 % H2O2 (20.5 MPa). The failure mode was microscopically characterized as cohesive and mixed pathways. The lowest bond strength values around 5 and 9 MPa and adhesive failure were recorded for the untreated GFRC group or specimens etched with HF. ConclusionsThe combination of acidic etching and silane conditioning with laser-texturing at moderate intensity promoted an adequate surface modification of GFRC posts and increased adhesion to a resin-matrix cement. Such combination of physicochemical approaches can enhance the long-term mechanical behavior of the restorative interface at endodontically treated teeth. Clinical relevanceCombining traditional and novel physicochemical approaches can provide promising adhesion pathways for glass fiber-reinforced composite posts to resin-matrix cements. A high mechanical interlocking of the resin-matrix cements and the stable retention of the teeth root intracanal posts can decrease the risks of clinical failures by fracture and detachment of the intraradicular interface.

Microleakage of Root Canal Sealed with Temporary Endodontic Sealing Materials

To measure the microleakage of different materials used as temporary endodontic sealing materials and to compare between them. Sixty sound human premolars extracted for orthodontic purpose, caries and cracks free were used. Teeth were divided into 6 groups depending on type of temporary materials (glass ionomer cement, zinc phosphate cement, amalgam, temporary filling "zinc oxide eugenol") for temporization and control groups (negative and positive). For each tooth, an access opening was done followed by instrumentation, irrigation and dryness. Then application of different temporary materials. Evaluation of marginal microleakag e (tooth – restoration interface) were done by using dye penetration test. The study was done in Department of Conservative Dentistry, College of Dentistry, University of Mosul. The results showed significant differences (p< 0.05) in marginal microleakage among groups tested. But there were no significant difference between buccal and lingual tooth restoration – interface for each group. Glass i onomer cement showed less microleakage at tooth – restoration interface when compared with other temporary filling mater ials which used in this study. Glass ionomer cement has sup erioer effect on reduction of microleakage when compared with other temporary filling,when used for temporization had more ability to reduce microleakage than zinc phosphate cement, amal gam and lastly temporary filling (zinc oxide eugenol).

Assessing dentists’ awareness of the orthodontic–restorative interface

ObjectivesAwareness of the interface between restorative and orthodontic treatments is essential for dentists to facilitate a meaningful interdisciplinary approach by integrating the knowledge and skills of different dental disciplines into patients’ treatment to enhance outcomes. The aim of this study was to investigate General Dental Practitioners’ (GDPs) awareness of the orthodontic–restorative interface. MethodsThis was a mixed-method study involving the collection of a) quantitative data via a bespoke online questionnaire and b) qualitative data through open questions. A weblink was created to the questionnaire using Opinio®. The questionnaire was distributed to GDPs practising in the UK. Clinical vignette-based questions assessed GDPs awareness and the results were categorised into two groups: aware and unaware. Two months after the primary survey, respondents were sent an email with follow-up (reliability) survey. Reliability responses were compared against the primary responses to assess the repeatability using intraclass correlation coefficient. Data were analysed using independent t-test and X2 test. Results118 complete responses were received. 63 GDPs (53.4 % [95 % CI 44 %–63 %]) demonstrated a good understanding of the orthodontic–restorative interface. These GDPs were characterised by greater age (t = 2.75, p = 0.007) and experience (t = 3.54, p < 0.001). Qualitative data showed that respondents perceived orthodontic-restorative treatments as minimally invasive and aesthetics enhancing. ConclusionsOrthodontic-restorative treatment aids in minimal invasive dentistry. GDPs lack adequate awareness of the orthodontic–restorative interface in relation to patient care and communication with patients. More quality and structured undergraduate and postgraduate training are imperative to facilitate GDPs to understand and utilise aspects of orthodontic-restorative treatments to raise the standard of patient care. Additionally, to support these patients, the educational pathway between GDPs and specialist orthodontists is crucial. Clinical SignificanceGDPs ability to assess and carry out orthodontic-restorative treatments would conserve natural teeth. Dependable access to orthodontic services would encourage GDPs to refer challenging cases to specialists or dentists with enhanced skills. When the circumstances call for it, patients should be given orthodontic-restorative alternatives, regardless of the potential consequences of their acceptance of the procedures.

Comparative evaluation on the effect of different cavity disinfectant nano gels; Chlorohexidine, Propolis, Liquorice versus Diode Laser in terms of composite microleakage (comparative in vitro study)

IntroductionThe application of different cavity disinfectants is an essential step that eliminates bacteria after cavity preparation. However, some of these materials may affect restoration sealing ability.AimThis study aimed to assess the degree of microleakage at the tooth restoration interface after using different nano prepared cavity disinfectants versus Diode Laser.Materials and methodsThree disinfectants were prepared on the nanoscale; Propolis, Liquorice and Chlorhexidine. A total of 40 extracted premolars with standard class V cavities were prepared on the facial surface. Teeth were divided into five groups according to the applied cavity disinfection protocol; no treatment, Chloehexidine, Propolis, Liquorice, and Diode Laser. After application of composite resin restoration, all teeth were subjected to thermocycling, afterwords the degree of microleakage was measured in micrometers. Data were analyzed by one-way analysis of variance (ANOVA) test, followed by Bonferroni’s and Tukey’s post hoc test.ResultsThe highest mean microlekage value was recorded in no treatment group, followed by Liquorice, Propolis. While Diode Laser group showed the lowest degree of microleakage.ConclusionDiode Laser cavity disinfectant has no negative effect on the restoration sealing ability. Nano prepared Propolis showed comparative results to nanoChloehexidine as both had low degree of microleakage.

Comparative Evaluation of Shear Bond Strength of Glass Ionomer Cement, Composite and Compomer in Primary Teeth: An In Vitro Study

Background: Because the main dislodging pressures at the tooth restoration interface have a shearing effect, shear bond strength is crucial for the restorative material clinically. Therefore, greater shear bond strength suggests improved material to tooth bonding. Glass ionomer cement and composite is the most popularly used restorative material. Composite resins have better mechanical properties and esthetics than many other types of cement, but they need bonding agents as they are hydrophobic and hence fail to adhere to the teeth. Compomers are polyacid modified resin composites. Compomer and composite resin have similar physical properties, as they are thought to bond to dentin by micromechanical bonding. As resin composites are used in this, the polymerized acid monomer shows acidity when it comes in contact with the saliva and there is a reaction of fluoride-containing basic glass resulting in the cariostatic effect. Aim: The purpose of this study was to evaluate and compare the shear bond strength of Glass Ionomer Cement (Fuji IX GP), Composite Resin (Filtek Z-250) and Compomer, (Compoglass, Ivoclar). Material and Method: An in-vitro, experimental study was conducted on 30 freshly extracted over-retained deciduous molars. Samples were randomly divided into three groups depending on the material to be used. Flat dentinal surface on tooth was prepared over which restorative materials were placed. The prepared specimen was subjected to shear test and the value obtained was compared. Descriptive statistical analysis was performed to calculate the mean shear bond strength of each group. Result: It was observed from the study that the composite resin had the highest shear bond strength value (17.13 ± 1.54), followed by compomer (11.32 ± 1.05) whereas GIC showed the least shear bond strength (6.56 ± 0.87). Conclusion: It was concluded that composite restorative materials show higher shear bond strength than glass ionomer cement and compomer in primary molars, but shear bond strength of compomer was higher than that of glass ionomer cement.

Influence of carbonated acid beverage on fracture resistance and marginal gap formation in different restorative approaches to non-carious cervical lesions.

This study is to evaluate fracture resistance, failure mode, and gap formation at the restorative interface of unrestored or restored non-carious cervical lesions (NCCLs) submitted to a short-term erosive environment. Artificial NCCLs were produced in vitro in bovine incisors, and were randomly divided into four restorative resins groups (n = 22): nanohybrid-NR; bulk-fill-BR; flow with a nanohybrid layer-FNR; bulk-fill with a nanohybrid layer-BNR; and a group unrestored-UR (n = 16). Half of the specimens were submitted to an erosive challenge (per 5min, 3 × a day for 7days, before and after restoration), and the other half, was immersed in artificial saliva. After, all teeth undergone thermal (5ºC, 37ºC, and 55ºC, 3600cycles) and mechanical (50N, 2Hz, 300,000cycles) aging. Eighty teeth were subjected to compressive loading, and resistance and failures were analyzed, while 24 teeth were evaluated for gaps by microcomputed tomography. Statistical tests were performed (p < 0.05). The restorative approaches affected fracture resistance (η2p = 0.14, p = 0.023), and gap formation (η2 = 0.18, p = 0.012) and so did the immersion medium (fracture η2p = 0.09, p = 0.008; gap η2 = 0.09, p = 0.017). BNR showed the highest resistance, while UR the lowest. FNR showed the highest gaps in both immersion media. Neither the resin groups nor the immersion media were associated with failure mode. The erosive immersion medium based in acid beverages has been shown to affect NCCLs with or without restoration, but when Bulk-Fill resin is covered by nanohybrid resin, the performance is good. Erosion negatively affects restorations, but unrestored NCCL shows worse biomechanical performance in stress-bearing situations.

Influence of Ascorbic Acid on Shear-Bond Strength at Tooth Restoration Interface After Immediate Bleaching Procedures

Purpose: This study evaluated the effect of ascorbic acid on shear bond strength at tooth restoration interface after immediate bleaching procedures. Materials and Methods: Sixty freshly extracted human premolars were used. Teeth were divided into two main groups (A& B) according to the application mode of the adhesive system (n=30). Group A: self-etch mode, Group B: Etch-and-rinse mode. Each group was subdivided into three subgroups (1,2,3) according to ascorbic acid application (n=10). Data were collected, tabulated, and statistically evaluated. Results: The immediately bonded specimens after the bleaching procedure showed the statistically lowest mean shear bond strength values. These results were in comparison to the other unbleached specimens due to enamel surface energy. The antioxidant treatment exerted a significant effect on shear bond strength. Conclusion: Bleaching had a direct effect on enamel. Bond strength is adversely affected by bleaching. Ascorbic acid improves the bond of enamel after bleaching

Contemporary Endodontic-Restorative Interface Techniques and Materials

The field of interface techniques and materials is constantly evolving with advancements in technology and research. In the past, the main focus of therapy was eliminating infection and preventing recontamination. The use of magnification and illumination techniques ensures preparation of access cavities, preserving tooth structure while improving visibility for procedures. Adhesive technology plays a role in establishing an endodontic restorative interface. This review highlights the flexibility of etch and self-etch systems, which can be adapted to various clinical scenarios. These systems do not create a bond but also help seal dentin tubules reducing the risk of micro leakage and bacterial ingress. Ultimately, this fortifies the longevity of treatments. The selection of materials is also explored in this review with composite resins gaining prominence due to their properties and versatility. Nano filled composites for restorations exhibit improved mechanical properties that provide durable solutions. To achieve outcomes, it is crucial to incorporate diagnostic tools, adopt conservative access cavity preparation techniques, carefully select appropriate adhesive systems and make strategic material choices. The review highlights the importance of staying vigilant, following up after treatment and taking an approach to overcome challenges in order to provide patient care. Moving ahead, the review suggests that we continue exploring materials and techniques to improve predictability and clinical outcomes at this junction reflecting our continuous commitment to delivering exceptional dental care.

ENDOCROWN: A SUBSTITUTE APPROACH TO POST AND CORE FOR REHABILITATION OF ENDODONTICALLY TREATED TOOTH

Restoration of endodontically treated teeth (ETT) is distinct from root canal treatment although they are mutually dependent in planning, treatment and prognosis. The fabrication of full coverage crowns with or without the use of posts remains the long-established means of restoration of endodontically treated teeth. Despite all the clinical success achieved with intraradicular posts, they have been criticized for removal of sound tissue and risk of root perforation. With the amelioration of adhesive techniques and invention of newer materials, the concept of endocrown has been considered as an alternative and viable method for restoration of root canal treated molars. It is an indirect monoblock restoration aimed to achieve a bonded biomimetic reconstruction. The preparation is simple following minimally invasive principles of adhesive dentistry compared to conventional crowns with post and core. They have the advantage of removing lower amounts of sound tissue compared to other techniques, and with much lower chair time needed. Also, the masticatory stresses received at the tooth/ restoration interface are more properly dissipated along the overall restored tooth structure when endocrowns are placed. The rationale of the preparation was to use surface area available in the pulp chamber to gain stability and retention through adhesive cementation. The supragingival positioning of restorative margins prevents interferences with periodontal tissues. This article highlights a case report where a porcelain fused to metal endocrown is fabricated to effectively manage a grossly mutilated endodontically treated tooth and was followed up for one year.

Cavosurface margins for various restorations

Many factors play a critical role in getting the best restoration, such as cavity design, operator skill, type of restorative material etc. However, the weakest link in any restoration is the tooth restoration interface. Every effort should be made to design and prepare these marginal peripheries to create the most favourable relationship with each other and for the longevity of the restoration. The restoration can survive in the biological environment of the oral cavity only if the margins are closely adapted to the cavosurface finish line of the preparation. One of the important aspects of cavity design is the cavosurface marginal seal/design. This review paper highlights the different cavosurface margins suitable for various restorations and their importance.

Internal and Marginal Adaptation of Adhesive Resin Cements Used for Luting Inlay Restorations: An In Vitro Micro-CT Study.

Adequate internal adaptation and marginal sealing of resin luting cements are of particular importance for the success of cemented ceramic inlays. The purpose of this study was to investigate the initial adaptation of different resin cements at the tooth-inlay restoration interface at enamel versus dentin surfaces. Thirty-two extracted human molars were allocated to four groups. One Class II cavity was prepared in each tooth. In each group, half of the cavities’ gingival floors were on enamel while the other halves were on cementum. Lava Ultimate CAD/CAM inlays were luted to the cavities using the following adhesive systems: RelyX Unicem, RelyX Ultimate, eCement, and Variolink Esthetic DC. After staining teeth with silver nitrate solution, marginal and internal gap volumes were determined using micro-CT images. Statistical analyses were conducted by independent t test and one-way ANOVA followed by post hoc Tukey test (p < 0.05). The internal and marginal gap volume values were the highest for Variolink Esthetic DC at the dentin surface (0.629 ± 0.363) and (2.519 ± 1.007), respectively, and the lowest for RelyX Unicem at the enamel surface (0.005 ± 0.004) and (0.009 ± 0.003), respectively. The internal and marginal adaptation on the enamel surface for RelyX Unicem and RelyX Ultimate resin cements were comparable to each other and to eCement but significantly better than Variolink Esthetic DC cement. Regardless of the adhesive resin system used, adaptation on enamel is superior to that on dentin surfaces.

Bacteria in the cavity-restoration interface after varying periods of clinical service — SEM description of distribution and 16S rRNA gene sequence identification of isolates

ObjectivesTo use extracted human teeth with amalgam (n = 26) or GIC (n = 3) restorations in service up to 20 years to evaluate microbiota at the cavity/restoration interface by SEM or culture.Materials and methodsExtracted teeth with intracoronal restorations (n = 20) of known history (2–20 years) were fixed, split, and prepared for SEM to ascertain the pattern and structure of bacterial aggregates on cavity and restoration surfaces. Another 9 teeth were anaerobically decontaminated, split and sampled (cavity/restorations), and cultured (anaerobically, aerobically); recovered isolates were identified by 16S rRNA gene sequencing.ResultsSEM showed rods, cocci, and filaments in 11/20 teeth (55%) on cavity and corresponding restoration surfaces; 4/20 (20%) on neither surface; 1/20 (5%) on just cavity; and 4/20 (20%) on just restoration. Microbial growth extended from marginal openings into the deeper interfacial microspace to varying extents but was not always evident. Restoration size or age did not predict bacterial presence. Bacteria-free surfaces (cavity/amalgam) showed possible calcification. Cultivation yielded 160 isolates, mainly Gram-positive (86%) and facultative (81%); and morphotypes of rods (43%), cocci (36%), and cocco-bacilli (18%) belonging to Actinobacteria (45%) and Firmicutes (50%). The most frequent genera were Staphylococcus, Streptococcus, Actinomyces, and Lactobacillus. Biofilms on cavity and restoration appeared independent of each other.ConclusionsCavity and amalgam surfaces were independently colonised and some not. The penetration of microbiota into marginal gaps varied; resembled root caries and was dominated by Gram-positive species.Clinical relevanceMarginal gaps around restorations are unavoidable but are not always colonised by bacteria after long-term clinical service. Calcification of biofilms in the restorative interface may prevent further colonisation. The viable microbiota in the restorative interface resembled root caries and may be subject to ecological fluxes of activity and arrest and therefore preventative management.

Comparative Microleakage Evaluation through the Interfaces between the Tooth and Cement after Stainless Steel Crown Cementation in Primary Molars: An In Vitro Study.

The longevity of stainless steel crowns is related to perfect adaptation and long-term union between restoration and teeth. In this respect, evaluation of marginal leakage of luting cement is essential. To compare and evaluate the ability of new adhesive cement to prevent microleakage under stainless steel crowns on primary teeth. Forty-five specimens were embedded, standardized preparations were made onto selected extracted primary molars, and stainless steel crowns were adapted. Samples were assigned randomly to cement groups: Glass ionomer (GI), resin-modified glass-ionomer (RMGI), and Adhesive resin (AR) cement, followed by storage in water, artificially aging, staining, sectioning, and the linear dye penetration and proportion of microleakage evaluation. AR showed the lowest microleakage, followed in increasing order by RMGIC and GIC showed the greatest microleakage (p-value < 0.0001). There are many kinds of luting agents that vary considerably from the viewpoint of solubility, strength, and ability to adhere to the tooth structure. Lack of adhesion of the luting cement to the tooth structure is one of the reasons for microleakage related to different types of crowns. Cement breakdown may result in the entrance of fluids and microorganisms along with the tooth restoration interface. In this study, attempts were made to simulate standard clinical procedures, although this is not a substitute for the complex oral environment, the results provide useful information to choosing the best cement materials. Adhesive resin cement can be recommended for cementation of Stainless Steel Crowns because of added advantages over others. Gundewar MS, Saha S, Arora D, et al. Comparative Microleakage Evaluation through the Interfaces between the Tooth and Cement after Stainless Steel Crown Cementation in Primary Molars: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(2):159-163.

Pro-inflammatory mediators expression by pulp cells following tooth whitening on restored enamel surface.

This paper aimed to assess the influence of adhesive restoration interface on the diffusion of hydrogen peroxide (H2O2), indirect toxicity, and pro-inflammatory mediators expression by odontoblast-like cells, after in-office tooth whitening. Dental cavities prepared in bovine enamel/dentin discs were adhesively restored and subjected or not to hydrolytic degradation (HD). A whitening gel with 35% H2O2 (WG) was applied for 45 min onto restored and non-restored specimens adapted to artificial pulp chambers giving rise to the groups: SD- intact discs (control); SD/HP- whitened intact discs; RT/HP- restored and whitened discs; and RT/HD/HP- restored and whitened discs subjected to HD. The extracts (culture medium + WG components diffused through enamel/dentin/restoration interface) were collected and applied to odontoblast-like MDPC-23 cells. The study evaluated the amount of H2O2 in the extracts, as well as the cell viability (CV), cell morphology (CM), and gene expression of inflammatory mediators (TNF-α and COX-2) by the pulp cells exposed to the extracts (ANOVA and Tukey tests; 5% significance). All whitened groups presented lower CV than SD (control; p<0.05). The highest CV reduction and gene expression of TNF-α and COX-2 was observed in the RT/HD/HP group in comparison with SD/HP and RT/HP (control; p<0.05). CM alterations occurred in all whitened groups. The intensity of these cell side effects was directly related with the amount of H2O2 in the extracts. We concluded that adhesive restoration of dental cavity increases the H2O2 diffusion after in-office whitening, enhancing the indirect toxicity of this therapy and trigger pro-inflammatory overexpression by MDPC-23 cells.

Fracture Behavior and Integrity of Different Direct Restorative Materials to Restore Noncarious Cervical Lesions.

The purpose of this study was to analyze the fracture resistance and marginal leakage of noncarious cervical lesion (NCCL) restorations made of different restorative materials. Eighty upper premolars were randomly divided into four groups (n = 20/group). Standardized NCCL cavity preparations were performed on the buccal surface of the teeth and then restored with four different materials. Group 1: Packable resin composite (PC); Group 2: Highly flowable resin composite (HF); Group 3: Low flowable resin composite (LF); Group 4: Resin modified glass ionomer cement (RMGIC). After restorations were completed, cyclic and static fracture behavior was evaluated using a loading testing machine. Extra restored teeth were sectioned and then stained (n = 5/group). The specimens were viewed under a stereo microscope and the percentage of microgaps at the tooth–restoration interface was calculated. All restored teeth survived after fatigue loading. There was no statistically significant (p > 0.05) difference between the tested restorations after the static loading test. NCCLs restored with highly filled flowable composite showed the least microleakage among the tested groups (p < 0.05). The investigated restorative materials are acceptable for NCCL restorations in terms of fracture resistance and microleakage.

Shear bond strength analysis and marginal gap evaluation of restoration–tooth interface of aesthetic restorations after simulated Co-60 gamma irradiation

Abstract Background: Radiotherapy to the head and neck region may cause considerable radiotherapy-induced changes in the surrounding tissues. These changes are oral mucositis, hyposalivation, dental caries, osteoradionecrosis, trismus and overall impact on patients’ quality of life. Tooth-coloured synthetic materials, unlike metallic restoration, did not influence radiation dose distribution. However, their exposure to a gamma radiation therapeutic dose during treatment might cause structural and compositional changes that alter their mechanical and physical properties. Aim: This study intends to evaluate the effect of Co 60 gamma rays on shear bond strength and marginal adaptation of already restored tooth surfaces, to help in material selection before the onset of radiotherapy. Materials and methods: Hundred freshly extracted human permanent mandibular molar teeth collected and stored in a 0·2% thymol solution for disinfection and were randomly divided into two groups of 50 each, to be tested for the shear bond strength of restoration to dentin and the marginal gap at tooth–restoration interface, respectively. Results: ANOVA showed a significant effect of both radiotherapy (F = 40·33, p &lt; 0·001) and restorations (134·00, p &lt; 0·001) on the marginal gap at the interface. In the without radiotherapy group, the mean marginal gap was least in Group Z250, and in with radiation, Bulk Fill has the least mean marginal gap. The mean shear bond strength was comparatively higher for all restorations without radiation than with radiation (p &lt; 0·001). Findings: Gamma radiation affects the physical or mechanical properties of tooth structure and the tooth restorative interface. Composites seem to be good restorative material when placed before the onset of radiotherapy in head and neck cancer patients.

Comparison of three different bulk-filling techniques for restoring class II cavities: μCT, SEM-EDS combined analyses for margins and internal fit assessments

ObjectiveEvaluation of the behavior of three different bulk-filling techniques in terms of internal adaptation and external marginal sealing for restoring class II cavities. MethodsFifteen extracted sound molar teeth were used. Two standardized class II mesio/disto-occlusal (MO/DO) slot cavities, 4 mm long, 4 mm wide and 3 mm deep were prepared in each tooth, obtaining n=30 cavity preparations. The cavities were randomly assigned into three groups (n=10 per group) according to three bulk filling techniques: Bulk Traditional (BT), Bulk&Go (BG) and Bulk&Flow (BF). The teeth were analyzed by scanning electron microscopy (SEM) to investigate the external marginal seal. Thereafter, the chemical composition of tooth-restoration interface was analyzed by energy-dispersive X-ray spectroscopy (EDS). Complementary information to the SEM and EDS were obtained by micro-computed tomography (μCT) to assess the internal fit. ResultsSEM analysis showed a proper external marginal seal for all groups tested as confirmed by the EDS investigation, highlighting the presence of adhesive layer at the tooth-restoration interface. The internal marginal adaptation by means of μCT analysis revealed gaps formation at the tooth–restoration interface only for BT group, while an intimate contact free of gaps were found in the other two groups. Moreover, in BT and BF groups voids were present within the restoration. SignificanceBG and BF techniques can be considered as reliable alternatives to BT technique, as they simplify the class II restoration without transforming it into class I, thus ensuring a successful result.

Impact of Resin Composite Viscosity and Fill-technique on Internal Gap in Class I Restorations: An OCT Evaluation.

The aim of this in vitro study was to quantitatively evaluate the internal gap of resin composites of high-and low-viscosity used in single- and incremental-fill techniques in Class I cavities exposed to thermal cycling (TC) using optical coherence tomography (OCT). Cavities of 4-mm depth and 3-mm diameter were prepared in 36 third molars randomly distributed into four groups, according to viscosity of restorative resin-based composite (high or low viscosity, all from 3M Oral Care) and technique application (bulk or incremental fill) used (n=9): RC, high-viscosity, incremental-fill, resin-based composite (Filtek Z350 XT Universal Restorative); BF, high-viscosity, bulk-fill, resin-based composite (Filtek One Bulk Fill); LRC, lowviscosity, incremental-fill, resin-based composite (Filtek Z350 XT Flowable Universal Restorative); and LBF, low-viscosity, bulk-fill, resin-based composite (Filtek Flowable Restorative). Single Bond Universal Adhesive system (3M Oral Care) was used in all the experimental groups. The incremental-fill technique was used for RC and LRC groups (2-mm increments), and a single-layer technique was used for BF and LBF groups, as recommended by the manufacturer. The internal adaptation of the resin at all dentin walls was evaluated before and after TC (5000 cycles between 5°C and 55°C) using OCT images. Five images of each restored tooth were obtained. Images were analyzed using ImageJ software that measured the entire length of the gaps at the dentin-restoration interface. The length of gaps (μm) was analyzed using two-way repeated measures ANOVA and the Tukey tests (α=0.05). There was a significant interaction between material types and TC (p=0.006), and a significant difference among all material types (p<0.0001), before and after TC (p<0.0001). Increased internal gaps at the dentin-restoration interface were noticed after TC for all groups. RC presented the lowest value of internal gap before and after TC, while LBF showed the highest values of internal gap after TC. In conclusion, TC negatively affected the integrity of internal gap, whereas high-viscosity, incremental-fill, resin-based composite presented better performance in terms of internal adaptation than low-viscosity, bulk-fill materials in Class I cavities.