Radiopacity of Methacrylate and Silorane Composite Resins Using a Digital Radiographic System.

The aim of this study was to evaluate the radiopacity of silorane and methacrylate resin composites, comparing them to the enamel, dentin, and aluminum penetrometer using a digital image. From six resin composites (Filtek™ P90, Filtek Z350, Filtek Z350 XT flow, Tetric Ceram, TPH Spectrum, and SureFil SDR flow) cylindrical disks (5 × 1 mm) were made and radiographed by a digital method, together with a 15-step aluminum step-wedge and a 1 mm slice of human tooth. The degree of radiopacity of each image was quantified using digital image processing. The mean values of the shades of gray of the tested materials were measured and the equivalent width of aluminum was calculated for each resin. The results of our work yielded the following radiopacity values, given here in descending order: Tetric Ceram > TPH > SDR > Z350 > Z350 flow > P90 > enamel > dentin. The radiopacity of the materials was different both for the enamel and for the dentin, except for resin P90, which was no different than enamel. In conclusion, silorane-based resin exhibited a radiopacity higher than dentin and closest to the enamel; a large portion of the methacrylate-based flow and conventional resins demonstrated greater radiopacity in comparison to dentin and enamel.

Shear Bond Strength of Orthodontic Brackets Fixed with Remineralizing Adhesive Systems after Simulating One Year of Orthodontic Treatment.

The objective of this study is to assess, in vitro, the shear bond strength of orthodontic brackets fixed with remineralizing adhesive systems submitted to thermomechanical cycling, simulating one year of orthodontic treatment. Sixty-four bovine incisor teeth were randomly divided into 4 experimental groups (n = 16): XT: Transbond XT, QC: Quick Cure, OL: Ortholite Color, and SEP: Transbond Plus Self-Etching Primer. The samples were submitted to thermomechanical cycling simulating one year of orthodontic treatment. Shear bond strength tests were carried out using a universal testing machine with a load cell of 50 KgF at 0.5 mm/minute. The samples were examined with a stereomicroscope and a scanning electron microscope (SEM) in order to analyze enamel surface and Adhesive Remnant Index (ARI). Kruskal-Wallis and Mann-Whitney (with Bonferroni correction) tests showed a significant difference between the studied groups (p < 0.05). Groups XT, QC, and SEP presented the highest values of adhesive resistance and no statistical differences were found between them. The highest frequency of failures between enamel and adhesive was observed in groups XT, QC, and OL. Quick Cure (QC) remineralizing adhesive system presented average adhesive resistance values similar to conventional (XT) and self-etching (SEP) adhesives, while remineralizing system (OL) provided the lowest values of adhesive resistance.

In vivo Evaluation of Proximal Resin Composite Restorations performed using Three Different Matrix Systems.

OBJECTIVE: The aim of this in vivo study was to radiographically evaluate the proximal contour of composite resin restorations performed using different matrix systems. MATERIALS AND METHODS: Patients with premolars needing class II type resin composite restorations involving the marginal ridge were selected. Thirty premolars were selected and randomly divided into three groups (n = 10 each) to receive restorations using different matrix systems: group 1: metal matrix coupled to a carrier matrix and wood wedge (G1-MMW); group 2: sectioned and precontoured metal matrix and elastic wedge (G2-SME); and group 3: a polyester strip and reflective wedge (G3-PMR). After the restorative procedure, bitewing radiographs were performed and analyzed by three calibrated professionals. The quality of the proximal contact and marginal adaptation of the proximal surfaces was classified as either correct or incorrect (undercontour/overcontour). RESULTS: The Pearson Chi-square statistical test (α = 5%) revealed a statistically difference between frequencies of correct and incorrect restorations (α(2) = 6.787, p < 0.05). The group G2 SME produced a higher frequency of correct proximal contours (90%), while G1-MMW and G3-PMR had a ratio of 40% correct and 60% incorrect contours respectively. CONCLUSION: None of the matrix systems was able to prevent the formation of incorrect proximal contours; however, the sectioned and precontoured metal matrix/elastic wedge configuration provided better results as compared to the other groups.

Can Whitening Strips interfere with the Bond Strength of Composite Resins?

AIM: The aim of this study was to investigate in vitro the bond strength of composite resins on enamel previously treated with whitening strips. MATERIALS AND METHODS: A total of 48 bovine incisors were allocated to four experimental groups (n = 12 each): G1 (WSC)- treated with 9.5% hydrogen peroxide whitening strips (3D White Whitestrips® Advanced Vivid/CREST); G2 (WSO)-treated with 10% hydrogen peroxide whitening strips (3D WhiteTM/Oral B); G3 (WG)-treated with 7.5% hydrogen peroxide gel with fluorine, calcium and potassium nitrate (White Class®/FGM); and G4 (C)-control not subjected to bleaching treatment. The specimens were subjected to bleaching over 2 weeks following the manufacturers' instructions. Following the elaboration of the composite resin test specimens, the samples were stored in artificial saliva and subsequently subjected to the micro-shear test using the universal testing machine (EMIC®). The bond strength values were analyzed by one-way ANOVA and Tukey's statistical test (5%). RESULTS: Significant differences were observed among the investigated groups (p < 0.05). The G3-WG exhibited greater values compared with the control group and the groups treated with strips, G1-WSC and G2-WSO. Analysis of the bond interface revealed that a large fraction of the failures occurred at the enamel-resin interface. CONCLUSION: The bond strength decreased following 14 days of treatment with bleaching strips, whereas the whitening gel with 7.5% hydrogen peroxide, calcium and fluorine increased the bond strength.

Overlays or ceramic fragments for tooth restoration: an analysis of fracture resistance.

PURPOSE: The aim of this study was to evaluate the mode of fracture and resistance of partial ceramic restorations of posterior teeth. MATERIALS AND METHODS: Thirty healthy upper premolars were selected and divided into three groups (n = 10): Group 1- control, healthy unrestored teeth, group 2-teeth restored with ceramic fragments; and group 3-teeth restored with ceramic overlays. The restorations were manufactured with feldspathic ceramic and cemented with RelyX ARC resin cement. After being stored in distilled water for 7 days, the teeth were subjected to axial compression mechanical testing with a universal testing machine. Force was applied to the long axis of the tooth at a speed of 0.5 mm/min until fracture. The data were analyzed with one-way ANOVA and Tukey's test (5%). The mode of fracture was scored according to the degree of involvement of the tooth structure and the type of restoration. RESULTS: A significant difference (p < 0.05) was showed between groups 2 (1155 N) and 3 (846.6 N), but there was no significant difference between group 1 and the other groups (1046 N), More extensive fractures were prevalent in the healthy teeth group (Group 1), which had no occlusal coverage; less severe fractures were found in groups 2 and 3. CONCLUSION: We conclude that teeth restored with ceramic fragments may offer greater resistance to fractures compared to teeth that have overlay restorations.

Atraumatic extraction, implant placement and immediate provisionalization.

Front tooth extraction typically results in significant loss of hard and soft tissue volume, both in the vestibular-lingual and mesiodistal directions. As these changes can compromise the esthetic results of prosthetic rehabilitation, extraction techniques that cause minimal trauma to the remnant tissues are applied in combination with immediate implant placement to minimize such alterations. The case reported in the present article illustrates a therapeutic plan consisting of atraumatic extraction followed by immediate implant placement and provisionalization. When carefully indicated and planned, our results indicate that this technique may provide promising immediate results relative to the maintenance and stability of the peri-implanted tissues.

Sealing moderate caries lesions with bioactive glass-ionomer: A split-mouth clinical trial.

Laboratory evidence has shown that 45S5 bioglass can help in dental remineralization, so its incorporation into resin-modified glass ionomer cement (RMGIC) has been studied. This randomized clinical trial aimed to determine the efficacy of RMGIC enriched with 10% 45S5 bioglass (RMGIC/45S5) in preventing the progression of moderate caries lesions. Sixty-six permanent molars with moderate caries lesions, were randomly sealed with RMGIC or RMGIC/45S5. After 1, 3-6 months, patients' oral health, material behavior, and caries evolution were evaluated. Chi-square and Fisher's exact test was employed. After one month, the RMGIC showed higher total retention and better clinical performance compared to RMGIC/45S5, both showed a predominance of sealed teeth or without caries progression. After 6 months, no materials retention, quality and caries progression difference was observed for both materials. Short-term clinical follow-up reveals worse retention and quality of RMGIC/45S5, only after 6 months no clinical/microscopic differences are observed between the materials.

Resin-modified glass ionomer enriched with BIOGLASS: Ion-release, bioactivity and antibacterial effect.

Developing dental materials for the prevention of remineralization or demineralization is important for high-risk caries patients. This study aimed to evaluate the physicochemical and microbiological effects of adding 45S5 bioglass to resin-modified glass ionomer cement (RMGIC). Samples belonged to the following groups: GIC: conventional glass ionomer cement (Vitro Fil), RMGIC: resin-modified GIC (Vitro Fil LC), and RMGIC/45S5: RMGIC with 10% (wt %) of 45S5. Changes in pH and release of fluoride, calcium, and phosphorus ions under acidic (pH 4) and neutral (pH 7) pH conditions were evaluated. Antibacterial activity was verified based on colony-forming units. Material sorption and solubility were analyzed after bacterial exposure. After 28 days, the bioactivity of the materials was evaluated using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Analysis of variance, post hoc Scheffe, and Tukey (α = 0.05) tests were employed for statistical analysis. RMGIC/45S5 showed higher alkalization activity, calcium release at pH 4 and 7, and sorption than GIC and RMGIC (p < .05). Release of phosphorus and fluoride at pH 4 and 7 was higher for GIC than that for RMGIC and RMGIC/45S5 (p < .05). RMGIC/45S5 showed higher values than RMGIC (p < .05). However, antibacterial activity did not differ among the groups. Precipitates of calcium and phosphorus were visualized in RMGIC/45S5 samples via SEM/EDS. These results indicate that the RMGIC/45S5 promotes alkalization and increases the release of calcium, phosphorus, and fluoride ions, resulting in precipitate deposition rich in calcium and phosphorus, thereby being a promising option to improve the bioactivity of RMGIC.

One-year follow-up of microscopical and clinical behavior of bioactive self-etching resin sealant.

Background: The development of early carious lesions can be prevented with the use of sealants. This study aimed to evaluate the retention and sealant quality of conventional and bioactive self-etching sealants by direct (clinical) and indirect (microscopical) assessment. Materials and Methods: Sixty newly erupted mandibular second molars (International Caries Detection and Assessment System ≤2) from adolescents were selected for the split-mouth trial study. The tooth was randomized and treated with conventional Fluoroshield (FS) and BeautiSealant (BS) bioactive self-etching sealants. Molds were taken and cast with epoxy resin after treatment. Indirect and direct assessments of retention degree and sealant remnant quality were performed after baseline, 1 month, and 1 year. The Chi-square test, ordinal regression, reasons of chance, and Fleiss' kappa statistical test were employed. Results: After 1 month, greater total retention was observed for FS, but 1-year follow-up demonstrated no retention difference for FS and BS. The odds ratios showed an 86% greater chance of FS showing better marginal adaptation, after 1 month. At 1 year, the clinical assessment showed better anatomical shape and marginal adaptation scores for FS, but no microscopical difference was observed. A pour agreement between clinical and microscopical data was observed. Conclusions: The 1-year follow-up showed no significant difference in the degree of retention, and in the microscopic evaluation of the conventional sealant (FS) and the bioactive self-etching sealant (BS), but in the clinical evaluation, better marginal and anatomical adaptation scores for FS were observed.

Effect of Bioactive Filler Addition on the Mechanical and Biological Properties of Resin-Modified Glass Ionomer.

The maintenance of affected dentin can promote the greater conservation of tooth structure. The development of materials that have properties capable of reducing the demineralizing potential and/or even helping in dental remineralization is important for conservative dentistry. This study aimed to evaluate, in vitro, the alkalizing potential, fluoride as well as calcium ion release ability, antimicrobial activity, and dentin remineralization properties of resin-modified glass ionomer cement (RMGIC) incorporated with a bioactive filler (niobium phosphate (NbG) and bioglass (45S5)). The study samples were grouped into RMGIC, NbG, and 45S5. The materials' alkalizing potential, ability to release calcium as well as fluoride ions, and antimicrobial properties concerning Streptococcus mutans UA159 biofilms were analyzed. The remineralization potential was evaluated using the Knoop microhardness test, which was performed at different depths. The alkalizing and fluoride release potential was higher for the 45S5 group (p < 0.001) over time. An increase in the microhardness of demineralized dentin was observed in the 45S5 and NbG groups (p < 0.001). No differences in biofilm formation were observed between the bioactive materials, although 45S5 exhibited lower biofilm acidogenicity at different time points (p < 0.001) and greater calcium ion release in the microbial environment. A resin-modified glass ionomer cement enriched with bioactive glasses, particularly 45S5, is a promising alternative for the treatment of demineralized dentin.

In vitro and in vivo performance of self-conditioning sealants with pre-reacted glass for caries prevention.

Bioactive materials capable of preventing the development of caries lesions can be an important preventive strategy. This study aims to evaluate in vitro the alkalizing potential, fluoride release, shear bond strength (SBS), and Knoop microhardness (HK) of self-conditioning sealants with pre-reacted glass (S-PRG) and in vivo their retention, quality and caries prevention using the randomized clinical trial (RCT). Dental sealants FS-conventional (Fluoroshield-Dentsply) and BS self-etching (BeautiSealant-Shofu) were evaluated. Sealants samples (n = 5 per group) were performed to verify the alkalizing potential and fluoride release at neutral and acid pH. For mechanical evaluation of both sealants, twenty bovine incisors were used for SBS test, and twenty sealant samples were performed for HK under 50 g load for 15 s. All measurements were taken after 24h and 30 d. A split-mouth RCT including 28 volunteers (10-14 years) with erupted permanent molars and initial enamel caries lesions was conducted to evaluate BS and FS behavior. Sealant retention (total, partial and total loss) and quality scores were analyzed after 30 d. In vitro and in vivo tests were assessed by T-test, and χ2 & Fisher tests (α = 0.05). BS demonstrated higher alkalinizing potential at neutral and acid pH and lower SBS and HK at 24h and 30 d (p < 0.05). However, the FS had greater fluoride release at neutral and acid pH. Clinically, BS also showed lower retention than FS (p = 0.02), but no sealant quality difference was observed. Both sealants contributed to the remission or non-evolution of caries. After 1 month, the bioactive S-PRG sealant showed in vitro a higher alkalizing potential and lower fluoride release, retention, and microhardness, while in vivo, despite the lower retention, the non-evolution of caries lesions was verified.

Bioactive self-etching sealant on newly erupted molars: A split-mouth clinical trial.

OBJECTIVES: This randomized clinical trial compares retention, survival rate, and evolution of caries of newly erupted permanent molars sealed with bioactive self-etching sealants with pre-reacted glass ionomer (S-PRG). METHODS: A split-mouth clinical trial was conducted with 56 permanent second molars in stages 2 and 3 of crown eruption; ICDAS (International Caries Detection and Assessment System) was between 0 and 2. The molars were randomized and blinded in relation to the side (right or left) that would receive the sealants; the conventional resin sealant (FS), Fluroshield (Dentsply), or bioactive self-etch sealant (BS), BeautiSealant with S-PRG (Shofu). The sealants were compared in terms of retention, quality of sealant remnant (anatomical shape, marginal adaptation, surface texture, and marginal discoloration), and development of caries by ICDAS after 1, 6, and 12 months. The Wilcoxon, x² of independence, Kaplan-Meier, and Mantel-Cox survival statistical tests were applied (α = 5%). RESULTS: The total retention was higher for FS (57.1%) at all periods, and there was no difference in the quality of sealants at all periods. The ICDAS decreased after 6 (p = 0.025) and 12 months (p = 0.027) for both materials. Despite the lower retention of BS, the clinical quality of sealants over 12 months were similar. CONCLUSION: Teeth sealed with BS presented higher sound teeth predominance (ICDAS 0) compared to FS sealant, even with a higher loss of material. CLINICAL RELEVANCE: Eruption of permanent molars is a relevant period, and the prevention/management of initial caries is essential in these critical stages. Sealants can be an important prevention strategy. After 12 months of follow-up, there was a major failure of the bioactive sealant but without the development of caries lesions.

Interaction effect of Nd:YAG laser and universal adhesive system for dentin sealing.

BACKGROUND: To evaluate the influence of the association of the universal adhesive system to different energy densities of the Nd:YAG laser on the hydraulic conductance of dentin. MATERIAL AND METHODS: Fifty bovine dentin discs were made. The samples were stratified into four groups (n = 10) according to the treatment performed; SBU- Adper Single Bond Universal (3M ESPE), SBU_60 - SBU associated with the Nd:YAG laser (60mJ, 10Hz, 0.6W - 47.77 J / cm²), SBU_80 - SBU associated with the Nd:YAG laser (80mJ, 10Hz, 0.8 W - 63.69 J / cm2) and C - dentin without treatment (smear layer). Hydraulic conductance measurements were taken 24 hours after the treatments (HC1) and after erosive challenge (HC2). Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) helped to visualize the dentin after the different treatments. Scheffe and Games-Howell statistical tests were used to analyze hydraulic conductance (α = 0.05). RESULTS: The treated dentin (SBU, SBU_60, and SBU_80) reduced HC1 when compared to dentin with smear layer (C) (p< 0.001). The erosive challenge has increased HC2 in SBU_60 and C (p< 0.001), and did not promote a significant difference in SBU_80 and SBU. The SEM / EDX analyzes showed an irregular and semi-permeable barrier on the surfaces of the treated dentin. CONCLUSIONS: The association of universal adhesive with Nd:YAG can be an effective alternative for the occlusion of dentinal tubules, whereas higher energy per pulse Nd:YAG (SBU_80) can increase the resistance to permeability when exposed to the erosive challenge. Key words:Dentin, permeability of dentin, Nd:YAG Laser, adhesives.

Effect of bioactive glasses and neodymium:yttrium-aluminum-garnet laser on dentin permeability.

CONTEXT: Dental hypersensitivity and loss of dental tissues are commonly observed in patients, and most of the problems are caused due to total or partial exposure of dentinal tubules. AIMS: The purpose of this study is to evaluate the performance of 45S5 bioactive glass and niobophosphate (NbG) associated with neodymium: yttrium-aluminum-garnet (Nd:YAG) laser for the reduction of dentin permeability. MATERIALS AND METHODS: Fifty bovine dentin discs were made and distributed randomly into five groups (n = 10). The Nd:YAG laser was applied with the bioactive glasses using the energy parameters (60 and 80 mJ), forming the groups; NbG_60: NbG + Nd:YAG (60 mJ); NbG_80: NbG + Nd:YAG (80 mJ), 45S5_60: 45S5 + Nd:YAG (60 mJ); 45S5_80: 45S5 + Nd:YAG (80 mJ) and C: control (untreated dentin). The permeability was measured with a split chamber device. The samples were subjected to the erosive challenge and a new permeability measurement was done. Furthermore, the dentin was analyzed by scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). STATISTICAL ANALYSIS USED: The data were analyzed using Kruskal-Wallis and Dunn's tests (α = 0.05). RESULTS: Greater reduction in dentinal permeability was observed for 45S5 bioactive glasses (45S5_60 and 45S5_80) followed by NbG_80 and NbG_60 (P < 0.05). The SEM/EDS analysis showed the formation of a barrier after the dentin treatment. CONCLUSIONS: Bioactive glasses with Nd:YAG laser on the dentin surface may be a promising alternative for the reduction of dentin permeability.

Could sonic delivery of bulk-fill resins improve the bond strength and cure depth in extended size class I cavities?

BACKGROUND: The implementation of restorative procedures that guarantee success and optimize clinical time is the target of investigations in Restorative Dentistry. This study aimed to analyze the influence of sonic insertion of bulk-fill (BF) and conventional (C) resin composites on the microtensile bond-strength (µ-TBS) and cure depth (CD) of large and deep class I restorations. MATERIAL AND METHODS: Fifty-six healthy human premolars were selected and occlusal cavities (4 x 4 x 3 mm; factor C = 5) were prepared. TC - Tetric N-Ceram (BF), SF - SonicFill (BF), and Z350 - Filtek Z350 XT (C) composite resins were used to restore the cavities, using sonic (S) and non-sonic (NS) insertion techniques. A group restored with conventional incremental insertion (I) using Z350 XT resin was performed serving as a control. Teeth were prepared for microtensile bond-strength test (µ-TBS). And also, restoration depths of 1 and 4 mm were measured with an automatic microhardness indenter (50 g -15 s) to determine the CD. Results were evaluated using ANOVA, Scheffe, and Games-Howel posthoc test (α = 0.05). RESULTS: Types of resins and insertion techniques present statistical differences for µ-TBS and CD (p ≤ 0.001). The µ-TBS was higher respectively for the groups SF > TC > Z350; however, the sonic insertion for SF and Z350 (I) did not present significant differences in µ-TBS. Higher microhardness values were observed on the surface (1mm). At a depth of 4 mm Z350 (I)> SF(S)> SF(NS)> TC(S/NS)> Z350(S/NS) (p< 0.001). Pearson's Correlation of bond strength and base micro-hardness was significant (p ≤ 0.001), strong, and positive (0.955). CONCLUSIONS: The influence of sonic insertion is material dependent, influenced only the microhardness of the SonicFill resin and did not interfere with the bond strength and cure depth of other bulk fill and conventional resin composite. Key words:Composite resins, dentin, hardness tests, tensile strength, Bulk-fill resins, sonic insertion.

Oral piercing complications among teenage students.

PURPOSE: The aim of this study was to assess the use of oral piercings and their possible associated complications among students aged 14 to 18 years. MATERIALS AND METHODS: A total of 927 students from private and state schools were invited to participate in this study. The participants were subjected to clinical examination, and a questionnaire was provided for collecting the following data: gender, piercing location, oral complications or alterations, and cleaning frequency. RESULTS: Among the students who were analysed, 33 had oral piercings (3.6%); 69.70% were from state schools and 30.30% were from private schools. There was a slight predominance of males (54.55%) compared with females (45.45%). The tongue was the most common location for piercing (66.6%). The complications and alterations associated with the use of piercing were observed in 74.3% of the cases. CONCLUSIONS: In the population that was studied, oral piercing was observed in a small percentage of teenage students (3.6%) and there were local complications associated with its use.

Efficacy of low-level laser therapy in the treatment of temporomandibular disorder.

AIMS: To evaluate the effectiveness of low-level laser therapy (LLLT) in patients presenting with temporomandibular disorder (TMD) in a random and placebo-controlled research design. METHODS: The sample consisted of 40 patients, divided into an experimental group (G1) and a placebo group (G2). The treatment was done with an infrared laser (830nm, 500mW, 20s, 4J/point) at the painful points, once a week for four consecutive weeks. The patients were evaluated before and after the treatment through a Visual Analogue Scale (VAS) and the Craniomandibular Index (CMI). RESULTS: The baseline and posttherapy values of VAS and CMI were compared by the paired T-test, separately for the placebo and laser groups. A significant difference was observed between initial and final values (p < 0.05) in both groups. Baseline and post-therapy values of pain and CMI were compared in the therapy groups by the two-sample T-test, yet no significant differences were observed regarding VAS and CMI (p > 0.05). CONCLUSION: After either placebo or laser therapy, pain and temporomandibular symptoms were significantly lower, although there was no significant difference between groups. The low-level laser therapy was not effective in the treatment of TMD, when compared to the placebo.

Double teeth in primary dentition: report of two clinical cases.

Odontogenic anomalies can occur as a result of conjoining or twinning defects. These include fusion, gemination and concrescence. This article presents two case reports of double teeth. In the first case reported, a 4 -year-old white boy presented primary double teeth associated to the absence of the right permanent mandibular lateral incisor. In the second case, a 5-year-old white girl had a family history of anomaly in primary dentition. The girl and her mother presented double teeth in the primary dentition. Her mother showed hypodontia in the permanent dentition. Extra and intra oral clinical examination was made in both cases. Radiographic analyses showed the involvement of the permanent tooth. Authors conclude that double teeth in primary dentition have to be carefully analysed as they may be associated with anomalies in the permanent dentition. Correct diagnosis of the condition implicates in a better prognosis for the patient.

Polymerization Shrinkage of Bulk Fill Composites and its Correlation with Bond Strength.

The present study aimed to evaluates polymerization shrinkage (PS) using microcomputed tomography (µCT) and microtensile bond strength (µTBS) in bulk fill composites (BFC) and conventional class I restorations as well as the correlation between these factors. Class I cavities (4 x 5 x 4 mm), factor-C = 4.2, were created in third molars that were free of caries, which were randomly divided in 4 groups (n = 6): XTI (Filtek Supreme XTE: incremental technique); XTB (Filtek Supreme XTE: single fill technique); TBF (Tetric Bulk Fill); and SF (SonicFill). Each tooth was scanned twice in µCT: T0 was after filling the cavity with composite, and T1 was after light curing. The data were analyzed by subtracting the composite volume for each time (T1 - T0). After 1 week, the teeth were sectioned crosswise in the buccolingual and mesiodistal directions to obtain specimens with approximately 1 mm² thickness and fixed in a universal testing machine to perform µTBS. The Kruskal-Wallis and Dunn tests showed a statistically significant difference for shrinkage in µCT among the XTI and XTB and between the SF and XTB. Regarding the µTBS, all the groups differed from XTB. Bulk fill composites type presents a PS similar to that of the conventional nanoparticulate composite inserted using the incremental technique, but the bond strength was higher for the incremental group, which presented a lower number of pre-test failures when compared to BFC. No correlation was observed between the polymerization shrinkage and bond strength in the studied composites.

Is there correlation between polymerization shrinkage, gap formation, and void in bulk fill composites? A µCT study.

This in vitro study aimed to evaluate the volume of polymerization shrinkage (VS), gap (VG), and void (VV) using computerized microtomography (µCT) in bulk fill resin composites and conventional class I restorations, and to establish a correlation between these factors. Class I cavities (4 x 5 x 4 mm), C-factor = 4.2, were performed on caries-free human third molars and randomly divided into five groups (n = 6): FSI (Filtek Supreme XTE incremental insertion); FSS [(Filtek Supreme XTE single insertion(SI)]; TBF [(Tetric Bulk Fill: SI and manual filling (MF)]; SFM (Sonic Fill: SI/MF); and SFS (SonicFill: SI and sonic filling). The teeth were scanned and analyzed by µCT at T0, after filling the cavity with resin, and at T1, after polymerization for VG and VV, and for VS (T1-T0). There was statistically significant difference in VS in µCT for the FSI and FSS groups and between SFS and FSS as well as some difference in VV for FSI and bulk fill resin composites and no difference in VG between the conventional technique and bulk fill composites. Bulk fill resin composites presented similar VS and gap formation to those of incrementally inserted conventional resin composites. There is a moderate and weak positive correlation between polymerization shrinkage and gap formation and void, respectively. The final gap formation was more dependent on the initial gap than on polymerization shrinkage or void volume.