Efficiency of 3D printed composite resin restorations compared with subtractive materials: Evaluation of fatigue behavior, cost, and time of production

STATEMENT OF PROBLEM

Three-dimensionally (3D)-printed composite resins have been marketed as materials for definitive restorations. However, limited information is available regarding the stability of the adhesive interface and the efficiency of 3D printed composite resins.

PURPOSE

The purpose of this in vitro study was to evaluate the integrity of the marginal adhesive interface before and after thermal and mechanical fatigue of an initial formulation of a 3D printed composite resin and to evaluate the efficiency of this manufacturing method.

MATERIAL AND METHODS

Freshly extracted molars were prepared for onlays and adhesively restored with either 3D printed composite resin (VarseoSmile Crown Plus) (Group 3D), milled composite resin (Tetric CAD) (Group MCOMP), milled PMMA (Telio CAD) (Group PMMA), and milled lithium disilicate (IPS e.max CAD) (Group EM). Marginal analysis was performed under a scanning electron microscope before and after fatigue by thermomechanical cyclic loading, and initial and terminal percentages of continuous margin (%CM) were compared. The time required for the production of each type of restoration was recorded, and the production costs were also compared.

RESULTS

Before aging, 3D, MCOMP, and EM presented comparable values of %CM (69.8%, 75.9%, and 63.1%, respectively) that were statistically significantly higher (P<.05) than those of PMMA (45.1%). After aging, 3D and EM had comparable results (44.7% and 43.7%, respectively), which were lower than those of the MCOMP group (68.5%) but higher than those of the PMMA group (20.5%). Regarding time efficiency, 3D printing took less time than MCOMP or PMMA if more than 8 restorations were fabricated. For the production costs, 3D printing was 5.5, 8.7, and 10.2 times less expensive than PMMA, MCOMP, and EM, respectively. The initial equipment cost was also lower for the additive manufacturing method. However, 3D printing did not always considerably reduce waste.

CONCLUSIONS

In terms of marginal adaptation, the evaluated initial formulation of a 3D printed composite resin behaved similarly to other well-established definitive restoration materials and better than milled PMMA, both before and after fatigue. Three-dimensionally printed resins present advantages in terms of equipment and consumable costs, even for a single restoration, but also for production time when more than 8 restorations were fabricated.

An in-vitro study on effects of laser activation on dye penetration in human root dentin

Objective

To evaluate the penetration of a dye in root dentin after activation with different laser wavelengths.

Materials

Palatal roots of 38 human molars were enlarged and disinfected. Irrigation activation was performed with an Er:YAG laser: @50 mJ, 15 Hz (Er:YAG); a 9.3 µm CO2 laser: @40% power (CO2); diode lasers 455 nm/970 nm: @0.8 W, 15 Hz (D455, D970) and 808/980 nm: @1 W (D808, D980) and compared to positive control: etching with 35% H3PO4 (POS); negative control: water (NEG) and conventional needle irrigation: NaOCl and ethylenediaminetetraacetic acid (EDTA) (CONV). Methylene blue solution was introduced in the canal and laser-activated or left untouched for 100 s before the roots were dried and cut into horizontal slices. Dye penetration was automatically calculated by color recognition of two samples per root third (n = 8 per group in each coronal, middle and apical root thirds). The presence and absence of a smear layer was checked in two additional samples of the negative and positive control under scanning electron microscopy (SEM).

Results

Full-depth infiltration was not achieved in any group. Dye penetration in CONV was significantly less than in Er:YAG, CO2, POS, D455, D970, D808 and similar to NEG and D980 when results of different root thirds were pooled.

Conclusion

Laser activation using certain parameters enhanced dye penetration compared to conventional needle irrigation with NaOCl and EDTA (CONV).

Micromorphology of Root Canal Walls After Laser Activated Irrigation

This study aims to investigate the effects of laser-activated irrigation on root canal dentin using different laser wavelengths. Sixty-six roots were prepared and split longitudinally. First, lasers with different power settings were tested on 34 samples, pre-etched with phosphoric acid, or remaining with a smear-layer to determine the test parameters. Selected parameters were then applied on thirty roots (9 groups) covered with smear layer: 1. Smear-layer removed; 2. Smear-layer untouched; 3. Conventional needle irrigation with NaOCl and EDTA; 4. ER:YAG laser; 5. 9.3 μm CO₂ laser; 6-9. Diode lasers. All lasers were applied in ultra-pure water as an irrigant. Root halves were examined by scanning electron microscope to analyze the intracanal dentin micromorphology on 9 consequent photos per specimen @ a magnification of 1000X. The results showed that conventional needle irrigation was effective in removing the smear-layer from coronal and middle root parts, while laser-activated irrigation had two main mechanisms: cleaning and opening of the dentinal tubules by removing the smear layer (Er:YAG laser) and melting of dentin (CO₂ and diode lasers) in all root parts. The study concluded that laseractivated irrigation with different wavelengths impacted the smear layer and root canal dentin differently through pure physical/mechanical effects.

Activation of endodontic irrigants using a 9.3 µm CO₂ and diode lasers: A laboratory proof of concept model

PURPOSE

To investigate the differences between irrigant propagation and temperature changes using laser-activated irrigation (LAI) at different settings in an artificial root canal model.

METHODS

Using an artificial resin root canal model, irrigant activation was achieved in 19 experimental groups with eight samples each. A 9,300 nm CO₂ laser, two diode lasers with different settings (wavelengths 455, 808, 970, and 980 nm) were compared to 2,940 nm Er:YAG laser and traditional needle irrigation. Er:YAG and CO₂ laser were activated in the pulpal chamber only, while diode lasers and needles were inserted into the main root canal. Lasers were activated for 5x 20 seconds resulting in 100 seconds of activation or rinsing for each sample. After each activation of 20 seconds, a photo was taken of the side canals and the propagation of the dye was measured with a digital measuring tool after calibration. Further, the temperature of the irrigant was reported after activation of 20 seconds and repeated 5 times. Data were checked for normality and statistically compared.

RESULTS

All lasers increased the irrigant propagation compared to conventional irrigation. Significant differences were found between groups regarding propagation and temperature (P< 0.0027). Er:YAG and CO₂ laser had similar effects on irrigant propagation in middle and apical located side-canals with specific power parameters and were superior to diode lasers and syringe irrigation. The irrigant's temperature increased significantly with the diode and CO₂ lasers.

CLINICAL SIGNIFICANCE

Diode lasers and CO₂ lasers have not been established for irrigant activation. 9,300 nm CO₂ lasers absorb well in water and were shown to introduce vapor bubble formation and streaming in water. Diode lasers are highly accepted in periodontics. The laser light is not absorbed in water but interacts with bacteria as well as soft tissues and contributes therefore to infection control. With a modified laser tip it was however possible to introduce cavitation and streaming in irrigants.

Marginal adaptation of two-step self-etch versus universal adhesives for Class V restorations: Effect of Er:YAG laser vs. bur prepared cavities

PURPOSE

To compare the in vitro effect of laser and bur preparation on marginal adaptation of Class V cavities restored with a 2-step self-etch and distinct universal one-component universal adhesives used in self-etching mode.

METHODS

96 Class V cavities were prepared with conventional burs or with an Er:YAG laser. Four universal self-etch (Unibond Extra Low Shrinkage, All Bond Universal, SKB-100 and Prime&Bond active) and a 2-step self-etch adhesive (Clearfil SE Bond) that served as control were used to restore the cavities with direct composite. The percentages of continuous margins were evaluated by quantitative SEM analysis before and after a fatigue test consisting of 240,000 occlusal loads and 600 warm/cold thermal cycles.

RESULTS

The marginal adaptation of bur prepared restorations was statistically superior to laser-prepared ones. Class V cavities restored with Clearfil SE Bond and the one-component self-etching universal adhesives All Bond Universal and Prime&Bond active presented the highest and statistically similar percentages of continuous margins before and after loading under both bur and laser cavity preparation. The lowest percentages of continuous margins were observed in the groups restored with the low shrinking adhesive (Unibond ELS), with medians of 49 and 21 for bur and laser prepared cavities after loading.

CLINICAL SIGNIFICANCE

Class V cavities presented smoother and higher percentages of continuous margins when prepared by bur rather than by laser. The 2-step self-etch adhesive Clearfil SE Bond and 1-step self-etch universal adhesives All Bond Universal and Prime&Bond active showed a comparable marginal performance.

Marginal Adaptation of In Vitro Class II Restorations Made Out of Bulk or Conventional Composite Using Single- or Multi-Layered Techniques

Objective: Testing the influence of various restorative materials (conventional or bulkfill composites) and filling techniques (single- or multi-layered techniques) on the in vitro marginal adaptation of large class II direct composites with supra and sub-gingival margins subjected to thermomechanical loading (TML). Methods: A total of 40 prepared teeth were attributed randomly to five experimental groups. In Group 1, restorations were made of multi-layered high-viscosity conventional composite (Tetric EvoCeram); in Groups 2 and 3, restorations were made of a high viscosity bulkfill composite (Tetric EvoCeram Bulk Fill) applied in one (Group 2) or three layers (Group 3); in Groups 4 and 5, restorations were made of a flowable bulkfill composite (SDR flow) applied in one (Group 4) or two layers (Group 5), covered with a layer of high-viscosity conventional composite (Ceram-X Universal). A single adhesive (OptiBond FL) was used in all groups. All specimens were submitted to a staged TML comprising three phases (2 × 500,000 and 1,000,000 cycles) at 50 N with 3350 thermal cycles (5 to 55 °C) every 500,000 cycles. The tooth-restoration interfaces on proximal surfaces were evaluated quantitatively by scanning electron microscopy, before and after each TML phase, hence at three timepoints (T0, T1, T2 and T3). The following segments were considered for evaluation: proximal, vertical enamel margins (assessed individually on both restoration sides), cervical enamel (restoration side above CEJ) and cervical dentin margin (restoration side below the CEJ). Results: TML induced a significant reduction in continuous adaptation at both enamel and dentin margins in all groups, with percentages of continuous margins ranging from 75.2 to 91.8% at T0, and decreasing to values ranging from 21.3 to 73.9% at T3. Both composite systems and layering protocols had a significant influence on marginal adaptation of the restorations, with statistical associations depending on the restoration group and the timepoint considered. Defective margins in enamel were all of a cohesive nature with micro-fractures, while in dentin, interfacial gaps were the main defect observed. Conclusions/Clinical significance: The present results highlighted significant degradation of marginal adaption after long-term in vitro fatigue test using materials even with high-viscosity conventional resin composites, applied with a proper layering approach in medium-large sub-gingival cavities. While no significant differences were observed at the dentin cervical margins, there was a tendency for better adaptation at the enamel margin when using a higher modulus material with a multi-layered technique.

In Vitro Evaluation of Tooth-Whitening Potential of Peroxide-Free OTC Dental Bleaching Agents

Purpose: To evaluate and compare the tooth-whitening potential of five over-the-counter (OTC), peroxide-free dental bleaching methods as well as an experimental tooth-whitening solution containing 0.1% hydrogen peroxide complexed with doping agents with a gold standard (positive control) containing 16% carbamide peroxide. Material and Methods: Eighty permanent bovine incisor teeth were randomly allocated to eight different groups. Two teeth from each group were immerged into five staining solutions represented by coffee, tea, red wine, and curry mixed in warm oil or distilled water (control group) and stored at 37 °C for 28 days in an incubator. The teeth were then reallocated to the eight groups, resulting in ten samples per group, and each group was matched with a bleaching product. The bleaching procedures were executed following the manufacturer’s recommendations. The color of each sample was assessed over a white and black background using a quantitative numerical measurement approach with a calibrated spectrophotometer. Spectrophotometric measurements were performed after exposing the teeth to the bleaching agent for 60 min (T2), 100 min (T3), and 200 min (T4), and ΔE00 was calculated. Results: When analyzed over a white background, the mean ΔE00 values ranged from 2.14 (placebo) to 6.32 (Opalescence PF). When analyzed over a black background, the mean ΔE00 values ranged from 2.31 (placebo) to 5.78 (Opalescence PF). Statistically significant ΔE00 color changes over time for the eight groups and five staining solutions at T1 and T4 were assessed for both backgrounds using repeated ANOVA followed by Fisher’s LSD post hoc test (p-value < 0.01). Conclusions: All tested over-the-counter whitening kits except one exhibited positive color variation. However, the individual performance differed vastly from one brand to the other, and the overall performance was less effective compared to the conventional carbamide-peroxide-based positive control.

Time-and cost-effective 3-dimensional-printing workflow to rehabilitate worn dentitions: A clinical report

Current restorative methods of restoring worn or eroded dentition present drawbacks that may deter dentists or patients from pursuing complete mouth rehabilitation. A novel additive manufacturing approach using 3D-printed definitive composite resin restorations is described as a less technique-sensitive and more cost-effective alternative. These restorations are straightforward to repair, modify, or replace.

Efficacy of one-time application of low-level laser therapy in the management of complications after third molar surgery: A retrospective practice-based study

PURPOSE

To evaluate in a retrospective practice-based clinical study, the effects of additional laser therapy on side effects following the removal of all four impacted third molars. The secondary objective was, based on those results, to rationalize a protocol for low-level laser therapy (LLLT) in terms of irradiation settings.

METHODS

96 subjects requiring simultaneous surgical removal of the four third molars were treated from 2017 to 2019. For each subject, one side was randomly assigned to laser treatment, the other receiving the placebo. LLLT was performed by applying an infrared diode laser of 810 nm. In the LLLT irradiated side of the mouth, three groups were randomly assigned to a specific protocol of irradiation. Controllable settings include power, energy density and also scanning technique. The main outcome was pain, registered on a visual analog scale (VAS) performed by the patients.

RESULTS

There was a statistically significant difference for one of the tested protocols. Self-reported annoyance and pain scores were lower for the side submitted to a 30-second laser radiation at a power of 0.3 W with the slow scanning technique (P< 0.05).

CLINICAL SIGNIFICANCE

The present treatment approach, using a one-time low-level laser therapy intra-oral application, showed a beneficial effect of LLLT reducing pain after third molar surgery, which should be confirmed through further study.

Effect of light-curing time and direction on microhardness of a light-cured resin composite to cement CAD-CAM restorations

PURPOSE

To evaluate the effect of light-curing exposure time and location on polymerization of a restorative bulk-fill resin composite to lute endocrowns.

METHODS

A light-cured restorative bulk-fill resin composite (Filtek One Bulk Fill) was submitted to direct light-curing by a high-power LED light-curing unit for 20 seconds as the positive control group (n= 10). Five more groups (n= 10) were light-cured in a natural tooth mold from two sites (labial and lingual) through a nanohybrid resin composite CAD-CAM restoration (Lava Ultimate A2 LT), for different irradiation times: 90 seconds per site, 40 seconds per site, 30 seconds per site, 20 seconds per site and 10 seconds per site. Vickers microhardness measurements were made at two different depths and test/control ratios were calculated. Ratios of 0.8 were considered as an adequate level of curing. A quantile regression was run to identify the minimally sufficient time of light-curing, and a two-way ANOVA was used to compare the results to previous findings and evaluate the effect of curing location.

RESULTS

Analysis showed that 40 seconds x 2 is the minimal irradiation time that presents a test/control ratio above 0.8. Quantile regressions showed that the required irradiation time to reach a test/control ratio of 0.8 at a confidence level of 95% is 41.5 seconds and 39.2 seconds at 200 µm and 500 µm depths in the luting agent, respectively. There was no statistically significant difference between microhardness of the two depths except for the irradiation time of 10 seconds. The two-site to three-site light curing comparison showed no statistically significant difference except for the 90-second time.

CLINICAL SIGNIFICANCE

Systematic light-curing through the labial, lingual and occlusal surfaces of thick indirect restorations is not always required for sufficient polymerization and can even waste valuable clinical time especially in the case of multiple restorations luted with resin composites.

Evaluation of the Validity of Digital Optical Microscopy in the Assessment of Marginal Adaptation of Dental Adhesive Interfaces

Analysis of marginal adaptation of dental adhesive interfaces using scanning electron microscopy has proven to be a powerful nondestructive method to evaluate the quality of adhesion. This methodology is, however, time-consuming and needs expensive equipment. The purpose of this study was to evaluate the possibility and efficiency of using a digital optical microscope (DOM) to perform marginal analysis and to compare it with the scanning electron microscope (SEM) analysis. Fifteen defect-free molars were selected for this study. Class V cavities were prepared and restored with resin composite, and epoxy replicas were obtained from silicone impressions of the restored teeth. Custom-made image analysis software was then used to measure the percentage of the noncontinuous margins (NCM) of each sample. To compare the DOM to the gold standard, SEM, each sample was analyzed 10 times using the DOM and three times using the SEM, by the same experienced operator. The repeatability coefficient and concordance were evaluated, and a Bland and Altman analysis was used for comparison of the two methods of measurements. To validate the DOM analysis method, an ANOVA approach (Gage R R) was used. Repeatability and reproducibility, which are two components of precision to validate the DOM analysis system, were calculated. For this, the same restorations were analyzed by two additional operators three times with the DOM. The duration of each step of the analysis using both methods was also recorded as a secondary outcome. Regarding the repeatability of each method, the Friedman test showed no statistically significant difference within the repetitions of measurements by SEM and DOM (p = 0.523 and p = 0.123, respectively). Moreover, the Bland-Altman analysis revealed a bias of 0.86 and concluded no statistically significant difference between the two methods, DOM and SEM. ANOVA evaluated DOM measurement system variation including the variances of repeatability and reproducibility that represented, respectively, 0.3% and 4% of the variance components. Reproducibility or inter-operator variability represented the principal source of variability with a statistically significant difference (p = 0.024). The time required for analysis with SEM was almost double that of DOM. The use of digital optical microscopy appears to be a valid alternative to the SEM for the analysis of marginal adaptation of dental adhesive interfaces. Further studies to evaluate the effect of training of operators in digital optical microscopy could reveal higher accuracy for this method and inter-operator agreement when experience is gained.

Functional assessment of the stomatognathic system. Part 2: The role of dynamic elements of analysis

OBJECTIVES

To review the dynamic analytical elements used in the functional assessment of the stomatognathic system, summarize the available scientific evidence, and consider interrelations with body posture and cognition.

METHOD AND MATERIALS

A thorough literature search was conducted using PubMed, the Cochrane Library database, and Google Scholar. Peer-reviewed articles and literature reviews provided up-to-date information addressing three topics: (a) the available knowledge and recent evidence on the relationship between the morphologic aspects of dental/craniofacial anatomy and oral function/dysfunction, (b) mandibular dynamics, considering mobility, functional activity, and existing methodologies of analysis, and (c) a possible correlation between the stomatognathic system, body posture, and cognition.

RESULTS

Modern dentistry may be regarded as a human adaptation strategy, helping to conserve healthy teeth for much longer without risking overall health. It is futile to treat patients using a mechanistic, sectorial approach that misrepresents patient behavior and requests, just as it is to affirm the absence of any structure-function relationships. However, it is also evident that there is a lack of general consensus on the precise functional assessment of the stomatognathic system, mostly due to the methodologic heterogeneity employed and the high risk of bias. Despite the abundant evidence produced with the aim of providing solid arguments to define dynamic models of functional assessment of the stomatognathic system, it is yet to become highly empirical, based as it is on operator experience in daily clinical practice.

CONCLUSIONS

Further efforts from the scientific and clinical community, with the help of progress in technology, remain should this gap be filled and should substantial data on differences between pathologic and physiologic dynamic models of function be provided. Dentistry needs to employ - on a larger scale - objective, dynamic methods of analysis for the functional evaluation of the stomatognathic system, embracing concepts of "personalized medicine" and "interprofessional collaborations."

Restoration of Severely Damaged Endodontically Treated Premolars: Influence of the Ferrule Effect on Marginal Integrity and Fracture Load of Resin Nano-ceramic CAD-CAM Endocrowns

OBJECTIVES

To explore the ferrule effect on Resin Nano-Ceramic (RNC) premolar endocrown marginal integrity and fracture resistance.

METHODS

Thirty-six root-canal-treated premolars were cut 2 mm above the cemento-enamel junction (CEJ). They were restored with standardized RNC computer-aided design/computer-aided manufacturing (CAD/CAM) restorations (Lava Ultimate, 3M Oral Care, St. Paul, MN, USA) and divided into three groups (n=12): endocrowns with a 3-mm endo-core (Group 1), endocrowns with a 3-mm endo-core and a 2-mm ferrule (Group 2), and conventional post-and-core crowns with a 2-mm ferrule (Group 3). All specimens were submitted to thermo-mechanical cycling loading (TMCL) (1.7 Hz, 49 N, 600 000 cycles, 1500 thermocycles). Margins were analyzed before and after the TMCL. In the second part of the experiment, the surviving specimens were submitted to unidirectional monotonic loading until fracture. Fragments were then analyzed using scanning electron microscopy (SEM) and the fracture mode was established.

RESULTS

Endocrowns of Groups 1 and 2 performed better than conventional crowns (Group 3) in terms of marginal continuity. Differences in fracture load values within all groups were not statistically significant. Most of the specimens fractured in a non-repairable way.

CONCLUSIONS

The present test failed to provide evidence of any kind of difference between endocrowns with and without a ferrule in terms of load-bearing capacity and marginal integrity after fatigue. Further studies are needed to confirm the role of the ferrule in adhesive restorations of endodontically treated teeth.

In vitro evaluation of marginal adaptation in medium- and large size direct class II restorations using a bulk-fill or layering technique

OBJECTIVES

to test if cavity dimensions and restorative protocol have potential to influence in-vitro adaptation of class II restoration after simulated thermo-occlusal stressing.

METHODS

A total of 32 prepared teeth were randomly assigned to one of the 4 experimental groups depending on cavity size, composite system and filling technique; group 1: small cavity and multi-layered conventional restorative composite (Tetric Evo-ceram: TEC), group 2: small cavity and flowable bulk-filled composite (SDRFlow: SDR) + one single occlusal layer of conventional restorative composite (TEC), group 3: large cavity and multilayered conventional restorative composite (TEC) and group 4: large cavity and bulk-filled flowable composite (SDR) + one single occlusal layer conventional restorative composite (TEC). All specimens were submitted to 500'000 cycles of thermomechanical loading (50 N, 5 to 55 °C). The proximal tooth-restoration interface was analyzed quantitatively by SEM, prior and after thermomechanical loading.

RESULTS

Before loading, continuous enamel adaptation varied from 61.49% (Gr 1) to 68.39% (Gr 4) proximally and from 50.93% (Gr2) to 68.65% (Gr1) cervically, with no statistical difference among groups for both segments. After thermomechanical loading, continuous enamel adaptation varied from 36.6% (Gr2) to 46.6% (Gr1) proximally, without significant difference, and from 20.2% (Gr4) to 51.3% (Gr1) cervically; statistical differences in cervical enamel adaptation were found in-between groups 1 and 2 (p = 0.0479), 1 and 4 (P = 0.0116), 2 and 3 (p = 0.0028) and 3 and 4 (p = 0.001). Before loading, dentin continuous adaptation varied from 55.32% (Gr3) to 81.82% (Gr4) with statistical difference in-between those groups (p = 0.045); after loading, dentin continuous adaptation varied from 31.56% (gr2) to 51% (Gr4) with a statistical difference between those 2 groups (p = 0.019). The drop in adaptations values after loading was significant in all groups and segments.

CONCLUSIONS

The impact of the restorative technique and cavity size on marginal adaptation appeared essentially after simulated fatigue for enamel adaptation. Cervical enamel and dentin continuous adaption of small and large bulk-filled restorations dropped significantly while the change was lower in layered restorations made of conventional restorative composite.

CLINICAL SIGNIFICANCE

Restorations made with bulk-filled flowable composite behaved differently from layered ones using conventional resin composite, according to cavity size and loading.

Functional assessment of the stomatognathic system. Part 1: The role of static elements of analysis

OBJECTIVES

To review the elements of static analysis in the functional assessment of the stomatognathic system, as promoted for more than a century by gnathologists, and summarize the available scientific evidence, including anthropologic observations.

METHOD AND MATERIALS

A thorough search was conducted using PubMed, the Cochrane Library database, and Google Scholar. From peer-reviewed articles and other scientific literature, up-to-date information addressing three topics was identified: (a) the anthropologic perspective with particular consideration for the role of progressive dental wear over time, (b) descriptions of gnathologic principles and evidence on their scientific validity, and (c) the methodologic inaccuracies introduced by seeking to correlate variables directly rather than allowing for causal inference.

RESULTS

For decades gnathology attempted to describe a structure-function correlation within the stomatognathic system by means of a model whose principles were static and mechanistic references. No scientific validation was ever achieved, placing clinical and research consensus out of reach.

CONCLUSIONS

A historical perspective helps to place the fundamentals of gnathology into context: They were conceived to solve technical difficulties but were then assumed to be physiologic stereotypes. This misconception led to a decades-long promotion of mechanistic theories to describe oral function, but the evidence available today supports a more flexible and adaptable approach. Gnathologic arguments have been relegated to become exclusively of technical relevance in oral rehabilitation.

Effect of Multiple Enamel Surface Treatments on Micro-Shear Bond Strength

Objectives: The aim of this study was to evaluate the effect of different enamel surface treatments on the micro-shear bond strength. Materials and methods: Sixty-four approximal surfaces from freshly extracted molars were randomly assigned to eight groups, according to combinations of the following enamel surface treatments: ground or unground, 37.5% phosphoric acid etching time of 15 or 30 s, and with or without primer application. The same bonding agent (Optibond FL™ Adhesive, Kerr) was then used for all groups, and a 1.8 mm diameter resin composite (Harmonize™, Kerr) cylinder was built up on the bonded surface. Samples underwent a shear force test at a crosshead speed of 1 mm/min until failure. Bond strength was calculated, and failure modes were inspected under an optical microscope. Results: Bond-strength values ranged from 8.2 MPa for 15 s etched unground enamel with primer application to 19.6 MPa for 30 s etched ground enamel without primer application. ANOVA and Fisher’s LSD post hoc tests revealed significant differences between the groups. Conclusions: Etching time and grinding have a statistically significant effect on the micro-shear bond strength of a three-step etch-and-rinse adhesive system on enamel. Primer application does not seem to be beneficial for enamel adhesion.

Gloss retention of direct composites and corresponding CAD/CAM composite blocks

Objectives

To compare gloss retention of four different resin composites with their corresponding CAD/CAM composite blocks.

Materials and methods

Four direct resin composites (Filtek Supreme XTE A2 Body (3M, USA), Tetric EvoCeram A2 (Ivoclar Vivadent, Liechtenstein), GrandioSO x‐tra A2 (VOCO, Germany), G‐aenial Universal A2 (GC, Japan)), and their corresponding CAD/CAM composite blocks were tested. A total of 288 samples were prepared and three different tests were performed: brushing, exposition to acidic fluoride gel and exposition to alcoholic solution. Gloss values were obtained by means of a glossmeter at T0 before aging and T60 after 1 h of aging.

Results

Mean gloss values ranged from 0.9 after brushing tests to 79.0 after the alcohol test witnessing a high gloss variability depending on the materials and the aging test. Statistical analysis by means of two‐way repeated measures ANOVA followed by Fisher's LSD post‐hoc test revealed significant differences between materials, storage media, and their interactions.

Conclusion

Gloss retention seems to be dependent on the composite type (direct or CAD/CAM block) and composite brand and varies in respect to the type of aging. CAD/CAM materials showed a higher resistance toward alcohol exposure.

Illuminant metameric effects on interbrand and intrabrand color differences of direct composite resins

STATEMENT OF PROBLEM

Information on the illuminant metameric effects on the intrabrand and interbrand differences in color of direct composite resins is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of different illuminations on the color differences of the same or different brands of composite resins.

MATERIAL AND METHODS

Sixty-four disks were prepared from 8 different direct dental composite resins of A3 shade, and, after polymerization and hydration for 48 hours, their color coordinates were measured in the Commission Internationale de I'Eclairage (CIE) L∗a∗b∗ color space with a portable colorimeter on a black and white background under D65 (daylight), F2 (cool white fluorescence), and A (incandescence) illuminations. Translucency parameters (TP) and fluorescence intensities (FI) of the brands were also measured to assist in the interpretation of brand behavior under the illuminations. The Kruskal-Wallis and Friedman nonparametric tests with post hoc multiple comparisons tests were applied to analyze the data for differences within and between brands under all illuminations (α=.05), while regression analysis was used to estimate the relationship between D65 and F2 or A illumination data.

RESULTS

Statistical analysis showed significant differences among brands (P<.05) for all color coordinates under all illuminations, with a strong linear relationship between them (R2=0.72-0.97). Intrabrand differences were significantly different across brands (P<.05) and ranged from 0.06 to 3.1 across illuminations in ΔE∗_ab units (0.05 to 2.4 in ΔΕ₀₀ units). Interbrand differences were also significantly different (P<.05), with a range of 0.15 to 8.7 ΔE∗_ab units or 0.14 to 5.7 ΔΕ₀₀ units.

CONCLUSIONS

Primary color coordinates of composite resins were affected by A or F2 illumination and were strongly associated with D65 values. Redder or yellower composite resins were affected more under A or F2 illumination. Intrabrand differences, although small, may contribute to clinical mismatches under A or F2 illuminations. Clinicians should be aware that certain brand pairs may present acceptable differences under D65 illumination but could become unacceptable under A or F2 illumination.

Effect of 9.3 μm CO2 and 2.94 μm Er:YAG Laser vs. Bur Preparations on Marginal Adaptation in Enamel and Dentin of Mixed Class V Cavities Restored With Different Restorative Systems

This study aimed to compare marginal adaptation in enamel and dentin before and after aging of laser vs. bur-prepared mixed class V cavities restored by different restorative systems. Seventy two caries-free human molars were distributed to nine experimental groups; cavities were prepared using two different lasers: a handpiece -integrated 2.94 μm Er:YAG laser at 4.5 W, 300 mJ, and 0.75 W, 50 mJ with 15 Hz (LiteTouch, Light Instruments, Israel) and a novel CO2 laser at 12.95 W, 19.3 mJ, and 4.1 W, 6.11 mJ with 671 Hz (Solea 9.3 μm, Convergent Dental, USA). Cavities prepared with conventional diamond burs (Intensiv, Switzerland) in a red contra angle at high speed under maximal water cooling served as control. Cavities were prepared under simulation of dentinal fluid and restored using three different self-etching universal adhesives in combination with three nanohybrid composites, applied in two layers: Scotchbond Universal with Filtek Supreme XTE (3M, USA), G-Premio BOND with Essentia Universal (GC, Japan), and OptiBond Universal with Harmonize Universal (Kerr, USA). After restorations' polishing and simultaneous thermal (5–50°C, 2 min each) and mechanical loading (max. 49 N; 200,000 cycles), replicas of restoration margins were examined under SEM at × 200 magnification. Percentages of continuous margins (CMs) were quantified before and after the fatigue test and statistically compared (two-way ANOVA with Fisher's least significant difference [LSD] post hoc test). Significant differences were found in almost all groups between the results before and after the fatigue test, as well as between the different preparation tools and restorative materials (p &lt; 0.05). Traditional bur preparations are confirmed as gold standard in enamel and dentin, as all three tested restorative systems provide results of marginal adaptation of more than 80% CM after loading. Er:YAG laser preparations can be equally effective in combination with SBU/Filtek Supreme XTE. CO2 laser ablation could not provide convincing results with the tested self-etching restorative systems. Marginal adaptation has been highly dependent on the substrate and showed impaired adhesion, especially in enamel. Scotchbond Universal/Filtek Supreme XTE showed the highest and most stable values of CM. The other two restorative systems were highly dependent on the preparation device of the substrate.

Restoration's thickness and bonding tooth substrate are determining factors in minimally invasive adhesive dentistry

Purpose To explore fracture strength and failure behaviour of minimally invasive CAD-CAM composite resin overlay restorations.Methods Eighty bi- and tri-layer cylindrical overlay model including the restoration bonded over bovine tooth dentin (Groups D) and enamel-dentin (Groups E) were assembled (diameter 9 mm). Restorations were milled from CAD-CAM composite resin blocks (Brilliant Crios, Coltène/Whaledent AG) in different thicknesses (0.5mm, 1mm, 1.5mm, 2mm) and equally distributed in four Groups D and four Groups E (n=10). All specimens were submitted to an Hertzian load-to-failure contact test with spherical indenter. Critical loads were recorded in Newton and data were analysed using Kruskal-Wallis test for multiple and Mann-Whitney test for 2-samples comparisons (p < 0.05). Fragments were examined using SEM. The stress distribution for specimens with restorations of 0.5 mm and 2 mm was also investigated with FEA.Results For all specimens, the mean static loads in Newton increased with an increase in restoration thickness. On contrary, restorations with the same thickness displayed higher resistance values when bonded over enamel than dentin, except for the 2-mm thick restorations. A damage competition was detected between cone/median cracks originating at the loading contact area of the restorations and radial cracks beginning at their inner surface, with the former prevailing in restorations bonded on enamel and the latter being dominant for restorations bonded on dentin.Conclusions For bonded ultra-thin resin composite restorations (0.5 mm to 1.5 mm) enamel as bonding substrate assures higher critical loads to fracture than dentin. This influence gradually decreases as restoration thickened.

Surface degradation of composite resins for direct restorations: effects on wear and gloss retention

The purpose of this in vitro study was to compare the 2-body wear resistance of 7 direct composite resin materials (Synergy, Filtek Supreme XTE, GrandioSO, Tetric EvoCeram, G-ænial Anterior, Venus Pearl, and Ceram.X Duo) following thermomechanical loading as well as their gloss stability following toothbrushing. For measurement of resistance to wear, 8 specimens of each material were thermomechanically challenged under 200,000 load cycles at a maximum force of 49 N and 500 thermal cycles between 5°C and 50°C simultaneously. Wear was analyzed by measuring the volume and vertical loss of the contact point area using a high-speed 3-dimensional scan. For gloss measurements, 8 additional specimens of each material were evaluated using a glossmeter after being subjected to 15 minutes of brushing with an electric toothbrush at a 200-N application force. Filtek Supreme XTE had the least volumetric wear, while G-ænial Anterior and Ceram.X Duo had the greatest. The greatest vertical loss was recorded for G-ænial Anterior and Ceram.X Duo. Ceram.X Duo also had the greatest loss of gloss units, together with Venus Pearl. The universal composite Filtek Supreme XTE demonstrated the lowest wear rates and the best gloss retention.

Fluorescence intensities of composite resins on photo images

Recording fluorescence using flash photography, may help reduce time of capture and apply effectively in clinical practice. To test methods for visualizing composite resins fluorescence by direct digital photography. Sixty-four specimen discs (1.5 × 10 mm) were prepared from 8 different composite resin brands. Their CIELAB color coordinates (L*, a*, b*) and fluorescence were measured using a portable colorimeter and a fluorescence spectrophotometer. The mean of three measurements was recorded and then specimens were photographed by a DSLR camera with two different filters (365 nm and 405 nm) mounted on a commercial macro flash. RGB values of all specimens on the photographs were measured by using Photoshop software and converted to CIELab. Data were then analyzed using Kruskal–Wallis and Dunn’s multiple comparisons tests. Correlation and regression analyses were also used to relate fluorescence and color parameters on the photographs at α = 0.05. Fluorescence and color data indicated significant differences among the materials (p < 0.05). L* a* and b* color coordinates from both photographs were highly correlated to fluorescence intensities found by the reference method (r₃₆₅ − 0.95, r₄₀₅ − 0.94), while regression analysis indicated a strong linear relationship (R²₃₆₅ − 0.88, R²₄₀₅ − 0.89). The study showed that filtered flash photography either by the use of a 365 nm or a 405 nm band pass filter can directly visualize fluorescence of composite resin materials and differences in fluorescence between them.

Influence of 9.3 µm CO2 and Er:YAG laser preparations on marginal adaptation of adhesive mixed Class V composite restorations with one component universal adhesive

PURPOSE

To examine the marginal adaptation in enamel and dentin of mixed Class V saucer shaped restorations where cavities were prepared by two different lasers.

METHODS

A handpiece-integrated Er:YAG laser @ 4.5 W, 300 mJ, 15 Hz (LiteTouch III) and a novel CO2 laser @ 12.95 W, 19.3 mJ, 671 Hz (Solea 9.3 µm). Diamond bur preparation with a 25 µm diamond bur (Intensiv) in a red contra angle at high speed under water spray cooling served as the control. Eight cavities per group were readied and restored under simulation of dentin fluid with a one bottle universal adhesive (One Coat 7 Universal) and a nanohybrid resin composite (Everglow), applied in two layers. For every preparation technique, the adhesive system was applied in the selective-etch and the self-etch mode, resulting in six experimental groups. Marginal analysis was performed immediately after polishing and after simultaneous thermal (5-50°C, 2 minutes each) and mechanical (max. 49 N; 200,000 cycles) loading by using a SEM (x200 magnification).

RESULTS

Significant differences were found for all groups - except groups 2 and 5 - between initial and terminal results and between the groups as well (P< 0.05, 2-way ANOVA with Fisher's post-hoc test). The bur prepared group with selective-etch technique showed the best overall results after loading, followed by Er:YAG prepared self-etch group and CO2-prepared selective-etch group.

CLINICAL SIGNIFICANCE

By using a universal one-component adhesive system, marginal adaptation in enamel and in dentin depended on the preparation method and on the adhesive's application technique as well. When using lasers, Er:YAG in self-etch mode and CO2 9.3 µm in selective-etch mode total marginal adaptation showed results which were comparable to conventional bur preparation with selective-etch technique.

Effect of light-curing time on microhardness of a restorative bulk-fill resin composite to lute CAD-CAM resin composite endocrowns

PURPOSE

To evaluate the minimal irradiation time to reach a sufficient polymerization of a photopolymerizable restorative bulk-fill resin composite to lute endocrowns.

METHODS

A photopolymerizable restorative bulk-fill resin composite (Filtek One Bulk Fill) was submitted to direct light-curing by a high power LED light-curing unit for 20 seconds as the positive control group (n = 10). Five more test groups (n= 10) were light-cured in a natural tooth mold from three sites (buccal, palatal and occlusal) under a 9.5 mm thick nanohybrid resin composite CAD-CAM endocrown (Lava Ultimate A2 LT), for different irradiation times: 90 seconds per site, 40 seconds per site, 30 seconds per site, 20 seconds per site and 10 seconds per site. Vickers microhardness measurements were made at two different depths and test/control ratios were calculated. Ratios of 0.8 were considered as an adequate level of curing.

RESULTS

Analysis shows that 30 seconds x 3 was the minimal irradiation time that presented a test/control ratio above 0.8. Quantile regressions showed that the required irradiation time to reach a test/control ratio of 0.8 at a confidence level of 95% was 38 seconds and 37 seconds for 200 µm and 500 µm, respectively. There was no statistically significant difference between microhardness of the two depths except for the irradiation time of 10 seconds. A 120-second (40 seconds per buccal, palatal and occlusal site) light-curing of photopolymerizable bulk-fill resin composite to lute a resin composite CAD-CAM endocrown restoration can be considered sufficient to reach adequate polymerization.

Efficacy of P11-4 for the treatment of initial buccal caries: a randomized clinical trial

To investigate the safety and efficacy of Self-Assembling Peptide P₁₁-4 (SAP P₁₁-4) compared to placebo or fluoride varnish (FV), a randomized, controlled, blinded, split-mouth study with sequential design was conducted. Subjects presenting two teeth with White-Spot-Lesions (WSLs) were included and teeth were randomly assigned to test or control. Control received placebo at baseline (D0) and test SAP P₁₁-4, all received FV at Day 90 (D90). Standardized photographs were taken at each visit, and WSL size changes were morphometrically assessed. Hierarchical Linear Modelling, considering paired and sequential design, was used to test four hypotheses. SAP P₁₁-4 lesions (test, D90–D0) showed significant WSL size reduction compared to placebo (control, D90–D0; p = 0.008) or FV (control, D180–D90; p = 0.001). Combination of SAP P₁₁-4 and delayed FV after 90 days (test, D180–D0), showed a significant difference compared to FV alone (control D270–D90; p = 0.003). No significant difference on FV efficacy was found when SAP P₁₁-4 was applied 3 months before FV (test D270–D90; control D270–D90, p = 0.70). SAP P₁₁-4 treatment resulted in superior caries regression compared to either placebo or FV, and FV efficacy seems not to be affected by SAP P₁₁-4. SAP P₁₁-4 was found to be a safe and effective WSL treatment.

Influence of mechanical and chemical degradation on surface gloss of direct and CAD-CAM resin composite materials

PURPOSE

To compare the gloss retention of four resin based materials, two direct resin composites (Tetric EvoCeram and Filtek Supreme) and two indirect resin composite CAD-CAM blocks (Tetric CAD and Lava Ultimate).

METHODS

36 samples of 1 mm thickness were readied of each test material and manually polished with polishing discs (Sof-Lex) up to the finest grit size. Three gloss measurements per sample were taken (one every 120 degrees of sample rotation) by means of a glossmeter (Novo-Curve) for a total of 60 values obtained per tested material. Samples of each material were then randomly divided into three equal groups and aged with 75% alcohol (Group 1), amine fluoride gel (Elmex gelée) (Group 2) or mechanical brushing (Group 3). Another set of gloss measurements was performed on all samples after 1 hour of aging. Gloss values were statistically evaluated by means of repeated measures ANOVA and Fisher's LSD post-hoc tests.

RESULTS

Gloss retention values ranged from 59.0 (Tetric EvoCeram) to 70.9 (Lava Ultimate) for alcohol, from 59.3 (Filtek Supreme) to 67.5 (Lava Ultimate) for Elmex gelèe and from 33.3 (Tetric EvoCeram) to 53.4 (Lava Ultimate) for mechanical brushing. Statistical analysis revealed: (1) significant difference between intial and final gloss values for all materials and groups; (2) significant difference between final gloss values of all the materials in the alcohol group; (3) significant difference between final gloss values of Lava Ultimate and all the other materials in the Elmex gelèe group; (4) significant difference between final gloss values of Lava Ultimate and Tetric CAD with the other tested materials in the brushing group.

CLINICAL SIGNIFICANCE

Direct resin composites in general are widely used, and CAD-CAM resin composite materials are becoming progressively more accessible. Making the choice between direct and indirect techniques is still a challenge, and understanding the advantages of CAD-CAM resin composites in the form of higher gloss retention, which translates into higher durability of esthetics, may be one the parameters facilitating the decision.

Optical Coherence Tomography (OCT) for the evaluation of internal adaptation of class V resin restorations on Dentin

Internal adaptation of adhesive restorations affects their longevity. In a clinical setting, the dentists use visual and tactile examination to evaluate marginal adaptation, while radiographs provide somewhat reliable information about adaptation or secondary caries present. For class V restorations located on the vestibular (buccal) surfaces, none of the tools available can provide any information about the internal adaptation or the presence of secondary caries. OCT has been proven to be a useful tool for non-destructive assessment of internal adaptation of adhesive restorations. This paper is evaluating the use of a new high-resolution handheld OCT prototype with a pen-shaped intraoral tip and an imaging depth of 8mm to examine the internal adaptation and the presence of demineralization under resin restorations on the vestibular dentin surface. The Axsun OCT system helped evaluate the internal adaptation of composite restorations, differentiate between healthy and demineralised dentin, adhesive, and restoration layers. OCT provided a unique visualization and characterization of internal structures as well as non-contact assessment of marginal adaptation.

Full-mouth rehabilitation of a severe tooth wear case: a digital, esthetic and functional approach

The proliferation of digital technology is progressively changing dentistry. Thanks to continual improvements in CAD/CAM devices and dental materials, it is possible nowadays to carry out a treatment plan for oral rehabilitations with fully digital approaches and noninvasive concepts. The availability of digital resources allows clinicians to increase the predictability of enhanced esthetics and good functional results. There is an increasing number of patients today who are affected by excessive tooth wear and may benefit from these kinds of treatments. This article provides a step-by-step documentation of a full-mouth rehabilitation performed with a digital approach and additive CAD/CAM composite resin restorations. An innovative functional evaluation is also documented and discussed. The initial situation was assessed and compared with the rehabilitation project through a snap-on device. After the intraoral adjustment and validation, the final rehabilitation was performed according to the information obtained in the provisional phase and digitally transmitted to the laboratory.

Coating of enamel and dentin with bioactive materials: Effect on adhesive interface of class V restorations

PURPOSE

To evaluate the effect of coating enamel and dentin with a calcium phosphate powder, a calcium fluoride silicon polymer, an oxalate and a functionalized tricalcium phosphate, on marginal adaptation of class V cavities restored with a universal adhesive containing the adhesive monomer with chemical bonding potential 10-MDP (Clearfil Universal Bond) and a hybrid composite (Clearfil APX).

METHODS

Class V cavities with margins located in enamel and dentin were coated with the different bioactive materials prior to the application of the adhesive and composite. After restoration polishing, the samples were subjected to a thermo-mechanical fatigue test. Gold coated resin-based replicas were readied to analyze the percentages of continuous margins (%CM) before and after loading to evidence differences between different enamel/dentin pre-treatments (Kruskal-Wallis, Duncan post hoc test).

RESULTS

The highest %CM was observed in the group in which enamel and dentin were coated with calcium phosphate powder prior to the application of the 10-MDP-containing adhesive. This was also the most stress-resistant group.

CLINICAL SIGNIFICANCE

The adhesive interface formed between 10-MDP-containing universal one component adhesive and enamel/dentin with enriched mineral content may improve the quality of restoration margins.

Enhancing the detection of proximal cavities on near infrared transillumination images with Indocyanine Green (ICG) as a contrast medium: In vitro proof of concept studies

OBJECTIVES

The use of near infrared transillumination for caries detection is gaining recognition in daily practice. Differentiation between cavitated and non cavitated proximal lesions is recognized as a threshold for restorative treatment. This investigation focused on the use of a near infrared absorbent dye which may enhance the detection of cavitation on near infrared transillumination images.

MATERIALS AND METHODS

1: Natural teeth with artificial proximal cavitation were images with 3 different dyes to establish that near infrared absorbent dye can act like a contrast medium. 2: Natural teeth with natural cavitated lesions were used to investigate the contrast enhancing effect of indocyanine green (ICG) on near infrared transillumination images. 3: Artificial teeth with artificial cavitations were used to determine the best consistency of ICG as a contrast medium. 4: natural teeth with proximal lesions were used to confirm that ICG can differentiate between cavitated and non cavitated proximal lesions.

RESULTS

1: ICG enhanced the contrast of cavitations compared to other dyes (ANOVA; p < 0.05). 2: ICG enhanced the contrast of the cavitated area on natural lesions but not significantly (t-test; p > 0.05). 3: ICG in a gel form enhanced the detection of cavitated lesions when compared to liquid ICG (t-test; p < 0.05). 4: ICG gel was able to differentiate between cavitated and non cavitated proximal lesions (ANOVA; p < 0.05).

CONCLUSION

ICG can potentially be used as a contrast medium to enhance the detection of cavitated proximal lesions in vitro on near infrared transillumination images. A clinical study is required to validate these results in vivo.

Caries Detection with Near-Infrared Transillumination Using Deep Learning

Dental caries is the most prevalent chronic condition worldwide. Early detection can significantly improve treatment outcomes and reduce the need for invasive procedures. Recently, near-infrared transillumination (TI) imaging has been shown to be effective for the detection of early stage lesions. In this work, we present a deep learning model for the automated detection and localization of dental lesions in TI images. Our method is based on a convolutional neural network (CNN) trained on a semantic segmentation task. We use various strategies to mitigate issues related to training data scarcity, class imbalance, and overfitting. With only 185 training samples, our model achieved an overall mean intersection-over-union (IOU) score of 72.7% on a 5-class segmentation task and specifically an IOU score of 49.5% and 49.0% for proximal and occlusal carious lesions, respectively. In addition, we constructed a simplified task, in which regions of interest were evaluated for the binary presence or absence of carious lesions. For this task, our model achieved an area under the receiver operating characteristic curve of 83.6% and 85.6% for occlusal and proximal lesions, respectively. Our work demonstrates that a deep learning approach for the analysis of dental images holds promise for increasing the speed and accuracy of caries detection, supporting the diagnoses of dental practitioners, and improving patient outcomes.

Influence of pulse duration when performing Er:YAG laser irradiation on dental tissues

PURPOSE

To evaluate the marginal adaptation of mixed Class V composite restorations in cavities prepared with the Quantum Square Pulse (QSP) mode Er:YAG laser, compared to Super Short Pulse (SSP) and diamond bur. The impact of Er:YAG laser finishing with low pulse energy and two irradiation distances was also evaluated.

METHODS

Class V cavities were prepared in enamel and dentin by varying the above parameters, and then restored with Clearfil SE Bond and Clearfil AP-X composite under dentin fluid simulation. The control groups were prepared and finished using conventional diamond burs (80 and 25 µm respectively). Scanning electron microscope (SEM) marginal adaptation analysis at x200 magnification was performed on replicas before and after thermo-mechanical cyclic loading in order to determine the percentage of continuous margins (i.e. from 0 to 100% of gap free margins). The differences between groups were analyzed with one-way ANOVA and Duncan post hoc test.

RESULTS

Dentin treated with SSP showed significantly lower percentages of "continuous margin" than the QSP and control groups. QSP was as effective as bur preparation.

CLINICAL SIGNIFICANCE

The preparation and finishing protocol may no longer be necessary when using the QSP mode, reducing clinical time without compromising marginal adaptation.

Staining susceptibility of resin composite materials

PURPOSE

To evaluate the color stability of three resin-based materials continuously exposed to various staining agents.

METHODS

144 disc-shaped specimens were made of each of the three tested composites (Essentia, Brillant, Inspiro). Half of them were 1 mm thick, the other half 1.2 mm thick. The thicker group was then polished up to 4,000 grit and reduced to 1 mm thickness, also. All specimens, after 24-hour dry storage in an incubator, received an initial color measurement by means of a calibrated reflectance spectrophotometer (SpectroShade). Specimens were then divided into six groups (n=6) and immersed in five staining solutions or artificial saliva (control). All specimens were kept in an incubator at 37°C for 28 days. Staining solutions (red wine, curry mixed in water, curry mixed in oil, tea and coffee) were changed every 7th day to avoid bacteria or yeast contamination. After 28 days of storage, spectrophotometric measurements were repeated and L*a*b* scores once more recorded to determine the color (ΔE00) changes.

RESULTS

All tested materials showed significant color changes after 28 days staining immersion. ΔE00 of polished samples varied from 1.1 (Essentia/distilled water measured over a white background as well as Essentia, Inspiro/distilled water measured over a black background) to 32.5 (Inspiro/wine measured over a white background).

CLINICAL SIGNIFICANCE

Staining of restorative materials seems to be dependent on the composition of the product itself. Unpolished samples were more prone to staining than the polished ones.

Clinical performance of direct anterior composite restorations: a systematic literature review and critical appraisal

OBJECTIVES

The aim of this study was to systematically review the literature on the clinical behavior of direct anterior composite restorations and to identify the factors potentially influencing restoration success and longevity.

MATERIALS AND METHODS

The search included all existing references until September 2016 cited in the PubMed database, the Cochrane central register of controlled trials and Cochrane Library, EMBASE, an internet search using Google internet search engine (possibly including unpublished data), a hand search (University of Geneva library), and the perusal of the references of relevant articles. Studies with appropriate research protocols and that clearly reported data about the performance of anterior composite restorations were included. Yearly failure rates (YFRs) were computed for each study based on survival rates or, when not reported, using United States Public Health Service (USPHS) scores leading to reintervention. The potential impact of the following factors was evaluated: composite filler technology (microfilled, macrofilled, nanofilled or hybrid), polymerization mode (chemical or light cured), treatment environment (academic, private or social) and operator (single or multiple). The studies were analyzed according to the observation time (< 2 years, 2 to 5 years, and > 5 years).

RESULTS

39 potential studies were identified, from which 24 met the review inclusion criteria: nine randomized controlled trials (CTs), two prospective CTs, one retrospective CT, six prospective case series (CSs), and four retrospective CSs.

CONCLUSION

This review followed a standard approach and explored an alternative review process that limited the significant data loss that occurs when the meta-analysis method is used. Overall, anterior composite restorations have shown a large heterogeneity in performance, as is typically observed in reviews of clinical studies, but the present appraisal identified influential factors such as treatment environment and the number of operators.

Non-invasive proximal adhesive restoration (NIPAR) compared to resin infiltration for treating initial proximal carious lesions

PURPOSE

To compare a new technique of non-invasive proximal adhesive restoration (NIPAR) to the infiltration concept technique (ICON).

METHODS

Extracted human posterior teeth with non-cavitated proximal carious lesions (ICDAS code 1-2) were cut vertically to obtain two symmetrical lesions. Group 1 (NIPAR):Half of the paired lesions surfaces (n=13) were abraded with metallic strips and etched with 37% H3PO4 for 120 seconds. Group 2 (ICON):The other half of the paired lesions' surfaces (n=13) were etched with 15% HCl gel for 120 seconds. All samples were then stained with rhodamine isothiocyanate (RITC). After ethanol drying and isolation of the cut surface, Group 1 samples were infiltrated with Scotchbond Universal for 180 seconds and coated with a thin film of Tetric flow. Group 2 samples were infiltrated with ICON infiltrant following manufacturer's instructions. After light curing, unbound rhodamine was bleached by immersion in 30% hydrogen peroxide for 12 hours. Remaining lesion pores were stained with sodium fluorescein solution. Samples were observed with confocal microscopy (CLSM) and the percentage of infiltration (area of resin infiltration/area of total demineralization ×100) was calculated using ImageJ.

RESULTS

11 samples out of 13 showed larger infiltrated area of the lesions in Group 1 (NIPAR) compared to Group 2 (ICON). Statistical analysis revealed a significant difference between the two groups (P< 0.05). Within the limitations of this study, NIPAR allowed for better infiltration of non-cavitated proximal carious lesions when compared to ICON.

CLINICAL SIGNIFICANCE

The combination of infiltration and sealing using non-invasive proximal adhesive restoration (NIPAR) offers a suitable non-invasive treatment option for non-cavitated proximal lesions combining the advantages of sealing and infiltration.

Non-invasive proximal adhesive restoration of natural non-cavitated proximal lesions

PURPOSE

To investigate the infiltration potential of different self-etch adhesives into natural non-cavitated proximal lesions and the effect of dehydration protocol on the infiltration of a self-etch adhesive.

METHODS

29 extracted molars and premolars with natural proximal lesions (ICDAS 1-2) were sectioned through the lesion providing two samples from each lesion. To compare the different adhesives, three groups of eight lesions were abraded with fine metallic strips and then etched with 37% H3PO4 acid for 120 seconds. All teeth were stained with rhodamine isothiocyanate. After drying with compressed air and ethanol application, lesions were infiltrated with Scotchbond Universal, Clearfil SE Protect or OneCoat 7 Universal for 180 seconds and then coated with a thin layer of flowable composite (Tetric Flow). To compare the effect of dehydration protocol on infiltration, two groups of nine paired lesions were pretreated as described above. One group was dried using compressed air alone and the second group was dried using compressed air and ethanol, both groups were then infiltrated with Scotchbond Universal then coated with a thin film of flowable composite. After light curing, un-encapsulated dye was bleached by immersion in hydrogen peroxide. Remaining lesion pores were stained with sodium fluorescein solution. Thin cuts of the teeth were observed with confocal microscopy and computer image analysis was performed (ImageJ).

RESULTS

ANOVA and Duncan post-hoc tests showed no significant differences of the infiltrated area between the three adhesives (P= 0.835), no significant difference was found between the group dried with air compared to the one dried with air and ethanol. It can be concluded that the tested adhesives may be used for infiltration of natural lesions following the described pretreatment.

CLINICAL SIGNIFICANCE

Enamel pretreatment with metallic strip and 37% H3PO4 acid promotes the infiltration of different adhesives into natural non-cavitated caries lesions.

3D Digital Smile Design With a Mobile Phone and Intraoral Optical Scanner

Extraoral facial scanning using a mobile phone has emerged as a viable, cost-effective option for certain applications not requiring high precision, such as patient education and 3-dimensional (3D) digital smile design. This technological development is particularly promising for general practitioners (GPs) who may not be able to invest in expensive,complex digital impressioning devices. This article describes and illustrates a relatively simple and accessible workflow that avails digital 3D facial scanning benefits to GPs.

Is the glass half empty or half full? A novel "philosophical" approach to the "mystery" of the so-called ferrule effect

The prognosis of endodontically treated teeth has traditionally been associated with the presence of the so-called ferrule effect that is generally related with the presence of a minimum of 1-2 mm of sound tooth structure at the cervical area of parallel axial walls that totally encircle the tooth. Even though all of these factors are well desired, one should question if their absence should condemn a tooth and compel extraction as the only logical treatment plan option. For this reason an hypothesis is being formed that associates the aforementioned factors not with the presence of the so-called ferrule effect, but rather with the resistance form of the preparation that is being provided by the sound tooth structure at the cervical area of the tooth. When the desired resistance form is provided by sound tooth structure of endodontically treated teeth, then less lateral forces are being transferred to the post & core and subsequently to the root of the teeth, thus minimizing the chances of decementation of the post & core or worst fracture of the root. Even more important, if this hypothesis may be further entertained, then even when the so-called ferrule effect is not present, the teeth may not be extracted, but alternative strategies for post & core restorations may be investigated, such a more flexible carbon- or glass-fiber posts & core build ups made from flowable resin composite that may accommodate for the increased lateral forced exerted to the post & core complex during function.

Correction to: Color stability of different composite resins after polishing

In the original publication of the article, the author's name "Prof. René Daher" was inadvertently missed in the author group. This has been updated in this erratum. Also, the original article has been corrected.

Restoration of discolored endodontically treated anterior teeth: a minimally invasive chemomechanical approach

In the case of discolored devitalized anterior teeth, several treatments are available to enhance the esthetic outcome, from noninvasive external/internal bleaching to freehand resin composites and more complex prosthetic solutions such as veneers or full crowns. Innovative computer-aided design/computer-aided manufacturing (CAD/CAM) chairside technologies and the introduction of new industrially polymerized composite resin blocks coupled with modern adhesive strategies have reduced both biological and financial costs compared to the classic post-core-crown approach. The aim of this article is to show how these new materials can be used in association with noninvasive internal and external tooth bleaching to restore a discolored, fractured, non-vital central incisor.

CAD/CAM-based chairside restorative technique with composite resin for full-mouth adhesive rehabilitation of excessively worn dentition

Since the first introduction of the Cerec system (Sirona) in the early 1980s, the use of computer-aided design/computer-aided manufacture (CAD/CAM) technology has spread widely in modern adhesive dentistry. Thanks to this innovative technology, it has been possible to carry out chairside restorations fully managed by the clinician, with the advantages of lower costs for the patient, more rapid execution of the restorations, and the exclusion of the provisional phase. With further improvements in chairside technologies and materials, specifically in the field of composite resin blocks, it is now possible to fabricate multiple ultrathin, minimally invasive or even noninvasive restorations in one single appointment. The clinical case presented here was solved using an innovative approach: It was entirely studied and realized chairside by a dentist on a computer, without any plaster cast or classic articulator. Vertical dimension of occlusion (VDO) augmentation was projected with the 'Incisal Tip' tool on the virtual articulator of the Cerec system. Eight composite resin overlays were designed on the non-prepared posterior teeth of a patient suffering from generalized tooth loss principally caused by a history of bulimia nervosa. The maxillary anterior teeth were restored with six palatal veneers modified with direct composites from the vestibular side, in order to improve the esthetic integration of the restorations. The mandibular posterior teeth were built up with direct composites.

Protection Against Discolouration by Two Over-the Counter Desensitising Products

PURPOSE

To determine in vitro the protection potential against discolouration of two OTC (over-the-counter) desensitising products on enamel and dentin in comparison to a standard toothpaste and water by means of a spectrophotometer.

MATERIALS AND METHODS

A total of 96 samples of bovine enamel-dentin complex and 48 of bovine dentin were alternatively immersed in red wine, tea, coffee or water after having been treated by a sodium monofluorophosphate- and calcium phosphate-based product (Curodont Protect), an amine fluoride-based toothpaste (Elmex Red), a stannous chloride-based toothpaste (Elmex Protection Erosion) or distilled water (negative control). Initial (T0) and final colour (T1, after 4 weeks of immersion in staining solutions) of each specimen were assessed by a spectrophotometer. Statistical analysis was done by means of repeated measures ANOVA followed by Fisher's LSD post-hoc test. Differences between T0 and T1 were considered stastistically significant at p ≤ 0.05.

RESULTS

When enamel samples were measured over a black background, ΔE00 values (T0-T1) varied from 2.2 (SD 0.7) for amine fluoride-based product/water to 53.9 (SD 7.6) for amine fluoride-based-product/red wine. When dentin samples were measured over a black background, ΔE00 values (T0-T1) varied from 5.4 (SD 0.9) stannous chloride based product/water to 61.6 (SD 3.7) amine fluoride-based product/red wine.

CONCLUSION

Specifically, the application of the sodium monofluorophosphate was able to statistically significantly (p ≤ 0.05) reduce discolouration induced by the staining solutions tested only on the enamel-dentin complex, while distilled water and the stannous fluoride-based product were able to statistically significantly (p ≤ 0.05) reduce discolouration induced by the staining solutions tested in pure dentin samples.

A Novel Method of Capturing Fluorescence in Clinical Dentistry

OBJECTIVES

A fully integrated esthetic restoration should emit levels of fluorescence similar to that of natural dentition. Also, dental practitioners should be able to monitor this property in their routine clinical setting. The aim of this study was to investigate the efficacy of a removable filter for a macro flash illumination set-up required for the digital photographic recording of the fluorescence emission of human teeth and dental restorations.

METHODS

The traditional fluorescence capturing method in clinical dentistry, using continuous lighting, was compared with the proposed flash lighting method. A digital single-lens reflex Canon 550D camera with a Canon 100-mm macro lens and a commercially available standard Canon MT-24EX twin light macro flash were used in this study. A custom-fabricated plastic o-ring was fixed with silicone to the original flash framework, which received a removable fluorescence filter composed of two 365-nm ultraviolet (UV) glass filters on both sides, covering the flash lamps. The original protective plastic diffusers in front of the flash lamps were replaced with clear plastic to release the full excitation wavelength range of the xenon flash lamps. No additional filter was placed in front of the lens.

RESULTS

The results showed that using the proposed custom-made flash/filter illumination source, f-numbers between 16 through 22, a shutter speed of 1/60, and ISO 800 or 1600 sensitivity settings attained satisfactory fluorescent digital images. Results were comparable to those accomplished using a traditional photographic technique, without the need for a dark room, extended exposure times, and time-consuming set-ups.

CONCLUSION

A contemporary photographic technique was demonstrated using macro flash UV-A 365-nm illumination that allowed fluorescent digital photograph acquisition under standard dental office conditions. Fluorescence documentation using a quick, straightforward procedure can take place during the restorative session to help increase the success rate of dental restorations.