Effects of dentin bonding agents and silanization on bond strength between 3D printed resin and composite resin.

This study aimed to evaluate the effects of dentin bonding agents and silanization on the bond strength between 3D printed resin and composite resin and compare it with a conventional composite resin. 3D printed resin cylinders (PCB) and composite resin substrates (Z250) were prepared and divided into eight subgroups based on the bonding agents used (n=12). The shear bond strength was measured using a universal testing machine, and the failure modes were evaluated. The bond strength was found to vary significantly among the bonding agents and substrate types. Silane application did not significantly improve the bond strength. Among the bonding agents, the universal adhesives exhibited the highest bond strengths for both substrates. Compared to PCB, Z250 demonstrated stronger bonds and exhibited more cohesive failures. Further research is needed to optimize the surface treatments and resin formulations for enhanced bond strength and durability between 3D printed and composite resins.

Food impaction on three-dimensional printed models with periodontal ligament simulation.

OBJECTIVE: This study aims to evaluate food impaction on three-dimensional (3D) printed models with periodontal ligament simulation. MATERIALS AND METHODS: Based on a commercial typodont pair, 3D maxillary and mandibular models were created with no teeth and with tooth sockets that were 1 mm wider than the original ones from 24 to 27 or 34 to 37 for periodontal ligament simulation with vinyl polysiloxane impression material. In total, 35 pairs of 7 combinations, including maxillary/mandibular typodonts in occlusion with maxillary/mandibular 3D models with/without a distal gap of canines on 3D models (tooth 23 or 33) were mounted on hinge articulators and divided into seven groups (n = 5). Each sample experienced the same manual chewing simulation on a customized device. The proximal surfaces were photographed to measure the percentage of food impaction area using ImageJ software. RESULTS: Group with fixed maxillary and mandibular teeth showed more food impaction than other groups with significant differences in the average of maxilla and the average of all proximal areas. CONCLUSION: The flexibility of the periodontal ligament and the degree of freedom of the teeth in their sockets may contribute to the extent of food impaction in proximal spaces.

Post-polymerization of three-dimensional printing resin using a dental light curing unit.

Background/Purpose: In vat photopolymerization, post-polymerization of the three-dimensional (3D) printing resin is necessary to ensure the optimum physical properties of the printed objects. This study aimed to evaluate the potential use of a handheld polywave light-emitting diode (LED) dental light-curing unit (LCU) for post-polymerizing 3D printed resins by measuring the microhardness and biaxial flexural strength of the post-polymerized resin. Material and methods: 3D printed 1- and 2-mm-thick disks were irradiated with a dental LCU at 3200 mW/cm2. Post-polymerization was repeated either on one side from the top surface: two cycles (T2), four cycles (T4), and eight cycles (T8), or on both sides from the top and bottom surfaces: one cycle (T1B1), two cycles (T2B2), and four cycles (T4B4) for each side. The microhardness and biaxial strength of the disks were compared to those post-polymerized by a conventional desktop polymerizing unit (PC) and those without post-polymerization (NC). Results: Microhardness of the disks varied between the top and bottom surfaces of the 1-mm and 2-mm-thick disks, depending on the post-polymerization methods. T8 and T4B4 produced comparable microhardness on the top surface to PC for both thicknesses. In contrast, PC, T2B2, and T4B4 exhibited the highest microhardness on the bottom surface. Except for NC, the 1-mm-thick disks had a higher biaxial flexural strength than the 2-mm-thick disks. T4B4 resulted in the highest biaxial flexural strength for both thicknesses, which was comparable to that of the desktop polymerizing unit. Conclusion: The microhardness and biaxial flexural strengths of the post-polymerized 3D-printed disks increase with polymerization time. With sufficient polymerization from both sides, the polywave LCU has the potential to be a viable alternative to desktop polymerization units.

Determinants of Dentist-Patient Relationships: A Scoping Review.

OBJECTIVES: The dentist-patient relationship (DPR) is considered to be a key element in dental clinical settings. This scoping review aimed to examine the extent of previous research on DPR, focussing on its determinants for the reification of the construct. METHODS: This research was directed by the guidance for systematic scoping reviews from the Joanna Briggs Institute. The inclusion/exclusion criteria were based on participants of general adults and dentists, the concept of determinants of DPR, and the context of dental health care encounters. A literature search was performed in 6 major electronic databases in July 2023. Key information from included articles was extracted to chart the results, mainly to identify the determinants of DPR. Each determinant of DPR was classified according to the conceptual model of DPR. RESULTS: A total of 1727 records were initially identified, and 16 articles were included in the review. Nine studies used a quantitative method and 7 were nonempirical articles. All but 2 articles were from the perspective of patients. Factors were grouped into 6 main domains: dentist, patient, society/environment, clinical structure, clinical process, and outcome. Amongst the 6 domains of DPR, most determining factors were related to the clinical process. "Communication" was most frequently counted, at 8 times, followed by "trust" (frequency, 6). At the patient level, "dental fear/anxiety" was frequently used to measure DPR. CONCLUSIONS: Previous literature about DPR indicated a few common and dentistry-specific determinants from the patient perspective. Further studies are encouraged to develop a more comprehensive framework and evaluation scale of DPR.

Investigating the role of chlorogenic acids and coffee type in coffee-induced teeth discoloration.

OBJECTIVE: Coffee is one of the most popular beverages in the world, with millions of people consuming it every day. The effect of coffee on teeth discoloration has long been a concern for both coffee drinkers and dental professionals. To address this concern, this study aimed to investigate the role of chlorogenic acids (CGAs) and the type of coffee in coffee-induced teeth discoloration. MATERIALS AND METHODS: High-performance liquid chromatography with a photodiode array detector was used to determine the CGA contents of instant coffee produced by five manufacturers (Starbucks, Dunkin' Donuts, Kanu, Ediya, Coffee Bean). A total of 180 bovine tooth specimens were immersed in the coffee samples for varying durations (3, 9, 24, 48, and 72 h), and the discoloration levels were measured using a spectrophotometer. A linear mixed-effects model analysis was used to determine the significance of L*, a*, and b* values in relation to the duration of coffee immersion and coffee type. RESULTS: Both immersion time and coffee type had significant effects on tooth discoloration (p < 0.001), with some types of coffee being more strongly associated with tooth discoloration than others. The amount of CGAs present in coffee was found to be positively correlated with the degree of discoloration (p = 0.030). CONCLUSIONS: Prolonged exposure to coffee can exacerbate teeth staining, and different types of coffee can cause varying degrees of discoloration. Furthermore, coffee with higher levels of CGAs may lead to greater tooth discoloration.

Assessing the efficacy of jet dispenser versus direct syringe injection for calcium hydroxide paste placement in artificial root canals.

This study aimed to evaluate the efficacy of a novel jet dispenser (JD) for filling simulated straight and curved canals with calcium hydroxide (Ca(OH)2) paste by comparing the level of intracanal medicament with traditional direct syringe delivery. The Ca(OH)2 paste was delivered into the canals using either a direct syringe with binding tip and unbinding tip or a JD. The analysis of the ratio of the canal filled area (RCFA) in the coronal, middle, and apical thirds was conducted using the Kruskal-Wallis and Mann-Whitney U tests (α = 0.05). The JD resulted in a significantly higher RCFA of 1.00 in the middle and apical thirds in both the straight and curved canals than the direct syringe method (p < 0.001). Voids were frequently observed in the direct syringe group, whereas JD showed no voids within the filled area. In the direct syringe groups, the apical area was more readily filled in both canal types when the tip was bound (p < 0.001). The JD was found to be more effective in filling the entire canal space than the binding and unbinding conditions of the direct injection method, particularly in the apical area.

Effect of vibration during bulk and incremental filling on adaptation of a bulk-fill composite resin.

This study evaluated the effect of vibration on adaptation of bulk-fill composite resin. A scanning laser doppler vibrometer measured the frequency and amplitude of a vibratory device (COMO; B&L Biotech) used for resin placement and visualized its effect on the resin according to depth. A bulk-fill composite resin (Filtek Bulk Fill; 3M ESPE) was placed in simulated cavities (4 mm diameter, 4 mm depth) by different layering methods (incremental filling with two 2-mm-thick layers vs. bulk filling with a single 4-mm-thick layer). The groups were further divided based on the application of vibration during restoration (no vibration vs. vibration). In addition to the surface void area at the cavity floor, the overall void volume and the void volumes of the bottom, middle, and top thirds were obtained for micro-computed tomography analysis. The frequency and amplitude of the COMO were approximately 149 Hz and between 26 and 51 µm, respectively. When vibration was not applied, incremental filling had a lower void volume in the bottom third of the cavity than did bulk filling (p < 0.05). Vibration applied with a 4-mm-thick bulk fill had no significant effect on the adaptation of composite resin (p > 0.05). In contrast, vibration reduced the amount of void formation in the bottom third of the cavity during incremental filling (p < 0.05). Application of vibration to resin with a 2-mm incremental-layering technique formed a smaller void at the interface between the cavity and resin and within the bulk-fill composite resin.

Performance of Universal Adhesives in Composite Resin Repair.

Aim: The objective of this in vitro study was to evaluate the bond strength of universal adhesive systems in self-etch and etch-and-rinse modes at the repair interface between aged and new composite resins. Materials and Methods: Composite resin (Filtek Z250) was thermocycled to represent aged composite resin to be repaired. New composite resin was placed over the aged substrate after surface conditioning: NC (negative control, no surface treatment), A (adhesive only), SBM (Scotchbond Multi-Purpose in etch-and-rinse mode), CSE (Clearfil SE Bond in self-etch mode), SBU (Single Bond Universal), ABU (All Bond Universal), and TBU (Tetric N-Bond Universal). Universal adhesives (SBU, ABU, and TBU) were applied both in etch-and-rinse and self-etch modes. 1 mm × 1 mm × 8 mm beams were sectioned, and microtensile bond strength was measured after 24 hours of water storage and 10,000 thermocycling processes (n = 20/group). The fracture surfaces were observed with a scanning electron microscope to evaluate the failure pattern. Results: The repair bond strength between the old and new composite resins was material-dependent. Universal adhesives significantly improved the repair bond strength (p < 0.05), while no significant difference was observed between the etch modes (self-etch or etch-and-rinse) for each universal adhesive (p > 0.05). Thermocycling significantly reduced the bond strength in all groups (p < 0.05). Conclusion: Universal adhesives in both etch-and-rinse and self-etch modes outperformed the conventional 3-step etch-and-rinse and 2-step self-etch adhesive systems in terms of resin repair bond strength.

Dimensional Accuracy Evaluation of Temporary Dental Restorations with Different 3D Printing Systems.

With the advent of 3D printing technologies in dentistry, the optimization of printing conditions has been of great interest, so this study analyzed the accuracy of 3D-printed temporary restorations of different sizes produced by digital light processing (DLP) and liquid crystal display (LCD) printers. Temporary restorations of 2-unit, 3-unit, 5-unit, 6-unit, and full-arch cases were designed and printed from a DLP printer using NextDent C&B or an LCD printer using Mazic D Temp (n = 10 each). The restorations were scanned, and each restoration standard tessellation language (STL) file was superimposed on the reference STL file, by the alignment functions, to evaluate the trueness through whole/point deviation. In the whole-deviation analysis, the root-mean-square (RMS) values were significantly higher in the 6-unit and full-arch cases for the DLP printer and in the 5-unit, 6-unit, and full-arch cases for the LCD printer. The significant difference between DLP and LCD printers was found in the 5-unit and full-arch cases, where the DLP printer exhibited lower RMS values. Color mapping demonstrated less shrinkage in the DLP printer. In the point deviation analysis, a significant difference in direction was exhibited in all the restorations from the DLP printer but only in some cases from the LCD printer. Within the limitations of this study, 3D printing was most accurate with less deviation and shrinkage when a DLP printer was used for short-unit restorations.

Trueness of ten intraoral scanners in determining the positions of simulated implant scan bodies.

Few investigations have evaluated the 3-dimensional (3D) accuracy of digital implant scans. The aim of this study was to evaluate the performance of 10 intraoral scanners (IOSs) (CEREC Omnicam, CEREC Primescan, CS 3600, DWIO, i500, iTero Element, PlanScan, Trios 2, Trios 3, and True Definition) in obtaining the accurate positions of 6 cylinders simulating implant scan bodies. Digital scans of each IOS were compared with the reference dataset obtained by means of a coordinate measuring machine. Deviation from the actual positions of the 6 cylinders along the XYZ axes and the overall 3D deviation of the digital scan were calculated. The type of IOSs and position of simulated cylindrical scan bodies affected the magnitude and direction of deviations on trueness. The lowest amount of deviation was found at the cylinder next to the reference origin, while the highest deviation was evident at the contralateral side for all IOSs (p < 0.001). Among the tested IOSs, the CEREC Primescan and Trios 3 had the highest trueness followed by i500, Trios 2, and iTero Element, albeit not statistically significant (p > 0.05), and the DWIO and PlasScan had the lowest trueness in partially edentulous mandible digital implant scans (p < 0.001).

Developing a clinical presentation dental education model and a pilot test.

INTRODUCTION: Accurate clinical decision-making of dentists should be based on their knowledge and experience. In the past 10 years, interest in competency-based dentistry education has rapidly increased, but there has been little attention paid to methods of improving dental education competency. The purpose of this study was to develop a clinical presentation education model that provides opportunities for students to practice problem-solving from the moment they greet the patient so that students can obtain the practical experience of competency-based education and the effectiveness of this model can be confirmed through pilot test. METHODS: This article is divided two parts: First, developing the clinical presentation dental education model (CPDEM) and Second, a pilot study adopted CPDEM. To confirm the effectiveness of this model, the students' satisfaction, their perception of self-achievement were analysed. RESULTS: Clinical presentation dental education model has been developed to provide practice-related education experience and provide linkage between basic science and clinical science. The result of applying this education model to 10 students as a pilot test was shown an overall high satisfaction level. In addition, self-achievement students' reported of all intended competencies was higher than for non-participating students of this model. CONCLUSIONS: This study focuses on practical education centring on clinical presentation. This model could get a meaningful and realistic experiences through the practice using clinical presentation of patients, use their metacognition for organizing and memorizing the patient's case by using concept map. It can be used as a future instructional method to enhance students' competency.

In vitro analysis of intraoral digital impression of inlay preparation according to tooth location and cavity type.

Purpose This study aimed to evaluate the influence of tooth location and inlay cavity type on the accuracy of intraoral digital impressions.Methods Class II inlay preparation was performed on anatomical models of the maxillary first molar (16) and mandibular first molar (46). Mesio-occlusal and disto-occlusal cavities were prepared, such that the axial wall of the proximal box measured 1 mm or 2 mm in height. Thus, four types of inlay cavities were prepared in 16 and 46, respectively. Ten digital impressions of each cavity were obtained using Cerec Primescan (Sirona). Reference scans were obtained with a laboratory scanner (E3, 3Shape). All scan data were exported for comparative analysis of the three-dimensional models. Mean absolute deviation values were calculated to evaluate the trueness and precision of the digital models. Color-coded maps were used for the qualitative analysis of deviations.Results The overall results showed that the trueness for 16 (10.43 ± 0.39 µm) was higher than that for 46 (12.42 ± 0.59 µm) (p < 0.05), while the precision was similar between 16 (3.08 ± 0.92 µm) and 46 (3.08 ± 0.76 µm). The cavity type affected the accuracy of the digital impressions. The highest deviation was observed in positive directions at the margins of the proximal boxes regardless of the cavity type.Conclusions Tooth location and cavity type affected the accuracy of intraoral digital impressions. Positive deviations were observed at the margins of the proximal boxes.

Most surface learning in the third year: Dental student learning approaches and implications for curriculum and assessment.

CONTEXT: Dental schools seek to educate students to become inclined toward self-directed, lifelong learning, an important mindset for healthcare professionals that may be linked to deep versus surface learning approaches. Students using a deep learning approach are more intrinsically motivated and actively engage in higher-order thinking, while those using a surface learning approach are more extrinsically motivated and aim for passive learning. OBJECTIVES: Because student learning approaches can be influenced by a wide variety of learning experiences, we sought to understand how student approaches to learning differ by year in dental school and are related to academic achievement. METHODS: A total of 244 students in a 4-year dental school program in South Korea voluntarily participated in this study. We collected data on school year and academic achievement, and approaches to learning of participants using the validated Study Processes Questionnaire to assess learning approach, which included the constructs of deep motive, deep strategy, surface motive, and surface strategy. RESULTS: We conducted 3 sets of statistical analyses and found that most students adopted a deep approach to learning (DAL) in their first and second years (Y1 and Y2), with third-year students (Y3) showing heavy dependence on a surface approach to learning (SAL) and sharp drops in intrinsic motives. Student approaches to learning were not significantly related to academic achievement. In the first 2 years of dental school, students tended to adopt a DAL, and viewed their learning as personal growth and their profession as necessitating deep intellectual inquiry. CONCLUSIONS: In the third year, the change from a DAL to a SAL coincided with entry to clinical training. The lack of integration of biomedical science (Y1 and Y2) and clinical science (Y3 and Y4), and increased stress in the initial clinical context may account for this difference. The poor correlation between a DAL and high achievement may indicate a need for change in assessment methods. This study hopes to stimulate reflection regarding student learning approaches and educational efforts that prepare future dentists for lifelong learning.

Comparative reproducibility analysis of 6 intraoral scanners used on complex intracoronal preparations.

STATEMENT OF PROBLEM: Although studies have reported the trueness and precision of intraoral scanners (IOSs), studies addressing the accuracy of IOSs in reproducing inlay preparations are lacking. PURPOSE: The purpose of this in vitro study was to compare the accuracy of representative IOSs in obtaining digital scans of inlay preparations and to evaluate whether the IOSs had sufficient depth of field to obtain accurate images of narrow and deep cavity preparations. MATERIAL AND METHODS: Digital scans of a bimaxillary typodont with cavity preparations for inlay restorations on the maxillary first premolar, first and second molar, mandibular second premolar, and first molar were obtained using 6 IOSs (CEREC Omnicam, E4D, FastScan, iTero, TRIOS, and Zfx IntraScan). Standard tessellation language (STL) data sets were analyzed using the 3-dimensional analysis software (Geomagic Verify). Color-coded maps were used to compare the magnitude and pattern of general deviation of the IOSs with those of a reference scan. Each tooth prepared for inlay restoration was digitally cut out, and the trueness and precision of each IOS were measured using the superimposition technique. Statistical analyses were conducted using statistical software (α=.05). RESULTS: The trueness values were lowest with the FastScan (22.1 µm), followed by TRIOS (22.7 µm), CEREC Omnicam (23.2 µm), iTero (26.8 µm), Zfx IntraScan (36.4 µm), and E4D (46.2 µm). In general, the digital scans of more complicated cavity design showed more deviation. Color-coded maps showed positive vertical discrepancy with the E4D and negative vertical discrepancy with the Zfx IntraScan, especially on the cavity floor. Regarding precision, the highest value was observed in the E4D (37.7 µm), while the lowest value was observed with the TRIOS (7.0 µm). However, no significant difference was found between teeth with different inlay preparations. Scanning errors were more frequently seen in the cervical area. CONCLUSIONS: Different IOSs and types of cavity design influenced the accuracy of the digital scans. Scans of more complex cavity geometry generally showed higher deviation. The E4D exhibited the most deviation in both trueness and precision, followed by the Zfx IntraScan. The E4D and Zfx IntraScan appeared to have less depth of field than the others to obtain digital scans for inlay preparation with different heights.

Trueness of digital intraoral impression in reproducing multiple implant position.

The aim of this study was to evaluate the trueness of 5 intraoral scanners (IOSs) for digital impression of simulated implant scan bodies in a partially edentulous model. A 3D printed partially edentulous mandible model made of Co-Cr with a total of 6 bilaterally positioned cylinders in the canine, second premolar, and second molar area served as the study model. Digital scans of the model were made with a reference scanner (steroSCAN neo) and 5 IOSs (CEREC Omnicam, CS3600, i500, iTero Element, and TRIOS 3) (n = 10). For each IOS's dataset, the XYZ coordinates of the cylinders were obtained from the reference point and the deviations from the reference scanner were calculated using a 3D reverse engineering program (Rapidform). The trueness values were analyzed by Kruskal-Wallis test and Mann-Whitney post hoc test. Direction and amount of deviation differed among cylinder position and among IOSs. Regardless of the IOS type, the cylinders positioned on the left second molar, nearest to the scanning start point, showed the smallest deviation. The deviation generally increased further away from scanning start point towards the right second molar. TRIOS 3 and i500 outperformed the other IOSs for partially edentulous digital impression. The accuracy of the CEREC Omnicam, CS3600, and iTero Element were similar on the left side, but they showed more deviations on the right side of the arch when compared to the other IOSs. The accuracy of IOS is still an area that needs to be improved.

Severity of dental caries and risk of coronary heart disease in middle-aged men and women: a population-based cohort study of Korean adults, 2002-2013.

We aimed to evaluate the risk of coronary heart disease (CHD) according to dental caries status in middle-aged patients using a population-based cohort database containing medical/dental claims, health examination, and death records in the Republic of Korea. A total of 234,597 patients were identified in the database who were without history of cardiovascular disease, including 104,638 patients without dental caries, 41,696 with incipient/moderate stage dental caries, and 88,262 advanced/severe dental caries. We used Cox proportional hazards model adjusted for sociodemographic, lifestyle, and medical characteristics to compute hazard ratio (HR) and 95% confidence intervals (95% CI) for CHD according to severity of dental caries. During 1,491,190 person-years of follow-up, there were a total of 6,015 CHD events. After adjustment for potential confounders, patients in the highest quartile of outpatient visits for advanced/severe stage dental caries was associated with an increase in CHD risk (HR = 1.13; 95% CI: 1.04-1.22) as compared with patients without dental caries. When the analysis was restricted to the patients with advanced/severe dental caries, dose-response relationship between number of outpatient visits for dental caries and risk of CHD was observed (Ptrend: <0.001). Prevention and control of dental caries might be worth promoting in clinical practice to prevent CHD.

Accuracy of 9 intraoral scanners for complete-arch image acquisition: A qualitative and quantitative evaluation.

STATEMENT OF PROBLEM: Different intraoral scanners (IOSs) are available for digital dentistry. However, information on the accuracy of various IOSs for complete-arch digital scans is limited. PURPOSE: The purpose of this in vitro study was to evaluate the trueness and precision of complete-arch digital scans produced by 9 IOSs, using the superimposition method, and to compare them based on characteristics including the data capture principle and mode and the need for powder coating. MATERIAL AND METHODS: Nine IOSs were used to obtain standard tessellation language (STL) data for a bimaxillary complete-arch model with various cavity preparations (N=10). The scanning performance was evaluated quantitatively and qualitatively. For quantitative evaluation, the images were processed and analyzed using 3-dimensional (3D) analysis software. After we superimposed the datasets, trueness was obtained by comparing it with the reference scan, and precision was obtained from intragroup comparisons. The IOSs were compared based on the data capture principle and mode and the need for powder coating. Statistical analyses were conducted using a Kruskal-Wallis test, followed by multiple Mann-Whitney U tests for pairwise comparisons among groups (α=.05). For qualitative evaluation, surface smoothness and sharp edge reproducibility of the digital images were compared. RESULTS: The median precision values were lowest in the TRIOS model (average, 34.70 µm; maximum, 263.55 µm) and highest in the E4D model (average, 357.05 µm; maximum 2309.45 µm). Median average trueness values were lowest in the TRIOS model (42.30 µm) and highest in the Zfx IntraScan model (153.80 µm). The CS 3500 model had the lowest median maximum trueness values (450.75 µm); the E4D model had the highest values (2680.55 µm). Individual image and video sequence data captures showed similar median average trueness values (P>.05); the median maximum values of individual images were higher than those of the video sequence (P<.05). Swept source optical coherence tomography (SS-OCT) exhibited higher trueness values than those of other scanning principles (P<.05). The FastScan and True Definition, which require powder coating, showed significantly better trueness than other IOSs that did not require powdering (P<.05). The E4D, PlanScan, and Zfx IntraScan models had an increased tendency to produce images with imperfect surface features and to round off sharp edges. CONCLUSIONS: The E4D and Zfx IntraScan models did not perform as accurately as the other IOSs. The data capture principle of SS-OCT and the mode of individual image acquisition exhibited inferior trueness. The FastScan and True Definition, which require powder coating, exhibited better trueness. The qualitative aspects of the IOSs varied in terms of polygon shapes, sharp edge reproducibility, and surface smoothness.

Thermographic analysis of the effect of composite type, layering method, and curing light on the temperature rise of photo-cured composites in tooth cavities.

OBJECTIVES: The purpose of this study was to investigate temperature rise in the composite and dentin of a class I cavity in extracted human molars under different restoration conditions, including the use of different composite types, layering methods, and curing lights. METHODS: Open occlusal cavities were prepared on 28 extracted human molars. A conventional (Filtek Z250) and a bulk-fill (Filtek Bulk Fill Posterior; BFP) composite were used to restore the preparations. BFP was incrementally layered or bulk-filled. Bulk-filled BFP was cured with two different lights, the Elipar S10 and the BeLite. Each layer was illuminated for 20s, while thermograms of the specimens were recorded for 100s using an infrared thermal camera. Temperature changes on the composite and dentin surfaces were obtained at points of interest (POI) pertaining to successive incremental distances of 0.75mm from the top of the cavity to the pulp. The polymerization kinetics of each composite was determined using photo-differential scanning calorimetry. RESULTS: The greatest temperature rise was observed 0.75mm apical from the top of the cavity. All groups showed over 6°C maximum temperature rise (ΔTmax) at the pulpal side of the dentin. Upon curing, Z250 reached ΔT=5°C faster than BFP; however, ΔTmax of the two composites were comparable at any POI. Bulk filling showed greater ΔTmax than incremental filling at 0.75mm apical from the top and in the middle of the cavity. The Elipar S10 light generated faster temperature changes in the curing composite at all recorded positions throughout the depth of the cavity and greater ΔTmax in all POIs compared to BeLite. SIGNIFICANCE: Real-time thermographic analysis demonstrated that the composite type and layering method did not influence the temperature rise at the pulpal side of dentin during composite restoration of an occlusal preparation in a tooth. The amount and initial rate of temperature increase was most affected by the radiant exposure of the light curing unit. Within the limitations of this in vitro study, when irradiation time is constant, a curing light with higher radiant power can induce relatively high thermal transfer, thereby increasing the risk of pulpal damage.

Evaluation of dentin tubule occlusion after laser irradiation and desensitizing agent application.

PURPOSE: To evaluate the effects of lasers (Nd:YAG and Er:YAG) and of topical desensitizing agents on dentin tubule occlusion by measuring real-time dentin fluid flow (DFF). METHODS: 32 molars were prepared with V-shape cavity at the cervical area, acid-etched, water rinsed, blotted dry, and treated with (1) Nd:YAG laser; (2) Er:YAG laser; (3) SuperSeal, a desensitizing agent; (4) ClinproXT, a resin-modified glass-ionomer (RMGI) varnish (n = 8 each). A real-time fluid flow measuring instrument (nano-Flow) was used to measure the DFF throughout the procedures. The DFF rates before and after the treatment were compared. Moreover, the surface topography of dentin tubules after each desensitizing method was examined using SEM. RESULTS: DFF varied among the groups. The DFF rate was significantly reduced after laser irradiation/application of the desensitizing agents (P < 0.05). ClinproXT showed the greatest reduction of DFF rate (71.9%), followed by the SuperSeal (34.8%) and laser groups (P< 0.05). However, there was no significant difference between the Nd:YAG (24.1%) and Er:YAG (20.6%) groups (P > 0.05). In SEM images, narrowed dentin tubules were observed in both lased groups and SuperSeal group. In the ClinproXT group, the occluded dentin tubules by the RMGI covering were observed.

Real-Time Analysis of Temperature Changes in Composite Increments and Pulp Chamber during Photopolymerization.

OBJECTIVE: The aim of this study was to evaluate the temperature change at various sites within the composite and on the pulpal side of dentin during polymerization of two composite increments. MATERIALS AND METHODS: Class I cavities prepared in third molars were restored in two composite increments (n = 5). Temperatures were measured for 110 s using eight thermocouples: bottom center of cavity (BC), top center of 1st increment (MC), top center of 2nd increment (TC), bottom corner of cavity (BE), top corner of 1st increment (ME), top corner of 2nd increment (TE), pulpal side of dentin (PD), and center of curing light guide tip (CL). RESULTS: Maximum temperature values (°C) measured during polymerization of 1st increment were MC (59.8); BC (52.8); ME (51.3); CL (50.7); BE (48.4); and PD (39.8). Maximum temperature values during polymerization of 2nd increment were TC 58.5; TE (52.6); MC (51.7); CL (50.0); ME (48.0); BC (46.7); BE (44.5); and PD (38.8). CONCLUSION: Temperature at the floor of the cavity was significantly higher during polymerization of 1st increment compared to 2nd increment. Temperature rise was higher at the center than at the corner and at the top surface than at the bottom surface of each increment.