Buccolingual Direction Research Articles

Customised abutment for achieving the predictable emergence profile for immediate implant in molar site

The alveolar bone undergoes a remodelling process after tooth extraction, which leads to horizontal and vertical bone loss. These resorption processes complicate dental rehabilitation, particularly in connection with implants. Clinical studies have suggested that retaining roots of hopeless teeth may avoid tissue alterations after tooth extraction. The aim is to seal the surgical site following the outline of extraction socket and to develop an ideal prosthetic emergence profile, modelled on the anatomy of the existing tooth. In present case report a non restorable mandibular molar was treated with socket sealing protocol followed by immediate implant placement. Using sequential osteotomy drills implant site was prepared and roots were dissected in buccolingual direction along the long axis. Roots were extracted using elevators and implant of desired size was placed. A Customized sealing socket abutment (SSA) was prepared to support the coronal emergence profile of the tooth. This technique is a minimally invasive that can preserve the hard and the soft tissue contour of the ridge.

Torqued and conventional cantilever for uprighting mesially impacted molars: A 3-dimensional finite element analysis

The objective of this study was to evaluate the effects of the torqued cantilever (TC) and conventional tip-back cantilever (CC) made of stainless steel (SS) and titanium-molybdenum alloy (TMA) on the uprighting of mesially impacted mandibular molars using three-dimensional finite element analysis. The 3-dimensional mandibular model included part of the mandible with mesially tipped and impacted mandibular second molar, periodontal ligament (PDL), molar tube, mini-implant, and cantilevers. Four finite element method models (TC-SS, TC-TMA, CC-SS, and CC-TMA) were created to simulate different skeletally anchored uprighting mechanics. CC mechanics involved a known 0.019 × 0.025-in helical cantilever acting on a buccal molar tube. TC mechanics included a 0.019 × 0.025-in cantilever capable of producing mesial root torque by acting on a tube positioned on the molar disto-occlusal surface with the slot in a buccolingual direction. Three-dimensional molar displacement and stress distribution on the molar PDL were recorded. The SS cantilever produced almost twice as much molar displacement as the TMA. TC mechanics showed more evident mesial displacement of the molar root apexes. CC mechanics had greater molar rotation. TC uprighting moment produced greater molar mesial extrusion and greater intrusion of the distal root apex. The dual deflection system of the TC mechanics induced the lowest stress on the PDL, regardless of the metallic alloy. TC delivered a more efficient uprighting moment to the molar with less unwanted tooth movement and stress on the PDL and a more accessible site for bonding the molar tube.

Esthetic Integration Area concept to improve the emergence profile of fixed restorations: A dental technique

A technique for obtaining the esthetic integration and optimal emergence profile of tooth-supported and implant-supported restorations is described. Using a computer-aided design software program, data captured with an intraoral scanner were used to establish the anatomic landmarks for determining the maximum buccal volume to which a restoration can be extended. This technique could be applicable to different types of fixed-dental prostheses treatments. Advantages of this technique include the establishment of periodontal-prosthetic criteria and the improvement of clinical and laboratory communication since the same guidelines for evaluating restorative space in the buccolingual direction of tooth preparations are used to avoid overcontoured restorations.

Evaluation of Nanoleakage Depth and Pattern of Cervical Restorations Bonded with Different Adhesive Systems.

AimTo evaluate nanoleakage depth and pattern of cervical restorations bonded with different adhesive systems.Materials and methodsThirty-six extracted human premolar teeth were used for the study and grouped according to different bonding agents.Group I: fifth generation dentin bonding agent—ONE COAT SL.Group II: sixth generation dentin bonding agent—PARABOND.Group III: seventh generation dentin bonding agent—ONE COAT 7.0.For nanoleakage depth evaluation, 36 teeth were divided into three groups of 12 teeth each, according to adhesive systems used. For each adhesive system, teeth were subdivided into three subgroups of four teeth each, according to storage period, 24 hours, 1 month, and 3 months before the examination. In each tooth, two cavities were prepared (buccal and lingual), each cavity was lined with different adhesive systems and restored using a nanohybrid composite. The restored teeth were then immersed in water bath at temperature 37oC for intended period of time and then stored in 50% silver nitrate for 24 hours and photo developing solution for 8 hours. After this, the teeth were cut in buccolingual direction and subjected to scanning electron microscope (SEM) analysis for nanoleakage depth analysis.ResultsGroup II showed the highest nanoleakage at all three periods. At 24 hours, group III showed more leakage than group I (mean = 0.2869 > 0.2506). At 1 month storage period, there was no significant difference in the leakage. At 3 months storage period, group III showed less leakage than group I (mean = 0.5544 < 0.7313).How to cite this articleBhupanapadu N, Sattar MA, Deb A. Evaluation of Nanoleakage Depth and Pattern of Cervical Restorations Bonded with Different Adhesive Systems. Int J Clin Pediatr Dent 2022;15(3):299-303.

DIFFERENT IRRIGANT ACTIVATION TECHNIQUES IN REMOVING DENTIN DEBRIS: AN IN-VITRO STUDY

During endodontic treatment, the efficiency of irrigation depends on two criteria: the antimicrobial and dissolving properties of the irrigation solution and the delivery system used that dictates the flushing action of the irrigant and consequently enable it to reach complex areas. The purpose of this in-vitro study was to compare the cleaning efficiency of EDDY sonic activation with needle irrigation and passive ultrasonic activation regarding elimination of dentin debris. Forty single rooted extracted teeth were instrumented and then were split in bucco-lingual direction. A longitudinal groove was performed in the inner surface of one root half of each tooth. Grooves were filled with dentine debris mixed with 5.25 % NaOCl in order to simulate an uninstrumented canal extension. Root halves were reassembled and were randomly divided into three groups: G1 needle irrigation, G2 passive ultrasonic activation (Acteon Satelec, Merignac, France) and G3 sonic activation using EDDY system (VDW, Munich, Germany). Ten roots served as control. After irrigation protocols, root halves were disassembled and digital images of grooves were taken using a stereomicroscope (Olympus, Japan). Evaluation of the amount of the remaining dentin debris was performed using a scoring system. No statistically significant difference existed between negative control and passive ultrasonic activation and EDDY activation respectively. Both activation techniques performed equally in removing dentine debris and significantly better than needle irrigation. No significant difference was found between needle irrigation and positive control.

Smear Layer Removal by 1% Phytic Acid after Root Canal Preparation with Three Different Rotary Systems

AIM: This study compared the removal of the smear layer using 1% phytic acid or 17% ethylenediaminetetraacetic acid (EDTA) after root canal instrumentation with SmartTrack X3, Endo*star E, and ProTaper Gold rotary systems using an environmental scanning electron microscope (ESEM). METHODS: Sixty single-rooted unidentified extracted human maxillary anterior teeth were selected. The length of all the roots used was adjusted to 16 mm from the apex. Modified access cavities were done. Roots were equally and randomly allocated to three main groups (n = 20) corresponding to the rotary systems: group A1, SmartTrack X3; group A2, Endo*star E3; and group A3, ProTaper Gold. Each group was divided into two equal subgroups (n = 10), corresponding to the chelating agents applied as a final rinse: subgroup B1, 1% phytic acid, and subgroup B2, 17% EDTA. Roots were split in a buccolingual direction into two equal halves and examined under ESEM in the presence or absence of a smear layer at the cervical, middle, and apical segments. RESULTS: 1% Phytic acid and 17% EDTA recorded no statistically significant for removing the smear layer. For all subgroups, there was a significant difference in smear layer removal and more open dentinal tubules in the cervical segment versus the apical segment. CONCLUSION: In smear layer removal from root canals, 1% phytic acid was effective as 17% EDTA in smear layer removal form root canals after SmartTrack X3, Endo*star E3, or ProTaper Gold rotary systems instrumentation.

Bracket Transfer Accuracy with the Indirect Bonding Technique-A Systematic Review and Meta-Analysis.

Purpose: To investigate the bracket transfer accuracy of the indirect bonding technique (IDB). Methods: Systematic search of the literature was conducted in PubMed MEDLINE, Web of Science, Embase, and Scopus through November 2021. Selection Criteria: In vivo and ex vivo studies investigating bracket transfer accuracy by comparing the planned and achieved bracket positions using the IDB technique were considered. Information concerning patients, samples, and applied methodology was collected. Measured mean transfer errors (MTE) for angular and linear directions were extracted. Risk of bias (RoB) in the studies was assessed using a tailored RoB tool. Meta-analysis of ex vivo studies was performed for overall linear and angular bracket transfer accuracy and for subgroup analyses by type of tray, tooth groups, jaw-related, side-related, and by assessment method. Results: A total of 16 studies met the eligibility criteria for this systematic review. The overall linear mean transfer errors (MTE) in mesiodistal, vertical and buccolingual direction were 0.08 mm (95% CI 0.05; 0.10), 0.09 mm (0.06; 0.11), 0.14 mm (0.10; 0.17), respectively. The overall angular mean transfer errors (MTE) regarding angulation, rotation, torque were 1.13° (0.75; 1.52), 0.93° (0.49; 1.37), and 1.11° (0.68; 1.53), respectively. Silicone trays showed the highest accuracy, followed by vacuum-formed trays and 3D printed trays. Subgroup analyses between tooth groups, right and left sides, and upper and lower jaw showed minor differences. Conclusions and implications: The overall accuracy of the indirect bonding technique can be considered clinically acceptable. Future studies should address the validation of the accuracy assessment methods used.

Accuracy of Guided Implant Surgery Using an Intraoral Scanner and Desktop 3D-Printed Tooth-Supported Guides.

The increasing popularity of desktop 3D printers makes guided surgery more accessible. The aim of this in vitro study was to evaluate the accuracy of single-tooth guided implant surgery by means of a 3D-printed tooth-supported guide. Fifteen implants were virtually planned to replace a missing first mandibular molar, using planning software for guided implant surgery (Exoplan, Exocad). A tooth-supported guide was designed and manufactured using a desktop 3D printer (Asiga MAX UV). The implants were placed fully guided in resin casts, and a digital impression was taken to register their position. This scan was compared with the virtual implant position in the planning software, and the internal fit of the guides was evaluated using metrology software. One planning was executed six times for measuring precision. For trueness, the mean angular deviation was 2.63 degrees (SD: 1.69 degrees; range: 0.38 to 5.99 degrees), the mean coronal deviation was 0.52 mm (SD: 0.25; range: 0.09 mm to 1.07 mm), and the mean apical deviation was 0.90 mm (SD: 0.47; range: 0.14 to 1.74 mm). The absolute apical mean deviation in the buccolingual direction (x-axis) was 0.70 mm (SD: 0.42, 0.12 to 1.65 mm; P < .001); in the mesiodistal direction (y-axis), it was 0.34 mm (SD: 0.26; range: 0.01 to 0.80 mm; P = .650); and in the vertical direction (z-axis), it was 0.32 mm (SD: 0.27; range: 0.02 to 1.00 mm; P = .010). The mean internal fit of the guides was 79.5 μm (SD: 19.6 μm; range: 51 to 118 μm). Desktop 3D-printed tooth-supported guides demonstrate an acceptable fit and acceptable level of accuracy for single implant placement.

Resonance frequency analysis for evaluation of the connecting condition between fixed prostheses and their abutment teeth: An in vitro and finite element analysis study

Statement of problemLoss of retention is a clinical complication for fixed partial dentures (FPDs). However, a method sensitive enough to measure the early retention loss of FPDs is lacking. PurposeThe purpose of this in vitro and finite element analysis (FEA) study was to determine whether resonance frequency analysis (RFA) with a newly developed system can detect lack of FPD retention caused by cement loss. Materials and methodsTwo evaluation methods were used: RFA of an in vitro model of a 3-unit FPD from the second premolar to the second molar and FEA by using a simplified model. The in vitro model was used to evaluate 4 connecting conditions: both crowns cemented, only the premolar crown cemented, only the molar crown cemented, and both crowns uncemented. Tapping stimulation (16 impulsive forces, 4 Hz) was directly applied to the buccal side of the second molar or the second premolar, and an attached 3D accelerometer sensor was used to record the resonance frequency (RF) of the tapped tooth. The amplitude, frequency, Q-value, and total area under the curve (AUC) of the RF values in the buccolingual direction were compared between connecting conditions. The FEA was done by using a simplified model of a 3-unit FPD with similar connecting conditions as the in vitro model study, and the RF amplitude and frequency of each tooth were calculated. Statistical evaluation included 1-way analysis of variance and the Tukey HSD test to compare the differences among each connecting condition under each parameter for measurement sites on the molar and the premolar, respectively (α=.05). ResultsFor both the molar and premolar measurements in both the in vitro and FEA models, when the measurement site was on the uncemented tooth, the amplitude of RF-1 increased, the Q-value of RF-2 decreased, and the area under the curve increased (P<.05). ConclusionsThe same 3 trends found between the measurement sites of the in vitro study and FEA indicated that RFA may be useful for detecting an FPD with loosening caused by cement loss, even partial cement loss.

Root Dentin Surface Roughness and Microhardness Influenced by Different Irrigation Regimens

Еndodontic irrigants could alter the mechanical properties of root canal dentin. The aim of the current study was tо compare the effect of three irrigation protocols on root canal dentin microhardness and roughness with respect to their concentration and additional ultrasonic activation for the same treatment period. Forty single-rooted, intact upper incisors were decoronated and sectioned longitudinally in buccolingual direction. The surfaces of all eighty samples were polished and randomly allocated into four equal groups (n=20): Group 1: Control group (distilled water); Group 2: 2% NaOCl/2 min followed by 17% EDTA/2 min; Group 3: 2% NaOCl/2 min followed by 17% EDTA/2 min, both ultrasonically activated Group 4: 5.25% NaOCl/2 min followed by 17% EDTA/2 min. Root dentin microhardness was significantly lowered by all of the irrigants regardless of their concentration and/or additional agitation (p&lt;0.05). The surface of root canal dentin was roughned to the greatest extent by the ultrasonically activated irrigation solutions (p&lt;0.001). The ultrasonic activation of the disinfection solutions significantly altered the biomechanical properties of dentin.

Comparative Evaluation of Microleakage Under APC Plus, APC Flash-Free and Conventional Stainless Steel Brackets: An In Vitro Study

Aim: The aim of the study was to compare and evaluate the microleakage under the Adhesive Precoated Plus (APCP), APC Flash-Free (APCF), and conventional stainless steel (SLS) brackets on the occlusal and gingival sides of the bracket base. Materials and Methods: 66 extracted premolar teeth were collected and divided equally into 3 groups. Bonding was done with APCP, APCF, and conventional SLS brackets using Transbond XT. After bonding, the samples were stored in a distilled water and thermocycled for 3000 cycles, followed by immersion in a 2% methylene blue for 24 h. After cleaning, the teeth were mounted in acrylic and sectioned longitudinally at about the center of the bracket in a buccolingual direction. Microleakage was recorded using a stereomicroscope. Results: Kruskal–Wallis H test showed a significant difference ( P &lt; .005) in the microleakage scores between the 3 groups. Mann–Whitney U test showed a significant difference between group 1 to group 2 and group 1 to group 3 ( P &lt; .005) and an insignificant difference between group 2 and group 3 on the occlusal side ( P = .116) and on the gingival side ( P = .063). Conclusion: Conventional SLS bracket group exhibited greater microleakage scores at both occlusal and gingival sides, when compared with APCP and APCF groups.

Cone-beam computed tomography assessment of root canal transportation and evaluation of canal centering using Protaper Gold, XP Endoshaper, and Edgefile X7

Aim: This study aims to access and evaluate canal transportation and canal centering ability of Protaper Gold (PTG), XP EndoShaper (XPS) and EdgeFile X7 using cone-beam computed tomography (CBCT). Materials and Methods: Sixty freshly extracted single-rooted premolars with mature apex and a canal curvature of 10°–20° were chosen and arbitrarily divided into three experimental groups (n = 20). After decoronation, the teeth measuring 16 mm were included in the study for standardization. According to the manufacturer's instructions, canals were shaped with PTG in Group 1, XPS in Group 2 and EdgeFile X7 in Group 3. For the evaluation of the root canal transportation at 2 mm, 4 mm, and 6 mm from the apex, canals were scanned before and after instrumentation using CBCT scanner. Independent t-tests and one-way ANOVA were used to analyze data and significance level was set at P &lt; 0.05. Results: XPS showed significantly lower canal transportation than PTG system. Moreover, the centering ability of the XPS significantly higher than EdgeFile X7 and PTG at all root levels (P &lt; 0.05). Conclusion: The XPS and EdgeFile X7 rotary file system showed the lowest transportation in both mesiodistal and buccolingual directions and also the highest centering ability. The PTG file showed the highest transportation and lowest centering ability.

Morphometric analysis of three-rooted mandibular first molars in a Slovene population: a macroscopic and cone-beam computed tomography analysis.

This study examined the root morphology of mandibular first molars (MFMs) with radix entomolaris (RE), which presents diagnostic and therapeutic challenges for clinicians. A total of 17 three-rooted MFMs were taken from a collection of extracted teeth. Root lengths and levels of furcations were measured with a digital calliper. The pulp floor configuration, root canal systems, and RE canal curvatures were evaluated using the cone-beam computed tomography scans. Radix entomolaris was either located disto-lingually, with its coronal portion fixed to the distal root (n = 16) or mid-lingually (n = 1). A literature search identified four additional cases of MFMs with RE located mid-lingually. In the present study, RE was significantly (p ≤ 0.001) shorter than the distal root (DR) and the mesial root, on average by 2.04 mm and 3.15 mm, respectively. The level of the distal furcation was significantly (p = 0.003) lower than that of the mesiodistal furcation, on average by 1.39 mm. The average divergence angle formed by the cervical portions of the RE and DR canals was 53.14°. All RE canals were severely curved (> 25°) in buccolingual direction. The RE orifice was located slightly disto-lingually to considerably mesio-lingually from the DR orifice. The traditional assumption of a disto-lingually located RE needs to be changed, even though this is the most prevalently found variant of this anatomy. The additional variant includes the presence of a mid-lingually located RE, which has implications for the endodontic access cavity design.

Atomic force microscopy study on the effect of different irrigation regimens on the surface roughness of human root canal dentin.

Endodontic irrigants could alter the mechanical properties of root canal dentin, such as its roughness. To compare the effect of various irrigation protocols on root canal dentin roughness with respect to their application time, concentration, and additional ultrasonic activation. Forty single-rooted, non-endodontically treated upper incisors were decoronated and further sectioned longitudinally in a buccolingual direction. The surfaces of all eighty samples were polished and randomly segregated to eight equal groups (n = 10): Group A: 2% NaOCl/2 min followed by 17% EDTA/2 min; Group B: 2% NaOCl/5 min followed by 17% EDTA/5 min; Group C: 5.25% NaOCl/2 min followed by 17% EDTA/2 min; Group D: 5.25% NaOCl/5 min followed by 17% EDTA/5 min; Group E: 2% NaOCl solution, ultrasonically activated for 2 min; Group F: 5.25% NaOCl, ultrasonically activated for 2 min; Group G: 2% NaOCl/2 min followed by 17% EDTA/2 min, both ultrasonically activated; Group H: Control group (distilled water). All irrigation regimens increased root dentin surface roughness in comparison with the control group. The analysis of the values revealed significant differences between the arithmetical average roughness values (Ra) in the groups (p < 0.001). A statistically significant increase in the Ra parameter was observed in groups E, F, G, and D. The irrigation protocol in Group A showed a significantly smoother dentin surface than those with the ultrasonic activation. All tested irrigants increased root canal dentin roughness and the effect was time and concentration-dependent. The ultrasonic activation of the disinfection solutions roughened the root dentin surface significantly.

Diagnosis of Vertical Root Fractures in Endodontically Treated Teeth by Cone-Beam Computed Tomography.

The purpose of this study was to investigate the characteristics and the detection ability of vertical root fractures in endodontically treated teeth by intraoral radiography and cone-beam computed tomography (CBCT). CBCT images of 50 patients with root fractures in endodontically treated teeth were reviewed, and 36 vertical root fractures were taken in this study. The cause of fracture, core construction, kind of teeth, and fracture direction (bucco-lingual and mesio-distal fractures) were investigated. Detection ability of vertical root fractures by intraoral radiography and CBCT was also examined. Statistical analyses concerning the characteristics were performed by χ2 test, and the detection ability was analyzed by cross-tabulation. All of the fractured teeth were nontraumatized teeth. The vertical root fracture occurrence was not differed by core construction. The vertical root fracture number was largest at the premolar teeth (p = 0.005), and the number of the bucco-lingual fracture was larger than the mesio-distal fracture (p = 0.046). Vertical root fractures were detectable using CBCT, while undetectable by intraoral radiography (p < 0.001). Vertical root fractures occurred easily in premolar teeth with bucco-lingual direction, and CBCT is an adequate radiographic method to diagnose vertical root fracture.

Linear and angular transfer accuracy of labial brackets using three dimensional-printed indirect bonding trays: A systematic review and meta-analysis

To assess the transfer accuracy of three dimensional-printed trays (3D-printed trays) and to compare the accuracy of this approach with the other methods used for the same purpose. An electronic search was performed in PubMed, Scopus, Web of science, Google Scholar and ProQuest (dissertation and theses). Studies were eligible for inclusion if they involved the assessment of transfer errors measured by the superimposition of the original set-up of brackets and the final positions after transfer. Risk of bias was assessed using Cochrane's tools. Seven studies were included. The pooled estimate of the transfer error in the linear dimensions showed an error of 0.095mm in the mesiodistal direction (95%CI: 0.035, 0.155), 0.114mm in the buccolingual direction (95%CI: 0.067, 0.160) and 0.111mm in the vertical direction (95%CI: -0.033, 0.255). Concerning the angular dimensions, the pooled estimate showed a tipping error of 1.3420 (95%CI: 0.444, 2.240), rotational error of 0.9980 (95%CI: 0.323, 1.672), and torque error of 1.9130 (95%CI: 0.922, 2.903). Thus, the maximum transfer error was in the bucco-lingual and torque directions. 3D-printed trays had better control in mesiodistal and vertical directions than vacuum-formed trays. Polyvinyl siloxane trays were more accurate in the vertical direction than 3D-printed trays. The scarcity of randomized clinical trials is the main risk of bias of the included studies. According to the available evidence, 3D-printed trays have an acceptable transfer accuracy, based on the American Board of Orthodontics Objective Grading System (ABO OGS), with maximum linear transfer error in the buccolingual direction and maximum angulation error in the torque. Conducting randomized clinical trials on this topic is highly recommended.

Reliability of dentin translucency and incremental cemental lines in age estimation using light and stereomicroscopes: A comparative study.

Age estimation of the dead and human remains has been challenging in forensic medicine, both in mass disasters and criminal investigations. There are several approaches to accurately evaluate age, each with its own benefits and drawbacks. Dentine translucency (DT) and incremental cemental lines (ICL) have often been used for age estimation in living adults and unknown skeletal remains. We attempted to estimate age using both these parameters and compare accuracy of age estimated using these parameters in a larger sample. A total of 300 extracted single-rooted permanent teeth were collected from the patients aged between 15 and 75years. Longitudinal ground sections in the buccolingual direction of 250μm thickness were prepared, and the images obtained were subsequently analyzed to measure the length of DT using the ImageJ software program. In addition, the number of ICL were also counted in each tooth section. The age of the individuals was estimated using both methods individually, and the results have shown that both parameters have shown reliable age estimates in the middle age groups. However, there was overestimation of age up to 10.6years in the younger age group using DT and an underestimation of age up to 13.4years in the older age group with ICL. Pearson's correlation statistics revealed a strong positive and statistically significant correlation of both the parameters with the chronological age (0.973 and 0.917). To conclude, the method using the ICL should be preferred due to the relatively higher number of errors (<±3years) which were considered excellent.

Comparison of root canal shaping ability of different heat-treated NiTi single files: a micro-CT study.

The purpose of this study was to evaluate the root canal shaping abilities of different heat-treated NiTi engine--driven single files. A total of 45 mandibular first molar teeth with a root canal curvature of between 25 and 35 degrees were selected for this in vitro study. The mesial roots were separated and scanned with micro-CT. The specimens were randomly divided into three groups. Root canal preparations were performed using HyFlex EDM OneFile in Group 1; OneCurve (25/06) in Group 2, and WaveOne Gold Primary in Group 3. Root canals were scanned again with micro-- CT after root canal preparation. Apical transportation value and centering ability ratio of files were evaluated using the preinstrumentation and postinstrumentation micro-CT images at 1, 2, 3, 4, and 7 mm. The data were statistically analyzed using the Kruskal-Wallis test. The Bonferroni-Dunn test was used for multiple comparisons. The level of statistical significance was set at P < .05. There was no significant difference between the apical transportation values of experimental groups in mesiodistal direction (P > .05) and buccolingual direction (P > .05). The OneCurve file group showed better centering ability in the buccolingual direction than the WaveOne Gold file group at 4 mm (P = .048). The difference between the centering ability values of experimental groups was not significant at other levels (P > .05). According to the results of this study, all tested single files caused apical transportation and showed similar centering ratio at most of the root sections.

Bracket transfer accuracy with two different three-dimensional printed transfer trays vs silicone transfer trays.

To compare the transfer accuracy of two different three-dimensional printed trays (Dreve FotoDent ITB [Dreve Dentamid, Unna, Germany] and NextDent Ortho ITB [NextDent, Soesterberg, the Netherlands]) to polyvinyl siloxane (PVS) trays for indirect bonding. A total of 10 dental models were constructed for each investigated material. Virtual bracket placement was performed on a scanned dental model using OnyxCeph (OnyxCeph 3D Lab, Chemnitz, Germany). Three-dimensional printed transfer trays using a digital light processing system three-dimensional printer and silicone transfer trays were produced. Bracket positions were scanned after the indirect bonding procedure. Linear and angular transfer errors were measured. Significant differences between mean transfer errors and frequency of clinically acceptable errors (<0.25 mm/1°) were analyzed using the Kruskal-Wallis and χ2 tests, respectively. All trays showed comparable accuracy of bracket placement. NextDent exhibited a significantly higher frequency of rotational error within the limit of 1° (P = .01) compared with the PVS tray. Although PVS showed significant differences between the tooth groups in all linear dimensions, Dreve exhibited a significant difference in the buccolingual direction only. All groups showed a similar distribution of directional bias. Three-dimensional printed trays achieved comparable results with the PVS trays in terms of bracket positioning accuracy. NextDent appears to be inferior compared with PVS regarding the frequency of clinically acceptable errors, whereas Dreve was found to be equal. The influence of tooth groups on the accuracy of bracket positioning may be reduced by using an appropriate three-dimensional printed transfer tray (Dreve).

EVALUATION OF BIOMECHANICAL EFFECTS OF PROSTHETIC COMPONENTS WITH DIFFERENT MATERIALS ON THE ABUTMENT SCREW

Objectives: The purpose of this study was to evaluate the effects of different resin-based and ceramic superstructure materials and two different abutment types on the stress distribution of the abutment screw using the three-dimensional finite element stress analysis method. Materials and Methods: A three dimensional implant, abutment (zirconia and titanium), abutment screw, crown (zirconia reinforced lithium silicate, lithium disilicate, polymer-infiltrated resin ceramic, and PEEK), and alveolar bone were designed using Rhinoceros 3D modeling software and VRMesh Studio software and combined to form 8 simulations. On the models prepared, loading was made on the lingual tubercule of the maxillary right first premolar crown at an angle of 30° with 150 N force obliquely in the buccolingual direction. The von Mises values obtained from the abutment screw were compared according to the types of abutment and crown materials. Results: The von Mises stress values in the abutment screw were higher in the models using a titanium abutment abutment (on average 1336.24 MPa), and the lower stress values were obtained in the models using a zirconia abutment (on average 964.26 MPa). When the prosthetic material used was changed, no apparent difference was observed in the stress values on the abutment screw. Conclusions: Considering that the abutment screw is the weakest link of the implant system, zirconia abutments can be used reliably in the maxillary first premolar region where aesthetic expectations are high.