Sterilization of extracted human teeth: A comparative analysis

Three-axis load analysis of high-speed handpiece on dental training teeth and computer-aided design/computer-aided manufacturing blocks

This study aimed to evaluate and compare the mechanical properties of dental training teeth with subtractive and additive computer-aided design/computer-aided manufacturing (CAD/CAM) materials used to fabricate dental simulation models. Therefore, the three-axis load generated during cutting movements, including drilling and milling performed using a dental handpiece, was measured and compared. The samples were cut vertically downward by 1.5 mm, horizontally by 6 mm, and vertically upward at a constant speed (1 mm/s), while the rotational speed of the bur was maintained at 200,000 rotations per minute. A three-axis load cell was used to measure the X-, Y-, and Z-axis loads on the specimen. The median value of the X-, Y-, and Z-axis measurements and the resultant load during the vertical-downward, horizontal, and vertical-upward movements were compared using a one-way analysis of variance and Tukey's post hoc test. For vertical downward movement, the drilling force of the dental training teeth was lower than that of Vita Enamic® and similar to that of Lava™ Ultimate. In contrast to subtractive CAD/CAM blocks, the drilling force of the dental training teeth was higher than that of 3D-printed resin blocks. Regarding horizontal movement, the milling force of dental training teeth was lower than that of Vita Enamic®. In contrast, the milling force of Nissin was similar to that of Lava™ Ultimate, while that of Frasaco was lower. Furthermore, compared to additive CAD/CAM blocks, the milling force of the dental training teeth was higher than that of 3D-printed resin blocks. Regarding vertical upward movement, the resultant loads of dental training teeth was lower than that of Vita Enamic®. Similarly, the resultant load of Nissin was similar to that of Lava™ Ultimate, while that of Frasaco was lower. Additionally, compared to additive CAD/CAM blocks, the resultant loads of the dental training teeth were similar to those of the 3D-printed resin blocks.

Evaluation of Retentive Strength of 50 Endodontically-Treated Single-Rooted Mandibular Second Premolars Restored with Cast Post Cores Using 5 Common Luting (Cement) Agents

BACKGROUND A luting agent is a dental cement used to secure a dental restoration. This study aimed to evaluate retentive strength of 50 endodontically-treated single-rooted mandibular second premolars (extracted) restored using 5 common luting (cement) agents. MATERIAL AND METHODS Fifty single-rooted mandibular second premolars with adequate root length and uniform size/shape were decoronated. After completing endodontic biomechanical preparation and obturation, root canals of all specimens were prepared to receive a cast post core. Depending upon cementation type, CPC specimens were divided in 5 groups (10 each) (Gp): Zinc phosphate (Gp ZP), polycarboxylate (Gp PC), glass ionomer (Gp GI), resin-modified glass ionomer (Gp RGI), and resin cement (Gp RC). Retentive strength was determined using the adhesive failure pull-out test. Mean/standard deviations were calculated for tensile forces (in kilograms) and differences were determined using analysis of variance (ANOVA). Multiple comparison was performed using the t test. A P value of ≤0.05 indicated a statistically significant difference. RESULTS The order of mean tensile strength from higher to lower was Gp RC (21.46) >Gp RGI (18.17) >Gp GI (16.07) >Gp ZP (15.33) >Gp PC (13.63). Differences in retentive strengths between the cements were significant (P≤0.05). Multiple-group comparisons showed that except for Gp ZP and Gp GI, all groups differed significantly from each other. CONCLUSIONS All investigated cements provided optimal retentive strengths, with wide differences between them. Resin cements should be used when CPC removal is not anticipated, while polycarboxylate or zinc phosphate should be used if CPC removal is anticipated.

Comparative evaluation of remaining dentin thickness, canal centering ability and apical deformity between ProFit S3 and Protaper gold - A nano CT study

Purpose

For the root canal treatment to be successful, the root canal system must be cleaned and shaped, and must be gradually widened from the apical to the coronal region in order to preserve dentin thickness. ProFit S3 (Profit Dental, India) patented rotary file with variable taper design preserves dentin. The study employs ultra-high-resolution nano-computed tomography to assess the volumetric changes of two new rotary files in permanent mandibular premolars.

Materials and methods

Based on inclusion and exclusion criteria, this in-vitro investigation used extracted premolars. Before the pre-operative scan, samples were made and the working length was determined using a high-precision nano-CT (SkyScan 2214, Bruker, Kontich, Belgium). A single skilled pediatric dentist used ProFit S3 (Profit Dental, India) and Protaper Gold (PTG; Dentsply, Tulsa Dental Specialties, Tulsa, OK, USA) to prepare the canals. Post-op scans were similar to pre-ops. For 3D root canal visualization and analysis, NRecon software was used to rebuild images.

Results

Profit S3 has a mean value of 0.65500 and Protaper gold 1.38800, indicating a significant range. Protaper gold followed Profit S3 in canal volume differential. The two rotating file systems differed significantly (p 0.05). ProFit S3 maintained mesiodistal and buccolingual dentin thickness at 4 mm, 8 mm, and 12 mm, followed by Protaper Gold.

Conclusions

ProFit S3 exhibited the lowest mean canal volume difference compared to Protaper gold. Unlike Protaper Gold, ProFit S3 offers a variable taper design that preserves root canal anatomy, peri cervical dentin, and dentin thickness.

Comparative evaluation of volumetric changes following rotary and hand files' canal preparation of primary maxillary canine: an in vitro nano-CT analysis

PURPOSE

To evaluate the volumetric changes of two recently introduced paediatric rotary file systems in comparison with conventional hand file systems in primary maxillary canines using an ultra-high-resolution nano-computed tomography.

METHODS

This in vitro study was performed in extracted primary maxillary canines based on certain inclusion and exclusion criteria. Samples were prepared, and working length was determined after the pre-operative scan using a high-resolution nano-CT device (SkyScan 2214, Bruker, Kontich, Belgium). A single well-experienced paediatric dentist prepared the canals using three file systems: Kedo-S plus, Kedo-SG blue and hand K-files. All samples were subjected to post-operative scans performed similar to pre-operative scans. Image reconstruction was performed with NRecon software for 3D volumetric visualisation and analysis of the root canals.

RESULTS

Kedo-SG blue file systems had the highest mean difference in the canal volume (4.05%). Hand K-files had the least difference at (3.71%) of canal volume. Kedo-S plus file system had a moderate mean canal volume difference (3.82%) which is closer to hand K-files. Intergroup comparison between the three groups showed that the mean difference in canal volume was statistically significant between all three file systems (p = 0.000).

CONCLUSION

Within the limitations of the current study, rotary file systems produced a significant enlargement of canals as compared to hand files. Kedo-SG blue created a uniform preparation of the canal cervico-apically. Kedo-S plus files were prepared more coronally with minimal preparation apically as close to the preparation of hand files.

TRIAL REGISTRATION

Trial registration number: IHEC/SDC/PEDO-2103/22/651, Date of registration: 2022.

Marginal adaptation of different monolithic zirconia crowns with horizontal and vertical finish lines: A comparative in vitro study

Background

This study evaluated the influence of different tooth preparation techniques and zirconia materials on marginal adaptation.

Methods

Forty-eight healthy human maxillary first premolars were divided into two primary groups based on preparation design: group A (chamfer) and group B (vertical). Within each main group, there were three subgroups, comprising eight teeth each, distinguished by the type of zirconia material employed (Zircad LT, MT, and Prime by Ivoclar Vivadent). All the samples were prepared by the same operator using a dental surveyor. Intraoral scanning was performed on the prepared teeth. SironaInLab CAD 20.0 software was used to design crowns, which were subsequently generated using a 5-axis milling machine. The crowns were cemented to their respective teeth with self-adhesive resin cement. Marginal gap measurements were taken in micrometers (μm) before and after cementation at 16 sites per sample using a digital microscope at×230 magnification. The collected data were evaluated using statistical analysis using the independent t-test, paired t-test, and ANOVA at an 0.05 significance level.

Results

The vertical preparation group exhibited the smallest marginal gap, while the chamfer group displayed the largest. This disparity was statistically significant (P<0.05) for pre- and post-cementation measurements across all materials. There were no significant differences between the different monolithic zirconia crowns.

Conclusion

The vertical preparation design illustrated significantly better marginal adaptation than the chamfer preparation design. Comparisons between materials showed comparable marginal gaps. The mean values of the marginal gaps in all groups increased significantly after cementation.

Effect of lactoferrin on enamel characteristics of primary and permanent teeth: an in-vitro study

BACKGROUND

Lactoferrin, a glycoprotein naturally found in breast milk, is known for its bactericidal and antiviral properties, as well as its capacity to modulate the immune system; therefore, pediatricians routinely recommend it as dietary support. The objective of this study was to determine how lactoferrin oral suspension could affect the enamel surface characteristics of primary and permanent teeth.

METHODS

This research was conducted on 40 unidentified extracted teeth, including primary and permanent teeth. Experimental teeth were free of cracks or enamel defects, as confirmed by careful examination using a dental operating microscope. The crowns were bisected into 80 specimens and assorted into two groups based on the type of dentition. Group DM included 40 specimens of second deciduous molars, while Group PM contained 40 samples of first premolars. Each of the DM and PM specimens was subsequently split based on the type of dispersion medium into two subgroups: a control subgroup (artificial saliva) and a test subgroup (lactoferrin suspension). The specimens were immersed in lactoferrin suspension for two minutes, then kept in artificial saliva for the rest of the 24 h for 30 successive days. This is a pioneering study about the effect of orally supplemented lactoferrin on teeth; therefore, we examined enamel hardness, ultra-morphology, and mineral contents.

RESULTS

Our findings indicated a highly significant decrease (p < 0.01) in the microhardness of the lactoferrin subgroup in Group DM (second deciduous molars) and a significant reduction (p < 0.05) in the microhardness of the lactoferrin subgroup in Group PM (premolars). Calcium weight% was not statistically different (p > 0.05) compared with a significant decline (p < 0.05) in phosphorus weight% in lactoferrin subgroups in both DM and PM groups. The enamel surface of lactoferrin subgroups in both DM and PM groups was demineralized and porous, with the enamel of deciduous teeth being more affected by lactoferrin than permanent teeth.

CONCLUSION

Lactoferrin suspension decreased the microhardness of enamel and both calcium and phosphorus weight percentages. Both dentitions exhibited erosions in the enamel surface, with primary teeth being more affected than the permanent teeth.

Can acid produced from probiotic bacteria alter the surface roughness, microhardness, and elemental composition of enamel? An in vitro study

Probiotics are live microorganisms that upon administration in adequate amounts provide various health benefits to the host. Probiotics are "lactic acid-producing bacteria" as they release large amounts of organic acids, particularly lactic acids, in their surrounding environment. Although the acids produced by probiotics are beneficial for gastrointestinal and vaginal health, the acidogenic nature of probiotics has raised concerns among dental professionals, especially concerning their effect on the enamel and dentin. Previous studies have found that probiotics can lower the pH of the saliva and cause essential elements like Calcium and Phosphorus to leach from the enamel. This can alter the surface topography of enamel and increase the risk of enamel defects. Studies have also noted that probiotic bacteria can replace cariogenic bacteria and lower the risk of tooth decay. However, the effect of acid produced by probiotics on the enamel surface remains unclear. Hence, the present study aims to evaluate the effect of probiotics on the surface roughness, microhardness, and elemental composition of enamel compared to 0.1 M Lactic acid (demineralizing agent). Twenty enamel sections were randomly divided into groups and subjected to a pH cycling model using a probiotic suspension and 0.1 M lactic acid. The changes in the surface roughness, microhardness, surface morphology, and elemental composition of the enamel with regard to Carbon, Oxygen, Sodium, Hydrogen, Magnesium, Phosphorus, Fluoride, Chlorine, and Calcium of the enamel were evaluated before and after the emersion in both the groups. The results showed a significant increase in the mean surface roughness in the probiotic group before and after the exposure. The microhardness of the enamel decreased along with altered arrangement of the enamel prisms, increased striations, scratch marks, and pitting after exposure to the probiotic group. A decrease in the atomic/weight% for Calcium, Phosphorous, Fluoride, Aluminium, and Oxygen and an increase in the weight/atomic% for Carbon, Nitrogen, and Sodium were noted compared to the baseline in the probiotic solution. The results in the probiotic group were comparable to the 0.1 M lactic acids. The pH changed from 5.78 to 3.06 at the end of 24 h in the probiotic group. Based on these findings, we conclude that exposure to probiotics can affect microhardness and surface roughness and cause leaching of essential elements like Calcium and Phosphorous from the enamel.

Evaluation of the efficacy of a charcoal-based tooth whitening dentifrice on coffee stains: an in vitro study

Background

Charcoal-based preparations have recently gained popularity, particularly in oral hygiene products such as tooth whitening dentifrices, owing to their abrasive and adsorptive properties. The present in vitro study evaluates the efficacy of a charcoal-based tooth whitening dentifrice compared with a non-charcoal-based whitening dentifrice in removing coffee stains on tooth surfaces.

Methods

Thirty-three human extracted tooth specimens were randomly assigned to 1 of 3 study groups: Group 1 (charcoal-based whitening dentifrice [CBWD]), Group 2 (non-charcoal-based whitening dentifrice [NCBWD]), and Group 3 (distilled water [DW]). All tooth specimens were immersed in a prepared coffee extract for 4 weeks to facilitate staining and then mounted on blocks where they were brushed with an electric toothbrush daily for 8 seconds with 1 of the 2 allocated dentifrices or with DW for 4 weeks following staining. Spectrophotometric analysis was conducted using the CIELAB system to measure the L*, a*, and b* values at 3 time points: before staining, after staining, and following the brushing protocol. These values were used to calculate the colour change (ΔE) between time points.

Results

Following the coffee staining, the tooth samples' whiteness (ΔL) decreased with the overall colour change (ΔE). Next, there was a significant improvement in the degree of tooth whiteness (ΔL) values following the brushing protocol in all 3 groups (p = 0.003), with the greatest improvement occurring in the CBWD group. However, the overall colour change (ΔE) was not significantly different between the groups.

Conclusion

CBWD, NCBWD, and DW were effective in removing coffee stains from the tooth surface. However, the amount of colour change (ΔE) produced by CBWD was not significantly different from NCBWD or DW.

Comparative Evaluation of Extrusion of Apical Debris in Primary Maxillary Anterior Teeth Using Two Different Rotary Systems and Hand Files: An In Vitro Study

Successful outcome of pulp therapy depends on good chemomechanical preparation of the canals. This is completed with the help of various upcoming rotary and hand files. However, during this preparation, there might be an apical extrusion of the debris which may result in postoperative complications. The aim of this study was to evaluate and compare the number of debris apically extruded during canal preparation using two different pediatric rotary file systems and conventional hand file systems in primary teeth. 60 primary maxillary central incisors that were extracted due to trauma or untreated dental caries with no signs of resorption were taken. Canal preparation was executed using three different file systems: Group A: Group A hand K file system, Group B Kedo S Plus, Group C Kedo SG Blue. For each of these files using the Myers and Montgomery model, the pre- and post-weight of the eppendorf tube was assessed to quantify the number of apical debris. The maximum extrusion of apical debris was noticed with the Hand K-file system. The least debris was noticed in the Kedo S Plus file system. Statistical analysis revealed that there were highly significant differences in apical extrusion and debris when comparing hand files and rotary files and also between the two rotary files used. Apical debris collection is an unavoidable outcome of canal instrumentation. Among the file systems compared, rotary files had lesser extrusion when compared to hand files. Among the rotary files, Kedo S plus showed normal extrusion compared to SG Blue.

Synthesis, Characterization, and Investigation of Novel Ionic Liquid-Based Tooth Bleaching Gels: A Step towards Safer and Cost-Effective Cosmetic Dentistry

The objective of this study was to synthesize a novel choline hydroxide ionic liquid-based tooth bleaching gel. Ionic liquid-based gels were synthesized and characterized using FTIR along with pH testing. Tooth sample preparation was carried out in line with ISO 28399:2020. The effects of synthesized gels on tooth samples were tested. Tooth samples were stained and grouped into three experimental groups: EAI (22% choline hydroxide gel), EAII (44% choline hydroxide gel), and EB (choline citrate gel) and two control groups: CA (commercial at-home 16% carbamide peroxide gel) and CB (deionized water). The tooth color analysis, which included shade matching with the Vitapan shade guide (n = 2), and digital colorimetric analysis (n = 2) were evaluated. The surface characteristics and hardness were analyzed with 3D optical profilometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and Microhardness testing (n = 3), respectively. The tooth color analysis (Vitapan shade guide) revealed that all the tooth samples treated with synthesized choline citrate gel (EB) showed an A1 shade as compared to the other four groups, giving a range of shades. An analysis of the ΔE values from digital colorimetry; EAI, EAII, CA, and CB showed ΔE values in a range that was clinically perceptible at a glance. However, EB showed the highest value of ΔE. The mean microhardness values for the five groups showed that the effects of three experimental gels i.e., 44% choline hydroxide, 22% choline hydroxide, and choline citrate, on the microhardness of the tooth samples were similar to that of the positive control, which comprised commercial at-home 16% carbamide peroxide gel. SEM with EDX of three tested subgroups was closely related in surface profile, elemental composition, and Ca/P ratio. The roughness average values from optical profilometry of four tested subgroups lie within approximately a similar range, showing a statistically insignificant difference (p > 0.05) between the tested subgroups. The synthesized novel experimental tooth bleaching gels displayed similar tooth bleaching actions without any deleterious effects on the surface characteristics and microhardness of the treated tooth samples when compared with the commercial at-home tooth bleaching gel.

Application of 3D-printed teeth models in teaching dentistry students: A scoping review

INTRODUCTION

Both regular teaching of dentistry students and various training schemes for dentists primarily make use of the series teeth models, resin blocks or extracted teeth, whereas the 3D teeth models may well offer an alternative in this respect.

METHODS

PubMed and EMBASE were searched in September 2020. Eligibility of the studies was determined on whether they had made use of the 3D-printed teeth models in both pre- and post-graduate education in dentistry.

RESULTS

The final review embraced 15 studies. There were 659 (89.54%) student participants, and 77 (10.46%) dentists involved in those studies. Five studies addressed the prosthetic and surgical procedures, two-endodontics, one-paediatric dentistry and one-trauma management. The 3D-printed models were also used in the study focused on enhancing the students' manual dexterity, whilst making use of the PhantHome tool.

DISCUSSION

The 3D-printed teeth models developed for teaching purposes are used in various areas of dentistry. Their overall usefulness in acquiring the necessary hands-on skills for clinical work was acknowledged in all the studies under review, regardless of a specific procedure at issue. The 3D models effectively eliminate the hazard of cross-infection. Overall effectiveness of the soft tissue reproduction appears to be their weakest point indicated to date, especially in the surgical models.

CONCLUSIONS

The 3D-printed teeth models provide an alternative to the extracted ones, and the series teeth models in regular teaching practice. Participants of the studies under review thoroughly recommend introducing 3D models into any hands-on practice.

Dosimetric parameters and radiotherapy simulation methods used in preclinical studies of radiation damage to the dentition: a systematic review

OBJECTIVE

This systematic review investigated the dosimetric parameters used in preclinical studies.

STUDY DESIGN

Searches were performed in 3 databases (PubMed, Scopus, and Embase) and gray literature to identify studies for review. In vitro and ex vivo studies that examined the effect of radiation on human permanent teeth were included. The modified Consolidated Standards Of Reporting Trials checklist of items for reporting preclinical in vitro studies was used to assess the risk of bias.

RESULTS

In total, 32 studies met the inclusion criteria. The average radiation dose of in vitro studies was 53 (±22) Gy and in ex vivo studies was 69 (±1) Gy. Twenty-two studies used 5 different fractionation schemes. Twenty-two of the included studies did not report the radiotherapy modality of those reporting. Twenty studies used linear accelerators, and 7 used Cobalt-60 with the source-surface-distance of radiation ranging from 1.5 to 100 cm. Distilled water was the storage solution for the dental structure used most commonly. Biases were observed, including small sample sizes, lack of randomization, and blinding processes.

CONCLUSION

The dosimetric parameters used in the preclinical studies, including radiation dose, radiotherapy modality, fractionation regime, and the storage solutions used did not support the hypothesis of direct effects of radiation on the dental structure.

A critical analysis of research methods and experimental models to study irrigants and irrigation systems

Irrigation plays an essential role in root canal treatment. The purpose of this narrative review was to critically appraise the experimental methods and models used to study irrigants and irrigation systems and to provide directions for future research. Studies on the antimicrobial effect of irrigants should use mature multispecies biofilms grown on dentine or inside root canals and should combine at least two complementary evaluation methods. Dissolution of pulp tissue remnants should be examined in the presence of dentine and, preferably, inside human root canals. Micro-computed tomography is currently the method of choice for the assessment of accumulated dentine debris and their removal. A combination of experiments in transparent root canals and numerical modeling is needed to address irrigant penetration. Finally, models to evaluate irrigant extrusion through the apical foramen should simulate the periapical tissues and provide quantitative data on the amount of extruded irrigant. Mimicking the in vivo conditions as close as possible and standardization of the specimens and experimental protocols are universal requirements irrespective of the surrogate endpoint studied. Obsolete and unrealistic models must be abandoned in favour of more appropriate and valid ones that have more direct application and translation to clinical Endodontics.

Evaluation of wear behaviour of various occlusal splint materials and manufacturing processes

OBJECTIVES

To investigate the volumetric and vertical loss of occlusal splints manufactured by conventional (heat-cure), subtractive (CAD/CAM) and additive (3D-printing) methods.

METHODS

Six occlusal splint materials were investigated (n = 126), using three manufacturing methods: heat-cured, CAD/CAM and 3D-printed built-in three different printing angles (0°,45°and 90°). Block-on-ring wear testing was performed with extracted human molars as the antagonist. All samples were tested with an applied force of 49N at 1 Hz and 60RPM in artificial saliva at 37 °C for six and 12 months. Scanning electron microscopy images were analysed to evaluate the wear on the tooth enamel and in the splint material. Volumetric and vertical wear loss were statistically analysed.

RESULTS

The lowest volumetric and vertical loss was observed in CAD-CAM materials (6.44 ± 1.77 mm³ and 48.3 ± 7.14 μm) with no statistical significance to the heat-cured material (17.22 ± 9.23 mm³ and 148 ± 121.1 μm) after 12 months (p < 0.172). The mean volumetric loss of 3D printed materials ranged from 0.25 ± 0.15 mm³ to 0.29 ± 0.1 4mm³ with no statistical difference, whereas, the differences in vertical loss from 131.63 ± 44.1 μm to 493 ± 79.19 μm were statistically significant (p < 0.001). The highest vertical loss was observed in the KeySplint Soft 3D printed at 90° (385.35 ± 82.37 μm), whereas FreePrint Splint 2.0 with a build angle of 0° had the highest volumetric loss (204.59 ± 25.67 mm³).

CONCLUSION

CAD-CAM material had the highest wear resistance followed by heat-cured material.KeySplint Soft and FreePrint Splint 2.0 3D printed materials would be preferred for patients that do not have severe bruxing episodes. No significant wear of human enamel after six and 12 months was observed under SEM for any tested materials.

Rehabilitation of severely-destructed endodontically treated premolar teeth with novel endocrown system: Biomechanical behavior assessment through 3D finite element and in vitro analyses

OBJECTIVE

Rehabilitation of endodontically treated premolars with extensive coronal destruction through endocrown approach remains a controversial topic in reconstructive dentistry. There is no clear consensus in the literature which endocrown design with which material is the most effective restoration option for severely-destructed endodontically treated premolars. The aim of this study was to assess the biomechanical behavior of endodontically treated maxillary first premolars restored with a novel endocrown system compared to the conventional one varying the applied load type through finite element and in vitro analyses.

MATERIALS AND METHODS

For finite element analysis, two models representing two endocrown systems used for restoration of severely-destructed endodontically treated maxillary first premolar tooth were generated: Model C for the conventional monolithic IPS e.max CAD endocrown and Model P for the novel bi-layered endocrown (PEKKTON ivory coping veneered with cemented IPS e.max CAD). Modified von Mises stress values on the remaining tooth structure, cement lines and restorative materials were evaluated separately under axial and oblique loading of 450 N. For in vitro analysis, forty sound human bifurcated maxillary first premolars were collected, endodontically-treated, and divided into 2 main groups (n = 20) according to the system used for endocrown fabrication; Group C: the conventional monolithic endocrowns and Group P: the novel bi-layered endocrowns. All specimens were subjected to an artificial thermomechanical aging protocol. Each main group was subdivided into two subgroups (n = 10) according to the loading type (axial and oblique) applied during the fracture resistance test. Qualitative analysis using Stereomicroscopy and Scanning Electron Microscopy was performed. Data were statistically analyzed at p-value ≤ 0.05.

RESULTS

Regarding stress distribution pattern of remaining tooth structure (enamel and dentin), both endocrown systems and cement lines under both axial and oblique load application, Model P resulted in lower stresses than Model C. The oblique stress values of all analyzed structures were higher than corresponding values resulted axially. Considering failure load, a significantly higher load was recorded for Group P when axial or oblique loading was applied (p = 0.00). A significantly higher failure load was recorded with axial loading for both main groups. With regard to failure mode, a statistically significant difference was observed between main groups (p = 0.033), with more favorable failures detected for Group P axially.

CONCLUSIONS

Compared to the conventional endocrown system, the studied novel system improved the biomechanical behavior within tooth/restoration complex of the restored severely-destructed endodontically treated maxillary first premolar teeth, whatever the applied load type.

CLINICAL SIGNIFICANCE

The novel endocrown system using a PEKK coping veneered with cemented IPS e.max CAD can be considered a favorable promising option for restoration of severely-destructed endodontically treated premolar teeth, with more protection for residual tooth structure. It can be considered as a conservative alternative option to the conventional treatment modalities not only for normal clinical conditions, but also for parafunctional cases.

Making use of three-dimensional models of teeth, manufactured by stereolithographic technology, in practical teaching of endodontics

INTRODUCTION

Making use of 3D printed teeth models in teaching students offers an innovative approach. The mistakes made by the students at the access cavity stage were assessed with the aid of 3D models, and their overall, hands-on learning progress was evaluated.

MATERIAL AND METHODS

Ninety 3D models of teeth were constructed using stereolithographic technology and then randomly divided into 9 groups. One dentistry student was randomly assigned to each group and then performed primary access cavity in 10 identical 3D models. Then the teeth were evaluated in the order of their preparation, relative to the model tooth.

RESULTS

The material of 14 (15.5%) out of 90 teeth models sustained significant damage during the preparation. As regards the remaining 76 (84.5%) 3D models, the students committed the greatest number of mistakes on the incisors, and fewer on the molars and the least in the premolars. The difference in the number of errors between particular groups of teeth was statistically significant (P = .0001). The number of errors committed in subsequent repetitions amongst all students was significantly different for the incisors (P = .00215) and premolars (P = .00383), whereas insignificant in the case of molars (P = .77116).

CONCLUSIONS

Thanks to perfect representation of teeth anatomy; making use of 3D models in the teaching of endodontics may well be recommended as holding substantial potential in improving overall quality of training at the pre-clinical stage, with a view to appreciably reducing overall risk of encountering complications during the actual clinical work.

Long-term retention of lithium disilicate crowns with a current bioactive cement

OBJECTIVE

To determine if a recent bioactive cement provides acceptable lithium disilicate crown retention after long-term aging with monthly thermocycling.

MATERIALS AND METHODS

Extracted molars prepared with flat occlusal, 20° taper, ~4 mm axial. Prepared teeth assigned to two groups for equal mean surface areas per group. Lithium disilicate crowns fabricated with occlusal bar to facilitate removal. Crowns etched with 9.5%HF and cleaned. Cements were Ceramir Crown & Bridge QuikCap (CM) and Ketac Cem Maxicap (KC). Before cementation, specimens stored in 37°C water. Crowns cemented with 196 N force, placed in 37°C, 100% humidity oven for setting. Specimens thermocycled (5-55°C) 5000 cycles monthly for 6 months; otherwise stored in phosphate buffered saline solution. Crowns removed axially at 0.5 mm/min. Removal forces recorded and stresses calculated using areas. Independent t-test (α = 0.05).

RESULTS

Levene test not significant (P = 0.649). CM removal stresses and forces (P < 0.001) were higher (1.93 MPa, 261.4 N) compared to KC (1.06 MPa, 139.4 N). CM cement found principally on crown intaglio, KC found with most cement on prepared tooth. Chi-square significant (P < 0.001).

CONCLUSIONS

Following long-term aging with monthly thermocycling, lithium disilicate crowns were best retained by CM cement, however both cements are capable of retaining lithium disilicate crowns with preparations of ideal taper and length.

CLINICAL SIGNIFICANCE

Results serve as a basis for bioactive cement selection for retaining lithium disilicate crowns. Without optimal axial length, taper of preparation or retentive features, Ceramir Crown and Bridge QuikCap offers a bioactive cement with improved long-term retention when compared to Ketac Cem Maxicap for lithium disilicate crowns.

Long-term retention of zirconia crowns cemented with current automixed cements

STATEMENT OF PROBLEM

Automixing and dispensing cements is a straightforward approach with consistent dosing. Previous studies have demonstrated clinically significant differences in crown retention between power-liquid and paste-paste forms of the same cement, as the composition between the 2 differs. A self-adhesive modified-resin (SAMR) and a resin-modified glass ionomer (RMGI) cement, originally offered as a powder-liquid, are now in common use as paste-paste automixed cements. With the increased use of zirconia restorations, the long-term retention of zirconia crowns for these 2 automixed cements should be evaluated.

PURPOSE

The purpose of this in vitro study was to determine whether zirconia crowns cemented with 2 automixed cements provided clinically acceptable retention after 6 months of aging with monthly thermocycling.

MATERIAL AND METHODS

Extracted molars were mounted in resin and prepared with a flat occlusal surface, 20-degree taper, approximately 4-mm axial length, and with the axio-occlusal line angle slightly rounded. Prepared teeth were equally distributed into 3 cementation groups (n=12) to achieve nearly equal mean preparation surface areas for each group. Zirconia crowns (IPS ZirCAD LT) were fabricated with an added occlusal bar to facilitate removal of the cemented crowns. Cement space was set at 45 μm axially and 55 μm occlusally. After sintering and before delivery, the intaglio surfaces were airborne-particle abraded with 50-μm alumina at 275-kPa pressure for 3 seconds and then steam cleaned. Cements were the original powder-liquid RelyX Luting (RMGI; RXL) as the control, paste-paste, automixed systems RelyX Luting Plus Automix (RMGI; RXLA), and RelyX Unicem 2 Automix (SAMR; RXUA). Crowns were cemented under 196 N force, placed in an oven at 37 °C and 100% humidity during setting and then thermocycled (5 °C-55 °C) for 5000 cycles monthly for 6 months. The crowns were removed axially with a universal testing machine at 0.5 mm/min. Removal forces were recorded and dislodgement stress calculated by using the surface area of each preparation. One-way ANOVA was used for dislodgement stress and force. Chi-square test was used for cement location after testing (α=.05).

RESULTS

RXLA demonstrated considerably lower crown retention (1.3 MPa) and differed significantly (P<.001) from RXUA (3.1 MPa) and RXL (3.1 MPa). Modes of failure showed most of the cement remaining only in the crown intaglio for RXLA for all specimens, whereas half of the crowns for RXL and RXUA demonstrated cement adhesion to both dentin and the intaglio surface, indicating cohesive failure of the cement at separation. As the Levene test was significant, the Games-Howell test was used for mean differences. The χ² analysis was significant.

CONCLUSIONS

After long-term aging with monthly thermocycling, high-strength zirconia crowns were strongly retained by 2 (RXL, RXUA) of the 3 cements. Crown retention for RelyX Luting Plus Automix was less than half in comparison and with cement found only on the intaglio surface after separation.

The effect of hydrochloric acid (HCl) on permanent molars: A scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) study

It is well established that acid disposal is a potentially effective method used by criminal syndicates to hinder the identification of victims. This study documents the effects of continuous immersion in hydrochloric acid (HCl, 37%) on molars using macroscopic analysis, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The goal of this study is to aid in distinguishing visually unrecognizable fragments of dental remains when drastic changes in morphology have occurred as a result of acid exposure. Macroscopic, SEM, and EDS analysis were conducted on seven maxillary molars before and after HCl treatment. Molars reduced in weight relative to the length of time immersed in HCl and the dissolution time was over 40 hours longer than reported in previous studies, at just over 66 hours. SEM and EDS analysis showed acid-treated teeth exhibited morphological patterns such as cracking and layering visible at high magnification. Calcium/phosphorous ratios fell within the expected range of 1.6-2.5, indicating that HCl-treated teeth are still identifiable as osseous or dental tissue even when not visually identifiable as teeth. This is the first study to present SEM images of molar cementum before and after immersion in HCl and to present EDS results. This information can assist researchers and investigators in determining the presence of dental tissue in a forensic context associated with acid disposal.

Awareness, Attitude and Practice Regarding Disinfection and Handling of Extracted Teeth among the Students in a Dental College in India

Objective:

The main objective of this study is to assess about the awareness, attitude, and practice regarding disinfection and handling of extracted teeth among the students of a dental college in Odisha, India.

Materials and Methods:

The survey was done with a self-designed questionnaire distributed among the students of a dental college in Odisha, India. Data analysis was done using the Statistical Package for the Social Sciences Software (SPSS for Windows, Version 16.0., Released 2007, Chicago, SPSS Inc.) and the results obtained.

Results:

Of the many methods available, the safest and practical methods to sterilize and disinfect the extracted human teeth could be autoclaving, submersion in 10% formalin and 5.25% sodium hypochlorite solutions. In addition, it was found that there is a significant need to educate the potential handlers of such extracted teeth about the latest statuary protocol and guidelines.

Conclusion:

Most of the participants in the study were aware of the established safety protocols regarding how to handle the pathogenic specimens and were putting in practice those standardized guidelines. But still another good number of handlers need to change their casual attitude while following the safety guidelines so as to protect themselves, others and the environment from the pathogenic clinical specimens.

Effects of two disinfection/sterilization methods for dentin specimens on dentin permeability

OBJECTIVES

To investigate the effects of two disinfection/sterilization methods on the permeability of dentin specimens.

MATERIALS AND METHODS

Forty intact human third molars were freshly extracted and cut, close to the pulp chamber, into dentin disks with a 500-μm thickness. The disks were randomized (n = 20 each) into a 70% ethanol group (acid-etched dentin disks soaked in 70% ethanol for 15 min) and a steam autoclaving group (acid-etched dentin disks autoclaved for 25 min). The permeability (Lp) of each dentin disk was measured before and after either treatment using a hydraulic device, and intra- and inter-group differences in values before and after treatment were analyzed using t tests. Field emission scanning electron microscopy (FE-SEM) micrographs of the dentin surface were acquired and examined. FE-SEM samples were prepared using the critical point drying (CPD) method.

RESULTS

Immersion in 70% ethanol increased the Lp values of dentin specimens by 17%, which was not statistically significant. Steam autoclaving significantly reduced dentin permeability by 66% because the dentin collagen mesh became compact and collapsed, as detected by FE-SEM.

CONCLUSIONS

The disinfection of acid-etched dentin disks using 70% ethanol for 15 min does not significantly affect dentin permeability, whereas sterilization of acid-etched dentin disks via autoclaving significantly reduces dentin permeability.

CLINICAL RELEVANCE

Considering the influences of dentin permeability by disinfection/sterilization methods, the disinfection of the acid-etched dentin disks using 70% ethanol for 15 min could be used for the study related to dentin permeability, while the sterilization of autoclaving could not.

Human teeth biobank: Microbiological analysis of the teeth storage solution

The cross-infections may occur during handling of dental elements, affecting the health of dental practitioners and researchers. This study aimed to analyze the influence of the storage medium temperature on the bacterial contingent of the human teeth used for research purposes. Thirty human teeth were donated to the Human Teeth Biobank immediately after extraction. The teeth were cleaned with tap water and neutral soap. The teeth were randomly distributed according to the temperature of the storage solution (deionized water): at 4 °C (refrigerator) or at -10 °C (freezer) and were stored individually in sterile vials during 60 days. After this period, a microbiological analysis (CFU/mL) of the storage solutions was performed and teeth were submitted to SEM analysis. Data were analyzed by Kruskal-Wallis test followed by Dunn's post-test (p ≤ .05). Total aerobic bacteria ranged from 5.8 to 8.4 log₁₀ CFU/mL for refrigerated solution and from 1.9 to 8.5 log₁₀ CFU/mL for frozen solution. No statistical differences were found between the storage solutions (p > .05). The counts of Streptococcus spp., Lactobacillus spp., and Staphylococcus spp. were similar for both storage solutions (p > .05). SEM analysis showed spiral- and rod-shaped bacteria attached on teeth stored under 4 °C, which may suggest the presence of Treponema spp. and Lactobacillus spp. Similar morphological forms were found on teeth stored under -10 °C. A biofilm organized in honeycomb-like form was found in the frozen teeth. Cocci were eventually found in all the samples. It was concluded that bacterial growth and survival were not influenced by the temperature of the teeth storage solution.

Simplified cementation of lithium disilicate crowns: Retention with various adhesive resin cement combinations

STATEMENT OF PROBLEM

A composite resin cement and matching self-etch adhesive was developed to simplify the dependable retention of lithium disilicate crowns. The efficacy of this new system is unknown.

PURPOSE

The purpose of this in vitro study was to determine whether lithium disilicate crowns cemented with a new composite resin and adhesive system and 2 other popular systems provide clinically acceptable crown retention after long-term aging with monthly thermocycling.

MATERIAL AND METHODS

Extracted human molars were prepared with a flat occlusal surface, 20-degree convergence, and 4 mm axial length. The axio-occlusal line angle was slightly rounded. The preparation surface area was determined by optical scanning and the analysis of the standard tessellation language (STL) files. The specimens were distributed into 3 cement groups (n=12) to obtain equal mean surface areas. Lithium disilicate crowns (IPS e.max Press) were fabricated for each preparation, etched with 9.5% hydrofluoric acid for 15 seconds, and cleaned. Cement systems were RelyX Ultimate with Scotch Bond Universal (3M Dental Products); Monobond S, Multilink Automix with Multilink Primer A and B (Ivoclar Vivadent AG); and NX3 Nexus with OptiBond XTR (Kerr Corp). Each adhesive provided self-etching of the dentin. Before cementation, the prepared specimens were stored in 35°C water. A force of 196 N was used to cement the crowns, and the specimens were polymerized in a 35°C oven at 100% humidity. After 24 hours of storage at 100% humidity, the cemented crowns were thermocycled (5°C to 55°C) for 5000 cycles each month for 6 months. The crowns were removed axially at 0.5 mm/min. The removal force was recorded and the dislodgement stress calculated using the preparation surface area. The type of cement failure was recorded, and the data were analyzed by 1-way ANOVA and the chi-square test (α=.05) after the equality of variances had been assessed with the Levene test.

RESULTS

The Levene test was nonsignificant (P=.936). The ANOVA revealed the mean removal stresses, and forces did not differ for RelyX Ultimate with Scotchbond Universal (3.9 MPa; 522 N) and Multilink Automix with Multilink Primer (3.7 MPa; 511 N); both differed significantly (P=.022) from the mean for NX3 Nexus with OptiBond XTR (2.9 MPa; 387 N). For all 3 cements, the modes of failure showed cement principally on the crown intaglio, and the chi-square analysis was nonsignificant (P=.601).

CONCLUSIONS

IPS e.max Press (lithium disilicate) crowns were well retained (2.9-3.9 MPa; 387-522 N) by the 3 cement-adhesive combinations after 6 months of aging with monthly thermocycling. These results can serve as a basis for cement selection for this type of crown because the values significantly exceeded those for zinc phosphate. Cements using their matched dentin bonding agent as the ceramic primer were as successful as cements with a separate silane coupling agent.

A systematic review of randomized controlled trials on sterilization methods of extracted human teeth

Aim of this Study:

The aim was to evaluate the efficiency of different sterilization methods on extracted human teeth (EHT) by a systematic review of in vitro randomized controlled trials.

Methodology:

An extensive electronic database literature search concerning the sterilization of EHT was conducted. The search terms used were “human teeth, sterilization, disinfection, randomized controlled trials, and infection control.” Randomized controlled trials which aim at comparing the efficiency of different methods of sterilization of EHT were all included in this systematic review.

Results:

Out of 1618 articles obtained, eight articles were selected for this systematic review. The sterilization methods reviewed were autoclaving, 10% formalin, 5.25% sodium hypochlorite, 3% hydrogen peroxide, 2% glutaraldehyde, 0.1% thymol, and boiling to 100°C. Data were extracted from the selected individual studies and their findings were summarized.

Conclusion:

Autoclaving and 10% formalin can be considered as 100% efficient and reliable methods. While the use of 5.25% sodium hypochlorite, 3% hydrogen peroxide, 2% glutaraldehyde, 0.1% thymol, and boiling to 100°C was inefficient and unreliable methods of sterilization of EHT.

Vinegar as a disinfectant of extracted human teeth for dental educational use

Context:

Extracted human teeth are routinely used in dentistry to learn technical and preclinical skills. Centers for Disease Control and Prevention (CDC) has adopted guidelines for infection control of extracted teeth used for research and teaching, requiring that teeth be sterilized before use. Many of the proposed disinfection methods starting from use of formalin, sodium hypochlorite and to autoclaving have their own drawbacks and may not be practical.

Aim:

To assess the effectiveness of vinegar for disinfection/sterilization of extracted human teeth.

Materials and Methods:

A total of 80 extracted non-carious human teeth were kept in seven disinfectant media—10% formalin, 3% hydrogen peroxide, 5.25% sodium hypochlorite, 70% alcohol, vinegar, neem extract and normal saline. Ten samples were placed in each disinfectant individually for a period of 7 days, at room temperature. In all, 10 teeth were treated with microwave irradiation at 650 W for 3 min. Later, teeth from each group were placed individually in separate test tubes containing 10 ml of tryptic soy broth at 37°C for 48 h to observe the evidence of growth of microorganisms. Semiquantitative analysis of all the samples was done in Clade agar at 37°C for 48 h.

Statistical Analysis Used:

The number of teeth disinfected in each group was compared using Chi square test.

Results:

10% formalin, 3% hydrogen peroxide and vinegar were totally effective. The result was statistically significant with a Chi square value of 61.414 and P < 0.001.

Conclusions:

Vinegar can be used as an effective disinfectant medium for extracted human teeth.