Precise tooth design using deep learning-based templates

OBJECTIVES

In prosthodontic procedures, traditional computer-aided design (CAD) is often time-consuming and lacks accuracy in shape restoration. In this study, we combined implicit template and deep learning (DL) to construct a precise neural network for personalized tooth defect restoration.

METHODS

Ninety models of right maxillary central incisor (80 for training, 10 for validation) were collected. A DL model named ToothDIT was trained to establish an implicit template and a neural network capable of predicting unique identifications. In the validation stage, teeth in validation set were processed into corner, incisive, and medium defects. The defective teeth were inputted into ToothDIT to predict the unique identification, which actuated the deformation of the implicit template to generate the highly customized template (DIT) for the target tooth. Morphological restorations were executed with templates from template shape library (TSL), average tooth template (ATT), and DIT in Exocad (GmbH, Germany). RMSestimate, width, length, aspect ratio, incisal edge curvature, incisive end retraction, and guiding inclination were introduced to assess the restorative accuracy. Statistical analysis was conducted using two-way ANOVA and paired t-test for overall and detailed differences.

RESULTS

DIT displayed significantly smaller RMSestimate than TSL and ATT. In 2D detailed analysis, DIT exhibited significantly less deviations from the natural teeth compared to TSL and ATT.

CONCLUSION

The proposed DL model successfully reconstructed the morphology of anterior teeth with various degrees of defects and achieved satisfactory accuracy. This approach provides a more reliable reference for prostheses design, resulting in enhanced accuracy in morphological restoration.

CLINICAL SIGNIFICANCE

This DL model holds promise in assisting dentists and technicians in obtaining morphology templates that closely resemble the original shape of the defective teeth. These customized templates serve as a foundation for enhancing the efficiency and precision of digital restorative design for defective teeth.

Effect of low-temperature degradation and sintering protocols on the color of monolithic zirconia crowns with different yttria contents

This study investigated the effects of low-temperature degradation (LTD) on the L*, a*, and b* values of highly translucent zirconia crowns. Four types of zirconia disks with different yttria contents (IPS e.max ZirCAD LT, IPS e.max ZirCAD MT, IPS e.max ZirCAD MT Multi, IPS e.max ZirCAD Prime, Ivoclar) and two shades (A2 and BL) were used. A crown was manufactured using four types of zirconia and LTD treated. Color measurements were performed, and the color difference (ΔE00) before and after LTD was calculated. The microstructure was determined through X-ray fluorescence and X-ray diffractometry. Highly translucent zirconia crowns showed greater changes in the a* and b* values than in the L* value after LTD, regardless of the shade. The Multi2 crowns exhibited a discernible color change due to the LTD treatment. The X-ray fluorescence results did not reveal any apparent change in the microstructure between sintering programs for all zirconia specimens.

New adhesive protocol improves shear bond strength of Polyetherketoneketone (PEKK)

OBJECTIVE

Inert surface of Polyetherketoneketone (PEKK) jeopardizes resin bonding. This study aimed to present a new adhesive protocol to improve PEKK bonding.

METHODS

A total of 360 PEKK blocks were milled, polished (maximum roughness of 0.20 µm), and randomly assigned to groups. The new protocol was applied (n = 36) and compared to conventional treatments (no treatment; sandblasting (110-µm Al2O3 and silica); no adhesive; Visiolink (Bredent); and PEKKbond (AnaxDent)) (n = 36). For the new protocol, the surface was blasted (110 µm Al2O3 and 96% isopropyl alcohol at 60 psi), followed by 96% isopropyl alcohol washing, and air drying. PEKKbond was applied (dried for 3 min at 77 °C), followed by Visiolink (dried for 3 min at 60 °C); both light-cured for 3 min (800 mW/cm2). Preopaque (GC Europe) and Opaque (AnaxDent) were applied and light-cured (5 min). Morphological topography was analyzed, and flowable gingiva-colored composite (AnaxGum, AnaxDent) was bonded. All specimens were aged for 24 h and thermocycled (5000 cycles, 5-55 °C). Shear bond strength (SBS) was measured (MPa) and data were analyzed by two-way ANOVA, Tukey, and Weibull moduli estimation (α = 0.05).

RESULTS

The highest SBS values were found in the new protocol (p < 0.05), regardless of aging. Thermocycling reduced SBS (p < 0.05), while Al2O3 and PEKKbond produced higher SBS values than silica and Visiolink, respectively (p < 0.05).

SIGNIFICANCE

The new protocol strongly improves PEKK adhesiveness, and this can reflect in the longevity of prostheses.

Machine learning model to predict the width of maxillary central incisor from anthropological measurements

PURPOSE

To improve smile esthetics, clinicians should comprehensively analyze the face and ensure that the sizes selected for the maxillary anterior teeth are compatible with the available anthropological measurements. The inter commissural (ICW), interalar (IAW), intermedial-canthus (MCW), interlateral-canthus (LCW), and interpupillary (IPW) widths are used to determine the width of maxillary central incisors (CW). The aim of this study was to develop an automated approach using machine learning (ML) algorithms to predict central incisor width in a young Turkish population using anthropological measurements. This automation can contribute to digital dentistry and clinical decision-making.

METHODS

In the initial phase of this cross-sectional study, several ML regression models-including multiple linear regression (MLR), multi-layer-perceptron (MLP), decision-tree (DT), and random forest (RF) models-were validated to confirm the central width prediction accuracy. Datasets containing only male and female measurements, as well as combined were considered for ML model implementation, and the performance of each model was evaluated for an unbiased population dataset.

RESULTS

Compared with the other algorithms, the RF algorithm showed improved performance for all cases, with an accuracy of 96%, which represents the percentage of correct predictions. The plot reveals the applicability of the RF model in predicting the CW from anthropological measurements irrespective of the candidate's sex.

CONCLUSIONS

These results demonstrated the possibility of predicting central incisor widths based on anthropometric measurements using ML models. The accurate central incisor width prediction from these trials also indicates the applicability of the proposed model to be deployed for enhanced clinical decision-making.

Reframing perceptions in operative dentistry relating evidence-based dentistry and clinical decision making: a cross-sectional study among Jordanian dentists

BACKGROUND

The aim of the current study was to investigate current dental practice in operative dentistry in Jordan, and the relationship between evidence-based dentistry in caries research and decision making in clinical practice in operative dentistry.

MATERIALS AND METHODS

This cross-sectional study was conducted through a survey of dentists in Jordan. The survey aimed to explore the degree of knowledge and practice of evidence-based dentistry in caries research the dentists possess regarding clinical decision making in operative dentistry. The sample size was composed of (5811) dentists whom registered in Jordan Dental Association database. Descriptive statistics were generated and Chi-square test was used to examine associations between the different variables and the significance level was set at P < 0.05.

RESULTS

4000 responses were collected from the web-survey, response rate (68.83%). Nearly half of the surveyed dentists focus on the chief complaint of their patients (n = 2032, 50.8%) rather than doing full mouth assessment. Nearly two-thirds of dentists (n = 2608, 65.2%) treat lesions confined to enamel with operative treatment. Half of dentists use operative treatment when asked about the routine management of radiographically detected proximal caries confined to enamel. When treating incipient lesions, the majority (n = 3220, 80.5%) use preventive treatment. Three-quarters of dentists (n = 2992, 74.8%) treat deep dentinal caries by removing just the soft infected carious dentin, and treated old failed restorations with replacement.

CONCLUSION

In operative dentistry, the evidence-based research is not implemented clinically. To optimize relationship between evidence-based dentistry and clinical decision-making, dental curriculum has to be updated and modified constantly.

A customized metal guide for controllable modification of anterior teeth contour prior to minimally invasive preparation

Objective

Optimal tooth reduction is a key requirement for aesthetics, function, and the longevity of fixed restorations. Research has demonstrated that controlled and conservative tooth preparation is crucial for the long-term success of adhesive restorations. Different techniques of fabricating reduction guides have been previously reported in literature. The present technical note describes the fabrication technique and clinical application of a customized metal preparation reduction guide.

Material and method

Patient presented with tilted maxillary left central incisor. The flared-out part of the tooth was modified prior to veneer restoration preparation. Resin pattern reduction guide was fabricated on the diagnostic cast with a window on the tilted mesial portion of the tooth. After intraoral evaluation, resin pattern guide was casted. Metal reduction guide was place intraorally and reduction was provided on the exposed surface of the tooth. After the removal of the tilted portion, a harmonious arch form allowed the clinician to provide adequate evaluation and preparation for veneer restorations.

Results

The device demonstrated good practical value, allowing for selective and controlled reduction of tooth structure, and definitive protection of adjacent tooth surfaces from iatrogenic damage. The clinical outcome successfully addressed the patient's restorative and aesthetic needs, and the veneer was stable 2 years postoperatively.

Conclusion

Use of a metal guide assists clinicians to provide a more predictable reduction of a desired tooth surface, while decreasing the risk of compromising the other/adjacent tooth surfaces.

Mathematical Tooth Proportions: A Systematic Review

PURPOSE

The aim of this systematic review was to evaluate and compare three commonly used proportions that include the golden proportion, golden percentage, and Recurring Esthetic Dental (RED) proportion to identify which of the mathematical formulas, if any, can be used to provide predictable and repeatable esthetic clinical outcomes.

METHODS

A comprehensive search of electronic databases that included EBSCO, ProQuest, SCOPUS, Science Direct, Wiley, Google Scholar and PubMed was conducted using the terms: "golden proportion," "golden percentage," and "Recurring Esthetic Dental (RED) proportions" alone or in concurrence with one or both ensuing terms: "tooth proportions" and "esthetic tooth proportions." In addition, the following journals were hand searched for relevant articles: Journal of Prosthodontics, Journal of Prosthetic Dentistry and Journal of Esthetic and Restorative Dentistry. Related citations were also considered.

RESULTS

Tooth proportions varied substantially in the natural dentition. No studies revealed findings that supported the use of one mathematical formula to predict esthetic success. The golden proportion is present between the central to lateral incisor in some cases, but rarely between the lateral incisor and the canine. When compared to the other proportions, the golden percentage provided better starting points for tooth shape and size, but only when values were adjusted to consider other factors such as ethnicity and/or facial proportions.

CONCLUSION

Mathematical formulas did not provide consistent results that would allow for their use as a standardized guide for esthetically pleasing smiles. Although the golden percentage may be a good starting point if the percentages are adjusted on a case-by-case basis, generalized esthetic ideals cannot be determined by a mathematical formula and are open to interpretation by both the clinician and the patient.

Effects of abutment tooth and luting agent colors on final color of high-translucent zirconia crowns

PURPOSE

This study aimed to evaluate the effects of the tooth portion evaluated and the colors of the abutment tooth and resin luting agent on the final color of monolithic zirconia crowns.

METHODS

Monolithic zirconia crowns were fabricated for left maxillary central incisors using two shades (A2 and A3) of highly translucent monolithic zirconia disks. A model of the abutment tooth was fabricated using resin core materials (white: W; dentin: D). The color of the crowns was measured with try-in pastes (clear: C; brown: B) as a resin-luting agent substitute. The measurement was performed after placing the crown on the model with the attached abutment tooth with try-in paste. The color of three labial portions (cervical, body, and incisal) was evaluated using a dental spectrophotometer. The color difference (ΔE) between the CIELab values of the zirconia disks and the final me asurement of zirconia crowns was calculated.

RESULTS

The ΔE between the crown of the A2 shade and the zirconia disk of the A2 shade had the highest ΔE value in the body portion with W-B (ΔE=3.92). Similarly, the A3 shade had the highest ΔE value in the cervical portion, with W-B (ΔE=4.27). The results of three-way ANOVA showed that the ΔE values were influenced by the tooth portion evaluated and the color of the abutment tooth.

CONCLUSIONS

The final color of the monolithic zirconia crowns was significantly in fluenced by the tooth portion evaluated and the color of the abutment tooth.

Critical review about two myths in fixed dental prostheses: Full-Coverage vs. Resin-Bonded, non-Cantilever vs. Cantilever

The purpose of this review was to assess the literature regarding four types of fixed dental prostheses (FDPs)/resin-bonded FDPs (RBFDPs) to provide clinicians with a comparative overview of two myths: “RBFDPs are easy to debond in patients’ mouths” and “cantilever RBFDPs still have some clinical problems, especially in terms of overloading the abutment teeth and being easy to debond”. A total of 782 papers were identified, 753 of which were judged unsuitable and thus excluded, leaving a total of 29 articles for inclusion in this review. The results indicated that 1) Two-retainer RBFDPs achieve clinical results comparable to full-coverage three-unit FDPs; 2) Cantilever RBFDPs show excellent long-term clinical outcomes (especially in incisor teeth) compared with other FDPs; 3) RBFDPs typically show less catastrophic failure than conventional FDPs, rebonding should be considered when debonding occurs; and 4) Cantilever RBFDPs can be recommended as defect replacement prostheses for maxillary lateral incisors and mandibular incisor teeth.

Scientific field: Prosthodontics, Adhesive dentistry, Esthetic dentistry

Current status and perspective of CAD/CAM-produced resin composite crowns: a review of clinical effectiveness

The purpose of the present review was to survey the available literature on computer-aided design/computer-aided manufacturing (CAD/CAM)-produced resin composite materials to provide clinicians with a current overview of the key components necessary for daily clinical use. An electronic search was conducted in the PubMed database. Peer-reviewed articles in English language on the use of resin composites in CAD/CAM dental crowns were included. A total of 122 full-text articles were identified, 15 of which were selected during the initial review. Two additional articles were also discovered through a manual search, to obtain a final total of 17 articles included in the present review. Of these, 16 were to in vitro studies, and one was an in vivo study. Findings from the in vitro studies indicate that resin composite block materials for CAD/CAM applications demonstrate excellent physical properties and are appropriate for the clinical restoration of premolars and molars. However, the in vivo study reported a low 3-year success rate, but high survival rate for resin composite CAD/CAM crowns placed in the premolar region. The key to ensuring the successful prognosis of a resin composite CAD/CAM crown is to ensure that all steps—such as proper case selection, abutment tooth preparation, occlusal adjustment, and bonding—are accurately performed.

Influence of Social Media towards the Selection of Hollywood Smile among the University Students in Riyadh City

Background:

Hollywood smile refers to the aesthetic development of dental appearance inspired by the beauty displayed by the movie actors. Therefore, the present study was conducted to determine the extent of social media effect on the decision making of university students towards selecting Hollywood smile as the choice of their aesthetic treatment.

Materials and Methods:

This cross-sectional study was conducted by utilizing a self-designed closed-ended questionnaire among under-graduate students from the various public as well as private universities of Riyadh city. The questionnaire was constructed online using Google forms and began with questions related to demographics; questions like Do you notice celebrity's smile on social media? Have you visited a dentist solely after getting inspired by a celebrity's smile? etc., Responses were on a 5-point likert scale ranging from highly dissatisfied or strongly disagree to highly satisfied or strongly agree whenever applicable. Chi-square test was used to compare the differences among the groups with the value of significance kept under 0.05 by using SPSS version 19.

Results:

The majority of the female participants reported noticing the celebrity's smile on social media. Influence by the celebrity smiles on social media was found more in the older age group participants. However, the term “Hollywood smile” was slightly more known among the younger aged participants.

Conclusion:

The overall effect of social media in decision making of opting for Hollywood smile was found to be moderate. More studies should be conducted to investigate how much social medial is effecting the perceptions of youngsters.

Dentist-Ceramist Communication: Protocols for an Effective Esthetic Team

No matter how skilled and well trained esthetic dentists or technicians may be, they cannot deliver results without a proper partnership. Close ceramist-clinician communication is a critical component of successful esthetic dentistry. In order to design an esthetic vision, convey this vision to the patient, and then execute the vision successfully, there must be effective communication between the ceramist, the clinician, and (most importantly) the patient. This article highlights some of the authors' philosophies, as well as an overview of the key communication protocols that have proved effective for this team.

A Beginning Guide for Dental Photography: A Simplified Introduction for Esthetic Dentistry

Photography is one of the most important skills dentists need to master in order to perform esthetic dentistry at a high level. Today, digital single-lens reflex cameras are commonplace. Young dentists have grown up with Internet, smartphones, and online platforms exposing them, and their patients, to cases that other dentists have shared, increasing the awareness and popularity of esthetic-focused treatment. This article provides readers with a simplified and attainable approach to begin the dental photography journey, as well as increase skill level, depending on practice style and desired investment.

The reproducibility of electronic color measurements of the marginal gingiva

INTRODUCTION

This study evaluated the reproducibility of electronic color determination system evaluations of the marginal gingiva, which could be important for adhesive cervical fillings or prosthetic restorations that imitate the gingiva.

MATERIAL AND METHODS

In 50 subjects, the L*, a*, and b* color coordinates were evaluated five times at a point in the marginal area of a central incisor using different electronic color determination systems: (SP) Shadepilot, (ES) Easyshade, (CE) Crystaleye, and (SV) X-Rite. The mean color difference (ΔE) and its standard deviation between the five measurements from each participant were calculated separately for each device. Further ICC for interdevice reliability was determined.

RESULTS

The L*, a*, and b* color coordinates and ΔE values differed significantly among the systems (p < 0.001). Within each patient and measurement system, ΔE ranged from 1.4 to 3.2 (SD 1.1-2.5), L* from 2.6 to 5.7 (SD 2.6-5.7), a* from 11.9 to 21.3 (SD 3.6-3.9), and b* from 15.1 to 28.9 (SD 1.7-4.3). Interdevice reliability ranged between 0.675 and 0.807.

CONCLUSIONS

Color determination of the marginal gingiva using the electronic tooth color determination systems tested herein showed limited reproducibility. The results obtained with the different measurement systems differed enormously.

CLINICAL RELEVANCE

These results show that the electronic color measurement devices tested allow no high reproducible determination of color coordinates of the marginal gingiva.

Adhesion to high-performance polymers applied in dentistry: A systematic review

OBJECTIVE

The aim of this systemic review, conducted in accordance with the PRISMA statement, was to investigate the impact of surface pretreatments on the bonding strength of high performance polymers (HPPs).

METHODS

Eight databases were searched through March 2019. Risk of bias was assessed and random effects meta-analyses were applied to analyze mean differences in shear bond strength (SBS) and tensile bond strength (TBS), considering surface pretreatments and bonding agents after 24h and thermocycling.

RESULTS

A total of 235 relevant titles and abstracts were found, yielding 11 final selections. Low risk of bias was observed in most studies. For polyetheretherketone (PEEK) specimens, random-effect models showed that, compared to non-treated controls, pretreatments associated with Visio.link® (Bredent, Senden, GE) increased TBS by 26.72MPa (95% confidence interval (CI), 19.69-33.76; p<0.00001) and increased SBS by 4.86MPa (95% CI, 2.61-7.10; p<0.00001). Air abrasion improved SBS by 4.90MPa (95% CI, 3.90-5.90; p<0.00001) (50μm alumina) and 4.51MPa (95% CI, 1.85-7.18; p=0.0009) (silica-coated CoJet). In comparison to non-treated controls, Visio.link® and Signum PEEK Bond® (Heraeus Kulzer, Hanau, GE) increased SBS by 33.76MPa (95% CI, 18.72-48.81; p<0.00001) and 33.28MPa (95% CI, 17.48-49.07; p<0.00001), respectively. No differences were found between Visio.link® and Signum PEEK Bond® or Monobond Plus/Heliobond® (Ivoclar Vivadent, Schaan, LH) (p>0.05). Similar results were observed for polyetherketoneketone (PEKK) specimens.

SIGNIFICANCE

This review shows improved HPP bonding following the application of various surface pretreatments, including air abrasion and bonding agents.

Concealment effect of resin infiltration on incisor of Grade I molar incisor hypomineralization patients: An in vivo study

Context

Molar incisor hypomineralization (MIH) is a commonly occurring esthetic setback among patients. Depending on the graveness of the lesion, esthetics of MIH can be improved by treatments such as enamel microabrasion, bleaching, composite resin bonding, and the combination of some or all of these techniques.

Aim

The aim of this study is to evaluate the esthetic results of resin infiltration treatment on incisors with Grade I molar incisor MIH.

Materials and Methods

A total of 22incisor lesions with MIH were infiltrated with resin. Photographs were captured before infiltration, just after infiltration, and 6 months after infiltration. The photographic evaluation was done by the CIE L*a*b* scoring method. The means of each parameter such as ΔL and ΔE were calculated.

Statistical Analysis

ANOVA in conjunction with Turkey's post hoc test was used to evaluate the means.

Results

The total color change observed was equal just after treatment and 6 months after treatment, with no statistically significant difference (P = 0.87) between these two time points. The mean of difference in total color change (ΔE₃) of white tooth discoloration was 13.2 SD 6.8, showing an overall color change.

Conclusion

Infiltration can conceal the white opaque appearance of Grade I MIH lesions, and also reduction in lesion whiteness is seen with time.

The application of parameters for comprehensive smile esthetics by digital smile design programs: A review of literature

Cosmetic dentistry is increasingly becoming an issue of concern to patients who hope to improve their smile. A systematic and comprehensive dentofacial analysis must be performed before commencing esthetic treatment. Several computer software programs have been developed for digital smile design (DSD) to assist clinicians in this process. This article compares DSD programs commonly used in cosmetic dentistry and their ability to assess esthetic parameters. A literature review was performed of current dentofacial aesthetic parameters and clinical applications of computer technology to assess facial, dentogingival and dental esthetics. Eight DSD programs (Photoshop CS6, Keynote, Planmeca Romexis Smile Design, Cerec SW 4.2, Aesthetic Digital Smile Design, Smile Designer Pro, DSD App and VisagiSMile) were compared. Photoshop, Keynote and Aesthetic Digital Smile Design included the largest number of esthetic analysis parameters. Other studied DSD programs presented deficiencies in their ability to analyze facial esthetic parameters but included comprehensive dentogingival and dental esthetic functions. The DSD App, Planmeca Romexis Smile Design, and Cerec SW 4.2 were able to perform 3D analysis; furthermore, Cerec SW 4.2 and PRSD could be used jointly with CAD/CAM. The DSD App and Smile Designer Pro are available as mobile phone applications. It can be concluded that despite the fact that they were not specifically designed for dental diagnosis, Photoshop CS6 and Keynote provide a more comprehensive smile analysis than most specialized DSD programs. However, other program functions should also be considered when deciding which DSD program is applicable to individual clinical setups.

Analysis of gaze points for mouth images using an eye tracking system

PURPOSE

We aimed to clarify whether people stare at non-esthetic restorations by analyzing the gaze point of laypersons looking at mouth images with intraoral non-esthetic restoration.

METHODS

The gaze points of 47 laypersons who do not visit dentists were measured using an eye tracker. The stimuli were 18 photographs of mouths with or without a non-esthetic tooth restoration, each randomly shown for 5s. The analysis sites included a tooth with non-esthetic restoration and the same tooth on the opposite side of the mouth. We measured the proportion of participants who first fixated on each analysis site, and total fixation time for each site.

RESULTS

In images without non-esthetic restorations, a similar proportion of participants first fixated on each analysis site. However, more participants first fixated on non-esthetic restorations when the images contained them. Total fixation time for each site did not differ significantly between the left and right sides in the images without non-esthetic restoration (P>0.05). Participants fixated on the non-esthetic restoration significantly more in the images containing them (P<0.01).

CONCLUSIONS

Within the limitations of this study, the present findings suggest that in photographs of the mouth with non-esthetic restoration on either side, the non-esthetic restoration is first gazed before the opposite side. In addition, the non-esthetic restoration is gazed longer than the opposite side, and there was no major difference in the fixation time regarding the state of non-esthetic restoration.

Lasers: The Magic Wand in Esthetic Dentistry!!

In this era of fast developing technologies and innovative ideas, the need for faster treatment has become a necessity. Treatment with lasers that is much less time-consuming and painless is accepted and appreciated by the patient. Use of Lasers is not new; they have been in use for decades since their development by Maiman in 1960. Lasers have travelled a long way from ruby lasers to erbium lasers and are being fondly used in every aspect of dental treatment. This article aims at elaborate the use and applications of lasers in the field of esthetic dentistry.

Semidirect Restorations in Multidisciplinary Treatment: Viable Option for Children and Teenagers

Due to the esthetic necessity required nowadays, the multidisciplinary treatment became a fundamental step in the restoration success. When the patient exhibits dental agenesis of one or more elements, he can show difficulty in social interactions. The age of the patient is a limiting factor to esthetic procedures, however, it should be evaluated as a real indicative with each case. The utilization of semi-direct restorations is a viable option due the cost, esthetic and improvement of physical and mechanical properties. The purpose of this paper is to present a case detailing the confection and cementation of anterior semi-direct restorations aimed at an anatomic reestablishment associated with integrated treatment with periodontics and orthodontics.

FEA and microstructure characterization of a one-piece Y-TZP abutment

OBJECTIVES

The most important drawback of dental implant/abutment assemblies is the need for a fixing screw. This study aimed to develop an esthetic one-piece Y-TZP abutment to suppress the use of the screw.

METHODS

Material characterization was performed using a bar-shaped specimen obtained by slip-casting to validate the method prior to prototype abutment fabrication by the same process. The mechanical behavior of the prototype abutment was verified and compared with a conventional abutment by finite element analysis (FEA). The abutment was evaluated by micro-CT analysis and its density was measured.

RESULTS

FEA showed stress concentration at the first thread pitch during installation and in the cervical region during oblique loading for both abutments. However, stress concentration was observed at the base of the screw head and stem in the conventional abutment. The relative density for the fabricated abutment was 95.68%. Micro-CT analysis revealed the presence of elongated cracks with sharp edges over the surface and porosity in the central region.

SIGNIFICANCE

In the light of these findings, the behavior of a one-piece abutment is expected to be better than that of the conventional model. New studies should be conducted to clarify the performance and longevity of this one-piece Y-TZP abutment.