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1.
Statement of problem
An assessment of the evidence for the antagonist enamel wear of tooth-supported monolithic zirconia posterior crowns is lacking.Purpose
The purpose of this systematic review was to identify and summarize clinical studies related to the antagonist enamel wear of tooth-supported monolithic zirconia posterior crowns.Material and methods
PubMed, Embase, and Cochrane library searches were performed and complemented by manual searches from database inception to December 25, 2017, for title and abstract analysis.Results
Initially, 198 articles were obtained through database searches. Twenty-one articles were selected for full-text analysis, and 5 studies met the inclusion criteria. Because of the heterogeneity in design, surface treatment, measurement methods, and wear parameters, a meta-analysis was not possible. The selected studies were analyzed regarding the antagonist natural enamel wear of zirconia, measurement methods, and surface treatment. The results of the antagonist enamel wear varied widely, which made comparing them scientifically with absolute values difficult.Conclusions
This review indicated that the antagonist enamel wear of zirconia was similar to or more than that of natural teeth but less than that of metal-ceramics. Additional properly designed, longer follow-up clinical trials with larger sample sizes are needed to evaluate the antagonist enamel wear of monolithic zirconia crowns in vivo. 相似文献2.
Seung-Won Yang Jong-Eun Kim Yooseok Shin June-Sung Shim Jee-Hwan Kim 《The Journal of prosthetic dentistry》2019,121(3):417-425
Statement of problem
Zirconia is a widely used restorative material. However, phase transformation on clinical application of zirconia has not yet been studied.Purpose
The purpose of this study was to evaluate the wear, surface roughness, and aging associated with polished translucent zirconia in both in vitro and clinical experiments.Material and methods
In vitro experiments were performed with Rainbow and Katana zirconia blocks and natural tooth enamel as the control. They were subjected to 100 000 loading cycles with a maxillary premolar antagonist. All specimens were analyzed for wear, and the zirconia specimens were evaluated for surface roughness and monoclinic phase (m-phase) transformation by X-ray diffractometry before and after cyclic loading. The clinical study included participants who required single-crown implant-supported restorations replacing the first or second molar. The participants received Rainbow or Katana zirconia prostheses (n=15, each). For wear analysis, impressions of each prosthesis, antagonist, and adjacent tooth were made at 1 week and 6 months after crown delivery. The occlusal relationship of the crowns in maximum intercuspation was evaluated by using the T-Scan 8 occlusal diagnostic system. The degree of transformation of zirconia to the m-phase was measured by using X-ray diffractometry of the crowns after 6 months of use.Results
Zirconia induced significantly greater enamel wear than the natural tooth control. Katana specimens exhibited significantly greater wear and surface roughness than the Rainbow specimens. The degrees of antagonistic wear and zirconia phase transformation in the clinical experiment were significantly greater than those in the in vitro experiment. The Katana groups showed significantly higher m-phase levels than the Rainbow groups.Conclusions
Phase transformation of zirconia occurs within 6 months of clinical use, and the wear and degrees of phase transformation varied according to the zirconia product used. 相似文献3.
Yiyi Zhang Yuxuan Liu Yahu She Ye Liang Fei Xu Changyun Fang 《Journal of endodontics》2019,45(3):316-321
Introduction
The purpose of this study was to predict the fracture resistance of an endodontically treated first maxillary molar with diverse access cavities using the extended finite element model (XFEM).Methods
Based on micro–computed tomographic data of first maxillary molars, the model of a natural tooth and 3 endodontically treated teeth with conservative endodontic cavity, modified endodontic cavity, and traditional endodontic cavity were generated. Four static loads (800 N in total) were applied vertically to the contact points. The distributions of von Mises stress and maximum principal stress were calculated. XFEM was performed to simulate crack initiation and propagation in enamel and dentin.Results
In the cervical region, larger stress concentration areas were found in the modified endodontics cavity and the traditional endodontic cavity compared with the natural tooth and the conservative endodontic cavity. Von Mises stress was concentrated around the palatal root, and tensile stress was concentrated on the mesiobuccal root. The XFEM results showed that the cracks in the enamel were initiated from the mesial groove, propagated to the central fossa, and finally initiated the damage in the dentin.Conclusions
The fracture resistance of an endodontically treated tooth was increased by preparing the conservative endodontic cavity. The fracture of the maxillary first molar originated from the mesial groove of the enamel, propagated through the groove, and finally induced the damage in the dentin. 相似文献4.
Oral Cenk Aktas Wolfgang Metzger Ayman Haidar Yahya Açil Aydin Gülses Jörg Wiltfang Catharina Marques Sacramento Frank Philipp Nothdurft 《Journal of cranio-maxillo-facial surgery》2019,47(4):661-667
Background
Promoting the directional attachment of gingiva to the dental implant leads to the formation of tight connective tissue which acts as a seal against the penetration of oral bacteria. Such a directional growth is mostly governed by the surface texture.Material and methods
In this study, three different methods, mechanical structuring, chemical etching and laser treatment, have been explored for their applicability in promoting cellular attachment and alignment of human primary gingival fibroblasts (HGFIBs).Results
The effectiveness of mechanical structuring was shown as a simple and a cost-effective method to create patterns to align HGIFIBs.Conclusion
Combining mechanical structuring with chemical etching enhanced both cellular attachment and the cellular alignment. 相似文献5.
Background
This study was undertaken to quantify how the Great Recession impacted the demand for general oral health care and orthodontic care in the United States. The authors conducted an analysis to help dentists anticipate changes in demand for care during future economic downturns.Methods
The authors analyzed Medical Expenditure Panel Survey data for the period 2003 through 2015. Data plotting for the various factors considered showed patient demand before, during, and after the Great Recession, including an indication of postrecession recovery. Statistical significance across time was determined using a χ2 test. The point estimates and statistical inferences took into account the complex survey design of the Medical Expenditure Panel Survey.Results
General dentist visits declined slowly and steadily during the Great Recession, reaching a low of 38.4% in 2010, and have not shown significant signs of recovery. Orthodontic visits also declined to an all-time low of 2.5% in 2010, although they have somewhat recovered. Out-of-pocket expenditures were lower in 2015 than in 2003 for general dental and orthodontic care.Conclusion
The effects of the Great Recession resulted in a decrease in the demand for oral health care, differing for general oral health care and orthodontic care.Practical Implications
These findings, especially in combination with leading indicators for economic downturns, will allow dentists to better plan and use strategies for maintaining practice stability during periods of reduced demand for care. 相似文献6.
Lisa A. Lang Sarah E. Hansen Norma Olvera Sorin Teich 《The Journal of prosthetic dentistry》2019,121(4):611-617
Statement of problem
Identifying factors that affect the clinical outcomes of implant therapy is important.Purpose
The purpose of this retrospective study was to determine whether implant location was a factor affecting the complication and failure rates of single-tooth implant-supported restorations in a predoctoral setting.Material and methods
The charts of 431 patients treated with a surgically placed dental implant and restored with a single crown in the predoctoral clinic were analyzed. Data on implant location, type of complication (surgical or prosthetic), and type of failure were collected and analyzed according to implant location using the Fisher Exact Test and Mantel-Haenszel Exact Chi Square Test analysis (α=.05).Results
The charts revealed 158 complications (68 surgical and 90 prosthetic) in 110 patients, and 3.9% of the implants failed. No statistically significant difference was found between the number of surgical complications or prosthetic complications in the maxilla and the mandible (P=.469).Conclusions
Jaw location (maxilla compared with mandible) of the implant had no statistically significant impact on the incidence of surgically or prosthetically related complications. No statistically significant difference was found in overall implant failures, surgical failures, and prosthetic failures between maxillary and mandibular implants. 相似文献7.
Paulo Valdeci Worm Guilherme Finger Tobias Ludwig do Nascimento Carla Bittencourt Rynkowski Marcus Vinicius Martins Collares 《Journal of cranio-maxillo-facial surgery》2019,47(5):715-719
Objective
To evaluate the quality of life in patients with moderate or large cranial bone defects before and after late cranioplasty.Methods
Authors performed a prospective clinical trial including all consecutive patients that filled inclusion criteria during a period of 1 year. All patients answered the quality of life SF-36 questionnaire in 5 different times. Besides authors gathered information about the primary trauma and demographic characteristics.Results
A total of 70 consecutive patients were admitted to the hospital during the study period, and 62 were included in the project. Cranioplasty statistically improved patients' quality of life in all 8 domains after a 24 months follow-up.Conclusion
Cranioplasty has a significant impact over the quality of life in brain trauma victims who survived the primary trauma and harbor a large cranial bone defect. 相似文献8.
Seung Gyun Chu Joon Seok Lee Jeong Woo Lee Jung Dug Yang Ho Yun Chung Byung Chae Cho Kang Young Choi 《Journal of cranio-maxillo-facial surgery》2019,47(3):383-388
Importance
Conventional plating systems include titanium plates for the fixation of facial bone fractures. However, titanium plates result in artifacts on computed tomography images and appear unstable on magnetic resonance images. Therefore, absorbable plates have been widely used for the fixation of facial bone fractures of late in Asia.Objective
To compare stability and symmetry among four different absorbable plates used for internal fixation of zygomaticomaxillary complex fractures.Participants
The subjects were patients with zygomaticomaxillary complex fractures that were diagnosed and treated by internal fixation with absorbable plates between January 2012 and April 2018. Patients aged ≤14 years and ≥76 years were excluded. Patients with other fracture types were also excluded.All patients underwent surgery within 2 weeks of the injury.Intervention
Internal fixation was performed with one of four types of absorbable plates, namely Inion®, Polymax®, Osteotrans®, and Biosorb®.Main outcome measures
The stability of the four plates was investigated by evaluation of the orbital height ratio (A’/A), zygoma angle (a’/a), distance (b’/b) from the midline, and gap (c) of the temporal process on three-dimensional facial computed tomography images obtained before, 3 weeks after, and 3–6 months after surgery. Any plate-associated complications were recorded.Results
In total, 400 patients were enrolled, and there were 100 patients in each of the four groups. There were no significant differences with regard to postoperative stability and relapse among the four plates. Moreover, facial symmetry showed no changes over time in any group. Complications such as infection and sensory disturbance were not frequent. All plates except Biosorb® were palpable for more than 6 months after surgery, with Osteotrans® remaining palpable for several years.Conclusions and relevance
Our findings suggest that all four types of absorbable plates are useful for treating isolated zygomaticomaxillary complex fractures. While Biosorb® is unsuitable for severe comminuted fractures. Polymax® and Inion® are not bendable at room temperature. It is important to select an appropriate absorbable plate according to each patient’s condition and the fracture severity. 相似文献9.
Kaidiliya Yalikun Manabu Kanazawa Mariko Tanoue Shunsuke Minakuchi 《The Journal of prosthetic dentistry》2019,121(3):492-497
Statement of problem
Single-implant–retained mandibular overdentures (1-IODs) may be an alternative to 2-IOD for maladaptive denture patients giving comparable satisfaction, lower cost, and shorter treatment times. However, studies evaluating the effect of the number of implants on the strain exerted around the implants of IODs using strain-gauge analysis are lacking.Purpose
The purpose of this in vitro study was to evaluate the effect of the number of implants on the strain in an IOD under various loading and dislodging conditions.Material and methods
A mandibular IOD with the Locator attachment system (pink nylon inserts) was fabricated on artificial mucosa. Three implant positions recorded the loading: 1-IOD (mid-anterior), 2-IOD (bilateral lateral incisor), and 3-IOD (mid-anterior and bilateral canine) were prepared. Strain gauges attached to the mid-anterior implant replica for the 1-IOD, the left lateral incisor replica for the 2-IOD, and the anterior and left canine replicas for the 3-IOD. Vertical loads of 50 N were applied to the experimental overdenture in the mid-anterior and right molar and left molar regions. Three dislodging tests were performed in 3 different areas: mid-anterior, posterior, and mid-anterior and bilateral molar. Six measurements were made under each loading and dislodging condition for each IOD (N=6). During the calibration test, the resultant strain measured by strain gauge was converted into a lateral force (F) value by using linear regression: Fanterior-posterior(N)=1.08×strain (με), Fposterior-anterior(N)=0.192×strain (με), Fleft-right(N)=0.590×strain (με), Fright-left(N)=0.560×strain (με). Statistical analysis was performed by using 1-way ANOVA and the Tukey honestly significant difference test (α=.05).Results
The 3-IOD demonstrated the significantly highest strain under loading and dislodging conditions (P<.05). The 1-IOD demonstrated the significantly highest strain during right-side loading (P<.05). Upon anterior and left-side loading, no significant difference was noted in strain between the 1-IOD and 2-IOD (P=.413, P=.272). Under dislodging conditions, the 1-IOD exhibited the significantly lowest strain (P<.05).Conclusions
Within the limitations of this study, the 3-IOD demonstrated the highest lateral resistance force during load and dislodge testing, whereas the 1-IOD exhibited the lowest. 相似文献10.
Mohammed Nadeem Ahmed Bijle Manikandan Ekambaram Edward C.M. Lo Cynthia Kar Yung Yiu 《Journal of Evidence》2019,19(1):28-33
Background
Several significant issues on clinical trials reporting the effect of arginine-containing dental products have been addressed in systematic reviews and meta-analyses identifying the need for high-quality randomized clinical trials. A further methodological analysis of the given systematic reviews with meta-analysis on arginine products might provide information for future high-quality randomized clinical trials and current clinical practice.Objective(s)
The objective was to perform a meta-epidemiological assessment of meta-analyses reporting the anticaries effect of arginine-containing formulations.Methods
The data on risk-of-bias assessment, effect size measure, dispersion of estimated precision, and follow-up period were summarized for the meta-epidemiological review analysis.Results
Studies with larger magnitude of effect sizes might present with unclear random sequence generation and unclear allocation concealment representing the selection bias. There was a significant strong negative correlation between the follow-up time and dispersion of precision estimates (rs = ?0.79, P = .034).Conclusion
Results show that clinical trials on arginine dental products have methodological shortcomings. Both the selection bias and follow-up period influence the effect size magnitude and subsequent precision dispersion during evidence synthesis in clinical trials on arginine-containing dental products. 相似文献11.
Mark A. Saxen Douglas E. Peterson Michael Mashni 《Journal of the American Dental Association (1939)》2019,150(3):193-199
Background
Specialty-based practice is a fundamental component of US medicine and dentistry, yet the recognition of new dental specialties has markedly diminished in the past 50 years while medical specialization has flourished.Methods
This article reviews the history of specialty development while focusing on the underlying scientific, educational, and cultural changes in both professions. The process of dental specialty recognition is also examined.Results
The current dental specialty recognition process provides a set of criteria aspiring specialties need to fulfill at the time of application, yet the relationship between the criteria and the sequence for attaining them is undefined. Scientific development and evidence-based practice have grown to become the cornerstone of contemporary health care specialization.Conclusions
A new paradigm for specialty and subspecialty development in dentistry is needed. A model is presented herein that recognizes scientific development as the basis for specialization and describes a formal, sequenced process for the development of emerging specialties and subspecialties.Practical Implications
This new paradigm for dental specialty recognition builds on the current criteria for specialization while encouraging cross-disciplinary interaction and nurturing the development of emerging specialties and subspecialties in dentistry. Doing so will allow dentistry to maintain its lead role in the maintenance of oral health and oral disease treatment in the US population. 相似文献12.
Ankur Dahiya Nadim Z. Baba Mathew T. Kattadiyil Charles J. Goodacre Akshita Mann 《The Journal of prosthetic dentistry》2019,121(3):504-509
Statement of problem
Excess cement around dental implants is a significant cause of peri-implant inflammation. Research has focused on approaches to cement removal, the type of cement used, and the different instruments used for cement removal with titanium abutments. However, data comparing zirconia with titanium abutments are lacking.Purpose
The purpose of this in vitro study was to compare the effectiveness of excess cement removal from zirconia and titanium custom abutments using an explorer and to compare the effects of cement removal on the abutment surfaces.Material and methods
Implant analogs were placed in a cast in the position of the 2 maxillary central incisors. After creating similar emergence profiles for both the implant abutments, 18 zirconia and titanium custom abutments were fabricated with 1-mm subgingival finish lines on the facial and interproximal areas and an equigingival finish line on the palatal side. The crowns were cemented with zinc oxide-eugenol cement, and a steel explorer was used to remove the excess cement. All abutments were analyzed under a scanning electron microscope for cement remnants and scratches.Results
The mean surface area of cement remnants on the zirconia abutments was 778 ±113 μm2, and for titanium abutments, it was 1123 ±252 μm2, which in terms of the mean percentage area was 3.27% of the total surface area of zirconia and 4.71% of titanium abutments. Only a few abutments from each group showed scratches, and no deep scratches or gouges were observed.Conclusions
Zirconia and titanium abutments had statistically similar cement remnants. Scratches were observed on only a few specimens. 相似文献13.
Francesco Saverio Ludovichetti Flávia Zardo Trindade Gelson Luis Adabo Luca Pezzato Renata Garcia Fonseca 《The Journal of prosthetic dentistry》2019,121(5):866.e1-866.e8
Statement of problem
The effect of clinical adjustments on the strength of cemented computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic materials under aging challenge is unclear.Purpose
The purpose of this in vitro study was to assess the surface roughness and fracture resistance (with or without mechanical aging) of cemented CAD-CAM monolithic materials submitted to grinding and polishing procedures.Material and methods
Disks of Lava Ultimate, Vita Enamic, crystallized Vita Suprinity, and IPS e.max CAD were analyzed for roughness after polishing by using silicon carbide papers (Lava Ultimate and Vita Enamic) or glazing (IPS e.max CAD and Vita Suprinity) (control), after grinding by using 30-μm grit diamond rotary instruments, and after grinding and polishing by using a polishing kit. For fracture resistance, a simplified trilayer model consisting of a restorative disk, an epoxy resin disk, and a steel ring was used. The bonded trilayer disks received the same treatments described for the roughness analysis. Half of the specimens underwent mechanical aging for 1×106 cycles. All specimens were loaded until failure. The Weibull modulus was calculated.Results
The IPS e.max CAD and Vita Suprinity showed the highest roughness after grinding and the lowest at baseline. For the Lava Ultimate and Vita Enamic, polishing provided lower roughness than at baseline. Grinding, followed or not by polishing, and mechanical aging did not adversely affect the fracture resistance or the reliability of the materials.Conclusions
Polishing did not recover the initial surface roughness of the glass-ceramic materials. Fracture resistance was not affected by grinding, followed or not by polishing, even after mechanical aging. 相似文献14.
Background
Dental caries is a widespread infectious disease caused by environmental and genetic factors. Thus far, studies have identified several environmental factors influencing dental caries; however, little remains known about the underlying genetic factors. Recent studies using mice have reported the major genes responsible for dental caries to be located on mouse chromosome 2. Using congenic mice, this study aimed to clarify if the chromosomal region on mouse chromosome 2 influenced dental caries.Materials and methods
We examined the dental caries scores obtained from caries induction, salivary secretion volume, and enamel hardness in the strains C57BL/6Slc, C3H/HeSlc, B6-Chr.2C3H, and three types of congenic mouse strains that we generated.Results
We successfully generated three types of congenic mouse strains. The caries scores of congenic mice, which had the C3H/HeSlc-derived interval between D2Mit126 (84 Mega base pair; Mbp) and D2Mit226 (163 Mbp), were significantly lower than that of any other mouse strain studied herein (p < 0.05). Moreover, the salivary secretion volume of the congenic mice described above tended to be more than that of any other congenic strain. However, enamel hardness was not significantly different among the strains.Conclusion
Several caries-resistant genes could be located between D2Mit126 and D2Mit226. Salivary secretion volume was one of the most important factors related to dental caries, and the genes influencing the rate of salivary secretion might be located in the same region. 相似文献15.
Majed Al-Akhali Matthias Kern Adham Elsayed Abdulaziz Samran Mohamed Sad Chaar 《The Journal of prosthetic dentistry》2019,121(4):644-650
Statement of problem
With the development of new computer-aided design and computer-aided manufacturing (CAD-CAM) restorative dental materials, limited data regarding their survival rate and fracture strength are available when they are used as occlusal veneers. Therefore, these materials should be evaluated under conditions similar to those of the oral environment before being recommended for clinical use.Purpose
To evaluate the influence of thermomechanical fatigue loading on the fracture strength of minimally invasive occlusal veneer restorations fabricated from different CAD-CAM materials and bonded to human maxillary premolars using self-etchnig bonding technique.Material and methods
Sixty-four CAD-CAM occlusal veneer restorations were fabricated from group LD (lithium disilicate [e.max CAD]), LS (zirconia-reinforced lithium silicate [Vita Suprinity]), PI (polymer-infiltrated ceramic [Vita Enamic]), and PM (polymethylmethacrylate [Telio CAD]). The occlusal veneers were luted to enamel (n=16) using a self-etching primer (Multilink Primer A/B) and a luting composite resin (Multilink Automix). Half of the specimens of each group (n=8) were randomly selected and subjected to thermomechanical fatigue loading in a masticatory simulator (1.2 million cycles at 98 N with 5°C-55°C thermocycling). All specimens were quasistatically loaded until fracture. The statistical analysis was made using the Kruskal-Wallis and Mann-Whitney U tests (α=.05).Results
According to the Kaplan-Meier analysis after the thermomechanical fatigue of the 4 groups, the cumulative survival rate was as follows: group LD, 50% group LS, 62.5% group PI, 37.5%; and group PM, 50%. Although some of the surviving specimens exhibited microcracking, their integrity or bonding to teeth was not affected. Thermomechanical fatigue significantly reduced the fracture strength of group PI (P=.047) and group PM (P=.025). Without thermomechanical fatigue, group PM showed significantly higher fracture strength than group LS (P=.015).Conclusions
In general, thermomechanical fatigue decreased the survival rate and fracture strength in all test groups. 相似文献16.
17.
Shajidan Kelimu Mariko Hattori Shataer Awuti Mahmoud E. Elbashti Yuka I. Sumita Hisashi Taniguchi 《The Journal of prosthetic dentistry》2019,121(4):671-675
Statement of problem
A palatogram aids prosthodontists and speech pathologists in evaluating the precise prosthetic treatment needed and the effectiveness of such treatment to improve speech intelligibility. Powder is commonly used to visualize tongue-palate contact, where wetted areas of powder in the oral cavity reveal such contact during palatography. However, discomfort and the risk of aspiration are among the shortcomings of this method, and an improved method is needed.Purpose
The purpose of this in vitro study was to examine the feasibility of a new method of palatography that uses airborne-particle–abraded acrylic resin so that wet areas can be easily distinguished from dry areas.Material and methods
Seventy-two specimens of heat-polymerized acrylic resin were prepared in 6 different resin colors. After the specimens had been airborne-particle abraded, CIELab color values for each specimen were measured using a colorimeter under dry and wet conditions and recorded. Color difference (ΔE) was then computed, and a paired Student t test, 1-way analysis of variance, and multiple comparison using the Tukey post hoc analysis were applied (α=.05).Results
A significant color difference was found between the 2 conditions in all acrylic resin specimens examined. Mean ΔE ranged from 5.58 to 6.76.Conclusions
The results indicated that an airborne-particle–abraded acrylic resin surface can show color differences made by wetting on palatograms. 相似文献18.
Priscilla Medina-Sotomayor Agustín Pascual-Moscardo Isabel Camps A 《The Journal of prosthetic dentistry》2019,121(5):811-820
Statement of problem
The accuracy of digital scanners is acceptable for scanning a complete dental arch. However, whether that accuracy is sufficient for only 1 tooth within the dental scan of a complete dental arch is unclear.Purpose
The purpose of this in vitro study was to evaluate and compare the accuracy of 4 intraoral scanners on a complete dental arch and on prepared teeth digitally isolated from the digital scan in terms of trueness and precision.Material and methods
A model of a complete dental arch with tooth preparations was scanned 40 times with each of the 4 digital scanners. Their accuracy was evaluated by using 3-dimensional (3D) software to compare the test models with a highly accurate reference model. The data were digitally processed to isolate the prepared teeth and evaluate them in the same way. The data were statistically analyzed using the Levene test and the Tamhane's T2 test (α=.05).Results
In scans of a complete dental arch, the True Definition scanner had the best accuracy values, followed by TRIOS, iTero, and Omnicam. For prepared teeth isolated from the dental arch, both True Definition and TRIOS had the best values, followed by iTero and Omnicam.Conclusions
In both long-span scans of the complete dental arch and isolated prepared teeth, the True Definition scanner had the greatest accuracy, closely followed by TRIOS. 相似文献19.
Kurt Erdelt Madalena Lucia Pinheiro Dias Engler Florian Beuer Jan-Frederik Güth Anja Liebermann Josef Schweiger 《The Journal of prosthetic dentistry》2019,121(4):683-689
Statement of problem
Determining the relationship between variable thicknesses and the translucency of dental ceramics is essential for optimizing esthetics in different clinical situations.Purpose
The purpose of this in vitro study was to analyze the relationship between layer thickness and translucency of 2 multi-layered monolithic zirconia materials and to develop an equation by which the grade of translucency can be calculated dependent on the materials' layer thicknesses in advance.Material and methods
Two semisintered multi-layered zirconia blanks, namely KATANA Zirconia Super Translucent Multi-Layered Disk (Noritake Dental Supply Co, Ltd) and Zirconia Ultra Translucent Multi-Layered Disk (UTML) (Noritake Dental Supply Co, Ltd), were sectioned (N=96) to separate the 4 layers (n=12 per layer): enamel layer, transition layer 1, transition layer 2, body layer. All specimens were sintered in a furnace (M2 Plus; Thermo-Star) at 1500°C for 2 hours and automatically polished under water cooling up to P2400 for the thicknesses of 1.6, 1.3, 1.0, 0.7, and 0.4 mm. Transmittance of visible light was measured using a spectrophotometer (Lambda 35; Perkin Elmer). Data were analyzed using the Kolmogorov-Smirnov, 2-way ANOVA, and Scheffé post hoc tests (α=.01) and curve fitting.Results
Analyzing the fitting of the values of the 8 material groups to the linear, exponential, and logarithmic curves, 7 of the 8 groups (not UTML body layer) fitted the most (R-square value closer to 1.0) to the logarithmic curve. Constants were obtained from the distance to the x-axis and the curvature.Conclusions
The methodology of this study provided the materials' specific constants a and b by analyzing the translucency behavior of KATANA Super Translucent Multi-Layered Disk and Ultra Translucent Multi-Layered Disk in different thicknesses, allowing further translucency calculation by applying the developed formula and the constants. 相似文献20.
Tyler V. Verhaeghe Bernie A. Linke Cheryl E. Cable Nesrine Mostafa 《The Journal of prosthetic dentistry》2019,121(4):604-610