Effect of exposure energy dose on lateral resolution and flexural strength of threedimensionally printed dental zirconia

PURPOSE@#. This study aims to evaluate the effects of exposure energy on the lateral resolution and mechanical strength of dental zirconia manufactured using digital light processing (DLP). @*MATERIALS AND METHODS@#. A zirconia suspension and a custom top-down DLP printer were used for in-office manufacturing. The viscosity of the suspension and uniformity of the exposed light intensity were controlled. Based on the exposure energy dose delivered to each layer, the specimens were classified into three groups: low-energy (LE), medium-energy (ME), and high-energy (HE). For each energy group, a simplified molar cube was used to measure the widths of the outline (Xo and Yo ) and isthmus (Xi and Yi ), and a bar-shaped specimen of the sintered body was tested. A Kruskal–Wallis test for the lateral resolution and one-way analysis of variance for the mechanical strength were performed (α = .05). @*RESULTS@#. The zirconia green bodies of the ME group showed better lateral resolution than those of the LE and HE groups (both P < .001). Regarding the flexural strength of the sintered bodies, the ME group had the highest mean value, whereas the LE group had the lowest mean value (both P < .05). The ME group exhibited fewer agglomerates than the LE group, with no distinctive interlayer pores or surface defects. @*CONCLUSION@#. Based on these findings, the lateral resolution of the green body and flexural strength of the sintered body of dental zirconia could be affected by the exposure energy dose during DLP. The exposure energy should be optimized when fabricating DLPbased dental zirconia.

Virtual Design Considerations for Fixed Dental Prosthesis Including Axial Contour and Proximal Contact to Maintain Periodontal Health and Physiologic Function:A Narrative Review

The axial contour and proximal contact of the prosthesis affect periodontal health, food impaction, and patient satisfaction. This narrative review provides a summary of articles regarding the axial contour and proximal contact of a fixed dental prosthesis on periodontal health and physiologic function. By acquiring a comprehensive understanding of the axial contour and proximal contact of teeth and prostheses, as well as their functional significance, the virtual design of fixed dental prosthesis can be optimized to maintain periodontal health and promote physiologic function effectively.

Full mouth rehabilitation of a worn dentition using digital guided tooth preparation: a case report / 대한치과보철학회지

With the development of digital dentistry, it is being applied in various ways of dental treatment. This case report presents the definitive prosthesis designed in advance with a re-established vertical dimension and the digital technology, which determined the amount of tooth preparation, in order to preserve as much tooth structure as possible in a patient with pathological wear of the posterior teeth and loss of vertical dimension. For accurate tooth preparation, the guides of the occlusal and axial surfaces were digitally and additively manufactured. Then, aesthetics and anterior guidance were established at the provisional stage. The information of the provisional restoration was delivered to the definitive stage by double scanning. The digital technology, including the virtual planning and the guided tooth removal, produced the definitive restorations satisfactory to both the patient and clinician.

Complete mouth rehabilitation with fixed implant-supported prosthesis using temporary denture and dental CAD-CAM / 대한치과보철학회지

Installation of dental implants at optimal angles and positions is critical in longterm stable implant-supported restorations. Surgery and prosthodontic procedures should be performed accurately as the treatment is planned. In this clinical case, Computer aided design and manufacturing technology was used not only to establish a precise surgical plan, but also to fabricate both provisional and definitive fixed prostheses. A surgical guide was designed to install the implants at proper positions for the definitive prostheses. The patient’s esthetic information, which was necessary for the new provisional and definitive fixed prostheses, was obtained from the existing temporary dentures. Finally, the complete mouth fixed implant-supported rehabilitation using monolithic zirconia provided the patient with functionally and esthetically satisfactory prostheses.

Comparative analysis on intaglio surface trueness, wear volume loss of antagonist, and fracture resistance of full-contour monolithic zirconia crown for single-visit dentistry under simulated mastication

PURPOSE@#This analysis aimed to evaluate the intaglio surface trueness, antagonist’s wear volume loss, and fracture resistance of full-contour crowns of (Y, Nb)-stabilized fully-sintered zirconia (FSZ), 4 mol% or 5 mol% yttria-stabilized partially sintered zirconia (4YZ or 5YZ) with high-speed sintering. @*MATERIALS AND METHODS@#A total of 42 zirconia crowns were separated into three groups: FSZ, 4YZ, and 5YZ (n = 14). The intaglio surface trueness of the crowns was evaluated at the inner surface, occlusal, margin, and axial areas and reported as root-mean-square, positive and negative average deviation. Half of the specimens were aged for 120,000 cycles in the chewing simulator, and the wear volume loss of antagonist was measured. Before and after chewing, the fracture load was measured for each group. The trueness values were analyzed with Welch's ANOVA, and the wear volume loss with the Kruskal-Wallis tests. Effect of the zirconia type and aging on fracture resistance of crowns was tested using two-way ANOVA. @*RESULTS@#The intaglio surface trueness measured at four different areas of the crown was less than 50 µm, regardless of the type of zirconia. No significant P in wear volume loss of antagonists were detected among the groups (P > .05). Both the type of zirconia and aging showed statistically significant effects on fracture resistance (P < .05). @*CONCLUSION@#The full-contour crowns of FSZ as well as 4YZ or 5YZ with high-speed sintering were clinically acceptable, in terms of intaglio surface trueness, antagonist’s wear volume loss, and fracture resistance after simulated mastication.

Analysis of surface characteristics of (Y, Nb)-TZP after finishing and polishing

PURPOSE@#. This in vitro study aimed to evaluate the surface characteristics of a full veneer crown fabricated chairside (CS) from a (Y, Nb)-TZP zirconia block in response to conventional zirconia grinding and polishing. @*MATERIALS AND METHODS@#. Zirconia crowns (n = 40) were first prepared and divided into two groups of materials: Labside (LS) and CS, after which each specimen went through a five-step grinding and polishing procedure. Following each surface treatment, surface characteristics were analyzed using confocal laser microscopy (CLSM), average surface roughness (Ra) values were processed from the profile data through Gaussian filtering, and X-ray diffraction pattern analysis was performed to evaluate the monoclinic (M) phase content. Then, a representative specimen was selected for field-emission scanning electron microscopy (FE-SEM), followed by a final analysis of the roughness and X-ray diffraction of the specimens using the independent t-test and repeated measures analysis of variance (RM-ANOVA). @*RESULTS@#. In every group, polishing significantly reduced the Ra values (P < .001).There was no significant difference in Ra between the polished state CS and LS.Furthermore, CLSM and FE-SEM investigations revealed that even though grain exposure was visible in CS specimens throughout the as-delivered and ground states, the exposure was reduced after polishing. Moreover, while no phase transformation was visible in the LS, phase transformation was visible in CS after every surface treatment, with the M phase content of the CS group showing a significant reduction after polishing (P < .001). CONCLUSION. Within the limits of this study, clinically acceptable level of surface finishing of (Y, Nb)-TZP can be achieved after conventional zirconia polishing sequence.

Evaluation of intaglio surface trueness, wear, and fracture resistance of zirconia crown under simulated mastication: a comparative analysis between subtractive and additive manufacturing

PURPOSE@#. This in-vitro analysis aimed to compare the intaglio trueness, the antagonist’s wear volume loss, and fracture load of various single-unit zirconia prostheses fabricated by different manufacturing techniques. @*MATERIALS AND METHODS@#. Zirconia crowns were prepared into four different groups (n = 14 per group) according to the manufacturing techniques and generations of the materials. The intaglio surface trueness (root-mean-square estimates, RMS) of the crown was measured at the marginal, axial, occlusal, and inner surface areas. Half of the specimens were artificially aged in the chewing simulator with 120,000 cycles, and the antagonist’s volume loss after aging was calculated. The fracture load for each crown group was measured before and after hydrothermal aging. The intaglio trueness was evaluated with Welch’s ANOVA and the antagonist’s volume loss was assessed by the Kruskal-Wallis tests. The effects of manufacturing and aging on the fracture resistance of the tested zirconia crowns were determined by two-way ANOVA. @*RESULTS@#. The trueness analysis of the crown intaglio surfaces showed surface deviation (RMS) within 50 µm, regardless of the manufacturing methods (P = .053). After simulated mastication, no significant differences in the volume loss of the antagonists were observed among the zirconia groups (P = .946). The manufacturing methods and simulated chewing had statistically significant effects on the fracture resistance (P < .001). @*CONCLUSION@#. The intaglio surface trueness, fracture resistance, and antagonist’s wear volume of the additively manufactured 3Y-TZP crown were clinically acceptable, as compared with those of the 4Y- or 5Y-PSZ crowns produced by subtractive milling.

Implant assisted removable partial denture with implant surveyed prostheses: A 9-year follow-up / 대한치과보철학회지

Implant placement may be restricted by anatomical and/or financial limitations in restoring a completely edentulous arch, or the patients’ unwillingness to have extensive surgical procedures. Implant assisted removable partial dentures (IARPD) in combination with anterior fixed implant prostheses can be proposed as an alternative treatment option for the restoration of a completely edentulous arch. In this case, a 56-year-old female patient who has a fully edentulous maxilla opposed by partially edentulous mandible was treated. The treatment option for the maxilla consisted of an implant-assisted removable partial denture supported by four anterior fixed implant prostheses. The mandible was restored with 8 anterior fixed partial dentures and posterior fixed implant-supported prostheses.Long-term follow-up and supportive periodontal treatment were performed for 9years, and the patient was satisfied with the overall appearance as well as masticatory function.

Wear of 3D printed and CAD/CAM milled interim resin materials after chewing simulation

PURPOSE@#The purpose of this in vitro study was to investigate the wear resistance and surface roughness of three interim resin materials, which were subjected to chewing simulation. @*MATERIALS AND METHODS@#Three interim resin materials were evaluated: (1) three-dimensional (3D) printed (digital light processing type), (2) computer-aided design and computer-aided manufacturing (CAD/CAM) milled, and (3) conventional polymethyl methacrylate interim resin materials. A total of 48 substrate specimens were prepared. The specimens were divided into two subgroups and subjected to 30,000 or 60,000 cycles of chewing simulation (n = 8). The wear volume loss and surface roughness of the materials were compared. Statistical analysis was performed using oneway analysis of variance and Tukey’s post-hoc test (α=.05). @*RESULTS@#The mean ± standard deviation values of wear volume loss (in mm 3 ) against the metal abrader after 60,000 cycles were 0.10 ± 0.01 for the 3D printed resin, 0.21 ± 0.02 for the milled resin, and 0.44 ± 0.01 for the conventional resin. Statistically significant differences among volume losses were found in the order of 3D printed, milled, and conventional interim materials (P <.001). After 60,000 cycles of simulated chewing, the mean surface roughness (Ra; µm) values for 3D printed, milled, and conventional materials were 0.59 ± 0.06, 1.27 ± 0.49, and 1.64 ± 0.44, respectively. A significant difference was found in the Ra value between 3D printed and conventional materials (P =.01). @*CONCLUSION@#The interim restorative materials for additive and subtractive manufacturing digital technologies exhibited less wear volume loss than the conventional interim resin.The 3D printed interim restorative material showed a smoother surface than the conventional interim material after simulated chewing.

Full mouth rehabilitation with implant-supported fixed prosthesis via dental CAD-CAM system / 대한치과보철학회지

Dental implants should be placed at ideal sites for implant-supported restorations. For a patient with insufficient residual ridge, mouth preparation including surgical intervention can be indicated to establish a soft and hard tissue environment favorable for a definitive prosthesis. Prosthodontic design based on computer-guided surgery and computer-aided design-computer-aided manufacturing (CAD-CAM) provides a visual blueprint allowing a clinician to assess the necessity of such a surgical intervention beforehand. In this case, a definitive restoration was planned and made via a CAD-CAM system according to the patient’s oral status before treatment, simulated surgical interventions and serial provisional restorations. Based on the planning, a guided template was made and the implants were installed with bone augmentation using the template. Customized abutments, the first and the second provisional restorations were designed and fabricated by CAD-CAM. The definitive restorations were digitally made following the shape of the second provisional prostheses, which were confirmed in the patient’s mouth. The patient was satisfied with the masticatory, phonetic and aesthetic functions of these definitive prostheses.

Fabrication of removable partial denture on scleroderma patient using 3-dimensional intraoral scanner / 대한치과보철학회지

A three-dimensional (3D) intraoral scanner, which is one of the major developments in digital dentistry, is widely used in fixed prosthodontics. The application of intraoral scanner is now increasing in removable prosthodontics. Sclerotic change induced by scleroderma causes the limitation of mouth opening and multiple loss of the teeth. Conventional prosthodontic procedures are challenging for patients with this disease. This study showed a case of digital approach to the removable prosthodontic treatment of a patient who had the scleroderma and the consequent microstomia. At the provisional stage, the optical impression of patient’s oral structures was digitally obtained. Using a 3D printer, the provisional dentures were fabricated. After extraction of hopeless tooth, the definitive digital impression was taken and the metal frameworks were fabricated, based on the data acquired from the impression. The definitive removable partial dentures were completed and delivered to the patient, who was satisfied with the prostheses.

Wear of 3D printed and CAD/CAM milled interim resin materials after chewing simulation

PURPOSE@#The purpose of this in vitro study was to investigate the wear resistance and surface roughness of three interim resin materials, which were subjected to chewing simulation. @*MATERIALS AND METHODS@#Three interim resin materials were evaluated: (1) three-dimensional (3D) printed (digital light processing type), (2) computer-aided design and computer-aided manufacturing (CAD/CAM) milled, and (3) conventional polymethyl methacrylate interim resin materials. A total of 48 substrate specimens were prepared. The specimens were divided into two subgroups and subjected to 30,000 or 60,000 cycles of chewing simulation (n = 8). The wear volume loss and surface roughness of the materials were compared. Statistical analysis was performed using oneway analysis of variance and Tukey’s post-hoc test (α=.05). @*RESULTS@#The mean ± standard deviation values of wear volume loss (in mm 3 ) against the metal abrader after 60,000 cycles were 0.10 ± 0.01 for the 3D printed resin, 0.21 ± 0.02 for the milled resin, and 0.44 ± 0.01 for the conventional resin. Statistically significant differences among volume losses were found in the order of 3D printed, milled, and conventional interim materials (P <.001). After 60,000 cycles of simulated chewing, the mean surface roughness (Ra; µm) values for 3D printed, milled, and conventional materials were 0.59 ± 0.06, 1.27 ± 0.49, and 1.64 ± 0.44, respectively. A significant difference was found in the Ra value between 3D printed and conventional materials (P =.01). @*CONCLUSION@#The interim restorative materials for additive and subtractive manufacturing digital technologies exhibited less wear volume loss than the conventional interim resin.The 3D printed interim restorative material showed a smoother surface than the conventional interim material after simulated chewing.

Full mouth rehabilitation of a severely worn dentition using intraoral scanner and the CAD/CAM double scanning technique / 대한치과보철학회지

With the evolution of the computer-aided design/computer-aided manufacturing (CAD/CAM) technology, the intraoral scanners are playing an increasingly important role, as they are the first step towards a completely digital workflow. The CAD/CAM double scanning technique has been used to transfer the information from provisional restorations to definitive restorations. In this case, a 67-year-old male with esthetically compromised anterior teeth, generalized severe attrition of teeth, and reduced vertical dimension was treated with full mouth rehabilitation including a re-establishment of the lost vertical dimension of occlusion assisted by the crown lengthening procedure. The provisional restorations were fabricated using an intraoral scanner and the CAD/CAM double scanning technique. After the period of adaption, the definitive monolithic zirconia restorations were delivered. The CAD/CAM double scanning technique successfully transferred the occlusal and morphological characteristics, obtained from the provisional restorations, to the definitive restorations.

Full mouth rehabilitation utilizing computer guided implant surgery and CAD/CAM / 대한치과보철학회지

Computer aided design and manufacturing and implant surgery using a guide template improve restoration-driven implant treatment procedures. This case utilized those digital technologies to make definitive prostheses for a patient. According to the work flow of digital dentistry, cone beam computed tomography established the treatment plan, which was followed to make the guide template for implant placement. The template guided the implants to be installed as planned. The customized abutments and surveyed fixed restorations were digitally designed and made. The metal framework of the removable partial denture was cast from resin pattern using an additive manufacturing technique, and the artificial resin teeth were replaced with the zirconia onlays for occlusal stability. These full mouth rehabilitation procedures provided functionally and aesthetically satisfactory results for the patient.

Computer-aided design and manufacturing-based full mouth rehabilitation for a patient with excessive attrition and restricted vertical dimension: A case report / 대한치과보철학회지

This study reported the treatment of a patient with excessive worn dentition and limited maxillo-mandibular space for restoration, utilizing the computer-aided design and computer-aided manufacturing (CAD/CAM) technology. After the thorough examination of the patient's occlusal vertical dimension (OVD), full mouth rehabilitation was planned with increase of the OVD. The patient was satisfied with the provisional restorations establishing the increased OVD. The horizontal and vertical data of the patient's jaw relation that the provisional restorations contained were transferred to the definitive metal ceramic fixed prostheses by double scanning and three-dimensional printing. After the fixed restorations were cemented to the abutments, electronic surveying and three-dimensional printing were used to fabricate metal frameworks for the patient's removable partial dentures. The mandibular definitive removable prostheses were delivered to the patient's mouth and the full mouth rehabilitation procedures were completed. The digital technologies used for this case produced fixed and removable restorations satisfactory in masticatory, phonetic and aesthetic functions to both the patient and the dental clinician.

Three-dimensional finite element analysis according to the insertion depth of an immediately loaded implant in the anterior maxilla / 대한치과보철학회지

PURPOSE: The purpose of this study was to investigate the effects of the insertion depth of an immediately loaded implant on the stress distribution of the surrounding bone and the micromovement of the implant using the three-dimensional finite element analysis. MATERIALS AND METHODS: A total of five bone models were constructed such that the implant platform was positioned at the levels of 0.00 mm, 0.25 mm, 0.50 mm, 0.75 mm, and 1.00 mm depth from the crest of the cortical bone. A frictional coefficient of 0.3 and the insertion torque of 35 Ncm were simulated on the interface between the implant and surrounding bone. A static load of 178 N was applied to the provisional prosthesis with a vertical load in the axial direction and an oblique load at 30°with respect to the central axis of the implant, then a finite element analysis was performed. RESULTS: The implant insertion depth significantly affected the stress distribution on the surrounding bone. The largest micromovement value of the implant was 39.34 µm. The oblique load contributed significantly to the stress distribution and micromovement in comparison to the vertical load. CONCLUSION: Increasing the implant insertion depth was advantageous in dispersing the concentrated stress in the cortical bone and did not significantly affect the micromovement associated with early osseointegration failure.

Full mouth rehabilitation of a patient using monolithic zirconia and dental CAD/CAM system: a case report

An accurate implant placement with ideal location is significant for long-term success of the implant. An exact evaluation of nearby anatomic structures such as quality of residual bone, an inferior alveolar bone and a maxillary sinus is required. For a prosthetic-driven treatment, planned surgery, precise prosthesis and communication with the patient are significant requisites especially for full-mouth rehabilitation. In this case, the patient with severe alveolar bone resorption had a CT guided surgery supported by CT data and the data from scanning diagnostic wax-up. Afterward, edentulous area was restored by full mouth implant-supported prosthesis by using monolithic zirconia and CAD/CAM technique. This paper reports the outcome of the procedure which was remarkable both esthetically and functionally.

The dimension analysis of prepared natural teeth for developing customized zirconia block / 대한치과보철학회지

PURPOSE: Unpredictable shrinkage of zirconia during sintering process causes discrepancy. Therefore, there have been attempts to reduce discrepancy by milling zirconia after sintering. However, due to the hardness of sintered zirconia, milling takes longer time, causes damage to the machine and causes chip formation. With customized zirconia block using the mean dimension of prepared natural dentition, it is expected to overcome these shortcomings. MATERIALS AND METHODS: The mean dimension of prepared natural dentition was analyzed as STL file after scanning of prepared teeth treated at SNUDH. The transverse, frontal and sagittal planes were set using Mimics and Photoshop. 3D volume was projected on each plane, and the outer line was measured through external tangent line, and the inner line was measured through inflection point of tangent line. RESULTS: The mean height of prepared incisal (N = 57) is 6.60 ± 1.05 mm, mesiodistal length is 2.98 ± 0.73 mm, buccolingual length is 2.04 ± 0.73 mm. The mean height of prepared premolar (N = 15) is 5.37 ± 1.49 mm, mesiodistal length is 4.10 ± 1.78 mm, buccolingual length is 5.86 ± 1.55 mm. And the mean height of prepared molar (N = 13) is 5.11 ± 1.29 mm, mesiodistal length is 6.80 ± 1.18 mm, buccolingual length is 7.34 ± 1.40 mm. CONCLUSION: Using the mean dimension of prepared natural dentition, it is expected to be able to fabricate customized zirconia block.

Full mouth rehabilitation of edentulous patient with intellectual disability using implants and monolithic zirconia / 대한치과보철학회지

People with class I intellectual disability need lifelong assistance and protection from their surroundings due to impaired adaptive functioning. They have poor oral health and show higher prevalence of dental caries, periapical inflammation and tooth loss that require proper prosthetic restoration. Because removable prostheses for intellectually disabled patients often lack stability, retention, and maintenance, fixed prostheses are essential and the only available option is dental implants. In this case, a 45 year-old male patient with class I intellectual disability had poor oral hygiene with most of his teeth missing and visited the clinic to recover his masticatory function. Due to such systemic conditions, the definitive restoration of choice was the implant-supported fixed dental prosthesis made of biocompatible and highly strong monolithic zirconia. In consequence of the treatment process, the patient was able to improve his oral environment aesthetically and functionally.

Detection of proximal caries using quantitative light-induced fluorescence-digital and laser fluorescence: a comparative study

PURPOSE: The purpose of this study was to evaluate the in vitro validity of quantitative light-induced fluorescence-digital (QLF-D) and laser fluorescence (DIAGNOdent) for assessing proximal caries in extracted premolars, using digital radiography as reference method. MATERIALS AND METHODS: A total of 102 extracted premolars with similar lengths and shapes were used. A single operator conducted all the examinations using three different detection methods (bitewing radiography, QLF-D, and DIAGNOdent). The bitewing x-ray scale, QLF-D fluorescence loss (ΔF), and DIAGNOdent peak readings were compared and statistically analyzed. RESULTS: Each method showed an excellent reliability. The correlation coefficient between bitewing radiography and QLF-D, DIAGNOdent were −0.644 and 0.448, respectively, while the value between QLF-D and DIAGNOdent was −0.382. The kappa statistics for bitewing radiography and QLF-D had a higher diagnosis consensus than those for bitewing radiography and DIAGNOdent. The QLF-D was moderately to highly accurate (AUC = 0.753 – 0.908), while DIAGNOdent was moderately to less accurate (AUC = 0.622 – 0.784). All detection methods showed statistically significant correlation and high correlation between the bitewing radiography and QLF-D. CONCLUSION: QLF-D was found to be a valid and reliable alternative diagnostic method to digital bitewing radiography for in vitro detection of proximal caries.