All-ceramic Crowns Research Articles

EFFECTS OF THREE-DIMENSIONAL-PRINTED ZIRCONIA ALL-CERAMIC CROWNS ON PERIODONTAL HEALTH AND AESTHETICS OF PATIENTS RECEIVING ANTERIOR TOOTH AESTHETIC RESTORATION

The aim of this study was to evaluate the effects of three-dimensional (3D)-printed zirconia all-ceramic crowns on the periodontal tissues and aesthetics of patients receiving anterior tooth aesthetic restoration. A total of 85 patients with anterior tooth defects treated from January 2018 to October 2019 were selected. We studied zirconia all-ceramic crowns made by computer-aided design and computer-aided manufacturing (CAD/CAM) (control group) and 3D printing (observation group). The short-term restoration effects, periodontal health indices, functional recovery, long-term clinical efficacy and aesthetic effects were compared. The gingival marginal fitness of the observation group was better than that of the control group, but the control group had better tooth color matching (P < 0.05). One year after the restoration, the bleeding index, probing depth, attachment loss, gingival index and plaque index all declined in the two groups, particularly in the observation group. Both the masticatory and language functions were improved in the two groups, especially in the observation group (P < 0.05). Both 3D-printed and CAD/CAM zirconia all-ceramic crowns have better cosmetic restoration effects on the anterior teeth. However, 3D-printed zirconia all-ceramic crowns have better gingival marginal fitness, which can benefit the periodontal tissue recovery, relieve gingival inflammation, and improve masticatory and language functions.

Evaluation and Comparison of Stress in Divergent and Convergent Collar Designs of Implants With Different Bone Densities: A Finite Element Study.

The failure and the success rate of an implant depends on biomechanical factors, esthetics and painless sterile implant surgery conditions, out of which stresses applied to the bone and its surrounding, bone-implant interface, material characteristics of the implant used and the strength of the bone and its surrounding are the important factors. This study aimed to evaluate the stress distribution of divergent collar design (DCD)and convergent collar design (CCD) implants placing them in four different densities of the bone (D1, D2, D3 and D4).The evaluation of the stress distribution of DCDand CCD was performed using the 3D finite element method (FEM), by placing them in four different bone densities.In addition to this, a comparison of the effect of DCD and CCD in terms of stressdistribution in the bone was also done. The softwareused to process the geometric characteristics of the missing first molar in the mandibular section were Ansys, version 19.2, CATIA, version 5, and Solidworks (Dassault Systèmes). Using these software, three models were designed and successfully restored using an all-ceramic crown implant. The first model was a geometric modelof the first molar mandibular bone section, the second model was a cylindrical implant (4x10mm) with a DCD and CCD, and the third model had titanium alloy (Ti-6Al-4V) properties incorporated into the implant. The D1 bone model showed the lowest stress concentration compared to D2, D3, D4. The DCD showed the lower stress and strain concentrations as compared to the CCD in the contiguous crestal bone in all the densities of the bone in both vertical and lateral or oblique loadings. The DCD with the D1 bone showed the least stress concentration around the crestal bone region. The results of this study also showed that the maximum von Mises stress was observed in the crestal region or the neck of the implant for both the convergent and divergent collar implant designs in all the four densities of the bone. Before a patient trial of a new implant design or a new implant material, finite element analysis (FEA) gives us a clear picture of what will be the patient bone response when an implant will be placed and loaded. FEA also gives us an opportunity to test a new implant material without putting a patient at risk. In this study, four different types of bone were incorporated with two different implant collar designs. Each implant assembly was subjected to vertical as well as oblique forces. The response of each bone type for the titanium alloy implant was recorded. A color-coded response for the magnitude and the location of the maximum stress received by the bone was observed.Maximum stresses were seen in the crestal region. As this is a computer-based model, dynamic loading was not possible. This study provided us with the possible outcome in patients under a static load. Further studies can be conducted invivo to record dynamic loading responses as well as long-time loading responses.

Shade match comparison of CAD-CAM single crowns to a lithium disilicate crown.

To assess the shade match ability of four varieties of all-ceramic crowns to a neighboring bilayered lithium disilicate crown. A dentiform was used to fabricate a bilayered lithium disilicate crown on the maxillary right central incisor, following the anatomy and shade of a selected natural tooth. Two crowns (one full-contour, one cutback) were then designed on a prepared maxillary left central incisor, following the contour of the neighboring crown. The designed crowns were used to manufacture monolithic lithium disilicate, bilayered lithium disilicate, bilayered zirconia, and monolithic zirconia crowns, 10 each. An intraoral scanner and a spectrophotometer were used to assess the frequency of matched shades and to calculate the color difference (ΔE) between the two central incisors at the incisal, middle, and cervical thirds. Kruskal-Wallis and two-way ANOVA were used to compare the frequency of matched shades and ΔE values, respectively (α=0.05). There was no significant (p>0.05) difference in frequencies of matched shades for each group at the three sites; except bilayered lithium disilicate crowns. Bilayered lithium disilicate crowns had significantly (p<0.05) higher match frequency than monolithic zirconia at the middle third. The ΔE value was not significantly (p>0.05) different among the groups at the cervical third. However, monolithic zirconia had significantly (p<0.05) higher ΔE values than bilayered lithium disilicate and zirconia at the incisal and middle thirds. Bilayered lithium disilicate and zirconia appeared to most closely match the shade of an existing bilayered lithium disilicate crown.

An Investigation of the Fracture Loads Involved in the Framework of Removable Partial Dentures Using Two Types of All-Ceramic Restorations.

Retention and support are needed for removable partial denture stability. The stability can be achieved by clasps, occlusal and cingulum rests on healthy abutment teeth. However, implants or crowns can be used to support the removable partial denture instated on unhealthy abutment teeth. This study was conducted to investigate the fracture strength of two types of all-ceramic restorations used as abutments for the removable partial denture framework. The crowns were manufactured with two types of ceramic materials: zirconia and IPS e.max Press ceramics. The metal alloy (cobalt-chrome) was cast to form the removable partial denture framework. A universal testing machine was used to evaluate the fracture strength of both ceramic crown materials. The results presented no fractures in all-ceramic crowns, but deformation of the partial denture frameworks occurred. With the limitation of this study, it can be concluded that zirconia and IPS e.max Press ceramic can be used as abutments to provide adequate support to the removable partial denture.

One-Piece Zirconia Oral Implants for Single Tooth Replacement: Five-Year Results from a Prospective Cohort Study

The intention of this 5-year prospective cohort investigation was to clinically and radiographically investigate the outcomes of a one-piece zirconia implant system for single tooth replacement. Sixty-five patients received a total of 66 single-tooth implants. All implants immediately received temporary restorations and were finally restored with all-ceramic crowns. Follow-ups were performed at the prosthetic delivery, after 1, 3, and 5 years. Peri-implant and dental soft-tissue parameters were evaluated and patient-reported outcomes recorded. To monitor peri-implant bone remodelling, standardised radiographs were taken at the implant insertion and at the 1-, 3-, and 5-year follow-ups. In the course of 5 years, 14 implants were lost, resulting in a cumulative implant survival rate of 78.2%. The mean marginal bone loss from the implant insertion to the 5-year follow-up amounted to 1.12 mm. Probing depth, clinical attachment level, bleeding, and plaque index increased over time. In 91.5% of the implants, the papilla index showed levels of 1 or 2, respectively. At the end of the study, the patient satisfaction was higher compared to the pre-treatment measurements. Due to the low survival rate after five years and the noticeably high frequency of advanced bone loss observed in this study, the implant has not met the launch criteria, as it would have not been recommended for routine clinical use.

Effect of finish line location and saliva contamination on the accuracy of crown finish line scanning.

Intraoral scanners are used widely as an alternative to conventional impressions, but studies on the influence of finish line location and saliva contamination on scanning trueness are lacking. The purpose of this in vitro study was to evaluate the influence of finish line location and saliva contamination on the scanning trueness of crown finish lines. Three ivorine teeth were prepared for all-ceramic crowns with finish lines placed equigingivally, 0.5mm subgingivally, and 1.0mm subgingivally. A single-cord technique was used for gingival retraction, and a total of 180 intraoral scans were made using two intraoral scanners (Emerald; Planmeca USA Inc., Hoffman Estates, IL, USA & Trios 3; 3Shape A/S, Copenhagen, Denmark). The prepared teeth were separated from the dentoform and scanned using the same intraoral scanners to create reference scans. All scans were imported to the design software (Dental System 2019; 3Shape A/S, Copenhagen, Denmark). After marking the finish lines of prepared teeth, intraoral scans were aligned to the reference scans for comparisons. Vertical and horizontal marginal discrepancies were measured at four different measuring points (buccal, lingual, mesial, and distal) and analyzed. Two-way ANOVA and Tukey HSD tests were used for statistical analysis (α=0.05). The average vertical and horizontal discrepancies from various groups ranged from -33 to 440µm. For both intraoral scanners, subgingival finish line groups showed greater vertical and horizontal discrepancies compared with equigingival finish line groups. Saliva contamination significantly increased both vertical and horizontal discrepancies for all finish line locations. The discrepancy increases due to saliva contamination were greater for the subgingival groups. Subgingival finish lines were not accurately captured using the intraoral scanners. The presence of saliva significantly reduced scanning trueness, and this was amplified when the finish lines were located subgingivally.

Same-Day Digital Dentistry Restorative Workflow for Single Immediate Provisionalization of Narrow-Diameter Implants: An Exploratory Prospective Study

This study evaluated the two-year clinical outcomes of 3.1 mm diameter dental implants, immediately provisionalized and later restored using same-day dentistry, in 10 patients receiving 11 narrow-diameter (3.1 mm) single implants. Each implant was placed and immediately restored with a provisional crown after placement. At least 2 months after placement, the implant was restored with a prefabricated titanium abutment and an all-ceramic crown using a same-day dentistry protocol. Clinical outcomes, including apical bone loss, probing depths, gingival index, and surgical and prosthetic complications, were documented. There was no implant failure over the course of two years. No surgical complications were reported. Two cases lost provisional crowns. One crown needed to be remade due to esthetic concern. The cumulative two-year survival rate of the implants was 100%. Implant bone loss after two years of functional loading was −0.56 ± 0.54 mm and −0.32 ± 0.68 mm for mesial and distal crestal bone, respectively. Two prosthetic complications included recementation of a crown and remaking of a crown. This exploratory study suggests that immediate provisionalization and a same-day restorative dentistry digital workflow protocol for narrow-diameter implants appear to be predictable clinical procedures with no reported surgical complications and minimal prosthetic complications.

Marginal gap distance and cyclic fatigue loading for different all-ceramic endocrowns.

The aim of the study was to evaluate the effect of the fabrication techniques of two types of glass ceramics on the marginal gap distance and the fracture resistance of endocrown restorations after cyclic loading. Forty extracted mandibular first molars were root canal treated. Decoronation was done for all the endodontically treated teeth 2 mm above the cemento-enamel junction. The teeth were individually fixed vertically into epoxy resin mounting cylinders. All teeth were prepared to receive endocrown restorations. The prepared teeth were randomly divided into four equal groups (n=10) according to the all-ceramic materials and technique used for endocrown construction as follows: Group I (n=10): Pressable lithium disilicate glass ceramics (IPS e-max Press), Group II (n=10): Pressable zirconia-reinforced lithium disilicate glass ceramics (Celtra Press), Group III (n=10): Machinable lithium disilicate glass ceramics (IPS e-max CAD), Group IV (n=10): Machinable zirconia-reinforced lithium disilicate glass ceramics (Celtra Duo). The endocrowns were cemented using dual-cure resin cement. All endocrowns were subjected to fatigue loading. The cycles were repeated 120,000 times to clinically simulate one year chewing condition. Marginal gap distance of all endocrowns was measured directly using a digital microscope with x100 magnification. The load required to failure was recorded in Newton. Data were collected, tabulated, and statistically analyzed. Fracture resistance testing of all-ceramic crowns revealed a statistically significant difference between all different ceramic materials used in this study (p-value <0.001). On the other hand, there was a statistically significant difference between all the four ceramic crowns for the marginal gap distance either before or after fatigue cyclic loading. After considering the limitation of the current study, the following conclusions were given: endocrowns are considered one of the promising minimally invasive restorations for root canal treated molars. CAD/CAM technology revealed better results than heat press technology regarding the fracture resistance of glass ceramics. Heat Press technology revealed better results than CAD/CAM technology regarding the marginal accuracy of glass ceramics.

The effect of surface treatments on the adhesive bond in all-ceramic dental crowns using four-point bending and dynamic loading tests

The aim of this study was to determine the effect of sandblasting, grinding and plasma treatment on the adhesive bond strength between framework ceramic (Y-TZP) and veneering ceramic (feldspar ceramic). Therefore, four-point bending specimens (n = 180) were cut from densely sintered 3Y-TZP blanks. Subsequently, 80 of these samples received surface treatment by sandblasting and 80 samples by grinding. A reference group (20 samples) was not processed. Half of the specimens that received a surface treatment were additionally exposed to an oxygen plasma treatment. After processing, all specimens were manually veneered with feldspar ceramic and examined with a four-point bending test to evaluate the strain energy release rate G. The surface treatment parameters that achieved the highest and lowest G were transferred to real geometries of a posterior crown (n = 45). The crowns’ ceramic framework was sandblasted and veneered by hand. The all-ceramic crowns were tested in a dynamic loading test and Wöhler curves were evaluated. Four-point bending samples blasted at an angle of 90° at 6 bar and a working distance of 1.5 cm without plasma treatment achieved the highest energy release rate. Samples blasted at an angle of 90° at 2 bar and a working distance of 1 cm with plasma treatment achieved the lowest energy release rate. Overall, plasma treatment did not improve bond strength. In the dynamic loading test, the group blasted with 2 bar showed the best results.

Implant–Prosthetic Rehabilitation of Maxillary Lateral Incisor Agenesis with Narrow Diameter Implants and Metal–Ceramic vs. All-Ceramic Single Crowns: A 16-Year Prospective Clinical Study

The main objectives of the present prospective clinical study were to evaluate the marginal bone resorption and the peri-implant soft tissue conditions around narrow diameter implants, as well as the clinical performances of metal–ceramic and all-ceramic single crowns in the implant–prosthetic treatment of maxillary lateral incisors agenesis. Seventy-two patients affected by monolateral or bilateral agenesis of the maxillary lateral incisors were included in the study, and a total of 105 narrow diameter implants were inserted. The final single crowns were fabricated 4 months after the surgical procedures by means of either titanium abutments with Auro-Galvan Crowns (AGC) veneered with feldspathic ceramics or zirconia abutments with all-ceramic (alumina or zirconia) crowns layered with dedicated veneering ceramics. Both marginal bone resorption and soft tissue quality were evaluated after a maximum period of 16 years. Two independent survival curves for patients wearing AGC or all-ceramic crowns were calculated by means of Kaplan–Meier analysis, and a log-rank test was performed in order to compare these curves (p &lt; 0.05). After 16 years of clinical function, a mean marginal bone resorption of 1.2 ± 0.61 mm and good response of peri-implant soft tissues were observed. Descriptive statistics resulted in 80% and 87.1% cumulative success rates for patients provided with AGC prostheses onto titanium abutments and all-ceramic crowns on-to zirconia abutments, respectively. The cumulative survival rate calculated for AGC group was 93.3%, whereas all-ceramic group showed a cumulative survival rate of 95.7%. No statistically significant differences were found with the log-rank tests. The overall success and survival rates calculated were 85% and 95% for all the restorations, respectively. Mucositis, abutment unscrewing, loss of retention, chipping, core fracture, and esthetic failure were the major complications reported. The implant–prosthetic approach can be considered an effective and viable solution to treat cases of maxillary lateral incisor agenesis in the long term.

Marginal Discrepancy of Five Contemporary Dental Ceramics for Anterior Restorations.

This study aimed to compare marginal accuracy of five contemporary all-ceramic crowns indicated for anterior restorations. A master die of maxillary central incisor was prepared for all-ceramic crown and duplicated to produce 50 replicas of epoxy resin material. Five ceramic materials were used to mill the crowns (n = 10). All crowns were manufactured following the same digital workflow; same master die, scanning unit and design software, and the recommended manufacturing protocol. Final seating of crown was secured by a small droplet of temporary cement on its incisal edge. Marginal accuracy was evaluated by scanning electronic microscope with a magnification of 300 × . Vertical marginal gap was measured for each crown at predefined four points. One-way analysis of variance was used to test differences between groups and Tukey test was used for multiple comparisons between group combinations. A level of significance at 95% was set for all statistics. The highest mean marginal gap and mean maximum gap calculated were for the e.max CAD crowns (49.2 µm, 87.6 µm), while the lowest values were for the Cercon xt crowns (10.2 µm, 21.7 µm). The mean marginal gap and the mean maximum gap of the e.max CAD crowns were statistically significantly greater than those of all other groups (p < 0.05). However, the differences between all other combinations were insignificant (p > 0.05). Marginal accuracy of lithium disilicate crowns is clinically acceptable. Zirconia and zirconia-reinforced lithium silicate materials can produce a greater level of marginal accuracy compared to lithium disilicate.

Effect of Repeated Heat-Pressing on Marginal and Internal Fit of Lithium Disilicate Glass Ceramic Crowns after Thermo-Mechanical Fatigue

Purpose: To evaluate the effect of repeated heat-pressing on marginal and internal fit of lithium disilicate glass ceramic crowns. Materials and Methods: A freshly extracted caries free human maxillary 1st premolar was prepared according to standardized preparation for all-ceramic crown restoration. The preparation was duplicated to produce thirty epoxy resin dies. The resin dies were divided into three groups (n=10) according to the number of heat-pressings of IPS e.max Press (Shade A2, LT) used for crowns construction. Group 1: Crowns constructed from freshly pressed ingots, Group 2: Crowns constructed from leftover repressed buttons for 1st time, and Group 3: Crowns constructed from leftover repressed buttons for 2nd time. The constructed crowns were cemented to their corresponding resin dies using adhesive resin cement, then samples were subjected to the thermo-mechanical fatigue with a ROBOTA chewing simulator. Each cemented ceramic crown was vertically sectioned bucco-lingually into 2 sections. Marginal, axial, and occlusal gaps were measured at seven defined points on each section using digital microscope. Data were tabulated and statistically analyzed using One-way ANOVA and Pearson’s correlation tests. The significance level was set at P<0.05. Results: The largest marginal and internal gap values were recorded in Group 1, while the lowest marginal and internal gap values were recorded in Group 3. Statistical analysis revealed that there were no significant differences in marginal and internal gaps between the tested groups (P<0.05). Conclusions: Repressing and thermomechanical fatigue have no significant effect on marginal and internal fit of IPS e.max Press crowns.

Advances in Diastema Closure and Tooth Shape Change

Diastema is a prevalent condition that causes poor aesthetics and increased self-consciousness among individuals. Diastema is defined as a gap or distance of two or more neighbouring teeth. Many patients desire the closure of diastemas for cosmetic reasons. In the event of normal physiological development, diastemas with widths of less than 2 mm in nine-year-old children frequently close on their own. Although if they fail to close split Essix plates or finger springs on a detachable device, they can be used for closure. However, to control the angulations of the crown and roots in adults with broader diastemas, fixed appliances are required for correction. By using a range of alternative treatment procedures, including all-ceramic crowns, metal-ceramic crowns, porcelain laminate veneers, direct composite veneers, and indirect composite veneers, the diastema closure can be conservatively completed without the need for braces. It has become difficult for endodontists to meet the needs of young people who are used to expecting speedier aesthetic outcomes in a set amount of time. A composite resin buildup provides a solution for all of the patients' vivid needs during this crisis. Various prosthodontic rehabilitation, restorative, and orthodontic procedures and their derivative techniques are employed in dental practice for the closure of diastemas. The availability of diverse procedures and techniques in recent times has allowed the patient to achieve an aesthetically pleasing smile. In this paper, we aim to review the existing evidence from the literature for advances in diastema closure and tooth shape change.

An in-vitro study comparing the mass of tooth structure removed following different restorative procedures in anterior teeth – An Original Research

Purpose – The aim of this study was to measure the mass of tooth structure removed in - Porcelain Laminate Veneers, Metal ceramic and All-ceramic crown preparation. To compare the mass of tooth structure removed from maxillary and mandibular incisors with canine teeth. Material and Methods – The study was conducted on a sample size of sixty teeth, selected based on the criteria that they had a single intact root, was free of caries, attrition, abrasion, erosion and had no sign of dental restoration. The bucco-lingual and mesio-distal dimensions of each specimen was measured at the cemento-enamel junction by using a thickness gauge and weighed. The specimen teeth were then prepared for receiving Porcelain laminate veneer, conventional metal ceramic and all-ceramic restoration according to pre-determined standardized preparation design. Results – There was statistically significant difference in mean final weight between laminate veneer &amp; metal ceramic. (P value &lt;0.05). In laminate veneers there was significantly less loss of weight as compared to the other types of preparations. Percentage of weight loss in laminate veneer was minimum followed by all ceramic &amp; metal ceramic. The percentage of loss of tooth structure for incisor and canine group for all selected types of restorations were not significantly difference. (P value &gt;0.05). Conclusions – Though the metal ceramic restorative procedure is most widely practiced across the world it demands highest amount of tooth structure removal. So, when clinical condition permits, considering this restorative procedure, the clinician may think over the other modalities of treatment once more.

Effect of Repeated Heat-Pressing on Color and Translucency of Lithium Disilicate Glass Ceramic Crowns

Purpose: To evaluate the effect of repeated heat-pressing and thermomechanical fatigue on color and translucency of lithium disilicate glass ceramic crowns. Materials and Methods: A freshly extracted human maxillary right 1st premolar was prepared according to standardized preparation for all-ceramic crown restoration. The preparation was duplicated to produce thirty epoxy resin dies. The resin dies were divided into three groups (n=10), according to the number of heat-pressings of IPS e.max Press used for crowns construction. Group 1: Control group using freshly pressed ingots, Group 2: Repressed 1 using leftover repressed buttons for 1st time, and Group 3: Repressed 2 using leftover repressed buttons for 2nd time. Thirty IPS e.max Press crowns were fabricated by heat-pressing technique. The constructed crowns were cemented by adhesive resin cement. Color and translucency were measured after cementation by X-Rite Reflective Spectrophotometer. Then samples were subjected to the thermo-mechanical fatigue with a ROBOTA chewing simulator, simulating 6 months chewing conditions. After thermo-mechanical fatigue, color and translucency were measured by X-Rite Reflective spectrophotometer. Results: IPS e.max Press showed no statistically significant color change after repressing and thermomechanical fatigue. Regarding translucency, IPS e.max Press showed no statistically significant difference in translucency after repressing, however, there was a statistically significant decrease in translucency after thermomechanical fatigue. Conclusions: Repressing and thermomechanical fatigue have no significant effect on color of IPS e.max Press crowns. Repressing has no significant effect on translucency, however, thermomechanical fatigue has a significant effect on translucency of freshly pressed and repressed e.max Press crowns.

In vitro effect of anodization of titanium abutments on their tensile bond strength to implant-supported lithium disilicate all-ceramic crowns

In vitro effect of anodization of titanium abutments on their tensile bond strength to implant-supported lithium disilicate all-ceramic crowns

Mechanical behavior of different machinable ceramic crowns using vertical and horizontal preparations: an in-vitro study

Objective: the aim of this study was to compare the mechanical behavior of different ceramics when used in thinvertical preparations versus traditional horizontal preparation. Material and Methods: two stainless-steel dieswere milled to simulate a minimally invasive vertical preparation (VP) and a traditional horizontal preparation(HP) for an all-ceramic crown of a maxillary first premolar. The stainless-steel dies were duplicated using epoxyresin. Eighty monolithic crowns were milled and divided into 2 groups according to preparation design. Eachdesign group was subdivided into 4 sub-groups according to material (n=10): IPS e.max CAD (lithium disilicate),Bruxzir shaded zirconia (full contour zirconia), CeraSmart (resin nanoceramic) and CEREC Tessera (advancedlithium disilicate). The crowns were cemented on their relevant epoxy resin dies using self-adhesive resin cement.All specimens were subjected to 15,000 thermocycles and then loaded to fracture in a universal testing machine.Data were analyzed using two-way ANOVA and Tukey pair wise comparison test. Results: the fracture resistancemean values of the VP (1344 + 118 N) was significantly lower than the HP design (1646 + 191 N). Ceramiccrowns made of full contour zirconia had higher fracture resistance mean values (2842 + 380 N) than advancedlithium disilicate (1272 + 125 N) followed by lithium disilicate crowns (983 + 52 N) and resin nanoceramic(882 + 61 N). Conclusion: both vertical and horizontal preparations, regardless the different ceramic materials,showed clinically acceptable fracture resistance values. KEYWORDSDental crown; Prosthodontics; Zirconia; Lithium disilicate; Hybrid ceramics.

Assessment of marginal gaps and image quality of crowns made of two different restorative materials: An in vitro study using CBCT images.

The present study assessed the quality of images and the presence of marginal gaps on cone-beam computed tomography (CBCT) images of teeth restored with all-ceramic and metal-ceramic crowns and compared the gap sizes observed on CBCT images with those obtained on micro-CT images. Thirty teeth restored with metal-ceramic and all-ceramic crowns, properly adapted and with gaps of 0.30 and 0.50 mm, were submitted to micro-CT and CBCT scans. Linear measurements corresponding to the marginal gap (MG) and the absolute marginal discrepancy (AMD) were obtained. The objective assessment of the quality of CBCT images was performed using the contrast-to-noise ratio (CNR), and the subjective assessment was defined by the diagnoses made by five examiners regarding the presence or absence of gaps. The measurements were always higher for CBCT, with a significant difference regarding AMD. No significant difference in image quality was observed using CNR between the crowns tested. Low accuracy and sensitivity values could be observed for both crowns. Marginal mismatch measures were overestimated in CBCT images. No difference in image quality was observed between the crowns. The correct diagnosis of gaps was considered low, irrespective of crown type and gap size.

Differences between ceramic and porcelain laminate veneers

In dental care, treating anterior dentition esthetically has always been difficult. Numerous restorative solutions, including resin composites, all-ceramic crowns, and ceramic veneers, become accessible with the advancement of dental materials. In such situations, practitioners and patients should pick the most appropriate option to enhance oral health and aesthetic outcomes. Any substance made of non-metallic inorganic matter and fired at an elevated temperature is referred to as ceramics (pyrochemical process). Ceramics called glass ceramics are those that commence in a glassy phase and later devitrify to a partly or wholly crystalline form. Dental ceramics that most closely optically resemble the characteristics of real teeth are primarily glassy materials, which are derived primarily from triaxial porcelain compositions of feldspar, quartz, and kaolin. Glass-ceramics possess much more toughness and strength than porcelain but are also less translucent. Tougher and more durable ceramics, primarily yttrium stabilized tetragonal zirconia polycrystals, have been developed recently (Y-TZP). Due to its limited translucency, Y-TZP presents a major drawback. A significant amount of current tooth structure must be removed in order to allow for a porcelain veneer that is wide enough to overlay an opaque zirconia base and replicate the optical characteristics of the surrounding natural teeth. Ceramic restoration effectiveness, in the end, relies on the material choice, production process, and restoration strategy.

Comparison the marginal and internal fitness of veneered and anatomical zirconia crowns milled by two different CAD/CAM systems (An in Vitro Study)

Background: Accuracy of fit is considered a very important factor in a crown fabricating procedure. Zirconium oxide ceramic is gaining popularity because of its remarkable mechanical capabilities and the potential aesthetic results obtained by using its recommended veneering porcelain, this study aimed to determine the effect of porcelain veneering on the marginal and internal fitness of zirconium-oxide crowns milled with two different CAD/CAM systems ( Wet and dry milling).&#x0D; Materials and methods: An ideal prepared tooth #16 to receive an all-ceramic crown restoration with 0.8mm chamfer finishing line was used as a master die. It duplicated and poured to get thirty-two stone working dies. The stone dies divided into two major groups according to the CAD/CAM systems being used, then each group subdivided into two subgroups (n=8) either zirconia crowns milled to full contour or traditional veneered zirconia crowns. Each crown then cemented to it stone die and sectioned longitudinally into four pieces. Stereomicroscope with aid of (image J) was used to examine the sample at a magnification of (140X). Four points of measurement were selected at each of the four-sectioned parts.&#x0D; Results: The final internal gap value of each sample was the arithmetical mean of the selected points of the four-sectioned pieces The data was evaluated statistically, using One-way ANOVA and LSD tests which revealed highly significant differences (p&lt;0.001) among groups.&#x0D; Conclusion: Full-contoured zirconia crowns have better marginal and internal fit than the traditionally veneered crown, (CEREC AC, Sirona) system showed the best internal fitness. The mean gap of all groups was within the clinically acceptance.