Fracture Resistance and Failure Mode of Monolithic Zirconia, Veneered Zirconia, and Metal-Ceramic Full-Coverage Restorations: A Comparative In Vitro Study.

PURPOSE: To evaluate and compare the fracture mode and strength of monolithic zirconia to veneered zirconia and metal-ceramic full-coverage restorations following artificial aging and to test the performance of translucent zirconia in terms of load-bearing capacity. MATERIALS AND METHODS: Two mandibular first molars were prepared and scanned for their respective groups of full-coverage restorations. A total of 75 full-coverage restorations were fabricated and divided into five groups: two groups for monolithic zirconia, two groups for veneered zirconia, and one group for metal-ceramic. Then, 75 light-cured hybrid composite resin dies were fabricated to serve as abutments. Before cementation, all full-coverage restorations were subjected to accelerated aging. After cementation, all full-coverage restorations were subjected to compressive loading until fracture in an electromechanical universal testing machine. A two-way nested ANOVA and Tukey test were used to analyze the results with 95% confidence levels. RESULTS: Monolithic zirconia full-coverage restorations showed the highest mean fracture resistance of 4,201.0 N, followed by metalceramic full-coverage restorations of 3,609.3 N, and veneered zirconia full-coverage restorations showed the lowest mean fracture resistance of 2,524.6 N. The main mode of failure was cohesive bulk fracture for the monolithic zirconia group, cohesive/adhesive failure with infrastructure damage for the veneered zirconia group, and cohesive/adhesive failure without infrastructure damage for the metal-ceramic group. CONCLUSIONS: Monolithic zirconia full-coverage restorations showed superior resistance to fracture compared to metal-ceramic full-coverage restorations and are highly reliable in terms of load-bearing capacity within the posterior regions of the mouth.

Fracture resistance and failure mode of monolithic zirconia, veneered zirconia, and metal-ceramic full-coverage restorations: A comparative in vitro study.

PURPOSE: To evaluate and compare the fracture mode and strength of monolithic zirconia to veneered zirconia and metal-ceramic full-coverage restorations following artificial aging. The main concern was to test the performance of translucent zirconia in terms of load-bearing capacity. MATERIALS AND METHODS: Two mandibular first molars were prepared and scanned for their respective groups of full-coverage restorations. 75 full-coverage restorations were fabricated and divided into five groups: two groups for monolithic zirconia, two groups for veneered zirconia, and one group for metal-ceramic. 75 light-cured hybrid composite resin dies were fabricated to serve as abutments. Before cementation, all full-coverage restorations were subjected to accelerated aging. After cementation, all full-coverage restorations were subjected to compressive loading until fracture in an electromechanical universal testing machine. A two-way nested analysis of variance and Tukey test were used to analyze the results with 95% confidence levels. RESULTS: Monolithic zirconia full-coverage restorations showed the highest mean fracture resistance of 4,201 N, followed by metal-ceramic full-coverage restorations of 3,609.3 N, and the veneered zirconia full-coverage restorations showed the lowest of 2,524.6 N. The main mode of failure was cohesive bulk fracture for the monolithic zirconia group, cohesive/adhesive failure along with infrastructure damage for the veneered zirconia group and cohesive/adhesive failure without infrastructure damage for the metal-ceramic group. CONCLUSIONS: Monolithic zirconia full-coverage restorations showed superior resistance to fracture in comparison to metal-ceramic full-coverage restorations and are highly reliable in terms of load-bearing capacity within the posterior regions of the mouth.

Effect of CAD-CAM tool deterioration on the trueness of ceramic restorations.

STATEMENT OF PROBLEM: Tools will gradually deteriorate with repetitive milling. However, tool lifetime can vary depending on the type of milling machine, the hardness of the ceramic material, and the size of the restoration. Studies evaluating the effect of tool deterioration on the trueness of milled restorations are lacking. PURPOSE: The purpose of this study was to evaluate the effect of tool deterioration on the trueness of milled restorations. MATERIAL AND METHODS: A patient requiring a ceramic crown was recruited. Repetitive milling of zirconia crowns (inCoris TZI; Dentsply Sirona) with tungsten carbide rotary instruments and glass-ceramic crowns (VITABLOCS mark II; Vita Zahnfabrik) with diamond rotary instruments was performed by using a 5-axis milling machine (inLab MC X5; Dentsply Sirona) until the machine software program indicated replacing the largest tool. The percentage of deterioration for the largest tool was recorded before each milling. The trueness for different crown areas was evaluated by using a 3-dimensional evaluation software program (Geomagic Control X; 3D systems), and the crowns were clinically evaluated. The crowns were grouped into 4 quadrants as per the deterioration percentage. The Pearson correlation (r) between the deterioration percentage and trueness and linear contrast analysis (partial eta squared [η]) among the groups were performed. RESULTS: Glass-ceramic crown areas had low correlation except for mesial (high, r=0.63, high, η=0.37) and distal (medium, r=0.42, high, η= 0.34) areas, whereas zirconia crowns had low correlation for inner and internal areas and medium to high correlation for mesial (r= -0.31, η=0.33), distal (r= -0.53, η=0.36), occlusal (r= -0.32, η=0.164), external (r= 0.69, η=0.52), and marginal (r= -0.44, η=0.19) areas. Zirconia crowns had excellent marginal fit and occlusal contact and light to excellent proximal contact, whereas glass-ceramic crowns had excellent marginal fit, minor to major occlusal correction, and heavy proximal contact. CONCLUSIONS: The effect of tool deterioration on trueness depended on material type and crown area. Only proximal areas were affected in the glass-ceramic crowns, whereas external, proximal, occlusal, and marginal areas were affected in the zirconia crowns. Trueness did not necessarily reflect the clinical quality of the crown, as both crown types were clinically satisfactory. Although zirconia crowns were overmilled in comparison with the reference design and glass-ceramic crowns, they had better clinical quality.

Effect of CAD/CAM Bur Deterioration on the Surface Roughness of Ceramic Crowns.

PURPOSE: To evaluate the effect of repetitive milling on the surface roughness of ceramic crowns. MATERIALS AND METHODS: Twenty feldspathic ceramic crowns (VITABLOCS Mark II; Vita Zahnfabrik, Bad Säckingen, Germany) milled with hard milling protocol, and 20 zirconia crowns (5Y-TZP, inCoris TZI; Dentsply Sirona, York, PA) milled with soft milling protocol, using a 5-axis milling machine (inLab MC X5; Dentsply Sirona) were investigated. Atomic force microscopy (SPM SmartSPM™-1000) was used for surface roughness measurements (Ra, RMS). Pearson correlation between bur deterioration percentage as provided by the software of the milling machine and surface roughness was performed with an (r) range between 1 and -1. Trend analysis between the 2-half and among the 4-quarter bur lifetime was performed with linear contrast analysis and partial eta squared (η) for estimate of effect size. Analysis of mean variance between the zirconia and feldspathic ceramic groups was performed with a t-test, with α = 0.05. RESULTS: Correlation analysis showed small correlation for Ra, RMS (r = -0.02, -0.16 for the feldspathic ceramic crowns and r = 0.044, 0.034 for the zirconia crowns), and no significant differences for the 2-half and 4-quarter groups (p > 0.05) for both crown types. Estimate of effect size was rated as medium for the 2-half groups (Ra = 0.420, RMS = 0.395) and large for the 4-quarter groups (RA = 0.22, F = 1.48, RMS = 0.19, F = 1.26) for the feldspathic ceramic crowns, and small effect size for the 2-half groups (Ra = 0.18, RMS = 0.20) and the 4-quarter groups (Ra = 0.035, RMS = 0.037) for the zirconia crowns. There was no significant difference (p = 0.178, F = 0.016. p = 0.088, F = 0.002) between the feldspathic ceramic and zirconia crowns with medium and large effect size (0.45, 0.57) for RA and RMS. CONCLUSIONS: Milling zirconia and feldspathic ceramic crowns had small correlation between bur deterioration and surface roughness when the burs were used within their recommended lifetime. However, hard milled feldspathic ceramic crowns had higher surface roughness than the soft milled zirconia crowns. Bur deterioration had a larger effect on the surface roughness of the feldspathic ceramic crowns than the zirconia crowns.

Comparison of the Accuracy of Fit of Metal, Zirconia, and Lithium Disilicate Crowns Made from Different Manufacturing Techniques.

PURPOSE: To evaluate the accuracy of fit of metal, lithium disilicate, and zirconia crowns, which were produced using different manufacturing techniques. MATERIALS AND METHODS: Ten patients in need of a molar crown were recruited. Eight crowns were fabricated for each patient: 2 zirconia, 3 lithium disilicate (e.max), and 3 metal-ceramic crowns using conventional, conventional/digital, and digital techniques. Marginal, axial, and occlusal gaps were measured using a replica technique. Replicas were sectioned mesiodistally and buccolingually and were observed under a stereomicroscope. A total of 32 measurements for each crown replica at 3 different points (12 marginal, 12 axial, and 8 occlusal) were performed. Statistical analysis was performed using two-way ANOVA and Tukey HSD tests. RESULTS: Marginal means ranged from 116.39 ± 32.76 µm for the conventional metal-ceramic group to 147.56 ± 31.56 µm for the digital e.max group. The smallest axial gap was recorded for the digital zirconia group (76.19 ± 23.94 µm), while the largest axial gap was recorded for the conventional e.max (101.80 ± 19.81 µm) and conventional/digital metal-ceramic groups (101.80 ± 35.31 µm). The conventional e.max crowns had the smallest occlusal mean gap (185.59 ± 59.09 µm), while the digital e.max group had the largest occlusal mean gap (295.38 ± 67.80 µm). Type of crown had no significant effect on marginal (p = 0.07, f = 2.71), axial (p = 0.75, f = 0.29), or occlusal fit (p = 0.099, f = 2.4), while fabrication method had a significant effect on axial gap only (p = 0.169, f = 1.82, p = 0.003, f = 6.21, and p = 0.144, f = 2 for marginal, axial, and occlusal fit, respectively). Digital fabrication produced significantly smaller axial gaps than the conventional method (p = 0.02), and the conventional digital method (p = 0.005). CONCLUSIONS: The type of crown and method of manufacturing had no effect on the marginal and occlusal gap of single posterior crown, while the method of manufacturing had a significant effect on the axial gap. The digital method produced the smallest axial fit in comparison with the other methods, while the type of crown had no effect on the axial gap.

The effect of antifungal agents on surface properties of poly(methyl methacrylate) and its relation to adherence of Candida albicans.

PURPOSE: Candida-associated denture stomatitis is the most prevalent form of oral candidosis affecting 65% of denture wearers. Failure of therapy and recurrence of infection are not uncommon and the continuous use of antifungal agents may affect the surface properties of the denture material and may contribute to Candida adhesion. This study aimed to investigate surface properties of poly(methyl methacrylate) PMMA denture material before and after exposure to antifungal agents and its relation to in vitro adhesion of Candida albicans. METHODS: Four groups of acrylic specimens (20 mm × 20 mm × 2.5mm) were prepared (25 specimens in each group). Specimens were immersed in nystatin (group 1), fluconazole (group 2), distilled water (group 3) and group 4 was not exposed. Specimens were tested for surface roughness, contact angle, surface hardness and in vitro Candida adherence to PMMA. RESULTS: The results showed that nystatin had no statistically significant effect on surface hardness (P>0.05), but had a statistically significant effect on surface roughness, contact angle, and Candida adhesion to PMMA (P<0.05). On the other hand, fluconazole had no statistically significant effect on surface hardness or roughness (P>0.05), but had a statistically significant effect on contact angle, and Candida adhesion to PMMA (P<0.05). Distilled water had no statistically significant effect on surface hardness, roughness, contact angle, or Candida adhesion to PMMA (P>0.05). CONCLUSIONS: Exposure of PMMA to nystatin may induce changes in roughness, wettability while exposure to fluconazole may affect surface free energy and therefore may increase Candida adhesion to it.

Passive fit and accuracy of three dental implant impression techniques.

OBJECTIVE: To reassess the accuracy of three impression techniques relative to the passive fit of the prosthesis. METHOD AND MATERIALS: An edentulous maxillary cast was fabricated in epoxy resin with four dental implants embedded and secured with heat-cured acrylic resin. Three techniques were tested: closed tray, open tray nonsplinted, and open tray splinted. One light-cured custom acrylic tray was fabricated for each impression technique, and transfer copings were attached to the implants. Fifteen impressions for each technique were prepared with medium-bodied consistency polyether. Subsequently, the impressions were poured in type IV die stone. The distances between the implants were measured using a digital micrometer. The statistical analysis of the data was performed with ANOVA and a one-sample t test at a 95% confidence interval. RESULTS: The lowest mean difference in dimensional accuracy was found within the direct (open tray) splinted technique. Also, the one-sample t test showed that the direct splinted technique has the least statistical significant difference from direct nonsplinted and indirect (closed tray) techniques. All discrepancies were less than 100 Μm. CONCLUSION: Within the limitations of this study, the best accuracy of the definitive prosthesis was achieved when the impression copings were splinted with autopolymerized acrylic resin, sectioned, and rejoined. However, the errors associated with all of these techniques were less than 100 Μm, and based on the current definitions of passive fit, they all would be clinically acceptable.

Single-tooth replacement: factors affecting different prosthetic treatment modalities.

BACKGROUND: The choice between several treatment options for replacing a single missing tooth is influenced by clinical, dentist- and patient-immanent factors. This study aimed to determine the patient factors that would affect the treatment decision to replace a single missing tooth and to assess the satisfaction with several options. METHOD: 200 volunteers involved (121 females and 79 males) divided into four groups, Group A: consisted of patients with conventional fixed partial dentures or patients with resin bonded fixed partial dentures. Group B: consisted of patients who received removable partial dentures while Group C: consisted of patients who received a single implant supported crown, and a control group D: consisted of patients who received no treatment. Data were collected using a questionnaire. RESULTS: The highest percentage of males within groups (58%) was within the removable prostheses category. The majority of the subjects in the study reported that the main reason for replacing a missing tooth was for esthetic and function. Most important factor affecting the choice between treatment modalities was damaging the neighboring teeth. Pain, post operative sensitivity and dental phobia were important factors in choosing the prosthesis type and affected the control group patients not to have any treatment. The highest satisfaction percentage among groups studied was recorded for dental implants then FPD groups, while the least percentage were in both the control and RPD groups, for all aspects of function, esthetic and speech efficiency. CONCLUSIONS: The final choice between FPD, RPD and implant depended on several factors which affected the decision making; among these is cost and patients' awareness of the different treatment options.

Efficacy and persistence of tooth bleaching using a diode laser with three different treatment regimens.

STATEMENT OF PROBLEM: Studies have measured the effectiveness of tooth bleaching, however there are very few studies that have measured the persistence in color change after a 6-month follow-up. PURPOSE: This study assessed the efficacy of the laser bleaching process using different regimens, and the persistence of color change over a 6-month period. METHOD AND MATERIALS: Sixty patients divided into three equal groups were subjected to bleaching using a diode laser with 34% hydrogen peroxide. Group 1: patients subjected to one session of laser bleaching. Group 2: patients subjected to two sessions of laser bleaching with a 1-week interval. Group 3: the same as Group 2 but followed by home bleaching once a month for 3 months. The color was assessed four times: before bleaching, directly after bleaching, 3 months after bleaching, and 6 months after bleaching. RESULTS: All teeth had a significant color change at 6 months, but all teeth had regressed from the maximum value. There was significantly less regression in color for Group 3, followed by Groups 2 and 1, respectively. CONCLUSION: The combined technique of in-office laser bleaching for two sessions with a 1-week interval, followed by home bleaching once a month for 3 months gave more persistence in color change. CLINICAL SIGNIFICANCE: In-office power bleaching using a laser assisted hydrogen peroxide system repeated after a week, combined with home bleaching once a month for 3 months, is an effective bleaching regimen with less color regression after 6 months compared to a regimen of in-office bleaching alone.

The position of the occlusal plane in natural and artificial dentitions as related to other craniofacial planes.

PURPOSE: This study aimed at determining the most reliable ala-tragus line as a guide for the orientation of the occlusal plane in complete denture patients by use of cephalometric landmarks on dentate volunteers. MATERIALS AND METHODS: Analysis was made for prosthodontically related craniofacial reference lines and angles of lateral cephalometric radiographs taken for 47 dentate adults. Variables were determined and data were analyzed using SPSS (SPSS, Inc., Chicago, IL). RESULTS: Occlusal plane angle formed between the occlusal plane and Camper's plane had the lowest mean value in the angle formed with Camper's I, which represents the measure taken from the superior border of the tragus of the ear with a score of 2.1°. The highest was measured in the angle formed with Camper's III with a score of 6.1°, while the angle formed with Camper's II was 3.2°. The differences between the three planes in relation to the occlusal plane was significant (p < 0.001). CONCLUSION: The superior border of the tragus with the inferior border of the ala of the nose was most accurate in orienting the occlusal plane.

Relationship between patients' oral health-related quality of life, satisfaction with dentition, and personality profiles.

AIM: The aim of this study was to investigate the relationship between patients' oral health-related quality of life, satisfaction with their dentition, and their personality profiles. METHODS AND MATERIALS: Eighty-four patients (30 males and 54 females; mean age 31.9+/-12.7 years) seeking routine dental treatment were recruited for this study. A "Dental Impact on Daily Living" (DIDL) questionnaire was used to assess dental satisfaction and impact on daily living. An "Oral Health Impact Profile" (OHIP) was used to measure self-reported discomfort, disability, and dysfunction caused by oral conditions. Oral health-related quality of life was assessed using the "United Kingdom Oral Health Related Quality of Life" measure (OHQoL-U.K). A "NEO Five Factor inventory" (NEO-FFI) was used to assess personality profiles. RESULTS: The dentition has a measurable impact on daily living as well as with satisfaction with appearance, pain levels, oral comfort, general performance, and eating capability (p=0.000). Younger patients had more profound oral health impacts (p=0.045) and higher neuroticism scores (0.043). OHIP scores were significantly related to OHQoL-UK scores (p=0.000). DIDL scores had significant correlations with OHIP and OHQoL-UK scores (p<0.05). Significant correlations were established between neuroticism and satisfaction with oral comfort, extraversion and total satisfaction and satisfaction with general performance, and openness and satisfaction with appearance (p<0.05). OHIP and OHQoL-UK scores had no significant correlations with psychological profiles. CONCLUSION: The status of the oral cavity can have a definitive impact on patients' daily living and quality of life regardless age, gender, and level of education. Patients' satisfaction with their dentition has definitive impacts on daily living, quality of life, and dental perceptions. Personality profiles (neuroticism; extraversion, and openness) may influence dental perceptions, play a significant role in shaping satisfaction with dentition, and help with the prediction of the dental impact on daily living. CLINICAL SIGNIFICANCE: Since patients' satisfaction with their dentitions impacts their daily living and quality of life while affected by their psychological profiles, this should be considered when formulating a treatment plan for management for their dentition in order to obtain patient acceptance of the proposed treatment.

Management of dental implant fractures. A case history.

The widespread use of endosseous osseointegrated implants to replace missing natural teeth increases the chances of implant complications and failures, despite the high initial success rate reported in the literature. Implant fracture is one possible complication that results in ultimate failure of the dental implant. Such a complication poses a management crisis even for the most experienced clinician. This article reports on a case of implant fracture, its possible causes, and how the case was managed.

Anterior midline point stop device (AMPS) in the treatment of myogenous TMDs: comparison with the stabilization splint and control group.

Two occlusal splints, the full-arch stabilization splint and the anterior midline point stop (AMPS) device, were evaluated for their efficiency in relieving myogenous temporomandibular disorders (TMD). One hundred and fourteen patients with myogenous TMD were distributed into 3 groups. The first group was treated with the AMPS device, the second with the stabilization splint, and the third group was the control group. Pain intensity was scored using the visual analogue scale before treatment and 1 month and 3 months after treatment. Statistical Package for the Social Sciences (SPSS, Chicago, Ill) and multiple comparisons tests were used to compare results before and after treatment and to compare the groups. The use of AMPS device in the first group resulted in a significant improvement after 1 month and 3 months (P < or = .001) and showed a 56.66% pain reduction. A significant improvement was also noticed in the second group (P = .001) with a 47.71% pain reduction. Although pain reduction percentage appeared more in the first group, this was not statistically significant. There was a highly significant difference between groups treated with both kinds of splints and the control group. It was concluded that both types of occlusal splints are beneficial to patients with myogenous TMD.

Torus palatinus and torus mandibularis in edentulous patients.

AIM: To determine the prevalence of tori in Jordanian edentulous patients, the sex variation in their distribution, and their clinical characteristics. METHODS: Three hundred and thirty eight patients were examined in the Prosthodontic Clinic in the Department of Restorative Dentistry at Jordan University of Science and Technology. The location, extent, and clinical presentation of tori were recorded related to the age and sex of patients. RESULTS: The overall prevalence of tori was 13.9%. The prevalence of torus palatinus was 29.8% (14/47), while that of torus mandibularis was significantly higher 42.6% (20/47). Both types of tori were associated with each other in 27.7% of cases (13/47). CONCLUSIONS: There was no significant difference in the prevalence of tori between males and females. There seems to be a strong association between mandibular and palatal tori.

A clinical evaluation of the clinical remount procedure.

One hundred patients were treated with complete dentures. The patients were divided into two equal groups; the first group (50 patients) received complete dentures and a clinical remount procedure was performed, while the second group received complete dentures without a clinical remount. A four point, nine scale Patient Denture Satisfaction questionnaire was used to evaluate the patients' satisfaction with their dentures. When the clinical remount procedure was used, results have shown a highly significant improvement in the comfort of the upper dentures and in the fit and comfort of the lower dentures. There was a significant improvement in the chewing ability as well. In conclusion it is highly recommended the clinical remount procedure be used because it improves the patient's satisfaction with their dentures in many important aspects as shown in this study.

Psychological profile in burning mouth syndrome.

Thirty-two patients with burning mouth syndrome and 32 matched control subjects were evaluated for their personality profile using a comprehensive, reliable, and validated inventory. All subjects were requested to complete the Neo PI-R questionnaire that measures the 5 dimensions of personality and their facets. A t-test and univariate correlations (Pearson's correlation coefficient) were used to compare the 2 groups. Results show high significant differences in some personality factors. Neuroticism and all its facets, which include anxiety, angry hostility, depression, self-consciousness, impulsiveness and vulnerability, were significant at P<.001. Other domains like extraversion, openness, and conscientiousness showed significant differences also (P<.05). Many personality characteristics differentiate burning mouth syndrome patients from controllers according to the Neo PI-R and this should affect the treatment plan according to the identified characteristics.