Impact of the Covid-19 pandemic on dental practices in Denmark.

OBJECTIVE: To investigate the impact of the Covid-19 pandemic on the patient flow and economy as experienced by dental practices in Denmark. MATERIAL AND METHODS: A survey regarding experience of patient flow, economical turnover, financial strain and willingness to pay for large treatments during the first year of the Covid-19 pandemic (March 2020 to March 2021), along with information on the characteristics of the practice (specialist practice, ownership, practice operation and size) was distributed to all dental practices in Denmark in March 2021. RESULTS: Of the 1728 practices, 581 (33.6%) answered the survey. A decline in patient flow and a decline in economical turnover were reported by 79% and 84.4% of the practices, respectively. Financial strain was reported by 15.8% and an increased willingness to pay for large treatments was reported by 32.1%. A large decline in turnover and financial strain were associated with non-specialized practices, practices with a single owner and small practices. Logistic regressions showed that practices not receiving referrals had an odds ratio of 2.34 (CI: 1.32-4.14) for having a large decline in economic turnover compared with practices receiving referrals and that small practices had an odds ratio of 1.92 (CI: 1.16-3.19) for reporting financial strain compared with large practices. CONCLUSIONS: Reportedly, the Covid-19 pandemic resulted in a decline in both patient flow and economical turnover in Danish dental practices. Large and more specialized practices seem to have managed the economic crisis better.

Accuracy of crowns based on digital intraoral scanning compared to conventional impression-a split-mouth randomised clinical study.

OBJECTIVES: The aim of this prospective in vivo study was to evaluate the accuracy of the marginal and internal fit of crowns based on conventional impression (CI) or intraoral scan (IOS) in a randomised, split-mouth set-up. MATERIALS AND METHODS: Nineteen patients needing full coverage crowns, fitting a split-mouth design, were provided with two lithium disilicate crowns: one based on a CI and one based on an IOS. The marginal and internal accuracy of the crowns were assessed with the replica technique and clinically using a modified California Dental Association (CDA) quality evaluation system. RESULTS: At the preparation margin, the median gap was 60 µm for IOS and 78 µm for CI. For the other points, the median gap ranged from 91 to 159 µm for IOS and 109 to 181 µm for CI. The accuracy of the IOS was statistically significantly better at all point except at the cusp tip. All crowns where rated R or S at both the 6- and 12-month follow-up appointments. The results for the clinical evaluation with CDA for marginal integrity showed no statistically significant difference between the two impression methods at both the 6- and 12-month evaluations. CONCLUSIONS: Crowns based on IOS show statistically significantly better marginal and internal adaptation before cementation compared to conventional impression. However, the clinical evaluation showed similar marginal adaptation. CLINICAL RELEVANCE: Crowns based on a fully digital workflow can provide clinically acceptable marginal adaptation, comparable to crowns based on CI.

Marginal bone level in two Danish cross-sectional population samples in 1997-1998 and 2007-2008.

OBJECTIVE: The aim of this study was to compare the marginal bone level of two randomly selected population samples from 1997/1998 and 2007/2008, with special emphasis on the role of smoking habits and gender. MATERIALS AND METHODS: Two cross-sectional randomly selected population samples [1997/1998 (N = 616) and 2007/2008 (N = 396)] were analysed with respect to the marginal bone level. The marginal bone level was measured in full-mouth intraoral radiographs. Information on smoking was gathered using questionnaires. Multiple regression analysis was used in order to adjust for correlating factors (gender, age, smoking habits and number of teeth). RESULTS: After adjusting for confounding factors, the population sample from 2007/2008 had on average a slightly, but statistically significantly, more reduced average marginal bone level (0.15 mm) than the population sample from 1997/1998. Men had more reduced marginal bone level than women (0.12 mm). Smokers in both population samples had more reduced marginal bone level than non-smokers (0.39 mm and 0.12 mm for 1997/1998; 0.65 mm and 0.16 mm for 2007/2008). CONCLUSIONS: In these populations, sampled 10 years apart, the 2007/2008 population sample had a slightly more reduced marginal bone level than the 1997/1998 population sample. Men had more reduced marginal bone level than women, and smoking is considered a major risk factor for a reduced marginal bone level.

Marginal Bone Loss after Ten Years in an Adult Danish Population: A Radiographic Study.

PURPOSE: To evaluate marginal bone loss over a 10-year period in individuals and in tooth groups in relation to age and level of marginal bone. MATERIALS AND METHODS: In 1997, 616 randomly selected individuals (mean age: 42 years, range: 21-63 years) underwent a full-mouth radiographic survey. In 2008, the survey was repeated in 362 of the same individuals (182 women and 180 men). The marginal bone level of each tooth was measured in mm from the cementoenamel junction to the marginal bone. These measurements were used to calculate marginal bone loss during the 10-year period for individuals and tooth groups in relation to age and to baseline marginal bone level, calculated as the average between measurements in 1997 and 2008 to circumvent regression towards the mean. RESULTS: The average annual marginal bone loss was 0.09 mm (SD ±â€¯0.04 mm) during the 10-year study period. The association between marginal bone loss and baseline marginal bone level was more pronounced in the youngest age group, compared to the other age groups. Molars displayed the most severe bone loss during the study period. CONCLUSION: Marginal bone loss over a 10-year period is associated with age and baseline marginal bone level. Younger individuals with a reduced marginal bone level were at higher risk for further bone loss. Molars lose marginal bone more rapidly than other tooth groups.

Correspondence between conventional and digitised radiographs for assessment of marginal bone.

PURPOSE: To compare reproducibility of marginal bone measurements in conventional film and digitised radiographs and to assess whether variations in reproducibility occurred in measurements taken in a longitudinal, epidemiological survey. MATERIALS AND METHODS: Triplicate measurements of the marginal bone level and of remaining bone were obtained from film and digitised full-mouth radiographic surveys from 20 individuals who were examined three times at five-year intervals in a longitudinal study design. The digitalisation of the films was conducted by scanning the film with a flatbed scanner. The standard deviation (SD) of the triplicate measurements served as the statistic for reproducibility. The time spent for recording one radiographic survey, which consisted of 14 periapicals and 2 bitewings, was documented. RESULTS: Statistically significant differences existed in the reproducibility of marginal bone level measurements obtained at the first examination and the two subsequent examinations both for film and digitised radiographs (P < 0.05). The difference in marginal bone level measurements (film vs digitised) was 0.16 mm (SD = 0.45 mm). Similarly, the overall difference in measurements of the remaining bone was 0.12 mm (SD = 0.61 mm). Recording of a digitised survey lasted on average 5 min (SD = 1.5 min), while the recording of a film survey lasted on average 14 min (SD = 1 min). CONCLUSIONS: Digitising film is an acceptable method for the purpose of assessing the marginal bone level and will save time in longitudinal, epidemiological studies.

Fracture resistance of endodontically treated maxillary incisors restored with single or bundled glass fiber-reinforced composite resin posts.

Background: To compare the fracture resistance of endodontically treated maxillary incisors restored with single versus bundled glass fiber-reinforced composite resin posts (FRC). Material and Methods: Twenty-four maxillary incisors underwent root canal preparation (1.5-mm-diameter post spaces after canal obturation). Teeth were randomly divided into two groups (n = 12). Two different FRC groups were used for the intracanal post treatment. Single FRC (Rebilda Post system, 1.5 mm diameter) and bundled FRC (Rebilda Post GT, 12 fiber bundles, 1.4 mm diameter) were bonded to the prepared canals using dual-cure resin-based luting cement. Specimens were kept in humid at 37°C for one day. The fracture resistance testing was performed using universal testing machine by applying a compressive static load at a 135° angel to the axis of the teeth. The failure type after fracture was examined by visual inspection. Results: The fracture resistance of teeth with single FRC (Rebilda Post) and bundled FRC (Rebilda Post GT) were 787 ± 156 and 850 ± 166 Newton, respectively. There was no statistical significant difference between the two groups. Root fracture was the major failure type in both groups. Conclusions: The fracture resistance of endodontically treated maxillary incisors with bundled FRC (Rebilda Post GT) did not differ from incisors with single FRC (Rebilda Post). Key words:Endodontically-treated teeth, fracture resistance, glass fiber post, intracanal post.

Prediction of future marginal bone level: a radiographic study.

AIM: The aim of the study was to predict the marginal bone level at a 5-year follow-up based on the information available from an initial radiographic examination and to evaluate the precision of the prediction by comparing the predicted bone levels with those actually observed at the follow-up. MATERIALS AND METHODS: In 1997, 616 randomly selected dentate individuals underwent a full-mouth radiographic survey. In 2003, 473 of those individuals (77%) participated in a second radiographic examination. Marginal bone level, caries lesions, fillings, crowns, root fillings and periapical status were recorded on all teeth. On the basis of data available from the first examination, a linear mixed model regression analysis with the tooth as the unit of analysis was used to predict the marginal bone level 5 years later. RESULTS: Number of teeth, smoking, and also presence of apical periodontitis and crowns were associated with bone loss and could be used as predictors of future marginal bone level. CONCLUSION: The analysis of all teeth showed that the number of tooth- and person-specific factors at the first examination influenced the prediction of the marginal bone level at the 5-year follow-up examination. However, the performance of the combined prediction model was less satisfactory.

Marginal and internal fit of crowns based on additive or subtractive manufacturing.

OBJECTIVE: To assess the marginal and internal fit of crowns manufactured by additive and subtractive manufacturing technique. MATERIALS AND METHODS: Twenty extracted teeth prepared for complete coverage crowns were scanned with an intra-oral scanner (Omnicam, DentsplySirona). For the subtractive manufacturing (SM) group, ten crowns were manufactured in a hybrid resin block (Vita Enamic, Vita Zahnfabrik). For the additive manufacturing (AM) group, the crowns were manufactured in a hybrid resin material (NextDent C&B, 3D systems). The design parameters were identical for the two groups. The marginal and internal fit (determined at the axial wall, the cusp tip and occlusally) was assessed before cementation with the replica technique and after cementation under stereomicroscope after sectioning of the crowned teeth. RESULTS: For the SM group, the marginal fit was 91 µm (±28 µm) before cementation and 85 µm (±18 µm) after cementation. In the AM group, the marginal fit was 75 µm (±29 µm) before cementation and 71 µm (±18 µm) after cementation. The differences were not statistically significant. As regards the internal fit, the fit at the axial wall was statistically significantly better in the SM group than in the AM group (p=.009 before cementation and .03 after cementation). Occlusally the fit in the AM group was significantly better than in the SM group after cementation (p<.001). CONCLUSION: Within the limitations of the current study, the marginal fit of additively manufactured crowns is comparable to crowns manufactured with chair-side subtractive technique and within the clinically acceptable range. As regards the internal fit no one technique was consistently superior.

Accuracy of Intra-Oral Scans Compared to Conventional Impression in Vitro.

AIM: The purpose of the present study was to assess the accuracy of intra-oral scans and conventional impression measured at various points on a single tooth preparation. METHODS: Ten conventional silicone impressions, and ten intra oral-scans using eight different digital intra oral digital scanners were taken of a prepared master tooth. The conventional impressions were directly digitised using a laboratory scanner. Each scan/impression was superimposed on a high-accuracy digital model of the prepared master tooth. For each superimposition, the deviation from the prepared master tooth was measured at six points on four two-dimensional cross-sections. Data was analysed using two-way analysis of variance (ANOVA). RESULTS: Most intra oral scanners had lower accuracy at the preparation margin compared to smooth surfaces. When only conventional impression and the latest intra oral scanners of various manufacturers are considered, the mean discrepancy at the preparation margin was 50µm (SD 16) for conventional impression, 15µm (SD 4) for trios 3, 26µm (SD 4) for LAVA TDS, 29µm (SD 7) for CEREC Omnicam, 30µm (SD 6) for CS 3600 and 64µm (SD 7) for GC aadva. The increased accuracy of trios 3 was statistically significant (p<0.05). CONCLUSIONS: At the preparation margin, Trios 3 performed significantly better than conventional impression and the other intra oral scanners. LAVA TDS, CEREC Omnicam and CS3600 showed similar accuracy at the margin, yet better than conventional impression and GC Aadva.

Risk factors for tooth loss in an adult population: a radiographic study.

AIM: The aim of the present study was to estimate the incidence and identify risk factors for tooth loss during a 5-year period in a randomly selected Danish population. MATERIAL AND METHODS: In 1997 and 2003, 473 randomly selected adults received a full-mouth radiographic examination. The total number of teeth was 12,444. For each tooth, the following information was recorded from the radiographs: marginal bone level, filling, crown, root canal post, root filling, apicectomy, periapical status and caries lesion. Unconditional and conditional logistic regression analyses were used to identify risk factors for tooth loss. RESULTS: During the study period, 107 teeth in 60 individuals were lost. On the individual level, reduced marginal bone level and apical periodontitis (AP) were highly associated with tooth loss. On the tooth level, a reduced marginal bone level, AP and apicectomy were strongly associated with tooth loss. Canines were not lost often, whereas tooth loss was more frequently observed in molars and premolars than in incisors. CONCLUSIONS: A reduced marginal bone level and AP were associated with tooth loss over time. Furthermore, there was a higher risk of tooth loss in the posterior regions than in the anterior region.

Effect of Software Version on the Accuracy of an Intraoral Scanning Device.

PURPOSE: To investigate the impact of software version on the accuracy of an intraoral scanning device. MATERIALS AND METHODS: A master tooth was scanned with a high-precision optical scanner and then 10 times with a CEREC Omnicam scanner with software versions 4.4.0 and 4.4.4. Discrepancies were measured using quality control software. RESULTS: Mean deviation for 4.4.0 was 36.2 ± 35 µm and for 4.4.4 was 20.7 ± 14.2 µm (P ≤ .001). CONCLUSION: Software version has a significant impact on the accuracy of an intraoral scanner. It is important that researchers also publish the software version of scanners when publishing their findings.

Evaluation of Operating Time and Patient Perception Using Conventional Impression Taking and Intraoral Scanning for Crown Manufacture: A Split-mouth, Randomized Clinical Study.

PURPOSE: To compare operating time and patient perception of conventional impression (CI) taking and intraoral scanning (IOS) for manufacture of a tooth-supported crown. MATERIALS AND METHODS: A total of 19 patients needing indirect full-coverage restorations fitting the requirements for a split-mouth design were recruited. Each patient received two lithium disilicate crowns, one manufactured from CI taking and one from IOS. Both teeth were prepared following the manufacturers' recommendations. For both impression techniques, two retraction cords soaked in 15% ferric sulphate were used for tissue management. CIs were taken in a full-arch metallic tray using one-step, two-viscosity technique with polyvinyl siloxane silicone. The operating time for each step of the two impression methods was registered. Patient perception associated with each method was scored using a 100-mm visual analog scale (VAS), with 100 indicating maximum discomfort. RESULTS: Median total operating time for CI taking was 15:47 minutes (interquartile range [IQR] 15:18 to 17:30), and for IOS was 5:05 minutes (IQR 4:35 to 5:23). The median VAS score for patient perception was 73 (IQR 16 to 89) for CI taking and 6 (IQR 2 to 9) for IOS. The differences between the two groups were statistically significant (P < .05) for both parameters. CONCLUSION: IOS was less time consuming than CI taking, and patient perception was in favor of IOS.

Marginal bone loss over 5 years in an adult Danish population.

PURPOSE: To evaluate marginal bone loss on the individual and tooth level, with focus on the importance of the baseline marginal bone level. MATERIALS AND METHODS: In 1997, 616 randomly selected individuals (mean age 42 years, range 21-63 years) underwent a full-mouth radiographic survey. In 2003, the survey was repeated for 473 of the same individuals (239 females and 234 males). The marginal bone level of each tooth was measured in mm from the cemento-enamel junction to the marginal bone. These measurements were used to calculate marginal bone loss during the 5-year period, and to analyse the average marginal bone loss for the individual, and tooth group in relation to age and to baseline marginal bone level, calculated as the average between measurements in 1997 and 2003 to circumvent regression to the mean. RESULTS: Marginal bone loss rate was on average 0.1 mm per year. For the individual, marginal bone loss was associated with both baseline marginal bone level and age. A significant difference was shown (p < 0.05) in marginal bone loss between different age groups, with a stronger association between marginal bone loss and baseline marginal bone level in the youngest age group. Moreover, marginal bone loss differed between tooth groups (p < 0.001), with molars and premolars losing marginal bone more rapidly than incisors and canines and showing a stronger association with baseline marginal bone level. CONCLUSIONS: Marginal bone loss over a 5-year period is associated with age and baseline marginal bone level. Younger individuals with a reduced marginal bone level were at high risk for further bone loss. Molars and premolars exhibit more rapid marginal bone loss than incisors and canines.

The impact of smoking on marginal bone loss in a 10-year prospective longitudinal study.

OBJECTIVES: The aim of this epidemiologic study was to determine the impact of smoking on marginal bone loss in a subsample derived from an original randomly selected adult sample, after adjusting for oral and general factors. METHODS: The number of participants at baseline in this 10-year longitudinal study was 616 (mean age: 42 years, range 21-63 years). The participants underwent a full-mouth radiographic survey. After recall in 2003, 473 (77%) of the participants accepted and completed an identical survey. In 2008, the survey was repeated, and 301 (48.9%) individuals were included in this study. The marginal bone level of each tooth was measured in mm. Age, gender, smoking habits, number of teeth, apical periodontitis, crowns and initial marginal bone level were also recorded for each individual. Only individuals who did not report a change in smoking habits during the 10-year period were included in the study. Multiple regression analyses were used to evaluate crude and adjusted associations between smoking and marginal bone loss. RESULTS: At the first, radiographic survey smokers had a statistically significantly more reduced marginal bone level (in average 0.9 mm) than nonsmokers. After 10 years, a progression of a mean marginal bone loss of > 2 mm was statistically significantly more common in smokers than in nonsmokers (7.1% and 0%, respectively). Furthermore, a marginal bone loss of 1-2 mm was observed in 29% of the smokers and 19% of the nonsmokers, and ≤ 1 mm marginal bone loss was found in 69% of smokers and 81% of nonsmokers. Even after adjusting for initial marginal bone level, gender, age, and also presence of apical periodontitis and crowns, the difference in progression of marginal bone loss was still statistically higher in smokers (on average 0.36 mm). CONCLUSIONS: The smokers started out with a more reduced marginal bone level than nonsmokers. However, even after adjusting for the initial marginal bone level, the progression of marginal bone loss in smokers was more pronounced than in nonsmokers. This shows that smoking is a factor with significant impact on the marginal bone level and can be assumed to be a true risk factor for marginal bone loss.

Risk indicators for a reduced marginal bone level in the individual.

PURPOSE: The aim of this study was to assess risk indicators for reduced marginal bone level in the individual, with emphasis on apical periodontitis. MATERIALS AND METHODS: Six hundred and sixteen randomly selected Danish adults (304 women and 312 men), mean age of 42 years, underwent a full-mouth radiographic survey. The marginal bone level was measured from the cemento-enamel junction to the marginal bone. The measurements were performed at the mesial (Am) and distal (Ad) aspect of the tooth. The marginal bone level for each individual was calculated: Aind = sigma Ateeth/nteeth, and Aind > or =4 mm was considered as reduced marginal bone level. The periapical status was assessed by the periapical index (PAI), which was dichotomised (healthy = PAI scores 1 and 2, and diseased = PAI scores 3, 4 and 5). Coronal restorations (crowns, fillings and inlays) and smoking status were also recorded. All variables were analysed in a logistic regression model with reduced marginal bone level as the outcome. RESULTS: The impact of age (odds ratio (OR) = 3.3), smoking (OR = 10.5) and apical periodontitis (OR = 4.7) on reduced marginal bone level was statistically significant (p < 0.01). CONCLUSIONS: Not surprisingly, this study showed that smoking and older age were risk indicators for having reduced marginal bone level > or =4 mm. Even when adjusted for these factors, individuals with > or =1 tooth with apical periodontitis were five times more at risk of having a reduced marginal bone level than those with no periapical infection.

Marginal bone level in an adult Danish Population.

PURPOSE: To investigate the prevalence and distribution of marginal bone loss in the Danish population. MATERIALS AND METHODS: Six hundred and sixteen randomly selected Danish adults (304 females and 312 males), mean age of 42 years (range 21-63 years) underwent a full-mouth radiographic survey consisting of 14 periapicals and two bitewings. The marginal bone level was measured with a digital caliper in mm, rounded off to the nearest 0.1 mm. The measurements were performed at the mesial and distal aspect of the tooth, from the cemento-enamel junction to the marginal bone. These measurements were used to calculate the marginal bone level (A) in mm for each tooth and each patient. Three thresholds were defined: normal marginal bone level (A < 3 mm), borderline marginal bone level (3 mm < or = A < 4 mm) and reduced marginal bone level (A > or = 4 mm). RESULTS: The prevalence of reduced marginal bone level in the individual and the frequency of teeth with reduced marginal bone level were almost similar. A reduced marginal bone level was evenly distributed among the tooth groups. Approximately 12% had reduced marginal bone level, 12% were in the borderline marginal bone level group, and the remaining 76% had a normal marginal bone level. The marginal bone level was ever more reduced with increasing age. No significant difference in bone level was observed between genders. CONCLUSIONS: The prevalence of reduced marginal bone level in a random Danish population is approximately 12% and is comparable to findings in other European countries.

Functional and Esthetic Comparison of Metal-Ceramic and All-Ceramic Posterior Three-Unit Fixed Dental Prostheses.

PURPOSE: The aim of this study was to assess functional and esthetic satisfaction plus evaluate changes in oral health-related quality of life (OHRQoL) using the Oral Health Impact Profile (OHIP-14) after insertion of a metal-ceramic (MC-FDP) or a veneered zirconia all-ceramic (AC-FDP) posterior three-unit fixed dental prosthesis (FDP). Additionally, patients' and professionals' esthetic evaluations were compared. MATERIALS AND METHODS: A convenience sample of 34 patients was randomized to receive a MC-FDP (n = 17) or an AC-FDP (n = 17). Patients were assessed using the OHIP-14 and also answered a questionnaire regarding satisfaction with function and esthetics using visual analog scales (VAS) before treatment and after 2 weeks, after 3 months, and after 1, 2, and 3 years. A fully dentate control group (n = 20) was also assessed using the OHIP-14. The operator and another observer evaluated the esthetics of the FDPs using VAS. RESULTS: The patients assessed the two FDP types similarly for all parameters. In contrast, there was a statistically significant difference in OHIP-14 results between the treated patients and the control group before treatment. After treatment, a statistically significant improvement in OHIP-14 was observed at all examinations. Patients were highly satisfied with the function and esthetics of the FDPs. The overall satisfaction with esthetics was statistically significantly higher among the patients than among the professionals at three out of five examinations. CONCLUSION: The patients experienced improved OHRQoL and increased satisfaction with function and esthetics after receiving a posterior three-unit FDP. No important differences were observed between the two types of FDPs when evaluated by the patient or the professionals.

Comparison of Metal-Ceramic and All-Ceramic Three-Unit Posterior Fixed Dental Prostheses: A 3-Year Randomized Clinical Trial.

PURPOSE: The aim of this randomized clinical study was to compare the 3-year clinical outcome of metal-ceramic fixed dental prostheses (MC-FDPs) and zirconia all-ceramic fixed dental prostheses (AC-FDPs) replacing a posterior tooth. MATERIALS AND METHODS: A sample of 34 patients with a missing posterior tooth were randomly chosen to receive either a MC-FDP (n = 17) or an AC-FDP (n = 17). The FDPs were evaluated at baseline and yearly until 3 years after cementation. They were assessed using the California Dental Association assessment system. Periodontal parameters were measured at the abutment teeth, and the contralateral teeth served as control. The statistical unit was the FDP/patient. RESULTS: The survival rates for MC-FDPs and AC-FDPs were 100%. The success rate was 76% and 71% for MC-FDPs and AC-FDPs, respectively. Three technical complications were observed in the MC-FDP group and five in the AC-FDP group, all chipping fractures of the ceramic veneer. Furthermore, one biologic complication in the MC-FDP group (an apical lesion) was observed. No framework fractures occurred. All patients had optimal oral hygiene and showed no bleeding on periodontal probing at any of the recalls. Only minor changes in the periodontal parameters were observed during the 3 years of observation. CONCLUSIONS: Three-unit posterior MC-FDPs and AC-FDPs showed similar high survival rates and acceptable success rates after 3 years of function, and ceramic veneer chipping fracture was the most frequent complication for both types of restorations.

Comparison of fatigue resistance and failure modes between metal-ceramic and all-ceramic crowns by cyclic loading in water.

OBJECTIVES: To compare fatigue resistance and fracture mode of metal-ceramic crowns with all-ceramic crowns containing yttria tetragonal zirconia polycrystal (Y-TZP) frameworks under compressive cycling loading in water. METHODS: Twenty specimens of ivory were randomized and individually prepared to receive anatomically shaped metal-ceramic (n=10) or veneered Y-TZP all-ceramic crowns (n=10). All steps in production were equivalent to clinical situations. Resistance to fatigue fracture was tested under compressive cyclic loading using a universal testing machine, with a loading frequency of 12Hz using a spherical tungsten carbide indenter (6mm diameter) in distilled water. The maximum compressive load was increased as the number of cycles increased (600,000 cycles at 400N, 200,000 cycles at 600 N, 200,000 cycles at 800 N and 200,000 cycles at 1000 N). The specimens were inspected after each loading sequence for initial failures such as infractions. Final failure was considered as any loss of material which automatically ended the test and the number of cycles until final failure was recorded. Fractographic analysis of the fractured specimens was performed with scanning electron microscopy (SEM). RESULTS: The two types of crowns exhibit similar fatigue resistance (P=0.87) to compressive cycling loading under wet conditions. The failure modes as observed with SEM were similar in the two groups and were found in the veneer ceramic, except that three veneered Y-TZP all-ceramic crowns displayed a complete framework fracture. CONCLUSIONS: Within the limitation of this study using simulated oral masticatory function, the results revealed that the fatigue resistance was similar for the two crown types. CLINICAL SIGNIFICANCE: In this study metal-ceramic crowns and veneered Y-TZP all-ceramic crowns showed similar fracture resistance to compressive cycling loading in water. The test conditions were simulating clinical conditions. Thus, the result may predict the long-term clinical performance of these types of crowns.

Detection of vertical root fractures by cone-beam computerized tomography in endodontically treated teeth with fiber-resin and titanium posts: an in vitro study.

OBJECTIVE: The aim of this study was to assess the performance of 2 cone-beam computerized tomography (CBCT) systems for detecting vertical fractures in root-filled teeth with fiber-resin or titanium posts. STUDY DESIGN: CBCT images acquired with the use of Scanora 3D and i-CAT of roots with fiber-resin (n = 30) or titanium (n = 29) posts, before and after the induction of fractures, were assessed by 6 radiologists using Ondemand 3D software. Interobserver agreement was analyzed using kappa statistics. Sensitivity, specificity, accuracy, and positive and negative predictive values were compared with analysis of variance/Student-Newman-Keuls test. RESULTS: Interobserver agreement for fiber-resin posts ranged from 0.5 to 0.7 (Scanora 3D) and 0.35-0.76 (i-CAT). For titanium posts, ranged from 0.42 to 0.80 (Scanora 3D) and 0.31-0.73 (i-CAT). Higher sensitivity (0.85; P < .05) and negative predictive values (0.88; P < .001) were observed for i-CAT in roots with fiber-resin posts than with other combinations. CONCLUSIONS: The diagnostic performance for detecting vertical fractures was higher for roots with fiber-resin than with titanium posts.