Exam evaluation in prosthodontics across preclinical and clinical years from students' perspective: A cross-sectional study

INTRODUCTION

The purpose of this study was to explore the students' perceptions and performance in prosthodontics theory exam.

METHODS

A cross-sectional descriptive study was conducted on 560 (80.82%) students of different levels (third, fourth and fifth years) to explore their opinions and performance with regard to a number of issues on a prosthodontics theory exam (exam evaluation, exam preparation, exam material, exam timing). Demographic data were also collected. Descriptive statistics were generated and Chi-square test, independent sample t-test, ANOVA test and Pearson's correlation coefficient were used to examine the associations between different variables. The significance level was set at p < .05.

RESULTS

Students' responses regarding exam evaluation was influenced by their gender, study level, high-school Grade Point Average (GPA) and undergraduate cumulative GPA. Perceived exam difficulty was significantly affected by gender (p = .03) and study level (p < .001), and negatively correlated to both high-school GPA (p < .001) and university GPA (p = .03). The vast majority (88.2%) depended on lecture hand-outs and lecture notes for study. Exam material and preparation were not significantly affected by any of the demographic variables with most respondents (76.8%) thinking that the lectures blended with prosthodontics laboratories/clinics would improve their understanding of the exam material. The suggested best time to conduct the exam was early afternoon (31.6%). Student performance was significantly affected by the study level (p < .001) and cumulative GPA (p < .001) with significant positive correlation between the high-school GPA and the mark in the exam (r = .29, p < .001) and by the amount of time students spent for exam preparation (p < .001). Those students who reported using textbooks to prepare for the exam got significantly higher marks (66.1 ± 8.7) compared to the students who did not (62.8 ± 9.7) (p = .03).

CONCLUSIONS

Course level, GPA and gender were identified as the most influential factors in different aspects of exam evaluation and students' performance. Regular study and use of textbooks were demonstrated to improve academic performance. Additional orientation and guidance relating to the exam (especially for third year students) would be welcomed, as would alternate teaching methods such as small group discussions or study groups.

Position of Fovea Palatinae relative to the vibrating line in various soft palate classifications among Jordanian edentulous population

This study aims to examine the relationship between the locations of Fovea Palatinae and the posterior vibrating line in different classes of soft palate angulation (House Classification), accordingly determine its reliability as a landmark and a tool for determining the posterior limit of the maxillary complete denture. 280 completely edentulous patients with normal healthy mucosa from both genders were randomly selected. The House classification of the soft palate angulation was identified and recorded as Class I, II, or III. Phonation was used to determine the position of the vibrating line. The Fovea Palatinae was then marked. Then, the distance between the Fovea Palatinae and the vibrating line was measured and recorded. Finally, the relative position of the Fovea Palatinae to the vibrating line was recorded as being anterior, posterior, or on the vibrating line. The Chi Square test, the effect size measures (Eta and Cramer's V tests), The Spearman's Rho rank correlation test, and multinominal logistic regression analysis were utilized to analyse the data. House classification percentages were measured among people whose Fovea Palatinae was detectable; Class II palate was the most prevalent (47.14%), followed by Class I (43.93%), and then Class III (8.93%). Based on vibrating line position, 129 (58%) had a vibrating line anterior to Fovea Palatinae, 57 (26%) on the Fovea Palatinae, 36 (16%) posterior to Fovea Palatinae, and in 58 (21%) Fovea Palatinae were not detected. The mean distance between the vibrating line and Fovea Palatinae was 3.66 ± 1.6 mm anteriorly and 2.97 ± 1.36 mm posteriorly. No significant differences were found between males and females in regard to House classification and vibrating line position. The odds of having the fovea posterior to the vibrating line would increase by 5% for each year increase in the age (P = 0.035, odds ratio = 1.050). Class II House classification of the soft palate was found to be the most prevalent among the study participants. Also, the vibrating line was anterior to the Fovea Palatinae in the majority of cases. The odds of having the fovea posterior to the vibrating line would increase by age. The Fovea Palatinae could be considered a useful guide for locating the vibrating line.

Biomechanical behavior and Weibull survival of CAD-CAM endocrowns with different marginal designs: A 3D finite element analysis

OBJECTIVES

To evaluate and compare the effect of tooth preparation designs and different CADCAM. materials on stress distribution and Weibull survival probability of endocrowns. applied to root canal-treated lower first permanent molar using the 3D finite element. analysis method.

METHODS

A root canal-treated lower first permanent molar was prepared for endocrowns with a. butt joint or with a ferrule design by placing, circumferentially, a 1-mm wide shoulder. finish line. The prepared molar was scanned for the two designs and modeled on a 3D. Finite element model. Monolithic zirconia (IPS e.max ZirCAD MT, FCZ), lithium. disilicate (IPS e.max CAD, EX), and nano-ceramic resin composite (Lava Ultimate, LU). CAD-CAM materials were used for each preparation to design the virtual endocrown. A. total of six models were built according to the different tooth preparation designs and. endocrown materials. An occlusal load of 600 N and a transverse load of 20 N in. magnitude that simulates the average occlusal load was directed toward the occlusal. surfaces. von Mises and maximum principle values were evaluated Weibull risk-ofrupture. analysis was used to analyze the survival probability of the restorations and. tooth in the different models.

RESULTS

The highest von Mises were found in the butt joint design for FCZ, EX, and LU (45.3. MPa, 35.2 MPa, and 24.2 MPa, respectively) compared to the ferrule design for the. same materials (42.6 MPa, 31.2 MPa, and 23.6 MPa, respectively). For von Mises. stress distribution in the remaining part of tooth structure (dentin), the highest stresses. were found in LUFerrule which was closely similar to LUButt joint (135.4 MPa and. 134.7 MPa, respectively), followed by EXFerrule and FCZFerrule (132.2 MPa and. 131.7 MPa, respectively), while the lowest stresses were found in EXButt joint and. FCZButt joint (129.0 MPa and 128.4 MPa, respectively). Shear stresses within the. resin cement were the highest in FCZ and EX compared to LU. EX was found to be the. most reliable material with the highest survival probability, while FCZ showed the. lowest survival probability according to the Weibull risk-of-fracture results.

SIGNIFICANCE

Materials with high elastic modulus transfer more stresses to the endocrown and less. to the remaining tooth structure. Endocrown tooth preparation with ferrule design has. better stress distribution and magnitude compared to the butt joint design.

Stress experienced by dental students performing clinical training in different dental disciplines: a cross-sectional study

OBJECTIVES

To assess the stress level, the impact of stress factors, and discrepancies between fourth- and fifth-year undergraduate clinical students at the University of Jordan.

METHODS

A cross-sectional study was conducted in the academic year 2022/2023. The study group included fourth- and fifth-year dental students at the University of Jordan (n = 382) who were asked to voluntarily fill in an online dental environment stress (DES) questionnaire. Analysis was conducted using Mann-Whitney U test, independent t-test, χ2 test, and Spearman ρ rank correlations. Statistical significance was inferred when P < .05.

RESULTS

Fourth-year students reported higher levels of nervousness before treating patients for the first time. Fifth-year students faced more difficulty, higher stress, and/or fear regarding the amount of assigned work, provided treatment, completed requirements, failing the course, time to finish assignments, patient comprehensive care, and financial expenses of the course. Comparison between groups revealed that the fifth-year students scored higher levels of stress on the total DES score and all partial DES scores. Furthermore, the total DES questionnaire scores were significantly correlated with grade point average (GPA) among the total study sample and the prosthodontics clinical course marks among the fourth-year students' group.

CONCLUSIONS

The stress level among students in clinical courses was influenced by their academic performance, gender, year level, and the type and time needed for the provided treatment. Completing course requirements was among the most commonly faced stressors. Future research endeavors might be considered to study each clinical factor, its impact on students' stress level, and how to manage and positively improve these factors.

Dental Students' Perception and Self-Perceived Confidence Level in Key Dental Procedures for General Practice and the Impact of Competency Implementation on Their Confidence Level, Part I (Prosthodontics and Conservative Dentistry)

Background

Evaluating the level of dental students' competence is crucial for validating their preparedness for graduation. Confidence has a significant role in achieving competence. There are limited studies that assess the level of self-perceived confidence among final-year dental students regarding their ability to conduct key dental procedures. This study aims to assess the self-perceived confidence level of final-year dental students in performing essential dental procedures across various dental disciplines and to assess the effect of implementing competencies in the curriculum on the self-perceived confidence level of students by comparing two cohorts of final-year students in two different years 2016 (Traditional Cohort) and 2019 (Competencies Cohort).

Materials and Methods

An questionnaire was answered by two cohorts of final-year dental students: one group in 2016 before the implementation of the competency-based assessment system (group 1, n = 153), and the other in 2019 after the implementation of this system (group 2, n = 199), the same questionnaire was used for both cohorts. The results from the two groups were compared regarding the degree of self-perceived confidence in conducting key dental procedures. The data were analysed using SPSS statistics and Levene's Test for Equality of Variances and t-test for Equality of Means calculated.

Results

Group 1 showed a significantly higher means of self-perceived confidence levels than group 2 in the ability to conduct seven out of the 20 prosthodontics procedures studied: providing patients with Cobalt-Chromium (Co-Cr) removable partial dentures (RPD) (3.77 vs. 3.56), providing the patient with Acrylic RPD (3.70 vs. 3.23), treatment planning for partially edentulous patients (3.83 vs. 3.34), giving OHIs for denture patients (4.17 vs. 3.95), dealing with CD postinsertion complaints (3.97 vs. 3.76), giving postinsertion instructions for removable prostheses cases (4.12 vs. 3.82), and providing patients with immediate dentures (2.67 vs. 2.32). The same applies to 6 out of 16 conservative dentistry procedures: placing anterior composite (4.41 vs. 4.12), placing posterior composite (4.43 vs. 3.88), placing posterior amalgam (4.29 vs. 4.02), placing matrix band for Class II restorations (4.24 vs. 3.71), placing a prefabricated post (3.34 vs. 2.88), and placing fiber post (3.45 vs. 3.34). On the other hand, group 2 shows higher means of self-perceived confidence than group 1 in only two conservative dentistry procedures: onlay restorations (2.18 vs. 2.76) and inlay restorations (2.22 vs. 2.75). No significant differences in means of self-perceived confidence were found between the two groups in the remaining 21 procedures studied.

Conclusions

This study has shown that final-year dental students have high self-perceived confidence levels in doing simple dental procedures yet less confidence in more complex ones. Although, students' self-perceived confidence decreases after the introduction of a competency-based assessment system. Competency implementation and execution criteria may differ between schools which may have an impact on final outcomes. Hence, there is a need for regular evaluation of competencies being assessed to maintain a curriculum that is up to date.

The effect of in-office bleaching agents on the Vickers hardness and surface topography of polished and unpolished CAD/CAM composite materials

In-office bleaching, using hydrogen peroxide, is effective to remove dental enamel stains. However, bleaching agents can deteriorate surface properties of CAD-CAM materials. This in vitro study aimed to investigate the effect of in-office bleaching agents on Vickers hardness and surface topography of polished and unpolished dental CAD-CAM composite materials (Grandio blocs, Lava Ultimate, BRILLIANT Crios, Cerasmart), and a polymer-infiltrated ceramic network block (Vita Enamic). The specimens were randomly divided into two groups: unpolished or polished. The micro-hardness and surface topography of each group were measured before bleaching, after a 60 min bleaching period, and 24-h and one-month post-bleaching. In-office bleaching significantly influenced the Vickers hardness of both the polished and unpolished CAD/CAM composite blocks, with Vita Enamic exhibiting the least hardness stability among all groups. Furthermore, in-office bleaching significantly influenced the surface roughness of unpolished CAD/CAM composite blocks. There was a significant difference in hardness reduction between the polished and unpolished specimens for most of the investigated materials at different time points. The bleaching did not influence the surface roughness of the investigated polished group, except for Vita Enamic and Lava Ultimate. However, it did influence the surface roughness of the investigated materials in the unpolished group.

The effect of water storage on nanoindentation creep of various CAD-CAM composite blocks

BACKGROUND

To study the effect of water storage (3 months) on the creep deformation of various CAD-CAM composite structures at the nanoscale and compare it to that at the macroscale.

METHODS

Seven CAD-CAM blocks were investigated: five resin-composite blocks (RCB), one polymer-infiltrated ceramic network (PICN) block, and one ceramic-filled polyetheretherketone (PEEK) block. Specimens of each material (n = 6) were separated into two groups (n = 3) according to their storage conditions (24 h dry storage at 23˚C and 3 months storage in 37˚C distilled water). Nano-indentation creep measurements were undertaken (creep depth measured in µm) using a nanoindenter (Nanovea) equipped with Berkovich three-sided pyramidal diamond tip. The machine was set for the chosen parameters: a load of 20 gf, a pause of 20 s, and the material type. Thirty indentations on 3 samples were made for each material for each test. Data were analysed using two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests and independent t-test (< 0.05) for comparisons between the materials.

RESULTS

The nanoindentation creep depth after 24 h storage ranged from 0.09 to 0.33 μm and increased after 3 months storage in distilled water to between 0.28 and 3.46 μm. There was a statistically significant difference in nanoindentation creep behaviour between the two storage conditions for each investigated material (independent t-test) and between all materials (Bonferroni post hoc). There was a non-significant negative correlation between nanoindentation creep (µm) and filler weight% at 24 h dry storage but a significant correlation at 3 months of water storage. A further non-significant positive correlation between nanoindentation creep (µm) and bulk compressive creep (%) was found.

CONCLUSION

The PICN material showed superior dimensional stability in terms of nanoindentation creep depth in both storage conditions. Other composite blocks showed comparable performance at 24 h dry condition, but an increased nanoindentation creep upon water storage.

Influence of Storing Composite Filling Materials in a Low-pH Artificial Saliva on Their Mechanical Properties-An In Vitro Study

Restorative composites are subjected to various influences in the oral cavity environment, such as high or low temperatures, the mechanical force generated during mastication, colonization of various microorganisms, and low pH, which may result from ingested food and the influence of microbial flora. This study aimed to investigate the effect of a recently developed commercial artificial saliva (pH = 4, highly acidic) on 17 commercially available restorative materials. After polymerization, the samples were stored in an artificial solution for 3 and 60 days and subjected to crushing resistance and flexural strength tests. The surface additions of the materials were examined in terms of the shapes and sizes of the fillers and elemental composition. When stored in an acidic environment, the resistance of the composite materials was reduced by 2-12%. Larger compressive and flexural strength resistance values were observed for composites that could be bonded to microfilled materials (invented before 2000). This may result from the filler structure taking an irregular form, which results in a faster hydrolysis of silane bonds. All composite materials meet the standard requirements when stored for a long period in an acidic environment. However, storage of the materials in an acid environment has a destructive impact on the materials' properties.

Effect of acidic media on flexural strength and fatigue of CAD-CAM dental materials

OBJECTIVE

To investigate the effect of acidic media, including beverages and gastric fluids on flexural strength and fatigue of CAD-CAM materials.

METHODS

Four CAD-CAM materials (high-translucency zirconia (Ceramill Zolid HT+), lithium disilicate (IPS e-max CAD), hybrid ceramic (Vita Enamic), and nanohybrid resin composite (Grandio Blocs) were prepared and immersed in one of five media (gastric HCl, white wine, Coca-Cola, orange juice, and artificial saliva) in an incubator (37 ℃, 24 h). Surface topography and roughness were obtained using a scanning electron microscope (SEM) and a stylus contact profilometer, respectively. Initial 3-point flexural strength was measured for half of the bars (n = 20/gp) using a universal testing machine (0.5 mm/min). The other bars underwent 10⁶ cyclic fatigue loadings before measurement of residual 3-point flexural strength. Data were statistically analyzed (two-way and three-way ANOVA, Tukey's post-hoc, p < 0.05). Weibull distributions were plotted for reliability analysis.

RESULTS

Zirconia bars has the highest initial flexural strengths followed by lithium disilicate, while resin composite and hybrid ceramic groups had the lowest strength regardless of the erosive medium. Cyclic fatigue significantly reduced initial flexural strengths for all materials except for hybrid ceramic and resin composite. Weibull moduli were the highest for zirconia, lithium disilicate and resin composite and lowest for hybrid ceramic.

SIGNIFICANCE

Erosive media significantly changed surface roughness of CAD-CAM materials except for zirconia and resin composite without jeopardizing the flexural strength of the CAD-CAM materials. Despite the higher flexural strengths for zirconia and lithium disilicate, resin composite and hybrid ceramic were more resistant to cyclic fatigue.

Human osteoblasts response to different dental implant abutment materials: An in-vitro study

OBJECTIVES

This study aimed to investigate human osteoblasts (HOB) response towards different dental implant abutment materials.

METHODS

Five dental implant abutment materials were investigated: (1) titanium (Ti), (2) titanium coated nitride (TiN), (3) cobalt chromium (CoCr), (4) zirconia (ZrO₂), and (5) modified polyether ether ketone (m-PEEK). HOBs were cultured, expanded, and seeded according to the supplier's protocol (PromoCell, UK). Cell proliferation and cytotoxicity were evaluated at days 1, 3, 5, and 10 using Alamar Blue (alamarBlue) and lactate dehydrogenase (LDH) colorimetric assays. Data were analysed via two-way ANOVA, one-way ANOVA and Tukey's post hoc test (significance was determined as p < 0.05 for all tests).

RESULTS

All the investigated materials showed high and comparable initial proliferation activities apart from ZrO₂ (46.92%), with P% of 79.91%, 68.77%, 73.20%, and 65.46% for Ti, TiN, CoCr, and m-PEEK, respectively. At day 10, all materials exhibited comparable and lower P% than day 1 apart from TiN (70.90%) with P% of 30.22%, 40.64%, 37.27%, and 50.65% for Ti, CoCr, ZrO₂, and m-PEEK, respectively. The cytotoxic effect of the investigated materials was generally low throughout the whole experiment. At day 10, the cytotoxicity % was 7.63%, 0.21%, 13.30%, 5.32%, 8.60% for Ti, TiN, CoCr, ZrO₂, and m-PEEK. The Two-way ANOVA and Tukey's Multiple Comparison Method highlighted significant material and time effects on cell proliferation and cytotoxicity, and a significant interaction (p < 0.0001) between the tested materials. Notably, TiN and m-PEEK showed improved HOB proliferation activity and cytotoxic levels than the other investigated materials. In addition, a non-significant negative correlation between viability and cytotoxicity was found for all tested materials. Ti (p = 0.07), TiN (p = 0.28), CoCr (p = 0.15), ZrO₂ (p = 0.17), and m-PEEK (p = 0.12).

SIGNIFICANCE

All the investigated materials showed excellent biocompatibility properties with more promising results for the newly introduced TiN and m-PEEK as alternatives to the traditionally used dental implant and abutment materials.

Long-term hydrolytic stability of CAD/CAM composite blocks

This study aimed to assess water sorption and solubility of CAD/CAM composite blocks compared to CAD/CAM ceramic after 8 months storage in water and artificial saliva. Eight CAD/CAM blocks were investigated: Five resin-composite blocks (RCBs), one polymer-infiltrated ceramic network (PICN) block, one ceramic-filled polyetheretherketone (PEEK) block, and one feldspathic ceramic block. One hundred and twelve specimens were prepared comprising 14 specimens of each of the eight materials. From each group of specimens, seven randomly selected specimens were immersed in 10 mL of water, while the other seven specimens were immersed in artificial saliva. All specimens were stored at 37°C and weighed at various time intervals. The data were analysed via repeat measures ANOVA, one-way ANOVA and Tukey's post hoc test (α = 0.05 for all tests). Sorption values (mean [SD]) in water were within the range -1.21 (0.4) to 39.3 (2.1) μg/mm³ and in artificial saliva between -0.7 (0.2) and 41.6 (1.3) μg/mm³ . Solubility values in water were between -0.43 (0.08) and 0.34 (0.18) μg/mm³ and in artificial saliva between -0.53 (0.07) μg/mm³ and 0.33 (0.2) μg/mm³ . CAD/CAM composite blocks were hydrolytically stable under long-term storage (according to ISO 4949:2009), although not as stable as ceramic. Water sorption of CAD/CAM composite blocks was dependent on the resin-matrix and was influenced by the filler weight %.

Relationship between dental caries, oral hygiene and malocclusion among Syrian refugee children and adolescents: a cross-sectional study

BACKGROUND

Little is known about the oral disease burden in refugee children and associated risk factors. This cross-sectional study aimed to explore the oral hygiene status and prevalence of caries, and to investigate their association with malocclusion characteristics in a child refugee population.

METHODS

606 Syrian refugee children and adolescents aged 7-19 years, registered as refugees in Jordan and residing in Zaatari camp, were recruited to the study. Oral hygiene and caries status were recorded using DMFT (mean of decayed, missing, and filled permanent teeth) and OHI-S (Simplified Oral Hygiene Index) according to WHO criteria. Oral health results were then cross tabulated with previously reported malocclusion traits for the same study sample (crowding, spacing, contact point deflection and IOTN) to detect any associations. Statistical analysis was conducted using chi-square test, independent sample t-test, one-way ANOVA, Welch test and Post Hoc testing (Gabriel and Games-Howell).

RESULTS

Overall DMFT and OHI-S were 4.32 and 1.33 respectively with no difference between males and females. Around 40% of the sample showed ≥ 5 DMFT score. 96.1% of the sample either do not brush or brush occasionally: females showed better oral hygiene practices (P = 0.002). No significant differences in DMFT scores were noted for gender or age, other than the 7-9.9 year old group having significantly higher mean DMFT scores than all other age groups (P < 0.01);the mean of OHI-S was not significantly different between different age groups (P = 0.927). Subjects with malocclusion, specifically crowding, contact point deflection and IOTN grades 3, 4 and 5 had higher scores in both arches for OHI-S and DMFT than subjects without malocclusion traits, although this was not statistically significant for DMFT scores. Overall, patients with generalized spacing had a significantly lower OHI-S score than those without spacing (P = 0.021). Significant correlations were found between parameters of intra-arch and inter-arch relationships and oral health indices (DMFT and OHI-S).

CONCLUSION

Malocclusion may increase the risk of caries and periodontal disease; the magnitude of this risk is amplified in populations with poor oral health and limited access to oral healthcare services, highlighting the need for preventive and curative oral health programs.

Response of two gingival cell lines to CAD/CAM composite blocks

OBJECTIVE

This study aimed to investigate the influence of CAD/CAM composite materials on human gingival fibroblasts (HGF) and gingival keratinocytes (HGK).

METHODS

Four materials were investigated: two resin-composite blocks (RCB), Grandio Blocs (GR) and Block HC (HC); one polymer-infiltrated ceramic network (PICN) (Enamic, EN); and one conventional resin-composite, Grandioso (GND). HGF and HGK were cultured as per the supplier's protocol (ATCC, UK). Cell proliferation and cytotoxicity were evaluated at 1, 3, 5 and 10 days using LDH and Alamar Blue assays. Indirect immunostaining was used to assess the Caspase-3 activity. Data were analysed via two-way ANOVA, one-way ANOVA and Tukey's post hoc test (α = 0.05 for all tests).

RESULTS

There was significant difference in cell proliferation of the HGK and HGF cells in contact with different composite materials but no significant differences in their cytotoxicity. There was a significant effect on cell proliferation and cytotoxicity with different exposure times, for each type of resin-composite. HGF cell proliferation was higher than HGK with almost all investigated materials and at all time points. No Caspase-3 activity was detected in either cell lines.

SIGNIFICANCE

HGK proliferation and cytotoxicity appeared to be more influenced by composite materials compared to HGF, demonstrating EN cytotoxic effects in HGK. Different manufacturing techniques of resin-composites (photo curing versus heat/pressure curing) had no significant effect on their biocompatibility.

Viscoelastic stability of pre-cured resin-composite CAD/CAM structures

OBJECTIVES

To study the effect of water storage (3 months) on the creep deformation and recovery of CAD/CAM composite materials to determine their viscoelastic stability.

MATERIALS AND METHODS

Five CAD/CAM composite blocks, with increasing filler loading, and one polymer-infiltrated ceramic network (PICN) were studied. Six specimens of each material were separated into two groups (n=3) according to their storage conditions (24 h dry storage at 23°C versus 3 months storage in 37°C distilled water). A constant static compressive stress of 20 MPa was applied on each specimen via a loading pin for 2 h followed by unloading and monitoring strain recovery for a further period of 2 h. The maximum creep-strain (%) and permanent set (%) were recorded. Data were analysed via two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests (<0.05) for comparisons between the materials. Homogeneity of variance was calculated via Levene's statistics.

RESULTS

The maximum creep strain after 24 h dry ranged from 0.45% to 1.09% and increased after 3-month storage in distilled water to between 0.71% and 1.85%. The permanent set after 24 h dry storage ranged from 0.033% to 0.15% and increased after 3-month water storage to between 0.087% and 0.18%. The maximum creep strain also reduced with increasing filler loading.

SIGNIFICANCE

The PICN material exhibited superior dimensional stability to all of the pre-cured resin composite blocks in both storage conditions with deformation being predominantly elastic rather than viscoelastic. Notwithstanding, two of the resin-matrix composite blocks approached the PICN performance, when dry, but less so after water storage.