In vivo wear of CAD-CAM composite versus lithium disilicate full coverage first-molar restorations: a pilot study over 2 years

Over 14-year survival of pressed e.max lithium disilicate glass-ceramic complete and partial coverage restorations in patients with severe wear: A prospective clinical study

STATEMENT OF PROBLEM

Long-term clinical data are lacking on the comparative survival of adhesively luted lithium disilicate glass-ceramic complete and partial coverage restorations in patients with severe wear and the effect that different clinical variables have on their survival.

PURPOSE

The purpose of this study was to examine the 14-year survival of pressed e.max lithium disilicate glass-ceramic complete and partial coverage restorations in patients with severe wear and to evaluate associated clinical parameters.

MATERIAL AND METHODS

Patients demonstrating severe wear and requiring single unit defect-specific partial or complete coverage restorations were recruited in a clinical private practice and received lithium disilicate restorations. The effect of various clinical parameters was evaluated using Kaplan-Meier survival curves to account for attrition bias and other causes of failure. The statistical significance of differences between parameters was determined by using the log rank test (α=.05).

RESULTS

A total of 53 participants (24 men and 29 women) requiring 662 lithium disilicate restorations were evaluated. The mean age of the participants at the time of restoration placement was 60 (range 25 to 85 years). Of 662 units, 551 were anterior and posterior complete and 111 were posterior partial coverage restorations. Six failures (bulk fracture or large chip) requiring replacement occurred with the average time to failure of 4.5 (range 2 to 8) years, yielding a crude estimate of annual failure of 0.1% (cumulative monitoring period of 4650 years, overall survival rate of 98.6%). Of the 551 complete coverage restorations, 4 failed (0 anterior, 4 posterior), yielding a crude estimate of 0.1% annual failure with the survival function time at 14 years. Of the 111 partial coverage restorations, 2 failed, yielding a crude estimate of 0.4% annual failure with the survival function time at 12 years. The only statistically significant difference was seen between anterior crowns and posterior onlays, with no failures in anterior crowns (P<.001). Other clinical variables had no significant effect on survival (P>.05).

CONCLUSIONS

Pressed e.max lithium disilicate partial and complete coverage restorations both showed high survival rates in patients with severe wear over 14 years with an overall yearly failure rate of 0.1%. Risk of failure at any age was minimal for both men and women. All anterior crowns survived. The highest annual failure rate (0.4%) was for posterior onlay partial coverage restorations.

Intraoral wear of PICN CAD-CAM composite restorations used in severe tooth wear treatment: 5-year results of a prospective clinical study using 3D profilometry

OBJECTIVES

To evaluate, in a prospective clinical study over 5 years with ex vivo 3D profilometry analyses, the intraoral wear of Polymer-Infiltrated Ceramic Network (PICN) CAD-CAM composite restorations used in severe tooth wear treatment with the One-Step No-Prep technique.

METHODS

192 PICN (Vita Enamic) restorations on molars and premolars were included in a prospective clinical study involving patients treated according to the One-step No-prep protocol (n = 7). All patients showed clinical signs of bruxism. Replicas of restorations on molars and premolars were realized at each evaluation time (baseline and then every year up to 5 years) and scanned to perform 3D profilometry. Baseline and recall scans were superimposed with Geomagic Control software. The mean material wear was calculated for the full occlusal area (FOA) and for the occlusal contact area (OCA), respectively. Clinical evaluation of restorations was performed at recall.

RESULTS

At 5 years, the estimated mean material wear for FOA was inferior to the accuracy threshold of the profilometry measurement chain. For OCA, the estimated mean wear of the material was - 27.97 µm. This material wear was shown to be significantly influenced by time (p < 0.0001) and patient (p = 0.026), while the type of tooth (molar or premolar) had no influence. At 5 years, the survival and the success rates of restorations were 99.48% and 90.62%, respectively.

SIGNIFICANCE

The PICN material exhibits a low wear process in the treatment of severe tooth wear despite the presence of clinical signs of bruxism, and it constitutes a suitable material for the One-step No-prep technique.

Intraoral scanner-based monitoring of tooth wear in young adults: 36-month results

OBJECTIVES

The study continues our longitudinal observation of wear aiming to further monitoring of progression and lesion morphology and to identify relationships with assumed aetiological factors.

MATERIALS AND METHODS

Molars (FDI #36 or #46) of 74 participants (23.8 ± 2.2 years) were scanned (Trios 3, 3Shape) at the third follow-up (T3; observation period 1,111 ± 10 days). Data sets from T3, T2 (24-month follow-up) and T1 (12-month follow-up) were superimposed with baseline in a 3D analysis software (GOM Inspect). Wear was quantified as maximum vertical tissue loss (µm; median, 95% CI) in various occlusal areas (4/5 cusps and 2 ridges). Morphologies were classified into cupping (C), facet (F), and combined cupping-facet (CF). Aetiological factors were assessed with questionnaires.

RESULTS

Wear increased at T3 significantly at low rates in all areas of the occlusal surface (median between 7.0 (4.0;10.5) and 9.5 (6.0;15.0) µm). There was a clear trend for higher loss values in males, but no association with other factors such as nutrition. C and CF showed significantly higher loss values than F. Areas without initial wear developed F first, which either persisted or developed into C and CF.

CONCLUSIONS

Wear continued at low rates with C/CF morphology and sex as significant factors. Cupped lesions seem to develop from facets and thus may not be a valid diagnostic criterion for erosive tooth wear.

CLINICAL RELEVANCE

Wear is a cumulative process that apparently follows complex mechanisms that cannot be conceptualized in simplified terms; C and CF may be indicators for higher progression rates.

Clinical performance and wear resistance of milled resin composite material versus direct nanohybrid bulk-fill resin composite in the restoration of endodontically treated posterior teeth over 1 year: Randomized clinical trial

Context

The restorative complexities associated with endodontically treated teeth surpass those encountered with vital ones. The field of adhesive dentistry experienced a significant advancement that led to a shift in treatment approach toward bonded restorations.

Aim

The aim of the study was to assess the clinical performance of using indirect Milled composite or direct bulk-fill resin composite restorations for endo-treated teeth, as well as to measure the amount of wear on the occlusal tables of both restorations using a digital scanner.

Subjects and Methods

Participants were divided into two groups, where R1 represents the endodontically treated teeth restored with Milled composite, R2 represents the endodontically treated teeth restored with direct bulk-fill composite where 13 patients in each group were treated with a total number of 26 restorations in all patients. Where each restoration was assessed immediately at baseline (T0), 6 months (T6), and 12 months (T12) using the modified United States Public Health Service criteria. Moreover, wear was measured immediately at (T0) and (T12) intraorally and extraorally using intraoral scanners and three-dimensional surface-based superimposition software.

Statistical Analysis Used

Chi-squared test, Mann-Whitney U-test, Friedman's test, Nemenyi post hoc test, Shapiro-Wilk test, paired t-tests, intraclass correlation coefficient.

Results

At all intervals, the majority of the cases in both groups had an alpha score. Some cases exhibited bravo scores in both groups at T6 and T12 regarding the color match, marginal adaptation, marginal discoloration, and marginal integrity without statistically significant difference (P > 0.05). Direct nanohybrid bulk-fill resin composite showed a greater amount of wear without a statistically significant difference (P > 0.05). Extraoral measurement was significantly higher than intraoral measurement (P < 0.001). There was no significant reliability/agreement between both methods.

Conclusions

Both milled composite and direct bulk-fill resin composite restorations in endodontically treated teeth demonstrated appropriate clinical performance and minimal wear over an 1-year follow-up period.

Antagonist enamel tooth wear produced by different dental ceramic systems: A systematic review and network meta-analysis of controlled clinical trials

OBJECTIVES

The aim of this study was to evaluate the amount of enamel tooth wear induced by different antagonistic ceramic crown materials in the posterior area within a follow-up period up to 24 months in function. A network meta-analysis was performed to assess the effect of the materials on the mean vertical loss (MVL) of the antagonist enamel tooth surface.

DATA

Main search terms used in combination: ceramic, dental materials, metal ceramic, tooth wear and dental enamel.

SOURCES

An electronic search was conducted in PubMed/Medline, Embase, and Cochrane CENTRAL plus hand-searching.

STUDY SELECTION

Eligibility criteria included clinical studies reporting on MVL on antagonist's tooth up to 24 months following the permanent crown placement. From a total of 5697 articles, 7 studies reporting on 261 crowns for 177 subjects with 3 ceramic materials (Lithium disilicate, metal-ceramic, monolithic zirconia) were included. Among all, metal-ceramic and zirconia caused significantly higher enamel tooth wear on antagonist teeth, representing 82.5 µm [54.4; 110.6]) and 40.1 µm [22.2; 58.0]) more MVL than natural teeth group. In contrast, lithium disilicate showed only 5.0 µm [-48.2; 58.1]) more MVL than occurs on opposing natural teeth.

CONCLUSIONS

This systematic review demonstrated that prosthodontic ceramic materials produced significantly more antagonist enamel tooth wear than opposing natural enamel tooth wear, and ceramic material type was correlated to the degree of enamel tooth wear. Additional well-conducted, randomized controlled trials with homogeneous specimens are required due to inadequate sample size and number of the clinical studies included in the analyses.

CLINICAL SIGNIFICANCE

The amount of wear caused by different restorative materials has a high influence on the antagonistic natural teeth and should therefore be evaluated intensively by the dentist.

Wear characteristics of esthetic resin matrix and zirconia reinforced lithium disilicate CAD/CAM materials: two-body wear and surface topography analysis

BACKGROUND

This in vitro study assessed the wear behavior of different CAD-CAM blocks and the abrasion of the enamel antagonist against these materials.

METHODS

64 disk-shaped specimens were prepared from 8 different CAD/CAM blocks as follow: one lithium disilicate glass ceramics block "IPS Emax CAD" as control group, two zirconia reinforced lithium silicate "Vita Suprinity & Celtra DUO," one interpenetrating network ceramic block "Vita Enamic," Three resin-based block composites "Lava Ultimate, Cerasmart & Brilliant-crios" as well as one hybrid nanoceramic "Shofu block HC". All specimens were mounted against canine and tested for two body wear analysis using a chewing simulating loading machine (100,000 cycles, 50 N, 5/55 °C). The amount of wear loss was measured for each specimen using a digital precise scale. Wear area before and after the chewing simulation were evaluated using an optical profilometer. Data analysed using one-way ANOVA test followed by Tukey's post hoc.

RESULTS

The results showed a significantly higher wear loss in resin matrix ceramics in comparison to glass ceramics. However, for tooth wear glass ceramics had significantly higher value than hybrid ceramics.

CONCLUSIONS

Resin based CAD/CAM Blocks gives a superior result when evaluating the wear behavior and its effect on the opposing tooth surface.

Total Rehabilitation Using Adhesive Dental Restorations in Patients with Severe Tooth Wear: A 5-Year Retrospective Case Series Study

INTRODUCTION

Currently, there is little clinical evidence to support the medium- and long-term survival and clinical performance of ultraconservative approaches using adhesive restorations in full-mouth restorations. The aim of this case series study was to evaluate the medium-term clinical performance of anterior and posterior adhesive restorations applied with direct and indirect techniques using resin composites and glass-ceramic-based materials.

MATERIALS AND METHODS

The inclusion criteria were an esthetic problem as the main reason for consultation and severe generalized wear of grade 2 to 4 according to the Tooth Wear Evaluation System (TWES 2.0). In addition, at each follow-up appointment, patients were required to submit a clinical-parameter-monitoring record according to the modified United States Public Health Service (USPHS) criteria.

RESULTS

Eight patients with severe tooth wear were treated through full rehabilitation in a private dental clinic in Spain by a single operator (AFC). A total of 212 restorations were performed, which were distributed as follows: 66 occlusal veneers, 26 palatal veneers and 120 vestibular veneers. No signs of marginal microleakage or postoperative sensitivity were observed in any occlusal, vestibular and/or palatal restoration after the follow-up period. The estimated survival rate of the 212 restorations was 90.1% over 60 months of observation, with a survival time of 57.6 months. Only 21 restorations had complications, which were mostly resolved with a direct composite resin. The dichotomous variables of the restoration type (posterior veneer, anterior veneer) and the type of restored tooth (anterior, posterior) were the risk predictors with statistically significant influences (p < 0.005) on the survival of the restorations.

CONCLUSION

According to the results of this study, there is a significantly higher risk of restorative complications in posterior teeth compared to anterior teeth. Also, it can be concluded that the indication of adhesive anterior and posterior restorations is justified in the total oral rehabilitation of patients with severe multifactorial tooth wear, as they are associated with a low risk of failure.

Intraoral scanner-based monitoring of tooth wear in young adults: 24-month results

OBJECTIVES

Tooth wear causes irreversible cumulated surface loss and already occurs at a young age. Therefore, the objective of this clinical prospective observational study was to monitor the occlusal surface of a mandibular first molar in young adults for a period of 24 months. Furthermore, potential aetiological factors obtained by a questionnaire were considered.

MATERIALS AND METHODS

The study teeth (FDI #36 or #46) of 81 participants (mean age 22.8 ± 2.2 years) were scanned with the intraoral scanner (IOS, Trios 3, 3Shape) at the second follow-up (T2) after an observation period of 24 months. Standard-tessellation-language datasets were superimposed with baseline (T0) and T2 scans in 3D analysis software (GOM Inspect). The maximum vertical substance loss was measured between T0 and T2 at 6/7 areas (4/5 cusps and 2 ridges) of each study tooth and data compared to the already published data of the first follow-up (T1) after 12-month observation period. The morphology of tooth wear was classified into three groups: cupping (C), facet (F) and combined cupping-facet (CF). The analysis of aetiological factors, such as acid impacts, was based on a questionnaire filled out by participants at time points T0, T1 and T2. Non-parametric tests were used for statistical analysis (p < 0.05).

RESULTS

The buccal load-bearing cusps (mesiobuccal: median 15 μm, 95%CI 11/18 μm; mesiolingual 8 μm, 0/11 μm) were most affected by tooth wear. Loss values increased significantly at T2 compared to T1 for all areas, although significantly less than in the first 12 months (T0-T1). Areas that already exhibited F at T0 mostly displayed them also at T2 and only rarely developed further into C or CF. The only association between aetiological factors and loss values could be detected for sex as males had significantly higher loss values than females.

CONCLUSIONS

Progression of tooth wear could be clearly shown with high interindividual variations in loss values among participants. This indicates the need for individual monitoring with IOS.

CLINICAL RELEVANCE

IOSs show the potential for patient-specific monitoring to detect the progression of tooth wear. Thus, data of 24 months fills the gap of tooth wear data for young adults in literature. Further studies over a longer observation period are highly recommended to gain more information about the dynamic of tooth wear and aetiological factors.

Thermo-flexible resin for the 3D printing of occlusal splints: a randomized pilot trial

OBJECTIVES

To compare the clinical performance of occlusal splints printed from thermo-flexible resin with milled splints.

METHODS

A parallel two-arm pilot trial was initiated. Forty-seven patients (n women=38) were recruited from a tertiary care center and randomized using an online tool (sealed envelope). Inclusion criterion was an indication for treatment with a centric relation occlusal splint due to bruxism or any form of painful temporomandibular disorder. Patients were excluded if they were younger than 18 years, unable to attend follow-up appointments, or required another type of splint therapy. Patients received either, a 3D-printed (intervention group, V-print splint comfort, VOCO) or a milled splint (control group, ProArt CAD splint, Ivoclar). Construction software Ceramill M-splint (AmannGirrbach), 3D-printer MAX UV 385 (Asiga) and milling unit PrograMill PM7 (Ivoclar) were used. Follow-up assessments were conducted after 2 weeks and 3 months. Outcome measures were survival, adherence, technical complications, patient satisfaction on a 10-point Likert scale, and maximum wear using superimposition of optical scans.

RESULTS

After 3 months, 20/23 intervention group and 18/24 control group participants were assessed. All splints survived. Minor complications were small crack formations on 6 printed and 4 milled splints. Mean patient satisfaction was 8 (SD 1.7) for printed, and 8.1 (SD 2.3) for milled splints (r= .1, p=.52). Median maximum wear was highly dispersed with 153 (IQR 140) in posterior and 195 (IQR 537) in frontal segments of printed, and 96 (IQR 78) respectively 123 (IQR 155) of milled splints, (both: r= .31, p=.084).

CONCLUSIONS

Within the limitations of a pilot trial, 3D-printed and milled splints performed similarly in terms of patient satisfaction, complication rates and wear behavior.

CLINICAL SIGNIFICANCE

Thermo-flexible material was proposed for 3D printing of occlusal splints to overcome mechanical weaknesses of previously available resins. This randomized pilot study provides evidence that this material is a viable alternative to milled splints for at least three months of clinical use. Further evidence on long-term use should be obtained.

Twenty-four months in vivo wear of enamel antagonists to lithium disilicate implant crowns - a pilot study

OBJECTIVES

To evaluate whether there is a significant difference between the ratio of wear of lithium disilicate implant crowns and their enamel antagonists and adjacent enamel/enamel antagonist contacts. Additionally, the movement of the adjacent teeth was determined.

MATERIALS AND METHODS

Intraoral scans of the occlusal surfaces of 41 patients were performed after insertion of the implant restoration (baseline), after 12 and 24 months. From the initial study cohort, eleven implant crown/enamel antagonist pairs with adjacent enamel antagonist pairs could be analyzed in nine patients after 12 months. After 24 months, ten implant crowns of eight patients were available due to one decementation of an implant crown. A semiautomatic specifically developed iterative closest point algorithm was used to superimpose the surfaces of the baseline scan with the follow-up scans to measure the maximum height loss of each identified wear side. The mean maximum tooth wear and the standard deviation (SD) were calculated per unit. The ratio of wear of enamel/enamel antagonist teeth and the wear ratio of adjacent lithium disilicate implant crowns and their enamel antagonist surfaces were evaluated. Tooth movements were described by translations and rotations using a separate measurement procedure. The surfaces of the scans were superimposed setting the implant as a reference structure for registration.

RESULTS

After 12 months the wear ratio between the enamel antagonist pairs was 0.95 ± 0.27 µm and the ratio between lithium disilicate/enamel was 0.73 ± 0.49 µm. After 24 months the ratio of enamel antagonist pairs was 1.04 ± 0.28 µm and the ratio of lithium disilicate/enamel was 0.73 ± 0.51 µm. The ratios did not differ significantly.

CONCLUSIONS

Intraoral scanning and computer analysis showed that the two-years wear ratios between enamel/enamel and enamel/lithium disilicate implant crowns did not differ significantly.

STATEMENT OF CLINICAL RELEVANCE

The methodology described in this study could measure tooth wear and detect long-term wear performance. In the future, digital monitoring of prosthetic restorations should be integrated into clinical workflow to identify potential factors affecting longevity.

Evaluation of wear behavior of dental restorative materials against zirconia in vitro

OBJECTIVES

To evaluate two-body wear (2BW) and three-body wear (3BW) of different CAD/CAM and direct restorative materials against zirconia using a dual-axis chewing simulator and an ACTA wear machine.

METHODS

3 CAD-CAM resin-based composite or polymer infiltrated ceramic network blocs, 1 lithium disilicate CAD-CAM ceramic (LS₂), 3 direct resin composites, amalgam and bovine enamel were tested. For 2BW, 8 flat specimens per material were produced, grinded, polished, stored wet (37 °C, 28d) and tested (49 N, 37 °C, 1,200,000 cycles) against zirconia. For 3BW, specimens (n = 10) were stored accordingly, and tested against a zirconia antagonist wheel (3Y-TZP, d = 20 mm, h = 6 mm; 200,000 cycles, F = 15 N, f = 1 Hz, 15% slip) in millet seed suspension. Wear resistance was analysed in a 3D optical non-contact profilometer, measuring vertical wear depth and volume loss for 2BW and mean wear depth and roughness (R_a) for 3BW. Vickers hardness (15 s, HV2) was measured. Statistical analysis was performed using non-parametric tests (Mann-Whitney-U test, p < 0.05).

RESULTS

2BW and 3BW have a different impact on material surfaces. Similar wear resistance was observed for direct and indirect resin based materials with analogous filler configurations in both methods. Bovine enamel exhibited the best wear resistance in 2BW, but the least wear resistance in 3BW against zirconia. Regarding 2BW, a direct/indirect composite material pair of the same manufacturer showed the significantly highest mean volume losses (2.72/2.85 mm³), followed by LS₂ (1.41 mm³). LS₂ presented the best wear resistance in 3BW (mean wear depth 2.85 µm), combined with the highest mean Vickers hardness (598 MPa). No linear correlation was found between Vickers hardness and both wear testing procedures. The zirconia antagonists showed no recordable signs of wear.

SIGNIFICANCE

Dental restorative materials behave differently in 2BW and 3BW laboratory testing. Vickers hardness testing alone cannot hold for a correlation with wear behavior of materials. Micromorphological investigation of material composition can reveal insights in wear mechanisms related to variations in filler technologies.

Intraoral scanner-based monitoring of tooth wear in young adults: 12-month results

OBJECTIVES

To investigate tooth wear in young adults, intraoral scanning was used for digital monitoring of the mandibular first molar over 12 months. A possible influence of aetiological factors obtained by a questionnaire on tooth wear was investigated.

MATERIALS AND METHODS

A total of 109 participants (mean age at the start of the study: 21.0 ± 2.2 years) were included in this clinical study. At baseline (T0), an intraoral scan (Trios 3, 3Shape) of the study tooth (FDI # 36 or #46) was conducted. After a mean observation period of 373 ± 19 days, a second intraoral scan (T1, n = 94) of the same tooth as at T0 was performed and standard tessellation language datasets were superimposed with 3D analysis software (GOM Inspect). The occlusal surface of the study tooth was divided into 7 areas (5 cusps, 2 ridges) and maximum vertical substance loss was measured between T0 and T1 (n = 91). Three types of tooth wear were defined: cupping (C), facet (F) and combined cupping-facet (CF). Furthermore, a questionnaire on aetiological factors, such as dietary behaviour, was filled out at T0. Data were analysed with non-parametric tests (p < 0.05).

RESULTS

Only one study tooth exhibited no tooth wear at T0, whereas 3 teeth showed C, 47 teeth F and 40 teeth CF. A progression of vertical substance loss for all three types was shown. Most affected were the mesiobuccal cusps (43, 38/47 µm; median, 95%CI) followed by distobuccal (36, 33/39 µm), mesiolingual (35, 26/40 µm), distolingual (34, 27/36 µm) and distal (31, 25/34 µm). On mesial and distal ridges, only F was detected with the lowest vertical substance loss of all areas (mesial ridge: 0, 0/0 µm; distal ridge: 0, 0/0 µm). An association between aetiological factors and loss values could not be shown.

CONCLUSIONS

All study teeth showed clear signs of wear, and after only 1 year, further substance loss was detectable. This result is of significance for young adults.

CLINICAL RELEVANCE

Since data of young adults regarding tooth wear are scarce, the results give a first idea of the amount of vertical loss per year and its relation to aetiological factors such as dietary behaviour. Therefore, further studies over a longer observation period are highly recommended.

In-vivo-wear in composite and ceramic full mouth rehabilitations over 3 years

The aim of this study was to quantify and to compare the wear rates of premolar (PM) and molar (M) restorations of lithium disilicate ceramic (LS2) and an experimental CAD/CAM polymer (COMP) in cases of complex rehabilitations with changes in vertical dimension of occlusion (VDO). Twelve patients with severe tooth wear underwent prosthetic rehabilitation, restoring the VDO with antagonistic occlusal coverage restorations either out of LS2 (n = 6 patients, n = 16 posterior restorations/patient; N = 96 restorations/year) or COMP (n = 6 patients; n = 16 posterior restorations/patient; N = 96 restorations/year). Data was obtained by digitalization of plaster casts with a laboratory scanner at annual recalls (350 ± 86 days; 755 ± 92 days; 1102 ± 97 days). Each annual recall dataset of premolar and molar restorations (N = 192) was overlaid individually with the corresponding baseline dataset using an iterative best-fit method. Mean vertical loss of the occlusal contact areas (OCAs) was calculated for each restoration and recall time. For LS2 restorations, the mean wear rate per month over 1 year was 7.5 ± 3.4 μm (PM), 7.8 ± 2.0 μm (M), over 2 years 3.8 ± 1.6 µm (PM), 4.4 ± 1.5 µm (M), over 3 years 2.8 ± 1.3 µm (PM), 3.4 ± 1.7 µm (M). For COMP restorations, the mean wear rate per month over 1 year was 15.5 ± 8.9 μm (PM), 28.5 ± 20.2 μm (M), over 2 years 9.2 ± 5.9 µm (PM), 16.7 ± 14.9 µm (M), over 3 years 8.6 ± 5.3 µm (PM), 9.5 ± 8.0 µm (M). Three COMP restorations fractured after two years and therefore were not considered in the 3-year results. The wear rates in the LS2 group showed significant differences between premolars and molars restorations (p = 0.041; p = 0.023; p = 0.045). The wear rates in COMP group differed significantly between premolars and molars only in the first two years (p < 0.0001; p = 0.007). COMP restorations show much higher wear rates compared to LS2. The presented results suggest that with increasing time in situ, the monthly wear rates for both materials decreased over time. On the basis of this limited dataset, both LS2 and COMP restorations show reasonable clinical wear rates after 3 years follow-up. Wear of COMP restorations was higher, however prosthodontic treatment was less invasive. LS2 showed less wear, yet tooth preparation was necessary. Clinicians should balance well between necessary preparation invasiveness and long-term occlusal stability in patients with worn dentitions.

Characterisation of the Filler Fraction in CAD/CAM Resin-Based Composites

The performance of dental resin-based composites (RBCs) heavily depends on the characteristic properties of the individual filler fraction. As specific information regarding the properties of the filler fraction is often missing, the current study aims to characterize the filler fractions of several contemporary computer-aided design/computer-aided manufacturing (CAD/CAM) RBCs from a material science point of view. The filler fractions of seven commercially available CAD/CAM RBCs featuring different translucency variants were analysed using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), Micro-X-ray Computed Tomography (µXCT), Thermogravimetric Analysis (TG) and X-ray Diffractometry (XRD). All CAD/CAM RBCs investigated included midifill hybrid type filler fractions, and the size of the individual particles was clearly larger than the individual specifications of the manufacturer. The fillers in Shofu Block HC featured a sphericity of ≈0.8, while it was <0.7 in all other RBCs. All RBCs featured only X-ray amorphous phases. However, in Lava Ultimate, zircon crystals with low crystallinity were detected. In some CAD/CAM RBCs, inhomogeneities (X-ray opaque fillers or pores) with a size <80 µm were identified, but the effects were minor in relation to the total volume (<0.01 vol.%). The characteristic parameters of the filler fraction in RBCs are essential for the interpretation of the individual material's mechanical and optical properties.