Traditional versus conservative endodontic access impact on fracture resistance of chairside CAD-CAM lithium disilicate anterior crowns: An in vitro study

Fracture Resistance of Zirconia Surveyed Crowns With Digitally Designed and Hand-Modified Occlusal Rest Seats

Background In light of the trend of using zirconia crowns, clinicians will likely face abutment included in removable partial dentures (RPD) designs with existing zirconia. However, the decision to replace the existing crown with a surveyed crown or modify the existing crown to accept the RPD is unclear. To the best of our knowledge, there is a lack of literature on the effect of preparing a rest seat on the existing monolithic zirconia crown in the patient's mouth on the fracture resistance of the crown. Therefore, in this study, we aimed to evaluate the fracture resistance of computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia surveyed crowns with digitally designed rest seats and hand-modified rest seats. Methods Thirty CAD/CAM zirconia surveyed crowns were digitally designed and fabricated and divided into groups (n=10 per group) as follows: Group 1 comprised surveyed crowns with no occlusal rest seat; Group 2 comprised surveyed crowns with a digitally designed mesial rest seat; and Group 3 comprised surveyed crowns with a hand-modified mesial rest seat. Then, with all the crowns cemented to metal dies, the specimens were subjected to a fracture resistance test using a universal testing machine (Model 8501 Instron, Norwood, MA, USA). Results Surveyed crowns without any rest seat and those with digitally created and hand-modified rest seats displayed different fracture resistances: crowns with no rest seat offered the highest fracture resistance (5831 ± 895.15 N), followed by those with a digitally designed and milled rest seat (5280 ± 1673.33 N). Crowns with a hand-modified rest seat provided the lowest fracture resistance (4976 ± 322.5 N). Based on our results, surveyed crowns without a rest seat displayed higher fracture resistance than those with a rest seat. Conclusion The fracture resistance of crowns with a digitally designed and milled rest seat was statistically similar to that of control crowns with no rest seat, whereas hand-modified rest seats significantly reduced the fracture resistance of surveyed zirconia crowns.

Fracture resistance of CAD/CAM milled versus direct hand-made interim laminate veneers

Background

Comparative studies of interim veneer restorations crafted using subtractive computer-aided manufacturing (s-CAM) milling technology and traditional direct hand-made approaches are needed.

Purpose

This comparative in vitro study evaluated the fracture resistance of two types of provisional veneer restorations for maxillary central incisors: milled (s-CAM) and traditional direct hand-made bis-acryl veneers.

Materials and methods

Fifty maxillary right central incisor veneers (25 specimens per group) were fabricated and divided according to the fabrication method: (1) s-CAM milled (Structure CAD, VOCO Dental); and (2) hand-made (Protemp Plus, 3M). The restorations were cemented onto 3D-printed resin dies using temporary cement and subjected to 1000 cycles of thermal cycling between 5° and 55 °C. These restorations subsequently were subjected to compressive loading until fracture occurred. Images of the fractured samples were captured using a scanning electron microscope (SEM). Statistical analysis was performed using the one-way ANOVA test and the Mann-Whitney U test.

Results

Significant differences (p < 0.001) in the fracture resistance were observed between the two groups. s-CAM milled interim veneers displayed higher fracture resistance values (439.60 ± 26 N) compared to the traditional method (149.15 ± 10 N).

Conclusion

The manufacturing method significantly influences the fracture resistance of interim veneer restorations. s-CAM interim laminate veneer restorations for maxillary central incisors exhibit a fracture resistance superior to that of the traditional method using bis-acryl.Clinical relevanceClinicians should consider CAD/CAM milled veneers for scenarios demanding long-term interim restoration and the withstanding of high occlusal forces.

Effects of Access Cavity Design and Placement Techniques on Mineral Trioxide Aggregate Obturation Quality in Simulated Immature Teeth: A Micro-Computed Tomography Study

Background and Objectives: In teeth with open apices, performing single session apexification is a challenging treatment due to the difficulty in handling mineral trioxide aggregate (MTA). Minimally invasive approaches in dentistry have also influenced the cavity designs in endodontics. Until now, different techniques have not been investigated in addition to manual condensation during the process of placing MTA in traditional (TradACs) or conservative (ConsACs) endodontic access cavities. The aim of this in vitro study was to compare and evaluate the obturation quality of MTA apical plugs placed with different techniques in TradACs or ConsACs. Materials and Methods: Sixty upper central teeth were divided into two main groups based on cavity design, and then each main group was further divided into three subgroups according to MTA placement techniques (n = 10): TradAC-manual, TradAC-manual + indirect ultrasonic activation, TradAC-manual + XP-endo Shaper (XPS), ConsAC-manual, ConsAC-manual + indirect ultrasonic activation, and ConsAC-manual + XPS. Subsequently, the porosity percentages in the MTA apical plug were analyzed using micro-computed tomography. The statistical analysis was performed using the Kruskal-Wallis H test and Mann-Whitney U test. Statistical significance was set at p < 0.05. Results: There were differences in volume of porosity percentages (%) according to cavity designs and MTA application techniques (p < 0.05). Except for the XPS group, more porosity was observed in ConsACs compared to TradACs. In TradACs, the significantly lowest open and total porosity was observed in the manual, ultrasonic, and XPS techniques, respectively. In ConsACs, the significantly lowest porosity was observed in the manual, XPS, and ultrasonic techniques, respectively (p < 0.05). Conclusions: In MTA obturation, cavity designs and application techniques had an impact on the MTA porosity. Creating an apical plug in ConsACs may result in more porosity compared to TradACs, especially when manual or indirect ultrasonic activation is preferred. Opting for the manual technique alone may be considered sufficient for controlling porosity for both TradACs and ConsACs.

Effect of preparation design and endodontic access on fracture resistance of zirconia overlays in mandibular molars: An in vitro study

PURPOSE

To evaluate the fracture resistance of zirconia overlays, considering various preparation designs and the presence of endodontic access.

MATERIALS AND METHODS

Ninety translucent zirconia (5Y-PSZ) overlay restorations were divided into six groups (n = 15/group) based on different preparation designs, with and without endodontic access: chamfer margin 4 mm above the gingival level without (group 1) and with endodontic access (group 2); margin 2 mm above the gingival level without (group 3) and with endodontic access (group 4); overlay with no chamfer margin without (group 5) and with endodontic access (group 6). Restorations were bonded to mandibular first molar resin dies, and the groups with endodontic access were sealed with flowable resin composite. All restorations underwent 100,000 cycles of thermal cycling between 5°C and 55°C, followed by loading until fracture. Maximum load and fracture resistance were recorded. ANOVA with Tukey post-hoc tests were used for statistical comparison (α < 0.05).

RESULTS

Fracture resistance significantly varied among overlay designs with and without endodontic access (p < 0.001), except for the no-margin overlays (groups 5 and 6). Overlays with a 2 mm margin above the gingival margin with endodontic access (group 4) exhibited significantly higher fracture resistance compared to both the 4-mm supragingival (group 2) and no-margin (group 6) designs, even when compared to their respective intact groups (groups 1 and 5). There were no significant differences between the no-margin and 4-mm supragingival overlays.

CONCLUSION

The more extensive zirconia overlay for mandibular molars is the first choice since the 2 mm margin above the gingival level design withstood considerable loads even after undergoing endodontic access. A no-margin overlay is preferred over the 4-mm supragingival design as it preserves more tooth structure and there was no outcome difference, irrespective of endodontic access. Caution is warranted in interpreting these findings due to the in vitro nature of the study.

Impact of restoration thickness and tooth shade background on the translucency of zirconia laminate veneers: An in vitro comparative study

Purpose

Our in vitro comparative study aimed to investigate the impact of thickness and tooth shade background on the translucency of highly translucent zirconia veneers.

Materials and Methods

A total of 75 5Y-TZP zirconia veneers of shade A1 were fabricated with thicknesses of 0.50 mm (n = 25), 0.75 mm (n = 25), and 1.0 mm (n = 25). The translucencies were measured on composite resin teeth with shades A1, A2, A3, A3.5, and A4 using a digital color imaging spectrophotometer. Data were analyzed using ANOVA and post hoc Tukey's test (p < 0.05).

Results

The translucency values were optimal for the veneers placed over the substrate teeth with shades A1 and A2, regardless of the veneer thickness. Additionally, veneers with a thickness of 0.50 mm exhibited significantly higher translucency than those with thicknesses of 0.75 mm and 1.0 mm.

Conclusions

Our study demonstrated that the translucency of the highly translucent zirconia veneers was influenced by both veneer thickness and tooth shade background. The optimal veneer thickness for achieving the highest translucency was 0.50 for the veneers with A1 and A2 shades placed over the substrate teeth.

Clinical Relevance

The optimal thickness for achieving the highest translucency of the highly translucent zirconia laminate veneers was 0.50 mm for the veneers with A1 and A2 shades placed over the substrate teeth. Clinicians and dental technicians could consider this when selecting materials for aesthetic restorations.

Pulpotomy versus root canal treatment in permanent teeth with spontaneous pain: comparable clinical and patient outcomes, but insufficient evidence

DESIGN

A systematic appraisal and statistical aggregation of primary studies.

DATA SOURCES

Scopus/ELSEVIER, PubMed/MEDLINE, Clarivate Analytics' Web of Science (i.e., Web of Science Core Collection-WoS, Korean Journal Database-KJD, Russian Science Citation Index-RSCI, SciELO Citation Index-SCIELO), and Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Library.The complementary searches consisted of OpenGrey, Google Scholar (first 100 returns), Networked Digital Library of Theses and Dissertations, Open Access Theses and Dissertations, DART-Europe E-theses Portal-DEEP, Opening access to UK theses-EThOS.

STUDY SELECTION

Human clinical trials studies in English language with at least 10 patients with mature or immature permanent teeth with pulpitis characterized by spontaneous pain in each arm (i.e., root canal treatment [RCT] and pulpotomy) at the end of the study, comparing the patient- (Primary: survival, pain, tenderness, swelling assessed by clinical history, clinical examination, and pain scales; Secondary: tooth function, need for further intervention, adverse effects; OHRQoL using a validated questionnaire) and clinical-reported outcomes (Primary: emerging apical radiolucency as per intraoral periapical radiograph or limited FOV CBCT scan; Secondary: radiological evidence of continued root formation and presence of sinus tract).

DATA EXTRACTION AND SYNTHESIS

Two independent review authors conducted study selection, data extraction and risk of bias (RoB) assessment and a third reviewer was consulted for solving disagreements. When insufficient or absent information, the corresponding author was reached out to for further explanation. The Cochrane RoB tool for randomized trials (RoB 2.0) was evaluated the quality of studies.The meta-analysis was performed on a fixed-effect model to estimate pooled effect size such as odds ratio (OR) and 95% confidence intervals (CIs) were performed using the R software. The quality of evidence assessed by the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach (GRADEpro GDT: GRADEpro Guideline Development Tool [software], McMaster University, 2015).

RESULTS

Five primary studies were included. Four studies referred to a multicentre trial assessing postoperative pain and long-term success rate after pulpotomy compared with one-visit RCT in 407 mature molars. The other study was a multicentre trial assessing postoperative pain in 550 mature molars treated with pulpotomy and pulp capping with the calcium-enriched mixture (CEM), pulpotomy and pulp capping with mineral trioxide aggregate (MTA) and one-visit RCT. Both trials primarily reported first molars from young adults. When looking at the results of postoperative pain, all the trials included had a low RoB. However, when evaluating the clinical and radiographic outcomes of the included reports, it was determined that there was a high RoB. The meta-analysis found that the likelihood of experiencing pain (i.e., mild, moderate, or severe) at the 7th postoperative day was not affected by the type of intervention (OR = 0.99, 95% CI 0.63-1.55, I2 = 0%).The study design, risk of bias, inconsistency, indirectness, imprecision, and publication bias domains were used to grade the quality of evidence for postoperative pain between RCT and full pulpotomy, resulting in a 'High' grade. In the first year, clinical success was high for both interventions, with a rate of 98%. However, the success rate declined over time, with pulpotomy showing a 78.1% success rate and RCT showing a 75.3% success rate at the 5-year follow up.

CONCLUSIONS

This systematic review was limited by the inclusion of only two trials, indicating a lack of sufficient evidence to draw definitive conclusions. Nonetheless, the available clinical data suggests that patient-reported pain outcomes do not differ significantly between RCT and pulpotomy at Day 7 postoperatively, and that the long-term clinical success rate of both treatments is comparable, as demonstrated by a single randomized control trial. However, to establish a more robust evidence base, additional high-quality randomized clinical trials, conducted by diverse research groups, are needed in this field. In conclusion, this review underscores the insufficiency of current evidence to draw solid recommendations.

Interdisciplinary Approaches for Integrating Materials Science and Dentistry

Dental materials science is a core course in most undergraduate dental curricula [...]