Effect of different cement types on monolithic lithium disilicate complete crowns with feather-edge preparation design in the posterior region

A micro-computed tomography analysis of internal and marginal fits of fixed partial dentures: Effect of preparation finish line designs on monolithic zirconia and heat-pressed zirconia-reinforced lithium disilicate

PURPOSE

To evaluate the effect of finish line design (chamfer and feather-edge) and ceramic type on the internal and marginal fits of fixed partial dentures on abutment teeth.

MATERIALS AND METHODS

Two typodont mandibular casts, missing right first premolar tooth, received tooth preparation on canine and second premolar abutments (one cast with chamfer finish line and the other cast with feather-edge finish line). The preparation segment of each typodont model was scanned, 3D printed in resin, and then invested and casted in metal to obtain two metal models. Polyvinyl siloxane impressions were made for the metal models and poured in type IV stone. The stone models (n = 40) were randomly assigned into four groups (n = 10): chamfer finish line with heat-pressed zirconia reinforced lithium disilicate fixed partial denture (CL), chamfer finish line with monolithic zirconia fixed partial denture (CZ), feather-edge finish line with heat-pressed zirconia-reinforced lithium disilicate fixed partial denture (FL), and feather-edge finish line with monolithic zirconia fixed partial denture (FZ). After the fabrication of ceramic restoration, micro-computed tomography was used to evaluate the internal and marginal fits of each fixed partial denture. Data were statistically analyzed with three-way ANOVA (α = 0.05).

RESULTS

There were no significant interactions between preparation type, material type, and tooth type at any of the areas assessed. There was significant difference (p = 0.01) between CZ (59.15 ± 4.6 µm) and FZ (73.6 ± 17.1 µm) groups at the finish line area. Regarding the horizontal marginal discrepancy area, there were significant differences between CZ (62.65 ± 10.5 µm) and FZ (90.05 ± 5.6 µm) groups (p < 0.001), CL (77.45 ± 8.1 µm) and CZ (62.65 ± 10.5 µm) groups (p < 0.001), and FZ (90.05 ± 5.6 µm) and CL (77.45 ± 8.1 µm) groups (p < 0.001). At finish line area, there was a significant difference (p = 0.018) between feather-edge with canine (72.75 ± 13.3 µm) and chamfer with canine (59.05 ± 5.8 µm); however, there was no significant difference (p = 0.774) between feather-edge with premolar (69.45 ± 12 µm) and chamfer with premolar (65.1 ± 7.4 µm). Moreover, there was no significant difference (p = 0.886) between feather-edge with canine and feather-edge with premolar.

CONCLUSIONS

The internal and marginal fits of the ceramic fixed partial dentures can be affected by the finish line design and ceramic type. The feather-edge finish line had a negative impact on the marginal and internal fits of ceramic fixed partial dentures at certain measurement points. Regarding the effect of finish line design on abutment teeth, the difference in fit was only detected at the finish line area of the anterior abutment (canine) with the feather-edge finish line.

Ceramic Crowns and Sleep Bruxism: First Results from a Randomized Trial

Background: This randomized clinical trial was conducted to assess whether sleep bruxism (SB) is associated with an increased rate of technical complications (ceramic defects) in lithium disilicate (LiDi) or zirconia (Z) molar single crowns (SCs). Methods: Adult patients were classified as affected or unaffected by SB based on structured questionnaires, clinical signs, and overnight portable electromyography (BruxOff) and block randomized into four groups according to SB status and crown material (LiDi or Z): LiDi-SB (n = 29), LiDi-no SB (n = 24), Z-SB (n = 23), and Z-no SB (n = 27). Differences in technical complications (main outcome) and survival and success rates (secondary outcomes) one year after crown cementation were assessed using Fisher’s exact test with significance level α = 0.05. Results: No technical complications occurred. Restoration survival rates were 100% in the LiDi-SB and LiDi-no SB groups, 95.7% in the Z-SB group, and 96.3% in the Z-no SB group (p > 0.999). Success rates were 96.6% in the LiDi-SB group, 95.8% in the LiDi-no SB group (p > 0.999), 91.3% in the Z-SB group, and 96.3% in the Z-no SB group (p ≥ 0.588). Conclusions: With a limited observation time and sample size, no effect of SB on technical complication, survival, and success rates of molar LiDi and Z SCs was detected.

Three-year clinical evaluation of zirconia and zirconia-reinforced lithium silicate crowns with minimally invasive vertical preparation technique

Objectives

Large part of the tooth is required to be removed during crown preparation. A minimally invasive method for preparing single crowns is required to increase the durability of teeth. The aim of this study was to evaluate the clinical performance of two ceramic systems fabricated with minimally invasive vertical preparation.

Materials and methods

Forty endodontically treated maxillary premolars were prepared with vertical preparation and received temporary crowns for a period of 21 days. Twenty zirconia-reinforced lithium silicate (Celtra Duo HT, Dentsply Sirona, Germany) and 20 monolithic high translucency zirconia (Katana HT, Kuarary Noritake, Japan) crowns were fabricated by CAD/CAM and cemented with dual-polymerizing luting resin. The crowns were evaluated clinically and radiographically for 36 months following modified FDI criteria. Statistical analysis was conducted with t Student test (Cochran Q).

Results

Over the follow-up period, there was no need to replace any of the study’s crowns. The overall survival rate of the 40 crowns was 100% according to the Kaplan–Meier survival method. The clinical quality of all crowns and the patient’s satisfaction were high. No caries was detected and no adverse soft tissue reactions around the crowns were observed. Periodontal probing depth was reported to be increased at mesial and distal sites more than the facial one in the 36-month follow-up with no statistically significant difference between both materials (P = 0.186).

Conclusions

Zirconia and zirconia-reinforced lithium silicate could be used as a material for restoration of teeth prepared with vertical preparation technique. Both ceramic materials achieved good esthetic results, promotes healthy and stable soft tissues with no mechanical complications after 3 years of clinical evaluation.

Clinical relevance

Monolithic high translucency zirconia and zirconia-reinforced lithium silicate ceramics can be used for the restorations of minimal invasive vertical preparation in premolar area with 0.5 mm margin thickness.

Clinical evaluation of 3D-printed zirconia crowns fabricated by selective laser melting (SLM) for posterior teeth restorations: Short-term pilot study

Background/purpose

Zirconia crowns (ZrC) without veneering porcelain have become an effective alternative in clinical practice. Monolithic zirconia restorations fabricated by the dry milling method do not have acceptable clinical properties. This study evaluated the periodontal qualities of three-dimensional printed ZrC using the modified United States Public Health Service (USPHS) criteria.

Materials and methods

A total of 15 patients who required dental crowns were recruited, and all 15 teeth were restored with digital 3D-printed ZrC. All crowns were assessed at the time of crown placement and 2, 6, and 24 weeks post-placement. Clinical parameters, including plaque index, gingival index, probing depth, crown marginal integrity, and attrition of the antagonist's teeth, were evaluated and recorded.

Results

According to the Modified California Dental Association quality evaluation system, 100% of the crowns received satisfactory grades. Despite the significant increase in plaque index and gingival index at two weeks post-ZrC placement, there was no deterioration in probing depth. Moreover, there was discard usage of ZrC on the antagonist's teeth at 24 weeks posttreatment. Of the 15 crowns, one tooth had to be extracted due to a vertical root fracture. Overall, the digital 3D-printed crowns showed no adverse effects on periodontal tissues after 24 weeks of follow-up.

Conclusion

The 3D-printed ZrC showed no periodontal problems. It can serve as an alternative for patients, particularly those with high esthetic expectations.

Bonding Strength of Lithium Disilicate Adhesive Crowns with Different Occluso-Cervical Preparation Heights and Cement Types

The aim of this study was to evaluate if adhesion technology with CAD/CAM can compensate for the reduction of occluso cervical preparation heights using different types of dental cement. The de-bonding failure types were then assessed. Here, 72 caries-free extracted human premolar teeth were prepared to have a remaining occlusal height of two, three, and four mm. IPS e.max lithium disilicate CAD/CAM crowns were cemented with adhesive resin cement Panavia SA, self-adhesive resin cement, RelyX Unicem Aplicap, and zinc phosphate cement. The cementation techniques were based on the manufacturer’s instructions. After thermocycling, all samples were tested for tensile bond strength via an Instron machine. One-way analysis of variance (ANOVA) with post hoc testing (P < 0.05) was performed. The means TBS for the two, three, and four-mm OCHP groups were 2.72±0.69, 3.06±0.82, and 3.25±0.79.0 MPa; ARC, SARC, and ZPC were 3.41±0.51, 3.45±0.41, 2.08±0.35 MPa, respectively with significant differences in both. The mixed cement had failures in the resin cement groups. Failure was predominantly cohesive in the zinc phosphate group. Resin cement had the highest SBS values versus ZPC values when both bonded to lithium disilicate crowns with different occlusal heights. The failure of the adhesive to the crown and/or to the tooth were the highest for the four types of resin cement. Around 25% were cohesive failures with resin cement, but this was predominately adhesive in crowns in zinc phosphate regardless of the preparation heights.

Fracture Strength of Monolithic Zirconia Crowns with Modified Vertical Preparation: A Comparative In Vitro Study

Objective  The aim of this study was to evaluate the influence of different marginal designs (deep chamfer, vertical, and modified vertical with reverse shoulder) on the fracture strength and failure modes of monolithic zirconia crowns.

Materials and Methods  Thirty sound human maxillary first premolar teeth with comparable size were used in this study. The teeth were divided randomly into three groups according to the preparation design ( n = 10): (1) group A: teeth prepared with a deep chamfer finish line; (2) group B: teeth prepared with vertical preparation; and (3) group C: teeth prepared with modified vertical preparation, where a reverse shoulder of 1 mm was placed on the buccal surface at the junction of middle and occlusal thirds. All samples were scanned by using an intraoral scanner (CEREC Omnicam, Sirona, Germany), and then the crowns were designed by using Sirona InLab 20.0 software and milled with a 5-axis machine. Each crown was then cemented on its respective tooth with self-adhesive resin cement by using a custom-made cementation device. A single load to failure test was used to assess the fracture load of each crown by using a computerized universal testing machine that automatically recorded the fracture load of each sample in Newton (N).

Statistical Analysis  The data were analyzed statistically by using one-way analysis of variance test and Bonferroni test at a level of significance of 0.05.

Results  The highest mean of fracture load was recorded by chamfer (2,969.8 N), which followed by modified vertical (2,899.3 N) and the lowest mean of fracture load was recorded by vertical (2,717.9 N). One-way ANOVA test revealed a significant difference among the three groups. Bonferroni test showed a significant difference between group A and group B, while a nonsignificant difference was revealed between group C with group A and group B.

Conclusion  Within the limitations of this in vitro study, the mean values of fracture strength of monolithic zirconia crowns of all groups were higher than the maximum occlusal forces in the premolar region. The modification of the vertical preparation with a reverse shoulder placed at the buccal surface improved the fracture strength up to the point that it was statistically nonsignificant with the chamfer group.

Evaluation of zirconia and zirconia-reinforced glass ceramic systems fabricated for minimal invasive preparations using a novel standardization method

OBJECTIVE

Currently, minimal invasive approaches combining less invasive finish line preparations and reduced ceramic thickness are required. The aim of this study was to evaluate the fracture resistance of two ceramic systems fabricated with two preparation designs using CAD/CAM standardization technology.

MATERIALS AND METHODS

Forty intact human maxillary premolars were divided into two main groups according to the preparation technique. Group H (Horizontal): teeth with shoulder finish line and group V (Vertical): teeth with feather edge. Each main group was subdivided randomly into two subgroups according to the material used. Group CD (Celtra Duo) zirconia-reinforced glass ceramics and group K (KATANA) monolithic zirconia. CAD/CAM was used for standardization of natural teeth preparation. After cementation using self-adhesive resin cement, all specimens were subjected to 5000 thermal cycles and then were loaded until fracture. Failure types were evaluated using Stereomicroscopy and Scanning Electron Microscopy (SEM).

RESULTS

Nonsignificant; the higher mean value was recorded with VCD group (482.5 ± 103.8 N) and VK group (1347.6 ± 177.4 N) vs HCD group (471 ± 107.6 N) and HK group (1255.6 ± 121.3 N). SEM findings showed that fractures occurred mainly at the occlusal side of the crowns.

CONCLUSIONS

Vertical preparation showed a promising alternative to horizontal preparation. Moreover, both Celtra Duo and KATANA crowns can be used in premolar area with 0.5 mm margin thickness.

CLINICAL SIGNIFICANCE

Zirconia-reinforced glass ceramic and monolithic zirconia crowns may not necessitate the preparation of invasive finish lines as the type of finish line did not impair the strength after aging conditions.

Single crowns on tooth root-resected molars: A retrospective multicentric study

STATEMENT OF PROBLEM

Data regarding single restorations on molars treated with root resection and separation are limited.

PURPOSE

The purpose of this retrospective study was to evaluate the clinical success and survival of single crowns on root-resected molars.

MATERIAL AND METHODS

Eighty-six molars were treated with root resection or hemisection, prepared with feather-edge margins and restored with single crowns in 73 patients. The patients were clinically evaluated during regular recall appointments in 2018. Data were analyzed with descriptive statistics.

RESULTS

The mean follow-up time was 88.7 months (standard deviation, 70.6; range, 6 to 284). Six failures were recorded during the observation period, with a cumulative survival rate of 93%.

CONCLUSIONS

In this retrospective evaluation, single crowns on root-resected molars with feather-edge margins had clinical outcomes similar to those reported for single crowns on implants in the molar area. First molars and molars with 2 retained roots showed a better survival rate than second molars.

A pilot trial on lithium disilicate partial crowns using a novel prosthodontic functional index for teeth (FIT)

Background

Lithium disilicate is now a well accepted material for indirect restorations. The aim of this trial was to evaluate two lithium disilicate systems using a novel prosthodontic Functional Index for Teeth (FIT).

Methods

Partial adhesive crowns on natural abutment posterior teeth were made on sixty patients. Patients were divided into two groups: Group 1 IPS e.max press (Ivoclar-Vivadent, Schaan, Liecthestein), and Group 2 Initial LiSi press (GC Co., Tokyo, Japan). The restorations were followed-up for 3 years, and the FIT evaluation was performed at last recall. The FIT is composed of seven variables (Interproximal, Occlusion, Design, Mucosa, Bone, Biology and Margins), each of them are evaluated using a 0–1-2 scoring scheme, and is investigated by an oral radiograph and occlusal and buccal pictures. More in details, three variables have the three scores made on the presence or not of major, minor or no discrepancy (for ‘Interproximal’, ‘Occlusion’ and ‘Design’), presence or not of keratinized and attached gingiva (‘Mucosa’), presence of bone loss > 1.5 mm, < 1.5 mm or not detectable (‘Bone’), presence or not of Bleeding on Probing and or Plaque Index (‘Biology’), presence of detectable gap and marginal stain or not (‘Margins’). The Mann-Whitney ‘U’ test was used and the level of significance was set at p < 0.05. Also, “success” of the crowns (restoration in place without any biological or technical complication) and “survival” (restoration still in place with biological or technical complication) were evaluated.

Results

Regarding FIT scores, all partial crowns showed a stable level of the alveolar crest without detectable signs of bone loss in the radiographic analysis. All other evaluated parameters showed a high score, between 1.73 and 2. No statistically significant difference emerged between the two groups in any of the assessed variables (p > 0.05). All FIT scores were compatible with the outcome of clinical success and no one restoration was replaced or repaired and the success rate was 100%.

Conclusions

The results showed that it is possible to evaluate the clinical performance of partial crowns using FIT. The FIT proved to be an effective tool to monitor the performance of the restorations and their compatibility with periodontal tissues at the recall. The FIT can be really helpful for a standardized evaluation of the quality of the therapy in prosthodontic dentistry. The two lithium disilicate materials showed similar results after 3 years of clinical service.

Trial registration

The study protocol was approved by the Ethical Committee of University of Siena (clinicaltrial.gov # NCT 01835821), ‘retrospectively registered’.

Biomaterials: Ceramic and Adhesive Technologies

This review highlights ceramic material options and their use. The newer high-strength ceramics in monolithic form have gained popularity despite the lack of long-term clinical data to support this paradigm shift. Although there are some encouraging clinical data available, there is a need to develop laboratory simulation models that can help predict long-term clinical performance for ceramic and adhesive cements.

A possible risk of CAD/CAM-produced composite resin premolar crowns on a removable partial denture abutment tooth: a 3-year retrospective cohort study

PURPOSE

To evaluate the early performance of computer-aided design/computer-aided manufacturing (CAD/CAM)-produced composite resin crown (CAD/CAM composite crown) treatment on premolars, specifically, placement on a removable partial denture (RPD) abutment tooth, and the distalmost tooth in the dental arch, as possible clinical risk factors.

METHODS

A retrospective cohort study (April 2014 to July 2017) was performed utilizing the clinical records of patients who received a premolar CAD/CAM composite crown treatment. The variables of time of treatment for (1) successful crowns (complication event-free) and (2) surviving crowns (clinically functional including re-luted) were estimated using Kaplan-Meier analysis. Survival distributions regarding "RPD abutment tooth" and "distalmost tooth" were analyzed with the log-rank test. Multilevel survival analyses were used to identify hazard ratios and associated risk factors.

RESULTS

Five hundred and forty-seven crowns were evaluated (mean follow-up time 1.3±0.9years) in 327 patients. A total of 87 crowns had at least one complication, with loss of crown retention being the most common (70 crowns). Estimated success and survival rates at 3 years were 71.7% and 96.4%, respectively. The risk of complications was significantly higher for an RPD abutment tooth than for a non-RPD abutment tooth. There was no significant difference between the distalmost tooth and non-distalmost tooth in the dental arch.

CONCLUSIONS

The demonstrated complication rate for CAD/CAM composite crowns placed on premolars was 15.9% over a period of up to 3 years. There was a substantial risk of complications with placement of such a crown on an RPD abutment tooth.

Influence of preparation design and spacing parameters on the risk of chipping of crowns made with Cerec Bluecam before cementation

PURPOSE

To evaluate the influence of the preparation design and spacing parameters on the risk of chipping of crowns made by CEREC Bluecam before cementation.

METHODS

A knife-edge preparation and a chamfer preparation were made on upper premolars. The teeth were scanned and two Co-Cr alloy replicas were made. Fifteen full crowns were manufactured for four groups using CEREC. The groups differed in type of preparation (knife-edge (KE) or chamfer (CHA)) and spacing parameters: spacer (0 or 150μm), marginal adhesive gap (10 or 50 or 150μm) and margin thickness (0 or 300μm). The four groups were: CHA 150 (spacer)- 50 (marginal adhesive gap)- 0 (margin thickness), KE 150-50-0, KE 150-50-300 and KE 150-150-300. The crowns were loaded before cementation by using an Instron machine to simulate the masticatory load applied during a trial. Differences in means were compared using two-way ANOVA and a post-hoc test (Tukey Test). The level of significance was set at P=0.05.

RESULTS

The fracture values, ordered from least to most resistant, were: KE 150-50-300 group, CHA 150-50-0 group, KE 150-50-0 group and KE 150-150-300 group. Two-way ANOVA revealed statistically significant differences between pairs of means (p<0.05). Tukey's test showed that restorations of the KE 150-150-300 group can withstand a load significantly higher than that of other groups (p<0.01). In this group, the failures were mostly minor chippings, while the other groups had mostly major chippings and fractures.

CONCLUSIONS

Marginal adhesive gap can affect the trial of a full crown.