Effect of immediate dentine sealing on the aging and fracture strength of lithium disilicate inlays and overlays

Objectives: The objectives of this study were to compare the in vitro, laboratory aging, fracture strength, failure mode and reparability of molars restored with lithium disilicate inlays and overlays in conjunction with or without immediate dentin sealing (IDS). Methods: Forty extracted, sound human molars were selected and divided into four groups: 1) Inlays with IDS; 2) Inlays without IDS; 3) Overlays with IDS; 4) Overlays without IDS. Standard MOD preparations were made (3 mm wide, 5 mm deep) and in groups 2 and 4, all the cusps were reduced by 2 mm. Directly following tooth preparation, IDS was applied in specimens belonging to groups 1 and 3. The indirect restorations were luted with a heated composite. The restored teeth were subsequently challenged during aging (1.2 million cycles) and thermocycling loading (8000 cycles, 5–55 degrees C). Subsequently, the fracture strength was tested by a load to failure test at 45°. A failure analysis was performed using light- and scanning electron microscopy. The results were analyzed using two-way ANOVA and a Fisher exact test. Results: Mean fracture load + SD (N) were: Group 1 (n = 12): 1610 ± 419; Group 2 (n = 12): 1115 ± 487; Group 3 (n = 12): 2011 ± 496; Group 4 (n = 12): 1837 ± 406. Teeth restored with an onlay were stronger than those restored with an inlay restoration (p <.001). Teeth with IDS were stronger overall than those without IDS (p =.026). The interaction between preparation type and the mode of dentin conditioning had no statistically significant influence on fracture strength (p =.272). Subsequently, custom hypothesis tests showed that there was no statistically significant difference in fracture strength between inlays with IDS and overlays without IDS (p =.27). Overlays tend to fail in a more destructive, non-reparable way (p =.003). Significance: Both variables IDS and overlay preparation improve overall fracture strength. Inlays with IDS and overlays without IDS didn't differ in fracture strength. Both inlays and overlays are strong enough to withstand physiological chewing forces

[Treatment of a single-tooth space in the occlusal system].

The space created by the absence of 1 not-free-ending tooth in an occlusal system can be indicated as a single-tooth space. For treating a single-tooth space, several options are available to restore the functions of the occlusal system. Feasible options are a resin-bonded fixed prosthesis, a conventional fixed prosthesis, and an implant-supported restoration. Implant-supported restorations have a good prognosis, high patient satisfaction, and the advantage that adjacent teeth are not involved in the treatment. Anxiety about surgical treatment, the width of the single-tooth space, and financial aspects may be reasons not to consider an implant-supported restoration as first-choice treatment.</p

Implant-Supported Three-Unit Fixed Dental Prosthesis Using Coded Healing Abutments and Fabricated Using a Digital Workflow:A 1-Year Prospective Case Series Study

PURPOSE: To test the applicability of coded healing abutments, intraoral scanners, and monolithic zirconia for the fabrication of three-unit fixed dental prostheses (FDPs) on two dental implants. MATERIALS AND METHODS: Patients with three missing teeth in the posterior region of either the maxilla or mandible received two dental implants. After healing, coded healing abutments were placed. Full-arch intraoral scans were made to produce individual titanium abutments and a three-unit FDP. Peri-implant tissues were assessed 2 weeks after placement of the FDP and again after 1 year. Patient-reported outcome measures were registered prior to treatment and after 1 year. The quality of the FDPs was assessed using modified United States Public Health Service criteria after 1 year of service. RESULTS: A total of 54 patients were treated with 60 restorations, and 51 patients with 56 restorations were available at the 1-year follow-up. Implant survival was 99.1%, and prosthesis survival was 100%. The peri-implant tissues remained healthy, and patient satisfaction was high. However, the USPHS evaluation showed that some prostheses exhibited fit or color issues that needed to be addressed, although most were rated as successful (80.4%). CONCLUSION: The use of coded healing abutments and intraoral scanners to produce full-zirconia three-unit FDPs on two dental implants proved to be a feasible technique, with promising objective and subjective results. However, technical challenges still impacted the treatment results, resulting in a number of restorations having clinical or radiographic marginal gaps or reduced color match

Dimensional changes of CAD/CAM polymer crowns after water aging - An in vitro experiment

Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) polymers can potentially replace traditional materials used for manufacturing indirect restorations. In 2012, Lava Ultimate (LU) was introduced as a highly suitable material for implant-supported single crowns. Three years after its introduction, the manufacturer issued a change in indication for the material, implying that they no longer considered the material to be suitable for crown indications due to debonding issues. A clinical trial with implant-borne Lava Ultimate crowns bonded to zirconia abutments revealed that 80 percent of the LU crowns showed debonding from the abutment within one year, whereas no debonding occurred when an alternative full-ceramic restoration material was used. These results suggest that the material itself had been the cause of the debonding. However, the exact reason for the debonding remained unclear. Water uptake in resin methacrylates like LU is known to cause dimensional changes resulting in mechanical stress on the RelyX Ultimate (RU) cement. The purpose of this study is to quantify the dimensional changes in LU caused by water uptake and relate these dimensional changes to the failure of the RU cement. Twenty-five identical LU-crowns were divided into three groups. 10 LU-crowns with abutment and 10 crowns without abutments were stored in water for 23 days and were only removed for measurement. Five crowns served as a control to calibrate the measurements. The internal diameter was measured eight times with a TS 460 Heidenhain touch probe. For visualization purposes, one crown was also 3D scanned before and after water treatment. The results showed that after 23 days in water the mean increase in diameter for the groups with and without abutment was 36.6 μm (SD = 35,1) and 36.7 μm (SD = 26,5) respectively. Mixed effects modelling indicated no significant between-group differences at any time point. Exposure of LU to water results in dimensional changes causing mechanical stress on the crown-abutment complex. It can be estimated that RU cement fails after an expansion of more than 4 μm. Within the limitations of this in vitro study, it can be concluded that the dimensional changes induced by water uptake can cause debonding issues. As more CAD/CAM polymers for restorative purposes are expected to be developed, the results of this study should stimulate manufacturers to quantify their products' dimensional changes in a wet environment before market release

Clinical performance of direct composite resin versus indirect restorations on endodontically treated posterior teeth:A systematic review and meta-analysis

STATEMENT OF PROBLEM: High-level evidence concerning the restoration of endodontically treated posterior teeth by means of direct composite resin or indirect restorations is lacking. PURPOSE: The purpose of this systematic review and meta-analysis was to analyze the current literature on the direct and indirect restoration of endodontically treated posterior teeth. MATERIAL AND METHODS: Databases MEDLINE, CENTRAL, and EMBASE were screened. Risk of bias was assessed by using the ROB2 tool for RCTs and the ROBINS-I tool for prospective and retrospective clinical studies. Randomized clinical trials (RCTs) and prospective and retrospective studies comparing direct composite resin and indirect restorations on endodontically treated posterior teeth were included. Outcomes were tooth and restoration survival. A meta-analysis was conducted for tooth retention and restorative success. RESULTS: Twenty-two studies were included (2 RCTs, 3 prospective, and 17 retrospective). Over the short term (2.5 to 3 years), low-quality evidence suggested no difference in tooth survival. For the prospective and retrospective clinical trials, the overall risk of bias was serious to critical from the risk of confounding because of a difference in restorative indication: Direct restorations were fabricated when one marginal ridge remained or when tooth prognosis was unfavorable. For short-term restorative success, low-quality evidence suggested no difference between the direct and indirect restorations. CONCLUSIONS: For the short term (2.5 to 3 years), low-quality evidence suggests no difference in tooth survival or restoration quality. To assess the influence of the type of restoration on the survival and restorative success of endodontically treated posterior teeth, clinical trials that control for the amount of coronal tooth tissue and other baseline characteristics are needed

Maxillary overdentures supported by four or six implants in the anterior region:5-year results from a randomized controlled trial

OBJECTIVE: To compare a four‐ and six‐implant maxillary overdenture after an observation period of 5 years. MATERIAL AND METHODS: Fifty subjects with functional problems concerning their maxillary denture, who had ample bone volume in the anterior region to place four or six implants, were included and randomly assigned to either group. Implant and overdenture survival, clinical performance, marginal bone loss and patient satisfaction were assessed. RESULTS: Forty‐six patients completed the 5‐year follow‐up. One implant failed in the six implants group (99.2% survival) and none in the four implants group (100% survival). No overdentures had to be replaced during the observation period and the number of complications was limited. Clinical function was good, with no difference in clinical parameters between the groups. Mean marginal bone resorption was 0.50 ± 0.37 and 0.52 ± 0.43 mm in the four and six implant group respectively. CONCLUSION: In patients with functional complaints of their maxillary denture, bar‐supported overdentures on four implants in the anterior maxillary region were not inferior to overdentures supported by six implants after 5 years of function. Implant survival and patient satisfaction were high, clinical parameters favourable, bone loss and complications to the denture were minor in both groups (Clinical trial registration number: NTR2969)

Three-unit fixed dental prostheses supported by either two abutment implants or two abutment teeth:A comparative retrospective cohort study

Objectives: In general, similar restorative constructions are made on natural teeth and on dental implants. The assumption is made that implants and their restoration perform the same as natural roots and their prosthetic restoration. Evaluating cohorts of three-unit bridges on teeth and on implants, this retrospective clinical study aimed to compare implants and teeth as supporting units, including the reconstructions, in terms of survival, success, clinical, radiographic, and patient-reported outcomes. Material and Methods: From an 8-year period, all patients treated with a posterior three-unit fixed reconstruction on either implants or teeth, with a follow-up of at least 2 years, were identified. For each implant-supported reconstruction, a comparable tooth-supported reconstruction was selected, based on the length of follow-up, the material of the reconstruction, and the location in either the maxilla or mandible. Results: For the Implant-group, 24 patients could be matched with 24 best matching patients with tooth-supported fixed dental prostheses (FPDs). Supporting implants and implant-supported reconstructions were all in function with a mean follow-up of 52 +/- 23 months. Two tooth-supported reconstructions had been replaced (91.7% survival) (mean follow-up: 52 +/- 19 months). Radiographic bone levels and soft tissue conditions were favorable in both groups with minor differences. There was no significant difference in overall patient satisfaction. The modified USPHS-score revealed an 87.5% overall success in the Implant-group and 91.7% in the Tooth-group. Conclusions: Implant-supported three-unit FDPs area reliable treatment option with survival and success rates not significantly different from the results of tooth-supported three-unit FDPs

Influence of Deep Margin Elevation and preparation design on the fracture strength of indirectly restored molars

The objectives of this in-vitro study were to investigate the influence of Deep Margin Elevation (DME) and the preparation design (cusp coverage) on the fracture strength and repairability of CAD/CAM manufactured lithium disilicate (LS2) restorations on molars. Sound extracted human molars (n = 60) were randomly divided into 4 groups (n = 15) (inlay without DME (InoD); inlay with DME (IWD); onlay without DME (OnoD); onlay with DME (OnWD)). All samples were aged (1.2 × 106 cycles of 50N, 8000 cycles of 5–55 °C) followed by oblique static loading until fracture. Fracture strength was measured in Newton and the fracture analysis was performed using a (scanning electron) microscope. Data was statistically analyzed using two-way ANOVA and contingency tables. DME did not affect the fracture strength of LS2 restorations to a statistically significant level (p =.15). Onlays were stronger compared to inlays (p =.00). DME and preparation design did not interact (p =.97). However, onlays with DME were significantly stronger than inlays without DME (p =.00). More repairable fractures were observed among inlays (p =.00). Catastrophic, crown-root fractures were more prevalent in onlays (p =.00). DME did not influence repairability of fractures or fracture types to a statistically significant level (p &gt;.05). Within the limitations of this in-vitro study, DME did not statistical significantly affect the fracture strength, nor the fracture type or repairability of LS2 restorations in molars. Cusp coverage did increase the fracture strength. However, oblique forces necessary to fracture both inlays and onlays, either with or without DME, by far exceeded the bite forces that can be expected under physiological clinical conditions. Hence, both inlays and onlays are likely to be fracture resistant during clinical service.</p

Influence of the ceramic translucency on the relative degree of conversion of a direct composite and dual-curing resin cement through lithium disilicate onlays and endocrowns

INTRODUCTION: The goal of this study was to investigate the influence of the ceramic translucency, restoration type and polymerization time on the relative degree of conversion of a dual-curing resin cement and a conventional microhybrid resin composite using a high-power light-curing device. METHODS AND MATERIALS: Two 4.0 mm thick onlay (O) and two 7.5 mm thick endocrown (E) lithium disilicate restorations in high and low translucency (HT/LT) were fabricated on a decapitated molar. The pulp chamber was prepared to accommodate a 2 mm layer of a microhybrid resin composite (MHC) or dual-curing resin cement (DCC). Composite specimens were light-cured (n = 15; 1200 mW/cm2) without or through an onlay or endocrown restoration. Fourier-transform infrared spectroscopy (FTIR) absorbance curves were collected for the same composite specimen after 3 × 20, 3 × 40, 3 × 60 and 3 × 90 s of light-curing. The relative degree of conversion (DC%) was calculated and results analyzed using Kruskal-Wallis test and Friedman's ANOVA. Alpha was set at 0.05. RESULTS: After 3 × 60 s, the DC of MHC was significantly lower (p = 0.03; r = 0.61) under LT/EC restorations (Mdn: 77.8%) than HT/EC restorations (Mdn: 95.2%). DC of the DCC was not significantly affected by the ceramic translucency or restoration type. MHC had a significant higher DC than DCC under the HT/O, LT/O and HT/E restorations. There were no significant differences between MHC and DCC cured through LT/E restorations. CONCLUSION: DC for DCC was not significantly affected by the ceramic translucency or restoration type. DC for MHC was significantly lower for LT/EC than HT/EC restorations after 3 × 60s polymerization, but not different for the high translucent restorations and low translucent onlays. CLINICAL RELEVANCE: the use of light-curing microhybrid composite for bonding high translucent onlays and endocrowns and low translucent onlays seems feasible