Trueness, precision, time-efficiency and cost analysis of chairside additive and subtractive versus lab-based workflows for manufacturing single crowns: An in vitro study

PURPOSE

To evaluate the trueness, precision, time efficiency, and cost of three different workflows for manufacturing single crowns (SCs).

METHODS

A plaster model with a prepared tooth (#15) was scanned with an industrial scanner, and an SC was designed in computer-assisted-design (CAD) software. Ten SCs were printed with a hybrid composite (additive chairside) and a stereolithographic (SLA) printer (Dfab®), 10 SCs were milled in lithium disilicate (subtractive chairside) using a chairside milling unit (inLab MC XL®), and 10 SCs were milled in zirconia (lab-based) using a five-axis laboratory machine (DWX-52D®). All SCs were scanned with the same scanner after polymerization/sinterization. Each scan was superimposed to the marginal area of the original CAD file to evaluate trueness: absolute average (ABS AVG), root mean square (RMS), and (90˚-10˚)/2 percentile were calculated for each group. Marginal adaptation and quality of the occlusal and interproximal contact points were also investigated by two prosthodontists on 3D printed and plaster models. Finally, the three workflows' time efficiency and costs were evaluated.

RESULTS

Additive chairside and subtractive lab-based SCs had significantly better marginal trueness than subtractive chairside SCs in all three parameters (ABS AVG, p < 0.01; RMS, p < 0.01; [90˚-10˚]/2, p < 0.01). However, the two prosthodontists found no significant differences between the three manufacturing procedures in the quality of the marginal closure (p = 0.186), interproximal (p = 0.319), and occlusal contacts (p = 0.218). Both time efficiency and cost show a trend favoring the chairside additive workflow.

CONCLUSIONS

Chairside additive technology seems to represent a valid alternative for manufacturing definitive SCs, given the high marginal trueness, precision, workflow efficiency and low costs.

STATEMENT OF CLINICAL RELEVANCE

Additive chairside manufacturing of definitive hybrid composite SCs is now possible and shows high accuracy, time efficiency, and competitive cost.

Efficiency of occlusal and interproximal adjustments in CAD-CAM manufactured single implant crowns - cast-free vs 3D printed cast-based

PURPOSE

The aim of this study was to evaluate the efficiency of occlusal and interproximal adjustments of single implant crowns (SIC), comparing a digital cast-free approach (CF) and a protocol using 3D printed casts (PC).

MATERIALS AND METHODS

A titanium implant was inserted at position of lower right first molar in a typodont. The implant position was scanned using an intraoral scanner and SICs were fabricated accordingly. Ten crowns (CF; n = 10) were subject to a digital cast-free workflow without any labside occlusal and interproximal modifications. Ten other identical crowns (PC) were adjusted to 3D printed casts before delivery. All crowns were then adapted to the testing model, simulating chair-side adjustments during clinical placement. Adjustment time, quantity of adjustments, and contact relationship were assessed. Data were analyzed using SPSS software (P < .05).

RESULTS

Median and interquartile range (IQR) of clinical adjustment time was 02:44 (IQR 00:45) minutes in group CF and 01:46 (IQR 00:21) minutes in group PC. Laboratory and clinical adjustment time in group PC was 04:25 (IQR 00:59) minutes in total. Mean and standard deviation (±SD) of root mean squared error (RMSE) of quantity of clinical adjustments was 45 ± 7 µm in group CF and 34 ± 6 µm in group PC. RMSE of total adjustments was 61 ± 11 µm in group PC. Quality of occlusal contacts was better in group CF.

CONCLUSION

Time effort for clinical adjustments was higher in the cast-free protocol, whereas quantity of modifications was lower, and the occlusal contact relationship was found more favourable.

High- or moderate-intensity training promotes change in cardiorespiratory fitness, but not visceral fat, in obese men: A randomised trial of equal energy expenditure exercise

This study compared the effects of two exercise programs performed in different intensities, but equal overall energy expenditure (EE). Adult men with obesity (29.6 ± 4.9 years; BMI = 35.1 ± 3.3 kg/m²) were randomised to one of three groups: High-intensity interval training (HIIT- 10 × 1:1 min 100% VO_2max; n = 13); Moderate-intensity continuous training (MICT - ˜35 min 65% VO_2max; n = 13) or Control (no training; n = 6). The session EE (HIIT = 278.0 ± 37.1; MICT = 299.4 ± 17.8 kcal) was calculated by adding the aerobic contribution (VO₂ of the session minus VO₂ at rest) and anaerobic (difference between the VO₂ estimated and VO₂ measured in session). The anaerobic contribution in HIIT was 30%, showing that a substantial portion of the energy for 10 x 1 min HIIT comes from non-oxidative metabolism. VO_2max improved in both trained groups (p =  0.006), while systolic blood pressure decreased (p <  0.001) and diastolic blood pressure was not altered. Visceral and subcutaneous fat stores did not change after the intervention, indicating a longer intervention may be necessary for changes in adiposity. Six weeks of HIIT or MICT were effective in improving cardiorespiratory fitness and blood pressure in previously inactive obese men.

A meta-analysis of the success rates of heartbeat restoration within the platinum 10 min among outpatients suffering from sudden cardiac arrest in China

BACKGROUND

The optimal time to save a person who has had a sudden cardiac arrest is within the first few minutes of the incident. Early compression and early defibrillation should be performed at this time. Timeliness is the key to successful CPR; as such, Prof. He proposed the "platinum 10 min" system to study early CPR issues. This paper systematically evaluates the success rates of heartbeat restoration within the "platinum 10 min" among patients suffering from sudden cardiac arrest.

METHODS

The clinical data of outpatients suffering from a cardiac arrest were retrieved from the China Knowledge Network (January 1975-January 2015), the Chongqing VIP database (January 1989-January 2015), and the Wanfang database (January 1990-January 2015). The success of the cardiopulmonary resuscitation (CPR) performed at different times after the patients had cardiac arrests was analyzed. Two researchers screened the literature and extracted the data independently. A meta-analysis was conducted using Stata12.0. A total of 57 papers met the inclusion criteria, including 29,269 patients. Of these patients, 1776 had their heartbeats successfully restored. The results showed high heterogeneity (X (2)  = 3428.85, P < 0.01, I(2) = 98.4 %). The meta-analysis was conducted using a random-effects model. The combined effect size was 0.171 (0.144-0.199).

RESULTS

(1) The success rate of heartbeat restoration did not differ among the four emergency treatment methods that patients received: the methods described in the 2000 Guidelines for CPR and Emergency Cardiovascular Care, that described in the 2005 version, 2010 version, and another CPR method. (2) The patients were divided into five groups based on the time when CPR was performed: the ≤1 min group, the 1- ≤ 5 min group, the 5- ≤ 10 min group, the 10- ≤ 15 min group and the >15 min group. The CPR success rates of these five groups were 0.247 (0.15-0.344), 0.353 (0.250-0.456), 0.136 (0.109-0.163), 0.058 (0.041-0.075), and 0.011 (0.004-0.019), respectively. The CPR success rates did not differ between the patients in the ≤1 min group and the 1- ≤ 5 min group. This success rate was higher for the patients in the 1- ≤ 5 min group than those in the 10- ≤ 15 min group, those in the 10- ≤ 15 min group, and those in the >15 min group. The CPR success rate was higher for the patients in the 5-10 min group than those in the 10- ≤ 15 min group and those in the >15 min group.

CONCLUSIONS

The CPR success rate was higher for the patients in the 10- ≤ 15 min group than those in the >15 min group. In addition, the patients were divided into two groups based on whether CPR was performed within the first 10 min after the cardiac arrest occurred: the ≤10 min group and the >10 min group. The CPR success rate was higher for the patients in the ≤10 min group (0.189 [0.161-0.218]) than those in the >10 min group (0.044 [0.032-0.056]). (3) Differences were not found between the CPR success rates among the patients in the telephone guidance group (0.167 [0.016-0.351]) and those in the ≤1 min, 1- ≤ 5 min, 5- ≤ 10 min, 10- ≤ 15 min, and >15 min groups. (4) The CPR success rates did not differ among in the patients in the witness + public group (0.329 [0.221-0.436]), those in the ≤1 min group, and those in the 1- ≤ 5 min group. However, this success rate was higher in the patients in the witness + public group than those in the 5- ≤ 10 min, 10- ≤ 15 min, and >15 min groups.

CONCLUSIONS

The success rate of heartbeat restoration did not differ among patients receiving CPR based on different guidelines. The success rate of CPR lies in its timeliness. The participation of the general population is the cornerstone of improving CPR. Providing complete emergency treatment equipment and perfecting comprehensive measures can improve the success rate of CPR among patients within the platinum 10 min. CPR research in China must be improved.