Effect of different fabrication workflows on the passive fit of screw-retained bar splinting two interforaminal implants: a parallel blinded randomised clinical trial

BACKGROUND

To clinically compare the effect of the conventional and the digital workflows on the passive fit of a screw retained bar splinting two inter-foraminal implants.

METHODS

The current study was designed to be a parallel triple blinded randomised clinical trial. Thirty six completely edentulous patients were selected and simply randomized into two groups; conventional group (CG) and digital group (DG). The participants, investigator and outcome assessor were blinded. In the group (CG), the bar was constructed following a conventional workflow in which an open top splinted impression and a lost wax casting technology were used. However, in group (DG), a digital workflow including a digital impression and a digital bar milling technology was adopted. Passive fit of each bar was then evaluated clinically by applying the screw resistance test using the "flag" technique in the passive and non passive situations. The screw resistance test parameter was also calculated. Unpaired t-test was used for intergroup comparison. P-value < 0.05 was the statistical significance level. The study protocol was reviewed by the Research Ethics Committee in the author's university (Rec IM051811). Registration of the clinical trial was made on clinical trials.gov ID NCT05770011. An informed consent was obtained from all participants.

RESULTS

Non statistically significant difference was denoted between both groups in all situations. In the passive situation, the mean ± standard deviation values were 1789.8° ± 20.7 and1786.1° ± 30.7 for the groups (CG) and (DG) respectively. In the non passive situation, they were 1572.8° ± 54.2 and 1609.2° ± 96.9. Regarding the screw resistance test parameter, they were 217° ± 55.3 and 176° ± 98.8.

CONCLUSION

Conventional and digital fabrication workflows had clinically comparable effect on the passive fit of screw retained bar attachments supported by two dental implants.

Effect of different framework materials on stresses induced in distal extension removable partial dentures: A strain gauge analysis

PURPOSE

Evaluation of the strain transmitted to the abutments and residual ridge by polyetherketoneketone material compared to the cobalt-chromium one in distal extension removable partial dentures (RPDs) to fulfill the objective of preservation of the supporting structures.

MATERIALS AND METHODS

A virtual model simulating a Kennedy class I partially edentulous mandibular arch was designed. Two models, one for each group, were printed. Five RPDs were made in each group. In group CR, the framework was milled from a cobalt-chromium alloy. While in group PK, it was milled from a polyetherketoneketone blank. Strain gauge rosettes were bonded distal to the last abutment and posteriorly in the distal end of the residual ridge. Unilateral vertical and oblique loadings were applied. Mann-Whitney U test was used for inter-group comparisons while the Friedman test was used for intra-group comparisons and corrected by Wilcoxon Signed-Rank Sum. The significance level was set at p ≤ 0.05.

RESULTS

During unilateral vertical load application, a statistically significant difference was found between both groups distal to the abutment in the loaded and unloaded sides as well as the residual ridge on the unloaded side. During oblique load application, a statistically significant difference was found between both groups in all slots.

CONCLUSION

Polyetherketoneketone material induces less stress on the abutments and more stress on the residual ridges compared to the cobalt-chromium ones. Therefore, it may be recommended for weak abutments supporting RPDs.

Strain Gauge Analysis of the Stresses Induced by Different Secondary Coping Materials in Tooth Supported Telescopic Overdentures

PURPOSE

To compare the stresses induced on the supporting abutments by different secondary coping materials; zirconia, Polyetheretherketone (PEEK) and Polyetherketone ketone (PEKK) in tooth supported telescopic overdentures using strain gauge analysis.

MATERIALS AND METHODS

A virtual model simulating a completely edentulous mandibular arch with two telescopic overdenture abutments in the canine region was designed and printed. The abutments received a milled zirconia primary coping. The secondary coping was milled out of zirconia in the model ZR, PEEK in the model PE and PEKK in the model PK. Five overdentures were made for each model. Strain gauge rosettes were bonded mesial and distal to each abutment. Unilateral and bilateral loadings were applied. An ANOVA test was used for statistical analysis between the three models.(α=0.01).

RESULTS

Significant differences were found between the three models during unilateral and bilateral loading. Post Hoc Tukey tests showed significant difference between ZR and PE models, ZR and PK models in addition to PE and PK models during unilateral and bilateral loading.

CONCLUSION

Zirconia copings induced the highest stress while the lowest stress values were induced by the PEKK copings.

Finite Element Analysis of the Stresses Induced by One-Piece and Two-Piece Dental Implants Supporting All-on-4 Implant-Supported Prostheses

PURPOSE

To find out the difference in the stresses induced by one-piece monophasic and two-piece dental implants supporting All-on-4 implant-supported prostheses using finite element analysis.

MATERIALS AND METHODS

Two finite element maxillary models were designed: In the two-piece model, two-piece dental implants were used, and in the one-piece model, one-piece dental implants were used. The dental implants were placed according to the All-on-4 treatment concept. The anterior implants were axially placed; however, the posterior implants were placed with a distal inclination of 15 degrees. In each model, the prosthetic superstructure was designed to be a titanium implant prosthesis with zirconia crowns. Three loading scenarios were applied in this study. The first scenario simulated biting function with a total load of 250 N. The second scenario simulated incision function in which 90-N horizontal static load was applied to the palatal surface of central incisors. The third scenario simulated biting in the presence of a cantilever.

RESULTS

In the three loading scenarios, the stresses were higher in the two-piece model. Higher stress values were recorded posteriorly rather than anteriorly in both models.

CONCLUSION

One-piece dental implants induce lower stress values compared with two-piece dental implants when used in All-on-4 implant-supported prostheses.

Comparison of tensile bond strength of ball attachments made of different materials to root canal dentin after chewing simulation

BACKGROUND

Debonding of ball attachments is one of the complications that annoy teeth supported overdenture wearers. The polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) polymers are widely applied in the dental field. The purpose of the current study was to compare the tensile bond strength of ball attachments made of such materials and the commonly used titanium ones after 5 years of overdenture insertion and removal (5000 cycles) in addition to chewing simulation (1,200,000 cycle).

METHODS

Extracted mandibular canines (N = 60) were randomly allocated into three groups and received ball attachments; titanium (group TI; N = 20), PEEK (group PE; N = 20), PEKK (group PK; N = 20). In each group, the samples were divided into two subgroups whereas tensile bond strength was measured pre aging (T0; n = 10) and post aging (T1; n = 10). Tensile bond strength was measured by the Pull out test using the Universal testing machine. Failure mode analysis was determined by examination of the samples' surfaces under 65X stereomicroscope. The resulting data followed normal distribution and the significance level was set at (α = 0.05).

RESULTS

One Way Anova showed statistically significant difference between the three groups (P < .00001). PostHoc Tukey test showed statistically significant difference between the groups TI and PE, TI and PK and no statistically significant difference between the groups PE and PK. Paired t test showed statistically significant difference in the tensile bond strength pre and post aging in each group.

CONCLUSIONS

PEEK and PEKK ball attachments could be concluded to have a higher tensile bond strength compared to the titanium ones when bonded to root dentin. Tensile bond strength of such attachments may decrease with aging as well. Clinically, the higher tensile bond strength may have a lesser rate of debonding and thus reduced patient apprehension.

Stresses induced by one piece and two piece dental implants in All-on-4® implant supported prosthesis under simulated lateral occlusal loading: non linear finite element analysis study

Background

Correct choice of the implant design and the occlusal scheme is important for the success of implant supported restorations. So, the aim of the current study was to find out the difference in the stresses induced by the one piece dental implants designed to be used in the All-on-4® concept and the conventional two piece ones under simulated lateral occlusal schemes using nonlinear finite element analysis.

Methods

Two finite element models of the maxilla, implants, and prostheses were designed according to the All-on-4® concept. In the model TP, two piece dental implants were placed while in the model OP one piece dental implants were used. Two loading scenarios were applied to each model; the first one simulated a group function occlusal scheme while the second scenario simulated a canine guided one.

Results

The highest stress value was recorded in the model TP with the group function occlusion and the lowest stress value was in the model OP with the canine guidance occlusion.

Conclusion

The one-piece dental implants can be concluded to induce less stress compared to the two piece dental implants when used in the All-on-4® implant supported prosthesis in the different lateral occlusal schemes. Canine guided occlusion can be concluded to cause lower stress values in comparison to the group function occlusal scheme.

A novel classification of prostate specific antigen (PSA) biosensors based on transducing elements

During the last few decades, there has been a tremendous rise in the number of research studies dedicated towards the development of diagnostic tools based on bio-sensing technology for the early detection of various diseases like cardiovascular diseases (CVD), many types of cancer, diabetes mellitus (DM) and many infectious diseases. Many breakthroughs have been developed in the areas of improving specificity, selectivity and repeatability of the biosensor devices. Innovations in the interdisciplinary areas like biotechnology, genetics, organic electronics and nanotechnology also had a great positive impact on the growth of bio-sensing technology. As a product of these improvements, fast and consistent sensing policies have been productively created for precise and ultrasensitive biomarker-based disease diagnostics. Prostate-specific antigen (PSA) is widely considered as an important biomarker used for diagnosing prostate cancer. There have been many publications based on various biosensors used for PSA detection, but a limited review was available for the classification of these biosensors used for the detection of PSA. This review highlights the various biosensors used for PSA detection and proposes a novel classification for PSA biosensors based on the transducer type used. We also highlight the advantages, disadvantages and limitations of each technique used for PSA biosensing which will make this article a complete reference tool for the future researches in PSA biosensing.