A technique for iris disk positioning on a custom ocular prosthesis.

Various techniques have been described for the rehabilitation of ocular defects with ocular prostheses to restore lost anatomical structures and correct cosmetic defects. This article describes a technique for optimizing the position of an iris disk over a custom-made ocular prosthesis, by using eyeglasses with customized graph paper pattern lenses. It presents a simplified method that will be useful for people with ocular defects in remote and distant service areas with limited resources.

Effect of using scan body accessories and inter-implant distances on the accuracy of complete arch implant digital impressions: An in vitro study.

PURPOSE: To introduce a novel design for scan body accessory parts that are reusable, easy to attach and detach without permanent change of the scan body, and can be used with different inter-implant distances to enhance the accuracy of complete arch implant scans. MATERIALS AND METHODS: A maxillary polymethylmethacrylate (PMMA) model with a soft tissue replica was fabricated with four implant analogs located at tooth positions 17, 13, 22, and 27 with 18, 25, and 30 mm inter-implant distances. Four scan bodies (SBs) were attached to the implants. The model was scanned with a laboratory scanner to be used as a reference scan. A total of 40 scans were made with the same intraoral scanner and they were divided equally into two groups. Group A: Complete arch implant scans without scan body accessories (n = 20), and Group B: Complete arch implant scans with scan body accessories (n = 20). Intraoral scans were exported and superimposed on the reference scan using reverse engineering inspection software to be evaluated for 3D deviations, angular deviations, and linear deviations. Statistical analysis was performed with student t-test and analysis of variance (ANOVA) with repeated measures followed by post hoc adjusted Bonferroni test. The level of significance was set at P = 0.05. RESULTS: The scan body accessories decreased both the 3D and linear deviations, with a statistically significant difference at SB4 for the 3D deviation (P = 0.043) and the linear inter-implant discrepancies between SB1-SB2 and SB3-SB4 (P = 0.029 and < 0.001), respectively. However, there was no statistically significant difference in angular deviation between the study groups. Implant positions had significant differences within each group. CONCLUSIONS:  A significant improvement in the accuracy of the complete arch implant digital impression was achieved by using the scan body accessories, particularly in reducing the 3D and linear deviations at the most distant implant positions.

Evaluation of the effect of diode laser application on the hydrophilicity, surface topography, and chemical composition of titanium dental implant surface.

PURPOSE: Attempts have been made to decontaminate the implant surface by using diode lasers. However, the parameters that provide efficient decontamination without altering the topography or surface characteristics of titanium implants are still unclear. The aim of the present study was to evaluate the effect of altering the power of diode laser (940 nm) application on the hydrophilicity, surface topography, and chemical composition of sandblasted, large grit, acid-etched (SLA) treated titanium alloy implant surface. MATERIALS AND METHODS: Thirty-six SLA-treated titanium discs (Dentis Co., Ltd.) were used in this study. The hydrophilicity of all discs was measured by using a contact angle goniometer (190 CA; Rame-hart Co, Ltd). Discs were randomly divided into four groups (n = 9 each) based on the power of the diode laser used. Group I (control, no lasing group), group II: treated with 1 W power, group III: 2 W power, and group IV: 3 W power. The chemical composition of the SLA discs was evaluated by using energy dispersive x-ray spectroscopy (EDX) before laser application. Hydrophilicity was reevaluated after the application of laser irradiation. The surface topography of all discs was examined. Changes in the chemical composition of the titanium discs were investigated following the lasing procedure. Morphometric analysis of the surface area (µm2 ) of the indentations created following laser application was also evaluated. Data were collected and the Shapiro-Wilk test of normality was used. Comparisons between the four study groups were done by using the Kruskal-Wallis test, while that to evaluate the morphometric analysis of the surface area was done by using One-way ANOVA (P < 0.05). RESULTS: The average contact angle of the drop of distilled water to the SLA discs significantly decreased after laser treatment (P < 0.05). The largest contact angle was measured in the control group, followed by the 1 W group, and the 2 W group. The smallest angle was measured in the 3 W group. Considerable surface alterations such as melting and flattening were observed on examination of the surface topography of the 3 W group followed by the 2 W group. The least changes were observed in association with the 1 W group in comparison to the control group. The EDX analysis showed the appearance of peaks of the oxygen and carbon elements after the lasing procedure with the highest percentage in the 3 W group. The average of the surface area of the created indentations significantly increased with increasing the power of the diode laser used (P < 0.05). CONCLUSIONS: The application of diode laser (940 nm) with 2 W and 3 W powers significantly altered the hydrophilicity, the surface topography, and the chemical composition of titanium discs. Diode laser (940 nm) with 1 W power can be safely used on SLA titanium implant surfaces with no damaging effect on the surface topography or hydrophilicity.

A Framework for the Development of Living Practice Guidelines in Health Care.

BACKGROUND: Living practice guidelines are increasingly being used to ensure that recommendations are responsive to rapidly emerging evidence. OBJECTIVE: To develop a framework that characterizes the processes of development of living practice guidelines in health care. DESIGN: First, 3 background reviews were conducted: a scoping review of methods papers, a review of handbooks of guideline-producing organizations, and an analytic review of selected living practice guidelines. Second, the core team drafted the first version of the framework. Finally, the core team refined the framework through an online survey and online discussions with a multidisciplinary international group of stakeholders. SETTING: International. PARTICIPANTS: Multidisciplinary group of 51 persons who have experience with guidelines. MEASUREMENTS: Not applicable. RESULTS: A major principle of the framework is that the unit of update in a living guideline is the individual recommendation. In addition to providing definitions, the framework addresses several processes. The planning process should address the organization's adoption of the living methodology as well as each specific guideline project. The production process consists of initiation, maintenance, and retirement phases. The reporting should cover the evidence surveillance time stamp, the outcome of reassessment of the body of evidence (when applicable), and the outcome of revisiting a recommendation (when applicable). The dissemination process may necessitate the use of different venues, including one for formal publication. LIMITATION: This study does not provide detailed or practical guidance for how the described concepts would be best implemented. CONCLUSION: The framework will help guideline developers in planning, producing, reporting, and disseminating living guideline projects. It will also help research methodologists study the processes of living guidelines. PRIMARY FUNDING SOURCE: None.

Effect of anodized titanium abutment collars on peri-implant soft tissue: A split-mouth clinical study.

STATEMENT OF PROBLEM: Anodic oxidation of titanium implant abutment collars has been used to mask their unesthetic grayish color. However, the effect of anodic oxidation on the health and appearance of peri-implant soft tissues is unclear. PURPOSE: The purpose of this split-mouth clinical study was to investigate the effect of anodized titanium on the health and esthetics of peri-implant soft tissues. MATERIAL AND METHODS: A total of 60 osseointegrated implants placed in 30 participants were included in the present study. Each participant received 2 randomly allocated abutments, one with a pink anodized collar and the other with an unanodized one to form 2 groups: unanodized group (control group) and anodized group (experimental group). All implants were restored with lithium disilicate restorations. Evaluations of the peri-implant soft tissues were performed at the time of definitive restoration insertion (baseline) and after 3, 6, 12, and 18 months: peri-implant probing depth, soft tissue recession, modified sulcus bleeding index, modified plaque index, and modified gingival index. The esthetics of peri-implant soft tissues were evaluated by using the modified pink esthetic score. The paired t test or Wilcoxon signed-rank test was used for comparing the 2 study groups at each point of time depending on the normality of the variables (α=.05). To compare each variable at different time points within each group separately, repeated measures ANOVA or Friedman tests were used according to the normality of the variables, followed by post hoc pairwise comparisons by using the Bonferroni adjusted significance (α=.05). RESULTS: Five peri-implant soft tissue indices were followed up throughout the study. No statistically significant differences were found among the mean values of the tested indices in the anodized and unanodized groups throughout the evaluation periods (P>.05). The collective mean values of the modified pink esthetic score also showed no statistically significant differences between the groups (P>.05). CONCLUSIONS: Based on this split-mouth clinical study, pink anodized titanium abutment collars do not produce a clinically significant effect on the health or esthetics of peri-implant soft tissues.

Registration of maxillomandibular relationship through a fully digital workflow for complete-mouth rehabilitation with screw-retained fixed implant-supported prostheses: A clinical report.

Digital recording of the maxillomandibular relationship by using intraoral scanning in completely edentulous patients for computer-aided design and computer-aided manufacture implant-supported prostheses can be challenging. This clinical report describes the fabrication of complete-arch, screw-retained implant-supported prostheses in a completely edentulous patient with a fully digital workflow.

Evaluation of debonding force of screw-retained lithium disilicate implant-supported crowns cemented to abutments of different designs and surface treatments.

STATEMENT OF PROBLEM: Straight preparable abutments provide an alternative to titanium bases (Ti-bases) for single-unit screw-retained implant-supported restorations. However, the debonding force between crowns with a screw access channel cemented to preparable abutments and Ti-bases of different designs and surface treatments is unclear. PURPOSE: The purpose of this in vitro study was to compare the debonding force of screw-retained lithium disilicate implant-supported crowns cemented to straight preparable abutments and Ti-bases of different designs and surface treatments. MATERIAL AND METHODS: Forty laboratory implant analogs (Straumann Bone Level) were embedded into epoxy resin blocks that were randomly divided into 4 groups (n=10 each) according to the abutment type used: CEREC group, Variobase group, airborne-particle abraded Variobase group, and airborne-particle abraded straight preparable abutment group. All specimens were restored with lithium disilicate crowns and cemented with resin cement to the corresponding abutments. They were thermocycled (from 5 to 55 °C for 2000 cycles) followed by cyclic loading (120 000 cycles). The tensile forces required to debond the crowns from the corresponding abutments were measured (N) by using a universal testing machine. The Shapiro-Wilk test of normality was used. Comparison between the study groups was done with 1-way ANOVA (α=.05). RESULTS: Tensile debonding force values were significantly different according to the type of abutment used (P<.05). The highest retentive force value was recorded in the straight preparable abutment group (928.1 ±222.2 N) followed by the airborne-particle abraded Variobase group (852.6 ±164.6 N), and the CEREC group (498.8 ±136.6 N); the lowest value was reported in the Variobase group (158.6 ±85.2 N). CONCLUSIONS: The retention of screw-retained lithium disilicate implant-supported crowns cemented to airborne-particle abraded straight preparable abutments is significantly higher than to non-surface treated Ti-bases and similar to airborne-particle abraded ones. Abrading abutments with 50-mm Al2O3 significantly increased the debonding force of the lithium disilicate crowns.

Digitization accuracy and scannability of different prosthodontic materials: An in vitro trial.

STATEMENT OF PROBLEM: Digital scanning of different prosthodontic materials is commonplace in contemporary practice. However, the scannability of prosthodontic materials has not been thoroughly investigated. PURPOSE: The purpose of this in vitro study was to evaluate the scanning accuracy and measure the unscanned area in a preset time limit of commonly used framework materials. MATERIAL AND METHODS: A mandibular acrylic resin reference dental typodont with 3 teeth, with the central one prepared for a complete coverage crown, was digitized by using a desktop scanner. A complete coverage crown was generated in standard tessellation language (STL) format. Three groups were created from the digital design according to the crown material: milled polyetheretherketone (PEEK), milled airborne-particle abraded titanium, and milled polymethylmethacrylate (PMMA). They were scanned with the desktop scanner to be used as reference files for each group. The intraoral scanner Medit i700 was used to digitize each specimen 10 times (n=10). Using a nonmetrology grade software program, the deviations between the test STL file of the intraoral scanner and the reference STL file of the desktop scanner were assessed by using the RMS values. The unscanned surface area in a preset time limit of 6 seconds (scannability) was assessed. Groups were compared by using 1-way ANOVA followed by the Tukey post hoc test with Bonferroni correction when the results were significant. All tests were 2-tailed (α=0.05). RESULTS: Regarding deviation analysis, RMS discrepancies were computed, and significant differences in trueness were found (P<.001) among the 3 studied groups. The titanium group had the highest trueness followed by the PEEK and PMMA groups, which were statistically similar (P>.05). Precision differed significantly among the 3 studied groups (P<.001). PEEK was the most precisely scanned material followed by titanium, and the PMMA group had the least precision. Regarding scannability, there were overall significant differences (P<.001). Titanium was the most scannable, followed by PEEK and then PMMA. CONCLUSIONS: Airborne-particle abraded titanium had better trueness and scannability than PEEK and PMMA. However, PEEK was the most precisely scanned material.

Evaluation of the virtual cement gap parameter of different CAD software programs in designing a single crown restoration: An in vitro study.

STATEMENT OF PROBLEM: The accuracy of different virtual cement gap parameters in designing a single crown in a computer-aided design (CAD) software program is still unclear. PURPOSE: The purpose of this in vitro study was to evaluate and compare the virtual cement gap settings of 3 different CAD software programs used to design a single crown restoration. MATERIAL AND METHODS: Three different CAD software programs (exocad, Dental System, and B4D) were evaluated for designing single crowns with similar virtual cement gap settings. Three experimental groups were created based on the CAD software program used (n=10). Three-dimensional analysis software program was used to assess the virtual cement gap in the CAD restoration. The Shapiro-Wilk test of normality was used. Comparisons were carried out by using 1-way ANOVA and the Scheffé post hoc test (α=.05). RESULTS: The Dental System software program had the lowest statistical mean error values at both tooth margin (4.6 µm) and axial wall (1.5 µm), followed by B4D then exocad. At the occlusal surface, the lowest statistical mean error value of 5 µm was achieved by the Dental System followed by exocad then B4D. CONCLUSIONS: Accuracy of the virtual cement gap parameter in single crown design varies based on the CAD software used. The highest accuracy was attained by the Dental System software program at all tooth surfaces, followed by B4D at the tooth margin and axial wall and by exocad at the occlusal surface.

Outcomes of bio-esthetic single implant-supported restorations after peri-implant soft tissue conditioning with two prosthetic techniques: A 1-year randomized clinical trial.

STATEMENT OF PROBLEM: Providing a definitive restoration with an emergence profile matching that of the contralateral or extracted tooth should result in an esthetic peri-implant soft tissue contour. Whether a custom healing abutment improves the outcome of a bio-copied definitive restoration compared with a stock abutment is unclear. PURPOSE: The purpose of this 1-year randomized clinical trial was to evaluate the peri-implant soft and hard tissues related to bio-esthetic single implant-supported restorations having a contralateral tooth-matching restorative emergence profile after peri-implant soft tissue conditioning with either custom or stock healing abutment for patients indicated for immediate implant placement. MATERIAL AND METHODS: Twenty-four participants indicated for immediate implant placement in the maxillary esthetic zone received bio-esthetic single implant-supported restorations after peri-implant soft tissue conditioning with either a custom healing abutment (n=12) or a stock healing abutment (n=12). The pink and white esthetic score (PES-WES) was evaluated 6 and 12 months after implant placement. Peri-implant bone changes were measured with cone beam computed tomography (CBCT) scans at the same intervals. RESULTS: The PES-WES showed significant difference between the 2 groups at 6 and 12 months. The CBCT scans did not show significant difference between the 2 groups. CONCLUSIONS: The use of the bio-esthetic concept for immediate single implant placement achieved successful esthetic restorations after conditioning the peri-implant tissues using either custom or stock healing abutments. However, the use of custom healing abutments was associated with higher PES-WES values in comparison with the use of stock healing abutments.

Evaluation of the masking ability, marginal adaptation, and fracture resistance of screw-retained lithium disilicate implant-supported crowns cemented to titanium bases versus preparable abutments.

BACKGROUND: Straight preparable abutments and titanium bases (ti-base) can be used to support single-unit screw-retained lithium disilicate implant-supported restorations. The choice between using both abutments depends on many factors. The purpose of this in vitro study was to compare the masking ability, marginal adaptation, and fracture resistance of screw-retained lithium disilicate implant-supported crowns cemented to straight preparable abutments and ti-bases. METHODS: Twenty laboratory implant analogs (Straumann Bone Level; Straumann AG) were randomly divided into 2 groups (n = 10 each) according to the type of the abutment used. Preparable abutment group and ti-base group. Lithium disilicate crowns were used to restore the specimens. All specimens were subjected to thermocycling (from 5 to 55 °C for 2000 cycles) followed by cyclic loading (120 000 cycles). The vertical marginal gap between the abutment finish line and the most apical part of the crown was measured in (µm) by using a stereomicroscope after cementation and after thermocycling and cyclic loading. A spectrophotometer was used to evaluate the masking ability of the specimens after cementation. The load required to fracture the crowns was measured in Newtons (N) by using a universal testing machine after thermocycling and cyclic loading. The Shapiro-Wilk test of normality was used. The appropriate statistical test was used. RESULTS: Regarding the masking ability, the color difference (∆E) showed no statistically significant difference between the ti-base group (2.6 ± 0.2) and the preparable abutment group (2.6 ± 0.3) (P = .888). The average of the microgap values (µm) was greater in ti-basegroup after cementation (13.9 ± 9.2) than preparable group (7.63 ± 1.78) with no statistically significant difference between the 2 groups (P = .49). After cyclic loading and thermocycling, the average microgap values (µm) was significantly greater in the ti base group (21.3 ± 7.4) than in preparable group (13.3 ± 1.5) (P = .02). The load required to fracture the specimens was greater in the preparable group (1671.5 ± 143.8) than in the ti-base group (1550.2 ± 157.5) with no statistically significant difference between the 2 groups (P = .089). CONCLUSION: The abutments used in the present study did not compromise the masking ability of the screw-retained lithium disilicate implant supported crowns. Moreover, the crowns cemented to preparable abutments had better marginal adaptation and higher fracture resistance when compared to those cemented to ti-bases. CLINICAL IMPLICATIONS: Straight preparable abutments are considered as an alternative to the ti-bases when restoring single screw-retained lithium disilicate implant-supported crowns with comparable fracture resistance, marginal adaptation, and masking ability.

Retention of zirconia crowns to titanium bases with straight versus angled screw access channels: an invitro study.

BACKGROUND: The aim of this study was to assess the impact of abutments with angled screw access channel on the retention of zirconia crowns. METHODS: Seven implant replicas were inserted in epoxy resin blocks. Fourteen zirconia crowns for central incisor tooth were digitally fabricated and cemented to titanium bases (Ti-bases) with resin cement. Titanium bases were categorized into 2 groups (n = 7). Control group (Group STA) included straight screw access channel abutments. Study group (Group ASC) included angled screw access channel abutments. Following aging (5 °C-55 °C, 60 s; 250,000 cycles, 100 N, 1.67 Hz), the pull-off forces (N) were recorded by using retention test (1 mm/min). Types of failure were defined as (Type 1; Adhesive failure when luting agent predominantly remained on the Ti-base surface (> 90%); Type 2; Cohesive failure when luting agent remained on both Ti-base and crown surfaces; and Type 3; Adhesive failure when luting agent predominantly remained on the crown (> 90%). Statistical analysis was conducted by using (IBM SPSS version 28). Normality was checked by using Shapiro Wilk test and Q-Q plots. Independent t-test was then used to analogize the groups. RESULTS: Mean ± standard deviation of retention force records ranged from 1731.57 (63.68) N (group STA) to 1032.29 (89.82) N (group ASC), and there was a statistically significant variation between the 2 groups (P < .05). Failure modes were Type 2 for group STA and Type 3 for group ASC. CONCLUSIONS: The retention of zirconia crowns to abutments with a straight screw access channel is significantly higher than abutments with angled screw access channel.

Evaluation of the dislodgement force of splinted restorations with engaging conical abutments over multiple nonparallel implants (in-vitro study).

BACKGROUND: Splinted multiunit cement-retained restorations with screw access channels over engaging abutments are viable implant prosthetic options. However, information regarding the maximum degree of divergence between multiple implants is lacking. The purpose of this in vitro study was to determine the maximum degree of divergence between 2 adjacent implants with conical connections that allows insertion and removal of splinted restorations with engaging preparable abutments or titanium base abutments. METHODS: Two implants were aligned in a stone base, one straight and the other at an angle ranging from 0 to 20 degrees. The implants represented an implant system that had an internal conical connection and a hexed abutment engaging the base of the connection. Two straight preparable engaging cement retained abutments were screwed onto the implants and splinted together using acrylic resin. A total of 11 angles were tested, with 7 specimens for every angle. Evaluation of dislodging force was performed by pulling out the splinted abutments after unscrewing them. This was performed subjectively by 3 blinded investigators who applied a tactile pulling force. A scale of 0-10 was used to estimate the pulling force. Objectively the dislodging force was measured in Newtons using a universal testing machine. A statistical correlation was made between the subjective and objective dislodging force values using Spearman's rank correlation coefficient. RESULTS: The mean subjective values increased gradually from 0 to 16 degrees. A sudden rise was noticed at 18 degrees (9.71 ± 0.23) and, at 20 degrees, the investigators were not able to remove the splinted abutments from the implants. The mean objective dislodgement force values increased gradually from 0 to16 degrees and abruptly from 16 degrees (13.57 ± 0.45 N) to 18 degrees (25.40 ± 0.66 N) and 20 degrees (35.22 ± 0.64). The correlation between the subjective and the objective evaluations assessed using the Spearman's rank correlation coefficient was 0.98 indicating a statistically significant correlation (P < .001). As the objective dislodging force increased, the subjective dislodgement difficulty increased. CONCLUSIONS: Splinting cement retained restorations with screw access channels on engaging abutments is possible when multiple implants with conical connections having an internal flare angle of 8 degrees are used, with implant divergence of up to 16 degrees.

Evaluation of the marginal adaptation and debonding strength of two types of CAD-CAM implant-supported cement-retained crowns.

BACKGROUND: In-vitro data from a clinically well-known lithium disilicate ceramic reference was used to assess the expected performance of resin-based materials in implant dentistry. The purpose of the study was to compare the bond strength and marginal adaptation of nano-ceramic hybrid composite crowns cemented to stock cement-retained abutments to lithium disilicate crowns. METHODS: Twenty abutment analogs were embedded into auto-polymerizing acrylic resin blocks. The blocks were divided into 2 groups according to the restorative crown material. The 2 groups were divided as follows: Resin nano-ceramic group and lithium disilicate group. Abutment analogs in both groups were scanned using a laboratory scanner, and the restorations were designed, manufactured, and cemented with resin cement over the corresponding group. All samples were tested for marginal adaptation and bond strength after storage for 24 hours at 37 °C in 100% humidity. Data were collected, tabulated, and statistically analysed using the appropriate tests. Normality was checked using Shapiro Wilk test and Q-Q plots. Data were normally distributed. Variables were presented using mean, 95% Confidence Interval (CI) and standard deviation in addition to median and Inter Quartile Range (IQR). Differences between groups regarding debonding forces was assessed using independent t test. Two Way ANOVA was performed to assess the effect of material and bonding on marginal gap. All tests were two tailed and p value was set at < 0.05. RESULTS: Marginal gap and debonding force values were significantly different according to the type of material used (P < .05). Resin nano-ceramic crowns presented lower marginal gap values before (20.80 ± 8.87 µm) and after (52.11 ± 22.92 µm) bonding than lithium disilicate crowns. The debonding force value for resin nano-ceramic crowns (284.30 ± 26.44 N) was significantly higher than that for lithium disilicate crowns (253.30 ± 33.26 N). Adhesive failure mode was detected in all the specimens in both groups. CONCLUSIONS: The type of material used for implant-supported cement-retained crowns had a statistically significant effect on marginal adaptation and bond strength. Resin nano-ceramic implant-supported cement-retained crowns had better marginal adaptation and higher bond strength than those manufactured using lithium disilicate.

Effect of screw access channel on the fracture rate of lithium disilicate cement-retained implant-supported posterior crowns.

STATEMENT OF PROBLEM: Whether the presence of a screw access channel on the occlusal surface of a lithium disilicate cement-retained single tooth implant restoration reduces its fracture rate is unclear. PURPOSE: The purpose of this randomized controlled clinical trial was to compare the fracture rate of lithium disilicate cement-retained posterior single tooth implant restorations with or without screw access channels. The study also evaluated whether the crown dimensions and location of the occlusal screw access channel would affect the fracture rate. MATERIAL AND METHODS: A split-mouth study was conducted where 40 participants having 2 implants placed to restore single missing posterior teeth with crowns were enrolled. Implants were randomly allocated into a conventional crown group or a screw access group, receiving cement-retained restorations fabricated from lithium disilicate glass-ceramic with and without an occlusal screw access channel. Crown dimensions were recorded in millimeters from the designing software program. Follow-up evaluations were made at 3, 6, and 12 months by observing visible cracks or fractures of the crowns. The Kolmogorov-Smirnov test of normality was used. Comparisons were carried out by using the Student and Welch t tests (α=.05). RESULTS: After a 12-month follow-up period, no crowns fractured or revealed visible cracks, resulting in a 100% success rate. No statistically significant differences were found between the conventional crown group and screw access channel group in all crown dimensions (P>.05). CONCLUSIONS: The presence of an occlusal screw access channel did not affect the short-term fracture rate of lithium disilicate cement-retained single implant-supported posterior crowns. The amount of axial cantilever, occlusal ceramic thickness, and location of the screw access channel on the occlusal surface of the restoration have no effect on its fracture rate.

Modified biblock versus monoblock mandibular advancement appliances for treatment of obstructive sleep apnea: A randomized controlled trial.

STATEMENT OF PROBLEM: The high prevalence of obstructive sleep apnea represents a serious public health problem. Oral appliances have gained wide acceptance among patients diagnosed with obstructive sleep apnea, who should wear them every night. A comfortable oral appliance is mandatory for successful treatment outcomes. PURPOSE: The purpose of this randomized controlled trial was the assessment of the influence of 2 different designs of the mandibular advancement appliance (MAA), modified biblock and monoblock, for the management of obstructive sleep apnea. MATERIAL AND METHODS: The study was designed as a prospective 2-arm randomized controlled clinical trial conducted in parallel. Twenty participants (aged 40 ±7.5 years) diagnosed with moderate obstructive sleep apnea were randomly assigned to a control group (n=10), receiving monoblock MAA, and a study group (n=10), receiving modified biblock MAA with elastics. Both appliances were fabricated by using computer-aided design and computer-aided manufacture (CAD-CAM) technology at different mandibular advancement levels (MALs): 50% and 75% of maximum MAL. A total of 60 cone beam computed tomography scans, 60 overnight full polysomnography sleep tests, 60 STOP-Bang questionnaires, and 40 Usability of Sleep Apnea Equipment-Oral Appliance (USE-OA) questionnaires were collected and analyzed blindly at baseline (initial visit), 50% MAL (3 months), and 75% MAL (6 months). The main outcome measures were the upper airway volume, linear anteroposterior and cross-sectional airway measurements, Apnea Hypopnea Index, Respiratory Disturbance Index, STOP-Bang questionnaire scoring, and USE-OA questionnaire scoring. Nonparametric statistical analysis was performed by using a statistical software program (α=.05). With a beta error accepted of up to 20%, the power of the study was 80%. RESULTS: At 75% MAL, the percentage change in upper airway volumetric measurements showed a favorable increase: biblock group (115%) and monoblock group (42%), with a statistically significant difference (P=.001). The linear anteroposterior airway measurements and the percentage change in cross-sectional airway measurements were statistically similar: biblock group (80%) and (75%) monoblock group (60%), (54%) (P=.450, P=.151, respectively). The percentage change in the Apnea Hypopnea Index significantly decreased: biblock group (-89%) and monoblock group (-54%) (P<.001). The percentage change in the Respiratory Disturbance Index decreased: biblock group (-78%) and monoblock group (-62%) (P<.023). From the STOP-Bang questionnaire scoring, 100% of both groups showed low risk for obstructive sleep apnea at 75% MAL. From the satisfaction scoring on the USE-OA questionnaire, the biblock group was 100% strong satisfaction and the monoblock group was 50% satisfaction and 50% fairly satisfied. CONCLUSIONS: The modified biblock MAA with elastics showed significant improvements in patients diagnosed with obstructive sleep apnea regarding upper airway measurements and full polysomnography vital parameters when compared with monoblock MAA.

CAD-CAM custom healing abutments: A dental technique.

Custom healing abutments are important in establishing optimal esthetics for prosthesis-driven, implant-supported restorations. This report demonstrates a technique for constructing a custom healing abutment with computer-aided design and computer-aided manufacturing to save chairside time and provide predictable results.

Evaluation of the accuracy of implant placement by using fully guided versus partially guided tissue-supported surgical guides with cylindrical versus C-shaped guiding holes: A split-mouth clinical study.

STATEMENT OF PROBLEM: The accuracy of partially guided implant placement protocols in comparison with fully guided protocols is still unclear. C-shaped guide holes have become popular; however, their effect on drilling and implant position accuracy has not been thoroughly investigated. PURPOSE: The purpose of this split-mouth clinical study was to evaluate the accuracy of implant placement by using fully guided versus partially guided surgical guides with cylindrical versus C-shaped guiding holes. MATERIAL AND METHODS: Adopting 80% power of the study in calculating sample size, a total of 48 implants were placed in the mandibular interforaminal area of 12 edentulous participants, who were randomly divided into 2 groups: a fully guided group, comprising 24 implants placed on 1 side by using a fully guided protocol and a partially guided group, comprising 24 implants placed on the other side in a partially guided protocol. Each group was further subdivided into 2 subgroups: cylindrical, including 12 implants placed through cylindrical guide holes, and C-shaped (12 implants) placed through C-shaped guiding holes. Postoperative cone beam computed tomography scans were made, and based on image fusion, the total deviations between the virtually preplanned and actual implant positions were determined and compared between both groups and subgroups. The linear horizontal deviation of the implant hexagon and apex, together with apical depth deviation and angular deviations between the position of the actually placed and virtually planned implants, were analyzed in 3 dimensions. The Kolmogorov-Smirnov test of normality was used. Comparisons were carried out by using the Kruskal-Wallis test. Post hoc pair-wise comparisons when the Kruskal-Wallis test was significant were carried out by using the Dunn-Sidak test (α=.05). RESULTS: No statistically significant differences were found in coronal linear deviation (P>.05), apical linear deviation (P>.05), apical depth deviation (P=.086), or angular deviation (P=.247), between the fully guided protocol and the partially guided protocol. CONCLUSIONS: The accuracy of partially guided implant placement was clinically comparable with that of fully guided placement whether the guiding holes were cylindrical or C-shaped.

Clinical and radiographic evaluation of implants placed with fully guided versus partially guided tissue-supported surgical guides: A split-mouth clinical study.

STATEMENT OF PROBLEM: The effect of placing implants by using a fully guided protocol versus a partially guided protocol on the peri-implant soft and hard tissues is unclear. C-shaped guide holes are often used; however, their effect on drilling and peri-implant tissues has not been thoroughly investigated. PURPOSE: The purpose of this split-mouth clinical study was to clinically and radiographically evaluate peri-implant soft and hard tissues after implant placement by using fully guided versus partially guided surgical guides with cylindrical versus C-shaped guide holes. MATERIAL AND METHODS: Adopting an 80% power of the study in calculating sample size, a total of 48 implants were placed in the mandibular interforaminal area of 12 edentulous participants. Implants were randomly divided into 2 groups: a fully guided group comprising 24 implants placed on 1 side by using a fully guided protocol and a partially guided group comprising 24 implants placed on the other side of the same participant by using a partially guided protocol. Each group was further subdivided into 2 subgroups: cylindrical, including 12 implants placed through cylindrical guide holes, and C-shaped (12 implants) placed through C-shaped guide holes. All participants were clinically evaluated in terms of a modified plaque index, modified gingival index, peri-implant probing depth, and probing attachment level at 2, 4, and 6 months. Implant stability, marginal bone level, and bone density were then evaluated immediately after implant placement at 2, 4, and 6 months. RESULTS: No statistically significant differences were found in the plaque index (P=.927), modified gingival index (P=.916), probing depth (P=.832), probing attachment level (P=.096), implant stability (P=.338), bone level (P=.063), or bone density (P=.390) between the fully guided protocol and partially guided protocol. CONCLUSIONS: The soft and hard tissues surrounding the implants placed by using fully guided surgical guides were clinically comparable with those placed by using partially guided surgical guides whether the guiding holes were cylindrical or C-shaped.

Selective removal of ammonia from wastewater using Cu(II)-loaded Amberlite IR-120 resin and its catalytic application for removal of dyes.

Cationic ligand exchange is one of the most predominant mechanisms for the removal of ammonia from wastewater through complex formation. The complexation technique occurs between the metal ions loaded on the surface of Amberlite IR-120 and ammonia which is present in the medium. Cu(II)-loaded Amberlite IR-120 (R-Cu2+) was prepared and described using FT-IR, TGA, SEM, and EDX techniques. The prepared R-Cu2+ was applied for the elimination of ammonia from an aqueous solution. Different cations such as Co2+ and Ni2+ were loaded onto Amberlite IR-120 to study the impact of counter cation on the removal efficiency of ammonia. The ammonia removal percentage followed the order; R-Cu2+ > R-Ni2+ > R-Co2+. The effects of contact time, pH, initial concentration, temperature, and coexisting ions on the removal of ammonia from wastewater by R-Cu2+ were investigated. The equilibrium adsorbed amount of ammonia was found to be 200 mg/g at pH = 8.6 and 303 K within 60 min using 0.1 g R-Cu2+ and an initial concentration of ammonia of 1060 mg/L. The removal of ammonia using R-Cu2+ obeyed the non-linear plot of both Freundlich and Langmuir isotherms. According to the thermodynamic parameters, the adsorption of ammonia onto R-Cu2+ was an endothermic and spontaneous process. The time-adsorption data followed the pseudo-second-order and intraparticle diffusion models. Moreover, the resulting product (R-Cu(II)-amine composite) from the adsorption process exhibited high catalytic activity and could be low-cost material for the elimination of dyes such as aniline blue (AB), methyl green (MG), and methyl violet 2B (MV2B) from wastewater.