Mechanical stability of posterior implant-supported monolithic zirconia cantilever on titanium-base abutments. An in vitro study.

PURPOSE: Investigate survival and technical complications of two-unit posterior implant-supported cantilever made of monolithic zirconia on titanium-base abutments (Zr-TiB) vs. porcelain-fused-to-metal on castable gold abutments (PFM-GA) using two different implant connections, internal butt-joint (IBJ) and internal conical (IC). MATERIALS AND METHODS: Forty-eight implants (4.3 mm diameter) were divided into four groups (n = 12) to support 2-unit mandibular premolar cantilevers with two different materials (Zr-TiB vs. PFM-GA) and two connection types (IBJ vs. IC). Tested groups were as follows: (1) IBJ/Zr-TiB; (2) IBJ/PFM-GA; (3) IC/Zr-TiB; and (4) IC/PFM-GA. Specimens were thermomechanical aged (1,200,000 cycles, 98 N, 5-55°C) with occlusal axial load on the pontic. Catastrophic and non-catastrophic events were registered, and removal torque values measured before and after aging. Specimens surviving aging were subjected to loading until failure. Survival, total complication rates, torque loss (%), and bending moments were calculated. RESULTS: From 48 specimens, 38 survived aging. Survival rates significantly varied from 16.7% (IC/PFM-GA) to 100% (IBJ/Zr-TiB; IBJ/PFM-GA; IC/Zr-TiB) (p < .01). Internal conical connection revealed significantly higher torque loss (IC/ZrTiB - 67%) compared to internal butt-joint (IBJ/Zr-TiB - 44%; IBJ/PFM-GA - 46%) (p < .01). Bending moments were higher in internal butt-joint connections than in internal conical (p < .05). CONCLUSION AND CLINICAL IMPLICATIONS: Two-unit posterior implant-supported cantilever FDPs replacing mandibular premolars composed of monolithic zirconia on titanium-base abutments demonstrated higher mechanical stability compared to porcelain-fused-to-metal on castable gold abutments in this in vitro study. The internal conical connection combined with porcelain-fused-to-metal on gold abutments revealed a high number of failures; therefore, their clinical use may be considered cautiously for this indication.

Influence of sterilization on the retention forces of lithium disilicate and polymer-infiltrated ceramic-network crowns bonded to titanium base abutments: An in-vitro study.

OBJECTIVES: The aim of this study was to evaluate the effect of sterilization on the retention forces of lithium disilicate (LD) and polymer-infiltrated ceramic network (PICN) crowns bonded to titanium base (Ti-base) abutments. MATERIALS AND METHODS: Forty LD and 40 PICN crowns were milled and then bonded to 80 Ti-bases with two resin composite cements: Multilink Hybrid Abutment (mh) and Panavia V5 (pv) for a total of 8 groups (n = 10). Half of the specimens (test) underwent an autoclaving protocol (pressure 1.1 bar, 121°C, 20.5 min) and the other half not (control). Restorations were screw-retained to implants, and retention forces (N) were measured with a pull-off testing machine. The surfaces of the Ti-bases and the crowns were inspected for the analysis of the integrity of the marginal bonding interface and failure mode. Student's t-test, chi-square test, and univariate linear regression model were performed to analyze the data (α = 0.05). RESULTS: The mean pull-off retention forces ranged from 487.7 ± 73.4 N to 742.2 ± 150.3 N. Sterilized groups showed statistically significant overall higher maximum retention forces (p < .05), except for one combination (LD + mh). Sterilization led to an increased presence of marginal gaps and deformities compared to no-sterilization (p < .001), while no statistically significant relationship was found between failure mode and sterilization (p > .05). CONCLUSIONS: Sterilization may have a beneficial effect on the retention forces of LD and PICN crowns bonded to titanium base abutments, although it may negatively influence the integrity of the marginal bonding interface.

A multicenter randomized controlled clinical pilot study of buccally micro-veneered lithium-disilicate and zirconia crowns supported by titanium base abutments: 1-year outcomes.

OBJECTIVES: To investigate survival rates, technical and biologic outcomes of buccally micro-veneered all-ceramic single implant crowns. MATERIAL AND METHODS: Sixty subjects randomly received immediately or early placed implants. Crowns out of lithium-disilicate (n = 30) and zirconia-ceramic (n = 30) were bonded to titanium-base-abutments. Restorations were inspected at baseline (BL) and during follow-up visits (6, 12 months). Technical and biologic parameters were recorded. Data were analysed descriptively. Differences between groups were tested with Student's t-test. Paired T-test was used when comparing data from the same implant or tooth over time. Linear model repeated measures were used to test differences between materials over time. Differences in counts were evaluated using Pearson Chi-square test. The level of significance was at p < .05. RESULTS: After a mean observation time of 13.2 ± 2.4 months, 54 restorations were re-examined. The implant survival rate was 98.3%, and the restoration survival rate was 100%. One early implant failure occurred. Two minor chippings occurred in lithium-disilicate restorations. No chippings or fractures occurred in any zirconia restorations at 1 year (0%). The technical complication rate was 3.7%, with 7.7% complications among the lithium-disilicate restorations and no differences between the two materials (p = .558). At 1-year follow-up, mean Bleeding on Probing (BOP) was higher at implants (0.27 ± 0.3) than adjacent teeth (0.17 ± 0.18) (p = .046) with no differences between materials (p = .36). Differences in pocket probing depth (PPD) between implants and adjacent teeth were significant (p < .01). Jemt Index improved significantly from BL to 1-y-follow-up (p < .001). CONCLUSIONS: Preliminary results were good, suggesting that the ceramic type does not impact technical and biologic parameters.

The influence of titanium-base abutment geometry and height on mechanical stability of implant-supported single crowns.

AIM: This study aimed to investigate the influence of titanium base (ti-base) abutment macro- and micro-geometry on the mechanical stability of polymer-infiltrated ceramic network (PICN) screw-retained implant-supported single crowns (iSCs). MATERIALS AND METHODS: Twelve specimens per group were used, comprising six different implant/ti-base abutment combinations restored with PICN iSCs: Nb-T (gingival height [GH]: 1.5 mm, prosthetic height [PH]: 4.3 mm), CC (GH: 0.8 mm, PH: 4.3 mm), CC-P (GH: 0.8 mm, PH: 7 mm), Nb-V (GH: 1.5 mm, PH: 6 mm), St (GH: 1.5 mm, PH: 5.5 mm), and Th (GH: 0.5 mm, PH: 9 mm). The specimens underwent thermo-mechanical aging, and those that survived were subsequently subjected to static loading until failure. The data were analyzed using a one-way ANOVA test followed by Tukey post hoc test (α = .05). RESULTS: All specimens survived thermo-mechanical aging without complications, namely, visible cracks, debonding, or screw loosening. Th group demonstrated the highest strength values among all the groups, with significant differences compared to Nb-T (p < .05), CC (p < .001), and St (p < .001). Additionally, CC-P group exhibited significantly superior fracture strength results compared to CC (p < .05) and St (p < .05). CONCLUSION: The choice of ti-base, particularly prosthetic height, had a significant influence on fracture resistance of PICN iSCs. Nevertheless, the height or geometrical features of the ti-base did not exhibit a significant influence on the mechanical behavior of the iSC/ti-base assembly under thermomechanical loading, as all specimens withstood the aging without complication or failure.

Effect of splinting scan bodies on the trueness of complete-arch digital implant scans with 5 different intraoral scanners.

STATEMENT OF PROBLEM: The absence of fixed reference points can affect the trueness of complete-arch intraoral digital implant scans. The effect of splinting intraoral scan bodies (ISBs) or the inclusion of artificial landmarks (AL) on the trueness of complete-arch digital implant scans is still unclear. PURPOSE: The purpose of this study was to analyze the effect of splinting ISBs or the inclusion of AL on the trueness of complete-arch digital implant scans with 5 intraoral scanners (IOSs). MATERIAL AND METHODS: Six tissue-level dental implants (Straumann Tissue Level) were placed in an edentulous patient, and the correspondent definitive cast was digitized with a desktop scanner (IScan4D LS3i) to obtain the reference digital cast. Digital scans (n=10) were performed with 5 IOSs: TRIOS 4, Virtuo Vivo, Medit i700, iTero Element 5D, and Cerec Primescan. Three different scanning techniques were evaluated: conventional (cIOSs), splinted (sIOSs), and AL (AL-IOSs). The scan data obtained were imported into a metrology software program and superimposed to the reference digital cast by using a best-fit algorithm. The overall deviations of the positions of the ISBs were evaluated by using the root-mean-square (RMS) error (α=.05). RESULTS: The mean ±standard deviation trueness values for the cIOSs, sIOSs, and AL-IOSs groups were 48 ±8 µm, 53 ±7 µm, and 49 ±11 µm, respectively, with no statistically significant differences (P=.06). Significant differences were found for the IOSs used with each technique (P<.001). Primescan (27 ±4 µm cIOSs; 28 ±3 µm sIOSs; 31 ±3 µm AL-IOSs) showed significantly higher trueness than iTero 5D (47 ±5 µm cIOSs; 47 ±4 µm sIOSs; 50 ±6 µm AL-IOSs) (P=.002) and TRIOS 4 (93 ±18 µm cIOSs; 76 ±18 µm sIOSs; 107 ±13 µm AL-IOSs) (P=.001) for all techniques. In addition, no significant differences were found between the techniques by using iTero 5D or Primescan (P=.348 and P=.059, respectively). CONCLUSIONS: The cIOSs, sIOSs, and AL-IOSs techniques showed similar trueness. The IOS used influenced the trueness of complete-arch digital implant scans.

Accuracy of Additively Manufactured and Milled Interim 3-Unit Fixed Dental Prostheses.

PURPOSE: To investigate the accuracy of additive manufacturing (AM) by means of internal fit of fixed dental prostheses (FDPs) fabricated with two AM technologies using different resins and printing modes (validated vs nonvalidated) compared to milling and direct manual methods. MATERIAL AND METHODS: Sixty 3-unit interim FDPs replacing the first mandibular molar were divided into 6 groups (n = 10): manual (Protemp 4), milled (Telio-CAD), and AM groups were subdivided based on AM technology (direct light processing (Rapidshape P30 [RS]) and stereolithography (FormLabs 2 [FL])) and the polymer type (P-Pro-C&B [St] and SHERAprint-cb [Sh]) (RS-St, RS-Sh, FL-St, FL-Sh). Validated (RS-Sh and RS-St) or nonvalidated (FL-St and FL-Sh) modes were adopted for AM. The specimens were scanned to 3D align (GOM inspect) according to the triple scan method. The internal space between the FDPs and preparation surfaces in four sites (marginal, axial, occlusal, and total) was measured using equidistant surface points (GOM Inspect). Statistical analysis was done using Kruskal Wallis and Dunn post-hoc tests. (α = 0.05). RESULTS: One AM group (FL-Sh) and milling exhibited better adaptation compared to manual and RS-St at molar site (p < 0.05). FDPs with St resin (FL-St and RS-St) displayed bigger marginal space than milled, FL-Sh, and RS-Sh. The nonvalidated printing mode showed better mean space results (p < 0.05) with higher predictability and repeatability (p < 0.001). CONCLUSIONS: The AM interim FDPs tested provided valid alternatives to the milled ones in regard to their accuracy results. The printing mode, resin, and the AM technology used significantly influenced the manufacturing accuracy of interim FDPs, particularly at the marginal area. The nonvalidated printing mode with lower-cost 3D printers is a promising solution for clinical applications.

In vitro and in vivo accuracy of full-arch digital implant impressions.

OBJECTIVES: The main objective of the study was to compare the accuracy of full-arch digital implant impressions for fixed dental prosthesis under in vitro and in vivo conditions. MATERIALS AND METHODS: Eight patients (five women and three men) with at least one edentulous arch and with 4-6 osseointegrated implants participated in this study. For each edentulous arch (n = 10), experimental screw-retained titanium bar with attached four scan bodies was fabricated. The bar containing four scan bodies was screw-retained intraorally on implants and scanned with Trios 3 intraoral scanner eight times (IOS group, in vivo). Then, the bar was attached to the master cast and scanned eight times again with the same intraoral scanner (MIOS group, in vitro). Finally, the bar with scan bodies was scanned 8 times with a laboratory scanner (reference). Precision and trueness were calculated for 3 distances and 3 angles between the scan bodies (1-2, 1-3, and 1-4) in IOS and MIOS groups. RESULTS: Precision and trueness for the largest distance (1-4) were found to be 44 ± 18 µm and 32 ± 19 µm for the IOS group and 31 ± 16 µm and 30 ± 14 µm for MIOS group, respectively. Precision and trueness for the angle between the most distant scan bodies (1-4) were 0.22 ± 0.14° and 0.18 ± 0.10° for the IOS group and 0.16 ± 0.11° and 0.07 ± 0.05° for MIOS group, respectively. CONCLUSIONS: Intraoral conditions moderately affected the precision and trueness of Trios 3 (3Shape) intraoral scanner. Results of in vitro accuracy studies cannot be directly transferred to the clinical field.

Mechanical stability and technical outcomes of monolithic CAD/CAM fabricated abutment-crowns supported by titanium bases: An in vitro study.

OBJECTIVES: To evaluate mechanical stability (survival and complication rates) and bending moments of different all-ceramic monolithic restorations bonded to titanium bases (hybrid abutment-crowns) or to customized titanium abutments compared to porcelain-fused-to-metal crowns (PFM) after thermo-mechanical aging. MATERIAL AND METHODS: Sixty conical connection implants (4.3 mm-diameter) were divided in five groups (n = 12): PFM using gold abutment (GAbut-PFM), lithium disilicate crown bonded to customized titanium abutment (TAbut+LDS), lithium disilicate abutment-crown bonded to titanium base (TiBase+LDS), zirconia abutment-crown bonded to titanium base (TiBase+ZR), polymer-infiltrated ceramic-network (PICN) abutment-crown bonded to titanium base (TiBase+PICN). Simultaneous thermocycling (5°-55°C) and chewing simulation (1,200,000-cycles, 49 N, 1.67 Hz) were applied. Catastrophic and non-catastrophic events were evaluated under light microscope, and survival and complication rates were calculated. Specimens that survived aging were loaded until failure and bending moments were calculated. RESULTS: Survival rates after aging were 100% (TAbut+LDS, TiBase+LDS), 91.7% (GA-PFM), 66.7% (TiBase+ZR) and 58.3% (TiBase+PICN) and differed among the groups (p = .006). Non-catastrophic events as screw loosening (GA-PFM) and loss of retention or micro-/macro-movement (TiBase groups) were observed. Complication rates varied among the groups (p < .001). TiBase+PICN had lower bending moment than all the other groups (p < .001). CONCLUSIONS: Hybrid abutment-crowns made of lithium disilicate can be an alternative to PFM-based restorations, although concerns regarding the bonded interface between the titanium base and abutment-crown can be raised. PICN and zirconia may not be recommended due to its inferior mechanical and bonding outcomes, respectively. Titanium customized abutment with bonded lithium disilicate crown appears to be the most stable combination.

Fabrication, workflow and delivery of reconstruction: Summary and consensus statements of group 4. The 6th EAO Consensus Conference 2021.

OBJECTIVES: To report assessments of four systematic reviews (SRs) on (i) clinical outcomes of all-ceramic implant-supported crowns (iSCs), (ii) production time, effectiveness, and costs of computer-assisted manufacturing (CAM), (iii) computer-assisted implant planning and surgery (CAIPS) time and costs, and (iv) patient-reported outcome measures (PROMS). MATERIAL AND METHODS: An author group consisting of experienced clinicians and content experts discussed and evaluated the SRs and formulated consensus on the main findings, statements, clinical recommendations, and need for future research. RESULTS: All four SRs were conducted and reported according to PRISMA and detailed comprehensive search strategies in at least three bibliometric databases and hand searching. The search strategies were deemed reproducible. Variation was noted regarding language restrictions and inclusion of grey literature, but the search comprehensiveness appeared persuasive. The SRs included bias risk assessments of the primary studies, and their study methodology impacted the interpretations of the extracted data. CONCLUSIONS: (i) There is limited evidence (49 NRCT) showing that veneered and monolithic all-ceramic iSCs have excellent outcomes observed up to 3 years. (ii) There is no evidence evaluating production time and effectiveness comparing subtractive and additive CAM of implant models, abutments and crowns. (iii) There is limited evidence (4 RCT) that CAIPS involves more time and costs when considering the entire workflow and for diagnostics, manufacturing, and insertion of the restoration. Time seems to be the decisive factor for higher costs. (iv) Patients' comfort increases when optical compared to conventional impressions are used for fabricating iSCs and short-span FPDs (2 RCT, 5 NRCT).

Effect of airborne-particle abrasion of a titanium base abutment on the stability of the bonded interface and retention forces of crowns after artificial aging.

STATEMENT OF PROBLEM: Published data have shown that a mechanical surface treatment of titanium surfaces increases bonding potential. However, most of the studies are based on shear or tensile tests performed on flat-surfaced specimens and do not take into consideration the retention given by the titanium base (ti-base) axial walls and the thermomechanical loading seen in a clinical setting. PURPOSE: The purpose of this in vitro study was to evaluate the influence of different airborne-particle abrasion (APA) methods of the ti-base surface on the stability of the bonded interface and retention forces between these titanium bases and lithium disilicate crowns after thermomechanical aging. MATERIAL AND METHODS: Sixty internal connection implants (Conelog) were restored with lithium disilicate crowns and bonded to the corresponding ti-bases (Conelog). The ti-bases were divided into 4 groups (n=15), 3 experimental groups applying different APA methods, 30-µm silica-modified Al2O3 particles (CoJet) (30-SiO-AlO), 50-µm Al2O3 (Cobra Aluoxyd) (50-AlO), 110-µm silica-modified Al2O3 particles (Rocatec Plus) (110-SiO-AlO), and 1 control group (NoT). Ti-bases were airborne-particle abraded (10 seconds, 0.25 MPa at a 10-mm distance) under standardized conditions in a custom-made APA device. All crowns were cemented with a resin cement (Multilink Hybrid Abutment). After aging (1 200 000 cycles, 49 N, 1.67 Hz; 5 °C-55 °C, 120 seconds), all specimens were assessed for the presence of bond failures by optical microscopy (×50). The retention forces (N) were tested by using a pull-off test (0.5mm/min). Modes of failure were classified (Type 1, 2, or 3). An additional ti-base representing each group was prepared for surface roughness (µm) calculation (Ra, Rc, Rz) with a noncontact laser profilometer, and representative scanning electron microscope (SEM) images were recorded (×1000). Chi-squared tests were performed to analyze the bonded interface failure and modes of failure, and a Kruskal-Wallis test was selected to evaluate retention force values (α=.05). RESULTS: The percentages of bonding failure after aging were 73.3% (NoT), 40% (30-SiO-AlO), 6.7% (50-AlO), and 40% (110-SiO-AlO). The stability of the bonded interface was influenced by the APA method applied (P<.05). Mean ±standard deviation retention force values varied from 206.3 ±86.3 N (NoT) to 420 ±139.5 N (50-AlO), and the differences between these 2 groups were significant (P<.05). Modes of failure were predominantly Type 2 (30-SiO-AlO; 50-AlO; 110-SiO-AlO) and Type 3 (NoT). CONCLUSIONS: Airborne-particle abrasion of the titanium surface increased the bond stability and retention forces between the ti-base and the respective crown. The use of 50-µm Al2O3 provided the most stable bonded interface among the different treatments.

Virtual diagnostics and guided tooth preparation for the minimally invasive rehabilitation of a patient with extensive tooth wear: A validation of a digital workflow.

The recent evolution of digital technologies in dentistry has enabled virtual 3D diagnostic analysis of a dentition before treatment, allowing for virtual, minimally invasive treatment planning. In this report, an extensively worn dentition was 3D virtual analyzed at an increased vertical dimension of occlusion. Virtual waxing (exocad DentalCAD; Exocad) and subsequent analysis of the need for minimally invasive preparations were performed. Areas of each tooth without adequate clearance for the minimal thickness of a definitive restoration (set at 1.5 mm in the software), including the amount of tooth substance to be removed (GOM Inspect; GOM), were visualized in color. A preparation guide was virtually designed according to this diagnostic plan (3-matic; Materialise) and 3D printed (Connex3 Objet260; Stratasys) from resin (VeroMagenta RGD851; Stratasys). The teeth were minimally prepared using the guide, and the amount of preparation was validated by superimposing the scan of the prepared model on the initial scan and comparing it with the diagnostic plan.

Latest advances in augmented reality technology and its integration into the digital workflow.

Smile reconstruction is achieved using rigorous and detailed methodologies that are technically demanding and both time and cost intensive. These methodologies do not include the patient during the primary conception phase. New digital technologies using augmented reality (AR) offer the option of immediate diagnosis and pre-visualization of the potential outcome before the start of treatment. A 22-year-old patient with a congenitally missing maxillary right canine, peg-shaped maxillary lateral incisors, and multiple visible diastemas required an esthetic rehabilitation. An AR virtual mock-up using specialized software was used to preview and modify the restoration proposal in real time. Using the novel 'CAD-link' workflow, the final AR proposal could be imported into CAD software and transformed into a digital wax-up with the new virtual wax copy function. After a minimally invasive preparation, the final veneer reconstructions were precisely planned according to the previously developed design proposal and bonded according to the well-known adhesive protocol. The workflow described in this article links AR with CAD/CAM technology and is expected to be time and cost efficient. This patient-centered approach involves the patient from the very beginning and is therefore an excellent communication tool between the patient and the restorative team.

Randomized controlled clinical trial of digital and conventional workflows for the fabrication of zirconia-ceramic fixed partial dentures. Part I: Time efficiency of complete-arch digital scans versus conventional impressions.

STATEMENT OF PROBLEM: Clinical trials are needed to evaluate digital and conventional technologies for providing fixed partial dentures. PURPOSE: The purpose of the first part of this clinical study was to test whether complete-arch digital scans were similar to or better than complete-arch conventional impressions regarding time efficiency and participant and clinician perceptions. MATERIAL AND METHODS: Ten participants in need of a posterior tooth-supported 3-unit fixed partial denture were included. Three intraoral digital scanners and subsequent workflows (Lava C.O.S.; 3M [Lava], iTero; Align Technology Inc [iTero], Cerec Bluecam; Dentsply Sirona [Cerec]) were compared with the conventional impression method using polyether (Permadyne; 3M) and the conventional workflow. A computer-generated randomization list was used to determine the sequence of the tested impression procedures for each participant. The time needed for the impression procedures, including the occlusal registration, was assessed. In addition, the participant and clinician perceptions of the comfort and difficulty of the impression were rated by means of visual analog scales. Data were analyzed with the nonparametric paired Wilcoxon test together with an appropriate Bonferroni correction to detect differences among the impression systems (α=.05). RESULTS: The total time for the complete-arch impressions, including the preparation (powdering) and the occlusal registration, was shorter for the conventional impression than for the digital scans (Lava 1091 ±523 seconds, iTero 1313 ±418 seconds, Cerec 1702 ±558 seconds, conventional 658 ±181 seconds). The difference was statistically significant for 2 of the 3 digital scanners (iTero P=.001, Cerec P<.001). The clinicians preferred the conventional impression to the digital scans. Of the scanning systems, the system without the need for powdering was preferred to the systems with powdering. No impression method was clearly preferred over others by the participants. CONCLUSIONS: For complete-arch impressions, the conventional impression procedures were objectively less time consuming and subjectively preferred by both clinicians and participants over digital scan procedures.

Randomized controlled clinical trial of digital and conventional workflows for the fabrication of zirconia-ceramic posterior fixed partial dentures. Part II: Time efficiency of CAD-CAM versus conventional laboratory procedures.

STATEMENT OF PROBLEM: Clinical trials are needed to evaluate the digital and conventional fabrication technology for providing fixed partial dentures (FPDs). PURPOSE: The purpose of the second part of this clinical study was to compare the laboratory production time for tooth-supported, 3-unit FPDs by means of computer-aided design and computer-aided manufacturing (CAD-CAM) systems and a conventional workflow. In addition, the quality of the 3-unit framework of each treatment group was evaluated clinically. MATERIAL AND METHODS: For each of 10 participants, a 3-unit FPD was fabricated. Zirconia was used as the framework material in the CAD-CAM systems and included Lava C.O.S. CAD software (3M) and centralized CAM (group L); CARES CAD software (Institut Straumann AG) and centralized CAM (group iT); and CEREC Connect CAD software (Dentsply Sirona) and centralized CAM (group C). The noble metal framework in the conventional workflow (group K) was fabricated by means of the traditional lost-wax technique. All frameworks were evaluated clinically before veneering. The time for the fabrication of the cast, the 3-unit framework, and the veneering process was recorded. In addition, chairside time during the clinical appointment for the evaluation of the framework was recorded. The paired Wilcoxon test together with appropriate Bonferroni correction was applied to detect differences among treatment groups (α=.05). RESULTS: The total effective working time (mean ±standard deviation) for the dental technician was 220 ±29 minutes in group L, 217 ±23 minutes in group iT, 262 ±22 minutes in group C, and 370 ±34 minutes in group K. The dental technician spent significantly more time in the conventional workflow than in the digital workflow, independent of the CAD-CAM systems used (P<.001). CONCLUSIONS: Irrespective of the CAD-CAM system, the overall laboratory time for the dental technician was significantly less for a digital workflow than for the conventional workflow.

Reliability of a three-dimensional facial camera for dental and medical applications: A pilot study.

STATEMENT OF PROBLEM: Three-dimensional visualization for pretreatment diagnostics and treatment planning is necessary for surgical and prosthetic rehabilitations. The reliability of a novel 3D facial camera is unclear. PURPOSE: The purpose of this clinical study was to evaluate the reliability of a novel medical facial camera system in capturing the 3D geometry of the face in a single exposure. MATERIAL AND METHODS: Twelve edentulous participants (7 women and 5 men; mean age: 74.6 years) were included, and digital images for facial reconstruction were captured using a custom-made static capturing system (Medusa Static; Disney Research Zurich). Eight extraoral soft-tissue facial landmarks were identified, which included the right outer canthus (OCR), left outer canthus (OCL), right cheilion (CmR), left cheilion (CmL), pronasale nostril tip, subnasale, philtrum, and gnathion (GN). Interlandmark distances of OCR-OCL, OCR-CmR, OCL-CmL, OCR-GN, OCL-GN, CmR-CmL, pronasale nostril tip-GN, and subnasale-GN were measured clinically and then on the 3D digital reconstructions. The absolute differences between the digital and clinical measurements were recorded. The intraclass correlation coefficient was applied to evaluate the reliability of digital measurement and interexaminer reliability. RESULTS: The mean ±standard deviation difference between the clinical and digital measurements was 1.95 ±0.33 mm. Intraclass correlation coefficients computed for the 2 examiners against clinical measurements were all above 0.5. The interexaminer reliability coefficient of digital measurement was above 0.909. CONCLUSIONS: The 3D facial geometry obtained from the novel medical facial camera system was found to be reliable and clinically acceptable. Inconsistencies in measurements for a few specific facial landmarks may arise, but these can be avoided by thorough examiner calibration before undertaking the digital measurements.

Fracture strength of zirconia implant abutments on narrow diameter implants with internal and external implant abutment connections: A study on the titanium resin base concept.

BACKGROUND: There is limited knowledge regarding the strength of zirconia abutments with internal and external implant abutment connections and zirconia abutments supported by a titanium resin base (Variobase, Straumann) for narrow diameter implants. OBJECTIVES: To compare the fracture strength of narrow diameter abutments with different types of implant abutment connections after chewing simulation. MATERIAL AND METHODS: Hundred and twenty identical customized abutments with different materials and implant abutment connections were fabricated for five groups: 1-piece zirconia abutment with internal connection (T1, Cares-abutment-Straumann BL-NC implant, Straumann Switzerland), 1-piece zirconia abutment with external hex connection (T2, Procera abutment-Branemark NP implant, Nobel Biocare, Sweden), 2-piece zirconia abutments with metallic insert for internal connection (T3, Procera abutment-Replace NP implant, Nobel Biocare), 2-piece zirconia abutment on titanium resin base (T4, LavaPlus abutment-VarioBase-Straumann BL-NC implant, 3M ESPE, Germany) and 1-piece titanium abutment with internal connection (C, Cares-abutment-Straumann BL-NC implant, Straumann, Switzerland). All implants had a narrow diameter ranging from 3.3 to 3.5 mm. Sixty un-restored abutments and 60 abutments restored with glass-ceramic crowns were tested. Mean bending moments were compared using ANOVA with p-values adjusted for multiple comparisons using Tukey's procedure. RESULTS: The mean bending moments were 521 ± 33 Ncm (T4), 404 ± 36 Ncm (C), 311 ± 106 Ncm (T1) 265 ± 22 Ncm (T3) and 225 ± 29 (T2) for un-restored abutments and 278 ± 84 Ncm (T4), 302 ± 170 Ncm (C), 190 ± 55 Ncm (T1) 80 ± 102 Ncm (T3) and 125 ± 57 (T2) for restored abutments. For un-restored abutments, C and T4 had similar mean bending moments, significantly higher than those of the three other groups (p < .05). Titanium abutments (C) had significantly higher bending moments than identical zirconia abutments (T1) (p < .05). Zirconia abutments (T1) with internal connection had higher bending moments than zirconia abutments with external connection (T2) (p < .05). For all test groups, the bending moments were significantly reduced when restored with all-ceramic crowns. CONCLUSIONS: For narrow diameter abutments, the fracture strength of 2-piece internal connected zirconia abutments fixed on titanium resin bases was similar to those obtained for 1-piece titanium abutments. Narrow diameter zirconia abutments with internal connection exhibited higher fracture strength than zirconia abutments with an external connection. Titanium abutments with an internal connection were significantly stronger than identical zirconia abutments.

Group 5 ITI Consensus Report: Digital technologies.

OBJECTIVES: Working Group 5 was assigned the task to review the current knowledge in the area of digital technologies. Focused questions on accuracy of linear measurements when using CBCT, digital vs. conventional implant planning, using digital vs. conventional impressions and assessing the accuracy of static computer-aided implant surgery (s-CAIS) and patient-related outcome measurements when using s-CAIS were addressed. MATERIALS AND METHODS: The literature was systematically searched, and in total, 232 articles were selected and critically reviewed following PRISMA guidelines. Four systematic reviews were produced in the four subject areas and amply discussed in the group. After emendation, they were presented to the plenary where after further modification, they were accepted. RESULTS: Static computer-aided surgery (s-CAIS), in terms of pain & discomfort, economics and intraoperative complications, is beneficial compared with conventional implant surgery. When using s-CAIS in partially edentulous cases, a higher level of accuracy can be achieved when compared to fully edentulous cases. When using an intraoral scanner in edentulous cases, the results are dependent on the protocol that has been followed. The accuracy of measurements on CBCT scans is software dependent. CONCLUSIONS: Because the precision intraoral scans and of measurements on CBCT scans and is not high enough to allow for the required accuracy, s-CAIS should be considered as an additional tool for comprehensive diagnosis, treatment planning, and surgical procedures. Flapless s-CAIS can lead to implant placement outside of the zone of keratinized mucosa and thus must be executed with utmost care.

Extending the service life of existing dental restorations with esthetic and functional limitations.

Adhesive cementation is a useful procedure not only for cementing restorations onto teeth but also for attaching new ceramic restorations to existing restorations to improve their esthetics and/or function. This clinical report presents a technique for modifying an existing nonsatisfactory implant-supported fixed dental prosthesis by means of adhesively cemented veneers and onlays bonded to the pre-existing metal-ceramic surface with resin cement. This modification may avoid the replacement of the fixed dental prosthesis, reducing both treatment costs and time while fulfilling the patient's demands.

Comparison of user satisfaction and image quality of fixed and mobile camera systems for 3-dimensional image capture of edentulous patients: A pilot clinical study.

STATEMENT OF PROBLEM: An evaluation of user satisfaction and image quality of a novel handheld purpose-built mobile camera system for 3-dimensional (3D) facial acquisition is lacking. PURPOSE: The purpose of this pilot clinical study was to assess and compare the effectiveness between a handheld mobile camera system designed for facial acquisition and a fixed static camera arrangement by comparing the time effectiveness and the operator and participant preference for the 2 techniques of image capture. MATERIAL AND METHODS: Completely edentulous participants (n=12: women=7, men=5; mean age: 74.6 years) were included in this pilot study. Images were captured with and without the prostheses in situ while maintaining "serious" and "full-smile" facial expressions. Images were captured using a mobile and a static system. The working times for the participant installation and image captures were recorded. Operator and participant perceptions of the entire experience were recorded by using visual analog scale questionnaires. Nonparametric tests were used for statistical analyses (α=.05). RESULTS: The installation time was significantly shorter for the mobile system (static=24 ±13 seconds; mobile=10 ±10 seconds), but the differences in the image capture times were not statistically significant (static: 29 ±5 seconds; mobile: 40 ±18 seconds). Operator preference was in favor of the mobile system with regard to working time (P=.002), difficulty in using (installation: P=.002; handling: P=.045), and camera weight (P=.002); however, they preferred the static arrangement for image quality (P=.003) and comfort (P=.013). The participants rated the entire photographic experience favorably, and 10 of 12 participants preferred the static camera over the mobile one. CONCLUSIONS: Despite the complexity of the installation, the static system was evaluated better for image quality; the mobile system was easier in installation and handling. The operators preferred the mobile system, and the participants preferred the static system.