Effect of different surface locking patterns on the trueness of complete arch digital implant scans: An in vitro study.

STATEMENT OF PROBLEM: The effect of different surface locking patterns on the trueness of a digital implant scan of a completely edentulous arch remains uncertain. PURPOSE: The purpose of this in vitro study was to evaluate whether locking surfaces with different patterns affected the trueness of complete arch implant digital scans. MATERIAL AND METHODS: An edentulous maxillary cast with 4 implants (2 anterior implants parallel and 2 posterior implants tilted at 17 degrees) was fabricated. Four implant-level scan bodies were fixed onto the implants, and the cast was scanned with a desktop scanner to create the reference file. Four groups (L0, L1, L2, and L3) were formed, each with a distinct locking surface configuration, and all scans were made using the same intraoral scanner. L0 kept all 4 implant-level scan bodies during scanning. L1 involved removing the right first premolar (RPM) scan body, scanning the other 3 implant scan bodies, then reattaching the RPM's scan body, and continuing scanning. In L2, the RPM and right lateral incisor (RIC) scan bodies were removed, followed by scanning the left implants to create a locking surface, and scanning the right implants. In L3, only the left posterior molar's (LPM) scan body was retained and scanned; then a locking surface was generated, and then the remaining implants were scanned. A metrology software program (Geomagic Control X) was used for comparison. Statistical analyses were performed using the Kruskal-Wallis, the 1-way ANOVA, the Welch ANOVA, the Friedman test, the repeated-measures ANOVA, the Bonferroni post hoc test, and the Games-Howell post hoc test (α=.05). RESULTS: Significant 3D surface deviations were observed in the coronal bevel (CB) region and in the entire scan bodies when assessing trueness in the L0, L1, L2, and L3 groups (P<.001). L2 exhibited the highest discrepancies in 3D surface deviation for CB (0.030 ±0.002 mm) and implant scan bodies (0.357 ±0.052 mm) and distance deviation, while the highest mean angular deviation values were found in L0 (0.924 ±0.131 degrees). CONCLUSIONS: Locking half of the arch showed the highest trueness discrepancies when performing digital scans for complete arch implant-supported prostheses.

Effect of Utilizing Cheek Retractors on Patient Satisfaction and Trueness of Peripheral Borders in Maxillary Digital Scans for Totally Edentulous Patients: An In Vivo Study.

PURPOSE: To evaluate the effect of cheek retractors on the accuracy of capturing peripheral borders in totally edentulous digital scans by comparing the conventional impression technique to digital scans made using two different cheek retractors. MATERIAL AND METHODS: Sixteen edentulous maxillary impressions were made using three techniques: the conventional impression technique, using modeling thermoplastic compound and zinc oxide eugenol paste; the digital intraoral scanning technique using the DIO scan retractor (DIO); and using the Br.nemark lip retractor (BRAN). The control impressions of each patient were poured, scanned using a desktop scanner, then transferred into a three-dimensional analysis software. DIO and BRAN groups were scanned using an intraoral scanner, imported, and superimposed using best fit algorithm on the corresponding control. The root mean square for the whole surface and for particular interest regions were calculated to assess the degree of trueness. The patients' perceptions of the impression techniques were the secondary outcomes. Statistical analyses were performed using the one sample T-test and Wilcoxon test (α=.05). RESULTS: Significant discrepancies were found for BRAN and DIO compared to the control. No significant discrepancies were found when comparing RMS of BRAN and DIO at different regions. Scan retractors had a significant impact on patient satisfaction, with patients preferring DIO. CONCLUSIONS: Edentulous intraoral scans made using cheek retractors had similar deviations when compared to each other but diverged from the conventional impression in edentulous maxilla. Patient preferences for intraoral scans over conventional impressions were confirmed. CLINICAL IMPLICATIONS: The use of different retracting methods during intraoral scanning of totally edentulous maxillary arches does not affect the peripheral border registration.

Fracture strength of preformed zirconia crown and CAD-CAM zirconia, ceramic, and hybrid composite crowns for the restoration of primary molars: An in vitro study.

BACKGROUND: Paediatric-preformed zirconia crowns have been associated with several issues, primarily their inability to be crimped and the need for extensive tooth preparation. Additionally, the capacity to adjust the size, shape, and fit of these crowns is very limited. AIM: To evaluate and compare the fracture strength of four different types of dental crowns intended for paediatric patients. DESIGN: The fracture resistance of four types of paediatric crowns was evaluated using the universal testing machine; freshly extracted primary molars received one of the following: preformed zirconia crowns, custom-made computer-aided design and computer-aided manufacturing (CAD-CAM) zirconia crowns, custom-made CAD-CAM ceramic crowns, and custom-made CAD-CAM hybrid composite crowns. Data were statistically compared using the Kruskal-Wallis test followed by the Bonferroni test, and the level of significance was set at 5%. RESULTS: Results showed that there was a statistically significant difference among the four groups (p < .001). The highest value of fracture force was observed for the milled zirconia crown and the lowest for the prefabricated zirconia. CONCLUSION: The implementation of the CAD-CAM digital crown fabrication technique has the potential to address issues associated with preformed crowns in paediatric patients, particularly in terms of fracture resistance.

Facially driven guided crown lengthening using a complete digital workflow: A dental technique.

A facially driven digital guided crown lengthening method using the virtual smile design approach supplemented with a static 3-dimensional face scan that demonstrates the digital data of extraoral soft tissue is presented. The technique enables the practitioner to virtually design the new smile and surgically plan the crown lengthening procedure.

Factors that influence the accuracy of maxillomandibular relationship at maximum intercuspation acquired by using intraoral scanners: A systematic review.

OBJECTIVE: To review the factors that influence the accuracy of the maxillomandibular relationship at maximum intercuspation (MIP) acquired by using intraoral scanners (IOSs). MATERIAL AND METHODS: A systematic search was performed using five databases: MEDLINE/PubMed, Cochrane, Embase, World of Science, and Scopus. A manual search was also completed. Studies assessing the factors that influence the MIP acquired by using IOSs were included and organized based on the analyzed factor. Studies were evaluated by applying the Joanna Briggs Institute Critical Appraisal Checklist. RESULTS: Twenty-nine articles were included. Seven factors have been identified: IOS system, scan extension, edentulous areas, number, location, and extension of occlusal records, occlusal force, tooth mobility, and alignment methods. Nine studies evaluated the influence of IOS system. Four studies assessed the influence of the extension of the arch scan. Three studies evaluated the effect of edentulous spaces. Four studies agreed on the impact of the number, location, and extension of the occlusal records on the MIP accuracy. One study assessed the influence of the occlusal force, showing a smaller average interocclusal space with increased occlusal force. One study evaluated the influence of tooth mobility. Seven studies analyzed the influence of the alignment method on the MIP accuracy. CONCLUSIONS: Most of the studies reported no difference on the MIP accuracy between half- and complete-arch scans. Areas with 2 or more missing teeth reduce the MIP accuracy. A bilateral and frontal record including 2 teeth or a bilateral posterior occlusal including at least 4-teeth is indicated for maximizing the MIP accuracy. CLINICAL IMPLICATIONS: When a complete-arch intraoral scans is obtained, a bilateral and frontal record including 2 teeth or a bilateral posterior occlusal record including at least 4-teeth is recommended for maximizing the accuracy of the MIP. When a half-arch intraoral scan is acquired, a posterior occlusal record including at least 4-teeth is indicated for optimizing the accuracy of the MIP.

Preorthodontic functional long-term trial restoration of a worn dentition for optimizing outcomes: A clinical report.

Orthodontic tooth movement is often required before restorative treatment to maximize the esthetic and functional outcomes. Diagnostic waxing is a crucial step before active treatment to validate the optimal tooth position for future restorations. In this clinical report, a bonded prototype of the diagnostic waxing was used to guide and facilitate orthodontic treatment with the definitive restorations mind. The orthodontic treatment created the required space between the teeth for the ceramic restorations, improved dental and facial features, and restored appropriate incisal guidance.

Comparison between stereophotogrammetric, digital, and conventional impression techniques in implant-supported fixed complete arch prostheses: An in vitro study.

STATEMENT OF PROBLEM: Conventional impressions and digital intraoral scanning for implant-supported fixed complete arch prostheses still have many problems that influence accuracy. Although stereophotogrammetry may offer a reliable alternative to other techniques, it has seldom been investigated. PURPOSE: The purpose of this in vitro study was to measure and compare the intraoral scan body deviations of the reference cast with the intraoral scan body distortions obtained by conventional, digital, and stereophotogrammetric techniques. MATERIALS AND METHODS: An edentulous maxillary "all-on-four" cast was prepared with 2 straight and two 17-degree angled screw-retained abutments screwed on the implant. Three capture techniques were compared: the conventional impression technique (CI group) using impression plaster (IP), the digital intraoral scanning (DIS group) technique, and the stereophotogrammetry (SPG group) technique. A calibrated extraoral scanner was used to digitize the definitive cast to compare its intraoral scan body positions with those of the other techniques in terms of global angular distortion and 3D deviations of the whole scan body and flat angled surface alone by using an inspection and metrology software program and the best fit alignment technique. The Kolmogorov-Smirnov and Shapiro-Wilk tests showed normal distribution of the quantitative variables. Thus, the repeated measures analyses of variance followed by univariate analysis and Bonferroni multiple comparison tests were performed to analyze the data (α=.05). RESULTS: Significant global angular discrepancies and 3D deviations of the whole scan body and flat angled surface were found among the CI, DI, and SPG groups for both trueness (P<.001) and precision (P<.001). CONCLUSIONS: The stereophotogrammetry capture technique reported the highest accuracy in terms of trueness and precision for the intraoral scan bodies of all the techniques evaluated. However, at the flat angled surface region of the scan body, higher trueness was detected with the digital technique. Conventional impressions showed better trueness results than the digital ones, but the opposite was true of precision.

Triple scan evaluation of internal and marginal adaptation of overlays using different restorative materials.

OBJECTIVE: Problems in the confection of indirect restorations may increase the marginal and internal gap. This study aimed to quantify the marginal and the internal fit of overlays fabricated with three different materials. MATERIALS AND METHODS: Standardized cavities were prepared on endodontically treated human third molars and digital impressions were done using an intraoral camera (Trios 3). Restorations were designed (n = 15) and fabricated with three materials: Hybrid ceramic (Cerasmart; GC Corp, EUROPE), high-strength lithium disilicate (GC Initial® LiSi Press; GC Corp, Tokyo, Japan), and zirconia reinforced Lithium Silicate Glass Ceramic (Vita Suprinity; Vita, Germany). Axial, marginal, pulpal, and gingival gaps were calculated by measuring the distance between the restoration and the tooth at several reference points. Two-Way analysis of variance was used for statistical analysis. The significance level was set at α = 0.05. RESULTS: Mean gap was significantly influenced by the material (p < 0.001), gap localization (p < 0.001), and interaction between the factors (p = 0.002). For all materials, the highest gap was observed at gingival and pulpal surfaces (p ≤ 0.015). LiSi Press achieved the overall lowest values at axial values measurements (p ≤ 0.003). CONCLUSIONS: The performance of a CAD/CAM system relative to marginal adaptation is influenced by the restorative material used. High-strength lithium disilicate seems to be showed the best marginal adaptation. CLINICAL SIGNIFICANCE: Marginal and internal adaptation of CAD/CAM restorations could be influenced by the type of material chosen.

Effect of implant scan body geometric modifications on the trueness and scanning time of complete arch intraoral implant digital scans: An in vitro study.

STATEMENT OF PROBLEM: The effect of the surface geometry of implant scan bodies (ISBs) on the accuracy and scanning time of complete-arch implant digital scans remains uncertain. PURPOSE: The purpose of this in vitro study was to evaluate whether geometric modifications on implant scan bodies (nonmodified, subtractively modified, and additively modified ISBs) affect the trueness and scanning time of complete-arch intraoral implant digital scans. MATERIAL AND METHODS: A completely edentulous maxillary cast with 2 anterior parallel and two 17-degree posteriorly tilted implant abutment analogs was prepared. A digitized reference was created from this cast with polyetheretherketone (PEEK) (CARES Mono Scanbody for screw-retained abutment) ISBs by using a desktop scanner (E3). Three different groups were created: nonmodified (NM group), subtractively modified (SM group), and additively modified (AM group). For the NM group, no modifications were made to the ISBs. For the SM group, 4 round-shaped grooves were created on the buccal, lingual, mesial, and distal sides. For the AM group, PEEK beads were printed and cemented on the same areas of the ISB of the SM group. Fifteen consecutive scans were captured with an intraoral scanner (TRIOS 3) for each group, and the scanning time was recorded. By using a metrology software program, scans of each group were superimposed on the reference file to determine the 3D surface, linear, and angular position discrepancies of each ISB. Repeated-measures analyses of variance followed by univariate analysis and Bonferroni multiple comparison tests were performed to analyze the data (α=.05). To compare the mean time among groups, 1-way analysis of variance was performed followed by the Tukey post hoc tests. RESULTS: Significant 3D surface, linear, and angular position discrepancies were found when measuring trueness among the NM, SM, and AM groups (P<.001). Discrepancies in 3D surface deviation were highest for the AM group (0.266 ±0.030 mm), and the lowest mean angular deviation values were for the SM group (0.993 ±0.062 degrees). However, the mean scanning time was not significantly different among the groups tested (P=.237). CONCLUSIONS: For complete-arch intraoral implant digital scans, subtractive modifications on ISBs enhanced scanning trueness, while additive modifications on ISBs decreased scanning trueness. However, implant scan body geometric modifications did not affect scanning time.

Guided Endodontic Treatment of Calcified Lower Incisors: A Case Report.

A 52-year-old female patient was diagnosed with chronic periapical periodontitis associated with severely calcified lower central incisors. Radiographic examination revealed no visible root canal in the coronal-third of the root. After choosing the guided endodontic treatment, an intraoral scan (Trios, 3shape, Copenhagen, Denmark), in conjunction with a cone beam computed tomography (CBCT) scan, was taken in order to design and fabricate a printed guide. Virtual implant software was used to visualize the surgical access into the sclerosed root canals. After locating the canals, the guide was removed, and the teeth were treated under a rubber dam. The guided approach allows predictable, efficient endodontic treatment of teeth presenting calcified canals, with minimal removal of sound dentine and less risk of root perforations.

Effect of different CAD-CAM materials on the marginal and internal adaptation of endocrown restorations: An in vitro study.

STATEMENT OF PROBLEM: Recent resin-based and ceramic-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials have been used to restore endodontically treated teeth. Adaptation of the restoration is important for clinical success, but studies evaluating the effect of these materials on the adaptation of endocrowns are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of resin-based and ceramic-based materials on the marginal and internal adaptation of endocrowns. MATERIAL AND METHODS: Forty mandibular molars were divided into 4 groups (n=10); each group was restored with a different CAD-CAM material: group C: hybrid nanoceramic (Cerasmart; GC Corp), group T: fiber-composite material (Trilor; Bioloren Srl), group E: lithium disilicate glass-ceramic (IPS e.max CAD; Ivoclar Vivadent AG), and group V: zirconia-reinforced lithium silicate glass-ceramic (Vita Suprinity; VITA Zahnfabrik GmbH). A digital scan was made with an intraoral digital scanner (TRIOS 3; 3Shape A/S), and endocrowns were milled with a 5-axis milling machine (Coritec 250i; imes-icore GmbH). The replica technique and a stereomicroscope (×70) were used to measure the marginal and internal adaptation of the endocrowns at 32 points. All data were statistically analyzed using 1-way ANOVA and the Tukey honestly significant difference test (α=.05). RESULTS: Statistical tests showed significant differences among the tested groups (P<.001). The resin-based groups displayed larger discrepancies than the ceramic-based groups. The resin-based groups showed a mean marginal gap larger than the mean internal gap C (P=.009), T (P<.001), whereas the ceramic-based groups showed similar gaps, V (P=.396), E (P=.936). The largest gap was observed at the pulpal floor (P<.001). CONCLUSIONS: All materials had clinically acceptable internal and marginal gaps (≤150 µm), except for the marginal gap of the Trilor group.

Retentive force variations of stud attachments for implant overdentures.

Implant overdentures are considered a standard treatment option by many practitioners, especially for edentulous mandibles. Stud attachments have been used extensively in the construction of these overdentures. In this study, the retentive forces of O-ring/ball and Locator overdenture attachments under various conditions in the mouth were investigated through pull-out tests. In dry testing, the retentive forces of the O-ring/ball attachment started higher than those of the Locator attachment but significantly decreased after 50 insertion-removal cycles (P = 0.014). The Locator attachment had no significant change in its retentive force over time (P = 0.328). In wet testing, a saliva substitute was applied to the stud attachments between cycles. The retentive force of the O-ring/ball attachment increased significantly in wet testing compared to dry testing (P < 0.0001). The retentive force of the Locator system during wet testing did not change significantly from that achieved during dry testing for the first 80 cycles, but then it increased to reach the same levels as the O-ring/ball system at 510 cycles (P < 0.05). Within the limitations of the present study, the results suggest that it is advisable to avoid using O-ring/ball attachments as anchors for implant overdentures in a dry mouth environment. In such cases, Locator attachment or metal-to-metal attachment components would be preferable as implant overdenture anchors. In a saliva-irrigated mouth, there is no significant difference between the retentive properties of the O-ring/ball and Locator attachments over 6-9 months' use.

Effect of Cyclic Dislodging on the Retention of Two Attachment Systems for Implant-supported Overdentures: An In Vitro Study.

PURPOSE: The aim of this study was to compare and evaluate the retention of two new attachment systems used for implant-supported overdentures subjected to insertion-removal cycles. MATERIALS AND METHODS: Twenty custom-manufactured polyvinyl chloride models mimicking implant-retained over-dentureresin blocks were fabricated and divided into two groups (n = 10): group 1 ('Kerator' attachment) and group 2 ('EMI' attachment). Each model received two parallel implants (JD evolution®) 20 mm apart and was subjected to cyclic retention forces of 10, 100, 1000, 5000, 10000 and 14600 cycles using a universal testing machine in a 0.9% sodium chloride water solution at 22° C. Data were analyzed using one-way analysis of variance; the level of significance was set at a < 0.05. RESULTS: The 'Kerator' and 'EMI' attachment systems reported a significant decrease in retention (64 and 56.6% respectively) after 14600 insertion-removal cycles (p < 0.001). The 'EMI' attachment showed significant higher loss of retention than the 'Kerator' attachment all along the 14600 cycles (p < 0.05) except for cycles 100 and 5000 (p > 0.05). CONCLUSION: Within the limitations of this in vitro study, both attachments reported satisfactory retentive values during the 14600 cycles, the 'Kerator' attachment showed better retention than the new 'EMI' attachment. The initial retentive force of both attachments has gradually decreased. CLINICAL SIGNIFICANCE: Both attachment systems evaluated in this study can be used in clinical practice for implant-supported overdentures.

Immediate, early (3 weeks) and conventional loading (4 months) of single implants: Preliminary data at 1 year after loading from a pragmatic multicenter randomised controlled trial.

PURPOSE: To compare the clinical outcome of single implants which underwent immediate nonocclusal loading with implants subjected to early non-occlusal loading at 3 weeks, and implants conventionally loaded at 4 months. MATERIALS AND METHODS: One hundred and five patients in five private practices requiring a single implant-supported crown were randomised to immediate loading (35 patients), early loading (35 patients) and conventional loading (35 patients) groups. To be immediately or early loaded, implants had to be inserted with a torque superior to 45 Ncm. Immediately and early loaded implants received non-occluding temporary crows, whereas conventionally loaded implants were directly restored with definitive crowns. Temporary crowns were replaced by definitive ones after 4 months. Outcome measures were crown and implant failures, complications and peri-implant marginal bone level changes recorded by a blinded assessor. RESULTS: Two patients dropped out from the immediate loading group up to 1-year post-loading. Two implants failed, one in the immediately loaded and one in the early loaded group (P=0.601). One immediately loaded implant and two early loaded implants were affected by one complication each (P=0.162). Mean peri-implant marginal bone loss after 1 year was -0.120±0.230 mm (95% CI -0.35, 0.10) for immediate, -0.390±0.840 mm (95% CI -1.23, 0.45) for early and -0.201±0.306 mm (95% CI -0.51; 0.11) for conventionally loaded implants. There were no statistically significant differences for any of the outcome measures between the three loading strategies up to 1-year post-loading. CONCLUSIONS: No major clinical differences were observed with regard to implant survival, complications and marginal bone level changes when loading single implants immediately, early or conventionally.