Midpalatal miniscrew insertion: The accuracy of digital planning and surgical placement.

INTRODUCTION: The objective of this study was to investigate the accuracy of palatal miniscrew insertion, evaluating the effect of guide fabrication and surgical placement. METHODS: Guided insertion of bilateral paramedian palatal miniscrews was undertaken using Appliance Designer software (3Shape, Copenhagen, Denmark). A resin surgical guide (P Pro Surgical Guide; Straumann AG, Basel, Switzerland) was used. Superimposition of the miniscrew position relative to the digital design was undertaken using bespoke software (Inspect 3D module, OnyxCeph; Image Instruments GmbH, Chemnitz, Germany) to assess surgical inaccuracy. Miniscrew position relative to the surgical guide was also assessed to isolate the effect of planning inaccuracies. Both horizontal and vertical discrepancies were evaluated at both implant locations. RESULTS: Twenty-seven patients having bilateral palatal insertions were examined. Mean discrepancies were <0.5 mm, both in the horizontal and vertical planes. The mean overall horizontal and vertical discrepancy between the digital design and final miniscrew position on the left side was 0.32 ± 0.15 mm and 0.34 ± 0.17 mm, respectively. The maximum horizontal discrepancy observed was 0.72 mm. No significant differences were observed in relation to the accuracy of mini-implant positioning on the basis of sidedness, either for horizontal (P = 0.29) or vertical (P = 0.86) discrepancy. CONCLUSIONS: High levels of accuracy associated with guided insertion of paramedian palatal implants were recorded with mean discrepancies of less than 0.5 mm both in the horizontal and vertical planes. No difference in accuracy was noted between the left and right sides. Very minor levels of inaccuracy associated both with surgical techniques and surgical guide fabrication were recorded.

Accuracy of trial complete dentures fabricated by using fused deposition modeling 3-dimensional printing: An in vitro study.

STATEMENT OF PROBLEM: Three-dimensional (3D) printing technologies commonly used for trial complete dentures use photopolymerizing resins. Although effective, some clinical, process-related, and practical issues associated with them are still unclear. The option of using alternative printing technologies may help in overcoming limitations. PURPOSE: The purpose of this in vitro study was to evaluate the trueness of trial dentures fabricated by using 3D-printing fused deposition modeling (FDM). MATERIAL AND METHODS: Ten maxillary and 10 mandibular digital complete trial dentures designed from intraoral scans were fabricated from polylactic acid by using a FDM 3D-printer. Each denture was scanned, and the scans were compared with the digital file of the designed denture by means of a surface-matching software program. The mean distance (both signed and absolute) was measured and recorded for the intaglio surface, as well as for the entire denture surface. Statistical analysis was performed to investigate the significance of the extent of measured distances, as well as differences between intaglio and global deviations; subgroup analysis for arch type was also performed (α=.05). RESULTS: Mean values of the intaglio distance were not significantly different from zero (P=.223). The manufacturing accuracy of the intaglio surface was higher than that measured for the entire denture (P<.001), confirmed both by the averaged signed (0 mm and -0.028 mm, respectively) and the absolute mean deviations (0.06 mm and 0.08 mm, respectively). No significant differences were found between maxillary and mandibular trial dentures. CONCLUSIONS: 3D-printing may constitute a valid and practical option for accurate and affordable digital trial dentures.

Assessment of tooth displacement during the cast-free digital processing of milled dentures.

STATEMENT OF PROBLEM: Denture tooth displacement may have a significant impact on denture occlusion. This aspect has seldom been investigated, especially for digital denture processing techniques. PURPOSE: The purpose of this clinical study was to evaluate the accuracy of tooth position with milled digital dentures processed without physical casts. MATERIAL AND METHODS: Ten maxillary and 10 mandibular dentures designed from intraoral scans, milled, and processed without physical casts were investigated. The standard tessellation language (STL) files of the digitally designed dentures were compared with the scan of the dentures after processing (milling the denture base, milling teeth in a complete arch, and then bonding teeth into the base). The STL files were superimposed by using a surface-matching software program. After a preliminary alignment, the STL meshes were trimmed and reoriented; then, the final alignment was carried out by using the cameo surface. Six reference points (the mesiobuccal cusp on the most distal molar, the canine cusp, the middle of the incisal edge of the central incisor on both the left and the right side) were selected to measure tooth displacements along the X-, Y-, and Z-axes, corresponding (from the preliminary reorientation) to anteroposterior, mediolateral, and occlusal displacement, respectively. Tooth position accuracy was assessed by using median and interquartile range values. Univariate and multivariate statistical analyses were used to investigate the significance of the extent of displacements, as well as differences among displacement directions, reference teeth, side, and denture arch type (α=.05). RESULTS: Only the median (0.2 mm; interquartile range: 0.27 mm) occlusal displacement was significantly different from zero. A generalized estimated equation model addressing occlusal displacement as a dependent variable showed no significant effect of tooth type, side, or denture arch type, either alone or in combination. CONCLUSIONS: The tooth position of both maxillary and mandibular milled digital dentures processed without physical casts was accurate in the anteroposterior and mediolateral directions. Occlusal displacement seemed to be within the range of clinical acceptability; its consistency throughout the arch allowed optimization or compensation at the design or manufacturing step.

Trueness of Intaglio Surface of Milled Digital Dentures Designed from Intraoral Scans.

PURPOSE: To asses trueness of the intaglio surface of milled dentures fabricated according to a fully digital protocol starting from intraoral scans in a clinical study by means of 3-dimensional (3D) digital analysis. MATERIALS AND METHODS: Ten maxillary and 10 mandibular dentures, designed from intraoral scans and milled in-house, were studied. Intraoral scans were compared with the scans of intaglio surface of milled dentures. To this end, they were aligned, trimmed and used in a metrology software to measure their mean 3D distance, absolute mean deviation, and other parameters. Measured differences for all parameters were statistically investigated. Subgroup analysis for the maxillary and mandibular dentures was performed using independent samples t-test or, in case of non-normal distribution, by means of Mann-Whitney test. RESULTS: Using a mean of 24.9 ±2.8 measurement points/mm2 , a mean 3D distance of 0.0006 ±0.007 mm between intraoral scans and the scans of the intaglio surface of milled dentures was measured. The corresponding absolute mean deviation was 0.055 ±0.032 for maxillary dentures and 0.061 ±0.016 for mandibular dentures; such a difference between arches was statistically significant (p = 0.035). CONCLUSIONS: Milled dentures fabricated using a fully digital protocol and intraoral scans have accurate intaglio surfaces. It is reasonable to assume that they may achieve an adequate fit.

Digital dentures: A protocol based on intraoral scans.

The use of intraoral scans for complete denture fabrication may improve patient comfort, clinic ergonomics, and laboratory efficiency. Techniques have been reported regarding specific tasks related to the use of intraoral scans for digital dentures, but an integrated workflow is still lacking. This technique article describes a complete workflow for the digital fabrication of complete dentures, starting from intraoral scans and with no physical casts; in addition, the presented workflow integrates partial and complete face scans in the design process to optimize tooth arrangement.

Intraoral Scans Alignment in Single Edentulous Arch Cases.

Using intraoral scans for removable denture fabrication requires proper alignment according to maxillo-mandibular relationships. The presented technique combines intraoral and extraoral scanning of the occlusion rim to obtain intraoral scan alignment and the transfer of all information for tooth arrangement to the digital workflow. The technique was developed for single edentulous arch cases and is particularly indicated for the edentulous mandible; nonetheless, it can also be used for the maxilla if a full-size occlusion rim is required for optimal stability.

A single procedure for the registration of maxillo-mandibular relationships and alignment of intraoral scans of edentulous maxillary and mandibular arches.

PURPOSE: The presented technique describes the intraoral scanning workflow to capture scans of edentulous arches and occlusion rims, align them as per maxillo-mandibular relationships registered in the occlusion rims, and incorporate data for tooth arrangement. METHODS: On preliminary intraoral scans of the edentulous arches, design the baseplates for the occlusion rims, make a 3D print of them and finalize by adding wax. Use occlusion rims to make jaw relation record and definitive intraoral scans. Use the "Pre-preparation scan" function to link scans of occlusion rims to scans of edentulous arches and align each other. CONCLUSIONS: Making and aligning, in a single procedure, intraoral scans of the edentulous arches and occlusion rims incorporating maxillo-mandibular relationships and information for tooth arrangement, allow to proceed directly with the denture design, thus, being sensible from the treatment time efficiency point of view. The technique is applicable to both partial and complete edentulous maxillary and mandibular arches. Nonetheless, care should be taken in stabilizing occlusion rims, whose shape is characterized by a reduction in size of the baseplates. In addition, its accuracy in comparison with the current clinical best practice based on conventional procedure requires to be addressed by further research.

Three-dimensional differences between intraoral scans and conventional impressions of edentulous jaws: A clinical study.

STATEMENT OF PROBLEM: Using intraoral scans for removable dentures has been questioned because of a suggested lack of accuracy. However, data regarding the accuracy of digital intraoral complete-arch scans are sparse, present some methodological issues, and mostly come from in vitro studies on dentate casts, which are very different from edentulous arches. PURPOSE: The purpose of this clinical study was to evaluate 3D differences between intraoral scans (IOS) and conventional impressions of edentulous arches by means of digital analysis. MATERIAL AND METHODS: Ten maxillary and 10 mandibular edentulous arches were investigated. For each of them, IOS was performed, and a custom tray was digitally designed based on these scans. Trays were built by using a 3D printer and used to make a conventional impression with a polysulfide impression material. The conventional impression was scanned immediately by using the same intraoral scanner and by the same dentist. Standard tessellation language (STL) files of IOS and the scans of the corresponding conventional impressions (CIS) were superimposed with a 2-phase best-fit alignment in a reverse engineering software program. The corresponding full-scan, 3D mean distance was measured. This procedure was repeated after trimming the IOS and CIS to eliminate peripheral areas not present in both files, as well as nonmatching areas caused by practical aspects related to obtaining the IOS (mobile tissue stretching) and the conventional impressions (mobile tissue compression and folding at the margin of impression), which could have impaired alignment and, consequently, measurement accuracy. The mean distance between the full and trimmed IOS and CIS was statistically investigated, and subgroup analysis was performed for the maxillary and mandibular arches. The statistical significance of the differences between the 2 impression methods was also investigated. RESULTS: The full-scan mean distance between the IOS and CIS (-0.19 ±0.18 mm) was significantly different from that of the trimmed scan mean distance (-0.02 ±0.05 mm), with no significant differences for maxillary and mandibular arches. The differences between the IOS and CIS were statistically significant for full scans; they were not significant for trimmed scans, except for the maxillary subgroup. CONCLUSIONS: The mean distance between the IOS and CIS may be significantly different if they are not properly superimposed. The mean distance (-0.02 ±0.05 mm) between the IOS and CIS falls within the range of mucosa resilience. Thus, 3D differences between the IOS and CIS can be attributed to the different physics behind the 2 impression methods and not to defects in accuracy of one method compared with the other. The size of the measured difference between the 2 impression methods was not statistically significant and was not clinically significant for removable denture fabrication.

Intraoral scans of edentulous arches for denture design in a single procedure.

Digital denture design requires anatomic information, an accurate maxillomandibular relationship, and parameters to guide tooth arrangement. Capturing all these data by intraoral scanning makes their immediate digitization, integration, and transfer to the computer-aided design workflow possible, which can be started without an additional procedure. The presented technique describes the digital workflow to automatically align intraoral scans of completely or partially edentulous maxillary and mandibular arches according to the maxillomandibular relationships registered in digitally designed occlusion rims adapted on the patient.

Integrating intraoral, perioral, and facial scans into the design of digital dentures.

Digital technologies offer the opportunity to integrate facial scans into the design of digital dentures and provide a beneficial 3D preview and simulation of the tooth arrangement for both treatment planning and communication. The presented technique describes a procedure of merging and aligning the intraoral scans of edentulous arches, the scans of the perioral area, and the scan of the nose made by using an intraoral scanner, as well as facial scans made by using a mobile phone. Thus, a digital patient can be obtained and used to optimize individual tooth arrangement during the design of the digital denture.

Alignment of intraoral scans and registration of maxillo-mandibular relationships for the edentulous maxillary arch.

One of the main issues in using intraoral scans for the fabrication of removable dentures is that scans need to be aligned to each other. The workflow presented provides aligned intraoral scans of the arches and of the occlusion rim incorporating maxillo-mandibular relationships and information for tooth arrangement in a single procedure. Thus, after intraoral scanning, the clinician can proceed directly with the denture design.

Effects of crown movement on periodontal biotype: a digital analysis.

Orthodontic treatment has important correlations with periodontal changes. Various mechanical and biological factors are involved in determining such changes, but anatomical and morphological variables, generally addressed as periodontal biotype, play a key role. In measurement of such modifications, digital and non-contact reverse engineering technologies may be of tremendous advantage. The aim of this study is to retrospectively evaluate, in a series of digitized dental casts, some of the parameters addressing periodontal biotype and correlate them to extent and direction of tooth movement. Pre- (T0) and post-treatment (T1) dental casts of 22 patients were scanned by 3Shape TRIOS 3® scanner. A number of variables (crown ratio, gingival margin position, gingival contour, papillae position, gingival scallop) were investigated and their variations calculated after digital measurements on single casts at T0 and T1, or after direct measurement (T1 vs T0) on the superimposition and alignment of digital models. Univariate and multivariate statistics were then performed. No significant correlation was detected between the sagittal or vertical movement of dental crown and displacement of the gingival margin. On the other hand, vestibular gingival contour resulted significantly altered by vestibular and extrusion movements. Further studies are needed to ascertain the differential effect of bone and soft tissue on such modifications. The relationship between orthodontic treatment and the periodontium overcomes the consideration of gingival recession and includes all the concepts of periodontal biotype with its characteristics. Digital technologies and non-contact reverse engineering techniques now available have the potential to allow a more precise definition of such a relationship.

Removable complete digital dentures: A workflow that integrates open technologies.

Digitalization of the design and manufacture of removable complete dentures has numerous advantages. The workflow as presented integrates current open digital technologies into a functional protocol, enabling complete dentures to be designed and fabricated without system-specific trays or instruments. This is done by using a conventional technique to acquire anatomic information.

Single-arch digital removable complete denture: A workflow that starts from the intraoral scan.

The production of removable dentures from intraoral scans has been problematic. In addition, the digital design and fabrication of a single-arch denture cannot be routinely managed. The workflow presented provides a proof of concept that an optical intraoral scan of the edentulous maxilla is feasible and that a functional single-arch maxillary denture can be designed and fabricated using a digital protocol.