Automated scoring and augmented reality visualization software program for evaluating tooth preparations.

STATEMENT OF PROBLEM: Tooth preparation is an essential part of prosthetic dentistry; however, traditional evaluation methods involve subjective visual inspection that is prone to examiner variability. PURPOSE: The purpose of this study was to investigate a newly developed automated scoring and augmented reality (ASAR) visualization software program for evaluating tooth preparations. MATERIAL AND METHODS: A total of 122 tooth models (61 anterior and 61 posterior teeth) prepared by dental students were evaluated by using visual assessments that were conducted by students and an expert, and auto assessment that was performed with an ASAR software program by using a 3-dimensional (3D) point-cloud comparison method. The software program offered comprehensive functions, including generating detailed reports for individual test models, producing a simultaneous summary score report for all tested models, creating 3D color-coded deviation maps, and forming augmented reality quick-response (AR-QR) codes for online data storage with AR visualization. The reliability and efficiency of the evaluation methods were measured by comparing tooth preparation assessment scores and evaluation time. The data underwent statistical analysis using the Kruskal-Wallis test, followed by Mann-Whitney U tests for pairwise comparisons adjusted with the Benjamini-Hochberg method (α=.05). RESULTS: Significant differences were found across the evaluation methods and tooth types in terms of preparation scores and evaluation time (P<.001). A significant difference was observed between the auto- and student self-assessment methods (P<.001) in scoring both the anterior and posterior tooth preparations. However, no significant difference was found between the auto- and expert-assessment methods for the anterior (P=.085) or posterior (P=.14) tooth preparation scores. Notably, the auto-assessment method required significantly shorter time than the expert- and self-assessment methods (P<.001) for both tooth types. Additionally, significant differences in evaluation time between the anterior and posterior tooth were observed in both self- and expert-assessment methods (P<.001), whereas the evaluation times for both the tooth types with the auto-assessment method were statistically similar (P=.32). CONCLUSIONS: ASAR-based evaluation is comparable with expert-assessment while exhibiting significantly higher time efficiency. Moreover, AR-QR codes enhance learning and training experiences by facilitating online data storage and AR visualization.

Effect of magnifying loupes on tooth preparation of complete coverage crown: A quantitative assessment using a digital approach.

OBJECTIVE: The purpose of this study was to evaluate the use of magnifying loupes (×2.5) on the quality of tooth preparation for complete coverage crowns; performed by predoctoral students using an objective and quantitative digital method. MATERIALS AND METHODS: Forty-two predoctoral students were randomly assigned into 2 groups to perform tooth preparation for a complete coverage crown on a mandibular first molar in a manikin, with and without the use of magnifying loupes. All preparations were digitally evaluated by PrepCheck 3.0 (Dentsply Sirona). Parameters including tooth reduction, total occlusal convergence (TOC), undercut, margin quality and surface quality were assessed. Continuous data were analysed using Paired t-tests or Wilcoxon Signed Ranks tests. Ordinal data were analysed by McNemer's tests. To further detect the majority pattern ( > 50%) in each group (with and without loupes), one-sample t-test or one-sample Wilcoxon Signed Rank test was performed. The level of significance was set at p = .001 after Bonferroni adjustments for multiple testing. RESULTS: No significant differences in the measured outcomes were found between the groups with or without the use of magnifying loupes (p > .002). The majority (>50%) of both groups had no undercuts (99.3% and 99.4% both p < .001) and the preparation type was within tolerance (81.6% and 85.3%, both p < .001) with acceptable margin (86.4% and 86.3%, both p < .001) and acceptable surface quality (99.0% and 99.1%, both p < .001). However, the majority of both groups underprepared occlusally (96.0% and 95.4%, both p < .001) and axially (65.3% and 67%, both p < .001). Only 30.0%-42.1% of the participants achieved the TOC within 0-20°. CONCLUSIONS: Within the limitations of this study, the use of magnification loupes does not appear to significantly improve the quality of tooth preparation for complete coverage crown. The TOC was also found to be overprepared and occlusally underprepared.

[Non-retentive adhesive restorations]. / Niet-retentieve adhesieve restauraties.

With the advent of adhesive dentistry, tooth preparation can be minimally invasive. An optimal adhesion to the dental tissues is a requirement. Rubberdam isolation, using a gold standard adhesive and bonding to freshly prepared dentin are all factors that improve the adhesion to tooth tissue. For non-retentive restorations, indirect composite and glass-ceramic materials are suitable. To date, several studies have shown a high survival rate of indirect adhesive restorations. The adage "if you can isolate the tooth, you can preserve it" may guide the choice of starting an adhesive procedure.

Replacement of maxillary incisor crowns over discolored substrates in a single visit with a CAD-CAM system and lithium silicate ceramic.

Discolored substrates constitute a challenge to the esthetics of the definitive restoration. Because of technique sensitivity, the generally prolonged treatment time is a drawback to both the patient and the dentist. The technique described presents the replacement of ceramic maxillary incisors crowns over discolored substrates in a single visit by using a milling machine. Translucent blocks of a lithium silicate ceramic reinforced with zirconium dioxide particles were used. Intraoral scans of the trial restorations and of the tooth preparations were performed. The crown parameters were defined in the software. Ceramic blocks were milled in the presintered phase and characterized. The crowns were cemented at the end of the appointment with excellent esthetics.

Marginal Fit of Metal-Ceramic Copings: Effect of Luting Cements and Tooth Preparation Design.

PURPOSE: To evaluate the effect of the triad finish line design, axial wall convergence angle, and luting cement on the marginal fit of metal copings used in metal-ceramic crowns. MATERIALS AND METHODS: Schematic dies and their respective copings were cast in NiCr alloy. The dies exhibited the following finish line/convergence angle combinations: sloping shoulder/6°, sloping shoulder/20°, shoulder/6°, shoulder/20°. Marginal fit was evaluated under a stereomicroscope, before and after cementation. Copings were air-abraded with 50 µm Al2 O3 particles and cemented with Cimento de Zinco, RelyX U100, or Panavia F cements (n = 10/group). Data were square-root transformed and analyzed by 3-way factorial random effect model and Tukey's post hoc test (α = 0.05). RESULTS: Statistical analysis showed significance for the interactions finish line and convergence angle (p < 0.05), convergence angle and time (p < 0.001), and luting cement and time (p < 0.001). Sloping shoulder/20° provided the highest marginal discrepancy when compared to the other finish line/convergence angle combinations, which were statistically similar among each other. For both convergence angles and for all luting cements, the marginal discrepancy was significantly higher after cementation. Before and after cementation, 6° provided better marginal fit than 20°. After cementation, Panavia F provided higher marginal discrepancy than Cimento de Zinco. CONCLUSION: Lower convergence angle combined with shoulder and a low-consistency luting cement is preferable to cement metal copings.

The influence of restorative material and glass fiber posts on fracture strength of endodontically treated premolars after extensive structure loss.

OBJECTIVE: The aim of this in vitro study was to investigate the fracture strength and cuspal deflection of endodontically treated premolars restored using different composite resins along with or without fiber post application. MATERIALS AND METHOD: Eighty intact premolars were randomly divided into eight groups (n = 10); CO group: intact teeth (control), OPR group: mesio-occlusal-distal-palatal (MODP) preparation (OPR) + endodontic treatment (ET), TC group: MODP preparation + ET + Tetric N-Ceram, TB group: MODP preparation + ET + Tetric EvoCeram Bulk Fill, SO group: MODP preparation + ET + SonicFill 2, TC-P group: MODP preparation + ET + Hahnenkratt glass fiber post + Tetric N-Ceram, TB-P group: MODP preparation + ET + Hahnenkratt glass fiber + Tetric EvoCeram Bulk Fill, and SO-P Group: MODP preparation + ET + Hahnenkratt glass fiber post + SonicFill 2. After thermocycling, specimens were subjected to a compressive load until fracture. Data were analyzed using analysis of variance and Tukey tests (P < 0.05). RESULTS: The mean fracture strength of groups which received post treatment showed similar fracture strength values [TC-P (931.6 ± 97.9), TB-P (882.0 ± 59.7), SO-P (862.0 ± 143.0) (P > 0.05)] and was significantly higher than OPR (530.6 ± 41.7), TC (841.2 ± 93.1), TB (774.5 ± 101.8), and SO (735.0 ± 178.01) groups (P < 0.05). No significant difference was detected among groups considering cuspal deflection (P > 0.05). The fiber post insertion resulted in more unfavorable fractures. CONCLUSION: Endodontically treated teeth restored with fiber post and bulk-fill or conventional composite resins demonstrated fracture strength values similar to intact teeth.

FDPS finish line design and tooth preparation technique.

The purpose of this research is to perform and verify the “modified 50° preparation” suggested by the authors. This procedure was performed with a scrupulous standardization of the tooth’s preparation and then of the laboratory techniques to produce a metal-ceramic crown, and the same for the crown cementation technique of on the preparation of the original sample. After the esthetic evaluations, the obtained sample was included in EPON resin and sectioned in the lingual-vestibular sense. The sections were then observed with an optical microscope in different magnifications for the final evaluations. The geometric design proposed presents the advantages of two great preparation techniques: 50° preparation and circumferential shoulder. The 50° bevel designed in first phase of preparation and the second phase of the circumferential 27° shoulder, together allowed to satisfy the following requirements: aesthetic, marginal accuracy, periodontal compliance, conservation and stability. However, this type of prosthetic preparation is not the only one, but it is one of the marginal designs in prosthetic dentistry.

Fracture Strength of Endodontically Treated Teeth Restored with Composite Overlays with and without Glass-fiber Reinforcement.

PURPOSE: To evaluate the fracture strength and the failure mode of endodontically treated teeth restored with composite resin overlays with and without glass-fiber reinforcement. MATERIALS AND METHODS: A total of 32 extracted molars were divided into four equal groups. In the NFR-NFRC (no foundation restoration, no fiber-reinforced composite) and NFR-FRC (no foundation restoration, fiber-reinforced composite) groups, only a 5-mm-thick composite resin layer sealed the pulp chamber floors, whereas in the FR-NFRC (foundation restoration, no fiber-reinforced composite) and FR-FRC (foundation restoration, fiber-reinforced composite) groups, a 3.0-mm foundation restoration was used. NFR-NFRC and FR-NFRC groups were restored with composite resin overlays, whereas NFR-FRC and FR-FRC groups were restored with fiber-reinforced composite resin overlays. All specimens were subjected to mechanical loading in a computer-controlled masticator and then the fracture resistance was evaluated. Differences in means were compared using two-way ANOVA and Tukey's test. The level of significance was set at ɑ = 0.05. RESULTS: All specimens successfully completed the fatigue test. The least fracture-resistant group was NFR-FRC, exceeded by FR-NFRC, NFR-NFRC, and FR-FRC, in that order, with FR-FRC being the most fracture-resistant group. Statistically significant differences were detected between the pairs NFR-NFRC/FR-FRC (p = 0.001), NFR-FRC/FR-FRC (p = 0.001), and FR-NFRC/FR-FRC (p = 0.001). Eight vertical root fractures occurred in group FR-NFRC, six in group NFR-NFRC, four in group NFR-FRC, and none occurred in group FR-FRC. CONCLUSIONS: Within the limitations of this in vitro study, the incorporation of glass fibers and the presence of a foundation restoration were found to increase the fracture resistance and can favorably influence the fracture mode.

Frequency of undercuts and favorable path of insertion in abutments prepared for fixed dental prostheses by preclinical dental students.

STATEMENT OF PROBLEM: Existing publications are lacking regarding guidelines to measure the path of insertion (POI) or placement of multiple abutments for fixed prostheses in terms of angle evaluation other than by the visual judgment of the operator. PURPOSE: The purpose of this preclinical study was to evaluate the incidence of undercuts and favorable path of insertion for prepared typodont abutments for 3-unit fixed dental prostheses by comparing different angles within and between both abutments of 3-dimensional (3D) scanned and digitized preparations and measured with computer-aided design (CAD) software. MATERIAL AND METHODS: Sixty-six maxillary first premolar and maxillary first molar prepared typodont abutments were 3D-scanned and digitized using the Prep-Assist optical 3D scanner and exported as stereolithography (STL) files. These files were imported into CAD software, and 18 different angles were measured within and between the 2 abutments to determine the incidence of undercuts and the frequency of obtaining a favorable path of insertion. RESULTS: Twenty-seven (40.9%) preparations had no clearly visible undercut when viewed virtually. Moreover, a minimum of 12 (44.4%) to a maximum of 26 (96.3%) of the 27 preparations had a favorable POI. CONCLUSIONS: Fewer than half of the fixed dental prosthesis preparations did not have a clearly visible undercut when viewed virtually. A favorable POI was found in 44.4% to 96.3% of the preparations. Favorable POIs were found to occur more frequently in the faciopalatal dimension than in the mesiodistal dimension.

Practice of Sealants and Preventive Resin Restorations Among Malaysian Dentists.

PURPOSE: To assess the knowledge, attitude and utilisation regarding fissure sealants (FS) and preventive resin restorations (PRR) among Malaysian dentists. MATERIALS AND METHODS: A questionnaire consisting of 35 questions was distributed by mail or an online survey to 425 registered dentists selected according to place of work by stratified random sampling. RESULTS: One hundred fifty-three dentists responded to the survey. A positive attitude towards FS and PRR was noted among most Malaysian dentists. About half of the respondents used FS/PRR occasionally (48.4%), while few (13.7%) applied them routinely. The majority of the dentists agreed that minimally invasive dentistry is important and FS are effective in caries prevention, using them on high caries-risk individuals. Most of the dentists used pumice or paste to clean teeth before placing FS/PRR. A significant number of dentists used a bonding agent prior to placing FS. Although only 57.5% dentists were aware of guidelines for FS use, most dentists agreed that guidelines are important. CONCLUSION: Although there was a positive attitude towards FS/PRR, few dentists applied them routinely. Some of the steps undertaken for placement of FS and PRR were outdated. Updating local guidelines for dentists to ensure uniform practice of FS and PRR is justified.

Indications for Cuspal Coverage.

Cuspal-coverage restorations are important to preserve the integrity of a weakened tooth against the forces of occlusion. This article discusses the clinical indications for both direct and indirect cuspal-coverage restorations and the evidence supporting their use. Factors that modify a tooth's ability to dissipate normal occlusal forces and the effect cuspal-coverage restorations have on force distribution are examined. Clinical criteria, choice of restorative material and methods for tooth preparation are also discussed. CPD/Clinical Relevance: Re-enforcement of weakened teeth with cuspal-coverage restorations provides a minimally invasive alternative to conventional crowns.

[Comparative analysis of 3D data visibility of the prepared tooth finishing line on a synthetic jaw model, captured by international scanners in a laboratory conditions]. / Sravnitel'noe laboratornoe issledovanie rezul'tatov otobrazheniya granitsy preparirovaniya kul'ti zuba, poluchennykh s pomoshch'yu intraoral'nykh skanerov.

The aim of the study was to compare accuracy of digital impression's finishing line and the zone under it taken by different intraoral scanning systems. Parameters of comparison were: different level of the finishing line to the gingiva and width of sulcus after retraction. For this purpose two synthetic jaw models with prepared teeth were scanned using intraoral scanning systems: 3D Progress (MHT S.P.A., IT - MHT Optic Research AG, CH); True Definition (3M ESPE, USA); Trios (3Shape A/S, DNK); CEREC AC Bluecam, CEREC Omnicam (Sirona Dental System GmbH, DE); Planscan (Planmeca, FIN) (each n=10). Reference-scanning was done by ATOS Core (GOM mbH, DE). The resulting digital impressions were superimposed with the master-scan. The lowest measured deviations (trueness) for intraoral scanners, where the finishing line was 0.5 mm above gingiva were with scanner True Definition - 18.8±6.63 (on the finishing line) and 51.0±14.33 µm (0.3 mm under the finishing line). In conditions where finishing line was on the same level with gingiva, scanner Trios showed the best results: 17.0±3.96 and 52.7±6.52 µm. When the finishing line was 0.5 mm under gingiva, none of the testing scanners could visualize the zone 0.3 mm lower the finishing line. The best results for accuracy o the finishing line in that circumstances showed Trios: 15.1±5.05 µm. The optimum visualization of the finishing line and the zone under it was reached when the sulcus was 0.3 mm after retraction. Thus, the best accuracy was obtained with Trios: 10.3±2.69 (on the finishing line) and 57.2±13.58 µm (0.3 mm under finishing line). The results show that intraoral scanners also provide enough accuracy for indicating finishing line and the zone under it in different conditions of preparation and gingiva retraction. However, not all of the testing scanners can properly indicate finishing line and the zone under it when shoulder is below gingiva and the width of sulcus is less than 0.2 mm.

Porcelain laminate veneer conditioning for orthodontic bonding: SEM-EDX analysis.

The purpose of this in vitro study was to evaluate and compare the effects of different surface treatments and laser irradiation on the bond strength of brackets bonded to porcelain laminate veneer. Porcelain laminate veneer specimens were embedded in the centers of acrylic resin blocks. Thirty-nine teeth were used for shear bond strength testing and the remaining three (one tooth for each group) were used for evaluation of the debonded bracket interface. Specimens were randomly divided into three groups, each containing 13 specimens. The details of the groups are as follows: Group SB, sandblasting with alumina particles (50 µm); Group HFA, 9.6 % hydrofluoric acid etching; Group ER, erbium-doped yttrium-aluminum-garnet (Er: YAG) irradiation (from 1 mm distance, 2 W, 10 Hz for 10 s). After conditioning, the upper central brackets were bonded to the porcelain surfaces. Porcelain laminate veneers were examined under stereomicroscope for adhesive remnant index and surface damage after debonding. The highest shear bond strength values were obtained with Group HFA (10.8 ± 3.8 MPa) and Group ER (9.3 ± 1.5 MPa), whereas Group SB revealed the lowest values. Scanning electron microscopy energy-dispersive X-ray (SEM-EDX) analysis revealed that the silicon level in the porcelain decreased after debonding in all groups. The sandblasting method did not demonstrate any ideal bond strength values; however, the 9.6 % hydrofluoric acid etching and Er: YAG laser did. There were no significant differences among all groups in terms of laminate surface damages. The Er: YAG laser therefore can be selected for ideal bond strength and minimal damage to porcelain laminates.

Three-dimensional evaluation of the repeatability of scanned conventional impressions of prepared teeth generated with white- and blue-light scanners.

STATEMENT OF PROBLEM: Digital scanning is increasingly used in prosthodontics. Three-dimensional (3D) evaluations that compare the repeatability of the blue-light scanner with that of the white-light scanner are required. PURPOSE: The purpose of this in vitro study was to evaluate the repeatability of conventional impressions of abutment teeth digitized with white- and blue-light scanners and compare the findings for different types of abutment teeth. MATERIAL AND METHODS: Impressions of the canine, premolar, and molar abutment teeth were made and repeatedly scanned with each scanner type to obtain 5 sets of 3D data for each tooth. Point clouds were compared, and error sizes per tooth and scanner type were measured (n=10). One-way ANOVA with Tukey honest significant differences multiple comparison and independent t tests were performed to evaluate repeatability (α=.05). RESULTS: Repeatability (mean ±SD) of the white- and blue-light scanners for canine, premolar, and molar teeth was statistically significant (means: P=.001, P<.001, P<.001; ±SD: P<.001, P<.001, P=.003). Means of discrepancies with the white-light scanner (P<.001) were 5.8 µm for the canine, 5.9 µm for the premolar, and 8.6 µm for the molar teeth and 4.4 µm, 2.9 µm, and 3.2 µm, respectively, with the blue-light scanner (P<.001). Corresponding SDs of discrepancies with the white-light scanner (P<.001) were 15.9 µm for the canine, 23.2 µm for the premolar, and 14.6 µm for the molar teeth and 9.8 µm, 10.6 µm, and 11.2 µm, respectively, with the blue-light scanner (P=.73). CONCLUSIONS: On evaluation of the digitized abutment tooth impressions, the blue-light scanner exhibited greater repeatability than the white-light scanner.

Esthetic anterior composite resin restorations using a single shade: Step-by-step technique.

Children and young adults often present to a dental practice after accidents that affect their anterior teeth. In many situations, only 1 tooth is affected by the trauma, and choosing the right treatment option can be complex. Esthetic restoration of the maxillary anterior dentition can be accomplished by using direct or indirect techniques. Direct resin composite restoration can be characterized as a life-like definitive restoration and is a predictable, conservative, and reliable chairside procedure. This article describes a straightforward protocol used to restore a patient's appearance with a single-shade composite resin after a Class IV fracture received during a sporting event.

Effects of the preparation technique and type of material on the penetrability of sealants.

The purpose of this in vitro study was to compare the penetration of 2 resin-based and 2 glass ionomer sealants into fissures after either conventional or mechanical preparation. All the materials placed in the conventionally prepared and mechanically prepared fissures penetrated the fissures beyond the standard (0.5-mm) reference line used in this study. For 1 glass ionomer sealant, the number of specimens showing complete penetration of sealant was significantly greater (P < 0.05) in mechanically prepared fissures than in conventionally prepared ones. No significant differences were found between mechanically and conventionally prepared fissures for the other sealants.

The use of the operating microscope in general dental practice. Part 2: If you can see it, you can treat it!

The use of magnification by dental clinicians when carrying out examinations and treatments is becoming more commonplace. The best instrument for this purpose is the operating microscope which has been shown to enhance quality, longevity and outcome of clinical work as well as facilitating better ergonomics for both the dentist and dental nurse. This paper, the second of two, explores the potential uses for the operating microscope in general dental as well as specialist practice (such as endodontics) and discusses how the interested clinician can use such equipment in a practical manner. Clinical Relevance: The operating microscope enhances the dental surgeon's vision so improving treatment outcomes not only in specialist fields, such as endodontics, but also in many of the disciplines which general dental practice encompasses.

The application of indirect composite onlays in the restoration of severely broken down posterior teeth.

Increasing interest has developed among dentists regarding alternatives to traditional full-coverage crowns for the restoration of extensively broken-down teeth that are both aesthetic and less destructive of remaining tooth structure. Indirectly fabricated resin composite onlays may offer a viable and cost-effective treatment option in such cases. This paper describes the clinical rationale for resin-based onlays, and includes a case report illustrating the author's experience with the technique to date.

An automatic robotic system for three-dimensional tooth crown preparation using a picosecond laser.

BACKGROUND: Laser techniques have been introduced into dentistry to overcome the drawbacks of traditional treatment methods. The existing methods in dental clinical operations for tooth crown preparation have several drawbacks which affect the long-term success of the dental treatment. OBJECTIVE: To develop an improved robotic system to manipulate the laser beam to achieve safe and accurate three-dimensional (3D) tooth ablation, and thus to realize automatic tooth crown preparation in clinical operations. METHOD: We present an automatic laser ablation system for tooth crown preparation in dental restorative operations. The system, combining robotics and laser technology, is developed to control the laser focus in three-dimensional motion aiming for high speed and accuracy crown preparation. The system consists of an end-effector, a real-time monitor and a tooth fixture. A layer-by-layer ablation method is developed to control the laser focus during the crown preparation. Experiments are carried out with picosecond laser on wax resin and teeth. RESULTS: The accuracy of the system is satisfying, achieving the average linear errors of 0.06 mm for wax resin and 0.05 mm for dentin. The angle errors are 4.33° for wax resin and 0.5° for dentin. The depth errors for wax resin and dentin are both within 0.1 mm. The ablation time is 1.5 hours for wax resin and 3.5 hours for dentin. CONCLUSIONS: The ablation experimental results show that the movement range and the resolution of the robotic system can meet the requirements of typical dental operations for tooth crown preparation. Also, the errors of tooth shape and preparation angle are able to satisfy the requirements of clinical crown preparation. Although the experimental results illustrate the potential of using picosecond lasers for 3D tooth crown preparation, many research issues still need to be studied before the system can be applied to clinical operations.

[Experimental rationale of hand stabilization devices use by teeth preparation].

This paper compares two methods of teeth preparation - with or without mechanical hand stabilization device preventing accidental angular deviations of dental handpiece during preparation. The results of two experiment series showed decreased convergence of side walls of the prepared teeth in cases when mechanical hand stabilizer corresponding to the values recommended in literature. It is concluded that mechanical hand stabilization device is a useful tool for improving the quality of preparations.