The impact of magnification on undergraduate dental students' performance during cavity preparations: A systematic review.

PURPOSE/OBJECTIVES: Loupe magnification is a commonly utilized tool within dental education due to its proposed benefits of improving working posture, visual acuity, and procedural quality. Although procedural quality has been researched at the graduate level, literature encompassing the undergraduate level remains scarce. Therefore, this systematic review aims to critically assess the available literature to ascertain the effects of loupe magnification on the performance of undergraduate dental students' cavity preparations. MATERIALS AND METHODS: A systematic search was conducted across electronic databases, including PubMed, MEDLINE via Ovid, The Cochrane Library for Cochrane Reviews, and Scopus, to identify relevant studies published from inception to February 15, 2023. We included English language studies that evaluated the effect of loupe magnification on the performance of undergraduate dental students in cavity preparations. RESULTS: In total, six studies fulfilled the inclusion criteria. The outcomes assessed encompassed tooth preparation accuracy. Of these six articles, one was conducted on endodontic access cavity preparations, four on restorative cavity preparations, and one on nonstandard cavity preparation designs performed on acrylic blocs. Four articles determined that loupes positively impacted undergraduate students' performance in cavity preparations, while two articles established no significant difference in performance between loupes and naked-eye cavity preparations. CONCLUSION: This systematic review suggests that loupe magnification positively impacts undergraduate dental students' performance in cavity preparations. However, the heterogeneity of the studies and the variations in methodologies limit the ability to draw definitive conclusions.

A Light Microscopic Study Comparing Pulp Histological Alterations Following Tooth Preparation Using a High-speed Handpiece and an Er: YAG Laser.

Introduction: Histological alterations were evaluated in this study after tooth preparation with carbide burs using a traditional handpiece and Er: YAG laser. Methods: Tooth preparation was done on 30 intact maxillary first premolars of healthy patients. Ten maxillary first premolars were used as control, wherein no tooth preparation was done. Box-shaped tooth preparation was done on the occlusal surface of maxillary first premolars using carbide bur in the handpiece and Er: YAG laser (n = 10). After performing the recommended procedure for different groups, each tooth was extracted and 4-5 µm thick sections were prepared and stained using H and E stains. A 4-40× microscope was used to examine the morphological alterations in the odontoblasts. The Chi-square test was used to compare the outcomes. Results: The high-speed drill group and the control group had statistically significant differences (P = 0.05). High-speed drill and laser group differences were not statistically significant (P > 0.05). Conclusion: The histological findings as seen with laser tooth preparation were nearly identical to those of control or nonmanipulated teeth under light microscope, whereas disruption of odontoblastic layer was seen with high-speed drills.

Clinical application principles and new developments of zirconia crown.

Zirconia crown has been widely used in the field of prosthodontics. Traditional zirconia exhibits excellent mechanical properties but lacks translucency. The introduction of transparent zirconia significantly enhances its aesthetic performance. In clinical applications, factors affecting the aesthetic results of full zirconia crown should be comprehensively considered, and the most suitable restoration should be chosen. Additionally, clinicians need to design appropriate tooth preparation dimensions and methods based on an individual patient's actual situation. During the clinical bonding process of zirconia, proper surface treatment of the tooth and restoration is essential. The selection of suitable adhesives is crucial for achieving optimal bonding strength and aesthetics.

Evaluating the effectiveness of a novel digital evaluation technology on dental preclinical crown preparation training.

OBJECTIVES: To evaluate the assessment scores of a novel digital training program versus traditional training in dental preclinical crown preparation. METHODS: Crown preparations in two consecutive preclinical training sessions were retrospectively collected and assigned to three groups: traditional group (TG), scanning group (SG), and digital evaluation group (DG). Students in the TG (n = 20) were taught by conventional visual grading, while students in the SG (n = 25) received three-dimensional feedback from digitally scanned preparations. All the SG students continued with supplementary digital evaluation and preparations were allocated into the DG (n = 25). Comparison of total scores between groups was investigated using independent samples t-test and paired samples t-test. Mann‒Whitney U-test and Wilcoxon signed-rank test were used to statistically analyze the differences in subdividing categories. The level of significance was p < 0.05. Questionnaires on the digital evaluation procedure were answered by students in DG. RESULTS: The results showed a significant improvement (p < 0.01) in the total scores of DG than those of TG and SG, while there were no statistically significant differences between TG and SG. Scores of surface finish and undercut improved significantly in DG compared to TG and SG. The reduction scores of DG were significantly higher than those of SG. Students' feedback indicated a positive perspective on the implementation of the novel digital evaluation technology. CONCLUSIONS: These findings suggest that digital evaluation technology is useful for preclinical crown preparation training. Attention should also be paid to studying the optimal integration of digital dentistry into traditional dental curricula and its effects on students' learning curves.

Biological shaping as a conservative alternative for crown lengthening: A review.

OBJECTIVES: The perio-restorative approach to maintaining supracrestal tissue attachment (STA; formerly known as biologic width) is a fundamental goal in modern dentistry. This article aims to review the clinical impact of biologic shaping (BS) as an innovative alternative to traditional crown lengthening procedures, reflecting over two decades of clinical experience. MATERIAL AND METHODS: As a review paper, it is crucial to highlight that BS stands as a unique approach designed to optimize STA while emphasizing minimal to no removal of supporting bone. The review spans over two decades, consistently demonstrating clinical efficacy and predictability. Remarkably, BS focuses on addressing issues such as root concavities, developmental grooves, irregularities, furcation lips, and CEJ offering a remarkable level of clinical precision. RESULTS: The reviewed literature underscores that BS has consistently achieved substantial clinical success in fulfilling its objectives. This method presents a biologically sound alternative to traditional crown lengthening, placing a strong emphasis on the preservation of essential bone tissue and the establishment of durable STA. CONCLUSIONS: The results suggest that BS is a logical and biologically driven approach for maintaining STA, making it a promising alternative to traditional crown lengthening. The method offers a predictable and reproducible way to preserve bone tissue while achieving durable STA. This innovation holds great promise in the field of periodontal and restorative dentistry.

Trueness and precision of an intraoral scanner on abutments with subgingival vertical margins: An in vitro study.

OBJECTIVES: This study aimed to evaluate the accuracy of an intraoral scanner (IOS - Medit i700) on tooth abutments with vertical preparations at 2 depths below the free gingival margin, and to determine if the IOS can reproduce the area beyond the finish surface of the tested preparation geometry. METHODS: Two abutments for a maxillary first molar were designed by means of CAD software, with vertical preparations set at 1 and 2 mm below the gingiva. These abutments were subsequently printed in resin and placed on a reference model. The reference files consisted of scans made using a metrological machine on these abutments. Ten scans were made with the tested IOS on each sample, resulting in two study groups. The scans from the experimental groups were labeled "V-1″ for vertical preparation at 1 mm below the gingival margin and "V-2″ for 2 mm below. The analysis of these scans was performed using Geomagic Control X (3D SYSTEMS) to assess their trueness and precision in µm. Descriptive statistics with a 95 % confidence interval were employed, alongside independent sample tests, to ascertain any differences between the groups (α=0.05). RESULTS: Statistically significant differences were not found both for trueness (p=.104) and precision (p=.409), between the tested geometries. The mean values for trueness were V-1 = 37.5[31.4-43.6]; V-2 = 32.6[30.6-34.6]. About the precision, the mean values were V-1 = 20.5[8.4-32.5]; V-2 = 18.4[8.2-28.5]. In both the study groups, it was possible to detect the surface beyond the finish area. CONCLUSIONS: Within the limitations of this study, vertical preparation design allows for registration of the tooth anatomy beyond the finish area with IOS. Moreover, the mean accuracy values were clinically acceptable at both 1 and 2 mm below the gingival margin.

Removable Partial Denture - Functional Impression Techniques: Review.

The objective of this article is to concisely review the main clinical techniques used to make the functional impression to manufacture a removable partial denture. Through this review, the dentist can develop his clinical knowledge.

An in vitro comparison of the marginal fit of provisional crowns using the virtual tooth preparation workflow against the traditional technique.

Aim: This study investigates the effectiveness of an innovative virtual tooth preparation workflow for the fabrication of dental crowns using cone-beam computed tomography (CBCT) and intraoral scanners (IOSs) with conventional workflow using extraoral/laboratory scanners. Settings and Design: This in vitro experimental study was conducted in the laboratory of a university in Chennai, India. The dental laboratory and research facilities at the institution were utilized for the fabrication of the temporary crowns and the data acquisition process. Materials and Methods: Institutional approval was obtained from the university. It was basically a comparison between the virtual prep technique using CBCT and IOS and the conventional digital technique using extra oral scanners (EOS) for temporary crown fabrication. The sample size was estimated using an effect size of 1.5004, assuming a normal distribution, a significance level of 0.05, and a power of 0.95 in G power software. Based on this calculation, an extracted second lower molar was used to fabricate 10 samples in each group. The samples were divided into three groups: the CBCT (Group 1), the IOS (Group 2), and laboratory scanner (Group 3 as control) groups. The vertical marginal gap of all the surfaces of the crown was evaluated using a scanning electron microscope. Statistical Analysis Used: Data were analyzed using one-way ANOVA using the SPSS software version 26.0, IBM, Armonk, NY, USA. Results: Acceptable marginal discrepancy values were obtained in all three groups. There was no significant difference in the marginal discrepancy recorded (P = 0.113). Conclusion: Virtual tooth preparation using CBCT and IOSs can be used as an alternative to the conventional workflow for provisional crown and bridge fabrication.

Freehand vs. depth-gauge rotary instruments for veneer preparation: A controlled randomized simulator study.

PURPOSE: To investigate whether depth-gauge burs in veneer preparations influence preparation depth in a randomized, controlled, single-blinded trial and whether inexperienced operators can perform adequate veneer preparations. METHODS: Participants were 20 undergraduate dental students with no prior veneer preparation experience. The instruments used were the "Laminate Veneer System" (LVS), "Keramik-Veneers. de" (KVD), and a "Freehand" group (FH) for reference. All participants prepared three educational acrylic resin maxillae and three mandibular central incisors mounted in typodonts in patient simulators. The objectives were to achieve a preparation depth of 0.6 mm (tooth 11) and 0.4 mm (tooth 31). The sequences of the instruments used and prepared teeth were randomized. The measurements were performed using a laser triangulation coordinate-measuring machine. The data were stratified according to tooth location. RESULTS: The preparation depths of both depth-gauge-instrument-groups LVS and KVD achieved the objectives significantly better than did the instruments from the "Freehand" group (P < 0.001). The differences between the depth gauge groups were insignificant, although the maximum preparation depths were smaller in the KVD group. Regarding the prepared teeth, the preparation depths in the mandibular incisors were lower, and the differences were smaller. CONCLUSIONS: The use of special depth-gauge burs for initial veneer preparation leads to significantly lower preparation depths than "Freehand" preparations. The tapered instruments resulted in a lower incidence of extreme preparation depths. The inexperienced operators performed veneer preparation remarkably well.

Evaluation of the Pulp Chamber Temperature during Tooth Veneer Preparation Using Burs with Different Degrees of Wear-A Preliminary In Vitro Study.

The heat produced during tooth preparation could be a source of damage for dental pulp, and many variables are involved in this process. The aim of this in vitro study was to evaluate whether the different degrees of wear of the diamond burs significantly influenced the temperature changes in the pulp chamber during tangential veneer preparation. The sample comprised 30 intact permanent monoradicular teeth, randomly assigned to three study groups of 10 teeth each, of which 5 had the pulp tissue preserved and 5 had thermoconductive paste in the pulp chamber. For prosthetic preparation, we used new burs in the first group, burs at their fifth use in the second group, and burs at their eighth use for the third group. The pulp chamber temperature was evaluated at the start, after one minute, and after three minutes of preparation, using a k-type thermocouple. The results of the three-way ANOVA and Tukey post hoc comparisons showed a highly significant effect of the time of measurement, while the pulp condition and the degree of wear of the burs had no effect. In conclusion, the different degrees of wear of conventional diamond burs do not produce statistically significant different changes in the pulp chamber temperature.

Simultaneous implantation and tooth preparation technology guided by 3D-printed guide.

Using digital technologies in concurrently performing missing tooth implantation and preparation of remaining teeth is a solution to reduce the number of visits and improve efficiency. This paper proposes a digital process for simultaneously implanting and preparing teeth. It integrates implant surgical guide and 3D-printed tooth preparation guide into a single guide and completes guided implant placement and precise tooth preparation. Based on "repair-oriented" virtual implant planning, the implant surgical guide can improve the efficiency and predictability of implant placement, and its linear accuracy is about 1 mm. The tooth preparation guide precisely guides tooth preparation and restoration space visualization, ensuring the quality of the tooth preparation. The two guides have different design accuracy requirements, and thus their combination improves the overall guiding accuracy requirements. The concurrent application of the two guides minimizes the clinical operation time, number of visits, and economic burden of patients.

Contemporary concepts on periodontal complications from prosthetic and restorative therapies.

The clinical outcome of every prosthetic and restorative procedure depends on the maintenance of a healthy periodontium. It is, therefore, important that the prosthodontist and restorative dentist cause no harm or permanent damage to the underlying hard and soft tissues when performing clinical procedures necessary to carry out the planned treatment. Several factors involved in these procedures have been described to have an impact on gingival health. For the present article, a selection of four of these factors are presented with the goal of evaluating the current trends and their influence on periodontal structures: (1) tooth preparation configuration and apical extension, (2) gingival tissue sulcular expansion/retraction, (3) prosthetic contours, and (4) prosthesis marginal adaptation and the consequences of excess cement remnants. Based on the available scientific evidence and clinical experience, recommendations for the practitioner are given.

Evaluation of video teaching on resident competency for all-ceramic crown tooth preparation.

PURPOSE: This study aimed to analyze the impact of live video instruction using digital evaluation of residents' performance in full ceramic crown preparation. METHODS: Digital evaluation using CEREC computer-aided design/computer-assisted manufacturing (CAD/CAM) 5.1.3 software was conducted of preparation on a typodont for all-ceramic crowns of mandibular first molars (MFMs) with a radial shoulder finish line, carried out by 30 residents. Each participant prepared two MFMs: group A prepared the right side without live video instruction, and group B prepared the left side after instruction. All prepared teeth were scanned by Dentsply Sirona chairside CAD/CAM system with Omnicom to assess the inter-occlusal space, undercut, the finish line of the preparation, and surface texture. The data were analyzed using Pearson Chi-square, Wilcoxon signed-rank test, and paired t-test. P-values less than 0.05 were considered to be statistically significant in all tests. RESULTS: Based on the Pearson Chi-square test, there were significant differences between the two groups in terms of inter-occlusal space on the buccal and lingual surface of the prepared tooth, in the presence of rough surfaces before and after the preparation, and difference in the type of finish line. The Wilcoxon signed-rank test revealed a significant difference in convergence angle buccolingually and the remaining height of the prepared teeth before and after the video instruction. CONCLUSIONS: The use of educational live video instruction can be helpful to residents in learning the principles of tooth preparation.

The Influence of a Novel, Crenelated Design of CAD-CAM Ceramic Veneers on the Debonding Strength.

(1) Background: Aesthetic dentistry has become one of the most dynamic fields in modern dental medicine. Ceramic veneers represent the most appropriate prosthetic restorations for smile enhancement, due to their minimal invasiveness and highly natural appearance. For long-term clinical success, accurate design of both tooth preparation and ceramic veneers is of paramount importance. The aims of this in vitro study were to assess the stress in anterior teeth restored with Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) ceramic veneers and compare the resistance to detachment and the fracture of ceramic veneers prepared using two different designs. (2) Methods: Sixteen lithium disilicate ceramic veneers were designed and milled using the CAD-CAM technology and divided into two groups according to the preparations (n = 8): Group 1, conventional (CO), with linear marginal contour and Group 2, crenelated (CR), the latter with our novel (patented) sinusoidal marginal design. All samples were bonded to anterior natural teeth. The mechanical resistance to detachment and fracture was investigated by applying bending forces on the incisal margin of the veneers in order to determine which type of preparation leads to better adhesion. An analytic method was employed, as well, and the results of the two approaches were compared. (3) Results: The mean values of the maximum force recorded at the veneer detachment were 78.82 ± 16.55 N for the CO group and 90.20 ± 29.81 N for the CR group. The relative increase, equal to 14.43%, demonstrated that the novel CR tooth preparation provided higher adhesive joints. In order to determine the stress distribution within the adhesive layer, a finite element analysis (FEA) was performed. The statistical t-test showed that the mean value of the maximum normal stresses is higher for the CR-type preparations. (4) Conclusions: The patented CR veneers represent a practical solution to augment the adhesion and mechanical properties of ceramic veneers. The obtained results demonstrated that CR adhesive joints triggered higher mechanical and adhesive forces, which subsequently led to a higher resistance to detachment and fracture.

An Innovative 3D Printed Tooth Reduction Guide for Precise Dental Ceramic Veneers.

Tooth reduction guides allow clinicians to obtain the ideal space required for ceramic restorations. This case report describes a novel design (CAD) for an additive computer-aided manufactured (a-CAM) tooth reduction guide with channels that permitted access for the preparation and evaluation of the reduction with the same guide. The guide features innovative vertical and horizontal channels that permit comprehensive access for preparation and evaluation of the reduction with a periodontal probe, ensuring uniform tooth reduction and avoiding overpreparation. This approach was successfully applied to a female patient with non-carious lesions and white spot lesions, resulting in minimally invasive tooth preparations and hand-crafted laminate veneer restorations that met the patient's aesthetic demands while preserving tooth structure. Compared to traditional silicone reduction guides, this novel design offers greater flexibility, enabling clinicians to evaluate tooth reduction in all directions and providing a more comprehensive assessment. Overall, this 3D printed tooth reduction guide represents a significant advancement in dental restoration technology, offering clinicians a useful tool for achieving optimal outcomes with minimal tooth reduction. Future work is warranted to compare tooth reductions and preparation time for this guide to other 3D printed guides.

Research Progress and Clinical Application of All-Ceramic Micro-Veneer.

Anterior teeth problems affect the patient's daily eating, communication, social activities, self-confidence, and mental health. The trend in dentistry is to address anterior tooth problems with minimally invasive and aesthetic treatments. With the development of adhesive materials and ceramics, micro-veneers have been proposed as an alternative treatment for enhancing the aesthetic appearance and avoiding unnecessary tooth reduction. A micro-veneer is a veneer that can be cemented to the surface without or with minimal tooth preparation. These benefits include no need for anesthesia, postoperative insensitivity, good adhesion to enamel, reversibility of treatment, and higher patient acceptance. However, the micro-veneer repair is suitable only for specific cases and must be strictly controlled regarding indication. Treatment planning is a crucial step to achieving functional and aesthetic rehabilitation, and following the clinical protocol is helpful for the longevity and success of micro-veneer restorations. However, more precise and predictable tooth preparation methods, such as minimally invasive microscopic tooth preparation and digitally guided veneer preparation, are recommended rather than the traditional free-hand method. Therefore, this paper clarifies micro-veneers and compares them with other restorations to gain a deeper and more comprehensive understanding. The authors also review indications, materials, cementation, and effect evaluation of micro-veneers to provide clinicians with valuable information. In conclusion, micro-veneers are minimally invasive treatments that provide good restoration results when used appropriately and are worthy of promotion for the aesthetic restoration of anterior teeth.

The Effect of Dentine Desensitizing Agents on the Retention of Cemented Fixed Dental Prostheses: A Systematic Review.

Background and Objectives: The use of desensitizing agents (DA) after tooth preparation to prevent hypersensitivity is well documented in the literature. A fixed dental prosthesis (FDP) should have good retention to be successful. Inadequate retention may result in microleakage, secondary caries, and, eventually, dislodgement of the FDP. The effect of DAs on the retention of FDPs has been widely studied in the literature, but the results are conflicting. Thus, this study aimed to conduct a systematic review to assess the effect of dentine desensitizing agents, used to prevent post-cementation hypersensitivity, on the retention of cemented FDPs. The null hypothesis framed was that there is no effect of dentine desensitizing agents on the retention of cemented FDPs. The focused PICO question was as follows: "Does the application of dentine desensitizing agents (I) affect the retention (O) of cemented fixed dental prosthesis (P) when compared to non-dentine desensitizing groups (C)"? Materials and Methods: Four electronic databases were systematically searched and, on the basis of the predefined inclusion and exclusion criteria, 23 articles were included in this systematic review. A modified CONSORT scale for in vitro studies was used to assess the quality of the selected studies, as all included studies were in vitro studies. Results: Most of the studies compared the effect of more than one type of DA on retention. The results of the selected studies varied due to differences in the composition of tested dentine DAs and types of luting cements. Conclusions: Within the limitations of this study, it can be concluded that the retention values of FDPs cemented using zinc phosphate cement were reduced with most of the DAs, whereas retention values increased when GIC, resin-modified GIC, and resin cements were used with the majority of DAs. These findings are important, as they can guide dentists in selecting the DA before cementing the crowns with the luting agent of their choice, without compromising the retention of the crowns.

Comparison of marginal accuracy in two different materials used in provisional crown and bridge - an in vitro experimental study.

OBJECTIVE: To determine the difference in the marginal accuracy at buccal, lingual, mesial and distal margins of temporary crowns fabricated with bisacryl-based temporary crown material. METHODS: The in-vitro, experimental, laboratory-based study was conducted at the Aga Khan University, Karachi, from September to December 2019, and comprised two bisacryl-based temporary crown material, Integrity and Protemp 4, which were used to fabricate a sample of 24 temporary crowns. A pre-operative polyvinyl siloxane impression served as a template for temporary crown fabrication. A right mandibular molar tooth on a typodont was prepared to receive a crown. The provisional crown material was syringed onto the template and was allowed to cure. All four surfaces of the crown were observed under a stereomicroscope equipped with digital single-lens reflex camera at 25.6x magnification. An image of each surface was captured and a photographic record was maintained. An image processing software was used for the measurement of marginal discrepancy. Marginal accuracy among the four surfaces was assessed. Data was analysed using SPSS 23. RESULTS: Mean marginal discrepancy for provisional crowns fabricated with Protemp 4 and Integrity was 410±222µm and 319±176µm, respectively. The marginal discrepancy between the two groups was statistically significant (p=0.027), with buccal margin exhibiting the most discrepancy (p<0.01). CONCLUSIONS: Integrity showed less microleakage than Protemp 4. Among all the walls, the buccal wall showed the most microleakage. Marginal accuracy was found to be dependent upon the type of provisional crown material and the side of the prepared axial wall.

Technique to restore the midline space of central incisors using a two-in-one template: A clinical report.

Using composite resin restoration of full-coverage crowns to obtain a completely symmetrical esthetic restoration of individual central incisors remains difficult. Freehand direct composite resin restoration is challenging even for highly skilled dentists. This clinical report describes a digital protocol for achieving symmetrical restoration of two central incisors using a custom-designed, two-in-one template.

The effect of color vision resolution on intra-oral shade-selection accuracy.

BACKGROUND: Dentists must be able to identify subtle color changes as shade-matching is crucial in aesthetic dentistry. OBJECTIVE: To determine whether color discrimination ability is related to shade-matching accuracy among dentists. METHODS: The sensitivity of the normal-color vision population to different colors was investigated using Farnsworth Munsell 100 Hue (FM-100) test results. The FM-100 test was administered to 37 dentists at the Hospital of Stomatology, Jilin University. Sensitivity of dentists with normal-color vision to different colors was investigated using the FM-100 test. Participants were instructed to arrange color caps of various colors according to the gradual change in colors and the results were scored. Visual shade matching test using Vita 3D-MASTER shade guide was performed to determine shade-matching accuracy. The relationship between color discrimination ability and shade-matching accuracy was analyzed. The number of misplaced color caps in the FM-100 test was also calculated. RESULTS: The FM-100 test revealed that 16 and 21 participants had excellent and average color discrimination ability, respectively, and their shade-matching accuracies were 68.75% and 66.67%, respectively. No significant difference was observed in the shade-matching accuracy between the two groups. No significant correlation was observed between the color discrimination ability and shade-matching accuracy. In addition, the number of wrong color caps on the 43-63 color tray with the transition from blue-green to blue-purple was the highest according to Friedman's test. CONCLUSION: Color discrimination ability of dentists does not affect their visual shade-matching accuracy. Additionally, people with normal color vision are not sensitive to the transition from blue-green to blue-purple.