Full Coverage Restorations Research Articles

Biologically Oriented Preparation Technique Through a Digital Workflow, a Case Report Part 1.

In every prosthetic treatment, the final purpose of the restoration is to restore function and esthetics for the patient, respecting biology and anatomical parameters. Regarding full coverage restorations, there are some factors to take into consideration: like the finish line (chamfer, shoulder, featheredge, etc.), the management of the provisional restoration and tissue healing, the material for the final restoration, and the impression technique. All these aspects will determine the treatment process and its possible results. In recent years, vertical preparation and more specifically biologically oriented preparation technique has generated great interest since its introduction in prosthodontics, changing the periodontal tissues, and providing long-term stability. With this technique, the objective is to change the position of the gingival margin, moving it more apically or coronally, depending on the modifications of the provisional. The relining of the provisional is a fundamental step of this technique: the intrasulcular part of the provisional is modified giving a new emergence profile and providing an augmentation of the tissue in the healing process. In vertical preparation, there is no predetermined margin. The dental technician should position the finish line more apically or coronally, depending on the depth of the sulcus and on the esthetic needs. Ceramic restorations should not invade the epithelial attachment, otherwise it may cause biological and mechanical problems, repetition of the impression, and of the crown restoration, which lead to increased clinical and laboratory time usage as well as expenses. One challenge is communicating the shape and contour of the temporary restoration to the dental lab to ensure accurate information for the final restoration. Finally, the objective of this article is to describe a technique for transferring all necessary information of the provisional and obtaining a predictable result for the final restoration by using an intraoral scanner system and the fabrication of two 3D printed prototypes. One for the final volume of the crowns and the other for the finish line position. The fabrication of 3D printed prototypes allows for a more predictable final restoration, reducing possible communication errors between clinician and technician when restoring with biologically oriented preparation technique. In any esthetic treatment where the restoration does not have a predetermined margin, it is possible with this additional clinical step to provide a more esthetic outcome.

Influence of post placement on single unit full coverage restorations in endodontically treated teeth - A systematic review

The aim of this systematic review is to analyse the effect of post placement on single unit full coverage restorations in endodontically treated teeth. Published articles related to post placement on single unit full coverage restorations in endodontically treated teeth which includes original research and literature review from databases such as PubMed, Scopus, Cochrane, Ovid Medline etc., were taken into the study for review. Articles from 2002 to 2023 were included. Two authors independently extracted data and assessed the quality of the selected studies.Six studies involving 991 patients were analyzed in this systematic review, which comprised 229 anterior and 910 posterior teeth. The risk of failure or the survival rate was associated with the teeth that had no post placement when the number of coronal walls was less than two. When three or four coronal walls present the success or survival rate seem to be higher with the post placement. Post-retained crowns are better, post-free crowns may be considered when three or four tooth walls are still present, whereas teeth with one or two remaining walls may be better candidates for post-retained crowns. When the ferrule is absent, prosthetic components may be explored

Treatment decisions of patients with Class II Division 2 malocclusion and severe tooth wear: a systematic review

BackgroundThe treatment strategy for patients with severe tooth wear associated with Class II Division 2 malocclusion remains a major challenge for dental practitioners.ObjectivesTo systematically review and summarize the literature on treatment strategies, restoration procedures and clinical outcomes for Class II Division 2 malocclusion patients with severe tooth wear.MethodsA literature review was conducted using Pubmed, Embase, the Cochrane Library, and Web of Science to identify eligible articles. Publications until October 16th, 2023 were searched independently and cross-checked by two researchers.ResultsOf 1513 articles screened, 10 reports detailed treatment processes, including six males and four females aged 34–68 years old. Four articles recorded pre-treatment freeway space (FWS) values ranging from 5 to 9 mm. All ten cases had significant occlusal vertical dimension (OVD) loss and the increase in OVD after treatment ranged from 1 to 7 mm. Pre-prosthetic orthodontic treatment was performed in two cases, in one of which only the maxillary region was orthodontically treated. The most common restorations provided were full coverage restorations. In most cases, temporary restorations were applied before the permanent restorations for eight weeks to six months. Four different sequences of final restoration were proposed. Follow-up ranged from four months to six years and included seven patients, one of them showed symptoms of temporomandibular disorder (TMD).ConclusionsA multidisciplinary team (MDT) approach to treatment is recommended. Consideration of pre-prosthetic orthodontic treatment is essential. Commonly used cephalometric measurements for anterior teeth include the interincisal angle and collum angle. The increases in OVD ranging from 1 to 7 mm can be effectively accommodated. Temporary restorations are recommended to accommodate the OVD, and the transition periods of 8 weeks to 6 months help the patients adapted well. Four different sequences for final rehabilitation have demonstrated positive clinical outcomes. Full crown restorations have emerged as the preferred choice for the ultimate restoration of these patients.

Post-Endodontic Restorative and Prosthetic Options - A Review

Background- In the past, conventional wisdom in post-endodontic care dictated the application of full coverage restorations to all teeth. However, recently a shift towards minimally invasive dentistry has gained traction among the restorative dentists. This change has been driven by accumulating evidence revealing that full coverage restorations often result in significant loss of healthy tooth structure. Consequently, clinicians and researchers have advocated for more conservative approaches to restoring endodontically treated teeth. These alternatives encompass partial coverage restorations such as inlays, onlays, overlays, and even simpler resin composite cores. While the allure of this minimally invasive strategy is evident, there are cases where greater coverage is necessary. Various factors, including tooth type, occlusal load, number of missing teeth, remaining healthy tooth structure, and tooth position, must be carefully considered before selecting an appropriate post- endodontic restoration.  Conclusion- The purpose of this review is to summarize the post- endodontic restorations, various new materials their indications depending on the remaining tooth structure and the teeth that needs to be restored. Light has been thrown on the recent advances in the prosthetic aspect in post-endodontic cases with minimally invasive dentistry in mind.

Evaluation of Lateral and Vertical Gingival Displacement Produced by Three Different Gingival Retraction Systems using Impression Scanning: An in-Vivo Original Study

Isolation of the prepared margin along with control of gingival fluid and haemorrhage is an important factor to register finish lines, which can be achieved by displacing the gingiva away from the abutment which helps in better visualization of the prepared tooth surface. This study utilized digital scanning of rubber based impression material to compare the amount of gingival displacement produced by 3M ESPE capsule, plain retraction cord and impregnated retraction cord.  Aims: The aim of the study was to compare lateral and vertical gingival displacement produced by the three materials  Settings and Design: Case-Control  Methods and Material: Twenty participants requiring a full coverage restoration were selected. Gingiva around each tooth requiring a crown was retracted using the three materials and a rubber based impression was made. The impression was scanned using EXOCAD software to obtain readings for gingival displacement for control group, non- impregnated cord, impregnated cord and retraction paste.  Statistical analysis used: The scores were analysed in SPSS software using one way ANNOVA and post hoc analysis  Results: Significant difference was seen among all trial groups when compared to control. Highest mean vertical displacement was seen in clinical trial II (non- impregnated cord) followed by trial III ( retraction paste).  Conclusions: Impregnated cord and retraction paste both produced adequate retraction for the margings to be registered. Use of paste was less time consuming and less traumatic for the patient and therefore can be substituted for retraction cords.

Evaluation of Convergence Angles in Posterior Crown Preparations by Dental Students at Zawia University

Background and objectives: Achieving optimal axial taper and occlusal convergence in crown preparations is a crucial concern among dental students. Proper preparation design is essential for the long-term success of full-coverage restorations. This study aimed to evaluate the convergence angles and axial taper achieved by dental students in their crown preparations. Methods. A total of 80 posterior tooth preparations (40 mandibular first molars and 40 mandibular second molars) created by second-year dental students on a dental simulator were analyzed. The total occlusal convergence (TOC), bucco-lingual (BL) and mesio-distal (MD) convergence angles, as well as the degree of taper on the axial walls, were measured using the B&B dental software (Guide system, B&B, Italy). Statistical analysis was performed using SPSS version 27. Results. The overall mean of the total convergence angle was 21.88°, with a BL convergence angle mean value of 23.11° (standard deviation of 13.3°) and an MD convergence angle mean value of 20.66° (standard deviation of 11.0°). The results showed a statistically significant difference between the mesial axial taper and the distal axial taper (p-value < 0.001). However, no significant differences were observed between the buccal axial taper and lingual axial taper (p-value > 0.05), or between the BL convergence angle and MD convergence angle (p-value > 0.05). Conclusion. The study revealed variations in the convergence angles of full metal crown preparations created by dental students. The recommended convergence angle was difficult for these students to achieve.

Comparative evaluation of marginal adaptation and fatigue resistance of endodontically treated premolars restored with direct and indirect coronal restorations: an in vitro study

BackgroundAn optimum restoration for reconstructing endodontically treated teeth should provide excellent marginal adaptation, high fracture resistance as well as maximum tooth structure conservation. The purpose of this study was to evaluate the marginal adaptation and fatigue resistance of different coronal restorations in endodontically treated premolars.MethodsThirty sound maxillary first premolars were endodontically treated and received MOD cavities. Teeth were randomly allocated into three groups (n = 10) according to the type of coronal restoration: Group R: polyethylene fibers (ribbond), fibers-reinforced composite (everX posterior) and final layer of nano-hybrid composite. Group O: indirect lithium disilicate overlay and Group C: fiber-post, resin composite restoration, and lithium disilicate crown. Marginal gap assessment was performed before and after thermocycling (5000 cycles) using stereomicroscope. Samples were subjected to stepwise-stress loading starting at 200 N, and increased by 100 N in each step until failure occurred. Statistical analysis was done by One-way ANOVA followed Tukey`s Post Hoc test for multiple comparison. Paired t test was used to compare the marginal adaptation before and after thermocycling. Survival probability was evaluated by Life table survival analysis. Failure mode analysis was performed with Chi-square test.ResultsMarginal gap was significantly the lowest in group R (37.49 ± 5.05) and (42.68 ± 2.38), while being the highest in group C (59.78 ± 5.67) and (71.52 ± 5.18) in before and after thermocycling respectively (P < 0.0001). Fatigue resistance was the highest for group O (1310.8 ± 196.7), and the lowest for group R (905.4 ± 170.51) with a significant difference between groups (P < 0.0001). Crown group had the highest percentage (80%) of catastrophic failure, while, overlay group exhibited the lowest (20%).ConclusionsDirect restoration without cuspal coverage using ribbon fibers with short FRC provided better marginal adaptation than indirect overlays and crowns, but fatigue resistance wasn’t significantly improved. Adhesive ceramic overlays showed the best fatigue performance and the least catastrophic failure rate compared to both direct fiber-reinforced composite and indirect ceramic full coverage restorations.Clinical significanceIndirect adhesive overlays are a suitable, more conservative restorative option for endodontically treated teeth than full coverage restorations, especially when tooth structure is severely compromised.

Managing Cracked Teeth with Root Extension: A Prospective Preliminary Study Using Biodentine™ Material.

The authors of this study proposed an innovative approach involving the use of Biodentine™ material as an intraorifice barrier in cracked teeth with root extension to promote internal crack sealing, preventing the possibility of microinfiltration and apical crack propagation. The dental records of 11 patients with 12 posterior cracked teeth with root extension were included with a precise protocol performed by a senior endodontist. The treatment protocol included pulp diagnosis, crack identification using a dental operating microscope (DOM), endodontic treatment, placing a Biodentine™ as an intraorifice barrier, and immediate full-coverage restoration. The effectiveness of the treatment was assessed at two intervals, 6 months, and 1-3 years posttreatment, evaluating clinical, radiographic, and tomographic aspects. The treatment was deemed successful if there were no indications of radiolucency, sinus tracts, edema, or periodontal pockets associated with the crack line. The study observed remarkably positive outcomes during the follow-up period, which spanned from 1 to 3 years. All the cracked teeth (100%) remained asymptomatic, meaning they were free of pain or discomfort. Furthermore, these teeth were in occlusal function. Both radiographic and tomographic assessments revealed the absence of bone loss along the crack line. This outcome signifies that the treatment effectively prevented further deterioration of the surrounding bone. Integrating advanced biomaterials and conservative restorative techniques has paved the way for innovative approaches in dental care. This protocol suggests a proactive step for managing cracked teeth with root extension. It addresses both biological aspects by sealing internal cracks and mechanical aspects by preventing crack progression, thereby improving these teeth' prognosis and long-term survival.

Comparative evaluation of stress generation in primary teeth restored with zirconia and BioFlx crowns: A finite element analysis

Background: Maintaining the functional integrity of primary teeth is important, as these teeth are integral in vital functions such as mastication, speech development, and space maintenance for permanent teeth; hence, premature loss of primary teeth can affect a child’s quality of life. Various restorative materials are available to restore the function of grossly decayed teeth. Stainless steel crowns and zirconia crowns are widely used in pediatric dentistry; however, there are certain disadvantages associated with these materials. Recently introduced BioFlx crowns provide acceptable esthetics with a conservative approach. Nevertheless, there is a lack of evidence regarding their strength and clinical acceptability. Finite element analysis measures the physical response of teeth and assesses the stress generation, which is important to estimate the integrity of the restorations and crowns. Purpose: The aim of this in vitro study was to evaluate and compare stress generation in primary teeth restored with zirconia and BioFlx crowns using finite element analysis. Methods: Models of extracted teeth restored with zirconia and BioFlx crowns were used for the study. The finite element analysis of these models was carried out through Analysis of Systems (ANSYS) software. The models were subjected to a simulated occlusal loading force of 245 N. Results: Von Mises stress generated in BioFlx crowns along with underlying dentin was much less compared to that which was generated in zirconia crowns. Conclusion: Restoring the functional integrity of carious teeth is essential. BioFlx crowns can be used as full coverage restorations and can be a suitable alternative to zirconia crowns and traditional stainless steel crowns.

Assessment of Interleukin-6 Levels and Lactobacillus casei Counts in Pediatric Stainless Steel and Zirconia Crowns: A Comparative Study.

Pediatric dental crowns play an integral role as they maintain the form and function and prolong the life of the affected tooth. However, placing a crown in the oral cavity creates a new niche for the adhesion of microorganisms that can lead to plaque accumulation, gingival inflammation, and the development of secondary caries, which in the long term might determine the clinical success of the restored tooth. The present study allowed us to assess the changes caused by the full coverage restorations at a clinical, immunological, and microbiological level using enzyme-linked immunosorbent assay (ELISA) and microbial analysis. The in vivo analysis consisted of a total of 26 children aged 3-10 years. They were divided into two groups, group I (n = 13) children receiving preformed zirconia crowns and group II receiving stainless steel crowns (SSCs). Plaque index (PI) scores, gingival index (GI) scores, and interleukin-6 (IL-6) levels were assessed at baseline and at 45 days of follow-up. The in vitro part of the study consisted of 13 preformed zirconia crowns and 13 SSCs which were immersed in artificial saliva containing strains of Lactobacillus casei which were then processed for their microbial analysis. On mean comparison, preformed zirconia crowns performed superiorly both clinically and immunologically compared to SSCs. Microbial analysis using independent t-test revealed that the colony-forming units (CFU) per milliliter was statistically significantly higher for the SSCs, and the mean difference among the groups was statistically significant (p < 0.01). Preformed zirconia crowns can be a relative replacement for SSCs in primary teeth with the advantage of esthetics and superior periodontal health. Saharia NP, Malik M, Jhingan P, et al. Assessment of Interleukin-6 Levels and Lactobacillus casei Counts in Pediatric Stainless Steel and Zirconia Crowns: A Comparative Study. Int J Clin Pediatr Dent 2024;17(4):395-403.

Unilateral Impaction of Mandibular Canine in a Down Syndrome Patient: A Case Report

A 12-year-old female patient, with large nasal bridge, mongoloid slants, clinodactyly, saddle gap of toes, slanting palpebral fissures, and a flat facies with ocular hypertelorism was reported. The patient’s medical history showed intellectual impairment, hypothyroidism, and allergy to penicillin and cow milk. Intraoral examination revealed that there was severe crowding, with Angles class I Dewey’s modification type I. A radiographic examination showed that the root of tooth 44 has sharp dilaceration toward the mesial in the apical third. Impacted canines were measured approximately 17.5 mm from the cusp till root apex. Treatment plan included prescription for pain relief. Oral prophylaxis was followed by root canal treatment and full coverage restoration. Induced eruption was planned. This case report provides insight into various oral conditions associated with Down syndrome (DS). The treatment was challenging and it needed a comprehensive approach with a preventive dentistry practice and regular screening. Dental practitioners should be aware of DS and its effect on oral health with the main focus on an effective treatment plan.

Fracture Resistance and Failure Mode of Monolithic Zirconia, Veneered Zirconia, and Metal-Ceramic Full-Coverage Restorations: A Comparative In Vitro Study.

To evaluate and compare the fracture mode and strength of monolithic zirconia to veneered zirconia and metal-ceramic full-coverage restorations following artificial aging and to test the performance of translucent zirconia in terms of load-bearing capacity. Two mandibular first molars were prepared and scanned for their respective groups of full-coverage restorations. A total of 75 full-coverage restorations were fabricated and divided into five groups: two groups for monolithic zirconia, two groups for veneered zirconia, and one group for metal-ceramic. Then, 75 light-cured hybrid composite resin dies were fabricated to serve as abutments. Before cementation, all full-coverage restorations were subjected to accelerated aging. After cementation, all full-coverage restorations were subjected to compressive loading until fracture in an electromechanical universal testing machine. A two-way nested ANOVA and Tukey test were used to analyze the results with 95% confidence levels. Monolithic zirconia full-coverage restorations showed the highest mean fracture resistance of 4,201.0 N, followed by metalceramic full-coverage restorations of 3,609.3 N, and veneered zirconia full-coverage restorations showed the lowest mean fracture resistance of 2,524.6 N. The main mode of failure was cohesive bulk fracture for the monolithic zirconia group, cohesive/adhesive failure with infrastructure damage for the veneered zirconia group, and cohesive/adhesive failure without infrastructure damage for the metal-ceramic group. Monolithic zirconia full-coverage restorations showed superior resistance to fracture compared to metal-ceramic full-coverage restorations and are highly reliable in terms of load-bearing capacity within the posterior regions of the mouth.

Outcome of chairside CAD/CAM ceramic restorations on endodontically treated posterior teeth: a prospective study

ObjectiveThe aim of this study was to evaluate the outcome and risk factors for chairside CAD/CAM full cusp coverage restorations on endodontically treated posterior teeth after 3 years of follow-up.MethodsA total of 245 endodontically treated posterior teeth of 224 patients were included and restored with CAD/CAM full cusp coverage all-ceramic restorations according to a standardized protocol. Patients were recalled after treatments 1 to 3 years and underwent clinical and radiological examinations. At recall, modified FDI criteria were used to determine treatment outcomes by 2 evaluators. Success was determined when FDI scores were 1–2, and failure was indicated when FDI scores were 5. Logistic regression analysis was performed to evaluate potential risk factors.ResultsA total of 183 patients presented at recall, and the clinical outcomes of 201 teeth were analyzed with a recall rate of 82.0% for teeth and 81.7% for patients after 1–3 years of follow-up.185 of 201 teeth were found to have FDI scores of 1–2, and the success rate was 92%. No teeth were extracted during the follow-up period. Fourteen failed cases with an FDI score of 5 presented restoration dislocation, fracture of restoration or/and tooth. Logistic regression analysis revealed that oral parafunction (OR 2.281, 95% CI 2.2 ~ 47.5, P value 0.01) was a risk factor for success rate.ConclusionChairside CAD/CAM all-ceramic full cusp coverage restoration was (could be) a promising alternative for restoring endodontically treated posterior teeth.

Fracture resistance evaluation of CAD/CAM zirconia and composite primary molar crowns with different occlusal thicknesses.

To evaluate the effect of different CAD/CAM materials and occlusal thicknesses on the fracture resistance of primary molar crowns. Sixty extracted primary molar teeth were prepared and randomly divided into six experimental groups according to the material and thickness. Primary molar crowns with a central groove thickness of 0.3 and 0.5 mm were fabricated from CAD/CAM zirconia (group Z), zirconia-reinforced lithium silicate (group ZLS), and pre-polymerized composite resin blocks (group C). Each crown was cemented with self-adhesive resin cement on the prepared tooth. All specimens were subjected to fracture tests until fracture. Fracture load values were recorded in Newtons (N). Data were statistically analyzed using a two-way analysis of variance (ANOVA) followed by Tukey multiple comparison test. The highest fracture load values were obtained in group Z at 0.5 mm occlusal thickness and were significantly higher compared with the other experimental groups (p < 0.05). Although the lowest fracture load values were obtained in group ZLS at 0.3 mm occlusal thickness, all the tested CAD/CAM primary molar crowns at both thicknesses demonstrated fracture load values exceeding reported chewing force in pediatric patients. CAD/CAM primary molar crowns with reduced occlusal thickness may be used for the full-coverage restoration of primary molar teeth.

Clinical Performance of Two CAD/CAM Fabricated Ceramic Restorations with Different Designs for MIH Rehabilitation: A Randomized Controlled Trial

Background: Molars affected with severe molar incisor hypomineralisation (MIH) require extensive restorations, which do not last for a long time and often require treatment in the form of onlays or full coverage restorations. Objective: A randomized clinical trial evaluated the clinical performance of two CAD/CAM fabricated ceramic restorations, Vita Suprinity (VS) and Vita Enamic (VE), with different preparation designs, occlusal veneer and endocrown, for rehabilitation of the first permanent molar affected by MIH. Materials and Methods: The study was registered with NCT05434884 clinical trial ID with 68 patients ranging from 8 to 13 years old, who attended the dental clinic of Al-Azhar University, Girls Branch, and suffering from a severe form of molar incisor hypomineralization. The patients were divided equally into two groups, group I, i.e., occlusal veneer (OV) group, and group II, i.e., endocrown (EN) group, according to different preparation designs related to different severity levels of first permanent molars’ hypomineralization (moderate and severe); each group was subdivided equally and randomly into two subgroups, subgroup A, i.e., Vita Suprinity (VS), and subgroup B, i.e., Vita Enamic (VE), according to the material used for fabrication of the restoration. The survival and success rates of restorations were assessed using the clinical United States Public Health Service (USPHS) criteria at 1 week, and 3, 6, 12, and 18 months' recall times after cementation, and statistical analysis was performed. Results: There was no statistically significant difference between groups and subgroups in terms of all evaluation parameters during the whole observational period. Conclusion: Based on observations, occlusal veneer and endocrown designs fabricated from CAD/CAM VS and VE showed similar clinical success in the rehabilitation of first permanent molars with severe MIH over 18 months of evaluation.

Esthetic Management of Child with Severe Early Childhood Caries: Two Case Reports

This case report represents the esthetic management of child with severe early childhood caries (ECC). Early loss of primary anterior teeth is caused by severe ECC. The child’s speech gets affected as it interferes with the pronunciation of consonants which could lead to the development of parafunctional habit. Two case reports are discussed with different approaches for rehabilitation of severely decayed primary anterior teeth. In Case 1, the primary anterior teeth were severely decayed. Teeth were restored with intracanal retainers followed by full coronal coverage restoration. In Case 2, one of the primary anterior tooth was mobile and rest of them were severely decayed. The tooth was extracted and fiber-reinforced bridge was placed. The other teeth were restored with intracanal retainers followed by full coronal coverage restoration. Additive effect of intracanal retainers with full coronal coverage restorations and fiber-reinforced bridge presented esthetic and functional success.

Fracture Resistance Comparative Analysis of Milled-Derived vs. 3D-Printed CAD/CAM Materials for Single-Unit Restorations.

The aim of this study was to evaluate and compare the fracture resistance of a single-unit fixed prosthesis, using a CAD/CAM PMMA material and two printed materials (3DPPa and 3DPPb). A typodont with a specific preparation for a full crown was used; a digital impression was made with a state-of-the-art scanner (PrimeScanTM, Dentsply-SironaTM, New York, NY, USA), and a full coverage restoration was designed using a biogeneric design proposal by means of specific software (InLAB 22.1, Dentsply-Sirona, NY, USA). Sixty crowns were prepared, divided into three groups according to the material: 3DPPa (n = 20), 3DPPb (n = 20), both 3D-printed from the .STL file with a resolution of 50 μm, and PMMA (n = 20) milled-derived, which were subjected to a thermocycling process. A universal testing machine (Universal/Tensile Testing Machine, Autograph AGS-X Series) with integrated software (TRAPEZIUM LITE X) equipped with a 20 kN load cell was used to determine the fracture resistance. Significant differences were found by Kruskal-Wallis test and multiple comparisons (p < 0.05) in fracture resistance between materials. The fracture resistance for the PMMA material was higher, and the standard deviation was lower (x = 1427.9; sd = 36.9 N) compared to the 3DPPa (x = 1231; sd = 380.1 N) and 3DPPb (x = 1029.9; sd = 166.46 N) prints. The restorations from the milled-derived group showed higher average fracture resistance than the provisional restorations obtained from the printed groups. However, the results demonstrated that all three materials analyzed in single-unit restorations are capable of withstanding the average masticatory forces.

COMPARATIVE EVALUATION OF COLOUR CHANGE, CRAZING AND DIMENSIONAL STABILITY OF STAINLESS STEEL, ZIRCONIA AND FIGARO CROWNS BY STERILIZATION

Introduction:Full coverage restorations are indicated in primary teeth following pulp therapy, in teeth with multi-surface caries, developmental defects and fractures. There are various types of restorations for complete coverage. In the process of trial and error, the crown gets contaminated and demands sterilization for the purpose of reuse. Therefore, the study was carried out to evaluate the physico-mechanical outcome after sterilization of paediatric preformed crowns. Aim: The purpose of the study was to compare the effect of sterilization on the colour, crazing and dimensional stability of Stainless steel, Zirconia and Figaro crowns. Methodology: The study was conducted on a total of 36 crowns consisting of 12 each, Stainless steel crowns, Zirconia crowns and Figaro crowns, which were divided into two groups: G1 in which crowns did not undergo any sterilization, G2 consisted of sterilization with steam autoclaving at 121°C, 15 psi pressure for 20 min. Following sterilization, all the crown samples were observed under a stereomicroscope at ×200 magnification and assessed for colour change, crazing and dimensional stability. Results:There was no color change or crazing following sterilization among crowns in any of the groups. Highest crazing was noted in stainless steel and the least in Zirconia crowns. Zirconia Crowns were the most dimensionally stable followed by Figaro crowns and SSCs were the least dimensionally stable. Conclusion: Zirconia Crown was the most dimensionally stable followed by Figaro Crowns and Stainless steel crowns.

Effects on different full-coverage designs and materials of crack propagation in first mandibular molar: an extended finite element method study.

Objectives: This study aims to investigate the biomechanical properties of fracture resistance in cracked teeth using five different full-coverage restorations made of three different materials. Materials and Methods: A 3D model of a mandibular first molar was created to design five different full-coverage repair models: crown, crown with composite resin filling inside, occlusal veneer, occlusal veneer with composite resin filling inside and onlay. These repair models were fabricated using three different materials, namely, zirconia, lithium disilicate (LDS), and a hybrid polymer-infiltrated ceramic network material (PIC). In total, 15 repair models were tested using the extended finite element method (XFEM), with an occlusal load of 5000N applied slowly to the occlusal surface of the restoration. The analysis of stress distribution in the restoration and dentin crack line was conducted to measure and record the crack initial load on the restoration and dentin. Results: The results showed that restorations on the occlusal surface significantly improved crack resistance, with zirconia exhibiting superior fracture resistance among the materials tested. Restorations of crown with composite resin filling inside demonstrated the highest resistance to fracture, while occlusal veneers showed the lowest. MPS concentration was observed at the interface between the restoration and dentin and at the root bifurcation, with the highest values at the top of crack development. Dentin covered by oxidized restorations had the highest displacement, while PIC restorations exhibited the lowest. Pulp analysis revealed selective MPS concentration and strain patterns in models with zirconia restorations and onlay, with pronounced pulp displacement in zirconia restorations and onlay. Enamel analysis indicated larger MPS values and displacements in zirconia restoration models and onlay, with higher strain in onlay. Restoration played a crucial role in protecting the tooth, with crack propagation initial loads in dentin surpassing restorations in experimental groups. Conclusion: This study confirms that full-coverage restorations significantly increased the fracture resistance of cracked teeth, with zirconia restorations significantly protecting the underlying cracked tooth. Elimination of fracture lines in the restoration design can improve fracture resistance in cracked teeth. The findings have implications for dental prosthetic design and clinical practice.

Frequency of Horizontal Crown Fracture in Endodontically Treated Posterior Teeth Restored with Amalgam

Objective: To evaluate the frequency of horizontal crown fracture in endodontically treated posterior teeth restored with amalgam when compared to other restorative materials. Study Design: Cross sectional comparative study. Place and Duration of study: Operative Department, Armed Forces Institute of Dentistry, Rawalpindi Pakistan, from Jan to Dec 2019. Methodology: Patients reporting to Operative Department, Armed Forces Institute of Dentistry, were studied for the frequency of horizontal crown fractured endodontically treated teeth restored with amalgam and other restorative materials. History, clinical examination, mobility and trans-illumination test were used to diagnose horizontal crown fracture. Fracture of one or more cusps of endodontically treated posterior teeth involving enamel and dentin was taken as Horizontal crown fracture. Results: A high percentage of patients with amalgam restoration after endodontic treatment of posterior teeth experienced horizontal crown fracture as compared to composite and glass ionomer cement. Out of 54 patients included in the study, 42(77.8%) patients were having amalgam restorations while 6(11.1%) patients were having composite and other 6(11.1%) were restored with glass ionomer cement material. Conclusion: Patients with endodontically treated posterior teeth restored with amalgam presented with a high percentage of horizontal crown fracture as compared to other restorative materials and there is a need to provide full coverage restoration of endodontically treated tooth as soon as possible to enhance its survival.