Proximal Box Research Articles

Management of subgingival proximal defects

Deep proximal cavities can be progressively elevated by a restorative procedure known as deep margin elevation (DME), which improves margins for either direct or indirect restorations. Dietschi and Spreafico (1998) introduced the non-surgical alternative procedure of DME for crown lengthening. Other names for the DME concept include “coronal margin relocation,” “proximal box elevation,” and “cervical margin relocation.” A DME treatment’s therapeutic effectiveness depends on a proper indication, and its clinical efficacy is largely dependent on how well the DME is adjusted. In addition to maintaining periodontal health, a suitable DME adaption may be able to lessen bacterial buildup and the occurrence of secondary caries. Here, we report on three cases of DME that were performed when adequate isolation was possible, and caries was progressing subgingivally.

Evaluating the accuracy of CEREC intraoral scanners for inlay restorations: impact of adjacent tooth materials

BackgroundThe accuracy of intraoral scanning is critical for computer-aided design/computer-aided manufacturing workflows in dentistry. However, data regarding the scanning accuracy of various adjacent restorative materials and intraoral scanners are lacking. This in vitro study aimed to evaluate the effect of adjacent restorative material type and CEREC's intraoral scanners on the accuracy of intraoral digital impressions for inlay cavities.MethodsThe artificial tooth was prepared with an occlusal cavity depth of 2 mm, a proximal box width at the gingival floor of 1.5 mm, and an equi-gingival margin extended disto-occlusally at the transition line angle on both the lingual and buccal sides for an inlay restoration. The adjacent teeth were veneered with crowns made of gold and zirconia, and an artificial tooth (resin) was utilized as the control group. The inlay cavity and adjacent teeth (Gold, Zirconia, and resin) were scanned 10 times using Chairside Economical Restoration of Esthetic Ceramics (CEREC) Primescan (PS), Omnicam (OC), and Bluecam (BC). A reference scan was obtained using a laboratory scanner (3-shape E3). Scanning was performed according to the manufacturer's instructions, including powder application for the BC group. Standard tesselation language files were analyzed using a three-dimensional analysis software program. Experimental data were analyzed using a two-way analysis of variance and the Tukey’s post-hoc comparison test.ResultsThe restorative materials of the adjacent teeth significantly affected the accuracy of the intraoral digital impressions (p < .05). The zirconia group exhibited the highest trueness deviation, followed by the resin and gold groups, with each demonstrating a statistically significant difference (p < .05). The resin group demonstrated the highest maximum positive deviation and deviation in precision. Gold exhibited the lowest average deviation value for trueness compared with those of the other adjacent restorative materials. Intraoral scanner type significantly influenced the trueness and precision of the scan data (p < .05). The average deviation of trueness according to the intraoral scanner type increased in the following order: BC > PS > OC. The average deviation in precision increased in the following order: PS>OC>BC (p < .05).ConclusionThe restorative materials of the adjacent tooth and the type of intraoral scanner affect the accuracy of the intraoral digital impression. The trueness of the digital images of the BC group, obtained by spraying the powder, was comparable to that of the PS group. Among the adjacent restorative materials, zirconia exhibited the lowest trueness. In contrast, PS demonstrated the highest precision among the intraoral scanners, while resin displayed the lowest precision among the adjacent restorative materials.

Enhanced personal protective equipment and dental students' experience and quality of a restorative procedure in a simulated clinical setting.

To evaluate the effects of enhanced personal protective equipment (Enhanced_PPE) on student-operator's experience and restorative procedure. Student-operators (N=29 Year 3 dental students) performed Class II composite restorations (SimpliShade, Kerr) in typodont upper molars (OneDental) equipped with N95 respirators, full-face shields, disposable headwear and gowns (Enhanced_PPE) or surgical masks, protective glasses/goggles and non-disposable gowns (Standard_PPE) 2 weeks later. Cavity dimensions were measured on cone beam computed tomography images. The quality of composite restorations was assessed using selected FDI criteria and Vickers hardness. A questionnaire assessed the operators' discomfort, anxiety, confidence, ability to perform, and procedure outcome. Data were analyzed using paired t-test and McNemar test (alpha=0.05). Student-operators experienced greater discomfort and anxiety, reduced confidence and ability to perform, and rated the procedure as less satisfactory with Enhanced_PPE (p<0.05). Differences in proximal box width were marginally significant (Enhanced_PPE 1.8±0.4mm, Standard_PPE 1.6±0.3mm) (p=0.047). Other cavity dimensions were similar between groups (p>0.05) as were restorations regarding surface luster, anatomical form, marginal adaptation, proximal contour, and contact (p>0.05). There were no differences in the hardness of composite restorations (top p=0.349, bottom p=0.334). Enhanced_PPE led to student-operator discomfort, anxiety, and reduced confidence, but did not impact the quality of Class II preparation and composite restorations versus Standard_PPE.

The effect of immediate dentin sealing on fracture resistance and failure modes of resin composite onlay restorations

Aim: This study aimed to investigate the fracture resistance, failure modes, and reparability of molars restored with laboratory-processed resin composite (Ceramage, SHOFU Inc., Kyoto, Japan) onlays above or below the cemento-enamel junction (CEJ) in the presence or absence of immediate dentin sealing (IDS). Methodology: Forty extracted sound human molars were selected and divided into four groups: 1) Below CEJ with IDS, 2) Below CEJ without IDS, 3) Above CEJ with IDS, and 4) Above CEJ without IDS. Standardized mesio-occlusal (MO) onlay preparations were made with the reduction of mesio-buccal and mesio-palatinal cusps. Butt-joint preparation was used in the proximal box area extending 1 mm below the CEJ (Groups 1 and 2) or 1 mm above the CEJ (Groups 3 and 4). In Groups 1 and 3, IDS was applied immediately after tooth preparation. After cementation (Variolink N, Ivoclar Vivadent AG, Schaan, Liechtenstein), the specimens were thermally aged (20000 cycles, 5–55 ºC) and then subjected to load to failure (1 mm/min). The failure types and reparability of the onlays were recorded, and the data were analyzed using two-way ANOVA and Fisher’s exact tests. Results: The restorations in Group 4 showed the highest mean fracture strength compared to Group 1 (p=0.038), Group 2 (p=0.008), and Group 3 (p=0.019). The interaction between the level of proximal extension and the presence of IDS did not influence fracture mode or reparability (p&gt;0.05). Conclusion: No difference in the fracture strength of resin composite onlays below CEJ with or without IDS was found; however, not using IDS for resin composite onlays above CEJ appears to be preferable. How to cite this article: Gözetici Çil B, Köymen SS, Ünal S, Dönmez N. The effect of immediate dentin sealing on fracture resistance and failure modes of resin composite onlay restorations. Int Dent Res 2024;14(1):27-33. https://doi.org/10.5577/intdentres.510

Analysis of the Marginal Continuity in Different Designs of Monolithic Zirconia Inlay-Retained Fixed Dental Prostheses: An In Vitro Study.

To evaluate the marginal integrity of three inlay-retained fixed dental prosthesis (IRFDP) designs fabricated using monolithic zirconia. In total, 30 IRFDPs were fabricated using 4-YTZP monolithic zirconia and randomly divided into three groups according to the cavity design. Groups ID2 and ID1.5 received an inlay cavity preparation, which includes a proximal box and an occlusal extension with a depth of 2 mm or 1.5 mm, respectively. Group PB received a proximal box cavity preparation without an occlusal extension. The restorations were fabricated and cemented using a dual-cure resin cement (Panavia V5) and subjected to an equivalent of 5 years of aging. The specimens were evaluated under an SEM to measure marginal continuity before and after the aging process. During the whole 5-year aging process, no specimens showed signs of cracking, fracture, or loss of retention in any restorations. In the SEM analysis, most marginal defects observed in the restorations were areas of microgaps at the tooth/cement interface (TC) or zirconia/cement interface (ZC), resulting in loss of adaptation. There was a significant difference between the groups after the aging process at both the TC (F = 4.762, P < .05) and ZC (F = 6.975, P < .05), with Group ID2 presenting the best performance. There was a significant difference between TC and ZC in all groups (P < .05), with ZC presenting more gaps in all groups. Inlay cavity designs including a proximal box and an occlusal extension exhibited better marginal stability than a proximal box without occlusal extension.

The Effect of Gravity on Marginal Integrity of Different Flowable Bulk-Fill Resin Composites.

Background and Objectives: The aim of this quantitative research was to investigate the effect of gravitational forces on the marginal integrity of different bulk-fill composites by micro-CT imaging. Materials and Methods: Fifty caries-free human third molars extracted for prophylactic purposes were used in this study. Each tooth was prepared with two proximal box cavities, with dimensions of 3 mm × 3 mm × 5 mm. Five distinct groups, each comprising 20 cavities, thus totaling 100 cavities for this study: (1, Group CON): Clearfil Majesty Flow + Clearfil Majesty Esthetic (as the control); (2, Group FBR): Filtek Bulk-fill Flowable Restorative + Clearfil Majesty Esthetic; (3, Group XTB): Voco Extrabase + Clearfil Majesty Esthetic; (4, Group SDR): SDR + Clearfil Majesty Esthetic; and (5, Group SNC): Sonicfill. When restoring the mesial cavities, the occlusal surfaces of the teeth in the mold were positioned upwards, counteracting the force of gravity. In contrast, for the restoration of the distal cavities, the occlusal surfaces were aligned downwards, to be parallel with the gravitational pull. After restorative procedures, each tooth was treated with 5000 thermal cycles. A solution of ammoniacal silver nitrate (AgNO3) was employed as a tracing agent. The micro-CT scans were conducted and the total volume of silver nitrate and the total volume of restorations within the relevant region of interest were calculated in "mm3" with software. Two-way ANOVA and Tukey tests were performed at a significance level of p = 0.05 with Graphpad Prism v 8.2.1 software. Results: Both gravity effect and interaction showed no statistical differences (p > 0.05). Statistically significant differences were observed in the restorative materials (p < 0.05). Conclusions: Gravitational forces do not emerge as a major factor affecting the marginal integrity of flowable bulk-fill composites in class II restorations. The chemical composition of the composites plays a more crucial role, with the XTB composite showing higher microleakage ratios compared to the others.

In Vitro Microleakage and Fracture Resistance of "Infinity Edge" and Cusp Reduction Preparation Designs for Moderate-sized Class II Composites.

This study aimed to evaluate the marginal microleakage and maximum occlusal fracture loads and fracture modes of two novel class II preparation designs, "infinity edge" and the "2.5 mm cusp reduction" preparations as compared to a traditional class II preparation without cuspal involvement. Thirty extracted human mandibular molars were prepared for moderate-sized class II restorations with extensions into all occlusal grooves. Of these, ten class II preparations served as control. Ten were modified for a 2.5 mm even reduction of the cusps adjacent to the interproximal box. An additional 10 preparations were modified with an "infinity edge" bevel on the interproximal and occlusal portions. All teeth were restored utilizing a flowable bulk-fill composite in the apical portion of the interproximal box and 2-4 mm of heated bulk-fill composite in one increment for the remainder. All groups were cyclic loaded and thermocycled, then imaged with microcomputed tomography (µCT) before and after infiltration with a silver nitrate solution. Images were subtracted to obtain volumetric measurements of microleakage and reported as a percentage of the total volume from the apical extent of the proximal box. All groups were loaded to failure and fracture load and mode were recorded. No significant differences were found in microleakage volume as a percentage of total tooth volume; however, the "infinity edge" group had significantly greater microleakage in the proximal box compared to the traditional class II group. No significant differences were found in fracture load or mode between the groups. Traditional class II, 2.5 mm cuspal reduction, and "infinity edge" preparation designs have similar fracture loads as well as volumes of microleakage; however, an "infinity edge" preparation has a higher ratio of microleakage in the proximal box. Clinicians should carefully consider the use of "infinity edge" margins, particularly on dentin in the apical extent of the proximal box. How to cite this article: Watson JC, Lien W, Raimondi JC, et al. In Vitro Microleakage and Fracture Resistance of "Infinity Edge" and Cusp Reduction Preparation Designs for Moderate-sized Class II Composites. J Contemp Dent Pract 2024;25(1):3-9.

Impact of Auxiliary Features on Retention of Short Dental Crowns: An In-Vitro Analysis of Box and Groove Preparations.

BACKGROUND Several auxiliary features have been proposed to achieve sustainable retention for short-prepared dental crowns; however, achieving retention is challenging. This study aimed to assess the impact of increased total occlusal convergence and auxiliary preparation factors like box and groove on the retention form of short tooth preparations. MATERIAL AND METHODS Eighty resin machine-milled dies with a height of 3 mm and a deep chamfer margin of 1 mm were prepared to mimic the short-prepared molar. Initially, 2 teeth were prepared following the guidelines, and the total occlusal convergence was kept at 10° and 20°, respectively. Auxiliary features such as the proximal box and buccal groove were prepared on separate 20° dies. Eighty dies were prepared with 10 samples each for 10°, 20°, 20° with proximal box and 20° with buccal groove for zirconia (n=40) and metal crowns (n=40). Cementation was done with glass ionomer luting cement, and a pull-off test was conducted. Data were analyzed using one-way analysis of variance and post hoc fisher least significant difference test (P<0.05). RESULTS The highest mean was observed in the proximal box group with the metal crown (14.59), and the lowest in the group with 20° zirconia crowns (9.12). Within groups, the highest retentive values were found for the 20° taper with proximal box preparation; the lowest was for the 20° taper group. CONCLUSIONS Within the study limitations, it could be concluded that incorporating a proximal box or buccal groove in short tooth preparations with an increased total occlusal convergence improved retentive values.

Full-ceramic resin-bonded fixed dental prostheses: A systematic review.

Despite the development of implant-supported prostheses, there are still patients for whom conservative treatments such as resin-bonded fixed dental prostheses (RBFDPs) are more appropriate. This study's objective was to analyze the available research on full-ceramic RBFDPs. In this study, Web of Science, MEDLINE/PubMed, Scopus, Embase, Cochrane Library, and Google Scholar databases were searched for articles published in English between 2010 and 2020. A total of 14 studies were reviewed based on the eligibility criteria. The results showed that using a cantilever design with one abutment had an advantage over two abutments. Additionally, it was proposed that preparations designed with retentive aids, such as a proximal box, groove, and pinhole, could improve RBFDP survival rates. IPS e.max ZirCAD, In-Ceram alumina, and zirconia CAD/CAM were the most commonly used framework materials. Most studies used air abrasion, salinization, or hydrofluoric acid for surface treatment. Adhesive resin cements were the most frequently used type of cement. The survival rate of In-Ceram ceramics (85.3%-94.8%) was lower than that of In-Ceram zirconia and IPS e.max ZirCAD. Debonding, followed by framework fracture, was the leading cause of failure. Following 3-10 years follow-up, the survival percentage of all-ceramic RBFDPs ranged from 76% to 100%. Although RBFDPs have demonstrated satisfactory success as a conservative treatment, long-term follow-ups and higher sample sizes in clinical research are required to gain more reliable outcomes on the clinical success rate of various RBFDP designs.

Influence of Proximal Box Elevation Using Two Different Resin Composite Viscosities on The Marginal Adaptation of CAD/CAM Ceramic Overlays Subjected to Thermomechanical Aging. An In Vitro Study

Influence of Proximal Box Elevation Using Two Different Resin Composite Viscosities on The Marginal Adaptation of CAD/CAM Ceramic Overlays Subjected to Thermomechanical Aging. An In Vitro Study

Effect of RMGI Roughness and Dentin Bonding Primer on Shear Bond Strength of Sandwich-type Restorations.

The open sandwich technique is a reliable alternative to amalgam placement in deep proximal box preparations, where proper isolation and enamel bonding may not be possible. It is often difficult to prepare the box for composite placement without affecting the resin-modified glass ionomer (RMGI) that has been placed in the gingival portion. We hypothesized that RMGI surfaces that are roughened or those that use all steps in the manufacturing bonding protocol, including the priming solution, applied before placing a bonded composite increment, would have greater composite/RMGI shear bond strength. Shear bond strengths (SBS) of RMGI tested in the presence and absence of SiC roughening and primer-coating were tested using a fourth-generation dentin bonding agent to composite after thermocycling. Twenty specimens for four test conditions were fabricated and investigated. Data were subjected to a two-way ANOVA and the Holm-Sidak post-hoc test. Placing dentin primer on unabraded RMGI provided a statistically significant improvement in SBS, but only modestly. Furthermore, because bond failure consistently occurred within the RMGI itself, none of the surface modifications have a clinically relevant impact on SBS at the RMGI to the composite interface. Clinicians should be aware that they need not avoid RMGI abrasion and do not need to incorporate all components of a fourth-generation bonding system when covering an RMGI sandwich layer with composite.

Scanning accuracy of an intraoral scanner according to different inlay preparation designs.

The accuracy of intraoral scanning plays a crucial role in the workflow of computer-assisted design/computer-assisted manufacturing. However, data regarding scanning accuracy for inlay preparation designs are lacking. The purpose of this in vitro study was to evaluate the influence of the depth of the occlusal cavity and width of the gingival floor of the proximal box on the trueness and precision of intraoral scans for inlay restoration. Artificial teeth were used in this study. Four types of preparations for mesio-occlusal inlay were performed on each #36 artificial tooth depending on two different depths of the occlusal cavity (1mm and 2mm) and widths of the gingival floor of the proximal box (1.5mm and 2.5mm). Artificial teeth were scanned 10 times each with Cerec Primescan AC, and another scan was performed subsequently with a laboratory scanner as a reference (n = 10). Standard tessellation language files were analyzed using a three-dimensional analysis software program. Experimental data were analyzed using two-way analysis of variance and the Bonferroni multiple comparison test. The narrow shallow group had significantly higher deviation values for trueness than the wide deep group (p < 0.05). The wide deep group had the lowest average deviation value for trueness and there was no significant difference between the narrow deep and wide shallow groups (p > 0.05). For the mean maximum positive deviation, the wide groups had significantly lower values than the narrow groups (p < 0.05). Trueness was affected by both the width and depth(p < 0.05), whereas the mean maximum positive deviation was affected by the width (p < 0.05). The mean maximum negative deviation was affected by all three factors (p < 0.05). Precision was affected by the depth and the interaction between the depth of the occlusal cavity and width of the gingival floor (p < 0.05). The design of different inlay cavity configurations affected the accuracy of the digital intraoral scanner. The highest average deviation for trueness was observed in the narrow shallow group and the lowest in the wide deep group. With regard to precision, the narrow shallow group showed the lowest average deviation, and the narrow deep group showed highest value.

3D-printed inlays with different cavity depths impact intraoral-scanner’s accuracy in-vitro

CAD/CAM restorations of deep cavities are the challenges faced by intraoral-scanner (IOS) for accurate 3D data acquisition. This study aimed to evaluate the influence of cavity depth on the accuracy of intraoral digital impressions. Three different mesio-occlusal class II inlay cavities on first maxillary molars were designed and 3D-printed with respective proximal box’s height of 1, 2 and 3mm (group 1, 2, 3 respectively), each of which was scanned 10 times using an IOS. The reference scans of inlay cavities were obtained by an industrial scanner. Data were 3D superimposed with reference impression for trueness (n=10) and intergroup superimposed (n=45) for precision. Outcome variables for value of trueness were mean average deviation (mm), minimum/maximum average deviation (mm) and unacceptable/total elements distribution ratio (%), and for value of precision was mean average deviation (mm). The 1mm-depth group resulted in the best trueness and precision significantly. For the trueness, there were significant differences between 3 groups with each other, the lowest deviation was for group 1 (21μm) statistically, followed by group 2 (24μm), group 3 (26μm). For the precision, group 1 showed the lowest scattered images statistically (mean deviation 4.7μm), then group 2, 3 (6μm and 13.8μm respectively). The deviated areas were located mostly at gingival walls of the cavity. The deeper the cavity, the less accurate the digital impressions, which may raise clinical concerns. It suggests the cavity elevation with resin composite might optimize the 3D acquisition of IOS to ensure the fitness of CAD-CAM restorations.

An In vitro Comparative Evaluation of the Fracture Resistance of Teeth with Mesio-Occluso-Distal Preparations Restored with Different Esthetic Materials by Bulk-Fill and Incremental Methods

Introduction: One of the most popular restorative materials today is resin-based composite. Volumetric shrinkage is brought on by polymerization, which can cause contraction stress, microleakage, and adhesion failure. Adhesive restorations have several benefits, including the ability to preserve more healthy tissue and “reinforce” the remaining tooth structure. These benefits go beyond just being attractive. Materials and Methods: Eighty extracted human maxillary premolars were entrenched in a self-cured acrylic resin in a rubber mold cylinder (2.5 cm width-3 cm height). These were arbitrarily divided into 5 groups: 2 control groups (positive control group and negative control group) (n = 10) and 3 experimental (n = 20) groups (microhybrid composite, nanocomposite, and Giomer). The mesio-occluso-distal (MOD) cavities were prepared in 70 samples. After MOD cavities preparation, groups were further subdivided into two subgroups for bulk-fill and incremental methods. Universal Tofflemire Retainer and band were placed on the prepared cavities. The self-etch adhesive was applied on all aspects of the preparations and then it was light-cured using a light-curing unit for 15 s. Now, cavities were restored with different esthetic materials and methods. In the bulk-fill method, the MOD cavity was restored with a solitary increase of restorative material and light cured from all directions of tooth for 20 s each. In the incremental technique, the proximal box on both sides was reconstructed first in a gradual manner, in which two oblique increments and one horizontal increment were restored and treated for 20 s. Then, two oblique increments of material were used to reestablish the occlusal component, and it was once more light-cured for 20 s. Fracture resistance was checked using a steel bar with a diameter of 4.5 mm that was positioned in the middle of the occlusal surface and a crosshead speed of 3 mm/min, all of the samples were compressed axially loaded. Results: The fracture resistance of microhybrid composite resins in bulk technique was significantly higher than that of nanocomposites and Giomer. However, the fracture resistance of nanocomposite in the incremental method was significantly higher than the other two restorative materials. Conclusion: The quality of restoration depends both on the material and method used during the restoration procedure. Both factors are dependent on each other. Superior fracture resistance was shown by microhybrid composites when restored with the bulk-fill technique and nanohybrid composites when restored with the incremental technique.

Comparison of Resin Composite and Biodentine Cervical Marginal Elevation on the Marginal Gap of Two Computer-Aided Design/Computer-Aided Manufacture Endocrown Materials: In Vitro Study

Objective: This study is the impact of resin composite and bio dentine cervical marginal elevation on vertical marginal gap using two CAD/CAM endo-crowns. Materials and Methods: 32 molars were employed, separated into two main groups: Group R, which included 16 molar teeth elevated distally with resin composite each; and Group B, which included 16 molar teeth elevated distally with dentine. The prepared teeth were then restored using endo-crown restorations. There were 2 equal subgroups for each main group (Vita MarkII and Lava Ultimate endo-crowns; n = 8). The samples underwent thermocycling (TC) after the restorations were bonded using dual-cure resin cement. A digital microscope was used to measure the vertical marginal gap. Results: A significant difference in the vertical marginal gap following thermocycling in all groups, except for the Resin composite. The polymer-based group demonstrated better marginal adaptation than other groups. The marginal accuracy produced by the marginal elevation approach, which involves placing a composite filling and dentine in the proximal box before the insertion of ceramic indirect restorations, is comparable to those of ceramics implanted in dentine without margin elevation. Conclusion: The margin elevation technique ensures that the margins created with these materials are as precise as those placed directly in dentin.

Newer Possibilities for Proximal Box Elevation – Tooth Substrate and Comparison with Conventional Materials: An Ex-vivo Study

Background: Adhesive bonding in deep sub-gingival areas is a challenge due moist environment leading to poor marginal seal and microleakage in deep class II cavities. The deep margin elevation technique is advocated in such areas.&#x0D; Aim: The aim of this study is to evaluate enamel, a natural substrate as an alternative material for deep margin elevation, and compare it with the resin-modified glass ionomer and composite material by evaluating microleakage at the tooth-restoration interface in Class II cavities.&#x0D; Materials and Methods: For this study 21 patients having at least one tooth indicated for extraction and 7 patients having at least two teeth indicated for extraction were included.Class II cavities were prepared on the 28 teeth with proximal margins 1mm below the CEJ and were divided into 4 groups(n=7) Group 1: flowable composite was used for deep margin elevation(DME) up till 2mm above CEJ, Group 2: RMGIC was used for DMEup till 2 mm above CEJ, Group 3: enamel slab luted with RMGIC (for DME)up till 2mm above CEJ,enamel slab obtained from other seven teeth of same patient also indicated for extraction, Group 4(control): no intermediate material was used for margin elevation. Then the remaining part of the cavities were restored using the FILTEK P60. The prepared teeth were extracted after one week. The class II cavities were evaluated for microleakage using dye penetration method.&#x0D; Results: RMGIC and enamel slab showed significantly less microleakage as compared to flowable composite and the control group. However there was insignificant difference between RMGIC and Enamel slab group. The control group exhibited highest microleakage as compared to all the other groups.&#x0D; Conclusion: RMGIC and enamel slab exhibit least microleakage when used as materials for deep-margin elevation.

Cervical Margin Relocation for Indirect Bonded Restorations: A Literature Review

Large posterior defects located beneath the gingival tissues complicate the use of indirect bonded restorations. It probably invades the biological width, during rubber dam isolation, impression taking and adhesive procedures. This article proposes a literature review of a new minimally invasive technique known as cervical margin relocation which allows to relocate subgingival margin to supragingival level using an appropriate material. A literature search was conducted in the Medline/PubMed database following the main key words: “cervical margin relocation», «deep margin elevation”, “proximal box elevation”, “indirect restorations”, “adhesion”, “marginal adaptation”, “subgingival margin”. A total number of 44 articles were included. Based on the reviewed literature, it can be concluded that cervical margin relocation technique emerged as an interesting alternative to surgical crown lengthening. However, further research, scientific evidence and randomized clinical trials with longer follow-up results are needed to clarify essentially the longevity of this technique and its compatibility with periodontal tissues.

Fracture Resistance Evaluation and Failure Modes Rating Agreement for Two Endocrown Designs: An In Vitro Study

This in vitro study aimed to evaluate the fracture resistance and mode of failure of endocrowns with proximal extension design compared to the conventional design, and to assess the agreement of evaluators on the failure mode. Twenty mandibular third molars free of caries with approximately similar root lengths and crown dimensions were sectioned parallel to the occlusal plane 2 mm above the cementoenamel junction (CEJ). Then, pulp chambers and canals were accessed, cleaned, and smoothed for the path of insertion. To achieve a symmetrical pulp chamber with an average depth of 3 mm, chambers were filled with flowable resin composite. Then, teeth were randomly divided into two groups (n = 10). The control group has all the walls at the same level. The test group had a box extension on the proximal wall 2 mm apical to the buccal and lingual wall level. Endocrowns (n = 20) of two different designs (conventional and proximal extensions) were fabricated using lithium disilicate (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein). After cementation, specimens were loaded with a round-end vertical loading tip at a rate of 0.5 mm per minute until fracture (INSTRON, Norwood, MA, USA). Then, the fractured specimens were collected for evaluation and assessment. Statistical analyses were performed using the Mann-Whitney U-test (α = 0.05) for fracture test analysis and Cohen’s Kappa for inter-rater reliability. The Mann-Whitney U-test showed a non-significant difference between the two groups (p = 0.142). However, the mode of failure of the endocrown with proximal extension showed more catastrophic failures than the conventional design. Adding proximal boxes to the endocrown design did not negatively impact the fracture resistance of the restoration. Visualization of the fracture line and tracing their apical end by direct vision or other diagnostic tools is an essential part of the evaluation of failures of endocrowns. Endodontically treated molar teeth with proximal caries extension might be restored with an endocrown with proximal extension. Clinicians should take extra care when visualizing the fracture lines and tracing their apical end as it might be very misleading.

Quality of CAD-CAM inlays placed on aged resin-based composite restorations used as deep margin elevation: a laboratory study

ObjectivesTo assess the impact of the age of resin-based composite (RBC) restorations used for deep margin elevation (DME) on the marginal quality and fracture resistance of inlays.Materials and methodsPermanent human molars with direct RBC restorations, involving the mesial, occlusal, and distal surface (MOD), were allocated to four groups (each n = 12). Half of the teeth underwent thermomechanical loading including 240,000 occlusal load cycles and 534 thermal cycles (TML, 5 °C/55 °C; 49 N, 1.7 Hz). With RBC left in one proximal box as DME, all teeth received MOD inlays, made from lithium disilicate (LDS) or a polymer-infiltrated ceramic network material (PICN). The restored teeth underwent TML including 1.2 million occlusal cyclic loadings and 2673 thermal cycles. The marginal quality was assessed at baseline and after both runs of TML. Load-to-fracture tests were performed. The statistical analysis comprised multiple linear regressions (α = 0.05).ResultsSimulated aging of RBC restorations had no significant effect on the marginal quality at the interface between the RBC and the tooth and the RBC and the inlay (p ≥ 0.247). Across time points, higher percentages of non-continuous margin were observed between the inlay and the tooth than between the tooth and the RBC (p ≤ 0.039). The age of the DME did not significantly affect the fracture resistance (p ≥ 0.052).ConclusionsArtificial aging of RBC restorations used for DME had no detrimental effect on the marginal quality and fracture resistance of LDS and PICN inlays.Clinical relevanceThis laboratory study suggests that—in select cases—intact, direct RBC restorations not placed immediately before the delivery of an indirect restoration may be used for DME.

Clinical performance of two onlay designs for molars after root canal treatment.

To evaluate the clinical performance of two proposed onlay designs. Molars with occlusal and/or mesial/distal defects after root canal treatment were classified by design into three groups. Onlays without shoulders were the control group (Group C, n = 50). The designed onlays were Group O (n = 50) and the designed mesio-occlusal/disto-occlusal onlays were Group MO/DO (n = 80). All onlays had an occlusal thickness of approximately 1.5-2.0 mm, and the designed onlays had a shoulder depth and width of approximately 1 mm. In Groups C and O, the box-shaped retention was 1.5 mm in depth. The proximal box was connected with a dovetail retention in Group MO/DO. Patients were examined every 6 months and followed for 36 months. Restorations were evaluated by using the modified United States Public Health Service Criteria. Statistical analysis was performed by using Kaplan-Meier analysis, the chi-square test, and Fisher's exact test. No tooth fracture, debonding, secondary caries, or gingivitis was observed in any group. Groups O and MO/DO had satisfactory survival and success rates, and there was no significant difference in performance characteristics among the three groups (P > 0.05). The two proposed onlay designs were effective in protecting molars.