Maintaining and enhancing gingival architecture in fixed prosthodontics

Vertical Edgeless Preparation: Periodontal Dominance in Prosthetic Crown Preparation

This article aims to describe Vertical Edgeless Preparation (VEP), a full-crown vertical preparation technique initially introduced by the Porta Mascarella Group in the 1980s. The method is defined as “periodontally driven” because its main indication is teeth with a loss of periodontal attachment, and it aims to obtain healthier periodontal tissues. This work describes the step-by-step procedure for performing this prosthetic technique and its indications, contraindications, impression phases, temporary crown management, and biological concepts.

Trueness of intraoral scanners according to subgingival depth of abutment for fixed prosthesis

This study aimed to compare the trueness of intraoral scanners (IOSs) according to the subgingival finish line depth of tooth preparation for fixed prostheses. The prepared maxillary right first molar was fabricated by using ceramic material. A computer-aided design (CAD) reference model (CRM) of the abutment was obtained by using a contact scanner. The subgingival finish line was located according to the depth at 0-mm, 0.25-mm, 0.5-mm, 0.75-mm, and 1-mm. CAD test models (CTMs) were obtained by using 2 IOSs (i500 and CS3600). CRM and CTM were superimposed and analyzed (Geomagic control X). The one-way analysis of variance (ANOVA) was used to compare the trueness according to the subgingival finish line depth. The paired t test was used to compare the trueness of IOSs with and without gingival retraction (α = .05). When the gingival displacement code was not used, it was observed that the trueness of both IOSs decreased significantly as the depth of the subgingival finish line increased (P < 0.001). When the subgingival finish line was positioned deeper than 0.5-mm, the trueness of both IOSs exceeded 100 µm in the marginal region. When the gingival displacement cord was used, the trueness of both IOSs did not exceed 100 µm regardless of the subgingival finish line depth. When gingival cord was used, it showed significantly higher trueness than when not used (P < 0.001). When the gingival displacement cord was not used, the trueness of IOSs decreased as the subgingival finish line depth increased. But the use of the gingival displacement cord improved the scanning trueness by 90%. Thus, it is necessary to use the gingival displacement cord according to the clinical situation to improve scan trueness at the subgingival finish line.

Comparative Evaluation of Surface Roughness of Porcelain Fused to Metal and Stainless-Steel Crown Following Ultrasonic and Hand Scaling: A Comparative Study

Introduction

Surface roughness encourages plaque retention and causes mechanical, chemical, and biological irritation to surrounding soft tissues. Hence, a smooth surface of restoration is preferred for optimal plaque control and the health of the periodontium.

Aim

The aim is to evaluate and compare the surface roughness of porcelain fused to metal and stainless-steel crowns following ultrasonic and hand scaling techniques.

Material and methods

An in-vitro study was conducted on 30 porcelain fused to metal crowns and 30 stainless-steel crowns. Their surface roughness following instrumentation was evaluated by scanning electron microscope (SEM) and profilometry.

Results

Evaluation by profilometry indicated that porcelain fused to metal following ultrasonic instrumentation has a statistically more significant surface roughness and indentation as compared to hand scaling with p-values < 0.05.

Conclusion

The surface roughness of any restoration may act as a plaque retentive factor which would affect the health of the periodontium. Ultrasonic scaling is capable of creating roughness to a more extent as compared to hand scaling and porcelain fused to the metal type of restorations is more vulnerable to roughness.

Comparative evaluation of three gingival displacement materials for efficacy in tissue management and dimensional accuracy

Aim:

Displacement of gingiva is essential for obtaining accurate impressions for the fabrication of fixed prostheses, particularly when the finish line is at or within the gingival sulcus. Various newer impression materials have been introduced to achieve gingival displacement while recording the impressions. A comparative evaluation of these new gingival displacement materials was deemed necessary for efficacy in tissue management and dimensional accuracy.

Materials and Methods:

Ten individuals were selected according to the inclusion and exclusion criteria for gingival displacement using retraction cord impregnated with aluminum chloride and two polyvinyl siloxane impression materials (Aquasil and NoCord VPS impression system) according to Latin block design. Intraoral scanner and Vernier caliper were used to study and compare the dimensional accuracy of each die obtained following which the dies were sectioned and evaluated under optical microscope with image analyzer to measure the amount of gingival retraction.

Results and Conclusion:

Statistical analysis showed that the amount of gingival retraction obtained by using retraction cord impregnated with aluminum chloride as gingival retraction agent was maximum as compared to NoCord followed by Aquasil. All three gingival displacement techniques could produce gingival displacement >0.2 mm which is the optimum amount of retraction required for impression making. All the three materials are found to be dimensionally accurate.

Reducing the effect of polymerization shrinkage of temporary fixed dental prostheses by using different materials and fabrication techniques

OBJECTIVE

The aim of this laboratory study was to evaluate the horizontal and vertical effects of the polymerization shrinkage of three-unit temporary fixed dental prostheses (FDPs) on the position of the prepared teeth. In addition, the reduction of these effects by using different fabrication techniques was evaluated.

METHODS

A total of 192 temporary FDPs were fabricated using one methacrylate (MA) and two dimethacrylate (DMA) materials. Each material group (n=64) was divided into two groups according to the fabrication methods (M1: curing on the prepared teeth, M2: curing in a silicone mold). Each fabrication group was divided into four subgroups (n=8) according to the relining method used (B: no relining, S: spacer foil 300μm, DG: grinding-out with 500μm cutting depth, and FG: free grinding). The experimental apparatus consisted of two abutment teeth lowered at right angles into a silicone mold. One prepared tooth was embedded in silicone to simulate the periodontium and permit slight horizontal tooth movement. The dimensional changes were recorded with an optical microscope. The test images were superimposed and measured using image analysis software.

RESULTS

The statistical analysis showed that there were significantly higher horizontal changes for the MA than the DMA resins in M1, while there was none in M2. Regarding the vertical changes, there were significant differences between the baseline group and all relining and fabrication groups in all materials.

SIGNIFICANCE

Relining of directly fabricated temporary FDPs significantly reduces the effect of polymerization shrinkage and thus secures the position of the prepared teeth.

Practice-based preclinical instruction for gingival displacement with animal models

STATEMENT OF PROBLEM

Gingival displacement is recognized as a substantive and difficult procedure in fixed prosthodontics. However, a realistic simulation of gingival displacement is unavailable for preclinical dental students.

PURPOSE

The purpose of this study was to evaluate whether practice-based preclinical instruction of gingival displacement with animal models could improve students' skill in patient care.

MATERIAL AND METHODS

Isolated bovine mandibles (calves were younger than 6 months of age) and isolated porcine hemimandibles were prepared for this study. Twenty-two general dental practitioners with at least 5 years of experience were randomly selected and assigned to perform gingival displacement on both bovine and porcine jaws. Those practitioners were then asked to assess the clinical similarity of gingival displacement between human teeth and animal teeth. The data were analyzed with the paired t test (α=.05). Upon confirmation that the animal jaw provided a similar gingival displacement environment to that of human teeth, 80 predoctoral dental students were enrolled and randomized into 2 groups. Half of them underwent the new practice-based instruction, while the others underwent traditional preclinical teaching only (lectures, online video, or live demonstration). After preclinical learning, clinical performance in gingival displacement was evaluated for all students in terms of the effect of gingival displacement and quality of impression. The data were analyzed with the chi-square test (α=.05).

RESULTS

The dentogingival environments of porcine and bovine jaws were similar to those of human jaws, and no significant difference was detected between these 2 animal models (P=.178). A significant increase occurred in the acceptable rate of the effect of gingival displacement (P<.001) and the quality of impression (P<.001) among students who received the practice-based instruction compared with those who received traditional teaching.

CONCLUSIONS

These findings suggest that this practice-based instruction of gingival displacement with animal models is an effective method of promoting dental students' learning of gingival displacement.

Easy Accurate Transfer of the Sculpted Soft Tissue Contours to the Working Cast: A Clinical Tip

Tooth replacement in the esthetic zone presents a myriad of challenges for the clinician. An ovate pontic accurately duplicates the emergence profile of the natural tooth it replaces in order to provide an esthetic, yet cleansable prosthesis. The accurate transfer of this sculpted tissue beneath the pontic of the provisional restoration is critical to provide the dental laboratory technician with the necessary information to fabricate a definitive restoration with an appropriate emergence profile. This article presents an innovative, simple and convenient impression technique for easy and accurate transfer of the tissue contours to the working cast, avoiding tissue collapse and tissue compression produced due to the impression material.

Comparative evaluation of the amount of gingival displacement produced by three different gingival retraction systems: An in vivo study

Statement of Problem:

Tetrahydrozoline has been introduced as new gingival retraction agent but its clinical efficacy with widely used conventional retraction agents has not been tested.

Purpose:

The study was designed to clinically evaluate efficacy of newer retraction agent tetrahydrozoline with two widely used retraction systems i.e., Expasyl retraction system and medicated retraction cords on basis of amount of gingival retraction.

Materials and Methods:

30 subjects were selected according to inclusion and exclusion criteria. Maxillary Impressions were made with irreversible hydrocolloid for all subjects. Tray material was used for making the special tray. Latin Block Design was Used in the Study to avoid tissue fatigue. Retraction was done with aluminium chloride; Tetrahydrozoline and Expasyl according to Latin block design. Impressions were poured with die stone. Casts were retrieved and sections were made with die cutter. 3 mm thin slices were obtained. Each slice was used to measure the amount of retraction under stereomicroscope under 20x and images were transferred to image analyser.

Results:

The amount of gingival retraction obtained by using aluminium chloride as gingival retraction agent was maximum (148238.33 μm²) compared to tetrahydrozoline (140737.87 μm²) and Expasyl (67784.90 μm²).

Congenitally missing maxillary lateral incisors: functional and periodontal aspects in patients treated with implants or space closure and tooth re-contouring

To evaluate functional and periodontal aspects in patients with unilateral or bilateral congenitally missing maxillary lateral incisors, treated with either implants or space closure and tooth re-contouring. The sample consisted of 68 volunteers, divided into 3 groups: SCR - space closure and tooth re-contouring with composite resin (n = 26); SOI – implants placed in the area of agenesis (n = 20); and CG - control group (n = 22). A modified Helkimo questionnaire and the Research Diagnostic Criteria for Temporomandibular Disorders were used by a single, previously calibrated evaluator to assess signs and symptoms of temporomandibular joint disorder. The periodontal assessment involved the following aspects: plaque index, bleeding upon probing, pocket depth greater than 3 mm, gingival recession, abfraction, periodontal biotype and papilla index. The data were analyzed using Fisher's exact test and the nonparametric Mann-Whitney and Kruskal-Wallis tests (α=.05). No differences in periodontal status were found between treatments. None of the groups were associated with signs and symptoms of temporomandibular joint disorder. Both treatment alternatives for patients with congenitally missing maxillary lateral incisors were satisfactory and achieved functional and periodontal results similar to those of the control group.

Clinical evaluation of three new gingival retraction systems: a research report

The purpose of this study was to evaluate the clinical efficacy of 3 new gingival retraction systems; Stay-put, Magic foam cord and expasyl, on the basis of their relative ease of handling, time taken for placement, hemorrhage control and the amount of gingival retraction. Thirty subjects were selected requiring fixed prosthesis. The 3 gingival retraction systems were used on the prepared abutments randomly. The time taken for placement of each retraction system was recorded. The vertical gingival retraction was measured before and after retraction using flexible measuring strip with 0.5 mm grading. The horizontal retraction was measured on polyether impressions made before the retraction and after retraction. Based on the results, magic foam cord retraction system can be considered more effective gingival retraction system among the three retraction systems used in the study.

A review of selected dental literature on contemporary provisional fixed prosthodontic treatment: report of the Committee on Research in Fixed Prosthodontics of the Academy of Fixed Prosthodontics

One goal of the American Academy of Fixed Prosthodontics is regularly to publish comprehensive literature reviews on selected topics germane to the discipline of fixed prosthodontics. The following report is the result of this goal and focuses on provisional fixed prosthodontic treatment. Major subtopics include materials science and clinical considerations involving natural teeth and dental implants. The interrelationship between provisional and definitive fixed prosthodontic treatment is multifaceted and significant. Provisional therapy involves numerous materials and techniques that require special knowledge and technical experience. In this analysis, technical, clinical, and investigational articles are detailed and presented as a comprehensive literature review to provide contemporary guidelines. Referenced publications were found by conducting a Medline search and were limited to peer-reviewed, English-language articles published from 1970 to the present. Materials used with provisional treatment are discussed in terms of clinical selection and the influence of their physical properties on treatment outcome. Specific product names and manufacturers are included in this report only when they are cited in the original referenced publications.

Using the existing prosthesis as a provisional restoration

The remaking of a fixed prosthesis provides a unique opportunity of converting the existing prosthesis to a provisional restoration for use while a replacement is being made. This article describes a technique for using existing prostheses that offers several advantages: less potential wear, increased provisional strength and retention, decreased clinical time and esthetically acceptable contours.