Fracture resistance and marginal discrepancy of porcelain laminate veneers influenced by preparation design and restorative material in vitro

Evaluation of marginal and internal adaptation of veneers generated by the guided prosthetic tooth preparation system

OBJECTIVE

This in vitro study aimed to assess and contrast the marginal and internal adaptation of all-ceramic prefabricated veneers manufactured via the FirstFit guided tooth preparation system against all-ceramic veneers produced using the chairside Computer-Aided Design/Computer Aided Manufacture (CAD/CAM) system following identical guided preparation protocols.

MATERIALS AND METHODS

Two main groups were included, with 16 lithium disilicate veneers per group. Four typodonts were used for the test (FirstFit) and control CAD/CAM groups. Intraoral scans created master casts and preparation guides. Guides performed preparations on typodont teeth (two central incisors and two lateral incisors). Prepared teeth were scanned (CEREC Omnicam) to design and mill CAD/CAM veneers. Marginal gap thickness and cement space thickness were measured using light microscopy at four locations: marginal, cervical internal, middle internal, and incisal internal.

RESULTS

No significant difference existed between groups for marginal adaptation (p = 0.058) or incisal internal adaptation (p = 0.076). The control group had significantly lower values for middle internal adaptation (p = 0.023) and cervical internal adaptation (p = 0.019).

CONCLUSIONS

Guided preparation evaluation showed no significant differences in marginal or incisal internal adaptation. The CAD/CAM group had significantly lower middle and cervical internal adaptation values.

Semidirect Resin Composite Veneers in a Patient with Bruxism

This case report details the esthetic rehabilitation of a 32-year-old male patient suffering from sleep bruxism, primarily manifesting as a fracture and significant loss of tooth structure in the anterior maxillary central incisors. To address these concerns, the patient underwent a restorative treatment involving the application of semidirect resin composite veneers on the maxillary incisors and direct resin composite restoration on the incisal regions of the maxillary canines. This approach not only restored the functional integrity of the teeth but also significantly enhanced the patient's esthetic appearance.

Marginal and internal fit of porcelain laminate veneers: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Marginal integrity and internal adaptation are key to the long-term success of porcelain laminate veneers. Evidence for their marginal and internal fit is unclear, and the factors affecting such fit have not been identified.

PURPOSE

The purpose of this systematic review and meta-analysis was to summarize the scientific literature assessing the effects of various parameters on the marginal and internal fit of porcelain laminate veneers.

MATERIAL AND METHODS

An electronic search was conducted to identify all relevant published articles on the fit accuracy of ceramic veneers between January 2000 and June 2021 in the PubMed-MEDLINE, Scopus, Embase, Google Scholar, and Web of Science databases. Information, including the study outcomes, in terms of the mean marginal gap, internal gap, and absolute marginal discrepancies of porcelain laminate veneers, was extracted from the selected studies. The inverse-variance random effects model was used to analyze the pooled results and estimate the overall effect based on the heterogeneity of studies (α=.05).

RESULTS

Twenty-one studies were selected for analysis, 2 clinical and 19 in vitro. The risk of bias was "medium" for most studies (19 of 21), and only 2 studies were classified as "high risk." A mean difference of -4.53 μm (95% CI: -21.46 to 12.41) was found, with no statistically significant difference in marginal gap between the pressed and milled fabrication modes (P=.600). As for the internal gap, significant differences were found (mean difference=-40.56 μm; 95% CI: -76.54 to -4.58), with pressed veneers performing better (P=.030). Butt joint preparation design produced significantly (P=.002) lower marginal gaps than the palatal chamfer (mean difference=-14.02 μm; 95% CI: -23.07 to -4.98).

CONCLUSIONS

No significant differences were found between the pressed and milled porcelain laminate veneers for marginal gap, but for the internal gap, the differences were significantly in favor of the pressed type. The butt joint veneer preparation design was significantly better than the palatal chamfer design in terms of marginal fit.

Risk Factors with Porcelain Laminate Veneers Experienced during Cementation: A Review

The clinical success of porcelain laminate veneers (PLVs) depends on many clinical and technical factors, from planning to execution, among which adhesive cementation is of significant importance. This procedure carries many risk factors if not optimally executed. The objective of this study was to document the clinical parameters affecting successful cementation procedures with a focus on the adhesive strength, integrity, and esthetics of the PLVs. A literature search was conducted through MEDLINE, complemented by a hand search using predefined keywords. Articles published in English between 1995 and 2023 were selected. According to this review, the success and longevity of PLVs rely in great part on the implementation of a precise cementation technique, starting from field isolation, adequate materials selection for adhesion, proper manipulation of the materials, the seating of the veneers, polymerization, and elimination of the excess cement. Several clinical steps performed before cementation, including treatment planning, preparation, impression, and adequate choice of the restorative material, could affect the quality of cementation. Scientific evidence suggests careful implementation of this process to achieve predictable outcomes with PLVs. The short- and long-term clinical success of adhesively luted PLVs is tributary to a deep understanding of the materials used and the implementation of clinical protocols. It is also contingent upon all the previous steps from case selection, treatment planning, and execution until and after the cementation.

Evaluation of Marginal and Internal Fit of Ceramic Laminate Veneers Fabricated with Five Intraoral Scanners and Indirect Digitization

The long-term success of ceramic laminate veneers (CLVs) is influenced by the marginal and internal fit of the restorations. However, studies comparing the fit of CLVs using different intraoral scanners or the indirect digitization technique are lacking. The purpose of this study was therefore to assess the marginal and internal fit of CAD/CAM-milled CLVs using different intraoral scanners and the indirect digitalization technique. An ivorine typodont maxillary left-central incisor was prepared; the tooth and the neighboring teeth were scanned and used as a template to print ninety 3D partial models. Thereafter, ceramic laminate veneers (CLVs) (N = 90) were milled from IPS-Emax CAD blocks and divided into six equal groups (15 specimens each) according to the type of intraoral scanner (IOS), as follows: Omnicam IOS, SC3600 IOS, Trios 3 IOS, Emerald IOS, I500 IOS. Fifteen further CLVs were fabricated using the conventional indirect digitalization technique. After cementation on the resin dies and embedding in clear epoxy resin, specimens were sectioned inciso-gingivally and mesio-distally. At the incisal and cervical positions, the marginal discrepancy was measured and evaluated in addition to the internal gap at six locations using SEM (200×). Differences between gap measurements among the six groups were determined using ANOVA. Games-Howell multiple comparisons for homogenous variances and LSD multiple comparisons for non-homogenous variances were used with 95% confidence intervals. The significance level was set at 0.05. The lowest mean absolute marginal gap at the incisal margins (AMGI) was recorded for Omnicam group (203.28 ± 80.14) µm, while the highest mean absolute marginal gap at the cervical margins (AMGC) was recorded for Omnicam group (147.16 ± 59.78) µm. The mean AMGC was reported to be significantly different between the conventional technique (146.75 ± 38.43) µm and Trios 3 (91.86 ± (35.51) µm; p = 0.001) and between Emerald (112.37 ± (50.31) µm; p = 0.042) and I500 (86.95 ± (41.55) µm; p < 0.001). The mean MGI was found to be significantly different between the conventional technique (114.11 ± (43.45) µm and I500 group (186.99 ± (73.84) µm) only (p = 0.035). However, no significant differences were found in the mean MGI between all types of IOSs. The means of AMG and MG were significantly different at incisal or cervical areas between the conventional technique and IOSs and within the scanner groups (p > 0.05). Marginal gaps were higher in the incisal region compared to the cervical region with both the indirect digitization technique and the IOSs. Ceramic laminate veneers (CLVs) fabricated using IOSs produced overall internal and marginal fit adaptation results comparable to CLVs fabricated from the indirect digitalization method, and both techniques produced clinically acceptable results.

Marginal Fit of Porcelain Laminate Veneer Materials under Thermocycling Condition: An In-Vitro Study

Objective: The purpose of this study was to evaluate the cervical marginal fit of porcelain laminate veneer (PLV) restorations made from two different types of CAD/CAM ceramic laminates: CEREC C PC and E.max (LD). Materials and Methods: This in-vitro experiment used a total of 32 human maxillary first premolars that were clean and free of any cracks or caries, extracted for orthodontic purposes. The samples were divided in a random way into two study groups: A and B (n = 16). Each sample was mounted on a dental surveyor and a silicon impression was made to create a silicone index for each tooth in both groups. Standardized preparation was carried out for all the samples by using preparation bur kit for the ceramic veneer system. Subsequently, digital impressions were made for all the samples by using Trios 3 shape intraoral camera (Sirona Dental Systems). The design of veneer restorations was made using Sirona inLab CAD SW 16.1 with CEREC inLab MC XL (Dentsply, Sirona Dental Systems, Bensheim, Germany). The veneer restorations were cemented using 3M RelyX veneer resin cement (3M ESPE, Seefeld, Germany) and the samples kept in distilled water for two weeks at 37 °C. All the specimens were subjected to thermocycling in a water bath with temperature varying between 5 °C and 55 °C for 500 cycles. The cervical marginal fit of veneers was evaluated by a digital microscope after sectioning the embedded teeth in acrylic resin. Results: The lowest mean of cervical marginal gap was recorded for Group A (91.59431 ± 1.626069) which was restored with CEREC CAD/CAM veneers, while the highest mean value of the gap was recorded for Group B (106.48863 ± 2.506684) which was restored with IPS E.max CAD. The t-test showed that the type of porcelain veneer restoration had a highly significant effect on the cervical marginal fit (p ≤ 0.01). Conclusions: CEREC CAD/CAM veneers showed smaller cervical marginal gaps, indicating a better fit compared to the IPS E.max CAD.

Marginal Adaptation of Veneers: A Systematic Review

This study aimed to systematically review the literature to evaluate the marginal adaptation of veneers using different fabrication methods, namely, conventional feldspathic porcelain laminate veneers (PLVs), computer-aided design-computer-aided machining (CAD-CAM) veneers, and pressed veneers. A comprehensive literature search was performed using electronic databases (PubMed and Google Scholar) as well as hand searches to identify all relevant studies related to veneers and marginal adaptation. The identified studies were screened for assessing the inclusion and exclusion criteria. The included articles were then subjected to data extraction and analysis. The search resulted in 130 articles, of which six were included in this systematic review. All included articles were assessed for adaptation of margins. Based on the findings of this systematic review, no significant differences were found in the marginal adaptation of CAD-CAM and conventional feldspathic PLVs. The marginal fidelity of ceramic veneers issuing from the various fabrication techniques was clinically acceptable.

Accuracy of Reduction Depths of Tooth Preparation for Porcelain Laminate Veneers Assisted by Different Tooth Preparation Guides: An In Vitro Study

PURPOSE

To evaluate the accuracy (trueness and precision) of reduction depths of guided veneer preparation assisted by four tooth preparation guides.

MATERIALS AND METHODS

Fifty resin artificial teeth were randomly divided into five groups (n = 10): a freehand group (F), silicone guide group (S), thermoplastic guide group (T), 3D printed uniform guide group (D), and 3D printed auto-stop guide group (A). A preparation for a window veneer on the maxillary right central incisor was performed by two surgeons who used tooth preparation guides for assistance. The maxillary right central incisors were scanned before and after the preparation. The reduction depths were measured in the cervical, middle, and incisal thirds of the prepared surface, and depth maps were created using Geomagic Control X software. The accuracy of the reduction depths at each third was evaluated using both trueness and precision values. The trueness of the reduction depths was determined by calculating the mean absolute differences (MADs) compared to the planning depth, and precision was determined by the standard deviation (SD). The collected data were statistically analyzed using one-way ANOVA and the least significant difference test (α = 0.05).

RESULTS

The MAD ± SD values of the reduction depths in the cervical-third region in groups F, S, T, D, and A were 0.19 ± 0.04, 0.12 ± 0.03, 0.09 ± 0.02, 0.07 ± 0.02, and 0.05 ± 0.01 mm, respectively. In the middle-third region, the MAD ± SD values of groups F-A were 0.19 ± 0.05, 0.13 ± 0.02, 0.09 ± 0.01, 0.06 ± 0.01, and 0.05 ± 0.01 mm. In the incisal-third region, the MAD ± SD values were 0.27 ± 0.05, 0.16 ± 0.04, 0.11 ± 0.03, 0.07 ± 0.01, and 0.05 ± 0.01 mm, respectively. Significant differences in trueness and precision values were found across different groups (F = 45.378, p = 0.000), where group F showed higher MADs than the other 4 groups (p = 0.000), and the highest MADs were detected in group S among the 4 groups in all regions (p = 0.000). Group T showed significantly higher MADs than groups D (P = 0.008) and A (p = 0.001), except in the cervical-third region, where no significant difference was observed between groups T and D (p = 0.077). There was no significant difference between groups D and A (p = 0.148). The deviation map showed significant differences among groups (F = 15.963, p = 0.000), group T presented less deviation than group F (p = 0.000) and group S (p = 0.027) and showed more deviation than group A (p = 0.007).

CONCLUSION

Tooth preparation guides provided more accuracy for veneer preparation than freehand preparation. Among the 4 guides, the 3D printed auto-stop guide presented the lowest absolute difference (0.05 mm) and the silicone guide showed the highest absolute difference of preparation (0.12-0.16 mm).

An in-vitro comparison of fracture resistance of three CAD/CAM Ceramic materials for fabricating Veneer

Aims

This research aims to measure and compare the fracture resistance and modes of failure of the following three chemically varied computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic veneering materials: IPS e.max CAD, Vita Enamic, and Shofu HC.

Materials and methods

Twenty-seven sound human upper premolars were collected and stored in saline at room temperature until the experiment started and were assigned to three groups at random (n = 9). Putty indices were prepared to ensure a standardized butt joint preparation. An InEos X5 scanner was used to scan all the samples, and the resulting data were transferred to a CAD/CAM milling machine for veneer fabrication based on the materials used. Twenty-seven machined ceramic veneers were milled from three different ceramic materials. The cementation process was conducted for each material according to the manufacturer's instructions. To quantify the fracture resistance, all the samples underwent 2000 water cycles in a thermocycler and were then mounted in a universal testing machine at a 90° angle at the occlusal part of the veneer. The modes of failure were determined under a stereomicroscope and grouped into type I, ceramic fracture; type II, combined ceramic and tooth fracture; and type III, root fracture.

Results

Shofu HC had the highest mean (±standard deviation) fracture resistance (480.8 ± 92.8 N), followed by IPS e.max CAD (415.9 ± 147.2 N) and Vita Enamic (372.3 ± 123.9 N). However, the results of a one-way analysis of variance did not reveal statistically significant differences among the experimental groups (p = 0.194). The different groups exhibited different modes of failure, with ceramic fracture being the most common type of failure.

Conclusion

All the materials tested in this study exhibited strong fracture resistance values, thereby indicating their use as veneering materials for the upper premolars.

Evaluation of Marginal and Internal Fit of a CAD/CAM Monolithic Zirconia-Reinforced Lithium Silicate Porcelain Laminate Veneer System

PURPOSE

To evaluate the marginal and internal fit of monolithic computer-aided design/computer-aided manufacturing (CAD/CAM) ZLS (Vita Suprinity) glass ceramic porcelain laminate veneers (PLVs), in terms of marginal and internal gap widths, in comparison to monolithic lithium disilicate (LDS) [IPS e.max CAD] CAD/CAM veneers, and, also, to analyze the effect of incisal preparation designs (butt joint and chamfer), on the marginal and internal fit accuracy.

MATERIALS AND METHODS

Forty dental stone dies poured from impressions made of two master metal dies with different incisal preparation designs were scanned to produce digital models. Forty ceramic veneers were designed and milled using the virtual models-10 ZLS butt joint, 10 ZLS chamfer, 10 LDS butt joint, and 10 LDS chamfer. The monolithic ceramic veneers produced were then subjected to marginal and internal gap width evaluation using X-ray nano-computed tomography and computerized digital analysis (n = 10). Descriptive analyses of data were performed and the influence of "material" and "preparation design" on the marginal and internal fit of veneers was assessed using 2-way ANOVA (α = 0.05). Bonferroni post-hoc multiple comparison tests were used to further analyze the interactions between the material and preparation design after adjusting the α value by Holm-Bonferroni method (α = 0.01).

RESULTS

Mean marginal and internal gaps for ZLS PLVs were 65 ±11 μm and 112 ±14 μm for butt joint, and 100 ±24 μm and 100 ±21 μm for chamfer, respectively. Corresponding values for LDS PLVs were 78 ±25 μm and 114 ±17 μm for butt joint, and 104 ±18 μm and 106 ±7 μm for chamfer. Marginal gap and internal gap differences between ZLS and LDS PLVs were not significant (marginal gap: F = 1.786, p = 0.190; internal gap: F = 0.807, p = 0.375). However, the preparation designs (butt joint and chamfer) differed significantly in terms of marginal gaps (F = 23.797, p = 0.000), but not internal gaps (F = 3.703; p = 0.059).

CONCLUSIONS

Butt joint margins produced better marginal accuracy in terms of marginal gap, compared to chamfers, for ZLS CAD/CAM laminate veneers.

Micro-CT and Microscopy Study of Internal and Marginal Gap to Tooth Surface of Crenelated versus Conventional Dental Indirect Veneers

Background and Objectives: Ceramic veneers represent the most appropriate treatment option for minimally invasive aesthetic rehabilitation. For long-term clinical success, the accurate marginal and internal adaptation of dental restorations are of paramount importance. The aim of this in vitro study is to assess the effect of a novel (patented) design of veneers compared to conventional ones on their marginal and internal gap to the prepared tooth surface. Materials and Methods: Twenty-four lithium disilicate ceramic veneers are obtained using Computer-Aided-Design (CAD) and then milled using Computer-Aided-Manufacturing (CAM). The samples are divided into two groups: 12 conventional (CO) veneers (i.e., with a linear marginal contour) and 12 crenelated (CR) veneers, the latter with the novel sinusoidal marginal design. All samples are bonded to frontal teeth, and the adhesive interfaces are analyzed using two methods, optical microscopy and micro-Computed Tomography (CT): the former for the accuracy of the marginal gap and the latter for the internal gap (as well as for the homogeneity of the luting cement) of ceramic veneers. Results: STATA and one-way ANOVA tests reveal significant differences between CO and CR veneers: (i) the marginal gap is smaller for CR (64 μm) than for CO veneers (236 μm); (ii) the internal adaptation is better for CR veneers: for a cement width of up to 120 μm, the covered surface for the CR group is 81.5%, while for the CO group it is 64.5%; (iii) the mean of the porosities within the cement is not significantly different (3.4·10⁶ μm³ for CO and 3.9·10⁶ μm³ for CR veneers), with a higher standard deviation for the CO group. Analytical modeling is achieved for internal gaps using the micro-CT results. The characteristic functions obtained allow us to compare the volume of luting cement for the two types of veneers. Conclusion: The novel veneers design produces an improvement in the marginal and internal adaptation of the restorations to the prepared tooth surface. Thus, it provides favorable premises for better clinical performances.

Evaluating the effect of repeated use of milling burs on surface roughness and adaptation of digitally fabricated ceramic veneers

Objectives

This study aimed to evaluate how repeated use of milling diamond burs with different coarseness affects surface roughness, and marginal and internal adaptation of CAD/CAM veneers.

Methods

Forty leucite-reinforced glass-ceramic veneers were milled in 2 groups based on the milling mode (with fine or extra-fine bur sets). In each group, every 10 veneers were milled with a new bur set. All veneers were cemented to bovine teeth and then polished. Labial surface roughness was measured before cementation, and after polishing. Marginal and internal discrepancies were measured using a field emission scanning electron microscope. Three-way and two-way mixed repeated measures ANOVA were applied to assess changes in surface roughness values of veneers and discrepancy values, respectively. The Bonferroni correction was applied for multiple comparisons.

Results

Repeated use of a milling diamond bur set had a significant effect on surface roughness of the veneers (P < .001). Mean surface roughness of the fine milling mode was significantly higher in comparison to that of extra-fine mode before (P = .002) and after (P = .01) polishing. After polishing a significant decrease in surface roughness occurred in fine (P = .02), but not in extra-fine milling mode (P = .99). Repeated use of milling burs significantly affected marginal and internal adaptation between some repeated uses.

Conclusions

Marginal and internal adaptation were significantly affected by repeated use of milling diamond burs up to 10 times between some repeated uses. However, no specific pattern could be established.

Clinical significance

Repeated use of milling burs could affect surface roughness, surface microcracks, critical defects, and adaptation of CAD/CAM restorations. Therefore, it plays a major role in clinical success of the restorations.

Effect of firing and fabrication technique on the marginal fit of heat-pressed lithium disilicate veneers

STATEMENT OF PROBLEM

Studies on the fit of heat-pressed anterior lithium disilicate veneers are sparse, and whether fit is affected by glaze firing or ceramic addition is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate and compare the marginal fit of heat-pressed anterior lithium disilicate veneers (IPS e.max Press) fabricated with the staining or cutback technique by using 3-dimensional analysis.

MATERIAL AND METHODS

Two groups of heat-pressed maxillary left central incisor lithium disilicate veneers were fabricated (n=10) differing only in core thickness and the fabrication process. The tooth preparation was standardized at 0.6 mm cervical and middle third and 0.7 mm incisal third, with 1.5 mm of incisal reduction. Group S (staining) was an anatomic contour veneer with 1 glaze firing. Group CB (cutback) had a cutback core of 0.6 mm on the cervical and middle third and 0.5 mm on the incisal areas for ceramic application with 3 firings (wash, incisal, and glaze firing). The amount of ceramic application was standardized, and all veneers had identical final dimensions. Marginal fit was evaluated at 2 stages: after pressing the copings (control) and after glaze firing or ceramic addition using the virtual replica technique and 3-dimensional analysis. The wax copings were invested, eliminated, and pressed with IPS e.max lithium disilicate high translucency ingots, and the overall marginal fit and change in marginal fit after firing were measured in the cervical, mesial, distal, and incisal areas. The Shapiro-Wilk test was used to evaluate normality. Repeated-measures ANOVAs were used to explore differences between the 2 groups (S and CB) as per time (before and after firing) for each location (cervical, mesial, distal, and incisal) (α=.05).

RESULTS

A statistically significant change in marginal fit after firing was found for the mesial and distal areas of the CB group (P<.05). In all other areas of measurements, no statistically significant differences were found (P>.05). The mean ±standard deviation marginal fit of group S was 63 ±13 μm and 62 ±9 μm for group CB.

CONCLUSIONS

The results suggest that firing affects the marginal fit of heat-pressed anterior lithium disilicate veneers fabricated with the cutback technique but not for the staining technique.

Conservative approach for management of fractured maxillary central incisors in young adults

Ceramic restorations could be an acceptable treatment choice for fractured central incisors. A successful esthetic and conservative result to restore damaged anterior teeth can be obtained through proper evaluation, diagnostic wax-up, guided minimal preparations, ceramic selection, and bonding protocols. Handcrafted glass-based restorations can mimic contours and shape of natural teeth.

Marginal discrepancy and load to fracture of monolithic zirconia laminate veneers: The effect of preparation design and sintering protocol

To investigate and analyze the impact of teeth preparation designs and sintering protocol on marginal fit and fracture resistance of monolithic translucent zirconia laminate veneers. A total of 40 extracted intact human maxillary central incisors were assigned into 4 groups (n=10/each group) to investigate 2 variables: (1) the design of tooth preparation (a 1.5 mm incisal reduction with or without palatal chamfer) and (2) the two different sintering programs used for translucent zirconia restoration (standard or speed sintering procedure). Marginal discrepancy was evaluated using a digital microscope. The specimens were loaded to failure in the compression mode, using a universal testing machine with a crosshead speed of 0.5 mm/min. Marginal adaptation of monolithic translucent zirconia laminates are affected by both tooth preparation design and sintering protocol. However, resistance to fracture of translucent zirconia laminates has affected mainly by sintering procedure regardless the teeth preparation design used.

A Conservative Approach to Ceramic Veneers: A Case Report

Bonding to enamel has been shown to provide reliable results, and thus conservative tooth preparations are key to the success of ceramic bonded restorations. The wax-up is the first diagnostic tool available to evaluate discrepancies between current and ideal tooth proportions. The clinician's diagnostic mock-up provides the patient with a visual perception of the size and shape of the proposed restorations. The use of reduction guides assists the restorative dentist in evaluating the specific amount of tooth structure to be removed during preparation. Furthermore, total isolation with a rubber dam prior to bonding the final restorations is crucial for the success of adhesive protocols. The aim of this report is to demonstrate a conservative approach to tooth preparation with a complete isolation technique prior to bonding eight ceramic restorations.

Esthetic rehabilitation of anterior teeth with different thicknesses of porcelain laminate veneers: An 8-year follow-up clinical evaluation

This clinical report describes an 8-year follow-up evaluation using different thicknesses of porcelain laminate veneers of diastema and malformed anterior teeth. Minimally invasive treatment with no preparation or minimal reduction options could be considered and chosen based on the characteristics of each case. Laminate veneers with or without reduction can offer an excellent result regarding esthetics and function. Despite its failure without reduction, this treatment is indicated because it can be applied regardless of the structure of the teeth. At first, no tooth preparation with rotatory instruments was performed, and porcelain laminates of minimum thickness were made for the four maxillary anterior teeth. After 6 years, the adhesive interfaces were stained, and the patient was unsatisfied with the esthetics of her smile. Therefore, at that time, the professional decided to prepare the anterior teeth for porcelain laminate veneers. Diastema closure and/or correction of malformed anterior teeth using porcelain laminate veneers is a viable option for the clinician because it restores esthetic harmony. The patient was very pleased with the new laminate veneers.

The Success of Dental Veneers According To Preparation Design and Material Type

BACKGROUND:

Due to their high aesthetic outcome and long-term predictability, laminate veneers have become a common restorative procedure for anterior teeth. However, because of the variety in the preparation designs and the material types, the clinician faces a dilemma of which approach to use.

AIM:

To compare the survival rate of dental veneers according to different preparation designs and different material types. The sub-aim is to reach a favourable preparation design and material based on scientific evidence.

METHODS:

Comprehensive electronic search of the dental literature via PUBMED, MEDLINE and Scopus databases was performed using the following keywords: “porcelain veneers”, “composite veneers”, “all-ceramic veneers”, “success of porcelain veneers”, “preparation design”, “preparation geometry”, “patient’s satisfaction”. Additionally, references from the selected studies and reviews were searched for more information.

RESULTS:

Under the limitations of the available literature, the clinician preference is the decisive factor for choosing the preparation design. Nonetheless, incisal overlap preparation seems to have the most predictable outcome from all the preparation designs.

CONCLUSION:

Porcelain veneers show excellent aesthetic results and predictable longevity of the treatment, while composite veneers can be considered as a good conservative option, but with less durability.

A comparison of the marginal and internal fit of porcelain laminate veneers fabricated by pressing and CAD-CAM milling and cemented with 2 different resin cements

STATEMENT OF PROBLEM

The marginal and internal adaptations of porcelain laminate veneers (PLVs) are key elements in their long-term success. However, the marginal and internal fit obtained with a pressable material compared with computer-aided design and computer-aided manufacturing (CAD-CAM) needs further investigation as does the choice of cement used.

PURPOSE

The purpose of this in vitro study was to evaluate the marginal and internal fit of PLVs fabricated using pressing and CAD-CAM milling and cemented using 2 types of composite resin cement.

MATERIAL AND METHODS

Twenty PLVs were fabricated from VITA PM9 pressable material, and 20 veneers were milled using VITA Blocs Mark II. Veneers were cemented to composite resin dies using either RelyX Veneer cement or Variolink-N cement. Specimens were embedded in clear resin and sectioned incisogingivally and mesiodistally. Marginal discrepancy at the incisal and cervical positions and the internal gap at 6 different locations were evaluated by using a scanning electron microscope. Two-way ANOVA followed by Tukey multiple comparisons were used to examine difference among groups (α=.05).

RESULTS

The cement and fabrication methods did not show any significant effect for absolute marginal gap (AMG) at the incisal edge, AMG at the cervical margin or marginal gap at the incisal edge. However, both had a significant effect on marginal gap at the cervical margin (P=.038 for the fabrication method and P=.050 for the cement used). Also, both cement and fabrication methods had a significant effect on internal gap average (P<.001). The lowest gap values were reported for veneers fabricated from VITA PM9 by using the press technique and cemented with RelyX Veneer cement. When the position of gap measurements was taken into consideration, it was the only significant factor (P<.001 for the effect of position on AMG and P<.001 for the effect of position on marginal gap). Gaps at the cervical position were significantly lower than gaps at the incisal position.

CONCLUSIONS

Smaller marginal and internal discrepancies were recorded for PLVs fabricated by using the pressing technique and cemented using RelyX Veneer cement compared with milled veneers and Variolink-N cement. Larger discrepancies were present incisally than cervically.

Evaluation of marginal discrepancy of pressable ceramic veneer fabricated using CAD/CAM system: Additive and subtractive manufacturing

PURPOSE

The purpose of this study was to evaluate the marginal discrepancy of heat-pressed ceramic veneers manufactured using a CAD/CAM system.

MATERIALS AND METHODS

The ceramic veneers for the abutment of a maxillary left central incisor were designed using a CAD/CAM software program. Ten veneers using a micro-stereolithography apparatus (AM group), ten veneers using a five-axis milling machine (SM group), and ten veneers using a traditional free-hand wax technique (TW group) were prepared according to the respective manufacturing method. The ceramic veneers were also fabricated using a heat-press technique, and a silicone replica was used to measure their marginal discrepancy. The marginal discrepancies were measured using a digital microscope (×160 magnification). The data were analyzed using a nonparametric Kruskal-Wallis H test. Finally, post-hoc comparisons were conducted using Bonferroni-corrected Mann-Whitney U tests (α=.05).

RESULTS

The mean±SD of the total marginal discrepancy was 99.68±28.01 µm for the AM group, 76.60±28.76 µm for the SM group, and 83.08±39.74 µm for the TW group. There were significant differences in the total marginal discrepancies of the ceramic veneers (P<.05).

CONCLUSION

The SM group showed a better fit than the AM and TW groups. However, all values were within the clinical tolerance. Therefore, CAD/CAM manufacturing methods can replace the traditional free-hand wax technique.

Marginal adaptation of lithium disilicate ceramic crowns cemented with three different resin cements

OBJECTIVES

The cementation process and cementation materials have an influence on the marginal adaptation of restorations. The gap could be affected by thermal and mechanical loading (TCML). The computerized x-ray microtomography (μCT) method offers the possibility of measuring the marginal gap without destruction of the restoration. The aim of this study was to evaluate the marginal gap (MG) and the absolute marginal discrepancy (AMD) before and after TCML.

MATERIALS AND METHODS

Thirty-nine human premolars were prepared for full ceramic crowns made of lithium disilicate. The crowns were cemented by three different resins-Panavia F 2.0, Variolink II, and Relyx Unicem. The MG and AMD were evaluated by μCT before and after TCML.

RESULTS

Panavia F 2.0 had the lowest MG (before 118 μm-after TMCL 124 μm) and AMD (before 145 μm-after TMCL 154 μm), followed by Relyx Unicem (MG: before 164 μm-after TCML 155 μm; AMD: before 213 μm-after TMCL 209 μm) and Variolink II (MG: before 317 μm-after TMCL 320 μm; AMD: before 412 μm-after TMCL 406 μm). The differences were statistically significant before and after TCML. Rather than TCML, it appeared the resin cement was responsible for differences between the MG and AMD before and after TCML.

CONCLUSIONS

μCT is an accurate technique for assessing cemented restorations. Panavia F 2.0 has the lowest MG and AMD before and after TCML.

CLINICAL RELEVANCE

The resin material that features a three-step protocol (Variolink II) produced higher MG and AMG values than the Panavia or Relyx Unicem varieties with less or no intermediate steps at all.

Comparison of Marginal and Internal Adaptation of Heat-Pressed and CAD/CAM Porcelain Laminate Veneers and a 2-Year Follow-Up

PURPOSE

To compare marginal and internal adaptations of porcelain laminate veneers fabricated with heat-pressed and CAD/CAM techniques, and to evaluate the clinical performances 2 years after cementation.

MATERIALS AND METHODS

Thirty heat-pressed and 31 CAD/CAM porcelain laminate veneers were fabricated for 12 patients. Silicone replicas of each veneer were obtained. Replicas were sectioned into 4 parts to measure adaptations of the veneers. A stereomicroscope was used to measure from 3 locations of replicas for marginal, and 9 locations for internal adaptations at 40x magnification. Clinical evaluations were done at baseline and 6, 12, 18, and 24 months after cementation according to the modified United States Public Health Service (USPHS) criteria. Independent samples t-test compared the adaptation values between heat-pressed and CAD/CAM groups. Paired t-test was used to evaluate marginal and internal adaptations of each group. Differences between the modified USPHS criteria ratings of heat-pressed and CAD/CAM groups were determined by the Mann-Whitney U test. Kaplan-Meier analysis was used to analyze the survival ratings of the veneers (p < 0.05).

RESULTS

The mean marginal adaptation values of heat-pressed and CAD/CAM veneers were 295 and 314.98 μm, respectively, and there was no statistically significant difference (p = 0.541). Internal adaptation values of groups were not statistically different either (201.82 μm for heat pressed; 195.47 μm for CAD/CAM p = 0.734). When marginal and internal adaptation values were compared within groups, there were significant differences both for heat-pressed (p < 0.001) and CAD/CAM (p < 0.001). All veneers were rated 100% satisfactory during the 2-year period.

CONCLUSION

Within the limitations of this study, fabrication method, whether CAD/CAM or heat-pressed, had no effect on the marginal and internal adaptation of porcelain laminate veneers. The results showed that both fabrication techniques performed well after 2 years of clinical performance.

Minimally Invasive Laminate Veneers: Clinical Aspects in Treatment Planning and Cementation Procedures

When a definitive aesthetic treatment is determined, it is crucial to grant the patient's wish with the necessary dental treatment. Thus, conservative treatments that are the solution to aesthetic problems involving morphologic modifications and provide the result that the patient expects should always be the first therapeutic option. In this context, ceramic laminate veneers, also known as “contact lens,” are capable of providing an extremely faithful reproduction of the natural teeth with great color stability and periodontal biocompatibility. Minimal or no preparation veneers are heavily advertised as the answer to our patients' cosmetic needs, which they can be if they are used correctly in the appropriate case. This report is about ultraconservative restorations to achieve functional and aesthetic rehabilitation through treatment planning. Thus, clinicians should be aware that the preparation for laminate veneers remains within enamel, to ensure the bond strength and avoid or minimize the occurrence of postoperative sensitivity.

Micrometric precision of prosthetic dental crowns obtained by optical scanning and computer-aided designing/computer-aided manufacturing system

The current study evaluated prosthetic dental crowns obtained by optical scanning and a computer-aided designing/computer-aided manufacturing system using micro-computed tomography to compare the marginal fit. The virtual models were obtained with four different scanning surfaces: typodont (T), regular impressions (RI), master casts (MC), and powdered master casts (PMC). Five virtual models were obtained for each group. For each model, a crown was designed on the software and milled from feldspathic ceramic blocks. Micro-CT images were obtained for marginal gap measurements and the data were statistically analyzed by one-way analysis of variance followed by Tukey's test. The mean vertical misfit was T = 62.6 ± 65.2 μm ; MC = 60.4 ± 38.4 μm; PMC = 58.1 ± 38.0 μm, and RI = 89.8 ± 62.8 μm. Considering a percentage of vertical marginal gap of up to 75 μm, the results were T = 71.5%, RI = 49.2%, MC = 69.6%, and PMC = 71.2%. The percentages of horizontal overextension were T = 8.5%, RI = 0%, MC = 0.8%, and PMC = 3.8%. Based on the results, virtual model acquisition by scanning the typodont (simulated mouth) or MC, with or without powder, showed acceptable values for the marginal gap. The higher result of marginal gap of the RI group suggests that it is preferable to scan this directly from the mouth or from MC.

Shear bond strength of porcelain laminate veneers to enamel, dentine and enamel-dentine complex bonded with different adhesive luting systems

OBJECTIVES

The aim of this study was to evaluate the shear bond strength of porcelain laminate veneers to 3 different surfaces by means of enamel, dentine, and enamel-dentine complex.

METHODS

One hundred thirty-five extracted human maxillary central teeth were used, and the teeth were randomly divided into 9 groups (n=15). The teeth were prepared with 3 different levels for bonding surfaces of enamel (E), dentine (D), and enamel-dentine complex (E-D). Porcelain discs (IPS e.max Press, Ivoclar Vivadent) of 2mm in thickness and 4mm in diameter were luted to the tooth surfaces by using 2 light-curing (RelyX Veneer [RV], 3M ESPE; Variolink Veneer [VV], Ivoclar Vivadent) and a dual-curing (Variolink II [V2], Ivoclar Vivadent) adhesive systems according to the manufacturers' instructions. Shear bond strength test was performed in a universal testing machine at 0.5mm/min until bonding failure. Failure modes were determined under a stereomicroscope, and fracture surfaces were evaluated with a scanning electron microscope. The data were statistically analysed (SPSS 17.0) (p=0.05).

RESULTS

Group RV-D exhibited the lowest bond strength value (5.42±6.6MPa). There was statistically no difference among RV-D, V2-D (13.78±8.8MPa) and VV-D (13.84±6.2MPa) groups (p>0.05). Group VV-E exhibited the highest bond strength value (24.76±8.8MPa).

CONCLUSIONS

The type of tooth structure affected the shear bond strength of the porcelain laminate veneers to the 3 different types of tooth structures (enamel, dentine, and enamel-dentine complex).

CLINICAL SIGNIFICANCE

When dentine exposure is necessary during preparation, enough sound enamel must be protected as much as possible to maintain a good bonding; to obtain maximum bond strength, preparation margins should be on sound enamel.