Clinical evaluation of all-ceramic crowns

Influence of crown-lengthening surgery on teeth rehabilitated with ceramic single crowns: A 12-month prospective clinical study

OBJECTIVE

To compare the clinical periodontal parameters of teeth restored with a single ceramic crown, with and without crown lengthening procedure.

METHODS

This prospective, longitudinal, controlled, and single-blinded clinical trial involved 22 patients with a total of forty-one teeth with ceramic crowns. The teeth were divided into two groups: test (n = 21), comprising teeth rehabilitated post crown-lengthening surgery, and control (n = 20), comprising teeth rehabilitated without crown-lengthening surgery. Plaque index (PI), gingival index (GI), probing depth (PD), bleeding on probing (BoP), and clinical attachment level (CAL) were compared between groups (surgically treated and non-surgically treated) and within each group for each type of site (treated -tt; adjacent - ad; and nonadjacent - nad). Additionally, gingival phenotype (GP), gingival recession (GR), and keratinized tissue width (KTW) were also assessed post- restoration. Statistical analyses used a significance level set at 5 %.

RESULTS

PI, GI, and BoP were reduced, but no statistically significant differences were observed within each group or between groups for most follow-up periods. CAL of the TT sites was consistently higher in the test group, and PD was also higher in the test group (p < 0.05), except at T3. adPD, nadPD, adCAL, and nadCAL demonstrated no significant differences between groups and periods. A significant association was identified between GP and the occurrence of GR, with the thick-flat phenotype demonstrating less association with GR, regardless of whether crown lengthening was performed or not.

CONCLUSION

Crown-lengthening surgery in rehabilitated teeth does not significantly affect PI and GI after 12 months. Although crown-lengthening surgery affected PD and CAL in TT sites, it did not affect adjacent and non-adjacent sites.

CLINICAL RELEVANCE

These findings emphasize the importance of considering individual patient factors and the potential impact on periodontal tissues when planning crown-lengthening surgery. Clinicians must have a comprehensive understanding of the dynamics of the periodontal tissues involved in restorative treatments to optimize the procedure, increase success rates, and minimize potential complications.

Biomechanical consideration in tooth-supported glass-ceramic restorations: A systematic review and meta-analysis of survival rates and irreparable failures

STATEMENT OF PROBLEM

Knowledge on the biomechanical behavior of glass-ceramics, their survival rate over time, and their potential failures is essential for decision-making in clinical practice. Systematic reviews and meta-analysis of their survival rates and irreparable failures are lacking.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the survival rates and irreparable failures of various monolithic glass-ceramic dental restorations to help determine biomechanical indications.

MATERIAL AND METHODS

A comprehensive literature search was conducted across the PubMed, Scopus, Web of Science, and EMBASE databases based on the population, intervention, comparison, and outcome (PICO) question, risk of bias assessment, data extraction, subgroup analysis, and meta-analysis. Both randomized and nonrandomized clinical trials that reported survival rate and irreparable failure were screened. The risk, with a 95% confidence interval, was calculated by using the Mantel-Haenszel method.

RESULTS

A total of 46 articles met the inclusion criteria: 8 for laminate veneers, 20 for partial coverage restorations, 11 for single crowns, and 6 for fixed partial dentures, encompassing 1715 participants rehabilitated with 4209 restorations. The estimated cumulative survival rate for partial coverage restorations was 90% over an average span of 6.2 years, with an irreparable failure occurrence of n=5.9. Laminate veneers had a survival rate of 90.2% over 6.5 years, with an irreparable failure occurrence of n=8.2. Single crowns had a survival rate of 96% over 4.6 years and an irreparable failure of n=2.7. Conversely, fixed partial dentures had a survival rate of 76.1% over 6.5 years with an irreparable failure of n=5.2.

CONCLUSIONS

Glass-ceramic materials demonstrate relatively high survival rates, indicating that they provide a safe and reliable option for partial coverage restorations, laminate veneers, and single crowns. However, fixed partial dentures had a higher proportion of irreparable failures and a lower survival rate, and caution is required.

Evaluation of E-max Porcelain Veneer Failures: A Retrospective Study

Aim This retrospective study aimed to evaluate if E-max veneers over five years caused changes in gingival, periodontal health, and veneer failures. Background As aesthetic dentistry progresses, dental veneers are becoming increasingly popular in both general and specialized dental practices. Due to technological advancements in dental ceramics and adhesive systems, porcelain veneers have become a highly sought-after solution for improving aesthetics in dental patients. The success of porcelain laminate veneers, a commonly used method for aesthetic restoration, relies on various factors. E-max veneers are frequently utilized, with their long-term durability contingent upon factors such as color stability, resistance to abrasion, as well as good compressive, tensile, and shear strength, along with maintaining marginal integrity. Methodology In this study, data was collected through a checklist form used to record clinical parameters. The clinical parameters evaluated were inflammation and bleeding on probing (BOP). The gingival health was evaluated by gingival index, gingival color, texture, and bleeding on probing, and periodontal health was evaluated by the pocket depth and radiographic evaluations. Finally, the veneer was visually inspected for chipping, staining, and debonding history. The score for most of the cases ranged between 0-1, with only 10 cases displaying moderate gingival inflammation and BOP (Gingival Index 2). Siemens Orthopantomogram (OPG) systems were used for radiological evaluation and documentation of cases. E-max porcelain veneers were only included in the research. Results Out of 28 patients, each with 6-to-10-unit veneer cases was examined, 18 patients (64.3%) displayed healthy gingival status with no bleeding area recorded in none of the veneers amongst the 6 to 10 units. In 10 patients (35.7%) most of the veneers had inflamed gingival tissue that was bleeding on probing. The majority revealed the presence of stippling (92.9%), absence of recession (96.4%), and pocket depth (67.9%). Half of our participants had their veneer for more than five years (50%) and the majority presented with no significant changes in veneer recorded like marginal staining, debonding, or chipping (89.3%). Conclusion Multiple factors such as patient selection, proper treatment planning, and design, including material selection, play a significant role in the long-lasting success of ceramic veneers. The retrospective study indicated that proper oral hygiene measures are vital for the long-term sustainability of E max veneers.

Two-year evaluation of porcelain laminate veneers using FDI criteria

PURPOSE

The use of porcelain laminate veneers (PLVs) is a minimally invasive technique that is often used in restorative dentistry due to esthetic considerations. The aim of this study was to evaluate PLVs according to the Fédération Dentaire Internationale (FDI) World Dental Federation clinical criteria.

MATERIALS AND METHODS

This clinical study included 11 patients (7 female and 4 male) who had been admitted to the Uşak University Faculty of Dentistry between February 2019 and February 2021. Before taking part in the study, patients were informed about alternative treatment procedure options. A total of 30 PLVs were fabricated and cemented, and patients were evaluated according to the FDI criteria (with a follow-up after 2 years).

RESULTS

Restorations were evaluated by two trained researchers. During the follow-up evaluation, no fractures or cracks were observed in any restoration. Further, 73% (n = 22) of the PLVs had perfect marginal adaptation and only 27% (n = 8) had small marginal fractures that could be removed by polishing. Moreover, 57% (n = 17) of the PLVs were evaluated as a good color match (no difference in shade and/or translucency), whereas 33% (n = 13) had only minor deviations. In periodontal examinations, 23% (n = 7) of the PLVs had no plaque, inflammation, or pockets, whereas 77% (n = 23) had minor plaque inflammation and no pocket development.

CONCLUSIONS

As there were no fractures, fails, or need for removal of the restorations after 2 years, PLVs showed clinically satisfactory performance. The performance of PLVs can be considered highly favorable due to the minimally invasive and periodontally-compatible nature, with a good color match when carefully planned.

Secondary caries in fixed dental prostheses: Long-term clinical evaluation

OBJECTIVES

Even with excellent fixed dental prostheses (FDPs), there will be a substantial risk of biological complications, such as caries, if proper oral hygiene is not maintained. This study aimed to evaluate the risks of developing secondary caries with FDPs in relation to the patient oral hygiene status.

MATERIAL AND METHODS

Clinical and radiographic examinations were performed for patients to collect data related to their FDP complications and oral hygiene status. The main clinical parameter analyzed was secondary caries. Complications such as a fracture, debonding, or the need for endodontic therapy were also analyzed. The interval survival rate and the cumulative survival rate of FDPs from the time of treatment to the time of follow-up were analyzed.

RESULTS

A total of 423 patients (with a total of 1116 FDPs) were examined in this study, with a mean age of 43.7 years and a mean follow-up time of 7 years. Regarding complications, secondary caries was detected in 94 FDPs (8.4%), fracture (or chipping) in 85 (7.6%) cases, need for endodontic treatment in 42 cases (3.7%), and debonding in four (0.3%) cases. Secondary caries was found in nine out of 219 FDPs (4%) in patients with good oral hygiene, 35 out of 634 FDPs (5.5%) in patients with fair oral hygiene, and 50 out of 272 FDPs (18.4%) in patients with poor oral hygiene (p ≤ .001).

CONCLUSIONS

Good oral hygiene has a great influence on reducing the risk of secondary caries in patients with FDPs. The occurrence of secondary caries is a common complication in patients with poor oral hygiene.

Analysis of the effects of prepared porcelain veneers and unprepared porcelain veneers on gingival crevicular flora based on high-throughput sequencing

The effect of tooth preparation on the gingival crevicular flora of abutment teeth during porcelain veneer treatment is not clear. The purpose of the present study was to analyze the difference between prepared porcelain veneers and unprepared porcelain veneers on gingival crevicular flora. High-throughput sequencing was used in the present study. A total of 20 patients (40 anterior teeth) with veneer restoration of anterior teeth were enrolled. They were divided into two groups: The prepared porcelain veneer group (group P, 11 cases, 19 anterior teeth) and unprepared porcelain veneer group (group U, 9 cases, 21 anterior teeth). After 2 years of follow-up, the restoration and healthy natural gingival crevicular fluid were collected to extract bacterial DNA. 16S ribosomal DNA high-throughput sequencing technique was used to compare the diversity of gingival sulcus flora structure between the prepared porcelain veneer and unprepared porcelain veneer groups. In addition, a healthy control group (group H) was also used for comparison. The Shannon index of the group U was lower than that of group H and group P. The abundance of Proteus in group U was higher than that in group H and group P at the phylum level (P<0.05). At the genus level, the abundance of Porphyromonas, Prevotella and Actinomycetes in group U was significantly higher than that in group H and group P (P<0.05). Compared with the group P, the bacterial diversity of the group U was lower, and the proportion of gingival sulcus pathogenic bacteria was higher. The unprepared porcelain veneer had a certain adverse effect on the periodontal tissue.

Effect of resin cement space on the fatigue behavior of bonded CAD/CAM leucite ceramic crowns

This study evaluated the influence of occlusal resin cement space on the fatigue performance of bonded-leucite crowns to a dentin-analogue material. Leucite anatomical crowns were adhesively cemented to dentin-like preparations having distinct occlusal cement space (50, 100 and 300 μm) (n = 18), and subjected to step-stress fatigue testing (150 N - 350 N; step-size: 25 N; 20,000 cycles/step; 20 Hz). Fatigue data (load and number of cycles for failure) were analyzed using Kaplan-Meier and Mantel-Cox (log-rank) tests (p <0.05). Fractographic analysis and occlusal internal space measurements were also performed. There was no significant difference for the distinct occlusal cement layer (50 μm: 289 N, 136,111 cycles; 100 μm: 285 N, 132,778 cycles; 300 μm: 246 N, 101,667 cycles). Occlusal internal space analysis showed a mean thickness of 120.4 (50 μm), 174.9 (100 μm) and 337.2 (300 μm). All failures were radial cracks originating at the ceramic-cement interface. Distinct occlusal cement spaces had no effect on the fatigue behavior of anatomical leucite crowns.

Clinical Outcomes of Monolithic Zirconia Crowns with CAD/CAM Technology. A 1-Year Follow-Up Prospective Clinical Study of 65 Patients

Aim/Purpose: The primary aim of this study was to examine the clinical performance of posterior monolithic single crowns in terms of failure or complications and the secondary aim was to assess the quality of these restorations according to the United States Public Health Service (USPHS) criteria. Methods: Ιn a private dental clinic, 65 patients with need of posterior crowns were restored with monolithic zirconia crowns. All the restorations were evaluated 6 and 12 months after their cementation. The modified United States Public Health Service (USPHS) criteria and periodontal parameters were applied for the clinical evaluation of the crowns. Restorations with Alpha or Bravo rating were considered a success. Results: Descriptive statistics and nonparametric tests were used for statistical analysis. Sixty-five patients (mean age: 49.52) were restored with 65 monolithic zirconia crowns. No fracture of the restorations was recorded. The overall success rate was 98.5%. The clinical quality of all crowns was acceptable except for the marginal discoloration of one crown at the 6- and 12-month follow-up examination. Conclusions: In this study, no fracture of single-tooth monolithic crowns occurred and the success rate was high. Monolithic zirconia restorations fabricated is a viable option for the restoration of single posterior teeth.

Evaluation of marginal fit and internal adaptation of zirconia copings fabricated by two CAD - CAM systems: An in vitro study

Statement of Problem:

Three main factors which determine the success of an All-ceramic restoration are esthetic value, resistance to fracture and third being the marginal fit. Marginal fit and internal adaptation are crucial factors in increasing the longevity of the restoration. Newer and economical CAD CAM systems have been introduced claiming better marginal fit and adaptation of All ceramic crowns. CAD CAM systems involves scanning of the die or the tooth preparation and milling of the restoration, which may have variations among the systems available.

Aim of the Study:

Our study intended to check the marginal fit and internal adaptation of commonly used CAD CAM systems namely CERAMILL and CEREC -In Lab MC XL.

Materials and Methods:

Two groups of typodont teeth (n = 10) were prepared using a standardized protocol to receive All ceramic copings. 10 samples of Group A were used for fabrication of copings using CERAMILL system and 10 samples of Group B were used for fabrication of copings using CEREC -In Lab MC XL system. They were then luted with glass ionomer cement under mild finger pressure. Samples were embedded in resin and sliced longitudinally. They were then viewed under stereomicroscope and readings were measured along 15 points using ImageScope software. The P value was set at 0.05 at 95% confidence interval with 80% power. The data were checked for normality and unpaired t-test was used to evaluate the results of the two groups.

Results:

The overall internal adaptation was 61.5 ± 5.2 μm for CERAMILL and 56.9 ± 5.7 μm for CEREC -In Lab MC XL (P < 0.05). The marginal fit for CERAMILL was 83 μm and for CEREC -In Lab MC XL was 68 μm (P < 0.05).

Conclusion:

The marginal adaptation of CEREC -In Lab MC XL (68 μm) was found to be superior to CERAMILL (83 μm) (P < 0.05). Both the CEREC -In Lab MC XL and CERAMILL copings demonstrated internal adaptation and marginal fit within acceptable discrepancy range. When corroborating both the internal adaptation and marginal fit, CEREC -In Lab MC XL was found to be better than CERAMILL.

Esthetic Prosthetic Restorations: Reliability and Effects on Antagonist Dentition

Recent advances in ceramics have greatly improved the functional and esthetic properties of restorative materials. New materials offer an esthetic and functional oral rehabilitation, however their impact on opposing teeth is not welldocumented. Peer-reviewed articles published till December 2014 were identified through Pubmed (Medline and Elsevier). Scientifically, there are several methods of measuring the wear process of natural dentition which enhances the comparison of the complicated results. This paper presents an overview of the newly used prosthetic materials and their implication on antagonist teeth or prostheses, especially emphasizing the behavior of zirconia restorations.

Periodontal response to two different subgingival restorative margin designs: a 12-month randomized clinical trial

OBJECTIVES

Subgingival margin placement is sometimes required due to different reasons and is often associated with adverse periodontal reactions. The purpose of this study was to determine if a single restoration with subgingival margin on a tooth, in the maxillary anterior zone, would affect its periodontal soft tissue parameters, and whether or not a deep chamfer preparation has a different influence in the periodontium when compared to a feather edge preparation.

MATERIAL AND METHODS

Plaque and gingival indexes, periodontal probing depth, bleeding on probing, and patient's biotype were registered. One hundred six teeth were prepared with a deep chamfer, while 94 were prepared with a feather edge finishing line. Twelve months after the restoration delivery, the same parameters were evaluated. Repeated measure one-way analysis of variance (ANOVA) (α = 0.05) was used.

RESULTS

A statistically significant difference between the baseline and the 12-month follow-up is present in regard to plaque index, gingival index, and periodontal probing depth, but no statistically significant difference between chamfer and feather edge finishing lines. There is a statistically significant difference between the baseline and the 12-month follow-up in regard to bleeding on probing. Feather edge preparation presents significantly more bleeding on probing and less gingival recession than the chamfer.

CONCLUSIONS

Subgingival margins do influence the periodontal soft tissue response. Statistically significant difference exists between feather edge and chamfer finishing lines in regard to bleeding on probing and gingival recession.

CLINICAL RELEVANCE

Subgingival margins should be carefully selected, especially when feather edge finishing line is utilized.

A systematic review of outcome measurements and quality of studies evaluating fixed tooth-supported restorations

PURPOSE

The purpose of this systematic review was to review clinical studies of fixed tooth-supported prostheses, and to assess the quality of evidence with an emphasis on the assessment of the reporting of outcome measurements. Multiple hypotheses were generated to compare the effect of study type on different outcome modifiers and to compare the quality of publications before and after January 2005.

MATERIALS AND METHODS

An electronic search was conducted using specific databases (MEDLINE via Ovid, EMBASE via Ovid, Cochrane Library) through July 2012. This was complemented by hand searching the past 10 years of issues of the Journal of Oral Rehabilitation, Journal of Prosthetic Dentistry, Journal of Prosthodontics, and the International Journal of Prosthodontics. All experimental and observational clinical studies evaluating survival, success, failure, and complications of tooth-supported extracoronal fixed partial dentures, crowns, and onlays were included. No restrictions on age or follow-up time were placed.

RESULTS

The electronic search generated 14,869 papers, of which 206 papers were included for full-text review. Hand-searching added 23 papers. Inclusion criteria were met by 182 papers and were included for the review. The majority were retrospective studies. Only 8 (4.4%) were randomized controlled trials. The majority of the studies measured survival and failure, and few studies recorded data on success; however, more than 60% of the studies failed to define survival, success, and failure. Many studies did not use any standardized criteria for assessment of the quality of the restorations and, when standardized criteria were used, they were modified, thereby not allowing for comparisons with other studies. There was an increase of 21.8% in the number of studies evaluating outcome measurements of all-ceramic restorations in past 8 years.

CONCLUSIONS

Prosthodontic literature presents with a reduced percentage of RCTs compared to other disciplines in dentistry. The overall quality of recording prosthodontic outcome measurements has not improved greatly in the past 8 years.

Effect of preparation surface area on the clinical outcome of full veneer crowns in dogs

Crown therapy is commonly used in veterinary medicine to provide support to teeth which have previously fractured, received root canal therapy, have significant wear, or experienced other detrimental removal of tooth substance. As with several aspects of veterinary medicine, many of the recommendations or guidelines for crown therapy originate from human dentistry, which are then transferred to veterinary patients. Due to the significant difference in the anatomy of teeth and function of the oral cavity between humans and dogs, these guidelines need to be studied to determine the appropriateness of their use in veterinary patients. This article evaluates the relationship between surface area of the preparation and clinical outcome of full veneer crown therapy of the canine tooth in dogs. Although there appeared to be a positive relationship between preparations with greater surface area and successful clinical outcome, it was not found to be statistically significant.

Crown preparation design: an evidence-based review

Evidence-based clinical guidelines for full metal crown preparation design are seldom encountered in the veterinary literature. The veterinary literature regarding prosthodontic treatment in companion animals is sparse and consists primarily of case reports and expert opinion based primarily on clinical experience. The goal of this manuscript is to present concepts of evidence-based practice, review common recommendations on crown preparation design from the veterinary literature, and to provide an assessment of the evidence for or against those recommendations.

Retentiveness of metal coping luted to teeth of uremic patients undergoing hemodialysis using five different luting cements

OBJECTIVES

This study aimed to assess the retention of metal copings luted to uremic teeth with five different luting agents.

METHODS

A total of 35 sound natural molars was collected from uremic patients and randomly assigned into five groups (n=7). The teeth were prepared for metal copings using diamond tips and water coolant. Metal copings with a loop on the occlusal surface were fabricated using base metal alloy (Rexillium III). The copings were luted using Fuji I, glass ionomer (GI); Fuji Plus, resin-modified glass ionomer (RMGI); Panavia F 2.0, resin cement; Rely X Unicem, self-adhesive cement (SA); and Adhesor, zinc phosphate cement (ZPh). All specimens were incubated at 37°C for 24 hours, conditioned in artificial saliva for 7 days, and then thermocycled for 5000 cycles (5°C-55°C). The dislodging force was measured using a universal testing machine at a crosshead speed of 2 mm/min. The mode of failure of the loaded adhesive copings was evaluated. Statistical analyses were performed using one-way analysis of variance and Tukey post hoc test.

RESULTS

GI and SA cements had the highest and the lowest mean retentive strength, respectively (580.90±17.3, 406.6±12.7). There was no significant difference between ZPh, SA, and resin cements. These cements were inferior to GI and RMGI cements (p<0.05), which showed statistically similar retentive strengths.

CONCLUSIONS

The results of this study support the use of glass ionomer and resin-modified glass ionomer cements for luting of metal copings to uremic teeth with retentive preparations.

How and when does fabrication damage adversely affect the clinical performance of ceramic restorations?

OBJECTIVES

As compared to factory-processed ceramic parts, one unique trait of all-ceramic dental restorations is that they are custom-fabricated, which implies a greater susceptibility to fabrication defects. A variety of processing techniques is now available for the custom fabrication of all-ceramic single and multi-unit restorations, these include sintering, heat-pressing, slip-casting, hard machining and soft machining, all in combination with a final staining or veneering step. All these fabrication techniques, from shaping to firing, are associated with the production of flaws of various shapes and sizes, in conjunction with thermal residual stresses, all of which are capable of inducing failure.

METHODS

This review will examine the various types of fabrication damage inherent to each technique and attempt to establish a relationship between fabrication defects and clinical performance of all-ceramic dental restorations with particular attention to their longevity in vivo.

RESULTS

Failure mechanisms in dental ceramics can be very complex and often involve the combination of physical factors, to which are added patient and clinician-related variables such as restoration design and in vivo conditions.

SIGNIFICANCE

Tremendous progress has been made in understanding the failure mechanisms of all-ceramic dental restorations over the past thirty years. It remains that there is still a need for laboratory tests that usefully simulate clinical conditions.

Effect of connector design on fracture resistance of zirconia all-ceramic fixed partial dentures

The purpose of the present study was to determine the relationship between cross-sectional design and fracture load using a static load bearing test in yttria-stabilized tetragonal zirconia polycrystal ceramic frameworks on a molar fixed partial denture. The test framework was designed as a 3-unit bridge with two abutment teeth at the second premolar and second molar of the mandible. The cross-sectional area of the connector was 9.0, 7.0, or 5.0mm(2). In terms of shape, the cross-section was either circular or oval, with a height/width ratio of 1:1, 3:4, or 2:3. For each of the 9 combinations of cross-sectional area and shape, 5 frameworks were prepared (45 in total). Frameworks were cemented to a metallic test model with adhesive resin cement. After fracture load was measured, the percentage of fracture sites was determined and the fracture surfaces observed. In terms of cross-sectional area, there was a statistically significant difference in fracture load between 9.0, 7.0, and 5.0mm(2). No significant difference in fracture load was observed between any two shapes of connector (p>0.05). The fracture load of all frameworks with a cross-sectional area of 9.0 or 7.0mm(2) was over 880 N, which was recognized as parafunctional occlusal force. Fracture occurred at the distal connector in 82.2% of all frameworks on average. Fracture load decreased as cross-sectional area of the connector became smaller. The cross-sectional shape used in the present study was less influential on fracture load. It appears to be clinical possible to apply a connector with a cross-sectional area of 7.0mm(2). Fracture often occurred at the distal connector between the pontic and the abutment, corresponding to the second molar.

The effect of dentin pretreatment on the microtensile bond strength of self-adhesive resin cements

STATEMENT OF PROBLEM

Self-adhesive cements have lower bond strength than conventional resin cements that rely on the application of etch-and-rinse adhesive systems.

PURPOSE

The purpose of this study was to evaluate the effect of tannic and polyacrylic acid on the microtensile bond strength of self-adhesive resin cements to dentin.

MATERIAL AND METHODS

Eighteen molar crowns were flattened to expose dentin and divided into 3 groups according to the dentin pretreatment: (1) control, without surface treatment; (2) 25% polyacrylic acid solution (Ketac Conditioner); (3) 20% tannic acid. Composite resin (Tescera) blocks were luted to dentin surfaces using 2 self-adhesive resin cements (RelyX Unicem or Maxcem Elite) (n=3). All specimens were stored in distilled water for 24 hours, sectioned into beams (1 mm(2)), and tested to failure using a microtensile method at a crosshead speed of 1 mm/min. The data were statistically analyzed using 2-way ANOVA and Fisher's PLSD tests (α=.05).

RESULTS

The polyacrylic acid significantly improved the microtensile bond strength of RelyX Unicem (14.92 ±4.94 MPa) when compared to the control group (8.35 ±1.99 MPa) and tannic acid treatment (8.38 ±2.67 MPa) (P<.001). Dentin surface treatment did not affect the microtensile bond strength of Maxcem Elite cemented groups (control, 8.45 ±3.21 MPa; polyacrylic acid, 9.53 ±9.95 MPa; tannic acid, 6.89 ±4.45 MPa).

CONCLUSIONS

Dentin pretreatment with polyacrylic acid improved the microtensile bond strength of RelyX Unicem.

Restorative options for the periodontal patient

Periodontal and restorative dentistry are mutually important facets of clinical dentistry. Today's clinicians have many treatment options at their disposal, including biotolerant restorative materials and implants, to maintain periodontal health. It is crucial for the clinician to understand the biologic principles that form the foundation for restorative reconstruction of the periodontally involved tooth. This article discusses new techniques and trends in the critical management of the restorations, particularly at the gingival margins, and explores the role of implant dentistry as an option for the restorative plan of the periodontal patient.

CAD/CAM Zirconia vs. slip-cast glass-infiltrated Alumina/Zirconia all-ceramic crowns: 2-year results of a randomized controlled clinical trial

The aim of this randomized controlled clinical trial was to compare the early clinical outcome of slip-cast glass-infiltrated Alumina/Zirconia and CAD/CAM Zirconia all-ceramic crowns. A total of 30 InCeram Zirconia and Cercon Zirconia crowns were fabricated and cemented with a glass ionomer cement in 20 patients. At baseline, 6-month, 1-year, and 2-year recall appointments, Californian Dental Association (CDA) quality evaluation system was used to evaluate the prosthetic replacements, and plaque and gingival index scores were used to explore the periodontal outcome of the treatments. No clinical sign of marginal discoloration, persistent pain and secondary caries was detected in any of the restorations. All InCeram Zirconia crowns survived during the 2-year period, although one nonvital tooth experienced root fracture coupled with the fracture of the veneering porcelain of the restoration. One Cercon Zirconia restoration fractured and was replaced. According to the CDA criteria, marginal integrity was rated excellent for InCeram Zirconia (73%) and Cercon Zirconia (80%) restorations, respectively. Slight color mismatch rate was higher for InCeram Zirconia restorations (66%) than Cercon Zirconia (26%) restorations. Plaque and gingival index scores were mostly zero and almost constant over time. Time-dependent changes in plaque and gingival index scores within and between groups were statistically similar (p>0.05). This clinical study demonstrates that single-tooth InCeram Zirconia and Cercon Zirconia crowns have comparable early clinical outcome, both seem as acceptable treatment modalities, and most importantly, all-ceramic alumina crowns strengthened by 25% zirconia can sufficiently withstand functional load in the posterior zone.

Fracture frequency of all-ceramic crowns during dynamic loading in a chewing simulator using different loading and luting protocols

OBJECTIVE

The purpose of this laboratory study was to compare the frequency of failures (complete fractures or partial cracks) of molar crowns made of two different all-ceramic materials during dynamic loading in a chewing simulator, as well as the fracture load when subjected to static loading, in relation to different dynamic loading and luting protocols.

METHODS

One hundred and forty-four molar crowns fabricated with IPS Empress or an experimental e.max Press material with high translucency (e.max Press Exp) were luted on CAD/CAM milled PMMA abutments (first lower molar, circular chamfer) either with Variolink or glass-ionomer cement (GIC). All crowns were loaded according to three different loading protocols (n=12 per group) and two force profiles (sinusoidal, rectangular) in a pneumatically driven chewing simulator with a steel stylus (Ø 8 mm) and they underwent simultaneous thermocycling (5 degrees C/55 degrees C). After each phase the crowns were evaluated with regard to fractures or cracks. After dynamic testing, the crowns that did not fail were subjected to compression loading until complete fracture in a universal testing machine (UTM). As control groups, unloaded crowns were also subjected to a UTM. Survival statistics with log-rank tests were applied for the results of the dynamic loading, while ANOVA with post hoc Tukey B was used for the fracture load results and two-way ANOVA was carried out for logarithmically transformed data. Weibull statistics were calculated for pooled fracture load data of the dynamically loaded and control groups.

RESULTS

In the 144 IPS Empress crowns, complete fractures were observed in 9 crowns and partial cracks in another 3 crowns. When the data was pooled, a statistically significant increase in fractures occurred when the sinusoidal force profile was applied compared to a rectangular force profile (log-rank, p<0.05). No fractures occurred in the e.max Press Exp crowns. The two-way ANOVA showed that the type of luting protocol used had the most significant effect on the fracture load of both materials. In conjunction with Empress, however, the luting material influenced the variability twice as much as in e.max Press Exp. There was no statistically significant difference in the fracture load of GIC-luted e.max Press Exp crowns and that of the Variolink luted Empress crowns. The force profile had a significant effect on the fracture load only of the Empress crowns but not of the e.max Press Exp crowns. Weibull statistics revealed a higher scattering of the data of dynamically loaded crowns compared to that of the control groups.

CONCLUSIONS

For testing all-ceramic materials, dynamic loading is indispensable to draw valid conclusions on clinical performance of all-ceramic molar crowns. A sinusoidal profile is advisable, while a gradual increase of the force amplitude does not significantly affect the results.

Wear of ceramic and antagonist—A systematic evaluation of influencing factors in vitro

OBJECTIVE

(1) To systematically review the existing literature on in vitro assessments of antagonist wear of ceramic materials; (2) To systematically evaluate possible influencing factors on material and antagonist wear of ceramic specimens.

METHODS

The database MEDLINE was searched with the terms "enamel," "wear" and "antagonist." The selected studies were analyzed with regard to wear parameters, type of antagonist and outcome. In the laboratory study, three ceramic materials were selected with different compositions and physical properties: IPS d.SIGN low-fusing metal ceramic, IPS Empress leucite ceramic, e.max Press lithium disilicate ceramic. These materials were subjected to the Ivoclar wear method (Willytec chewing simulator, 120,000cycles, 5kg weight) by systematically modifying the following variables which resulted in 36 tests with 8 specimens in each group: (1) configuration (flat, crown specimen), (2) surface treatment (polish, glaze), (3) type of antagonist (ceramic, two types of enamel stylus). Furthermore, the enamel styluses were cut to measure the enamel thickness and cusp width. Wear of both the material and the antagonist was quantified by scanning plaster replicas of the specimens with a laser scanner (etkon es1) and matching baseline and follow-up data with the Match 3D software (Willytec). The data were log-transformed to stabilize the variance and achieve near normality. To test the influence of specific test parameters, a four-way ANOVA with post hoc tests and Bonferroni correction was applied.

RESULTS

The systematic review revealed 20 in vitro studies in which a material and the antagonist wear of the same material was examined. However, the results were inconsistent mainly due to the fact that the test parameters differed widely. Most studies used prepared enamel from extracted molars as the antagonist and flat polished ceramic specimens. The test chamber was filled with water and some sort of sliding movement was integrated in the wear generating process. However, there was a huge variation in relation to the applied force, the used force actuator, the number of cycles, and the frequency of cycles per time as well as the number of specimens. The results of the systematic laboratory tests revealed that the following factors strongly influence the wear: configuration (more material wear of flat versus crown specimens), surface treatment (more antagonist wear of glazed versus polished specimens), the antagonist system (more material wear and less antagonist wear for ceramic stylus versus enamel stylus), and enamel thickness (less wear for thicker enamel). Material wear was not very much different between the materials. However, e.max Press generally caused more antagonist wear than the other two materials, which were quite similar. However, the main influencing factors did not yield consistent results for all the subgroups and there was a huge variability of results within the subgroups especially in those groups that used enamel as antagonist.

SIGNIFICANCE

As far as consistency and correlation with clinical studies is concerned, the set-up that consists of unprepared enamel of molar cusps against glazed crowns seems to be the most appropriate method to evaluate a ceramic material with regard to antagonist wear. However, due to the high variability of results large sample sizes are necessary to differentiate between materials, which calls the whole in vitro approach into question.

Clinical performance and wear characteristics of veneered lithia-disilicate-based ceramic crowns

OBJECTIVES

The objectives of this study were to characterize the clinical performance and wear characteristics of lithia-disilicate-based ceramic crowns.

METHODS

Thirty posterior crowns were made using the heat-pressing technique and lithia-disilicate-based core ceramic. Subjects were recalled annually. The quality of crowns and adjacent gingival tissues were examined using nine criteria for acceptability. All crowns were examined and ranked from 4 (Excellent) to 1 (Unacceptable) for each criterion. Impressions were made for replica models at each appointment. Wear characteristics of dental ceramic and enamel were obtained by comparing the surface of the original model with the follow-up model using a laser scanner.

RESULTS

Twenty-nine subjects returned for the 1-year recall examination. The maximum clenching force for the 30 subjects ranged from 125 to 815 N. All clinical criteria were ranked good to excellent at the 1-year recall exam and no fractures were observed. The mean occlusal wear volumes for the ceramic crowns after 1 year were 0.19 (0.065)mm3 for premolar sites and 0.34 (0.08)mm3 for molar sites. The mean occlusal wear volumes of opposing enamel after 1 year were 0.21 (0.06)mm3 for premolar teeth and 0.50 (0.22)mm3 for molar teeth. The mean occlusal wear volume of ceramic molar crowns was significantly lower than the volume of enamel wear of the opposing teeth (p<or=0.05).

CONCLUSIONS

The quality of the overall prostheses and the gingival tissues were acceptable after 1 year. The mean occlusal wear volume of ceramic molar crowns was significantly lower than the enamel wear volume of the opposing teeth.

The effect of tooth bleaching on the bond strength of an experimental primer to enamel

This study evaluated the effect of tooth bleaching on the microtensile bond strength (microTBS) of an experimental primer to enamel. Materials used were an experimental tooth manicure system (Shofu) composed of primer and light-cured flowable resin composite. Flattened enamel surfaces of bovine teeth were bleached with Nite White Excel (Discus Dental) or Hi-Lite (Shofu), with nonbleached teeth used as a control group. Each bleaching group was subdivided into three bonding modes. These were group A, application of primer for 3 s, followed by 5 s of air blowing; group B, application of primer for 10 s, followed by 5 s of air blowing; and group C, application of 20% phosphoric acid for 10 s, spraying with water for 5 s, and then air blowing for 5 s. The flowable resin paste was placed and polymerized after each enamel surface treatment. Using a low-speed diamond saw, the specimens were sectioned into beam-shaped samples with a cross-sectional area of approximately 1 mm(2) at the bonded interface. The samples were subjected to the microTBS test with a 1.0 mm/min crosshead speed. Data were statistically analyzed using two-way analysis of variance (ANOVA) followed by the Bonferroni/Dunn post-hoc test. The two-way ANOVA revealed significant differences in the effects of the bleaching systems and bonding mode, and significant differences were also found for the interaction between them (P < 0.01). There were no statistically significant differences in microTBS values among the specimens in groups A and B regardless of bleaching or nonbleaching (P > 0.05). In contrast, the microTBS value of group C without bleaching was significantly higher than that of all other experimental groups (P < 0.01).

Two-year clinical evaluation of lithia-disilicate-based all-ceramic crowns and fixed partial dentures

OBJECTIVES

The aim of this study was to evaluate the clinical performance of crowns and fixed partial dentures (FPDs) made with the Empress 2 system over a 2-year period.

METHODS

Twenty anterior or posterior all-ceramic (Empress 2) crowns and 20 anterior or posterior, three-unit fixed partial dentures were fabricated for 15 patients. Evaluations of the restorations were performed at baseline and once a year during the 2-year follow-up period. U.S. Public Health Service criteria were used to examine the marginal adaptation, color match, secondary caries and visible fractures in the restorations. Survival rate of the restorations were determined using Kaplan-Meier statistical analysis.

RESULTS

U.S. Public Health Service criteria showed 100% Alpha scores concerning recurrent caries for both crowns and FPDs. No crown fractures were observed during the 2-year follow-up, however, 10 (50%) catastrophic failures of FPDs occurred. Five (25%) failures occurred within the 1-year clinical period and the others (25%) within the second year.

SIGNIFICANCE

Single unit Empress 2 all-ceramic crowns exhibited a satisfactory clinical performance over 2-year period. Furthermore, the high fracture rate of Empress 2 FPDs limits the usage of Empress 2 for the fabrication of all-ceramic FPD.

Maxillary Single-tooth Replacement Utilizing a Novel Ceramic Restorative System: Results to 30 Months

This study reports on the first longitudinal results of an alumina (70%)-zirconia (30%) ceramic restorative system for implant-supported, single-tooth replacement in the anterior maxillary jaw. Eighteen patients (9 men, 9 women, mean age = 42.4 years) were treated with 22 implants placed into 19 extraction sockets and 3 residual ridges. Eight implants were immediately loaded with nonoccluding provisional prostheses. All implants were definitively loaded with fully occluding ceramic restorations after osseointegration and soft tissue maturation. Patients were monitored from 7 to 30 months (mean = 18.1 months) after loading. All implants osseointegrated and were successfully restored. One case of abutment screw loosening occurred because of patient parafunction (bruxing), and another patient reported chewing pain attributed to malocclusion. Both problems were successfully resolved without further incidence. Within the context of this study, single-tooth replacement in the anterior maxillary jaw was successfully achieved with alumina-zirconia ceramic single-tooth restorations with up to 30 months of clinical function.

Clinical performance of posterior metal-free polymer crowns with and without fiber reinforcement: one-year results of a randomised clinical trial

OBJECTIVES

The aim of this study was to evaluate the clinical performance of posterior, metal-free polymer crowns with and without a glass-fiber framework, in comparison to metal-ceramic crowns.

METHODS

After randomisation, 80 single crowns, manufactured from a newly designed polymer composite, were set in posterior teeth. Half of these received a glass-fiber framework, while half were prepared without any framework stabilisation. All polymer crowns were adhesively luted with resin cement. As the control group, 40 conventional metal-ceramic crowns were inserted with hybrid cement. Documentation included failures and other complications, as well as gingival/plaque status and aesthetic performance.

RESULTS

During the 12-month observation period, eight polymer crowns and three metal-ceramic crowns showed clinically relevant complications. The most frequent complications were root canal treatments (n=4) and decementation (n=4) of the crowns. A total of two crowns (one polymer crown with fiber network and one crown of the control group) had to be replaced. After 12 months, polymer crowns with glass-fiber framework exhibited significantly higher plaque accumulation (p=0.005) and gingival index (p=0.04) than metal-ceramic crowns, while no significant differences could be demonstrated for polymer crowns without fiber reinforcement. Postoperative sensibility and aesthetic performance did not differ significantly between the groups.

CONCLUSIONS

Within a 12-month observation period, posterior polymer crowns with and without glass-fiber framework demonstrated acceptable stability and aesthetic performance. Polymer crowns with fiber framework showed significant higher plaque accumulation and gingival index than metal-ceramic crowns.

Effect of silica coating and silanization on flexural and composite-resin bond strengths of zirconia posts: An in vitro study

STATEMENT OF PROBLEM

The bond strength of composite resin cores to the smooth surface of prefabricated zirconia-based ceramic posts is problematic because it might not be sufficient to ensure stability of the post-and-core system. It is also not clear whether any alteration of the post surface to provide additional mechanical or chemical retention would compromise flexural strength of the posts.

PURPOSE

This study tested the effect of a tribochemical treatment on the bond strength (BS) between zirconia-based ceramic posts and composite resin and on the flexural strength (FS) of the posts.

MATERIAL AND METHODS

For the BS test, 2 groups of specimens (n = 10) were prepared as follows: In the experimental (E) group, zirconia-based ceramic posts (Cosmopost), 21 mm long and 1.7 mm in diameter, were treated with a tribochemical silica coating and silanization system (Rocatec). For the control (C) group, zirconia-based ceramic posts were used as supplied by the manufacturer. For the 2 groups, posts were centered and vertically positioned in a metal mold, and composite resin (Tetric Ceram) was polymerized around the posts to form rings (6 mm diameter x 4 mm height). All specimens were positioned in a universal testing machine, and a load was applied axially on the protruding heads of posts in a shear push-out mode test until bond failure (MPa). Fracture mode was assessed as cohesive, cohesive/adhesive, or adhesive. Following this, the FS of the posts was measured in MPa using a 3-point bending test. Data were recorded and statistically analyzed using the Student t test for both tests (alpha = .01).

RESULTS

Mean fracture load values +/- SDs for the BS test were 28.1 +/- 2.3 MPa and 8.9 +/- 3.97 MPa for the E and C groups, respectively. The mean FS values were 1544.9 +/- 214.1 MPa and 844.8 +/- 50.8 MPa for the E and C groups, respectively. The tribochemically treated posts exhibited significantly higher values for both bond strength to composite resin and resistance to fracture when compared to posts in the control group (P < .001). Fracture analysis showed 100% cohesive/adhesive fractures for group E specimens and 100% adhesive fractures for group C specimens.

CONCLUSIONS

The use of a tribochemical silica coating process and silanization on zirconia-based ceramic posts increased both the bond strength to composite resin as well as the fracture strength of posts.

Periodontal response to all-ceramic crowns (IPS Empress) in general practice

OBJECTIVE

The purpose of this study was to investigate the periodontal response to the presence of all-ceramic crowns (IPS Empress) in general practice patients.

METHODS

The convenience sample included 82 IPS Empress crowns placed in 64 patients. These crowns had been in place for an average of 16.27 (SD 9.26) months and ranged from 6.2 to 48.87 months at the time of clinical examination. Periodontal health status (as determined by dental plaque, gingival health status, periodontal pockets) was assessed around all crowned teeth and around matched contralateral teeth by one calibrated examiner. Periodontal indices utilized included the Plaque Index (PI), Gingival Index (GI) and pocket depth (PD) with calibrated probes graduated in millimetres. Plaque, gingival and PD values for crowned teeth were compared with those for control teeth using Wilcoxon signed-rank test for each clinical parameters. Chi-square was used to test the significance of the difference in their distribution between crowns and control teeth.

RESULTS

Statistically, PI (0.35), GI (0.41) and mean PD scores (1.42) of IPS Empress crowned teeth compared less favourably with scores of the control teeth (0.27, 0.23 and 0.86 respectively).

CONCLUSION

Teeth with IPS Empress crowns had poorer periodontal health and more clinically evident plaque than uncrowned teeth.

Fracture resistance of endodontically treated maxillary premolars restored with CAD/CAM ceramic inlays

STATEMENT OF PROBLEM

Endodontically treated posterior teeth are more likely to fracture compared to posterior teeth with vital pulps. Reinforcement with an extracoronal restoration that covers the cusps is the most commonly recommended method for reducing the risk of fracture. It is not known whether bonded intracoronal restorations without cuspal coverage will reduce the risk of fracture.

PURPOSE

The aim of this in vitro study was to investigate whether reinforcement of endodontically treated premolars with MOD preparations could be achieved by insertion of bonded CAD/CAM ceramic inlays.

MATERIAL AND METHODS

Forty-five extracted maxillary premolars were equally distributed among 3 groups (END, CER, CTR). In group END (n=15), root canals were enlarged with a rotary NiTi system and obturated with heat-softened gutta-percha around a plastic carrier (Thermafil). After filling of the endodontic access cavities with autopolymerizing composite resin (Luxacore), standardized MOD cavity preparations were made and CAD/CAM ceramic inlays (CEREC) were fabricated and then bonded to the teeth with composite resin (Tetric) and an adhesive system (Syntac Classic). In group CER (n=15), teeth without endodontic treatment were restored with bonded inlays (CEREC). Sound premolars served as controls (group CTR, n=15). Teeth were then thermal cycled (1445 cycles, dwell time: 30 seconds, 5 degrees /55 degrees C). An eccentric load was applied on the buccal incline of the palatal cusp in a universal testing machine until cusp fracture (N). Fracture load was evaluated with the Mann-Whitney test, and type of fracture, with a chi-square analysis (alpha=.05). The type of fracture was determined by visual inspection: type I - supragingival fracture within the palatal cusp; type II - fracture below cemento-enamel junction of palatal cusp; and type III - fracture of palatal cusp and central portion of the tooth exposing the root canal cavity.

RESULTS

No significant difference was found among the 3 groups with respect to load required for fracture. Mean fracture load +/- SD was recorded as follows: 291.6 +/- 113.7 N for group END, 363.2 +/- 140.3 N for group CER, and 296.5 +/- 170.5 N for group CTR. Regarding fracture modes, significantly more teeth from group END exhibited fractures of type III and II compared with control specimens.

CONCLUSION

Teeth restored with bonded CAD/CAM ceramic inlays (CEREC) fractured with a significantly higher number of severe fractures compared to the control group.