Effect of Dentin Bonding Agents, Various Resin Composites and Curing Modes on Bond Strength to Human Dentin

This study investigated the influence of several dentin bonding agents, resin composites and curing modes on push-out bond strength to human dentin. 360 extracted caries-free third molars were prepared, cut into slices, embedded in epoxy resin and perforated centrally. One half of the specimens (180) were treated by using one-step adhesive systems and the other half (180) with multi-step adhesive systems. Subsequently, the cavities were filled with either universal, flowable or bulk-fill resin composite according to the manufactures’ product line and cured with either turbo or soft start program. After storage the push-out test was performed. The data was analyzed using Kolmogorov-Smirnov, three- and one-way ANOVA followed by the Scheffé post-hoc test, unpaired two-sample t-test (p < 0.05). The strongest influence on push-out bond strength was exerted by the resin composite type (partial eta squared η_P² = 0.505, p < 0.001), followed by the adhesive system (η_P² = 0.138, p < 0.001), while the choice of the curing intensity was not significant (p = 0.465). The effect of the binary or ternary combinations of the three parameters was significant for the combinations resin composite type coupled adhesive system (η_P² = 0.054, p < 0.001), only. The flowable resin composites showed predominantly mixed, while the universal and bulk-fill resin composite showed adhesive failure types. Cohesive failure types were not observed in any group. Multi-step adhesive systems are preferable to one-step adhesive systems due to their higher bond strength to dentin. Flowable resin composites showed the highest bond strength and should become more important as restoration material especially in cavity lining. The use of a soft start modus for polymerization of resin composites does not enhance the bond strength to dentin.

Dental treatment under general anesthesia in adults with special needs at the University Hospital of Dental Prosthetics and Restorative Dentistry of Innsbruck, Austria: a retrospective study of 12 years

OBJECTIVES

Special needs patients are prone to insufficient oral care and subsequent caries or periodontitis. The aim of this retrospective study was the assessment of demand for restorative therapy and tooth extractions under general anesthesia in adults with intellectual and/or physical disablement (IPD) or psychiatric disorders (PDs) with inherent dentist phobia at the University Hospital of Innsbruck with regard to demographic factors.

MATERIALS AND METHODS

A total of 444 consecutive cases of scheduled dental general anesthesia (DGA) in adults from 2003 to 2014 were included. From patient files, demographic data, the presence of either IPD or a PD, attested by a mandatory certificate, and restorative therapy and tooth extractions performed under DGA were obtained. Data analysis was carried out by means of descriptive and comparative statistics.

RESULTS

Four hundred two cases (mean age 37.5 ± 13.87 years) assigned to 283 individuals with IPD and 42 cases (mean age 36.09 ± 13.03 years) assigned to 39 individuals with PDs arose in the observed period. Patients with PDs required significantly more restorations (in 7.98 ± 5.4 versus 5.34 ± 4.41 teeth; p = 0.002; Mann-Whitney U test) and extractions (of 4.86 ± 4.51 versus 2.6 ± 3.96 teeth; p < 0.001; Mann-Whitney U test) than patients with IPD.

CONCLUSIONS

Demand for dental treatment was high in the collective of special needs patients. Oral health status was worse in patients with PDs than in patients suffering IPD.

CLINICAL RELEVANCE

While in patients with severe disablement, DGA presents the only treatment option, specific preventive programs should be implemented for patients with minor disablement or dentist phobia. In these patients, alternative approaches should be promoted.

Zirconia Primers Improve the Shear Bond Strength of Dental Zirconia

PURPOSE

Various resin cements and priming agents are available for adhesive luting of zirconia restorations. The purpose of this study was to investigate how cement type and priming protocol affect the shear bond strength on zirconia ceramics.

MATERIALS AND METHODS

Yttria-stabilized tetragonal zirconia polycrystalline ceramic cylinders were bonded to flat zirconia ceramic surfaces using 7 commercially available resin cements. Ten specimens of each cement group were pretreated with a universal primer, and 10 specimens per group were bonded without pretreatment. In addition, 10 specimens per group were pretreated with system-specific zirconia primers, which were available for 3 cements. Altogether, 170 bonded specimens were water-stored, thermal-cycled, and then submitted to shear bond strength tests. The shear bond strength and the fracture types were documented. Differences in shear bond strengths were assessed using 2-way ANOVA with post-hoc test (α = 0.05). A point-biserial correlation was run between the fracture patterns and the shear bond strengths.

RESULTS

The mean shear bond strengths of cements in the unprimed group showed large variations between 2.52 ± 3.01 (mean ± SD) MPa and 33.15 ± 7.35 MPa. Pretreating the specimens with a universal primer improved the shear bond strengths significantly in all groups (p < 0.05) with a range of 21.80 ± 12.51 to 57.20 ± 11.40 MPa. The system-specific primers also improved the shear bond strength significantly, compared to the unprimed group (p < 0.01); however, only one system-specific primer achieved a shear bond strength superior to the universal primer (p < 0.01). There was also a statistical correlation between the fracture type and the shear bond strength (p < 0.0005), with cohesively fractured specimens showing higher shear bond strengths (37.24 ± 19.87 MPa) than adhesively fractured specimens (23.10 ± 17.65 MPa) (p < 0.001).

CONCLUSION

Using universal primer can enhance the maximal shear bond strength of zirconia.

Testing the Clinical Applicability of Resin Infiltration of Developmental Enamel Hypomineralization Lesions Using an In Vitro Model

Aim

The aim of this study is to investigate the penetration abilities of a commercially available low-viscosity resin infiltrant into developmentally hypomineralized teeth in vitro.

Materials and methods

Four extracted third molars of a 17-year-old patient with signs of developmental enamel hypomineralization (discoloration, increased opacity, and surface roughness) were infiltrated with a low-viscosity resin mixed with a fluorescent dye, according to the manufacturer's standard protocol. Four extracted molars with sound enamel or showing only initial fissure caries were used as a control group. Specimens were embedded in polymethylmethacrylate, and grindings were prepared. High-resolution projectional radiography of the grindings was performed, and, for one specimen, quantitative micro-computed tomography was used to measure hydroxyapatite density in enamel and dentin lesions. After decalcification, the grindings were examined by reflected bright-field microscopy, wide-field fluorescence microscopy, and confocal laser scanning microscopy. Fluorescence micrographs were superimposed on the radiographs and analyzed correlatively.

Results

The pattern of hypo-/demineralization in enamel and dentin in developmentally hypomineralized teeth showed a good congruence with the pattern of resin infiltration. Cavitations and dentin tubules up to a depth of 2 mm beyond cavitations were filled by the infiltrant. In control teeth, the penetration of the infiltrant was limited to decalcified enamel areas (initial fissure caries).

Conclusions

In vitro infiltration of developmentally hypomineralized enamel was successful.

Clinical significance

Resin infiltration might be considered as a routine procedure in the treatment of developmentally hypomineralized teeth. Further investigations with higher sample sizes, different degrees of severity, different stages of lesion extension, and modified treatment protocols are necessary.

How to cite this article

Schnabl D, Dudasne-Orosz V, et al. Testing the Clinical Applicability of Resin Infiltration of Developmental Enamel Hypomineralization Lesions Using an In Vitro Model. Int J Clin Pediatr Dent 2019;12(2):126-132.

Novel Molecular Spectroscopic Multimethod Approach for Monitoring Water Absorption/Desorption Kinetics of CAD/CAM Poly(Methyl Methacrylate) Prosthodontics

Water absorbed to poly(methyl methacrylate) (PMMA)-based CAD/CAM (computer-assisted design/computer-assisted manufacturing) prosthodontics can alter their properties including hardness and stability. In the present contribution, water absorption and desorption kinetics under defined experimental conditions were monitored employing several supplementary and advanced Fourier transform infrared (FT-IR) spectroscopic techniques in combination with multivariate analysis (MVA). In this synergistic vibrational spectroscopic multimethod approach, first a novel near-infrared (NIR) diffuse fiber optic probe reflection spectroscopic method was established for time-resolved analysis of water uptake within seven days under controlled conditions. Near-infrared water absorbance spectra in a wavenumber range between 5288-5100 cm^-1 (combination band) and 5424-5352 cm^-1 (second overtone) were used establishing corresponding calibration and validation models to quantify the amount of water in the milligram range. Therefore, 14 well-defined samples exposed to prior optimized experimental conditions were taken into consideration. The average daily water uptake conducting reference analysis was calculated as 22 mg/day for one week. Additionally, in this study for the first time NIR two-dimensional correlation spectroscopy (2D-COS) was conducted to monitor and interpret the spectral dynamics of water absorption on the prosthodontics in a wavenumber range of 5100-5300 cm^-1. For sensitive time-resolved recording of water desorption, a recently developed high-temperature, high-pressure FT-IR reaction cell with water-free ultra-dry in situ and operando operation was applied. The reaction cell, as well as the sample holder, was fully made of quartz glass, with no hot metal or ceramic parts in the vicinity of the high temperature zone. Applying a temperature gradient in the range of 25-150 ℃, mid-infrared (MIR) 2D-COS was successfully conducted to get insights into the dynamic behavior of O-H (1400-1800 cm^-1) absorption bands with increasing temperature over time and the release of CO₂ (2450 cm^-1) from the polymers. In addition, an ATR FT-IR imaging setup was optimized in order to investigate the surface homogeneity of the PMMA-based resins with a spatial resolution to 2 µm. From this vibrational spectroscopic multimethod approach and the collection of several analytical data, conclusions were drawn as to which degree the surface structure and/or its porosity have an impact onto the amount of water absorption.

Do CAD/CAM dentures really release less monomer than conventional dentures?

Objectives

Computer-aided design (CAD)/computer-aided manufacturing (CAM) dentures are assumed to have more favourable material properties than conventionally fabricated dentures, among them a lower methacrylate monomer release. The aim of this study was to test this hypothesis.

Materials and methods

CAD/CAM dentures were generated from ten different master casts by using four different CAD/CAM systems. Conventional, heat-polymerised dentures served as control group. Denture weight and volume were measured; the density was calculated, and the denture surface area was assessed digitally. The monomer release after 7 days of water storage was measured by high-performance liquid chromatography.

Results

Whole You Nexteeth and Wieland Digital Dentures had significantly lower mean volume and weight than conventional dentures. Baltic Denture System and Whole You Nexteeth had a significantly increased density. Baltic Denture System had a significantly smaller surface area. None of the CAD/CAM dentures released significantly less monomer than the control group.

Conclusions

All tested dentures released very low amounts of methacrylate monomer, but not significantly less than conventional dentures. A statistically significant difference might nevertheless exist in comparison to other, less recommendable denture base materials, such as the frequently used autopolymerising resins.

Clinical relevance

CAD/CAM denture fabrication has numerous advantages. It enables the fabrication of dentures with lower resin volume and lower denture weight. Both could increase the patient comfort. Dentures with higher density might exhibit more favourable mechanical properties. The hypothesis that CAD/CAM dentures release less monomer than conventional dentures could, however, not be verified.

Is Cognitive Status Related to Oral Hygiene Level and Appropriate for Determining Need for Oral Hygiene Assistance?

BACKGROUND

With declining general health, the maintenance of oral health becomes increasingly difficult. Unfortunately, health care resources are limited. An assessment tool for detecting a patient's need for oral health care assistance would promote its adequate distribution. The aim of this study is to evaluate if the Shulman clock-drawing test score is a suitable assessment tool for determining the need for oral hygiene assistance.

METHODS

Data collected from recent dental checkups of 126 inhabitants of five Austrian residential care facilities were analyzed. The Shulman clock-drawing test score was used as a measure for cognitive abilities and related to tooth and denture hygiene indices, which were assessed using the approximal space plaque index (API) and the denture plaque index (DPI).

RESULTS

Shulman score values were distributed almost evenly in the study population. The mean API was 83.6% (SD 20.2%) for the maxilla and 94.9% (SD 15.6%) for the mandible. The mean DPI was 43.9% (SD 31.4%). Cognitive impairment was not statistically related to the dental or denture hygiene index.

CONCLUSIONS

A high Shulman clock-drawing test score indicates the need for oral hygiene assistance, but it is not suitable as a single tool to assess this need. Patients with other disabilities might equally qualify for assistance. Dentures, however, can be cleaned quickly and efficiently independently of patient compliance; therefore, cleaning the patients' dentures should be part of nursing personnel's daily care routine for every patient.

Shortcomings of prosthodontic rehabilitation of patients living in long-term care facilities

Removable dentures are a non-invasive, cost-effective prosthodontic solution for the reduced dentition. Their intended purpose is the rehabilitation of harmonious oral function and aesthetics on a long-term basis. The prevalence of removable dentures among patients of advanced age is high and the quality of the dentures is often poor. The aim of this study was to find the most important shortcomings of removable dentures and address the main targets for improving the quality of prosthodontic rehabilitation. The records from dental check-ups in Austrian residential homes were analysed retrospectively. Dental anamnesis questionnaires and data from the clinical examinations of 105 denture wearers were analysed. The functional condition and retention of 192 dentures had been assessed, as well as the impact of the dentures on the intra-oral tissues. Insufficient denture retention was very common, particularly in the lower jaw (56·0%). Problems with the masticatory function were reported by 26.7% of the denture wearers, 11·4% were dissatisfied with the denture aesthetics, and 4·8% had difficulties with phonetics. Traumatic ulcers were found in 18·1%. Cracks, broken pieces (6·3%) or missing denture teeth (2·1%) were rare. It may be assumed that the findings of the present study also apply to a great percentage of community-dwelling seniors. The most important issues in prosthodontic rehabilitation with removable dentures are denture retention and masticatory function. Regular dental check-ups, denture adjustment and, when necessary, relining can maintain the primary denture quality and prevent damages of the oral tissues caused by ill-fitting dentures.

Longevity of silicate ceramic restorations

The demand for esthetic restorations has resulted in an increased use of dental ceramics as a biocompatible and functionally sufficient alternative to conventional restorative materials. Silicate ceramic restorations are widely used for veneers, inlays, onlays, and crowns in dentistry. Long-term data are of crucial importance to optimize clinical practice. The purpose of the present article is to summarize data of the Innsbruck ceramic evaluation up to 261 months with the focus on longevity and failure characteristics.

Instant dentin hypersensitivity relief of a single topical application of an in-office desensitizing paste containing 8% arginine and calcium carbonate: a split-mouth, randomized-controlled study

OBJECTIVE

The aim of this study was to evaluate the clinical efficacy of an in-office desensitizing paste containing 8% arginine and calcium carbonate relative to calcium carbonate alone in the reduction of dentin hypersensitivity in a randomized, double-blind, split-mouth clinical trial.

MATERIALS AND METHODS

Sixty teeth (30 subjects) with an air blast hypersensitivity score of 2 or 3 (Schiff Cold Air Sensitivity Scale) were randomly assigned to one of two treatment groups: (1) test paste containing 8% arginine and calcium carbonate (elmex sensitive professional desensitizing paste) and (2) control paste: paris white (calcium carbonate). Tactile and air blast dentin hypersensitivity examinations were performed at baseline, immediately after paste application and 4 and 12 weeks later.

RESULTS

A statistically significant difference in air blast (p = 0.001) and tactile (p = 0.047) hypersensitivity reduction over time was observed between the two therapy modes. After 12-weeks, statistically significant differences were indicated between the test and control group with respect to baseline-adjusted mean tactile (41.94%; p = 0.038) and air blast hypersensitivity scores (46.5%; p = 0.017).

CONCLUSIONS

The tested in-office desensitizing paste containing 8.0% arginine and calcium carbonate provides significantly greater hypersensitivity relief compared to calcium carbonate alone.

Comparison of two different veneer preparation designs in vital teeth

OBJECTIVE

To compare the clinical performance of two different veneer preparation designs (overlap and nonoverlap) on anterior veneer restorations in vital teeth in a retrospective clinical study.

METHOD AND MATERIALS

In this study, 292 anterior all-ceramic veneer restorations in vital teeth were clinically examined in 74 patients. The preparation designs were categorized by the amount of tooth reduction on the final casts, with 245 in the overlap and 47 nonoverlap group.

RESULTS

After a mean ± SD observation time of 124.25 ± 60.61 months, 20 failures occurred. All failures occurred in the overlap design. Restorations with nonoverlap preparation designs showed significantly fewer failures than restorations with overlap preparation design (P = .018, log-rank).

CONCLUSION

Based on the findings of this study, whenever feasible, a preparation design without incisal overlap is recommended, especially in vital teeth..

Clinical performance of all-ceramic inlay and onlay restorations in posterior teeth

PURPOSE

The aim of this clinical retrospective study was to evaluate the clinical performance and longevity of glass-ceramic onlays and inlays in stress-bearing posterior teeth.

MATERIALS AND METHOD

Five hundred forty-seven posterior teeth in the maxillae and mandibles of 120 patients (46 males, 74 females) were restored with 213 onlays, 38 single-surface inlays, 141 two-surface inlays, and 155 three-surface inlays between 1987 and 2009 at Innsbruck Medical University, Innsbruck, Austria, by two experienced dentists. The restoration sample included 9 (1.6%) nonvital teeth and 40 (33%) patients diagnosed with bruxism. The study population was examined clinically during regularly scheduled maintenance appointments. The risk of failure was determined using Kaplan-Meier survival analyses.

RESULTS

The mean observation periods for onlays and all inlays were 80 ± 34 months and 111 ± 63 months, respectively. Twenty-seven failures were recorded. The estimated survival rates for onlays and all inlays after 5, 10, and 12 years were 98.9% and 98.9%, 92.4% and 96.8%, and 92.4% and 89.6%, respectively. Nonvital teeth showed a significantly higher risk of failure (P < .001). There was no greater risk of failure associated with existing parafunction (bruxism) (P = .408). Restorations on premolars survived longer in the first 15 years than restorations on molars, but no statistical significance was found (P = .913).

CONCLUSION

Glass-ceramic onlays and inlays were demonstrated to be successful in posterior teeth; however, at this time, their efficacy is inferior to that of cast gold restorations.

Surgical resection technique of a fused supernumerary lateral incisor: a clinical report and review of the literature

This case report presents the surgical and restorative management of a fused supernumerary left lateral incisor. The diagnosis was confirmed using conventional radiographs and CT. The case report discusses the value of CT for evaluation of the root relationships and describes the varied morphology associated with supernumerary incisors, the surgical resection technique, partial pulpotomy, and restoration with composite resin after mechanical exposure of the remaining tooth's pulp.

Impact of a prior medical degree on students' dental school performance in Innsbruck, Austria

The purpose of this study was to identify the performance differences between two groups of Austrian dental students (one with a prior medical degree and one without a medical degree) during their dental school training and final dental licensure examination. A specific aim was to determine if having a medical degree is a predictive factor for dental students' scores on the Austrian Dental Admission Test (Austrian DAT), performance in the dental clinic, and scores on final exam. The study consisted of a retrospective analysis of 122 students (thirty-nine with a medical degree and eighty-three without a medical degree) who were enrolled in the Dental Clinic at Innsbruck Medical University, Innsbruck, Austria, between 2001 and 2006. Three performance categories were considered: Austrian DAT results, clinical performance after the first clinical year in dental school, and performance on the final dental licensure examination. Information on students' age, gender, and previous medical degree was collected from official records. Analyses with student's t-test and Pearson's chi-square test revealed that the students with a medical degree had significantly higher Austrian DAT total test scores, grade point averages after the first clinical year, and scores on the final exam. Additionally, those students had significantly better performance on the final exam in prosthodontics and oral and maxillofacial surgery. The linear regression analysis showed that a medical degree had an independent effect on average scores on the final exam, age, and Austrian DAT test scores, while gender showed no statistically significant effect. Overall, the study found that dental students with a prior medical degree had significantly higher Austrian DAT total test scores and performed significantly better in the first clinical year and on the final exam than those without a prior medical degree.

Clinical long-term evaluation and failure characteristics of 1,335 all-ceramic restorations

PURPOSE

The aim of this clinical retrospective study was to evaluate the clinical quality, estimated survival rate, and failure analysis of different all-ceramic restorations in a long-term analysis of up to 20 years.

MATERIALS AND METHODS

Different all-ceramic restorations (crowns [n = 470], veneers [n = 318], onlays [n = 213], and inlays ]n = 334[) were placed in 302 patients (120 men, 182 women) between 1987 and 2009 at Medical University Innsbruck, Innsbruck, Austria. Clinical examination was performed during patients' regularly scheduled maintenance appointments. Esthetic match, porcelain surface, marginal discoloration, and integrity were evaluated following modified California Dental Association/Ryge criteria. Number of restoration failures and reasons for failure were recorded. The study population included 106 (35.1%) individuals diagnosed with bruxism. The success rate was determined using Kaplan-Meier survival analysis.

RESULTS

The mean observation time was 102 ± 60 months. Ninety-five failures were recorded. The main reason for failure was fracture of the ceramic (33.68%). The estimated survival rate was 97.3% after 5 years, 93.5% at 10 years, and 78.5% at 20 years. Nonvital teeth showed a significantly higher risk of failure (P < .0001). There was a 2.3-times greater risk of failure associated with existing parafunction (bruxism, P = .0045). Cementation using Variolink showed significantly fewer failures than Optec Cement (P = .0217) and Dual Cement (P = .0099). No significant differences were found for type of restoration and distribution in the mouth.

CONCLUSION

All-ceramic restorations offer a predictable and successful restoration with an estimated survival probability of 93.5% over 10 years. Significantly increased failure rates are associated with bruxism, nonvital teeth, and specific cementation agents.

Clinical performance of porcelain laminate veneers for up to 20 years

PURPOSE

The aim of this clinical retrospective study was to evaluate the clinical quality, success rate, and estimated survival rate of anterior veneers made of silicate glass-ceramic in a long-term analysis of up to 20 years.

MATERIALS AND METHODS

Anterior teeth in the maxillae and mandibles of 84 patients (38 men, 46 women) were restored with 318 porcelain veneer restorations between 1987 and 2009 at the Medical University Innsbruck, Innsbruck, Austria. Clinical examination was performed during patients' regularly scheduled maintenance appointments. Esthetic match, porcelain surface, marginal discoloration, and integrity were evaluated following modified California Dental Association/Ryge criteria. Veneer failures and reasons for failure were recorded. The study population included 42 (50.0%) patients diagnosed with bruxism and 23 (27.38%) smokers. The success rate was determined using Kaplan-Meier survival analysis.

RESULTS

The mean observation time was 118 ± 63 months. Twenty-nine failures (absolute: 82.76%, relative: 17.24%) were recorded. The main reason for failure was fracture of the ceramic (44.83%). The estimated survival rate was 94.4% after 5 years, 93.5% at 10 years, and 82.93% at 20 years. Nonvital teeth showed a significantly higher failure risk (P = .0012). There was a 7.7-times greater risk of failure associated with existing parafunction (bruxism, P = .0004). Marginal discoloration was significantly greater in smokers (P ⋜ .01).

CONCLUSION

Porcelain laminate veneers offer a predictable and successful restoration with an estimated survival probability of 93.5% over 10 years. Significantly increased failure rates were associated with bruxism and nonvital teeth, and marginal discoloration was worse in patients who smoked.

Impact of a novel dental school admission test on student performance at Innsbruck Medical University, Austria

Since the year 2000, prospective dental students at Innsbruck Medical University, Innsbruck, Austria, have undergone both theoretical and practical preadmission exams, called the Dental Admission Test (DAT). The aim of this investigation was to assess the suitability and outcome of this selection practice. Five classes from 2001 to 2005 (N=97; forty-three female, fifty-four male) were retrospectively reviewed. DAT results were compared with student performance, gender, ability to graduate on time, and dropout rates. Furthermore, the influence of a previous medical degree was evaluated. The t-test was used to analyze correlations between the results of the DAT and the following: gender, students who graduated on time, and students who had previously completed a medical degree. Pearson's correlation coefficient (r) was applied to analyze correlations among test scores, age, and students' performance during the first clinical year. Students graduating on time were noted to have significantly better DAT results; students with a previous medical degree showed significantly better grades during their first clinical year. The difference between the performance of male and female applicants on the DAT was not significant. Correlation was found between DAT results and dental school performance (r=-0.462). We conclude that the DAT may reduce dropout rates by excluding applicants unlikely to be successful in practical courses and that DAT scores are a reliable tool to predict student performance during the first clinical year of dental school in Innsbruck.

Quality of impressions after use of the Magic FoamCord gingival retraction system--a clinical study of 269 abutment teeth

PURPOSE

The aim of this study was to evaluate a new gingival retraction system relative to clinical success for fixed dental restorations under various clinical conditions.

MATERIALS AND METHODS

Two hundred sixty-nine abutment teeth were evaluated. The ability to displace gingiva was indirectly measured by the quality of the final impression. Preparation finish line with respect to the crest of the marginal gingiva (Level I through III) and type of preparation finish line (ie, shoulder or beveled) were recorded. The reproduction of the preparation finish line and an absence of bubbles or voids (Criteria I through III) were assesed. The results were compared with an established retraction system using one retraction cord.

RESULTS

Of the 269 impressions evaluated, 93.7% were clinically acceptable and showed complete reproduction of the preparation finish line; 17.5% showed small defects but the impressions were still rated clinically acceptable and categorized as Criteria II. Only 6.3% of the impressions were unacceptable and categorized as Criteria III. A significant influence on the quality of the impressions was found when the preparation finish line was more than 2 mm subgingivally for shoulder (P < .004) as well as beveled preparations (P < .004). Nearly twice as many impressions were rated Criteria III when using the Magic FoamCord (MFC) system compared to impressions done with the single cord retraction technique.

CONCLUSIONS

In cases of epigingival and subgingival (< 2 mm) preparation margins, MFC was a less traumatic alternative method of gingival retraction. However, when there were deep subgingival margins and a beveled preparation, the material was less effective than the single cord retraction technique.

Quality of impressions using hydrophilic polyvinyl siloxane in a clinical study of 249 patients

PURPOSE

This study aimed to evaluate the clinical success of a hydrophilic polyvinyl siloxane impression material for fixed dental restorations under various clinical conditions.

MATERIALS AND METHODS

A total of 1,466 preparations for fixed restorations in maxillary and mandibular anterior and posterior teeth were evaluated. The study contained inlay, onlay, crown, veneer, post, and adhesive-wing preparations and implants for gold, porcelain-fused-to-metal, and ceramic restorations. The preparation finish line relative to the crest of the marginal gingiva, type of restoration, and position of the teeth were recorded. Three categories were established to rate impression quality: perfect impressions, with an absence of any voids or bubbles and perfect reproduction of the preparation finish line, were rated Criteria I; acceptable impressions, with minimal defects (< or = 2 mm) not involving the preparation finish line, were rated Criteria II; and unacceptable impressions, with larger voids or bubbles (> 2 mm) or defects involving the preparation finish line, were rated Criteria III.

RESULTS

Overall, 96.86% of the final impressions were clinically acceptable, 89.43% of which were rated Criteria I and 7.43% of which were rated Criteria II. Only 3.14% of the impressions were unacceptable and rated Criteria III. A significant influence on impression quality was found when the preparation finish line was more than 2 mm subgingival (P < .004), as well as when a beveled preparation was used (P < .004). The position of the teeth (P > .404) had no significant effect.

CONCLUSION

Surface-activated polyvinyl siloxane impression material offers high predictability to avoid bubbles and voids in the final impression.

Porcelain laminate veneers. A retrospective evaluation after 1 to 10 years of service: Part II--Clinical results

PURPOSE

The objective of this study was to evaluate the clinical quality of 191 porcelain laminate veneers and to explore the gingival response in a long-term survey.

MATERIALS AND METHODS

The clinical examination was made by two calibrated examiners following modified California Dental Association/Ryge criteria. In addition, margin index, papillary bleeding index, sulcus probing depth, and increase in gingival recession were recorded. Two age groups were formed to evaluate the influence of wearing time upon the clinical results. The results were statistically evaluated using the Kaplan-Meier survival estimation method, Chi-squared test, and Kruskal-Wallis test.

RESULTS

A failure rate of 4% was found. Six of the total of seven failures were seen when veneers were partially bonded to dentin. Marginal integrity was acceptable in 99% and was rated as excellent in 63%. Superficial marginal discoloration was present in 17%. Slight marginal recession was detected in 31%, and bleeding on probing was found in 25%.

CONCLUSION

Porcelain laminate veneers offer a predictable and successful treatment modality that preserves a maximum of sound tooth structure. An increased risk of failure is present only when veneers are partially bonded to dentin. The estimated survival probability over a period of 10 years is 91%.

Porcelain laminate veneers. A retrospective evaluation after 1 to 10 years of service: Part I--Clinical procedure

PURPOSE

Currently available clinical studies on porcelain laminate veneers seem to support their use as a standard treatment method in modern restorative dentistry. The purpose of this study, which comprises 3 parts, was to evaluate the clinical applicability and the survival probability of porcelain laminate veneers for an observation period of up to 10 years. This first part of the study describes the step-by-step clinical procedure.

MATERIALS AND METHODS

The reasons for provision of porcelain laminate veneers were mainly for the treatment of worn anterior teeth, surface enamel defects, intrinsic discolorations, and hypoplasia. As the treatment time for try-in, cementation, and finishing of veneers differs significantly from that needed for conventional restorations, the total time required for veneer treatment was evaluated.

RESULTS

A total of 205 porcelain laminate veneers, 117 in the maxilla and 88 in the mandible, was placed in 72 patients (43 females and 29 males). Mean cementation time was 38.7 minutes, which increased significantly to 43.9 minutes if single discolored teeth were being restored. Clinical experience and a familiarity with the strict step-by-step procedure followed throughout the study reduced the mean treatment time from 40.8 minutes during the first 5 years to 36.7 minutes in the following years.

CONCLUSION

The porcelain laminate veneer concept provides excellent esthetic and conservative restorations, but it should be stated that the cementation and finishing procedure is highly time consuming.

Bonding porcelain laminate veneer provisional restorations: An experimental study

STATEMENT OF PROBLEM

Minimal tooth preparation is required for porcelain laminate veneers, but an interim restoration is anticipated by patients to protect their teeth against thermal insult, chemical irritation, and to provide esthetics. Cement remaining after the removal of the provisional restoration can impair the etching quality of the tooth surface and the fit and final bonding of the porcelain laminate veneer.

PURPOSE

This in vitro study inspected the tooth surface for remaining debris from cement after removal of a provisional restoration.

MATERIAL AND METHODS

Seventy-two extracted natural anterior teeth were prepared for porcelain laminate veneers. For half of the teeth, the smear layer was removed before luting provisional restorations. Veneer provisional restorations were fabricated and luted to teeth with 3 bonding methods: temporary eugenol-free cement, spot etching combined with dual-curing luting cement, and polyurethane adhesive combined with dual-curing luting cement. After removal of provisional restorations 1 week later, the tooth surface was examined for residual luting material with an SEM.

RESULTS

Traces of cement debris were found on provisionally prepared teeth for all 3 material methods.

CONCLUSION

The use of polyurethane adhesive combined with the dual-curing cement revealed significantly less teeth with debris than the other methods. This difference was less distinct when the smear layer was removed.

A new approach in restorative treatment of external root resorption. A case report

This case report describes the treatment of an external root resorption with extensive loss of tooth structure and bone at the labial surface of an upper left central incisor. The area of bone loss and root resorption was surgically exposed and an impression was taken using curing silicone. An individual ceramic insert was fabricated, allowing endodontic retreatment through an artificial root canal. The insert was incorporated using a dentin bonding system and a dual curing luting composite. Following endodontic retreatment and internal bleaching, a ceramic veneer was bonded to the tooth to obtain good esthetics and to improve stability. Twenty months after surgical treatment no further root resorption could be detected radiographically. A shallow residual pocket but no bleeding on probing was found.

[The biomechanics of space closure and its dependence on the periodontal attachment]

The biomechanics of space closure in adult patients with loss of periodontal attachment is described. In order to achieve an even force distribution in the periodontium, force was reduced and the moment to force relationship was increased. beta-TMA-T Loops of 0.016 inch x 0.022 inch and 0.017 inch x 0.025 inch cross sections were investigated. With an automatic testing device force and moment values were determined.

[Transverse dimensional stability of whole jaw models of different materials]

Whole jaw models of 6 different materials were examined for their transverse dimensional stability. Under standardized conditions impressions were made of a mandibular phantom with 4 stylized crown stumps using the double mix-spray technique with additively cross-linking silicon. Of these, test models were prepared and measured using the original model as reference. The high-strength dental stones Die Keen and Fuji Rock showed the highest dimensional stability. On account of their shrinkage during polymerization, the epoxy resins Blue Star E and Metapox as well as Blue Star P, a polyurethane, were found to have smaller transverse stump interspaces. Data for electroplated silver models were between those for dental stones and plastic materials.

[Shear strength measurements for the clinical evaluation of bonded ceramic systems]

The shear bond strength of dental ceramic (Dicor, Optec) and luting composite (Dicor, Optec, Dual-cement) bonded to dentin and to etched enamel was evaluated. The mean bond strength was 23.8 N/mm2 to enamel and 0.60 N/mm2 to dentin. Using the Optec dentinal bonding agents increased these values to 2.00 N/mm2.

[Material testing for the use of titanium in bonded prosthodontic restorations]

The effects of chemically etching cast pure titanium to achieve a microretentive surface morphology were studied by SEM. Etching failed to produce an effective improvement of the retentive structures compared to air brushing with Al2 O3 of 50 microns grain size. The bond strength values of the Silicoater-treated retentive surfaces of titanium and Wiron 88 (bonding agent Comspan) determined by shear tests were considerably higher than those of the air-brushed or chemically etched surfaces (bonding agents Comspan, ABC-Zement, Superbond). The clinical use of the Silicoater procedure in bonded restorations seems to provide a suitable retentive mechanism for titanium frameworks.

[Long-lasting treatment technic in the periodontally reduced dentition]

A precondition for satisfactory (long-lasting) prosthetic results is a good occlusion. This can sometimes only be achieved with the aid of orthodontics. This article concludes that orthodontics can be carried out in patients with reduced periodontal support provided thorough periodontal treatment is carried out initially and treatment goals and biomechanics are carefully considered.

Distance alterations of dies in sagittal direction in dependence of the die material

The distance alterations between the first premolar and second molar in the sagittal direction were measured on complete arch models in two planes. Two dental stones, three resins, and silver-plating were used to make reproductions of a master cast under standardized conditions. Special emphasis was directed to the distinction between the right half of the model with teeth between the dies and the left side edentulous between the dies. The stones Die Keen and Fuji Rock showed the least distortion, identical bilaterally. The epoxy resins Blue Star E and Metapox exhibited a significant distinction between the right and the left sides. In addition to the pronounced distance reduction caused by polymerization shrinkage, a divergence between the dies and the model base on the side with teeth was measured. This phenomenon was also observed with polyurethane Blue Star P resin, but was less substantial. Silver-plating recorded a slightly greater reduction in distance between the dies than Fuji Rock. However, no significant differences were found between both sides.

[The use of modern ceramics for inlays and onlays]

If ceramic inlays and onlays are considered in restorative work, some operations which, more than in other areas of dental engineering, decide upon the success or failure should be given special attention. During the preparation of ceramic inlays care should be taken to produce well rounded rather than rectangular edges approximally. In the case of onlays there should ideally be a smooth circular step rounded axially with a sharp-edged near-rectangular interface with the non-ground tooth. Ceramic inlays and onlays are best inserted with the adhesive technique, which provides for an improved strength of the ceramic material, an adequate marginal adaptation and a satisfactory cosmetic appearance. As long-term results are not yet available, the use of ceramic inlays and onlays is still experimental.

[Free mucosal grafting--clinical experiences]

Free mucosal grafting is a simple, safe and predictable procedure. It is indicated in the treatment of progressive recessions in patients with reduced attached gingiva, in recurrent traumatic marginal lesions inspite of correct tooth brushing, in refractory dental neck hypersensitivity and for cosmetic reasons in patients with recessions. In these situations advancement grafting is done as a secondary procedure. To prevent the potential occurrence of recessions free mucosal grafting may also be indicated prophylactically before orthodontic or prosthetic management. The management concept in patients with recessions as well as the indications of the procedure, the technique used at our department and aspects of planning surgery are discussed.