Comparison of a novel photogrammetric technique and modified USPHS criteria to monitor the wear of restorations

Measurements of surface scale changes in different denture base materials by stereophotogrammetric technique

Background. This study aimed to evaluate the surface scale changes in the denture base material using different polymerization techniques, such as heat-cure/pressure polymerization system and injection molding technique with the stereophotogrammetric technique. The function of a complete denture is related to the adaptation of its base to the supporting areas. Proper adaptation of the base depends on the stability and retention of dentures. The surface scale changes of dentures during processing and in service are of great importance since they affect the denture base material's fit. Methods. This study focused on the use of a computer-assisted stereophotogrammetric method for measuring changes in the volume of three different denture base resins of an edentulous maxillary ridge. A stone master model simulating the shape of an edentulous maxillary arch was used to prepare three groups of denture base resins. The stereophotographs were evaluated to determine the surface scale differences of maxillary jaws. Results. The results showed no significant differences between the denture borders for three denture base materials (P > 0.05). Conclusion. In the evaluation made using this technique, no significant difference was found in the different polymerization techniques in terms of surface scale changes for three denture base materials. Stereophotogrammetry, especially the digital stereophotogrammetric technique, has several useful research applications in prosthodontics.

Marginal Integrity of CAD/CAM Ceramic Crowns Using Two Different Finish Line Designs

OBJECTIVE

Research on evaluation of crowns made by the latest contemporary dental computer-aided design/computer-aided manufacturing (CAD/CAM) systems for their marginal adaptation is scarce. The purpose of this in vitro study was to evaluate the marginal integrity of crowns fabricated by the latest Chairside Economical Restorations of Esthetic Ceramic (CEREC) system using 2 different finish line preparation designs: chamfer and shoulder.

MATERIALS AND METHODS

Typodont teeth were divided equally into 2 groups, A and B. The teeth were prepared for full coverage crowns with a shoulder (group A) and chamfer (group B) finish line design. An experienced prosthodontist prepared all crown preparations. Evaluation of 6 sites per sample was completed by 2 calibrated, experienced prosthodontists using the modified US Public Health Services (USPHS) criteria. The descriptive statistics and Z-test were used to evaluate the results.

RESULTS

A total of 180 teeth were included in the study (90 teeth in each group). Only 2 crowns in group A and 1 crown in group B were clinically unacceptable. There was no statistical significance (p = 0.282) between the 2 groups regarding finish line design.

CONCLUSIONS

The CEREC system provides clinically acceptable crowns and can safely be utilized in dental treatment. Therefore, CAD/CAM restorations could be considered as a safe treatment modality by dental professionals.

Wear measurement of dental tissues and materials in clinical studies: A systematic review

OBJECTIVES

This study aims to systematically review the different methods used for wear measurement of dental tissues and materials in clinical studies, their relevance and reliability in terms of accuracy and precision, and the performance of the different steps of the workflow taken independently.

METHODS

An exhaustive search of clinical studies related to wear of dental tissues and materials reporting a quantitative measurement method was conducted. MedLine, Embase, Scopus, Cochrane Library and Web of Science databases were used. Prospective studies, pilot studies and case series (>10 patients), as long as they contained a description of wear measurement methodology. Only studies published after 1995 were considered.

RESULTS

After duplicates' removal, 495 studies were identified, and 41 remained for quantitative analysis. Thirty-four described wear-measurement protocols, using digital profilometry and superimposition, whereas 7 used alternative protocols. A specific form was designed to analyze the risk of bias. The methods were described in terms of material analyzed; study design; device used for surface acquisition; matching software details and settings; type of analysis (vertical height-loss measurement vs volume loss measurement); type of area investigated (entire occlusal area or selective areas); and results.

SINIFICANCE

There is a need of standardization of clinical wear measurement. Current methods exhibit accuracy, which is not sufficient to monitor wear of restorative materials and tooth tissues. Their performance could be improved, notably limiting the use of replicas, using standardized calibration procedures and positive controls, optimizing the settings of scanners and matching softwares, and taking into account unusable data.

Tooth wear against ceramic crowns in posterior region: a systematic literature review

The objective of this systematic review was to assess tooth wear against ceramic crowns in posterior region in vitro and in vivo. An electronic PubMed search was conducted to identify studies on tooth wear against ceramic crowns in posterior region. The selected studies were analyzed in regard to type of crowns, natural antagonist, measuring protocol and outcome. From a yield of 1 000 titles, 43 articles were selected for full-text analysis; finally, no in vitro and only five in vivo studies met the inclusion criteria. As there is heterogeneity in design, used measuring method, ceramics and analysis-form, a meta-analysis was not possible. Results of these studies are very controversial which makes a scientifically valid comparison impossible. This review indicated that some all-ceramic crowns are as wear friendly as metal-ceramic crowns. Up to now, it has been impossible to associate tooth wear with any specific causal agent. The role of ceramic surface treatment that might be responsible for the changing in rate of tooth wear seems undetermined as yet through clinical trials. The literature reveals that studies on this topic are subject to a substantial amount of bias. Therefore, additional clinical studies, properly designed to diminish bias, are warranted.

Clinical Measurement of Palatal Tooth Wear Following Coating by a Resin Sealing System

This randomized clinical study presents the results of applying a resin-based dentin bonding agent to the palatal surfaces of worn and eroded anterior teeth. The application of the barrier protected the teeth for up to three months.

Marginal Adaptation of Cerec 3 CAD/CAM Composite Crowns Using Two Different Finish Line Preparation Designs

PURPOSE

The purpose of this study was to compare marginal discrepancies of Cerec 3 CAD/CAM composite crowns, fabricated on human prepared teeth with two different finish line designs, chamfer and shoulder.

MATERIALS AND METHODS

Sixteen human molar teeth were used to prepare full crowns. Eight teeth were prepared with a 1-mm-wide chamfer finish line and the other eight with a 1.2- to 1.5-mm circumferential shoulder. Cerec 3 crowns were fabricated from optical impressions using Paradigm MZ100 composite polymer. Marginal adaptation was evaluated in two ways: (1) using modified United States Public Health Service (USPHS) criteria to evaluate eight preselected sites on each crown margin, and (2) using scanning electron microscopy (SEM) to measure marginal gaps on all four axial walls with 15 measurements on each wall (60 measurements per crown). An evaluation of the number of acceptable crowns, determined by having all measured sites per tooth with margin gap size less than 100 microm, as a function of finish line design was also conducted.

RESULTS

In both chamfer and shoulder groups, there were only two crowns (out of eight) with clinically acceptable ratings for all eight measurement sites according to USPHS criteria. Fisher's chi-square analysis showed that there was no statistically significant difference in marginal adaptability as a function of finish line design ( p>0.05). With SEM imaging, overall mean marginal gaps for the chamfer group were 65.9+/-38.7 microm (range 35.0 to 130.0 microm), and for the shoulder group were 46.0+/-9.2 microm (range 26.3 to 55.6 microm); this difference was not found to be statistically significant ( p>0.05). While crown assessment based on mean marginal discrepancy measurements indicated that both the chamfer and shoulder groups were considered clinically acceptable (<100 microm); crown acceptability based on all measurement sites being less than 100 mum indicated that in the chamfer and shoulder groups there were four and three acceptable crowns out of eight, respectively. The Fisher's chi-square test indicated no statistically significant difference between the groups ( p>0.05). An agreement rate of 81.2% was calculated between the two evaluation methods, modified USPHS criteria and SEM measurements.

CONCLUSIONS

Based on mean marginal discrepancy measurements, the typical marginal assessment technique, Cerec 3 Paradigm MZ100 crown restorations appear to have acceptable marginal adaptability (mean discrepancies <100 microm). Thus, the evidence from this investigation would suggest that the finish line preparation design had no effect on marginal adaptation for Cerec 3 composite crowns.

The Use of Ozone in Dentistry and Medicine

There is growing interest in the use of ozone in oral healthcare and the National Institute for Clinical Excellence (NICE) is at present reviewing the evidence for its effectiveness in the management of occlusal and plain surface caries. These are only two of the clinical problems for which ozone can, and has, been used; it has also been employed for a wide variety of other purposes in both dentistry and medicine. This pale blue-coloured gas plays an important role as a natural constituent in the higher layer of the Earth's atmosphere. There is growing evidence that it can be employed as a useful therapeutic agent. This paper reviews its therapeutic uses to date and suggests its possible future clinical applications. Consumer demands for this strong oxidant may increase as the general public becomes increasingly aware of its therapeutic capacity and the non-invasive manner in which it can be administered.

Effects of cyclic loading on occlusal contact area wear of composite restoratives

OBJECTIVES

To investigate the effects of cyclic loading on occlusal contact area (OCA) wear and the possible presence of fatigue wear mechanisms in four composite resins (Silux, Z100, Ariston and Surefil) using a reciprocal compression-sliding test apparatus.

METHODS

Six specimens were made for each composite material and the amalgam alloy (Dispersalloy) control. The wear specimens were subjected to wear testing at 20 MPa with artificial saliva as lubricant. Wear depth (microm) was measured using profilometry every 20,000 cycles up to 120,000 cycles. The worn specimens were subjected to SEM to determine the presence of fatigue wear mechanisms. Results were analyzed using ANOVA/Scheffe's test (P<0.05) and Pearson's Correlation (P<0.01).

RESULTS

Dispersalloy had the lowest wear at all cyclic intervals. For all materials, OCA wear increased with increased number of cycles. Although Dispersalloy, Ariston and Surefil experienced no significant increase in wear between each 20,000 cycles increment, a significant increase was observed with Silux. For Z100, a significant difference was observed only from 40,000 cycles onwards. Both Z100 and Dispersalloy exhibited fatigue wear after wear testing for 120,000 cycles. Cyclic loading resulted in deep and wide microcracks in Silux. Fatigue wear was not observed with Silux, Ariston and Surefil.

SIGNIFICANCE

The effects of cyclic loading on wear is material dependent. While some restorative materials exhibit fatigue wear, others exhibit deep microcrack formation with extended cyclic loading. The latter may precipitate catastrophic failure despite the low wear observed. Care should, therefore, be exercised when selecting materials for posterior stress-bearing areas.

Three-dimensional quantification of color-marked occlusal paths on anatomically oriented casts

STATEMENT OF PROBLEM

The analysis of occlusal contacts on mounted diagnostic casts is an important task in prosthetic diagnostics. However, it is still restricted mainly to qualitative aspects because existing measuring techniques fail to provide 3-dimensional data for more than a few single points in acceptable time.

PURPOSE

The aim of this study was to develop a method for quantifying occlusal contacts and paths by using anatomically oriented diagnostic casts and to design the method to allow fast acquisition of digital 3-dimensional coordinates.

MATERIAL AND METHODS

Plaster casts with color-marked contacts were digitized optically with a profilometric system based on the fringe projection technique. Digital camera images taken simultaneously were used to define the contact areas by marking them either manually or automatically with the help of image-processing routines. Three-dimensional coordinates were determined by finding the corresponding points within the profilometric data set.

RESULTS

Color-marked contact areas on diagnostic casts were successfully digitized with a computer-controlled, automatic setup in approximately 30 seconds. The accuracy of the acquired 3-dimensional data was estimated to be better than 60 microm in lateral and 30 microm in height resolution. The data set was visualized and evaluated in a skull related coordinate system.

SUMMARY

This study verified the use of a new tool to quantify color-marked occlusal contacts on diagnostic casts in terms of spatial coordinates. The resulting digital data may be stored easily and analyzed numerically as well as visualized 3-dimensionally with computer graphic equipment. Because the anatomic orientation of the casts is maintained throughout the measurement process, it is possible to compare the data with electronically registered condyle paths and therefore to investigate, for example, their relation to the corresponding guidance paths of the frontal teeth and the canines in dynamic occlusion.

Three-year clinical evaluation of direct and indirect composite restorations in posterior teeth

STATEMENT OF THE PROBLEM

Objective long-term clinical data are necessary to assess the performance of modern posterior composites as direct and indirect restorations.

PURPOSE

This prospective, long-term clinical trial evaluated direct and indirect composite restorations for clinical acceptability as posterior restoratives in single or multisurface cavities and provided a survey on the 3-year results.

MATERIAL AND METHODS

Under the supervision of an experienced dentist, 9 dental students placed 88 composite restorations (Tetric, blend-a-lux, Pertac-Hybrid Unifil), 43 direct composite restorations, and 45 indirect inlays. Clinical evaluation was performed at baseline and in yearly intervals after placement by 2 other experienced dentists, using modified USPHS criteria. A third follow-up of 60 restorations took place within 33 to 36 months after placement.

RESULTS

A total of 93% of indirect and 87% of direct restorations were assessed to be clinically excellent or acceptable. During the third year, 1 direct restoration in a molar failed because of margin opening. Indirect inlays exhibited a significantly better anatomic form of the surface than direct composite restorations. Premolars revealed a significantly better marginal integrity and anatomic form of the surface than molars. Restorations in molars exhibited a significantly higher failure rate compared with premolars.

CONCLUSION

Posterior composite restorations provided a satisfactory clinical performance over a 3-year period, even if placed by relatively inexperienced but supervised students.

Influence of water exposure on three-body wear of composite restoratives

The objective of this investigation was to study the influence of water exposure on the three-body wear of composite restoratives. A three-body wear instrumentation was used to investigate the wear resistance of five composite restoratives [Silux Plus (SX), Z100 (ZO), Ariston pHc (AR), Surefil (SF) and Tetric Ceram (TC)] with and without exposure to water. An amalgam alloy [Dispersalloy (DA)] was used as control. Ten specimens were made for each material. The specimens were conditioned in artificial saliva at 37 degrees C for 24 h and randomly divided into two groups of 5. The first group was subjected to wear testing immediately after the 24 h conditioning period, while the second group was conditioned in distilled water at 37 degrees C for 7 days prior to wear testing. All materials were wear tested at 15 N contact force against SS304 counter-bodies for 20,000 cycles with millet seed slurry as third-body. Wear depth (microm) was measured using profilometry, and results were analyzed by ANOVA/Scheffe's and independent sample t-tests at significance level 0.05. Ranking of wear resistance was as follows: without water exposure: DA > ZO > SF > AR > SX > TC; with water exposure: DA > ZO > SX > SF > AR > TC. Wear factor ranged from 2.20 for ZO to 7.13 for TC without water exposure and from 46.00 for ZO to 143.00 for TC with exposure to water. Exposure to water significantly increased three-body wear for all composite restoratives, but did not affect wear of the amalgam alloy. The effects of water exposure must be considered for the evaluation of wear in all polymeric composite restoratives.

Two-year clinical evaluation of direct and indirect composite restorations in posterior teeth

STATEMENT OF PROBLEM

Few long-term clinical studies have reported data of modern posterior composites as direct and indirect restorations.

PURPOSE

This prospective, long-term clinical trial (1) evaluated direct and indirect composite restorations for clinical acceptability as posterior restoratives in single or multisurface carious teeth and (2) provided a survey on the 2-year results.

MATERIAL AND METHODS

Nine dental students placed 88 composite restorations (Tetric, blend-a-lux, Pertac-Hybrid Unifil), 43 direct composite restorations and 45 indirect inlays, under the supervision of an experienced dentist. The first clinical evaluation was performed 11 to 13 months after placement by 2 other experienced dentists, using modified USPHS criteria. A second follow-up of 60 restorations took place within 20 to 26 months after placement.

RESULTS

A total of 93% of indirect and 90% of direct composite restorations were assessed to be clinically excellent or acceptable. Two restorations (1 indirect composite inlay and 1 margin of a direct composite restoration) failed during the second year because of fracture. Indirect inlays demonstrated a significantly better "anatomic form of the surface" than direct composite restorations. Premolars revealed a significantly better margin integrity and postoperative symptoms than molars.

CONCLUSION

Posterior composite restorations provided a satisfactory clinical performance over a 2-year period when placed by relatively inexperienced but supervised students.

One-year clinical evaluation of composite and ceramic inlays in posterior teeth

STATEMENT OF PROBLEM

There are only a few studies available that deal with the clinical behavior of composite and ceramic inlay systems as potential substitutes for amalgam restorations.

PURPOSE

This prospective clinical trial evaluated composite and ceramic inlay systems for clinical acceptability as restorative materials in single or multisurface cavities of posterior teeth and provided 1-year results.

MATERIAL AND METHODS

Forty-seven composite inlays (Tetric, Blend-a-lux, Pertac) and 24 heat-pressed ceramic inlays (IPS Empress) were placed in 45 patients by 7 student operators under the supervision of an experienced dentist. The first clinical evaluation was performed 11 to 13 months after placement of the restorations and used modified United States Public Health Services criteria.

RESULTS

Satisfactory results over this period were found, as 100% of ceramic inlays and 94% of composite inlays were assessed to be clinically excellent and acceptable. Only 3 composite inlay restorations were scored delta (unacceptable). Two inlays exhibited secondary caries and 1 demonstrated loss of pulp vitality. For the criteria "anatomic form of the surface" and "marginal integrity," ceramic inlays were significantly better than composite inlays.

CONCLUSION

Posterior tooth-colored inlays provided acceptable and excellent clinical service, even if they are placed by relatively inexperienced student operators.

A new optical 3-D device for the detection of wear

For the clinical performance of new dental restorative materials to be accurately assessed, the three-dimensional anatomical changes of the functional surfaces of the restoration must be elucidated over time. To this end, a highly accurate 3-D optical scanner has been developed that utilizes the principles of triangulation and a reference-free automated 3-D superimposition software. The aim of this study was to assess the accuracy and the precision of the new system with and without referenced positioning. Additionally, the ability of the system to determine wear of posterior fillings three-dimensionally has been shown. Gypsum replicas of restored teeth were evaluated. The tooth surfaces were scanned with a resolution of 250,000 surface points within a measuring time of 20 to 40 sec. The results show that the precision and accuracy of 3-D data acquisition depend on the surface inclination. Up to an angle of 60 degrees, the precision is better than 3 microns, and the accuracy is better than 6 microns. If exact repositioning of the object before and after occlusal loading is possible, e.g., with in vitro studies, differences on the surface can be determined with a precision of 2.2 microns. In reference-free measurements, which are a necessity in clinical studies, the 3-D data acquisition in combination with the automatic matching program can detect wear with an accuracy of 10 microns. The application of this measuring device for the detection of wear of a composite filling functioning in the mouth has been shown. Since this measuring technique is automated, and measurements of high accuracy can be attained in a short period of time, this system offers the possibility for complex analyses of three-dimensional wear to be conducted on a large number of samples in clinical studies.

In vitro wear of composite with varied cure, filler level, and filler treatment

For the clinical wear of composite filing materials to be reduced, compositional factors such as degree of cure, filler level, and silanation level should be optimized. An oral-wear-stimulating machine was used to explore the effects of these factors on abrasion and attrition wear as well as on opposing enamel wear. The composites were made from Sr glass (1-2 micron avg) and a 50/50 Bis-GMA/TEGDMA resin. Series I (A-D, E) were light-cured (Triad II) for 9, 12, 25, and 40 sec/side to produce degree of cure (DC) as measured by FTIR of 56, 60, 61, and 63%, respectively. E received an additional heat cure (120 degrees C for 10 min) to reach a DC of 66%. Series II (D, F-I) were filled to 62, 53, 48, 37, and 28 vol%, respectively. In series III (D, J-M), the portion of fillers treated with a silane coupler (MPS) was 100, 80, 60, 40, and 20%, respectively. Samples were cycled 50,000 times against an enamel antagonist in a poppy seed/PMMA slurry in the oral wear simulator to produce abrasion (load = 20 N) and attrition (load = 70 N) simultaneously. Wear depth (micron: n = 5) was measured by profilometry. Results for each series were analysed by ANOVA/Turkey's (p < or = 0.05). The wear depths did reflect cure values, though only the abrasion difference for E < A was significant. Greater wear was correlated with lower filler levels (r2 = 0.88; p < 0.05), significantly increasing below 48 vol% (G). Wear increased linearly as the percent of silane-treated fillers was reduced (r2 = 0.99; p < 0.05). Abrasion and attrition did not differ significantly for any composite. Wear of the opposing enamel was largely unchanged by these factors. Compositional factors including degree of cure, filler level, and silanation directly affected the wear resistance of dental composites evaluated in an oral wear simulator.

Development of a novel system for assessing tooth and restoration wear

OBJECTIVES

This investigation sought to develop a mapping apparatus for use in the assessment of both tooth and restoration wear.

METHODS

A computer controlled mapping device, capable of scanning a suitably prepared electroconductive tooth replica by means of an electrical feedback mechanism, was constructed and its accuracy assessed by measuring the thicknesses of four engineers' slip gauges 12 times each. The reproducibility of three potential methods of rendering a die stone replica electroconductive was also investigated. Finally, tooth replicas were surface profiled and compared empirically with the originals using a commercial surface mapping program.

RESULTS

The overall mean accuracy of the mean thicknesses of the slip gauges was 4.4 (2.8) microns. Surface deposition of either nickel spray or gold leaf, upon a ready formed replica, did not give a reproducible thickness. Precoating silicone impressions with nickel spray prior to replica production overcame this problem. On an empirical basis the instrument yielded accurate digital terrain models of tooth replicas.

CONCLUSIONS

A surface mapping device has been developed which is both accurate and reproducible. A satisfactory electroconductive surface may be produced upon a tooth replica by precoating a silicone impression with nickel spray before casting the replica. The technique should prove invaluable for monitoring both tooth and restoration wear but further work is necessary to examine how such an approach will perform clinically.

Occlusal wear simulation with the ACTA wear machine

This paper describes how the clinical conditions in stress bearing areas are thought to be simulated in the ACTA wear machine. The wear types simulated are erosive wear and contact sliding wear in the presence of a third-body medium, consisting of natural food substances. Wear due to surface fatigue may also be studied with the wear machine. Wear rates for a wide range of resin composites, an amalgam and a glass polyalkenoate (ionomer) cement obtained with the ACTA wear machine correlated with an average correlation coefficient of 0.90 with data collected from clinical trials. The results justify the experimental set-up as being one that includes a realistic simulation of the complexity of clinical wear.

Close range photogrammetry--a clinical dental research tool

Photogrammetry is the art, science and technology of obtaining reliable information about physical objects through processes of recording and interpreting photographic images. This review outlines the principles of the technique and summarizes the various methodologies and applications in clinical dental research.

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The committee screened several hundred articles, citing 518 published papers. Some are present quality in research, others provide clinical interest, and some are identified as misleading. New techniques in pulp physiology and pathology are reported. Laser use and techniques in prevention, restorative dentistry, and materials use are reported. Epidemiology of selected diseases and the results of various formulations for treatment are cited. Diagnosis of craniomandibular dysfunction is well represented as well as references to literature reviews and other sophisticated scientific investigation. Research on adhesives is presented in respect to bonding agents for dentin and enamel. Several clinical studies are included, along with customary laboratory reports on several materials.