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PubMed1998

An in vivo evaluation of an electronic apex locator that uses the ratio method in vital and necrotic canals.

The purpose of this study was to compare the canal length determined by an apex locator to the apical constriction in both vital and necrotic canals. Informed consent was obtained from patients waiting to have teeth extracted. The teeth were anesthetized, isolated, and accessed. The pulp was considered vital if bleeding was present in the pulp chamber. The Root ZX was used to measure the root canal length. The file was cemented into place, and the tooth was extracted. Twenty-nine teeth containing 34 cemented files were studied, and the distance from the apical constriction was measured. The Root ZX was 82.3% accurate to within 0.5 mm of the apical constriction. The mean distance from the apical constriction was 0.21 mm in vital cases versus 0.49 mm for necrotic cases. There was no statistical difference between the ability of the Root ZX to determine the apical constriction in vital canals versus necrotic canals.

Adult↗

PubMed1997

Posterior bridges retained by resin-bonded cast metal inlay retainers: a report of 60 cases followed for 6 years.

Between May 1989 and July 1994, 60 adhesive fixed partial posterior dentures retained by resin-bonded cast metal inlays were placed under controlled conditions. The influence of various prognostic factors on the event free and overall service duration was investigated with univariate and multivariate analysis. The majority of the failures (16 of 18) were caused by loss of adhesion at the metal cement interface and were observed either as debonding of the restorations completely or dislodgement of a single retainer. The other two failures appeared as secondary caries. Univariate analysis demonstrated that, retainer type, approximal configuration and dentine exposition had no effect on the event free service duration. On the other hand, gingival finishing level and luting agent were found to have an effect. Univariate testing was also conducted for the overall service duration and none of the variables were found to have an effect. Multivariate Cox Regression Analysis was performed to estimate the influence of categorical covariates: type of retainer, approximal preparation modification, gingival finishing level, preparation depth and luting agent on survival rates of event free and overall service duration. Luting agent was found to be the single independent prognostic variate (P < 0.0001) for the event free service duration and the other covariates were rejected. For overall service duration, none of the variables were found to be effective.

Adolescent↗

PubMed2001

Fracture strength of different core build-up designs.

PURPOSE: To investigate the resistance to fracture of three crown and core combinations, made with different core build-up systems on human teeth, using a standardized test method. MATERIALS AND METHODS: The anatomic crowns were removed from six groups (n = 8) of endodontically treated, human premolars in conformity with a brass master dye, using the Celay duplicating device. Three of these groups were provided with a core build-up with-out an endodontic post (Ti-Core, Photo-Core and Ketac-Molar); two other groups were provided with a core build-up with an endodontic post (a cast post and core, and a composite with a silica post), and one group was not provided with a core. All groups were then prepared in conformity with a master dye. This preparation ended in axial dentin, 2 mm apical from the core build-up. Thus in the sixth group (premolars without a core build-up), this preparation only affected the 2 mm axial dentin (ferrule), which resulted in a small retention area (2 mm axial dentine) for the crown. Finally, a standard crown was cemented and 24 hrs afterwards loaded until fracture in an Instron testing machine at an angle of 45 degrees. For comparison with the standardized procedures, a seventh group (Photo-core without post) was prepared manually, with dimensions similar to the standardized groups. RESULTS: Within the standardized test set-up no significant difference in strength between the 6 groups could be demonstrated. Only in the case of the hand-made Photo-Core and the cast core was the fracture load significantly different (P= 0.01). In addition, this hand-made group displayed a larger standard deviation than the standardized groups. Taking into consideration the fact that the maximum bite force in the bicuspid region is about 580 N, these tests showed that within the limitations of the standardized test set-up, where the samples had no history of fatiguing, a core build-up without a post is an alternative for the conventional cast core. In this study, the fabrication of the standardized samples proved to be accurate, fast and economical. This method also enables the evaluation of the performance of core and crown design combinations in relationship to the amount of remaining tooth structure by using different master dies and, moreover, to reduce the high standard deviation in this kind of research.

Analysis of Variance↗

PubMed1999

Fracture resistance of teeth restored with dentin-bonded crowns constructed in a leucite-reinforced ceramic.

OBJECTIVES: Laboratory studies and preliminary clinical data have demonstrated satisfactory fracture resistance of all-ceramic crowns placed using a resin-composite luting material and a dentin-bonding system. This study investigates the fracture resistance of crowns constructed in a leucite-reinforced ceramic when placed using a dentin-bonding system and a dual-cure resin composite luting material and compares this with the fracture resistance of feldspathic porcelain crowns. METHOD: Standardised preparations were carried out on 10 sound, unrestored, maxillary premolar teeth, the mean bucco-palatal width of which did not vary by more than 2.5%. Ceramic crowns (Fortress; Chameleon Dental, KS, US) were constructed using a standardised technique. Their fitting surface was etched with hydrofluoric acid. The crowns were placed using the dentin-bonding system Mirage ABC and the luting system Mirage FLC (Chameleon Dental, KS, US). The restored teeth were loaded in compression at 1 mm/min through a 4 mm steel bar placed along the midline fissure. RESULTS: A mean fracture load of 0.88 kN was recorded. Results from previous work indicate a fracture resistance of 0.77 kN for feldspathic porcelain crowns placed using the same luting systems on similarly standardised preparations. Statistical analysis by one-way ANOVA and Tukey's multiple comparison procedure indicated that there was no significant difference in the mean fracture resistance of the teeth restored using the leucite reinforced ceramic and the teeth restored with feldspathic porcelain. SIGNIFICANCE: Crowns constructed in a leucite-reinforced ceramic and placed using dentin-bonding and dual-cure resin composite luting materials may provide some increase in fracture resistance, but the results may not be significantly different from the feldspathic porcelain.

Aluminum Silicates↗

PubMedDate not supplied

11-year follow-up study of resin-bonded fixed partial dentures.

The clinical performance of 325 resin-bonded fixed partial dentures (RBFPD) placed between 1984 and 1995 was reviewed. The primary indications of the 264 patients treated were trauma and aplasia. Two hundred eighty-three of the resin-bonded fixed partial dentures were primary restorations, and 42 of the restorations were secondary and tertiary after the loss of the primary resin-bonded fixed partial denture. Including the rebonded restorations, the survival rate calculated using the Kaplan-Meier method was 76% after 5 years and 60% after 10 years. Analysis of the data showed that casting alloy, pretreatment of the bonding surfaces, luting agent, and mobility of the abutment teeth were decisive prognostic factors for success. Base metal alloys, silicoating, mesh retention, and immobile abutments were positive factors. In contrast to other reports in the literature, retentive abutment preparation did not result in a higher survival rate than unprepared abutments. Small restorations in the bonding area did not affect the survival. No differences in survival rate were found for resin-bonded fixed partial dentures in the maxillae or mandible, or in the anterior and posterior regions. Multiunit resin-bonded fixed partial dentures had a smaller probability of survival than three-unit resin-bonded fixed partial dentures. Carious lesions were found on 4% of the abutment teeth.

Adult↗

PubMed2001

Treatment planning for porcelain veneer restoration of crowded teeth by modifying stone models.

UNLABELLED: The three-dimensional result attainable through porcelain veneer restoration of crowded teeth can be preoperatively determined by diagnostically altering stone study models of the patient's dentition. Techniques for diagnostically preparing and waxing the stone dental models are described in this article, along with the corresponding postoperative restorative results of representative cases. CLINICAL SIGNIFICANCE: Patients with malaligned teeth who are not willing or able to undergo straightening of their teeth with orthodontics, nonetheless may be able to attain straight teeth concomitant with the restoration of their teeth with modified porcelain veneer restorations. This article describes a straight forward treatment planning technique for altering study casts preoperatively, to accurately predict and guide the postoperative outcome.

Adult↗

PubMed2006

Resin adhesion to caries-affected dentine after different removal methods.

BACKGROUND: Caries-affected dentine is the common bonding substrate when treating a patient. At present, there are many methods used for caries removal. The aim of this study was to evaluate the microtensile bond strength of two adhesives (Clearfil Protect Bond and OptiBond Solo Plus Total-Etch) to caries-affected dentine after three different caries removal methods. METHODS: Extracted carious human third molars were used and caries-affected dentine surfaces were obtained from one of the three removal methods: (i) round steel bur in a slow-speed handpiece; (ii) Er:YAG laser; or (iii) 600-grit silicon carbide abrasive paper. Each of the adhesives was used to bond resin composite to the caries-affected dentine according to the manufacturers' instructions. Hourglass-shaped specimens were prepared and stressed in tension at 1mm/min. Data were analysed using two-way analysis of variance and least significant difference test. RESULTS: Clearfil Protect Bond showed significantly lower bond strength than OptiBond Solo Plus Total-Etch after caries removal with round steel bur, but the opposite was found for specimens treated with silicon carbide abrasive paper. For laser-treated dentine, no significant differences between the adhesives were revealed. CONCLUSIONS: Besides the differences in adhesives, different caries removal methods seem to influence resin adhesion to caries-affected dentine.

Analysis of Variance↗

PubMed2005

Comparison of convergence angles achieved in posterior teeth prepared for full veneer crowns.

This study compares the convergence angle of preparations for posterior gold crowns made by fourth/ fifth year undergraduate dental students, clinical teaching staff and general dental practitioners. Sixty dies were cast from impressions previously taken of clinical preparations by clinicians within each of the four groups. Each die was trimmed and sectioned in both mesio-distal and bucco-lingual planes before being projected using an overhead projector, thereby enabling the convergence angle silhouette to be measured. The results show the greatest convergence angle range to be produced by the least experienced students (10 degrees - 82 degrees). However, no significant difference (p > 0.05) was found when students with one further year of experience were compared to experienced staff. The degree of conformity to the ideal taper (4 degrees - 14 degrees) was no greater than 50% for any of the groups.

Analysis of Variance↗

PubMedDate not supplied

Preparation of teeth for esthetic restorations.

Preparation details have been described for a porcelain veneer restoration on the most commonly used teeth. With operator knowledge of the preparation, sharp instrumentation, and, most of all, patience, it is possible to place a restoration that may last as long as any others outside of those made of cast or direct gold. It is imperative to remember that this type of conservative "esthetic" dentistry should be performed only on canine-guided occlusions after equilibration (if necessary) (Fig. 13). Even then, it still is possible to fracture a veneer accidentally (Fig. 14). Prior to beginning treatment, it is prudent to inform the patient of the pros and cons of using porcelain veneers, including a warning of possible failure.

Bicuspid↗

PubMed1998

[Periodontal aspects of cementation: materials, technics and their biologic reactions].

Cementation of crowns and bridges has an influence on the health of marginal periodontal structures. Ideally, the marginal discrepancy should be less than 50 microns which has been considered clinically acceptable. With discrepancies larger than 80 microns, the bleeding tendency and sulcus fluid flow rate increased. A shoulder-bevel preparation results in the smallest marginal discrepancy. Cytotoxicity of cements has been studied in cultures of gingival cells and fibroblasts. Composite has always a more pronounced cytotoxicity as compared to glass-ionomers and zinc phosphate cements. However, large differences exist in cytotoxicity between materials of the same group. Erosion of the cement leads to leakage of toxic materials and the formation of niches colonised by oral plaque bacteria. A number of clinical recommendations are made to minimize the effect of cements and cementation on the periodontal structures.

Cells, Cultured↗

PubMedDate not supplied

Resin-bonded fixed partial dentures: ten-year follow-up.

PURPOSE: The aim of the study was to evaluate the survival rate of resin-bonded fixed partial dentures delivered between 1993 and 2003 in the Department of Prosthodontics of the University of Turin and in several private practices. MATERIALS AND METHODS: The analysis took into consideration the following variables: preparations, metallic alloys, metal preparation and conditioning of the inner surfaces, isolation during cementation, type of cement, kind of prostheses, number of abutments, and number of missing teeth included in the prostheses. RESULTS: The estimated survival probability for the first debonding or failure was 85% after 5 years and 71% after 10 years. CONCLUSIONS: The use of dental dam during cementation reduced the risk of debonding. No differences in survival rate were found for the other parameters.

Cementation↗

PubMedDate not supplied

Diffusion of monomers from bonding resin-resin composite combinations through dentine in vitro.

OBJECTIVES: Previous work has demonstrated diffusion of the monomer triethylene glycol dimethacrylate (TEGDMA) from resin composite through dentine in vitro. The objective of the present work was to examine monomer diffusion from bonding resins and resin composites used in combination. METHODS: Occlusal cavities were prepared in tooth crowns and restored with bonding resin-resin composite combinations. Aqueous samples from the 'pulpal chamber' of each tooth were removed at timed intervals for analysis by reversed phase-high performance liquid chromatography and mass spectrometry. RESULTS: Bonding resins contributed to monomer diffusion. A TEDGMA-containing bonding resin used in combination with a TEGDMA-containing resin composite hastened and increased TEGDMA diffusion through dentine. A 2-hydroxyethyl methacrylate (HEMA)-containing bonding resin used in combination with a TEGDMA-containing resin composite reduced TEGDMA diffusion only slightly compared with the resin composite alone and added substantial diffusion of HEMA. CONCLUSION: The bonding resins tested contributed to monomer passage to the pulp space and did not prevent movement of monomer from resin composites to the pulp.

Adolescent↗

PubMed2003

An in vivo comparison of two frequency-based electronic apex locators.

The purpose of this study was to compare the accuracy of a two-frequency (Root ZX) and a five-frequency (Endo Analyzer Model 8005) electronic apex locator under clinical conditions. Thirty-two teeth planned for extraction were used. The coronal portion of each canal was flared using Gates Glidden drills and Orifice Shapers. The canals were irrigated with 2.6% sodium hypochlorite. A K-type file was used to determine a separate working length in each canal using the electronic apex locators. The teeth were extracted and the apical 4 mm of each root canal was exposed along the long axis of the tooth. Photographic slides of each canal were projected and the file position in relation to the minor diameter was determined by two investigators. The mean distance between the electronic apex locator working length and minor diameter was 1.03 mm for the Endo Analyzer and 0.19 mm for the Root ZX. A paired sample t test showed that the Endo Analyzer had significantly longer readings beyond the minor diameter than the Root ZX (p < 0.0001). The ability to locate the minor diameter (+/- 0.5 mm) was 90.7% for the Root ZX and 34.4% for the Endo Analyzer Model 8005.

Adult↗

PubMed2005

Effect of resin coating as a means of preventing marginal leakage beneath full cast crowns.

The purpose of this study was to evaluate the effectiveness of resin coating as a means of preventing marginal leakage beneath full cast crowns which were emplaced using different cements. Standard full cast crown preparation was made on 64 extracted premolars. These samples were then divided into four groups, with half of each group coated with dentin coating material after preparation. Crowns were cemented onto the teeth using zinc cement, Fuji I, Vitremer, or C&B Metabond. The samples were thermal-cycled for 10,000 cycles. They were then immersed in erythrosine solution, sectioned, and observed under a microscope. Microleakage analyses were performed using a 0-4 point system. The data were statistically analyzed. There were significant differences between the coated specimens and the uncoated specimens using Fuji I and Vitremer. The results showed that a resin coating could decrease the amount of marginal leakage when applied with these two cements.

Bicuspid↗

PubMed1996

Retention of metal ceramic crowns cemented with resin cements: effects of preparation taper and height.

This study investigated the effect of varying crown preparation taper and height on the retention of metal ceramic crowns cemented with resin cements. In part 1, 32 extracted molars were divided into four groups. All groups received complete-veneer crown preparations, two with a 12-degree wall angle and two with a 35-degree wall angle. Crowns were cemented with zinc phosphate and dentin-bonded resin cements. After 24 hour water storage at 37 degrees C, the crowns were separated in tension. Crowns cemented with zinc phosphate were cleaned and recemented with another dentin-bonded resin cement and after similar storage, the crowns were separated. Mean separation forces of resin-cemented crowns were higher than those of crowns cemented with zinc phosphate cement. Mean separation force of 35-degree crowns cemented with one dentin-bonded resin cement was found to be significantly higher than for the 12-degree crowns cemented with zinc phosphate cement. In part II, 32 extracted molars were divided into two groups of complete-veneer crown preparations (group I preparations were 3 mm high and group II were 5 mm high). Crowns for all teeth were cast and cemented with zinc phosphate. After 48 hours' water storage at 37 degrees C, the crowns were separated in tension. Crowns and teeth were then cleaned and each group was subdivided into 2 equal subgroups. In one subgroup of teeth with 3 mm and in one with 5 mm high preparations, the crowns were recemented with one of the two resin cement systems and the other two subgroups were recemented with the other resin cement. After 48-hour water storage, the crowns were separated. Mean separation forces of the resin-cemented crowns were greater than those of crowns cemented with zinc phosphate. Also, mean separation force of 3 mm crowns cemented with one resin cement was significantly greater than the 5 mm crowns cemented with zinc phosphate. Cohesive dentin fracture on separation was observed with some resin-cemented crowns but never with crowns cemented with zinc phosphate.

Analysis of Variance↗

PubMedDate not supplied

Fracture resistance of metal- and galvano-ceramic crowns cemented with different luting cements: in vitro comparative study.

This study aimed to compare the fracture resistance of galvano-ceramic crowns with metal-ceramic crowns cemented to natural premolar teeth with different luting cements. Sixty intact maxillary premolars were prepared to receive full-coverage crown restorations and were divided into 2 equal groups (n = 30): galvano-ceramic crowns and metal-ceramic crowns. Each group was further subdivided into 3 equal subgroups (n = 10) according to the luting cement used: zinc-phosphate, glass-ionomer, or adhesive-resin cement. The specimens were then compressively loaded until failure in a universal testing machine. The metal-ceramic crowns exhibited higher resistance to fracture compared to galvano-ceramic crowns, but both exceeded the normal documented values of occlusal masticatory forces.

Bicuspid↗

PubMed2000

Effect of crown lengthening and ferrule placement on static load failure of cemented cast post-cores and crowns.

STATEMENT OF PROBLEM: Restoration of mandibular second premolars with completely missing clinical crowns in the Kennedy Class I and II arches is costly and the risk of failure is high. Should the dentist choose crown-lengthening to allow the addition of a ferrule, despite incurring the disadvantage of an increased crown/root ratio? PURPOSE: This in vitro study determined the combined effect of crown lengthening and placement of a ferrule on the failure resistance to static load of decoronated and restored mandibular second premolar analog teeth. MATERIAL AND METHODS: An extracted mandibular second premolar of average dimensions was selected to form molded composite root analogs and metal crowns. Ten specimens prepared with no-ferrule root and negligible axial wall lengths and 10 specimens with ferrule root, apically repositioned finish lines, were made. Cast gold alloy post and cores and complete crowns were made and cemented. Each root was placed in bone-simulating resin located 3 mm from the finish line. Crown lengthened/ferrule and no-crown lengthened/no-ferrule groups were equally subdivided, whereby 5 crowns were compressively loaded on the buccal cusp tip and 5 were compressively loaded on the mesial marginal ridge. A testing machine applied force until failure occurred. Failure loads were examined with 2-way ANOVA. Significant differences were accepted at P </=.05. RESULTS: Mean failure loads for the crown lengthened/ferrule and no-crown lengthened/no-ferrule groups were as follows: buccal load, 0.61 kN (SD +/- 0.11) and 0.83 kN (SD +/- 0.08); mesial load, 0.70 kN (SD +/- 0.08) and 1.00 kN (SD +/- 0.15), respectively. Crown lengthened/ferrule and no-crown lengthened/no-ferrule groups were significantly different (P <.001). CONCLUSION: The combination of simulated surgical crown-lengthening and more apical crown margin placement to provide a 2-mm crown ferrule on a decoronated mandibular second premolar analog resulted in a reduction of static load failure for the restored analog tooth.

Analysis of Variance↗

PubMed2006

Comparison of the contact surface pattern between virtual and milled Cerec 3D full-ceramic crowns.

PURPOSE: The objective of this study was to compare resulting contact point patterns in the context of crown production with the Cerec 3D system. The contact surface patterns of full-ceramic crowns milled with the Cerec 3D system were examined for agreement with the corresponding virtually produced crowns. MATERIALS AND METHODS: The agreement was determined with regard to the parameters number, size, position, and shape. Twenty-eight models were mounted centrally in a mechanical articulator. In these model cases, at least one second premolar and one first molar in the maxilla and mandible had to be prepared for crown production (preparation). A total of 50 teeth was prepared. Crowns were then designed with the aid of the Cerec 3D system. The crown designs were milled and integrated in the model. Silicone bite registrations, the contact point patterns of which were compared with the virtually designed crowns, were produced in static occlusion in the region of the crowns. Different evaluation methods were used for the comparison. RESULTS: There was an agreement of 78% with regard to number, 76% in terms of localization, 65% regarding size, and 65% in terms of shape. CONCLUSION: It was thus confirmed that very good, highly reproducible results can be achieved with the Cerec 3D system.

Bicuspid↗