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PubMed2005

Influence of casting methods on marginal and internal discrepancies of complete cast crowns.

The relationship between the application of die-spacer prior to wax pattern fabrication and metal removal from the inner surface of the casting on marginal and internal discrepancies of complete cast crowns was evaluated. One hundred and twenty complete crowns were cast with palladium-silver alloy melted by gas-oxygen torch or electrical resistance and cast with a centrifuge casting machine. After casting, the crowns were seated on each type of different marginal configuration dies (90-degree shoulder, 20-degree beveled shoulder, and 45-degree chamfered shoulder) with a static load of 90 N during 1 min. Evaluation of the marginal fit of the specimens was made using a digital micrometer. The crowns were embedded in acrylic resin and longitudinally sectioned to verify the internal discrepancy that occurred in lateral and occlusal interfaces with a digital micrometer. The data were submitted to ANOVA and Tukey's test with a significance level of 5%. The best marginal and inner fits were obtained with the gas-oxygen torch source. The 45-degree chamfered shoulder showed the best marginal and inner fit, and better internal relief was obtained in the crowns abraded with 50 microm Al2O3 particles.

Analysis of Variance↗
PubMed2005

Influence of cervical preflaring on determination of apical file size in maxillary premolars: SEM analysis.

The purpose of this study was to investigate the influence of cervical preflaring on the determination of the first file that binds at working length (WL) in buccal roots of maxillary premolars. Five groups (n=10) were formed at random and, after standard access cavities, the WL was determined 1 mm short from the apex. In group 1, the initial apical file was inserted without preflaring of cervical and middle thirds of the root canals. In groups 2 to 5, the cervical and middle thirds were enlarged with sizes 90 and 110 Gates-Glidden drills, K(3) Orifice Opener instruments, ProTaper instruments and LA Axxess burs, respectively. Canals were sized manually with K-files, starting with No. 08 K-files inserted passively up to the WL. File sizes were increased until a binding sensation was felt at the WL and the size of the instrument was recorded. Transversal sections of the WL regions were examined under scanning electron microscopy and the discrepancies between the canal diameter and first file to bind at the WL were assessed. Significant differences (p<0.001) were found between the groups. The major discrepancy was found without preflaring (mean 157.8 microm). LA Axxess burs produced the smallest discrepancy (mean 0.8 microm). Gates-Glidden drills and K(3) Orifice Opener instruments showed no significant differences (p>0.05) between their results (83.2 microm and 73.6 microm, respectively). The discrepancy for ProTaper instruments was 35.4 microm on average. In conclusion, the instrument binding technique for determination of the anatomical diameter at the WL was not precise. Preflaring of the cervical and middle thirds improved the determination of the anatomical diameter at the WL, and the type of instrument played a major role. Canals preflared with LA Axxess burs showed a more accurate binding of the files to anatomical diameter.

Analysis of Variance↗
PubMed2006

The importance of apical patency and cleaning of the apical foramen on root canal preparation.

The apical limit of root canal instrumentation has always been a matter of great controversy. Despite the large number of published studies on this subject, a consensus has not yet been reached. In fact, the recent discussion on apical patency and cleaning of the apical foramen, as well as the incorporation of these procedures to the endodontic treatment, seem to have raised even more polemics. It is likely that all this polemics has its roots in the lack of interrelation between the theoretical knowledge of pulp stump and periapical tissues and the real clinical practice. By addressing the most important aspects of this theme, this paper aims to present news concepts about the importance of apical patency and cleaning of the apical foramen during root canal preparation.

Humans↗
PubMed2006

The influence of the surgical operating microscope in locating the mesiolingual canal orifice: a laboratory analysis.

The aim of this study was to evaluate the influence of using the surgical operating microscope (SOM) for detection of the mesiolingual (ML) canal orifice in extracted first maxillary permanent molars. One hundred and eight human first maxillary permanent molars were randomly selected and mounted onto a dental chair mannequin. Conventional access cavity was prepared and an attempt was made to locate the mesiolingual canal orifice using only a sharp explorer, a mirror and a #10 K-file. A mesiolingual canal orifice was either located or not located. If not located, the teeth were then evaluated by using a surgical operating microscope (SOM). The mesiobuccal roots of all teeth where the ML canal orifice had not been located were sectioned in an axial plane and the sections were explored with an adjunctive use of the SOM at a 25 X magnification. ML canal orifices were detected in 58 teeth using only a sharp explorer, a mirror and #10 K-file. In the remaining 50 teeth, 37 ML canal orifices were located by using the SOM and 3 ML canal orifices were located after root sectioning. In 10 teeth, the ML canal orifices were not found. The results of this study showed a high incidence of a ML canal in the mesiobuccal roots of the first maxillary molars (90.7%) and demonstrated that the adjunctive use of the SOM increased the ability of the dental clinician to locate the ML canal orifice.

Dental Equipment↗
PubMed2003

Crown lengthening in mandibular molars: a 5-year retrospective radiographic analysis.

BACKGROUND: Crown lengthening procedures are a significant part of the periodontist's armamentarium. In order to recreate the clinical space lost to caries or trauma necessary for prosthetic restoration, osseous surgery is often required. If the procedure is not carefully planned, it may result in furcation involvement of multirooted teeth. METHODS: Twenty-six subjects with 26 mandibular molar teeth requiring crown lengthening procedures prior to prosthetic crown placement were evaluated. Nineteen subjects with 24 prosthetic crowns on lower molars which had not undergone crown lengthening were included as control teeth. Bite-wing radiographs prior to surgery (for the test group) or placement of the crown (control group) and 5 years after completion of the prosthesis were compared and analyzed. RESULTS: Of the 26 test teeth, 10 teeth (38.5%) were found to have radiographic evidence of furcation involvement, whereas none of the control teeth developed furcation invasions. CONCLUSION: A critical distance from the furcation (CDF) of 4 mm was established as a landmark under which, if surgery was performed on mandibular molars, chances of furcation involvement in the future were very high.

Adult↗
PubMed2006

[Effectiveness of methacrylamide monomer for dentin bonding].

PURPOSE: In this study, we investigated the conditioning efficacy of a self-etching primer consisting of methacrylamide, N-methacryloyl-omega-amino acid (M omega A) derivatives for enhancing the bond strength of resin to crown and root dentins. METHODS: A series of four M omega A derivatives, with different methylene chain numbers, were synthesized, as follows. 1: N-methacrylole glycine (Gly); 2: N-methacrylole-beta-alanine (beta Ala); 3: N-methacrylole-4-aminobutyric acid (Bu); 4: N-methacrylole-5-aminovaleric acid (Va). The dissociation equilibrium pH (pKa) of carboxylic acid in each of the M omega A derivatives was determined. The shear bond strengths of resin to the crown and root dentins, primed with the Gly solution were measured for various conditioning times. We also measured the bond strength to both the dentins following application of the M omega A adhesives with different pKa values for 30 seconds. RESULTS: For the Gly primer, the bond strength of resin to both dentins increased with the conditioning time until 30 seconds, leveled off thereafter by increase in the methylene chain number. The effects of conditioning time on the bond strength to the crown and the root dentin were the same. Furthermore, the bond strengths to the dentins, conditioned with each of the four M omega A derivatives for 30 seconds, were the same, even though the decalcified amounts of the dentin apatite noted following conditioning with Bu and Va were lower than that noted following conditioning with Gly. This was attributed to the pKa value of the acidic groups in the acidic monomer directly relating to the decalcified amount of dentin apatite. CONCLUSIONS: Application of the M omega A solutions, resulted in an increase in the bond strength of resin to both crown and root dentins. In particular, the Bu and Va primers were very useful as primers promoting the bond of resin to dentin, since the etching potential was very low.

Acrylamides↗
PubMed2006

Critical appraisal. Porcelain veneer outcomes, part I.

Etched porcelain veneers have now been used clinically for about 20 years. The profession was originally very skeptical about bonding thin shells of a brittle ceramic material to teeth. However, ceramic veneers have proved to be not only very esthetic but also extremely durable restorations. This two-part Clinical Appraisal reviews several articles related to veneer longevity and clinical factors contributing to--or detracting from--longevity. Part II will appear in the next issue of JERD.

Adolescent↗
PubMed2002

The accuracy of three different electronic root canal measuring devices: an in vitro evaluation.

The main objective of this in vitro study was to evaluate the effects of the operator's experience level and pre-flaring on the accuracy of the results of three different brands of a new generation of root canal measuring devices, as well as the comparison among them. Extracted human teeth were prepared and then actual length and electronic length measurements were made by three different operators according to a double-blind technique. Three different operators performed electronic measurements on each specimen separately with three different electronic root canal measuring devices using in vitro models. Measurements were repeated by all operators after the pre-flaring. Taking the clinical tolerance of +/- 0.5 mm into account, there was no statistically significant difference between the accuracy of the instruments (P > 0.01). However, the results obtained from the Bingo electronic apex locator in pre-flared canals by the beginner operator were statistically significant (P < 0.01). All of the instruments had a clinically acceptable result at the tolerance of +/- 0.5 mm. If the instruments are used in accordance with the manufacturer's instructions, experience with electronic root canal measurement is not essential. However, the operator has to be more careful when working on pre-flared canals.

Analysis of Variance↗
PubMedDate not supplied

The microtensile bond strength of self-etching adhesives to ground enamel.

It is uncertain whether single-phase self-etching adhesives form bonds to enamel as reliable as those of etch-and-rinse adhesives. This study compared the microtensile bond strengths to ground enamel of three self-etching adhesive systems, a self-etching primer system and an etchand-rinse adhesive system. Human enamel was ground flat with 320-grit silicone carbide paper. The self-etching adhesives iBond (Heraeus Kulzer), Prompt L-Pop (3M ESPE) and Xeno III (Caulk/Dentsply), the adhesive with a self-etching primer Clearfil SE Bond (Kuraray) and the etch-and-rinse adhesive Scotchbond Multipur-pose (3M/ESPE) were applied as directed, followed by a core of the same manufacturers' hybrid resin composite. A microtensile bond strength evaluation was performed after 48 hours of water storage, using untrimmed beams approximately 0.9 mm2 in cross-sectional area at a crosshead speed of 0.6 mm/minute. There were no pretest failures in any group, and failures were predominately adhesive or mixed. Adhesion to enamel of Clearfil SE was not significantly different from Scotchbond Multi-Purpose, while the three self-etching adhesive systems demonstrated significantly lower bond strengths (One-way ANOVA, Tukey-Kramer Multiple-Comparison Test, p < 0.00001).

Acid Etching, Dental↗
PubMedDate not supplied

Light protection of fiber-reinforced strip using aluminum foil for the direct splinting technique.

The critical point of the clinical procedure of direct splinting is the placement of the fiber-reinforced strip, which has to be well adapted to tooth surfaces. This article describes the use of aluminum foil to cover and protect the fiber-reinforced strip from light polymerization during the direct splinting technique. The advantage of using aluminum foil is to prevent premature curing of the fiber-reinforced strip, which would necessitate repetition of the procedure. With this technique, the strip is gradually exposed and adapted to the lingual/palatal surfaces of the teeth and light cured, allowing for ample working time.

Acid Etching, Dental↗
PubMed2004

Abutment forms and restorative materials in adhesive prosthesis: a finite element analysis.

This study evaluated experimental abutment forms utilizing adhesion for clinical treatment by the three-dimensional finite element method. Three experimental abutment forms with no axial wall were evaluated: Form 1 was the occlusal surface reduced by 1.5 mm, Forms 2 and 3 were the crown cut perpendicular to the tooth axis 2 mm or 4 mm from the central groove. The restorations were made of 3 types of materials: composite resin, porcelain, and a gold-based alloy. Restorations were bonded to the abutments with an adhesive resin. A vertical load of 500 N was applied to the center of the inner incline of the buccal cusp. The stresses in the adhesives were largest in Form 1 with composite resin and in Form 3. It was indicated that the stresses were greatly affected by the form of the abutment and the restorative materials.

Bicuspid↗
PubMed2005

Resistance to cyclic fatigue and fracture of structurally compromised root restored with different post and core restorations.

The aim of this study was to evaluate the resistance to fracture of endodontically treated teeth with flared canals restored with different post and core restorations under static and cyclic fatigue loadings. Sixty human maxillary central incisors were used. Two main groups (non-ferrule and 1-mm ferrule) were divided into three types of restoration: custom cast post-and-core (MPC), resin composite post-and-core (RCP), and resin composite core in combination with prefabricated carbon fiber post (FRC). Half of each group was subjected to a static loading test, and the other to a cyclic fatigue test. FRC exhibited a significantly higher number of load cycles than the other groups, and MPC showed the highest failure load among the tested groups. However, all FRC and MPC specimens demonstrated unfavorable root fractures. The results of this study suggested that RCP prepared with 1-mm ferrule was the most desirable restoration for structurally compromised roots, as relatively strong resistance to cyclic fatigue and fracture was revealed--given that all RCP specimens demonstrated favorable root fracture.

Analysis of Variance↗
PubMed2005

In vitro study on marginal and internal fit of CAD/CAM all-ceramic crowns.

The purpose of this study was to evaluate the marginal and internal fit of all-ceramic crowns fabricated using the Decsy CAD/CAM system. A master die of maxillary first premolar was measured, and experimental crowns were fabricated. Four conditions were established by combining two convergence angles (4 degrees and 12 degrees) of the abutment with two different luting space settings (15 microm and 55 microm). The results showed that the experimental crowns had a marginal gap of 42 to 56 microm. When the luting space setting was 15 microm, the internal gap was 85-88 microm; when the setting was 55 microm, the internal gap was 126-138 microm. The marginal gap for each experimental crown met the clinically acceptable criterion.

Aluminum Silicates↗
PubMed2005

Effective factors including periodontal ligament on vertical root fractures.

The purpose of the present study was to analyze effective factors including periodontal ligament on vertical root fractures (VRFs). Eighty maxillary central incisors were assigned to eight groups, depending on master apical file (MAF) size, loading point and existence of a simulated periodontal ligament (PDL). The gutta-percha in the root canal was vertically pressed with a Co-Cr rod using a universal testing machine. An ordinal logistic analysis was employed to determine significant factors. VRFs were observed in 88.8% of the specimens but no horizontal fractures were found. There were three types of VRFs: partial fracture not involving the apex (PF, 41.3%), partial fracture involving the apex (AF, 40.0%), and complete fracture (CF, 7.5%). MAF size significantly affected VRFs (p < 0.05); large MAF size exhibited more partial fractures involving the apex. Loading point and existence of PDL did not affect VRFs.

Dental Instruments↗
PubMed2005

An in vitro comparison of root canal measurement in primary teeth.

To compare the accuracy of root canal lengths in primary teeth determined by tactile sense, electronic apex locator, conventional radiography, and digital radiography in primary teeth. The study sample consisted of twenty 20 extracted, single-rooted primary teeth. A comparison was made between the working length measurements obtained by tactile sensation, electronic apex locator, conventional film, and digital radiography, using stereomicroscopic measurements to obtain real canal length. The mean readings obtained were 15.91+/-2.06 by tactile measurement, 15.94 94+/-1.42 by apex locator, 16.06+/-1.73 by conventional radiography, and 15.91+/-1.60 by digital radiography. No statistically significant differences were seen between the techniques.

Dental Pulp Cavity↗
PubMed1999

Porcelain veneers: a challenging case.

A patient in his early 20s with teeth badly discoloured by tetracycline was seeking treatment to improve his esthetics. Because retreatment and cost were important considerations, porcelain veneers were the treatment of choice. The challenge in this case was to mask the underlying tetracycline stain before the final cementation and thus gain more control over the final shade of the veneers.

Adult↗
PubMed1998

Restorative and periodontal considerations of short clinical crowns.

The purpose of this review was to examine the periodontal and restorative factors related to restoring teeth with short clinical crowns. Modes of therapy are usually combined to meet the biologic, restorative, and esthetic requirements imposed by short clinical crowns. The complications presented by teeth with short clinical crowns demand a comprehensive treatment plan and proper sequencing of therapy to ensure a satisfactory result. Visualization of the desired result is a prerequisite of successful therapy. Short clinical crowns present many problems to the restorative dentist. Restorations should have proper form, function, and esthetics while promoting the maintenance of tissue health in the surrounding areas. However, adequate tooth structure for achieving these goals may not always be available. While it is difficult to precisely define minimum crown length, this study offers guidelines for defining a short clinical crown and suggests procedures for achieving a predictable result without compromising the periodontium. The consequences of placing a restoration on a tooth with insufficient crown length are discussed and various treatment methods are reviewed.

Alveolar Process↗