Effects of tooth surface preparation on the shear bond strength of resin-modified glass ionomer cements.
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Nondestructive, in vitro quantification of crown margins.
STATEMENT OF PROBLEM: It is important that artificial crowns fit the prepared tooth accurately, as marginal deficiencies are predisposed to plaque accumulation and lead to increased risk of periodontal disease. Various methods of evaluation for marginal fit are described in the literature, but most approaches are limited by destructive methods of assessment and/or small points of measurement. PURPOSE: This study compared, in vitro, the marginal fit of 4 types of complete crowns on human premolar teeth with the use of nondestructive profilometry. This method determined whether fit was influenced by type of crown or surface morphology of the tooth, namely, grooved or ungrooved surfaces. MATERIAL AND METHODS: Four groups of specimens were prepared for complete crowns: group BA, bonding alloy with chamfer finish line; group G, gold alloy with chamfer finish line; group PC, porcelain with a chamfer finish line; and group PS, porcelain with a shoulder finish line. Two profiles of grooved mesial and ungrooved distal surfaces of the teeth were performed: (1) teeth prepared for each type of crown and (2) teeth with crowns seated but not cemented. Marginal fit (absolute marginal discrepancy) from the finish line edge of the tooth preparations to crown edges (CE) and leading edges (LE) of crowns were measured. RESULTS: A 2-way analysis of variance for crown type and tooth surface morphology revealed significant differences between crown types for all measurement parameters, except vertical LE. The effect of surface morphology was not significant, except for vertical LE (P<.05). For all parameters, except vertical LE, the ranking of marginal fit discrepancies from greatest to least was as follows: group PC, G, BA, and PS. For vertical LE distances, the ranking was PS, BA, G, and PC (P<.05). CONCLUSION: Profilometry was used as a nondestructive, accurate method of evaluating the absolute marginal fit of different types of crowns. Marginal fits varied continuously around the circumference of each crown and made clinical assessment of fit accuracy subjective and arduous.
Analysis of Variance↗
The Carolina bridge: a novel interim all-porcelain bonded prosthesis.
UNLABELLED: Numerous bonded bridge designs have been advocated over the years for the temporary or permanent replacement of missing teeth. Both metal and all-porcelain designs of bonded bridges have been advocated, with varying degrees of success. However, all of these designs involve some degree of tooth preparation, making them irreversible in nature. The Carolina bridge, a novel all-porcelain bonded pontic, requires no significant tooth preparation, making it an outstanding option as an interim prosthesis. The key to success is the availability of adequate surface area interproximally to ensure optimally strong resin composite connectors. CLINICAL SIGNIFICANCE: This article describes the indications, contraindications, and clinical technique for the placement of an ultraconservative all-porcelain bonded bridge for the interim replacement of single incisors.
Composite Resins↗
A survey of the pre-bonding preparation of denture teeth and the efficiency of dewaxing methods.
OBJECTIVES: Denture tooth debonding remains a significant problem, with the surface condition of the tooth playing a pivotal role. The purpose of this investigation was to determine the methods used in tooth preparation. The efficiency of wax removal from teeth using a range of water temperatures was also investigated. METHODS: (a) A postal survey on the methods of denture tooth preparation, prior to denture processing, was conducted amongst dental instructors in prosthodontic departments of dental schools in Great Britain and Ireland. (b) Tooth surfaces contaminated with fluorescence wax were subjected to agitation in water at a range of temperatures and the surfaces examined under ultraviolet radiation. RESULTS: (a) The majority of operators did not use a solvent for the removal of the wax film from the teeth. Modification of the tooth ridge lap surface was carried out by 52% of the respondents on initial processing but increased to 85% when rebonding teeth. (b) Dewaxing denture teeth at a range of water temperatures showed wax retention on the tooth surfaces up to 90 degrees C. Rough surfaces retained more wax than smooth surfaces. Wax eliminator was shown to be necessary for complete wax removal. CONCLUSIONS: No standard technique exists amongst dental instructors for the preparation of denture teeth prior to acrylic resin polymerization. The use of a wax solvent is to be recommended.
Acrylic Resins↗
Effect of adhesive resin cement on design of partial veneer crowns.
STATEMENT OF PROBLEM: Procedures involved in the tooth preparation, impression, and casting of partial veneer three-quarter crowns are considered to be complex. PURPOSE: This study assessed whether a simplified partial veneer crown design, when cemented with a 4-META adhesive resin, had a comparable resistance to displacement forces compared with a conventionally prepared partial veneer crown cemented with a traditional luting agent. MATERIAL AND METHODS: Conventional partial veneer crowns were prepared on 20 natural premolars, and 20 other premolars received modified partial veneer crown tooth preparations without proximal grooves. Artificial crowns were made for these teeth with Students alloy. Half the crowns in each of the 2 groups were luted with 4-META resin; the other half were luted with a zinc phosphate cement. Loads required to displace the partial veneer crowns were recorded after 24 hours and thermocycling, then the mode of separation was recorded for each crown. Average force required to displace partial veneer crowns for the 4 groups were subjected to 2-way analysis of variance and Scheffé test. RESULTS: The 2 groups luted with 4-META resin and the group with proximal grooves luted with zinc phosphate were not significantly different. However, they were all greater than the group without proximal grooves luted with zinc phosphate cement. CONCLUSION: Forces required to displace partial veneer crowns prepared in a traditional manner and those teeth prepared without proximal grooves were similar if the artificial crowns were luted with adhesive resin cement.
Acrylic Resins↗
Marginal accuracy and fracture strength of ceromer/fiber-reinforced composite crowns: effect of variations in preparation design.
STATEMENT OF THE PROBLEM: Targis/Vectris restorations provide excellent esthetics and clinical success; however, the relationship of their marginal accuracy and fracture strength to the tooth preparation design requires further investigation. PURPOSE: The aim of this study was to evaluate the effect of variations in tooth preparation design on the marginal accuracy before and after cementation and on the fracture strength of the ceromer/fiber reinforced composite crown. MATERIAL AND METHODS: Three metal dies with varying total occlusal convergence angles (6 degrees, 10 degrees, 15 degrees) were prepared. A total of 30 (10 for each angle) Targis/Vectris crowns were fabricated. The restorations were evaluated at 48 points on the entire circumferential margin with a stereomicroscope measuring in micrometers for margin adaptation before and after cementation. The specimens then were compressively loaded to failure in a universal testing machine. Marginal adaptation was analyzed with Kruskal-Wallis test and post-hoc Dunnett test (alpha=0.05). The fracture strength was analyzed with analysis of variance and the Scheffe adjustment at the 95% significance level. Fracture surfaces of the crowns were examined with a scanning electron microscope to determine the mode of fracture. RESULTS: The smallest marginal gap was recorded in angled crowns with a 6-degree convergence (47 microm mean). The marginal gap of most (95.6%) of the crowns was within a clinically acceptable level (established as </=100 microm). The mean marginal gap increased significantly after cementation, with the largest increase in the 6 degree group (76 microm mean). The 6-degree angled crowns had a significantly higher fracture strength (1,543 N) than the more convergent crowns (1,366 N) (P<.001). Mean fracture strength of all the crowns was 1,390 N. Scanning electron microscope observation showed that all crowns exhibited a 2-phase fracture pattern: a crack and chipping of the Targis layer followed by adhesive failure. CONCLUSION: Within the limitations of this experimental design, decreasing the axial convergence angle of the ceromer/fiber-reinforced composite crowns diminished their marginal gap and increased their fracture strength.
Analysis of Variance↗
[The influence of the operating positions on the prepared abutment contour of full cast crowns. Unanatomical artificial teeth for fixed bridge].
With a view to research the effect of the crown form, we made the unanatomical artificial teeth and some doctors to do the abutment tooth preparation with full cast crowns for the maxillar left fixed prosthodontics three-unit bridge in random position. After that, following are the results of a study made on the influence to the prepared tooth form. The prepared teeth are the second premolar and the second molar (The "second premolar" is abbreviated to "5" and the "second molar" is abbreviated to "7"). 1. The reductions of occlusal surface was excessively larger at 5 and 7 buccal cusp regions, while it was excessively smaller at central groove area. 2. The reductions of axial surface and subgingival area were excessively smaller at 5 and 7. 3. As for the degree of axial taper, its was steeper toward the buccal and distal surfaces at 5 and 7. 4. As for the relative degree of axial taper, it get the largest in degree on both sides between 5 medial surface and 7 distal surface. The results of this experiment are similar to the results that used anatomical artificial teeth. These results are affected by the operating posture.
Crowns↗
A provisional and new crown to fit into a clasp of an existing removable partial denture.
A technique that forms an abutment crown to fit into an existing clasp of a removable partial denture by relining an acrylic resin pattern is described. The outer contour of the pattern is made within an irreversible hydrocolloid impression by use of Duralay autopolymerizing acrylic resin applied with precision dispensers. The pattern is formed before tooth preparation and is made approximately 0.4 mm thick. After tooth preparation, the shell pattern is relined with the same autopolymerizing resin and the existing removable partial denture is fitted over it. The gross pattern is trimmed and the margins refined on a die made from an elastomer impression. The refined pattern is cast and finished, avoiding reduction of the contours established. A second crown is similarly formed in tooth-colored autopolymerizing acrylic resin. It serves as a provisional restoration that allows the patient to wear the removable partial denture while the laboratory procedures are performed.
Crowns↗
Comparison of two tooth-saving preparation techniques for one-surface cavities.
The atraumatic restorative treatment technique (ART) is based on removing infected tooth material using only hand instruments and filling the subsequently cleaned cavity with adhesive material such as glass ionomer. As its name suggests, the ART technique should be atraumatic during treatment, as well as for the tooth itself as for the patient. It was primarily developed for treating people living in underserved areas of the world where resources and facilities such as electricity and trained manpower are limited. Many studies have evaluated the ART technique and the results have supported its application. However, a very limited number of studies have compared ART with more conventional techniques. For that reason, a study was conducted in Pakistan, to compare the ART technique with another more conventional treatment technique. The results of this study show that the preparations with hand instruments resulted in smaller sized cavities and therefore may be less traumatic to the tooth. It was also associated with less pain reactions compared to the more conventional technique. Although preparations with hand instruments required more time, this did not seem to affect the survival of restorations. The survival of glass ionomer cement restorations made with hand instruments was comparable with single surface amalgam restorations made with a more conventional technique. Recurrent caries was not associated with any glass ionomer cement restorations made with hand instruments. The retention rate of glass ionomer sealants was low, however one dentist had a sealant retention rate of 81.5 percent that suggests that this procedure can be performed satisfactorily in conjunction with a glass ionomer cement restoration. Operator variances did seem to affect the restorations. Survival of glass ionomer restorations made with both hand and rotary instruments varied for different operators. Similarly, the retention of fissure sealant also varied amongst operators. Operator differences also influenced the extent of tooth substance lost due to cavity preparation. The ART technique is a feasible approach towards the treatment of dental caries especially of one-surface lesions for underserved populations.
Adolescent↗
Pulp histology after Er:YAG laser cavity preparation in subhuman primates--a pilot study.
UNLABELLED: The aim of the study was to make a direct comparison of the pulpal effects of laser and turbine preparations in subhuman primates. One female baboon (Papio Ursinus ursinus), weighing 15 kg, was used. General anaesthesia was administered (ketamine 100 mg/ml/kg body weight) and maintained with acepromazine (10 mg/ml/kg body weight). Class V cavities were prepared buccally in a total of 28 teeth (7 in each quadrant). Teeth in the upper right and lower left quadrants were prepared using a conventional 330 carbide bur in a high-speed fibre-optic handpiece with copious water spray. Teeth in the upper left and lower right quadrants were prepared using an Er:YAG laser drill (Fotona Twinlight, Llubljana, Slovenia) delivering 500 mJ at a pulse rate of 10 Hz and a wavelength of 2940 nm. The animal was sacrificed after 25 days. After general anaesthesia as described before, perfusion fixation of the head was accomplished with 10% neutral buffered formalin, pumped through a catheter inserted into the left carotid artery. The jaws were removed and, using a 330 carbide bur in a high speed handpiece, a continuous groove was cut through the bone and the roots at the level of the middle third of all the roots to promote thorough fixation of pulpal tissue. Decalcification and grading of the severity of the pulpal responses were conducted according to standard procedures. RESULTS: Owing to procedural errors seven teeth, FDI numbers 23, 24, 31, 34, 35, 44 and 45, had to be eliminated. The turbine-prepared teeth (N = 11) had a mean remaining dentine thickness (RDT) of 0.77 mm (SD = 0.42) and the laser-prepared teeth (N = 10) had a mean RDT of 0.81 mm (SD = 0.60). All pulps appeared normal except in one turbine-prepared tooth (12 with RDT = 0.20) and one laser-prepared tooth (27 with RDT = 0.30, where irreversible damage was caused. The only other deviations from normal were seen in the laser-treated 41 (RDT = 0.69) and the turbine-treated 36 (RDT = 0.77) where moderate hyperaemia was seen. Within the limitations of this study it can be concluded that there is no significant difference between dental pulp of teeth where Class V cavities were prepared with an Er:YAG laser drill compared with those prepared with a standard turbine drill.
Animals↗
[Clinical variation in the preparation of tooth stumps].
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Crowns↗
Aesthetic tooth modification for patients with cleft lip and palate.
Alongside orthodontic treatment, tooth shape modification may be indicated for teeth associated with clefts of the lip and alveolus, and in non-carious teeth, minimal tooth preparation techniques appear to be most appropriate. Two methods of tooth shape modification are described. In one, hybrid composite materials, bonded to tooth enamel using the acid-etch technique, may be considered to provide a permanent, low cost, aesthetically satisfactory result, often without tooth preparation and with minimal operating time. Alternatively, indirect veneers may be appropriate for treatment of more severely malformed teeth.
Anodontia↗
Ultraconservative sealed restorations: three-year results.
The overall objective of this clinical study was to determine the feasibility of using a sealed composite restoration to arrest caries without the removal of the carious lesion and without the traditional cavity preparation. The minimal tooth preparation (a bevel in enamel) usually did not require any anesthetic injection and conserved tooth structure. These ultraconservative sealed composite restorations placed over caries (CompS/C) have been compared with ultraconservative sealed amalgam restorations (AGS) and with the traditional outline form (unsealed) amalgam restorations (AGU). This clinical study has shown that: (1) caries can be arrested by the CompS/C restoration for a period of three years; (2) the marginal integrity of the AGS restorations showed a definite trend toward improvement as compared to the AGU restorations; and (3) complete sealant retention over posterior restorations was similar in both the CompS/C and the AGS groups during the first two years; however, at Year 3 complete sealant retention was 16 percent higher in the CompS/C than in the AGS group.
Adolescent↗
Clinical evaluation of sealants and preventive resin restorations in a group of environmentally homogeneous children.
PURPOSE: Pit and fissure sealants reduce occlusal caries when proper patient selection and application techniques are followed. To increase retention rate of sealants over time, good adaptation and deep sealant penetration are important. Studies remain inconclusive, however, as to determining if the bur preparation of pits and fissures would increase the adaptation and penetration thus improving sealant retention. The aim of this study was to assess if tooth preparation prior to sealant application improves sealant retention. METHODS: In this prospective cohort study, 43 children and adolescents from 4 Hutterites colonies were, for 3 years, bussed to the University of Manitoba pediatric dental clinic, Winnipeg, Manitoba, Canada, for comprehensive dental care including sealant placement using standard procedures. These came from a community with homogeneous social economical status, dietary habits, fluoride intake, and lifestyles. The decision of tooth preparation prior to sealant application was made ad hoc. Of 122 treated permanent posterior teeth, 54 had been treated as preventive resin restorations (PRRs, type A or B) and 68 were nonprepared sealants. RESULTS: After 1 year, teeth prepared (type B PRRs) and restored with flowable composite resins had significantly (P<.01) lower retention rates (27% vs 63%) than did teeth with nonprepared sealants or typeA PRRs. Teeth prepared (type B PRRs) were also significantly (P<.001) more likely to have caries on follow-up examination (50% vs 11%) than were teeth with nonprepared sealants or type A PRRs. CONCLUSIONS: These results suggest that preventive resin type B restorations restored with flowable composites are not helpful in terms of retention or caries reduction.
Adolescent↗
The tilted posterior tooth. Part III: Abutment for a fixed partial denture.
The problem of achieving a common path of insertion for a fixed partial denture when a tilted posterior abutment is involved can usually be solved by well planned tooth preparation in conjunction at times with intentional endodontic therapy. When tooth preparation alone cannot solve the problem, the mechanical solutions of the locked attachment and the telescopic retainer are available and must be considered. Other problems involved with the tilted abutment, adjacent tilted teeth, space reduction, supraversion of the antagonist, and the problem of a long-span fixed partial denture were discussed.
Bicuspid↗
The construction of crowns for removable partial denture abutment teeth.
The construction of crowns for teeth that will serve as abutment teeth for removable partial dentures is an important and technically demanding procedure. The preparation of the tooth itself must include provision for the components and path of placement of the removable partial denture and at the same time conform to all the parameters associated with proper tooth preparation. Some of the factors unique to surveyed crowns that must be considered include the position of the tooth in relation to the proposed occlusal plane with the removable partial denture, the type of facial and lingual tooth contours desired for the direct retainer, the size and suitability of existing restorations, and the proposed path of placement and removal of the removable partial denture relative to the orientation of the abutment tooth as well as to other adjacent teeth if the abutment also is to be used as a fixed partial denture retainer. The design requirements for the removable partial denture must be determined before treatment is initiated, to account for all of these factors.
Crowns↗
Marginal adaptation of inlay-retained adhesive fixed partial dentures after mechanical and thermal stress: an in vitro study.
STATEMENT OF PROBLEM: There are no studies that analyze the long-term durability of minimally invasive fixed partial dentures (FPDs) by comparing different methods of adhesive bonding. PURPOSE: This in vitro study examined the influence of cavity design and operative technique on the marginal adaptation of resin-bonded composite FPDs. MATERIAL AND METHODS: Slot-inlay tooth preparations with cavity margins located in enamel were prepared in 18 maxillary canines and 18 maxillary first molars designated as abutments. The specimens were divided equally into 3 experimental groups. In all groups, butt joint tooth preparations were created in canines and molars. In group 2, canines were prepared additionally with a 1.5-mm wide palatal bevel in enamel. After pretests with modification spaces of 11 and 17 mm (length), 2 missing premolars were replaced by the ceromer Targis and reinforced with the glass-fiber material Vectris. The prostheses were inserted with Tetric Ceram with use of an ultrasonic-supported, high-viscosity technique. Restorations were selectively bonded to cavity finish lines in groups 1 and 2 ("selective bonding"). In group 3, restorations were bonded totally to the whole cavity surface ("total bonding"). The restorations were stressed in a computer-controlled masticator. Marginal quality was examined with an SEM at x 200. RESULTS: The percent area of optimal margins after thermomechanical loading between composite and enamel in each group was as follows: group 1, 86.2% +/- 12.3% for canines and 95.5% +/- 3.5% for molars; group 2, 95.3% +/- 2.1% for canines and 96.2% +/- 2.7% for molars; and group 3, 95% +/- 0.9% for canines and 86.4% +/- 3.2% for molars. The marginal quality for molars inserted with total bonding was significantly lower (P< or =.05). CONCLUSION: Within the limitations of this study, the selective bonding technique for slot inlay-retained fixed partial dentures resulted in a negligible loss of marginal quality after extensive mechanical and thermal stress. The selective bonding technique is recommended for box-shaped cavity preparations.
Acid Etching, Dental↗
Sealed restorations: 4-year results.
The overall objective of this clinical study was to determine the feasibility of using a sealed composite restoration to arrest caries. This objective was to be achieved using minimal tooth preparation for Class I lesions, without the traditional Class I cavity preparation and without the removal of the carious lesion. The minimal tooth preparation consisted of no [corrected] removal of the carious lesion, bevel in enamel only, and usually not requiring any anesthetic injection. These ultra-conservative sealed composite restorations placed over caries (CompS/C) were compared with ultra-conservative sealed amalgam restorations (AGS) and with the traditional (unsealed) amalgam restorations (AGU). This study showed that: 1) caries is arrested under the CompS/C restoration for a period of 4 years; 2) sealant retention is similar in both the CompS/C and the AGS groups; 3) the marginal integrity of the AGS restorations is markedly superior to that of the AGU restorations; and 4) sealant appears to prevent wear of posterior composite restorations.
Adolescent↗