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PubMed2004

Tooth preparation: a study on the effect of different variables and a comparison between conventional and channeled diamond burs.

PURPOSE: The purpose of this study was to evaluate the different variables involved in tooth cutting to characterize intrapulpal temperature generation, cutting efficiency, and bur durability when using conventional and channeled diamond burs. MATERIALS AND METHODS: Forty premolars and 60 molars were selected for the study. Four diamond burs were paired according to grit size: 125-microm grit: Brasseler Coarse (Control 1) and TDA System (Test 1) burs; and 180-microm grit: Brasseler CRF (Control 2) and NTI Turbo Diamond (Test 2) burs. Each bur was used twice when cutting the premolar teeth, whereas it was used for 60 cuts when cutting the molar teeth. The data were analyzed to compare the correlation of bur design, grit and wear, amount of pressure, advancement rate, revolutions per minute, cutting time and rate, and proximity to the pulp chamber with intrapulpal temperature generation, cutting efficiency, and bur longevity. The mean values of test and control burs in each group were compared using an ANOVA (p < 0.05 for significant differences) for temperature generation and an ANOVA and the Tukey multiple range test (p< or = 0.05) for cutting efficiency and bur longevity. RESULTS: No significant difference was found in intrapulpal temperature generation while cutting premolar and molar teeth with conventional and channeled diamond burs. In both groups, the mean temperature recorded during and after the cutting procedure was lower than the baseline temperature. For premolar teeth, no significant difference was established for control and test burs for the load required to cut into the tooth and the cutting rate. However, both test burs showed significantly fewer revolutions per minute when compared to their control counterparts. For the molar teeth, the Brasseler CRF bur required a significantly lower cutting load when compared to the NTI bur, whereas no difference was noted between the other pair of burs. The cutting rate was significantly higher for both control burs, whereas revolutions per minute (rpm) were greater for control coarser burs only. Overall, channeled burs showed a significantly lower cutting efficiency when compared to conventionally designed burs. CONCLUSION: Within the limitations of this study, channeled burs showed no significant advantage over conventional diamond burs when evaluating temperature generation and bur durability. Moreover, the cutting efficiency of conventional burs was greater than that of channeled burs.

Analysis of Variance↗
PubMed2006

Dynamometric assessment of the mechanical resistance of porcelain veneers related to tooth preparation: a comparison between two techniques.

STATEMENT OF PROBLEM: There is little agreement regarding a palatal extension of the preparation for porcelain veneers, as it represents a more invasive technique than a preparation limited to the facial surface of a tooth. PURPOSE: The purpose of this study was to detect the stress in maxillary anterior teeth restored with porcelain veneers and compare the resistance to fracture of porcelain veneers prepared using different preparation designs. MATERIAL AND METHODS: Forty-five maxillary anterior teeth were restored with porcelain veneers and divided into 9 groups as follows: Ca, canines with no preparation; Ca-Ch, canines with palatal chamfer preparation; Ca-W, canines with window preparation; LI, lateral incisors with no preparation; LI-Ch, lateral incisors with palatal chamfer preparation; LI-W, lateral incisors with window preparation; CI, central incisors with no preparation; CI-Ch, central incisors with palatal chamfer preparation; CI-W, central incisors with window preparation. Shear-flexural fracture tests were performed. The fractured specimens were subjected to scanning electron microscope (SEM) analysis. Data were statistically analyzed with univariate analysis of variance and the Tukey post hoc test for multiple comparisons (alpha=.05). RESULTS: The following mean fracture load values (N) were recorded: Ca, 395 +/- 6; Ca-Ch, 310 +/- 8; Ca-W, 322 +/- 8; LI, 309 +/- 8; LI-Ch, 242 +/- 6; LI-W, 225 +/- 8; CI, 298 +/- 8; CI-Ch, 255 +/- 8; CI-W, 221 +/- 6. The SEM analysis showed that both adhesive and cohesive fractures were primarily concentrated at the cervical region. Statistical analysis showed that both the type of tooth and the design of the preparation significantly influenced the resistance to fracture of the restored teeth (P<.001). CONCLUSION: The chamfer preparation is recommended for central incisors, whereas the window preparation showed better results for canines. Both preparations can be adopted in the restoration of lateral incisors.

Analysis of Variance↗
PubMed2000

Building up tooth preparations for full crowns--2000.

Many factors influence whether teeth planned for crowns or fixed prosthesis abutments need to be built up. Teeth may now be treated more conservatively with minimal fillers because of the greater strength of current cements, including hybrid ionomers and resins. Teeth planned as fixed prosthesis abutments require more remaining tooth structure and greater buildup strength than those designed for single full crowns. It appears that crown buildup is still necessary, but this procedure is needed less frequently than it was in previous years. Fillers can be used to fill holes left when previous restorations were removed, and are more commonly placed than build-ups.

Composite Resins↗
PubMedDate not supplied

Finite element analysis of stress distribution of 2 different tooth preparation designs in porcelain-fused-to-metal crowns.

PURPOSE: The aim of this clinical simulation study was to investigate the effect of anatomic and nonanatomic occlusal preparation design on stress distribution in different metal-ceramic crowns and tooth and bone. MATERIALS AND METHODS: For the finite element analysis method, a 2-dimensional mathematical model of a mandibular second premolar tooth and its supporting tissues was used. The analysis was performed by using a structural analysis program. Four groups were designed: gold-palladium alloy/anatomic occlusal preparation (Au-Pd/A), Au-Pd alloy/nonanatomic (flat) occlusal preparation (Au-Pd/N), nickel-chromium alloy/anatomic occlusal preparation (Ni-Cr/A), and Ni-Cr alloy/nonanatomic occlusal preparation (Ni-Cr/N). A distributed type load of 400 N (total) was applied to the centric stop points on the tip of the buccal cusp and on the central developmental groove in centric occlusion to all types of restorations. RESULTS: The results demonstrated that shear stresses in the dentin tissues and restorations in Au-Pd/A and Ni-Cr/A were similar. The shear stresses within the restorations in Au-Pd/N and Ni-Cr/N were similar. CONCLUSION: Anatomic occlusal preparation designs were advantageous in stress distribution in the dentin tissue. Nonanatomic occlusal preparation designs were found to be advantageous in the stress amount and distribution in the porcelain structure. Occlusal preparation designs and restorative materials showed no differences in stress distribution and amount in the pulp tissue and bone tissues.

Alveolar Process↗
PubMed2004

Resistance form in tooth preparation.

Theoretical and clinical studies of resistance form are reviewed, supporting the basic prosthodontic principle that resistance form is an essential element in preparation design. Concepts of the"on-off" nature of resistance form, its application in guidelines for minimally acceptable preparation taper, and the controversy over whether there is a relationship with clinical success or failure are discussed. It is more challenging to obtain resistive molar preparations than resistive anterior preparations, and uneven preparation margins can make parallel 0 degree taper preparations lack resistance form. The usefulness of grooves, especially in molar preparations with uneven margins, is illustrated. The Lewis and Zuckerman techniques for evaluating resistive areas of a preparation are shown to be consistent with each other but not with the Weed method.

Crowns↗
PubMed2001

Tooth preparation.

This final article in the series describes the modification of teeth to improve their shape for the support and retention of RPDs.

Denture, Partial, Removable↗
PubMed1995

An in vitro assessment of tooth preparation for porcelain veneer restorations.

OBJECTIVES: This in vitro study aimed to examine the depth of preparation and incidence of dentine exposure resulting from the use of a 'freehand' technique to prepare maxillary central incisors for porcelain veneers. METHODS: Twenty-two maxillary central incisors were selected. Prior to preparation an index of the labial surface of each tooth was recorded and the tooth secured in a jig to permit accurate relocation. Two operators each prepared 11 teeth aiming to reduce the labial thickness evenly by 0.5 mm. Low viscosity silicone impression material was then placed on the index and the teeth relocated into the jig. Upon removal, this material was sectioned in the cervical, middle and incisal thirds of the tooth and its thickness measured using a toolmaker's microscope. The teeth were acid etched and also stained with a dentine dye to identify any area of dentine exposed during preparation. RESULTS: Significant differences (P < 0.001) in the depth of preparation at different sites, with least reduction in the mid-incisal region, were found. Greater reduction was found at the cervical and proximal margins with areas of dentine exposed at those sites in the majority of teeth. CONCLUSIONS: In view of the incidence and position of dentine exposure found in this study, the use of a dentine bonding system during the placement of porcelain veneers would appear essential when employing a 'freehand' preparation technique.

Dental Cavity Preparation↗
PubMed2001

Burs with guide pins for standardized tooth preparation.

OBJECTIVE: The aim of this study was to develop and test self-limiting diamond burs to ease precise chamfer preparation and to fulfill the special requirements of computer-aided design/computer-aided manufacturing and all-ceramic restorations. METHOD AND MATERIALS: Rounded cylinder (based on ISO 881) and torpedo (based on ISO 879) diamond burs with a polished guide pin, 0.5 mm in length and 0.15 mm in radius, at the front end were developed in cooperation with an industrial partner. The in vitro testing involved a total of 140 human teeth. Experimental variables were the quality of the finish line, the microhardness of the enamel, and the thermal alteration of the dentin. Conventional diamonds served as a control. RESULTS: No mechanical or thermal damage related to the bur design was found in the hard tissues that had potentially been in contact with or in close proximity to the guide pin. Microhardness of the enamel at the finish line was significantly higher when prepared with burs with a guide pin compared to conventional burs. The results of using the guide pin might indicate the beneficial effect of reduced vibration. CONCLUSION: The guide pins of the self-limiting diamond burs reduce, rather than increase, the risk of hard tissue damage at the preparation margin. No adverse effects were found. Clinical use is justified.

Body Temperature↗
PubMed1997

An evaluation of operator preference of diamond burs in coronal tooth preparation.

Three postgraduate prosthodontic students served as clinicians/evaluators in a study rating their preferences for three different diamond cutting instruments from three manufacturers. Each evaluator prepared the axial walls of complete veneer crowns on extracted molar teeth and then ranked their preference of the instruments. To prepare nine teeth, each of the three instruments was used in random order and without knowledge of the specific manufacturer. The methodology for analyzing the evaluators' preferences and the results are discussed.

Analysis of Variance↗
PubMed1996

Fracture resistance of teeth restored with dentin-bonded crowns: the effect of increased tooth preparation.

This investigation assessed the effect of variations in preparation on fracture resistance of teeth restored with all-ceramic crowns placed with a resin composite luting material after the dentinal surface had been treated with a dentinal bonding system. Four groups of 10 sound, unrestored, maxillary premolars were prepared. In group A, minimal preparations of 6-degree taper, 2-mm occlusal reduction, and a knife-edged margin were carried out. Preparations in group B received 6-degree taper, 3-mm occlusal reduction, and a 1-mm shoulder. Preparations in group C were as in group B, but with 2-mm occlusal reduction over buccal cusp and minimal cervical preparation buccally. Preparations in group D were as in group B, but with 2-mm occlusal reduction. The restored teeth were subjected to compressive loading. Mean fracture loads of 0.77 kN, 0.99 kN, 0.91 kN, and 0.78 kN were recorded for groups A, B, C, and D, respectively. Statistical analysis failed to reveal any difference among the groups.

Analysis of Variance↗
PubMed1999

Localization and changes in superoxide dismutase immunoreactivity in rat pulp after tooth preparation.

OBJECTIVE: To examine the distribution of superoxide in the uninflamed and inflamed dental pulp by characterizing the immunoreactivity of the detoxifying antioxidant enzymes, manganese and copper-zinc superoxide dismutases (MnSOD and CuZnSOD, respectively). STUDY DESIGN: In 12 rats, mesial cavity preparations were made on the maxillary right first molar; left molars were unoperated controls. After 5 days, the rats were killed, and histologic sections were processed by using MnSOD and CuZnSOD immunoreactivity, and the extent of inflammation was evaluated on alternate sections stained with hematoxylin and eosin. RESULTS: In the hematoxylin and eosin-stained sections, inflammation was consistent with round-cells: macrophages, lymphocytes, and plasma cells that coalesced into a distinct leukocytic "lesion", which obliterated portions of the underlying pulp. Both MnSOD and CuZnSOD immunoreactivity increased dramatically in inflammatory cells within the leukocytic lesion and in the tissue surrounding the lesion. CONCLUSIONS: The findings suggest that the protective role of SOD increases within pulp cells that are undergoing inflammatory stimulation. SOD immunoreactivity may be an early indicator of stress in pulp.

Animals↗
PubMedDate not supplied

The effect of tooth preparation on the retention of stainless steel crowns.

Preparations maintaining the greatest amount of buccal and lingual tooth structure were the most retentive. Cement significantly increased the retention capacity of all preparations. Mechanical retention did not contribute significantly to the separation-resistance of the stainless steel crown. Factors other than retention may be of greater importance to the clinical success of stainless steel crowns.

Cementation↗