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PubMed1998

Microleakage of endodontically treated teeth restored with posts.

A fluid filtration system using 15 psi of pressure on the penetrating fluid was used to quantify the amount of microleakage of a stainless-steel post and a carbon-fiber post system, each placed with various cements. Statistical analysis showed that there was a significant difference in microleakage between the cements (p < 0.001). Zinc phosphate cement showed the most microleakage, whereas C & B Metabond cement showed the least. There was no significant difference in microleakage between the stainless-steel and carbon-fiber posts. The results of this study showed that both posts, when cemented with dentin-bonding resin cements (C & B Metabond and Panavia-21), exhibited less microleakage than when cemented with non-dentin-bonding cements (glass ionomer and zinc phosphate).

Analysis of Variance↗
PubMed2003

The effect of amalgam bonding on the stiffness of teeth weakened by cavity preparation.

OBJECTIVE: The objective of this study is to evaluate the effect of amalgam bonding on the stiffness of teeth weakened by cavity preparation. METHODS: Strain gages were bonded to maxillary premolars. The rigidity was tested by applying a load to a sequence of sound, prepared and restored teeth as follows: sound tooth, MOD preparation, amalgam restoration, amalgam removed recovering the MOD preparation, bonded amalgam restoration, bonded amalgam removed recovering the MOD preparation, bonded composite restoration. The relative stiffness (RS) and relative deformation (RD) of each condition for each cusp to that of the sound tooth was determined. RESULTS: The premolar cusps were deformed 1.80, 2.14, and 2.32 times more than the cusps of the sound tooth for the three succeeding MOD preparations. For these three preparations, the stiffness of the premolar cusps was 0.58, 0.48, and 0.46 relative to a stiffness of 1.00 for the sound tooth. The deformation was 1.77, 1.27, and 1.16 for the non-bonded amalgam, the bonded amalgam, and the bonded composite, respectively, corresponding to a mean RS of 0.59, 0.80, and 0.88. The calculated mean stiffness parameter C (standard deviation) was 2.6% (6.9) for the amalgam restoration, 62.5% (12.8) for the bonded amalgam restoration, and 77.8% (15.8) for the bonded composite restoration. The stiffness parameter C measured the extent to which the procedure returned the stiffness of the restored tooth to the original stiffness of the intact tooth (100%). SIGNIFICANCE: Cavity preparation reduced the stiffness and weakened the tooth. Restoring the prepared tooth with unbonded amalgam did not restore the lost tooth stiffness. Restoring the prepared tooth with bonded amalgam or with bonded composite recovered a significant portion of the lost tooth stiffness. It was concluded that bonding amalgam to tooth structure could partly restore the strength and rigidity lost by the cavity preparation. This might lead to a reduction in cuspal flexure and the incidence of tooth fracture due to fatigue.

Analysis of Variance↗
PubMed1996

Thermal expansion coefficient of dental composites measured with strain gauges.

OBJECTIVES: A simple test method was developed to determine the coefficient of thermal expansion of prevailing restorative resin composites and to study the transient behavior as a function of temperature and repeated thermocycles. METHODS: Strain gauges were used to determine the thermal expansion for seven commonly used restorative resin composites by measuring the instantaneous strain along with temperature change. The temperature was measured by means of a thermocouple, the tip of which was embedded in the composite. The differences among the test groups were analyzed using ANOVA, followed by Scheffé's multiple comparisons test. RESULTS: The coefficient of thermal expansion determined for the composites tested was: 22.5 +/- 1.4 x 10(-6)/degree C (Z-100), 23.5 +/- 1.4 x 10(-6)/degree C (P-50), 32.6 +/- 1.6 x 10(-6)/degree C (Herculite XR), 34.1 +/- 1.8 x 10(-6)/degree C (APH), 35.4 +/- 1.4 x 10(-6)/degree C (Conquest), 41.6 +/- 1.5 x 10(-6)/degree C (Silux Plus), 44.7 +/- 1.2 x 10(-6)/degree C (Heliomolar). The coefficient was almost linear in the considered temperature range (26-75 degrees C) for all composites (r > 0.99) and decreased with each consecutive thermocycle (p < 0.1). SIGNIFICANCE: Thermally induced loads, introduced into restored teeth by the mismatch of the coefficient of thermal expansion of the tooth and the restorative material, may be related to microleakage and wear problems. A highly filled hybrid composite such as Z-100 had a coefficient of thermal expansion closest to that of the tooth crown, confirming other studies which demonstrated the benefits of high filler loading in matching the properties of the dental hard tissues.

Acrylic Resins↗
PubMed1998

Computer aided prediction and control of shrinkage porosity in titanium dental castings.

OBJECTIVES: The main objectives were to investigate the possibility and reliability of quantitative prediction and control of the concentrated shrinkage porosity (macroporosity) in titanium dental castings by means of a numerical simulation technique; and finally to optimize the filling and feeding system design for dental castings. METHODS: A commercial software, MAGMASOFT (Giessereitechnologie GmbH, Germany), was employed to simulate the mold filling and solidification process, and predict the shrinkage tendency in a sample dental casting, two simplified tooth crowns with a connector bar between them. The numerically predicted shrinkages were compared with the experimental results. The experiments were carried out on a centrifugal casting machine. The same geometric and processing parameters of the casting as in the simulations were strictly controlled. RESULTS: The computer predicted shrinkage porosity coincided with the performed experiments, demonstrating the reliability of the numerical model and the thermal physical data chosen for the calculations. Based on the above numerical model, several filling and feeding systems for the same casting were numerically simulated and compared. Finally an optimized design for this sample casting was proposed, and porosity-free castings were obtained. SIGNIFICANCE: It was expected that the numerical simulation technique could be further developed for dental laboratories to aid the real dental casting design.

Computer Simulation↗
PubMed1997

Trismus and pain after removal of impacted lower third molars.

PURPOSE: This study evaluated trismus and pain after removal of impacted lower third molars and investigated whether these responses were related to difficulty of surgery. PATIENTS AND METHODS: A consecutive series of 104 patients, all of whom underwent removal of an impacted lower third molar under local surgery, was studied. Difficulty of surgery was evaluated on a modified version of the Parant scale: I, extraction with forceps only; II, extraction by ostectomy; III, extraction by ostectomy and coronal section; IV, complex procedures. Trismus was evaluated in terms of maximum interincisal distance (MID) 1 and 5 days after surgery. Pain was evaluated on the basis of reported analgesic use 1 and 5 days after surgery. RESULTS: Among group I subjects, mean day 1 MID did not differ significantly (P > .05) from mean presurgery MID, whereas mean day 1 MID in groups II, III, and IV was significantly lower than before surgery. In groups II, III, and IV, mean day 5 MID remained lower than before surgery. The proportion of group I patients using analgesics was significantly lower on both days 1 and 5 than the proportion of patients using analgesics in groups II, III, and IV. In all groups, the proportion of patients using analgesics dropped significantly between days 1 and 5. CONCLUSION: Trismus is less severe after simple (forceps-only, grade I) extractions than after surgical extractions (grades II to IV). However, trismus severity after surgical extraction does not depend on difficulty of surgery. Pain, as revealed by reported analgesic use, is likewise less severe after simple extractions. Regardless of extraction type, pain declines between days 1 and 5 postsurgery.

Adolescent↗
PubMed2000

Enamel demineralisation assessed by computerised image analysis of clinical photographs.

OBJECTIVES: To investigate the use of computerised image analysis to measure the area of demineralisation on the buccal surface of a tooth and to analyse the effect on that measurement of varying the angle at which a photographic image of the buccal surface of a tooth is taken. METHODS: Twenty-two teeth with areas of incremental demineralisation on the buccal surface were photographed perpendicular to the buccal surface and at angles of 20 and 40 degrees, above (Cuspal) and below (Gingival) the perpendicular. The images were captured and analysed using computerised image analysis. RESULTS: The Gingival views showed lower limits of agreement than the Cuspal views, probably due to the positioning of the masking on the lower part of the flash, to reduce reflection. There was a significant difference between the areas of demineralisation measured for the three angles from the Gingival views (p<0.001). The mean differences in areas measured were not linear, but there was a significantly greater reduction in area measured for the 40 degrees views. CONCLUSIONS: Computerised image analysis to measure areas of demineralisation from a captured 35mm slide is reproducible. The position of the masking on the camera flash and the angle of the camera makes a difference to the area measured and the grey scales recorded. Images taken at a larger angle than 20 degrees to the perpendicular will record a significantly reduced area of demineralisation. Standardisation of photographs with the use of calibration markers and manipulation of images is discussed.

Analysis of Variance↗
PubMed2001

A comparison of the mechanical behavior of posterior teeth with amalgam and composite MOD restorations.

OBJECTIVE: To compare the mechanical behavior, and infer differences in fracture resistance, of mandibular molars with amalgam and composite MOD restorations to that of an unrestored molar. METHOD: Finite element models were developed for an unrestored molar and molars with MOD amalgam and composite restorations. The location and magnitude of maximum principal stress resulting from simultaneous mechanical and thermal loads were determined for each molar using a series of designed experiments. An analysis of variance was conducted with the components of stress to distinguish the relative influence of oral parameters and restoration on the stress distribution in each molar. RESULTS: The maximum principal stress in the unrestored molar was the largest of all three molars examined and occurred within the dentin along the pulpal wall. Maximum principal stresses in the molars with amalgam and composite restorations both occurred along the cavosurface margin. Maximum principal stresses in the molar with amalgam restoration occurred at the pulpal floor and lingual wall junction and resulted from large occlusal loads. Although occlusal loading had minimal effects on the stress distribution within the molar with composite restoration, low oral temperatures were responsible for the maximum principal stresses, which were found at the lingual margin and occlusal surface junction. CONCLUSION: There was no significant difference in the magnitude of maximum stress that occurred in the molars with amalgam and light curing composite restorations. However, the location and orientation of maximum stress in the restored molars were largely dependent on the restorative material. Although clinical studies report that tooth fracture occurs predominately to restored molars, the unrestored molar experienced the highest stress in this investigation. Therefore, the reduction in fracture resistance of restored posterior teeth appears to result from changes in the location of maximum stress resulting from mastication and temperature changes.

Analysis of Variance↗
PubMed2001

Effect of CO2 laser on pulpal temperature and surface morphology: an in vitro study.

OBJECTIVES: The objective of this study was to evaluate the potential effects on underlying dental hard tissues of a high pulse rate carbon dioxide (CO2) laser that was designed for soft tissue surgery. METHODS: Eighteen extracted human teeth were sectioned longitudinally, cleaned, and varnished, leaving nine exposed windows on each: six on the coronal surface (enamel) and three on the root surface (cementum, dentin). The CO2 irradiation conditions used were: wave length 10.6 microm; 1.2-2.6J/cm(2) fluence per pulse; repetition rate 120-1000Hz; 100-200ms pulse duration; and cumulative fluences ranging from 14 to 2200J/cm(2). Each window was irradiated with a 0.3mm beam diameter at one of nine power settings for 0.1, 0.5, or 1.0s. The pulp chamber temperature was measured with a microthermocouple. The irradiated teeth were evaluated by Polarized Light Microscopy (PLM) and Scanning Electron Microscopy (SEM). RESULTS: The pulp chamber temperature rise ranged from 0.5 to 19 degrees C depending on the location of the window and distance to pulp chamber. SEM revealed crystal fusion in both enamel and dentin at all cumulative fluences. At cumulative fluences of 40J/cm(2), 200 pulses/second and higher, measurable tissue loss was observed with PLM both in dentin and enamel. CONCLUSIONS: These results indicate there are threshold conditions above which pulsed CO2 laser light used for soft tissue surgery may cause detrimental changes to underlying oral hard tissue and to the pulp.

Body Temperature↗
PubMed2003

The effect of magnification on the iatrogenic damage to adjacent tooth surfaces during class II preparation.

OBJECTIVES: To determine the amount of damage to adjacent surfaces during cavity preparation of approximal box-cavities by using either no magnification or an individually adapted surgical telescope. MATERIALS AND METHODS: Nine dentists prepared in a mannequin head 4 approximal (class II) box-cavities without magnification using a high speed handpiece with lighting from a dental unit. At least 2 months later the test was repeated with a surgical telescope system with integrated light. The degree of damage the 72 adjacent surfaces suffered was determined. RESULTS: The average time needed to prepare one cavity was 14.9min without and 18.3min with magnification (p=0.01). Altogether, 29.7% of adjacent area were damaged when no surgical telescopes were used and 34.5% when surgical telescopes were applied (p>0.05). When the mesial-facing and distal-facing surfaces were analysed independently a statistically significant increase of damage was found on distal surfaces (p=0.03) when using surgical telescopes. Seventy surfaces (=97%) had a preparation trauma. CONCLUSIONS: Surgical telescopes do not decrease damage of adjacent tooth surfaces.

Adult↗
PubMed2002

Dental age estimation and third molars: a preliminary study.

The aim of the present investigation was to reconstruct the chronological age based on the dental developmental stages of third molars evaluated on orthopantomograms. A total of 1175 orthopantomograms were assembled from patients of Caucasian origin between 16 and 22 years of age. Each third molar present was scored by two observers according to a 10-stage developmental scale. The kappa statistics measured the intra- and inter-observer reliability. The general statistical analysis was based on multiple regression analysis in order to obtain multiple regression formulas for dental age estimation based on the number of third molars present on the evaluated orthopantomogram. No regression models were statistically significant when there was only one-third molar present because of the relatively small number of orthopantomograms that fitted this criterion. A strong agreement was found between the intra- and inter-observer measurements. The statistical analysis revealed both for males and females high Pearson correlation coefficients between contralateral third molars and smaller coefficients between antimeres. The obtained multiple regression formulas are only applicable in certain specified conditions, for instance when four third molars are present the following formulas should be used in a Caucasian male "age=10.2000+0.5122UL+0.5273LL" (developmental stage of upper and lower left third molars) or in case of a female "age=13.6206+0.1933UR+0.5080LR" (developmental stage of upper and lower right third molars). This investigation revealed that the chronological age of a Caucasian individual may be estimated based on regression formulas with a S.D. of 1.52 or 1.56 years for males and females, respectively, when all four third molars are present.

Adolescent↗
PubMed2003

Prediction of maxillary canine impaction using sectors and angular measurement.

Maxillary canine impaction has an incidence of 1 in 100 in the general population and has been reported as much higher in an individual orthodontic practice. Because patients with canine impactions generally have longer treatment times, depending on the location of the impacted tooth, early identification of impaction is of critical interest to the orthodontist. Sector location and angulation of the unerupted tooth have been analyzed previously as predictors of canine eruption after deciduous extraction. Additionally, sector location has been studied as an indicator of eventual impaction, resulting in good predictive success. In this study, angulation of the unerupted tooth was measured from panoramic radiographs and added to sector location to see whether the combination of these factors could predict impaction more accurately than sector alone. Results verified earlier findings for sector: canines that become impacted will overlap the adjacent lateral incisor in 82% of cases. Logistic regression analysis also determined that once the canine overlaps the midline of the lateral incisor, there is a greater than 0.87 chance of impaction. Sector was found to be the better predictor of impaction, with angulation adding little supplementary predictive value.

Child↗
PubMed1998

Mixed dentition analysis for Asian-Americans.

One of the important aspects of diagnosis in the mixed dentition is the determination of the tooth size-arch length relationship. Such a determination is often made before eruption of the permanent canines and first and second premolars. The most commonly used prediction method of Tanaka and Johnston is based on data from a sample of children of Northern European descent. The accuracy of this method when applied to a different ethnic population is questionable. In this study, 201 dental plaster casts of Asia-Pacific-American subjects, all of whom were under the age of 21 years, were used. The actual measurements were compared with the predicted values derived from the Tanaka and Johnston equations and significant differences were found. The data illustrate the limitations of the Tanaka and Johnston method when applied to a sample population of other than European descent. From this data, two linear regression equations were developed for tooth size prediction in Asian-American children.

Adult↗
PubMed1998

Posttreatment assessment of surgically exposed and orthodontically aligned impacted maxillary canines.

The records of 96 consecutively treated patients, with a total of 110 exposed maxillary canines, were reviewed after orthodontic alignment of the exposed teeth. In view of the high degree of clinical and patient satisfaction with the results, a random sample of 25 patients, with a total of 30 exposed canines, were critically assessed. The assessment involved scoring for clinical impression, mobility, gingival condition and pocketing, oral hygiene, vitality, and radiographic appearances. The results indicate that the technique of surgical exposure and orthodontic alignment of ectopic maxillary canines provides a satisfactory method of treatment.

Adolescent↗
PubMed1999

Radiographic localization of unerupted maxillary anterior teeth using the vertical tube shift technique: the history and application of the method with some case reports.

The preferred means of radiographic localization is the parallax method introduced by Clark in 1910. He used 2 periapical radiographs and shifted the tube in the horizontal plane. In 1952, Richards appreciated that a vertical tube shift could also be carried out. No major changes then occurred in the technique until Keur, in Australia, in 1986 replaced the periapical radiographs with occlusal radiographs. This modification enables a greater tube movement and therefore a greater shift of the image of the impacted tooth; it also ensures that the whole of the tooth is captured on the radiograph. For the vertical tube shift, Keur introduced the use of a rotational panoramic radiograph with an occlusal radiograph. In 1987, Southall and Gravely discussed this vertical tube shift combination in the English dental literature, and it is now the preferred combination of radiographs for localizing impacted maxillary anterior teeth. Jacobs introduced this method to the American literature in 1999, but it has yet to gain acceptance in the continental European literature. Jacobs recommended, when using this combination, to routinely increase the vertical angulation for the occlusal radiograph by 10 degrees to achieve a greater image shift. Four case reports are presented in this article. Three have photographs taken at surgical exposure to illustrate how the position of the impacted tooth can be accurately predicted by appropriate interpretation of the radiographs.

Adolescent↗
PubMed1997

Ekman-Westborg-Julin syndrome. A case report.

A rare case of the Ekman-Westborg-Julin syndrome in a 15-year-old boy is presented. The patient had general macrodontia with gigantic mandibular third molars. Other dental anomalies, such as peak-shaped cuspids, central cusps, dens in dente, multituberculism, and single conical molar roots, were also present.

Adolescent↗
PubMed1994

The influence of altered occlusion on the condylar cartilage of the mandible and on the growth of the entire skull.

The effect of the loss of the suspensory zones of the upper jaw on the cartilage of the mandibular condyles and on the growth of both the viscerocranium and the neurocranium was examined after tooth crowns had been reduced in Wistar rats. We measured the thickness of the individual layers of the condylar cartilage and its total thickness. Alterations in the developmental processes involving the condylar cartilage expressed themselves as accelerated maturation, particularly in the centrally compressed areas of the cartilage. Alterations in occlusion influenced the development of the viscerocranium, whereas no influence on the growth of the neurocranium was detected.

Aging↗
PubMed2000

Early soft tissue pathosis associated with impacted third molars without pericoronal radiolucency.

OBJECTIVES: This study was performed to histologically evaluate soft tissue pathosis in pericoronal tissues of impacted third molars that did not exhibit pathologic pericoronal radiolucency. STUDY DESIGN: One hundred impacted third molars without evidence of abnormal pericoronal radiolucency (follicular space <2.0 mm) were removed for reasons other than participation in this study, and the pericoronal tissues were submitted for histopathologic examination. Specimens were fixed and processed routinely and were stained with hematoxylin and eosin before independent evaluation by each of 2 oral pathologists. A subset of both diseased and healthy tissues underwent additional evaluation for the presence of proliferating cell nuclear antigen (PCNA) for assessment of cellular activity. RESULTS: Of the specimens submitted, 34% showed squamous metaplasia suggestive of cystic change equivalent to that found in dentigerous cysts. Soft tissue pathosis was significantly higher in patients over 21 years of age (P =.001). Five of 8 diseased specimens demonstrated PCNA uptake, whereas none of 10 healthy specimens were PCNA positive. CONCLUSIONS: These findings suggest that radiographic appearance may not be a reliable indicator of the absence of disease within a dental follicle. We conclude that the incidence of soft tissue pathologic conditions is higher than generally assumed from radiographic examination alone.

Adolescent↗
PubMed1997

In vitro magnetic resonance imaging of rodent teeth.

OBJECTIVE: The anatomic structure of rat teeth was studied and observed using magnetic resonance imaging with high spatial resolution. STUDY DESIGN: The right part of the low mandible of two rats of 3 and 12 weeks old were analyzed. Images with different orientations were performed in a 2 Tesla magnetic field using the spin-echo imaging technique. RESULTS: Highly spatially resolved images revealed details of teeth, and anatomic differences between a young and an adult rat were demonstrated. CONCLUSION: Magnetic resonance imaging is well suited to image the buccal area and may be a useful tool for the diagnosis of dental diseases.

Aging↗