The three-dimensional relationship on a virtual model between the maxillary anterior teeth and incisive papilla

A Contemporary Review of Clinical Factors Involved in Speech-Perspectives from a Prosthodontist Point of View

Background and Objectives: Learning to speak properly requires a fully formed brain, good eyesight, and a functioning auditory system. Defective phonation is the outcome of a failure in the development of any of the systems or components involved in speech production. Dentures with strong phonetic skills can be fabricated with the help of a dentist who has a firm grasp of speech production and phonetic characteristics. Every dentist strives to perfect their craft by perfecting the balance between the technical, cosmetic, and acoustic aspects of dentistry, or "phonetics". The ideal prosthesis for a patient is one that not only sounds good but also functions well mechanically and aesthetically. Words are spoken by using articulators that alter their size and form. Conclusions: Therefore, a prosthesis should be made in such a way that it does not interfere with the ability to communicate. As a result, a prosthodontist has to have a solid grasp of how speech is made and the numerous parts that go into it.

An in vitro trial on the effect of arch form on connector size requirements in long span anterior zirconia fixed dental prostheses

PURPOSE

To test the fracture resistance of maxillary canine to canine fixed partial denture with four missing incisors, with increasing anterior-cantilevers of the pontics and varying connector sizes.

MATERIAL AND METHODS

Two 3D-printed titanium alloy (Ti6Al4V) models mimicking a maxillary canine to canine fixed partial denture (FPD) with four pontics replacing the incisors were used as master models. Zirconia FPDs were digitally designed and milled with two different connector sizes (9 and 12 mm² ) each with three different anterior cantilevers (7, 10, and 13 mm) accounting for 6 test groups. Seven samples were milled for each group generating a total of 42 samples. The Zi FPDs were cemented on the titanium model using resin modified glass ionomer cement and the model fixated to a variable angle vice. A sinusoidal cyclic wave form load from 50N to 280N was applied using a universal testing machine at a frequency of 30 cycles per second and a total of 5 million cycles.

RESULTS

The results of Fisher's exact tests showed that the difference in the proportion of fractured versus non fractured fixed partial dentures was not statistically significant when comparing the 9 with the 12 mm² connector size (p = 1.00), as well as when comparing the six test groups (p = 0.2338); on the other hand, it proved to be statistically significant when comparing the 7 mm cantilever with the 10 and 13 mm cantilevers combined (p = 0.0407) indicating that a 7 mm anterior spread of the pontics showed a significantly greater proportion of fixed partial dentures that fractured.

CONCLUSIONS

Fracture susceptibility was not a function of cantilever length in this testing configuration for anterior FPDs. Retainer crown thickness seems to be a more important parameter than connector size thickness. Based on the results, a smaller connector size (9 mm² ) can be used to improve the esthetics of pontics in long span anterior FPDs. This article is protected by copyright. All rights reserved.

Comparison of two computerized occlusal analysis systems for indicating occlusal contacts

PURPOSE

The purpose of this study was to compare the performance of Accura to that of the T-scan for indicating occlusal contacts.

MATERIALS AND METHODS

Twenty-four subjects were selected. Their maxillary dental casts were scanned with a model scanner. The Stereolithography files of the casts were positioned to align with the occlusal plane. Occlusal surfaces of every tooth were divided into three to six anatomic regions. T-scan and Accura recordings were made during two masticatory cycles. The T-scan and Accura images were captured at the maximum bite force and overlapped to the cast. Photographs of interocclusal records were used as the reference during overlap. The occlusal contacts were counted to compare the T-scan and Accura. McNemar's test was used for statistical significance and the corresponding P-values were calculated from a chi-square distribution with one degree of freedom. The accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Accura were calculated relative to the T-scan values as a control.

RESULTS

No statistical differences (P>.05) were found between the T-scan and Accura methods. The accuracy of Accura was 75.8%, sensitivity was 82.1%, specificity was 60.1%, PPV was 82.9%, and NPV was 60.1%.

CONCLUSION

Accura could be another possible option as a computerized occlusal analysis system for indicating occlusal contacts at maximum intercuspation.

Morphometric Study of the Hard Palate and Its Relevance to Dental and Forensic Sciences

This study was conducted to identify the morphometric features of the hard palate and to test the reliability of using palatal morphology in sex determination. Three hundred maxillary casts were collected from dental clinics in north Jordan. The age and gender of the patient and the serial number for each cast were recorded. The age range was 6 to 50 years old. A caliper was used to perform the following measurements: the length, width, and depth of the hard palate. In addition, the size, shape, and position of the incisive papilla were also determined. All measurements were done by a trained examiner who was able to perform the measurements in a reproducible manner. Statistical analysis showed that the mean palatal length, width, and depth, and size of dental papilla in both groups were the highest in males. The full logistic regression model including all the three predictors (length, width, and depth) indicated that the three parameters were significantly correlated with gender in the adult group. However, in the child group, only width and length were significantly (p=0.001, p > 0.042 respectively) correlated with gender. Regarding the shape and size of the incisive papilla, they were significantly different between males and females in both adult (p > 0.03) and child (p=0.001) groups. These findings might be potentially relevant to anthropological studies aiming at individual and/or sex identification. Moreover, the results might have clinical value in prosthodontics, especially in fabricating complete maxillary dentures for edentulous patients.

Maxillary first molar wear: a longitudinal study of children

The aim of this study is to examine the correlation between tooth wear and age by quantitatively measuring maxillary first molar wear in children. A total of 150 maxillary dental models were analyzed in 30 subjects (male, 11; female, 19) with an age range of 6-14 years. Maxillary first molar wear were assessed based on area, volume and the shortest distance from the buccal occlusal plane to the central pit point (BCPH). The area and volume of the tooth cusps were measured at four different offset-plane heights (0.2, 0.4, 0.6, and 0.8 mm). Relationship between age and the amount of wear or BCPH were statistically analyzed. Correlation and regression analyses were also performed, and age estimation was obtained with linear regression analysis. Repeated measures analysis of variance (ANOVA) revealed significant differences between age and the amount of wear based on area, volume, and offset-plane height. Except age of 8 and 10, 12 and 14's 0.2-mm offset-plane-measured volume, all area and volume measurement of all ages and offset-plane height showed a significant amount of increase. Wear speeds were calculated using the BCPH. Among age and measurement variables, the correlation coefficient was strongest when the volume was measured from the 0.4-mm offset-plane. As age increases, the amount of wear, as quantified by area and volume measurements, also increases. According to this study, a regression equation that can be used for age estimation is follows: Age (y)=0.16×0.4V+0.85 (R ²=0.490) using volume.

An In-vivo Comparison of Vertical and Horizontal Distance between Incisive Papilla and Incisal Edge of Maxillary Central Incisors in Dentates with Different Arch Forms

INTRODUCTION

The incisive papilla is one of the most stable landmarks for assessing the original position of certain key teeth. To place anterior artificial teeth back in its original position such as in denture construction and full mouth rehabilitation cases vertical and horizontal distance from incisive papilla in different arch forms, imparts a significant role. The average distance will be helpful for arrangement of teeth in its original position which not only provides a pleasing appearance and normal function but also will save the dentists' chair side effort.

AIM

To determine the average vertical and horizontal distance of the maxillary central incisors from the incisive papilla in dentate individuals with different arch forms.

MATERIALS AND METHODS

Primary impressions and casts were made for 72 dentate patients, sorted into different arch forms and mid point of the incisive papilla was established. The vertical and horizontal distances were measured with the digital vernier caliper. The mean and standard deviation were subjected to Students t-test.

RESULTS

The range of horizontal distance was 4-7 mm, 6-8 mm, 5-8 mm and vertical distance was 4-6 mm in ovoid, square and tapered arch forms respectively.

CONCLUSION

Horizontal distance of the maxillary central incisors from the incisive papilla varies in different arch forms whereas, vertical distance is almost same in all the arch forms.

Correlation between the size of the incisive papilla and the distance from the incisive papilla to the maxillary anterior teeth

Background/purpose

The incisive papilla remains relatively constant in position and is frequently used as an anatomic landmark for anterior teeth. Several attempts have been made to use the incisive papilla as guides to arrange maxillary anterior teeth for edentulous patients. The aim of the present study was to determine the relationship between maxillary anterior teeth and the incisive papilla, while comparing the findings with the classical estimate value.

Materials and methods

Horizontal distances between the labial surface of the central incisors and the incisive papilla [the distance from the labial surface of the central incisors and the posterior border of the incisive papilla (CPIP), the distance from the labial surface of the central incisors and the anterior border of the incisive papilla (CAIP), and the distance from the labial surface of the central incisors and the center of the incisive papilla (CCIP)] and the size of the incisive papilla (SIP) were measured by a digital caliper on the stone casts formed for 103 dentate persons. The Pearson correlation coefficient was used to investigate and quantify the correlation, while simple linear regression analyses were conducted to determine the strength of the association between the variables (α = 0.05).

Results

Pearson correlation coefficients for SIP and the distance between the labial surface of the central incisors and the incisive papilla (CPIP, CAIP, and CCIP) were significant (P < 0.05). A simple linear regression analysis of the data was performed, which showed that SIP contributed significantly to the prediction of the distances between the labial surface of the central incisors and the incisive papilla (CPIP and CCIP; P < 0.05).

Conclusion

Using regression methods within the population tested, it was determined that the distance between the labial surface of the central incisors and the incisive papilla could be predicted by the size of the incisive papilla.

Relationship of Incisive Papilla to Maxillary Incisors and Canines

AIM

The study was carried to find a relationship between the postextraction stable landmark, the incisive papilla, and the most labial position of the maxillary central incisor teeth, which occurred in Nepalese population.

MATERIALS AND METHODS

Casts of the subjects selected by nonprobability random sampling meeting the inclusion criteria were obtained. Each casts were standardized with respect to the occlusal plane and a photographic technique was used to measure the distance from the tangent of the labial surface of the central incisors to the posterior border of the incisive papilla. The measurements were made using Adobe Photoshop and results were analyzed by using appropriate statistical methods. Most appropriate software (SPSS) for the purpose was used to generate all desired values.

RESULTS

The data obtained suggested that the distance from the labial surface of maxillary central incisors to the posterior border of the incisive papilla ranged from 9 to 15.9 mm with a mean of 11.59 mm (SD 1.3). Various other results were also found after evaluation of the arch forms in relation to sex and race.

CONCLUSION

Within the limitations of the study, these results suggested that there is a relationship between the maxillary central incisors and the incisive papilla aiding in the anteroposterior positioning of the anterior tooth. The clinical relevance of the study lies in application of the incisive papilla as a starting point in the preliminary location of maxillary incisors and canines during construction of the denture in absence of preextraction records.

Different mandibular first molar shapes according to groove and cusp configuration in relation to suggested bracket position

The aim of this study was to explore the shape differences in the mandibular first molars through orthographic measurements using three-dimensional (3D) virtual models, and study the possibility of new morphologic categories that require more than subjective visual inspection. A total of 164 mandibular first molars with five cusps were selected for classification. Using 3D laser scanning and reconstruction software, virtual casts were constructed. After several linear and angular measurements on the virtual occlusal plane, the teeth were clustered using the partitioning around medoids methods-an unsupervised classification. The cluster analysis presented two clusters that showed statistically significant differences in the measurements over the cusp locations and groove configurations. However, gender differences were not shown in the angular groove and cusp configurations. Two clusters were found in the population of the present study, and this result suggested the existence of a diverse morphologic trait in the mandibular molar even in the same origin and could be considered in positioning orthodontic brackets that have built-in prescriptions.

Making three-dimensional Monson's sphere using virtual dental models

OBJECTIVES

The Monson's sphere and curve of Wilson can be used as reference for prosthetic reconstructions or orthodontic treatments. This study aimed to generate and measure the three-dimensional (3-D) Monson's sphere and curve of Wilson using virtual dental models and custom software.

METHODS

Mandibular dental casts from 79 young adults of Korean descent were scanned and rendered as virtual dental models using a 3-D digitizing scanner. 26 landmarks were digitized on the virtual dental models using a custom made software program. The Monson's sphere was estimated by fitting a sphere to the cusp tips using a least-squares method. Two curves of Wilson were generated by finding the intersecting circle between the Monson's sphere and two vertical planes orthogonal to a virtual occlusal plane. Non-parametric Mann-Whitney and Kruskal-Wallis tests were performed to test for difference between sex and in cusp number within tooth position.

RESULTS

The mean radius of Monson's sphere was 110.89 ± 25.75 mm. There were significant differences between males and females in all measurements taken (p<0.01), within 16.87-17.27 mm. Furthermore, morphological variation derived from variability in cusp number in the second premolar and second molar were not found to influence occlusal curvature (p>0.05).

CONCLUSIONS

This study describes a best-fit algorithm for generating 3-D Monson's sphere using occlusal curves quantified from virtual dental models. The radius of Monson's sphere in Korean subjects was greater than the original four-inch value suggested by Monson.

CLINICAL SIGNIFICANCE

The Monson's sphere and curve of Wilson can be used as a reference for prosthetic reconstruction and orthodontic treatment. The data found in this study may be applied to improve dental treatment results.

Discriminant analysis for the thin periodontal biotype based on the data acquired from three-dimensional virtual models of Korean young adults

BACKGROUND

There have been no objective criteria for classifying the periodontal biotype. The purpose of this study is to suggest clinical guidelines for discriminating the thin biotype, which might be susceptible to gingival recession, using statistical analyses based on the measurement of the dento-gingival complex on three-dimensional virtual models.

METHODS

From canine to canine, the area of the facial papilla, the facial surface area of the anterior tooth, the proportion of the dento-papillary complex, clinical papillary length, and the clinical papillary angle were measured on a three-dimensional virtual model of 133 young participants. In the clinical exam, the gingival transparency when probing was evaluated, and the classification into thin and non-thin biotype groups was used as the gold standard. The data were analyzed by discriminant analysis.

RESULTS

Twenty-nine participants (17 males and 12 females) belonged to the "thin group" according to the clinical evaluation. All variables were significantly different between groups (P <0.001). The results of discriminant function analysis showed that the sum of the area between each canine and lateral incisor, each lateral and central incisor, and the two central incisors was the best single determinant of biotype, and the sum of the papillary lengths between each canine and lateral incisor, each lateral and central incisor, and the two central incisors (PLSum5) was the next best choice. The cutoff value of PLSum5 was calculated to be 23.73 mm.

CONCLUSIONS

PLSum5 >24 mm is the suggested criterion for identifying high-risk thin biotype patients based on the comparison with the results from gingival transparency inspection. A clinical reevaluation of this criterion should be examined in additional studies for application in real clinical situations.

The incisive papilla: a significant landmark in prosthodontics

Several investigators have studied the horizontal relationship between incisive papilla and maxillary central incisor and measured the papilla incisor distance in dentate subjects to extrapolate this distance as a guide to place maxillary central incisors in complete dentures. Based on this premise, incisive papilla is recognized as an important landmark in complete denture construction. Papilla incisor measurements were made either from the middle or posterior border of the papilla and certain ethnic and national norms have been recommended to set the central incisors in complete dentures. This study was done on Dravidian dentate subjects to relate incisive papilla to central incisors and canines and also to ascertain its shape. During its transition to the edentulous state, incisive papilla changes its shape consequent to remodeling of the alveolar bone, palatal mucosa and interdental papilla following extraction of central incisor teeth. It was found that the papilla in dentate is not always round but seen in several forms. In some it was a double papilla and in a few it was rudimentary. The center of the papilla also changes from its dentulous to edentulous state. The posterior border is a relatively stable landmark since it undergoes least change after extraction of anterior teeth.

A three-dimensional analysis of the perceived proportions of maxillary anterior teeth

OBJECTIVE

The proportions of the anterior dentition, which is important for excellent esthetics, have been extensively studied, but there have been no 3-dimensional interpretations. This study was conducted to compare real tooth sizes and perceived tooth sizes between different genders and populations and to analyze the effects of 3-dimensional tooth position and alignment.

MATERIALS AND METHODS

Complete dental stone casts were prepared for a total of 139 subjects (50 males and 44 females from Korea and 46 females from Japan). Using 3-dimensional scanning and reconstructions, virtual models were constructed and the widths, lengths and rotations of maxillary anterior teeth were measured. Parameters related to the arch form were measured orthographically. Descriptive statistics and ANOVA were performed to determine the differences among the three groups. A regression model was created to interpret the values of 2-dimensional perceived widths with 3-dimensional measurements and other parameters.

RESULTS

This study observed differences in the average mesiodistal perceived and real dimensions of the maxillary central incisors between Japanese and Korean females, as well as differences in lateral incisor/central incisor ratios and canine/lateral incisor ratios in the perceived 2-dimensional measurements. There were no differences in individual tooth rotations between groups. The r(2) values of the regression model decreased from the central incisors to the canine.

CONCLUSIONS

Several differences were found between Japanese and Korean females and the regression models that used real dimensions, rotations and arch form parameters as independent factors were not sufficient to explain the perceived widths of anterior teeth in the study samples.