Occlusal plane orientation: a statistical and clinical analysis in different clinical situations

Prediction accuracy of incisal points in determining occlusal plane of digital complete dentures

PURPOSE

This study aimed to predict the positional coordinates of incisor points from the scan data of conventional complete dentures and verify their accuracy.

MATERIALS AND METHODS

The standard triangulated language (STL) data of the scanned 100 pairs of complete upper and lower dentures were imported into the computer-aided design software from which the position coordinates of the points corresponding to each landmark of the jaw were obtained. The x, y, and z coordinates of the incisor point (XP, YP, and ZP) were obtained from the maxillary and mandibular landmark coordinates using regression or calculation formulas, and the accuracy was verified to determine the deviation between the measured and predicted coordinate values. YP was obtained in two ways using the hamular-incisive-papilla plane (HIP) and facial measurements. Multiple regression analysis was used to predict ZP. The root mean squared error (RMSE) values were used to verify the accuracy of the XP and YP. The RMSE value was obtained after cross-validation using the remaining 30 cases of denture STL data to verify the accuracy of ZP.

RESULTS

The RMSE was 2.22 for predicting XP. When predicting YP, the RMSE of the method using the HIP plane and facial measurements was 3.18 and 0.73, respectively. Cross-validation revealed the RMSE to be 1.53.

CONCLUSION

YP and ZP could be predicted from anatomical landmarks of the maxillary and mandibular edentulous jaw, suggesting that YP could be predicted with better accuracy with the addition of the position of the lower border of the upper lip.

A Cephalometric Analysis Assessing the Validity of Camper’s Plane to Establishing the Occlusal Plane in Edentulous Patients

Complete denture fabrication requires multiple clinical and laboratory steps. One of the most critical clinical steps is establishing an anatomical occlusal plane based on hard and soft tissue references. The aim of this study was to determine whether age or gender affects the level of the Ala-Tragus plane to establish which reference point on the Tragus should be used when fabricating the occlusal plane in edentulous patients. Clinical photographs and lateral cephalometric radiographs with complete dentitions were taken from 58 volunteers at the DMD clinic at the University of Kentucky. Each photograph was superimposed over its corresponding cephalometric image. An analysis was conducted to establish the angle of the occlusal plane relative to the Ala-Tragus landmarks; this data was then grouped according to age and gender. The analysis shows that age and gender did not significantly affect where the Camper’s plane should be approximated for complete denture treatment. However, it was found that the most parallel line to the occlusal plane was Ala’s inferior border to the ‘Tragus’s inferior border. It should be noted that the volunteers’ skeletal classification was significantly related to a Cl III malocclusion tendency. Still, with this new information, functionality and esthetics can be more adequately addressed for patients undergoing complete denture treatment. Given our results, we suggest redefining the ‘Camper’s plane with a line extending from ‘Ala’s inferior border to the ‘Tragus’s inferior border instead of the superior border. Further consideration should be taken if the patient is a skeletal CL III malocclusion.

Comparison of the effect of using panoramic and cone-beam computed tomography on the accuracy of root position in indirect digital bracket placement: A retrospective study

OBJECTIVE

The purpose of this study was to compare the root position accuracy of the use of panoramic radiography and cone-beam computed tomography (CBCT) in the indirect digital bracket placement.

METHODS

Two hundred and eighty-six maxillary and 300 mandibular teeth of 27 patients who have digital model, panoramic image and CBCT scan were included to the study. Indirect digital bonding was performed by using digital models and panoramic images in Group 1 and by superimposing the CBCT on the digital models with the OrthoAnalyzer™ 2020 (3Shape, Copenhagen, Denmark) software in Group 2. Angular measurements were calculated with 3-dimensional superimposition of the positions of the brackets placed with the Gom Inspect 2020 software. In the statistical analysis, One-way Analysis of Variance (ANOVA) and the Paired t test were used.

RESULTS

Maxillary canines had the highest angular deviation at 5.56°± 4.01° in comparison with the maxillary teeth (P < .001). Mandibular canines and second premolars had the highest angular deviation in the comparison between mandibular teeth (P < .001). Considering the groups of ranges by clinical limits of the deviations, these differences were significant in the angular dimensions with 3.57° ± 2.59° (P < .001). The amount of deviation of all teeth was found 3.57° ± 2.59°in the study.

CONCLUSIONS

Using panoramic images or CBCT in the digital bonding had clinical significantly effects on the angular deviation of bracket position. These findings may be taken into consideration when implementing bracket placement in indirect digital bonding. Despite the successful results, indirect digital bonding should not be the single reason to take the CBCT from the patients.

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.

Analysis of Relative Parallelism Between Hamular-Incisive-Papilla Plane and Campers Plane in Edentulous Subjects: A Comparative Study

The study was undertaken to evaluate the parallelism between hamular-incisive-papilla plane (HIP) and the Campers plane. And to determine which part of the posterior reference of the tragus i.e., the superior, middle or the inferior of the Camper's plane is parallel to HIP using digital lateral cephalograms. Fifty edentulous subjects with well formed ridges were selected for the study. The master casts were obtained using the standard selective pressure impression procedure. On the deepest point of the hamular notches and the centre of the incisive papilla stainless steel spherical bearings were glued to the cast at the marked points. The study templates were fabricated with autopolymerizing acrylic resin. The subjects were prepared for the lateral cephalograms. Stainless steel spherical bearings were adhered to the superior, middle, inferior points of the tragus of the ear and inferior border of the ala of the nose using surgical adhesive tape. The subjects with study templates were subjected to lateral cephalograms. Cephalometric tracings were done using Autocad 2010 software. Lines were drawn connecting the incisive papilla and hamular notch and the stainless steel spherical bearings placed on the superior, middle and inferior points on the tragus and the ala of the nose i.e., the Campers line S, Campers line M, Campers line I. The angles between the three Camper's line and the HIP were measured and recorded. Higher mean angulation was recorded in Campers line S -HIP (8.03) followed by Campers line M-HIP (4.60). Campers line I-HIP recorded the least angulation (3.80). The HIP is parallel to the Camper's plane. The Camper's plane formed with the posterior reference point as inferior point of the tragus is relatively parallel to the HIP.

Systematic assessment of the various controversies, difficulties, and current trends in the reestablishment of lost occlusal planes in edentulous patients

Accurate occlusal plane orientation is an essential factor in the fabrication of complete denture prosthesis. Over the years, it has received a number of methodologies by several researchers utilizing various anatomical landmarks however none of them is considered as perfect that could orient ideal occlusal plane. The presented literature review is an attempt to enlighten historical perspectives, pioneer researches, different controversies, difficulties and current trends for re-establishment of lost occlusal plane in edentulous patients. An extensive literature search was performed using Medline/PubMed interface and other scholarly research bibliographic databases using Medical Subject Headings. Studies describing research studies, case series and assorted clinical reports were retrieved and evaluated from 1963 to 2013. Most of the studies have suggest and evidence to consider Camper's plane for artificial orientation of occlusal plane however there is a substantial lack of genuine long term studies and authentic data that could recommend a single reliable landmark for perfect occlusal plane reorientation in a variety of cases.

Fabrication of occlusal rims to record the maxillomandibular relation for complete dentures

This article describes an alternative method to establish the inclination of the occlusal plane by using the hamular notch, incisive papilla plane. By using this plane, the fabrication of occlusal rims that conform to an ideal relationship may make chairside trimming of the rims more straightforward.

Occlusal plane location in edentulous patients: a review

Occlusal plane orientation is an important factor in the construction of a complete denture. Occlusal plane could be oriented using landmarks in the mandibular arch as well as in the maxillary arch. In the mandibular arch there are few landmarks which could be used to orient the occlusal plane like the retromolar pad, corner of the lips (lower lip length) whereas the maxillary arch has a number of landmarks, of which the ala-tragal line is the most commonly used and the same being the most controversial. In the following article different landmarks and its accuracy for orientating the occlusal plane in an edentulous subject as studied by various authors has been discussed.

Cephalometrically assessing the validity of superior, middle and inferior tragus points on ala-tragus line while establishing the occlusal plane in edentulous patient

PURPOSE

The purpose of this study was to decide the most appropriate point on tragus to be used as a reference point at time of marking ala tragus line while establishing occlusal plane.

MATERIALS AND METHODS

The data was collected in two groups of subjects: 1) Dentulous 2) Edentulous group having sample size of 30 for each group with equal gender distribution (15 males, 15 females each). Downs analysis was used for base value. Lateral cephalographs were taken for all selected subjects. Three points were marked on tragus as Superior (S), Middle (M), and Inferior (I) and were joined with ala (A) of the nose to form ala-tragus lines. The angle formed by each line (SA plane, MA plane, IA plane) with Frankfort Horizontal (FH) plane was measured by using custom made device and modified protractor in all dentulous and edentulous subjects. Also, in dentulous subjects angle between Frankfort Horizontal plane and natural occlusal plane was measured. The measurements obtained were subjected to the following statistical tests; descriptive analysis, Student's unpaired t-test and Pearson's correlation coefficient.

RESULTS

The results demonstrated, the mean angle COO (cant of occlusal plane) as 9.76°, inferior point on tragus had given the mean angular value of IFH [Angle between IA plane (plane formed by joining inferior point-I on tragus and ala of nose- A) and FH plane) as 10.40° and 10.56° in dentulous and edentulous subjects respectively which was the closest value to the angle COO and was comparable with the values of angle COO value in Downs analysis. Angulations of ala-tragus line marked from inferior point with occlusal plane in dentulous subject had given the smallest value 2.46° which showed that this ala-tragus line was nearly parallel to occlusal plane.

CONCLUSION

The inferior point marked on tragus is the most appropriate point for marking ala-tragus line.

Relationship between the occlusal plane corresponding to the lateral borders of the tongue and ala-tragus line in edentulous patients

AIM

Definitions of the ala-tragus line (ATL) cause confusion, because the exact points of reference for this line do not agree. This study determined the relationship between the prosthetic occlusal plane (OP) corresponding to the lateral borders of the tongue and ATL which was established by using the inferior border of the ala of the nose and (1) the superior border of the tragus (ATL 1), (2) the tip (ATL 2) and (3) the inferior border of the tragus (ATL 3).

MATERIALS AND METHODS

Neutral zone moldings using phonation and autopolymerizing acrylic resin were recorded and leveled with the lateral borders of the tongue. Lateral cephalometric radiographs were taken of each subject by a standard method. Tracings were obtained on acetate paper to show the prosthetic OP and the three ATLs. The relationship between the prosthetic OP and each of ATL was measured for each subject. Mean and standard deviation values were then calculated for the relationship. Statistical analysis was performed using repeated measure analysis of variance followed by Bonferroni pairwise comparisons and Student's t-test (α = 0.05).

RESULTS

Significant difference was found between the three mean angles (p = 0.001). There was no significant difference between the mean angle (5.00° ± 4.38) formed by OP and ATL 2, and the mean angle (4.90° ± 3.50) formed by OP and ATL 3 (p = 1.00) which revealed the smallest.

CONCLUSION

The findings of this study indicated that ATLs, extending from the inferior border of the ala of the nose to (1) the tip of the tragus of the ear, and (2) the inferior border of the tragus presented the closest relationship to the prosthetic OP corresponding to the lateral borders of the tongue.

CLINICAL SIGNIFICANCE

When the ATL is used for orientation of the OP in denture construction, it would seem preferable to define it as running from the inferior border of the ala of the nose to the tip or to the inferior border of the tragus of the ear.

Relationship of maxillary incisors in complete dentures to the incisive papilla

We investigated the relationship of the maxillary central incisors to the incisive papilla in wearers of complete dentures. First, image analyzer software was used to examine the relationship of the midpoint of the incisive papilla to the labial surface of the maxillary central incisors on occlusal photographs of 120 maxillary casts from dentate Malaysian adults. Then, an Alma denture gauge was used to identify the position of the labial surface of the maxillary central incisors in relation to the midpoint of the incisive papilla in complete dentures from 51 patients who requested replacement dentures at the Faculty of Dentistry, University of Malaya. The mean incisor distance to the incisive papilla in dentate adults was 9.59 ± 1.00 mm, while the mean incisor distance to the incisive papilla in complete dentures was 6.34 ± 1.87 mm. Thus, in our sample of edentulous patients, the anterior teeth in complete dentures were positioned approximately 3 mm closer to the incisive papilla, as compared with the position of the central incisors in natural dentition, and did not duplicate the position of the natural anterior teeth.

The occlusal plane in the facial context: inter-operator repeatability of a new three-dimensional method

The repeatability of a non-invasive digital protocol proposed to evaluate the three-dimensional (3D) position of the occlusal plane in the face is assessed. Dental virtual models and soft tissue facial morphology of 20 adult subjects were digitally integrated using a 3D stereophotogrammetric imaging system. The digital 3D coordinates of facial and dental landmarks were obtained by two different operators. Camper's (facial) and occlusal (dental) planes were individuated, and their 3D relationships were measured. The repeatability of the protocol was investigated and showed no significant differences in repeated digitizations. The angle between occlusal and Camper's planes was smaller than 2° in the frontal and horizontal projections. In the sagittal projection, the angle was observed to be, on average, 4.9°. The determined occlusal plane pitch, roll and yaw values show good agreement with previously published data obtained by different protocols. The current non-invasive method was repeatable, without inter-operator differences and can facilitate assessment of healthy subjects.