Occlusal plane is the average plane established by the incisal and occlusal surfaces of the teeth; it is not a plane but represents the planar mean of the curvature of these surfaces. Plane of orientation is one of the important factors of Hanau’s Quint. The occlusal plane also acts as a guide for teeth arrangement for the construction of a dental prosthesis.
Parallelism to the line joining the inferior border of the ala of the nose and the superior border of the tragus of the ear, known as the ala-tragus/Camper’s line, is the most commonly used reference for establishing the occlusal plane in completely edentulous patients. The ala-tragus line is preferred due to its reliability, repeatability, and ease of visualization. Conventionally, a fox plane (stainless steel or plastic frame with two parallel wings and a center mouthpiece) is used to determine the parallelism to the ala-tragus line. However, this technique can lead to errors due to the indirect visualization of parallelism. The accuracy can be affected due to parallax errors, movement of patient’s head, and inexperience of the clinician. To address this, a modification of the fox plane with the addition of laser lights has been designed which has been discussed in the report.
An acrylic fox plane was initially used as a template to design a metal fox plane with the addition of extensions on either side to support the laser lights [Figure 1]. An electrical circuit was established to supply power to the lights when turned on. The device consists of the following parts [Figure 2]: (a) custom-made fox plane (medical grade aluminum alloy), (b) adjustable horizontal and vertical extensions (industrial-grade steel), (c) two 650-nm red line laser (MOKCUM, China), (d) power unit (3V lithium-ion coin cell, CR2032, Duracell), (e) button switch 1.5 A (Jia Teng, China), and (f) spirit bubble level acrylic vial (QASE, China). The laser light used in the device projects a vertical red line on any surface and can be manually adjusted to sharpen the focus.
The procedure using this device is similar to the conventional denture-making process and differs only while determining the occlusal plane. The device was used on a completely edentulous patient during the jaw relation procedure. The occlusal rims were adjusted according to the desired vertical dimension, labial fullness, and lip support for the patient. A trial of the device is done before placing the occlusal rim with the laser light switched on which projects a straight line directly on the patient’s face. The thumbscrews in the extensions can be used to adjust the level of projections according to the patient’s lower facial height such that it passes through the ala-tragus line. Once that is established, the maxillary occlusal rim is then placed in the patient’s mouth, and the device is positioned on the occlusal rim, and held with the operator’s or patient’s hand against the rim. The rims are then adjusted until the laser light accurately passes through the ala-tragus line [Figure 3]. Finally, to check parallelism to the interpupillary line, it is ensured that the bubble in the spirit level is in the center and between the lines of the spirit vial [Figure 4].
While using the regular fox plane, the parallelism is determined by viewing from different angles and squinting one eye. Clinicians may additionally use a scale, tongue blade, or a line marked on the patient’s face to be able to visualize the parallelism directly. An opinion from an assistant is also taken to cross-check the assessment. To address this, various design modifications of the occlusal plane device have been attempted using additional plates parallel to the interpupillary line such as Camper’s plane indicator and occlusal plane indicator.[6–8] The use of laser lights to project a bright line on the patient’s face allows direct visualization of the parallelism. Such laser lights have also been utilized in orthopantomography machines for accurate patient positioning. The advantages of this technique are the reduced chances of errors in judgment, eliminates the need for an additional reference line, and the need for assistance. The patient has the freedom to move his head slightly, thus improving patient comfort without significantly disturbing the clinicians work during the procedure. It could be helpful to dental students who often doubt their judgments and improve the learning curve. The device can also be used in occlusal plane assessment in dentulous patients prior orthodontic treatment and in the case of patients with unilaterally missing ears. The lasers used in the device belong to Class 2 (International Electrotechnical Commission – IEC classification) visible laser and are considered safe for use, and eye protection is afforded by aversion response. However, it is advisable to educate the patient to avoid directly staring into the light source.
The technique for occlusal plane determination using the device discussed in the report improves the accuracy of the clinical procedure by facilitating direct visualization of parallelism, thereby avoiding parallax errors.
The device was approved by the institutional review board, and prior consent of the patient has been taken for the use of photographs.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that their name and initials will not be published, and due efforts will be made to conceal the identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
The development of the device was self-funded.
Conflicts of interest
The prototype of device has been published by the Intellectual Property of India Patent No: 201641040160 by the authors.
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