The masticatory system is a functional unit composed of the teeth; their supporting structures, the jaws; the temporomandibular joints; the muscles involved directly or indirectly in mastication (including the muscles of the lips and tongue); and the vascular and nervous systems supplying these tissues. Functional and structural disturbances in any one of the components of the masticatory system may be reflected by functional or structural disorders in one or more of its other components [1] [2] . However, there is a lot of evidence that the masticatory system has ability to the wide range of adaptive modalities. These adaptations can be functional and/or structural and may respond to transient and/or permanent demands. Therefore, this system, like any biological system, cannot be viewed as a rigid and immutable [2] [3] .

Knowledge of how the mandible moves during mastication has greatly influenced procedures in clinical dentistry. Historically, an understanding of mandibular movement was considered important in removable prosthodontics. Later, this information was used in the design and setting of articulators, and in the design of the dentures and denture teeth themselves. Today the importance of jaw movements has become apparent in fixed prosthodontics, periodontics, orthodontics, and in the diagnosis and treatment of pain disorders of the masticatory system [2] [4] .

In regard to the occlusion of the teeth, there are two concepts to be recognized; the first is the morphological or anatomical concept as the name implies an occlusion based on the forms of the teeth while the second is the physiologic concept. The physiologic occlusion is a living-dynamic as it participates as one of the components of the masticatory system.

Abnormal functional relationship of the teeth may vary in degree of abnormality from mild to extreme. In the first instance certain teeth may occlude slightly in advance of the other teeth. This is premature contact of the teeth. This condition may also exist in the functional movements of the mandible during mastication [5] .

Dental professionals must consider the importance of occlusal contacts for the success of dental treatment, maintaining occlusal stability and orofacial harmony, as occlusal interferences may implicate potential damages to the whole stomatognathic system, which includes teeth, supporting structures, neuromuscular system and temporomandibular joints [6] -[12] .

This paper presents a clinical case which is demonstrating orthodontic management of premature contacts in early mixed dentition.

Typically, an orthodontic case begins with a basic evaluation of the patient’s occlusion in static state. The view of occlusion has been enlarged so that it must be thought of as it functions as an integral part of the dynamic masticatory system.

The tooth interference may be more pronounced than premature contact and the mandible may be deflected from its normal functional path, now more than the teeth and supporting tissues are involved and the abnormal function may extend into the temporomandibular joints and musculature [5] . If the interferences cannot be

avoided comfortably by mandibular displacement in chewing and swallowing by neuromuscular mechanisms (functional adapatation), if the tooth becomes mobile and is moved out of position (structural adapation) and or if the patient cannot ignore the discomfort or the presence of change even for a short period (behavioral adaptation) overt symptoms of dysfunction of the muscles, joints, periodontium or teeth (pulp) may occur [13] .

The CR position rarely coincides with MI position in the majority of the population, and about 90% of people have a deviation up to 1.75 mm between these two positions [14] . In the cases in which this deviation alters the sagittal relationship between the upper and lower arches, it seems obvious that the diagnosis and orthodontic planning of treatment must be elaborated based on the patient’s examination in CR. When this protocol is neglected, one can obtain an incorrect diagnosis and make an incorrect treatment planning for the real malocclusion. For a clinical example, this error is more common in cases of false class III and unilateral posterior crossbite [15] .

In the presented case, as the upper central incisors are retroclined, so there is premature contact which avoided by forward mandibular displacement associated with functional shift to the left to achieve more comfortable bite in centric occlusion (functional adaptation). While, in contrast an edge to edge relationship between upper and lower teeth with posterior open bite when the mandible is manipulated in centric relation which is not comfortable.

In the current case the method used to eliminate the premature contact was not occlusal adjustment by selective grinding which involves the selective reshaping of tooth surfaces that interfere with normal jaw function, it was an orthodontic occlusal adjustment by correction of the position of the retroclined upper central incisors to procline them forward by using the protrusive arch wire [16] -[20] .

1) Functional and structural disturbances in any one of the components of the masticatory system may be reflected by functional or structural disorders in one or more of its other components.

2) Occlusal prematurity can be corrected by fixed orthodontic appliance.

First and foremost I would like to thank my family: Dad “Mohammad Naeem Mahfouz” Mom “Wedad Jarrad” Brother Allam Mahfouz, Sisters, Hanin Mahfouz, Suha Mahfouz, Bayan Mahfouz, Wife Yara Mansour and my kids, Omar Mahfouz, Noor Mahfouz and Sara Mahfouz for their valuable great support, guidance and advice.