Bone grafting (addition)

MAXILLARY ANATOMY

The maxilla is the superior fixed bone, part of the skull

Mandible or inferior maxilla represents the mobile bone, which is articulated to the skull through the temporomandibular joint (TMJ).

Teeth are supported by the maxillaries, through roots. Milk dentition involves 20 teeth and the definitive dentition 32 teeth, including the 4 wisdom teeth.

Teeth can have a single root (incisors and canines), 2 roots (premolars) and 3 roots (molars). Atypical situations occur with incisors and canines having 2 roots or molars (especially wisdom ones) having 4 or multiple roots.

Generally, a root houses a dental canal. Superior molars generally present 3 roots and 3 canals, and the inferior molars 2 roots and 3 canals.

The superior maxillary, in its thickness, houses the nasal cavity, and from one side to another we encounter maxillary sinuses, one for each side.

Mandible (inferior maxillary) houses in its depth a sizeable channel through which the inferior alveolar nerve passes being an important anatomical formation in this level.

 

WHY DO WE NEED BONE?

Maxillary bone supports the tooth through its root. Periodontal disease, in its various stages, determines a progressive atrophy of the respective bone until the root loses its implantation, becomes mobile and the tooth is lost.

The artificial root is called dental implant. A dental implant is generally made of medical titanium degree 4 or 5 and has the shape of a screw inserted within bone.

To the implant, a dental artificial crown is attached through a connection element called prosthetic abutment.

The more horizontally resorbed (narrowed) bone the more we are forced to use thinner implants. The more vertically resorbed (shortened) bone the more we are forced to use shorter implants. Nevertheless, this means compromise…

 

WHY IS BONE LOST?

The human body functions based on the principle “if it’s not used, it’s lost”. If a person is practicing heavy lifting sports, his muscular mass increases. Training once stopped, the muscular mass decreases, muscles decreasing volume, right up to atrophy for a total rest. The muscle will adapt volume according with the daily medium effort.

The human bone functions by the same principle. In case it is solicited through weight lifting, it will increase and harden to sustain muscles. When teeth are present on the maxillary arcade, the mastication act will stimulate bone through them, maintaining volume unaltered. When a tooth is lost, bone will no longer compensate a function and will start a progressive atrophy, decreasing volume. Natural dental roots as well as dental implants stimulate bone, preserving its volume.

 

TYPES OF BONE ATROPHY

A. VERTICAL RESORPTION AFTER EXTRACTION (LOSING HEIGHT)

B. HORIZONTAL RESORPTION AFTER EXTRACTION (LOSING THICKNESS)

With the tooth in position, the surrounding bone will be stimulated with every bite. A tooth extraction leaves behind a great emptiness within bone (dental alveoli) which immediately initiates the bone resorption process. The affected area, in absence of stimulation, will continue to lose increasingly more bone mass, statistics proving that in the first 6 months after extraction up to 60% of bone volume can be lost.

Osseous loss will continue to manifest through time. The loss rate depends on several factors and it is not identical for each individual. Some patients lose bone faster than others. Eventually, if no treatment is initiated, bone will be lost in such a large quantity that a dental implant could not be inserted.

C. SINUS EXPANSION AFTER MAXILLARY MOLARS EXTRACTION

Areas (right/left) in the superior maxillary back are found in the maxillary sinuses vicinity. These represent large and empty (filled) cavities within the maxillary bone depth. Bone under the sinuses has a fairly low density (porous) and once with the molar extraction it starts to atrophy (resorb) quite fast under external forces action during mastication. Through sinuses, an internal atrophy is also produces, because sinuses increase their volume, occupying increasingly more space, concurrent with bone volume decrease. Reduce bone quantity under the sinus makes dental implant insertion impossible, remaining bone being shorter (1-6 mm) then the dental implant’s length (10-12 mm).

D. LOSS OF LATERAL MANDIBULAR TEETH (INFERIOR MAXILLARY)

Losing a group of teeth will lead to extended bone atrophy, as seen in the image above. It is notable that once with the bone atrophy emphasis (resorption), the nerve (inferior alveolar), with a large caliber and an important role, becomes increasingly close to the superior part of the remained bone. Eventually, bone height that remains above the nerve is so small that an implant couldn’t be inserted. Extreme atrophy situations also exist (especially after wearing mobile dentures for a long period of time) where the nerve starts to become exposed, causing serious neuralgia for the patient, when having contact with chewed food or dentures.

In case a patient loses all teeth, the entire maxillary arcade will begin to progressively atrophy, as seen in the image above. Extreme bone atrophy leads to nerve exposure (one for each mandible side) that were once located deep within the bone’s depth.

E. TOTAL TEETH LOSS AND TOTAL MAXILLARY ATROPHY

In case a patient loses all teeth, the entire maxillary arcade will begin to progressively atrophy, as seen in the image above. Extreme bone atrophy leads to nerve exposure (one for each mandible side) that were once located deep within the bone’s depth.

F. SEVERE ATROPHY – FACIAL ASPECT ALTERATION

Radical alteration of facial aspect is produced especially when the patient loses all teeth from both maxillary arcades. The height loss around the inferior facial segment, excessive skin wrinkling and ditch emphasis surrounding mouth or nose are to be noted. Bone and muscle decreases volume, being underused by avoiding normal food chewing, and begin a progressively atrophy. Severe maxillary bone atrophy on which muscles and skin are supported lead to a prematurely aged aspect of the patient’s face.