بسم الله الرحمن الرحيمVascularity and Innervation of the PDL ByFatemah Mahmoud Oraby(208)
Topics to be discussed: Vascularity of the PDL Orthodontic movement Innervation of the PDL Periodontitis Laser Therapy
The Periodontal Ligament Is a thin, fibrous ligament that connects the tooth to the bony socket. Normally, teeth do not contact the bone directly; a tooth is suspended in its socket by the fibers of the ligament. This arrangement allows each tooth limited individual movement. The fibers act as shock absorbers to cushion the force of the chewing impact of mastication.
PDL Vascularity The PDL receives its main blood supply through vessels that enter the PDL space through the alveolar bone, but it also receives contributions from the apical and gingival vessels. The main blood vessels within the PDL course are parallel to the long axis of the tooth and run between the collagen fiber bundles near the alveolar bone. Many arterio-venous anastomoses occur in the ligament, particularly in the apical and alveolar crest regions.
Arterial Supply of the PDL 1. Branches from the apical vessels supplying the pulp. 2. Branches from intra-alveolar vessels penetrating the alveolar bone. 3.branches from gingival vessels entering from a coronal direction.
The PDL main blood supply is from the superior and inferior alveolar arteries that ascend within the bone giving Interalveolar arteries.
These branches penetrate the alveolar bone and enter the PDL space as Perforating arteries.
They are more abundant in the mandibular posterior teeth than maxillary and anterior teeth.
In single-rooted teeth, they are found most frequently in the gingival third, followed by the apical third.
This last pattern of distribution has a clinical importance. In healing of extraction wounds; formation of blood clots occupying the gingival third is more rapid than the apical areas. Blood clot forms (B), which becomes new bone with gum tissue over the top (C). If the blood clot does not form or falls out, a dry socket occurs (D). No new bone forms, and the nerves are exposed, causing pain.
Interstitial Areas Are located between the bundles of principal fibers. They contain finer collagen fibers termed interstitial fibers which support blood vessels, nerves and lymphatics.
In addition to the constituents of the interstitial areas, observe the Volkmann's canal of the alveolar bone and the epithelial rests of the periodontal ligament.
Orthodontic Tooth Movement
It is a pathological process from which the tissue recovers.
Histology of tooth movement:
Orthodontic movement brings about areas of pressure and tension around the tooth. The histologic changes seen during tooth movement vary according to the amount and duration of force applied.
Changes on pressure side:
The PDL in direction of tooth movement gets compressed to almost 1/3rd of it’s original thickness.
A marked increase in the vascularity of PDL due to increase in capillary blood supply.
This helps in mobilization of fibroblasts and osteoclasts(bone resorbing cells that lie in Howship’s lacunae).
when forces applied are within physiologic limits, the resorption is in alveolar plate adjacent to the ligament. This is called frontal resorption.
Changes on tension side:
Distance between alveolar process & tooth is widened.
Mobilization of fibroblasts & osteoblasts.
Osteoid is laid down by osteoblast in PDL immediately adjacent to lamina dura.
Innervation of the PDL 1. Nerve fibers run from the apical region towards the gingival margin and being joined laterally by fibers entering through the foramina of the socket wall. 2. There are variations in the termination of the neural elements , with the apical region of the PDL containing more endings than elsewhere.
Nerves supplying the PDL are : Superior Alveolar Nerve & Inferior Alveolar Nerve.
3.There are four types of neural terminations in the PDL that have been described: 1- Free endings 2- Ruffini’s Corpuscles 3- Tactile (meissner’s) corpuscles 4- Spindle type nerve endings
Periodontitis Characterized by the following: Gum inflammation, with redness and bleeding Deep pockets (greater than 3 mm in depth) that form between the gum and the tooth Loose teeth, caused by loss of connective tissue structures and bone
The Use of Lasers in Periodontal Therapy Laser optical fiber is significantly thinner and therefore less invasive than most hand instruments. Patients can resume their daily activities including eating immediately after treatment. Each pulse of light vaporizes a specific number of cell layers within the area of the beam. Laser periodontal therapy removes only the diseased tissue without removing any healthy tissue.
Advantages Maintains the height of tissue around the teeth Minimizes Minimizes bleeding Minimizes discomfort to healing time the patient
Disadvantages Each laser has different wavelengths and power levels that can be used safely during different periodontal procedures. Damage to periodontal tissues can result if an inappropriate wavelength and/or power level is used during a periodontal procedure.