LESSON 5-APPLIED ANATOMY.pdf

APPLIED ANTOMY FOR DETNAL IMPLANTS CONTENTS — Introduction — Mandibular structure — Muscle attachment to mandible — Maxillary structure — Blood supply to maxilla INTRODUCTION — Basic anatomy understanding prior to implant therapy is an important first step in dental implant surgery, we should be fam...

APPLIED ANTOMY FOR DETNAL IMPLANTS CONTENTS — Introduction — Mandibular structure — Muscle attachment to mandible — Maxillary structure — Blood supply to maxilla INTRODUCTION — Basic anatomy understanding prior to implant therapy is an important first step in dental implant surgery, we should be familiar with all anatomical landmarks, muscles attachments, vascularization and innervations of both soft tissues and bone, for a successful and functional implant therapy. MANDIBULAR STRUCTURES 1. MANDIBULAR FORAMEN — Mandibular foramen is found 6-10 mm superior to the occlusal plane. — The distance to the mandibular foramen is within the reach of a short needle (needle length = 21 mm) — additional innervation from C2 and C3 (infiltrate on lingual side of molar) 2. MENTAL FORAMEN Anatomical configuration of mental nerve1)lower gently 2)sharp turn 3)drape down in catenary fashion. — Inferior Alveolar nerve is located mid way between the buccal and lingual cortical plates of bone at first molar, it crosses lingual to buccal side by the first molar and divides into mental and incisive branch at mental foramen. — Implant placement buccal or lingual to the IAN is a risky maneuverer and should not be attempted without MRI. — 3. MANDIBULAR CANAL — The canal is3.4mmwide, and the nerve is2.2mm thick. — Bone surrounding the canal is cortical, which may provide resistance — The mean distance to the second molar, first molar, and premolar 3.7, 6.9, and 4.7 mm, respectively. — The mandibular canal bifurcates. More than one mental foramen and, the bifurcation may not be seen on panoramic or periapical films. — Result in an incorrect estimation of available bone superior to the mandibular canal. 4. MENTAL FORAMEN & NERVE Location varies in both horizontal and vertical dimension. — HORIZONTALLYFrom canine to first molar. — VERTICALLYCoronal to apex- 38.6% Situated at apex-15.4% Apical to apex- 46.0%. — — caution must be exercised, especially when placing immediate implants in the premolar area, because in25%to 38%of cases the foramen is located coronal to the bicuspid’s apex. — Anterior loop of the mental foramen. — Loop dimensions varies from 0.0 to 7.5mm — Many false-positive and false-negative findings occur when identifying the anterior loop with x-rays. — To avoid this misguidance. Surgical exposure of mental foramen is better. — Safety margin of 2mm should be kept. — SAFETY attained by measuring from crest of alveolar ridge to roof of foramen— 1)The foramen coincides with the buccal plate and the osteotomy is placed lingual to the foramen and its contents. — 2) The foramen is cone shaped, and nerve emerges from a path inferior to the foramen. — 3)The mental nerve comes out of the mental canal, which is angled upward at 50O from the mandibular canal. Making the inferior alveolar nerve lateral and apical to the mental foramen. — If we want to place an implant above safety margins following things should be done— 1) A CTscan should be done to determine whether an anterior loop is present, OR — Use Naber’s 2N probe curved probe to probe within the foramen to ascertain if there is an anterior loop. — Three nerve branches of the mental nerve emerge from the mental foramen (each 1mm in diameter). — Occasionally, the mental nerve emerges from the buccal plate of bone and reenters the alveolar bone to provide innervation for the incisor teeth. 5. INCISIVE CANAL — ‘‘True’’ incisive canal mesial to the mental foramen, which is a continuation of the mandibular canal. — Appear as a maze of intertrabecular spaces, which include neurovascular bundles — It usually narrows as it approaches the midline and only reaches the midline18% of the time. — The incisive canal’s width is 0.5 – 1.8mm. — High chances of missing it in an OPG. Can be found out clearly in CT scan. — When mental foramen & anterior loop of mental foramen are avoided, implants can be placed safely. If incisive canal is large consideration should be given before placing an implant. 6. LINGUAL FORAMEN AND LATERAL CANALS — Minute vascular canals with mean diameter 0.7 mm and 0.6 mm are usually present in the midline and lateral to the midline in 99% of the mandibles. — Midline insertion of implants can be complicated by bleeding from this site if larger canal exist. Guide pin use can help to complete the operation. — The lingual foramen was detected in 99% of the mandibles when evaluating skull dissections. However, the foramen was only found on 49% of the periapical films because the angulation of the x-ray beam affected its image. — The lingual foramen harbours an artery that corresponds to an anastomosis of the right and left sublingual arteries. — If excessive bleeding from an osteotomy in this area occurs, guide pins or the implant fixture itself can serve as effective methods of tamponade. 6) SUBMENTAL AND SUBLINGUAL ARTERIES major nutrient vessel of floor of mouth- (2mm in diameter) — The sublingual and submental arteries are in close proximity to the lingual plate, — Inadvertent penetration through the lingual cortical plate into the floor of the mouth while preparing an osteotomy can cause arterial trauma, thereby resulting in development of a sublingual or submandibular hematoma. — It was mentioned that severing an artery 2mm in diameter with a probable blood flow of 0.2 ml per beat (70 beats per minute) can result in 420 ml blood loss in 30 minutes. 7) SUBMANDIBULAR AND SUBLINGUAL FOSSAE — The submandibular and sublingual Fossae must be palpated prior to osteotomy development; if there is a large undercut, the lingual bony plate can be perforated inadvertently, resulting in haemorrhage. — Lingual concavities with a depth of 6 mm were reported in 2.4% of assessed jaws. — An instrument can be placed to measure the under cut or — A CT scan with a radiopaque marker can be taken for accurate information. 8) THE LINGUAL AND MYLOHYOID NERVES — The lingual nerve is usually located 3 mm apical to the osseous crest and 2 mm horizontally from the lingual cortical plate in the flap. — Incisions distal to the second molar should be made on the buccal aspect of the ridge to provide additional room for safety, because the lingual nerve may be lying over the retromolar ridge — Mylohyoid nerve may also contribute to an inability to attain complete anaesthesia due to accessory sensory innervation to the anterior and posterior mandibular teeth. 9) LONG BUCCAL NERVE- — An anatomic variation-, called Turner’s variation, — Nerve emerging from a foramen in the retromolar fossa. — When this variation exists, trauma in this region can cause paraesthesia to the adjacent gingiva and mucosa. MUSCLE ATTACHMENT TO MANDIBLE 1) MENTALIS MUSCLE — Complete stripping of mentalis from mandible may result an appearance referred to as a witch’s chin (double chin). Due to inability to attach well. — If, in case reflected, double layer suturing should be done. 1st muscle layer followed by mucosal layer. 2) MYLOHYOID MUSCLE Severely resorbed ridgeOrigins approximates to crest of mandibular region. Especially in molar region. — Edematous swelling lingually spread of infection. — Mylohyoid nerve 3)GENIAL TUBERCLE GENIOGLOSSUS — The lingual foramen may be found in the middle of the tubercles. The average height of the superior genial tubercle is 6.17mm,and its width is 7.01mm — Genial tubercle may get located near the crest. — Care should be taken to prevent injury during impression making for subperiosteal implant. — Reflection of this muscle may cause possible retrusion of tongue and obstruction of airway. — Hypoglossal neve 4) DEPRESSOR ANGULI ORIS AND DEPRESSOR LABII INFERIORUS— These muscle overlie mental foramen. While reflecting the muscle and wet gauze can be used to push back the flap. 5) BUCCINATOR AND ORBICULARIS ORIS— Any procedure done in this area one of these muscles, such as GBR, a soft tissue flap often needs to be advanced to attain primary closure. — In this regard, it may be necessary to create an incision that provides periosteal fenestration and penetrates several millimetres into the submucosa, thereby incising one or both of these muscles to facilitate coronal positioning of the flap 6) MASSETER MUSCLE— When the mandibular ramus area is used as a donor site for bone grafting, part of the masseter muscle is released from the ramus when the periosteum is elevated in this region 7) MEDIAL PTERYGOID- A part of this fiber may get reflected when panning for implant placement. — Insertion of subperiosteal Implant usually involves Pterygomandibular space. This space is important as it may latter on invlove Paraphryngeal space passing on infection to mediatinum. — — Mandibular nerve 8)LATERAL PTERYGOID- — Rarely involved in implant Surgery. However the flexure or opening and the effect of this phenomenon on subperiosteal implant or prosthetic full arch splinting of mandibular implants in the molar region warrants consideration. — Because of angulation of lateral pterygoid muscle, many authors believe mandibular flexure causing an alteration in mandibular arch width, and sometime pain in patient with full arch subperiosteal implant or prosthetic splint, may cause contraction of muscles. — Mandibular nerve 9) TEMPORALIS— ORGIN-temporal fossa. — Inserted – coronoid process, ant. Border of ramus and Retromolar preocess inferiorly — TEMPORALIS TENDON FASCIATemporalis tendon and their fascia serves as a common point for attachment to masseter, medial pterygoid, buccinator and superior pharyngeal constictor muscle. — This complex extends to retromolar area — Surgical exposure of the mandibular ramus medially lead to exposure of this tendon complex and cause tendonitis and postoperative pain. — Prevention- incision placed on ant. Ascending ramus should be placed inferior to the insertion of two tendons of temporalis — Mandibular nerve MAXILLARY STRUCTURES 1) THICKNESS OF GINGIVA AND PALATAL MUCOSA— Average gingival thickness ranges from 0.53 to 2.62 mm (mean, 1.56 mm), and palatal width varies from 2.0 to 3.7 mm, with a mean of 2.8 mm. — Width can be determined by probe or needle with endodontic stopper. — The best location for harvesting a connective tissue graft is in the maxillary canine–premolar region. — Grafts of 5mm can be obtained from tuberosity region — Graft height is limited due to presence from greater palatine artery. 2) NASOPALATINE FORAMEN— Width-4.6mm — located 7.4 mm from the labial surface of an unresorbed ridge. — The nasopalatine canal (mean length, 8.1 mm) exits the incisive foramen — large incisive canal - obstacle to implant placement in the central incisor region. — When a large canal was present, Artzi et al. displaced its contents (moved it over without elimination) and placed an implant. — In contrast, Rosenquist and Nystrom enucleated the canal, inserted a bone graft, and subsequently placed an implant. It is also often possible to angle an implant and avoid the canal. — Intraconal orbital displacement of a dental implant treated with an endoscopically-assisted approach British Journal of Oral and Maxillofacial Surgery Volume 58, Issue 4, May 2020, Pages 469-471 3) INFRAORBITAL FORAMEN — The infraorbital nerve is found 5mm below the inferior portion of the infraorbital ridge. — a lateral window extending ;15mmfromthe alveolar ridge crest usually avoids encroaching on the infraorbital nerve 4) GREATER PALATINE FORAMEN— Location- halfway between the osseous crest and the median raphe. — Severing the palatal artery close to the foramen can present a problem, because it can retract into the bone, which precludes ligating it. — The precise location of the foramen can be determined prior to flap elevation by sounding the bone with an anesthetic needle. — found opposite the 3rd molar in 86% of cases, — between the second and third molar in 13% of cases, — opposite the second molar in 1% of cases Blood Supply in the Maxilla 1) GREATER PALATINE ARTERY12.07+_2.9mm 14.07 +_2.9mm — It is advantageous to leave 2mm gap between the artery and — — — — — the end of the surgical incision. Based upon the shape of the palatal vault, it is possible to estimate how far the palatine artery is from the cementoenamel junction: low vault (flat) =7mm, average palate = 12 mm, and high vault (U-shaped) =17 mm. The mean palatal vault height for males and females is 14.9 and 12.7 mm, respectively — When performing a split thickness palatal flap, the surgeon should be ready to manage accidental injury to the greater palatine artery. — If the artery is deemed to be close to the site of surgery, it may be advantageous to place ‘‘deep’’ sutures to lasso and ligate the greater palatine artery distal to the surgical site prior to initiating therapy. 2) SPHENOPALATINE ARTERY- When doing a sinus lift, caution must be exercised to avoid damaging these vessels if the procedure is being extended to the posterior wall of the sinus 4) INFRAORBITAL AND POSTERIOR SUPERIOR ALVEOLAR ARTERY — The intraosseous artery is