Relation of the inferior alveolar nerve and vessels ..consideration for dental implants in the posterior mandible

From Jay Matani and Mohit Kheur

The anatomic inter relationship of the neurovascular structures within the inferior alveolar canal: A Cadaveric and Histological study.

Abstract

Objective: The location and inter relationship of the structures of the inferior alveolar neurovascular bundle within the mandibular canal has not been clearly defined. The knowledge of the same is important while planning surgeries in the posterior mandible

Methods: 8 cadaveric mandibles were dissected and sections were made at the distal aspect of every tooth. The inferior alveolar neurovascular bundle was identified and examined for the location of the inferior alveolar artery, vein and nerve. Hematoxylin and Eosin sections were made for each specimen to confirm the position of these structures.

Results: All the sections in all the specimens confirmed that a blood vessel lies superior to the nerve. This position appeared consistent in all the positions relative to all the posterior teeth. There was a variation in the bucco-lingual positioning of these structures relative to each other for the various mandibles.

Conclusion: A blood vessel is found to always lie superior to the inferior alveolar nerve within the mandibular canal. Variations in the inter relationship of the structures is present.

Significance: This cadaveric study proves that all along the course of the neurovascular bundle, at various cross sections studied, the inferior nerve is always inferior to a blood vessel. There can be great variations to the positioning of the structures within the neurovascular in the bucco-lingual dimension and also in the exit of the nerve in various mandibles. Knowledge of the location of the structures is of importance during surgical procedures carried out in the vicinity of these structures.

Keywords: mandible; alveolar nerve, inferior; anatomy; dental implants.

Introduction:

The knowledge of the anatomical position of the structures within the inferior alveolar canal is important for any surgical procedure in the posterior mandible. The inferior alveolar neurovascular bundle enters the mandible at the mandibular foramen and runs downward and medial within the mandibular canal (MC) to exist from the mental foramen. The neurovascular bundle that occupies the inferior alveolar canal contains the inferior alveolar nerve, the inferior alveolar artery and the inferior alveolar vein.

Osteotomies for endosseous implants should not be made until the position of the mandibular canal is established. Prior to any surgical procedure, radiographic examination is carried out either using panoramic radiographs or conventional or computerized tomographies. Peker reported that the mandibular canal could not be located in 19.4 % of the panoramic radiographs and 13.9% of the conventional tomographs [1]. During various surgical procedures of the posterior mandible there is a risk of complications involving the inferior alveolar neurovascular bundle. These could include altered sensation, numbness and pain, complete loss of sensation or excessive bleeding. Inferior alveolar nerve (IAN) injury occurs as a complication of mandibular third molar surgery with a frequency varying from 0.5% to 8% [2, 3].

Encountering anatomic variations is possible during surgical procedures and such incidences can manifest from ineffective mandibular blocks to major complications after surgery. Kilic examined the mandibular canal in hemimandibles of cadavers and reported the presence of several branches of the inferior alveolar nerve at different sections [4]. Pogrel examined cadaveric mandibles for understanding the relationship of the neurovascular bundle in the 3^rd molar region [5]. He reported that there was a consistent presence of the vein along with the nerve. The artery was solitarily present. The precise location of these structures in relation to each other at different location in the mandibular canal has not been reported. This knowledge may be of some importance in procedures involving third molars and implant-related procedures.

The aim of this study is to understand the intracanal relationship of these structures during the course traversed by the neurovascular bundle from the 3^rd molar up to its exit from the body of the mandible.

Materials and methods:

Eight fully dentate hemi mandibles were selected from preserved human cadavers. Following gross dissection, the mandibles were carefully separated from all muscle attachments keeping the inferior alveolar neurovascular bundle intact at the mandibular and mental foramen region. A water cooled carborundum disc was used to make vertical sections distal to each tooth. The neurovascular bundle was exposed and the vein, artery, and nerve were visually identified to determine their exact orientation within the canal and in the mandible (Figure 1a to 1f). The gross identification of the structures was done under 6x magnification.

A histological evaluation was done for all the sections to identify and confirm the location of the artery, vein and nerve to each other (Figure 2). The sectioned specimens were fixed for 24 hours in 10% neutral buffered formalin and then kept in decalcifying agent (20% EDTA) for 15 days. The specimens were then immersed in a combination of 5 % formic and 10 % nitric acid for a period of 15 days.  After decalcification was complete, the mandibles were processed and embedded in paraffin and sectioned into 5-µm slices. The sections were stained with routine Hematoxylin and Eosin stain and then studied under a compound microscope for further evaluation. The sections were taken at 4x (objective) magnification scanner view.

Results:

The mandibular canal and neurovascular bundle of the mandibular canal were visible in all hemimandibles. The relationship of the artery, vein and nerve to each was examined from the external cortices of the mandible, from distal of the 3^rd molar until its exit from the mental foramen. A schematic representation of the structures was made to understand their relationship to each other (Figure 3). In all the cross sections studied a blood vessel was evident superior to the position of the nerve. Out of the 25 cross sections studied, a vein was present superior to the nerve in 19 (76%) of the sections. Both the blood vessels were present superior to the nerve in 16 (64%) out of the 25 cross sections. The bucco-lingual relationship of the structures had variation. In only 12 out of 25 sections (48%) one blood vessel was present buccal to the inferior alveolar nerve.

Discussion:

The anatomy of inferior alveolar canal has been documented in various textbooks and previous cadaveric studies. However the relationship of the structures within the canal is still unclear. The relative location of the inferior alveolar canal and associated foramina in adults remain fairly constant without regard to age and sex [6]. Levine reported that the bucco-lingual IAN canal position varied with the age and race of the patient [7]. Many variations have been reported in the literature with regards to the inferior alveolar nerve and it course. Lui classified the course of the IAN as linear curve, spoon-shape curve, elliptic-arc curve and turning curve [8]. These variations were seen on the pantomographs. Juodzbalys reported that the mandibular canal bifurcates in the inferior superior or medial lateral plane [9]. Observation of the MC shape from the mandibular foramen towards the anterior part of the mandible showed several characteristic variations in the form of round/oval, tear-drop and dumbbell shape [10]. The identification of these variations may not be possible without conventional or computerized tomography. Therefore there is a need to understand the relationship of the structures within the canal.

Pogrel reported the relationship of these structures in the third molar region and concluded the presence of the vein superior to the nerve [5]. The artery was found to be lingual to the nerve. This concurs with the results obtained from this cadaveric study. However his study reports the locations in the 3^rdmolar regions only, which are not significant for dental implant surgery. When the roof of the inferior alveolar canal is breached bleeding may occur and this may be due to the damage to the vein. However if the insertion of the implant is halted at this point, damage to the nerve can be avoided.

Conclusion:

1.    Variations were seen in the intra canal position of the inferior alveolar nerve, artery and vein in different regions of the same mandible and in different mandibles.

2.    A blood vessel was found to always lie superior to the inferior alveolar nerve within the mandibular canal.

3.    Variations are seen in the bucco-lingual positions of the structures within the mandibular canal in different regions of the same mandible and in different mandibles.

References:

1.    Peker I, Alkurt MT, Mihcioglu T. The use of 3 different imaging methods for the localization of the mandibular canal in dental implant planning. The International Journal of Oral & Maxillofacial Implants 2008; 23: 463-70.

2.    Blaeser BF, August MA, Donoff RB, et al: Panoramic radiographic risk factors for inferior alveolar nerve injury after third molar extraction. Journal of Oral and Maxillofacial Surgery 2003; 61:417- 21.

3.    Nakagawa Y, Ishii H, Nomura Y, et al: Third molar position: Reliability of panoramic radiography. Journal of Oral and Maxillofacial Surgery 2007; 65:1303- 8.

4.    Kilic C, Kamburoglu K, Ozen T, Balcioglu HA, Kurt B, Kutoglu T, et al. The Position of the Mandibular Canal and Histologic Feature of the Inferior Alveolar Nerve. Clinical Anatomy. 2010; 23:34–42.

5.    Pogrel MA, Dorfman D and Fallah H. The Anatomic Structure of the Inferior Alveolar Neurovascular Bundle in the Third Molar Region. Journal of Oral and Maxillofacial Surgery 2009; 67:2452-2454.

6.    Angel JS, Mincer HH, Chaudhry J and Scarbecz M. Cone-beam Computed Tomography for Analyzing Variations in Inferior Alveolar Canal Location in Adults in Relation to Age and Sex. Journal of Forensic Sciences, 2011; 56: 216-19.

7.    Levine MH, Goddard AL and Dodson TB. Inferior Alveolar Nerve Canal Position: A Clinical and Radiographic Study. Journal of Oral and Maxillofacial Surgery 2007; 65:470-474.

8.    Liu T, Xia B, Gu Z. Inferior alveolar canal course: a radiographic study. Clinical Oral Implants Research. 2009; 20: 1212–1218.

9.    Juodzbalys G, Wang HL, Sabalys G. Anatomy of Mandibular Vital Structures. Part I: Mandibular Canal and Inferior Alveolar Neurovascular Bundle in relation with Dental Implantology. Journal of Oral & Maxillofacial Research 2010 1(1):e2.

10. Megumi Ueda, Kenji Nakamori, Kaori Shiratori, Tomohiro Igarashi, Takanori Sasaki, Naoki Anbo, et al. Clinical Significance of Computed Tomographic Assessment and Anatomic Features of the Inferior Alveolar Canal as Risk Factors for Injury of the Inferior Alveolar Nerve at Third Molar Surgery. Journal of Oral and Maxillofacial Surgery 2012; 70:514-520.

Legends:

Figure 1a to 1f: Cross-sections of cadaveric mandibles

Figure 2: Histologic examination of the specimen showing Inferior alveolar nerve, artery and vein

Figure 3: Schematic representation of the neurovascular bundle

Scaffolds and tissue engineering applications in dentistry- Visiting the basic principles

BIOENGINEERED SCAFFOLDS FOR USE IN MAXILLOFACIAL DEFECTS

Mohit Kheur¹ and Jay Matani²

*¹Dept. of Prosthodontics,

*²Dept. of Prosthodontics

ABSTRACT

Patients present with large defects of the face and the oral cavity following maxillofacial surgeries. Conventional treatment includes the use of artificial appliances. Surgical closure of these defects is also advocated routinely. Regrowth of the tissues within the defects is possible with the advancement of tissue engineering methods. The use of scaffolds has emerged as a promising alternative approach in the treatment of these defects. This paper discusses the different materials and techniques used in tissue engineering for scaffold fabrication.

Keywords: Maxillofacial defects, scaffold tissue engineering

INTRODUCTION

Patients having undergone maxillofacial surgeries tend to present with large defects involving parts of the mouth and the face (Figure 1). An interdisciplinary treatment approach of surgical reconstruction and prosthetic rehabilitation of these defects has been advocated.

Figure 1: Patient presenting with a Maxillofacial Defect

 

Aramany (1978, 2001) and McKinstry (1985) have suggested conventional methods of treating such defects by using prosthetic (artificial devices) appliances. However these prosthetic treatment options are not able to replace all the functions of a damaged or lost organ or tissue. Modern approaches to restore such defects are aimed at regenerating the lost tissue rather than trying to replace it by artificial means. 

Grafting these defects with various biocompatible materials has been carried out. Usually grafting is carried out by the hard tissues obtained from the patient itself. These grafts are referred to as autogenous grafts. However the inherent disadvantages of the autografts include the need for surgeries to harvest the graft and the chance of the donor site morbidity as reported by Raghoebar (2001). Other graft types like allogenic grafts (grafts from the same species), xenografts (grafts from animal sources) and alloplasts (powdered ceramic grafts) have documented disadvantages as reported by Eid K (2001).

Current trends of re-growing tissue in these defects revolve around using scaffold matrices to promote bone growth using tissue engineering techniques. These procedures involve the use of cells (with growth potential), certain signalling molecules and drugs. These agents need to be fabricated and delivered either sequentially or together onto the scaffold. Langer (1993) has suggested that these three methods should be adopted to create new tissue.

A 3-dimensional fill of the defects can be achieved by the use of scaffolds. Scaffolds are matrices which are essentially porous in nature in which the required cells can be seeded. The ideal requirements of these scaffold as stated by Sachlos (2003) are that they (1) should be incorporated with pores of appropriate size to favour tissue integration and vascularisation, (2) be made from material with controlled biodegradability or resorbability so that the scaffold forms the desired tissue, (3) possess the chemical composition to favour cellular attachment and proliferation and (4) be biocompatible so that no adverse response is induced.

This paper will discuss the newer trends in scaffold fabrication with respect to the techniques and the materials used.

The Microarchitecture of the scaffold

The success of a scaffold largely depends on its microstructure. This includes the pore size, pore distribution and the interconnectivity between the pores. The interconnectivity of the pores to form a network is for vascularization, the growth of the desired cells and for the transport of the nutrients and the metabolic waste products. The interconnecting network of these pores increases the surface area to the volume ratio of the scaffold. The pore size plays a substantial part in vascularization of the scaffolds. Chiu (2011) studied the role of the size of the pores on vascularization in PEG hydrogels. They reported that pores of 25-50 μm in size provided with cell and vessel perfusion only onto the external surface. Larger pores (50-100 and 100-150 μm) permitted mature vascularized tissue formation throughout the entire material volume. Kovacina (2011) has described various modifications in the technique parameters to increase the sizes of the pores. Sultana (2011) obtained highly organized three-dimensional porous scaffolds by modification of fabrication parameters.

Material Science

According to Holzwarth (2011), apart from the high porosity, the other requirements that a scaffold must present with are mechanical integrity and biodegradability. These properties are greatly dependant on the choice of the scaffold material. Various materials have been used for the fabrication of scaffolds. A wide range of polymers have been used for the use of bone tissue engineering. These polymers can be classified as natural and synthetic polymers.

The synthetic polymers include polyesters, polyanhydride, polyorthoester and polycaprolactone (PCL). The more commonly used synthetic polymers are the polyesters such as poly (glycolic acid) (PGA), poly (lactic acid) (PLA), and their copolymer of poly [lactic-co-(glycolic acid)] (PLGA). (Figure 2) These polymers are easier to fabricate and modify. However they lack the required bioactivity as documented by Holzwarth (2011).

	Figure 2: PLA Scaffold

 

This is however not an issue with the use of natural polymers. The natural polymers used for tissue engineering are collagen, silk, gelatin and chitosan amongst the other materials. They have promoted cell adhesion and proliferation as an inherent property. Kohara and co-workers (2011) induced bone formation when they used gelatin sponges with bone morphogenetic proteins. They also concluded that the use of gelatin scaffold incorporating multiple osteoinductive agents could be effective in inducing bone formation.

However since both the polymers have certain advantages, a combination of them can be used to create composite scaffolds with significantly better biological and mechanical properties. Yang (2009) combined PCL with chitosan to create bioactive nanofibers. This novel hybrid scaffold takes advantage of the physical properties of the synthetic polymer and the bioactivity of the natural polymer while minimizing the disadvantages of both. A collagen and PLA hybrid scaffold with parallel collagen fibres embedded within a PLA matrix has been fabricated by Dunn and co-workers (1997). (Figure 3)

	Figure 3: PLA + Collagen Scaffold

 

Scaffolds with mineral content have been explored for better bone tissue engineering. Hydroxyapatite (HA) has been frequently used for the same (Figure 4). Calcium phosphate ceramics, calcium phosphate cement and Bioglass are amongst the other mineralized materials that have been used. They not only improve the skeletal integrity of the scaffold but also make the scaffold osteoconductive. The calcium phosphate cements can be injectable and hence they have better delivery to the defect site. Lanao and co-workers (2011) studied the efficacy of these injectable calcium phosphate cements containing PLGA microparticles and documented excellent biocompatibility and osteoconductivity.

The minerals can be added to the polymer scaffolds. Marelli (2011) used the combination of dense nanofibrillar collagen and nano-sized bioactive glass to produce scaffolds for bone tissue engineering purposes. Wei (2004) created a scaffold of nano-hydroxyapatite in PLA (30:70) by the Thermally-induced phase separation (TIPS) technique. Seyedjafari and co-workers (2010) compared electrospun PLA scaffolds without hydroxyapatite and showed no calcium deposition and were surrounded by a granulomatous inflammatory response while scaffolds with hydroxyapatite showed significant mineralization with little inflammatory response.

    

Engineering techniques employed for scaffold fabrication

The main techniques that are used for bone tissue engineering according to Holzwarth (2011) are Electrospinning and Phase separation. As discussed earlier, electrospun scaffolds of a combination of minerals and synthetic polymers have been fabricated. Boland (2001) readily electrospun Poly (glycolic acid) fibres ranging from about 0.15 to 1.5 μm in diameter. These fine fibres were considered to be an attractive option of tissue engineering. However the challenge in maxillofacial rehabilitation is to create a scaffold that three-dimensionally fills in the defect with the desired tissue. It remains difficult to create clinically relevant three-dimensional constructs beyond a relatively two-dimensional mat. The problem posed by electrospinning is somewhat overcome by the process of phase separation. The polymer solutions used in tissue engineering are thermodynamically unstable at certain temperatures. The Thermally-Induced Phase Separation (TIPS) is a technique that uses this property of the polymers for fabrication of scaffolds.

The size and the shape of a maxillofacial defect can be diagnosed using advanced imaging procedures like Computed Tomography scan (CT scan) or a Cone Beam Computed Tomography scan (CBCT) and Magnetic Resonance Imaging (MRI). Using these images a Stereolithographic model of the defect can be fabricated. The shape of the scaffold as a whole can be hence controlled. Bone defects are never uniform in geometry so the ability to create a custom mold and scaffold for each patient allows for a smooth transition onto the operating table. The versatility of stereolithography has showed techniques for fabrication of porous scaffolds. Melchels and co-workers (2010) have showed how stereolithography fabrication methods can be used to accurately prepare tissue engineering scaffolds with designs that can be modelled according to various geometries.

However in spite of the actually macro geometry of the scaffolds, the key is to control the pore geometry. According to Park (2011), Solid Freeform Fabrication technique is capable of controlling the geometry of the pores. They fabricated computer aided hydrogel scaffolds using a solid freeform fabrication system (3-dimensional cell plotting). Solid freeform fabrication (SFF) uses layer-manufacturing strategies to create physical objects directly from computer-generated models. It can

improve current scaffold design by controlling scaffold parameters such as pore size, porosity and pore distribution, as well as incorporating an artificial vascular system, thereby increasing the mass transport of oxygen and nutrients into the interior of the scaffold and supporting cellular growth in that region.

With the constant improvement in technology and the advent of newer techniques various experiments have been conducted to create the most favourable scaffold. Diagnostic images obtained from CT/MRI and using them in solid freeform fabrication are the two most important technologies in computer aided tissue engineering. As mentioned before, a combination of both makes it possible to design and manufacture an arbitrarily-shaped complex human bone scaffold model for use in maxillofacial rehabilitation. By introducing a hybrid new method based on the distance field and Triply Periodic Minimal Surface (TPMS), Dong Yoo (2011) has reported that a variety of porous scaffolds can be fabricated.

CONCLUSION

The engineering techniques for scaffold fabrication have seen a tremendous growth in the last few years. The exponential growth in tissue engineering towards regenerating lost human body parts has led to increase interest in development of newer techniques.

REFERENCES

Mohamed A. Aramany and Eugene N Myers (1978).  Prosthetic reconstruction following resection of the hard and soft palate. Journal of Prosthetic Dentistry. 40(2) 174-78.

Robert E. McKinstry and Mohamed A. Aramany (1985). Prosthodontic considerations in the management of surgically compromised cleft palate patients. Journal of Prosthetic Dentistry 53(6) 827-31.

Mohamed A. Aramany (2001). Basic principles of obturator design for partially edentulous patients. Part II: Design principles. Journal of Prosthetic Dentistry 86(6) 562-68.

Gerry M. Raghoebar, Charlotte Louwerse, Wouter W. I. Kalk, Arjan Vissink (2001). Morbidity of chin bone harvesting. Clinical Oral Implants Research 12(5) 503–507.

Eid K, Zelicof S, Perona BP, Sledge CB, Glowacki J (2001). Tissue reactions to particles of bone-substitute materials in intraosseous and heterotopic sites in rats: discrimination of osteoinduction, osteocompatibility, and inflammation. Journal of Orthopaedic Research. 19(5) 962-969.

Robert Langer and Joseph P. Vacanti. (1993) Tissue Engineering. Science, New Series 260(5110)  920-926.

E. Sachlos and J.T. Czernuszka (2003). Making tissue engineering scaffolds work. Review on the application of solid freeform fabrication technology to the production of tissue engineering scaffolds. European Cells and Materials. 5 29-40.

Chiu YC (2011). The role of pore size on vascularization and tissue remodeling in PEG hydrogels. Biomaterials. 32(26) 6045-51.

Rnjak-Kovacina J and Weiss AS (2011). Increasing the pore size of electrospun scaffolds. Tissue Engineering Part B Reviews. 17(5) 365-72.

Naznin Sultana and Min Wang (2011). PHBV Tissue Engineering Scaffolds Fabricated via Emulsion Freezing / Freeze-drying: Effects of Processing Parameters. International Conference on Biomedical Engineering and Technology 11 29-34.

Holzwarth JM and Ma PX (2011). Biomimetic nanofibrous scaffolds for bone tissue engineering, Biomaterials 32(36) 9622-9629.

Hiroshi Kohara and Yasuhiko Tabata (2011). Enhancement of ectopic osteoid formation following the dual release of bone morphogenetic protein 2 and Wnt1 inducible signaling pathway protein 1 from gelatin sponges. Biomaterials 32(24) 5726-5732.

Yang X, Chen X, Wang H (2009). Acceleration of osteogenic differentiation of preosteoblastic cells by chitosan containing nanofibrous scaffolds. Biomacromolecules 10(10) 2772-2778.

Michael G. Dunn, Lisa D. Bellincampi, Alfred J. Tria Jr., and Joseph P. Zawadsky. (1997) Preliminary development of a collagen-PLA composite for ACL reconstruction. Journal of Applied Polymer Science. 63(11) 1423–1428.

Rosa P. Félix Lanao, Sander C.G. Leeuwenburgh, Joop G.C. Wolke, John A. Jansen (2011). Bone response to fast-degrading, injectable calcium phosphate cements containing PLGA microparticles. Biomaterials 32(34) 8839-8847.

Benedetto Marelli, Chiara E. Ghezzi, Dirk Mohn, Wendelin J. Stark, Jake E. Barralet, Aldo R. Boccaccini, Showan N. Nazhat (2011). Accelerated mineralization of dense collagen-nano bioactive glass hybrid gels increases scaffold stiffness and regulates osteoblastic function. Biomaterials 32(34)  8915-8926.

Wei G, Ma PX (2004). Structure and properties of nano-hydroxyapatite/polymer composite scaffolds for bone tissue engineering. Biomaterials 25(19) 4749 -4757.

Seyedjafari E, Soleimani M, Ghaemi N, Shabani I (2010). Nanohydroxyapatite-coated electrospun poly(L-lactide) nanofibers enhance osteogenic differentiation of stem cells and induce ectopic bone formation. Biomacromolecules 11(11) 3118- 3125.

Eugene D. Boland, Gary E. Wnek, David G. Simpson, Kristin J. Pawlowski, and Gary L. Bowlin (2001). Tailoring tissue engineering scaffolds using electrostatic processing techniques: a study of poly (glycolic acid) electrospinning. Journal of Macromolecular Science: Pure and Applied Chemistry 38(12) 1231–1243.

Ferry P.W. Melchels, Katia Bertoldi, Ruggero Gabbrielli, Aldrik H. Velders, Jan Feijen and Dirk W. Grijpma (2010). Mathematically defined tissue engineering scaffold architectures prepared by stereolithography. Biomaterials 31(27) 6909-6916

Su A Park, Su Hee Lee, and Wan Doo Kim (2011). Fabrication of Hydrogel Scaffolds Using Rapid Prototyping for Soft Tissue Engineering. Macromolecular Research.19(7) 694-698.

Dong J. Yoo (2011). Porous scaffold design using the distance field and triply periodic minimal surface models. Biomaterials 32(31) 7741-7754.

a)      PGLA   b)      PGLA + Collagen

 

Customized Impression Post: An Innovative Approach for Esthetic Implant Restorations

An esthetic and functional implant supported restoration in the esthetic zone is a clinical challenge. The correct three dimensional positioning of the implant in the apico-coronal, mesio-distal and bucco-lingual dimensions and proper management of the peri-implant soft tissue is required to achieve the desired emergence profile. Various surgical and restorative techniques have been employed for achieving ideal soft tissue contours ^{1, 2}. Use of customised abutments to develop and maintain the interdental papilla is one such example of a non-surgical technique ³.  The soft tissue profile around a central incisor is rounded triangular in shape. The geometry of the stock impression posts is generally round cylindrical in shape. Due to this discrepancy in shape, they do not allow proper reproduction of the desired soft tissue emergence profile onto the master cast. Customized impression posts prevent soft tissue collapse or distension of the gingival cuff during the impression procedure and a better record of the soft tissue is obtained. This results in a proper reproduction of the implant and soft tissue situation onto the master cast ⁴.

An impression post can be easily customised to support the soft tissue profile present around the implant ^{5, 6}. A simple and cost effective technique has been described below by which the soft tissue contours around the implants can be recorded and transferred to the master cast.

Procedure:

At the second stage surgery, the healing abutment is customized to the preferred emergence profile using light cured composite resin (Filtek Z350, 3M, St. Paul, MN, U.S.) (Photo 1). At the appointment for recording the impression, the customized healing abutment is removed from the mouth and is attached to the laboratory analog. This assembly is then embedded in

                                                           

                                                                                                                                                2

silicone putty. (Speedex, Coltene Whaledent, Coltène Whaledent AG, Altstätten, Switzerland) The buccal surface of the abutment is marked out on the putty block to assist in orientation of the impression post in the future (Photo 2(a,b).

Keeping the laboratory analog in place within the putty, the customized healing abutments is then unscrewed and a stock impression post is attached in its place. Customization of the impression post is done by flowing Protemp 4 (3M, St. Paul, MN, U.S) within the space between the impression post and the silicone putty (Photo 3).  On setting, the resin portion of the customised impression post is smoothened and polished (Photo 4). The other materials that can be used to customise the impression posts can be pattern resin and flowable composites.

The customised impression post is then fitted onto the implant and the soft tissue contours are checked (Photo 5). An open tray impression is made using vinyl poly siloxane. A laboratory analog is attached to the customized impression post and a gingival silicone (Gingitech, Ivoclar Vivadent Inc, Amherst, New York) is flowed around the impression post. The master cast is made thereafter. In this case an abutment was customized using zirconia (Photo 6) (Lava, 3M, St. Paul, MN, U.S.) in the per mucosal region to support the recorded soft tissue contour and an Emax crown (Ivoclar Vivadent, Ivoclar Vivadent Inc, Amherst, New York) was used as the final restoration (Photo 7).

Summary:

The technique discussed above is a precise and simple way of recording the peri-implant soft tissue contours. It can be routinely used to record and transfer the desired emergence profile onto the master models in order to fabricate well contoured, esthetic implant restorations.

                                                                                                                                                3

References:

1. Walter F. Biggs and Allen L. Litvak, Jr. Immediate provisional restorations to aid in gingival healing and optimal contours for implant patients. J Prosthet Dent 2001; 86:177-80.
2. Daniel C.T. Macintosh and Mark Sutherland. Method for developing an optimal emergence profile using heat-polymerized provisional restorations for single-tooth implant-supported restorations. J Prosthet Dent 2004; 91:289-92.
3. Avi Donitza. Prosthetic procedures for optimal aesthetics in single tooth implant restorations: A case report. Pract Periodont Aesthet Dent 2000; 12(4): 347-352.
4. Larry C. Breeding et al. Transfer of gingival contours to a master cast. J Prosthet Dent 1996; 75: 341-43.
5. Mariano A. Polack. Simple method of fabricating an impression coping to reproduce peri-implant gingiva on the master cast. J Prosthet Dent 2002; 88: 221-3.
6. Panagiota-Eirini Spyropoulou et al. Restoring implants in the esthetic zone after sculpting and capturing the periimplant tissues in rest position: A clinical report. J Prosthet Dent 2009;102:345-347

Figure 1: Healing abutment in situ

Figure 2: Healing abutment and lab analog embedded in a silicone putty block

Figure 3: Temporary restorative resin (Protemp 4) flowed around the stock impression post attached to the lab analog

 

Figure 4: Customized impression post

Figure 5: Customized impression post in situ

Figure 6: Final restorations in situ on the day of cementation