preprosthetic surgery edit.pdf

BDS 10052 Principles of preprosthetic surgery Aims & objectives Aims: The aim of this lecture is to provide an overview of the surgical procedures that may be required prior to definitive prosthodontic treatment. Objectives: On completion of this lecture, the student should be able to: • Understa...

BDS 10052 Principles of preprosthetic surgery Aims & objectives Aims: The aim of this lecture is to provide an overview of the surgical procedures that may be required prior to definitive prosthodontic treatment. Objectives: On completion of this lecture, the student should be able to: • Understand the rationale and surgical techniques of preprosthetic surgery of the oral tissues. • Have an awareness of the oral and dental aspects of diabetes mellitus. Preprosthetic surgery Refers to the surgical procedures that are used to modify the oral anatomy to facilitate the placement of prosthetic appliances. Procedures required to enable successful implant placement are also included but will be discussed later After the loss of natural teeth, bony changes in the jaws begin to take place immediately. NO forces on teeth, periodontal ligament in the area → bone resorption Ridge resorption is more prominent in the mandible due to the lower surface area and less favourable occlusal force distribution Accelerated by different systemic and local factors; e.g. denture wearing The objective of preprosthetic surgery is to create proper supporting structures for subsequent placement of prosthetic appliances What are the ideal characteristics of alveolar ridge for best denture support??? Characteristics of an ideal arch for denture construction • No evidence of intra/extraoral pathologies • Proper interarch relationship in all dimensions • Large alveolar processes (ideal shape is a broad U-shaped ridge, with parallel vertical components ) • No bony or soft tissue protuberances or undercuts • Good tuberosity and palatal vault configuration • Adequate keratinized mucosa in the denture bearing area • Adequate vestibular depth for prosthesis extension • Added strength where mandibular fracture may occur & neurovascular bundle protection (mental foramen not crestal) Residual ridge form has been described and classified by Cawood and Howell as follows: • Class I—dentate • Class II—postextraction • Class III—convex ridge form, with adequate height and width of alveolar process • Class IV—knife-edge form with adequate height but inadequate width of alveolar process • Class V—flat-ridge form with loss of alveolar process • Class VI—loss of basal bone that may be extensive but follows no predictable pattern Classification of resorption of maxillary alveolar ridge: Adapted from Cawood JI, Howell Bone adjusting procedures Alveolplasty Tori removal Ridge augmentation Nerve repositioning Soft tissue adjusting procedures Flabby ridge Frenectomy Vestibuloplasty Alveoplasty Irregularities of the alveolar bone which occur after extraction or after a period of bone remodeling must be recontoured before denture construction to avoid painful pressure spots and instability. Types: - Simple alveoloplasty after multiple extractions - Intraseptal Alveoplasty - Localized alveoplasties ( tuberosity / mylohyoid ridge / knife ridge/ bony exostoses) Simple alveoloplasty Removal of the buccal irregularities and undercut areas to improve ridge contour for prosthetic rehabilitation Done by a bur / bone rongeur / bone file A: Clinical appearance of maxillary ridge after removal of teeth. B: Minimal flap reflection for recontouring. C: Proper alveolar ridge form free of irregularities and bony undercuts after recontouring. Intraseptal alveoloplasty Knife-edge ridge adjustment Maxillary tuberosity adjustment ( only to remove undercuts) Tori removal Tori (palatal or mandibular) may cause denture rocking and instability. So large tori must be removed to enable successful denture placement Palatal torus removal A Y or Double Y incision is made down to bone and reflected • The torus is split into smaller parts by a bur under copious irrigation • A unibeveled chisel may be cautiously used to break it off the palate • Region is smoothed on completion and irrigated and sutured In cases of large tori a palatal stent may be fabricated and placed postoperatively to reduce the accumulation of blood and inflammatory fluids which will delay healing and may cause infection Mandibular torus removal is done in the same manner Exostosis removal Exostosis removal Adjustment of mandibular buccal undercut by grafting to avoid reducing the bucco-lingual width of the ridge A tunneling technique is used to keep the graft securely in place Ridge augmentation In cases of deficient alveolar ridge height / width , ridge augmentation is carried out. The grafts may be autogenous / allografts / xeno grafts / alloplastic materials according to their origin (to be discussed in details with implant lectures) Grafts may be used as : - Onlay gafts : placed on the ridge and fixed by screws - Interpositional graft: graft placed between alveolar and basal bone - Sinus floor elevation Soft tissue adjustments Soft tissue abnormalitlies requiring repair are either : - Congenital abnormalities, such as a hypertrophic frenum, etc. - Abnormalities created after the use of dentures (e.g., fibrous hyperplasia of the mucosa – denture hyperplasia / epulis fissuratum) Long-term use of ill-fitting dentures can lead to hyperplasia of the mucosa. This may prevent construction of well-fitting dentures. Small amounts of hyperplastic tissue may be excised under local anaesthesia. Larger amounts should be excised with a laser or cutting diathermy or the defect grafted with palatal mucosa to facilitate haemostasis and reduce scar contracture When areas of gross tissue redundancy are found, excision frequently results in total elimination of the vestibule. In such cases, excision of the epulis, with peripheral mucosal repositioning and secondary epithelialization is preferable. Frenectomy Frenectomy may be needed for orthodontic or preprosthetic purposes (labial frenum) The lingual frenum may cause ankyloglossia due to its attachment to the floor of the mouth or alveolar mucosa; or may even be the result of a short frenum connected to the tip of the tongue. Ankyloglossia limits tongue movement → speech difficulties. Frenectomy procedures may be carried out with traditional surgical approaches or using laser or electrocautery devices Labial frenectomy The frenum is grasped using two hemostats and the incision is made below the lower one and above the upper one to excise the grasped tissue The remaining hyperplastic tissue is removed from between the centrals The mucosa is undermined and a key suture is made in the middle of the suture The rest of the wound is sutured Lingual frenectomy The lingual frenum is grasped with a hemostat and a suture at the tip of tongue used for retraction A scalpel is approached adherent to the hemostat first parallel to the floor to excise the area attached to the floor of the mouth then a similar approach to remove the area attached to the ventral surface of the tongue. Lingual frenectomy The remaining rhomboidal defect is undermined and sutured Z-plasty procedures may be used to reduce the amount of vestibular ablation which may be seen after linear excision of a frenum After excision of the fibrous tissue, two oblique incisions are made in a Z fashion, one at each end of the previous area of excision The two pointed flaps are then gently undermined and rotated to close the initial vertical incision horizontally. The two small oblique extensions also require closure Sulcus deepening (Vestibuloplasty) Inadequate alveolar ridge height can be treated by deepening the sulcus by a vestibuloplasty procedure rather than augmenting the ridge. May leave a raw area of soft tissue, which can be covered by a skin or mucosal graft. The major problem with these techniques is the significant wound contracture, which reduces the sulcus height again. Many variants of the surgical procedure have been developed in an attempt to improve the long-term outcome from these operations Transpositional Flap Vestibuloplasty (Kazanjian Lip Switch) Initially a labial mucosa was made and sutured at a deeper level to deepen the vestibule and the labial mucosa was left to heal by 2ry intention A common modification was made where the labial mucosa was sutured at the desired depth of vestibule and the periosteum used to cover the exposed labial tissue Submucosal Vestibuloplasty In this technique a submucosal tunnel is made and the submucosal tissue is removed to reduce tissue attachments , a stent is then placed with extended flanges to force the tissues to heal at a deeper vestibular level Vestibuloplasty with tissue Grafting When insufficient labio/vestibular mucosa exists and lip shortening would result from a submucosal vestibuloplasty a technique using mucosa pedicled from the upper lip and sutured at the depth of the maxillary vestibule after a supraperiosteal dissection can be used. The use of a labially pedicled mucosal flap combined with tissue grafting over the exposed periosteum of the maxilla provides the added benefits of more rapid healing over the area of previously exposed periosteum and more predictable long-term maintenance of vestibular depth To sum it all up …. • Bony / soft tissue adjustments are sometimes necessary prior to denture construction • Removal of bony undercuts / sharp bony edges / overgrowths may be needed • Ridge augmentation to increase height/width of the alveolar ridge are common procedures • Removal of flabby soft tissue / hypertrophic tissue / deepening of the vestibule are common procedures. • Preparation of an ideal ridge for successful denture construction (retentive and stable) is the target Aims & objectives Aims: The aim of this lecture is to provide an overview of the surgical procedures that may be required prior to definitive prosthodontic treatment. Objectives: On completion of this lecture, the student should be able to: • Understand the rationale and surgical techniques of preprosthetic surgery of the oral tissues. • Have an awareness of the oral and dental aspects of diabetes mellitus. Further reading Students are advised to review any relevant teaching provided in the first year. In addition they are advised to read relevant sections of the following texts: 1. Wray D et al; Textbook of General and Oral Surgery, Churchill Livingstone 2003 pp 243-249 2. Coulthard P et al, Oral and Maxillofacial Surgery, Radiology, Pathology and Oral Medicine Churchill Livingstone 2003 pp 88-90 3. Hupp J et al. Contemporary Oral and maxillofacial surgery , Sixth edition 2014