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Maxillary advancement for mandibular prognathism: Indications and rationale
J Oral Maxillofac Surg 50:201-204.1992
Abstracts Radiologic-Prosthetic Planning of the Surgical Phase of the Treatment of Edentulism by Osseointegrated Implants: An In Vitro Study. Modica F, et al. J Prosthet Dent 65:541, 199 1 Many techniques have been developed for the planning of the surgical and prosthodontic phases of implantation dentistry, This article describes a combined prosthodontic and radiographic technique that gives the surgeon a template to be used in the precise placement of implants. The technique was developed in vitro using three edentulous human mandibles. Panoramic radiographs and metal markers were used to define the area between the mental foramina where the implants could be inserted. A resin base was made on a plaster cast of each mandible and teeth were set as for a routine complete denture. A plaster matrix of tooth placement was made and used to mark implant insertion sites on the resin base. Hollow aluminum cylinders were placed perpendicular to the occlusal plane in a diagnostic position and a reference point for computed tomography (CT) images was determined. Radial CT images were constructed, one for each perforation guide, from a series of axial scans. These diagnostic scans were traced onto transparent graph paper. The surgeon and prosthodontist then plotted the ideal angulation for placement of the implants. A positioner device with curved and horizontal scales was used to reset each guide into the ideal position by using the horizontal and angular corrections as determined from the tracings. The hollow guides were used in surgery to guide implant placement. Similar CT sections were repeated after placement and traced on graph paper. The results showed that as angular and horizontal correction increased, the final error was proportionately greater. When the positioner device was used in initial perpendicular placement of the guides, the final error became zero. This technique using the CT scan can be a useful diagnostic aid for fabricating a template to aid the surgeon in estimating position, angulation, and depth of implant placement.-T. A. TROWE~RIDGE Reprint requests to Dr PII& School of Dentistry, University of Turin, C. Polonia 14, Turin, Italy.
Management of the Medial Canthal Tendon in Nasoethmoid Orbital Fractures. The Importance of the Central Fragment in Classification and Treatment. Markowitz BL, Manson PN, Sargent L, et al. Plast Reconstr Surg 87:843, 1991 A nasoethmoid orbital fracture isolates only the lower two thirds of the medial orbital rim as an unstable fragment permitting canthal displacement. Essentially four of the following fractures must be present to create this particular injury: the lateral nose, the inferior orbital rim, the medial orbital wall, the nasomaxillary buttress at the periform aperature, and the frontal process of the maxilla at the internal angular process of the frontal bone. Injuries are defined as either unilateral or bilateral. Analysis of the fractured pattern in patients between 1985 and 1986 identifies the fracture pattern in the central fragment. The three patterns of fracture are type 1, a single segment fracture at the internal angular process of the frontal bone that is either displaced or nondisplaced; type 2, comminution in the central fragment in which the bone frac-
201
tures do not extend into the area of the canthal insertion; and type 3, a comminution of the central fragment in which the bone fractures extend into the bone providing canthal insertion. The fracture pattern determines the exposure and fixation. The superior nasoethmoidal orbital region is preferably exposed by means of a bicoronal incision. The inferior portion of the nasoethmoid fractures is exposed with a lower eyelid subscillary skin muscle flap as well as a maxillary gingival buccal sulcus incision. The fracture pattern determines exposure and fixation. Subcillary approaches alone are advised for unilateral single-segment injuries that are nondisplaced superiorly. Bicoronal and subcillary approaches are required for displaced unilateral single-segment injuries, for bilateral single-segment injuries, and for all comminuted fractures. Complete interfragment wiring of all segments is stabilized by junctional rigid fixation. All comminuted fractures require transnasal wiring of the bones of the central bone fragment. The transnasal reduction of the canthal tendon-bearing bone fragment is the most important step in preserving the intercanthal distance.-D. D. CARR Reprint requests to Dr Manson: The Johns Hopkins Hospital, Department of Surgery, Division of Plastic Surgery, 600 N Wolfe St, Baltimore, MD 2 1205.
Maxillary Advancement for Mandibular Prognathism: Indications and Rationale. Rosen HM. Plast Reconstr Surg 87: 823, 1991 The surgical correction of mandibular prognathism has traditionally involved posterior repositioning of the mandib ular body. Although cephalometrically appropriate, this treatment approach corrects the skeletal disproportion at the expense of reducing facial skeletal volume and can frequently and unpredictably result in inadequately supported sofi tissues with a loss of skeletal definition. In this study, 18 patients with a diagnosis of class III malocclusion with mandibular prognathism were treated with maxillary advancement surgery at the Le Fort I level. The clinical impression of mandibular prognathism was conhrrned cephalometrically using both the hard- and soft-tissue analysis. Skeletal analysis used Frankfort horizontal and the Sella-nasim reference planes. In this study the mean SNA angle was 82.8” and the mean SNB angle was 85.2”. Using the Frankfort horizontal as a reference plane, the mean patient maxillary depth angle was 89.8” (normal, 90” rf: 3”). The mean patient facial depth angle was 94.5” (normal, 89” f 3”). Therefore, using both cranial base and Frankfort horizontal as skeletal reference planes, the mandible could be viewed as being sag&ally excessive and responsible for the class III malocclusion. All patients underwent maxillary advancement at the, high Le Fort I level to correct the entire anteroposterior discrepancy between the maxilla and the mandible. The mean maxillary advancement was 6.9 mm with a range of 4.5 to ‘8.8 mm. All patients required a genioplasty to either align the chin point with the midsagittal plane or to reduce a vertical chin height. The mean follow-up was 16.2 months and at this time cephalometric tracings using both hard- and soft-tissue analysis suggested large mandibles and excessive anterior fa-
202 cial divergence. It was a clinical impression at follow-up that all patients faces were skeletally well proportioned despite lower face protrusion that was beyond the norman anthropometric standards. No patient considered his or her lower facial protrusion to be excessive. Postoperative appearances were characterized by a well-supported soft-tissue envelope and a highlighted skeletal foundation creating angular welldefined lower faces. This study supports the use of maxillary advancement as the procedure of choice in selected patients with mandibular prognathism. The considerations, indications, and contraindications for the use of mandibular advancement to correct mandibular prognathism are reviewed.-D. C. CARR Reprint requests to Dr Rosen: Pennsylvania Hospital, 800 Spruce St, Philadelphia, PA 19107. Mersilene Tip Implants in Rhinoplasty: A Review of 98 Cases. Fanous N. Plast Reconstr Surg 87:662, 1991 The Mersilene tip implant was used in 98 patients with follow-up ranging from 4 months to 3 years, with an average of I 1.4 years. Indications for Mersilene tip implants include recessed tip, thick-skin tip, boxing tip, asymmetrical tip, thinskin tip, bifid tip, turned-up tip, and turned-down tip. The implant is prepared by generously wetting the mesh in saline or water. Pads seven layers thick are formed by folding the mesh on itself. A 4-O chromic transfixion suture is placed in the center to keep the layers together after it is shaped. The outline of the implant is drawn on the nasal tip preoperatively. A unilateral rim incision 2 cm long is made, followed by direction of a large subcutaneous pocket twice as large as the implant. The implant is soaked in bacitracin solution and placed into the pocket. The incision is closed with 4-O chromic gut suture. Postoperative antibiotics are administered for 1 week. Infection was the most significant complication, with eight cases resulting in rejection (8.2%). All occurred within 7 months, except one at 14 months. In all cases, removal of the implant was followed by rapid disappearance of the infection. One case of insufficient tip implant was corrected under local anesthesia by adding more implant material. No cases of implant asymmetry were detected. The “PEPSI” rule is a list of five essential guidelines to a successful alloplastic mesh implant. The pocket should be twice as large as the implant. Experience of the surgeon, proper positioning, adequate size and shape, and a rim incision large enough for good exposure all are important factors. Advantages of Mersilene over cartilage is its versatility and more predictable and refined esthetic result. The disadvantages of cartilage includes resorption, displacement, sharp edges beneath the skin, limited volume, and curling. The disadvantages of Mersilene is infection. Supramid mesh, another alloplastic implant that closely resembles Mersilene has a lower infection rate than Mersilene but has a real disadvantage of shrinkage up to 25% within 2 years. Silastic has a low infection rate but is difficult to place.-D. D. CARR Reprint requests to Dr Fanous: I Westmount Square, Suite 1380, Westmount, C.Q. Canada H3Z2P9.
The Case for Early Bone Grafting in Cleft Lip and Palate: A Second Report. Rosenstein S, Dado D, Kemahan D, et al. Plast Reconstr Surg 87:644, 199 1 The optimal timing for bone grafting clefts has been very controversial, with the majority favoring grafts during the
CURRENT LITERATURE
late mixed and/or permanent dentition. Primary bone grafting of both unilateral and bilateral clefts was performed in which an infant maxillary appliance is placed prior to lip closure to keep the arch segments in proper alignment and to facilitate feeding. The cleft lip is subsequently repaired at 6 to 8 weeks of age using a repair that incorporates muscle realignment. Molding of the maxillary segments proceeds and come together as a butt joint. When this occurs, at usually 4 to 6 months of age, the segments are stabilized with a rib graft placed on the maxillae. The graft is inserted into a small pocket just above the alveolar segments, on the maxillae, with limited vomer and premaxillary area dissection. The graft does not bridge the gap, but overlies the butt joint. The appliance is continued for 6 to 8 weeks. At approximately 1 year of age, the palate is closed with an intravelar veloplasty. Cephalomettic measurements were compared between 20 grafted unilateral clefts and ungrafted clefts of a previous study at a mean age of 13.9 years. Also cephalometric measurements were compared between 17 bilateral complete clefts (grafted) and 4 bilateral clefts with no bone graft, the mean age being 12 years and 7 months. The cephalometric analysis in both groups (unilateral and bilateral clefts) in grafted and nongrafted patients are similar, indicating that no adverse growth constraints occurred because of the early bone grafts. This protocol has added advantage over delayed bone grafting of establishing an early correct foundation for some of the soft tissue deficiencies associated with the cleft condition-D. D. CARR Reprint requests to Dr Rosenstein: 4801 W Peterson Ave, Chicago, IL 60646.
Effect of Parainflueuza Infection on Gas Exchange and FRC Response to Anesthesia in Sheep. Dueck R, Prutow R, Richman D. Anesthesiology 74: 1044, 199 1 Smoking, obesity, and chronic obstructive pulmonary disease are well known to impair pulmonary gas exchange during general anesthesia. Conflicting reports exist, however, regarding the effects of acute viral respiratory infection on anesthesia outcome. Because a wide variety of clinical variables could account for the disparity in observations, a welldocumented animal model was used to better define the effects of viral infection on gas exchange during general anesthesia. Six healthy sheep underwent tracheostomy and carotid artery exteriorization 2 weeks prior to the study. Ventilationperfusion ratios, arterial blood gases, and functional residual capacity (FRC) were measured in awake and anesthetized sheep before and after viral infection with ovine parainfluenza virus. General anesthesia was induced and maintained with 1.25% halothane and 70% nitrous oxide. A state of general anesthesia significantly reduced FRC from the awake state, but the presence of infection did not significantly alter awake or asleep FRC. Viral infection produced a significantly higher intrapulmonary shunt, lower arterial oxygen partial pressure, and higher peak airway pressure in both awake and anesthetized sheep. The authors found no evidence of synergism between the effects of general anesthesia and viral infection. The hypoxemia recorded was greater than expected, and the authors were able to ascribe this to increased uptake of oxygen by the lung. In determining how long elective general anesthesia should be delayed after acute viral infection, the authors speculate that one should consider the severity of tracheobronchial damage, severity of inflammation, presence of bacterial superinfection, and preexisting lung disease. The
Abstracts Radiologic-Prosthetic Planning of the Surgical Phase of the Treatment of Edentulism by Osseointegrated Implants: An In Vitro Study. Modica F, et al. J Prosthet Dent 65:541, 199 1 Many techniques have been developed for the planning of the surgical and prosthodontic phases of implantation dentistry, This article describes a combined prosthodontic and radiographic technique that gives the surgeon a template to be used in the precise placement of implants. The technique was developed in vitro using three edentulous human mandibles. Panoramic radiographs and metal markers were used to define the area between the mental foramina where the implants could be inserted. A resin base was made on a plaster cast of each mandible and teeth were set as for a routine complete denture. A plaster matrix of tooth placement was made and used to mark implant insertion sites on the resin base. Hollow aluminum cylinders were placed perpendicular to the occlusal plane in a diagnostic position and a reference point for computed tomography (CT) images was determined. Radial CT images were constructed, one for each perforation guide, from a series of axial scans. These diagnostic scans were traced onto transparent graph paper. The surgeon and prosthodontist then plotted the ideal angulation for placement of the implants. A positioner device with curved and horizontal scales was used to reset each guide into the ideal position by using the horizontal and angular corrections as determined from the tracings. The hollow guides were used in surgery to guide implant placement. Similar CT sections were repeated after placement and traced on graph paper. The results showed that as angular and horizontal correction increased, the final error was proportionately greater. When the positioner device was used in initial perpendicular placement of the guides, the final error became zero. This technique using the CT scan can be a useful diagnostic aid for fabricating a template to aid the surgeon in estimating position, angulation, and depth of implant placement.-T. A. TROWE~RIDGE Reprint requests to Dr PII& School of Dentistry, University of Turin, C. Polonia 14, Turin, Italy.
Management of the Medial Canthal Tendon in Nasoethmoid Orbital Fractures. The Importance of the Central Fragment in Classification and Treatment. Markowitz BL, Manson PN, Sargent L, et al. Plast Reconstr Surg 87:843, 1991 A nasoethmoid orbital fracture isolates only the lower two thirds of the medial orbital rim as an unstable fragment permitting canthal displacement. Essentially four of the following fractures must be present to create this particular injury: the lateral nose, the inferior orbital rim, the medial orbital wall, the nasomaxillary buttress at the periform aperature, and the frontal process of the maxilla at the internal angular process of the frontal bone. Injuries are defined as either unilateral or bilateral. Analysis of the fractured pattern in patients between 1985 and 1986 identifies the fracture pattern in the central fragment. The three patterns of fracture are type 1, a single segment fracture at the internal angular process of the frontal bone that is either displaced or nondisplaced; type 2, comminution in the central fragment in which the bone frac-
201
tures do not extend into the area of the canthal insertion; and type 3, a comminution of the central fragment in which the bone fractures extend into the bone providing canthal insertion. The fracture pattern determines the exposure and fixation. The superior nasoethmoidal orbital region is preferably exposed by means of a bicoronal incision. The inferior portion of the nasoethmoid fractures is exposed with a lower eyelid subscillary skin muscle flap as well as a maxillary gingival buccal sulcus incision. The fracture pattern determines exposure and fixation. Subcillary approaches alone are advised for unilateral single-segment injuries that are nondisplaced superiorly. Bicoronal and subcillary approaches are required for displaced unilateral single-segment injuries, for bilateral single-segment injuries, and for all comminuted fractures. Complete interfragment wiring of all segments is stabilized by junctional rigid fixation. All comminuted fractures require transnasal wiring of the bones of the central bone fragment. The transnasal reduction of the canthal tendon-bearing bone fragment is the most important step in preserving the intercanthal distance.-D. D. CARR Reprint requests to Dr Manson: The Johns Hopkins Hospital, Department of Surgery, Division of Plastic Surgery, 600 N Wolfe St, Baltimore, MD 2 1205.
Maxillary Advancement for Mandibular Prognathism: Indications and Rationale. Rosen HM. Plast Reconstr Surg 87: 823, 1991 The surgical correction of mandibular prognathism has traditionally involved posterior repositioning of the mandib ular body. Although cephalometrically appropriate, this treatment approach corrects the skeletal disproportion at the expense of reducing facial skeletal volume and can frequently and unpredictably result in inadequately supported sofi tissues with a loss of skeletal definition. In this study, 18 patients with a diagnosis of class III malocclusion with mandibular prognathism were treated with maxillary advancement surgery at the Le Fort I level. The clinical impression of mandibular prognathism was conhrrned cephalometrically using both the hard- and soft-tissue analysis. Skeletal analysis used Frankfort horizontal and the Sella-nasim reference planes. In this study the mean SNA angle was 82.8” and the mean SNB angle was 85.2”. Using the Frankfort horizontal as a reference plane, the mean patient maxillary depth angle was 89.8” (normal, 90” rf: 3”). The mean patient facial depth angle was 94.5” (normal, 89” f 3”). Therefore, using both cranial base and Frankfort horizontal as skeletal reference planes, the mandible could be viewed as being sag&ally excessive and responsible for the class III malocclusion. All patients underwent maxillary advancement at the, high Le Fort I level to correct the entire anteroposterior discrepancy between the maxilla and the mandible. The mean maxillary advancement was 6.9 mm with a range of 4.5 to ‘8.8 mm. All patients required a genioplasty to either align the chin point with the midsagittal plane or to reduce a vertical chin height. The mean follow-up was 16.2 months and at this time cephalometric tracings using both hard- and soft-tissue analysis suggested large mandibles and excessive anterior fa-
202 cial divergence. It was a clinical impression at follow-up that all patients faces were skeletally well proportioned despite lower face protrusion that was beyond the norman anthropometric standards. No patient considered his or her lower facial protrusion to be excessive. Postoperative appearances were characterized by a well-supported soft-tissue envelope and a highlighted skeletal foundation creating angular welldefined lower faces. This study supports the use of maxillary advancement as the procedure of choice in selected patients with mandibular prognathism. The considerations, indications, and contraindications for the use of mandibular advancement to correct mandibular prognathism are reviewed.-D. C. CARR Reprint requests to Dr Rosen: Pennsylvania Hospital, 800 Spruce St, Philadelphia, PA 19107. Mersilene Tip Implants in Rhinoplasty: A Review of 98 Cases. Fanous N. Plast Reconstr Surg 87:662, 1991 The Mersilene tip implant was used in 98 patients with follow-up ranging from 4 months to 3 years, with an average of I 1.4 years. Indications for Mersilene tip implants include recessed tip, thick-skin tip, boxing tip, asymmetrical tip, thinskin tip, bifid tip, turned-up tip, and turned-down tip. The implant is prepared by generously wetting the mesh in saline or water. Pads seven layers thick are formed by folding the mesh on itself. A 4-O chromic transfixion suture is placed in the center to keep the layers together after it is shaped. The outline of the implant is drawn on the nasal tip preoperatively. A unilateral rim incision 2 cm long is made, followed by direction of a large subcutaneous pocket twice as large as the implant. The implant is soaked in bacitracin solution and placed into the pocket. The incision is closed with 4-O chromic gut suture. Postoperative antibiotics are administered for 1 week. Infection was the most significant complication, with eight cases resulting in rejection (8.2%). All occurred within 7 months, except one at 14 months. In all cases, removal of the implant was followed by rapid disappearance of the infection. One case of insufficient tip implant was corrected under local anesthesia by adding more implant material. No cases of implant asymmetry were detected. The “PEPSI” rule is a list of five essential guidelines to a successful alloplastic mesh implant. The pocket should be twice as large as the implant. Experience of the surgeon, proper positioning, adequate size and shape, and a rim incision large enough for good exposure all are important factors. Advantages of Mersilene over cartilage is its versatility and more predictable and refined esthetic result. The disadvantages of cartilage includes resorption, displacement, sharp edges beneath the skin, limited volume, and curling. The disadvantages of Mersilene is infection. Supramid mesh, another alloplastic implant that closely resembles Mersilene has a lower infection rate than Mersilene but has a real disadvantage of shrinkage up to 25% within 2 years. Silastic has a low infection rate but is difficult to place.-D. D. CARR Reprint requests to Dr Fanous: I Westmount Square, Suite 1380, Westmount, C.Q. Canada H3Z2P9.
The Case for Early Bone Grafting in Cleft Lip and Palate: A Second Report. Rosenstein S, Dado D, Kemahan D, et al. Plast Reconstr Surg 87:644, 199 1 The optimal timing for bone grafting clefts has been very controversial, with the majority favoring grafts during the
CURRENT LITERATURE
late mixed and/or permanent dentition. Primary bone grafting of both unilateral and bilateral clefts was performed in which an infant maxillary appliance is placed prior to lip closure to keep the arch segments in proper alignment and to facilitate feeding. The cleft lip is subsequently repaired at 6 to 8 weeks of age using a repair that incorporates muscle realignment. Molding of the maxillary segments proceeds and come together as a butt joint. When this occurs, at usually 4 to 6 months of age, the segments are stabilized with a rib graft placed on the maxillae. The graft is inserted into a small pocket just above the alveolar segments, on the maxillae, with limited vomer and premaxillary area dissection. The graft does not bridge the gap, but overlies the butt joint. The appliance is continued for 6 to 8 weeks. At approximately 1 year of age, the palate is closed with an intravelar veloplasty. Cephalomettic measurements were compared between 20 grafted unilateral clefts and ungrafted clefts of a previous study at a mean age of 13.9 years. Also cephalometric measurements were compared between 17 bilateral complete clefts (grafted) and 4 bilateral clefts with no bone graft, the mean age being 12 years and 7 months. The cephalometric analysis in both groups (unilateral and bilateral clefts) in grafted and nongrafted patients are similar, indicating that no adverse growth constraints occurred because of the early bone grafts. This protocol has added advantage over delayed bone grafting of establishing an early correct foundation for some of the soft tissue deficiencies associated with the cleft condition-D. D. CARR Reprint requests to Dr Rosenstein: 4801 W Peterson Ave, Chicago, IL 60646.
Effect of Parainflueuza Infection on Gas Exchange and FRC Response to Anesthesia in Sheep. Dueck R, Prutow R, Richman D. Anesthesiology 74: 1044, 199 1 Smoking, obesity, and chronic obstructive pulmonary disease are well known to impair pulmonary gas exchange during general anesthesia. Conflicting reports exist, however, regarding the effects of acute viral respiratory infection on anesthesia outcome. Because a wide variety of clinical variables could account for the disparity in observations, a welldocumented animal model was used to better define the effects of viral infection on gas exchange during general anesthesia. Six healthy sheep underwent tracheostomy and carotid artery exteriorization 2 weeks prior to the study. Ventilationperfusion ratios, arterial blood gases, and functional residual capacity (FRC) were measured in awake and anesthetized sheep before and after viral infection with ovine parainfluenza virus. General anesthesia was induced and maintained with 1.25% halothane and 70% nitrous oxide. A state of general anesthesia significantly reduced FRC from the awake state, but the presence of infection did not significantly alter awake or asleep FRC. Viral infection produced a significantly higher intrapulmonary shunt, lower arterial oxygen partial pressure, and higher peak airway pressure in both awake and anesthetized sheep. The authors found no evidence of synergism between the effects of general anesthesia and viral infection. The hypoxemia recorded was greater than expected, and the authors were able to ascribe this to increased uptake of oxygen by the lung. In determining how long elective general anesthesia should be delayed after acute viral infection, the authors speculate that one should consider the severity of tracheobronchial damage, severity of inflammation, presence of bacterial superinfection, and preexisting lung disease. The