Introduction
Orthognathic surgery involves three-dimensional movements based on a series of non-surgical and surgical procedures. This is particularly evident in osteotomies which change the occlusal level.
The main planning concerns are:
· prediction of the tooth-bone-soft tissue changes,
· operative reproducibility of the treatment plan, and
· postoperative dentoskeletal stability.
Confounding factors are:
a) planning data transfer inadequacies,
b) the adaptation of the TMJ complex,
c) diversity of surgical skills, and
d) relapse forces.
The definitive preoperative planning process has the following stages:
· clinical estimated measurements,
· impressions,
· occlusal record (squash bite),
· face bow registration,
· face bow transfer to the articulator and mounting of the maxillary model,
· mounting of the mandibular model,
· maxillary model surgery,
· intermediate occlusal wafer fabrication,
· mandibular model surgery, and
· final occlusal wafer fabrication.
These ten processes all require care but are subject to inaccuracies which render fine degrees of planned measurement inappropriate.
With a single jaw mandibular osteotomy, precise model surgery planning using a facebow and anatomical articulator is not required. However, all maxillary and bimaxillary procedures require an accurate transfer of the jaw relationship to the articulator, for surgical planning.
The Planning Process
1. Clinical Measurements
There are inherent difficulties in accurately recording the clinical data. For instance patients may camouflage an occlusal cant by tilting the head and many Class II division 1 patients posture their mandible forwards. There are also important occlusal changes due to the effects of gravity in the conscious patient compared to the loss of muscle tone in the anaesthetised patient.
2. Impression Procedure
a) The impression procedure is more demanding than for standard impressions for dental appliances. Apart from the jaw deformity, malocclusion and postural camouflage, the presence of orthodontic brackets create a challenge for the inexperienced. It is important that the orthdodontic archwire is passive in the brackets at the time of taking the impressions.
b) The impressions must be taken as near to the surgery as possible. Soft red wax may be applied on the gingival side of the orthodontic brackets to avoid splitting adherent alginate. The application or flow of wax onto the occlusal side of the bracket can obliterate the occlusion. Two full upper and lower impressions which detail all the teeth are taken using irreversible hydrocolloid impression material (Claudius Ash. UK). It is essential to include the terminal cusps of the most posterior molars as failure to record these could lead to unplanned prematurities in occlusal contact at the time of surgery. The impressions are cast in Crystacal R Class III stone plaster (Newark Works, Bowbridge Lane, Newark, Nottinghamshire) and based in plaster (British Gypsum). One set of models is anatomically trimmed for model surgery (Figure 7.1a) and the second angle trimmed as study models (Figure 7.1b).
Figure 7.1 (a) Upper and lower models after removing non-anatomical parts, ready to articulate. (b) Standard angle trimmed study models.
3. Recording the Occlusal Relationship
The dental occlusion is dynamic with a three-dimensional envelope of movement which will change with altered patterns of neuromus-cular function such as, postural habits, gravity, the level of consciousness and even psychiatric factors. It is crucial to recognise that preoperative planning is conventionally done on a conscious upright patient using centric occlusal records (CO), i.e maximal intercuspation in the X axis, despite the osteotomy taking place with the mandible in an anaesthetised supine centric relation position (CR), i.e the occlusal retruded position in the Y-axis (Figures 7.2a and 7.2b).
Figure 7.2 (a) and (b) Osteotomies are planned in the upright X-axis but carried out in a supine anaesthetised Y-axis.
A significant difference between the conscious CO and supine anaesthetised CR will produce unexpected discrepancies between the planned and postoperative occlusion, for instance when the osteotomised maxilla is temporarily fixed to the unoperated mandible and rotated upwards and forwards into its planned position for plate fixation. The anaesthetised mandibular CR will give rise to a loss of maxillary advancement which is seen when the patient wakes and sits up with the mandible recoiling forwards.
This may not be apparent in the bimaxillary procedure as the osteotomised mandible is then related to the previously fixed maxilla.
Conversely with a Class III mandibular setback there will be a loss of push back with the conscious upright recoil (Figures 7.3a and 7.3b). This is beneficial in a Class II division 1 mandibular advancement and helps to compensate for any distal relapse.
To avoid these potential problems the osteotomy should be planned from the CR occlusal registration, taken in a relaxed supine patient. Any minor residual CO-CR discrepancies are usually compensated for by proprioceptive adaptation within the envelope of movement of the condyle-disc-fossa relationship.
Figure 7.3 (a) Fixation in supine and (b) occlusion when upright.
Figure 7.4 The centric jaw relation recording in supine conscious posture using bilateral manipulation technique.
The Registration of Supine Centric Relation
Centric relation is recorded using the bilateral manipulation technique, with the patient in a relaxed supine position and the operator seated behind and with the patient's head between the two arms. The operator supports the patient's mandible bilaterally by placing the fingers of each hand below the lower border of the mandible on each side and the thumbs in the depression of the labiomental fold (Figure 7.4). This technique emphasises the “posterior” placement of the condyles in the fossae. With the softened wax occlusal wafer in place the mandible is then guided into the centric relation position.
Appreciation of this plasticity of the condyle-disc-fossa relationship is essential in orthognathic surgery planning.
4. Facebow Recording
a) The facebow is designed to record the relationship of the maxilla to the terminal hinge axis of the patient's mandibular condyles and a Frankfort-like plane. When transferred to the articulator this becomes the relationship of the maxillary cast to the condylar assemblies of an articulator. Although this axis can vary with posture, when standardised, the facebow/articulator transfer method has proved to be reproducible for orthognathic planning.
a) The Denar (and similar systems) is clinically reliable except where there is gross facial asymmetry. It has a reference point of 43 mm above the lateral incisor edge which defines the anterior point on an arbitary plane within the maxilla (Figure 7.5). The posterior reference point is the bony margin of the external auditory meatus, conveniently located by the facebow earplugs.
Figure 7.5 Clinical picture of Denar Slidematic facebow with ear plugs for hinge axis point and an anterior reference point 43 mm above central incisor.
Although careful facebow registration shows a high degree of accuracy in the vertical plane there is a wider variation in the horizontal plane which together with the eight other variables in the transfer process, may invalidate the use of small planning movements. Furthermore small variations cannot be controlled surgically nor perceived by the eye. For this reason forward and backward movements of the maxilla are most reliably planned in 3 mm units which also simplifies clinical decision making when translated into minor 3 mm, moderate 6 mm and major 9 mm moves. Similarly vertical movements are more accurately estimated as 2, 4 or 6 mm. impactions again representing minor, intermediate and major defects. The exception to this “3-unit rule” is the cleft palate case with a major iatrogenic disturbance to facial growth.
b) The facebow registration procedure: Facebow ear pieces are placed into the external auditory meati and manipulated until the subject feels equal pressure in both ears. The anterior reference pointer is adjusted to the pre-determined reference mark 43 mm above the incisal edge of the right maxillary lateral incisor and the transfer jig screws are tightened (Figure 7.5).
The facebow bite fork registration can be taken using a silicon based material which gives definition of the occlusal surfaces (Figure 7.6a) and can be easily trimmed with a scalpel should the material inadvertently encapsulate the orthodontic brackets.
Prior to mounting the upper and lower models, silicon moulds of the master casts/models can be prepared (Figure 7.6b). This enables copies of the models to be prepared should damage occur during the construction of the splints and for one to be kept in the patient's study model box for record purposes.
5. Facebow Transfer to the Articulator and the
Mounting of the Casts
Only the Denar transfer jig and bite fork need to be sent to the laboratory, the facebow does not have to leave the clinic. Unless the procedure is carried out very carefully errors can be introduced when seating the cast into the bite fork indentation and during the subsequent mounting
Figure 7.6 (a) Silicon bite fork registration. (b) Silicon mould of master models for duplication and record keeping.
Using a small amount of dental plaster mixed with an anti-expansion solution (Alan Pharmaceuticals Ltd., London) the maxillary model is mounted on the articulator (Figure 7.7a).
Figure 7.7 (a) The Denar facebow transfer jig assembled in an articulator with upper cast ready to be mounted. (b) Lower cast ready to be mounted in the Denar articulator.
This is followed by mounting the mandibular cast using the supine centric relation record (Figure 7.7b). The models are mounted in two stages; firstly using plaster mixed with anti-expansion solution as described, to eliminate any potential distortion. When set, the models together with their respective assembly plates are removed from the articulator and “anatomically” shaped with white plaster vacuum mixed in plain water.
The upright centric occlusal record is used for articulation of the study models.
Facial Asymmetry
The planning and correction of transverse occlusal plane asymmetry can be a challenge. Unfortunately articulators, facebows and cephalostats are designed for symmetrical faces.
With a facebow record, the patient's anatomical hinge axis (the external auditory meati) determine the orientation of the maxillary cast within the articulator. If this anatomic hinge axis is at right angles to the mid-sagittal plane, the resulting articulator model assembly will accurately represent the facial midline of the patient in an upright position (Figure 7.8).
Figure 7.8 Symmetrical ears give symmetrical alignment with facebow recording.
With an asymmetrical face or external auditory meati, the patient's eccentric anatomical hinge axis will be transferred by the facebow to the articulator but made to coincide with its horizontal mechanical hinge axis (Figure 7.9a). This will rotate the maxilla in the articulator space and so the facial and the dental midlines will not coincide with the articulator incisal pin. When due to asymmetrical external auditory meati, a pseudocant will suggest the need to correct a facial midline discrepancy, which does not exist (Figures 7.9b and 7.9c). For this reason it is very important that the patient's facial midline is recorded clinically and independently of the facebow with a facial midline jig, and transferred to the articulated models for the preoperative work-up. Figure 7.9c shows how the inferiorly placed left ear has been recorded as a pseudocant with the true midline traced obliquely to the left. Planning is done supporting the articulator in space to render the midline vertical.
Figure 7.9 (a) Asymmetrical ears would give asymmetrical recording when using a standard facebow transfer. (b) The midline jig records the true facial midline. (c) The ear asymmetry is reflected in the mounted models as a pseudo cant when using the facebow record.
The anatomical structures used to determine the vertical facial midline are:
(i) from the centre of the glabella to the centre of the chin, unless the chin is deviated to one side;
(ii) the centre of the philtrum unless it is deformed; and
(iii) a right angle to the interpupillary line at a point midway between the pupils when the patient is looking directly forward (Figures 7.10a and 7.10b).
The Transfer of the Facebow Record of Maxillary Asymmetry
Figure 7.10 (a) Clinical picture of a midline jig in use with facial midline marker. (b) Jig transfer of midline to articulated models.
The facebow record is taken with the midline mark on the facebow bite fork matching the patient's facial midline, not the dental midline.
Figure 7.11 Midline jig: (a) Components: 4 mm nickel silver (NS) tube and 3 mm oval wire. (b) 3 mm oval NS wire is bent into a U shape and soldered on the end of the 4 mm NS tube, and two 3 mm NS wires with V cut are ready to be soldered on the tube at right angle to the U shape bite fork. (c) Midline jig with all components soldered together (d) with wax squash bite.
With asymmetry a facial midline indicator (FMI) jig is used which has a U shaped nickel silver wire tray, to take composition, silicon or wax, similar to a facebow bite fork. Its extraoral extension has two parallel vertical bars to register the long axis of the face. Each bar has notches on the upper and lower ends to help to align them to the facial midline (Figures 7.11a-7.11d). Wax or composition is softened and applied to the U shaped part of the jig. While soft, the jig is placed in the mouth and the patient asked to close slowly into centric occlusion while the operator adjusts the vertical bars so that they match exactly the patients facial midline (Figure 7.10a). Heavy body silicon can also be used. When the material has set the jig is removed from the mouth and chilled.
The dental casts are mounted in the articulator using the facebow record. The jig is then located by the impression of the cast teeth. Using the notches on the parallel vertical bars two reference points are marked on the surfaces of upper and lower mounting assembly plaster work. A third reference point is then taken from the facebow bite fork midline mark and the facial midline is drawn, using these three reference points, from the upper mounting plate A line to the lower mounting plate A line (Figures 7.10 and 7.12). This line represents the patient's true facial midline and the long axis of the face. This jig is an invaluable device, which facilitates the correction of the maxillary midline and occlusal cant with accuracy. Figure 7.10 shows a true occlusal cant with a symmetrical face. The maxillary model shows the planned bone removal to level the occlusion. Figures 7.9 and 7.12 are both pseudocants where the occlusal plane is at right angles to the midline jig alignment.
Figure 7.12 The midline jig is transferred to the articulator for midline cast marking.
6. Model Surgery
Bimaxillary surgery is usually sequenced with the maxilla mobilised and repositioned first although some surgeons correct the mandible at the outset. Regardless of which jaw, it is imperative that it is planned accurately because once fixed, it becomes the basis for repositioning the other jaw. For example a false asymmetrical maxilla will show itself by asymmetry of the mandible.
The following are important.
a) Midline dental discrepancies or an occlusal cant are corrected to the facial midline as drawn on the articulated models from the midline jig and not the articulator pin (Figure 7.9c).
b) The angular relationship of the occlusal to the Frankfort horizontal plane;
(80 ± 40) is also important in treatment planning.
Changes in the occlusal plane angle are used to
i) close an anterior open bite and
ii) retrocline maxillary incisal inclination.
In both cases the amount of occlusal plane alteration be carefully estimated clinically and radiolographically and then carried out on the articulated models.
c) Model Surgery Technique (Figures 7.13a to 7.13e)
· The preoperative relationships of the maxillary and mandibular models are recorded by horizontal lines (A, B and O) and vertical lines.
· The A lines are within half a centimetre of their mounting plates and the B line is at the estimated apices of the canines (Figure 7.13a).
· The O line (Figure 7.13b) is drawn to represent the site of the estimated osteotomy cut. The vertical lines are drawn through the following reference points: VM, molar buccal cusp tip; VB, buccal cusp tip of the second bicuspid; VC, canine cusp tip; and VF, interincisal edge or marker of the facial midline. The distance from each cusp reference point to its A line and the transpalatal intercanine and intermolar distances are measured with a Vernier calliper and metal ruler or Ericsson model platform and recorded on the models (Figures 7.13c to 7.13e).
Figure 7.13 (a) Horizontal reference lines A and B are drawn with a fine tipped felt pen. (b) Models mounted in the preoperative position on the Denar articulator, using the Slidematic facebow and centric relation records, The anatomically-orientated models in preoperative positions showing the cusp reference points (as pointed out with arrows) used for pre-and postoperative measurements. VM = Mesial buccal cusp of a molar tooth; VB = buccal cusp of a premolar; VC = canine cusp; and VF = interincisor midline at the crown tip, unless the teeth or the maxilla are asymmetrically rotated in which case the most anterior
· The model is cut at the O osteotomy line with a hand or electric saw, and where an impaction is to be carried out, the required amount of plaster is removed with the saw or electric sander to achieve the planned jaw movements. The segments are assembled in the postoperative position using red ribbon wax, which allows easy manipulation into the required position. When the final position is achieved the red soft wax is replaced with sticky wax. If any adjustments are necessary the wax can be softened and the maxillary or mandibular segments repositioned.
· The relative postoperative positions of the jaw segments are measured as the distances between the references points and the actual movements are indicated in boxes with direction arrows.
· It is advisable to complete the whole model surgery procedure, check the final occlusion and see if any adjustment is required in the maxillary position before making any occlusal wafer.
· For the intermediate wafer fabrication the postoperative mandibular model can be replaced with the preoperative mandibular model mounted with the supine CR wax occlusal record (Figures 7.14a and 7.14b).
point at the incisor edge is used, where it coincides with the facial midline. Note: A and B base lines, O = simulated osteotomy line and the vertical reference lines. (c) The vertical maxillary movements measured with a digital Vernier calliper from the A line to the cusp tips of maxillary teeth. (d) The modified articulator anterior pin with a slot for the steel rule is used to confirm anteroposterior jaw movements. (e) Occlusal view of a patient cast showing 4 mm intercanine and 12 mm intermolar maxillary expansion.
Figure 7.14 Models in (a) intermediate and (b) final position after the model surgery and before making intermediate and final occlusal wafers.
The Ericsson Table for Model Surgery (Great Lakes Orthodontics)
This is a precise tool for carrying out the model surgery. The registration bite and transfer jig are used for the articulation of the upper then lower models as described previously. Once the plaster has set both mountings are allowed to dry completely overnight in a drying oven.
· The Ericsson system consists of a highly polished smooth granite platform (Figure 7.15a) with an electronic calliper mount inserted into the base at 90 degrees to the surface platform and a model block (Figure 7.15b). The models mounted on the model block can be measured in three planes. The calliper's tip in addition to measuring can also be used to scribe lines onto the plaster models.
· The plaster model with its articulator ring is mounted on the rectangular model block in an identical manner to that on the anatomical articulator. The surface of the model block is therefore equivalent to the mounting surface of the articulator arm and is the reference plane for measuring vertical impaction changes (Y) (Figure 7.15b).
· With the model block on its posterior side on the granite table measurements are recorded from the platform surface to the dental midline and cusp reference points to simulate “horizontal — anteroposterior (X) movements.
· Transverse measurements (Z). are recorded with the block on its lateral side (Figures 7.15c and 7.15d).
· The measurements are taken as described in the previous technique, from the tip of the mesio-buccal cusps of the maxillary right and left first molars, the tips of the maxillary right and left canines, and the incisal edges of the maxillary central incisors to the appropriate mounting block surface .
· All measurements are recorded on a model surgery planning grid, drawn on a blank paper or lab-card and are repeated to ensure accuracy.
· The facial midline has already been drawn on the model when mounted on the articulator. The simulated O osteotomy line is drawn parallel to the granite base on the plaster mounting (Figure 7.15e).
When undertaking model surgery it is important to ensure that the clinically planned movements are in agreement with the reference points and measurements applied during the model surgery procedure.
· Planned vertical impaction movements can be first measured from the O line opposite the first molar cusps and incisor reference points and scribed on the plaster model mounting. (Figures 7.15f and 7.15g). Using a band saw, the mounting is cut along the O line. Plaster corresponding to the amount of maxillary impaction is removed from the model plaster mounting using a model trimmer. The total amount of plaster removed will be slightly greater that that required. This is taken up by flowing a thin layer of warmed carding wax between the cut model and the mounting base to relocate the two elements (Figure 7.15h).
Figure 7.15 (a) Ericsson model platform with caliper and mounted casts. (b) Model with mounting ring on block. (c) and (d) Electronic caliper assembly showing identification of incisor and bicuspid reference points. To be measured against platform plane. (e) O osteotomy line for sectioning the model. (f) and (g) Measuring planned impaction to be removed from plaster base. (h) Assembled model after “surgery”.
· Planned anteroposterior or rotational movements of the maxilla are checked against the marked centre line and cusp reference points.
· Transverse or segmental surgery requires additional cuts to the plaster model but the same principal is applied.
· The recombined cut maxilla is then replaced on the model block and Ericcson table and the measurements are confirmed using the electronic calliper.
· Warming the interpositional wax by flaming, allows fine adjustments to be made to to ensure the new planned postsur-gical measurements to correspond to those recorded on the planning grid. The model is then sealed to the mount using either sticky wax or a glue gun, and rechecked.
· Fabrication of the intermediate and final wafers is as described below.
7. Occlusal Wafers
Osteotomy wafers locate the dental arches in any preplanned relationship and eliminate unreliable intraoperative guesswork. Wafers are used for the following purposes.
a) To reposition the mobilised maxilla relative to the intact mandible (or vice versa). This intermediate wafer has a horizontal inaccuracy of about 2 mm of the planned position due to the discrepancy between the distalised centre of mandibular rotation in the supine anaesthetised patient and the mandibular rotation in the conscious upright patient. Overcorrection of the maxilla is therefore essential in a single jaw maxillary osteotomy to ensure the planned advancement. This maxillary discrepancy is masked in a bimaxillary procedure when the mandible is placed in a Class I incisor relationship to the maxilla regardless of its position.
b) To achieve the planned intermediate and final occlusion.
c) For postoperative proprioceptive guidance. After rigid fixation of the mandible the wafer may be wired to the maxilla or mandible to provide postoperative proprioceptive guidance for up to two weeks, with or without the help of elastics. However this causes discomfort to the patient and appears to have no proven value except to reassure the surgeon.
d) To stabilise the segments in the planned position when the dental arch is segmented and mobilised whilst an orthodontic supplemental arch wire or arch bar is secured into place. Without an occlusal wafer, this can be difficult and will give poor results. Without the supplemental arch wire the planned occlusal relationship may be unstable.
e) The wafer is invaluable when the postoperative occlusion is not sufficiently stable after the release of intraoperative IMF in cases requiring substantial postoperative orthodontics or with poorly contoured crowns or bridges which need to be replaced.
Wafer Fabrication (Figures 7.16a to 7.16d)
Wafers may be fabricated from cold cured (autopolymerising) or quick cure methylmethacrylate. A poorly designed inaccurate wafer will spoil the most skilful surgical technique. It is common practice to construct both the intermediate and the final wafers as thin as possible. The justification has been that thick wafers introduce discrepancies in the final occlusion.
As stated the condylar recoil from the distalised anaesthetised centric relation to active conscious centric occlusion can reduce the setback in Class III corrections. This is anticipated by overcorrection of the planned posterior position of the mandible by at least 2mm.
Figure 7.16 (a), (b), (c) and (d) After the model surgery, the maxillary and mandibular models with the mounting assembly are removed from the articulator for wafer fabrication — see text.
Similarly, the inevitable degree of postoperative distal relapse in the Class II mandibular advancement justifies a forward overcor-rection to an incisor edge to edge final occlusion.
The Construction Technique Using Quick Cure Acrylic
After the model surgery, the maxillary and mandibular models with the mounting assembly are removed from the articulator. All the undercuts along the palatal, lingual and buccal aspects of the dental arches are relieved by applying a strip of soft red beading wax (Utility Wax, Kem-Dent, Associated Dental Products Ltd, UK).
The occlusal margins of the orthodontic brackets are the limit of the coronal extension of the wafer. It is advisable to have about 1 mm space between the acrylic wafer and the orthodontics brackets or arch bar to avoid any interference at the time of insertion. The Interproximal spaces are blocked out with the wax to ensure that the wafer does not extend into these unwanted areas and impair fit during the surgery.
The tips of the plaster teeth are soaked in the water for 10 minutes and the dental arches are coated with sodium alginate separating medium for easy separation of the acrylic from the casts. The upper postoperative and the lower preoperative models are placed back onto the articulator to fabricate the intermediate occlusal wafer.
A quick cure high impact acrylic is mixed using 70% high impact polymer (Austenal Dental Products Ltd., The Crystal Centre, Harrow, UK), and 30% rapid repair polymer with its monomer. When the mix is at the dough stage, a U-shaped role is placed over the occlusal surface of the mandibular arch. The acrylic dough is moulded and directed towards the buccal and lingual surfaces of the teeth with a spatula, ensuring full coverage of the occlusal surfaces.
The upper arm of the articulator is closed down firmly until its incisal pin touches the incisal table. The acrylic material is thus sandwiched between the maxillary and mandibular dental arches indexing the occlusal surfaces of the teeth. While still soft, the excess acrylic is trimmed with a pair of scissors. At the initial polymerisation stage, the articulator is carefully opened and closed, to ensure that the wafer could be removed from both the upper and lower models when processed. This will also eliminate acrylic contraction around the incisal tips and minimise any damage to the teeth at wafer removal, when fully polymerised and hard.
After removal of the excess acrylic and ensuring that the dental arches are fully covered, the articulator with the models and wafer is secured with a rubber band and placed in the hydro-flask for 10 minutes for curing. Once processed, the upper arm of the articu-lator is unlocked and removed gently before removing the wafer. It is then trimmed and polished, avoiding frictional heat, which may warp the acrylic. The process is repeated with both postsurgical models for the final wafer.
Figure 7.17 (a) The buccal and lingual aspect of the wafers should blend into the tooth morphology. (b) On buccal aspects of the wafer small holes are drilled using a round bur No. 5 to pass wires through to suspend the wafer to orthodontic brackets or arch bars. (c) Final occlusal wafer is tried in on the models. (d) For identification letter (I) for intermediate and (F) for final is engraved and a groove representing the midline can also be marked with No. 2 bur. These letters can be reinforced with lumocolor permanent pen (Staedtler, Germany).
The completed wafers are seated on each model for a final check. The buccal, labial and lingual aspects should blend into the tooth morphology. On the buccal sides, small holes are drilled using a round No. 5 bur for suspensory wires to orthodontic brackets or arch bar (Figures 7.17a to 7.17d).
It is essential for ready intraoperative identification to engrave I or F with a No. 5 round bur. A groove representing the facial midline should also be marked with a No. 2 flat fissure bur. These are reinforced with a Lumocolor permanent pen (Staedtler, Germany) and can be embedded with self-curing clear resin, thus ensuring ready identification.
Although it is convenient to drill small holes for wire loop maxillary suspension, embedded ball end clasps are occasionally a useful alternative.