Mouth Gags Compared: Doyen, Jennings and Boyle-Davis

In 1910 an American anaesthesiologist named S. Griffith Davis took an existing Hartman gag and adapted it for tonsil work. Henry Boyle in London picked up the modification, and the combination became the Boyle-Davis gag — still, more than a century later, the instrument on which most tonsillectomies in the Commonwealth are performed. At least twenty further modifications of the Davis design were published between the 1920s and the 1990s.

That lineage matters when you are buying. “Mouth gag” is not one instrument. It is four distinct mechanical families that happen to share a name, and hospitals routinely order the wrong one because a tender line simply says mouth gag, adult.

The Four Families

Doyen-Jansen

A scissor-action gag inserted at the corner of the mouth with a ratchet on the handle. The jaws are curved and usually supplied with black rubber or silicone sleeves to spread load across the teeth. Sizes typically run in three: infant, child and adult, with adult jaw span around 40–45 mm at full ratchet.

It gives you mouth opening and nothing else. No tongue control, no tube protection, no fixed working corridor. That makes it the right choice for a quick look, a dental extraction under sedation, or emergency airway access — and the wrong choice for anything where a surgeon needs two free hands inside the oropharynx.

Jennings

The Jennings is the pattern most oral surgeons picture when they hear the term. Sprung open by design, held closed by a sliding locking bar on the handle, with broad ribbed jaw plates. Two lengths are standard — adult around 130 mm, paediatric around 100 mm.

Its advantage is that it sits stably without a ratchet needing constant adjustment, and the wide jaw plates distribute pressure over several teeth rather than concentrating it on one. Its limitation is the same as the Doyen: it opens the mouth, and that is the entirety of its contribution.

Boyle-Davis

This is the working instrument of tonsil surgery, and it is a system rather than a single tool.

The frame joins a handle to an interchangeable tongue blade. The blade paddle depresses the tongue and, critically, carries a channel that seats the tracheal tube and holds it out of the surgical field. Rubber-lined extensions at the top of the frame bear against the upper teeth. The whole assembly is then suspended from a Draffin bipod — two rods on a stand — so the gag holds itself open and the surgeon works without an assistant maintaining retraction.

Blades are the part hospitals under-order. A functioning tonsillectomy set needs a graduated range because the blade must match the mandible, not the age on the chart:

Blades are supplied in plain, split (for a nasal tube), and slotted patterns. Buying a frame with a single blade is the most common procurement error in this category — the frame is cheap relative to the blade set, and a theatre with two blades will eventually be forced into a compromise on a patient whose anatomy does not match either.

Denhardt and the trismus problem

The Denhardt gag has short, flat, padded jaws and a fine ratchet. It exists to open a mouth that does not want to open — trismus from infection, fibrosis, or post-radiotherapy contracture. The jaws are inserted between the molars and advanced in small ratchet increments over minutes rather than seconds.

It is not an access instrument. Once the jaw is released, a Jennings or Doyen usually takes over.

The Suspension Nobody Budgets For

A Boyle-Davis gag quoted on its own is an incomplete purchase, and this is where tender lines routinely fall short.

The frame is designed to be suspended. Draffin rods — a pair of telescopic bipod legs that stand on the operating table and cradle the gag’s frame arms — hold the assembly at a fixed height and angle once the surgeon has set it. Without them, someone has to hold the gag by hand for the duration of the case, which defeats the purpose of the design and reintroduces every stability problem the frame was built to solve.

Draffin rods are sold as a pair, usually in stainless steel with a knurled adjustment collar, and they are consumed slowly — they bend if a table is moved with the gag suspended, and a bent rod will not telescope smoothly. Most units keep a spare pair.

The other frequently omitted component is the tongue depressor itself as a separate consumable line. Blades wear at the tube channel, get dropped, and go missing between sets. A theatre running a regular tonsil list should carry replacements against its most-used two or three sizes rather than ordering reactively.

Self-retaining alternatives

The McIvor and Davis-Meyer patterns achieve the same result by different means. McIvor gags carry a hinged frame that locks against the upper teeth and self-retains without a suspension, which suits units that prefer a table-independent setup or operate in an environment where a bipod stand is impractical.

The trade-off is adjustability. A suspended Boyle-Davis can be repositioned in fine increments mid-case by loosening one collar. A self-retaining gag is repositioned by releasing and resetting it, which means briefly losing the airway corridor. Neither is wrong; it is a preference that should be established with the surgical team before a set is specified, because the two are not interchangeable once blades and suspensions have been bought.

Choosing Between Them

The question that resolves nearly every case: does the surgeon need to work inside the mouth with both hands, or just look inside it?

If the answer is look, a Jennings or Doyen-Jansen is sufficient and faster to place. If the answer is work — tonsils, adenoids, palate, posterior tongue — you need a Boyle-Davis or McIvor with a suspension, because the instrument has to hold the tongue, the tube and the jaw simultaneously while the surgeon operates.

A secondary question is duration. Ratcheted side-of-mouth gags concentrate force on a small number of teeth. Over a long case that is a real risk to dentition, particularly in patients with restorations or in the mixed dentition years. Frame gags spread load across the arch.

Safety Considerations Worth Knowing Before You Buy

Two published concerns shape how these instruments are specified.

Tube compression. Placement and opening of a Boyle-Davis gag can kink or compress a tracheal tube seated in the blade channel — the anaesthetic literature has documented this repeatedly. It is an argument for buying blades with a properly formed, deburred tube channel rather than a stamped slot, and for maintaining a full blade range so the tube is never forced into an undersized groove.

Positional effects. Recent observational work has looked at intracranial pressure changes during gag placement in children undergoing tonsillectomy, in the context of head extension and jaw opening. This is a clinical-practice issue rather than a manufacturing one, but it reinforces the case for a suspension system that holds a stable, deliberately chosen position rather than an assistant holding a gag by hand.

Materials and Construction

Frames and jaws are forged from AISI 420 martensitic stainless steel. Tongue blades are typically AISI 304 austenitic — that grade is chosen deliberately, because the blade is a formed sheet component that needs corrosion resistance and formability more than hardness, and it is not a cutting surface.

Points to inspect on delivery:

• Ratchet engagement. Every tooth should hold under load. A ratchet that skips under moderate spread will release inside a patient’s mouth.
• Blade channel edges. Run a gloved finger along the tube groove. Any burr will abrade a tracheal tube cuff.
• Blade-to-frame fit. Interchangeable blades must seat with no rock. Mixed-manufacturer frames and blades often nearly fit, which is worse than not fitting at all.
• Rubber and silicone sleeves. Confirm they are autoclavable and separately replaceable. Sleeves are consumables; a gag that needs replacing because its sleeve perished is a waste.

Reprocessing follows standard steam protocol at 134°C, but disassemble first: blades off frames, sleeves off jaws, ratchets fully open. Our CSSD sterilization guide covers loading and cycle selection in detail.

Where They Sit in an ENT Set

A complete tonsillectomy tray pairs the gag with Draffin rods, a tongue depressor, Negus or Waugh forceps, a tonsil dissector, Boyle-Davis-compatible suction, and either a snare or bipolar diathermy. Our tonsillectomy instrument set guide lists the full composition, and the snare versus cold dissection comparison covers the technique choice that determines the rest of the tray.

For oral and maxillofacial work, the mouth gag sits alongside cheek retractors and bite blocks rather than in a tonsil tray. Fizza Surgical manufactures the full range across our surgical instruments catalogue, forged and finished in Sialkot under ISO 13485 with CE marking under MDR 2017/745.