diff --git a/frontend/messages/en.json b/frontend/messages/en.json
index 66fb8d5..1c05114 100644
--- a/frontend/messages/en.json
+++ b/frontend/messages/en.json
@@ -930,6 +930,7 @@
     "voiceNotUnderstood": "Not understood",
     "voicePickTooth": "Which tooth?",
     "voicePickJaw": "Which jaw?",
+    "voiceTypeForcedByProsthesis": "Prosthesis work sets this type — it cannot be unticked.",
     "voiceTeethAndProsthesis": "Teeth and prosthesis",
     "voiceNoProsthesisHeard": "no prosthesis heard",
     "voiceStackRefused": "not added — cannot be combined",
diff --git a/frontend/messages/fa.json b/frontend/messages/fa.json
index 9dd9436..23f800d 100644
--- a/frontend/messages/fa.json
+++ b/frontend/messages/fa.json
@@ -931,6 +931,7 @@
     "voiceNotUnderstood": "شناسایی نشد",
     "voicePickTooth": "کدام دندان؟",
     "voicePickJaw": "کدام فک؟",
+    "voiceTypeForcedByProsthesis": "کار پروتز این نوع درمان را تعیین می‌کند — قابل برداشتن نیست.",
     "voiceTeethAndProsthesis": "دندان‌ها و پروتز",
     "voiceNoProsthesisHeard": "پروتزی شنیده نشد",
     "voiceStackRefused": "افزوده نشد — قابل ترکیب نیست",
diff --git a/frontend/messages/nl.json b/frontend/messages/nl.json
index 08f94ed..749a281 100644
--- a/frontend/messages/nl.json
+++ b/frontend/messages/nl.json
@@ -930,6 +930,7 @@
     "voiceNotUnderstood": "Niet begrepen",
     "voicePickTooth": "Welk element?",
     "voicePickJaw": "Welke kaak?",
+    "voiceTypeForcedByProsthesis": "Prothesewerk bepaalt dit type — dit kan niet worden uitgevinkt.",
     "voiceTeethAndProsthesis": "Elementen en prothese",
     "voiceNoProsthesisHeard": "geen prothese gehoord",
     "voiceStackRefused": "niet toegevoegd — kan niet worden gecombineerd",
diff --git a/frontend/src/components/ui/treatment/TreatmentWorkspace.tsx b/frontend/src/components/ui/treatment/TreatmentWorkspace.tsx
index 6287483..dd659c9 100644
--- a/frontend/src/components/ui/treatment/TreatmentWorkspace.tsx
+++ b/frontend/src/components/ui/treatment/TreatmentWorkspace.tsx
@@ -62,10 +62,7 @@ import {
   unlinkAdjacentTeeth,
 } from '@/components/treatment/toothSelectionGroups';
 import { hasArchJobs, pruneDetailTeethToJobs } from '@/components/treatment/prosthesisTree';
-import {
-  isLabDependentResult,
-  prosthesisTargetLines,
-} from '@/components/treatment/voiceReviewRows';
+import { prosthesisTargetLines } from '@/components/treatment/voiceReviewRows';
 import type { LabDispatchAttentionItem } from '@/components/treatment/labDispatchAttention';
 import { collectLabDispatchAttention } from '@/components/treatment/labDispatchAttention';
 import {
@@ -2211,7 +2208,10 @@ export function TreatmentWorkspace({
       // "teeth" independently of "prosthesis" could save an empty detail, since
       // `persistDraft` prunes a lab-dependent detail down to its jobs. `selection.prosthesis`
       // alone drives both below; `selection.teeth` only ever applies to the plain row.
-      const labDependent = isLabDependentResult(result, labDependentCodes);
+      // Derived from the detail actually being written, never from `result.treatmentType`.
+      // Reading the result meant that unticking the type row still took the prosthesis branch,
+      // saving lab rows on whatever type the appointment purpose had seeded (decision 41).
+      const labDependent = labDependentCodes.has(detail.treatmentType);
       if (!labDependent && selection.teeth) {
         detail.teeth = [...result.teeth];
         detail.toothSelectionGroups = result.toothSelectionGroups.map((group) => ({
diff --git a/frontend/src/components/ui/treatment/VoiceReviewSheet.tsx b/frontend/src/components/ui/treatment/VoiceReviewSheet.tsx
index 71bc0ad..072263f 100644
--- a/frontend/src/components/ui/treatment/VoiceReviewSheet.tsx
+++ b/frontend/src/components/ui/treatment/VoiceReviewSheet.tsx
@@ -110,6 +110,12 @@ export function VoiceReviewSheet({
     () => prosthesisChartData(prosthesisLines, joblessTargets, prosthesisCatalog),
     [prosthesisLines, joblessTargets, prosthesisCatalog],
   );
+  // Decision 41: prosthesis jobs exist on one treatment type only, so a ticked prosthesis row
+  // pins the type row. Locking it is what makes "restoration detail carrying lab rows"
+  // unreachable rather than merely discouraged.
+  const typeForcedByProsthesis =
+    available.prosthesis && selection.prosthesis && effective.treatmentType != null;
+
   const nothingToApply = !hasAnythingToApply(effective, labDependentCodes);
   const selectedCount = countSelected(selection, available);
 
@@ -134,6 +140,12 @@ export function VoiceReviewSheet({
     return chosenTeeth.includes(code as FdiToothId);
   };
 
+  /**
+   * A picked candidate has no meaning unless its own row is ticked, so each branch ticks the
+   * row it feeds. Never derive that from `available`: it is memoised from `effective`, which
+   * this handler is in the middle of changing, so it still reports the row as unavailable and
+   * the pick would apply nothing.
+   */
   const pickCandidate = (item: VoiceUnresolvedItem, code: string) => {
     const index = item.assignmentIndex;
     if (item.reason === 'arch_not_spoken' && index != null) {
@@ -145,12 +157,18 @@ export function VoiceReviewSheet({
           [index]: cur.includes(arch) ? cur.filter((a) => a !== arch) : [...cur, arch],
         };
       });
-    } else if (item.reason === 'prosthesis_type_ambiguous' && index != null) {
+      setSelection((prev) => ({ ...prev, prosthesis: true }));
+      return;
+    }
+    if (item.reason === 'prosthesis_type_ambiguous' && index != null) {
       setChosenLeaves((prev) => {
         const cur = prev[index] ?? [];
         return { ...prev, [index]: cur.includes(code) ? cur.filter((l) => l !== code) : [...cur, code] };
       });
-    } else if (index != null) {
+      setSelection((prev) => ({ ...prev, prosthesis: true }));
+      return;
+    }
+    if (index != null) {
       setChosenAssignmentTeeth((prev) => {
         const cur = prev[index] ?? [];
         const tooth = code as FdiToothId;
@@ -159,16 +177,12 @@ export function VoiceReviewSheet({
           [index]: cur.includes(tooth) ? cur.filter((t2) => t2 !== tooth) : [...cur, tooth],
         };
       });
-    } else {
-      const tooth = code as FdiToothId;
-      setChosenTeeth((prev) => (prev.includes(tooth) ? prev.filter((t2) => t2 !== tooth) : [...prev, tooth]));
+      setSelection((prev) => ({ ...prev, prosthesis: true }));
+      return;
     }
-    // A picked candidate has no meaning unless its row is ticked.
-    setSelection((prev) => ({
-      ...prev,
-      teeth: prev.teeth || available.teeth,
-      prosthesis: true,
-    }));
+    const tooth = code as FdiToothId;
+    setChosenTeeth((prev) => (prev.includes(tooth) ? prev.filter((t2) => t2 !== tooth) : [...prev, tooth]));
+    setSelection((prev) => ({ ...prev, teeth: true }));
   };
 
   const candidateLabel = (item: VoiceUnresolvedItem, code: string): string => {
@@ -209,8 +223,10 @@ export function VoiceReviewSheet({
             {available.treatmentType ? (
               <Row
                 label={t('treatmentType')}
-                checked={selection.treatmentType}
+                checked={selection.treatmentType || typeForcedByProsthesis}
                 onChange={toggle('treatmentType')}
+                locked={typeForcedByProsthesis}
+                warning={typeForcedByProsthesis ? t('voiceTypeForcedByProsthesis') : undefined}
               >
                 <span className="text-sm text-text-primary">
                   {labelFor(effective.treatmentType, treatmentCatalog)}
@@ -378,7 +394,13 @@ export function VoiceReviewSheet({
             type="button"
             variant="primary"
             disabled={selectedCount === 0}
-            onClick={() => onApply(selection, effective)}
+            onClick={() =>
+              onApply(
+                // The locked type row is ticked in the UI, so it must be ticked in what applies.
+                typeForcedByProsthesis ? { ...selection, treatmentType: true } : selection,
+                effective,
+              )
+            }
             fullWidth
             className="sm:w-auto"
           >
@@ -395,17 +417,20 @@ function Row({
   checked,
   onChange,
   warning,
+  locked,
   children,
 }: {
   label: string;
   checked: boolean;
   onChange: (checked: boolean) => void;
   warning?: string;
+  /** Ticked and not untickable — the value is implied by another row (decision 41). */
+  locked?: boolean;
   children: React.ReactNode;
 }) {
   return (
     <div className="rounded-[var(--radius-md)] border border-border/70 px-3 py-2">
-      <Checkbox checked={checked} onChange={onChange} label={label} />
+      <Checkbox checked={checked} onChange={onChange} label={label} disabled={locked} />
       <div className="mt-1 ps-7 min-w-0">{children}</div>
       {warning ? (
         <p className="mt-1 ps-7 flex items-start gap-1 text-xs text-amber-700 dark:text-amber-400">